id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0303010 | Alejandro Jakubi | Juan M. Aguirregabiria, Luis P. Chimento, Alejandro S. Jakubi, and
Ruth Lazkoz | Symmetries leading to inflation | 16 pages, uses RevTeX 4, to appear in Phys. Rev. D | Phys.Rev. D67 (2003) 083518 | 10.1103/PhysRevD.67.083518 | null | gr-qc astro-ph | null | We present here the general transformation that leaves unchanged the form of
the field equations for perfect fluid Friedmann--Robertson--Walker and Bianchi
V cosmologies. The symmetries found can be used as algorithms for generating
new cosmological models from existing ones. A particular case of the general
transformation is used to illustrate the crucial role played by the number of
scalar fields in the occurrence of inflation. Related to this, we also study
the existence and stability of Bianchi V power law solutions.
| [
{
"created": "Mon, 3 Mar 2003 16:10:49 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Aguirregabiria",
"Juan M.",
""
],
[
"Chimento",
"Luis P.",
""
],
[
"Jakubi",
"Alejandro S.",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | We present here the general transformation that leaves unchanged the form of the field equations for perfect fluid Friedmann--Robertson--Walker and Bianchi V cosmologies. The symmetries found can be used as algorithms for generating new cosmological models from existing ones. A particular case of the general transformation is used to illustrate the crucial role played by the number of scalar fields in the occurrence of inflation. Related to this, we also study the existence and stability of Bianchi V power law solutions. |
2007.06790 | Simran Arora | Simran Arora, Snehasish Bhattacharjee, P.K. Sahoo | Late-Time Viscous Cosmology in $f(R,T)$ Gravity | New Astronomy accepted version | New Astronomy, 82 (2021) 101452 | 10.1016/j.newast.2020.101452 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The article communicates an alternative route to suffice the late-time
acceleration considering a bulk viscous fluid with viscosity coefficient $\zeta
=\zeta _{0}+ \zeta _{1} H + \zeta _{2} H^{2}$, where $\zeta _{0}, \zeta _{1},
\zeta _{2}$ are constants in the framework of $f(R,T)$ modified gravity. We
presume the $f(R,T)$ functional form to be $f=R+2\alpha T$ where $\alpha$ is a
constant. We then solve the field equations for the Hubble Parameter and study
the cosmological dynamics of kinematic variables such as deceleration, jerk,
snap and lerk parameters as a function of cosmic time. We observe the
deceleration parameter to be highly sensitive to $\alpha$ and undergoes a
signature flipping at around $t\sim 10$ Gyrs for $\alpha=-0.179$ which is
favored by observations. The EoS parameter for our model assumes values close
to $-1$ at $t_{0}=13.7$Gyrs which is in remarkable agreement with the latest
Planck measurements. Next, we study the evolution of energy conditions and find
that our model violate the Strong Energy Condition in order to explain the
late-time cosmic acceleration. To understand the nature of dark energy mimicked
by the bulk viscous baryonic fluid, we perform some geometrical diagnostics
like the $\{r,s\}$ and $\{r,q\}$ plane. We found the model to mimic the nature
of a Chaplygin gas type dark energy model at early times while a Quintessence
type in distant future. Finally, we study the violation of continuity equation
for our model and show that in order to explain the cosmic acceleration at the
present epoch, energy-momentum must violate.
| [
{
"created": "Tue, 14 Jul 2020 03:22:47 GMT",
"version": "v1"
}
] | 2020-07-20 | [
[
"Arora",
"Simran",
""
],
[
"Bhattacharjee",
"Snehasish",
""
],
[
"Sahoo",
"P. K.",
""
]
] | The article communicates an alternative route to suffice the late-time acceleration considering a bulk viscous fluid with viscosity coefficient $\zeta =\zeta _{0}+ \zeta _{1} H + \zeta _{2} H^{2}$, where $\zeta _{0}, \zeta _{1}, \zeta _{2}$ are constants in the framework of $f(R,T)$ modified gravity. We presume the $f(R,T)$ functional form to be $f=R+2\alpha T$ where $\alpha$ is a constant. We then solve the field equations for the Hubble Parameter and study the cosmological dynamics of kinematic variables such as deceleration, jerk, snap and lerk parameters as a function of cosmic time. We observe the deceleration parameter to be highly sensitive to $\alpha$ and undergoes a signature flipping at around $t\sim 10$ Gyrs for $\alpha=-0.179$ which is favored by observations. The EoS parameter for our model assumes values close to $-1$ at $t_{0}=13.7$Gyrs which is in remarkable agreement with the latest Planck measurements. Next, we study the evolution of energy conditions and find that our model violate the Strong Energy Condition in order to explain the late-time cosmic acceleration. To understand the nature of dark energy mimicked by the bulk viscous baryonic fluid, we perform some geometrical diagnostics like the $\{r,s\}$ and $\{r,q\}$ plane. We found the model to mimic the nature of a Chaplygin gas type dark energy model at early times while a Quintessence type in distant future. Finally, we study the violation of continuity equation for our model and show that in order to explain the cosmic acceleration at the present epoch, energy-momentum must violate. |
gr-qc/0602036 | Peter Dunsby | Caroline Zunckel, Gerold Betschart, Peter K S Dunsby, Mattias Marklund | On inhomogeneous magnetic seed fields and gravitational waves within the
MHD limit | 14 pages revtex | Phys.Rev. D73 (2006) 103509 | 10.1103/PhysRevD.73.103509 | null | gr-qc | null | In this paper we apply second-order gauge-invariant perturbation theory to
investigate the possibility that the non-linear coupling between gravitational
waves (GW) and a large scale inhomogeneous magnetic field acts as an
amplification mechanism in an `almost' Friedmann-Lemaitre-Robertson-Walker
(FLRW) Universe. The spatial inhomogeneities in the magnetic field are
consistently implemented using the magnetohydrodynamic (MHD) approximation,
which yields an additional source term due to the interaction of the magnetic
field with velocity perturbations in the plasma. Comparing the solutions with
the corresponding results in our previous work indicates that, on super-horizon
scales, the interaction with the spatially inhomogeneous field in the dust
regime induces the same boost as the case of a homogeneous field, at least in
the ideal MHD approximation. This is attributed to the observation that the MHD
induced part of the generated field effectively only contributes on scales
where the coherence length of the initial field is less than the Hubble scale.
At sub-horizon scales, the GW induced magnetic field is completely negligible
in relation to the MHD induced field. Moreover, there is no amplification found
in the long-wavelength limit.
| [
{
"created": "Thu, 9 Feb 2006 22:27:19 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Zunckel",
"Caroline",
""
],
[
"Betschart",
"Gerold",
""
],
[
"Dunsby",
"Peter K S",
""
],
[
"Marklund",
"Mattias",
""
]
] | In this paper we apply second-order gauge-invariant perturbation theory to investigate the possibility that the non-linear coupling between gravitational waves (GW) and a large scale inhomogeneous magnetic field acts as an amplification mechanism in an `almost' Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe. The spatial inhomogeneities in the magnetic field are consistently implemented using the magnetohydrodynamic (MHD) approximation, which yields an additional source term due to the interaction of the magnetic field with velocity perturbations in the plasma. Comparing the solutions with the corresponding results in our previous work indicates that, on super-horizon scales, the interaction with the spatially inhomogeneous field in the dust regime induces the same boost as the case of a homogeneous field, at least in the ideal MHD approximation. This is attributed to the observation that the MHD induced part of the generated field effectively only contributes on scales where the coherence length of the initial field is less than the Hubble scale. At sub-horizon scales, the GW induced magnetic field is completely negligible in relation to the MHD induced field. Moreover, there is no amplification found in the long-wavelength limit. |
gr-qc/9910032 | Charles W. Misner | Keith Watt and Charles W. Misner (University of Maryland) | Relativistic Scalar Gravity: A Laboratory for Numerical Relativity | 7 pages including 2 postscript figures; uses revtex.sty | null | null | UMD PP-00-029 | gr-qc | null | We present here a relativistic theory of gravity in which the spacetime
metric is derived from a single scalar field $\Phi$. The field equation,
derived from a simple variational principle, is a non-linear flat-space
four-dimensional wave equation which is particularly suited for numerical
evolution. We demonstrate that while this theory does not generate results
which are exactly identical quantitatively to those of general relativity (GR),
many of the qualitative features of the full GR theory are reproduced to a
reasonable approximation. The advantage of this formulation lies in the fact
that 3D numerical grids can be numerically evolved in minutes or hours instead
of the days and weeks required by GR, thus drastically reducing the development
time of new relativistic hydrodynamical codes. Scalar gravity therefore serves
as a meaningful testbed for the development of larger routines destined for use
under the full theory of general relativity.
| [
{
"created": "Sun, 10 Oct 1999 02:08:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Watt",
"Keith",
"",
"University of Maryland"
],
[
"Misner",
"Charles W.",
"",
"University of Maryland"
]
] | We present here a relativistic theory of gravity in which the spacetime metric is derived from a single scalar field $\Phi$. The field equation, derived from a simple variational principle, is a non-linear flat-space four-dimensional wave equation which is particularly suited for numerical evolution. We demonstrate that while this theory does not generate results which are exactly identical quantitatively to those of general relativity (GR), many of the qualitative features of the full GR theory are reproduced to a reasonable approximation. The advantage of this formulation lies in the fact that 3D numerical grids can be numerically evolved in minutes or hours instead of the days and weeks required by GR, thus drastically reducing the development time of new relativistic hydrodynamical codes. Scalar gravity therefore serves as a meaningful testbed for the development of larger routines destined for use under the full theory of general relativity. |
2005.08507 | Jean-Marc Hur\'e | J.-M. Hur\'e, B. Basillais, V. Karas, A. Trova and O. Semer\'ak | The exterior gravitational potential of toroids | 15 pages, 12 figures, accepted for publication in MNRAS | null | 10.1093/mnras/staa980 | null | gr-qc astro-ph.IM physics.plasm-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a bivariate Taylor expansion of the axisymmetric Green function in
order to determine the exterior potential of a static thin toroidal shell
having a circular section, as given by the Laplace equation. This expansion,
performed at the centre of the section, consists in an infinite series in the
powers of the minor-to-major radius ratio $e$ of the shell. It is appropriate
for a solid, homogeneous torus, as well as for inhomogeneous bodies (the case
of a core stratification is considered). We show that the leading term is
identical to the potential of a loop having the same main radius and the same
mass | this "similarity" is shown to hold in the ${\cal O}(e^2)$ order. The
series converges very well, especially close to the surface of the toroid where
the average relative precision is $\sim 10^{-3}$ for $e\! = \!0.1$ at order
zero, and as low as a few $10^{-6}$ at second order. The Laplace equation is
satisfied {\em exactly} in every order, so no extra density is induced by
truncation. The gravitational acceleration, important in dynamical studies, is
reproduced with the same accuracy. The technique also applies to the magnetic
potential and field generated by azimuthal currents as met in terrestrial and
astrophysical plasmas.
| [
{
"created": "Mon, 18 May 2020 07:49:07 GMT",
"version": "v1"
}
] | 2020-05-27 | [
[
"Huré",
"J. -M.",
""
],
[
"Basillais",
"B.",
""
],
[
"Karas",
"V.",
""
],
[
"Trova",
"A.",
""
],
[
"Semerák",
"O.",
""
]
] | We perform a bivariate Taylor expansion of the axisymmetric Green function in order to determine the exterior potential of a static thin toroidal shell having a circular section, as given by the Laplace equation. This expansion, performed at the centre of the section, consists in an infinite series in the powers of the minor-to-major radius ratio $e$ of the shell. It is appropriate for a solid, homogeneous torus, as well as for inhomogeneous bodies (the case of a core stratification is considered). We show that the leading term is identical to the potential of a loop having the same main radius and the same mass | this "similarity" is shown to hold in the ${\cal O}(e^2)$ order. The series converges very well, especially close to the surface of the toroid where the average relative precision is $\sim 10^{-3}$ for $e\! = \!0.1$ at order zero, and as low as a few $10^{-6}$ at second order. The Laplace equation is satisfied {\em exactly} in every order, so no extra density is induced by truncation. The gravitational acceleration, important in dynamical studies, is reproduced with the same accuracy. The technique also applies to the magnetic potential and field generated by azimuthal currents as met in terrestrial and astrophysical plasmas. |
2105.09676 | Shuichi Yokoyama | Shuichi Yokoyama | An analytic model for gravitational collapse of spherical matter under
mixed pressure | 17 pages, 5 figures, v2: The continuity condition imposed at
interface, the equation of state imposed near interface, more explanations
and discussions, other minor modifications, v3: 21 pages, 9 figures,
discussion of energy conditions, figures improved, published version | null | null | YITP-21-35 | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate spherically symmetric gravitational collapse of thick matter
shell without radiation in the Einstein gravity with cosmological constant. The
orbit of the infalling thick matter is determined by imposing an equation of
state for the matter near interface, where pressure constituted of the
transverse component and the longitudinal one is proportional to energy
density. We present analytic solutions for the equation of state and discuss
parameter region to satisfy physical conditions such as the absence of the
shell crossing singularity, the monotonic increase of the emergent infinite
redshift surface and energy conditions. We finally show that adopting the
definition presented in arXiv:2005.13233 the total energy in this
time-dependent system is invariant under the given time evolution.
| [
{
"created": "Thu, 20 May 2021 11:30:23 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Nov 2021 11:15:54 GMT",
"version": "v2"
},
{
"created": "Mon, 9 Jan 2023 13:51:51 GMT",
"version": "v3"
}
] | 2023-01-10 | [
[
"Yokoyama",
"Shuichi",
""
]
] | We investigate spherically symmetric gravitational collapse of thick matter shell without radiation in the Einstein gravity with cosmological constant. The orbit of the infalling thick matter is determined by imposing an equation of state for the matter near interface, where pressure constituted of the transverse component and the longitudinal one is proportional to energy density. We present analytic solutions for the equation of state and discuss parameter region to satisfy physical conditions such as the absence of the shell crossing singularity, the monotonic increase of the emergent infinite redshift surface and energy conditions. We finally show that adopting the definition presented in arXiv:2005.13233 the total energy in this time-dependent system is invariant under the given time evolution. |
gr-qc/9809045 | Fredrik Andersson | F. Andersson and S. B. Edgar | Spinors, Spin Coefficients and Lanczos Potentials | 10 pages, LaTeX-file | null | null | null | gr-qc | null | It has been demonstrated, in a number of special situations, that the spin
coefficients of a canonical spinor dyad can be used to define a Lanczos
potential of the Weyl curvature spinor. In this paper we explore some of these
potentials and show that they can be defined directly from the spinor dyad in a
very simple way, but that the results do not generalize significantly, in any
direct manner. A link to metric, asymmetric, curvature-free connections, which
suggests a more natural relationship between the Lanczos potential and spin
coefficients, is also considered.
| [
{
"created": "Tue, 15 Sep 1998 14:18:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Andersson",
"F.",
""
],
[
"Edgar",
"S. B.",
""
]
] | It has been demonstrated, in a number of special situations, that the spin coefficients of a canonical spinor dyad can be used to define a Lanczos potential of the Weyl curvature spinor. In this paper we explore some of these potentials and show that they can be defined directly from the spinor dyad in a very simple way, but that the results do not generalize significantly, in any direct manner. A link to metric, asymmetric, curvature-free connections, which suggests a more natural relationship between the Lanczos potential and spin coefficients, is also considered. |
2401.04170 | Leonhard Kehrberger | Leonhard Kehrberger | The Case Against Smooth Null Infinity IV: Linearised Gravity Around
Schwarzschild -- An Overview | 28 pages + references, 6 Figures. Comments and questions welcome! v2:
Fixed an incorrect cross-reference | Philosophical Transactions of the Royal Society A, 2024 | 10.1098/rsta.2023.0039 | null | gr-qc math-ph math.AP math.MP | http://creativecommons.org/licenses/by-sa/4.0/ | This paper is the fourth in a series dedicated to the mathematically rigorous
asymptotic analysis of gravitational radiation under astrophysically realistic
setups. It provides an overview of the physical ideas involved in setting up
the mathematical problem, the mathematical challenges that need to be overcome
once the problem is posed, as well as the main new results we obtain in the
companion paper [KM24].
From the physical perspective, this includes a discussion of how
Post-Newtonian theory provides a prediction on the gravitational radiation
emitted by $N$ infalling masses from the infinite past in the intermediate
zone, i.e. up to some finite advanced time.
From the mathematical perspective, we then take this prediction, together
with the condition that there be no incoming radiation from $\mathcal{I}^-$, as
a starting point to set up a scattering problem for the linearised Einstein
vacuum equations around Schwarzschild and near spacelike infinity, and we
outline how to solve this scattering problem and obtain the asymptotic
properties of the scattering solution near $i^0$ and $\mathcal{I}^+$.
The full mathematical details are presented in the companion paper [KM24].
| [
{
"created": "Mon, 8 Jan 2024 19:00:03 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Apr 2024 16:13:20 GMT",
"version": "v2"
}
] | 2024-04-30 | [
[
"Kehrberger",
"Leonhard",
""
]
] | This paper is the fourth in a series dedicated to the mathematically rigorous asymptotic analysis of gravitational radiation under astrophysically realistic setups. It provides an overview of the physical ideas involved in setting up the mathematical problem, the mathematical challenges that need to be overcome once the problem is posed, as well as the main new results we obtain in the companion paper [KM24]. From the physical perspective, this includes a discussion of how Post-Newtonian theory provides a prediction on the gravitational radiation emitted by $N$ infalling masses from the infinite past in the intermediate zone, i.e. up to some finite advanced time. From the mathematical perspective, we then take this prediction, together with the condition that there be no incoming radiation from $\mathcal{I}^-$, as a starting point to set up a scattering problem for the linearised Einstein vacuum equations around Schwarzschild and near spacelike infinity, and we outline how to solve this scattering problem and obtain the asymptotic properties of the scattering solution near $i^0$ and $\mathcal{I}^+$. The full mathematical details are presented in the companion paper [KM24]. |
1111.3438 | Arkady A. Popov | Arkady A. Popov | Renormalization for self-potential of a scalar charge in static
space-times | 7 pages | Physical Review D 84, 064009 (2011) | 10.1103/PhysRevD.84.064009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A method is presented which allows for the renormalization of the
self-potential for a scalar point charge at rest in static curved space-time.
The method is suitable for the scalar field with arbitrary mass $m$ and
coupling to the scalar curvature. The asymptotic behavior of self-potential is
obtained in the limit in which the Compton wave-length $1/m$ of the massive
scalar field is much smaller than the characteristic scale of curvature of the
background gravitational field. The self-force is calculated in this limit.
| [
{
"created": "Tue, 15 Nov 2011 06:52:19 GMT",
"version": "v1"
}
] | 2011-11-16 | [
[
"Popov",
"Arkady A.",
""
]
] | A method is presented which allows for the renormalization of the self-potential for a scalar point charge at rest in static curved space-time. The method is suitable for the scalar field with arbitrary mass $m$ and coupling to the scalar curvature. The asymptotic behavior of self-potential is obtained in the limit in which the Compton wave-length $1/m$ of the massive scalar field is much smaller than the characteristic scale of curvature of the background gravitational field. The self-force is calculated in this limit. |
gr-qc/0505002 | Ghanashyam Date | Ghanashyam Date | Absence of the Kasner singularity in the effective dynamics from loop
quantum cosmology | 4 pages, revtex4, no figures | Phys.Rev. D71 (2005) 127502 | 10.1103/PhysRevD.71.127502 | IMSc/2005/4/11 | gr-qc astro-ph hep-th | null | In classical general relativity, the generic approach to the initial
singularity is usually understood in terms of the BKL scenario. In this
scenario, along with the Bianchi IX model, the exact, singular, Kasner solution
of vacuum Bianchi I model also plays a pivotal role. Using an effective
classical Hamiltonian obtained from loop quantization of vacuum Bianchi I
model, exact solution is obtained which is non-singular due to a discreteness
parameter. The solution is parameterized in exactly the same manner as the
usual Kasner solution and reduces to the Kasner solution as discreteness
parameter is taken to zero. At the effective Hamiltonian level, the avoidance
of Kasner singularity uses a mechanism distinct from the `inverse volume'
modifications characteristic of loop quantum cosmology.
| [
{
"created": "Sat, 30 Apr 2005 12:37:04 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Date",
"Ghanashyam",
""
]
] | In classical general relativity, the generic approach to the initial singularity is usually understood in terms of the BKL scenario. In this scenario, along with the Bianchi IX model, the exact, singular, Kasner solution of vacuum Bianchi I model also plays a pivotal role. Using an effective classical Hamiltonian obtained from loop quantization of vacuum Bianchi I model, exact solution is obtained which is non-singular due to a discreteness parameter. The solution is parameterized in exactly the same manner as the usual Kasner solution and reduces to the Kasner solution as discreteness parameter is taken to zero. At the effective Hamiltonian level, the avoidance of Kasner singularity uses a mechanism distinct from the `inverse volume' modifications characteristic of loop quantum cosmology. |
2107.14520 | Seramika Ariwahjoedi | Seramika Ariwahjoedi, Agus Suroso, F. P. Zen | (3+1)-Formulation for Gravity with Torsion and Non-Metricity II: The
Hypermomentum Equation | 28 pages | Class. Quantum Grav. 38 225006 2021 | 10.1088/1361-6382/ac2c1c | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we consider a special case of Metric-Affine f(R)-gravity for
f(R) = R, i.e. the Metric-Affine General Relativity (MAGR). As a companion to
the first article in the series, we perform the (3+1) decomposition to the
hypermomentum equation, obtained from the minimization of the MAGR action S [g,
{\omega}] with respect to the connection {\omega}. Moreover, we show that the
hypermomentum tensor H could be constructed completely from 10 hypersurfaces
variables that arise from its dilation, shear, and rotational (spin) parts. The
(3+1) hypermomentum equations consists of 1 scalar, 3 vector, 3 matrix, and 1
tensor equation of order-(2,1). Together with the (3+1) decomposition of the
traceless torsion constraint, consisting of 1 scalar and 1 vector equation, we
obtain 10 hypersurface equations, which are the main result in this article.
