id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1203.2872 | Alberto Soria | Marc Mars and Alberto Soria | On the Penrose inequality for dust null shells in the Minkowski
spacetime of arbitrary dimension | 25 pages, 2 figures, Latex | null | 10.1088/0264-9381/29/13/135005 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A particular, yet relevant, particular case of the Penrose inequality
involves null shells propagating in the Minkowski spacetime. Despite previous
claims in the literature, the validity of this inequality remains open. In this
paper we rewrite this inequality in terms of the geometry of the surface
obtained by intersecting the past null cone of the original surface S with a
constant time hyperplane and the "time height" function of S over this
hyperplane. We also specialize to the case when S lies in the past null cone of
a point and show the validity of the corresponding inequality in any dimension
(in four dimensions this inequality was proved by Tod). Exploiting properties
of convex hypersurfaces in Euclidean space we write down the Penrose inequality
in the Minkowski spacetime of arbitrary dimension n+2 as an inequality for two
smooth functions on the sphere. We finally obtain a sufficient condition for
the validity of the Penrose inequality in the four dimensional Minkowski
spacetime and show that this condition is satisfied by a large class of
surfaces.
| [
{
"created": "Tue, 13 Mar 2012 17:30:10 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Mars",
"Marc",
""
],
[
"Soria",
"Alberto",
""
]
] | A particular, yet relevant, particular case of the Penrose inequality involves null shells propagating in the Minkowski spacetime. Despite previous claims in the literature, the validity of this inequality remains open. In this paper we rewrite this inequality in terms of the geometry of the surface obtained by intersecting the past null cone of the original surface S with a constant time hyperplane and the "time height" function of S over this hyperplane. We also specialize to the case when S lies in the past null cone of a point and show the validity of the corresponding inequality in any dimension (in four dimensions this inequality was proved by Tod). Exploiting properties of convex hypersurfaces in Euclidean space we write down the Penrose inequality in the Minkowski spacetime of arbitrary dimension n+2 as an inequality for two smooth functions on the sphere. We finally obtain a sufficient condition for the validity of the Penrose inequality in the four dimensional Minkowski spacetime and show that this condition is satisfied by a large class of surfaces. |
2405.11488 | Ye Shen | Bin Chen, Yehui Hou, Junyi Li and Ye Shen | Energy Extraction from a Kerr Black Hole via Magnetic Reconnection
within the Plunging Region | null | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Magnetic reconnection within a highly magnetized plasma has been seen as a
viable mechanism to extract the energy from a rotating black hole, as it can
generate negative energy plasmoids in the ergoregion. For a typical accreting
black hole, the ergoregion is filled with bulk plasma plunging from the
innermost-stable-circular orbit (ISCO). In this study, we present an analytical
study of the energy extraction via magnetic reconnection process in the
plunging region. In contrast to the toroidal plasma, where the magnetic field
cannot be derived from the MHD scheme, the magnetic field in the plunging
plasma was determined by the ideal-MHD condition. We derive the global magnetic
field structure in a fast reconnection model, and we read the expressions for
the energies of plasmoids ejected from the reconnection region, for general
stationary and axisymmetric spacetimes. Then, we demonstrate the behaviors of
ejected energies varying with the reconnection locations in the Kerr spacetime,
and identify the region where a negative-energy plasmoid can be produced. We
find that for a certain magnetization there exists a critical value of the
black hole spin, beyond which the energy extraction can occur, and the energy
extraction is most efficient for the near-extreme black hole. Moreover, we
study the conditions necessary for a plasmoid with positive energy to escape to
the infinity, a crucial requirement for effective energy extractions.
Considering the escaping conditions, we provide the parameter space in the
radius-spin plane in which the energy extraction mechanism is effective.
| [
{
"created": "Sun, 19 May 2024 09:15:59 GMT",
"version": "v1"
}
] | 2024-05-21 | [
[
"Chen",
"Bin",
""
],
[
"Hou",
"Yehui",
""
],
[
"Li",
"Junyi",
""
],
[
"Shen",
"Ye",
""
]
] | Magnetic reconnection within a highly magnetized plasma has been seen as a viable mechanism to extract the energy from a rotating black hole, as it can generate negative energy plasmoids in the ergoregion. For a typical accreting black hole, the ergoregion is filled with bulk plasma plunging from the innermost-stable-circular orbit (ISCO). In this study, we present an analytical study of the energy extraction via magnetic reconnection process in the plunging region. In contrast to the toroidal plasma, where the magnetic field cannot be derived from the MHD scheme, the magnetic field in the plunging plasma was determined by the ideal-MHD condition. We derive the global magnetic field structure in a fast reconnection model, and we read the expressions for the energies of plasmoids ejected from the reconnection region, for general stationary and axisymmetric spacetimes. Then, we demonstrate the behaviors of ejected energies varying with the reconnection locations in the Kerr spacetime, and identify the region where a negative-energy plasmoid can be produced. We find that for a certain magnetization there exists a critical value of the black hole spin, beyond which the energy extraction can occur, and the energy extraction is most efficient for the near-extreme black hole. Moreover, we study the conditions necessary for a plasmoid with positive energy to escape to the infinity, a crucial requirement for effective energy extractions. Considering the escaping conditions, we provide the parameter space in the radius-spin plane in which the energy extraction mechanism is effective. |
2407.09616 | C Fairoos | C. Fairoos, T. K. Safir and Deepak Mishra | Phase-space Path Integral Approach to the Kinetics of Black Hole Phase
Transition in Massive Gravity | 13 pages, 10 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of the state-switching process of black holes in dRGT massive
gravity theory is presented using free energy landscape and stochastic Langevin
equations. The free energy landscape is constructed using the Gibbons-Hawking
path integral method. The black hole phases are characterized by taking its
horizon radius as the order parameter. The free energy landscape provides three
black hole phases: small, intermediate, and large. The small and large black
holes are thermodynamically stable whereas the intermediate one is unstable.
The Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) functional describes the
stochastic dynamics of black hole phase transition. The Hamiltonian flow lines
are obtained from the MSRJD functional and are used to analyze the stability
and the phase transition properties. The dominant kinetic path between
different phases is discussed for various configurations of the free energy
landscape. We discuss the effect of black hole charge and the graviton mass on
the critical behavior of black hole phase transition.
| [
{
"created": "Fri, 12 Jul 2024 18:02:07 GMT",
"version": "v1"
}
] | 2024-07-16 | [
[
"Fairoos",
"C.",
""
],
[
"Safir",
"T. K.",
""
],
[
"Mishra",
"Deepak",
""
]
] | The dynamics of the state-switching process of black holes in dRGT massive gravity theory is presented using free energy landscape and stochastic Langevin equations. The free energy landscape is constructed using the Gibbons-Hawking path integral method. The black hole phases are characterized by taking its horizon radius as the order parameter. The free energy landscape provides three black hole phases: small, intermediate, and large. The small and large black holes are thermodynamically stable whereas the intermediate one is unstable. The Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) functional describes the stochastic dynamics of black hole phase transition. The Hamiltonian flow lines are obtained from the MSRJD functional and are used to analyze the stability and the phase transition properties. The dominant kinetic path between different phases is discussed for various configurations of the free energy landscape. We discuss the effect of black hole charge and the graviton mass on the critical behavior of black hole phase transition. |
1110.6768 | Torsten Asselmeyer-Maluga | T. Asselmeyer-Maluga, R. Mader, J. Krol | On 4-dimensional Lorentz-structures, Dark energy and Exotic smoothness | 7 pages, no figures, PACS 04.20.Gz, 98.80.Jk, 95.36.+x an obvious
error in the notation of the hyperbolic 3-manifold was fixed | null | null | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Usually, the topology of a 4-manifolds $M$ is restricted to admit a global
hyperbolic structure $\Sigma\times\mathbb{R}$. The result was obtained by using
two conditions: existence of a Lorentz structure and causality (no time-like
closed curves). In this paper we study the influence of the smoothness
structure to show its independence of the two conditions. Then we obtain the
possibility for a topology-change of the 3-manifold $\Sigma$ keeping fix its
homology. We will study the example $S^{3}\times\mathbb{R}$ with an exotic
differential structure more carefully to show some implications for cosmology.
Especially we obtain an interpretation of the transition in topology as dark
energy.
| [
{
"created": "Mon, 31 Oct 2011 12:22:29 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 2011 09:31:30 GMT",
"version": "v2"
}
] | 2011-11-04 | [
[
"Asselmeyer-Maluga",
"T.",
""
],
[
"Mader",
"R.",
""
],
[
"Krol",
"J.",
""
]
] | Usually, the topology of a 4-manifolds $M$ is restricted to admit a global hyperbolic structure $\Sigma\times\mathbb{R}$. The result was obtained by using two conditions: existence of a Lorentz structure and causality (no time-like closed curves). In this paper we study the influence of the smoothness structure to show its independence of the two conditions. Then we obtain the possibility for a topology-change of the 3-manifold $\Sigma$ keeping fix its homology. We will study the example $S^{3}\times\mathbb{R}$ with an exotic differential structure more carefully to show some implications for cosmology. Especially we obtain an interpretation of the transition in topology as dark energy. |
1602.03883 | Erminia Calabrese | Erminia Calabrese, Nicholas Battaglia, and David N. Spergel | Testing Gravity with Gravitational Wave Source Counts | minor updates to match the version accepted by Classical and Quantum
Gravity | null | 10.1088/0264-9381/33/16/165004 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the gravitational wave source counts distribution can test how
gravitational radiation propagates on cosmological scales. This test does not
require obtaining redshifts for the sources. If the signal-to-noise ratio (SNR,
$\rho$) from a gravitational wave source is proportional to the strain then it
falls as $R^{-1}$, thus we expect the source counts to follow $dN/d\rho \propto
\rho^{-4}$. However, if gravitational waves decay as they propagate or
propagate into other dimensions, then there can be deviations from this generic
prediction. We consider the possibility that the strain falls as $R^{-\gamma}$,
where $\gamma=1$ recovers the expected predictions in a Euclidean
uniformly-filled universe, and forecast the sensitivity of future observations
to deviations from standard General Relativity. We first consider the case of
few objects, 7 sources, with a signal-to-noise from 8 to 24, and impose a lower
limit on $\gamma$, finding $\gamma>0.33$ at $95\%$ confidence level. The
distribution of our simulated sample is very consistent with the distribution
of the trigger events reported by Advanced LIGO. Future measurements will
improve these constraints: with 100 events, we estimate that $\gamma$ can be
measured with an uncertainty of $15\%$. We generalize the formalism to account
for a range of chirp masses and the possibility that the signal falls as
$\exp(-R/R_0)/R^\gamma$.
| [
{
"created": "Thu, 11 Feb 2016 20:56:49 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Feb 2016 17:02:27 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Jun 2016 14:38:33 GMT",
"version": "v3"
}
] | 2016-07-27 | [
[
"Calabrese",
"Erminia",
""
],
[
"Battaglia",
"Nicholas",
""
],
[
"Spergel",
"David N.",
""
]
] | We show that the gravitational wave source counts distribution can test how gravitational radiation propagates on cosmological scales. This test does not require obtaining redshifts for the sources. If the signal-to-noise ratio (SNR, $\rho$) from a gravitational wave source is proportional to the strain then it falls as $R^{-1}$, thus we expect the source counts to follow $dN/d\rho \propto \rho^{-4}$. However, if gravitational waves decay as they propagate or propagate into other dimensions, then there can be deviations from this generic prediction. We consider the possibility that the strain falls as $R^{-\gamma}$, where $\gamma=1$ recovers the expected predictions in a Euclidean uniformly-filled universe, and forecast the sensitivity of future observations to deviations from standard General Relativity. We first consider the case of few objects, 7 sources, with a signal-to-noise from 8 to 24, and impose a lower limit on $\gamma$, finding $\gamma>0.33$ at $95\%$ confidence level. The distribution of our simulated sample is very consistent with the distribution of the trigger events reported by Advanced LIGO. Future measurements will improve these constraints: with 100 events, we estimate that $\gamma$ can be measured with an uncertainty of $15\%$. We generalize the formalism to account for a range of chirp masses and the possibility that the signal falls as $\exp(-R/R_0)/R^\gamma$. |
gr-qc/0307042 | Laurent Nottale | Laurent Nottale | The Pioneer anomalous acceleration: can we measure the cosmological
constant at the scale of the solar system ? | 12 pages, updated version, added references, result changed | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An anomalous constant acceleration of (8.7 \pm 1.3) x 10^-8 cm/s^2 directed
toward the Sun has been discovered by Anderson et al. in the motion of the
Pioneer 10/11 and Galileo spacecrafts. In parallel, the WMAP results have
definitively established the existence of a cosmological constant Lambda=1/
L_U^2, and therefore of an invariant cosmic length-scale L_U=(2.72 \pm 0.10)
Gpc. We show that the existence of this invariant scale definitively implements
Mach's principle in Einstein's theory of general relativity. Then we
demonstrate, in the framework of an exact cosmological solution of Einstein's
field equations which is valid both locally and globally, that the definition
of inertial systems ultimately depends on this length-scale. As a consequence,
usual local coordinates are not inertial, so that the motion of a free body of
speed v is expected to contain an additional constant acceleration
a_P=v^2(\surd3 L_U), which is, using the WMAP five years results, (6.02 \pm
0.34) x 10^-8 cm/s^2 when v \approx c. Such an effect is too small to
contribute significantly to the Pioneer acceleration (since v_Pioneer \approx
12 km/s << c), but could be possibly observed in a dedicated space mission.
| [
{
"created": "Wed, 9 Jul 2003 16:39:39 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 2011 15:36:45 GMT",
"version": "v2"
}
] | 2011-11-04 | [
[
"Nottale",
"Laurent",
""
]
] | An anomalous constant acceleration of (8.7 \pm 1.3) x 10^-8 cm/s^2 directed toward the Sun has been discovered by Anderson et al. in the motion of the Pioneer 10/11 and Galileo spacecrafts. In parallel, the WMAP results have definitively established the existence of a cosmological constant Lambda=1/ L_U^2, and therefore of an invariant cosmic length-scale L_U=(2.72 \pm 0.10) Gpc. We show that the existence of this invariant scale definitively implements Mach's principle in Einstein's theory of general relativity. Then we demonstrate, in the framework of an exact cosmological solution of Einstein's field equations which is valid both locally and globally, that the definition of inertial systems ultimately depends on this length-scale. As a consequence, usual local coordinates are not inertial, so that the motion of a free body of speed v is expected to contain an additional constant acceleration a_P=v^2(\surd3 L_U), which is, using the WMAP five years results, (6.02 \pm 0.34) x 10^-8 cm/s^2 when v \approx c. Such an effect is too small to contribute significantly to the Pioneer acceleration (since v_Pioneer \approx 12 km/s << c), but could be possibly observed in a dedicated space mission. |
2206.10417 | Claes Cramer | Claes Cramer | Classical Aspects of a Distributional 3+1 Foam Model | The model and the conclusions are not accurate! | null | null | null | gr-qc math-ph math.MP quant-ph | http://creativecommons.org/licenses/by/4.0/ | A 3+1 spacetime, with a shift vector that is the unique fundamental solution
to the linearized wave operator, is introduced to model an interpretation of
Wheeler's layman's analogy of the Quantum foam. To understand the
distributional aspects of this model is the guaranteed existence of a sequence
of compactly supported shift vectors that converge to the fundamental solution
used to introduce a sequence of 3+1 globally hyperbolic spacetimes. Using the
sequence of these causally stable spacetimes it is shown that there exists a
positive integer such that for all elements in the sequence with a greater
index value than this integer and for any Eulerian observer will the shift
vector increase more rapidly than any polynomial and the volume expansion is
more rapid than a polynomial in all directions. The same conclusion remains
valid for the trace of the extrinsic curvature. Nonetheless, it is shown, no
matter how volatile the extrinsic curvature is for these elements there also
exists elements in the other end of the sequence where the extrinsic curvature
is negligible and the spacetime flat.
| [
{
"created": "Tue, 21 Jun 2022 14:16:30 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Aug 2022 15:13:03 GMT",
"version": "v10"
},
{
"created": "Sat, 27 May 2023 04:39:39 GMT",
"version": "v11"
},
{
"created": "Wed, 22 Jun 2022 12:50:53 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Jun 2022 19:53:05 GMT",
"version": "v3"
},
{
"created": "Thu, 30 Jun 2022 20:56:19 GMT",
"version": "v4"
},
{
"created": "Mon, 11 Jul 2022 16:57:00 GMT",
"version": "v5"
},
{
"created": "Wed, 13 Jul 2022 16:35:24 GMT",
"version": "v6"
},
{
"created": "Mon, 18 Jul 2022 16:05:02 GMT",
"version": "v7"
},
{
"created": "Tue, 26 Jul 2022 11:39:13 GMT",
"version": "v8"
},
{
"created": "Mon, 1 Aug 2022 11:51:15 GMT",
"version": "v9"
}
] | 2023-05-30 | [
[
"Cramer",
"Claes",
""
]
] | A 3+1 spacetime, with a shift vector that is the unique fundamental solution to the linearized wave operator, is introduced to model an interpretation of Wheeler's layman's analogy of the Quantum foam. To understand the distributional aspects of this model is the guaranteed existence of a sequence of compactly supported shift vectors that converge to the fundamental solution used to introduce a sequence of 3+1 globally hyperbolic spacetimes. Using the sequence of these causally stable spacetimes it is shown that there exists a positive integer such that for all elements in the sequence with a greater index value than this integer and for any Eulerian observer will the shift vector increase more rapidly than any polynomial and the volume expansion is more rapid than a polynomial in all directions. The same conclusion remains valid for the trace of the extrinsic curvature. Nonetheless, it is shown, no matter how volatile the extrinsic curvature is for these elements there also exists elements in the other end of the sequence where the extrinsic curvature is negligible and the spacetime flat. |
2109.00330 | Surojit Dalui | Avijit Bera, Surojit Dalui, Subir Ghosh, Elias C. Vagenas | Quantum corrections enhance chaos: study of particle motion near a
generalized Schwarzschild black hole | 15 pages, 19 figures, revtex4, tltle changed, clarifications added,
now 4 appendices, no change in physics | Phys.Lett.B 829 (2022) 137033 | 10.1016/j.physletb.2022.137033 | null | gr-qc hep-th nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper is devoted to a detailed study of the effects of quantum
corrections on the chaotic behavior in the dynamics of a (massless) probe
particle near the horizon of a generalized Schwarzschild black hole. Two
possible origins inducing the modification of black hole metric are considered
separately; the noncommutative geometry inspired metric (suggested by Nicolini,
Smailagic and Spallucci) and the metric with quantum field theoretic
corrections (derived by Donoghue). Our results clearly show that in both cases,
the metric extensions favour chaotic behavior, namely chaos is attained for
relatively lower particle energy. This is demonstrated numerically by
exhibiting the breaking of the KAM tori in Poincar\'e sections of particle
trajectories and also via explicit computation of the (positive) Lyapunov
exponents of the trajectories.
| [
{
"created": "Wed, 1 Sep 2021 12:25:20 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Apr 2022 07:03:06 GMT",
"version": "v2"
}
] | 2022-04-08 | [
[
"Bera",
"Avijit",
""
],
[
"Dalui",
"Surojit",
""
],
[
"Ghosh",
"Subir",
""
],
[
"Vagenas",
"Elias C.",
""
]
] | The paper is devoted to a detailed study of the effects of quantum corrections on the chaotic behavior in the dynamics of a (massless) probe particle near the horizon of a generalized Schwarzschild black hole. Two possible origins inducing the modification of black hole metric are considered separately; the noncommutative geometry inspired metric (suggested by Nicolini, Smailagic and Spallucci) and the metric with quantum field theoretic corrections (derived by Donoghue). Our results clearly show that in both cases, the metric extensions favour chaotic behavior, namely chaos is attained for relatively lower particle energy. This is demonstrated numerically by exhibiting the breaking of the KAM tori in Poincar\'e sections of particle trajectories and also via explicit computation of the (positive) Lyapunov exponents of the trajectories. |
2012.08971 | Anil Yadav dr | Anil Kumar Yadav | Reexamining RHDE Models in FRW Universe with two IR cut-off with
redshift parametrization | 4 Pages, 1 Figure | Indian J. Physics 96, 3355 (2022) | 10.1007/s12648-021-02253-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have investigated that the gravitational field equations
are not compatible with conservation equation in Dixit et al.
\textcolor{blue}{[Dixit et al. Euro. Phys. J. Plus \textbf{135}, 831 (2020)]}.
Therefore, the expression for equation of state parameter along with the
dynamics of $\omega_{T}$ - $\omega_{T}^{\prime}$ plane does not reflect the
actual behaviors of RHDE models in $f(R,T)$ gravity and thus the method and
technique given in Dixit et al. \textcolor{blue}{[Dixit et al. Euro. Phys. J.
Plus \textbf{135}, 831 (2020)]} represents a fractured way for analyzing RHDE
models in $f(R,T)$. We also investigate that the derived Universe is in
decelerating phase of expansion for $0 \leq \beta \leq 1.5$ which is contrary
to the result obtained in above targeted paper.
| [
{
"created": "Tue, 15 Dec 2020 10:19:40 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jan 2021 07:43:29 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Jun 2021 05:06:04 GMT",
"version": "v3"
}
] | 2023-11-14 | [
[
"Yadav",
"Anil Kumar",
""
]
] | In this paper, we have investigated that the gravitational field equations are not compatible with conservation equation in Dixit et al. \textcolor{blue}{[Dixit et al. Euro. Phys. J. Plus \textbf{135}, 831 (2020)]}. Therefore, the expression for equation of state parameter along with the dynamics of $\omega_{T}$ - $\omega_{T}^{\prime}$ plane does not reflect the actual behaviors of RHDE models in $f(R,T)$ gravity and thus the method and technique given in Dixit et al. \textcolor{blue}{[Dixit et al. Euro. Phys. J. Plus \textbf{135}, 831 (2020)]} represents a fractured way for analyzing RHDE models in $f(R,T)$. We also investigate that the derived Universe is in decelerating phase of expansion for $0 \leq \beta \leq 1.5$ which is contrary to the result obtained in above targeted paper. |
gr-qc/0501083 | Daniel Pollack | James Isenberg, David Maxwell and Daniel Pollack | A gluing construction for non-vacuum solutions of the Einstein
constraint equations | null | Adv.Theor.Math.Phys. 9 (2005) 129-172 | null | null | gr-qc math.DG | null | We extend the conformal gluing construction of Isenberg-Mazzeo-Pollack [18]
by establishing an analogous gluing result for field theories obtained by
minimally coupling Einstein's gravitational theory with matter fields. We treat
classical fields such as perfect fluids and the Yang-Mills equations as well as
the Einstein-Vlasov system, which is an important example coming from kinetic
theory. In carrying out these extensions, we extend the conformal gluing
technique to higher dimensions and codify it in such a way as to make more
transparent where it can, and can not, be applied. In particular, we show
exactly what criteria need to be met in order to apply the construction, in its
present form, to any other non-vacuum field theory.
| [
{
"created": "Wed, 26 Jan 2005 22:24:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Isenberg",
"James",
""
],
[
"Maxwell",
"David",
""
],
[
"Pollack",
"Daniel",
""
]
] | We extend the conformal gluing construction of Isenberg-Mazzeo-Pollack [18] by establishing an analogous gluing result for field theories obtained by minimally coupling Einstein's gravitational theory with matter fields. We treat classical fields such as perfect fluids and the Yang-Mills equations as well as the Einstein-Vlasov system, which is an important example coming from kinetic theory. In carrying out these extensions, we extend the conformal gluing technique to higher dimensions and codify it in such a way as to make more transparent where it can, and can not, be applied. In particular, we show exactly what criteria need to be met in order to apply the construction, in its present form, to any other non-vacuum field theory. |
1011.2445 | Alexandre Filippov | A.T. Filippov | An old Einstein - Eddington generalized gravity and modern ideas on
branes and cosmology | 13 pages | null | 10.1142/9789814350198_0044 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly discuss new models of an `affine' theory of gravity in
multidimensional space-times with symmetric connections. We use and generalize
Einstein's proposal to specify the space-time geometry by use of the Hamilton
principle to determine the connection coefficients from a geometric Lagrangian
that is an arbitrary function of the generalized Ricci curvature tensor and of
other fundamental tensors. Such a theory supplements the standard Einstein
gravity with dark energy (the cosmological constant, in the first
approximation), a neutral massive (or tachyonic) vector field vecton, and
massive (or tachyonic) scalar fields. These fields couple only to gravity and
can generate dark matter and/or inflation. The concrete choice of the geometric
Lagrangian determines further details of the theory. The most natural geometric
models look similar to recently proposed brane models of cosmology usually
derived from string theory.
| [
{
"created": "Wed, 10 Nov 2010 17:51:18 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Filippov",
"A. T.",
""
]
] | We briefly discuss new models of an `affine' theory of gravity in multidimensional space-times with symmetric connections. We use and generalize Einstein's proposal to specify the space-time geometry by use of the Hamilton principle to determine the connection coefficients from a geometric Lagrangian that is an arbitrary function of the generalized Ricci curvature tensor and of other fundamental tensors. Such a theory supplements the standard Einstein gravity with dark energy (the cosmological constant, in the first approximation), a neutral massive (or tachyonic) vector field vecton, and massive (or tachyonic) scalar fields. These fields couple only to gravity and can generate dark matter and/or inflation. The concrete choice of the geometric Lagrangian determines further details of the theory. The most natural geometric models look similar to recently proposed brane models of cosmology usually derived from string theory. |
2306.17505 | Giulio Neri | Giulio Neri and Stefano Liberati | On the resilience of the gravitational variational principle under
renormalization | 27 pages | null | 10.1007/JHEP10(2023)054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A well-defined variational principle for gravitational actions typically
requires to cancel boundary terms produced by the variation of the bulk action
with a suitable set of boundary counterterms. This can be achieved by carefully
balancing the coefficients multiplying the bulk operators with those
multiplying the boundary ones. A typical example of this construction is the
Gibbons-Hawking-York boundary action that needs to be added to the
Einstein-Hilbert one in order to have a well-defined metric variation for
General Relativity with Dirichlet boundary conditions. Quantum fluctuations of
matter fields lead to the renormalization of said coefficients which may or may
not preserve this balance. Indeed, already at the level of General Relativity,
the resilience of the matching between bulk and boundary constants is far from
obvious and it is anyway incomplete given that matter generically induces
quadratic curvature operators. We investigate here the resilience of the
matching of higher-order couplings upon renormalization by a non-minimally
coupled scalar field and show that a problem is present. Even though we do not
completely solve the latter, we show that it can be greatly ameliorated by a
wise splitting between dynamical and topological contributions. Doing so, we
find that the bulk-boundary matching is preserved up to a universal term, whose
nature and possible cancellation we shall discuss in the end.
| [
{
"created": "Fri, 30 Jun 2023 09:36:39 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jul 2023 10:00:21 GMT",
"version": "v2"
}
] | 2024-04-29 | [
[
"Neri",
"Giulio",
""
],
[
"Liberati",
"Stefano",
""
]
] | A well-defined variational principle for gravitational actions typically requires to cancel boundary terms produced by the variation of the bulk action with a suitable set of boundary counterterms. This can be achieved by carefully balancing the coefficients multiplying the bulk operators with those multiplying the boundary ones. A typical example of this construction is the Gibbons-Hawking-York boundary action that needs to be added to the Einstein-Hilbert one in order to have a well-defined metric variation for General Relativity with Dirichlet boundary conditions. Quantum fluctuations of matter fields lead to the renormalization of said coefficients which may or may not preserve this balance. Indeed, already at the level of General Relativity, the resilience of the matching between bulk and boundary constants is far from obvious and it is anyway incomplete given that matter generically induces quadratic curvature operators. We investigate here the resilience of the matching of higher-order couplings upon renormalization by a non-minimally coupled scalar field and show that a problem is present. Even though we do not completely solve the latter, we show that it can be greatly ameliorated by a wise splitting between dynamical and topological contributions. Doing so, we find that the bulk-boundary matching is preserved up to a universal term, whose nature and possible cancellation we shall discuss in the end. |
gr-qc/0011084 | Alejandro Corichi | Alejandro Corichi and Daniel Sudarsky (ICN-UNAM) | Hair from the Isolated Horizon Perspective | 5 pages, no figures. To be published in the proceedings of the 9th
Marcel Grossmann Meeting | null | null | ICN-UNAM-00/15 | gr-qc | null | The recently introduced Isolated Horizons (IH) formalism has become a
powerful tool for realistic black hole physics. In particular, it generalizes
the zeroth and first laws of black hole mechanics in terms of quasi-local
quantities and serves as a starting point for quantum entropy calculations. In
this note we consider theories which admit hair, and analyze some new results
that the IH provides, when considering solitons and stationary solutions.
