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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0311067 | Diego Pavon | Winfried Zimdahl, Diego Pavon | Statefinder parameters for interacting dark energy | 11 pages, two encapsulated eps figures, key words: cosmology,
accelerated expansion, statefinder parameters | Gen.Rel.Grav. 36 (2004) 1483-1491 | 10.1023/B:GERG.0000022584.54115.9e | null | gr-qc astro-ph hep-ph hep-th | null | We argue that the recently introduced "statefinder parameters" (Sahni et al.,
JETP Lett. 77, 201 (2003)), that include the third derivative of the cosmic
scale factor, are useful tools to characterize interacting quitessence models.
We specify the statefinder parameters for two classes of models that solve, or
at least alleviate, the coincidence problem.
| [
{
"created": "Thu, 20 Nov 2003 16:08:03 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Zimdahl",
"Winfried",
""
],
[
"Pavon",
"Diego",
""
]
] | We argue that the recently introduced "statefinder parameters" (Sahni et al., JETP Lett. 77, 201 (2003)), that include the third derivative of the cosmic scale factor, are useful tools to characterize interacting quitessence models. We specify the statefinder parameters for two classes of models that solve, or at least alleviate, the coincidence problem. |
gr-qc/9412072 | Ed Seidel | Steven R. Brandt and Edward Seidel | The Evolution of Distorted Rotating Black Holes I: Methods and Tests | 22 pages, LaTeX with RevTeX 3.0 macros. 16 uuencoded gz-compressed
postscript figures. Also available at http://jean-luc.ncsa.uiuc.edu/Papers/
Submitted to Physical Review D | Phys.Rev. D52 (1995) 856-869 | 10.1103/PhysRevD.52.856 | null | gr-qc | null | We have developed a new numerical code to study the evolution of distorted,
rotating black holes. We discuss the numerical methods and gauge conditions we
developed to evolve such spacetimes. The code has been put through a series of
tests, and we report on (a) results of comparisons with codes designed to
evolve non-rotating holes, (b) evolution of Kerr spacetimes for which analytic
properties are known, and (c) the evolution of distorted rotating holes. The
code accurately reproduces results of the previous NCSA non-rotating code and
passes convergence tests. New features of the evolution of rotating black holes
not seen in non-rotating holes are identified. With this code we can evolve
rotating black holes up to about $t=100M$, depending on the resolution and
angular momentum. We also describe a new family of black hole initial data sets
which represent rotating holes with a wide range of distortion parameters, and
distorted non-rotating black holes with odd-parity radiation. Finally, we study
the limiting slices for a maximally sliced rotating black hole and find good
agreement with theoretical predictions.
| [
{
"created": "Thu, 22 Dec 1994 17:48:45 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Brandt",
"Steven R.",
""
],
[
"Seidel",
"Edward",
""
]
] | We have developed a new numerical code to study the evolution of distorted, rotating black holes. We discuss the numerical methods and gauge conditions we developed to evolve such spacetimes. The code has been put through a series of tests, and we report on (a) results of comparisons with codes designed to evolve non-rotating holes, (b) evolution of Kerr spacetimes for which analytic properties are known, and (c) the evolution of distorted rotating holes. The code accurately reproduces results of the previous NCSA non-rotating code and passes convergence tests. New features of the evolution of rotating black holes not seen in non-rotating holes are identified. With this code we can evolve rotating black holes up to about $t=100M$, depending on the resolution and angular momentum. We also describe a new family of black hole initial data sets which represent rotating holes with a wide range of distortion parameters, and distorted non-rotating black holes with odd-parity radiation. Finally, we study the limiting slices for a maximally sliced rotating black hole and find good agreement with theoretical predictions. |
2203.10872 | Gihyuk Cho | Gihyuk Cho | Third post-Newtonian gravitational radiation from two-body scattering
II. Hereditary Energy radiation | null | null | 10.1103/PhysRevD.105.104035 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We compute the hereditary part of the third post-Newtonian accurate
gravitational energy radiation from hyperbolic scatterings (and parabolic
scatterings) of non-spinning compact objects. We employ large angular momentum
($j$) expansion, and compute it to the relative $1/j^{11}$ order (so the first
12 terms). For parabolic scattering case, the exact solution is computed. At
the end, the completely collected expression of the energy radiation upto the
third post-Newtonian and from $1/j^{3}$ to $1/j^{15}$ order, is presented
including the instantaneous contribution.
| [
{
"created": "Mon, 21 Mar 2022 10:51:40 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Oct 2022 01:25:30 GMT",
"version": "v2"
}
] | 2022-10-04 | [
[
"Cho",
"Gihyuk",
""
]
] | We compute the hereditary part of the third post-Newtonian accurate gravitational energy radiation from hyperbolic scatterings (and parabolic scatterings) of non-spinning compact objects. We employ large angular momentum ($j$) expansion, and compute it to the relative $1/j^{11}$ order (so the first 12 terms). For parabolic scattering case, the exact solution is computed. At the end, the completely collected expression of the energy radiation upto the third post-Newtonian and from $1/j^{3}$ to $1/j^{15}$ order, is presented including the instantaneous contribution. |
1201.3504 | Jose Navarro | J. Navarro, J. B. Sancho | Energy and electromagnetism of a differential form | 28 pages. Referee's suggestions added. To appear in Journal of
Mathematical Physics | J. Math. Phys. 53, 102501 (2012) | 10.1063/1.4754817 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Let X be a smooth manifold of dimension 1+n endowed with a lorentzian metric
g, and let T be the electromagnetic energy tensor associated to a 2-form F. In
this paper we characterize this tensor T as the only 2-covariant natural tensor
associated to a lorentzian metric and a 2-form that is independent of the unit
of scale and satisfies certain condition on its divergence. This
characterization is motivated on physical grounds, and can be used to justify
the Einstein-Maxwell field equations. More generally, we characterize in a
similar manner the energy tensor associated to a differential form of arbitrary
order k. Finally, we develop a generalized theory of electromagnetism where
charged particles are not punctual, but of an arbitrary fixed dimension p. In
this theory, the electromagnetic field F is a differential form of order 2+p
and its electromagnetic energy tensor is precisely the energy tensor associated
to F.
| [
{
"created": "Tue, 17 Jan 2012 13:00:35 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Feb 2012 12:49:51 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Sep 2012 10:34:45 GMT",
"version": "v3"
}
] | 2012-10-23 | [
[
"Navarro",
"J.",
""
],
[
"Sancho",
"J. B.",
""
]
] | Let X be a smooth manifold of dimension 1+n endowed with a lorentzian metric g, and let T be the electromagnetic energy tensor associated to a 2-form F. In this paper we characterize this tensor T as the only 2-covariant natural tensor associated to a lorentzian metric and a 2-form that is independent of the unit of scale and satisfies certain condition on its divergence. This characterization is motivated on physical grounds, and can be used to justify the Einstein-Maxwell field equations. More generally, we characterize in a similar manner the energy tensor associated to a differential form of arbitrary order k. Finally, we develop a generalized theory of electromagnetism where charged particles are not punctual, but of an arbitrary fixed dimension p. In this theory, the electromagnetic field F is a differential form of order 2+p and its electromagnetic energy tensor is precisely the energy tensor associated to F. |
2306.08081 | Muhammad Zubair | M. Zubair, Mushayydha Farooq | Bouncing behaviours in four dimensional Einstein Gauss-Bonnet gravity
with Cosmography and Observational constraints | 24 pages, 25 figures | Eur. Phys. J. Plus (2023) 138:173 | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This manuscript is based on an investigation of bouncing cosmology in a 4D
Einstein Gauss-Bonnet gravity. Various bouncing models such as symmetric
bounce, matter bounce, super bounce, and oscillatory bounce have been examined.
Expressions for energy density, pressure, equation of state parameter have been
derived in the most general manner and then reduced to 4D Einstein Gauss-Bonnet
gravity for isotropic, homogenous, FLRW cosmos. Physical interpretation of
Hubble and deceleration parameters has also been discussed and plotted for each
model from non-vanishing scale factors. Non-singular bouncing models indulge in
accelerating late-time cosmic acceleration phenomenon. It has been analysed
that the Gauss-Bonnet coupling parameter has a lesser contribution to the
dynamics of modified gravity while the bouncing parameter has noticeable
effects. We have examined various energy conditions and witnessed the violation
of strong and null energy conditions in bouncing models. Analytical expressions
for jerk and snap parameters have also been calculated in terms of cosmic time
and redshift. We have explored bouncing models through specific cosmographic
tests to check their validity. Also, through stability analysis, matter bounce
becomes the most stable model by increasing the value of the bouncing
parameter. To find best-fit values, bouncing models have been constrained with
Hubble data set and $\Lambda$CDM. We have calculated the values of parameters
by applying the least-square fitting method. To make this analysis quantified,
we have employed reduced chi-squared method on $H(z)$ data sets for each model.
| [
{
"created": "Wed, 31 May 2023 07:12:49 GMT",
"version": "v1"
}
] | 2023-06-16 | [
[
"Zubair",
"M.",
""
],
[
"Farooq",
"Mushayydha",
""
]
] | This manuscript is based on an investigation of bouncing cosmology in a 4D Einstein Gauss-Bonnet gravity. Various bouncing models such as symmetric bounce, matter bounce, super bounce, and oscillatory bounce have been examined. Expressions for energy density, pressure, equation of state parameter have been derived in the most general manner and then reduced to 4D Einstein Gauss-Bonnet gravity for isotropic, homogenous, FLRW cosmos. Physical interpretation of Hubble and deceleration parameters has also been discussed and plotted for each model from non-vanishing scale factors. Non-singular bouncing models indulge in accelerating late-time cosmic acceleration phenomenon. It has been analysed that the Gauss-Bonnet coupling parameter has a lesser contribution to the dynamics of modified gravity while the bouncing parameter has noticeable effects. We have examined various energy conditions and witnessed the violation of strong and null energy conditions in bouncing models. Analytical expressions for jerk and snap parameters have also been calculated in terms of cosmic time and redshift. We have explored bouncing models through specific cosmographic tests to check their validity. Also, through stability analysis, matter bounce becomes the most stable model by increasing the value of the bouncing parameter. To find best-fit values, bouncing models have been constrained with Hubble data set and $\Lambda$CDM. We have calculated the values of parameters by applying the least-square fitting method. To make this analysis quantified, we have employed reduced chi-squared method on $H(z)$ data sets for each model. |
1506.02497 | Prado Martin-Moruno | Prado Martin-Moruno, Nelson J. Nunes | Attracted to de Sitter II: cosmology of the shift-symmetric Horndeski
models | V1: 20 pages, 11 figures. V2: 1 reference added. V3: 21 pages.
Clarifications in the discussion; no physics changes. This version accepted
for publication in JCAP | JCAP 09 (2015) 056 | 10.1088/1475-7516/2015/09/056 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Horndeski models with a de Sitter critical point for any kind of material
content may provide a mechanism to alleviate the cosmological constant problem.
Moreover, they could allow us to understand the current accelerated expansion
of the universe as the result of the dynamical approach to the critical point
when it is an attractor. We show that this critical point is indeed an
attractor for the shift- symmetric subfamily of models with these
characteristics. We study the cosmological scenario that results when
considering radiation and matter content, and conclude that their background
dynamics is compatible with the latest observational data.
| [
{
"created": "Mon, 8 Jun 2015 13:42:31 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jun 2015 10:00:50 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Sep 2015 14:26:12 GMT",
"version": "v3"
}
] | 2015-09-30 | [
[
"Martin-Moruno",
"Prado",
""
],
[
"Nunes",
"Nelson J.",
""
]
] | Horndeski models with a de Sitter critical point for any kind of material content may provide a mechanism to alleviate the cosmological constant problem. Moreover, they could allow us to understand the current accelerated expansion of the universe as the result of the dynamical approach to the critical point when it is an attractor. We show that this critical point is indeed an attractor for the shift- symmetric subfamily of models with these characteristics. We study the cosmological scenario that results when considering radiation and matter content, and conclude that their background dynamics is compatible with the latest observational data. |
gr-qc/9712043 | Andrew T. Sornborger | Peter D'Eath and Andrew Sornborger | Persistence Amplitudes from Numerical Quantum Gravity | 22 pages, 12 figures (bitmapped postscript), a postscript version of
this paper with high quality postscript figures may be found at
http://www-astro-theory.fnal.gov/Personal/ats/welcome.html | Class.Quant.Grav.15:3435-3447,1998 | 10.1088/0264-9381/15/11/010 | DAMTP Relativity Group Preprint: DAMTP-R97/56 and Fermilab Preprint:
Pub-97/364-A | gr-qc | null | The Euclidean quantum amplitude to go between data specified on an initial
and a final hypersurface may be approximated by the tree amplitude
exp(-I_{classical}/\hbar), where I_{classical} is the Euclidean action of the
classical solution joining the initial and final data. In certain cases the
tree amplitude is exact. We study I_{classical} hence the quantum amplitude, in
the case of a spherically symmetric Riemannian gravitational field coupled to a
spherically symmetric scalar field. The classical scalar field obeys an
elliptic equation, which we solve using relaxation techniques, in conjunction
with the field equations giving the gravitational field. An example of the
transition from linearity to non-linearity is presented and power law behavior
of the action is demonstrated.
| [
{
"created": "Tue, 9 Dec 1997 17:13:45 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"D'Eath",
"Peter",
""
],
[
"Sornborger",
"Andrew",
""
]
] | The Euclidean quantum amplitude to go between data specified on an initial and a final hypersurface may be approximated by the tree amplitude exp(-I_{classical}/\hbar), where I_{classical} is the Euclidean action of the classical solution joining the initial and final data. In certain cases the tree amplitude is exact. We study I_{classical} hence the quantum amplitude, in the case of a spherically symmetric Riemannian gravitational field coupled to a spherically symmetric scalar field. The classical scalar field obeys an elliptic equation, which we solve using relaxation techniques, in conjunction with the field equations giving the gravitational field. An example of the transition from linearity to non-linearity is presented and power law behavior of the action is demonstrated. |
gr-qc/9703015 | Markus Heusler | Markus Heusler | Mass formulae for a class of nonrotating black holes | 18 pages, revtex, no figures | null | 10.1103/PhysRevD.56.961 | ZU-TH 6/97 | gr-qc | null | In the presence of a Killing symmetry, various self-gravitating field
theories with massless scalars (moduli) and vector fields reduce to
sigma-models, effectively coupled to 3-dimensional gravity. We argue that this
particular structure of the Einstein-matter equations gives rise to quadratic
relations between the asymptotic flux integrals and the area and surface
gravity (Hawking temperature) of the horizon. The method is first illustrated
for the Einstein-Maxwell system. A derivation of the quadratic formula is then
also presented for the Einstein-Maxwell-axion-dilaton model, which is relevant
to the bosonic sector of heterotic string theory.
| [
{
"created": "Thu, 6 Mar 1997 13:55:54 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Heusler",
"Markus",
""
]
] | In the presence of a Killing symmetry, various self-gravitating field theories with massless scalars (moduli) and vector fields reduce to sigma-models, effectively coupled to 3-dimensional gravity. We argue that this particular structure of the Einstein-matter equations gives rise to quadratic relations between the asymptotic flux integrals and the area and surface gravity (Hawking temperature) of the horizon. The method is first illustrated for the Einstein-Maxwell system. A derivation of the quadratic formula is then also presented for the Einstein-Maxwell-axion-dilaton model, which is relevant to the bosonic sector of heterotic string theory. |
gr-qc/9801102 | Herman Julio Mosqueira Cuesta | H. J. Mosquera Cuesta(1), J. C. N. de Araujo(1), O. D. Aguiar(1), and
J. E. Horvath(2) ((1) Divisao Astrofisica - Instituto Nacional de Pesquisas
Espaciais - INPE (2) Instituto Astronomico e Geofisico - Universidade de Sao
Paulo) | Gravitational-wave bursts from soft gamma-ray repeaters: Can they be
detected? | 5 pages, [prl]{revtex}, 1 PS figure included. To appear in Physical
Review Letters | Phys.Rev.Lett.80:2988-2991,1998 | 10.1103/PhysRevLett.80.2988 | null | gr-qc astro-ph | null | In this letter we suggest a scenario for simultaneous emission of
gravitational-wave and $\gamma$-ray bursts (GRBs) from soft gamma-ray repeaters
(SGRs). we argue that both of the radiations can be generated by a
super-Eddington accreting neutron stars in X-ray binaries. In this model a
supercritical accretion transient takes back onto the remnant star the disk
leftover by the hydrodynamic instability phase of a low magnetized, rapidly
rotating neutron star in a X-ray binary system. We estimate the rise timescale
$\Delta t_c = 0.21 ms$, minimum mass accretion rate needed to trigger the
$\gamma$-ray emission, $\dot{M}_\lambda = 4.5 \times 10^{28} g$, and its
effective associated temperature $T_{eff} = 740 keV$, and the timescale for
repeating a burst of $\gamma$-rays $\Delta \tau_R = 11.3 yr$. Altogether, we
find the associated GW amplitude and frequency to be $h_c = 2.7 \times
10^{-23}/{(Hz)}^{1/2}$ and $f_{gw} = 966 Hz$, for a source distance $\sim 55
kpc$. Detectability of the pulses by t he forthcoming GW anntenas is discussed
and found likely.
| [
{
"created": "Thu, 29 Jan 1998 15:59:54 GMT",
"version": "v1"
}
] | 2011-05-24 | [
[
"Cuesta",
"H. J. Mosquera",
""
],
[
"de Araujo",
"J. C. N.",
""
],
[
"Aguiar",
"O. D.",
""
],
[
"Horvath",
"J. E.",
""
]
] | In this letter we suggest a scenario for simultaneous emission of gravitational-wave and $\gamma$-ray bursts (GRBs) from soft gamma-ray repeaters (SGRs). we argue that both of the radiations can be generated by a super-Eddington accreting neutron stars in X-ray binaries. In this model a supercritical accretion transient takes back onto the remnant star the disk leftover by the hydrodynamic instability phase of a low magnetized, rapidly rotating neutron star in a X-ray binary system. We estimate the rise timescale $\Delta t_c = 0.21 ms$, minimum mass accretion rate needed to trigger the $\gamma$-ray emission, $\dot{M}_\lambda = 4.5 \times 10^{28} g$, and its effective associated temperature $T_{eff} = 740 keV$, and the timescale for repeating a burst of $\gamma$-rays $\Delta \tau_R = 11.3 yr$. Altogether, we find the associated GW amplitude and frequency to be $h_c = 2.7 \times 10^{-23}/{(Hz)}^{1/2}$ and $f_{gw} = 966 Hz$, for a source distance $\sim 55 kpc$. Detectability of the pulses by t he forthcoming GW anntenas is discussed and found likely. |
1811.09589 | Camilo Posada | Camilo Posada and Cecilia Chirenti | On the radial stability of ultra compact Schwarzschild stars beyond the
Buchdahl limit | 16 pages, 8 figures; minor revisions, two plots and references added,
accepted for publication in CQG | Class. Quantum Grav. 36, 065004 (2019) | 10.1088/1361-6382/ab0526 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we used the theory of adiabatic radial oscillations developed
by Chandrasekhar to study the conditions for dynamical stability of constant
energy-density stars, or Schwarzschild stars, in the unstudied ultra compact
regime beyond the Buchdahl limit, that is, for configurations with radius $R$
in the range $R_{\rm S}<R<(9/8)R_{\rm S}$, where $R_{\rm S}$ is the
Schwarzschild radius of the star. These recently found analytical solutions
exhibit a negative pressure region in their centre and, in the limit when $R\to
R_{\rm S}$, the full interior region of the star becomes filled with negative
pressure. Here we present a systematic analysis of the stability of these
configurations against radial perturbations. We found that, contrary to the
usual expectation found in many classical works, the ultra compact
Schwarzschild star is stable against radial oscillations. We computed values of
the critical adiabatic index $\gamma_{c}$ for several stellar models with
varying radius $R/R_{\rm S}$ and found that it also approaches a finite value
as $R/R_{\rm S} \to 1$
| [
{
"created": "Fri, 23 Nov 2018 18:26:05 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Feb 2019 17:22:00 GMT",
"version": "v2"
}
] | 2019-02-20 | [
[
"Posada",
"Camilo",
""
],
[
"Chirenti",
"Cecilia",
""
]
] | In this paper we used the theory of adiabatic radial oscillations developed by Chandrasekhar to study the conditions for dynamical stability of constant energy-density stars, or Schwarzschild stars, in the unstudied ultra compact regime beyond the Buchdahl limit, that is, for configurations with radius $R$ in the range $R_{\rm S}<R<(9/8)R_{\rm S}$, where $R_{\rm S}$ is the Schwarzschild radius of the star. These recently found analytical solutions exhibit a negative pressure region in their centre and, in the limit when $R\to R_{\rm S}$, the full interior region of the star becomes filled with negative pressure. Here we present a systematic analysis of the stability of these configurations against radial perturbations. We found that, contrary to the usual expectation found in many classical works, the ultra compact Schwarzschild star is stable against radial oscillations. We computed values of the critical adiabatic index $\gamma_{c}$ for several stellar models with varying radius $R/R_{\rm S}$ and found that it also approaches a finite value as $R/R_{\rm S} \to 1$ |
0902.2356 | Christian Corda | Christian Corda | Interferometric detection of gravitational waves arising from extended
theories of gravity | To appear in Proceedings of the 3rd Stueckelberg Workshop, July 2008,
Pescara, Italy | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Even if Einstein's General Relativity achieved a great success and overcame
lots of experimental tests, it also showed some shortcomings and flaws which
today advise theorists to ask if it is the definitive theory of gravity. In
this letter Proceeding we show that, by assuming that advanced projects on the
detection of Gravitational Waves (GWs) will improve their sensitivity, allowing
to perform a GWs astronomy, accurate angular and frequency dependent response
functions of interferometers for GWs arising from various Theories of Gravity,
i.e. General Relativity and Extended Theories of Gravity, could aim in
discriminating among various theories.
| [
{
"created": "Fri, 13 Feb 2009 17:28:44 GMT",
"version": "v1"
}
] | 2009-02-16 | [
[
"Corda",
"Christian",
""
]
] | Even if Einstein's General Relativity achieved a great success and overcame lots of experimental tests, it also showed some shortcomings and flaws which today advise theorists to ask if it is the definitive theory of gravity. In this letter Proceeding we show that, by assuming that advanced projects on the detection of Gravitational Waves (GWs) will improve their sensitivity, allowing to perform a GWs astronomy, accurate angular and frequency dependent response functions of interferometers for GWs arising from various Theories of Gravity, i.e. General Relativity and Extended Theories of Gravity, could aim in discriminating among various theories. |
1009.4109 | Jonathan Luk | Jonathan Luk | The Null Condition and Global Existence for Nonlinear Wave Equations on
Slowly Rotating Kerr Spacetimes | null | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a semilinear equation with derivatives satisfying a null condition
on slowly rotating Kerr spacetimes. We prove that given sufficiently small
initial data, the solution exists globally in time and decays with a
quantitative rate to the trivial solution. The proof uses the robust vector
field method. It makes use of the decay properties of the linear wave equation
on Kerr spacetime, in particular the improved decay rates in the region
$\{r\leq \frac{t}{4}\}$.
