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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9811038 | Marcelo Jose Reboucas | G.I. Gomero, A.F.F. Teixeira, M.J. Reboucas, A. Bernui | Spikes in Cosmic Crystallography | 25 pages, LaTeX2e. References updated. To appear in Int. J. Mod.
Phys. D (2002) in the present form | Int.J.Mod.Phys. D11 (2002) 869-892 | 10.1142/S0218271802002074 | null | gr-qc astro-ph hep-ph | null | If the universe is multiply connected and small the sky shows multiple images
of cosmic objects, correlated by the covering group of the 3-manifold used to
model it. These correlations were originally thought to manifest as spikes in
pair separation histograms (PSH) built from suitable catalogues. Using
probability theory we derive an expression for the expected pair separation
histogram (EPSH) in a rather general topological-geometrical-observational
setting. As a major consequence we show that the spikes of topological origin
in PSH's are due to translations, whereas other isometries manifest as tiny
deformations of the PSH corresponding to the simply connected case. This result
holds for all Robertson-Walker spacetimes and gives rise to two basic
corollaries: (i) that PSH's of Euclidean manifolds that have the same
translations in their covering groups exhibit identical spike spectra of
topological origin, making clear that even if the universe is flat the
topological spikes alone are not sufficient for determining its topology; and
(ii) that PSH's of hyperbolic 3-manifolds exhibit no spikes of topological
origin. These corollaries ensure that cosmic crystallography, as originally
formulated, is not a conclusive method for unveiling the shape of the universe.
We also present a method that reduces the statistical fluctuations in PSH's
built from simulated catalogues.
| [
{
"created": "Wed, 11 Nov 1998 20:54:33 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 1999 01:02:46 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Feb 2000 23:28:31 GMT",
"version": "v3"
},
{
"created": "Thu, 21 Feb 2002 02:33:04 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Gomero",
"G. I.",
""
],
[
"Teixeira",
"A. F. F.",
""
],
[
"Reboucas",
"M. J.",
""
],
[
"Bernui",
"A.",
""
]
] | If the universe is multiply connected and small the sky shows multiple images of cosmic objects, correlated by the covering group of the 3-manifold used to model it. These correlations were originally thought to manifest as spikes in pair separation histograms (PSH) built from suitable catalogues. Using probability theory we derive an expression for the expected pair separation histogram (EPSH) in a rather general topological-geometrical-observational setting. As a major consequence we show that the spikes of topological origin in PSH's are due to translations, whereas other isometries manifest as tiny deformations of the PSH corresponding to the simply connected case. This result holds for all Robertson-Walker spacetimes and gives rise to two basic corollaries: (i) that PSH's of Euclidean manifolds that have the same translations in their covering groups exhibit identical spike spectra of topological origin, making clear that even if the universe is flat the topological spikes alone are not sufficient for determining its topology; and (ii) that PSH's of hyperbolic 3-manifolds exhibit no spikes of topological origin. These corollaries ensure that cosmic crystallography, as originally formulated, is not a conclusive method for unveiling the shape of the universe. We also present a method that reduces the statistical fluctuations in PSH's built from simulated catalogues. |
1010.0869 | Josep M. Pons | Naresh Dadhich, Josep M. Pons | On the equivalence of the Einstein-Hilbert and the Einstein-Palatini
formulations of general relativity for an arbitrary connection | 18 pages. Slight change in the title and wording of some sections to
emphasize the main results. References added. Matches published version | Gen.Rel.Grav. 44 (2012) 2337-2352 | 10.1007/s10714-012-1393-9 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the Einstein-Palatini formalism, even though the
projective transformation connecting the arbitrary connection with the Levi
Civita connection has been floating in the literature for a long time and
perhaps the result was implicitly known in the affine gravity community, yet as
far as we know Julia and Silva were the first to realise its gauge character.
We rederive this result by using the Rosenfeld-Dirac-Bergmann approach to
constrained Hamiltonian systems and do a comprehensive self contained analysis
establishing the equivalence of the Einstein-Palatini and the metric
formulations without having to impose the gauge choice that the connection is
symmetric. We also make contact with the the Einstein-Cartan theory when the
matter Lagrangian has fermions.
| [
{
"created": "Tue, 5 Oct 2010 12:44:44 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Oct 2010 11:48:50 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Jul 2011 09:11:10 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Jun 2012 16:27:24 GMT",
"version": "v4"
}
] | 2015-05-20 | [
[
"Dadhich",
"Naresh",
""
],
[
"Pons",
"Josep M.",
""
]
] | In the framework of the Einstein-Palatini formalism, even though the projective transformation connecting the arbitrary connection with the Levi Civita connection has been floating in the literature for a long time and perhaps the result was implicitly known in the affine gravity community, yet as far as we know Julia and Silva were the first to realise its gauge character. We rederive this result by using the Rosenfeld-Dirac-Bergmann approach to constrained Hamiltonian systems and do a comprehensive self contained analysis establishing the equivalence of the Einstein-Palatini and the metric formulations without having to impose the gauge choice that the connection is symmetric. We also make contact with the the Einstein-Cartan theory when the matter Lagrangian has fermions. |
gr-qc/0206088 | Zoltan Perjes | Zolt\'an Perj\'es | Fundamental equations for the gravitational and electromagnetic
perturbations of a charged black hole | 4 pages | null | null | null | gr-qc | null | A pair of wave equations is presented for the gravitational and
electromagnetic perturbations of a charged black hole. One of the equations is
uncoupled and determines the propagation of the electromagnetic perturbation.
The other is for the propagation of the shear of a principal null direction and
has a source term given by the solution of the first equation. This result is
expected to have important applications in astrophysical models.
| [
{
"created": "Fri, 28 Jun 2002 15:19:51 GMT",
"version": "v1"
}
] | 2016-08-16 | [
[
"Perjés",
"Zoltán",
""
]
] | A pair of wave equations is presented for the gravitational and electromagnetic perturbations of a charged black hole. One of the equations is uncoupled and determines the propagation of the electromagnetic perturbation. The other is for the propagation of the shear of a principal null direction and has a source term given by the solution of the first equation. This result is expected to have important applications in astrophysical models. |
gr-qc/0508011 | \.Ibrahim Semiz | Ibrahim Semiz | Dyonic Kerr-Newman black holes, complex scalar field and Cosmic
Censorship | Refined emphasis on the weak cosmic censorship conjecture,
conclusions otherwise unchanged. Also, two sections merged, literature review
updated, references added, a few typos corrected | Gen.Rel.Grav.43:833-846,2011 | 10.1007/s10714-010-1108-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a gedanken experiment, in which a weak wave packet of the
complex massive scalar field interacts with a four-parameter (mass, angular
momentum, electric and magnetic charges) Kerr-Newman black hole. We show that
this interaction cannot convert an extreme the black hole into a naked
sigularity for any black hole parameters and any generic wave packet
configuration. The analysis therefore provides support for the weak cosmic
censorship conjecture.
| [
{
"created": "Tue, 2 Aug 2005 15:06:39 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Oct 2010 17:25:33 GMT",
"version": "v2"
}
] | 2011-02-23 | [
[
"Semiz",
"Ibrahim",
""
]
] | We construct a gedanken experiment, in which a weak wave packet of the complex massive scalar field interacts with a four-parameter (mass, angular momentum, electric and magnetic charges) Kerr-Newman black hole. We show that this interaction cannot convert an extreme the black hole into a naked sigularity for any black hole parameters and any generic wave packet configuration. The analysis therefore provides support for the weak cosmic censorship conjecture. |
1801.08084 | Bo-Qiang Ma | Haowei Xu, Bo-Qiang Ma | Regularity of high energy photon events from gamma ray bursts | 15 latex pages, 9 figures | JCAP 1801 (2018) 050 | 10.1088/1475-7516/2018/01/050 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effect of Quantum Gravity (QG) may bring a tiny light speed variation as
$v(E)=c(1-E/E_{\rm LV})$, where $E$ is the photon energy and $E_{\rm LV}$ is a
Lorentz violation scale. A remarkable regularity was suggested in previous
studies to look for the light speed variation from high energy photon events of
Gamma Ray Bursts (GRBs). We provide a general analysis on the data of 25 bright
GRBs observed by the Fermi Gamma-ray Space Telescope (FGST). Such method allows
a completed scan over all possibilities in a more clean and impartial way
without any bias compared to previous intuitive analysis. The results show that
with the increase in the intrinsic energies of photons, such regularity truly
emerges and gradually becomes significant. For photons with intrinsic energies
higher than 40~GeV, the regularity exists at a significance of 3-5~$\sigma$
with $E_{\rm LV}=3.6\times 10^{17}~\rm GeV$ determined by the GRB data.
| [
{
"created": "Wed, 24 Jan 2018 17:20:10 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Feb 2018 01:29:33 GMT",
"version": "v2"
}
] | 2018-02-07 | [
[
"Xu",
"Haowei",
""
],
[
"Ma",
"Bo-Qiang",
""
]
] | The effect of Quantum Gravity (QG) may bring a tiny light speed variation as $v(E)=c(1-E/E_{\rm LV})$, where $E$ is the photon energy and $E_{\rm LV}$ is a Lorentz violation scale. A remarkable regularity was suggested in previous studies to look for the light speed variation from high energy photon events of Gamma Ray Bursts (GRBs). We provide a general analysis on the data of 25 bright GRBs observed by the Fermi Gamma-ray Space Telescope (FGST). Such method allows a completed scan over all possibilities in a more clean and impartial way without any bias compared to previous intuitive analysis. The results show that with the increase in the intrinsic energies of photons, such regularity truly emerges and gradually becomes significant. For photons with intrinsic energies higher than 40~GeV, the regularity exists at a significance of 3-5~$\sigma$ with $E_{\rm LV}=3.6\times 10^{17}~\rm GeV$ determined by the GRB data. |
2009.02167 | Abraao Capistrano | Abra\~ao J. S. Capistrano, Lu\'is A. Cabral, Jos\'e A. P. F. Mar\~ao,
Carlos H. Coimbra-Ara\'ujo | Linear Nash-Greene fluctuations on the evolution of $S_8$ and $H_0$
tensions | Update title, corrected typos and figures, new results. To appear in
EPJC | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the perturbation equations in an embedded four space-time from the
linear Nash-Greene fluctuations of background metric. In the context of a
five-dimensional bulk, we show that the cosmological perturbations are only
propagated by the gravitational tensorial field equation. In Newtonian
conformal gauge, we study the matter density evolution in sub-horizon regime
and on how such scale may be affected by the extrinsic curvature. We apply a
joint likelihood analysis to the data by means of the Markov Chain Monte Carlo
(MCMC) method for parameter estimation using a pack of recent datasets as the
Pantheon Supernovae type Ia, the Baryon Acoustic Oscillations (BAO) from DR12
galaxy sample and Dark Energy Survey (DESY$1$). We discuss the tensions on the
Hubble constant $H_0$ and the growth amplitude factor $S_8$ of the observations
from Planck 2018 Cosmic Microwave Background (CMB) and the local measurements
of $H_0$ with Hubble Space Telescope (HST) photometry and Gaia EDR3. As a
result, we obtain an alleviation below $\sim 1\sigma$ in the contours
($S_8$-$\Omega_m$) at $68.4\%$ confidence level (CL) when compared with DESY1
data. On the other hand, the $H_0$ tension persists with $\sim 2.6\sigma$ at
$68.4\%$ CL and $1.95\sigma$ at $95.7\%$ CL, aggravated with the inclusion of
BAO data.
| [
{
"created": "Thu, 3 Sep 2020 14:42:17 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Mar 2021 18:43:57 GMT",
"version": "v2"
},
{
"created": "Tue, 17 May 2022 15:48:49 GMT",
"version": "v3"
}
] | 2022-05-18 | [
[
"Capistrano",
"Abraão J. S.",
""
],
[
"Cabral",
"Luís A.",
""
],
[
"Marão",
"José A. P. F.",
""
],
[
"Coimbra-Araújo",
"Carlos H.",
""
]
] | We present the perturbation equations in an embedded four space-time from the linear Nash-Greene fluctuations of background metric. In the context of a five-dimensional bulk, we show that the cosmological perturbations are only propagated by the gravitational tensorial field equation. In Newtonian conformal gauge, we study the matter density evolution in sub-horizon regime and on how such scale may be affected by the extrinsic curvature. We apply a joint likelihood analysis to the data by means of the Markov Chain Monte Carlo (MCMC) method for parameter estimation using a pack of recent datasets as the Pantheon Supernovae type Ia, the Baryon Acoustic Oscillations (BAO) from DR12 galaxy sample and Dark Energy Survey (DESY$1$). We discuss the tensions on the Hubble constant $H_0$ and the growth amplitude factor $S_8$ of the observations from Planck 2018 Cosmic Microwave Background (CMB) and the local measurements of $H_0$ with Hubble Space Telescope (HST) photometry and Gaia EDR3. As a result, we obtain an alleviation below $\sim 1\sigma$ in the contours ($S_8$-$\Omega_m$) at $68.4\%$ confidence level (CL) when compared with DESY1 data. On the other hand, the $H_0$ tension persists with $\sim 2.6\sigma$ at $68.4\%$ CL and $1.95\sigma$ at $95.7\%$ CL, aggravated with the inclusion of BAO data. |
gr-qc/9511018 | Cenalo Vaz | Cenalo Vaz and Louis Witten | Do Naked Singularities Form? | 7 pages (21 Kb), PHYZZX. Revised version to appear in Class. & Quant.
Grav. Letts. A discussion of the consistency of the Sine-Gordon model is
included | Class.Quant.Grav.13:L59-L65,1996 | 10.1088/0264-9381/13/5/004 | UATP-95/03 | gr-qc | null | A naked singularity is formed by the collapse of a Sine-Gordon soliton in 1+1
dimensional dilaton gravity with a negative cosmological constant. We examine
the quantum stress tensor resulting from the formation of the singularity.
Consistent boundary conditions require that the incoming soliton is accompanied
by a flux of incoming radiation across past null infinity, but neglecting the
back reaction of the spacetime leads to the absurd conclusion that the total
energy entering the system by the time the observer is able to receive
information from the singularity is infinite. We conclude that the back
reaction must prevent the formation of the naked singularity.
| [
{
"created": "Sun, 5 Nov 1995 19:59:40 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Mar 1996 22:01:06 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Vaz",
"Cenalo",
""
],
[
"Witten",
"Louis",
""
]
] | A naked singularity is formed by the collapse of a Sine-Gordon soliton in 1+1 dimensional dilaton gravity with a negative cosmological constant. We examine the quantum stress tensor resulting from the formation of the singularity. Consistent boundary conditions require that the incoming soliton is accompanied by a flux of incoming radiation across past null infinity, but neglecting the back reaction of the spacetime leads to the absurd conclusion that the total energy entering the system by the time the observer is able to receive information from the singularity is infinite. We conclude that the back reaction must prevent the formation of the naked singularity. |
gr-qc/9310021 | null | A.Economou and C.O.Lousto | Charged Black Holes In Quadratic Theories | 11 pages, LaTeX/RevTeX3.0 | Phys.Rev. D49 (1994) 5278-5285 | 10.1103/PhysRevD.49.5278 | null | gr-qc astro-ph | null | We point out that in general the Reissner-Nordstr\"om (RN) charged black
holes of general relativity are not solutions of the four dimensional quadratic
gravitational theories. They are, e.g., exact solutions of the $R+R^2$
quadratic theory but not of a theory where a $R_{ab}R^{ab}$ term is present in
the gravitational Lagrangian. In the case where such a non linear curvature
term is present with sufficiently small coupling, we obtain an approximate
solution for a charged black hole of charge $Q$ and mass $M$. For $Q\ll M$ the
validity of this solution extends down to the horizon. This allows us to
explore the thermodynamic properties of the quadratic charged black hole and we
find that, to our approximation, its thermodynamics is identical to that of a
RN black hole. However our black hole's entropy is not equal to the one fourth
of the horizon area. Finally we extend our analysis to the rotating charged
black hole and qualitatively similar results are obtained.
| [
{
"created": "Thu, 14 Oct 1993 11:52:40 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Economou",
"A.",
""
],
[
"Lousto",
"C. O.",
""
]
] | We point out that in general the Reissner-Nordstr\"om (RN) charged black holes of general relativity are not solutions of the four dimensional quadratic gravitational theories. They are, e.g., exact solutions of the $R+R^2$ quadratic theory but not of a theory where a $R_{ab}R^{ab}$ term is present in the gravitational Lagrangian. In the case where such a non linear curvature term is present with sufficiently small coupling, we obtain an approximate solution for a charged black hole of charge $Q$ and mass $M$. For $Q\ll M$ the validity of this solution extends down to the horizon. This allows us to explore the thermodynamic properties of the quadratic charged black hole and we find that, to our approximation, its thermodynamics is identical to that of a RN black hole. However our black hole's entropy is not equal to the one fourth of the horizon area. Finally we extend our analysis to the rotating charged black hole and qualitatively similar results are obtained. |
1704.02810 | Krzysztof Bolejko | Krzysztof Bolejko | Cosmological backreaction within the Szekeres model and emergence of
spatial curvature | 23 pages, 7 figures; v3 - matches published version | JCAP06(2017)025 | 10.1088/1475-7516/2017/06/025 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper discusses the phenomenon of backreaction within the Szekeres
model. Cosmological backreaction describes how the mean global evolution of the
Universe deviates from the Friedmannian evolution. The analysis is based on
models of a single cosmological environment and the global ensemble of the
Szekeres models (of the Swiss-Cheese-type and Styrofoam-type). The obtained
results show that non-linear growth of cosmic structures is associated with the
growth of the spatial curvature $\Omega_{\cal R}$ (in the FLRW limit
$\Omega_{\cal R} \to \Omega_k$). If averaged over global scales the result
depends on the assumed global model of the Universe. Within the Swiss-Cheese
model, which does have a fixed background, the volume average follows the
evolution of the background, and the global spatial curvature averages out to
zero (the background model is the $\Lambda$CDM model, which is spatially flat).
In the Styrofoam-type model, which does not have a fixed background, the mean
evolution deviates from the spatially flat $\Lambda$CDM model, and the mean
spatial curvature evolves to from $\Omega_{\cal R} =0 $ at the CMB to
$\Omega_{\cal R} \sim 0.1$ at $z =0$. If the Styrofoam-type model correctly
captures evolutionary features of the real Universe then one should expect that
in our Universe, the spatial curvature should build up (local growth of cosmic
structures) and its mean global average should deviate from zero
(backreaction). As a result, this paper predicts that the low-redshift Universe
should not be spatially flat (i.e. $\Omega_k \ne 0$, even if in the early
Universe $\Omega_k = 0$) and therefore when analysing low-$z$ cosmological data
one should keep $\Omega_k$ as a free parameter and independent from the CMB
constraints.
| [
{
"created": "Mon, 10 Apr 2017 11:37:30 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 2017 08:33:09 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Jun 2017 06:25:58 GMT",
"version": "v3"
}
] | 2017-06-15 | [
[
"Bolejko",
"Krzysztof",
""
]
] | This paper discusses the phenomenon of backreaction within the Szekeres model. Cosmological backreaction describes how the mean global evolution of the Universe deviates from the Friedmannian evolution. The analysis is based on models of a single cosmological environment and the global ensemble of the Szekeres models (of the Swiss-Cheese-type and Styrofoam-type). The obtained results show that non-linear growth of cosmic structures is associated with the growth of the spatial curvature $\Omega_{\cal R}$ (in the FLRW limit $\Omega_{\cal R} \to \Omega_k$). If averaged over global scales the result depends on the assumed global model of the Universe. Within the Swiss-Cheese model, which does have a fixed background, the volume average follows the evolution of the background, and the global spatial curvature averages out to zero (the background model is the $\Lambda$CDM model, which is spatially flat). In the Styrofoam-type model, which does not have a fixed background, the mean evolution deviates from the spatially flat $\Lambda$CDM model, and the mean spatial curvature evolves to from $\Omega_{\cal R} =0 $ at the CMB to $\Omega_{\cal R} \sim 0.1$ at $z =0$. If the Styrofoam-type model correctly captures evolutionary features of the real Universe then one should expect that in our Universe, the spatial curvature should build up (local growth of cosmic structures) and its mean global average should deviate from zero (backreaction). As a result, this paper predicts that the low-redshift Universe should not be spatially flat (i.e. $\Omega_k \ne 0$, even if in the early Universe $\Omega_k = 0$) and therefore when analysing low-$z$ cosmological data one should keep $\Omega_k$ as a free parameter and independent from the CMB constraints. |
2404.12496 | Fabio Dahia | J. M. Rocha and F. Dahia | Constraints on extra dimensions theories from gravitational quantum
barrier experiments | null | null | null | null | gr-qc hep-ph nucl-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the quantum-bouncer experiment involving ultracold neutrons in a
braneworld scenario. Extra-dimensional theories typically predict the
strengthening of gravitational interactions over short distances. In this
paper, we specifically study the anomalous gravitational interaction between
the bouncing neutron and the reflecting mirror, resulting from hidden
dimensions, and its effect on the outcome of this experiment in the context of
a thickbrane model. This analysis allows us to identify which physical quantity
of this extra-dimensional theory this neutron experiment is capable of
constraining. Based on the experimental data, we found a new and independent
empirical bound on free parameters of the model: the higher-dimensional
gravitational constant and a parameter related to a transverse width of the
confined matter inside the thickbrane. This new bound is valid in scenarios
with an arbitrary number of extra dimensions greater than two. In this manner,
by considering the thickness of the brane, we have been able to extend previous
studies on this topic, which were limited to models with few codimensions, due
to non-computability problems of power-law corrections of the gravitational
potential.
| [
{
"created": "Thu, 18 Apr 2024 20:20:30 GMT",
"version": "v1"
}
] | 2024-04-22 | [
[
"Rocha",
"J. M.",
""
],
[
"Dahia",
"F.",
""
]
] | We discuss the quantum-bouncer experiment involving ultracold neutrons in a braneworld scenario. Extra-dimensional theories typically predict the strengthening of gravitational interactions over short distances. In this paper, we specifically study the anomalous gravitational interaction between the bouncing neutron and the reflecting mirror, resulting from hidden dimensions, and its effect on the outcome of this experiment in the context of a thickbrane model. This analysis allows us to identify which physical quantity of this extra-dimensional theory this neutron experiment is capable of constraining. Based on the experimental data, we found a new and independent empirical bound on free parameters of the model: the higher-dimensional gravitational constant and a parameter related to a transverse width of the confined matter inside the thickbrane. This new bound is valid in scenarios with an arbitrary number of extra dimensions greater than two. In this manner, by considering the thickness of the brane, we have been able to extend previous studies on this topic, which were limited to models with few codimensions, due to non-computability problems of power-law corrections of the gravitational potential. |
1709.08807 | Naritaka Oshita | Naritaka Oshita | The generalized second law of thermodynamics and cosmological
decoherence | 5 pages, 2 figures; v2: minor corrections, references added, accepted
for publication in PRD | Phys. Rev. D 97, 023510 (2018) | 10.1103/PhysRevD.97.023510 | RESCEU-10/17 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We pointed out that the generalized second law of thermodynamics on a de
Sitter universe whose energy density stochastically fluctuates due to quantum
fluctuations is seemingly violated. We have shown that even in such a case, the
generalized second law is unviolated by taking cosmological decoherence into
account. It has been well known that the decoherence is necessary to give a
reasonable reason why our universe looks classical. Our proposal can support
the importance of decoherence from another aspect, i.e. the generalized second
law of thermodynamics.
| [
{
"created": "Tue, 26 Sep 2017 03:58:28 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Dec 2017 04:54:37 GMT",
"version": "v2"
}
] | 2018-01-17 | [
[
"Oshita",
"Naritaka",
""
]
] | We pointed out that the generalized second law of thermodynamics on a de Sitter universe whose energy density stochastically fluctuates due to quantum fluctuations is seemingly violated. We have shown that even in such a case, the generalized second law is unviolated by taking cosmological decoherence into account. It has been well known that the decoherence is necessary to give a reasonable reason why our universe looks classical. Our proposal can support the importance of decoherence from another aspect, i.e. the generalized second law of thermodynamics. |
1002.1844 | Ralf Schutzhold | Ralf Sch\"utzhold and William G. Unruh | On Quantum Correlations across the Black Hole Horizon | 5 pages RevTeX, 1 figure | Phys.Rev.D81:124033,2010 | 10.1103/PhysRevD.81.124033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by the condensed-matter analogues of black holes, we study the
quantum correlations across the event horizon reflecting the entanglement
between the outgoing particles of the Hawking radiation and their in-falling
partners. For a perfectly covariant theory, the total correlation is conserved
in time and piles up arbitrary close to the horizon in the past, where it
merges into the singularity of the vacuum two-point function at the light cone.
