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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2406.03588 | Mohammad Reza Mehdizadeh | Mohammad Reza Mehdizadeh and Amir Hadi Ziaie | Novel Casimir wormholes in Einstein gravity | 32 pages and 22 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the context of General Relativity (GR), violation of the null energy
condition (NEC) is necessary for existence of static spherically symmetric
wormhole solutions. Also, it is a well-known fact that the energy conditions
are violated by certain quantum fields, such as the Casimir effect. The
magnitude and sign of the Casimir energy depend on Dirichlet or Neumann
boundary conditions and geometrical configuration of the objects involved in a
Casimir setup. The Casimir energy may act as an ideal candidate for the matter
that supports the wormhole geometry. In the present work, we firstly find
traversable wormhole solutions supported by a general form for the Casimir
energy density assuming a constant redshift function. As well, in this
framework, assuming that the radial pressure and energy density obey a linear
equation of state, we derive for the first time Casimir traversable wormhole
solutions admitting suitable shape function. Then, we consider three geometric
configurations of the Casimir effect such as (i) two parallel plates, (ii) two
parallel cylindrical shells, and (iii) two spheres. We study wormhole solutions
for each case and their property in detail. We also check the weak and strong
energy conditions in the spacetime for the obtained wormhole solutions. The
stability of the Casimir traversable wormhole solutions are investigated using
the Tolman-Oppenheimer-Volkoff (TOV) equation. Finally, we study trajectory of
null as well as timelike particles in the wormhole spacetime.
| [
{
"created": "Wed, 5 Jun 2024 19:12:16 GMT",
"version": "v1"
}
] | 2024-06-07 | [
[
"Mehdizadeh",
"Mohammad Reza",
""
],
[
"Ziaie",
"Amir Hadi",
""
]
] | In the context of General Relativity (GR), violation of the null energy condition (NEC) is necessary for existence of static spherically symmetric wormhole solutions. Also, it is a well-known fact that the energy conditions are violated by certain quantum fields, such as the Casimir effect. The magnitude and sign of the Casimir energy depend on Dirichlet or Neumann boundary conditions and geometrical configuration of the objects involved in a Casimir setup. The Casimir energy may act as an ideal candidate for the matter that supports the wormhole geometry. In the present work, we firstly find traversable wormhole solutions supported by a general form for the Casimir energy density assuming a constant redshift function. As well, in this framework, assuming that the radial pressure and energy density obey a linear equation of state, we derive for the first time Casimir traversable wormhole solutions admitting suitable shape function. Then, we consider three geometric configurations of the Casimir effect such as (i) two parallel plates, (ii) two parallel cylindrical shells, and (iii) two spheres. We study wormhole solutions for each case and their property in detail. We also check the weak and strong energy conditions in the spacetime for the obtained wormhole solutions. The stability of the Casimir traversable wormhole solutions are investigated using the Tolman-Oppenheimer-Volkoff (TOV) equation. Finally, we study trajectory of null as well as timelike particles in the wormhole spacetime. |
gr-qc/0412062 | Luis Lehner | Dave Neilsen, Luis Lehner, Olivier Sarbach and Manuel Tiglio | Recent analytical and numerical techniques applied to the Einstein
equations | Contribution to appear in the Proceedings of the March-2004 Heraeus
Seminar in Bad Honnef (Eds D. Giulini, J. Frauendiener and V. Perlick) | Lect.Notes Phys. 692 (2006) 223-249 | 10.1007/11550259_11 | LSU-REL-121304 | gr-qc | null | Combining deeper insight of Einstein's equations with sophisticated numerical
techniques promises the ability to construct accurate numerical implementations
of these equations. We illustrate this in two examples, the numerical evolution
of ``bubble'' and single black hole spacetimes. The former is chosen to
demonstrate how accurate numerical solutions can answer open questions and even
reveal unexpected phenomena. The latter illustrates some of the difficulties
encountered in three-dimensional black hole simulations, and presents some
possible remedies.
| [
{
"created": "Mon, 13 Dec 2004 21:29:14 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Neilsen",
"Dave",
""
],
[
"Lehner",
"Luis",
""
],
[
"Sarbach",
"Olivier",
""
],
[
"Tiglio",
"Manuel",
""
]
] | Combining deeper insight of Einstein's equations with sophisticated numerical techniques promises the ability to construct accurate numerical implementations of these equations. We illustrate this in two examples, the numerical evolution of ``bubble'' and single black hole spacetimes. The former is chosen to demonstrate how accurate numerical solutions can answer open questions and even reveal unexpected phenomena. The latter illustrates some of the difficulties encountered in three-dimensional black hole simulations, and presents some possible remedies. |
1410.3830 | Carlos O. Lousto | Carlos O. Lousto and James Healy | Flip-flopping binary black holes | 5 pages, 5 figures. To appear in Physical Review Letters | Phys. Rev. Lett. 114, 141101 (2015) | 10.1103/PhysRevLett.114.141101 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study binary spinning black holes to display the long term individual spin
dynamics. We perform a full numerical simulation starting at an initial proper
separation of $d\approx25M$ between equal mass holes and evolve them down to
merger for nearly 48 orbits, 3 precession cycles, and half of a flip-flop
cycle. The simulation lasts for $t=20000M$ and displays a total change in the
orientation of the spin of one of the black holes from initially aligned with
the orbital angular momentum to a complete anti-alignment after half of a
flip-flop cycle. We compare this evolution with an integration of the 3.5
Post-Newtonian equations of motion and spin evolution to show that this process
continuously flip-flops the spin during the lifetime of the binary until
merger. We also provide lower order analytic expressions for the maximum
flip-flop angle and frequency. We discuss the effects this dynamics may have on
spin growth in accreting binaries and on the observational consequences for
galactic and supermassive binary black holes.
| [
{
"created": "Tue, 14 Oct 2014 20:00:08 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Mar 2015 01:10:33 GMT",
"version": "v2"
}
] | 2015-04-16 | [
[
"Lousto",
"Carlos O.",
""
],
[
"Healy",
"James",
""
]
] | We study binary spinning black holes to display the long term individual spin dynamics. We perform a full numerical simulation starting at an initial proper separation of $d\approx25M$ between equal mass holes and evolve them down to merger for nearly 48 orbits, 3 precession cycles, and half of a flip-flop cycle. The simulation lasts for $t=20000M$ and displays a total change in the orientation of the spin of one of the black holes from initially aligned with the orbital angular momentum to a complete anti-alignment after half of a flip-flop cycle. We compare this evolution with an integration of the 3.5 Post-Newtonian equations of motion and spin evolution to show that this process continuously flip-flops the spin during the lifetime of the binary until merger. We also provide lower order analytic expressions for the maximum flip-flop angle and frequency. We discuss the effects this dynamics may have on spin growth in accreting binaries and on the observational consequences for galactic and supermassive binary black holes. |
1704.00996 | Shahram Panahiyan | S. H. Hendi, B. Eslam Panah, S. Panahiyan and M. Momennia | Three dimensional magnetic solutions in massive gravity with (non)linear
field | 16 pages, 12 figures. Matches published version | Phys. Lett. B 775, 251 (2017) | 10.1016/j.physletb.2017.10.053 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Noble Prize in physics 2016 motivates one to study different aspects of
topological properties and topological defects as their related objects.
Considering the significant role of the topological defects (especially
magnetic strings) in cosmology, here, we will investigate three dimensional
horizonless magnetic solutions in the presence of two generalizations: massive
gravity and nonlinear electromagnetic field. The effects of these two
generalizations on properties of the solutions and their geometrical structure
are investigated. The differences between de Sitter and anti de Sitter
solutions are highlighted and conditions regarding the existence of phase
transition in geometrical structure of the solutions are studied.
| [
{
"created": "Sat, 1 Apr 2017 09:16:18 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Apr 2017 05:18:26 GMT",
"version": "v2"
},
{
"created": "Mon, 13 Nov 2017 19:30:36 GMT",
"version": "v3"
}
] | 2017-11-15 | [
[
"Hendi",
"S. H.",
""
],
[
"Panah",
"B. Eslam",
""
],
[
"Panahiyan",
"S.",
""
],
[
"Momennia",
"M.",
""
]
] | The Noble Prize in physics 2016 motivates one to study different aspects of topological properties and topological defects as their related objects. Considering the significant role of the topological defects (especially magnetic strings) in cosmology, here, we will investigate three dimensional horizonless magnetic solutions in the presence of two generalizations: massive gravity and nonlinear electromagnetic field. The effects of these two generalizations on properties of the solutions and their geometrical structure are investigated. The differences between de Sitter and anti de Sitter solutions are highlighted and conditions regarding the existence of phase transition in geometrical structure of the solutions are studied. |
1505.02512 | Meng Sun | Meng Sun, Yong-Chang Huang | Thermodynamic fluctuation in black string flow | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has long been noticed that Laudau-Lifshitz theory can be used to study the
fluctuation of a system that contains a black hole. Since the black string can
be constructed by extending n-dimensional black hole into one extra dimension.
We study the fluctuation of black string flow with a Schwarzschlid-like metric
in D=n+1 dimensional spacetime and a charged solution in D=5 dimensional
spacetime and get the second moments of the fluctuation of the mass flux and
charge flux.
| [
{
"created": "Mon, 11 May 2015 07:57:07 GMT",
"version": "v1"
}
] | 2015-05-12 | [
[
"Sun",
"Meng",
""
],
[
"Huang",
"Yong-Chang",
""
]
] | It has long been noticed that Laudau-Lifshitz theory can be used to study the fluctuation of a system that contains a black hole. Since the black string can be constructed by extending n-dimensional black hole into one extra dimension. We study the fluctuation of black string flow with a Schwarzschlid-like metric in D=n+1 dimensional spacetime and a charged solution in D=5 dimensional spacetime and get the second moments of the fluctuation of the mass flux and charge flux. |
gr-qc/0108067 | Irina Radinschi | I-Ching Yang and Irina Radinschi (Department of Natural Science
Education, National Taitung Teachers College, Taitung, Taiwan, Republic of
China and Department of Physics, "Gh. Asachi" Technical University, Iasi,
Romania) | Energy associated with a static spherically symmetric nonsingular black
hole | null | Chin.J.Phys. 41 (2003) 326 | null | null | gr-qc | null | We evaluate the energy distributions of the Dymnikova space-time using the
Weinberg, Papapetrou, and M{\o}ller energy-momentum complexes. This result
sustain the importance of the energy-momentum complexes in the evaluation of
the energy distribution of a given space-time. To compare the energy
distributions obtained by using several definitions, these results show that
the Einstein, Tolman, and Weinberg energy complexes are the same in
Schwarzschild Cartesian coordinates, but the Papapetrou and the M{\o}ller are
not.
| [
{
"created": "Mon, 27 Aug 2001 10:24:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Yang",
"I-Ching",
"",
"Department of Natural Science\n Education, National Taitung Teachers College, Taitung, Taiwan, Republic of\n China and Department of Physics, \"Gh. Asachi\" Technical University, Iasi,\n Romania"
],
[
"Radinschi",
"Irina",
"",
"Department of Natural S... | We evaluate the energy distributions of the Dymnikova space-time using the Weinberg, Papapetrou, and M{\o}ller energy-momentum complexes. This result sustain the importance of the energy-momentum complexes in the evaluation of the energy distribution of a given space-time. To compare the energy distributions obtained by using several definitions, these results show that the Einstein, Tolman, and Weinberg energy complexes are the same in Schwarzschild Cartesian coordinates, but the Papapetrou and the M{\o}ller are not. |
0705.1772 | Marek Szydlowski | Marek Szydlowski and Wlodzimierz Godlowski | Acceleration of the Universe driven by the Casimir force | RevTeX4, 17 pages, 9 figures | Int.J.Mod.Phys.D17:343-366,2008 | 10.1142/S021827180801205X | null | gr-qc | null | We investigate an evolutional scenario of the FRW universe with the Casimir
energy scaling like $(-)(1+z)^4$. The Casimir effect is used to explain the
vacuum energy differences (its value measured from astrophysics is so small
compared to value obtained from quantum field theory calculations). The
dynamics of the FRW model is represented in terms of a two-dimensional
dynamical system to show all evolutional paths of this model in the phase space
for all admissible initial conditions. We find also an exact solution for non
flat evolutional paths of Universe driven by the Casimir effect. The main
difference between the FRW model with the Casimir force and the $\Lambda$CDM
model is that their generic solutions are a set of evolutional paths with a
bounce solution and an initial singularity, respectively. The evolutional
scenario are tested by using the SNIa data, FRIIb radiogalaxies, baryon
oscillation peak and CMB observation. We compare the power of explanation of
the model considered and the $\Lambda$CDM model using the Bayesian information
criterion and Bayesian factor. Our investigation of the information criteria of
model selection showed the preference of the $\Lambda$CDM model over the model
considered. However the presence of negative like the radiation term can remove
a tension between the theoretical and observed primordial ${}^4$He and D
abundance.
| [
{
"created": "Sat, 12 May 2007 13:45:30 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Szydlowski",
"Marek",
""
],
[
"Godlowski",
"Wlodzimierz",
""
]
] | We investigate an evolutional scenario of the FRW universe with the Casimir energy scaling like $(-)(1+z)^4$. The Casimir effect is used to explain the vacuum energy differences (its value measured from astrophysics is so small compared to value obtained from quantum field theory calculations). The dynamics of the FRW model is represented in terms of a two-dimensional dynamical system to show all evolutional paths of this model in the phase space for all admissible initial conditions. We find also an exact solution for non flat evolutional paths of Universe driven by the Casimir effect. The main difference between the FRW model with the Casimir force and the $\Lambda$CDM model is that their generic solutions are a set of evolutional paths with a bounce solution and an initial singularity, respectively. The evolutional scenario are tested by using the SNIa data, FRIIb radiogalaxies, baryon oscillation peak and CMB observation. We compare the power of explanation of the model considered and the $\Lambda$CDM model using the Bayesian information criterion and Bayesian factor. Our investigation of the information criteria of model selection showed the preference of the $\Lambda$CDM model over the model considered. However the presence of negative like the radiation term can remove a tension between the theoretical and observed primordial ${}^4$He and D abundance. |
2204.03568 | Nosratollah Jafari Sonbolabadi | Nosratollah Jafari | Precession of perihelia in the Fisher metric | 7 pages | null | null | null | gr-qc astro-ph.EP astro-ph.SR hep-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We study the precession of perihelia in the Fisher metric. Fisher metric is
the solution of the Einstein's Equations with a massless scalar field as a
coupling. We find an expression for the precession of perihelia in this metric.
This expression contains general relativistic term for the precession of the
perihelia and also an additional term which depends on the scalar field. Also,
we obtain an upper bound on scalar charge $\sigma$ by using the observational
value of the precession of perihelia for the Mercury planet and the discrepancy
between this value and the general relativistic value.
| [
{
"created": "Wed, 6 Apr 2022 00:25:11 GMT",
"version": "v1"
}
] | 2022-04-08 | [
[
"Jafari",
"Nosratollah",
""
]
] | We study the precession of perihelia in the Fisher metric. Fisher metric is the solution of the Einstein's Equations with a massless scalar field as a coupling. We find an expression for the precession of perihelia in this metric. This expression contains general relativistic term for the precession of the perihelia and also an additional term which depends on the scalar field. Also, we obtain an upper bound on scalar charge $\sigma$ by using the observational value of the precession of perihelia for the Mercury planet and the discrepancy between this value and the general relativistic value. |
gr-qc/0612047 | Gonzalo Olmo | Gonzalo J. Olmo | Limit to General Relativity in f(R) theories of gravity | 8 pages; small changes to match published version (some comments,
references added, title corrected); to appear in Phys.Rev.D | Phys.Rev.D75:023511,2007 | 10.1103/PhysRevD.75.023511 | null | gr-qc astro-ph hep-th | null | We discuss two aspects of f(R) theories of gravity in metric formalism. We
first study the reasons to introduce a scalar-tensor representation for these
theories and the behavior of this representation in the limit to General
Relativity, f(R)--> R. We find that the scalar-tensor representation is well
behaved even in this limit. Then we work out the exact equations for
spherically symmetric sources using the original f(R) representation, solve the
linearized equations, and compare our results with recent calculations of the
literature. We observe that the linearized solutions are strongly affected by
the cosmic evolution, which makes very unlikely that the cosmic speedup be due
to f(R) models with correcting terms relevant at low curvatures.
| [
{
"created": "Thu, 7 Dec 2006 20:26:53 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jan 2007 10:19:24 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Olmo",
"Gonzalo J.",
""
]
] | We discuss two aspects of f(R) theories of gravity in metric formalism. We first study the reasons to introduce a scalar-tensor representation for these theories and the behavior of this representation in the limit to General Relativity, f(R)--> R. We find that the scalar-tensor representation is well behaved even in this limit. Then we work out the exact equations for spherically symmetric sources using the original f(R) representation, solve the linearized equations, and compare our results with recent calculations of the literature. We observe that the linearized solutions are strongly affected by the cosmic evolution, which makes very unlikely that the cosmic speedup be due to f(R) models with correcting terms relevant at low curvatures. |
1702.02168 | Mariya Ivanovna Trukhanova | Mariya Iv. Trukhanova and Shipov Gennady | The Geometro-Hydrodynamical Representation of the Torsion Field | null | null | 10.1016/j.physleta.2017.06.052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the geometro-hydrodynamical formalism for a spinning particle
based on the six-dimensional manifold of autoparallelism geometry which is
represented as a vector bundle with a base formed by the manifold of the
translational coordinates and a fibre specified at each point by the field of
an orthogonal coordinate frame underlying the classical spin. We show that the
geometry of oriented points leads to the existence of torsion field with the
source - the classical spin. We expand the geometro-hydrodynamical
representation of Pauli field developed by Takabayasi and Vigier. We show that
the external torsion field has a force effect on the velocity and spin fields
via the spin-vorticity, which is characteristic of the space structure with the
inhomogene triad field. The possible experimental effects of torsion field are
discussed.
| [
{
"created": "Tue, 7 Feb 2017 19:12:22 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jun 2017 13:54:16 GMT",
"version": "v2"
}
] | 2017-08-01 | [
[
"Trukhanova",
"Mariya Iv.",
""
],
[
"Gennady",
"Shipov",
""
]
] | We construct the geometro-hydrodynamical formalism for a spinning particle based on the six-dimensional manifold of autoparallelism geometry which is represented as a vector bundle with a base formed by the manifold of the translational coordinates and a fibre specified at each point by the field of an orthogonal coordinate frame underlying the classical spin. We show that the geometry of oriented points leads to the existence of torsion field with the source - the classical spin. We expand the geometro-hydrodynamical representation of Pauli field developed by Takabayasi and Vigier. We show that the external torsion field has a force effect on the velocity and spin fields via the spin-vorticity, which is characteristic of the space structure with the inhomogene triad field. The possible experimental effects of torsion field are discussed. |
1001.1875 | Klein David | David Klein and Peter Collas | Recessional velocities and Hubble's law in Schwarzschild-de Sitter space | This published version includes minor stylistic changes and
corrections to the bibliography. The paper extends the results of, and
replaces, a previous paper by the same authors entitled: "Superluminal
velocities in Schwarzschild-de Sitter space," arXiv:0910.5254v1 | Phys.Rev.D81:063518,2010 | 10.1103/PhysRevD.81.063518 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a spacetime with empty Schwarzschild-de Sitter exterior and
Schwarzschild-de Sitter interior metric for a spherical fluid with constant
density. The fluid interior may be taken to represent a galaxy supercluster,
for which the proper distance from the center of the supercluster to the
cosmological horizon has the same order of magnitude as the Hubble radius
derived from Friedmann-Robertson-Walker (FRW) cosmologies. The fluid interior
and surrounding vacuum may also be considered as a model of the Local Group of
galaxies in the far future. Particle motion is subject both to the attractive
gravity exerted by the fluid and the repelling cosmological constant. Using
global Fermi coordinates for the central observer within the fluid, the Fermi
velocity, the astrometric velocity, the kinematic velocity, and the
spectroscopic velocity, relative to the central (Fermi) observer, of a radially
receding test particle are calculated and compared. We find that the Fermi
relative velocity can exceed the speed of light in this model, but the presence
of a positive cosmological constant causes recessional speeds of distant high
energy particles to decrease rather than increase. We derive a version of
Hubble's law for this spacetime which might be applicable for the analysis of a
receding mass within a great void adjacent to a supercluster, relatively
isolated from gravitational sources other than the supercluster. We also
compare some of our results to related behavior in FRW cosmologies and consider
implications to arguments regarding the expansion of space.
| [
{
"created": "Tue, 12 Jan 2010 13:29:35 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Feb 2010 02:53:53 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Mar 2010 15:02:34 GMT",
"version": "v3"
}
] | 2010-04-29 | [
[
"Klein",
"David",
""
],
[
"Collas",
"Peter",
""
]
] | We consider a spacetime with empty Schwarzschild-de Sitter exterior and Schwarzschild-de Sitter interior metric for a spherical fluid with constant density. The fluid interior may be taken to represent a galaxy supercluster, for which the proper distance from the center of the supercluster to the cosmological horizon has the same order of magnitude as the Hubble radius derived from Friedmann-Robertson-Walker (FRW) cosmologies. The fluid interior and surrounding vacuum may also be considered as a model of the Local Group of galaxies in the far future. Particle motion is subject both to the attractive gravity exerted by the fluid and the repelling cosmological constant. Using global Fermi coordinates for the central observer within the fluid, the Fermi velocity, the astrometric velocity, the kinematic velocity, and the spectroscopic velocity, relative to the central (Fermi) observer, of a radially receding test particle are calculated and compared. We find that the Fermi relative velocity can exceed the speed of light in this model, but the presence of a positive cosmological constant causes recessional speeds of distant high energy particles to decrease rather than increase. We derive a version of Hubble's law for this spacetime which might be applicable for the analysis of a receding mass within a great void adjacent to a supercluster, relatively isolated from gravitational sources other than the supercluster. We also compare some of our results to related behavior in FRW cosmologies and consider implications to arguments regarding the expansion of space. |
2310.05332 | Wilfredo Yupanqui Carpio | Brayan Melchor, Rolando Perca and Wilfredo Yupanqui | Semiclassical resolution of the black hole singularity inspired in the
minimal uncertainty approach | The paper contains 23 pages and 7 figures | null | 10.1016/j.nuclphysb.2024.116584 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new lapse function that simplifies the Hamiltonian constraint,
describing the interior of the black hole in terms of the Ashtekar-Barbero
variables, into a more straightforward form. The new Hamiltonian leads to
different equations of motion than those found in the literature, but through a
suitable transformation between temporal parameters, it is found that such a
choice leads us to the classical solutions of the Schwarzschild metric, still
preserving the physical singularity. In order to resolve this singularity, and
inspired by the minimal uncertainty approach, we modify the classical algebra
between the dynamic variables of the model, imposing an effective dynamics
within the black hole. As a consequence, one of the dynamic variables, denoted
by $p_b$, acquires a minimum value at the singularity $t=0$, and on the other
hand, the variable related to the radius of the 2-sphere, $p_c$, leads to the
resolution of the classical singularity of the black hole by replacing it with
a bounce that connects the interior of the black hole with the interior of the
white hole. This bounce occurs in the Planck-scale region, where a new event
horizon manifests. Upon crossing this horizon, the nature of the interval
changes from spatial to temporal outside the white hole.
| [
{
"created": "Mon, 9 Oct 2023 01:26:15 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Oct 2023 01:12:10 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Jun 2024 19:48:17 GMT",
"version": "v3"
}
] | 2024-06-10 | [
[
"Melchor",
"Brayan",
""
],
[
"Perca",
"Rolando",
""
],
[
"Yupanqui",
"Wilfredo",
""
]
] | We propose a new lapse function that simplifies the Hamiltonian constraint, describing the interior of the black hole in terms of the Ashtekar-Barbero variables, into a more straightforward form. The new Hamiltonian leads to different equations of motion than those found in the literature, but through a suitable transformation between temporal parameters, it is found that such a choice leads us to the classical solutions of the Schwarzschild metric, still preserving the physical singularity. In order to resolve this singularity, and inspired by the minimal uncertainty approach, we modify the classical algebra between the dynamic variables of the model, imposing an effective dynamics within the black hole. As a consequence, one of the dynamic variables, denoted by $p_b$, acquires a minimum value at the singularity $t=0$, and on the other hand, the variable related to the radius of the 2-sphere, $p_c$, leads to the resolution of the classical singularity of the black hole by replacing it with a bounce that connects the interior of the black hole with the interior of the white hole. This bounce occurs in the Planck-scale region, where a new event horizon manifests. Upon crossing this horizon, the nature of the interval changes from spatial to temporal outside the white hole. |
1006.1842 | Khaled Saaidi | Kh. Saaidi, A. Aghamohammadi | Equivalence Principle (EP) and Solar System Constraints on $R(1\pm
\epsilon \ln({R \over R_c}))$ model of Gravity | 6 pages, no figure, Accepted for publication in Astrophysics & Space
Science | Astrophys. Space Sci. 333 (2011) 327 | 10.1007/s10509-011-0621-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Experiments on the violation of equivalence principle (EP) and solar system
give a number of constraints in which any modified gravity model must satisfy
them. We study these constraints on a kind of $f(R)$ gravity as $f(R) = R(1\pm
\epsilon \ln({R \over R_c}))$. For this investigation we use of chameleon
mechanism and show that a spherically body has thin-shell in this model. So
that we obtain an effective coupling of the fifth force which is suppressed
through a chameleon mechanism. Also, we obtain $\gamma_{PPN} = 1 \pm 1.13
\times10^{-5}$ which is agreement with experiment results. At last, we show
that for $R_c \thickapprox \rho_c$ this model is consistent with EP, thin shell
condition and fifth force of chameleon mechanism for $\epsilon \backsimeq
10^{-14}$.
| [
{
"created": "Wed, 9 Jun 2010 16:11:27 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jan 2011 11:41:35 GMT",
"version": "v2"
}
] | 2014-01-20 | [
[
"Saaidi",
"Kh.",
""
],
[
"Aghamohammadi",
"A.",
""
]
] | Experiments on the violation of equivalence principle (EP) and solar system give a number of constraints in which any modified gravity model must satisfy them. We study these constraints on a kind of $f(R)$ gravity as $f(R) = R(1\pm \epsilon \ln({R \over R_c}))$. For this investigation we use of chameleon mechanism and show that a spherically body has thin-shell in this model. So that we obtain an effective coupling of the fifth force which is suppressed through a chameleon mechanism. Also, we obtain $\gamma_{PPN} = 1 \pm 1.13 \times10^{-5}$ which is agreement with experiment results. At last, we show that for $R_c \thickapprox \rho_c$ this model is consistent with EP, thin shell condition and fifth force of chameleon mechanism for $\epsilon \backsimeq 10^{-14}$. |
2305.06752 | Xing Zhang | Xing Zhang, Bo Wang, Rui Niu | Constraining the attractive fifth force in the general free
scalar-tensor gravity with solar system experiments | 11 pages, 2 figures, 2 tables | Eur. Phys. J. C (2024) 84:381 | 10.1140/epjc/s10052-024-12723-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we focus on the general free scalar-tensor gravity with three
free coupling functions, which in the near-field region looks like general
relativity (GR) plus a fifth force of Yukawa-type induced by the scalar field.
