id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9911090 | Norimasa Sugiura | Norimasa Sugiura, Ken-ichi Nakao and Tomohiro Harada | Distance-redshift relation in an isotropic inhomogeneous universe II:
Spherically symmetric dust-shell universe | 17 pages, 7 figures | Phys.Rev. D60 (1999) 103508 | 10.1103/PhysRevD.60.103508 | KUNS-1550 | gr-qc | null | The relation between the angular diameter distance and redshift in a
spherically symmetric dust-shell universe is studied. We have discovered that
the relation agrees with that of an appropriate Friedmann-Lemaitre (FL) model
if we set a ``homogeneous'' expansion law and a ``homogeneous'' averaged
density field. This will support the averaging hypothesis that a universe looks
like a FL model in spite of small-scale fluctuations of density field, if its
averaged density field is homogeneous on large scales. We also study the
connection of the proper mass of a shell with the mass of gravitationally bound
objects. Combining this with the results of the distance-redshift relation, we
discuss an impact of the local inhomogeneities on determination of the
cosmological parameters through the observation of the locally inhomogeneous
universe.
| [
{
"created": "Wed, 24 Nov 1999 06:22:12 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Sugiura",
"Norimasa",
""
],
[
"Nakao",
"Ken-ichi",
""
],
[
"Harada",
"Tomohiro",
""
]
] | The relation between the angular diameter distance and redshift in a spherically symmetric dust-shell universe is studied. We have discovered that the relation agrees with that of an appropriate Friedmann-Lemaitre (FL) model if we set a ``homogeneous'' expansion law and a ``homogeneous'' averaged density field. This will support the averaging hypothesis that a universe looks like a FL model in spite of small-scale fluctuations of density field, if its averaged density field is homogeneous on large scales. We also study the connection of the proper mass of a shell with the mass of gravitationally bound objects. Combining this with the results of the distance-redshift relation, we discuss an impact of the local inhomogeneities on determination of the cosmological parameters through the observation of the locally inhomogeneous universe. |
2009.01397 | Matt Visser | Joshua Baines (Victoria University of Wellington), Thomas Berry
(Victoria University of Wellington), Alex Simpson (Victoria University of
Wellington), and Matt Visser (Victoria University of Wellington) | Darboux diagonalization of the spatial 3-metric in Kerr spacetime | 18 pages | null | 10.1007/s10714-020-02765-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The astrophysical importance of the Kerr spacetime cannot be overstated. Of
the currently known exact solutions to the Einstein field equations, the Kerr
spacetime stands out in terms of its direct applicability to describing
astronomical black hole candidates. In counterpoint, purely mathematically,
there is an old classical result of differential geometry, due to Darboux, that
all 3-manifolds can have their metrics recast into diagonal form. In the case
of the Kerr spacetime the Boyer-Lindquist coordinates provide an explicit
example of a diagonal spatial 3-metric. Unfortunately, as we demonstrate
herein, Darboux diagonalization of the spatial 3-slices of the Kerr spacetime
is incompatible with simultaneously putting the Kerr metric into unit-lapse
form while retaining manifest axial symmetry. This no-go theorem is somewhat
reminiscent of the no-go theorem to the effect that the spatial 3-slices of the
Kerr spacetime cannot be chosen to be conformally flat.
| [
{
"created": "Thu, 3 Sep 2020 00:44:41 GMT",
"version": "v1"
}
] | 2021-01-13 | [
[
"Baines",
"Joshua",
"",
"Victoria University of Wellington"
],
[
"Berry",
"Thomas",
"",
"Victoria University of Wellington"
],
[
"Simpson",
"Alex",
"",
"Victoria University of\n Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | The astrophysical importance of the Kerr spacetime cannot be overstated. Of the currently known exact solutions to the Einstein field equations, the Kerr spacetime stands out in terms of its direct applicability to describing astronomical black hole candidates. In counterpoint, purely mathematically, there is an old classical result of differential geometry, due to Darboux, that all 3-manifolds can have their metrics recast into diagonal form. In the case of the Kerr spacetime the Boyer-Lindquist coordinates provide an explicit example of a diagonal spatial 3-metric. Unfortunately, as we demonstrate herein, Darboux diagonalization of the spatial 3-slices of the Kerr spacetime is incompatible with simultaneously putting the Kerr metric into unit-lapse form while retaining manifest axial symmetry. This no-go theorem is somewhat reminiscent of the no-go theorem to the effect that the spatial 3-slices of the Kerr spacetime cannot be chosen to be conformally flat. |
2401.00703 | Rajes Ghosh | Chanchal Sharma, Rajes Ghosh and Sudipta Sarkar | Exploring Ladder Symmetry and Love Numbers for Static and Rotating Black
Holes | Title changed, References added, Matches with the version to be
published in Physical Review D as a Letter | Phys.Rev.D 109 (2024) 4, L041505 | 10.1103/PhysRevD.109.L041505 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole solutions of general relativity exhibit a symmetry for the static
perturbations around these spacetimes, known as "ladder symmetry". This
symmetry proves useful in constructing a tower of solutions for perturbations
and elucidating their general properties. Specifically, the presence of this
symmetry leads to vanishing of the tidal love number associated with black
holes. In this work, we find the most general spherical symmetric and static
black hole spacetime that accommodates this ladder symmetry for scalar
perturbation. Furthermore, we extend our calculations beyond spherical symmetry
to find the class of stationary Konoplya-Rezzolla-Zhidenko black holes, which
also possess a similar ladder structure.
| [
{
"created": "Mon, 1 Jan 2024 09:08:22 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jan 2024 12:48:18 GMT",
"version": "v2"
},
{
"created": "Fri, 23 Feb 2024 13:12:48 GMT",
"version": "v3"
}
] | 2024-06-14 | [
[
"Sharma",
"Chanchal",
""
],
[
"Ghosh",
"Rajes",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | Black hole solutions of general relativity exhibit a symmetry for the static perturbations around these spacetimes, known as "ladder symmetry". This symmetry proves useful in constructing a tower of solutions for perturbations and elucidating their general properties. Specifically, the presence of this symmetry leads to vanishing of the tidal love number associated with black holes. In this work, we find the most general spherical symmetric and static black hole spacetime that accommodates this ladder symmetry for scalar perturbation. Furthermore, we extend our calculations beyond spherical symmetry to find the class of stationary Konoplya-Rezzolla-Zhidenko black holes, which also possess a similar ladder structure. |
1812.01798 | Carlos A. S. Almeida | R. Oliveira, D. M. Dantas, Victor Santos and C. A. S. Almeida | Quasi-normal modes of bumblebee wormhole | 14 pages, 10 figures | null | 10.1088/1361-6382/ab1873 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we calculate the quasi-normal frequencies from a bumblebee
traversable wormhole. The bumblebee wormhole model is based on the bumblebee
gravity, which exhibits a spontaneous Lorentz symmetry breaking. Supporting by
the Lorentz violation parameter $\lambda$, this model allows the fulfillment of
the flare-out and energy conditions, granted non-exotic matter to the wormhole.
We analyze the parameters of bumblebee wormhole in order to obtain a
Reege-Wheeler's equation with a bell-shaped potential. We obtain the
quasi-normal modes (QNMs) via the WKB approximation method for both scalar and
gravitational perturbations. All frequencies obtained are stable and the time
domain profiles have decreasing oscillation (damping) profiles for the
bumblebee wormhole.
| [
{
"created": "Wed, 5 Dec 2018 03:17:21 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Oliveira",
"R.",
""
],
[
"Dantas",
"D. M.",
""
],
[
"Santos",
"Victor",
""
],
[
"Almeida",
"C. A. S.",
""
]
] | In this work, we calculate the quasi-normal frequencies from a bumblebee traversable wormhole. The bumblebee wormhole model is based on the bumblebee gravity, which exhibits a spontaneous Lorentz symmetry breaking. Supporting by the Lorentz violation parameter $\lambda$, this model allows the fulfillment of the flare-out and energy conditions, granted non-exotic matter to the wormhole. We analyze the parameters of bumblebee wormhole in order to obtain a Reege-Wheeler's equation with a bell-shaped potential. We obtain the quasi-normal modes (QNMs) via the WKB approximation method for both scalar and gravitational perturbations. All frequencies obtained are stable and the time domain profiles have decreasing oscillation (damping) profiles for the bumblebee wormhole. |
2201.00141 | Muhammad Sharif | M. Sharif and Amal Majid | Isotropization and Complexity of Decoupled Solutions in Self-interacting
Brans-Dicke Gravity | 26 pages, 10 figures, to appear in EPJP | Eur. Phys. J. Plus 137(2022)114 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of this work is to formulate two new solutions by decoupling the
field equations via a minimal geometric deformation in the context of
self-interacting Brans-Dicke gravity. We introduce an extra source in the
anisotropic fluid distribution to generate new analogs of existing solutions.
The radial metric function is transformed to decouple the field equations into
two sets such that each array corresponds to one source only. The system
corresponding to the original matter distribution is specified by metric
functions of well-behaved solutions. On the other hand, the second set is
closed by imposing constraints on the additional matter source. For this
purpose, we have applied the isotropization condition as well as vanishing
complexity condition on the new source. Smooth matching of interior and
exterior spacetimes at the junction provides values of the unknown constants.
Interesting physical features of corresponding models are checked by employing
the mass and radius of the star PSR J1614-2230. It is concluded that both
extensions yield viable and stable models for certain values of the decoupling
parameter.
| [
{
"created": "Sat, 1 Jan 2022 07:40:24 GMT",
"version": "v1"
}
] | 2022-01-14 | [
[
"Sharif",
"M.",
""
],
[
"Majid",
"Amal",
""
]
] | The aim of this work is to formulate two new solutions by decoupling the field equations via a minimal geometric deformation in the context of self-interacting Brans-Dicke gravity. We introduce an extra source in the anisotropic fluid distribution to generate new analogs of existing solutions. The radial metric function is transformed to decouple the field equations into two sets such that each array corresponds to one source only. The system corresponding to the original matter distribution is specified by metric functions of well-behaved solutions. On the other hand, the second set is closed by imposing constraints on the additional matter source. For this purpose, we have applied the isotropization condition as well as vanishing complexity condition on the new source. Smooth matching of interior and exterior spacetimes at the junction provides values of the unknown constants. Interesting physical features of corresponding models are checked by employing the mass and radius of the star PSR J1614-2230. It is concluded that both extensions yield viable and stable models for certain values of the decoupling parameter. |
1103.4172 | Patrizia Vitale | Patrizia Vitale | A field-theoretic approach to Spin Foam models in Quantum Gravity | 16 pages, 3 figures. Proceedings of the Workshop on Non Commutative
Field Theory and Gravity, September 8-12, 2010 Corfu Greece | PoS CNCFG2010:032,2011 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an introduction to Group Field Theory models, motivating them on
the basis of their relationship with discretized BF models of gravity. We
derive the Feynmann rules and compute quantum corrections in the coherent
states basis.
| [
{
"created": "Mon, 21 Mar 2011 22:53:39 GMT",
"version": "v1"
}
] | 2011-05-18 | [
[
"Vitale",
"Patrizia",
""
]
] | We present an introduction to Group Field Theory models, motivating them on the basis of their relationship with discretized BF models of gravity. We derive the Feynmann rules and compute quantum corrections in the coherent states basis. |
2211.11017 | Vaibhav Kalvakota | Vaibhav Kalvakota | Weyl entropy behaviour and Naked Singularities | Based on presentation to be given at the 32nd meeting of the Indian
Association for General Relativity and Gravitation, IISER Kolkata | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In order to show that there exists a relation between the validity of the
Weyl entropy and the cosmic censorship hypothesis, we discuss the relation
between naked singularities and the gravitational entropy estimator using the
Weyl invariant. We look at the examples of Vaidya and Tolman-Bondi spacetimes
in asymptotically flat and de Sitter spacetime and look at Weyl entropy as a
possible indicator of the prohibition of naked singularities.
| [
{
"created": "Sun, 20 Nov 2022 16:37:03 GMT",
"version": "v1"
}
] | 2022-11-22 | [
[
"Kalvakota",
"Vaibhav",
""
]
] | In order to show that there exists a relation between the validity of the Weyl entropy and the cosmic censorship hypothesis, we discuss the relation between naked singularities and the gravitational entropy estimator using the Weyl invariant. We look at the examples of Vaidya and Tolman-Bondi spacetimes in asymptotically flat and de Sitter spacetime and look at Weyl entropy as a possible indicator of the prohibition of naked singularities. |
2209.05043 | Mohammad M. Sheikh-Jabbari | M.M. Sheikh-Jabbari | On Symplectic Form for Null Boundary Phase Space | 9 pages, 1 figure. Prepared in memory of Prof. T. Padmanabhan, to
appear in the Topical Collection (TC) of General Relativity and Gravitation
(GERG) | null | 10.1007/s10714-022-02997-2 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | To formulate gravity in spacetimes bounded by a null boundary, an arbitrary
hypothetical null surface, boundary degrees of freedom (d.o.f) should be added
to account for the d.o.f and dynamics in the spacetime regions excised behind
the null boundary. In the D dimensional example, boundary d.o.f are labelled by
D charges defined at D-2 dimensional spacelike slices at the null boundary.
While boundary modes can have their own boundary dynamics, their interaction
with the bulk modes is governed by flux-balance equations which may be
interpreted as a diffusion equation describing "dissolution" of bulk gravitons
into the boundary. From boundary viewpoint, boundary d.o.f obey local
thermodynamical equations at the boundary. Our description suggests a new
"semiclassical" quantization of the system in which boundary d.o.f are
quantized while bulk is classical. This semiclassical treatment may be relevant
to questions in black hole physics.
| [
{
"created": "Mon, 12 Sep 2022 06:48:49 GMT",
"version": "v1"
}
] | 2022-11-16 | [
[
"Sheikh-Jabbari",
"M. M.",
""
]
] | To formulate gravity in spacetimes bounded by a null boundary, an arbitrary hypothetical null surface, boundary degrees of freedom (d.o.f) should be added to account for the d.o.f and dynamics in the spacetime regions excised behind the null boundary. In the D dimensional example, boundary d.o.f are labelled by D charges defined at D-2 dimensional spacelike slices at the null boundary. While boundary modes can have their own boundary dynamics, their interaction with the bulk modes is governed by flux-balance equations which may be interpreted as a diffusion equation describing "dissolution" of bulk gravitons into the boundary. From boundary viewpoint, boundary d.o.f obey local thermodynamical equations at the boundary. Our description suggests a new "semiclassical" quantization of the system in which boundary d.o.f are quantized while bulk is classical. This semiclassical treatment may be relevant to questions in black hole physics. |
1210.5396 | Yungui Gong | Yungui Gong | Observational constraints on massive gravity | corrected an error in Fig. 2b | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ghost free massive gravity modified Friedmann equations at cosmic scale
and provided an explanation of cosmic acceleration without dark energy. We
analyzed the cosmological solutions of the massive gravity in detail and
confronted the cosmological model with current observational data. We found
that the model parameters $\alpha_3$ and $\alpha_4$ which are the coefficients
of the third and fourth order nonlinear interactions cannot be constrained by
current data at the background level. The mass of graviton is found to be the
order of current Hubble constant if $\alpha_3=\alpha_4=0$, and the mass of
graviton can be as small as possible in the most general case.
| [
{
"created": "Fri, 19 Oct 2012 12:26:16 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Nov 2021 11:06:40 GMT",
"version": "v2"
}
] | 2021-11-30 | [
[
"Gong",
"Yungui",
""
]
] | The ghost free massive gravity modified Friedmann equations at cosmic scale and provided an explanation of cosmic acceleration without dark energy. We analyzed the cosmological solutions of the massive gravity in detail and confronted the cosmological model with current observational data. We found that the model parameters $\alpha_3$ and $\alpha_4$ which are the coefficients of the third and fourth order nonlinear interactions cannot be constrained by current data at the background level. The mass of graviton is found to be the order of current Hubble constant if $\alpha_3=\alpha_4=0$, and the mass of graviton can be as small as possible in the most general case. |
2101.09956 | Tiberiu Harko | Jin-Zhao Yang, Shahab Shahidi, Tiberiu Harko, Shi-Dong Liang | Geodesic deviation, Raychaudhuri equation, Newtonian limit, and tidal
forces in Weyl-type $f(Q,T)$ gravity | 18 pages, no figures, accepted for publication in EPJC; minor
corrections; references added | null | 10.1140/epjc/s10052-021-08910-6 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the geodesic deviation equation, describing the relative
accelerations of nearby particles, and the Raychaudhuri equation, giving the
evolution of the kinematical quantities associated with deformations
(expansion, shear and rotation) in the Weyl type $f(Q,T)$ gravity, in which the
nonmetricity $Q$ is represented in the standard Weyl form, fully determined by
the Weyl vector, while $T$ represents the trace of the matter energy-momentum
tensor. The effects of the Weyl geometry and of the extra force induced by the
nonmetricity-matter coupling are explicitly taken into account. The Newtonian
limit of the theory is investigated, and the generalized Poisson equation,
containing correction terms coming from the Weyl geometry, and from the
geometry matter coupling, is derived. As a physical application of the geodesic
deviation equation the modifications of the tidal forces, due to the
nonmetricity-matter coupling, are obtained in the weak field approximation. The
tidal motion of test particles is directly influenced by the gradients of the
extra force, and of the Weyl vector. As a concrete astrophysical example we
obtain the expression of the Roche limit (the orbital distance at which a
satellite begins to be tidally torn apart by the body it orbits) in the Weyl
type $f(Q,T)$ gravity.
| [
{
"created": "Mon, 25 Jan 2021 08:54:34 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Jan 2021 16:36:53 GMT",
"version": "v2"
}
] | 2021-02-24 | [
[
"Yang",
"Jin-Zhao",
""
],
[
"Shahidi",
"Shahab",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Liang",
"Shi-Dong",
""
]
] | We consider the geodesic deviation equation, describing the relative accelerations of nearby particles, and the Raychaudhuri equation, giving the evolution of the kinematical quantities associated with deformations (expansion, shear and rotation) in the Weyl type $f(Q,T)$ gravity, in which the nonmetricity $Q$ is represented in the standard Weyl form, fully determined by the Weyl vector, while $T$ represents the trace of the matter energy-momentum tensor. The effects of the Weyl geometry and of the extra force induced by the nonmetricity-matter coupling are explicitly taken into account. The Newtonian limit of the theory is investigated, and the generalized Poisson equation, containing correction terms coming from the Weyl geometry, and from the geometry matter coupling, is derived. As a physical application of the geodesic deviation equation the modifications of the tidal forces, due to the nonmetricity-matter coupling, are obtained in the weak field approximation. The tidal motion of test particles is directly influenced by the gradients of the extra force, and of the Weyl vector. As a concrete astrophysical example we obtain the expression of the Roche limit (the orbital distance at which a satellite begins to be tidally torn apart by the body it orbits) in the Weyl type $f(Q,T)$ gravity. |
gr-qc/9904054 | Takeshi Chiba | Takeshi Chiba | Apparent Horizon Formation and Hoop Conjecture in Non-axisymmetric
Spaces | 18 pages, typos fixed, to be published in Phys.Rev.D | Phys.Rev.D60:044003,1999; Erratum-ibid.D60:089902,1999 | 10.1103/PhysRevD.60.044003 10.1103/PhysRevD.60.089902 | null | gr-qc | null | We investigate the validity of Thorne's hoop conjecture in non-axisymmetric
spacetimes by examining the formation of apparent horizons numerically. If
spaces have a discrete symmetry about one axis, we can specify the boundary
conditions to determine an apparent horizon even in non-axisymmetric spaces. We
implement, for the first time, the ``hoop finder'' in non-axisymmetric spaces
with a discrete symmetry. We construct asymptotically flat vacuum solutions at
a moment of time symmetry. Two cases are examined: black holes distributed on a
ring, and black holes on a spherical surface. It turns out that calculating
${\cal C}$ is reduced to solving an ordinary differential equation. We find
that even in non-axisymmetric spaces the existence or nonexistence of an
apparent horizon is consistent with the inequality: ${\cal C} \siml 4\pi M$.
| [
{
"created": "Wed, 21 Apr 1999 08:14:31 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Jul 1999 09:52:59 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Chiba",
"Takeshi",
""
]
] | We investigate the validity of Thorne's hoop conjecture in non-axisymmetric spacetimes by examining the formation of apparent horizons numerically. If spaces have a discrete symmetry about one axis, we can specify the boundary conditions to determine an apparent horizon even in non-axisymmetric spaces. We implement, for the first time, the ``hoop finder'' in non-axisymmetric spaces with a discrete symmetry. We construct asymptotically flat vacuum solutions at a moment of time symmetry. Two cases are examined: black holes distributed on a ring, and black holes on a spherical surface. It turns out that calculating ${\cal C}$ is reduced to solving an ordinary differential equation. We find that even in non-axisymmetric spaces the existence or nonexistence of an apparent horizon is consistent with the inequality: ${\cal C} \siml 4\pi M$. |
1707.03867 | Sergio Gimeno-Soler | Sergio Gimeno-Soler and Jos\'e A. Font | Magnetised Polish doughnuts revisited | 9 pages, 6 figures. Accepted for publication in Astronomy &
Astrophysics July 12, 2017 | A&A 607, A68 (2017) | 10.1051/0004-6361/201730935 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a procedure to build new sequences of magnetised, equilibrium tori
around Kerr black holes which combines two approaches previously considered in
the literature. For simplicity we assume that the test-fluid approximation
holds, and hence we neglect the self-gravity of the fluid. The models are built
assuming a particular form of the angular momentum distribution from which the
location and morphology of equipotential surfaces can be computed. This ansatz
includes, in particular, the constant angular momentum case originally employed
in the construction of thick tori - or Polish doughnuts - and it has already
been used to build equilibrium sequences of purely hydrodynamical models. We
discuss the properties of the new models and their dependence on the initial
parameters. These new sequences can be used as initial data for
magnetohydrodynamical evolutions in general relativity.
| [
{
"created": "Wed, 12 Jul 2017 18:58:35 GMT",
"version": "v1"
}
] | 2017-11-15 | [
[
"Gimeno-Soler",
"Sergio",
""
],
[
"Font",
"José A.",
""
]
] | We discuss a procedure to build new sequences of magnetised, equilibrium tori around Kerr black holes which combines two approaches previously considered in the literature. For simplicity we assume that the test-fluid approximation holds, and hence we neglect the self-gravity of the fluid. The models are built assuming a particular form of the angular momentum distribution from which the location and morphology of equipotential surfaces can be computed. This ansatz includes, in particular, the constant angular momentum case originally employed in the construction of thick tori - or Polish doughnuts - and it has already been used to build equilibrium sequences of purely hydrodynamical models. We discuss the properties of the new models and their dependence on the initial parameters. These new sequences can be used as initial data for magnetohydrodynamical evolutions in general relativity. |
gr-qc/0605070 | Sunil Maharaj | S. Hansraj and S. D. Maharaj | Charged analogue of Finch-Skea stars | 17 pages, To appear in Int. J. Mod. Phys. D | Int.J.Mod.Phys.D15:1311-1327,2006 | 10.1142/S0218271806008826 | null | gr-qc | null | We present solutions to the Einstein-Maxwell system of equations in
spherically symmetric gravitational fields for static interior spacetimes with
a specified form of the electric field intensity. The condition of pressure
isotropy yields three category of solutions. The first category is expressible
in terms of elementary functions and does not have an uncharged limit. The
second category is given in terms of Bessel functions of half-integer order.
These charged solutions satisfy a barotropic equation of state and contain
Finch-Skea uncharged stars. The third category is obtained in terms of modified
Bessel functions of half-integer order and does not have an uncharged limit.