Furthermore, the IH formalism allows to state uniqueness conjectures (i.e.
horizon `no-hair conjectures') for the existence of solutions.
| [
{
"created": "Thu, 23 Nov 2000 23:25:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Corichi",
"Alejandro",
"",
"ICN-UNAM"
],
[
"Sudarsky",
"Daniel",
"",
"ICN-UNAM"
]
] | The recently introduced Isolated Horizons (IH) formalism has become a powerful tool for realistic black hole physics. In particular, it generalizes the zeroth and first laws of black hole mechanics in terms of quasi-local quantities and serves as a starting point for quantum entropy calculations. In this note we consider theories which admit hair, and analyze some new results that the IH provides, when considering solitons and stationary solutions. Furthermore, the IH formalism allows to state uniqueness conjectures (i.e. horizon `no-hair conjectures') for the existence of solutions. |
gr-qc/0205029 | Homer G. Ellis | Homer G. Ellis | Space-Time--Time | 29 pages, AMSTeX. This is the original (long) version that
gr-qc/0107023 is based on | null | null | null | gr-qc | null | Space-time--time is a natural hybrid of Kaluza's five-dimensional geometry
and Weyl's conformal space-time geometry. Translations along the secondary time
dimension produce the electromagnetic gauge transformations of Kaluza--Klein
theory and the metric gauge transformations of Weyl theory, related as Weyl
postulated. Geometrically, this phenomenon resides in an exponential-expansion
producing ``conformality constraint'', which replaces Kaluza's ``cylinder
condition''. The curvature tensors exhibit a wealth of ``interactions'' among
geometrical entities with physical interpretations. Unique to the conformally
constrained geometry is a sectionally isotropic, ultralocally determined
``residual curvature'', useful in construction of an action density for field
equations. A space-time--time geodesic describes a test particle whose rest
mass m and electric charge q evolve according to definite laws. The particls's
motion is governed by four apparent forces: the Einstein gravitational force,
the Lorentz electromagnetic force, a force proportional to the electromagnetic
potential, and a force proportional to a gradient d(ln phi), where the scalar
field phi is essentially the space-time--time residual radius of curvature. The
particle appears suddenly at an event E1 with q = -phi(E1) and vanishes at an
event E2 with q = phi(E2). At E1 and E2 the phi-force infinitely dominates the
others, causing E1 and E2 to tend to occur near where phi has an extreme value;
application to the modeling of orbital transitions of atomic electrons suggests
itself. The equivalence of a test particle's inertial mass and its passive
gravitational mass follows from the gravitational force's proportionality to m.
No connection is apparent between m and active gravitational mass or between q
and active electric charge, nor does the theory seem to require any.
| [
{
"created": "Wed, 8 May 2002 01:51:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ellis",
"Homer G.",
""
]
] | Space-time--time is a natural hybrid of Kaluza's five-dimensional geometry and Weyl's conformal space-time geometry. Translations along the secondary time dimension produce the electromagnetic gauge transformations of Kaluza--Klein theory and the metric gauge transformations of Weyl theory, related as Weyl postulated. Geometrically, this phenomenon resides in an exponential-expansion producing ``conformality constraint'', which replaces Kaluza's ``cylinder condition''. The curvature tensors exhibit a wealth of ``interactions'' among geometrical entities with physical interpretations. Unique to the conformally constrained geometry is a sectionally isotropic, ultralocally determined ``residual curvature'', useful in construction of an action density for field equations. A space-time--time geodesic describes a test particle whose rest mass m and electric charge q evolve according to definite laws. The particls's motion is governed by four apparent forces: the Einstein gravitational force, the Lorentz electromagnetic force, a force proportional to the electromagnetic potential, and a force proportional to a gradient d(ln phi), where the scalar field phi is essentially the space-time--time residual radius of curvature. The particle appears suddenly at an event E1 with q = -phi(E1) and vanishes at an event E2 with q = phi(E2). At E1 and E2 the phi-force infinitely dominates the others, causing E1 and E2 to tend to occur near where phi has an extreme value; application to the modeling of orbital transitions of atomic electrons suggests itself. The equivalence of a test particle's inertial mass and its passive gravitational mass follows from the gravitational force's proportionality to m. No connection is apparent between m and active gravitational mass or between q and active electric charge, nor does the theory seem to require any. |
1405.7249 | Cosimo Bambi | Yue Liu, Daniele Malafarina, Leonardo Modesto, Cosimo Bambi | Singularity avoidance in quantum-inspired inhomogeneous dust collapse | 8 pages, 5 figures. v2: refereed version | Phys. Rev. D 90, 044040 (2014) | 10.1103/PhysRevD.90.044040 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a previous paper, some of us studied general relativistic homogeneous
gravitational collapses for dust and radiation, in which the density profile
was replaced by an effective density justified by some quantum gravity models.
It was found that the effective density introduces an effective pressure that
becomes negative and dominant in the strong-field regime. With this set-up, the
central singularity is replaced by a bounce, after which the cloud starts
expanding. Motivated by the fact that in the classical case homogeneous and
inhomogeneous collapse models have different properties, here we extend our
previous work to the inhomogeneous case. As in the quantum-inspired homogeneous
collapse model, the classical central singularity is replaced by a bounce, but
the inhomogeneities strongly affect the structure of the bounce curve and of
the trapped region.
| [
{
"created": "Wed, 28 May 2014 14:14:51 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Aug 2014 16:19:27 GMT",
"version": "v2"
}
] | 2014-08-19 | [
[
"Liu",
"Yue",
""
],
[
"Malafarina",
"Daniele",
""
],
[
"Modesto",
"Leonardo",
""
],
[
"Bambi",
"Cosimo",
""
]
] | In a previous paper, some of us studied general relativistic homogeneous gravitational collapses for dust and radiation, in which the density profile was replaced by an effective density justified by some quantum gravity models. It was found that the effective density introduces an effective pressure that becomes negative and dominant in the strong-field regime. With this set-up, the central singularity is replaced by a bounce, after which the cloud starts expanding. Motivated by the fact that in the classical case homogeneous and inhomogeneous collapse models have different properties, here we extend our previous work to the inhomogeneous case. As in the quantum-inspired homogeneous collapse model, the classical central singularity is replaced by a bounce, but the inhomogeneities strongly affect the structure of the bounce curve and of the trapped region. |
0906.4263 | Kourosh Nozari | Kourosh Nozari and Narges Rashidi | Modified GBIG Scenario as an Alternative for Dark Energy | 16 pages, 6 figures, Accepted for publication in JCAP | JCAP 0909:014,2009 | 10.1088/1475-7516/2009/09/014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a DGP-inspired braneworld model where induced gravity on the
brane is modified in the spirit of $f(R)$ gravity and stringy effects are taken
into account by incorporation of the Gauss-Bonnet term in the bulk action. We
explore cosmological dynamics of this model and we show that this scenario is a
successful alternative for dark energy proposal. Interestingly, it realizes the
phantom-like behavior without introduction of any phantom field on the brane
and the effective equation of state parameter crosses the cosmological constant
line naturally in the same way as observational data suggest.
| [
{
"created": "Tue, 23 Jun 2009 13:52:05 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Sep 2009 08:53:42 GMT",
"version": "v2"
}
] | 2009-09-28 | [
[
"Nozari",
"Kourosh",
""
],
[
"Rashidi",
"Narges",
""
]
] | We construct a DGP-inspired braneworld model where induced gravity on the brane is modified in the spirit of $f(R)$ gravity and stringy effects are taken into account by incorporation of the Gauss-Bonnet term in the bulk action. We explore cosmological dynamics of this model and we show that this scenario is a successful alternative for dark energy proposal. Interestingly, it realizes the phantom-like behavior without introduction of any phantom field on the brane and the effective equation of state parameter crosses the cosmological constant line naturally in the same way as observational data suggest. |
0804.3075 | Benjamin Knispel | B. Knispel and B. Allen | Blandford's Argument: The Strongest Continuous Gravitational Wave Signal | 12 pages, 6 Figures, published in Phys. Rev. D, v3: final published
version | Phys.Rev.D78:044031,2008 | 10.1103/PhysRevD.78.044031 | AEI-2008-027 | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a uniform population of neutron stars whose spin-down is dominated by the
emission of gravitational radiation, an old argument of Blandford states that
the expected gravitational-wave amplitude of the nearest source is independent
of the deformation and rotation frequency of the objects. Recent work has
improved and extended this argument to set upper limits on the expected
amplitude from neutron stars that also emit electromagnetic radiation. We
restate these arguments in a more general framework, and simulate the evolution
of such a population of stars in the gravitational potential of our galaxy. The
simulations allow us to test the assumptions of Blandford's argument on a
realistic model of our galaxy. We show that the two key assumptions of the
argument (two dimensionality of the spatial distribution and a steady-state
frequency distribution) are in general not fulfilled. The effective scaling
dimension D of the spatial distribution of neutron stars is significantly
larger than two, and for frequencies detectable by terrestrial instruments the
frequency distribution is not in a steady state unless the ellipticity is
unrealistically large. Thus, in the cases of most interest, the maximum
expected gravitational-wave amplitude does have a strong dependence on the
deformation and rotation frequency of the population. The results strengthen
the previous upper limits on the expected gravitational-wave amplitude from
neutron stars by a factor of 6 for realistic values of ellipticity.
| [
{
"created": "Fri, 18 Apr 2008 18:01:35 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Apr 2008 06:24:39 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Aug 2008 07:12:55 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Knispel",
"B.",
""
],
[
"Allen",
"B.",
""
]
] | For a uniform population of neutron stars whose spin-down is dominated by the emission of gravitational radiation, an old argument of Blandford states that the expected gravitational-wave amplitude of the nearest source is independent of the deformation and rotation frequency of the objects. Recent work has improved and extended this argument to set upper limits on the expected amplitude from neutron stars that also emit electromagnetic radiation. We restate these arguments in a more general framework, and simulate the evolution of such a population of stars in the gravitational potential of our galaxy. The simulations allow us to test the assumptions of Blandford's argument on a realistic model of our galaxy. We show that the two key assumptions of the argument (two dimensionality of the spatial distribution and a steady-state frequency distribution) are in general not fulfilled. The effective scaling dimension D of the spatial distribution of neutron stars is significantly larger than two, and for frequencies detectable by terrestrial instruments the frequency distribution is not in a steady state unless the ellipticity is unrealistically large. Thus, in the cases of most interest, the maximum expected gravitational-wave amplitude does have a strong dependence on the deformation and rotation frequency of the population. The results strengthen the previous upper limits on the expected gravitational-wave amplitude from neutron stars by a factor of 6 for realistic values of ellipticity. |
2303.11232 | Dishari Malakar | Dishari Malakar, K Rajesh Nayak | Possibility of Over-spinning Kerr Blackhole | 6 pages, 4 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We have developed a methodology to test the age-old cosmic censorship
hypothesis in Kerr geometry. We have shown that the Kerr black hole can be
overspun by particles captured from the innermost stable circular orbit.
However, it appears that this does not happen for particles coming from
infinity. We have also observed that overspinning becomes possible only when
the black hole approaches a near-extremal limit, which approaches as we
increase the black hole's mass. Our study demonstrates that an extremal black
hole cannot be overspun. However, our methodology neglects backreaction and
self-force effects, which could affect the overspinning.
| [
{
"created": "Mon, 20 Mar 2023 16:12:43 GMT",
"version": "v1"
}
] | 2023-03-21 | [
[
"Malakar",
"Dishari",
""
],
[
"Nayak",
"K Rajesh",
""
]
] | We have developed a methodology to test the age-old cosmic censorship hypothesis in Kerr geometry. We have shown that the Kerr black hole can be overspun by particles captured from the innermost stable circular orbit. However, it appears that this does not happen for particles coming from infinity. We have also observed that overspinning becomes possible only when the black hole approaches a near-extremal limit, which approaches as we increase the black hole's mass. Our study demonstrates that an extremal black hole cannot be overspun. However, our methodology neglects backreaction and self-force effects, which could affect the overspinning. |
2111.09494 | Georgios Mavrogiannis | Georgios Mavrogiannis | Morawetz estimates without relative degeneration and exponential decay
on Schwarzschild-de Sitter spacetimes | 29 pages, 4 figures | null | 10.1007/s00023-023-01293-2 | null | gr-qc math-ph math.AP math.MP | http://creativecommons.org/licenses/by/4.0/ | We use a novel physical space method to prove relatively non-degenerate
integrated energy estimates for the wave equation on subextremal
Schwarzschild-de Sitter spacetimes with parameters $(M,\Lambda)$. These are
integrated decay statements whose bulk energy density, though degenerate at
highest order, is everywhere comparable to the energy density of the boundary
fluxes. As a corollary, we prove that solutions of the wave equation decay
exponentially on the exterior region.
The main ingredients are a previous Morawetz estimate of Dafermos-Rodnianski
and an additional argument based on commutation with a vector field which can
be expressed in the form
$r\sqrt{1-\frac{2M}{r}-\frac{\Lambda}{3}r^2}\frac{\partial}{\partial r}$, where
$\partial_r$ here denotes the coordinate vector field corresponding to a well
chosen system of hyperboloidal coordinates.
Our argument gives exponential decay also for small first order perturbations
of the wave operator. In the limit $\Lambda=0$, our commutation corresponds to
the one introduced by Holzegel-Kauffman.
| [
{
"created": "Thu, 18 Nov 2021 03:10:36 GMT",
"version": "v1"
}
] | 2023-08-09 | [
[
"Mavrogiannis",
"Georgios",
""
]
] | We use a novel physical space method to prove relatively non-degenerate integrated energy estimates for the wave equation on subextremal Schwarzschild-de Sitter spacetimes with parameters $(M,\Lambda)$. These are integrated decay statements whose bulk energy density, though degenerate at highest order, is everywhere comparable to the energy density of the boundary fluxes. As a corollary, we prove that solutions of the wave equation decay exponentially on the exterior region. The main ingredients are a previous Morawetz estimate of Dafermos-Rodnianski and an additional argument based on commutation with a vector field which can be expressed in the form $r\sqrt{1-\frac{2M}{r}-\frac{\Lambda}{3}r^2}\frac{\partial}{\partial r}$, where $\partial_r$ here denotes the coordinate vector field corresponding to a well chosen system of hyperboloidal coordinates. Our argument gives exponential decay also for small first order perturbations of the wave operator. In the limit $\Lambda=0$, our commutation corresponds to the one introduced by Holzegel-Kauffman. |
gr-qc/0309131 | Eugen Radu | Dumitru Astefanesei, Eugen Radu | Boson stars with negative cosmological constant | 33 pages, 14 eps figures; to be published in Nucl. Phys. B | Nucl.Phys. B665 (2003) 594-622 | 10.1016/S0550-3213(03)00482-6 | FREIBURG-THEP-03-15 | gr-qc hep-th | null | We consider boson star solutions in a $D$-dimensional, asymptotically anti-de
Sitter spacetime and investigate the influence of the cosmological term on
their properties. We find that for $D>4$ the boson star properties are close to
those in four dimensions with a vanishing cosmological constant. A different
behavior is noticed for the solutions in the three dimensional case. We
establish also the non-existence of static, spherically symmetric black holes
with a harmonically time-dependent complex scalar field in any dimension
greater than two.
| [
{
"created": "Mon, 29 Sep 2003 12:46:41 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Astefanesei",
"Dumitru",
""
],
[
"Radu",
"Eugen",
""
]
] | We consider boson star solutions in a $D$-dimensional, asymptotically anti-de Sitter spacetime and investigate the influence of the cosmological term on their properties. We find that for $D>4$ the boson star properties are close to those in four dimensions with a vanishing cosmological constant. A different behavior is noticed for the solutions in the three dimensional case. We establish also the non-existence of static, spherically symmetric black holes with a harmonically time-dependent complex scalar field in any dimension greater than two. |
gr-qc/0404030 | Giovanni Montani | Giovanni Montani | A Scenario for the Dimensional Compactification in Eleven-Dimensional
Space-Time | 8 pages, no figures, to appear on Int. Journal of Mod. Phys. D | Int.J.Mod.Phys. D13 (2004) 1029-1036 | 10.1142/S0218271804004967 | null | gr-qc astro-ph | null | We discuss the inhomogeneous multidimensional mixmaster model in view of
appearing, near the cosmological singularity, a scenario for the dimensional
compactification in correspondence to an 11-dimensional space-time. Our
analysis candidates such a collapsing picture toward the singularity to
describe the actual expanding 3-dimensional Universe and an associated
collapsed 7-dimensional space. To this end, a conformal factor is determined in
front of the 4-dimensional metric to remove the 4-curvature divergences and the
resulting Universe expands with a power-law.inflation. Thus we provide an
additional peculiarity of the eleven space-time dimensions in view of
implementing a geometrical theory of unification.
| [
{
"created": "Wed, 7 Apr 2004 09:56:57 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Montani",
"Giovanni",
""
]
] | We discuss the inhomogeneous multidimensional mixmaster model in view of appearing, near the cosmological singularity, a scenario for the dimensional compactification in correspondence to an 11-dimensional space-time. Our analysis candidates such a collapsing picture toward the singularity to describe the actual expanding 3-dimensional Universe and an associated collapsed 7-dimensional space. To this end, a conformal factor is determined in front of the 4-dimensional metric to remove the 4-curvature divergences and the resulting Universe expands with a power-law.inflation. Thus we provide an additional peculiarity of the eleven space-time dimensions in view of implementing a geometrical theory of unification. |
1811.10303 | Alfonso Garc\'ia-Parrado G\'omez-Lobo Dr. | Alfonso Garc\'ia-Parrado and Filipe C. Mena | Gravitational radiation and the evolution of gravitational collapse in
cylindrical symmetry | 15 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Sparling form and a geometric construction adapted to spacetimes
with a 2-dimensional isometry group, we analyse a quasi-local measure of
gravitational energy. We then study the gravitational radiation through
spacetime junctions in cylindrically symmetric models of gravitational collapse
to singularities. The models result from the matching of collapsing dust fluids
interiors with gravitational wave exteriors, given by the Einstein-Rosen type
solutions. For a given choice of a frame adapted to the symmetry of the
matching hypersurface, we are able to compute the total gravitational energy
radiated during the collapse and state whether the gravitational radiation is
incoming or outgoing, in each case. This also enables us to distinguish whether
a gravitational collapse is being enhanced by the gravitational radiation.
| [
{
"created": "Mon, 26 Nov 2018 11:44:16 GMT",
"version": "v1"
}
] | 2018-11-27 | [
[
"García-Parrado",
"Alfonso",
""
],
[
"Mena",
"Filipe C.",
""
]
] | Using the Sparling form and a geometric construction adapted to spacetimes with a 2-dimensional isometry group, we analyse a quasi-local measure of gravitational energy. We then study the gravitational radiation through spacetime junctions in cylindrically symmetric models of gravitational collapse to singularities. The models result from the matching of collapsing dust fluids interiors with gravitational wave exteriors, given by the Einstein-Rosen type solutions. For a given choice of a frame adapted to the symmetry of the matching hypersurface, we are able to compute the total gravitational energy radiated during the collapse and state whether the gravitational radiation is incoming or outgoing, in each case. This also enables us to distinguish whether a gravitational collapse is being enhanced by the gravitational radiation. |
1002.1129 | Shankaranarayanan S | Saurya Das, S. Shankaranarayanan, Sourav Sur | Entanglement and corrections to Bekenstein-Hawking entropy | 3 Pages, 1 Figure, Talk given by SSh at the 12th Marcel Grossmann
meeting | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this talk, we focus on the corrections to Bekenstein-Hawking entropy by
associating it with the entanglement between degrees of freedom inside and
outside the horizon. Using numerical techniques, we show that the corrections
proportional to fractional power of area result when the field is in a
superposition of ground and excited states. We explain this result by
identifying that the degrees of freedom contributing to such corrections are
different from those contributing to Bekenstein-Hawking entropy.
| [
{
"created": "Fri, 5 Feb 2010 05:51:03 GMT",
"version": "v1"
}
] | 2010-03-05 | [
[
"Das",
"Saurya",
""
],
[
"Shankaranarayanan",
"S.",
""
],
[
"Sur",
"Sourav",
""
]
] | In this talk, we focus on the corrections to Bekenstein-Hawking entropy by associating it with the entanglement between degrees of freedom inside and outside the horizon. Using numerical techniques, we show that the corrections proportional to fractional power of area result when the field is in a superposition of ground and excited states. We explain this result by identifying that the degrees of freedom contributing to such corrections are different from those contributing to Bekenstein-Hawking entropy. |
2308.06941 | Bivudutta Mishra Dr. | Abhilipsa Sahoo, S.K. Tripathy, B. Mishra, Saibal Ray | Casimir wormhole with GUP correction in extended symmetric teleparallel
gravity | 14 pages, 7 figures | Eur. Phys. J. C (2024) 84:325 | 10.1140/epjc/s10052-024-12638-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum mechanical concept such as the Casimir effect is explored to model
traversable wormholes in an extended teleparallel gravity theory. The minimal
length concept leading to the generalized uncertainty principle (GUP) is used
to obtain the Casimir energy density. The effect of the GUP correction in the
geometrical and physical properties of traversable Casimir wormholes are
investigated. It is noted that the GUP correction has a substantial effect on
the wormhole geometry and it modifies the energy condition. From a detailed
calculation of the exotic matter content of the GUP corrected Casimir wormhole,
it is shown that, a minimal amount of exotic matter is sufficient to support
the stability of the wormhole.
| [
{
"created": "Mon, 14 Aug 2023 05:16:15 GMT",
"version": "v1"
}
] | 2024-04-09 | [
[
"Sahoo",
"Abhilipsa",
""
],
[
"Tripathy",
"S. K.",
""
],
[
"Mishra",
"B.",
""
],
[
"Ray",
"Saibal",
""
]
] | Quantum mechanical concept such as the Casimir effect is explored to model traversable wormholes in an extended teleparallel gravity theory. The minimal length concept leading to the generalized uncertainty principle (GUP) is used to obtain the Casimir energy density. The effect of the GUP correction in the geometrical and physical properties of traversable Casimir wormholes are investigated. It is noted that the GUP correction has a substantial effect on the wormhole geometry and it modifies the energy condition. From a detailed calculation of the exotic matter content of the GUP corrected Casimir wormhole, it is shown that, a minimal amount of exotic matter is sufficient to support the stability of the wormhole. |
1305.7374 | J. Navarro-Salas | Aitor Landete, Jose Navarro-Salas and Francisco Torrenti | Adiabatic regularization for spin-1/2 fields | A new section has been added | Physical Review D (Rapid Communications) 061501(R), 2013 | 10.1103/PhysRevD.88.061501 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the adiabatic regularization method to spin-1/2 fields. The ansatz
for the adiabatic expansion for fermionic modes differs significantly from the
WKB-type template that works for scalar modes. We give explicit expressions for
the first adiabatic orders and analyze particle creation in de Sitter
spacetime. As for scalar fields, the adiabatic method can be distinguished by
its capability to overcome the UV divergences of the particle number operator.