Finally, we consider some special cases of MAGR, namely, the zero
hypermomentum, metric, and torsionless cases. For vanishing hypermomentum, we
could retrieve the metric compatibility and torsionless condition in the (3+1)
framework, hence forcing the affine connection to be Levi-Civita as in the
standard General Relativity.
| [
{
"created": "Fri, 30 Jul 2021 10:04:29 GMT",
"version": "v1"
}
] | 2021-10-29 | [
[
"Ariwahjoedi",
"Seramika",
""
],
[
"Suroso",
"Agus",
""
],
[
"Zen",
"F. P.",
""
]
] | In this article, we consider a special case of Metric-Affine f(R)-gravity for f(R) = R, i.e. the Metric-Affine General Relativity (MAGR). As a companion to the first article in the series, we perform the (3+1) decomposition to the hypermomentum equation, obtained from the minimization of the MAGR action S [g, {\omega}] with respect to the connection {\omega}. Moreover, we show that the hypermomentum tensor H could be constructed completely from 10 hypersurfaces variables that arise from its dilation, shear, and rotational (spin) parts. The (3+1) hypermomentum equations consists of 1 scalar, 3 vector, 3 matrix, and 1 tensor equation of order-(2,1). Together with the (3+1) decomposition of the traceless torsion constraint, consisting of 1 scalar and 1 vector equation, we obtain 10 hypersurface equations, which are the main result in this article. Finally, we consider some special cases of MAGR, namely, the zero hypermomentum, metric, and torsionless cases. For vanishing hypermomentum, we could retrieve the metric compatibility and torsionless condition in the (3+1) framework, hence forcing the affine connection to be Levi-Civita as in the standard General Relativity. |
gr-qc/9601019 | Doug Eardley | Douglas M. Eardley and Eric W. Hirschmann | Comment on "Instabilities in Close Neutron Star Binaries" | 3 pages LaTeX (revtex, epsf) and 1 figure; figure also available at
ftp://ftp.itp.ucsb.edu/figures/nsf-itp-95-165.eps | null | null | NSF-ITP-95-165 | gr-qc | null | In a recent Physical Review Letter, Wilson and Mathews presented some
interesting numerical calculations of a system of two equally massive neutron
stars in strong-field gravity. In particular they estimated the innermost
stable circular orbit in their system. Here we point out a possibly important
consequence of their results: Their calculated configurations have total
angular momentum $J$ and total mass $M$ too large to form any Kerr black hole:
$J>M^2$, in constrast to previous calculations of the innermost stable circular
orbit.
| [
{
"created": "Thu, 11 Jan 1996 17:27:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Eardley",
"Douglas M.",
""
],
[
"Hirschmann",
"Eric W.",
""
]
] | In a recent Physical Review Letter, Wilson and Mathews presented some interesting numerical calculations of a system of two equally massive neutron stars in strong-field gravity. In particular they estimated the innermost stable circular orbit in their system. Here we point out a possibly important consequence of their results: Their calculated configurations have total angular momentum $J$ and total mass $M$ too large to form any Kerr black hole: $J>M^2$, in constrast to previous calculations of the innermost stable circular orbit. |
2111.12329 | Alexander Simpson | Alex Simpson and Matt Visser | The eye of the storm: A regular Kerr black hole | V1: 27 pages, 71 references. V2: Now 28 pages, 83 references; some
discourse added with relevant citations, small physics changes with inclusion
of Maxwell separability | null | 10.1088/1475-7516/2022/03/011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a highly tractable non-singular modification of the Kerr geometry,
dubbed the "eye of the storm" -- a rotating regular black hole with an
asymptotically Minkowski core. This is achieved by "exponentially suppressing"
the mass parameter in the Kerr spacetime: $m\to m \; e^{-\ell/r}$. The single
parameter $\ell$ quantifies the deviation from the usual Kerr spacetime. Some
of the classical energy conditions are globally satisfied, whilst certain
choices for $\ell$ force any energy-condition-violating physics into the deep
core. The geometry possesses the full "Killing tower'" of principal tensor,
Killing--Yano tensor, and nontrivial Killing tensor, with associated Carter
constant; hence the Hamilton--Jacobi equations are separable, and the geodesics
integrable. The Klein--Gordon equation is also separable on this candidate
spacetime. The tightly controlled deviation from Kerr renders the physics
extraordinarily tractable when compared with analogous results in the current
literature. This spacetime will be amenable to straightforward extraction of
astrophysical observables falsifiable/ verifiable by the experimental
community.
| [
{
"created": "Wed, 24 Nov 2021 08:23:10 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Dec 2021 22:10:21 GMT",
"version": "v2"
}
] | 2022-03-14 | [
[
"Simpson",
"Alex",
""
],
[
"Visser",
"Matt",
""
]
] | We present a highly tractable non-singular modification of the Kerr geometry, dubbed the "eye of the storm" -- a rotating regular black hole with an asymptotically Minkowski core. This is achieved by "exponentially suppressing" the mass parameter in the Kerr spacetime: $m\to m \; e^{-\ell/r}$. The single parameter $\ell$ quantifies the deviation from the usual Kerr spacetime. Some of the classical energy conditions are globally satisfied, whilst certain choices for $\ell$ force any energy-condition-violating physics into the deep core. The geometry possesses the full "Killing tower'" of principal tensor, Killing--Yano tensor, and nontrivial Killing tensor, with associated Carter constant; hence the Hamilton--Jacobi equations are separable, and the geodesics integrable. The Klein--Gordon equation is also separable on this candidate spacetime. The tightly controlled deviation from Kerr renders the physics extraordinarily tractable when compared with analogous results in the current literature. This spacetime will be amenable to straightforward extraction of astrophysical observables falsifiable/ verifiable by the experimental community. |
2003.10169 | Hari K | Hari K and Dawood Kothawala | Normal coordinates based on curved tangent space | 13 pages, 4 figures, comments added and typos fixed, matches version
accepted in Phys. Rev. D | Phys. Rev. D 101, 124066 (2020) | 10.1103/PhysRevD.101.124066 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Riemann normal coordinates (RNC) at a regular event $p_0$ of a spacetime
manifold $\mathcal{M}$ are constructed by imposing: (i)
$g_{\textsf{ab}}|_{p_0}=\eta_{ab}$, and (ii)
$\Gamma^\textsf{a}_{\phantom{\textsf a}\textsf{bc}}|_{p_0}=0$. There is,
however, a third, $independent$, assumption in the definition of RNC which
essentially fixes the $density$ $of$ $geodesics$ emanating from $p_0$ to its
value in flat spacetime, viz.: (iii) the tangent space
$\mathcal{T}_{p_0}(\mathcal{M})$ is $flat$. We relax (iii) and obtain the
normal coordinates, along with the metric $g_{\textsf{ab}}$, when
$\mathcal{T}_{p_0}(\mathcal{M})$ is a maximally symmetric manifold
$\widetilde{\mathcal M}_{\Lambda}$ with curvature length $|\Lambda|^{-1/2}$. In
general, the "rest" frame defined by these coordinates is non-inertial with an
additional acceleration $\boldsymbol a = - ({\Lambda}/3) \, \boldsymbol x$
depending on the curvature of tangent space. Our geometric set-up provides a
convenient probe of local physics in a universe with a cosmological constant
$\Lambda$, now embedded into the local structure of spacetime as a fundamental
constant associated with a curved tangent space. We discuss classical and
quantum implications of the same.
| [
{
"created": "Mon, 23 Mar 2020 10:36:12 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jun 2020 06:40:02 GMT",
"version": "v2"
}
] | 2020-06-30 | [
[
"K",
"Hari",
""
],
[
"Kothawala",
"Dawood",
""
]
] | Riemann normal coordinates (RNC) at a regular event $p_0$ of a spacetime manifold $\mathcal{M}$ are constructed by imposing: (i) $g_{\textsf{ab}}|_{p_0}=\eta_{ab}$, and (ii) $\Gamma^\textsf{a}_{\phantom{\textsf a}\textsf{bc}}|_{p_0}=0$. There is, however, a third, $independent$, assumption in the definition of RNC which essentially fixes the $density$ $of$ $geodesics$ emanating from $p_0$ to its value in flat spacetime, viz.: (iii) the tangent space $\mathcal{T}_{p_0}(\mathcal{M})$ is $flat$. We relax (iii) and obtain the normal coordinates, along with the metric $g_{\textsf{ab}}$, when $\mathcal{T}_{p_0}(\mathcal{M})$ is a maximally symmetric manifold $\widetilde{\mathcal M}_{\Lambda}$ with curvature length $|\Lambda|^{-1/2}$. In general, the "rest" frame defined by these coordinates is non-inertial with an additional acceleration $\boldsymbol a = - ({\Lambda}/3) \, \boldsymbol x$ depending on the curvature of tangent space. Our geometric set-up provides a convenient probe of local physics in a universe with a cosmological constant $\Lambda$, now embedded into the local structure of spacetime as a fundamental constant associated with a curved tangent space. We discuss classical and quantum implications of the same. |
1906.09796 | Avijit Chowdhury | Avijit Chowdhury and Narayan Banerjee | Superradiant stability of Mutated Reissner-Nordstr\"{o}m black holes | 8 pages; 1 figure; Published Version in GERG | Gen. Relativ. Gravit. 51, 99 (2019) | 10.1007/s10714-019-2580-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A scalar hair is used to generate a mutated black hole, which mimics an
Einstein-Rosen bridge or a wormhole. The superradiant stability of the
spacetime is studied under perturbation by an electrically charged massive
scalar field. The system appears to be stable against superradiance
irrespective of the mass of the test field.
| [
{
"created": "Mon, 24 Jun 2019 09:09:33 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Oct 2019 14:04:44 GMT",
"version": "v2"
}
] | 2019-11-01 | [
[
"Chowdhury",
"Avijit",
""
],
[
"Banerjee",
"Narayan",
""
]
] | A scalar hair is used to generate a mutated black hole, which mimics an Einstein-Rosen bridge or a wormhole. The superradiant stability of the spacetime is studied under perturbation by an electrically charged massive scalar field. The system appears to be stable against superradiance irrespective of the mass of the test field. |
1901.01790 | Nick Kwidzinski | Nick Kwidzinski, W{\l}odzimierz Piechocki | Curvature invariants for the Bianchi IX spacetime filled with tilted
dust | 16 pages, 6 figures, Revision: minor editing and references added,
accepted for publication in Euro. Phys. J. C | Eur. Phys. J. C (2019) 79:199 | 10.1140/epjc/s10052-019-6701-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an analysis of the Kretschmann and Weyl squared scalars for the
general Bianchi IX model filled with tilted dust. Particular attention is given
to the asymptotic regime close to the singularity for which we provide
heuristic considerations supported by numerical simulations. The present paper
is an extension of our earlier publication [1].
| [
{
"created": "Mon, 7 Jan 2019 13:15:58 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Feb 2019 13:22:18 GMT",
"version": "v2"
}
] | 2019-08-23 | [
[
"Kwidzinski",
"Nick",
""
],
[
"Piechocki",
"Włodzimierz",
""
]
] | We present an analysis of the Kretschmann and Weyl squared scalars for the general Bianchi IX model filled with tilted dust. Particular attention is given to the asymptotic regime close to the singularity for which we provide heuristic considerations supported by numerical simulations. The present paper is an extension of our earlier publication [1]. |
0807.3281 | Simone Zonetti | Francesco Cianfrani (1), Giovanni Montani (1, 2 and 3), Simone Zonetti
(4) ((1) Dipartimento di Fisica, Universita degli Studi di Roma "La Sapienza"
(2) ENEA C.R. Frascati (Dipartimento F.P.N.), (3) ICRANet C.C. Pescara, (4)
Center for Particle Physics and Phenomenology (CP3), Universit\`e Catholique
de Louvain) | Definition of a time variable with Entropy of a perfect fluid in
Canonical Quantum Gravity | 13 pages, no figures. To be published in Classical and Quantum
Gravity. v2: major changes | Class.Quant.Grav.26:125002,2009 | 10.1088/0264-9381/26/12/125002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Brown-Kuchar mechanism is applied in the case of General Relativity
coupled with the Schutz model for a perfect fluid. Using the canonical
formalism and manipulating the set of modified constraints one is able to
recover the definition of a time evolution operator, i.e. a physical
Hamiltonian, expressed as a functional of gravitational variables and the
entropy.
| [
{
"created": "Mon, 21 Jul 2008 14:49:49 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Apr 2009 17:04:23 GMT",
"version": "v2"
}
] | 2009-07-30 | [
[
"Cianfrani",
"Francesco",
"",
"1, 2 and 3"
],
[
"Montani",
"Giovanni",
"",
"1, 2 and 3"
],
[
"Zonetti",
"Simone",
""
]
] | The Brown-Kuchar mechanism is applied in the case of General Relativity coupled with the Schutz model for a perfect fluid. Using the canonical formalism and manipulating the set of modified constraints one is able to recover the definition of a time evolution operator, i.e. a physical Hamiltonian, expressed as a functional of gravitational variables and the entropy. |
1612.07756 | Yen Chin Ong | Yen Chin Ong, Dong-han Yeom | Instanton Tunneling for De Sitter Space with Real Projective Spatial
Sections | 10 pages, 11 figures, slightly elaborated version accepted by JCAP | JCAP 04 (2017) 040 | 10.1088/1475-7516/2017/04/040 | NORDITA-2016-138 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The physics of tunneling from one spacetime into another is often understood
in terms of instantons. For some instantons, it was recently shown in the
literature that there are two complementary "interpretations" for their
analytic continuations. Dubbed "something-to-something" and
"nothing-to-something" interpretations, respectively, the former involves
situation in which the initial and final hypersurfaces are connected by a
Euclidean manifold, whereas the initial and final hypersurfaces in the latter
case are not connected in such a way. We consider a de Sitter space with real
projective space $\mathbb{R}\text{P}^3$ spatial sections, as was originally
understood by de Sitter himself. This original version of de Sitter space has
several advantages over the usual de Sitter space with $\text{S}^3$ spatial
sections. In particular, the interpretation of the de Sitter entropy as
entanglement entropy is much more natural. We discuss the subtleties involved
in the tunneling of such a de Sitter space.
| [
{
"created": "Thu, 22 Dec 2016 19:17:13 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Apr 2017 15:34:14 GMT",
"version": "v2"
}
] | 2017-04-27 | [
[
"Ong",
"Yen Chin",
""
],
[
"Yeom",
"Dong-han",
""
]
] | The physics of tunneling from one spacetime into another is often understood in terms of instantons. For some instantons, it was recently shown in the literature that there are two complementary "interpretations" for their analytic continuations. Dubbed "something-to-something" and "nothing-to-something" interpretations, respectively, the former involves situation in which the initial and final hypersurfaces are connected by a Euclidean manifold, whereas the initial and final hypersurfaces in the latter case are not connected in such a way. We consider a de Sitter space with real projective space $\mathbb{R}\text{P}^3$ spatial sections, as was originally understood by de Sitter himself. This original version of de Sitter space has several advantages over the usual de Sitter space with $\text{S}^3$ spatial sections. In particular, the interpretation of the de Sitter entropy as entanglement entropy is much more natural. We discuss the subtleties involved in the tunneling of such a de Sitter space. |
1706.04444 | Sergey Gubanov | Sergey Gubanov | The spherically symmetric gravitational field | 18 pages, no figures | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-th physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The general solution of the system of General Relativity equations has been
found for isotropic Universe with the flat spatial distribution and
synchronized time taking into account a perfect dust and the cosmological
constant. Schwarzschild, Friedmann and Einstein-de Sitter solutions (as well as
all of their fusion with each other) are special cases of the found general
solution. A method of generating an infinite number of Tolman's like solutions
has been found. Exact solutions has been found for the spherically symmetric
gravitational field of perfect dust clouds in the expanding Universe filled
with radiation. A system of ordinary differential equations has been obtained
for the spherically symmetric gravitational field of perfect dust clouds in the
expanding Universe filled with radiation and nonrelativistic gas. A system of
equations has been obtained for the spherically symmetric gravitational field
of ultrarelativistic celestial body explosion (supernova, quasar). The problem
of a negative density of a perfect dust cloud in General Relativity has been
considered.
| [
{
"created": "Wed, 14 Jun 2017 12:33:37 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Jun 2017 20:11:16 GMT",
"version": "v2"
}
] | 2017-06-20 | [
[
"Gubanov",
"Sergey",
""
]
] | The general solution of the system of General Relativity equations has been found for isotropic Universe with the flat spatial distribution and synchronized time taking into account a perfect dust and the cosmological constant. Schwarzschild, Friedmann and Einstein-de Sitter solutions (as well as all of their fusion with each other) are special cases of the found general solution. A method of generating an infinite number of Tolman's like solutions has been found. Exact solutions has been found for the spherically symmetric gravitational field of perfect dust clouds in the expanding Universe filled with radiation. A system of ordinary differential equations has been obtained for the spherically symmetric gravitational field of perfect dust clouds in the expanding Universe filled with radiation and nonrelativistic gas. A system of equations has been obtained for the spherically symmetric gravitational field of ultrarelativistic celestial body explosion (supernova, quasar). The problem of a negative density of a perfect dust cloud in General Relativity has been considered. |
gr-qc/9703063 | Sung S.-T. | S.-T. Sung | Notes on the Generalised Second Law of Thermodynamics | 10 pages, Latex | null | null | null | gr-qc | null | Several comments are given to previous proofs of the generalised second law
of thermodynamics: black hole entropy plus ordinary matter entropy never
decreases for a thermally closed system. Arguments in favour of its truism are
given in the spirit of conventional thermodynamics.
| [
{
"created": "Sat, 22 Mar 1997 22:56:25 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sung",
"S. -T.",
""
]
] | Several comments are given to previous proofs of the generalised second law of thermodynamics: black hole entropy plus ordinary matter entropy never decreases for a thermally closed system. Arguments in favour of its truism are given in the spirit of conventional thermodynamics. |
gr-qc/0301113 | Alejandro Perez | Alejandro Perez | Spin Foam Models for Quantum Gravity | Topical review, to appear in CQG. Typos corrected and new references
added | Class.Quant.Grav. 20 (2003) R43 | 10.1088/0264-9381/20/6/202 | null | gr-qc hep-th | null | In this article we review the present status of the spin foam formulation of
non-perturbative (background independent) quantum gravity. The article is
divided in two parts. In the first part we present a general introduction to
the main ideas emphasizing their motivations from various perspectives.
Riemannian 3-dimensional gravity is used as a simple example to illustrate
conceptual issues and the main goals of the approach. The main features of the
various existing models for 4-dimensional gravity are also presented here. We
conclude with a discussion of important questions to be addressed in four
dimensions (gauge invariance, discretization independence, etc.).
In the second part we concentrate on the definition of the Barrett-Crane
model. We present the main results obtained in this framework from a critical
perspective. Finally we review the combinatorial formulation of spin foam
models based on the dual group field theory technology. We present the
Barrett-Crane model in this framework and review the finiteness results
obtained for both its Riemannian as well as its Lorentzian variants.
| [
{
"created": "Mon, 27 Jan 2003 22:59:37 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Feb 2003 23:25:44 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Perez",
"Alejandro",
""
]
] | In this article we review the present status of the spin foam formulation of non-perturbative (background independent) quantum gravity. The article is divided in two parts. In the first part we present a general introduction to the main ideas emphasizing their motivations from various perspectives. Riemannian 3-dimensional gravity is used as a simple example to illustrate conceptual issues and the main goals of the approach. The main features of the various existing models for 4-dimensional gravity are also presented here. We conclude with a discussion of important questions to be addressed in four dimensions (gauge invariance, discretization independence, etc.). In the second part we concentrate on the definition of the Barrett-Crane model. We present the main results obtained in this framework from a critical perspective. Finally we review the combinatorial formulation of spin foam models based on the dual group field theory technology. We present the Barrett-Crane model in this framework and review the finiteness results obtained for both its Riemannian as well as its Lorentzian variants. |
1502.07518 | Francisco Jose Herranz | Angel Ballesteros, Francisco J. Herranz and Pedro Naranjo | Towards (3+1) gravity through Drinfel'd doubles with cosmological
constant | 12 pages. References and comments added. One misprint corrected | Phys. Lett. B 746 (2015) 37-43 | 10.1016/j.physletb.2015.04.041 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the generalisation to (3+1) dimensions of a quantum deformation of
the (2+1) (Anti)-de Sitter and Poincar\'e Lie algebras that is compatible with
the conditions imposed by the Chern-Simons formulation of (2+1) gravity. Since
such compatibility is automatically fulfilled by deformations coming from
Drinfel'd double structures, we believe said structures are worth being
analysed also in the (3+1) scenario as a possible guiding principle towards the
description of (3+1) gravity. To this aim, a canonical classical $r$-matrix
arising from a Drinfel'd double structure for the three (3+1) Lorentzian
algebras is obtained. This $r$-matrix turns out to be a twisted version of the
one corresponding to the (3+1) $\kappa$-deformation, and the main properties of
its associated noncommutative spacetime are analysed. In particular, it is
shown that this new quantum spacetime is not isomorphic to the
$\kappa$-Minkowski one, and that the isotropy of the quantum space coordinates
can be preserved through a suitable change of basis of the quantum algebra
generators. Throughout the paper the cosmological constant appears as an
explicit parameter, thus allowing the (flat) Poincar\'e limit to be
straightforwardly obtained.
| [
{
"created": "Thu, 26 Feb 2015 12:06:02 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Apr 2015 10:24:42 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Apr 2015 19:49:50 GMT",
"version": "v3"
}
] | 2015-05-18 | [
[
"Ballesteros",
"Angel",
""
],
[
"Herranz",
"Francisco J.",
""
],
[
"Naranjo",
"Pedro",
""
]
] | We present the generalisation to (3+1) dimensions of a quantum deformation of the (2+1) (Anti)-de Sitter and Poincar\'e Lie algebras that is compatible with the conditions imposed by the Chern-Simons formulation of (2+1) gravity. Since such compatibility is automatically fulfilled by deformations coming from Drinfel'd double structures, we believe said structures are worth being analysed also in the (3+1) scenario as a possible guiding principle towards the description of (3+1) gravity. To this aim, a canonical classical $r$-matrix arising from a Drinfel'd double structure for the three (3+1) Lorentzian algebras is obtained. This $r$-matrix turns out to be a twisted version of the one corresponding to the (3+1) $\kappa$-deformation, and the main properties of its associated noncommutative spacetime are analysed. In particular, it is shown that this new quantum spacetime is not isomorphic to the $\kappa$-Minkowski one, and that the isotropy of the quantum space coordinates can be preserved through a suitable change of basis of the quantum algebra generators. Throughout the paper the cosmological constant appears as an explicit parameter, thus allowing the (flat) Poincar\'e limit to be straightforwardly obtained. |
1908.07543 | Klaus Liegener Dr | Klaus Liegener, Parampreet Singh | Some physical implications of regularization ambiguities in SU(2)
gauge-invariant loop quantum cosmology | 31 pages, 10 figures. References and a figure added. To appear in PRD | Phys. Rev. D 100, 124049 (2019) | 10.1103/PhysRevD.100.124049 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The way physics of loop quantum gravity is affected by the underlying
quantization ambiguities is an open question. We address this issue in the
context of loop quantum cosmology using gauge-covariant fluxes. Consequences
are explored for two choices of regularization parameters: $\mu_0$ and $\bar
\mu$ in presence of a positive cosmological constant, and two choices of
regularizations of the Hamiltonian constraint in loop quantum cosmology: the
standard and the Thiemann regularization. We show that novel features of
singularity resolution and bounce, occurring due to gauge-covariant fluxes,
exist also for Thiemann-regularized dynamics. The $\mu_0$-scheme is found to be
unviable as in standard loop quantum cosmology when a positive cosmological
constant is included. Our investigation brings out a surprising result that the
nature of emergent matter in the pre-bounce regime is determined by the choice
of regulator in the Thiemann regularization of the scalar constraint whether or
not one uses gauge-covaraint fluxes. Unlike $\bar \mu$-scheme where the
emergent matter is a cosmological constant, the emergent matter in
$\mu_0$-scheme behaves as a string gas.
| [
{
"created": "Tue, 20 Aug 2019 18:01:16 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Nov 2019 22:22:23 GMT",
"version": "v2"
}
] | 2019-12-25 | [
[
"Liegener",
"Klaus",
""
],
[
"Singh",
"Parampreet",
""
]
] | The way physics of loop quantum gravity is affected by the underlying quantization ambiguities is an open question. We address this issue in the context of loop quantum cosmology using gauge-covariant fluxes. Consequences are explored for two choices of regularization parameters: $\mu_0$ and $\bar \mu$ in presence of a positive cosmological constant, and two choices of regularizations of the Hamiltonian constraint in loop quantum cosmology: the standard and the Thiemann regularization. We show that novel features of singularity resolution and bounce, occurring due to gauge-covariant fluxes, exist also for Thiemann-regularized dynamics. The $\mu_0$-scheme is found to be unviable as in standard loop quantum cosmology when a positive cosmological constant is included. Our investigation brings out a surprising result that the nature of emergent matter in the pre-bounce regime is determined by the choice of regulator in the Thiemann regularization of the scalar constraint whether or not one uses gauge-covaraint fluxes. Unlike $\bar \mu$-scheme where the emergent matter is a cosmological constant, the emergent matter in $\mu_0$-scheme behaves as a string gas. |
2103.13972 | Philip D. Mannheim | Philip D. Mannheim and John W. Moffat | External Field Effect in Gravity | 9 pages, 4 figures. Essay written for the Gravity Research Foundation
2021 Awards for Essays on Gravitation | null | 10.1142/S0218271821420098 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In both Newtonian gravity and Einstein gravity there is no force on a test
particle located inside a spherical cavity cut out of a static, spherically
symmetric mass distribution. Inside the cavity exterior matter is decoupled and
there is no external field effect that could act on the test particle. However,
for potentials other than the Newtonian potential or for geometries other than
Ricci flat ones this is no longer the case, and there then is an external field
effect. We explore this possibility in various alternate gravity scenarios, and
suggest that such (Machian) external field effects can serve as a diagnostic
for gravitational theory.
| [
{
"created": "Thu, 25 Mar 2021 17:00:24 GMT",
"version": "v1"
}
] | 2022-01-26 | [
[
"Mannheim",
"Philip D.",
""
],
[
"Moffat",
"John W.",
""
]
] | In both Newtonian gravity and Einstein gravity there is no force on a test particle located inside a spherical cavity cut out of a static, spherically symmetric mass distribution. Inside the cavity exterior matter is decoupled and there is no external field effect that could act on the test particle. However, for potentials other than the Newtonian potential or for geometries other than Ricci flat ones this is no longer the case, and there then is an external field effect. We explore this possibility in various alternate gravity scenarios, and suggest that such (Machian) external field effects can serve as a diagnostic for gravitational theory. |
1903.06005 | Alexander Oliveros | A. Oliveros and Marcos A. Jaraba | Inflation driven by massive vector fields with derivative
self-interactions | 13 pages, 3 figures | Int. J. Mod. Phys. D 28 (2019) 1950064 | 10.1142/S0218271819500640 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by the Generalized Proca Theory, we study a vector-tensor model of
inflation with massive vector fields and derivative self-interactions. The
action under consideration contains a usual Maxwell-like kinetic term, a
general potential term and a term with non-minimal derivative coupling between
the vector field and gravity, via the dual Riemann tensor. In this theory, the
last term contains a free parameter, $\lambda$, which quantifies the
non-minimal derivative coupling. In this scenario, taking into account a
spatially flat FRW universe and a general vector field, we obtain the general
expressions for the equation of motion and the total energy momentum tensor.