The physical features of the charged analogue of the Finch-Skea stars are
studied in detail. In particular the condition of causality is satisfied and
the speed of sound does not exceed the speed of light. The physical analysis
indicates that this analogue is a realistic model for static charged
relativistic perfect fluid spheres.
| [
{
"created": "Thu, 11 May 2006 13:59:30 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Hansraj",
"S.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | We present solutions to the Einstein-Maxwell system of equations in spherically symmetric gravitational fields for static interior spacetimes with a specified form of the electric field intensity. The condition of pressure isotropy yields three category of solutions. The first category is expressible in terms of elementary functions and does not have an uncharged limit. The second category is given in terms of Bessel functions of half-integer order. These charged solutions satisfy a barotropic equation of state and contain Finch-Skea uncharged stars. The third category is obtained in terms of modified Bessel functions of half-integer order and does not have an uncharged limit. The physical features of the charged analogue of the Finch-Skea stars are studied in detail. In particular the condition of causality is satisfied and the speed of sound does not exceed the speed of light. The physical analysis indicates that this analogue is a realistic model for static charged relativistic perfect fluid spheres. |
gr-qc/0407072 | Irina Dymnikova | Irina Dymnikova | Regular electrically charged structures in Nonlinear Electrodynamics
coupled to General Relativity | two references added concerning effective photon space-time | Class.Quant.Grav.21:4417-4429,2004 | 10.1088/0264-9381/21/18/009 | null | gr-qc | null | We address the question of existence of regular spherically symmetric
electrically charged solutions in Nonlinear Electrodynamics coupled to General
Relativity. Stress-energy tensor of the electromagnetic field has the algebraic
structure $T_0^0=T_1^1$. In this case the Weak Energy Condition leads to the de
Sitter asymptotic at approaching a regular center. In de Sitter center of an
electrically charged NED structure, electric field, geometry and stress-energy
tensor are regular without Maxwell limit which is replaced by de Sitter limit:
energy density of a field is maximal and gives an effective cut-off on
self-energy density, produced by NED coupled to gravity and related to
cosmological constant $\Lambda$. Regular electric solutions satisfying WEC,
suffer from one cusp in the Lagrangian ${\cal L}(F)$, which creates the problem
in an effective geometry whose geodesics are world lines of NED photons. We
investigate propagation of photons and show that their world lines never
terminate which suggests absence of singularities in the effective geometry. To
illustrate these results we present the new exact analytic spherically
symmetric electric solution with the de Sitter center.
| [
{
"created": "Mon, 19 Jul 2004 11:21:36 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jul 2004 10:51:38 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Aug 2004 08:05:53 GMT",
"version": "v3"
}
] | 2011-07-19 | [
[
"Dymnikova",
"Irina",
""
]
] | We address the question of existence of regular spherically symmetric electrically charged solutions in Nonlinear Electrodynamics coupled to General Relativity. Stress-energy tensor of the electromagnetic field has the algebraic structure $T_0^0=T_1^1$. In this case the Weak Energy Condition leads to the de Sitter asymptotic at approaching a regular center. In de Sitter center of an electrically charged NED structure, electric field, geometry and stress-energy tensor are regular without Maxwell limit which is replaced by de Sitter limit: energy density of a field is maximal and gives an effective cut-off on self-energy density, produced by NED coupled to gravity and related to cosmological constant $\Lambda$. Regular electric solutions satisfying WEC, suffer from one cusp in the Lagrangian ${\cal L}(F)$, which creates the problem in an effective geometry whose geodesics are world lines of NED photons. We investigate propagation of photons and show that their world lines never terminate which suggests absence of singularities in the effective geometry. To illustrate these results we present the new exact analytic spherically symmetric electric solution with the de Sitter center. |
1012.0505 | Alfredo Sandoval-Villalbazo | D. Brun-Battistini and A. Sandoval-Villalbazo | Light Cone analysis of relativistic first-order in the gradients
hydrodynamics | 6 pages, no figures | AIP Conf. Proc. 1312 57 AIP Conference Proceedings 1312 AIP
Conference Proceedings 1312 AIP Conference Proceedings 1312 AIP Conference
Proceedings 1312 AIP Conference Proceedings 1312 AIP Conference proceedings,
1312, 57-63 (2010) | 10.1063/1.3533207 | null | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work applies a Rayleigh-Brillouin light spectrum analysis in order to
establish a causality test by means of a frequency cone. This technique allows
to identify forbidden and unforbidden regions in light scattering experiments
and establishes if a set of linearized transport equations admits causal
solutions. It is shown that, when studying a relativistic fluid with its
acoustic modes interacting with light, Eckart's formalism yields a non causal
behavior. In this case the solutions describing temperature, density and
pressure fluctuations are located outside the frequency cone. In contrast, the
set of equations that arises from modified Eckart's theory (based on
relativistic kinetic theory) yields solutions that lie within the cone, so that
they are causal.
| [
{
"created": "Thu, 2 Dec 2010 17:13:32 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Brun-Battistini",
"D.",
""
],
[
"Sandoval-Villalbazo",
"A.",
""
]
] | This work applies a Rayleigh-Brillouin light spectrum analysis in order to establish a causality test by means of a frequency cone. This technique allows to identify forbidden and unforbidden regions in light scattering experiments and establishes if a set of linearized transport equations admits causal solutions. It is shown that, when studying a relativistic fluid with its acoustic modes interacting with light, Eckart's formalism yields a non causal behavior. In this case the solutions describing temperature, density and pressure fluctuations are located outside the frequency cone. In contrast, the set of equations that arises from modified Eckart's theory (based on relativistic kinetic theory) yields solutions that lie within the cone, so that they are causal. |
gr-qc/0603072 | R. M. Kiehn | R. M. Kiehn | Thermodynamics and quantum cosmology -- Continuous topological evolution
of topologically coherent defects | 57 pages | null | null | null | gr-qc | null | As a point of departure it is suggested that Quantum Cosmology is a
topological concept independent from metrical constraints. Methods of
continuous topological evolution and topological thermodynamics are used to
construct a cosmological model of the present universe, using the techniques
based upon Cartan's theory of exterior differential systems. Thermodynamic
domains, which are either Open, Closed, Isolated, or in Equilibrium, can be put
into correspondence with topological systems of Pfaff topological dimension 4,
3, 2 and 1. If the environment of the universe is assumed to be a physical
vacuum of Pfaff topological dimension 4, then continuous but irreversible
topological evolution can cause the emergence of topologically coherent defect
structures of Pfaff topological dimension less than 4. As galaxies and stars
exchange radiation but not matter with the environment, they are emergent
topological defects of Pfaff topological dimension 3 which are far from
equilibrium. DeRham topological theory of period integrals over closed but not
exact exterior differential systems leads to the emergence of quantized,
deformable, but topologically coherent, singular macrostates at all scales. The
method leads to the conjecture that dark matter and energy is represented by
those thermodynamic topological defect structures of Pfaff dimension 2 or less.
| [
{
"created": "Fri, 17 Mar 2006 18:22:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kiehn",
"R. M.",
""
]
] | As a point of departure it is suggested that Quantum Cosmology is a topological concept independent from metrical constraints. Methods of continuous topological evolution and topological thermodynamics are used to construct a cosmological model of the present universe, using the techniques based upon Cartan's theory of exterior differential systems. Thermodynamic domains, which are either Open, Closed, Isolated, or in Equilibrium, can be put into correspondence with topological systems of Pfaff topological dimension 4, 3, 2 and 1. If the environment of the universe is assumed to be a physical vacuum of Pfaff topological dimension 4, then continuous but irreversible topological evolution can cause the emergence of topologically coherent defect structures of Pfaff topological dimension less than 4. As galaxies and stars exchange radiation but not matter with the environment, they are emergent topological defects of Pfaff topological dimension 3 which are far from equilibrium. DeRham topological theory of period integrals over closed but not exact exterior differential systems leads to the emergence of quantized, deformable, but topologically coherent, singular macrostates at all scales. The method leads to the conjecture that dark matter and energy is represented by those thermodynamic topological defect structures of Pfaff dimension 2 or less. |
1706.01173 | Yun Soo Myung | Yun Soo Myung | Renormalizability, vDVZ discontinuity and Newtonian singularity in
higher-derivative gravity | 15 pages, no figures,version to appear in PRD | Phys. Rev. D 96, 064026 (2017) | 10.1103/PhysRevD.96.064026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was proposed that if a higher-derivative gravity is renormalizable, it
implies necessarily a finite Newtonian potential at the origin, but the reverse
of this statement is not true. Here we show that the reverse is true when
taking into account the vDVZ discontinuity which states that the theory
obtained from massive one by taking zero mass limit is not equivalent to the
theory obtained in the zero mass case. The surviving degree of freedom in the
zero mass limit is an extra scalar which does not affect the light bending
angle, but affects the Newtonian potential. This asserts that in order to make
the singularity cancellation, the number of massive ghost and healthy tensors
matches with that of massive ghost and healthy scalars.
| [
{
"created": "Mon, 5 Jun 2017 01:18:02 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Sep 2017 03:16:26 GMT",
"version": "v2"
}
] | 2017-09-20 | [
[
"Myung",
"Yun Soo",
""
]
] | It was proposed that if a higher-derivative gravity is renormalizable, it implies necessarily a finite Newtonian potential at the origin, but the reverse of this statement is not true. Here we show that the reverse is true when taking into account the vDVZ discontinuity which states that the theory obtained from massive one by taking zero mass limit is not equivalent to the theory obtained in the zero mass case. The surviving degree of freedom in the zero mass limit is an extra scalar which does not affect the light bending angle, but affects the Newtonian potential. This asserts that in order to make the singularity cancellation, the number of massive ghost and healthy tensors matches with that of massive ghost and healthy scalars. |
gr-qc/0309065 | Jorge Pullin | Jorge Pullin | Matters of Gravity, the newsletter of the APS Topical Group on
Gravitation, Fall 2003 | 26 pages, LaTex, 2 figures, with html.sty and psfig.sty | null | null | MOG-22 | gr-qc | null | Contents:
Community news:
- We hear that... by Jorge Pullin
Research briefs:
- Update on a busy year for LIGO, by Stan Whitcomb
- First year results from WMAP, by Rachel Bean
- Short range searches for non-Newtonian gravity, by M. Varney and J. Long
Conference reports:
- Xth Brazilian school of cosmology and gravitation, by Mario Novello
- 6th East coast gravity meeting, by David Fiske
- 5th Edoardo Amaldi meeting, by Alain Brillet
- Pacific coast gravity meeting, by Charles Torre
- Astrophysics of gravitational wave sources, by Joan Centrella
- Gravitational interaction of compact objects, by M. Choptuik, E. Flanagan,
L. Lehner
- PriceFest, by John Whelan
- Gravitation: a decennial perspective, by Jorge Pullin
| [
{
"created": "Mon, 15 Sep 2003 18:52:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pullin",
"Jorge",
""
]
] | Contents: Community news: - We hear that... by Jorge Pullin Research briefs: - Update on a busy year for LIGO, by Stan Whitcomb - First year results from WMAP, by Rachel Bean - Short range searches for non-Newtonian gravity, by M. Varney and J. Long Conference reports: - Xth Brazilian school of cosmology and gravitation, by Mario Novello - 6th East coast gravity meeting, by David Fiske - 5th Edoardo Amaldi meeting, by Alain Brillet - Pacific coast gravity meeting, by Charles Torre - Astrophysics of gravitational wave sources, by Joan Centrella - Gravitational interaction of compact objects, by M. Choptuik, E. Flanagan, L. Lehner - PriceFest, by John Whelan - Gravitation: a decennial perspective, by Jorge Pullin |
1505.06215 | Ivan Arraut Dr. | Ivan Arraut | The dynamical origin of the graviton mass in the non-linear theory of
massive gravity | Published version, new section added | Universe 2019, 5(7), 166 | 10.3390/universe5070166 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare the standard Higgs mechanism corresponding to the scalar field,
with the dynamical origin of the graviton mass inside the scenario of the dRGT
theory of massive gravity. We demonstrate that the effective mass perceived
locally by different observers, depends on the way how they define the local
time with respect to the preferred notion of time defined by the St\"uckelberg
function $T_0(r,t)$.
| [
{
"created": "Sun, 24 May 2015 16:59:31 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jul 2015 14:22:08 GMT",
"version": "v2"
},
{
"created": "Tue, 31 May 2016 15:34:03 GMT",
"version": "v3"
},
{
"created": "Mon, 8 Jul 2019 00:56:38 GMT",
"version": "v4"
}
] | 2019-07-09 | [
[
"Arraut",
"Ivan",
""
]
] | We compare the standard Higgs mechanism corresponding to the scalar field, with the dynamical origin of the graviton mass inside the scenario of the dRGT theory of massive gravity. We demonstrate that the effective mass perceived locally by different observers, depends on the way how they define the local time with respect to the preferred notion of time defined by the St\"uckelberg function $T_0(r,t)$. |
gr-qc/0110008 | Hisaaki Shinkai | Hisa-aki Shinkai (RIKEN) and Gen Yoneda (Waseda U.) | Adjusted ADM systems and their expected stability properties: constraint
propagation analysis in Schwarzschild spacetime | 23 pages, RevTeX4, many figures. Revised version. Added subtitle,
reduced figures, rephrased introduction, and a native checked. :-) | Class.Quant.Grav.19:1027-1050,2002 | 10.1088/0264-9381/19/6/302 | null | gr-qc | null | In order to find a way to have a better formulation for numerical evolution
of the Einstein equations, we study the propagation equations of the
constraints based on the Arnowitt-Deser-Misner formulation. By adjusting
constraint terms in the evolution equations, we try to construct an
"asymptotically constrained system" which is expected to be robust against
violation of the constraints, and to enable a long-term stable and accurate
numerical simulation. We first provide useful expressions for analyzing
constraint propagation in a general spacetime, then apply it to Schwarzschild
spacetime. We search when and where the negative real or non-zero imaginary
eigenvalues of the homogenized constraint propagation matrix appear, and how
they depend on the choice of coordinate system and adjustments. Our analysis
includes the proposal of Detweiler (1987), which is still the best one
according to our conjecture but has a growing mode of error near the horizon.
Some examples are snapshots of a maximally sliced Schwarzschild black hole. The
predictions here may help the community to make further improvements.
| [
{
"created": "Mon, 1 Oct 2001 00:38:48 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jan 2002 02:02:40 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Shinkai",
"Hisa-aki",
"",
"RIKEN"
],
[
"Yoneda",
"Gen",
"",
"Waseda U."
]
] | In order to find a way to have a better formulation for numerical evolution of the Einstein equations, we study the propagation equations of the constraints based on the Arnowitt-Deser-Misner formulation. By adjusting constraint terms in the evolution equations, we try to construct an "asymptotically constrained system" which is expected to be robust against violation of the constraints, and to enable a long-term stable and accurate numerical simulation. We first provide useful expressions for analyzing constraint propagation in a general spacetime, then apply it to Schwarzschild spacetime. We search when and where the negative real or non-zero imaginary eigenvalues of the homogenized constraint propagation matrix appear, and how they depend on the choice of coordinate system and adjustments. Our analysis includes the proposal of Detweiler (1987), which is still the best one according to our conjecture but has a growing mode of error near the horizon. Some examples are snapshots of a maximally sliced Schwarzschild black hole. The predictions here may help the community to make further improvements. |
1207.5837 | Andr\'as L\'aszl\'o | Peter Csizmadia, Andras Laszlo, Istvan Racz | On the Use of Multipole Expansion in Time Evolution of Non-linear
Dynamical Systems and Some Surprises Related to Superradiance | 49 pages, 11 figures | Class. Quantum Grav. 30 (2013) 015010 | 10.1088/0264-9381/30/1/015010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new numerical method is introduced to study the problem of time evolution
of generic non-linear dynamical systems in four-dimensional spacetimes. It is
assumed that the time level surfaces are foliated by a one-parameter family of
codimension two compact surfaces with no boundary and which are conformal to a
Riemannian manifold C. The method is based on the use of a multipole expansion
determined uniquely by the induced metric structure on C. The approach is fully
spectral in the angular directions. The dynamics in the complementary 1+1
Lorentzian spacetime is followed by making use of a fourth order finite
differencing scheme with adaptive mesh refinement.
In checking the reliability of the introduced new method the evolution of a
massless scalar field on a fixed Kerr spacetime is investigated. In particular,
the angular distribution of the evolving field in to be superradiant scattering
is studied. The primary aim was to check the validity of some of the recent
arguments claiming that the Penrose process, or its field theoretical
correspondence---superradiance---does play crucial role in jet formation in
black hole spacetimes while matter accretes onto the central object. Our
findings appear to be on contrary to these claims as the angular dependence of
a to be superradiant scattering of a massless scalar field does not show any
preference of the axis of rotation. In addition, the process of superradiance,
in case of a massless scalar field, was also investigated. On contrary to the
general expectations no energy extraction from black hole was found even though
the incident wave packets was fine tuned to be maximally superradiant. Instead
of energy extraction the to be superradiant part of the incident wave packet
fails to reach the ergoregion rather it suffers a total reflection which
appears to be a new phenomenon.
| [
{
"created": "Tue, 24 Jul 2012 21:49:17 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Dec 2012 17:51:50 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Csizmadia",
"Peter",
""
],
[
"Laszlo",
"Andras",
""
],
[
"Racz",
"Istvan",
""
]
] | A new numerical method is introduced to study the problem of time evolution of generic non-linear dynamical systems in four-dimensional spacetimes. It is assumed that the time level surfaces are foliated by a one-parameter family of codimension two compact surfaces with no boundary and which are conformal to a Riemannian manifold C. The method is based on the use of a multipole expansion determined uniquely by the induced metric structure on C. The approach is fully spectral in the angular directions. The dynamics in the complementary 1+1 Lorentzian spacetime is followed by making use of a fourth order finite differencing scheme with adaptive mesh refinement. In checking the reliability of the introduced new method the evolution of a massless scalar field on a fixed Kerr spacetime is investigated. In particular, the angular distribution of the evolving field in to be superradiant scattering is studied. The primary aim was to check the validity of some of the recent arguments claiming that the Penrose process, or its field theoretical correspondence---superradiance---does play crucial role in jet formation in black hole spacetimes while matter accretes onto the central object. Our findings appear to be on contrary to these claims as the angular dependence of a to be superradiant scattering of a massless scalar field does not show any preference of the axis of rotation. In addition, the process of superradiance, in case of a massless scalar field, was also investigated. On contrary to the general expectations no energy extraction from black hole was found even though the incident wave packets was fine tuned to be maximally superradiant. Instead of energy extraction the to be superradiant part of the incident wave packet fails to reach the ergoregion rather it suffers a total reflection which appears to be a new phenomenon. |
1408.0044 | Brien C. Nolan | Brien C. Nolan | Particle and photon orbits in McVittie spacetimes | 26 pages, 12 figures | null | 10.1088/0264-9381/31/23/235008 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | McVittie spacetimes represent an embedding of the Schwarzschild field in
isotropic cosmological backgrounds. Depending on the scale factor of the
background, the resulting spacetime may contain black and white hole horizons,
as well as other interesting boundary features. In order to further clarify the
nature of these spacetimes, we address this question: do there exist bound
particle and photon orbits in McVittie spacetimes? Considering first circular
photon orbits, we obtain an explicit characterization of all McVittie
spacetimes for which such orbits exist: there is a 2-parameter class of such
spacetimes, and so the existence of a circular photon orbit is a highly
specialised feature of a McVittie spacetime. However, we prove that in two
large classes of McVittie spacetimes, there are bound particle and photon
orbits: future-complete non-radial timelike and null geodesics along which the
areal radius $r$ has a finite upper bound. These geodesics are asymptotic at
large times to circular orbits of a corresponding Schwarzschild or
Schwarzschild-de Sitter spacetime. The existence of these geodesics lays the
foundations for and shows the theoretical possibility of the formation of
accretion disks in McVittie spacetimes. We also summarize and extend some
previous results on the global structure of McVittie spacetimes. The results on
bound orbits are established using centre manifold and other techniques from
the theory of dynamical systems.
| [
{
"created": "Thu, 31 Jul 2014 23:33:28 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Nolan",
"Brien C.",
""
]
] | McVittie spacetimes represent an embedding of the Schwarzschild field in isotropic cosmological backgrounds. Depending on the scale factor of the background, the resulting spacetime may contain black and white hole horizons, as well as other interesting boundary features. In order to further clarify the nature of these spacetimes, we address this question: do there exist bound particle and photon orbits in McVittie spacetimes? Considering first circular photon orbits, we obtain an explicit characterization of all McVittie spacetimes for which such orbits exist: there is a 2-parameter class of such spacetimes, and so the existence of a circular photon orbit is a highly specialised feature of a McVittie spacetime. However, we prove that in two large classes of McVittie spacetimes, there are bound particle and photon orbits: future-complete non-radial timelike and null geodesics along which the areal radius $r$ has a finite upper bound. These geodesics are asymptotic at large times to circular orbits of a corresponding Schwarzschild or Schwarzschild-de Sitter spacetime. The existence of these geodesics lays the foundations for and shows the theoretical possibility of the formation of accretion disks in McVittie spacetimes. We also summarize and extend some previous results on the global structure of McVittie spacetimes. The results on bound orbits are established using centre manifold and other techniques from the theory of dynamical systems. |
2404.06552 | Cristian Martinez | Mat\'ias Brice\~no, Cristi\'an Mart\'inez and Jorge Zanelli | On the central singularity of the BTZ geometries | 22 pages, 2 figures, 1 table | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The nature of the central singularity of the BTZ geometries -- stationary
vacuum solutions of 2+1 gravity with negative cosmological constant
$\Lambda=-\ell^{-2}$ and $SO(2)\times \mathbb{R}$ isometry -- is discussed. The
essential tool for this analysis is the holonomy operator on a closed path
(i.e., Wilson loop) around the central singularity. The study considers the
holonomies for the Lorentz and AdS$_3$ connections. The analysis is carried out
for all values of the mass $M$ and angular momentum $J$, namely, for black
holes ($M \ell \ge |J|$) and naked singularities ($M \ell < |J|$). In general,
both Lorentz and AdS$_3$ holonomies are nontrivial in the zero-radius limit
revealing the presence of delta-like singularity at the origin in the curvature
and torsion two-forms. However, in the cases $M\pm J/\ell=-n_{\pm}^2$, with
$n_{\pm} \in \mathbb{N}$, recently identified in \cite{GMYZ} as BPS
configurations, the AdS$_3$ holonomy reduces to the identity. Nevertheless,
except for the AdS$_{3}$ spacetime ($M=-1$, $J=0$), all BTZ geometries have a
central singularity which is not revealed by local operations.
| [
{
"created": "Tue, 9 Apr 2024 18:05:11 GMT",
"version": "v1"
}
] | 2024-04-11 | [
[
"Briceño",
"Matías",
""
],
[
"Martínez",
"Cristián",
""
],
[
"Zanelli",
"Jorge",
""
]
] | The nature of the central singularity of the BTZ geometries -- stationary vacuum solutions of 2+1 gravity with negative cosmological constant $\Lambda=-\ell^{-2}$ and $SO(2)\times \mathbb{R}$ isometry -- is discussed. The essential tool for this analysis is the holonomy operator on a closed path (i.e., Wilson loop) around the central singularity. The study considers the holonomies for the Lorentz and AdS$_3$ connections. The analysis is carried out for all values of the mass $M$ and angular momentum $J$, namely, for black holes ($M \ell \ge |J|$) and naked singularities ($M \ell < |J|$). In general, both Lorentz and AdS$_3$ holonomies are nontrivial in the zero-radius limit revealing the presence of delta-like singularity at the origin in the curvature and torsion two-forms. However, in the cases $M\pm J/\ell=-n_{\pm}^2$, with $n_{\pm} \in \mathbb{N}$, recently identified in \cite{GMYZ} as BPS configurations, the AdS$_3$ holonomy reduces to the identity. Nevertheless, except for the AdS$_{3}$ spacetime ($M=-1$, $J=0$), all BTZ geometries have a central singularity which is not revealed by local operations. |
2008.08924 | Feiyu Yao | Feiyu Yao, Jun Tao | Extended Phase Space Thermodynamics for Dyonic Black Holes with a Power
Maxwell Field | arXiv admin note: text overlap with arXiv:1808.04506 | null | null | CTP-SCU/2020027 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the thermodynamics of dyonic black holes with
the presence of power Maxwell electromagnetic field in the extended phase
space, which includes the cosmological constant $\Lambda$ as a thermodynamic
variable. For a generic power Maxwell black hole with the electric charge and
magnetic charge, the equation of state is given as the function of rescaled
temperature $\tilde{T}$ in terms of other rescaled variables $ \tilde{r}_{+}$,
$\tilde{q}$ and $\tilde{h}$, where $r_{+}$ is the horizon radius, $q$ is the
electric charge and $h$ is some magnetic parameter. For some values of
$\tilde{q}$ and $\tilde{h}$, the phase structure of the black hole is uniquely
determined. Moreover the peculiarity of multiple temperature with some fixed
parameter configurations results in more rich phase structures. Focusing on the
power Maxwell Lagrangian with $\mathcal{L} \left( s\right) =s^{2}$, we obtain
the corresponding phase diagrams in the $ \tilde{q}$-$\tilde{h}$ plane, then
analyse the black holes phase structure and critical behaviour. For this case,
the critical line is semi-infinite and extends to $\tilde{h}=\infty$. We also
examine thermal stabilities of these black holes.
| [
{
"created": "Wed, 19 Aug 2020 02:31:33 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2020 09:36:22 GMT",
"version": "v2"
}
] | 2020-09-01 | [
[
"Yao",
"Feiyu",
""
],
[
"Tao",
"Jun",
""
]
] | In this paper, we investigate the thermodynamics of dyonic black holes with the presence of power Maxwell electromagnetic field in the extended phase space, which includes the cosmological constant $\Lambda$ as a thermodynamic variable. For a generic power Maxwell black hole with the electric charge and magnetic charge, the equation of state is given as the function of rescaled temperature $\tilde{T}$ in terms of other rescaled variables $ \tilde{r}_{+}$, $\tilde{q}$ and $\tilde{h}$, where $r_{+}$ is the horizon radius, $q$ is the electric charge and $h$ is some magnetic parameter. For some values of $\tilde{q}$ and $\tilde{h}$, the phase structure of the black hole is uniquely determined. Moreover the peculiarity of multiple temperature with some fixed parameter configurations results in more rich phase structures. Focusing on the power Maxwell Lagrangian with $\mathcal{L} \left( s\right) =s^{2}$, we obtain the corresponding phase diagrams in the $ \tilde{q}$-$\tilde{h}$ plane, then analyse the black holes phase structure and critical behaviour. For this case, the critical line is semi-infinite and extends to $\tilde{h}=\infty$. We also examine thermal stabilities of these black holes. |
1911.11027 | Justin Ripley | Justin L. Ripley, Frans Pretorius | Scalarized Black Hole dynamics in Einstein dilaton Gauss-Bonnet Gravity | updated for journal version | Phys. Rev. D 101, 044015 (2020) | 10.1103/PhysRevD.101.044015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on a numerical investigation of the stability of scalarized black
holes in Einstein dilaton Gauss-Bonnet (EdGB) gravity in the full dynamical
theory, though restricted to spherical symmetry. We find evidence that for
sufficiently small curvature-couplings the resulting scalarized black hole
solutions are nonlinearly stable. For such small couplings, we show that an
elliptic region forms inside these EdGB black hole spacetimes (prior to any
curvature singularity), and give evidence that this region remains censored
from asymptotic view. However, for coupling values "superextremal" relative to
a given black hole mass, an elliptic region forms exterior to the horizon,
implying the exterior Cauchy problem is ill-posed in this regime.