| [
{
"created": "Tue, 21 Sep 2010 14:22:35 GMT",
"version": "v1"
}
] | 2010-09-22 | [
[
"Luk",
"Jonathan",
""
]
] | We study a semilinear equation with derivatives satisfying a null condition on slowly rotating Kerr spacetimes. We prove that given sufficiently small initial data, the solution exists globally in time and decays with a quantitative rate to the trivial solution. The proof uses the robust vector field method. It makes use of the decay properties of the linear wave equation on Kerr spacetime, in particular the improved decay rates in the region $\{r\leq \frac{t}{4}\}$. |
2406.03909 | Saeed Rastgoo | Federica Fragomeno, Douglas M. Gingrich, Samantha Hergott, Saeed
Rastgoo, Evan Vienneau | A generalized uncertainty-inspired quantum black hole | 35 pages, 7 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the full spacetime metric of a generalized uncertainty-inspired
quantum black hole. We examine a previous model of the interior in this
approach and show that extending its metric to the full spacetime leads to
serious issues in the asymptotic region. To remedy this, we introduce an
"improved scheme" mimicking a similar prescription used in loop quantum
gravity, where the quantum parameters are made momentum-dependent. Under this
scheme, we rework the interior of the black hole and extend it to the full
spacetime. We find that the resulting metric is asymptotically flat and its
associated Kretschmann scalar is regular everywhere. We also show that the null
expansion and Raychaudhuri equation are regular everywhere in this spacetime,
implying that the classical singularity is resolved.
| [
{
"created": "Thu, 6 Jun 2024 09:44:00 GMT",
"version": "v1"
}
] | 2024-06-07 | [
[
"Fragomeno",
"Federica",
""
],
[
"Gingrich",
"Douglas M.",
""
],
[
"Hergott",
"Samantha",
""
],
[
"Rastgoo",
"Saeed",
""
],
[
"Vienneau",
"Evan",
""
]
] | We derive the full spacetime metric of a generalized uncertainty-inspired quantum black hole. We examine a previous model of the interior in this approach and show that extending its metric to the full spacetime leads to serious issues in the asymptotic region. To remedy this, we introduce an "improved scheme" mimicking a similar prescription used in loop quantum gravity, where the quantum parameters are made momentum-dependent. Under this scheme, we rework the interior of the black hole and extend it to the full spacetime. We find that the resulting metric is asymptotically flat and its associated Kretschmann scalar is regular everywhere. We also show that the null expansion and Raychaudhuri equation are regular everywhere in this spacetime, implying that the classical singularity is resolved. |
gr-qc/9704008 | Robert Manuel Wald | Robert M. Wald | The ``Nernst Theorem'' and Black Hole Thermodynamics | 20 pages, plain LaTeX file | Phys. Rev. D 56, 6467 (1997) | 10.1103/PhysRevD.56.6467 | null | gr-qc cond-mat.stat-mech hep-th | null | The Nernst formulation of the third law of ordinary thermodynamics (often
referred to as the ``Nernst theorem'') asserts that the entropy, $S$, of a
system must go to zero (or a ``universal constant'') as its temperature, $T$,
goes to zero. This assertion is commonly considered to be a fundamental law of
thermodynamics. As such, it seems to spoil the otherwise perfect analogy
between the ordinary laws of thermodynamics and the laws of black hole
mechanics, since rotating black holes in general relativity do not satisfy the
analog of the ``Nernst theorem''. The main purpose of this paper is to attempt
to lay to rest the ``Nernst theorem'' as a law of thermodynamics. We consider a
boson (or fermion) ideal gas with its total angular momentum, $J$, as an
additional state parameter, and we analyze the conditions on the single
particle density of states, $g(\epsilon,j)$, needed for the Nernst formulation
of the third law to hold. (Here, $\epsilon$ and $j$ denote the single particle
energy and angular momentum.) Although it is shown that the Nernst formulation
of the third law does indeed hold under a wide range of conditions, some simple
classes of examples of densities of states which violate the ``Nernst theorem''
are given. In particular, at zero temperature, a boson (or fermion) gas
confined to a circular string (whose energy is proportional to its length) not
only violates the ``Nernst theorem'' also but reproduces some other
thermodynamic properties of an extremal rotating black hole.
| [
{
"created": "Thu, 3 Apr 1997 19:40:21 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Wald",
"Robert M.",
""
]
] | The Nernst formulation of the third law of ordinary thermodynamics (often referred to as the ``Nernst theorem'') asserts that the entropy, $S$, of a system must go to zero (or a ``universal constant'') as its temperature, $T$, goes to zero. This assertion is commonly considered to be a fundamental law of thermodynamics. As such, it seems to spoil the otherwise perfect analogy between the ordinary laws of thermodynamics and the laws of black hole mechanics, since rotating black holes in general relativity do not satisfy the analog of the ``Nernst theorem''. The main purpose of this paper is to attempt to lay to rest the ``Nernst theorem'' as a law of thermodynamics. We consider a boson (or fermion) ideal gas with its total angular momentum, $J$, as an additional state parameter, and we analyze the conditions on the single particle density of states, $g(\epsilon,j)$, needed for the Nernst formulation of the third law to hold. (Here, $\epsilon$ and $j$ denote the single particle energy and angular momentum.) Although it is shown that the Nernst formulation of the third law does indeed hold under a wide range of conditions, some simple classes of examples of densities of states which violate the ``Nernst theorem'' are given. In particular, at zero temperature, a boson (or fermion) gas confined to a circular string (whose energy is proportional to its length) not only violates the ``Nernst theorem'' also but reproduces some other thermodynamic properties of an extremal rotating black hole. |
gr-qc/9811023 | Garcia | L.C.Garcia de Andrade | Space-time defects :Domain walls and torsion | J.Math.Phys.39,(1998),Jan. issue | J.Math.Phys. 39 (1998) 372-379 | 10.1063/1.532318 | null | gr-qc | null | The theory of distributions in non-Riemannian spaces is used to obtain exact
static thin domain wall solutions of Einstein-Cartan equations of gravity.
Curvature $ \delta $-singularities are found while Cartan torsion is given by
Heaviside functions. Weitzenb\"{o}ck planar walls are caracterized by torsion
$\delta$-singularities and zero curvature. It is shown that Weitzenb\"{o}ck
static thin domain walls do not exist exactly as in general relativity. The
global structure of Weitzenb\"{o}ck nonstatic torsion walls is investigated.
| [
{
"created": "Fri, 6 Nov 1998 20:51:40 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | The theory of distributions in non-Riemannian spaces is used to obtain exact static thin domain wall solutions of Einstein-Cartan equations of gravity. Curvature $ \delta $-singularities are found while Cartan torsion is given by Heaviside functions. Weitzenb\"{o}ck planar walls are caracterized by torsion $\delta$-singularities and zero curvature. It is shown that Weitzenb\"{o}ck static thin domain walls do not exist exactly as in general relativity. The global structure of Weitzenb\"{o}ck nonstatic torsion walls is investigated. |
1112.3567 | Benjamin Bahr | Benjamin Bahr | Operator Spin Foams: holonomy formulation and coarse graining | 5 pages, 3 figures, to appear in Journal of Physics: Conference
Series. (JPCS) | null | 10.1088/1742-6596/360/1/012042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A dual holonomy version of operator spin foam models is presented, which is
particularly adapted to the notion of coarse graining. We discuss how this
leads to a natural way of comparing models on different discretization scales,
and a notion of renormalization group flow on the partially ordered set of
2-complexes.
| [
{
"created": "Thu, 15 Dec 2011 16:52:42 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Bahr",
"Benjamin",
""
]
] | A dual holonomy version of operator spin foam models is presented, which is particularly adapted to the notion of coarse graining. We discuss how this leads to a natural way of comparing models on different discretization scales, and a notion of renormalization group flow on the partially ordered set of 2-complexes. |
1505.06691 | Fatimah Shojai | F. Shojai and A. Shojai | The equivalence principle and the relative velocity of local inertial
frames | 1 Figure | Am. J. Phys., Vol. 83, No. 6, June 2015 | 10.1119/1.4913901 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we explicitly show that in general relativity, the relative
velocity of two local inertial frames is always less than the velocity of
light. This fact is a by-product of the equivalence principle. The general
result is then illustrated within two examples, the FLRW cosmological model and
the Schwarzschild metric.
| [
{
"created": "Mon, 25 May 2015 16:57:55 GMT",
"version": "v1"
}
] | 2015-05-26 | [
[
"Shojai",
"F.",
""
],
[
"Shojai",
"A.",
""
]
] | In this paper we explicitly show that in general relativity, the relative velocity of two local inertial frames is always less than the velocity of light. This fact is a by-product of the equivalence principle. The general result is then illustrated within two examples, the FLRW cosmological model and the Schwarzschild metric. |
gr-qc/9301013 | null | M.Campanelli and C.O.Lousto | "Are Black Holes in Brans-Dicke Theory precisely the same as in General
Relativity?" | 13pages, Plain Tex | Int.J.Mod.Phys.D2:451-462,1993 | 10.1142/S0218271893000325 | null | gr-qc astro-ph hep-th | null | We study a three-parameters family of solutions of the Brans-Dicke field
equations. They are static and spherically symmetric. We find the range of
parameters for which this solution represents a black hole different from the
Schwarzschild one. We find a subfamily of solutions which agrees with
experiments and observations in the solar system. We discuss some astrophysical
applications and the consequences on the "no hair" theorems for black holes.
| [
{
"created": "Thu, 14 Jan 1993 13:08:56 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Jan 1993 16:06:55 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Jan 1993 17:34:34 GMT",
"version": "v3"
}
] | 2010-11-01 | [
[
"Campanelli",
"M.",
""
],
[
"Lousto",
"C. O.",
""
]
] | We study a three-parameters family of solutions of the Brans-Dicke field equations. They are static and spherically symmetric. We find the range of parameters for which this solution represents a black hole different from the Schwarzschild one. We find a subfamily of solutions which agrees with experiments and observations in the solar system. We discuss some astrophysical applications and the consequences on the "no hair" theorems for black holes. |
1510.05593 | Abhay Ashtekar | Abhay Ashtekar, B\'eatrice Bonga, Aruna Kesavan | Asymptotics with a positive cosmological constant: III. The quadrupole
formula | 31 pages, 2 figures | Phys. Rev. D92, 10432 (21 pages) (2015) | 10.1103/PhysRevD.92.104032 | IGC-1509/2 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Almost a century ago, Einstein used a weak field approximation around
Minkowski space-time to calculate the energy carried away by gravitational
waves emitted by a time changing mass-quadrupole. However, by now there is
strong observational evidence for a positive cosmological constant, $\Lambda$.
To incorporate this fact, Einstein's celebrated derivation is generalized by
replacing Minkowski space-time with de Sitter space-time. The investigation is
motivated by the fact that, because of the significant differences between the
asymptotic structures of Minkowski and de Sitter space-times, many of the
standard techniques, including the standard $1/r$ expansions, can not be used
for $\Lambda >0$. Furthermore since, e.g., the energy carried by gravitational
waves is always positive in Minkowski space-time but can be arbitrarily
negative in de Sitter space-time \emph{irrespective of how small $\Lambda$ is},
the limit $\Lambda\to 0$ can fail to be continuous. Therefore, a priori it is
not clear that a small $\Lambda$ would introduce only negligible corrections to
Einstein's formula. We show that, while even a tiny cosmological constant does
introduce qualitatively new features, in the end, corrections to Einstein's
formula are negligible for astrophysical sources currently under consideration
by gravitational wave observatories.
| [
{
"created": "Mon, 19 Oct 2015 17:26:31 GMT",
"version": "v1"
}
] | 2015-11-17 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Bonga",
"Béatrice",
""
],
[
"Kesavan",
"Aruna",
""
]
] | Almost a century ago, Einstein used a weak field approximation around Minkowski space-time to calculate the energy carried away by gravitational waves emitted by a time changing mass-quadrupole. However, by now there is strong observational evidence for a positive cosmological constant, $\Lambda$. To incorporate this fact, Einstein's celebrated derivation is generalized by replacing Minkowski space-time with de Sitter space-time. The investigation is motivated by the fact that, because of the significant differences between the asymptotic structures of Minkowski and de Sitter space-times, many of the standard techniques, including the standard $1/r$ expansions, can not be used for $\Lambda >0$. Furthermore since, e.g., the energy carried by gravitational waves is always positive in Minkowski space-time but can be arbitrarily negative in de Sitter space-time \emph{irrespective of how small $\Lambda$ is}, the limit $\Lambda\to 0$ can fail to be continuous. Therefore, a priori it is not clear that a small $\Lambda$ would introduce only negligible corrections to Einstein's formula. We show that, while even a tiny cosmological constant does introduce qualitatively new features, in the end, corrections to Einstein's formula are negligible for astrophysical sources currently under consideration by gravitational wave observatories. |
1807.10085 | Donato Bini | Donato Bini, Andrea Geralico, Robert T. Jantzen | Black hole geodesic parallel transport and the Marck recipe for
isolating cumulative precession effects | 18 pages, RevTex macros | Phys. Rev. D 99, 064041 (2019) | 10.1103/PhysRevD.99.064041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Wigner rotations arising from the combination of boosts along two
different directions are rederived from a relative boost point of view and
applied to gyroscope spin precession along timelike geodesics in a Kerr
spacetime, clarifying the geometrical properties of Marck's recipe for
describing parallel transport along such world lines expressed in terms of the
constants of the motion. His final angular velocity isolates the cumulative
spin precession angular velocity independent of the spacetime tilting required
to keep the spin 4-vector orthogonal to the gyro 4-velocity. As an explicit
example the cumulative precession effects are computed for a test gyroscope
moving along both bound and unbound equatorial plane geodesic orbits.
| [
{
"created": "Thu, 26 Jul 2018 12:09:58 GMT",
"version": "v1"
}
] | 2019-04-03 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Jantzen",
"Robert T.",
""
]
] | The Wigner rotations arising from the combination of boosts along two different directions are rederived from a relative boost point of view and applied to gyroscope spin precession along timelike geodesics in a Kerr spacetime, clarifying the geometrical properties of Marck's recipe for describing parallel transport along such world lines expressed in terms of the constants of the motion. His final angular velocity isolates the cumulative spin precession angular velocity independent of the spacetime tilting required to keep the spin 4-vector orthogonal to the gyro 4-velocity. As an explicit example the cumulative precession effects are computed for a test gyroscope moving along both bound and unbound equatorial plane geodesic orbits. |
1609.01253 | Anna Ijjas | Anna Ijjas and Paul J. Steinhardt | Fully stable cosmological solutions with a non-singular classical bounce | 6 pages, 4 figures. Version 5 contains minor corrections to
coefficients in the first paragraph of Sec. 5 and to the labeling in Fig 2 | Phys. Lett. B 764 (2017) pp. 289-294 | 10.1016/j.physletb.2016.11.047 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We recently showed how it is possible to use a cubic Galileon action to
construct classical cosmological solutions that enter a contracting null energy
condition (NEC) violating phase, bounce at finite values of the scale factor
and exit into an expanding NEC-satisfying phase without encountering any
singularities or pathologies. A drawback of these examples is that singular
behavior is encountered at some time either just before or just after the
NEC-violating phase. In this Letter, we show that it is possible to circumvent
this problem by extending our method to actions that include the next order
${\cal L}_4$ Galileon interaction. Using this approach, we construct
non-singular classical bouncing cosmological solutions that are
non-pathological for all times.
| [
{
"created": "Mon, 5 Sep 2016 18:54:09 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2016 04:42:28 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Nov 2016 00:51:54 GMT",
"version": "v3"
},
{
"created": "Wed, 7 Dec 2016 16:31:32 GMT",
"version": "v4"
},
{
"created": "Wed, 18 Nov 2020 07:46:25 GMT",
"version": "v5"
}
] | 2020-11-19 | [
[
"Ijjas",
"Anna",
""
],
[
"Steinhardt",
"Paul J.",
""
]
] | We recently showed how it is possible to use a cubic Galileon action to construct classical cosmological solutions that enter a contracting null energy condition (NEC) violating phase, bounce at finite values of the scale factor and exit into an expanding NEC-satisfying phase without encountering any singularities or pathologies. A drawback of these examples is that singular behavior is encountered at some time either just before or just after the NEC-violating phase. In this Letter, we show that it is possible to circumvent this problem by extending our method to actions that include the next order ${\cal L}_4$ Galileon interaction. Using this approach, we construct non-singular classical bouncing cosmological solutions that are non-pathological for all times. |
0904.0422 | Jose Socorro Garcia | J. Socorro, M. Sabido, and L. Arturo Ure\~na-L\'opez | Classical and quantum Cosmology of the S\'aez-Ballester theory | 9 pages, latex | Fizika B19:177-186,2010 | null | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | We study the generalization of the S\'aez-Ballester theory applied to a flat
FRW cosmological model. Classical exact solutions up to quadratures are easily
obtained using the Hamilton-Jacobi approach. Contrary to claims in the
specialized literature, it is shown that the S\'aez-Ballester theory cannot
provide a realistic solution to the dark matter problem of Cosmology.
Furthermore the quantization procedure of the theory can be simplified by
reinterpreting the theory in the Einstein frame, where the scalar field can be
interpreted as part of the matter content of the theory, in this approach,
exact solutions are also found for the Wheeler-DeWitt equation in the quantum
regime.
| [
{
"created": "Thu, 2 Apr 2009 16:27:29 GMT",
"version": "v1"
}
] | 2011-08-09 | [
[
"Socorro",
"J.",
""
],
[
"Sabido",
"M.",
""
],
[
"Ureña-López",
"L. Arturo",
""
]
] | We study the generalization of the S\'aez-Ballester theory applied to a flat FRW cosmological model. Classical exact solutions up to quadratures are easily obtained using the Hamilton-Jacobi approach. Contrary to claims in the specialized literature, it is shown that the S\'aez-Ballester theory cannot provide a realistic solution to the dark matter problem of Cosmology. Furthermore the quantization procedure of the theory can be simplified by reinterpreting the theory in the Einstein frame, where the scalar field can be interpreted as part of the matter content of the theory, in this approach, exact solutions are also found for the Wheeler-DeWitt equation in the quantum regime. |
2006.05392 | T. P. Singh | Meghraj M S, Abhishek Pandey and Tejinder P. Singh | Why does the Kerr-Newman black hole have the same gyromagnetic ratio as
the electron? | 30 pages | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have recently proposed a deterministic matrix dynamics at the Planck
scale, for gravity coupled to Dirac fermions, evolving in the so-called Connes
time. By coarse-graining this dynamics over time intervals much larger than
Planck time, we derived the space-time manifold, quantum theory, and classical
general relativity, as low energy emergent approximations to the underlying
matrix dynamics. In the present article, we show how to include Yang-Mills
gauge fields in this Planck scale matrix dynamics. We do this by appropriately
modifying the fundamental action for the previously introduced `atom' of
space-time-matter [which we now call an `aikyon']. This is achieved by
modifying the Dirac operator to include a `potential' for the Yang-Mills
aspect, and a `current' for the Yang-Mills charge. Our work opens up an avenue
for unification of gravity with gauge-fields and Dirac fermions. We show how
spontaneous localisation in the matrix dynamics gives rise to general
relativity coupled to gauge-fields and relativistic point particles, in the
classical limit. We use this formalism to explain the remarkable fact that the
Kerr-Newman black hole has the same value for the gyromagnetic ratio as that
for a Dirac fermion, both being twice the classical value.
| [
{
"created": "Tue, 9 Jun 2020 16:42:35 GMT",
"version": "v1"
}
] | 2020-06-11 | [
[
"S",
"Meghraj M",
""
],
[
"Pandey",
"Abhishek",
""
],
[
"Singh",
"Tejinder P.",
""
]
] | We have recently proposed a deterministic matrix dynamics at the Planck scale, for gravity coupled to Dirac fermions, evolving in the so-called Connes time. By coarse-graining this dynamics over time intervals much larger than Planck time, we derived the space-time manifold, quantum theory, and classical general relativity, as low energy emergent approximations to the underlying matrix dynamics. In the present article, we show how to include Yang-Mills gauge fields in this Planck scale matrix dynamics. We do this by appropriately modifying the fundamental action for the previously introduced `atom' of space-time-matter [which we now call an `aikyon']. This is achieved by modifying the Dirac operator to include a `potential' for the Yang-Mills aspect, and a `current' for the Yang-Mills charge. Our work opens up an avenue for unification of gravity with gauge-fields and Dirac fermions. We show how spontaneous localisation in the matrix dynamics gives rise to general relativity coupled to gauge-fields and relativistic point particles, in the classical limit. We use this formalism to explain the remarkable fact that the Kerr-Newman black hole has the same value for the gyromagnetic ratio as that for a Dirac fermion, both being twice the classical value. |
2210.05322 | Cosimo Bambi | Cosimo Bambi | Testing Gravity with Black Hole X-Ray Data | 35 pages, 13 figures. Chapter for the book "Recent Progress on
Gravity Tests" (Eds. C. Bambi and A. C\'ardenas-Avenda\~no, Springer
Singapore, expected in 2023). It reviews current X-ray constraints on the
Kerr hypothesis and discusses the systematic uncertainties | null | 10.1007/978-981-97-2871-8_5 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The analysis of the properties of the X-ray radiation emitted from
geometrically thin accretion disks around black holes can be a powerful tool to
test General Relativity in the strong field regime. This chapter reviews the
state-of-the-art of gravity tests with black hole X-ray data. So far, most
efforts have been devoted to test the Kerr hypothesis - namely that the
spacetime around astrophysical black holes is described by the Kerr solution -
and X-ray data can currently provide among the most stringent constraints on
possible deviations from the Kerr geometry. As of now, all X-ray analyses are
consistent with the predictions of General Relativity.
| [
{
"created": "Tue, 11 Oct 2022 10:25:41 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Bambi",
"Cosimo",
""
]
] | The analysis of the properties of the X-ray radiation emitted from geometrically thin accretion disks around black holes can be a powerful tool to test General Relativity in the strong field regime. This chapter reviews the state-of-the-art of gravity tests with black hole X-ray data. So far, most efforts have been devoted to test the Kerr hypothesis - namely that the spacetime around astrophysical black holes is described by the Kerr solution - and X-ray data can currently provide among the most stringent constraints on possible deviations from the Kerr geometry. As of now, all X-ray analyses are consistent with the predictions of General Relativity. |
1104.4464 | Lorenzo Iorio | L. Iorio | On Some Critical Issues of the LAGEOS-Based Tests of the Lense-Thirring
Effect | Latex2e, 14 pages, no figures, no tables, 67 references. I thank M.