After modifying the dispersion relation (i.e., breaking Lorentz invariance) for
large $k$, on the other hand, the light cone is smeared out and the
entanglement is not conserved but actually created in a given rate per unit
time.
| [
{
"created": "Tue, 9 Feb 2010 12:56:10 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Schützhold",
"Ralf",
""
],
[
"Unruh",
"William G.",
""
]
] | Inspired by the condensed-matter analogues of black holes, we study the quantum correlations across the event horizon reflecting the entanglement between the outgoing particles of the Hawking radiation and their in-falling partners. For a perfectly covariant theory, the total correlation is conserved in time and piles up arbitrary close to the horizon in the past, where it merges into the singularity of the vacuum two-point function at the light cone. After modifying the dispersion relation (i.e., breaking Lorentz invariance) for large $k$, on the other hand, the light cone is smeared out and the entanglement is not conserved but actually created in a given rate per unit time. |
gr-qc/0310012 | Suresh Paingalil Kunjan | P.K.Suresh | Particle creation in the oscillatory phase of inflaton | 11 pages | Int.J.Theor.Phys. 43 (2004) 425-436 | 10.1023/B:IJTP.0000028875.07382.4e | null | gr-qc | null | A thermal squeezed state representation of inflaton is constructed for a flat
Friedmann-Robertson-Walker background metric and the phenomenon of particle
creation is examined during the oscillatory phase of inflaton, in the
semiclassical theory of gravity. An approximate solution to the semiclassical
Einstein equation is obtained in thermal squeezed state formalism by
perturbatively and is found obey the same power-law expansion as that of
classical Einstein equation. In addition to that the solution shows oscillatory
in nature except on a particular condition. It is also noted that, the
coherently oscillating nonclassical inflaton, in thermal squeezed vacuum state,
thermal squeezed state and thermal coherent state, suffer particle production
and the created particles exhibit oscillatory behavior. The present study can
account for the post inflation particle creation due to thermal and quantum
effects of inflaton in a flat FRW universe.
| [
{
"created": "Thu, 2 Oct 2003 10:51:09 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Suresh",
"P. K.",
""
]
] | A thermal squeezed state representation of inflaton is constructed for a flat Friedmann-Robertson-Walker background metric and the phenomenon of particle creation is examined during the oscillatory phase of inflaton, in the semiclassical theory of gravity. An approximate solution to the semiclassical Einstein equation is obtained in thermal squeezed state formalism by perturbatively and is found obey the same power-law expansion as that of classical Einstein equation. In addition to that the solution shows oscillatory in nature except on a particular condition. It is also noted that, the coherently oscillating nonclassical inflaton, in thermal squeezed vacuum state, thermal squeezed state and thermal coherent state, suffer particle production and the created particles exhibit oscillatory behavior. The present study can account for the post inflation particle creation due to thermal and quantum effects of inflaton in a flat FRW universe. |
2308.05781 | Ion I. Cotaescu | Ion I. Cotaescu | Conserved spin operator of Dirac's theory in spatially flat FLRW
spacetimes | 22 pages no figures. arXiv admin note: text overlap with
arXiv:2304.12182 | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | New conserved spin and orbital angular momentum operators of Dirac's theory
on spatially flat FLRW spacetimes are proposed generalizing thus recent results
concerning the role of Pryce's spin operator in the flat case [I. I. Cot\u
aescu, Eur. Phys. J. C (2022) 82:1073]. These operators split the conserved
total angular momentum generating the new spin and orbital symmetries that form
the rotations of the isometry groups. The new spin operator is defined and
studied in active mode with the help of a suitable spectral representation
giving its Fourier transfor. Moreover, in the same manner is defined the
operator of the fermion polarization. The orbital angular momentum is derived
in passive mode using a new method, inspired by Wigner's theory of induced
representations, but working properly only for global rotations. In this
approach the quantization is performed finding that the one-particle spin and
orbital angular momentum operators have the same form in any FLRW spacetime
regardless their concrete geometries given by various scale factors.
| [
{
"created": "Thu, 10 Aug 2023 15:02:52 GMT",
"version": "v1"
}
] | 2023-08-14 | [
[
"Cotaescu",
"Ion I.",
""
]
] | New conserved spin and orbital angular momentum operators of Dirac's theory on spatially flat FLRW spacetimes are proposed generalizing thus recent results concerning the role of Pryce's spin operator in the flat case [I. I. Cot\u aescu, Eur. Phys. J. C (2022) 82:1073]. These operators split the conserved total angular momentum generating the new spin and orbital symmetries that form the rotations of the isometry groups. The new spin operator is defined and studied in active mode with the help of a suitable spectral representation giving its Fourier transfor. Moreover, in the same manner is defined the operator of the fermion polarization. The orbital angular momentum is derived in passive mode using a new method, inspired by Wigner's theory of induced representations, but working properly only for global rotations. In this approach the quantization is performed finding that the one-particle spin and orbital angular momentum operators have the same form in any FLRW spacetime regardless their concrete geometries given by various scale factors. |
1407.3977 | David Sloan | David Sloan | Minimal Coupling and Attractors | 11 pages | Class. Quant. Grav. 31 (2014) 245015 | 10.1088/0264-9381/31/24/245015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effects of minimally coupling a gravity to matter on a flat
Robertson-Walker geometry are explored. Particular attention is paid to the
evolution of the symplectic structure and the Liouville measure it defines. We
show that the rescaling freedom introduced by choice of fiducial cell leads to
a symmetry between dynamical trajectories, which together with the Liouville
measure provides a natural volume weighting explanation for the generic
existence of attractors.
| [
{
"created": "Tue, 15 Jul 2014 13:05:30 GMT",
"version": "v1"
}
] | 2015-07-28 | [
[
"Sloan",
"David",
""
]
] | The effects of minimally coupling a gravity to matter on a flat Robertson-Walker geometry are explored. Particular attention is paid to the evolution of the symplectic structure and the Liouville measure it defines. We show that the rescaling freedom introduced by choice of fiducial cell leads to a symmetry between dynamical trajectories, which together with the Liouville measure provides a natural volume weighting explanation for the generic existence of attractors. |
gr-qc/0012061 | Avshalom C. Elitzur | Avshalom C. Elitzur and Shahar Dolev | Indeterminism and Time Symmetry are Incompatible: Reply to Rebilas | 3 pages, 4 figures | Phys.Lett. A266 (2000) 268-270 | 10.1016/S0375-9601(00)00057-8 | null | gr-qc | null | Rebilas argues that time-reversal can occur even in an indeterministic
system. This hypothesis is untestable, hence lying beyond physics.
| [
{
"created": "Sat, 16 Dec 2000 19:59:32 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Elitzur",
"Avshalom C.",
""
],
[
"Dolev",
"Shahar",
""
]
] | Rebilas argues that time-reversal can occur even in an indeterministic system. This hypothesis is untestable, hence lying beyond physics. |
2111.00013 | Antonios Tsokaros A. | Antonios Tsokaros, Milton Ruiz, Stuart L. Shapiro, K\=oji Ury\=u | Magnetohydrodynamic simulations of self-consistent rotating neutron
stars with mixed poloidal and toroidal magnetic fields | 8 pages | null | 10.1103/PhysRevLett.128.061101 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We perform the first magnetohydrodynamic simulations in full general
relativity of self-consistent rotating neutron stars (NSs) with ultrastrong
mixed poloidal and toroidal magnetic fields. The initial uniformly rotating NS
models are computed assuming perfect conductivity, stationarity, and
axisymmetry. Although the specific geometry of the mixed field configuration
can delay or accelerate the development of various instabilities known from
analytic perturbative studies, all our models finally succumb to them.
Differential rotation is developed spontaneously in the cores of our magnetars
which, after sufficient time, is converted back to uniform rotation. The
rapidly rotating magnetars show a significant amount of ejecta, which can be
responsible for transient kilonova signatures. However no highly collimated,
helical magnetic fields or incipient jets, which are necessary for gamma-ray
bursts, arise at the poles of these magnetars by the time our simulations are
terminated.
| [
{
"created": "Fri, 29 Oct 2021 18:00:00 GMT",
"version": "v1"
}
] | 2022-02-23 | [
[
"Tsokaros",
"Antonios",
""
],
[
"Ruiz",
"Milton",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Uryū",
"Kōji",
""
]
] | We perform the first magnetohydrodynamic simulations in full general relativity of self-consistent rotating neutron stars (NSs) with ultrastrong mixed poloidal and toroidal magnetic fields. The initial uniformly rotating NS models are computed assuming perfect conductivity, stationarity, and axisymmetry. Although the specific geometry of the mixed field configuration can delay or accelerate the development of various instabilities known from analytic perturbative studies, all our models finally succumb to them. Differential rotation is developed spontaneously in the cores of our magnetars which, after sufficient time, is converted back to uniform rotation. The rapidly rotating magnetars show a significant amount of ejecta, which can be responsible for transient kilonova signatures. However no highly collimated, helical magnetic fields or incipient jets, which are necessary for gamma-ray bursts, arise at the poles of these magnetars by the time our simulations are terminated. |
1508.07137 | B. S. Ratanpal | B. S. Ratanpal and Jaita Sharma | Charged Anisotropic Star on Paraboloidal Spacetime | 10 pages, 7 figures, Accepted for Publication in Pramana Journal of
Physics | Pramana Journal of Physics, V. 86, p. 527, 2016 | 10.1007/s12043-015-1036-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The charged anisotropic star on paraboloidal spacetime is reported by
choosing particular form of radial pressure and electric field intensity. The
non-singular solution of Einstein-Maxwell system of equation have been derived
and it is shown that model satisfy all the physical plausibility conditions. It
is observed that in the absence of electric field intensity, model reduces to
particular case of uncharged Sharma \& Ratanpal model. It is also observed that
the parameter used in electric field intensity directly effects the mass of the
star.
| [
{
"created": "Fri, 28 Aug 2015 09:10:21 GMT",
"version": "v1"
}
] | 2016-04-07 | [
[
"Ratanpal",
"B. S.",
""
],
[
"Sharma",
"Jaita",
""
]
] | The charged anisotropic star on paraboloidal spacetime is reported by choosing particular form of radial pressure and electric field intensity. The non-singular solution of Einstein-Maxwell system of equation have been derived and it is shown that model satisfy all the physical plausibility conditions. It is observed that in the absence of electric field intensity, model reduces to particular case of uncharged Sharma \& Ratanpal model. It is also observed that the parameter used in electric field intensity directly effects the mass of the star. |
1902.05090 | Andrzej Rostworowski | Andrzej Rostworowski | Cosmological perturbations in the Regge-Wheeler formalism | 5 pages, no figures | Phys. Rev. D 101, 083512 (2020) | 10.1103/PhysRevD.101.083512 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study linear perturbations of the Friedmann-Lemaitre-Robertson-Walker
(FLRW) cosmological model in the Regge-Wheeler formalism which is a standard
framework to study perturbations of spherically-symmetric black holes. In
particular, we show that the general solution of linear perturbation equations
can be given in terms of two copies of a master scalar satisfying scalar wave
equation on the FLRW background (with a Regge-Wheeler/Zerilli type potential)
thus representing two gravitational degrees of freedom, and one scalar
satisfying a transport type equation representing (conformal) matter
perturbation. We expect the Regge-Wheeler formalism to be easily extended to
include nonlinear perturbations, akin to to the recent work [Phys. Rev. D 96,
124026 (2017)].
| [
{
"created": "Wed, 13 Feb 2019 19:17:14 GMT",
"version": "v1"
}
] | 2020-04-15 | [
[
"Rostworowski",
"Andrzej",
""
]
] | We study linear perturbations of the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model in the Regge-Wheeler formalism which is a standard framework to study perturbations of spherically-symmetric black holes. In particular, we show that the general solution of linear perturbation equations can be given in terms of two copies of a master scalar satisfying scalar wave equation on the FLRW background (with a Regge-Wheeler/Zerilli type potential) thus representing two gravitational degrees of freedom, and one scalar satisfying a transport type equation representing (conformal) matter perturbation. We expect the Regge-Wheeler formalism to be easily extended to include nonlinear perturbations, akin to to the recent work [Phys. Rev. D 96, 124026 (2017)]. |
1309.1948 | Kourosh Nozari | Faeze Kiani and Kourosh Nozari | Energy conditions in $F(T,\Theta)$ gravity and compatibility with a
stable de Sitter solution | 16 pages, no figure, revised version with new references | Phys. Lett. B 728 (2014) 554-561 | 10.1016/j.physletb.2013.12.036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a new type of the modified teleparallel gravity of the form
$F(T,\,\Theta)$ in which $T$, the torsion scalar, is coupled with $\Theta$, the
trace of the stress-energy tensor. In a perturbational approach, we study the
stability of the solutions and as a special case we find a condition for
stability of the de Sitter phase. Then we adopt a suitable form for
$F(T,\Theta)$ that realizes a stable de Sitter solution so that the stability
condition creates a specific constraint on the parametric space of the model.
Finally, the energy conditions in the framework of $F(T,\Theta)$ gravity is
investigated.
| [
{
"created": "Sun, 8 Sep 2013 11:54:07 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Sep 2013 12:34:13 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Sep 2013 06:30:06 GMT",
"version": "v3"
}
] | 2015-06-17 | [
[
"Kiani",
"Faeze",
""
],
[
"Nozari",
"Kourosh",
""
]
] | We study a new type of the modified teleparallel gravity of the form $F(T,\,\Theta)$ in which $T$, the torsion scalar, is coupled with $\Theta$, the trace of the stress-energy tensor. In a perturbational approach, we study the stability of the solutions and as a special case we find a condition for stability of the de Sitter phase. Then we adopt a suitable form for $F(T,\Theta)$ that realizes a stable de Sitter solution so that the stability condition creates a specific constraint on the parametric space of the model. Finally, the energy conditions in the framework of $F(T,\Theta)$ gravity is investigated. |
1001.2316 | Yosef Zlochower | Carlos O. Lousto, Hiroyuki Nakano, Yosef Zlochower, Manuela Campanelli | Intermediate Mass Ratio Black Hole Binaries: Numerical Relativity meets
Perturbation Theory | 4 pages, 5 figures, revtex4 | Phys.Rev.Lett.104:211101,2010 | 10.1103/PhysRevLett.104.211101 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study black-hole binaries in the intermediate-mass-ratio regime 0.01 < q <
0.1 with a new technique that makes use of nonlinear numerical trajectories and
efficient perturbative evolutions to compute waveforms at large radii for the
leading and nonleading modes. As a proof-of-concept, we compute waveforms for
q=1/10. We discuss applications of these techniques for LIGO/VIRGO data
analysis and the possibility that our technique can be extended to produce
accurate waveform templates from a modest number of fully-nonlinear numerical
simulations.
| [
{
"created": "Wed, 13 Jan 2010 21:23:15 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Lousto",
"Carlos O.",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Zlochower",
"Yosef",
""
],
[
"Campanelli",
"Manuela",
""
]
] | We study black-hole binaries in the intermediate-mass-ratio regime 0.01 < q < 0.1 with a new technique that makes use of nonlinear numerical trajectories and efficient perturbative evolutions to compute waveforms at large radii for the leading and nonleading modes. As a proof-of-concept, we compute waveforms for q=1/10. We discuss applications of these techniques for LIGO/VIRGO data analysis and the possibility that our technique can be extended to produce accurate waveform templates from a modest number of fully-nonlinear numerical simulations. |
gr-qc/0303095 | Alec Maassen van den Brink | Alec Maassen van den Brink | WKB analysis of the Regge-Wheeler equation down in the frequency plane | REVTeX4, 11pp with one EPS figure. N.B.: 'Alec' is my first, and
'Maassen van den Brink' my family name. v2: discussion and Refs. expanded;
overall grooming. v3: added calculation of the highly damped QNMs, incl. the
leading correction. v4: a few clarifications and minor corrections; final, to
appear in JMP | J.Math.Phys. 45 (2004) 327 | 10.1063/1.1626805 | null | gr-qc hep-th math-ph math.MP | null | The Regge-Wheeler equation for black-hole gravitational waves is analyzed for
large negative imaginary frequencies, leading to a calculation of the cut
strength for waves outgoing to infinity. In the--limited--region of overlap,
the results agree well with numerical findings [Class. Quantum Grav._20_, L217
(2003)]. Requiring these waves to be outgoing into the horizon as well
subsequently yields an analytic formula for the highly damped Schwarzschild
quasinormal modes,_including_ the leading correction. Just as in the WKB
quantization of, e.g., the harmonic oscillator, solutions in different regions
of space have to be joined through a connection formula, valid near the
boundary between them where WKB breaks down. For the oscillator, this boundary
is given by the classical turning points; fascinatingly, the connection here
involves an expansion around the black-hole singularity r=0.
| [
{
"created": "Tue, 25 Mar 2003 18:15:30 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Apr 2003 01:10:58 GMT",
"version": "v2"
},
{
"created": "Wed, 16 Apr 2003 17:00:10 GMT",
"version": "v3"
},
{
"created": "Wed, 12 Nov 2003 19:32:05 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Brink",
"Alec Maassen van den",
""
]
] | The Regge-Wheeler equation for black-hole gravitational waves is analyzed for large negative imaginary frequencies, leading to a calculation of the cut strength for waves outgoing to infinity. In the--limited--region of overlap, the results agree well with numerical findings [Class. Quantum Grav._20_, L217 (2003)]. Requiring these waves to be outgoing into the horizon as well subsequently yields an analytic formula for the highly damped Schwarzschild quasinormal modes,_including_ the leading correction. Just as in the WKB quantization of, e.g., the harmonic oscillator, solutions in different regions of space have to be joined through a connection formula, valid near the boundary between them where WKB breaks down. For the oscillator, this boundary is given by the classical turning points; fascinatingly, the connection here involves an expansion around the black-hole singularity r=0. |
1308.0300 | Andrzej Banburski | Andrzej Banburski and Laurent Freidel | Snyder Momentum Space in Relative Locality | 22 pages, 6 figures, matches version accepted in PRD | Phys. Rev. D 90, 076010 (2014) | 10.1103/PhysRevD.90.076010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard approaches of phenomenology of Quantum Gravity have usually
explicitly violated Lorentz invariance, either in the dispersion relation or in
the addition rule for momenta. We investigate whether it is possible in 3+1
dimensions to have a non local deformation that preserves fully Lorentz
invariance, as it is the case in 2+1D Quantum Gravity. We answer positively to
this question and show for the first time how to construct a homogeneously
curved momentum space preserving the full action of the Lorentz group in
dimension 4 and higher, despite relaxing locality. We study the property of
this relative locality deformation and show that this space leads to a
noncommutativity related to Snyder spacetime.
| [
{
"created": "Thu, 1 Aug 2013 18:53:54 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Oct 2014 19:58:24 GMT",
"version": "v2"
}
] | 2014-11-05 | [
[
"Banburski",
"Andrzej",
""
],
[
"Freidel",
"Laurent",
""
]
] | The standard approaches of phenomenology of Quantum Gravity have usually explicitly violated Lorentz invariance, either in the dispersion relation or in the addition rule for momenta. We investigate whether it is possible in 3+1 dimensions to have a non local deformation that preserves fully Lorentz invariance, as it is the case in 2+1D Quantum Gravity. We answer positively to this question and show for the first time how to construct a homogeneously curved momentum space preserving the full action of the Lorentz group in dimension 4 and higher, despite relaxing locality. We study the property of this relative locality deformation and show that this space leads to a noncommutativity related to Snyder spacetime. |
1802.07293 | Paolo Valtancoli | P. Valtancoli | Remarks on cosmological gravitational waves | 7 pages, no figures | null | 10.1016/j.aop.2018.05.003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the propagation of a gravitational wave in an Ads spacetime. We find
that, in presence of the cosmological constant, the graviton mass cannot be
measured with higher precision than the square root of the cosmological
constant.
| [
{
"created": "Tue, 20 Feb 2018 19:19:45 GMT",
"version": "v1"
}
] | 2018-06-13 | [
[
"Valtancoli",
"P.",
""
]
] | We study the propagation of a gravitational wave in an Ads spacetime. We find that, in presence of the cosmological constant, the graviton mass cannot be measured with higher precision than the square root of the cosmological constant. |
1603.03749 | Gustavo Dotti | Gustavo Dotti | Black hole nonmodal linear stability: the Schwarzschild (A)dS cases | Typos corrected, changes in the Introduction (including example of
nonmodal instability) | Class.Quant.Grav. 33 (2016) 205005 | 10.1088/0264-9381/33/20/205005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nonmodal linear stability of the Schwarzschild black hole established in
Phys. Rev. Lett. 112 (2014) 191101 is generalized to the case of a nonnegative
cosmological constant $\Lambda$. Two gauge invariant combinations $G_{\pm}$ of
perturbed scalars made out of the Weyl tensor and its first covariant
derivative are found such that the map $[h_{\alpha \beta}] \to \left( G_-
\left([h_{\alpha \beta}] \right), G_+ \left([h_{\alpha \beta}] \right) \right)$
with domain the set of equivalent classes $[h_{\alpha \beta}]$ under gauge
transformations of solutions of the linearized Einstein's equation, is
invertible. The way to reconstruct a representative of $[h_{\alpha \beta}]$ in
terms of $(G_-,G_+)$ is given. It is proved that, for an arbitrary perturbation
consistent with the background asymptote, $G_+$ and $G_-$ are bounded in the
the outer static region. At large times, the perturbation decays leaving a
linearized Kerr black hole around the Schwarzschild or Schwarschild de Sitter
background solution. For negative cosmological constant it is shown that there
is a choice of boundary conditions at the time-like boundary under which the
Schwarzschild anti de Sitter black hole is unstable. The root of
Chandrasekhar's duality relating odd and even modes is exhibited, and some
technicalities related to this duality and omitted in the original proof of the
$\Lambda=0$ case are explained in detail.
| [
{
"created": "Fri, 11 Mar 2016 20:28:48 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Mar 2016 14:59:35 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Jun 2016 16:20:27 GMT",
"version": "v3"
},
{
"created": "Tue, 6 Sep 2016 12:49:08 GMT",
"version": "v4"
},
{
"created": "Mon, 19 Sep 2016 00:24:44 GMT",
"version": "v5"
}
] | 2016-09-26 | [
[
"Dotti",
"Gustavo",
""
]
] | The nonmodal linear stability of the Schwarzschild black hole established in Phys. Rev. Lett. 112 (2014) 191101 is generalized to the case of a nonnegative cosmological constant $\Lambda$. Two gauge invariant combinations $G_{\pm}$ of perturbed scalars made out of the Weyl tensor and its first covariant derivative are found such that the map $[h_{\alpha \beta}] \to \left( G_- \left([h_{\alpha \beta}] \right), G_+ \left([h_{\alpha \beta}] \right) \right)$ with domain the set of equivalent classes $[h_{\alpha \beta}]$ under gauge transformations of solutions of the linearized Einstein's equation, is invertible. The way to reconstruct a representative of $[h_{\alpha \beta}]$ in terms of $(G_-,G_+)$ is given. It is proved that, for an arbitrary perturbation consistent with the background asymptote, $G_+$ and $G_-$ are bounded in the the outer static region. At large times, the perturbation decays leaving a linearized Kerr black hole around the Schwarzschild or Schwarschild de Sitter background solution. For negative cosmological constant it is shown that there is a choice of boundary conditions at the time-like boundary under which the Schwarzschild anti de Sitter black hole is unstable. The root of Chandrasekhar's duality relating odd and even modes is exhibited, and some technicalities related to this duality and omitted in the original proof of the $\Lambda=0$ case are explained in detail. |
1908.10872 | T. Padmanabhan | T. Padmanabhan | A Measure for Quantum Paths, Gravity and Spacetime Microstructure | Extended version of the essay which received an Honorable Mention in
the Gravity Research Foundation Essay Competition, 2019; publication in the
special issue of IJMPD; 23 pages; no figures | Int. Jour. Mod. Phys D, (2019), 1944009 | 10.1142/S0218271819440097 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The number of classical paths of a given length, connecting any two events in
a (pseudo) Riemannian spacetime is, of course, infinite. It is, however,
possible to define a useful, finite, measure $N(x_2,x_1;\sigma)$ for the
effective number of quantum paths [of length $\sigma$ connecting two events
$(x_1,x_2)$] in an arbitrary spacetime. When $x_2=x_1$, this reduces to
$C(x,\sigma)$ giving the measure for closed quantum loops of length $\sigma$
containing an event $x$. Both $N(x_2,x_1;\sigma)$ and $C(x,\sigma)$ are
well-defined and depend only on the geometry of the spacetime. Various other
physical quantities like, for e.g., the effective Lagrangian, can be expressed
in terms of $N(x_2,x_1;\sigma)$. The corresponding measure for the total path
length contributed by the closed loops, in a spacetime region $\mathcal{V}$, is
given by the integral of $L(\sigma;x) \equiv\sigma C(\sigma;x)$ over
$\mathcal{V}$. Remarkably enough $L(0;x) \propto R(x)$, the Ricci scalar; i.e,
the measure for the total length contributed by infinitesimal closed loops in a
region of spacetime gives us the Einstein-Hilbert action. Its variation, when
we vary the metric, can provide a new route towards induced/emergent gravity
descriptions. In the presence of a background electromagnetic field, the
corresponding expressions for $N(x_2,x_1;\sigma)$ and $C(x,\sigma)$ can be
related to the holonomies of the field. The measure $N(x_2,x_1;\sigma)$ can
also be used to evaluate a wide class of path integrals for which the action
and the measure are arbitrary functions of the path length. As an example, I
compute a modified path integral which incorporates the zero-point-length in
the spacetime. I also describe several other properties of $N(x_2,x_1;\sigma)$
and outline a few simple applications.
