id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1703.09555 | Javier Chagoya | Javier Chagoya, Gustavo Niz, Gianmassimo Tasinato | Black Holes and Neutron Stars in Vector Galileons | 16 pages plus appendices, 9 figures | null | 10.1088/1361-6382/aa7c01 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct detection of gravitational waves opens new perspectives for
measuring properties of gravitationally bound compact objects. It is then
important to investigate black holes and neutron stars in alternative theories
of gravity, since they can have features that make them observationally
distinguishable from their General Relativity (GR) counterparts. In this work,
we examine a special case of vector Galileons, a vector-tensor theory of
gravity with interesting cosmological properties, which consists of a one
parameter modification of the Einstein-Maxwell action. Within this theory, we
study configurations describing asymptotically flat, spherically symmetric
black holes and neutron stars. The set of black hole solutions in this theory
is surprisingly rich, generalising results found in GR or in related
scalar-tensor theories. We investigate the properties and conserved charges of
black holes, using both analytical and numerical techniques, highlighting
configurations that are more compact than in GR. We then study properties of
neutron stars, showing how the vector profile can influence the star internal
structure. Depending on properties of matter and fields inside the star,
neutron stars can be more massive than in GR, and they can be even more compact
than Schwarzschild black holes, making these objects observationally
interesting. We also comment on possible extensions of our configurations to
magnetically charged or rotating configurations.
| [
{
"created": "Tue, 28 Mar 2017 12:57:30 GMT",
"version": "v1"
}
] | 2017-07-26 | [
[
"Chagoya",
"Javier",
""
],
[
"Niz",
"Gustavo",
""
],
[
"Tasinato",
"Gianmassimo",
""
]
] | The direct detection of gravitational waves opens new perspectives for measuring properties of gravitationally bound compact objects. It is then important to investigate black holes and neutron stars in alternative theories of gravity, since they can have features that make them observationally distinguishable from their General Relativity (GR) counterparts. In this work, we examine a special case of vector Galileons, a vector-tensor theory of gravity with interesting cosmological properties, which consists of a one parameter modification of the Einstein-Maxwell action. Within this theory, we study configurations describing asymptotically flat, spherically symmetric black holes and neutron stars. The set of black hole solutions in this theory is surprisingly rich, generalising results found in GR or in related scalar-tensor theories. We investigate the properties and conserved charges of black holes, using both analytical and numerical techniques, highlighting configurations that are more compact than in GR. We then study properties of neutron stars, showing how the vector profile can influence the star internal structure. Depending on properties of matter and fields inside the star, neutron stars can be more massive than in GR, and they can be even more compact than Schwarzschild black holes, making these objects observationally interesting. We also comment on possible extensions of our configurations to magnetically charged or rotating configurations. |
0811.0793 | Alexander Kaganovich B. | E. I. Guendelman and A. B. Kaganovich | Physical Consequences of a Theory with Dynamical Volume Element | 23 pages, 7 figures, plenary talk given at the Workshop Geometry,
Topology, QFT and Cosmology, Paris, 28-30 May 2008 | null | null | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We survey motivation, basic ideas and physical consequences of a theory where
the underlying action involves terms both with the usual volume element
$\sqrt{-g}d^{4}x$ and with the new one $\Phi d^{4}x={4!}d\varphi_{1}\wedge
d\varphi_{2}\wedge d\varphi_{3}\wedge d\varphi_{4}$. The latter may be
interpreted as the 4-form determined on the 4-D space-time manifold (not
necessary Riemannian). Regarding the scalar fields $\varphi_{a} (a=1,...4)$ as
new dynamical variables and proceeding in the first order formalism we realize
the so-called Two Measures Theory which possesses a number of attractive
features. We discuss new physical effects which arise from this theory and in
particular strong gravity effect in high energy physics experiments.
| [
{
"created": "Wed, 5 Nov 2008 18:43:34 GMT",
"version": "v1"
}
] | 2008-11-06 | [
[
"Guendelman",
"E. I.",
""
],
[
"Kaganovich",
"A. B.",
""
]
] | We survey motivation, basic ideas and physical consequences of a theory where the underlying action involves terms both with the usual volume element $\sqrt{-g}d^{4}x$ and with the new one $\Phi d^{4}x={4!}d\varphi_{1}\wedge d\varphi_{2}\wedge d\varphi_{3}\wedge d\varphi_{4}$. The latter may be interpreted as the 4-form determined on the 4-D space-time manifold (not necessary Riemannian). Regarding the scalar fields $\varphi_{a} (a=1,...4)$ as new dynamical variables and proceeding in the first order formalism we realize the so-called Two Measures Theory which possesses a number of attractive features. We discuss new physical effects which arise from this theory and in particular strong gravity effect in high energy physics experiments. |
gr-qc/0303093 | Ernesto F. Eiroa | Ernesto F. Eiroa and Gustavo E. Romero | Linearized stability of charged thin-shell wormholes | 8 pages, 2 figures; v2: minor changes. Accepted for publication in
General Relativity and Gravitation | Gen.Rel.Grav. 36 (2004) 651-659 | 10.1023/B:GERG.0000016916.79221.24 | null | gr-qc | null | The linearized stability of charged thin shell wormholes under spherically
symmetric perturbations is analized. It is shown that the presence of a large
value of charge provides stabilization to the system, in the sense that the
constrains onto the equation of state are less severe than for non-charged
wormholes.
| [
{
"created": "Mon, 24 Mar 2003 17:54:13 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Oct 2003 15:16:59 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Eiroa",
"Ernesto F.",
""
],
[
"Romero",
"Gustavo E.",
""
]
] | The linearized stability of charged thin shell wormholes under spherically symmetric perturbations is analized. It is shown that the presence of a large value of charge provides stabilization to the system, in the sense that the constrains onto the equation of state are less severe than for non-charged wormholes. |
1505.06015 | Sante Carloni Dr | Sante Carloni | A new approach to the analysis of the phase space of f(R)-gravity | 32 pages, 13 figures, typos corrected, updated bibliography | null | 10.1088/1475-7516/2015/09/013 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new dynamical system formalism for the analysis of f(R)
cosmologies. The new approach eliminates the need for cumbersome inversions to
close the dynamical system and allows the analysis of the phase space of
f(R)-gravity models which cannot be investigated using the standard technique.
Differently form previously proposed similar techniques, the new method is
constructed in such a way to associate to the fixed points scale factors, which
contain four integration constants (i.e. solutions of fourth order differential
equations). In this way a new light is shed on the physical meaning of the
fixed points. We apply this technique to some f(R) Lagrangians relevant for
inflationary and dark energy models.
| [
{
"created": "Fri, 22 May 2015 10:20:15 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Oct 2015 10:46:37 GMT",
"version": "v2"
}
] | 2015-10-27 | [
[
"Carloni",
"Sante",
""
]
] | We propose a new dynamical system formalism for the analysis of f(R) cosmologies. The new approach eliminates the need for cumbersome inversions to close the dynamical system and allows the analysis of the phase space of f(R)-gravity models which cannot be investigated using the standard technique. Differently form previously proposed similar techniques, the new method is constructed in such a way to associate to the fixed points scale factors, which contain four integration constants (i.e. solutions of fourth order differential equations). In this way a new light is shed on the physical meaning of the fixed points. We apply this technique to some f(R) Lagrangians relevant for inflationary and dark energy models. |
0912.1541 | Kayoomars Karami | K. Karami, J. Fehri | New holographic scalar field models of dark energy in non-flat universe | 11 pages | Phys.Lett.B684:61-68,2010 | 10.1016/j.physletb.2009.12.060 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the work of Granda and Oliveros [L.N. Granda, A. Oliveros, Phys.
Lett. B {\bf 671}, 199 (2009)], we generalize their work to the non-flat case.
We study the correspondence between the quintessence, tachyon, K-essence and
dilaton scalar field models with the new holographic dark energy model in the
non-flat FRW universe. We reconstruct the potentials and the dynamics for these
scalar field models, which describe accelerated expansion of the universe. In
the limiting case of a flat universe, i.e. $k = 0$, all results given in [L.N.
Granda, A. Oliveros, Phys. Lett. B {\bf 671}, 199 (2009)] are obtained.
| [
{
"created": "Tue, 8 Dec 2009 16:59:40 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Karami",
"K.",
""
],
[
"Fehri",
"J.",
""
]
] | Motivated by the work of Granda and Oliveros [L.N. Granda, A. Oliveros, Phys. Lett. B {\bf 671}, 199 (2009)], we generalize their work to the non-flat case. We study the correspondence between the quintessence, tachyon, K-essence and dilaton scalar field models with the new holographic dark energy model in the non-flat FRW universe. We reconstruct the potentials and the dynamics for these scalar field models, which describe accelerated expansion of the universe. In the limiting case of a flat universe, i.e. $k = 0$, all results given in [L.N. Granda, A. Oliveros, Phys. Lett. B {\bf 671}, 199 (2009)] are obtained. |
1608.01982 | Miguel Zumalacarregui | Dario Bettoni (1), Jose Mar\'ia Ezquiaga (2), Kurt Hinterbichler (3),
Miguel Zumalac\'arregui (1 and 4) ((1) Nordita, (2) Madrid IFT, (3) Perimeter
Institute, (4) UC Berkeley) | Speed of Gravitational Waves and the Fate of Scalar-Tensor Gravity | 7 pages, comments welcome | Phys. Rev. D 95, 084029 (2017) | 10.1103/PhysRevD.95.084029 | NORDITA-2016-86, IFT-UAM/CSIC-16-074 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct detection of gravitational waves (GWs) is an invaluable new tool
to probe gravity and the nature of cosmic acceleration. A large class of
scalar-tensor theories predict that GWs propagate with velocity different than
the speed of light, a difference that can be $\mathcal{O}(1)$ for many models
of dark energy. We determine the conditions behind the anomalous GW speed,
namely that the scalar field spontaneously breaks Lorentz invariance and
couples to the metric perturbations via the Weyl tensor. If these conditions
are realized in nature, the delay between GW and electromagnetic (EM) signals
from distant events will run beyond human timescales, making it impossible to
measure the speed of GWs using neutron star mergers or other violent events. We
present a robust strategy to exclude or confirm an anomalous speed of GWs using
eclipsing binary systems, whose EM phase can be exquisitely determined. he
white dwarf binary J0651+2844 is a known example of such system that can be
used to probe deviations in the GW speed as small as $c_g/c-1\gtrsim 2\cdot
10^{-12}$ when LISA comes online. This test will either eliminate many
contender models for cosmic acceleration or wreck a fundamental pillar of
general relativity.
| [
{
"created": "Fri, 5 Aug 2016 19:30:55 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Mar 2017 15:34:11 GMT",
"version": "v2"
},
{
"created": "Sun, 9 Apr 2017 22:32:16 GMT",
"version": "v3"
}
] | 2017-04-19 | [
[
"Bettoni",
"Dario",
"",
"1 and 4"
],
[
"Ezquiaga",
"Jose María",
"",
"1 and 4"
],
[
"Hinterbichler",
"Kurt",
"",
"1 and 4"
],
[
"Zumalacárregui",
"Miguel",
"",
"1 and 4"
]
] | The direct detection of gravitational waves (GWs) is an invaluable new tool to probe gravity and the nature of cosmic acceleration. A large class of scalar-tensor theories predict that GWs propagate with velocity different than the speed of light, a difference that can be $\mathcal{O}(1)$ for many models of dark energy. We determine the conditions behind the anomalous GW speed, namely that the scalar field spontaneously breaks Lorentz invariance and couples to the metric perturbations via the Weyl tensor. If these conditions are realized in nature, the delay between GW and electromagnetic (EM) signals from distant events will run beyond human timescales, making it impossible to measure the speed of GWs using neutron star mergers or other violent events. We present a robust strategy to exclude or confirm an anomalous speed of GWs using eclipsing binary systems, whose EM phase can be exquisitely determined. he white dwarf binary J0651+2844 is a known example of such system that can be used to probe deviations in the GW speed as small as $c_g/c-1\gtrsim 2\cdot 10^{-12}$ when LISA comes online. This test will either eliminate many contender models for cosmic acceleration or wreck a fundamental pillar of general relativity. |
2201.09142 | Inna Ivanova | V. A. Berezin, I. D. Ivanova | Lightlike singular hypersurfaces in quadratic gravity | 32 pages, to be submitted to IJMPD | Int.J.Mod.Phys.D 31 (2022) 10, 2250077 | 10.1142/S0218271822500778 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Using the principle of least action, the motion equations for a singular
hypersurface of arbitrary type in quadratic gravity are derived. Equations
containing the "external pressure" and the "external flow" components of the
surface energy-momentum tensor together with the Lichnerowicz conditions serve
to find the hypersurface itself, while the remaining ones define arbitrary
functions that arise due to the implicit presence of the delta function
derivative. It turns out that neither double layers nor thin shells exist for
the quadratic Gauss-Bonnet term. It is shown that there is no "external
pressure" for null singular hypersurfaces. The Lichnerowicz conditions imply
the continuity of the scalar curvature in the case of spherically symmetric
null singular hypersurfaces. These hypersurfaces must be thin shells if the
Lichnerowicz conditions are necessary. It is shown that for this particular
case the Lichnerowicz conditions can be completely removed therefore a
spherically symmetric null double layer exists. Spherically symmetric null
singular hypersurfaces in conformal gravity are explored as application.
| [
{
"created": "Sat, 22 Jan 2022 22:56:56 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jan 2022 14:10:45 GMT",
"version": "v2"
}
] | 2023-02-02 | [
[
"Berezin",
"V. A.",
""
],
[
"Ivanova",
"I. D.",
""
]
] | Using the principle of least action, the motion equations for a singular hypersurface of arbitrary type in quadratic gravity are derived. Equations containing the "external pressure" and the "external flow" components of the surface energy-momentum tensor together with the Lichnerowicz conditions serve to find the hypersurface itself, while the remaining ones define arbitrary functions that arise due to the implicit presence of the delta function derivative. It turns out that neither double layers nor thin shells exist for the quadratic Gauss-Bonnet term. It is shown that there is no "external pressure" for null singular hypersurfaces. The Lichnerowicz conditions imply the continuity of the scalar curvature in the case of spherically symmetric null singular hypersurfaces. These hypersurfaces must be thin shells if the Lichnerowicz conditions are necessary. It is shown that for this particular case the Lichnerowicz conditions can be completely removed therefore a spherically symmetric null double layer exists. Spherically symmetric null singular hypersurfaces in conformal gravity are explored as application. |
0805.0718 | Riccardo Sturani | Stefano Foffa and Riccardo Sturani (University of Geneva) | Events trigger generator for resonant spherical detectors of
gravitational waves | 14 pages, 8 figures. Version accepted for publication on CQG.
Proceedings of the 12th Gravitational Wave Data Analysis Workshop | Class.Quant.Grav.25:184036,2008 | 10.1088/0264-9381/25/18/184036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have set up and tested a pipeline for processing the data from a spherical
gravitational wave detector with six transducers. The algorithm exploits the
multichannel capability of the system and provides a list of candidate events
with their arrival direction. The analysis starts with the conversion of the
six detector outputs into the scalar and the five quadrupolar modes of the
sphere, which are proportional to the corresponding gravitational wave
spherical components. Event triggers are then generated by an adaptation of the
WaveBurst algorithm. Event validation and direction reconstruction are made by
cross-checking two methods of different inspiration: geometrical (lowest
eigenvalue) and probabilistic (maximum likelihood). The combination of the two
methods is able to keep substantially unaltered the efficiency and can reduce
drastically the detections of fake events (to less than ten per cent). We show
a quantitative test of these ideas by simulating the operation of the resonant
spherical detector miniGRAIL, whose planned sensitivity in its frequency band
(few hundred Hertz's around 3 kHz) is comparable with the present LIGO one.
| [
{
"created": "Tue, 6 May 2008 13:15:16 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Dec 2008 09:14:14 GMT",
"version": "v2"
}
] | 2008-12-22 | [
[
"Foffa",
"Stefano",
"",
"University of Geneva"
],
[
"Sturani",
"Riccardo",
"",
"University of Geneva"
]
] | We have set up and tested a pipeline for processing the data from a spherical gravitational wave detector with six transducers. The algorithm exploits the multichannel capability of the system and provides a list of candidate events with their arrival direction. The analysis starts with the conversion of the six detector outputs into the scalar and the five quadrupolar modes of the sphere, which are proportional to the corresponding gravitational wave spherical components. Event triggers are then generated by an adaptation of the WaveBurst algorithm. Event validation and direction reconstruction are made by cross-checking two methods of different inspiration: geometrical (lowest eigenvalue) and probabilistic (maximum likelihood). The combination of the two methods is able to keep substantially unaltered the efficiency and can reduce drastically the detections of fake events (to less than ten per cent). We show a quantitative test of these ideas by simulating the operation of the resonant spherical detector miniGRAIL, whose planned sensitivity in its frequency band (few hundred Hertz's around 3 kHz) is comparable with the present LIGO one. |
1710.05717 | Muhammad Zaeem-Ul-Haq Bhatti | Z. Yousaf, M. Sharif, M. Ilyas, M. Z. Bhatti | Influence of $f(R)$ Models on the Existence of Anisotropic
Self-Gravitating Systems | 23 pages, 13 figures, version accepted for publication in European
Physical Journal C | Eur. Phys. J. C 77, 691 (2017) | 10.1140/epjc/s10052-017-5280-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper aims to explore some realistic configurations of anisotropic
spherical structures in the background of metric $f(R)$ gravity, where $R$ is
the Ricci scalar. The solutions obtained by Krori and Barua are used to examine
the nature of particular compact stars with three different modified gravity
models. The behavior of material variables is analyzed through plots and the
physical viability of compact stars is investigated through energy conditions.
We also discuss the behavior of different forces, equation of state parameter,
measure of anisotropy and Tolman-Oppenheimer-Volkoff equation in the modeling
of stellar structures. The comparison from our graphical representations may
provide evidences for the realistic and viable $f(R)$ gravity models at both
theoretical and astrophysical scale.
| [
{
"created": "Mon, 9 Oct 2017 07:13:06 GMT",
"version": "v1"
}
] | 2017-11-08 | [
[
"Yousaf",
"Z.",
""
],
[
"Sharif",
"M.",
""
],
[
"Ilyas",
"M.",
""
],
[
"Bhatti",
"M. Z.",
""
]
] | This paper aims to explore some realistic configurations of anisotropic spherical structures in the background of metric $f(R)$ gravity, where $R$ is the Ricci scalar. The solutions obtained by Krori and Barua are used to examine the nature of particular compact stars with three different modified gravity models. The behavior of material variables is analyzed through plots and the physical viability of compact stars is investigated through energy conditions. We also discuss the behavior of different forces, equation of state parameter, measure of anisotropy and Tolman-Oppenheimer-Volkoff equation in the modeling of stellar structures. The comparison from our graphical representations may provide evidences for the realistic and viable $f(R)$ gravity models at both theoretical and astrophysical scale. |
gr-qc/0510045 | Sachie Shiomi | Sachie Shiomi | Acceleration disturbances due to local gravity gradients in ASTROD I | 6 pages, presented at the 6th Edoardo Amaldi Conference (Okinawa
Japan, June 2005); to be published in Journal of Physics: Conference Series | J.Phys.Conf.Ser. 32 (2006) 186-191 | 10.1088/1742-6596/32/1/028 | null | gr-qc | null | The Astrodynamical Space Test of Relativity using Optical Devices (ASTROD)
mission consists of three spacecraft in separate solar orbits and carries out
laser interferometric ranging. ASTROD aims at testing relativistic gravity,
measuring the solar system and detecting gravitational waves. Because of the
larger arm length, the sensitivity of ASTROD to gravitational waves is
estimated to be about 30 times better than Laser Interferometer Space Antenna
(LISA) in the frequency range lower than about 0.1 mHz. ASTROD I is a simple
version of ASTROD, employing one spacecraft in a solar orbit. It is the first
step for ASTROD and serves as a technology demonstration mission for ASTROD. In
addition, several scientific results are expected in the ASTROD I experiment.
The required acceleration noise level of ASTROD I is 10^-13 m s^-2 Hz^{-1/2} at
the frequency of 0.1 mHz. In this paper, we focus on local gravity gradient
noise that could be one of the largest acceleration disturbances in the ASTROD
I experiment. We have carried out gravitational modelling for the current
test-mass design and simplified configurations of ASTROD I by using an
analytical method and the Monte Carlo method. Our analyses can be applied to
figure out the optimal designs of the test mass and the constructing materials
of the spacecraft, and the configuration of compensation mass to reduce local
gravity gradients.
| [
{
"created": "Mon, 10 Oct 2005 03:04:24 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Feb 2006 06:59:29 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Shiomi",
"Sachie",
""
]
] | The Astrodynamical Space Test of Relativity using Optical Devices (ASTROD) mission consists of three spacecraft in separate solar orbits and carries out laser interferometric ranging. ASTROD aims at testing relativistic gravity, measuring the solar system and detecting gravitational waves. Because of the larger arm length, the sensitivity of ASTROD to gravitational waves is estimated to be about 30 times better than Laser Interferometer Space Antenna (LISA) in the frequency range lower than about 0.1 mHz. ASTROD I is a simple version of ASTROD, employing one spacecraft in a solar orbit. It is the first step for ASTROD and serves as a technology demonstration mission for ASTROD. In addition, several scientific results are expected in the ASTROD I experiment. The required acceleration noise level of ASTROD I is 10^-13 m s^-2 Hz^{-1/2} at the frequency of 0.1 mHz. In this paper, we focus on local gravity gradient noise that could be one of the largest acceleration disturbances in the ASTROD I experiment. We have carried out gravitational modelling for the current test-mass design and simplified configurations of ASTROD I by using an analytical method and the Monte Carlo method. Our analyses can be applied to figure out the optimal designs of the test mass and the constructing materials of the spacecraft, and the configuration of compensation mass to reduce local gravity gradients. |
1808.00032 | Hor\'acio Vieira | H. S. Vieira, V. B. Bezerra, C. R. Muniz and M. S. Cunha | Some exact results on quantum Newtonian cosmology | 15 pages, 4 figures | J. Math. Phys. 60, 102301 (2019) | 10.1063/1.5086370 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the wave functions associated to the quantum Newtonian universe
with a cosmological constant which is described by the Schr\"{o}dinger equation
and discuss some aspects of its dynamics for all forms of energy density,
namely, matter, radiation, vacuum, dark energy, and quintessence. These wave
functions of the quantum Newtonian universe are obtained in terms of the Heun's
functions and the respective energy levels are shown. We use these solutions to
investigate the expansion of the universe and found that the asymptotic
behavior for the scale factor is $R \sim \mbox{e}^{t}$ for whatever the form of
energy density is. We also analyze the behavior of the universe at early
stages.
| [
{
"created": "Tue, 31 Jul 2018 19:13:48 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Apr 2019 12:50:24 GMT",
"version": "v2"
},
{
"created": "Sat, 5 Oct 2019 22:54:20 GMT",
"version": "v3"
}
] | 2019-10-08 | [
[
"Vieira",
"H. S.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Muniz",
"C. R.",
""
],
[
"Cunha",
"M. S.",
""
]
] | We obtain the wave functions associated to the quantum Newtonian universe with a cosmological constant which is described by the Schr\"{o}dinger equation and discuss some aspects of its dynamics for all forms of energy density, namely, matter, radiation, vacuum, dark energy, and quintessence. These wave functions of the quantum Newtonian universe are obtained in terms of the Heun's functions and the respective energy levels are shown. We use these solutions to investigate the expansion of the universe and found that the asymptotic behavior for the scale factor is $R \sim \mbox{e}^{t}$ for whatever the form of energy density is. We also analyze the behavior of the universe at early stages. |
1310.6392 | Dimitry Ayzenberg | Dimitry Ayzenberg, Kent Yagi, Nicolas Yunes | Linear Stability Analysis of Dynamical Quadratic Gravity | 9 pages, no figures, updated to published version | Phys. Rev. D 89, 044023 (2014) | 10.1103/PhysRevD.89.044023 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a linear stability analysis of dynamical, quadratic gravity in the
high-frequency, geometric optics approximation. This analysis is based on a
study of gravitational and scalar modes propagating on spherically-symmetric
and axially-symmetric, vacuum solutions of the theory. We find dispersion
relations that do no lead to exponential growth of the propagating modes,
suggesting the theory is linearly stable on these backgrounds. The modes are
found to propagate at subluminal and superluminal speeds, depending on the
propagating modes' direction relative to the background geometry, just as in
dynamical Chern-Simons gravity.
| [
{
"created": "Wed, 23 Oct 2013 20:58:27 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Mar 2014 04:59:24 GMT",
"version": "v2"
}
] | 2014-03-19 | [
[
"Ayzenberg",
"Dimitry",
""
],
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolas",
""
]
] | We perform a linear stability analysis of dynamical, quadratic gravity in the high-frequency, geometric optics approximation. This analysis is based on a study of gravitational and scalar modes propagating on spherically-symmetric and axially-symmetric, vacuum solutions of the theory. We find dispersion relations that do no lead to exponential growth of the propagating modes, suggesting the theory is linearly stable on these backgrounds. The modes are found to propagate at subluminal and superluminal speeds, depending on the propagating modes' direction relative to the background geometry, just as in dynamical Chern-Simons gravity. |
gr-qc/0210077 | Achim Kempf | Achim Kempf | On the Vacuum Energy in Expanding Space-Times | 5 pages, LaTeX, Proceedings 18th IAP Colloquium, Paris July 1-5, 2002 | null | null | null | gr-qc hep-th | null | If there is a shortest length in nature, for example at the Planck scale of
10^-35m, then the cosmic expansion should continually create new comoving
modes. A priori, each of the new modes comes with its own vacuum energy, which
could contribute to the cosmological constant. I discuss possible mathematical
models for a shortest length and an explicit model for a corresponding
mode-generating mechanism.
| [
{
"created": "Wed, 23 Oct 2002 01:00:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kempf",
"Achim",
""
]
] | If there is a shortest length in nature, for example at the Planck scale of 10^-35m, then the cosmic expansion should continually create new comoving modes. A priori, each of the new modes comes with its own vacuum energy, which could contribute to the cosmological constant. I discuss possible mathematical models for a shortest length and an explicit model for a corresponding mode-generating mechanism. |
1404.1220 | Subhajit Saha | Subhajit Saha, Atreyee Biswas and Subenoy Chakraborty | Irreversible Thermodynamics of the Universe: Constraints from Planck
Data | 15 pages, 8 figures | Advances in High Energy Physics 2014, 652962 (2014) | 10.1155/2014/652962 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work deals with irreversible Universal thermodynamics. The
homogenous and isotropic flat model of the universe is chosen as open
thermodynamical system and non-equilibrium thermodynamics comes into picture
due to the mechanism of particle creation. For simplicity, entropy flow is
considered only due to heat conduction. Further, due to Maxwell-Cattaneo
modified Fourier law for non-equilibrium phenomenon, the temperature satisfies
damped wave equation instead of heat conduction equation. Validity of
generalized second law of thermodynamics (GSLT) has been investigated for
Universe bounded by apparent or event horizon with cosmic substrutum as perfect
fluid with constant or variable equation of state or interacting dark species.