Cerdonio for private communication (September 2010) | J.Mod.Phys.2:210-218,2011 | 10.4236/jmp.2011.24029 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We summarize some critical issues pertaining the tests of the general
relativistic Lense-Thirring effect performed by I. Ciufolini and coworkers in
the gravitational field of the Earth with the geodetic satellites LAGEOS and
LAGEOS II tracked with the Satellite Laser Ranging technique.
| [
{
"created": "Fri, 22 Apr 2011 15:15:43 GMT",
"version": "v1"
}
] | 2011-05-24 | [
[
"Iorio",
"L.",
""
]
] | We summarize some critical issues pertaining the tests of the general relativistic Lense-Thirring effect performed by I. Ciufolini and coworkers in the gravitational field of the Earth with the geodetic satellites LAGEOS and LAGEOS II tracked with the Satellite Laser Ranging technique. |
2003.08424 | Eduardo Bittencourt | Eduardo Bittencourt, Gabriel G. Carvalho, Iarley P. Lobo, Leandro
Santana | On the hypotheses of Penrose's singularity theorem under disformal
transformations | 10 pages, 3 figures | null | 10.1140/epjc/s10052-020-7830-0 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze how the hypotheses of Penrose's singularity theorem (1965) are
modified by the action of disformal transformations (defined in terms of
light-like vectors) upon a given space-time metric. In particular, we
investigate the transformation of the null energy condition and the existence
of closed trapped surfaces in such scenario, in order to derive conditions upon
the background metric and the disformal vector that guarantee the validity of
Penrose's theorem for disformal metrics. Then, we explain how to apply this
technique for static and spherically symmetric space-times in general.
| [
{
"created": "Wed, 18 Mar 2020 18:32:33 GMT",
"version": "v1"
}
] | 2020-03-20 | [
[
"Bittencourt",
"Eduardo",
""
],
[
"Carvalho",
"Gabriel G.",
""
],
[
"Lobo",
"Iarley P.",
""
],
[
"Santana",
"Leandro",
""
]
] | We analyze how the hypotheses of Penrose's singularity theorem (1965) are modified by the action of disformal transformations (defined in terms of light-like vectors) upon a given space-time metric. In particular, we investigate the transformation of the null energy condition and the existence of closed trapped surfaces in such scenario, in order to derive conditions upon the background metric and the disformal vector that guarantee the validity of Penrose's theorem for disformal metrics. Then, we explain how to apply this technique for static and spherically symmetric space-times in general. |
2112.00918 | James Quach Dr | Salman Sajad Wani, James Q. Quach, Mir Faizal, Sebastian Bahamonde,
Behnam Pourhassan | A Quantum Informational Approach to the Problem of Time | 10 pages, 1 figure | Found Phys 52, 25 (2022) | 10.1007/s10701-022-00540-6 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Several novel approaches have been proposed to resolve the problem of time by
relating it to change. We argue using quantum information theory that the
Hamiltonian constraint in quantum gravity cannot probe change, so it cannot be
used to obtain a meaningful notion of time. This is due to the absence of
quantum Fisher information with respect to the quantum Hamiltonian of a
time-reparametization invariant system. We also observe that the inability of
this Hamiltonian to probe change can be related to its inability to
discriminate between states of such a system. However, if the
time-reparametization symmetry is spontaneously broken due to the formation of
quantum cosmological time crystals, these problems can be resolved, and it is
possible for time to emerge in quantum gravity.
| [
{
"created": "Thu, 2 Dec 2021 01:30:53 GMT",
"version": "v1"
}
] | 2022-02-07 | [
[
"Wani",
"Salman Sajad",
""
],
[
"Quach",
"James Q.",
""
],
[
"Faizal",
"Mir",
""
],
[
"Bahamonde",
"Sebastian",
""
],
[
"Pourhassan",
"Behnam",
""
]
] | Several novel approaches have been proposed to resolve the problem of time by relating it to change. We argue using quantum information theory that the Hamiltonian constraint in quantum gravity cannot probe change, so it cannot be used to obtain a meaningful notion of time. This is due to the absence of quantum Fisher information with respect to the quantum Hamiltonian of a time-reparametization invariant system. We also observe that the inability of this Hamiltonian to probe change can be related to its inability to discriminate between states of such a system. However, if the time-reparametization symmetry is spontaneously broken due to the formation of quantum cosmological time crystals, these problems can be resolved, and it is possible for time to emerge in quantum gravity. |
2212.06814 | Muhammad Sharif | M. Sharif and Tayyab Naseer | Isotropization and Complexity Analysis of Decoupled Solutions in
$f(\mathbb{R},\mathbb{T})$ Theory | 29 pages, 11 figures | Eur. Phys. J. Plus 137(2022)1304 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper formulates some new exact solutions to the field equations by
means of minimal gravitational decoupling in the context of
$f(\mathbb{R},\mathbb{T})$ gravity. For this purpose, we consider anisotropic
spherical matter distribution and add an extra source to extend the existing
solutions. We apply the transformation only on the radial metric potential that
results in two different sets of the modified field equations, each of them
corresponding to their parent source. The initial anisotropic source is
represented by the first set, and we consider two different well-behaved
solutions to close that system. On the other hand, we impose constraints on the
additional source to make the second set solvable. We, firstly, employ the
isotropization condition which leads to an isotropic system for a particular
value of the decoupling parameter. We then use the condition of zero complexity
of the total configuration to obtain the other solution. The unknowns are
determined by smoothly matching the interior and exterior spacetimes at the
hypersurface. The physical viability and stability of the obtained solutions is
analyzed by using the mass and radius of a compact star $4U 1820-30$. It is
concluded that both of our extended solutions meet all the physical
requirements for considered values of the coupling/decoupling parameters.
| [
{
"created": "Fri, 9 Dec 2022 02:23:05 GMT",
"version": "v1"
}
] | 2022-12-14 | [
[
"Sharif",
"M.",
""
],
[
"Naseer",
"Tayyab",
""
]
] | This paper formulates some new exact solutions to the field equations by means of minimal gravitational decoupling in the context of $f(\mathbb{R},\mathbb{T})$ gravity. For this purpose, we consider anisotropic spherical matter distribution and add an extra source to extend the existing solutions. We apply the transformation only on the radial metric potential that results in two different sets of the modified field equations, each of them corresponding to their parent source. The initial anisotropic source is represented by the first set, and we consider two different well-behaved solutions to close that system. On the other hand, we impose constraints on the additional source to make the second set solvable. We, firstly, employ the isotropization condition which leads to an isotropic system for a particular value of the decoupling parameter. We then use the condition of zero complexity of the total configuration to obtain the other solution. The unknowns are determined by smoothly matching the interior and exterior spacetimes at the hypersurface. The physical viability and stability of the obtained solutions is analyzed by using the mass and radius of a compact star $4U 1820-30$. It is concluded that both of our extended solutions meet all the physical requirements for considered values of the coupling/decoupling parameters. |
2010.08602 | Arnab Dhani | Arnab Dhani | Importance of mirror modes in binary black hole ringdown waveform | null | Phys. Rev. D 103, 104048 (2021) | 10.1103/PhysRevD.103.104048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The post-merger signal in binary black hole merger is described by linear,
black-hole perturbation theory. Historically, this has been modeled using the
dominant positive-frequency (corotating) fundamental mode. Recently, there has
been a renewed effort in modeling the post-merger waveform using higher,
positive-frequency overtones in an attempt to achieve greater accuracy in
describing the waveform at earlier times using linear perturbation theory. It
has been shown that the inclusion of higher overtones can shift the linear
regime to the peak of $(l,m)=(2,2)$ spherical harmonic mode. In this work, we
show that the inclusion of negative-frequency (counterrotating) modes, called
'mirror' modes, extends the validity of linear perturbation theory to even
earlier times, with far lower systematic uncertainties in the model in
recovering the remnant parameters at these early times. A good description of
the signal at early times also enables for a greater signal-to-noise ratio to
be accumulated in the ringdown phase, thereby, allowing for a more accurate
measurement of remnant parameters and tests of general relativity.
| [
{
"created": "Fri, 16 Oct 2020 19:44:32 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Oct 2020 16:47:18 GMT",
"version": "v2"
}
] | 2021-05-26 | [
[
"Dhani",
"Arnab",
""
]
] | The post-merger signal in binary black hole merger is described by linear, black-hole perturbation theory. Historically, this has been modeled using the dominant positive-frequency (corotating) fundamental mode. Recently, there has been a renewed effort in modeling the post-merger waveform using higher, positive-frequency overtones in an attempt to achieve greater accuracy in describing the waveform at earlier times using linear perturbation theory. It has been shown that the inclusion of higher overtones can shift the linear regime to the peak of $(l,m)=(2,2)$ spherical harmonic mode. In this work, we show that the inclusion of negative-frequency (counterrotating) modes, called 'mirror' modes, extends the validity of linear perturbation theory to even earlier times, with far lower systematic uncertainties in the model in recovering the remnant parameters at these early times. A good description of the signal at early times also enables for a greater signal-to-noise ratio to be accumulated in the ringdown phase, thereby, allowing for a more accurate measurement of remnant parameters and tests of general relativity. |
1811.05117 | Fabio Briscese | Fabio Briscese, Leonardo Modesto | Nonlinear stability of Minkowski spacetime in Nonlocal Gravity | null | JCAP07(2019)009 | 10.1088/1475-7516/2019/07/009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that the Minkowski spacetime is stable at nonlinear level and to all
perturbative orders in the gravitational perturbation in a general class of
nonlocal gravitational theories that are unitary and finite at quantum level.
| [
{
"created": "Tue, 13 Nov 2018 05:46:37 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jul 2019 16:36:19 GMT",
"version": "v2"
}
] | 2019-07-05 | [
[
"Briscese",
"Fabio",
""
],
[
"Modesto",
"Leonardo",
""
]
] | We prove that the Minkowski spacetime is stable at nonlinear level and to all perturbative orders in the gravitational perturbation in a general class of nonlocal gravitational theories that are unitary and finite at quantum level. |
gr-qc/0505135 | Gonzalo Olmo | Gonzalo J. Olmo | Post-Newtonian constraints on f(R) cosmologies in metric formalism | 10 pages, no figures, revtex4 | Phys.Rev.D 72, 083505 (2005) [combined with gr-qc/0505136] | 10.1103/PhysRevD.72.083505 | null | gr-qc astro-ph hep-th | null | We compute the complete post-Newtonian limit of the metric form of f(R)
gravities using a scalar-tensor representation. By comparing the predictions of
these theories with laboratory and solar system experiments, we find a set of
inequalities that any lagrangian f(R) must satisfy. The constraints imposed by
those inequalities allow us to find explicit bounds to the possible nonlinear
terms of the lagrangian. We conclude that the lagrangian f(R) must be almost
linear in R and that corrections that grow at low curvatures are incompatible
with observations. This result shows that modifications of gravity at very low
cosmic densities cannot be responsible for the observed cosmic speed-up.
| [
{
"created": "Thu, 26 May 2005 22:52:50 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Olmo",
"Gonzalo J.",
""
]
] | We compute the complete post-Newtonian limit of the metric form of f(R) gravities using a scalar-tensor representation. By comparing the predictions of these theories with laboratory and solar system experiments, we find a set of inequalities that any lagrangian f(R) must satisfy. The constraints imposed by those inequalities allow us to find explicit bounds to the possible nonlinear terms of the lagrangian. We conclude that the lagrangian f(R) must be almost linear in R and that corrections that grow at low curvatures are incompatible with observations. This result shows that modifications of gravity at very low cosmic densities cannot be responsible for the observed cosmic speed-up. |
1903.11364 | Sandeep Aashish | Sandeep Aashish, Sukanta Panda | Quantum aspects of antisymmetric tensor field with spontaneous Lorentz
violation | 20 pages; minor corrections, text improvements, references added;
published version | Phys. Rev. D 100, 065010 (2019) | 10.1103/PhysRevD.100.065010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantization of a simple model of antisymmetric tensor field
with spontaneous Lorentz violation in curved spacetime. We evaluate the 1-loop
corrections at first order of metric perturbation, using a general covariant
effective action approach. We revisit the issue of quantum equivalence, and
find that it holds for non-Lorentz-violating modes but breaks down for Lorentz
violating modes.
| [
{
"created": "Wed, 27 Mar 2019 11:46:45 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Sep 2019 15:09:50 GMT",
"version": "v2"
}
] | 2019-09-19 | [
[
"Aashish",
"Sandeep",
""
],
[
"Panda",
"Sukanta",
""
]
] | We study the quantization of a simple model of antisymmetric tensor field with spontaneous Lorentz violation in curved spacetime. We evaluate the 1-loop corrections at first order of metric perturbation, using a general covariant effective action approach. We revisit the issue of quantum equivalence, and find that it holds for non-Lorentz-violating modes but breaks down for Lorentz violating modes. |
1406.7029 | Casey Handmer | Casey J. Handmer and B\'ela Szil\'agyi | Spectral Characteristic Evolution: A New Algorithm for Gravitational
Wave Propagation | 28 pages, 9 figures | null | 10.1088/0264-9381/32/2/025008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a spectral algorithm for solving the full nonlinear vacuum
Einstein field equations in the Bondi framework. Developed within the Spectral
Einstein Code (SpEC), we demonstrate spectral characteristic evolution as a
technical precursor to Cauchy Characteristic Extraction (CCE), a rigorous
method for obtaining gauge-invariant gravitational waveforms from existing and
future astrophysical simulations. We demonstrate the new algorithm's stability,
convergence, and agreement with existing evolution methods. We explain how an
innovative spectral approach enables a two orders of magnitude improvement in
computational efficiency.
| [
{
"created": "Thu, 26 Jun 2014 21:04:17 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Sep 2014 22:10:11 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Handmer",
"Casey J.",
""
],
[
"Szilágyi",
"Béla",
""
]
] | We present a spectral algorithm for solving the full nonlinear vacuum Einstein field equations in the Bondi framework. Developed within the Spectral Einstein Code (SpEC), we demonstrate spectral characteristic evolution as a technical precursor to Cauchy Characteristic Extraction (CCE), a rigorous method for obtaining gauge-invariant gravitational waveforms from existing and future astrophysical simulations. We demonstrate the new algorithm's stability, convergence, and agreement with existing evolution methods. We explain how an innovative spectral approach enables a two orders of magnitude improvement in computational efficiency. |
gr-qc/0505040 | Istvan Ozsvath | Juergen Ehlers, Istvan Ozsvath, Engelbert Schucking | Active Mass Under Pressure | 28 pages, 4 figures | Am.J.Phys. 74 (2006) 607-613 | 10.1119/1.2198881 | null | gr-qc | null | After a historical introduction to Poisson's equation for Newtonian gravity,
its analog for static gravitational fields in Einstein's theory is reviewed. It
appears that the pressure contribution to the active mass density in Einstein's
theory might also be noticeable at the Newtonian level. A form of its
surprising appearance, first noticed by Richard Chase Tolman, was discussed
half a century ago in the Hamburg Relativity Seminar and is resolved here.
| [
{
"created": "Tue, 10 May 2005 00:35:58 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Ehlers",
"Juergen",
""
],
[
"Ozsvath",
"Istvan",
""
],
[
"Schucking",
"Engelbert",
""
]
] | After a historical introduction to Poisson's equation for Newtonian gravity, its analog for static gravitational fields in Einstein's theory is reviewed. It appears that the pressure contribution to the active mass density in Einstein's theory might also be noticeable at the Newtonian level. A form of its surprising appearance, first noticed by Richard Chase Tolman, was discussed half a century ago in the Hamburg Relativity Seminar and is resolved here. |
2310.14190 | Taimur Mohammadi | Behrooz Malekolkalami and Taimur Mohammadi | Magnetic Dipole and Noncommutativity | 17 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The noncommutativity concept has wide range of applications in physical and
mathematical theories. Noncommutativity in the position-time coordinates
concerns the microscale structure of space-time. the noncommutativity is an
intrinsic property of the space-time and it could be different from usual
properties when one encounters the high energy phenomena. on the other hand,
the space-time is assumed to be as a background for the occurrence of physical
events. therefore, it is not far-fetched to expect the emergence of new physics
or dynamics when the fine geometric structure of space-time is deformed. In
this work, we consider a common form of this deformation and try to answer the
question as: a physical (or dynamical) model can be described by the
noncommutative effects?. This can also be asked this way: dose the
noncommutativity could have a physical manifestations in the nature?. Our model
here is a magnetic dipole.
| [
{
"created": "Sun, 22 Oct 2023 05:35:47 GMT",
"version": "v1"
}
] | 2023-10-24 | [
[
"Malekolkalami",
"Behrooz",
""
],
[
"Mohammadi",
"Taimur",
""
]
] | The noncommutativity concept has wide range of applications in physical and mathematical theories. Noncommutativity in the position-time coordinates concerns the microscale structure of space-time. the noncommutativity is an intrinsic property of the space-time and it could be different from usual properties when one encounters the high energy phenomena. on the other hand, the space-time is assumed to be as a background for the occurrence of physical events. therefore, it is not far-fetched to expect the emergence of new physics or dynamics when the fine geometric structure of space-time is deformed. In this work, we consider a common form of this deformation and try to answer the question as: a physical (or dynamical) model can be described by the noncommutative effects?. This can also be asked this way: dose the noncommutativity could have a physical manifestations in the nature?. Our model here is a magnetic dipole. |
1502.05219 | Gamal G.L. Nashed | G.G.L. Nashed | A special exact spherically symmetric solution in f(T) gravity theories | 14 pages | Gen Relativ Gravit (2013) 45: 1887 | 10.1007/s10714-013-1566-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A non-diagonal spherically symmetric tetrad field, involving four unknown
functions of radial coordinate $r$, is applied to the equations of motion of
f(T) gravity theory. A special exact vacuum solution with one constant of
integration is obtained. The scalar torsion related to this special solution
vanishes. To understand the physical meaning of the constant of integration we
calculate the energy associated with this solution and show how it is related
to the gravitational mass of the system.
| [
{
"created": "Tue, 17 Feb 2015 10:26:13 GMT",
"version": "v1"
}
] | 2015-02-19 | [
[
"Nashed",
"G. G. L.",
""
]
] | A non-diagonal spherically symmetric tetrad field, involving four unknown functions of radial coordinate $r$, is applied to the equations of motion of f(T) gravity theory. A special exact vacuum solution with one constant of integration is obtained. The scalar torsion related to this special solution vanishes. To understand the physical meaning of the constant of integration we calculate the energy associated with this solution and show how it is related to the gravitational mass of the system. |
1107.0948 | Diego S\'aez-G\'omez | Salvatore Capozziello and Diego S\'aez-G\'omez | Scalar-tensor representation of $f(R)$ gravity and Birkhoff's theorem | 8 pages. Version to be published in Annalen der Physik | null | 10.1002/andp.201100244 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Birkhoff's theorem is discussed in the frame of f(R) gravity by using its
scalar-tensor representation. Modified gravity has become very popular at
recent times as it is able to reproduce the unification of inflation and
late-time acceleration with no need of a dark energy component or an inflaton
field. Here, another aspect of modified f(R) gravity is studied, specifically
the range of validity of Birkhoff's theorem, compared with another alternative
to General Relativity, the well known Brans-Dicke theory. As a novelty, here
both theories are studied by using a conformal transformation and writing the
actions in the Einstein frame, where spherically symmetric solutions are
studied by using perturbation techniques. The differences between both theories
are analyzed as well as the validity of the theorem within the Jordan and
Einstein frames, where interesting results are obtained.
| [
{
"created": "Tue, 5 Jul 2011 19:03:37 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Nov 2011 15:01:38 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Dec 2011 19:24:47 GMT",
"version": "v3"
}
] | 2015-05-28 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Sáez-Gómez",
"Diego",
""
]
] | Birkhoff's theorem is discussed in the frame of f(R) gravity by using its scalar-tensor representation. Modified gravity has become very popular at recent times as it is able to reproduce the unification of inflation and late-time acceleration with no need of a dark energy component or an inflaton field. Here, another aspect of modified f(R) gravity is studied, specifically the range of validity of Birkhoff's theorem, compared with another alternative to General Relativity, the well known Brans-Dicke theory. As a novelty, here both theories are studied by using a conformal transformation and writing the actions in the Einstein frame, where spherically symmetric solutions are studied by using perturbation techniques. The differences between both theories are analyzed as well as the validity of the theorem within the Jordan and Einstein frames, where interesting results are obtained. |
gr-qc/9607054 | Nils Andersson | Nils Andersson and Hisashi Onozawa | Quasinormal modes of nearly extreme Reissner-Nordstrom black holes | 3 postscript figures | Phys.Rev. D54 (1996) 7470-7475 | 10.1103/PhysRevD.54.7470 | null | gr-qc | null | We present detailed calculations of the quasinormal modes of
Reissner-Nordstrom black holes. While the first few, slowly damped, modes
depend on the charge of the black hole in a relatively simple way, we find that
the rapidly damped modes show several peculiar features. The higher modes
generally spiral into the value for the extreme black hole as the charge
increases. We also discuss the possible existence of a purely imaginary mode
for the Schwarzschild black hole: Our data suggest that there is a quasinormal
mode that limits to $\omega M = -2i$ as $Q\to 0$.
| [
{
"created": "Tue, 23 Jul 1996 15:59:20 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Andersson",
"Nils",
""
],
[
"Onozawa",
"Hisashi",
""
]
] | We present detailed calculations of the quasinormal modes of Reissner-Nordstrom black holes. While the first few, slowly damped, modes depend on the charge of the black hole in a relatively simple way, we find that the rapidly damped modes show several peculiar features. The higher modes generally spiral into the value for the extreme black hole as the charge increases. We also discuss the possible existence of a purely imaginary mode for the Schwarzschild black hole: Our data suggest that there is a quasinormal mode that limits to $\omega M = -2i$ as $Q\to 0$. |
1401.8117 | Titus K Mathew | Praseetha P. and Titus K. Mathew | Entropy of the holographic dark energy and generalized second law | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we have considered the holographic dark energy and studied it's
cosmology and thermodynamics. We have analysed the generalized second law (GSL)
of thermodynamics in a flat universe consists of interacting dark energy and
dark matter. We did the analysis both under thermal equilibrium and
non-equilibrium conditions. If the apparent horizon is taken as the boundary of
the universe, we have shown that the rate of change of the total entropy of the
universe is proportional to $(1+q)^2,$ which in fact shows that the GSL is
valid at the apparent horizon irrespective of the sign of $q,$ the deceleration
parameter. Hence for any form of dark energy the apparent horizon can be
considered as a perfect thermodynamic boundary of the universe. We made a
confirmation of this conclusion by using the holographic dark energy. When
event horizon is taken as the boundary, we found that the GSL is only partially
satisfied. The analysis under non-equilibrium conditions revealed that the GSL
is satisfied if the dark energy temperature is greater than the temperature of
dark matter.
| [
{
"created": "Fri, 31 Jan 2014 10:29:45 GMT",
"version": "v1"
}
] | 2014-02-03 | [
[
"P.",
"Praseetha",
""
],
[
"Mathew",
"Titus K.",
""
]
] | In this paper we have considered the holographic dark energy and studied it's cosmology and thermodynamics. We have analysed the generalized second law (GSL) of thermodynamics in a flat universe consists of interacting dark energy and dark matter. We did the analysis both under thermal equilibrium and non-equilibrium conditions. If the apparent horizon is taken as the boundary of the universe, we have shown that the rate of change of the total entropy of the universe is proportional to $(1+q)^2,$ which in fact shows that the GSL is valid at the apparent horizon irrespective of the sign of $q,$ the deceleration parameter. Hence for any form of dark energy the apparent horizon can be considered as a perfect thermodynamic boundary of the universe. We made a confirmation of this conclusion by using the holographic dark energy. When event horizon is taken as the boundary, we found that the GSL is only partially satisfied. The analysis under non-equilibrium conditions revealed that the GSL is satisfied if the dark energy temperature is greater than the temperature of dark matter. |
2202.06349 | Tiberiu Harko | Tiberiu Harko, Shahab Shahidi | Coupling matter and curvature in Weyl geometry: conformally invariant
$f\left(R,L_m\right)$ gravity | 22 pages, 2 figures, accepted for publication in EPJC | null | 10.1140/epjc/s10052-022-10126-1 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the coupling of matter to geometry in conformal quadratic Weyl
gravity, by assuming a coupling term of the form $L_m\tilde{R}^2$, where $L_m$
is the ordinary matter Lagrangian, and $\tilde{R}$ is the Weyl scalar. The
coupling explicitly satisfies the conformal invariance of the theory. By
expressing $\tilde{R}^2$ with the help of an auxiliary scalar field and of the
Weyl scalar, the gravitational action can be linearized, leading in the Riemann
space to a conformally invariant $f\left(R,L_m\right)$ type theory, with the
matter Lagrangian nonminimally coupled to the Ricci scalar. We obtain the
gravitational field equations of the theory, as well as the energy-momentum
balance equations. The divergence of the matter energy-momentum tensor does not
vanish, and an extra force, depending on the Weyl vector, and matter Lagrangian
is generated. The thermodynamic interpretation of the theory is also discussed.