Choosing a Proca-type potential, a suitable inflationary regimen driven by
massive vector fields is studied. In this model, the isotropy of expansion is
guaranteed by considering a triplet of orthogonal vector fields. In order to
obtain an inflationary solution with this model, the quasi de Sitter expansion
was considered. In this case the vector field behaves as a constant. Finally,
slow roll analysis is performed and slow-roll conditions are defined for this
model, which, for suitable constraints of the model parameters, can give the
required number of e-folds for sufficient inflation.
| [
{
"created": "Mon, 11 Mar 2019 20:52:59 GMT",
"version": "v1"
}
] | 2019-03-15 | [
[
"Oliveros",
"A.",
""
],
[
"Jaraba",
"Marcos A.",
""
]
] | Inspired by the Generalized Proca Theory, we study a vector-tensor model of inflation with massive vector fields and derivative self-interactions. The action under consideration contains a usual Maxwell-like kinetic term, a general potential term and a term with non-minimal derivative coupling between the vector field and gravity, via the dual Riemann tensor. In this theory, the last term contains a free parameter, $\lambda$, which quantifies the non-minimal derivative coupling. In this scenario, taking into account a spatially flat FRW universe and a general vector field, we obtain the general expressions for the equation of motion and the total energy momentum tensor. Choosing a Proca-type potential, a suitable inflationary regimen driven by massive vector fields is studied. In this model, the isotropy of expansion is guaranteed by considering a triplet of orthogonal vector fields. In order to obtain an inflationary solution with this model, the quasi de Sitter expansion was considered. In this case the vector field behaves as a constant. Finally, slow roll analysis is performed and slow-roll conditions are defined for this model, which, for suitable constraints of the model parameters, can give the required number of e-folds for sufficient inflation. |
gr-qc/0309060 | Albert V. Minkevich | A.V. Minkevich | Comments on astro-ph/0305039 and gr-qc/0309036 | Some changes made | null | null | null | gr-qc | null | The main results of papers gr-qc/0307026 and gr-qc/0312068 are formulated.
These results are opposite to conclusions of paper astro-ph/0305039 and
comments gr-qc/0309036.
| [
{
"created": "Thu, 11 Sep 2003 18:04:09 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Sep 2003 06:46:00 GMT",
"version": "v2"
},
{
"created": "Sun, 14 Sep 2003 17:33:21 GMT",
"version": "v3"
},
{
"created": "Tue, 2 Mar 2004 12:11:27 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Minkevich",
"A. V.",
""
]
] | The main results of papers gr-qc/0307026 and gr-qc/0312068 are formulated. These results are opposite to conclusions of paper astro-ph/0305039 and comments gr-qc/0309036. |
gr-qc/0701065 | Fredy Dubeibe | F. L. Dubeibe, Leonardo A. Pachon and Jose D. Sanabria-Gomez | Chaotic dynamics around astrophysical objects with nonisotropic stresses | 7 pages, 5 figures | Phys.Rev. D75:023008,2007 | 10.1103/PhysRevD.75.023008 | null | gr-qc | null | The existence of chaotic behavior for the geodesics of the test particles
orbiting compact objects is a subject of much current research. Some years ago,
Gu\'eron and Letelier [Phys. Rev. E \textbf{66}, 046611 (2002)] reported the
existence of chaotic behavior for the geodesics of the test particles orbiting
compact objects like black holes induced by specific values of the quadrupolar
deformation of the source using as models the Erez--Rosen solution and the Kerr
black hole deformed by an internal multipole term. In this work, we are
interesting in the study of the dynamic behavior of geodesics around
astrophysical objects with intrinsic quadrupolar deformation or nonisotropic
stresses, which induces nonvanishing quadrupolar deformation for the
nonrotating limit. For our purpose, we use the Tomimatsu-Sato spacetime [Phys.
Rev. Lett. \textbf{29} 1344 (1972)] and its arbitrary deformed generalization
obtained as the particular vacuum case of the five parametric solution of Manko
et al [Phys. Rev. D 62, 044048 (2000)], characterizing the geodesic dynamics
throughout the Poincar\'e sections method. In contrast to the results by
Gu\'eron and Letelier we find chaotic motion for oblate deformations instead of
prolate deformations. It opens the possibility that the particles forming the
accretion disk around a large variety of different astrophysical bodies
(nonprolate, e.g., neutron stars) could exhibit chaotic dynamics. We also
conjecture that the existence of an arbitrary deformation parameter is
necessary for the existence of chaotic dynamics.
| [
{
"created": "Thu, 11 Jan 2007 23:17:56 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Feb 2007 22:59:35 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Dubeibe",
"F. L.",
""
],
[
"Pachon",
"Leonardo A.",
""
],
[
"Sanabria-Gomez",
"Jose D.",
""
]
] | The existence of chaotic behavior for the geodesics of the test particles orbiting compact objects is a subject of much current research. Some years ago, Gu\'eron and Letelier [Phys. Rev. E \textbf{66}, 046611 (2002)] reported the existence of chaotic behavior for the geodesics of the test particles orbiting compact objects like black holes induced by specific values of the quadrupolar deformation of the source using as models the Erez--Rosen solution and the Kerr black hole deformed by an internal multipole term. In this work, we are interesting in the study of the dynamic behavior of geodesics around astrophysical objects with intrinsic quadrupolar deformation or nonisotropic stresses, which induces nonvanishing quadrupolar deformation for the nonrotating limit. For our purpose, we use the Tomimatsu-Sato spacetime [Phys. Rev. Lett. \textbf{29} 1344 (1972)] and its arbitrary deformed generalization obtained as the particular vacuum case of the five parametric solution of Manko et al [Phys. Rev. D 62, 044048 (2000)], characterizing the geodesic dynamics throughout the Poincar\'e sections method. In contrast to the results by Gu\'eron and Letelier we find chaotic motion for oblate deformations instead of prolate deformations. It opens the possibility that the particles forming the accretion disk around a large variety of different astrophysical bodies (nonprolate, e.g., neutron stars) could exhibit chaotic dynamics. We also conjecture that the existence of an arbitrary deformation parameter is necessary for the existence of chaotic dynamics. |
2210.12898 | Martin Reiris | Javier Peraza and Mart\'in Reiris and Omar E. Ortiz | Periodic analogues of the Kerr solutions: a numerical study | 25 pages | null | 10.1088/1361-6382/ace7a7 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In recent years black hole configurations with non standard topology or with
non-standard asymptotic have gained considerable attention. In this article we
carry out numerical investigations aimed to find periodic coaxial
configurations of co-rotating 3+1 vacuum black holes, for which existence and
uniqueness has not yet been theoretically proven. The aimed configurations
would extend Myers/Korotkin-Nicolai's family of non-rotating (static) coaxial
arrays of black holes. We find that numerical solutions with a given value for
the area A and for the angular momentum J of the horizons appear to exist only
when the separation between consecutive horizons is larger than a certain
critical value that depends only on A and |J|. We also establish that the
solutions have the same Lewis's cylindrical asymptotic as Stockum's infinite
rotating cylinders. Below the mentioned critical value the rotational energy
appears to be too big to sustain a global equilibrium and a singularity shows
up at a finite distance from the bulk. This phenomenon is a relative of
Stockum's asymptotic's collapse, manifesting when the angular momentum (per
unit of axial length) reaches a critical value compared to the mass (per unit
of axial length), and that results from a transition in the Lewis's class of
the cylindrical exterior solution. This remarkable phenomenon seems to be
unexplored in the context of coaxial arrays of black holes. Ergospheres and
other global properties are also presented in detail.
| [
{
"created": "Mon, 24 Oct 2022 00:57:05 GMT",
"version": "v1"
}
] | 2023-08-16 | [
[
"Peraza",
"Javier",
""
],
[
"Reiris",
"Martín",
""
],
[
"Ortiz",
"Omar E.",
""
]
] | In recent years black hole configurations with non standard topology or with non-standard asymptotic have gained considerable attention. In this article we carry out numerical investigations aimed to find periodic coaxial configurations of co-rotating 3+1 vacuum black holes, for which existence and uniqueness has not yet been theoretically proven. The aimed configurations would extend Myers/Korotkin-Nicolai's family of non-rotating (static) coaxial arrays of black holes. We find that numerical solutions with a given value for the area A and for the angular momentum J of the horizons appear to exist only when the separation between consecutive horizons is larger than a certain critical value that depends only on A and |J|. We also establish that the solutions have the same Lewis's cylindrical asymptotic as Stockum's infinite rotating cylinders. Below the mentioned critical value the rotational energy appears to be too big to sustain a global equilibrium and a singularity shows up at a finite distance from the bulk. This phenomenon is a relative of Stockum's asymptotic's collapse, manifesting when the angular momentum (per unit of axial length) reaches a critical value compared to the mass (per unit of axial length), and that results from a transition in the Lewis's class of the cylindrical exterior solution. This remarkable phenomenon seems to be unexplored in the context of coaxial arrays of black holes. Ergospheres and other global properties are also presented in detail. |
1101.0366 | Yurii Ignatyev | Yu.G.Ignatyev, D.Yu.Ignatyev | A Kinetics Of The Non-Equilibrium Universe. II. A Kinetics Of The Local
Thermodynamical Equilibrium's Recovery | 29 pages, 11 figures, 13 references | Gravitation & Cosmology, Vol. 13, No 2, 2007, p. 101-113 | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been researched the kinetics of the thermal equilibrium's
establishment in an early Universe under the assumption of the recovery of
interaction scaling of elementary particles in range of superhigh energies. The
case of the thermal equilibrium's weak initial violation and basic cosmological
consequences of the thermal equilibrium's violation have been researched.
| [
{
"created": "Sat, 1 Jan 2011 19:51:13 GMT",
"version": "v1"
}
] | 2011-01-04 | [
[
"Ignatyev",
"Yu. G.",
""
],
[
"Ignatyev",
"D. Yu.",
""
]
] | It has been researched the kinetics of the thermal equilibrium's establishment in an early Universe under the assumption of the recovery of interaction scaling of elementary particles in range of superhigh energies. The case of the thermal equilibrium's weak initial violation and basic cosmological consequences of the thermal equilibrium's violation have been researched. |
gr-qc/9810078 | Joy Christian | Joy Christian (Oxford University) | Why the Quantum Must Yield to Gravity | 33 pages (TeX, uses mtexsis) plus 3 figures (epsf). To appear in
``Physics Meets Philosophy at the Planck Scale'' (Cambridge University
Press). Two footnotes added | null | 10.1017/CBO9780511612909.015 | null | gr-qc quant-ph | null | After providing an extensive overview of the conceptual elements -- such as
Einstein's `hole argument' -- that underpin Penrose's proposal for
gravitationally induced quantum state reduction, the proposal is constructively
criticised. Penrose has suggested a mechanism for objective reduction of
quantum states with postulated collapse time T = h/E, where E is an
ill-definedness in the gravitational self-energy stemming from the profound
conflict between the principles of superposition and general covariance. Here
it is argued that, even if Penrose's overall conceptual scheme for the
breakdown of quantum mechanics is unreservedly accepted, his formula for the
collapse time of superpositions reduces to T --> oo (E --> 0) in the strictly
Newtonian regime, which is the domain of his proposed experiment to corroborate
the effect. A suggestion is made to rectify this situation. In particular,
recognising the cogency of Penrose's reasoning in the domain of full `quantum
gravity', it is demonstrated that an appropriate experiment which could in
principle corroborate his argued `macroscopic' breakdown of superpositions is
not the one involving non-rotating mass distributions as he has suggested, but
a Leggett-type SQUID or BEC experiment involving superposed mass distributions
in relative rotation. The demonstration thereby brings out one of the
distinctive characteristics of Penrose's scheme, rendering it empirically
distinguishable from other state reduction theories involving gravity. As an
aside, a new geometrical measure of gravity-induced deviation from quantum
mechanics in the manner of Penrose is proposed, but now for the canonical
commutation relations [Q, P] = ih.
| [
{
"created": "Mon, 26 Oct 1998 21:14:55 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Nov 1998 14:51:20 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Mar 1999 16:56:57 GMT",
"version": "v3"
}
] | 2016-07-05 | [
[
"Christian",
"Joy",
"",
"Oxford University"
]
] | After providing an extensive overview of the conceptual elements -- such as Einstein's `hole argument' -- that underpin Penrose's proposal for gravitationally induced quantum state reduction, the proposal is constructively criticised. Penrose has suggested a mechanism for objective reduction of quantum states with postulated collapse time T = h/E, where E is an ill-definedness in the gravitational self-energy stemming from the profound conflict between the principles of superposition and general covariance. Here it is argued that, even if Penrose's overall conceptual scheme for the breakdown of quantum mechanics is unreservedly accepted, his formula for the collapse time of superpositions reduces to T --> oo (E --> 0) in the strictly Newtonian regime, which is the domain of his proposed experiment to corroborate the effect. A suggestion is made to rectify this situation. In particular, recognising the cogency of Penrose's reasoning in the domain of full `quantum gravity', it is demonstrated that an appropriate experiment which could in principle corroborate his argued `macroscopic' breakdown of superpositions is not the one involving non-rotating mass distributions as he has suggested, but a Leggett-type SQUID or BEC experiment involving superposed mass distributions in relative rotation. The demonstration thereby brings out one of the distinctive characteristics of Penrose's scheme, rendering it empirically distinguishable from other state reduction theories involving gravity. As an aside, a new geometrical measure of gravity-induced deviation from quantum mechanics in the manner of Penrose is proposed, but now for the canonical commutation relations [Q, P] = ih. |
gr-qc/0210069 | Alberto Saa | L. Raul Abramo, Leon Brenig, Edgard Gunzig, and Alberto Saa | On the singularities of gravity in the presence of non-minimally coupled
scalar fields | To appear in PRD | Phys.Rev. D67 (2003) 027301 | 10.1103/PhysRevD.67.027301 | null | gr-qc | null | We investigate the robustness of some recent results obtained for homogeneous
and isotropic cosmological models with conformally coupled scalar fields. For
this purpose, we investigate anisotropic homogeneous solutions of the models
described by the action $$ S=\int d^4x \sqrt{-g}\left\{F(\phi)R -
\partial_a\phi\partial^a\phi -2V(\phi) \right\}, $$ with general $F(\phi)$ and
$V(\phi)$. We show that such a class of models leads generically to geometrical
singularities if for some value of $\phi$, $F(\phi)=0$, rendering previous
cosmological results obtained for the conformal coupling case highly unstable.
We show that stable models can be obtained for suitable choices of $F(\phi)$
and $V(\phi)$. Implications for other recent results are also discussed.
| [
{
"created": "Sun, 20 Oct 2002 18:51:49 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Abramo",
"L. Raul",
""
],
[
"Brenig",
"Leon",
""
],
[
"Gunzig",
"Edgard",
""
],
[
"Saa",
"Alberto",
""
]
] | We investigate the robustness of some recent results obtained for homogeneous and isotropic cosmological models with conformally coupled scalar fields. For this purpose, we investigate anisotropic homogeneous solutions of the models described by the action $$ S=\int d^4x \sqrt{-g}\left\{F(\phi)R - \partial_a\phi\partial^a\phi -2V(\phi) \right\}, $$ with general $F(\phi)$ and $V(\phi)$. We show that such a class of models leads generically to geometrical singularities if for some value of $\phi$, $F(\phi)=0$, rendering previous cosmological results obtained for the conformal coupling case highly unstable. We show that stable models can be obtained for suitable choices of $F(\phi)$ and $V(\phi)$. Implications for other recent results are also discussed. |
1408.4949 | Andrea Geralico | Donato Bini, Fernando de Felice, Andrea Geralico | Accelerated orbits in black hole fields: the static case | 21 pages, 6 figures; published version | Class. Quantum Grav. 28, 225012 (2011) | 10.1088/0264-9381/28/22/225012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study non-geodesic orbits of test particles endowed with a structure,
assuming the Schwarzschild spacetime as background. We develop a formalism
which allows one to recognize the geometrical characterization of those orbits
in terms of their Frenet-Serret parameters and apply it to explicit cases as
those of spatially circular orbits which witness the equilibrium under
conflicting types of interactions. In our general analysis we solve the
equations of motion offering a detailed picture of the dynamics having in mind
a check with a possible astronomical set up. We focus on certain ambiguities
which plague the interpretation of the measurements preventing one from
identifying the particular structure carried by the particle.
| [
{
"created": "Thu, 21 Aug 2014 10:53:50 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"de Felice",
"Fernando",
""
],
[
"Geralico",
"Andrea",
""
]
] | We study non-geodesic orbits of test particles endowed with a structure, assuming the Schwarzschild spacetime as background. We develop a formalism which allows one to recognize the geometrical characterization of those orbits in terms of their Frenet-Serret parameters and apply it to explicit cases as those of spatially circular orbits which witness the equilibrium under conflicting types of interactions. In our general analysis we solve the equations of motion offering a detailed picture of the dynamics having in mind a check with a possible astronomical set up. We focus on certain ambiguities which plague the interpretation of the measurements preventing one from identifying the particular structure carried by the particle. |
1805.06036 | Natacha Leite | Natacha Leite and Petar Pavlovi\'c | Magnetogenesis in Cyclical Universe | 21 pages, 4 figures | null | 10.1088/1361-6382/aae2d6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a simple solution to the magnetogenesis problem based on cyclic
cosmology. It is demonstrated that magnetic fields, of sufficient strengths to
account for the present observational bounds, can be created in the contracting
phase preceding the beginning of the current cosmological cycle. The basic
assumption of this model is that the Universe enters a contraction phase
essentially empty, characterized by small seed electric fields. In this
framework, there is no need for any new theoretical additions to explain
magnetogenesis, such as new scalar fields or non-minimal couplings between
curvature, scalar fields and the electromagnetic sector. Moreover, the proposed
model is general in the sense that it does not assume any specific modified
gravity theory to enable the cosmological bounce. When compared to the
inflationary magnetogenesis paradigm, the proposed model also has the advantage
of not leading to the backreaction and strong coupling problems.
| [
{
"created": "Tue, 15 May 2018 21:18:17 GMT",
"version": "v1"
}
] | 2018-10-24 | [
[
"Leite",
"Natacha",
""
],
[
"Pavlović",
"Petar",
""
]
] | We propose a simple solution to the magnetogenesis problem based on cyclic cosmology. It is demonstrated that magnetic fields, of sufficient strengths to account for the present observational bounds, can be created in the contracting phase preceding the beginning of the current cosmological cycle. The basic assumption of this model is that the Universe enters a contraction phase essentially empty, characterized by small seed electric fields. In this framework, there is no need for any new theoretical additions to explain magnetogenesis, such as new scalar fields or non-minimal couplings between curvature, scalar fields and the electromagnetic sector. Moreover, the proposed model is general in the sense that it does not assume any specific modified gravity theory to enable the cosmological bounce. When compared to the inflationary magnetogenesis paradigm, the proposed model also has the advantage of not leading to the backreaction and strong coupling problems. |
1511.07955 | Nilanjana Mahata | Nilanjana Mahata and Subenoy Chakraborty | A Dynamical System Analysis of Holographic Dark Energy Models with
Different IR Cutoff | 13 pages, 9 figures | Modern Physics Letters A, Vol. 30, No. 27(2015) 1550134 | 10.1142/S0217732315501345 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper deals with a dynamical system analysis of the cosmological
evolution of an holographic dark energy (HDE) model interacting with dark
matter (DM) which is chosen in the form of dust. The infrared cut-off of the
holographic model is chosen as future event horizon or Ricci length scale. The
interaction term between dark energy and dark matter is chosen of following
three types i) proportional to the sum of the energy densities of the two dark
components ii) proportional to the product of the matter energy densities and
iii) proportional to dark energy density. The dynamical equations are reduced
to an autonomous system for the three cases and corresponding phase space is
analyzed.
| [
{
"created": "Wed, 25 Nov 2015 05:38:00 GMT",
"version": "v1"
}
] | 2015-11-26 | [
[
"Mahata",
"Nilanjana",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The paper deals with a dynamical system analysis of the cosmological evolution of an holographic dark energy (HDE) model interacting with dark matter (DM) which is chosen in the form of dust. The infrared cut-off of the holographic model is chosen as future event horizon or Ricci length scale. The interaction term between dark energy and dark matter is chosen of following three types i) proportional to the sum of the energy densities of the two dark components ii) proportional to the product of the matter energy densities and iii) proportional to dark energy density. The dynamical equations are reduced to an autonomous system for the three cases and corresponding phase space is analyzed. |
gr-qc/9911061 | Masoud Alimohammadi | M. Alimohammadi, A. shariati | Quantum reflection of massless neutrinos from a torsion-induced
potential | 8 pages, LaTex | Int.J.Mod.Phys. A15 (2000) 4099-4106 | 10.1142/S0217751X00001130 | null | gr-qc hep-th | null | In the context of the Einstein-Cartan-Dirac model, where the torsion of the
space-time couples to the axial currents of the fermions, we study the effects
of this quantum-gravitational interaction on a massless neutrino beam crossing
through a medium with high number density of fermions at rest. We calculate the
reflection amplitude and show that a specific fraction of the incident
neutrinos reflects from this potential if the polarization of the medium is
different from zero. We also discuss the order of magnitude of the fermionic
number density in which this phenomenon is observable, in other theoretical
contexts, for example the strong-gravity regime and the effective field theory
approach.
| [
{
"created": "Wed, 17 Nov 1999 15:01:50 GMT",
"version": "v1"
}
] | 2016-12-21 | [
[
"Alimohammadi",
"M.",
""
],
[
"shariati",
"A.",
""
]
] | In the context of the Einstein-Cartan-Dirac model, where the torsion of the space-time couples to the axial currents of the fermions, we study the effects of this quantum-gravitational interaction on a massless neutrino beam crossing through a medium with high number density of fermions at rest. We calculate the reflection amplitude and show that a specific fraction of the incident neutrinos reflects from this potential if the polarization of the medium is different from zero. We also discuss the order of magnitude of the fermionic number density in which this phenomenon is observable, in other theoretical contexts, for example the strong-gravity regime and the effective field theory approach. |
2010.08711 | Jasel Berra-Montiel | Jasel Berra-Montiel, Alberto Molgado and Eduardo Torres-Cordero | Star product approach for Loop Quantum Cosmology | 21 pages, no figures | null | null | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Guided by recent developments towards the implementation of the deformation
quantization program within the Loop Quantum Cosmology (LQC) formalism, in this
paper we address the introduction of both the integral and differential
representation of the star product for LQC. To this end, we consider the Weyl
quantization map for cylindrical functions defined on the Bohr compactification
of the reals. The integral representation contains all of the common properties
that characterize a star product which, in the case under study here, stands
for a deformation of the usual pointwise product of cylindrical functions. Our
construction also admits a direct comparison with the integral representation
of the Moyal product which may be reproduced from our formulation by
judiciously substituting the appropriate characters that identify such
representation. Further, we introduce a suitable star commutator that correctly
reproduces both the quantum representation of the holonomy-flux algebra for LQC
and, in the proper limit, the holonomy-flux classical Poisson algebra emerging
in the cosmological setup. Finally, we propose a natural way to obtain the
quantum dynamical evolution in LQC in terms of this star commutator for
cylindrical functions as well as a differential representation of the star
product using discrete finite differences. We expect that our findings may
contribute to a better understanding of certain issues arising within the LQC
program, in particular, those related to the semiclassical limit and the
dynamical evolution of quantum states.
| [
{
"created": "Sat, 17 Oct 2020 04:02:52 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Oct 2022 16:11:47 GMT",
"version": "v2"
}
] | 2022-10-04 | [
[
"Berra-Montiel",
"Jasel",
""
],
[
"Molgado",
"Alberto",
""
],
[
"Torres-Cordero",
"Eduardo",
""
]
] | Guided by recent developments towards the implementation of the deformation quantization program within the Loop Quantum Cosmology (LQC) formalism, in this paper we address the introduction of both the integral and differential representation of the star product for LQC. To this end, we consider the Weyl quantization map for cylindrical functions defined on the Bohr compactification of the reals. The integral representation contains all of the common properties that characterize a star product which, in the case under study here, stands for a deformation of the usual pointwise product of cylindrical functions. Our construction also admits a direct comparison with the integral representation of the Moyal product which may be reproduced from our formulation by judiciously substituting the appropriate characters that identify such representation. Further, we introduce a suitable star commutator that correctly reproduces both the quantum representation of the holonomy-flux algebra for LQC and, in the proper limit, the holonomy-flux classical Poisson algebra emerging in the cosmological setup. Finally, we propose a natural way to obtain the quantum dynamical evolution in LQC in terms of this star commutator for cylindrical functions as well as a differential representation of the star product using discrete finite differences. We expect that our findings may contribute to a better understanding of certain issues arising within the LQC program, in particular, those related to the semiclassical limit and the dynamical evolution of quantum states. |
0909.2747 | Guido Cognola | G. Cognola, E. Elizalde, S. Nojiri, S.D. Odintsov | Vacuum energy fluctuations, the induced cosmological constant and
cosmological reconstruction in non-minimal modified gravity models | Latex file, 14 pages, no figures | Open Astron.J.3:20-29,2010 | 10.2174/1874381101003020020 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The one-loop effective action for non-minimal scalar modified gravity on de
Sitter background with a constant scalar field is found. The corresponding
induced cosmological constant is evaluated. It is shown that quantum effects in
non-minimal modified gravity may induce an early-time de Sitter universe even
in the situation when such solution does not occur on the classical level.