Finally, we have used three Planck data sets to constrain the thermal
conductivity \lambda and the coupling parameter b^2. These constraints must be
satisfied in order for GSLT to hold for Universe bounded by apparent or event
horizons.
| [
{
"created": "Fri, 4 Apr 2014 11:41:30 GMT",
"version": "v1"
}
] | 2016-05-17 | [
[
"Saha",
"Subhajit",
""
],
[
"Biswas",
"Atreyee",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present work deals with irreversible Universal thermodynamics. The homogenous and isotropic flat model of the universe is chosen as open thermodynamical system and non-equilibrium thermodynamics comes into picture due to the mechanism of particle creation. For simplicity, entropy flow is considered only due to heat conduction. Further, due to Maxwell-Cattaneo modified Fourier law for non-equilibrium phenomenon, the temperature satisfies damped wave equation instead of heat conduction equation. Validity of generalized second law of thermodynamics (GSLT) has been investigated for Universe bounded by apparent or event horizon with cosmic substrutum as perfect fluid with constant or variable equation of state or interacting dark species. Finally, we have used three Planck data sets to constrain the thermal conductivity \lambda and the coupling parameter b^2. These constraints must be satisfied in order for GSLT to hold for Universe bounded by apparent or event horizons. |
2005.01312 | Xiao Yan Chew | Xiao Yan Chew, Yen Chin Ong | The Interior Volume of Kerr-AdS Black Holes | 15 pages, 31 figures | Phys. Rev. D 102, 064055 (2020) | 10.1103/PhysRevD.102.064055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The interior volume of black holes as defined by Christodoulou and Rovelli
exhibits many surprising features. For example, it increases with time, even
under Hawking evaporation. For some black holes, the interior volume is not
even a monotonic increasing function of its area, which means one cannot infer
how large a black hole is by just looking from the outside. Such a notion of
volume, however, turns out to be useful in the context of holography, as it
seems to be dual to the complexity of the boundary field theory. In this study,
we investigate the properties of the interior volume of 4-dimensional Kerr-AdS
black holes, fixing either the mass parameter $M$ or the physical mass $E$,
whilst varying the values of the cosmological constant. We found that the
volume as a function of the radial coordinate features a "double lobe" while
fixing $M$, whereas fixing $E$ yields behaviors that are qualitatively similar
to the asymptotically flat case. We briefly comment on the holographic
complexity of Kerr-AdS black holes.
| [
{
"created": "Mon, 4 May 2020 08:12:55 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Sep 2020 02:50:24 GMT",
"version": "v2"
}
] | 2020-10-07 | [
[
"Chew",
"Xiao Yan",
""
],
[
"Ong",
"Yen Chin",
""
]
] | The interior volume of black holes as defined by Christodoulou and Rovelli exhibits many surprising features. For example, it increases with time, even under Hawking evaporation. For some black holes, the interior volume is not even a monotonic increasing function of its area, which means one cannot infer how large a black hole is by just looking from the outside. Such a notion of volume, however, turns out to be useful in the context of holography, as it seems to be dual to the complexity of the boundary field theory. In this study, we investigate the properties of the interior volume of 4-dimensional Kerr-AdS black holes, fixing either the mass parameter $M$ or the physical mass $E$, whilst varying the values of the cosmological constant. We found that the volume as a function of the radial coordinate features a "double lobe" while fixing $M$, whereas fixing $E$ yields behaviors that are qualitatively similar to the asymptotically flat case. We briefly comment on the holographic complexity of Kerr-AdS black holes. |
1309.5620 | Robert Lompay | Robert R. Lompay and Alexander N. Petrov | Covariant Differential Identities and Conservation Laws in
Metric-Torsion Theories of Gravitation. II. Manifestly Generally Covariant
Theories | 34 pages, 0 figures, revtex 4.1 | J. Math. Phys. 54, 102504 (2013) | 10.1063/1.4826478 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper continues the work of the authors [arXiv:1306.6887
[gr-qc]]. Here, we study generally covariant metric-torsion theories of gravity
presented more concretely, setting that their Lagrangians are \emph{manifestly}
generally covariant scalars. It is assumed that Lagrangians depend on metric
tensor, curvature tensor, torsion tensor and its first and second covariant
derivatives, besides, on an arbitrary set of other tensor (matter) fields and
their first and second covariant derivatives. Thus, both the standard minimal
coupling with the Riemann-Cartan geometry and non-minimal coupling with the
curvature and torsion tensors are considered.
The studies and results are as follow. (a) A physical interpretation of the
Noether and Klein identities is examined. It was found that they are the basis
for constructing equations of balance of energy-momentum tensors of various
types (canonical, metrical and Belinfante symmetrized). The equations of
balance are presented. (b) Using the generalized equations of balance, new
(generalized) manifestly generally covariant expressions for canonical
energy-momentum and spin tensors of the matter fields are constructed. In the
cases, when the matter Lagrangian contains both the higher derivatives and
non-minimal coupling with curvature and torsion, such generalizations are
non-trivial. (c) The Belinfante procedure is generalized for an arbitrary
Riemann-Cartan space. (d) A more convenient in applications generalized
expression for the canonical superpotential is obtained. (e) A total system of
equations for the gravitational fields and matter sources are presented in the
form more naturally generalizing the Einstein-Cartan equations with matter.
This result, being a one of more important results itself, is to be also a
basis for constructing physically sensible conservation laws and their
applications.
| [
{
"created": "Sun, 22 Sep 2013 17:31:50 GMT",
"version": "v1"
}
] | 2014-01-14 | [
[
"Lompay",
"Robert R.",
""
],
[
"Petrov",
"Alexander N.",
""
]
] | The present paper continues the work of the authors [arXiv:1306.6887 [gr-qc]]. Here, we study generally covariant metric-torsion theories of gravity presented more concretely, setting that their Lagrangians are \emph{manifestly} generally covariant scalars. It is assumed that Lagrangians depend on metric tensor, curvature tensor, torsion tensor and its first and second covariant derivatives, besides, on an arbitrary set of other tensor (matter) fields and their first and second covariant derivatives. Thus, both the standard minimal coupling with the Riemann-Cartan geometry and non-minimal coupling with the curvature and torsion tensors are considered. The studies and results are as follow. (a) A physical interpretation of the Noether and Klein identities is examined. It was found that they are the basis for constructing equations of balance of energy-momentum tensors of various types (canonical, metrical and Belinfante symmetrized). The equations of balance are presented. (b) Using the generalized equations of balance, new (generalized) manifestly generally covariant expressions for canonical energy-momentum and spin tensors of the matter fields are constructed. In the cases, when the matter Lagrangian contains both the higher derivatives and non-minimal coupling with curvature and torsion, such generalizations are non-trivial. (c) The Belinfante procedure is generalized for an arbitrary Riemann-Cartan space. (d) A more convenient in applications generalized expression for the canonical superpotential is obtained. (e) A total system of equations for the gravitational fields and matter sources are presented in the form more naturally generalizing the Einstein-Cartan equations with matter. This result, being a one of more important results itself, is to be also a basis for constructing physically sensible conservation laws and their applications. |
gr-qc/0305088 | Sushant G. Ghosh | Naresh Dadhich, S.G. Ghosh, and D.W. Deshkar | The role of the equation of state and the space-time dimension in
spherical collapse | 4 Pages, RevTeX, no figures, minor changes, new references added,
Detailed version to follow | Int.J.Mod.Phys. A20 (2005) 1495-1502 | 10.1142/S0217751X05021038 | null | gr-qc | null | We study the spherically symmetric collapse of a fluid with non-vanishing
radial pressure in higher dimensional space-time. We obtain the general exact
solution in the closed form for the equation of state ($P_r = \gamma \rho$)
which leads to the explicit construction of the root equation governing the
nature (black hole versus naked singularity) of the central singularity. A
remarkable feature of the root equation is its invariance for the three cases:
(${D+1}, {\gamma = -1}$),
(${D}, {\gamma = 0}$) and (${D - 1}, {\gamma = 1}$) where $D$ is the
dimension of space-time. That is, for the ultimate end result of the collapse,
$D$-dimensional dust, ${D+1}$ - AdS (anti de Sitter)-like and ${D-1}$ - dS-like
are absolutely equivalent.
| [
{
"created": "Fri, 23 May 2003 03:49:22 GMT",
"version": "v1"
},
{
"created": "Fri, 30 May 2003 07:19:58 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Dadhich",
"Naresh",
""
],
[
"Ghosh",
"S. G.",
""
],
[
"Deshkar",
"D. W.",
""
]
] | We study the spherically symmetric collapse of a fluid with non-vanishing radial pressure in higher dimensional space-time. We obtain the general exact solution in the closed form for the equation of state ($P_r = \gamma \rho$) which leads to the explicit construction of the root equation governing the nature (black hole versus naked singularity) of the central singularity. A remarkable feature of the root equation is its invariance for the three cases: (${D+1}, {\gamma = -1}$), (${D}, {\gamma = 0}$) and (${D - 1}, {\gamma = 1}$) where $D$ is the dimension of space-time. That is, for the ultimate end result of the collapse, $D$-dimensional dust, ${D+1}$ - AdS (anti de Sitter)-like and ${D-1}$ - dS-like are absolutely equivalent. |
gr-qc/0102010 | Jaume Garriga | Jaume Garriga and Alexander Vilenkin | Many worlds in one | 9 pages, 2 figures, comments and references added | Phys.Rev. D64 (2001) 043511 | 10.1103/PhysRevD.64.043511 | null | gr-qc astro-ph hep-th quant-ph | null | A generic prediction of inflation is that the thermalized region we inhabit
is spatially infinite. Thus, it contains an infinite number of regions of the
same size as our observable universe, which we shall denote as $\O$-regions. We
argue that the number of possible histories which may take place inside of an
$\O$-region, from the time of recombination up to the present time, is finite.
Hence, there are an infinite number of $\O$-regions with identical histories up
to the present, but which need not be identical in the future. Moreover, all
histories which are not forbidden by conservation laws will occur in a finite
fraction of all $\O$-regions. The ensemble of $\O$-regions is reminiscent of
the ensemble of universes in the many-world picture of quantum mechanics. An
important difference, however, is that other $\O$-regions are unquestionably
real.
| [
{
"created": "Sat, 3 Feb 2001 22:59:07 GMT",
"version": "v1"
},
{
"created": "Wed, 2 May 2001 13:20:11 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Garriga",
"Jaume",
""
],
[
"Vilenkin",
"Alexander",
""
]
] | A generic prediction of inflation is that the thermalized region we inhabit is spatially infinite. Thus, it contains an infinite number of regions of the same size as our observable universe, which we shall denote as $\O$-regions. We argue that the number of possible histories which may take place inside of an $\O$-region, from the time of recombination up to the present time, is finite. Hence, there are an infinite number of $\O$-regions with identical histories up to the present, but which need not be identical in the future. Moreover, all histories which are not forbidden by conservation laws will occur in a finite fraction of all $\O$-regions. The ensemble of $\O$-regions is reminiscent of the ensemble of universes in the many-world picture of quantum mechanics. An important difference, however, is that other $\O$-regions are unquestionably real. |
2211.04239 | Naoki Tsukamoto | Naoki Tsukamoto | Gravitational lensing by using the 0th order of affine perturbation
series of the deflection angle of a ray near a photon sphere | 13 pages, 4 figures, minor changes, accepted for publication in The
European Physical Journal C | The European Physical Journal C 83, 284 (2023) | 10.1140/epjc/s10052-023-11419-9 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The 0th order of affine perturbation series of the deflection angle of a ray
near a photon sphere is more accurate than a deflection angle in a strong
deflection limit, which is used often, because the later has hidden error
terms. We investigate gravitational lensing by using 0th order affine
perturbation series of the deflection angle in a general asymptotically-flat,
static, and spherical symmetric spacetime with the photon sphere. We apply our
formula to Schwarzschild black hole, Reissner-Nordstr\"om black hole, and
Ellis-Bronnikov wormhole spacetimes as examples. By comparing observables by
using the deflection angles, we show that we can ignore the effect of the
hidden error terms in the deflection angle in the strong deflection limit on
the observables in a usual lens configuration with the photon sphere since the
hidden error terms are tiny. On the other hand, in a retro lensing
configuration, the deflection angle in the strong-deflection-limit analysis
have error of several percent and the 0th order of affine perturbation series
of the deflection angle has almost half of the error. Thus, in the retro
lensing configuration, we should use the 0th order of affine perturbation
series of the deflection angle rather than the deflection angle in the
strong-deflection-limit analysis. The 0th order of affine perturbation series
of the deflection angle can give a brighter magnification by a dozen percent
than the one by using the deflection angle in the strong-deflection-limit
analysis.
| [
{
"created": "Tue, 8 Nov 2022 13:34:37 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2023 10:50:11 GMT",
"version": "v2"
}
] | 2023-04-14 | [
[
"Tsukamoto",
"Naoki",
""
]
] | The 0th order of affine perturbation series of the deflection angle of a ray near a photon sphere is more accurate than a deflection angle in a strong deflection limit, which is used often, because the later has hidden error terms. We investigate gravitational lensing by using 0th order affine perturbation series of the deflection angle in a general asymptotically-flat, static, and spherical symmetric spacetime with the photon sphere. We apply our formula to Schwarzschild black hole, Reissner-Nordstr\"om black hole, and Ellis-Bronnikov wormhole spacetimes as examples. By comparing observables by using the deflection angles, we show that we can ignore the effect of the hidden error terms in the deflection angle in the strong deflection limit on the observables in a usual lens configuration with the photon sphere since the hidden error terms are tiny. On the other hand, in a retro lensing configuration, the deflection angle in the strong-deflection-limit analysis have error of several percent and the 0th order of affine perturbation series of the deflection angle has almost half of the error. Thus, in the retro lensing configuration, we should use the 0th order of affine perturbation series of the deflection angle rather than the deflection angle in the strong-deflection-limit analysis. The 0th order of affine perturbation series of the deflection angle can give a brighter magnification by a dozen percent than the one by using the deflection angle in the strong-deflection-limit analysis. |
1711.02744 | Miguel Socolovsky | M. Socolovsky | Schwarzschild Black Hole in Anti-De Sitter Space | 39 pages, 12 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review several aspects of anti-De Sitter (AdS) spaces in different
dimensions, and of four dimensional Schwarzschild anti-De Sitter (SAdS) black
hole.
| [
{
"created": "Tue, 7 Nov 2017 21:59:37 GMT",
"version": "v1"
}
] | 2017-11-09 | [
[
"Socolovsky",
"M.",
""
]
] | We review several aspects of anti-De Sitter (AdS) spaces in different dimensions, and of four dimensional Schwarzschild anti-De Sitter (SAdS) black hole. |
1112.4580 | Ali Kaya | Ali Kaya | Uncertainty relations for cosmological particle creation and existence
of large fluctuations in reheating | 6 pages, essay written for the Gravity Research Foundation 2011
Awards for Essays on Gravitation, Received Honorable Mention | Int.J.Mod.Phys. D20 (2011) 2795-2801 | 10.1142/S021827181102069X | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive an uncertainty relation for the energy density and pressure of a
quantum scalar field in a time-dependent, homogeneous and isotropic, classical
background, which implies the existence of large fluctuations comparable to
their vacuum expectation values. A similar uncertainty relation is known to
hold for the field square since the field can be viewed as a Gaussian random
variable. We discuss possible implications of these results for the reheating
process in scalar field driven inflationary models, where reheating is achieved
by the decay of the coherently oscillating inflaton field. Specifically we
argue that the evolution after backreaction can seriously be altered by the
existence of these fluctuations. For example, in one model the coherence of the
inflaton oscillations is found to be completely lost in a very short time after
backreaction starts. Therefore we argue that entering a smooth phase in thermal
equilibrium is questionable in such models and reheating might destroy the
smoothness attained by inflation.
| [
{
"created": "Tue, 20 Dec 2011 06:34:18 GMT",
"version": "v1"
}
] | 2013-06-04 | [
[
"Kaya",
"Ali",
""
]
] | We derive an uncertainty relation for the energy density and pressure of a quantum scalar field in a time-dependent, homogeneous and isotropic, classical background, which implies the existence of large fluctuations comparable to their vacuum expectation values. A similar uncertainty relation is known to hold for the field square since the field can be viewed as a Gaussian random variable. We discuss possible implications of these results for the reheating process in scalar field driven inflationary models, where reheating is achieved by the decay of the coherently oscillating inflaton field. Specifically we argue that the evolution after backreaction can seriously be altered by the existence of these fluctuations. For example, in one model the coherence of the inflaton oscillations is found to be completely lost in a very short time after backreaction starts. Therefore we argue that entering a smooth phase in thermal equilibrium is questionable in such models and reheating might destroy the smoothness attained by inflation. |
1505.07628 | Jose Luis Bl\'azquez-Salcedo | Jose Luis Blazquez-Salcedo | Extremal rotating black holes in Einstein-Maxwell-Chern-Simons theory:
radially excited solutions and non-uniqueness | Accepted for publication in IJMPD, in a special volume dedicated to
the VII Black Holes Workshop, Aveiro, Portugal, 18-19 December 2014 | Int. J. Mod. Phys. D, 24, 1542016 (2015) | 10.1142/S021827181542016X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study 5-dimensional black holes in Einstein-Maxwell-Chern-Simons theory
with free Chern-Simons coupling parameter. We consider an event horizon with
spherical topology, and both angular momenta of equal magnitude. In particular,
we study extremal black holes, which can be used to obtain the boundary of the
domain of existence. Above a critical value of the Chern-Simons coupling
constant we find non-static extremal solutions with vanishing angular momentum.
These solutions form a sequence which can be labeled by the node number of the
magnetic $U(1)$ potential or the inertial dragging. As the node number
increases, their mass converges to the mass of the extremal
Reissner-Nordstr\"om solution. The near-horizon geometry of the solutions of
this sequence is the same. In general not all near-horizon solutions are found
as global solutions, and we show non-uniqueness between extremal solutions and
non-extremal ones.
| [
{
"created": "Thu, 28 May 2015 10:20:15 GMT",
"version": "v1"
}
] | 2017-09-11 | [
[
"Blazquez-Salcedo",
"Jose Luis",
""
]
] | We study 5-dimensional black holes in Einstein-Maxwell-Chern-Simons theory with free Chern-Simons coupling parameter. We consider an event horizon with spherical topology, and both angular momenta of equal magnitude. In particular, we study extremal black holes, which can be used to obtain the boundary of the domain of existence. Above a critical value of the Chern-Simons coupling constant we find non-static extremal solutions with vanishing angular momentum. These solutions form a sequence which can be labeled by the node number of the magnetic $U(1)$ potential or the inertial dragging. As the node number increases, their mass converges to the mass of the extremal Reissner-Nordstr\"om solution. The near-horizon geometry of the solutions of this sequence is the same. In general not all near-horizon solutions are found as global solutions, and we show non-uniqueness between extremal solutions and non-extremal ones. |
2106.04454 | Abhik Kumar Sanyal Dr. | A. Banerjee, Abhik Kumar Sanyal and S. Chakraborty | String cosmology in Bianchi I space-time | 9 pages, 0 figures | Pramana- J. Phys., Vol. 34, No. 1, January 1990, pp. 1-11 | 10.1007/BF02846104 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some cosmological solutions of massive strings are obtained in Bianchi I
space-time following the techniques used by Letelier and Stachel. A class of
solutions corresponds to string cosmology associated with/without a magnetic
field and the other class consists of pure massive strings, obeying the
Takabayashi equation of state.
| [
{
"created": "Tue, 8 Jun 2021 15:38:30 GMT",
"version": "v1"
}
] | 2021-06-16 | [
[
"Banerjee",
"A.",
""
],
[
"Sanyal",
"Abhik Kumar",
""
],
[
"Chakraborty",
"S.",
""
]
] | Some cosmological solutions of massive strings are obtained in Bianchi I space-time following the techniques used by Letelier and Stachel. A class of solutions corresponds to string cosmology associated with/without a magnetic field and the other class consists of pure massive strings, obeying the Takabayashi equation of state. |
1311.3279 | Simone Speziale | Simone Speziale and Mingyi Zhang | Null twisted geometries | 22 pages, 3 figures. v2: minor corrections, improved presentation in
section 4, references updated | Phys. Rev. D 89, 084070 (2014) | 10.1103/PhysRevD.89.084070 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We define and investigate a quantisation of null hypersurfaces in the context
of loop quantum gravity on a fixed graph. The main tool we use is the
parametrisation of the theory in terms of twistors, which has already proved
useful in discussing the interpretation of spin networks as the quantization of
twisted geometries. The classical formalism can be extended in a natural way to
null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra
with space-like faces, and SU(2) by the little group ISO(2). The main
difference is that the simplicity constraints present in the formalims are all
first class, and the symplectic reduction selects only the helicity subgroup of
the little group. As a consequence, information on the shapes of the polyhedra
is lost, and the result is a much simpler, abelian geometric picture. It can be
described by an Euclidean singular structure on the 2-dimensional space-like
surface defined by a foliation of space-time by null hypersurfaces. This
geometric structure is naturally decomposed into a conformal metric and scale
factors, forming locally conjugate pairs. Proper action-angle variables on the
gauge-invariant phase space are described by the eigenvectors of the Laplacian
of the dual graph. We also identify the variables of the phase space amenable
to characterize the extrinsic geometry of the foliation. Finally, we quantise
the phase space and its algebra using Dirac's algorithm, obtaining a notion of
spin networks for null hypersurfaces. Such spin networks are labelled by SO(2)
quantum numbers, and are embedded non-trivially in the unitary,
infinite-dimensional irreducible representations of the Lorentz group.
| [
{
"created": "Wed, 13 Nov 2013 20:19:36 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Apr 2014 08:34:08 GMT",
"version": "v2"
}
] | 2014-04-30 | [
[
"Speziale",
"Simone",
""
],
[
"Zhang",
"Mingyi",
""
]
] | We define and investigate a quantisation of null hypersurfaces in the context of loop quantum gravity on a fixed graph. The main tool we use is the parametrisation of the theory in terms of twistors, which has already proved useful in discussing the interpretation of spin networks as the quantization of twisted geometries. The classical formalism can be extended in a natural way to null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra with space-like faces, and SU(2) by the little group ISO(2). The main difference is that the simplicity constraints present in the formalims are all first class, and the symplectic reduction selects only the helicity subgroup of the little group. As a consequence, information on the shapes of the polyhedra is lost, and the result is a much simpler, abelian geometric picture. It can be described by an Euclidean singular structure on the 2-dimensional space-like surface defined by a foliation of space-time by null hypersurfaces. This geometric structure is naturally decomposed into a conformal metric and scale factors, forming locally conjugate pairs. Proper action-angle variables on the gauge-invariant phase space are described by the eigenvectors of the Laplacian of the dual graph. We also identify the variables of the phase space amenable to characterize the extrinsic geometry of the foliation. Finally, we quantise the phase space and its algebra using Dirac's algorithm, obtaining a notion of spin networks for null hypersurfaces. Such spin networks are labelled by SO(2) quantum numbers, and are embedded non-trivially in the unitary, infinite-dimensional irreducible representations of the Lorentz group. |
gr-qc/9310033 | null | Dieter R. Brill | Comments on Dragging Effects | 4 pages, TEX, UMD 94-51 | null | null | null | gr-qc | null | This is a reply, given at the conference ``Mach's Principle" in T\"ubingen in
July 1993, to the paper by Pfister (1993). Unfortunately the Pfister paper
itself was not sent to gr-qc.