We also test the consistency of the extended method by working out the
conformal and axial anomalies for a Dirac field in a FLRW spacetime, in exact
agreement with those obtained from other renormalization prescriptions. We
finally show its power by computing the renormalized stress-energy tensor for
Dirac fermions in de Sitter space.
| [
{
"created": "Fri, 31 May 2013 12:06:48 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Sep 2013 06:19:05 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Landete",
"Aitor",
""
],
[
"Navarro-Salas",
"Jose",
""
],
[
"Torrenti",
"Francisco",
""
]
] | We extend the adiabatic regularization method to spin-1/2 fields. The ansatz for the adiabatic expansion for fermionic modes differs significantly from the WKB-type template that works for scalar modes. We give explicit expressions for the first adiabatic orders and analyze particle creation in de Sitter spacetime. As for scalar fields, the adiabatic method can be distinguished by its capability to overcome the UV divergences of the particle number operator. We also test the consistency of the extended method by working out the conformal and axial anomalies for a Dirac field in a FLRW spacetime, in exact agreement with those obtained from other renormalization prescriptions. We finally show its power by computing the renormalized stress-energy tensor for Dirac fermions in de Sitter space. |
gr-qc/0309004 | Scott Funkhouser | Scott Funkhouser | An Inertial Reaction to Cosmological Accelerations | 3 pages; 1 Fig.; removed section on Sciama's force law; no change in
main result | null | null | null | gr-qc astro-ph | null | Mach's "fixed stars" are actually not fixed at all. The distant clusters of
galaxies are not only receding from each observer but they are also
accelerating since the rate of cosmological expansion is not constant. If the
distant cosmic masses in someway constitute the frame of inertial reference
then an additional force should be generated among local bodies in reaction to
the apparent cosmological accelerations of the distant galaxies.
| [
{
"created": "Mon, 1 Sep 2003 13:33:43 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Sep 2003 16:38:49 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Sep 2003 05:53:28 GMT",
"version": "v3"
},
{
"created": "Wed, 12 Jan 2005 00:48:24 GMT",
"version": "v4"
},
{
"created": "Tue, 17 May 2005 04:47:40 GMT",
"version": "v5"
}
] | 2007-05-23 | [
[
"Funkhouser",
"Scott",
""
]
] | Mach's "fixed stars" are actually not fixed at all. The distant clusters of galaxies are not only receding from each observer but they are also accelerating since the rate of cosmological expansion is not constant. If the distant cosmic masses in someway constitute the frame of inertial reference then an additional force should be generated among local bodies in reaction to the apparent cosmological accelerations of the distant galaxies. |
1702.00478 | Omar Edel Nu\~nez Soltero | J. Socorro and Omar E. N\'u\~nez | Scalar potentials with Multi-scalar fields from quantum cosmology and
supersymmetric quantum mechanics | 12 pages, send for reviewing to The European Physical Journal Plus on
January 2017 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Multi-scalar field cosmology of the anisotropic Bianchi type I model is
used in order to construct a family of potentials that are the best suited to
model the inflation phenomenon. We employ the quantum potential approach to
quantum mechanics due to Bohm in order to solve the corresponding
Wheeler-DeWitt equation; which in turn enables us to restrict sensibly the
aforementioned family of potentials. Supersymmetric Quantum Mechanics (SUSYQM)
is also employed in order to constrain the superpotential function, at the same
time the tools from SUSY Quantum Mechanics are used to test the family of
potentials in order to infer which is the most convenient for the inflation
epoch. For completeness solutions to the wave function of the universe are also
presented.
| [
{
"created": "Wed, 1 Feb 2017 22:17:33 GMT",
"version": "v1"
}
] | 2017-02-03 | [
[
"Socorro",
"J.",
""
],
[
"Núñez",
"Omar E.",
""
]
] | The Multi-scalar field cosmology of the anisotropic Bianchi type I model is used in order to construct a family of potentials that are the best suited to model the inflation phenomenon. We employ the quantum potential approach to quantum mechanics due to Bohm in order to solve the corresponding Wheeler-DeWitt equation; which in turn enables us to restrict sensibly the aforementioned family of potentials. Supersymmetric Quantum Mechanics (SUSYQM) is also employed in order to constrain the superpotential function, at the same time the tools from SUSY Quantum Mechanics are used to test the family of potentials in order to infer which is the most convenient for the inflation epoch. For completeness solutions to the wave function of the universe are also presented. |
1008.4763 | Mubasher Jamil | M.R. Setare and Mubasher Jamil | Statefinder diagnostic and stability of modified gravity consistent with
holographic and new agegraphic dark energy | 12 pages, 2 figures, accepted by Gen. Relativ. Gravit | Gen. Relativ. Gravit. (2011) 43:293-303 | 10.1007/s10714-010-1087-0 | arXiv:1008.4763v1 [gr-qc] | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently one of us derived the action of modified gravity consistent with the
holographic and new-agegraphic dark energy. In this paper, we investigate the
stability of the Lagrangians of the modified gravity as discussed in [M. R.
Setare, Int. J. Mod. Phys. D 17 (2008) 2219; M. R. Setare, Astrophys. Space
Sci. 326 (2010) 27]. We also calculate the statefinder parameters which
classify our dark energy model.
| [
{
"created": "Fri, 27 Aug 2010 16:53:43 GMT",
"version": "v1"
}
] | 2011-01-04 | [
[
"Setare",
"M. R.",
""
],
[
"Jamil",
"Mubasher",
""
]
] | Recently one of us derived the action of modified gravity consistent with the holographic and new-agegraphic dark energy. In this paper, we investigate the stability of the Lagrangians of the modified gravity as discussed in [M. R. Setare, Int. J. Mod. Phys. D 17 (2008) 2219; M. R. Setare, Astrophys. Space Sci. 326 (2010) 27]. We also calculate the statefinder parameters which classify our dark energy model. |
0812.0864 | Molin Liu | Molin Liu, Yuanxing Gui and Hongya Liu | Quantum Statistical Entropy and Minimal Length of 5D Ricci-flat Black
String with Generalized Uncertainty Principle | 11pages and this work is dedicated to the memory of Professor Hongya
Liu | Phys.Rev.D78:124003,2008 | 10.1103/PhysRevD.78.124003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the quantum statistical entropy in a 5D Ricci-flat
black string solution, which contains a 4D Schwarzschild-de Sitter black hole
on the brane, by using the improved thin-layer method with the generalized
uncertainty principle. The entropy is the linear sum of the areas of the event
horizon and the cosmological horizon without any cut-off and any constraint on
the bulk's configuration rather than the usual uncertainty principle. The
system's density of state and free energy are convergent in the neighborhood of
horizon. The small-mass approximation is determined by the asymptotic behavior
of metric function near horizons. Meanwhile, we obtain the minimal length of
the position $\Delta x$ which is restrained by the surface gravities and the
thickness of layer near horizons.
| [
{
"created": "Thu, 4 Dec 2008 05:42:27 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Liu",
"Molin",
""
],
[
"Gui",
"Yuanxing",
""
],
[
"Liu",
"Hongya",
""
]
] | In this paper, we study the quantum statistical entropy in a 5D Ricci-flat black string solution, which contains a 4D Schwarzschild-de Sitter black hole on the brane, by using the improved thin-layer method with the generalized uncertainty principle. The entropy is the linear sum of the areas of the event horizon and the cosmological horizon without any cut-off and any constraint on the bulk's configuration rather than the usual uncertainty principle. The system's density of state and free energy are convergent in the neighborhood of horizon. The small-mass approximation is determined by the asymptotic behavior of metric function near horizons. Meanwhile, we obtain the minimal length of the position $\Delta x$ which is restrained by the surface gravities and the thickness of layer near horizons. |
2311.08341 | Ernesto Contreras | J. Palacios, A. Di Teodoro, E. fuenmayor and E. Contreras | A fractional matter sector for general relativity | null | Eur. Phys. J. C 83, 894 (2023) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we construct a fractional matter sector for general relativity.
In particular, we propose a suitable fractional anisotropy function relating
both the tangential and radial pressure of a spherically symmetric fluid based
on the Gr\"unwald-Letnikov fractional derivative. The system is closed by
implementing the polytropic equation of state for the radial pressure. We solve
the system of integro-differential equations by Euler's method and explore the
behavior of the physical quantities, namely, the normalized density energy, the
normalized mass function, and the compactness.
| [
{
"created": "Tue, 14 Nov 2023 17:36:33 GMT",
"version": "v1"
}
] | 2023-11-15 | [
[
"Palacios",
"J.",
""
],
[
"Di Teodoro",
"A.",
""
],
[
"fuenmayor",
"E.",
""
],
[
"Contreras",
"E.",
""
]
] | In this work, we construct a fractional matter sector for general relativity. In particular, we propose a suitable fractional anisotropy function relating both the tangential and radial pressure of a spherically symmetric fluid based on the Gr\"unwald-Letnikov fractional derivative. The system is closed by implementing the polytropic equation of state for the radial pressure. We solve the system of integro-differential equations by Euler's method and explore the behavior of the physical quantities, namely, the normalized density energy, the normalized mass function, and the compactness. |
1506.08384 | Johannes Th\"urigen | Johannes Th\"urigen | Group field theories generating polyhedral complexes | accepted for publication in PoS, Frontiers of Fundamental Physics 14
(AMU Marseille) | PoS(FFP14)177, 2015 | 10.22323/1.224.0177 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Group field theories are a generalization of matrix models which provide both
a second quantized reformulation of loop quantum gravity as well as generating
functions for spin foam models. While states in canonical loop quantum gravity,
in the traditional continuum setting, are based on graphs with vertices of
arbitrary valence, group field theories have been defined so far in a
simplicial setting such that states have support only on graphs of fixed
valency. This has led to the question whether group field theory can indeed
cover the whole state space of loop quantum gravity. In this contribution based
on [1] I present two new classes of group field theories which satisfy this
objective: i) a straightforward, but rather formal generalization to multiple
fields, one for each valency and ii) a simplicial group field theory which
effectively covers the larger state space through a dual weighting, a technique
common in matrix and tensor models. To this end I will further discuss in some
detail the combinatorial structure of the complexes generated by the group
field theory partition function. The new group field theories do not only
strengthen the links between the mentioned quantum gravity approaches but,
broadening the theory space of group field theories, they might also prove
useful in the investigation of renormalizability.
| [
{
"created": "Sun, 28 Jun 2015 11:38:37 GMT",
"version": "v1"
}
] | 2018-08-01 | [
[
"Thürigen",
"Johannes",
""
]
] | Group field theories are a generalization of matrix models which provide both a second quantized reformulation of loop quantum gravity as well as generating functions for spin foam models. While states in canonical loop quantum gravity, in the traditional continuum setting, are based on graphs with vertices of arbitrary valence, group field theories have been defined so far in a simplicial setting such that states have support only on graphs of fixed valency. This has led to the question whether group field theory can indeed cover the whole state space of loop quantum gravity. In this contribution based on [1] I present two new classes of group field theories which satisfy this objective: i) a straightforward, but rather formal generalization to multiple fields, one for each valency and ii) a simplicial group field theory which effectively covers the larger state space through a dual weighting, a technique common in matrix and tensor models. To this end I will further discuss in some detail the combinatorial structure of the complexes generated by the group field theory partition function. The new group field theories do not only strengthen the links between the mentioned quantum gravity approaches but, broadening the theory space of group field theories, they might also prove useful in the investigation of renormalizability. |
0903.2438 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Quantum cosmic censor: gravitation makes reality undecidable | 3 Pages, This essay received an honorable mention from the Gravity
Research Foundation essay competition in 2008 | Int. J. Mod. Phys. D17, 2535-2538 (2008) | 10.1142/S0218271808014047 | LSU-REL031309 | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When one takes into account gravitation, the measurement of space and time
cannot be carried out with infinite accuracy. When quantum mechanics is
reformulated taking into account this lack of accuracy, the resolution of the
measurement problem can be implemented via decoherence without the usual
pitfalls. The resulting theory has the same physical predictions of quantum
mechanics with a reduction postulate, but is radically different, with the
quantum states evolving unitarily in terms of the underlying variables.
Gravitation therefore makes this worrisome situation, potentially leading to
two completely different views of reality, irrelevant from an empirical point
of view. It may however be highly relevant from a philosophical point of view.
| [
{
"created": "Fri, 13 Mar 2009 17:25:45 GMT",
"version": "v1"
}
] | 2009-03-16 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | When one takes into account gravitation, the measurement of space and time cannot be carried out with infinite accuracy. When quantum mechanics is reformulated taking into account this lack of accuracy, the resolution of the measurement problem can be implemented via decoherence without the usual pitfalls. The resulting theory has the same physical predictions of quantum mechanics with a reduction postulate, but is radically different, with the quantum states evolving unitarily in terms of the underlying variables. Gravitation therefore makes this worrisome situation, potentially leading to two completely different views of reality, irrelevant from an empirical point of view. It may however be highly relevant from a philosophical point of view. |
0808.3701 | Kourosh Nozari | Kourosh Nozari and Mahin Pourghasemi | Crossing the Phantom Divide Line in a DGP-Inspired $F(R,\phi)$-Gravity | 23 Pages, 10 figs, Submitted to JCAP | JCAP 10 (2008) 044 | 10.1088/1475-7516/2008/10/044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study possible crossing of the phantom divide line in a DGP-inspired
$F(R,\phi)$ braneworld scenario where scalar field and curvature quintessence
are treated in a unified framework. With some specific form of $F(R,\phi)$ and
by adopting a suitable ansatz, we show that there are appropriate regions of
the parameters space which account for late-time acceleration and admit
crossing of the phantom divide line.
| [
{
"created": "Wed, 27 Aug 2008 13:22:34 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Nozari",
"Kourosh",
""
],
[
"Pourghasemi",
"Mahin",
""
]
] | We study possible crossing of the phantom divide line in a DGP-inspired $F(R,\phi)$ braneworld scenario where scalar field and curvature quintessence are treated in a unified framework. With some specific form of $F(R,\phi)$ and by adopting a suitable ansatz, we show that there are appropriate regions of the parameters space which account for late-time acceleration and admit crossing of the phantom divide line. |
1708.06310 | Salvatore Capozziello | Sebastian Bahamonde, Salvatore Capozziello, and Konstantinos F.
Dialektopoulos | Constraining Generalized Non-local Cosmology from Noether Symmetries | 15 pages, to be published in Eur.Phys.J. C | null | 10.1140/epjc/s10052-017-5283-x | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a generalized nonlocal theory of gravity which, in specific limits,
can become either the curvature non-local or teleparallel non-local theory.
Using the Noether Symmetry Approach, we find that the coupling functions coming
from the non-local terms are constrained to be either exponential or linear in
form. It is well known that in some non-local theories, a certain kind of
exponential non-local couplings are needed in order to achieve a renormalizable
theory. In this paper, we explicitly show that this kind of coupling does not
need to by introduced by hand, instead, it appears naturally from the
symmetries of the Lagrangian in flat Friedmann-Robertson-Walker cosmology.
Finally, we find de-Sitter and power law cosmological solutions for different
nonlocal theories. The symmetries for the generalized non-local theory is also
found and some cosmological solutions are also achieved under the full theory.
| [
{
"created": "Mon, 21 Aug 2017 16:15:09 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Oct 2017 07:28:50 GMT",
"version": "v2"
}
] | 2017-11-22 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Dialektopoulos",
"Konstantinos F.",
""
]
] | We study a generalized nonlocal theory of gravity which, in specific limits, can become either the curvature non-local or teleparallel non-local theory. Using the Noether Symmetry Approach, we find that the coupling functions coming from the non-local terms are constrained to be either exponential or linear in form. It is well known that in some non-local theories, a certain kind of exponential non-local couplings are needed in order to achieve a renormalizable theory. In this paper, we explicitly show that this kind of coupling does not need to by introduced by hand, instead, it appears naturally from the symmetries of the Lagrangian in flat Friedmann-Robertson-Walker cosmology. Finally, we find de-Sitter and power law cosmological solutions for different nonlocal theories. The symmetries for the generalized non-local theory is also found and some cosmological solutions are also achieved under the full theory. |
2407.09914 | Liu Zhao | Yifan Cai, Tao Wang and Liu Zhao | Fluctuation theorems in general relativistic stochastic thermodynamics | 30 pages, 2 figures. v2: fixed a typo and updated the detail of a
reference | null | null | null | gr-qc cond-mat.stat-mech | http://creativecommons.org/licenses/by/4.0/ | Based on the recently proposed framework of general relativistic stochastic
mechanics and stochastic thermodynamics at the ensemble level, this work
focuses on general relativistic stochastic thermodynamics at the trajectory
level. The first law of stochastic thermodynamics is reformulated and the
fluctuation theorems are proved on this level, with emphasis on maintaining
fully general covariance and on the choice of observers.
| [
{
"created": "Sat, 13 Jul 2024 15:16:26 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jul 2024 10:46:49 GMT",
"version": "v2"
}
] | 2024-07-17 | [
[
"Cai",
"Yifan",
""
],
[
"Wang",
"Tao",
""
],
[
"Zhao",
"Liu",
""
]
] | Based on the recently proposed framework of general relativistic stochastic mechanics and stochastic thermodynamics at the ensemble level, this work focuses on general relativistic stochastic thermodynamics at the trajectory level. The first law of stochastic thermodynamics is reformulated and the fluctuation theorems are proved on this level, with emphasis on maintaining fully general covariance and on the choice of observers. |
1310.0023 | Joao Morais | Joao Morais, Mariam Bouhmadi-Lopez, Alfredo B. Henriques | The energy spectrum of gravitational waves in a loop quantum
cosmological model | 8 pages, 4 figures. RevTex4-1 Expanded version. Version accepted in
PRD | Phys. Rev. D 89, 023513 (2014) | 10.1103/PhysRevD.89.023513 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the consequences of loop quantum cosmology (inverse-volume
corrections) in the spectrum of the gravitational waves using the method of the
Bogoliubov coefficients. These corrections are taken into account at the
background level of the theory as well as at the first order in the
perturbations theory framework. We show that these corrections lead to an
intense graviton production during the loop super-inflationary phase prior to
the standard slow-roll era, which leave their imprints through new features on
the energy spectrum of the gravitational waves as would be measured today,
including a new maximum on the low frequency end of the spectrum.
| [
{
"created": "Mon, 30 Sep 2013 20:00:17 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Dec 2013 13:27:12 GMT",
"version": "v2"
}
] | 2014-01-22 | [
[
"Morais",
"Joao",
""
],
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Henriques",
"Alfredo B.",
""
]
] | We explore the consequences of loop quantum cosmology (inverse-volume corrections) in the spectrum of the gravitational waves using the method of the Bogoliubov coefficients. These corrections are taken into account at the background level of the theory as well as at the first order in the perturbations theory framework. We show that these corrections lead to an intense graviton production during the loop super-inflationary phase prior to the standard slow-roll era, which leave their imprints through new features on the energy spectrum of the gravitational waves as would be measured today, including a new maximum on the low frequency end of the spectrum. |
2301.08876 | Pardyumn Kumar Sahoo | Gaurav N. Gadbail, Simran Arora, P.K. Sahoo | Reconstruction of $f(Q,T)$ Lagrangian for various cosmological scenario | PLB published version | Physics Letters B, 838 (2023) 137710 | 10.1016/j.physletb.2023.137710 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The variety of theories that can account for the dark energy phenomenon
encourages current research to concentrate on a more in-depth examination of
the potential impacts of modified gravity on both local and cosmic scales. We
discuss some cosmological reconstruction in $f(Q,T)$ cosmology (where $Q$ is
the non-metricity scalar, and $T$ is the trace of the energy-momentum tensor)
corresponding to the evolution background in
Friedmann-La\^imatre-Robertson-Walker (FLRW) universe. This helps us to
determine how any FLRW cosmology can arise from a specific $f(Q,T)$ theory. We
use the reconstruction technique to derive explicit forms of $f(Q,T)$
Lagrangian for the different kinds of matter sources and Einstein's static
universe. We also formulate the models using several ansatz forms of the
$f(Q,T)$ function for $p=\omega \rho$. We demonstrate that several classes of
$f(Q,T)$ theories admit the power-law and de-Sitter solutions in some ranges of
$\omega$. Additionally, we reconstruct the cosmological model for the scalar
field with a specific form of $f(Q,T)$. These new models with cosmological
inspiration may impact gravitational phenomena at other cosmological scales.
| [
{
"created": "Sat, 21 Jan 2023 03:46:05 GMT",
"version": "v1"
}
] | 2023-01-27 | [
[
"Gadbail",
"Gaurav N.",
""
],
[
"Arora",
"Simran",
""
],
[
"Sahoo",
"P. K.",
""
]
] | The variety of theories that can account for the dark energy phenomenon encourages current research to concentrate on a more in-depth examination of the potential impacts of modified gravity on both local and cosmic scales. We discuss some cosmological reconstruction in $f(Q,T)$ cosmology (where $Q$ is the non-metricity scalar, and $T$ is the trace of the energy-momentum tensor) corresponding to the evolution background in Friedmann-La\^imatre-Robertson-Walker (FLRW) universe. This helps us to determine how any FLRW cosmology can arise from a specific $f(Q,T)$ theory. We use the reconstruction technique to derive explicit forms of $f(Q,T)$ Lagrangian for the different kinds of matter sources and Einstein's static universe. We also formulate the models using several ansatz forms of the $f(Q,T)$ function for $p=\omega \rho$. We demonstrate that several classes of $f(Q,T)$ theories admit the power-law and de-Sitter solutions in some ranges of $\omega$. Additionally, we reconstruct the cosmological model for the scalar field with a specific form of $f(Q,T)$. These new models with cosmological inspiration may impact gravitational phenomena at other cosmological scales. |
2401.01821 | Francisco Lobo | Ednaldo L. B. Junior, Jos\'e Tarciso S. S. Junior, Francisco S. N.
Lobo, Manuel E. Rodrigues, Lu\'is F. Dias da Silva, Henrique A. Vieira | Observations on the massive particle surface method | 15 pages, 1 figure; comments are welcome | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geodesic method has played a crucial role in understanding the circular
orbits generated by compact objects, culminating in the definition of the
photon sphere, which was later generalized to a photon surface in arbitrary
spacetimes. This new formulation extends the concept of the photon sphere in a
broader sense, including dynamical spacetimes, as shown by the Vaidya solution.
The photon surface essentially defines the null geodesics, which are originally
tangent to the temporal surface, and keeps them confined to this surface.
