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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0911.1968 | I-Ching Yang | I-Ching Yang, Chi-Long Lin and I. Radinschi | Energy Distribution of a Regular Class of Exact Black Hole Solutions | 9 pages | Int.J.Theor.Phys.48:2454-2461,2009 | 10.1007/s10773-009-0039-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present the expressions for the energy of a regular class of
exact black hole solutions of Einstein's equations coupled with a nonlinear
electrodynamics source. We calculate the energy distribution using the
Einstein, Weinberg and M{\o}ller prescriptions. We make a discussion of the
results in function of two specific parameters, a sort of dipole and quadrupole
moments of the nonlinear source $\alpha$ and $\beta$, and in addition a study
of some particular cases is performed.
| [
{
"created": "Tue, 10 Nov 2009 18:52:19 GMT",
"version": "v1"
}
] | 2011-01-27 | [
[
"Yang",
"I-Ching",
""
],
[
"Lin",
"Chi-Long",
""
],
[
"Radinschi",
"I.",
""
]
] | In this paper we present the expressions for the energy of a regular class of exact black hole solutions of Einstein's equations coupled with a nonlinear electrodynamics source. We calculate the energy distribution using the Einstein, Weinberg and M{\o}ller prescriptions. We make a discussion of the results in function of two specific parameters, a sort of dipole and quadrupole moments of the nonlinear source $\alpha$ and $\beta$, and in addition a study of some particular cases is performed. |
1806.01588 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | A Study of Finite-time Singularities of Loop Quantum Cosmology
Interacting Multifluids | PRD Accepted | null | 10.1103/PhysRevD.97.124042 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the occurrence of finite-time cosmological
singularities in a cosmological system comprising from three fluids.
Particularly, the system contains two dark fluids, namely that of dark energy
and dark matter, which are interacting, and of a non-interacting baryonic
fluid. For the study we adopt the phase space approach by constructing the
cosmological dynamical system in such a way so that it rendered to be an
autonomous polynomial dynamical system, and in order to achieve this, we
appropriately choose the variables of the dynamical system. By employing a
rigid mathematical framework, that of dominant balances analysis, we
demonstrate that there exist non-singular solutions of the dynamical system,
which correspond to a general set of initial conditions, which proves that no
Big Rip or Type III finite-time singularities occur in this LQC multifluid
dynamical system. Thus the new feature of this work is that we are able to do
this using an analytic technique instead of adopting a numerical approach. In
addition, we perform a fixed point analysis of the cosmological dynamical
system, and we examine the behavior of the total effective equation of state
parameter, at the fixed points, as a function of the free parameters of the
system. Finally, we investigate the phenomenological implications of the dark
energy equation of state which we assumed that it governs the dark energy
fluid.
| [
{
"created": "Tue, 5 Jun 2018 10:02:31 GMT",
"version": "v1"
}
] | 2018-08-01 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | In this work we study the occurrence of finite-time cosmological singularities in a cosmological system comprising from three fluids. Particularly, the system contains two dark fluids, namely that of dark energy and dark matter, which are interacting, and of a non-interacting baryonic fluid. For the study we adopt the phase space approach by constructing the cosmological dynamical system in such a way so that it rendered to be an autonomous polynomial dynamical system, and in order to achieve this, we appropriately choose the variables of the dynamical system. By employing a rigid mathematical framework, that of dominant balances analysis, we demonstrate that there exist non-singular solutions of the dynamical system, which correspond to a general set of initial conditions, which proves that no Big Rip or Type III finite-time singularities occur in this LQC multifluid dynamical system. Thus the new feature of this work is that we are able to do this using an analytic technique instead of adopting a numerical approach. In addition, we perform a fixed point analysis of the cosmological dynamical system, and we examine the behavior of the total effective equation of state parameter, at the fixed points, as a function of the free parameters of the system. Finally, we investigate the phenomenological implications of the dark energy equation of state which we assumed that it governs the dark energy fluid. |