| [
{
"created": "Mon, 25 Oct 1993 21:30:43 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Brill",
"Dieter R.",
""
]
] | This is a reply, given at the conference ``Mach's Principle" in T\"ubingen in July 1993, to the paper by Pfister (1993). Unfortunately the Pfister paper itself was not sent to gr-qc. |
gr-qc/9601025 | Max welling | M. Welling and M. Bijlsma | Pauli-Lubanski scalar in the Polygon Approach to 2+1-Dimensional Gravity | Some errors are corrected and a new introduction and discussion are
added. 6 pages Latex, 4 eps-figures | Class.Quant.Grav. 13 (1996) 1769-1774 | 10.1088/0264-9381/13/7/010 | THU-96/03 | gr-qc | null | In this paper we derive an expression for the conserved Pauli-Lubanski scalar
in 't Hooft's polygon approach to 2+1-dimensional gravity coupled to point
particles. We find that it is represented by an extra spatial shift $\Delta$ in
addition to the usual identification rule (being a rotation over the cut). For
two particles this invariant is expressed in terms of 't Hooft's phase-space
variables and we check its classical limit.
| [
{
"created": "Wed, 17 Jan 1996 14:34:37 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jun 1996 16:08:40 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Welling",
"M.",
""
],
[
"Bijlsma",
"M.",
""
]
] | In this paper we derive an expression for the conserved Pauli-Lubanski scalar in 't Hooft's polygon approach to 2+1-dimensional gravity coupled to point particles. We find that it is represented by an extra spatial shift $\Delta$ in addition to the usual identification rule (being a rotation over the cut). For two particles this invariant is expressed in terms of 't Hooft's phase-space variables and we check its classical limit. |
1802.09577 | Zbigniew Haba | Z. Haba | Stochastic inflation with quantum and thermal noise | 8 pages | Eur.Phys.J. C(2018)78:596 | 10.1140/epjc/s10052-018-6078-4 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We add a thermal noise to Starobinsky equation of slow roll inflation. We
calculate the number of e-folds of the stochastic system. The power spectrum
and the spectral index are evaluated from the fluctuations of e-folds using an
expansion in the quantum and thermal noise terms.
| [
{
"created": "Mon, 26 Feb 2018 20:03:38 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Jul 2018 19:03:57 GMT",
"version": "v2"
}
] | 2018-08-01 | [
[
"Haba",
"Z.",
""
]
] | We add a thermal noise to Starobinsky equation of slow roll inflation. We calculate the number of e-folds of the stochastic system. The power spectrum and the spectral index are evaluated from the fluctuations of e-folds using an expansion in the quantum and thermal noise terms. |
gr-qc/0601073 | Gordon McCabe | Gordon McCabe | Possible physical universes | null | null | null | null | gr-qc | null | The purpose of this paper is to discuss the various types of physical
universe which could exist according to modern mathematical physics. The paper
begins with an introduction that approaches the question from the viewpoint of
ontic structural realism. Section 2 takes the case of the 'multiverse' of
spatially homogeneous universes, and analyses the famous Collins-Hawking
argument, which purports to show that our own universe is a very special member
of this collection. Section 3 considers the multiverse of all solutions to the
Einstein field equations, and continues the discussion of whether the notions
of special and typical can be defined within such a collection.
| [
{
"created": "Wed, 18 Jan 2006 12:27:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"McCabe",
"Gordon",
""
]
] | The purpose of this paper is to discuss the various types of physical universe which could exist according to modern mathematical physics. The paper begins with an introduction that approaches the question from the viewpoint of ontic structural realism. Section 2 takes the case of the 'multiverse' of spatially homogeneous universes, and analyses the famous Collins-Hawking argument, which purports to show that our own universe is a very special member of this collection. Section 3 considers the multiverse of all solutions to the Einstein field equations, and continues the discussion of whether the notions of special and typical can be defined within such a collection. |
2212.01149 | Stav Zalel | Fay Dowker and Stav Zalel | Observables for cyclic causal set cosmologies | 11 pages, 7 figures | Class.Quant.Grav. 40 (2023) 15, 155015 | 10.1088/1361-6382/ace149 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In causal set theory, cycles of cosmic expansion and collapse are modelled by
causal sets with "breaks" and "posts" and a special role is played by cyclic
dynamics in which the universe goes through perpetual cycles. We identify and
characterise two algebras of observables for cyclic dynamics in which the
causal set universe has infinitely many breaks. The first algebra is
constructed from the cylinder sets associated with finite causal sets that have
a single maximal element and offers a new framework for defining cyclic
dynamics as random walks on a novel tree. The second algebra is generated by a
collection of stem-sets and offers a physical interpretation of the observables
in these models as statements about unlabeled stems with a single maximal
element. There are analogous theorems for cyclic dynamics in which the causal
set universe has infinitely many posts.
| [
{
"created": "Fri, 2 Dec 2022 12:56:52 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jul 2023 15:58:08 GMT",
"version": "v2"
}
] | 2023-07-18 | [
[
"Dowker",
"Fay",
""
],
[
"Zalel",
"Stav",
""
]
] | In causal set theory, cycles of cosmic expansion and collapse are modelled by causal sets with "breaks" and "posts" and a special role is played by cyclic dynamics in which the universe goes through perpetual cycles. We identify and characterise two algebras of observables for cyclic dynamics in which the causal set universe has infinitely many breaks. The first algebra is constructed from the cylinder sets associated with finite causal sets that have a single maximal element and offers a new framework for defining cyclic dynamics as random walks on a novel tree. The second algebra is generated by a collection of stem-sets and offers a physical interpretation of the observables in these models as statements about unlabeled stems with a single maximal element. There are analogous theorems for cyclic dynamics in which the causal set universe has infinitely many posts. |
1509.06552 | Alexey Golovnev | Alexey Golovnev, Tomi Koivisto, Marit Sandstad | Effectively nonlocal metric-affine gravity | 12 pages; minor changes; published version | Phys. Rev. D 93, 064081 (2016) | 10.1103/PhysRevD.93.064081 | NORDITA-2015-116 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In metric-affine theories of gravity such as the C-theories, the spacetime
connection is associated to a metric that is nontrivially related to the
physical metric. In this article, such theories are rewritten in terms of a
single metric and it is shown that they can be recast as effectively nonlocal
gravity. With some assumptions, known ghost-free theories with non-singular and
cosmologically interesting properties may be recovered. Relations between
different formulations are analysed at both perturbative and nonperturbative
levels taking carefully into account subtleties with boundary conditions in the
presence of integral operators in the action, and equivalences between theories
related by nonlocal redefinitions of the fields are verified at the level of
equations of motion. This suggests a possible geometrical interpretation of
nonlocal gravity as an emergent property of non-Riemannian spacetime structure.
| [
{
"created": "Tue, 22 Sep 2015 11:35:49 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2016 16:32:17 GMT",
"version": "v2"
}
] | 2016-04-06 | [
[
"Golovnev",
"Alexey",
""
],
[
"Koivisto",
"Tomi",
""
],
[
"Sandstad",
"Marit",
""
]
] | In metric-affine theories of gravity such as the C-theories, the spacetime connection is associated to a metric that is nontrivially related to the physical metric. In this article, such theories are rewritten in terms of a single metric and it is shown that they can be recast as effectively nonlocal gravity. With some assumptions, known ghost-free theories with non-singular and cosmologically interesting properties may be recovered. Relations between different formulations are analysed at both perturbative and nonperturbative levels taking carefully into account subtleties with boundary conditions in the presence of integral operators in the action, and equivalences between theories related by nonlocal redefinitions of the fields are verified at the level of equations of motion. This suggests a possible geometrical interpretation of nonlocal gravity as an emergent property of non-Riemannian spacetime structure. |
2307.07467 | Claudio Iuliano | Claudio Iuliano, Jochen Zahn | Canonical Quantization of Teukolsky fields on Kerr Background | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Electromagnetic and gravitational perturbations on Kerr spacetime can be
reconstructed from solutions to the Teukolsky equations. We study the canonical
quantization of solutions to these equations for any integer spin. Our
quantization scheme involves the analysis of the Hertz potential and one of the
Newman-Penrose scalars, which must be related via the Teukolsky-Starobinsky
identities. We show that the canonical commutation relations between the fields
can be implemented if and only if the Teukolsky-Starobinsky constants are
positive, which is the case both for gravitational perturbations and Maxwell
fields. We also obtain the Hadamard parametrix of the Teukolsky equation, which
is the basic ingredient for a local and covariant renormalization scheme for
non-linear observables. We also discuss the relation of the canonical energy of
Teukolsky fields to that of gravitational perturbations.
| [
{
"created": "Fri, 14 Jul 2023 16:48:39 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Nov 2023 09:39:29 GMT",
"version": "v2"
}
] | 2023-11-15 | [
[
"Iuliano",
"Claudio",
""
],
[
"Zahn",
"Jochen",
""
]
] | Electromagnetic and gravitational perturbations on Kerr spacetime can be reconstructed from solutions to the Teukolsky equations. We study the canonical quantization of solutions to these equations for any integer spin. Our quantization scheme involves the analysis of the Hertz potential and one of the Newman-Penrose scalars, which must be related via the Teukolsky-Starobinsky identities. We show that the canonical commutation relations between the fields can be implemented if and only if the Teukolsky-Starobinsky constants are positive, which is the case both for gravitational perturbations and Maxwell fields. We also obtain the Hadamard parametrix of the Teukolsky equation, which is the basic ingredient for a local and covariant renormalization scheme for non-linear observables. We also discuss the relation of the canonical energy of Teukolsky fields to that of gravitational perturbations. |
gr-qc/0002063 | Ruth A. W. Gregory | Filipe Bonjour, Christos Charmousis and Ruth Gregory | The dynamics of curved gravitating walls | 19 pages revtex, 3 figures, references added, equations corrected | Phys.Rev. D62 (2000) 083504 | 10.1103/PhysRevD.62.083504 | DTP/99/57 | gr-qc hep-ph hep-th | null | We examine the dynamics of a self-gravitating domain wall using the $\lambda
\Phi^4$ model as a specific example. We find that the Nambu motion of the wall
is quite generic and dominates the wall motion even in the presence of gravity.
We calculate the corrections to this leading order motion, and estimate the
effect of the inclusion of gravity on the dynamics of the wall. We then treat
the case of a spherical gravitating thick wall as a particular example, solving
the field equations and calculating the corrections to the Nambu motion
analytically for this specific case. We find that the presence of gravity
retards collapse in this case.
| [
{
"created": "Thu, 17 Feb 2000 18:10:27 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 2000 15:17:04 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Bonjour",
"Filipe",
""
],
[
"Charmousis",
"Christos",
""
],
[
"Gregory",
"Ruth",
""
]
] | We examine the dynamics of a self-gravitating domain wall using the $\lambda \Phi^4$ model as a specific example. We find that the Nambu motion of the wall is quite generic and dominates the wall motion even in the presence of gravity. We calculate the corrections to this leading order motion, and estimate the effect of the inclusion of gravity on the dynamics of the wall. We then treat the case of a spherical gravitating thick wall as a particular example, solving the field equations and calculating the corrections to the Nambu motion analytically for this specific case. We find that the presence of gravity retards collapse in this case. |
1112.5105 | Vincenzo Pierro | Rocco P. Croce, Vincenzo Pierro, Fabio Postiglione, Maria Principe and
Innocenzo M. Pinto | Robust Gravitational Wave Burst Detection and Source Localization in a
Network of Interferometers Using Cross Wigner Spectra | accepted in Class. Quantum Gravity | null | 10.1088/0264-9381/29/4/045001 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a fast cross-Wigner transform based technique for detecting
gravitational wave bursts, and estimating the direction of arrival, using a
network of (three) non co-located interferometric detectors. The performances
of the detector as a function of signal strength and source location, and the
accuracy of the direction of arrival estimation are investigated by numerical
simulations.
| [
{
"created": "Wed, 21 Dec 2011 17:32:07 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Croce",
"Rocco P.",
""
],
[
"Pierro",
"Vincenzo",
""
],
[
"Postiglione",
"Fabio",
""
],
[
"Principe",
"Maria",
""
],
[
"Pinto",
"Innocenzo M.",
""
]
] | We discuss a fast cross-Wigner transform based technique for detecting gravitational wave bursts, and estimating the direction of arrival, using a network of (three) non co-located interferometric detectors. The performances of the detector as a function of signal strength and source location, and the accuracy of the direction of arrival estimation are investigated by numerical simulations. |
gr-qc/0304034 | Chun-Hsien Wu | Chun-Hsien Wu and Da-Shin Lee | Fluctuations of Quantum Radiation Pressure in Dissipative Fluid | 8 pages. Version published in Physics Letters A | Phys.Lett. A318 (2003) 303-312 | 10.1016/j.physleta.2003.09.039 | null | gr-qc hep-ph hep-th | null | Using the generalized Langevin equations involving the stress tensor
approach, we study the dynamics of a perfectly reflecting mirror which is
exposed to the electromagnetic radiation pressure by a laser beam in a fluid at
finite temperature. Based on the fluctuation-dissipation theorem, the minimum
uncertainty of the mirror's position measurement from both quantum and thermal
noises effects including the photon counting error in the laser interferometer
is obtained in the small time limit as compared with the "standard quantum
limit".
The result of the large time behavior of fluctuations of the mirror's
velocity in a dissipative environment can be applied to the laser
interferometer of the ground-based gravitational wave detector.
| [
{
"created": "Tue, 8 Apr 2003 07:58:07 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Nov 2003 04:33:57 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Wu",
"Chun-Hsien",
""
],
[
"Lee",
"Da-Shin",
""
]
] | Using the generalized Langevin equations involving the stress tensor approach, we study the dynamics of a perfectly reflecting mirror which is exposed to the electromagnetic radiation pressure by a laser beam in a fluid at finite temperature. Based on the fluctuation-dissipation theorem, the minimum uncertainty of the mirror's position measurement from both quantum and thermal noises effects including the photon counting error in the laser interferometer is obtained in the small time limit as compared with the "standard quantum limit". The result of the large time behavior of fluctuations of the mirror's velocity in a dissipative environment can be applied to the laser interferometer of the ground-based gravitational wave detector. |
1910.00070 | Yohan Potaux | Piotr T. Chru\'sciel, Gregory J. Galloway, Yohan Potaux | Uniqueness and energy bounds for static AdS metrics | null | Phys. Rev. D 101, 064034 (2020) | 10.1103/PhysRevD.101.064034 | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that Wang's proof of uniqueness of Anti-de Sitter spacetime can be
adapted to provide uniqueness results for strictly static asymptotically
locally hyperbolic vacuum metrics with toroidal infinity, and to prove
negativity of the free energy $E-TS$ of asymptotically AdS black holes with
higher-genus horizons.
| [
{
"created": "Mon, 30 Sep 2019 19:48:07 GMT",
"version": "v1"
}
] | 2020-03-25 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Galloway",
"Gregory J.",
""
],
[
"Potaux",
"Yohan",
""
]
] | We show that Wang's proof of uniqueness of Anti-de Sitter spacetime can be adapted to provide uniqueness results for strictly static asymptotically locally hyperbolic vacuum metrics with toroidal infinity, and to prove negativity of the free energy $E-TS$ of asymptotically AdS black holes with higher-genus horizons. |
2202.00688 | Shahar Hod | Shahar Hod | No-short scalar hair theorem for spinning acoustic black holes in a
photon-fluid model | 8 pages | Physical Review D 104, 104041 (2021) | 10.1103/PhysRevD.104.104041 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | It has recently been revealed that spinning black holes of the photon-fluid
model can support acoustic `clouds', stationary density fluctuations whose
spatially regular radial eigenfunctions are determined by the
$(2+1)$-dimensional Klein-Gordon equation of an effective massive scalar field.
Motivated by this intriguing observation, we use {\it analytical} techniques in
order to prove a no-short hair theorem for the composed
acoustic-black-hole-scalar-clouds configurations. In particular, it is proved
that the effective lengths of the stationary bound-state co-rotating acoustic
scalar clouds are bounded from below by the series of inequalities
$r_{\text{hair}}>{{1+\sqrt{5}}\over{2}}\cdot r_{\text{H}}>r_{\text{null}}$,
where $r_{\text{H}}$ and $r_{\text{null}}$ are respectively the horizon radius
of the supporting black hole and the radius of the co-rotating null circular
geodesic that characterizes the acoustic spinning black-hole spacetime.
| [
{
"created": "Tue, 1 Feb 2022 19:00:01 GMT",
"version": "v1"
}
] | 2022-02-09 | [
[
"Hod",
"Shahar",
""
]
] | It has recently been revealed that spinning black holes of the photon-fluid model can support acoustic `clouds', stationary density fluctuations whose spatially regular radial eigenfunctions are determined by the $(2+1)$-dimensional Klein-Gordon equation of an effective massive scalar field. Motivated by this intriguing observation, we use {\it analytical} techniques in order to prove a no-short hair theorem for the composed acoustic-black-hole-scalar-clouds configurations. In particular, it is proved that the effective lengths of the stationary bound-state co-rotating acoustic scalar clouds are bounded from below by the series of inequalities $r_{\text{hair}}>{{1+\sqrt{5}}\over{2}}\cdot r_{\text{H}}>r_{\text{null}}$, where $r_{\text{H}}$ and $r_{\text{null}}$ are respectively the horizon radius of the supporting black hole and the radius of the co-rotating null circular geodesic that characterizes the acoustic spinning black-hole spacetime. |
gr-qc/9408042 | Wai Suen | Peter Anninos, David Hobill, Edward Seidel, Larry Smarr and Wai-Mo
Suen | The Head-On Collision of Two Equal Mass Black Holes: Numerical Methods | 16 pages, NCSA technical report 94-024, WUGRAV-94-8 | null | null | null | gr-qc | null | The head-on collision of two nonrotating axisymmetric equal mass black holes
is treated numerically. We take as initial data the single parameter family of
time-symmetric solutions discovered by Misner which consists of two
Einstein-Rosen bridges that can be placed arbitrarily distant from one another.
A number of problems associated with previous attempts to evolve these data
sets have been overcome. In this article, we discuss our choices for coordinate
systems, gauges, and the numerical algorithms that we have developed to evolve
this system.
| [
{
"created": "Wed, 31 Aug 1994 23:37:31 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Anninos",
"Peter",
""
],
[
"Hobill",
"David",
""
],
[
"Seidel",
"Edward",
""
],
[
"Smarr",
"Larry",
""
],
[
"Suen",
"Wai-Mo",
""
]
] | The head-on collision of two nonrotating axisymmetric equal mass black holes is treated numerically. We take as initial data the single parameter family of time-symmetric solutions discovered by Misner which consists of two Einstein-Rosen bridges that can be placed arbitrarily distant from one another. A number of problems associated with previous attempts to evolve these data sets have been overcome. In this article, we discuss our choices for coordinate systems, gauges, and the numerical algorithms that we have developed to evolve this system. |
2206.13009 | Hai-Chao Zhang | Hai-Chao Zhang, Xin-Ping Xu, Jing-Fang Zhang, Chuan Wang | Could trapped quintessence account for the laser-detuning-dependent
acceleration of cold atoms in varying-frequency time-of-flight experiments? | 25 pages,10 figures | Physical Review D 105, 102006 (2022) | 10.1103/PhysRevD.105.102006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a trapped quintessence model, a series of time-of-flight (TOF)
experiments with a different frequency of probe light were designed and
performed. The varying-frequency TOF (VFTOF) experiments demonstrated that the
fall acceleration of test atoms is dependent on the detuning of the probe light
frequency with respect to the atomic transition frequency. In appropriately
designed experiments, if the scalar field in the model accounts for the
accelerated expansion of the Universe entirely, the field will result in an
observable fifth force. Meanwhile, the trapped quintessence model still
satisfies all experimental bounds on deviations from general relativity due to
both the saturation effect and the short interaction range of the scalar field.
The scalar saturates at a value corresponding to the cosmological constant when
the microscopic nonrelativistic matter density is large enough. The interaction
range of the scalar is inversely proportional to the square root of the
microscopic nonrelativistic matter density. The interaction range has been
estimated to be several $\mu \rm{m}$ in the current cosmic density. The
Universe is assumed to be permeated with fuzzy dark matter, which means that
the microscopic nonrelativistic matter density defined through the quantum
wavefunctions of the ultralight particles can be used on the cosmic scale.
By measuring the fall acceleration of the test atoms with the TOF method
step-by-step in the detuning frequency domain of the probe light, we derived
the dispersion curves of the measured acceleration versus the frequency
detuning of the probe light. When the nonrelativistic matter density of the
source increased due to the energy gained from the laser light, the test atoms
were pulled to the center of the source, and vice versa.
| [
{
"created": "Mon, 27 Jun 2022 01:35:02 GMT",
"version": "v1"
}
] | 2022-06-28 | [
[
"Zhang",
"Hai-Chao",
""
],
[
"Xu",
"Xin-Ping",
""
],
[
"Zhang",
"Jing-Fang",
""
],
[
"Wang",
"Chuan",
""
]
] | Using a trapped quintessence model, a series of time-of-flight (TOF) experiments with a different frequency of probe light were designed and performed. The varying-frequency TOF (VFTOF) experiments demonstrated that the fall acceleration of test atoms is dependent on the detuning of the probe light frequency with respect to the atomic transition frequency. In appropriately designed experiments, if the scalar field in the model accounts for the accelerated expansion of the Universe entirely, the field will result in an observable fifth force. Meanwhile, the trapped quintessence model still satisfies all experimental bounds on deviations from general relativity due to both the saturation effect and the short interaction range of the scalar field. The scalar saturates at a value corresponding to the cosmological constant when the microscopic nonrelativistic matter density is large enough. The interaction range of the scalar is inversely proportional to the square root of the microscopic nonrelativistic matter density. The interaction range has been estimated to be several $\mu \rm{m}$ in the current cosmic density. The Universe is assumed to be permeated with fuzzy dark matter, which means that the microscopic nonrelativistic matter density defined through the quantum wavefunctions of the ultralight particles can be used on the cosmic scale. By measuring the fall acceleration of the test atoms with the TOF method step-by-step in the detuning frequency domain of the probe light, we derived the dispersion curves of the measured acceleration versus the frequency detuning of the probe light. When the nonrelativistic matter density of the source increased due to the energy gained from the laser light, the test atoms were pulled to the center of the source, and vice versa. |
1710.06434 | Francesco Torsello | Francesco Torsello, Mikica Kocic, Marcus H\"og{\aa}s, Edvard Mortsell | Spacetime symmetries and topology in bimetric relativity | 19 pages. It matches with the published version. Comments are
welcome. Attached Mathematica notebook available in the ancillary files and
at https://tinyurl.com/y9r7nuuh | Phys. Rev. D 97, 084022 (2018) | 10.1103/PhysRevD.97.084022 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore spacetime symmetries and topologies of the two metric sectors in
Hassan-Rosen bimetric theory. We show that, in vacuum, the two sectors can
either share or have separate spacetime symmetries. If stress-energy tensors
are present, a third case can arise, with different spacetime symmetries within
the same sector. This raises the question of the best definition of spacetime
symmetry in Hassan-Rosen bimetric theory. We emphasize the possibility of
imposing ans\"atze and looking for solutions having different Killing vector
fields or different isometries in the two sectors, which has gained little
attention so far. We also point out that the topology of spacetime imposes a
constraint on possible metric combinations.
| [
{
"created": "Tue, 17 Oct 2017 18:00:01 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Apr 2018 06:55:01 GMT",
"version": "v2"
}
] | 2018-04-20 | [
[
"Torsello",
"Francesco",
""
],
[
"Kocic",
"Mikica",
""
],
[
"Högås",
"Marcus",
""
],
[
"Mortsell",
"Edvard",
""
]
] | We explore spacetime symmetries and topologies of the two metric sectors in Hassan-Rosen bimetric theory. We show that, in vacuum, the two sectors can either share or have separate spacetime symmetries. If stress-energy tensors are present, a third case can arise, with different spacetime symmetries within the same sector. This raises the question of the best definition of spacetime symmetry in Hassan-Rosen bimetric theory. We emphasize the possibility of imposing ans\"atze and looking for solutions having different Killing vector fields or different isometries in the two sectors, which has gained little attention so far. We also point out that the topology of spacetime imposes a constraint on possible metric combinations. |
2106.10184 | Urs Wiedemann A | Stefan Floerchinger, Nikolaos Tetradis and Urs Achim Wiedemann | Backreaction from inhomogeneous matter fields during large-scale
structure formation | 11 pages, 3 figures | Phys. Rev. D 104, 083522 (2021) | 10.1103/PhysRevD.104.083522 | CERN-TH-2021-095 | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We study how inhomogeneities of the cosmological fluid fields backreact on
the homogeneous part of energy density and how they modify the Friedmann
equations. In general, backreaction requires to go beyond the pressureless
ideal fluid approximation, and this can lead to a reduced growth of
cosmological large scale structure. Since observational evidence favours
evolution close to the standard growing mode in the linear regime, we focus on
two-component fluids in which the non-ideal fluid is gravitationally coupled to
cold dark matter and in which a standard growing mode persists. This is
realized, e.g. for a baryonic fluid coupled to cold dark matter. We calculate
the backreaction for this case and for a wide range of other two-fluid models.