Classical reconstruction of the theory is presented in such a way that the
resulting theory has a cosmological solution unifying early-time inflation with
late-time acceleration.
| [
{
"created": "Tue, 15 Sep 2009 08:47:46 GMT",
"version": "v1"
}
] | 2011-04-07 | [
[
"Cognola",
"G.",
""
],
[
"Elizalde",
"E.",
""
],
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
]
] | The one-loop effective action for non-minimal scalar modified gravity on de Sitter background with a constant scalar field is found. The corresponding induced cosmological constant is evaluated. It is shown that quantum effects in non-minimal modified gravity may induce an early-time de Sitter universe even in the situation when such solution does not occur on the classical level. Classical reconstruction of the theory is presented in such a way that the resulting theory has a cosmological solution unifying early-time inflation with late-time acceleration. |
gr-qc/9805040 | Esposito Giampiero | Giampiero Esposito and Alexander Yu. Kamenshchik | Two-boundary problems in Euclidean quantum gravity | 19 pages, plain Tex | Nuovo Cim. B114 (1999) 57-70 | null | DSF preprint 98/13 | gr-qc | null | Recent work in the literature has studied a new set of local boundary
conditions for the quantized gravitational field, where the spatial components
of metric perturbations, and ghost modes, are subject to Robin boundary
conditions, whereas normal components of metric perturbations obey Dirichlet
boundary conditions. Such boundary conditions are here applied to evaluate the
one-loop divergence on a portion of flat Euclidean four-space bounded by two
concentric three-spheres.
| [
{
"created": "Tue, 12 May 1998 06:30:10 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Esposito",
"Giampiero",
""
],
[
"Kamenshchik",
"Alexander Yu.",
""
]
] | Recent work in the literature has studied a new set of local boundary conditions for the quantized gravitational field, where the spatial components of metric perturbations, and ghost modes, are subject to Robin boundary conditions, whereas normal components of metric perturbations obey Dirichlet boundary conditions. Such boundary conditions are here applied to evaluate the one-loop divergence on a portion of flat Euclidean four-space bounded by two concentric three-spheres. |
gr-qc/0703057 | Eyo Ita III | Eyo Eyo Ita III | Instanton representation of Plebanski gravity. Gravitational instantons
from the classical formalism | 33 pages. Background information for revised journal article | The Abraham Zelmanov Journal, 2011, Vol. 4 (pages 36-71) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a reformulation of general relativity as a `generalized'
Yang--Mills theory of gravity, using a SO(3,C) gauge connection and the
self-dual Weyl tensor as dynamical variables. This formulation uses Plebanski's
theory as the starting point, and obtains a new action called the instanton
representation (IRPG). This paper has yielded a collection of various new
results, which show that the IRPG is indeed a fundamentally new approach to GR
which should not be confused with existing approaches. Additionally, the IRPG
appears to provide a realization of the relation amongst general relativity,
Yang--Mills theory and instantons.
| [
{
"created": "Thu, 8 Mar 2007 12:10:03 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 2010 15:53:09 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Mar 2011 06:18:18 GMT",
"version": "v3"
}
] | 2012-02-20 | [
[
"Ita",
"Eyo Eyo",
"III"
]
] | We present a reformulation of general relativity as a `generalized' Yang--Mills theory of gravity, using a SO(3,C) gauge connection and the self-dual Weyl tensor as dynamical variables. This formulation uses Plebanski's theory as the starting point, and obtains a new action called the instanton representation (IRPG). This paper has yielded a collection of various new results, which show that the IRPG is indeed a fundamentally new approach to GR which should not be confused with existing approaches. Additionally, the IRPG appears to provide a realization of the relation amongst general relativity, Yang--Mills theory and instantons. |
2102.00187 | Babak Vakili | Fatimah Tavakoli, Babak Vakili and Hossein Ardehali | Ho\v{r}ava-Lifshitz scalar field cosmology: classical and quantum
viewpoints | 17 pages, 12 figures, typos corrected, Refs. added, Final version | Adv. High Energy Phys. (2021), 6617910 | 10.1155/2021/6617910 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study a projectable Ho\v{r}ava-Lifshitz cosmology without
the detailed balance condition minimally coupled to a non-linear self-coupling
scalar field. In the minisuperspace framework, the super Hamiltonian of the
presented model is constructed by means of which, some classical solutions for
scale factor and scalar field are obtained. Since these solutions exhibit
various types of singularities, we came up with the quantization of the model
in the context of the Wheeler-DeWitt approach of quantum cosmology. The
resulting quantum wave functions are then used to investigate the possibility
of the avoidance of classical singularities due to quantum effects which show
themselves important near these singularities.
| [
{
"created": "Sat, 30 Jan 2021 08:42:49 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Feb 2021 14:15:05 GMT",
"version": "v2"
}
] | 2021-02-25 | [
[
"Tavakoli",
"Fatimah",
""
],
[
"Vakili",
"Babak",
""
],
[
"Ardehali",
"Hossein",
""
]
] | In this paper, we study a projectable Ho\v{r}ava-Lifshitz cosmology without the detailed balance condition minimally coupled to a non-linear self-coupling scalar field. In the minisuperspace framework, the super Hamiltonian of the presented model is constructed by means of which, some classical solutions for scale factor and scalar field are obtained. Since these solutions exhibit various types of singularities, we came up with the quantization of the model in the context of the Wheeler-DeWitt approach of quantum cosmology. The resulting quantum wave functions are then used to investigate the possibility of the avoidance of classical singularities due to quantum effects which show themselves important near these singularities. |
1512.08198 | Rodrigo Turcati | Bethan Cropp, Stefano Liberati, Rodrigo Turcati | Vorticity in analogue gravity | 12 pages. Final version matching the published one in CQG | Class. Quantum Grav. 33 125009 (2016) | 10.1088/0264-9381/33/12/125009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the analogue gravity framework, the acoustic disturbances in a moving
fluid can be described by an equation of motion identical to a relativistic
scalar massless field propagating in a curved spacetime. This description is
possible only when the fluid under consideration is barotropic, inviscid and
irrotational. In this case, the propagation of the perturbations is governed by
an acoustic metric which depends algebrically on the local speed of sound,
density and the background flow velocity, the latter assumed to be vorticity
free. In this work we provide an straightforward extension in order to go
beyond the irrotational constraint. Using a charged --- relativistic and
non-relativistic --- Bose--Einstein condensate as a physical system, we show
that in the low momentum limit and performing the eikonal approximation we can
derive a d'Alembertian equation of motion for the charged phonons where the
emergent acoustic metric depends on a flow velocity in the presence of
vorticity.
| [
{
"created": "Sun, 27 Dec 2015 10:33:20 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jun 2016 10:59:44 GMT",
"version": "v2"
}
] | 2016-06-06 | [
[
"Cropp",
"Bethan",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Turcati",
"Rodrigo",
""
]
] | In the analogue gravity framework, the acoustic disturbances in a moving fluid can be described by an equation of motion identical to a relativistic scalar massless field propagating in a curved spacetime. This description is possible only when the fluid under consideration is barotropic, inviscid and irrotational. In this case, the propagation of the perturbations is governed by an acoustic metric which depends algebrically on the local speed of sound, density and the background flow velocity, the latter assumed to be vorticity free. In this work we provide an straightforward extension in order to go beyond the irrotational constraint. Using a charged --- relativistic and non-relativistic --- Bose--Einstein condensate as a physical system, we show that in the low momentum limit and performing the eikonal approximation we can derive a d'Alembertian equation of motion for the charged phonons where the emergent acoustic metric depends on a flow velocity in the presence of vorticity. |
gr-qc/9710079 | Bernard F. Schutz | B. F. Schutz | Low-Frequency Sources of Gravitational Waves: A Tutorial | 12 pages, 2 figures | null | null | AEI-044(A) | gr-qc | null | Gravitational wave detectors in space, particularly the LISA project, can
study a rich variety of astronomical systems whose gravitational radiation is
not detectable from the ground, because it is emitted in the low-frequency
gravitational wave band (0.1 mHz to 1 Hz) that is inaccessible to ground-based
detectors. Sources include binary systems in our Galaxy and massive black holes
in distant galaxies. The radiation from many of these sources will be so strong
that it will be possible to make remarkably detailed studies of the physics of
the systems. These studies will have importance both for astrophysics (most
notably in binary evolution theory and models for active galaxies) and for
fundamental physics. In particular, it should be possible to make decisive
measurements to confirm the existence of black holes and to test, with
accuracies better than 1%, general relativity's description of them. Other
observations can have fundamental implications for cosmology and for physical
theories of the unification of forces. In order to understand these
conclusions, one must know how to estimate the gravitational radiation produced
by different sources. In the first part of this lecture I review the dynamics
of gravitational wave sources, and I derive simple formulas for estimating wave
amplitudes and the reaction effects on sources of producing this radiation.
With these formulas one can estimate, usually to much better than an order of
magnitude, the physics of most of the interesting low-frequency sources. In the
second part of the lecture I use these estimates to discuss, in the context of
the expected sensitivity of LISA, what we can learn by from observations of
binary systems, massive black holes, and the early Universe itself.
| [
{
"created": "Wed, 15 Oct 1997 09:18:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Schutz",
"B. F.",
""
]
] | Gravitational wave detectors in space, particularly the LISA project, can study a rich variety of astronomical systems whose gravitational radiation is not detectable from the ground, because it is emitted in the low-frequency gravitational wave band (0.1 mHz to 1 Hz) that is inaccessible to ground-based detectors. Sources include binary systems in our Galaxy and massive black holes in distant galaxies. The radiation from many of these sources will be so strong that it will be possible to make remarkably detailed studies of the physics of the systems. These studies will have importance both for astrophysics (most notably in binary evolution theory and models for active galaxies) and for fundamental physics. In particular, it should be possible to make decisive measurements to confirm the existence of black holes and to test, with accuracies better than 1%, general relativity's description of them. Other observations can have fundamental implications for cosmology and for physical theories of the unification of forces. In order to understand these conclusions, one must know how to estimate the gravitational radiation produced by different sources. In the first part of this lecture I review the dynamics of gravitational wave sources, and I derive simple formulas for estimating wave amplitudes and the reaction effects on sources of producing this radiation. With these formulas one can estimate, usually to much better than an order of magnitude, the physics of most of the interesting low-frequency sources. In the second part of the lecture I use these estimates to discuss, in the context of the expected sensitivity of LISA, what we can learn by from observations of binary systems, massive black holes, and the early Universe itself. |
gr-qc/0405042 | Clovis Jacinto de Matos | Orfeu Bertolami, Clovis Jacinto de Matos, Jean Christophe
Grenouilleau, Olivier Minster, Sergio Volonte | Perspectives in Fundamental Physics in Space | Gravitational waves, gravitomagnetism, Equivalence Principle,
Antimatter, Pioneer Anomaly, Lorentz invariance. To appear in IAA - Acta
Astronautica Journal (2006) | Acta Astronaut. 59 (2006) 490-498 | 10.1016/j.actaastro.2006.04.008 | null | gr-qc | null | We discuss the fundamental principles underlying the current physical
theories and the prospects of further improving their knowledge through
experiments in space.
| [
{
"created": "Fri, 7 May 2004 15:49:21 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jul 2006 13:27:35 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Bertolami",
"Orfeu",
""
],
[
"de Matos",
"Clovis Jacinto",
""
],
[
"Grenouilleau",
"Jean Christophe",
""
],
[
"Minster",
"Olivier",
""
],
[
"Volonte",
"Sergio",
""
]
] | We discuss the fundamental principles underlying the current physical theories and the prospects of further improving their knowledge through experiments in space. |
2311.14879 | Jos\'e Eloy Ottoni | E. Goulart and J. E. Ottoni | Remarks on the algebraic structure of (2, 2) double forms | null | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the algebraic features of covariant tensors of valence four
containing two blocks of skew indices. After a rather general treatment, we
specialize ourselves to four-dimensional spacetimes and discuss several
complementary aspects of these objects. In particular, we focus our attention
on the corresponding invariant subspaces and generalise previous relations such
as the Ruse-Lanczos identity, the Bel-Matte decomposition and the Lovelock-like
quadratic identities. We conclude pointing out some possible applications of
the formalism.
| [
{
"created": "Sat, 25 Nov 2023 00:03:21 GMT",
"version": "v1"
}
] | 2023-11-28 | [
[
"Goulart",
"E.",
""
],
[
"Ottoni",
"J. E.",
""
]
] | We study the algebraic features of covariant tensors of valence four containing two blocks of skew indices. After a rather general treatment, we specialize ourselves to four-dimensional spacetimes and discuss several complementary aspects of these objects. In particular, we focus our attention on the corresponding invariant subspaces and generalise previous relations such as the Ruse-Lanczos identity, the Bel-Matte decomposition and the Lovelock-like quadratic identities. We conclude pointing out some possible applications of the formalism. |
1311.4853 | Mauricio Bellini | Jos\'e Edgar Madriz Aguilar, Claudia Moreno (Dept. of Mathematics,
CUCEI - UdG), Mauricio Bellini (Physics Department & IFIMAR - UNMdP &
CONICET) | The primordial explosion of a false white hole from a 5D vacuum | Final version to be published in PLB. arXiv admin note: substantial
text overlap with arXiv:1304.6982 | null | 10.1016/j.physletb.2013.12.005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the cosmological consequences of some possible big bang produced
by a black-hole with mass $M$ in an 5D extended SdS. Under these particular
circumstances, the effective 4D metric obtained by the use of a constant
foliation on the extra coordinate is comported as a false white-hole (FWH),
which evaporates for all unstable modes that have wavelengths bigger than the
size of the FWH. Outside the white hole the repulsive gravitational field can
be considered as weak, so that the dynamics for fluctuations of the inflaton
field and the scalar perturbations of the metric can be linearized.
| [
{
"created": "Tue, 19 Nov 2013 19:45:55 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Dec 2013 16:31:11 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Dec 2013 15:08:14 GMT",
"version": "v3"
}
] | 2015-06-17 | [
[
"Aguilar",
"José Edgar Madriz",
"",
"Dept. of Mathematics,\n CUCEI - UdG"
],
[
"Moreno",
"Claudia",
"",
"Dept. of Mathematics,\n CUCEI - UdG"
],
[
"Bellini",
"Mauricio",
"",
"Physics Department & IFIMAR - UNMdP &\n CONICET"
]
] | We explore the cosmological consequences of some possible big bang produced by a black-hole with mass $M$ in an 5D extended SdS. Under these particular circumstances, the effective 4D metric obtained by the use of a constant foliation on the extra coordinate is comported as a false white-hole (FWH), which evaporates for all unstable modes that have wavelengths bigger than the size of the FWH. Outside the white hole the repulsive gravitational field can be considered as weak, so that the dynamics for fluctuations of the inflaton field and the scalar perturbations of the metric can be linearized. |
1610.08039 | Viraj Sanghai | Viraj A. A. Sanghai, Timothy Clifton | Parameterized Post-Newtonian Cosmology | 30 pages, no figures, v2: matches published version | Class. Quantum Grav. 34 (2017) 065003 | 10.1088/1361-6382/aa5d75 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein's theory of gravity has been extensively tested on solar system
scales, and for isolated astrophysical systems, using the perturbative
framework known as the parameterized post-Newtonian (PPN) formalism. This
framework is designed for use in the weak-field and slow-motion limit of
gravity, and can be used to constrain a large class of metric theories of
gravity with data collected from the aforementioned systems. Given the
potential of future surveys to probe cosmological scales to high precision, it
is a topic of much contemporary interest to construct a similar framework to
link Einstein's theory of gravity and its alternatives to observations on
cosmological scales. Our approach to this problem is to adapt and extend the
existing PPN formalism for use in cosmology. We derive a set of equations that
use the same parameters to consistently model both weak fields and cosmology.
This allows us to parameterize a large class of modified theories of gravity
and dark energy models on cosmological scales, using just four functions of
time. These four functions can be directly linked to the background expansion
of the universe, first-order cosmological perturbations, and the weak-field
limit of the theory. They also reduce to the standard PPN parameters on solar
system scales. We illustrate how dark energy models and scalar-tensor and
vector-tensor theories of gravity fit into this framework, which we refer to as
"parameterized post-Newtonian cosmology" (PPNC).
| [
{
"created": "Tue, 25 Oct 2016 19:46:12 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Feb 2017 21:39:07 GMT",
"version": "v2"
}
] | 2017-02-24 | [
[
"Sanghai",
"Viraj A. A.",
""
],
[
"Clifton",
"Timothy",
""
]
] | Einstein's theory of gravity has been extensively tested on solar system scales, and for isolated astrophysical systems, using the perturbative framework known as the parameterized post-Newtonian (PPN) formalism. This framework is designed for use in the weak-field and slow-motion limit of gravity, and can be used to constrain a large class of metric theories of gravity with data collected from the aforementioned systems. Given the potential of future surveys to probe cosmological scales to high precision, it is a topic of much contemporary interest to construct a similar framework to link Einstein's theory of gravity and its alternatives to observations on cosmological scales. Our approach to this problem is to adapt and extend the existing PPN formalism for use in cosmology. We derive a set of equations that use the same parameters to consistently model both weak fields and cosmology. This allows us to parameterize a large class of modified theories of gravity and dark energy models on cosmological scales, using just four functions of time. These four functions can be directly linked to the background expansion of the universe, first-order cosmological perturbations, and the weak-field limit of the theory. They also reduce to the standard PPN parameters on solar system scales. We illustrate how dark energy models and scalar-tensor and vector-tensor theories of gravity fit into this framework, which we refer to as "parameterized post-Newtonian cosmology" (PPNC). |
gr-qc/0504128 | Hirotaka Takahashi | Stephen Fairhurst (for the LIGO Scientific Collaboration) and Hirotaka
Takahashi (for the TAMA Collaboration) | Status of the joint LIGO--TAMA300 inspiral analysis | 10 page, 8 figures, accepted for publication in Classical and Quantum
Gravity for the special issue of the GWDAW9 Proceedings ; Corrected typos,
minor changes | Class.Quant.Grav. 22 (2005) S1109-S1118 | 10.1088/0264-9381/22/18/S25 | OU-TAP 257 | gr-qc | null | We present the status of the joint search for gravitational waves from
inspiraling neutron star binaries in the LIGO Science Run 2 and TAMA300 Data
Taking Run 8 data, which was taken from February 14 to April 14, 2003, by the
LIGO and TAMA collaborations. In this paper we discuss what has been learned
from an analysis of a subset of the data sample reserved as a ``playground''.
We determine the coincidence conditions for parameters such as the coalescence
time and chirp mass by injecting simulated Galactic binary neutron star signals
into the data stream. We select coincidence conditions so as to maximize our
efficiency of detecting simulated signals. We obtain an efficiency for our
coincident search of 78 %, and show that we are missing primarily very distant
signals for TAMA300. We perform a time slide analysis to estimate the
background due to accidental coincidence of noise triggers. We find that the
background triggers have a very different character from the triggers of
simulated signals.
| [
{
"created": "Tue, 26 Apr 2005 01:28:38 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2005 04:25:51 GMT",
"version": "v2"
}
] | 2019-08-15 | [
[
"Fairhurst",
"Stephen",
"",
"for the LIGO Scientific Collaboration"
],
[
"Takahashi",
"Hirotaka",
"",
"for the TAMA Collaboration"
]
] | We present the status of the joint search for gravitational waves from inspiraling neutron star binaries in the LIGO Science Run 2 and TAMA300 Data Taking Run 8 data, which was taken from February 14 to April 14, 2003, by the LIGO and TAMA collaborations. In this paper we discuss what has been learned from an analysis of a subset of the data sample reserved as a ``playground''. We determine the coincidence conditions for parameters such as the coalescence time and chirp mass by injecting simulated Galactic binary neutron star signals into the data stream. We select coincidence conditions so as to maximize our efficiency of detecting simulated signals. We obtain an efficiency for our coincident search of 78 %, and show that we are missing primarily very distant signals for TAMA300. We perform a time slide analysis to estimate the background due to accidental coincidence of noise triggers. We find that the background triggers have a very different character from the triggers of simulated signals. |
1504.03883 | Bijan Saha Dr. | Bijan Saha | Nonlinear Spinor Fields in Bianchi type-$VI_0$ spacetime | 14 pages | Eur. Phys. J. Plus (2015) 130: 208 | 10.1140/epjp/i2015-15208-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the scope of Bianchi type-$VI_0$ spacetime we study the role of spinor
field on the evolution of the Universe. It is found that the presence of
nontrivial non-diagonal components of energy-momentum tensor of the spinor
field plays vital role on the evolution of the Universe. As a result of their
mutual influence there occur two different scenarios. In one case the
invariants constructed from the bilinear forms of the spinor field become
trivial, thus giving rise to a massless and linear spinor field Lagrangian.
According to the second scenario massive and nonlinear terms do not vanish and
depending on the sign of coupling constants we have either an expanding mode of
expansion or the one that after obtaining some maximum value contracts and ends
in big crunch generating spacetime singularity. This result shows that the
spinor field is highly sensitive to the gravitational one.
| [
{
"created": "Wed, 15 Apr 2015 12:24:58 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Oct 2015 10:41:42 GMT",
"version": "v2"
}
] | 2015-10-21 | [
[
"Saha",
"Bijan",
""
]
] | Within the scope of Bianchi type-$VI_0$ spacetime we study the role of spinor field on the evolution of the Universe. It is found that the presence of nontrivial non-diagonal components of energy-momentum tensor of the spinor field plays vital role on the evolution of the Universe. As a result of their mutual influence there occur two different scenarios. In one case the invariants constructed from the bilinear forms of the spinor field become trivial, thus giving rise to a massless and linear spinor field Lagrangian. According to the second scenario massive and nonlinear terms do not vanish and depending on the sign of coupling constants we have either an expanding mode of expansion or the one that after obtaining some maximum value contracts and ends in big crunch generating spacetime singularity. This result shows that the spinor field is highly sensitive to the gravitational one. |
gr-qc/0603065 | Diego Julio Cirilo-Lombardo | D.J. Cirilo-Lombardo | New spherically symmetric monopole and regular solutions in
Einstein-Born-Infeld theories | Final version in journal. Amplied version with new results that
previous talk in Protvino workshop | J.Math.Phys.46:042501,2005 | 10.1063/1.1862308 | null | gr-qc hep-th | null | In this work a new asymptotically flat solution of the coupled
Einstein-Born-Infeld equations for a static spherically symmetric space-time is
obtained. When the intrinsic mass is zero the resulting spacetime is regular
everywhere, in the sense given by B. Hoffmann and L. Infeld in 1937, and the
Einstein-Born-Infeld theory leads to the identification of the gravitational
with the electromagnetic mass. This means that the metric, the electromagnetic
field and their derivatives have not discontinuities in all the manifold. In
particular, there are not conical singularities at the origin, in contrast to
well known monopole solution studied by B. Hoffmann in 1935. The lack of
uniqueness of the action function in Non-Linear-Electrodynamics is discussed.
| [
{
"created": "Thu, 16 Mar 2006 08:27:25 GMT",
"version": "v1"
}
] | 2010-01-15 | [
[
"Cirilo-Lombardo",
"D. J.",
""
]
] | In this work a new asymptotically flat solution of the coupled Einstein-Born-Infeld equations for a static spherically symmetric space-time is obtained. When the intrinsic mass is zero the resulting spacetime is regular everywhere, in the sense given by B. Hoffmann and L. Infeld in 1937, and the Einstein-Born-Infeld theory leads to the identification of the gravitational with the electromagnetic mass. This means that the metric, the electromagnetic field and their derivatives have not discontinuities in all the manifold. In particular, there are not conical singularities at the origin, in contrast to well known monopole solution studied by B. Hoffmann in 1935. The lack of uniqueness of the action function in Non-Linear-Electrodynamics is discussed. |
gr-qc/0003023 | Miguel Sabido | O. Obregon, M. Sabido, and V. I. Tkach | Entropy using Path Integrals for Quantum Black Hole Models | 7 pages, LaTeX, no figures | Gen.Rel.Grav.33:913-919,2001 | 10.1023/A:1010216126590 | null | gr-qc hep-th | null | Several eigenvalue equations that could describe quantum black holes have
been proposed in the canonical quantum gravity approach. In this paper, we
choose one of the simplest of these quantum equations to show how the usual
Feynman's path integral method can be applied to obtain the corresponding
statistical properties. We get a logarithmic correction to the
Bekenstein-Hawking entropy as already obtained by other authors by other means.
| [
{
"created": "Wed, 8 Mar 2000 00:20:20 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Apr 2000 18:18:58 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Obregon",
"O.",
""
],
[
"Sabido",
"M.",
""
],
[
"Tkach",
"V. I.",
""
]
] | Several eigenvalue equations that could describe quantum black holes have been proposed in the canonical quantum gravity approach. In this paper, we choose one of the simplest of these quantum equations to show how the usual Feynman's path integral method can be applied to obtain the corresponding statistical properties. We get a logarithmic correction to the Bekenstein-Hawking entropy as already obtained by other authors by other means. |
1411.7871 | Cacciatori Sergio | F. Belgiorno, S.L. Cacciatori, F. Dalla Piazza | Tunneling approach and thermality in dispersive models of analogue
gravity | 18 pages and 1 figure | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We set up a tunneling approach to the analogue Hawking effect in the case of
models of analogue gravity which are affected by dispersive effects. An
effective Schroedinger-like equation for the basic scattering phenomenon
IN->P+N*, where IN is the incident mode, P is the positive norm reflected mode,
and N* is the negative norm one, signalling particle creation, is derived,
aimed to an approximate description of the phenomenon. Horizons and barrier
penetration play manifestly a key-role in giving rise to pair-creation. The
non-dispersive limit is also correctly recovered. Drawbacks of the model are
also pointed out and a possible solution ad hoc is suggested.
| [
{
"created": "Fri, 28 Nov 2014 14:01:04 GMT",
"version": "v1"
}
] | 2014-12-01 | [
[
"Belgiorno",
"F.",
""
],
[
"Cacciatori",
"S. L.",
""
],
[
"Piazza",
"F. Dalla",
""
]
] | We set up a tunneling approach to the analogue Hawking effect in the case of models of analogue gravity which are affected by dispersive effects. An effective Schroedinger-like equation for the basic scattering phenomenon IN->P+N*, where IN is the incident mode, P is the positive norm reflected mode, and N* is the negative norm one, signalling particle creation, is derived, aimed to an approximate description of the phenomenon. Horizons and barrier penetration play manifestly a key-role in giving rise to pair-creation. The non-dispersive limit is also correctly recovered. Drawbacks of the model are also pointed out and a possible solution ad hoc is suggested. |
gr-qc/0612107 | Ozay Gurtug | Mustafa Halilsoy and Ozay Gurtug | Search For Gravitational Waves Through the Electromagnetic Faraday
Rotation | Final version. Minor revision, new figures and references are added.