The generalized Poisson equation is derived, and the Newtonian limit of the
equations of motion is considered in detail. The perihelion precession of a
planet in the presence of an extra force is also considered, and constraints on
the magnitude of the Weyl vector in the Solar System are obtained from the
observational data of Mercury. The cosmological implications of the theory are
also considered for the case of a flat, homogeneous and isotropic
Friedmann-Lemaitre-Robertson-Walker geometry, and it is shown that the model
can give a good description of the observational data for the Hubble function
up to a redshift of the order of $z\approx 3$.
| [
{
"created": "Sun, 13 Feb 2022 15:48:10 GMT",
"version": "v1"
}
] | 2022-03-30 | [
[
"Harko",
"Tiberiu",
""
],
[
"Shahidi",
"Shahab",
""
]
] | We investigate the coupling of matter to geometry in conformal quadratic Weyl gravity, by assuming a coupling term of the form $L_m\tilde{R}^2$, where $L_m$ is the ordinary matter Lagrangian, and $\tilde{R}$ is the Weyl scalar. The coupling explicitly satisfies the conformal invariance of the theory. By expressing $\tilde{R}^2$ with the help of an auxiliary scalar field and of the Weyl scalar, the gravitational action can be linearized, leading in the Riemann space to a conformally invariant $f\left(R,L_m\right)$ type theory, with the matter Lagrangian nonminimally coupled to the Ricci scalar. We obtain the gravitational field equations of the theory, as well as the energy-momentum balance equations. The divergence of the matter energy-momentum tensor does not vanish, and an extra force, depending on the Weyl vector, and matter Lagrangian is generated. The thermodynamic interpretation of the theory is also discussed. The generalized Poisson equation is derived, and the Newtonian limit of the equations of motion is considered in detail. The perihelion precession of a planet in the presence of an extra force is also considered, and constraints on the magnitude of the Weyl vector in the Solar System are obtained from the observational data of Mercury. The cosmological implications of the theory are also considered for the case of a flat, homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker geometry, and it is shown that the model can give a good description of the observational data for the Hubble function up to a redshift of the order of $z\approx 3$. |
2212.06762 | Marcus Khuri | Marcus A. Khuri, Jordan F. Rainone | Black Lenses in Kaluza-Klein Matter | 6 pages; Phys. Rev. Lett., to appear; A Quanta Magazine article based
on the results of this paper may be found here:
https://www.quantamagazine.org/mathematicians-find-an-infinity-of-possible-black-hole-shapes-20230124/ | Phys. Rev. Lett., 131 (2023), 041402 | 10.1103/PhysRevLett.131.041402 | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first examples of formally asymptotically flat black hole
solutions with horizons of general lens space topology $L(p,q)$. These
5-dimensional static/stationary spacetimes are regular on and outside the event
horizon for any choice of relatively prime integers $1\leq q<p$, in particular
conical singularities are absent. They are supported by Kaluza-Klein matter
fields arising from higher dimensional vacuum solutions through reduction on
tori. The technique is sufficiently robust that it leads to the explicit
construction of regular solutions, in any dimension, realising the full range
of possible topologies for the horizon as well as the domain of outer
communication, that are allowable with multi-axisymmetry. Lastly, as a by
product, we obtain new examples of regular gravitational instantons in higher
dimensions.
| [
{
"created": "Tue, 13 Dec 2022 17:45:05 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jul 2023 01:41:45 GMT",
"version": "v2"
}
] | 2023-08-09 | [
[
"Khuri",
"Marcus A.",
""
],
[
"Rainone",
"Jordan F.",
""
]
] | We present the first examples of formally asymptotically flat black hole solutions with horizons of general lens space topology $L(p,q)$. These 5-dimensional static/stationary spacetimes are regular on and outside the event horizon for any choice of relatively prime integers $1\leq q<p$, in particular conical singularities are absent. They are supported by Kaluza-Klein matter fields arising from higher dimensional vacuum solutions through reduction on tori. The technique is sufficiently robust that it leads to the explicit construction of regular solutions, in any dimension, realising the full range of possible topologies for the horizon as well as the domain of outer communication, that are allowable with multi-axisymmetry. Lastly, as a by product, we obtain new examples of regular gravitational instantons in higher dimensions. |
1309.2768 | Bob Osano | Bob Osano | The Weyl Curvature Tensor, Cotton-York Tensor and Gravitational Waves: A
covariant consideration | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | 1+3 covariant approach to cosmological perturbation theory often employs the
electric part ($E_{ab}$), the magnetic part ($H_{ab}$) of the Weyl tensor or
the shear tensor ($\sigma_{ab}$) in a phenomenological description of
gravitational waves. The Cotton-York tensor is rarely mentioned in connection
with gravitational waves in this approach. This tensor acts as a source for the
magnetic part of the Weyl tensor which should not be neglected in studies of
gravitational waves in the 1+3 formalism. The tensor is only mentioned in
connection with studies of 'silent model' but even there the connection with
gravitational waves is not exhaustively explored. In this study, we demonstrate
that the Cotton-York tensor encodes contributions from both electric, magnetic
part of the Weyl tensor and in directly from the shear tensor. In our opinion,
this makes the Cotton-York tensor arguably the natural choice for linear
gravitational waves in the 1+3 covariant formalism. The tensor is cumbersome to
work with but that should negate its usefulness. It is conceivable that the
tensor would equally be useful in the metric approach, although we have not
demonstrated this in the current study. We contend that the use of only one of
the Weyl tensor or the shear tensor, although phenomenologically correct, leads
to loss of information. Such information is vital particularly when examining
the contribution of gravitational waves to the anisotropy of an almost
-Friedmann-Lamitre-Robertson-Walker (FLRW) universe. The recourse to this loss
is the use Cotton-York tensor.
| [
{
"created": "Wed, 11 Sep 2013 09:26:23 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Oct 2013 12:07:43 GMT",
"version": "v2"
},
{
"created": "Sat, 28 Oct 2017 16:02:26 GMT",
"version": "v3"
}
] | 2017-10-31 | [
[
"Osano",
"Bob",
""
]
] | 1+3 covariant approach to cosmological perturbation theory often employs the electric part ($E_{ab}$), the magnetic part ($H_{ab}$) of the Weyl tensor or the shear tensor ($\sigma_{ab}$) in a phenomenological description of gravitational waves. The Cotton-York tensor is rarely mentioned in connection with gravitational waves in this approach. This tensor acts as a source for the magnetic part of the Weyl tensor which should not be neglected in studies of gravitational waves in the 1+3 formalism. The tensor is only mentioned in connection with studies of 'silent model' but even there the connection with gravitational waves is not exhaustively explored. In this study, we demonstrate that the Cotton-York tensor encodes contributions from both electric, magnetic part of the Weyl tensor and in directly from the shear tensor. In our opinion, this makes the Cotton-York tensor arguably the natural choice for linear gravitational waves in the 1+3 covariant formalism. The tensor is cumbersome to work with but that should negate its usefulness. It is conceivable that the tensor would equally be useful in the metric approach, although we have not demonstrated this in the current study. We contend that the use of only one of the Weyl tensor or the shear tensor, although phenomenologically correct, leads to loss of information. Such information is vital particularly when examining the contribution of gravitational waves to the anisotropy of an almost -Friedmann-Lamitre-Robertson-Walker (FLRW) universe. The recourse to this loss is the use Cotton-York tensor. |
1003.3623 | Jerry B. Griffiths | J. B. Griffiths and N. O. Santos | A rotating cylinder in an asymptotically locally anti-de Sitter
background | To appear in Classical and Quantum Gravity | null | 10.1088/0264-9381/27/12/125004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A family of exact solutions is presented which represents a rigidly rotating
cylinder of dust in a background with a negative cosmological constant. The
interior of the infinite cylinder is described by the Godel solution. An exact
solution for the exterior solution is found which depends both on the rotation
of the interior and on its radius. For values of these parameters less than a
certain limit, the exterior solution is shown to be locally isomorphic to the
Linet-Tian solution. For values larger than another limit, it is shown that the
exterior solution extends into a region which contains closed timelike curves.
At large distances from the source, the space-time is shown to be asymptotic
locally to anti-de Sitter space.
| [
{
"created": "Thu, 18 Mar 2010 16:32:47 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Griffiths",
"J. B.",
""
],
[
"Santos",
"N. O.",
""
]
] | A family of exact solutions is presented which represents a rigidly rotating cylinder of dust in a background with a negative cosmological constant. The interior of the infinite cylinder is described by the Godel solution. An exact solution for the exterior solution is found which depends both on the rotation of the interior and on its radius. For values of these parameters less than a certain limit, the exterior solution is shown to be locally isomorphic to the Linet-Tian solution. For values larger than another limit, it is shown that the exterior solution extends into a region which contains closed timelike curves. At large distances from the source, the space-time is shown to be asymptotic locally to anti-de Sitter space. |
2402.07272 | Tsvetan Vetsov Assoc. Prof. Dr. | V. Avramov, H. Dimov, M. Radomirov, R. C. Rashkov, T. Vetsov | On Thermodynamic Stability of Black Holes. Part II: AdS Family of
Solutions | Minor update: 1) Minor changes in the text, 2) Mising references were
added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study is aimed at providing a thorough analysis of the classical
thermodynamic stability of black holes within the Anti-de Sitter (AdS) family.
We utilize the Nambu bracket formalism to calculate local heat capacities and
employ Sylvester's criterion in the mass-energy ensemble to determine both
local and global thermodynamic stability regions. Emphasizing the crucial role
of the cosmological constant, we establish the conditions necessary for the
existence of thermodynamically stable black hole configurations. Our work
highlights the applicability of classical thermodynamics in understanding black
hole physics, while acknowledging the potential deviations that may impact the
observables of the system beyond the classical level.
| [
{
"created": "Sun, 11 Feb 2024 18:30:33 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Apr 2024 16:29:20 GMT",
"version": "v2"
}
] | 2024-04-10 | [
[
"Avramov",
"V.",
""
],
[
"Dimov",
"H.",
""
],
[
"Radomirov",
"M.",
""
],
[
"Rashkov",
"R. C.",
""
],
[
"Vetsov",
"T.",
""
]
] | This study is aimed at providing a thorough analysis of the classical thermodynamic stability of black holes within the Anti-de Sitter (AdS) family. We utilize the Nambu bracket formalism to calculate local heat capacities and employ Sylvester's criterion in the mass-energy ensemble to determine both local and global thermodynamic stability regions. Emphasizing the crucial role of the cosmological constant, we establish the conditions necessary for the existence of thermodynamically stable black hole configurations. Our work highlights the applicability of classical thermodynamics in understanding black hole physics, while acknowledging the potential deviations that may impact the observables of the system beyond the classical level. |
2405.09714 | Seturumane Tema | Saurya Das, S. Shajidul Haque and Seturumane Tema | Cosmological Singularity and Power-Law Solutions in Modified Gravity | null | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | A bouncing Universe avoids the big-bang singularity. Using the time-like and
null Raychaudhhuri equations, we explore whether the bounce near the big-bang,
within a broad spectrum of modified theories of gravity, allows for
cosmologically relevant power-law solutions under reasonable physical
conditions. Our study shows that certain modified theories of gravity, such as
Stelle gravity, do not demonstrate singularity resolution under any reasonable
conditions, while others including $f(R)$ gravity and Brans-Dicke theory can
demonstrate singularity resolution under suitable conditions. For these
theories, we show that the accelerating solution is slightly favoured over
ekypyrosis.
| [
{
"created": "Wed, 15 May 2024 21:58:56 GMT",
"version": "v1"
}
] | 2024-05-24 | [
[
"Das",
"Saurya",
""
],
[
"Haque",
"S. Shajidul",
""
],
[
"Tema",
"Seturumane",
""
]
] | A bouncing Universe avoids the big-bang singularity. Using the time-like and null Raychaudhhuri equations, we explore whether the bounce near the big-bang, within a broad spectrum of modified theories of gravity, allows for cosmologically relevant power-law solutions under reasonable physical conditions. Our study shows that certain modified theories of gravity, such as Stelle gravity, do not demonstrate singularity resolution under any reasonable conditions, while others including $f(R)$ gravity and Brans-Dicke theory can demonstrate singularity resolution under suitable conditions. For these theories, we show that the accelerating solution is slightly favoured over ekypyrosis. |
1903.11638 | Raissa Mendes | Raissa F. P. Mendes and Tulio Ottoni | Scalar charges and pulsar-timing observables in the presence of
nonminimally coupled scalar fields | 12 pages, 6 figures | Phys. Rev. D 99, 124003 (2019) | 10.1103/PhysRevD.99.124003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Pulsar-timing has become a celebrated tool for probing modifications to
General Relativity in the strong-field surroundings of neutron stars. Here we
investigate whether scalar-tensor theories that incorporate a nonminimally
coupled scalar degree of freedom may pass pulsar-timing tests, by computing the
scalar charges entering such observables. In particular we show that for
positive values of the nonminimal coupling $\xi$, pulsar-timing constraints may
be evaded even in the presence of spontaneous scalarization.
| [
{
"created": "Wed, 27 Mar 2019 18:28:12 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jun 2019 13:11:38 GMT",
"version": "v2"
}
] | 2019-06-19 | [
[
"Mendes",
"Raissa F. P.",
""
],
[
"Ottoni",
"Tulio",
""
]
] | Pulsar-timing has become a celebrated tool for probing modifications to General Relativity in the strong-field surroundings of neutron stars. Here we investigate whether scalar-tensor theories that incorporate a nonminimally coupled scalar degree of freedom may pass pulsar-timing tests, by computing the scalar charges entering such observables. In particular we show that for positive values of the nonminimal coupling $\xi$, pulsar-timing constraints may be evaded even in the presence of spontaneous scalarization. |
1504.02702 | Peter Phillips | Peter R. Phillips | Broken symmetry can yield a positive effective G in conformal gravity | 4 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We modify the action of Mannheim's conformally invariant model by changing
the sign of two coefficients. This breaks conformal symmetry, but results in a
cosmology that has a positive effective G and at the same time retains one of
the main advantages of the Mannheim model, a possible solution of the
cosmological constant problem.
| [
{
"created": "Fri, 10 Apr 2015 15:04:57 GMT",
"version": "v1"
}
] | 2015-04-13 | [
[
"Phillips",
"Peter R.",
""
]
] | We modify the action of Mannheim's conformally invariant model by changing the sign of two coefficients. This breaks conformal symmetry, but results in a cosmology that has a positive effective G and at the same time retains one of the main advantages of the Mannheim model, a possible solution of the cosmological constant problem. |
0903.4381 | Philip D. Mannheim | Philip D. Mannheim, James G. O'Brien and David Eric Cox | Limitations of the Standard Gravitational Perfect Fluid Paradigm | Final version to appear in General Relativity and Gravitation (the
final publication is available at http://www.springerlink.com). 29 pages, 1
figure | null | 10.1007/s10714-010-0997-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the standard perfect fluid paradigm is not necessarily a valid
description of a curved space steady state gravitational source. Simply by
virtue of not being flat, curved space geometries have to possess intrinsic
length scales, and such length scales can affect the fluid structure. For modes
of wavelength of order or greater than such scales eikonalized geometrical
optics cannot apply and rays are not geodesic. Covariantizing thus entails not
only the replacing of flat space functions by covariant ones, but also the
introduction of intrinsic scales that were absent in flat space. In principle
it is thus unreliable to construct the curved space energy-momentum tensor as
the covariant generalization of a geodesic-based flat spacetime energy-momentum
tensor. By constructing the partition function as an incoherent average over a
complete set of modes of a scalar field propagating in a curved space
background, we show that for the specific case of a static, spherically
symmetric geometry, the steady state energy-momentum tensor that ensues will in
general be of the form
$T_{\mu\nu}=(\rho+p)U_{\mu}U_{\nu}+pg_{\mu\nu}+\pi_{\mu\nu}$ where the
anisotropic $\pi_{\mu\nu}$ is a symmetric, traceless rank two tensor which
obeys $U^{\mu}\pi_{\mu\nu}=0$. Such a $\pi_{\mu\nu}$ type term is absent for an
incoherently averaged steady state fluid in a spacetime where there are no
intrinsic length scales, and in principle would thus be missed in a
covariantizing of a flat spacetime $T_{\mu\nu}$. While the significance of such
$\pi_{\mu\nu}$ type terms would need to be evaluated on a case by case basis,
through the use of kinetic theory we reassuringly find that the effect of such
$\pi_{\mu\nu}$ type terms is small for weak gravity stars where perfect fluid
sources are commonly used.
| [
{
"created": "Wed, 25 Mar 2009 16:08:51 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Sep 2010 16:29:46 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Mannheim",
"Philip D.",
""
],
[
"O'Brien",
"James G.",
""
],
[
"Cox",
"David Eric",
""
]
] | We show that the standard perfect fluid paradigm is not necessarily a valid description of a curved space steady state gravitational source. Simply by virtue of not being flat, curved space geometries have to possess intrinsic length scales, and such length scales can affect the fluid structure. For modes of wavelength of order or greater than such scales eikonalized geometrical optics cannot apply and rays are not geodesic. Covariantizing thus entails not only the replacing of flat space functions by covariant ones, but also the introduction of intrinsic scales that were absent in flat space. In principle it is thus unreliable to construct the curved space energy-momentum tensor as the covariant generalization of a geodesic-based flat spacetime energy-momentum tensor. By constructing the partition function as an incoherent average over a complete set of modes of a scalar field propagating in a curved space background, we show that for the specific case of a static, spherically symmetric geometry, the steady state energy-momentum tensor that ensues will in general be of the form $T_{\mu\nu}=(\rho+p)U_{\mu}U_{\nu}+pg_{\mu\nu}+\pi_{\mu\nu}$ where the anisotropic $\pi_{\mu\nu}$ is a symmetric, traceless rank two tensor which obeys $U^{\mu}\pi_{\mu\nu}=0$. Such a $\pi_{\mu\nu}$ type term is absent for an incoherently averaged steady state fluid in a spacetime where there are no intrinsic length scales, and in principle would thus be missed in a covariantizing of a flat spacetime $T_{\mu\nu}$. While the significance of such $\pi_{\mu\nu}$ type terms would need to be evaluated on a case by case basis, through the use of kinetic theory we reassuringly find that the effect of such $\pi_{\mu\nu}$ type terms is small for weak gravity stars where perfect fluid sources are commonly used. |
2210.06558 | Khadijeh Jafarzade | S. Mahmoudi, Kh. Jafarzade, S. H. Hendi | Gauss-Bonnet black holes in a special anisotropic scaling spacetime | 17 pages, 11 figures | JHEP 12 (2022) 009 | 10.1007/JHEP12(2022)009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by the Lifshitz gravity as a theory with anisotropic scaling
behavior, we suggest a new $(n+1)-$dimensional metric in which the time and
spatial coordinates scale anisotropically as $(t,r,\theta_{i})\,\to
(\lambda^{z}t,\lambda^{-1}r,\lambda^{x_i}\,\theta_{i})$. Due to the anisotropic
scaling dimension of the spatial coordinates, this spacetime does not support
the full Schr\"{o}dinger symmetry group. We look for the analytical solution of
Gauss-Bonnet gravity in the context of the mentioned geometry. We show that
Gauss-Bonnet gravity admits an analytical solution provided that the constants
of the theory are properly adjusted. We obtain an exact vacuum solution,
independent of the value of the dynamical exponent $z$, which is a black hole
solution for the pseudo-hyperbolic horizon structure and a naked singularity
for the pseudo-spherical boundary. We also obtain another exact solution of
Gauss-Bonnet gravity under certain conditions. After investigating some
geometrical properties of the obtained solutions, we consider the thermodynamic
properties of these topological black holes and study the stability of the
obtained solutions for each geometrical structure.
| [
{
"created": "Wed, 12 Oct 2022 19:56:48 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Dec 2022 07:09:32 GMT",
"version": "v2"
}
] | 2022-12-06 | [
[
"Mahmoudi",
"S.",
""
],
[
"Jafarzade",
"Kh.",
""
],
[
"Hendi",
"S. H.",
""
]
] | Inspired by the Lifshitz gravity as a theory with anisotropic scaling behavior, we suggest a new $(n+1)-$dimensional metric in which the time and spatial coordinates scale anisotropically as $(t,r,\theta_{i})\,\to (\lambda^{z}t,\lambda^{-1}r,\lambda^{x_i}\,\theta_{i})$. Due to the anisotropic scaling dimension of the spatial coordinates, this spacetime does not support the full Schr\"{o}dinger symmetry group. We look for the analytical solution of Gauss-Bonnet gravity in the context of the mentioned geometry. We show that Gauss-Bonnet gravity admits an analytical solution provided that the constants of the theory are properly adjusted. We obtain an exact vacuum solution, independent of the value of the dynamical exponent $z$, which is a black hole solution for the pseudo-hyperbolic horizon structure and a naked singularity for the pseudo-spherical boundary. We also obtain another exact solution of Gauss-Bonnet gravity under certain conditions. After investigating some geometrical properties of the obtained solutions, we consider the thermodynamic properties of these topological black holes and study the stability of the obtained solutions for each geometrical structure. |
1101.0030 | Shankaranarayanan S | S. Shankaranarayanan (IISER-Trivandrum) | Corrections to Bekenstein-Hawking entropy --- Quantum or not-so quantum? | 10 pages; Article for the Special Issue "Entropy in Quantum Gravity"
in the Journal Entropy | Entropy 13(1), 11-16 (2011); | 10.3390/e13010011 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation and Bekenstein--Hawking entropy are the two robust
predictions of a yet unknown quantum theory of gravity. Any theory which fails
to reproduce these predictions is certainly incorrect. While several approaches
lead to Bekenstein--Hawking entropy, they all lead to different sub-leading
corrections. In this article, we ask a question that is relevant for any
approach: Using simple techniques, can we know whether an approach contains
quantum or semi-classical degrees of freedom? Using naive dimensional analysis,
we show that the semi-classical black-hole entropy has the same dimensional
dependence as the gravity action. Among others, this provides a plausible
explanation for the connection between Einstein's equations and thermodynamic
equation of state, and that the quantum corrections should have a different
scaling behavior.
| [
{
"created": "Thu, 30 Dec 2010 02:05:33 GMT",
"version": "v1"
}
] | 2011-01-04 | [
[
"Shankaranarayanan",
"S.",
"",
"IISER-Trivandrum"
]
] | Hawking radiation and Bekenstein--Hawking entropy are the two robust predictions of a yet unknown quantum theory of gravity. Any theory which fails to reproduce these predictions is certainly incorrect. While several approaches lead to Bekenstein--Hawking entropy, they all lead to different sub-leading corrections. In this article, we ask a question that is relevant for any approach: Using simple techniques, can we know whether an approach contains quantum or semi-classical degrees of freedom? Using naive dimensional analysis, we show that the semi-classical black-hole entropy has the same dimensional dependence as the gravity action. Among others, this provides a plausible explanation for the connection between Einstein's equations and thermodynamic equation of state, and that the quantum corrections should have a different scaling behavior. |
1401.5985 | Matej \v{S}kovran | Matej \v{S}kovran | Analytical solutions for cosmological perturbations in a one-component
universe with shear stress | 10 pages | Int. J. Mod. Phys. D 24 (2015) 1550063 | 10.1142/S0218271815500637 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct explicit solutions for scalar, vector and tensor perturbations
in a less known setting, a flat universe filled by an isotropic elastic solid
with pressure and shear modulus proportional to energy density. The solutions
generalize the well known formulas for cosmological perturbations in a universe
filled by ideal fluid.
| [
{
"created": "Thu, 23 Jan 2014 14:28:19 GMT",
"version": "v1"
},
{
"created": "Thu, 21 May 2015 09:33:17 GMT",
"version": "v2"
}
] | 2015-05-22 | [
[
"Škovran",
"Matej",
""
]
] | We construct explicit solutions for scalar, vector and tensor perturbations in a less known setting, a flat universe filled by an isotropic elastic solid with pressure and shear modulus proportional to energy density. The solutions generalize the well known formulas for cosmological perturbations in a universe filled by ideal fluid. |
2111.00706 | Zhi-Wei Wang | Zhi-Wei Wang, Samuel L. Braunstein, Saurya Das | Information recovery from evaporating rotating charged black holes | 8 pages, 5 figures, Proceeding of the Sixteenth Marcel Grossmann
Meeting (will be published in IJMPD). arXiv admin note: text overlap with
arXiv:2105.00198 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In classical gravity, nothing can escape from a black hole, not even light.
In particular, this happens for stationary black holes because their horizons
are null. We show, on the other hand, that the apparent horizon and the region
near r = 0 of an evaporating charged, rotating black hole are both timelike.