0901.3344 | Ramin Nowbakht Ghalati | R. N. Ghalati | A Novel Hamiltonian Formulation of First Order Einstein-Hilbert Action:
Connection with ADM, Diffeomorphism Invariance and Linearized Theory | 35 pages | null | null | UWO-TH-09/1 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A novel Dirac Hamiltonian formulation of the first order Einstein-Hilbert
(EH) action, in which algebraic constraints are not solved to eliminate fields
from the action at the Lagrangian level, has been shown to lead to an action
and a constraint structure apparently distinct from the ADM action and the ADM
constraint structure in that secondary first class constraints as well as
tertiary first class constraints arise with an unusual Poisson Bracket (PB)
algebra [24]. By canonical transformations of the fundamental fields we show
how from the tertiary constraints one may derive the Hamiltonian and momentum
constraints. Special attention is paid to the Hamiltonian formulation of the
first order EH action in terms of the variables h, h^i and q^{ij} employed in
[19,20]. It is shown that the variables h and h^i are left undetermined in the
formalism. This fact is used for a proper gauge fixation of the secondary
constraints and reduction to the Faddeev action [19,20]. Considering
invariances of the total action, the generator of the gauge transformations of
the EH Lagrangian action is derived. Using this generator, the explicit form of
the gauge invariance of the field h is obtained, by which the relation between
the gauge functions and the descriptors of the diffeomorphism invariance is
determined in order for the gauge transformations to correspond to
diffeomorphism invariance. By linearizing the novel Hamiltonian formulation of
[24], the Hamiltonian formulation of the first order action for the free spin
two field [4,24] is derived.
| [
{
"created": "Wed, 21 Jan 2009 20:09:34 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Apr 2009 02:19:19 GMT",
"version": "v2"
}
] | 2009-04-07 | [
[
"Ghalati",
"R. N.",
""
]
] | A novel Dirac Hamiltonian formulation of the first order Einstein-Hilbert (EH) action, in which algebraic constraints are not solved to eliminate fields from the action at the Lagrangian level, has been shown to lead to an action and a constraint structure apparently distinct from the ADM action and the ADM constraint structure in that secondary first class constraints as well as tertiary first class constraints arise with an unusual Poisson Bracket (PB) algebra [24]. By canonical transformations of the fundamental fields we show how from the tertiary constraints one may derive the Hamiltonian and momentum constraints. Special attention is paid to the Hamiltonian formulation of the first order EH action in terms of the variables h, h^i and q^{ij} employed in [19,20]. It is shown that the variables h and h^i are left undetermined in the formalism. This fact is used for a proper gauge fixation of the secondary constraints and reduction to the Faddeev action [19,20]. Considering invariances of the total action, the generator of the gauge transformations of the EH Lagrangian action is derived. Using this generator, the explicit form of the gauge invariance of the field h is obtained, by which the relation between the gauge functions and the descriptors of the diffeomorphism invariance is determined in order for the gauge transformations to correspond to diffeomorphism invariance. By linearizing the novel Hamiltonian formulation of [24], the Hamiltonian formulation of the first order action for the free spin two field [4,24] is derived. |
1412.6344 | Inyong Cho | Inyong Cho and Naveen K. Singh | Scalar Perturbation Produced at the Pre-inflationary Stage in
Eddington-inspired Born-Infeld Gravity | 12 pages, 1 figure, version to appear in EPJC | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the scalar perturbation produced at the pre-inflationary stage
driven by a massive scalar field in Eddington-inspired Born-Infeld gravity. The
scalar power spectrum exhibits a peculiar rise for low $k$-modes. The
tensor-to-scalar ratio can be significantly lowered compared with that in the
standard chaotic inflation model in general relativity. This result is very
affirmative considering the recent dispute on the detection of the
gravitational wave radiation between PLANCK and BICEP2.
