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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0704.0048 | Alexander Stroeer | Alexander Stroeer, John Veitch, Christian Roever, Ed Bloomer, James
Clark, Nelson Christensen, Martin Hendry, Chris Messenger, Renate Meyer,
Matthew Pitkin, Jennifer Toher, Richard Umstaetter, Alberto Vecchio and
Graham Woan | Inference on white dwarf binary systems using the first round Mock LISA
Data Challenges data sets | GWDAW-11 proceeding, submitted to CQG, 10 pages, 3 figures, 1 table;
revised values in table | Class.Quant.Grav.24:S541-S550,2007 | 10.1088/0264-9381/24/19/S17 | null | gr-qc astro-ph | null | We report on the analysis of selected single source data sets from the first
round of the Mock LISA Data Challenges (MLDC) for white dwarf binaries. We
implemented an end-to-end pipeline consisting of a grid-based coherent
pre-processing unit for signal detection, and an automatic Markov Chain Monte
Carlo post-processing unit for signal evaluation. We demonstrate that signal
detection with our coherent approach is secure and accurate, and is increased
in accuracy and supplemented with additional information on the signal
parameters by our Markov Chain Monte Carlo approach. We also demonstrate that
the Markov Chain Monte Carlo routine is additionally able to determine
accurately the noise level in the frequency window of interest.
| [
{
"created": "Sat, 31 Mar 2007 19:17:47 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Apr 2007 22:26:37 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Stroeer",
"Alexander",
""
],
[
"Veitch",
"John",
""
],
[
"Roever",
"Christian",
""
],
[
"Bloomer",
"Ed",
""
],
[
"Clark",
"James",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Hendry",
"Martin",
""
],
[
"Messenger",
"Chris",
""
],
[
"Meyer",
"Renate",
""
],
[
"Pitkin",
"Matthew",
""
],
[
"Toher",
"Jennifer",
""
],
[
"Umstaetter",
"Richard",
""
],
[
"Vecchio",
"Alberto",
""
],
[
"Woan",
"Graham",
""
]
] | We report on the analysis of selected single source data sets from the first round of the Mock LISA Data Challenges (MLDC) for white dwarf binaries. We implemented an end-to-end pipeline consisting of a grid-based coherent pre-processing unit for signal detection, and an automatic Markov Chain Monte Carlo post-processing unit for signal evaluation. We demonstrate that signal detection with our coherent approach is secure and accurate, and is increased in accuracy and supplemented with additional information on the signal parameters by our Markov Chain Monte Carlo approach. We also demonstrate that the Markov Chain Monte Carlo routine is additionally able to determine accurately the noise level in the frequency window of interest. |
2407.03775 | Orlando Luongo | Alessio Belfiglio, S. Mahesh Chandran, Orlando Luongo, Stefano Mancini | Horizon entanglement area law from regular black hole thermodynamics | 14 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the thermodynamics of regular black hole configurations via
quantum analogs of entropy and energy -- namely, the entanglement entropy and
entanglement energy -- near the event horizon of Bardeen and Hayward black
holes. Following standard approaches, we introduce a quantum scalar field
propagating in such black hole spacetimes and discretize the field degrees of
freedom on a lattice of spherical shells. We observe that, at leading order,
the entanglement entropy associated with the scalar field is proportional to
Bekestein-Hawking entropy, while the corresponding entanglement energy scales
proportionally to Komar energy. We then compute the heat capacity in both
scenarios, discussing the black hole stability conditions and the possible
appearance of second-order phase transitions. Finally, we extend our analysis
to the black hole core, showing that in this sector entanglement energy serves
as a valuable tool towards discriminating between singular and regular
solutions.
| [
{
"created": "Thu, 4 Jul 2024 09:34:41 GMT",
"version": "v1"
}
] | 2024-07-08 | [
[
"Belfiglio",
"Alessio",
""
],
[
"Chandran",
"S. Mahesh",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Mancini",
"Stefano",
""
]
] | We investigate the thermodynamics of regular black hole configurations via quantum analogs of entropy and energy -- namely, the entanglement entropy and entanglement energy -- near the event horizon of Bardeen and Hayward black holes. Following standard approaches, we introduce a quantum scalar field propagating in such black hole spacetimes and discretize the field degrees of freedom on a lattice of spherical shells. We observe that, at leading order, the entanglement entropy associated with the scalar field is proportional to Bekestein-Hawking entropy, while the corresponding entanglement energy scales proportionally to Komar energy. We then compute the heat capacity in both scenarios, discussing the black hole stability conditions and the possible appearance of second-order phase transitions. Finally, we extend our analysis to the black hole core, showing that in this sector entanglement energy serves as a valuable tool towards discriminating between singular and regular solutions. |
1209.3567 | Nami Uchikata | Nami Uchikata, Shijun Yoshida, and Toshifumi Futamase | New solutions of charged regular black holes and their stability | 11 pages, 8 figures, to be published in Physical Review D | null | 10.1103/PhysRevD.86.084025 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct new regular black hole solutions by matching the de Sitter
solution and the Reissner-Nordstrom solution with a timelike thin shell. The
thin shell is assumed to have mass but no pressure and obeys an equation of
motion derived from Israel's junction conditions. By investigating the equation
of motion for the shell, we obtain stationary solutions of charged regular
black holes and examine stability of the solutions. Stationary solutions are
found in limited ranges of 0.87L < m < 1.99L, and they are stable against small
radial displacement of the shell with fixed values of m, M, and Q if M>0, where
L is the de Sitter horizon radius, m the black hole mass, M the proper mass of
the shell and Q the black hole charge. All the solutions obtained are highly
charged in the sense of Q/m >0.866. By taking the massless limit of the shell
in the present regular black hole solutions, we obtain the charged regular
black hole with a massless shell obtained by Lemos and Zanchin and investigate
stability of the solutions. It is found that Lemos and Zanchin's regular black
hole solutions given by the massless limit of the present regular black hole
solutions permit stable solutions, which are obtained by the limit of M -> 0.
| [
{
"created": "Mon, 17 Sep 2012 07:46:13 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Uchikata",
"Nami",
""
],
[
"Yoshida",
"Shijun",
""
],
[
"Futamase",
"Toshifumi",
""
]
] | We construct new regular black hole solutions by matching the de Sitter solution and the Reissner-Nordstrom solution with a timelike thin shell. The thin shell is assumed to have mass but no pressure and obeys an equation of motion derived from Israel's junction conditions. By investigating the equation of motion for the shell, we obtain stationary solutions of charged regular black holes and examine stability of the solutions. Stationary solutions are found in limited ranges of 0.87L < m < 1.99L, and they are stable against small radial displacement of the shell with fixed values of m, M, and Q if M>0, where L is the de Sitter horizon radius, m the black hole mass, M the proper mass of the shell and Q the black hole charge. All the solutions obtained are highly charged in the sense of Q/m >0.866. By taking the massless limit of the shell in the present regular black hole solutions, we obtain the charged regular black hole with a massless shell obtained by Lemos and Zanchin and investigate stability of the solutions. It is found that Lemos and Zanchin's regular black hole solutions given by the massless limit of the present regular black hole solutions permit stable solutions, which are obtained by the limit of M -> 0. |
1905.08648 | Ritabrata Biswas | Amritendu Haldar and Ritabrata Biswas | Thermodynamics of $d$-Dimensional Charged AdS (Anti-de Sitter) Black
Holes: Hamiltonian Approach and Clapeyron Equation | 16 pages, 9 figures | Modern Physics Letters A Modern Physics Letters A Vol. 34 (2019)
1950170 | 10.1142/S0217732319501700 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The study of thermodynamics in the view of the Hamiltonian approach is a
newest tool to analyze the thermodynamic properties of the black holes. In this
letter, we investigate the thermodynamics of $d$-dimensional ($d>3$)
asymptotically AntideSitter black holes. A thermodynamic representation based
on symplectic geometry is introduced in this letter. We extend the
thermodynamics of $d-$dimensional charged AntideSitter black holes in the views
of a Hamiltonian approach. Firstly, we study the thermodynamics in reduced
phase space and correlate with the Schwarzschild solution. Then we enhance it
in the extended phase space. In an extended phase space the thermodynamic
equations of state are stated as constraints. We apply the canonical
transformation to analyze the thermodynamics of said type of black holes. We
plot $P$-$v$ diagrams for different dimensions $d$ taking the temperatures
$T<T_c, T=T_c $ and $T>T_c$ and analyze the natures of the graphs and the
dependencies on $d$. In theses diagrams, we point out the regions of
coexistence. We also examine the phase transition by applying "Maxwell's equal
area law" of the said black holes. Here we find the regions of coexistence of
two phases which are also depicted graphically. Finally, we derive the
"Clapeyron equation" and investigate the latent heat of isothermal phase
transition.
| [
{
"created": "Sun, 19 May 2019 14:19:19 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Haldar",
"Amritendu",
""
],
[
"Biswas",
"Ritabrata",
""
]
] | The study of thermodynamics in the view of the Hamiltonian approach is a newest tool to analyze the thermodynamic properties of the black holes. In this letter, we investigate the thermodynamics of $d$-dimensional ($d>3$) asymptotically AntideSitter black holes. A thermodynamic representation based on symplectic geometry is introduced in this letter. We extend the thermodynamics of $d-$dimensional charged AntideSitter black holes in the views of a Hamiltonian approach. Firstly, we study the thermodynamics in reduced phase space and correlate with the Schwarzschild solution. Then we enhance it in the extended phase space. In an extended phase space the thermodynamic equations of state are stated as constraints. We apply the canonical transformation to analyze the thermodynamics of said type of black holes. We plot $P$-$v$ diagrams for different dimensions $d$ taking the temperatures $T<T_c, T=T_c $ and $T>T_c$ and analyze the natures of the graphs and the dependencies on $d$. In theses diagrams, we point out the regions of coexistence. We also examine the phase transition by applying "Maxwell's equal area law" of the said black holes. Here we find the regions of coexistence of two phases which are also depicted graphically. Finally, we derive the "Clapeyron equation" and investigate the latent heat of isothermal phase transition. |
2012.02348 | Joshua Foo | Joshua Foo, Michael R.R. Good, Robert B. Mann | Analog Particle Production Model for General Classes of Taub-NUT Black
Holes | 9+3 pages, 14 figures | Universe 2021, 7(9), 350 | 10.3390/universe7090350 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We derive a correspondence between the Hawking radiation spectra emitted from
general classes of Taub-NUT black holes with that induced by the relativistic
motion of an accelerated Dirichlet boundary condition (i.e.\ a perfectly
reflecting mirror) in (1+1)-dimensional flat spacetime. We demonstrate that the
particle and energy spectra is thermal at late-times and that particle
production is suppressed by the NUT parameter. We also compute the radiation
spectrum in the rotating, electrically charged (Kerr-Newman) Taub-NUT scenario,
and the extremal case, showing explicitly how these parameters affect the
outgoing particle and energy fluxes.
| [
{
"created": "Fri, 4 Dec 2020 00:57:29 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Nov 2021 22:36:35 GMT",
"version": "v2"
}
] | 2021-11-17 | [
[
"Foo",
"Joshua",
""
],
[
"Good",
"Michael R. R.",
""
],
[
"Mann",
"Robert B.",
""
]
] | We derive a correspondence between the Hawking radiation spectra emitted from general classes of Taub-NUT black holes with that induced by the relativistic motion of an accelerated Dirichlet boundary condition (i.e.\ a perfectly reflecting mirror) in (1+1)-dimensional flat spacetime. We demonstrate that the particle and energy spectra is thermal at late-times and that particle production is suppressed by the NUT parameter. We also compute the radiation spectrum in the rotating, electrically charged (Kerr-Newman) Taub-NUT scenario, and the extremal case, showing explicitly how these parameters affect the outgoing particle and energy fluxes. |
1704.02280 | Majid Abdollahi Zadeh | M. Abdollahi Zadeh, A. Sheykhi, H. Moradpour | Ghost dark energy with sign-changeable interaction term | 15 pages, 16 figures | Int J Theor Phys 56 (2017) 3477 | 10.1007/s10773-017-3513-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Regarding the Veneziano ghost of QCD and its generalized form, we consider a
Friedmann-Robertson-Walker (FRW) universe filled by a pressureless matter and a
dark energy component interacting with each other through a mutual
sign-changeable interaction of positive coupling constant. Our study shows
that, at the late time, for the deceleration parameter we have
$q\rightarrow-1$, while the equation of state parameter of the interacting
ghost dark energy (GDE) does not cross the phantom line, namely
$\omega_D\geq-1$. We also extend our study to the generalized ghost dark energy
(GGDE) model and show that, at late time, the equation of state parameter of
the interacting GGDE also respects the phantom line in both flat and non-flat
universes. Moreover, we find out that, unlike the non-flat universe, we have
$q\rightarrow-1$ at late time for flat FRW universe. In order to make the
behavior of the underlying models more clear, the deceleration parameter $q$ as
well as the equation of state parameter $w_D$ for flat and closed universes
have been plotted against the redshift parameter, $z$. All of the studied cases
admit a transition in the expansion history of universe from a deceleration
phase to an accelerated one around $z\approx 0.6$
| [
{
"created": "Fri, 7 Apr 2017 16:22:55 GMT",
"version": "v1"
}
] | 2018-04-10 | [
[
"Zadeh",
"M. Abdollahi",
""
],
[
"Sheykhi",
"A.",
""
],
[
"Moradpour",
"H.",
""
]
] | Regarding the Veneziano ghost of QCD and its generalized form, we consider a Friedmann-Robertson-Walker (FRW) universe filled by a pressureless matter and a dark energy component interacting with each other through a mutual sign-changeable interaction of positive coupling constant. Our study shows that, at the late time, for the deceleration parameter we have $q\rightarrow-1$, while the equation of state parameter of the interacting ghost dark energy (GDE) does not cross the phantom line, namely $\omega_D\geq-1$. We also extend our study to the generalized ghost dark energy (GGDE) model and show that, at late time, the equation of state parameter of the interacting GGDE also respects the phantom line in both flat and non-flat universes. Moreover, we find out that, unlike the non-flat universe, we have $q\rightarrow-1$ at late time for flat FRW universe. In order to make the behavior of the underlying models more clear, the deceleration parameter $q$ as well as the equation of state parameter $w_D$ for flat and closed universes have been plotted against the redshift parameter, $z$. All of the studied cases admit a transition in the expansion history of universe from a deceleration phase to an accelerated one around $z\approx 0.6$ |
2407.19738 | Vishva Patel | Divyesh P. Viththani (1), Tapobroto Bhanja (1), Vishva Patel (1) and
Pankaj S. Joshi (2) ((1) PDPIAS, Charusat University, Anand, Guj, India, (2)
International Centre for Space and Cosmology, Ahmedabad University,
Ahmedabad, GUJ, India) | Magnetic Penrose Process and Kerr Black Hole Mimickers | 12 pages, 5 figures and 2 tables (comments are welcome!) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The present study investigates the negative energy orbits and energy
extraction efficiency using the magnetic Penrose process in various regular
black hole geometries surrounded by electromagnetic fields. Utilizing numerical
simulations, we analyze the efficiency of this process in Kerr and
Simpson-Visser geometries, focusing on extremal black holes. Interestingly, our
study demonstrates that the energy extraction efficiency remains
indistinguishable between Kerr and Simpson-Visser geometries, regardless of the
regularization parameter ($l$); this trend is consistent with previous studies
of the Penrose process and superradiance. Additionally, we present results for
the rotating Hayward black hole, showing that efficiency is influenced by spin
and deviation parameters ($g$), as well as the induced magnetic field and
charge of the compact object. Notably, we observe that energy extraction
efficiency is highest in the rotating Hayward black hole compared to Kerr and
Simpson-Visser geometries, particularly in scenarios where the magnetic field
and charge are minimal. Our study highlights the significant role of spin,
charge and magnetic field characteristics in maximizing energy extraction
efficiency, particularly in the rotating Hayward black hole context.
| [
{
"created": "Mon, 29 Jul 2024 07:02:37 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Viththani",
"Divyesh P.",
""
],
[
"Bhanja",
"Tapobroto",
""
],
[
"Patel",
"Vishva",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | The present study investigates the negative energy orbits and energy extraction efficiency using the magnetic Penrose process in various regular black hole geometries surrounded by electromagnetic fields. Utilizing numerical simulations, we analyze the efficiency of this process in Kerr and Simpson-Visser geometries, focusing on extremal black holes. Interestingly, our study demonstrates that the energy extraction efficiency remains indistinguishable between Kerr and Simpson-Visser geometries, regardless of the regularization parameter ($l$); this trend is consistent with previous studies of the Penrose process and superradiance. Additionally, we present results for the rotating Hayward black hole, showing that efficiency is influenced by spin and deviation parameters ($g$), as well as the induced magnetic field and charge of the compact object. Notably, we observe that energy extraction efficiency is highest in the rotating Hayward black hole compared to Kerr and Simpson-Visser geometries, particularly in scenarios where the magnetic field and charge are minimal. Our study highlights the significant role of spin, charge and magnetic field characteristics in maximizing energy extraction efficiency, particularly in the rotating Hayward black hole context. |
gr-qc/9805075 | Diego Torres | Diego F. Torres, Gustavo E. Romero and Luis A. Anchordoqui | Wormholes, Gamma Ray Bursts and the Amount of Negative Mass in the
Universe | Essay awarded ``Honorable Mention'' in the Gravity Foundation
Research Awards, 1998 | Mod.Phys.Lett.A13:1575-1582,1998 | 10.1142/S0217732398001650 | null | gr-qc | null | In this essay, we assume that negative mass objects can exist in the
extragalactic space and analyze the consequences of their microlensing on light
from distant Active Galactic Nuclei. We find that such events have very similar
features to some observed Gamma Ray Bursts and use recent satellite data to set
an upper bound to the amount of negative mass in the universe.
| [
{
"created": "Tue, 19 May 1998 16:36:31 GMT",
"version": "v1"
}
] | 2010-12-03 | [
[
"Torres",
"Diego F.",
""
],
[
"Romero",
"Gustavo E.",
""
],
[
"Anchordoqui",
"Luis A.",
""
]
] | In this essay, we assume that negative mass objects can exist in the extragalactic space and analyze the consequences of their microlensing on light from distant Active Galactic Nuclei. We find that such events have very similar features to some observed Gamma Ray Bursts and use recent satellite data to set an upper bound to the amount of negative mass in the universe. |
gr-qc/9911077 | Angelo Loinger | A.Loinger (Dipartimento di Fisica, Universita' di Milano, Italy) | On Kerr's corpuscle | 4 pages, PDF from MS-Word97, submitted to Il Nuovo Cimento, Section
B, pag.1 first row after eq.(1): replaced "a and r are nonnegative
parameters" with "a and M are nonnegative parameters" | null | null | null | gr-qc astro-ph | null | Simple changes of the radial co-ordinate deprive Kerr's spinning corpuscle of
its marvellous properties.
| [
{
"created": "Sat, 20 Nov 1999 13:38:20 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jan 2000 09:44:35 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Loinger",
"A.",
"",
"Dipartimento di Fisica, Universita' di Milano, Italy"
]
] | Simple changes of the radial co-ordinate deprive Kerr's spinning corpuscle of its marvellous properties. |
gr-qc/0503068 | Yury Eroshenko | Victor Berezin, Vyacheslav Dokuchaev, Yury Eroshenko, Alexei Smirnov | Phantom shell around black hole and global geometry | null | Class.Quant.Grav. 22 (2005) 4443-4456 | 10.1088/0264-9381/22/21/003 | null | gr-qc | null | We describe the possible scenarios for the evolution of a thin spherically
symmetric self-gravitating phantom shell around the Schwarzschild black hole.
The general equations describing the motion of the shell with a general form of
equation of state are derived and analyzed. The different types of space-time
R- and T-regions and shell motion are classified depending on the parameters of
the problem. It is shown that in the case of a positive shell mass there exist
three scenarios for the shell evolution with an infinite motion and two
distinctive types of collapse. Analogous scenarios were classified for the case
of a negative shell mass. In particular this classification shows that it is
impossible for the physical observer to detect the fantom energy flow. We
shortly discuss the importance of our results for astrophysical applications.
| [
{
"created": "Wed, 16 Mar 2005 14:27:51 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Berezin",
"Victor",
""
],
[
"Dokuchaev",
"Vyacheslav",
""
],
[
"Eroshenko",
"Yury",
""
],
[
"Smirnov",
"Alexei",
""
]
] | We describe the possible scenarios for the evolution of a thin spherically symmetric self-gravitating phantom shell around the Schwarzschild black hole. The general equations describing the motion of the shell with a general form of equation of state are derived and analyzed. The different types of space-time R- and T-regions and shell motion are classified depending on the parameters of the problem. It is shown that in the case of a positive shell mass there exist three scenarios for the shell evolution with an infinite motion and two distinctive types of collapse. Analogous scenarios were classified for the case of a negative shell mass. In particular this classification shows that it is impossible for the physical observer to detect the fantom energy flow. We shortly discuss the importance of our results for astrophysical applications. |
2003.08088 | Aharon Davidson | Aharon Davidson and Tomer Ygael | Ricci linear Weyl/Maxwell mutual sourcing | Essay awarded Honorable Mention by the Gravity Research Foundation
2020. v.2 Title shorten, abstract modified to include the co-scalar VEV | Universe 6, 151 (2020) | 10.3390/Universe6090151 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We elevate the field theoretical similarities between Maxwell and Weyl vector
fields into a full local scale/gauge invariant Weyl/Maxwell mutual sourcing
theory. In its preliminary form, and exclusively in four dimensions, the
associated Lagrangian is dynamical scalar field free, hosts no fermion matter
fields, and Holdom kinetic mixing is switched off. The mutual sourcing term is
then necessarily spacetime curvature (not just metric) dependent, and
inevitably Ricci linear, suggesting that a non-vanishing spacetime curvature
can in principle induce an electromagnetic current. In its mature form,
however, the Weyl/Maxwell mutual sourcing idea serendipitously constitutes a
novel variant of the gravitational Weyl-Dirac (incorporating Brans-Dicke)
theory. Counter intuitively, and again exclusively in four dimensions, the
optional quartic scalar potential gets consistently replaced by a Higgs-like
potential, such that the co-divergence of the Maxwell vector field resembles a
conformal vacuum expectation value.
| [
{
"created": "Wed, 18 Mar 2020 08:32:50 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Sep 2020 18:50:37 GMT",
"version": "v2"
}
] | 2020-09-16 | [
[
"Davidson",
"Aharon",
""
],
[
"Ygael",
"Tomer",
""
]
] | We elevate the field theoretical similarities between Maxwell and Weyl vector fields into a full local scale/gauge invariant Weyl/Maxwell mutual sourcing theory. In its preliminary form, and exclusively in four dimensions, the associated Lagrangian is dynamical scalar field free, hosts no fermion matter fields, and Holdom kinetic mixing is switched off. The mutual sourcing term is then necessarily spacetime curvature (not just metric) dependent, and inevitably Ricci linear, suggesting that a non-vanishing spacetime curvature can in principle induce an electromagnetic current. In its mature form, however, the Weyl/Maxwell mutual sourcing idea serendipitously constitutes a novel variant of the gravitational Weyl-Dirac (incorporating Brans-Dicke) theory. Counter intuitively, and again exclusively in four dimensions, the optional quartic scalar potential gets consistently replaced by a Higgs-like potential, such that the co-divergence of the Maxwell vector field resembles a conformal vacuum expectation value. |
1410.5608 | Norbert Bodendorfer | Norbert Bodendorfer | A quantum reduction to Bianchi I models in loop quantum gravity | 5 pages. v2: partly rewritten to clarify derivation, gauge group
enlarged from U(1) to R_Bohr, relation to old and new LQC dynamics discussed,
previous results unchanged. v3: journal version, minor clarifications | Phys. Rev. D 91, 081502 (2015) | 10.1103/PhysRevD.91.081502 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a quantum symmetry reduction of loop quantum gravity to Bianchi I
spacetimes. To this end, we choose the diagonal metric gauge for the spatial
diffeomorphism constraint at the classical level, leading to an
$\mathbb{R}_{\text{Bohr}}$ gauge theory, and quantise the resulting theory via
loop quantum gravity methods. Constraints which lead classically to a suitable
reduction are imposed at the quantum level. The dynamics of the resulting model
turn out to be very simple and manifestly coincide with those of a polymer
quantisation of a Bianchi I model for the simplest choice of full theory
quantum states compatible with the Bianchi I reduction. In particular, the
"improved" $\bar{\mu}$ dynamics of loop quantum cosmology can be obtained by
modifying the regularisation of the Hamiltonian constraint with similar ideas,
in turn yielding insights into the full theory dynamics.