Here the effect is either suppressed because the non-ideal matter properties
are numerically too small, or because they lead to a too stringent UV cut-off
of the integral over the power spectrum that determines backreaction. We
discuss then matter field backreaction from a broader perspective and
generalize the formalism such that also far-from-equilibrium scenarios relevant
to late cosmological times and non-linear scales can be addressed in the
future.
| [
{
"created": "Fri, 18 Jun 2021 15:21:06 GMT",
"version": "v1"
}
] | 2021-10-13 | [
[
"Floerchinger",
"Stefan",
""
],
[
"Tetradis",
"Nikolaos",
""
],
[
"Wiedemann",
"Urs Achim",
""
]
] | We study how inhomogeneities of the cosmological fluid fields backreact on the homogeneous part of energy density and how they modify the Friedmann equations. In general, backreaction requires to go beyond the pressureless ideal fluid approximation, and this can lead to a reduced growth of cosmological large scale structure. Since observational evidence favours evolution close to the standard growing mode in the linear regime, we focus on two-component fluids in which the non-ideal fluid is gravitationally coupled to cold dark matter and in which a standard growing mode persists. This is realized, e.g. for a baryonic fluid coupled to cold dark matter. We calculate the backreaction for this case and for a wide range of other two-fluid models. Here the effect is either suppressed because the non-ideal matter properties are numerically too small, or because they lead to a too stringent UV cut-off of the integral over the power spectrum that determines backreaction. We discuss then matter field backreaction from a broader perspective and generalize the formalism such that also far-from-equilibrium scenarios relevant to late cosmological times and non-linear scales can be addressed in the future. |
1201.4249 | Jan-Hendrik Treude | Jan-Hendrik Treude, James D.E. Grant | Volume Comparison for Hypersurfaces in Lorentzian Manifolds and
Singularity Theorems | 15 pages, LaTeX | Annals of Global Analysis and Geometry, Volume 43, Issue 3,
233-251, Springer (2013) | 10.1007/s10455-012-9343-z | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop area and volume comparison theorems for the evolution of
spacelike, acausal, causally complete hypersurfaces in Lorentzian manifolds,
where one has a lower bound on the Ricci tensor along timelike curves, and an
upper bound on the mean curvature of the hypersurface. Using these results, we
give a new proof of Hawking's singularity theorem.
| [
{
"created": "Fri, 20 Jan 2012 10:22:14 GMT",
"version": "v1"
}
] | 2013-03-19 | [
[
"Treude",
"Jan-Hendrik",
""
],
[
"Grant",
"James D. E.",
""
]
] | We develop area and volume comparison theorems for the evolution of spacelike, acausal, causally complete hypersurfaces in Lorentzian manifolds, where one has a lower bound on the Ricci tensor along timelike curves, and an upper bound on the mean curvature of the hypersurface. Using these results, we give a new proof of Hawking's singularity theorem. |
0809.4228 | Ignazio Bombaci | I. Bombaci | Quark matter in compact stars: astrophysical implications and possible
signatures | Invited talk at "the Eleventh Marcel Grossman Meeting on General
Relativity", Berlin 2006 | null | 10.1142/9789812834300_0025 | null | gr-qc astro-ph nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After a brief non technical introduction of the basic properties of strange
quark matter (SQM) in compact stars, we consider some of the late important
advances in the field, and discuss some recent astrophysical observational data
that could shed new light on the possible presence of SQM in compact stars. We
show that above a threshold value of the gravitational mass a neutron star
(pure hadronic star) is metastable to the decay (conversion) to an hybrid
neutron star or to a strange star. We explore the consequences of the
metastability of "massive" neutron stars and of the existence of stable compact
"quark" stars (hybrid neutron stars or strange stars) on the concept of
limiting mass of compact stars, and we give an extension of this concept with
respect to the "classical" one given in 1939 by Oppenheimer and Volkoff.
| [
{
"created": "Wed, 24 Sep 2008 16:30:46 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Bombaci",
"I.",
""
]
] | After a brief non technical introduction of the basic properties of strange quark matter (SQM) in compact stars, we consider some of the late important advances in the field, and discuss some recent astrophysical observational data that could shed new light on the possible presence of SQM in compact stars. We show that above a threshold value of the gravitational mass a neutron star (pure hadronic star) is metastable to the decay (conversion) to an hybrid neutron star or to a strange star. We explore the consequences of the metastability of "massive" neutron stars and of the existence of stable compact "quark" stars (hybrid neutron stars or strange stars) on the concept of limiting mass of compact stars, and we give an extension of this concept with respect to the "classical" one given in 1939 by Oppenheimer and Volkoff. |
2401.14061 | Pradip Kumar Chattopadhyay Dr. | Debadri Bhattacharjee and Pradip Kumar Chattopadhyay | Charged gravastar model in Rastall theory of gravity | 21 pages, 5 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Gravastars are considered as one of the prime exotic type compact objects
which may be found at the end state of gravitational collapse of massive stars
with a view to resolve the complexities that are pertinent in case of a black
hole \cite{Mazur}-\cite{Mazur2}. In this paper, we analyse the role of charge
on the possible formation of isotropic spherically symmetric gravastar
configuration in the framework of Rastall gravity. Gravastar contains three
distinct layers {\it viz.} i) Interior region, ii) Thin shell and iii) Exterior
region. The interior region is characterised by the equation of state $p=-\rho$
that defines the repulsive outward pressure in radial direction at all points
on the thin shell. The thin shell, contains ultra-relativistic stiff fluid
which is denoted by the equation of state $p=\rho$ following Zel'dovich's
criteria \cite{Zeldovich,Zeldovich1} for cold baryonic universe, can withstand
the repulsive pressure exerted by the interior region. The exterior region is
the vacuum space-time represented by the Reissner-Nordstr$\ddot{o}$m solution.
In view of the above specifications, we construct and analyse a charged
gravastar model in Rastall theory of gravity which represents several salient
features. The basic physical attributes, {\it viz.} proper length, energy,
entropy and equation of state parameter of the shell are investigated. In this
model, it is interesting to note that for large value of the radius of
hyper-surface (R) the EoS parameter of the thin shell corresponds to dark
energy EoS with $\mathcal{W}(R)\rightarrow-1$. However, for small value of $R$
the EoS parameter $\mathcal{W}(R)\rightarrow0$, defines a dust shell. The
stability of the model is ensured through the study of gravitational surface
redshift and maximisation of shell entropy within the framework of Rastall
theory of gravity.
| [
{
"created": "Thu, 25 Jan 2024 10:35:38 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Feb 2024 10:26:48 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Feb 2024 12:31:32 GMT",
"version": "v3"
},
{
"created": "Tue, 5 Mar 2024 09:47:24 GMT",
"version": "v4"
}
] | 2024-03-06 | [
[
"Bhattacharjee",
"Debadri",
""
],
[
"Chattopadhyay",
"Pradip Kumar",
""
]
] | Gravastars are considered as one of the prime exotic type compact objects which may be found at the end state of gravitational collapse of massive stars with a view to resolve the complexities that are pertinent in case of a black hole \cite{Mazur}-\cite{Mazur2}. In this paper, we analyse the role of charge on the possible formation of isotropic spherically symmetric gravastar configuration in the framework of Rastall gravity. Gravastar contains three distinct layers {\it viz.} i) Interior region, ii) Thin shell and iii) Exterior region. The interior region is characterised by the equation of state $p=-\rho$ that defines the repulsive outward pressure in radial direction at all points on the thin shell. The thin shell, contains ultra-relativistic stiff fluid which is denoted by the equation of state $p=\rho$ following Zel'dovich's criteria \cite{Zeldovich,Zeldovich1} for cold baryonic universe, can withstand the repulsive pressure exerted by the interior region. The exterior region is the vacuum space-time represented by the Reissner-Nordstr$\ddot{o}$m solution. In view of the above specifications, we construct and analyse a charged gravastar model in Rastall theory of gravity which represents several salient features. The basic physical attributes, {\it viz.} proper length, energy, entropy and equation of state parameter of the shell are investigated. In this model, it is interesting to note that for large value of the radius of hyper-surface (R) the EoS parameter of the thin shell corresponds to dark energy EoS with $\mathcal{W}(R)\rightarrow-1$. However, for small value of $R$ the EoS parameter $\mathcal{W}(R)\rightarrow0$, defines a dust shell. The stability of the model is ensured through the study of gravitational surface redshift and maximisation of shell entropy within the framework of Rastall theory of gravity. |
2005.14054 | Nayan Das | Nayan Das, Sukanta Panda | Inflation and Reheating in f(R,h) theory formulated in the Palatini
formalism | 20 pages, 17 figures | null | 10.1088/1475-7516/2021/05/019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new model for inflation using modified gravity in the Palatini formalism is
constructed. Here non-minimal coupling of scalar field h with the curvature R
as a general function f(R,h) is considered. Explicit inflation models for some
choices of f(R,h) are developed. By writing an equivalent scalar-tensor action
for this model and going over to Einstein frame, slow roll parameters are
constructed. There exists a large parameter space which satisfies values of n_s
and limits on r compatible with Planck 2018 data. Further, we calculate
reheating temperature and the number of e-folds at the end of reheating for
different values of equation of state parameter for all the constructed models.
| [
{
"created": "Thu, 28 May 2020 14:35:24 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2020 11:19:57 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"Das",
"Nayan",
""
],
[
"Panda",
"Sukanta",
""
]
] | A new model for inflation using modified gravity in the Palatini formalism is constructed. Here non-minimal coupling of scalar field h with the curvature R as a general function f(R,h) is considered. Explicit inflation models for some choices of f(R,h) are developed. By writing an equivalent scalar-tensor action for this model and going over to Einstein frame, slow roll parameters are constructed. There exists a large parameter space which satisfies values of n_s and limits on r compatible with Planck 2018 data. Further, we calculate reheating temperature and the number of e-folds at the end of reheating for different values of equation of state parameter for all the constructed models. |
gr-qc/0502097 | David Mattingly | David Mattingly | Modern tests of Lorentz invariance | Modified and expanded discussions of various points. Numerous
references added. Version matches that accepted by Living Reviews in
Relativity | Living Rev.Rel.8:5,2005 | 10.12942/lrr-2005-5 | null | gr-qc astro-ph hep-ph | null | Motivated by ideas about quantum gravity, a tremendous amount of effort over
the past decade has gone into testing Lorentz invariance in various regimes.
This review summarizes both the theoretical frameworks for tests of Lorentz
invariance and experimental advances that have made new high precision tests
possible. The current constraints on Lorentz violating effects from both
terrestrial experiments and astrophysical observations are presented.
| [
{
"created": "Tue, 22 Feb 2005 19:23:05 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jul 2005 20:10:57 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Mattingly",
"David",
""
]
] | Motivated by ideas about quantum gravity, a tremendous amount of effort over the past decade has gone into testing Lorentz invariance in various regimes. This review summarizes both the theoretical frameworks for tests of Lorentz invariance and experimental advances that have made new high precision tests possible. The current constraints on Lorentz violating effects from both terrestrial experiments and astrophysical observations are presented. |
gr-qc/9710136 | Arkadiusz Blaut | A.Blaut & J. Kowalski-Glikman | The Time Evolution of Quantum Universe in The Quantum Potential Picture | 9 pages, LaTeX | Phys.Lett. A245 (1998) 197-202 | 10.1016/S0375-9601(98)00410-1 | null | gr-qc | null | We use the quantum potential approach to analyse the quantum cosmological
model of the universe. The quantum potential arises from exact solutions of the
full Wheeler-De Witt equation.
| [
{
"created": "Fri, 31 Oct 1997 13:24:23 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Blaut",
"A.",
""
],
[
"Kowalski-Glikman",
"J.",
""
]
] | We use the quantum potential approach to analyse the quantum cosmological model of the universe. The quantum potential arises from exact solutions of the full Wheeler-De Witt equation. |
1401.1056 | Sven Zschocke | Sven Zschocke | A detailed proof of the fundamental theorem of STF multipole expansion
in linearized gravity | 28 pages, 1 figure | International Journal of Modern Physics D 23 (2014), 1450003 | 10.1142/S0218271814500035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The linearized field equations of general relativity in harmonic coordinates
are given by an inhomogeneous wave equation. In the region exterior to the
matter field, the retarded solution of this wave equation can be expanded in
terms of 10 Cartesian symmetric and tracefree (STF) multipoles in
post-Minkowskian approximation. For such a multipole decomposition only three
and rather weak assumptions are required:
1. No-incoming radiation condition.
2. The matter source is spatially compact.
3. A spherical expansion for the metric outside the matter source is
possible.
During the last decades, the STF multipole expansion has been established as
a powerful tool in several fields of gravitational physics: celestial
mechanics, theory of gravitational waves and in the theory of light propagation
and astrometry. But despite its formidable importance, an explicit proof of the
fundamental theorem of STF multipole expansion has not been presented thus far,
while only some parts of it are distributed into several publications. In a
technical but more didactical form, an explicit and detailed mathematical proof
of each individual step of this important theorem of STF multipole expansion is
represented.
| [
{
"created": "Mon, 6 Jan 2014 12:23:20 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Zschocke",
"Sven",
""
]
] | The linearized field equations of general relativity in harmonic coordinates are given by an inhomogeneous wave equation. In the region exterior to the matter field, the retarded solution of this wave equation can be expanded in terms of 10 Cartesian symmetric and tracefree (STF) multipoles in post-Minkowskian approximation. For such a multipole decomposition only three and rather weak assumptions are required: 1. No-incoming radiation condition. 2. The matter source is spatially compact. 3. A spherical expansion for the metric outside the matter source is possible. During the last decades, the STF multipole expansion has been established as a powerful tool in several fields of gravitational physics: celestial mechanics, theory of gravitational waves and in the theory of light propagation and astrometry. But despite its formidable importance, an explicit proof of the fundamental theorem of STF multipole expansion has not been presented thus far, while only some parts of it are distributed into several publications. In a technical but more didactical form, an explicit and detailed mathematical proof of each individual step of this important theorem of STF multipole expansion is represented. |
gr-qc/9505028 | Karen Brewster | Lee Smolin | Linking Topological Quantum Field Theory and Nonperturbative Quantum
Gravity | TEX File, Minor Changes Made, 59 pages | J.Math.Phys.36:6417-6455,1995 | 10.1063/1.531251 | CGPG-95/4-5, IASSNS-95/29 | gr-qc hep-th | null | Quantum gravity is studied nonperturbatively in the case in which space has a
boundary with finite area. A natural set of boundary conditions is studied in
the Euclidean signature theory, in which the pullback of the curvature to the
boundary is self-dual (with a cosmological constant). A Hilbert space which
describes all the information accessible by measuring the metric and connection
induced in the boundary is constructed and is found to be the direct sum of the
state spaces of all $SU(2)$ Chern-Simon theories defined by all choices of
punctures and representations on the spatial boundary $\cal S$. The integer
level $k$ of Chern-Simons theory is found to be given by $k= 6\pi /G^2 \Lambda
+ \alpha$, where $\Lambda$ is the cosmological constant and $\alpha$ is a $CP$
breaking phase. Using these results, expectation values of observables which
are functions of fields on the boundary may be evaluated in closed form. The
Beckenstein bound and 't Hooft-Susskind holographic hypothesis are confirmed,
(in the limit of large area and small cosmological constant) in the sense that
once the two metric of the boundary has been measured, the subspace of the
physical state space that describes the further information that the observer
on the boundary may obtain about the interior has finite dimension equal to the
exponent of the area of the boundary, in Planck units, times a fixed constant.
Finally,the construction of the state space for quantum gravity in a region
from that of all Chern-Simon theories defined on its boundary confirms the
categorical-theoretic ``ladder of dimensions picture" of Crane.
| [
{
"created": "Wed, 17 May 1995 19:08:54 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jan 1996 21:30:44 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Smolin",
"Lee",
""
]
] | Quantum gravity is studied nonperturbatively in the case in which space has a boundary with finite area. A natural set of boundary conditions is studied in the Euclidean signature theory, in which the pullback of the curvature to the boundary is self-dual (with a cosmological constant). A Hilbert space which describes all the information accessible by measuring the metric and connection induced in the boundary is constructed and is found to be the direct sum of the state spaces of all $SU(2)$ Chern-Simon theories defined by all choices of punctures and representations on the spatial boundary $\cal S$. The integer level $k$ of Chern-Simons theory is found to be given by $k= 6\pi /G^2 \Lambda + \alpha$, where $\Lambda$ is the cosmological constant and $\alpha$ is a $CP$ breaking phase. Using these results, expectation values of observables which are functions of fields on the boundary may be evaluated in closed form. The Beckenstein bound and 't Hooft-Susskind holographic hypothesis are confirmed, (in the limit of large area and small cosmological constant) in the sense that once the two metric of the boundary has been measured, the subspace of the physical state space that describes the further information that the observer on the boundary may obtain about the interior has finite dimension equal to the exponent of the area of the boundary, in Planck units, times a fixed constant. Finally,the construction of the state space for quantum gravity in a region from that of all Chern-Simon theories defined on its boundary confirms the categorical-theoretic ``ladder of dimensions picture" of Crane. |
gr-qc/0601083 | Serena Fagnocchi | Roberto Balbinot, Alessandro Fabbri, Serena Fagnocchi and Alessandro
Nagar | Numerical analysis of backreaction in acoustic black holes | 7 pages, 5 figures | Nuovo Cim. B121 (2006) 201-212 | 10.1393/ncb/i2006-10016-y | null | gr-qc hep-th | null | Using methods of Quantum Field Theory in curved spacetime, the first order in
hbar quantum corrections to the motion of a fluid in an acoustic black hole
configuration are numerically computed. These corrections arise from the non
linear backreaction of the emitted phonons. Time dependent (isolated system)
and equilibrium configurations (hole in a sonic cavity) are both analyzed.
| [
{
"created": "Fri, 20 Jan 2006 11:30:35 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Balbinot",
"Roberto",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Fagnocchi",
"Serena",
""
],
[
"Nagar",
"Alessandro",
""
]
] | Using methods of Quantum Field Theory in curved spacetime, the first order in hbar quantum corrections to the motion of a fluid in an acoustic black hole configuration are numerically computed. These corrections arise from the non linear backreaction of the emitted phonons. Time dependent (isolated system) and equilibrium configurations (hole in a sonic cavity) are both analyzed. |
2307.07797 | Farshid Soltani | Francesco Fazzini, Carlo Rovelli and Farshid Soltani | Painlev\'e-Gullstrand coordinates discontinuity in the quantum
Oppenheimer-Snyder model | 5 pages, 2 figures; v2: Corrected typos | Phys. Rev. D 108, 044009 (2023) | 10.1103/PhysRevD.108.044009 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A metric that describes a collapsing star and the surrounding black hole
geometry accounting for quantum gravity effects has been derived independently
by different research groups. There is consensus regarding this metric up until
the star reaches its minimum radius, but there is disagreement about what
happens past this event. The discrepancy stems from the appearance of a
discontinuity in the Hamiltonian evolution of the metric components in
Painlev\'e-Gullstrand coordinates. Here we show that the continuous geometry
that describes this phenomenon is represented by a discontinuous metric when
written in these coordinates. The discontinuity disappears by changing
coordinates. The discontinuity found in the Hamiltonian approach can therefore
be interpreted as a coordinate effect. The geometry continues regularly into an
expanding white hole phase, without the occurrence of a shock wave caused by a
physical discontinuity.
| [
{
"created": "Sat, 15 Jul 2023 13:06:06 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Aug 2023 08:08:33 GMT",
"version": "v2"
}
] | 2023-08-04 | [
[
"Fazzini",
"Francesco",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Soltani",
"Farshid",
""
]
] | A metric that describes a collapsing star and the surrounding black hole geometry accounting for quantum gravity effects has been derived independently by different research groups. There is consensus regarding this metric up until the star reaches its minimum radius, but there is disagreement about what happens past this event. The discrepancy stems from the appearance of a discontinuity in the Hamiltonian evolution of the metric components in Painlev\'e-Gullstrand coordinates. Here we show that the continuous geometry that describes this phenomenon is represented by a discontinuous metric when written in these coordinates. The discontinuity disappears by changing coordinates. The discontinuity found in the Hamiltonian approach can therefore be interpreted as a coordinate effect. The geometry continues regularly into an expanding white hole phase, without the occurrence of a shock wave caused by a physical discontinuity. |
1003.0165 | Kamal Nandi | Amrita Bhattacharya, Ruslan Isaev, K.B. Vijayakumar, and Kamal K.
Nandi | Upper Limit on the Size of Galactic Halo via Hamiltonian Approach | 7 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the approach of autonomous Hamiltonian dynamical system, we attempt to
estimate the as yet unknown upper limit on the size of the galactic halo
surrounding galaxies (lenses). The key to determine the size of the halo is to
determine the maximum radius up to which stable material circular orbits are
admissible. We shall illustrate the approach by considering a solution of the
Weyl gravity containing a halo parameter $\gamma$. The upper limit for several
observed lenses are calculated for a typical value of $gamma$ for definiteness,
with and without the cosmological constant $\Lambda $. These lenses (all having
Einstein radius $R_{\text{E}}\approx 10^{23}$ cm) consistently yield an upper
limit $R_{\text{max}}^{\text{stable}}$($\simeq 4.25\times 10^{27}$ cm) inside
the de Sitter radius only when $\gamma$ is \textit{negative}, while a positive
$\gamma$ yields $R_{\text{max}}^{\text{% stable}}$ always exceeding the de
Sitter radius.
| [
{
"created": "Mon, 1 Mar 2010 17:16:47 GMT",
"version": "v1"
}
] | 2010-03-02 | [
[
"Bhattacharya",
"Amrita",
""
],
[
"Isaev",
"Ruslan",
""
],
[
"Vijayakumar",
"K. B.",
""
],
[
"Nandi",
"Kamal K.",
""
]
] | Using the approach of autonomous Hamiltonian dynamical system, we attempt to estimate the as yet unknown upper limit on the size of the galactic halo surrounding galaxies (lenses). The key to determine the size of the halo is to determine the maximum radius up to which stable material circular orbits are admissible. We shall illustrate the approach by considering a solution of the Weyl gravity containing a halo parameter $\gamma$. The upper limit for several observed lenses are calculated for a typical value of $gamma$ for definiteness, with and without the cosmological constant $\Lambda $. These lenses (all having Einstein radius $R_{\text{E}}\approx 10^{23}$ cm) consistently yield an upper limit $R_{\text{max}}^{\text{stable}}$($\simeq 4.25\times 10^{27}$ cm) inside the de Sitter radius only when $\gamma$ is \textit{negative}, while a positive $\gamma$ yields $R_{\text{max}}^{\text{% stable}}$ always exceeding the de Sitter radius. |
gr-qc/0702072 | Hiroko Koyama | Hiroko Koyama, Kenta Kiuchi, Tetsuro Konishi | 1/f fluctuations in spinning-particle motions around Schwarzschild black
hole | 14 pages, 22 figures, submitted to PRD, revised version | Phys.Rev.D76:064031,2007 | 10.1103/PhysRevD.76.064031 | WU-AP/259/07 | gr-qc nlin.CD | null | We study the properties of chaos in the motions of a spinning test particle
in Schwarzschild spacetime. We characterize the chaos using the power spectrum
of the time series of $z$ components of the particle's position. It is found
that the pattern of the power spectrum shows not only white noise but also
$1/f$-type fluctuation, depending on the value of the total angular momentum
$J$ and the spin $S$ of the test particle. Therefore we succeed in classifying
the chaotic motions, which have been classified as simply chaotic ones in
former works, into the two distinct types. One is $1/f$, and the other is white
noise. Based on this classification, we plot, in the two-dimensional parameter
space $(J,S)$, the phase diagram for the properties of the chaos. This phase
diagram enables us in principle to guess the properties of the system $(J,S)$
by observing the dynamics of the test particle, even if the motion is chaotic.
