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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1607.07488
|
Yves Brihaye
|
Y. Brihaye, T. Delsate
|
Boson stars, neutron stars and black holes in five dimensions
|
14 pages, 6 figures
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Different types of gravitating compact objects occuring in d=5 space-time are
considered: boson stars, hairy black holes and perfect fluid solutions. All
these solutions of the Einstein equations coupled to matter have well
established counterparts in d=4; in particular neutron stars can be
modell{\S}ed more or less realistically by a perfect fluid. A special emphasis
is set on the possibility -and/or the necessity- for these solutions to have an
intrinsic angular momentum or spin. The influence of a cosmological constant on
their pattern is also studied.
Several physical properties are presented from which common features to boson
and neutron stars clearly emerge.
We finally point out qualitative differences of the gravitational interaction
supporting these classical lumps between four and five dimensions.
|
[
{
"created": "Mon, 25 Jul 2016 21:30:36 GMT",
"version": "v1"
}
] |
2016-07-27
|
[
[
"Brihaye",
"Y.",
""
],
[
"Delsate",
"T.",
""
]
] |
Different types of gravitating compact objects occuring in d=5 space-time are considered: boson stars, hairy black holes and perfect fluid solutions. All these solutions of the Einstein equations coupled to matter have well established counterparts in d=4; in particular neutron stars can be modell{\S}ed more or less realistically by a perfect fluid. A special emphasis is set on the possibility -and/or the necessity- for these solutions to have an intrinsic angular momentum or spin. The influence of a cosmological constant on their pattern is also studied. Several physical properties are presented from which common features to boson and neutron stars clearly emerge. We finally point out qualitative differences of the gravitational interaction supporting these classical lumps between four and five dimensions.
|
2011.04032
|
Ruifeng Dong
|
Ruifeng Dong and Dejan Stojkovic
|
Gravitational wave echoes from black holes in massive gravity
|
8 pages, 3 figures. Accepted for publication in Phys. Rev. D
|
Phys. Rev. D 103, 024058 (2021)
|
10.1103/PhysRevD.103.024058
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Gravitational waves are rapidly becoming a very reliable tool for testing
alternative theories of gravity. In particular, features in the gravitational
wave emission during black hole ringdown phase provide a direct probe of the
spacetime outside the black hole. In this article, we consider black holes in
ghost-free massive gravity. These black holes generically have scalar hair. We
found that a simple coupling between gravitational perturbations and this
scalar hair can change the quasinormal ringing of the black hole, and in
particular, produce echoes in the emitted gravitational waves. This finding
provides a clear-cut way to test massive gravity theory using gravitational
wave observations.
|
[
{
"created": "Sun, 8 Nov 2020 17:30:55 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jan 2021 14:22:33 GMT",
"version": "v2"
}
] |
2021-02-03
|
[
[
"Dong",
"Ruifeng",
""
],
[
"Stojkovic",
"Dejan",
""
]
] |
Gravitational waves are rapidly becoming a very reliable tool for testing alternative theories of gravity. In particular, features in the gravitational wave emission during black hole ringdown phase provide a direct probe of the spacetime outside the black hole. In this article, we consider black holes in ghost-free massive gravity. These black holes generically have scalar hair. We found that a simple coupling between gravitational perturbations and this scalar hair can change the quasinormal ringing of the black hole, and in particular, produce echoes in the emitted gravitational waves. This finding provides a clear-cut way to test massive gravity theory using gravitational wave observations.
|
2405.19385
|
Mir Faizal
|
Lawrence M. Krauss, Francesco Marino, Samuel L. Braunstein, Mir
Faizal, Naveed A. Shah
|
Listening to Quantum Gravity?
|
16 pages; Essay received an honorable mention in the Gravity Research
Foundation Essay Competition 2024. arXiv admin note: text overlap with
arXiv:2402.16136
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Recent experimental progresses in controlling classical and quantum fluids
have made it possible to realize acoustic analogues of gravitational black
holes, where a flowing fluid provides an effective spacetime on which sound
waves propagate, demonstrating Hawking-like radiation and Penrose
superradiance. We propose the exciting possibility that new hydrodynamic
systems might provide insights to help resolve mysteries associated with
quantum gravity, including the black hole information-loss paradox and the
removal of spacetime singularities.
|
[
{
"created": "Wed, 29 May 2024 14:31:52 GMT",
"version": "v1"
}
] |
2024-05-31
|
[
[
"Krauss",
"Lawrence M.",
""
],
[
"Marino",
"Francesco",
""
],
[
"Braunstein",
"Samuel L.",
""
],
[
"Faizal",
"Mir",
""
],
[
"Shah",
"Naveed A.",
""
]
] |
Recent experimental progresses in controlling classical and quantum fluids have made it possible to realize acoustic analogues of gravitational black holes, where a flowing fluid provides an effective spacetime on which sound waves propagate, demonstrating Hawking-like radiation and Penrose superradiance. We propose the exciting possibility that new hydrodynamic systems might provide insights to help resolve mysteries associated with quantum gravity, including the black hole information-loss paradox and the removal of spacetime singularities.
|
2103.13993
|
Santiago Ontanon
|
Santiago Ontanon and Miguel Alcubierre
|
Rotating Boson Stars Using Finite Differences and Global Newton Methods
|
45 pages, 13 figures
| null |
10.1088/1361-6382/ac0b53
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We study Rotating Boson Star initial data for Numerical Relativity as
previously considered by Yoshida and Eriguchi, Lai (arXiv:gr-qc/0410040v2), and
Grandclement, Som\'e and Gourgoulhon (arXiv:1405.4837v3). We use a 3 + 1
decomposition as presented by Gourgoulhon (arXiv:1003.5015v2) and Alcubierre,
adapted to an axisymmetric quasi-isotropic spacetime with added regularization
at the axis following work by Ru\'iz, Alcubierre and N\'u\~nez
(arXiv:0706.0923v2) and Torres. The Einstein-Klein-Gordon equations result in a
system of six-coupled, elliptic, nonlinear equations with an added unknown for
the scalar field's frequency $\omega$. Utilizing a Cartesian two-dimensional
grid, finite differences, Global Newton Methods adapted from Deuflhard, the
sparse direct linear solver PARDISO, and properly constraining all variables
generates data sets for rotation azimuthal integers $l \in [0, 6]$. Our
numerical implementation, published in GitHub, is shown to correctly converge
both with respect to the resolution size and boundary extension (fourth-order
and third-order, respectively). Thus, global parameters such as the Komar
masses and angular momenta can be precisely calculated to characterize these
spacetimes. Furthermore, analyzing the full family at fixed rotation integer
produces maximum masses and minimum frequencies. These coincide with previous
results in literature for $l \in [0,2]$ and are new for $l > 2$. In particular,
the study of high-amplitude and localized scalar fields in axial symmetry is
revealed to be only possible by adding the sixth regularization variable.
|
[
{
"created": "Thu, 25 Mar 2021 17:31:44 GMT",
"version": "v1"
}
] |
2021-08-11
|
[
[
"Ontanon",
"Santiago",
""
],
[
"Alcubierre",
"Miguel",
""
]
] |
We study Rotating Boson Star initial data for Numerical Relativity as previously considered by Yoshida and Eriguchi, Lai (arXiv:gr-qc/0410040v2), and Grandclement, Som\'e and Gourgoulhon (arXiv:1405.4837v3). We use a 3 + 1 decomposition as presented by Gourgoulhon (arXiv:1003.5015v2) and Alcubierre, adapted to an axisymmetric quasi-isotropic spacetime with added regularization at the axis following work by Ru\'iz, Alcubierre and N\'u\~nez (arXiv:0706.0923v2) and Torres. The Einstein-Klein-Gordon equations result in a system of six-coupled, elliptic, nonlinear equations with an added unknown for the scalar field's frequency $\omega$. Utilizing a Cartesian two-dimensional grid, finite differences, Global Newton Methods adapted from Deuflhard, the sparse direct linear solver PARDISO, and properly constraining all variables generates data sets for rotation azimuthal integers $l \in [0, 6]$. Our numerical implementation, published in GitHub, is shown to correctly converge both with respect to the resolution size and boundary extension (fourth-order and third-order, respectively). Thus, global parameters such as the Komar masses and angular momenta can be precisely calculated to characterize these spacetimes. Furthermore, analyzing the full family at fixed rotation integer produces maximum masses and minimum frequencies. These coincide with previous results in literature for $l \in [0,2]$ and are new for $l > 2$. In particular, the study of high-amplitude and localized scalar fields in axial symmetry is revealed to be only possible by adding the sixth regularization variable.
|
1602.03336
|
Oleg Zaslavskii
|
O. B. Zaslavskii
|
High energy particle collisions and geometry of horizon
|
14 pages. Presentation expanded, typos corrected. To appear in IJMP D
|
Int. J. Mod. Phys. D (2016) 1650095
|
10.1142/S0218271816500954
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider collision of two geodesic particles near the horizon of such an
axially symmetric black hole (rotating or static) that the metric coefficient
$g_{\phi \phi }\rightarrow 0$ there. It is shown that (both for regular and
singular horizons) the energy in the centre of mass frame $% E_{c.m.}$ is
indefinitely large even without fine-tuning of particles' parameters.
Kinematically, this is collision between two rapid particles that approach the
horizon almost with the speed of light but at different angles. The latter is
the reason why the relative velocity tends to that of light, hence to high
$E_{c.m.}$. Our approach is model-independent. It relies on general properties
of geometry and is insensitive to the details of material source that supports
the geometies of the type under consideration. For several particular models
(the stringy black hole, the Brans-Dicke analogue of the Schwarzschild metric
and the Janis-Newman-Winicour one) we recover the results found in literature
previously.
|
[
{
"created": "Wed, 10 Feb 2016 11:53:24 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jun 2016 20:35:02 GMT",
"version": "v2"
}
] |
2016-09-07
|
[
[
"Zaslavskii",
"O. B.",
""
]
] |
We consider collision of two geodesic particles near the horizon of such an axially symmetric black hole (rotating or static) that the metric coefficient $g_{\phi \phi }\rightarrow 0$ there. It is shown that (both for regular and singular horizons) the energy in the centre of mass frame $% E_{c.m.}$ is indefinitely large even without fine-tuning of particles' parameters. Kinematically, this is collision between two rapid particles that approach the horizon almost with the speed of light but at different angles. The latter is the reason why the relative velocity tends to that of light, hence to high $E_{c.m.}$. Our approach is model-independent. It relies on general properties of geometry and is insensitive to the details of material source that supports the geometies of the type under consideration. For several particular models (the stringy black hole, the Brans-Dicke analogue of the Schwarzschild metric and the Janis-Newman-Winicour one) we recover the results found in literature previously.
|
2112.11825
|
Hamid R. Bakhtiarizadeh
|
Hamid R. Bakhtiarizadeh
|
Charged rotating black strings in Einsteinian quartic gravity
|
LaTex file, 18 pages, no figure, v2: some corrections have been made,
to appear in NPB
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We find an analytic asymptotically anti-de Sitter solution for charged
rotating black strings in Einsteinian quartic gravity. By studying the
near-horizon behavior of the solutions, we independently extract their
thermodynamic properties, analytically. As a consistency check, we show that
the first law of thermodynamics for rotating black strings holds exactly in
both charged and uncharged cases.
|
[
{
"created": "Wed, 22 Dec 2021 12:04:09 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jun 2022 21:24:11 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Jan 2023 18:41:53 GMT",
"version": "v3"
}
] |
2023-01-18
|
[
[
"Bakhtiarizadeh",
"Hamid R.",
""
]
] |
We find an analytic asymptotically anti-de Sitter solution for charged rotating black strings in Einsteinian quartic gravity. By studying the near-horizon behavior of the solutions, we independently extract their thermodynamic properties, analytically. As a consistency check, we show that the first law of thermodynamics for rotating black strings holds exactly in both charged and uncharged cases.
|
1409.3378
|
Anirban Saha Dr.
|
Sunandan Gangopadhyay, Anirban Saha, Swarup Saha
|
Noncommutative quantum mechanics of simple matter systems interacting
with circularly polarized gravitational waves
|
11 pages, LaTex
|
Gen.Rel.Grav. 47 (2015) 3, 28
|
10.1007/s10714-015-1867-7
| null |
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The response of a test particle, both for the free case and under the
harmonic oscillator potential, to circularly polarized gravitational waves is
investigated in a noncommutative quantum mechanical setting. The system is
quantized following the prescription in \cite{ncgw1}. Standard algebraic
techniques are then employed to solve the Hamiltonian of the system. The
solutions, in both cases, show signatures of the coordinate noncommutativity.
In the harmonic oscillator case, this signature plays a key role in altering
the resonance point and the oscillation frequency of the system.
|
[
{
"created": "Thu, 11 Sep 2014 10:43:01 GMT",
"version": "v1"
}
] |
2015-06-03
|
[
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Saha",
"Anirban",
""
],
[
"Saha",
"Swarup",
""
]
] |
The response of a test particle, both for the free case and under the harmonic oscillator potential, to circularly polarized gravitational waves is investigated in a noncommutative quantum mechanical setting. The system is quantized following the prescription in \cite{ncgw1}. Standard algebraic techniques are then employed to solve the Hamiltonian of the system. The solutions, in both cases, show signatures of the coordinate noncommutativity. In the harmonic oscillator case, this signature plays a key role in altering the resonance point and the oscillation frequency of the system.
|
1106.0711
|
Fei-Hung Ho
|
Fei-Hung Ho, James M. Nester
|
Poincar\'e Gauge Theory With Coupled Even And Odd Parity Dynamic Spin-0
Modes: Dynamic Equations For Isotropic Bianchi Cosmologies
|
13 pages, 2 figures
|
Int. J. Mod. Phys. D 20, 2125 (2011)
|
10.1002/andp.201100101
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We are investigating the dynamics of a new Poincar\'e gauge theory of gravity
model, which has cross coupling between the spin-0$^+$ and spin-0$^-$ modes. To
this end we here consider a very appropriate situation---homogeneous-isotropic
cosmologies---which is relatively simple, and yet all the modes have
non-trivial dynamics which reveals physically interesting and possibly
observable results. More specifically we consider manifestly isotropic Bianchi
class A cosmologies; for this case we find an effective Lagrangian and
Hamiltonian for the dynamical system. The Lagrange equations for these models
lead to a set of first order equations that are compatible with those found for
the FLRW models and provide a foundation for further investigations. Typical
numerical evolution of these equations shows the expected effects of the cross
parity coupling.
|
[
{
"created": "Fri, 3 Jun 2011 17:34:44 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2011 08:54:31 GMT",
"version": "v2"
}
] |
2016-10-26
|
[
[
"Ho",
"Fei-Hung",
""
],
[
"Nester",
"James M.",
""
]
] |
We are investigating the dynamics of a new Poincar\'e gauge theory of gravity model, which has cross coupling between the spin-0$^+$ and spin-0$^-$ modes. To this end we here consider a very appropriate situation---homogeneous-isotropic cosmologies---which is relatively simple, and yet all the modes have non-trivial dynamics which reveals physically interesting and possibly observable results. More specifically we consider manifestly isotropic Bianchi class A cosmologies; for this case we find an effective Lagrangian and Hamiltonian for the dynamical system. The Lagrange equations for these models lead to a set of first order equations that are compatible with those found for the FLRW models and provide a foundation for further investigations. Typical numerical evolution of these equations shows the expected effects of the cross parity coupling.
|
gr-qc/0112062
|
Petr Hajicek
|
I. Kouletsis and P. Hajicek
|
Pair of null gravitating shells III. Algebra of Dirac's observables
|
26 pages, Latex file using amstex, some references corrected
|
Class.Quant.Grav. 19 (2002) 2567-2586
|
10.1088/0264-9381/19/10/304
|
BUTP-01/26
|
gr-qc
| null |
The study of the two-shell system started in ``Pair of null gravitating
shells I and II'' (gr-qc/0112060--061) is continued. The pull back of the
Liouville form to the constraint surface, which contains complete information
about the Poisson brackets of Dirac observables, is computed in the singular
double-null Eddington-Finkelstein (DNEF) gauge. The resulting formula shows
that the variables conjugate to the Schwarzschild masses of the intershell
spacetimes are simple combinations of the values of the DNEF coordinates on
these spacetimes at the shells. The formula is valid for any number of in- and
out-going shells. After applying it to the two-shell system, the symplectic
form is calculated for each component of the physical phase space; regular
coordinates are found, defining it as a symplectic manifold. The symplectic
transformation between the initial and final values of observables for the
shell-crossing case is written down.
|
[
{
"created": "Sat, 22 Dec 2001 10:53:08 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Dec 2001 14:06:59 GMT",
"version": "v2"
}
] |
2009-11-07
|
[
[
"Kouletsis",
"I.",
""
],
[
"Hajicek",
"P.",
""
]
] |
The study of the two-shell system started in ``Pair of null gravitating shells I and II'' (gr-qc/0112060--061) is continued. The pull back of the Liouville form to the constraint surface, which contains complete information about the Poisson brackets of Dirac observables, is computed in the singular double-null Eddington-Finkelstein (DNEF) gauge. The resulting formula shows that the variables conjugate to the Schwarzschild masses of the intershell spacetimes are simple combinations of the values of the DNEF coordinates on these spacetimes at the shells. The formula is valid for any number of in- and out-going shells. After applying it to the two-shell system, the symplectic form is calculated for each component of the physical phase space; regular coordinates are found, defining it as a symplectic manifold. The symplectic transformation between the initial and final values of observables for the shell-crossing case is written down.
|
2303.16218
|
William C. C. Lima
|
Markus B. Fr\"ob, William C. C. Lima
|
Synchronous coordinates and gauge-invariant observables in cosmological
spacetimes
|
57 pages. Some discussions improved, references added and typos
corrected, matches published version
|
Class. Quantum Grav. 40, 215006 (2023)
|
10.1088/1361-6382/acf98a
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the relational approach to construct gauge-invariant observables
in cosmological perturbation theory using synchronous coordinates. We construct
dynamical synchronous coordinates as non-local scalar functionals of the metric
perturbation in the fully non-linear theory in an arbitrary gauge. We show that
the observables defined in this dynamical coordinate system are
gauge-independent, and that the full perturbed metric has the expected form in
these coordinates. Our construction generalises the familiar synchronous gauge
in linearised gravity, widely used in cosmological perturbation theory, to the
non-linear theory. We also work out the expressions for the gauge-invariant
Einstein equation, sourced either by an ideal fluid or a scalar field up to
second order in perturbation theory, and give explicit expressions for the
Hubble rate -- as measured by synchronous observers or by observers co-moving
with the matter field -- up to that order. Finally, we consider quantised
linear perturbations around Minkowski and de~Sitter backgrounds, and compute
the two-point function of the gauge-invariant metric perturbation in
synchronous coordinates, starting with two-point function in a general linear
covariant gauge. Although the gauge-fixed two-point function contains gauge
modes, we show that the resulting gauge-invariant two-point function only
contains the physical tensor modes and it is thus positive, \ie, it has a
spectral representation.
|
[
{
"created": "Tue, 28 Mar 2023 18:00:01 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Oct 2023 00:18:02 GMT",
"version": "v2"
}
] |
2023-10-05
|
[
[
"Fröb",
"Markus B.",
""
],
[
"Lima",
"William C. C.",
""
]
] |
We consider the relational approach to construct gauge-invariant observables in cosmological perturbation theory using synchronous coordinates. We construct dynamical synchronous coordinates as non-local scalar functionals of the metric perturbation in the fully non-linear theory in an arbitrary gauge. We show that the observables defined in this dynamical coordinate system are gauge-independent, and that the full perturbed metric has the expected form in these coordinates. Our construction generalises the familiar synchronous gauge in linearised gravity, widely used in cosmological perturbation theory, to the non-linear theory. We also work out the expressions for the gauge-invariant Einstein equation, sourced either by an ideal fluid or a scalar field up to second order in perturbation theory, and give explicit expressions for the Hubble rate -- as measured by synchronous observers or by observers co-moving with the matter field -- up to that order. Finally, we consider quantised linear perturbations around Minkowski and de~Sitter backgrounds, and compute the two-point function of the gauge-invariant metric perturbation in synchronous coordinates, starting with two-point function in a general linear covariant gauge. Although the gauge-fixed two-point function contains gauge modes, we show that the resulting gauge-invariant two-point function only contains the physical tensor modes and it is thus positive, \ie, it has a spectral representation.
|
2402.17429
|
Jun-Jin Peng
|
Jun-Jin Peng, Hua Li
|
Field equations and Noether potentials for higher-order theories of
gravity with Lagrangians involving $\Box^i R$, $\Box^i R_{\mu\nu}$ and
$\Box^i R_{\mu\nu\rho\sigma}$
|
73 pages, No figures
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we aim to perform a systematical investigation on the field
equations and Noether potentials for the higher-order gravity theories endowed
with Lagrangians depending on the metric and the Riemann curvature tensor,
together with $i$th ($i=1,2,\cdot\cdot\cdot$) powers of the
Beltrami-d'Alembertian operator $\Box$ acting on the latter. We start with a
detailed derivation of the field equations and the Noether potential
corresponding to the Lagrangian $\sqrt{-g}L_R(R,\Box R,\cdot\cdot\cdot,\Box^m
R)$ through the direct variation of the Lagrangian and a method based upon the
conserved current. Next the parallel analysis is extended to a more generic
Lagrangian $\sqrt{-g}L_{\text{Ric}}(g^{\mu\nu}, R_{\mu\nu},\Box R_{\mu\nu},
\cdot\cdot\cdot,\Box^m R_{\mu\nu})$, as well as to the generalization of the
Lagrangian $\sqrt{-g}L_{\text{Ric}}$, which depends on the metric $g^{\mu\nu}$,
the Riemann tensor $R_{\mu\nu\rho\sigma}$ and $\Box^i R_{\mu\nu\rho\sigma}$s.
Finally, all the results associated to the three types of Lagrangians are
extended to the Lagrangian relying on an arbitrary tensor and the variables via
$\Box^i$ acting on such a tensor. In particular, we take into consideration of
equations of motion and Noether potentials for nonlocal gravity models. For
Lagrangians involving the variables $\Box^i R$, $\Box^i R_{\mu\nu}$ and $\Box^i
R_{\mu\nu\rho\sigma}$, our investigation provides their concrete Noether
potentials and the field equations without the derivative of the Lagrangian
density with respect to the metric. Besides, the Iyer-Wald potentials
associated to these Lagrangians are also presented.
|
[
{
"created": "Tue, 27 Feb 2024 11:42:18 GMT",
"version": "v1"
}
] |
2024-02-28
|
[
[
"Peng",
"Jun-Jin",
""
],
[
"Li",
"Hua",
""
]
] |
In this paper, we aim to perform a systematical investigation on the field equations and Noether potentials for the higher-order gravity theories endowed with Lagrangians depending on the metric and the Riemann curvature tensor, together with $i$th ($i=1,2,\cdot\cdot\cdot$) powers of the Beltrami-d'Alembertian operator $\Box$ acting on the latter. We start with a detailed derivation of the field equations and the Noether potential corresponding to the Lagrangian $\sqrt{-g}L_R(R,\Box R,\cdot\cdot\cdot,\Box^m R)$ through the direct variation of the Lagrangian and a method based upon the conserved current. Next the parallel analysis is extended to a more generic Lagrangian $\sqrt{-g}L_{\text{Ric}}(g^{\mu\nu}, R_{\mu\nu},\Box R_{\mu\nu}, \cdot\cdot\cdot,\Box^m R_{\mu\nu})$, as well as to the generalization of the Lagrangian $\sqrt{-g}L_{\text{Ric}}$, which depends on the metric $g^{\mu\nu}$, the Riemann tensor $R_{\mu\nu\rho\sigma}$ and $\Box^i R_{\mu\nu\rho\sigma}$s. Finally, all the results associated to the three types of Lagrangians are extended to the Lagrangian relying on an arbitrary tensor and the variables via $\Box^i$ acting on such a tensor. In particular, we take into consideration of equations of motion and Noether potentials for nonlocal gravity models. For Lagrangians involving the variables $\Box^i R$, $\Box^i R_{\mu\nu}$ and $\Box^i R_{\mu\nu\rho\sigma}$, our investigation provides their concrete Noether potentials and the field equations without the derivative of the Lagrangian density with respect to the metric. Besides, the Iyer-Wald potentials associated to these Lagrangians are also presented.
|
1308.1819
|
Hoda Farahani
|
J. Sadeghi, M. Khurshudyan, H. Farahani
|
Phenomenological Varying Modified Chaplygin Gas with Variable $G$ and
$\Lambda$: Toy Models for Our Universe
|
16 pages, 12 figure
|
Int J Theor Phys 55 (2016) 81
|
10.1007/s10773-015-2635-x
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This article motivated by the recent articles and results of two authors.