However, this formalism does not cover all classes of particles, and to
overcome this limitation, a more comprehensive approach, denoted as the
"massive particle surface", has been proposed that also accounts for charged
massive particles. Indeed, the photon surface concept is recovered when the
charge and mass of the particles are zero. In this work, we use these three
formalisms to check the consistency of the results for the values of the radius
of the photon sphere ($r_{ps}$) and the radius of the "innermost stable
circular orbit" (ISCO) ($r_{\rm ISCO}$) for some gravitational models. In our
results, the first model is described by conformal gravity, with the
peculiarity that $g_{00}\neq-g_{11}^{-1}$. The second model, i.e. the Culetu
solution, is developed by coupling General Relativity with nonlinear
electrodynamics, which requires the consideration of the effective metric
($g_{\rm eff}^{\mu\nu}$) for geodesic approaches. Furthermore, we have also
analysed the expressions for $r_{ps}$ and $r_{\rm ISCO}$ in a general static
and spherically symmetric metric. Under these circumstances, we have found a
discrepancy of $r_{ps}$ and $r_{\rm ISCO}$ obtained by the massive particle
surface formalism as compared to the geodesic and photon surface formalisms.
| [
{
"created": "Wed, 3 Jan 2024 16:28:05 GMT",
"version": "v1"
}
] | 2024-01-04 | [
[
"Junior",
"Ednaldo L. B.",
""
],
[
"Junior",
"José Tarciso S. S.",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Rodrigues",
"Manuel E.",
""
],
[
"da Silva",
"Luís F. Dias",
""
],
[
"Vieira",
"Henrique A.",
""
]
] | The geodesic method has played a crucial role in understanding the circular orbits generated by compact objects, culminating in the definition of the photon sphere, which was later generalized to a photon surface in arbitrary spacetimes. This new formulation extends the concept of the photon sphere in a broader sense, including dynamical spacetimes, as shown by the Vaidya solution. The photon surface essentially defines the null geodesics, which are originally tangent to the temporal surface, and keeps them confined to this surface. However, this formalism does not cover all classes of particles, and to overcome this limitation, a more comprehensive approach, denoted as the "massive particle surface", has been proposed that also accounts for charged massive particles. Indeed, the photon surface concept is recovered when the charge and mass of the particles are zero. In this work, we use these three formalisms to check the consistency of the results for the values of the radius of the photon sphere ($r_{ps}$) and the radius of the "innermost stable circular orbit" (ISCO) ($r_{\rm ISCO}$) for some gravitational models. In our results, the first model is described by conformal gravity, with the peculiarity that $g_{00}\neq-g_{11}^{-1}$. The second model, i.e. the Culetu solution, is developed by coupling General Relativity with nonlinear electrodynamics, which requires the consideration of the effective metric ($g_{\rm eff}^{\mu\nu}$) for geodesic approaches. Furthermore, we have also analysed the expressions for $r_{ps}$ and $r_{\rm ISCO}$ in a general static and spherically symmetric metric. Under these circumstances, we have found a discrepancy of $r_{ps}$ and $r_{\rm ISCO}$ obtained by the massive particle surface formalism as compared to the geodesic and photon surface formalisms. |
gr-qc/9510001 | Grisha Volovik | G.E. Volovik (Low Temperature Laboratory, Helsinki University of
Technology, Finland and L.D. Landau Institute for Theoretical Physics,
Moscow, Russia) | Is there analogy between quantized vortex and black hole? | Revised to improve clarity and physical content 27 pages, LaTeX file,
3 figures are available at
ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-95006.ps | null | null | LTL-95006 | gr-qc | null | An attempt is made to promote an analogy between quantized vortex in
condensed matter and black hole: both compact objects have fermion zero modes
which induce the finite temperature of these objects. The motion of the
quantized vortex lines in Fermi superfluids and superconductors leads to the
spectral flow of fermion zero mode. This results in finite temperature and
entropy of the moving vortex. The tunneling transition rate between the
fermionic levels under the influence of the vortex motion suggests the
effective temperature of the vortex core $T_{\rm eff}=(2/\pi) p_Fv_L$, where
$v_L$ is the velocity of the vortex with respect to the heat bath reference
frame and $p_F$ the Fermi momentum. This is an analogue of the Unruh
temperature of the accelerating object in the relativistic system. For the
vortex ring with the radius $R$ this leads to the Hawking type temperature
$T_{\rm vortex~ring}=(\hbar v_F / 2\pi R) \ln (R/r_c)$, where $v_F$ is the
Fermi velocity and $r_c$ is the radius of the vortex core. The corresponding
"Hawking" entropy of the vortex ring of radius $R$ and area $A=\pi R^2$ appears
to be ${\cal S}_{\rm vortex ~ring}=(1/6) A p_F^2$. Similar expression but with
different numerical factor is obtained for the instanton action for the quantum
nucleation of the vortex loop from the homogeneous vacuum, and also for the
"Bekenstein" entropy obtained by counting the number of fermionic bound states
which appear when the vortex loop is created. For the superfluid $^3$He-A,
where some components of the order parameter play the part of the gravitational
field, the Fermi momentum $p_F$ corresponds to the Planck scale for this
effective gravity. The effective action for the gravity field is obtained after
integration over the fermion fields in correspondence with the Sakharov
| [
{
"created": "Mon, 2 Oct 1995 16:20:32 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Nov 1995 14:54:40 GMT",
"version": "v2"
}
] | 2009-09-25 | [
[
"Volovik",
"G. E.",
"",
"Low Temperature Laboratory, Helsinki University of\n Technology, Finland and L.D. Landau Institute for Theoretical Physics,\n Moscow, Russia"
]
] | An attempt is made to promote an analogy between quantized vortex in condensed matter and black hole: both compact objects have fermion zero modes which induce the finite temperature of these objects. The motion of the quantized vortex lines in Fermi superfluids and superconductors leads to the spectral flow of fermion zero mode. This results in finite temperature and entropy of the moving vortex. The tunneling transition rate between the fermionic levels under the influence of the vortex motion suggests the effective temperature of the vortex core $T_{\rm eff}=(2/\pi) p_Fv_L$, where $v_L$ is the velocity of the vortex with respect to the heat bath reference frame and $p_F$ the Fermi momentum. This is an analogue of the Unruh temperature of the accelerating object in the relativistic system. For the vortex ring with the radius $R$ this leads to the Hawking type temperature $T_{\rm vortex~ring}=(\hbar v_F / 2\pi R) \ln (R/r_c)$, where $v_F$ is the Fermi velocity and $r_c$ is the radius of the vortex core. The corresponding "Hawking" entropy of the vortex ring of radius $R$ and area $A=\pi R^2$ appears to be ${\cal S}_{\rm vortex ~ring}=(1/6) A p_F^2$. Similar expression but with different numerical factor is obtained for the instanton action for the quantum nucleation of the vortex loop from the homogeneous vacuum, and also for the "Bekenstein" entropy obtained by counting the number of fermionic bound states which appear when the vortex loop is created. For the superfluid $^3$He-A, where some components of the order parameter play the part of the gravitational field, the Fermi momentum $p_F$ corresponds to the Planck scale for this effective gravity. The effective action for the gravity field is obtained after integration over the fermion fields in correspondence with the Sakharov |
1111.6025 | Nigel Bishop | P.J. van der Walt and N.T. Bishop | Observational cosmology using characteristic numerical relativity:
Characteristic formalism on null geodesics | 18 pages, 9 figures, 1 Table. arXiv admin note: some text overlap
with arXiv:some 1007.3189 | null | 10.1103/PhysRevD.85.044016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The characteristic formalism of numerical relativity is based on a system of
coordinates aligned with outgoing null cones. While these coordinates were
designed for studying gravitational waves, they can also be easily adapted to
model cosmological past null cones (PNCs). Similar to observational coordinates
in the observational approach to cosmology, this then provides a model that
only makes use of information causally connected to an observer. However, the
diameter distance, which is used as a radial coordinate, limits the model's
cosmological application to the region prior to the PNC refocussing. This is
because after refocussing, the diameter distance ceases to be a unique measure
of distance. This paper addresses the problem by introducing a metric based on
the Bondi-Sachs metric where the radial coordinate is replaced by an affine
parameter. A model is derived from this metric and it is then shown how an
existing numerical scheme can be adapted for simulation of cosmological PNC
behaviour. Numerical calculations on this model are found to have the same
stability and convergence properties as the standard characteristic formalism.
| [
{
"created": "Fri, 25 Nov 2011 15:33:45 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"van der Walt",
"P. J.",
""
],
[
"Bishop",
"N. T.",
""
]
] | The characteristic formalism of numerical relativity is based on a system of coordinates aligned with outgoing null cones. While these coordinates were designed for studying gravitational waves, they can also be easily adapted to model cosmological past null cones (PNCs). Similar to observational coordinates in the observational approach to cosmology, this then provides a model that only makes use of information causally connected to an observer. However, the diameter distance, which is used as a radial coordinate, limits the model's cosmological application to the region prior to the PNC refocussing. This is because after refocussing, the diameter distance ceases to be a unique measure of distance. This paper addresses the problem by introducing a metric based on the Bondi-Sachs metric where the radial coordinate is replaced by an affine parameter. A model is derived from this metric and it is then shown how an existing numerical scheme can be adapted for simulation of cosmological PNC behaviour. Numerical calculations on this model are found to have the same stability and convergence properties as the standard characteristic formalism. |
1602.04764 | John Ellis | John Ellis, Nick E. Mavromatos, Dimitri V. Nanopoulos | Comments on Graviton Propagation in Light of GW150914 | 9 pages, no figures; v2 contains additional description and a Noted
Added about constraints from GW151226 | Mod. Phys. Lett. A, Vol. 31, No. 26 (2016) 1650155 | 10.1142/S0217732316750018 | KCL-PH-TH/2016-06, LCTS/2016-04, CERN-TH/2016-032, ACT-02-16,
MI-TH-1608 | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observation of gravitational waves from the Laser Interferometer
Gravitational-Wave Observatory (LIGO) event GW150914 may be used to constrain
the possibility of Lorentz violation in graviton propagation, and the
observation by the Fermi Gamma-Ray Burst Monitor of a transient source in
apparent coincidence may be used to constrain the difference between the
velocities of light and gravitational waves: $c_g - c_\gamma < 10^{-17}$.
| [
{
"created": "Mon, 15 Feb 2016 18:52:37 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jun 2016 16:44:46 GMT",
"version": "v2"
}
] | 2016-08-03 | [
[
"Ellis",
"John",
""
],
[
"Mavromatos",
"Nick E.",
""
],
[
"Nanopoulos",
"Dimitri V.",
""
]
] | The observation of gravitational waves from the Laser Interferometer Gravitational-Wave Observatory (LIGO) event GW150914 may be used to constrain the possibility of Lorentz violation in graviton propagation, and the observation by the Fermi Gamma-Ray Burst Monitor of a transient source in apparent coincidence may be used to constrain the difference between the velocities of light and gravitational waves: $c_g - c_\gamma < 10^{-17}$. |
1404.3163 | Gilberto Medeiros Kremer | Marlos O. Ribas, Pedro Zambianchi Jr., Fernando P. Devecchi and
Gilberto M. Kremer | Exit from accelerated regimes by symmetry breaking in a universe filled
with fermionic and bosonic sources | 9 pages, 2 figures, to be published in Modern Physics Letters A | Mod. Phys. Lett. A, Vol. 29, No. 17 (2014) 1450086 | 10.1142/S0217732314500862 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate a universe filled with a fermionic field and a
complex scalar field, exchanging energy through a Yukawa potential; the model
encodes a symmetry breaking mechanism (on the bosonic sector). In a first case,
when the mechanism is not included, the cosmological model furnishes a pure
accelerated regime. In a second case, when including the symmetry breaking
mechanism, we verify that the fermion and one of the bosons, of Higgs type,
become massive, while the other boson is massless. Besides, the mechanism shows
to be responsible for a transition from an accelerated to a decelerated regime,
which certifies the importance, in cosmological terms, of its role. After
symmetry breaking, the total pressure of the fields change its sign from
negative to positive corresponding to the accelerated-decelerated transition.
For large times the universe becomes a dust (pressureless) dominated Universe.
| [
{
"created": "Fri, 11 Apr 2014 17:33:53 GMT",
"version": "v1"
}
] | 2014-05-23 | [
[
"Ribas",
"Marlos O.",
""
],
[
"Zambianchi",
"Pedro",
"Jr."
],
[
"Devecchi",
"Fernando P.",
""
],
[
"Kremer",
"Gilberto M.",
""
]
] | In this work we investigate a universe filled with a fermionic field and a complex scalar field, exchanging energy through a Yukawa potential; the model encodes a symmetry breaking mechanism (on the bosonic sector). In a first case, when the mechanism is not included, the cosmological model furnishes a pure accelerated regime. In a second case, when including the symmetry breaking mechanism, we verify that the fermion and one of the bosons, of Higgs type, become massive, while the other boson is massless. Besides, the mechanism shows to be responsible for a transition from an accelerated to a decelerated regime, which certifies the importance, in cosmological terms, of its role. After symmetry breaking, the total pressure of the fields change its sign from negative to positive corresponding to the accelerated-decelerated transition. For large times the universe becomes a dust (pressureless) dominated Universe. |
gr-qc/0512135 | R. R. Cuzinatto | R. Aldrovandi, R. R. Cuzinatto and L. G. Medeiros | Cosmic Acceleration from Elementary Interactions | 4 pages, 3 figures, 1 table | null | null | null | gr-qc | null | It is possible to generate an accelerated period of expansion from reasonable
potentials acting between the universe particle constituents. The pressure of
primordial nucleons interacting via a simple nuclear potential is obtained via
Mayer's cluster expansion technique. The attractive part of the potential
engenders a negative pressure and may therefore be responsible for the cosmic
acceleration.
| [
{
"created": "Thu, 22 Dec 2005 20:27:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Aldrovandi",
"R.",
""
],
[
"Cuzinatto",
"R. R.",
""
],
[
"Medeiros",
"L. G.",
""
]
] | It is possible to generate an accelerated period of expansion from reasonable potentials acting between the universe particle constituents. The pressure of primordial nucleons interacting via a simple nuclear potential is obtained via Mayer's cluster expansion technique. The attractive part of the potential engenders a negative pressure and may therefore be responsible for the cosmic acceleration. |
gr-qc/9307023 | Adam Helfer | Adam D. Helfer | How to Estimate Energy Lost to Gravitational Waves (revised) | 12 pages, plain Tex | Phys.Rev. D48 (1993) 3625-3629 | 10.1103/PhysRevD.48.3625 | null | gr-qc | null | The energy--momentum radiated in gravitational waves by an isolated source is
given by a formula of Bondi. This formula is highly non--local: the
energy--momentum is not given as the integral of a well--defined local density.
It has therefore been unclear whether the Bondi formula can be used to get
information from gravity--wave measurements. In this note, we obtain, from
local knowledge of the radiation field, a lower bound on the Bondi flux.
| [
{
"created": "Mon, 19 Jul 1993 16:18:39 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Helfer",
"Adam D.",
""
]
] | The energy--momentum radiated in gravitational waves by an isolated source is given by a formula of Bondi. This formula is highly non--local: the energy--momentum is not given as the integral of a well--defined local density. It has therefore been unclear whether the Bondi formula can be used to get information from gravity--wave measurements. In this note, we obtain, from local knowledge of the radiation field, a lower bound on the Bondi flux. |
gr-qc/0210028 | Naoki Seto | Naoki Seto | Effects of finite arm-length of LISA on analysis of gravitational waves
from MBH binaries | 10 pages, 3 figures, to appear in Phys.Rev.D | Phys.Rev. D66 (2002) 122001 | 10.1103/PhysRevD.66.122001 | null | gr-qc astro-ph | null | Response of an interferometer becomes complicated for gravitational wave
shorter than the arm-length of the detector, as nature of wave appears
strongly. We have studied how parameter estimation for merging massive black
hole binaries are affected by this complicated effect in the case of LISA. It
is shown that three dimensional positions of some binaries might be determined
much better than the past estimations that use the long wave approximation. For
equal mass binaries this improvement is most prominent at $\sim 10^5\sol$.
| [
{
"created": "Wed, 9 Oct 2002 12:00:59 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Seto",
"Naoki",
""
]
] | Response of an interferometer becomes complicated for gravitational wave shorter than the arm-length of the detector, as nature of wave appears strongly. We have studied how parameter estimation for merging massive black hole binaries are affected by this complicated effect in the case of LISA. It is shown that three dimensional positions of some binaries might be determined much better than the past estimations that use the long wave approximation. For equal mass binaries this improvement is most prominent at $\sim 10^5\sol$. |
gr-qc/0505082 | Badri Krishnan | Curt Cutler, Iraj Gholami and Badri Krishnan | Improved Stack-Slide Searches for Gravitational-Wave Pulsars | 19 pages, 7 figures, RevTeX 4 | Phys.Rev. D72 (2005) 042004 | 10.1103/PhysRevD.72.042004 | AEI-2005-104 | gr-qc | null | We formulate and optimize a computational search strategy for detecting
gravitational waves from isolated, previously-unknown neutron stars (that is,
neutron stars with unknown sky positions, spin frequencies, and spin-down
parameters). It is well known that fully coherent searches over the relevant
parameter-space volumes are not computationally feasible, and so more
computationally efficient methods are called for. The first step in this
direction was taken by Brady & Creighton (2000), who proposed and optimized a
two-stage, stack-slide search algorithm. We generalize and otherwise improve
upon the Brady-Creighton scheme in several ways. Like Brady & Creighton, we
consider a stack-slide scheme, but here with an arbitrary number of
semi-coherent stages and with a coherent follow-up stage at the end. We find
that searches with three semi-coherent stages are significantly more efficient
than two-stage searches (requiring about 2-5 times less computational power for
the same sensitivity) and are only slightly less efficient than searches with
four or more stages. We calculate the signal-to-noise ratio required for
detection, as a function of computing power and neutron star spin-down-age,
using our optimized searches.
| [
{
"created": "Tue, 17 May 2005 14:15:47 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Cutler",
"Curt",
""
],
[
"Gholami",
"Iraj",
""
],
[
"Krishnan",
"Badri",
""
]
] | We formulate and optimize a computational search strategy for detecting gravitational waves from isolated, previously-unknown neutron stars (that is, neutron stars with unknown sky positions, spin frequencies, and spin-down parameters). It is well known that fully coherent searches over the relevant parameter-space volumes are not computationally feasible, and so more computationally efficient methods are called for. The first step in this direction was taken by Brady & Creighton (2000), who proposed and optimized a two-stage, stack-slide search algorithm. We generalize and otherwise improve upon the Brady-Creighton scheme in several ways. Like Brady & Creighton, we consider a stack-slide scheme, but here with an arbitrary number of semi-coherent stages and with a coherent follow-up stage at the end. We find that searches with three semi-coherent stages are significantly more efficient than two-stage searches (requiring about 2-5 times less computational power for the same sensitivity) and are only slightly less efficient than searches with four or more stages. We calculate the signal-to-noise ratio required for detection, as a function of computing power and neutron star spin-down-age, using our optimized searches. |
2006.06735 | Jorge Ovalle | J. Ovalle, R. Casadio, E. Contreras, A. Sotomayor | Hairy black holes by gravitational decoupling | 11 pages, 4 figures | null | 10.1016/j.dark.2020.100744 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes with hair represented by generic fields surrounding the central
source of the vacuum Schwarzschild metric are examined under the minimal set of
requirements consisting of i) the existence of a well defined event horizon and
ii) the strong or dominant energy condition for the hair outside the horizon.
We develop our analysis by means of the gravitational decoupling approach. We
find that trivial deformations of the seed Schwarzschild vacuum preserve the
energy conditions and provide a new mechanism to evade the no-hair theorem
based on a primary hair associated with the charge generating these
transformations. Under the above conditions i) and ii), this charge
consistently increases the entropy from the minimum value given by the
Schwarzschild geometry. As a direct application, we find a non-trivial
extension of the Reissner-Nordstrom black hole showing a surprisingly simple
horizon. Finally, the non-linear electrodynamics generating this new solution
is fully specified.
| [
{
"created": "Thu, 11 Jun 2020 18:50:35 GMT",
"version": "v1"
}
] | 2020-11-17 | [
[
"Ovalle",
"J.",
""
],
[
"Casadio",
"R.",
""
],
[
"Contreras",
"E.",
""
],
[
"Sotomayor",
"A.",
""
]
] | Black holes with hair represented by generic fields surrounding the central source of the vacuum Schwarzschild metric are examined under the minimal set of requirements consisting of i) the existence of a well defined event horizon and ii) the strong or dominant energy condition for the hair outside the horizon. We develop our analysis by means of the gravitational decoupling approach. We find that trivial deformations of the seed Schwarzschild vacuum preserve the energy conditions and provide a new mechanism to evade the no-hair theorem based on a primary hair associated with the charge generating these transformations. Under the above conditions i) and ii), this charge consistently increases the entropy from the minimum value given by the Schwarzschild geometry. As a direct application, we find a non-trivial extension of the Reissner-Nordstrom black hole showing a surprisingly simple horizon. Finally, the non-linear electrodynamics generating this new solution is fully specified. |
2105.13860 | Rodrigo Tenorio | Rodrigo Tenorio, David Keitel, Alicia M. Sintes | Application of a hierarchical MCMC follow-up to Advanced LIGO continuous
gravitational-wave candidates | 23 pages, 15 figures, matches PRD published version | Phys. Rev. D 104, 084012 (2021) | 10.1103/PhysRevD.104.084012 | LIGO-P2100187 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first application of a hierarchical Markov Chain Monte Carlo
(MCMC) follow-up on continuous gravitational-wave candidates from real-data
searches. The follow-up uses an MCMC sampler to draw parameter-space points
from the posterior distribution, constructed using the matched-filter as a
log-likelihood. As outliers are narrowed down, coherence time increases,
imposing more restrictive phase-evolution templates. We introduce a novel Bayes
factor to compare results from different stages: The signal hypothesis is
derived from first principles, while the noise hypothesis uses extreme value
theory to derive a background model. The effectiveness of our proposal is
evaluated on fake Gaussian data and applied to a set of 30 outliers produced by
different continuous wave searches on O2 Advanced LIGO data. The results of our
analysis suggest all but five outliers are inconsistent with an astrophysical
origin under the standard continuous wave signal model. We successfully ascribe
four of the surviving outliers to instrumental artifacts and a strong hardware
injection present in the data. The behavior of the fifth outlier suggests an
instrumental origin as well, but we could not relate it to any known
instrumental cause.
| [
{
"created": "Fri, 28 May 2021 14:12:57 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Sep 2021 09:11:35 GMT",
"version": "v2"
},
{
"created": "Fri, 1 Oct 2021 15:53:06 GMT",
"version": "v3"
}
] | 2021-10-04 | [
[
"Tenorio",
"Rodrigo",
""
],
[
"Keitel",
"David",
""
],
[
"Sintes",
"Alicia M.",
""
]
] | We present the first application of a hierarchical Markov Chain Monte Carlo (MCMC) follow-up on continuous gravitational-wave candidates from real-data searches. The follow-up uses an MCMC sampler to draw parameter-space points from the posterior distribution, constructed using the matched-filter as a log-likelihood. As outliers are narrowed down, coherence time increases, imposing more restrictive phase-evolution templates. We introduce a novel Bayes factor to compare results from different stages: The signal hypothesis is derived from first principles, while the noise hypothesis uses extreme value theory to derive a background model. The effectiveness of our proposal is evaluated on fake Gaussian data and applied to a set of 30 outliers produced by different continuous wave searches on O2 Advanced LIGO data. The results of our analysis suggest all but five outliers are inconsistent with an astrophysical origin under the standard continuous wave signal model. We successfully ascribe four of the surviving outliers to instrumental artifacts and a strong hardware injection present in the data. The behavior of the fifth outlier suggests an instrumental origin as well, but we could not relate it to any known instrumental cause. |
1611.01770 | Michael Edmund Tobar | Cheng-Gang Shao, Ya-Fen Chen, Yu-Jie Tan, Jun Luo, Shan-Qing Yang,
Michael Edmund Tobar | Enhanced sensitivity to Lorentz invariance violations in short-range
gravity experiments | Accepted Phys. Rev. D | null | 10.1103/PhysRevD.94.104061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, first limits on putative Lorentz invariance violation coefficients
in the pure gravity sector were determined by the reanalysis of short-range
gravity experiments. Such experiments search for new physics at sidereal
frequencies. They are not, however, designed to optimize the signal strength of
a Lorentz invariance violation force; in fact the Lorentz violating signal is
suppressed in the planar test mass geometry employed in those experiments. We
describe a short-range torsion pendulum experiment with enhanced sensitivity to
possible Lorentz violating signals. A periodic, striped test mass geometry is
used to augment the signal. Careful arrangement of the phases of the striped
patterns on opposite ends of the pendulum further enhances the signal while
simultaneously suppressing the Newtonian background.
| [
{
"created": "Sun, 6 Nov 2016 12:55:52 GMT",
"version": "v1"
}
] | 2016-12-21 | [
[
"Shao",
"Cheng-Gang",
""
],
[
"Chen",
"Ya-Fen",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Luo",
"Jun",
""
],
[
"Yang",
"Shan-Qing",
""
],
[
"Tobar",
"Michael Edmund",
""
]
] | Recently, first limits on putative Lorentz invariance violation coefficients in the pure gravity sector were determined by the reanalysis of short-range gravity experiments. Such experiments search for new physics at sidereal frequencies. They are not, however, designed to optimize the signal strength of a Lorentz invariance violation force; in fact the Lorentz violating signal is suppressed in the planar test mass geometry employed in those experiments. We describe a short-range torsion pendulum experiment with enhanced sensitivity to possible Lorentz violating signals. A periodic, striped test mass geometry is used to augment the signal. Careful arrangement of the phases of the striped patterns on opposite ends of the pendulum further enhances the signal while simultaneously suppressing the Newtonian background. |
1207.2655 | Stefan Liebscher | Stefan Liebscher, Alan D. Rendall, Sophonie Blaise Tchapnda | Oscillatory singularities in Bianchi models with magnetic fields | null | null | 10.1007/s00023-012-0207-7 | null | gr-qc math.DS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An idea which has been around in general relativity for more than forty years
is that in the approach to a big bang singularity solutions of the Einstein
equations can be approximated by the Kasner map, which describes a succession
of Kasner epochs. This is already a highly non-trivial statement in the
spatially homogeneous case. There the Einstein equations reduce to ordinary
differential equations and it becomes a statement that the solutions of the
Einstein equations can be approximated by heteroclinic chains of the
corresponding dynamical system. For a long time progress on proving a statement
of this kind rigorously was very slow but recently there has been new progress
in this area, particularly in the case of the vacuum Einstein equations. In
this paper we generalize some of these results to the Einstein-Maxwell
equations. It turns out that this requires new techniques since certain
eigenvalues are in a less favourable configuration in the case with a magnetic
field. The difficulties which arise in that case are overcome by using the fact
that the dynamical system of interest is of geometrical origin and thus has
useful invariant manifolds.