Furthermore, we detect that the origin of the $1/f$ fluctuation is that the
particle motion stagnates around regular orbits (tori), while traveling back
and forth between them, which is called ``stagnant motion'' or ``sticky
motion'' in Hamiltonian dynamical systems. The point is that the difference of
the property of the chaos or the power spectra is due to the topological
structure of the phase space, which in turn is governed by the physical
parameter set $(J,S)$ of the system. From this point of view, the chaos we
found in this system is not always merely random.
| [
{
"created": "Tue, 13 Feb 2007 14:00:12 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Feb 2007 07:13:23 GMT",
"version": "v2"
},
{
"created": "Sat, 23 Jun 2007 15:39:59 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Koyama",
"Hiroko",
""
],
[
"Kiuchi",
"Kenta",
""
],
[
"Konishi",
"Tetsuro",
""
]
] | We study the properties of chaos in the motions of a spinning test particle in Schwarzschild spacetime. We characterize the chaos using the power spectrum of the time series of $z$ components of the particle's position. It is found that the pattern of the power spectrum shows not only white noise but also $1/f$-type fluctuation, depending on the value of the total angular momentum $J$ and the spin $S$ of the test particle. Therefore we succeed in classifying the chaotic motions, which have been classified as simply chaotic ones in former works, into the two distinct types. One is $1/f$, and the other is white noise. Based on this classification, we plot, in the two-dimensional parameter space $(J,S)$, the phase diagram for the properties of the chaos. This phase diagram enables us in principle to guess the properties of the system $(J,S)$ by observing the dynamics of the test particle, even if the motion is chaotic. Furthermore, we detect that the origin of the $1/f$ fluctuation is that the particle motion stagnates around regular orbits (tori), while traveling back and forth between them, which is called ``stagnant motion'' or ``sticky motion'' in Hamiltonian dynamical systems. The point is that the difference of the property of the chaos or the power spectra is due to the topological structure of the phase space, which in turn is governed by the physical parameter set $(J,S)$ of the system. From this point of view, the chaos we found in this system is not always merely random. |
1001.5463 | Kayll Lake | Kayll Lake | Particle Accelerators inside Spinning Black Holes | Erratum added | Phys.Rev.Lett.104:211102,2010; Erratum-ibid.104:259903,2010 | 10.1103/PhysRevLett.104.211102 10.1103/PhysRevLett.104.259903 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of the Kerr metric as a model for a spinning black hole
accreting test particles from rest at infinity, I show that the center-of-mass
energy for a pair of colliding particles is generically divergent at the inner
horizon. This shows that not only are classical black holes internally
unstable, but also that Planck-scale physics is a characteristic feature within
black holes at scales much larger that the Planck length. The novel feature of
the divergence discussed here is that the phenomenon is present only for black
holes with rotation and in this sense it is distinct from the well known Cauchy
horizon instability.
| [
{
"created": "Fri, 29 Jan 2010 19:33:57 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Feb 2010 23:09:23 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Feb 2010 21:43:38 GMT",
"version": "v3"
},
{
"created": "Fri, 14 May 2010 17:00:06 GMT",
"version": "v4"
},
{
"cr... | 2014-11-20 | [
[
"Lake",
"Kayll",
""
]
] | On the basis of the Kerr metric as a model for a spinning black hole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows that not only are classical black holes internally unstable, but also that Planck-scale physics is a characteristic feature within black holes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for black holes with rotation and in this sense it is distinct from the well known Cauchy horizon instability. |
2212.13508 | Abhijith Ajith | Abhijith Ajith, Sukanta Panda | Inflation using a triplet of Antisymmetric tensor fields | 23 pages, 5 figures | Eur. Phys. J. C 83, 770 (2023) | 10.1140/epjc/s10052-023-11932-x | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study an inflation model driven by a triplet of antisymmetric tensor
fields, with minimal and nonminimal couplings to gravity. First, we show that
the presence of a triplet of antisymmetric tensor fields can provide inherent
background isotropy in the stress-energy tensor contrary to the past studies
using an antisymmetric tensor field. Inflation is supported in the presence of
non-minimal couplings with gravity. We perform the slow roll analysis and also
analyse perturbations to the antisymmetric tensor field as well as the tensor
modes of perturbed metric. The speed of gravitational waves manifested from the
tensor perturbations is tuned to $c$. We also study the evolution of the
gravitational waves, calculate their power spectrum and tensor spectral index.
| [
{
"created": "Tue, 27 Dec 2022 14:45:22 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Oct 2023 07:56:42 GMT",
"version": "v2"
}
] | 2023-10-23 | [
[
"Ajith",
"Abhijith",
""
],
[
"Panda",
"Sukanta",
""
]
] | We study an inflation model driven by a triplet of antisymmetric tensor fields, with minimal and nonminimal couplings to gravity. First, we show that the presence of a triplet of antisymmetric tensor fields can provide inherent background isotropy in the stress-energy tensor contrary to the past studies using an antisymmetric tensor field. Inflation is supported in the presence of non-minimal couplings with gravity. We perform the slow roll analysis and also analyse perturbations to the antisymmetric tensor field as well as the tensor modes of perturbed metric. The speed of gravitational waves manifested from the tensor perturbations is tuned to $c$. We also study the evolution of the gravitational waves, calculate their power spectrum and tensor spectral index. |
gr-qc/0203045 | Vladimir Mashkevich | Vladimir S. Mashkevich (CUNY) | Cosmological Quantum Jump Dynamics I. The Principle of Cosmic Energy
Determinacy, Equations of Motion, and Jumps Probabilities | 11 pages, LATEX 2e | null | null | null | gr-qc quant-ph | null | The universe, as a closed system, is for all time in a state with a
determinate value of energy, i.e., in an eigenstate of the Hamiltonian. That is
the principle of cosmic energy determinacy. The Hamiltonian depends on cosmic
time through metric. Therefore there are confluence and branch points of energy
levels. At branch points, quantum jumps must happen to prevent the violation of
energy determinacy. Thus quantum jumps are a reaction against the propensity of
the universe dynamics to that violation. On the basis of this idea, an
internally consistent quantum jump dynamics is developed.
| [
{
"created": "Wed, 13 Mar 2002 04:29:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mashkevich",
"Vladimir S.",
"",
"CUNY"
]
] | The universe, as a closed system, is for all time in a state with a determinate value of energy, i.e., in an eigenstate of the Hamiltonian. That is the principle of cosmic energy determinacy. The Hamiltonian depends on cosmic time through metric. Therefore there are confluence and branch points of energy levels. At branch points, quantum jumps must happen to prevent the violation of energy determinacy. Thus quantum jumps are a reaction against the propensity of the universe dynamics to that violation. On the basis of this idea, an internally consistent quantum jump dynamics is developed. |
1812.07615 | Guilherme Raposo | Guilherme Raposo, Paolo Pani, Roberto Emparan | Exotic compact objects with soft hair | 16 pages, 1 figure. Online repository with explicit solutions and
embedding diagrams available at https://www.darkgra.org/projects.html ;
Version accepted to PRD | Phys. Rev. D 99, 104050 (2019) | 10.1103/PhysRevD.99.104050 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the lack of a general parametrization for exotic compact
objects, we construct a class of perturbative solutions valid for small (but
otherwise generic) multipolar deviations from a Schwarzschild metric in general
relativity. We introduce two classes of exotic compact objects, with "soft" and
"hard" hair, for which the curvature at the surface is respectively comparable
to or much larger than that at the corresponding black-hole horizon. We extend
the Hartle-Thorne formalism to relax the assumption of equatorial symmetry and
to include deformations induced by multipole moments higher than the spin, thus
constructing the most general, axisymmetric quasi-Schwarzschild solution to
Einstein's vacuum equations. We explicitly construct several particular
solutions of objects with soft hair, which might be useful for tests of
quasi-black-hole metrics, and also to study deformed neutron stars. We show
that the more compact a soft exotic object is, the less hairy it will be. All
its multipole moments can approach their corresponding Kerr values only in two
ways as their compactness increases: either logarithmically (or faster) if the
moments are spin-induced, or linearly (or faster) otherwise. Our results
suggest that it is challenging (but possibly feasible with next-generation
gravitational-wave detectors) to distinguish Kerr black holes from a large
class of ultracompact exotic objects on the basis of their different multipolar
structure.
| [
{
"created": "Tue, 18 Dec 2018 19:30:38 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Apr 2019 09:52:32 GMT",
"version": "v2"
}
] | 2019-05-29 | [
[
"Raposo",
"Guilherme",
""
],
[
"Pani",
"Paolo",
""
],
[
"Emparan",
"Roberto",
""
]
] | Motivated by the lack of a general parametrization for exotic compact objects, we construct a class of perturbative solutions valid for small (but otherwise generic) multipolar deviations from a Schwarzschild metric in general relativity. We introduce two classes of exotic compact objects, with "soft" and "hard" hair, for which the curvature at the surface is respectively comparable to or much larger than that at the corresponding black-hole horizon. We extend the Hartle-Thorne formalism to relax the assumption of equatorial symmetry and to include deformations induced by multipole moments higher than the spin, thus constructing the most general, axisymmetric quasi-Schwarzschild solution to Einstein's vacuum equations. We explicitly construct several particular solutions of objects with soft hair, which might be useful for tests of quasi-black-hole metrics, and also to study deformed neutron stars. We show that the more compact a soft exotic object is, the less hairy it will be. All its multipole moments can approach their corresponding Kerr values only in two ways as their compactness increases: either logarithmically (or faster) if the moments are spin-induced, or linearly (or faster) otherwise. Our results suggest that it is challenging (but possibly feasible with next-generation gravitational-wave detectors) to distinguish Kerr black holes from a large class of ultracompact exotic objects on the basis of their different multipolar structure. |
2109.01024 | Davide Batic | Davide Batic and Deena Asem Abuhejleh and Marek Nowakowski | Fuzzy dark matter black holes and droplets | 20 pages, 15 figures | Eur. Phys. J. C 81, 777 (2021) | 10.1140/epjc/s10052-021-09552-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the possibility of having Dark Matter (DM) black holes motivated
by the Einasto density profile. This generalizes both the noncommutative mini
black hole model and allows DM to enter as the matter constituent which makes
up the black hole. We show that it is possible to construct a black hole
solution for each value of the Einasto index and for different values of the
mass parameter, provided that the we work with the energy-momentum tensor of an
anisotropic fluid. In particular, we achieve that by first considering the
equation of state (EOS) $p_r=-\rho$. It turns out that the corresponding black
hole solution exhibits a horizon structure similar to that of a
Reissner-Nordstr\"{o}m black hole and the central singularity is replaced by a
regular de Sitter core. We also show that if the previous EOS is replaced by a
nonlocal one, it is possible to construct a self-gravitating fuzzy DM droplet
but also in this case, the radial pressure is negative. Finally, we contemplate
scenarios of different dark matter black holes with moderate mass values which
could have formed in galaxies. In particular, we probe the possibility whether
such black holes could also be the central galactic objects.
| [
{
"created": "Thu, 2 Sep 2021 15:35:48 GMT",
"version": "v1"
}
] | 2021-09-03 | [
[
"Batic",
"Davide",
""
],
[
"Abuhejleh",
"Deena Asem",
""
],
[
"Nowakowski",
"Marek",
""
]
] | We consider the possibility of having Dark Matter (DM) black holes motivated by the Einasto density profile. This generalizes both the noncommutative mini black hole model and allows DM to enter as the matter constituent which makes up the black hole. We show that it is possible to construct a black hole solution for each value of the Einasto index and for different values of the mass parameter, provided that the we work with the energy-momentum tensor of an anisotropic fluid. In particular, we achieve that by first considering the equation of state (EOS) $p_r=-\rho$. It turns out that the corresponding black hole solution exhibits a horizon structure similar to that of a Reissner-Nordstr\"{o}m black hole and the central singularity is replaced by a regular de Sitter core. We also show that if the previous EOS is replaced by a nonlocal one, it is possible to construct a self-gravitating fuzzy DM droplet but also in this case, the radial pressure is negative. Finally, we contemplate scenarios of different dark matter black holes with moderate mass values which could have formed in galaxies. In particular, we probe the possibility whether such black holes could also be the central galactic objects. |
gr-qc/0202079 | Carlo Rovelli | Carlo Rovelli | A note on the foundation of relativistic mechanics. II: Covariant
hamiltonian general relativity | 7 pages, no figures, 2nd part of gr-qc/0111037 | null | null | null | gr-qc | null | I illustrate a simple hamiltonian formulation of general relativity, derived
from the work of Esposito, Gionti and Stornaiolo, which is manifestly 4d
generally covariant and is defined over a finite dimensional space. The
spacetime coordinates drop out of the formalism, reflecting the fact that they
are not related to observability. The formulation can be interpreted in terms
of Toller's reference system transformations, and provides a physical
interpretation for the spinnetwork to spinnetwork transition amplitudes
computable in principle in loop quantum gravity and in the spin foam models.
| [
{
"created": "Thu, 21 Feb 2002 16:20:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rovelli",
"Carlo",
""
]
] | I illustrate a simple hamiltonian formulation of general relativity, derived from the work of Esposito, Gionti and Stornaiolo, which is manifestly 4d generally covariant and is defined over a finite dimensional space. The spacetime coordinates drop out of the formalism, reflecting the fact that they are not related to observability. The formulation can be interpreted in terms of Toller's reference system transformations, and provides a physical interpretation for the spinnetwork to spinnetwork transition amplitudes computable in principle in loop quantum gravity and in the spin foam models. |
1905.08156 | Xiang-Qian Li | Xiang-Qian Li, Bo Chen, Li-li Xing | Charged Lovelock black holes in the presence of dark fluid with a
nonlinear equation of state | 17 pages, 10 figures. arXiv admin note: text overlap with
arXiv:1708.03884 by other authors | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a model that charged static spherically-symmetric black hole is
surrounded by dark fluid with nonlinear equation of state $p_d=-B/\rho_d$. We
find that the energy density of the dark fluid can be characterized by two
parameters. The derivation of metric solution, as well as the calculation of
black hole thermodynamical quantities as functions of horizon radius, are
performed. Specially, in $D$-dimensional Einstein gravity and Gauss-Bonnet
gravity cases, we plot the metric functions and corresponding thermodynamical
quantities, such as mass, Hawking temperature and heat capacity, by varying the
values of spacetime dimensions and dark fluid parameters. The effects of the
dark fluid parameters on black hole solutions as well as on thermodynamical
stability of black holes are discussed.
| [
{
"created": "Mon, 20 May 2019 15:04:21 GMT",
"version": "v1"
}
] | 2019-05-21 | [
[
"Li",
"Xiang-Qian",
""
],
[
"Chen",
"Bo",
""
],
[
"Xing",
"Li-li",
""
]
] | We consider a model that charged static spherically-symmetric black hole is surrounded by dark fluid with nonlinear equation of state $p_d=-B/\rho_d$. We find that the energy density of the dark fluid can be characterized by two parameters. The derivation of metric solution, as well as the calculation of black hole thermodynamical quantities as functions of horizon radius, are performed. Specially, in $D$-dimensional Einstein gravity and Gauss-Bonnet gravity cases, we plot the metric functions and corresponding thermodynamical quantities, such as mass, Hawking temperature and heat capacity, by varying the values of spacetime dimensions and dark fluid parameters. The effects of the dark fluid parameters on black hole solutions as well as on thermodynamical stability of black holes are discussed. |
1206.3803 | Enrico Barausse | Enrico Barausse, Viktoriya Morozova and Luciano Rezzolla | On the mass radiated by coalescing black-hole binaries | 9 pages (emulateapj), 4 figures. Matches version in ApJ but includes
slight changes to fig 4 described in Barausse, et al ApJ 786, 76 (2014)
(doi:10.1088/0004-637X/786/1/76), see also
http://www2.iap.fr/users/barausse/erratum_mass_formula.pdf | Astrophys. J. 758, 63 (2012), erratum ibidem 786, 76 (2014) | 10.1088/0004-637X/758/1/63 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive an analytic phenomenological expression that predicts the final
mass of the black-hole remnant resulting from the merger of a generic binary
system of black holes on quasi-circular orbits. Besides recovering the correct
test-particle limit for extreme mass-ratio binaries, our formula reproduces
well the results of all the numerical-relativity simulations published so far,
both when applied at separations of a few gravitational radii, and when applied
at separations of tens of thousands of gravitational radii. These validations
make our formula a useful tool in a variety of contexts ranging from
gravitational-wave physics to cosmology. As representative examples, we first
illustrate how it can be used to decrease the phase error of the
effective-one-body waveforms during the ringdown phase. Second, we show that,
when combined with the recently computed self-force correction to the binding
energy of nonspinning black-hole binaries, it provides an estimate of the
energy emitted during the merger and ringdown. Finally, we use it to calculate
the energy radiated in gravitational waves by massive black-hole binaries as a
function of redshift, using different models for the seeds of the black-hole
population.
| [
{
"created": "Sun, 17 Jun 2012 22:41:50 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Sep 2012 22:40:55 GMT",
"version": "v2"
},
{
"created": "Wed, 16 Apr 2014 17:07:43 GMT",
"version": "v3"
}
] | 2014-04-17 | [
[
"Barausse",
"Enrico",
""
],
[
"Morozova",
"Viktoriya",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | We derive an analytic phenomenological expression that predicts the final mass of the black-hole remnant resulting from the merger of a generic binary system of black holes on quasi-circular orbits. Besides recovering the correct test-particle limit for extreme mass-ratio binaries, our formula reproduces well the results of all the numerical-relativity simulations published so far, both when applied at separations of a few gravitational radii, and when applied at separations of tens of thousands of gravitational radii. These validations make our formula a useful tool in a variety of contexts ranging from gravitational-wave physics to cosmology. As representative examples, we first illustrate how it can be used to decrease the phase error of the effective-one-body waveforms during the ringdown phase. Second, we show that, when combined with the recently computed self-force correction to the binding energy of nonspinning black-hole binaries, it provides an estimate of the energy emitted during the merger and ringdown. Finally, we use it to calculate the energy radiated in gravitational waves by massive black-hole binaries as a function of redshift, using different models for the seeds of the black-hole population. |
1106.4841 | Maria Babiuc | M. C. Babiuc, J. Winicour, Y. Zlochower | Binary Black Hole Waveform Extraction at Null Infinity | 11 pages, 7 figures | Class. Quantum Grav. 28 (2011) 134006 | 10.1088/0264-9381/28/13/134006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we present a work in progress towards an efficient and
economical computational module which interfaces between Cauchy and
characteristic evolution codes. Our goal is to provide a standardized waveform
extraction tool for the numerical relativity community which will allow CCE to
be readily applied to a generic Cauchy code. The tool provides a means of
unambiguous comparison between the waveforms generated by evolution codes based
upon different formulations of the Einstein equations and different numerical
approximation.
| [
{
"created": "Thu, 23 Jun 2011 21:46:52 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Babiuc",
"M. C.",
""
],
[
"Winicour",
"J.",
""
],
[
"Zlochower",
"Y.",
""
]
] | In this work, we present a work in progress towards an efficient and economical computational module which interfaces between Cauchy and characteristic evolution codes. Our goal is to provide a standardized waveform extraction tool for the numerical relativity community which will allow CCE to be readily applied to a generic Cauchy code. The tool provides a means of unambiguous comparison between the waveforms generated by evolution codes based upon different formulations of the Einstein equations and different numerical approximation. |
2304.00576 | Katherine Jones-Smith | Katherine Jones-Smith, Harsh Mathur | Modified Newtonian Dynamics as an Alternative to the Planet Nine
Hypothesis | Accepted at the Astronomical Journal. Supplementary Information
included here as Appendices. Complementary to the findings of Migaszewski in
arXiv:2303.13339 | null | null | null | gr-qc astro-ph.EP astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | A new class of Kuiper belt objects that lie beyond Neptune with semimajor
axes greater than 250 astronomical units show orbital anomalies that have been
interpreted as evidence for an undiscovered ninth planet. We show that a
modified gravity theory known as MOND (Modified Newtonian Dynamics) provides an
alternative explanation for the anomalies using the well-established secular
approximation. We predict that the major axes of the orbits will be aligned
with the direction towards the galactic center and that the orbits cluster in
phase space, in agreement with observations of Kuiper belt objects from the new
class. Thus MOND, which can explain galactic rotation without invoking dark
matter, might also be observable in the outer solar system.
| [
{
"created": "Sun, 2 Apr 2023 16:50:51 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Aug 2023 11:44:22 GMT",
"version": "v2"
}
] | 2023-08-25 | [
[
"Jones-Smith",
"Katherine",
""
],
[
"Mathur",
"Harsh",
""
]
] | A new class of Kuiper belt objects that lie beyond Neptune with semimajor axes greater than 250 astronomical units show orbital anomalies that have been interpreted as evidence for an undiscovered ninth planet. We show that a modified gravity theory known as MOND (Modified Newtonian Dynamics) provides an alternative explanation for the anomalies using the well-established secular approximation. We predict that the major axes of the orbits will be aligned with the direction towards the galactic center and that the orbits cluster in phase space, in agreement with observations of Kuiper belt objects from the new class. Thus MOND, which can explain galactic rotation without invoking dark matter, might also be observable in the outer solar system. |
2007.11556 | Nikodem Poplawski | Nikodem Pop{\l}awski | The universe as a closed anisotropic universe born in a black hole | 6 pages | Gen. Relativ. Gravit. 53, 18 (2021) | 10.1007/s10714-021-02790-7 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a universe formed in a black hole in the Einstein--Cartan theory
of gravity. The interior of a Schwarzschild black hole can be represented by
the Kantowski--Sachs metric that describes a closed anisotropic universe. We
use this metric to derive the field equations with a relativistic spin fluid as
a source. We show that torsion may prevent a singularity and replace it with a
nonsingular bounce if particle production dominates over shear. Particle
production after the last bounce can generate a finite period of inflation,
during which the universe expands and isotropizes to the currently observed
state. Our universe might have therefore originated from a black hole.
| [
{
"created": "Wed, 22 Jul 2020 17:21:53 GMT",
"version": "v1"
}
] | 2021-02-19 | [
[
"Popławski",
"Nikodem",
""
]
] | We consider a universe formed in a black hole in the Einstein--Cartan theory of gravity. The interior of a Schwarzschild black hole can be represented by the Kantowski--Sachs metric that describes a closed anisotropic universe. We use this metric to derive the field equations with a relativistic spin fluid as a source. We show that torsion may prevent a singularity and replace it with a nonsingular bounce if particle production dominates over shear. Particle production after the last bounce can generate a finite period of inflation, during which the universe expands and isotropizes to the currently observed state. Our universe might have therefore originated from a black hole. |
1512.08260 | Yakov Shlapentokh-Rothman | Mihalis Dafermos and Yakov Shlapentokh-Rothman | Time-Translation Invariance of Scattering Maps and Blue-Shift
Instabilities on Kerr Black Hole Spacetimes | 26 pages, 12 figures | null | 10.1007/s00220-016-2771-z | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we provide an elementary, unified treatment of two distinct
blue-shift instabilities for the scalar wave equation on a fixed Kerr black
hole background: the celebrated blue-shift at the Cauchy horizon (familiar from
the strong cosmic censorship conjecture) and the time-reversed red-shift at the
event horizon (relevant in classical scattering theory).
Our first theorem concerns the latter and constructs solutions to the wave
equation on Kerr spacetimes such that the radiation field along the future
event horizon vanishes and the radiation field along future null infinity
decays at an arbitrarily fast polynomial rate, yet, the local energy of the
solution is infinite near any point on the future event horizon. Our second
theorem constructs solutions to the wave equation on rotating Kerr spacetimes
such that the radiation field along the past event horizon (extended into the
black hole) vanishes and the radiation field along past null infinity decays at
an arbitrarily fast polynomial rate, yet, the local energy of the solution is
infinite near any point on the Cauchy horizon.
The results make essential use of the scattering theory developed in [M.
Dafermos, I. Rodnianski and Y. Shlapentokh-Rothman, A scattering theory for the
wave equation on Kerr black hole exteriors, preprint (2014) available at
\url{http://arxiv.org/abs/1412.8379}] and exploit directly the time-translation
invariance of the scattering map and the non-triviality of the transmission
map.
| [
{
"created": "Sun, 27 Dec 2015 18:30:00 GMT",
"version": "v1"
}
] | 2016-11-23 | [
[
"Dafermos",
"Mihalis",
""
],
[
"Shlapentokh-Rothman",
"Yakov",
""
]
] | In this paper, we provide an elementary, unified treatment of two distinct blue-shift instabilities for the scalar wave equation on a fixed Kerr black hole background: the celebrated blue-shift at the Cauchy horizon (familiar from the strong cosmic censorship conjecture) and the time-reversed red-shift at the event horizon (relevant in classical scattering theory). Our first theorem concerns the latter and constructs solutions to the wave equation on Kerr spacetimes such that the radiation field along the future event horizon vanishes and the radiation field along future null infinity decays at an arbitrarily fast polynomial rate, yet, the local energy of the solution is infinite near any point on the future event horizon. Our second theorem constructs solutions to the wave equation on rotating Kerr spacetimes such that the radiation field along the past event horizon (extended into the black hole) vanishes and the radiation field along past null infinity decays at an arbitrarily fast polynomial rate, yet, the local energy of the solution is infinite near any point on the Cauchy horizon. The results make essential use of the scattering theory developed in [M. Dafermos, I. Rodnianski and Y. Shlapentokh-Rothman, A scattering theory for the wave equation on Kerr black hole exteriors, preprint (2014) available at \url{http://arxiv.org/abs/1412.8379}] and exploit directly the time-translation invariance of the scattering map and the non-triviality of the transmission map. |
1704.07246 | J\"urgen Struckmeier | J. Struckmeier, J. Muench, D. Vasak, J. Kirsch, M. Hanauske, H.