Recently, J. Sadeghi and H. Farahani presented a work [1], where they include
viscosity and analyze general model, by this way they extended models
considered by M. Khurshudyan [2] and [3]. In this article, We tempt to consider
varying Modified Chaplygin gas model in case of variable $G$ and $\Lambda$. It
is well known, that varying $G$ and $\Lambda$ gives rise to modified field
equations and modified conservation laws. We will consider two different toy
models. First model is a Universe with one component phenomenological gas of
our consideration, while for the second model we assume existence of a composed
fluid of gas and a matter with $P=\omega(t)\rho_{m}$. Sign changeable
interaction between fluids is accepted. We will analyze important cosmological
parameters like EoS parameter of a fluid, deceleration parameter $q$ of the
model.
|
[
{
"created": "Thu, 8 Aug 2013 11:40:25 GMT",
"version": "v1"
}
] |
2016-01-05
|
[
[
"Sadeghi",
"J.",
""
],
[
"Khurshudyan",
"M.",
""
],
[
"Farahani",
"H.",
""
]
] |
This article motivated by the recent articles and results of two authors. Recently, J. Sadeghi and H. Farahani presented a work [1], where they include viscosity and analyze general model, by this way they extended models considered by M. Khurshudyan [2] and [3]. In this article, We tempt to consider varying Modified Chaplygin gas model in case of variable $G$ and $\Lambda$. It is well known, that varying $G$ and $\Lambda$ gives rise to modified field equations and modified conservation laws. We will consider two different toy models. First model is a Universe with one component phenomenological gas of our consideration, while for the second model we assume existence of a composed fluid of gas and a matter with $P=\omega(t)\rho_{m}$. Sign changeable interaction between fluids is accepted. We will analyze important cosmological parameters like EoS parameter of a fluid, deceleration parameter $q$ of the model.
|
1806.08364
|
Kyle Slinker
|
Kyle Slinker, Charles R. Evans, Mark Hannam
|
Trumpet Initial Data for Boosted Black Holes
|
18 pages, 18 figures
|
Phys. Rev. D 98, 044014 (2018)
|
10.1103/PhysRevD.98.044014
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We describe a procedure for constructing initial data for boosted black holes
in the moving-punctures approach to numerical relativity that endows the
initial time slice from the outset with trumpet geometry within the black hole
interiors. We then demonstrate the procedure in numerical simulations using an
evolution code from the Einstein Toolkit that employs 1+log slicing. The
Lorentz boost of a single black hole can be precisely specified and multiple,
widely separated black holes can be treated approximately by superposition of
single hole data. There is room within the scheme for later improvement to
re-solve (iterate) the constraint equations in the multiple black hole case.
The approach is shown to yield an initial trumpet slice for one black hole that
is close to, and rapidly settles to, a stationary trumpet geometry. Initial
data in this new approach is shown to contain initial transient (or "junk")
radiation that is suppressed by as much as two orders of magnitude relative to
that in comparable Bowen-York initial data.
|
[
{
"created": "Thu, 21 Jun 2018 18:00:04 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Aug 2018 01:11:37 GMT",
"version": "v2"
}
] |
2018-08-15
|
[
[
"Slinker",
"Kyle",
""
],
[
"Evans",
"Charles R.",
""
],
[
"Hannam",
"Mark",
""
]
] |
We describe a procedure for constructing initial data for boosted black holes in the moving-punctures approach to numerical relativity that endows the initial time slice from the outset with trumpet geometry within the black hole interiors. We then demonstrate the procedure in numerical simulations using an evolution code from the Einstein Toolkit that employs 1+log slicing. The Lorentz boost of a single black hole can be precisely specified and multiple, widely separated black holes can be treated approximately by superposition of single hole data. There is room within the scheme for later improvement to re-solve (iterate) the constraint equations in the multiple black hole case. The approach is shown to yield an initial trumpet slice for one black hole that is close to, and rapidly settles to, a stationary trumpet geometry. Initial data in this new approach is shown to contain initial transient (or "junk") radiation that is suppressed by as much as two orders of magnitude relative to that in comparable Bowen-York initial data.
|
1006.1610
|
Lorenzo Sebastiani
|
Lorenzo Sebastiani
|
Dark Viscous Fluid coupled with Dark Matter and future singularity
|
11 pages
|
Eur.Phys.J.C69:547-553,2010
|
10.1140/epjc/s10052-010-1398-z
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study effects of viscous fluid coupled with dark matter in our universe.
We consider bulk viscosity in the cosmic fluid and we suppose the existence of
a coupling between fluid and dark matter, in order to reproduce a stable de
Sitter universe protected against future-time singularities. More general
inhomogeneous fluids are studied related to future singularities.
|
[
{
"created": "Tue, 8 Jun 2010 16:48:21 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jun 2010 12:42:47 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Jun 2010 07:39:52 GMT",
"version": "v3"
}
] |
2013-10-30
|
[
[
"Sebastiani",
"Lorenzo",
""
]
] |
We study effects of viscous fluid coupled with dark matter in our universe. We consider bulk viscosity in the cosmic fluid and we suppose the existence of a coupling between fluid and dark matter, in order to reproduce a stable de Sitter universe protected against future-time singularities. More general inhomogeneous fluids are studied related to future singularities.
|
1801.03207
|
Marko Vojinovic
|
Francisco Pipa, Nikola Paunkovic, Marko Vojinovic
|
Entanglement-induced deviation from the geodesic motion in quantum
gravity
|
v4: published version, 37 pages
|
Jour. Cosmol. Astropart. Phys. 09, 057 (2019)
|
10.1088/1475-7516/2019/09/057
| null |
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the derivation of the effective equation of motion for a pointlike
particle in the framework of quantum gravity. Just like the geodesic motion of
a classical particle is a consequence of classical field theory coupled to
general relativity, we introduce the similar notion of an effective equation of
motion, but starting from an abstract quantum gravity description. In the
presence of entanglement between gravity and matter, quantum effects give rise
to modifications of the geodesic trajectory, primarily as a consequence of the
nonzero overlap between various coherent states of the gravity-matter system.
Finally, we discuss the status of the weak equivalence principle in quantum
gravity and its possible violation due to the nongeodesic motion.
|
[
{
"created": "Wed, 10 Jan 2018 01:22:04 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Sep 2018 07:03:44 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Nov 2018 11:46:45 GMT",
"version": "v3"
},
{
"created": "Fri, 27 Sep 2019 22:45:30 GMT",
"version": "v4"
}
] |
2019-10-01
|
[
[
"Pipa",
"Francisco",
""
],
[
"Paunkovic",
"Nikola",
""
],
[
"Vojinovic",
"Marko",
""
]
] |
We study the derivation of the effective equation of motion for a pointlike particle in the framework of quantum gravity. Just like the geodesic motion of a classical particle is a consequence of classical field theory coupled to general relativity, we introduce the similar notion of an effective equation of motion, but starting from an abstract quantum gravity description. In the presence of entanglement between gravity and matter, quantum effects give rise to modifications of the geodesic trajectory, primarily as a consequence of the nonzero overlap between various coherent states of the gravity-matter system. Finally, we discuss the status of the weak equivalence principle in quantum gravity and its possible violation due to the nongeodesic motion.
|
1601.05172
|
Narayan Banerjee
|
Ankan Mukherjee and Narayan Banerjee
|
A parametric reconstruction of the cosmological jerk from diverse
observational data sets
|
12 pages, 44 figures; Accepted for publication in Phys. Rev. D
| null |
10.1103/PhysRevD.93.043002
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A parametric reconstruction of the jerk parameter, the third order derivative
of the scale factor expressed in a dimensionless way, has been discussed.
Observational constraints on the model parameters have been obtained by Maximum
Likelihood Analysis of the models using Supernova Distance Modulus data (SNe),
Observational Hubble Data (OHD), Baryon Acoustic Oscillation (BAO) data and CMB
shift parameter data (CMBShift). The present value of the jerk parameter has
been kept open to start with, but the plots of various cosmological parameter
like deceleration parameter $q(z)$, jerk parameter $j(z)$, dark energy equation
of state parameter $w_{DE}(z)$ indicate that the reconstructed models are very
close to a $\Lambda$CDM model with a slight inclination towards a non-phantom
behaviour of the evolution.
|
[
{
"created": "Wed, 20 Jan 2016 05:19:04 GMT",
"version": "v1"
}
] |
2016-03-23
|
[
[
"Mukherjee",
"Ankan",
""
],
[
"Banerjee",
"Narayan",
""
]
] |
A parametric reconstruction of the jerk parameter, the third order derivative of the scale factor expressed in a dimensionless way, has been discussed. Observational constraints on the model parameters have been obtained by Maximum Likelihood Analysis of the models using Supernova Distance Modulus data (SNe), Observational Hubble Data (OHD), Baryon Acoustic Oscillation (BAO) data and CMB shift parameter data (CMBShift). The present value of the jerk parameter has been kept open to start with, but the plots of various cosmological parameter like deceleration parameter $q(z)$, jerk parameter $j(z)$, dark energy equation of state parameter $w_{DE}(z)$ indicate that the reconstructed models are very close to a $\Lambda$CDM model with a slight inclination towards a non-phantom behaviour of the evolution.
|
1706.06443
|
Jose Geraldo Pereira
|
A. Araujo, D. F. Lopez, J. G. Pereira
|
de Sitter invariant special relativity and galaxy rotation curves
|
12 pages, 1 figure. V2: presentation changes aiming at clarifying the
text, 13 pages, 1 figure; matches published version. arXiv admin note: text
overlap with arXiv:1704.02120
|
Grav. Cosm. 25 (2019) 157-163
|
10.1134/S0202289319020026
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Owing to the existence of an invariant length at the Planck scale, Einstein
special relativity breaks down at that scale. A possible solution to this
problem is arguably to replace the Poincar\'e invariant Einstein special
relativity by a de Sitter invariant special relativity. In addition to
reconciling Lorentz symmetry with the existence of an invariant length, such
replacement produces concomitant changes in all relativistic theories,
including general relativity, which becomes what we have called 'de Sitter
modified general relativity'. In this paper, the Newtonian limit of this theory
is used to study the circular velocity of stars around the galactic center. It
is shown that the de Sitter modified Newtonian force---which includes
corrections coming from the underlying local kinematics---could possibly
explain the rotation curve of galaxies without the necessity of supposing the
existence of a dark matter halo.
|
[
{
"created": "Sat, 17 Jun 2017 14:11:25 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2019 18:18:34 GMT",
"version": "v2"
}
] |
2019-06-14
|
[
[
"Araujo",
"A.",
""
],
[
"Lopez",
"D. F.",
""
],
[
"Pereira",
"J. G.",
""
]
] |
Owing to the existence of an invariant length at the Planck scale, Einstein special relativity breaks down at that scale. A possible solution to this problem is arguably to replace the Poincar\'e invariant Einstein special relativity by a de Sitter invariant special relativity. In addition to reconciling Lorentz symmetry with the existence of an invariant length, such replacement produces concomitant changes in all relativistic theories, including general relativity, which becomes what we have called 'de Sitter modified general relativity'. In this paper, the Newtonian limit of this theory is used to study the circular velocity of stars around the galactic center. It is shown that the de Sitter modified Newtonian force---which includes corrections coming from the underlying local kinematics---could possibly explain the rotation curve of galaxies without the necessity of supposing the existence of a dark matter halo.
|
gr-qc/9701065
|
Andy Shiekh
|
S. Bellucci and A. Shiekh
|
Gravity Quantized (the high tension string)
|
7 pages, no figures, LaTeX, talk for the XX International Workshop on
the Fundamantal Problems of High Energy Physics and Field Theory, Protvino,
Russia, June 1997
|
XX International Workshop on High Energy Physics and Field Theory,
Protvino, Russia, June 1997
| null |
LNF-97/012 (P)
|
gr-qc hep-ph hep-th
| null |
A candidate theory of gravity quantized is reviewed.
|
[
{
"created": "Thu, 30 Jan 1997 13:39:18 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Aug 1997 05:50:57 GMT",
"version": "v2"
}
] |
2008-02-03
|
[
[
"Bellucci",
"S.",
""
],
[
"Shiekh",
"A.",
""
]
] |
A candidate theory of gravity quantized is reviewed.
|
1512.08972
|
Sunil Maharaj
|
Sunil D. Maharaj, Brian Chilambwe, Sudan Hansraj
|
Exact barotropic distributions in Einstein-Gauss-Bonnet gravity
|
15 pages, submitted for publication
|
Phys. Rev. D 91, 084049 (2015)
|
10.1103/PhysRevD.91.084049
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
New exact solutions to the field equations in the Einstein--Gauss--Bonnet
modified theory of gravity for a 5--dimensional spherically symmetric static
distribution of a perfect fluid is obtained. The Frobenius method is used to
obtain this solution in terms of an infinite series. Exact solutions are
generated in terms of polynomials from the infinite series. The 5--dimensional
Einstein solution is also found by setting the coupling constant to be zero.
All models admit a barotropic equation of state. Linear equations of state are
admitted in particular models with the energy density profile of isothermal
distributions. We examine the physicality of the solution by studying
graphically the isotropic pressure and the energy density. The model is well
behaved in the interior and the weak, strong and dominant energy conditions are
satisfied.
|
[
{
"created": "Wed, 30 Dec 2015 15:19:44 GMT",
"version": "v1"
}
] |
2016-01-06
|
[
[
"Maharaj",
"Sunil D.",
""
],
[
"Chilambwe",
"Brian",
""
],
[
"Hansraj",
"Sudan",
""
]
] |
New exact solutions to the field equations in the Einstein--Gauss--Bonnet modified theory of gravity for a 5--dimensional spherically symmetric static distribution of a perfect fluid is obtained. The Frobenius method is used to obtain this solution in terms of an infinite series. Exact solutions are generated in terms of polynomials from the infinite series. The 5--dimensional Einstein solution is also found by setting the coupling constant to be zero. All models admit a barotropic equation of state. Linear equations of state are admitted in particular models with the energy density profile of isothermal distributions. We examine the physicality of the solution by studying graphically the isotropic pressure and the energy density. The model is well behaved in the interior and the weak, strong and dominant energy conditions are satisfied.
|
1311.6203
|
Steven Willison
|
Steven Willison
|
A Re-examination of the isometric embedding approach to General
Relativity
|
28 pages, no figures. v3- some clarifications and minor corrections
| null | null | null |
gr-qc math-ph math.AP math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider gravitational field equations which are Einstein equations
written in terms of embedding coordinates in some higher dimensional Minkowski
space. Our main focus is to address some tricky issues relating to the Cauchy
problem and possible non-equivalence with the intrinsic Einstein theory. The
well known theory introduced by Regge and Teitelboim in 9+1 dimensions is cast
in Cauchy-Kowalevskaya form and therefore local existence and uniqueness
results follow for \emph{analytic} initial data. In seeking a weakening of the
regularity conditions for initial data, we are led naturally to propose a 13+1
dimensional theory. By imposing an appropriate conserved initial value
constraint we are able, in the neighbourhood of a generic (free) embedding, to
obtain a system of nonlinear hyperbolic differential equations. The questions
of long time or global existence and uniqueness are formidable, but we offer
arguments to suggest that the situation is not hopeless if the theory is
modified in an appropriate way. We also present a modification of the
perturbation method of G\"{u}nther to weighted Sobolev spaces, appropriate to
noncompact initial data surfaces with asymptotic fall-off conditions.
|
[
{
"created": "Mon, 25 Nov 2013 03:39:59 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Dec 2013 13:22:17 GMT",
"version": "v2"
},
{
"created": "Sat, 24 May 2014 16:07:03 GMT",
"version": "v3"
}
] |
2014-05-27
|
[
[
"Willison",
"Steven",
""
]
] |
We consider gravitational field equations which are Einstein equations written in terms of embedding coordinates in some higher dimensional Minkowski space. Our main focus is to address some tricky issues relating to the Cauchy problem and possible non-equivalence with the intrinsic Einstein theory. The well known theory introduced by Regge and Teitelboim in 9+1 dimensions is cast in Cauchy-Kowalevskaya form and therefore local existence and uniqueness results follow for \emph{analytic} initial data. In seeking a weakening of the regularity conditions for initial data, we are led naturally to propose a 13+1 dimensional theory. By imposing an appropriate conserved initial value constraint we are able, in the neighbourhood of a generic (free) embedding, to obtain a system of nonlinear hyperbolic differential equations. The questions of long time or global existence and uniqueness are formidable, but we offer arguments to suggest that the situation is not hopeless if the theory is modified in an appropriate way. We also present a modification of the perturbation method of G\"{u}nther to weighted Sobolev spaces, appropriate to noncompact initial data surfaces with asymptotic fall-off conditions.
|
2301.08070
|
Javier Relancio
|
J. M. Carmona, J. L. Cort\'es, J. J. Relancio, M. A. Reyes
|
A new perspective on Doubly Special Relativity
|
8 pages, 1 figure
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Doubly special relativity considers a deformation of the special relativistic
kinematics parametrized by a high-energy scale, in such a way that it preserves
a relativity principle. When this deformation is assumed to be applied to any
interaction between particles one faces some inconsistencies. In order to avoid
them, we propose a new perspective where the deformation affects only the
interactions between elementary particles. A consequence of this proposal is
that the deformation cannot modify the special relativistic energy-momentum
relation of a particle.
|
[
{
"created": "Thu, 19 Jan 2023 13:30:19 GMT",
"version": "v1"
}
] |
2023-01-20
|
[
[
"Carmona",
"J. M.",
""
],
[
"Cortés",
"J. L.",
""
],
[
"Relancio",
"J. J.",
""
],
[
"Reyes",
"M. A.",
""
]
] |
Doubly special relativity considers a deformation of the special relativistic kinematics parametrized by a high-energy scale, in such a way that it preserves a relativity principle. When this deformation is assumed to be applied to any interaction between particles one faces some inconsistencies. In order to avoid them, we propose a new perspective where the deformation affects only the interactions between elementary particles. A consequence of this proposal is that the deformation cannot modify the special relativistic energy-momentum relation of a particle.
|
2401.12314
|
Sotirios Karamitsos
|
Laur J\"arv, Sotirios Karamitsos, Margus Saal
|
Global Portraits of Nonminimal Inflation: Metric and Palatini
|
32 pages, 4 figures; improved wordings, added references and
corrected typos
|
Phys. Rev. D 109, 084073 (2024)
|
10.1103/PhysRevD.109.084073
| null |
gr-qc hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we study the global phase space dynamics of single
nonminimally coupled scalar field inflation models in the metric and Palatini
formalisms. Working in the Jordan frame, we derive the scalar-tensor general
field equations and flat FLRW cosmological equations, and present the Palatini
and metric equations in a common framework. We show that inflation is
characterized by a "master" trajectory from a saddle-type de Sitter fixed point
to a stable node fixed point, approximated by slow roll conditions (presented
for the first time in the Palatini formalism). We show that, despite different
underlying equations, the fixed point structure and properties of many models
are congruent in metric and Palatini, which explains their qualitative
similarities and their suitability for driving inflation. On the other hand,
the global phase portraits reveal how even models which predict the same values
for observable perturbations differ, both to the extent of the phase space
physically available to their trajectories, as well as their past asymptotic
states. We also note how the slow roll conditions tend to underestimate the end
of inflationary accelerated expansion experienced by the true nonlinear
"master" solution. The explicit examples we consider range from the metric and
Palatini induced gravity quintic potential with a Coleman-Weinberg correction
factor to Starobinsky, metric and Palatini nonminimal Higgs, second order pole,
and several nontrivial Palatini models.
|
[
{
"created": "Mon, 22 Jan 2024 19:17:16 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jun 2024 20:08:48 GMT",
"version": "v2"
}
] |
2024-06-25
|
[
[
"Järv",
"Laur",
""
],
[
"Karamitsos",
"Sotirios",
""
],
[
"Saal",
"Margus",
""
]
] |
In this paper, we study the global phase space dynamics of single nonminimally coupled scalar field inflation models in the metric and Palatini formalisms. Working in the Jordan frame, we derive the scalar-tensor general field equations and flat FLRW cosmological equations, and present the Palatini and metric equations in a common framework. We show that inflation is characterized by a "master" trajectory from a saddle-type de Sitter fixed point to a stable node fixed point, approximated by slow roll conditions (presented for the first time in the Palatini formalism). We show that, despite different underlying equations, the fixed point structure and properties of many models are congruent in metric and Palatini, which explains their qualitative similarities and their suitability for driving inflation. On the other hand, the global phase portraits reveal how even models which predict the same values for observable perturbations differ, both to the extent of the phase space physically available to their trajectories, as well as their past asymptotic states. We also note how the slow roll conditions tend to underestimate the end of inflationary accelerated expansion experienced by the true nonlinear "master" solution. The explicit examples we consider range from the metric and Palatini induced gravity quintic potential with a Coleman-Weinberg correction factor to Starobinsky, metric and Palatini nonminimal Higgs, second order pole, and several nontrivial Palatini models.
|
1511.08652
|
Reinoud Slagter
|
Reinoud Jan Slagter
|
Tangled up in Spinning Cosmic Strings
|
preliminary version. 12 figures. A short version was presented at the
second Time Machine Factory conference in Turin, 25-28 oct 2015
| null | null | null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is known for a long time that the space time around a spinning cylindrical
symmetric compact object such as the cosmic string, show un-physical behavior,
i.e., they would possess closed time like curves (CTC). This controversy with
Hawking's chronology protection conjecture is unpleasant but can be understood
if one solves the coupled scalar-gauge field equations and the matching
conditions at the core of the string. A new interior numerical solution is
found of a self gravitating spinning cosmic string with a U(1) scalar gauge
field and the matching on the exterior space time is revealed. It is
conjectured that the experience of CTC's close to the core of the string is
exceedingly unlikely. It occurs when the causality breaking boundary, $r_\mu$,
approaches the boundary of the cosmic string, $r_{CS}$. Then the metric
components become singular and the proper time on the core of the string stops
flowing. Further, we expect that the angular momentum $J$ will decrease due to
the emission of gravitational energy triggered by the scalar perturbations.
When a complete loop is taken around the string, the interior time jumps by a
factor $2\pi J$. The proper time it takes to make a complete loop becomes
infinite and will be equal to the period that $g_{\varphi\varphi}$ remains
positive. In this time interval the angular momentum will be reduced to zero by
emission of wave energy. The physical situation of an observer who experience
$r_{\mu}\rightarrow r_{CS}$ is very unpleasant: the energy-momentum tensor
components diverge.
|
[
{
"created": "Fri, 27 Nov 2015 13:00:24 GMT",
"version": "v1"
}
] |
2015-11-30
|
[
[
"Slagter",
"Reinoud Jan",
""
]
] |
It is known for a long time that the space time around a spinning cylindrical symmetric compact object such as the cosmic string, show un-physical behavior, i.e., they would possess closed time like curves (CTC). This controversy with Hawking's chronology protection conjecture is unpleasant but can be understood if one solves the coupled scalar-gauge field equations and the matching conditions at the core of the string. A new interior numerical solution is found of a self gravitating spinning cosmic string with a U(1) scalar gauge field and the matching on the exterior space time is revealed. It is conjectured that the experience of CTC's close to the core of the string is exceedingly unlikely. It occurs when the causality breaking boundary, $r_\mu$, approaches the boundary of the cosmic string, $r_{CS}$. Then the metric components become singular and the proper time on the core of the string stops flowing. Further, we expect that the angular momentum $J$ will decrease due to the emission of gravitational energy triggered by the scalar perturbations. When a complete loop is taken around the string, the interior time jumps by a factor $2\pi J$. The proper time it takes to make a complete loop becomes infinite and will be equal to the period that $g_{\varphi\varphi}$ remains positive. In this time interval the angular momentum will be reduced to zero by emission of wave energy. The physical situation of an observer who experience $r_{\mu}\rightarrow r_{CS}$ is very unpleasant: the energy-momentum tensor components diverge.
|
1908.06501
|
Magd Elias Kahil
|
Magd E. Kahil
|
Spinning and Spinning Deviation Equations of Bi-metric Type Theories
|
18 LaTeX pages
| null |
10.1007/s12648-020-01793-5
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Spinning equations of bi-metric types theories of gravity, the counterpart of
the Papapetrou spinning equations of motion have been derived as well as their
corresponding spinning deviation equations. Due to introducing different types
of bi-metric theories, the influence of different curvatures based upon
different affine connections , have been examined. A specific Lagrangian
function for each type theory has been proposed, in order to derive the set of
spinning motions and their corresponding spinning deviation equations.
|
[
{
"created": "Sun, 18 Aug 2019 18:58:05 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Oct 2019 21:41:29 GMT",
"version": "v2"
}
] |
2020-08-26
|
[
[
"Kahil",
"Magd E.",
""
]
] |
Spinning equations of bi-metric types theories of gravity, the counterpart of the Papapetrou spinning equations of motion have been derived as well as their corresponding spinning deviation equations. Due to introducing different types of bi-metric theories, the influence of different curvatures based upon different affine connections , have been examined. A specific Lagrangian function for each type theory has been proposed, in order to derive the set of spinning motions and their corresponding spinning deviation equations.
|
2310.17781
|
Soumen Koley
|
Soumen Koley, Jan Harms, Annalisa Allocca, Enrico Calloni, Rosario De
Rosa, Luciano Errico, Marina Esposito, Francesca Badaracco, Luca Rei,
Alessandro Bertolini, Tomasz Bulik, Marek Cieslar, Mateusz Pietrzak, Mariusz
Suchenek, Irene Fiori, Andrea Paoli, Maria Concetta Tringali, Paolo Ruggi,
Stefan Hild, Ayatri Singha, Bartosz Idzkowski, Maciej Suchinski, Alain
Masserot, Loic Rolland, Benoit Mours, and Federico Paoletti
|
Design and implementation of a seismic Newtonian-noise cancellation
system for the Virgo gravitational-wave detector
| null | null | null | null |
gr-qc astro-ph.IM physics.ins-det
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Terrestrial gravity perturbations caused by seismic fields produce the
so-called Newtonian noise in gravitational-wave detectors, which is predicted
to limit their sensitivity in the upcoming observing runs. In the past, this
noise was seen as an infrastructural limitation, i.e., something that cannot be
overcome without major investments to improve a detector's infrastructure.