To appear in Physical Review D | Phys.Rev.D75:124021,2007 | 10.1103/PhysRevD.75.124021 | null | gr-qc | null | A method is given which renders indirect detection of strong gravitational
waves possible. This is based on the reflection (collision) of a linearly
polarized electromagnetic shock wave from (with) a cross polarized impulsive
and shock gravitational waves in accordance with the general theory of
relativity. This highly non-linear process induces a detectable Faraday
rotation in the polarization vector of the electromagnetic field.
| [
{
"created": "Mon, 18 Dec 2006 06:31:42 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jun 2007 11:18:54 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Jun 2007 05:56:43 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Halilsoy",
"Mustafa",
""
],
[
"Gurtug",
"Ozay",
""
]
] | A method is given which renders indirect detection of strong gravitational waves possible. This is based on the reflection (collision) of a linearly polarized electromagnetic shock wave from (with) a cross polarized impulsive and shock gravitational waves in accordance with the general theory of relativity. This highly non-linear process induces a detectable Faraday rotation in the polarization vector of the electromagnetic field. |
1906.00450 | Gopi Kant Goswami Dr | G. K. Goswami, Anirudh Pradhan and A. Beesham | FLRW accelerating universe with interactive dark energy | 11 pages, 7 figures | Pramana-J. Phys. Vol. 93, No. 6, Dec (2019), 89 (9 pages) | 10.1007/s12043-019-1856-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have developed an accelerating cosmological model for the present universe
which is phantom for the period $ (0 \leq z \leq 1.99)$ and quintessence phase
for $(1.99 \leq z \leq 2.0315)$. The universe is assumed to be filled with
barotropic and dark energy(DE) perfect fluid in which DE interact with matter.
For a deceleration parameter(DP) having decelerating-accelerating transition
phase of universe, we assume hybrid expansion law for scale factor. The
transition red shift for the model is obtained as $z_t = 0.956$. The model
satisfies current observational constraints.
| [
{
"created": "Sun, 2 Jun 2019 16:57:41 GMT",
"version": "v1"
}
] | 2021-08-02 | [
[
"Goswami",
"G. K.",
""
],
[
"Pradhan",
"Anirudh",
""
],
[
"Beesham",
"A.",
""
]
] | We have developed an accelerating cosmological model for the present universe which is phantom for the period $ (0 \leq z \leq 1.99)$ and quintessence phase for $(1.99 \leq z \leq 2.0315)$. The universe is assumed to be filled with barotropic and dark energy(DE) perfect fluid in which DE interact with matter. For a deceleration parameter(DP) having decelerating-accelerating transition phase of universe, we assume hybrid expansion law for scale factor. The transition red shift for the model is obtained as $z_t = 0.956$. The model satisfies current observational constraints. |
2309.05093 | Do\u{g}a Veske | Lavinia Heisenberg, David Maibach, Do\u{g}a Veske | Topological Dark Matter in LIGO Data | 13 pages with 12 figures. Comments are welcome | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the efforts of searching for dark matter, gravitational wave
interferometers have been recently proposed as a promising probe. These highly
sensitive instruments are potentially be able to detect the interactions of
dark matter with the detectors. In this work, we explored the possibilities of
discovering topological dark matter with LIGO detectors. We analyzed domain
walls consisting of axion-like dark matter passing through Earth, leaving
traces in multiple detectors simultaneously. Considering dark matter
interactions with the light in the interferometer and with the beamsplitter, we
performed the first analysis of the topological dark matter with the
gravitational-wave strain data. We examined whether astrophysically unexpected
triggers could be explained by domain wall passages. We found that all of the
binary black hole mergers we analyzed favored the binary black hole merger
hypothesis rather than the domain wall hypothesis, with the closest being
GW190521. Moreover we found that some of topological dark matter signals can be
caught by binary black hole searches. Finally, we found that glitches in the
data can inevitably limit the dark matter searches for certain parameters.
These results are expected to guide the future searches and analyses.
| [
{
"created": "Sun, 10 Sep 2023 17:38:56 GMT",
"version": "v1"
}
] | 2023-09-14 | [
[
"Heisenberg",
"Lavinia",
""
],
[
"Maibach",
"David",
""
],
[
"Veske",
"Doğa",
""
]
] | In the efforts of searching for dark matter, gravitational wave interferometers have been recently proposed as a promising probe. These highly sensitive instruments are potentially be able to detect the interactions of dark matter with the detectors. In this work, we explored the possibilities of discovering topological dark matter with LIGO detectors. We analyzed domain walls consisting of axion-like dark matter passing through Earth, leaving traces in multiple detectors simultaneously. Considering dark matter interactions with the light in the interferometer and with the beamsplitter, we performed the first analysis of the topological dark matter with the gravitational-wave strain data. We examined whether astrophysically unexpected triggers could be explained by domain wall passages. We found that all of the binary black hole mergers we analyzed favored the binary black hole merger hypothesis rather than the domain wall hypothesis, with the closest being GW190521. Moreover we found that some of topological dark matter signals can be caught by binary black hole searches. Finally, we found that glitches in the data can inevitably limit the dark matter searches for certain parameters. These results are expected to guide the future searches and analyses. |
1411.7066 | Ramin G. Daghigh | Ramin G. Daghigh and Michael D. Green | High Overtone Quasinormal Modes of Analog Black Holes and the Small
Scale Structure of the Background Fluid | 14 pages, 3 figures | null | 10.1088/0264-9381/32/9/095003 | null | gr-qc cond-mat.other | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this paper is to build a foundation for, and explore the
possibility of, using high overtone quasinormal modes of analog black holes to
probe the small scale (microscopic) structure of a background fluid in which an
analog black hole is formed. This may provide a tool to study the small scale
structure of some interesting quantum systems such as Bose-Einstein
condensates. In order to build this foundation, we first look into the
hydrodynamic case where we calculate the high overtone quasinormal mode
frequencies of a 3+1 dimensional canonical non-rotating acoustic black hole.
The leading order calculations have been done earlier in the literature. Here,
we obtain the first order correction. We then analyze the high overtone
quasinormal modes of acoustic black holes in a Bose-Einstein condensate using
the linearized Gross-Pitaevskii equation. We point out that at the high
overtone quasinormal mode limit, the only term that is important in the
linearized Gross-Pitaevskii equation is the quantum potential term, which is a
small scale effect.
| [
{
"created": "Tue, 25 Nov 2014 23:25:06 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Daghigh",
"Ramin G.",
""
],
[
"Green",
"Michael D.",
""
]
] | The goal of this paper is to build a foundation for, and explore the possibility of, using high overtone quasinormal modes of analog black holes to probe the small scale (microscopic) structure of a background fluid in which an analog black hole is formed. This may provide a tool to study the small scale structure of some interesting quantum systems such as Bose-Einstein condensates. In order to build this foundation, we first look into the hydrodynamic case where we calculate the high overtone quasinormal mode frequencies of a 3+1 dimensional canonical non-rotating acoustic black hole. The leading order calculations have been done earlier in the literature. Here, we obtain the first order correction. We then analyze the high overtone quasinormal modes of acoustic black holes in a Bose-Einstein condensate using the linearized Gross-Pitaevskii equation. We point out that at the high overtone quasinormal mode limit, the only term that is important in the linearized Gross-Pitaevskii equation is the quantum potential term, which is a small scale effect. |
1708.07430 | Yusuf Kucukakca | Ganim Gecim and Yusuf Kucukakca | Scalar-Tensor Teleparallel Gravity With Boundary Term by Noether
Symmetries | 9 pages, 5 figures | null | 10.1142/S0219887818501517 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of teleparallel gravity, the Friedman-Robertson-Walker
cosmological model with scalar tensor theory where scalar field is
non-minimally coupled to both the torsion scalar and boundary term is studied.
Utilizing the Noether symmetry approach in such a theory, we obtain the
explicit forms of the couplings and potential as a function the scalar field.
We present some important cosmological solutions for the modified field
equations using these functions getting via the Noether symmetry approach.
Finally, the interesting cosmological properties of these solutions are
discussed in detail, and it is shown that they can describe a universe lead to
the late time accelerating expansion.
| [
{
"created": "Thu, 24 Aug 2017 14:13:24 GMT",
"version": "v1"
}
] | 2018-08-29 | [
[
"Gecim",
"Ganim",
""
],
[
"Kucukakca",
"Yusuf",
""
]
] | In the framework of teleparallel gravity, the Friedman-Robertson-Walker cosmological model with scalar tensor theory where scalar field is non-minimally coupled to both the torsion scalar and boundary term is studied. Utilizing the Noether symmetry approach in such a theory, we obtain the explicit forms of the couplings and potential as a function the scalar field. We present some important cosmological solutions for the modified field equations using these functions getting via the Noether symmetry approach. Finally, the interesting cosmological properties of these solutions are discussed in detail, and it is shown that they can describe a universe lead to the late time accelerating expansion. |
1107.1034 | Mehrdad Farhoudi Prof. | Mehrdad Farhoudi | Third Order Lagrangians, Weyl Invariants & Classical Trace Anomaly in
Six Dimensions | 26 pages, appendix and references added | Inter. J. Theor. Phys. Vol. 52, 4110-4138 (2013) | 10.1007/s10773-013-1725-x | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have proceeded analogy of Einstein tensor and alternative form of Einstein
field equations for generic coeffcients of eight terms in third order of
Lovelock Lagrangian. We have found constraint between the coeffcients into two
forms, an independent and a dimensional dependent versions. Each form has three
degrees of freedom, and not only the exact coeffcients of third order Lovelock
Lagrangian satisfy the two forms of constraints, also the two independent cubic
of Weyl tensor satisfy the independent constraint in six dimensions and yield
the dimensional dependent version identically independent of dimension. We have
introduced most general effective expression for a total third order type
Lagrangian with the homogeneity degree number three which includes the previous
eight terms plus new three ones among all seventeen independent terms. We have
proceeded analogy for this combination, and have achieved relevant constraint.
We have shown that expressions given in literature as third Weyl invariant
combination in six dimensions satisfy this constraint. Thus, we suggest that
these constraint relations to be considered as the necessary consistency
conditions on the numerical coeffcients that a Weyl invariant in six dimensions
should satisfy. We have calculated the "classical" trace anomaly (an approach
that was presented in our previous works) for introduced total third order type
Lagrangian and have achieved general expression with four degrees of freedom in
more than six dimensions. We have demonstrated that resulted expression
contains exactly relevant coeffcient of Schwinger-DeWitt proper time method
(linked with relevant heat kernel coeffcient) in six dimensions, as a
particular case. Our approach can be regarded as alternative derivation of
trace anomaly which also gives general expression with the relevant degrees of
freedom.
| [
{
"created": "Wed, 6 Jul 2011 06:42:21 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Aug 2011 15:09:56 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Aug 2013 13:46:01 GMT",
"version": "v3"
}
] | 2013-10-04 | [
[
"Farhoudi",
"Mehrdad",
""
]
] | We have proceeded analogy of Einstein tensor and alternative form of Einstein field equations for generic coeffcients of eight terms in third order of Lovelock Lagrangian. We have found constraint between the coeffcients into two forms, an independent and a dimensional dependent versions. Each form has three degrees of freedom, and not only the exact coeffcients of third order Lovelock Lagrangian satisfy the two forms of constraints, also the two independent cubic of Weyl tensor satisfy the independent constraint in six dimensions and yield the dimensional dependent version identically independent of dimension. We have introduced most general effective expression for a total third order type Lagrangian with the homogeneity degree number three which includes the previous eight terms plus new three ones among all seventeen independent terms. We have proceeded analogy for this combination, and have achieved relevant constraint. We have shown that expressions given in literature as third Weyl invariant combination in six dimensions satisfy this constraint. Thus, we suggest that these constraint relations to be considered as the necessary consistency conditions on the numerical coeffcients that a Weyl invariant in six dimensions should satisfy. We have calculated the "classical" trace anomaly (an approach that was presented in our previous works) for introduced total third order type Lagrangian and have achieved general expression with four degrees of freedom in more than six dimensions. We have demonstrated that resulted expression contains exactly relevant coeffcient of Schwinger-DeWitt proper time method (linked with relevant heat kernel coeffcient) in six dimensions, as a particular case. Our approach can be regarded as alternative derivation of trace anomaly which also gives general expression with the relevant degrees of freedom. |
2009.11894 | Oleg Zaslavskii | O. B. Zaslavskii | New scenarios of high-energy particle collisions near wormholes | 13 pages. One more scenario considered, ref. 15 added. To appear in
Universe (special issue on wormholes) | Universe 6, 227 (2020) | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We suggest two new scenarios of high-energy particle collisions in the
background of a wormhole. In scenario 1 the novelty consists in that the effect
does not require two particles coming from different mouths. Instead, all such
scenarios of high energy collisions develop, when an experimenter sends
particles towards a wormhole from the same side of the throat. For static
wormholes, this approach leads to indefinitely large energy in the center of
mass. For rotating wormholes, it makes possible the super-Penrose process
(unbounded energies measured at infinity). In scenario 2, one of colliding
particles oscillates near the wormhole throat from the very beginning. In this
sense, scenario 2 is intermediate between the standard one and scenario 1 since
the particle under discussion does not come from infinity at all.
| [
{
"created": "Thu, 24 Sep 2020 18:37:57 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Sep 2020 18:07:01 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Nov 2020 11:47:46 GMT",
"version": "v3"
}
] | 2020-12-01 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We suggest two new scenarios of high-energy particle collisions in the background of a wormhole. In scenario 1 the novelty consists in that the effect does not require two particles coming from different mouths. Instead, all such scenarios of high energy collisions develop, when an experimenter sends particles towards a wormhole from the same side of the throat. For static wormholes, this approach leads to indefinitely large energy in the center of mass. For rotating wormholes, it makes possible the super-Penrose process (unbounded energies measured at infinity). In scenario 2, one of colliding particles oscillates near the wormhole throat from the very beginning. In this sense, scenario 2 is intermediate between the standard one and scenario 1 since the particle under discussion does not come from infinity at all. |
2206.03500 | Maximilian Koegler | Ottavia Balducci, Stefan Hofmann, Maximilian Koegler | Dark Matter Jets of Rotating Black Holes | 5 pages, 3 figures | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel approach which produces Dark Matter jets along the
rotation axis of Kerr black holes utilizing the Penrose process. The properties
of these jets are investigated, as well as their potential to create Dark
Matter overdensities in the solar system and in the vicinity of the black hole.
We discover a highly collimated and long-range Dark Matter jet with a density
that is most sensitive to the mass and distance to the black hole.
| [
{
"created": "Tue, 7 Jun 2022 18:00:00 GMT",
"version": "v1"
}
] | 2022-06-09 | [
[
"Balducci",
"Ottavia",
""
],
[
"Hofmann",
"Stefan",
""
],
[
"Koegler",
"Maximilian",
""
]
] | We present a novel approach which produces Dark Matter jets along the rotation axis of Kerr black holes utilizing the Penrose process. The properties of these jets are investigated, as well as their potential to create Dark Matter overdensities in the solar system and in the vicinity of the black hole. We discover a highly collimated and long-range Dark Matter jet with a density that is most sensitive to the mass and distance to the black hole. |
1204.1401 | Xin-Zhou Li | Xin-zhou Li, Ping Xi, Qun Zhang | Gravitating tensor monopole in a Lorentz-violating field theory | 5 pages, 4 figures | Phys. Rev. D85:085030,2012 | 10.1103/physRevD.85.085030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a solution of the coupled Einstein and rank-two antisymmetric
tensor field equations where Lorentz symmetry is spontaneously broken, and we
discuss its observational signatures. Especially, the deflection angles have
important qualitative differences between tensor and scalar monopoles. If a
monopole were to be detected, it would be discriminated whether or not to
correspond to a tensor one. This phenomenon might open up new direction in the
search of Lorentz violation with future astrophysical observations.
| [
{
"created": "Fri, 6 Apr 2012 03:25:27 GMT",
"version": "v1"
}
] | 2012-04-30 | [
[
"Li",
"Xin-zhou",
""
],
[
"Xi",
"Ping",
""
],
[
"Zhang",
"Qun",
""
]
] | We present a solution of the coupled Einstein and rank-two antisymmetric tensor field equations where Lorentz symmetry is spontaneously broken, and we discuss its observational signatures. Especially, the deflection angles have important qualitative differences between tensor and scalar monopoles. If a monopole were to be detected, it would be discriminated whether or not to correspond to a tensor one. This phenomenon might open up new direction in the search of Lorentz violation with future astrophysical observations. |
2011.10836 | Marco Maceda | Daniel Flores-Alfonso and Blanca Ang\'elica Gonz\'alez-Morales and
Rom\'an Linares and Marco Maceda | Black holes and gravitational waves sourced by non-linear duality
rotation-invariant conformal electromagnetic matter | 9 pages, 1 figure | Phys. Lett. B 812 (2021) 136011 | 10.1016/j.physletb.2020.136011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Maxwell's equations are invariant under both duality rotations and conformal
transformations. Recently Bandos, Lechner, Sorokin, and Townsend have found a
nonlinear generalisation of electrodynamics which possesses both of these
symmetries. We couple this theory to General Relativity and explore
self-gravitating configurations with a clear physical interpretation. We find
charged black holes and exact gravitational waves. The black hole geometry is
Reissner-Nordstr\"om, however, the non-linearity parameter acts as a screening
factor allowing extremal configurations where the mass of the black hole is
smaller than its charge. Furthermore, we also discuss the phenomenon of
birefringence and determine the optical metrics associated to the propagation
of photons.
| [
{
"created": "Sat, 21 Nov 2020 18:20:49 GMT",
"version": "v1"
}
] | 2020-12-14 | [
[
"Flores-Alfonso",
"Daniel",
""
],
[
"González-Morales",
"Blanca Angélica",
""
],
[
"Linares",
"Román",
""
],
[
"Maceda",
"Marco",
""
]
] | Maxwell's equations are invariant under both duality rotations and conformal transformations. Recently Bandos, Lechner, Sorokin, and Townsend have found a nonlinear generalisation of electrodynamics which possesses both of these symmetries. We couple this theory to General Relativity and explore self-gravitating configurations with a clear physical interpretation. We find charged black holes and exact gravitational waves. The black hole geometry is Reissner-Nordstr\"om, however, the non-linearity parameter acts as a screening factor allowing extremal configurations where the mass of the black hole is smaller than its charge. Furthermore, we also discuss the phenomenon of birefringence and determine the optical metrics associated to the propagation of photons. |
1008.3111 | Peter K.F. Kuhfittig | Peter K. F. Kuhfittig | The stability of thin-shell wormholes with a phantom-like equation of
state | 7 pages, 4 figures | Acta Phys.Polon.B41:2017-2019,2010 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper discusses the stability to linearized radial perturbations of
spherically symmetric thin-shell wormholes with a "phantom-like" equation of
state for the exotic matter at the throat: $P=\omega\sigma$, $\omega<0$, where
$\sigma$ is the energy-density of the shell and $P$ the surface pressure. This
equation is analogous to the generalized Chaplygin-gas equation of state used
by E.F. Eiroa. The analysis, which differes from Eiroa's in its basic approach,
is carried out for wormholes constructed from the following spacetimes:
Schwarzschild, de Sitter and anti de Sitter, Reissner-Nordstrom, and regular
charged black-hole spacetimes, as well as from black holes in dilaton and
generalized dilaton-axion gravity.
| [
{
"created": "Wed, 18 Aug 2010 15:25:44 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Oct 2010 23:41:53 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Apr 2012 21:11:27 GMT",
"version": "v3"
},
{
"created": "Thu, 9 Jun 2016 14:01:20 GMT",
"version": "v4"
}
] | 2016-06-10 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | This paper discusses the stability to linearized radial perturbations of spherically symmetric thin-shell wormholes with a "phantom-like" equation of state for the exotic matter at the throat: $P=\omega\sigma$, $\omega<0$, where $\sigma$ is the energy-density of the shell and $P$ the surface pressure. This equation is analogous to the generalized Chaplygin-gas equation of state used by E.F. Eiroa. The analysis, which differes from Eiroa's in its basic approach, is carried out for wormholes constructed from the following spacetimes: Schwarzschild, de Sitter and anti de Sitter, Reissner-Nordstrom, and regular charged black-hole spacetimes, as well as from black holes in dilaton and generalized dilaton-axion gravity. |
1812.01993 | Jae-Weon Lee Prof. | Jae-Weon Lee, Hyeong-Chan Kim, Jungjai Lee | Holographic Dark Energy and Quantum Entanglement | to be published in JKPS | Journal of the Korean Physical Society, Volume 74, Issue 1, pp 1
(2019) | 10.3938/jkps.74.1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we briefly review the holographic dark energy model and
introduce the idea that dark energy is a kind of thermal energy related to the
quantum entanglement of the vacuum across a cosmic future event horizon. The
holographic dark energy model comes from a theoretical attempt to apply the
holographic principle to the dark energy problem and follows the idea that the
short distance cut-off or ultraviolet (UV) cut-off is related to the long
distance cut-off or infrared (IR) cut-off. The IR cut-off relevant to dark
energy is the size of the future event horizon. This model gives a holographic
dark energy comparable to the observational data. Though this model is in good
agreement with observational data, some problems (non-locality, circular logic,
causality problem, $\it etc.$) exist due to the use of the future event horizon
as a present IR cut-off. These problems of the holographic dark energy model
are considerably resolved using action principle and equations of motion.
Finally, we discuss the relation between quantum entanglement and dark energy
which is connected to the more fundamental relation between entanglement and
gravity.
| [
{
"created": "Mon, 3 Dec 2018 04:46:59 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Dec 2018 02:56:39 GMT",
"version": "v2"
}
] | 2019-01-30 | [
[
"Lee",
"Jae-Weon",
""
],
[
"Kim",
"Hyeong-Chan",
""
],
[
"Lee",
"Jungjai",
""
]
] | In this paper, we briefly review the holographic dark energy model and introduce the idea that dark energy is a kind of thermal energy related to the quantum entanglement of the vacuum across a cosmic future event horizon. The holographic dark energy model comes from a theoretical attempt to apply the holographic principle to the dark energy problem and follows the idea that the short distance cut-off or ultraviolet (UV) cut-off is related to the long distance cut-off or infrared (IR) cut-off. The IR cut-off relevant to dark energy is the size of the future event horizon. This model gives a holographic dark energy comparable to the observational data. Though this model is in good agreement with observational data, some problems (non-locality, circular logic, causality problem, $\it etc.$) exist due to the use of the future event horizon as a present IR cut-off. These problems of the holographic dark energy model are considerably resolved using action principle and equations of motion. Finally, we discuss the relation between quantum entanglement and dark energy which is connected to the more fundamental relation between entanglement and gravity. |
1109.6201 | Matteo Luca Ruggiero | Angelo Tartaglia, Matteo Luca Ruggiero, Emiliano Capolongo | A relativistic navigation system for space | 11 pages | Acta Futura 4 (2011) 33.40 | 10.2420/AF04.2011.33 | null | gr-qc physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present here a method for the relativistic positioning in spacetime based
on the reception of pulses from sources of electromagnetic signals whose
worldline is known. The method is based on the use of a four-dimensional grid
covering the whole spacetime and made of the null hypersurfaces representing
the propagating pulses. In our first approach to the problem of positioning we
consider radio-pulsars at infinity as primary sources of the required signals.