| [
{
"created": "Wed, 28 Aug 2019 18:00:04 GMT",
"version": "v1"
}
] | 2019-08-30 | [
[
"Padmanabhan",
"T.",
""
]
] | The number of classical paths of a given length, connecting any two events in a (pseudo) Riemannian spacetime is, of course, infinite. It is, however, possible to define a useful, finite, measure $N(x_2,x_1;\sigma)$ for the effective number of quantum paths [of length $\sigma$ connecting two events $(x_1,x_2)$] in an arbitrary spacetime. When $x_2=x_1$, this reduces to $C(x,\sigma)$ giving the measure for closed quantum loops of length $\sigma$ containing an event $x$. Both $N(x_2,x_1;\sigma)$ and $C(x,\sigma)$ are well-defined and depend only on the geometry of the spacetime. Various other physical quantities like, for e.g., the effective Lagrangian, can be expressed in terms of $N(x_2,x_1;\sigma)$. The corresponding measure for the total path length contributed by the closed loops, in a spacetime region $\mathcal{V}$, is given by the integral of $L(\sigma;x) \equiv\sigma C(\sigma;x)$ over $\mathcal{V}$. Remarkably enough $L(0;x) \propto R(x)$, the Ricci scalar; i.e, the measure for the total length contributed by infinitesimal closed loops in a region of spacetime gives us the Einstein-Hilbert action. Its variation, when we vary the metric, can provide a new route towards induced/emergent gravity descriptions. In the presence of a background electromagnetic field, the corresponding expressions for $N(x_2,x_1;\sigma)$ and $C(x,\sigma)$ can be related to the holonomies of the field. The measure $N(x_2,x_1;\sigma)$ can also be used to evaluate a wide class of path integrals for which the action and the measure are arbitrary functions of the path length. As an example, I compute a modified path integral which incorporates the zero-point-length in the spacetime. I also describe several other properties of $N(x_2,x_1;\sigma)$ and outline a few simple applications. |
gr-qc/0003043 | Rafael D. Sorkin | Rafael D. Sorkin (Syracuse University) | Indications of causal set cosmology | 7 pages, plainTeX. Wording has been clarified further in places Text
of a talk entitled ``Causal Sets and Stochastic Spacetime'' | Int.J.Theor.Phys.39:1731-1736,2000 | 10.1023/A:1003629312096 | SU-GP-00/02-1 | gr-qc astro-ph hep-th | null | Within the context of a recently proposed family of stochastic dynamical laws
for causal sets, one can ask whether the universe might have emerged from the
quantum-gravity era with a large enough size and with sufficient homogeneity to
explain its present-day large-scale structure. In general, such a scenario
would be expected to require the introduction of very large or very small
fundamental parameters into the theory. However, there are indications that
such ``fine tuning'' is not necessary, and a large homogeneous and isotropic
cosmos can emerge naturally, thanks to the action of a kind of renormalization
group associated with cosmic cycles of expansion and re-contraction.
| [
{
"created": "Fri, 10 Mar 2000 04:38:49 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jul 2000 06:53:11 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Nov 2001 20:09:15 GMT",
"version": "v3"
}
] | 2011-04-15 | [
[
"Sorkin",
"Rafael D.",
"",
"Syracuse University"
]
] | Within the context of a recently proposed family of stochastic dynamical laws for causal sets, one can ask whether the universe might have emerged from the quantum-gravity era with a large enough size and with sufficient homogeneity to explain its present-day large-scale structure. In general, such a scenario would be expected to require the introduction of very large or very small fundamental parameters into the theory. However, there are indications that such ``fine tuning'' is not necessary, and a large homogeneous and isotropic cosmos can emerge naturally, thanks to the action of a kind of renormalization group associated with cosmic cycles of expansion and re-contraction. |
gr-qc/0102016 | Peter Dunsby | Deon Solomons, Peter Dunsby and George Ellis | Exact Inflation Braneworlds | 6 pages RevTeX. Submitted to Physical Review D | null | null | uct-cosmology-01/02 | gr-qc | null | In Randall-Sundrum type braneworld cosmologies, the dynamical equations on
the three-brane differ from the general relativity equations by terms that
carry the effects of embedding and of the free gravitational field in the
five-dimensional bulk. In a FRW ansatze for the metric, we present two methods
for deriving inflationary solutions to the covariant non-linear dynamical
equations for the gravitational and matter fields on the brane. In the first
approach we examine the constraints on the dynamical relationship between the
cosmological scale factor and the scalar field driving self-interaction
potential, imposed by the weak energy condition. We then investigate
inflationary solutions obtained from a scalar field superpotential. Both these
techniques for solving the braneworld field equations are illustrated by flat
curvature models.
| [
{
"created": "Mon, 5 Feb 2001 12:34:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Solomons",
"Deon",
""
],
[
"Dunsby",
"Peter",
""
],
[
"Ellis",
"George",
""
]
] | In Randall-Sundrum type braneworld cosmologies, the dynamical equations on the three-brane differ from the general relativity equations by terms that carry the effects of embedding and of the free gravitational field in the five-dimensional bulk. In a FRW ansatze for the metric, we present two methods for deriving inflationary solutions to the covariant non-linear dynamical equations for the gravitational and matter fields on the brane. In the first approach we examine the constraints on the dynamical relationship between the cosmological scale factor and the scalar field driving self-interaction potential, imposed by the weak energy condition. We then investigate inflationary solutions obtained from a scalar field superpotential. Both these techniques for solving the braneworld field equations are illustrated by flat curvature models. |
2306.17262 | Henri Inchausp\'e Dr. | Lavinia Heisenberg, Henri Inchausp\'e, Dam Quang Nam, Orion Sauter,
Ricardo Waibel and Peter Wass | LISA Dynamics & Control: Closed-loop Simulation and Numerical
Demonstration of Time Delay Interferometry | 26 pages, 8 figures. Revision of Subsection VII.C, and of the
physical interpretation of the comparison between Linear and Non-linear
simulations. In addition to a few editorial improvements (rephrasings, figure
and text formatting). The dynamical models, the simulations, and the results
of the article (aside from VII.C) remain unchanged | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Laser Interferometer Space Antenna (LISA), space-based gravitational wave
observatory involves a complex multidimensional closed-loop dynamical system.
Its instrument performance is expected to be less efficiently isolated from
platform motion than was its simpler technological demonstrator, LISA
Pathfinder. It is of crucial importance to understand and model LISA dynamical
behavior accurately to understand the propagation of dynamical excitations
through the response of the instrument down to the interferometer data streams.
More generally, simulation of the system allows for the preparation of the
processing and interpretation of in-flight metrology data. In this work, we
present a comprehensive mathematical modeling of the closed-loop system
dynamics and its numerical implementation within the LISA Consortium simulation
suite. We provide, for the first time, a full time-domain numerical
demonstration of post-processing Time Delay Interferometer techniques combining
multiple position measurements with realistic control loops to create a
synthetic Michelson interferometer. We show that in the absence of physical
coupling to spacecraft and telescope motion (through tilt-to-length, stiffness
and actuation cross-talk) the effect of noisy spacecraft motion is efficiently
suppressed to a level below the noise originating in the rest of the
instrument.
| [
{
"created": "Thu, 29 Jun 2023 19:01:49 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Aug 2023 12:56:40 GMT",
"version": "v2"
}
] | 2023-09-05 | [
[
"Heisenberg",
"Lavinia",
""
],
[
"Inchauspé",
"Henri",
""
],
[
"Nam",
"Dam Quang",
""
],
[
"Sauter",
"Orion",
""
],
[
"Waibel",
"Ricardo",
""
],
[
"Wass",
"Peter",
""
]
] | The Laser Interferometer Space Antenna (LISA), space-based gravitational wave observatory involves a complex multidimensional closed-loop dynamical system. Its instrument performance is expected to be less efficiently isolated from platform motion than was its simpler technological demonstrator, LISA Pathfinder. It is of crucial importance to understand and model LISA dynamical behavior accurately to understand the propagation of dynamical excitations through the response of the instrument down to the interferometer data streams. More generally, simulation of the system allows for the preparation of the processing and interpretation of in-flight metrology data. In this work, we present a comprehensive mathematical modeling of the closed-loop system dynamics and its numerical implementation within the LISA Consortium simulation suite. We provide, for the first time, a full time-domain numerical demonstration of post-processing Time Delay Interferometer techniques combining multiple position measurements with realistic control loops to create a synthetic Michelson interferometer. We show that in the absence of physical coupling to spacecraft and telescope motion (through tilt-to-length, stiffness and actuation cross-talk) the effect of noisy spacecraft motion is efficiently suppressed to a level below the noise originating in the rest of the instrument. |
1707.09945 | Matteo Tuveri | Mariano Cadoni, Roberto Casadio, Andrea Giusti, Wolfgang M\"uck,
Matteo Tuveri | Effective Fluid Description of the Dark Universe | 13 pages, no figures. Replaced version: major revisions in the
introduction, microscopic derivation of Tully-Fisher relation using
Bose-Einstein condensate of gravitons. Some typos corrected | Phys. Lett. B 776 (2018) 242 | 10.1016/j.physletb.2017.11.058 | null | gr-qc astro-ph.CO astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose an effective anisotropic fluid description for a generic
infrared-modified theory of gravity. In our framework, the additional component
of the acceleration, commonly attributed to dark matter, is explained as a
radial pressure generated by the reaction of the dark energy fluid to the
presence of baryonic matter. Using quite general assumptions, and a microscopic
description of the fluid in terms of a Bose-Einstein condensate of gravitons,
we find the static, spherically symmetric solution for the metric in terms of
the Misner-Sharp mass function and the fluid pressure. At galactic scales, we
correctly reproduce the leading MOND-like $\log(r)$ and subleading
$(1/r)\,\log(r)$ terms in the weak-field expansion of the potential. Our
description also predicts a tiny (of order $10^{-6}$ for a typical spiral
galaxy) Machian modification of the Newtonian potential at galactic scales,
which is controlled by the cosmological acceleration.
| [
{
"created": "Mon, 31 Jul 2017 16:33:51 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Oct 2017 13:50:03 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Dec 2017 10:20:58 GMT",
"version": "v3"
}
] | 2017-12-06 | [
[
"Cadoni",
"Mariano",
""
],
[
"Casadio",
"Roberto",
""
],
[
"Giusti",
"Andrea",
""
],
[
"Mück",
"Wolfgang",
""
],
[
"Tuveri",
"Matteo",
""
]
] | We propose an effective anisotropic fluid description for a generic infrared-modified theory of gravity. In our framework, the additional component of the acceleration, commonly attributed to dark matter, is explained as a radial pressure generated by the reaction of the dark energy fluid to the presence of baryonic matter. Using quite general assumptions, and a microscopic description of the fluid in terms of a Bose-Einstein condensate of gravitons, we find the static, spherically symmetric solution for the metric in terms of the Misner-Sharp mass function and the fluid pressure. At galactic scales, we correctly reproduce the leading MOND-like $\log(r)$ and subleading $(1/r)\,\log(r)$ terms in the weak-field expansion of the potential. Our description also predicts a tiny (of order $10^{-6}$ for a typical spiral galaxy) Machian modification of the Newtonian potential at galactic scales, which is controlled by the cosmological acceleration. |
2404.18128 | Christian Corda Prof. | Christian Corda and Carlo Cafaro | Universality of the thermodynamics of a quantum-mechanically radiating
black hole departing from thermality | 13 pages, to appear in Physics Letters B | Phys. Lett. B, 856, 138948 (2024) | 10.1016/j.physletb.2024.138948 | null | gr-qc astro-ph.HE hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mathur and Mehta won the third prize in the 2023 Gravity Research Foundation
Essay Competition for proving the universality of black hole (BH)
thermodynamics. Specifically, they demonstrated that any Extremely Compact
Object (ECO) must have the same BH thermodynamic properties regardless of
whether or not the ECO possesses an event horizon. The result is remarkable,
but it was obtained under the approximation according to which the BH emission
spectrum has an exactly thermal character. In fact, strong arguments based on
energy conservation and BH back reaction imply that the spectrum of the Hawking
radiation cannot be exactly thermal. In this work the result of Mathur and
Mehta will be extended to the case where the radiation spectrum is not exactly
thermal using the concept of BH dynamical state.
| [
{
"created": "Sun, 28 Apr 2024 09:52:58 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jul 2024 20:22:01 GMT",
"version": "v2"
}
] | 2024-08-15 | [
[
"Corda",
"Christian",
""
],
[
"Cafaro",
"Carlo",
""
]
] | Mathur and Mehta won the third prize in the 2023 Gravity Research Foundation Essay Competition for proving the universality of black hole (BH) thermodynamics. Specifically, they demonstrated that any Extremely Compact Object (ECO) must have the same BH thermodynamic properties regardless of whether or not the ECO possesses an event horizon. The result is remarkable, but it was obtained under the approximation according to which the BH emission spectrum has an exactly thermal character. In fact, strong arguments based on energy conservation and BH back reaction imply that the spectrum of the Hawking radiation cannot be exactly thermal. In this work the result of Mathur and Mehta will be extended to the case where the radiation spectrum is not exactly thermal using the concept of BH dynamical state. |
2108.02782 | Kyriakos Destounis Dr. | Kyriakos Destounis and Kostas D. Kokkotas | Gravitational-wave glitches: resonant islands and frequency jumps in
non-integrable extreme-mass-ratio inspirals | 13 pages, 4 figures, accepted for publication in Phys. Rev. D | Phys. Rev. D 104, 064023 (2021) | 10.1103/PhysRevD.104.064023 | null | gr-qc astro-ph.HE nlin.CD | http://creativecommons.org/licenses/by/4.0/ | The detection of gravitational waves from extreme-mass-ratio inspirals with
upcoming space-borne detectors will allow for unprecedented tests of general
relativity in the strong-field regime. Aside from assessing whether black holes
are unequivocally described by the Kerr metric, such detections may place
constraints on the degree of spacetime symmetry. In particular, depending on
exactly how a hypothetical departure from the Kerr metric manifests, the Carter
symmetry, which implies the integrability of the geodesic equations, may be
broken. Here, we examine the gravitational waveforms associated with
non-integrable extreme-mass-ratio inspirals involving a small-mass companion
and a supermassive compact object of general relativity, namely the
Manko-Novikov spacetime. We show that the waveforms displays sudden frequency
jumps, when the companion transverses resonant islands. These findings
demonstrate that such abrupt manifestations in the gravitational-wave
frequencies are generic, have a genuine astrophysical origin and function as a
distinctive signature of chaotic phenomena in extreme-mass-ratio binaries.
| [
{
"created": "Thu, 5 Aug 2021 18:00:01 GMT",
"version": "v1"
}
] | 2021-09-08 | [
[
"Destounis",
"Kyriakos",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | The detection of gravitational waves from extreme-mass-ratio inspirals with upcoming space-borne detectors will allow for unprecedented tests of general relativity in the strong-field regime. Aside from assessing whether black holes are unequivocally described by the Kerr metric, such detections may place constraints on the degree of spacetime symmetry. In particular, depending on exactly how a hypothetical departure from the Kerr metric manifests, the Carter symmetry, which implies the integrability of the geodesic equations, may be broken. Here, we examine the gravitational waveforms associated with non-integrable extreme-mass-ratio inspirals involving a small-mass companion and a supermassive compact object of general relativity, namely the Manko-Novikov spacetime. We show that the waveforms displays sudden frequency jumps, when the companion transverses resonant islands. These findings demonstrate that such abrupt manifestations in the gravitational-wave frequencies are generic, have a genuine astrophysical origin and function as a distinctive signature of chaotic phenomena in extreme-mass-ratio binaries. |
gr-qc/0608061 | Guillermo A. Mena Marugan | Pablo Galan and Guillermo A. Mena Marugan | Entropy and temperature of black holes in a gravity's rainbow | 11 pages, 2 new references added, version accepted for publication in
Physical Review D | Phys.Rev. D74 (2006) 044035 | 10.1103/PhysRevD.74.044035 | null | gr-qc | null | The linear relation between the entropy and area of a black hole can be
derived from the Heisenberg principle, the energy-momentum dispersion relation
of special relativity, and general considerations about black holes. There
exist results in quantum gravity and related contexts suggesting the
modification of the usual dispersion relation and uncertainty principle. One of
these contexts is the gravity's rainbow formalism. We analyze the consequences
of such a modification for black hole thermodynamics from the perspective of
two distinct rainbow realizations built from doubly special relativity. One is
the proposal of Magueijo and Smolin and the other is based on a canonical
implementation of doubly special relativity put forward recently by the
authors. In these scenarios, we obtain modified expressions for the entropy and
temperature of black holes. We show that, for a family of doubly special
relativity theories satisfying certain properties, the temperature can vanish
in the limit of zero black hole mass. For the Magueijo and Smolin proposal,
this is only possible for some restricted class of models with bounded energy
and unbounded momentum. With the proposal of a canonical implementation, on the
other hand, the temperature may vanish for more general theories; in
particular, the momentum may also be bounded, with bounded or unbounded energy.
This opens new possibilities for the outcome of black hole evaporation in the
framework of a gravity's rainbow.
| [
{
"created": "Fri, 11 Aug 2006 16:22:44 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Aug 2006 15:20:29 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Galan",
"Pablo",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] | The linear relation between the entropy and area of a black hole can be derived from the Heisenberg principle, the energy-momentum dispersion relation of special relativity, and general considerations about black holes. There exist results in quantum gravity and related contexts suggesting the modification of the usual dispersion relation and uncertainty principle. One of these contexts is the gravity's rainbow formalism. We analyze the consequences of such a modification for black hole thermodynamics from the perspective of two distinct rainbow realizations built from doubly special relativity. One is the proposal of Magueijo and Smolin and the other is based on a canonical implementation of doubly special relativity put forward recently by the authors. In these scenarios, we obtain modified expressions for the entropy and temperature of black holes. We show that, for a family of doubly special relativity theories satisfying certain properties, the temperature can vanish in the limit of zero black hole mass. For the Magueijo and Smolin proposal, this is only possible for some restricted class of models with bounded energy and unbounded momentum. With the proposal of a canonical implementation, on the other hand, the temperature may vanish for more general theories; in particular, the momentum may also be bounded, with bounded or unbounded energy. This opens new possibilities for the outcome of black hole evaporation in the framework of a gravity's rainbow. |
2001.10196 | Susobhan Mandal | Athira B S, Susobhan Mandal, Subhashish Banerjee | Characteristics of interaction between Gravitons and Photons | 22 pages, 2 figures | null | 10.1140/epjp/s13360-021-01361-8 | null | gr-qc hep-th physics.optics quant-ph | http://creativecommons.org/licenses/by/4.0/ | The direct detection of gravitational waves from binary mergers has been
hailed as the discovery of the century. In the light of recent evidence on the
existence of gravitational waves, it is now possible to know about the
properties of matter under extreme conditions in compact astrophysical objects
and different dynamical spacetimes. The foremost theme of the present article
is to bring out the various features of the interaction between photons and
gravitons that can be used in astrophysical observations. The effective action
of interacting photons containing light-matter coupling and self-interaction
term is constructed by eliminating the graviton degrees of freedom coupled to
both matter and photons. It is shown that the equation of state of matter can
be probed from the dynamics of light in this theory. The vacuum birefringence
is also shown to be a generic property in this theory that arises from the
non-linear nature of the self-interaction between gauge fields. Further, the
non-local nature of quantum effective action with modified dispersion relation
is also discussed in great detail. The above results also open an alternate way
to infer the properties of gravitational waves without their direct measurement
using the features of photon-graviton interaction.
| [
{
"created": "Tue, 28 Jan 2020 07:36:49 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Apr 2021 04:04:55 GMT",
"version": "v2"
}
] | 2021-04-27 | [
[
"S",
"Athira B",
""
],
[
"Mandal",
"Susobhan",
""
],
[
"Banerjee",
"Subhashish",
""
]
] | The direct detection of gravitational waves from binary mergers has been hailed as the discovery of the century. In the light of recent evidence on the existence of gravitational waves, it is now possible to know about the properties of matter under extreme conditions in compact astrophysical objects and different dynamical spacetimes. The foremost theme of the present article is to bring out the various features of the interaction between photons and gravitons that can be used in astrophysical observations. The effective action of interacting photons containing light-matter coupling and self-interaction term is constructed by eliminating the graviton degrees of freedom coupled to both matter and photons. It is shown that the equation of state of matter can be probed from the dynamics of light in this theory. The vacuum birefringence is also shown to be a generic property in this theory that arises from the non-linear nature of the self-interaction between gauge fields. Further, the non-local nature of quantum effective action with modified dispersion relation is also discussed in great detail. The above results also open an alternate way to infer the properties of gravitational waves without their direct measurement using the features of photon-graviton interaction. |
1709.00219 | Cosimo Bambi | Zheng Cao, Sourabh Nampalliwar, Cosimo Bambi, Thomas Dauser, Javier A.
Garcia | Testing general relativity with the reflection spectrum of the
supermassive black hole in 1H0707$-$495 | 10 pages, 7 figures. v2: refereed version | Phys. Rev. Lett. 120, 051101 (2018) | 10.1103/PhysRevLett.120.051101 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, we have extended the X-ray reflection model relxill to test the
spacetime metric in the strong gravitational field of astrophysical black
holes. In the present Letter, we employ this extended model to analyze
XMM-Newton, NuSTAR, and Swift data of the supermassive black hole in 1H0707-495
and test deviations from a Kerr metric parametrized by the Johannsen
deformation parameter $\alpha_{13}$. Our results are consistent with the
hypothesis that the spacetime metric around the black hole in 1H0707-495 is
described by the Kerr solution.
| [
{
"created": "Fri, 1 Sep 2017 09:43:43 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Feb 2018 00:23:20 GMT",
"version": "v2"
}
] | 2018-02-05 | [
[
"Cao",
"Zheng",
""
],
[
"Nampalliwar",
"Sourabh",
""
],
[
"Bambi",
"Cosimo",
""
],
[
"Dauser",
"Thomas",
""
],
[
"Garcia",
"Javier A.",
""
]
] | Recently, we have extended the X-ray reflection model relxill to test the spacetime metric in the strong gravitational field of astrophysical black holes. In the present Letter, we employ this extended model to analyze XMM-Newton, NuSTAR, and Swift data of the supermassive black hole in 1H0707-495 and test deviations from a Kerr metric parametrized by the Johannsen deformation parameter $\alpha_{13}$. Our results are consistent with the hypothesis that the spacetime metric around the black hole in 1H0707-495 is described by the Kerr solution. |
1311.6898 | Amalaya Khurshudyan | M. Khurshudyan | Phenomenological models of Universe with varying $G$ and $\Lambda$ | 19 pages. revisited according to the comments of referees. arXiv
admin note: text overlap with arXiv:astro-ph/0004125, arXiv:1304.1961 by
other authors | Central Eur.J.Phys. 12 (2014) 348-366 | 10.2478/s11534-014-0453-z | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we will consider several phenomenological models for the
Universe with varying $G$ and $\Lambda(t)$, where $G$ is the gravitational
"constant" and $\Lambda(t)$ is a varying cosmological "constant". Two-component
fluid model taken into account. An interaction of the phenomenological form
between a barotropic fluid and a quintessence DE is supposed. Three different
forms of $\Lambda(t)$ will be considered. The problem is analysed numerically
and behavior of different cosmological parameters investigated graphically.