| [
{
"created": "Mon, 25 Nov 2019 16:22:44 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Feb 2020 16:31:21 GMT",
"version": "v2"
}
] | 2020-02-19 | [
[
"Ripley",
"Justin L.",
""
],
[
"Pretorius",
"Frans",
""
]
] | We report on a numerical investigation of the stability of scalarized black holes in Einstein dilaton Gauss-Bonnet (EdGB) gravity in the full dynamical theory, though restricted to spherical symmetry. We find evidence that for sufficiently small curvature-couplings the resulting scalarized black hole solutions are nonlinearly stable. For such small couplings, we show that an elliptic region forms inside these EdGB black hole spacetimes (prior to any curvature singularity), and give evidence that this region remains censored from asymptotic view. However, for coupling values "superextremal" relative to a given black hole mass, an elliptic region forms exterior to the horizon, implying the exterior Cauchy problem is ill-posed in this regime. |
2302.06400 | Anna M. Nobili | Anna M. Nobili, Alberto Anselmi | On the first test of the Weak Equivalence Principle in low Earth orbit | 12 pages, 3 figures | null | null | null | gr-qc astro-ph.IM physics.ins-det | http://creativecommons.org/licenses/by/4.0/ | The Weak Equivalence Principle is the founding pillar of General Relativity
and as such should be verified as precisely as possible. The Microscope
experiment tested it in low Earth orbit, finding that Pt and Ti test masses
fall toward Earth with the same acceleration to about 1e-15, an improvement of
about two orders of magnitude over ground tests. Space missions, even if small,
are expensive and hard to replicate; yet, the essence of physics is
repeatability. This work is an assessment of the Microscope results based on
the laws of physics and knowledge from previous experiments, focusing on the
limiting thermal noise and the treatment of acceleration outliers. Thermal
noise reveals anomalies that we explain by stray sub-microVolt potentials
caused by patch charges, giving rise to an unstable zero. The measurements were
affected by numerous acceleration spikes occurring at the synodic frequencies
relative to the Earth (the signal frequency) and the Sun, which we interpret as
evidence of a thermal origin. In Microscope authors' analysis, the spikes were
removed and the resulting gaps replaced with artificial data (up to 35, 40 per
cent of the sessions data), which retain memory of the gaps and may simulate or
cancel an effect (signal or systematic). An alternative approach based
exclusively on real measured data would avoid any ambiguity. The lessons of
Microscope are crucial to any futures improved mission.
| [
{
"created": "Mon, 13 Feb 2023 14:37:46 GMT",
"version": "v1"
},
{
"created": "Wed, 3 May 2023 17:00:54 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Apr 2024 21:12:43 GMT",
"version": "v3"
},
{
"created": "Thu, 13 Jun 2024 22:46:26 GMT",
"version": "v4"
}
] | 2024-06-17 | [
[
"Nobili",
"Anna M.",
""
],
[
"Anselmi",
"Alberto",
""
]
] | The Weak Equivalence Principle is the founding pillar of General Relativity and as such should be verified as precisely as possible. The Microscope experiment tested it in low Earth orbit, finding that Pt and Ti test masses fall toward Earth with the same acceleration to about 1e-15, an improvement of about two orders of magnitude over ground tests. Space missions, even if small, are expensive and hard to replicate; yet, the essence of physics is repeatability. This work is an assessment of the Microscope results based on the laws of physics and knowledge from previous experiments, focusing on the limiting thermal noise and the treatment of acceleration outliers. Thermal noise reveals anomalies that we explain by stray sub-microVolt potentials caused by patch charges, giving rise to an unstable zero. The measurements were affected by numerous acceleration spikes occurring at the synodic frequencies relative to the Earth (the signal frequency) and the Sun, which we interpret as evidence of a thermal origin. In Microscope authors' analysis, the spikes were removed and the resulting gaps replaced with artificial data (up to 35, 40 per cent of the sessions data), which retain memory of the gaps and may simulate or cancel an effect (signal or systematic). An alternative approach based exclusively on real measured data would avoid any ambiguity. The lessons of Microscope are crucial to any futures improved mission. |
gr-qc/9805021 | Leonardo Palacios | L. Palacios and J.F. Plebanski | A note on the iterative approach to twisting type N solutions | 9 pages, Tex file; corrected typos, some rephrasing and added
reference | null | null | CINVESTAV CIEA-FIS-30/98, Ecole Polytechnique CPHT-S6110598 | gr-qc | null | We present the results of the computation of a twisting type N solution to
vacuum Einstein equations following an iterative approach. Our results show
that the higher order terms fail to provide a full exact solution with
non-vanishing twist. Nevertheless, our fourth-order solution still represents a
regular and twisting type N solution.
| [
{
"created": "Thu, 7 May 1998 10:16:31 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Sep 1998 13:57:50 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Palacios",
"L.",
""
],
[
"Plebanski",
"J. F.",
""
]
] | We present the results of the computation of a twisting type N solution to vacuum Einstein equations following an iterative approach. Our results show that the higher order terms fail to provide a full exact solution with non-vanishing twist. Nevertheless, our fourth-order solution still represents a regular and twisting type N solution. |
2306.17847 | Adam Pound | Andrew Spiers, Adam Pound, Barry Wardell | Second-order perturbations of the Schwarzschild spacetime: practical,
covariant and gauge-invariant formalisms | 41 pages. v2 contains additional material and corrects minor errors.
v3 corrects additional minor errors. v4 makes minor changes in response to
referee comments | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | High-accuracy gravitational-wave modeling demands going beyond linear,
first-order perturbation theory. Particularly motivated by the need for
second-order perturbative models of extreme-mass-ratio inspirals and black hole
ringdowns, we present practical spherical-harmonic decompositions of the
Einstein equation, Regge-Wheeler-Zerilli equations, and Teukolsky equation at
second perturbative order in a Schwarzschild background. Our formulations are
covariant on the $t$--$r$ plane and on the two-sphere, and we express the field
equations in terms of gauge-invariant metric perturbations. In a companion
Mathematica package, PerturbationEquations, we provide these invariant formulas
as well as the analogous formulas in terms of raw, gauge-dependent metric
perturbations. Our decomposition of the second-order Einstein equation, when
specialized to the Lorenz gauge, was a key ingredient in recent second-order
self-force calculations [Phys. Rev. Lett. 124, 021101 (2020); ibid. 127, 151102
(2021); ibid. 130, 241402 (2023)].
| [
{
"created": "Fri, 30 Jun 2023 17:59:22 GMT",
"version": "v1"
},
{
"created": "Sun, 12 May 2024 19:20:02 GMT",
"version": "v2"
},
{
"created": "Thu, 16 May 2024 18:38:07 GMT",
"version": "v3"
},
{
"created": "Thu, 4 Jul 2024 12:08:25 GMT",
"version": "v4"
}
] | 2024-07-08 | [
[
"Spiers",
"Andrew",
""
],
[
"Pound",
"Adam",
""
],
[
"Wardell",
"Barry",
""
]
] | High-accuracy gravitational-wave modeling demands going beyond linear, first-order perturbation theory. Particularly motivated by the need for second-order perturbative models of extreme-mass-ratio inspirals and black hole ringdowns, we present practical spherical-harmonic decompositions of the Einstein equation, Regge-Wheeler-Zerilli equations, and Teukolsky equation at second perturbative order in a Schwarzschild background. Our formulations are covariant on the $t$--$r$ plane and on the two-sphere, and we express the field equations in terms of gauge-invariant metric perturbations. In a companion Mathematica package, PerturbationEquations, we provide these invariant formulas as well as the analogous formulas in terms of raw, gauge-dependent metric perturbations. Our decomposition of the second-order Einstein equation, when specialized to the Lorenz gauge, was a key ingredient in recent second-order self-force calculations [Phys. Rev. Lett. 124, 021101 (2020); ibid. 127, 151102 (2021); ibid. 130, 241402 (2023)]. |
2012.07022 | Zezhou Hu | Zezhou Hu, Zhen Zhong, Peng-Cheng Li, Minyong Guo, Bin Chen | QED Effect on Black Hole Shadow | 27 pages and 14 figures, some references added | Phys. Rev. D 103, 044057 (2021) | 10.1103/PhysRevD.103.044057 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | In this work, taking the QED effect into account, we investigate the shadows
of the static black hole with magnetic monopoles and neutral black holes in
magnetic fields through the numerical backward ray-tracing method. For a static
black holes with magnetic monopole, we obtain the relation between the shadow
radius and the coupling constant. For neutral black holes in the uniform
magnetic fields, we find that the shadow curves deviate very small from the
ellipses for equatorial observer, and we read the linear relation between the
eccentricity and the coupling constant. For $\theta_o\neq\pi/2$, we find that
the shadow curves can be well approximated by ellipses in most cases, except
the case that the magnetic field is very strong and the observer sits around
the angle $\theta_o=\pi/4$ or $3\pi/4$. Moreover we extend our investigation to
a neutral static black hole surrounded with a current loop.
| [
{
"created": "Sun, 13 Dec 2020 10:23:33 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Dec 2020 14:08:05 GMT",
"version": "v2"
}
] | 2021-03-03 | [
[
"Hu",
"Zezhou",
""
],
[
"Zhong",
"Zhen",
""
],
[
"Li",
"Peng-Cheng",
""
],
[
"Guo",
"Minyong",
""
],
[
"Chen",
"Bin",
""
]
] | In this work, taking the QED effect into account, we investigate the shadows of the static black hole with magnetic monopoles and neutral black holes in magnetic fields through the numerical backward ray-tracing method. For a static black holes with magnetic monopole, we obtain the relation between the shadow radius and the coupling constant. For neutral black holes in the uniform magnetic fields, we find that the shadow curves deviate very small from the ellipses for equatorial observer, and we read the linear relation between the eccentricity and the coupling constant. For $\theta_o\neq\pi/2$, we find that the shadow curves can be well approximated by ellipses in most cases, except the case that the magnetic field is very strong and the observer sits around the angle $\theta_o=\pi/4$ or $3\pi/4$. Moreover we extend our investigation to a neutral static black hole surrounded with a current loop. |
1201.1738 | Naoki Tsukamoto | Naoki Tsukamoto, Tomohiro Harada | A No-Go Theorem for Rotating Stars of a Perfect Fluid without Radial
Motion in Projectable Ho\v{r}ava--Lifshitz Gravity | 18 pages, no figures, minor correction, title changed, accepted for
publication in Galaxies | Galaxies 1, 261 (2013) | 10.3390/galaxies1030261 | RUP-11-5 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ho\v{r}ava--Lifshitz gravity has covariance only under the
foliation-preserving diffeomorphism. This implies that the quantities on the
constant-time hypersurfaces should be regular. In the original theory, the
projectability condition, which strongly restricts the lapse function, is
proposed. We assume that a star is filled with a perfect fluid with no-radial
motion and that it has reflection symmetry about the equatorial plane. As a
result, we find a no-go theorem for stationary and axisymmetric star solutions
in projectable Ho\v{r}ava--Lifshitz gravity under the physically reasonable
assumptions in the matter sector. Since we do not use the gravitational action
to prove it, our result also works out in other projectable theories and
applies to not only strong gravitational fields, but also weak gravitational
ones.
| [
{
"created": "Mon, 9 Jan 2012 11:17:52 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Dec 2013 16:02:32 GMT",
"version": "v2"
}
] | 2013-12-18 | [
[
"Tsukamoto",
"Naoki",
""
],
[
"Harada",
"Tomohiro",
""
]
] | Ho\v{r}ava--Lifshitz gravity has covariance only under the foliation-preserving diffeomorphism. This implies that the quantities on the constant-time hypersurfaces should be regular. In the original theory, the projectability condition, which strongly restricts the lapse function, is proposed. We assume that a star is filled with a perfect fluid with no-radial motion and that it has reflection symmetry about the equatorial plane. As a result, we find a no-go theorem for stationary and axisymmetric star solutions in projectable Ho\v{r}ava--Lifshitz gravity under the physically reasonable assumptions in the matter sector. Since we do not use the gravitational action to prove it, our result also works out in other projectable theories and applies to not only strong gravitational fields, but also weak gravitational ones. |
gr-qc/0306085 | Reinaldo J. Gleiser | Reinaldo J. Gleiser and Alfredo E. Dominguez (FaMAF, Universidad
Nacional de Cordoba, Argentina) | A gravitational memory effect in "boosted" black hole perturbation
theory | REVTexIV, 15 pages, 2 EPS figures | Phys.Rev. D68 (2003) 104018 | 10.1103/PhysRevD.68.104018 | null | gr-qc | null | Black hole perturbation theory, or more generally, perturbation theory on a
Schwarzschild bockground, has been applied in several contexts, but usually
under the simplifying assumption that the ADM momentum vanishes, namely, that
the evolution is carried out and observed in the ``center of momentum frame''.
In this paper we consider some consequences of the inclusion of a non vanishing
ADM momentum in the initial data. We first provide a justification for the
validity of the transformation of the initial data to the ``center of momentum
frame'', and then analyze the effect of this transformation on the
gravitational wave amplitude. The most significant result is the possibility of
a type of gravitational memory effect that appears to have no simple relation
with the well known Christodoulou effect.
| [
{
"created": "Wed, 18 Jun 2003 17:58:33 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Gleiser",
"Reinaldo J.",
"",
"FaMAF, Universidad\n Nacional de Cordoba, Argentina"
],
[
"Dominguez",
"Alfredo E.",
"",
"FaMAF, Universidad\n Nacional de Cordoba, Argentina"
]
] | Black hole perturbation theory, or more generally, perturbation theory on a Schwarzschild bockground, has been applied in several contexts, but usually under the simplifying assumption that the ADM momentum vanishes, namely, that the evolution is carried out and observed in the ``center of momentum frame''. In this paper we consider some consequences of the inclusion of a non vanishing ADM momentum in the initial data. We first provide a justification for the validity of the transformation of the initial data to the ``center of momentum frame'', and then analyze the effect of this transformation on the gravitational wave amplitude. The most significant result is the possibility of a type of gravitational memory effect that appears to have no simple relation with the well known Christodoulou effect. |
1209.2619 | Qiang Xu | Qiang Xu, Sheng-yu Tan | Singularity problem in f(R) model with non-minimal coupling | 13 pages, 4 figures | Phys. Rev. D 86, 123526 (2012) | 10.1103/PhysRevD.86.123526 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the non-minimal coupling between matter and the geometry in the
f(R) theory. In the new theory which we established, a new scalar $\psi$ has
been defined and we give it a certain stability condition. We intend to take a
closer look at the dark energy oscillating behavior in the de-Sitter universe
and the matter era, from which we derive the oscillating frequency, and the
oscillating condition. More importantly, we present the condition of coupling
form that the singularity can be solved. We discuss several specific coupling
forms, and find logarithmic coupling with an oscillating period $\Delta
T\sim\Delta z$ in the matter era $z>4$, can improve singularity in the early
universe. The result of numerical calculation verifies our theoretic
calculation about the oscillating frequency. Considering two toy models, we
find the cosmic evolution in the coupling model is nearly the same as that in
the normal f(R) theory when $lna>4$. We also discuss the local tests of the
non-minimal coupling f(R) model, and show the constraint on the coupling form.
| [
{
"created": "Wed, 12 Sep 2012 14:15:41 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Sep 2012 01:02:51 GMT",
"version": "v2"
},
{
"created": "Sun, 16 Sep 2012 10:32:18 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"Xu",
"Qiang",
""
],
[
"Tan",
"Sheng-yu",
""
]
] | We consider the non-minimal coupling between matter and the geometry in the f(R) theory. In the new theory which we established, a new scalar $\psi$ has been defined and we give it a certain stability condition. We intend to take a closer look at the dark energy oscillating behavior in the de-Sitter universe and the matter era, from which we derive the oscillating frequency, and the oscillating condition. More importantly, we present the condition of coupling form that the singularity can be solved. We discuss several specific coupling forms, and find logarithmic coupling with an oscillating period $\Delta T\sim\Delta z$ in the matter era $z>4$, can improve singularity in the early universe. The result of numerical calculation verifies our theoretic calculation about the oscillating frequency. Considering two toy models, we find the cosmic evolution in the coupling model is nearly the same as that in the normal f(R) theory when $lna>4$. We also discuss the local tests of the non-minimal coupling f(R) model, and show the constraint on the coupling form. |
2209.11594 | Stefano Foffa | Gabriel Luz Almeida, Stefano Foffa and Riccardo Sturani | Gravitational radiation contributions to the two-body scattering angle | 13 pages, 1 figure, final version published on PRD | null | 10.1103/PhysRevD.107.024020 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the contribution to the two-body scattering angle of a specific
class of interactions involving the exchange of gravitational radiative degrees
of freedom, including the nonlinear memory process and square of radiation
reaction effects. Our computation is performed directly from the equations of
motion, thus computing the overall effect of both conservative and dissipative
processes. Such contributions provide in principle the last missing ingredients
to compute the scattering angle at fifth post-Newtonian, at fourth
post-Minkowskian order.
| [
{
"created": "Fri, 23 Sep 2022 13:56:52 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jan 2023 08:26:53 GMT",
"version": "v2"
}
] | 2023-02-01 | [
[
"Almeida",
"Gabriel Luz",
""
],
[
"Foffa",
"Stefano",
""
],
[
"Sturani",
"Riccardo",
""
]
] | We compute the contribution to the two-body scattering angle of a specific class of interactions involving the exchange of gravitational radiative degrees of freedom, including the nonlinear memory process and square of radiation reaction effects. Our computation is performed directly from the equations of motion, thus computing the overall effect of both conservative and dissipative processes. Such contributions provide in principle the last missing ingredients to compute the scattering angle at fifth post-Newtonian, at fourth post-Minkowskian order. |
1008.5167 | Philippe G. LeFloch | James D.E. Grant and Philippe G. LeFloch | Null injectivity estimate under an upper bound on the curvature | 19 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish a uniform estimate for the injectivity radius of the past null
cone of a point in a general Lorentzian manifold foliated by spacelike
hypersurfaces and satisfying an upper curvature bound. Precisely, our main
assumptions are, on one hand, upper bounds on the null curvature of the
spacetime and the lapse function of the foliation, and sup-norm bounds on the
deformation tensors of the foliation. Our proof is inspired by techniques from
Riemannian geometry, and it should be noted that we impose no restriction on
the size of the curvature or deformation tensors, and allow for metrics that
are "far" from the Minkowski one. The relevance of our estimate is illustrated
with a class of plane-symmetric spacetimes which satisfy our assumptions but
admit no uniform lower bound on the curvature not even in the L2 norm. The
conditions we put forward, therefore, lead to a uniform control of the
spacetime geometry and should be useful in the context of general relativity.
| [
{
"created": "Mon, 30 Aug 2010 21:06:53 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Apr 2011 01:22:53 GMT",
"version": "v2"
},
{
"created": "Tue, 31 May 2011 06:19:27 GMT",
"version": "v3"
}
] | 2011-06-01 | [
[
"Grant",
"James D. E.",
""
],
[
"LeFloch",
"Philippe G.",
""
]
] | We establish a uniform estimate for the injectivity radius of the past null cone of a point in a general Lorentzian manifold foliated by spacelike hypersurfaces and satisfying an upper curvature bound. Precisely, our main assumptions are, on one hand, upper bounds on the null curvature of the spacetime and the lapse function of the foliation, and sup-norm bounds on the deformation tensors of the foliation. Our proof is inspired by techniques from Riemannian geometry, and it should be noted that we impose no restriction on the size of the curvature or deformation tensors, and allow for metrics that are "far" from the Minkowski one. The relevance of our estimate is illustrated with a class of plane-symmetric spacetimes which satisfy our assumptions but admit no uniform lower bound on the curvature not even in the L2 norm. The conditions we put forward, therefore, lead to a uniform control of the spacetime geometry and should be useful in the context of general relativity. |
0911.4068 | Christopher Duston | Christopher L Duston | Exotic Smoothness in Four Dimensions and Euclidean Quantum Gravity | 20 pages, 1 figure | Int.J.Geom.Meth.Mod.Phys.08:459-484,2011 | 10.1142/S0219887811005233 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we calculate the effect of the inclusion of exotic smooth
structures on typical observables in Euclidean quantum gravity. We do this in
the semiclassical regime for several gravitational free-field actions and find
that the results are similar, independent of the particular action that is
chosen. These are the first results of their kind in dimension four, which we
extend to include one-loop contributions as well. We find these topological
features can have physically significant results without the need for
additional exotic physics.
| [
{
"created": "Fri, 20 Nov 2009 15:39:43 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 2010 19:07:25 GMT",
"version": "v2"
}
] | 2013-08-13 | [
[
"Duston",
"Christopher L",
""
]
] | In this paper we calculate the effect of the inclusion of exotic smooth structures on typical observables in Euclidean quantum gravity. We do this in the semiclassical regime for several gravitational free-field actions and find that the results are similar, independent of the particular action that is chosen. These are the first results of their kind in dimension four, which we extend to include one-loop contributions as well. We find these topological features can have physically significant results without the need for additional exotic physics. |
1801.08955 | Grigoris Panotopoulos | Kyriakos Destounis, Grigoris Panotopoulos, \'Angel Rincon | Stability under scalar perturbations and quasinormal modes of 4D
Einstein-Born-Infeld dilaton spacetime: Exact spectrum | Minor corrections | null | 10.1140/epjc/s10052-018-5576-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the stability under scalar perturbations, and we compute the
quasinormal modes of the Einstein-Born-Infeld dilaton spacetime in 1+3
dimensions. Solving the full radial equation in terms of hypergeometric
functions, we provide an exact analytical expression for the spectrum. We find
that the frequencies are purely imaginary, and we confirm our results by
computing them numerically. Although the scalar field that perturbs the black
hole is electrically neutral, an instability similar to that seen in charged
scalar perturbations of the Reissner-Nordstr\"om black hole is observed.
| [
{
"created": "Fri, 26 Jan 2018 19:39:02 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Apr 2018 19:23:42 GMT",
"version": "v2"
}
] | 2018-08-29 | [
[
"Destounis",
"Kyriakos",
""
],
[
"Panotopoulos",
"Grigoris",
""
],
[
"Rincon",
"Ángel",
""
]
] | We study the stability under scalar perturbations, and we compute the quasinormal modes of the Einstein-Born-Infeld dilaton spacetime in 1+3 dimensions. Solving the full radial equation in terms of hypergeometric functions, we provide an exact analytical expression for the spectrum. We find that the frequencies are purely imaginary, and we confirm our results by computing them numerically. Although the scalar field that perturbs the black hole is electrically neutral, an instability similar to that seen in charged scalar perturbations of the Reissner-Nordstr\"om black hole is observed. |
1304.0778 | Ernesto Contreras | Ernesto Contreras and Lorenzo Leal | Abelian Ashtekar formulation from the ADM action | 13 pages | International Journal of Modern Physics D Vol. 23, No. 5 (2014)
1450047 | 10.1142/S0218271814500473 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Ashtekar formulation of linear gravity starting from the ADM
first order action for the non linear theory, linearizing it, and performing a
canonical transformation that coordinatizes the phase space in terms of the
already linearized Ashtekar variables. The results obtained in this way are in
accordance with those obtained through the standard method, in which, after
introducing the Ashtekar variables for the full theory, a linearization around
the flat Abelian connection and its conjugate momentum is performed.
| [
{
"created": "Tue, 2 Apr 2013 20:04:01 GMT",
"version": "v1"
}
] | 2019-04-01 | [
[
"Contreras",
"Ernesto",
""
],
[
"Leal",
"Lorenzo",
""
]
] | We study the Ashtekar formulation of linear gravity starting from the ADM first order action for the non linear theory, linearizing it, and performing a canonical transformation that coordinatizes the phase space in terms of the already linearized Ashtekar variables. The results obtained in this way are in accordance with those obtained through the standard method, in which, after introducing the Ashtekar variables for the full theory, a linearization around the flat Abelian connection and its conjugate momentum is performed. |
2310.04324 | Angel Rincon | Raul Carrasco, Angel Rincon, Joel Saavedra and Nelson Videla | Discriminating interacting dark energy models using Statefinder
diagnostic | 37 pages, 19 figures, 1 table | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we perform a comparative study of different interacting
dark energy (DE) models using the Statefinder diagnostics. In particular, 17
different forms of the energy transfer rate $Q$ between DE and dark matter (DM)
were focused on, belonging to the following categories: i) linear models in
energy densities of DE and DM, ii) non-linear models, iii) models with a change
of direction of energy transfer between DE and DM, iv) models involving
derivatives of the energy densities, v) parametrized interactions through a
function of the coincidence parameter $\tilde{r}$, and finally we also consider
vi) two kinds of models with a self-interaction between DM, without DE. These
models have been already studied in the literature and constrained with
observational data available at that time. In order to discriminate between
them at background level, we use the Statefinder diagnostic, based on the
computation and study of the so-called Statefinder parameters $r$, $s$ in
addition to the deceleration parameter $q$. We plot the evolution trajectories
for the several interacting models on the $r-q$, $r-s$ planes, and we find some
distinctive features and departures from $\Lambda$CDM and other DE models, as
Quintessence, Chaplygin Gas, running vacuum models (RVM) and Galileon.
| [
{
"created": "Fri, 6 Oct 2023 15:34:56 GMT",
"version": "v1"
}
] | 2023-10-09 | [
[
"Carrasco",
"Raul",
""
],
[
"Rincon",
"Angel",
""
],
[
"Saavedra",
"Joel",
""
],
[
"Videla",
"Nelson",
""
]
] | In the present work, we perform a comparative study of different interacting dark energy (DE) models using the Statefinder diagnostics. In particular, 17 different forms of the energy transfer rate $Q$ between DE and dark matter (DM) were focused on, belonging to the following categories: i) linear models in energy densities of DE and DM, ii) non-linear models, iii) models with a change of direction of energy transfer between DE and DM, iv) models involving derivatives of the energy densities, v) parametrized interactions through a function of the coincidence parameter $\tilde{r}$, and finally we also consider vi) two kinds of models with a self-interaction between DM, without DE. These models have been already studied in the literature and constrained with observational data available at that time. In order to discriminate between them at background level, we use the Statefinder diagnostic, based on the computation and study of the so-called Statefinder parameters $r$, $s$ in addition to the deceleration parameter $q$. We plot the evolution trajectories for the several interacting models on the $r-q$, $r-s$ planes, and we find some distinctive features and departures from $\Lambda$CDM and other DE models, as Quintessence, Chaplygin Gas, running vacuum models (RVM) and Galileon. |
1309.5020 | Abraham Harte | Abraham I. Harte | Tails of plane wave spacetimes: Wave-wave scattering in general
relativity | 13 pages, 1 figure, minor typos corrected | Phys. Rev. D 88, 084059 (2013) | 10.1103/PhysRevD.88.084059 | AEI-2013-251 | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most important characteristics of light in flat spacetime is that
it satisfies Huygens' principle: Initial data for the vacuum Maxwell equations
evolves sharply along null (and not timelike) geodesics. In flat spacetime,
there are no tails which linger behind expanding wavefronts. Tails generically
do exist, however, if the background spacetime is curved. The only non-flat
vacuum geometries where electromagnetic fields satisfy Huygens' principle are
known to be those associated with gravitational plane waves. This paper
investigates whether perturbations to the plane wave geometry itself also
propagate without tails. First-order perturbations to all locally-constructed
curvature scalars are indeed found to satisfy Huygens' principles. Despite
this, gravitational tails do exist. Locally, they can only perturb one plane
wave spacetime into another plane wave spacetime. A weak localized beam of
gravitational radiation passing through an arbitrarily-strong plane wave
therefore leaves behind only a slight perturbation to the waveform of the
background plane wave. The planar symmetry of that wave cannot be disturbed by
any linear tail. These results are obtained by first deriving the retarded
Green function for Lorenz-gauge metric perturbations and then analyzing its
consequences for generic initial-value problems.
| [
{
"created": "Thu, 19 Sep 2013 15:25:10 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Oct 2013 14:36:28 GMT",
"version": "v2"
}
] | 2013-11-13 | [
[
"Harte",
"Abraham I.",
""
]
] | One of the most important characteristics of light in flat spacetime is that it satisfies Huygens' principle: Initial data for the vacuum Maxwell equations evolves sharply along null (and not timelike) geodesics. In flat spacetime, there are no tails which linger behind expanding wavefronts. Tails generically do exist, however, if the background spacetime is curved. The only non-flat vacuum geometries where electromagnetic fields satisfy Huygens' principle are known to be those associated with gravitational plane waves. This paper investigates whether perturbations to the plane wave geometry itself also propagate without tails. First-order perturbations to all locally-constructed curvature scalars are indeed found to satisfy Huygens' principles. Despite this, gravitational tails do exist. Locally, they can only perturb one plane wave spacetime into another plane wave spacetime. A weak localized beam of gravitational radiation passing through an arbitrarily-strong plane wave therefore leaves behind only a slight perturbation to the waveform of the background plane wave. The planar symmetry of that wave cannot be disturbed by any linear tail. These results are obtained by first deriving the retarded Green function for Lorenz-gauge metric perturbations and then analyzing its consequences for generic initial-value problems. |
1207.0047 | Naoki Tsukamoto | Naoki Tsukamoto, Tomohiro Harada and Kohji Yajima | Can we distinguish between black holes and wormholes by their
Einstein-ring systems? | 13 pages, 2 figures, minor changes from v2 | Phys Rev. D 86, 104062 (2012) | 10.1103/PhysRevD.86.104062 | RUP-12-5 | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/3.0/ | For the last decade, the gravitational lensing in the strong gravitational
field has been studied eagerly. It is well known that, for the lensing by a
black hole, infinite number of Einstein rings are formed by the light rays
which wind around the black hole nearly on the photon sphere, which are called
relativistic Einstein rings. This is also the case for the lensing by a
wormhole. In this paper, we study the Einstein ring and relativistic Einstein
rings for the Schwarzschild black hole and the Ellis wormhole, the latter of
which is an example of traversable wormholes of the Morris-Thorne class. Given
the configuration of the gravitational lensing and the radii of the Einstein
ring and relativistic Einstein rings, we can distinguish between a black hole
and a wormhole in principle. We conclude that we can detect the relativistic
Einstein rings by wormholes which have the radii of the throat $a\simeq 0.5$pc
at a galactic center with the distance 10Mpc and which have $a\simeq 10$AU in
our galaxy using by the most powerful modern instruments which have the
resolution of $10^{-2}$arcsecond such as a 10-meter optical-infrared telescope.