| [
{
"created": "Fri, 19 Dec 2014 13:49:38 GMT",
"version": "v1"
},
{
"created": "Fri, 29 May 2015 10:26:25 GMT",
"version": "v2"
}
] | 2015-06-01 | [
[
"Cho",
"Inyong",
""
],
[
"Singh",
"Naveen K.",
""
]
] | We investigate the scalar perturbation produced at the pre-inflationary stage driven by a massive scalar field in Eddington-inspired Born-Infeld gravity. The scalar power spectrum exhibits a peculiar rise for low $k$-modes. The tensor-to-scalar ratio can be significantly lowered compared with that in the standard chaotic inflation model in general relativity. This result is very affirmative considering the recent dispute on the detection of the gravitational wave radiation between PLANCK and BICEP2. |
1911.06059 | Alejandro Perez | Alejandro Perez and Daniel Sudarsky | Black holes, Planckian granularity, and the changing cosmological
`constant' | null | null | null | null | gr-qc astro-ph.CO astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent work we have argued that nosy energy momentum diffusion due to
space-time discreteness at the Planck scale (naturally expected to arise from
quantum gravity) can be responsible for the generation of a cosmological
constant during the electro-weak phase transition era of the cosmic evolution.
Simple dimensional analysis and an effectively Brownian description of the
propagation of fundamental particles on a granular background yields a
cosmological constant of the order of magnitude of the observed value, without
fine tuning. While the energy diffusion is negligible for matter in standard
astrophysical configurations (from ordinary stars to neutron stars) here we
argue that a similar diffusion mechanism could, nonetheless be important for
black holes. If such effects are taken into account two observational puzzles
might be solved by a single mechanism: the `$H_0$ tension' and the relatively
low rotational spin of the black holes detected via gravitational wave
astronomy.
| [
{
"created": "Thu, 14 Nov 2019 12:22:16 GMT",
"version": "v1"
}
] | 2019-11-15 | [
[
"Perez",
"Alejandro",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | In a recent work we have argued that nosy energy momentum diffusion due to space-time discreteness at the Planck scale (naturally expected to arise from quantum gravity) can be responsible for the generation of a cosmological constant during the electro-weak phase transition era of the cosmic evolution. Simple dimensional analysis and an effectively Brownian description of the propagation of fundamental particles on a granular background yields a cosmological constant of the order of magnitude of the observed value, without fine tuning. While the energy diffusion is negligible for matter in standard astrophysical configurations (from ordinary stars to neutron stars) here we argue that a similar diffusion mechanism could, nonetheless be important for black holes. If such effects are taken into account two observational puzzles might be solved by a single mechanism: the `$H_0$ tension' and the relatively low rotational spin of the black holes detected via gravitational wave astronomy. |
1906.05632 | Khalid Saifullah | Rehana Rahim and Khalid Saifullah | Particle dynamics and geometric optics in Chern-Simons black holes | Some improvements carried out and title changed. Now it matches the
published version | Annals of Physics 428 (2021) 168435 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the effects of the coupling constant of the
Chern-Simons modified gravity on some physical properties of black holes. The
Hawking mass is one of the proposed definitions of quasilocal mass. We find
that, for slowly rotating Chern-Simons black holes, the Hawking mass is
independent of the coupling constant. Next, we show the dependence on the
centre of mass energy, for two neutral colliding particles, of coupling
constant and the rotation parameter. We also investigate energy extraction
through Penrose process and find that the energy gain and efficiency of the
Penrose process are independent of this coupling constant. Rotation of the
polarization vector is also studied for dependence on the Chern-Simons coupling
constant.
| [
{
"created": "Thu, 13 Jun 2019 12:30:47 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Aug 2021 18:08:16 GMT",
"version": "v2"
}
] | 2021-08-18 | [
[
"Rahim",
"Rehana",
""
],
[
"Saifullah",
"Khalid",
""
]
] | In this paper we study the effects of the coupling constant of the Chern-Simons modified gravity on some physical properties of black holes. The Hawking mass is one of the proposed definitions of quasilocal mass. We find that, for slowly rotating Chern-Simons black holes, the Hawking mass is independent of the coupling constant. Next, we show the dependence on the centre of mass energy, for two neutral colliding particles, of coupling constant and the rotation parameter. We also investigate energy extraction through Penrose process and find that the energy gain and efficiency of the Penrose process are independent of this coupling constant. Rotation of the polarization vector is also studied for dependence on the Chern-Simons coupling constant. |
gr-qc/9510062 | Hans-Juergen Schmidt | Hans - Juergen Schmidt | Classical mechanics with lapse | 13 pages, latex, no figures, J. Math. Phys. in print | J.Math.Phys. 37 (1996) 1244-1252 | 10.1063/1.531459 | Revised version of Potsdam/Math 93/10 | gr-qc | null | Mechanics is developed over a differentiable manifold as space of possible
positions. Time is considered to fill a one--dimensional Riemannian manifold,
so having the metric as lapse. Then the system is quantized with covariant
instead of partial derivatives in the Schr\"odinger operator. Consequences for
quantum cosmology are shortly discussed.