Conclusion and discussions are given at the end of the work. In an Appendix an
information concerning to the other cosmological parameters is presented.
| [
{
"created": "Wed, 27 Nov 2013 08:42:41 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Mar 2014 06:22:52 GMT",
"version": "v2"
}
] | 2015-09-16 | [
[
"Khurshudyan",
"M.",
""
]
] | In this article we will consider several phenomenological models for the Universe with varying $G$ and $\Lambda(t)$, where $G$ is the gravitational "constant" and $\Lambda(t)$ is a varying cosmological "constant". Two-component fluid model taken into account. An interaction of the phenomenological form between a barotropic fluid and a quintessence DE is supposed. Three different forms of $\Lambda(t)$ will be considered. The problem is analysed numerically and behavior of different cosmological parameters investigated graphically. Conclusion and discussions are given at the end of the work. In an Appendix an information concerning to the other cosmological parameters is presented. |
1908.03845 | Xiao-Xiong Zeng | Xiao-Xiong Zeng, Xin-Yun Hu | Thermodynamics and weak cosmic censorship conjecture with pressure in
the rotating BTZ black holes | 5 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | As a charged spinning fermion drops into a charged rotating BTZ black hole,
we investigate the laws of thermodynamics and weak cosmic censorship conjecture
with and without pressure respectively. For the case without pressure, the
first law, second law, as well as the weak cosmic censorship are found to be
valid. While for the case with pressure, though the first law is still valid,
the second law and the weak cosmic censorship conjecture are found to be
violable, depending on the charge, angular momentum, AdS radius, and their
variations. In addition, in both cases, the configurations of the extremal
black holes are found to be stable since the final states of the extremal black
holes are still extremal black holes. While for the near-extremal black holes,
their configurations are not stable.
| [
{
"created": "Sun, 11 Aug 2019 03:22:36 GMT",
"version": "v1"
}
] | 2019-08-13 | [
[
"Zeng",
"Xiao-Xiong",
""
],
[
"Hu",
"Xin-Yun",
""
]
] | As a charged spinning fermion drops into a charged rotating BTZ black hole, we investigate the laws of thermodynamics and weak cosmic censorship conjecture with and without pressure respectively. For the case without pressure, the first law, second law, as well as the weak cosmic censorship are found to be valid. While for the case with pressure, though the first law is still valid, the second law and the weak cosmic censorship conjecture are found to be violable, depending on the charge, angular momentum, AdS radius, and their variations. In addition, in both cases, the configurations of the extremal black holes are found to be stable since the final states of the extremal black holes are still extremal black holes. While for the near-extremal black holes, their configurations are not stable. |
gr-qc/0412055 | Jos\'e Wadih Maluf | Jose Wadih Maluf | Accelerated observers and gravitational radiation | 12 pages, Latex file, no figures. Version to appear in Gravitation
and Cosmology | Grav.Cosmol. 11 (2005) 284-288 | null | null | gr-qc | null | We evaluate the energy-momentum of the gravitational field of a Schwarzschild
black hole of mass M in the frame of a moving observer that asymptotically
undergoes a Lorentz boost. The analysis is carried out in the framework of the
teleparallel equivalent of general relativity (TEGR). We find that the total
expression for the energy-momentum of the gravitational field is similar to the
usual relativistic expression for the energy-momentum four-vector of a particle
of inertial mass M under a Lorentz boost in flat space-time. Moreover we
conclude that if the observer accelerates with respect to the black hole he
will experience gravitational energy radiation, in similarity to the expected
radiation of an accelerated charged particle in electrodynamics. We show that
the increase of the mass of the black hole by the usual factor gamma as
observed in the moving frame, which is a typical feature of special relativity
if the black hole is considered asymptotically as a body of mass M, is due to
gravitational radiation.
| [
{
"created": "Sun, 12 Dec 2004 17:40:09 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2005 13:27:13 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Maluf",
"Jose Wadih",
""
]
] | We evaluate the energy-momentum of the gravitational field of a Schwarzschild black hole of mass M in the frame of a moving observer that asymptotically undergoes a Lorentz boost. The analysis is carried out in the framework of the teleparallel equivalent of general relativity (TEGR). We find that the total expression for the energy-momentum of the gravitational field is similar to the usual relativistic expression for the energy-momentum four-vector of a particle of inertial mass M under a Lorentz boost in flat space-time. Moreover we conclude that if the observer accelerates with respect to the black hole he will experience gravitational energy radiation, in similarity to the expected radiation of an accelerated charged particle in electrodynamics. We show that the increase of the mass of the black hole by the usual factor gamma as observed in the moving frame, which is a typical feature of special relativity if the black hole is considered asymptotically as a body of mass M, is due to gravitational radiation. |
gr-qc/9403011 | Wai Suen | Peter Anninos, David Bernstein, Steven Brandt, Joseph Libson, Joan
Masso, Edward Seidel, Larry Smarr, Wai-Mo Suen, Paul Walker | Dynamics of Apparent and Event Horizons | 4 pages, 94-2 | Phys.Rev.Lett. 74 (1995) 630-633 | 10.1103/PhysRevLett.74.630 | null | gr-qc | null | The dynamics of apparent and event horizons of various black hole spacetimes,
including those containing distorted, rotating and colliding black holes, are
studied. We have developed a powerful and efficient new method for locating the
event horizon, making possible the study of both types of horizons in numerical
relativity. We show that both the event and apparent horizons, in all dynamical
black hole spacetimes studied, oscillate with the quasinormal frequency.
| [
{
"created": "Thu, 3 Mar 1994 16:18:25 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Anninos",
"Peter",
""
],
[
"Bernstein",
"David",
""
],
[
"Brandt",
"Steven",
""
],
[
"Libson",
"Joseph",
""
],
[
"Masso",
"Joan",
""
],
[
"Seidel",
"Edward",
""
],
[
"Smarr",
"Larry",
""
],
[
"Suen",
"Wai-Mo",
""
],
[
"Walker",
"Paul",
""
]
] | The dynamics of apparent and event horizons of various black hole spacetimes, including those containing distorted, rotating and colliding black holes, are studied. We have developed a powerful and efficient new method for locating the event horizon, making possible the study of both types of horizons in numerical relativity. We show that both the event and apparent horizons, in all dynamical black hole spacetimes studied, oscillate with the quasinormal frequency. |
gr-qc/9912025 | William Pezzaglia . D. | William M. Pezzaglia (Physics, Santa Clara University, CA) | Dimensionally Democratic Calculus and Principles of Polydimensional
Physics | 22 pages, LaTeX, no figures. Submitted to Proceedings of the 5th
International Conference on Clifford Algebras and their Applications in
Mathematical Physics, Ixtapa-Zihuatanejo, Mexico, June 27-July 4, 1999, (R.
Ablamowicz and B. Fauser eds.). Presentation slides available at
http://www.clifford.org/wpezzag/talk/99mexico/ | null | null | PEZZ9903, clf-alg/pezz9903 | gr-qc | null | A solution to the 50 year old problem of a spinning particle in curved space
has been recently derived using an extension of Clifford calculus in which each
geometric element has its own coordinate. This leads us to propose that all the
laws of physics should obey new polydimensional metaprinciples, for which
Clifford algebra is the natural language of expression, just as tensors were
for general relativity. Specifically, phenomena and physical laws should be
invariant under local automorphism transformations which reshuffle the physical
geometry. This leads to a new generalized unified basis for classical
mechanics, which includes string theory, membrane theory and the hypergravity
formulation of Crawford[J. Math. Phys., {\bf 35}, 2701-2718 (1994)]. Most
important is that the broad themes presented can be exploited by nearly
everyone in the field as a framework to generalize both the Clifford calculus
and multivector physics.
| [
{
"created": "Wed, 8 Dec 1999 00:45:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pezzaglia",
"William M.",
"",
"Physics, Santa Clara University, CA"
]
] | A solution to the 50 year old problem of a spinning particle in curved space has been recently derived using an extension of Clifford calculus in which each geometric element has its own coordinate. This leads us to propose that all the laws of physics should obey new polydimensional metaprinciples, for which Clifford algebra is the natural language of expression, just as tensors were for general relativity. Specifically, phenomena and physical laws should be invariant under local automorphism transformations which reshuffle the physical geometry. This leads to a new generalized unified basis for classical mechanics, which includes string theory, membrane theory and the hypergravity formulation of Crawford[J. Math. Phys., {\bf 35}, 2701-2718 (1994)]. Most important is that the broad themes presented can be exploited by nearly everyone in the field as a framework to generalize both the Clifford calculus and multivector physics. |
2109.06843 | Martin Bojowald | Martin Bojowald and Brenda Jones | Tunneling dynamics in cosmological bounce models | 18 pages, 5 figures | JCAP 11 (2021) 037 | 10.1088/1475-7516/2021/11/037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasiclassical methods are used to define dynamical tunneling times in models
of quantum cosmological bounces. These methods provide relevant new information
compared with the traditional treatment of quantum tunneling by means of
tunneling probabilities. As shown here, the quantum dynamics in bounce models
is not secure from reaching zero scale factor, re-opening the question of how
the classical singularity may be avoided. Moreover, in the examples studied
here, tunneling times remain small even for large barriers, highlighting the
quantum instability of underlying bounce models.
| [
{
"created": "Tue, 14 Sep 2021 17:30:31 GMT",
"version": "v1"
}
] | 2021-11-18 | [
[
"Bojowald",
"Martin",
""
],
[
"Jones",
"Brenda",
""
]
] | Quasiclassical methods are used to define dynamical tunneling times in models of quantum cosmological bounces. These methods provide relevant new information compared with the traditional treatment of quantum tunneling by means of tunneling probabilities. As shown here, the quantum dynamics in bounce models is not secure from reaching zero scale factor, re-opening the question of how the classical singularity may be avoided. Moreover, in the examples studied here, tunneling times remain small even for large barriers, highlighting the quantum instability of underlying bounce models. |
gr-qc/9607027 | Gary Horowitz | Gary T. Horowitz and Harrison J. Sheinblatt | Tests of Cosmic Censorship in the Ernst Spacetime | 15 pages | Phys.Rev. D55 (1997) 650-657 | 10.1103/PhysRevD.55.650 | null | gr-qc | null | The Ernst spacetime is a solution of the Einstein-Maxwell equations
describing two charged black holes accelerating apart in a uniform electric (or
magnetic) field. As the field approaches a critical value, the black hole
horizon appears to touch the acceleration horizon. We show that weak cosmic
censorship cannot be violated by increasing the field past this critical value:
The event horizon remains intact. On the other hand, strong cosmic censorship
does appear to be violated in this spacetime: For a certain range of
parameters, we find evidence that the inner horizon is classically stable.
| [
{
"created": "Thu, 11 Jul 1996 23:19:31 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Horowitz",
"Gary T.",
""
],
[
"Sheinblatt",
"Harrison J.",
""
]
] | The Ernst spacetime is a solution of the Einstein-Maxwell equations describing two charged black holes accelerating apart in a uniform electric (or magnetic) field. As the field approaches a critical value, the black hole horizon appears to touch the acceleration horizon. We show that weak cosmic censorship cannot be violated by increasing the field past this critical value: The event horizon remains intact. On the other hand, strong cosmic censorship does appear to be violated in this spacetime: For a certain range of parameters, we find evidence that the inner horizon is classically stable. |
1711.04423 | Soumya Chakrabarti | Soumya Chakrabarti, Jackson Levi Said, and Gabriel Farrugia | Some aspects of reconstruction using a scalar field in f (T ) Gravity | 22 pages, 19 figures, to appear in EPJC | null | 10.1140/epjc/s10052-017-5404-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity characterizes gravity as a geometric property exhibited on
spacetime by massive objects while teleparallel gravity achieves the same
results, at the level of equations, by taking a torsional perspective of
gravity. Similar to f (R) theory, teleparallel gravity can also be generalized
to f (T ), with the resulting field equations being inherently distinct from f
(R) gravity in that they are second order, while in the former case they turn
out to be fourth order. In the present case, a minimally coupled scalar field
is investigated in the f (T ) gravity context for several forms of the scalar
field potential. A number of new f (T ) solutions are found for these
potentials, with their respective state parameters also being examined.
| [
{
"created": "Mon, 13 Nov 2017 05:22:08 GMT",
"version": "v1"
}
] | 2018-01-17 | [
[
"Chakrabarti",
"Soumya",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Farrugia",
"Gabriel",
""
]
] | General relativity characterizes gravity as a geometric property exhibited on spacetime by massive objects while teleparallel gravity achieves the same results, at the level of equations, by taking a torsional perspective of gravity. Similar to f (R) theory, teleparallel gravity can also be generalized to f (T ), with the resulting field equations being inherently distinct from f (R) gravity in that they are second order, while in the former case they turn out to be fourth order. In the present case, a minimally coupled scalar field is investigated in the f (T ) gravity context for several forms of the scalar field potential. A number of new f (T ) solutions are found for these potentials, with their respective state parameters also being examined. |
1811.03003 | Tanwi Bandyopadhyay | Tanwi Bandyopadhyay and Ujjal Debnath | Parameterizing Dark Energy Models and Study of Finite Time Future
Singularities | 15 pages, 45 figures | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A review on spatially flat D-dimensional Friedmann-Robertson-Walker (FRW)
model of the universe has been performed. Some standard parameterizations of
the equation of state parameter of the Dark Energy models are proposed and the
possibilities of finite time future singularities are investigated. It is found
that certain types of these singularities may appear by tuning some parameters
appropriately. Moreover, for a scalar field theoretic description of the model,
it was found that the model undergoes bouncing solutions in some favorable
cases.
| [
{
"created": "Mon, 5 Nov 2018 05:28:29 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Mar 2019 05:54:09 GMT",
"version": "v2"
}
] | 2019-03-26 | [
[
"Bandyopadhyay",
"Tanwi",
""
],
[
"Debnath",
"Ujjal",
""
]
] | A review on spatially flat D-dimensional Friedmann-Robertson-Walker (FRW) model of the universe has been performed. Some standard parameterizations of the equation of state parameter of the Dark Energy models are proposed and the possibilities of finite time future singularities are investigated. It is found that certain types of these singularities may appear by tuning some parameters appropriately. Moreover, for a scalar field theoretic description of the model, it was found that the model undergoes bouncing solutions in some favorable cases. |
gr-qc/9910083 | Yakov Itin | Shmuel Kaniel and Yakov Itin | Equation of motion in a scalar model of gravity | null | null | null | null | gr-qc math-ph math.MP | null | A scalar model of gravity is considered. We propose Lorentz invariant field
equation $\square f = k\eta_{ab}f_{,a}f_{,b}$. The aim of this model is to get,
approximately, Newton's law of gravity. It is shown that $f=-\frac
1k\ln(1-k\frac mr)$ is the unique spherical symmetric static solution of the
field equation. $f$ is taken to be the field of a particle at the origin,
having the mass $m$. The field of a particle moving with a constant velocity is
taken to be the appropriate Lorentz transformation of $f$. The field $F$ of $N$
particles moving on trajectories ${\psi_j(t)}$ is taken to be, to first order,
the superposition of the fields of the particles, where the instantaneous
Lorentz transformation of the fields pertaining to the $j$-th particle is
${\dot\psi_j(t)}$. When this field is inserted to the field equation the
outcome is singular at $({\psi_j(t)},t)$. The singular terms of the l.h.s. and
of the r.h.s. are both $O(R^{-2})$. The only way to reduce the singularity in
the field equation is by postulating Newton's law of force. It is hoped that
this model will be generalized to system of equations that are covariant under
general diffeomorphism.
| [
{
"created": "Mon, 25 Oct 1999 10:54:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kaniel",
"Shmuel",
""
],
[
"Itin",
"Yakov",
""
]
] | A scalar model of gravity is considered. We propose Lorentz invariant field equation $\square f = k\eta_{ab}f_{,a}f_{,b}$. The aim of this model is to get, approximately, Newton's law of gravity. It is shown that $f=-\frac 1k\ln(1-k\frac mr)$ is the unique spherical symmetric static solution of the field equation. $f$ is taken to be the field of a particle at the origin, having the mass $m$. The field of a particle moving with a constant velocity is taken to be the appropriate Lorentz transformation of $f$. The field $F$ of $N$ particles moving on trajectories ${\psi_j(t)}$ is taken to be, to first order, the superposition of the fields of the particles, where the instantaneous Lorentz transformation of the fields pertaining to the $j$-th particle is ${\dot\psi_j(t)}$. When this field is inserted to the field equation the outcome is singular at $({\psi_j(t)},t)$. The singular terms of the l.h.s. and of the r.h.s. are both $O(R^{-2})$. The only way to reduce the singularity in the field equation is by postulating Newton's law of force. It is hoped that this model will be generalized to system of equations that are covariant under general diffeomorphism. |
1709.02284 | Anton Sheykin | N. V. Kharuk, S. A. Paston, A. A. Sheykin | Classical electromagnetic potential as a part of gravitational
connection: ideas and history | LaTeX, 17 pages | Gravitation and Cosmology 24:3 (2018) 209 | 10.1134/S0202289318030076 | null | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a natural form of unified theory of gravity and electromagnetism
which was somehow missed at the time of intense search for such an unification,
and was noticed only in 1978 but remained quite unknown. The basic idea of this
unification is to use the metric and non-symmetric connection as independent
variables, which generalizes the so-called Palatini formalism. The certain
components of connection in the appearing theory can be naturally identified
with electromagnetic potential, and with the proper choice of action the
Einstein-Maxwell equations are reproducing. In this paper we compare such an
approach with the known ideas of unification. Also we propose the more
consistent way of including matter (in the form of classical particles) in the
theory and briefly discuss the perspectives of further development of this
approach.
| [
{
"created": "Thu, 7 Sep 2017 14:44:53 GMT",
"version": "v1"
}
] | 2018-12-27 | [
[
"Kharuk",
"N. V.",
""
],
[
"Paston",
"S. A.",
""
],
[
"Sheykin",
"A. A.",
""
]
] | We consider a natural form of unified theory of gravity and electromagnetism which was somehow missed at the time of intense search for such an unification, and was noticed only in 1978 but remained quite unknown. The basic idea of this unification is to use the metric and non-symmetric connection as independent variables, which generalizes the so-called Palatini formalism. The certain components of connection in the appearing theory can be naturally identified with electromagnetic potential, and with the proper choice of action the Einstein-Maxwell equations are reproducing. In this paper we compare such an approach with the known ideas of unification. Also we propose the more consistent way of including matter (in the form of classical particles) in the theory and briefly discuss the perspectives of further development of this approach. |
1104.1904 | Farhad Darabi | A. R. Rastkar, M. R. Setare, F. Darabi | Phantom phase power-law solution in $f(G)$ gravity | 10 pages, Published online in Astrophysics and Space Science | Astrophys Space Sci (2012) 337:487-491 | 10.1007/s10509-011-0849-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Power-law solutions for $f(G)$ gravity coupled with perfect fluid have been
studied for spatially flat universe. It is shown that despite the matter
dominated and accelerating power-law solutions, the power-law solution exists
for an special form of $f(G)$ when this universe enters a Phantom phase.
| [
{
"created": "Mon, 11 Apr 2011 11:14:42 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Oct 2011 20:33:03 GMT",
"version": "v2"
}
] | 2012-02-09 | [
[
"Rastkar",
"A. R.",
""
],
[
"Setare",
"M. R.",
""
],
[
"Darabi",
"F.",
""
]
] | Power-law solutions for $f(G)$ gravity coupled with perfect fluid have been studied for spatially flat universe. It is shown that despite the matter dominated and accelerating power-law solutions, the power-law solution exists for an special form of $f(G)$ when this universe enters a Phantom phase. |
0906.5315 | Ivan Agullo | Ivan Agullo, Jose Navarro-Salas, Gonzalo J. Olmo, Leonard Parker | Insensitivity of Hawking radiation to an invariant Planck-scale cutoff | 4 pages | Phys.Rev.D80:047503,2009 | 10.1103/PhysRevD.80.047503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A disturbing aspect of Hawking's derivation of black hole radiance is the
need to invoke extreme conditions for the quantum field that originates the
emitted quanta. It is widely argued that the derivation requires the validity
of the conventional relativistic field theory to arbitrarily high,
trans-Planckian scales. We stress in this note that this is not necessarily the
case if the question is presented in a covariant way. We point out that Hawking
radiation is immediately robust against an invariant Planck-scale cutoff. This
important feature of Hawking radiation is relevant for a quantum gravity theory
that preserves, in some way, the Lorentz symmetry.
| [
{
"created": "Mon, 29 Jun 2009 16:54:56 GMT",
"version": "v1"
}
] | 2015-03-12 | [
[
"Agullo",
"Ivan",
""
],
[
"Navarro-Salas",
"Jose",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Parker",
"Leonard",
""
]
] | A disturbing aspect of Hawking's derivation of black hole radiance is the need to invoke extreme conditions for the quantum field that originates the emitted quanta. It is widely argued that the derivation requires the validity of the conventional relativistic field theory to arbitrarily high, trans-Planckian scales. We stress in this note that this is not necessarily the case if the question is presented in a covariant way. We point out that Hawking radiation is immediately robust against an invariant Planck-scale cutoff. This important feature of Hawking radiation is relevant for a quantum gravity theory that preserves, in some way, the Lorentz symmetry. |
1203.2733 | Hanno Sahlmann | Kristina Giesel and Hanno Sahlmann | From Classical To Quantum Gravity: Introduction to Loop Quantum Gravity | 56 pages. Contribution to the Proceedings of the 3rd Quantum Geometry
and Quantum Gravity School in Zakopane (2011). v2: Typos corrected, various
small changes in presentation, version as published in PoS | null | 10.22323/1.140.0002 | APCTP Pre2012-004 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an introduction to the canonical quantization of gravity performed
in loop quantum gravity, based on lectures held at the 3rd quantum geometry and
quantum gravity school in Zakopane in 2011. A special feature of this
introduction is the inclusion of new proposals for coupling matter to gravity
that can be used to deparametrize the theory, thus making its dynamics more
tractable. The classical and quantum aspects of these new proposals are
explained alongside the standard quantization of vacuum general relativity in
loop quantum gravity.
| [
{
"created": "Tue, 13 Mar 2012 08:20:00 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Jan 2013 09:23:41 GMT",
"version": "v2"
}
] | 2022-12-07 | [
[
"Giesel",
"Kristina",
""
],
[
"Sahlmann",
"Hanno",
""
]
] | We present an introduction to the canonical quantization of gravity performed in loop quantum gravity, based on lectures held at the 3rd quantum geometry and quantum gravity school in Zakopane in 2011. A special feature of this introduction is the inclusion of new proposals for coupling matter to gravity that can be used to deparametrize the theory, thus making its dynamics more tractable. The classical and quantum aspects of these new proposals are explained alongside the standard quantization of vacuum general relativity in loop quantum gravity. |
gr-qc/0010020 | Matthew Benacquista | M J Benacquista, S Portegies Zwart, F A Rasio | LISA Sources in Globular Clusters | Contribution to Proceedings of 3rd LISA Symposium 7 pages, added
references | Class.Quant.Grav. 18 (2001) 4025-4032 | 10.1088/0264-9381/18/19/308 | null | gr-qc astro-ph | null | Globular clusters house a population of compact binaries that will be
interesting gravitational wave sources for LISA. We provide estimates for the
numbers of sources of several categories and discuss the sensitivity of LISA to
detecting these sources. The estimated total number of detectable sources
ranges from about 10 to about 1000 with gravitational wave frequencies above 1
mHz. These sources are typically undetectable by any other means and thus offer
an opportunity for doing true gravitational-wave astronomy. The detection of
these sources would provide information about both binary star evolution and
the dynamics of globular clusters.
| [
{
"created": "Thu, 5 Oct 2000 17:34:46 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Oct 2000 23:22:36 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Benacquista",
"M J",
""
],
[
"Zwart",
"S Portegies",
""
],
[
"Rasio",
"F A",
""
]
] | Globular clusters house a population of compact binaries that will be interesting gravitational wave sources for LISA. We provide estimates for the numbers of sources of several categories and discuss the sensitivity of LISA to detecting these sources. The estimated total number of detectable sources ranges from about 10 to about 1000 with gravitational wave frequencies above 1 mHz. These sources are typically undetectable by any other means and thus offer an opportunity for doing true gravitational-wave astronomy. The detection of these sources would provide information about both binary star evolution and the dynamics of globular clusters. |
gr-qc/0109015 | Eugen Radu | Eugen Radu | Static axially symmetric solutions of Einstein-Yang-Mills equations with
a negative cosmological constant: the regular case | 55 pages, 38 Encapsulated PostScript figures; high-resolution figures
are available on request | Phys.Rev.D65:044005,2002 | 10.1103/PhysRevD.65.044005 | Freiburg-THEP 01/14 | gr-qc | null | Numerical solutions of the Einstein-Yang-Mills equations with a negative
cosmological constant are constructed. These axially symmetric solutions
approach asymptotically the anti-de Sitter spacetime and are regular
everywhere. They are characterized by the winding number $n>1$, the mass and
the non-Abelian magnetic charge. The main properties of the solutions and the
differences with respect to the asymptotically flat case are discussed. The
existence of axially symmetric monopole and dyon solutions in fixed anti-de
Sitter spacetime is also discussed.
| [
{
"created": "Wed, 5 Sep 2001 11:47:57 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Oct 2001 15:09:39 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Radu",
"Eugen",
""
]
] | Numerical solutions of the Einstein-Yang-Mills equations with a negative cosmological constant are constructed. These axially symmetric solutions approach asymptotically the anti-de Sitter spacetime and are regular everywhere. They are characterized by the winding number $n>1$, the mass and the non-Abelian magnetic charge. The main properties of the solutions and the differences with respect to the asymptotically flat case are discussed. The existence of axially symmetric monopole and dyon solutions in fixed anti-de Sitter spacetime is also discussed. |
gr-qc/0010092 | Somasri Sen | S. Sen and A. A. Sen | Late time acceleration in Brans Dicke Cosmology | 8 pages, RevTex style, 3 postscript figures, some more Comments made
about the feature of the model, references included, typos corrected.
Accepted for publication in Phys.Rev.D | Phys.Rev. D63 (2001) 124006 | 10.1103/PhysRevD.63.124006 | MRI-P-P001002 | gr-qc astro-ph | null | In this work we have investigated the possibility of having a late time
accelerated phase of the universe, suggested by recent supernova observation,
in the context of Brans Dicke (BD) theory with a symmetry breaking potential
and a matter field. We find that a perfect fluid matter field (pressureless and
with pressure) cannot support this acceleration but a fluid with dissipative
pressure can drive this late time acceleration. We have also calculated some
cosmological parameters in our model to match with observations.
| [
{
"created": "Wed, 25 Oct 2000 08:54:21 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Mar 2001 11:43:15 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Sen",
"S.",
""
],
[
"Sen",
"A. A.",
""
]
] | In this work we have investigated the possibility of having a late time accelerated phase of the universe, suggested by recent supernova observation, in the context of Brans Dicke (BD) theory with a symmetry breaking potential and a matter field. We find that a perfect fluid matter field (pressureless and with pressure) cannot support this acceleration but a fluid with dissipative pressure can drive this late time acceleration. We have also calculated some cosmological parameters in our model to match with observations. |
2301.08049 | Justine Tarrant Dr | Justine Tarrant and Geoff Beck | Primordial black holes and the Sunyaev-Zel'dovich effect | 5 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Primordial black holes are a popular candidate for dark matter. In the mass
regime where their conjectured Hawking evaporation is significant, they have
been subject to many constraints via X-rays, gamma-rays, and even radio
emission. Previously the Sunyaev-Zel'dovich effect has been considered to place
further limits on the M > 10M? primordial black hole abundance via the effects
of their accretion of ambient gas. In this work, we will present a novel and
robust means of placing abundance limits on low-mass black holes, using the
Sunyaev-Zel'dovich effect induced by electrons produced via their Hawking
radiation within galaxy clusters.
| [
{
"created": "Thu, 19 Jan 2023 12:51:15 GMT",
"version": "v1"
}
] | 2023-01-20 | [
[
"Tarrant",
"Justine",
""
],
[
"Beck",
"Geoff",
""
]
] | Primordial black holes are a popular candidate for dark matter. In the mass regime where their conjectured Hawking evaporation is significant, they have been subject to many constraints via X-rays, gamma-rays, and even radio emission. Previously the Sunyaev-Zel'dovich effect has been considered to place further limits on the M > 10M? primordial black hole abundance via the effects of their accretion of ambient gas. In this work, we will present a novel and robust means of placing abundance limits on low-mass black holes, using the Sunyaev-Zel'dovich effect induced by electrons produced via their Hawking radiation within galaxy clusters. |
2207.08088 | XueHeng Zheng | X H Zheng and J X Zheng | Wheeler equation in Kerr background and astrophysical jet collimation | 7 pages, 4 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The Wheeler equation has an extension in the Kerr background. It has an exact
solution representing a running harmonic wave in the tortoise coordinate. The
wave models astrophysical jets in a new light because it collimates along the
axis of spacetime rotation, increasingly tightly when rotation quickens. The
model endorses a previous numerical work suggesting intrinsic collimation of
jet fuelled by a Penrose-like process. It also endorses a previous theoretical
work to crop one-way running waves from the exact solutions to Heun's equation.
| [
{
"created": "Sun, 17 Jul 2022 06:50:38 GMT",
"version": "v1"
}
] | 2022-07-19 | [
[
"Zheng",
"X H",
""
],
[
"Zheng",
"J X",
""
]
] | The Wheeler equation has an extension in the Kerr background. It has an exact solution representing a running harmonic wave in the tortoise coordinate. The wave models astrophysical jets in a new light because it collimates along the axis of spacetime rotation, increasingly tightly when rotation quickens. The model endorses a previous numerical work suggesting intrinsic collimation of jet fuelled by a Penrose-like process. It also endorses a previous theoretical work to crop one-way running waves from the exact solutions to Heun's equation. |
2202.09290 | Tao Zhu | Qiang Wu, Shao-Wen Wei, and Tao Zhu | Are the black hole remnants produced from binary black hole mergers in
GWTC-3 thermodynamically stable? | 5 pages, 3 figures; v2: 7 GW events in GWTC-2.1 are included | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Black hole thermodynamics has brought strong hints of a profound and
fundamental connection between gravity, thermodynamics, and quantum theory. If
the black hole does behave like a natural thermodynamic system, it should be
thermodynamically stable in a clean environment. In this paper, using the
observational data of binary black hole (BBH) mergers observed by LIGO, Virgo,
and KAGRA detectors, we check whether the black hole remnants produced from BBH
mergers in the LIGO-Virgo-KAGRA catalog GWTC-3 are thermodynamically stable.