The black holes which make the Einstein rings of the same size as the ones by
the wormholes are galactic supermassive black holes and the relativistic
Einstein rings by the black holes are too small to measure at this moment. We
may test some hypotheses of astrophysical wormholes by using the Einstein ring
and relativistic Einstein rings in the future.
| [
{
"created": "Sat, 30 Jun 2012 04:55:30 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Oct 2012 11:34:26 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Dec 2012 07:58:31 GMT",
"version": "v3"
}
] | 2012-12-07 | [
[
"Tsukamoto",
"Naoki",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Yajima",
"Kohji",
""
]
] | For the last decade, the gravitational lensing in the strong gravitational field has been studied eagerly. It is well known that, for the lensing by a black hole, infinite number of Einstein rings are formed by the light rays which wind around the black hole nearly on the photon sphere, which are called relativistic Einstein rings. This is also the case for the lensing by a wormhole. In this paper, we study the Einstein ring and relativistic Einstein rings for the Schwarzschild black hole and the Ellis wormhole, the latter of which is an example of traversable wormholes of the Morris-Thorne class. Given the configuration of the gravitational lensing and the radii of the Einstein ring and relativistic Einstein rings, we can distinguish between a black hole and a wormhole in principle. We conclude that we can detect the relativistic Einstein rings by wormholes which have the radii of the throat $a\simeq 0.5$pc at a galactic center with the distance 10Mpc and which have $a\simeq 10$AU in our galaxy using by the most powerful modern instruments which have the resolution of $10^{-2}$arcsecond such as a 10-meter optical-infrared telescope. The black holes which make the Einstein rings of the same size as the ones by the wormholes are galactic supermassive black holes and the relativistic Einstein rings by the black holes are too small to measure at this moment. We may test some hypotheses of astrophysical wormholes by using the Einstein ring and relativistic Einstein rings in the future. |
2007.07889 | Jeremy Sakstein | Djuna Croon, Samuel D. McDermott, Jeremy Sakstein | Missing in Action: New Physics and the Black Hole Mass Gap | 16 pages, 10 figures | Phys. Rev. D 102, 115024 (2020) | 10.1103/PhysRevD.102.115024 | FERMILAB-PUB-20-328-T | gr-qc astro-ph.CO astro-ph.HE astro-ph.SR hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate the power of the black hole mass gap as a novel probe of
fundamental physics. New light particles that couple to the Standard Model can
act as an additional source of energy loss in the cores of population-III
stars, dramatically altering their evolution. We investigate the effects of two
paradigmatic weakly coupled, low-mass particles, axions and hidden photons, and
find that the pulsational pair instability, which causes a substantial amount
of mass loss, is suppressed. As a result, it is possible to form black holes of
$72\msun$ or heavier, deep inside the black hole mass gap predicted by the
Standard Model. The upper edge of the mass gap is raised to $>130{\rm
M}_\odot$, implying that heavier black holes, anticipated to be observed after
LIGO's sensitivity is upgraded, would also be impacted. In contrast, thermally
produced heavy particles would remain in the core, leading to the tantalizing
possibility that they drive a new instability akin to the electron-positron
pair instability. We investigate this effect analytically and find that stars
that avoid the electron-positron pair instability could experience this new
instability. We discuss our results in light of current and upcoming
gravitational wave interferometer detections of binary black hole mergers.
| [
{
"created": "Wed, 15 Jul 2020 18:00:00 GMT",
"version": "v1"
}
] | 2021-01-04 | [
[
"Croon",
"Djuna",
""
],
[
"McDermott",
"Samuel D.",
""
],
[
"Sakstein",
"Jeremy",
""
]
] | We demonstrate the power of the black hole mass gap as a novel probe of fundamental physics. New light particles that couple to the Standard Model can act as an additional source of energy loss in the cores of population-III stars, dramatically altering their evolution. We investigate the effects of two paradigmatic weakly coupled, low-mass particles, axions and hidden photons, and find that the pulsational pair instability, which causes a substantial amount of mass loss, is suppressed. As a result, it is possible to form black holes of $72\msun$ or heavier, deep inside the black hole mass gap predicted by the Standard Model. The upper edge of the mass gap is raised to $>130{\rm M}_\odot$, implying that heavier black holes, anticipated to be observed after LIGO's sensitivity is upgraded, would also be impacted. In contrast, thermally produced heavy particles would remain in the core, leading to the tantalizing possibility that they drive a new instability akin to the electron-positron pair instability. We investigate this effect analytically and find that stars that avoid the electron-positron pair instability could experience this new instability. We discuss our results in light of current and upcoming gravitational wave interferometer detections of binary black hole mergers. |
gr-qc/0010042 | S. Shankaranarayanan | S. Shankaranarayanan, T. Padmanabhan and K. Srinivasan | Hawking radiation in different coordinate settings: Complex paths
approach | 18 pages, 2 figures, Uses IOP style file; final version; accepted in
Class. Quant. Grav | Class.Quant.Grav. 19 (2002) 2671-2688 | 10.1088/0264-9381/19/10/310 | null | gr-qc | null | We apply the technique of complex paths to obtain Hawking radiation in
different coordinate representations of the Schwarzschild space-time. The
coordinate representations we consider do not possess a singularity at the
horizon unlike the standard Schwarzschild coordinate. However, the event
horizon manifests itself as a singularity in the expression for the
semiclassical action. This singularity is regularized by using the method of
complex paths and we find that Hawking radiation is recovered in these
coordinates indicating the covariance of Hawking radiation as far as these
coordinates are concerned.
| [
{
"created": "Wed, 11 Oct 2000 06:35:47 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jan 2001 05:53:04 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Jun 2001 08:56:54 GMT",
"version": "v3"
},
{
"created": "Mon, 1 Apr 2002 17:09:48 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Shankaranarayanan",
"S.",
""
],
[
"Padmanabhan",
"T.",
""
],
[
"Srinivasan",
"K.",
""
]
] | We apply the technique of complex paths to obtain Hawking radiation in different coordinate representations of the Schwarzschild space-time. The coordinate representations we consider do not possess a singularity at the horizon unlike the standard Schwarzschild coordinate. However, the event horizon manifests itself as a singularity in the expression for the semiclassical action. This singularity is regularized by using the method of complex paths and we find that Hawking radiation is recovered in these coordinates indicating the covariance of Hawking radiation as far as these coordinates are concerned. |
1302.5013 | Pisin Chen | Mariam Bouhmadi-Lopez, Che-Yu Chen, Pisin Chen | Is Eddington-Born-Infeld theory really free of cosmological
singularities? | 5 pages | Eur. Phys. J. C (2014) 74:2802 | 10.1140/epjc/s10052-014-2802-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Eddington-inspired-Born-Infeld (EiBI) theory has been recently
resurrected. Such a theory is characterized by being equivalent to Einstein
theory in vacuum but differing from it in the presence of matter. One of the
virtues of the theory is to avoid the Big Bang singularity for a radiation
filled universe. In this paper, we analyze singularity avoidance in this kind
of model. More precisely, we analyze the behavior of a homogeneous and
isotropic universe filled with phantom energy in addition to the dark and
baryonic matter. Unlike the Big Bang singularity that can be avoided in this
kind of model through a bounce or a loitering effect on the physical metric, we
find that the Big Rip singularity is unavoidable in the EiBI phantom model even
though it can be postponed towards a slightly further future cosmic time as
compared with the same singularity in other models based on the standard
general relativity and with the same matter content described above.
| [
{
"created": "Wed, 20 Feb 2013 16:13:36 GMT",
"version": "v1"
}
] | 2014-05-26 | [
[
"Bouhmadi-Lopez",
"Mariam",
""
],
[
"Chen",
"Che-Yu",
""
],
[
"Chen",
"Pisin",
""
]
] | The Eddington-inspired-Born-Infeld (EiBI) theory has been recently resurrected. Such a theory is characterized by being equivalent to Einstein theory in vacuum but differing from it in the presence of matter. One of the virtues of the theory is to avoid the Big Bang singularity for a radiation filled universe. In this paper, we analyze singularity avoidance in this kind of model. More precisely, we analyze the behavior of a homogeneous and isotropic universe filled with phantom energy in addition to the dark and baryonic matter. Unlike the Big Bang singularity that can be avoided in this kind of model through a bounce or a loitering effect on the physical metric, we find that the Big Rip singularity is unavoidable in the EiBI phantom model even though it can be postponed towards a slightly further future cosmic time as compared with the same singularity in other models based on the standard general relativity and with the same matter content described above. |
gr-qc/9901066 | Portnoy Jacob | E.I. Guendelman and Jacov Portnoy | The Universe out of an Elementary Particle? | null | Class.Quant.Grav.16:3315-3320,1999 | 10.1088/0264-9381/16/10/320 | null | gr-qc | null | We consider a model of an elementary particle as a 2 + 1 dimensional brane
evolving in a 3 + 1 dimensional space. Introducing gauge fields that live in
the brane as well as normal surface tension can lead to a stable "elementary
particle" configuration. Considering the possibility of non vanishing vacuum
energy inside the bubble leads, when gravitational effects are considered, to
the possibility of a quantum decay of such "elementary particle" into an
infinite universe. Some remarkable features of the quantum mechanics of this
process are discussed, in particular the relation between possible boundary
conditions and the question of instability towards Universe formation is
analyzed.
| [
{
"created": "Sun, 24 Jan 1999 09:05:16 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Guendelman",
"E. I.",
""
],
[
"Portnoy",
"Jacov",
""
]
] | We consider a model of an elementary particle as a 2 + 1 dimensional brane evolving in a 3 + 1 dimensional space. Introducing gauge fields that live in the brane as well as normal surface tension can lead to a stable "elementary particle" configuration. Considering the possibility of non vanishing vacuum energy inside the bubble leads, when gravitational effects are considered, to the possibility of a quantum decay of such "elementary particle" into an infinite universe. Some remarkable features of the quantum mechanics of this process are discussed, in particular the relation between possible boundary conditions and the question of instability towards Universe formation is analyzed. |
1503.07860 | Christof Wetterich | C. Wetterich | Cosmic fluctuations from quantum effective action | Extended discussion, assertional references, 39 pages, 6 figures | Phys. Rev. D 92, 083507 (2015) | 10.1103/PhysRevD.92.083507 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Does the observable spectrum of cosmic fluctuations depend on detailed
initial conditions? This addresses the question if the general inflationary
paradigm is sufficient to predict within a given model the spectrum and
amplitude of cosmic fluctuations, or if additional particular assumptions about
the initial conditions are needed. The answer depends on the number of
e-foldings $N_{in}$ between the beginning of inflation and horizon crossing of
the observable fluctuations. We discuss an interacting inflaton field in an
arbitrary homogeneous and isotropic geometry, employing the quantum effective
action $\Gamma$. An exact time evolution equation for the correlation function
involves the second functional derivative $\Gamma^{(2)}$. The operator
formalism and quantum vacua for interacting fields are not needed. Use of the
effective action also allows one to address the change of frames by field
transformations (field relativity). Within the approximation of a derivative
expansion for the effective action we find the most general solution for the
correlation function, including mixed quantum states. For not too large
$N_{in}$ the memory of the initial conditions is preserved. In this case the
cosmic microwave background cannot disentangle between the initial spectrum and
its processing at horizon crossing. The inflaton potential cannot be
reconstructed without assumptions about the initial state of the universe. We
argue that for very large $N_{in}$ a universal scaling form of the correlation
function is reached for the range of observable modes. This can be due to
symmetrization and equilibration effects, not yet contained in our
approximation, which drive the short distance tail of the correlation function
towards the Lorentz invariant propagator in flat space.
| [
{
"created": "Thu, 26 Mar 2015 15:33:53 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Sep 2015 16:58:02 GMT",
"version": "v2"
}
] | 2015-10-14 | [
[
"Wetterich",
"C.",
""
]
] | Does the observable spectrum of cosmic fluctuations depend on detailed initial conditions? This addresses the question if the general inflationary paradigm is sufficient to predict within a given model the spectrum and amplitude of cosmic fluctuations, or if additional particular assumptions about the initial conditions are needed. The answer depends on the number of e-foldings $N_{in}$ between the beginning of inflation and horizon crossing of the observable fluctuations. We discuss an interacting inflaton field in an arbitrary homogeneous and isotropic geometry, employing the quantum effective action $\Gamma$. An exact time evolution equation for the correlation function involves the second functional derivative $\Gamma^{(2)}$. The operator formalism and quantum vacua for interacting fields are not needed. Use of the effective action also allows one to address the change of frames by field transformations (field relativity). Within the approximation of a derivative expansion for the effective action we find the most general solution for the correlation function, including mixed quantum states. For not too large $N_{in}$ the memory of the initial conditions is preserved. In this case the cosmic microwave background cannot disentangle between the initial spectrum and its processing at horizon crossing. The inflaton potential cannot be reconstructed without assumptions about the initial state of the universe. We argue that for very large $N_{in}$ a universal scaling form of the correlation function is reached for the range of observable modes. This can be due to symmetrization and equilibration effects, not yet contained in our approximation, which drive the short distance tail of the correlation function towards the Lorentz invariant propagator in flat space. |
2401.06553 | Uddeepta Deka | Uddeepta Deka, Sumanta Chakraborty, Shasvath J. Kapadia, Md Arif
Shaikh, Parameswaran Ajith | Probing black hole charge with gravitational microlensing of
gravitational waves | 15 pages, 8 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Gravitational microlensing of gravitational waves (GWs) opens up the exciting
possibility of studying the spacetime geometry around the lens. In this work,
we investigate the prospects of constraining the `charged' hair of a black hole
(BH) from the observation of a GW signal microlensed by the BH. The charge can
have electromagnetic or modified gravity origin. We compute the analytic form
of the lensing potential with charge and construct the lensed waveforms for a
range of BH mass, charge and impact parameters, assuming non-spinning BHs.
Using an approximate likelihood function, we explore how future observations of
microlensed GWs can constrain the charge of the BH lens. We find that positive
values of the charge parameter (that can be of electromagnetic or modified
gravity origin) can be tightly constrained using lensed GW signals, while the
constraints on negative values of the charge parameter (modified gravity
origin) are modest.
| [
{
"created": "Fri, 12 Jan 2024 12:58:53 GMT",
"version": "v1"
}
] | 2024-01-15 | [
[
"Deka",
"Uddeepta",
""
],
[
"Chakraborty",
"Sumanta",
""
],
[
"Kapadia",
"Shasvath J.",
""
],
[
"Shaikh",
"Md Arif",
""
],
[
"Ajith",
"Parameswaran",
""
]
] | Gravitational microlensing of gravitational waves (GWs) opens up the exciting possibility of studying the spacetime geometry around the lens. In this work, we investigate the prospects of constraining the `charged' hair of a black hole (BH) from the observation of a GW signal microlensed by the BH. The charge can have electromagnetic or modified gravity origin. We compute the analytic form of the lensing potential with charge and construct the lensed waveforms for a range of BH mass, charge and impact parameters, assuming non-spinning BHs. Using an approximate likelihood function, we explore how future observations of microlensed GWs can constrain the charge of the BH lens. We find that positive values of the charge parameter (that can be of electromagnetic or modified gravity origin) can be tightly constrained using lensed GW signals, while the constraints on negative values of the charge parameter (modified gravity origin) are modest. |
1803.04472 | David Sloan | David Sloan | Dynamical Similarity | 17 pages. Updated to remove a flaw in section II and align with
standard terminology | Phys. Rev. D 97, 123541 (2018) | 10.1103/PhysRevD.97.123541 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine "dynamical similarities" in the Lagrangian framework. These are
symmetries of an intrinsically determined physical system under which
observables remain unaffected, but the extraneous information is changed. We
establish three central results in this context: i) Given a system with such a
symmetry there exists a system of invariants which form a subalgebra of phase
space, whose evolution is autonomous; ii) this subalgebra of autonomous
observables evolves as a contact system, in which the friction-like term
describes evolution along the direction of similarity; iii) the contact
Hamiltonian and one-form are invariants, and reproduce the dynamics of the
invariants. As the subalgebra of invariants is smaller than phase space,
dynamics is determined only in terms of this smaller space. We show how to
obtain the contact system from the symplectic system, and the embedding which
inverts the process. These results are then illustrated in the case of
homogeneous Lagrangians, including flat cosmologies minimally coupled to
matter; the n-body problem and homogeneous, anisotropic cosmology.
| [
{
"created": "Mon, 12 Mar 2018 19:21:17 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Apr 2018 16:40:44 GMT",
"version": "v2"
}
] | 2018-07-04 | [
[
"Sloan",
"David",
""
]
] | We examine "dynamical similarities" in the Lagrangian framework. These are symmetries of an intrinsically determined physical system under which observables remain unaffected, but the extraneous information is changed. We establish three central results in this context: i) Given a system with such a symmetry there exists a system of invariants which form a subalgebra of phase space, whose evolution is autonomous; ii) this subalgebra of autonomous observables evolves as a contact system, in which the friction-like term describes evolution along the direction of similarity; iii) the contact Hamiltonian and one-form are invariants, and reproduce the dynamics of the invariants. As the subalgebra of invariants is smaller than phase space, dynamics is determined only in terms of this smaller space. We show how to obtain the contact system from the symplectic system, and the embedding which inverts the process. These results are then illustrated in the case of homogeneous Lagrangians, including flat cosmologies minimally coupled to matter; the n-body problem and homogeneous, anisotropic cosmology. |
gr-qc/0205106 | Pisin Chen | Pisin Chen and Ronald J. Adler | Black Hole Remnants and Dark Matter | 4 pages; to appear in the Proceedings of the 5th UCLA Dark Matter
Symposium, Marina del Rey, Ca, Feb. 20-22, 2002 | Nucl.Phys.Proc.Suppl. 124 (2003) 103-106 | 10.1016/S0920-5632(03)02088-7 | null | gr-qc | null | We argue that, when the gravity effect is included, the generalized
uncertainty principle (GUP) may prevent black holes from total evaporation in a
similar way that the standard uncertainty principle prevents the hydrogen atom
from total collapse. Specifically we invoke the GUP to obtain a modified
Hawking temperature, which indicates that there should exist non-radiating
remnants (BHR) of about Planck mass. BHRs are an attractive candidate for cold
dark matter. We investigate an alternative cosmology in which primordial BHRs
are the primary source of dark matter.
| [
{
"created": "Fri, 24 May 2002 19:30:09 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Chen",
"Pisin",
""
],
[
"Adler",
"Ronald J.",
""
]
] | We argue that, when the gravity effect is included, the generalized uncertainty principle (GUP) may prevent black holes from total evaporation in a similar way that the standard uncertainty principle prevents the hydrogen atom from total collapse. Specifically we invoke the GUP to obtain a modified Hawking temperature, which indicates that there should exist non-radiating remnants (BHR) of about Planck mass. BHRs are an attractive candidate for cold dark matter. We investigate an alternative cosmology in which primordial BHRs are the primary source of dark matter. |
2306.11561 | Jun-Jin Peng | Jun-Jin Peng | A note on field equations in generalized theories of gravity | 39 pages, no figures, some details and one reference are added,
several typos are corrected | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the work (arXiv:1109.3846 [gr-qc]), to obtain a simple and economic
formulation of field equations for generalised theories of gravity described by
the Lagrangian $\sqrt{-g}L\big(g^{\alpha\beta},R_{\mu\nu\rho\sigma}\big)$, the
key equality $\big(\partial L/\partial
g^{\mu\nu}\big)_{R_{\alpha\beta\kappa\omega}}
=2P_{\mu}^{~\lambda\rho\sigma}R_{\nu\lambda\rho\sigma}$ was derived. In this
note, it is demonstrated that such an equality can be directly derived from an
off-shell Noether current associated with an arbitrary vector field. As
byproducts, a generalized Bianchi identity related to the divergence for the
expression of field equations, together with the Noether potential, is
obtained. On the basis of the above, we further propose a systematic procedure
to derive the equations of motion from the Noether current, and then this
procedure is extended to more general higher-order gravities endowed with the
Lagrangian encompassing additional terms of the covariant derivatives of the
Riemann tensor. To our knowledge, both the detailed expressions for field
equations and the Noether potential associated with such theories are first
given at a general level. All the results reveal that using the Noether current
to determine field equations establishes a straightforward connection between
the symmetry of the Lagrangian and the equations of motion and such a remedy
even can avoid calculating the derivative of the Lagrangian density with
respect to the metric.
| [
{
"created": "Tue, 20 Jun 2023 14:28:00 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Jun 2023 07:41:08 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Jul 2023 00:50:57 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Jul 2023 09:48:49 GMT",
"version": "v4"
},
{
"created": "Thu, 17 Aug 2023 01:23:03 GMT",
"version": "v5"
},
{
"created": "Mon, 16 Oct 2023 02:03:17 GMT",
"version": "v6"
},
{
"created": "Tue, 14 Nov 2023 08:37:29 GMT",
"version": "v7"
},
{
"created": "Tue, 25 Jun 2024 13:24:43 GMT",
"version": "v8"
}
] | 2024-06-26 | [
[
"Peng",
"Jun-Jin",
""
]
] | In the work (arXiv:1109.3846 [gr-qc]), to obtain a simple and economic formulation of field equations for generalised theories of gravity described by the Lagrangian $\sqrt{-g}L\big(g^{\alpha\beta},R_{\mu\nu\rho\sigma}\big)$, the key equality $\big(\partial L/\partial g^{\mu\nu}\big)_{R_{\alpha\beta\kappa\omega}} =2P_{\mu}^{~\lambda\rho\sigma}R_{\nu\lambda\rho\sigma}$ was derived. In this note, it is demonstrated that such an equality can be directly derived from an off-shell Noether current associated with an arbitrary vector field. As byproducts, a generalized Bianchi identity related to the divergence for the expression of field equations, together with the Noether potential, is obtained. On the basis of the above, we further propose a systematic procedure to derive the equations of motion from the Noether current, and then this procedure is extended to more general higher-order gravities endowed with the Lagrangian encompassing additional terms of the covariant derivatives of the Riemann tensor. To our knowledge, both the detailed expressions for field equations and the Noether potential associated with such theories are first given at a general level. All the results reveal that using the Noether current to determine field equations establishes a straightforward connection between the symmetry of the Lagrangian and the equations of motion and such a remedy even can avoid calculating the derivative of the Lagrangian density with respect to the metric. |
gr-qc/0306013 | Leonid Grishchuk | L. P. Grishchuk | Electromagnetic Generators and Detectors of Gravitational Waves | 7 pages including 1 figure; invited talk at the first conference on
High-Frequency Gravitational Waves, May 2003, The MITRE Corporation, McLean,
Virginia, USA | null | null | null | gr-qc astro-ph hep-ph hep-th | null | The renewed serious interest to possible practical applications of
gravitational waves is encouraging. Building on previous work, I am arguing
that the strong variable electromagnetic fields are appropriate systems for the
generation and detection of high-frequency gravitational waves (HFGW). The
advantages of electromagnetic systems are clearly seen in the proposed complete
laboratory experiment, where one has to ensure the efficiency of, both, the
process of generation and the process of detection of HFGW. Within the family
of electromagnetic systems, one still has a great variety of possible
geometrical configurations, classical and quantum states of the electromagnetic
field, detection strategies, etc. According to evaluations performed 30 years
ago, the gap between the HFGW laboratory signal and its level of detectability
is at least 4 orders of magnitude. Hopefully, new technologies of today can
remove this gap and can make the laboratory experiment feasible. The laboratory
experiment is bound to be expensive, but one should remember that a part of the
cost is likely to be reimbursed from the Nobel prize money ! Electromagnetic
systems seem also appropriate for the detection of high-frequency end of the
spectrum of relic gravitational waves. Although the current effort to observe
the stochastic background of relic gravitational waves is focused on the
opposite, very low-frequency, end of the spectrum, it would be extremely
valuable for fundamental science to detect, or put sensible upper limits on,
the high-frequency relic gravitational waves. I will briefly discuss the origin
of relic gravitational waves, the expected level of their high-frequency
signal, and the existing estimates of its detectability.