| [
{
"created": "Tue, 21 Oct 2014 10:27:25 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Dec 2014 09:42:41 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Apr 2015 07:21:53 GMT",
"version": "v3"
}
] | 2015-04-16 | [
[
"Bodendorfer",
"Norbert",
""
]
] | We propose a quantum symmetry reduction of loop quantum gravity to Bianchi I spacetimes. To this end, we choose the diagonal metric gauge for the spatial diffeomorphism constraint at the classical level, leading to an $\mathbb{R}_{\text{Bohr}}$ gauge theory, and quantise the resulting theory via loop quantum gravity methods. Constraints which lead classically to a suitable reduction are imposed at the quantum level. The dynamics of the resulting model turn out to be very simple and manifestly coincide with those of a polymer quantisation of a Bianchi I model for the simplest choice of full theory quantum states compatible with the Bianchi I reduction. In particular, the "improved" $\bar{\mu}$ dynamics of loop quantum cosmology can be obtained by modifying the regularisation of the Hamiltonian constraint with similar ideas, in turn yielding insights into the full theory dynamics. |
2111.03667 | Nuno M. Santos | Carlos A. R. Herdeiro, Eugen Radu, Nuno M. Santos | A bound on energy extraction (and hairiness) from superradiance | 11 pages, 4 figures, 2 tables. Comments are welcome | null | 10.1016/j.physletb.2021.136835 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possibility of mining the rotational energy from black holes has
far--reaching implications. Such energy extraction could occur even for
isolated black holes, if hypothetical ultralight bosonic particles exist in
Nature, leading to a new equilibrium state $-$ a black hole with synchronised
bosonic hair $-$ whose lifetime could exceed the age of the Universe. A natural
question is then: for an isolated black hole and at maximal efficiency, how
large is the energy fraction $\epsilon$ that can be extracted from a Kerr black
hole by the superradiant growth of the dominant mode? In other words, how hairy
can the resulting black hole become? A thermodynamical bound for the total
superradiance efficiency, $\epsilon\lesssim 0.29$ (as a fraction of the initial
black hole mass), has long been known, from the area law. However, numerical
simulations exhibiting the growth of the dominant mode only reached about one
third of this value. We show that if the development of superradiant
instabilities is approximately conservative (as suggest by the numerical
evolutions), this efficiency is limited to $\epsilon\lesssim 0.10$, regardless
of the spin of the bosonic field. This is in agreement with the maximum energy
extraction obtained in numerical simulations for a vector field and predicts
the result of similar simulations with a scalar field, yet to be performed.
| [
{
"created": "Fri, 5 Nov 2021 18:00:00 GMT",
"version": "v1"
}
] | 2021-12-15 | [
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
],
[
"Santos",
"Nuno M.",
""
]
] | The possibility of mining the rotational energy from black holes has far--reaching implications. Such energy extraction could occur even for isolated black holes, if hypothetical ultralight bosonic particles exist in Nature, leading to a new equilibrium state $-$ a black hole with synchronised bosonic hair $-$ whose lifetime could exceed the age of the Universe. A natural question is then: for an isolated black hole and at maximal efficiency, how large is the energy fraction $\epsilon$ that can be extracted from a Kerr black hole by the superradiant growth of the dominant mode? In other words, how hairy can the resulting black hole become? A thermodynamical bound for the total superradiance efficiency, $\epsilon\lesssim 0.29$ (as a fraction of the initial black hole mass), has long been known, from the area law. However, numerical simulations exhibiting the growth of the dominant mode only reached about one third of this value. We show that if the development of superradiant instabilities is approximately conservative (as suggest by the numerical evolutions), this efficiency is limited to $\epsilon\lesssim 0.10$, regardless of the spin of the bosonic field. This is in agreement with the maximum energy extraction obtained in numerical simulations for a vector field and predicts the result of similar simulations with a scalar field, yet to be performed. |
1904.05056 | Abhishek Parida | Abhishek Parida, Jishnu Suresh, Sanjit Mitra, Sanjay Jhingan | Component separation map-making for stochastic gravitational wave
background | 20 pages, 10 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superposition of unresolved sources of gravitational waves (GW) is expected
to create a persistent background of stochastic gravitational wave background
(SGWB). Different types of astrophysical and cosmological sources are however
likely to be present in the background. We present an algorithm for separation
of the components with distinct frequency spectral indices into individual
sky-maps. To demonstrate the method, we simulate GW signals for different
spectral indices and corresponding sky-maps, e.g., point sources like the Virgo
cluster and extended ones like the Milky Way Galaxy, and apply our method to
recover the injected maps.
| [
{
"created": "Wed, 10 Apr 2019 08:24:45 GMT",
"version": "v1"
}
] | 2019-04-11 | [
[
"Parida",
"Abhishek",
""
],
[
"Suresh",
"Jishnu",
""
],
[
"Mitra",
"Sanjit",
""
],
[
"Jhingan",
"Sanjay",
""
]
] | Superposition of unresolved sources of gravitational waves (GW) is expected to create a persistent background of stochastic gravitational wave background (SGWB). Different types of astrophysical and cosmological sources are however likely to be present in the background. We present an algorithm for separation of the components with distinct frequency spectral indices into individual sky-maps. To demonstrate the method, we simulate GW signals for different spectral indices and corresponding sky-maps, e.g., point sources like the Virgo cluster and extended ones like the Milky Way Galaxy, and apply our method to recover the injected maps. |
1704.07107 | Vinod Dagwal | V. J. Dagwal and D. D. Pawar | Tilted Two Fluids Cosmological Models with Variable G and {\Lambda} In
General Relativity | 13 pages | International Journal of Mathematical Archive-9(2), 2018, 120-128 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tilted two fluids cosmological models with variable G and {\Lambda} In
General Relativity are presented. Here one fluid is matter field modelling
material content of the universe and another fluid is radiation field modelling
the cosmic microwave background (CMB). The tiltedness is also considered .To
get the deterministic model, we have assumed a supplementary condition where s
and n are constants. We have also discussed the behaviours of some physical
parameters.
| [
{
"created": "Mon, 24 Apr 2017 09:28:01 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Apr 2018 08:43:39 GMT",
"version": "v2"
}
] | 2018-04-26 | [
[
"Dagwal",
"V. J.",
""
],
[
"Pawar",
"D. D.",
""
]
] | Tilted two fluids cosmological models with variable G and {\Lambda} In General Relativity are presented. Here one fluid is matter field modelling material content of the universe and another fluid is radiation field modelling the cosmic microwave background (CMB). The tiltedness is also considered .To get the deterministic model, we have assumed a supplementary condition where s and n are constants. We have also discussed the behaviours of some physical parameters. |
gr-qc/0003100 | Jose Geraldo Pereira | V. C. de Andrade, L. C. T. Guillen and J. G. Pereira | Gravitational Energy-Momentum Density in Teleparallel Gravity | RevTeX, 4 pages, no figures, to appear in Phys. Rev. Lett | Phys.Rev.Lett. 84 (2000) 4533-4536 | 10.1103/PhysRevLett.84.4533 | IFT-P.032/2000 | gr-qc hep-th | null | In the context of a gauge theory for the translation group, a conserved
energy-momentum gauge current for the gravitational field is obtained. It is a
true spacetime and gauge tensor, and transforms covariantly under global
Lorentz transformations. By rewriting the gauge gravitational field equation in
a purely spacetime form, it becomes the teleparallel equivalent of Einstein's
equation, and the gauge current reduces to the M{\o}ller's canonical
energy-momentum density of the gravitational field.
| [
{
"created": "Mon, 27 Mar 2000 17:43:39 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"de Andrade",
"V. C.",
""
],
[
"Guillen",
"L. C. T.",
""
],
[
"Pereira",
"J. G.",
""
]
] | In the context of a gauge theory for the translation group, a conserved energy-momentum gauge current for the gravitational field is obtained. It is a true spacetime and gauge tensor, and transforms covariantly under global Lorentz transformations. By rewriting the gauge gravitational field equation in a purely spacetime form, it becomes the teleparallel equivalent of Einstein's equation, and the gauge current reduces to the M{\o}ller's canonical energy-momentum density of the gravitational field. |
gr-qc/9804088 | Don N. Page | Don N. Page (Canadian Institute for Advanced Research and Theoretical
Physics Institute, University of Alberta, Edmonton, Canada) | Gravitational Capture and Scattering of Straight Test Strings with Large
Impact Parameters | 27 pages, no figures, Latex | Phys. Rev. D 58, 105026 (1998) | 10.1103/PhysRevD.58.105026 | Alberta-Thy-05-98 | gr-qc | null | The capture or scattering of an initially straight infinite test cosmic
string by a Kerr-Newman black hole, or by any other small source of an
electrovac gravitational field, is analyzed analytically when the string moves
with initial velocity v and large impact parameter b >> M so that the string
stays very nearly straight (except during the final capture process, if that
occurs, or except far behind the gravitating object, if b is not much greater
than the energy of the object in the frame of the string). The critical impact
parameter for capture at low velocities is shown to be
[(pi/2)(M^2-Q^2)/v]^{1/2}. For all larger b, the displacement of the string
from the plane of the gravitating object after the scattering approaches the
final value [b^2 - (pi/2)(M^2-Q^2)/v]^{1/2} - 2 pi M v/(1-v^2)^{1/2}, for any
v, so long as b >> M.
| [
{
"created": "Thu, 30 Apr 1998 23:36:32 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Page",
"Don N.",
"",
"Canadian Institute for Advanced Research and Theoretical\n Physics Institute, University of Alberta, Edmonton, Canada"
]
] | The capture or scattering of an initially straight infinite test cosmic string by a Kerr-Newman black hole, or by any other small source of an electrovac gravitational field, is analyzed analytically when the string moves with initial velocity v and large impact parameter b >> M so that the string stays very nearly straight (except during the final capture process, if that occurs, or except far behind the gravitating object, if b is not much greater than the energy of the object in the frame of the string). The critical impact parameter for capture at low velocities is shown to be [(pi/2)(M^2-Q^2)/v]^{1/2}. For all larger b, the displacement of the string from the plane of the gravitating object after the scattering approaches the final value [b^2 - (pi/2)(M^2-Q^2)/v]^{1/2} - 2 pi M v/(1-v^2)^{1/2}, for any v, so long as b >> M. |
1105.3312 | Eduardo Guendelman I | E. I. Guendelman | Non Singular Origin of the Universe and the Cosmological Constant
Problem (CCP) | awarded an honorable mention in the Gravity Research Foundation 2011
Awards for Essays in Gravitation for 2011 | null | 10.1142/S0218271811020718 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a non singular origin for the Universe starting from an Einstein
static Universe in the framework of a theory which uses two volume elements
$\sqrt{-{g}}d^{4}x$ and $\Phi d^{4}x$, where $\Phi $ is a metric independent
density, also curvature, curvature square terms, first order formalism and for
scale invariance a dilaton field $\phi$ are considered in the action. In the
Einstein frame we also add a cosmological term that parametrizes the zero point
fluctuations. The resulting effective potential for the dilaton contains two
flat regions, for $\phi \rightarrow \infty$ relevant for the non singular
origin of the Universe and $\phi \rightarrow -\infty$, describing our present
Universe. Surprisingly, avoidance of singularities and stability as $\phi
\rightarrow \infty$ imply a positive but small vacuum energy as $\phi
\rightarrow -\infty$. Zero vacuum energy density for the present universe is
the "threshold" for universe creation.
| [
{
"created": "Tue, 17 May 2011 09:19:41 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Guendelman",
"E. I.",
""
]
] | We consider a non singular origin for the Universe starting from an Einstein static Universe in the framework of a theory which uses two volume elements $\sqrt{-{g}}d^{4}x$ and $\Phi d^{4}x$, where $\Phi $ is a metric independent density, also curvature, curvature square terms, first order formalism and for scale invariance a dilaton field $\phi$ are considered in the action. In the Einstein frame we also add a cosmological term that parametrizes the zero point fluctuations. The resulting effective potential for the dilaton contains two flat regions, for $\phi \rightarrow \infty$ relevant for the non singular origin of the Universe and $\phi \rightarrow -\infty$, describing our present Universe. Surprisingly, avoidance of singularities and stability as $\phi \rightarrow \infty$ imply a positive but small vacuum energy as $\phi \rightarrow -\infty$. Zero vacuum energy density for the present universe is the "threshold" for universe creation. |
2207.01654 | Koustav Chandra | Koustav Chandra, Juan Calder\'on Bustillo, Archana Pai, Ian Harry | First gravitational-wave search for intermediate-mass black hole mergers
with higher order harmonics | 15 pages, 8 figures, matches published version | null | 10.1103/PhysRevD.106.123003 | LIGO-P2200182 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Current matched-filter searches for gravitational waves from binary
black-hole mergers compare the calibrated detector data to waveform templates
that omit the higher-order mode content of the signals predicted by General
Relativity. However, higher-order emission modes become important for highly
inclined asymmetric sources with masses above $\simeq 100 M_\odot$, causing
current searches to be ill-suited at detecting them. We present a new
gravitational-wave search that implements templates including higher-order
modes, adapted signal-glitch discriminators, and trigger-ranking statistics to
specifically target signals displaying strong higher modes, corresponding to
nearly edge-on sources with total redshifted masses in the intermediate-mass
black-hole range $M_T(1+z) \in (100,500) M_\odot$ and mass-ratios $q\in(1,10)$.
Our search shows a volumetric sensitivity gain of up to $450\%$ to these
signals compared to existing searches omitting higher-order modes. We deploy
our search on public data from the third observing run of Advanced LIGO. While
we find no statistically significant candidates beyond those already reported
elsewhere, our search sets the stage to search for higher-mode rich signals in
future observing runs. The efficient detection of such signals is crucial to
performing detailed tests of General Relativity, observing strong-field
phenomena, and maximizing the chances of observing the yet uncharted realm of
intermediate-mass black hole binaries.
| [
{
"created": "Mon, 4 Jul 2022 18:08:37 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Dec 2022 04:26:00 GMT",
"version": "v2"
}
] | 2022-12-14 | [
[
"Chandra",
"Koustav",
""
],
[
"Bustillo",
"Juan Calderón",
""
],
[
"Pai",
"Archana",
""
],
[
"Harry",
"Ian",
""
]
] | Current matched-filter searches for gravitational waves from binary black-hole mergers compare the calibrated detector data to waveform templates that omit the higher-order mode content of the signals predicted by General Relativity. However, higher-order emission modes become important for highly inclined asymmetric sources with masses above $\simeq 100 M_\odot$, causing current searches to be ill-suited at detecting them. We present a new gravitational-wave search that implements templates including higher-order modes, adapted signal-glitch discriminators, and trigger-ranking statistics to specifically target signals displaying strong higher modes, corresponding to nearly edge-on sources with total redshifted masses in the intermediate-mass black-hole range $M_T(1+z) \in (100,500) M_\odot$ and mass-ratios $q\in(1,10)$. Our search shows a volumetric sensitivity gain of up to $450\%$ to these signals compared to existing searches omitting higher-order modes. We deploy our search on public data from the third observing run of Advanced LIGO. While we find no statistically significant candidates beyond those already reported elsewhere, our search sets the stage to search for higher-mode rich signals in future observing runs. The efficient detection of such signals is crucial to performing detailed tests of General Relativity, observing strong-field phenomena, and maximizing the chances of observing the yet uncharted realm of intermediate-mass black hole binaries. |
0810.4022 | Xin-Zhou Li | Ping Xi | Quasinormal modes of a black hole with quintessence-like matter and a
deficit solid angle: scalar and gravitational perturbations | 5pages | Astrophys.Space Sci.321:47-51,2009 | 10.1007/s10509-009-9994-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the previous paper (Li, X. Z., Xi, P., Zhai, X. H.: Phys. Lett. B{\bf666},
125-130 (2008)), we show the solutions of Einstein equations with static
spherically-symmetric quintessence-like matter surrounding a global monopole.
Furthermore, this monopole become a black hole with quintessence-like matter
and a deficit solid angle when it is swallowed by an ordinary black hole. We
study its quasinormal modes by WKB method in this paper. The numerical results
show that both the real part of the quasinormal frequencies and the imaginary
part decrease as the state parameter $w$, for scalar and gravitational
perturbations. And we also show variations of quasinormal frequencies of scalar
and gravitational fields via different $\epsilon$ (deficit solid angel
parameter) and different $\rho_0$ (density of static spherically-symmetric
quintessence-like matter at $r=1$), respectively.
| [
{
"created": "Wed, 22 Oct 2008 09:54:56 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jun 2009 02:59:35 GMT",
"version": "v2"
}
] | 2009-06-04 | [
[
"Xi",
"Ping",
""
]
] | In the previous paper (Li, X. Z., Xi, P., Zhai, X. H.: Phys. Lett. B{\bf666}, 125-130 (2008)), we show the solutions of Einstein equations with static spherically-symmetric quintessence-like matter surrounding a global monopole. Furthermore, this monopole become a black hole with quintessence-like matter and a deficit solid angle when it is swallowed by an ordinary black hole. We study its quasinormal modes by WKB method in this paper. The numerical results show that both the real part of the quasinormal frequencies and the imaginary part decrease as the state parameter $w$, for scalar and gravitational perturbations. And we also show variations of quasinormal frequencies of scalar and gravitational fields via different $\epsilon$ (deficit solid angel parameter) and different $\rho_0$ (density of static spherically-symmetric quintessence-like matter at $r=1$), respectively. |
2003.05318 | Joe Kennedy Dr | Joe Kennedy, Lucas Lombriser | Positivity bounds on reconstructed Horndeski models | 11 pages, 3 figures | Phys. Rev. D 102, 044062 (2020) | 10.1103/PhysRevD.102.044062 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Positivity bounds provide conditions that a consistent UV-completion exists
for a quantum field theory. We examine their application to Horndeski gravity
models reconstructed from the effective field theory (EFT) of dark energy. This
enables us to assess whether particular phenomenological parameterizations of
the EFT functions reconstruct theories that respect or violate the positivity
bounds. We find that commonly adopted EFT parametrizations, cast in terms of
the dark energy density or power laws of the scale factor, only satisfy the
positivity bounds in non-trivial regions of the parameter space. We then
examine parameterizations of the inherently stable EFT basis, constructed to
avoid gradient and ghost instabilities by default. In stark contrast, in this
basis the positivity bounds either only provide constraints in a-priori
unrealistic regions of the parameter space or do not provide any constraints on
parameter values at all. The application of positivity bounds to common
parametrizations of the standard EFT functions can therefore lead to artificial
conclusions that the region of viable Horndeski modifications of gravity is
highly constrained. Our results provide a strong motivation, in addition to the
default avoidance of theoretical instabilities, for instead adopting
parametrizations of the inherently stable EFT basis when testing dark energy
and modified gravity models with forthcoming cosmological survey data.
| [
{
"created": "Tue, 10 Mar 2020 15:54:34 GMT",
"version": "v1"
}
] | 2020-09-09 | [
[
"Kennedy",
"Joe",
""
],
[
"Lombriser",
"Lucas",
""
]
] | Positivity bounds provide conditions that a consistent UV-completion exists for a quantum field theory. We examine their application to Horndeski gravity models reconstructed from the effective field theory (EFT) of dark energy. This enables us to assess whether particular phenomenological parameterizations of the EFT functions reconstruct theories that respect or violate the positivity bounds. We find that commonly adopted EFT parametrizations, cast in terms of the dark energy density or power laws of the scale factor, only satisfy the positivity bounds in non-trivial regions of the parameter space. We then examine parameterizations of the inherently stable EFT basis, constructed to avoid gradient and ghost instabilities by default. In stark contrast, in this basis the positivity bounds either only provide constraints in a-priori unrealistic regions of the parameter space or do not provide any constraints on parameter values at all. The application of positivity bounds to common parametrizations of the standard EFT functions can therefore lead to artificial conclusions that the region of viable Horndeski modifications of gravity is highly constrained. Our results provide a strong motivation, in addition to the default avoidance of theoretical instabilities, for instead adopting parametrizations of the inherently stable EFT basis when testing dark energy and modified gravity models with forthcoming cosmological survey data. |
1509.06491 | Somenath Chakrabarty | Sanchari De and Somenath Chakrabarty | Wien's Displacement Law in Rindler Space | 9 Pages REVTEX file, a new section is added, conclusion part is
rewritten | null | null | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we have developed the formalisms for the modified form of
Wien displacement laws for both the gas of electromagnetic waves and a gas of
de Broglie waves in Rindler space. In the case of de Broglie waves we assume
both fermion type and boson type materials. Following the classic work of Wien,
we assume that the wall of the enclosure containing the photon gas or the gas
of de Broglie waves, is expanding adiabatically with a uniform acceleration.
| [
{
"created": "Tue, 22 Sep 2015 08:08:14 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Aug 2016 11:40:35 GMT",
"version": "v2"
}
] | 2016-08-12 | [
[
"De",
"Sanchari",
""
],
[
"Chakrabarty",
"Somenath",
""
]
] | In this article we have developed the formalisms for the modified form of Wien displacement laws for both the gas of electromagnetic waves and a gas of de Broglie waves in Rindler space. In the case of de Broglie waves we assume both fermion type and boson type materials. Following the classic work of Wien, we assume that the wall of the enclosure containing the photon gas or the gas of de Broglie waves, is expanding adiabatically with a uniform acceleration. |
gr-qc/0501002 | Gamal Nashed G. L. | Gamal G.L. Nashed | Charged Axially Symmetric Solution, Energy and Angular Momentum in
Tetrad Theory of Gravitation | LaTex file, 16 pages. accepted for publication in Modern physics
letter A | Int.J.Mod.Phys.A21:3181-3197,2006 | 10.1142/S0217751X06031478 | null | gr-qc | null | Charged axially symmetric solution of the coupled gravitational and
electromagnetic fields in the tetrad theory of gravitation is derived. The
metric associated with this solution is an axially symmetric metric which is
characterized by three parameters ``$ $the gravitational mass $M$, the charge
parameter $Q$ and the rotation parameter $a$". The parallel vector fields and
the electromagnetic vector potential are axially symmetric. We calculate the
total exterior energy. The energy-momentum complex given by M{\o}ller in the
framework of the Weitzenb$\ddot{o}$ck geometry ``$ ${\it characterized by
vanishing the curvature tensor constructed from the connection of this
geometry}" has been used. This energy-momentum complex is considered as a
better definition for calculation of energy and momentum than those of general
relativity theory. The energy contained in a sphere is found to be consistent
with pervious results which is shared by its interior and exterior. Switching
off the charge parameter, one finds that no energy is shared by the exterior of
the charged axially symmetric solution. The components of the momentum density
are also calculated and used to evaluate the angular momentum distribution. We
found no angular momentum contributes to the exterior of the charged axially
symmetric solution if zero charge parameter is used.
| [
{
"created": "Sat, 1 Jan 2005 11:17:33 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jul 2005 11:49:35 GMT",
"version": "v2"
}
] | 2010-11-05 | [
[
"Nashed",
"Gamal G. L.",
""
]
] | Charged axially symmetric solution of the coupled gravitational and electromagnetic fields in the tetrad theory of gravitation is derived. The metric associated with this solution is an axially symmetric metric which is characterized by three parameters ``$ $the gravitational mass $M$, the charge parameter $Q$ and the rotation parameter $a$". The parallel vector fields and the electromagnetic vector potential are axially symmetric. We calculate the total exterior energy. The energy-momentum complex given by M{\o}ller in the framework of the Weitzenb$\ddot{o}$ck geometry ``$ ${\it characterized by vanishing the curvature tensor constructed from the connection of this geometry}" has been used. This energy-momentum complex is considered as a better definition for calculation of energy and momentum than those of general relativity theory. The energy contained in a sphere is found to be consistent with pervious results which is shared by its interior and exterior. Switching off the charge parameter, one finds that no energy is shared by the exterior of the charged axially symmetric solution. The components of the momentum density are also calculated and used to evaluate the angular momentum distribution. We found no angular momentum contributes to the exterior of the charged axially symmetric solution if zero charge parameter is used. |
gr-qc/9307018 | null | Chopin Soo and Lay Nam Chang | Superspace Dynamics and Perturbations Around "Emptiness" | 16 pages.(Revised 9/93) Preprint VPI-IHEP-93-5, CGPG-93/9-2,
gr-qc/9307018 | Int.J.Mod.Phys.D3:529-544,1994 | 10.1142/S021827189400068X | null | gr-qc hep-th | null | Superspace parametrized by gauge potentials instead of metric
three-geometries is discussed in the context of the Ashtekar variables. Among
other things, an "internal clock" for the full theory can be identified.