However, it is possible to have at least an indirect estimate of this noise by
using the data from a large number of seismometers deployed around a detector's
suspended test masses. The noise estimate can be subtracted from the
gravitational-wave data; a process called Newtonian-noise cancellation (NNC).
In this article, we present the design and implementation of the first NNC
system at the Virgo detector as part of its AdV+ upgrade. It uses data from 110
vertical geophones deployed inside the Virgo buildings in optimized array
configurations. We use a separate tiltmeter channel to test the pipeline in a
proof-of-principle. The system has been running with good performance over
months.
|
[
{
"created": "Thu, 26 Oct 2023 21:13:55 GMT",
"version": "v1"
}
] |
2023-10-30
|
[
[
"Koley",
"Soumen",
""
],
[
"Harms",
"Jan",
""
],
[
"Allocca",
"Annalisa",
""
],
[
"Calloni",
"Enrico",
""
],
[
"De Rosa",
"Rosario",
""
],
[
"Errico",
"Luciano",
""
],
[
"Esposito",
"Marina",
""
],
[
"Badaracco",
"Francesca",
""
],
[
"Rei",
"Luca",
""
],
[
"Bertolini",
"Alessandro",
""
],
[
"Bulik",
"Tomasz",
""
],
[
"Cieslar",
"Marek",
""
],
[
"Pietrzak",
"Mateusz",
""
],
[
"Suchenek",
"Mariusz",
""
],
[
"Fiori",
"Irene",
""
],
[
"Paoli",
"Andrea",
""
],
[
"Tringali",
"Maria Concetta",
""
],
[
"Ruggi",
"Paolo",
""
],
[
"Hild",
"Stefan",
""
],
[
"Singha",
"Ayatri",
""
],
[
"Idzkowski",
"Bartosz",
""
],
[
"Suchinski",
"Maciej",
""
],
[
"Masserot",
"Alain",
""
],
[
"Rolland",
"Loic",
""
],
[
"Mours",
"Benoit",
""
],
[
"Paoletti",
"Federico",
""
]
] |
Terrestrial gravity perturbations caused by seismic fields produce the so-called Newtonian noise in gravitational-wave detectors, which is predicted to limit their sensitivity in the upcoming observing runs. In the past, this noise was seen as an infrastructural limitation, i.e., something that cannot be overcome without major investments to improve a detector's infrastructure. However, it is possible to have at least an indirect estimate of this noise by using the data from a large number of seismometers deployed around a detector's suspended test masses. The noise estimate can be subtracted from the gravitational-wave data; a process called Newtonian-noise cancellation (NNC). In this article, we present the design and implementation of the first NNC system at the Virgo detector as part of its AdV+ upgrade. It uses data from 110 vertical geophones deployed inside the Virgo buildings in optimized array configurations. We use a separate tiltmeter channel to test the pipeline in a proof-of-principle. The system has been running with good performance over months.
|
gr-qc/0403021
|
Jason Steffen
|
E. C. Berg (1), J. H. Steffen (2), M. K. Bantel (1), P. E. Boynton
(2), W. D. Cross (1), T. Inoue (1), M. W. Moore (2), R. D. Newman (1) ((1)
University of California, Irvine, (2) University of Washington)
|
Laboratory Tests of Gravitational Physics Using a Cryogenic Torsion
Pendulum
|
17 pages, 11 figures, contribution to the 10th Marcel Grossman
Conference Proceedings (Rio de Janeiro, July 20 - 26, 2003) - changed wording
in first paragraph of section 5
| null |
10.1142/9789812704030_0061
| null |
gr-qc
| null |
Progress and plans are reported for a program of gravitational physics
experiments using cryogenic torsion pendula undergoing large amplitude
torsional oscillation. The program includes a UC Irvine project to measure the
gravitational constant G and joint UC Irvine - U. Washington projects to test
the gravitational inverse square law at a range of about 10 cm and to test the
weak equivalence principle.
|
[
{
"created": "Thu, 4 Mar 2004 00:40:27 GMT",
"version": "v1"
},
{
"created": "Tue, 18 May 2004 18:02:05 GMT",
"version": "v2"
}
] |
2016-11-09
|
[
[
"Berg",
"E. C.",
""
],
[
"Steffen",
"J. H.",
""
],
[
"Bantel",
"M. K.",
""
],
[
"Boynton",
"P. E.",
""
],
[
"Cross",
"W. D.",
""
],
[
"Inoue",
"T.",
""
],
[
"Moore",
"M. W.",
""
],
[
"Newman",
"R. D.",
""
]
] |
Progress and plans are reported for a program of gravitational physics experiments using cryogenic torsion pendula undergoing large amplitude torsional oscillation. The program includes a UC Irvine project to measure the gravitational constant G and joint UC Irvine - U. Washington projects to test the gravitational inverse square law at a range of about 10 cm and to test the weak equivalence principle.
|
0812.4342
|
Kamal Nandi
|
K.K. Nandi, I.R. Kizirgulov, O.V. Mikolaychuk, N.P. Mikolaychuk, A.A.
Potapov
|
Quantum Phase Shift in Chern-Simons Modified Gravity
|
16 pages, minor errors corrected. Accepted for publication in Phys.
Rev. D
|
Phys.Rev.D79:083006,2009
|
10.1103/PhysRevD.79.083006
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Using a unified approach of optical-mechanical analogy in a semiclassical
formula, we evaluate the effect of Chern-Simons modified gravity on the quantum
phase shift of de Broglie waves in neutron interferometry. The phase shift
calculated here reveals, in a single equation, a combination of effects coming
from Newtonian gravity, inertial forces, Schwarzschild and Chern-Simons
modified gravity. However the last two effects, though new, turn out to be too
tiny to be observed, and hence only of academic interest at present. The
approximations, wherever used, as well as the drawbacks of the non-dynamical
approach are clearly indicated.
|
[
{
"created": "Tue, 23 Dec 2008 07:17:23 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Dec 2008 03:13:39 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Apr 2009 09:26:11 GMT",
"version": "v3"
}
] |
2009-11-06
|
[
[
"Nandi",
"K. K.",
""
],
[
"Kizirgulov",
"I. R.",
""
],
[
"Mikolaychuk",
"O. V.",
""
],
[
"Mikolaychuk",
"N. P.",
""
],
[
"Potapov",
"A. A.",
""
]
] |
Using a unified approach of optical-mechanical analogy in a semiclassical formula, we evaluate the effect of Chern-Simons modified gravity on the quantum phase shift of de Broglie waves in neutron interferometry. The phase shift calculated here reveals, in a single equation, a combination of effects coming from Newtonian gravity, inertial forces, Schwarzschild and Chern-Simons modified gravity. However the last two effects, though new, turn out to be too tiny to be observed, and hence only of academic interest at present. The approximations, wherever used, as well as the drawbacks of the non-dynamical approach are clearly indicated.
|
1103.3898
|
Charis Anastopoulos
|
Charis Anastopoulos and Ntina Savvidou
|
Entropy of singularities in self-gravitating radiation
|
28 pages, 9 figures. Revised version with additional comments and
references, and a section on physical interpretation. Version to appear in
CQG
|
Class. Quantum Grav. 29, 025004 (2012)
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Bekenstein-Hawking entropy suggests that thermodynamics is an intrinsic
ingredient of gravity. Here, we explore the idea that requirements of
thermodynamic consistency could determine the gravitational entropy in other
set-ups. We implement this idea in a simple model: static, spherically
symmetric solutions to Einstein's equations corresponding to self-gravitating
radiation. We find that the principle of maximum entropy provides a consistent
thermodynamic description of the system, only if the entropy includes a
contribution from the spacetime singularities that appear in the solutions of
Einstein's equations. The form of the singularity entropy is stringently
constrained from consistency requirements, so that the existence of a simple
expression satisfying these constraints is highly non-trivial, and suggests of
a fundamental origin. We find that the system is characterized by three
equilibrium phases, and we conduct a preliminary investigation of the
associated phase transitions. These results demonstrate the point that
gravitational entities other than horizons are endowed with thermodynamic
properties.
|
[
{
"created": "Sun, 20 Mar 2011 22:42:47 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Nov 2011 12:24:29 GMT",
"version": "v2"
}
] |
2011-12-23
|
[
[
"Anastopoulos",
"Charis",
""
],
[
"Savvidou",
"Ntina",
""
]
] |
The Bekenstein-Hawking entropy suggests that thermodynamics is an intrinsic ingredient of gravity. Here, we explore the idea that requirements of thermodynamic consistency could determine the gravitational entropy in other set-ups. We implement this idea in a simple model: static, spherically symmetric solutions to Einstein's equations corresponding to self-gravitating radiation. We find that the principle of maximum entropy provides a consistent thermodynamic description of the system, only if the entropy includes a contribution from the spacetime singularities that appear in the solutions of Einstein's equations. The form of the singularity entropy is stringently constrained from consistency requirements, so that the existence of a simple expression satisfying these constraints is highly non-trivial, and suggests of a fundamental origin. We find that the system is characterized by three equilibrium phases, and we conduct a preliminary investigation of the associated phase transitions. These results demonstrate the point that gravitational entities other than horizons are endowed with thermodynamic properties.
|
2305.04321
|
Hoang Nguyen
|
Hoang Ky Nguyen, Mustapha Azreg-A\"inou
|
Traversable Morris-Thorne-Buchdahl wormholes in quadratic gravity
|
11 pages, 4 figures. Major improvements in Fig. 3 and in body of
text. Several relevant references added. Accepted for Eur. Phys. J. C
|
Eur.Phys.J.C 83 (2023) 7, 626
|
10.1140/epjc/s10052-023-11805-3
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The special Buchdahl-inspired metric obtained in a recent paper [Phys. Rev. D
107, 104008 (2023)] describes asymptotically flat spacetimes in pure
$\mathcal{R}^{2}$ gravity. The metric depends on a new (Buchdahl) parameter
$\tilde{k}$ of higher-derivative characteristic, and recovers the Schwarzschild
metric when $\tilde{k}=0$. It is shown that the special Buchdahl-inspired
metric supports a two-way traversable Morris-Thorne wormhole for
$\tilde{k}\in(-1,0)$ in which case the Weak Energy Condition is formally
violated, a naked singularity for $\tilde{k}\in(-\infty,-1)\cup(0,+\infty)$,
and a non-Schwarzschild structure for $\tilde{k}=-1$.
|
[
{
"created": "Sun, 7 May 2023 16:09:16 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Jul 2023 04:05:10 GMT",
"version": "v2"
}
] |
2023-07-26
|
[
[
"Nguyen",
"Hoang Ky",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
]
] |
The special Buchdahl-inspired metric obtained in a recent paper [Phys. Rev. D 107, 104008 (2023)] describes asymptotically flat spacetimes in pure $\mathcal{R}^{2}$ gravity. The metric depends on a new (Buchdahl) parameter $\tilde{k}$ of higher-derivative characteristic, and recovers the Schwarzschild metric when $\tilde{k}=0$. It is shown that the special Buchdahl-inspired metric supports a two-way traversable Morris-Thorne wormhole for $\tilde{k}\in(-1,0)$ in which case the Weak Energy Condition is formally violated, a naked singularity for $\tilde{k}\in(-\infty,-1)\cup(0,+\infty)$, and a non-Schwarzschild structure for $\tilde{k}=-1$.
|
gr-qc/9312007
| null |
Vu B Ho
|
Spacetime structure and Quantum physics
|
10 pages, Latex
| null | null | null |
gr-qc hep-th
| null |
A description of electromagnetism as four-dimensional spacetime structure
leads to the dynamics of a charged particle being determined only by the
four-vector potential and the existence of an electromagnetic field depending
on the topological structure of the background spacetime. When the spacetime
structure of electromagnetism is complex it is possible to connect spacetime
structure and quantum physics via the method of path integration. (This paper
is a consequence of an attempt to incorporate gravitation into electromagnetism
by describing gravity as a coupling of two electromagnetic fields.)
|
[
{
"created": "Fri, 3 Dec 1993 14:10:58 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Ho",
"Vu B",
""
]
] |
A description of electromagnetism as four-dimensional spacetime structure leads to the dynamics of a charged particle being determined only by the four-vector potential and the existence of an electromagnetic field depending on the topological structure of the background spacetime. When the spacetime structure of electromagnetism is complex it is possible to connect spacetime structure and quantum physics via the method of path integration. (This paper is a consequence of an attempt to incorporate gravitation into electromagnetism by describing gravity as a coupling of two electromagnetic fields.)
|
1407.4748
|
Richard Woodard
|
R. P. Woodard (University of Florida)
|
Perturbative Quantum Gravity Comes of Age
|
64 pages, 6 figures, review article written for "One Hundred Years of
General Relativity"
| null |
10.1142/S0218271814300201
|
UFIFT-QG-14-05
|
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
I argue that cosmological data from the epoch of primordial inflation is
catalyzing the maturation of quantum gravity from speculation into a hard
science. I explain why quantum gravitational effects from primordial inflation
are observable. I then review what has been done, both theoretically and
observationally, and what the future holds. I also discuss what this tells us
about quantum gravity.
|
[
{
"created": "Thu, 17 Jul 2014 17:34:37 GMT",
"version": "v1"
}
] |
2015-06-22
|
[
[
"Woodard",
"R. P.",
"",
"University of Florida"
]
] |
I argue that cosmological data from the epoch of primordial inflation is catalyzing the maturation of quantum gravity from speculation into a hard science. I explain why quantum gravitational effects from primordial inflation are observable. I then review what has been done, both theoretically and observationally, and what the future holds. I also discuss what this tells us about quantum gravity.
|
1302.1846
|
Aneta Wojnar
|
Andrzej Borowiec and Aneta Wojnar
|
Geometry of almost-product Lorentzian manifolds and relativistic
observer
|
13 pages, 2 tables, Talk during the conference Barcelona Postgrad
Encounters on Fundamental Physics, October 2012
| null | null | null |
gr-qc math-ph math.DG math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The notion of relativistic observer is confronted with Naveira's
classification of (pseudo-)Riemannian almost-product structures on space-time
manifolds. Some physical properties and their geometrical counterparts are
shortly discussed.
|
[
{
"created": "Thu, 7 Feb 2013 20:08:02 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Feb 2013 21:24:02 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Jun 2013 18:09:24 GMT",
"version": "v3"
}
] |
2014-12-04
|
[
[
"Borowiec",
"Andrzej",
""
],
[
"Wojnar",
"Aneta",
""
]
] |
The notion of relativistic observer is confronted with Naveira's classification of (pseudo-)Riemannian almost-product structures on space-time manifolds. Some physical properties and their geometrical counterparts are shortly discussed.
|
1003.2689
|
Kengo Maeda
|
Kengo Maeda, Jun-ichirou Koga, and Shunsuke Fujii
|
The final fate of instability of Reissner-Nordstr\"om-anti-de Sitter
black holes by charged complex scalar fields
|
9 pages, 4 figures. To appear in PRD
|
Phys.Rev.D81:124020,2010
|
10.1103/PhysRevD.81.124020
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate instability of 4-dimensional Reissner-Nordstr\"om-anti-de
Sitter (RN-AdS$_4$) black holes with various topologies by charged scalar field
perturbations. We numerically find that the RN-AdS$_4$ black holes become
unstable against the linear perturbations below a critical temperature. It is
analytically shown that charge extraction from the black holes occurs during
the unstable evolution. To explore the end state of the instability, we
perturbatively construct static black hole solutions with the scalar hair near
the critical temperature. It is numerically found that the entropy of the
hairly black hole is always larger than the one of the unstable RN-AdS$_4$
black hole in the microcanonical ensemble. Our results support the speculation
that the black hole with charged scalar hair always appears as the final fate
of the instability of the RN-AdS$_4$ black hole.
|
[
{
"created": "Sat, 13 Mar 2010 08:03:33 GMT",
"version": "v1"
},
{
"created": "Fri, 21 May 2010 04:12:55 GMT",
"version": "v2"
}
] |
2015-03-13
|
[
[
"Maeda",
"Kengo",
""
],
[
"Koga",
"Jun-ichirou",
""
],
[
"Fujii",
"Shunsuke",
""
]
] |
We investigate instability of 4-dimensional Reissner-Nordstr\"om-anti-de Sitter (RN-AdS$_4$) black holes with various topologies by charged scalar field perturbations. We numerically find that the RN-AdS$_4$ black holes become unstable against the linear perturbations below a critical temperature. It is analytically shown that charge extraction from the black holes occurs during the unstable evolution. To explore the end state of the instability, we perturbatively construct static black hole solutions with the scalar hair near the critical temperature. It is numerically found that the entropy of the hairly black hole is always larger than the one of the unstable RN-AdS$_4$ black hole in the microcanonical ensemble. Our results support the speculation that the black hole with charged scalar hair always appears as the final fate of the instability of the RN-AdS$_4$ black hole.
|
1208.5772
|
Oscar J. C. Dias
|
Oscar J. C. Dias, Gary T. Horowitz, Don Marolf, Jorge E. Santos
|
On the Nonlinear Stability of Asymptotically Anti-de Sitter Solutions
|
26 pages. 5 figures
| null |
10.1088/0264-9381/29/23/235019
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Despite the recent evidence that anti-de Sitter spacetime is nonlinearly
unstable, we argue that many asymptotically anti-de Sitter solutions are
nonlinearly stable. This includes geons, boson stars, and black holes. As part
of our argument, we calculate the frequencies of long-lived gravitational
quasinormal modes of AdS black holes in various dimensions. We also discuss a
new class of asymptotically anti-de Sitter solutions describing noncoalescing
black hole binaries.
|
[
{
"created": "Tue, 28 Aug 2012 20:00:06 GMT",
"version": "v1"
}
] |
2015-06-11
|
[
[
"Dias",
"Oscar J. C.",
""
],
[
"Horowitz",
"Gary T.",
""
],
[
"Marolf",
"Don",
""
],
[
"Santos",
"Jorge E.",
""
]
] |
Despite the recent evidence that anti-de Sitter spacetime is nonlinearly unstable, we argue that many asymptotically anti-de Sitter solutions are nonlinearly stable. This includes geons, boson stars, and black holes. As part of our argument, we calculate the frequencies of long-lived gravitational quasinormal modes of AdS black holes in various dimensions. We also discuss a new class of asymptotically anti-de Sitter solutions describing noncoalescing black hole binaries.
|
2402.08089
|
Massimo Giovannini
|
Massimo Giovannini
|
Fuzzy Bounces
|
40 pages, 7 figures; improved discussions and corrected typos to
match the published version
|
Class. Quantum Grav. 41 (2024) 105010
| null | null |
gr-qc astro-ph.CO hep-ph hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
We observe that the energy and the enthalpy densities can be smeared by two
fudge factors that are constrained by the contracted Bianchi identities.
Depending on the analytic properties of the smearing functions the underlying
cosmological solutions belong to two physically different classes, namely the
bounces of the scale factor and the curvature bounces. While the curvature
bounces are naturally compatible with a stage of accelerated expansion, the
bounces of the scale factor demand an early phase of accelerated contraction
even if a short inflationary stage may arise prior to the decelerated regime.
Despite the regularity of the underlying solutions, gradient instabilities and
singularities do occasionally appear in the evolution of curvature
inhomogeneities. After deducing the specific criteria behind these occurrences,
the background-independent conclusions are corroborated by a series of concrete
examples associated with different forms of the smearing functions. The
evolution of the curvature inhomogeneities restricts the ranges of the
solutions that turn out to be unsuitable even for a limited description of the
pre-inflationary initial data. The same observation holds in the case of the
gauge-invariant evolution of the matter density contrast. It is however not
excluded that a class of scenarios (mainly associated with the curvature
bounces) could indeed avoid the potential instabilities. All in all the present
analysis explore a general approach whose results are relevant in all the
contexts where bouncing solutions are invoked either as complementary or as
alternative to the conventional inflationary scenarios.
|
[
{
"created": "Mon, 12 Feb 2024 22:15:16 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Apr 2024 17:52:24 GMT",
"version": "v2"
}
] |
2024-04-25
|
[
[
"Giovannini",
"Massimo",
""
]
] |
We observe that the energy and the enthalpy densities can be smeared by two fudge factors that are constrained by the contracted Bianchi identities. Depending on the analytic properties of the smearing functions the underlying cosmological solutions belong to two physically different classes, namely the bounces of the scale factor and the curvature bounces. While the curvature bounces are naturally compatible with a stage of accelerated expansion, the bounces of the scale factor demand an early phase of accelerated contraction even if a short inflationary stage may arise prior to the decelerated regime. Despite the regularity of the underlying solutions, gradient instabilities and singularities do occasionally appear in the evolution of curvature inhomogeneities. After deducing the specific criteria behind these occurrences, the background-independent conclusions are corroborated by a series of concrete examples associated with different forms of the smearing functions. The evolution of the curvature inhomogeneities restricts the ranges of the solutions that turn out to be unsuitable even for a limited description of the pre-inflationary initial data. The same observation holds in the case of the gauge-invariant evolution of the matter density contrast. It is however not excluded that a class of scenarios (mainly associated with the curvature bounces) could indeed avoid the potential instabilities. All in all the present analysis explore a general approach whose results are relevant in all the contexts where bouncing solutions are invoked either as complementary or as alternative to the conventional inflationary scenarios.
|
1705.07882
|
Luke Bovard
|
Luke Bovard, Luciano Rezzolla
|
On the use of tracer particles in simulations of binary neutron stars
|
26 pages, 11 figures, matches version accepted to CQG
|
Classical and Quantum Gravity, 34, 21 2017
|
10.1088/1361-6382/aa8d98
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In grid-based codes that provide the combined solution of the Einstein
equations and of relativistic hydrodynamics, the history of the fluid is not
simple to track, especially when compared with particle-based codes. The use of
tracers, namely massless particles that are advected with the flow, represents
a simple and effective way to solve this problem. Yet, the use of tracers in
numerical relativity is far from being settled and several issues, such as the
impact of different placements in time and space of the tracers, or the
relation between the placement and the description of the underlying fluid,
have not yet been addressed. In this paper we present the first detailed
discussion of the use tracers in numerical-relativity simulations focussing on
both unbound material -- such as the one leading to r-process nucleosynthesis
in binary mergers of neutron stars -- and on bound material -- such as the one
in the core of the object produced from the merger of two neutron stars. In
particular, when interested in unbound matter, we have evaluated four different
placement schemes that could be used to initially distribute the tracers and
how well their predictions match those obtained when using information from the
actual fluid flow. Countering our naive expectations, we found that the most
effective method does not rely on the rest-mass density distribution nor on the
fluid that is unbound, but simply distributes tracers uniformly in rest-mass
density. This prescription leads to the closest matching with the information
obtained from the hydrodynamical solution. When considering bound matter, we
demonstrate that tracers can provide insight into the fine details of the fluid
motion as they can be used to track the evolution of fluid elements or to
calculate the variation of quantities that are conserved along streamlines of
adiabatic flows.
|
[
{
"created": "Mon, 22 May 2017 17:54:46 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Sep 2017 13:49:57 GMT",
"version": "v2"
}
] |
2018-03-28
|
[
[
"Bovard",
"Luke",
""
],
[
"Rezzolla",
"Luciano",
""
]
] |
In grid-based codes that provide the combined solution of the Einstein equations and of relativistic hydrodynamics, the history of the fluid is not simple to track, especially when compared with particle-based codes. The use of tracers, namely massless particles that are advected with the flow, represents a simple and effective way to solve this problem. Yet, the use of tracers in numerical relativity is far from being settled and several issues, such as the impact of different placements in time and space of the tracers, or the relation between the placement and the description of the underlying fluid, have not yet been addressed. In this paper we present the first detailed discussion of the use tracers in numerical-relativity simulations focussing on both unbound material -- such as the one leading to r-process nucleosynthesis in binary mergers of neutron stars -- and on bound material -- such as the one in the core of the object produced from the merger of two neutron stars. In particular, when interested in unbound matter, we have evaluated four different placement schemes that could be used to initially distribute the tracers and how well their predictions match those obtained when using information from the actual fluid flow. Countering our naive expectations, we found that the most effective method does not rely on the rest-mass density distribution nor on the fluid that is unbound, but simply distributes tracers uniformly in rest-mass density. This prescription leads to the closest matching with the information obtained from the hydrodynamical solution. When considering bound matter, we demonstrate that tracers can provide insight into the fine details of the fluid motion as they can be used to track the evolution of fluid elements or to calculate the variation of quantities that are conserved along streamlines of adiabatic flows.
|
2102.06023
|
Mariniel Galvao Jr
|
M. S. Galv\~ao Jr
|
Symplectic analysis for the Holst action with Dirac fields
| null | null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
In this work we review the canonical analysis of the Holst-Dirac action from
the point of view of the Faddeev-Jackiw symplectic procedure using the Barcelo
Neto-Wotzasek algorithm. We replicate the results found in the literature for
the theory's constraints, recover some of the expressions for gauge symmetries
of the main fields and perform the counting of the degrees of freedom.
|
[
{
"created": "Wed, 10 Feb 2021 18:59:20 GMT",
"version": "v1"
}
] |
2021-02-12
|
[
[
"Galvão",
"M. S.",
"Jr"
]
] |
In this work we review the canonical analysis of the Holst-Dirac action from the point of view of the Faddeev-Jackiw symplectic procedure using the Barcelo Neto-Wotzasek algorithm. We replicate the results found in the literature for the theory's constraints, recover some of the expressions for gauge symmetries of the main fields and perform the counting of the degrees of freedom.