We show that the fifth force is always attractive in the theory. We investigate
the effects of the attractive fifth force and calculate in detail the fifth
force-induced orbital precession rate $\delta\omega/\omega$ and the
parameterized post-Newtonian parameters $\gamma$ and $\beta$, all of which
depend on the fifth force parameters and the interaction distance. It turns out
that, due to the attractive fifth force, $\delta\omega/\omega$ is always
greater than zero, $\gamma$ is always less than one, $\beta$ is greater than
one at large distances, and additionally this class of theories is ruled out as
an alternative theory to dark matter. We place stringent constraints on the
fifth force parameters by combining the lunar laser ranging (LLR), Cassini, and
Mercury precession experiments, and derive the upper bounds on the strength
ratio of the fifth force to gravitational force at different scales from the
LLR observation. We find that the Mercury constraint is not competitive with
the LLR and Cassini constraints and the LLR observation imposes much more
stringent bounds on the strength ratio on large scales than on small scales.
Our results show that this theory is sufficiently close to GR for a small
enough fifth force strength and can reduce to GR with a minimally coupled
scalar field in the absence of fifth force.
| [
{
"created": "Thu, 11 May 2023 12:18:42 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2024 00:08:54 GMT",
"version": "v2"
}
] | 2024-04-11 | [
[
"Zhang",
"Xing",
""
],
[
"Wang",
"Bo",
""
],
[
"Niu",
"Rui",
""
]
] | In this paper, we focus on the general free scalar-tensor gravity with three free coupling functions, which in the near-field region looks like general relativity (GR) plus a fifth force of Yukawa-type induced by the scalar field. We show that the fifth force is always attractive in the theory. We investigate the effects of the attractive fifth force and calculate in detail the fifth force-induced orbital precession rate $\delta\omega/\omega$ and the parameterized post-Newtonian parameters $\gamma$ and $\beta$, all of which depend on the fifth force parameters and the interaction distance. It turns out that, due to the attractive fifth force, $\delta\omega/\omega$ is always greater than zero, $\gamma$ is always less than one, $\beta$ is greater than one at large distances, and additionally this class of theories is ruled out as an alternative theory to dark matter. We place stringent constraints on the fifth force parameters by combining the lunar laser ranging (LLR), Cassini, and Mercury precession experiments, and derive the upper bounds on the strength ratio of the fifth force to gravitational force at different scales from the LLR observation. We find that the Mercury constraint is not competitive with the LLR and Cassini constraints and the LLR observation imposes much more stringent bounds on the strength ratio on large scales than on small scales. Our results show that this theory is sufficiently close to GR for a small enough fifth force strength and can reduce to GR with a minimally coupled scalar field in the absence of fifth force. |
1504.02545 | Rana X. Adhikari | Huan Yang, Larry R. Price, Nicolas D. Smith, Rana X Adhikari, Haixing
Miao, Yanbei Chen | Towards the Laboratory Search for Space-Time Dissipation | 18 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been speculated that gravity could be an emergent phenomenon, with
classical general relativity as an effective, macroscopic theory, valid only
for classical systems at large temporal and spatial scales. As in classical
continuum dynamics, the existence of underlying microscopic degrees of freedom
may lead to macroscopic dissipative behaviors. With the hope that such
dissipative behaviors of gravity could be revealed by carefully designed
experiments in the laboratory, we consider a phenomenological model that adds
dissipations to the gravitational field, much similar to frictions in solids
and fluids. Constraints to such dissipative behavior can already be imposed by
astrophysical observations and existing experiments, but mostly in lower
frequencies. We propose a series of experiments working in higher frequency
regimes, which may potentially put more stringent bounds on these models.
| [
{
"created": "Fri, 10 Apr 2015 03:55:34 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jun 2015 06:14:15 GMT",
"version": "v2"
}
] | 2015-06-24 | [
[
"Yang",
"Huan",
""
],
[
"Price",
"Larry R.",
""
],
[
"Smith",
"Nicolas D.",
""
],
[
"Adhikari",
"Rana X",
""
],
[
"Miao",
"Haixing",
""
],
[
"Chen",
"Yanbei",
""
]
] | It has been speculated that gravity could be an emergent phenomenon, with classical general relativity as an effective, macroscopic theory, valid only for classical systems at large temporal and spatial scales. As in classical continuum dynamics, the existence of underlying microscopic degrees of freedom may lead to macroscopic dissipative behaviors. With the hope that such dissipative behaviors of gravity could be revealed by carefully designed experiments in the laboratory, we consider a phenomenological model that adds dissipations to the gravitational field, much similar to frictions in solids and fluids. Constraints to such dissipative behavior can already be imposed by astrophysical observations and existing experiments, but mostly in lower frequencies. We propose a series of experiments working in higher frequency regimes, which may potentially put more stringent bounds on these models. |
2209.00589 | Juliano Neves | Juliano C. S. Neves | Kasner cosmology in bumblebee gravity | 7 pages. Published in Annals of Physics | Ann. Phys. 454, 169338 (2023) | 10.1016/j.aop.2023.169338 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Kasner cosmology is a vacuum and anisotropically expanding spacetime in the
general relativity context. In this work, such a cosmological model is studied
in another context, the bumblebee model, where the Lorentz symmetry is
spontaneously broken. By using the bumblebee context it is possible to justify
the anisotropic feature of the Kasner cosmology. Thus, the origin of the
anisotropy in this cosmological model could be in the Lorentz symmetry
breaking. Lastly, an application in the pre-inflationary cosmology is
suggested.
| [
{
"created": "Thu, 1 Sep 2022 17:03:17 GMT",
"version": "v1"
},
{
"created": "Wed, 10 May 2023 15:00:54 GMT",
"version": "v2"
}
] | 2023-05-11 | [
[
"Neves",
"Juliano C. S.",
""
]
] | Kasner cosmology is a vacuum and anisotropically expanding spacetime in the general relativity context. In this work, such a cosmological model is studied in another context, the bumblebee model, where the Lorentz symmetry is spontaneously broken. By using the bumblebee context it is possible to justify the anisotropic feature of the Kasner cosmology. Thus, the origin of the anisotropy in this cosmological model could be in the Lorentz symmetry breaking. Lastly, an application in the pre-inflationary cosmology is suggested. |
2205.06878 | Vasil Todorinov | Vasil Todorinov, Saurya Das, and Pasquale Bosso | Effective field theory from Relativistic Generalized Uncertainty | Sixteenth Marcel Grossmann Meeting - MG16 2021, 19 pages, 2 tables | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories of Quantum Gravity predict a minimum measurable length and a
corresponding modification of the Heisenberg Uncertainty Principle to the
so-called Generalized Uncertainty Principle (GUP). However, this modification
is usually formulated in non-relativistic language, making it unclear whether
the minimum length is Lorentz invariant. We have formulated a Relativistic
Generalized Uncertainty Principle, resulting in a Lorentz invariant minimum
measurable length and the resolution of the composition law problem. This
proved to be an important step in the formulation of Quantum Field Theory with
minimum length. We derived the Lagrangians consistent with the existence of
minimal length and describing the behaviour of scalar, spinor, and U(1) gauge
fields. We calculated the Feynman rules (propagators and vertices) associated
with these Lagrangians. Furthermore, we calculated the Quantum Gravity
corrected scattering cross-sections for a lepton-lepton scattering. Finally, we
compared our results with current experiments, which allowed us to improve the
bounds on the scale at which quantum gravity phenomena will become relevant.
| [
{
"created": "Fri, 13 May 2022 20:23:08 GMT",
"version": "v1"
}
] | 2022-05-17 | [
[
"Todorinov",
"Vasil",
""
],
[
"Das",
"Saurya",
""
],
[
"Bosso",
"Pasquale",
""
]
] | Theories of Quantum Gravity predict a minimum measurable length and a corresponding modification of the Heisenberg Uncertainty Principle to the so-called Generalized Uncertainty Principle (GUP). However, this modification is usually formulated in non-relativistic language, making it unclear whether the minimum length is Lorentz invariant. We have formulated a Relativistic Generalized Uncertainty Principle, resulting in a Lorentz invariant minimum measurable length and the resolution of the composition law problem. This proved to be an important step in the formulation of Quantum Field Theory with minimum length. We derived the Lagrangians consistent with the existence of minimal length and describing the behaviour of scalar, spinor, and U(1) gauge fields. We calculated the Feynman rules (propagators and vertices) associated with these Lagrangians. Furthermore, we calculated the Quantum Gravity corrected scattering cross-sections for a lepton-lepton scattering. Finally, we compared our results with current experiments, which allowed us to improve the bounds on the scale at which quantum gravity phenomena will become relevant. |
1508.02642 | Pavel Krtous | Pavel Krtous, David Kubiznak, Ivan Kolar | Killing-Yano forms and Killing tensors on a warped space | 10 pages, no figures | Phys. Rev. D 93, 024057 (2016) | 10.1103/PhysRevD.93.024057 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We formulate several criteria under which the symmetries associated with the
Killing and Killing-Yano tensors on the base space can be lifted to the
symmetries of the full warped geometry. The procedure is explicitly illustrated
on several examples, providing new prototypes of spacetimes admitting such
tensors. In particular, we study a warped product of two Kerr-NUT-(A)dS
spacetimes and show that it gives rise to a new class of highly symmetric
vacuum (with cosmological constant) black hole solutions that inherit many of
the properties of the Kerr-NUT-(A)dS geometry.
| [
{
"created": "Tue, 11 Aug 2015 16:09:24 GMT",
"version": "v1"
}
] | 2016-02-03 | [
[
"Krtous",
"Pavel",
""
],
[
"Kubiznak",
"David",
""
],
[
"Kolar",
"Ivan",
""
]
] | We formulate several criteria under which the symmetries associated with the Killing and Killing-Yano tensors on the base space can be lifted to the symmetries of the full warped geometry. The procedure is explicitly illustrated on several examples, providing new prototypes of spacetimes admitting such tensors. In particular, we study a warped product of two Kerr-NUT-(A)dS spacetimes and show that it gives rise to a new class of highly symmetric vacuum (with cosmological constant) black hole solutions that inherit many of the properties of the Kerr-NUT-(A)dS geometry. |
1710.08765 | Wu-Sheng Dai | Wen-Du Li, Shi-Lin Li, Yu-Jie Chen, Yu-Zhu Chen, and Wu-Sheng Dai | Gravitational wave scattering theory without large-distance asymptotics | null | Annals of Physics 427 (2021) 168424 | 10.1016/j.aop.2021.168424 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In conventional gravitational wave scattering theory, a large-distance
asymptotic approximation is employed. In this approximation, the gravitational
wave is approximated by its large-distance asymptotics. In this paper, we
establish a gravitational wave scattering theory without the large-distance
asymptotic approximation.
| [
{
"created": "Tue, 24 Oct 2017 13:37:42 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Feb 2021 13:35:28 GMT",
"version": "v2"
}
] | 2021-03-02 | [
[
"Li",
"Wen-Du",
""
],
[
"Li",
"Shi-Lin",
""
],
[
"Chen",
"Yu-Jie",
""
],
[
"Chen",
"Yu-Zhu",
""
],
[
"Dai",
"Wu-Sheng",
""
]
] | In conventional gravitational wave scattering theory, a large-distance asymptotic approximation is employed. In this approximation, the gravitational wave is approximated by its large-distance asymptotics. In this paper, we establish a gravitational wave scattering theory without the large-distance asymptotic approximation. |
1402.2748 | Parthapratim Pradhan | Parthapratim Pradhan | Regular Black Holes as Particle Accelerators | 30 pages, 18 figures | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the possibility of arbitrarily high energy in the center of
mass(CM) frame of colliding particles in the vicinity of the infinite red-shift
surface of the spherically symmetric, static charged regular black holes
(Bardeen black hole, Ay\'{o}n-Beato and Garc\'{i}a black hole, and Hayward
black hole). We show that the CM energy of colliding particles near the
infinite red-shift surface of the \emph{extreme} regular black holes are
arbitrarily large while the non-extreme regular black holes have the finite
energy. We also compute the equation of innermost stable circular orbit(ISCO),
marginally bound circular orbit(MBCO) and circular photon orbit(CPO) of the
above regular black holes, which are most relevant to black hole accretion disk
theory.
| [
{
"created": "Wed, 12 Feb 2014 07:31:46 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Feb 2014 14:10:25 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Oct 2014 21:12:06 GMT",
"version": "v3"
}
] | 2014-10-14 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We investigate the possibility of arbitrarily high energy in the center of mass(CM) frame of colliding particles in the vicinity of the infinite red-shift surface of the spherically symmetric, static charged regular black holes (Bardeen black hole, Ay\'{o}n-Beato and Garc\'{i}a black hole, and Hayward black hole). We show that the CM energy of colliding particles near the infinite red-shift surface of the \emph{extreme} regular black holes are arbitrarily large while the non-extreme regular black holes have the finite energy. We also compute the equation of innermost stable circular orbit(ISCO), marginally bound circular orbit(MBCO) and circular photon orbit(CPO) of the above regular black holes, which are most relevant to black hole accretion disk theory. |
2207.14286 | Benjamin Steltner | Benjamin Steltner, Thorben Menne, Maria Alessandra Papa, Heinz-Bernd
Eggenstein | Density-clustering of continuous gravitational wave candidates from
large surveys | 7 pages, 3 figures | null | 10.1103/PhysRevD.106.104063 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Searches for continuous gravitational waves target nearly monochromatic
gravitational wave emission from e.g. non-axysmmetric fast-spinning neutron
stars. Broad surveys often require to explicitly search for a very large number
of different waveforms, easily exceeding $\sim10^{17}$ templates. In such
cases, for practical reasons, only the top, say $\sim10^{10}$, results are
saved and followed-up through a hierarchy of stages. Most of these candidates
are not completely independent of neighbouring ones, but arise due to some
common cause: a fluctuation, a signal or a disturbance. By judiciously
clustering together candidates stemming from the same root cause, the
subsequent follow-ups become more effective. A number of clustering algorithms
have been employed in past searches based on iteratively finding symmetric and
compact over-densities around candidates with high detection statistic values.
The new clustering method presented in this paper is a significant improvement
over previous methods: it is agnostic about the shape of the over-densities, is
very efficient and it is effective: at a very high detection efficiency, it has
a noise rejection of $99.99\%$ , is capable of clustering two orders of
magnitude more candidates than attainable before and, at fixed sensitivity it
enables more than a factor of 30 faster follow-ups. We also demonstrate how to
optimally choose the clustering parameters.
| [
{
"created": "Thu, 28 Jul 2022 17:59:30 GMT",
"version": "v1"
}
] | 2022-12-14 | [
[
"Steltner",
"Benjamin",
""
],
[
"Menne",
"Thorben",
""
],
[
"Papa",
"Maria Alessandra",
""
],
[
"Eggenstein",
"Heinz-Bernd",
""
]
] | Searches for continuous gravitational waves target nearly monochromatic gravitational wave emission from e.g. non-axysmmetric fast-spinning neutron stars. Broad surveys often require to explicitly search for a very large number of different waveforms, easily exceeding $\sim10^{17}$ templates. In such cases, for practical reasons, only the top, say $\sim10^{10}$, results are saved and followed-up through a hierarchy of stages. Most of these candidates are not completely independent of neighbouring ones, but arise due to some common cause: a fluctuation, a signal or a disturbance. By judiciously clustering together candidates stemming from the same root cause, the subsequent follow-ups become more effective. A number of clustering algorithms have been employed in past searches based on iteratively finding symmetric and compact over-densities around candidates with high detection statistic values. The new clustering method presented in this paper is a significant improvement over previous methods: it is agnostic about the shape of the over-densities, is very efficient and it is effective: at a very high detection efficiency, it has a noise rejection of $99.99\%$ , is capable of clustering two orders of magnitude more candidates than attainable before and, at fixed sensitivity it enables more than a factor of 30 faster follow-ups. We also demonstrate how to optimally choose the clustering parameters. |
1301.6794 | Marco Astorino | Marco Astorino | Embedding hairy black holes in a magnetic universe | 17 pages, V2: final version, to appear in Phys. Rev. D | Phys. Rev. D 87, 084029 (2013) | 10.1103/PhysRevD.87.084029 | CECS-PHY-13/01 | gr-qc hep-th nlin.SI | http://creativecommons.org/licenses/by-nc-sa/3.0/ | Ernst's solution generating technique is adapted to Einstein-Maxwell theory
conformally (and minimally) coupled to a scalar field. This integrable system
enjoys a SU(2,1) symmetry which enables one to move, by Kinnersley
transformations, though the axisymmetric and stationary solution space,
building an infinite tower of physically inequivalent solutions. As a specific
application, metrics associated to scalar hairy black holes, such as the ones
discovered by Bocharova, Bronnikov, Melnikov and Bekenstein, are embedded in
the external magnetic field of the Melvin universe.
| [
{
"created": "Mon, 28 Jan 2013 22:11:51 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Mar 2013 16:58:05 GMT",
"version": "v2"
}
] | 2013-04-24 | [
[
"Astorino",
"Marco",
""
]
] | Ernst's solution generating technique is adapted to Einstein-Maxwell theory conformally (and minimally) coupled to a scalar field. This integrable system enjoys a SU(2,1) symmetry which enables one to move, by Kinnersley transformations, though the axisymmetric and stationary solution space, building an infinite tower of physically inequivalent solutions. As a specific application, metrics associated to scalar hairy black holes, such as the ones discovered by Bocharova, Bronnikov, Melnikov and Bekenstein, are embedded in the external magnetic field of the Melvin universe. |
2310.08253 | Christopher Straub | Christopher Straub and Sebastian Wolfschmidt | EVStabilityNet: Predicting the Stability of Star Clusters in General
Relativity | 16 pages, 4 figures | Class. Quantum Grav. (2024) | 10.1088/1361-6382/ad228a | null | gr-qc astro-ph.GA math-ph math.MP | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We present a deep neural network which predicts the stability of isotropic
steady states of the asymptotically flat, spherically symmetric Einstein-Vlasov
system in Schwarzschild coordinates. The network takes as input the energy
profile and the redshift of the steady state. Its architecture consists of a
U-Net with a dense bridge. The network was trained on more than ten thousand
steady states using an active learning scheme and has high accuracy on test
data. As first applications, we analyze the validity of physical hypotheses
regarding the stability of the steady states.
| [
{
"created": "Thu, 12 Oct 2023 11:56:02 GMT",
"version": "v1"
}
] | 2024-01-29 | [
[
"Straub",
"Christopher",
""
],
[
"Wolfschmidt",
"Sebastian",
""
]
] | We present a deep neural network which predicts the stability of isotropic steady states of the asymptotically flat, spherically symmetric Einstein-Vlasov system in Schwarzschild coordinates. The network takes as input the energy profile and the redshift of the steady state. Its architecture consists of a U-Net with a dense bridge. The network was trained on more than ten thousand steady states using an active learning scheme and has high accuracy on test data. As first applications, we analyze the validity of physical hypotheses regarding the stability of the steady states. |
0909.2867 | P Ajith | P. Ajith, M. Hannam, S. Husa, Y. Chen, B. Bruegmann, N. Dorband, D.
Mueller, F. Ohme, D. Pollney, C. Reisswig, L. Santamaria, J. Seiler | Inspiral-merger-ringdown waveforms for black-hole binaries with
non-precessing spins | To appear in Phys. Rev. Lett. Significant new results. One figure
removed due to page limitation | Phys.Rev.Lett.106:241101,2011 | 10.1103/PhysRevLett.106.241101 | LIGO-P0900085-v5 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first analytical inspiral-merger-ringdown gravitational
waveforms from binary black holes (BBHs) with non-precessing spins, that is
based on a description of the late-inspiral, merger and ringdown in full
general relativity. By matching a post-Newtonian description of the inspiral to
a set of numerical-relativity simulations, we obtain a waveform family with a
conveniently small number of physical parameters. These waveforms will allow us
to detect a larger parameter space of BBH coalescence, including a considerable
fraction of precessing binaries in the comparable-mass regime, thus
significantly improving the expected detection rates.
| [
{
"created": "Tue, 15 Sep 2009 20:15:41 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Sep 2010 22:31:34 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Jun 2011 20:13:06 GMT",
"version": "v3"
}
] | 2011-06-27 | [
[
"Ajith",
"P.",
""
],
[
"Hannam",
"M.",
""
],
[
"Husa",
"S.",
""
],
[
"Chen",
"Y.",
""
],
[
"Bruegmann",
"B.",
""
],
[
"Dorband",
"N.",
""
],
[
"Mueller",
"D.",
""
],
[
"Ohme",
"F.",
""
],
... | We present the first analytical inspiral-merger-ringdown gravitational waveforms from binary black holes (BBHs) with non-precessing spins, that is based on a description of the late-inspiral, merger and ringdown in full general relativity. By matching a post-Newtonian description of the inspiral to a set of numerical-relativity simulations, we obtain a waveform family with a conveniently small number of physical parameters. These waveforms will allow us to detect a larger parameter space of BBH coalescence, including a considerable fraction of precessing binaries in the comparable-mass regime, thus significantly improving the expected detection rates. |
0709.4610 | Marco Valerio Battisti | Marco Valerio Battisti and Giovanni Montani | Minisuperspace dynamics in a generalized uncertainty principle framework | 8 pages, 4 figures; to appear in the proceedings of the 4th
Italian-Sino Workshop on Relativistic Astrophysics, AIP Conference Series | AIPConf.Proc.966:219-226,2008 | 10.1063/1.2836998 | null | gr-qc hep-th | null | The minisuperspace dynamics of the Friedmann-Robertson-Walker (FRW) and of
the Taub Universes in the context of a Generalized Uncertainty Principle is
analyzed in detail. In particular, the motion of the wave packets is
investigated and, in both the models, the classical singularity appear to be
probabilistic suppressed. Moreover, the FRW wave packets approach the Planckian
region in a stationary way and no evidences for a Big-Bounce, as predicted in
Loop Quantum Cosmology, appear. On the other hand, the Taub wave packets
provide the right behavior in predicting an isotropic Universe.
| [
{
"created": "Fri, 28 Sep 2007 13:56:41 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Oct 2007 09:15:59 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Battisti",
"Marco Valerio",
""
],
[
"Montani",
"Giovanni",
""
]
] | The minisuperspace dynamics of the Friedmann-Robertson-Walker (FRW) and of the Taub Universes in the context of a Generalized Uncertainty Principle is analyzed in detail. In particular, the motion of the wave packets is investigated and, in both the models, the classical singularity appear to be probabilistic suppressed. Moreover, the FRW wave packets approach the Planckian region in a stationary way and no evidences for a Big-Bounce, as predicted in Loop Quantum Cosmology, appear. On the other hand, the Taub wave packets provide the right behavior in predicting an isotropic Universe. |
1806.08062 | Ryouta Matsuyama | Ryouta Matsuyama and Michiyasu Nagasawa | Gravity in Extreme Regions Based on Noncommutative Quantization of
Teleparallel Gravity | 28 pages, 2 figures | Class. Quantum Grav. 35 (2018) 155010 | 10.1088/1361-6382/aacddc | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, a noncommutative gravitational theory is constructed by
applying Moyal deformation quantization and the Seiberg-Witten map to
teleparallel gravity, a classical gravitational theory, as a gauge theory of
local translational symmetry. Since our model is based on teleparallel gravity,
it is an extremely simple noncommutative gravitational theory. We also clearly
divide the role of the products, such that the metric is responsible for the
rule of the inner product (which is calculated by taking the sum over the
subscripts) and the Moyal product is responsible for tensor and field
noncommutativity. This solves problems related to the order of the products and
the relationship between the metric and the Moyal product. Furthermore, we
analyze the cosmic evolution of the very early universe and the spacetime
features around black holes using the constructed noncommutative gravitational
theory, and find that gravity acts repulsively in the extreme region where its
quantum effects become prominent.
| [
{
"created": "Thu, 21 Jun 2018 04:34:28 GMT",
"version": "v1"
}
] | 2018-07-20 | [
[
"Matsuyama",
"Ryouta",
""
],
[
"Nagasawa",
"Michiyasu",
""
]
] | In this paper, a noncommutative gravitational theory is constructed by applying Moyal deformation quantization and the Seiberg-Witten map to teleparallel gravity, a classical gravitational theory, as a gauge theory of local translational symmetry. Since our model is based on teleparallel gravity, it is an extremely simple noncommutative gravitational theory. We also clearly divide the role of the products, such that the metric is responsible for the rule of the inner product (which is calculated by taking the sum over the subscripts) and the Moyal product is responsible for tensor and field noncommutativity. This solves problems related to the order of the products and the relationship between the metric and the Moyal product. Furthermore, we analyze the cosmic evolution of the very early universe and the spacetime features around black holes using the constructed noncommutative gravitational theory, and find that gravity acts repulsively in the extreme region where its quantum effects become prominent. |
1610.05662 | Hyerim Noh | Jai-chan Hwang and Hyerim Noh | Special relativistic hydrodynamics with gravitation | 15 pages, no figure. Accepted in ApJ | null | 10.3847/1538-4357/833/2/180 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The special relativistic hydrodynamics with weak gravity is hitherto unknown
in the literature. Whether such an asymmetric combination is possible was
unclear. Here, the hydrodynamic equations with Poisson-type gravity considering
fully relativistic velocity and pressure under the weak gravity and the
action-at-a-distance limit are consistently derived from Einstein's general
relativity. Analysis is made in the maximal slicing where the Poisson's
equation becomes much simpler than our previous study in the zero-shear gauge.