| [
{
"created": "Wed, 11 Jul 2012 14:31:12 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Liebscher",
"Stefan",
""
],
[
"Rendall",
"Alan D.",
""
],
[
"Tchapnda",
"Sophonie Blaise",
""
]
] | An idea which has been around in general relativity for more than forty years is that in the approach to a big bang singularity solutions of the Einstein equations can be approximated by the Kasner map, which describes a succession of Kasner epochs. This is already a highly non-trivial statement in the spatially homogeneous case. There the Einstein equations reduce to ordinary differential equations and it becomes a statement that the solutions of the Einstein equations can be approximated by heteroclinic chains of the corresponding dynamical system. For a long time progress on proving a statement of this kind rigorously was very slow but recently there has been new progress in this area, particularly in the case of the vacuum Einstein equations. In this paper we generalize some of these results to the Einstein-Maxwell equations. It turns out that this requires new techniques since certain eigenvalues are in a less favourable configuration in the case with a magnetic field. The difficulties which arise in that case are overcome by using the fact that the dynamical system of interest is of geometrical origin and thus has useful invariant manifolds. |
2312.07801 | Valeri Frolov P | Valeri Frolov | Motion of a rotating black hole in a homogeneous scalar field | 12 pages 4 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In the present paper, we consider a rotating black hole moving in a
homogeneous massless scalar field. We assume that the field is weak and neglect
its backreaction, so that the metric at far distance from the black hole is
practically flat. In this domain one can introduce two reference frames, $K$
and $\tilde{K}$. The frame $\tilde{K}$ is associated with the homogeneous
scalar field, in which its constant gradient has only time component. The other
frame, $K$, is the frame in which the black hole is at rest. To describe the
Kerr metric of the black hole we use its Kerr-Schild form
$g_{\mu\nu}=\eta_{\mu\nu}+\Phi l_{\mu}l_{\mu}$, where $\eta_{\mu\nu}$ is the
(asymptotic) flat metric in $K$ frame. We find an explicit solution of the
scalar field equation which is regular at the horizon and properly reproduce
the asymptotic form of the scalar field at the infinity. Using this solution we
calculate the fluxes of the energy, momentum and the angular momentum of the
scalar field into the black hole. This allows us to derive the equation of
motion of the rotating black hole. We discuss main general properties of
solutions of these equations and obtain explicit solutions for special type of
the motion of the black hole.
| [
{
"created": "Tue, 12 Dec 2023 23:40:45 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Dec 2023 01:52:42 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Jan 2024 00:35:37 GMT",
"version": "v3"
}
] | 2024-01-05 | [
[
"Frolov",
"Valeri",
""
]
] | In the present paper, we consider a rotating black hole moving in a homogeneous massless scalar field. We assume that the field is weak and neglect its backreaction, so that the metric at far distance from the black hole is practically flat. In this domain one can introduce two reference frames, $K$ and $\tilde{K}$. The frame $\tilde{K}$ is associated with the homogeneous scalar field, in which its constant gradient has only time component. The other frame, $K$, is the frame in which the black hole is at rest. To describe the Kerr metric of the black hole we use its Kerr-Schild form $g_{\mu\nu}=\eta_{\mu\nu}+\Phi l_{\mu}l_{\mu}$, where $\eta_{\mu\nu}$ is the (asymptotic) flat metric in $K$ frame. We find an explicit solution of the scalar field equation which is regular at the horizon and properly reproduce the asymptotic form of the scalar field at the infinity. Using this solution we calculate the fluxes of the energy, momentum and the angular momentum of the scalar field into the black hole. This allows us to derive the equation of motion of the rotating black hole. We discuss main general properties of solutions of these equations and obtain explicit solutions for special type of the motion of the black hole. |
1906.01501 | Martin Bojowald | Martin Bojowald | Effective Field Theory of Loop Quantum Cosmology | 21 pages, invited contribution to special issue "Loop Quantum Gravity
and Non-Perturbative Approaches to Quantum Cosmology" | Universe 5 (2019) 44 | 10.3390/universe5020044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum cosmology is traditionally formulated in a minisuperspace setting,
implicitly averaging fields over space to obtain homogeneous models. For
universal reasons related to the uncertainty principle, quantum corrections
then depend on the size of the averaging volume. In minisuperspace truncations,
the value of this volume remains an arbitrary parameter devoid of physical
meaning, but in an effective field theory it is identified with the infrared
scale of inhomogeneous modes. Moreover, the infrared scale is running during
gravitational collapse, when regions in which homogeneity remains approximately
valid shrink to increasingly smaller co-moving sizes. Conceptual implications
of this infrared renormalization for perturbative inhomogeneity in quantum
cosmology are presented here, mainly for the example of loop quantum cosmology.
Several claims made in this framework are altered by infrared renormalization.
| [
{
"created": "Tue, 4 Jun 2019 15:11:05 GMT",
"version": "v1"
}
] | 2019-06-05 | [
[
"Bojowald",
"Martin",
""
]
] | Quantum cosmology is traditionally formulated in a minisuperspace setting, implicitly averaging fields over space to obtain homogeneous models. For universal reasons related to the uncertainty principle, quantum corrections then depend on the size of the averaging volume. In minisuperspace truncations, the value of this volume remains an arbitrary parameter devoid of physical meaning, but in an effective field theory it is identified with the infrared scale of inhomogeneous modes. Moreover, the infrared scale is running during gravitational collapse, when regions in which homogeneity remains approximately valid shrink to increasingly smaller co-moving sizes. Conceptual implications of this infrared renormalization for perturbative inhomogeneity in quantum cosmology are presented here, mainly for the example of loop quantum cosmology. Several claims made in this framework are altered by infrared renormalization. |
1605.00552 | Yaghoub Heydarzade | H. Hadi, Y. Heydarzade, M. Hashemi and F. Darabi | Emergent Cosmos in Einstein-Cartan Theory | 12 Pages, Accepted for Publication in Eur. Phys. J. C | Eur. Phys. J. C (2018) 78: 38 | 10.1140/epjc/s10052-017-5494-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the Padmanabhan's proposal, the accelerated expansion of the
universe can be driven by the difference between the surface and bulk degrees
of freedom in a region of space, described by the relation
$dV/dt=N_{sur}-N_{bulk}$ where $N_{sur}$ and $N_{bulk}=-N_{em}+N_{de}$ are the
degrees of freedom assigned to the surface area and the matter-energy content
inside the bulk such that the indexes $"em"$ and $"de"$ represent
energy-momentum and dark energy, respectively. In the present work, the
dynamical effect of the Weyssenhoff perfect fluid with intrinsic spin and its
corresponding spin degrees of freedom in the framework of Einstein-Cartan (EC)
theory are investigated. Based on the modification of Friedmann equations due
to the spin-spin interactions, a correction term for the Padmanabhan's original
relation $dV/dt=N_{sur}+N_{em}-N_{de}$ including the number of degrees of
freedom related to this spin interactions is obtained through the modification
in $N_{bulk}$ term as $N_{bulk}=-N_{em}+N_{spin}+N_{de}$ leading to $dV /d
t=N_{sur}+N_{em}-N_{spin} -N_{de}$ in which $N_{spin}$ is the corresponding
degrees of freedom related to the intrinsic spin of the matter content of the
universe. Moreover, the validity of the unified first law and the generalized
second law of thermodynamics for the Einstein-Cartan cosmos are investigated.
Finally, by considering the covariant entropy conjecture and the bound
resulting from the emergent scenario, a total entropy bound is obtained. Using
this bound, it is shown that the for the universe as an expanding
thermodynamical system, the total effective Komar energy never exceeds the
square of the expansion rate with a factor of $\frac{3}{4\pi}$.
| [
{
"created": "Mon, 2 May 2016 16:34:08 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jan 2018 13:41:47 GMT",
"version": "v2"
}
] | 2018-01-25 | [
[
"Hadi",
"H.",
""
],
[
"Heydarzade",
"Y.",
""
],
[
"Hashemi",
"M.",
""
],
[
"Darabi",
"F.",
""
]
] | Based on the Padmanabhan's proposal, the accelerated expansion of the universe can be driven by the difference between the surface and bulk degrees of freedom in a region of space, described by the relation $dV/dt=N_{sur}-N_{bulk}$ where $N_{sur}$ and $N_{bulk}=-N_{em}+N_{de}$ are the degrees of freedom assigned to the surface area and the matter-energy content inside the bulk such that the indexes $"em"$ and $"de"$ represent energy-momentum and dark energy, respectively. In the present work, the dynamical effect of the Weyssenhoff perfect fluid with intrinsic spin and its corresponding spin degrees of freedom in the framework of Einstein-Cartan (EC) theory are investigated. Based on the modification of Friedmann equations due to the spin-spin interactions, a correction term for the Padmanabhan's original relation $dV/dt=N_{sur}+N_{em}-N_{de}$ including the number of degrees of freedom related to this spin interactions is obtained through the modification in $N_{bulk}$ term as $N_{bulk}=-N_{em}+N_{spin}+N_{de}$ leading to $dV /d t=N_{sur}+N_{em}-N_{spin} -N_{de}$ in which $N_{spin}$ is the corresponding degrees of freedom related to the intrinsic spin of the matter content of the universe. Moreover, the validity of the unified first law and the generalized second law of thermodynamics for the Einstein-Cartan cosmos are investigated. Finally, by considering the covariant entropy conjecture and the bound resulting from the emergent scenario, a total entropy bound is obtained. Using this bound, it is shown that the for the universe as an expanding thermodynamical system, the total effective Komar energy never exceeds the square of the expansion rate with a factor of $\frac{3}{4\pi}$. |
2101.12659 | Sachin Pandey | Sachin Pandey | Aspects of Quantum Cosmology | Thesis submitted to IISER Kolkata for the Degree of Doctor of
Philosophy in Science, December 2020 | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this thesis, we try to resolve the alleged problem of non-unitarity for
various anisotropic cosmological models. Using Wheeler-DeWitt formulation, we
quantized the anisotropic models with variable spatial curvature, namely
Bianchi II and Bianchi VI. We showed that Hamiltonian of respective models
admits self-adjoint extension, thus unitary evolution. We further extended the
unitary evolution for higher dimensional anisotropic cosmological models. We
also showed that unitarity of the model preserves the Noether symmetry but
loses the scale invariance. In later part of this thesis, we showed the
equivalence of Jordan and Einstein frames at the quantum level for the flat FRW
model. Obtained expressions for wave packet matched exactly in both the frames
indicating the equivalence of frames. We also showed that equivalence holds
true for various anisotropic quantum cosmological models, i.e., Bianchi I, V,
X, LRS Bianchi-I and Kantowski-Sachs models.
| [
{
"created": "Fri, 29 Jan 2021 15:54:25 GMT",
"version": "v1"
}
] | 2021-02-01 | [
[
"Pandey",
"Sachin",
""
]
] | In this thesis, we try to resolve the alleged problem of non-unitarity for various anisotropic cosmological models. Using Wheeler-DeWitt formulation, we quantized the anisotropic models with variable spatial curvature, namely Bianchi II and Bianchi VI. We showed that Hamiltonian of respective models admits self-adjoint extension, thus unitary evolution. We further extended the unitary evolution for higher dimensional anisotropic cosmological models. We also showed that unitarity of the model preserves the Noether symmetry but loses the scale invariance. In later part of this thesis, we showed the equivalence of Jordan and Einstein frames at the quantum level for the flat FRW model. Obtained expressions for wave packet matched exactly in both the frames indicating the equivalence of frames. We also showed that equivalence holds true for various anisotropic quantum cosmological models, i.e., Bianchi I, V, X, LRS Bianchi-I and Kantowski-Sachs models. |
2307.13302 | Nils A. Nilsson | Nils A. Nilsson and Christophe Le-Poncin Lafitte | Spacetime-symmetry breaking effects in gravitational-wave generation at
the first post-Newtonian order | 14 pages, 3 figures, accepted for publication in Physical Review D | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Current searches for signals of departures from the fundamental symmetries of
General Relativity using gravitational waves are largely dominated by
propagation effects like dispersion and birefringence from highly dynamic
sources such as coalescing binary-black holes and neutron stars. In this paper
we take steps towards probing the nature of spacetime symmetries in the {\it
generation-stage} of gravitational waves; by using a generic effective-field
theory, we solve the modified Einstein equations order-by-order (in the
coefficients for the symmetry breaking) for a generic source, and we write down
the the first Post-Newtonian corrections, which includes contributions from the
spacetime-symmetry breaking terms. Choosing as the source a system of point
particles allows us to write down a simple toy solution explicitly, and we see
that in contrast to General Relativity, the monopolar and dipolar contributions
are non-vanishing. We comment on the detectability of such signals by the Laser
Interferometer Space Antenna (LISA) space mission, which has high
signal-to-noise galactic binaries (which can be modelled as point particles)
well inside its predicted sensitivity band, sources which are inaccessible for
current ground-based detectors, and we also discuss the possibility of going
beyond the quadrupole formula and the first Post-Newtonian order, which would
reveal effects which could be probed by ground-based detectors observing
coalescence events.
| [
{
"created": "Tue, 25 Jul 2023 07:34:20 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Dec 2023 10:40:21 GMT",
"version": "v2"
}
] | 2023-12-08 | [
[
"Nilsson",
"Nils A.",
""
],
[
"Lafitte",
"Christophe Le-Poncin",
""
]
] | Current searches for signals of departures from the fundamental symmetries of General Relativity using gravitational waves are largely dominated by propagation effects like dispersion and birefringence from highly dynamic sources such as coalescing binary-black holes and neutron stars. In this paper we take steps towards probing the nature of spacetime symmetries in the {\it generation-stage} of gravitational waves; by using a generic effective-field theory, we solve the modified Einstein equations order-by-order (in the coefficients for the symmetry breaking) for a generic source, and we write down the the first Post-Newtonian corrections, which includes contributions from the spacetime-symmetry breaking terms. Choosing as the source a system of point particles allows us to write down a simple toy solution explicitly, and we see that in contrast to General Relativity, the monopolar and dipolar contributions are non-vanishing. We comment on the detectability of such signals by the Laser Interferometer Space Antenna (LISA) space mission, which has high signal-to-noise galactic binaries (which can be modelled as point particles) well inside its predicted sensitivity band, sources which are inaccessible for current ground-based detectors, and we also discuss the possibility of going beyond the quadrupole formula and the first Post-Newtonian order, which would reveal effects which could be probed by ground-based detectors observing coalescence events. |
1604.07222 | Tommaso De Lorenzo | Marios Christodoulou and Tommaso De Lorenzo | On the volume inside old black holes | 9 pages, 5 figures | Phys. Rev. D 94, 104002 (2016) | 10.1103/PhysRevD.94.104002 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes that have nearly evaporated are often thought of as small
objects, due to their tiny exterior area. However, the horizon bounds large
spacelike hypersurfaces. A compelling geometric perspective on the evolution of
the interior geometry was recently shown to be provided by a generally
covariant definition of the volume inside a black hole using maximal surfaces.
In this article, we expand on previous results and show that finding the
maximal surfaces in an arbitrary spherically symmetric spacetime is equivalent
to a 1+1 geodesic problem. We then study the effect of Hawking radiation on the
volume by computing the volume of maximal surfaces inside the apparent horizon
of an evaporating black hole as a function of time at infinity: while the area
is shrinking, the volume of these surfaces grows monotonically with advanced
time, up to when the horizon has reached Planckian dimensions. The physical
relevance of these results for the information paradox and the remnant
scenarios are discussed.
| [
{
"created": "Mon, 25 Apr 2016 12:05:59 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 2016 12:56:38 GMT",
"version": "v2"
}
] | 2016-11-04 | [
[
"Christodoulou",
"Marios",
""
],
[
"De Lorenzo",
"Tommaso",
""
]
] | Black holes that have nearly evaporated are often thought of as small objects, due to their tiny exterior area. However, the horizon bounds large spacelike hypersurfaces. A compelling geometric perspective on the evolution of the interior geometry was recently shown to be provided by a generally covariant definition of the volume inside a black hole using maximal surfaces. In this article, we expand on previous results and show that finding the maximal surfaces in an arbitrary spherically symmetric spacetime is equivalent to a 1+1 geodesic problem. We then study the effect of Hawking radiation on the volume by computing the volume of maximal surfaces inside the apparent horizon of an evaporating black hole as a function of time at infinity: while the area is shrinking, the volume of these surfaces grows monotonically with advanced time, up to when the horizon has reached Planckian dimensions. The physical relevance of these results for the information paradox and the remnant scenarios are discussed. |
2009.13886 | Xiangdong Zhang | Xianglong Wu and Xiangdong Zhang | Collisional Penrose process of BTZ black holes | 16 pages,3 figures | Phys. Rev. D 103, 044048 (2021) | 10.1103/PhysRevD.103.044048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Penrose process in the vicinity of an extremal
Ban\~ados-Teitelboim-Zanelli(BTZ) black hole is studied. Due to the existence
of negative cosmological constant, only massless particles could escape to
infinity. Hence we analyse the Penrose process by one massless particle
collides with another massive particle near the horizon of BTZ black holes.
Calculations of the maximum energy extraction efficiency of this process is
carried out for both spinless and spinning particles. Our results show that the
spinning particle have a higher energy extraction efficiency than the spinless
particle. Moreover, our calculation also indicates that the maximum energy
extraction efficiency is independent of the value of the cosmological constant
of BTZ black holes.
| [
{
"created": "Tue, 29 Sep 2020 09:25:11 GMT",
"version": "v1"
}
] | 2021-03-03 | [
[
"Wu",
"Xianglong",
""
],
[
"Zhang",
"Xiangdong",
""
]
] | The Penrose process in the vicinity of an extremal Ban\~ados-Teitelboim-Zanelli(BTZ) black hole is studied. Due to the existence of negative cosmological constant, only massless particles could escape to infinity. Hence we analyse the Penrose process by one massless particle collides with another massive particle near the horizon of BTZ black holes. Calculations of the maximum energy extraction efficiency of this process is carried out for both spinless and spinning particles. Our results show that the spinning particle have a higher energy extraction efficiency than the spinless particle. Moreover, our calculation also indicates that the maximum energy extraction efficiency is independent of the value of the cosmological constant of BTZ black holes. |
0904.4311 | Masashi Kimura | Masashi Kimura | Dynamical Black Rings with a Positive Cosmological Constant | 11 pages, 16 figures, references added | Phys.Rev.D80:044012,2009 | 10.1103/PhysRevD.80.044012 | OCU-PHYS 312, AP-GR 66 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct dynamical black ring solutions in the five dimensional
Einstein-Maxwell system with a positive cosmological constant and investigate
the geometrical structure. The solutions describe the physical process such
that a thin black ring at early time shrinks and changes into a single black
hole as time increase. We also discuss the multi-black rings and the
coalescence of them.
| [
{
"created": "Tue, 28 Apr 2009 06:00:51 GMT",
"version": "v1"
},
{
"created": "Sat, 2 May 2009 09:27:06 GMT",
"version": "v2"
}
] | 2009-11-19 | [
[
"Kimura",
"Masashi",
""
]
] | We construct dynamical black ring solutions in the five dimensional Einstein-Maxwell system with a positive cosmological constant and investigate the geometrical structure. The solutions describe the physical process such that a thin black ring at early time shrinks and changes into a single black hole as time increase. We also discuss the multi-black rings and the coalescence of them. |
2309.01080 | Manabendra Sharma | Manabendra Sharma, Gustavo S. Vicente, Leila L. Graef, Rudnei O. Ramos
and Anzhong Wang | Quantum geometric formulation of Brans-Dicke theory for Bianchi I
spacetime | 13 pages, 4 figures | null | null | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We consider a formulation of the Brans-Dicke theory in Jordan's frame for
Bianchi-I spacetime within the framework of loop quantum gravity. The
robustness of singularity resolutions due to the quantum effects is explicitly
verified in the context of two quantization schemes typically used in the
literature. We present an exploration of the effects of quantum geometry on the
background dynamics, which is also illustrated through some explicit numerical
examples and showing the absence of the singularity.
| [
{
"created": "Sun, 3 Sep 2023 05:16:42 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Aug 2024 14:34:07 GMT",
"version": "v2"
}
] | 2024-08-06 | [
[
"Sharma",
"Manabendra",
""
],
[
"Vicente",
"Gustavo S.",
""
],
[
"Graef",
"Leila L.",
""
],
[
"Ramos",
"Rudnei O.",
""
],
[
"Wang",
"Anzhong",
""
]
] | We consider a formulation of the Brans-Dicke theory in Jordan's frame for Bianchi-I spacetime within the framework of loop quantum gravity. The robustness of singularity resolutions due to the quantum effects is explicitly verified in the context of two quantization schemes typically used in the literature. We present an exploration of the effects of quantum geometry on the background dynamics, which is also illustrated through some explicit numerical examples and showing the absence of the singularity. |
1410.4758 | Hui-Ling Li | Hui-Ling Li, Zhong-Wen Feng, Xiao-Tao Zu | Quantum tunneling from high dimensional G\"odel black hole | 12 pages, no figures | Gen Relativ Gravit (2016) 48:18 | 10.1007/s10714-015-2015-0 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | Considering quantum gravity effect, we investigate the quantum tunneling from
high dimensional Kerr-G\"odel black hole using generalized Dirac equation. As a
result, revised tunneling probability is obtained, and the corrected Hawking
temperature is also presented.
| [
{
"created": "Fri, 17 Oct 2014 15:27:20 GMT",
"version": "v1"
}
] | 2017-06-20 | [
[
"Li",
"Hui-Ling",
""
],
[
"Feng",
"Zhong-Wen",
""
],
[
"Zu",
"Xiao-Tao",
""
]
] | Considering quantum gravity effect, we investigate the quantum tunneling from high dimensional Kerr-G\"odel black hole using generalized Dirac equation. As a result, revised tunneling probability is obtained, and the corrected Hawking temperature is also presented. |
1511.03857 | Sergey Rubin | Sergey G. Rubin | The problem of small physical parameters and its possible solution | 20 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The mechanism of continuous set of different universes formation is
elaborated. It provides tool to solve the problem of observed smallness of
physical parameters. Solution of two puzzles - the hierarchy and the
cosmological constant problems based on multidimensional gravity is discussed.
| [
{
"created": "Thu, 12 Nov 2015 11:16:16 GMT",
"version": "v1"
}
] | 2015-11-13 | [
[
"Rubin",
"Sergey G.",
""
]
] | The mechanism of continuous set of different universes formation is elaborated. It provides tool to solve the problem of observed smallness of physical parameters. Solution of two puzzles - the hierarchy and the cosmological constant problems based on multidimensional gravity is discussed. |
gr-qc/9511003 | Viqar Husain | Viqar Husain | Black hole solutions in 2+1 dimensions | 8 pages, RevTeX (to appear in Phys. Rev. D) References to Mann and
Ross, and Mann, Chan and Chan added | Phys.Rev. D52 (1995) 6860-6862 | 10.1103/PhysRevD.52.6860 | CGPG-95/10-8 | gr-qc hep-th | null | We give circularly symmetric solutions for null fluid collapse in
2+1-dimensional Einstein gravity with a cosmological constant. The fluid
pressure $P$ and energy density $\rho$ are related by $P=k\rho$ $(k\le 1)$. The
long time limit of the solutions are black holes whose horizon structures
depend on the value of $k$. The $k=1$ solution is the
Banados-Teitelboim-Zanelli black hole metric in the long time static limit,
while the $k<1$ solutions give other, `hairy' black hole metrics in this limit.
| [
{
"created": "Wed, 1 Nov 1995 21:15:59 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Nov 1995 20:50:28 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Husain",
"Viqar",
""
]
] | We give circularly symmetric solutions for null fluid collapse in 2+1-dimensional Einstein gravity with a cosmological constant. The fluid pressure $P$ and energy density $\rho$ are related by $P=k\rho$ $(k\le 1)$. The long time limit of the solutions are black holes whose horizon structures depend on the value of $k$. The $k=1$ solution is the Banados-Teitelboim-Zanelli black hole metric in the long time static limit, while the $k<1$ solutions give other, `hairy' black hole metrics in this limit. |
1303.4707 | Plyatsko Roman | Roman Plyatsko and Mykola Fenyk | Highly relativistic circular orbits of spinning particle in the Kerr
field | 10 pages, 16 figures | Phys. Rev. D, v.87, 044019 (2013) | 10.1103/PhysRevD.87.044019 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Mathisson-Papapetrou equations in Kerr's background are considered. The
region of existence of highly relativistic planar circular orbits of a spinning
particle in this background and dependence of the particle's Lorentz
$\gamma$-factor on its spin and radial coordinate are investigated. It is shown
that in contrast to the highly relativistic circular orbits of a spinless
particle the corresponding orbits of a spinning particle are allowed in much
wider space region. Some of these orbits show the significant attractive action
of the spin-gravity coupling on a particle and others are caused by the
significant repulsive action. Numerical estimates for electrons, protons and
neutrinos in the gravitational field of black holes are presented.
| [
{
"created": "Tue, 19 Mar 2013 19:25:41 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Plyatsko",
"Roman",
""
],
[
"Fenyk",
"Mykola",
""
]
] | The Mathisson-Papapetrou equations in Kerr's background are considered. The region of existence of highly relativistic planar circular orbits of a spinning particle in this background and dependence of the particle's Lorentz $\gamma$-factor on its spin and radial coordinate are investigated. It is shown that in contrast to the highly relativistic circular orbits of a spinless particle the corresponding orbits of a spinning particle are allowed in much wider space region. Some of these orbits show the significant attractive action of the spin-gravity coupling on a particle and others are caused by the significant repulsive action. Numerical estimates for electrons, protons and neutrinos in the gravitational field of black holes are presented. |
1702.02552 | Tomonori Totani | Tomonori Totani (Univ. Tokyo) | Gravity with free initial conditions: a solution to the cosmological
constant problem testable by CMB B-mode polarization | 10 pages, no figure. Accepted by Phys. Rev. D | Phys. Rev. D 96, 084062 (2017) | 10.1103/PhysRevD.96.084062 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In standard general relativity the universe cannot be started with arbitrary
initial conditions, because four of the ten components of the Einstein's field
equations (EFE) are constraints on initial conditions. In the previous work it
was proposed to extend the gravity theory to allow free initial conditions,
with a motivation to solve the cosmological constant problem. This was done by
setting four constraints on metric variations in the action principle, which is
reasonable because the gravity's physical degrees of freedom are at most six.