| [
{
"created": "Tue, 31 Oct 1995 08:51:10 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Schmidt",
"Hans - Juergen",
""
]
] | Mechanics is developed over a differentiable manifold as space of possible positions. Time is considered to fill a one--dimensional Riemannian manifold, so having the metric as lapse. Then the system is quantized with covariant instead of partial derivatives in the Schr\"odinger operator. Consequences for quantum cosmology are shortly discussed. |
1103.6180 | Jose Luis Jaramillo | Jos\'e Luis Jaramillo, Marcus Ansorg and Nicolas Vasset | Application of initial data sequences to the study of Black Hole
dynamical trapping horizons | Contribution to the proceedings volume of the Spanish Relativity
Meeting 2008: Physics and Mathematics of Gravitation, Salamanca, Spain, 15-19
Sep 2008 | AIP Conf.Proc.1122:308-311,2009 | 10.1063/1.3141305 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-continuous "jumps" of Apparent Horizons occur generically in 3+1 (binary)
black hole evolutions. The dynamical trapping horizon framework suggests a
spacetime picture in which these "Apparent Horizon jumps" are understood as
spatial cuts of a single spacetime hypersurface foliated by (compact)
marginally outer trapped surfaces. We present here some work in progress which
makes use of uni-parametric sequences of (axisymmetric) binary black hole
initial data for exploring the plausibility of this spacetime picture. The
modelling of Einstein evolutions by sequences of initial data has proved to be
a successful methodological tool in other settings for the understanding of
certain qualitative features of evolutions in restricted physical regimes.
| [
{
"created": "Thu, 31 Mar 2011 13:49:41 GMT",
"version": "v1"
}
] | 2011-04-05 | [
[
"Jaramillo",
"José Luis",
""
],
[
"Ansorg",
"Marcus",
""
],
[
"Vasset",
"Nicolas",
""
]
] | Non-continuous "jumps" of Apparent Horizons occur generically in 3+1 (binary) black hole evolutions. The dynamical trapping horizon framework suggests a spacetime picture in which these "Apparent Horizon jumps" are understood as spatial cuts of a single spacetime hypersurface foliated by (compact) marginally outer trapped surfaces. We present here some work in progress which makes use of uni-parametric sequences of (axisymmetric) binary black hole initial data for exploring the plausibility of this spacetime picture. The modelling of Einstein evolutions by sequences of initial data has proved to be a successful methodological tool in other settings for the understanding of certain qualitative features of evolutions in restricted physical regimes. |
2305.01607 | Miguel Sabido | Javier Chagoya, I. D\'iaz-Salda\~na, J. C. L\'opez-Dom\'inguez, M.
Sabido | Cosmic acceleration in entropic cosmology | 11 pages, 3 figures. Version accepted for Publication in Phys. Lett.
B | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the viability of an entropic cosmological model. The
effects of entropic gravity are derived from a modified entropy-area
relationship with a volumetric entropy term. This model describes a late time
limit cosmic acceleration, whose origin is related to a volumetric term in the
entropy. Moreover, we analyze the phenomenological implications of the entropic
model using the Supernovae Pantheon compilation and the observational Hubble
parameter data to find consistency with cosmological observations. Finally, we
show the equivalence between the entropic model and a brane world cosmological
model, by means of an effective geometrical construction.