The reason is that, besides being very good clocks, pulsars can be considered
as being fixed stars for reasonably long times. The positioning is obtained
linearizing the worldline of the observer for times of the order of a few
periods of the signals. We present an exercise where the use of our method
applied to the signals from four real pulsars permits the reconstruction of the
motion of the Earth with respect to the fixed stars during three days. The
uncertainties and the constraints of the method are discussed and the
possibilities of using moving artificial sources carried around by celestial
bodies or spacecrafts in the Solar System is also discussed.
| [
{
"created": "Wed, 28 Sep 2011 13:34:12 GMT",
"version": "v1"
}
] | 2011-09-29 | [
[
"Tartaglia",
"Angelo",
""
],
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Capolongo",
"Emiliano",
""
]
] | We present here a method for the relativistic positioning in spacetime based on the reception of pulses from sources of electromagnetic signals whose worldline is known. The method is based on the use of a four-dimensional grid covering the whole spacetime and made of the null hypersurfaces representing the propagating pulses. In our first approach to the problem of positioning we consider radio-pulsars at infinity as primary sources of the required signals. The reason is that, besides being very good clocks, pulsars can be considered as being fixed stars for reasonably long times. The positioning is obtained linearizing the worldline of the observer for times of the order of a few periods of the signals. We present an exercise where the use of our method applied to the signals from four real pulsars permits the reconstruction of the motion of the Earth with respect to the fixed stars during three days. The uncertainties and the constraints of the method are discussed and the possibilities of using moving artificial sources carried around by celestial bodies or spacecrafts in the Solar System is also discussed. |
0908.0779 | Cristian R. Ghezzi | Cristian R. Ghezzi | Anisotropic dark energy stars | 12 pages, 6 figures, final manuscript, Accepted for publication in
Astrophysics & Space Science | Astrophys.Space Sci.333:437-447,2011 | 10.1007/s10509-011-0663-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A model of compact object coupled to inhomogeneous anisotropic dark energy is
studied. It is assumed a variable dark energy that suffers a phase transition
at a critical density. The anisotropic Lambda-Tolman-Oppenheimer-Volkoff
equations are integrated to know the structure of these objects. The anisotropy
is concentrated on a thin shell where the phase transition takes place, while
the rest of the star remains isotropic. The family of solutions obtained
depends on the coupling parameter between the dark energy and the fermion
matter. The solutions share several features in common with the gravastar
model. There is a critical coupling parameter that gives non-singular black
hole solutions. The mass-radius relations are studied as well as the internal
structure of the compact objects. The hydrodynamic stability of the models is
analyzed using a standard test from the mass-radius relation. For each
permissible value of the coupling parameter there is a maximum mass, so the
existence of black holes is unavoidable within this model.
| [
{
"created": "Thu, 6 Aug 2009 01:16:13 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Sep 2009 01:55:23 GMT",
"version": "v2"
},
{
"created": "Mon, 21 Feb 2011 23:17:26 GMT",
"version": "v3"
}
] | 2011-05-12 | [
[
"Ghezzi",
"Cristian R.",
""
]
] | A model of compact object coupled to inhomogeneous anisotropic dark energy is studied. It is assumed a variable dark energy that suffers a phase transition at a critical density. The anisotropic Lambda-Tolman-Oppenheimer-Volkoff equations are integrated to know the structure of these objects. The anisotropy is concentrated on a thin shell where the phase transition takes place, while the rest of the star remains isotropic. The family of solutions obtained depends on the coupling parameter between the dark energy and the fermion matter. The solutions share several features in common with the gravastar model. There is a critical coupling parameter that gives non-singular black hole solutions. The mass-radius relations are studied as well as the internal structure of the compact objects. The hydrodynamic stability of the models is analyzed using a standard test from the mass-radius relation. For each permissible value of the coupling parameter there is a maximum mass, so the existence of black holes is unavoidable within this model. |
1509.09197 | Javier Olmedo | Javier Olmedo, Daniel Mart\'in de Blas and Tomasz Paw{\l}owski | Local rotational symmetry Gowdy model in Loop Quantum Gravity | 5 pages, new version adapted to the MG14 proceeding, title and
abstract changed | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a complete quantization for the Gowdy model with local rotational
symmetry in vacuum. We start with a redefinition of the classical constraint
algebra such that the Hamiltonian constraint has a vanishing Poisson bracket
with itself. We apply a canonical quantization within loop quantum gravity and
an improved dynamics scheme. We construct the exact solutions to the
constraints and the physical Hilbert space, together with the physical
observables. The quantization provides a physical picture without
singularities. Besides, a genuine discretization of the spatial geometry
emerges by means of a new quantum observable without classical analogue.
| [
{
"created": "Wed, 30 Sep 2015 14:44:59 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jun 2017 16:21:16 GMT",
"version": "v2"
}
] | 2017-06-21 | [
[
"Olmedo",
"Javier",
""
],
[
"de Blas",
"Daniel Martín",
""
],
[
"Pawłowski",
"Tomasz",
""
]
] | We provide a complete quantization for the Gowdy model with local rotational symmetry in vacuum. We start with a redefinition of the classical constraint algebra such that the Hamiltonian constraint has a vanishing Poisson bracket with itself. We apply a canonical quantization within loop quantum gravity and an improved dynamics scheme. We construct the exact solutions to the constraints and the physical Hilbert space, together with the physical observables. The quantization provides a physical picture without singularities. Besides, a genuine discretization of the spatial geometry emerges by means of a new quantum observable without classical analogue. |
0704.3485 | Xing-Hao Ye | Xing-Hao Ye, Qiang Lin | A Simple Optical Analysis of Gravitational Lensing | 4 pages, 6 figures | null | 10.1080/09500340701618395 | null | gr-qc | null | We analyzed the influence of static gravitational field on the vacuum and
proposed the concept of inhomogeneous vacuum. According to the corresponding
Fermat's principle in the general relativity, we derived a graded refractive
index of vacuum in a static gravitational field. We found that the light
deflection in a gravitational field can be calculated correctly with the use of
this refractive index and therefore the gravitational lensing can be treated
conveniently with the optical method. For illustration, we simulated the
imaging of gravitational lensing, figured out the time delay between the two
images and calculated the lens mass in a conventional optical way.
| [
{
"created": "Thu, 26 Apr 2007 12:07:47 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Ye",
"Xing-Hao",
""
],
[
"Lin",
"Qiang",
""
]
] | We analyzed the influence of static gravitational field on the vacuum and proposed the concept of inhomogeneous vacuum. According to the corresponding Fermat's principle in the general relativity, we derived a graded refractive index of vacuum in a static gravitational field. We found that the light deflection in a gravitational field can be calculated correctly with the use of this refractive index and therefore the gravitational lensing can be treated conveniently with the optical method. For illustration, we simulated the imaging of gravitational lensing, figured out the time delay between the two images and calculated the lens mass in a conventional optical way. |
1403.2623 | Kourosh Nozari | M. A. Gorji, K. Nozari and B. Vakili | Spacetime singularity resolution in Snyder noncommutative space | 11 pages, 4 figures, Revised for PRD, title changed | Phys. Rev. D 89, 084072 (2014) | 10.1103/PhysRevD.89.084072 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by quantum gravity proposal, we construct a deformed phase space
which supports the UV and IR cutoffs. We show that the Liouville theorem is
satisfied in the deformed phase space which allows us to formulate the
thermodynamics of the early Universe in the semiclassical regime. Applying the
proposed method to the Snyder noncommutative space, we find a temperature
dependent equation of state which opens a new window for natural realization of
inflation as a phase transition from quantum gravity regime to the standard
radiation dominated era. Also we obtain finite energy and entropy densities for
the Universe, when at least the Weak Energy Condition is satisfied. We show
that there is a minimum size for the Universe which is proportional to the
Planck length and consequently the Big Bang singularity is removed.
| [
{
"created": "Tue, 11 Mar 2014 16:01:59 GMT",
"version": "v1"
},
{
"created": "Sun, 18 May 2014 15:53:42 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Gorji",
"M. A.",
""
],
[
"Nozari",
"K.",
""
],
[
"Vakili",
"B.",
""
]
] | Inspired by quantum gravity proposal, we construct a deformed phase space which supports the UV and IR cutoffs. We show that the Liouville theorem is satisfied in the deformed phase space which allows us to formulate the thermodynamics of the early Universe in the semiclassical regime. Applying the proposed method to the Snyder noncommutative space, we find a temperature dependent equation of state which opens a new window for natural realization of inflation as a phase transition from quantum gravity regime to the standard radiation dominated era. Also we obtain finite energy and entropy densities for the Universe, when at least the Weak Energy Condition is satisfied. We show that there is a minimum size for the Universe which is proportional to the Planck length and consequently the Big Bang singularity is removed. |
1901.10448 | Artur Sergyeyev | A. Sergyeyev, A. Wojnar | The Palatini star: exact solutions of the modified Lane-Emden equation | 6 pages, 1 figure | null | 10.1140/epjc/s10052-020-7876-z | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two exact solutions for $n=0$ and $n=1$ of the Palatini-modified Lane-Emden
equation are found. We have employed these solutions to describe a
Palatini-Newtonian neutron star and compared the result with the pure Newtonian
counterpart. It turned out that for the negative parameter of the Starobinsky
model the star is heavier and larger.
| [
{
"created": "Tue, 29 Jan 2019 18:54:54 GMT",
"version": "v1"
}
] | 2020-04-22 | [
[
"Sergyeyev",
"A.",
""
],
[
"Wojnar",
"A.",
""
]
] | Two exact solutions for $n=0$ and $n=1$ of the Palatini-modified Lane-Emden equation are found. We have employed these solutions to describe a Palatini-Newtonian neutron star and compared the result with the pure Newtonian counterpart. It turned out that for the negative parameter of the Starobinsky model the star is heavier and larger. |
1603.06206 | Seema Satin | Seema Satin, H.T.Cho, Bei Lok Hu | Conformally-related Einstein-Langevin equations for metric fluctuations
in stochastic gravity | null | Phys. Rev. D 94, 064019 (2016) | 10.1103/PhysRevD.94.064019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a conformally-coupled scalar field we obtain the conformally-related
Einstein-Langevin equations, using appropriate transformations for all the
quantities in the equations between two conformally-related spacetimes. In
particular, we analyze the transformations of the influence action, the stress
energy tensor, the noise kernel and the dissipation kernel. In due course the
fluctuation-dissipation relation is also discussed. The analysis in this paper
thereby facilitates a general solution to the Einstein-Langevin equation once
the solution of the equation in a simpler, conformally-related spacetime is
known. For example, from the Minkowski solution of Martin and Verdaguer, those
of the Einstein-Langevin equations in conformally-flat spacetimes, especially
for spatially-flat Friedmann-Robertson-Walker models, can be readily obtained.
| [
{
"created": "Sun, 20 Mar 2016 12:03:23 GMT",
"version": "v1"
}
] | 2016-09-14 | [
[
"Satin",
"Seema",
""
],
[
"Cho",
"H. T.",
""
],
[
"Hu",
"Bei Lok",
""
]
] | For a conformally-coupled scalar field we obtain the conformally-related Einstein-Langevin equations, using appropriate transformations for all the quantities in the equations between two conformally-related spacetimes. In particular, we analyze the transformations of the influence action, the stress energy tensor, the noise kernel and the dissipation kernel. In due course the fluctuation-dissipation relation is also discussed. The analysis in this paper thereby facilitates a general solution to the Einstein-Langevin equation once the solution of the equation in a simpler, conformally-related spacetime is known. For example, from the Minkowski solution of Martin and Verdaguer, those of the Einstein-Langevin equations in conformally-flat spacetimes, especially for spatially-flat Friedmann-Robertson-Walker models, can be readily obtained. |
1011.1916 | Lorenzo Iorio | Lorenzo Iorio | Dynamical orbital effects of General Relativity on the
satellite-to-satellite range and range-rate in the GRACE mission: a
sensitivity analysis | LaTex, 24 pages, 5 figures, 9 tables. Accepted for publication in
Advances in Space Research (ASR) | Adv.Sp.Res.50:334-345,2012 | 10.1016/j.asr.2012.04.012 | null | gr-qc astro-ph.EP hep-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically investigate the impact of GTR on the orbital part of the
satellite-to-satellite range \rho and range-rate \dot\rho of the twin GRACE A/B
spacecrafts through their dynamical equations of motion integrated in an
Earth-centered frame over a time span \Delta t=1 d. Instead, the GTR effects
connected with the propagation of the electromagnetic waves linking the
spacecrafts are neglected. The present-day accuracies in measuring the GRACE
biased range and range-rate are \sigma_\rho\sim 1-10 \mum, \sigma_\dot\rho\sim
0.1-1 \mum s^-1; studies for a follow-on of such a mission points toward a
range-rate accuracy of the order of \sigma_\dot\rho\sim 1 nm s^-1 or better.
The GTR range and range-rate effects turn out to be \Delta\rho=80 \mum and
\Delta\dot\rho=0.012 \mum s^-1 (Lense-Thirring), and \Delta\rho=6000 \mum and
\Delta\dot\rho=10 \mum s^-1 (Schwarzschild). We also compute the dynamical
range and range-rate perturbations caused by the first six zonal harmonic
coefficients J_L, L=2,3,4,5,6,7 of the classical multipolar expansion of the
terrestrial gravitational potential in order to evaluate their aliasing impact
on the relativistic effects. Conversely, we also quantitatively, and
preliminarily, assess the possible a-priori \virg{imprinting} of GTR itself,
not solved-for in all the GRACE-based Earth's gravity models produced so far,
on the estimated values of the low degree zonals of the geopotential. The
present sensitivity analysis can also be extended, in principle, to different
orbital configurations in order to design a suitable dedicated mission able to
accurately measure the relativistic effects considered.
| [
{
"created": "Mon, 8 Nov 2010 21:07:23 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Nov 2010 09:58:24 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Mar 2011 11:31:19 GMT",
"version": "v3"
},
{
"created": "Sat, 29 Oct 2011 17:28:01 GMT",
"version": "v4"
},
{
"cre... | 2012-06-12 | [
[
"Iorio",
"Lorenzo",
""
]
] | We numerically investigate the impact of GTR on the orbital part of the satellite-to-satellite range \rho and range-rate \dot\rho of the twin GRACE A/B spacecrafts through their dynamical equations of motion integrated in an Earth-centered frame over a time span \Delta t=1 d. Instead, the GTR effects connected with the propagation of the electromagnetic waves linking the spacecrafts are neglected. The present-day accuracies in measuring the GRACE biased range and range-rate are \sigma_\rho\sim 1-10 \mum, \sigma_\dot\rho\sim 0.1-1 \mum s^-1; studies for a follow-on of such a mission points toward a range-rate accuracy of the order of \sigma_\dot\rho\sim 1 nm s^-1 or better. The GTR range and range-rate effects turn out to be \Delta\rho=80 \mum and \Delta\dot\rho=0.012 \mum s^-1 (Lense-Thirring), and \Delta\rho=6000 \mum and \Delta\dot\rho=10 \mum s^-1 (Schwarzschild). We also compute the dynamical range and range-rate perturbations caused by the first six zonal harmonic coefficients J_L, L=2,3,4,5,6,7 of the classical multipolar expansion of the terrestrial gravitational potential in order to evaluate their aliasing impact on the relativistic effects. Conversely, we also quantitatively, and preliminarily, assess the possible a-priori \virg{imprinting} of GTR itself, not solved-for in all the GRACE-based Earth's gravity models produced so far, on the estimated values of the low degree zonals of the geopotential. The present sensitivity analysis can also be extended, in principle, to different orbital configurations in order to design a suitable dedicated mission able to accurately measure the relativistic effects considered. |
gr-qc/9503002 | Arlen Anderson | Arlen Anderson | Unitarity Restoration for the Product of Nonunitary Operators | 5 pages, LaTeX. | null | null | null | gr-qc | null | A proof is given that the polar decomposition procedure for unitarity
restoration works for products of invertible nonunitary operators. A brief
discussion follows that the unitarity restoration procedure, applied to
propagators in spacetimes containing closed timelike curves, is analogous to
the original introduction by Feynman of ghosts to restore unitarity in
non-abelian gauge theories. (The substance of this paper will be a note added
in proof to the published version of gr-qc/9405058, to appear in Phys Rev D.)
| [
{
"created": "Wed, 1 Mar 1995 18:59:12 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Anderson",
"Arlen",
""
]
] | A proof is given that the polar decomposition procedure for unitarity restoration works for products of invertible nonunitary operators. A brief discussion follows that the unitarity restoration procedure, applied to propagators in spacetimes containing closed timelike curves, is analogous to the original introduction by Feynman of ghosts to restore unitarity in non-abelian gauge theories. (The substance of this paper will be a note added in proof to the published version of gr-qc/9405058, to appear in Phys Rev D.) |
1008.5169 | Alexey Krugly | Alexey L. Krugly | Discrete mechanics: a kinematics for a particular case of causal sets | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The model is a particular case of causal set. This is a discrete model of
spacetime in a microscopic level. In paper the most general properties of the
model are investigated without any reference to a dynamics. The dynamics of the
model is introduced in [arXiv: 1004.5077]. These two papers introduce a
consistent description of the model.
| [
{
"created": "Mon, 30 Aug 2010 21:15:23 GMT",
"version": "v1"
}
] | 2010-09-01 | [
[
"Krugly",
"Alexey L.",
""
]
] | The model is a particular case of causal set. This is a discrete model of spacetime in a microscopic level. In paper the most general properties of the model are investigated without any reference to a dynamics. The dynamics of the model is introduced in [arXiv: 1004.5077]. These two papers introduce a consistent description of the model. |
gr-qc/0608092 | Cristian Stelea | Brenda Chng, Robert Mann and Cristian Stelea | Accelerating Taub-NUT and Eguchi-Hanson solitons in four dimensions | 16 pages | Phys.Rev.D74:084031,2006 | 10.1103/PhysRevD.74.084031 | null | gr-qc | null | We construct new solutions of the vacuum Einstein field equations in four
dimensions via a solution generating method utilizing the SL(2,R) symmetry of
the reduced Lagrangian. We apply the method to an accelerating version of the
Zipoy-Voorhees solution and generate new solutions which we interpret to be the
accelerating versions of the Zipoy-Voorhees generalisation of the Taub-NUT
solution (with Lorentzian signature) and the Zipoy-Voorhees generalisation of
the Eguchi-Hanson solitons (with Euclidean signature). As an intermediary in
the solution-generating process we obtain charged versions of the accelerated
Zipoy-Voorhees-like families of solutions. Finally we present the accelerating
version of the Taub-NUT solution and discuss its properties.
| [
{
"created": "Sat, 19 Aug 2006 00:11:46 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Chng",
"Brenda",
""
],
[
"Mann",
"Robert",
""
],
[
"Stelea",
"Cristian",
""
]
] | We construct new solutions of the vacuum Einstein field equations in four dimensions via a solution generating method utilizing the SL(2,R) symmetry of the reduced Lagrangian. We apply the method to an accelerating version of the Zipoy-Voorhees solution and generate new solutions which we interpret to be the accelerating versions of the Zipoy-Voorhees generalisation of the Taub-NUT solution (with Lorentzian signature) and the Zipoy-Voorhees generalisation of the Eguchi-Hanson solitons (with Euclidean signature). As an intermediary in the solution-generating process we obtain charged versions of the accelerated Zipoy-Voorhees-like families of solutions. Finally we present the accelerating version of the Taub-NUT solution and discuss its properties. |
2312.07074 | Zheng-Wen Long | Dong Liu, Yi Yang, Zheng-Wen Long | Probing the black holes in a dark matter halo of M87 using gravitational
wave echoes | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Variations at the event horizon structure of a black hole will emit the
signals of the gravitational wave echoes associated with the ringdown phase of
the binary black hole merger. In this work, combining the mass model of M87 and
the Einasto profile for a dark matter halo, we construct one solution of the
black holes in a dark matter halo through the relativistic analysis, which
includes black hole for the case $a \leq 2M$ and the travesable wormhole for
the case $a>2M$. Then, we test this solution in the axial gravitational
perturbation and calculated their gravitational ringings of this black hole,
that is the quasinormal mode (QNM). Where, when the geometric parameter $a>2M$,
a series of gravitational wave echoes appear after the QNM, and the distinctive
feature of the gravitational wave echoes is the double barrier feature.
Besides, we also study the impacts of the shape parameters of the Einasto
profile both on the QNM and gravitational wave echoes of this black hole, and
extract their frequencies using the WKB method and Prony method. In particular,
from the perspective that the QNM frequencies between different black hole
parameters are distinguishable, we give an upper limit for the shape parameters
of the Einasto profile, which is approximately $\alpha<0.20$. These signals of
the gravitational wave echoes based on this black hole in a dark matter halo
may be detected in the near future, and these characteristics in the time
evolution of the gravitational wave echoes can serve as local measurements of
dark matter.
| [
{
"created": "Tue, 12 Dec 2023 08:52:14 GMT",
"version": "v1"
}
] | 2023-12-13 | [
[
"Liu",
"Dong",
""
],
[
"Yang",
"Yi",
""
],
[
"Long",
"Zheng-Wen",
""
]
] | Variations at the event horizon structure of a black hole will emit the signals of the gravitational wave echoes associated with the ringdown phase of the binary black hole merger. In this work, combining the mass model of M87 and the Einasto profile for a dark matter halo, we construct one solution of the black holes in a dark matter halo through the relativistic analysis, which includes black hole for the case $a \leq 2M$ and the travesable wormhole for the case $a>2M$. Then, we test this solution in the axial gravitational perturbation and calculated their gravitational ringings of this black hole, that is the quasinormal mode (QNM). Where, when the geometric parameter $a>2M$, a series of gravitational wave echoes appear after the QNM, and the distinctive feature of the gravitational wave echoes is the double barrier feature. Besides, we also study the impacts of the shape parameters of the Einasto profile both on the QNM and gravitational wave echoes of this black hole, and extract their frequencies using the WKB method and Prony method. In particular, from the perspective that the QNM frequencies between different black hole parameters are distinguishable, we give an upper limit for the shape parameters of the Einasto profile, which is approximately $\alpha<0.20$. These signals of the gravitational wave echoes based on this black hole in a dark matter halo may be detected in the near future, and these characteristics in the time evolution of the gravitational wave echoes can serve as local measurements of dark matter. |
2004.07959 | Ujjal Debnath | I. G. Salako, M. Khlopov, Saibal Ray, M. Z. Arouko, Pameli Saha, Ujjal
Debnath | Study on anisotropic strange stars in $f(\mathbb{T},\mathcal{T})$
gravity | 16 pages, 19 figures | null | 10.1134/S0040577921090105 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we study the existence of strange star in the background of
$f(\mathbb{T},\mathcal{T})$ gravity in the Einstein spacetime geometry, where
$\mathbb{T}$ is the torsion tensor and $\mathcal{T}$ is the trace of the
energy-momentum tensor. The equations of motion are derived for anisotropic
pressure within the spherically symmetric strange star. We explore the physical
features like energy conditions, mass-radius relations, modified TOV equations,
principal of causality, adiabatic index, redshift and stability analysis of our
model. These features are realistic and appealing to further investigation of
properties of compact objects in $f(\mathbb{T},\mathcal{T})$ gravity as well as
their observational signatures.
| [
{
"created": "Wed, 15 Apr 2020 07:03:14 GMT",
"version": "v1"
}
] | 2021-10-13 | [
[
"Salako",
"I. G.",
""
],
[
"Khlopov",
"M.",
""
],
[
"Ray",
"Saibal",
""
],
[
"Arouko",
"M. Z.",
""
],
[
"Saha",
"Pameli",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this work, we study the existence of strange star in the background of $f(\mathbb{T},\mathcal{T})$ gravity in the Einstein spacetime geometry, where $\mathbb{T}$ is the torsion tensor and $\mathcal{T}$ is the trace of the energy-momentum tensor. The equations of motion are derived for anisotropic pressure within the spherically symmetric strange star. We explore the physical features like energy conditions, mass-radius relations, modified TOV equations, principal of causality, adiabatic index, redshift and stability analysis of our model. These features are realistic and appealing to further investigation of properties of compact objects in $f(\mathbb{T},\mathcal{T})$ gravity as well as their observational signatures. |
1708.02113 | Nicola Franchini | Nicola Franchini, Andrew Coates, Thomas P. Sotiriou | Constructing Neutron Stars with a Gravitational Higgs Mechanism | 8 pages, 5 figures | Phys. Rev. D 97, 064013 (2018) | 10.1103/PhysRevD.97.064013 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In scalar-tensor theories, spontaneous scalarization is a phase transition
that can occur in ultra-dense environments such as neutron stars. The scalar
field develops a non-trivial configuration once the stars exceeds a compactness
threshold. We recently pointed out that, if the scalar exhibits some additional
coupling to matter, it could give rise to significantly different microphysics
in these environments. In this work we study, at the non-perturbative level, a
toy model in which the photon is given a large mass when spontaneous
scalarization occurs. Our results demonstrate clearly the effectiveness of
spontaneous scalarization as a Higgs-like mechanism in neutron stars.