The criterion for the thermodynamic stability is quite simple and is directly
related to the black hole's spin, which states that a thermodynamically stable
black hole remnant requires its dimensionless spin $a>a_* \simeq 0.68$. We
check the posterior distributions of final spin $a_f$ for 83 black hole
remnants in GWTC-3 and find the whole remnant population is consistent with the
thermodynamically stable black hole with $99.98\%$ probability. This is the
first verification of the thermodynamic stability of black hole remnants
produced from BBH mergers.
| [
{
"created": "Fri, 18 Feb 2022 16:32:00 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 2022 07:30:04 GMT",
"version": "v2"
}
] | 2022-02-23 | [
[
"Wu",
"Qiang",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Zhu",
"Tao",
""
]
] | Black hole thermodynamics has brought strong hints of a profound and fundamental connection between gravity, thermodynamics, and quantum theory. If the black hole does behave like a natural thermodynamic system, it should be thermodynamically stable in a clean environment. In this paper, using the observational data of binary black hole (BBH) mergers observed by LIGO, Virgo, and KAGRA detectors, we check whether the black hole remnants produced from BBH mergers in the LIGO-Virgo-KAGRA catalog GWTC-3 are thermodynamically stable. The criterion for the thermodynamic stability is quite simple and is directly related to the black hole's spin, which states that a thermodynamically stable black hole remnant requires its dimensionless spin $a>a_* \simeq 0.68$. We check the posterior distributions of final spin $a_f$ for 83 black hole remnants in GWTC-3 and find the whole remnant population is consistent with the thermodynamically stable black hole with $99.98\%$ probability. This is the first verification of the thermodynamic stability of black hole remnants produced from BBH mergers. |
2003.12079 | Roberto Cotesta | Roberto Cotesta, Sylvain Marsat, Michael P\"urrer | Frequency domain reduced order model of aligned-spin effective-one-body
waveforms with higher-order modes | Fix label in Fig.10 | Phys. Rev. D 101, 124040 (2020) | 10.1103/PhysRevD.101.124040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a frequency domain reduced order model (ROM) for the aligned-spin
effective-one-body (EOB) model for binary black holes (BBHs) SEOBNRv4HM that
includes the spherical harmonics modes $(\ell, |m|) = (2,1),(3,3),(4,4),(5,5)$
beyond the dominant $(\ell, |m|) = (2,2)$ mode. These higher modes are crucial
to accurately represent the waveform emitted from asymmetric BBHs. We discuss a
decomposition of the waveform, extending other methods in the literature, that
allows us to accurately and efficiently capture the morphology of higher mode
waveforms. We show that the ROM is very accurate with median (maximum) values
of the unfaithfulness against SEOBNRv4HM lower than $0.001\% (0.03\%)$ for
total masses in $[2.8,100] M_\odot$. For a total mass of $M = 300 M_\odot$ the
median (maximum) value of the unfaithfulness increases up to $0.004\%
(0.17\%)$. This is still at least an order of magnitude lower than the
estimated accuracy of SEOBNRv4HM compared to numerical relativity simulations.
The ROM is two orders of magnitude faster in generating a waveform compared to
SEOBNRv4HM. Data analysis applications typically require
$\mathcal{O}(10^6-10^8)$ waveform evaluations for which SEOBNRv4HM is in
general too slow. The ROM is therefore crucial to allow the SEOBNRv4HM waveform
to be used in searches and Bayesian parameter inference. We present a targeted
parameter estimation study that shows the improvements in measuring binary
parameters when using waveforms that includes higher modes and compare against
three other waveform models.
| [
{
"created": "Thu, 26 Mar 2020 18:00:22 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Mar 2020 10:20:44 GMT",
"version": "v2"
}
] | 2020-07-01 | [
[
"Cotesta",
"Roberto",
""
],
[
"Marsat",
"Sylvain",
""
],
[
"Pürrer",
"Michael",
""
]
] | We present a frequency domain reduced order model (ROM) for the aligned-spin effective-one-body (EOB) model for binary black holes (BBHs) SEOBNRv4HM that includes the spherical harmonics modes $(\ell, |m|) = (2,1),(3,3),(4,4),(5,5)$ beyond the dominant $(\ell, |m|) = (2,2)$ mode. These higher modes are crucial to accurately represent the waveform emitted from asymmetric BBHs. We discuss a decomposition of the waveform, extending other methods in the literature, that allows us to accurately and efficiently capture the morphology of higher mode waveforms. We show that the ROM is very accurate with median (maximum) values of the unfaithfulness against SEOBNRv4HM lower than $0.001\% (0.03\%)$ for total masses in $[2.8,100] M_\odot$. For a total mass of $M = 300 M_\odot$ the median (maximum) value of the unfaithfulness increases up to $0.004\% (0.17\%)$. This is still at least an order of magnitude lower than the estimated accuracy of SEOBNRv4HM compared to numerical relativity simulations. The ROM is two orders of magnitude faster in generating a waveform compared to SEOBNRv4HM. Data analysis applications typically require $\mathcal{O}(10^6-10^8)$ waveform evaluations for which SEOBNRv4HM is in general too slow. The ROM is therefore crucial to allow the SEOBNRv4HM waveform to be used in searches and Bayesian parameter inference. We present a targeted parameter estimation study that shows the improvements in measuring binary parameters when using waveforms that includes higher modes and compare against three other waveform models. |
1703.00639 | Hongchao Zhang | Hongchao Zhang and Lixin Xu | Poincar\'e Gauge Gravity Cosmology | 5 pages, 3 figures, 2 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we construct the logical framework of the Poincar\'e gauge
gravity cosmology based on five postulations, and introduce the modified
redshift relation within this framework. Then we solve a system with quadratic
action and some other assumptions to get an analytic solution on background
level. The evolution of the Universe on background can be reproduced from this
solution without hypothesizing dark energy. Further, we use the type Ia
supernova data set JLA to test the effect of the modified redshift relation
under the constraints of system parameters. The results show that the
constraint on some parameters are compact.
| [
{
"created": "Thu, 2 Mar 2017 07:10:16 GMT",
"version": "v1"
}
] | 2017-03-03 | [
[
"Zhang",
"Hongchao",
""
],
[
"Xu",
"Lixin",
""
]
] | In this work, we construct the logical framework of the Poincar\'e gauge gravity cosmology based on five postulations, and introduce the modified redshift relation within this framework. Then we solve a system with quadratic action and some other assumptions to get an analytic solution on background level. The evolution of the Universe on background can be reproduced from this solution without hypothesizing dark energy. Further, we use the type Ia supernova data set JLA to test the effect of the modified redshift relation under the constraints of system parameters. The results show that the constraint on some parameters are compact. |
2107.04869 | Jorge Ananias Neto | Everton M. C. Abreu and Jorge Ananias Neto | Statistical approaches on the apparent horizon entropy and the
generalized second law of thermodynamics | Enlarged version, to appear in PLB | null | 10.1016/j.physletb.2021.136803 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we have investigated the effects of three nongaussian entropies,
namely, the modified R\'enyi entropy (MRE), the Sharma-Mittal entropy (SME) and
the dual Kaniadakis entropy (DKE) in the investigation of the generalized
second law (GSL) of thermodynamics violation. The GSL is an extension of the
second law for black holes. Recently, it was concluded that a total entropy is
the sum of the entropy enclosed by the apparent horizon plus the entropy of the
horizon itself when the apparent horizon is described by the Barrow entropy. It
was assumed that the universe is filled with matter and dark energy fluids.
Here, the apparent horizon will be described by MRE, SME, and then by DKE
proposals. Since GSL holds for usual entropy, but it is conditionally violated
in the extended entropies, this implies that the parameter of these entropies
should be constrained in small values in order for the GSL to be satisfied.
Hence, we have established conditions where the second law of thermodynamics
can or cannot be obeyed considering these three statistical concepts just as it
was made in Barrow's entropy. Considering the $\Lambda CDM$ cosmology we can
observe that for MRE, SME and DKE, the GSL of thermodynamics is not obeyed for
small redshift values.
| [
{
"created": "Sat, 10 Jul 2021 16:23:12 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Nov 2021 16:31:34 GMT",
"version": "v2"
}
] | 2022-01-05 | [
[
"Abreu",
"Everton M. C.",
""
],
[
"Neto",
"Jorge Ananias",
""
]
] | In this work we have investigated the effects of three nongaussian entropies, namely, the modified R\'enyi entropy (MRE), the Sharma-Mittal entropy (SME) and the dual Kaniadakis entropy (DKE) in the investigation of the generalized second law (GSL) of thermodynamics violation. The GSL is an extension of the second law for black holes. Recently, it was concluded that a total entropy is the sum of the entropy enclosed by the apparent horizon plus the entropy of the horizon itself when the apparent horizon is described by the Barrow entropy. It was assumed that the universe is filled with matter and dark energy fluids. Here, the apparent horizon will be described by MRE, SME, and then by DKE proposals. Since GSL holds for usual entropy, but it is conditionally violated in the extended entropies, this implies that the parameter of these entropies should be constrained in small values in order for the GSL to be satisfied. Hence, we have established conditions where the second law of thermodynamics can or cannot be obeyed considering these three statistical concepts just as it was made in Barrow's entropy. Considering the $\Lambda CDM$ cosmology we can observe that for MRE, SME and DKE, the GSL of thermodynamics is not obeyed for small redshift values. |
1405.2173 | Olivier Sarbach | Francisco Astorga, Olivier Sarbach, Thomas Zannias | The evolution of a spatially homogeneous and isotropic universe filled
with a collisionless gas | Typos corrected, references added, 13 pages, 1 figure, prepared for
the proceedings of the X Workshop on Gravitation and Mathematical Physics,
Pachuca, Mexico, December 2013 | null | 10.1088/1742-6596/545/1/012001 | UWThPh-2014-12 | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the evolution of a spatially homogeneous and isotropic universe
described by a Friedmann-Robertson-Walker spacetime filled with a
collisionless, neutral, simple, massive gas. The gas is described by a
one-particle distribution function which satisfies the Liouville equation and
is assumed to be homogeneous and isotropic. Making use of the isometries of the
spacetime, we define precisely the homogeneity and isotropicity property of the
distribution function, and based on this definition we give a concise
derivation of the most general family of such distribution functions. For this
family, we construct the particle current density and the stress-energy tensor
and consider the coupled Einstein-Liouville system of equations. We find that
as long as the distribution function is collisionless, homogenous and
isotropic, the evolution of a Friedmann-Robertson-Walker universe exhibits a
singular origin. Its future development depends upon the curvature of the
spatial sections: spatially flat or hyperboloid universes expand forever and
this expansion dilutes the energy density and pressure of the gas, while a
universe with compact spherical sections reaches a maximal expansion, after
which it reverses its motion and recollapses to a final crunch singularity
where the energy density and isotropic pressure diverge. Finally, we analyze
the evolution of the universe filled with the collisionless gas once a
cosmological constant is included.
| [
{
"created": "Fri, 9 May 2014 08:47:29 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Jun 2014 12:36:18 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Astorga",
"Francisco",
""
],
[
"Sarbach",
"Olivier",
""
],
[
"Zannias",
"Thomas",
""
]
] | We review the evolution of a spatially homogeneous and isotropic universe described by a Friedmann-Robertson-Walker spacetime filled with a collisionless, neutral, simple, massive gas. The gas is described by a one-particle distribution function which satisfies the Liouville equation and is assumed to be homogeneous and isotropic. Making use of the isometries of the spacetime, we define precisely the homogeneity and isotropicity property of the distribution function, and based on this definition we give a concise derivation of the most general family of such distribution functions. For this family, we construct the particle current density and the stress-energy tensor and consider the coupled Einstein-Liouville system of equations. We find that as long as the distribution function is collisionless, homogenous and isotropic, the evolution of a Friedmann-Robertson-Walker universe exhibits a singular origin. Its future development depends upon the curvature of the spatial sections: spatially flat or hyperboloid universes expand forever and this expansion dilutes the energy density and pressure of the gas, while a universe with compact spherical sections reaches a maximal expansion, after which it reverses its motion and recollapses to a final crunch singularity where the energy density and isotropic pressure diverge. Finally, we analyze the evolution of the universe filled with the collisionless gas once a cosmological constant is included. |
1012.0056 | Florian Beyer | Florian Beyer | The cosmic no-hair conjecture: A study of the Nariai solutions | Prepared for the Proceedings of the 12th Marcel Grossman Meeting
(MG12), Paris, France, 12-18 July, 2009 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this talk, we investigate the cosmic no-hair conjecture for perturbed
Nariai solutions within the class of Gowdy symmetric solutions of Einstein's
field equations in vacuum with a positive cosmological constant. In particular,
we are interested whether these perturbations allow to construct new
cosmological black hole solutions.
| [
{
"created": "Tue, 30 Nov 2010 22:50:30 GMT",
"version": "v1"
}
] | 2010-12-02 | [
[
"Beyer",
"Florian",
""
]
] | In this talk, we investigate the cosmic no-hair conjecture for perturbed Nariai solutions within the class of Gowdy symmetric solutions of Einstein's field equations in vacuum with a positive cosmological constant. In particular, we are interested whether these perturbations allow to construct new cosmological black hole solutions. |
2007.00600 | Lorenzo Iorio | Lorenzo Iorio | On the 2PN pericentre precession in the general theory of relativity and
the recently discovered fast orbiting S-stars in Sgr A$^\ast$ | LaTex2e, 15 pages, 1 table, 1 figure. Typo in Eq.(7) of the previous
version, equal to Eq.(53) in Iorio L., 2020, Universe, 6, 53, corrected. Eqs.
(25)-(26) correct Eqs. (51)-(52) in Iorio L., 2020a, Universe, 6, 53.
Accepted for publication in Universe | Universe 2021, 7(2), 37 | 10.3390/universe7020037 | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the secular pericentre precession was analytically computed to the
second post-Newtonian (2PN) order by the present author with the Gauss
equations in terms of the osculating Keplerian orbital elements in order to
obtain closer contact with the observations in astronomical and astrophysical
scenarios of potential interest. A discrepancy with previous results by other
authors was found. Moreover, some of such findings by the same authors were
deemed as mutually inconsistent. In this paper, it is demonstrated that, in
fact, two calculational errors plagued the most recent calculation by the
present author. They are explicitly disclosed and corrected. As a result, all
the examined approaches mutually agree yielding the same analytical expression
for the total 2PN pericentre precession once the appropriate conversions from
the adopted parameterizations are made. It is also shown that, in future, it
may become measurable, at least in principle, for some of the recently
discovered short-period S-stars in Sgr A$^\ast$ like S62 and S4714.
| [
{
"created": "Wed, 1 Jul 2020 16:36:31 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Aug 2020 15:38:39 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Sep 2020 13:33:53 GMT",
"version": "v3"
},
{
"created": "Wed, 7 Oct 2020 21:26:09 GMT",
"version": "v4"
},
{
"created": "Tue, 2 Feb 2021 13:57:57 GMT",
"version": "v5"
}
] | 2021-02-08 | [
[
"Iorio",
"Lorenzo",
""
]
] | Recently, the secular pericentre precession was analytically computed to the second post-Newtonian (2PN) order by the present author with the Gauss equations in terms of the osculating Keplerian orbital elements in order to obtain closer contact with the observations in astronomical and astrophysical scenarios of potential interest. A discrepancy with previous results by other authors was found. Moreover, some of such findings by the same authors were deemed as mutually inconsistent. In this paper, it is demonstrated that, in fact, two calculational errors plagued the most recent calculation by the present author. They are explicitly disclosed and corrected. As a result, all the examined approaches mutually agree yielding the same analytical expression for the total 2PN pericentre precession once the appropriate conversions from the adopted parameterizations are made. It is also shown that, in future, it may become measurable, at least in principle, for some of the recently discovered short-period S-stars in Sgr A$^\ast$ like S62 and S4714. |
1705.08017 | Dmitri Gal'tsov | G\'erard Cl\'ement and Dmitri Gal'tsov | A tale of two dyons | 10 pages, one figure, published version | Phys.Lett. B771 (2017) 457-461 | 10.1016/j.physletb.2017.05.096 | LAPTH-016/17 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a one-parameter family of stationary, asymptotically flat
solutions of the Einstein-Maxwell equations with only a mild singularity, which
are endowed with mass, angular momentum, a dipole magnetic moment and a
quadrupole electric moment. We briefly analyze the structure of this solution,
which we interpret as a system of two extreme co-rotating black holes with
equal masses and electric charges, and opposite magnetic and gravimagnetic
charges, held apart by an electrically charged, magnetized string which also
acts as a Dirac-Misner string.
| [
{
"created": "Mon, 22 May 2017 21:45:26 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2017 21:08:15 GMT",
"version": "v2"
}
] | 2017-06-15 | [
[
"Clément",
"Gérard",
""
],
[
"Gal'tsov",
"Dmitri",
""
]
] | We present a one-parameter family of stationary, asymptotically flat solutions of the Einstein-Maxwell equations with only a mild singularity, which are endowed with mass, angular momentum, a dipole magnetic moment and a quadrupole electric moment. We briefly analyze the structure of this solution, which we interpret as a system of two extreme co-rotating black holes with equal masses and electric charges, and opposite magnetic and gravimagnetic charges, held apart by an electrically charged, magnetized string which also acts as a Dirac-Misner string. |
gr-qc/0102044 | Jorge Pullin | Jorge Pullin | Matters of Gravity, the newsletter of the APS Topical Group on
Gravitation, Spring 2001 | 23 pages, LaTeX with html.sty. PDF and html versions in
http://gravity.phys.psu.edu/mog.html | null | null | MOG-17 | gr-qc | null | News:
- APS Prize on gravitation, by Cliff Will
- TGG elections, by David Garfinkle
- We hear that... by Jorge Pullin
Research Briefs:
- Experimental Unruh radiation?, by Matt Visser
- Why is the universe accelerating?, by Beverly Berger
- The Lazarus Project, by Richard Price
- LIGO locks its first detector!, by Stan Whitcomb
- Progress on the nonlinear r-mode problem, by Keith Lockitch
Conference reports:
- Analog models of general relativity, by Matt Visser
- Astrophysical Sources of Gravitational radiation by Joan Centrella
- Numerical relativity at the 20th Texas meeting, by Pablo Laguna
| [
{
"created": "Sun, 11 Feb 2001 19:43:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pullin",
"Jorge",
""
]
] | News: - APS Prize on gravitation, by Cliff Will - TGG elections, by David Garfinkle - We hear that... by Jorge Pullin Research Briefs: - Experimental Unruh radiation?, by Matt Visser - Why is the universe accelerating?, by Beverly Berger - The Lazarus Project, by Richard Price - LIGO locks its first detector!, by Stan Whitcomb - Progress on the nonlinear r-mode problem, by Keith Lockitch Conference reports: - Analog models of general relativity, by Matt Visser - Astrophysical Sources of Gravitational radiation by Joan Centrella - Numerical relativity at the 20th Texas meeting, by Pablo Laguna |
1701.00811 | C. Q. Geng | Chao-Qiang Geng, Chung-Chi Lee and Kaituo Zhang | Cosmological perturbation and matter power spectrum in bimetric massive
gravity | 18 pages, 4 figures, revised version accepted by Annals of Physics | Annals of Physics 391 (2018) 16-26 | 10.1016/j.aop.2018.02.001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the linear perturbation equations with the synchronous gauge in a
minimal scenario of the bimetric massive gravity theory. We find that the
matter density perturbation and matter power spectrum are suppressed. We also
examine the ghost and stability problems and show that the allowed deviation of
this gravitational theory from the cosmological constant is constrained to be
smaller than $\mathcal{O}(10^{-2})$ by the large scale structure observational
data.
| [
{
"created": "Thu, 22 Dec 2016 02:44:43 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Jan 2017 04:18:14 GMT",
"version": "v2"
},
{
"created": "Sun, 4 Feb 2018 03:29:53 GMT",
"version": "v3"
}
] | 2018-02-27 | [
[
"Geng",
"Chao-Qiang",
""
],
[
"Lee",
"Chung-Chi",
""
],
[
"Zhang",
"Kaituo",
""
]
] | We discuss the linear perturbation equations with the synchronous gauge in a minimal scenario of the bimetric massive gravity theory. We find that the matter density perturbation and matter power spectrum are suppressed. We also examine the ghost and stability problems and show that the allowed deviation of this gravitational theory from the cosmological constant is constrained to be smaller than $\mathcal{O}(10^{-2})$ by the large scale structure observational data. |
2407.12908 | Giovanni Maria Tomaselli | Giovanni Maria Tomaselli, Thomas F.M. Spieksma, Gianfranco Bertone | The legacy of boson clouds on black hole binaries | Accepted for publication in Phys. Rev. Letters. Companion paper of
2403.03147 | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superradiant clouds of ultralight bosons can leave an imprint on the
gravitational waveform of black hole binaries through "ionization" and
"resonances". We study the sequence of resonances as the binary evolves, and
show that there are only two possible outcomes, each with a distinct imprint on
the waveform. If the cloud and the binary are nearly counter-rotating, then the
cloud survives in its original state until it enters the sensitivity band of
future gravitational wave detectors, such as LISA. In all other cases,
resonances destroy the cloud, while driving the binary to co-rotate with it and
its eccentricity close to a fixed point. This opens up the possibility of
inferring the existence of a new boson from the statistical analysis of a
population of black holes binaries.
| [
{
"created": "Wed, 17 Jul 2024 18:00:00 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Tomaselli",
"Giovanni Maria",
""
],
[
"Spieksma",
"Thomas F. M.",
""
],
[
"Bertone",
"Gianfranco",
""
]
] | Superradiant clouds of ultralight bosons can leave an imprint on the gravitational waveform of black hole binaries through "ionization" and "resonances". We study the sequence of resonances as the binary evolves, and show that there are only two possible outcomes, each with a distinct imprint on the waveform. If the cloud and the binary are nearly counter-rotating, then the cloud survives in its original state until it enters the sensitivity band of future gravitational wave detectors, such as LISA. In all other cases, resonances destroy the cloud, while driving the binary to co-rotate with it and its eccentricity close to a fixed point. This opens up the possibility of inferring the existence of a new boson from the statistical analysis of a population of black holes binaries. |
2307.15888 | Gustavo Enrique Garc\'ia De Jes\'us | Gustavo Garc\'ia and Marcelo Salgado | Regular scalar clouds around a Kerr-Newman black hole: subextremal and
extremal scenarios | 25 pages, 19 Figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work we analyze the existence of electrically charged scalar clouds
which are bound states of a complex-valued massive scalar field in the
background of subextremal and extremal Kerr-Newman black holes (BH). In
particular, we reanalyze neutral (uncharged) clouds in extremal Kerr BH's. For
the extremal scenarios we have implemented a novel technique which allows us to
obtain regular clouds at the BH horizon ${\cal H}^+$ which turn out to be
connected ``continuously'' with the cloud solutions in the subextremal case
even if some derivatives of the scalar field are unbounded at the horizon. In
particular, for subextremal BH's we have established regularity conditions at
${\cal H}^+$, by demanding that the field and its radial derivatives are
bounded there, but in the extremal scenarios we relax this last condition while
demanding that some scalar invariants are well behaved at ${\cal H}^+$.