|
1806.11193
|
Dmitri Gal'tsov
|
G\'erard Cl\'ement and Dmitri Gal'tsov
|
Stationary double black hole without naked ring singularity
|
35 pages revtex4, 8 figures
|
Class. Quantum Grav. 35 (2018) 214002
|
10.1088/1361-6382/aae4ed
|
LAPTH-026/18
|
gr-qc astro-ph.HE hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Recently double black hole vacuum and electrovacuum metrics attracted
attention as exact solutions suitable for visualization of ultra-compact
objects beyond the Kerr paradigm. However, many of the proposed systems are
plagued with ring curvature singularities. Here we present a new simple
solution of this type which is asymptotically Kerr, has zero electric and
magnetic charges, but is endowed with magnetic dipole moment and electric
quadrupole moment. It is manifestly free of ring singularities, and contains
only a mild string-like singularity on the axis corresponding to a
distributional energy-momentum tensor.Its main constituents are two extreme
co-rotating black holes carrying equal electric andopposite magnetic and NUT
charges.
|
[
{
"created": "Thu, 28 Jun 2018 21:09:30 GMT",
"version": "v1"
}
] |
2018-11-01
|
[
[
"Clément",
"Gérard",
""
],
[
"Gal'tsov",
"Dmitri",
""
]
] |
Recently double black hole vacuum and electrovacuum metrics attracted attention as exact solutions suitable for visualization of ultra-compact objects beyond the Kerr paradigm. However, many of the proposed systems are plagued with ring curvature singularities. Here we present a new simple solution of this type which is asymptotically Kerr, has zero electric and magnetic charges, but is endowed with magnetic dipole moment and electric quadrupole moment. It is manifestly free of ring singularities, and contains only a mild string-like singularity on the axis corresponding to a distributional energy-momentum tensor.Its main constituents are two extreme co-rotating black holes carrying equal electric andopposite magnetic and NUT charges.
|
0807.0103
|
Ettore Minguzzi
|
E. Minguzzi
|
Chronological null complete spacetimes admit a global time
|
Latex2e, 4 pages, 1 figure. To appear in the Proceedings of the
"Spanish Relativity Meeting: Physics and Mathematics of Gravitation",
Salamanca (Spain), September 15-19, 2008
|
AIP Conf.Proc.1122:352-355,2009
|
10.1063/1.3141324
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The result "chronological spacetimes without lightlike lines are stably
causal" is announced and motivated. It implies that chronological spacetimes
which are null geodesically complete and satisfy the null genericity and the
null (averaged) energy condition admit a time function.
|
[
{
"created": "Tue, 1 Jul 2008 10:16:23 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Dec 2008 17:23:38 GMT",
"version": "v2"
}
] |
2011-06-24
|
[
[
"Minguzzi",
"E.",
""
]
] |
The result "chronological spacetimes without lightlike lines are stably causal" is announced and motivated. It implies that chronological spacetimes which are null geodesically complete and satisfy the null genericity and the null (averaged) energy condition admit a time function.
|
1301.2801
|
Oleg Zaslavskii
|
O. B. Zaslavskii
|
Acceleration of particles by acceleration horizons
|
30 pages. Presentation improved and expanded, Sec. VI and VII and
Appendix added. Matches version accepted in PRD. I thank the referee for
helping in the improvement of this paper
|
Phys. Rev. D 88, 104016 (2013)
|
10.1103/PhysRevD.88.104016
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider collision of two particles in the vicinity of the extremal
acceleration horizon (charged or rotating) that includes the Bertotti-Robinson
space-time and the geometry of the Kerr throat. It is shown that the energy in
the centre of mass frame E_{c.m.} can become indefinitely large if parameters
of one of the particles are fine-tuned, so the Ba\~nados-Silk-West (BSW) effect
manifests itself. There exists coordinate transformation which brings the
metric into the form free of the horizon. This leads to some paradox since (i)
the BSW effect exists due to the horizon, (ii) E_{c.m.} is a scalar and cannot
depend on the frame. Careful comparison of near-horizon trajectories in both
frames enables us to resolve this paradox. Although globally the space-time
structure of the metrics with acceleration horizons and black holes are
completely different, locally the vicinity of the extremal black hole horizon
can be approximated by the metric of the acceleration one. The energy of one
particle from the viewpoint of the Kruskal observer (or the one obtained from
it by finite local boost) diverges although in the stationary frame energies of
both colliding particles are finite. This suggests a new explanation of the BSW
effect for black holes given from the viewpoint of an observer who crosses the
horizon. It is complementary to the previously found explanation from the point
of view of a static or stationary observer.
|
[
{
"created": "Sun, 13 Jan 2013 17:49:20 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Jan 2013 22:56:52 GMT",
"version": "v2"
},
{
"created": "Sun, 4 Aug 2013 12:14:45 GMT",
"version": "v3"
},
{
"created": "Thu, 24 Oct 2013 21:58:47 GMT",
"version": "v4"
}
] |
2013-11-19
|
[
[
"Zaslavskii",
"O. B.",
""
]
] |
We consider collision of two particles in the vicinity of the extremal acceleration horizon (charged or rotating) that includes the Bertotti-Robinson space-time and the geometry of the Kerr throat. It is shown that the energy in the centre of mass frame E_{c.m.} can become indefinitely large if parameters of one of the particles are fine-tuned, so the Ba\~nados-Silk-West (BSW) effect manifests itself. There exists coordinate transformation which brings the metric into the form free of the horizon. This leads to some paradox since (i) the BSW effect exists due to the horizon, (ii) E_{c.m.} is a scalar and cannot depend on the frame. Careful comparison of near-horizon trajectories in both frames enables us to resolve this paradox. Although globally the space-time structure of the metrics with acceleration horizons and black holes are completely different, locally the vicinity of the extremal black hole horizon can be approximated by the metric of the acceleration one. The energy of one particle from the viewpoint of the Kruskal observer (or the one obtained from it by finite local boost) diverges although in the stationary frame energies of both colliding particles are finite. This suggests a new explanation of the BSW effect for black holes given from the viewpoint of an observer who crosses the horizon. It is complementary to the previously found explanation from the point of view of a static or stationary observer.
|
2212.11869
|
Christian Dioguardi
|
Christian Dioguardi, Antonio Racioppi, Eemeli Tomberg
|
Beyond (and back to) Palatini quadratic gravity and inflation
|
22 pages, 7 figures, revised version: added a section on $F(R,X)$
models, title, abstract and conclusions revised
|
JCAP 03 (2024) 041
|
10.1088/1475-7516/2024/03/041
| null |
gr-qc astro-ph.CO hep-ph
|
http://creativecommons.org/licenses/by/4.0/
|
We study single-field slow-roll inflation embedded in Palatini $F(R)$ gravity
where $F(R)$ grows faster than $R^2$. Surprisingly, the consistency of the
theory requires the Jordan frame inflaton potential to be unbounded from below.
Even more surprisingly, this corresponds to an Einstein frame inflaton
potential bounded from below and positive definite. We prove that for all such
Palatini $F(R)$'s, there exists a universal strong coupling limit corresponding
to a quadratic $F(R)$ with the wrong sign for the linear term and a
cosmological constant in the Jordan frame. In such a limit, the
tensor-to-scalar ratio $r$ does not depend on the original inflaton potential,
while the scalar spectral index $n_s$ does. Unfortunately, the system is
ill-defined out of the slow-roll regime. A possible way out is to upgrade to a
$F(R,X)$ model, with $X$ the Jordan frame inflaton kinetic term. Such a
modification essentially leaves the inflationary predictions unaffected.
|
[
{
"created": "Thu, 22 Dec 2022 17:02:57 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Feb 2023 17:56:26 GMT",
"version": "v2"
},
{
"created": "Mon, 10 Jul 2023 13:29:46 GMT",
"version": "v3"
},
{
"created": "Wed, 20 Mar 2024 15:12:07 GMT",
"version": "v4"
}
] |
2024-03-21
|
[
[
"Dioguardi",
"Christian",
""
],
[
"Racioppi",
"Antonio",
""
],
[
"Tomberg",
"Eemeli",
""
]
] |
We study single-field slow-roll inflation embedded in Palatini $F(R)$ gravity where $F(R)$ grows faster than $R^2$. Surprisingly, the consistency of the theory requires the Jordan frame inflaton potential to be unbounded from below. Even more surprisingly, this corresponds to an Einstein frame inflaton potential bounded from below and positive definite. We prove that for all such Palatini $F(R)$'s, there exists a universal strong coupling limit corresponding to a quadratic $F(R)$ with the wrong sign for the linear term and a cosmological constant in the Jordan frame. In such a limit, the tensor-to-scalar ratio $r$ does not depend on the original inflaton potential, while the scalar spectral index $n_s$ does. Unfortunately, the system is ill-defined out of the slow-roll regime. A possible way out is to upgrade to a $F(R,X)$ model, with $X$ the Jordan frame inflaton kinetic term. Such a modification essentially leaves the inflationary predictions unaffected.
|
1604.08038
|
Sebasti\'an C\'espedes
|
Clare Burrage, Sebastian Cespedes and Anne-Christine Davis
|
Disformal transformations on the CMB
| null | null |
10.1088/1475-7516/2016/08/024
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we study the role of disformal transformation on cosmological
backgrounds and its relation to the speed of sound for tensor modes. A speed
different from one for tensor modes can arise in several contexts, such as
Galileons theories or massive gravity, nevertheless the speed is very
constrained to be one by observations of gravitational wave emission. It has
been shown that in inflation a disformal trans- formation allows to set the
speed for tensor modes to one without making changes to the curvature power
spectrum. Here we show that this invariance does not hold when considering the
CMB anisotropy power spectrum. It turns out that the after doing the
transformation there is an imprint on the acoustic peaks and the diffusion
damping. This has interesting consequences; here we explore quartic galileon
theories which allow a modified speed for tensor modes. For these theories the
transformation can be used to constraint the parameter space in different
regimes.
|
[
{
"created": "Mon, 25 Apr 2016 20:00:03 GMT",
"version": "v1"
}
] |
2016-08-17
|
[
[
"Burrage",
"Clare",
""
],
[
"Cespedes",
"Sebastian",
""
],
[
"Davis",
"Anne-Christine",
""
]
] |
In this work we study the role of disformal transformation on cosmological backgrounds and its relation to the speed of sound for tensor modes. A speed different from one for tensor modes can arise in several contexts, such as Galileons theories or massive gravity, nevertheless the speed is very constrained to be one by observations of gravitational wave emission. It has been shown that in inflation a disformal trans- formation allows to set the speed for tensor modes to one without making changes to the curvature power spectrum. Here we show that this invariance does not hold when considering the CMB anisotropy power spectrum. It turns out that the after doing the transformation there is an imprint on the acoustic peaks and the diffusion damping. This has interesting consequences; here we explore quartic galileon theories which allow a modified speed for tensor modes. For these theories the transformation can be used to constraint the parameter space in different regimes.
|
gr-qc/9907001
|
Shahar Hod
|
Shahar Hod
|
Black-Hole Polarization and Cosmic Censorship
|
10 pages
|
Phys.Rev. D60 (1999) 104031
|
10.1103/PhysRevD.60.104031
| null |
gr-qc
| null |
The destruction of the black-hole event horizon is ruled out by both cosmic
censorship and the generalized second law of thermodynamics. We test the
consistency of this prediction in a (more) `dangerous' version of the gedanken
experiment suggested by Bekenstein and Rosenzweig. A U(1)-charged particle is
lowered {\it slowly} into a near extremal black hole which is not endowed with
a U(1) gauge field. The energy delivered to the black hole can be {\it
red-shifted} by letting the assimilation point approach the black-hole horizon.
At first sight, therefore, the particle is not hindered from entering the black
hole and removing its horizon. However, we show that this dangerous situation
is excluded by a combination of {\it two} factors not considered in former
gedanken experiments: the effect of the spacetime curvature on the
electrostatic {\it self-interaction} of the charged system (the black-hole
polarization), and the {\it finite} size of the charged body.
|
[
{
"created": "Thu, 1 Jul 1999 12:27:06 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Nov 1999 08:29:08 GMT",
"version": "v2"
}
] |
2009-10-31
|
[
[
"Hod",
"Shahar",
""
]
] |
The destruction of the black-hole event horizon is ruled out by both cosmic censorship and the generalized second law of thermodynamics. We test the consistency of this prediction in a (more) `dangerous' version of the gedanken experiment suggested by Bekenstein and Rosenzweig. A U(1)-charged particle is lowered {\it slowly} into a near extremal black hole which is not endowed with a U(1) gauge field. The energy delivered to the black hole can be {\it red-shifted} by letting the assimilation point approach the black-hole horizon. At first sight, therefore, the particle is not hindered from entering the black hole and removing its horizon. However, we show that this dangerous situation is excluded by a combination of {\it two} factors not considered in former gedanken experiments: the effect of the spacetime curvature on the electrostatic {\it self-interaction} of the charged system (the black-hole polarization), and the {\it finite} size of the charged body.
|
1309.4900
|
Valerio Faraoni
|
Valerio Faraoni (Bishop's University)
|
Conformally coupled inflation
|
12 pages, no figures, invited paper to appear in "Cosmology with
Fluid Components", special issue of "Galaxies" edited by I. Brevik
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A massive scalar field in a curved spacetime can propagate along the light
cone, a causal pathology, which can, in principle, be eliminated only if the
scalar couples conformally to the Ricci curvature of spacetime. This property
mandates conformal coupling for the field driving inflation in the early
universe. During slow-roll inflation, this coupling can cause
super-acceleration and, as a signature, a blue spectrum of primordial
gravitational waves.
|
[
{
"created": "Thu, 19 Sep 2013 09:07:06 GMT",
"version": "v1"
}
] |
2013-09-20
|
[
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] |
A massive scalar field in a curved spacetime can propagate along the light cone, a causal pathology, which can, in principle, be eliminated only if the scalar couples conformally to the Ricci curvature of spacetime. This property mandates conformal coupling for the field driving inflation in the early universe. During slow-roll inflation, this coupling can cause super-acceleration and, as a signature, a blue spectrum of primordial gravitational waves.
|
2206.13233
|
Mohammed Khalil
|
Mohammed Khalil, Raissa F. P. Mendes, N\'estor Ortiz, Jan Steinhoff
|
Effective-action model for dynamical scalarization beyond the adiabatic
approximation
|
15 pages, 11 figures. v2: matches published version
| null |
10.1103/PhysRevD.106.104016
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In certain scalar-field extensions to general relativity, scalar charges can
develop on compact objects in an inspiraling binary -- an effect known as
dynamical scalarization. This effect can be modeled using
effective-field-theory methods applied to the binary within the post-Newtonian
approximation. Past analytic investigations focused on the adiabatic (or
quasi-stationary) case for quasi-circular orbits. In this work, we explore the
full dynamical evolution around the phase transition to the scalarized regime.
This allows for generic (eccentric) orbits and to quantify nonadiabatic (e.g.,
oscillatory) behavior during the phase transition. We also find that even in
the circular-orbit case, the onset of scalarization can only be predicted
reliably when taking the full dynamics into account, i.e., the adiabatic
approximation is not appropriate. Our results pave the way for accurate
post-Newtonian predictions for dynamical scalarization effects in gravitational
waves from compact binaries.
|
[
{
"created": "Mon, 27 Jun 2022 12:25:41 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Nov 2022 16:12:14 GMT",
"version": "v2"
}
] |
2022-11-23
|
[
[
"Khalil",
"Mohammed",
""
],
[
"Mendes",
"Raissa F. P.",
""
],
[
"Ortiz",
"Néstor",
""
],
[
"Steinhoff",
"Jan",
""
]
] |
In certain scalar-field extensions to general relativity, scalar charges can develop on compact objects in an inspiraling binary -- an effect known as dynamical scalarization. This effect can be modeled using effective-field-theory methods applied to the binary within the post-Newtonian approximation. Past analytic investigations focused on the adiabatic (or quasi-stationary) case for quasi-circular orbits. In this work, we explore the full dynamical evolution around the phase transition to the scalarized regime. This allows for generic (eccentric) orbits and to quantify nonadiabatic (e.g., oscillatory) behavior during the phase transition. We also find that even in the circular-orbit case, the onset of scalarization can only be predicted reliably when taking the full dynamics into account, i.e., the adiabatic approximation is not appropriate. Our results pave the way for accurate post-Newtonian predictions for dynamical scalarization effects in gravitational waves from compact binaries.
|
1812.06457
|
Valerio Faraoni
|
Valerio Faraoni and Jeremy C\^ot\'e
|
Scalar field as a null dust
| null | null |
10.1140/epjc/s10052-019-6829-x
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We show that a canonical, minimally coupled scalar field which is non-self
interacting and massless is equivalent to a null dust fluid (whether it is a
test or a gravitating field), in a spacetime region in which its gradient is
null. Under similar conditions, the gravitating and nonminimally coupled
Brans-Dicke-like scalar of scalar-tensor gravity, instead, cannot be
represented as a null dust unless its gradient is also a Killing vector field.
|
[
{
"created": "Sun, 16 Dec 2018 13:10:32 GMT",
"version": "v1"
}
] |
2019-05-01
|
[
[
"Faraoni",
"Valerio",
""
],
[
"Côté",
"Jeremy",
""
]
] |
We show that a canonical, minimally coupled scalar field which is non-self interacting and massless is equivalent to a null dust fluid (whether it is a test or a gravitating field), in a spacetime region in which its gradient is null. Under similar conditions, the gravitating and nonminimally coupled Brans-Dicke-like scalar of scalar-tensor gravity, instead, cannot be represented as a null dust unless its gradient is also a Killing vector field.
|
1610.01754
|
Iftikar Hossain Sardar
|
M.Zubair, I.H.Sardar, F.Rahaman, G.Abbas
|
Interior Solutions of Fluid Sphere in f(R,T) Gravity Admitting Conformal
Killing Vectors
|
6 Pages, 6 Figures
|
Astrophys Space Sci (2016) 361:238
|
10.1007/s10509-016-2828-7
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss the interior solutions of fluid Sphere in f(R,T) gravity admitting
conformal killing vectors, where R is Ricci scalar and T is trace of energy
momentum tensor. The solutions corresponding to isotropic and anisotropic
configurations have been investigated explicitly. Further, the anisotropic case
has been dealt by the utilization of linear equation of state. The results for
both cases have been interpreted graphically. The equation of state parameter,
integration constants and other parameters of the theory have been chosen to
find the central density equal to standard value of central density of the
compact objects. The energy conditions as well as stability of the solutions
have been investigated in the background of f(R,T) gravity.
|
[
{
"created": "Thu, 6 Oct 2016 07:08:23 GMT",
"version": "v1"
}
] |
2018-11-15
|
[
[
"Zubair",
"M.",
""
],
[
"Sardar",
"I. H.",
""
],
[
"Rahaman",
"F.",
""
],
[
"Abbas",
"G.",
""
]
] |
We discuss the interior solutions of fluid Sphere in f(R,T) gravity admitting conformal killing vectors, where R is Ricci scalar and T is trace of energy momentum tensor. The solutions corresponding to isotropic and anisotropic configurations have been investigated explicitly. Further, the anisotropic case has been dealt by the utilization of linear equation of state. The results for both cases have been interpreted graphically. The equation of state parameter, integration constants and other parameters of the theory have been chosen to find the central density equal to standard value of central density of the compact objects. The energy conditions as well as stability of the solutions have been investigated in the background of f(R,T) gravity.
|
1207.7089
|
Elizabeth Winstanley
|
Marc Casals, Sam R. Dolan, Brien C. Nolan, Adrian C. Ottewill and
Elizabeth Winstanley
|
Kermions: quantization of fermions on Kerr space-time
|
38 pages, 9 figures, explanations improved in Section III, matches
published version
|
Phys.Rev.D87:064027,2013
|
10.1103/PhysRevD.87.064027
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study a quantum fermion field on a background non-extremal Kerr black
hole. We discuss the definition of the standard black hole quantum states
(Boulware, Unruh and Hartle-Hawking), focussing particularly on the differences
between fermionic and bosonic quantum field theory. Since all fermion modes
(both particle and anti-particle) have positive norm, there is much greater
flexibility in how quantum states are defined compared with the bosonic case.
In particular, we are able to define a candidate `Boulware'-like state, empty
at both past and future null infinity; and a candidate `Hartle-Hawking'-like
equilibrium state, representing a thermal bath of fermions surrounding the
black hole. Neither of these states have analogues for bosons on a non-extremal
Kerr black hole and both have physically attractive regularity properties. We
also define a number of other quantum states, numerically compute differences
in expectation values of the fermion current and stress-energy tensor between
two states, and discuss their physical properties.
|
[
{
"created": "Mon, 30 Jul 2012 20:19:56 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2013 10:56:54 GMT",
"version": "v2"
}
] |
2015-03-20
|
[
[
"Casals",
"Marc",
""
],
[
"Dolan",
"Sam R.",
""
],
[
"Nolan",
"Brien C.",
""
],
[
"Ottewill",
"Adrian C.",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] |
We study a quantum fermion field on a background non-extremal Kerr black hole. We discuss the definition of the standard black hole quantum states (Boulware, Unruh and Hartle-Hawking), focussing particularly on the differences between fermionic and bosonic quantum field theory. Since all fermion modes (both particle and anti-particle) have positive norm, there is much greater flexibility in how quantum states are defined compared with the bosonic case. In particular, we are able to define a candidate `Boulware'-like state, empty at both past and future null infinity; and a candidate `Hartle-Hawking'-like equilibrium state, representing a thermal bath of fermions surrounding the black hole. Neither of these states have analogues for bosons on a non-extremal Kerr black hole and both have physically attractive regularity properties. We also define a number of other quantum states, numerically compute differences in expectation values of the fermion current and stress-energy tensor between two states, and discuss their physical properties.
|
2105.10933
|
Mariusz P. Dabrowski
|
Roberto Caroli, Mariusz P. Dabrowski, Vincenzo Salzano
|
Ricci cosmology in light of astronomical data
|
14 pages, 5 tables, no figures, Revtex 4-1, an improved version
| null |
10.1140/epjc/s10052-021-09666-9
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Recently, a new cosmological framework, dubbed Ricci Cosmology, has been
proposed. Such a framework has emerged from the study of relativistic dynamics
of fluids out of equilibrium in a curved background and is characterised by the
presence of deviations from the equilibrium pressure in the energy-momentum
tensor which are due to linear terms in the Ricci scalar and the Ricci tensor.
The coefficients in front of such terms are called the second order transport
coefficients and they parametrise the fluid response to the pressure terms
arising from the spacetime curvature.