| [
{
"created": "Tue, 2 May 2023 17:11:24 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2024 03:18:52 GMT",
"version": "v2"
}
] | 2024-03-07 | [
[
"Chagoya",
"Javier",
""
],
[
"Díaz-Saldaña",
"I.",
""
],
[
"López-Domínguez",
"J. C.",
""
],
[
"Sabido",
"M.",
""
]
] | In this paper we study the viability of an entropic cosmological model. The effects of entropic gravity are derived from a modified entropy-area relationship with a volumetric entropy term. This model describes a late time limit cosmic acceleration, whose origin is related to a volumetric term in the entropy. Moreover, we analyze the phenomenological implications of the entropic model using the Supernovae Pantheon compilation and the observational Hubble parameter data to find consistency with cosmological observations. Finally, we show the equivalence between the entropic model and a brane world cosmological model, by means of an effective geometrical construction. |
gr-qc/0511001 | Nergis Mavalvala | T. Corbitt, Y. Chen, F. Khalili, D. Ottaway, S. Vyatchanin, S.
Whitcomb, and N. Mavalvala | A squeezed state source using radiation pressure induced rigidity | 15 pages, 6 figures, submitted to Phys. Rev. A | null | 10.1103/PhysRevA.73.023801 | null | gr-qc quant-ph | null | We propose an experiment to extract ponderomotive squeezing from an
interferometer with high circulating power and low mass mirrors. In this
interferometer, optical resonances of the arm cavities are detuned from the
laser frequency, creating a mechanical rigidity that dramatically suppresses
displacement noise. After taking into account imperfection of optical elements,
laser noise, and other technical noise consistent with existing laser and
optical technologies and typical laboratory environments, we expect the output
light from the interferometer to have measurable squeezing of ~5 dB, with a
frequency-independent squeeze angle for frequencies below 1 kHz. This squeeze
source is well suited for injection into a gravitational-wave interferometer,
leading to improved sensitivity from reduction in the quantum noise.
Furthermore, this design provides an experimental test of quantum-limited
radiation pressure effects, which have not previously been tested.
| [
{
"created": "Tue, 1 Nov 2005 03:36:24 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Corbitt",
"T.",
""
],
[
"Chen",
"Y.",
""
],
[
"Khalili",
"F.",
""
],
[
"Ottaway",
"D.",
""
],
[
"Vyatchanin",
"S.",
""
],
[
"Whitcomb",
"S.",
""
],
[
"Mavalvala",
"N.",
""
]
] | We propose an experiment to extract ponderomotive squeezing from an interferometer with high circulating power and low mass mirrors. In this interferometer, optical resonances of the arm cavities are detuned from the laser frequency, creating a mechanical rigidity that dramatically suppresses displacement noise. After taking into account imperfection of optical elements, laser noise, and other technical noise consistent with existing laser and optical technologies and typical laboratory environments, we expect the output light from the interferometer to have measurable squeezing of ~5 dB, with a frequency-independent squeeze angle for frequencies below 1 kHz. This squeeze source is well suited for injection into a gravitational-wave interferometer, leading to improved sensitivity from reduction in the quantum noise. Furthermore, this design provides an experimental test of quantum-limited radiation pressure effects, which have not previously been tested. |
gr-qc/9910047 | Felix Finster | Felix Finster, Joel Smoller, and Shing-Tung Yau | The Interaction of Dirac Particles with Non-Abelian Gauge Fields and
Gravity - Black Holes | 9 pages, LaTeX (published version) | Michigan Math.J. 47 (2000) 199-208 | 10.1307/mmj/1030374678 | null | gr-qc hep-th math-ph math.AP math.MP | null | We consider a static, spherically symmetric system of a Dirac particle in a
classical gravitational and SU(2) Yang-Mills field. We prove that the only
black-hole solutions of the corresponding Einstein-Dirac-Yang/Mills equations
are the Bartnik-McKinnon black-hole solutions of the SU(2) Einstein-Yang/Mills
equations; thus the spinors must vanish identically. This indicates that the
Dirac particles must either disappear into the black-hole or escape to
infinity.