Also presented is the hydrodynamic equations in the first post-Newtonian
approximation, now under the {\it general} hypersurface condition. Our
formulation includes the anisotropic stress.
| [
{
"created": "Mon, 17 Oct 2016 06:46:16 GMT",
"version": "v1"
}
] | 2016-12-21 | [
[
"Hwang",
"Jai-chan",
""
],
[
"Noh",
"Hyerim",
""
]
] | The special relativistic hydrodynamics with weak gravity is hitherto unknown in the literature. Whether such an asymmetric combination is possible was unclear. Here, the hydrodynamic equations with Poisson-type gravity considering fully relativistic velocity and pressure under the weak gravity and the action-at-a-distance limit are consistently derived from Einstein's general relativity. Analysis is made in the maximal slicing where the Poisson's equation becomes much simpler than our previous study in the zero-shear gauge. Also presented is the hydrodynamic equations in the first post-Newtonian approximation, now under the {\it general} hypersurface condition. Our formulation includes the anisotropic stress. |
2211.00991 | Beyhan Pulice | Durmus Demir, Beyhan Pulice | Geometric Proca with Matter in Metric-Palatini Gravity | 11 pages, 6 figures. v2: Added references | Eur. Phys. J. C 82, 996 (2022) | 10.1140/epjc/s10052-022-10986-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we study linear, torsion-free metric-Palatini gravity,
extended by the quadratics of the antisymmetric part of the Ricci tensor and
extended also by the presence of the affine connection in the matter sector. We
show that this extended metric-Palatini gravity reduces dynamically to the
general relativity plus a geometrical massive vector field corresponding to
non-metricity of the connection. We also show that this geometric Proca field
couples to fermions universally. We derive static, spherically symmetric field
equations of this Einstein-geometric Proca theory. We study possibility of
black hole solutions by taking into account the presence of a dust distribution
that couples to the geometric Proca. Our analytical and numerical analyses show
that the presence of this dust worsens the possibility of horizon formation. We
briefly discuss possible roles of this universally-coupled geometric Proca in
the astrophysical and collider processes.
| [
{
"created": "Wed, 2 Nov 2022 09:52:47 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2023 12:10:52 GMT",
"version": "v2"
}
] | 2023-01-25 | [
[
"Demir",
"Durmus",
""
],
[
"Pulice",
"Beyhan",
""
]
] | In the present work, we study linear, torsion-free metric-Palatini gravity, extended by the quadratics of the antisymmetric part of the Ricci tensor and extended also by the presence of the affine connection in the matter sector. We show that this extended metric-Palatini gravity reduces dynamically to the general relativity plus a geometrical massive vector field corresponding to non-metricity of the connection. We also show that this geometric Proca field couples to fermions universally. We derive static, spherically symmetric field equations of this Einstein-geometric Proca theory. We study possibility of black hole solutions by taking into account the presence of a dust distribution that couples to the geometric Proca. Our analytical and numerical analyses show that the presence of this dust worsens the possibility of horizon formation. We briefly discuss possible roles of this universally-coupled geometric Proca in the astrophysical and collider processes. |
2012.09305 | Antonio Ferreiro | Antonio Ferreiro | Instantaneous vacuum for Dirac fields with a Yukawa interaction in
cosmological space-times | null | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We propose a suitable vacuum state for a quantized Dirac field interacting
with a classical scalar field in a Friedman-Robertson-Walker-Lemaitre
spacetime. This state is constructed from an extended version of the adiabatic
expansion of the associated Fourier modes of the field. We compute the full
renormalized stress-energy tensor. For any given initial time, this
instantaneous vacuum can always be chosen to have vanishing Fourier modes for
the renormalized stress-energy tensor. We check the consistency of the solution
for several inflationary models.
| [
{
"created": "Wed, 16 Dec 2020 22:50:55 GMT",
"version": "v1"
}
] | 2020-12-18 | [
[
"Ferreiro",
"Antonio",
""
]
] | We propose a suitable vacuum state for a quantized Dirac field interacting with a classical scalar field in a Friedman-Robertson-Walker-Lemaitre spacetime. This state is constructed from an extended version of the adiabatic expansion of the associated Fourier modes of the field. We compute the full renormalized stress-energy tensor. For any given initial time, this instantaneous vacuum can always be chosen to have vanishing Fourier modes for the renormalized stress-energy tensor. We check the consistency of the solution for several inflationary models. |
1511.00611 | Antonio Pasqua Dr. | Antonio Pasqua, Surajit Chattopadhyay, Ratbay Myrzakulov | Power-Law Entropy-Corrected Holographic Dark Energy in
Ho\v{r}ava-Lifshitz Cosmology with Granda-Oliveros Cut-off | More information added; Figures inserted | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the Power Law Entropy Corrected Holographic Dark
Energy (PLECHDE) model in the framework of a non-flat Universe and of
Ho\v{r}ava-Lifshitz cosmology with infrared cut-off given by recently proposed
Granda-Oliveros cut-off, which contains one term proportional to the Hubble
parameter squared $H^2$ and one term proportional to the first time derivative
of the Hubble parameter $\dot{H}$. Moreover, this cut-off is characterized by
two constant parameters, $\alpha$ and $\beta$. For the two cases corresponding
to non-interacting and interacting DE and Dark Matter (DM), we derive the
evolutionary form of the energy density of DE $\Omega_D'$, the Equation of
State (EoS) parameter of DE $\omega_D$ and the deceleration parameter $q$.
Using the parametrization of the EoS parameter
$\omega_D\left(z\right)=\omega_0+\omega_1 z$, we obtain the expressions of the
two parameters $\omega_0$ and $\omega_1$. We also study the statefinder
parameters $\left\{ r,s \right\}$, the snap and lerk cosmographic parameters
and the squared speed of the sound $v_s^2$. We also calculate the values of the
quantities we study for different values of the running parameter $\lambda$ and
for different set of values of $\alpha$ and $\beta$.
| [
{
"created": "Mon, 26 Oct 2015 07:28:23 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Mar 2016 15:02:19 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Mar 2016 18:07:46 GMT",
"version": "v3"
}
] | 2016-03-25 | [
[
"Pasqua",
"Antonio",
""
],
[
"Chattopadhyay",
"Surajit",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In this paper, we study the Power Law Entropy Corrected Holographic Dark Energy (PLECHDE) model in the framework of a non-flat Universe and of Ho\v{r}ava-Lifshitz cosmology with infrared cut-off given by recently proposed Granda-Oliveros cut-off, which contains one term proportional to the Hubble parameter squared $H^2$ and one term proportional to the first time derivative of the Hubble parameter $\dot{H}$. Moreover, this cut-off is characterized by two constant parameters, $\alpha$ and $\beta$. For the two cases corresponding to non-interacting and interacting DE and Dark Matter (DM), we derive the evolutionary form of the energy density of DE $\Omega_D'$, the Equation of State (EoS) parameter of DE $\omega_D$ and the deceleration parameter $q$. Using the parametrization of the EoS parameter $\omega_D\left(z\right)=\omega_0+\omega_1 z$, we obtain the expressions of the two parameters $\omega_0$ and $\omega_1$. We also study the statefinder parameters $\left\{ r,s \right\}$, the snap and lerk cosmographic parameters and the squared speed of the sound $v_s^2$. We also calculate the values of the quantities we study for different values of the running parameter $\lambda$ and for different set of values of $\alpha$ and $\beta$. |
gr-qc/0409122 | Edward Anderson | E. Anderson | The Campbell--Magaard Theorem is inadequate and inappropriate as a
protective theorem for relativistic field equations | 23 pages including 8 figures. This update has improved clarity and a
couple of new references | null | null | null | gr-qc | null | Given a particular prescription for the Einstein field equations (EFE's), it
is important to have general protective theorems that lend support to it. The
prescription of data on a timelike hypersurface for the (n + 1)-d EFE's arises
in `noncompact Kaluza--Klein theory', and in certain kinds of braneworlds and
low-energy string theory. The Campbell--Magaard (CM) theorem, which asserts
local existence (and, with extra conditions, uniqueness) of analytic embeddings
of completely general n-d manifolds into vacuum (n + 1)-d manifolds, has often
recently been invoked as a protective theorem for such prescriptions. But in
this paper I argue that there are problems with loosening the CM thoerem of
restrictive meanings in its statement, which is worthwhile thing to do in
pursuit of the proposed applications. While I remedy some problems by
identifying the required topology, delineating what `local' can be taken to
mean, and offering a new, more robust and covariant proof, other problems
remain unsurmountable. The theorem lends only inadequate support, both because
it offers no guarantee of continuous dependence on the data and because it
disregards causality. Furthermore, the theorem is only for the analytic
functions which renders it inappropriate for the study of the relativistic
equations of modern physics. Unfortunately, there are no known general theorems
that offer adequate protection to the proposed applications' prescription. I
conclude by making some suggestions for more modest progress.
| [
{
"created": "Thu, 30 Sep 2004 19:45:23 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Dec 2004 20:30:17 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Anderson",
"E.",
""
]
] | Given a particular prescription for the Einstein field equations (EFE's), it is important to have general protective theorems that lend support to it. The prescription of data on a timelike hypersurface for the (n + 1)-d EFE's arises in `noncompact Kaluza--Klein theory', and in certain kinds of braneworlds and low-energy string theory. The Campbell--Magaard (CM) theorem, which asserts local existence (and, with extra conditions, uniqueness) of analytic embeddings of completely general n-d manifolds into vacuum (n + 1)-d manifolds, has often recently been invoked as a protective theorem for such prescriptions. But in this paper I argue that there are problems with loosening the CM thoerem of restrictive meanings in its statement, which is worthwhile thing to do in pursuit of the proposed applications. While I remedy some problems by identifying the required topology, delineating what `local' can be taken to mean, and offering a new, more robust and covariant proof, other problems remain unsurmountable. The theorem lends only inadequate support, both because it offers no guarantee of continuous dependence on the data and because it disregards causality. Furthermore, the theorem is only for the analytic functions which renders it inappropriate for the study of the relativistic equations of modern physics. Unfortunately, there are no known general theorems that offer adequate protection to the proposed applications' prescription. I conclude by making some suggestions for more modest progress. |
1707.05162 | Muhammad Sharif | M. Sharif and Ayesha Ikram | Existence of Static Wormholes in $f(\mathcal{G},T)$ Gravity | 23 pages, 11 figures | Int. J. Mod. Phys. D 27(2018)1750182 | 10.1142/S0218271817501826 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigates static spherically symmetric traversable wormhole
solutions in $f(\mathcal{G},T)$ gravity ($\mathcal{G}$ and $T$ represent the
Gauss-Bonnet invariant and trace of the energy-momentum tensor, respectively).
We construct explicit expressions for ordinary matter by taking specific form
of red-shift function and $f(\mathcal{G},T)$ model. To analyze possible
existence of wormholes, we consider anisotropic, isotropic as well as
barotropic matter distributions. The graphical analysis shows the violation of
null energy condition for the effective energy-momentum tensor throughout the
evolution while ordinary matter meets energy constraints in certain regions for
each case of matter distribution. It is concluded that traversable WH solutions
are physically acceptable in this theory.
| [
{
"created": "Fri, 14 Jul 2017 03:41:00 GMT",
"version": "v1"
}
] | 2018-01-10 | [
[
"Sharif",
"M.",
""
],
[
"Ikram",
"Ayesha",
""
]
] | This paper investigates static spherically symmetric traversable wormhole solutions in $f(\mathcal{G},T)$ gravity ($\mathcal{G}$ and $T$ represent the Gauss-Bonnet invariant and trace of the energy-momentum tensor, respectively). We construct explicit expressions for ordinary matter by taking specific form of red-shift function and $f(\mathcal{G},T)$ model. To analyze possible existence of wormholes, we consider anisotropic, isotropic as well as barotropic matter distributions. The graphical analysis shows the violation of null energy condition for the effective energy-momentum tensor throughout the evolution while ordinary matter meets energy constraints in certain regions for each case of matter distribution. It is concluded that traversable WH solutions are physically acceptable in this theory. |
1007.4077 | Christian Corda cordac | Christian Corda | Massive relic gravitational waves from f(R) theories of gravity:
production and potential detection | Published by The European Physical Journal C | Eur.Phys.J.C65:257-267,2010 | 10.1140/epjc/s10052-009-1100-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The production of a stochastic background of relic gravitational waves is
well known in various works in the literature, where, by using the so called
adiabatically-amplified zero-point fluctuations process, it has been shown how
the standard inflationary scenario for the early universe can in principle
provide a distinctive spectrum of relic gravitational waves. In this paper, it
is shown that, in general, f(R) theories of gravity produce a third massive
polarization of gravitational waves and the primordial production of this
polarization is analysed adapting the adiabatically-amplified zero-point
fluctuations process at this case. In this way, previous results, where only
particular cases of f(R) theories have been analysed, will be generalized. The
presence of the mass could also have important applications in cosmology,
because the fact that gravitational waves can have mass could give a
contribution to the dark matter of the Universe. An upper bound for these relic
gravitational waves, which arises from the WMAP constrains, is also released.
At the end of the paper, the potential detection of such massive gravitational
waves using interferometers like Virgo and LIGO is discussed.
| [
{
"created": "Fri, 23 Jul 2010 09:12:26 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Corda",
"Christian",
""
]
] | The production of a stochastic background of relic gravitational waves is well known in various works in the literature, where, by using the so called adiabatically-amplified zero-point fluctuations process, it has been shown how the standard inflationary scenario for the early universe can in principle provide a distinctive spectrum of relic gravitational waves. In this paper, it is shown that, in general, f(R) theories of gravity produce a third massive polarization of gravitational waves and the primordial production of this polarization is analysed adapting the adiabatically-amplified zero-point fluctuations process at this case. In this way, previous results, where only particular cases of f(R) theories have been analysed, will be generalized. The presence of the mass could also have important applications in cosmology, because the fact that gravitational waves can have mass could give a contribution to the dark matter of the Universe. An upper bound for these relic gravitational waves, which arises from the WMAP constrains, is also released. At the end of the paper, the potential detection of such massive gravitational waves using interferometers like Virgo and LIGO is discussed. |
2102.13489 | Jitendra Kumar Dr. | Jitendra Kumar, Puja Bharti | Pulsar PSR B0943+10 as an isotropic Vaidya-Tikekar type compact star : A
comprehensive study | NA | null | 10.1007/s12043-022-02400-4 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have constructed a model for well behaved isotropic compact
star in the presence of charged perfect fluid, by considering a static and
spherically symmetric metric in Schwarzschild's canonical coordinate system. To
put the resulting differential equations into a closed system, we have employed
the Vaidya & Tikekar (J. Astrophys. Astron. 3:325, 1982) form of the metric
potential grr. The resulting energy-momentum components, i.e., energy density
and pressure contain six constants; two of these are determined through the
junction condition (matching the interior with the exterior Schwarzschild
solution) and by the property of vanishing pressure on the boundary. The
remaining constants are constrained by requirements of a real compact star. The
physical acceptability of our model is tested using the data of the pulsar PSR
B0943+10. Using graphical analysis and tabular information we have shown that
our model obeys all the physical requirements. The stability of this model is
evaluated using the Tolman-Oppenheimer-Volkoff equation, the adiabatic index
and the Harrison-Zeldovich-Novikov Criterion and it has passed the evaluation.
| [
{
"created": "Thu, 25 Feb 2021 09:19:25 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Sep 2021 13:05:23 GMT",
"version": "v2"
}
] | 2022-09-07 | [
[
"Kumar",
"Jitendra",
""
],
[
"Bharti",
"Puja",
""
]
] | In this paper, we have constructed a model for well behaved isotropic compact star in the presence of charged perfect fluid, by considering a static and spherically symmetric metric in Schwarzschild's canonical coordinate system. To put the resulting differential equations into a closed system, we have employed the Vaidya & Tikekar (J. Astrophys. Astron. 3:325, 1982) form of the metric potential grr. The resulting energy-momentum components, i.e., energy density and pressure contain six constants; two of these are determined through the junction condition (matching the interior with the exterior Schwarzschild solution) and by the property of vanishing pressure on the boundary. The remaining constants are constrained by requirements of a real compact star. The physical acceptability of our model is tested using the data of the pulsar PSR B0943+10. Using graphical analysis and tabular information we have shown that our model obeys all the physical requirements. The stability of this model is evaluated using the Tolman-Oppenheimer-Volkoff equation, the adiabatic index and the Harrison-Zeldovich-Novikov Criterion and it has passed the evaluation. |
1904.04843 | Manus R. Visser | Ted Jacobson, Manus R. Visser | Spacetime Equilibrium at Negative Temperature and the Attraction of
Gravity | 7 pages, Essay written for the Gravity Research Foundation 2019
Awards for Essays on Gravitation | null | 10.1142/S0218271819440164 | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | We derive the Einstein equation from the condition that every small causal
diamond is a variation of a flat empty diamond with the same free conformal
energy, as would be expected for a near-equilibrium state. The attractiveness
of gravity hinges on the negativity of the absolute temperature of these
diamonds, a property we infer from the generalized entropy.
| [
{
"created": "Tue, 9 Apr 2019 18:00:06 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jun 2019 19:50:16 GMT",
"version": "v2"
}
] | 2019-11-26 | [
[
"Jacobson",
"Ted",
""
],
[
"Visser",
"Manus R.",
""
]
] | We derive the Einstein equation from the condition that every small causal diamond is a variation of a flat empty diamond with the same free conformal energy, as would be expected for a near-equilibrium state. The attractiveness of gravity hinges on the negativity of the absolute temperature of these diamonds, a property we infer from the generalized entropy. |
1109.5753 | O-Kab Kwon | Inyong Cho, O-Kab Kwon | Scalar Perturbation in Symmetric Lee-Wick Bouncing Universe | 21 pages, 6 figures, references are added | null | 10.1088/1475-7516/2011/11/043 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the scalar perturbation in the Lee-Wick bouncing universe
driven by an ordinary scalar field plus a ghost field. We consider only a
symmetric evolution of the universe and the scalar fields about the bouncing
point. The gauge invariant Sasaki-Mukhanov variable is numerically solved in
the spatially flat gauge. We find a new form of the initial perturbation
growing during the contracting phase. After the bouncing, this growing mode
stabilizes to a constant mode which is responsible for the late-time power
spectrum.
| [
{
"created": "Tue, 27 Sep 2011 00:27:33 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Oct 2011 15:10:09 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Cho",
"Inyong",
""
],
[
"Kwon",
"O-Kab",
""
]
] | We investigate the scalar perturbation in the Lee-Wick bouncing universe driven by an ordinary scalar field plus a ghost field. We consider only a symmetric evolution of the universe and the scalar fields about the bouncing point. The gauge invariant Sasaki-Mukhanov variable is numerically solved in the spatially flat gauge. We find a new form of the initial perturbation growing during the contracting phase. After the bouncing, this growing mode stabilizes to a constant mode which is responsible for the late-time power spectrum. |
2402.07068 | Cetin Senturk | Metin Gurses, Cetin Senturk, Bayram Tekin | Minimal Einstein-Aether Theory | 5 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that there is a minimal Einstein-Aether theory, obtained as a
phenomenologically and theoretically consistent limit from the generic
Einstein-Aether theory, that supports Einstein metrics as solutions with a
reduced cosmological constant. The minimal theory is obtained by taking three
of the coupling constants to be zero but keeping the expansion coupling
constant to be nonzero. The square of the expansion of the unit-timelike aether
field depletes the bare cosmological constant and thus provides, via local
Lorentz symmetry breaking inherent in the Einstein-Aether theories, a novel
mechanism for reconciling the observed, small cosmological constant (or dark
energy) with the large theoretical prediction coming from quantum field
theories. The crucial point here is that minimal Einstein-Aether theory does
not modify the well-tested aspects of General Relativity such as solar systems
tests and black hole physics including gravitational waves.
| [
{
"created": "Sat, 10 Feb 2024 23:51:04 GMT",
"version": "v1"
}
] | 2024-02-13 | [
[
"Gurses",
"Metin",
""
],
[
"Senturk",
"Cetin",
""
],
[
"Tekin",
"Bayram",
""
]
] | We show that there is a minimal Einstein-Aether theory, obtained as a phenomenologically and theoretically consistent limit from the generic Einstein-Aether theory, that supports Einstein metrics as solutions with a reduced cosmological constant. The minimal theory is obtained by taking three of the coupling constants to be zero but keeping the expansion coupling constant to be nonzero. The square of the expansion of the unit-timelike aether field depletes the bare cosmological constant and thus provides, via local Lorentz symmetry breaking inherent in the Einstein-Aether theories, a novel mechanism for reconciling the observed, small cosmological constant (or dark energy) with the large theoretical prediction coming from quantum field theories. The crucial point here is that minimal Einstein-Aether theory does not modify the well-tested aspects of General Relativity such as solar systems tests and black hole physics including gravitational waves. |
2110.14379 | Semin Xavier | Semin Xavier (IITB), Alan Sunny (CUTN), and S. Shankaranarayanan
(IITB) | An exact model for evaporating primordial black holes in cosmological
space-time | V2: 11 pages,2 figures, added 2 appendices, accepted in PRD | null | 10.1103/PhysRevD.105.104038 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Primordial black holes (PBHs) in the mass range $10^{17} - 10^{23}~{\rm gm}$
are considered as possible dark matter candidates as they are not subject to
big-bang nucleosynthesis constraints and behave like cold dark matter. If PBHs
are indeed dark matter, they cannot be treated as isolated objects in
asymptotic flat space-time. Furthermore, when compared to stellar-mass black
holes, the rate at which the Hawking particles radiate out from PBHs is
significantly faster. In this work, we obtain an exact time-dependent solution
that models evaporating black holes in the cosmological background. As a
result, the solution considers all three aspects of PBHs -- mass-loss due to
Hawking radiation, black hole surrounded by mass distribution, and cosmological
background. Furthermore, our model predicts that the decay of PBHs occurs
faster for larger masses; however, \emph{the decay rate reduces for lower
mass}. Finally, we discuss the implications of theoretical constraints on PBHs
as dark matter.
| [
{
"created": "Wed, 27 Oct 2021 12:27:12 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Apr 2022 17:39:34 GMT",
"version": "v2"
}
] | 2022-06-01 | [
[
"Xavier",
"Semin",
"",
"IITB"
],
[
"Sunny",
"Alan",
"",
"CUTN"
],
[
"Shankaranarayanan",
"S.",
"",
"IITB"
]
] | Primordial black holes (PBHs) in the mass range $10^{17} - 10^{23}~{\rm gm}$ are considered as possible dark matter candidates as they are not subject to big-bang nucleosynthesis constraints and behave like cold dark matter. If PBHs are indeed dark matter, they cannot be treated as isolated objects in asymptotic flat space-time. Furthermore, when compared to stellar-mass black holes, the rate at which the Hawking particles radiate out from PBHs is significantly faster. In this work, we obtain an exact time-dependent solution that models evaporating black holes in the cosmological background. As a result, the solution considers all three aspects of PBHs -- mass-loss due to Hawking radiation, black hole surrounded by mass distribution, and cosmological background. Furthermore, our model predicts that the decay of PBHs occurs faster for larger masses; however, \emph{the decay rate reduces for lower mass}. Finally, we discuss the implications of theoretical constraints on PBHs as dark matter. |
1507.04161 | Paul Klinger | Paul Klinger | A New Class of Asymptotically Non-Chaotic Vacuum Singularities | MSc Thesis, 42 pages; v2: appendix on cosmological constant added,
typos corrected; v3: typos corrected | Annals of Physics 363 (2015) 1-35 | 10.1016/j.aop.2015.09.010 | UWThPh-2015-17 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The BKL conjecture, stated in the 60s and early 70s by Belinski, Khalatnikov
and Lifshitz, proposes a detailed description of the generic asymptotic
dynamics of spacetimes as they approach a spacelike singularity. It predicts
complicated chaotic behaviour in the generic case, but simpler non-chaotic one
in cases with symmetry assumptions or certain kinds of matter fields.