Under the preliminary assumption that the second order transport coefficients
are constant, we find the simplest solution of Ricci cosmology in which the
presence of pressure terms causes a departure from the perfect fluid redshift
scaling for matter components filling the Universe. In order to test the
viability of this solution, we make four different ans\"{a}tze on the transport
coefficients, giving rise to four different cases of our model. On the physical
ground of the second law of thermodynamics for fluids with non-equilibrium
pressure, we find some theoretical bounds (priors) on the parameters of the
models. Our main concern is then the check of each of the case against the
standard set of cosmological data in order to obtain the observational bounds
on the second order transport coefficients. We find those bounds also realising
that Ricci cosmology model is compatible with $\Lambda$CDM cosmology for all
the ans\"{a}tze.
|
[
{
"created": "Sun, 23 May 2021 13:17:36 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jul 2021 12:12:37 GMT",
"version": "v2"
}
] |
2021-10-27
|
[
[
"Caroli",
"Roberto",
""
],
[
"Dabrowski",
"Mariusz P.",
""
],
[
"Salzano",
"Vincenzo",
""
]
] |
Recently, a new cosmological framework, dubbed Ricci Cosmology, has been proposed. Such a framework has emerged from the study of relativistic dynamics of fluids out of equilibrium in a curved background and is characterised by the presence of deviations from the equilibrium pressure in the energy-momentum tensor which are due to linear terms in the Ricci scalar and the Ricci tensor. The coefficients in front of such terms are called the second order transport coefficients and they parametrise the fluid response to the pressure terms arising from the spacetime curvature. Under the preliminary assumption that the second order transport coefficients are constant, we find the simplest solution of Ricci cosmology in which the presence of pressure terms causes a departure from the perfect fluid redshift scaling for matter components filling the Universe. In order to test the viability of this solution, we make four different ans\"{a}tze on the transport coefficients, giving rise to four different cases of our model. On the physical ground of the second law of thermodynamics for fluids with non-equilibrium pressure, we find some theoretical bounds (priors) on the parameters of the models. Our main concern is then the check of each of the case against the standard set of cosmological data in order to obtain the observational bounds on the second order transport coefficients. We find those bounds also realising that Ricci cosmology model is compatible with $\Lambda$CDM cosmology for all the ans\"{a}tze.
|
gr-qc/0207024
|
Dr. Anirudh Pradhan
|
Anirudh Pradhan, I. Iotemshi and G. P. Singh
|
Plane Symmetric Domain Wall in Lyra Geometry
|
Latex, 15 pages
|
Astrophys.Space Sci. 288 (2003) 315-325
|
10.1023/B:ASTR.0000006061.77421.c9
| null |
gr-qc
| null |
In this paper general solutions are found for domain walls in Lyra geometry
in the plane symmetric spacetime metric given by Taub. Expressions for the
energy density and pressure of domain walls are derived in both cases of
uniform and time varying displacement field $\beta$. It is also shown that the
results obtained by Rahaman et al [IJMPD, {\bf 10}, 735 (2001)] are particular
case of our solutions. Finally, the geodesic equations and acceleration of the
test particle are discussed.
|
[
{
"created": "Thu, 4 Jul 2002 07:26:04 GMT",
"version": "v1"
}
] |
2009-11-07
|
[
[
"Pradhan",
"Anirudh",
""
],
[
"Iotemshi",
"I.",
""
],
[
"Singh",
"G. P.",
""
]
] |
In this paper general solutions are found for domain walls in Lyra geometry in the plane symmetric spacetime metric given by Taub. Expressions for the energy density and pressure of domain walls are derived in both cases of uniform and time varying displacement field $\beta$. It is also shown that the results obtained by Rahaman et al [IJMPD, {\bf 10}, 735 (2001)] are particular case of our solutions. Finally, the geodesic equations and acceleration of the test particle are discussed.
|
2012.10237
|
Jingkai Wang
|
Jingkai Wang
|
Multiple Rings in the Shadow of Extremely Compact Objects
|
12 pages, 5 figures
| null |
10.1142/S0218271821501121
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Event Horizon Telescope's image of the M87 black hole provides an
exciting opportunity to study black hole physics. Since a black hole's event
horizon absorbs all electromagnetic waves, it is difficult to actively probe
the horizon's existence. However, with the help of a family of extremely
compact, horizon-less objects, named gravastars", whose external space-times
nearly identical to those of black holes, one can test the absence of event
horizons: absences of additional features that arise due to the existence of
the gravastar, or its surface, can be used as quantitative evidence for black
holes. We apply Gralla et al.'s approach to studying black hole images to study
the images of two types of gravastars: transparent ones and reflective ones. In
both cases, the transmission of rays through gravastars, or their reflections
on their surfaces, lead to more rings in their images. For simple emission
models, where the redshifted emissivity of the disk is peaked at a particular
radius r-peak, the position of a series of rings can be related in a simple
manner to light ray propagation: a ring shows up around impact parameter b
whenever rays incident from infinity at b intersects the disk at r-peak. We
show that additional rings will appear in the images of transparent and
reflective gravastars. In particular, one of the additional rings for the
reflective gravastar is due to the prompt reflection of light on the gravastar
surface and appears to be well separated from the others. This can be a robust
feature, which may be reliably used to constrain the reflectivity of the black
hole's horizon.
|
[
{
"created": "Thu, 17 Dec 2020 00:37:30 GMT",
"version": "v1"
}
] |
2022-01-05
|
[
[
"Wang",
"Jingkai",
""
]
] |
The Event Horizon Telescope's image of the M87 black hole provides an exciting opportunity to study black hole physics. Since a black hole's event horizon absorbs all electromagnetic waves, it is difficult to actively probe the horizon's existence. However, with the help of a family of extremely compact, horizon-less objects, named gravastars", whose external space-times nearly identical to those of black holes, one can test the absence of event horizons: absences of additional features that arise due to the existence of the gravastar, or its surface, can be used as quantitative evidence for black holes. We apply Gralla et al.'s approach to studying black hole images to study the images of two types of gravastars: transparent ones and reflective ones. In both cases, the transmission of rays through gravastars, or their reflections on their surfaces, lead to more rings in their images. For simple emission models, where the redshifted emissivity of the disk is peaked at a particular radius r-peak, the position of a series of rings can be related in a simple manner to light ray propagation: a ring shows up around impact parameter b whenever rays incident from infinity at b intersects the disk at r-peak. We show that additional rings will appear in the images of transparent and reflective gravastars. In particular, one of the additional rings for the reflective gravastar is due to the prompt reflection of light on the gravastar surface and appears to be well separated from the others. This can be a robust feature, which may be reliably used to constrain the reflectivity of the black hole's horizon.
|
1801.02001
|
Nelson Christensen
|
Duo Tao, Nelson Christensen
|
Optimizing signal recycling for detecting a stochastic
gravitational-wave background
| null |
Classical and Quantum Gravity, Volume 35, Number 12, p. 125002
(2018)
|
10.1088/1361-6382/aac148
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Signal recycling is applied in laser interferometers such as the Advanced
Laser Interferometer Gravitational-Wave Observatory (aLIGO) to increase their
sensitivity to gravitational waves. In this study, signal recycling
configurations for detecting a stochastic gravitational wave background are
optimized based on aLIGO parameters. Optimal transmission of the signal
recycling mirror (SRM) and detuning phase of the signal recycling cavity (SRC)
under a fixed laser power and low-frequency cutoff are calculated. Based on the
optimal configurations, the compatibility with a binary neutron star (BNS)
search is discussed. Then, different laser powers and low-frequency cutoffs are
considered. Two models for the dimensionless energy density of gravitational
waves $\Omega_{gw}(f) = \Omega_{\alpha} (f/f_{ref})^{\alpha}$, the flat model
$\alpha = 0$ and the $\alpha = 2/3$ model, are studied. For a stochastic
background search, it is found that an interferometer using signal recycling
has a better sensitivity than an interferometer not using it. The optimal
stochastic search configurations are typically found when both the SRM
transmission and the SRC detuning phase are low. In this region, the BNS range
mostly lies between 160 and 180 Mpc. When a lower laser power is used (reducing
radiation pressure at low frequencies), the optimal SRC detuning phase
increases, the optimal SRM transmission increases and the optimal sensitivity
improves. A reduced low-frequency cutoff gives a better sensitivity limit. For
both models of $\Omega_{gw}$, a typical optimal sensitivity limit on the order
of $10^{-10}$ is achieved at a reference frequency of $f_{ref} = 25$ Hz.
|
[
{
"created": "Sat, 6 Jan 2018 10:47:55 GMT",
"version": "v1"
},
{
"created": "Thu, 24 May 2018 08:41:09 GMT",
"version": "v2"
}
] |
2018-05-25
|
[
[
"Tao",
"Duo",
""
],
[
"Christensen",
"Nelson",
""
]
] |
Signal recycling is applied in laser interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) to increase their sensitivity to gravitational waves. In this study, signal recycling configurations for detecting a stochastic gravitational wave background are optimized based on aLIGO parameters. Optimal transmission of the signal recycling mirror (SRM) and detuning phase of the signal recycling cavity (SRC) under a fixed laser power and low-frequency cutoff are calculated. Based on the optimal configurations, the compatibility with a binary neutron star (BNS) search is discussed. Then, different laser powers and low-frequency cutoffs are considered. Two models for the dimensionless energy density of gravitational waves $\Omega_{gw}(f) = \Omega_{\alpha} (f/f_{ref})^{\alpha}$, the flat model $\alpha = 0$ and the $\alpha = 2/3$ model, are studied. For a stochastic background search, it is found that an interferometer using signal recycling has a better sensitivity than an interferometer not using it. The optimal stochastic search configurations are typically found when both the SRM transmission and the SRC detuning phase are low. In this region, the BNS range mostly lies between 160 and 180 Mpc. When a lower laser power is used (reducing radiation pressure at low frequencies), the optimal SRC detuning phase increases, the optimal SRM transmission increases and the optimal sensitivity improves. A reduced low-frequency cutoff gives a better sensitivity limit. For both models of $\Omega_{gw}$, a typical optimal sensitivity limit on the order of $10^{-10}$ is achieved at a reference frequency of $f_{ref} = 25$ Hz.
|
2302.04405
|
Tayyab Naseer
|
M. Sharif, Tayyab Naseer
|
Extended Decoupled Anisotropic Solutions in
$f(\mathcal{R},\mathcal{T},\mathcal{R}_{\gamma\chi}\mathcal{T}^{\gamma\chi})$
Gravity
|
28 pages, 8 figures
|
Int. J. Mod. Phys. D 31(2022)2240017
|
10.1142/S021827182240017X
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we consider static spherical structure to develop some
anisotropic solutions by employing the extended gravitational decoupling scheme
in the background of
$f(\mathcal{R},\mathcal{T},\mathcal{R}_{\gamma\chi}\mathcal{T}^{\gamma\chi})$
gravity, where $\mathcal{R}$ and $\mathcal{T}$ indicate the Ricci scalar and
trace of the energy-momentum tensor, respectively. We transform both radial as
well as temporal metric functions and apply them on the field equations that
produce two different sets corresponding to the decoupling parameter $\xi$. The
first set is associated with isotropic distribution, i.e., modified Krori-Barua
solution. The second set is influenced from anisotropic factor and contains
unknowns which are determined by taking some constraints. The impact of
decoupling parameter is then analyzed on the obtained physical variables and
anisotropy. We also investigate energy conditions and some other parameters
such as mass, compactness and redshift graphically. It is found that our
solution corresponding to pressure-like constraint shows stable behavior
throughout in this gravity for the considered range of $\xi$.
|
[
{
"created": "Thu, 9 Feb 2023 02:18:25 GMT",
"version": "v1"
}
] |
2023-02-10
|
[
[
"Sharif",
"M.",
""
],
[
"Naseer",
"Tayyab",
""
]
] |
In this paper, we consider static spherical structure to develop some anisotropic solutions by employing the extended gravitational decoupling scheme in the background of $f(\mathcal{R},\mathcal{T},\mathcal{R}_{\gamma\chi}\mathcal{T}^{\gamma\chi})$ gravity, where $\mathcal{R}$ and $\mathcal{T}$ indicate the Ricci scalar and trace of the energy-momentum tensor, respectively. We transform both radial as well as temporal metric functions and apply them on the field equations that produce two different sets corresponding to the decoupling parameter $\xi$. The first set is associated with isotropic distribution, i.e., modified Krori-Barua solution. The second set is influenced from anisotropic factor and contains unknowns which are determined by taking some constraints. The impact of decoupling parameter is then analyzed on the obtained physical variables and anisotropy. We also investigate energy conditions and some other parameters such as mass, compactness and redshift graphically. It is found that our solution corresponding to pressure-like constraint shows stable behavior throughout in this gravity for the considered range of $\xi$.
|
1212.0153
|
Peter K.F. Kuhfittig
|
Peter K.F. Kuhfittig
|
Wormholes supported by a combination of normal and quintessential matter
in Einstein and Einstein-Maxwell gravity
|
10 pages; two figures
|
Journal of Modern Physics, 4, 30 (2013)
|
10.4236/jmp.2013.41006
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is shown in the first part of this paper that a combined model comprising
ordinary and quintessential matter can support a traversable wormhole in
Einstein-Maxwell gravity. Since the solution allows zero tidal forces, the
wormhole is suitable for a humanoid traveler. The second part of the paper
shows that the electric field can be eliminated (Einstein gravity), but only by
tolerating enormous tidal forces. Such a wormhole would still be capable of
transmitting signals.
|
[
{
"created": "Sat, 1 Dec 2012 20:10:37 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Feb 2013 00:47:03 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Jun 2013 15:45:22 GMT",
"version": "v3"
},
{
"created": "Sun, 2 Feb 2014 20:15:03 GMT",
"version": "v4"
}
] |
2014-02-04
|
[
[
"Kuhfittig",
"Peter K. F.",
""
]
] |
It is shown in the first part of this paper that a combined model comprising ordinary and quintessential matter can support a traversable wormhole in Einstein-Maxwell gravity. Since the solution allows zero tidal forces, the wormhole is suitable for a humanoid traveler. The second part of the paper shows that the electric field can be eliminated (Einstein gravity), but only by tolerating enormous tidal forces. Such a wormhole would still be capable of transmitting signals.
|
2312.06772
|
Flavio Tonioni
|
Gary Shiu, Flavio Tonioni, Hung V. Tran
|
Collapsing universe before time
|
13 pages + appendices + references, 2 figures; v2: minor typos
corrected and refs. added
| null | null | null |
gr-qc astro-ph.CO hep-th math.DS
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this note, we prove analytic bounds on the equation of state of a
cosmological fluid composed of an arbitrary number of canonical scalars
evolving in a negative multi-exponential potential. Because of the negative
energy, the universe is contracting and eventually undergoes a big crunch. A
contracting universe is a fundamental feature of models of ekpyrosis and cyclic
universes, which are a proposed alternative to cosmic inflation to solve the
flatness and horizon problems. Our analytic bounds set quantitative constraints
on general effective theories of ekpyrosis. When applied to specific top-down
constructions, our bounds can be used to determine whether ekpyrosis could in
principle be realized. We point out some possible sources of tension in
realizing the ekpyrotic universe in controlled constructions of string theory.
|
[
{
"created": "Mon, 11 Dec 2023 19:00:06 GMT",
"version": "v1"
},
{
"created": "Thu, 30 May 2024 14:46:48 GMT",
"version": "v2"
}
] |
2024-05-31
|
[
[
"Shiu",
"Gary",
""
],
[
"Tonioni",
"Flavio",
""
],
[
"Tran",
"Hung V.",
""
]
] |
In this note, we prove analytic bounds on the equation of state of a cosmological fluid composed of an arbitrary number of canonical scalars evolving in a negative multi-exponential potential. Because of the negative energy, the universe is contracting and eventually undergoes a big crunch. A contracting universe is a fundamental feature of models of ekpyrosis and cyclic universes, which are a proposed alternative to cosmic inflation to solve the flatness and horizon problems. Our analytic bounds set quantitative constraints on general effective theories of ekpyrosis. When applied to specific top-down constructions, our bounds can be used to determine whether ekpyrosis could in principle be realized. We point out some possible sources of tension in realizing the ekpyrotic universe in controlled constructions of string theory.
|
1906.03140
|
Marco Antonelli
|
Lorenzo Gavassino and Marco Antonelli
|
Thermodynamics of uncharged relativistic multifluids
|
22 pages, preprint version (typos fixed and minor changes), comments
welcome
|
Classical and Quantum Gravity, Volume 37, Number 2 - Published 31
December 2019
|
10.1088/1361-6382/ab5f23
|
INT-PUB-19-022
|
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The internal layers of neutron stars are expected to contain several
superfluid components that can significantly affect their dynamics. The
description of such objects should rely on hydrodynamic models in which it is
possible to unambiguously assign the value of the thermodynamic variables from
microscopic calculations of the properties of matter. In this work we consider
the phenomenological approach to multifluids modelling championed by Carter
and, studying the relaxation of the system towards equilibrium, we assign a
precise thermodynamic interpretation to its variables. We show that in
thermodynamic equilibrium the equation of state contains less state variables
than those needed in the phenomenological model, implying the existence of a
gauge freedom of the theory that can be used to simplify the hydrodynamic
formulation in the non-dissipative limit. Once this is understood, it becomes
easy to translate the different multifluid formalisms that have been proposed
in the literature into Carter's form. Finally, we show that the usual concepts
of affinity and reaction coordinates, as they are introduced in chemistry, are
not affected by the presence of superfluid currents. In an effort to make the
concepts clear, the formalism is developed step-by-step from first principles,
providing model examples and several applications of practical relevance for
the study of superfluid neutron star interiors.
|
[
{
"created": "Fri, 7 Jun 2019 14:55:38 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jun 2019 11:05:05 GMT",
"version": "v2"
}
] |
2020-01-14
|
[
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
]
] |
The internal layers of neutron stars are expected to contain several superfluid components that can significantly affect their dynamics. The description of such objects should rely on hydrodynamic models in which it is possible to unambiguously assign the value of the thermodynamic variables from microscopic calculations of the properties of matter. In this work we consider the phenomenological approach to multifluids modelling championed by Carter and, studying the relaxation of the system towards equilibrium, we assign a precise thermodynamic interpretation to its variables. We show that in thermodynamic equilibrium the equation of state contains less state variables than those needed in the phenomenological model, implying the existence of a gauge freedom of the theory that can be used to simplify the hydrodynamic formulation in the non-dissipative limit. Once this is understood, it becomes easy to translate the different multifluid formalisms that have been proposed in the literature into Carter's form. Finally, we show that the usual concepts of affinity and reaction coordinates, as they are introduced in chemistry, are not affected by the presence of superfluid currents. In an effort to make the concepts clear, the formalism is developed step-by-step from first principles, providing model examples and several applications of practical relevance for the study of superfluid neutron star interiors.
|
gr-qc/0304106
|
Jose Geraldo Pereira
|
R. Aldrovandi, J. G. Pereira and K. H. Vu
|
Gravitation without the equivalence principle
|
Latex, 11 pages, no figures. Minor presentation changes. Version to
appear in Gen. Rel. Grav. (2004)
|
Gen.Rel.Grav. 36 (2004) 101-110
|
10.1023/B:GERG.0000006696.98824.4d
| null |
gr-qc hep-th
| null |
In the general relativistic description of gravitation, geometry replaces the
concept of force. This is possible because of the universal character of free
fall, and would break down in its absence. On the other hand, the teleparallel
version of general relativity is a gauge theory for the translation group and,
as such, describes the gravitational interaction by a force similar to the
Lorentz force of electromagnetism, a non-universal interaction. Relying on this
analogy it is shown that, although the geometric description of general
relativity necessarily requires the existence of the equivalence principle, the
teleparallel gauge approach remains a consistent theory for gravitation in its
absence.
|
[
{
"created": "Tue, 29 Apr 2003 18:32:08 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Aug 2003 13:50:54 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"Aldrovandi",
"R.",
""
],
[
"Pereira",
"J. G.",
""
],
[
"Vu",
"K. H.",
""
]
] |
In the general relativistic description of gravitation, geometry replaces the concept of force. This is possible because of the universal character of free fall, and would break down in its absence. On the other hand, the teleparallel version of general relativity is a gauge theory for the translation group and, as such, describes the gravitational interaction by a force similar to the Lorentz force of electromagnetism, a non-universal interaction. Relying on this analogy it is shown that, although the geometric description of general relativity necessarily requires the existence of the equivalence principle, the teleparallel gauge approach remains a consistent theory for gravitation in its absence.
|
1501.01355
|
Edward Teo
|
Yu Chen, Yen-Kheng Lim, Edward Teo
|
A new form of the C-metric with cosmological constant
|
37 pages, 7 figures, LaTeX; v2: minor changes, published version
|
Phys. Rev. D 91, 064014 (2015)
|
10.1103/PhysRevD.91.064014
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The new form of the C-metric proposed by Hong and Teo, in which the two
structure functions are factorised, has proved useful in its analysis. In this
paper, we extend this form to the case when a cosmological constant is present.
The new form of this solution has two structure functions which are partially
factorised; moreover, the roots of the structure functions are now regarded as
fundamental parameters. This leads to a natural representation of the solution
in terms of its so-called domain structure, in which the allowed coordinate
range can be visualised as a "box" in a two-dimensional plot. The solution is
then completely parameterised by the locations of the edges of this box, at
least in the uncharged case. We also briefly analyse other possible domain
structures---in the shape of a triangle and trapezoid---that might describe
physically interesting space-times within the AdS C-metric.
|
[
{
"created": "Wed, 7 Jan 2015 02:56:36 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Feb 2015 12:03:24 GMT",
"version": "v2"
}
] |
2015-03-11
|
[
[
"Chen",
"Yu",
""
],
[
"Lim",
"Yen-Kheng",
""
],
[
"Teo",
"Edward",
""
]
] |
The new form of the C-metric proposed by Hong and Teo, in which the two structure functions are factorised, has proved useful in its analysis. In this paper, we extend this form to the case when a cosmological constant is present. The new form of this solution has two structure functions which are partially factorised; moreover, the roots of the structure functions are now regarded as fundamental parameters. This leads to a natural representation of the solution in terms of its so-called domain structure, in which the allowed coordinate range can be visualised as a "box" in a two-dimensional plot. The solution is then completely parameterised by the locations of the edges of this box, at least in the uncharged case. We also briefly analyse other possible domain structures---in the shape of a triangle and trapezoid---that might describe physically interesting space-times within the AdS C-metric.
|
1405.5219
|
Justin Khoury
|
Justin Khoury, Godfrey E. J. Miller and Andrew J. Tolley
|
How General Relativity and Lorentz Covariance Arise from the Spatially
Covariant Effective Field Theory of the Transverse, Traceless Graviton
|
Essay received honorable mention in the Gravity Research Foundation
2014 essay competition. arXiv admin note: text overlap with arXiv:1305.0822
| null |
10.1142/S0218271814420127
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Traditional derivations of general relativity from the graviton degrees of
freedom assume space-time Lorentz covariance as an axiom. In this essay, we
survey recent evidence that general relativity is the unique
spatially-covariant effective field theory of the transverse, traceless
graviton degrees of freedom. The Lorentz covariance of general relativity,
having not been assumed in our analysis, is thus plausibly interpreted as an
accidental or emergent symmetry of the gravitational sector. From this point of
view, Lorentz covariance is a necessary feature of low-energy graviton
dynamics, not a property of space-time. This result has revolutionary
implications for fundamental physics.
|
[
{
"created": "Tue, 20 May 2014 20:00:20 GMT",
"version": "v1"
}
] |
2015-06-19
|
[
[
"Khoury",
"Justin",
""
],
[
"Miller",
"Godfrey E. J.",
""
],
[
"Tolley",
"Andrew J.",
""
]
] |
Traditional derivations of general relativity from the graviton degrees of freedom assume space-time Lorentz covariance as an axiom. In this essay, we survey recent evidence that general relativity is the unique spatially-covariant effective field theory of the transverse, traceless graviton degrees of freedom. The Lorentz covariance of general relativity, having not been assumed in our analysis, is thus plausibly interpreted as an accidental or emergent symmetry of the gravitational sector. From this point of view, Lorentz covariance is a necessary feature of low-energy graviton dynamics, not a property of space-time. This result has revolutionary implications for fundamental physics.
|
0709.0324
|
Chi Wai Lai
|
Chi Wai Lai, Matthew W. Choptuik
|
Final Fate of Subcritical Evolutions of Boson Stars
|
16 pages, 10 figures
| null | null |
AEI-2007-135
|
gr-qc
| null |
We present results from a study of Type I critical phenomena in the dynamics
of general relativistic boson stars in spherical symmetry. The boson stars are
modelled with a minimally coupled, massive complex field (with no explicit
self-interaction), and are driven to the threshold of black hole formation via
their gravitational interaction with an initially imploding pulse of massless
scalar field. Using a distinct coordinate system, we reproduce previous results
[1,2], including the scaling of the lifetime of near-critical configurations,
as well as the fact that such configurations are well described as perturbed,
one-mode-unstable boson stars. In addition, we make a detailed study of the
long-time evolution of marginally subcritical configurations. Contrary to
previous claims [1,2], we find that the end state in such cases does not
involve dispersal of the bulk of the boson star field to large radial
distances, but instead can be generically described by a stable boson star
executing large amplitude oscillations. Furthermore we show that these
oscillations can be largely identified as excitations of the fundamental mode
associated with the final boson star, as computed in perturbation theory.
|
[
{
"created": "Tue, 4 Sep 2007 02:52:23 GMT",
"version": "v1"
}
] |
2007-09-05
|
[
[
"Lai",
"Chi Wai",
""
],
[
"Choptuik",
"Matthew W.",
""
]
] |
We present results from a study of Type I critical phenomena in the dynamics of general relativistic boson stars in spherical symmetry. The boson stars are modelled with a minimally coupled, massive complex field (with no explicit self-interaction), and are driven to the threshold of black hole formation via their gravitational interaction with an initially imploding pulse of massless scalar field. Using a distinct coordinate system, we reproduce previous results [1,2], including the scaling of the lifetime of near-critical configurations, as well as the fact that such configurations are well described as perturbed, one-mode-unstable boson stars. In addition, we make a detailed study of the long-time evolution of marginally subcritical configurations. Contrary to previous claims [1,2], we find that the end state in such cases does not involve dispersal of the bulk of the boson star field to large radial distances, but instead can be generically described by a stable boson star executing large amplitude oscillations. Furthermore we show that these oscillations can be largely identified as excitations of the fundamental mode associated with the final boson star, as computed in perturbation theory.
|
gr-qc/9711051
|
Heller Michal
|
M. Heller, W. Sasin
|
Emergence of Time
|
13 pages, latex, no figures
|
Phys.Lett.A250:48-54,1998
|
10.1016/S0375-9601(98)00824-X
|
CGC-94-04
|
gr-qc
| null |
In the groupoid approach to noncommutative quantization of gravity,
gravitational field is quantized in terms of a C*-algebra A of complex valued
funcions on a groupoid G (with convolution as multiplication). In the
noncommutative quantum gravitational regime the concepts of space and time are
meaningless. We study the "emergence of time" in the transition process from
the noncommutative regime to the standard space-time geometry. Precise
conditions are specified under which modular groups of the von Neumann algebra
generated by A can be defined. These groups are interpreted as a state
depending time flow. If the above conditions are further refined one obtains a
state independent time flow. We show that quantum gravitational dynamics can be
expressed in terms of modular groups.
|
[
{
"created": "Mon, 17 Nov 1997 17:32:01 GMT",
"version": "v1"
}
] |
2011-07-19
|
[
[
"Heller",
"M.",
""
],
[
"Sasin",
"W.",
""
]
] |
In the groupoid approach to noncommutative quantization of gravity, gravitational field is quantized in terms of a C*-algebra A of complex valued funcions on a groupoid G (with convolution as multiplication). In the noncommutative quantum gravitational regime the concepts of space and time are meaningless. We study the "emergence of time" in the transition process from the noncommutative regime to the standard space-time geometry. Precise conditions are specified under which modular groups of the von Neumann algebra generated by A can be defined. These groups are interpreted as a state depending time flow. If the above conditions are further refined one obtains a state independent time flow. We show that quantum gravitational dynamics can be expressed in terms of modular groups.