| [
{
"created": "Tue, 3 Jun 2003 14:48:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Grishchuk",
"L. P.",
""
]
] | The renewed serious interest to possible practical applications of gravitational waves is encouraging. Building on previous work, I am arguing that the strong variable electromagnetic fields are appropriate systems for the generation and detection of high-frequency gravitational waves (HFGW). The advantages of electromagnetic systems are clearly seen in the proposed complete laboratory experiment, where one has to ensure the efficiency of, both, the process of generation and the process of detection of HFGW. Within the family of electromagnetic systems, one still has a great variety of possible geometrical configurations, classical and quantum states of the electromagnetic field, detection strategies, etc. According to evaluations performed 30 years ago, the gap between the HFGW laboratory signal and its level of detectability is at least 4 orders of magnitude. Hopefully, new technologies of today can remove this gap and can make the laboratory experiment feasible. The laboratory experiment is bound to be expensive, but one should remember that a part of the cost is likely to be reimbursed from the Nobel prize money ! Electromagnetic systems seem also appropriate for the detection of high-frequency end of the spectrum of relic gravitational waves. Although the current effort to observe the stochastic background of relic gravitational waves is focused on the opposite, very low-frequency, end of the spectrum, it would be extremely valuable for fundamental science to detect, or put sensible upper limits on, the high-frequency relic gravitational waves. I will briefly discuss the origin of relic gravitational waves, the expected level of their high-frequency signal, and the existing estimates of its detectability. |
gr-qc/0507115 | Narayan Banerjee | Sudipta Das and Narayan Banerjee | An interacting scalar field and the recent cosmic acceleration | 10 pages, 2 figures | Gen.Rel.Grav. 38 (2006) 785-794 | 10.1007/s10714-006-0296-z | null | gr-qc | null | In this paper it is shown that the Brans - Dicke scalar field itself can
serve the purpose of providing an early deceleration and a late time
acceleration of the universe without any need of quintessence field if one
considers an interaction, i.e, transfer of energy between the dark matter and
the Brans - Dicke scalar field.
| [
{
"created": "Wed, 27 Jul 2005 12:59:29 GMT",
"version": "v1"
},
{
"created": "Fri, 19 May 2006 13:26:07 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Das",
"Sudipta",
""
],
[
"Banerjee",
"Narayan",
""
]
] | In this paper it is shown that the Brans - Dicke scalar field itself can serve the purpose of providing an early deceleration and a late time acceleration of the universe without any need of quintessence field if one considers an interaction, i.e, transfer of energy between the dark matter and the Brans - Dicke scalar field. |
1302.3470 | Maurice H. P. M. van Putten | Maurice H.P.M. van Putten | A holographic bound on the total number of computations in the visible
Universe | published version | IJMP-D, 24, 1550024 (2015) | 10.1142/S0218271815500248 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Information $I$ in holographic imaging of massive particles by star-like
screens is shown to represent the probability of detection based on their
propagator. Results are derived for screens in the shape of a plane, cube and
sphere from unitarity in the exponentially small transition probability for a
detection outside. We derive $I=2\pi \Delta\varphi$ in $\log2$ bits for the
imaging of a particle by a spherical screen at a relative de Broglie phase
$\Delta\varphi$. Encoding mass, charge, angular momentum or radiation requires
at minimum four bits. Minimal screens at maximal information density hereby
recover Reissner-Nordstr\"om and extremal Kerr black holes. Applied to the
visible Universe, the Hubble flow of galaxies through the cosmological event
horizon leaves $10^{121}$ computations in the future.
| [
{
"created": "Thu, 14 Feb 2013 16:58:43 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Aug 2014 03:04:11 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Mar 2015 11:05:34 GMT",
"version": "v3"
}
] | 2015-06-15 | [
[
"van Putten",
"Maurice H. P. M.",
""
]
] | Information $I$ in holographic imaging of massive particles by star-like screens is shown to represent the probability of detection based on their propagator. Results are derived for screens in the shape of a plane, cube and sphere from unitarity in the exponentially small transition probability for a detection outside. We derive $I=2\pi \Delta\varphi$ in $\log2$ bits for the imaging of a particle by a spherical screen at a relative de Broglie phase $\Delta\varphi$. Encoding mass, charge, angular momentum or radiation requires at minimum four bits. Minimal screens at maximal information density hereby recover Reissner-Nordstr\"om and extremal Kerr black holes. Applied to the visible Universe, the Hubble flow of galaxies through the cosmological event horizon leaves $10^{121}$ computations in the future. |
2204.13108 | Manuel D. Malaver | Manuel Malaver and Rajan Iyer | Analytical Model of Compact Star with a new version of Modified
Chaplygin Equation of State | 28 pages, 14 figures. arXiv admin note: text overlap with
arXiv:2106.09520 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper we found a new model for compact star with anisotropic matter
distribution considering the new version of Chaplygin fluid equation of state
of Errehymy and Daoud (2021). We specify the particular form of the metric
potential proposed for Thirukanesh and Ragel (2012) and generalized for Malaver
(2014) in order to integrate the Einstein`s field equations. The obtained model
satisfies all physical properties expected in a realistic star. The radial
pressure, energy density, metric coefficients, anisotropy and mass are well
defined and are regular in the stellar interior. The results of this research
can be useful in the development and description of new models of compact
structures.
| [
{
"created": "Wed, 27 Apr 2022 03:20:27 GMT",
"version": "v1"
}
] | 2022-04-29 | [
[
"Malaver",
"Manuel",
""
],
[
"Iyer",
"Rajan",
""
]
] | In this paper we found a new model for compact star with anisotropic matter distribution considering the new version of Chaplygin fluid equation of state of Errehymy and Daoud (2021). We specify the particular form of the metric potential proposed for Thirukanesh and Ragel (2012) and generalized for Malaver (2014) in order to integrate the Einstein`s field equations. The obtained model satisfies all physical properties expected in a realistic star. The radial pressure, energy density, metric coefficients, anisotropy and mass are well defined and are regular in the stellar interior. The results of this research can be useful in the development and description of new models of compact structures. |
2008.01395 | Andronikos Paliathanasis | Alex Giacomini, Genly Leon, Andronikos Paliathanasis and Supriya Pan | Dynamics of Quintessence in Generalized Uncertainty Principle | 16 pages, 7 figures | null | 10.1140/epjc/s10052-020-08508-4 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the quintessence scalar field model modified by the
Generalized Uncertainty Principle in the background of a spatially flat
homogeneous and isotropic universe. By performing a dynamical system analysis
we examine the nature of the critical points and their stability for two
potentials, one is the exponential potential and the other is a general
potential. In the case of an exponential potential, we find some new critical
points for this modified quintessence scenario that describe the de Sitter
universe, and these critical points do not appear in the standard quintessence
model with an exponential potential. This is one of the main results of this
work. Now for the general potential our analysis shows that the physical
properties of the critical points remain exactly the same as for the
exponential potential which means that within this modified quintessence
scenario all kind of potentials have same behaviour. This kind of result is
completely new in cosmology because with the change of the potential,
differences are usually expected in all respect.
| [
{
"created": "Tue, 4 Aug 2020 08:11:11 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Giacomini",
"Alex",
""
],
[
"Leon",
"Genly",
""
],
[
"Paliathanasis",
"Andronikos",
""
],
[
"Pan",
"Supriya",
""
]
] | We investigate the quintessence scalar field model modified by the Generalized Uncertainty Principle in the background of a spatially flat homogeneous and isotropic universe. By performing a dynamical system analysis we examine the nature of the critical points and their stability for two potentials, one is the exponential potential and the other is a general potential. In the case of an exponential potential, we find some new critical points for this modified quintessence scenario that describe the de Sitter universe, and these critical points do not appear in the standard quintessence model with an exponential potential. This is one of the main results of this work. Now for the general potential our analysis shows that the physical properties of the critical points remain exactly the same as for the exponential potential which means that within this modified quintessence scenario all kind of potentials have same behaviour. This kind of result is completely new in cosmology because with the change of the potential, differences are usually expected in all respect. |
1804.03912 | Fr\'ed\'eric Lamy | Pierre Bin\'etruy, Alexis Helou, Fr\'ed\'eric Lamy | Closed trapping horizons without singularity | 26 pages, 20 figures | Phys. Rev. D 98, 064058 (2018) | 10.1103/PhysRevD.98.064058 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In gravitational collapse leading to black hole formation, trapping horizons
typically develop inside the contracting matter. Classically, an ingoing
trapping horizon moves towards the centre where it reaches a curvature
singularity, while an outgoing horizon moves towards the surface of the star
where it becomes an isolated, null horizon. However, strong quantum effects at
high curvature close to the centre could modify the classical picture
substantially, e.g. by deflecting the ingoing horizon to larger radii, until it
eventually reunites with the outgoing horizon. We here analyse some existing
models of regular "black holes" of finite lifespan formed out of ingoing null
shells collapsing from $\mathscr{I}^-$, after giving general conditions for the
existence of (singularity-free) closed trapping horizons. We study the
energy-momentum tensor of such models by solving Einstein's equations in
reverse and give an explicit form of the metric to model a Hawking radiation
reaching $\mathscr{I}^+$. A major flaw of the models aiming at describing the
formation of black holes (with a Vaidya limit on $\mathscr{I}^-$) as well as
their evaporation is finally exhibited: they necessarily violate the null
energy condition up to $\mathscr{I}^-$, i.e. in a non-compact region of
spacetime.
| [
{
"created": "Wed, 11 Apr 2018 10:26:31 GMT",
"version": "v1"
}
] | 2018-10-03 | [
[
"Binétruy",
"Pierre",
""
],
[
"Helou",
"Alexis",
""
],
[
"Lamy",
"Frédéric",
""
]
] | In gravitational collapse leading to black hole formation, trapping horizons typically develop inside the contracting matter. Classically, an ingoing trapping horizon moves towards the centre where it reaches a curvature singularity, while an outgoing horizon moves towards the surface of the star where it becomes an isolated, null horizon. However, strong quantum effects at high curvature close to the centre could modify the classical picture substantially, e.g. by deflecting the ingoing horizon to larger radii, until it eventually reunites with the outgoing horizon. We here analyse some existing models of regular "black holes" of finite lifespan formed out of ingoing null shells collapsing from $\mathscr{I}^-$, after giving general conditions for the existence of (singularity-free) closed trapping horizons. We study the energy-momentum tensor of such models by solving Einstein's equations in reverse and give an explicit form of the metric to model a Hawking radiation reaching $\mathscr{I}^+$. A major flaw of the models aiming at describing the formation of black holes (with a Vaidya limit on $\mathscr{I}^-$) as well as their evaporation is finally exhibited: they necessarily violate the null energy condition up to $\mathscr{I}^-$, i.e. in a non-compact region of spacetime. |
2206.09632 | Aurelien Barrau | Cyril Renevey, Aur\'elien Barrau, Killian Martineau | Detailed analysis of the curvature bounce: background dynamics and
imprints in the CMB | null | null | 10.1140/epjc/s10052-022-10745-8 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If the spatial sections of the Universe are positively curved, extrapolating
the inflationary stage backward in time inevitably leads to a classical bounce.
This simple scenario, non-singular and free of exotic physics, deserves to be
investigated in details. The background dynamics exhibits interesting features
and is shown to be mostly insensitive to initial conditions as long as
observational consequences are considered. The primordial scalar power spectrum
is explicitly computed, for different inflaton potentials, and the subsequent
CMB temperature anisotropies are calculated. The results are compatible with
current measurements. Some deviations with respect to the standard paradigm can
however appear at large scales and we carefully disentangle what is associated
with the vacuum choice with what is more fundamentally due to the bounce
itself.
| [
{
"created": "Mon, 20 Jun 2022 08:30:38 GMT",
"version": "v1"
}
] | 2022-09-21 | [
[
"Renevey",
"Cyril",
""
],
[
"Barrau",
"Aurélien",
""
],
[
"Martineau",
"Killian",
""
]
] | If the spatial sections of the Universe are positively curved, extrapolating the inflationary stage backward in time inevitably leads to a classical bounce. This simple scenario, non-singular and free of exotic physics, deserves to be investigated in details. The background dynamics exhibits interesting features and is shown to be mostly insensitive to initial conditions as long as observational consequences are considered. The primordial scalar power spectrum is explicitly computed, for different inflaton potentials, and the subsequent CMB temperature anisotropies are calculated. The results are compatible with current measurements. Some deviations with respect to the standard paradigm can however appear at large scales and we carefully disentangle what is associated with the vacuum choice with what is more fundamentally due to the bounce itself. |
0907.3797 | Guillermo A. Mena Marugan | Guillermo A. Mena Marugan, Mercedes Martin-Benito | Hybrid Quantum Cosmology: Combining Loop and Fock Quantizations | 24 pages, published in International Journal of Modern Physics A,
Special Issue: Proceedings of the Second Workshop on Quantum Gravity and
Noncommutative Geometry (Lisbon, Portugal) | Int.J.Mod.Phys.A24:2820-2838,2009 | 10.1142/S0217751X09046187 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As a necessary step towards the extraction of realistic results from Loop
Quantum Cosmology, we analyze the physical consequences of including
inhomogeneities. We consider in detail the quantization of a gravitational
model in vacuo which possesses local degrees of freedom, namely, the linearly
polarized Gowdy cosmologies with the spatial topology of a three-torus. We
carry out a hybrid quantization which combines loop and Fock techniques. We
discuss the main aspects and results of this hybrid quantization, which include
the resolution of the cosmological singularity, the polymeric quantization of
the internal time, a rigorous definition of the quantum constraints and the
construction of their solutions, the Hilbert structure of the physical states,
and the recovery of a conventional Fock quantization for the inhomogeneities.
| [
{
"created": "Wed, 22 Jul 2009 08:33:47 GMT",
"version": "v1"
}
] | 2009-07-23 | [
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Martin-Benito",
"Mercedes",
""
]
] | As a necessary step towards the extraction of realistic results from Loop Quantum Cosmology, we analyze the physical consequences of including inhomogeneities. We consider in detail the quantization of a gravitational model in vacuo which possesses local degrees of freedom, namely, the linearly polarized Gowdy cosmologies with the spatial topology of a three-torus. We carry out a hybrid quantization which combines loop and Fock techniques. We discuss the main aspects and results of this hybrid quantization, which include the resolution of the cosmological singularity, the polymeric quantization of the internal time, a rigorous definition of the quantum constraints and the construction of their solutions, the Hilbert structure of the physical states, and the recovery of a conventional Fock quantization for the inhomogeneities. |
2203.05190 | Sobhan Kazempour | Sobhan Kazempour, Yuan-Chuan Zou, and Amin Rezaei Akbarieh | Analysis of accretion disk around a black hole in dRGT massive gravity | null | European Physical Journal C volume 82, Article number: 190 (2022) | 10.1140/epjc/s10052-022-10153-y | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We show the analysis of a thin accretion disk around a static and spherically
symmetric black hole in dRGT massive gravity. We present the accretion disk
analysis in a gravitational theory with a nonzero graviton mass. Also, we study
the event horizons of the black hole and we calculate the equations of motion
and effective potential. In the following, we obtain the specific energy,
specific angular momentum, and angular velocity of the particles which move in
circular orbits. In addition, we plot the effective potentials for two cases
and we show the locations of stable circular orbits. At last, we show the
possibility of constraining the parameter space of dRGT massive gravity by the
astrophysical gamma-ray bursts.
| [
{
"created": "Thu, 10 Mar 2022 06:59:54 GMT",
"version": "v1"
}
] | 2022-03-11 | [
[
"Kazempour",
"Sobhan",
""
],
[
"Zou",
"Yuan-Chuan",
""
],
[
"Akbarieh",
"Amin Rezaei",
""
]
] | We show the analysis of a thin accretion disk around a static and spherically symmetric black hole in dRGT massive gravity. We present the accretion disk analysis in a gravitational theory with a nonzero graviton mass. Also, we study the event horizons of the black hole and we calculate the equations of motion and effective potential. In the following, we obtain the specific energy, specific angular momentum, and angular velocity of the particles which move in circular orbits. In addition, we plot the effective potentials for two cases and we show the locations of stable circular orbits. At last, we show the possibility of constraining the parameter space of dRGT massive gravity by the astrophysical gamma-ray bursts. |
2305.05625 | Becca Ewing | Becca Ewing, Rachael Huxford, Divya Singh, Leo Tsukada, Chad Hanna,
Yun-Jing Huang, Prathamesh Joshi, Alvin K. Y. Li, Ryan Magee, Cody Messick,
Alex Pace, Anarya Ray, Surabhi Sachdev, Shio Sakon, Ron Tapia, Shomik
Adhicary, Pratyusava Baral, Amanda Baylor, Kipp Cannon, Sarah Caudill,
Sushant Sharma Chaudhary, Michael W. Coughlin, Bryce Cousins, Jolien D. E.
Creighton, Reed Essick, Heather Fong, Richard N. George, Patrick Godwin,
Reiko Harada, James Kennington, Soichiro Kuwahara, Duncan Meacher, Soichiro
Morisaki, Debnandini Mukherjee, Wanting Niu, Cort Posnansky, Andrew Toivonen,
Takuya Tsutsui, Koh Ueno, Aaron Viets, Leslie Wade, Madeline Wade, Gaurav
Waratkar | Performance of the low-latency GstLAL inspiral search towards LIGO,
Virgo, and KAGRA's fourth observing run | 19 pages, 21 figures | null | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | GstLAL is a stream-based matched-filtering search pipeline aiming at the
prompt discovery of gravitational waves from compact binary coalescences such
as the mergers of black holes and neutron stars. Over the past three
observation runs by the LIGO, Virgo, and KAGRA (LVK) collaboration, the GstLAL
search pipeline has participated in several tens of gravitational wave
discoveries. The fourth observing run (O4) is set to begin in May 2023 and is
expected to see the discovery of many new and interesting gravitational wave
signals which will inform our understanding of astrophysics and cosmology. We
describe the current configuration of the GstLAL low-latency search and show
its readiness for the upcoming observation run by presenting its performance on
a mock data challenge. The mock data challenge includes 40 days of LIGO
Hanford, LIGO Livingston, and Virgo strain data along with an injection
campaign in order to fully characterize the performance of the search. We find
an improved performance in terms of detection rate and significance estimation
as compared to that observed in the O3 online analysis. The improvements are
attributed to several incremental advances in the likelihood ratio ranking
statistic computation and the method of background estimation.
| [
{
"created": "Tue, 9 May 2023 17:10:06 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jul 2023 14:06:52 GMT",
"version": "v2"
}
] | 2023-07-14 | [
[
"Ewing",
"Becca",
""
],
[
"Huxford",
"Rachael",
""
],
[
"Singh",
"Divya",
""
],
[
"Tsukada",
"Leo",
""
],
[
"Hanna",
"Chad",
""
],
[
"Huang",
"Yun-Jing",
""
],
[
"Joshi",
"Prathamesh",
""
],
[
"Li",
"Alvin K. Y.",
""
],
[
"Magee",
"Ryan",
""
],
[
"Messick",
"Cody",
""
],
[
"Pace",
"Alex",
""
],
[
"Ray",
"Anarya",
""
],
[
"Sachdev",
"Surabhi",
""
],
[
"Sakon",
"Shio",
""
],
[
"Tapia",
"Ron",
""
],
[
"Adhicary",
"Shomik",
""
],
[
"Baral",
"Pratyusava",
""
],
[
"Baylor",
"Amanda",
""
],
[
"Cannon",
"Kipp",
""
],
[
"Caudill",
"Sarah",
""
],
[
"Chaudhary",
"Sushant Sharma",
""
],
[
"Coughlin",
"Michael W.",
""
],
[
"Cousins",
"Bryce",
""
],
[
"Creighton",
"Jolien D. E.",
""
],
[
"Essick",
"Reed",
""
],
[
"Fong",
"Heather",
""
],
[
"George",
"Richard N.",
""
],
[
"Godwin",
"Patrick",
""
],
[
"Harada",
"Reiko",
""
],
[
"Kennington",
"James",
""
],
[
"Kuwahara",
"Soichiro",
""
],
[
"Meacher",
"Duncan",
""
],
[
"Morisaki",
"Soichiro",
""
],
[
"Mukherjee",
"Debnandini",
""
],
[
"Niu",
"Wanting",
""
],
[
"Posnansky",
"Cort",
""
],
[
"Toivonen",
"Andrew",
""
],
[
"Tsutsui",
"Takuya",
""
],
[
"Ueno",
"Koh",
""
],
[
"Viets",
"Aaron",
""
],
[
"Wade",
"Leslie",
""
],
[
"Wade",
"Madeline",
""
],
[
"Waratkar",
"Gaurav",
""
]
] | GstLAL is a stream-based matched-filtering search pipeline aiming at the prompt discovery of gravitational waves from compact binary coalescences such as the mergers of black holes and neutron stars. Over the past three observation runs by the LIGO, Virgo, and KAGRA (LVK) collaboration, the GstLAL search pipeline has participated in several tens of gravitational wave discoveries. The fourth observing run (O4) is set to begin in May 2023 and is expected to see the discovery of many new and interesting gravitational wave signals which will inform our understanding of astrophysics and cosmology. We describe the current configuration of the GstLAL low-latency search and show its readiness for the upcoming observation run by presenting its performance on a mock data challenge. The mock data challenge includes 40 days of LIGO Hanford, LIGO Livingston, and Virgo strain data along with an injection campaign in order to fully characterize the performance of the search. We find an improved performance in terms of detection rate and significance estimation as compared to that observed in the O3 online analysis. The improvements are attributed to several incremental advances in the likelihood ratio ranking statistic computation and the method of background estimation. |
1001.4752 | James Phillips | Robert D. Reasenberg and James D. Phillips (Smithsonian Astrophysical
Observatory, Harvard-Smithsonian Center for Astrophysics) | A weak equivalence principle test on a suborbital rocket | To be published in Classical and Quantum Gravity. 14 pages, 6
figures. Further information available at http://www.cfa.harvard.edu/poem/ | null | 10.1088/0264-9381/27/9/095005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a Galilean test of the weak equivalence principle, to be
conducted during the free fall portion of a sounding rocket flight. The test of
a single pair of substances is aimed at a measurement uncertainty of sigma(eta)
< 10^-16 after averaging the results of eight separate drops. The weak
equivalence principle measurement is made with a set of four laser gauges that
are expected to achieve 0.1 pm Hz^-1/2. The discovery of a violation (eta not
equal to 0) would have profound implications for physics, astrophysics, and
cosmology.
| [
{
"created": "Tue, 26 Jan 2010 17:42:51 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Reasenberg",
"Robert D.",
"",
"Smithsonian Astrophysical\n Observatory, Harvard-Smithsonian Center for Astrophysics"
],
[
"Phillips",
"James D.",
"",
"Smithsonian Astrophysical\n Observatory, Harvard-Smithsonian Center for Astrophysics"
]
] | We describe a Galilean test of the weak equivalence principle, to be conducted during the free fall portion of a sounding rocket flight. The test of a single pair of substances is aimed at a measurement uncertainty of sigma(eta) < 10^-16 after averaging the results of eight separate drops. The weak equivalence principle measurement is made with a set of four laser gauges that are expected to achieve 0.1 pm Hz^-1/2. The discovery of a violation (eta not equal to 0) would have profound implications for physics, astrophysics, and cosmology. |
1912.01654 | Swagat Saurav Mishra | Swagat S. Mishra, Daniel M\"uller and Aleksey V. Toporensky | Generality of Starobinsky and Higgs inflation in the Jordan frame | 15 pages, 8 figures, additional text and references, typos corrected,
matches published version in PRD | Phys. Rev. D 102, 063523 (2020) | 10.1103/PhysRevD.102.063523 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the problem of generality of Starobinsky and Higgs inflation. The
known results obtained in the Einstein frame are generalized for the case of an
arbitrary initial energy of the scalar field. These results are compared with
the results obtained directly in the Jordan frame, which, to our knowledge, has
not been thoroughly explored in the literature previously. We demonstrate that
the qualitative picture of initial conditions zone in the $(\phi, \dot \phi)$
plane, which leads to sufficient amount of inflation, is quite similar for both
the frames in the case of Higgs inflation. For Starobinsky inflation, the
conformal transformation between the frames relates the geometrical variables
in the Jordan frame with the properties of an effective scalar field in the
Einstein frame. We show that the transformation $(H, R) \to (\phi, \dot \phi)$
is not regular everywhere, leading to some peculiarities in the zone of good
initial conditions in the $(H, R)$ plane.
| [
{
"created": "Tue, 3 Dec 2019 19:49:12 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 2020 17:19:41 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Jun 2021 07:26:09 GMT",
"version": "v3"
}
] | 2021-06-21 | [
[
"Mishra",
"Swagat S.",
""
],
[
"Müller",
"Daniel",
""
],
[
"Toporensky",
"Aleksey V.",
""
]
] | We revisit the problem of generality of Starobinsky and Higgs inflation. The known results obtained in the Einstein frame are generalized for the case of an arbitrary initial energy of the scalar field. These results are compared with the results obtained directly in the Jordan frame, which, to our knowledge, has not been thoroughly explored in the literature previously. We demonstrate that the qualitative picture of initial conditions zone in the $(\phi, \dot \phi)$ plane, which leads to sufficient amount of inflation, is quite similar for both the frames in the case of Higgs inflation. For Starobinsky inflation, the conformal transformation between the frames relates the geometrical variables in the Jordan frame with the properties of an effective scalar field in the Einstein frame. We show that the transformation $(H, R) \to (\phi, \dot \phi)$ is not regular everywhere, leading to some peculiarities in the zone of good initial conditions in the $(H, R)$ plane. |
gr-qc/9606024 | Eric Poisson | Eric Poisson | Measuring black-hole parameters and testing general relativity using
gravitational-wave data from space-based interferometers | ReVTeX, 16 pages, 5 postscript figures | Phys.Rev. D54 (1996) 5939-5953 | 10.1103/PhysRevD.54.5939 | null | gr-qc | null | Among the expected sources of gravitational waves for the Laser
Interferometer Space Antenna (LISA) is the capture of solar-mass compact stars
by massive black holes residing in galactic centers. We construct a simple
model for such a capture, in which the compact star moves freely on a circular
orbit in the equatorial plane of the massive black hole. We consider the
gravitational waves emitted during the late stages of orbital evolution,
shortly before the orbiting mass reaches the innermost stable circular orbit.