| [
{
"created": "Wed, 13 Oct 1999 19:44:59 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jun 2000 12:19:41 GMT",
"version": "v2"
}
] | 2014-01-28 | [
[
"Finster",
"Felix",
""
],
[
"Smoller",
"Joel",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | We consider a static, spherically symmetric system of a Dirac particle in a classical gravitational and SU(2) Yang-Mills field. We prove that the only black-hole solutions of the corresponding Einstein-Dirac-Yang/Mills equations are the Bartnik-McKinnon black-hole solutions of the SU(2) Einstein-Yang/Mills equations; thus the spinors must vanish identically. This indicates that the Dirac particles must either disappear into the black-hole or escape to infinity. |
1712.10016 | Zeinab Teimoori | Zeinab Teimoori, Kayoomars Karami | Galileon intermediate inflation | 30 pages, 5 figures | ApJ 864, 41(2018) | 10.3847/1538-4357/aad3b3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate intermediate inflation in the framework of a Galileon scalar
field. To this aim, we first obtain the inflationary observables, including the
scalar spectral index, the tensor-to-scalar ratio, the running of the scalar
spectral index, as well as the non-Gaussianity parameters. Then, we examine the
observational viability of the intermediate inflation within the framework of a
Galileon scenario. Our results show that although the prediction of
intermediate inflation in the standard framework is completely ruled out by the
Planck 2015 observations, it can be put inside the allowed regions of the
Planck 2015 TT,TE,EE+lowP data in the Galileon setting. Moreover, we determine
the parameter space of the Galileon intermediate inflation for which the model
is consistent with the Planck 2015 data. Besides, we derive the consistency
relation in the Galileon scenario, and find that it differs from the standard
inflation. We also estimate the running of the scalar spectral index and find
that it is in well agreement with the 95\% CL constraint of the Planck 2015
results. Finally, we evaluate the local, equilateral, orthogonal, and enfolded
non-Gaussianity parameters, and conclude that not only is the shape of
non-Gaussianity approximately close to the equilateral one, but that it also
satisfies the 68\% CL bound from the Planck 2015 data.
| [
{
"created": "Thu, 28 Dec 2017 11:39:09 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Feb 2018 20:54:04 GMT",
"version": "v2"
},
{
"created": "Fri, 31 Aug 2018 12:44:05 GMT",
"version": "v3"
}
] | 2018-09-03 | [
[
"Teimoori",
"Zeinab",
""
],
[
"Karami",
"Kayoomars",
""
]
] | We investigate intermediate inflation in the framework of a Galileon scalar field. To this aim, we first obtain the inflationary observables, including the scalar spectral index, the tensor-to-scalar ratio, the running of the scalar spectral index, as well as the non-Gaussianity parameters. Then, we examine the observational viability of the intermediate inflation within the framework of a Galileon scenario. Our results show that although the prediction of intermediate inflation in the standard framework is completely ruled out by the Planck 2015 observations, it can be put inside the allowed regions of the Planck 2015 TT,TE,EE+lowP data in the Galileon setting. Moreover, we determine the parameter space of the Galileon intermediate inflation for which the model is consistent with the Planck 2015 data. Besides, we derive the consistency relation in the Galileon scenario, and find that it differs from the standard inflation. We also estimate the running of the scalar spectral index and find that it is in well agreement with the 95\% CL constraint of the Planck 2015 results. Finally, we evaluate the local, equilateral, orthogonal, and enfolded non-Gaussianity parameters, and conclude that not only is the shape of non-Gaussianity approximately close to the equilateral one, but that it also satisfies the 68\% CL bound from the Planck 2015 data. |
gr-qc/0006075 | Yuan-Zhong Zhang | Yuan-Zhong Zhang, Jun Luo, and Yu-Xin Nie | Gravitational Effects of Rotating Bodies | LaTex, 6 pages | Mod. Phys. lett. A 16 (2001) 789-794 | 10.1142/S021773230100370X | null | gr-qc | null | We study two type effects of gravitational field on mechanical gyroscopes
(i.e. rotating extended bodies). The first depends on special relativity and
equivalence principle. The second is related to the coupling (i.e. a new force)
between the spins of mechanical gyroscopes, which would violate the equivalent
principle. In order to give a theoretical prediction to the second we suggest a
spin-spin coupling model for two mechanical gyroscopes. An upper limit on the
coupling strength is then determined by using the observed perihelion
precession of the planet's orbits in solar system. We also give predictions
violating the equivalence principle for free-fall gyroscopes .