|
gr-qc/0503076
|
Jose' P. S. Lemos
|
Alexander B. Balakin and Jos\'e P. S. Lemos
|
Non-minimal coupling for the gravitational and electromagnetic fields: A
general system of equations
|
15 pages
|
Class.Quant.Grav. 22 (2005) 1867-1880
|
10.1088/0264-9381/22/9/024
| null |
gr-qc astro-ph hep-th
| null |
We establish a new self-consistent system of equations for the gravitational
and electromagnetic fields. The procedure is based on a non-minimal non-linear
extension of the standard Einstein-Hilbert-Maxwell action. General properties
of a three-parameter family of non-minimal linear models are discussed. In
addition, we show explicitly, that a static spherically symmetric charged
object can be described by a non-minimal model, second order in the derivatives
of the metric, when the susceptibility tensor is proportional to the
double-dual Riemann tensor
|
[
{
"created": "Thu, 17 Mar 2005 18:23:40 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Apr 2005 18:28:18 GMT",
"version": "v2"
}
] |
2009-11-11
|
[
[
"Balakin",
"Alexander B.",
""
],
[
"Lemos",
"José P. S.",
""
]
] |
We establish a new self-consistent system of equations for the gravitational and electromagnetic fields. The procedure is based on a non-minimal non-linear extension of the standard Einstein-Hilbert-Maxwell action. General properties of a three-parameter family of non-minimal linear models are discussed. In addition, we show explicitly, that a static spherically symmetric charged object can be described by a non-minimal model, second order in the derivatives of the metric, when the susceptibility tensor is proportional to the double-dual Riemann tensor
|
gr-qc/0011027
|
Mauricio Cataldo
|
M. Cataldo, S. del Campo and P. Salgado
|
Viscous cosmologies in scalar-tensor theories for Kasner type metrics
|
6 pages, Latex, accepted in Phys. Rev. D
|
Phys.Rev. D63 (2001) 063503
|
10.1103/PhysRevD.63.063503
| null |
gr-qc astro-ph hep-th
| null |
In a viscous Bianchi type I metric of the Kasner form, it is well known that
it is not possible to describe an anisotropic physical model of the universe,
which satisfies the second law of thermodynamics and the dominant energy
condition (DEC) in Einstein's theory of gravity. We examine this problem in
scalar-tensor theories of gravity. In this theory we show that it is possible
to describe the growth of entropy, keeping the thermodynamics and the dominant
energy condition.
|
[
{
"created": "Tue, 7 Nov 2000 20:26:25 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Cataldo",
"M.",
""
],
[
"del Campo",
"S.",
""
],
[
"Salgado",
"P.",
""
]
] |
In a viscous Bianchi type I metric of the Kasner form, it is well known that it is not possible to describe an anisotropic physical model of the universe, which satisfies the second law of thermodynamics and the dominant energy condition (DEC) in Einstein's theory of gravity. We examine this problem in scalar-tensor theories of gravity. In this theory we show that it is possible to describe the growth of entropy, keeping the thermodynamics and the dominant energy condition.
|
1510.04030
|
Edgardo Franzin
|
Mariano Cadoni, Edgardo Franzin, Salvatore Mignemi
|
Inflation as de Sitter instability
|
11 pages, 4 figures. Matches published version
|
Eur. Phys. J. C76 (2016) 483
|
10.1140/epjc/s10052-016-4322-3
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider cosmological inflation generated by a scalar field slowly rolling
off from a de Sitter maximum of its potential. The models belong to the class
of hilltop models and represent the most general model of this kind in which
the scalar potential can be written as the sum of two exponentials. The
minimally coupled Einstein-scalar gravity theory obtained in this way is the
cosmological version of a two-scale generalization of known holographic models,
allowing for solitonic solutions interpolating between an AdS spacetime in the
infrared and scaling solutions in the ultraviolet. We then investigate
cosmological inflation in the slow-roll approximation. Our model reproduces
correctly, for a wide range of its parameters, the most recent experimental
data for the power spectrum of primordial perturbations. Moreover, it predicts
inflation at energy scales of four to five orders of magnitude below the Planck
scale. At the onset of inflation, the mass of the tachyonic excitation, i.e. of
the inflaton, turns out to be seven to eight orders of magnitude smaller than
the Planck mass.
|
[
{
"created": "Wed, 14 Oct 2015 10:14:57 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Oct 2015 12:46:29 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Sep 2016 08:46:55 GMT",
"version": "v3"
}
] |
2016-09-05
|
[
[
"Cadoni",
"Mariano",
""
],
[
"Franzin",
"Edgardo",
""
],
[
"Mignemi",
"Salvatore",
""
]
] |
We consider cosmological inflation generated by a scalar field slowly rolling off from a de Sitter maximum of its potential. The models belong to the class of hilltop models and represent the most general model of this kind in which the scalar potential can be written as the sum of two exponentials. The minimally coupled Einstein-scalar gravity theory obtained in this way is the cosmological version of a two-scale generalization of known holographic models, allowing for solitonic solutions interpolating between an AdS spacetime in the infrared and scaling solutions in the ultraviolet. We then investigate cosmological inflation in the slow-roll approximation. Our model reproduces correctly, for a wide range of its parameters, the most recent experimental data for the power spectrum of primordial perturbations. Moreover, it predicts inflation at energy scales of four to five orders of magnitude below the Planck scale. At the onset of inflation, the mass of the tachyonic excitation, i.e. of the inflaton, turns out to be seven to eight orders of magnitude smaller than the Planck mass.
|
gr-qc/0303030
|
Parthasarathi Majumdar
|
Ashok Chatterjee and Parthasarathi Majumdar
|
Black hole entropy: quantum vs thermal fluctuations
|
11 Pages Revtex, no figures
| null | null | null |
gr-qc
| null |
The relation between logarithmic corrections to the area law for black hole
entropy, due to thermal fluctuations around an equilibrium canonical ensemble,
and those originating from quantum spacetime fluctuations within a
microcanonical framework, is explored for three and four dimensional
asymptotically anti-de Sitter black holes. For the BTZ black hole, the two
logarithmic corrections are seen to precisely cancel each other, while for four
dimensional adS-Schwarzschild black holes a partial cancellation is obtained.
We discuss the possibility of extending the analysis to asymptotically flat
black holes.
|
[
{
"created": "Fri, 7 Mar 2003 13:10:15 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Chatterjee",
"Ashok",
""
],
[
"Majumdar",
"Parthasarathi",
""
]
] |
The relation between logarithmic corrections to the area law for black hole entropy, due to thermal fluctuations around an equilibrium canonical ensemble, and those originating from quantum spacetime fluctuations within a microcanonical framework, is explored for three and four dimensional asymptotically anti-de Sitter black holes. For the BTZ black hole, the two logarithmic corrections are seen to precisely cancel each other, while for four dimensional adS-Schwarzschild black holes a partial cancellation is obtained. We discuss the possibility of extending the analysis to asymptotically flat black holes.
|
2104.08442
|
Slava G. Turyshev
|
Slava G. Turyshev, Viktor T. Toth
|
Imaging point sources with the gravitational lens of an extended Sun
|
13 pages, 8 figures
|
Phys. Rev. D 104, 044032 (2021)
|
10.1103/PhysRevD.104.044032
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the optical properties of the solar gravitational lens (SGL) while
treating the Sun as an extended, axisymmetric and rotating body. The
gravitational field of the Sun is represented using a set of zonal harmonics.
We develop an analytical description of the intensity of light that is observed
in the image plane in the strong interference region of a realistic SGL. This
formalism makes it possible to model not only the point-spread function of
point sources, but also actual observables, images that form in the focal plane
of an imaging telescope positioned in the image plane. Perturbations of the
monopole gravitational field of the Sun are dominated by the solar quadrupole
moment, which results in forming an astroid caustic on the image plane.
Consequently, an imaging telescope placed inside the astroid caustic observes
four bright spots, forming the well-known pattern of an Einstein cross. The
relative intensities and positions of these spots change as the telescope is
moved in the image plane, with spots merging into bright arcs when the
telescope approaches the caustic boundary. Outside the astroid caustic, only
two spots remain and the observed pattern eventually becomes indistinguishable
from the imaging pattern of a monopole lens at greater distances from the
optical axis. We present results from extensive numerical simulations, forming
the basis of our ongoing study of prospective exoplanet imaging with the SGL.
These results are also applicable to describe a large class of gravitational
lensing scenarios involving axisymmetric lenses that can be represented using
zonal harmonics.
|
[
{
"created": "Sat, 17 Apr 2021 04:30:27 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Aug 2021 16:00:37 GMT",
"version": "v2"
}
] |
2021-08-16
|
[
[
"Turyshev",
"Slava G.",
""
],
[
"Toth",
"Viktor T.",
""
]
] |
We study the optical properties of the solar gravitational lens (SGL) while treating the Sun as an extended, axisymmetric and rotating body. The gravitational field of the Sun is represented using a set of zonal harmonics. We develop an analytical description of the intensity of light that is observed in the image plane in the strong interference region of a realistic SGL. This formalism makes it possible to model not only the point-spread function of point sources, but also actual observables, images that form in the focal plane of an imaging telescope positioned in the image plane. Perturbations of the monopole gravitational field of the Sun are dominated by the solar quadrupole moment, which results in forming an astroid caustic on the image plane. Consequently, an imaging telescope placed inside the astroid caustic observes four bright spots, forming the well-known pattern of an Einstein cross. The relative intensities and positions of these spots change as the telescope is moved in the image plane, with spots merging into bright arcs when the telescope approaches the caustic boundary. Outside the astroid caustic, only two spots remain and the observed pattern eventually becomes indistinguishable from the imaging pattern of a monopole lens at greater distances from the optical axis. We present results from extensive numerical simulations, forming the basis of our ongoing study of prospective exoplanet imaging with the SGL. These results are also applicable to describe a large class of gravitational lensing scenarios involving axisymmetric lenses that can be represented using zonal harmonics.
|
1507.02348
|
Michel Miranda
|
Tonatiuh Matos and Galaxia Miranda
|
Exact Rotating Magnetic Traversable Wormholes satisfying the Energy
Conditions
| null |
Phys. Rev. D99, (2019), 124045
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we wonder if there is a way to generate a wormhole (WH) in
nature using "normal" matter. In order to give a first answer to this question,
we study a massless scalar field coupled to an electromagnetic one (dilatonic
field) with an arbitrary coupling constant, as source of gravitation. We obtain
an exact solution of the Einstein equations using this source that represents a
magnetized rotating WH. This space-time has a naked ring singularity, probably
untouchable as in \cite{Matos:2012gj}, but otherwise regular. The WH throat
lies on the disc bounded by the ring singularity, which keeps the throat open
without requiring exotic matter, that means, satisfying all the energy
conditions. After analyzing the geodesic motion and the tidal forces we find
that a test particle can go through the WH without troubles.
|
[
{
"created": "Thu, 9 Jul 2015 02:12:58 GMT",
"version": "v1"
}
] |
2021-02-09
|
[
[
"Matos",
"Tonatiuh",
""
],
[
"Miranda",
"Galaxia",
""
]
] |
In this work we wonder if there is a way to generate a wormhole (WH) in nature using "normal" matter. In order to give a first answer to this question, we study a massless scalar field coupled to an electromagnetic one (dilatonic field) with an arbitrary coupling constant, as source of gravitation. We obtain an exact solution of the Einstein equations using this source that represents a magnetized rotating WH. This space-time has a naked ring singularity, probably untouchable as in \cite{Matos:2012gj}, but otherwise regular. The WH throat lies on the disc bounded by the ring singularity, which keeps the throat open without requiring exotic matter, that means, satisfying all the energy conditions. After analyzing the geodesic motion and the tidal forces we find that a test particle can go through the WH without troubles.
|
1310.2303
|
James Dilts
|
James Dilts
|
The Einstein Constraint Equations on Compact Manifolds with Boundary
|
34 pages. arXiv admin note: text overlap with arXiv:1306.1801 by
other authors
| null |
10.1088/0264-9381/31/12/125009
| null |
gr-qc math.AP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We continue the study of the Einstein constraint equations on compact
manifolds with boundary initiated by Holst and Tsogtgerel. In particular, we
consider the full system and prove existence of solutions in both the near-CMC
and far-from-CMC (for Yamabe positive metrics) cases. We also make partial
progress in proving the results of previous "limit equation" papers by Dahl,
Gicquaud, Humbert and Sakovich.
|
[
{
"created": "Tue, 8 Oct 2013 23:12:35 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Nov 2013 22:46:25 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Feb 2014 17:35:37 GMT",
"version": "v3"
}
] |
2015-06-17
|
[
[
"Dilts",
"James",
""
]
] |
We continue the study of the Einstein constraint equations on compact manifolds with boundary initiated by Holst and Tsogtgerel. In particular, we consider the full system and prove existence of solutions in both the near-CMC and far-from-CMC (for Yamabe positive metrics) cases. We also make partial progress in proving the results of previous "limit equation" papers by Dahl, Gicquaud, Humbert and Sakovich.
|
1608.04014
|
Burin Gumjudpai
|
Narakorn Kaewkhao (IF Naresuan) and Burin Gumjudpai (IF Naresuan)
|
Cosmology of non-minimal derivative coupling to gravity in Palatini
formalism and its chaotic inflation
|
12 pages, no figures, chaotic inflation potential section and
appendices added, minor correction on Planck unit
|
Physics of the Dark Universe 20 (2018) 20
|
10.1016/j.dark.2018.02.004
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider, in Palatini formalism, a modified gravity of which the scalar
field derivative couples to Einstein tensor. In this scenario, Ricci scalar,
Ricci tensor and Einstein tensor are functions of connection field. As a
result, the connection field gives rise to relation, $h_{\mu\nu} = f
g_{\mu\nu}$ between effective metric, $h_{\mu\nu}$ and the usual metric
$g_{\mu\nu}$ where $f \,=\,1 - \kappa{\phi}^{,\alpha}{\phi}_{,\alpha}/2 $. In
FLRW universe, NMDC coupling constant is limited in a range of $ -2/
\dot{\phi}^{2} < \kappa \leq \infty $ preserving Lorentz signature of the
effective metric. Slowly-rolling regime provides $\kappa < 0$ forbidding
graviton from travelling at superluminal speed. Effective gravitational
coupling and entropy of blackhole's apparent horizon are derived.
In case of negative coupling, acceleration could happen even with $w_{\rm
eff} > -1/3$. Power-law potentials of chaotic inflation are considered. For $V
\propto \phi^2$ and $V \propto \phi^4$, it is possible to obtain
tensor-to-scalar ratio lower than that of GR so that it satisfies $r < 0.12$ as
constrained by Planck 2015 \cite{Ade:2015lrj}. The $V \propto \phi^2$ case
yields acceptable range of spectrum index and $r$ values. The quartic
potential's spectrum index is disfavored by the Planck results. Viable range of
$\k$ for $V \propto \phi^2$ case lies in positive region, resulting in less
blackhole's entropy, superluminal metric, more amount of inflation, avoidance
of super-Planckian field initial value and stronger gravitational constant.
|
[
{
"created": "Sat, 13 Aug 2016 18:35:06 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Mar 2017 16:08:17 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Jul 2017 10:17:29 GMT",
"version": "v3"
},
{
"created": "Thu, 1 Mar 2018 17:47:09 GMT",
"version": "v4"
},
{
"created": "Sun, 18 Mar 2018 17:40:45 GMT",
"version": "v5"
}
] |
2018-03-20
|
[
[
"Kaewkhao",
"Narakorn",
"",
"IF Naresuan"
],
[
"Gumjudpai",
"Burin",
"",
"IF Naresuan"
]
] |
We consider, in Palatini formalism, a modified gravity of which the scalar field derivative couples to Einstein tensor. In this scenario, Ricci scalar, Ricci tensor and Einstein tensor are functions of connection field. As a result, the connection field gives rise to relation, $h_{\mu\nu} = f g_{\mu\nu}$ between effective metric, $h_{\mu\nu}$ and the usual metric $g_{\mu\nu}$ where $f \,=\,1 - \kappa{\phi}^{,\alpha}{\phi}_{,\alpha}/2 $. In FLRW universe, NMDC coupling constant is limited in a range of $ -2/ \dot{\phi}^{2} < \kappa \leq \infty $ preserving Lorentz signature of the effective metric. Slowly-rolling regime provides $\kappa < 0$ forbidding graviton from travelling at superluminal speed. Effective gravitational coupling and entropy of blackhole's apparent horizon are derived. In case of negative coupling, acceleration could happen even with $w_{\rm eff} > -1/3$. Power-law potentials of chaotic inflation are considered. For $V \propto \phi^2$ and $V \propto \phi^4$, it is possible to obtain tensor-to-scalar ratio lower than that of GR so that it satisfies $r < 0.12$ as constrained by Planck 2015 \cite{Ade:2015lrj}. The $V \propto \phi^2$ case yields acceptable range of spectrum index and $r$ values. The quartic potential's spectrum index is disfavored by the Planck results. Viable range of $\k$ for $V \propto \phi^2$ case lies in positive region, resulting in less blackhole's entropy, superluminal metric, more amount of inflation, avoidance of super-Planckian field initial value and stronger gravitational constant.
|
2111.04489
|
Siyuan Ma
|
Siyuan Ma, Lin Zhang
|
Sharp decay for Teukolsky equation in Kerr spacetimes
|
The published version
|
Commun. Math. Phys. 401, 333-434 (2023)
|
10.1007/s00220-023-04640-w
| null |
gr-qc math.AP
|
http://creativecommons.org/licenses/by/4.0/
|
In this work, we derive the global sharp decay, as both a lower and an upper
bounds, for the spin $\pm \mathfrak{s}$ components, which are solutions to the
Teukolsky equation, in the black hole exterior and on the event horizon of a
slowly rotating Kerr spacetime. These estimates are generalized to any
subextreme Kerr background under an integrated local energy decay estimate. Our
results apply to the scalar field $(\mathfrak{s}=0)$, the Maxwell field
$(\mathfrak{s}=1)$ and the linearized gravity $(\mathfrak{s}=2)$ and confirm
the Price's law decay that is conjectured to be sharp. Our analyses rely on a
novel global conservation law for the Teukolsky equation, and this new approach
can be applied to derive the precise asymptotics for solutions to semilinear
wave equations.
|
[
{
"created": "Mon, 8 Nov 2021 13:25:23 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Nov 2021 15:49:20 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Jul 2023 02:43:04 GMT",
"version": "v3"
}
] |
2023-07-06
|
[
[
"Ma",
"Siyuan",
""
],
[
"Zhang",
"Lin",
""
]
] |
In this work, we derive the global sharp decay, as both a lower and an upper bounds, for the spin $\pm \mathfrak{s}$ components, which are solutions to the Teukolsky equation, in the black hole exterior and on the event horizon of a slowly rotating Kerr spacetime. These estimates are generalized to any subextreme Kerr background under an integrated local energy decay estimate. Our results apply to the scalar field $(\mathfrak{s}=0)$, the Maxwell field $(\mathfrak{s}=1)$ and the linearized gravity $(\mathfrak{s}=2)$ and confirm the Price's law decay that is conjectured to be sharp. Our analyses rely on a novel global conservation law for the Teukolsky equation, and this new approach can be applied to derive the precise asymptotics for solutions to semilinear wave equations.
|
2002.03630
|
Avijit Chowdhury
|
Avijit Chowdhury and Narayan Banerjee
|
Greybody factor and sparsity of Hawking radiation from a charged
spherical black hole with scalar hair
|
Version accepted for publication in PLB
|
Phys. Lett. B 805, 135417 (2020)
|
10.1016/j.physletb.2020.135417
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The `no-hair' conjecture claims that for a spherically symmetric black hole,
only the information regarding the mass and charge of the black hole is
available to an external observer. However, there are numerous counterexamples
to the `no-hair' conjecture. In this work, we consider a particular
counter-example to the `no-hair' conjecture in (3+1) dimensions, namely, a
static spherically symmetric charged black hole with a scalar hair. We provide
semi-analytic bounds on the greybody factors and study the sparsity of Hawking
radiation of mass-less uncharged scalar fields. Our results show that the
scalar and electric charges contribute oppositely to the greybody factor and
the sparsity of the Hawking radiation cascade. Also, the greybody factor
decreases and the Hawking emission spectra become more sparse with the
reduction in the black hole (ADM) mass.
|
[
{
"created": "Mon, 10 Feb 2020 10:14:19 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Apr 2020 09:38:54 GMT",
"version": "v2"
}
] |
2020-04-20
|
[
[
"Chowdhury",
"Avijit",
""
],
[
"Banerjee",
"Narayan",
""
]
] |
The `no-hair' conjecture claims that for a spherically symmetric black hole, only the information regarding the mass and charge of the black hole is available to an external observer. However, there are numerous counterexamples to the `no-hair' conjecture. In this work, we consider a particular counter-example to the `no-hair' conjecture in (3+1) dimensions, namely, a static spherically symmetric charged black hole with a scalar hair. We provide semi-analytic bounds on the greybody factors and study the sparsity of Hawking radiation of mass-less uncharged scalar fields. Our results show that the scalar and electric charges contribute oppositely to the greybody factor and the sparsity of the Hawking radiation cascade. Also, the greybody factor decreases and the Hawking emission spectra become more sparse with the reduction in the black hole (ADM) mass.
|
gr-qc/0212105
|
Kostas Kokkotas
|
K.D.Kokkotas and J.Ruoff
|
Instabilities of Relativistic Stars
|
41 pages, 12 figures, Proceedings of the 25th John Hopkins Workshop,
Florence
| null |
10.1142/9789812791368_0019
| null |
gr-qc astro-ph
| null |
Recent developments on the rotational instabilities of relativistic stars are
reviewed. The article provides an account of the theory of stellar
instabilities with emphasis on the rotational ones. Special attention is being
paid to the study of these instabilities in the general relativistic regime.
Issues such as the existence relativistic r-modes, the existence of a
continuous spectrum and the CFS instability of the w-modes are discussed in the
second half of the article.
|
[
{
"created": "Thu, 26 Dec 2002 01:44:54 GMT",
"version": "v1"
}
] |
2017-08-23
|
[
[
"Kokkotas",
"K. D.",
""
],
[
"Ruoff",
"J.",
""
]
] |
Recent developments on the rotational instabilities of relativistic stars are reviewed. The article provides an account of the theory of stellar instabilities with emphasis on the rotational ones. Special attention is being paid to the study of these instabilities in the general relativistic regime. Issues such as the existence relativistic r-modes, the existence of a continuous spectrum and the CFS instability of the w-modes are discussed in the second half of the article.
|
gr-qc/9404063
|
Andrew Barvinski
|
A.O.Barvinsky, Yu.V.Gusev, G.A.Vilkovisky and V.V.Zhytnikov
|
Asymptotic behaviours of the heat kernel in covariant perturbation
theory
|
22 pages, REVTeX, Alberta Thy 45-93
|
J.Math.Phys. 35 (1994) 3543-3559
|
10.1063/1.530428
| null |
gr-qc
| null |
The trace of the heat kernel is expanded in a basis of nonlocal curvature
invariants of $N$th order. The coefficients of this expansion (the nonlocal
form factors) are calculated to third order in the curvature inclusive. The
early-time and late-time asymptotic behaviours of the trace of the heat kernel
are presented with this accuracy. The late-time behaviour gives the criterion
of analyticity of the effective action in quantum field theory. The latter
point is exemplified by deriving the effective action in two dimensions.
|
[
{
"created": "Fri, 29 Apr 1994 22:29:02 GMT",
"version": "v1"
}
] |
2016-08-31
|
[
[
"Barvinsky",
"A. O.",
""
],
[
"Gusev",
"Yu. V.",
""
],
[
"Vilkovisky",
"G. A.",
""
],
[
"Zhytnikov",
"V. V.",
""
]
] |
The trace of the heat kernel is expanded in a basis of nonlocal curvature invariants of $N$th order. The coefficients of this expansion (the nonlocal form factors) are calculated to third order in the curvature inclusive. The early-time and late-time asymptotic behaviours of the trace of the heat kernel are presented with this accuracy. The late-time behaviour gives the criterion of analyticity of the effective action in quantum field theory. The latter point is exemplified by deriving the effective action in two dimensions.
|
1812.03551
|
Masato Minamitsuji
|
Masato Minamitsuji and Taishi Ikeda
|
Scalarized black holes in the presence of the coupling to Gauss-Bonnet
gravity
|
25 pages, 13 figures, references added, published version
|
Phys. Rev. D 99, 044017 (2019)
|
10.1103/PhysRevD.99.044017
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we study static and spherically symmetric black hole (BH)
solutions in the scalar-tensor theories with the coupling of the scalar field
to the Gauss-Bonnet (GB) term $\xi (\phi) R_{\rm GB}$, where $R_{\rm
GB}:=R^2-4R^{\alpha\beta}R_{\alpha\beta}+R^{\alpha\beta\mu\nu}R_{\alpha\beta\mu\nu}$
is the GB invariant and $\xi(\phi)$ is a function of the scalar field $\phi$.