We construct a simple model for the gravitational-wave signal, in which the
phasing of the waves plays the dominant role. The signal's behavior depends on
a number of parameters, including $\mu$, the mass of the orbiting star, $M$,
the mass of the central black hole, and $J$, the black hole's angular momentum.
We calculate, using our simplified model, and in the limit of large
signal-to-noise ratio, the accuracy with which these quantities can be
estimated during a gravitational-wave measurement. Our simplified model also
suggests a method for experimentally testing the strong-field predictions of
general relativity.
| [
{
"created": "Wed, 12 Jun 1996 17:30:10 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Poisson",
"Eric",
""
]
] | Among the expected sources of gravitational waves for the Laser Interferometer Space Antenna (LISA) is the capture of solar-mass compact stars by massive black holes residing in galactic centers. We construct a simple model for such a capture, in which the compact star moves freely on a circular orbit in the equatorial plane of the massive black hole. We consider the gravitational waves emitted during the late stages of orbital evolution, shortly before the orbiting mass reaches the innermost stable circular orbit. We construct a simple model for the gravitational-wave signal, in which the phasing of the waves plays the dominant role. The signal's behavior depends on a number of parameters, including $\mu$, the mass of the orbiting star, $M$, the mass of the central black hole, and $J$, the black hole's angular momentum. We calculate, using our simplified model, and in the limit of large signal-to-noise ratio, the accuracy with which these quantities can be estimated during a gravitational-wave measurement. Our simplified model also suggests a method for experimentally testing the strong-field predictions of general relativity. |
2011.12122 | Alexandre Toubiana | Alexandre Toubiana, Stanislav Babak, Enrico Barausse and Luis Lehner | Modeling gravitational waves from exotic compact objects | 11 pages (13 with appendix) Matches the version published in PRD | Phys. Rev. D 103, 064042 (2021) | 10.1103/PhysRevD.103.064042 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | Exotic compact objects can be difficult to distinguish from black holes in
the inspiral phase of the binaries observed by gravitational-wave detectors,
but significant differences may be present in the merger and post-merger
signal. We introduce a toy model capturing the salient features of binaries of
exotic compact objects with compactness below $0.2$, which do not collapse
promptly following the merger. We use it to assess their detectability with
current and future detectors, and whether they can be distinguished from black
hole binaries. We find that the Einstein Telescope (LISA) could observe exotic
binaries with total mass $\mathcal{O}(10^2) \ M_{\odot}$ ($10^4-10^6 \
M_{\odot}$), and potentially distinguish them from black hole binaries,
throughout the observable Universe, as compared to $z\lesssim 1$ for Advanced
LIGO. Moreover, we show that using standard black hole templates for detection
could lead to a loss of up to $60\%$ in the signal-to-noise ratio, greatly
reducing our chances of observing these signals. Finally, we estimate that if
the loudest events in the O1/O2 catalog released by the LIGO/Virgo
collaboration were ECO binaries as the ones considered in this paper, they
would have left a post-merger signal detectable with model-agnostic searches,
making this hypothesis unlikely.
| [
{
"created": "Tue, 24 Nov 2020 14:30:15 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Apr 2021 18:48:38 GMT",
"version": "v2"
}
] | 2021-04-13 | [
[
"Toubiana",
"Alexandre",
""
],
[
"Babak",
"Stanislav",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Lehner",
"Luis",
""
]
] | Exotic compact objects can be difficult to distinguish from black holes in the inspiral phase of the binaries observed by gravitational-wave detectors, but significant differences may be present in the merger and post-merger signal. We introduce a toy model capturing the salient features of binaries of exotic compact objects with compactness below $0.2$, which do not collapse promptly following the merger. We use it to assess their detectability with current and future detectors, and whether they can be distinguished from black hole binaries. We find that the Einstein Telescope (LISA) could observe exotic binaries with total mass $\mathcal{O}(10^2) \ M_{\odot}$ ($10^4-10^6 \ M_{\odot}$), and potentially distinguish them from black hole binaries, throughout the observable Universe, as compared to $z\lesssim 1$ for Advanced LIGO. Moreover, we show that using standard black hole templates for detection could lead to a loss of up to $60\%$ in the signal-to-noise ratio, greatly reducing our chances of observing these signals. Finally, we estimate that if the loudest events in the O1/O2 catalog released by the LIGO/Virgo collaboration were ECO binaries as the ones considered in this paper, they would have left a post-merger signal detectable with model-agnostic searches, making this hypothesis unlikely. |
1712.02992 | Tim Dietrich | Tim Dietrich, Sebastiano Bernuzzi, Bernd Bruegmann, Maximiliano
Ujevic, Wolfgang Tichy | Numerical Relativity Simulations of Precessing Binary Neutron Star
Mergers | 12 pages, 10 figures, comments are welcome | Phys. Rev. D 97, 064002 (2018) | 10.1103/PhysRevD.97.064002 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first set of numerical relativity simulations of binary
neutron mergers that include spin precession effects and are evolved with
multiple resolutions. Our simulations employ consistent initial data in general
relativity with different spin configurations and dimensionless spin magnitudes
$\sim 0.1$. They start at a gravitational-wave frequency of $\sim392$~Hz and
cover more than $1$ precession period and about 15 orbits up to merger. We
discuss the spin precession dynamics by analyzing coordinate trajectories,
quasi-local spin measurements, and energetics, by comparing spin aligned,
antialigned, and irrotational configurations. Gravitational waveforms from
different spin configuration are compared by calculating the mismatch between
pairs of waveforms in the late inspiral. We find that precession effects are
not distinguishable from nonprecessing configurations with aligned spins for
approximately face-on binaries, while the latter are distinguishable from a
nonspinning configurations. Spin precession effects are instead clearly visible
for approximately edge-on binaries.
For the parameters considered here, precession does not significantly affect
the characteristic postmerger gravitational-wave frequencies nor the mass
ejection. Our results pave the way for the modeling of spin precession effects
in the gravitational waveform from binary neutron star events.
| [
{
"created": "Fri, 8 Dec 2017 09:32:11 GMT",
"version": "v1"
}
] | 2018-03-14 | [
[
"Dietrich",
"Tim",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Ujevic",
"Maximiliano",
""
],
[
"Tichy",
"Wolfgang",
""
]
] | We present the first set of numerical relativity simulations of binary neutron mergers that include spin precession effects and are evolved with multiple resolutions. Our simulations employ consistent initial data in general relativity with different spin configurations and dimensionless spin magnitudes $\sim 0.1$. They start at a gravitational-wave frequency of $\sim392$~Hz and cover more than $1$ precession period and about 15 orbits up to merger. We discuss the spin precession dynamics by analyzing coordinate trajectories, quasi-local spin measurements, and energetics, by comparing spin aligned, antialigned, and irrotational configurations. Gravitational waveforms from different spin configuration are compared by calculating the mismatch between pairs of waveforms in the late inspiral. We find that precession effects are not distinguishable from nonprecessing configurations with aligned spins for approximately face-on binaries, while the latter are distinguishable from a nonspinning configurations. Spin precession effects are instead clearly visible for approximately edge-on binaries. For the parameters considered here, precession does not significantly affect the characteristic postmerger gravitational-wave frequencies nor the mass ejection. Our results pave the way for the modeling of spin precession effects in the gravitational waveform from binary neutron star events. |
2404.03345 | D\'ebora Aguiar Gomes | Aneta Wojnar, D\'ebora Aguiar Gomes | Bose and Fermi gases in metric-affine gravity and linear Generalized
Uncertainty Principle | 8 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We examine the relationship between Palatini-like theories of gravity and
models incorporating linear generalized uncertainty principles. Additionally,
we delve into the thermodynamics of systems comprising both Bose and Fermi
gases. Our analysis encompasses the equations of state for various systems,
including general Fermi gases, degenerate Fermi gases, Boltzmann gases, Bose
gases such as phonons and photons, as well as Bose-Einstein condensates and
liquid helium.
| [
{
"created": "Thu, 4 Apr 2024 10:21:24 GMT",
"version": "v1"
}
] | 2024-04-05 | [
[
"Wojnar",
"Aneta",
""
],
[
"Gomes",
"Débora Aguiar",
""
]
] | We examine the relationship between Palatini-like theories of gravity and models incorporating linear generalized uncertainty principles. Additionally, we delve into the thermodynamics of systems comprising both Bose and Fermi gases. Our analysis encompasses the equations of state for various systems, including general Fermi gases, degenerate Fermi gases, Boltzmann gases, Bose gases such as phonons and photons, as well as Bose-Einstein condensates and liquid helium. |
2405.19407 | Bassel Saleh | Bassel Saleh, Aaron Zimmerman, Peng Chen, Omar Ghattas | Tempered Multifidelity Importance Sampling for Gravitational Wave
Parameter Estimation | 19 pages, 10 figures, 1 table | null | null | null | gr-qc astro-ph.IM stat.ME | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Estimating the parameters of compact binaries which coalesce and produce
gravitational waves is a challenging Bayesian inverse problem.
Gravitational-wave parameter estimation lies within the class of multifidelity
problems, where a variety of models with differing assumptions, levels of
fidelity, and computational cost are available for use in inference. In an
effort to accelerate the solution of a Bayesian inverse problem, cheaper
surrogates for the best models may be used to reduce the cost of likelihood
evaluations when sampling the posterior. Importance sampling can then be used
to reweight these samples to represent the true target posterior, incurring a
reduction in the effective sample size. In cases when the problem is high
dimensional, or when the surrogate model produces a poor approximation of the
true posterior, this reduction in effective samples can be dramatic and render
multifidelity importance sampling ineffective. We propose a novel method of
tempered multifidelity importance sampling in order to remedy this issue. With
this method the biasing distribution produced by the low-fidelity model is
tempered, allowing for potentially better overlap with the target distribution.
There is an optimal temperature which maximizes the efficiency in this setting,
and we propose a low-cost strategy for approximating this optimal temperature
using samples from the untempered distribution. In this paper, we motivate this
method by applying it to Gaussian target and biasing distributions. Finally, we
apply it to a series of problems in gravitational wave parameter estimation and
demonstrate improved efficiencies when applying the method to real
gravitational wave detections.
| [
{
"created": "Wed, 29 May 2024 18:00:02 GMT",
"version": "v1"
}
] | 2024-05-31 | [
[
"Saleh",
"Bassel",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Chen",
"Peng",
""
],
[
"Ghattas",
"Omar",
""
]
] | Estimating the parameters of compact binaries which coalesce and produce gravitational waves is a challenging Bayesian inverse problem. Gravitational-wave parameter estimation lies within the class of multifidelity problems, where a variety of models with differing assumptions, levels of fidelity, and computational cost are available for use in inference. In an effort to accelerate the solution of a Bayesian inverse problem, cheaper surrogates for the best models may be used to reduce the cost of likelihood evaluations when sampling the posterior. Importance sampling can then be used to reweight these samples to represent the true target posterior, incurring a reduction in the effective sample size. In cases when the problem is high dimensional, or when the surrogate model produces a poor approximation of the true posterior, this reduction in effective samples can be dramatic and render multifidelity importance sampling ineffective. We propose a novel method of tempered multifidelity importance sampling in order to remedy this issue. With this method the biasing distribution produced by the low-fidelity model is tempered, allowing for potentially better overlap with the target distribution. There is an optimal temperature which maximizes the efficiency in this setting, and we propose a low-cost strategy for approximating this optimal temperature using samples from the untempered distribution. In this paper, we motivate this method by applying it to Gaussian target and biasing distributions. Finally, we apply it to a series of problems in gravitational wave parameter estimation and demonstrate improved efficiencies when applying the method to real gravitational wave detections. |
2302.10482 | Tao Zhu | Jian-Ming Yan, Cheng Liu, Tao Zhu, Qiang Wu, and Anzhong Wang | Observational tests of quantum extension of Schwarzschild spacetime in
loop quantum gravity with stars in the galactic center | 12 pages, 6 figures | Phys. Rev. D 107, 084043 (2023) | 10.1103/PhysRevD.107.084043 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we use the publicly available observational data of 17 stellar
stars orbiting Sgr A* to test the quantum extension of Schwarzschild spacetime
in loop quantum gravity (LQG). For our purpose, we transform the geodesical
evolution of a massive particle in the quantum-extended Schwarzschild black
hole to the perturbed Kepler problem and calculate the effects of LQG on the
pericentre advance of the stellar stars. With these effects, one is able to
compare them with the publicly available astrometric and spectroscopic data of
stellar stars in the galactic center. We perform Monte Carlo Markov Chain
(MCMC) simulations to probe the possible LQG effects on the orbit of S-stars.
No significant evidence of the quantum-extended Schwarzschild black hole from
LQG is found. Among the posterior analyses of 17 S-stars, the result of S2
gives the strongest bound on the LQG parameter $A_\lambda$, which places an
upper bound at 95\% confidence level on $A_\lambda$ to be $A_\lambda < 0.302$.
| [
{
"created": "Tue, 21 Feb 2023 07:08:59 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Apr 2023 04:01:02 GMT",
"version": "v2"
}
] | 2023-05-02 | [
[
"Yan",
"Jian-Ming",
""
],
[
"Liu",
"Cheng",
""
],
[
"Zhu",
"Tao",
""
],
[
"Wu",
"Qiang",
""
],
[
"Wang",
"Anzhong",
""
]
] | In this paper, we use the publicly available observational data of 17 stellar stars orbiting Sgr A* to test the quantum extension of Schwarzschild spacetime in loop quantum gravity (LQG). For our purpose, we transform the geodesical evolution of a massive particle in the quantum-extended Schwarzschild black hole to the perturbed Kepler problem and calculate the effects of LQG on the pericentre advance of the stellar stars. With these effects, one is able to compare them with the publicly available astrometric and spectroscopic data of stellar stars in the galactic center. We perform Monte Carlo Markov Chain (MCMC) simulations to probe the possible LQG effects on the orbit of S-stars. No significant evidence of the quantum-extended Schwarzschild black hole from LQG is found. Among the posterior analyses of 17 S-stars, the result of S2 gives the strongest bound on the LQG parameter $A_\lambda$, which places an upper bound at 95\% confidence level on $A_\lambda$ to be $A_\lambda < 0.302$. |
1201.0005 | Alexey Krugly | Alexey L. Krugly | The dynamics of binary alternatives for a discrete pregeometry | 13 pages, 9 figures, work presented at the "International conference
on theoretical physics 2011" held on 20-23 June 2011 at the Moscow State Open
University, Moscow, Russia | in Theoretical physics, Proceeding of the international
conference, 20-23 June 2011, State Open University, Moscow, Russia, pp.
16-29, State Open University press, Moscow, 2012 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A particular case of a causal set is considered that is a directed dyadic
acyclic graph. This is a model of a discrete pregeometry on a microscopic
scale. The dynamics is a stochastic sequential growth of the graph. New
vertexes of the graph are added one by one. The probability of each step
depends on the structure of existed graph. The particular case of dynamics is
based on binary alternatives. Each directed path is considered as a sequence of
outcomes of binary alternatives. The probabilities of a stochastic sequential
growth are functions of these paths. The goal is to describe physical objects
as some self-organized structures of the graph. A problem to find
self-organized structures is discussed.
| [
{
"created": "Wed, 28 Dec 2011 02:29:10 GMT",
"version": "v1"
}
] | 2012-10-12 | [
[
"Krugly",
"Alexey L.",
""
]
] | A particular case of a causal set is considered that is a directed dyadic acyclic graph. This is a model of a discrete pregeometry on a microscopic scale. The dynamics is a stochastic sequential growth of the graph. New vertexes of the graph are added one by one. The probability of each step depends on the structure of existed graph. The particular case of dynamics is based on binary alternatives. Each directed path is considered as a sequence of outcomes of binary alternatives. The probabilities of a stochastic sequential growth are functions of these paths. The goal is to describe physical objects as some self-organized structures of the graph. A problem to find self-organized structures is discussed. |
1911.09690 | Merced Montesinos | Merced Montesinos, Jorge Romero, Mariano Celada | Canonical analysis of Holst action without second-class constraints | Paper's title was changed, expanded analysis, notation was changed a
bit, added references, corrected typos | Phys. Rev. D 101, 084003 (2020) | 10.1103/PhysRevD.101.084003 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform the canonical analysis of the Holst action for general relativity
with a cosmological constant without introducing second-class constraints. Our
approach consists in identifying the dynamical and nondynamical parts of the
involved variables from the very outset. After integrating out the nondynamical
variables associated with the connection, we obtain the description of phase
space in terms of manifestly $SO(3,1)$ [or $SO(4)$, depending on the signature]
covariant canonical variables and first-class constraints only. We impose the
time gauge on them and show that the Ashtekar-Barbero formulation of general
relativity emerges. Later, we discuss a family of canonical transformations
that allows us to construct new $SO(3,1)$ [or $SO(4)$] covariant canonical
variables for the phase space of the theory and compare them with the ones
already reported in the literature, pointing out the presence of a set of
canonical variables not considered before. Finally, we resort to the time gauge
again and find that the theory, when written in terms of the new canonical
variables, either collapses to the $SO(3)$ ADM formalism or to the
Ashtekar-Barbero formalism with a rescaled Immirzi parameter.
| [
{
"created": "Thu, 21 Nov 2019 19:00:12 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Apr 2020 18:04:14 GMT",
"version": "v2"
}
] | 2020-04-08 | [
[
"Montesinos",
"Merced",
""
],
[
"Romero",
"Jorge",
""
],
[
"Celada",
"Mariano",
""
]
] | We perform the canonical analysis of the Holst action for general relativity with a cosmological constant without introducing second-class constraints. Our approach consists in identifying the dynamical and nondynamical parts of the involved variables from the very outset. After integrating out the nondynamical variables associated with the connection, we obtain the description of phase space in terms of manifestly $SO(3,1)$ [or $SO(4)$, depending on the signature] covariant canonical variables and first-class constraints only. We impose the time gauge on them and show that the Ashtekar-Barbero formulation of general relativity emerges. Later, we discuss a family of canonical transformations that allows us to construct new $SO(3,1)$ [or $SO(4)$] covariant canonical variables for the phase space of the theory and compare them with the ones already reported in the literature, pointing out the presence of a set of canonical variables not considered before. Finally, we resort to the time gauge again and find that the theory, when written in terms of the new canonical variables, either collapses to the $SO(3)$ ADM formalism or to the Ashtekar-Barbero formalism with a rescaled Immirzi parameter. |
2205.06962 | Che-Yu Chen | Che-Yu Chen | Testing black hole equatorial reflection symmetry using Sgr A* shadow
images | 15 pages, 3 figures, updated to match the published version | Phys. Rev. D 106 (2022) 044009 | 10.1103/PhysRevD.106.044009 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recently released images of the supermassive black holes in the M87
galaxy and the galaxy of our own make probing black hole spacetimes and testing
general relativity (GR) possible. The violation of equatorial reflection
symmetry of black hole spacetimes is clearly a smoking gun of physics beyond
GR. In this paper, we place constraints on the violation of black hole
reflection symmetry using the bounds on the ring size of the Sgr A* black hole
images, which are consistent with the critical curve radius predicted in GR
within $\sim10\%$. Adopting a theory-agnostic framework, we consider a
Kerr-like metric in which the violation of reflection symmetry is parametrized
by a single parameter, without altering the multipoles of the black hole. The
critical curves are always vertically symmetric due to the existence of hidden
symmetry associated with the Killing tensor, even though the spacetime is
reflection asymmetric. We find that the size of critical curves is sensitive to
the amount of reflection symmetry being violated, and place the first
constraints on the parameter space of the model using the Sgr A* images.
| [
{
"created": "Sat, 14 May 2022 04:18:51 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Aug 2022 18:40:30 GMT",
"version": "v2"
}
] | 2022-08-04 | [
[
"Chen",
"Che-Yu",
""
]
] | The recently released images of the supermassive black holes in the M87 galaxy and the galaxy of our own make probing black hole spacetimes and testing general relativity (GR) possible. The violation of equatorial reflection symmetry of black hole spacetimes is clearly a smoking gun of physics beyond GR. In this paper, we place constraints on the violation of black hole reflection symmetry using the bounds on the ring size of the Sgr A* black hole images, which are consistent with the critical curve radius predicted in GR within $\sim10\%$. Adopting a theory-agnostic framework, we consider a Kerr-like metric in which the violation of reflection symmetry is parametrized by a single parameter, without altering the multipoles of the black hole. The critical curves are always vertically symmetric due to the existence of hidden symmetry associated with the Killing tensor, even though the spacetime is reflection asymmetric. We find that the size of critical curves is sensitive to the amount of reflection symmetry being violated, and place the first constraints on the parameter space of the model using the Sgr A* images. |
gr-qc/9605066 | Fernando Barbero | J. Fernando Barbero G. (LAEFF, Madrid, Spain) | From Euclidean to Lorentzian General Relativity: The Real Way | 20 pages uuencoded gzipped tar format. Accepted in Phys. Rev. D. Some
references added | Phys.Rev.D54:1492-1499,1996 | 10.1103/PhysRevD.54.1492 | LAEFF-95/25 | gr-qc | null | We study in this paper a new approach to the problem of relating solutions to
the Einstein field equations with Riemannian and Lorentzian signatures. The
procedure can be thought of as a "real Wick rotation". We give a modified
action for general relativity, depending on two real parameters, that can be
used to control the signature of the solutions to the field equations. We show
how this procedure works for the Schwarzschild metric and discuss some possible
applications of the formalism in the context of signature change, the problem
of time, black hole thermodynamics...
| [
{
"created": "Wed, 29 May 1996 15:37:22 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jun 1996 14:24:13 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"G.",
"J. Fernando Barbero",
"",
"LAEFF, Madrid, Spain"
]
] | We study in this paper a new approach to the problem of relating solutions to the Einstein field equations with Riemannian and Lorentzian signatures. The procedure can be thought of as a "real Wick rotation". We give a modified action for general relativity, depending on two real parameters, that can be used to control the signature of the solutions to the field equations. We show how this procedure works for the Schwarzschild metric and discuss some possible applications of the formalism in the context of signature change, the problem of time, black hole thermodynamics... |
2010.16086 | Shailesh Kumar | Srijit Bhattacharjee, Shailesh Kumar and Arpan Bhattacharyya | Displacement memory effect near the horizon of black holes | V3: 28 pages, 1 figure, 1 reference added, and Substantial changes to
the texts, matches with the version to appear in Journal of High Energy
Physics | JHEP 03 (2021) 134 | 10.1007/JHEP03(2021)134 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the displacement memory effect and its connection with the
extended-BMS symmetries near the horizon of black holes. We show there is a
permanent shift in the geodesic deviation vector relating two nearby timelike
geodesics placed close to the horizon of black holes, upon the passage of
gravitational waves. We also relate this memory effect with the asymptotic
symmetries near the horizon of asymptotic black hole spacetimes. The shift of
the relative position of the detectors is shown to be induced by a combination
of BMS generators near the horizon. The displacement memory effect near the
horizon possesses similarities to the same obtained in the far region.
| [
{
"created": "Fri, 30 Oct 2020 05:53:12 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2020 18:33:26 GMT",
"version": "v2"
},
{
"created": "Sat, 6 Feb 2021 04:47:56 GMT",
"version": "v3"
}
] | 2021-03-16 | [
[
"Bhattacharjee",
"Srijit",
""
],
[
"Kumar",
"Shailesh",
""
],
[
"Bhattacharyya",
"Arpan",
""
]
] | We study the displacement memory effect and its connection with the extended-BMS symmetries near the horizon of black holes. We show there is a permanent shift in the geodesic deviation vector relating two nearby timelike geodesics placed close to the horizon of black holes, upon the passage of gravitational waves. We also relate this memory effect with the asymptotic symmetries near the horizon of asymptotic black hole spacetimes. The shift of the relative position of the detectors is shown to be induced by a combination of BMS generators near the horizon. The displacement memory effect near the horizon possesses similarities to the same obtained in the far region. |
gr-qc/0204086 | Edward Malec | Janusz Karkowski, Edward Malec and Zdobyslaw Swierczynski | Schwarzschild black holes and propagation of electromagnetic and
gravitational waves | 3 figures eps | Acta Phys.Polon. B32 (2001) 3593-3603 | null | null | gr-qc | null | Disturbing of a spacetime geometry may result in the appearance of an
oscillating and damped radiation - the so-called quasinormal modes. Their
periods of oscillations and damping coefficients carry unique information about
the mass and the angular momentum, that would allow one to identify the source
of the gravitational field. In this talk we present recent bounds on the
diffused energy, applicable to the Schwarzschild spacetime, that give also
rough estimates of the energy of excited quasinormal modes.
| [
{
"created": "Mon, 29 Apr 2002 12:26:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Karkowski",
"Janusz",
""
],
[
"Malec",
"Edward",
""
],
[
"Swierczynski",
"Zdobyslaw",
""
]
] | Disturbing of a spacetime geometry may result in the appearance of an oscillating and damped radiation - the so-called quasinormal modes. Their periods of oscillations and damping coefficients carry unique information about the mass and the angular momentum, that would allow one to identify the source of the gravitational field. In this talk we present recent bounds on the diffused energy, applicable to the Schwarzschild spacetime, that give also rough estimates of the energy of excited quasinormal modes. |
2405.02380 | Quentin Ansel | Quentin Ansel | Emergent gravity from the correlation of spin-$\tfrac{1}{2}$ systems
coupled with a scalar field | null | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | This paper introduces several ideas of emergent gravity, which come from a
system similar to an ensemble of quantum spin-$\tfrac{1}{2}$ particles. To
derive a physically relevant theory, the model is constructed by quantizing a
scalar field in curved space-time. The quantization is based on a classical
discretization of the system, but contrary to famous approaches, like loop
quantum gravity or causal triangulation, a Monte-Carlo based approach is used
instead of a simplicial approximation of the space-time manifold. This avoids
conceptual issues related to the choice of the lattice. Moreover, this allows
us to easily encode the geometric structures of space, given by the geodesic
length between points, into the mean value of a correlation operator between
two spin-like systems. Numerical investigations show the relevance of the
approach, and the presence of two regimes: a classical and a quantum regime.