Furthermore we have implemented an integral technique to understand and justify
in a simple and heuristic way the existence of such cloud configurations in
those BH backgrounds.
| [
{
"created": "Sat, 29 Jul 2023 05:18:58 GMT",
"version": "v1"
}
] | 2023-08-01 | [
[
"García",
"Gustavo",
""
],
[
"Salgado",
"Marcelo",
""
]
] | In this work we analyze the existence of electrically charged scalar clouds which are bound states of a complex-valued massive scalar field in the background of subextremal and extremal Kerr-Newman black holes (BH). In particular, we reanalyze neutral (uncharged) clouds in extremal Kerr BH's. For the extremal scenarios we have implemented a novel technique which allows us to obtain regular clouds at the BH horizon ${\cal H}^+$ which turn out to be connected ``continuously'' with the cloud solutions in the subextremal case even if some derivatives of the scalar field are unbounded at the horizon. In particular, for subextremal BH's we have established regularity conditions at ${\cal H}^+$, by demanding that the field and its radial derivatives are bounded there, but in the extremal scenarios we relax this last condition while demanding that some scalar invariants are well behaved at ${\cal H}^+$. Furthermore we have implemented an integral technique to understand and justify in a simple and heuristic way the existence of such cloud configurations in those BH backgrounds. |
2305.11216 | Alex Davey | Alex Davey, Oscar J.C. Dias, Jorge E. Santos | Scalar QNM spectra of Kerr and Reissner-Nordstr\"om revealed by
eigenvalue repulsions in Kerr-Newman | 62 pages, 20 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent studies of the gravito-electromagnetic frequency spectra of
Kerr-Newman (KN) black holes have revealed two families of quasinormal modes
(QNMs), namely photon sphere modes and near-horizon modes. However, they can
only be unambiguously distinguished in the Reissner-Nordstr\"om (RN) limit, due
to a phenomenon called eigenvalue repulsion (also known as level repulsion,
avoided crossing or the Wigner-Teller effect), whereby the two families can
interact strongly near extremality. We find that these features are also
present in the QNM spectra of a scalar field in KN, where the perturbation
modes are described by ODEs and thus easier to explore. Starting from the RN
limit, we study how the scalar QNM spectra of KN dramatically changes as we
vary the ratio of charge to angular momentum, all the way until the Kerr limit,
while staying at a fixed distance from extremality. This scalar field case
clarifies the (so far puzzling) relationship between the QNM spectra of RN and
Kerr black holes and the nature of the eigenvalue repulsions in KN, that
ultimately settle the fate of the QNM spectra in Kerr. We study not just the
slowest-decaying QNMs (both for $\ell=m=0$ and $\ell=m=2$), but several
sub-dominant overtones as well, as these turn out to play a crucial role
understanding the KN QNM spectra. We also give a new high-order WKB expansion
of KN QNMs that typically describes the photon sphere modes beyond the eikonal
limit, and use a matched asymptotic expansion to get a very good approximation
of the near-horizon modes near extremality.
| [
{
"created": "Thu, 18 May 2023 18:00:01 GMT",
"version": "v1"
}
] | 2023-05-22 | [
[
"Davey",
"Alex",
""
],
[
"Dias",
"Oscar J. C.",
""
],
[
"Santos",
"Jorge E.",
""
]
] | Recent studies of the gravito-electromagnetic frequency spectra of Kerr-Newman (KN) black holes have revealed two families of quasinormal modes (QNMs), namely photon sphere modes and near-horizon modes. However, they can only be unambiguously distinguished in the Reissner-Nordstr\"om (RN) limit, due to a phenomenon called eigenvalue repulsion (also known as level repulsion, avoided crossing or the Wigner-Teller effect), whereby the two families can interact strongly near extremality. We find that these features are also present in the QNM spectra of a scalar field in KN, where the perturbation modes are described by ODEs and thus easier to explore. Starting from the RN limit, we study how the scalar QNM spectra of KN dramatically changes as we vary the ratio of charge to angular momentum, all the way until the Kerr limit, while staying at a fixed distance from extremality. This scalar field case clarifies the (so far puzzling) relationship between the QNM spectra of RN and Kerr black holes and the nature of the eigenvalue repulsions in KN, that ultimately settle the fate of the QNM spectra in Kerr. We study not just the slowest-decaying QNMs (both for $\ell=m=0$ and $\ell=m=2$), but several sub-dominant overtones as well, as these turn out to play a crucial role understanding the KN QNM spectra. We also give a new high-order WKB expansion of KN QNMs that typically describes the photon sphere modes beyond the eikonal limit, and use a matched asymptotic expansion to get a very good approximation of the near-horizon modes near extremality. |
2010.00916 | Sajal Mukherjee | Sajal Mukherjee, Sanjit Mitra and Sourav Chatterjee | Gravitational Wave observatories may be able to detect hyperbolic
encounters of Black Holes | 10 pages, 4 figures | Monthly Notices of the Royal Astronomical Society, 508 (2021),
5064-5073 | 10.1093/mnras/stab2721 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational Wave (GW) astronomy promises to observe different kinds of
astrophysical sources. Here we explore the possibility of detection of GWs from
hyperbolic interactions of compact stars with ground-based interferometric
detectors. It is believed that a bound compact cluster, such as a globular
cluster, can be a primary environment for these interactions. We estimate the
detection rates for such events by considering local geometry within the
cluster, accounting for scattering probability of compact stars at finite
distances, and assuming realistic cluster properties guided by available
numerical models, their formation times, and evolution of stars inside them. We
find that, even in the conservative limit, it may be possible to detect such
black hole encounters in the next few years by the present network of
observatories with the ongoing sensitivity upgrades and one to few events per
year with the next generation observatories. In practice, actual detection
rates can significantly surpass the estimated average rates, since the chances
of finding outliers in a very large population can be high. Such observations
(or, no observation) may provide crucial constraints to estimate the number of
isolated compact stars in the universe. These detections will be exciting
discoveries on their own and will be complimentary to observations of binary
mergers bringing us one step closer to address a fundamental question, how many
black holes are there in the observable universe.
| [
{
"created": "Fri, 2 Oct 2020 10:49:26 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Oct 2020 17:06:36 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Oct 2020 13:51:41 GMT",
"version": "v3"
},
{
"created": "Thu, 28 Oct 2021 11:36:08 GMT",
"version": "v4"
}
] | 2021-10-29 | [
[
"Mukherjee",
"Sajal",
""
],
[
"Mitra",
"Sanjit",
""
],
[
"Chatterjee",
"Sourav",
""
]
] | Gravitational Wave (GW) astronomy promises to observe different kinds of astrophysical sources. Here we explore the possibility of detection of GWs from hyperbolic interactions of compact stars with ground-based interferometric detectors. It is believed that a bound compact cluster, such as a globular cluster, can be a primary environment for these interactions. We estimate the detection rates for such events by considering local geometry within the cluster, accounting for scattering probability of compact stars at finite distances, and assuming realistic cluster properties guided by available numerical models, their formation times, and evolution of stars inside them. We find that, even in the conservative limit, it may be possible to detect such black hole encounters in the next few years by the present network of observatories with the ongoing sensitivity upgrades and one to few events per year with the next generation observatories. In practice, actual detection rates can significantly surpass the estimated average rates, since the chances of finding outliers in a very large population can be high. Such observations (or, no observation) may provide crucial constraints to estimate the number of isolated compact stars in the universe. These detections will be exciting discoveries on their own and will be complimentary to observations of binary mergers bringing us one step closer to address a fundamental question, how many black holes are there in the observable universe. |
1806.09778 | Dimitris Christodoulou | Dimitris M. Christodoulou and Demosthenes Kazanas | Interposing a Varying Gravitational Constant Between Modified Newtonian
Dynamics and Weak Weyl Gravity | An original letter to appear in MNRAS | null | 10.1093/mnrasl/sly118 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Newtonian gravitational constant $G$ obeys the dimensional relation $[G]
[M] [a] = [v]^4$, where $M$, $a$, and $v$ denote mass, acceleration, and speed,
respectively. Since the baryonic Tully-Fisher (BTF) and Faber-Jackson (BFJ)
relations are observed facts, this relation implies that $G\, a = {\rm
constant}$. This result cannot be obtained in Newtonian dynamics which cannot
explain the origin of the BTF and BFJ relations. An alternative, modified
Newtonian dynamics (MOND) assumes that $G=G_0$ is constant in space and derives
naturally a characteristic constant acceleration $a=a_0$, as well as the BTF
and BFJ relations. This is overkill and it comes with a penalty: MOND cannot
explain the origin of $a_0$. A solid physical resolution of this issue is that
$G \propto a^{-1}$, which implies that in lower-acceleration environments the
gravitational force is boosted relative to its Newtonian value because $G$
increases. This eliminates all problems related to MOND's empirical cutoff
$a_0$ and yields a quantitative method for mapping the detailed variations of
$G(a)$ across each individual galaxy as well as on larger and smaller scales.
On the opposite end, the large accelerations produced by $G(a)$ appear to be
linked to the weak-field limit of the fourth-order theory of conformal Weyl
gravity.
| [
{
"created": "Tue, 26 Jun 2018 03:10:27 GMT",
"version": "v1"
}
] | 2018-07-11 | [
[
"Christodoulou",
"Dimitris M.",
""
],
[
"Kazanas",
"Demosthenes",
""
]
] | The Newtonian gravitational constant $G$ obeys the dimensional relation $[G] [M] [a] = [v]^4$, where $M$, $a$, and $v$ denote mass, acceleration, and speed, respectively. Since the baryonic Tully-Fisher (BTF) and Faber-Jackson (BFJ) relations are observed facts, this relation implies that $G\, a = {\rm constant}$. This result cannot be obtained in Newtonian dynamics which cannot explain the origin of the BTF and BFJ relations. An alternative, modified Newtonian dynamics (MOND) assumes that $G=G_0$ is constant in space and derives naturally a characteristic constant acceleration $a=a_0$, as well as the BTF and BFJ relations. This is overkill and it comes with a penalty: MOND cannot explain the origin of $a_0$. A solid physical resolution of this issue is that $G \propto a^{-1}$, which implies that in lower-acceleration environments the gravitational force is boosted relative to its Newtonian value because $G$ increases. This eliminates all problems related to MOND's empirical cutoff $a_0$ and yields a quantitative method for mapping the detailed variations of $G(a)$ across each individual galaxy as well as on larger and smaller scales. On the opposite end, the large accelerations produced by $G(a)$ appear to be linked to the weak-field limit of the fourth-order theory of conformal Weyl gravity. |
2108.11339 | Subhra Bhattacharya | Subhra Bhattacharya, Tanwi Bandyopadhyay | Revisiting the Evolving Lorentzian Wormhole: a General Perspective | null | Gen Relativ Gravit, 2021 | 10.1007/s10714-021-02878-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wormholes can be described as geometrical structures in space and time that
can serve as connection between distant regions of the universe.
Mathematically, general wormholes can be defined both on stationary as well as
on dynamic line elements. However, general relativistic and evolving Lorentzian
wormholes are less studied than their static wormhole counterpart. Accordingly,
in this work we shall focus on some evolving wormhole geometries. Starting from
a general class of spherically symmetric line element supporting wormhole
geometries, we shall use the Einstein's field equations to develop viable
astatic wormhole solutions. We will also discuss various evolving wormhole
solutions together with their physical significance, properties and throat
energy conditions. We claim that the method discussed in this work shall be
applicable for developing wormhole solutions corresponding to any general
Lorentzian wormhole metric.
| [
{
"created": "Tue, 24 Aug 2021 07:44:27 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Nov 2021 05:04:06 GMT",
"version": "v2"
}
] | 2021-11-22 | [
[
"Bhattacharya",
"Subhra",
""
],
[
"Bandyopadhyay",
"Tanwi",
""
]
] | Wormholes can be described as geometrical structures in space and time that can serve as connection between distant regions of the universe. Mathematically, general wormholes can be defined both on stationary as well as on dynamic line elements. However, general relativistic and evolving Lorentzian wormholes are less studied than their static wormhole counterpart. Accordingly, in this work we shall focus on some evolving wormhole geometries. Starting from a general class of spherically symmetric line element supporting wormhole geometries, we shall use the Einstein's field equations to develop viable astatic wormhole solutions. We will also discuss various evolving wormhole solutions together with their physical significance, properties and throat energy conditions. We claim that the method discussed in this work shall be applicable for developing wormhole solutions corresponding to any general Lorentzian wormhole metric. |
gr-qc/9810056 | George Davies | George Davies | Second-Order Black Hole Perturbations: A Computer Algebra Approach, I -
The Schwarzschild Spacetime | 20 pages + 12 page appendix, also available at
http://www.astro.queensu.ca/~grtensor | null | null | null | gr-qc astro-ph | null | This article outlines our derivation of the second order perturbations to a
Schwarzschild black hole, highlighting our use of, and necessary reliance on,
computer algebra. The particular perturbation scenario that is presented here
is the case of the linear quadrapole seeding the second order quadrapole. This
problem amounts to finding the second order Zerilli wave equation, and in
particular the effective source term due to the linear quadrapole. With one
minor exception, our calculations confirm the earlier findings of Gleiser,
et.al. On route to these results we also illustrate that, with the aid of
computer algebra, the linear Schwarzschild problem can be solved in a very
direct manner (i.e., without resorting to the usual function transformations),
and it is this ``direct method'' that drives the higher order perturbation
analysis. The calculations were performed using the GRTensorII computer algebra
package, running on the Maple V platform, along with several new Maple routines
that we have written specifically for these types of problems. Although we have
chosen to consider only the ``quadrapole-quadrapole'' calculation in this
article, the GRTensor environment, with the inclusion of these new routines,
would allow this analysis to be repeated for a far more general problem. These
routines, along with Maple worksheets that reproduce our calculations, are
publicly available at the GRTensor website: www.astro.queensu.ca/~grtensor .
The interested reader is invited to download and use them to reproduce our
results and experiment.
| [
{
"created": "Sun, 18 Oct 1998 06:19:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Davies",
"George",
""
]
] | This article outlines our derivation of the second order perturbations to a Schwarzschild black hole, highlighting our use of, and necessary reliance on, computer algebra. The particular perturbation scenario that is presented here is the case of the linear quadrapole seeding the second order quadrapole. This problem amounts to finding the second order Zerilli wave equation, and in particular the effective source term due to the linear quadrapole. With one minor exception, our calculations confirm the earlier findings of Gleiser, et.al. On route to these results we also illustrate that, with the aid of computer algebra, the linear Schwarzschild problem can be solved in a very direct manner (i.e., without resorting to the usual function transformations), and it is this ``direct method'' that drives the higher order perturbation analysis. The calculations were performed using the GRTensorII computer algebra package, running on the Maple V platform, along with several new Maple routines that we have written specifically for these types of problems. Although we have chosen to consider only the ``quadrapole-quadrapole'' calculation in this article, the GRTensor environment, with the inclusion of these new routines, would allow this analysis to be repeated for a far more general problem. These routines, along with Maple worksheets that reproduce our calculations, are publicly available at the GRTensor website: www.astro.queensu.ca/~grtensor . The interested reader is invited to download and use them to reproduce our results and experiment. |
gr-qc/9405047 | Roberto De Pietri dottVI | R. De Pietri, L. Lusanna & M. Pauri | Standard and Generalized Newtonian Gravities as ``Gauge'' Theories of
the Extended Galilei Group - II: Dynamical Three-Space Theories | 29 pages , compress, uuencode LaTex file, gr-qc/95050xx | Class.Quant.Grav.12:255-272,1995 | 10.1088/0264-9381/12/1/020 | null | gr-qc | null | In a preceding paper we developed a reformulation of Newtonian gravitation as
a {\it gauge} theory of the extended Galilei group. In the present one we
derive two true generalizations of Newton's theory (a {\it ten-fields} and an
{\it eleven-fields} theory), in terms of an explicit Lagrangian realization of
the {\it absolute time} dynamics of a Riemannian three-space. They turn out to
be {\it gauge invariant} theories of the extended Galilei group in the same
sense in which general relativity is said to be a {\it gauge} theory of the
Poincar\'e group. The {\it ten-fields} theory provides a dynamical realization
of some of the so-called ``Newtonian space-time structures'' which have been
geometrically classified by K\"{u}nzle and Kucha\v{r}. The {\it eleven-fields}
theory involves a {\it dilaton-like} scalar potential in addition to Newton's
potential and, like general relativity, has a three-metric with {\it two}
dynamical degrees of freedom. It is interesting to find that, within the linear
approximation, such degrees of freedom show {\it graviton-like} features: they
satisfy a wave equation and propagate with a velocity related to the scalar
Newtonian potential.
| [
{
"created": "Sun, 22 May 1994 13:40:30 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"De Pietri",
"R.",
""
],
[
"Lusanna",
"L.",
""
],
[
"Pauri",
"M.",
""
]
] | In a preceding paper we developed a reformulation of Newtonian gravitation as a {\it gauge} theory of the extended Galilei group. In the present one we derive two true generalizations of Newton's theory (a {\it ten-fields} and an {\it eleven-fields} theory), in terms of an explicit Lagrangian realization of the {\it absolute time} dynamics of a Riemannian three-space. They turn out to be {\it gauge invariant} theories of the extended Galilei group in the same sense in which general relativity is said to be a {\it gauge} theory of the Poincar\'e group. The {\it ten-fields} theory provides a dynamical realization of some of the so-called ``Newtonian space-time structures'' which have been geometrically classified by K\"{u}nzle and Kucha\v{r}. The {\it eleven-fields} theory involves a {\it dilaton-like} scalar potential in addition to Newton's potential and, like general relativity, has a three-metric with {\it two} dynamical degrees of freedom. It is interesting to find that, within the linear approximation, such degrees of freedom show {\it graviton-like} features: they satisfy a wave equation and propagate with a velocity related to the scalar Newtonian potential. |
1404.5836 | Sergey Chervon | Renat R. Abbyazov and Sergey V. Chervon | Unified dark matter and dark energy description in a chiral cosmological
model | 19 pages, 7 figures | Mod. Phys. Lett. A 28, 1350024 (2013) [19 pages] | 10.1142/S0217732313500247 | NIL GCA 2/2014 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show the way of dark matter and dark energy presentation via ansatzs on
the kinetic energies of the fields in the two-component chiral cosmological
model. To connect a kinetic interaction of dark matter and dark energy with
observational data the reconstruction procedure for the chiral metric component
$h_{22}$ and the potential of (self)interaction $V$ has been developed. The
reconstruction of $h_{22}$ and $V$ for the early and later inflation have been
performed. The proposed model is confronted to $\Lambda CDM$ model as well.
| [
{
"created": "Wed, 23 Apr 2014 14:34:45 GMT",
"version": "v1"
}
] | 2014-04-24 | [
[
"Abbyazov",
"Renat R.",
""
],
[
"Chervon",
"Sergey V.",
""
]
] | We show the way of dark matter and dark energy presentation via ansatzs on the kinetic energies of the fields in the two-component chiral cosmological model. To connect a kinetic interaction of dark matter and dark energy with observational data the reconstruction procedure for the chiral metric component $h_{22}$ and the potential of (self)interaction $V$ has been developed. The reconstruction of $h_{22}$ and $V$ for the early and later inflation have been performed. The proposed model is confronted to $\Lambda CDM$ model as well. |
1305.1640 | Jose Socorro Garcia | J. Socorro, Priscila Romero, Luis O. Pimentel and M. Aguero | Quintom potentials from quantum cosmology using the FRW cosmological
model | Latex2e, 10 pages, 1 figure | Acepted in Int. J. of Theor. Phys. (2013) | 10.1007/s10773-013-1565-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the quintom potential of dark energy models in the framework of
spatially flat Friedmann-Robertson Walker universe in the inflationary epoch,
using the Bohm like approach, known as amplitude-real-phase. We find some
potentials for which the wave function of the universe is found analytically
and we have obtained the classical trajectories in the inflation era.
| [
{
"created": "Tue, 7 May 2013 20:33:06 GMT",
"version": "v1"
}
] | 2013-05-09 | [
[
"Socorro",
"J.",
""
],
[
"Romero",
"Priscila",
""
],
[
"Pimentel",
"Luis O.",
""
],
[
"Aguero",
"M.",
""
]
] | We construct the quintom potential of dark energy models in the framework of spatially flat Friedmann-Robertson Walker universe in the inflationary epoch, using the Bohm like approach, known as amplitude-real-phase. We find some potentials for which the wave function of the universe is found analytically and we have obtained the classical trajectories in the inflation era. |
gr-qc/9910064 | Shingo Suzuki | Shingo Suzuki and Kei-ichi Maeda | Signature of chaos in gravitational waves from a spinning particle | 14 pages, LaTeX, to appear in Phys. Rev. D | Phys.Rev. D61 (2000) 024005 | 10.1103/PhysRevD.61.024005 | WU-AP/83/99 | gr-qc | null | A spinning test particle around a Schwarzschild black hole shows a chaotic
behavior, if its spin is larger than a critical value. We discuss whether or
not some peculiar signature of chaos appears in the gravitational waves emitted
from such a system. Calculating the emitted gravitational waves by use of the
quadrupole formula, we find that the energy emission rate of gravitational
waves for a chaotic orbit is about 10 times larger than that for a circular
orbit, but the same enhancement is also obtained by a regular "elliptic" orbit.
A chaotic motion is not always enhance the energy emission rate maximally. As
for the energy spectra of the gravitational waves, we find some characteristic
feature for a chaotic orbit. It may tell us how to find out a chaotic behavior
of the system. Such a peculiar behavior, if it will be found, may also provide
us some additional informations to determine parameters of a system such as a
spin.
| [
{
"created": "Wed, 20 Oct 1999 06:07:34 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Suzuki",
"Shingo",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | A spinning test particle around a Schwarzschild black hole shows a chaotic behavior, if its spin is larger than a critical value. We discuss whether or not some peculiar signature of chaos appears in the gravitational waves emitted from such a system. Calculating the emitted gravitational waves by use of the quadrupole formula, we find that the energy emission rate of gravitational waves for a chaotic orbit is about 10 times larger than that for a circular orbit, but the same enhancement is also obtained by a regular "elliptic" orbit. A chaotic motion is not always enhance the energy emission rate maximally. As for the energy spectra of the gravitational waves, we find some characteristic feature for a chaotic orbit. It may tell us how to find out a chaotic behavior of the system. Such a peculiar behavior, if it will be found, may also provide us some additional informations to determine parameters of a system such as a spin. |
gr-qc/0701166 | Juan A. Valiente-Kroon | J. A. Valiente Kroon | Asymptotic properties of the development of conformally flat data near
spatial infinity | 24 pages, 1 figure | Class.Quant.Grav.24:3037-3054,2007 | 10.1088/0264-9381/24/11/016 | null | gr-qc | null | Certain aspects of the behaviour of the gravitational field near null and
spatial infinity for the developments of asymptotically Euclidean, conformally
flat initial data sets are analysed. Ideas and results from two different
approaches are combined: on the one hand the null infinity formalism related to
the asymptotic characteristic initial value problem and on the other the
regular Cauchy initial value problem at spatial infinity which uses Friedrich's
representation of spatial infinity as a cylinder. The decay of the Weyl tensor
for the developments of the class of initial data under consideration is
analysed under some existence and regularity assumptions for the asymptotic
expansions obtained using the cylinder at spatial infinity. Conditions on the
initial data to obtain developments satisfying the Peeling Behaviour are
identified. Further, the decay of the asymptotic shear on null infinity is also
examined as one approaches spatial infinity. This decay is related to the
possibility of selecting the Poincar\'e group out of the BMS group in a
canonical fashion. It is found that for the class of initial data under
consideration, if the development peels, then the asymptotic shear goes to zero
at spatial infinity. Expansions of the Bondi mass are also examined. Finally,
the Newman-Penrose constants of the spacetime are written in terms of initial
data quantities and it is shown that the constants defined at future null
infinity are equal to those at past null infinity.
| [
{
"created": "Tue, 30 Jan 2007 09:53:52 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kroon",
"J. A. Valiente",
""
]
] | Certain aspects of the behaviour of the gravitational field near null and spatial infinity for the developments of asymptotically Euclidean, conformally flat initial data sets are analysed. Ideas and results from two different approaches are combined: on the one hand the null infinity formalism related to the asymptotic characteristic initial value problem and on the other the regular Cauchy initial value problem at spatial infinity which uses Friedrich's representation of spatial infinity as a cylinder. The decay of the Weyl tensor for the developments of the class of initial data under consideration is analysed under some existence and regularity assumptions for the asymptotic expansions obtained using the cylinder at spatial infinity. Conditions on the initial data to obtain developments satisfying the Peeling Behaviour are identified. Further, the decay of the asymptotic shear on null infinity is also examined as one approaches spatial infinity. This decay is related to the possibility of selecting the Poincar\'e group out of the BMS group in a canonical fashion. It is found that for the class of initial data under consideration, if the development peels, then the asymptotic shear goes to zero at spatial infinity. Expansions of the Bondi mass are also examined. Finally, the Newman-Penrose constants of the spacetime are written in terms of initial data quantities and it is shown that the constants defined at future null infinity are equal to those at past null infinity. |
1307.2227 | Matteo Smerlak | Matteo Smerlak | The two faces of Hawking radiation | Honorable Mention in the Gravity Research Foundation 2013 Essay
Competition | Int. J. Mod. Phys. D Vol. 22, No. 12 (2013) 1342019 | 10.1142/S0218271813420194 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | What happens when Alice falls into a black hole? In spite of recent
challenges by Almheiri et al. -- the ""firewall" hypothesis -- the consensus on
this question tends to remain "nothing special". Here I argue that something
rather special can happen near the horizon, already at the semiclassical level:
besides the standard Hawking outgoing modes, Alice can records a quasi-thermal
spectrum of ingoing modes, whose temperature and intensity diverges as Alice's
Killing energy $E$ goes to zero. I suggest that this effect can be thought of
in terms a "horizon-infinity duality", which relates the perception of
near-horizon and asymptotic geodesic observers -- the two faces of Hawking
radiation.