This implies that there exists a channel, via which classical or quantum
information can escape to the outside, as the black hole evaporates. Since
astrophysical black holes have at least some rotation, our results apply to all
black holes in nature. We discuss the implications of our result.
| [
{
"created": "Mon, 1 Nov 2021 04:57:15 GMT",
"version": "v1"
}
] | 2021-11-02 | [
[
"Wang",
"Zhi-Wei",
""
],
[
"Braunstein",
"Samuel L.",
""
],
[
"Das",
"Saurya",
""
]
] | In classical gravity, nothing can escape from a black hole, not even light. In particular, this happens for stationary black holes because their horizons are null. We show, on the other hand, that the apparent horizon and the region near r = 0 of an evaporating charged, rotating black hole are both timelike. This implies that there exists a channel, via which classical or quantum information can escape to the outside, as the black hole evaporates. Since astrophysical black holes have at least some rotation, our results apply to all black holes in nature. We discuss the implications of our result. |
2303.11885 | Hyat Huang | Hyat Huang, Jutta Kunz, Jinbo Yang and Cong Zhang | Light Ring behind Wormhole Throat: Geodesics, Images and Shadows | 26 pages, 14 figures, add references | null | 10.1103/PhysRevD.107.104060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geodesics of the Ellis-Bronnikov wormhole with two parameters are
studied. The asymmetric wormhole has only one light ring and one innermost
stable circular orbit located on one side of the wormhole throat. Consequently,
certain light rays can be reflected back by the wormhole. Additionally, the
same wormhole can have different appearances on both sides of the throat. We
present novel images of the wormhole with a light ring behind the throat in a
scenario with an accretion disk as the light source and in a backlit wormhole
scenario, which are distinct from the images of other compact objects and have
the potential to be observed.
| [
{
"created": "Tue, 21 Mar 2023 14:26:19 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Mar 2023 10:54:52 GMT",
"version": "v2"
}
] | 2023-06-14 | [
[
"Huang",
"Hyat",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Yang",
"Jinbo",
""
],
[
"Zhang",
"Cong",
""
]
] | The geodesics of the Ellis-Bronnikov wormhole with two parameters are studied. The asymmetric wormhole has only one light ring and one innermost stable circular orbit located on one side of the wormhole throat. Consequently, certain light rays can be reflected back by the wormhole. Additionally, the same wormhole can have different appearances on both sides of the throat. We present novel images of the wormhole with a light ring behind the throat in a scenario with an accretion disk as the light source and in a backlit wormhole scenario, which are distinct from the images of other compact objects and have the potential to be observed. |
2109.13949 | Oscar J. C. Dias | Oscar J.C. Dias, Mahdi Godazgar, Jorge E. Santos, and Gregorio
Carullo, Walter Del Pozzo, Danny Laghi | Eigenvalue repulsions in the quasinormal spectra of the Kerr-Newman
black hole | 9 pages, 2 figures | null | 10.1103/PhysRevD.105.084044 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We study the gravito-electromagnetic perturbations of the Kerr-Newman (KN)
black hole metric and identify the two $-$ photon sphere and near-horizon $-$
families of quasinormal modes (QNMs) of the KN black hole, computing the
frequency spectra (for all the KN parameter space) of the modes with the
slowest decay rate. We uncover a novel phenomenon for QNMs that is unique to
the KN system, namely eigenvalue repulsion between QNM families. Such a feature
is common in solid state physics where \eg it is responsible for energy
bands/gaps in the spectra of electrons moving in certain Schr\"odinger
potentials. Exploiting the enhanced symmetries of the near-horizon limit of the
near-extremal KN geometry we also develop a matching asymptotic expansion that
allows us to solve the perturbation problem using separation of variables and
provides an excellent approximation to the KN QNM spectra near extremality. The
KN QNM spectra here derived are required not only to account for the
gravitational emission in astrophysical environments, such as the ones probed
by LIGO, Virgo and LISA, but also allow to extract observational implications
on several new physics scenarios, such as mini-charged dark-matter or certain
modified theories of gravity, degenerate with the KN solution at the scales of
binary mergers.
| [
{
"created": "Tue, 28 Sep 2021 18:00:06 GMT",
"version": "v1"
}
] | 2022-05-04 | [
[
"Dias",
"Oscar J. C.",
""
],
[
"Godazgar",
"Mahdi",
""
],
[
"Santos",
"Jorge E.",
""
],
[
"Carullo",
"Gregorio",
""
],
[
"Del Pozzo",
"Walter",
""
],
[
"Laghi",
"Danny",
""
]
] | We study the gravito-electromagnetic perturbations of the Kerr-Newman (KN) black hole metric and identify the two $-$ photon sphere and near-horizon $-$ families of quasinormal modes (QNMs) of the KN black hole, computing the frequency spectra (for all the KN parameter space) of the modes with the slowest decay rate. We uncover a novel phenomenon for QNMs that is unique to the KN system, namely eigenvalue repulsion between QNM families. Such a feature is common in solid state physics where \eg it is responsible for energy bands/gaps in the spectra of electrons moving in certain Schr\"odinger potentials. Exploiting the enhanced symmetries of the near-horizon limit of the near-extremal KN geometry we also develop a matching asymptotic expansion that allows us to solve the perturbation problem using separation of variables and provides an excellent approximation to the KN QNM spectra near extremality. The KN QNM spectra here derived are required not only to account for the gravitational emission in astrophysical environments, such as the ones probed by LIGO, Virgo and LISA, but also allow to extract observational implications on several new physics scenarios, such as mini-charged dark-matter or certain modified theories of gravity, degenerate with the KN solution at the scales of binary mergers. |
2106.09721 | Emanuele Berti | Enrico Barausse, Emanuele Berti, Vitor Cardoso, Scott A. Hughes,
Gaurav Khanna | Divergences in gravitational-wave emission and absorption from extreme
mass ratio binaries | 11 pages, 6 figures, matches version published in Physical Review D | Phys. Rev. D 104, 064031 (2021) | 10.1103/PhysRevD.104.064031 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A powerful technique to calculate gravitational radiation from binary systems
involves a perturbative expansion: if the masses of the two bodies are very
different, the "small" body is treated as a point particle of mass $m_p$ moving
in the gravitational field generated by the large mass $M$, and one keeps only
linear terms in the small mass ratio $m_p/M$. This technique usually yields
finite answers, which are often in good agreement with fully nonlinear
numerical relativity results, even when extrapolated to nearly comparable mass
ratios. Here we study two situations in which the point-particle approximation
yields a divergent result: the instantaneous flux emitted by a small body as it
orbits the light ring of a black hole, and the total energy absorbed by the
horizon when a small body plunges into a black hole. By integrating the
Teukolsky (or Zerilli/Regge-Wheeler) equations in the frequency and time
domains we show that both of these quantities diverge. We find that these
divergences are an artifact of the point-particle idealization, and are able to
interpret and regularize this behavior by introducing a finite size for the
point particle. These divergences do not play a role in black-hole imaging,
e.g. by the Event Horizon Telescope.
| [
{
"created": "Thu, 17 Jun 2021 18:00:00 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Sep 2021 14:59:27 GMT",
"version": "v2"
}
] | 2021-09-22 | [
[
"Barausse",
"Enrico",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Hughes",
"Scott A.",
""
],
[
"Khanna",
"Gaurav",
""
]
] | A powerful technique to calculate gravitational radiation from binary systems involves a perturbative expansion: if the masses of the two bodies are very different, the "small" body is treated as a point particle of mass $m_p$ moving in the gravitational field generated by the large mass $M$, and one keeps only linear terms in the small mass ratio $m_p/M$. This technique usually yields finite answers, which are often in good agreement with fully nonlinear numerical relativity results, even when extrapolated to nearly comparable mass ratios. Here we study two situations in which the point-particle approximation yields a divergent result: the instantaneous flux emitted by a small body as it orbits the light ring of a black hole, and the total energy absorbed by the horizon when a small body plunges into a black hole. By integrating the Teukolsky (or Zerilli/Regge-Wheeler) equations in the frequency and time domains we show that both of these quantities diverge. We find that these divergences are an artifact of the point-particle idealization, and are able to interpret and regularize this behavior by introducing a finite size for the point particle. These divergences do not play a role in black-hole imaging, e.g. by the Event Horizon Telescope. |
0802.1885 | Marc Casals | Marc Casals | Electromagnetic Quantum Field Theory on Kerr-Newman Black Holes | Ph.D. thesis. University College Dublin, 2004. Advisor: Adrian C.
Ottewill | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study classical and quantum aspects of electromagnetic perturbations on
black hole space-times. We develop an elegant formalism introduced by Wald,
which sets up the theory of linear perturbations in a Type-D background in a
compact and transparent manner. We derive expressions for the electromagnetic
potential in terms of the single Newman-Penrose scalar \phi_0.This enables the
formulation of the quantum theory of the electromagnetic field as that of a
complex scalar field.
We study the separable field equations obeyed by the various Newman-Penrose
scalars in the Kerr-Newman background and find, for various limits, the
asymptotic behaviour of the radial and angular solutions. We correct and build
on a study by Breuer, Ryan and Waller to find a uniformly valid asymptotic
behaviour for large frequency of the angular solutions and the eigenvalues.
We follow Candelas, Chrzanowski and Howard (CCH) in their canonical
quantization of the electromagnetic potential and field. We perform an
asymptotic analysis of the form of the renormalized stress-energy tensor (RSET)
in the past Boulware state close to the horizon. Unlike results in CCH, its
leading order behaviour close to the horizon corresponds to minus the stress
tensor of a thermal distribution at the Hawking temperature rigidly rotating
with the horizon. We prove that expressions in CCH for the expectation value of
the stress tensor in the past Boulware, past Unruh and |CCH> states lead to a
lack of symmetry of the RSET under parity, even though this is a symmetry of
the physical system. We derive the correct symmetric expressions and present a
detailed analysis of the resulting RSETs.
| [
{
"created": "Wed, 13 Feb 2008 18:14:37 GMT",
"version": "v1"
}
] | 2008-02-14 | [
[
"Casals",
"Marc",
""
]
] | We study classical and quantum aspects of electromagnetic perturbations on black hole space-times. We develop an elegant formalism introduced by Wald, which sets up the theory of linear perturbations in a Type-D background in a compact and transparent manner. We derive expressions for the electromagnetic potential in terms of the single Newman-Penrose scalar \phi_0.This enables the formulation of the quantum theory of the electromagnetic field as that of a complex scalar field. We study the separable field equations obeyed by the various Newman-Penrose scalars in the Kerr-Newman background and find, for various limits, the asymptotic behaviour of the radial and angular solutions. We correct and build on a study by Breuer, Ryan and Waller to find a uniformly valid asymptotic behaviour for large frequency of the angular solutions and the eigenvalues. We follow Candelas, Chrzanowski and Howard (CCH) in their canonical quantization of the electromagnetic potential and field. We perform an asymptotic analysis of the form of the renormalized stress-energy tensor (RSET) in the past Boulware state close to the horizon. Unlike results in CCH, its leading order behaviour close to the horizon corresponds to minus the stress tensor of a thermal distribution at the Hawking temperature rigidly rotating with the horizon. We prove that expressions in CCH for the expectation value of the stress tensor in the past Boulware, past Unruh and |CCH> states lead to a lack of symmetry of the RSET under parity, even though this is a symmetry of the physical system. We derive the correct symmetric expressions and present a detailed analysis of the resulting RSETs. |
1611.03418 | Adam Lewis | Adam G.M. Lewis, Aaron Zimmerman, Harald P. Pfeiffer | Fundamental frequencies and resonances from eccentric and precessing
binary black hole inspirals | 40 pages, 15 figures Revised in response to reviewer comments. Figure
12, which previously had been incorrectly computed, is now correct | null | 10.1088/1361-6382/aa66f4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary black holes which are both eccentric and undergo precession remain
unexplored in numerical simulations. We present simulations of such systems
which cover about 50 orbits at comparatively high mass ratios 5 and 7. The
configurations correspond to the generic motion of a nonspinning body in a Kerr
spacetime, and are chosen to study the transition from finite mass-ratio
inspirals to point particle motion in Kerr. We develop techniques to extract
analogs of the three fundamental frequencies of Kerr geodesics, compare our
frequencies to those of Kerr, and show that the differences are consistent with
self-force corrections entering at first order in mass ratio. This analysis
also locates orbital resonances where the ratios of our frequencies take
rational values. At the considered mass ratios, the binaries pass through
resonances in one to two resonant cycles, and we find no discernible effects on
the orbital evolution. We also compute the decay of eccentricity during the
inspiral and find good agreement with the leading order post-Newtonian
prediction.
| [
{
"created": "Thu, 10 Nov 2016 17:41:55 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Feb 2017 16:12:48 GMT",
"version": "v2"
}
] | 2017-05-31 | [
[
"Lewis",
"Adam G. M.",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] | Binary black holes which are both eccentric and undergo precession remain unexplored in numerical simulations. We present simulations of such systems which cover about 50 orbits at comparatively high mass ratios 5 and 7. The configurations correspond to the generic motion of a nonspinning body in a Kerr spacetime, and are chosen to study the transition from finite mass-ratio inspirals to point particle motion in Kerr. We develop techniques to extract analogs of the three fundamental frequencies of Kerr geodesics, compare our frequencies to those of Kerr, and show that the differences are consistent with self-force corrections entering at first order in mass ratio. This analysis also locates orbital resonances where the ratios of our frequencies take rational values. At the considered mass ratios, the binaries pass through resonances in one to two resonant cycles, and we find no discernible effects on the orbital evolution. We also compute the decay of eccentricity during the inspiral and find good agreement with the leading order post-Newtonian prediction. |
1607.05986 | Sumanta Chakraborty | Sumanta Chakraborty | Boundary terms of the Einstein-Hilbert action | 26 pages, no figures; Dedicated to Prof. Padmanabhan on the occasion
of his sixtieth birthday; Published in the book "Gravity and the Quantum",
Eds. Jasjeet Singh Bagla and Sunu Engineer (Springer, 2017) | Fundam.Theor.Phys. 187 (2017) 43-59 | 10.1007/978-3-319-51700-1_5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein-Hilbert action for general relativity is not well posed in terms
of the metric $g_{ab}$ as a dynamical variable. There have been many proposals
to obtain an well posed action principle for general relativity, e.g., addition
of the Gibbons-Hawking-York boundary term to the Einstein-Hilbert action. These
boundary terms are dependent on what one fixes on the boundary and in
particular on spacetime dimensions as well. Following recent works of
Padmanabhan we will introduce two new variables to describe general relativity
and the action principle with these new dynamical variables will turn out to be
well posed. Then we will connect these dynamical variables and boundary term
obtained thereof to existing literature and shall comment on a few properties
of Einstein-Hilbert action which might have been unnoticed earlier in the
literature. Before concluding with future prospects and discussions, we will
perform a general analysis of the boundary term of Einstein-Hilbert action for
null surfaces as well.
| [
{
"created": "Tue, 19 Jul 2016 03:36:45 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Mar 2017 07:17:33 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Mar 2017 04:17:21 GMT",
"version": "v3"
}
] | 2017-03-16 | [
[
"Chakraborty",
"Sumanta",
""
]
] | The Einstein-Hilbert action for general relativity is not well posed in terms of the metric $g_{ab}$ as a dynamical variable. There have been many proposals to obtain an well posed action principle for general relativity, e.g., addition of the Gibbons-Hawking-York boundary term to the Einstein-Hilbert action. These boundary terms are dependent on what one fixes on the boundary and in particular on spacetime dimensions as well. Following recent works of Padmanabhan we will introduce two new variables to describe general relativity and the action principle with these new dynamical variables will turn out to be well posed. Then we will connect these dynamical variables and boundary term obtained thereof to existing literature and shall comment on a few properties of Einstein-Hilbert action which might have been unnoticed earlier in the literature. Before concluding with future prospects and discussions, we will perform a general analysis of the boundary term of Einstein-Hilbert action for null surfaces as well. |
0906.0093 | Theocharis Apostolatos | Theocharis A. Apostolatos, Georgios Lukes-Gerakopoulos, George
Contopoulos | How to observe a non-Kerr spacetime | 4 pages, 2 figures | Phys.Rev.Lett.103:111101,2009 | 10.1103/PhysRevLett.103.111101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a generic criterion which can be used in gravitational-wave data
analysis to distinguish an extreme-mass-ratio inspiral into a Kerr background
spacetime from one into a non-Kerr background spacetime. The criterion exploits
the fact that when an integrable system, such as the system that describes
geodesic orbits in a Kerr spacetime, is perturbed, the tori in phase space
which initially corresponded to resonances disintegrate so as to form the so
called Birkhoff chains on a surface of section, according to the
Poincar\'{e}-Birkhoff theorem. The KAM curves of these islands in such a chain
share the same ratio of frequencies, even though the frequencies themselves
vary from one KAM curve to another inside an island. On the other hand, the KAM
curves, which do not lie in a Birkhoff chain, do not share this characteristic
property. Such a temporal constancy of the ratio of frequencies during the
evolution of the gravitational-wave signal will signal a non-Kerr spacetime
which could then be further explored.
| [
{
"created": "Sat, 30 May 2009 16:59:41 GMT",
"version": "v1"
}
] | 2009-11-06 | [
[
"Apostolatos",
"Theocharis A.",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Contopoulos",
"George",
""
]
] | We present a generic criterion which can be used in gravitational-wave data analysis to distinguish an extreme-mass-ratio inspiral into a Kerr background spacetime from one into a non-Kerr background spacetime. The criterion exploits the fact that when an integrable system, such as the system that describes geodesic orbits in a Kerr spacetime, is perturbed, the tori in phase space which initially corresponded to resonances disintegrate so as to form the so called Birkhoff chains on a surface of section, according to the Poincar\'{e}-Birkhoff theorem. The KAM curves of these islands in such a chain share the same ratio of frequencies, even though the frequencies themselves vary from one KAM curve to another inside an island. On the other hand, the KAM curves, which do not lie in a Birkhoff chain, do not share this characteristic property. Such a temporal constancy of the ratio of frequencies during the evolution of the gravitational-wave signal will signal a non-Kerr spacetime which could then be further explored. |
0712.1413 | Rakesh Tibrewala | Rakesh Tibrewala, Sashideep Gutti, T.P. Singh, Cenalo Vaz | Classical and Quantum Gravitational Collapse in d-dim AdS Spacetime I.
Classical Solutions | 19 pages, sections on surface gravity removed, section on self
similar solution expanded, appendix removed, references added. To appear in
Phys. Rev.D | Phys.Rev.D77:064012,2008 | 10.1103/PhysRevD.77.064012 | null | gr-qc astro-ph hep-th | null | We study the collapse of a spherically symmetric dust distribution in
$d$-dimensional AdS spacetime. We investigate the role of dimensionality, and
the presence of a negative cosmological constant, in determining the formation
of trapped surfaces and the end state of gravitational collapse. We obtain the
self-similar solution for the case of zero cosmological constant, and show that
one cannot construct a self-similar solution when a cosmological constant is
included.
| [
{
"created": "Mon, 10 Dec 2007 09:25:15 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Feb 2008 09:53:47 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Tibrewala",
"Rakesh",
""
],
[
"Gutti",
"Sashideep",
""
],
[
"Singh",
"T. P.",
""
],
[
"Vaz",
"Cenalo",
""
]
] | We study the collapse of a spherically symmetric dust distribution in $d$-dimensional AdS spacetime. We investigate the role of dimensionality, and the presence of a negative cosmological constant, in determining the formation of trapped surfaces and the end state of gravitational collapse. We obtain the self-similar solution for the case of zero cosmological constant, and show that one cannot construct a self-similar solution when a cosmological constant is included. |
1812.11603 | Borja Reina | Brien C. Nolan, Borja Reina, Kepa Sousa | First order perturbations of hypersurfaces of arbitrary causal character | 31 pages + appendices, 2 figures | null | 10.1088/1361-6382/ab300b | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the problem of first order perturbations of a general
hypersurface, i.e. with arbitrary causal character at each point. We extend the
framework by Mars (Class. Quantum Grav. 22 3325 (2005)) where this problem was
studied to second order for everywhere timelike or spacelike hypersurfaces, and
we adapt it to cover the general case. We apply the formalism to the matching
of spacetimes across a general hypersurface to first order in perturbation
theory.
| [
{
"created": "Sun, 30 Dec 2018 20:19:41 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Nolan",
"Brien C.",
""
],
[
"Reina",
"Borja",
""
],
[
"Sousa",
"Kepa",
""
]
] | In this work we study the problem of first order perturbations of a general hypersurface, i.e. with arbitrary causal character at each point. We extend the framework by Mars (Class. Quantum Grav. 22 3325 (2005)) where this problem was studied to second order for everywhere timelike or spacelike hypersurfaces, and we adapt it to cover the general case. We apply the formalism to the matching of spacetimes across a general hypersurface to first order in perturbation theory. |
2407.21076 | Saulo Carneiro | I. P. R. Baranov, H. A. Borges, F. C. Sobrinho and S. Carneiro | Non-singular naked solutions in quantum spacetime | 10 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Polymer models have been used to describe non-singular quantum black holes,
where the classical singularity is replaced by a transition from a black hole
to a white hole. In a previous letter, in the context of a uni-parametric model
with asymptotic flat exterior metric, we fixed the radius of the transition
surface through the identification of its area with the area gap of Loop
Quantum Gravity. This revealed a dependence of the polymerisation parameter on
the black hole mass, where the former increases as the latter decreases, and it
also enabled the extension of the model to Planck-scale black holes. We have
identified the existence of limiting states with masses $m \geq \sqrt{2}/4$ and
zero surface gravity, showing that Hawking evaporation asymptotically leads to
remnant black holes of Planck size. In the present paper we consider solutions
with $m < \sqrt{2}/4$, observing again the presence of a minimal radius, but
without formation of horizons. Diversely from the previous mass range, only
charged solutions are allowed in this case.
| [
{
"created": "Mon, 29 Jul 2024 19:09:30 GMT",
"version": "v1"
}
] | 2024-08-01 | [
[
"Baranov",
"I. P. R.",
""
],
[
"Borges",
"H. A.",
""
],
[
"Sobrinho",
"F. C.",
""
],
[
"Carneiro",
"S.",
""
]
] | Polymer models have been used to describe non-singular quantum black holes, where the classical singularity is replaced by a transition from a black hole to a white hole. In a previous letter, in the context of a uni-parametric model with asymptotic flat exterior metric, we fixed the radius of the transition surface through the identification of its area with the area gap of Loop Quantum Gravity. This revealed a dependence of the polymerisation parameter on the black hole mass, where the former increases as the latter decreases, and it also enabled the extension of the model to Planck-scale black holes. We have identified the existence of limiting states with masses $m \geq \sqrt{2}/4$ and zero surface gravity, showing that Hawking evaporation asymptotically leads to remnant black holes of Planck size. In the present paper we consider solutions with $m < \sqrt{2}/4$, observing again the presence of a minimal radius, but without formation of horizons. Diversely from the previous mass range, only charged solutions are allowed in this case. |
2009.06311 | Klaus Liegener Dr | Wojciech Kami\'nski, Klaus Liegener | Symmetry restriction and its application to gravity | 69 pages | Class. Quantum Grav. 38, 065013 (2021) | 10.1088/1361-6382/abdf29 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Hamiltonian formulation, it is not a priori clear whether a symmetric
configuration will keep its symmetry during evolution. In this paper, we give
precise requirements of when this is the case and propose a symmetry
restriction to the phase space of the symmetric variables. This can often ease
computation, especially when transcending from the infinite dimensional phase
space of a field theory to a possibly finite dimensional subspace. We will
demonstrate this in the case of gravity. A prominent example is the restriction
of full Hamiltonian general relativity to the cosmological configurations of
Robertson-Walker type. We will demonstrate our procedure in this setting and
extend it to examples which appear useful in certain approaches to quantum
gravity.
| [
{
"created": "Mon, 14 Sep 2020 10:24:19 GMT",
"version": "v1"
}
] | 2021-11-01 | [
[
"Kamiński",
"Wojciech",
""
],
[
"Liegener",
"Klaus",
""
]
] | In the Hamiltonian formulation, it is not a priori clear whether a symmetric configuration will keep its symmetry during evolution. In this paper, we give precise requirements of when this is the case and propose a symmetry restriction to the phase space of the symmetric variables. This can often ease computation, especially when transcending from the infinite dimensional phase space of a field theory to a possibly finite dimensional subspace. We will demonstrate this in the case of gravity. A prominent example is the restriction of full Hamiltonian general relativity to the cosmological configurations of Robertson-Walker type. We will demonstrate our procedure in this setting and extend it to examples which appear useful in certain approaches to quantum gravity. |
1705.00889 | Stefano Lucat | Stefano Lucat and Tomislav Prokopec | Observing Geometrical Torsion | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical (propagating) torsion can be observed by using conventional
gravitational wave detectors such as LIGO, Virgo, LISA and bar detectors. We
discuss specific signatures of different types of torsion, in particular those
of vector and mixed symmetric torsion (skew symmetric torsion cannot be
detected in this way). These signatures are specific to torsion and therefore
they can be unambiguously distinguished from those of gravitational waves.
| [
{
"created": "Tue, 2 May 2017 10:26:00 GMT",
"version": "v1"
}
] | 2017-05-03 | [
[
"Lucat",
"Stefano",
""
],
[
"Prokopec",
"Tomislav",
""
]
] | Dynamical (propagating) torsion can be observed by using conventional gravitational wave detectors such as LIGO, Virgo, LISA and bar detectors. We discuss specific signatures of different types of torsion, in particular those of vector and mixed symmetric torsion (skew symmetric torsion cannot be detected in this way). These signatures are specific to torsion and therefore they can be unambiguously distinguished from those of gravitational waves. |
1406.1705 | Andrew Makarenko | Andrey N. Makarenko | Unification of the inflation with late-time acceleration in
Born-Infeld-$f(R)$ gravity | null | Astrophys.Space Sci. 352 (2014) 921-924 | 10.1007/s10509-014-1955-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study accelerating dynamics from Born-Infeld-$f(R)$ gravity in a
simplified conformal approach without matter. In our work (A.N. Makarenko, S.