The latter is obtained when the density of points reaches a given threshold.
Finally, a multi-scale analysis is given, where the classical model is
recovered from the full quantum one. Each step of the classical limit is
illustrated with numerical computations, showing the very good convergence
towards the classical limit and the computational efficiency of the theory.
| [
{
"created": "Fri, 3 May 2024 14:34:48 GMT",
"version": "v1"
}
] | 2024-05-07 | [
[
"Ansel",
"Quentin",
""
]
] | This paper introduces several ideas of emergent gravity, which come from a system similar to an ensemble of quantum spin-$\tfrac{1}{2}$ particles. To derive a physically relevant theory, the model is constructed by quantizing a scalar field in curved space-time. The quantization is based on a classical discretization of the system, but contrary to famous approaches, like loop quantum gravity or causal triangulation, a Monte-Carlo based approach is used instead of a simplicial approximation of the space-time manifold. This avoids conceptual issues related to the choice of the lattice. Moreover, this allows us to easily encode the geometric structures of space, given by the geodesic length between points, into the mean value of a correlation operator between two spin-like systems. Numerical investigations show the relevance of the approach, and the presence of two regimes: a classical and a quantum regime. The latter is obtained when the density of points reaches a given threshold. Finally, a multi-scale analysis is given, where the classical model is recovered from the full quantum one. Each step of the classical limit is illustrated with numerical computations, showing the very good convergence towards the classical limit and the computational efficiency of the theory. |
gr-qc/0207125 | Stoytcho Yazadjiev | Stoytcho Yazadjiev, Ventseslav Rizov | Singularity free cosmological solutions of Einstein-Maxwell equations | 8 pages,latex; v2 some typos corrected | Mod.Phys.Lett. A18 (2003) 2555-2562 | 10.1142/S0217732303012271 | null | gr-qc | null | We report on a new two-parameter class of cosmological solutions to the
Einstein-Maxwell equations. The solutions have everywhere regular curvature
invariants. We prove that the solutions are geodesically complete and globally
hyperbolic.
| [
{
"created": "Wed, 31 Jul 2002 18:00:41 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Aug 2002 07:50:42 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Yazadjiev",
"Stoytcho",
""
],
[
"Rizov",
"Ventseslav",
""
]
] | We report on a new two-parameter class of cosmological solutions to the Einstein-Maxwell equations. The solutions have everywhere regular curvature invariants. We prove that the solutions are geodesically complete and globally hyperbolic. |
1112.2311 | Isabeau Pr\'emont-Schwarz | Isabeau Pr\'emont-Schwarz | Experimenting with Quantum Fields in Curved Spacetime in the Lab | 5 pages, to be published in the proceedings of LOOPS '11 in Journal
of Physics: Conference Series | null | null | null | gr-qc cond-mat.mes-hall cond-mat.mtrl-sci | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we will investigate how one can create emergent curved
spacetimes by locally tuning the coupling constants of condensed matter
systems. In the continuum limit we thus obtain continuous effective quantum
fields living on curved spacetimes. In particular, using Stingnet condensates
we can obtain effective electromagnetism. We will show for example how we
obtain quantum electrodynamics in a blackhole (Schwarzschild) spacetime.
| [
{
"created": "Sun, 11 Dec 2011 00:01:22 GMT",
"version": "v1"
}
] | 2011-12-13 | [
[
"Prémont-Schwarz",
"Isabeau",
""
]
] | In this paper we will investigate how one can create emergent curved spacetimes by locally tuning the coupling constants of condensed matter systems. In the continuum limit we thus obtain continuous effective quantum fields living on curved spacetimes. In particular, using Stingnet condensates we can obtain effective electromagnetism. We will show for example how we obtain quantum electrodynamics in a blackhole (Schwarzschild) spacetime. |
gr-qc/0008052 | Martin Bojowald | Martin Bojowald | Loop Quantum Cosmology III: Wheeler-DeWitt Operators | 19 pages | Class.Quant.Grav. 18 (2001) 1055-1070 | 10.1088/0264-9381/18/6/307 | PITHA 00/17 | gr-qc hep-th | null | In the framework of loop quantum cosmology anomaly free quantizations of the
Hamiltonian constraint for Bianchi class A, locally rotationally symmetric and
isotropic models are given. Basic ideas of the construction in (non-symmetric)
loop quantum gravity can be used, but there are also further inputs because the
special structure of symmetric models has to be respected by operators. In
particular, the basic building blocks of the homogeneous models are point
holonomies rather than holonomies necessitating a new regularization procedure.
In this respect, our construction is applicable also for other
(non-homogeneous) symmetric models, e.g. the spherically symmetric one.
| [
{
"created": "Tue, 22 Aug 2000 10:18:31 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bojowald",
"Martin",
""
]
] | In the framework of loop quantum cosmology anomaly free quantizations of the Hamiltonian constraint for Bianchi class A, locally rotationally symmetric and isotropic models are given. Basic ideas of the construction in (non-symmetric) loop quantum gravity can be used, but there are also further inputs because the special structure of symmetric models has to be respected by operators. In particular, the basic building blocks of the homogeneous models are point holonomies rather than holonomies necessitating a new regularization procedure. In this respect, our construction is applicable also for other (non-homogeneous) symmetric models, e.g. the spherically symmetric one. |
gr-qc/0310008 | Michael Kuchiev | M. Yu. Kuchiev | Reflection from black holes | null | null | null | null | gr-qc astro-ph hep-th | null | Black holes are presumed to have an ideal ability to absorb and keep matter.
Whatever comes close to the event horizon, a boundary separating the inside
region of a black hole from the outside world, inevitably goes in and remains
inside forever. This work shows, however, that quantum corrections make
possible a surprising process, reflection: a particle can bounce back from the
event horizon. For low energy particles this process is efficient, black holes
behave not as holes, but as mirrors, which changes our perception of their
physical nature. Possible ways for observations of the reflection and its
relation to the Hawking radiation process are outlined.
| [
{
"created": "Thu, 2 Oct 2003 00:36:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kuchiev",
"M. Yu.",
""
]
] | Black holes are presumed to have an ideal ability to absorb and keep matter. Whatever comes close to the event horizon, a boundary separating the inside region of a black hole from the outside world, inevitably goes in and remains inside forever. This work shows, however, that quantum corrections make possible a surprising process, reflection: a particle can bounce back from the event horizon. For low energy particles this process is efficient, black holes behave not as holes, but as mirrors, which changes our perception of their physical nature. Possible ways for observations of the reflection and its relation to the Hawking radiation process are outlined. |
1511.04316 | Javad Taghizadeh Firouzjaee | Javad T. Firouzjaee and George F R Ellis | Particle creation rate for dynamical black holes | 10 pages, 1 figure. The paper was rewritten in more clear
presentation and one more appendix is added | null | 10.1140/epjc/s10052-016-4479-9 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We present the particle creation probability rate around a general black hole
as an outcome of quantum fluctuations. Using the uncertainty principle for
these fluctuation, we derive a new ultraviolet frequency cutoff for the
radiation spectrum of a dynamical black hole. Using this frequency cutoff, we
define the probability creation rate function for such black holes. We consider
a dynamical Vaidya model, and calculate the probability creation rate for this
case when its horizon is in a slowly evolving phase. Our results show that one
can expect the usual Hawking radiation emission process in the case of a
dynamical black hole when it has a slowly evolving horizon. Moreover,
calculating the probability rate for a dynamical black hole gives a measure of
when Hawking radiation can be killed off by an incoming flux of matter or
radiation. Our result strictly suggests that we have to revise the Hawking
radiation expectation for primordial black holes that have grown substantially
since they were created in the early universe. We also infer that this
frequency cut off can be a parameter that shows the primordial black hole
growth at the emission moment.
| [
{
"created": "Fri, 13 Nov 2015 15:30:13 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 2016 13:30:50 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Oct 2016 11:31:12 GMT",
"version": "v3"
}
] | 2016-12-21 | [
[
"Firouzjaee",
"Javad T.",
""
],
[
"Ellis",
"George F R",
""
]
] | We present the particle creation probability rate around a general black hole as an outcome of quantum fluctuations. Using the uncertainty principle for these fluctuation, we derive a new ultraviolet frequency cutoff for the radiation spectrum of a dynamical black hole. Using this frequency cutoff, we define the probability creation rate function for such black holes. We consider a dynamical Vaidya model, and calculate the probability creation rate for this case when its horizon is in a slowly evolving phase. Our results show that one can expect the usual Hawking radiation emission process in the case of a dynamical black hole when it has a slowly evolving horizon. Moreover, calculating the probability rate for a dynamical black hole gives a measure of when Hawking radiation can be killed off by an incoming flux of matter or radiation. Our result strictly suggests that we have to revise the Hawking radiation expectation for primordial black holes that have grown substantially since they were created in the early universe. We also infer that this frequency cut off can be a parameter that shows the primordial black hole growth at the emission moment. |
gr-qc/9711018 | Steve Brandt | S. R. Brandt, P. Walker, P. Anninos | New Coordinate Systems for Axisymmetric Black Hole Collisions | 3 pages, 5 postscript figures, LaTeX, uses mprocl.sty (available at
http://shemesh.fiz.huji.ac.il/MG8/submission.html) To appear in the
proceedings of the Marcel Grossmann 8 (Jerusalem, 1997) | null | null | null | gr-qc | null | We describe a numerical grid generating procedure to construct new classes of
orthogonal coordinate systems that are specially adapted to binary black hole
spacetimes. The new coordinates offer an alternative approach to the
conventional \v{C}ade\v{z} coordinates, in addition to providing a potentially
more stable and flexible platform to extend previous calculations of binary
black hole collisions.
| [
{
"created": "Thu, 6 Nov 1997 07:57:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Brandt",
"S. R.",
""
],
[
"Walker",
"P.",
""
],
[
"Anninos",
"P.",
""
]
] | We describe a numerical grid generating procedure to construct new classes of orthogonal coordinate systems that are specially adapted to binary black hole spacetimes. The new coordinates offer an alternative approach to the conventional \v{C}ade\v{z} coordinates, in addition to providing a potentially more stable and flexible platform to extend previous calculations of binary black hole collisions. |
2010.10281 | Iver Brevik | Iver Brevik | Classical and quantal aspects of Minkowski's four-momentum in analog
gravity | 13 pages, no figures. To appear in Phys. Rev. A | Phys. Rev. A 102, 052201 (2020) | 10.1103/PhysRevA.102.052201 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The electrodynamic theory of continuous media is probably the most convenient
platform when trying to construct analog gravity theories. Quite naturally,
this topic has gained considerable interest. One peculiar but not so very known
feature in this context is the unconventional behavior of radiation energy and
momentum in cases where superluminal fluid velocities are encountered, what, as
known, is a major ingredient in analog gravity theories. These peculiar
features are intimately connected with the spacelike character of Minkowski's
four-momentum in electrodynamics. Here, we first consider an artificial model
in which a Kerr-induced superluminal region is created in the right-hand region
($z>0$) in a left-moving, originally subluminal, fluid. We analyze the behavior
of energy density, Poynting vector, and momentum density, and calculate the
force on the artificial black hole horizon. Also, we delve into quantal
aspects, looking for eventual production of particles associated with the
sudden creation of the horizon, finding, however, that no particles are
predicted to occur. The present paper continues a previous investigation by the
author on the same topic, in Phys. Rev. A {\bf 100}, 032109 (2019). The subject
as such is closely related to the famous Abraham-Minkowski problem.
| [
{
"created": "Tue, 20 Oct 2020 13:53:28 GMT",
"version": "v1"
}
] | 2020-11-05 | [
[
"Brevik",
"Iver",
""
]
] | The electrodynamic theory of continuous media is probably the most convenient platform when trying to construct analog gravity theories. Quite naturally, this topic has gained considerable interest. One peculiar but not so very known feature in this context is the unconventional behavior of radiation energy and momentum in cases where superluminal fluid velocities are encountered, what, as known, is a major ingredient in analog gravity theories. These peculiar features are intimately connected with the spacelike character of Minkowski's four-momentum in electrodynamics. Here, we first consider an artificial model in which a Kerr-induced superluminal region is created in the right-hand region ($z>0$) in a left-moving, originally subluminal, fluid. We analyze the behavior of energy density, Poynting vector, and momentum density, and calculate the force on the artificial black hole horizon. Also, we delve into quantal aspects, looking for eventual production of particles associated with the sudden creation of the horizon, finding, however, that no particles are predicted to occur. The present paper continues a previous investigation by the author on the same topic, in Phys. Rev. A {\bf 100}, 032109 (2019). The subject as such is closely related to the famous Abraham-Minkowski problem. |
1707.09156 | Meng-Sen Ma | Meng-Sen Ma, Rui-Hong Wang | Peculiar $P-V$ criticality of topological Ho\v{r}ava-Lifshitz black
holes | 16 pages, 8 figures. some typos are corrected. a note is added at the
last of the paper | Phys. Rev. D 96, 024052 (2017) | 10.1103/PhysRevD.96.024052 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate the existence of $P-V$ criticality of the topological
Ho\v{r}ava-Lifshitz(HL) black holes with a spherical horizon $(k=1)$ in the
extended phase space. With the electric charge, we find that the critical
behaviors of the HL black hole are nearly the same as those of van der
Waals(VdW) system. For the uncharged case, the HL black hole has a peculiar
$P-V$ criticality. The critical behavior is completely controlled by a
parameter $\epsilon$, but not the temperature $T$. When $\epsilon$ is larger
than a critical value $\epsilon_c$, no matter what the temperature is, there
will be the first-order phase transition. Moreover, we find that there is an
infinite number of critical points which form a "critical curve". As far as we
know, this is the first time to find this kind of peculiar $P-V$ criticality.
| [
{
"created": "Fri, 28 Jul 2017 09:02:49 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Aug 2017 15:58:30 GMT",
"version": "v2"
}
] | 2017-08-09 | [
[
"Ma",
"Meng-Sen",
""
],
[
"Wang",
"Rui-Hong",
""
]
] | We demonstrate the existence of $P-V$ criticality of the topological Ho\v{r}ava-Lifshitz(HL) black holes with a spherical horizon $(k=1)$ in the extended phase space. With the electric charge, we find that the critical behaviors of the HL black hole are nearly the same as those of van der Waals(VdW) system. For the uncharged case, the HL black hole has a peculiar $P-V$ criticality. The critical behavior is completely controlled by a parameter $\epsilon$, but not the temperature $T$. When $\epsilon$ is larger than a critical value $\epsilon_c$, no matter what the temperature is, there will be the first-order phase transition. Moreover, we find that there is an infinite number of critical points which form a "critical curve". As far as we know, this is the first time to find this kind of peculiar $P-V$ criticality. |
1507.04172 | Bibhas Majhi Ranjan | Bibhas Ranjan Majhi | Gravitational anomalies and one dimensional behaviour of black holes | Comments added, to appear in EPJC | Eur. Phys. J. C (2015) 75: 578 | 10.1140/epjc/s10052-015-3812-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been pointed out by Bekenstein and Mayo that the behavior of the Black
hole's entropy or information flow is similar to that through one-dimensional
channel. Here I analyse the same issue with the use of gravitational anomalies.
The rate of the entropy change ($\dot{S}$) and the power ($P$) of the Hawking
emission are calculated from the relevant components of the anomalous
stress-tensor under the Unruh vacuum condition. I show that the dependence of
$\dot{S}$ on power is $\dot{S}\propto P^{1/2}$ which is identical to that for
the information flow in one dimensional system. This is established by using
the ($1+1$) dimensional gravitational anomalies first. Then the fact is further
bolstered by considering the ($1+3$) dimensional gravitational anomalies. It is
found that in the former case, the proportionality constant is exactly
identical to one dimensional situation, known as Pendry's formula, while in
later situation its value decreases.
| [
{
"created": "Wed, 15 Jul 2015 11:38:34 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 2015 14:04:05 GMT",
"version": "v2"
}
] | 2015-12-18 | [
[
"Majhi",
"Bibhas Ranjan",
""
]
] | It has been pointed out by Bekenstein and Mayo that the behavior of the Black hole's entropy or information flow is similar to that through one-dimensional channel. Here I analyse the same issue with the use of gravitational anomalies. The rate of the entropy change ($\dot{S}$) and the power ($P$) of the Hawking emission are calculated from the relevant components of the anomalous stress-tensor under the Unruh vacuum condition. I show that the dependence of $\dot{S}$ on power is $\dot{S}\propto P^{1/2}$ which is identical to that for the information flow in one dimensional system. This is established by using the ($1+1$) dimensional gravitational anomalies first. Then the fact is further bolstered by considering the ($1+3$) dimensional gravitational anomalies. It is found that in the former case, the proportionality constant is exactly identical to one dimensional situation, known as Pendry's formula, while in later situation its value decreases. |
1306.5285 | Jos\'e Villanueva | Marco Olivares, Yerko V\'asquez, J. R. Villanueva and Felipe Moncada | Motion of particles on a $z=2$ Lifshitz black hole in 3+1 dimensions | 11 pages, 6 figures | Celest Mech Dyn Astr (2014) 119: 207-217 | 10.1007/s10569-014-9555-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geodesic structure of a $z=2$ Lifshitz black hole in 3+1
spacetime dimensions that is an exact solution to the Einstein-scalar-Maxwell
theory. We investigate the motion of massless and massive particles in this
background using the standard Lagrangian procedure. Analytical expressions are
obtained for radial and angular motions of the test particles, where the polar
trajectories are given in terms of the $\wp$ - Weierstrass elliptic function.
It is shown that confined orbits are not allowed on this spacetime, this result
agrees with the obtained recently in the literature for other Lifshitz black
holes.
| [
{
"created": "Sat, 22 Jun 2013 02:46:36 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jun 2014 16:25:08 GMT",
"version": "v2"
}
] | 2014-06-20 | [
[
"Olivares",
"Marco",
""
],
[
"Vásquez",
"Yerko",
""
],
[
"Villanueva",
"J. R.",
""
],
[
"Moncada",
"Felipe",
""
]
] | We study the geodesic structure of a $z=2$ Lifshitz black hole in 3+1 spacetime dimensions that is an exact solution to the Einstein-scalar-Maxwell theory. We investigate the motion of massless and massive particles in this background using the standard Lagrangian procedure. Analytical expressions are obtained for radial and angular motions of the test particles, where the polar trajectories are given in terms of the $\wp$ - Weierstrass elliptic function. It is shown that confined orbits are not allowed on this spacetime, this result agrees with the obtained recently in the literature for other Lifshitz black holes. |
2203.04000 | Simon Boudet | Simon Boudet, Flavio Bombacigno, Gonzalo J. Olmo and Paulo J. Porfirio | Quasinormal modes of Schwarzschild black holes in projective invariant
Chern-Simons modified gravity | null | JCAP 05 (2022) 032 | 10.1088/1475-7516/2022/05/032 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We generalize the Chern-Simons modified gravity to the metric-affine case and
impose projective invariance by supplementing the Pontryagin density with
homothetic curvature terms which do not spoil topologicity. The latter is then
broken by promoting the coupling of the Chern-Simons term to a (pseudo)-scalar
field. The solutions for torsion and nonmetricity are derived perturbatively,
showing that they can be iteratively obtained from the background fields. This
allows us to describe the dynamics for the metric and the scalar field
perturbations in a self-consistent way, and we apply the formalism to the study
of quasinormal modes in a Schwarzschild black hole background. Unlike in the
metric formulation of this theory, we show that the scalar field is endowed
with dynamics even in the absence of its kinetic term in the action. Finally,
using numerical methods we compute the quasinormal frequencies and characterize
the late-time power law tails for scalar and metric perturbations, comparing
the results with the outcomes of the purely metric approach.
| [
{
"created": "Tue, 8 Mar 2022 10:56:08 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Apr 2022 08:24:35 GMT",
"version": "v2"
}
] | 2022-05-20 | [
[
"Boudet",
"Simon",
""
],
[
"Bombacigno",
"Flavio",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Porfirio",
"Paulo J.",
""
]
] | We generalize the Chern-Simons modified gravity to the metric-affine case and impose projective invariance by supplementing the Pontryagin density with homothetic curvature terms which do not spoil topologicity. The latter is then broken by promoting the coupling of the Chern-Simons term to a (pseudo)-scalar field. The solutions for torsion and nonmetricity are derived perturbatively, showing that they can be iteratively obtained from the background fields. This allows us to describe the dynamics for the metric and the scalar field perturbations in a self-consistent way, and we apply the formalism to the study of quasinormal modes in a Schwarzschild black hole background. Unlike in the metric formulation of this theory, we show that the scalar field is endowed with dynamics even in the absence of its kinetic term in the action. Finally, using numerical methods we compute the quasinormal frequencies and characterize the late-time power law tails for scalar and metric perturbations, comparing the results with the outcomes of the purely metric approach. |
1106.2749 | Jerzy Matyjasek | Jerzy Matyjasek and Katarzyna Zwierzchowska | Lukewarm black holes in quadratic gravity | null | Mod. Phys. Lett. A26, 999 (2011) | 10.1142/S0217732311035560 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Perturbative solutions to the fourth-order gravity describing
spherically-symmetric, static and electrically charged black hole in an
asymptotically de Sitter universe is constructed and discussed. Special
emphasis is put on the lukewarm configurations, in which the temperature of the
event horizon equals the temperature of the cosmological horizon.
| [
{
"created": "Tue, 14 Jun 2011 16:00:03 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Matyjasek",
"Jerzy",
""
],
[
"Zwierzchowska",
"Katarzyna",
""
]
] | Perturbative solutions to the fourth-order gravity describing spherically-symmetric, static and electrically charged black hole in an asymptotically de Sitter universe is constructed and discussed. Special emphasis is put on the lukewarm configurations, in which the temperature of the event horizon equals the temperature of the cosmological horizon. |
0901.1242 | Bahtiyar Ozgur Sarioglu | Ozgur Sarioglu, Bayram Tekin | A note on cosmological Levi-Civita spacetimes in higher dimensions | 3 pages; version to appear in Phys. Rev. D | Phys.Rev.D79:087502,2009 | 10.1103/PhysRevD.79.087502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find a class of solutions to cosmological Einstein equations that
generalizes the four dimensional cylindrically symmetric spacetimes to higher
dimensions. The AdS soliton is a special member of this class with a unique
singularity structure.
| [
{
"created": "Fri, 9 Jan 2009 13:29:06 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Apr 2009 09:38:03 GMT",
"version": "v2"
}
] | 2009-07-30 | [
[
"Sarioglu",
"Ozgur",
""
],
[
"Tekin",
"Bayram",
""
]
] | We find a class of solutions to cosmological Einstein equations that generalizes the four dimensional cylindrically symmetric spacetimes to higher dimensions. The AdS soliton is a special member of this class with a unique singularity structure. |
2302.08782 | Subenoy Chakraborty | Madhukrishna Chakraborty, Akash Bose and Subenoy Chakraborty | The Raychaudhuri Equation in inhomogeneous FLRW space-time : A
$f(R)$-gravity model | 19 pages, 6 figures | null | 10.1088/1402-4896/acb020 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In general description of the Raychaudhuri equation it is found that this
first order non-linear differential equation can be written as a second order
linear differential equation in the form of Harmonic Oscillator with varying
frequency. Further, the integrability of the Raychaudhuri equation has been
studied and also the expansion scalar is obtained in an explicit form.