| [
{
"created": "Fri, 5 Jul 2013 20:35:13 GMT",
"version": "v1"
}
] | 2013-09-16 | [
[
"Smerlak",
"Matteo",
""
]
] | What happens when Alice falls into a black hole? In spite of recent challenges by Almheiri et al. -- the ""firewall" hypothesis -- the consensus on this question tends to remain "nothing special". Here I argue that something rather special can happen near the horizon, already at the semiclassical level: besides the standard Hawking outgoing modes, Alice can records a quasi-thermal spectrum of ingoing modes, whose temperature and intensity diverges as Alice's Killing energy $E$ goes to zero. I suggest that this effect can be thought of in terms a "horizon-infinity duality", which relates the perception of near-horizon and asymptotic geodesic observers -- the two faces of Hawking radiation. |
2209.03751 | V. G. Gurzadyan | A. Stepanian, Sh. Khlghatyan, V.G. Gurzadyan | Tidal disruption effects near black holes and Lambda-gravity | 6 pages, 3 figures; Eur.Phys.J.Plus (in press) | Eur. Phys. J. Plus, 137: 965 (2022) | 10.1140/epjp/s13360-022-03143-2 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The tidal disruption of stars in the vicinity of massive black holes is
discussed in the context of $\Lambda$-gravity. The latter provides an
explanation to the Hubble tension as a possible consequence of two Hubble
flows, the local and global ones. The bunch of notions which play role for the
considered tidal effect are obtained, along with the rate of the disrupted
stars. The role of pulsars is emphasized due to their ability to penetrate up
to the horizon of the massive black hole as for them the tidal radius can reach
the horizon. Tidal disruption mechanism also can lead to segregation of stars
by their mean density vs the distance from the black hole, the denser stars
surviving at shorter distances. The interplay of the central gravity field and
the repulsive $\Lambda$-term increasing with radius and its certain
observational consequences are discussed.
| [
{
"created": "Thu, 1 Sep 2022 02:47:02 GMT",
"version": "v1"
}
] | 2022-09-09 | [
[
"Stepanian",
"A.",
""
],
[
"Khlghatyan",
"Sh.",
""
],
[
"Gurzadyan",
"V. G.",
""
]
] | The tidal disruption of stars in the vicinity of massive black holes is discussed in the context of $\Lambda$-gravity. The latter provides an explanation to the Hubble tension as a possible consequence of two Hubble flows, the local and global ones. The bunch of notions which play role for the considered tidal effect are obtained, along with the rate of the disrupted stars. The role of pulsars is emphasized due to their ability to penetrate up to the horizon of the massive black hole as for them the tidal radius can reach the horizon. Tidal disruption mechanism also can lead to segregation of stars by their mean density vs the distance from the black hole, the denser stars surviving at shorter distances. The interplay of the central gravity field and the repulsive $\Lambda$-term increasing with radius and its certain observational consequences are discussed. |
2102.07099 | Shyam Das | Shyam Das, Saibal Ray, Maxim Khlopov, K.K. Nandi, Bikram Keshari
Parida | Anisotropic compact stars: Constraining model parameters to account for
physical features of tidal Love numbers | Major Revision based on the referee reports; 31 pages; 11 figures | Annals of Physics 433 (2021) 168597 | 10.1016/j.aop.2021.168597 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we develop a new class of models for a compact star with
anisotropic stresses inside the matter distribution. By assuming a linear
equation of state for the anisotropic matter composition of the star we solve
the Einstein field equations. In our approach, for the interior solutions we
use a particular form of the ansatz for the metric function $g_{rr}$. The
exterior solution is assumed as Schwarzschild metric and is joined with the
interior metric obtained across the boundary of the star. These matching of the
metrices along with the condition of the vanishing radial pressure at the
boundary lead us to determine the model parameters. The physical acceptability
of the solutions has verified by making use of the current estimated data
available from the pulsar 4U1608-52. Thereafter, assuming anisotropy due to
tidal effects we calculate the Love numbers from our model and compare the
results with the observed compact stars, viz. KS 1731- 260,4U 1608- 52,4U 1724-
207,4U 1820- 30,SAX J1748.9-2021 and EXO 1745-268. The overall situation
confirms physical viability of the proposed approach,which can shed new light
on the interior of the compact relativistic objects.
| [
{
"created": "Sun, 14 Feb 2021 08:19:30 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Nov 2021 12:11:06 GMT",
"version": "v2"
}
] | 2021-11-16 | [
[
"Das",
"Shyam",
""
],
[
"Ray",
"Saibal",
""
],
[
"Khlopov",
"Maxim",
""
],
[
"Nandi",
"K. K.",
""
],
[
"Parida",
"Bikram Keshari",
""
]
] | In this paper, we develop a new class of models for a compact star with anisotropic stresses inside the matter distribution. By assuming a linear equation of state for the anisotropic matter composition of the star we solve the Einstein field equations. In our approach, for the interior solutions we use a particular form of the ansatz for the metric function $g_{rr}$. The exterior solution is assumed as Schwarzschild metric and is joined with the interior metric obtained across the boundary of the star. These matching of the metrices along with the condition of the vanishing radial pressure at the boundary lead us to determine the model parameters. The physical acceptability of the solutions has verified by making use of the current estimated data available from the pulsar 4U1608-52. Thereafter, assuming anisotropy due to tidal effects we calculate the Love numbers from our model and compare the results with the observed compact stars, viz. KS 1731- 260,4U 1608- 52,4U 1724- 207,4U 1820- 30,SAX J1748.9-2021 and EXO 1745-268. The overall situation confirms physical viability of the proposed approach,which can shed new light on the interior of the compact relativistic objects. |
1211.5051 | Joan Josep Ferrando | Joan Josep Ferrando and Juan Antonio S\'aez | On the super-energy radiative gravitational fields | 16 pages; 1 figure | Class. Quantum Grav. 30 (2013) 095013 | 10.1088/0264-9381/30/9/095013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend our recent analysis (Ferrando J J and S\'aez J A 2012 Class.
Quantum Grav. 29 075012) on the Bel radiative gravitational fields to the
super-energy radiative gravitational fields defined by Garc\'{\i}a-Parrado
(Class. Quantum Grav. 25 015006). We give an intrinsic characterization of the
{\it new radiative fields}, and consider some distinguished classes of both
radiative and non radiative fields. Several super-energy inequalities are
improved.
| [
{
"created": "Wed, 21 Nov 2012 14:58:53 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Apr 2013 09:28:36 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Ferrando",
"Joan Josep",
""
],
[
"Sáez",
"Juan Antonio",
""
]
] | We extend our recent analysis (Ferrando J J and S\'aez J A 2012 Class. Quantum Grav. 29 075012) on the Bel radiative gravitational fields to the super-energy radiative gravitational fields defined by Garc\'{\i}a-Parrado (Class. Quantum Grav. 25 015006). We give an intrinsic characterization of the {\it new radiative fields}, and consider some distinguished classes of both radiative and non radiative fields. Several super-energy inequalities are improved. |
1610.01203 | Amna Ali | Debabrata Adak and Amna Ali | Bounce and Collapse in the Slotheonic Universe | 7 pages, 6figures | International Journal of Modern Physics D Vol. 26 (2017) 1750089 | 10.1142/S0218271817500894 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we examine the cosmological dynamics of a slotheon field in a
linear potential. The slotheon correction term
$\frac{G^{\mu\nu}}{2M^2}\pi_{;\mu}\pi_{;\nu}$ respects the galileon symmetry in
curved space time. We demonstrate the future evolution of universe in this
model. We show that in this scenario, the universe ends with the Big Crunch
singularity like the standard case. The difference being that the time at which
the singularity occurs is delayed in the slotheon gravity. The delay crucially
depends upon the strength of slotheon correction.
| [
{
"created": "Mon, 3 Oct 2016 10:16:48 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2017 07:25:58 GMT",
"version": "v2"
}
] | 2017-04-12 | [
[
"Adak",
"Debabrata",
""
],
[
"Ali",
"Amna",
""
]
] | In this paper, we examine the cosmological dynamics of a slotheon field in a linear potential. The slotheon correction term $\frac{G^{\mu\nu}}{2M^2}\pi_{;\mu}\pi_{;\nu}$ respects the galileon symmetry in curved space time. We demonstrate the future evolution of universe in this model. We show that in this scenario, the universe ends with the Big Crunch singularity like the standard case. The difference being that the time at which the singularity occurs is delayed in the slotheon gravity. The delay crucially depends upon the strength of slotheon correction. |
gr-qc/0607101 | Kristina Giesel | K. Giesel, T. Thiemann | Algebraic Quantum Gravity (AQG) III. Semiclassical Perturbation Theory | null | Class.Quant.Grav.24:2565-2588,2007 | 10.1088/0264-9381/24/10/005 | AEI-2006-60 | gr-qc hep-th math-ph math.MP | null | In the two previous papers of this series we defined a new combinatorical
approach to quantum gravity, Algebraic Quantum Gravity (AQG). We showed that
AQG reproduces the correct infinitesimal dynamics in the semiclassical limit,
provided one incorrectly substitutes the non -- Abelean group SU(2) by the
Abelean group $U(1)^3$ in the calculations. The mere reason why that
substitution was performed at all is that in the non -- Abelean case the volume
operator, pivotal for the definition of the dynamics, is not diagonisable by
analytical methods. This, in contrast to the Abelean case, so far prohibited
semiclassical computations. In this paper we show why this unjustified
substitution nevertheless reproduces the correct physical result: Namely, we
introduce for the first time semiclassical perturbation theory within AQG (and
LQG) which allows to compute expectation values of interesting operators such
as the master constraint as a power series in $\hbar$ with error control. That
is, in particular matrix elements of fractional powers of the volume operator
can be computed with extremely high precision for sufficiently large power of
$\hbar$ in the $\hbar$ expansion. With this new tool, the non -- Abelean
calculation, although technically more involved, is then exactly analogous to
the Abelean calculation, thus justifying the Abelean analysis in retrospect.
The results of this paper turn AQG into a calculational discipline.
| [
{
"created": "Sun, 23 Jul 2006 21:30:29 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Giesel",
"K.",
""
],
[
"Thiemann",
"T.",
""
]
] | In the two previous papers of this series we defined a new combinatorical approach to quantum gravity, Algebraic Quantum Gravity (AQG). We showed that AQG reproduces the correct infinitesimal dynamics in the semiclassical limit, provided one incorrectly substitutes the non -- Abelean group SU(2) by the Abelean group $U(1)^3$ in the calculations. The mere reason why that substitution was performed at all is that in the non -- Abelean case the volume operator, pivotal for the definition of the dynamics, is not diagonisable by analytical methods. This, in contrast to the Abelean case, so far prohibited semiclassical computations. In this paper we show why this unjustified substitution nevertheless reproduces the correct physical result: Namely, we introduce for the first time semiclassical perturbation theory within AQG (and LQG) which allows to compute expectation values of interesting operators such as the master constraint as a power series in $\hbar$ with error control. That is, in particular matrix elements of fractional powers of the volume operator can be computed with extremely high precision for sufficiently large power of $\hbar$ in the $\hbar$ expansion. With this new tool, the non -- Abelean calculation, although technically more involved, is then exactly analogous to the Abelean calculation, thus justifying the Abelean analysis in retrospect. The results of this paper turn AQG into a calculational discipline. |
2110.02263 | Chris Timberlake | Chris Timberlake (1), Andrea Vinante (1 and 2), Francesco Shankar (1),
Andrea Lapi (3), Hendrik Ulbricht (1) ((1) University of Southampton and (2)
Istituto di Fotonica e Nanotecnologie CNR and (3) SISSA) | Probing modified gravity with magnetically levitated resonators | 6 pages, 3 figures | null | 10.1103/PhysRevD.104.L101101 | null | gr-qc cond-mat.supr-con physics.class-ph | http://creativecommons.org/licenses/by/4.0/ | We present an experimental procedure, based on Meissner effect levitation of
neodymium ferromagnets, as a method of measuring the gravitational interactions
between mg masses. The scheme consists of two superconducting lead traps, with
a magnet levitating in each trap. The levitating magnets behave as harmonic
oscillators, and by carefully driving the motion of one magnet on resonance
with the other, we find that it should be easily possible to measure the
gravitational field produced by a 4~mg sphere, with the gravitational
attraction from masses as small as 30~$\mu$g predicted to be measurable within
realistic a realistic measurement time frame. We apply this acceleration
sensitivity to one concrete example and show the ability of testing models of
modified Newtonian dynamics.
| [
{
"created": "Tue, 5 Oct 2021 18:10:58 GMT",
"version": "v1"
}
] | 2021-11-17 | [
[
"Timberlake",
"Chris",
"",
"1 and 2"
],
[
"Vinante",
"Andrea",
"",
"1 and 2"
],
[
"Shankar",
"Francesco",
""
],
[
"Lapi",
"Andrea",
""
],
[
"Ulbricht",
"Hendrik",
""
]
] | We present an experimental procedure, based on Meissner effect levitation of neodymium ferromagnets, as a method of measuring the gravitational interactions between mg masses. The scheme consists of two superconducting lead traps, with a magnet levitating in each trap. The levitating magnets behave as harmonic oscillators, and by carefully driving the motion of one magnet on resonance with the other, we find that it should be easily possible to measure the gravitational field produced by a 4~mg sphere, with the gravitational attraction from masses as small as 30~$\mu$g predicted to be measurable within realistic a realistic measurement time frame. We apply this acceleration sensitivity to one concrete example and show the ability of testing models of modified Newtonian dynamics. |
gr-qc/0501085 | Vicente Jos\'e Bol\'os | V. J. Bol\'os | Lightlike simultaneity, comoving observers and distances in general
relativity | 17 pages, 5 figures. Since "lightlike distance" is in fact the known
"affine distance", the notation has been changed | J.Geom.Phys. 56 (2006) 813-829 | 10.1016/j.geomphys.2005.05.001 | null | gr-qc | null | We state a condition for an observer to be comoving with another observer in
general relativity, based on the concept of lightlike simultaneity. Taking into
account this condition, we study relative velocities, Doppler effect and light
aberration. We obtain that comoving observers observe the same light ray with
the same frequency and direction, and so gravitational redshift effect is a
particular case of Doppler effect. We also define a distance between an
observer and the events that it observes, that coincides with the known affine
distance. We show that affine distance is a particular case of radar distance
in the Minkowski space-time and generalizes the proper radial distance in the
Schwarzschild space-time. Finally, we show that affine distance gives us a new
concept of distance in Robertson-Walker space-times, according to Hubble law.
| [
{
"created": "Thu, 27 Jan 2005 12:07:39 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Jan 2005 11:20:58 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Apr 2005 09:35:53 GMT",
"version": "v3"
},
{
"created": "Thu, 9 Mar 2006 19:25:14 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Bolós",
"V. J.",
""
]
] | We state a condition for an observer to be comoving with another observer in general relativity, based on the concept of lightlike simultaneity. Taking into account this condition, we study relative velocities, Doppler effect and light aberration. We obtain that comoving observers observe the same light ray with the same frequency and direction, and so gravitational redshift effect is a particular case of Doppler effect. We also define a distance between an observer and the events that it observes, that coincides with the known affine distance. We show that affine distance is a particular case of radar distance in the Minkowski space-time and generalizes the proper radial distance in the Schwarzschild space-time. Finally, we show that affine distance gives us a new concept of distance in Robertson-Walker space-times, according to Hubble law. |
1807.09495 | Zong-Kuan Guo | Wen-Hong Ruan, Zong-Kuan Guo, Rong-Gen Cai, Yuan-Zhong Zhang | Taiji Program: Gravitational-Wave Sources | 15 pages, for the strain sensitivity of Taiji please send an email to
<guozk@itp.ac.cn> | Int. J. Mod. Phys. A35 (2020) 2050075 | 10.1142/S0217751X2050075X | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review potential low-frequency gravitational-wave sources, which are
expected to be detected by Taiji, a Chinese space-based gravitational-wave
detector, estimate the detection rates of these gravitational-wave sources and
present the parameter estimation of massive black hole binaries.
| [
{
"created": "Wed, 25 Jul 2018 09:11:17 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Aug 2019 11:54:48 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Jun 2020 08:56:43 GMT",
"version": "v3"
}
] | 2020-06-05 | [
[
"Ruan",
"Wen-Hong",
""
],
[
"Guo",
"Zong-Kuan",
""
],
[
"Cai",
"Rong-Gen",
""
],
[
"Zhang",
"Yuan-Zhong",
""
]
] | We review potential low-frequency gravitational-wave sources, which are expected to be detected by Taiji, a Chinese space-based gravitational-wave detector, estimate the detection rates of these gravitational-wave sources and present the parameter estimation of massive black hole binaries. |
1605.03204 | Karan Jani | Karan Jani, James Healy, James A. Clark, Lionel London, Pablo Laguna
and Deirdre Shoemaker | Georgia Tech Catalog of Gravitational Waveforms | null | null | 10.1088/0264-9381/33/20/204001 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper introduces a catalog of gravitational waveforms from the bank of
simulations by the numerical relativity effort at Georgia Tech. Currently, the
catalog consists of 452 distinct waveforms from more than 600 binary black hole
simulations: 128 of the waveforms are from binaries with black hole spins
aligned with the orbital angular momentum, and 324 are from precessing binary
black hole systems. The waveforms from binaries with non-spinning black holes
have mass-ratios $q = m_1/m_2 \le 15$, and those with precessing, spinning
black holes have $q \le 8$. The waveforms expand a moderate number of orbits in
the late inspiral, the burst during coalescence, and the ring-down of the final
black hole. Examples of waveforms in the catalog matched against the widely
used approximate models are presented. In addition, predictions of the mass and
spin of the final black hole by phenomenological fits are tested against the
results from the simulation bank. The role of the catalog in interpreting the
GW150914 event and future massive binary black-hole search in LIGO is
discussed. The Georgia Tech catalog is publicly available at
einstein.gatech.edu/catalog.
| [
{
"created": "Tue, 10 May 2016 20:31:49 GMT",
"version": "v1"
}
] | 2016-10-05 | [
[
"Jani",
"Karan",
""
],
[
"Healy",
"James",
""
],
[
"Clark",
"James A.",
""
],
[
"London",
"Lionel",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | This paper introduces a catalog of gravitational waveforms from the bank of simulations by the numerical relativity effort at Georgia Tech. Currently, the catalog consists of 452 distinct waveforms from more than 600 binary black hole simulations: 128 of the waveforms are from binaries with black hole spins aligned with the orbital angular momentum, and 324 are from precessing binary black hole systems. The waveforms from binaries with non-spinning black holes have mass-ratios $q = m_1/m_2 \le 15$, and those with precessing, spinning black holes have $q \le 8$. The waveforms expand a moderate number of orbits in the late inspiral, the burst during coalescence, and the ring-down of the final black hole. Examples of waveforms in the catalog matched against the widely used approximate models are presented. In addition, predictions of the mass and spin of the final black hole by phenomenological fits are tested against the results from the simulation bank. The role of the catalog in interpreting the GW150914 event and future massive binary black-hole search in LIGO is discussed. The Georgia Tech catalog is publicly available at einstein.gatech.edu/catalog. |
gr-qc/0601053 | C. R. Keeton | Charles R. Keeton (Rutgers), A. O. Petters (Duke) | Formalism for testing theories of gravity using lensing by compact
objects. II: Probing Post-Post-Newtonian metrics | submitted | Phys.Rev. D73 (2006) 044024 | 10.1103/PhysRevD.73.044024 | null | gr-qc astro-ph | null | We study gravitational lensing by compact objects in gravity theories that
can be written in a Post-Post-Newtonian (PPN) framework: i.e., the metric is
static and spherically symmetric, and can be written as a Taylor series in m/r,
where m is the gravitational radius of the compact object. Working invariantly,
we compute corrections to standard weak-deflection lensing observables at first
and second order in the ratio of the angular gravitational radius to the
angular Einstein ring radius of the lens. We show that the first-order
corrections to the total magnification and centroid position vanish universally
for gravity theories that can be written in the PPN framework. This arises from
some surprising, fundamental relations among the lensing observables in PPN
gravity models. We derive these relations for the image positions,
magnifications, and time delays. A deep consequence is that any violation of
the universal relations would signal the need for a gravity model outside the
PPN framework (provided that some basic assumptions hold). In practical terms,
the relations will guide observational programs to test general relativity,
modified gravity theories, and possibly the Cosmic Censorship conjecture. We
use the new relations to identify lensing observables that are accessible to
current or near-future technology, and to find combinations of observables that
are most useful for probing the spacetime metric. We give explicit applications
to the Galactic black hole, microlensing, and the binary pulsar J0737-3039.
| [
{
"created": "Fri, 13 Jan 2006 17:21:44 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Keeton",
"Charles R.",
"",
"Rutgers"
],
[
"Petters",
"A. O.",
"",
"Duke"
]
] | We study gravitational lensing by compact objects in gravity theories that can be written in a Post-Post-Newtonian (PPN) framework: i.e., the metric is static and spherically symmetric, and can be written as a Taylor series in m/r, where m is the gravitational radius of the compact object. Working invariantly, we compute corrections to standard weak-deflection lensing observables at first and second order in the ratio of the angular gravitational radius to the angular Einstein ring radius of the lens. We show that the first-order corrections to the total magnification and centroid position vanish universally for gravity theories that can be written in the PPN framework. This arises from some surprising, fundamental relations among the lensing observables in PPN gravity models. We derive these relations for the image positions, magnifications, and time delays. A deep consequence is that any violation of the universal relations would signal the need for a gravity model outside the PPN framework (provided that some basic assumptions hold). In practical terms, the relations will guide observational programs to test general relativity, modified gravity theories, and possibly the Cosmic Censorship conjecture. We use the new relations to identify lensing observables that are accessible to current or near-future technology, and to find combinations of observables that are most useful for probing the spacetime metric. We give explicit applications to the Galactic black hole, microlensing, and the binary pulsar J0737-3039. |
0906.5153 | Lee Lindblom | Lee Lindblom | Optimal Calibration Accuracy for Gravitational Wave Detectors | v2: minor changes, updated to version accepted in Phys. Rev. D | null | 10.1103/PhysRevD.80.042005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Calibration errors in the response function of a gravitational wave detector
degrade its ability to detect and then to measure the properties of any
detected signals. This paper derives the needed levels of calibration accuracy
for each of these data-analysis tasks. The levels derived here are optimal in
the sense that lower accuracy would result in missed detections and/or a loss
of measurement precision, while higher accuracy would be made irrelevant by the
intrinsic noise level of the detector. Calibration errors affect the
data-analysis process in much the same way as errors in theoretical waveform
templates. The optimal level of calibration accuracy is expressed therefore as
a joint limit on modeling and calibration errors: increased accuracy in one
reduces the accuracy requirement in the other.
| [
{
"created": "Sun, 28 Jun 2009 18:19:58 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Aug 2009 20:35:00 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Lindblom",
"Lee",
""
]
] | Calibration errors in the response function of a gravitational wave detector degrade its ability to detect and then to measure the properties of any detected signals. This paper derives the needed levels of calibration accuracy for each of these data-analysis tasks. The levels derived here are optimal in the sense that lower accuracy would result in missed detections and/or a loss of measurement precision, while higher accuracy would be made irrelevant by the intrinsic noise level of the detector. Calibration errors affect the data-analysis process in much the same way as errors in theoretical waveform templates. The optimal level of calibration accuracy is expressed therefore as a joint limit on modeling and calibration errors: increased accuracy in one reduces the accuracy requirement in the other. |
1507.08546 | Oleg Tsupko | G. S. Bisnovatyi-Kogan and O. Yu. Tsupko | Regular and chaotic dynamics of non-spherical bodies. Zeldovich's
pancakes and emission of very long gravitational waves | Review for special issue: 'Macroscopic randomness in astrophysical
plasmas: The legacy and vision of Ya. B. Zeldovich'; see also our previous
papers: arXiv:astro-ph/0212268, arXiv:astro-ph/0410573,
arXiv:astro-ph/0512309, arXiv:0801.2538, arXiv:0809.1007 | Journal of Plasma Physics / Volume 81 / Issue 05 / October 2015,
395810501 (29 pages) | 10.1017/S0022377815000525 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we review a recently developed approximate method for
investigation of dynamics of compressible ellipsoidal figures. Collapse and
subsequent behaviour are described by a system of ordinary differential
equations for time evolution of semi-axes of a uniformly rotating, three-axis,
uniform-density ellipsoid. First, we apply this approach to investigate dynamic
stability of non-spherical bodies. We solve the equations that describe, in a
simplified way, the Newtonian dynamics of a self-gravitating non-rotating
spheroidal body. We find that, after loss of stability, a contraction to a
singularity occurs only in a pure spherical collapse, and deviations from
spherical symmetry prevent the contraction to the singularity through a
stabilizing action of nonlinear non-spherical oscillations. The development of
instability leads to the formation of a regularly or chaotically oscillating
body, in which dynamical motion prevents the formation of the singularity. We
find regions of chaotic and regular pulsations by constructing a Poincare
diagram. A real collapse occurs after damping of the oscillations because of
energy losses, shock wave formation or viscosity. We use our approach to
investigate approximately the first stages of collapse during the large scale
structure formation. The theory of this process started from ideas of Ya. B.