Recently, it was shown that in these theories scalarized static and spherically
symmetric BH solutions which are different from the Schwarzschild solution and
possess the nontrivial profiles of the scalar field can be realized for certain
choices of the coupling functions and parameters. These scalarized BH solutions
are classified in terms of the number of nodes of the scalar field. It was then
pointed out that in the case of the pure quadratic order coupling to the GB
term, $\xi(\phi)=\eta \phi^2/8$, scalarized BH solutions with any number of
nodes are unstable against the radial perturbation. In order to see how a
higher order power of $\phi$ in the coupling function $\xi(\phi)$ affects the
properties of the scalarized BHs and their stability, we investigate scalarized
BH solutions in the presence of the quartic order term in the GB coupling
function, $\xi(\phi)=\eta \phi^2 (1+\alpha \phi^2)/8$. We clarify that the
existence of the higher order term in the coupling function can realize
scalarized BHs with zero nodes of the scalar field which are stable against the
radial perturbation.
|
[
{
"created": "Sun, 9 Dec 2018 19:49:06 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2019 19:57:29 GMT",
"version": "v2"
}
] |
2019-02-14
|
[
[
"Minamitsuji",
"Masato",
""
],
[
"Ikeda",
"Taishi",
""
]
] |
In this paper, we study static and spherically symmetric black hole (BH) solutions in the scalar-tensor theories with the coupling of the scalar field to the Gauss-Bonnet (GB) term $\xi (\phi) R_{\rm GB}$, where $R_{\rm GB}:=R^2-4R^{\alpha\beta}R_{\alpha\beta}+R^{\alpha\beta\mu\nu}R_{\alpha\beta\mu\nu}$ is the GB invariant and $\xi(\phi)$ is a function of the scalar field $\phi$. Recently, it was shown that in these theories scalarized static and spherically symmetric BH solutions which are different from the Schwarzschild solution and possess the nontrivial profiles of the scalar field can be realized for certain choices of the coupling functions and parameters. These scalarized BH solutions are classified in terms of the number of nodes of the scalar field. It was then pointed out that in the case of the pure quadratic order coupling to the GB term, $\xi(\phi)=\eta \phi^2/8$, scalarized BH solutions with any number of nodes are unstable against the radial perturbation. In order to see how a higher order power of $\phi$ in the coupling function $\xi(\phi)$ affects the properties of the scalarized BHs and their stability, we investigate scalarized BH solutions in the presence of the quartic order term in the GB coupling function, $\xi(\phi)=\eta \phi^2 (1+\alpha \phi^2)/8$. We clarify that the existence of the higher order term in the coupling function can realize scalarized BHs with zero nodes of the scalar field which are stable against the radial perturbation.
|
gr-qc/0603127
|
Alex Nielsen
|
Alex B. Nielsen
|
Skyrme Black Holes in the Isolated Horizons Formalism
|
Full journal version, 6 pages, 5 figures
|
Phys.Rev.D74:044038,2006
|
10.1103/PhysRevD.74.044038
| null |
gr-qc
| null |
We study static, spherically symmetric, Skyrme black holes in the context of
the assumption that they can be viewed as bound states between ordinary bare
black holes and solitons. This assumption and results stemming from the
isolated horizons formalism lead to several conjectures about the static black
hole solutions. These conjectures are tested against the Skyrme black hole
solutions. It is shown that, while there is in general good agreement with the
conjectures, a crucial aspect seems to violate one of the conjectures.
|
[
{
"created": "Fri, 31 Mar 2006 05:20:10 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Sep 2006 00:13:23 GMT",
"version": "v2"
}
] |
2008-12-18
|
[
[
"Nielsen",
"Alex B.",
""
]
] |
We study static, spherically symmetric, Skyrme black holes in the context of the assumption that they can be viewed as bound states between ordinary bare black holes and solitons. This assumption and results stemming from the isolated horizons formalism lead to several conjectures about the static black hole solutions. These conjectures are tested against the Skyrme black hole solutions. It is shown that, while there is in general good agreement with the conjectures, a crucial aspect seems to violate one of the conjectures.
|
gr-qc/9604040
|
R. Beig, Univ. Wien.
|
R.Beig (Institut f\"ur Theoretische Physik, Universit\"at Wien) Piotr
T. Chrusciel (Departement de Mathematique Faculte des Sciences Tours)
|
Killing Initial Data
|
17 pages
|
Class.Quant.Grav.14:A83-A92,1997
|
10.1088/0264-9381/14/1A/007
| null |
gr-qc
| null |
We study space-time Killing vectors in terms of their "lapse and shift"
relative to some spacelike slice. We give a necessary and sufficient condition
in order for these lapse-shift pairs, which we call Killing initial data
(KID'S), to form a Lie algebra under the bracket operation induced by the Lie
commutator of vector fields on space-time. This result is applied to obtain a
theorem on the periodicity of orbits for a class of Killing vector fields in
asymptotically flat space-times.
|
[
{
"created": "Mon, 22 Apr 1996 14:01:26 GMT",
"version": "v1"
}
] |
2010-04-06
|
[
[
"Beig",
"R.",
"",
"Institut für Theoretische Physik, Universität Wien"
],
[
"Chrusciel",
"Piotr T.",
"",
"Departement de Mathematique Faculte des Sciences Tours"
]
] |
We study space-time Killing vectors in terms of their "lapse and shift" relative to some spacelike slice. We give a necessary and sufficient condition in order for these lapse-shift pairs, which we call Killing initial data (KID'S), to form a Lie algebra under the bracket operation induced by the Lie commutator of vector fields on space-time. This result is applied to obtain a theorem on the periodicity of orbits for a class of Killing vector fields in asymptotically flat space-times.
|
gr-qc/9511051
|
Antonio Lopez Pinto
|
A.Lopez-Pinto, A.Tiemblo and R.Tresguerres
|
Non-Linear Affine Embedding of the Dirac Field from the
Multiplicity-Free SL(4,R) Unirreps
|
13 pages, plain TeX, macros included
|
Class.Quant.Grav. 13 (1996) 2255-2266
|
10.1088/0264-9381/13/8/018
|
preprint IMAFF 95/9
|
gr-qc hep-th
| null |
The correspondence between the linear multiplicity-free unirreps of SL(4, R)
studied by Ne'eman and {\~{S}}ija{\~{c}}ki and the non-linear realizations of
the affine group is worked out. The results obtained clarify the inclusion of
spinorial fields in a non-linear affine gauge theory of gravitation.
|
[
{
"created": "Fri, 17 Nov 1995 16:15:47 GMT",
"version": "v1"
}
] |
2009-10-28
|
[
[
"Lopez-Pinto",
"A.",
""
],
[
"Tiemblo",
"A.",
""
],
[
"Tresguerres",
"R.",
""
]
] |
The correspondence between the linear multiplicity-free unirreps of SL(4, R) studied by Ne'eman and {\~{S}}ija{\~{c}}ki and the non-linear realizations of the affine group is worked out. The results obtained clarify the inclusion of spinorial fields in a non-linear affine gauge theory of gravitation.
|
0808.3005
|
Dinesh Singh
|
Dinesh Singh
|
Perturbation Method for Classical Spinning Particle Motion: I. Kerr
Space-Time
|
23 pages; REVTeX file; 9 figures; Accepted for publication in Phys.
Rev. D
|
Phys.Rev.D78:104028,2008
|
10.1103/PhysRevD.78.104028
| null |
gr-qc astro-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper presents an analytic perturbation approach to the dynamics of a
classical spinning particle, according to the Mathisson-Papapetrou-Dixon (MPD)
equations of motion, with a direct application to circular motion around a Kerr
black hole. The formalism is established in terms of a power series expansion
with respect to the particle's spin magnitude, where the particle's kinematic
and dynamical degrees are expressed in a completely general form that can be
constructed to infinite order in the expansion parameter. It is further shown
that the particle's squared mass and spin magnitude can shift due to a
classical analogue of radiative corrections that arise from spin-curvature
coupling. Explicit expressions are determined for the case of circular motion
near the event horizon a Kerr black hole, where the mass and spin shift
contributions are dependent on the initial conditions of the particle's spin
orientation. A preliminary analysis of the stability properties of the orbital
motion in the Kerr background due to spin-curvature interactions is explored
and briefly discussed.
|
[
{
"created": "Fri, 22 Aug 2008 19:32:23 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Oct 2008 14:50:30 GMT",
"version": "v2"
}
] |
2008-12-18
|
[
[
"Singh",
"Dinesh",
""
]
] |
This paper presents an analytic perturbation approach to the dynamics of a classical spinning particle, according to the Mathisson-Papapetrou-Dixon (MPD) equations of motion, with a direct application to circular motion around a Kerr black hole. The formalism is established in terms of a power series expansion with respect to the particle's spin magnitude, where the particle's kinematic and dynamical degrees are expressed in a completely general form that can be constructed to infinite order in the expansion parameter. It is further shown that the particle's squared mass and spin magnitude can shift due to a classical analogue of radiative corrections that arise from spin-curvature coupling. Explicit expressions are determined for the case of circular motion near the event horizon a Kerr black hole, where the mass and spin shift contributions are dependent on the initial conditions of the particle's spin orientation. A preliminary analysis of the stability properties of the orbital motion in the Kerr background due to spin-curvature interactions is explored and briefly discussed.
|
2205.01667
|
Francisco M. Blanco
|
Francisco M. Blanco and \'Eanna \'E. Flanagan
|
Particle motion under the conservative piece of the self-force is
Hamiltonian
|
6 pages
| null |
10.1103/PhysRevLett.130.051201
| null |
gr-qc astro-ph.HE
|
http://creativecommons.org/licenses/by/4.0/
|
We consider the motion of a point particle in a stationary spacetime under
the influence of a scalar, electromagnetic or gravitational self-force. We show
that the conservative piece of the first-order self-force gives rise to
Hamiltonian dynamics, and we derive an explicit expression for the Hamiltonian
on phase space. Specialized to the Kerr spacetime, our result generalizes the
Hamiltonian function previously obtained by Fujita et. al., which is valid only
for non-resonant orbits. We discuss implications for the first law of binary
black hole mechanics.
|
[
{
"created": "Tue, 3 May 2022 17:57:19 GMT",
"version": "v1"
}
] |
2023-02-15
|
[
[
"Blanco",
"Francisco M.",
""
],
[
"Flanagan",
"Éanna É.",
""
]
] |
We consider the motion of a point particle in a stationary spacetime under the influence of a scalar, electromagnetic or gravitational self-force. We show that the conservative piece of the first-order self-force gives rise to Hamiltonian dynamics, and we derive an explicit expression for the Hamiltonian on phase space. Specialized to the Kerr spacetime, our result generalizes the Hamiltonian function previously obtained by Fujita et. al., which is valid only for non-resonant orbits. We discuss implications for the first law of binary black hole mechanics.
|
1311.3153
|
Jeffrey Hazboun
|
Jeffrey S. Hazboun, Manuel Pichardo Marcano and Shane L. Larson
|
Limiting alternative theories of gravity using gravitational wave
observations across the spectrum
|
Now covers test using interferometers and PTA's 20 pages, 6 figures
| null | null | null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The advent of gravitational wave astronomy provides new proving grounds for
testing theories of gravity. Recent work has reinvigorated the study of
bimetric theories of gravity and massive gravity theories. One of the most
interesting predictions of these theories, as well as some string theories, is
the subluminal speed of propagating gravitational waves. Multi-messenger
astronomy provides a unique opportunity to put limits on the difference (either
positive or negative) between the propagation speed of electromagnetic and
gravitational waves from these sources. This paper considers limits from
multi-messenger cases across the planned measurable spectrum: first, the limits
from isolated pulsars based on the current best limits from LIGO on
gravitational wave emission, second, the limits from ultra-compact binaries
that will be visible to a low-frequency space-based gravitational wave
observatory like LISA, and third, limits from super massive black hole binaries
using pulsar timing arrays. The required phase comparison between the
electromagnetic signal and the gravitational wave signal is derived and,
assuming a null result in that comparison, the current bounds on emission are
used to place limits on alternative theories that exhibit propagation delays.
Observations of the pulsars in the most sensitive range of LIGO could put an
upper limit on the graviton mass as low as $10^{-38}\frac{eV}{c^{2}}$ and an
upper limit on the fractional difference between the gravitational wave and
electromagnetic wave speeds as low as $10^{-9}$. This paper shows results from
the initial LIGO limit catalog of known pulsars. The bounds are stronger for
binaries. A LISA-like mission bounds $m_{g}<10^{-40}\frac{eV}{c^{2}}$ and
$\delta<10^{-12}$. A PTA source gives even better bounds of
$m_{g}<10^{-45}\frac{eV}{c^{2}}$ and $\delta<10^{-14}$.
|
[
{
"created": "Wed, 13 Nov 2013 14:58:13 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Nov 2014 05:10:31 GMT",
"version": "v2"
}
] |
2014-11-14
|
[
[
"Hazboun",
"Jeffrey S.",
""
],
[
"Marcano",
"Manuel Pichardo",
""
],
[
"Larson",
"Shane L.",
""
]
] |
The advent of gravitational wave astronomy provides new proving grounds for testing theories of gravity. Recent work has reinvigorated the study of bimetric theories of gravity and massive gravity theories. One of the most interesting predictions of these theories, as well as some string theories, is the subluminal speed of propagating gravitational waves. Multi-messenger astronomy provides a unique opportunity to put limits on the difference (either positive or negative) between the propagation speed of electromagnetic and gravitational waves from these sources. This paper considers limits from multi-messenger cases across the planned measurable spectrum: first, the limits from isolated pulsars based on the current best limits from LIGO on gravitational wave emission, second, the limits from ultra-compact binaries that will be visible to a low-frequency space-based gravitational wave observatory like LISA, and third, limits from super massive black hole binaries using pulsar timing arrays. The required phase comparison between the electromagnetic signal and the gravitational wave signal is derived and, assuming a null result in that comparison, the current bounds on emission are used to place limits on alternative theories that exhibit propagation delays. Observations of the pulsars in the most sensitive range of LIGO could put an upper limit on the graviton mass as low as $10^{-38}\frac{eV}{c^{2}}$ and an upper limit on the fractional difference between the gravitational wave and electromagnetic wave speeds as low as $10^{-9}$. This paper shows results from the initial LIGO limit catalog of known pulsars. The bounds are stronger for binaries. A LISA-like mission bounds $m_{g}<10^{-40}\frac{eV}{c^{2}}$ and $\delta<10^{-12}$. A PTA source gives even better bounds of $m_{g}<10^{-45}\frac{eV}{c^{2}}$ and $\delta<10^{-14}$.
|
2204.01972
|
Tousif Islam
|
Tousif Islam, Scott E. Field, Scott A. Hughes, Gaurav Khanna, Vijay
Varma, Matthew Giesler, Mark A. Scheel, Lawrence E. Kidder and Harald P.
Pfeiffer
|
Surrogate model for gravitational wave signals from non-spinning,
comparable- to large-mass-ratio black hole binaries built on black hole
perturbation theory waveforms calibrated to numerical relativity
|
20 pages, 15 figures
| null |
10.1103/PhysRevD.106.104025
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a reduced-order surrogate model of gravitational waveforms from
non-spinning binary black hole systems with comparable to large mass-ratio
configurations. This surrogate model, \texttt{BHPTNRSur1dq1e4}, is trained on
waveform data generated by point-particle black hole perturbation theory
(ppBHPT) with mass ratios varying from 2.5 to 10,000. \texttt{BHPTNRSur1dq1e4}
extends an earlier waveform model, \texttt{EMRISur1dq1e4}, by using an updated
transition-to-plunge model, covering longer durations up to 30,500 $m_1$ (where
$m_1$ is the mass of the primary black hole), includes several more spherical
harmonic modes up to $\ell=10$, and calibrates subdominant modes to numerical
relativity (NR) data. In the comparable mass-ratio regime, including mass
ratios as low as $2.5$, the gravitational waveforms generated through ppBHPT
agree surprisingly well with those from NR after this simple calibration step.
We also compare our model to recent SXS and RIT NR simulations at mass ratios
ranging from $15$ to $32$, and find the dominant quadrupolar modes agree to
better than $\approx 10^{-3}$. We expect our model to be useful to study
intermediate-mass-ratio binary systems in current and future gravitational-wave
detectors.
|
[
{
"created": "Tue, 5 Apr 2022 03:55:25 GMT",
"version": "v1"
}
] |
2022-11-23
|
[
[
"Islam",
"Tousif",
""
],
[
"Field",
"Scott E.",
""
],
[
"Hughes",
"Scott A.",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Varma",
"Vijay",
""
],
[
"Giesler",
"Matthew",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
]
] |
We present a reduced-order surrogate model of gravitational waveforms from non-spinning binary black hole systems with comparable to large mass-ratio configurations. This surrogate model, \texttt{BHPTNRSur1dq1e4}, is trained on waveform data generated by point-particle black hole perturbation theory (ppBHPT) with mass ratios varying from 2.5 to 10,000. \texttt{BHPTNRSur1dq1e4} extends an earlier waveform model, \texttt{EMRISur1dq1e4}, by using an updated transition-to-plunge model, covering longer durations up to 30,500 $m_1$ (where $m_1$ is the mass of the primary black hole), includes several more spherical harmonic modes up to $\ell=10$, and calibrates subdominant modes to numerical relativity (NR) data. In the comparable mass-ratio regime, including mass ratios as low as $2.5$, the gravitational waveforms generated through ppBHPT agree surprisingly well with those from NR after this simple calibration step. We also compare our model to recent SXS and RIT NR simulations at mass ratios ranging from $15$ to $32$, and find the dominant quadrupolar modes agree to better than $\approx 10^{-3}$. We expect our model to be useful to study intermediate-mass-ratio binary systems in current and future gravitational-wave detectors.
|
2111.10877
|
Ruslan Muharlyamov
|
Ruslan K. Muharlyamov and Tatiana N. Pankratyeva
|
Reconstruction in the Horndeski theory within the scope of the Bianchi I
cosmology
| null |
Modern Physics Letters A, 2250108 (2022)
|
10.1142/S0217732322501085
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
In the previous article Eur. Phys. J. Plus 136, 590 (2021) (arXiv:
2110.15396) we have proposed a reconstruction method for the kinetic gravity
braiding theory in the framework of the flat Friedman-Robertson-Walker
spacetime. Here we develop this method in the Bianchi I spacetime model for a
subclass of the Horndeski theory: $G_5 \sim \phi $, $G_2(X)\neq0$,
$G_3(X)\neq0$. The Hubble parameter $H(t)$ and the canonical kinetic term
$X(t)$ are set a priori. The choice of the function $X(t)$ determines the
anisotropic properties of the Universe. This makes it possible to provide
believable anisotropy. The presented method allows for a realistic model of the
Universe to simply reconstruct some scalar field theory. Reconstruction example
is given for anisotropic model of a post-inflationary transition to the
radiation-dominated phase. The model is investigated for the absence ghosts and
Laplacian instabilities.
|
[
{
"created": "Sun, 21 Nov 2021 18:52:55 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Nov 2021 16:38:55 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Nov 2021 06:50:13 GMT",
"version": "v3"
},
{
"created": "Tue, 1 Feb 2022 15:15:06 GMT",
"version": "v4"
}
] |
2022-07-05
|
[
[
"Muharlyamov",
"Ruslan K.",
""
],
[
"Pankratyeva",
"Tatiana N.",
""
]
] |
In the previous article Eur. Phys. J. Plus 136, 590 (2021) (arXiv: 2110.15396) we have proposed a reconstruction method for the kinetic gravity braiding theory in the framework of the flat Friedman-Robertson-Walker spacetime. Here we develop this method in the Bianchi I spacetime model for a subclass of the Horndeski theory: $G_5 \sim \phi $, $G_2(X)\neq0$, $G_3(X)\neq0$. The Hubble parameter $H(t)$ and the canonical kinetic term $X(t)$ are set a priori. The choice of the function $X(t)$ determines the anisotropic properties of the Universe. This makes it possible to provide believable anisotropy. The presented method allows for a realistic model of the Universe to simply reconstruct some scalar field theory. Reconstruction example is given for anisotropic model of a post-inflationary transition to the radiation-dominated phase. The model is investigated for the absence ghosts and Laplacian instabilities.
|
gr-qc/0311005
|
Jose M. M. Senovilla
|
Jos\'e M. M. Senovilla
|
Novel results on trapped surfaces
|
8 pages, no figures. Contribution to the conference "Mathematics of
Gravitation II", Warsaw, September 1-9, 2003
|
https://www.impan.pl/BC/Arch/2003/Gravitation/ConfProc/ (A
Kr\'olak and K Borkowski eds, 2003)
| null | null |
gr-qc
| null |
A unifying definition of trapped submanifold for arbitrary codimension by
means of its mean curvature vector is presented. Then, the interplay between
(generalized) symmetries and trapped submanifolds is studied, proving in
particular that (i) stationary spacetimes cannot contain closed trapped nor
marginally trapped submanifolds S of any codimension; (ii) S can be within the
subset where there is a null Killing vector only if it is marginally trapped
with mean curvature vector parallel to the null Killing; (iii) any submanifold
orthogonal to a timelike or null Killing vector has a mean curvature vector
orthogonal to it. All results are purely geometric, hold in arbitrary
dimension, and can be appropriately generalized to many non-Killing vector
fields, such as conformal Killing vectors and the like. A simple criterion to
ascertain the trapping or not of a family of codimension-2 submanifolds is
given. A path allowing to generalize the singularity theorems is conjectured as
feasible and discussed.
|
[
{
"created": "Mon, 3 Nov 2003 12:37:51 GMT",
"version": "v1"
}
] |
2019-06-25
|
[
[
"Senovilla",
"José M. M.",
""
]
] |
A unifying definition of trapped submanifold for arbitrary codimension by means of its mean curvature vector is presented. Then, the interplay between (generalized) symmetries and trapped submanifolds is studied, proving in particular that (i) stationary spacetimes cannot contain closed trapped nor marginally trapped submanifolds S of any codimension; (ii) S can be within the subset where there is a null Killing vector only if it is marginally trapped with mean curvature vector parallel to the null Killing; (iii) any submanifold orthogonal to a timelike or null Killing vector has a mean curvature vector orthogonal to it. All results are purely geometric, hold in arbitrary dimension, and can be appropriately generalized to many non-Killing vector fields, such as conformal Killing vectors and the like. A simple criterion to ascertain the trapping or not of a family of codimension-2 submanifolds is given. A path allowing to generalize the singularity theorems is conjectured as feasible and discussed.
|
1903.00223
|
Marcus Werner
|
Gary W. Gibbons, Marcus C. Werner
|
The gravitational magnetoelectric effect
|
13 pages
| null | null |
YITP-19-13
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Electromagnetism in spacetime can be treated in terms of an analogue linear
dielectric medium. In this paper, we discuss the gravitational analogue of the
linear magnetoelectric effect, which can be found in multiferroic materials.
While this is known to occur for metrics with non-zero mixed components, we
show how it depends on the choice of spatial formalism for the electromagnetic
fields, including in differences in tensor weight, and also on the choice of
coordinate chart. This is illustrated for Langevin-Minkowski, four charts of
Schwarzschild spacetime, and two charts of pp gravitational waves.
|
[
{
"created": "Fri, 1 Mar 2019 09:42:26 GMT",
"version": "v1"
}
] |
2019-03-04
|
[
[
"Gibbons",
"Gary W.",
""
],
[
"Werner",
"Marcus C.",
""
]
] |
Electromagnetism in spacetime can be treated in terms of an analogue linear dielectric medium. In this paper, we discuss the gravitational analogue of the linear magnetoelectric effect, which can be found in multiferroic materials. While this is known to occur for metrics with non-zero mixed components, we show how it depends on the choice of spatial formalism for the electromagnetic fields, including in differences in tensor weight, and also on the choice of coordinate chart. This is illustrated for Langevin-Minkowski, four charts of Schwarzschild spacetime, and two charts of pp gravitational waves.
|
1503.04402
|
Vladimir Dzhunushaliev
|
Vladimir Dzhunushaliev and Vladimir Folomeev
|
Modeling a nonperturbative spinor vacuum interacting with a strong
gravitational wave
|
9 pages, 2 figures
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the propagation of strong gravitational waves interacting with a
nonperturbative vacuum of spinor fields. To described the latter, we suggest an
approximate model. The corresponding Einstein equation has the form of the
Schr\"odinger equation. Its gravitational-wave solution is analogous to the
solution of the Schr\"odinger equation for an electron moving in a periodic
potential. The general solution for the periodic gravitational waves is found.