Subsequently, $f(R)$ gravity theory has been studied in the background of
inhomogeneous FLRW spacetime with an aim to formulate the Raychaudhuri
Equation. A congruence of time-like geodesics has been investigated using the
Raychaudhuri Equation to examine whether the geodesics converge or not and some
possible conditions are determined to avoid singularity. Finally, a brief
quantum description has been presented.
| [
{
"created": "Fri, 17 Feb 2023 09:45:56 GMT",
"version": "v1"
}
] | 2023-02-20 | [
[
"Chakraborty",
"Madhukrishna",
""
],
[
"Bose",
"Akash",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In general description of the Raychaudhuri equation it is found that this first order non-linear differential equation can be written as a second order linear differential equation in the form of Harmonic Oscillator with varying frequency. Further, the integrability of the Raychaudhuri equation has been studied and also the expansion scalar is obtained in an explicit form. Subsequently, $f(R)$ gravity theory has been studied in the background of inhomogeneous FLRW spacetime with an aim to formulate the Raychaudhuri Equation. A congruence of time-like geodesics has been investigated using the Raychaudhuri Equation to examine whether the geodesics converge or not and some possible conditions are determined to avoid singularity. Finally, a brief quantum description has been presented. |
2405.20537 | Jong Hyuk Yoon | Jong Hyuk Yoon and Seung Hun Oh | Poisson algebra of quasilocal angular momentum and its asymptotic limit | null | Classical and Quantum Gravity 35, 015003 (2018) | 10.1088/1361-6382/aa8ab2 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We study the previously proposed quasilocal angular momentum of gravitational
fields in the absence of isometries. The quasilocal angular momentum $L(\xi)$
has the following attractive properties; ({\it i}) it follows from the
Einstein's constraint equations, ({\it ii}) it satisfies the Poisson algebra
$\{L(\xi), L(\eta) \}_{\rm P.B.} =({1/16\pi)}\, L( [\xi, \eta]_{\rm L} )$,
({\it iii}) its Poisson algebra reduces to the standard $SO(3)$ algebra of
angular momentum at null infinity, and ({\it iv}) it reproduces the standard
value for the Kerr spacetime at null infinity. It will be argued that our
definition is a quasilocal and canonical generalization of A. Rizzi's geometric
definition at null infinity. We also propose a new definition of an {\it
invariant} quasilocal angular momentum $L^{2}$ such that $\{ L^2, L(\xi)
\}_{\rm P.B.} = 0$, which becomes $(ma)^{2}$ at the null infinity of the Kerr
spacetime. Therefore, it may be regarded as a quasilocal generalization of the
Casimir invariant of ordinary angular momentum in the flat spacetime.
| [
{
"created": "Thu, 30 May 2024 23:21:28 GMT",
"version": "v1"
}
] | 2024-06-03 | [
[
"Yoon",
"Jong Hyuk",
""
],
[
"Oh",
"Seung Hun",
""
]
] | We study the previously proposed quasilocal angular momentum of gravitational fields in the absence of isometries. The quasilocal angular momentum $L(\xi)$ has the following attractive properties; ({\it i}) it follows from the Einstein's constraint equations, ({\it ii}) it satisfies the Poisson algebra $\{L(\xi), L(\eta) \}_{\rm P.B.} =({1/16\pi)}\, L( [\xi, \eta]_{\rm L} )$, ({\it iii}) its Poisson algebra reduces to the standard $SO(3)$ algebra of angular momentum at null infinity, and ({\it iv}) it reproduces the standard value for the Kerr spacetime at null infinity. It will be argued that our definition is a quasilocal and canonical generalization of A. Rizzi's geometric definition at null infinity. We also propose a new definition of an {\it invariant} quasilocal angular momentum $L^{2}$ such that $\{ L^2, L(\xi) \}_{\rm P.B.} = 0$, which becomes $(ma)^{2}$ at the null infinity of the Kerr spacetime. Therefore, it may be regarded as a quasilocal generalization of the Casimir invariant of ordinary angular momentum in the flat spacetime. |
gr-qc/0103036 | Clifford M. Will | Clifford M. Will | The Confrontation between General Relativity and Experiment | 103 pages, 10 figures, accepted for publication in Living Reviews in
Relativity | LivingRev.Rel.4:4,2001 | 10.12942/lrr-2001-4 | null | gr-qc | null | The status of experimental tests of general relativity and of theoretical
frameworks for analysing them are reviewed. Einstein's equivalence principle
(EEP) is well supported by experiments such as the E\"otv\"os experiment, tests
of special relativity, and the gravitational redshift experiment. Future tests
of EEP and of the inverse square law will search for new interactions arising
from unification or quantum gravity. Tests of general relativity at the
post-Newtonian level have reached high precision, including the light
deflection, the Shapiro time delay, the perihelion advance of Mercury, and the
Nordtvedt effect in lunar motion. Gravitational wave damping has been detected
to half a percent using the binary pulsar, and new binary pulsar systems may
yield further improvements. When direct observation of gravitational radiation
from astrophysical sources begins, new tests of general relativity will be
possible.
| [
{
"created": "Mon, 12 Mar 2001 16:24:04 GMT",
"version": "v1"
}
] | 2016-10-19 | [
[
"Will",
"Clifford M.",
""
]
] | The status of experimental tests of general relativity and of theoretical frameworks for analysing them are reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the E\"otv\"os experiment, tests of special relativity, and the gravitational redshift experiment. Future tests of EEP and of the inverse square law will search for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected to half a percent using the binary pulsar, and new binary pulsar systems may yield further improvements. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible. |
gr-qc/0201028 | Jan Ambjorn | J. Ambjorn | Simplicial Euclidean and Lorentzian Quantum Gravity | 23 pages, 4 eps figures, Plenary talk GR16 | null | 10.1142/9789812776556_0001 | null | gr-qc hep-lat hep-th | null | One can try to define the theory of quantum gravity as the sum over
geometries. In two dimensions the sum over {\it Euclidean} geometries can be
performed constructively by the method of {\it dynamical triangulations}. One
can define a {\it proper-time} propagator. This propagator can be used to
calculate generalized Hartle-Hawking amplitudes and it can be used to
understand the the fractal structure of {\it quantum geometry}. In higher
dimensions the philosophy of defining the quantum theory, starting from a sum
over Euclidean geometries, regularized by a reparametrization invariant cut off
which is taken to zero, seems not to lead to an interesting continuum theory.
The reason for this is the dominance of singular Euclidean geometries.
Lorentzian geometries with a global causal structure are less singular. Using
the framework of dynamical triangulations it is possible to give a constructive
definition of the sum over such geometries, In two dimensions the theory can be
solved analytically. It differs from two-dimensional Euclidean quantum gravity,
and the relation between the two theories can be understood. In three
dimensions the theory avoids the pathologies of three-dimensional Euclidean
quantum gravity. General properties of the four-dimensional discretized theory
have been established, but a detailed study of the continuum limit in the
spirit of the renormalization group and {\it asymptotic safety} is till
awaiting.
| [
{
"created": "Wed, 9 Jan 2002 10:32:25 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Ambjorn",
"J.",
""
]
] | One can try to define the theory of quantum gravity as the sum over geometries. In two dimensions the sum over {\it Euclidean} geometries can be performed constructively by the method of {\it dynamical triangulations}. One can define a {\it proper-time} propagator. This propagator can be used to calculate generalized Hartle-Hawking amplitudes and it can be used to understand the the fractal structure of {\it quantum geometry}. In higher dimensions the philosophy of defining the quantum theory, starting from a sum over Euclidean geometries, regularized by a reparametrization invariant cut off which is taken to zero, seems not to lead to an interesting continuum theory. The reason for this is the dominance of singular Euclidean geometries. Lorentzian geometries with a global causal structure are less singular. Using the framework of dynamical triangulations it is possible to give a constructive definition of the sum over such geometries, In two dimensions the theory can be solved analytically. It differs from two-dimensional Euclidean quantum gravity, and the relation between the two theories can be understood. In three dimensions the theory avoids the pathologies of three-dimensional Euclidean quantum gravity. General properties of the four-dimensional discretized theory have been established, but a detailed study of the continuum limit in the spirit of the renormalization group and {\it asymptotic safety} is till awaiting. |
1002.2591 | Scott A. Hughes | Scott A. Hughes | Probing strong-field gravity and black holes with gravitational waves | 19 pages, 5 figures, for the Proceedings of the 19th Workshop on
General Relativity and Gravitation in Japan. Content very similar to recent
reviews by the author | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave observations will be excellent tools for making precise
measurements of processes that occur in very strong-field regions of spacetime.
Extreme mass ratio systems, formed by the capture of a stellar mass body
compact by a massive black hole, will be targets for planned space-based
interferometers such as LISA and DECIGO. These systems will be especially
powerful tools for testing the spacetime nature of black hole candidates. In
this writeup of the talk I gave at JGRG19, I describe how the properties of
black holes are imprinted on their waveforms, and how measurements can be used
to study these properties and thereby learn about the astrophysics of black
holes and about strong-field gravity.
| [
{
"created": "Fri, 12 Feb 2010 16:37:25 GMT",
"version": "v1"
}
] | 2010-02-15 | [
[
"Hughes",
"Scott A.",
""
]
] | Gravitational wave observations will be excellent tools for making precise measurements of processes that occur in very strong-field regions of spacetime. Extreme mass ratio systems, formed by the capture of a stellar mass body compact by a massive black hole, will be targets for planned space-based interferometers such as LISA and DECIGO. These systems will be especially powerful tools for testing the spacetime nature of black hole candidates. In this writeup of the talk I gave at JGRG19, I describe how the properties of black holes are imprinted on their waveforms, and how measurements can be used to study these properties and thereby learn about the astrophysics of black holes and about strong-field gravity. |
gr-qc/0208058 | Mauricio Bellini | Mauricio Bellini (IFM, Michoacana University) | Ultralight particle creation during fresh inflation | 8 pages, 2 figures (to appear in Il Nuovo Cimento B) | Nuovo Cim.B117:653-658,2002 | null | null | gr-qc hep-ph | null | I study ultralight particle creation which becomes from the Yukawa
interaction between the inflaton and the thermal bath during fresh inflation.
Particle creation is important in the first stages of fresh inflation, when the
nonequilibrium thermal effects are important. I find that the number density of
the ultralight created particles is more important as the scale factor growth
rate is more large (i.e., for $p$ large -- $a \sim t^p$). Ultralight boson
fields created during fresh inflation could be an alternative mechanism to
cosmological constant to explain the discrepancy between the observed $\Omega_m
\simeq 0.2$ and $\Omega_{tot} \simeq 1$, predicted by inflationary models.
| [
{
"created": "Mon, 19 Aug 2002 22:18:59 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Aug 2002 00:12:17 GMT",
"version": "v2"
}
] | 2010-11-11 | [
[
"Bellini",
"Mauricio",
"",
"IFM, Michoacana University"
]
] | I study ultralight particle creation which becomes from the Yukawa interaction between the inflaton and the thermal bath during fresh inflation. Particle creation is important in the first stages of fresh inflation, when the nonequilibrium thermal effects are important. I find that the number density of the ultralight created particles is more important as the scale factor growth rate is more large (i.e., for $p$ large -- $a \sim t^p$). Ultralight boson fields created during fresh inflation could be an alternative mechanism to cosmological constant to explain the discrepancy between the observed $\Omega_m \simeq 0.2$ and $\Omega_{tot} \simeq 1$, predicted by inflationary models. |
1504.05284 | Hongwei Yu | Qihong Huang, Puxun Wu and Hongwei Yu | Emergent scenario in the Einstein-Cartan theory | 16 pages, 5 figures, to appear in PRD | Physical Review D 91, 103502 (2015) | 10.1103/PhysRevD.91.103502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the emergent scenario, which is proposed to avoid the big bang
singularity, in the Einstein-Cartan (EC) theory with a positive cosmological
constant and a perfect fluid by analyzing the existence and stability of the
Einstein static (ES) solutions. We find that there is no stable ES solution for
a spatially flat or open universe. However, for a spatially closed universe,
the stable ES solution does exist, and in the same existence parameter regions,
there also exists an unstable one. With the slow decrease of the equation of
state $w$ of the perfect fluid, the stable and unstable critical points move
close gradually and coincide once $w$ reaches a critical value, so that the
stable critical point becomes an unstable one. As a result, if $w$ approaches a
constant at $t\rightarrow -\infty$, the universe can stay at the stable ES
state past eternally, and furthermore it can naturally exit from this state and
evolve into an inflationary era if $w$ decreases slowly as time goes forward.
Therefore, the emergent scenario that avoids the big bang singularity can be
successfully implemented in the EC theory of gravity.
| [
{
"created": "Tue, 21 Apr 2015 02:49:07 GMT",
"version": "v1"
}
] | 2015-10-19 | [
[
"Huang",
"Qihong",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | We study the emergent scenario, which is proposed to avoid the big bang singularity, in the Einstein-Cartan (EC) theory with a positive cosmological constant and a perfect fluid by analyzing the existence and stability of the Einstein static (ES) solutions. We find that there is no stable ES solution for a spatially flat or open universe. However, for a spatially closed universe, the stable ES solution does exist, and in the same existence parameter regions, there also exists an unstable one. With the slow decrease of the equation of state $w$ of the perfect fluid, the stable and unstable critical points move close gradually and coincide once $w$ reaches a critical value, so that the stable critical point becomes an unstable one. As a result, if $w$ approaches a constant at $t\rightarrow -\infty$, the universe can stay at the stable ES state past eternally, and furthermore it can naturally exit from this state and evolve into an inflationary era if $w$ decreases slowly as time goes forward. Therefore, the emergent scenario that avoids the big bang singularity can be successfully implemented in the EC theory of gravity. |
0707.1351 | Mustapha Ishak | James Richardson and Mustapha Ishak (The University of Texas at
Dallas) | Inverse approach to Einstein's equations for fluids with vanishing
anisotropic stress tensor | 15 pages, matches version to appear in Phys.Rev.D | Phys.Rev.D77:044005,2008 | 10.1103/PhysRevD.77.044005 | null | gr-qc astro-ph.CO | null | We expand previous work on an inverse approach to Einstein Field Equations
where we include fluids with energy flux and consider the vanishing of the
anisotropic stress tensor. We consider the approach using warped product
spacetimes of class $B_1$. Although restricted, these spacetimes include many
exact solutions of interest to compact object studies and to cosmological
models studies. The question explored here is as follows: given a spacetime
metric, what fluid flow (timelike congruence), if any, could generate the
spacetime via Einstein's equations. We calculate the flow from the condition of
a vanishing anisotropic stress tensor and give results in terms of the metric
functions in the three canonical types of coordinates. A condition for perfect
fluid sources is also provided. The framework developed is algorithmic and
suited for the study and validation of exact solutions using computer algebra
systems. The framework can be applied to solutions in comoving and non-comoving
frames of reference, and examples in different types of coordinates are worked
out.
| [
{
"created": "Tue, 10 Jul 2007 00:31:17 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Dec 2007 17:29:40 GMT",
"version": "v2"
}
] | 2011-02-01 | [
[
"Richardson",
"James",
"",
"The University of Texas at\n Dallas"
],
[
"Ishak",
"Mustapha",
"",
"The University of Texas at\n Dallas"
]
] | We expand previous work on an inverse approach to Einstein Field Equations where we include fluids with energy flux and consider the vanishing of the anisotropic stress tensor. We consider the approach using warped product spacetimes of class $B_1$. Although restricted, these spacetimes include many exact solutions of interest to compact object studies and to cosmological models studies. The question explored here is as follows: given a spacetime metric, what fluid flow (timelike congruence), if any, could generate the spacetime via Einstein's equations. We calculate the flow from the condition of a vanishing anisotropic stress tensor and give results in terms of the metric functions in the three canonical types of coordinates. A condition for perfect fluid sources is also provided. The framework developed is algorithmic and suited for the study and validation of exact solutions using computer algebra systems. The framework can be applied to solutions in comoving and non-comoving frames of reference, and examples in different types of coordinates are worked out. |
0911.0473 | L\'aszl\'o \'A Gergely | L\'aszl\'o Ver\'eb, Zolt\'an Keresztes, P\'eter Raffai, Szabolcs
M\'esz\'aros, L\'aszl\'o \'A. Gergely | Recovering a spinning inspiralling compact binary waveform immersed in
LIGO-like noise with spinning templates | 5 pages, 1 figure + 4 figure panels; Proceedings of the Eight Edoardo
Amaldi Conference on Gravitational Waves (Amaldi8), New York, 2009; to be
published in J. Phys.: Conf. Series (JPCS) | J.Phys.Conf.Ser.228:012003,2010 | 10.1088/1742-6596/228/1/012003 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the recovery chances of highly spinning waveforms immersed in
LIGO S5-like noise by performing a matched filtering with 10^6 randomly chosen
spinning waveforms generated with the LAL package. While the masses of the
compact binary are reasonably well recovered (slightly overestimated), the same
does not hold true for the spins. We show the best fit matches both in the
time-domain and the frequency-domain. These encompass some of the spinning
characteristics of the signal, but far less than what would be required to
identify the astrophysical parameters of the system. An improvement of the
matching method is necessary, though may be difficult due to the noisy signal.
| [
{
"created": "Tue, 3 Nov 2009 02:58:07 GMT",
"version": "v1"
},
{
"created": "Tue, 11 May 2010 05:58:02 GMT",
"version": "v2"
},
{
"created": "Wed, 12 May 2010 07:38:43 GMT",
"version": "v3"
}
] | 2010-08-05 | [
[
"Veréb",
"László",
""
],
[
"Keresztes",
"Zoltán",
""
],
[
"Raffai",
"Péter",
""
],
[
"Mészáros",
"Szabolcs",
""
],
[
"Gergely",
"László Á.",
""
]
] | We investigate the recovery chances of highly spinning waveforms immersed in LIGO S5-like noise by performing a matched filtering with 10^6 randomly chosen spinning waveforms generated with the LAL package. While the masses of the compact binary are reasonably well recovered (slightly overestimated), the same does not hold true for the spins. We show the best fit matches both in the time-domain and the frequency-domain. These encompass some of the spinning characteristics of the signal, but far less than what would be required to identify the astrophysical parameters of the system. An improvement of the matching method is necessary, though may be difficult due to the noisy signal. |
2401.08106 | Martin Kr\v{s}\v{s}\'ak | Martin Kr\v{s}\v{s}\'ak | Teleparallel Gravity, Covariance and Their Geometrical Meaning | 21 pages, to appear in "Tribute to Ruben Aldrovandi", F. Caruso, J.G.
Pereira and A. Santoro (Eds.) (Editora Livraria da F\'isica, S\~ao Paulo,
2024) | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We explore the geometrical meaning of teleparallel geometries and the role of
covariance in their definition. We argue that pure gauge connections are a
necessary ingredient for describing geometry and gravity in terms of torsion
and non-metricity. We show the other viable alternative is using the Einstein
and Moller Lagrangians, but these are defined through the Riemannian connection
coefficients and hence do not involve torsion nor non-metricity. We argue that
the teleparallel geometries can be defined on the manifold without introducing
any additional structures and that they naturally provide the covariant
framework for the Einstein and Moller Lagrangians. We explore some consequences
of this viewpoint for the modified theories of gravity as well.
| [
{
"created": "Tue, 16 Jan 2024 04:18:47 GMT",
"version": "v1"
}
] | 2024-01-17 | [
[
"Krššák",
"Martin",
""
]
] | We explore the geometrical meaning of teleparallel geometries and the role of covariance in their definition. We argue that pure gauge connections are a necessary ingredient for describing geometry and gravity in terms of torsion and non-metricity. We show the other viable alternative is using the Einstein and Moller Lagrangians, but these are defined through the Riemannian connection coefficients and hence do not involve torsion nor non-metricity. We argue that the teleparallel geometries can be defined on the manifold without introducing any additional structures and that they naturally provide the covariant framework for the Einstein and Moller Lagrangians. We explore some consequences of this viewpoint for the modified theories of gravity as well. |
2311.11830 | Yongqiang Wang | Jun-Ru Chen, Shi-Xian Sun, Long-Xing Huang, Yong-Qiang Wang | Tidal Love numbers of Axion stars | 22 pages, 5 figures | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the tidal deformability of spherically symmetric axion stars
on the stable branches, including the Newtonian and relativistic branches. The
results suggest that on the stable branch, the electric Love numbers of axion
star are positive, while the magnetic Love numbers are negative. On the
Newtonian stable branch, the electric tidal Love numbers are much larger than
the magnetic ones, while on the relativistic stable branch, they are slightly
larger. Furthermore, the relativistic stable branch has much smaller tidal Love
numbers than the Newtonian stable branch, indicating weaker deformability of
axion stars on the relativistic stable branch. This could be attributed to the
fact that on the relativistic branch, axion stars are more compact, resulting
hardly distorted by tidal forces.
| [
{
"created": "Mon, 20 Nov 2023 15:05:02 GMT",
"version": "v1"
}
] | 2023-11-21 | [
[
"Chen",
"Jun-Ru",
""
],
[
"Sun",
"Shi-Xian",
""
],
[
"Huang",
"Long-Xing",
""
],
[
"Wang",
"Yong-Qiang",
""
]
] | We investigate the tidal deformability of spherically symmetric axion stars on the stable branches, including the Newtonian and relativistic branches. The results suggest that on the stable branch, the electric Love numbers of axion star are positive, while the magnetic Love numbers are negative. On the Newtonian stable branch, the electric tidal Love numbers are much larger than the magnetic ones, while on the relativistic stable branch, they are slightly larger. Furthermore, the relativistic stable branch has much smaller tidal Love numbers than the Newtonian stable branch, indicating weaker deformability of axion stars on the relativistic stable branch. This could be attributed to the fact that on the relativistic branch, axion stars are more compact, resulting hardly distorted by tidal forces. |
1804.04877 | Archisman Ghosh | Ka Wa Tsang, Michiel Rollier, Archisman Ghosh, Anuradha Samajdar,
Michalis Agathos, Katerina Chatziioannou, Vitor Cardoso, Gaurav Khanna, Chris
Van Den Broeck | A morphology-independent data analysis method for detecting and
characterizing gravitational wave echoes | 5 pages, 4 figures | Phys. Rev. D 98, 024023 (2018) | 10.1103/PhysRevD.98.024023 | LIGO-P1800089 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ability to directly detect gravitational waves has enabled us to
empirically probe the nature of ultra-compact relativistic objects. Several
alternatives to the black holes of classical general relativity have been
proposed which do not have a horizon, in which case a newly formed object (e.g.
as a result of binary merger) may emit echoes: bursts of gravitational
radiation with varying amplitude and duration, but arriving at regular time
intervals. Unlike in previous template-based approaches, we present a
morphology-independent search method to find echoes in the data from
gravitational wave detectors, based on a decomposition of the signal in terms
of generalized wavelets consisting of multiple sine-Gaussians. The ability of
the method to discriminate between echoes and instrumental noise is assessed by
inserting into the noise two different signals: a train of sine-Gaussians, and
an echoing signal from an extreme mass-ratio inspiral of a particle into a
Schwarzschild vacuum spacetime, with reflective boundary conditions close to
the horizon. We find that both types of signals are detectable for plausible
signal-to-noise ratios in existing detectors and their near-future upgrades.
Finally, we show how the algorithm can provide a characterization of the echoes
in terms of the time between successive bursts, and damping and widening from
one echo to the next.
| [
{
"created": "Fri, 13 Apr 2018 10:37:57 GMT",
"version": "v1"
}
] | 2018-07-18 | [
[
"Tsang",
"Ka Wa",
""
],
[
"Rollier",
"Michiel",
""
],
[
"Ghosh",
"Archisman",
""
],
[
"Samajdar",
"Anuradha",
""
],
[
"Agathos",
"Michalis",
""
],
[
"Chatziioannou",
"Katerina",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Broeck",
"Chris Van Den",
""
]
] | The ability to directly detect gravitational waves has enabled us to empirically probe the nature of ultra-compact relativistic objects. Several alternatives to the black holes of classical general relativity have been proposed which do not have a horizon, in which case a newly formed object (e.g. as a result of binary merger) may emit echoes: bursts of gravitational radiation with varying amplitude and duration, but arriving at regular time intervals. Unlike in previous template-based approaches, we present a morphology-independent search method to find echoes in the data from gravitational wave detectors, based on a decomposition of the signal in terms of generalized wavelets consisting of multiple sine-Gaussians. The ability of the method to discriminate between echoes and instrumental noise is assessed by inserting into the noise two different signals: a train of sine-Gaussians, and an echoing signal from an extreme mass-ratio inspiral of a particle into a Schwarzschild vacuum spacetime, with reflective boundary conditions close to the horizon. We find that both types of signals are detectable for plausible signal-to-noise ratios in existing detectors and their near-future upgrades. Finally, we show how the algorithm can provide a characterization of the echoes in terms of the time between successive bursts, and damping and widening from one echo to the next. |
gr-qc/0402005 | Theodore A. Jacobson | T. Jacobson and D. Mattingly | Einstein-Aether Waves | 5 pages; v2: Remarks added concerning gauge invariance of the waves
and hyperbolicity of the equations. Essentially the version published in PRD | Phys.Rev.D70:024003,2004 | 10.1103/PhysRevD.70.024003 | null | gr-qc astro-ph hep-th | null | Local Lorentz invariance violation can be realized by introducing extra
tensor fields in the action that couple to matter. If the Lorentz violation is
rotationally invariant in some frame, then it is characterized by an
``aether'', i.e. a unit timelike vector field. General covariance requires that
the aether field be dynamical. In this paper we study the linearized theory of
such an aether coupled to gravity and find the speeds and polarizations of all
the wave modes in terms of the four constants appearing in the most general
action at second order in derivatives. We find that in addition to the usual
two transverse traceless metric modes, there are three coupled aether-metric
modes.
| [
{
"created": "Tue, 3 Feb 2004 12:19:08 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jul 2004 12:04:12 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Jacobson",
"T.",
""
],
[
"Mattingly",
"D.",
""
]
] | Local Lorentz invariance violation can be realized by introducing extra tensor fields in the action that couple to matter. If the Lorentz violation is rotationally invariant in some frame, then it is characterized by an ``aether'', i.e. a unit timelike vector field. General covariance requires that the aether field be dynamical. In this paper we study the linearized theory of such an aether coupled to gravity and find the speeds and polarizations of all the wave modes in terms of the four constants appearing in the most general action at second order in derivatives. We find that in addition to the usual two transverse traceless metric modes, there are three coupled aether-metric modes. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.