Zeldovich, concerning the formation of strongly non-spherical structures during
nonlinear stages of the development of gravitational instability, known as
'Zeldovich's pancakes'. In this paper the collapse of non-collisional dark
matter and the formation of pancake structures are investigated approximately.
We estimate an emission of very long gravitational waves during the collapse,
and discuss the possibility of gravitational lensing and polarization of the
cosmic microwave background by these waves.
| [
{
"created": "Fri, 24 Jul 2015 15:23:11 GMT",
"version": "v1"
}
] | 2015-08-03 | [
[
"Bisnovatyi-Kogan",
"G. S.",
""
],
[
"Tsupko",
"O. Yu.",
""
]
] | In this paper we review a recently developed approximate method for investigation of dynamics of compressible ellipsoidal figures. Collapse and subsequent behaviour are described by a system of ordinary differential equations for time evolution of semi-axes of a uniformly rotating, three-axis, uniform-density ellipsoid. First, we apply this approach to investigate dynamic stability of non-spherical bodies. We solve the equations that describe, in a simplified way, the Newtonian dynamics of a self-gravitating non-rotating spheroidal body. We find that, after loss of stability, a contraction to a singularity occurs only in a pure spherical collapse, and deviations from spherical symmetry prevent the contraction to the singularity through a stabilizing action of nonlinear non-spherical oscillations. The development of instability leads to the formation of a regularly or chaotically oscillating body, in which dynamical motion prevents the formation of the singularity. We find regions of chaotic and regular pulsations by constructing a Poincare diagram. A real collapse occurs after damping of the oscillations because of energy losses, shock wave formation or viscosity. We use our approach to investigate approximately the first stages of collapse during the large scale structure formation. The theory of this process started from ideas of Ya. B. Zeldovich, concerning the formation of strongly non-spherical structures during nonlinear stages of the development of gravitational instability, known as 'Zeldovich's pancakes'. In this paper the collapse of non-collisional dark matter and the formation of pancake structures are investigated approximately. We estimate an emission of very long gravitational waves during the collapse, and discuss the possibility of gravitational lensing and polarization of the cosmic microwave background by these waves. |
1102.0894 | Stefano Viaggiu | Luca Tomassini, Stefano Viaggiu | Physically motivated uncertainty relations at the Planck length for an
emergent non commutative spacetime | Final version published in "Class. Quantum Grav." | Class. Quantum Grav. 28 (2011) 075001 | 10.1088/0264-9381/28/7/075001 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive new space-time uncertainty relations (STUR) at the fundamental
Planck length $L_P$ from quantum mechanics and general relativity (GR), both in
flat and curved backgrounds. Contrary to claims present in the literature, our
approach suggests that no minimal uncertainty appears for lengths, but instead
for minimal space and four-volumes. Moreover, we derive a maximal absolute
value for the energy density. Finally, some considerations on possible
commutators among quantum operators implying our STUR are done.
| [
{
"created": "Fri, 4 Feb 2011 12:24:48 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Mar 2011 12:22:26 GMT",
"version": "v2"
}
] | 2011-03-02 | [
[
"Tomassini",
"Luca",
""
],
[
"Viaggiu",
"Stefano",
""
]
] | We derive new space-time uncertainty relations (STUR) at the fundamental Planck length $L_P$ from quantum mechanics and general relativity (GR), both in flat and curved backgrounds. Contrary to claims present in the literature, our approach suggests that no minimal uncertainty appears for lengths, but instead for minimal space and four-volumes. Moreover, we derive a maximal absolute value for the energy density. Finally, some considerations on possible commutators among quantum operators implying our STUR are done. |
gr-qc/0107051 | Carlos F. Sopuerta | Philippos Papadopoulos and Carlos F. Sopuerta (RCG, Portsmouth U.) | Evolution systems for non-linear perturbations of background geometries | 12 pages, 3 figures, Revtex v3.0. Revised version to appear in
Physical Review D | Phys.Rev. D65 (2002) 044008 | 10.1103/PhysRevD.65.044008 | null | gr-qc | null | The formulation of the initial value problem for the Einstein equations is at
the heart of obtaining interesting new solutions using numerical relativity and
still very much under theoretical and applied scrutiny. We develop a
specialised background geometry approach, for systems where there is
non-trivial a priori knowledge about the spacetime under study. The background
three-geometry and associated connection are used to express the ADM evolution
equations in terms of physical non-linear deviations from that background.
Expressing the equations in first order form leads naturally to a system
closely linked to the Einstein-Christoffel system, introduced by Anderson and
York, and sharing its hyperbolicity properties. We illustrate the drastic
alteration of the source structure of the equations, and discuss why this is
likely to be numerically advantageous.
| [
{
"created": "Fri, 13 Jul 2001 15:16:18 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Oct 2001 17:22:36 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Papadopoulos",
"Philippos",
"",
"RCG, Portsmouth U."
],
[
"Sopuerta",
"Carlos F.",
"",
"RCG, Portsmouth U."
]
] | The formulation of the initial value problem for the Einstein equations is at the heart of obtaining interesting new solutions using numerical relativity and still very much under theoretical and applied scrutiny. We develop a specialised background geometry approach, for systems where there is non-trivial a priori knowledge about the spacetime under study. The background three-geometry and associated connection are used to express the ADM evolution equations in terms of physical non-linear deviations from that background. Expressing the equations in first order form leads naturally to a system closely linked to the Einstein-Christoffel system, introduced by Anderson and York, and sharing its hyperbolicity properties. We illustrate the drastic alteration of the source structure of the equations, and discuss why this is likely to be numerically advantageous. |
gr-qc/0304097 | Ron Wiltshire | Ron Wiltshire | Slowly rotating, compact fluid sources embedded in Kerr empty space-time | null | null | 10.1023/B:GERG.0000018288.52206.ea | null | gr-qc | null | Spherically symmetric static fluid sources are endowed with rotation and
embedded in Kerr empty space-time up to an including quadratic terms in an
angular velocity parameter using Darmois junction conditions. Einstein's
equation's for the system are developed in terms of linear ordinary
differential equations. The boundary of the rotating source is expressed
explicitly in terms of sinusoidal functions of the polar angle which differ
somewhat according to whether an equation of state exists between internal
density and supporting pressure.
| [
{
"created": "Fri, 25 Apr 2003 08:32:02 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Wiltshire",
"Ron",
""
]
] | Spherically symmetric static fluid sources are endowed with rotation and embedded in Kerr empty space-time up to an including quadratic terms in an angular velocity parameter using Darmois junction conditions. Einstein's equation's for the system are developed in terms of linear ordinary differential equations. The boundary of the rotating source is expressed explicitly in terms of sinusoidal functions of the polar angle which differ somewhat according to whether an equation of state exists between internal density and supporting pressure. |
2112.05408 | Basundhara Ghosh | Chitrak Sarkar, Arunoday Sarkar, Basundhara Ghosh and Buddhadeb Ghosh | Can breakdown of perturbation in the $\alpha$-attractor inflation lead
to PBH formation? | 29 pages, 11 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | With the basic $\alpha$-attractor potentials, we investigate an inflationary
regime in the high-$k$ limit, where the cosmological perturbation breaks down
due to large enhancement in the scalar power spectrum and generation of large
negative values of the Bardeen potential. We analyze that, this deep
sub-horizon regime creates a situation, which is congenial to the formation of
the primordial black holes (PBHs). We work in the spatially flat gauge with
$\delta\phi\neq$ 0 and thus explicitly show the roles of perturbations in the
inflaton field as well as in the background gravitational field in the
mentioned enhancements and thereby in the PBH formation. We calculate the
values of $\sigma(M)$, $\beta(M)$ and $f_\mathrm{PBH}(M)$ around the peaks in
the density contrast profile and thus estimate the fraction of PBH in the dark
matter of the present universe, corresponding to certain mass scales. We
observe the formation of PBHs in the $k$ range $0.43\times 10^{13}$ Mpc$^{-1}$
to $9.8\times 10^{13}$ Mpc$^{-1}$ with masses $1.35\times 10^{-13}M_\odot$ to
$2.60\times 10^{-16}M_\odot$, evaporation times $7.74\times 10^{33}$ sec to
$5.53\times 10^{25}$ sec, Hawking temperatures $3.72\times 10^{-8}$ GeV to
$1.93\times 10^{-5}$ GeV and $f_\mathrm{PBH}(M)$ $\sim 6.12\times 10^{-6}$ to
$3.63\times 10^{-1}$. The calculated mass range lies in the regions of
forecasts by LISA, WD, NS, DECIGO/AI, FL, SIGWs and the $f_\mathrm{PBH} (M)$
results overlap with those of DECIGO/AI, FL, SIGWs.
| [
{
"created": "Fri, 10 Dec 2021 09:28:17 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Mar 2022 07:14:00 GMT",
"version": "v2"
}
] | 2022-03-08 | [
[
"Sarkar",
"Chitrak",
""
],
[
"Sarkar",
"Arunoday",
""
],
[
"Ghosh",
"Basundhara",
""
],
[
"Ghosh",
"Buddhadeb",
""
]
] | With the basic $\alpha$-attractor potentials, we investigate an inflationary regime in the high-$k$ limit, where the cosmological perturbation breaks down due to large enhancement in the scalar power spectrum and generation of large negative values of the Bardeen potential. We analyze that, this deep sub-horizon regime creates a situation, which is congenial to the formation of the primordial black holes (PBHs). We work in the spatially flat gauge with $\delta\phi\neq$ 0 and thus explicitly show the roles of perturbations in the inflaton field as well as in the background gravitational field in the mentioned enhancements and thereby in the PBH formation. We calculate the values of $\sigma(M)$, $\beta(M)$ and $f_\mathrm{PBH}(M)$ around the peaks in the density contrast profile and thus estimate the fraction of PBH in the dark matter of the present universe, corresponding to certain mass scales. We observe the formation of PBHs in the $k$ range $0.43\times 10^{13}$ Mpc$^{-1}$ to $9.8\times 10^{13}$ Mpc$^{-1}$ with masses $1.35\times 10^{-13}M_\odot$ to $2.60\times 10^{-16}M_\odot$, evaporation times $7.74\times 10^{33}$ sec to $5.53\times 10^{25}$ sec, Hawking temperatures $3.72\times 10^{-8}$ GeV to $1.93\times 10^{-5}$ GeV and $f_\mathrm{PBH}(M)$ $\sim 6.12\times 10^{-6}$ to $3.63\times 10^{-1}$. The calculated mass range lies in the regions of forecasts by LISA, WD, NS, DECIGO/AI, FL, SIGWs and the $f_\mathrm{PBH} (M)$ results overlap with those of DECIGO/AI, FL, SIGWs. |
1405.7627 | Pablo Galindo Salgado | Pablo Galindo and Marc Mars | McGehee regularization of general SO(3)-invariant potentials and
applications to stationary and spherically symmetric spacetimes | LaTeX file, 37 pages, 11 figures | Class. Quantum Grav. 31 (2014) 245008 | 10.1088/0264-9381/31/24/245008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The McGehee regularization is a method to study the singularity at the origin
of the dynamical system describing a point particle in a plane moving under the
action of a power-law potential. It was used by Belbruno and Pretorius to
perform a dynamical system regularization of the singularity at the center of
the motion of massless test particles in the Schwarzschild spacetime. In this
paper, we generalize the McGehee transformation so that we can regularize the
singularity at the origin of the dynamical system describing the motion of
causal geodesics (timelike or null) in any stationary and spherically symmetric
spacetime of Kerr-Schild form. We first show that the geodesics for both
massive and massless particles can be described globally in the Kerr-Schild
spacetime as the motion of a Newtonian point particle in a suitable radial
potential and study the conditions under which the central singularity can be
regularized using an extension of the McGehee method. As an example, we apply
these results to causal geodesics in the Schwarzschild and Reissner-Nordstr\"om
spacetimes. Interestingly, the geodesic trajectories in the whole maximal
extension of both spacetimes can be described by a single two-dimensional phase
space with non-trivial topology. This topology arises from the presence of
excluded regions in the phase space determined by the condition that the
tangent vector of the geodesic be causal and future directed.
| [
{
"created": "Thu, 29 May 2014 17:42:05 GMT",
"version": "v1"
}
] | 2014-12-03 | [
[
"Galindo",
"Pablo",
""
],
[
"Mars",
"Marc",
""
]
] | The McGehee regularization is a method to study the singularity at the origin of the dynamical system describing a point particle in a plane moving under the action of a power-law potential. It was used by Belbruno and Pretorius to perform a dynamical system regularization of the singularity at the center of the motion of massless test particles in the Schwarzschild spacetime. In this paper, we generalize the McGehee transformation so that we can regularize the singularity at the origin of the dynamical system describing the motion of causal geodesics (timelike or null) in any stationary and spherically symmetric spacetime of Kerr-Schild form. We first show that the geodesics for both massive and massless particles can be described globally in the Kerr-Schild spacetime as the motion of a Newtonian point particle in a suitable radial potential and study the conditions under which the central singularity can be regularized using an extension of the McGehee method. As an example, we apply these results to causal geodesics in the Schwarzschild and Reissner-Nordstr\"om spacetimes. Interestingly, the geodesic trajectories in the whole maximal extension of both spacetimes can be described by a single two-dimensional phase space with non-trivial topology. This topology arises from the presence of excluded regions in the phase space determined by the condition that the tangent vector of the geodesic be causal and future directed. |
gr-qc/9601039 | Shobit Mahajan Dr. | Daksh Lohiya, Annu Batra, Sameer Mehra, Shobhit Mahajan, Amitabha
Mukherjee | Studies in Structure Formation in theories with a repulsive long range
gravitational force | Normal Tex, 7 pages, 5 figures available from the authors | null | 10.1080/10556799708202991 | DUCOS-96-001 | gr-qc | null | This article reports on emergence of structures in a class of alternative
theories of gravity. These theories do not have any horizon, flatness, initial
cosmological singularity and (possibly) quantization problems. The model is
characterised by a dynamically induced gravitational constant with a ``wrong''
sign corresponding to repulsive gravitation on the large scale. A non - minimal
coupling of a scalar field in the model can give rise to non - topological
solitons in the theory. This results in domains (gravity - balls) inside which
an effective, canonical, attractive gravitational constant is induced. We
consider simulations of the formation and evolution of such solutions. Starting
with a single gravity - ball, we consider its fragmentation into smaller (lower
mass) balls - evolving by mutual repulsion. After several runs, we have been
able to identify two parameters: the strength of the long range gravitational
constant and the size of the gravity balls, which can be used to generate
appropriate two point correlations of the distribution of these balls.
| [
{
"created": "Thu, 25 Jan 1996 08:20:52 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Lohiya",
"Daksh",
""
],
[
"Batra",
"Annu",
""
],
[
"Mehra",
"Sameer",
""
],
[
"Mahajan",
"Shobhit",
""
],
[
"Mukherjee",
"Amitabha",
""
]
] | This article reports on emergence of structures in a class of alternative theories of gravity. These theories do not have any horizon, flatness, initial cosmological singularity and (possibly) quantization problems. The model is characterised by a dynamically induced gravitational constant with a ``wrong'' sign corresponding to repulsive gravitation on the large scale. A non - minimal coupling of a scalar field in the model can give rise to non - topological solitons in the theory. This results in domains (gravity - balls) inside which an effective, canonical, attractive gravitational constant is induced. We consider simulations of the formation and evolution of such solutions. Starting with a single gravity - ball, we consider its fragmentation into smaller (lower mass) balls - evolving by mutual repulsion. After several runs, we have been able to identify two parameters: the strength of the long range gravitational constant and the size of the gravity balls, which can be used to generate appropriate two point correlations of the distribution of these balls. |
2201.03569 | Daniel Mayerson | Kwinten Fransen, Daniel R. Mayerson | On Detecting Equatorial Symmetry Breaking with LISA | 16 pages + appendices; 2 figures and 4 tables | null | 10.1103/PhysRevD.106.064035 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The equatorial symmetry of the Kerr black hole is generically broken in
models of quantum gravity. Nevertheless, most phenomenological models start
from the assumption of equatorial symmetry, and little attention has been given
to the observability of this smoking gun signature of beyond-GR physics.
Extreme mass-ratio inspirals (EMRIs), in particular, are known to sensitively
probe supermassive black holes near their horizon; yet estimates for
constraints on deviations from Kerr in space-based gravitational wave
observations (e.g. with LISA) of such systems are currently based on
equatorially symmetric models. We use modified "analytic kludge" waveforms to
estimate how accurately LISA will be able to measure or constrain equatorial
symmetry breaking, in the form of the lowest-lying odd parity multipole moments
$S_2, M_3$. We find that the dimensionless multipole ratios such as $S_2/M^3$
will typically be detectable for LISA EMRIs with a measurement accuracy of
$\Delta(S_2/M^3) \sim 1\%$; this will set a strong constraint on the breaking
of equatorial symmetry.
| [
{
"created": "Mon, 10 Jan 2022 19:00:01 GMT",
"version": "v1"
}
] | 2022-10-05 | [
[
"Fransen",
"Kwinten",
""
],
[
"Mayerson",
"Daniel R.",
""
]
] | The equatorial symmetry of the Kerr black hole is generically broken in models of quantum gravity. Nevertheless, most phenomenological models start from the assumption of equatorial symmetry, and little attention has been given to the observability of this smoking gun signature of beyond-GR physics. Extreme mass-ratio inspirals (EMRIs), in particular, are known to sensitively probe supermassive black holes near their horizon; yet estimates for constraints on deviations from Kerr in space-based gravitational wave observations (e.g. with LISA) of such systems are currently based on equatorially symmetric models. We use modified "analytic kludge" waveforms to estimate how accurately LISA will be able to measure or constrain equatorial symmetry breaking, in the form of the lowest-lying odd parity multipole moments $S_2, M_3$. We find that the dimensionless multipole ratios such as $S_2/M^3$ will typically be detectable for LISA EMRIs with a measurement accuracy of $\Delta(S_2/M^3) \sim 1\%$; this will set a strong constraint on the breaking of equatorial symmetry. |
gr-qc/0606082 | Mikhail Kagan | Martin Bojowald and Mikhail Kagan | Loop cosmological implications of a non-minimally coupled scalar field | 10 pages, 4 figures | Phys.Rev. D74 (2006) 044033 | 10.1103/PhysRevD.74.044033 | IGPG-06/6-2 | gr-qc astro-ph | null | Non-minimal actions with matter represented by a scalar field coupled to
gravity are considered in the context of a homogeneous and isotropic universe.
The coupling is of the form $-\xi/2 \phi^2 R$. The possibility of successful
inflation is investigated taking into account features of loop cosmology. For
that end a conformal transformation is performed. That brings the theory into
the standard minimally coupled form (Einstein frame) with some effective field
and its potential. Both analytical and numerical estimates show that a negative
coupling constant is preferable for successful inflation. Moreover, provided
fixed initial conditions, larger $|\xi|$ leads to a greater number of {\em
e}-folds. The latter is obtained for a reasonable range of initial conditions
and the coupling parameter and indicates a possibility for successful
inflation.
| [
{
"created": "Mon, 19 Jun 2006 20:23:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bojowald",
"Martin",
""
],
[
"Kagan",
"Mikhail",
""
]
] | Non-minimal actions with matter represented by a scalar field coupled to gravity are considered in the context of a homogeneous and isotropic universe. The coupling is of the form $-\xi/2 \phi^2 R$. The possibility of successful inflation is investigated taking into account features of loop cosmology. For that end a conformal transformation is performed. That brings the theory into the standard minimally coupled form (Einstein frame) with some effective field and its potential. Both analytical and numerical estimates show that a negative coupling constant is preferable for successful inflation. Moreover, provided fixed initial conditions, larger $|\xi|$ leads to a greater number of {\em e}-folds. The latter is obtained for a reasonable range of initial conditions and the coupling parameter and indicates a possibility for successful inflation. |
1001.1180 | Gabriel Abreu | Gabriel Abreu (Victoria University of Wellington), Matt Visser
(Victoria University of Wellington) | The quantum interest conjecture in (3+1)-dimensional Minkowski space | 3 pages. Prepared for the proceedings of the 12th Marcel Grossmann
conference. (Paris, July 2009.) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantum inequalities, and the closely related quantum interest
conjecture, impose restrictions on the distribution of the energy density
measured by any time-like observer, potentially preventing the existence of
exotic phenomena such as Alcubierre warp-drives or traversable wormholes. It
has already been proved that both assertions can be reduced to statements
concerning the existence or non-existence of bound states of a certain
1-dimensional quantum mechanical Hamiltonian. Using this approach, we will
informally review a simple variational proof of one version of the Quantum
Interest conjecture in (3+1)-dimensional Minkowski space.
| [
{
"created": "Thu, 7 Jan 2010 23:18:19 GMT",
"version": "v1"
}
] | 2010-01-11 | [
[
"Abreu",
"Gabriel",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | The quantum inequalities, and the closely related quantum interest conjecture, impose restrictions on the distribution of the energy density measured by any time-like observer, potentially preventing the existence of exotic phenomena such as Alcubierre warp-drives or traversable wormholes. It has already been proved that both assertions can be reduced to statements concerning the existence or non-existence of bound states of a certain 1-dimensional quantum mechanical Hamiltonian. Using this approach, we will informally review a simple variational proof of one version of the Quantum Interest conjecture in (3+1)-dimensional Minkowski space. |
2204.08533 | Boris Goncharov | Boris Goncharov, Alexander H. Nitz, Jan Harms | Utilizing the null stream of the Einstein Telescope | 15 pages, 7 figures | Phys. Rev. D 105, 122007 (2022) | 10.1103/PhysRevD.105.122007 | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Among third-generation ground-based gravitational-wave detectors proposed for
the next decade, the Einstein Telescope provides a unique kind of null stream
$\unicode{x2014}$ the signal-free linear combination of data $\unicode{x2014}$
that enables otherwise inaccessible tests of the noise models. We project and
showcase challenges in modeling the noise in the 2030s and how it will affect
the performance of third-generation detectors. We find that the null stream of
the Einstein Telescope is capable of eliminating transient detector glitches
that are known to limit current gravitational-wave searches. The techniques we
discuss are computationally efficient and do not require a priori knowledge
about glitch models. Furthermore, we show how the null stream can be used to
provide an unbiased estimation of the noise power spectrum necessary for online
and offline data analyses even with multiple loud signals in the band. We
overview other approaches to utilizing the null stream. Finally, we comment on
the limitations and future challenges of null-stream analyses for the Einstein
Telescope and arbitrary detector networks.
| [
{
"created": "Mon, 18 Apr 2022 19:34:12 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jun 2022 07:09:08 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Jun 2022 13:57:49 GMT",
"version": "v3"
},
{
"created": "Mon, 14 Nov 2022 15:32:18 GMT",
"version": "v4"
}
] | 2022-11-15 | [
[
"Goncharov",
"Boris",
""
],
[
"Nitz",
"Alexander H.",
""
],
[
"Harms",
"Jan",
""
]
] | Among third-generation ground-based gravitational-wave detectors proposed for the next decade, the Einstein Telescope provides a unique kind of null stream $\unicode{x2014}$ the signal-free linear combination of data $\unicode{x2014}$ that enables otherwise inaccessible tests of the noise models. We project and showcase challenges in modeling the noise in the 2030s and how it will affect the performance of third-generation detectors. We find that the null stream of the Einstein Telescope is capable of eliminating transient detector glitches that are known to limit current gravitational-wave searches. The techniques we discuss are computationally efficient and do not require a priori knowledge about glitch models. Furthermore, we show how the null stream can be used to provide an unbiased estimation of the noise power spectrum necessary for online and offline data analyses even with multiple loud signals in the band. We overview other approaches to utilizing the null stream. Finally, we comment on the limitations and future challenges of null-stream analyses for the Einstein Telescope and arbitrary detector networks. |
1007.1754 | Luca Baiotti | Luca Baiotti, Masaru Shibata, Tetsuro Yamamoto | Binary neutron-star mergers with Whisky and SACRA: First quantitative
comparison of results from independent general-relativistic hydrodynamics
codes | Published on Phys. Rev. D | Phys.Rev.D82:064015,2010 | 10.1103/PhysRevD.82.064015 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first quantitative comparison of two independent
general-relativistic hydrodynamics codes, the Whisky code and the SACRA code.
We compare the output of simulations starting from the same initial data and
carried out with the configuration (numerical methods, grid setup, resolution,
gauges) which for each code has been found to give consistent and sufficiently
accurate results, in particular in terms of cleanness of gravitational
waveforms. We focus on the quantities that should be conserved during the
evolution (rest mass, total mass energy, and total angular momentum) and on the
gravitational-wave amplitude and frequency. We find that the results produced
by the two codes agree at a reasonable level, with variations in the different
quantities but always at better than about 10%.
| [
{
"created": "Sun, 11 Jul 2010 03:34:15 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Sep 2010 01:23:21 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Baiotti",
"Luca",
""
],
[
"Shibata",
"Masaru",
""
],
[
"Yamamoto",
"Tetsuro",
""
]
] | We present the first quantitative comparison of two independent general-relativistic hydrodynamics codes, the Whisky code and the SACRA code. We compare the output of simulations starting from the same initial data and carried out with the configuration (numerical methods, grid setup, resolution, gauges) which for each code has been found to give consistent and sufficiently accurate results, in particular in terms of cleanness of gravitational waveforms. We focus on the quantities that should be conserved during the evolution (rest mass, total mass energy, and total angular momentum) and on the gravitational-wave amplitude and frequency. We find that the results produced by the two codes agree at a reasonable level, with variations in the different quantities but always at better than about 10%. |
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