Odintsov, G.J. Olmo, Phys.Lett. B734 (2014) 36, [arXiv:1403.2850]) it was
derived eventually any Dark Energy cosmology from above theory. In this Letter
we apply the technique of (arXiv:1403.2850) to show that Born-Infeld-$f(R)$
gravity may describe very realistic universe admitting the unification of
early-time inflation with late-time acceleration. Specifically, the evolution
with periodic as well as non-periodic behavior is considered with possibility
to cross the phantom-divide at early or late-times.
| [
{
"created": "Fri, 6 Jun 2014 15:23:25 GMT",
"version": "v1"
}
] | 2014-07-22 | [
[
"Makarenko",
"Andrey N.",
""
]
] | We study accelerating dynamics from Born-Infeld-$f(R)$ gravity in a simplified conformal approach without matter. In our work (A.N. Makarenko, S. Odintsov, G.J. Olmo, Phys.Lett. B734 (2014) 36, [arXiv:1403.2850]) it was derived eventually any Dark Energy cosmology from above theory. In this Letter we apply the technique of (arXiv:1403.2850) to show that Born-Infeld-$f(R)$ gravity may describe very realistic universe admitting the unification of early-time inflation with late-time acceleration. Specifically, the evolution with periodic as well as non-periodic behavior is considered with possibility to cross the phantom-divide at early or late-times. |
1802.06596 | Michael Kalisch | Michael Kalisch | Numerical construction and critical behavior of Kaluza-Klein black holes | This PhD thesis is based on arXiv:1607.03099 and arXiv:1706.02323 but
it provides a wider introduction and a more detailed discussion of the
pseudo-spectral method used in this work | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The idea of extra dimensions provides a promising approach to overcome
various problems in modern physics. This includes theoretical as well as
phenomenological aspects, such as the unification of the fundamental
interactions or the hierarchy problem. Based on the seminal works by Kaluza and
Klein that were published nearly 100 years ago, we denote theories with at
least one compact periodic dimension as Kaluza-Klein theories. From a
gravitational point of view the question arises, what are the fundamental
solutions to Einstein's field equations of general relativity under these
assumptions. In particular, in this work we are concerned with black hole
solutions in Kaluza-Klein theory. Considering only the static case without
electric charge, it turns out that there is a much richer phase space than in
the usual four-dimensional theory, where only the Schwarzschild solution
exists. There are at least two types of solutions with a completely different
horizon topology: localized black holes with an ordinary spherical horizon and
black strings with a horizon that wraps the compact dimension. Several
arguments favor the conjecture that the solution branches of both types are
connected via a singular topology changing solution that is controlled by the
so-called double-cone metric. We study the regime close to this singular
transit solution in five and six spacetime dimensions with the help of a highly
accurate numerical scheme that we describe in detail. Consequently, for the
first time we are able to show that in this regime the black objects exhibit a
critical behavior, indicating that physical quantities are governed by
universal critical exponents. Such exponents were already derived from the
double-cone metric. We show that our data confirms these values extremely well.
This provides compelling evidence in favor of the double-cone metric as the
local model of the transit solution.
| [
{
"created": "Mon, 19 Feb 2018 11:59:17 GMT",
"version": "v1"
}
] | 2018-02-20 | [
[
"Kalisch",
"Michael",
""
]
] | The idea of extra dimensions provides a promising approach to overcome various problems in modern physics. This includes theoretical as well as phenomenological aspects, such as the unification of the fundamental interactions or the hierarchy problem. Based on the seminal works by Kaluza and Klein that were published nearly 100 years ago, we denote theories with at least one compact periodic dimension as Kaluza-Klein theories. From a gravitational point of view the question arises, what are the fundamental solutions to Einstein's field equations of general relativity under these assumptions. In particular, in this work we are concerned with black hole solutions in Kaluza-Klein theory. Considering only the static case without electric charge, it turns out that there is a much richer phase space than in the usual four-dimensional theory, where only the Schwarzschild solution exists. There are at least two types of solutions with a completely different horizon topology: localized black holes with an ordinary spherical horizon and black strings with a horizon that wraps the compact dimension. Several arguments favor the conjecture that the solution branches of both types are connected via a singular topology changing solution that is controlled by the so-called double-cone metric. We study the regime close to this singular transit solution in five and six spacetime dimensions with the help of a highly accurate numerical scheme that we describe in detail. Consequently, for the first time we are able to show that in this regime the black objects exhibit a critical behavior, indicating that physical quantities are governed by universal critical exponents. Such exponents were already derived from the double-cone metric. We show that our data confirms these values extremely well. This provides compelling evidence in favor of the double-cone metric as the local model of the transit solution. |
2111.12693 | Albert Escriv\`a | Albert Escriv\`a | PBH formation from spherically symmetric hydrodynamical perturbations: a
review | Invited review article. Published in the "Universe" journal on the
Special Issue: Primordial Black Holes from Inflation. Feature Paper. 60 pages
and 24 figures. v3: matches the published version | Universe 2022, 8(2), 66 | 10.3390/universe8020066 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Primordial black holes, which could have been formed in the very early
Universe due to the collapse of large curvature fluctuations, are nowadays one
of the most attractive and fascinating research areas in cosmology for their
possible theoretical and observational implications. This review article
presents the current results and developments on the conditions for primordial
black hole formation from the collapse of curvature fluctuations in spherical
symmetry on a Friedman-Lemaitre-Robertson-Walker background and its numerical
simulation. We review the appropriate formalism for the conditions of
primordial black hole formation, and we detail a numerical implementation. We
then focus on different results regarding the threshold and the black hole mass
using different sets of curvature fluctuations. Finally, we present the current
state of analytical estimations for the primordial black hole formation
threshold, contrasted with numerical simulations.
| [
{
"created": "Wed, 24 Nov 2021 18:42:16 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jan 2022 17:23:34 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Jan 2022 18:16:28 GMT",
"version": "v3"
}
] | 2022-01-27 | [
[
"Escrivà",
"Albert",
""
]
] | Primordial black holes, which could have been formed in the very early Universe due to the collapse of large curvature fluctuations, are nowadays one of the most attractive and fascinating research areas in cosmology for their possible theoretical and observational implications. This review article presents the current results and developments on the conditions for primordial black hole formation from the collapse of curvature fluctuations in spherical symmetry on a Friedman-Lemaitre-Robertson-Walker background and its numerical simulation. We review the appropriate formalism for the conditions of primordial black hole formation, and we detail a numerical implementation. We then focus on different results regarding the threshold and the black hole mass using different sets of curvature fluctuations. Finally, we present the current state of analytical estimations for the primordial black hole formation threshold, contrasted with numerical simulations. |
gr-qc/9605021 | Franz Embacher | Franz Embacher | Quantum cosmology in the energy representation | 38 pages, LaTeX (no figures), referenced updated | Nucl.Phys. B479 (1996) 461-494 | 10.1016/0550-3213(96)00444-0 | UWThPh-1996-32 | gr-qc | null | The Hawking minisuperspace model (closed FRW geometry with a homogeneous
massive scalar field) provides a fairly non-trivial testing ground for
fundamental problems in quantum cosmology. We provide evidence that the
Wheeler-DeWitt equation admits a basis of solutions that is distinguished by
analyticity properities in a large scale factor expansion. As a consequence,
the space of solutions decomposes in a preferred way into two Hilbert spaces
with positive and negative definite scalar product, respectively. These results
may be viewed as a hint for a deeper significance of analyticity. If a similar
structure exists in full (non-minisuperspace) models as well, severe
implications on the foundations of quantum cosmology are to be expected.
Semiclassically, the elements of the preferred basis describe contracting and
expanding universes with a prescribed value of the matter (scalar field)
energy. Half of the basis elements have previously been constructed by Hawking
and Page in a wormhole context, and they appear in a new light here. The
technical tools to arrive at these conclusions are transformations of the wave
function into several alternative representations that are based on the
harmonic oscillator form of the matter energy operator, and that are called
oscillator, energy and Fock representation. The framework defined by these may
be of some help in analyzing the Wheeler-DeWitt equation for other purposes as
well.
| [
{
"created": "Thu, 9 May 1996 17:46:16 GMT",
"version": "v1"
},
{
"created": "Fri, 10 May 1996 12:29:14 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Embacher",
"Franz",
""
]
] | The Hawking minisuperspace model (closed FRW geometry with a homogeneous massive scalar field) provides a fairly non-trivial testing ground for fundamental problems in quantum cosmology. We provide evidence that the Wheeler-DeWitt equation admits a basis of solutions that is distinguished by analyticity properities in a large scale factor expansion. As a consequence, the space of solutions decomposes in a preferred way into two Hilbert spaces with positive and negative definite scalar product, respectively. These results may be viewed as a hint for a deeper significance of analyticity. If a similar structure exists in full (non-minisuperspace) models as well, severe implications on the foundations of quantum cosmology are to be expected. Semiclassically, the elements of the preferred basis describe contracting and expanding universes with a prescribed value of the matter (scalar field) energy. Half of the basis elements have previously been constructed by Hawking and Page in a wormhole context, and they appear in a new light here. The technical tools to arrive at these conclusions are transformations of the wave function into several alternative representations that are based on the harmonic oscillator form of the matter energy operator, and that are called oscillator, energy and Fock representation. The framework defined by these may be of some help in analyzing the Wheeler-DeWitt equation for other purposes as well. |
2206.11874 | Zichang Huang | Zichang Huang, Shan Huang, Yidun Wan | A saddle-point finder and its application to the spin foam model | 27 pages, 4 figures | null | 10.1103/PhysRevD.107.046011 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a saddle-point finder that can find the complex saddle points
for any analytically continued action. We showcase our saddle-point finder by
two examples in the EPRL spin foam model: the single vertex case and the case
of triangulation $\Delta_3$. In both cases, the complex saddle points are
found, and each saddle point's contribution to the partition function is
estimated. We also discuss the geometrical interpretation of each saddle point.
| [
{
"created": "Thu, 23 Jun 2022 17:26:44 GMT",
"version": "v1"
}
] | 2023-03-08 | [
[
"Huang",
"Zichang",
""
],
[
"Huang",
"Shan",
""
],
[
"Wan",
"Yidun",
""
]
] | We introduce a saddle-point finder that can find the complex saddle points for any analytically continued action. We showcase our saddle-point finder by two examples in the EPRL spin foam model: the single vertex case and the case of triangulation $\Delta_3$. In both cases, the complex saddle points are found, and each saddle point's contribution to the partition function is estimated. We also discuss the geometrical interpretation of each saddle point. |
1110.1191 | Amare Abebe Mr | Amare Abebe, Mohamed Abdelwahab, Alvaro de la Cruz-Dombriz, Peter K.
S. Dunsby | Covariant gauge-invariant perturbations in multifluid f(R) gravity | 32 pages, 3 figures, published version | Class. Quantum Grav. 29 (2012) 135011 | 10.1088/0264-9381/29/13/135011 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of scalar cosmological perturbations in the (1+3)-
covariant gauge-invariant formalism for generic $f(R)$ theories of gravity.
Extending previous works, we give a complete set of equations describing the
evolution of matter and curvature fluctuations for a multi-fluid cosmological
medium. We then specialize to a radiation-dust fluid described by barotropic
equations of state and solve the perturbation equations around a background
solution of $R^{n}$ gravity. In particular we study exact solutions for scales
much smaller and much larger than the Hubble radius and show that $n>2/3$ in
order to have a growth rate compatible with the M\'esz\'aros effect.
| [
{
"created": "Thu, 6 Oct 2011 09:03:43 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Oct 2011 11:44:45 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Jun 2012 11:43:28 GMT",
"version": "v3"
}
] | 2012-06-08 | [
[
"Abebe",
"Amare",
""
],
[
"Abdelwahab",
"Mohamed",
""
],
[
"de la Cruz-Dombriz",
"Alvaro",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | We study the evolution of scalar cosmological perturbations in the (1+3)- covariant gauge-invariant formalism for generic $f(R)$ theories of gravity. Extending previous works, we give a complete set of equations describing the evolution of matter and curvature fluctuations for a multi-fluid cosmological medium. We then specialize to a radiation-dust fluid described by barotropic equations of state and solve the perturbation equations around a background solution of $R^{n}$ gravity. In particular we study exact solutions for scales much smaller and much larger than the Hubble radius and show that $n>2/3$ in order to have a growth rate compatible with the M\'esz\'aros effect. |
1903.07779 | Alexander Saffer | Alexander Saffer, Hector O. Silva, and Nico Yunes | The exterior spacetime of relativistic stars in scalar-Gauss-Bonnet
gravity | 13 pages, 9 figures. Updated to published version. Corrected typos | Phys. Rev. D 100, 044030 (2019) | 10.1103/PhysRevD.100.044030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spacetime around compact objects is an excellent place to study gravity
in the strong, nonlinear, dynamical regime where solar system tests cannot
account for the effects of large curvature. Understanding the dynamics of this
spacetime is important for testing theories of gravity and probing a regime
which has not yet been studied with observations. In this paper, we construct
an analytical solution for the exterior spacetime of a neutron star in
scalar-Gauss-Bonnet gravity that is independent of the equation of state
chosen. The aim is to provide a metric that can be used to probe the
strong-field regime near a neutron star and create predictions that can be
compared with future observations to place possible constraints on the theory.
In addition to constructing the metric, we examine a number of physical systems
in order to see what deviations exist between our spacetime and that of general
relativity. We find these deviations to be small and of higher post-Newtonian
order than previous results using black hole solutions. The metric derived here
can be used to further the study of scalar-Gauss-Bonnet gravity in the strong
field, and allow for constraints on corrections to general relativity with
future observations.
| [
{
"created": "Tue, 19 Mar 2019 00:39:49 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 2019 20:28:54 GMT",
"version": "v2"
}
] | 2019-09-02 | [
[
"Saffer",
"Alexander",
""
],
[
"Silva",
"Hector O.",
""
],
[
"Yunes",
"Nico",
""
]
] | The spacetime around compact objects is an excellent place to study gravity in the strong, nonlinear, dynamical regime where solar system tests cannot account for the effects of large curvature. Understanding the dynamics of this spacetime is important for testing theories of gravity and probing a regime which has not yet been studied with observations. In this paper, we construct an analytical solution for the exterior spacetime of a neutron star in scalar-Gauss-Bonnet gravity that is independent of the equation of state chosen. The aim is to provide a metric that can be used to probe the strong-field regime near a neutron star and create predictions that can be compared with future observations to place possible constraints on the theory. In addition to constructing the metric, we examine a number of physical systems in order to see what deviations exist between our spacetime and that of general relativity. We find these deviations to be small and of higher post-Newtonian order than previous results using black hole solutions. The metric derived here can be used to further the study of scalar-Gauss-Bonnet gravity in the strong field, and allow for constraints on corrections to general relativity with future observations. |
gr-qc/0306096 | Neil J. Cornish | Neil J. Cornish and Ronald W. Hellings | The Effects of Orbital Motion on LISA Time Delay Interferometry | 12 pages, 2 figures | Class.Quant.Grav.20:4851-4860,2003 | 10.1088/0264-9381/20/22/009 | null | gr-qc | null | In an effort to eliminate laser phase noise in laser interferometer
spaceborne gravitational wave detectors, several combinations of signals have
been found that allow the laser noise to be canceled out while gravitational
wave signals remain. This process is called time delay interferometry (TDI). In
the papers that defined the TDI variables, their performance was evaluated in
the limit that the gravitational wave detector is fixed in space. However, the
performance depends on certain symmetries in the armlengths that are available
if the detector is fixed in space, but that will be broken in the actual
rotating and flexing configuration produced by the LISA orbits. In this paper
we investigate the performance of these TDI variables for the real LISA orbits.
First, addressing the effects of rotation, we verify Daniel Shaddock's result
that the Sagnac variables will not cancel out the laser phase noise, and we
also find the same result for the symmetric Sagnac variable. The loss of the
latter variable would be particularly unfortunate since this variable also
cancels out gravitational wave signal, allowing instrument noise in the
detector to be isolated and measured. Fortunately, we have found a set of more
complicated TDI variables, which we call Delta-Sagnac variables, one of which
accomplishes the same goal as the symmetric Sagnac variable to good accuracy.
Finally, however, as we investigate the effects of the flexing of the detector
arms due to non-circular orbital motion, we show that all variables, including
the interferometer variables, which survive the rotation-induced loss of
direction symmetry, will not completely cancel laser phase noise when the
armlengths are changing with time. This unavoidable problem will place a
stringent requirement on laser stability of 5 Hz per root Hz.
| [
{
"created": "Fri, 20 Jun 2003 19:54:14 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Jun 2003 00:59:50 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Cornish",
"Neil J.",
""
],
[
"Hellings",
"Ronald W.",
""
]
] | In an effort to eliminate laser phase noise in laser interferometer spaceborne gravitational wave detectors, several combinations of signals have been found that allow the laser noise to be canceled out while gravitational wave signals remain. This process is called time delay interferometry (TDI). In the papers that defined the TDI variables, their performance was evaluated in the limit that the gravitational wave detector is fixed in space. However, the performance depends on certain symmetries in the armlengths that are available if the detector is fixed in space, but that will be broken in the actual rotating and flexing configuration produced by the LISA orbits. In this paper we investigate the performance of these TDI variables for the real LISA orbits. First, addressing the effects of rotation, we verify Daniel Shaddock's result that the Sagnac variables will not cancel out the laser phase noise, and we also find the same result for the symmetric Sagnac variable. The loss of the latter variable would be particularly unfortunate since this variable also cancels out gravitational wave signal, allowing instrument noise in the detector to be isolated and measured. Fortunately, we have found a set of more complicated TDI variables, which we call Delta-Sagnac variables, one of which accomplishes the same goal as the symmetric Sagnac variable to good accuracy. Finally, however, as we investigate the effects of the flexing of the detector arms due to non-circular orbital motion, we show that all variables, including the interferometer variables, which survive the rotation-induced loss of direction symmetry, will not completely cancel laser phase noise when the armlengths are changing with time. This unavoidable problem will place a stringent requirement on laser stability of 5 Hz per root Hz. |
gr-qc/0012063 | Graham Shore | G.M. Shore | Accelerating Photons with Gravitational Radiation | 14 pages, TeX, uses harvmac | Nucl.Phys. B605 (2001) 455-466 | 10.1016/S0550-3213(01)00137-7 | CERN-TH/2000-285, SWAT/266, UGVA-DPT-00-9-1088 | gr-qc | null | The nature of superluminal photon propagation in the gravitational field
describing radiation from a time-dependent, isolated source (the Bondi-Sachs
metric) is considered in an effective theory which includes interactions which
violate the strong equivalence principle. Such interactions are, for example,
generated by vacuum polarisation in conventional QED in curved spacetime. The
relation of the resulting light-cone modifications to the Peeling Theorem for
the Bondi-Sachs spacetime is explained.
| [
{
"created": "Sun, 17 Dec 2000 13:02:52 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Shore",
"G. M.",
""
]
] | The nature of superluminal photon propagation in the gravitational field describing radiation from a time-dependent, isolated source (the Bondi-Sachs metric) is considered in an effective theory which includes interactions which violate the strong equivalence principle. Such interactions are, for example, generated by vacuum polarisation in conventional QED in curved spacetime. The relation of the resulting light-cone modifications to the Peeling Theorem for the Bondi-Sachs spacetime is explained. |
gr-qc/0404084 | Miguel Sanchez | Antonio N. Bernal and Miguel S\'anchez | Smooth globally hyperbolic splittings and temporal functions | 11 pages, Contribution to Proc. II Int. Meeting on Lorentzian
Geometry, Murcia (Spain), November 12-14, 2003 | null | null | null | gr-qc math.DG | null | Geroch's theorem about the splitting of globally hyperbolic spacetimes is a
central result in global Lorentzian Geometry. Nevertheless, this result was
obtained at a topological level, and the possibility to obtain a metric (or, at
least, smooth) version has been controversial since its publication in 1970. In
fact, this problem has remained open until a definitive proof, recently
provided by the authors. Our purpose is to summarize the history of the
problem, explain the smooth and metric splitting results (including
smoothability of time functions in stably causal spacetimes), and sketch the
ideas of the solution.
| [
{
"created": "Tue, 20 Apr 2004 09:48:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bernal",
"Antonio N.",
""
],
[
"Sánchez",
"Miguel",
""
]
] | Geroch's theorem about the splitting of globally hyperbolic spacetimes is a central result in global Lorentzian Geometry. Nevertheless, this result was obtained at a topological level, and the possibility to obtain a metric (or, at least, smooth) version has been controversial since its publication in 1970. In fact, this problem has remained open until a definitive proof, recently provided by the authors. Our purpose is to summarize the history of the problem, explain the smooth and metric splitting results (including smoothability of time functions in stably causal spacetimes), and sketch the ideas of the solution. |
2207.13822 | Bogeun Gwak | Bogeun Gwak | Weak Cosmic Censorship Conjecture in Myers-Perry Black Hole with
Separability | 17 pages, 3 figures | JCAP 10 (2022) 077 | 10.1088/1475-7516/2022/10/077 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the weak cosmic censorship conjecture in Myers-Perry black
holes with arbitrary rotations in general dimensions based on the scattering of
a massless scalar field. From the fluxes of the scalar field flowing into the
black hole, the changes in mass and angular momenta of the black hole are
obtained. However, the extremal and near-extremal black holes with the
aforementioned changes are still black holes in the final state. Hence, the
conjecture is valid for our investigation. Furthermore, we analyze the changes
in the black hole from a thermodynamic perspective to highlight that the laws
of thermodynamics support the conjecture.
| [
{
"created": "Wed, 27 Jul 2022 23:08:14 GMT",
"version": "v1"
}
] | 2022-10-28 | [
[
"Gwak",
"Bogeun",
""
]
] | We investigate the weak cosmic censorship conjecture in Myers-Perry black holes with arbitrary rotations in general dimensions based on the scattering of a massless scalar field. From the fluxes of the scalar field flowing into the black hole, the changes in mass and angular momenta of the black hole are obtained. However, the extremal and near-extremal black holes with the aforementioned changes are still black holes in the final state. Hence, the conjecture is valid for our investigation. Furthermore, we analyze the changes in the black hole from a thermodynamic perspective to highlight that the laws of thermodynamics support the conjecture. |
gr-qc/9602017 | null | Roy Maartens and Conrad Mellin | Anisotropic universes with conformal motion | 8 pages, latex | Class. Quant. Grav. 13 (1996) 1571 | 10.1088/0264-9381/13/6/021 | RCG 96/4 | gr-qc | null | By imposing natural geometrical and kinematical conditions on a conformal
Killing vector in Bianchi I spacetime, we show that a class of axisymmetric
metrics admits a conformal motion. This class contains new exact solutions of
Einstein's equations, including anisotropic radiation universes that isotropise
at late times.
| [
{
"created": "Fri, 9 Feb 1996 18:11:17 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Maartens",
"Roy",
""
],
[
"Mellin",
"Conrad",
""
]
] | By imposing natural geometrical and kinematical conditions on a conformal Killing vector in Bianchi I spacetime, we show that a class of axisymmetric metrics admits a conformal motion. This class contains new exact solutions of Einstein's equations, including anisotropic radiation universes that isotropise at late times. |
0810.4786 | David Brizuela | David Brizuela, Jose M. Martin-Garcia | Hamiltonian theory for the axial perturbations of a dynamical spherical
background | 12 pages, accepted by Classical and Quantum Gravity | Class.Quant.Grav.26:015003,2009 | 10.1088/0264-9381/26/1/015003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop the Hamiltonian theory of axial perturbations around a general
time-dependent spherical background spacetime. Using the fact that the
linearized constraints are gauge generators, we isolate the physical and
unconstrained axial gravitational wave in a Hamiltonian pair of variables.