However, there are two problems about this theory; the three constraints in
addition to the unimodular condition were introduced without clear physical
meanings, and the flat Minkowski spacetime is unstable against perturbations.
Here a new set of gravitational field equations is derived by replacing the
three constraints with new ones requiring that geodesic paths remain geodesic
against metric variations. The instability problem is then naturally solved.
Implications for the cosmological constant $\Lambda$ are unchanged; the theory
converges into EFE with nonzero $\Lambda$ by inflation, but $\Lambda$ varies on
scales much larger than the present Hubble horizon. Then galaxies are formed
only in small $\Lambda$ regions, and the cosmological constant problem is
solved by the anthropic argument. Because of the increased degrees of freedom
in metric dynamics, the theory predicts new non-oscillatory modes of metric
anisotropy generated by quantum fluctuation during inflation, and CMB B-mode
polarization would be observed differently from the standard predictions by
general relativity.
| [
{
"created": "Wed, 8 Feb 2017 18:20:42 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Oct 2017 08:42:29 GMT",
"version": "v2"
}
] | 2017-11-08 | [
[
"Totani",
"Tomonori",
"",
"Univ. Tokyo"
]
] | In standard general relativity the universe cannot be started with arbitrary initial conditions, because four of the ten components of the Einstein's field equations (EFE) are constraints on initial conditions. In the previous work it was proposed to extend the gravity theory to allow free initial conditions, with a motivation to solve the cosmological constant problem. This was done by setting four constraints on metric variations in the action principle, which is reasonable because the gravity's physical degrees of freedom are at most six. However, there are two problems about this theory; the three constraints in addition to the unimodular condition were introduced without clear physical meanings, and the flat Minkowski spacetime is unstable against perturbations. Here a new set of gravitational field equations is derived by replacing the three constraints with new ones requiring that geodesic paths remain geodesic against metric variations. The instability problem is then naturally solved. Implications for the cosmological constant $\Lambda$ are unchanged; the theory converges into EFE with nonzero $\Lambda$ by inflation, but $\Lambda$ varies on scales much larger than the present Hubble horizon. Then galaxies are formed only in small $\Lambda$ regions, and the cosmological constant problem is solved by the anthropic argument. Because of the increased degrees of freedom in metric dynamics, the theory predicts new non-oscillatory modes of metric anisotropy generated by quantum fluctuation during inflation, and CMB B-mode polarization would be observed differently from the standard predictions by general relativity. |
2101.11567 | Orlando Luongo | Alessio Belfiglio, Orlando Luongo, Stefano Mancini | Entanglement production in Einstein-Cartan theory | 10 pages, 4 figures | Phys. Rev. D 104, 043523 (2021) | 10.1103/PhysRevD.104.043523 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the entanglement production for Dirac and Klein-Gordon fields in an
expanding spacetime characterized by the presence of torsion. Torsion is here
considered according to the Einstein-Cartan theory with a conformally flat
Friedmann-Robertson-Walker spacetime. In this framework, torsion is seen as an
external field, fulfilling precise constraints directly got from the
cosmological constant principle. For Dirac field, we find that torsion
increases the amount of entanglement. This turns out to be particularly evident
for small values of particle momentum. We discuss the roles of Pauli exclusion
principle in view of our results, and, in particular, we propose an
interpretation of the two maxima that occur for the entanglement entropy in
presence of torsion. For Klein-Gordon field, and differently from the Dirac
case, the model can be exactly solved by adopting the same scale factor as in
the Dirac case. Again, we show how torsion affects the amount of entanglement,
providing a robust physical motivation behind the increase or decrease of
entanglement entropy. A direct comparison of our findings is also discussed in
view of previous results derived in absence of torsion. To this end, we give
prominence on how our expectations would change in terms of the coupling
between torsion and the scale factor for both Dirac and Klein-Gordon fields.
| [
{
"created": "Wed, 27 Jan 2021 17:48:05 GMT",
"version": "v1"
}
] | 2021-08-25 | [
[
"Belfiglio",
"Alessio",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Mancini",
"Stefano",
""
]
] | We study the entanglement production for Dirac and Klein-Gordon fields in an expanding spacetime characterized by the presence of torsion. Torsion is here considered according to the Einstein-Cartan theory with a conformally flat Friedmann-Robertson-Walker spacetime. In this framework, torsion is seen as an external field, fulfilling precise constraints directly got from the cosmological constant principle. For Dirac field, we find that torsion increases the amount of entanglement. This turns out to be particularly evident for small values of particle momentum. We discuss the roles of Pauli exclusion principle in view of our results, and, in particular, we propose an interpretation of the two maxima that occur for the entanglement entropy in presence of torsion. For Klein-Gordon field, and differently from the Dirac case, the model can be exactly solved by adopting the same scale factor as in the Dirac case. Again, we show how torsion affects the amount of entanglement, providing a robust physical motivation behind the increase or decrease of entanglement entropy. A direct comparison of our findings is also discussed in view of previous results derived in absence of torsion. To this end, we give prominence on how our expectations would change in terms of the coupling between torsion and the scale factor for both Dirac and Klein-Gordon fields. |
gr-qc/0010007 | Carlos Lousto | Carlos O. Lousto (AEI-Golm) | Towards the solution of the relativistic gravitational radiation
reaction problem for binary black holes | Contribution to the Proceedings of the 3rd LISA Symposium | Class.Quant.Grav. 18 (2001) 3989-3994 | 10.1088/0264-9381/18/19/304 | AEI-2000-061 | gr-qc | null | Here we present the results of applying the generalized Riemann zeta-function
regularization method to the gravitational radiation reaction problem. We
analyze in detail the headon collision of two nonspinning black holes with
extreme mass ratio. The resulting reaction force on the smaller hole is
repulsive. We discuss the possible extensions of these method to generic orbits
and spinning black holes. The determination of corrected trajectories allows to
add second perturbative corrections with the consequent increase in the
accuracy of computed waveforms.
| [
{
"created": "Tue, 3 Oct 2000 13:16:06 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jul 2001 15:31:15 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Lousto",
"Carlos O.",
"",
"AEI-Golm"
]
] | Here we present the results of applying the generalized Riemann zeta-function regularization method to the gravitational radiation reaction problem. We analyze in detail the headon collision of two nonspinning black holes with extreme mass ratio. The resulting reaction force on the smaller hole is repulsive. We discuss the possible extensions of these method to generic orbits and spinning black holes. The determination of corrected trajectories allows to add second perturbative corrections with the consequent increase in the accuracy of computed waveforms. |
2406.19147 | Sjors Heefer | Sjors Heefer, Lorens F. Niehof, Andrea Fuster | A new class of non-Einstein pp-wave solutions to quadratic gravity | null | null | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We obtain a new family of exact vacuum solutions to quadratic gravity that
describe pp-waves with two-dimensional wave surfaces that can have any
prescribed constant curvature. When the wave surfaces are flat we recover the
Peres waves obtained by Madsen, a subset of which forms precisely the vacuum
pp-waves of general relativity. If, on the other hand, the wave surfaces have
non-vanishing constant curvature then all our solutions are non-Einstein (i.e.
they do not solve Einstein's equations in vacuum, with or without cosmological
constant) and we find that the curvature is linearly related to the value of
the cosmological constant. We show that the vacuum field equations reduce to a
simple linear biharmonic equation on the curved wave surfaces, and as
consequence, the general solution can be written down. We also provide some
simple explicit examples.
| [
{
"created": "Thu, 27 Jun 2024 13:06:08 GMT",
"version": "v1"
}
] | 2024-06-28 | [
[
"Heefer",
"Sjors",
""
],
[
"Niehof",
"Lorens F.",
""
],
[
"Fuster",
"Andrea",
""
]
] | We obtain a new family of exact vacuum solutions to quadratic gravity that describe pp-waves with two-dimensional wave surfaces that can have any prescribed constant curvature. When the wave surfaces are flat we recover the Peres waves obtained by Madsen, a subset of which forms precisely the vacuum pp-waves of general relativity. If, on the other hand, the wave surfaces have non-vanishing constant curvature then all our solutions are non-Einstein (i.e. they do not solve Einstein's equations in vacuum, with or without cosmological constant) and we find that the curvature is linearly related to the value of the cosmological constant. We show that the vacuum field equations reduce to a simple linear biharmonic equation on the curved wave surfaces, and as consequence, the general solution can be written down. We also provide some simple explicit examples. |
1710.01910 | Kourosh Nozari | F. Rajabi and K. Nozari | Unimodular $f(R,T)$ Gravity | 24 pages, 3 figures, to appear in PRD | Phys. Rev. D 96, 084061 (2017) | 10.1103/PhysRevD.96.084061 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the idea of unimodular gravity to the modified $f(R,T)$ theories. A
new class of cosmological solutions, that the unimodular constraint on the
metric imposes on the $f(R,T)$ theories, are studied. This extension is done in
both Jordan and Einstein frames. We show that while the Lagrange multiplier
(that imposes the unimodular constraint on the action) depends on the cosmic
time in Jordan frame and therefore, can act as an evolving scalar field in the
universe history, in the Einstein frame it acts as a cosmological constant.
Then a general reconstruction method is used to realize an explicit form of the
unimodular $f(R,T)$ corresponding to a given cosmological solution. By adopting
a specific form of $f(R,T)$, the issue of cosmological inflation is studied in
this setup. To see the observational viability of this model, a numerical
analysis on the model parameter space is done in the background of Planck2015
observational data.
| [
{
"created": "Thu, 5 Oct 2017 08:23:46 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Oct 2017 09:19:56 GMT",
"version": "v2"
}
] | 2017-11-22 | [
[
"Rajabi",
"F.",
""
],
[
"Nozari",
"K.",
""
]
] | We extend the idea of unimodular gravity to the modified $f(R,T)$ theories. A new class of cosmological solutions, that the unimodular constraint on the metric imposes on the $f(R,T)$ theories, are studied. This extension is done in both Jordan and Einstein frames. We show that while the Lagrange multiplier (that imposes the unimodular constraint on the action) depends on the cosmic time in Jordan frame and therefore, can act as an evolving scalar field in the universe history, in the Einstein frame it acts as a cosmological constant. Then a general reconstruction method is used to realize an explicit form of the unimodular $f(R,T)$ corresponding to a given cosmological solution. By adopting a specific form of $f(R,T)$, the issue of cosmological inflation is studied in this setup. To see the observational viability of this model, a numerical analysis on the model parameter space is done in the background of Planck2015 observational data. |
1909.01254 | Andrew Coates | Andrew Coates, Sebastian H. V\"olkel, Kostas D. Kokkotas | Spectral Lines of Quantized, Spinning Black Holes and their
Astrophysical Relevance | 5 pages, 1 figure, minor changes for clarity and some additional
references | Phys. Rev. Lett. 123, 171104, 2019 | 10.1103/PhysRevLett.123.171104 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this Letter, we study black hole area quantization in the context of
gravitational wave physics. It was recently argued that black hole area
quantization could be a mechanism to produce so-called echoes as well as
characteristic absorption lines in gravitational wave observations of merging
black holes. One can match the spontaneous decay of these quantum black holes
to Hawking radiation calculations. Using some assumptions, one can then
estimate the natural widths of these states. As can be seen from a classical
paper by Bekenstein and Mukhanov, the ratio between width and spacing of
nonspinning black hole states approaches a small constant, which seems to
confirm the claim. However, we find that, including the effect of black hole
spin, the natural widths increase. To properly address any claim about
astrophysical black holes, one should examine the spinning case, as real black
holes spin. Thus, the word spinning is key to the question of whether or not
black holes should have an observable spectrum in nature. Our results suggest
that it should be possible to distinguish between any scenarios for which the
answer to this question is yes. However, for all of the commonly discussed
scenarios, our answer is almost certainly no.
| [
{
"created": "Tue, 3 Sep 2019 15:31:27 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Oct 2019 14:47:17 GMT",
"version": "v2"
}
] | 2019-10-29 | [
[
"Coates",
"Andrew",
""
],
[
"Völkel",
"Sebastian H.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | In this Letter, we study black hole area quantization in the context of gravitational wave physics. It was recently argued that black hole area quantization could be a mechanism to produce so-called echoes as well as characteristic absorption lines in gravitational wave observations of merging black holes. One can match the spontaneous decay of these quantum black holes to Hawking radiation calculations. Using some assumptions, one can then estimate the natural widths of these states. As can be seen from a classical paper by Bekenstein and Mukhanov, the ratio between width and spacing of nonspinning black hole states approaches a small constant, which seems to confirm the claim. However, we find that, including the effect of black hole spin, the natural widths increase. To properly address any claim about astrophysical black holes, one should examine the spinning case, as real black holes spin. Thus, the word spinning is key to the question of whether or not black holes should have an observable spectrum in nature. Our results suggest that it should be possible to distinguish between any scenarios for which the answer to this question is yes. However, for all of the commonly discussed scenarios, our answer is almost certainly no. |
1005.1107 | Marek Nowakowski | I. Arraut, D. Batic, M. Nowakowski | Velocity and velocity bounds in static spherically symmetric metrics | 20 pages, 5 figures | Central Eur.J.Phys.9:926-938,2011 | 10.2478/s11534-010-0147-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find simple expressions for velocity of massless particles in dependence
of the distance $r$ in Schwarzschild coordinates. For massive particles these
expressions put an upper bound for the velocity. Our results apply to static
spherically symmetric metrics. We use these results to calculate the velocity
for different cases: Schwarzschild, Schwarzschild-de Sitter and
Reissner-Nordstr\"om with and without the cosmological constant. We emphasize
the differences between the behavior of the velocity in the different metrics
and find that in cases with naked singularity there exists always a region
where the massless particle moves with a velocity bigger than the velocity of
light in vacuum. In the case of Reissner-Nordstr\"om-de Sitter we completely
characterize the radial velocity and the metric in an algebraic way. We
contrast the case of classical naked singularities with naked singularities
emerging from metric inspired by noncommutative geometry where the radial
velocity never exceeds one. Furthermore, we solve the Einstein equations for a
constant and polytropic density profile and calculate the radial velocity of a
photon moving in spaces with interior metric. The polytropic case of radial
velocity displays an unexpected variation bounded by a local minimum and
maximum.
| [
{
"created": "Thu, 6 May 2010 23:28:16 GMT",
"version": "v1"
}
] | 2011-05-19 | [
[
"Arraut",
"I.",
""
],
[
"Batic",
"D.",
""
],
[
"Nowakowski",
"M.",
""
]
] | We find simple expressions for velocity of massless particles in dependence of the distance $r$ in Schwarzschild coordinates. For massive particles these expressions put an upper bound for the velocity. Our results apply to static spherically symmetric metrics. We use these results to calculate the velocity for different cases: Schwarzschild, Schwarzschild-de Sitter and Reissner-Nordstr\"om with and without the cosmological constant. We emphasize the differences between the behavior of the velocity in the different metrics and find that in cases with naked singularity there exists always a region where the massless particle moves with a velocity bigger than the velocity of light in vacuum. In the case of Reissner-Nordstr\"om-de Sitter we completely characterize the radial velocity and the metric in an algebraic way. We contrast the case of classical naked singularities with naked singularities emerging from metric inspired by noncommutative geometry where the radial velocity never exceeds one. Furthermore, we solve the Einstein equations for a constant and polytropic density profile and calculate the radial velocity of a photon moving in spaces with interior metric. The polytropic case of radial velocity displays an unexpected variation bounded by a local minimum and maximum. |
2111.03166 | Carlo Rovelli | Jonathan Engle, Carlo Rovelli | The accidental flatness constraint does not mean a wrong classical limit | 6 pages | null | 10.1088/1361-6382/ac655e | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We shed some light on the reason why the accidental flatness constraint
appears in certain limits of the amplitudes of covariant loop quantum gravity.
We show why this constraint is harmless, by displaying how analogous accidental
constraints appear in transition amplitudes of simple systems, when certain
limits are considered.
| [
{
"created": "Thu, 4 Nov 2021 21:23:13 GMT",
"version": "v1"
}
] | 2022-05-25 | [
[
"Engle",
"Jonathan",
""
],
[
"Rovelli",
"Carlo",
""
]
] | We shed some light on the reason why the accidental flatness constraint appears in certain limits of the amplitudes of covariant loop quantum gravity. We show why this constraint is harmless, by displaying how analogous accidental constraints appear in transition amplitudes of simple systems, when certain limits are considered. |
0806.1370 | Olivier Sarbach | J.A. Gonzalez, F.S. Guzman, O. Sarbach | Instability of wormholes supported by a ghost scalar field. II.
Nonlinear evolution | 16 pages, 15 figures, minor modifications, to appear in Classical and
Quantum Gravity | Class.Quant.Grav.26:015011,2009 | 10.1088/0264-9381/26/1/015011 | UMSNH-IFM-F-2008-19 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the nonlinear evolution of spherically symmetric wormhole
solutions coupled to a massless ghost scalar field using numerical methods. In
a previous article we have shown that static wormholes with these properties
are unstable with respect to linear perturbations. Here we show that depending
on the initial perturbation the wormholes either expand or decay to a
Schwarzschild black hole. We estimate the time scale of the expanding solutions
and the ones collapsing to a black hole and show that they are consistent in
the regime of small perturbations with those predicted from perturbation
theory. In the collapsing case, we also present a systematic study of the final
black hole horizon and discuss the possibility for a luminous signal to travel
from one universe to the other and back before the black hole forms. In the
expanding case, the wormholes seem to undergo an exponential expansion, at
least during the run time of our simulations.
| [
{
"created": "Mon, 9 Jun 2008 04:58:55 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Nov 2008 05:24:27 GMT",
"version": "v2"
}
] | 2008-12-25 | [
[
"Gonzalez",
"J. A.",
""
],
[
"Guzman",
"F. S.",
""
],
[
"Sarbach",
"O.",
""
]
] | We analyze the nonlinear evolution of spherically symmetric wormhole solutions coupled to a massless ghost scalar field using numerical methods. In a previous article we have shown that static wormholes with these properties are unstable with respect to linear perturbations. Here we show that depending on the initial perturbation the wormholes either expand or decay to a Schwarzschild black hole. We estimate the time scale of the expanding solutions and the ones collapsing to a black hole and show that they are consistent in the regime of small perturbations with those predicted from perturbation theory. In the collapsing case, we also present a systematic study of the final black hole horizon and discuss the possibility for a luminous signal to travel from one universe to the other and back before the black hole forms. In the expanding case, the wormholes seem to undergo an exponential expansion, at least during the run time of our simulations. |
gr-qc/9806076 | Renato Klippert | V.A. De Lorenci, R. Klippert (EFEI/Itajuba), M. Novello, J.M. Salim
(CBPF) | Nonlinear electrodynamics and FRW cosmology | 5 pages, 3 eps figures, REVTeX 3 with epsf and multicol sty files,
new solutions, improved version with emphasis in math content Journal-refby:
Phys. Rev. D 65, 063501 (2002) | null | null | null | gr-qc | null | Maxwell electrodynamics, considered as a source of the classical Einstein
field equations, leads to the singular isotropic Friedmann solutions. We show
that this singular behavior does not occur for a class of nonlinear
generalizations of the electromagnetic theory. A mathematical toy model is
proposed for which the analytical nonsingular extension of FRW solutions is
obtained.
| [
{
"created": "Thu, 18 Jun 1998 20:16:36 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2002 16:37:14 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"De Lorenci",
"V. A.",
"",
"EFEI/Itajuba"
],
[
"Klippert",
"R.",
"",
"EFEI/Itajuba"
],
[
"Novello",
"M.",
"",
"CBPF"
],
[
"Salim",
"J. M.",
"",
"CBPF"
]
] | Maxwell electrodynamics, considered as a source of the classical Einstein field equations, leads to the singular isotropic Friedmann solutions. We show that this singular behavior does not occur for a class of nonlinear generalizations of the electromagnetic theory. A mathematical toy model is proposed for which the analytical nonsingular extension of FRW solutions is obtained. |
gr-qc/0205115 | Livia Conti | L. Conti, M. De Rosa, F. Marin, L. Taffarello and M. Cerdonio | Room temperature GW bar detector with opto-mechanical readout | 7 figures, submitted to Phys. Rev. D | null | 10.1063/1.1544077 | null | gr-qc | null | We present the full implementation of a room-temperature gravitational wave
bar detector equipped with an opto-mechanical readout. The mechanical
vibrations are read by a Fabry--Perot interferometer whose length changes are
compared with a stable reference optical cavity by means of a resonant laser.
The detector performance is completely characterized in terms of spectral
sensitivity and statistical properties of the fluctuations in the system output
signal. The new kind of readout technique allows for wide-band detection
sensitivity and we can accurately test the model of the coupled oscillators for
thermal noise. Our results are very promising in view of cryogenic operation
and represent an important step towards significant improvements in the
performance of massive gravitational wave detectors.
| [
{
"created": "Tue, 28 May 2002 13:20:32 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Conti",
"L.",
""
],
[
"De Rosa",
"M.",
""
],
[
"Marin",
"F.",
""
],
[
"Taffarello",
"L.",
""
],
[
"Cerdonio",
"M.",
""
]
] | We present the full implementation of a room-temperature gravitational wave bar detector equipped with an opto-mechanical readout. The mechanical vibrations are read by a Fabry--Perot interferometer whose length changes are compared with a stable reference optical cavity by means of a resonant laser. The detector performance is completely characterized in terms of spectral sensitivity and statistical properties of the fluctuations in the system output signal. The new kind of readout technique allows for wide-band detection sensitivity and we can accurately test the model of the coupled oscillators for thermal noise. Our results are very promising in view of cryogenic operation and represent an important step towards significant improvements in the performance of massive gravitational wave detectors. |
gr-qc/9309013 | Jesus Ibanez Medrano | J.M. Aguirregabiria, A. Feinstein and J. Ibanez | Exponential-Potential Scalar Field Universes I: The Bianchi I Models | 16 pages, Plain LaTeX, 1 Figure to be sent on request, to appear in
Phys. Rev. D | Phys.Rev.D48:4662-4668,1993 | 10.1103/PhysRevD.48.4662 | null | gr-qc | null | We obtain a general exact solution of the Einstein field equations for the
anisotropic Bianchi type I universes filled with an exponential-potential
scalar field and study their dynamics. It is shown, in agreement with previous
studies, that for a wide range of initial conditions the late-time behaviour of
the models is that of a power-law inflating FRW universe. This property, does
not hold, in contrast, when some degree of inhomogeneity is introduced, as
discussed in our following paper II.
| [
{
"created": "Tue, 14 Sep 1993 15:17:44 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Aguirregabiria",
"J. M.",
""
],
[
"Feinstein",
"A.",
""
],
[
"Ibanez",
"J.",
""
]
] | We obtain a general exact solution of the Einstein field equations for the anisotropic Bianchi type I universes filled with an exponential-potential scalar field and study their dynamics. It is shown, in agreement with previous studies, that for a wide range of initial conditions the late-time behaviour of the models is that of a power-law inflating FRW universe. This property, does not hold, in contrast, when some degree of inhomogeneity is introduced, as discussed in our following paper II. |
2105.05581 | Masashi Kimura | Masashi Kimura, Tomohiro Harada, Atsushi Naruko and Kenji Toma | Backreaction of Mass and Angular Momentum Accretion on Black Holes:
General Formulation of the Metric Perturbations and Application to the
Blandford-Znajek Process | 35 pages, v2: minor revisions, v3: minor revisions, accepted for
publication in PTEP | PTEP 2021 (2021) 9, 093E03 | 10.1093/ptep/ptab101 | RUP-21-7, YITP-21-43 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the metric backreaction of mass and angular momentum accretion on
black holes. We first develop the formalism of monopole and dipole linear
gravitational perturbations around the Schwarzschild black holes in the
Eddington-Finkelstein coordinates against the generic time-dependent matters.
We derive the relation between the time dependence of the mass and angular
momentum of the black hole and the energy-momentum tensors of accreting
matters. As a concrete example, we apply our formalism to the Blandford-Znajek
process around the slowly rotating black holes. We find that the time
dependence of the monopole and dipole perturbations can be interpreted as the
slowly rotating Kerr metric with time-dependent mass and spin parameters, which
are determined from the energy and angular momentum extraction rates of the
Blandford-Znajek process. We also show that the Komar angular momentum and the
area of the apparent horizon are decreasing and increasing in time,
respectively, while they are consistent with the Blandford-Znajek argument of
energy extraction in term of black hole mechanics if we regard the
time-dependent mass parameter as the energy of the black hole.
| [
{
"created": "Wed, 12 May 2021 11:01:25 GMT",
"version": "v1"
},
{
"created": "Fri, 28 May 2021 09:20:31 GMT",
"version": "v2"
},
{
"created": "Sat, 31 Jul 2021 12:12:45 GMT",
"version": "v3"
}
] | 2021-10-20 | [
[
"Kimura",
"Masashi",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Naruko",
"Atsushi",
""
],
[
"Toma",
"Kenji",
""
]
] | We study the metric backreaction of mass and angular momentum accretion on black holes. We first develop the formalism of monopole and dipole linear gravitational perturbations around the Schwarzschild black holes in the Eddington-Finkelstein coordinates against the generic time-dependent matters. We derive the relation between the time dependence of the mass and angular momentum of the black hole and the energy-momentum tensors of accreting matters. As a concrete example, we apply our formalism to the Blandford-Znajek process around the slowly rotating black holes. We find that the time dependence of the monopole and dipole perturbations can be interpreted as the slowly rotating Kerr metric with time-dependent mass and spin parameters, which are determined from the energy and angular momentum extraction rates of the Blandford-Znajek process. We also show that the Komar angular momentum and the area of the apparent horizon are decreasing and increasing in time, respectively, while they are consistent with the Blandford-Znajek argument of energy extraction in term of black hole mechanics if we regard the time-dependent mass parameter as the energy of the black hole. |
1308.1642 | Vincenzo Vitagliano | Vincenzo Vitagliano | The role of nonmetricity in metric-affine theories of gravity | 15 pages. v2: some misconceptions clarified, references added.