Here we construct a new class of four-dimensional vacuum spacetimes
containing spacelike singularities which show non-chaotic behaviour. In
contrast with previous constructions, no symmetry assumptions are made. Rather,
the metric is decomposed in Iwasawa variables and conditions on the asymptotic
evolution of some of them are imposed. The constructed solutions contain five
free functions of all space coordinates, two of which are constrained by
inequalities. We investigate continuous and discrete isometries and compare the
solutions to previous constructions. Finally, we give the asymptotic behaviour
of the metric components and curvature.
| [
{
"created": "Wed, 15 Jul 2015 10:46:44 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2015 16:18:51 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Dec 2015 16:55:33 GMT",
"version": "v3"
}
] | 2015-12-11 | [
[
"Klinger",
"Paul",
""
]
] | The BKL conjecture, stated in the 60s and early 70s by Belinski, Khalatnikov and Lifshitz, proposes a detailed description of the generic asymptotic dynamics of spacetimes as they approach a spacelike singularity. It predicts complicated chaotic behaviour in the generic case, but simpler non-chaotic one in cases with symmetry assumptions or certain kinds of matter fields. Here we construct a new class of four-dimensional vacuum spacetimes containing spacelike singularities which show non-chaotic behaviour. In contrast with previous constructions, no symmetry assumptions are made. Rather, the metric is decomposed in Iwasawa variables and conditions on the asymptotic evolution of some of them are imposed. The constructed solutions contain five free functions of all space coordinates, two of which are constrained by inequalities. We investigate continuous and discrete isometries and compare the solutions to previous constructions. Finally, we give the asymptotic behaviour of the metric components and curvature. |
1606.03423 | Marc Casals | Marc Casals and Adrian C. Ottewill | Spin-1 Quasi-normal Frequencies in Schwarzschild space-time for Large
Overtone Number | 10 pages, 2 figures. In this version we give more details of the
calculation and correct some typographical errors of the previous version | Phys. Rev. D 97, 024048 (2018) | 10.1103/PhysRevD.97.024048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically investigate the spin-1 quasinormal mode frequencies of
Schwarzschild black hole space-time. We formally determine these frequencies to
arbitrary order as an expansion for large imaginary part (i.e., large-n, where
n is the overtone number). As an example of the practicality of this formal
procedure, we explicitly calculate the asymptotic behaviour of the frequencies
up to order $n^{-5/2}$.
| [
{
"created": "Fri, 10 Jun 2016 18:47:54 GMT",
"version": "v1"
},
{
"created": "Sat, 27 May 2017 13:48:35 GMT",
"version": "v2"
}
] | 2018-02-07 | [
[
"Casals",
"Marc",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | We analytically investigate the spin-1 quasinormal mode frequencies of Schwarzschild black hole space-time. We formally determine these frequencies to arbitrary order as an expansion for large imaginary part (i.e., large-n, where n is the overtone number). As an example of the practicality of this formal procedure, we explicitly calculate the asymptotic behaviour of the frequencies up to order $n^{-5/2}$. |
1612.04414 | Jorge Bellor\'in | Jorge Bellorin and Alvaro Restuccia | Einstein's quadrupole formula from the kinetic-conformal Horava theory | v2: 26 pages, one section added. Changes in presentation and more
references added. Title changed | International Journal of Modern Physics D 26 (2017) 1750174 | 10.1142/S0218271817501747 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the radiative and nonradiative linearized variables in a gravity
theory within the familiy of the nonprojectable Horava theories, the Horava
theory at the kinetic-conformal point. There is no extra mode in this
formulation, the theory shares the same number of degrees of freedom with
general relativity. The large-distance effective action, which is the one we
consider, can be given in a generally-covariant form under asymptotically flat
boundary conditions, the Einstein-aether theory under the condition of
hypersurface orthogonality on the aether vector. In the linearized theory we
find that only the transverse-traceless tensorial modes obey a sourced wave
equation, as in general relativity. The rest of variables are nonradiative. The
result is gauge-independent at the level of the linearized theory. For the case
of a weak source, we find that the leading mode in the far zone is exactly
Einstein's quadrupole formula of general relativity, if some coupling constants
are properly identified. There are no monopoles nor dipoles in this
formulation, in distinction to the nonprojectable Horava theory outside the
kinetic-conformal point. We also discuss some constraints on the theory arising
from the observational bounds on Lorentz-violating theories.
| [
{
"created": "Tue, 13 Dec 2016 21:57:36 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jul 2017 16:24:54 GMT",
"version": "v2"
}
] | 2017-10-27 | [
[
"Bellorin",
"Jorge",
""
],
[
"Restuccia",
"Alvaro",
""
]
] | We analyze the radiative and nonradiative linearized variables in a gravity theory within the familiy of the nonprojectable Horava theories, the Horava theory at the kinetic-conformal point. There is no extra mode in this formulation, the theory shares the same number of degrees of freedom with general relativity. The large-distance effective action, which is the one we consider, can be given in a generally-covariant form under asymptotically flat boundary conditions, the Einstein-aether theory under the condition of hypersurface orthogonality on the aether vector. In the linearized theory we find that only the transverse-traceless tensorial modes obey a sourced wave equation, as in general relativity. The rest of variables are nonradiative. The result is gauge-independent at the level of the linearized theory. For the case of a weak source, we find that the leading mode in the far zone is exactly Einstein's quadrupole formula of general relativity, if some coupling constants are properly identified. There are no monopoles nor dipoles in this formulation, in distinction to the nonprojectable Horava theory outside the kinetic-conformal point. We also discuss some constraints on the theory arising from the observational bounds on Lorentz-violating theories. |
1004.1964 | Eric Chassande-Mottin | Eric Chassande-Mottin, Martin Hendry, Patrick J. Sutton and Szabolcs
M\'arka | Multimessenger astronomy with the Einstein Telescope | 26 pages. 3 figures. Special issue of GRG on the Einstein Telescope.
Minor corrections included | Gen.Rel.Grav.43:437-464,2011 | 10.1007/s10714-010-1019-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves (GWs) are expected to play a crucial role in the
development of multimessenger astrophysics. The combination of GW observations
with other astrophysical triggers, such as from gamma-ray and X-ray satellites,
optical/radio telescopes, and neutrino detectors allows us to decipher science
that would otherwise be inaccessible. In this paper, we provide a broad review
from the multimessenger perspective of the science reach offered by the third
generation interferometric GW detectors and by the Einstein Telescope (ET) in
particular. We focus on cosmic transients, and base our estimates on the
results obtained by ET's predecessors GEO, LIGO, and Virgo.
| [
{
"created": "Mon, 12 Apr 2010 14:07:27 GMT",
"version": "v1"
},
{
"created": "Tue, 11 May 2010 19:38:45 GMT",
"version": "v2"
}
] | 2011-01-28 | [
[
"Chassande-Mottin",
"Eric",
""
],
[
"Hendry",
"Martin",
""
],
[
"Sutton",
"Patrick J.",
""
],
[
"Márka",
"Szabolcs",
""
]
] | Gravitational waves (GWs) are expected to play a crucial role in the development of multimessenger astrophysics. The combination of GW observations with other astrophysical triggers, such as from gamma-ray and X-ray satellites, optical/radio telescopes, and neutrino detectors allows us to decipher science that would otherwise be inaccessible. In this paper, we provide a broad review from the multimessenger perspective of the science reach offered by the third generation interferometric GW detectors and by the Einstein Telescope (ET) in particular. We focus on cosmic transients, and base our estimates on the results obtained by ET's predecessors GEO, LIGO, and Virgo. |
1506.02648 | Ginestra Bianconi | Ginestra Bianconi and Christoph Rahmede | Complex Quantum Network Manifolds in Dimension $d>2$ are Scale-Free | (29 pages, 4 figures) | Scientific Reports 5, 13979 (2015) | 10.1038/srep13979 | KA-TP-12-2015 | gr-qc cond-mat.dis-nn cond-mat.stat-mech physics.soc-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In quantum gravity, several approaches have been proposed until now for the
quantum description of discrete geometries. These theoretical frameworks
include loop quantum gravity, causal dynamical triangulations, causal sets,
quantum graphity, and energetic spin networks. Most of these approaches
describe discrete spaces as homogeneous network manifolds. Here we define
Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum
network states, and constructed from growing simplicial complexes of dimension
$d$. We show that in $d=2$ CQNM are homogeneous networks while for $d>2$ they
are scale-free i.e. they are characterized by large inhomogeneities of degrees
like most complex networks. From the self-organized evolution of CQNM quantum
statistics emerge spontaneously. Here we define the generalized degrees
associated with the $\delta$-faces of the $d$-dimensional CQNMs, and we show
that the statistics of these generalized degrees can either follow Fermi-Dirac,
Boltzmann or Bose-Einstein distributions depending on the dimension of the
$\delta$-faces.
| [
{
"created": "Mon, 8 Jun 2015 09:36:55 GMT",
"version": "v1"
}
] | 2015-09-14 | [
[
"Bianconi",
"Ginestra",
""
],
[
"Rahmede",
"Christoph",
""
]
] | In quantum gravity, several approaches have been proposed until now for the quantum description of discrete geometries. These theoretical frameworks include loop quantum gravity, causal dynamical triangulations, causal sets, quantum graphity, and energetic spin networks. Most of these approaches describe discrete spaces as homogeneous network manifolds. Here we define Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum network states, and constructed from growing simplicial complexes of dimension $d$. We show that in $d=2$ CQNM are homogeneous networks while for $d>2$ they are scale-free i.e. they are characterized by large inhomogeneities of degrees like most complex networks. From the self-organized evolution of CQNM quantum statistics emerge spontaneously. Here we define the generalized degrees associated with the $\delta$-faces of the $d$-dimensional CQNMs, and we show that the statistics of these generalized degrees can either follow Fermi-Dirac, Boltzmann or Bose-Einstein distributions depending on the dimension of the $\delta$-faces. |
0807.3292 | Pablo Laguna | James Healy, Frank Herrmann, Ian Hinder, Deirdre M. Shoemaker, Pablo
Laguna, Richard A. Matzner | Superkicks in Hyperbolic Encounters of Binary Black Holes | 4 pages, 5 figures, 1 table | Phys.Rev.Lett.102:041101,2009 | 10.1103/PhysRevLett.102.041101 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Generic inspirals and mergers of binary black holes produce beamed emission
of gravitational radiation that can lead to a gravitational recoil or kick of
the final black hole. The kick velocity depends on the mass ratio and spins of
the binary as well as on the dynamics of the binary configuration. Studies have
focused so far on the most astrophysically relevant configuration of
quasi-circular inspirals, for which kicks as large as 3,300 km/s have been
found. We present the first study of gravitational recoil in hyperbolic
encounters. Contrary to quasi-circular configurations, in which the beamed
radiation tends to average during the inspiral, radiation from hyperbolic
encounters is plunge dominated, resulting in an enhancement of preferential
beaming. As a consequence, it is possible to achieve kick velocities as large
as 10,000 km/s.
| [
{
"created": "Mon, 21 Jul 2008 16:11:13 GMT",
"version": "v1"
}
] | 2009-02-23 | [
[
"Healy",
"James",
""
],
[
"Herrmann",
"Frank",
""
],
[
"Hinder",
"Ian",
""
],
[
"Shoemaker",
"Deirdre M.",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Matzner",
"Richard A.",
""
]
] | Generic inspirals and mergers of binary black holes produce beamed emission of gravitational radiation that can lead to a gravitational recoil or kick of the final black hole. The kick velocity depends on the mass ratio and spins of the binary as well as on the dynamics of the binary configuration. Studies have focused so far on the most astrophysically relevant configuration of quasi-circular inspirals, for which kicks as large as 3,300 km/s have been found. We present the first study of gravitational recoil in hyperbolic encounters. Contrary to quasi-circular configurations, in which the beamed radiation tends to average during the inspiral, radiation from hyperbolic encounters is plunge dominated, resulting in an enhancement of preferential beaming. As a consequence, it is possible to achieve kick velocities as large as 10,000 km/s. |
2105.02731 | Tayyaba Naz | Tayyaba Naz, Ammara Usman, M. Farasat Shamir | Embedded Class-I Solution of Compact Stars in $f(R)$ Gravity with
Karmarkar Condition | Published in Annals of Physics | Annals of Physics 429 (2021) 168491 | 10.1016/j.aop.2021.168491 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | This paper's main aim is to investigate the existence of a new classification
of embedded class-I solutions of compact stars, by using Karmarkar condition in
$f(R)$ gravity background. To achieve that goal, we consider two different
models of the $f(R)$ theory of gravity for the static spherically symmetric
spacetime by considering anisotropic matter distribution. Further, we employ
Karmarkar condition to relate the two components of metric potentials $g_{rr}$
and $g_{tt}$. We assume a particular model for one metric potential and obtain
the second one by Karmarkar condition. Moreover, we also calculate the values
of constant parameters by using the observational data of these compact stars,
namely, $Vela~ X-1,$ $PSR~J1614-2230,$ $4U~1608-52,$ $Cen~X-3$ and
$4U~1820-30.$ We perform different physical tests like variational behavior of
energy density and pressure components, stability and equilibrium conditions,
energy constraints, mass function and adiabatic index to check the viability of
$f(R)$ gravity models. All these physical attributes indicate the consistent
behavior of our models. Our investigation also suggests that $f(R)$ theory of
gravity appears as a suitable theory in describing the viability of a new
classification of embedded class-I solutions of compact objects.
| [
{
"created": "Thu, 6 May 2021 14:49:31 GMT",
"version": "v1"
}
] | 2021-05-07 | [
[
"Naz",
"Tayyaba",
""
],
[
"Usman",
"Ammara",
""
],
[
"Shamir",
"M. Farasat",
""
]
] | This paper's main aim is to investigate the existence of a new classification of embedded class-I solutions of compact stars, by using Karmarkar condition in $f(R)$ gravity background. To achieve that goal, we consider two different models of the $f(R)$ theory of gravity for the static spherically symmetric spacetime by considering anisotropic matter distribution. Further, we employ Karmarkar condition to relate the two components of metric potentials $g_{rr}$ and $g_{tt}$. We assume a particular model for one metric potential and obtain the second one by Karmarkar condition. Moreover, we also calculate the values of constant parameters by using the observational data of these compact stars, namely, $Vela~ X-1,$ $PSR~J1614-2230,$ $4U~1608-52,$ $Cen~X-3$ and $4U~1820-30.$ We perform different physical tests like variational behavior of energy density and pressure components, stability and equilibrium conditions, energy constraints, mass function and adiabatic index to check the viability of $f(R)$ gravity models. All these physical attributes indicate the consistent behavior of our models. Our investigation also suggests that $f(R)$ theory of gravity appears as a suitable theory in describing the viability of a new classification of embedded class-I solutions of compact objects. |
gr-qc/9706080 | Jose Socorro Garcia Diaz | Alfredo Mac\'ias, Eckehard W. Mielke and Jos\'e Socorro | Supersymmetric quantum cosmology for Bianchi class A models | 10 pages, Revtex | Int.J.Mod.Phys.D7:701-712,1998 | 10.1142/S0218271898000462 | IFUG-97-05 | gr-qc | null | The canonical theory of (N=1) supergravity, with a matrix representation for
the gravitino covector-spinor, is applied to the Bianchi class A spatially
homogeneous cosmologies. The full Lorentz constraint and its implications for
the wave function of the universe are analyzed in detail. We found that in this
model no physical states other than the trivial "rest frame" type occur.
| [
{
"created": "Thu, 26 Jun 1997 16:19:48 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Macías",
"Alfredo",
""
],
[
"Mielke",
"Eckehard W.",
""
],
[
"Socorro",
"José",
""
]
] | The canonical theory of (N=1) supergravity, with a matrix representation for the gravitino covector-spinor, is applied to the Bianchi class A spatially homogeneous cosmologies. The full Lorentz constraint and its implications for the wave function of the universe are analyzed in detail. We found that in this model no physical states other than the trivial "rest frame" type occur. |
1710.09125 | Yusuf Sucu | Ganim Gecim and Yusuf Sucu | Quantum Gravity Effect on the Tunneling Particles from 2+1 dimensional
New-type Black Hole | 11 pages | Adv. High Energy Phys. (2018) 8728564 | 10.1155/2018/8728564 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the Generalized Uncertainty Principle (GUP) effect on the
Hawking temperature for the 2+1 dimensional New-type black hole by using the
quantum tunneling method for both the spin-1/2 Dirac and the spin-0 scalar
particles. In computation of the GUP correction for the Hawking temperature of
the black hole, we modified Dirac and Klein-Gordon equations. We observed that
the modified Hawking temperature of the black hole depends not only on the
black hole properties, but also on the graviton mass and the intrinsic
properties of the tunneling particle, such as total angular momentum, energy
and mass. Also, we see that the Hawking temperature was found to be probed by
these particles in different manners. The modified Hawking temperature for the
scalar particle seems to be lower compared to its standard Hawking temperature.
Also, we find that the modified Hawking temperature of the black hole caused by
Dirac particle's tunnelling rised by the total angular momentum of the
particle. It is diminishable by the energy and mass of the particle and
graviton mass as well. These intrinsic properties of the particle, except total
angular momentum for the Dirac particle, and graviton mass may cause screening
for the black hole radiation.
| [
{
"created": "Wed, 25 Oct 2017 08:55:27 GMT",
"version": "v1"
}
] | 2018-09-27 | [
[
"Gecim",
"Ganim",
""
],
[
"Sucu",
"Yusuf",
""
]
] | We investigate the Generalized Uncertainty Principle (GUP) effect on the Hawking temperature for the 2+1 dimensional New-type black hole by using the quantum tunneling method for both the spin-1/2 Dirac and the spin-0 scalar particles. In computation of the GUP correction for the Hawking temperature of the black hole, we modified Dirac and Klein-Gordon equations. We observed that the modified Hawking temperature of the black hole depends not only on the black hole properties, but also on the graviton mass and the intrinsic properties of the tunneling particle, such as total angular momentum, energy and mass. Also, we see that the Hawking temperature was found to be probed by these particles in different manners. The modified Hawking temperature for the scalar particle seems to be lower compared to its standard Hawking temperature. Also, we find that the modified Hawking temperature of the black hole caused by Dirac particle's tunnelling rised by the total angular momentum of the particle. It is diminishable by the energy and mass of the particle and graviton mass as well. These intrinsic properties of the particle, except total angular momentum for the Dirac particle, and graviton mass may cause screening for the black hole radiation. |
0707.1181 | Subenoy Chakraborty | Subenoy Chakraborty and Tanwi Bandyopadhyay | Wormhole and its Analogue in Brane World | 4 pages | Astrophys.SpaceSci.317:209-212,2008 | 10.1007/s10509-008-9875-7 | null | gr-qc | null | In Einstein gravity, for an inhomogeneous phantom energy distribution having
linear equation of state (but anisotropic), there exists simple exact solution
for spherically symmetric space time describing a wormhole. At infinity, the
space time is not asymptotically flat and possesses a regular cosmological
Killing horizon with an infinite area. In this work, we have shown that, this
wormhole solution is also possible in brane world for various matter
distribution, which are not necessarily phantom in nature.
| [
{
"created": "Mon, 9 Jul 2007 05:57:59 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Chakraborty",
"Subenoy",
""
],
[
"Bandyopadhyay",
"Tanwi",
""
]
] | In Einstein gravity, for an inhomogeneous phantom energy distribution having linear equation of state (but anisotropic), there exists simple exact solution for spherically symmetric space time describing a wormhole. At infinity, the space time is not asymptotically flat and possesses a regular cosmological Killing horizon with an infinite area. In this work, we have shown that, this wormhole solution is also possible in brane world for various matter distribution, which are not necessarily phantom in nature. |
2305.01469 | Venkatesha Venkatesha | N. S. Kavya, V. Venkatesha, G. Mustafa, P.K. Sahoo, S. V. Divya Rashmi | Static traversable wormhole solutions in $f(R,L_m)$ gravity | Chinese Journal of Physics accepted version | Chinese Journal of Physics (2023) | 10.1016/j.cjph.2023.05.002 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this study, we explore the new wormhole solutions in the framework of new
modified $f(R,L_m)$ gravity. To obtain a characteristic wormhole solution, we
use anisotropic matter distribution and a specific form of energy density. As
second adopt the isotropic case with a linear EoS relation as a general
technique for the system and discuss several physical attributes of the system
under the wormhole geometry. Detailed analytical and graphical discussion about
the matter contents via energy conditions is discussed. In both cases, the
shape function of wormhole geometry satisfies the required conditions. Several
interesting points have evolved from the entire investigation along with the
features of the exotic matter within the wormhole geometry. Finally, we have
concluding remarks.
| [
{
"created": "Tue, 2 May 2023 14:51:27 GMT",
"version": "v1"
}
] | 2023-05-12 | [
[
"Kavya",
"N. S.",
""
],
[
"Venkatesha",
"V.",
""
],
[
"Mustafa",
"G.",
""
],
[
"Sahoo",
"P. K.",
""
],
[
"Rashmi",
"S. V. Divya",
""
]
] | In this study, we explore the new wormhole solutions in the framework of new modified $f(R,L_m)$ gravity. To obtain a characteristic wormhole solution, we use anisotropic matter distribution and a specific form of energy density. As second adopt the isotropic case with a linear EoS relation as a general technique for the system and discuss several physical attributes of the system under the wormhole geometry. Detailed analytical and graphical discussion about the matter contents via energy conditions is discussed. In both cases, the shape function of wormhole geometry satisfies the required conditions. Several interesting points have evolved from the entire investigation along with the features of the exotic matter within the wormhole geometry. Finally, we have concluding remarks. |
2111.07223 | Xin Zhang | Qi-Ming Fu, Xin Zhang | Gravitational lensing by a black hole in effective loop quantum gravity | 14 pages, 6 figures; accepted for publication in Physical Review D | null | 10.1103/PhysRevD.105.064020 | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | It is well known that general relativity is an effective theory of gravity at
low energy scale, and actually quantum effects cannot be ignored in the
strong-field regime. As a strong gravitational object, black hole plays a key
role in testing the quantum effects of gravity in the strong-field regime. In
this paper, we focus on black hole in effective loop quantum gravity and
investigate what the influences are of the quantum effects on the weak and
strong bending angles of light rays. We find that this black hole could be a
Schwarzschild black hole, a regular black hole, a one-way traversable wormhole,
or a two-way traversable wormhole for the different values of the quantum
parameter, and the strong bending angle for this compact object exhibits two
different divergent behaviors, i.e., the logarithmic divergence and
non-logarithmic divergence. There are a series of relativistic images on both
sides of the optical axis. Only the outermost one can be resolved as a single
image, and all others are packed together at the limiting angular position. It
is interesting to note that the angular separation between the outermost
relativistic image and the others initially increases and then decreases as the
quantum parameter increases, indicating that there is a maximum in the angular
separation. The maximum is reached after the black hole becomes a wormhole,
which can be taken as a signal for the formation of the wormhole. Moreover, the
limiting angular position decreases as the quantum parameter increases but a
little bounce occurs after the formation of the wormhole, and the relative
magnification in magnitudes first decreases and then increases as the quantum
parameter increases.
| [
{
"created": "Sun, 14 Nov 2021 02:25:41 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Feb 2022 03:16:08 GMT",
"version": "v2"
}
] | 2022-03-23 | [
[
"Fu",
"Qi-Ming",
""
],
[
"Zhang",
"Xin",
""
]
] | It is well known that general relativity is an effective theory of gravity at low energy scale, and actually quantum effects cannot be ignored in the strong-field regime. As a strong gravitational object, black hole plays a key role in testing the quantum effects of gravity in the strong-field regime. In this paper, we focus on black hole in effective loop quantum gravity and investigate what the influences are of the quantum effects on the weak and strong bending angles of light rays. We find that this black hole could be a Schwarzschild black hole, a regular black hole, a one-way traversable wormhole, or a two-way traversable wormhole for the different values of the quantum parameter, and the strong bending angle for this compact object exhibits two different divergent behaviors, i.e., the logarithmic divergence and non-logarithmic divergence. There are a series of relativistic images on both sides of the optical axis. Only the outermost one can be resolved as a single image, and all others are packed together at the limiting angular position. It is interesting to note that the angular separation between the outermost relativistic image and the others initially increases and then decreases as the quantum parameter increases, indicating that there is a maximum in the angular separation. The maximum is reached after the black hole becomes a wormhole, which can be taken as a signal for the formation of the wormhole. Moreover, the limiting angular position decreases as the quantum parameter increases but a little bounce occurs after the formation of the wormhole, and the relative magnification in magnitudes first decreases and then increases as the quantum parameter increases. |
1010.3986 | William Nelson | William Nelson | Static Solutions for 4th order gravity | 19 pages, minor changes to match published version | Phys.Rev.D82:104026,2010 | 10.1103/PhysRevD.82.104026 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Lichnerowicz and Israel theorems are extended to higher order theories of
gravity. In particular it is shown that Schwarzschild is the unique spherically
symmetric, static, asymptotically flat, black-hole solution, provided the
spatial curvature is less than the quantum gravity scale outside the horizon.