| [
{
"created": "Mon, 7 Aug 2017 13:31:04 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Mar 2018 14:33:38 GMT",
"version": "v2"
}
] | 2018-03-21 | [
[
"Franchini",
"Nicola",
""
],
[
"Coates",
"Andrew",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | In scalar-tensor theories, spontaneous scalarization is a phase transition that can occur in ultra-dense environments such as neutron stars. The scalar field develops a non-trivial configuration once the stars exceeds a compactness threshold. We recently pointed out that, if the scalar exhibits some additional coupling to matter, it could give rise to significantly different microphysics in these environments. In this work we study, at the non-perturbative level, a toy model in which the photon is given a large mass when spontaneous scalarization occurs. Our results demonstrate clearly the effectiveness of spontaneous scalarization as a Higgs-like mechanism in neutron stars. |
0806.1426 | M. Hossein Dehghani | M. H. Dehghani and N. Farhangkhah | Asymptotically Flat Radiating Solutions in Third Order Lovelock Gravity | 15 pages, no figure, references added, two appendix added | Phys.Rev.D78:064015,2008 | 10.1103/PhysRevD.78.064015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present an exact spherically symmetric solution of third
order Lovelock gravity in $n$ dimensions which describes the gravitational
collapse of a null dust fluid. This solution is asymptotically (anti-)de Sitter
or flat depending on the choice of the cosmological constant. Using the
asymptotically flat solution for $n \geq 7$ with a power-law form of the mass
as a function of the null coordinate, we present a model for a gravitational
collapse in which a null dust fluid radially injects into an initially flat and
empty region. It is found that a naked singularity is inevitably formed whose
strength is different for the $n = 7$ and $n \geq 8$ cases. In the $n=7$ case,
the limiting focusing condition for the strength of curvature singularity is
satisfied. But for $n \geq 8$, the strength of curvature singularity depends on
the rate of increase of mass of the spacetime. These considerations show that
the third order Lovelock term weakens the strength of the curvature
singularity.
| [
{
"created": "Mon, 9 Jun 2008 11:21:00 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Aug 2008 12:20:48 GMT",
"version": "v2"
}
] | 2009-02-20 | [
[
"Dehghani",
"M. H.",
""
],
[
"Farhangkhah",
"N.",
""
]
] | In this paper, we present an exact spherically symmetric solution of third order Lovelock gravity in $n$ dimensions which describes the gravitational collapse of a null dust fluid. This solution is asymptotically (anti-)de Sitter or flat depending on the choice of the cosmological constant. Using the asymptotically flat solution for $n \geq 7$ with a power-law form of the mass as a function of the null coordinate, we present a model for a gravitational collapse in which a null dust fluid radially injects into an initially flat and empty region. It is found that a naked singularity is inevitably formed whose strength is different for the $n = 7$ and $n \geq 8$ cases. In the $n=7$ case, the limiting focusing condition for the strength of curvature singularity is satisfied. But for $n \geq 8$, the strength of curvature singularity depends on the rate of increase of mass of the spacetime. These considerations show that the third order Lovelock term weakens the strength of the curvature singularity. |
1502.02256 | Sai Wang | Xin Li, Sai Wang, Zhe Chang | Anisotropic inflation in Finsler spacetime | 15 pages, 8 figures. Minor revision | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We suggest the universe is Finslerian in the stage of inflation. The
Finslerian background spacetime breaks rotational symmetry and induces parity
violation. The primordial power spectrum is given for quantum fluctuation of
the inflation field. It depends not only on the magnitude of wavenumber but
also on the preferred direction. We derive the gravitational field equations in
the perturbed Finslerian background spacetime, and obtain a conserved quantity
outside the Hubble horizon. The angular correlation coefficients are presented
in our anisotropic inflation model. The parity violation feature of Finslerian
background spacetime requires that the anisotropic effect only appears in
angular correlation coefficients if $l'=l+1$. The numerical results of the
angular correlation coefficients are given to describe the anisotropic effect.
| [
{
"created": "Sun, 8 Feb 2015 14:51:21 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Feb 2015 09:42:23 GMT",
"version": "v2"
}
] | 2015-02-16 | [
[
"Li",
"Xin",
""
],
[
"Wang",
"Sai",
""
],
[
"Chang",
"Zhe",
""
]
] | We suggest the universe is Finslerian in the stage of inflation. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. The primordial power spectrum is given for quantum fluctuation of the inflation field. It depends not only on the magnitude of wavenumber but also on the preferred direction. We derive the gravitational field equations in the perturbed Finslerian background spacetime, and obtain a conserved quantity outside the Hubble horizon. The angular correlation coefficients are presented in our anisotropic inflation model. The parity violation feature of Finslerian background spacetime requires that the anisotropic effect only appears in angular correlation coefficients if $l'=l+1$. The numerical results of the angular correlation coefficients are given to describe the anisotropic effect. |
1107.3083 | Niall \'O Murchadha | G. Waxenegger, R. Beig, N.\'O Murchadha | Existence and uniqueness of Bowen-York Trumpets | This corresponds to the published version in Class. Quantum Grav. 28
(2011) 245002 | Class. Quantum Grav. 28 (2011) 245002 | 10.1088/0264-9381/28/24/245002 | UWThPh-2011-23 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove the existence of initial data sets which possess an asymptotically
flat and an asymptotically cylindrical end. Such geometries are known as
trumpets in the community of numerical relativists.
| [
{
"created": "Fri, 15 Jul 2011 14:55:02 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jan 2012 16:58:27 GMT",
"version": "v2"
}
] | 2015-05-28 | [
[
"Waxenegger",
"G.",
""
],
[
"Beig",
"R.",
""
],
[
"Murchadha",
"N. Ó",
""
]
] | We prove the existence of initial data sets which possess an asymptotically flat and an asymptotically cylindrical end. Such geometries are known as trumpets in the community of numerical relativists. |
gr-qc/0311064 | T. Roy Choudhury | T. Roy Choudhury, T. Padmanabhan | Quasi normal modes in Schwarzschild-DeSitter spacetime: A simple
derivation of the level spacing of the frequencies | Revised version. Accepted in Phys. Rev. D | Phys.Rev. D69 (2004) 064033 | 10.1103/PhysRevD.69.064033 | null | gr-qc astro-ph hep-th | null | It is known that the imaginary parts of the quasi normal mode (QNM)
frequencies for the Schwarzschild black hole are evenly spaced with a spacing
that depends only on the surface gravity. On the other hand, for massless
minimally coupled scalar fields, there exist no QNMs in the pure DeSitter
spacetime. It is not clear what the structure of the QNMs would be for the
Schwarzschild-DeSitter (SDS) spacetime, which is characterized by two different
surface gravities. We provide a simple derivation of the imaginary parts of the
QNM frequencies for the SDS spacetime by calculating the scattering amplitude
in the first Born approximation and determining its poles. We find that, for
the usual set of boundary conditions in which the incident wave is scattered
off the black hole horizon, the imaginary parts of the QNM frequencies have a
equally spaced structure with the level spacing depending on the surface
gravity of the black hole. Several conceptual issues related to the QNM are
discussed in the light of this result and comparison with previous work is
presented.
| [
{
"created": "Thu, 20 Nov 2003 09:10:29 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jan 2004 14:12:16 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Choudhury",
"T. Roy",
""
],
[
"Padmanabhan",
"T.",
""
]
] | It is known that the imaginary parts of the quasi normal mode (QNM) frequencies for the Schwarzschild black hole are evenly spaced with a spacing that depends only on the surface gravity. On the other hand, for massless minimally coupled scalar fields, there exist no QNMs in the pure DeSitter spacetime. It is not clear what the structure of the QNMs would be for the Schwarzschild-DeSitter (SDS) spacetime, which is characterized by two different surface gravities. We provide a simple derivation of the imaginary parts of the QNM frequencies for the SDS spacetime by calculating the scattering amplitude in the first Born approximation and determining its poles. We find that, for the usual set of boundary conditions in which the incident wave is scattered off the black hole horizon, the imaginary parts of the QNM frequencies have a equally spaced structure with the level spacing depending on the surface gravity of the black hole. Several conceptual issues related to the QNM are discussed in the light of this result and comparison with previous work is presented. |
0907.4165 | Yerko Vasquez | P.A. Gonz\'alez and Yerko V\'asquez | Exact solutions in 3D gravity with torsion | 21 pages, no figures, version that matches the published one | JHEP 1108:089,2011 | 10.1007/JHEP08(2011)089 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the three-dimensional gravity with torsion given by the
Mielke-Baekler (MB) model coupled to gravitational Chern-Simons term, and that
possess electric charge described by Maxwell-Chern-Simons electrodynamics. We
find and discuss this theory's charged black holes solutions and uncharged
solutions. We find that for vanishing torsion our solutions by means of a
coordinate transformation can be written as three-dimensional Chern-Simons
black holes. We also discuss a special case of this theory, Topologically
Massive Gravity (TMG) at chiral point, and we show that the logarithmic
solution of TMG is also a solution of the MB model at a fixed point in the
space of parameters. Furthermore, we show that our solutions generalize Godel
type solutions in a particular case. Also, we recover BTZ black hole in
Riemann-Cartan spacetime for vanishing charge.
| [
{
"created": "Thu, 23 Jul 2009 20:43:58 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Aug 2009 08:42:24 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Mar 2011 13:13:11 GMT",
"version": "v3"
},
{
"created": "Wed, 20 Apr 2011 14:47:41 GMT",
"version": "v4"
},
{
"cr... | 2011-10-03 | [
[
"González",
"P. A.",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We study the three-dimensional gravity with torsion given by the Mielke-Baekler (MB) model coupled to gravitational Chern-Simons term, and that possess electric charge described by Maxwell-Chern-Simons electrodynamics. We find and discuss this theory's charged black holes solutions and uncharged solutions. We find that for vanishing torsion our solutions by means of a coordinate transformation can be written as three-dimensional Chern-Simons black holes. We also discuss a special case of this theory, Topologically Massive Gravity (TMG) at chiral point, and we show that the logarithmic solution of TMG is also a solution of the MB model at a fixed point in the space of parameters. Furthermore, we show that our solutions generalize Godel type solutions in a particular case. Also, we recover BTZ black hole in Riemann-Cartan spacetime for vanishing charge. |
2111.11020 | I-Ching Yang | I-Ching Yang | The Einstein and M{\o}ller energy-momentum complexes in post-Newtonian
approximation | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the first and second post-Newtonian approximation of the Schwarzschild
metric, I obtain the energy component of the Einstein and M{\o}ller
energy-momentum complex. Both energies involve the rest-mass energy $m$, the
energy stored in the configuration and that in the gravitational field, but the
energies of Schwarzschild spacetime in the Einstein and M{\o}ller prescriptions
are the total mass-energy $M$. First, for general relativity, the rest-mass
energy $m$ in the flat spacetime behaves like the bare mass, and the total
mass-energy $M$ in the curved spacetime behaves like the experimentally
observed mass. Second, the zero-potential surface is important condition for
defining the energy of gravitational field, and plays an important role in the
energy-momentum localization of general relativity.
| [
{
"created": "Mon, 22 Nov 2021 07:07:33 GMT",
"version": "v1"
}
] | 2021-11-23 | [
[
"Yang",
"I-Ching",
""
]
] | In the first and second post-Newtonian approximation of the Schwarzschild metric, I obtain the energy component of the Einstein and M{\o}ller energy-momentum complex. Both energies involve the rest-mass energy $m$, the energy stored in the configuration and that in the gravitational field, but the energies of Schwarzschild spacetime in the Einstein and M{\o}ller prescriptions are the total mass-energy $M$. First, for general relativity, the rest-mass energy $m$ in the flat spacetime behaves like the bare mass, and the total mass-energy $M$ in the curved spacetime behaves like the experimentally observed mass. Second, the zero-potential surface is important condition for defining the energy of gravitational field, and plays an important role in the energy-momentum localization of general relativity. |
2205.10523 | Hajime Sotani | Hajime Sotani | Accuracy of one-dimensional approximation in neutron star quasi-normal
modes | accepted in EPJC | null | 10.1140/epjc/s10052-022-10439-1 | RIKEN-iTHEMS-Report-22 | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Since the eigenfrequency of gravitational waves from cold neutron stars
becomes a complex number, where the real and imaginary parts respectively
correspond to an oscillation frequency and damping rate, one has to somehow
solve the eigenvalue problem concerning the eigenvalue in two-dimensional
parameter space. To avoid this bother, one sometimes adopts an approximation,
where the eigenvalue is in one-dimensional parameter space. In this study,
first, we show the accuracy of the zero-damping approximation, which is one of
the one-dimensional approximations, for the fundamental and 1st pressure modes.
But, this approximation is not applicable to the spacetime mode, because the
damping rate of the spacetime mode is generally comparable to the oscillation
frequency. Nevertheless, we find the empirical relation for the ratio of the
imaginary part to the real part of the eigenfrequency, which is expressed as a
function of the steller compactness almost independently of the adopted
equations of state for neutron star matter. Adopting this empirical relation,
one can express the eigenfrequency in terms of just the real part, i.e., the
problem to solve becomes an eigenvalue problem with a one-dimensional
eigenvalue. Then, we find that the frequencies are estimated with good accuracy
even with such approximations even for the 1st spacetime mode.
| [
{
"created": "Sat, 21 May 2022 07:29:33 GMT",
"version": "v1"
}
] | 2022-06-08 | [
[
"Sotani",
"Hajime",
""
]
] | Since the eigenfrequency of gravitational waves from cold neutron stars becomes a complex number, where the real and imaginary parts respectively correspond to an oscillation frequency and damping rate, one has to somehow solve the eigenvalue problem concerning the eigenvalue in two-dimensional parameter space. To avoid this bother, one sometimes adopts an approximation, where the eigenvalue is in one-dimensional parameter space. In this study, first, we show the accuracy of the zero-damping approximation, which is one of the one-dimensional approximations, for the fundamental and 1st pressure modes. But, this approximation is not applicable to the spacetime mode, because the damping rate of the spacetime mode is generally comparable to the oscillation frequency. Nevertheless, we find the empirical relation for the ratio of the imaginary part to the real part of the eigenfrequency, which is expressed as a function of the steller compactness almost independently of the adopted equations of state for neutron star matter. Adopting this empirical relation, one can express the eigenfrequency in terms of just the real part, i.e., the problem to solve becomes an eigenvalue problem with a one-dimensional eigenvalue. Then, we find that the frequencies are estimated with good accuracy even with such approximations even for the 1st spacetime mode. |
1805.09796 | Gerard Clement | G\'erard Cl\'ement and Khireddine Nouicer | Hairy black hole solutions in a three-dimensional Galileon model | 21 pages. Title changed. Revised version published in CQG | Classical and Quantum Gravity 35 (2018) 185010 | 10.1088/1361-6382/aad84a | LAPTH-016/18 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate stationary rotationally symmetric solutions of a particular
truncation of Horndeski theory in three dimensions, including a non-minimal
scalar kinetic coupling to the curvature. After discussing the special case of
a vanishing scalar charge, which includes most of the previously known
solutions, we reduce the general case to an effective mechanical model in a
three-dimensional target space. We analyze the possible near-horizon behaviors,
and conclude that black hole solutions with degenerate horizons and constant
curvature asymptotics may exist if the minimal and non-minimal scalar coupling
constants have the same sign. In a special case, we find a new analytic
rotating black hole solution with scalar hair and degenerate horizon. This is
geodesically and causally complete, and asymptotic to the extreme BTZ metric.
We also briefly discuss soliton solutions in another special case.
| [
{
"created": "Thu, 24 May 2018 17:40:51 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Aug 2018 12:32:37 GMT",
"version": "v2"
}
] | 2018-08-28 | [
[
"Clément",
"Gérard",
""
],
[
"Nouicer",
"Khireddine",
""
]
] | We investigate stationary rotationally symmetric solutions of a particular truncation of Horndeski theory in three dimensions, including a non-minimal scalar kinetic coupling to the curvature. After discussing the special case of a vanishing scalar charge, which includes most of the previously known solutions, we reduce the general case to an effective mechanical model in a three-dimensional target space. We analyze the possible near-horizon behaviors, and conclude that black hole solutions with degenerate horizons and constant curvature asymptotics may exist if the minimal and non-minimal scalar coupling constants have the same sign. In a special case, we find a new analytic rotating black hole solution with scalar hair and degenerate horizon. This is geodesically and causally complete, and asymptotic to the extreme BTZ metric. We also briefly discuss soliton solutions in another special case. |
2312.17706 | Philippe G. LeFloch | Bruno Le Floch and Philippe G. LeFloch | Optimal localization for the Einstein constraints | 91 pages | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider asymptotically Euclidean, initial data sets for Einstein's field
equations and solve the localization problem at infinity, also called gluing
problem. We achieve optimal gluing and optimal decay, in the sense that we
encompass solutions with possibly arbitrarily low decay at infinity and
establish (super-)harmonic estimates within possibly arbitrarily narrow conical
domains. In the localized seed-to-solution method (as we call it), we define a
variational projection operator which associates the solution to the Einstein
constraints that is closest to any given localized seed data set (as we call
it). Our main contribution concerns the derivation of harmonic estimates for
the linearized Einstein operator and its formal adjoint which, in particular,
includes new analysis on the linearized scalar curvature operator. The
statement of harmonic estimates requires the notion of energy-momentum
modulators (as we call them), which arise as correctors to the localized seed
data sets. For the Hamiltonian and momentum operators, we introduce a notion of
harmonic-spherical decomposition and we uncover stability conditions on the
localization function, which are localized Poincare and Hardy-type inequalities
and, for instance, hold for arbitrarily narrow gluing domains. Our localized
seed-to-solution method builds upon the gluing techniques pioneered by
Carlotto, Chrusciel, Corvino, Delay, Isenberg, Maxwell, and Schoen, while
providing a proof of a conjecture by Carlotto and Schoen on the localization
problem and generalize P. LeFloch and Nguyen's theorem on the asymptotic
localization problem.
| [
{
"created": "Fri, 29 Dec 2023 17:50:28 GMT",
"version": "v1"
}
] | 2024-01-01 | [
[
"Floch",
"Bruno Le",
""
],
[
"LeFloch",
"Philippe G.",
""
]
] | We consider asymptotically Euclidean, initial data sets for Einstein's field equations and solve the localization problem at infinity, also called gluing problem. We achieve optimal gluing and optimal decay, in the sense that we encompass solutions with possibly arbitrarily low decay at infinity and establish (super-)harmonic estimates within possibly arbitrarily narrow conical domains. In the localized seed-to-solution method (as we call it), we define a variational projection operator which associates the solution to the Einstein constraints that is closest to any given localized seed data set (as we call it). Our main contribution concerns the derivation of harmonic estimates for the linearized Einstein operator and its formal adjoint which, in particular, includes new analysis on the linearized scalar curvature operator. The statement of harmonic estimates requires the notion of energy-momentum modulators (as we call them), which arise as correctors to the localized seed data sets. For the Hamiltonian and momentum operators, we introduce a notion of harmonic-spherical decomposition and we uncover stability conditions on the localization function, which are localized Poincare and Hardy-type inequalities and, for instance, hold for arbitrarily narrow gluing domains. Our localized seed-to-solution method builds upon the gluing techniques pioneered by Carlotto, Chrusciel, Corvino, Delay, Isenberg, Maxwell, and Schoen, while providing a proof of a conjecture by Carlotto and Schoen on the localization problem and generalize P. LeFloch and Nguyen's theorem on the asymptotic localization problem. |
1412.8247 | Lin-Qing Chen | Andrzej Banburski, Lin-Qing Chen, Laurent Freidel, Jeff Hnybida | Pachner moves in a 4d Riemannian holomorphic Spin Foam model | 48 pages, 30 figures | Phys. Rev. D 92, 124014 (2015) | 10.1103/PhysRevD.92.124014 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study a Spin Foam model for 4d Riemannian gravity, and
propose a new way of imposing the simplicity constraints that uses the recently
developed holomorphic representation. Using the power of the holomorphic
integration techniques, and with the introduction of two new tools: the
homogeneity map and the loop identity, for the first time we give the analytic
expressions for the behaviour of the Spin Foam amplitudes under 4-dimensional
Pachner moves. It turns out that this behaviour is controlled by an insertion
of nonlocal mixing operators. In the case of the 5-1 move, the expression
governing the change of the amplitude can be interpreted as a vertex
renormalisation equation. We find a natural truncation scheme that allows us to
get an invariance up to an overall factor for the 4-2 and 5-1 moves, but not
for the 3-3 move. The study of the divergences shows that there is a range of
parameter space for which the 4-2 move is finite while the 5-1 move diverges.
This opens up the possibility to recover diffeomorphism invariance in the
continuum limit of Spin Foam models for 4D Quantum Gravity.
| [
{
"created": "Mon, 29 Dec 2014 02:36:57 GMT",
"version": "v1"
}
] | 2015-12-16 | [
[
"Banburski",
"Andrzej",
""
],
[
"Chen",
"Lin-Qing",
""
],
[
"Freidel",
"Laurent",
""
],
[
"Hnybida",
"Jeff",
""
]
] | In this work we study a Spin Foam model for 4d Riemannian gravity, and propose a new way of imposing the simplicity constraints that uses the recently developed holomorphic representation. Using the power of the holomorphic integration techniques, and with the introduction of two new tools: the homogeneity map and the loop identity, for the first time we give the analytic expressions for the behaviour of the Spin Foam amplitudes under 4-dimensional Pachner moves. It turns out that this behaviour is controlled by an insertion of nonlocal mixing operators. In the case of the 5-1 move, the expression governing the change of the amplitude can be interpreted as a vertex renormalisation equation. We find a natural truncation scheme that allows us to get an invariance up to an overall factor for the 4-2 and 5-1 moves, but not for the 3-3 move. The study of the divergences shows that there is a range of parameter space for which the 4-2 move is finite while the 5-1 move diverges. This opens up the possibility to recover diffeomorphism invariance in the continuum limit of Spin Foam models for 4D Quantum Gravity. |
1502.03808 | Kip S. Thorne | Oliver James, Eugenie von Tunzelmann, Paul Franklin, and Kip S. Thorne | Gravitational Lensing by Spinning Black Holes in Astrophysics, and in
the Movie Interstellar | 46 pages, 17 figures | Classical and Quantum Gravity 32 (2015) 065001 | 10.1088/0264-9381/32/6/065001 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-sa/3.0/ | Interstellar is the first Hollywood movie to attempt depicting a black hole
as it would actually be seen by somebody nearby. For this we developed a code
called DNGR (Double Negative Gravitational Renderer) to solve the equations for
ray-bundle (light-beam) propagation through the curved spacetime of a spinning
(Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our
ray-bundle techniques were crucial for achieving IMAX-quality smoothness
without flickering.