Stoecker | Canonical Transformation Path to Gauge Theories of Gravity | 17 pages | Phys. Rev. D 95, 124048 (2017) | 10.1103/PhysRevD.95.124048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the generic part of the gauge theory of gravity is derived,
based merely on the action principle and on the general principle of
relativity. We apply the canonical transformation framework to formulate
geometrodynamics as a gauge theory. The starting point of our paper is
constituted by the general De~Donder-Weyl Hamiltonian of a system of scalar and
vector fields, which is supposed to be form-invariant under (global) Lorentz
transformations. Following the reasoning of gauge theories, the corresponding
locally form-invariant system is worked out by means of canonical
transformations. The canonical transformation approach ensures by construction
that the form of the action functional is maintained. We thus encounter amended
Hamiltonian systems which are form-invariant under arbitrary spacetime
transformations. This amended system complies with the general principle of
relativity and describes both, the dynamics of the given physical system's
fields and their coupling to those quantities which describe the dynamics of
the spacetime geometry. In this way, it is unambiguously determined how spin-0
and spin-1 fields couple to the dynamics of spacetime.
A term that describes the dynamics of the free gauge fields must finally be
added to the amended Hamiltonian, as common to all gauge theories, to allow for
a dynamic spacetime geometry. The choice of this "dynamics Hamiltonian" is
outside of the scope of gauge theory as presented in this paper. It accounts
for the remaining indefiniteness of any gauge theory of gravity and must be
chosen "by hand" on the basis of physical reasoning. The final Hamiltonian of
the gauge theory of gravity is shown to be at least quadratic in the conjugate
momenta of the gauge fields -- this is beyond the Einstein-Hilbert theory of
General Relativity.
| [
{
"created": "Mon, 24 Apr 2017 14:13:50 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Nov 2023 18:27:42 GMT",
"version": "v10"
},
{
"created": "Tue, 25 Apr 2017 12:20:39 GMT",
"version": "v2"
},
{
"created": "Sat, 3 Jun 2017 07:08:13 GMT",
"version": "v3"
},
{
"cr... | 2023-11-10 | [
[
"Struckmeier",
"J.",
""
],
[
"Muench",
"J.",
""
],
[
"Vasak",
"D.",
""
],
[
"Kirsch",
"J.",
""
],
[
"Hanauske",
"M.",
""
],
[
"Stoecker",
"H.",
""
]
] | In this paper, the generic part of the gauge theory of gravity is derived, based merely on the action principle and on the general principle of relativity. We apply the canonical transformation framework to formulate geometrodynamics as a gauge theory. The starting point of our paper is constituted by the general De~Donder-Weyl Hamiltonian of a system of scalar and vector fields, which is supposed to be form-invariant under (global) Lorentz transformations. Following the reasoning of gauge theories, the corresponding locally form-invariant system is worked out by means of canonical transformations. The canonical transformation approach ensures by construction that the form of the action functional is maintained. We thus encounter amended Hamiltonian systems which are form-invariant under arbitrary spacetime transformations. This amended system complies with the general principle of relativity and describes both, the dynamics of the given physical system's fields and their coupling to those quantities which describe the dynamics of the spacetime geometry. In this way, it is unambiguously determined how spin-0 and spin-1 fields couple to the dynamics of spacetime. A term that describes the dynamics of the free gauge fields must finally be added to the amended Hamiltonian, as common to all gauge theories, to allow for a dynamic spacetime geometry. The choice of this "dynamics Hamiltonian" is outside of the scope of gauge theory as presented in this paper. It accounts for the remaining indefiniteness of any gauge theory of gravity and must be chosen "by hand" on the basis of physical reasoning. The final Hamiltonian of the gauge theory of gravity is shown to be at least quadratic in the conjugate momenta of the gauge fields -- this is beyond the Einstein-Hilbert theory of General Relativity. |
2011.12522 | Takahiro Yamamoto S. | Takahiro S. Yamamoto, Takahiro Tanaka | Use of Excess Power Method and Convolutional Neural Network in All-Sky
Search for Continuous Gravitational Waves | 14 pages, 7 figures | Phys. Rev. D 103, 084049 (2021) | 10.1103/PhysRevD.103.084049 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The signal of continuous gravitational waves has a longer duration than the
observation period. Even if the waveform in the source frame is monochromatic,
we will observe the waveform with modulated frequencies due to the motion of
the detector. If the source location is unknown, a lot of templates having
different sky positions are required to demodulate the frequency, and the
required huge computational cost restricts the applicable parameter region of
coherent search. In this work, we propose and examine a new method to select
candidates, which reduces the cost of coherent search by following-up only the
selected candidates. As a first step, we consider an idealized situation in
which only a single-detector having 100\% duty cycle is available and its
detector noise is approximated by the stationary Gaussian noise. Also, we
assume the signal has no spindown and the polarization angle, the inclination
angle, and the initial phase are fixed to be $\psi=0$, $\cos\iota=1$, and
$\phi_0=0$, and they are treated as known parameters. We combine several
methods: 1) the short-time Fourier transform with the re-sampled data such that
the Earth motion for the source is canceled in some reference direction, 2) the
excess power search in the Fourier transform of the time series obtained by
picking up the amplitude in a particular frequency bin from the short-time
Fourier transform data, and 3) the deep learning method to further constrain
the source sky position. The computational cost and the detection probability
are estimated. The injection test is carried out to check the validity of the
detection probability. We find that our method is worthy of further study for
analyzing $O(10^7)$sec strain data.
| [
{
"created": "Wed, 25 Nov 2020 05:42:07 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Mar 2021 04:55:51 GMT",
"version": "v2"
}
] | 2021-05-05 | [
[
"Yamamoto",
"Takahiro S.",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | The signal of continuous gravitational waves has a longer duration than the observation period. Even if the waveform in the source frame is monochromatic, we will observe the waveform with modulated frequencies due to the motion of the detector. If the source location is unknown, a lot of templates having different sky positions are required to demodulate the frequency, and the required huge computational cost restricts the applicable parameter region of coherent search. In this work, we propose and examine a new method to select candidates, which reduces the cost of coherent search by following-up only the selected candidates. As a first step, we consider an idealized situation in which only a single-detector having 100\% duty cycle is available and its detector noise is approximated by the stationary Gaussian noise. Also, we assume the signal has no spindown and the polarization angle, the inclination angle, and the initial phase are fixed to be $\psi=0$, $\cos\iota=1$, and $\phi_0=0$, and they are treated as known parameters. We combine several methods: 1) the short-time Fourier transform with the re-sampled data such that the Earth motion for the source is canceled in some reference direction, 2) the excess power search in the Fourier transform of the time series obtained by picking up the amplitude in a particular frequency bin from the short-time Fourier transform data, and 3) the deep learning method to further constrain the source sky position. The computational cost and the detection probability are estimated. The injection test is carried out to check the validity of the detection probability. We find that our method is worthy of further study for analyzing $O(10^7)$sec strain data. |
2211.08801 | Jonas Wildberger | Jonas Wildberger, Maximilian Dax, Stephen R. Green, Jonathan Gair,
Michael P\"urrer, Jakob H. Macke, Alessandra Buonanno, Bernhard Sch\"olkopf | Adapting to noise distribution shifts in flow-based gravitational-wave
inference | null | null | 10.1103/PhysRevD.107.084046 | null | gr-qc astro-ph.IM cs.LG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Deep learning techniques for gravitational-wave parameter estimation have
emerged as a fast alternative to standard samplers $\unicode{x2013}$ producing
results of comparable accuracy. These approaches (e.g., DINGO) enable amortized
inference by training a normalizing flow to represent the Bayesian posterior
conditional on observed data. By conditioning also on the noise power spectral
density (PSD) they can even account for changing detector characteristics.
However, training such networks requires knowing in advance the distribution of
PSDs expected to be observed, and therefore can only take place once all data
to be analyzed have been gathered. Here, we develop a probabilistic model to
forecast future PSDs, greatly increasing the temporal scope of DINGO networks.
Using PSDs from the second LIGO-Virgo observing run (O2) $\unicode{x2013}$ plus
just a single PSD from the beginning of the third (O3) $\unicode{x2013}$ we
show that we can train a DINGO network to perform accurate inference throughout
O3 (on 37 real events). We therefore expect this approach to be a key component
to enable the use of deep learning techniques for low-latency analyses of
gravitational waves.
| [
{
"created": "Wed, 16 Nov 2022 09:56:23 GMT",
"version": "v1"
}
] | 2023-05-10 | [
[
"Wildberger",
"Jonas",
""
],
[
"Dax",
"Maximilian",
""
],
[
"Green",
"Stephen R.",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Pürrer",
"Michael",
""
],
[
"Macke",
"Jakob H.",
""
],
[
"Buonanno",
"Alessandra",
""
... | Deep learning techniques for gravitational-wave parameter estimation have emerged as a fast alternative to standard samplers $\unicode{x2013}$ producing results of comparable accuracy. These approaches (e.g., DINGO) enable amortized inference by training a normalizing flow to represent the Bayesian posterior conditional on observed data. By conditioning also on the noise power spectral density (PSD) they can even account for changing detector characteristics. However, training such networks requires knowing in advance the distribution of PSDs expected to be observed, and therefore can only take place once all data to be analyzed have been gathered. Here, we develop a probabilistic model to forecast future PSDs, greatly increasing the temporal scope of DINGO networks. Using PSDs from the second LIGO-Virgo observing run (O2) $\unicode{x2013}$ plus just a single PSD from the beginning of the third (O3) $\unicode{x2013}$ we show that we can train a DINGO network to perform accurate inference throughout O3 (on 37 real events). We therefore expect this approach to be a key component to enable the use of deep learning techniques for low-latency analyses of gravitational waves. |
gr-qc/0112025 | Dag {\O}stvang | Dag {\O}stvang | Quasi-Metric Relativity | 40 pages, no figures, LaTeX; v3: connection changed; v4: extended and
local conservation laws changed; v5: major revision; v7: must have
non-universal gravitational coupling; v8: rewritten with fully coupled
theory; v9: major revision (fully coupled theory abandoned); v12:
inconsistent equation replaced (oh well). arXiv admin note: text overlap with
arXiv:gr-qc/0111110 | Grav.Cosmol.11:205-219,2005 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a survey of a new type of relativistic space-time framework; the
so-called quasi-metric framework. The basic geometric structure underlying
quasi-metric relativity is quasi-metric space-time; this is defined as a
4-dimensional differentiable manifold ${\cal N}$ equipped with two
one-parameter families ${\bf {\bar g}}_t$ and ${\bf g}_t$ of Lorentzian
4-metrics parametrized by a global time function $t$. The metric family ${\bf
{\bar g}}_t$ is found from field equations, whereas the metric family ${\bf
g}_t$ is used to propagate sources and to compare predictions to experiments. A
linear and symmetric affine connection compatible with the family ${\bf g}_t$
is defined, giving rise to equations of motion.
Furthermore a quasi-metric theory of gravity, including field equations and
local conservation laws, is presented. Just as for General Relativity, the
field equations accommodate two independent propagating dynamical degrees of
freedom. On the other hand, the particular structure of quasi-metric geometry
allows only a partial coupling of space-time geometry to the active
stress-energy tensor. Besides, the field equations are defined from projections
of physical and geometrical tensors with respect to a "preferred" foliation of
quasi-metric space-time into spatial hypersurfaces. Moreover, a number of
non-standard features make the field equations unsuitable for a standard
PPN-analysis. This implies that the experimental status of the theory is not
completely clear at this point in time. The theory seems to be consistent with
a number of cosmological observations and it satisfies all the classical solar
system tests, though. In additon, in its non-metric sector, the new theory has
experimental support where General Relativity fails or is irrelevant.
| [
{
"created": "Tue, 11 Dec 2001 23:55:20 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Dec 2020 15:41:26 GMT",
"version": "v10"
},
{
"created": "Wed, 1 Feb 2023 15:02:00 GMT",
"version": "v11"
},
{
"created": "Tue, 19 Mar 2024 15:32:08 GMT",
"version": "v12"
},
{
... | 2024-03-20 | [
[
"Østvang",
"Dag",
""
]
] | This is a survey of a new type of relativistic space-time framework; the so-called quasi-metric framework. The basic geometric structure underlying quasi-metric relativity is quasi-metric space-time; this is defined as a 4-dimensional differentiable manifold ${\cal N}$ equipped with two one-parameter families ${\bf {\bar g}}_t$ and ${\bf g}_t$ of Lorentzian 4-metrics parametrized by a global time function $t$. The metric family ${\bf {\bar g}}_t$ is found from field equations, whereas the metric family ${\bf g}_t$ is used to propagate sources and to compare predictions to experiments. A linear and symmetric affine connection compatible with the family ${\bf g}_t$ is defined, giving rise to equations of motion. Furthermore a quasi-metric theory of gravity, including field equations and local conservation laws, is presented. Just as for General Relativity, the field equations accommodate two independent propagating dynamical degrees of freedom. On the other hand, the particular structure of quasi-metric geometry allows only a partial coupling of space-time geometry to the active stress-energy tensor. Besides, the field equations are defined from projections of physical and geometrical tensors with respect to a "preferred" foliation of quasi-metric space-time into spatial hypersurfaces. Moreover, a number of non-standard features make the field equations unsuitable for a standard PPN-analysis. This implies that the experimental status of the theory is not completely clear at this point in time. The theory seems to be consistent with a number of cosmological observations and it satisfies all the classical solar system tests, though. In additon, in its non-metric sector, the new theory has experimental support where General Relativity fails or is irrelevant. |
1107.0766 | Chad Galley | Chad R. Galley | A nonlinear scalar model of extreme mass ratio inspirals in effective
field theory II. Scalar perturbations and a master source | For Part 1 of this series, see arXiv:1012.4488. 20 pages, 7 figures | null | 10.1088/0264-9381/29/1/015011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of a small compact object (SCO) in a background spacetime is
investigated further in a class of model nonlinear scalar field theories having
a perturbative structure analogous to the General Relativistic description of
extreme mass ratio inspirals (EMRIs). We derive regular expressions for the
scalar perturbations generated by the SCO's motion valid through third order in
$\epsilon$, the size of the SCO to the background curvature length scale. Our
expressions are compared to those calculated through second order in $\epsilon$
by Rosenthal in [E. Rosenthal, CQG 22, S859 (2005)] and found to agree but our
procedure for regularizing the scalar perturbations is considerably simpler.
Following the Detweiler-Whiting (DW) scheme, we use our regular expressions for
the field and derive the regular self-force corrections through third order. We
find agreement with our previous derivation based on a variational principle of
an effective action for the worldline associated with the SCO thus
demonstrating the internal consistency of our formalism. This also explicitly
demonstrates that the DW decomposition of Green's functions is a valid and
practical method of self force computation at higher orders in perturbation
theory and, as we show in an appendix, at all orders in perturbation theory.
Finally, we identify a master source from which all other physically relevant
quantities are derivable. Knowing the master source perturbatively allows one
to construct the waveform measured by an observer, the regular part of the
field on the worldline, the regular part of the self force, and orbital
quantities such as shifts of the innermost stable circular orbit, etc. The
existence of a master source together with the regularization methods
implemented in this series should be indispensable for derivations of
higher-order gravitational self force corrections.
| [
{
"created": "Tue, 5 Jul 2011 02:04:06 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Galley",
"Chad R.",
""
]
] | The motion of a small compact object (SCO) in a background spacetime is investigated further in a class of model nonlinear scalar field theories having a perturbative structure analogous to the General Relativistic description of extreme mass ratio inspirals (EMRIs). We derive regular expressions for the scalar perturbations generated by the SCO's motion valid through third order in $\epsilon$, the size of the SCO to the background curvature length scale. Our expressions are compared to those calculated through second order in $\epsilon$ by Rosenthal in [E. Rosenthal, CQG 22, S859 (2005)] and found to agree but our procedure for regularizing the scalar perturbations is considerably simpler. Following the Detweiler-Whiting (DW) scheme, we use our regular expressions for the field and derive the regular self-force corrections through third order. We find agreement with our previous derivation based on a variational principle of an effective action for the worldline associated with the SCO thus demonstrating the internal consistency of our formalism. This also explicitly demonstrates that the DW decomposition of Green's functions is a valid and practical method of self force computation at higher orders in perturbation theory and, as we show in an appendix, at all orders in perturbation theory. Finally, we identify a master source from which all other physically relevant quantities are derivable. Knowing the master source perturbatively allows one to construct the waveform measured by an observer, the regular part of the field on the worldline, the regular part of the self force, and orbital quantities such as shifts of the innermost stable circular orbit, etc. The existence of a master source together with the regularization methods implemented in this series should be indispensable for derivations of higher-order gravitational self force corrections. |
1705.06910 | Mushtaq Ahmad Sial | M. Farasat Shamir, Mushtaq Ahmad | Emerging Anisotropic Compact Stars in $f(\mathcal{G},T)$ Gravity | 27 pages, 43 figures, 1 table, minor changes | Eur. Phys. J. C 77 (2017) 674 | 10.1140/epjc/s10052-017-5239-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possible emergence of compact stars has been investigated in the recently
introduced modified Gauss-Bonnet $f(\mathcal{G},T)$ gravity, where
$\mathcal{G}$ is the Gauss-Bonnet term and ${T}$ is the trace of the
energy-momentum tensor. Specifically, for this modified $f(\mathcal{G}, T)$
theory, the analytic solutions of Krori and Barua have been applied to
anisotropic matter distribution. To determine the unknown constants appearing
in Krori and Barua metric, the well-known three models of the compact stars
namely 4U1820-30, Her X-I, and SAX J 1808.4-3658 have been used. The analysis
of the physical behavior of the compact stars has been presented and the
physical features like energy density and pressure, energy conditions, static
equilibrium, stability, measure of anisotropy, and regularity of the compact
stars, have been discussed.
| [
{
"created": "Fri, 19 May 2017 09:49:14 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Oct 2017 07:26:31 GMT",
"version": "v2"
}
] | 2017-10-18 | [
[
"Shamir",
"M. Farasat",
""
],
[
"Ahmad",
"Mushtaq",
""
]
] | The possible emergence of compact stars has been investigated in the recently introduced modified Gauss-Bonnet $f(\mathcal{G},T)$ gravity, where $\mathcal{G}$ is the Gauss-Bonnet term and ${T}$ is the trace of the energy-momentum tensor. Specifically, for this modified $f(\mathcal{G}, T)$ theory, the analytic solutions of Krori and Barua have been applied to anisotropic matter distribution. To determine the unknown constants appearing in Krori and Barua metric, the well-known three models of the compact stars namely 4U1820-30, Her X-I, and SAX J 1808.4-3658 have been used. The analysis of the physical behavior of the compact stars has been presented and the physical features like energy density and pressure, energy conditions, static equilibrium, stability, measure of anisotropy, and regularity of the compact stars, have been discussed. |
gr-qc/9704054 | Peter Leifer | Peter Leifer | The Nonlinear Quantum Gauge Theory-Superrelativity | 11 pages, LaTeX, 1 eps-figure, has been submitted at the 43rd Meeting
of the Israel Physical Society | Int.J.Theor.Phys. 37, (1) 387 (1998) | null | null | gr-qc | null | A new type of a nonlinear gauge quantum theory (superrelativity) has been
proposed. Such theory demands a radical reconstruction of both the quantum
field conception and spacetime structure, and this paves presumably way to the
comprehension of the quantum nature of inertia.
| [
{
"created": "Sat, 19 Apr 1997 11:36:51 GMT",
"version": "v1"
}
] | 2012-09-13 | [
[
"Leifer",
"Peter",
""
]
] | A new type of a nonlinear gauge quantum theory (superrelativity) has been proposed. Such theory demands a radical reconstruction of both the quantum field conception and spacetime structure, and this paves presumably way to the comprehension of the quantum nature of inertia. |
1510.00758 | Benjamin C. Harms | Paul H. Cox, Benjamin C. Harms, and Shaoqi Hou | Stability of Einstein-Maxwell-Kalb-Ramond Wormholes | 8 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:1108.1184 | Phys. Rev. D 93, 044014 (2016) | 10.1103/PhysRevD.93.044014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigates a particular type of wormhole. The wormhole solutions
studied are obtained by sewing together two static, spherically symmetric,
charged black-hole metrics at their horizons. The charged wormholes are in a
background Kalb-Ramond field, which is the source of the necessary tension in
the gravitational field. The metric-tensor elements are studied by numerically
solving Einstein's equations with stress-energy-tensor elements given by the
combination of static electric and Kalb-Ramond fields. For a certain range of
electric charge the tension is positive away from the wormhole throat, but the
tension is negative near the throat, making it non-traversable. The wormholes
are found to be quasi-stable against decay via gravitational instanton
tunnelling.
| [
{
"created": "Fri, 2 Oct 2015 23:35:14 GMT",
"version": "v1"
}
] | 2016-02-08 | [
[
"Cox",
"Paul H.",
""
],
[
"Harms",
"Benjamin C.",
""
],
[
"Hou",
"Shaoqi",
""
]
] | This paper investigates a particular type of wormhole. The wormhole solutions studied are obtained by sewing together two static, spherically symmetric, charged black-hole metrics at their horizons. The charged wormholes are in a background Kalb-Ramond field, which is the source of the necessary tension in the gravitational field. The metric-tensor elements are studied by numerically solving Einstein's equations with stress-energy-tensor elements given by the combination of static electric and Kalb-Ramond fields. For a certain range of electric charge the tension is positive away from the wormhole throat, but the tension is negative near the throat, making it non-traversable. The wormholes are found to be quasi-stable against decay via gravitational instanton tunnelling. |
2001.04993 | Yigit Yargic | Yigit Yargic, Laura Sberna, Achim Kempf | Which part of the stress-energy tensor gravitates? | 15 pages, 1 figure. Accepted to PRD | null | 10.1103/PhysRevD.101.043513 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the possibility that, in the semiclassical Einstein equation for
cosmological spacetimes, gravity is sourced by the amount of stress-energy that
is above that of the instantaneous ground state. For this possibility to be
consistent, the Bianchi identities must continue to hold. This is nontrivial
because it means that the ground state expectation value of the stress-energy
tensor must be covariantly conserved in spite of the fact that the ground state
is generally a different state at different times. We prove that this
consistency condition does hold. As a consequence, we find that the vacuum
stress-energy which is above the instantaneous ground state does not
renormalize the cosmological constant, as long as the instantaneous ground
states and the instantaneous adiabatic vacua exist.
| [
{
"created": "Tue, 14 Jan 2020 19:00:03 GMT",
"version": "v1"
}
] | 2020-02-26 | [
[
"Yargic",
"Yigit",
""
],
[
"Sberna",
"Laura",
""
],
[
"Kempf",
"Achim",
""
]
] | We consider the possibility that, in the semiclassical Einstein equation for cosmological spacetimes, gravity is sourced by the amount of stress-energy that is above that of the instantaneous ground state. For this possibility to be consistent, the Bianchi identities must continue to hold. This is nontrivial because it means that the ground state expectation value of the stress-energy tensor must be covariantly conserved in spite of the fact that the ground state is generally a different state at different times. We prove that this consistency condition does hold. As a consequence, we find that the vacuum stress-energy which is above the instantaneous ground state does not renormalize the cosmological constant, as long as the instantaneous ground states and the instantaneous adiabatic vacua exist. |
gr-qc/0205053 | Abhik Kumar Sanyal | Abhik Kumar Sanyal | Quantum Mechanical Probability Interpretation In The Mini-superspace
Model Of Higher Order Gravity Theory | 11 pages, Latex | Phys.Lett. B542 (2002) 147-159 | 10.1016/S0370-2693(02)02338-9 | null | gr-qc | null | It has been shown that inclusion of higher order curvature invariant terms in
the Robertson-Walker minisuperspace model of the Einstein-Hilbert action leads
to Schrodinger like equation, whose corresponding effective action is
hermitian. Thus, it is possible to write the continuity equation in a straight
forward manner, which reveals a quantum mechanical probability interpretation
of the theory.
| [
{
"created": "Tue, 14 May 2002 08:47:06 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Sanyal",
"Abhik Kumar",
""
]
] | It has been shown that inclusion of higher order curvature invariant terms in the Robertson-Walker minisuperspace model of the Einstein-Hilbert action leads to Schrodinger like equation, whose corresponding effective action is hermitian. Thus, it is possible to write the continuity equation in a straight forward manner, which reveals a quantum mechanical probability interpretation of the theory. |
1805.05978 | Seyed Meraj Mousavi Rasouli | S. M. M. Rasouli, J. Marto and P. V. Moniz | Kinetic inflation in deformed phase space Brans-Dicke cosmology | 31 pages, 10 figures | Physics of the Dark Universe 24 (2019) 100269 | 10.1016/j.dark.2019.100269 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, by establishing a Brans-Dicke (BD) cosmology by means of a
deformed phase space, in the absence of any scalar potential, cosmological
constant and ordinary matter, we show that it is feasible to overcome obstacles
reported in the corresponding commutative (non-deformed) frameworks. More
concretely, by applying the Hamiltonian formalism and introducing a dynamical
deformation, between the momenta associated to the FLRW scale factor and the BD
scalar field, we obtain the modified equations of motion. In particular, these
equations reduce to their standard counterparts when the noncommutative (NC)
parameter is switched off. By focusing on a specific branch of solutions, in
contrast to standard frameworks (even with a varying BD coupling parameter), we
show that we can obtain an adequate appropriate inflationary epoch possessing a
suitable graceful exit. In other words, in the Jordan frame (JF), such branch
of solutions properly satisfy the sufficient condition required for
satisfactory inflation, which is equivalent to get an inflationary phase in the
conformal Einstein frame (EF) without branch change. Concerning the
cosmological dynamics, we further show that our NC framework bears close
resemblance to the $R^2$ (Starobinsky) inflationary model.
| [
{
"created": "Tue, 15 May 2018 18:21:56 GMT",
"version": "v1"
},
{
"created": "Tue, 22 May 2018 22:18:44 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Feb 2019 04:07:05 GMT",
"version": "v3"
}
] | 2019-02-13 | [
[
"Rasouli",
"S. M. M.",
""
],
[
"Marto",
"J.",
""
],
[
"Moniz",
"P. V.",
""
]
] | In this paper, by establishing a Brans-Dicke (BD) cosmology by means of a deformed phase space, in the absence of any scalar potential, cosmological constant and ordinary matter, we show that it is feasible to overcome obstacles reported in the corresponding commutative (non-deformed) frameworks. More concretely, by applying the Hamiltonian formalism and introducing a dynamical deformation, between the momenta associated to the FLRW scale factor and the BD scalar field, we obtain the modified equations of motion. In particular, these equations reduce to their standard counterparts when the noncommutative (NC) parameter is switched off. By focusing on a specific branch of solutions, in contrast to standard frameworks (even with a varying BD coupling parameter), we show that we can obtain an adequate appropriate inflationary epoch possessing a suitable graceful exit. In other words, in the Jordan frame (JF), such branch of solutions properly satisfy the sufficient condition required for satisfactory inflation, which is equivalent to get an inflationary phase in the conformal Einstein frame (EF) without branch change. Concerning the cosmological dynamics, we further show that our NC framework bears close resemblance to the $R^2$ (Starobinsky) inflationary model. |
2405.01430 | Jonas Neuser | Jonas Neuser | Quantum Field Theory of Black Hole Perturbations with Backreaction IV.