It is then shown that in the presence of matter (satisfying certain positivity
requirements), the only static and asymptotically flat solutions of General
Relativity that are also solutions of higher order gravity are the vacuum
solutions
| [
{
"created": "Tue, 19 Oct 2010 17:29:39 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Nov 2010 20:15:50 GMT",
"version": "v2"
}
] | 2010-12-28 | [
[
"Nelson",
"William",
""
]
] | The Lichnerowicz and Israel theorems are extended to higher order theories of gravity. In particular it is shown that Schwarzschild is the unique spherically symmetric, static, asymptotically flat, black-hole solution, provided the spatial curvature is less than the quantum gravity scale outside the horizon. It is then shown that in the presence of matter (satisfying certain positivity requirements), the only static and asymptotically flat solutions of General Relativity that are also solutions of higher order gravity are the vacuum solutions |
0905.4792 | Takeshi Fukuyama | Takeshi Fukuyama | Comments on the Tetrad (Vielbeins) | 8 pages, no Figure | Mod.Phys.Lett.A24:2459-2466,2009 | 10.1142/S0217732309031739 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We want to correct the misunderstandings on the tetrad (or veilbeins in
general) appeared in many text books or review articles. The tetrad should be
defined without any condition. $e_{\mu a}=\partial_\mu X_a$ with local Lorentz
coordinates $X_a$ ia wrong in many sences: it gives the condition $\partial_\mu
e_{\nu a}=\partial_\nu e_{\mu a}$, which leads us to the trivial result that
the cyclic coefficients vanish identically and to the null Riemannian tensor.
Also $e_{\mu a}e_\nu^a=g_{\mu\nu}$ is not scalar under the local Lorentz
transformation etc. We show how these deficits are remedied by the correct
definition, $e_{\mu a}=D_\mu Z_a$ with local (Anti) de Sitter coordinates
$Z_A$.
| [
{
"created": "Fri, 29 May 2009 06:40:24 GMT",
"version": "v1"
}
] | 2010-02-02 | [
[
"Fukuyama",
"Takeshi",
""
]
] | We want to correct the misunderstandings on the tetrad (or veilbeins in general) appeared in many text books or review articles. The tetrad should be defined without any condition. $e_{\mu a}=\partial_\mu X_a$ with local Lorentz coordinates $X_a$ ia wrong in many sences: it gives the condition $\partial_\mu e_{\nu a}=\partial_\nu e_{\mu a}$, which leads us to the trivial result that the cyclic coefficients vanish identically and to the null Riemannian tensor. Also $e_{\mu a}e_\nu^a=g_{\mu\nu}$ is not scalar under the local Lorentz transformation etc. We show how these deficits are remedied by the correct definition, $e_{\mu a}=D_\mu Z_a$ with local (Anti) de Sitter coordinates $Z_A$. |
1505.07888 | Erwan Allys | Erwan Allys | Bosonic condensates in realistic supersymmetric GUT cosmic strings | 18 pages, 0 figures. Discussion clarified and simplified. Matches
version published in JCAP | JCAP04(2016)009 | 10.1088/1475-7516/2016/04/009 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the realistic structure of F-term Nambu-Goto cosmic strings forming
in a general supersymmetric Grand Unified Theory implementation, assuming
standard hybrid inflation. Examining the symmetry breaking of the unification
gauge group down to the Standard Model, we discuss the minimal field content
necessary to describe abelian cosmic strings appearing at the end of inflation.
We find that several fields will condense in most theories, questioning the
plausible occurrence of associated currents (bosonic and fermionic). We
perturbatively evaluate the modification of their energy per unit length due to
the condensates. We provide a criterion for comparing the usual abelian Higgs
approximation used in cosmology to realistic situations.
| [
{
"created": "Thu, 28 May 2015 23:47:28 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Dec 2015 13:44:23 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Apr 2016 07:55:51 GMT",
"version": "v3"
}
] | 2016-04-26 | [
[
"Allys",
"Erwan",
""
]
] | We study the realistic structure of F-term Nambu-Goto cosmic strings forming in a general supersymmetric Grand Unified Theory implementation, assuming standard hybrid inflation. Examining the symmetry breaking of the unification gauge group down to the Standard Model, we discuss the minimal field content necessary to describe abelian cosmic strings appearing at the end of inflation. We find that several fields will condense in most theories, questioning the plausible occurrence of associated currents (bosonic and fermionic). We perturbatively evaluate the modification of their energy per unit length due to the condensates. We provide a criterion for comparing the usual abelian Higgs approximation used in cosmology to realistic situations. |
2105.03451 | Rodrigo Panosso Macedo | Jos\'e Luis Jaramillo, Rodrigo Panosso Macedo, Lamis Al Sheikh | Gravitational wave signatures of black hole quasi-normal mode
instability | 4 pages, 3 figures, 1 table + Supplemental Material (3 additional
figures) | null | 10.1103/PhysRevLett.128.211102 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole (BH) spectroscopy has emerged as a powerful approach to extract
spacetime information from gravitational wave (GW) observed signals. Yet,
quasinormal mode (QNM) spectral instability under high wave-number
perturbations has been recently shown to be a common classical general
relativistic phenomenon [1]. This requires to assess its impact on the BH QNM
spectrum, in particular on BH QNM overtone frequencies. We conclude: i)
perturbed BH QNM overtones are indeed potentially observable in the GW
waveform, providing information on small-scale environment BH physics, and ii)
their detection poses a challenging data analysis problem of singular interest
for LISA astrophysics. We adopt a two-fold approach, combining theoretical
results from scattering theory with a fine-tuned data analysis on a
highly-accurate numerical GW ringdown signal. The former introduces a set of
effective parameters (partially lying on a BH Weyl law) to characterise QNM
instability physics. The latter provides a proof-of-principle demonstrating
that the QNM spectral instability is indeed accessible in the time-domain GW
waveform, though certainly requiring large signal-to-noise ratios. Particular
attention is devoted to discuss the patterns of isospectrality loss under QNM
instability, since the disentanglement between axial and polar GW parities may
already occur within the near-future detection range.
| [
{
"created": "Fri, 7 May 2021 18:02:59 GMT",
"version": "v1"
},
{
"created": "Fri, 14 May 2021 16:46:02 GMT",
"version": "v2"
},
{
"created": "Tue, 14 Sep 2021 16:38:13 GMT",
"version": "v3"
}
] | 2022-06-08 | [
[
"Jaramillo",
"José Luis",
""
],
[
"Macedo",
"Rodrigo Panosso",
""
],
[
"Sheikh",
"Lamis Al",
""
]
] | Black hole (BH) spectroscopy has emerged as a powerful approach to extract spacetime information from gravitational wave (GW) observed signals. Yet, quasinormal mode (QNM) spectral instability under high wave-number perturbations has been recently shown to be a common classical general relativistic phenomenon [1]. This requires to assess its impact on the BH QNM spectrum, in particular on BH QNM overtone frequencies. We conclude: i) perturbed BH QNM overtones are indeed potentially observable in the GW waveform, providing information on small-scale environment BH physics, and ii) their detection poses a challenging data analysis problem of singular interest for LISA astrophysics. We adopt a two-fold approach, combining theoretical results from scattering theory with a fine-tuned data analysis on a highly-accurate numerical GW ringdown signal. The former introduces a set of effective parameters (partially lying on a BH Weyl law) to characterise QNM instability physics. The latter provides a proof-of-principle demonstrating that the QNM spectral instability is indeed accessible in the time-domain GW waveform, though certainly requiring large signal-to-noise ratios. Particular attention is devoted to discuss the patterns of isospectrality loss under QNM instability, since the disentanglement between axial and polar GW parities may already occur within the near-future detection range. |
1111.0092 | Takeshi Chiba | Takeshi Chiba | The Constancy of the Constants of Nature: Updates | 27 pages, 2 figures, to be published in Prog.Theor.Phys, ref. added | Prog. Theor. Phys. 126 (2011), 993-1019 | 10.1143/PTP.126.993 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The current observational and experimental bounds on the time variation of
the constants of nature (the fine structure constant $\alpha$, the
gravitational constant $G$ and the proton-electron mass ratio $\mu=m_p/m_e$)
are reviewed.
| [
{
"created": "Tue, 1 Nov 2011 00:24:13 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Nov 2011 06:41:50 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Nov 2011 02:15:26 GMT",
"version": "v3"
},
{
"created": "Fri, 23 Dec 2011 02:19:43 GMT",
"version": "v4"
}
] | 2012-01-03 | [
[
"Chiba",
"Takeshi",
""
]
] | The current observational and experimental bounds on the time variation of the constants of nature (the fine structure constant $\alpha$, the gravitational constant $G$ and the proton-electron mass ratio $\mu=m_p/m_e$) are reviewed. |
2310.10447 | Lijing Shao | Hua-Peng Gu, Hai-Tian Wang, Lijing Shao | Constraints on charged black holes from merger-ringdown signals in
GWTC-3 and prospects for the Einstein Telescope | 13 pages, 7 figures; accepted by PRD | Phys. Rev. D 109 (2024) 024058 | 10.1103/PhysRevD.109.024058 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Whether astrophysical black holes (BHs) can have charge is a question to be
addressed by observations. In the era of gravitational wave (GW) astronomy, one
can constrain the charge of a merged BH remnant using the merger-ringdown
signal of the GW data. Extending earlier studies, we analyze five GW events in
GWTC-3, assuming Kerr-Newman BHs. Our results show no strong evidence for a
charged BH, and give a limit on the charge-to-mass-ratio $Q<0.37$ at $90\%$
credible level (CL). Due to the charge-spin degeneracy in the waveform and the
limited signal-to-noise ratios (SNRs), it is challenging for LIGO/Virgo/KAGRA
observations to provide better constraints. We further simulate data for the
Einstein Telescope (ET), where SNRs can be as large as $\sim270$ in the
ringdown signal. These simulated events allow us to consider the 220, 221, and
330 ringdown modes altogether, which can help break the charge-spin degeneracy.
The analysis of a simulated GW150914-like signal shows that ET can improve the
constraints on the charge-to-mass-ratio to $Q \lesssim 0.2$ at $90\%$ CL with
one ringdown signal.
| [
{
"created": "Mon, 16 Oct 2023 14:31:13 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jan 2024 19:53:57 GMT",
"version": "v2"
}
] | 2024-01-31 | [
[
"Gu",
"Hua-Peng",
""
],
[
"Wang",
"Hai-Tian",
""
],
[
"Shao",
"Lijing",
""
]
] | Whether astrophysical black holes (BHs) can have charge is a question to be addressed by observations. In the era of gravitational wave (GW) astronomy, one can constrain the charge of a merged BH remnant using the merger-ringdown signal of the GW data. Extending earlier studies, we analyze five GW events in GWTC-3, assuming Kerr-Newman BHs. Our results show no strong evidence for a charged BH, and give a limit on the charge-to-mass-ratio $Q<0.37$ at $90\%$ credible level (CL). Due to the charge-spin degeneracy in the waveform and the limited signal-to-noise ratios (SNRs), it is challenging for LIGO/Virgo/KAGRA observations to provide better constraints. We further simulate data for the Einstein Telescope (ET), where SNRs can be as large as $\sim270$ in the ringdown signal. These simulated events allow us to consider the 220, 221, and 330 ringdown modes altogether, which can help break the charge-spin degeneracy. The analysis of a simulated GW150914-like signal shows that ET can improve the constraints on the charge-to-mass-ratio to $Q \lesssim 0.2$ at $90\%$ CL with one ringdown signal. |
gr-qc/0510103 | Roberto Casadio | R. Casadio, F. Finelli, M. Luzzi, G. Venturi | Improved WKB analysis of Slow-Roll Inflation | REVTeX 4, 13 pages, no figures, final version to appear in Phys. Rev.
D | Phys.Rev. D72 (2005) 103516 | 10.1103/PhysRevD.72.103516 | null | gr-qc astro-ph hep-th | null | We extend the WKB method for the computation of cosmological perturbations
during inflation beyond leading order and provide the power spectra of scalar
and tensor perturbations to second order in the slow-roll parameters. Our
method does not require that the slow-roll parameters be constant. Although
leading and next-to-leading results in the slow-roll parameters depend on the
approximation technique used in the computation, we find that the inflationary
theoretical predictions obtained may reach the accuracy required by planned
observations. In two technical appendices, we compare our techniques and
results with previous findings.
| [
{
"created": "Mon, 24 Oct 2005 09:21:43 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Nov 2005 09:32:08 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Casadio",
"R.",
""
],
[
"Finelli",
"F.",
""
],
[
"Luzzi",
"M.",
""
],
[
"Venturi",
"G.",
""
]
] | We extend the WKB method for the computation of cosmological perturbations during inflation beyond leading order and provide the power spectra of scalar and tensor perturbations to second order in the slow-roll parameters. Our method does not require that the slow-roll parameters be constant. Although leading and next-to-leading results in the slow-roll parameters depend on the approximation technique used in the computation, we find that the inflationary theoretical predictions obtained may reach the accuracy required by planned observations. In two technical appendices, we compare our techniques and results with previous findings. |
gr-qc/0508066 | Christoph Schmid | Christoph Schmid (ETH Zurich) | Cosmological gravitomagnetism and Mach's principle | 18 pages, 1 figure. Comments and references added | Phys.Rev. D74 (2006) 044031 | 10.1103/PhysRevD.74.044031 | null | gr-qc astro-ph | null | The spin axes of gyroscopes experimentally define local non-rotating frames.
But what physical cause governs the time-evolution of gyroscope axes? We
consider linear perturbations of Friedmann-Robertson-Walker cosmologies with
k=0. We ask: Will cosmological vorticity perturbations exactly drag the spin
axes of gyroscopes relative to the directions of geodesics to quasars in the
asymptotic unperturbed FRW space? Using Cartan's formalism with local
orthonormal bases we cast the laws of linear cosmological gravitomagnetism into
a form showing the close correspondence with the laws of ordinary magnetism.
Our results, valid for any equation of state for cosmological matter, are: 1)
The dragging of a gyroscope axis by rotational perturbations of matter beyond
the Hubble-dot radius from the gyroscope is exponentially suppressed, where dot
is the derivative with respect to cosmic time. 2) If the perturbation of matter
is a homogeneous rotation inside some radius around a gyroscope, then exact
dragging of the gyroscope axis by the rotational perturbation is reached
exponentially fast as the rotation radius grows beyond the H-dot radius. 3) For
the most general linear cosmological perturbations the time-evolution of all
gyroscope spin axes exactly follow a weighted average of the energy currents of
cosmological matter. The weight function is the same as in Ampere's law except
that the inverse square law is replaced by the Yukawa force with the Hubble-dot
cutoff. Our results demonstrate (in first order perturbation theory for FRW
cosmologies with k = 0) the validity of Mach's hypothesis that axes of local
non-rotating frames precisely follow an average of the motion of cosmic matter.
| [
{
"created": "Tue, 16 Aug 2005 15:34:25 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Sep 2006 12:41:56 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Schmid",
"Christoph",
"",
"ETH Zurich"
]
] | The spin axes of gyroscopes experimentally define local non-rotating frames. But what physical cause governs the time-evolution of gyroscope axes? We consider linear perturbations of Friedmann-Robertson-Walker cosmologies with k=0. We ask: Will cosmological vorticity perturbations exactly drag the spin axes of gyroscopes relative to the directions of geodesics to quasars in the asymptotic unperturbed FRW space? Using Cartan's formalism with local orthonormal bases we cast the laws of linear cosmological gravitomagnetism into a form showing the close correspondence with the laws of ordinary magnetism. Our results, valid for any equation of state for cosmological matter, are: 1) The dragging of a gyroscope axis by rotational perturbations of matter beyond the Hubble-dot radius from the gyroscope is exponentially suppressed, where dot is the derivative with respect to cosmic time. 2) If the perturbation of matter is a homogeneous rotation inside some radius around a gyroscope, then exact dragging of the gyroscope axis by the rotational perturbation is reached exponentially fast as the rotation radius grows beyond the H-dot radius. 3) For the most general linear cosmological perturbations the time-evolution of all gyroscope spin axes exactly follow a weighted average of the energy currents of cosmological matter. The weight function is the same as in Ampere's law except that the inverse square law is replaced by the Yukawa force with the Hubble-dot cutoff. Our results demonstrate (in first order perturbation theory for FRW cosmologies with k = 0) the validity of Mach's hypothesis that axes of local non-rotating frames precisely follow an average of the motion of cosmic matter. |
1901.03758 | Jafar Sadeghi | J. Sadeghi, M. R. Alipour | Klein Gordon particle near R-N black hole, generalized sl(2) algebra and
harmonic oscillator energy | 12 pages. arXiv admin note: text overlap with arXiv:1001.0785 by
other authors | null | 10.1142/S0217751X19501963 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider Klein Gordon particle near Reissner-Nordstr\"{o}m
black hole. The symmetry of such background lead us to compare the
corresponding Laplace equation with the generalized Heun functions. Such
relation help us achieve the generalized $sl(2)$ algebra and some suitable
results for describing the above mentioned symmetry. On the other hand in case
of $r\rightarrow r_{+}$ which is near the proximity black hole, we obtain the
energy spectrum and wave function. When we compare the equation of $R-N$
background with Laguerre differential equation, we show that the obtained
energy spectrum is same as three dimensional harmonic oscillator. So, finally
we take advantage of harmonic oscillator energy and make suitable partition
function. Such function help us to obtain all thermodynamical properties of
black hole. Also, the structure of obtained entropy lead us to have some bit
and information theory in the $R-N$ black hole.
| [
{
"created": "Wed, 9 Jan 2019 07:47:07 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Sadeghi",
"J.",
""
],
[
"Alipour",
"M. R.",
""
]
] | In this paper, we consider Klein Gordon particle near Reissner-Nordstr\"{o}m black hole. The symmetry of such background lead us to compare the corresponding Laplace equation with the generalized Heun functions. Such relation help us achieve the generalized $sl(2)$ algebra and some suitable results for describing the above mentioned symmetry. On the other hand in case of $r\rightarrow r_{+}$ which is near the proximity black hole, we obtain the energy spectrum and wave function. When we compare the equation of $R-N$ background with Laguerre differential equation, we show that the obtained energy spectrum is same as three dimensional harmonic oscillator. So, finally we take advantage of harmonic oscillator energy and make suitable partition function. Such function help us to obtain all thermodynamical properties of black hole. Also, the structure of obtained entropy lead us to have some bit and information theory in the $R-N$ black hole. |
1508.05864 | Macarena Lagos | Macarena Lagos and Johannes Noller | New massive bigravity cosmologies with double matter coupling | Last version includes minor changes to text and references | JCAP01(2016)023 | 10.1088/1475-7516/2016/01/023 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a previously largely unexplored branch of homogeneous and isotropic
background solutions in ghost-free massive bigravity with consistent double
matter coupling. For a certain family of parameters we find `self-inflated'
FLRW cosmologies, i.e. solutions with an accelerated early-time period during
the radiation-dominated era. In addition, these solutions also display an
accelerated late-time period closely mimicking GR with a cosmological constant.
Interestingly, within this family, the particular case of $\beta_1=\beta_3=0$
gives bouncing cosmologies, where there is an infinite contracting past, a
non-zero minimum value of the scale factor at the bounce, and an infinite
expanding future.
| [
{
"created": "Fri, 21 Aug 2015 19:26:34 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jan 2016 17:18:30 GMT",
"version": "v2"
}
] | 2016-01-15 | [
[
"Lagos",
"Macarena",
""
],
[
"Noller",
"Johannes",
""
]
] | We study a previously largely unexplored branch of homogeneous and isotropic background solutions in ghost-free massive bigravity with consistent double matter coupling. For a certain family of parameters we find `self-inflated' FLRW cosmologies, i.e. solutions with an accelerated early-time period during the radiation-dominated era. In addition, these solutions also display an accelerated late-time period closely mimicking GR with a cosmological constant. Interestingly, within this family, the particular case of $\beta_1=\beta_3=0$ gives bouncing cosmologies, where there is an infinite contracting past, a non-zero minimum value of the scale factor at the bounce, and an infinite expanding future. |
1909.08692 | Yousef Bisabr | Yousef Bisabr (Farzan-Nahad) | Redshift Dependence of CMB Temperature in BSBM $\alpha$-Varying Theories | To appear in EuroPhysics Letters | EPL 134, 49002 (2021) | 10.1209/0295-5075/134/49002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have investigated some cosmological consequences of variation of the fine
structure constant, $\alpha$, in the context of the
Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model. In this context, such a
variation is attributed to electric charge by letting the latter take on the
value of a real scalar field, $\phi$, which varies generally in space and time.
We consider the dynamics of $\phi$ in the case that it is allowed to have an
exponential potential. We have found solutions for evolutions of $\phi$ and
$\alpha$ in the radiation and the matter dominated eras. By employing
observational bounds on the temporal variation of $\alpha$, we constrain the
model parameters. We then investigate the impact of $\alpha$-variation on
redshift dependence of CMB temperature. It is shown that there is a deviation
from the standard evolution of the temperature which contains two different
contributions, one is important at high redshift eras and the other is mostly
effective at low redshift eras.
| [
{
"created": "Tue, 17 Sep 2019 06:53:27 GMT",
"version": "v1"
},
{
"created": "Mon, 24 May 2021 13:42:06 GMT",
"version": "v2"
}
] | 2021-08-10 | [
[
"Bisabr",
"Yousef",
"",
"Farzan-Nahad"
]
] | We have investigated some cosmological consequences of variation of the fine structure constant, $\alpha$, in the context of the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model. In this context, such a variation is attributed to electric charge by letting the latter take on the value of a real scalar field, $\phi$, which varies generally in space and time. We consider the dynamics of $\phi$ in the case that it is allowed to have an exponential potential. We have found solutions for evolutions of $\phi$ and $\alpha$ in the radiation and the matter dominated eras. By employing observational bounds on the temporal variation of $\alpha$, we constrain the model parameters. We then investigate the impact of $\alpha$-variation on redshift dependence of CMB temperature. It is shown that there is a deviation from the standard evolution of the temperature which contains two different contributions, one is important at high redshift eras and the other is mostly effective at low redshift eras. |
1409.3163 | Luis O. Pimentel | J. Socorro, Luis O. Pimentel and Abraham Espinoza-Garc\'ia | Classical Bianchi type I cosmology in K-essence theory | 15 pages with one figure, accepted in Advances in High Energy Physics | null | null | UAMIFIS-14-31 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use one of the simplest forms of the K-essence theory and we apply it to
the classical anisotropic Bianchi type I cosmological model, with a barotropic
perfect fluid modeling the usual matter content and with cosmological constant.