Gauge-fixing conditions which lead to the natural geometrical separation of
physical from gauge modes are derived with the use of the metric in
connection-superspace. A perturbation scheme about an unconventional background
which is inaccessible to conventional variables is presented. The resultant
expansion retains much of the simplicity of Ashtekar's formulation of General
Relativity.
| [
{
"created": "Wed, 14 Jul 1993 19:59:20 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Sep 1993 17:27:55 GMT",
"version": "v2"
}
] | 2010-11-01 | [
[
"Soo",
"Chopin",
""
],
[
"Chang",
"Lay Nam",
""
]
] | Superspace parametrized by gauge potentials instead of metric three-geometries is discussed in the context of the Ashtekar variables. Among other things, an "internal clock" for the full theory can be identified. Gauge-fixing conditions which lead to the natural geometrical separation of physical from gauge modes are derived with the use of the metric in connection-superspace. A perturbation scheme about an unconventional background which is inaccessible to conventional variables is presented. The resultant expansion retains much of the simplicity of Ashtekar's formulation of General Relativity. |
1303.6824 | Tapobrata Sarkar | Anshuman Dey, Pratim Roy, Tapobrata Sarkar | Scalar Radiation in the Background of a Naked Singularity | 1 + 15 Pages, LaTeX, 6 .eps figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study scalar radiation spectra from a particle in circular orbit, in the
background of the Janis-Newman-Winicour (JNW) naked singularity. The
differences in the nature of the spectra, from what one obtains with a
Schwarzschild black hole, is established. We also compute the angular
distribution of the spectra.
| [
{
"created": "Wed, 27 Mar 2013 13:30:40 GMT",
"version": "v1"
}
] | 2013-03-28 | [
[
"Dey",
"Anshuman",
""
],
[
"Roy",
"Pratim",
""
],
[
"Sarkar",
"Tapobrata",
""
]
] | We study scalar radiation spectra from a particle in circular orbit, in the background of the Janis-Newman-Winicour (JNW) naked singularity. The differences in the nature of the spectra, from what one obtains with a Schwarzschild black hole, is established. We also compute the angular distribution of the spectra. |
1105.6296 | Jurjen Koksma | Jurjen F. Koksma, Tomislav Prokopec | The Cosmological Constant and Lorentz Invariance of the Vacuum State | null | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One hope to solve the cosmological constant problem is to identify a symmetry
principle, based on which the cosmological constant can be reduced either to
zero, or to a tiny value. Here, we note that requiring that the vacuum state is
Lorentz invariant significantly reduces the theoretical value of the vacuum
energy density. Hence, this also reduces the discrepancy between the observed
value of the cosmological constant and its theoretical expectation, down from
123 orders of magnitude to 56 orders of magnitude. We find that, at one loop
level, massless particles do not yield any contribution to the cosmological
constant. Another important consequence of Lorentz symmetry is stabilization of
the gravitational hierarchy: the cosmological constant (divided by Newton's
constant) does not run as the quartic power of the renormalization group scale,
but instead only logarithmically.
| [
{
"created": "Tue, 31 May 2011 14:20:29 GMT",
"version": "v1"
}
] | 2011-06-01 | [
[
"Koksma",
"Jurjen F.",
""
],
[
"Prokopec",
"Tomislav",
""
]
] | One hope to solve the cosmological constant problem is to identify a symmetry principle, based on which the cosmological constant can be reduced either to zero, or to a tiny value. Here, we note that requiring that the vacuum state is Lorentz invariant significantly reduces the theoretical value of the vacuum energy density. Hence, this also reduces the discrepancy between the observed value of the cosmological constant and its theoretical expectation, down from 123 orders of magnitude to 56 orders of magnitude. We find that, at one loop level, massless particles do not yield any contribution to the cosmological constant. Another important consequence of Lorentz symmetry is stabilization of the gravitational hierarchy: the cosmological constant (divided by Newton's constant) does not run as the quartic power of the renormalization group scale, but instead only logarithmically. |
gr-qc/9703036 | Alan Rendall | Alan D. Rendall | Global dynamics of the mixmaster model | 16 pages | Class.Quant.Grav. 14 (1997) 2341-2356 | 10.1088/0264-9381/14/8/028 | null | gr-qc | null | The asymptotic behaviour of vacuum Bianchi models of class A near the initial
singularity is studied, in an effort to confirm the standard picture arising
from heuristic and numerical approaches by mathematical proofs. It is shown
that for solutions of types other than VIII and IX the singularity is velocity
dominated and that the Kretschmann scalar is unbounded there, except in the
explicitly known cases where the spacetime can be smoothly extended through a
Cauchy horizon. For types VIII and IX it is shown that there are at most two
possibilities for the evolution. When the first possibility is realized, and if
the spacetime is not one of the explicitly known solutions which can be
smoothly extended through a Cauchy horizon, then there are infinitely many
oscillations near the singularity and the Kretschmann scalar is unbounded
there. The second possibility remains mysterious and it is left open whether it
ever occurs. It is also shown that any finite sequence of distinct points
generated by iterating the Belinskii-Khalatnikov-Lifschitz mapping can be
realized approximately by a solution of the vacuum Einstein equations of
Bianchi type IX.
| [
{
"created": "Fri, 14 Mar 1997 12:30:08 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Rendall",
"Alan D.",
""
]
] | The asymptotic behaviour of vacuum Bianchi models of class A near the initial singularity is studied, in an effort to confirm the standard picture arising from heuristic and numerical approaches by mathematical proofs. It is shown that for solutions of types other than VIII and IX the singularity is velocity dominated and that the Kretschmann scalar is unbounded there, except in the explicitly known cases where the spacetime can be smoothly extended through a Cauchy horizon. For types VIII and IX it is shown that there are at most two possibilities for the evolution. When the first possibility is realized, and if the spacetime is not one of the explicitly known solutions which can be smoothly extended through a Cauchy horizon, then there are infinitely many oscillations near the singularity and the Kretschmann scalar is unbounded there. The second possibility remains mysterious and it is left open whether it ever occurs. It is also shown that any finite sequence of distinct points generated by iterating the Belinskii-Khalatnikov-Lifschitz mapping can be realized approximately by a solution of the vacuum Einstein equations of Bianchi type IX. |
gr-qc/0302077 | Stoytcho Yazadjiev | Stoytcho S. Yazadjiev (Sofia University) | Self-similar collapse of a scalar field in dilaton gravity and critical
behaviour | 9 pages, LaTex; v2 references and a comment added | Int.J.Mod.Phys. A19 (2004) 2495-2504 | 10.1142/S0217751X04017793 | null | gr-qc | null | We present new analytical self-similar solutions describing a collapse of a
massless scalar field in scalar-tensor theories. The solutions exhibit a type
of critical behavior. The black hole mass for the near critical evolution is
analytically obtained for several scalar-tensor theories and the critical
exponent is calculated. Within the framework of the analytical models we
consider it is found that the black hole mass law for some scalar-tensor
theories is of the form $M_{BH}=f(p-p_{cr})(p-p_{cr})^\gamma$ which is slightly
different from the general relativistic law $M_{BH}=const (p-p_{cr})^\gamma$.
| [
{
"created": "Wed, 19 Feb 2003 10:04:48 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Feb 2003 09:51:40 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Yazadjiev",
"Stoytcho S.",
"",
"Sofia University"
]
] | We present new analytical self-similar solutions describing a collapse of a massless scalar field in scalar-tensor theories. The solutions exhibit a type of critical behavior. The black hole mass for the near critical evolution is analytically obtained for several scalar-tensor theories and the critical exponent is calculated. Within the framework of the analytical models we consider it is found that the black hole mass law for some scalar-tensor theories is of the form $M_{BH}=f(p-p_{cr})(p-p_{cr})^\gamma$ which is slightly different from the general relativistic law $M_{BH}=const (p-p_{cr})^\gamma$. |
2201.00444 | Wei Fang | Qile Zhang, Wei Fang, Chenggang Shu | Dynamical Stability of the Power Law K-essence Dark Energy Model with a
New Interaction | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the cosmological evolution of the power law K-essence dark
energy (DE) model $F(X)= -\sqrt{X} + X$ with a new interaction $Q = \alpha\rho
_m\rho _{\phi }H^{-1}$ in FRWL spacetime. The evolution behavior of dark energy
under this interaction is analyzed by using dynamical systems method, and ten
critical points are obtained. Among those critical points, a new stable point,
which we called Scaling-like dark energy(DE) solution, is very important and
interesting. The cosmological meaning of this attractor is different from the
Scaling solution and dark energy dominated solution. For some value of model
parameters, the universe will evolve to the attractor solution with the dark
energy density parameter $\Omega_{\phi}=0.682946$ and the the equation of state
$w_{\phi}=-0.99$, which can be in good agreement with the observed data, and
alleviate the Coincidence Problem.
| [
{
"created": "Mon, 3 Jan 2022 00:57:13 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Jan 2022 12:58:21 GMT",
"version": "v2"
}
] | 2022-01-21 | [
[
"Zhang",
"Qile",
""
],
[
"Fang",
"Wei",
""
],
[
"Shu",
"Chenggang",
""
]
] | We investigate the cosmological evolution of the power law K-essence dark energy (DE) model $F(X)= -\sqrt{X} + X$ with a new interaction $Q = \alpha\rho _m\rho _{\phi }H^{-1}$ in FRWL spacetime. The evolution behavior of dark energy under this interaction is analyzed by using dynamical systems method, and ten critical points are obtained. Among those critical points, a new stable point, which we called Scaling-like dark energy(DE) solution, is very important and interesting. The cosmological meaning of this attractor is different from the Scaling solution and dark energy dominated solution. For some value of model parameters, the universe will evolve to the attractor solution with the dark energy density parameter $\Omega_{\phi}=0.682946$ and the the equation of state $w_{\phi}=-0.99$, which can be in good agreement with the observed data, and alleviate the Coincidence Problem. |
gr-qc/0403006 | Luis Herrera | L.Herrera, A. Di Prisco, J. Martin, J. Ospino, N.O.Santos, O.Troconis | Spherically symmetric dissipative anisotropic fluids: A general study | 28 pages Latex. To appear in Phys.Rev.D | Phys.Rev.D69:084026,2004 | 10.1103/PhysRevD.69.084026 | null | gr-qc astro-ph | null | The full set of equations governing the evolution of self--gravitating
spherically symmetric dissipative fluids with anisotropic stresses is deployed
and used to carry out a general study on the behaviour of such systems, in the
context of general relativity. Emphasis is given to the link between the Weyl
tensor, the shear tensor, the anisotropy of the pressure and the density
inhomogeneity. In particular we provide the general, necessary and sufficient,
condition for the vanishing of the spatial gradients of energy density, which
in turn suggests a possible definition of a gravitational arrow of time. Some
solutions are also exhibited to illustrate the discussion.
| [
{
"created": "Sun, 29 Feb 2004 21:11:22 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Herrera",
"L.",
""
],
[
"Di Prisco",
"A.",
""
],
[
"Martin",
"J.",
""
],
[
"Ospino",
"J.",
""
],
[
"Santos",
"N. O.",
""
],
[
"Troconis",
"O.",
""
]
] | The full set of equations governing the evolution of self--gravitating spherically symmetric dissipative fluids with anisotropic stresses is deployed and used to carry out a general study on the behaviour of such systems, in the context of general relativity. Emphasis is given to the link between the Weyl tensor, the shear tensor, the anisotropy of the pressure and the density inhomogeneity. In particular we provide the general, necessary and sufficient, condition for the vanishing of the spatial gradients of energy density, which in turn suggests a possible definition of a gravitational arrow of time. Some solutions are also exhibited to illustrate the discussion. |
gr-qc/9812083 | null | Reginald T. Cahill, Christopher M. Klinger (Department of Physics,
Flinders University) | Self-Referential Noise and the Synthesis of Three-Dimensional Space | Figure labels corrected | Gen. Rel.Grav. 32:529,2000 | 10.1023/A:1001984518976 | null | gr-qc adap-org nlin.AO | null | Generalising results from Godel and Chaitin in mathematics suggests that
self-referential systems contain intrinsic randomness. We argue that this is
relevant to modelling the universe and show how three-dimensional space may
arise from a non-geometric order-disorder model driven by self-referential
noise.
| [
{
"created": "Thu, 24 Dec 1998 01:20:09 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Dec 1998 06:40:30 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Cahill",
"Reginald T.",
"",
"Department of Physics,\n Flinders University"
],
[
"Klinger",
"Christopher M.",
"",
"Department of Physics,\n Flinders University"
]
] | Generalising results from Godel and Chaitin in mathematics suggests that self-referential systems contain intrinsic randomness. We argue that this is relevant to modelling the universe and show how three-dimensional space may arise from a non-geometric order-disorder model driven by self-referential noise. |
gr-qc/0203031 | J. E. Horvath | P.S. Custodio and J.E. Horvath (IAG/USP, Sao Paulo) | The evolution of primordial black hole masses in the radiation-
dominated era | 9 pages, 1 .eps figure. submitted to GRG | Gen.Rel.Grav. 34 (2002) 1895-1907 | null | IAG/USP 02-24 | gr-qc | null | We revisit the problem of PBH mass evolution in the radiation-dominated era.
We solve the complete differential equation in the semiclassical regime with
absorption and evaporation terms and show that PBHs can gain very little mass,
if at all, in this era. Relativistic proper motion of PBHs respect to the CMBR,
as a possible loophole in the growth argument, is shown to be unlikely. Finally
we demonstrate that PBHs can not remain in thermodynamical equilibrium with the
ambient radiation, and therefore initially non-evaporating black holes must
enter the evaporating regime, supporting several efforts to look for
observational signatures.
| [
{
"created": "Sun, 10 Mar 2002 02:37:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Custodio",
"P. S.",
"",
"IAG/USP, Sao Paulo"
],
[
"Horvath",
"J. E.",
"",
"IAG/USP, Sao Paulo"
]
] | We revisit the problem of PBH mass evolution in the radiation-dominated era. We solve the complete differential equation in the semiclassical regime with absorption and evaporation terms and show that PBHs can gain very little mass, if at all, in this era. Relativistic proper motion of PBHs respect to the CMBR, as a possible loophole in the growth argument, is shown to be unlikely. Finally we demonstrate that PBHs can not remain in thermodynamical equilibrium with the ambient radiation, and therefore initially non-evaporating black holes must enter the evaporating regime, supporting several efforts to look for observational signatures. |
1711.10483 | Jose Luis Bl\'azquez-Salcedo | Jose Luis Bl\'azquez-Salcedo, Jutta Kunz, Francisco Navarro-L\'erida,
Eugen Radu | Squashed, magnetized black holes in $D=5$ minimal gauged supergravity | 45 pages, 15 figures, corrected typos, matches version published in
JHEP | JHEP 1802 (2018) 061 | 10.1007/JHEP02(2018)061 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a new class of black hole solutions in five-dimensional
Einstein-Maxwell-Chern-Simons theory with a negative cosmological constant.
These configurations are cohomogeneity-1, with two equal-magnitude angular
momenta. In the generic case, they possess a non-vanishing magnetic potential
at infinity with a boundary metric which is the product of time and a squashed
three-dimensional sphere. Both extremal and non-extremal black holes are
studied. The non-extremal black holes satisfying a certain relation between
electric charge, angular momenta and magnitude of the magnetic potential at
infinity do not trivialize in the limit of vanishing event horizon size,
becoming particle-like (non-topological) solitonic configurations. Among the
extremal black holes, we show the existence of a new one-parameter family of
supersymmetric solutions, which bifurcate from a critical Gutowski-Reall
configuration.
| [
{
"created": "Tue, 28 Nov 2017 17:11:49 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Dec 2017 17:46:34 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Mar 2018 16:44:55 GMT",
"version": "v3"
}
] | 2018-03-05 | [
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Navarro-Lérida",
"Francisco",
""
],
[
"Radu",
"Eugen",
""
]
] | We construct a new class of black hole solutions in five-dimensional Einstein-Maxwell-Chern-Simons theory with a negative cosmological constant. These configurations are cohomogeneity-1, with two equal-magnitude angular momenta. In the generic case, they possess a non-vanishing magnetic potential at infinity with a boundary metric which is the product of time and a squashed three-dimensional sphere. Both extremal and non-extremal black holes are studied. The non-extremal black holes satisfying a certain relation between electric charge, angular momenta and magnitude of the magnetic potential at infinity do not trivialize in the limit of vanishing event horizon size, becoming particle-like (non-topological) solitonic configurations. Among the extremal black holes, we show the existence of a new one-parameter family of supersymmetric solutions, which bifurcate from a critical Gutowski-Reall configuration. |
gr-qc/0111113 | Jozef Sima | Jozef Sima and Miroslav Sukenik | Formation of Complex Matter Structures and Mutual Relations Between the
Mass of Elementary Particles | 6 pages, LaTeX | null | null | SS-01-10 | gr-qc | null | The model of Expansive Nondecelerative Universe leads to a conclusion stating
that at the end of radiation era the Jeans mass was equal to the upper mass
limit of a black hole and, at the same time, the effective gravitational range
of nucleons was identical to their Compton wavelength. At that time nucleons
started to exert gravitational impact on their environment which enabled to
large scale structures become formed. Moreover, it is shown that there is a
deep relationships between the inertial mass of various leptons and bosons and
that such relations can be extended also into the realm of other kinds of
elementary particles.
| [
{
"created": "Fri, 30 Nov 2001 11:06:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sima",
"Jozef",
""
],
[
"Sukenik",
"Miroslav",
""
]
] | The model of Expansive Nondecelerative Universe leads to a conclusion stating that at the end of radiation era the Jeans mass was equal to the upper mass limit of a black hole and, at the same time, the effective gravitational range of nucleons was identical to their Compton wavelength. At that time nucleons started to exert gravitational impact on their environment which enabled to large scale structures become formed. Moreover, it is shown that there is a deep relationships between the inertial mass of various leptons and bosons and that such relations can be extended also into the realm of other kinds of elementary particles. |
2402.05485 | Wei-Liang Qian | Wei-Liang Qian, Qiyuan Pan, Bean Wang, Rui-Hong Yue | Late-time tail and echoes of Damour-Solodukhin wormholes | 20 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Damour-Solodukhin wormholes are intriguing theoretical constructs, closely
mimicking many properties of black holes. This study delves into two distinct
characteristics of the waveforms emitted from such wormholes, namely, the
late-time tails and echoes, which can substantially be used to distinguish its
identity. Notably, both features appear in the latter stages of quasinormal
oscillations and stem from the singularities of the Green's function. The
late-time tail, on the one hand, arises due to the branch cuts in the relevant
Green's function. Within the Damour-Solodukhin wormhole paradigm, singularities
are present in both ingoing and outgoing waveforms, which entails a
generalization of the existing recipe for black hole metrics. On the other
hand, the echoes are attributed to a new set of quasinormal poles,
supplementing those of the respective black holes, reminiscent of the scenario
where the spacetime metric possesses a discontinuity. It is inferred that both
features are observationally relevant in distinguishing a wormhole from its
black hole counterpart. Moreover, we suggest a potential interplay concerning
the late-time evolution between the two mechanisms in question.
| [
{
"created": "Thu, 8 Feb 2024 08:27:43 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jun 2024 13:02:47 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Aug 2024 12:52:50 GMT",
"version": "v3"
}
] | 2024-08-02 | [
[
"Qian",
"Wei-Liang",
""
],
[
"Pan",
"Qiyuan",
""
],
[
"Wang",
"Bean",
""
],
[
"Yue",
"Rui-Hong",
""
]
] | Damour-Solodukhin wormholes are intriguing theoretical constructs, closely mimicking many properties of black holes. This study delves into two distinct characteristics of the waveforms emitted from such wormholes, namely, the late-time tails and echoes, which can substantially be used to distinguish its identity. Notably, both features appear in the latter stages of quasinormal oscillations and stem from the singularities of the Green's function. The late-time tail, on the one hand, arises due to the branch cuts in the relevant Green's function. Within the Damour-Solodukhin wormhole paradigm, singularities are present in both ingoing and outgoing waveforms, which entails a generalization of the existing recipe for black hole metrics. On the other hand, the echoes are attributed to a new set of quasinormal poles, supplementing those of the respective black holes, reminiscent of the scenario where the spacetime metric possesses a discontinuity. It is inferred that both features are observationally relevant in distinguishing a wormhole from its black hole counterpart. Moreover, we suggest a potential interplay concerning the late-time evolution between the two mechanisms in question. |
2208.01771 | Chen-Kai Qiao | Chen-Kai Qiao | Curvatures, Photon Spheres and Black Hole Shadows | 14 pages, 3 figures, 3 tables (text overlap with arXiv:2204.07297).
V2: Minor Revision, Accepted by Physical Review D | Physical Review D 106, 084060 (2022) | 10.1103/PhysRevD.106.084060 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In a recent work PRD 106, L021501 (2022), a new geometric approach is
proposed to obtain the photon sphere (circular photon orbit) and the black hole
shadow radius. In this approach, photon spheres and the black hole shadow
radius are determined using geodesic curvature and Gaussian curvature in the
optical geometry of black hole spacetimes. However, the calculations in PRD
106, L021501 (2022) only restricted to a subclass of static and spherically
symmetric black holes with spacetime metric $g_{tt} \cdot g_{rr}=-1$,
$g_{\theta\theta}=r^{2}$ and $g_{\phi\phi}=r^{2}\sin^{2}\theta$. In this work,
we extend this approach to more general spherically symmetric black holes (with
spacetime metric
$ds^{2}=g_{tt}dt^{2}+g_{rr}dr^{2}+g_{\theta\theta}d\theta^{2}+g_{\phi\phi}d\phi^{2}$).
Furthermore, it can be proved that our results from the geometric approach are
completely equivalent to those from conventional approach based on effective
potentials of test particles.
| [
{
"created": "Tue, 2 Aug 2022 22:08:26 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Oct 2022 12:12:00 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Nov 2022 16:50:37 GMT",
"version": "v3"
}
] | 2022-11-11 | [
[
"Qiao",
"Chen-Kai",
""
]
] | In a recent work PRD 106, L021501 (2022), a new geometric approach is proposed to obtain the photon sphere (circular photon orbit) and the black hole shadow radius. In this approach, photon spheres and the black hole shadow radius are determined using geodesic curvature and Gaussian curvature in the optical geometry of black hole spacetimes. However, the calculations in PRD 106, L021501 (2022) only restricted to a subclass of static and spherically symmetric black holes with spacetime metric $g_{tt} \cdot g_{rr}=-1$, $g_{\theta\theta}=r^{2}$ and $g_{\phi\phi}=r^{2}\sin^{2}\theta$. In this work, we extend this approach to more general spherically symmetric black holes (with spacetime metric $ds^{2}=g_{tt}dt^{2}+g_{rr}dr^{2}+g_{\theta\theta}d\theta^{2}+g_{\phi\phi}d\phi^{2}$). Furthermore, it can be proved that our results from the geometric approach are completely equivalent to those from conventional approach based on effective potentials of test particles. |
gr-qc/9312033 | Eli John Hawkins | Eli Hawkins | Quantum Gravitational Collapse of a Charged Dust Shell | 12 pages, UMDGR--94--76 | Phys.Rev.D49:6556,1994; Erratum-ibid.D50:7744,1994;
Phys.Rev.D50:7744,1994 | 10.1103/PhysRevD.49.6556 10.1103/PhysRevD.50.7744 | null | gr-qc | null | A simple self gravitating system --- a thin spherical shell of charged
pressureless matter --- is naively quantized as a test case of quantum
gravitational collapse. The model is interpreted in terms of an inner product
on the positive energy states. An S-matrix is constructed describing scattering
between negatively and positively infinite radius.
| [
{
"created": "Tue, 21 Dec 1993 22:03:37 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Dec 1993 20:15:07 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Hawkins",
"Eli",
""
]
] | A simple self gravitating system --- a thin spherical shell of charged pressureless matter --- is naively quantized as a test case of quantum gravitational collapse. The model is interpreted in terms of an inner product on the positive energy states. An S-matrix is constructed describing scattering between negatively and positively infinite radius. |
0712.3246 | Remo Garattini | Remo Garattini | Extracting the Cosmological Constant from the Wheeler DeWitt Equation in
a Modified Gravity Theory | Talk given at QFEXT 07, Workshop on Quantum Field Theory Under the
Influence of External Conditions, Leipzig, 17-21 Sep 2007 and talk given at
9th International Conference on Path Integrals - New Trends and Perspectives,
Dresden, 23-28 September 2007. 8 pages, accepted for publication in Journal
of Physics A | J.Phys.A41:164057,2008 | 10.1088/1751-8113/41/16/164057 | null | gr-qc hep-th | null | We discuss how to extract information about the cosmological constant from
the Wheeler-DeWitt equation, considered as an eigenvalue of a Sturm-Liouville
problem. A generalization to a f(R)theory is taken under examination. The
equation is approximated to one loop with the help of a variational approach
with Gaussian trial wave functionals. We use a zeta function regularization to
handle with divergences. A renormalization procedure is introduced to remove
the infinities together with a renormalization group equation.
| [
{
"created": "Wed, 19 Dec 2007 18:03:26 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Garattini",
"Remo",
""
]
] | We discuss how to extract information about the cosmological constant from the Wheeler-DeWitt equation, considered as an eigenvalue of a Sturm-Liouville problem. A generalization to a f(R)theory is taken under examination. The equation is approximated to one loop with the help of a variational approach with Gaussian trial wave functionals. We use a zeta function regularization to handle with divergences. A renormalization procedure is introduced to remove the infinities together with a renormalization group equation. |
0903.3684 | Peter Komorowski | P. G. Komorowski, S. R. Valluri, M. Houde | A Study of Elliptical Last Stable Orbits About a Massive Kerr Black Hole | 42 pages, 9 figures, accepted for publication in Classical and
Quantum Gravity | Class.Quant.Grav.26:085001,2009 | 10.1088/0264-9381/26/8/085001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The last stable orbit (LSO) of a compact object (CO) is an important boundary
condition when performing numerical analysis of orbit evolution. Although the
LSO is already well understood for the case where a test-particle is in an
elliptical orbit around a Schwarzschild black hole (SBH) and for the case of a
circular orbit about a Kerr black hole (KBH) of normalised spin, S (|J|/M^2,
where J is the spin angular momentum of the KBH); it is worthwhile to extend
our knowledge to include elliptical orbits about a KBH. This extension helps to
lay the foundation for a better understanding of gravitational wave (GW)
emission. The mathematical developments described in this work sprang from the
use of an effective potential (V) derived from the Kerr metric, which
encapsulates the Lense-Thirring precession. That allowed us to develop a new
form of analytical expression to calculate the LSO Radius for circular orbits
(R_LSO) of arbitrary KBH spin. We were then able to construct a numerical
method to calculate the latus rectum (l_LSO) for an elliptical LSO.