Accepted for publication on Classical and Quantum Gravity | null | 10.1088/0264-9381/31/4/045006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The intriguing choice to treat alternative theories of gravity by means of
the Palatini approach, namely elevating the affine connection to the role of
independent variable, contains the seed of some interesting (usually
under-explored) generalizations of General Relativity, the metric-affine
theories of gravity. The peculiar aspect of these theories is to provide a
natural way for matter fields to be coupled to the independent connection
through the covariant derivative built from the connection itself. Adopting a
procedure borrowed from the effective field theory prescriptions, we study the
dynamics of metric-affine theories of increasing order, that in the complete
version include invariants built from curvature, nonmetricity and torsion. We
show that even including terms obtained from nonmetricity and torsion to the
second order density Lagrangian, the connection lacks dynamics and acts as an
auxiliary field that can be algebraically eliminated, resulting in some extra
interactions between metric and matter fields.
| [
{
"created": "Wed, 7 Aug 2013 17:37:02 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jan 2014 11:23:39 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Vitagliano",
"Vincenzo",
""
]
] | The intriguing choice to treat alternative theories of gravity by means of the Palatini approach, namely elevating the affine connection to the role of independent variable, contains the seed of some interesting (usually under-explored) generalizations of General Relativity, the metric-affine theories of gravity. The peculiar aspect of these theories is to provide a natural way for matter fields to be coupled to the independent connection through the covariant derivative built from the connection itself. Adopting a procedure borrowed from the effective field theory prescriptions, we study the dynamics of metric-affine theories of increasing order, that in the complete version include invariants built from curvature, nonmetricity and torsion. We show that even including terms obtained from nonmetricity and torsion to the second order density Lagrangian, the connection lacks dynamics and acts as an auxiliary field that can be algebraically eliminated, resulting in some extra interactions between metric and matter fields. |
2304.04419 | Nikolaos Dimakis | N. Dimakis, M. Roumeliotis, A. Paliathanasis and T. Christodoulakis | Anisotropic Solutions in Symmetric Teleparallel $f\left(
Q\right)$-theory: Kantowski-Sachs and Bianchi III LRS Cosmologies | 42 pages, no figures, Latex2e source file, EPJC accepted version | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the existence of anisotropic self-similar exact solutions in
symmetric teleparallel $f\left( Q\right)$-theory. For the background geometry
we consider the Kantowski-Sachs and the Locally Rotationally Symmetric Bianchi
type III geometries. These two anisotropic spacetimes are of special interest
because in the limit of isotropy they are related to the closed and open
Friedmann--Lema\^{\i}tre--Robertson--Walker cosmologies respectively. For each
spacetime there exist two distinct families of flat, symmetric connections,
which share the symmetries of the spacetime. We present the field equations,
and from them, we determine the functional form of the $f\left( Q\right)$
Lagrangian which yields self-similar solutions. We initially consider the
vacuum case and subsequently we introduce a matter source in terms of a perfect
fluid. Last but not least, we report some self-similar solutions corresponding
to static spherically symmetric spacetimes.
| [
{
"created": "Mon, 10 Apr 2023 07:00:32 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Aug 2023 12:27:19 GMT",
"version": "v2"
}
] | 2023-08-29 | [
[
"Dimakis",
"N.",
""
],
[
"Roumeliotis",
"M.",
""
],
[
"Paliathanasis",
"A.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | We investigate the existence of anisotropic self-similar exact solutions in symmetric teleparallel $f\left( Q\right)$-theory. For the background geometry we consider the Kantowski-Sachs and the Locally Rotationally Symmetric Bianchi type III geometries. These two anisotropic spacetimes are of special interest because in the limit of isotropy they are related to the closed and open Friedmann--Lema\^{\i}tre--Robertson--Walker cosmologies respectively. For each spacetime there exist two distinct families of flat, symmetric connections, which share the symmetries of the spacetime. We present the field equations, and from them, we determine the functional form of the $f\left( Q\right)$ Lagrangian which yields self-similar solutions. We initially consider the vacuum case and subsequently we introduce a matter source in terms of a perfect fluid. Last but not least, we report some self-similar solutions corresponding to static spherically symmetric spacetimes. |
0811.0282 | Dennis Lorek | Claus Laemmerzahl, Dennis Lorek, Hansjoerg Dittus | Confronting Finsler space-time with experiment | To be published in General Relativity and Gravitation | Gen.Rel.Grav.41:1345-1353,2009 | 10.1007/s10714-008-0710-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within all approaches to quantum gravity small violations of the Einstein
Equivalence Principle are expected. This includes violations of Lorentz
invariance. While usually violations of Lorentz invariance are introduced
through the coupling to additional tensor fields, here a Finslerian approach is
employed where violations of Lorentz invariance are incorporated as an integral
part of the space-time metrics. Within such a Finslerian framework a modified
dispersion relation is derived which is confronted with current high precision
experiments. As a result, Finsler type deviations from the Minkowskian metric
are excluded with an accuracy of 10^{-16}.
| [
{
"created": "Mon, 3 Nov 2008 12:49:11 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Laemmerzahl",
"Claus",
""
],
[
"Lorek",
"Dennis",
""
],
[
"Dittus",
"Hansjoerg",
""
]
] | Within all approaches to quantum gravity small violations of the Einstein Equivalence Principle are expected. This includes violations of Lorentz invariance. While usually violations of Lorentz invariance are introduced through the coupling to additional tensor fields, here a Finslerian approach is employed where violations of Lorentz invariance are incorporated as an integral part of the space-time metrics. Within such a Finslerian framework a modified dispersion relation is derived which is confronted with current high precision experiments. As a result, Finsler type deviations from the Minkowskian metric are excluded with an accuracy of 10^{-16}. |
gr-qc/9701059 | Shin'ji Mukouyama | Shinji Mukohyama, Masafumi Seriu and Hideo Kodama | Can the entanglement entropy be the origin of black-hole entropy ? | 40 pages, Latex file, one figure | Phys.Rev. D55 (1997) 7666-7679 | 10.1103/PhysRevD.55.7666 | YITP-96-36 | gr-qc | null | Entanglement entropy is often speculated as a strong candidate for the origin
of the black-hole entropy. To judge whether this speculation is true or not, it
is effective to investigate the whole structure of thermodynamics obtained from
the entanglement entropy, rather than just to examine the apparent structure of
the entropy alone or to compare it with that of the black hole entropy. It is
because entropy acquires a physical significance only when it is related to the
energy and the temperature of a system. From this point of view, we construct a
`thermodynamics of entanglement' by introducing an entanglement energy and
compare it with the black-hole thermodynamics. We consider two possible
definitions of entanglement energy. Then we construct two different kinds of
thermodynamics by combining each of these different definitions of entanglement
energy with the entanglement entropy. We find that both of these two kinds of
thermodynamics show significant differences from the black-hole thermodynamics
if no gravitational effects are taken into account. These differences are in
particular highlighted in the context of the third law of thermodynamics.
Finally we see how inclusion of gravity alter the thermodynamics of the
entanglement. We give a suggestive argument that the thermodynamics of the
entanglement behaves like the black-hole thermodynamics if the gravitational
effects are included properly. Thus the entanglement entropy passes a
non-trivial check to be the origin of the black-hole entropy.
| [
{
"created": "Tue, 28 Jan 1997 10:25:32 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Jan 1997 09:20:02 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Feb 1997 04:49:27 GMT",
"version": "v3"
},
{
"created": "Sat, 15 Mar 1997 01:21:50 GMT",
"version": "v4"
}
] | 2009-10-30 | [
[
"Mukohyama",
"Shinji",
""
],
[
"Seriu",
"Masafumi",
""
],
[
"Kodama",
"Hideo",
""
]
] | Entanglement entropy is often speculated as a strong candidate for the origin of the black-hole entropy. To judge whether this speculation is true or not, it is effective to investigate the whole structure of thermodynamics obtained from the entanglement entropy, rather than just to examine the apparent structure of the entropy alone or to compare it with that of the black hole entropy. It is because entropy acquires a physical significance only when it is related to the energy and the temperature of a system. From this point of view, we construct a `thermodynamics of entanglement' by introducing an entanglement energy and compare it with the black-hole thermodynamics. We consider two possible definitions of entanglement energy. Then we construct two different kinds of thermodynamics by combining each of these different definitions of entanglement energy with the entanglement entropy. We find that both of these two kinds of thermodynamics show significant differences from the black-hole thermodynamics if no gravitational effects are taken into account. These differences are in particular highlighted in the context of the third law of thermodynamics. Finally we see how inclusion of gravity alter the thermodynamics of the entanglement. We give a suggestive argument that the thermodynamics of the entanglement behaves like the black-hole thermodynamics if the gravitational effects are included properly. Thus the entanglement entropy passes a non-trivial check to be the origin of the black-hole entropy. |
1907.04178 | Barak Shoshany | Barak Shoshany | Lectures on Faster-than-Light Travel and Time Travel | 64 pages, 8 figures; updated figures; version published in SciPost
Physics Lecture Notes | SciPost Phys. Lect. Notes 10 (2019) | 10.21468/SciPostPhysLectNotes.10 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | These lecture notes were prepared for a 25-hour course for advanced
undergraduate students participating in Perimeter Institute's Undergraduate
Summer Program. The lectures cover some of what is currently known about the
possibility of superluminal travel and time travel within the context of
established science, that is, general relativity and quantum field theory.
Previous knowledge of general relativity at the level of a standard
undergraduate-level introductory course is recommended, but all the relevant
material is included for completion and reference. No previous knowledge of
quantum field theory, or anything else beyond the standard undergraduate
curriculum, is required. Advanced topics in relativity, such as causal
structures, the Raychaudhuri equation, and the energy conditions are presented
in detail. Once the required background is covered, concepts related to
faster-than-light travel and time travel are discussed. After introducing
tachyons in special relativity as a warm-up, exotic spacetime geometries in
general relativity such as warp drives and wormholes are discussed and
analyzed, including their limitations. Time travel paradoxes are also discussed
in detail, including some of their proposed resolutions.
| [
{
"created": "Sat, 6 Jul 2019 02:08:20 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Sep 2019 23:12:27 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Oct 2019 13:04:26 GMT",
"version": "v3"
}
] | 2019-10-02 | [
[
"Shoshany",
"Barak",
""
]
] | These lecture notes were prepared for a 25-hour course for advanced undergraduate students participating in Perimeter Institute's Undergraduate Summer Program. The lectures cover some of what is currently known about the possibility of superluminal travel and time travel within the context of established science, that is, general relativity and quantum field theory. Previous knowledge of general relativity at the level of a standard undergraduate-level introductory course is recommended, but all the relevant material is included for completion and reference. No previous knowledge of quantum field theory, or anything else beyond the standard undergraduate curriculum, is required. Advanced topics in relativity, such as causal structures, the Raychaudhuri equation, and the energy conditions are presented in detail. Once the required background is covered, concepts related to faster-than-light travel and time travel are discussed. After introducing tachyons in special relativity as a warm-up, exotic spacetime geometries in general relativity such as warp drives and wormholes are discussed and analyzed, including their limitations. Time travel paradoxes are also discussed in detail, including some of their proposed resolutions. |
2001.00460 | Rahul Kumar | Rahul Kumar, Sushant G. Ghosh, and Anzhong Wang | Gravitational deflection of light and shadow cast by rotating
Kalb-Ramond black holes | 18 pages, 12 figures, and 4 tables. Matched with the published
version | Phys.Rev.D 101, 104001 (2020) | 10.1103/PhysRevD.101.104001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nonminimal coupling of the nonzero vacuum expectation value of the
self-interacting antisymmetric Kalb-Ramond field with gravity leads to a
power-law hairy black hole having a parameter $s$, which encompasses the
Reissner$-$Nordstrom black hole ($s=1$). We obtain the axially symmetric
counterpart of this hairy solution, namely, the rotating Kalb-Ramond black
hole, which encompasses, as special cases, Kerr ($s=0$) and Kerr-Newman ($s=1$)
black holes. Interestingly, for a set of parameters ($M, a$, and $\Gamma$),
there exists an extremal value of the Kalb-Ramond parameter ($s=s_{e}$), which
corresponds to an extremal black hole with degenerate horizons, while for
$s<s_{e}$, it describes a nonextremal black hole with Cauchy and event
horizons, and no black hole for $s>s_{e}$. We find that the extremal value
$s_e$ is also influenced by these parameters. The black hole shadow size
decreases monotonically and the shape gets more distorted with an increasing
$s$; in turn, shadows of rotating Kalb-Ramond black holes are smaller and more
distorted than the corresponding Kerr black hole shadows. We investigate the
effect of the Kalb-Ramond field on the rotating black hole spacetime geometry
and analytically deduced corrections to the light deflection angle from the
Kerr and Schwarzschild black hole values. The deflection angle for Sgr A* and
the shadow caused by the supermassive black hole M87* are included and compared
with analogous results of Kerr black holes. The inferred circularity deviation
$\Delta C\leq 0.10$ for the M87* black hole merely constrains the Kalb-Ramond
field parameter, whereas shadow angular diameter $\theta_d=42\pm 3\, \mu$as,
within the $1\sigma$ region, places bounds $\Gamma\leq 0.09205$ for $s=1$ and
$\Gamma\leq 0.02178$ for $s=3$.
| [
{
"created": "Thu, 2 Jan 2020 14:42:47 GMT",
"version": "v1"
},
{
"created": "Fri, 8 May 2020 08:45:47 GMT",
"version": "v2"
}
] | 2020-05-13 | [
[
"Kumar",
"Rahul",
""
],
[
"Ghosh",
"Sushant G.",
""
],
[
"Wang",
"Anzhong",
""
]
] | The nonminimal coupling of the nonzero vacuum expectation value of the self-interacting antisymmetric Kalb-Ramond field with gravity leads to a power-law hairy black hole having a parameter $s$, which encompasses the Reissner$-$Nordstrom black hole ($s=1$). We obtain the axially symmetric counterpart of this hairy solution, namely, the rotating Kalb-Ramond black hole, which encompasses, as special cases, Kerr ($s=0$) and Kerr-Newman ($s=1$) black holes. Interestingly, for a set of parameters ($M, a$, and $\Gamma$), there exists an extremal value of the Kalb-Ramond parameter ($s=s_{e}$), which corresponds to an extremal black hole with degenerate horizons, while for $s<s_{e}$, it describes a nonextremal black hole with Cauchy and event horizons, and no black hole for $s>s_{e}$. We find that the extremal value $s_e$ is also influenced by these parameters. The black hole shadow size decreases monotonically and the shape gets more distorted with an increasing $s$; in turn, shadows of rotating Kalb-Ramond black holes are smaller and more distorted than the corresponding Kerr black hole shadows. We investigate the effect of the Kalb-Ramond field on the rotating black hole spacetime geometry and analytically deduced corrections to the light deflection angle from the Kerr and Schwarzschild black hole values. The deflection angle for Sgr A* and the shadow caused by the supermassive black hole M87* are included and compared with analogous results of Kerr black holes. The inferred circularity deviation $\Delta C\leq 0.10$ for the M87* black hole merely constrains the Kalb-Ramond field parameter, whereas shadow angular diameter $\theta_d=42\pm 3\, \mu$as, within the $1\sigma$ region, places bounds $\Gamma\leq 0.09205$ for $s=1$ and $\Gamma\leq 0.02178$ for $s=3$. |
gr-qc/9905071 | Israel Quiroz | Israel Quiros (Dpto.Fisica. Universidad Central de Las Villas. Santa
Clara. Cuba.) | Dual geometries and spacetime singularities | 11 pages, LaTeX, no figures, version accepted for publication in PRD | Phys.Rev. D61 (2000) 124026 | 10.1103/PhysRevD.61.124026 | null | gr-qc | null | The notion of geometrical duality is discussed in the context of both
Brans-Dicke theory and general relativity. It is shown that, in some particular
solutions, the spacetime singularities that arise in usual Riemannian general
relativity may be avoided in its dual representation (Weyl-type general
relativity). This dual representation provides a singularity-free picture of
the World that is physicaly equivalent to the canonical general relativistic
one.
| [
{
"created": "Wed, 19 May 1999 23:00:10 GMT",
"version": "v1"
},
{
"created": "Mon, 31 May 1999 16:56:32 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Nov 1999 20:03:00 GMT",
"version": "v3"
},
{
"created": "Mon, 21 Feb 2000 12:57:05 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Quiros",
"Israel",
"",
"Dpto.Fisica. Universidad Central de Las Villas. Santa\n Clara. Cuba."
]
] | The notion of geometrical duality is discussed in the context of both Brans-Dicke theory and general relativity. It is shown that, in some particular solutions, the spacetime singularities that arise in usual Riemannian general relativity may be avoided in its dual representation (Weyl-type general relativity). This dual representation provides a singularity-free picture of the World that is physicaly equivalent to the canonical general relativistic one. |
gr-qc/0111009 | L. C. Garcia de Andrade | C.Sivaram and L.C.Garcia de Andrade | Torsion Gravity Effects on Charged-Particles and Neutron Interferometers | Latex file | null | null | null | gr-qc | null | Torsion gravitational effects in the quantum interference of charged
particles are investigated. The influence of axial torsion in the
Schiff-Banhill effect (SB) inside a metallic shell is given. The effect of
torsion on the surface of the earth on (SB) experiment is estimated. Torsion
gravity effects on the Sagnac phase-shift of neutron interferometry are also
computed.
| [
{
"created": "Sun, 4 Nov 2001 19:42:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sivaram",
"C.",
""
],
[
"de Andrade",
"L. C. Garcia",
""
]
] | Torsion gravitational effects in the quantum interference of charged particles are investigated. The influence of axial torsion in the Schiff-Banhill effect (SB) inside a metallic shell is given. The effect of torsion on the surface of the earth on (SB) experiment is estimated. Torsion gravity effects on the Sagnac phase-shift of neutron interferometry are also computed. |
1308.3907 | Yun Soo Myung | Yun Soo Myung | Unstable Schwarzschild-Tangherlini black holes in fourth-order gravity | 10 pages. version to appear in PRD | Phys. Rev. D 88, 084006 (2013) | 10.1103/PhysRevD.88.084006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stability of Schwarzschild-Tangherlini (ST) black holes in
fourth-order gravity which provides a higher dimensional linearized massive
equation. The linearized-Ricci tensor perturbation is employed to exhibit
unstable modes featuring the Gregory-Laflamme (GL) instability of higher
dimensional black strings, in comparison to the stable ST black holes in
Einstein gravity. It turns out that the GL instability of the ST black holes in
the fourth-order gravity originates from the massiveness, but not a nature of
fourth-order derivative theories giving ghost states.
| [
{
"created": "Mon, 19 Aug 2013 01:16:09 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Sep 2013 22:37:13 GMT",
"version": "v2"
}
] | 2013-10-30 | [
[
"Myung",
"Yun Soo",
""
]
] | We study the stability of Schwarzschild-Tangherlini (ST) black holes in fourth-order gravity which provides a higher dimensional linearized massive equation. The linearized-Ricci tensor perturbation is employed to exhibit unstable modes featuring the Gregory-Laflamme (GL) instability of higher dimensional black strings, in comparison to the stable ST black holes in Einstein gravity. It turns out that the GL instability of the ST black holes in the fourth-order gravity originates from the massiveness, but not a nature of fourth-order derivative theories giving ghost states. |
1810.09766 | Abbas Sherif | Abbas Sherif and Gareth Amery | Relating a Geroch-like boundary and the abstract boundary constructions
for spacetimes | Minor changes to the last version. 23 pages and 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a Geroch-like boundary (when restricted to geodesic curves, this
boundary contains as a subset the Geroch's $g$ boundary), which we denote by
$\tilde{g}$, and establish an explicit embedding of the $\tilde{g}$ boundary
into the $a$ boundary of Scott and Szekeres. This construction, and
subsequently the explicit embedding, is done in a 'natural' way (the emphasis
on the word natural here will be clarified in the text), thereby answering in
the affirmative the outstanding question as to whether there exists a natural
way to relate the $g$ and the $a$ boundary constructions.
| [
{
"created": "Tue, 23 Oct 2018 10:52:17 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Mar 2019 09:55:27 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Oct 2020 14:30:56 GMT",
"version": "v3"
},
{
"created": "Sat, 7 Nov 2020 11:34:20 GMT",
"version": "v4"
}
] | 2020-11-10 | [
[
"Sherif",
"Abbas",
""
],
[
"Amery",
"Gareth",
""
]
] | We construct a Geroch-like boundary (when restricted to geodesic curves, this boundary contains as a subset the Geroch's $g$ boundary), which we denote by $\tilde{g}$, and establish an explicit embedding of the $\tilde{g}$ boundary into the $a$ boundary of Scott and Szekeres. This construction, and subsequently the explicit embedding, is done in a 'natural' way (the emphasis on the word natural here will be clarified in the text), thereby answering in the affirmative the outstanding question as to whether there exists a natural way to relate the $g$ and the $a$ boundary constructions. |
1312.1821 | Sven Zschocke | S. Zschocke, S.A. Klioner, M.H. Soffel | Towards sub-microarcsecond models for relativistic astrometry | Proceeding to the Conference Les Journees: "Scientific developments
from highly accurate space-time reference systems", 16-18 September 2013,
Observatoire de Paris, France | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astrometric space missions like Gaia have stimulated a rapid advance in the
field of relativistic astrometry. Present investigations in that field aim at
accuracies significantly less than a microarcsecond. We review the present
status of relativistic astrometry. As far as the problem of light propagation
is concerned we face two problems: the form of the BCRS metric and solutions to
the light-ray equation. Finally, work in progress in that field is briefly
mentioned.
| [
{
"created": "Fri, 6 Dec 2013 10:09:58 GMT",
"version": "v1"
}
] | 2013-12-09 | [
[
"Zschocke",
"S.",
""
],
[
"Klioner",
"S. A.",
""
],
[
"Soffel",
"M. H.",
""
]
] | Astrometric space missions like Gaia have stimulated a rapid advance in the field of relativistic astrometry. Present investigations in that field aim at accuracies significantly less than a microarcsecond. We review the present status of relativistic astrometry. As far as the problem of light propagation is concerned we face two problems: the form of the BCRS metric and solutions to the light-ray equation. Finally, work in progress in that field is briefly mentioned. |
2203.16704 | Pablo Le\'on | C. Las Heras and P. Leon | Complexity factor of spherically anisotropic polytropes from
gravitational decoupling | version that matches the published | General Relativity and Gravitation volume 54, Article number: 138
(2022) | 10.1007/s10714-022-03031-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we will analyse the complexity factor, proposed by L. Herrera,
for spherically symmetric static matter distributions satisfying a polytropic
equation through the gravitational decoupling method. Specifically, we will use
the 2-step GD, which is a particular case of the extended geometric deformation
(EGD), to obtain analytic polytropic solutions of Einstein's equations. In
order to give an example, we construct a model satisfying a polytropic equation
of state using Tolman IV as a seed solution.
| [
{
"created": "Wed, 30 Mar 2022 23:02:39 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 2022 13:58:19 GMT",
"version": "v2"
}
] | 2022-11-04 | [
[
"Heras",
"C. Las",
""
],
[
"Leon",
"P.",
""
]
] | In this work we will analyse the complexity factor, proposed by L. Herrera, for spherically symmetric static matter distributions satisfying a polytropic equation through the gravitational decoupling method. Specifically, we will use the 2-step GD, which is a particular case of the extended geometric deformation (EGD), to obtain analytic polytropic solutions of Einstein's equations. In order to give an example, we construct a model satisfying a polytropic equation of state using Tolman IV as a seed solution. |
2210.09063 | David Wallace | Oliver Pooley and David Wallace | First-class constraints generate gauge transformations in
electromagnetism (reply to Pitts) | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Brian Pitts has recently claimed to show via straightforward calculation
that, at least in the case of Hamiltonian electromagnetism, an arbitrary
first-class constraint ``generates not a gauge transformation, but a bad
physical change'' (Annals of Physics 351 (2014) pp.382-406; arXiv:1310.2756).