Spherically symmetric 2nd order Einstein-Maxwell sector in generalised gauges | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In previous papers of this series we analysed the reduced phase space
approach to perturbations of Einstein-Maxwell theory to second order around
spherically symmetric backgrounds in the Gullstrand Painlev\'e Gauge and
confirmed consistency with previous approaches. In this paper we generalize
this result and show that the analysis can be performed in gauges for the
background variables compatible with the Gullstrand Painlev\'e gauge. We obtain
the same structure for the reduced Hamiltonian that contains the well known
Regge-Wheeler and Zerilli potentials. Possible applications of this
generalization are discussed.
| [
{
"created": "Thu, 2 May 2024 16:18:51 GMT",
"version": "v1"
}
] | 2024-05-03 | [
[
"Neuser",
"Jonas",
""
]
] | In previous papers of this series we analysed the reduced phase space approach to perturbations of Einstein-Maxwell theory to second order around spherically symmetric backgrounds in the Gullstrand Painlev\'e Gauge and confirmed consistency with previous approaches. In this paper we generalize this result and show that the analysis can be performed in gauges for the background variables compatible with the Gullstrand Painlev\'e gauge. We obtain the same structure for the reduced Hamiltonian that contains the well known Regge-Wheeler and Zerilli potentials. Possible applications of this generalization are discussed. |
gr-qc/9705022 | James Hartle | James B. Hartle (Institute for Theoretical Physics, University of
California, Santa Barbara) | Generalized Quantum Theory in Evaporating Black Hole Spacetimes | 23 pages, ReVTeX, 8 figures, titles supplied for some references | in Black Holes and Relativistic Stars, ed by R.M. Wald, University
of Chicago Press, 1998. | null | UCSBTH-97-04, NSF-ITP-97-024 | gr-qc hep-th quant-ph | null | Quantum mechanics for matter fields moving in an evaporating black hole
spacetime is formulated in fully four-dimensional form according to the
principles of generalized quantum theory. The resulting quantum theory cannot
be expressed in a 3+1 form in terms of a state evolving unitarily or by
reduction through a foliating family of spacelike surfaces. That is because
evaporating black hole geometries cannot be foliated by a non-singular family
of spacelike surfaces. A four-dimensional notion of information is reviewed.
Although complete information may not be available on every spacelike surface,
information is not lost in a spacetime sense in an evaporating black hole
spacetime. Rather complete information is distributed about the
four-dimensional spacetime. Black hole evaporation is thus not in conflict with
the principles of quantum mechanics when suitably generally stated. (Talk
presented at Black Holes and Relativistic Stars: A Symposium in Honor of S.
Chandrasekhar, Chicago, Dec 14-15,1996.)
| [
{
"created": "Sat, 10 May 1997 20:21:22 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Jun 1997 00:05:53 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Aug 1997 19:33:35 GMT",
"version": "v3"
},
{
"created": "Sat, 6 Sep 1997 19:07:46 GMT",
"version": "v4"
},
{
"cr... | 2008-02-03 | [
[
"Hartle",
"James B.",
"",
"Institute for Theoretical Physics, University of\n California, Santa Barbara"
]
] | Quantum mechanics for matter fields moving in an evaporating black hole spacetime is formulated in fully four-dimensional form according to the principles of generalized quantum theory. The resulting quantum theory cannot be expressed in a 3+1 form in terms of a state evolving unitarily or by reduction through a foliating family of spacelike surfaces. That is because evaporating black hole geometries cannot be foliated by a non-singular family of spacelike surfaces. A four-dimensional notion of information is reviewed. Although complete information may not be available on every spacelike surface, information is not lost in a spacetime sense in an evaporating black hole spacetime. Rather complete information is distributed about the four-dimensional spacetime. Black hole evaporation is thus not in conflict with the principles of quantum mechanics when suitably generally stated. (Talk presented at Black Holes and Relativistic Stars: A Symposium in Honor of S. Chandrasekhar, Chicago, Dec 14-15,1996.) |
2102.04015 | Guangzhou Guo | Guangzhou Guo, Peng Wang, Houwen Wu, and Haitang Yang | Scalarized Einstein-Maxwell-scalar Black Holes in Anti-de Sitter
Spacetime | v1: 14 pages, 3 figures; v2: 14 pages, 3 figures, references added | null | null | CTP-SCU/2021003 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study spontaneous scalarization of asymptotically anti-de
Sitter charged black holes in the Einstein-Maxwell-scalar model with a
non-minimal coupling between the scalar and Maxwell fields. In this model,
Reissner-Nordstr\"om-AdS (RNAdS) black holes are scalar-free black hole
solutions, and may induce scalarized black holes due to the presence of a
tachyonic instability of the scalar field near the event horizon. For RNAdS and
scalarized black hole solutions, we investigate the domain of existence,
perturbative stability against spherical perturbations and phase structure. In
a micro-canonical ensemble, scalarized solutions are always thermodynamically
preferred over RNAdS black holes. However, the system has much rich phase
structure and phase transitions in a canonical ensemble. In particular, we
report a RNAdS BH/scalarized BH/RNAdS BH reentrant phase transition, which is
composed of a zeroth-order phase transition and a second-order one.
| [
{
"created": "Mon, 8 Feb 2021 06:09:51 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Feb 2021 16:25:07 GMT",
"version": "v2"
}
] | 2021-02-16 | [
[
"Guo",
"Guangzhou",
""
],
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] | In this paper, we study spontaneous scalarization of asymptotically anti-de Sitter charged black holes in the Einstein-Maxwell-scalar model with a non-minimal coupling between the scalar and Maxwell fields. In this model, Reissner-Nordstr\"om-AdS (RNAdS) black holes are scalar-free black hole solutions, and may induce scalarized black holes due to the presence of a tachyonic instability of the scalar field near the event horizon. For RNAdS and scalarized black hole solutions, we investigate the domain of existence, perturbative stability against spherical perturbations and phase structure. In a micro-canonical ensemble, scalarized solutions are always thermodynamically preferred over RNAdS black holes. However, the system has much rich phase structure and phase transitions in a canonical ensemble. In particular, we report a RNAdS BH/scalarized BH/RNAdS BH reentrant phase transition, which is composed of a zeroth-order phase transition and a second-order one. |
0809.4014 | Lorenzo Iorio | Lorenzo Iorio | Will it be possible to measure intrinsic gravitomagnetism with Lunar
Laser Ranging? | LaTex2e, 8 pages, 1 table, no figures, 49 references. Discussion on
the DGP braneworld gravity model added. To appear in International Journal of
Modern Physics D (IJMPD) | Int. J. Mod. Phys. D 18 (2009) 1319-1326 | 10.1142/S0218271809015114 | null | gr-qc astro-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we mainly explore the possibility of measuring the action of the
intrinsic gravitomagnetic field of the rotating Earth on the orbital motion of
the Moon with the Lunar Laser Ranging (LLR) technique. Expected improvements in
it should push the precision in measuring the Earth-Moon range to the mm level;
the present-day Root-Mean-Square (RMS) accuracy in reconstructing the radial
component of the lunar orbit is about 2 cm; its harmonic terms can be
determined at the mm level. The current uncertainty in measuring the lunar
precession rates is about 10^-1 milliarcseconds per year. The Lense-Thirring
secular, i.e. averaged over one orbital period, precessions of the node and the
perigee of the Moon induced by the Earth's spin angular momentum amount to
10^-3 milliarcseconds per year yielding transverse and normal shifts of
10^-1-10^-2 cm yr^-1. In the radial direction there is only a short-period,
i.e. non-averaged over one orbital revolution, oscillation with an amplitude of
10^-5 m. Major limitations come also from some systematic errors induced by
orbital perturbations of classical origin like, e.g., the secular precessions
induced by the Sun and the oblateness of the Moon whose mismodelled parts are
several times larger than the Lense-Thirring signal. The present analysis holds
also for the Lue-Starkman perigee precession due to the multidimensional
braneworld model by Dvali, Gabadadze and Porrati (DGP); indeed, it amounts to
about 5 X 10^-3 milliarcseconds per year.
| [
{
"created": "Tue, 23 Sep 2008 20:16:05 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Sep 2008 07:06:44 GMT",
"version": "v2"
},
{
"created": "Sun, 28 Sep 2008 10:22:57 GMT",
"version": "v3"
},
{
"created": "Thu, 12 Feb 2009 13:10:19 GMT",
"version": "v4"
}
] | 2009-09-02 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this note we mainly explore the possibility of measuring the action of the intrinsic gravitomagnetic field of the rotating Earth on the orbital motion of the Moon with the Lunar Laser Ranging (LLR) technique. Expected improvements in it should push the precision in measuring the Earth-Moon range to the mm level; the present-day Root-Mean-Square (RMS) accuracy in reconstructing the radial component of the lunar orbit is about 2 cm; its harmonic terms can be determined at the mm level. The current uncertainty in measuring the lunar precession rates is about 10^-1 milliarcseconds per year. The Lense-Thirring secular, i.e. averaged over one orbital period, precessions of the node and the perigee of the Moon induced by the Earth's spin angular momentum amount to 10^-3 milliarcseconds per year yielding transverse and normal shifts of 10^-1-10^-2 cm yr^-1. In the radial direction there is only a short-period, i.e. non-averaged over one orbital revolution, oscillation with an amplitude of 10^-5 m. Major limitations come also from some systematic errors induced by orbital perturbations of classical origin like, e.g., the secular precessions induced by the Sun and the oblateness of the Moon whose mismodelled parts are several times larger than the Lense-Thirring signal. The present analysis holds also for the Lue-Starkman perigee precession due to the multidimensional braneworld model by Dvali, Gabadadze and Porrati (DGP); indeed, it amounts to about 5 X 10^-3 milliarcseconds per year. |
2010.10142 | Benjamin Berczi | Benjamin Berczi, Paul M. Saffin, Shuang-Yong Zhou | Gravitational collapse with quantum fields | Updated version with new figures, accepted for publication to PRD, 6
pages, 4 figures | Phys. Rev. D 104, 041703 (2021) | 10.1103/PhysRevD.104.L041703 | USTC-ICTS/PCFT-20-34 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational collapse into a black hole has been extensively studied with
classical sources. We develop a new formalism to simulate quantum fields
forming a black hole. This formalism utilizes well-established techniques used
for classical collapse by choosing a convenient coherent state, and simulates
the matter fields quantum mechanically. Divergences are regularized with the
cosmological constant and Pauli-Villars fields. Using a massless spherically
symmetric scalar field as an example, we demonstrate the effectiveness of the
formalism by reproducing some classical results in gravitational collapse, and
identifying the difference due to quantum effects.
| [
{
"created": "Tue, 20 Oct 2020 09:15:33 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2020 16:03:51 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Aug 2021 09:26:53 GMT",
"version": "v3"
}
] | 2021-08-18 | [
[
"Berczi",
"Benjamin",
""
],
[
"Saffin",
"Paul M.",
""
],
[
"Zhou",
"Shuang-Yong",
""
]
] | Gravitational collapse into a black hole has been extensively studied with classical sources. We develop a new formalism to simulate quantum fields forming a black hole. This formalism utilizes well-established techniques used for classical collapse by choosing a convenient coherent state, and simulates the matter fields quantum mechanically. Divergences are regularized with the cosmological constant and Pauli-Villars fields. Using a massless spherically symmetric scalar field as an example, we demonstrate the effectiveness of the formalism by reproducing some classical results in gravitational collapse, and identifying the difference due to quantum effects. |
gr-qc/0002061 | Murat Ozer sci | Murat \"Ozer | Metric Unification of Gravitation and Electromagnetism Solves the
Cosmological Constant Problem | LaTex, 6 pages. An erroneous statement has been corrected | null | null | null | gr-qc astro-ph hep-ph | null | We first review the cosmological constant problem, and then mention a
conjecture of Feynman according to which the general relativistic theory of
gravity should be reformulated in such a way that energy does not couple to
gravity. We point out that our recent unification of gravitation and
electromagnetism through a symmetric tensor has the property that the free
electromagnetic energy and the vacuum energy do not contribute explicitly to
the curvature of spacetime just like the free gravitational energy. Therefore
in this formulation of general relativity, the vacuum energy density has its
very large value today as in the early universe, while the cosmological
constant does not exist at all.
| [
{
"created": "Thu, 17 Feb 2000 13:20:08 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Feb 2000 11:41:00 GMT",
"version": "v2"
},
{
"created": "Sat, 26 Feb 2000 17:03:35 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Özer",
"Murat",
""
]
] | We first review the cosmological constant problem, and then mention a conjecture of Feynman according to which the general relativistic theory of gravity should be reformulated in such a way that energy does not couple to gravity. We point out that our recent unification of gravitation and electromagnetism through a symmetric tensor has the property that the free electromagnetic energy and the vacuum energy do not contribute explicitly to the curvature of spacetime just like the free gravitational energy. Therefore in this formulation of general relativity, the vacuum energy density has its very large value today as in the early universe, while the cosmological constant does not exist at all. |
0802.3034 | Naresh Dadhich | Naresh Dadhich | Characterization of the Lovelock gravity by Bianchi derivative | Agrees with the published version | Pramana 74:875-882,2010 | 10.1007/s12043-010-0080-1 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove the theorem: The second order quasi-linear differential operator as
a second rank divergence free tensor in the equation of motion for gravitation
could always be derived from the trace of the Bianchi derivative of the fourth
rank tensor, which is a homogeneous polynomial in curvatures. The existence of
such a tensor for each term in the polynomial Lagrangian is a new
characterization of the Lovelock gravity.
| [
{
"created": "Thu, 21 Feb 2008 12:54:18 GMT",
"version": "v1"
},
{
"created": "Fri, 2 May 2008 06:59:42 GMT",
"version": "v2"
},
{
"created": "Wed, 24 Sep 2008 10:16:42 GMT",
"version": "v3"
},
{
"created": "Sun, 5 Oct 2008 12:09:23 GMT",
"version": "v4"
},
{
"cre... | 2011-04-07 | [
[
"Dadhich",
"Naresh",
""
]
] | We prove the theorem: The second order quasi-linear differential operator as a second rank divergence free tensor in the equation of motion for gravitation could always be derived from the trace of the Bianchi derivative of the fourth rank tensor, which is a homogeneous polynomial in curvatures. The existence of such a tensor for each term in the polynomial Lagrangian is a new characterization of the Lovelock gravity. |
1103.2238 | Lorenzo Iorio Dr. | Lorenzo Iorio | Orbital effects of non-isotropic mass depletion of the atmospheres of
evaporating hot Jupiters in extrasolar systems | LaTex2e, 16 pages, no tables, 6 figures. To appear in New Astronomy
(NA) | New Astron.17: 356-361,2012 | 10.1016/j.newast.2011.09.010 | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically and numerically investigate the long-term, i.e. averaged over
one full revolution, orbital effects of the non-isotropic percent mass loss
\dot m/m experienced by several transiting hot Jupiters whose atmospheres are
hit by severe radiations flows coming from their close parent stars. The
semi-major axis a, the argument of pericenter \omega and the mean anomaly M
experience net variations, while the eccentricity e, the inclination I and the
longitude of the ascending node remain unchanged, on average. In particular, a
increases independently of e and of the speed Vesc of the ejected mass. By
assuming |\dot m| <= 10^17 kg yr-1, corresponding to |\dot m/m| <= 10^-10 yr-1
for a Jupiter-like planet, it turns out \dot a = 2.5 m yr^-1 for orbits with a
= 0.05 au. Such an effect may play a role in the dynamical history of the hot
Jupiters, especially in connection with the still unresolved issue of the
arrest of the planetary inward migrations after a distance a >= 0.01 au is
reached. The retrograde pericenter variation depends, instead, on e and V_esc.
It may, in principle, act as a source of systematic uncertainty in some
proposed measurements of the general relativistic pericenter precession;
however, it turns out to be smaller than it by several orders of magnitude.
| [
{
"created": "Fri, 11 Mar 2011 10:42:34 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jun 2011 10:04:12 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Sep 2011 13:29:51 GMT",
"version": "v3"
}
] | 2015-03-19 | [
[
"Iorio",
"Lorenzo",
""
]
] | We analytically and numerically investigate the long-term, i.e. averaged over one full revolution, orbital effects of the non-isotropic percent mass loss \dot m/m experienced by several transiting hot Jupiters whose atmospheres are hit by severe radiations flows coming from their close parent stars. The semi-major axis a, the argument of pericenter \omega and the mean anomaly M experience net variations, while the eccentricity e, the inclination I and the longitude of the ascending node remain unchanged, on average. In particular, a increases independently of e and of the speed Vesc of the ejected mass. By assuming |\dot m| <= 10^17 kg yr-1, corresponding to |\dot m/m| <= 10^-10 yr-1 for a Jupiter-like planet, it turns out \dot a = 2.5 m yr^-1 for orbits with a = 0.05 au. Such an effect may play a role in the dynamical history of the hot Jupiters, especially in connection with the still unresolved issue of the arrest of the planetary inward migrations after a distance a >= 0.01 au is reached. The retrograde pericenter variation depends, instead, on e and V_esc. It may, in principle, act as a source of systematic uncertainty in some proposed measurements of the general relativistic pericenter precession; however, it turns out to be smaller than it by several orders of magnitude. |
0811.4238 | Qasem Exirifard | Qasem Exirifard (IPM) | Effectively Emergent Quantum Mechanics | 2 p | null | null | IPM/P-2008/063 | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider non minimal coupling between matters and gravity in modified
theories of gravity. In contrary to the current common sense, we report that
quantum mechanics can effectively emerge when the space-time geometry is
sufficiently flat. In other words, quantum mechanics might play no role when
and where the space-time geometry is highly curved.
We study the first two simple models of Effectively Emergent Quantum
Mechanics(EEQM): R-dependent EEQM and G-dependent EEQM where R is the Ricci
scalar and G is the Gauss-Bonnet Lagrangian density. We discuss that these EEQM
theories might be fine tuned to remain consistent with all the implemented
experiments and performed observations. In particular, we observe that
G-dependent EEQM softens the problem of quantum gravity.
| [
{
"created": "Wed, 26 Nov 2008 11:30:27 GMT",
"version": "v1"
}
] | 2008-11-27 | [
[
"Exirifard",
"Qasem",
"",
"IPM"
]
] | We consider non minimal coupling between matters and gravity in modified theories of gravity. In contrary to the current common sense, we report that quantum mechanics can effectively emerge when the space-time geometry is sufficiently flat. In other words, quantum mechanics might play no role when and where the space-time geometry is highly curved. We study the first two simple models of Effectively Emergent Quantum Mechanics(EEQM): R-dependent EEQM and G-dependent EEQM where R is the Ricci scalar and G is the Gauss-Bonnet Lagrangian density. We discuss that these EEQM theories might be fine tuned to remain consistent with all the implemented experiments and performed observations. In particular, we observe that G-dependent EEQM softens the problem of quantum gravity. |
2302.11935 | Robert Svarc | David Kofron, Michal Karamazov, Robert Svarc | An interpretation of spacetimes with expanding impulsive gravitational
waves generated by snapped cosmic strings | 26 pages, 22 figures. To be submitted | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The geometric properties of spacetimes representing expanding impulsive
gravitational waves, propagating on a flat background and generated by snapped
cosmic strings, are studied. The construction of the line element is reviewed,
and suitable forms of the string-generating complex mapping are derived for
various configurations such as previously studied examples of a pair of
snapping cosmic strings. Moreover, these mappings are related to the topology
of the flat half-space in front of the wave. Their understanding seems to be
crucial for further analysis of the global geometry, the relation between
half-spaces on both sides of the impulse, and the physical interpretation of,
in principle, observable effects. The spacetime structure is connected with the
motion of free test particles crossing the impulse, where the recent results
allow us to discuss their displacement and induced velocities that are caused
by the interaction with the expanding gravitational impulsive wave.
| [
{
"created": "Thu, 23 Feb 2023 11:31:59 GMT",
"version": "v1"
}
] | 2023-02-24 | [
[
"Kofron",
"David",
""
],
[
"Karamazov",
"Michal",
""
],
[
"Svarc",
"Robert",
""
]
] | The geometric properties of spacetimes representing expanding impulsive gravitational waves, propagating on a flat background and generated by snapped cosmic strings, are studied. The construction of the line element is reviewed, and suitable forms of the string-generating complex mapping are derived for various configurations such as previously studied examples of a pair of snapping cosmic strings. Moreover, these mappings are related to the topology of the flat half-space in front of the wave. Their understanding seems to be crucial for further analysis of the global geometry, the relation between half-spaces on both sides of the impulse, and the physical interpretation of, in principle, observable effects. The spacetime structure is connected with the motion of free test particles crossing the impulse, where the recent results allow us to discuss their displacement and induced velocities that are caused by the interaction with the expanding gravitational impulsive wave. |
1901.08516 | Ssohrab Borhanian | Ssohrab Borhanian, K.G. Arun, Harald P. Pfeiffer, B.S. Sathyaprakash | Comparison of post-Newtonian mode amplitudes with numerical relativity
simulations of binary black holes | 17 pages, 5 figures | Class. Quantum Grav. 37 065006 (2020) | 10.1088/1361-6382/ab6a21 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Gravitational waves from the coalescence of two black holes carry the
signature of the strong field dynamics of binary black holes. In this work we
have used numerical relativity simulations and post-Newtonian theory to
investigate this dynamics. Post-Newtonian theory is a low-velocity expansion
that assumes the companion bodies to be point-particles, while numerical
relativity treats black holes as extended objects with horizons and fully
captures their dynamics. There is a priori no reason for the waveforms computed
using these disparate methods to agree with each other, especially at late
times when the black holes move close to the speed of light. We find,
remarkably, that the leading order amplitudes in post-Newtonian theory agree
well with the full general relativity solution for a large set of spherical
harmonic modes, even in the most dynamical part of the binary evolution, with
only some modes showing distinctly different behavior than that found by
numerical relativity simulations. In particular, modes with spherical harmonic
indices l = m as well as l = 2, m = 1 are least modified from their dominant
post-Newtonian behavior. Understanding the nature of these modes in terms of
the post-Newtonian description will aid in formulating better models of the
emitted waveforms in the strong field regime of the dynamics.