Abstract Formulae for E^2 (square of normalised orbital energy) and L^2
(square of normalised orbital angular momentum) in terms of eccentricity, e,
and latus rectum, l, were previously developed by others for elliptical orbits
around an SBH and then extended to the KBH case; we used these results to
generalise our analytical l_LSO equations to elliptical orbits. LSO data
calculated from our analytical equations and numerical procedures, and those
previously published, are then compared and found to be in excellent agreement.
| [
{
"created": "Sat, 21 Mar 2009 19:51:34 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Komorowski",
"P. G.",
""
],
[
"Valluri",
"S. R.",
""
],
[
"Houde",
"M.",
""
]
] | The last stable orbit (LSO) of a compact object (CO) is an important boundary condition when performing numerical analysis of orbit evolution. Although the LSO is already well understood for the case where a test-particle is in an elliptical orbit around a Schwarzschild black hole (SBH) and for the case of a circular orbit about a Kerr black hole (KBH) of normalised spin, S (|J|/M^2, where J is the spin angular momentum of the KBH); it is worthwhile to extend our knowledge to include elliptical orbits about a KBH. This extension helps to lay the foundation for a better understanding of gravitational wave (GW) emission. The mathematical developments described in this work sprang from the use of an effective potential (V) derived from the Kerr metric, which encapsulates the Lense-Thirring precession. That allowed us to develop a new form of analytical expression to calculate the LSO Radius for circular orbits (R_LSO) of arbitrary KBH spin. We were then able to construct a numerical method to calculate the latus rectum (l_LSO) for an elliptical LSO. Abstract Formulae for E^2 (square of normalised orbital energy) and L^2 (square of normalised orbital angular momentum) in terms of eccentricity, e, and latus rectum, l, were previously developed by others for elliptical orbits around an SBH and then extended to the KBH case; we used these results to generalise our analytical l_LSO equations to elliptical orbits. LSO data calculated from our analytical equations and numerical procedures, and those previously published, are then compared and found to be in excellent agreement. |
1803.02429 | Huan Yang | Huan Yang, Denis Martynov | Testing Gravitational Memory Generation with Compact Binary Mergers | 9 pages, 5 figures | Phys. Rev. Lett. 121, 071102 (2018) | 10.1103/PhysRevLett.121.071102 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational memory is an important prediction of classical General
Relativity, which is intimately related to asymptotic symmetries at null
infinity and the so-called soft graviton theorem first shown by Weinberg. For a
given transient astronomical event, the angular distributions of energy and
angular momentum flux uniquely determine the displacement and spin memory
effect in the sky. We investigate the possibility of using the binary black
hole merger events detected by Advanced LIGO/Virgo to test the relation between
source energy emissions and gravitational memory measured on earth, as
predicted by General Relativity. We find that while it is difficult for
Advanced LIGO/Virgo, one-year detection of a third-generation detector network
will easily rule out the hypothesis assuming isotropic memory distribution. In
addition, we have constructed a phenomenological model for memory waveforms of
binary neutron star mergers, and use it to address the detectability of memory
from these events in the third-generation detector era. We find that measuring
gravitational memory from neutron star mergers is a possible way to distinguish
between different neutron star equations of state.
| [
{
"created": "Tue, 6 Mar 2018 21:19:34 GMT",
"version": "v1"
}
] | 2018-08-22 | [
[
"Yang",
"Huan",
""
],
[
"Martynov",
"Denis",
""
]
] | Gravitational memory is an important prediction of classical General Relativity, which is intimately related to asymptotic symmetries at null infinity and the so-called soft graviton theorem first shown by Weinberg. For a given transient astronomical event, the angular distributions of energy and angular momentum flux uniquely determine the displacement and spin memory effect in the sky. We investigate the possibility of using the binary black hole merger events detected by Advanced LIGO/Virgo to test the relation between source energy emissions and gravitational memory measured on earth, as predicted by General Relativity. We find that while it is difficult for Advanced LIGO/Virgo, one-year detection of a third-generation detector network will easily rule out the hypothesis assuming isotropic memory distribution. In addition, we have constructed a phenomenological model for memory waveforms of binary neutron star mergers, and use it to address the detectability of memory from these events in the third-generation detector era. We find that measuring gravitational memory from neutron star mergers is a possible way to distinguish between different neutron star equations of state. |
2101.05318 | Ratbay Myrzakulov | T. Myrzakul, K. Yesmakhanova, N. Myrzakulov, S. Myrzakul, K.
Myrzakulov, K. Yerzhanov, R. Myrzakulov, G. Nugmanova | Metric-affine Myrzakulov gravity theories with Gauss-Bonnet and boundary
term scalars | 41 pages. arXiv admin note: substantial text overlap with
arXiv:1205.5266 | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | In this paper, we consider some metric-affine Myrzakulov gravity (MG)
theories with Gauss-Bonnet scalars. Also we consider the MG theories with the
boundary term scalars. Note that these MG theories with the Gauss-Bonnet and
boundary term scalars were proposed in [arXiv:1205.5266]. Some examples of
Metric-Affine Gravity (MAG) theories are reviewed in the context of the
$F(R,T,Q,{\cal T}, {\cal D})$ type models. Then the generalized MAG theory with
the curvature, torsion and nonmetricity (the so-called MG-VIII) was studied.
For the FRW spacetime case, in particular, the Lagrangian, Hamilatonian and
gravitational equations are obtained. The particular case $F(R,T)=\alpha
R+\beta T+\mu Q+\nu{\cal T}$ is investigated in detail. In quantum case, the
corresponding Wheeler-DeWitt equation is obtained. Finally, some gravity
theories with the curvature, torsion and nonmetricity are presented.
| [
{
"created": "Wed, 13 Jan 2021 19:46:14 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Mar 2021 15:41:23 GMT",
"version": "v2"
},
{
"created": "Sun, 28 Apr 2024 13:50:24 GMT",
"version": "v3"
}
] | 2024-04-30 | [
[
"Myrzakul",
"T.",
""
],
[
"Yesmakhanova",
"K.",
""
],
[
"Myrzakulov",
"N.",
""
],
[
"Myrzakul",
"S.",
""
],
[
"Myrzakulov",
"K.",
""
],
[
"Yerzhanov",
"K.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Nugmanova",
"G.",
""
]
] | In this paper, we consider some metric-affine Myrzakulov gravity (MG) theories with Gauss-Bonnet scalars. Also we consider the MG theories with the boundary term scalars. Note that these MG theories with the Gauss-Bonnet and boundary term scalars were proposed in [arXiv:1205.5266]. Some examples of Metric-Affine Gravity (MAG) theories are reviewed in the context of the $F(R,T,Q,{\cal T}, {\cal D})$ type models. Then the generalized MAG theory with the curvature, torsion and nonmetricity (the so-called MG-VIII) was studied. For the FRW spacetime case, in particular, the Lagrangian, Hamilatonian and gravitational equations are obtained. The particular case $F(R,T)=\alpha R+\beta T+\mu Q+\nu{\cal T}$ is investigated in detail. In quantum case, the corresponding Wheeler-DeWitt equation is obtained. Finally, some gravity theories with the curvature, torsion and nonmetricity are presented. |
gr-qc/9803047 | Andrew Chamblin | Raphael Bousso (Stanford) and Andrew Chamblin (Cambridge) | Patching up the No-Boundary Proposal with virtual Euclidean wormholes | 23 pages REVTeX plus 7 figures | Phys.Rev. D59 (1999) 084004 | 10.1103/PhysRevD.59.084004 | DAMTP-R-97/37, SU-ITP-98/11 | gr-qc hep-th | null | In quantum cosmology, one often considers tunneling phenomena which may have
occurred in the early universe. Processes requiring quantum penetration of a
potential barrier include black hole pair creation and the decay of vacuum
domain walls. Ideally, one calculates the rates for such processes by finding
an instanton, or Euclidean solution of the field equations, which interpolates
between the initial and final states. In practice, however, it has become
customary to calculate such amplitudes using the No-Boundary Proposal of Hartle
and Hawking. A criticism of this method is that it does not use a single path
which interpolates between the initial and final states, but two disjoint
instantons: One divides the probability to create the final state from nothing
by the probability to create the initial state from nothing and decrees the
answer to be the rate of tunneling from the initial to the final state. Here,
we demonstrate the validity of this approach by constructing continuous paths
connecting the ingoing and outgoing data, which may be viewed as perturbations
of the set of disconnected instantons. They are off-shell, but will still
dominate the path integral as they have action arbitrarily close to the
no-boundary action. In this picture, a virtual domain wall, or wormhole, is
created and annihilated in such a way as to interface between the disjoint
instantons. Decay rates calculated using our construction differ from decay
rates calculated using the No-Boundary Proposal only in the prefactor; the
exponent, which usually dominates the result, remains unchanged.
| [
{
"created": "Fri, 13 Mar 1998 02:31:20 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bousso",
"Raphael",
"",
"Stanford"
],
[
"Chamblin",
"Andrew",
"",
"Cambridge"
]
] | In quantum cosmology, one often considers tunneling phenomena which may have occurred in the early universe. Processes requiring quantum penetration of a potential barrier include black hole pair creation and the decay of vacuum domain walls. Ideally, one calculates the rates for such processes by finding an instanton, or Euclidean solution of the field equations, which interpolates between the initial and final states. In practice, however, it has become customary to calculate such amplitudes using the No-Boundary Proposal of Hartle and Hawking. A criticism of this method is that it does not use a single path which interpolates between the initial and final states, but two disjoint instantons: One divides the probability to create the final state from nothing by the probability to create the initial state from nothing and decrees the answer to be the rate of tunneling from the initial to the final state. Here, we demonstrate the validity of this approach by constructing continuous paths connecting the ingoing and outgoing data, which may be viewed as perturbations of the set of disconnected instantons. They are off-shell, but will still dominate the path integral as they have action arbitrarily close to the no-boundary action. In this picture, a virtual domain wall, or wormhole, is created and annihilated in such a way as to interface between the disjoint instantons. Decay rates calculated using our construction differ from decay rates calculated using the No-Boundary Proposal only in the prefactor; the exponent, which usually dominates the result, remains unchanged. |
gr-qc/0610044 | Iver Brevik | Iver Brevik and John Quiroga Hurtado | Vanishing Cosmological Constant in Modified Gauss-Bonnet Gravity with
Conformal Anomaly | 8 pages latex, 1 figure. To appear in Int. J. Mod. Phys. D | Int.J.Mod.Phys.D16:817-826,2007 | 10.1142/S0218271807010419 | null | gr-qc | null | We consider dark energy cosmology in a de Sitter universe filled with quantum
conformal matter. Our model represents a Gauss-Bonnet model of gravity with
contributions from quantum effects. To the General Relativity action an
arbitrary function of the GB invariant, f(G), is added, and taking into account
quantum effects from matter the cosmological constant is studied. For the
considered model the conditions for a vanishing cosmological constant are
considered. Creation of a de Sitter universe by quantum effects in a GB
modified gravity is discussed.
| [
{
"created": "Tue, 10 Oct 2006 11:46:39 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Brevik",
"Iver",
""
],
[
"Hurtado",
"John Quiroga",
""
]
] | We consider dark energy cosmology in a de Sitter universe filled with quantum conformal matter. Our model represents a Gauss-Bonnet model of gravity with contributions from quantum effects. To the General Relativity action an arbitrary function of the GB invariant, f(G), is added, and taking into account quantum effects from matter the cosmological constant is studied. For the considered model the conditions for a vanishing cosmological constant are considered. Creation of a de Sitter universe by quantum effects in a GB modified gravity is discussed. |
2206.10653 | Aaron Zimmerman | Asad Hussain and Aaron Zimmerman | An approach to computing spectral shifts for black holes beyond Kerr | 23 pages, 1 figure | null | 10.1103/PhysRevD.106.104018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent measurements of gravitational-wave ringdown following the merger of
binary black holes raise the prospect of precision black hole spectroscopy in
the near future. To perform the most sensitive tests of the nature of black
holes using ringdown measurements, it is critical to compute the deviations to
the spectrum of black holes in particular extensions of relativity. These
spectral shifts are also needed to interpret any violations of the predictions
of relativity that may be detected during ringdown. Here we present a first
step towards computing the shifts to the spectrum of Kerr black holes with
arbitrary spins, by deriving a modified Teukolsky equation governing the
perturbations of black holes in theories beyond GR. Our approach applies to a
class of theories which includes dynamical Chern-Simons gravity and
shift-symmetric scalar Gauss-Bonnet gravity, in the case where the deviations
from relativity are small. This allows for a perturbative approach to solving
the equations of motion. Further, we show how to use the modified equation to
compute the leading-order spectral shifts of Kerr black holes, using eigenvalue
perturbation methods. Our formalism provides a practical approach to predicting
ringdown for black holes in a range of promising extensions to relativity,
enabling future precision searches for their signatures in black hole ringdown.
| [
{
"created": "Tue, 21 Jun 2022 18:06:02 GMT",
"version": "v1"
}
] | 2022-11-23 | [
[
"Hussain",
"Asad",
""
],
[
"Zimmerman",
"Aaron",
""
]
] | Recent measurements of gravitational-wave ringdown following the merger of binary black holes raise the prospect of precision black hole spectroscopy in the near future. To perform the most sensitive tests of the nature of black holes using ringdown measurements, it is critical to compute the deviations to the spectrum of black holes in particular extensions of relativity. These spectral shifts are also needed to interpret any violations of the predictions of relativity that may be detected during ringdown. Here we present a first step towards computing the shifts to the spectrum of Kerr black holes with arbitrary spins, by deriving a modified Teukolsky equation governing the perturbations of black holes in theories beyond GR. Our approach applies to a class of theories which includes dynamical Chern-Simons gravity and shift-symmetric scalar Gauss-Bonnet gravity, in the case where the deviations from relativity are small. This allows for a perturbative approach to solving the equations of motion. Further, we show how to use the modified equation to compute the leading-order spectral shifts of Kerr black holes, using eigenvalue perturbation methods. Our formalism provides a practical approach to predicting ringdown for black holes in a range of promising extensions to relativity, enabling future precision searches for their signatures in black hole ringdown. |
0805.2106 | Roberto Chan | C. F. C. Brandt, R. Chan, M. F. A. da Silva, J. F. Villas da Rocha | Dressing a Naked Singularity: an Example | 14 pages, 1 figure. This version corrects an error in the calculus of
the pressure and in the conclusions | Int.J.Mod.Phys.D19:317,2010 | 10.1142/S0218271810016439 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering the evolution of a perfect fluid with self-similarity of the
second kind, we have found that an initial naked singularity can be trapped by
an event horizon due to collapsing matter. The fluid moves along time-like
geodesics with a self-similar parameter $\alpha = -3$. Since the metric
obtained is not asymptotically flat, we match the spacetime of the fluid with a
Schwarzschild spacetime. All the energy conditions are fulfilled until the
naked singularity.
| [
{
"created": "Wed, 14 May 2008 16:27:10 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2009 16:06:09 GMT",
"version": "v2"
}
] | 2012-10-25 | [
[
"Brandt",
"C. F. C.",
""
],
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"da Rocha",
"J. F. Villas",
""
]
] | Considering the evolution of a perfect fluid with self-similarity of the second kind, we have found that an initial naked singularity can be trapped by an event horizon due to collapsing matter. The fluid moves along time-like geodesics with a self-similar parameter $\alpha = -3$. Since the metric obtained is not asymptotically flat, we match the spacetime of the fluid with a Schwarzschild spacetime. All the energy conditions are fulfilled until the naked singularity. |
1205.3097 | Markus B. Fr\"ob | Markus B. Fr\"ob, Albert Roura, Enric Verdaguer | One-loop gravitational wave spectrum in de Sitter spacetime | 42 pages, 2 figures, includes three new paragraphs in response to
referee's comments | JCAP08(2012)009 | 10.1088/1475-7516/2012/08/009 | AEI-2011-066 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The two-point function for tensor metric perturbations around de Sitter
spacetime including one-loop corrections from massless conformally coupled
scalar fields is calculated exactly. We work in the Poincar\'e patch (with
spatially flat sections) and employ dimensional regularization for the
renormalization process. Unlike previous studies we obtain the result for
arbitrary time separations rather than just equal times. Moreover, in contrast
to existing results for tensor perturbations, ours is manifestly invariant with
respect to the subgroup of de Sitter isometries corresponding to a simultaneous
time translation and rescaling of the spatial coordinates. Having selected the
right initial state for the interacting theory via an appropriate i\epsilon
prescription is crucial for that. Finally, we show that although the two-point
function is a well-defined spacetime distribution, the equal-time limit of its
spatial Fourier transform is divergent. Therefore, contrary to the well-defined
distribution for arbitrary time separations, the power spectrum is strictly
speaking ill-defined when loop corrections are included.
| [
{
"created": "Mon, 14 May 2012 16:57:53 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Sep 2012 12:33:51 GMT",
"version": "v2"
}
] | 2012-09-06 | [
[
"Fröb",
"Markus B.",
""
],
[
"Roura",
"Albert",
""
],
[
"Verdaguer",
"Enric",
""
]
] | The two-point function for tensor metric perturbations around de Sitter spacetime including one-loop corrections from massless conformally coupled scalar fields is calculated exactly. We work in the Poincar\'e patch (with spatially flat sections) and employ dimensional regularization for the renormalization process. Unlike previous studies we obtain the result for arbitrary time separations rather than just equal times. Moreover, in contrast to existing results for tensor perturbations, ours is manifestly invariant with respect to the subgroup of de Sitter isometries corresponding to a simultaneous time translation and rescaling of the spatial coordinates. Having selected the right initial state for the interacting theory via an appropriate i\epsilon prescription is crucial for that. Finally, we show that although the two-point function is a well-defined spacetime distribution, the equal-time limit of its spatial Fourier transform is divergent. Therefore, contrary to the well-defined distribution for arbitrary time separations, the power spectrum is strictly speaking ill-defined when loop corrections are included. |
2002.12095 | Takahiro Yamamoto S. | Takahiro S. Yamamoto and Takahiro Tanaka | Use of conditional variational auto encoder to analyze ringdown
gravitational waves | 9 pages, 5 figures | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, several deep learning methods are proposed for the gravitational
wave data analysis. One is conditional variational auto encoder (CVAE),
proposed by Gabbard et al. [1]. We study the accuracy of a CVAE in the context
of the estimation of the QNM frequency of the ringdown. We show that the
accuracy of the estimation by the CVAE is better than the matched filtering.
The areas of confidence regions are also compared and it is shown that the CVAE
can return smaller confidence regions. Also, we assess the reliability of the
confidence regions estimated by the CVAE. Our work confirms that the deep
learning method has ability to compete with or overcome the matched filtering.
| [
{
"created": "Thu, 27 Feb 2020 13:59:55 GMT",
"version": "v1"
}
] | 2020-02-28 | [
[
"Yamamoto",
"Takahiro S.",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | Recently, several deep learning methods are proposed for the gravitational wave data analysis. One is conditional variational auto encoder (CVAE), proposed by Gabbard et al. [1]. We study the accuracy of a CVAE in the context of the estimation of the QNM frequency of the ringdown. We show that the accuracy of the estimation by the CVAE is better than the matched filtering. The areas of confidence regions are also compared and it is shown that the CVAE can return smaller confidence regions. Also, we assess the reliability of the confidence regions estimated by the CVAE. Our work confirms that the deep learning method has ability to compete with or overcome the matched filtering. |
1305.6645 | Sergio Dain | Sergio Dain | Inequality between size and angular momentum for bodies | Improvements in the heuristic arguments. 5 pages | Phys. Rev. Lett. 112, 041101 (2014) | 10.1103/PhysRevLett.112.041101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A universal inequality that bounds the angular momentum of a body by the
square of its size is presented and heuristic physical arguments are given to
support it. We prove a version of this inequality, as consequence of Einstein
equations, for the case of rotating axially symmetric, constant density,
bodies. Finally, the physical relevance of this result is discussed.
| [
{
"created": "Tue, 28 May 2013 22:12:18 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jan 2014 12:06:56 GMT",
"version": "v2"
}
] | 2014-02-05 | [
[
"Dain",
"Sergio",
""
]
] | A universal inequality that bounds the angular momentum of a body by the square of its size is presented and heuristic physical arguments are given to support it. We prove a version of this inequality, as consequence of Einstein equations, for the case of rotating axially symmetric, constant density, bodies. Finally, the physical relevance of this result is discussed. |
gr-qc/9411073 | James Anglin | J.R. Anglin, R. Laflamme, W.H. Zurek, and J.P. Paz | Decoherence, Re-coherence, and the Black Hole Information Paradox | 23 pages, 2 figures included, figures 3.1 - 3.3 available at
http://qso.lanl.gov/papers/Papers.html | Phys.Rev.D52:2221-2231,1995 | 10.1103/PhysRevD.52.2221 | LA-UR-94-3817 | gr-qc hep-th quant-ph | null | We analyze a system consisting of an oscillator coupled to a field. With the
field traced out as an environment, the oscillator loses coherence on a very
short {\it decoherence timescale}; but, on a much longer {\it relaxation
timescale}, predictably evolves into a unique, pure (ground) state. This
example of {\it re-coherence} has interesting implications both for the
interpretation of quantum theory and for the loss of information during black
hole evaporation. We examine these implications by investigating the
intermediate and final states of the quantum field, treated as an open system
coupled to an unobserved oscillator.
| [
{
"created": "Wed, 30 Nov 1994 00:36:36 GMT",
"version": "v1"
}
] | 2011-08-04 | [
[
"Anglin",
"J. R.",
""
],
[
"Laflamme",
"R.",
""
],
[
"Zurek",
"W. H.",
""
],
[
"Paz",
"J. P.",
""
]
] | We analyze a system consisting of an oscillator coupled to a field. With the field traced out as an environment, the oscillator loses coherence on a very short {\it decoherence timescale}; but, on a much longer {\it relaxation timescale}, predictably evolves into a unique, pure (ground) state. This example of {\it re-coherence} has interesting implications both for the interpretation of quantum theory and for the loss of information during black hole evaporation. We examine these implications by investigating the intermediate and final states of the quantum field, treated as an open system coupled to an unobserved oscillator. |
gr-qc/0006109 | J. Alberto Lobo | J. Alberto Lobo | The mathematical theory of resonant transducers in a spherical gravity
wave antenna | 31 pages, 7 figures, LaTeX2e, \usepackage{graphicx,deleq} | Mon.Not.Roy.Astron.Soc. 316 (2000) 173-194 | 10.1046/j.1365-8711.2000.03492.x | null | gr-qc | null | The rigoruos mathematical theory of the coupling and response of a spherical
gravitational wave detector endowed with a set of resonant transducers is
presented and developed. A perturbative series in ascending powers of the
square root of the ratio of the resonator to the sphere mass is seen to be the
key to the solution of the problem. General layouts of arbitrary numbers of
transducers can be assessed, and a specific proposal (PHC), alternative to the
highly symmetric TIGA of Merkowitz and Johnson, is described in detail.