Then, switching to a more geometrical description of the system, we construct
the only scalar combination of them. We obtain the well-known Gerlach and
Sengupta scalar for axial perturbations, with no known equivalent for polar
perturbations. The strategy suggested and tested here will be applied to the
polar case in a separate article.
| [
{
"created": "Mon, 27 Oct 2008 11:10:35 GMT",
"version": "v1"
}
] | 2009-02-09 | [
[
"Brizuela",
"David",
""
],
[
"Martin-Garcia",
"Jose M.",
""
]
] | We develop the Hamiltonian theory of axial perturbations around a general time-dependent spherical background spacetime. Using the fact that the linearized constraints are gauge generators, we isolate the physical and unconstrained axial gravitational wave in a Hamiltonian pair of variables. Then, switching to a more geometrical description of the system, we construct the only scalar combination of them. We obtain the well-known Gerlach and Sengupta scalar for axial perturbations, with no known equivalent for polar perturbations. The strategy suggested and tested here will be applied to the polar case in a separate article. |
1005.2327 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | Black hole entropy in scalar-tensor and f(R) gravity: an overview | 24 pages, latex, to appear in "Entropy in Quantum Gravity", special
issue of Entropy, R. Garattini editor. | null | 10.3390/e12051246 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A short overview of black hole entropy in alternative gravitational theories
is presented. Motivated by the recent attempts to explain the cosmic
acceleration without dark energy, we focus on metric and Palatini f(R) gravity
and on scalar-tensor theories.
| [
{
"created": "Thu, 13 May 2010 14:21:55 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | A short overview of black hole entropy in alternative gravitational theories is presented. Motivated by the recent attempts to explain the cosmic acceleration without dark energy, we focus on metric and Palatini f(R) gravity and on scalar-tensor theories. |
gr-qc/9309008 | null | Pedro F. Gonzalez-Diaz | Quantum State and Spontaneous Symmetry Breaking in Gravity | 4p | Int.J.Mod.Phys.D3:191-194,1994 | 10.1142/S0218271894000265 | IMAFF-RC-05-93 | gr-qc | null | A spontaneous symmetry breaking mechanism is used in quantum gravity to
obtain a convergent positive definite density-matrix as the most general
quantum state of Euclidean wormholes
| [
{
"created": "Mon, 13 Sep 1993 17:12:54 GMT",
"version": "v1"
}
] | 2011-04-20 | [
[
"Gonzalez-Diaz",
"Pedro F.",
""
]
] | A spontaneous symmetry breaking mechanism is used in quantum gravity to obtain a convergent positive definite density-matrix as the most general quantum state of Euclidean wormholes |
2105.00646 | Heba Sami | Heba Sami, Shambel Sahlu, Amare Abebe and Peter K. S. Dunsby | Covariant density and velocity perturbations of the quasi-Newtonian
cosmological model in $f(T)$ gravity | 30 pages, 8 figures. arXiv admin note: substantial text overlap with
arXiv:2012.06721 | null | 10.1140/epjc/s10052-021-09615-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate classes of shear-free cosmological dust models with
irrotational fluid flows within the framework of $f(T)$ gravity. In particular,
we use the $1 + 3$ covariant formalism and present the covariant linearised
evolution and constraint equations describing such models. We then derive the
integrability conditions describing a consistent evolution of the linearised
field equations of these quasi-Newtonian universes in the $f(T)$ gravitational
theory. Finally, we derive the evolution equations for the density and velocity
perturbations of the quasi-Newtonian universe. We explore the behaviour of the
matter density contrast for two models - $f(T)= \mu T_{0}(T/T_{0})^{n}$ and the
more generalised case, where $f(T)= T+ \mu T_{0} (T/T_{0})^{n}$, with and
without the application of the quasi-static approximation. Our numerical
solutions show that these $f(T)$ theories can be suitable alternatives to study
the background dynamics, whereas the growth of energy density fluctuations
change dramatically from the expected $\Lambda$CDM behaviour even for small
deviations away from the general relativistic limits of the underlying $f(T)$
theory. Moreover, applying the so-called quasi-static approximation yields
exact-solution results that are orders of magnitude different from the
numerically integrated solutions of the full system, suggesting that these
approximations are not applicable here.
| [
{
"created": "Mon, 3 May 2021 06:40:12 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Sami",
"Heba",
""
],
[
"Sahlu",
"Shambel",
""
],
[
"Abebe",
"Amare",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | We investigate classes of shear-free cosmological dust models with irrotational fluid flows within the framework of $f(T)$ gravity. In particular, we use the $1 + 3$ covariant formalism and present the covariant linearised evolution and constraint equations describing such models. We then derive the integrability conditions describing a consistent evolution of the linearised field equations of these quasi-Newtonian universes in the $f(T)$ gravitational theory. Finally, we derive the evolution equations for the density and velocity perturbations of the quasi-Newtonian universe. We explore the behaviour of the matter density contrast for two models - $f(T)= \mu T_{0}(T/T_{0})^{n}$ and the more generalised case, where $f(T)= T+ \mu T_{0} (T/T_{0})^{n}$, with and without the application of the quasi-static approximation. Our numerical solutions show that these $f(T)$ theories can be suitable alternatives to study the background dynamics, whereas the growth of energy density fluctuations change dramatically from the expected $\Lambda$CDM behaviour even for small deviations away from the general relativistic limits of the underlying $f(T)$ theory. Moreover, applying the so-called quasi-static approximation yields exact-solution results that are orders of magnitude different from the numerically integrated solutions of the full system, suggesting that these approximations are not applicable here. |
0812.0110 | Clifford M. Will | Clifford M. Will | Carter-like constants of the motion in Newtonian gravity and
electrodynamics | 4 pages | Phys.Rev.Lett.102:061101,2009 | 10.1103/PhysRevLett.102.061101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a test body orbiting an axisymmetric body in Newtonian gravitational
theory with multipole moments Q_L, (and for a charge in a non-relativistic
orbit about a charge distribution with the same multipole moments) we show that
there exists, in addition to the energy and angular momentum component along
the symmetry axis, a conserved quantity analogous to the Carter constant of
Kerr spacetimes in general relativity, if the odd-L moments vanish, and the
even-L moments satisfy Q_2L = m (Q_2/m)^L. Strangely, this is precisely the
relation among mass moments enforced by the no-hair theorems of rotating black
holes. By contrast, if Newtonian gravity is supplemented by a multipolar
gravitomagnetic field, whose leading term represents frame-dragging (or if the
electrostatic field is supplemented by a multipolar magnetic field), we are
unable to find an analogous Carter-like constant. This further highlights the
very special nature of the Kerr geometry of general relativity.
| [
{
"created": "Sat, 29 Nov 2008 21:50:16 GMT",
"version": "v1"
}
] | 2009-02-27 | [
[
"Will",
"Clifford M.",
""
]
] | For a test body orbiting an axisymmetric body in Newtonian gravitational theory with multipole moments Q_L, (and for a charge in a non-relativistic orbit about a charge distribution with the same multipole moments) we show that there exists, in addition to the energy and angular momentum component along the symmetry axis, a conserved quantity analogous to the Carter constant of Kerr spacetimes in general relativity, if the odd-L moments vanish, and the even-L moments satisfy Q_2L = m (Q_2/m)^L. Strangely, this is precisely the relation among mass moments enforced by the no-hair theorems of rotating black holes. By contrast, if Newtonian gravity is supplemented by a multipolar gravitomagnetic field, whose leading term represents frame-dragging (or if the electrostatic field is supplemented by a multipolar magnetic field), we are unable to find an analogous Carter-like constant. This further highlights the very special nature of the Kerr geometry of general relativity. |
2011.01605 | Hiroaki Tahara | Hiroaki W. H. Tahara, Tsutomu Kobayashi | Nanohertz gravitational waves from NEC violation in the early universe | 11 pages, 8 figures | Phys. Rev. D 102, 123533 (2020) | 10.1103/PhysRevD.102.123533 | RUP-20-32 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study nanohertz gravitational waves relevant to pulsar timing array
experiments from quantum fluctuations in the early universe with null energy
condition (NEC) violation. The NEC violation admits accelerated expansion with
the scale factor $a\propto (-t)^{-p}$ ($p>0$), which gives the tensor spectral
index $n_t=2/(p+1)>0$. To evade the constraint from Big Bang nucleosynthesis
(BBN), we connect the NEC-violating phase to a subsequent short slow-roll
inflationary phase which ends with standard reheating, and thereby reduce the
high frequency part of the spectrum. An explicit model is constructed within
the cubic Horndeski theory which allows for stable violation of the NEC. We
present numerical examples of the background evolution having the different
maximal Hubble parameters (which determine the peak amplitude of gravitational
waves), the different inflationary Hubble parameters (which determine the
amplitudes of high frequency gravitational waves), and different durations of
the inflationary phase (which essentially determine the peak frequency of the
spectrum). We display the spectra with $n_t=0.8$, $0.9$, and $0.95$ for
$f\lesssim 1/{\rm yr}$, which are consistent with the recent NANOGrav result.
We also check that they do not contradict the BBN constraint. We discuss how
the nearly scale-invariant spectrum of curvature perturbations is produced in
the NEC-violating phase.
| [
{
"created": "Tue, 3 Nov 2020 10:19:42 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2020 07:21:35 GMT",
"version": "v2"
}
] | 2021-01-04 | [
[
"Tahara",
"Hiroaki W. H.",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] | We study nanohertz gravitational waves relevant to pulsar timing array experiments from quantum fluctuations in the early universe with null energy condition (NEC) violation. The NEC violation admits accelerated expansion with the scale factor $a\propto (-t)^{-p}$ ($p>0$), which gives the tensor spectral index $n_t=2/(p+1)>0$. To evade the constraint from Big Bang nucleosynthesis (BBN), we connect the NEC-violating phase to a subsequent short slow-roll inflationary phase which ends with standard reheating, and thereby reduce the high frequency part of the spectrum. An explicit model is constructed within the cubic Horndeski theory which allows for stable violation of the NEC. We present numerical examples of the background evolution having the different maximal Hubble parameters (which determine the peak amplitude of gravitational waves), the different inflationary Hubble parameters (which determine the amplitudes of high frequency gravitational waves), and different durations of the inflationary phase (which essentially determine the peak frequency of the spectrum). We display the spectra with $n_t=0.8$, $0.9$, and $0.95$ for $f\lesssim 1/{\rm yr}$, which are consistent with the recent NANOGrav result. We also check that they do not contradict the BBN constraint. We discuss how the nearly scale-invariant spectrum of curvature perturbations is produced in the NEC-violating phase. |
1010.1031 | Taylor Hughes | Andrew Randono and Taylor L. Hughes | Torsional Monopoles and Torqued Geometries in Gravity and Condensed
Matter | 4+epsilon, 1 figure | Phys.Rev.Lett.106:161102,2011 | 10.1103/PhysRevLett.106.161102 | null | gr-qc cond-mat.other hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Torsional degrees of freedom play an important role in modern gravity
theories as well as in condensed matter systems where they can be modeled by
defects in solids. Here we isolate a class of torsion models that support
torsion configurations with a localized, conserved charge that adopts integer
values. The charge is topological in nature and the torsional configurations
can be thought of as torsional `monopole' solutions. We explore some of the
properties of these configurations in gravity models with non-vanishing
curvature, and discuss the possible existence of such monopoles in condensed
matter systems. To conclude, we show how the monopoles can be thought of as a
natural generalization of the Cartan spiral staircase.
| [
{
"created": "Tue, 5 Oct 2010 21:57:07 GMT",
"version": "v1"
}
] | 2012-06-15 | [
[
"Randono",
"Andrew",
""
],
[
"Hughes",
"Taylor L.",
""
]
] | Torsional degrees of freedom play an important role in modern gravity theories as well as in condensed matter systems where they can be modeled by defects in solids. Here we isolate a class of torsion models that support torsion configurations with a localized, conserved charge that adopts integer values. The charge is topological in nature and the torsional configurations can be thought of as torsional `monopole' solutions. We explore some of the properties of these configurations in gravity models with non-vanishing curvature, and discuss the possible existence of such monopoles in condensed matter systems. To conclude, we show how the monopoles can be thought of as a natural generalization of the Cartan spiral staircase. |
2305.18537 | Damianos Iosifidis | Damianos Iosifidis, Konstantinos Pallikaris | Biconnection Gravity as a Statistical Manifold | 16 pages, no figures | null | null | null | gr-qc cs.IT hep-th math.IT | http://creativecommons.org/licenses/by/4.0/ | We formulate a bi-Connection Theory of Gravity whose Gravitational action
consists of a recently defined mutual curvature scalar. Namely, we build a
gravitational theory consisting of one metric and two affine connections, in a
Metric-Affine Gravity setup. Consequently, coupling the two connections on an
equal footing with matter, we show that the geometry of the resulting theory
is, quite intriguingly, that of Statistical Manifold. This ultimately indicates
a remarkable mathematical correspondence between Gravity and Information
Geometry.
| [
{
"created": "Mon, 29 May 2023 18:09:06 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Aug 2023 16:30:30 GMT",
"version": "v2"
}
] | 2023-08-23 | [
[
"Iosifidis",
"Damianos",
""
],
[
"Pallikaris",
"Konstantinos",
""
]
] | We formulate a bi-Connection Theory of Gravity whose Gravitational action consists of a recently defined mutual curvature scalar. Namely, we build a gravitational theory consisting of one metric and two affine connections, in a Metric-Affine Gravity setup. Consequently, coupling the two connections on an equal footing with matter, we show that the geometry of the resulting theory is, quite intriguingly, that of Statistical Manifold. This ultimately indicates a remarkable mathematical correspondence between Gravity and Information Geometry. |
1402.2848 | Sergio Dain | Sergio Dain and Ivan Gentile de Austria | On the linear stability of the extreme Kerr black hole under axially
symmetric perturbations | 35 pages. 2 figures. Relevant improvement in the presentation in
section 2.2 | Class. Quantum Grav. 31 195009, 2014 | 10.1088/0264-9381/31/19/195009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that for axially symmetric linear gravitational perturbations of the
extreme Kerr black hole there exists a positive definite and conserved energy.
This provides a basic criteria for linear stability in axial symmetry. In the
particular case of Minkowski, using this energy we also prove pointwise
boundedness of the perturbation in a remarkable simple way.
| [
{
"created": "Wed, 12 Feb 2014 15:20:21 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Sep 2014 13:40:28 GMT",
"version": "v2"
}
] | 2014-09-22 | [
[
"Dain",
"Sergio",
""
],
[
"de Austria",
"Ivan Gentile",
""
]
] | We prove that for axially symmetric linear gravitational perturbations of the extreme Kerr black hole there exists a positive definite and conserved energy. This provides a basic criteria for linear stability in axial symmetry. In the particular case of Minkowski, using this energy we also prove pointwise boundedness of the perturbation in a remarkable simple way. |
1911.04896 | Haomin Rao | Haomin Rao, Dehao Zhao | Eddington-inspired Born-Infeld Gravity with Varying Cosmological
Constant | 7 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we modify the EiBI model to realize a varying cosmological
constant which is determined by matter distribution. We find that the Newton's
constant is also variable and its change is related to the change of
cosmological constant. And then we study its cosmological behavior. We find
that the early universe will have different behaviors if we take different
forms of pending functions. And we can avoid singularity in early universe just
like the original EiBI model.
| [
{
"created": "Tue, 12 Nov 2019 14:39:01 GMT",
"version": "v1"
}
] | 2019-11-13 | [
[
"Rao",
"Haomin",
""
],
[
"Zhao",
"Dehao",
""
]
] | In this paper we modify the EiBI model to realize a varying cosmological constant which is determined by matter distribution. We find that the Newton's constant is also variable and its change is related to the change of cosmological constant. And then we study its cosmological behavior. We find that the early universe will have different behaviors if we take different forms of pending functions. And we can avoid singularity in early universe just like the original EiBI model. |
1308.4390 | Alfonso Garc\'ia-Parrado G\'omez-Lobo Dr. | Alfonso Garc\'ia-Parrado G\'omez-Lobo | On the conservation of Superenergy and its applications | 11 pages, 1 figure. Section 5 is new. Minor change in the title to
take this into account (see abstract). To appear in "Classical and Quantum
Gravity" | null | 10.1088/0264-9381/31/13/135008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present a geometric identity involving the Bel-Robinson
tensor which is formally similar to the Sparling identity (which involves the
Einstein tensor through the Einstein 3-form). In our identity the Bel-Robinson
tensor enters through the {\em Bel-Robinson 3-form} which, we believe, is
introduced in the literature for the first time. The meaning of this identity
is that it is possible to formulate a {\em generic} conservation law for the
quantity represented by the Bel-Robinson tensor (superenergy). We also show how
one can use the Bel-Robinson 3-form to estimate the components of the
Bel-Robinson tensor which are computed with respect to the causal elements of a
frame. This estimate could be useful in a global existence proof of the
solutions of a theory of gravitation in dimension four.
| [
{
"created": "Tue, 20 Aug 2013 19:29:44 GMT",
"version": "v1"
},
{
"created": "Sat, 3 May 2014 17:27:42 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Gómez-Lobo",
"Alfonso García-Parrado",
""
]
] | In this work we present a geometric identity involving the Bel-Robinson tensor which is formally similar to the Sparling identity (which involves the Einstein tensor through the Einstein 3-form). In our identity the Bel-Robinson tensor enters through the {\em Bel-Robinson 3-form} which, we believe, is introduced in the literature for the first time. The meaning of this identity is that it is possible to formulate a {\em generic} conservation law for the quantity represented by the Bel-Robinson tensor (superenergy). We also show how one can use the Bel-Robinson 3-form to estimate the components of the Bel-Robinson tensor which are computed with respect to the causal elements of a frame. This estimate could be useful in a global existence proof of the solutions of a theory of gravitation in dimension four. |
gr-qc/9801040 | Manoelito Martins de Souza | Manoelito M. de Souza and Robson N. Silveira | Discrete and finite Genral Relativity | Modified conform the version to appear in Classical and Quantum
Gravity | Class.Quant.Grav. 16 (1999) 619-630 | 10.1088/0264-9381/16/2/023 | UFES-DF-MMS-98/1 | gr-qc hep-ph hep-th | null | We develop the General Theory of Relativity in a formalism with extended
causality that describes physical interaction through discrete, transversal and
localized pointlike fields. The homogeneous field equations are then solved for
a finite, singularity-free, point-like field that we associate to a ``classical
graviton". The standard Einstein's continuous formalism is retrieved by means
of an averaging process, and its continuous solutions are determined by the
chosen imposed symetry. The Schwarzschild metric is obtained by the imposition
of spherical symmetry on the averaged field.
| [
{
"created": "Tue, 13 Jan 1998 01:07:23 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Feb 1998 21:33:13 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Nov 1998 20:39:35 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"de Souza",
"Manoelito M.",
""
],
[
"Silveira",
"Robson N.",
""
]
] | We develop the General Theory of Relativity in a formalism with extended causality that describes physical interaction through discrete, transversal and localized pointlike fields. The homogeneous field equations are then solved for a finite, singularity-free, point-like field that we associate to a ``classical graviton". The standard Einstein's continuous formalism is retrieved by means of an averaging process, and its continuous solutions are determined by the chosen imposed symetry. The Schwarzschild metric is obtained by the imposition of spherical symmetry on the averaged field. |
gr-qc/0701078 | Jia-Rui Sun | Chao-Guang Huang and Jia-Rui Sun | Thermodynamic Properties of Spherically-Symmetric, Uniformly-Accelerated
Reference Frames | 8 pages | Commun.Theor.Phys.49:928-932,2008 | 10.1088/0253-6102/49/4/26 | null | gr-qc | null | We aim to study the thermodynamic properties of the spherically symmetric
reference frames with uniform acceleration, including the spherically symmetric
generalization of Rindler reference frame and the new kind of uniformly
accelerated reference frame. We find that, unlike the general studies about the
horizon thermodynamics, one cannot obtain the laws of thermodynamics for their
horizons in the usual approaches, despite that one can formally define an area
entropy (Bekenstein-Hawking entropy). In fact, the common horizon for a set of
uniformly accelerated observers is not always exist, even though the
Hawking-Unruh temperature is still well-defined. This result indicates that the
Hawking-Unruh temperature is only a kinematic effect, to gain the laws of
thermodynamics for the horizon, one needs the help of dynamics. Our result is
in accordance with those from the various studies about the acoustic black
holes.
| [
{
"created": "Mon, 15 Jan 2007 12:19:41 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Huang",
"Chao-Guang",
""
],
[
"Sun",
"Jia-Rui",
""
]
] | We aim to study the thermodynamic properties of the spherically symmetric reference frames with uniform acceleration, including the spherically symmetric generalization of Rindler reference frame and the new kind of uniformly accelerated reference frame. We find that, unlike the general studies about the horizon thermodynamics, one cannot obtain the laws of thermodynamics for their horizons in the usual approaches, despite that one can formally define an area entropy (Bekenstein-Hawking entropy). In fact, the common horizon for a set of uniformly accelerated observers is not always exist, even though the Hawking-Unruh temperature is still well-defined. This result indicates that the Hawking-Unruh temperature is only a kinematic effect, to gain the laws of thermodynamics for the horizon, one needs the help of dynamics. Our result is in accordance with those from the various studies about the acoustic black holes. |
0704.3963 | Andreas Mueller | Andreas Mueller and Bernd Aschenbach | Non-monotonic orbital velocity profiles around rapidly rotating
Kerr-(anti-)de Sitter black holes | 9 pages, 4 figures, accepted for Class. Quant. Grav | Class.Quant.Grav.24:2637-2644,2007 | 10.1088/0264-9381/24/10/009 | null | gr-qc astro-ph | null | It has been recently demonstrated that the orbital velocity profile around
Kerr black holes in the equatorial plane as observed in the locally
non-rotating frame exhibits a non-monotonic radial behaviour. We show here that
this unexpected minimum-maximum feature of the orbital velocity remains if the
Kerr vacuum is generalized to the Kerr-de Sitter or Kerr-anti-de Sitter metric.