The analog of the Kronig-Penney model for gravitational waves is considered. It
is shown that the suggested gravitational-wave model permits the existence of
weak electric charge and current densities concomitant with the gravitational
wave. Based on this observation, a possible experimental verification of the
model is suggested.
|
[
{
"created": "Sun, 15 Mar 2015 09:14:43 GMT",
"version": "v1"
}
] |
2015-03-17
|
[
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
]
] |
We consider the propagation of strong gravitational waves interacting with a nonperturbative vacuum of spinor fields. To described the latter, we suggest an approximate model. The corresponding Einstein equation has the form of the Schr\"odinger equation. Its gravitational-wave solution is analogous to the solution of the Schr\"odinger equation for an electron moving in a periodic potential. The general solution for the periodic gravitational waves is found. The analog of the Kronig-Penney model for gravitational waves is considered. It is shown that the suggested gravitational-wave model permits the existence of weak electric charge and current densities concomitant with the gravitational wave. Based on this observation, a possible experimental verification of the model is suggested.
|
1703.07510
|
Rashmi Uniyal
|
Rashmi Uniyal, Hemwati Nandan K. D. Purohit
|
Null Geodesics and Observables around Kerr-Sen Black Hole
| null |
Class.Quant.Grav. 35 (2018) no.2, 025003
|
10.1088/1361-6382/aa9ad9
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate the geodesic motion in the background of Kerr-Sen Black Hole
arising in the heterotic string theory. The nature of effective potential is
discussed in radial as well as latitudinal direction. A special class of
spherical photon orbits is obtained along with the expression for the turning
point for radial photons. Dependence of photon motion within this class of
solution is discussed explicitly in view of the different Black Hole
parameters. We have discussed the allowed regions for geodesic motion of
massless test particles around Kerr- Sen Black Hole in more generalised way by
including non-equatorial motion of the photons into the account. The conditions
for different types of possible orbits are discussed with specific parameter
values along with the corresponding orbit structure. No terminating orbits are
possible for photons due to non-zero Black Hole charge. Observables on the
angular plane (viz. bending of light and perihelion precession for massive test
particles) are analysed as special cases. We have also calculated the rotation
and mass parameters for Kerr-Sen Black Hole in terms of the red/blue shifts of
the photons in circular and equatorial orbits emitted by the massive test
particles which represent stars or other probable sources of photons.
|
[
{
"created": "Wed, 22 Mar 2017 04:19:20 GMT",
"version": "v1"
}
] |
2018-01-30
|
[
[
"Uniyal",
"Rashmi",
""
],
[
"Purohit",
"Hemwati Nandan K. D.",
""
]
] |
We investigate the geodesic motion in the background of Kerr-Sen Black Hole arising in the heterotic string theory. The nature of effective potential is discussed in radial as well as latitudinal direction. A special class of spherical photon orbits is obtained along with the expression for the turning point for radial photons. Dependence of photon motion within this class of solution is discussed explicitly in view of the different Black Hole parameters. We have discussed the allowed regions for geodesic motion of massless test particles around Kerr- Sen Black Hole in more generalised way by including non-equatorial motion of the photons into the account. The conditions for different types of possible orbits are discussed with specific parameter values along with the corresponding orbit structure. No terminating orbits are possible for photons due to non-zero Black Hole charge. Observables on the angular plane (viz. bending of light and perihelion precession for massive test particles) are analysed as special cases. We have also calculated the rotation and mass parameters for Kerr-Sen Black Hole in terms of the red/blue shifts of the photons in circular and equatorial orbits emitted by the massive test particles which represent stars or other probable sources of photons.
|
1401.3789
|
Tim-Torben Paetz
|
Piotr T. Chru\'sciel, Tim-Torben Paetz
|
The mass of light-cones
|
11 pages, short section added where the Bondi mass of space-times
containing white hole regions is considered, this version corresponds to the
one published in CQG
|
Class. Quantum Grav. 31 (2014) 102001
|
10.1088/0264-9381/31/10/102001
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We give an elementary proof of positivity of total gravitational energy in
space-times containing complete smooth light-cones.
|
[
{
"created": "Wed, 15 Jan 2014 23:28:51 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jun 2014 16:02:54 GMT",
"version": "v2"
}
] |
2015-06-18
|
[
[
"Chruściel",
"Piotr T.",
""
],
[
"Paetz",
"Tim-Torben",
""
]
] |
We give an elementary proof of positivity of total gravitational energy in space-times containing complete smooth light-cones.
|
1109.5023
|
Marcin Kisielowski M.Sc.
|
Wojciech Kaminski, Marcin Kisielowski, Jerzy Lewandowski
|
The kernel and the injectivity of the EPRL map
|
17 pages, 3 figures
| null |
10.1088/0264-9381/29/8/085001
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we prove injectivity of the EPRL map for |\gamma|<1, filling
the gap of our previous paper.
|
[
{
"created": "Fri, 23 Sep 2011 09:21:41 GMT",
"version": "v1"
}
] |
2015-05-30
|
[
[
"Kaminski",
"Wojciech",
""
],
[
"Kisielowski",
"Marcin",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] |
In this paper we prove injectivity of the EPRL map for |\gamma|<1, filling the gap of our previous paper.
|
2103.00330
|
Branislav Cvetkovi\'c
|
Milutin Blagojevi\'c and Branislav Cvetkovi\'c
|
Thermodynamics of Riemannian Kerr-AdS black holes in Poincar\'e gauge
theory
|
LaTex, 10 pages
| null |
10.1016/j.physletb.2021.136242
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A Hamiltonian approach to black hole entropy is used to study Riemannian
Kerr-AdS solutions in the general, parity-violating Poincar\'e gauge theory.
Entropy and the asymptotic charges are entirely determined by the parity-even
sector of the theory, whereas the parity-odd contributions vanish. Entropy is
found to be proportional to the horizon area, and the first law of black hole
thermodynamics is confirmed.
|
[
{
"created": "Sat, 27 Feb 2021 21:31:52 GMT",
"version": "v1"
}
] |
2021-03-31
|
[
[
"Blagojević",
"Milutin",
""
],
[
"Cvetković",
"Branislav",
""
]
] |
A Hamiltonian approach to black hole entropy is used to study Riemannian Kerr-AdS solutions in the general, parity-violating Poincar\'e gauge theory. Entropy and the asymptotic charges are entirely determined by the parity-even sector of the theory, whereas the parity-odd contributions vanish. Entropy is found to be proportional to the horizon area, and the first law of black hole thermodynamics is confirmed.
|
1407.1391
|
Luis J. Garay
|
Carlos Barcel\'o, Ra\'ul Carballo-Rubio, Luis J. Garay
|
Mutiny at the white-hole district
|
8 pages, 1 figure. Essay awarded a honorable mention in the 2014
Gravity Research Foundation essay competition
|
International Journal of Modern Physics D Vol. 23, No. 12 (2014)
1442022 (6 pages)
|
10.1142/S021827181442022X
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The white-hole sector of Kruskal's solution is almost never used in physical
applications. However, it might contain the solution to many of the problems
associated with gravitational collapse and evaporation. This essay tries to
draw attention to some bouncing geometries that make a democratic use of the
black- and white-hole sectors. We will argue that these types of behaviour
could be perfectly natural in some approaches to the next physical level beyond
classical general relativity.
|
[
{
"created": "Sat, 5 Jul 2014 11:16:06 GMT",
"version": "v1"
}
] |
2015-05-19
|
[
[
"Barceló",
"Carlos",
""
],
[
"Carballo-Rubio",
"Raúl",
""
],
[
"Garay",
"Luis J.",
""
]
] |
The white-hole sector of Kruskal's solution is almost never used in physical applications. However, it might contain the solution to many of the problems associated with gravitational collapse and evaporation. This essay tries to draw attention to some bouncing geometries that make a democratic use of the black- and white-hole sectors. We will argue that these types of behaviour could be perfectly natural in some approaches to the next physical level beyond classical general relativity.
|
1306.6582
|
Edward Wilson-Ewing
|
Edward Wilson-Ewing
|
Ekpyrotic loop quantum cosmology
|
11 pages, v2: Clarifications and references added
|
JCAP 1308:015,2013
|
10.1088/1475-7516/2013/08/015
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the ekpyrotic paradigm in the context of loop quantum cosmology.
In loop quantum cosmology the classical big-bang singularity is resolved due to
quantum gravity effects, and so the contracting ekpyrotic branch of the
universe and its later expanding phase are connected by a smooth bounce. Thus,
it is possible to explicitly determine the evolution of scalar perturbations,
from the contracting ekpyrotic phase through the bounce and to the post-bounce
expanding epoch. The possibilities of having either one or two scalar fields
have been suggested for the ekpyrotic universe, and both cases will be
considered here. In the case of a single scalar field, the constant mode of the
curvature perturbations after the bounce is found to have a blue spectrum. On
the other hand, for the two scalar field ekpyrotic model where scale-invariant
entropy perturbations source additional terms in the curvature perturbations,
the power spectrum in the post-bounce expanding cosmology is shown to be nearly
scale-invariant and so agrees with observations.
|
[
{
"created": "Thu, 27 Jun 2013 17:36:06 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jul 2013 16:27:19 GMT",
"version": "v2"
}
] |
2015-06-16
|
[
[
"Wilson-Ewing",
"Edward",
""
]
] |
We consider the ekpyrotic paradigm in the context of loop quantum cosmology. In loop quantum cosmology the classical big-bang singularity is resolved due to quantum gravity effects, and so the contracting ekpyrotic branch of the universe and its later expanding phase are connected by a smooth bounce. Thus, it is possible to explicitly determine the evolution of scalar perturbations, from the contracting ekpyrotic phase through the bounce and to the post-bounce expanding epoch. The possibilities of having either one or two scalar fields have been suggested for the ekpyrotic universe, and both cases will be considered here. In the case of a single scalar field, the constant mode of the curvature perturbations after the bounce is found to have a blue spectrum. On the other hand, for the two scalar field ekpyrotic model where scale-invariant entropy perturbations source additional terms in the curvature perturbations, the power spectrum in the post-bounce expanding cosmology is shown to be nearly scale-invariant and so agrees with observations.
|
0904.3686
|
Salvatore Capozziello
|
S. Capozziello and S. Vignolo
|
The Cauchy problem for metric-affine f(R)-gravity in presence of
perfect-fluid matter
|
8 pages
|
Class.Quant.Grav.26:175013,2009
|
10.1088/0264-9381/26/17/175013
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Cauchy problem for metric-affine f(R)-gravity `a la Palatini and with
torsion, in presence of perfect fluid matter acting as source, is discussed
following the well-known Bruhat prescriptions for General Relativity. The
problem results well-formulated and well-posed when the perfect-fluid form of
the stress-energy tensor is preserved under conformal transformations. The key
role of conservation laws in Jordan and in Einstein frame is also discussed.
|
[
{
"created": "Thu, 23 Apr 2009 13:13:23 GMT",
"version": "v1"
}
] |
2009-08-24
|
[
[
"Capozziello",
"S.",
""
],
[
"Vignolo",
"S.",
""
]
] |
The Cauchy problem for metric-affine f(R)-gravity `a la Palatini and with torsion, in presence of perfect fluid matter acting as source, is discussed following the well-known Bruhat prescriptions for General Relativity. The problem results well-formulated and well-posed when the perfect-fluid form of the stress-energy tensor is preserved under conformal transformations. The key role of conservation laws in Jordan and in Einstein frame is also discussed.
|
1102.1682
|
Babak Vakili
|
Babak Vakili
|
Quantization of the Schwarzschild black hole: a Noether symmetry
approach
|
11 pages, no figures, revised version
|
Int. J. Theor. Phys. 51 (2012) 133
|
10.1007/s10773-011-0887-7
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the canonical formalism of a spherically symmetric space-time. In
the context of the 3+1 decomposition with respect to the radial coordinate $r$,
we set up an effective Lagrangian in which a couple of metric functions play
the role of independent variables. We show that the resulting $r$-Hamiltonian
yields the correct classical solutions which can be identified with the
Schwarzschild black hole. The Noether symmetry of model is then investigated by
utilizing the behavior of the corresponding Lagrangian under the infinitesimal
generators of the desired symmetry. According to the Noether symmetry approach,
we also quantize the model and show that the existence of a Noether symmetry
yields a general solution to the Wheeler-DeWitt equation where exhibits a good
correlation with the classical regime. We use the resulting wave function in
order to (qualitative) investigate the possibility of the avoidance of
classical singularities.
|
[
{
"created": "Tue, 8 Feb 2011 18:43:39 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jul 2011 14:58:02 GMT",
"version": "v2"
}
] |
2011-12-30
|
[
[
"Vakili",
"Babak",
""
]
] |
We study the canonical formalism of a spherically symmetric space-time. In the context of the 3+1 decomposition with respect to the radial coordinate $r$, we set up an effective Lagrangian in which a couple of metric functions play the role of independent variables. We show that the resulting $r$-Hamiltonian yields the correct classical solutions which can be identified with the Schwarzschild black hole. The Noether symmetry of model is then investigated by utilizing the behavior of the corresponding Lagrangian under the infinitesimal generators of the desired symmetry. According to the Noether symmetry approach, we also quantize the model and show that the existence of a Noether symmetry yields a general solution to the Wheeler-DeWitt equation where exhibits a good correlation with the classical regime. We use the resulting wave function in order to (qualitative) investigate the possibility of the avoidance of classical singularities.
|
2012.13193
|
Buddhadeb Ghosh
|
Arunoday Sarkar, Chitrak Sarkar and Buddhadeb Ghosh
|
Mode analysis of cosmological perturbations with the $E$-model
$\alpha$-attractor inflaton potentials
|
12 figures, 14 pages
| null | null | null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
We have carried out detailed $k$-mode analysis of single-inflaton slow-roll
inflationary perturbations including quantum fluctuations by setting up
non-linear coupled differential equations of inflaton field ($\phi$), its
perturbation ($\delta\phi$) and the metric perturbation (the Bardeen potential,
$\Phi_B$), and calculated the number of e-folds ($N$), scalar spectral index
($n_s$), tensor spectral index ($n_h$), scalar power spectrum ($\Delta_s$),
tensor power spectrum ($\Delta_h$), tensor-to-scalar ratio ($r$) and the Hubble
parameter ($H$) for different $k$ values at the horizon crossing. In these
calculations we have employed the $E$-model $\alpha$-attractor potentials which
are found to display slow-roll behaviour. The values of $n_s$ and $r$ obtained
by us are consistent with those given by the well-known universal
$\alpha$-attractor formulae. We got $n_s = 0.956908$ and $r= 0.005571 $ at $k =
10^6$ Planck unit for the value of the potential parameter $n = 1$. These can
be compared with the Planck-2018 data viz., $n_s = 0.9649\pm 0.0042$ at $68\%$
CL, $r<0.064$ at $95\%$ CL and ACT-2020 data viz., $n_s = 0.9691\pm 0.0041$ at
$68\%$ CL.
|
[
{
"created": "Thu, 24 Dec 2020 10:46:14 GMT",
"version": "v1"
}
] |
2020-12-25
|
[
[
"Sarkar",
"Arunoday",
""
],
[
"Sarkar",
"Chitrak",
""
],
[
"Ghosh",
"Buddhadeb",
""
]
] |
We have carried out detailed $k$-mode analysis of single-inflaton slow-roll inflationary perturbations including quantum fluctuations by setting up non-linear coupled differential equations of inflaton field ($\phi$), its perturbation ($\delta\phi$) and the metric perturbation (the Bardeen potential, $\Phi_B$), and calculated the number of e-folds ($N$), scalar spectral index ($n_s$), tensor spectral index ($n_h$), scalar power spectrum ($\Delta_s$), tensor power spectrum ($\Delta_h$), tensor-to-scalar ratio ($r$) and the Hubble parameter ($H$) for different $k$ values at the horizon crossing. In these calculations we have employed the $E$-model $\alpha$-attractor potentials which are found to display slow-roll behaviour. The values of $n_s$ and $r$ obtained by us are consistent with those given by the well-known universal $\alpha$-attractor formulae. We got $n_s = 0.956908$ and $r= 0.005571 $ at $k = 10^6$ Planck unit for the value of the potential parameter $n = 1$. These can be compared with the Planck-2018 data viz., $n_s = 0.9649\pm 0.0042$ at $68\%$ CL, $r<0.064$ at $95\%$ CL and ACT-2020 data viz., $n_s = 0.9691\pm 0.0041$ at $68\%$ CL.
|
2305.15674
|
Zheng-Wen Long
|
Meng-Yao Zhang, Hao Chen, Hassan Hassanabadi, Zheng-Wen Long, and Hui
Yang
|
Topology of nonlinearly charged black hole chemistry via massive gravity
|
16 pages,22 figures
|
European Physical Journal C (2023)
|
10.1140/epjc/s10052-023-11933-w
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The classification of critical points of charged topological black holes
(TBHs) in anti-de Sitter spacetime (AdS) under the Power Maxwell Invariant
(PMI)-massive gravity is accomplished within the framework of black hole
chemistry (BHC). Considering the grand canonical ensemble (GCE), we show that
$d=4$ black hole have only one topological class, whereas $d\ge 5$ black holes
belong to two different topology classes. Furthermore, the conventional
critical point characterized by negative topological charge coincides with the
maximum extreme point of temperature; and the novel critical point featuring
opposite topological charge corresponds to the minimum extreme point of
temperature. With increasing pressure, new phases emerge at the novel critical
point while disappear from the conventional one. Moreover, a atypical van der
Waals (vdW) behavior is found in $d\ge 6$ dimensions, and the anomaly
disappears at the traditional critical point. In the limit of nonlinearity
parameter $s\to1$, different topology classes are only obtained in the GCE and
they may not exist within the canonical ensemble. With the absence of electric
potential $\Phi$, the neutral TBHs share the same topological classification
results as the charged TBHs in the GCE of Maxwell-massive gravity.
|
[
{
"created": "Thu, 25 May 2023 02:57:15 GMT",
"version": "v1"
},
{
"created": "Wed, 31 May 2023 13:07:39 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Aug 2023 07:28:46 GMT",
"version": "v3"
},
{
"created": "Sun, 3 Sep 2023 01:50:28 GMT",
"version": "v4"
}
] |
2023-09-06
|
[
[
"Zhang",
"Meng-Yao",
""
],
[
"Chen",
"Hao",
""
],
[
"Hassanabadi",
"Hassan",
""
],
[
"Long",
"Zheng-Wen",
""
],
[
"Yang",
"Hui",
""
]
] |
The classification of critical points of charged topological black holes (TBHs) in anti-de Sitter spacetime (AdS) under the Power Maxwell Invariant (PMI)-massive gravity is accomplished within the framework of black hole chemistry (BHC). Considering the grand canonical ensemble (GCE), we show that $d=4$ black hole have only one topological class, whereas $d\ge 5$ black holes belong to two different topology classes. Furthermore, the conventional critical point characterized by negative topological charge coincides with the maximum extreme point of temperature; and the novel critical point featuring opposite topological charge corresponds to the minimum extreme point of temperature. With increasing pressure, new phases emerge at the novel critical point while disappear from the conventional one. Moreover, a atypical van der Waals (vdW) behavior is found in $d\ge 6$ dimensions, and the anomaly disappears at the traditional critical point. In the limit of nonlinearity parameter $s\to1$, different topology classes are only obtained in the GCE and they may not exist within the canonical ensemble. With the absence of electric potential $\Phi$, the neutral TBHs share the same topological classification results as the charged TBHs in the GCE of Maxwell-massive gravity.
|
2403.02362
|
Yu Hao
|
Hao Yu, Zi-Chao Lin, Jin Li
|
Holographic entropy bound and a special class of spatial systems in
cosmology
|
14 pages; comments are welcome
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The holographic entropy bound is discussed in cosmology. We try to define a
special class of spatial systems in cosmology, inside which the entropy of
matter satisfies the holographic entropy bound throughout the evolution of the
universe. We first take a universe composed of black holes as an example and
demonstrate that such a special class of systems does exist. Then, from the
perspective of entropy inside the co-moving volume, we find that there exists a
universal definition for this special class of spatial systems, i.e., the
definition is independent of the components of the universe. Finally, we prove
that in some specific cosmological models, multiple definitions can arise for
this special class of spatial systems, and we analyze the underlying reasons
for the emergence of these multiple definitions.
|
[
{
"created": "Mon, 4 Mar 2024 07:36:31 GMT",
"version": "v1"
}
] |
2024-03-06
|
[
[
"Yu",
"Hao",
""
],
[
"Lin",
"Zi-Chao",
""
],
[
"Li",
"Jin",
""
]
] |
The holographic entropy bound is discussed in cosmology. We try to define a special class of spatial systems in cosmology, inside which the entropy of matter satisfies the holographic entropy bound throughout the evolution of the universe. We first take a universe composed of black holes as an example and demonstrate that such a special class of systems does exist. Then, from the perspective of entropy inside the co-moving volume, we find that there exists a universal definition for this special class of spatial systems, i.e., the definition is independent of the components of the universe. Finally, we prove that in some specific cosmological models, multiple definitions can arise for this special class of spatial systems, and we analyze the underlying reasons for the emergence of these multiple definitions.
|
1605.02430
|
Dmitry Shogin
|
Dmitry Shogin and Per Amund Amundsen
|
On Radiative Fluids in Anisotropic Spacetimes
|
13 pages, no figures
| null | null | null |
gr-qc physics.flu-dyn
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We apply the second-order Israel-Stewart theory of relativistic fluid- and
thermodynamics to a physically realistic model of a radiative fluid in a simple
anisotropic cosmological background. We investigate the asymptotic future of
the resulting cosmological model and review the role of the dissipative
phenomena in the early Universe. We demonstrate that the transport properties
of the fluid alone, if described appropriately, do not explain the presently
observed accelerated expansion of the Universe. Also, we show that, in
constrast to the mathematical fluid models widely used before, the radiative
fluid does approach local thermal equilibrium at late times, although very
slowly, due to the cosmological expansion.
|
[
{
"created": "Mon, 9 May 2016 06:45:10 GMT",
"version": "v1"
}
] |
2016-05-10
|
[
[
"Shogin",
"Dmitry",
""
],
[
"Amundsen",
"Per Amund",
""
]
] |
We apply the second-order Israel-Stewart theory of relativistic fluid- and thermodynamics to a physically realistic model of a radiative fluid in a simple anisotropic cosmological background. We investigate the asymptotic future of the resulting cosmological model and review the role of the dissipative phenomena in the early Universe. We demonstrate that the transport properties of the fluid alone, if described appropriately, do not explain the presently observed accelerated expansion of the Universe. Also, we show that, in constrast to the mathematical fluid models widely used before, the radiative fluid does approach local thermal equilibrium at late times, although very slowly, due to the cosmological expansion.
|
1408.6754
|
Josep M. Pons
|
Josep M. Pons and Naresh Dadhich
|
On static black holes solutions in Einstein and Einstein-Gauss-Bonnet
gravity with topology ${\bf SO(n) \times SO(n)}$
|
22 pages, 2 figures. Relevant references added and changes made
accordingly
| null | null | null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study static black hole solutions in Einstein and Einstein-Gauss-Bonnet
gravity with product two-spheres topology, ${\bf SO(n) \times SO(n)}$, in
higher dimensions. There is an unusual new feature of Gauss-Bonnet black hole
that the avoidance of non-central naked singularity prescribes a mass range for
black hole in terms of $\Lambda>0$. For Einstein-Gauss-Bonnet black hole a
limited window of negative values for $\Lambda$ is also permitted. This
topology encompasses black string and brane as well as a generalized Nariai
metric. We also give new solutions with product two-spheres of constant
curvatures.
|
[
{
"created": "Thu, 28 Aug 2014 15:33:22 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Dec 2014 08:11:02 GMT",
"version": "v2"
}
] |
2014-12-22
|
[
[
"Pons",
"Josep M.",
""
],
[
"Dadhich",
"Naresh",
""
]
] |
We study static black hole solutions in Einstein and Einstein-Gauss-Bonnet gravity with product two-spheres topology, ${\bf SO(n) \times SO(n)}$, in higher dimensions. There is an unusual new feature of Gauss-Bonnet black hole that the avoidance of non-central naked singularity prescribes a mass range for black hole in terms of $\Lambda>0$. For Einstein-Gauss-Bonnet black hole a limited window of negative values for $\Lambda$ is also permitted. This topology encompasses black string and brane as well as a generalized Nariai metric. We also give new solutions with product two-spheres of constant curvatures.
|
gr-qc/9609017
|
Dario Nunez
|
Bahram Mashhoon, James C. McClune, Enrique Chavez and Hernando Quevedo
|
On the Energy of Rotating Gravitational Waves
|
Plain tex, 22 pages, 2 figures
| null | null | null |
gr-qc
| null |
A class of solutions of the gravitational field equations describing vacuum
spacetimes outside rotating cylindrical sources is presented. A subclass of
these solutions corresponds to the exterior gravitational fields of rotating
cylindrical systems that emit gravitational radiation. The properties of these
rotating gravitational wave spacetimes are investigated. In particular, we
discuss the energy density of these waves using the gravitational stress-energy
tensor.
|
[
{
"created": "Fri, 6 Sep 1996 21:32:42 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Mashhoon",
"Bahram",
""
],
[
"McClune",
"James C.",
""
],
[
"Chavez",
"Enrique",
""
],
[
"Quevedo",
"Hernando",
""
]
] |
A class of solutions of the gravitational field equations describing vacuum spacetimes outside rotating cylindrical sources is presented. A subclass of these solutions corresponds to the exterior gravitational fields of rotating cylindrical systems that emit gravitational radiation. The properties of these rotating gravitational wave spacetimes are investigated. In particular, we discuss the energy density of these waves using the gravitational stress-energy tensor.
|
gr-qc/0312105
|
Gianluca Cruciani
|
Donato Bini, Christian Cherubini, Gianluca Cruciani and Andrea Lunari
|
Neutrino current in a gravitational plane wave collision background
|
17 pages, 6 Postscript figures, accepted by International Journal of
Modern Physics D
|
Int.J.Mod.Phys. D12 (2003) 1983-2000
|
10.1142/S0218271803003876
| null |
gr-qc
| null |
The behaviour of a massless Dirac field on a general spacetime background
representing two colliding gravitational plane waves is discussed in the
Newman-Penrose formalism. The geometrical properties of the neutrino current
are analysed and explicit results are given for the special Ferrari-Ibanez
solution.
|
[
{
"created": "Tue, 23 Dec 2003 18:12:47 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Dec 2003 10:42:28 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"Bini",
"Donato",
""
],
[
"Cherubini",
"Christian",
""
],
[
"Cruciani",
"Gianluca",
""
],
[
"Lunari",
"Andrea",
""
]
] |
The behaviour of a massless Dirac field on a general spacetime background representing two colliding gravitational plane waves is discussed in the Newman-Penrose formalism. The geometrical properties of the neutrino current are analysed and explicit results are given for the special Ferrari-Ibanez solution.
|
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