The classical solutions for any but the stiff fluid and without cosmological
constant are found in closed form, using a time transformation. We also present
the solution whith cosmological constant and some particular values of the
barotropic parameter. We present the possible isotropization of the
cosmological model, using the ratio between the anisotropic parameters and the
volume of the universe and show that this tend to a constant or to zero for
different cases. We include also a qualitative analysis of the analog of the
Friedmann equation.
| [
{
"created": "Wed, 10 Sep 2014 17:55:33 GMT",
"version": "v1"
}
] | 2014-09-11 | [
[
"Socorro",
"J.",
""
],
[
"Pimentel",
"Luis O.",
""
],
[
"Espinoza-García",
"Abraham",
""
]
] | We use one of the simplest forms of the K-essence theory and we apply it to the classical anisotropic Bianchi type I cosmological model, with a barotropic perfect fluid modeling the usual matter content and with cosmological constant. The classical solutions for any but the stiff fluid and without cosmological constant are found in closed form, using a time transformation. We also present the solution whith cosmological constant and some particular values of the barotropic parameter. We present the possible isotropization of the cosmological model, using the ratio between the anisotropic parameters and the volume of the universe and show that this tend to a constant or to zero for different cases. We include also a qualitative analysis of the analog of the Friedmann equation. |
1909.06433 | Muhammad Zubair | G. Abbas, Asif Mahmood, M. Zubair | Strong Gravitational Lensing for Photon Coupled to Weyl Tensor in
Kiselev Black Hole | 26 pages, 10 figures, major revision included and accepted for
publications in Chinese Physics C. arXiv admin note: text overlap with
arXiv:1611.08783, arXiv:1502.01088 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ambition of the present work is to highlight the phenomena of strong
gravitational lensing and deflection angle for the photons coupling with Weyl
tensor in a Kiselev black hole. Here, we have extended the prior work of Chen
and Jing \cite{1} for Schwarzschild black hole to Kiselev black hole. For this
purpose, the equation of motion for the photons coupled to Weyl tensor, null
geodesic and equation of photon sphere in a Kiselev black hole spacetime have
been formulated. It is found that the equation of motion of the photons depends
not only on the coupling between photon and Weyl tensor, but also on the
polarization direction of the photons. There is a critical value of the
coupling parameter $\alpha$ for existence of the marginally circular photon
orbit outside the event horizon, which depends on the parameters of black hole
and the polarization direction of photons. Further, the polarization directions
of coupled photon and the coupling parameter $\alpha$, both modify the features
of the photon sphere, the angle of deflection and the functions $(\bar{a}$ and
$\bar{b})$ for the strong gravitational lensing in Kiselev black hole
spacetime. In addition to this, the observable gravitational lensing quantities
and the shadows of the Kiselev black hole spacetime are presented in detail.
| [
{
"created": "Tue, 6 Aug 2019 11:44:37 GMT",
"version": "v1"
},
{
"created": "Mon, 11 May 2020 07:15:32 GMT",
"version": "v2"
}
] | 2020-05-12 | [
[
"Abbas",
"G.",
""
],
[
"Mahmood",
"Asif",
""
],
[
"Zubair",
"M.",
""
]
] | The ambition of the present work is to highlight the phenomena of strong gravitational lensing and deflection angle for the photons coupling with Weyl tensor in a Kiselev black hole. Here, we have extended the prior work of Chen and Jing \cite{1} for Schwarzschild black hole to Kiselev black hole. For this purpose, the equation of motion for the photons coupled to Weyl tensor, null geodesic and equation of photon sphere in a Kiselev black hole spacetime have been formulated. It is found that the equation of motion of the photons depends not only on the coupling between photon and Weyl tensor, but also on the polarization direction of the photons. There is a critical value of the coupling parameter $\alpha$ for existence of the marginally circular photon orbit outside the event horizon, which depends on the parameters of black hole and the polarization direction of photons. Further, the polarization directions of coupled photon and the coupling parameter $\alpha$, both modify the features of the photon sphere, the angle of deflection and the functions $(\bar{a}$ and $\bar{b})$ for the strong gravitational lensing in Kiselev black hole spacetime. In addition to this, the observable gravitational lensing quantities and the shadows of the Kiselev black hole spacetime are presented in detail. |
gr-qc/0505085 | Chad Galley | Chad R. Galley and B. L. Hu | Self-Force with a Stochastic Component from Radiation Reaction of a
Scalar Charge Moving in Curved Spacetime | One appendix added, minor revisions, 20 pages, 2 figures; submitted
to PRD | Phys.Rev. D72 (2005) 084023 | 10.1103/PhysRevD.72.084023 | null | gr-qc hep-th | null | We give a quantum field theoretical derivation of the scalar
Abraham-Lorentz-Dirac (ALD) equation and the self-force for a scalar charged
particle interacting with a quantum scalar field in curved spacetime. We
regularize the causal Green's function using a quasi-local expansion in the
spirit of effective field theory and obtain a regular expression for the
self-force. The scalar ALD equation obtained in this way for the classical
motion of the particle checks with the equation obtained by Quinn earlier
\cite{Quinn}. We further derive a scalar ALD-Langevin equation with a classical
stochastic force accounting for the effect of quantum fluctuations in the
field, which causes small fluctuations on the particle trajectory. This
equation will be useful for the study of stochastic motion of charges under the
influence of both quantum and classical noise sources, derived either
self-consistently (as done here) or put in by hand (with warnings). We show the
possibility of secular effects from such stochastic influences on the
trajectory that may impact on the present calculations of gravitational
waveform templates.
| [
{
"created": "Tue, 17 May 2005 21:06:41 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Jul 2005 19:11:37 GMT",
"version": "v2"
}
] | 2013-05-29 | [
[
"Galley",
"Chad R.",
""
],
[
"Hu",
"B. L.",
""
]
] | We give a quantum field theoretical derivation of the scalar Abraham-Lorentz-Dirac (ALD) equation and the self-force for a scalar charged particle interacting with a quantum scalar field in curved spacetime. We regularize the causal Green's function using a quasi-local expansion in the spirit of effective field theory and obtain a regular expression for the self-force. The scalar ALD equation obtained in this way for the classical motion of the particle checks with the equation obtained by Quinn earlier \cite{Quinn}. We further derive a scalar ALD-Langevin equation with a classical stochastic force accounting for the effect of quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. This equation will be useful for the study of stochastic motion of charges under the influence of both quantum and classical noise sources, derived either self-consistently (as done here) or put in by hand (with warnings). We show the possibility of secular effects from such stochastic influences on the trajectory that may impact on the present calculations of gravitational waveform templates. |
gr-qc/9405026 | Martin B. Einhorn | A. D. Dolgov, M. B. Einhorn, and V. I. Zakharov | The Vacuum of de~Sitter Space | 31 pages, no figures, UM-TH-94-14. (Compile twice with LaTeX.)
Amended 5/13/94 to add a citation | Acta Phys.Polon. B26 (1995) 65-90 | null | null | gr-qc hep-th | null | To resolve infrared problems with the de~Sitter invariant vacuum, we argue
that the history of the de~Sitter phase is crucial. We illustrate how either
(1)~the diagonalization of the Hamiltonian for long-wavelength modes or (2)~an
explicit modification of the metric in the distant past leads to natural
infrared cutoffs. The former case resembles a bosonic superconductor in which
graviton-pairing occurs between non-adiabatic modes. While the dynamical
equations respect de~Sitter symmetry, the vacuum is not de~Sitter invariant
because of the introduction of an initial condition at a finite time. The
implications for the one-loop stress tensor and the production of particles are
also discussed.
| [
{
"created": "Tue, 10 May 1994 21:30:12 GMT",
"version": "v1"
},
{
"created": "Fri, 13 May 1994 22:41:00 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Dolgov",
"A. D.",
""
],
[
"Einhorn",
"M. B.",
""
],
[
"Zakharov",
"V. I.",
""
]
] | To resolve infrared problems with the de~Sitter invariant vacuum, we argue that the history of the de~Sitter phase is crucial. We illustrate how either (1)~the diagonalization of the Hamiltonian for long-wavelength modes or (2)~an explicit modification of the metric in the distant past leads to natural infrared cutoffs. The former case resembles a bosonic superconductor in which graviton-pairing occurs between non-adiabatic modes. While the dynamical equations respect de~Sitter symmetry, the vacuum is not de~Sitter invariant because of the introduction of an initial condition at a finite time. The implications for the one-loop stress tensor and the production of particles are also discussed. |
gr-qc/9704080 | Mikhail Yu. Zotov | Mikhail Zotov (NPI, Moscow State University) | Einstein-Yang-Mills Black Hole Interiors: Serious Problems But Simple
Solution | REVTeX, 3 pages including 5 eps figures, uses boxedeps.tex. Minor
style changes, a typo in eqs. (6) removed | null | null | null | gr-qc | null | Recently E. E. Donets, D. V. Galtsov, and the author reported the results of
numerical and analytical investigation of the SU(2) Einstein-Yang-Mills black
hole interior solutions (gr-qc/9612067). It was shown that a generic interior
solution develops a new type of an infinitely oscillating behavior with
exponentially growing amplitude. Numerical data for three sequential
oscillations were presented. The numerical integration technique was not
discussed. Later P. Breitenlohner, G. Lavrelashvili, and D. Maison confirmed
our main results (gr-qc/9703047). But they have made some misleading
statements. In particular, they claimed, discussing the oscillations, that ``as
one performs the numerical integration one quickly runs into serious
problems...'' so that ``it is practically impossible to follow more than one or
two of them numerically'' because ``the numerical integration procedure breaks
down''. It is shown here that trivial logarithmic substitutions and integration
along the integral curve solve these ``serious problems'' easily.
| [
{
"created": "Tue, 29 Apr 1997 07:43:28 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jun 1997 08:45:03 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Zotov",
"Mikhail",
"",
"NPI, Moscow State University"
]
] | Recently E. E. Donets, D. V. Galtsov, and the author reported the results of numerical and analytical investigation of the SU(2) Einstein-Yang-Mills black hole interior solutions (gr-qc/9612067). It was shown that a generic interior solution develops a new type of an infinitely oscillating behavior with exponentially growing amplitude. Numerical data for three sequential oscillations were presented. The numerical integration technique was not discussed. Later P. Breitenlohner, G. Lavrelashvili, and D. Maison confirmed our main results (gr-qc/9703047). But they have made some misleading statements. In particular, they claimed, discussing the oscillations, that ``as one performs the numerical integration one quickly runs into serious problems...'' so that ``it is practically impossible to follow more than one or two of them numerically'' because ``the numerical integration procedure breaks down''. It is shown here that trivial logarithmic substitutions and integration along the integral curve solve these ``serious problems'' easily. |
1410.0802 | Christodoulakis Theodosios | Petros A. Terzis, N. Dimakis, T. Christodoulakis | Noether analysis of Scalar-Tensor Cosmology | Latex 2e source file, 26 pages, 2 figures | null | 10.1103/PhysRevD.90.123543 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A scalar--tensor theory of gravity, containing an arbitrary coupling function
$F(\phi)$ and a general potential $V(\phi)$, is considered in the context of a
spatially flat FLRW model. The use of reparametrization invariance enables a
particular lapse parametrization in which the mini--superspace metric
completely specifies the dynamics of the system. A requirement of existence of
the maximal possible number of autonomous integrals of motion is imposed. This
leads to a flat mini--superspace metric realized by a particular relation
between the coupling function and the potential. The space of solutions is
completely described in terms of the three autonomous integrals of motion
constructed by the Killing fields of the mini--supermetric and an additional
rheonomous emanating from the homothetic field. The solutions contain the
arbitrary function which remains after the imposition of the relation between
$F(\phi)$ and $V(\phi)$. To exemplify the use of the general results, we select
some particular cases and study their physical implications through an
effective energy--momentum tensor, which tends out to be that of a perfect
fluid.
| [
{
"created": "Fri, 3 Oct 2014 10:02:07 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Terzis",
"Petros A.",
""
],
[
"Dimakis",
"N.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | A scalar--tensor theory of gravity, containing an arbitrary coupling function $F(\phi)$ and a general potential $V(\phi)$, is considered in the context of a spatially flat FLRW model. The use of reparametrization invariance enables a particular lapse parametrization in which the mini--superspace metric completely specifies the dynamics of the system. A requirement of existence of the maximal possible number of autonomous integrals of motion is imposed. This leads to a flat mini--superspace metric realized by a particular relation between the coupling function and the potential. The space of solutions is completely described in terms of the three autonomous integrals of motion constructed by the Killing fields of the mini--supermetric and an additional rheonomous emanating from the homothetic field. The solutions contain the arbitrary function which remains after the imposition of the relation between $F(\phi)$ and $V(\phi)$. To exemplify the use of the general results, we select some particular cases and study their physical implications through an effective energy--momentum tensor, which tends out to be that of a perfect fluid. |
1006.2126 | Giacomo Rosati | Giovanni Amelino-Camelia, Marco Matassa, Flavio Mercati, Giacomo
Rosati | Taming nonlocality in theories with Planck-scale-deformed Lorentz
symmetry | results generalized to 3+1D case; presentation streamlined | Phys.Rev.Lett.106:071301,2011 | 10.1103/PhysRevLett.106.071301 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report a general analysis of worldlines for theories with deformed
relativistic symmetries and momentum dependence of the speed of photons. Our
formalization is faithful to Einstein's program, with spacetime points viewed
as an abstraction of physical events. The emerging picture imposes the
renunciation of the idealization of absolutely coincident events, but is free
from some pathologies which had been previously conjectured.
| [
{
"created": "Thu, 10 Jun 2010 19:43:14 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jun 2010 21:38:45 GMT",
"version": "v2"
},
{
"created": "Fri, 17 Feb 2012 09:42:12 GMT",
"version": "v3"
}
] | 2012-02-20 | [
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Matassa",
"Marco",
""
],
[
"Mercati",
"Flavio",
""
],
[
"Rosati",
"Giacomo",
""
]
] | We report a general analysis of worldlines for theories with deformed relativistic symmetries and momentum dependence of the speed of photons. Our formalization is faithful to Einstein's program, with spacetime points viewed as an abstraction of physical events. The emerging picture imposes the renunciation of the idealization of absolutely coincident events, but is free from some pathologies which had been previously conjectured. |
2009.06669 | Ricard Aguilera-Miret | Ricard Aguilera-Miret, Daniele Vigan\`o, Federico Carrasco, Borja
Mi\~nano, Carlos Palenzuela | Turbulent magnetic-field amplification in the first 10 milliseconds
after a binary neutron star merger: comparing high-resolution and large eddy
simulations | 14 pages, 7 figures | Phys. Rev. D 102, 103006 (2020) | 10.1103/PhysRevD.102.103006 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of binary neutron star mergers represents one of the most
important and complex astrophysical discoveries of the recent years. One of the
unclear aspects of the problem is the turbulent magnetic field amplification,
initially triggered by the Kelvin-Helmholtz instability at much smaller scales
than any reachable numerical resolution nowadays. Here we present numerical
simulations of the first ten milliseconds of a binary neutron star merger.
First, we confirm in detail how the simulated amplification depends on the
numerical resolution and is distributed on a broad range of scales, as expected
from turbulent MHD theory. We find that an initial large-scale magnetic field
of $10^{11}\,$G inside each star is amplified in the remnant to
root-mean-square values above $10^{16}\,$G within the first $5$ milliseconds
for our highest-resolution run. Then, we run large eddy simulations, exploring
the performance of the subgrid-scale gradient model, already tested
successfully in previous turbulent box simulations. We show that the addition
of this model is especially important in the induction equation, since it leads
to an amplification of the magnetic field comparable to a higher-resolution
run, but with a greatly reduced computational cost. In the first 10
milliseconds, there is no clear hint for an ordered, large-scale magnetic
field, which should indeed occur in longer timescales through magnetic winding
and the magneto-rotational instability.
| [
{
"created": "Mon, 14 Sep 2020 18:10:36 GMT",
"version": "v1"
}
] | 2020-11-11 | [
[
"Aguilera-Miret",
"Ricard",
""
],
[
"Viganò",
"Daniele",
""
],
[
"Carrasco",
"Federico",
""
],
[
"Miñano",
"Borja",
""
],
[
"Palenzuela",
"Carlos",
""
]
] | The detection of binary neutron star mergers represents one of the most important and complex astrophysical discoveries of the recent years. One of the unclear aspects of the problem is the turbulent magnetic field amplification, initially triggered by the Kelvin-Helmholtz instability at much smaller scales than any reachable numerical resolution nowadays. Here we present numerical simulations of the first ten milliseconds of a binary neutron star merger. First, we confirm in detail how the simulated amplification depends on the numerical resolution and is distributed on a broad range of scales, as expected from turbulent MHD theory. We find that an initial large-scale magnetic field of $10^{11}\,$G inside each star is amplified in the remnant to root-mean-square values above $10^{16}\,$G within the first $5$ milliseconds for our highest-resolution run. Then, we run large eddy simulations, exploring the performance of the subgrid-scale gradient model, already tested successfully in previous turbulent box simulations. We show that the addition of this model is especially important in the induction equation, since it leads to an amplification of the magnetic field comparable to a higher-resolution run, but with a greatly reduced computational cost. In the first 10 milliseconds, there is no clear hint for an ordered, large-scale magnetic field, which should indeed occur in longer timescales through magnetic winding and the magneto-rotational instability. |
gr-qc/9807084 | Phlogiston | Eric Baird | GR without SR: A gravitational-domain description of first-order Doppler
effects | HTML+GIF, with three GIF equations and three GIF figures, 58 refs.
~6500-word discussion of a radical approach to merging classical and quantum
models | null | null | null | gr-qc | null | Equivalence principles are a major part of modern relativity theory.
Gravitational shifts can already be calculated within the time domain as motion
shifts, and we examine the consequences of reversing this argument and
describing motion shifts outside the time domain, as effects of curvature
associated with relative velocity. This unusual "Doppler mass shift" approach
appears to resolve some of Einstein's own criticisms of the "SR+GR" model and
seems to remove some barriers to the reconciliation of classical and quantum
theory. The disadvantage of this model is that constant-velocity problems no
longer obey Euclidean geometry. By bypassing special relativity and the special
theory's flat-space assumptions, the model also suggests an alternative
non-transverse frequency-shift relationship. This difference should be
testable.
| [
{
"created": "Thu, 30 Jul 1998 21:44:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Baird",
"Eric",
""
]
] | Equivalence principles are a major part of modern relativity theory. Gravitational shifts can already be calculated within the time domain as motion shifts, and we examine the consequences of reversing this argument and describing motion shifts outside the time domain, as effects of curvature associated with relative velocity. This unusual "Doppler mass shift" approach appears to resolve some of Einstein's own criticisms of the "SR+GR" model and seems to remove some barriers to the reconciliation of classical and quantum theory. The disadvantage of this model is that constant-velocity problems no longer obey Euclidean geometry. By bypassing special relativity and the special theory's flat-space assumptions, the model also suggests an alternative non-transverse frequency-shift relationship. This difference should be testable. |
gr-qc/0207056 | Paul Halpern | Paul Halpern | The Mixmaster Universe in Five Dimensions | 13 pages | Gen.Rel.Grav. 35 (2003) 251-261 | 10.1023/A:1022341026460 | null | gr-qc | null | We consider a five dimensional vacuum cosmology with Bianchi type-IX spatial
geometry and an extra non-compact coordinate. Finding a new class of solutions,
we examine and rule out the possibility of deterministic chaos. We interpret
this result within the context of induced matter theory.
| [
{
"created": "Mon, 15 Jul 2002 21:20:50 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Halpern",
"Paul",
""
]
] | We consider a five dimensional vacuum cosmology with Bianchi type-IX spatial geometry and an extra non-compact coordinate. Finding a new class of solutions, we examine and rule out the possibility of deterministic chaos. We interpret this result within the context of induced matter theory. |
2404.07888 | Yiran Liu | Yi-Ran Liu, Jing-Rui Zhang, Yun-Long Zhang | Slowly rotating charges from Weyl double copy for Kerr black hole with
Chern-Simons correction | 9 pages | Commun. Theor. Phys. (2024) | 10.1088/1572-9494/ad4a37 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Weyl double copy builds the relation between gauge theory and gravity
theory, especially the correspondence between gauge solutions and gravity
solutions. In this paper, we obtain the slowly rotating charge solutions from
Weyl double copy for the Kerr black hole with small Chern-Simons correction.
Based on the Weyl double copy relation, for the Petrov type D solution, we find
the additional correction to the electromagnetic field strength tensor of
rotating charge. For the Petrov type I solution, we find that the additional
electromagnetic field strength tensors have the exogenous properties, while the
total sources vanish at the leading order.
| [
{
"created": "Thu, 11 Apr 2024 16:18:01 GMT",
"version": "v1"
}
] | 2024-05-21 | [
[
"Liu",
"Yi-Ran",
""
],
[
"Zhang",
"Jing-Rui",
""
],
[
"Zhang",
"Yun-Long",
""
]
] | The Weyl double copy builds the relation between gauge theory and gravity theory, especially the correspondence between gauge solutions and gravity solutions. In this paper, we obtain the slowly rotating charge solutions from Weyl double copy for the Kerr black hole with small Chern-Simons correction. Based on the Weyl double copy relation, for the Petrov type D solution, we find the additional correction to the electromagnetic field strength tensor of rotating charge. For the Petrov type I solution, we find that the additional electromagnetic field strength tensors have the exogenous properties, while the total sources vanish at the leading order. |
gr-qc/0403033 | Mihalis Dafermos | Mihalis Dafermos | On naked singularities and the collapse of self-gravitating Higgs fields | 15 pages, 4 figures | Adv.Theor.Math.Phys. 9 (2005) 575-591 | null | null | gr-qc | null | We consider the problem of collapse of a self-gravitating Higgs field, with
potential bounded below by a (possibly negative) constant. The behaviour at
infinity may be either asymptotically flat or asymptotically AdS. This problem
has received much attention as a source for possible violations of weak cosmic
censorship in string theory. In this paper, we prove under spherical symmetry
that ``first singularities'' arising in the non-trapped region must necessarily
emanate from the centre. In particular, this excludes the formation of a
certain type of naked singularity which was recently conjectured to occur.
| [
{
"created": "Mon, 8 Mar 2004 18:00:21 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Nov 2004 15:05:35 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Dafermos",
"Mihalis",
""
]
] | We consider the problem of collapse of a self-gravitating Higgs field, with potential bounded below by a (possibly negative) constant. The behaviour at infinity may be either asymptotically flat or asymptotically AdS. This problem has received much attention as a source for possible violations of weak cosmic censorship in string theory. In this paper, we prove under spherical symmetry that ``first singularities'' arising in the non-trapped region must necessarily emanate from the centre. In particular, this excludes the formation of a certain type of naked singularity which was recently conjectured to occur. |
2401.03098 | Tyler McMaken | Tyler McMaken, Andrew J. S. Hamilton | Hawking radiation inside a rotating black hole | 29 pages, 12 figures, 2 appendices | Phys. Rev. D 109, 065023 (2024) | 10.1103/PhysRevD.109.065023 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In semiclassical gravity, the vacuum expectation value
${\langle\hat{N}\rangle}$ of the particle number operator for a quantum field
gives rise to the perception of thermal radiation in the vicinity of a black
hole. This Hawking effect has been examined only for observers asymptotically
far from a Kerr black hole; here we generalize the analysis to various classes
of freely falling observers both outside and inside the Kerr event horizon. Of
note, we find that the effective temperature of the ${\langle\hat{N}\rangle}$
distribution remains regular for observers at the event horizon but becomes
negative and divergent for observers reaching the inner Cauchy horizon.
Furthermore, the perception of Hawking radiation varies greatly for different
classes of observers, though the spectrum is generally a graybody that
decreases in intensity with black hole spin and increases in temperature when
looking toward the edges of the black hole shadow.
| [
{
"created": "Sat, 6 Jan 2024 00:07:47 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Mar 2024 18:21:59 GMT",
"version": "v2"
}
] | 2024-03-22 | [
[
"McMaken",
"Tyler",
""
],
[
"Hamilton",
"Andrew J. S.",
""
]
] | In semiclassical gravity, the vacuum expectation value ${\langle\hat{N}\rangle}$ of the particle number operator for a quantum field gives rise to the perception of thermal radiation in the vicinity of a black hole. This Hawking effect has been examined only for observers asymptotically far from a Kerr black hole; here we generalize the analysis to various classes of freely falling observers both outside and inside the Kerr event horizon. Of note, we find that the effective temperature of the ${\langle\hat{N}\rangle}$ distribution remains regular for observers at the event horizon but becomes negative and divergent for observers reaching the inner Cauchy horizon. Furthermore, the perception of Hawking radiation varies greatly for different classes of observers, though the spectrum is generally a graybody that decreases in intensity with black hole spin and increases in temperature when looking toward the edges of the black hole shadow. |
2301.00053 | Oleg Tsupko | Gennady S. Bisnovatyi-Kogan and Oleg Yu. Tsupko | Time delay induced by plasma in strong lens systems | 8 pages, 1 figure | null | 10.1093/mnras/stad2030 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If the gravitational lens is surrounded by non-homoheneous plasma, in
addition to the vacuum gravitational deflection, chromatic refraction occurs.