Frequency spectra of the coupled system are seen to be theoretically recovered
in full agreement with experimental determinations.
| [
{
"created": "Fri, 30 Jun 2000 14:50:11 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Lobo",
"J. Alberto",
""
]
] | The rigoruos mathematical theory of the coupling and response of a spherical gravitational wave detector endowed with a set of resonant transducers is presented and developed. A perturbative series in ascending powers of the square root of the ratio of the resonator to the sphere mass is seen to be the key to the solution of the problem. General layouts of arbitrary numbers of transducers can be assessed, and a specific proposal (PHC), alternative to the highly symmetric TIGA of Merkowitz and Johnson, is described in detail. Frequency spectra of the coupled system are seen to be theoretically recovered in full agreement with experimental determinations. |
1911.09083 | Gabriele Vajente | Gabriele Vajente, Yiwen Huang, Maximiliano Isi, Jenne C. Driggers,
Jeffrey S. Kissel, Marek J. Szczepanczyk, Salvatore Vitale | Machine-learning non-stationary noise out of gravitational wave
detectors | null | Phys. Rev. D 101, 042003 (2020) | 10.1103/PhysRevD.101.042003 | null | gr-qc astro-ph.IM cs.LG physics.data-an physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Signal extraction out of background noise is a common challenge in high
precision physics experiments, where the measurement output is often a
continuous data stream. To improve the signal to noise ratio of the detection,
witness sensors are often used to independently measure background noises and
subtract them from the main signal. If the noise coupling is linear and
stationary, optimal techniques already exist and are routinely implemented in
many experiments. However, when the noise coupling is non-stationary, linear
techniques often fail or are sub-optimal. Inspired by the properties of the
background noise in gravitational wave detectors, this work develops a novel
algorithm to efficiently characterize and remove non-stationary noise
couplings, provided there exist witnesses of the noise source and of the
modulation. In this work, the algorithm is described in its most general
formulation, and its efficiency is demonstrated with examples from the data of
the Advanced LIGO gravitational wave observatory, where we could obtain an
improvement of the detector gravitational wave reach without introducing any
bias on the source parameter estimation.
| [
{
"created": "Wed, 20 Nov 2019 18:41:24 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jan 2020 21:45:19 GMT",
"version": "v2"
},
{
"created": "Tue, 28 Jan 2020 23:57:39 GMT",
"version": "v3"
}
] | 2020-02-26 | [
[
"Vajente",
"Gabriele",
""
],
[
"Huang",
"Yiwen",
""
],
[
"Isi",
"Maximiliano",
""
],
[
"Driggers",
"Jenne C.",
""
],
[
"Kissel",
"Jeffrey S.",
""
],
[
"Szczepanczyk",
"Marek J.",
""
],
[
"Vitale",
"Salvatore",
""
]
] | Signal extraction out of background noise is a common challenge in high precision physics experiments, where the measurement output is often a continuous data stream. To improve the signal to noise ratio of the detection, witness sensors are often used to independently measure background noises and subtract them from the main signal. If the noise coupling is linear and stationary, optimal techniques already exist and are routinely implemented in many experiments. However, when the noise coupling is non-stationary, linear techniques often fail or are sub-optimal. Inspired by the properties of the background noise in gravitational wave detectors, this work develops a novel algorithm to efficiently characterize and remove non-stationary noise couplings, provided there exist witnesses of the noise source and of the modulation. In this work, the algorithm is described in its most general formulation, and its efficiency is demonstrated with examples from the data of the Advanced LIGO gravitational wave observatory, where we could obtain an improvement of the detector gravitational wave reach without introducing any bias on the source parameter estimation. |
1305.6770 | Tiberiu Harko | Tiberiu Harko, Francisco S. N. Lobo, M. K. Mak, Sergey V. Sushkov | Structure of neutron, quark and exotic stars in Eddington-inspired
Born-Infeld gravity | 12 pages, 8 figures | Phys.Rev.D88:044032,2013 | 10.1103/PhysRevD.88.044032 | null | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the structure and physical properties of specific classes of
neutron, quark and "exoti"' stars in Eddington-inspired Born-Infeld (EiBI)
gravity. The latter reduces to standard general relativity in vacuum, but
presents a different behavior of the gravitational field in the presence of
matter. The equilibrium equations for a spherically symmetric configuration
(mass continuity and Tolman-Oppenheimer-Volkoff) are derived, and their
solutions are obtained numerically for different equations of state of neutron
and quark matter. More specifically, stellar models, described by the stiff
fluid, radiation-like, polytropic and the bag model quark equations of state
are explicitly constructed in both general relativity and EiBI gravity, thus
allowing a comparison between the predictions of these two gravitational
models. As a general result it turns out that for all the considered equations
of state, EiBI gravity stars are more massive than their general relativistic
counterparts. Furthermore, an exact solution of the spherically symmetric field
equations in EiBI gravity, describing an "exotic" star, with decreasing
pressure but increasing energy density, is also obtained. As a possible
astrophysical application of the obtained results we suggest that stellar mass
black holes, with masses in the range of $3.8M_{\odot}$ and $6M_{\odot}$,
respectively, could be in fact EiBI neutron or quark stars.
| [
{
"created": "Tue, 28 May 2013 06:16:36 GMT",
"version": "v1"
}
] | 2013-08-21 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Mak",
"M. K.",
""
],
[
"Sushkov",
"Sergey V.",
""
]
] | We consider the structure and physical properties of specific classes of neutron, quark and "exoti"' stars in Eddington-inspired Born-Infeld (EiBI) gravity. The latter reduces to standard general relativity in vacuum, but presents a different behavior of the gravitational field in the presence of matter. The equilibrium equations for a spherically symmetric configuration (mass continuity and Tolman-Oppenheimer-Volkoff) are derived, and their solutions are obtained numerically for different equations of state of neutron and quark matter. More specifically, stellar models, described by the stiff fluid, radiation-like, polytropic and the bag model quark equations of state are explicitly constructed in both general relativity and EiBI gravity, thus allowing a comparison between the predictions of these two gravitational models. As a general result it turns out that for all the considered equations of state, EiBI gravity stars are more massive than their general relativistic counterparts. Furthermore, an exact solution of the spherically symmetric field equations in EiBI gravity, describing an "exotic" star, with decreasing pressure but increasing energy density, is also obtained. As a possible astrophysical application of the obtained results we suggest that stellar mass black holes, with masses in the range of $3.8M_{\odot}$ and $6M_{\odot}$, respectively, could be in fact EiBI neutron or quark stars. |
1702.02209 | Roberto Ivan Cabrera Munguia Dr. | I. Cabrera-Munguia, V. E. Ceron, L. A. L\'opez, and Omar Pedraza | Corotating two-body system of identical Kerr sources | 7 pages, 7 figures, improved figures, typos corrected | Phys. Lett. B 772: 10-15 (2017) | 10.1016/j.physletb.2017.06.021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A binary system of identical corotating Kerr sources is studied after
deriving the corresponding 3-parametric asymptotically flat exact solution.
Both sources are apart from each other by means of a massless strut (conical
singularity). In the context of black holes, the analytical functional form of
each horizon {\sigma} is expressed in terms of arbitrary Komar physical
parameters: mass M, angular momentum J (with parallel spin), and the coordinate
distance R between the center of each horizon. Later on, all the
thermodynamical properties related to the horizon are depicted by concise
formulae. Finally, the extreme limit case is obtained as a 2-parametric
subclass of Kinnersley-Chitre metric.
| [
{
"created": "Tue, 7 Feb 2017 21:39:35 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jun 2017 09:05:27 GMT",
"version": "v2"
}
] | 2018-11-02 | [
[
"Cabrera-Munguia",
"I.",
""
],
[
"Ceron",
"V. E.",
""
],
[
"López",
"L. A.",
""
],
[
"Pedraza",
"Omar",
""
]
] | A binary system of identical corotating Kerr sources is studied after deriving the corresponding 3-parametric asymptotically flat exact solution. Both sources are apart from each other by means of a massless strut (conical singularity). In the context of black holes, the analytical functional form of each horizon {\sigma} is expressed in terms of arbitrary Komar physical parameters: mass M, angular momentum J (with parallel spin), and the coordinate distance R between the center of each horizon. Later on, all the thermodynamical properties related to the horizon are depicted by concise formulae. Finally, the extreme limit case is obtained as a 2-parametric subclass of Kinnersley-Chitre metric. |
1903.03343 | Subhra Bhattacharya | Shibaji Halder, Subhra Bhattacharya, Subenoy Chakraborty | Spherically symmetric wormhole solutions in a general anisotropic matter
field | Accepted in Phys. Lett. B | null | 10.1016/j.physletb.2019.02.041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work is an attempt to find possible traversable wormhole
solutions in static spherically symmetric space-time supported by anisotropic
matter field. Part of the work could be considered as a generalization of the
work in Phys. Lett. B 757 (2016), 130 in the sense that it extends the work
done therein. The paper provides several examples of wormholes in anisotropic
pressure and provides general mechanisms for finding them. Finally the work
examines the energy conditions corresponding to suggested wormhole solutions.
| [
{
"created": "Fri, 8 Mar 2019 09:55:52 GMT",
"version": "v1"
}
] | 2019-03-11 | [
[
"Halder",
"Shibaji",
""
],
[
"Bhattacharya",
"Subhra",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present work is an attempt to find possible traversable wormhole solutions in static spherically symmetric space-time supported by anisotropic matter field. Part of the work could be considered as a generalization of the work in Phys. Lett. B 757 (2016), 130 in the sense that it extends the work done therein. The paper provides several examples of wormholes in anisotropic pressure and provides general mechanisms for finding them. Finally the work examines the energy conditions corresponding to suggested wormhole solutions. |
2301.05915 | Chao Zhang | Chao Zhang, Hong Guo, Yungui Gong and Bin Wang | Detecting vector charge with extreme mass ratio inspirals onto Kerr
black holes | 35 pages, 12 figures; accepted for publication by JCAP | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extreme mass ratio inspirals (EMRIs) are excellent sources for space-based
observatories to explore the properties of black holes and test no-hair
theorems. We consider EMRIs with a charged compact object inspiralling onto a
Kerr black hole in quasi-circular orbits. Using the Teukolsky and generalized
Sasaki-Nakamura formalisms for the gravitational and vector perturbations about
a Kerr black hole, we numerically calculate the energy fluxes for both
gravitational and vector perturbations induced by a charged particle moving in
equatorial circular orbits. With one-year observations of EMRIs, we apply the
Fisher information matrix method to estimate the charge uncertainty detected by
space-based gravitational wave detectors such as the Laser Interferometer Space
Antenna, TianQin, and Taiji, and we find that it is possible to detect vector
charge as small as $q\sim 0.0049$. The results show that EMRIs composed of a
Kerr black hole with a higher spin $a$ and lighter mass $M$, and a secondary
charged object with more vector charge give smaller relative error on the
charge, thus constrain the charge better. The positive spin of the Kerr black
hole can decrease the charge uncertainty by about one or two orders of
magnitude.
| [
{
"created": "Sat, 14 Jan 2023 13:23:54 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jun 2023 02:28:40 GMT",
"version": "v2"
}
] | 2023-06-29 | [
[
"Zhang",
"Chao",
""
],
[
"Guo",
"Hong",
""
],
[
"Gong",
"Yungui",
""
],
[
"Wang",
"Bin",
""
]
] | Extreme mass ratio inspirals (EMRIs) are excellent sources for space-based observatories to explore the properties of black holes and test no-hair theorems. We consider EMRIs with a charged compact object inspiralling onto a Kerr black hole in quasi-circular orbits. Using the Teukolsky and generalized Sasaki-Nakamura formalisms for the gravitational and vector perturbations about a Kerr black hole, we numerically calculate the energy fluxes for both gravitational and vector perturbations induced by a charged particle moving in equatorial circular orbits. With one-year observations of EMRIs, we apply the Fisher information matrix method to estimate the charge uncertainty detected by space-based gravitational wave detectors such as the Laser Interferometer Space Antenna, TianQin, and Taiji, and we find that it is possible to detect vector charge as small as $q\sim 0.0049$. The results show that EMRIs composed of a Kerr black hole with a higher spin $a$ and lighter mass $M$, and a secondary charged object with more vector charge give smaller relative error on the charge, thus constrain the charge better. The positive spin of the Kerr black hole can decrease the charge uncertainty by about one or two orders of magnitude. |
1107.2732 | De-Cheng Zou | Kang Zhou, Zhan-Ying Yang, De-Cheng Zou and Rui-Hong Yue | Static spherically symmetric star in Gauss-Bonnet gravity | 11 pages, 2 figures and some new references added | null | 10.1088/1674-1056/21/2/020401 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore static spherically symmetric stars in the Gauss-Bonnet gravity
without cosmological constant, and present an exact internal solution which
attaches to the exterior vacuum solution outside stars. It turns out that the
presence of the Gauss-Bonnet term with a positive coupling constant completely
changes thermal and gravitational energies, and the upper bound of red shift of
spectral lines from the surface of stars. Unlike in general relativity, the
upper bound of red shift is dependent on the density of stars in our case.
Moreover, we have proven that two theorems for judging the stability of
equilibrium of stars in general relativity can be hold in Gauss-Bonnet gravity.
| [
{
"created": "Thu, 14 Jul 2011 05:50:21 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Oct 2011 07:28:23 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Nov 2011 11:28:23 GMT",
"version": "v3"
}
] | 2015-05-28 | [
[
"Zhou",
"Kang",
""
],
[
"Yang",
"Zhan-Ying",
""
],
[
"Zou",
"De-Cheng",
""
],
[
"Yue",
"Rui-Hong",
""
]
] | We explore static spherically symmetric stars in the Gauss-Bonnet gravity without cosmological constant, and present an exact internal solution which attaches to the exterior vacuum solution outside stars. It turns out that the presence of the Gauss-Bonnet term with a positive coupling constant completely changes thermal and gravitational energies, and the upper bound of red shift of spectral lines from the surface of stars. Unlike in general relativity, the upper bound of red shift is dependent on the density of stars in our case. Moreover, we have proven that two theorems for judging the stability of equilibrium of stars in general relativity can be hold in Gauss-Bonnet gravity. |
1703.06434 | Rafael A. Porto | Rafael A. Porto | The Lamb shift and the gravitational binding energy for binary black
holes | 18 pages. 6 figures. To appear in Phys. Rev. D | Phys. Rev. D 96, 024063 (2017) | 10.1103/PhysRevD.96.024063 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the correction to the gravitational binding energy for binary
black holes due to the tail effect resembles the Lamb shift in the Hydrogen
atom. In both cases a 'conservative' effect arises from interactions with
'radiation' modes, and moreover an explicit cancelation between near and far
zone divergences is at work. In addition, regularization scheme-dependence may
introduce ambiguity parameters. This is remediated, within an effective field
theory approach, by the implementation of the zero-bin subtraction. We
illustrate the procedure explicitly for the Lamb shift, by performing an
ambiguity-free derivation within the framework of non-relativistic
electrodynamics. We also derive the renormalization group equations from which
we reproduce Bethe logarithm (at order $\alpha_e^5 \log \alpha_e$), and
likewise the contribution to the gravitational potential from the tail effect
(proportional to $v^8 \log v$).
| [
{
"created": "Sun, 19 Mar 2017 13:31:29 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Jul 2017 14:58:36 GMT",
"version": "v2"
}
] | 2017-08-09 | [
[
"Porto",
"Rafael A.",
""
]
] | We show that the correction to the gravitational binding energy for binary black holes due to the tail effect resembles the Lamb shift in the Hydrogen atom. In both cases a 'conservative' effect arises from interactions with 'radiation' modes, and moreover an explicit cancelation between near and far zone divergences is at work. In addition, regularization scheme-dependence may introduce ambiguity parameters. This is remediated, within an effective field theory approach, by the implementation of the zero-bin subtraction. We illustrate the procedure explicitly for the Lamb shift, by performing an ambiguity-free derivation within the framework of non-relativistic electrodynamics. We also derive the renormalization group equations from which we reproduce Bethe logarithm (at order $\alpha_e^5 \log \alpha_e$), and likewise the contribution to the gravitational potential from the tail effect (proportional to $v^8 \log v$). |
2312.05857 | Cosimo Bambi | Cosimo Bambi | Testing General Relativity with black hole X-ray data | 10 pages, 2 figures. Talk given at the "XXXV International Workshop
on High Energy Physics - From Quarks to Galaxies: Elucidating Dark Sides"
(Protvino, Russia, 28 November - 1 December 2023) | Physics of Particles and Nuclei 55, 1418-1423 (2024) | 10.1134/S106377962470103X | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of General Relativity has successfully passed a large number of
observational tests without requiring any adjustment from its original version
proposed by Einstein in 1915. The past 8 years have seen significant
advancements in the study of the strong-field regime, which can now be tested
with gravitational waves, X-ray data, and black hole imaging. This is a compact
and pedagogical review on the state-of-the-art of the tests of General
Relativity with black hole X-ray data.
| [
{
"created": "Sun, 10 Dec 2023 11:44:18 GMT",
"version": "v1"
}
] | 2024-08-15 | [
[
"Bambi",
"Cosimo",
""
]
] | The theory of General Relativity has successfully passed a large number of observational tests without requiring any adjustment from its original version proposed by Einstein in 1915. The past 8 years have seen significant advancements in the study of the strong-field regime, which can now be tested with gravitational waves, X-ray data, and black hole imaging. This is a compact and pedagogical review on the state-of-the-art of the tests of General Relativity with black hole X-ray data. |
1711.08234 | Gopal Sardar | Nirmalya Kajuri and Gopal Sardar | Low Energy Lorentz Violation in Polymer Quantization Revisited | Acknowledgements updated | null | 10.1016/j.physletb.2017.11.071 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In previous work, it had been shown that polymer quantized scalar field
theory predicts that even an inertial observer can experience spontaneous
excitations. This prediction was shown to hold at low energies. However, in
these papers it was assumed that the polymer scale is constant. But it is
possible to relax this condition and obtain a larger class of theories where
the polymer scale is a function of momentum. Does the prediction of low energy
Lorentz violation hold for all of these theories? In this paper we prove that
it does. We also obtain the modified rates of radiation for some of these
theories.
| [
{
"created": "Wed, 22 Nov 2017 11:30:40 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Nov 2017 12:42:51 GMT",
"version": "v2"
}
] | 2018-01-17 | [
[
"Kajuri",
"Nirmalya",
""
],
[
"Sardar",
"Gopal",
""
]
] | In previous work, it had been shown that polymer quantized scalar field theory predicts that even an inertial observer can experience spontaneous excitations. This prediction was shown to hold at low energies. However, in these papers it was assumed that the polymer scale is constant. But it is possible to relax this condition and obtain a larger class of theories where the polymer scale is a function of momentum. Does the prediction of low energy Lorentz violation hold for all of these theories? In this paper we prove that it does. We also obtain the modified rates of radiation for some of these theories. |
1605.04629 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu | Implementing black hole as efficient power plant | 17 pages, 6 figures, and 2 tables | Commun. Theor. Phys. 71, 711 (2019) | 10.1088/0253-6102/71/6/711 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Treating the black hole molecules as working substance and considering its
phase structure, we study the black hole heat engine by a charged anti-de
Sitter black hole. In the reduced temperature-entropy chart, it is found that
the work, heat, and efficiency of the engine are free of the black hole charge.
Applying the Rankine cycle with or without a back pressure mechanism to the
black hole heat engine, the compact formula for the efficiency is obtained. And
the heat, work and efficiency are worked out. The result shows that the black
hole engine working along the Rankine cycle with a back pressure mechanism has
a higher efficiency. This provides a novel and efficient mechanism to produce
the useful mechanical work, and such black hole heat engine may act as a
possible energy source for the high energy astrophysical phenomena near the
black hole.
| [
{
"created": "Mon, 16 May 2016 02:03:46 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jun 2019 21:42:23 GMT",
"version": "v2"
}
] | 2019-06-11 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Treating the black hole molecules as working substance and considering its phase structure, we study the black hole heat engine by a charged anti-de Sitter black hole. In the reduced temperature-entropy chart, it is found that the work, heat, and efficiency of the engine are free of the black hole charge. Applying the Rankine cycle with or without a back pressure mechanism to the black hole heat engine, the compact formula for the efficiency is obtained. And the heat, work and efficiency are worked out. The result shows that the black hole engine working along the Rankine cycle with a back pressure mechanism has a higher efficiency. This provides a novel and efficient mechanism to produce the useful mechanical work, and such black hole heat engine may act as a possible energy source for the high energy astrophysical phenomena near the black hole. |
gr-qc/9406043 | null | M.Carfora, G.F.R.Ellis | The Geometry of classical change of signature | 20pages | Int.J.Mod.Phys.D4:175-188,1995 | 10.1142/S0218271895000120 | null | gr-qc | null | The proposal of the possibility of change of signature in quantum cosmology
has led to the study of this phenomenon in classical general relativity theory,
where there has been some controversy about what is and is not possible. We
here present a new analysis of such a change of signature, based on previous
studies of the initial value problem in general relativity. We emphasize that
there are various continuity suppositions one can make at a classical change of
signature, and consider more general assumptions than made up to now. We
confirm that in general such a change can take place even when the second
fundamental form of the surface of change does not vanish.
| [
{
"created": "Thu, 23 Jun 1994 14:29:28 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Carfora",
"M.",
""
],
[
"Ellis",
"G. F. R.",
""
]
] | The proposal of the possibility of change of signature in quantum cosmology has led to the study of this phenomenon in classical general relativity theory, where there has been some controversy about what is and is not possible. We here present a new analysis of such a change of signature, based on previous studies of the initial value problem in general relativity. We emphasize that there are various continuity suppositions one can make at a classical change of signature, and consider more general assumptions than made up to now. We confirm that in general such a change can take place even when the second fundamental form of the surface of change does not vanish. |
1109.6627 | Muhammad Sharif | M. Sharif and Wajiha Javed | Thermodynamics of a Bardeen black hole in noncommutative space | 17 pages, 9 figures, accepted for publication in Canadian J. Physics | Can. J. Phys. 89(2011)1027-1033 | 10.1139/p11-089 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we examine the effects of space noncommutativity on the
thermodynamics of a Bardeen charged regular black hole. For a suitable choice
of sets of parameters, the behavior of the singularity, horizon, mass function,
black hole mass, temperature, entropy and its differential, area and energy
distribution of the Bardeen solution have been discussed graphically for both
noncommutative and commutative spaces. Graphs show that the commutative
coordinates extrapolate all such quantities (except temperature) for a given
set of parameters. It is interesting to mention here that these sets of
parameters provide the singularity (essential for $r_h>0$) and horizon
($f(r_h)=0$ for $r_h>0$) for the black hole solution in noncommutative space,
while for commutative space no such quantity exists.
| [
{
"created": "Wed, 28 Sep 2011 07:20:18 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Sharif",
"M.",
""
],
[
"Javed",
"Wajiha",
""
]
] | In this paper, we examine the effects of space noncommutativity on the thermodynamics of a Bardeen charged regular black hole. For a suitable choice of sets of parameters, the behavior of the singularity, horizon, mass function, black hole mass, temperature, entropy and its differential, area and energy distribution of the Bardeen solution have been discussed graphically for both noncommutative and commutative spaces. Graphs show that the commutative coordinates extrapolate all such quantities (except temperature) for a given set of parameters. It is interesting to mention here that these sets of parameters provide the singularity (essential for $r_h>0$) and horizon ($f(r_h)=0$ for $r_h>0$) for the black hole solution in noncommutative space, while for commutative space no such quantity exists. |
gr-qc/0311045 | Bijan Saha | Bijan Saha and Todor Boyadjiev | Bianchi type I cosmology with scalar and spinor fields | 22 pages, 11 figures | Phys.Rev. D69 (2004) 124010 | 10.1103/PhysRevD.69.124010 | null | gr-qc | null | We consider a system of interacting spinor and scalar fields in a
gravitational field given by a Bianchi type-I cosmological model filled with
perfect fluid. The interacting term in the Lagrangian is chosen in the form of
derivative coupling, i.e., ${\cal L}_{\rm int} = \frac{\lambda}{2}
\vf_{,\alpha}\vf^{,\alpha} F$, with $F$ being a function of the invariants $I$
an $J$ constructed from bilinear spinor forms $S$ and $P$. We consider the
cases when $F$ is the power or trigonometric functions of its arguments.