This paper has four purposes: (i) To describe DNGR for physicists and CGI
practitioners . (ii) To present the equations we use, when the camera is in
arbitrary motion at an arbitrary location near a Kerr black hole, for mapping
light sources to camera images via elliptical ray bundles. (iii) To describe
new insights, from DNGR, into gravitational lensing when the camera is near the
spinning black hole, rather than far away as in almost all prior studies. (iv)
To describe how the images of the black hole Gargantua and its accretion disk,
in the movie \emph{Interstellar}, were generated with DNGR. There are no new
astrophysical insights in this accretion-disk section of the paper, but disk
novices may find it pedagogically interesting, and movie buffs may find its
discussions of Interstellar interesting.
| [
{
"created": "Thu, 12 Feb 2015 20:56:05 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Feb 2015 04:19:05 GMT",
"version": "v2"
}
] | 2015-02-17 | [
[
"James",
"Oliver",
""
],
[
"von Tunzelmann",
"Eugenie",
""
],
[
"Franklin",
"Paul",
""
],
[
"Thorne",
"Kip S.",
""
]
] | Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this we developed a code called DNGR (Double Negative Gravitational Renderer) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering. This paper has four purposes: (i) To describe DNGR for physicists and CGI practitioners . (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie \emph{Interstellar}, were generated with DNGR. There are no new astrophysical insights in this accretion-disk section of the paper, but disk novices may find it pedagogically interesting, and movie buffs may find its discussions of Interstellar interesting. |
gr-qc/0102107 | Adonai S. Sant'Anna | Newton C. A. da Costa and Adonai S. Sant'Anna | The mathematical role of time and space-time in classical physics | LaTeX, 12 pages, no figures. This is a new version | Found.Phys.Lett. 14 (2001) 553-563 | null | null | gr-qc | null | We use Padoa's principle of independence of primitive symbols in axiomatic
systems in order to discuss the mathematical role of time and space-time in
some classical physical theories. We show that time is eliminable in Newtonian
mechanics and that space-time is also dispensable in Hamiltonian mechanics,
Maxwell's electromagnetic theory, the Dirac electron, classical gauge fields,
and general relativity.
| [
{
"created": "Tue, 27 Feb 2001 14:47:10 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Apr 2001 12:00:00 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"da Costa",
"Newton C. A.",
""
],
[
"Sant'Anna",
"Adonai S.",
""
]
] | We use Padoa's principle of independence of primitive symbols in axiomatic systems in order to discuss the mathematical role of time and space-time in some classical physical theories. We show that time is eliminable in Newtonian mechanics and that space-time is also dispensable in Hamiltonian mechanics, Maxwell's electromagnetic theory, the Dirac electron, classical gauge fields, and general relativity. |
2206.08601 | Mohsen Khodadi | Mohsen Khodadi and Gaetano Lambiase | Probing the Lorentz Symmetry Violation Using the First Image of
Sagittarius A*: Constraints on Standard-Model Extension Coefficients | 16 pages, 5 figures. v3:discussion improved, references added,
figures revised; matches the version accepted for publication in PRD | Phys. Rev. D 106, 104050 (2022) | 10.1103/PhysRevD.106.104050 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thanks to unparalleled near-horizon images of the shadows of Messier 87*
(M87*) and Sagittarius A* (Sgr A*) delivered by the Event Horizon Telescope
(EHT), two amazing windows opened up to us for the strong-field test of the
gravity theories as well as fundamental physics. Information recently published
from EHT about the Sgr A*'s shadow lets us have a novel possibility of
exploration of Lorentz symmetry violation (LSV) within the Standard-Model
Extension (SME) framework. Despite the agreement between the shadow image of
Sgr A* and the prediction of the general theory of relativity, there is still a
slight difference which is expected to be fixed by taking some fundamental
corrections into account. We bring up the idea that the recent inferred shadow
image of Sgr A* is explicable by a minimal SME-inspired Schwarzschild metric
containing the Lorentz violating (LV) terms obtained from the post-Newtonian
approximation. The LV terms embedded in Schwarzschild metric are dimensionless
spatial coefficients ${\bar s}^{jk}$ associated with the field responsible for
LSV in the gravitational sector of the minimal SME theory. In this way, one can
control Lorentz invariance violation in the allowed sensitivity level of the
first shadow image of Sgr A*. Actually, using the bounds released within
$1\sigma$ uncertainty for the shadow size of Sgr A* and whose fractional
deviation from standard Schwarzschild, we set upper limits for the two
different combinations of spatial diagonal coefficients and the time-time
coefficient of the SME, as well. The best upper bound is at the $10^{-2}$
level, which should be interpreted differently from those constraints
previously extracted from well-known frameworks since unlike standard SME
studies it is not obtained from a Sun-centered celestial frame but comes from
probing the black hole horizon scale.
| [
{
"created": "Fri, 17 Jun 2022 07:58:06 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jun 2022 10:14:34 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Nov 2022 17:34:02 GMT",
"version": "v3"
}
] | 2022-11-29 | [
[
"Khodadi",
"Mohsen",
""
],
[
"Lambiase",
"Gaetano",
""
]
] | Thanks to unparalleled near-horizon images of the shadows of Messier 87* (M87*) and Sagittarius A* (Sgr A*) delivered by the Event Horizon Telescope (EHT), two amazing windows opened up to us for the strong-field test of the gravity theories as well as fundamental physics. Information recently published from EHT about the Sgr A*'s shadow lets us have a novel possibility of exploration of Lorentz symmetry violation (LSV) within the Standard-Model Extension (SME) framework. Despite the agreement between the shadow image of Sgr A* and the prediction of the general theory of relativity, there is still a slight difference which is expected to be fixed by taking some fundamental corrections into account. We bring up the idea that the recent inferred shadow image of Sgr A* is explicable by a minimal SME-inspired Schwarzschild metric containing the Lorentz violating (LV) terms obtained from the post-Newtonian approximation. The LV terms embedded in Schwarzschild metric are dimensionless spatial coefficients ${\bar s}^{jk}$ associated with the field responsible for LSV in the gravitational sector of the minimal SME theory. In this way, one can control Lorentz invariance violation in the allowed sensitivity level of the first shadow image of Sgr A*. Actually, using the bounds released within $1\sigma$ uncertainty for the shadow size of Sgr A* and whose fractional deviation from standard Schwarzschild, we set upper limits for the two different combinations of spatial diagonal coefficients and the time-time coefficient of the SME, as well. The best upper bound is at the $10^{-2}$ level, which should be interpreted differently from those constraints previously extracted from well-known frameworks since unlike standard SME studies it is not obtained from a Sun-centered celestial frame but comes from probing the black hole horizon scale. |
gr-qc/0604003 | Salvatore Antoci | S. Antoci, D.-E. Liebscher, L. Mihich | Confinement in Einstein's unified field theory | 17 pages, added comment in Section 6 about Petrov eigenvalue equation | Annales Fond.Broglie.33:221-239,2008 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After recalling the mathematical structure of Einstein's Hermitian extension
of the gravitational theory of 1915, the problem, whether its field equations
should admit of phenomenological sources at their right-hand sides, and how
this addition should be done, is expounded by relying on a thread of essential
insights and achievements by Schr\"odinger, Kursunoglu, Lichnerowicz, H\'ely
and Borchsenius. When sources are appended to all the field equations, from the
latter and from the contracted Bianchi identities a sort of
gravoelectrodynamics appears, that totally departs from the so called
Einstein-Maxwell theory, since its constitutive equation, that rules the link
between inductions and fields, is a very complicated differential relation that
allows for a much wider, still practically unexplored range of possible
occurrences. In this sort of theory one can allow for both an electric and a
magnetic four-current, which are not a physically wrong replica of each other,
like it would occur if both these currents were allowed in Maxwell's vacuum.
Particular static exact solutions show that, due to the peculiar constitutive
equation, while electric charges with a pole structure behave according to
Coulomb's law, magnetic charges with a pole structure interact with forces not
depending on their mutual distance. The latter behaviour was already discovered
by Treder in 1957 with an approximate calculation, while looking for ordinary
electromagnetism in the theory. He also showed that in the Hermitian theory
magnetic charges of unlike sign mutually attract, hence they are permanently
confined entities. The exact solutions confirm this finding, already
interpreted in 1980 by Treder in a chromodynamic sense.
| [
{
"created": "Sat, 1 Apr 2006 15:12:46 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jul 2012 15:28:48 GMT",
"version": "v2"
}
] | 2012-07-19 | [
[
"Antoci",
"S.",
""
],
[
"Liebscher",
"D. -E.",
""
],
[
"Mihich",
"L.",
""
]
] | After recalling the mathematical structure of Einstein's Hermitian extension of the gravitational theory of 1915, the problem, whether its field equations should admit of phenomenological sources at their right-hand sides, and how this addition should be done, is expounded by relying on a thread of essential insights and achievements by Schr\"odinger, Kursunoglu, Lichnerowicz, H\'ely and Borchsenius. When sources are appended to all the field equations, from the latter and from the contracted Bianchi identities a sort of gravoelectrodynamics appears, that totally departs from the so called Einstein-Maxwell theory, since its constitutive equation, that rules the link between inductions and fields, is a very complicated differential relation that allows for a much wider, still practically unexplored range of possible occurrences. In this sort of theory one can allow for both an electric and a magnetic four-current, which are not a physically wrong replica of each other, like it would occur if both these currents were allowed in Maxwell's vacuum. Particular static exact solutions show that, due to the peculiar constitutive equation, while electric charges with a pole structure behave according to Coulomb's law, magnetic charges with a pole structure interact with forces not depending on their mutual distance. The latter behaviour was already discovered by Treder in 1957 with an approximate calculation, while looking for ordinary electromagnetism in the theory. He also showed that in the Hermitian theory magnetic charges of unlike sign mutually attract, hence they are permanently confined entities. The exact solutions confirm this finding, already interpreted in 1980 by Treder in a chromodynamic sense. |
1107.3468 | Bogus{\l}aw Broda | Bogus{\l}aw Broda | Quantum gravity stability of isotropy in homogeneous cosmology | 9 pages, 1 figure | Phys.Lett.B704:655-658,2011 | 10.1016/j.physletb.2011.09.087 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that anisotropy of homogeneous spacetime described by the
general Kasner metric can be damped by quantum fluctuations coming from
perturbative quantum gravity in one-loop approximation. Also, a formal
argument, not limited to one-loop approximation, is put forward in favor of
stability of isotropy in the exactly isotropic case.
| [
{
"created": "Mon, 18 Jul 2011 15:19:11 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jul 2011 13:49:20 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Sep 2011 14:48:25 GMT",
"version": "v3"
},
{
"created": "Fri, 7 Oct 2011 07:52:11 GMT",
"version": "v4"
}
] | 2011-10-11 | [
[
"Broda",
"Bogusław",
""
]
] | It has been shown that anisotropy of homogeneous spacetime described by the general Kasner metric can be damped by quantum fluctuations coming from perturbative quantum gravity in one-loop approximation. Also, a formal argument, not limited to one-loop approximation, is put forward in favor of stability of isotropy in the exactly isotropic case. |
1303.6229 | P Huang | Peng Huang, Yong-chang Huang | $f(T)$ theories from holographic dark energy models | 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reconstruct $f(T)$ theories from three different holographic dark energy
models in different time durations. For the HDE model, the dark energy
dominated era with new setting up is chosen for reconstruction, and the
radiation dominated era is chosen when the involved model changes into NADE.
For the RDE model, radiation, matter and dark energy dominated time durations
are all investigated. We also investigate the limitation which prevents an
arbitrary choice of the time duration for reconstruction in HDE and NADE, and
find that an improved boundary condition is needed for a more precise
reconstruction of $f(T)$ theory.
| [
{
"created": "Mon, 25 Mar 2013 17:50:28 GMT",
"version": "v1"
}
] | 2013-03-26 | [
[
"Huang",
"Peng",
""
],
[
"Huang",
"Yong-chang",
""
]
] | We reconstruct $f(T)$ theories from three different holographic dark energy models in different time durations. For the HDE model, the dark energy dominated era with new setting up is chosen for reconstruction, and the radiation dominated era is chosen when the involved model changes into NADE. For the RDE model, radiation, matter and dark energy dominated time durations are all investigated. We also investigate the limitation which prevents an arbitrary choice of the time duration for reconstruction in HDE and NADE, and find that an improved boundary condition is needed for a more precise reconstruction of $f(T)$ theory. |
1403.1684 | Victor P. Ruban | V. P. Ruban | Ideal hydrodynamics inside as well as outside non-rotating black hole:
Hamiltonian description in the Painlev{\'e}-Gullstrand coordinates | revtex4, 7 pages, no figures | ZhETF 146, 96-104 (2014) [Russian original] | 10.1134/S1063776114070061 | null | gr-qc astro-ph.GA physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is demonstrated that with using Painlev{\'e}-Gullstrand coordinates in
their quasi-Cartesian variant, the Hamiltonian functional for relativistic
perfect fluid hydrodynamics near a non-rotating black hole differs from the
corresponding flat-spacetime Hamiltonian just by a simple term. Moreover, the
internal region of the black hole is then described uniformly together with the
external region, because in Painlev{\'e}-Gullstrand coordinates there is no
singularity at the event horizon. An exact solution is presented which
describes stationary accretion of an ultra-hard matter ($\varepsilon\propto
n^2$) onto a moving black hole until reaching the central singularity. Equation
of motion for a thin vortex filament on such accretion background is derived in
the local induction approximation. The Hamiltonian for a fluid having
ultra-relativistic equation of state $\varepsilon\propto n^{4/3}$ is calculated
in explicit form, and the problem of centrally-symmetric stationary flow of
such matter is solved analytically.
| [
{
"created": "Fri, 7 Mar 2014 08:49:28 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Ruban",
"V. P.",
""
]
] | It is demonstrated that with using Painlev{\'e}-Gullstrand coordinates in their quasi-Cartesian variant, the Hamiltonian functional for relativistic perfect fluid hydrodynamics near a non-rotating black hole differs from the corresponding flat-spacetime Hamiltonian just by a simple term. Moreover, the internal region of the black hole is then described uniformly together with the external region, because in Painlev{\'e}-Gullstrand coordinates there is no singularity at the event horizon. An exact solution is presented which describes stationary accretion of an ultra-hard matter ($\varepsilon\propto n^2$) onto a moving black hole until reaching the central singularity. Equation of motion for a thin vortex filament on such accretion background is derived in the local induction approximation. The Hamiltonian for a fluid having ultra-relativistic equation of state $\varepsilon\propto n^{4/3}$ is calculated in explicit form, and the problem of centrally-symmetric stationary flow of such matter is solved analytically. |
2305.04970 | Marco de Cesare | Marco de Cesare and Roberto Oliveri | Backreaction of scalar waves on black holes at low frequencies | 10 pages, 3 figures; v2: updated references, matches published
version in PRD | Phys. Rev. D 108 (2023), 044050 | 10.1103/PhysRevD.108.044050 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the accretion of a Schwarzschild black hole due to spherically
symmetric perturbations sourced by a minimally coupled massless scalar field.
The backreaction of the black hole to low-frequency ingoing scalar waves is
computed analytically as a second-order perturbative effect, using matched
asymptotic expansions to relate the behaviour of the scalar field in the
vicinity of the horizon and at null infinity. As an application of our results,
we compute the mass increase due to (i) ingoing wave packets with an arbitrary
profile and (ii) incoherent radiation. Our results could serve as a model for
the backreaction of environmental scalar fields on black holes.
| [
{
"created": "Mon, 8 May 2023 18:03:40 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Aug 2023 16:50:02 GMT",
"version": "v2"
}
] | 2023-08-24 | [
[
"de Cesare",
"Marco",
""
],
[
"Oliveri",
"Roberto",
""
]
] | We study the accretion of a Schwarzschild black hole due to spherically symmetric perturbations sourced by a minimally coupled massless scalar field. The backreaction of the black hole to low-frequency ingoing scalar waves is computed analytically as a second-order perturbative effect, using matched asymptotic expansions to relate the behaviour of the scalar field in the vicinity of the horizon and at null infinity. As an application of our results, we compute the mass increase due to (i) ingoing wave packets with an arbitrary profile and (ii) incoherent radiation. Our results could serve as a model for the backreaction of environmental scalar fields on black holes. |
2311.13264 | Orlando Luongo | Orlando Luongo, Hernando Quevedo, S. N. Sajadi | Gravitational repulsive effects in 3D regular black holes | 12 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we consider the effects of repulsive gravity in an invariant
way for four static 3D regular black holes, using the eigenvalues of the
Riemann curvature tensor, the Ricci scalar, and the strong energy conditions.
The eigenvalues of the solutions are non-vanishing asymptotically (in
asymptotically AdS) and increase as the source of gravity is approached,
providing a radius at which the passage from attractive to repulsive gravity
might occur. We compute the onsets and the regions of repulsive gravity and
conclude that the regular behavior of the solutions at the origin of
coordinates can be interpreted as due to the presence of repulsive gravity,
which also turns out to be related with the violation of the strong energy
condition. We showed that in all of the solutions for the allowed region of
parameters, gravity changes its sign, but the repulsive regions only for the
non-logarithmic solution are affected by the mass that generates the regular
black hole. The repulsive regions for the logarithmic solutions are dependent
on electric charge and the AdS$_{3}$ length. The implications and physical
consequences of these results are discussed in detail.
| [
{
"created": "Wed, 22 Nov 2023 09:28:15 GMT",
"version": "v1"
}
] | 2023-11-23 | [
[
"Luongo",
"Orlando",
""
],
[
"Quevedo",
"Hernando",
""
],
[
"Sajadi",
"S. N.",
""
]
] | In this work, we consider the effects of repulsive gravity in an invariant way for four static 3D regular black holes, using the eigenvalues of the Riemann curvature tensor, the Ricci scalar, and the strong energy conditions. The eigenvalues of the solutions are non-vanishing asymptotically (in asymptotically AdS) and increase as the source of gravity is approached, providing a radius at which the passage from attractive to repulsive gravity might occur. We compute the onsets and the regions of repulsive gravity and conclude that the regular behavior of the solutions at the origin of coordinates can be interpreted as due to the presence of repulsive gravity, which also turns out to be related with the violation of the strong energy condition. We showed that in all of the solutions for the allowed region of parameters, gravity changes its sign, but the repulsive regions only for the non-logarithmic solution are affected by the mass that generates the regular black hole. The repulsive regions for the logarithmic solutions are dependent on electric charge and the AdS$_{3}$ length. The implications and physical consequences of these results are discussed in detail. |
gr-qc/0102066 | Spiros Cotsakis | Spiros Cotsakis and Peter Leach | Is Nature Generic? | 17 pages, latex | Lect.Notes Phys. 592 (2002) 3-15 | null | null | gr-qc astro-ph hep-th | null | An introductory guide to mathematical cosmology is given focusing on the
issue of the genericity of various important results which have been obtained
during the last thirty or so years. Some of the unsolved problems along with
certain new and potentially powerful methods which may be used for future
progress are also given from a unified perspective.
| [
{
"created": "Wed, 14 Feb 2001 10:50:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cotsakis",
"Spiros",
""
],
[
"Leach",
"Peter",
""
]
] | An introductory guide to mathematical cosmology is given focusing on the issue of the genericity of various important results which have been obtained during the last thirty or so years. Some of the unsolved problems along with certain new and potentially powerful methods which may be used for future progress are also given from a unified perspective. |
2405.08069 | Matt Visser | Francesco Di Filippo (Charles University of Prague), Stefano Liberati
(SISSA, Trieste), Matt Visser (Victoria University of Wellington) | Fully extremal black holes: a black hole graveyard? | Essay awarded the Fifth Prize in the Gravity Research Foundation 2024
Awards; 18 pages. V2: Minor clarifications and re-phrasing | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While the standard point of view is that the ultimate endpoint of black hole
evolution is determined by Hawking evaporation, there is a growing evidence
that classical and semi-classical instabilities affect both black holes with
inner horizons as well as their ultra-compact counterparts. In this essay we
start from this evidence pointing towards extremal black holes as stable
endpoints of the gravitational collapse, and develop a general class of
spherical and axisymmetric solutions with multiple extremal horizons. Excluding
more exotic possibilities, entailing regular cores supporting wormhole throats,
we argue that these configuration could be the asymptotic graveyard, the
end-point, of dynamical black hole evolution -- albeit the timescale of such
evolution are still unclear and possibly long and compatible with current
astrophysical observations.
| [
{
"created": "Mon, 13 May 2024 18:00:02 GMT",
"version": "v1"
},
{
"created": "Thu, 23 May 2024 23:16:53 GMT",
"version": "v2"
}
] | 2024-05-27 | [
[
"Di Filippo",
"Francesco",
"",
"Charles University of Prague"
],
[
"Liberati",
"Stefano",
"",
"SISSA, Trieste"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | While the standard point of view is that the ultimate endpoint of black hole evolution is determined by Hawking evaporation, there is a growing evidence that classical and semi-classical instabilities affect both black holes with inner horizons as well as their ultra-compact counterparts. In this essay we start from this evidence pointing towards extremal black holes as stable endpoints of the gravitational collapse, and develop a general class of spherical and axisymmetric solutions with multiple extremal horizons. Excluding more exotic possibilities, entailing regular cores supporting wormhole throats, we argue that these configuration could be the asymptotic graveyard, the end-point, of dynamical black hole evolution -- albeit the timescale of such evolution are still unclear and possibly long and compatible with current astrophysical observations. |
2003.05784 | Gabriele Umberto Varieschi | Gabriele U. Varieschi | Newtonian Fractional-Dimension Gravity and MOND | 25 pages, including 4 figures: change of title and other minor
changes after peer review. Final version to be published in Foundations of
Physics, Springer | Found Phys 50, 1608-1644 (2020) | 10.1007/s10701-020-00389-7 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper introduces a possible alternative model of gravity based on the
theory of fractional-dimension spaces and its applications to Newtonian
gravity. In particular, Gauss's law for gravity as well as other fundamental
classical laws are extended to a $D$-dimensional metric space, where $D$ can be
a non-integer dimension.
We show a possible connection between this Newtonian Fractional-Dimension
Gravity (NFDG) and Modified Newtonian Dynamics (MOND), a leading alternative
gravity model which accounts for the observed properties of galaxies and other
astrophysical structures without requiring the dark matter hypothesis. The MOND
acceleration constant $a_{0} \simeq 1.2 \times 10^{ -10}\mbox{m}\thinspace
\mbox{s}^{ -2}$ can be related to a natural scale length $l_{0}$ in NFDG, i.e.,
$a_{0} \approx GM/l_{0}^{2}$, for astrophysical structures of mass $M$, and the
deep-MOND regime is present in regions of space where the dimension is reduced
to $D \approx 2$.
For several fundamental spherically-symmetric structures, we compare MOND
results, such as the empirical Radial Acceleration Relation (RAR), circular
speed plots, and logarithmic plots of the observed radial acceleration
$g_{obs}$ vs. the baryonic radial acceleration $g_{bar}$, with NFDG results. We
show that our model is capable of reproducing these results using a variable
local dimension $D\left (w\right )$, where $w =r/l_{0}$ is a dimensionless
radial coordinate. At the moment, we are unable to derive explicitly this
dimension function $D\left (w\right )$ from first principles, but it can be
obtained empirically in each case from the general RAR.
Additional work on the subject, including studies of axially-symmetric
structures, detailed galactic rotation curves fitting, and a possible
relativistic extension, will be needed to establish NFDG as a viable
alternative model of gravity.
| [
{
"created": "Wed, 11 Mar 2020 13:26:19 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Apr 2020 06:27:19 GMT",
"version": "v2"
},
{
"created": "Sun, 16 Aug 2020 19:20:50 GMT",
"version": "v3"
},
{
"created": "Tue, 29 Sep 2020 21:17:40 GMT",
"version": "v4"
}
] | 2021-02-09 | [
[
"Varieschi",
"Gabriele U.",
""
]
] | This paper introduces a possible alternative model of gravity based on the theory of fractional-dimension spaces and its applications to Newtonian gravity. In particular, Gauss's law for gravity as well as other fundamental classical laws are extended to a $D$-dimensional metric space, where $D$ can be a non-integer dimension. We show a possible connection between this Newtonian Fractional-Dimension Gravity (NFDG) and Modified Newtonian Dynamics (MOND), a leading alternative gravity model which accounts for the observed properties of galaxies and other astrophysical structures without requiring the dark matter hypothesis. The MOND acceleration constant $a_{0} \simeq 1.2 \times 10^{ -10}\mbox{m}\thinspace \mbox{s}^{ -2}$ can be related to a natural scale length $l_{0}$ in NFDG, i.e., $a_{0} \approx GM/l_{0}^{2}$, for astrophysical structures of mass $M$, and the deep-MOND regime is present in regions of space where the dimension is reduced to $D \approx 2$. For several fundamental spherically-symmetric structures, we compare MOND results, such as the empirical Radial Acceleration Relation (RAR), circular speed plots, and logarithmic plots of the observed radial acceleration $g_{obs}$ vs. the baryonic radial acceleration $g_{bar}$, with NFDG results. We show that our model is capable of reproducing these results using a variable local dimension $D\left (w\right )$, where $w =r/l_{0}$ is a dimensionless radial coordinate. At the moment, we are unable to derive explicitly this dimension function $D\left (w\right )$ from first principles, but it can be obtained empirically in each case from the general RAR. Additional work on the subject, including studies of axially-symmetric structures, detailed galactic rotation curves fitting, and a possible relativistic extension, will be needed to establish NFDG as a viable alternative model of gravity. |
gr-qc/9809014 | M. A. Clayton | M. A. Clayton, L. Demopoulos and J. Legare | The dynamical stability of the static real scalar field solutions to the
Einstein-Klein-Gordon equations revisited | 13 pages, uses Elsevier style files. To appear in Phys. Lett. A | Phys.Lett.A248:131-138,1998 | 10.1016/S0375-9601(98)00646-X | CERN-TH/98-93, UTPT-98-04 | gr-qc | null | We re-examine the dynamical stability of the nakedly singular, static,
spherical ly symmetric solutions of the Einstein-Klein Gordon system. We
correct an earlier proof of the instability of these solutions, and demonstrate
that there are solutions to the massive Klein-Gordon system that are
perturbatively stable.
| [
{
"created": "Wed, 2 Sep 1998 20:35:20 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Clayton",
"M. A.",
""
],
[
"Demopoulos",
"L.",
""
],
[
"Legare",
"J.",
""
]
] | We re-examine the dynamical stability of the nakedly singular, static, spherical ly symmetric solutions of the Einstein-Klein Gordon system. We correct an earlier proof of the instability of these solutions, and demonstrate that there are solutions to the massive Klein-Gordon system that are perturbatively stable. |
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