We show, via a straightforward calculation, that a transformation generated by
an arbitrary first-class constraint relates gauge-equivalent phase space
points, vindicating orthodoxy. Pitts, however, is primarily concerned with
transformations of entire histories, rather than of instantaneous states. We
show that, even in this context, a transformation generated by an arbitrary
first-class constraint is also a gauge transformation, once the empirically
observed electric field is correctly identified via its dynamical interactions
with charge, and not simply given stipulatively as a certain combination of the
potential and its derivatives.
| [
{
"created": "Mon, 17 Oct 2022 13:02:34 GMT",
"version": "v1"
}
] | 2022-10-18 | [
[
"Pooley",
"Oliver",
""
],
[
"Wallace",
"David",
""
]
] | Brian Pitts has recently claimed to show via straightforward calculation that, at least in the case of Hamiltonian electromagnetism, an arbitrary first-class constraint ``generates not a gauge transformation, but a bad physical change'' (Annals of Physics 351 (2014) pp.382-406; arXiv:1310.2756). We show, via a straightforward calculation, that a transformation generated by an arbitrary first-class constraint relates gauge-equivalent phase space points, vindicating orthodoxy. Pitts, however, is primarily concerned with transformations of entire histories, rather than of instantaneous states. We show that, even in this context, a transformation generated by an arbitrary first-class constraint is also a gauge transformation, once the empirically observed electric field is correctly identified via its dynamical interactions with charge, and not simply given stipulatively as a certain combination of the potential and its derivatives. |
1310.4699 | David Schinkel | David Schinkel, Rodrigo Panosso Macedo, Marcus Ansorg | Axisymmetric constant mean curvature slices in the Kerr space-time | 14 pages, 4 figures, Version published in CQG | David Schinkel et al 2014 Class. Quantum Grav. 31 075017 | 10.1088/0264-9381/31/7/075017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, there have been efforts to solve Einstein's equation in the context
of a conformal compactification of space-time. Of particular importance in this
regard are the so called CMC-foliations, characterized by spatial hyperboloidal
hypersurfaces with a constant extrinsic mean curvature K. However, although of
interest for general space-times, CMC-slices are known explicitly only for the
spherically symmetric Schwarzschild metric. This work is devoted to numerically
determining axisymmetric CMC-slices within the Kerr solution. We construct such
slices outside the black hole horizon through an appropriate coordinate
transformation in which an unknown auxiliary function A is involved. The
condition K=const. throughout the slice leads to a nonlinear partial
differential equation for the function A, which is solved with a
pseudo-spectral method. The results exhibit exponential convergence, as is to
be expected in a pseudo-spectral scheme for analytic solutions. As a
by-product, we identify CMC-slices of the Schwarzschild solution which are not
spherically symmetric.
| [
{
"created": "Thu, 17 Oct 2013 13:37:07 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Apr 2014 10:15:26 GMT",
"version": "v2"
}
] | 2014-04-14 | [
[
"Schinkel",
"David",
""
],
[
"Macedo",
"Rodrigo Panosso",
""
],
[
"Ansorg",
"Marcus",
""
]
] | Recently, there have been efforts to solve Einstein's equation in the context of a conformal compactification of space-time. Of particular importance in this regard are the so called CMC-foliations, characterized by spatial hyperboloidal hypersurfaces with a constant extrinsic mean curvature K. However, although of interest for general space-times, CMC-slices are known explicitly only for the spherically symmetric Schwarzschild metric. This work is devoted to numerically determining axisymmetric CMC-slices within the Kerr solution. We construct such slices outside the black hole horizon through an appropriate coordinate transformation in which an unknown auxiliary function A is involved. The condition K=const. throughout the slice leads to a nonlinear partial differential equation for the function A, which is solved with a pseudo-spectral method. The results exhibit exponential convergence, as is to be expected in a pseudo-spectral scheme for analytic solutions. As a by-product, we identify CMC-slices of the Schwarzschild solution which are not spherically symmetric. |
2005.05183 | Gaurav Narain | Gaurav Narain, Hai-Qing Zhang | Cosmic evolution in novel-Gauss Bonnet Gravity | v2: references added, minor typos corrected | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this short paper we investigate any non-trivial effect the novel
Gauss-Bonnet gravity may give rise in the cosmic evolution of the Universe in
four spacetime dimensions. We start by considering a generic
Friedmann-Lema\^itre-Robertson-Walker (FLRW) metric respecting homogeneity and
isotropicity in arbitrary space-time dimension $D$. The metric depends on two
functions: scale factor and lapse. Plugging this metric in novel
Einstein-Gauss-Bonnet (EGB) gravity action, doing an integration by parts and
then take the limit of $D\to4$ give us a dynamical action in four spacetime
dimensions for scale factor and lapse. The peculiar rescaling of Gauss-Bonnet
coupling by factor of $D-4$ results in a non-trivial contribution in the action
of the theory. In this paper we study this action. We investigate the dynamics
of scale-factor and behavior of lapse in an empty Universe (no matter). Due to
complexity of the problem we study the theory to first order in Gauss-Bonnet
coupling and solve system of equation to the first order. We compute the first
order correction to the on-shell action of the empty Universe and find that its
sign is opposite of the leading order part. We discuss it consequences.
| [
{
"created": "Mon, 11 May 2020 15:18:48 GMT",
"version": "v1"
},
{
"created": "Wed, 20 May 2020 12:19:20 GMT",
"version": "v2"
}
] | 2020-05-21 | [
[
"Narain",
"Gaurav",
""
],
[
"Zhang",
"Hai-Qing",
""
]
] | In this short paper we investigate any non-trivial effect the novel Gauss-Bonnet gravity may give rise in the cosmic evolution of the Universe in four spacetime dimensions. We start by considering a generic Friedmann-Lema\^itre-Robertson-Walker (FLRW) metric respecting homogeneity and isotropicity in arbitrary space-time dimension $D$. The metric depends on two functions: scale factor and lapse. Plugging this metric in novel Einstein-Gauss-Bonnet (EGB) gravity action, doing an integration by parts and then take the limit of $D\to4$ give us a dynamical action in four spacetime dimensions for scale factor and lapse. The peculiar rescaling of Gauss-Bonnet coupling by factor of $D-4$ results in a non-trivial contribution in the action of the theory. In this paper we study this action. We investigate the dynamics of scale-factor and behavior of lapse in an empty Universe (no matter). Due to complexity of the problem we study the theory to first order in Gauss-Bonnet coupling and solve system of equation to the first order. We compute the first order correction to the on-shell action of the empty Universe and find that its sign is opposite of the leading order part. We discuss it consequences. |
2402.04017 | Mert Mangut | Mustafa Halilsoy, Chia-Li Hsieh and Mert Mangut | Colliding null matter with a specific stress tensor | Accepted by Physica Scripta | Phys. Scr. 99, 035023 (2024) | 10.1088/1402-4896/ad2757 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accretion disks around black holes consist of infalling matter boosted
almost to the speed of light making collisions with opposite counterpart. This
is the rough picture occurring near black holes or other strongly gravitating
centers that produce observed phenomena such as astrophysical jets. A toy model
that can be considered imitating such a process is colliding null sources in
general relativity. We present such a simple model projected into the plane of
null coordinates that takes into account only neutral sources. We show that
even at such a simplified model, uncharged and non-rotating, it is possible to
obtain jet-like ejections albeit they lie below the horizon. In the present
study the spacetime consists of either one of i) a cloud of strings, ii) a
global monopole, iii) a particular model of bumblebee gravity, all described by
a similar class of stress-energy tensor. There are gravitational waves
accompanying the null sources and naturally collision of gravitational waves is
also taken into account. After the collision, the spacetime contains both null
and non-null sources, followed by trailing gravitational radiations. Locally
the interaction region of the colliding null-sources and gravitational waves is
isometric to the static background spacetime.
| [
{
"created": "Tue, 6 Feb 2024 14:09:13 GMT",
"version": "v1"
}
] | 2024-02-19 | [
[
"Halilsoy",
"Mustafa",
""
],
[
"Hsieh",
"Chia-Li",
""
],
[
"Mangut",
"Mert",
""
]
] | The accretion disks around black holes consist of infalling matter boosted almost to the speed of light making collisions with opposite counterpart. This is the rough picture occurring near black holes or other strongly gravitating centers that produce observed phenomena such as astrophysical jets. A toy model that can be considered imitating such a process is colliding null sources in general relativity. We present such a simple model projected into the plane of null coordinates that takes into account only neutral sources. We show that even at such a simplified model, uncharged and non-rotating, it is possible to obtain jet-like ejections albeit they lie below the horizon. In the present study the spacetime consists of either one of i) a cloud of strings, ii) a global monopole, iii) a particular model of bumblebee gravity, all described by a similar class of stress-energy tensor. There are gravitational waves accompanying the null sources and naturally collision of gravitational waves is also taken into account. After the collision, the spacetime contains both null and non-null sources, followed by trailing gravitational radiations. Locally the interaction region of the colliding null-sources and gravitational waves is isometric to the static background spacetime. |
1602.05223 | Dnyaneshwar Pawar Dr | D. D. Pawar and V. J. Dagwal, S. P. Shahare | Tilted and Non Tilted C-Field Cosmological Models | 12 pages no figure | IOSR Journal of Mathematics (IOSR-JM) (Nov. - Dec.2016) | 10.9790/5728-120604104109 | Volume 12, Issue 6 Ver. IV (Nov. - Dec.2016), PP 104-109 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tilted and non tilted homogeneous plane symmetric C-field cosmological models
are investigated. Using the method of Narlikar and Padmanabhan [4], the
solutions have been presented when the creation field C is function of time t
only. To get the deterministic model, we have assumed the supplementary
condition between pressure and density . The behaviour of different stages of
the universe has been studied in non tilted models. We have also investigated
the behaviours of some physical parameters.
| [
{
"created": "Wed, 10 Feb 2016 12:48:59 GMT",
"version": "v1"
}
] | 2018-04-25 | [
[
"Pawar",
"D. D.",
""
],
[
"Dagwal",
"V. J.",
""
],
[
"Shahare",
"S. P.",
""
]
] | Tilted and non tilted homogeneous plane symmetric C-field cosmological models are investigated. Using the method of Narlikar and Padmanabhan [4], the solutions have been presented when the creation field C is function of time t only. To get the deterministic model, we have assumed the supplementary condition between pressure and density . The behaviour of different stages of the universe has been studied in non tilted models. We have also investigated the behaviours of some physical parameters. |
2110.09522 | Alexei Deriglazov A | Alexei A. Deriglazov | Comment on "Frame-dragging: meaning, myths, and misconceptions" by L. F.
O. Costa and J. Nat\'ario | 2 pages, +1 page. Taking into account the authors Reply, I added
further comments on the difference between their and Landau-Lifshitz
interpretations | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I point out that the authors' interpretation of their calculations differs
from the standard interpretation, described in Sect. 84 of Landau-Lifshitz
book. This casts doubt on the authors' claim that Sagnac effect "arises also in
apparatuses which are fixed relative to the distant stars (i.e., to
asymptotically inertial frames); in this case one talks about frame-dragging".
| [
{
"created": "Sun, 17 Oct 2021 18:14:46 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Nov 2021 23:29:57 GMT",
"version": "v2"
}
] | 2021-11-09 | [
[
"Deriglazov",
"Alexei A.",
""
]
] | I point out that the authors' interpretation of their calculations differs from the standard interpretation, described in Sect. 84 of Landau-Lifshitz book. This casts doubt on the authors' claim that Sagnac effect "arises also in apparatuses which are fixed relative to the distant stars (i.e., to asymptotically inertial frames); in this case one talks about frame-dragging". |
2112.05784 | Thomas Mieling | Thomas Mieling, Stefan Palenta | The Resolution of Ambiguities in Light Perturbation by Gravitational
Waves | 10 pages, 2 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Some previously published expressions for the perturbation of light by
gravitational waves exhibit pathological behaviour in the limit of parallel
propagation. We show that this is caused by similarly pathological initial or
boundary data and can thus be remedied by implementing better-behaved initial
conditions.
| [
{
"created": "Fri, 10 Dec 2021 19:12:04 GMT",
"version": "v1"
}
] | 2021-12-14 | [
[
"Mieling",
"Thomas",
""
],
[
"Palenta",
"Stefan",
""
]
] | Some previously published expressions for the perturbation of light by gravitational waves exhibit pathological behaviour in the limit of parallel propagation. We show that this is caused by similarly pathological initial or boundary data and can thus be remedied by implementing better-behaved initial conditions. |
1906.08532 | Titus K Mathew | Paxy George and Titus K Mathew | Bayesian analysis of running holographic Ricci dark energy | 15 pages and 7 figures | null | 10.1093/mnras/staa3156 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Holographic Ricci dark energy evolving through its interaction with dark
matter is a natural choice for the running vacuum energy model. We have
analyzed the relative significance of two versions of this model in the light
of SNIa, CMB, BAO and Hubble data sets using the method Bayesian inferences.
The first one, model 1, is the running holographic Ricci dark energy (rhrde)
having a constant additive term in its density form and the second is one,
model 2, having no additive constant, instead the interaction of rhrde with
dark matter is accounted through a phenomenological coupling term. The Bayes
factor of these models in comparison with the standard $\Lambda$CDM have been
obtained by calculating the likelihood of each model for four different data
combinations, SNIa(307)+CMB+BAO, SNIa(307)+CMB+BAO+Hubble data,
SNIa(580)+CMB+BAO and SNIa(580)+CMB+BAO+Hubble data. Suitable flat priors for
the model parameters has been assumed for calculating the likelihood in both
cases. Our analysis shows that, according to the Jeffreys scale, the evidence
for $\Lambda$CDM against both model 1 and model 2 is very strong as the Bayes
factor of both models are much less than one for all the data combinations.
| [
{
"created": "Thu, 20 Jun 2019 10:02:18 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jul 2019 09:50:40 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Oct 2020 11:08:48 GMT",
"version": "v3"
}
] | 2020-10-21 | [
[
"George",
"Paxy",
""
],
[
"Mathew",
"Titus K",
""
]
] | Holographic Ricci dark energy evolving through its interaction with dark matter is a natural choice for the running vacuum energy model. We have analyzed the relative significance of two versions of this model in the light of SNIa, CMB, BAO and Hubble data sets using the method Bayesian inferences. The first one, model 1, is the running holographic Ricci dark energy (rhrde) having a constant additive term in its density form and the second is one, model 2, having no additive constant, instead the interaction of rhrde with dark matter is accounted through a phenomenological coupling term. The Bayes factor of these models in comparison with the standard $\Lambda$CDM have been obtained by calculating the likelihood of each model for four different data combinations, SNIa(307)+CMB+BAO, SNIa(307)+CMB+BAO+Hubble data, SNIa(580)+CMB+BAO and SNIa(580)+CMB+BAO+Hubble data. Suitable flat priors for the model parameters has been assumed for calculating the likelihood in both cases. Our analysis shows that, according to the Jeffreys scale, the evidence for $\Lambda$CDM against both model 1 and model 2 is very strong as the Bayes factor of both models are much less than one for all the data combinations. |
2210.11057 | Matt Visser | Matt Visser (Victoria University of Wellington) and Stefano Liberati
(SISSA, IFPU, and INFN Trieste) | Painleve-Gullstrand coordinates versus Kerr spacetime geometry | 22 pages. Dedicated to the memory of Professor Thanu Padmanabhan. To
appear in the Professor Thanu Padmanabhan memorial volume published by
General Relativity and Gravitation | null | 10.1007/s10714-022-03025-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the tension between the possible existence of Painleve-Gullstrand
coordinate systems versus the explicit geometrical features of the Kerr
spacetime; a subject of interest to Professor Thanu Padmanabhan in the weeks
immediately preceding his unexpected death. We shall carefully distinguish
strong and weak Painleve-Gullstrand coordinate systems, and conformal variants
thereof, cataloguing what we know can and cannot be done -- sometimes we can
make explicit global statements, sometimes we must resort to implicit local
statements. For the Kerr spacetime the best that seems to be achievable is to
set the lapse function to unity and represent the spatial slices with a
3-metric in factorized unimodular form; this arises from considering the Doran
version of Kerr spacetime in Cartesian coordinates. We finish by exploring the
(limited) extent to which this construction might possibly lead to implementing
an "analogue spacetime" model suitable for laboratory simulations of the Kerr
spacetime.
| [
{
"created": "Thu, 20 Oct 2022 07:24:59 GMT",
"version": "v1"
}
] | 2022-11-30 | [
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
],
[
"Liberati",
"Stefano",
"",
"SISSA, IFPU, and INFN Trieste"
]
] | We discuss the tension between the possible existence of Painleve-Gullstrand coordinate systems versus the explicit geometrical features of the Kerr spacetime; a subject of interest to Professor Thanu Padmanabhan in the weeks immediately preceding his unexpected death. We shall carefully distinguish strong and weak Painleve-Gullstrand coordinate systems, and conformal variants thereof, cataloguing what we know can and cannot be done -- sometimes we can make explicit global statements, sometimes we must resort to implicit local statements. For the Kerr spacetime the best that seems to be achievable is to set the lapse function to unity and represent the spatial slices with a 3-metric in factorized unimodular form; this arises from considering the Doran version of Kerr spacetime in Cartesian coordinates. We finish by exploring the (limited) extent to which this construction might possibly lead to implementing an "analogue spacetime" model suitable for laboratory simulations of the Kerr spacetime. |
1301.4569 | Sergei Maydanyuk | Sergei P. Maydanyuk, Antonino Del Popolo, Vladislav S. Olkhovsky | A fully quantum model of Big Bang | 29 pages, 12 figures. arXiv admin note: substantial text overlap with
arXiv:0812.5081, arXiv:1005.5447, arXiv:0707.0585 | null | null | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the paper the closed Friedmann-Robertson-Walker model with quantization in
the presence of the positive cosmological constant and radiation is studied.
For analysis of tunneling probability for birth of an asymptotically deSitter,
inflationary Universe as a function of the radiation energy a new definition of
a "free" wave propagating inside strong fields is proposed. On such a basis,
tunneling boundary condition is corrected, penetrability and reflection
concerning to the barrier are calculated in fully quantum stationary approach.
For the first time non-zero interference between the incident and reflected
waves has been taken into account which turns out to play important role inside
cosmological potentials and could be explained by non-locality of barriers in
quantum mechanics. Inside whole region of energy of radiation the tunneling
probability for the birth of the inflationary Universe is found to be close to
its value obtained in semiclassical approach. The reflection from the barrier
is determined for the first time (which is essentially differs on 1 at the
energy of radiation close to the barrier height). The proposed method could be
easily generalized on the cosmological models with the barriers of arbitrary
shape, that has been demonstrated for the FRW-model with included Chaplygin
gas. Result is stable for variations of the studied barriers, accuracy are
found to be 11--18 digits for all coefficients and energies below the barrier
height.
| [
{
"created": "Sat, 19 Jan 2013 15:09:55 GMT",
"version": "v1"
}
] | 2013-01-22 | [
[
"Maydanyuk",
"Sergei P.",
""
],
[
"Del Popolo",
"Antonino",
""
],
[
"Olkhovsky",
"Vladislav S.",
""
]
] | In the paper the closed Friedmann-Robertson-Walker model with quantization in the presence of the positive cosmological constant and radiation is studied. For analysis of tunneling probability for birth of an asymptotically deSitter, inflationary Universe as a function of the radiation energy a new definition of a "free" wave propagating inside strong fields is proposed. On such a basis, tunneling boundary condition is corrected, penetrability and reflection concerning to the barrier are calculated in fully quantum stationary approach. For the first time non-zero interference between the incident and reflected waves has been taken into account which turns out to play important role inside cosmological potentials and could be explained by non-locality of barriers in quantum mechanics. Inside whole region of energy of radiation the tunneling probability for the birth of the inflationary Universe is found to be close to its value obtained in semiclassical approach. The reflection from the barrier is determined for the first time (which is essentially differs on 1 at the energy of radiation close to the barrier height). The proposed method could be easily generalized on the cosmological models with the barriers of arbitrary shape, that has been demonstrated for the FRW-model with included Chaplygin gas. Result is stable for variations of the studied barriers, accuracy are found to be 11--18 digits for all coefficients and energies below the barrier height. |
1607.04202 | Alexandre Le Tiec | Alexandre Le Tiec, J\'er\^ome Novak | Theory of Gravitational Waves | 40 pages, 10 figures, 2 tables; to appear in An Overview of
Gravitational Waves: Theory and Detection, edited by G. Auger and E. Plagnol
(World Scientific, 2016) | null | 10.1142/9789813141766_0001 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of gravitational radiation is a natural prediction of any
relativistic description of the gravitational interaction. In this chapter, we
focus on gravitational waves, as predicted by Einstein's general theory of
relativity. First, we introduce those mathematical concepts that are necessary
to properly formulate the physical theory, such as the notions of manifold,
vector, tensor, metric, connection and curvature. Second, we motivate,
formulate and then discuss Einstein's equation, which relates the geometry of
spacetime to its matter content. Gravitational waves are later introduced as
solutions of the linearized Einstein equation around flat spacetime. These
waves are shown to propagate at the speed of light and to possess two
polarization states. Gravitational waves can interact with matter, allowing for
their direct detection by means of laser interferometers. Finally, Einstein's
quadrupole formulas are derived and used to show that nonspherical compact
objects moving at relativistic speeds are powerful gravitational wave sources.
| [
{
"created": "Wed, 13 Jul 2016 16:07:23 GMT",
"version": "v1"
}
] | 2017-04-26 | [
[
"Tiec",
"Alexandre Le",
""
],
[
"Novak",
"Jérôme",
""
]
] | The existence of gravitational radiation is a natural prediction of any relativistic description of the gravitational interaction. In this chapter, we focus on gravitational waves, as predicted by Einstein's general theory of relativity. First, we introduce those mathematical concepts that are necessary to properly formulate the physical theory, such as the notions of manifold, vector, tensor, metric, connection and curvature. Second, we motivate, formulate and then discuss Einstein's equation, which relates the geometry of spacetime to its matter content. Gravitational waves are later introduced as solutions of the linearized Einstein equation around flat spacetime. These waves are shown to propagate at the speed of light and to possess two polarization states. Gravitational waves can interact with matter, allowing for their direct detection by means of laser interferometers. Finally, Einstein's quadrupole formulas are derived and used to show that nonspherical compact objects moving at relativistic speeds are powerful gravitational wave sources. |
1809.07795 | Gabriele Benomio | Gabriele Benomio | The Stable Trapping Phenomenon for Black Strings and Black Rings and its
Obstructions on the Decay of Linear Waves | 60 pages | Analysis & PDE 14 (2021) 2427-2496 | 10.2140/apde.2021.14.2427 | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The geometry of solutions to the higher dimensional Einstein vacuum equations
presents aspects that are absent in four dimensions, one of the most remarkable
being the existence of stably trapped null geodesics in the exterior of
asymptotically flat black holes. This paper investigates the stable trapping
phenomenon for two families of higher dimensional black holes, namely black
strings and black rings, and how this trapping structure is responsible for the
slow decay of linear waves on their exterior. More precisely, we study decay
properties for the energy of solutions to the scalar, linear wave equation
$\Box_{g_{\textup{ring}}} \Psi=0$, where $g_{\textup{ring}}$ is the metric of a
fixed black ring solution to the five-dimensional Einstein vacuum equations.
For a class $\mathfrak{g}$ of black ring metrics, we prove a logarithmic lower
bound for the uniform energy decay rate on the black ring exterior
$(\mathcal{D},g_{\textup{ring}})$, with $g_{\textup{ring}}\in\mathfrak{g}$. The
proof generalizes the perturbation argument and quasimode construction of
Holzegel--Smulevici \cite{SharpLogHolz} to the case of a non-separable wave
equation and crucially relies on the presence of stably trapped null geodesics
on $\mathcal{D}$. As a by-product, the same logarithmic lower bound can be
established for any five-dimensional black string.
Our result is the first mathematically rigorous statement supporting the
expectation that black rings are dynamically unstable to generic perturbations.
In particular, we conjecture a new \textit{nonlinear} instability for
five-dimensional black strings and thin black rings which is already present at
the level of scalar perturbations and clearly differs from the mechanism driven
by the well-known Gregory--Laflamme instability.
| [
{
"created": "Thu, 20 Sep 2018 18:36:08 GMT",
"version": "v1"
}
] | 2022-02-09 | [
[
"Benomio",
"Gabriele",
""
]
] | The geometry of solutions to the higher dimensional Einstein vacuum equations presents aspects that are absent in four dimensions, one of the most remarkable being the existence of stably trapped null geodesics in the exterior of asymptotically flat black holes. This paper investigates the stable trapping phenomenon for two families of higher dimensional black holes, namely black strings and black rings, and how this trapping structure is responsible for the slow decay of linear waves on their exterior. More precisely, we study decay properties for the energy of solutions to the scalar, linear wave equation $\Box_{g_{\textup{ring}}} \Psi=0$, where $g_{\textup{ring}}$ is the metric of a fixed black ring solution to the five-dimensional Einstein vacuum equations. For a class $\mathfrak{g}$ of black ring metrics, we prove a logarithmic lower bound for the uniform energy decay rate on the black ring exterior $(\mathcal{D},g_{\textup{ring}})$, with $g_{\textup{ring}}\in\mathfrak{g}$. The proof generalizes the perturbation argument and quasimode construction of Holzegel--Smulevici \cite{SharpLogHolz} to the case of a non-separable wave equation and crucially relies on the presence of stably trapped null geodesics on $\mathcal{D}$. As a by-product, the same logarithmic lower bound can be established for any five-dimensional black string. Our result is the first mathematically rigorous statement supporting the expectation that black rings are dynamically unstable to generic perturbations. In particular, we conjecture a new \textit{nonlinear} instability for five-dimensional black strings and thin black rings which is already present at the level of scalar perturbations and clearly differs from the mechanism driven by the well-known Gregory--Laflamme instability. |
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