Self-consistent solutions to the spinor, scalar and BI gravitational field
equations are obtained. The problems of initial singularity and asymptotically
isotropization process of the initially anisotropic space-time are studied. It
is also shown that the introduction of the Cosmological constant
($\Lambda$-term) in the Lagrangian generates oscillations of the BI model,
which is not the case in absence of $\Lambda$ term. Unlike the case when spinor
field nonlinearity is induced by self-action, in the case in question, wehere
nonlinearity is induced by the scalar field, there exist regular solutions even
without broken dominant energy condition.
| [
{
"created": "Fri, 14 Nov 2003 09:52:21 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Saha",
"Bijan",
""
],
[
"Boyadjiev",
"Todor",
""
]
] | We consider a system of interacting spinor and scalar fields in a gravitational field given by a Bianchi type-I cosmological model filled with perfect fluid. The interacting term in the Lagrangian is chosen in the form of derivative coupling, i.e., ${\cal L}_{\rm int} = \frac{\lambda}{2} \vf_{,\alpha}\vf^{,\alpha} F$, with $F$ being a function of the invariants $I$ an $J$ constructed from bilinear spinor forms $S$ and $P$. We consider the cases when $F$ is the power or trigonometric functions of its arguments. Self-consistent solutions to the spinor, scalar and BI gravitational field equations are obtained. The problems of initial singularity and asymptotically isotropization process of the initially anisotropic space-time are studied. It is also shown that the introduction of the Cosmological constant ($\Lambda$-term) in the Lagrangian generates oscillations of the BI model, which is not the case in absence of $\Lambda$ term. Unlike the case when spinor field nonlinearity is induced by self-action, in the case in question, wehere nonlinearity is induced by the scalar field, there exist regular solutions even without broken dominant energy condition. |
1901.01902 | David Garfinkle | David Garfinkle | Black hole entropy as a consequence of excision | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole entropy is shown to be a consequence of restricting our
description of physics to the exterior of black holes. This precludes the need
for a statistical mechanical description of this entropy in terms of
microstates.
| [
{
"created": "Mon, 7 Jan 2019 16:23:55 GMT",
"version": "v1"
}
] | 2019-01-08 | [
[
"Garfinkle",
"David",
""
]
] | Black hole entropy is shown to be a consequence of restricting our description of physics to the exterior of black holes. This precludes the need for a statistical mechanical description of this entropy in terms of microstates. |
gr-qc/0205008 | Eric Gourgoulhon | Eric Gourgoulhon, Philippe Grandclement, Silvano Bonazzola | Last orbits of binary black holes | 4 pages, 2 figures, invited talk at Journees Relativistes 2001, to
appear in International Journal of Modern Physics A | Int.J.Mod.Phys. A17 (2002) 2689-2694 | 10.1142/S0217751X02011618 | null | gr-qc astro-ph | null | Binary black hole systems in the pre-coalescence stage are numerically
constructed by demanding that the associated spacetime admits a helical Killing
vector. Comparison with third order post-Newtonian calculations indicates a
rather good agreement until the innermost stable circular orbit.
| [
{
"created": "Thu, 2 May 2002 08:36:17 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Gourgoulhon",
"Eric",
""
],
[
"Grandclement",
"Philippe",
""
],
[
"Bonazzola",
"Silvano",
""
]
] | Binary black hole systems in the pre-coalescence stage are numerically constructed by demanding that the associated spacetime admits a helical Killing vector. Comparison with third order post-Newtonian calculations indicates a rather good agreement until the innermost stable circular orbit. |
gr-qc/0510099 | Ragab Gad | A. H. Khater, D. K. Callebaut, S. F. Abdul-Aziz and T. N. Abdelhameed | Potential symmetry and invariant solutions of Fokker-Planck equation in
cylindrical coordinates related to magnetic field diffusion in
magnetohydrodynamics including the Hall current | 14 pages, 9 figures | null | 10.1140/epjb/e2006-00138-5 | null | gr-qc | null | Lie groups involving potential symmetries are applied in connection with the
system of magnetohydrodynamic equations for incompressible matter with Ohm's
law for finite resistivity and Hall current in cylindrical geometry. Some
simplifications allow to obtain a Fokker-Planck type equation. Invariant
solutions are obtained involving the effects of time-dependent flow and the
Hall-current. Some interesting side results of this approach are new exact
solutions that do not seem to have been reported in the literature.
| [
{
"created": "Sun, 23 Oct 2005 09:45:18 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Khater",
"A. H.",
""
],
[
"Callebaut",
"D. K.",
""
],
[
"Abdul-Aziz",
"S. F.",
""
],
[
"Abdelhameed",
"T. N.",
""
]
] | Lie groups involving potential symmetries are applied in connection with the system of magnetohydrodynamic equations for incompressible matter with Ohm's law for finite resistivity and Hall current in cylindrical geometry. Some simplifications allow to obtain a Fokker-Planck type equation. Invariant solutions are obtained involving the effects of time-dependent flow and the Hall-current. Some interesting side results of this approach are new exact solutions that do not seem to have been reported in the literature. |
1301.3098 | Kirill Bronnikov | K.A. Bronnikov, V.N. Melnikov, S.G. Rubin, I.V. Svadkovsky | Nonlinear multidimensional gravity and the Australian dipole | 15 pages, 1 figure. Comments and references added | null | 10.1007/s10714-013-1601-2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existing observational data on possible variations of fundamental
physical constants (FPC) confirm more or less confidently only a variability of
the fine structure constant $\alpha$ in space and time. A model construction
method is described, where variations of $\alpha$ and other FPCs (including the
gravitational constant $G$) follow from the dynamics of extra space-time
dimensions in the framework of curvature-nonlinear multidimensional theories of
gravity. An advantage of this method is a unified approach to variations of
different FPCs. A particular model explaining the observable variations of
$\alpha$ in space and time has been constructed. It comprises a FRW cosmology
with accelerated expansion, perturbed due to slightly inhomogeneous initial
data.
| [
{
"created": "Mon, 14 Jan 2013 19:18:26 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2013 15:56:18 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Melnikov",
"V. N.",
""
],
[
"Rubin",
"S. G.",
""
],
[
"Svadkovsky",
"I. V.",
""
]
] | The existing observational data on possible variations of fundamental physical constants (FPC) confirm more or less confidently only a variability of the fine structure constant $\alpha$ in space and time. A model construction method is described, where variations of $\alpha$ and other FPCs (including the gravitational constant $G$) follow from the dynamics of extra space-time dimensions in the framework of curvature-nonlinear multidimensional theories of gravity. An advantage of this method is a unified approach to variations of different FPCs. A particular model explaining the observable variations of $\alpha$ in space and time has been constructed. It comprises a FRW cosmology with accelerated expansion, perturbed due to slightly inhomogeneous initial data. |
1106.0925 | Richard Woodard | S. P. Miao, N. C. Tsamis and R. P. Woodard | The Graviton Propagator in de Donder Gauge on de Sitter Background | 39 pages, no figures, uses LaTeX2e | J.Math.Phys.52:122301,2011 | 10.1063/1.3664760 | UFIFT-QG-11-03 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the graviton propagator on de Sitter background in exact de
Donder gauge. We prove that it must break de Sitter invariance, just like the
propagator of the massless, minimally coupled scalar. Our explicit solutions
for its two scalar structure functions preserve spatial homogeneity and
isotropy so that the propagator can be used within the larger context of
inflationary cosmology, however, it is simple to alter the residual symmetry.
Because our gauge condition is de Sitter invariant (although no solution for
the propagator can be) renormalization should be simpler using this propagator
than one based on a noncovariant gauge. It remains to be seen how other
computational steps compare.
| [
{
"created": "Sun, 5 Jun 2011 19:55:26 GMT",
"version": "v1"
}
] | 2011-12-30 | [
[
"Miao",
"S. P.",
""
],
[
"Tsamis",
"N. C.",
""
],
[
"Woodard",
"R. P.",
""
]
] | We construct the graviton propagator on de Sitter background in exact de Donder gauge. We prove that it must break de Sitter invariance, just like the propagator of the massless, minimally coupled scalar. Our explicit solutions for its two scalar structure functions preserve spatial homogeneity and isotropy so that the propagator can be used within the larger context of inflationary cosmology, however, it is simple to alter the residual symmetry. Because our gauge condition is de Sitter invariant (although no solution for the propagator can be) renormalization should be simpler using this propagator than one based on a noncovariant gauge. It remains to be seen how other computational steps compare. |
1505.01030 | Hooman Moradpour Hooman | H. Ebadi, H. Moradpour | Thermodynamic of universe with a varying dark energy component | Accepted for Publishing in IJMPD | Vol. 24, No. 14 (2015) 1550098 | 10.1142/S0218271815500984 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a FRW universe filled by a dark energy candidate together with
other possible sources which may include the baryonic and non-baryonic matters.
Thereinafter, we consider a situation in which the cosmos sectors do not
interact with each other. By applying the unified first law of thermodynamics
on the apparent horizon of the FRW universe, we show that the dark energy
candidate may modify the apparent horizon entropy and thus the Bekenstein
limit. Moreover, we generalize our study to the models in which the cosmos
sectors have a mutual interaction. Our final result indicates that the mutual
interaction between the cosmos sectors may add an additional term to the
apparent horizon entropy leading to modify the Bekenstein limit. Relationships
with previous works have been addressed throughout the paper. Finally, we
investigate the validity of the second law of thermodynamics and its
generalized form in the interacting and non-interacting cosmoses.
| [
{
"created": "Mon, 4 May 2015 14:37:53 GMT",
"version": "v1"
},
{
"created": "Thu, 7 May 2015 08:38:51 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Aug 2015 12:40:14 GMT",
"version": "v3"
}
] | 2015-08-24 | [
[
"Ebadi",
"H.",
""
],
[
"Moradpour",
"H.",
""
]
] | We consider a FRW universe filled by a dark energy candidate together with other possible sources which may include the baryonic and non-baryonic matters. Thereinafter, we consider a situation in which the cosmos sectors do not interact with each other. By applying the unified first law of thermodynamics on the apparent horizon of the FRW universe, we show that the dark energy candidate may modify the apparent horizon entropy and thus the Bekenstein limit. Moreover, we generalize our study to the models in which the cosmos sectors have a mutual interaction. Our final result indicates that the mutual interaction between the cosmos sectors may add an additional term to the apparent horizon entropy leading to modify the Bekenstein limit. Relationships with previous works have been addressed throughout the paper. Finally, we investigate the validity of the second law of thermodynamics and its generalized form in the interacting and non-interacting cosmoses. |
2111.02880 | Julius Serbenta | Julius Serbenta, Miko{\l}aj Korzy\'nski | Bilocal geodesic operators in static spherically-symmetric spacetimes | 30 pages, 3 figures | null | 10.1088/1361-6382/ac79f3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method to compute exact expressions for optical observables for
static spherically symmetric spacetimes in the framework of the bilocal
geodesic operator formalism. The expressions are obtained by solving the linear
geodesic deviation equations for null geodesics, using the spacetime symmetries
and the associated conserved quantities. We solve the equations in two
different ways: by varying the geodesics with respect to their initial data and
by directly integrating the equation for the geodesic deviation. The results
are very general and can be applied to a variety of spacetime models and
configurations of the emitter and the observer. We illustrate some of the
aspects with an example of Schwarzschild spacetime, focusing on the behaviour
of the angular diameter distance, the parallax distance, and the distance slip
between the observer and the emitter outside the photon sphere.
| [
{
"created": "Thu, 4 Nov 2021 14:11:42 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Serbenta",
"Julius",
""
],
[
"Korzyński",
"Mikołaj",
""
]
] | We present a method to compute exact expressions for optical observables for static spherically symmetric spacetimes in the framework of the bilocal geodesic operator formalism. The expressions are obtained by solving the linear geodesic deviation equations for null geodesics, using the spacetime symmetries and the associated conserved quantities. We solve the equations in two different ways: by varying the geodesics with respect to their initial data and by directly integrating the equation for the geodesic deviation. The results are very general and can be applied to a variety of spacetime models and configurations of the emitter and the observer. We illustrate some of the aspects with an example of Schwarzschild spacetime, focusing on the behaviour of the angular diameter distance, the parallax distance, and the distance slip between the observer and the emitter outside the photon sphere. |
2205.07470 | Ivan Costa e Silva | Ivan P. Costa e Silva, Jose Luis Flores, Jonatan Herrera | Omniscient foliations and the geometry of cosmological spacetimes | 19 pages, no figures | null | 10.1007/s10714-022-03033-z | null | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | We identify certain general geometric conditions on a foliation of a
spacetime (M,g) by timelike curves that will impede the existence of null
geodesic lines, especially if (M,g) possesses a compact Cauchy hypersurface.
The absence of such lines, in turn, yields well-known restrictions on the
geometry of cosmological spacetimes, in the context of Bartnik's splitting
conjecture. Since the (non)existence of null lines is actually a conformally
invariant property, such conditions only need to apply for some suitable
conformal rescaling of g.
| [
{
"created": "Mon, 16 May 2022 06:43:05 GMT",
"version": "v1"
}
] | 2022-11-30 | [
[
"Silva",
"Ivan P. Costa e",
""
],
[
"Flores",
"Jose Luis",
""
],
[
"Herrera",
"Jonatan",
""
]
] | We identify certain general geometric conditions on a foliation of a spacetime (M,g) by timelike curves that will impede the existence of null geodesic lines, especially if (M,g) possesses a compact Cauchy hypersurface. The absence of such lines, in turn, yields well-known restrictions on the geometry of cosmological spacetimes, in the context of Bartnik's splitting conjecture. Since the (non)existence of null lines is actually a conformally invariant property, such conditions only need to apply for some suitable conformal rescaling of g. |
gr-qc/9503059 | Jorge Pullin | Cayetano Di Bartolo, Rodolfo Gambini, Jorge Griego, Jorge Pullin | The space of states of quantum gravity in terms of loops and extended
loops: some remarks | 16 Pages, Revtex/epsf, one figure included. | J.Math.Phys. 36 (1995) 6510-6528 | 10.1063/1.531254 | CGPG-95/3-5 | gr-qc hep-th | null | This article reviews the status of several solutions to all the constraints
of quantum gravity that have been proposed in terms of loops and extended
loops. We discuss pitfalls of several of the results and in particular discuss
the issues of covariance and regularization of the constraints in terms of
extended loops. We also propose a formalism for ``thickened out loops'' which
does not face the covariance problems of extended loops and may allow to
regularize expressions in a consistent manner.
| [
{
"created": "Wed, 29 Mar 1995 21:35:07 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Di Bartolo",
"Cayetano",
""
],
[
"Gambini",
"Rodolfo",
""
],
[
"Griego",
"Jorge",
""
],
[
"Pullin",
"Jorge",
""
]
] | This article reviews the status of several solutions to all the constraints of quantum gravity that have been proposed in terms of loops and extended loops. We discuss pitfalls of several of the results and in particular discuss the issues of covariance and regularization of the constraints in terms of extended loops. We also propose a formalism for ``thickened out loops'' which does not face the covariance problems of extended loops and may allow to regularize expressions in a consistent manner. |
2302.09041 | Daniel Mata-Pacheco | H. Garcia-Compean, D. Mata-Pacheco, L. Zapata | Ho\v{r}ava-Lifshitz $F(\bar{R})$ theories and the Swampland | 34 pages, 6 figures. All sections were improved. Subsection 4.5
added. References added | null | 10.3390/universe9110460 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The compatibility between the de Sitter Swampland conjecture and
Ho\v{r}ava--Lifshitz $F(\bar{R})$ theories with a flat FLRW metric is studied.
We first study the standard $f(R)$ theories and show that the only way in which
the dS conjecture can be made independent of $R$ is by considering a power law
of the form $f(R)\sim R^{\gamma}$. The conjecture and the consistency of the
theory puts restrictions on $\gamma$ to be greater but close to one. For
$F(\bar{R})$ theories described by its two parameters $\lambda$ and $\mu$, we
use the equations of motion to construct the function starting with an ansatz
for the scale factor in the Jordan frame of the power law form. By performing a
conformal transformation on the three metric to the Einstein frame, we can
obtain an action of gravity plus a scalar field by relating the parameters of
the theory. The non-projectable and projectable cases are studied and the
differences are outlined. The obtained $F(\bar{R})$ function consists of terms
of the form $\bar{R}^{\gamma}$ with the possibility of having negative power
terms. The dS conjecture leads to inequalities for the $\lambda$ parameter; in
both versions, it becomes restricted to be greater but close to $1/3$. We can
also study the general case in which $\mu$ and $\lambda$ are considered as
independent. The obtained $F$ function has the same form as before. The
consistency of the theory and the dS conjecture lead to a set of inequalities
on both parameters that are studied numerically. In all cases, $\lambda$ is
restricted by $\mu$ around $1/3$, and we obtain $\lambda\to1/3$ if $\mu\to0$.
We consider the $f(R)$ limit $\mu,\lambda \to 1$ and we obtain consistent
results. Finally, we study the case of a constant Hubble parameter. The dS
conjecture can be fulfilled by restricting the parameters of the theory;
however, the constraint makes this compatibility exclusive to these kinds of
theories.
| [
{
"created": "Fri, 17 Feb 2023 18:16:55 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Oct 2023 20:21:08 GMT",
"version": "v2"
}
] | 2023-11-02 | [
[
"Garcia-Compean",
"H.",
""
],
[
"Mata-Pacheco",
"D.",
""
],
[
"Zapata",
"L.",
""
]
] | The compatibility between the de Sitter Swampland conjecture and Ho\v{r}ava--Lifshitz $F(\bar{R})$ theories with a flat FLRW metric is studied. We first study the standard $f(R)$ theories and show that the only way in which the dS conjecture can be made independent of $R$ is by considering a power law of the form $f(R)\sim R^{\gamma}$. The conjecture and the consistency of the theory puts restrictions on $\gamma$ to be greater but close to one. For $F(\bar{R})$ theories described by its two parameters $\lambda$ and $\mu$, we use the equations of motion to construct the function starting with an ansatz for the scale factor in the Jordan frame of the power law form. By performing a conformal transformation on the three metric to the Einstein frame, we can obtain an action of gravity plus a scalar field by relating the parameters of the theory. The non-projectable and projectable cases are studied and the differences are outlined. The obtained $F(\bar{R})$ function consists of terms of the form $\bar{R}^{\gamma}$ with the possibility of having negative power terms. The dS conjecture leads to inequalities for the $\lambda$ parameter; in both versions, it becomes restricted to be greater but close to $1/3$. We can also study the general case in which $\mu$ and $\lambda$ are considered as independent. The obtained $F$ function has the same form as before. The consistency of the theory and the dS conjecture lead to a set of inequalities on both parameters that are studied numerically. In all cases, $\lambda$ is restricted by $\mu$ around $1/3$, and we obtain $\lambda\to1/3$ if $\mu\to0$. We consider the $f(R)$ limit $\mu,\lambda \to 1$ and we obtain consistent results. Finally, we study the case of a constant Hubble parameter. The dS conjecture can be fulfilled by restricting the parameters of the theory; however, the constraint makes this compatibility exclusive to these kinds of theories. |
1703.06415 | Fabio M. Mele | Fabio M. Mele | Quantum Metric and Entanglement on Spin Networks | 162 pages, 11 figures, Master Thesis | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the idea that, in the background-independent framework of a
Quantum Theory of Gravity, entanglement is expected to play a key role in the
reconstruction of spacetime geometry, we investigate the possibility of using
the formalism of Geometric Quantum Mechanics (GQM) to give a tensorial
characterization of entanglement on spin network states. Our analysis focuses
on the simple case of a single link graph (Wilson line state) for which we
define a dictionary to construct a Riemannian metric tensor and a symplectic
structure on the space of states. The manifold of (pure) quantum states is then
stratified in terms of orbits of equally entangled states and the
block-coefficient matrices of the corresponding pulled-back tensors fully
encode the information about separability and entanglement. In particular, the
off-diagonal blocks define an entanglement monotone interpreted as a distance
with respect to the separable state. As such, it provides a measure of graph
connectivity. Finally, in the maximally entangled gauge-invariant case, the
entanglement monotone is proportional to a power of the area of the surface
dual to the link. This suggests a connection between the GQM formalism and the
(simplicial) geometric properties of spin network states through entanglement.
| [
{
"created": "Sun, 19 Mar 2017 10:28:20 GMT",
"version": "v1"
}
] | 2017-03-21 | [
[
"Mele",
"Fabio M.",
""
]
] | Motivated by the idea that, in the background-independent framework of a Quantum Theory of Gravity, entanglement is expected to play a key role in the reconstruction of spacetime geometry, we investigate the possibility of using the formalism of Geometric Quantum Mechanics (GQM) to give a tensorial characterization of entanglement on spin network states. Our analysis focuses on the simple case of a single link graph (Wilson line state) for which we define a dictionary to construct a Riemannian metric tensor and a symplectic structure on the space of states. The manifold of (pure) quantum states is then stratified in terms of orbits of equally entangled states and the block-coefficient matrices of the corresponding pulled-back tensors fully encode the information about separability and entanglement. In particular, the off-diagonal blocks define an entanglement monotone interpreted as a distance with respect to the separable state. As such, it provides a measure of graph connectivity. Finally, in the maximally entangled gauge-invariant case, the entanglement monotone is proportional to a power of the area of the surface dual to the link. This suggests a connection between the GQM formalism and the (simplicial) geometric properties of spin network states through entanglement. |
gr-qc/0307007 | Adrian P. Gentle | Adrian P. Gentle, Nathan D. George, Arkady Kheyfets and Warner A.