This is a new general relativity effect in Kerr spacetimes with non-vanishing
cosmological constant. Assuming that the profile of the orbital velocity is
known, this effect constrains the spacetime parameters.
| [
{
"created": "Mon, 30 Apr 2007 15:32:14 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mueller",
"Andreas",
""
],
[
"Aschenbach",
"Bernd",
""
]
] | It has been recently demonstrated that the orbital velocity profile around Kerr black holes in the equatorial plane as observed in the locally non-rotating frame exhibits a non-monotonic radial behaviour. We show here that this unexpected minimum-maximum feature of the orbital velocity remains if the Kerr vacuum is generalized to the Kerr-de Sitter or Kerr-anti-de Sitter metric. This is a new general relativity effect in Kerr spacetimes with non-vanishing cosmological constant. Assuming that the profile of the orbital velocity is known, this effect constrains the spacetime parameters. |
gr-qc/0604086 | Luca Lusanna | David Alba (Firenze Univ.) and Luca Lusanna (INFN, Firenze) | The York map as a Shanmugadhasan canonical transformation in tetrad
gravity and the role of non-inertial frames in the geometrical view of the
gravitational field | 90 pages | Gen.Rel.Grav.39:2149-2203,2007 | 10.1007/s10714-007-0507-2 | null | gr-qc astro-ph hep-th | null | A new parametrization of the 3-metric allows to find explicitly a York map in
canonical ADM tetrad gravity, the two pairs of physical tidal degrees of
freedom and 14 gauge variables. These gauge quantities (generalized inertial
effects) are all configurational except the trace ${}^3K(\tau ,\vec \sigma)$ of
the extrinsic curvature of the instantaneous 3-spaces $\Sigma_{\tau}$ (clock
synchronization convention) of a non-inertial frame. The Dirac hamiltonian is
the sum of the weak ADM energy $E_{ADM} = \int d^3\sigma {\cal E}_{ADM}(\tau
,\vec \sigma)$ (whose density is coordinate-dependent due to the inertial
potentials) and of the first-class constraints. Then: i) The explicit form of
the Hamilton equations for the two tidal degrees of freedom in an arbitrary
gauge: a deterministic evolution can be defined only in a completely fixed
gauge, i.e. in a non-inertial frame with its pattern of inertial forces. ii) A
general solution of the super-momentum constraints, which shows the existence
of a generalized Gribov ambiguity associated to the 3-diffeomorphism gauge
group. It influences: a) the explicit form of the weak ADM energy and of the
super-momentum constraint; b) the determination of the shift functions and then
of the lapse one. iii) The dependence of the Hamilton equations for the two
pairs of dynamical gravitational degrees of freedom (the generalized tidal
effects) and for the matter, written in a completely fixed 3-orthogonal
Schwinger time gauge, upon the gauge variable ${}^3K(\tau ,\vec \sigma)$,
determining the convention of clock synchronization. Therefore it should be
possible (for instance in the weak field limit but with relativistic motion) to
try to check whether in Einstein's theory the {\it dark matter} is a gauge
relativistic inertial effect induced by ${}^3K(\tau ,\vec \sigma)$.
| [
{
"created": "Thu, 20 Apr 2006 10:40:28 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Aug 2007 10:40:45 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Alba",
"David",
"",
"Firenze Univ."
],
[
"Lusanna",
"Luca",
"",
"INFN, Firenze"
]
] | A new parametrization of the 3-metric allows to find explicitly a York map in canonical ADM tetrad gravity, the two pairs of physical tidal degrees of freedom and 14 gauge variables. These gauge quantities (generalized inertial effects) are all configurational except the trace ${}^3K(\tau ,\vec \sigma)$ of the extrinsic curvature of the instantaneous 3-spaces $\Sigma_{\tau}$ (clock synchronization convention) of a non-inertial frame. The Dirac hamiltonian is the sum of the weak ADM energy $E_{ADM} = \int d^3\sigma {\cal E}_{ADM}(\tau ,\vec \sigma)$ (whose density is coordinate-dependent due to the inertial potentials) and of the first-class constraints. Then: i) The explicit form of the Hamilton equations for the two tidal degrees of freedom in an arbitrary gauge: a deterministic evolution can be defined only in a completely fixed gauge, i.e. in a non-inertial frame with its pattern of inertial forces. ii) A general solution of the super-momentum constraints, which shows the existence of a generalized Gribov ambiguity associated to the 3-diffeomorphism gauge group. It influences: a) the explicit form of the weak ADM energy and of the super-momentum constraint; b) the determination of the shift functions and then of the lapse one. iii) The dependence of the Hamilton equations for the two pairs of dynamical gravitational degrees of freedom (the generalized tidal effects) and for the matter, written in a completely fixed 3-orthogonal Schwinger time gauge, upon the gauge variable ${}^3K(\tau ,\vec \sigma)$, determining the convention of clock synchronization. Therefore it should be possible (for instance in the weak field limit but with relativistic motion) to try to check whether in Einstein's theory the {\it dark matter} is a gauge relativistic inertial effect induced by ${}^3K(\tau ,\vec \sigma)$. |
2009.12306 | Zbigniew Haba | Z. Haba | State-dependent graviton noise in the equation of geodesic deviation | 11 pages | Eur.Phys.J.C81,40(2021) | 10.1140/epjc/s10052-020-08805-y | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an equation of the geodesic deviation appearing in the problem of
gravitational wave detection in an environment of gravitons. We investigate a
state-dependent graviton noise (as discussed in a recent paper of
Parikh,Wilczek and Zahariade) from the point of view of the Feynman integral
and stochastic differential equations. The evolution of the density matrix and
the transition probability in an environment of gravitons is obtained. We
express the time evolution by a solution of a stochastic geodesic deviation
equation with a noise dependent on the quantum state of the gravitational
field.
| [
{
"created": "Fri, 25 Sep 2020 15:59:20 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2020 18:57:13 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Jan 2021 12:47:17 GMT",
"version": "v3"
}
] | 2021-01-19 | [
[
"Haba",
"Z.",
""
]
] | We consider an equation of the geodesic deviation appearing in the problem of gravitational wave detection in an environment of gravitons. We investigate a state-dependent graviton noise (as discussed in a recent paper of Parikh,Wilczek and Zahariade) from the point of view of the Feynman integral and stochastic differential equations. The evolution of the density matrix and the transition probability in an environment of gravitons is obtained. We express the time evolution by a solution of a stochastic geodesic deviation equation with a noise dependent on the quantum state of the gravitational field. |
2109.10663 | Fabio M. Mele | Fabio M. Mele, Johannes M\"unch | The Physical Relevance of the Fiducial Cell in Loop Quantum Cosmology | Published version, 13 pages (REVTeX format), 1 figure. Minor
clarifications added | Phys. Rev. D 108, 106004 (2023) | 10.1103/PhysRevD.108.106004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A common way to avoid divergent integrals in homogeneous spatially
non-compact gravitational systems is to introduce a fiducial cell by
cutting-off the spatial slice at a finite region $V_o$. This is usually
considered as an auxiliary regulator to be removed after computations by
sending $V_o\to\infty$. In this paper, we analyse the dependence of the
classical and quantum theory of homogeneous, isotropic and spatially flat
cosmology on $V_o$. We show that each fixed $V_o$ regularisation leads to a
different canonically independent theory. At the classical level, the dynamics
of observables is not affected by the regularisation on-shell. For the quantum
theory, however, this leads to a family of regulator dependent quantum
representations and the limit $V_o\to\infty$ becomes then more subtle. First,
we construct a novel isomorphism between different $V_o$-regularisations, which
allows us to identify states in the different $V_o$-labelled Hilbert spaces to
ensure equivalent dynamics for any value of $V_o$. The $V_o\to\infty$ limit
would then correspond to choosing a state for which the volume assigned to the
fiducial cell becomes infinite as appropriate in the late-time regime. As
second main result of our analysis, quantum fluctuations of observables smeared
over subregions $V\subset V_o$, unlike those smeared over the full $V_o$,
explicitly depend on the size of the fiducial cell through the ratio $V/V_o$
interpreted as the (inverse) number of subcells $V$ homogeneously patched
together into $V_o$. Physically relevant fluctuations for a finite region, as
e.g. in the early-time regime, which would be unreasonably suppressed in a
na\"ive $V_o\to\infty$ limit, become appreciable at small volumes. Our results
suggest that the fiducial cell is not playing the role of a mere regularisation
but is physically relevant at the quantum level and complement previous
statements in the literature.
| [
{
"created": "Wed, 22 Sep 2021 11:41:34 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Dec 2023 19:00:02 GMT",
"version": "v2"
}
] | 2024-01-25 | [
[
"Mele",
"Fabio M.",
""
],
[
"Münch",
"Johannes",
""
]
] | A common way to avoid divergent integrals in homogeneous spatially non-compact gravitational systems is to introduce a fiducial cell by cutting-off the spatial slice at a finite region $V_o$. This is usually considered as an auxiliary regulator to be removed after computations by sending $V_o\to\infty$. In this paper, we analyse the dependence of the classical and quantum theory of homogeneous, isotropic and spatially flat cosmology on $V_o$. We show that each fixed $V_o$ regularisation leads to a different canonically independent theory. At the classical level, the dynamics of observables is not affected by the regularisation on-shell. For the quantum theory, however, this leads to a family of regulator dependent quantum representations and the limit $V_o\to\infty$ becomes then more subtle. First, we construct a novel isomorphism between different $V_o$-regularisations, which allows us to identify states in the different $V_o$-labelled Hilbert spaces to ensure equivalent dynamics for any value of $V_o$. The $V_o\to\infty$ limit would then correspond to choosing a state for which the volume assigned to the fiducial cell becomes infinite as appropriate in the late-time regime. As second main result of our analysis, quantum fluctuations of observables smeared over subregions $V\subset V_o$, unlike those smeared over the full $V_o$, explicitly depend on the size of the fiducial cell through the ratio $V/V_o$ interpreted as the (inverse) number of subcells $V$ homogeneously patched together into $V_o$. Physically relevant fluctuations for a finite region, as e.g. in the early-time regime, which would be unreasonably suppressed in a na\"ive $V_o\to\infty$ limit, become appreciable at small volumes. Our results suggest that the fiducial cell is not playing the role of a mere regularisation but is physically relevant at the quantum level and complement previous statements in the literature. |
1905.01618 | Hai-Qing Zhang | Xiao-Xiong Zeng and Hai-Qing Zhang | Thermodynamics and weak cosmic censorship conjecture in the Kerr-AdS
black hole | 21 pages, 2 figures; References added; Version compatible with NPB | Nucl.Phys.B 959 (2020) 115162 | 10.1016/j.nuclphysb.2020.115162 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the laws of thermodynamics and weak cosmic censorship
conjecture in the normal and extended phase space of a Kerr-AdS black hole by
analyzing the energy-momentum relation of the absorbed fermion dropping into
the horizon. In the normal phase space, the first law, second law as well as
the weak cosmic censorship conjecture are found to be valid in all the initial
states of the black hole. However, in the extended phase space, although the
first law and weak cosmic censorship conjecture are still valid, the second law
becomes more subtle. We find that the validity or violation of the second law
depends on the spin parameter, the radius of the AdS spacetime, and their
variations. In addition, in the extended phase space, the configurations of the
extremal and near-extremal Kerr-AdS black holes are unchanged as the fermions
are absorbed since the final and initial states are the same.
| [
{
"created": "Sun, 5 May 2019 06:36:04 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Sep 2020 11:20:32 GMT",
"version": "v2"
}
] | 2020-09-29 | [
[
"Zeng",
"Xiao-Xiong",
""
],
[
"Zhang",
"Hai-Qing",
""
]
] | We investigate the laws of thermodynamics and weak cosmic censorship conjecture in the normal and extended phase space of a Kerr-AdS black hole by analyzing the energy-momentum relation of the absorbed fermion dropping into the horizon. In the normal phase space, the first law, second law as well as the weak cosmic censorship conjecture are found to be valid in all the initial states of the black hole. However, in the extended phase space, although the first law and weak cosmic censorship conjecture are still valid, the second law becomes more subtle. We find that the validity or violation of the second law depends on the spin parameter, the radius of the AdS spacetime, and their variations. In addition, in the extended phase space, the configurations of the extremal and near-extremal Kerr-AdS black holes are unchanged as the fermions are absorbed since the final and initial states are the same. |
0804.3827 | Zhong Chao Wu | Zhong Chao Wu | Inverse Temperature 4-vector in Special Relativity | 11 pages, revised version | Europhys.Lett.88:20005,2009 | 10.1209/0295-5075/88/20005 | ZJUT-0803 | gr-qc astro-ph cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There exist several prescriptions for identifying the notion of temperature
in special relativity. We argue that the inverse temperature 4-vector $\bf
\beta$ is the only viable option from the laws of thermodynamics, and $\bf
\beta$ is a future-directed timelike 4-vector. Using a superfluidity thought
experiment, one can show that $\bf \beta$ is not necessarily along the time
direction of the comoving frame of the system, as is usually thought. It is
conjectured that, for an isolated system, the 4-vector is determined from the
entropy-maximum principle.
| [
{
"created": "Thu, 24 Apr 2008 19:54:48 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Apr 2008 16:03:28 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Mar 2009 20:27:09 GMT",
"version": "v3"
},
{
"created": "Wed, 11 Nov 2009 22:11:32 GMT",
"version": "v4"
}
] | 2009-11-12 | [
[
"Wu",
"Zhong Chao",
""
]
] | There exist several prescriptions for identifying the notion of temperature in special relativity. We argue that the inverse temperature 4-vector $\bf \beta$ is the only viable option from the laws of thermodynamics, and $\bf \beta$ is a future-directed timelike 4-vector. Using a superfluidity thought experiment, one can show that $\bf \beta$ is not necessarily along the time direction of the comoving frame of the system, as is usually thought. It is conjectured that, for an isolated system, the 4-vector is determined from the entropy-maximum principle. |
2406.11719 | Moreshwar Tayde | Moreshwar Tayde, P.K. Sahoo | Exploring wormhole solutions with global monopole charge in the context
of $f(Q)$ gravity | EPJ C published version | Eur. Phys. J. C 84 (2024) 643 | 10.1140/epjc/s10052-024-13002-2 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This study explores the potential existence of traversable wormholes
influenced by a global monopole charge within the $f(Q)$ gravity framework. To
elucidate the characteristics of these wormholes, we conducted a comprehensive
analysis of wormhole solutions employing three different forms of redshift
function under a linear $f(Q)$ model. Wormhole shape functions were derived for
barotropic, anisotropic, and isotropic Equations of State (EoS) cases. However,
in the isotropic EoS case, the calculated shape function failed to satisfy the
asymptotic flatness condition. Additionally, we observed that our obtained
shape functions adhered to the flaring-out conditions under an asymptotic
background for the remaining EoS cases. Furthermore, we examined the energy
conditions at the wormhole throat with a radius $r_0$. We noted the influences
of the global monopole's parameter $\eta$, the EoS parameter $\omega$, and $n$
in violating energy conditions, particularly the null energy conditions.
Finally, we conducted a stability analysis utilizing the
Tolman-Oppenheimer-Volkov (TOV) equation and found that our obtained wormhole
solution is stable.
| [
{
"created": "Mon, 17 Jun 2024 16:38:10 GMT",
"version": "v1"
}
] | 2024-06-26 | [
[
"Tayde",
"Moreshwar",
""
],
[
"Sahoo",
"P. K.",
""
]
] | This study explores the potential existence of traversable wormholes influenced by a global monopole charge within the $f(Q)$ gravity framework. To elucidate the characteristics of these wormholes, we conducted a comprehensive analysis of wormhole solutions employing three different forms of redshift function under a linear $f(Q)$ model. Wormhole shape functions were derived for barotropic, anisotropic, and isotropic Equations of State (EoS) cases. However, in the isotropic EoS case, the calculated shape function failed to satisfy the asymptotic flatness condition. Additionally, we observed that our obtained shape functions adhered to the flaring-out conditions under an asymptotic background for the remaining EoS cases. Furthermore, we examined the energy conditions at the wormhole throat with a radius $r_0$. We noted the influences of the global monopole's parameter $\eta$, the EoS parameter $\omega$, and $n$ in violating energy conditions, particularly the null energy conditions. Finally, we conducted a stability analysis utilizing the Tolman-Oppenheimer-Volkov (TOV) equation and found that our obtained wormhole solution is stable. |
1212.4921 | Jun Wang | Jun Wang, Ya-Bo Wu, Yong-Xin Guo, Wei-Qiang Yang, Lei Wang | Energy Conditions and Stability in generalized $f(R)$ gravity with
arbitrary coupling between matter and geometry | 12 pages. arXiv admin note: substantial text overlap with
arXiv:1203.5593, arXiv:1212.4656 | Phys. Lett. B 689 (2010) 133-138 | 10.1016/j.physletb.2010.04.063 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The energy conditions and the Dolgov-Kawasaki criterion in generalized $f(R)$
gravity with arbitrary coupling between matter and geometry are derived in this
paper, which are quite general and can degenerate to the well-known energy
conditions in GR and $f(R)$ gravity with non-minimal coupling and non-coupling
as special cases. In order to get some insight on the meaning of these energy
conditions and the Dolgov- Kawasaki criterion, we apply them to a class of
models in the FRW cosmology and give some corresponding results.
| [
{
"created": "Thu, 20 Dec 2012 04:44:17 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Wang",
"Jun",
""
],
[
"Wu",
"Ya-Bo",
""
],
[
"Guo",
"Yong-Xin",
""
],
[
"Yang",
"Wei-Qiang",
""
],
[
"Wang",
"Lei",
""
]
] | The energy conditions and the Dolgov-Kawasaki criterion in generalized $f(R)$ gravity with arbitrary coupling between matter and geometry are derived in this paper, which are quite general and can degenerate to the well-known energy conditions in GR and $f(R)$ gravity with non-minimal coupling and non-coupling as special cases. In order to get some insight on the meaning of these energy conditions and the Dolgov- Kawasaki criterion, we apply them to a class of models in the FRW cosmology and give some corresponding results. |
1205.1108 | Sergei Rubin | A. A. Kirillov, A. A. Korotkevich and S.G. Rubin | Emergence of symmetries | 9 pages | Physics Letters B 718 (2012) 237-240 | 10.1016/j.physletb.2012.10.044 | PLB28961 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mechanism of symmetry formation is discussed in the framework of
multidimensional gravity. It is shown that this process is strictly connected
to the entropy decrease of compact space. The existence of low energy
symmetries is not postulated from the beginning. They could be absent during
the inflationary stage under certain conditions discussed in the paper.
| [
{
"created": "Sat, 5 May 2012 06:55:41 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Aug 2012 20:33:09 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Oct 2012 13:12:56 GMT",
"version": "v3"
}
] | 2012-11-22 | [
[
"Kirillov",
"A. A.",
""
],
[
"Korotkevich",
"A. A.",
""
],
[
"Rubin",
"S. G.",
""
]
] | The mechanism of symmetry formation is discussed in the framework of multidimensional gravity. It is shown that this process is strictly connected to the entropy decrease of compact space. The existence of low energy symmetries is not postulated from the beginning. They could be absent during the inflationary stage under certain conditions discussed in the paper. |
gr-qc/0310068 | Daniel Grumiller | D. Grumiller, W. Kummer | How to approach Quantum Gravity - Background independence in 1+1
dimensions | 15 pages, 1 (eps-)figure, joint proceedings contribution to the
EURESCO conference "What comes beyond the Standard Model?" in Portoroz,
Slovenia, July 2003, v2: added and rearranged references, minor modifications
of text | null | null | ESI 1388, TUW-03-28 | gr-qc hep-th | null | The application of quantum theory to gravity is beset with many technical and
conceptual problems. After a short tour d'horizon of recent attempts to master
those problems by the introduction of new approaches, we show that the aim, a
background independent quantum theory of gravity, can be reached in a
particular area, 2d dilaton quantum gravity, without any assumptions beyond
standard quantum field theory.
| [
{
"created": "Tue, 14 Oct 2003 10:01:40 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Oct 2003 11:49:32 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Grumiller",
"D.",
""
],
[
"Kummer",
"W.",
""
]
] | The application of quantum theory to gravity is beset with many technical and conceptual problems. After a short tour d'horizon of recent attempts to master those problems by the introduction of new approaches, we show that the aim, a background independent quantum theory of gravity, can be reached in a particular area, 2d dilaton quantum gravity, without any assumptions beyond standard quantum field theory. |
2311.09159 | Sudarshan Ghonge | Sudarshan Ghonge, Joshua Brandt, J. M. Sullivan, Margaret Millhouse,
Katerina Chatziioannou, James A. Clark, Tyson Littenberg, Neil Cornish,
Sophie Hourihane, and Laura Cadonati | Characterizing the efficacy of methods to subtract terrestrial transient
noise near gravitational wave events and the effects on parameter estimation | 22 pages, 17 figures | null | null | LIGO Document P2300385-v2 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the impact of transient noise artifacts, or {\it glitches}, on
gravitational wave inference, and the efficacy of data cleaning procedures in
recovering unbiased source properties. Due to their time-frequency morphology,
broadband glitches demonstrate moderate to significant biasing of posterior
distributions away from true values. In contrast, narrowband glitches have
negligible biasing effects owing to distinct signal and glitch morphologies. We
inject simulated binary black hole signals into data containing three common
glitch types from past LIGO-Virgo observing runs, and reconstruct both signal
and glitch waveforms using {\tt BayesWave}, a wavelet-based Bayesian analysis.
We apply the standard LIGO-Virgo-KAGRA deglitching procedure to the detector
data - we subtract the glitch waveform estimated by the joint {\tt BayesWave}
inference before performing parameter estimation with detailed compact binary
waveform models. We find that this deglitching effectively mitigates bias from
broadband glitches, with posterior peaks aligning with true values post
deglitching. This provides a baseline validation of existing techniques, while
demonstrating waveform reconstruction improvements to the Bayesian algorithm
for robust astrophysical characterization in glitch-prone detector data.
| [
{
"created": "Wed, 15 Nov 2023 17:56:42 GMT",
"version": "v1"
}
] | 2023-11-16 | [
[
"Ghonge",
"Sudarshan",
""
],
[
"Brandt",
"Joshua",
""
],
[
"Sullivan",
"J. M.",
""
],
[
"Millhouse",
"Margaret",
""
],
[
"Chatziioannou",
"Katerina",
""
],
[
"Clark",
"James A.",
""
],
[
"Littenberg",
"Tyson",
""
],
[
"Cornish",
"Neil",
""
],
[
"Hourihane",
"Sophie",
""
],
[
"Cadonati",
"Laura",
""
]
] | We investigate the impact of transient noise artifacts, or {\it glitches}, on gravitational wave inference, and the efficacy of data cleaning procedures in recovering unbiased source properties. Due to their time-frequency morphology, broadband glitches demonstrate moderate to significant biasing of posterior distributions away from true values. In contrast, narrowband glitches have negligible biasing effects owing to distinct signal and glitch morphologies. We inject simulated binary black hole signals into data containing three common glitch types from past LIGO-Virgo observing runs, and reconstruct both signal and glitch waveforms using {\tt BayesWave}, a wavelet-based Bayesian analysis. We apply the standard LIGO-Virgo-KAGRA deglitching procedure to the detector data - we subtract the glitch waveform estimated by the joint {\tt BayesWave} inference before performing parameter estimation with detailed compact binary waveform models. We find that this deglitching effectively mitigates bias from broadband glitches, with posterior peaks aligning with true values post deglitching. This provides a baseline validation of existing techniques, while demonstrating waveform reconstruction improvements to the Bayesian algorithm for robust astrophysical characterization in glitch-prone detector data. |
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