Also, the speed of signal propagation decreases compared to vacuum. In this
article, we investigate analytically the time delay in the case of
gravitational lensing in plasma, focusing on strong lens systems. We take into
account the following contributions: geometric delay due to trajectory bending
in the presence of both gravity and plasma; potential delay of the ray in the
gravitational field of the lens; dispersion delay in the plasma due to decrease
of speed of light signal in the medium. We consider singular isothermal sphere
as a model of gravitational lens, and arbitrary spherically symmetric
distribution of surrounding plasma. For this scenario, plasma corrections for
the time delay between two images are found in compact analytical form
convenient for estimates. We discuss also the possible influence of the plasma
on the value of the Hubble constant, determined from observations of the time
delay in strong lens systems.
| [
{
"created": "Fri, 30 Dec 2022 20:42:19 GMT",
"version": "v1"
}
] | 2023-07-12 | [
[
"Bisnovatyi-Kogan",
"Gennady S.",
""
],
[
"Tsupko",
"Oleg Yu.",
""
]
] | If the gravitational lens is surrounded by non-homoheneous plasma, in addition to the vacuum gravitational deflection, chromatic refraction occurs. Also, the speed of signal propagation decreases compared to vacuum. In this article, we investigate analytically the time delay in the case of gravitational lensing in plasma, focusing on strong lens systems. We take into account the following contributions: geometric delay due to trajectory bending in the presence of both gravity and plasma; potential delay of the ray in the gravitational field of the lens; dispersion delay in the plasma due to decrease of speed of light signal in the medium. We consider singular isothermal sphere as a model of gravitational lens, and arbitrary spherically symmetric distribution of surrounding plasma. For this scenario, plasma corrections for the time delay between two images are found in compact analytical form convenient for estimates. We discuss also the possible influence of the plasma on the value of the Hubble constant, determined from observations of the time delay in strong lens systems. |
1403.6915 | Hideyuki Tagoshi | Hideyuki Tagoshi, Chandra Kant Mishra, Archana Pai, K. G. Arun | Parameter estimation of neutron star-black hole binaries using an
advanced gravitational-wave detector network: Effects of the full
post-Newtonian waveform | 29 pages, 25 figures, version published in PRD | Phys. Rev. D 90, 024053 (2014) | 10.1103/PhysRevD.90.024053 | LIGO-P1400030, OUTAP-353 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the effects of using the {\it full} waveform (FWF) over the
conventional {\it restricted} waveform (RWF) of the inspiral signal from a
coalescing compact binary (CCB) system in extracting the parameters of the
source, using a global network of second generation interferometric detectors.
We study a hypothetical population of (1.4-10)$M_\odot$ NS-BH binaries
(uniformly distributed and oriented in the sky) by employing the full
post-Newtonian waveforms, which not only include contributions from various
harmonics other than the dominant one (quadrupolar mode) but also the
post-Newtonian amplitude corrections associated with each harmonic, of the
inspiral signal expected from this system. It is expected that the GW detector
network consisting of the two LIGO detectors and a Virgo detector will be
joined by KAGRA and by proposed LIGO-India. We study the problem of parameter
estimation with all 16 possible detector configurations. Comparing medians of
error distributions obtained using FWFs with those obtained using RWFs (which
only include contributions from the dominant harmonic with Newtonian amplitude)
we find that the measurement accuracies for luminosity distance and the cosine
of the inclination angle improve almost by a factor of 1.5-2 depending upon the
network under consideration. Although the use of FWF does not improve the
source localization accuracy much, the global network consisting of five
detectors will improve the source localization accuracy by a factor of 4 as
compared to the estimates using a 3 detector LIGO-Virgo network for the same
waveform model.
| [
{
"created": "Thu, 27 Mar 2014 04:57:49 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Dec 2014 02:31:13 GMT",
"version": "v2"
}
] | 2014-12-15 | [
[
"Tagoshi",
"Hideyuki",
""
],
[
"Mishra",
"Chandra Kant",
""
],
[
"Pai",
"Archana",
""
],
[
"Arun",
"K. G.",
""
]
] | We investigate the effects of using the {\it full} waveform (FWF) over the conventional {\it restricted} waveform (RWF) of the inspiral signal from a coalescing compact binary (CCB) system in extracting the parameters of the source, using a global network of second generation interferometric detectors. We study a hypothetical population of (1.4-10)$M_\odot$ NS-BH binaries (uniformly distributed and oriented in the sky) by employing the full post-Newtonian waveforms, which not only include contributions from various harmonics other than the dominant one (quadrupolar mode) but also the post-Newtonian amplitude corrections associated with each harmonic, of the inspiral signal expected from this system. It is expected that the GW detector network consisting of the two LIGO detectors and a Virgo detector will be joined by KAGRA and by proposed LIGO-India. We study the problem of parameter estimation with all 16 possible detector configurations. Comparing medians of error distributions obtained using FWFs with those obtained using RWFs (which only include contributions from the dominant harmonic with Newtonian amplitude) we find that the measurement accuracies for luminosity distance and the cosine of the inclination angle improve almost by a factor of 1.5-2 depending upon the network under consideration. Although the use of FWF does not improve the source localization accuracy much, the global network consisting of five detectors will improve the source localization accuracy by a factor of 4 as compared to the estimates using a 3 detector LIGO-Virgo network for the same waveform model. |
1910.06105 | Muhammad Sharif | M. Sharif and Amal Majid | Complexity Factor for Static Sphere in Self-interacting Brans-Dicke
Gravity | 18 pages, no figure | Chin. J. Phys. 61(2019)38-46 | 10.1016/j.cjph.2019.08.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the complexity factor of a static anisotropic sphere
in the context of self-interacting Brans-Dicke theory. We split the Riemann
tensor using Bel's approach to obtain structure scalars relating to comoving
congruence and Tolman mass in the presence of a scalar field. We then define
the complexity factor with the help of these scalars to demonstrate the complex
nature of the system. We also evaluate the vanishing complexity condition to
obtain solutions for two stellar models. It is concluded that the complexity of
the system increases with the inclusion of the scalar field and potential
function.
| [
{
"created": "Fri, 11 Oct 2019 03:39:23 GMT",
"version": "v1"
}
] | 2019-10-23 | [
[
"Sharif",
"M.",
""
],
[
"Majid",
"Amal",
""
]
] | In this paper, we study the complexity factor of a static anisotropic sphere in the context of self-interacting Brans-Dicke theory. We split the Riemann tensor using Bel's approach to obtain structure scalars relating to comoving congruence and Tolman mass in the presence of a scalar field. We then define the complexity factor with the help of these scalars to demonstrate the complex nature of the system. We also evaluate the vanishing complexity condition to obtain solutions for two stellar models. It is concluded that the complexity of the system increases with the inclusion of the scalar field and potential function. |
gr-qc/0602058 | Gianluca Gemme | R. Ballantini, M. Bassan, A. Chincarini, G. Gemme, R. Parodi and R.
Vaccarone | Superconducting cavity transducer for resonant gravitational radiation
antennas | 7 pages, 3 eps figures. Presented at the 6th Amaldi Conference on
Gravitational Waves (2005). Accepted for publication in Journal of Physics:
Conference Series | J.Phys.Conf.Ser. 32 (2006) 339-345 | 10.1088/1742-6596/32/1/052 | null | gr-qc | null | Parametric transducers, such as superconducting rf cavities, can boost the
bandwidth and sensitivity of the next generation resonant antennas, thanks to a
readily available technology. We have developed a fully coupled dynamic model
of the system "antenna--transducer" and worked out some estimates of
signal--to--noise ratio and the stability conditions in various experimental
configurations. We also show the design and the prototype of a rf cavity which,
together with a suitable read--out electronic, will be used as a test bench for
the parametric transducer.
| [
{
"created": "Wed, 15 Feb 2006 10:22:54 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Ballantini",
"R.",
""
],
[
"Bassan",
"M.",
""
],
[
"Chincarini",
"A.",
""
],
[
"Gemme",
"G.",
""
],
[
"Parodi",
"R.",
""
],
[
"Vaccarone",
"R.",
""
]
] | Parametric transducers, such as superconducting rf cavities, can boost the bandwidth and sensitivity of the next generation resonant antennas, thanks to a readily available technology. We have developed a fully coupled dynamic model of the system "antenna--transducer" and worked out some estimates of signal--to--noise ratio and the stability conditions in various experimental configurations. We also show the design and the prototype of a rf cavity which, together with a suitable read--out electronic, will be used as a test bench for the parametric transducer. |
1401.7093 | Vladimir Folomeev | Vladimir Dzhunushaliev, Vladimir Folomeev, Burkhard Kleihaus, Jutta
Kunz | Hiding a neutron star inside a wormhole | 17 pages, 7 figures, minor corrections to content, new references
added, version published in PRD. arXiv admin note: text overlap with
arXiv:1302.5217 | Phys. Rev. D 89, 084018 (2014) | 10.1103/PhysRevD.89.084018 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider neutron-star-plus-wormhole configurations supported by a massless
ghost scalar field. The neutron fluid is modeled by an anisotropic equation of
state. When the central energy density of the fluid is of comparable magnitude
to the one of the scalar field, configurations with an equator at the center
and a double throat arise. These double-throat wormholes can be either
partially or completely filled by the neutron fluid. In the latter case, the
passage of light - radiated by the neutron matter - through these wormholes is
studied. A stability analysis indicates that all considered configurations are
unstable with respect to linear perturbations, independent of whether the fluid
is isotropic or anisotropic.
| [
{
"created": "Tue, 28 Jan 2014 06:29:31 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Apr 2014 04:51:15 GMT",
"version": "v2"
}
] | 2014-04-15 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We consider neutron-star-plus-wormhole configurations supported by a massless ghost scalar field. The neutron fluid is modeled by an anisotropic equation of state. When the central energy density of the fluid is of comparable magnitude to the one of the scalar field, configurations with an equator at the center and a double throat arise. These double-throat wormholes can be either partially or completely filled by the neutron fluid. In the latter case, the passage of light - radiated by the neutron matter - through these wormholes is studied. A stability analysis indicates that all considered configurations are unstable with respect to linear perturbations, independent of whether the fluid is isotropic or anisotropic. |
1601.07382 | Vladimi Toussaint | Jorma Louko and Vladimir Toussaint | Unruh-DeWitt Fermion Detector on a (1+1)-Dimensional Cylindrical
Spacetime: Arbitrary Worldlines and Inequivalent Spin Structures | null | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine an Unruh-DeWitt particle detector which couples linearly to the
scalar density of a massless Dirac field on the static cylindrical quotient of
the (1+1)-dimensional Minkowski spacetime, allowing the detector's motion to
remain arbitrary and working to leading order in perturbation theory. We show
that the detector's response distinguishes the periodic and antiperiodic spin
structures, and the zero mode that is present for periodic spinors contributes
to the response by a state-dependent but well defined and controllable amount.
| [
{
"created": "Tue, 26 Jan 2016 16:20:58 GMT",
"version": "v1"
}
] | 2016-01-28 | [
[
"Louko",
"Jorma",
""
],
[
"Toussaint",
"Vladimir",
""
]
] | We examine an Unruh-DeWitt particle detector which couples linearly to the scalar density of a massless Dirac field on the static cylindrical quotient of the (1+1)-dimensional Minkowski spacetime, allowing the detector's motion to remain arbitrary and working to leading order in perturbation theory. We show that the detector's response distinguishes the periodic and antiperiodic spin structures, and the zero mode that is present for periodic spinors contributes to the response by a state-dependent but well defined and controllable amount. |
gr-qc/0303034 | Teofilo Vargas | T. Vargas Auccalla | The energy of the universe in teleparallel gravity | 9 pages, no figures | Gen.Rel.Grav. 36 (2004) 1255 | 10.1023/B:GERG.0000022386.29438.be | null | gr-qc | null | The teleparallel versions of the Einstein and the Landau-Lifshitz
energy-momentum complexes of the gravitational field are obtained. By using
these complexes, the total energy of the universe, which includes the energy of
both the matter and the gravitational fields, is then obtained. It is shown
that the total energy vanishes independently of both the curvature parameter
and the three dimensionless coupling constants of teleparallel gravity.
| [
{
"created": "Sun, 9 Mar 2003 22:48:36 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Auccalla",
"T. Vargas",
""
]
] | The teleparallel versions of the Einstein and the Landau-Lifshitz energy-momentum complexes of the gravitational field are obtained. By using these complexes, the total energy of the universe, which includes the energy of both the matter and the gravitational fields, is then obtained. It is shown that the total energy vanishes independently of both the curvature parameter and the three dimensionless coupling constants of teleparallel gravity. |
1607.08234 | Remo Garattini | Remo Garattini and Gianluca Mandanici | Rainbow's Stars | 18 pages | null | 10.1140/epjc/s10052-017-4618-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent years, a growing interest on the equilibrium of compact
astrophysical objects like white dwarf and neutron stars has been manifested.
In particular, various modifications due to Planck scale energy effects have
been considered. In this paper we analyze the modification induced by Gravity's
Rainbow on the equilibrium configurations described by the
Tolman-Oppenheimer-Volkoff (TOV) equation. Our purpose is to explore the
possibility that the Rainbow Planck-scale deformation of space-time could
support the existence of different compact stars.
| [
{
"created": "Wed, 27 Jul 2016 13:53:59 GMT",
"version": "v1"
}
] | 2017-03-08 | [
[
"Garattini",
"Remo",
""
],
[
"Mandanici",
"Gianluca",
""
]
] | In recent years, a growing interest on the equilibrium of compact astrophysical objects like white dwarf and neutron stars has been manifested. In particular, various modifications due to Planck scale energy effects have been considered. In this paper we analyze the modification induced by Gravity's Rainbow on the equilibrium configurations described by the Tolman-Oppenheimer-Volkoff (TOV) equation. Our purpose is to explore the possibility that the Rainbow Planck-scale deformation of space-time could support the existence of different compact stars. |
gr-qc/9708018 | Sanjay Jain | Sanjay Jain (Indian Institute of Science) | Absence of initial singularities in superstring cosmology | 20 pages, revtex, including 2 PostScript figures appended using epsf.
Based on talk given at the Conference on Big Bang and Alternative
Cosmologies: A Critical Appraisal, Bangalore, India, January 1997 | null | 10.1007/BF02709328 | IISc-CTS-5/97 | gr-qc hep-th | null | In a universe whose elementary constituents are point particles there does
not seem to be any obvious mechanism for avoiding the initial singularities in
physical quantities in the standard model of cosmology. In contrast in string
theory these singularities can be absent even at the level where spacetime is
treated classically. This is a consequence of the basic degrees of freedom of
strings in compact spaces, which necessitate a reinterpretation of what one
means by a very small universe. We discuss the basic degrees of freedom of a
string at the classical and quantum level, the minimum size of strings (string
uncertainty principle), the t-duality symmetry, and string thermodynamics at
high energy densities, and then describe how these considerations suggest a
resolution of the initial singularity problem. An effort has been made to keep
this writeup self-contained and accessible to non-string theorists.
| [
{
"created": "Sun, 10 Aug 1997 17:31:22 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Jain",
"Sanjay",
"",
"Indian Institute of Science"
]
] | In a universe whose elementary constituents are point particles there does not seem to be any obvious mechanism for avoiding the initial singularities in physical quantities in the standard model of cosmology. In contrast in string theory these singularities can be absent even at the level where spacetime is treated classically. This is a consequence of the basic degrees of freedom of strings in compact spaces, which necessitate a reinterpretation of what one means by a very small universe. We discuss the basic degrees of freedom of a string at the classical and quantum level, the minimum size of strings (string uncertainty principle), the t-duality symmetry, and string thermodynamics at high energy densities, and then describe how these considerations suggest a resolution of the initial singularity problem. An effort has been made to keep this writeup self-contained and accessible to non-string theorists. |
1406.0677 | Keisuke Izumi | Keisuke Izumi | Causal Structures in Gauss-Bonnet gravity | Version accepted by PRD (v2): 11pages, 1 figure | Phys. Rev. D 90, 044037 (2014) | 10.1103/PhysRevD.90.044037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze causal structures in Gauss-Bonnet gravity. It is known that
Gauss-Bonnet gravity potentially has superluminal propagation of gravitons due
to its noncanonical kinetic terms. In a theory with superluminal modes, an
analysis of causality based on null curves makes no sense, and thus, we need to
analyze them in a different way. In this paper, using the method of the
characteristics, we analyze the causal structure in Gauss-Bonnet gravity. We
have the result that, on a Killing horizon, gravitons can propagate in the null
direction tangent to the Killing horizon. Therefore, a Killing horizon can be a
causal edge as in the case of general relativity, i.e. a Killing horizon is the
"event horizon" in the sense of causality. We also analyze causal structures on
nonstationary solutions with $(D-2)$-dimensional maximal symmetry, including
spherically symmetric and flat spaces. If the geometrical null energy
condition, $R_{AB}N^AN^B \ge 0$ for any null vector $N^A$, is satisfied, the
radial velocity of gravitons must be less than or equal to that of light.
However, if the geometrical null energy condition is violated, gravitons can
propagate faster than light. Hence, on an evaporating black hole where the
geometrical null energy condition is expected not to hold, classical gravitons
can escape from the "black hole" defined with null curves. That is, the causal
structures become nontrivial. It may be one of the possible solutions for the
information loss paradox of evaporating black holes.
| [
{
"created": "Tue, 3 Jun 2014 11:55:32 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Sep 2014 00:50:56 GMT",
"version": "v2"
}
] | 2014-09-04 | [
[
"Izumi",
"Keisuke",
""
]
] | We analyze causal structures in Gauss-Bonnet gravity. It is known that Gauss-Bonnet gravity potentially has superluminal propagation of gravitons due to its noncanonical kinetic terms. In a theory with superluminal modes, an analysis of causality based on null curves makes no sense, and thus, we need to analyze them in a different way. In this paper, using the method of the characteristics, we analyze the causal structure in Gauss-Bonnet gravity. We have the result that, on a Killing horizon, gravitons can propagate in the null direction tangent to the Killing horizon. Therefore, a Killing horizon can be a causal edge as in the case of general relativity, i.e. a Killing horizon is the "event horizon" in the sense of causality. We also analyze causal structures on nonstationary solutions with $(D-2)$-dimensional maximal symmetry, including spherically symmetric and flat spaces. If the geometrical null energy condition, $R_{AB}N^AN^B \ge 0$ for any null vector $N^A$, is satisfied, the radial velocity of gravitons must be less than or equal to that of light. However, if the geometrical null energy condition is violated, gravitons can propagate faster than light. Hence, on an evaporating black hole where the geometrical null energy condition is expected not to hold, classical gravitons can escape from the "black hole" defined with null curves. That is, the causal structures become nontrivial. It may be one of the possible solutions for the information loss paradox of evaporating black holes. |
gr-qc/9802006 | John Baker | John Baker and Raymond Stanley Puzio | A New Method for Solving the Initial Value Problem with Application to
Multiple Black Holes | 10 pages | Phys.Rev. D59 (1999) 044030 | 10.1103/PhysRevD.59.044030 | CGPG-97/12-2 | gr-qc | null | This work consists of two distinct parts. In the first part we present a new
method for solving the initial value problem of general relativity. Given any
spatial metric with a surface orthogonal Killing field and two freely specified
components of the extrinsic curvature we solve for extrinsic curvature's
remaining components. For the second part, after noting that initial data for
the Kerr spacetime can be derived within our formalism we construct data for
axisymmetric configurations of spinning black holes. Though our method is
limited to axisymmetry, it offers an advantage over the Bowen-York proceedure
that our data approach those for Kerr holes in the limit of large separations
and in the close limit.
| [
{
"created": "Tue, 3 Feb 1998 05:34:01 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Baker",
"John",
""
],
[
"Puzio",
"Raymond Stanley",
""
]
] | This work consists of two distinct parts. In the first part we present a new method for solving the initial value problem of general relativity. Given any spatial metric with a surface orthogonal Killing field and two freely specified components of the extrinsic curvature we solve for extrinsic curvature's remaining components. For the second part, after noting that initial data for the Kerr spacetime can be derived within our formalism we construct data for axisymmetric configurations of spinning black holes. Though our method is limited to axisymmetry, it offers an advantage over the Bowen-York proceedure that our data approach those for Kerr holes in the limit of large separations and in the close limit. |
0705.4339 | Ran Li | Ji-Rong Ren, Ran Li | Unified First Law and Thermodynamics of Dynamical Black Hole in
n-dimensional Vaidya Spacetime | 3 pages, no figure | Mod.Phys.Lett.A23:3265-3270,2008 | 10.1142/S0217732308028831 | null | gr-qc | null | As a simple but important example of dynamical black hole, we analysis the
dynamical black hole in $n$-dimensional Vaidya spacetime in detail. We
investigated the thermodynamics of field equation in $n$-dimensional Vaidya
spacetime. The unified first law was derived in terms of the methods proposed
by Sean A Hayward. The first law of dynamical black hole was obtained by
projecting the unified first law along the trapping horizon. At last, the
second law of dynamical black hole is also discussed.
| [
{
"created": "Wed, 30 May 2007 05:12:17 GMT",
"version": "v1"
},
{
"created": "Thu, 31 May 2007 13:39:49 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Ren",
"Ji-Rong",
""
],
[
"Li",
"Ran",
""
]
] | As a simple but important example of dynamical black hole, we analysis the dynamical black hole in $n$-dimensional Vaidya spacetime in detail. We investigated the thermodynamics of field equation in $n$-dimensional Vaidya spacetime. The unified first law was derived in terms of the methods proposed by Sean A Hayward. The first law of dynamical black hole was obtained by projecting the unified first law along the trapping horizon. At last, the second law of dynamical black hole is also discussed. |
1810.02915 | Joseph Sultana Dr. | Joseph Sultana, Demosthenes Kazanas | A no-hair theorem for spherically symmetric black holes in $R^2$ gravity | 10 pages | null | 10.1007/s10714-018-2463-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper Ca\~nate (CQG, {\bf 35}, 025018 (2018)) proved a no hair
theorem to static and spherically symmetric or stationary axisymmetric black
holes in general $f(R)$ gravity. The theorem applies for isolated
asymptotically flat or asymptotically de Sitter black holes and also in the
case when vacuum is replaced by a minimally coupled source having a traceless
energy momentum tensor. This theorem excludes the case of pure quadratic
gravity, $f(R) = R^2$. In this paper we use the scalar tensor representation of
general $f(R)$ theory to show that there are no hairy black hole in pure $R^2$
gravity. The result is limited to spherically symmetric black holes but does
not assume asymptotic flatness or de-Sitter asymptotics as in most of the
no-hair theorems encountered in the literature. We include an example of a
static and spherically symmetric black hole in $R^2$ gravity with a conformally
coupled scalar field having a Higgs-type quartic potential.
| [
{
"created": "Sat, 6 Oct 2018 00:45:19 GMT",
"version": "v1"
}
] | 2018-10-09 | [
[
"Sultana",
"Joseph",
""
],
[
"Kazanas",
"Demosthenes",
""
]
] | In a recent paper Ca\~nate (CQG, {\bf 35}, 025018 (2018)) proved a no hair theorem to static and spherically symmetric or stationary axisymmetric black holes in general $f(R)$ gravity. The theorem applies for isolated asymptotically flat or asymptotically de Sitter black holes and also in the case when vacuum is replaced by a minimally coupled source having a traceless energy momentum tensor. This theorem excludes the case of pure quadratic gravity, $f(R) = R^2$. In this paper we use the scalar tensor representation of general $f(R)$ theory to show that there are no hairy black hole in pure $R^2$ gravity. The result is limited to spherically symmetric black holes but does not assume asymptotic flatness or de-Sitter asymptotics as in most of the no-hair theorems encountered in the literature. We include an example of a static and spherically symmetric black hole in $R^2$ gravity with a conformally coupled scalar field having a Higgs-type quartic potential. |
2106.06492 | Andrea Sylvia Biscoveanu | Sylvia Biscoveanu, Maximiliano Isi, Vijay Varma, Salvatore Vitale | Measuring the spins of heavy binary black holes | Version accepted in PRD | Phys. Rev. D 104, 103018 (2021) | 10.1103/PhysRevD.104.103018 | LIGO document number P2100204 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An accurate and precise measurement of the spins of individual merging black
holes is required to understand their origin. While previous studies have
indicated that most of the spin information comes from the inspiral part of the
signal, the informative spin measurement of the heavy binary black hole system
GW190521 suggests that the merger and ringdown can contribute significantly to
the spin constraints for such massive systems. We perform a systematic study
into the measurability of the spin parameters of individual heavy binary black
hole mergers using a numerical relativity surrogate waveform model including
the effects of both spin-induced precession and higher-order modes. We find
that the spin measurements are driven by the merger and ringdown parts of the
signal for GW190521-like systems, but the uncertainty in the measurement
increases with the total mass of the system. We are able to place meaningful
constraints on the spin parameters even for systems observed at moderate
signal-to-noise ratios, but the measurability depends on the exact
six-dimensional spin configuration of the system. Finally, we find that the
azimuthal angle between the in-plane projections of the component spin vectors
at a given reference frequency cannot be well-measured for most of our
simulated configurations even for signals observed with high signal-to-noise
ratios.
| [
{
"created": "Fri, 11 Jun 2021 16:26:04 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jun 2021 18:59:36 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Nov 2021 03:13:12 GMT",
"version": "v3"
}
] | 2021-11-17 | [
[
"Biscoveanu",
"Sylvia",
""
],
[
"Isi",
"Maximiliano",
""
],
[
"Varma",
"Vijay",
""
],
[
"Vitale",
"Salvatore",
""
]
] | An accurate and precise measurement of the spins of individual merging black holes is required to understand their origin. While previous studies have indicated that most of the spin information comes from the inspiral part of the signal, the informative spin measurement of the heavy binary black hole system GW190521 suggests that the merger and ringdown can contribute significantly to the spin constraints for such massive systems. We perform a systematic study into the measurability of the spin parameters of individual heavy binary black hole mergers using a numerical relativity surrogate waveform model including the effects of both spin-induced precession and higher-order modes. We find that the spin measurements are driven by the merger and ringdown parts of the signal for GW190521-like systems, but the uncertainty in the measurement increases with the total mass of the system. We are able to place meaningful constraints on the spin parameters even for systems observed at moderate signal-to-noise ratios, but the measurability depends on the exact six-dimensional spin configuration of the system. Finally, we find that the azimuthal angle between the in-plane projections of the component spin vectors at a given reference frequency cannot be well-measured for most of our simulated configurations even for signals observed with high signal-to-noise ratios. |
1107.2948 | Joshua Smith | Joshua R Smith, Thomas Abbott, Eiichi Hirose, Nicolas Leroy, Duncan
Macleod, Jessica McIver, Peter Saulson, Peter Shawhan | A hierarchical method for vetoing noise transients in gravitational-wave
detectors | 13 pages | Class. Quantum Grav. 28 235005 (2011) | 10.1088/0264-9381/28/23/235005 | LIGO Document P1100045 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-Gaussian noise transients in interferometric gravitational-wave detectors
increase the background in searches for short-duration and un-modelled signals.