Miller | The constraints as evolution equations for numerical relativity | 10 pages, updated to match published version | Class.Quant.Grav. 21 (2004) 83-92 | 10.1088/0264-9381/21/1/006 | null | gr-qc | null | The Einstein equations have proven surprisingly difficult to solve
numerically. A standard diagnostic of the problems which plague the field is
the failure of computational schemes to satisfy the constraints, which are
known to be mathematically conserved by the evolution equations. We describe a
new approach to rewriting the constraints as first-order evolution equations,
thereby guaranteeing that they are satisfied to a chosen accuracy by any
discretization scheme. This introduces a set of four subsidiary constraints
which are far simpler than the standard constraint equations, and which should
be more easily conserved in computational applications. We explore the manner
in which the momentum constraints are already incorporated in several existing
formulations of the Einstein equations, and demonstrate the ease with which our
new constraint-conserving approach can be incorporated into these schemes.
| [
{
"created": "Tue, 1 Jul 2003 16:53:41 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Oct 2003 16:50:17 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Gentle",
"Adrian P.",
""
],
[
"George",
"Nathan D.",
""
],
[
"Kheyfets",
"Arkady",
""
],
[
"Miller",
"Warner A.",
""
]
] | The Einstein equations have proven surprisingly difficult to solve numerically. A standard diagnostic of the problems which plague the field is the failure of computational schemes to satisfy the constraints, which are known to be mathematically conserved by the evolution equations. We describe a new approach to rewriting the constraints as first-order evolution equations, thereby guaranteeing that they are satisfied to a chosen accuracy by any discretization scheme. This introduces a set of four subsidiary constraints which are far simpler than the standard constraint equations, and which should be more easily conserved in computational applications. We explore the manner in which the momentum constraints are already incorporated in several existing formulations of the Einstein equations, and demonstrate the ease with which our new constraint-conserving approach can be incorporated into these schemes. |
1504.06014 | Tiberiu Harko | Bogdan D\u{a}nil\u{a}, Tiberiu Harko, Zolt\'an Kov\'acs | Thin accretion disks around cold Bose-Einstein Condensate stars | 21 pages, 12 figures, accepted for publication in EPJC; reference
added | Eur. Phys. J. C (2015) 75:203 | 10.1140/epjc/s10052-015-3428-3 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Due to their superfluid properties some compact astrophysical objects, like
neutron or quark stars, may contain a significant part of their matter in the
form of a Bose-Einstein Condensate. Observationally distinguishing between
neutron/quark stars and Bose-Einstein Condensate stars is a major challenge for
this latter theoretical model. An observational possibility of indirectly
distinguishing Bose-Einstein Condensate stars from neutron/quark stars is
through the study of the thin accretion disks around compact general
relativistic objects. In the present paper, we perform a detailed comparative
study of the electromagnetic and thermodynamic properties of the thin accretion
disks around rapidly rotating Bose-Einstein Condensate stars, neutron stars and
quark stars, respectively. Due to the differences in the exterior geometry, the
thermodynamic and electromagnetic properties of the disks (energy flux,
temperature distribution, equilibrium radiation spectrum and efficiency of
energy conversion) are different for these classes of compact objects. Hence in
this preliminary study we have pointed out some astrophysical signatures that
may allow to observationally discriminate between Bose-Einstein Condensate
stars and neutron/quark stars, respectively.
| [
{
"created": "Thu, 23 Apr 2015 00:16:20 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Apr 2015 10:54:40 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Dănilă",
"Bogdan",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Kovács",
"Zoltán",
""
]
] | Due to their superfluid properties some compact astrophysical objects, like neutron or quark stars, may contain a significant part of their matter in the form of a Bose-Einstein Condensate. Observationally distinguishing between neutron/quark stars and Bose-Einstein Condensate stars is a major challenge for this latter theoretical model. An observational possibility of indirectly distinguishing Bose-Einstein Condensate stars from neutron/quark stars is through the study of the thin accretion disks around compact general relativistic objects. In the present paper, we perform a detailed comparative study of the electromagnetic and thermodynamic properties of the thin accretion disks around rapidly rotating Bose-Einstein Condensate stars, neutron stars and quark stars, respectively. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution, equilibrium radiation spectrum and efficiency of energy conversion) are different for these classes of compact objects. Hence in this preliminary study we have pointed out some astrophysical signatures that may allow to observationally discriminate between Bose-Einstein Condensate stars and neutron/quark stars, respectively. |
2106.07958 | Philippe G. LeFloch | Philippe G. LeFloch | Singularity scattering laws for bouncing cosmologies: a brief overview | 16 pages | Developments in Lorentzian Geometry: GeLoCor 2020, Cordoba, Spain,
Feb. 1-5. Edited by: A.L. Albujer, M. Caballero, A. Garc\'ia-Parrado, J.
Herrera and R. Rubio. Springer Proc. Math. Stat., 2022 | null | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | For contracting/expanding bouncing cosmologies, the formulation of junction
conditions at a bouncing was recently revisited by the author in collaboration
with B. Le Floch and G. Veneziano. The regime of interest here is the so-called
quiescent regime, in which a monotone behavior of the metric is observed and
asymptotic expansions can be derived. Here, we overview our new methodology
based on the notion of {\sl singularity scattering maps} and {\sl cyclic
spacetimes}, and we present our main conclusions. In particular, we provide a
classification of all allowed bouncing junction conditions, including three
universal laws.
| [
{
"created": "Tue, 15 Jun 2021 08:19:07 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Mar 2022 16:23:32 GMT",
"version": "v2"
}
] | 2022-03-15 | [
[
"LeFloch",
"Philippe G.",
""
]
] | For contracting/expanding bouncing cosmologies, the formulation of junction conditions at a bouncing was recently revisited by the author in collaboration with B. Le Floch and G. Veneziano. The regime of interest here is the so-called quiescent regime, in which a monotone behavior of the metric is observed and asymptotic expansions can be derived. Here, we overview our new methodology based on the notion of {\sl singularity scattering maps} and {\sl cyclic spacetimes}, and we present our main conclusions. In particular, we provide a classification of all allowed bouncing junction conditions, including three universal laws. |
2205.03830 | Yuxuan Peng | Yuxuan Peng | New Anisotropic Gauss-Bonnet Black Holes in Five Dimensions at the
Critical Point | 8pages, no figures. arXiv admin note: text overlap with
arXiv:2105.08482 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain new vacuum static black hole solutions with anisotropic horizons in
Einstein-Gauss-Bonnet gravity with a negative cosmological constant in five
dimensions. The translational invariance along one direction on the
3-dimensional horizon cross section is broken. The Gauss-Bonnet coupling
{\alpha} is at the critical point where there is one single AdS vacuum. These
solutions does not appear in the form of a warped product, i.e. they lack a
common warping factor, and the metric contains 2 arbitrary functions, h(r) of
the radial coordinate r and H(y) of the horizon coordinate y -- some degeneracy
in the metric. The nontrivial horizon and the degeneracy may be closely related
to the critical value of {\alpha}. We introduce the process of obtaining the
solutions and some of their properties, and also prove a uniqueness theorem for
the case when there is a common warping factor for the rest two directions.
| [
{
"created": "Sun, 8 May 2022 10:06:08 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jun 2022 03:37:32 GMT",
"version": "v2"
},
{
"created": "Sun, 14 Jan 2024 03:33:20 GMT",
"version": "v3"
}
] | 2024-01-17 | [
[
"Peng",
"Yuxuan",
""
]
] | We obtain new vacuum static black hole solutions with anisotropic horizons in Einstein-Gauss-Bonnet gravity with a negative cosmological constant in five dimensions. The translational invariance along one direction on the 3-dimensional horizon cross section is broken. The Gauss-Bonnet coupling {\alpha} is at the critical point where there is one single AdS vacuum. These solutions does not appear in the form of a warped product, i.e. they lack a common warping factor, and the metric contains 2 arbitrary functions, h(r) of the radial coordinate r and H(y) of the horizon coordinate y -- some degeneracy in the metric. The nontrivial horizon and the degeneracy may be closely related to the critical value of {\alpha}. We introduce the process of obtaining the solutions and some of their properties, and also prove a uniqueness theorem for the case when there is a common warping factor for the rest two directions. |
2101.04458 | Bibhas Majhi Ranjan | Bibhas Ranjan Majhi | Is instability near a black hole key for "thermalization'' of its
horizon? | Few comments added, to appear in General Relativity and Gravitation | null | null | null | gr-qc hep-th math-ph math.MP nlin.CD quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We put forward an attempt towards building a possible theoretical model to
understand the observer dependent thermalization of black hole horizon. The
near horizon Hamiltonian for a massless, chargeless particle is $xp$ type. This
is unstable in nature and so the horizon can induce instability in a system.
The particle in turn finds the horizon thermal when it interacts with it. We
explicitly show this in the Schrodinger as well as in Heisenberg pictures by
taking into account the time evolution of the system under this Hamiltonian.
Hence we postulate that existing instability near the horizon can be one of the
potential candidates for explaining the black hole thermalization.
| [
{
"created": "Tue, 12 Jan 2021 13:05:37 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jan 2021 10:25:06 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Aug 2021 11:34:24 GMT",
"version": "v3"
},
{
"created": "Thu, 11 Aug 2022 16:16:46 GMT",
"version": "v4"
}
] | 2022-08-12 | [
[
"Majhi",
"Bibhas Ranjan",
""
]
] | We put forward an attempt towards building a possible theoretical model to understand the observer dependent thermalization of black hole horizon. The near horizon Hamiltonian for a massless, chargeless particle is $xp$ type. This is unstable in nature and so the horizon can induce instability in a system. The particle in turn finds the horizon thermal when it interacts with it. We explicitly show this in the Schrodinger as well as in Heisenberg pictures by taking into account the time evolution of the system under this Hamiltonian. Hence we postulate that existing instability near the horizon can be one of the potential candidates for explaining the black hole thermalization. |
gr-qc/0110020 | Andreas Freise | A. Freise, M. M. Casey, S. Gossler, H. Grote, G. Heinzel, H. Lueck, D.
I. Robertson, K. A. Strain, H. Ward, B. Willke, J. Hough and K. Danzmann | Performance of a 1200m long suspended Fabry-Perot cavity | Amaldi 4 (Perth 2001) conference proceedings, 10 pages, 8 figures | null | 10.1088/0264-9381/19/7/322 | null | gr-qc | null | Using one arm of the Michelson interferometer and the power recycling mirror
of the interferometric gravitational wave detector GEO600, we created a
Fabry-Perot cavity with a length of 1200 m. The main purpose of this experiment
was to gather first experience with the main optics, its suspensions and the
corresponding control systems. The residual displacement of a main mirror is
about 150 nm rms. By stabilising the length of the 1200 m long cavity to the
pre-stabilised laser beam we achieved an error point frequency noise of 0.1
mHz/sqrt(Hz) at 100 Hz Fourier frequency. In addition we demonstrated the
reliable performance of all included subsystems by several 10-hour-periods of
continuous stable operation. Thus the full frequency stabilisation scheme for
GEO600 was successfully tested.
| [
{
"created": "Tue, 2 Oct 2001 14:55:02 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Nov 2001 15:07:32 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Freise",
"A.",
""
],
[
"Casey",
"M. M.",
""
],
[
"Gossler",
"S.",
""
],
[
"Grote",
"H.",
""
],
[
"Heinzel",
"G.",
""
],
[
"Lueck",
"H.",
""
],
[
"Robertson",
"D. I.",
""
],
[
"Strain",
"K. A.",
""
],
[
"Ward",
"H.",
""
],
[
"Willke",
"B.",
""
],
[
"Hough",
"J.",
""
],
[
"Danzmann",
"K.",
""
]
] | Using one arm of the Michelson interferometer and the power recycling mirror of the interferometric gravitational wave detector GEO600, we created a Fabry-Perot cavity with a length of 1200 m. The main purpose of this experiment was to gather first experience with the main optics, its suspensions and the corresponding control systems. The residual displacement of a main mirror is about 150 nm rms. By stabilising the length of the 1200 m long cavity to the pre-stabilised laser beam we achieved an error point frequency noise of 0.1 mHz/sqrt(Hz) at 100 Hz Fourier frequency. In addition we demonstrated the reliable performance of all included subsystems by several 10-hour-periods of continuous stable operation. Thus the full frequency stabilisation scheme for GEO600 was successfully tested. |
gr-qc/0302001 | Lawrence P. Horwitz | O. Oron and L.P. Horwitz | The conformal metric associated with the U(1) gauge of the Stueckelberg-
Schr\"odinger equation | Plain TeX, 9 pages | Found.Phys. 33 (2003) 1177-1187 | null | TAUP 2729-03 | gr-qc | null | We review the classical and quantum mechanics of Stueckelberg, and introduce
the compensation fields necessary for the gauge covariance of the Stueckelberg-
Schr\"odinger equation. To achieve this, one must introduce a fifth, Lorentz
scalar, compensation field, in addition to the four vector fields which
compensate the action of the space-time derivatives. A generalized Lorentz
force can be derived from the classical Hamilton equations associated with this
evolution function. We show that the fifth (scalar) field can be eliminated
through the introduction of a conformal metric on the spacetime manifold. The
geodesic equation associated with this metric coincides with the Lorentz force,
and is therefore dynamically equivalent. Since the generalized Maxwell
equations for the five dimensional fields provide an equation relating the
fifth field with the spacetime density of events, one can derive the spacetime
event density associated with the Friedmann-Robertson-Walker solution of the
Einstein equations. The resulting density, in the conformal coordinate space,
is isotropic and homogeneous, decreasing as the square of the Robertson-Walker
scale factor. Using the Einstein equations, one sees that both for the static
and matter dominated models, the conformal time slice in which the events which
generate the world lines are contained becomes progressively thinner as the
inverse square of the scale factor, establishing a simple correspondence
between the configurations predicted by the underlying
Friedmann-Robertson-Walker dynamical model and the configurations in the
conformal coordinates.
| [
{
"created": "Sun, 2 Feb 2003 11:15:59 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Feb 2003 07:12:31 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Oron",
"O.",
""
],
[
"Horwitz",
"L. P.",
""
]
] | We review the classical and quantum mechanics of Stueckelberg, and introduce the compensation fields necessary for the gauge covariance of the Stueckelberg- Schr\"odinger equation. To achieve this, one must introduce a fifth, Lorentz scalar, compensation field, in addition to the four vector fields which compensate the action of the space-time derivatives. A generalized Lorentz force can be derived from the classical Hamilton equations associated with this evolution function. We show that the fifth (scalar) field can be eliminated through the introduction of a conformal metric on the spacetime manifold. The geodesic equation associated with this metric coincides with the Lorentz force, and is therefore dynamically equivalent. Since the generalized Maxwell equations for the five dimensional fields provide an equation relating the fifth field with the spacetime density of events, one can derive the spacetime event density associated with the Friedmann-Robertson-Walker solution of the Einstein equations. The resulting density, in the conformal coordinate space, is isotropic and homogeneous, decreasing as the square of the Robertson-Walker scale factor. Using the Einstein equations, one sees that both for the static and matter dominated models, the conformal time slice in which the events which generate the world lines are contained becomes progressively thinner as the inverse square of the scale factor, establishing a simple correspondence between the configurations predicted by the underlying Friedmann-Robertson-Walker dynamical model and the configurations in the conformal coordinates. |
gr-qc/0511117 | Rafael Montemayor | Santiago A. Martinez, R. Montemayor and Luis F. Urrutia | Reality and causality in quantum gravity modified electrodynamics | 15 pages, LaTex, minor changes to clarify some points, version
accepted for publication | Phys.Rev. D74 (2006) 065020 | 10.1103/PhysRevD.74.065020 | null | gr-qc astro-ph hep-ph | null | We present a general description of the propagation properties of quantum
gravity modified electrodynamics characterized by constitutive relations up to
second order in the correction parameter. The effective description corresponds
to an electrodynamics in a dispersive and absorptive non-local medium, where
the Green functions and the refraction indices can be explicitly calculated.
The reality of the electromagnetic field together with the requirement of
causal propagation in a given referrence frame leads to restrictions in the
form of such refraction indices. In particular, absorption must be present in
all cases and, contrary to the usual assumption, it is the dominant aspect in
those effective models which exhibit linear effects in the correction parameter
not related to birefringence. In such a situation absorption is linear while
propagation is quadratical in the correction parameter.
| [
{
"created": "Mon, 21 Nov 2005 19:38:12 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Jun 2006 14:45:15 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Sep 2006 10:57:06 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Martinez",
"Santiago A.",
""
],
[
"Montemayor",
"R.",
""
],
[
"Urrutia",
"Luis F.",
""
]
] | We present a general description of the propagation properties of quantum gravity modified electrodynamics characterized by constitutive relations up to second order in the correction parameter. The effective description corresponds to an electrodynamics in a dispersive and absorptive non-local medium, where the Green functions and the refraction indices can be explicitly calculated. The reality of the electromagnetic field together with the requirement of causal propagation in a given referrence frame leads to restrictions in the form of such refraction indices. In particular, absorption must be present in all cases and, contrary to the usual assumption, it is the dominant aspect in those effective models which exhibit linear effects in the correction parameter not related to birefringence. In such a situation absorption is linear while propagation is quadratical in the correction parameter. |
2309.08497 | Takahiro Tanaka | Takahiro Tanaka and Yuko Urakawa | Statistical anisotropy of primordial gravitational waves from
generalized $\delta N$ formalism | 5pages, no figure | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In this letter, we demonstrate how to use the generalized $\delta N$
formalism, which enables us to compute all the large scale fluctuations,
including the gravitational waves, solely by solving the evolution of the
background homogeneous Universe. Using the Noether charge density, we derive an
analytic formula which describes the mapping between the fluctuations at the
horizon crossing and the sourced gravitational waves at the end of inflation.
This formula can apply also to an inflation model with an anisotropic
background.
| [
{
"created": "Fri, 15 Sep 2023 16:01:41 GMT",
"version": "v1"
}
] | 2023-09-18 | [
[
"Tanaka",
"Takahiro",
""
],
[
"Urakawa",
"Yuko",
""
]
] | In this letter, we demonstrate how to use the generalized $\delta N$ formalism, which enables us to compute all the large scale fluctuations, including the gravitational waves, solely by solving the evolution of the background homogeneous Universe. Using the Noether charge density, we derive an analytic formula which describes the mapping between the fluctuations at the horizon crossing and the sourced gravitational waves at the end of inflation. This formula can apply also to an inflation model with an anisotropic background. |
gr-qc/0205097 | U\u{g}ur Camci | Yusuf Sucu and Nuri Unal | Solution of Massless Spin One Wave Equation in Robertson-Walker
Space-time | 16 Pages, Latex, no figures, An expanded version of paper published
in International Journal of Modern Physics A, 17 (2002) 1137 | Int.J.Mod.Phys. A17 (2002) 1137-1147 | 10.1142/S0217751X02005852 | null | gr-qc | null | We generalize the quantum spinor wave equation for photon into the curved
space-time and discuss the solutions of this equation in Robertson-Walker
space-time and compare them with the solution of the Maxwell equations in the
same space-time.
| [
{
"created": "Wed, 22 May 2002 11:57:08 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Apr 2005 14:38:47 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Sucu",
"Yusuf",
""
],
[
"Unal",
"Nuri",
""
]
] | We generalize the quantum spinor wave equation for photon into the curved space-time and discuss the solutions of this equation in Robertson-Walker space-time and compare them with the solution of the Maxwell equations in the same space-time. |
1410.5882 | John Miller | John Miller, Lisa Barsotti, Salvatore Vitale, Peter Fritschel, Daniel
Sigg and Matthew Evans | Prospects for doubling the range of Advanced LIGO | null | Phys. Rev. D 91, 062005 2015 | 10.1103/PhysRevD.91.062005 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the coming years, the gravitational wave community will be optimizing
detector performance for a variety of astrophysical sources that make competing
demands on the detector sensitivity in different frequency bands. In this paper
we describe a number of technologies that are being developed as anticipated
upgrades to the Advanced LIGO detector, and quantify the potential sensitivity
improvement they offer. Specifically, we consider squeezed light injection for
reduction of quantum noise, detector design and materials changes which reduce
thermal noise, and mirrors with significantly increased mass. We explore how
each of these technologies impacts the detection of the most promising
gravitational wave sources, and suggest an effective progression of upgrades
which culminate in a factor of two broadband sensitivity improvement.
| [
{
"created": "Tue, 21 Oct 2014 23:27:47 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Dec 2014 18:28:18 GMT",
"version": "v2"
}
] | 2015-03-31 | [
[
"Miller",
"John",
""
],
[
"Barsotti",
"Lisa",
""
],
[
"Vitale",
"Salvatore",
""
],
[
"Fritschel",
"Peter",
""
],
[
"Sigg",
"Daniel",
""
],
[
"Evans",
"Matthew",
""
]
] | In the coming years, the gravitational wave community will be optimizing detector performance for a variety of astrophysical sources that make competing demands on the detector sensitivity in different frequency bands. In this paper we describe a number of technologies that are being developed as anticipated upgrades to the Advanced LIGO detector, and quantify the potential sensitivity improvement they offer. Specifically, we consider squeezed light injection for reduction of quantum noise, detector design and materials changes which reduce thermal noise, and mirrors with significantly increased mass. We explore how each of these technologies impacts the detection of the most promising gravitational wave sources, and suggest an effective progression of upgrades which culminate in a factor of two broadband sensitivity improvement. |
2108.05772 | Hemwati Nandan | Shobhit Giri, Hemwati Nandan | Stability Analysis of Geodesics and Quasinormal Modes of a Dual Stringy
Black Hole Via Lyapunov Exponents | null | General Relativity and Gravitation, 53(8), pp.1-27 (2021) | 10.1007/s10714-021-02845-9 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the stability of both timelike as well as null circular
geodesics in the vicinity of a dual (3+1) dimensional stringy black hole (BH)
spacetime by using an excellent tool so-called Lyapunov exponent. The proper
time ($\tau$) Lyapunov exponent ($\lambda_{p}$) and coordinate time ($t$)
Lyapunov exponent~($\lambda_{c}$) are explicitly derived to analyze the
stability of equatorial circular geodesics for the stringy BH spacetime with
\emph{electric charge} parameter ($\alpha$) and \emph{magnetic charge}
parameter~($Q$). By computing these exponents for both the cases of BH
spacetime, it is observed that the coordinate time Lyapunov exponent of
magnetically charged stringy BH for both timelike and null geodesics are
independent of magnetic charge parameter $(Q)$. The variation of the ratio of
Lyapunov exponents with radius of timelike circular orbits ($r_{0}/M$) for both
the cases of stringy BH are presented. The behavior of instability exponent for
null circular geodesics with respect to charge parameters ($\alpha$ and $Q$)
are also observed for both the cases of BH. Further, by establishing a relation
between quasinormal modes (QNMs) and parameters related to null circular
geodesics (like angular frequency and Lyapunov exponent), we deduced the QNMs
(or QNM frequencies) for a massless scalar field perturbation around
\emph{both} the cases of stringy BH spacetime in the eikonal limit. The
variation of scalar field potential with charge parameters and angular momentum
of perturbation ($l$) are visually presented and discussed accordingly.
| [
{
"created": "Thu, 12 Aug 2021 14:31:52 GMT",
"version": "v1"
}
] | 2021-08-13 | [
[
"Giri",
"Shobhit",
""
],
[
"Nandan",
"Hemwati",
""
]
] | We investigate the stability of both timelike as well as null circular geodesics in the vicinity of a dual (3+1) dimensional stringy black hole (BH) spacetime by using an excellent tool so-called Lyapunov exponent. The proper time ($\tau$) Lyapunov exponent ($\lambda_{p}$) and coordinate time ($t$) Lyapunov exponent~($\lambda_{c}$) are explicitly derived to analyze the stability of equatorial circular geodesics for the stringy BH spacetime with \emph{electric charge} parameter ($\alpha$) and \emph{magnetic charge} parameter~($Q$). By computing these exponents for both the cases of BH spacetime, it is observed that the coordinate time Lyapunov exponent of magnetically charged stringy BH for both timelike and null geodesics are independent of magnetic charge parameter $(Q)$. The variation of the ratio of Lyapunov exponents with radius of timelike circular orbits ($r_{0}/M$) for both the cases of stringy BH are presented. The behavior of instability exponent for null circular geodesics with respect to charge parameters ($\alpha$ and $Q$) are also observed for both the cases of BH. Further, by establishing a relation between quasinormal modes (QNMs) and parameters related to null circular geodesics (like angular frequency and Lyapunov exponent), we deduced the QNMs (or QNM frequencies) for a massless scalar field perturbation around \emph{both} the cases of stringy BH spacetime in the eikonal limit. The variation of scalar field potential with charge parameters and angular momentum of perturbation ($l$) are visually presented and discussed accordingly. |
gr-qc/9909081 | Vesselin Petkov | Vesselin Petkov | Propagation of light in non-inertial reference frames | 14 pages, 1 figure, LaTeX, Section 4 has been devoted to the Sagnac
effect | Chap. 7 of "Relativity and the Nature of Spacetime," 2nd ed
(Springer, 2009) | null | null | gr-qc | null | It is shown that the complete description of the propagation of light in a
gravitational field and in non-inertial reference frames in general requires an
average coordinate and an average proper velocity of light. The need for an
average coordinate velocity of light in non-inertial frames is demonstrated by
considering the propagation of two vertical light rays in the Einstein elevator
(in addition to the horizontal ray originally discussed by Einstein). As an
average proper velocity of light is implicitly used in the Shapiro time delay
(as shown in the Appendix) it is explicitly derived and it is shown that for a
round trip of a light signal between two points in a gravitational field the
Shapiro time delay not only depends on which point it is measured at, but in
the case of a parallel gravitational field it is not always a delay effect. The
propagation of light in rotating frames (the Sagnac effect) is also discussed
and an expression for the coordinate velocity of light is derived. The use of
this coordinate velocity naturally explains why an observer on a rotating disk
finds that two light signals emitted from a point on the rim of the disk and
propagating in opposite directions along the rim do not arrive simultaneously
at the same point.