| [
{
"created": "Thu, 24 Jan 2019 17:18:34 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jul 2020 16:46:52 GMT",
"version": "v2"
}
] | 2020-07-08 | [
[
"Borhanian",
"Ssohrab",
""
],
[
"Arun",
"K. G.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Sathyaprakash",
"B. S.",
""
]
] | Gravitational waves from the coalescence of two black holes carry the signature of the strong field dynamics of binary black holes. In this work we have used numerical relativity simulations and post-Newtonian theory to investigate this dynamics. Post-Newtonian theory is a low-velocity expansion that assumes the companion bodies to be point-particles, while numerical relativity treats black holes as extended objects with horizons and fully captures their dynamics. There is a priori no reason for the waveforms computed using these disparate methods to agree with each other, especially at late times when the black holes move close to the speed of light. We find, remarkably, that the leading order amplitudes in post-Newtonian theory agree well with the full general relativity solution for a large set of spherical harmonic modes, even in the most dynamical part of the binary evolution, with only some modes showing distinctly different behavior than that found by numerical relativity simulations. In particular, modes with spherical harmonic indices l = m as well as l = 2, m = 1 are least modified from their dominant post-Newtonian behavior. Understanding the nature of these modes in terms of the post-Newtonian description will aid in formulating better models of the emitted waveforms in the strong field regime of the dynamics. |
gr-qc/0508063 | Hirotaka Yoshino | Hirotaka Yoshino, Tetsuya Shiromizu, Masaru Shibata | Close-limit analysis for head-on collision of two black holes in higher
dimensions: Brill-Lindquist initial data | 27 pages, 8 figures, published version | Phys.Rev. D72 (2005) 084020 | 10.1103/PhysRevD.72.084020 | null | gr-qc hep-ph hep-th | null | Motivated by the TeV-scale gravity scenarios, we study gravitational
radiation in the head-on collision of two black holes in higher dimensional
spacetimes using a close-limit approximation. We prepare time-symmetric initial
data sets for two black holes (the so-called Brill-Lindquist initial data) and
numerically evolve the spacetime in terms of a gauge invariant formulation for
the perturbation around the higher-dimensional Schwarzschild black holes. The
waveform and radiated energy of gravitational waves emitted in the head-on
collision are clarified. Also, the complex frequencies of fundamental
quasinormal modes of higher-dimensional Schwarzschild black holes, which have
not been accurately derived so far, are determined.
| [
{
"created": "Tue, 16 Aug 2005 08:20:39 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Oct 2005 03:00:56 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Yoshino",
"Hirotaka",
""
],
[
"Shiromizu",
"Tetsuya",
""
],
[
"Shibata",
"Masaru",
""
]
] | Motivated by the TeV-scale gravity scenarios, we study gravitational radiation in the head-on collision of two black holes in higher dimensional spacetimes using a close-limit approximation. We prepare time-symmetric initial data sets for two black holes (the so-called Brill-Lindquist initial data) and numerically evolve the spacetime in terms of a gauge invariant formulation for the perturbation around the higher-dimensional Schwarzschild black holes. The waveform and radiated energy of gravitational waves emitted in the head-on collision are clarified. Also, the complex frequencies of fundamental quasinormal modes of higher-dimensional Schwarzschild black holes, which have not been accurately derived so far, are determined. |
0905.3517 | Mariano Cadoni | M. Cadoni, C. Monni | BPS-like bound and thermodynamics of the charged BTZ black hole | Two references and a footnote added | Phys.Rev.D80:024034,2009 | 10.1103/PhysRevD.80.024034 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The charged Banados-Teitelboim-Zanelli (BTZ) black hole is plagued by several
pathologies: a) Presence of divergent boundary terms in the action, hence of a
divergent black hole mass; b) Once a finite, renormalized, mass M is defined
black hole states exist for arbitrarily negative values of M; c) There is no
upper bound on the charge Q. We show that these pathological features are an
artifact of the renormalization procedure. They can be completely removed by
using an alternative renormalization scheme leading to a different definition
M_0 of the black hole mass, which is the total energy inside the horizon. The
new mass satisfies a BPS-like bound M_0\ge (\pi/2)Q^2 and the heat capacity of
the hole is positive. We also discuss the black hole thermodynamics that arises
when M_0 is interpreted as the internal energy of the system. We show, using
three independent approaches (black hole thermodynamics, Einstein equations,
Euclidean action formulation) that M_0 satisfies the first law if a term
describing the mechanical work done by the electrostatic pressure is
introduced.
| [
{
"created": "Thu, 21 May 2009 16:12:05 GMT",
"version": "v1"
},
{
"created": "Fri, 29 May 2009 07:33:50 GMT",
"version": "v2"
}
] | 2010-04-30 | [
[
"Cadoni",
"M.",
""
],
[
"Monni",
"C.",
""
]
] | The charged Banados-Teitelboim-Zanelli (BTZ) black hole is plagued by several pathologies: a) Presence of divergent boundary terms in the action, hence of a divergent black hole mass; b) Once a finite, renormalized, mass M is defined black hole states exist for arbitrarily negative values of M; c) There is no upper bound on the charge Q. We show that these pathological features are an artifact of the renormalization procedure. They can be completely removed by using an alternative renormalization scheme leading to a different definition M_0 of the black hole mass, which is the total energy inside the horizon. The new mass satisfies a BPS-like bound M_0\ge (\pi/2)Q^2 and the heat capacity of the hole is positive. We also discuss the black hole thermodynamics that arises when M_0 is interpreted as the internal energy of the system. We show, using three independent approaches (black hole thermodynamics, Einstein equations, Euclidean action formulation) that M_0 satisfies the first law if a term describing the mechanical work done by the electrostatic pressure is introduced. |
1806.00845 | James Edholm | James Edholm | Gravitational radiation in Infinite Derivative Gravity and connections
to Effective Quantum Gravity | 7 pages, accepted for publication in Physical Review D | Phys. Rev. D 98, 044049 (2018) | 10.1103/PhysRevD.98.044049 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hulse-Taylor binary provides possibly the best test of GR to date. We
find the modified quadrupole formula for Infinite Derivative Gravity (IDG). We
extend the backreaction formula for propagation of gravitational waves, found
previously for Effective Quantum Gravity (EQG) for a flat background and extend
this calculation to a de Sitter background for both EQG and IDG. We put tighter
constraints on EQG using new LIGO data. We also find the power emitted by a
binary system within the IDG framework for both circular and elliptical orbits
and use the example of the Hulse-Taylor binary. IDG predicts a slightly lower
power than GR, which is exactly the observed result. We also find a lower bound
on our mass scale of $M>4.0$ keV, which is $10^6$ larger than the previous
result.
| [
{
"created": "Sun, 3 Jun 2018 17:58:38 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jun 2018 18:06:09 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Jun 2018 14:54:38 GMT",
"version": "v3"
},
{
"created": "Sun, 19 Aug 2018 12:45:50 GMT",
"version": "v4"
}
] | 2018-09-12 | [
[
"Edholm",
"James",
""
]
] | The Hulse-Taylor binary provides possibly the best test of GR to date. We find the modified quadrupole formula for Infinite Derivative Gravity (IDG). We extend the backreaction formula for propagation of gravitational waves, found previously for Effective Quantum Gravity (EQG) for a flat background and extend this calculation to a de Sitter background for both EQG and IDG. We put tighter constraints on EQG using new LIGO data. We also find the power emitted by a binary system within the IDG framework for both circular and elliptical orbits and use the example of the Hulse-Taylor binary. IDG predicts a slightly lower power than GR, which is exactly the observed result. We also find a lower bound on our mass scale of $M>4.0$ keV, which is $10^6$ larger than the previous result. |
gr-qc/9507003 | Fred Dilkes | F.A. Dilkes (University of Western Ontario) | A Normal Coordinate Expansion for the Gauge Potential | LaTeX, 7 pages. Serious errors in the original version of this paper
demanded a significantly different (albeit somewhat trivial) approach. I
apologize for the errors | null | null | null | gr-qc hep-th | null | In this pedagogical note, I present a method for constructing a fully
covariant normal coordinate expansion of the gauge potential on a curved
space-time manifold. Although the content of this paper is elementary, the
results may prove useful in some applications and have not, to the best of my
knowledge, been discussed explicitly in the literature.
| [
{
"created": "Mon, 3 Jul 1995 20:48:05 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jul 1995 18:18:31 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Dilkes",
"F. A.",
"",
"University of Western Ontario"
]
] | In this pedagogical note, I present a method for constructing a fully covariant normal coordinate expansion of the gauge potential on a curved space-time manifold. Although the content of this paper is elementary, the results may prove useful in some applications and have not, to the best of my knowledge, been discussed explicitly in the literature. |
gr-qc/9408024 | null | D.H. Coule | Quantum cosmology and the value of $\Lambda$ | 10 pages Latex, University of Cape town | Mod.Phys.Lett. A10 (1995) 1989-1996 | 10.1142/S0217732395002131 | null | gr-qc | null | We analyse a simple model with just a $\Lambda$ term present. Differing
results are obtained depending on the boundary conditions applied. HH boundary
conditions give the factor exp(1/Lambda) but in agreement with Rubakov et al.
is badly behaved for negative lambda. Tunneling boundary conditions suggests a
large initial lambda. If only a Lorentzian region is considered all boundary
conditions suggest a large value of Lambda. This differs from the result of
Strominger for such models.
| [
{
"created": "Fri, 19 Aug 1994 15:56:54 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Coule",
"D. H.",
""
]
] | We analyse a simple model with just a $\Lambda$ term present. Differing results are obtained depending on the boundary conditions applied. HH boundary conditions give the factor exp(1/Lambda) but in agreement with Rubakov et al. is badly behaved for negative lambda. Tunneling boundary conditions suggests a large initial lambda. If only a Lorentzian region is considered all boundary conditions suggest a large value of Lambda. This differs from the result of Strominger for such models. |
0904.0961 | Richard Woodard | C. Deffayet (APC) and R. P. Woodard (U. Florida) | Reconstructing the Distortion Function for Nonlocal Cosmology | 17 pages, 1 figure, dedicated to Stanley Deser on the occasion of his
78th birthday, revised version for publication in JCAP | JCAP 0908:023,2009 | 10.1088/1475-7516/2009/08/023 | UFIFT-QG-08-07 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the cosmology of modified gravity models in which Newton's
constant is distorted by a function of the inverse d'Alembertian acting on the
Ricci scalar. We derive a technique for choosing the distortion function so as
to fit an arbitrary expansion history. This technique is applied numerically to
the case of LambdaCDM cosmology, and the result agrees well with a simple
hyperbolic tangent.
| [
{
"created": "Mon, 6 Apr 2009 16:21:15 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Aug 2009 11:42:47 GMT",
"version": "v2"
}
] | 2009-08-24 | [
[
"Deffayet",
"C.",
"",
"APC"
],
[
"Woodard",
"R. P.",
"",
"U. Florida"
]
] | We consider the cosmology of modified gravity models in which Newton's constant is distorted by a function of the inverse d'Alembertian acting on the Ricci scalar. We derive a technique for choosing the distortion function so as to fit an arbitrary expansion history. This technique is applied numerically to the case of LambdaCDM cosmology, and the result agrees well with a simple hyperbolic tangent. |
gr-qc/9605004 | Robert Mann | T. Ohta and R.B. Mann | Canonical reduction of two-dimensional gravity for Particle Dynamics | 21 pages, latex | Class.Quant.Grav. 13 (1996) 2585-2602 | 10.1088/0264-9381/13/9/022 | WATPHYS-TH96/05 | gr-qc | null | We develop the formalism for canonical reduction of $(1+1)$--dimensional
gravity coupled with a set of point particles by eliminating constraints and
imposing coordinate conditions. The formalism itself is quite analogous to the
$(3+1)$--dimensional case; however in $(1+1)$ dimensions an auxiliary scalar
field is shown to have an important role. The reduced Hamiltonian is expressed
as a form of spatial integral of the second derivative of the scalar field.
Since in $(1+1)$ dimensions there exists no dynamical degree of freedom of the
gravitational field ({\it i.e.} the transverse-traceless part of the metric
tensor is zero), the reduced Hamiltonian is completely determined in terms of
the particles' canonical variables (coordinates and momenta). The explicit form
of the Hamiltonian is calculated both in post-linear and post-Newtonian
approximations.
| [
{
"created": "Wed, 1 May 1996 18:13:26 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Ohta",
"T.",
""
],
[
"Mann",
"R. B.",
""
]
] | We develop the formalism for canonical reduction of $(1+1)$--dimensional gravity coupled with a set of point particles by eliminating constraints and imposing coordinate conditions. The formalism itself is quite analogous to the $(3+1)$--dimensional case; however in $(1+1)$ dimensions an auxiliary scalar field is shown to have an important role. The reduced Hamiltonian is expressed as a form of spatial integral of the second derivative of the scalar field. Since in $(1+1)$ dimensions there exists no dynamical degree of freedom of the gravitational field ({\it i.e.} the transverse-traceless part of the metric tensor is zero), the reduced Hamiltonian is completely determined in terms of the particles' canonical variables (coordinates and momenta). The explicit form of the Hamiltonian is calculated both in post-linear and post-Newtonian approximations. |
1010.1630 | Valter Moretti | Valter Moretti (Trento University) | Local $\zeta$-functions, stress-energy tensor, field fluctuations, and
all that, in curved static spacetime | LaTeX 10 Pages. Submitted to the volume "Cosmology, Quantum Vacuum,
and Zeta Functions", in honour of Professor Emilio Elizalde on the occasion
of his 60th birthday | Springer Proc.Phys.137:323-332,2011 | 10.1007/978-3-642-19760-4_30 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a quick review on some technology concerning the local zeta function
applied to Quantum Field Theory in curved static (thermal) spacetime to
regularize the stress-energy tensor and the field fluctuations.
| [
{
"created": "Fri, 8 Oct 2010 08:42:00 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Moretti",
"Valter",
"",
"Trento University"
]
] | This is a quick review on some technology concerning the local zeta function applied to Quantum Field Theory in curved static (thermal) spacetime to regularize the stress-energy tensor and the field fluctuations. |
2402.00141 | Yuri Bonder | J.E. Herrera and Y. Bonder | Unimodular gravity as an initial value problem | 8+1 pages. Accepted in PRD | Phys. Rev. D 109, 104025 (2024) | 10.1103/PhysRevD.109.104025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unimodular gravity is a compelling modified theory of gravity that offers a
natural solution to the cosmological constant problem. However, for unimodular
gravity to be considered a viable theory of gravity, one has to show that it
has a well-posed initial value formulation. Working in vacuum, we apply Dirac's
algorithm to find all the constraints of the theory. Then we prove that, for
initial data compatible with these constraints, the evolution is well posed.
Finally, we find sufficient conditions for a matter action to preserve the
well-posedness of the initial value problem of unimodular gravity. As a
corollary, we argue that the "unimodular" restriction on the spacetime volume
element can be satisfied by a suitable choice of the lapse function.
| [
{
"created": "Wed, 31 Jan 2024 19:37:34 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2024 19:32:54 GMT",
"version": "v2"
},
{
"created": "Tue, 30 Apr 2024 15:12:06 GMT",
"version": "v3"
}
] | 2024-05-10 | [
[
"Herrera",
"J. E.",
""
],
[
"Bonder",
"Y.",
""
]
] | Unimodular gravity is a compelling modified theory of gravity that offers a natural solution to the cosmological constant problem. However, for unimodular gravity to be considered a viable theory of gravity, one has to show that it has a well-posed initial value formulation. Working in vacuum, we apply Dirac's algorithm to find all the constraints of the theory. Then we prove that, for initial data compatible with these constraints, the evolution is well posed. Finally, we find sufficient conditions for a matter action to preserve the well-posedness of the initial value problem of unimodular gravity. As a corollary, we argue that the "unimodular" restriction on the spacetime volume element can be satisfied by a suitable choice of the lapse function. |
gr-qc/0404070 | Simonetta Frittelli | Simonetta Frittelli (Duquesne University) and Roberto Gomez
(Pittsburgh Supercomputing Center) | Einstein boundary conditions for the Einstein equations in the
conformal-traceless decomposition | 11 pages | Phys.Rev. D70 (2004) 064008 | 10.1103/PhysRevD.70.064008 | null | gr-qc | null | In relation to the BSSN formulation of the Einstein equations, we write down
the boundary conditions that result from the vanishing of the projection of the
Einstein tensor normally to a timelike hypersurface. Furthermore, by setting up
a well-posed system of propagation equations for the constraints, we show
explicitly that there are three constraints that are incoming at the boundary
surface and that the boundary equations are linearly related to them. This
indicates that such boundary conditions play a role in enforcing the
propagation of the constraints in the region interior to the boundary.
Additionally, we examine the related problem for a strongly hyperbolic
first-order reduction of the BSSN equations and determine the characteristic
fields that are prescribed by the three boundary conditions, as well as those
that are left arbitrary.
| [
{
"created": "Fri, 16 Apr 2004 14:04:11 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Frittelli",
"Simonetta",
"",
"Duquesne University"
],
[
"Gomez",
"Roberto",
"",
"Pittsburgh Supercomputing Center"
]
] | In relation to the BSSN formulation of the Einstein equations, we write down the boundary conditions that result from the vanishing of the projection of the Einstein tensor normally to a timelike hypersurface. Furthermore, by setting up a well-posed system of propagation equations for the constraints, we show explicitly that there are three constraints that are incoming at the boundary surface and that the boundary equations are linearly related to them. This indicates that such boundary conditions play a role in enforcing the propagation of the constraints in the region interior to the boundary. Additionally, we examine the related problem for a strongly hyperbolic first-order reduction of the BSSN equations and determine the characteristic fields that are prescribed by the three boundary conditions, as well as those that are left arbitrary. |
2210.16699 | A. Emrah Y\"ukselci | A. Sava\c{s} Arapo\u{g}lu and A. Emrah Y\"ukselci | The Effect of Non-minimally Coupled Scalar Field on Gravitational Waves
from First-order Vacuum Phase Transitions | 18 pages, 8 figures, appendix added, typos corrected, matches with
the published version | Physics of the Dark Universe 40 (2023) 101176 | 10.1016/j.dark.2023.101176 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate first-order vacuum phase transitions in the presence of a
non-minimally coupled scalar field starting with the coupling effect on the
initial dynamics of phase transitions by defining an effective potential for
the scalar field and then performing three dimensional numerical simulations to
observe any possible distinction in gravitational wave power spectrum. Although
we give a description of the model with the expanding background, in this
particular paper, we exclude the scale factor contribution since we primarily
focus on the immediate impact of the non-minimal coupling at initial phases of
the transition. Even in this case we found that this modification has
discernible effect on the power spectrum of the gravitational wave energy
density.
| [
{
"created": "Sat, 29 Oct 2022 22:08:13 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Feb 2023 21:21:38 GMT",
"version": "v2"
}
] | 2023-02-06 | [
[
"Arapoğlu",
"A. Savaş",
""
],
[
"Yükselci",
"A. Emrah",
""
]
] | We investigate first-order vacuum phase transitions in the presence of a non-minimally coupled scalar field starting with the coupling effect on the initial dynamics of phase transitions by defining an effective potential for the scalar field and then performing three dimensional numerical simulations to observe any possible distinction in gravitational wave power spectrum. Although we give a description of the model with the expanding background, in this particular paper, we exclude the scale factor contribution since we primarily focus on the immediate impact of the non-minimal coupling at initial phases of the transition. Even in this case we found that this modification has discernible effect on the power spectrum of the gravitational wave energy density. |
gr-qc/0109079 | Pio J. Arias | Rolando Gaitan (Universidad de Carabobo, Venezuela) | A possible gauge formulation for gravity? | 10 pages, LaTex, to appear in Ciencia 9 (2001), Julio-Septiembre.
More references added | null | null | null | gr-qc | null | A possible Yang-Mills like lagrangian formulation for gravity is explored.
The starting point consists on two next assumptions. First, the metric is
assumed as a real map from a given gauge group. Second, a gauge invariant
lagrangian density is considered with the condition that it is related to the
Einstein one up to a bound term. We study a stationary solution of the abelian
case for the spherical symmetry, which is connected to the M\"oller's Maxwell
like formulation for gravity. Finally, it is showed the consistence of this
formulation with the Newtonian limit.
| [
{
"created": "Sat, 22 Sep 2001 02:36:54 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Oct 2001 03:06:33 GMT",
"version": "v2"
},
{
"created": "Sun, 14 Oct 2001 16:29:11 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Gaitan",
"Rolando",
"",
"Universidad de Carabobo, Venezuela"
]
] | A possible Yang-Mills like lagrangian formulation for gravity is explored. The starting point consists on two next assumptions. First, the metric is assumed as a real map from a given gauge group. Second, a gauge invariant lagrangian density is considered with the condition that it is related to the Einstein one up to a bound term. We study a stationary solution of the abelian case for the spherical symmetry, which is connected to the M\"oller's Maxwell like formulation for gravity. Finally, it is showed the consistence of this formulation with the Newtonian limit. |
2206.09729 | Zhi Luo | Zhi Luo, Hao Yu, Jin Li | Effects of a global monopole on thermodynamic phase transition of the
charged AdS black hole | 21 pages, 7 figures, 1 table | null | 10.1088/1674-1137/ac878b | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the dynamical properties of thermodynamic phase
transition (PT) for the charged AdS black hole (BH) with a global monopole via
the Gibbs free energy landscape and reveal the effects of a global monopole on
the kinetics of the AdS BH thermodynamic PT. First, we briefly review the
thermodynamics of the charged AdS BH with a global monopole. Then, we introduce
the Gibbs free energy landscape to study the thermodynamic stability of the BH
state. Because of thermal fluctuations, the small black hole (SBH) state can
transit to the large black hole (LBH) state, and vice versa. We use the
Fokker-Planck equation with the reflecting boundary condition to study the
probability evolution of the BH state with and without a global monopole
separately. We find that for both the SBH and LBH states, the global monopole
could slow down the evolution of the BH state. In addition, we obtain the
relationship between the first passage time and the monopole parameter $\eta$.
The result shows that as the monopole parameter $\eta$ increases, the mean
first passage time will be longer for both the SBH and LBH states.
| [
{
"created": "Mon, 20 Jun 2022 12:01:30 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Luo",
"Zhi",
""
],
[
"Yu",
"Hao",
""
],
[
"Li",
"Jin",
""
]
] | In this paper, we study the dynamical properties of thermodynamic phase transition (PT) for the charged AdS black hole (BH) with a global monopole via the Gibbs free energy landscape and reveal the effects of a global monopole on the kinetics of the AdS BH thermodynamic PT. First, we briefly review the thermodynamics of the charged AdS BH with a global monopole. Then, we introduce the Gibbs free energy landscape to study the thermodynamic stability of the BH state. Because of thermal fluctuations, the small black hole (SBH) state can transit to the large black hole (LBH) state, and vice versa. We use the Fokker-Planck equation with the reflecting boundary condition to study the probability evolution of the BH state with and without a global monopole separately. We find that for both the SBH and LBH states, the global monopole could slow down the evolution of the BH state. In addition, we obtain the relationship between the first passage time and the monopole parameter $\eta$. The result shows that as the monopole parameter $\eta$ increases, the mean first passage time will be longer for both the SBH and LBH states. |
2010.07196 | Alexander Petrov Nikolaevich | A. N. Petrov | Conserved quantities for black hole solutions in pure Lovelock gravity | 34 pages | null | 10.1088/1361-6382/ac0e18 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct conserved quantities in pure Lovelock gravity for both static
and dynamic Vaydia-type black holes with AdS, dS and flat asymptotics, applying
field-theoretical formalism developed earlier. Global energy (where
applicable), quasi-local energy together with fluxes of these quantities are
presented for both types of black holes, considering asymptotic spacetime as
background. The same quantities are constructed for dynamic black holes on the
background of the related static black holes. Besides, for the dynamic black
holes, energy densities and densities of energy flux are calculated in the
frame of freely and radially falling observer on the background of the related
static black holes. All the constructed energetic characteristics are analyzed
and discussed in detail.
| [
{
"created": "Wed, 14 Oct 2020 16:08:01 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Oct 2020 08:36:32 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Jun 2021 14:32:28 GMT",
"version": "v3"
}
] | 2021-06-25 | [
[
"Petrov",
"A. N.",
""
]
] | We construct conserved quantities in pure Lovelock gravity for both static and dynamic Vaydia-type black holes with AdS, dS and flat asymptotics, applying field-theoretical formalism developed earlier. Global energy (where applicable), quasi-local energy together with fluxes of these quantities are presented for both types of black holes, considering asymptotic spacetime as background. The same quantities are constructed for dynamic black holes on the background of the related static black holes. Besides, for the dynamic black holes, energy densities and densities of energy flux are calculated in the frame of freely and radially falling observer on the background of the related static black holes. All the constructed energetic characteristics are analyzed and discussed in detail. |
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