We describe a method for vetoing noise transients by ranking the statistical
relationship between triggers in auxiliary channels that have negligible
sensitivity to gravitational waves and putative gravitational-wave triggers in
the detector output. The novelty of the algorithm lies in its hierarchical
approach, which leads to a minimal set of veto conditions with high performance
and low deadtime. After a given channel has been selected it is used to veto
triggers from the detector output, then the algorithm selects a new channel
that performs well on the remaining triggers and the process is repeated. This
method has been demonstrated to reduce the background in searches for transient
gravitational waves by the LIGO and Virgo collaborations.
| [
{
"created": "Thu, 14 Jul 2011 20:51:06 GMT",
"version": "v1"
}
] | 2012-04-16 | [
[
"Smith",
"Joshua R",
""
],
[
"Abbott",
"Thomas",
""
],
[
"Hirose",
"Eiichi",
""
],
[
"Leroy",
"Nicolas",
""
],
[
"Macleod",
"Duncan",
""
],
[
"McIver",
"Jessica",
""
],
[
"Saulson",
"Peter",
""
],
[
... | Non-Gaussian noise transients in interferometric gravitational-wave detectors increase the background in searches for short-duration and un-modelled signals. We describe a method for vetoing noise transients by ranking the statistical relationship between triggers in auxiliary channels that have negligible sensitivity to gravitational waves and putative gravitational-wave triggers in the detector output. The novelty of the algorithm lies in its hierarchical approach, which leads to a minimal set of veto conditions with high performance and low deadtime. After a given channel has been selected it is used to veto triggers from the detector output, then the algorithm selects a new channel that performs well on the remaining triggers and the process is repeated. This method has been demonstrated to reduce the background in searches for transient gravitational waves by the LIGO and Virgo collaborations. |
gr-qc/9508030 | null | Giampiero Esposito | The Geometry of Complex Space-Times with Torsion | 3 pages, plain-tex, published in Proceedings of the X Italian
Conference on General Relativity and Gravitational Physics, editors M.
Cerdonio et al., 1993, pages 481-483 (Singapore: World Scientific) | null | null | SISSA Ref. 86/92/A | gr-qc | null | The necessary and sufficient condition for the existence of $\alpha$-surfaces
in complex space-time manifolds with nonvanishing torsion is derived. For these
manifolds, Lie brackets of vector fields and spinor Ricci identities contain
explicitly the effects of torsion. This leads to an integrability condition for
$\alpha$-surfaces which does not involve just the self-dual Weyl spinor, as in
complex general relativity, but also the torsion spinor, in a nonlinear way,
and its covariant derivative. A similar result also holds for four-dimensional,
smooth real manifolds with a positive-definite metric. Interestingly, a
particular solution of the integrability condition is given by conformally
right-flat and right-torsion-free space-times.
| [
{
"created": "Mon, 14 Aug 1995 13:06:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Esposito",
"Giampiero",
""
]
] | The necessary and sufficient condition for the existence of $\alpha$-surfaces in complex space-time manifolds with nonvanishing torsion is derived. For these manifolds, Lie brackets of vector fields and spinor Ricci identities contain explicitly the effects of torsion. This leads to an integrability condition for $\alpha$-surfaces which does not involve just the self-dual Weyl spinor, as in complex general relativity, but also the torsion spinor, in a nonlinear way, and its covariant derivative. A similar result also holds for four-dimensional, smooth real manifolds with a positive-definite metric. Interestingly, a particular solution of the integrability condition is given by conformally right-flat and right-torsion-free space-times. |
1811.09159 | Jia-An Lu | Jia-An Lu | de Sitter-covariant Hamiltonian formalism of Einstein--Cartan gravity | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamiltonian formalism of Einstein--Cartan (EC) gravity is a starting
point for canonical quantum gravity. The existing formalisms are at most
Lorentz covariant, or diffeomorphism covariant. Here we analyze the Hamiltonian
EC gravity in a 5d covariant way, with the gauge group being the de Sitter (dS)
group, which unifies the Lorentz transformations and translation in an elegant
manner, and also coincides with the acceleration of the universe. We
reformulate the EC equations into a dS-covariant form, then find out the
dS-covariant constraints of the phase space, and make all the constraint
functions constitute a closed algebra by constructing a dS-invariant Dirac
bracket, for the purpose of quantization.
| [
{
"created": "Thu, 22 Nov 2018 13:07:17 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Mar 2019 12:28:46 GMT",
"version": "v2"
}
] | 2019-03-26 | [
[
"Lu",
"Jia-An",
""
]
] | The Hamiltonian formalism of Einstein--Cartan (EC) gravity is a starting point for canonical quantum gravity. The existing formalisms are at most Lorentz covariant, or diffeomorphism covariant. Here we analyze the Hamiltonian EC gravity in a 5d covariant way, with the gauge group being the de Sitter (dS) group, which unifies the Lorentz transformations and translation in an elegant manner, and also coincides with the acceleration of the universe. We reformulate the EC equations into a dS-covariant form, then find out the dS-covariant constraints of the phase space, and make all the constraint functions constitute a closed algebra by constructing a dS-invariant Dirac bracket, for the purpose of quantization. |
gr-qc/9910009 | Thomas Thiemann | T. Thiemann | Complete quantization of a diffeomorphism invariant field theory | 32p, LATEX | Class.Quant.Grav.12:59-88,1995 | 10.1088/0264-9381/12/1/006 | PITHA 93-33 | gr-qc | null | In order to test the canonical quantization programme for general relativity
we introduce a reduced model for a real sector of complexified Ashtekar gravity
which captures important properties of the full theory. While it does not
correspond to a subset of Einstein's gravity it has the advantage that the
programme of canonical quantization can be carried out completely and
explicitly, both, via the reduced phase space approach or along the lines of
the algebraic quantization programme. This model stands in close correspondence
to the frequently treated cylindrically symmetric waves. In contrast to other
models that have been looked at up to now in terms of the new variables the
reduced phase space is infinite dimensional while the scalar constraint is
genuinely bilinear in the momenta. The infinite number of Dirac observables can
be expressed in compact and explicit form in terms of the original phase space
variables. They turn out, as expected, to be non-local and form naturally a set
of countable cardinality.
| [
{
"created": "Mon, 4 Oct 1999 17:14:52 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Thiemann",
"T.",
""
]
] | In order to test the canonical quantization programme for general relativity we introduce a reduced model for a real sector of complexified Ashtekar gravity which captures important properties of the full theory. While it does not correspond to a subset of Einstein's gravity it has the advantage that the programme of canonical quantization can be carried out completely and explicitly, both, via the reduced phase space approach or along the lines of the algebraic quantization programme. This model stands in close correspondence to the frequently treated cylindrically symmetric waves. In contrast to other models that have been looked at up to now in terms of the new variables the reduced phase space is infinite dimensional while the scalar constraint is genuinely bilinear in the momenta. The infinite number of Dirac observables can be expressed in compact and explicit form in terms of the original phase space variables. They turn out, as expected, to be non-local and form naturally a set of countable cardinality. |
1902.09208 | Kalin Staykov Dr. | Kalin V. Staykov, Daniela D. Doneva, Stoytcho S. Yazadjiev | Orbital and epicyclic frequencies in massive scalar-tensor theory with
self-interaction | 10 pages, 6 figures | null | 10.1007/s10509-019-3666-1 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Testing modified theories of gravity with direct observations of the
parameters of a neutron star is not the optimal way of testing gravitational
theories. However, observing electromagnetic signals originating from the close
vicinity of the compact object my turn out an excellent way of probing
spacetime in strong field regime. A promising candidate for doing so are the
so-called quasi-periodic oscillations, observed in the X-ray light curves of
some pulsars. Although the origin of those oscillations is unknown, one thing
most of the models describing them have in common is that in one way or another
they incorporate the radius of the innermost stable circular obit, and the
orbital and the epicyclic frequencies of particles moving around the compact
object. In this paper we study the aforementioned quantities in the context of
massive scalar-tensor theory and massive scalar-tensor theory with
self-interaction, both of which in strong regime allow for significant
deviations from General relativity for values for the free parameters of the
theory in correlation with the observations.
| [
{
"created": "Mon, 25 Feb 2019 11:47:42 GMT",
"version": "v1"
}
] | 2019-11-06 | [
[
"Staykov",
"Kalin V.",
""
],
[
"Doneva",
"Daniela D.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | Testing modified theories of gravity with direct observations of the parameters of a neutron star is not the optimal way of testing gravitational theories. However, observing electromagnetic signals originating from the close vicinity of the compact object my turn out an excellent way of probing spacetime in strong field regime. A promising candidate for doing so are the so-called quasi-periodic oscillations, observed in the X-ray light curves of some pulsars. Although the origin of those oscillations is unknown, one thing most of the models describing them have in common is that in one way or another they incorporate the radius of the innermost stable circular obit, and the orbital and the epicyclic frequencies of particles moving around the compact object. In this paper we study the aforementioned quantities in the context of massive scalar-tensor theory and massive scalar-tensor theory with self-interaction, both of which in strong regime allow for significant deviations from General relativity for values for the free parameters of the theory in correlation with the observations. |
2406.08452 | Martin Kr\v{s}\v{s}\'ak | Martin Kr\v{s}\v{s}\'ak | Einstein Gravity from Einstein Action: Counterterms and Covariance | 12 pages; an earlier version was submitted to Gravity Research
Foundation 2024 Awards for Essays on Gravitation | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The field equations of general relativity can be derived from the Einstein
action, which is quadratic in connection coefficients, rather than the standard
action involving the Gibbons-Hawking-York term and counterterm. We show that it
is possible to construct a new counterterm directly for the Einstein action,
which removes divergences and naturally introduces a flat reference spacetime.
The total action is then covariant under simultaneous transformation of both
the spacetime and reference tetrads, and argue that this is analogous to the
Gibbons-Hawking action. We then explore different perspectives arising
naturally from different uses of the reference tetrad, and explore implications
of viewing gravity as fundamentally described in terms of non-covariant
connection coefficients.
| [
{
"created": "Wed, 12 Jun 2024 17:44:32 GMT",
"version": "v1"
}
] | 2024-06-13 | [
[
"Krššák",
"Martin",
""
]
] | The field equations of general relativity can be derived from the Einstein action, which is quadratic in connection coefficients, rather than the standard action involving the Gibbons-Hawking-York term and counterterm. We show that it is possible to construct a new counterterm directly for the Einstein action, which removes divergences and naturally introduces a flat reference spacetime. The total action is then covariant under simultaneous transformation of both the spacetime and reference tetrads, and argue that this is analogous to the Gibbons-Hawking action. We then explore different perspectives arising naturally from different uses of the reference tetrad, and explore implications of viewing gravity as fundamentally described in terms of non-covariant connection coefficients. |
2403.00070 | Mariam Campbell | Mariam Campbell, Sante Carloni, Peter K. S. Dunsby and Nolene F. Naidu | Reconstructing exact solutions to relativistic stars in $f(R)$ gravity | 15 pages, 17 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We present a covariant description of non-vacuum static spherically symmetric
spacetimes in $f(R)$-gravity applying the (1+1+2) covariant formalism. The
propagation equations are then used to derive a covariant and dimensionless
form of the Tolman-Oppenheimer-Volkoff (TOV) equations. We then give a solution
strategy to these equations and obtain a new exact solution for the particular
case $f(R)=R+\alpha R^{2}$.
| [
{
"created": "Thu, 29 Feb 2024 19:01:06 GMT",
"version": "v1"
}
] | 2024-03-04 | [
[
"Campbell",
"Mariam",
""
],
[
"Carloni",
"Sante",
""
],
[
"Dunsby",
"Peter K. S.",
""
],
[
"Naidu",
"Nolene F.",
""
]
] | We present a covariant description of non-vacuum static spherically symmetric spacetimes in $f(R)$-gravity applying the (1+1+2) covariant formalism. The propagation equations are then used to derive a covariant and dimensionless form of the Tolman-Oppenheimer-Volkoff (TOV) equations. We then give a solution strategy to these equations and obtain a new exact solution for the particular case $f(R)=R+\alpha R^{2}$. |
1201.2489 | Aron Wall | Aron C. Wall | A discrete, unitary, causal theory of quantum gravity | 38 pages, 9 figures, v3 added to exposition and references, v4
expanded prospects section | Class. Quantum Grav. 30, 115002 (2013) | 10.1088/0264-9381/30/11/115002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A discrete model of Lorentzian quantum gravity is proposed. The theory is
completely background free, containing no reference to absolute space, time, or
simultaneity. The states at one slice of time are networks in which each vertex
is labelled with two arrows, which point along an adjacent edge, or to the
vertex itself. The dynamics is specified by a set of unitary replacement rules,
which causally propagate the local degrees of freedom. The inner product
between any two states is given by a sum over histories. Assuming it converges
(or can be Abel resummed), this inner product is proven to be hermitian and
fully gauge-degenerate under spacetime diffeomorphisms. At least for states
with a finite past, the inner product is also positive. This allows a Hilbert
space of physical states to be constructed.
| [
{
"created": "Thu, 12 Jan 2012 07:14:13 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Apr 2012 22:03:59 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Aug 2012 23:13:11 GMT",
"version": "v3"
},
{
"created": "Tue, 14 May 2013 00:55:06 GMT",
"version": "v4"
}
] | 2015-06-03 | [
[
"Wall",
"Aron C.",
""
]
] | A discrete model of Lorentzian quantum gravity is proposed. The theory is completely background free, containing no reference to absolute space, time, or simultaneity. The states at one slice of time are networks in which each vertex is labelled with two arrows, which point along an adjacent edge, or to the vertex itself. The dynamics is specified by a set of unitary replacement rules, which causally propagate the local degrees of freedom. The inner product between any two states is given by a sum over histories. Assuming it converges (or can be Abel resummed), this inner product is proven to be hermitian and fully gauge-degenerate under spacetime diffeomorphisms. At least for states with a finite past, the inner product is also positive. This allows a Hilbert space of physical states to be constructed. |
1304.8042 | Ikjyot Singh Kohli | Ikjyot Singh Kohli and Michael C. Haslam | A Dynamical Systems Approach to a Bianchi Type I Viscous
Magnetohydrodynamic Model | null | Phys. Rev. D 88, 063518 (2013) | 10.1103/PhysRevD.88.063518 | null | gr-qc math.DS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the expansion-normalized variables approach to study the dynamics of a
non-tilted Bianchi Type I cosmological model with both a homogeneous magnetic
field and a viscous fluid. In our model the perfect magnetohydrodynamic
approximation is made, and both bulk and shear viscous effects are retained.
The dynamical system is studied in detail through a fixed-point analysis which
determines the local sink and source behavior of the system. We show that the
fixed points may be associated with Kasner-type solutions, a flat universe FLRW
solution, and interestingly, a new solution to the Einstein Field equations
involving non-zero magnetic fields, and non-zero viscous coefficients. It is
further shown that for certain values of the bulk and shear viscosity and
equation of state parameters, the model isotropizes at late times.
| [
{
"created": "Tue, 30 Apr 2013 15:52:54 GMT",
"version": "v1"
},
{
"created": "Wed, 1 May 2013 02:01:13 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Jul 2013 03:25:41 GMT",
"version": "v3"
},
{
"created": "Wed, 4 Sep 2013 22:24:20 GMT",
"version": "v4"
},
{
"cre... | 2014-02-26 | [
[
"Kohli",
"Ikjyot Singh",
""
],
[
"Haslam",
"Michael C.",
""
]
] | We use the expansion-normalized variables approach to study the dynamics of a non-tilted Bianchi Type I cosmological model with both a homogeneous magnetic field and a viscous fluid. In our model the perfect magnetohydrodynamic approximation is made, and both bulk and shear viscous effects are retained. The dynamical system is studied in detail through a fixed-point analysis which determines the local sink and source behavior of the system. We show that the fixed points may be associated with Kasner-type solutions, a flat universe FLRW solution, and interestingly, a new solution to the Einstein Field equations involving non-zero magnetic fields, and non-zero viscous coefficients. It is further shown that for certain values of the bulk and shear viscosity and equation of state parameters, the model isotropizes at late times. |
1207.4253 | Huan Yang | Huan Yang, David A. Nichols, Fan Zhang, Aaron Zimmerman, Zhongyang
Zhang, and Yanbei Chen | Quasinormal-mode spectrum of Kerr black holes and its geometric
interpretation | 22 pages, 16 figures | Phys. Rev. D 86, 104006 (2012) | 10.1103/PhysRevD.86.104006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is a well-known, intuitive geometric correspondence between
high-frequency QNMs of Schwarzschild black holes and null geodesics that reside
on the light-ring : the real part of the mode's frequency relates to the
geodesic's orbital frequency, and the imaginary part of the frequency
corresponds to the Lyapunov exponent of the orbit. For slowly rotating black
holes, the QNM real frequency is a linear combination of a the orbit's
precessional and orbital frequencies, but the correspondence is otherwise
unchanged. In this paper, we find a relationship between the QNM frequencies of
Kerr black holes of arbitrary (astrophysical) spins and general spherical
photon orbits, which is analogous to the relationship for slowly rotating
holes. To derive this result, we first use the WKB approximation to compute
accurate algebraic expressions for large-l QNM frequencies. Comparing our WKB
calculation to the leading-order, geometric-optics approximation to scalar-wave
propagation in the Kerr spacetime, we then draw a correspondence between the
real parts of the parameters of a QNM and the conserved quantities of spherical
photon orbits. At next-to-leading order in this comparison, we relate the
imaginary parts of the QNM parameters to coefficients that modify the amplitude
of the scalar wave. With this correspondence, we find a geometric
interpretation to two features of the QNM spectrum of Kerr black holes: First,
for Kerr holes rotating near the maximal rate, a large number of modes have
nearly zero damping; we connect this characteristic to the fact that a large
number of spherical photon orbits approach the horizon in this limit. Second,
for black holes of any spins, the frequencies of specific sets of modes are
degenerate; we find that this feature arises when the spherical photon orbits
corresponding to these modes form closed (as opposed to ergodically winding)
curves.
| [
{
"created": "Wed, 18 Jul 2012 02:22:40 GMT",
"version": "v1"
}
] | 2012-12-19 | [
[
"Yang",
"Huan",
""
],
[
"Nichols",
"David A.",
""
],
[
"Zhang",
"Fan",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Zhang",
"Zhongyang",
""
],
[
"Chen",
"Yanbei",
""
]
] | There is a well-known, intuitive geometric correspondence between high-frequency QNMs of Schwarzschild black holes and null geodesics that reside on the light-ring : the real part of the mode's frequency relates to the geodesic's orbital frequency, and the imaginary part of the frequency corresponds to the Lyapunov exponent of the orbit. For slowly rotating black holes, the QNM real frequency is a linear combination of a the orbit's precessional and orbital frequencies, but the correspondence is otherwise unchanged. In this paper, we find a relationship between the QNM frequencies of Kerr black holes of arbitrary (astrophysical) spins and general spherical photon orbits, which is analogous to the relationship for slowly rotating holes. To derive this result, we first use the WKB approximation to compute accurate algebraic expressions for large-l QNM frequencies. Comparing our WKB calculation to the leading-order, geometric-optics approximation to scalar-wave propagation in the Kerr spacetime, we then draw a correspondence between the real parts of the parameters of a QNM and the conserved quantities of spherical photon orbits. At next-to-leading order in this comparison, we relate the imaginary parts of the QNM parameters to coefficients that modify the amplitude of the scalar wave. With this correspondence, we find a geometric interpretation to two features of the QNM spectrum of Kerr black holes: First, for Kerr holes rotating near the maximal rate, a large number of modes have nearly zero damping; we connect this characteristic to the fact that a large number of spherical photon orbits approach the horizon in this limit. Second, for black holes of any spins, the frequencies of specific sets of modes are degenerate; we find that this feature arises when the spherical photon orbits corresponding to these modes form closed (as opposed to ergodically winding) curves. |
1211.3816 | Jacob D. Bekenstein | Jacob D. Bekenstein | Is a tabletop search for Planck scale signals feasible? | 9 pages, two jpg figures, RevTeX, added references, effects of
dispersion shown negligible, quantum black hole argument tightened, more
noise sources analyzed, summary section added. To appear in Physical Review D | Phys. Rev. D 86, 124040 (2012) | 10.1103/PhysRevD.86.124040 | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravity theory is untested experimentally. Could it be tested with
tabletop experiments? While the common feeling is pessimistic, a detailed
inquiry shows it possible to sidestep the onerous requirement of localization
of a probe on Planck length scale. I suggest a tabletop experiment which, given
state of the art ultrahigh vacuum and cryogenic technology, could already be
sensitive enough to detect Planck scale signals. The experiment combines a
single photon's degree of freedom with one of a macroscopic probe to test
Wheeler's conception of "quantum foam", the assertion that on length scales of
the order Planck's, spacetime is no longer a smooth manifold. The scheme makes
few assumptions beyond energy and momentum conservations, and is not based on a
specific quantum gravity scheme.
| [
{
"created": "Fri, 16 Nov 2012 07:47:36 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Dec 2012 13:42:39 GMT",
"version": "v2"
}
] | 2013-11-06 | [
[
"Bekenstein",
"Jacob D.",
""
]
] | Quantum gravity theory is untested experimentally. Could it be tested with tabletop experiments? While the common feeling is pessimistic, a detailed inquiry shows it possible to sidestep the onerous requirement of localization of a probe on Planck length scale. I suggest a tabletop experiment which, given state of the art ultrahigh vacuum and cryogenic technology, could already be sensitive enough to detect Planck scale signals. The experiment combines a single photon's degree of freedom with one of a macroscopic probe to test Wheeler's conception of "quantum foam", the assertion that on length scales of the order Planck's, spacetime is no longer a smooth manifold. The scheme makes few assumptions beyond energy and momentum conservations, and is not based on a specific quantum gravity scheme. |
1811.10291 | Theodosios Christodoulakis | M. Roumeliotis, A. Paliathanasis, Petros A. Terzis and T.
Christodoulakis | Reduced Lagrangians and analytic solutions in Einstein-\ae ther
Cosmology | 11 pages, Latex2e source file, no figures | null | 10.1140/epjc/s10052-019-6868-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the solution space of the field equations in the Einstein-\ae ther
theory for the case of a $FLRW$ and a LRS Bianchi Type $III$ space-time. We
also find that there are portions of the initial parameters space for which no
solution is admitted by the reduced equations. The reduced Lagrangians deduced
from the full action are, in general, correctly describing the dynamics
whenever solutions do exist
| [
{
"created": "Mon, 26 Nov 2018 11:13:33 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Roumeliotis",
"M.",
""
],
[
"Paliathanasis",
"A.",
""
],
[
"Terzis",
"Petros A.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | We present the solution space of the field equations in the Einstein-\ae ther theory for the case of a $FLRW$ and a LRS Bianchi Type $III$ space-time. We also find that there are portions of the initial parameters space for which no solution is admitted by the reduced equations. The reduced Lagrangians deduced from the full action are, in general, correctly describing the dynamics whenever solutions do exist |
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