| [
{
"created": "Mon, 27 Sep 1999 05:39:19 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Sep 1999 02:36:17 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Jan 2000 04:18:56 GMT",
"version": "v3"
},
{
"created": "Sun, 24 Jun 2001 22:11:46 GMT",
"version": "v4"
},
{
"created": "Mon, 22 Jul 2002 23:31:36 GMT",
"version": "v5"
},
{
"created": "Tue, 23 Jul 2002 20:46:56 GMT",
"version": "v6"
},
{
"created": "Sun, 14 Dec 2003 21:02:12 GMT",
"version": "v7"
}
] | 2011-11-18 | [
[
"Petkov",
"Vesselin",
""
]
] | It is shown that the complete description of the propagation of light in a gravitational field and in non-inertial reference frames in general requires an average coordinate and an average proper velocity of light. The need for an average coordinate velocity of light in non-inertial frames is demonstrated by considering the propagation of two vertical light rays in the Einstein elevator (in addition to the horizontal ray originally discussed by Einstein). As an average proper velocity of light is implicitly used in the Shapiro time delay (as shown in the Appendix) it is explicitly derived and it is shown that for a round trip of a light signal between two points in a gravitational field the Shapiro time delay not only depends on which point it is measured at, but in the case of a parallel gravitational field it is not always a delay effect. The propagation of light in rotating frames (the Sagnac effect) is also discussed and an expression for the coordinate velocity of light is derived. The use of this coordinate velocity naturally explains why an observer on a rotating disk finds that two light signals emitted from a point on the rim of the disk and propagating in opposite directions along the rim do not arrive simultaneously at the same point. |
1910.09690 | Wolfgang Tichy | Wolfgang Tichy, Alireza Rashti, Tim Dietrich, Reetika Dudi, Bernd
Br\"ugmann | Constructing Binary Neutron Star Initial Data with High Spins, High
Compactness, and High Mass-Ratios | 16 pages, 11 figures | Phys. Rev. D 100, 124046 (2019) | 10.1103/PhysRevD.100.124046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The construction of accurate and consistent initial data for various binary
parameters is a critical ingredient for numerical relativity simulations of the
compact binary coalescence. In this article, we present an upgrade of the
pseudospectral SGRID code, which enables us to access even larger regions of
the binary neutron star parameter space. As a proof of principle, we present a
selected set of first simulations based on initial configurations computed with
the new code version. In particular, we simulate two millisecond pulsars close
to their breakup spin, highly compact neutron stars with masses at about $98\%$
of the maximum supported mass of the employed equation of state, and an unequal
mass systems with mass ratios even outside the range predicted by population
synthesis models ($q = 2.03$). The discussed code extension will help us to
simulate previously unexplored binary configurations. This is a necessary step
to construct and test new gravitational wave approximants and to interpret
upcoming binary neutron star merger observations. When we construct initial
data, one has to specify various parameters, such as a rotation parameter for
each star. Some of these parameters do not have direct physical meaning, which
makes comparisons with other methods or models difficult. To facilitate this,
we introduce simple estimates for the initial spin, momentum, mass, and center
of mass of each individual star.
| [
{
"created": "Mon, 21 Oct 2019 23:07:14 GMT",
"version": "v1"
}
] | 2019-12-25 | [
[
"Tichy",
"Wolfgang",
""
],
[
"Rashti",
"Alireza",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Dudi",
"Reetika",
""
],
[
"Brügmann",
"Bernd",
""
]
] | The construction of accurate and consistent initial data for various binary parameters is a critical ingredient for numerical relativity simulations of the compact binary coalescence. In this article, we present an upgrade of the pseudospectral SGRID code, which enables us to access even larger regions of the binary neutron star parameter space. As a proof of principle, we present a selected set of first simulations based on initial configurations computed with the new code version. In particular, we simulate two millisecond pulsars close to their breakup spin, highly compact neutron stars with masses at about $98\%$ of the maximum supported mass of the employed equation of state, and an unequal mass systems with mass ratios even outside the range predicted by population synthesis models ($q = 2.03$). The discussed code extension will help us to simulate previously unexplored binary configurations. This is a necessary step to construct and test new gravitational wave approximants and to interpret upcoming binary neutron star merger observations. When we construct initial data, one has to specify various parameters, such as a rotation parameter for each star. Some of these parameters do not have direct physical meaning, which makes comparisons with other methods or models difficult. To facilitate this, we introduce simple estimates for the initial spin, momentum, mass, and center of mass of each individual star. |
gr-qc/0601098 | Cristian Stelea | Eugen Radu, Cristian Stelea, D. H. Tchrakian | Features of gravity-Yang-Mills hierarchies in d-dimensions | 19 pages, 9 figures | Phys.Rev. D73 (2006) 084015 | 10.1103/PhysRevD.73.084015 | null | gr-qc hep-th | null | Higher dimensional, direct analogues of the usual d=4 Einstein--Yang-Mills
(EYM) systems are studied. These consist of the gravitational and Yang-Mills
hierarchies in d=4p dimensional spacetimes, both consisting of 2p-form
curvature terms only. Regular and black hole solutions are constructed in
$2p+2\le d \le 4p$, in which dimensions the total mass-energy is finite,
generalising the familiar Bartnik-McKinnon solutions in EYM theory for p=1. In
d=4p, this similarity is complete. In the special case of d=2p+1, just beyond
the finite energy range of d, exact solutions in closed form are found.
Finally, d=2p+1 purely gravitational systems, whose solutions generalise the
static d=3 BTZ solutions, are discussed.
| [
{
"created": "Mon, 23 Jan 2006 23:12:24 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Radu",
"Eugen",
""
],
[
"Stelea",
"Cristian",
""
],
[
"Tchrakian",
"D. H.",
""
]
] | Higher dimensional, direct analogues of the usual d=4 Einstein--Yang-Mills (EYM) systems are studied. These consist of the gravitational and Yang-Mills hierarchies in d=4p dimensional spacetimes, both consisting of 2p-form curvature terms only. Regular and black hole solutions are constructed in $2p+2\le d \le 4p$, in which dimensions the total mass-energy is finite, generalising the familiar Bartnik-McKinnon solutions in EYM theory for p=1. In d=4p, this similarity is complete. In the special case of d=2p+1, just beyond the finite energy range of d, exact solutions in closed form are found. Finally, d=2p+1 purely gravitational systems, whose solutions generalise the static d=3 BTZ solutions, are discussed. |
2003.12571 | Akira Dohi | Akira Dohi, Ryotaro Kase, Rampei Kimura, Kazuhiro Yamamoto, Masa-aki
Hashimoto | Neutron star cooling in modified gravity theories | 34 pages, 35 figures; v2 - significantly revised with several
additional calculations, accepted for publication in PTEP | null | null | null | gr-qc astro-ph.CO astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study thermal evolution of isolated neutron stars in scalar-tensor
theories for the first time. Whether the rapid cooling due to the direct Urca
process occurs or not is an interesting question in the viewpoint of the
temperature observation of isolated neutron stars. Moreover, investigation of
the cooling effect of nucleon superfluidity also has the large uncertainties
though it is important in modern cooling theory. The cooling effect is
typically influenced by the proton fraction and the central density. If a fifth
force is mediated due to modification of gravity, the relation between the
central density and mass of neutron stars differs from one in general
relativity, and the cooling curve is also naively expected to be varied. We
find that an unscreened fifth force near the surface of neutron stars changes
mass-central density relation, and the direct Urca process can be triggered
even for neutron stars with smaller mass. We also present cooling curves
including nucleon superfluidity under the scalar-tensor theory. These results
show that it might be useful to test gravitational theories with cooling
observations of neutron stars.
| [
{
"created": "Fri, 27 Mar 2020 07:49:10 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jul 2021 05:42:02 GMT",
"version": "v2"
}
] | 2021-07-27 | [
[
"Dohi",
"Akira",
""
],
[
"Kase",
"Ryotaro",
""
],
[
"Kimura",
"Rampei",
""
],
[
"Yamamoto",
"Kazuhiro",
""
],
[
"Hashimoto",
"Masa-aki",
""
]
] | We study thermal evolution of isolated neutron stars in scalar-tensor theories for the first time. Whether the rapid cooling due to the direct Urca process occurs or not is an interesting question in the viewpoint of the temperature observation of isolated neutron stars. Moreover, investigation of the cooling effect of nucleon superfluidity also has the large uncertainties though it is important in modern cooling theory. The cooling effect is typically influenced by the proton fraction and the central density. If a fifth force is mediated due to modification of gravity, the relation between the central density and mass of neutron stars differs from one in general relativity, and the cooling curve is also naively expected to be varied. We find that an unscreened fifth force near the surface of neutron stars changes mass-central density relation, and the direct Urca process can be triggered even for neutron stars with smaller mass. We also present cooling curves including nucleon superfluidity under the scalar-tensor theory. These results show that it might be useful to test gravitational theories with cooling observations of neutron stars. |
gr-qc/0410002 | Edward Teo | Kenneth Hong and Edward Teo | A new form of the rotating C-metric | 13 pages, LaTeX | Class.Quant.Grav.22:109-118,2005 | 10.1088/0264-9381/22/1/007 | null | gr-qc | null | In a previous paper, we showed that the traditional form of the charged
C-metric can be transformed, by a change of coordinates, into one with an
explicitly factorizable structure function. This new form of the C-metric has
the advantage that its properties become much simpler to analyze. In this
paper, we propose an analogous new form for the rotating charged C-metric, with
structure function G(\xi)=(1-\xi^2)(1+r_{+}A\xi)(1+r_{-}A\xi), where r_\pm are
the usual locations of the horizons in the Kerr-Newman black hole. Unlike the
non-rotating case, this new form is not related to the traditional one by a
coordinate transformation. We show that the physical distinction between these
two forms of the rotating C-metric lies in the nature of the conical
singularities causing the black holes to accelerate apart: the new form is free
of torsion singularities and therefore does not contain any closed timelike
curves. We claim that this new form should be considered the natural
generalization of the C-metric with rotation.
| [
{
"created": "Thu, 30 Sep 2004 23:35:00 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Hong",
"Kenneth",
""
],
[
"Teo",
"Edward",
""
]
] | In a previous paper, we showed that the traditional form of the charged C-metric can be transformed, by a change of coordinates, into one with an explicitly factorizable structure function. This new form of the C-metric has the advantage that its properties become much simpler to analyze. In this paper, we propose an analogous new form for the rotating charged C-metric, with structure function G(\xi)=(1-\xi^2)(1+r_{+}A\xi)(1+r_{-}A\xi), where r_\pm are the usual locations of the horizons in the Kerr-Newman black hole. Unlike the non-rotating case, this new form is not related to the traditional one by a coordinate transformation. We show that the physical distinction between these two forms of the rotating C-metric lies in the nature of the conical singularities causing the black holes to accelerate apart: the new form is free of torsion singularities and therefore does not contain any closed timelike curves. We claim that this new form should be considered the natural generalization of the C-metric with rotation. |
2207.08513 | Diego S\'aez-Chill\'on G\'omez | Sergei D. Odintsov, Diego Saez-Chillon Gomez and German S. Sharov | Testing viable extensions of Einstein-Gauss-Bonnet gravity | 11 pages, 3 figures. To be published in Phys. of the Dark Universe | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some models within the framework of Gauss-Bonnet gravities are considered in
the presence of a non-minimally coupled scalar field. By imposing a particular
constraint on the scalar field coupling, an extension of the called
Einstein-Gauss-Bonnet gravity that keeps the correct speed of propagation for
gravitational waves, is considered. The cosmological evolution for this viable
class of models is studied and compared with observational data (BAO, CMB, Sne
Ia,..), where we obtain the corresponding bounds for these theories and show
that such theories fit well the data and provide a well-behaved cosmological
evolution in comparison to the standard model of cosmology. Some statistical
parameters show that the goodness of the fits are slightly better than those
for $\Lambda$CDM model.
| [
{
"created": "Mon, 18 Jul 2022 11:09:26 GMT",
"version": "v1"
}
] | 2022-07-19 | [
[
"Odintsov",
"Sergei D.",
""
],
[
"Gomez",
"Diego Saez-Chillon",
""
],
[
"Sharov",
"German S.",
""
]
] | Some models within the framework of Gauss-Bonnet gravities are considered in the presence of a non-minimally coupled scalar field. By imposing a particular constraint on the scalar field coupling, an extension of the called Einstein-Gauss-Bonnet gravity that keeps the correct speed of propagation for gravitational waves, is considered. The cosmological evolution for this viable class of models is studied and compared with observational data (BAO, CMB, Sne Ia,..), where we obtain the corresponding bounds for these theories and show that such theories fit well the data and provide a well-behaved cosmological evolution in comparison to the standard model of cosmology. Some statistical parameters show that the goodness of the fits are slightly better than those for $\Lambda$CDM model. |
1007.2481 | Marc Lachieze-Rey | Marc Lachieze-Rey (APC) | Spin and Clifford algebras, an introduction | 40 pages ; published version with slight modifications for on-line
reading | 7th International Conference on Clifford Algebras and their
Applications, Toulouse (France) : France (2005) | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this short pedagogical presentation, we introduce the spin groups and the
spinors from the point of view of group theory. We also present, independently,
the construction of the low dimensional Clifford algebras. And we establish the
link between the two approaches. Finally, we give some notions of the
generalisations to arbitrary spacetimes, by the introduction of the spin and
spinor bundles.
| [
{
"created": "Thu, 15 Jul 2010 06:00:33 GMT",
"version": "v1"
}
] | 2010-07-19 | [
[
"Lachieze-Rey",
"Marc",
"",
"APC"
]
] | In this short pedagogical presentation, we introduce the spin groups and the spinors from the point of view of group theory. We also present, independently, the construction of the low dimensional Clifford algebras. And we establish the link between the two approaches. Finally, we give some notions of the generalisations to arbitrary spacetimes, by the introduction of the spin and spinor bundles. |
gr-qc/0502106 | L. C. Garcia de Andrade | L.C. Garcia de Andrade | The necessity of non-Riemannian acoustic spacetime in the fluids with
vorticity | Latex file | Phys.Lett. A346 (2005) 327-329 | 10.1016/j.physleta.2005.07.023 | null | gr-qc | null | The necessity of a newly proposed (PRD 70 (2004) 64004) non-Riemannian
acoustic spacetime structure called acoustic torsion of sound wave equation in
fluids with vorticity are discussed. It is shown that this structure, although
not always necessary is present in fluids with vorticity even when the
perturbation is rotational. This can be done by solving the Bergliaffa et al
(Physica D (2004)) gauge invariant equations for sound, superposed to a general
background flow, needs to support a non-Riemannian acoustic geometry in
effective spacetime. Bergliaffa et al have previously shown that a Riemannian
structure cannot be associated to this gauge invariant general system.
| [
{
"created": "Fri, 25 Feb 2005 07:08:01 GMT",
"version": "v1"
}
] | 2010-04-05 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | The necessity of a newly proposed (PRD 70 (2004) 64004) non-Riemannian acoustic spacetime structure called acoustic torsion of sound wave equation in fluids with vorticity are discussed. It is shown that this structure, although not always necessary is present in fluids with vorticity even when the perturbation is rotational. This can be done by solving the Bergliaffa et al (Physica D (2004)) gauge invariant equations for sound, superposed to a general background flow, needs to support a non-Riemannian acoustic geometry in effective spacetime. Bergliaffa et al have previously shown that a Riemannian structure cannot be associated to this gauge invariant general system. |
gr-qc/9711057 | Jelle Boersma | Jelle Boersma | Averaging in Cosmology | 24 pages, Latex, accepted for publication in Phys. Rev. D | Phys.Rev. D57 (1998) 798-810 | 10.1103/PhysRevD.57.798 | null | gr-qc | null | In this paper we discuss the effect of local inhomogeneities on the global
expansion of nearly FLRW universes, in a perturbative setting. We derive a
generic linearized averaging operation for metric perturbations from basic
assumptions, and we explicify the issue of gauge invariance. We derive a gauge
invariant expression for the back-reaction of density inhomogeneities on the
global expansion of perturbed FLRW spacetimes, in terms of observable
quantities, and we calculate the effect quantitatively. Since we do not adopt a
comoving gauge, our result incorporates the back-reaction on the metric due to
scalar velocity and vorticity perturbations. The results are compared with the
results by other authors in this field.
| [
{
"created": "Wed, 19 Nov 1997 13:31:23 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Boersma",
"Jelle",
""
]
] | In this paper we discuss the effect of local inhomogeneities on the global expansion of nearly FLRW universes, in a perturbative setting. We derive a generic linearized averaging operation for metric perturbations from basic assumptions, and we explicify the issue of gauge invariance. We derive a gauge invariant expression for the back-reaction of density inhomogeneities on the global expansion of perturbed FLRW spacetimes, in terms of observable quantities, and we calculate the effect quantitatively. Since we do not adopt a comoving gauge, our result incorporates the back-reaction on the metric due to scalar velocity and vorticity perturbations. The results are compared with the results by other authors in this field. |
gr-qc/0603018 | Mauricio Bellini | Alfredo Raya, Jose Edgar Madriz Aguilar (IFM, Michoacana University),
Mauricio Bellini (Mar del Plata University & CONICET) | Gravitoelectromagnetic inflation from a 5D vacuum state: a new formalism | final version (figure included) | Phys.Lett.B638:314-319,2006 | 10.1016/j.physletb.2006.05.068 | null | gr-qc | null | We propose a novel formalism for inflation from a 5D vacuum state which could
explain both, seeds of matter and magnetic fields in the early universe.
| [
{
"created": "Tue, 7 Mar 2006 22:35:35 GMT",
"version": "v1"
},
{
"created": "Wed, 3 May 2006 21:42:57 GMT",
"version": "v2"
},
{
"created": "Fri, 26 May 2006 20:42:24 GMT",
"version": "v3"
},
{
"created": "Wed, 7 Jun 2006 19:05:07 GMT",
"version": "v4"
},
{
"created": "Tue, 22 May 2007 19:28:32 GMT",
"version": "v5"
}
] | 2008-11-26 | [
[
"Raya",
"Alfredo",
"",
"IFM, Michoacana University"
],
[
"Aguilar",
"Jose Edgar Madriz",
"",
"IFM, Michoacana University"
],
[
"Bellini",
"Mauricio",
"",
"Mar del Plata University & CONICET"
]
] | We propose a novel formalism for inflation from a 5D vacuum state which could explain both, seeds of matter and magnetic fields in the early universe. |
1311.0744 | Lorenzo Sebastiani | L. Sebastiani, G. Cognola, R. Myrzakulov, S.D. Odintsov and S. Zerbini | Nearly Starobinsky inflation from modified gravity | 23 pages, minor revision done | Phys. Rev. D 89, 023518 (2014) | 10.1103/PhysRevD.89.023518 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study inflation induced by (power-low) scalar curvature corrections to
General Relativity. The class of inflationary scalar potentials
$V(\sigma)\sim\exp[n\,\sigma]$, $n$ general parameter, is investigated in the
Einsein frame and the corresponding actions in the Jordan frame are derived. We
found the conditions for which these potentials are able to reproduce viable
inflation according with the last cosmological data and lead to large scalar
curvature corrections which emerge only at a mass scale larger than the Planck
mass. Cosmological constant may appear or be set equal to zero in the Jordan
frame action without changing the behaviour of the model during inflation.
Moreover, polynomial corrections to General Relativity are analyzed in detail.
When de Sitter space-time emerges as an exact solution of the models, it is
necessary to use perturbative equations in the Jordan framework to study their
dynamics during the inflation. In this case, we demonstrate that the Ricci
scalar decreases after a correct amount of inflation, making the models
consistent with the observable evolution of the universe.
| [
{
"created": "Mon, 4 Nov 2013 16:00:38 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Sep 2014 10:41:00 GMT",
"version": "v2"
}
] | 2014-09-22 | [
[
"Sebastiani",
"L.",
""
],
[
"Cognola",
"G.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Zerbini",
"S.",
""
]
] | We study inflation induced by (power-low) scalar curvature corrections to General Relativity. The class of inflationary scalar potentials $V(\sigma)\sim\exp[n\,\sigma]$, $n$ general parameter, is investigated in the Einsein frame and the corresponding actions in the Jordan frame are derived. We found the conditions for which these potentials are able to reproduce viable inflation according with the last cosmological data and lead to large scalar curvature corrections which emerge only at a mass scale larger than the Planck mass. Cosmological constant may appear or be set equal to zero in the Jordan frame action without changing the behaviour of the model during inflation. Moreover, polynomial corrections to General Relativity are analyzed in detail. When de Sitter space-time emerges as an exact solution of the models, it is necessary to use perturbative equations in the Jordan framework to study their dynamics during the inflation. In this case, we demonstrate that the Ricci scalar decreases after a correct amount of inflation, making the models consistent with the observable evolution of the universe. |
1312.3057 | Jia Wang | Jia Wang, Wei Xu and Xin-he Meng | The Entropy Relations of Black Holes with Multihorizons in Higher
Dimensions | 9 pages, revtex4-1, Accepted for publication in Physical Review D | Phys. Rev. D 89, 044034 (2014) | 10.1103/PhysRevD.89.044034 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the entropy relations of multi-horizons black holes in higher
dimensional (A)dS spacetime with maximal symmetries, including Einstein-Maxwell
gravity and $f(R)$(-Maxwell) gravity. These additional equalities in
thermodynamics are expected to be useful to understanding the origin of black
hole entropy at the microscopic level. Revisiting the entropy product
introduced by Cvetic etc, in our case, it has an unexpected behavior. It is
shown that this electric charge $Q$ plays an important role in this entropy
product. The entropy product of charged black holes only depends on the
electric charge $Q$ and is mass independence. When $Q$ vanishes in the
solution, it turns to mass dependence, even when including the effect of the
un-physical ``virtual'' horizons. In this sense, the ``universal relation'' of
this entropy product is destroyed. Then we introduce another kind of
``universal'' entropy relation, which only depends on the cosmological constant
$\Lambda$ and the background topology $k$, and which does not depend on the
conserved charges $Q$, nor even the mass $M$.
| [
{
"created": "Wed, 11 Dec 2013 07:45:01 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Mar 2014 13:05:39 GMT",
"version": "v2"
}
] | 2014-03-04 | [
[
"Wang",
"Jia",
""
],
[
"Xu",
"Wei",
""
],
[
"Meng",
"Xin-he",
""
]
] | We study the entropy relations of multi-horizons black holes in higher dimensional (A)dS spacetime with maximal symmetries, including Einstein-Maxwell gravity and $f(R)$(-Maxwell) gravity. These additional equalities in thermodynamics are expected to be useful to understanding the origin of black hole entropy at the microscopic level. Revisiting the entropy product introduced by Cvetic etc, in our case, it has an unexpected behavior. It is shown that this electric charge $Q$ plays an important role in this entropy product. The entropy product of charged black holes only depends on the electric charge $Q$ and is mass independence. When $Q$ vanishes in the solution, it turns to mass dependence, even when including the effect of the un-physical ``virtual'' horizons. In this sense, the ``universal relation'' of this entropy product is destroyed. Then we introduce another kind of ``universal'' entropy relation, which only depends on the cosmological constant $\Lambda$ and the background topology $k$, and which does not depend on the conserved charges $Q$, nor even the mass $M$. |
gr-qc/0510060 | Filimonova Irina V | S.S. Gershtein, A.A. Logunov, M.A. Mestvirishvili | On Boundedness of the Admissible Time Slowing Down by the Gravitational
Field | 5 pages | null | 10.1134/S1028335806020017 | null | gr-qc | null | It is shown that there exists, in the field theory of gravitation, contrary
to the General Theory of Relativity (GTR), a bound for admissible time slowing
down by the gravitational field which excludes a possibility of unbounded
compression of matter by the gravity forces.
| [
{
"created": "Thu, 13 Oct 2005 08:24:51 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Gershtein",
"S. S.",
""
],
[
"Logunov",
"A. A.",
""
],
[
"Mestvirishvili",
"M. A.",
""
]
] | It is shown that there exists, in the field theory of gravitation, contrary to the General Theory of Relativity (GTR), a bound for admissible time slowing down by the gravitational field which excludes a possibility of unbounded compression of matter by the gravity forces. |
gr-qc/9512006 | Hans-Juergen Schmidt | Hans - Juergen Schmidt | How to measure spatial distances? | 4 pages, latex, no figures | Gen.Rel.Grav. 28 (1996) 899-903 | 10.1007/BF02104755 | Potsdam/Math 95/10 | gr-qc | null | The use of time--like geodesics to measure temporal distances is better
justified than the use of space--like geodesics for a measurement of spatial
distances. We give examples where a ''spatial distance'' cannot be
appropriately determined by the length of a space--like geodesic.
| [
{
"created": "Wed, 29 Nov 1995 17:17:28 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Schmidt",
"Hans - Juergen",
""
]
] | The use of time--like geodesics to measure temporal distances is better justified than the use of space--like geodesics for a measurement of spatial distances. We give examples where a ''spatial distance'' cannot be appropriately determined by the length of a space--like geodesic. |
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