| [
{
"created": "Wed, 21 Jun 2000 09:29:40 GMT",
"version": "v1"
},
{
"created": "Mon, 28 May 2001 09:02:32 GMT",
"version": "v2"
}
] | 2016-12-21 | [
[
"Zhang",
"Yuan-Zhong",
""
],
[
"Luo",
"Jun",
""
],
[
"Nie",
"Yu-Xin",
""
]
] | We study two type effects of gravitational field on mechanical gyroscopes (i.e. rotating extended bodies). The first depends on special relativity and equivalence principle. The second is related to the coupling (i.e. a new force) between the spins of mechanical gyroscopes, which would violate the equivalent principle. In order to give a theoretical prediction to the second we suggest a spin-spin coupling model for two mechanical gyroscopes. An upper limit on the coupling strength is then determined by using the observed perihelion precession of the planet's orbits in solar system. We also give predictions violating the equivalence principle for free-fall gyroscopes . |
1412.6447 | Daniela Pugliese Dr | O. Zanotti and D. Pugliese | Von Zeipel's theorem for a magnetized circular flow around a compact
object | 14 pages | null | 10.1007/s10714-015-1886-4 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze a class of physical properties, forming the content of the
so-called von Zeipel theorem, which characterizes stationary, axisymmetric,
non-selfgravitating perfect fluids in circular motion in the gravitational
field of a compact object. We consider the extension of the theorem to the
magnetohydrodynamic regime, under the assumption of an infinitely conductive
fluid, both in the Newtonian and in the relativistic framework. When the
magnetic field is toroidal, the conditions required by the theorem are
equivalent to integrability conditions, as it is the case for purely
hydrodynamic flows. When the magnetic field is poloidal, the analysis for the
relativistic regime is substantially different with respect to the Newtonian
case and additional constraints, in the form of PDEs, must be imposed on the
magnetic field in order to guarantee that the angular velocity $\Omega$ depends
only on the specific angular momentum $\ell$. In order to deduce such physical
constraints, it is crucial to adopt special coordinates, which are adapted to
the $\Omega={\rm const}$ surfaces. The physical significance of these results
is briefly discussed.
| [
{
"created": "Fri, 19 Dec 2014 17:21:04 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Zanotti",
"O.",
""
],
[
"Pugliese",
"D.",
""
]
] | We analyze a class of physical properties, forming the content of the so-called von Zeipel theorem, which characterizes stationary, axisymmetric, non-selfgravitating perfect fluids in circular motion in the gravitational field of a compact object. We consider the extension of the theorem to the magnetohydrodynamic regime, under the assumption of an infinitely conductive fluid, both in the Newtonian and in the relativistic framework. When the magnetic field is toroidal, the conditions required by the theorem are equivalent to integrability conditions, as it is the case for purely hydrodynamic flows. When the magnetic field is poloidal, the analysis for the relativistic regime is substantially different with respect to the Newtonian case and additional constraints, in the form of PDEs, must be imposed on the magnetic field in order to guarantee that the angular velocity $\Omega$ depends only on the specific angular momentum $\ell$. In order to deduce such physical constraints, it is crucial to adopt special coordinates, which are adapted to the $\Omega={\rm const}$ surfaces. The physical significance of these results is briefly discussed. |
1904.10920 | Vitor Silveira Barroso | Vitor S. Barroso and J. P. M. Pitelli | Boundary Conditions and Vacuum Fluctuations in $\mathrm{AdS}_4$ | 23 pages, 4 figures | null | 10.1007/s10714-020-02672-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Initial conditions given on a spacelike, static slice of a non-globally
hyperbolic spacetime may not define the fates of classical and quantum fields
uniquely. Such lack of global hyperbolicity is a well-known property of the
anti-de Sitter solution and led many authors to question how is it possible to
develop a quantum field theory on this spacetime. Wald and Ishibashi took a
step towards the healing of that causal issue when considering the propagation
of scalar fields on AdS. They proposed a systematic procedure to obtain a
physically consistent dynamical evolution. Their prescription relies on
determining the self-adjoint extensions of the spatial component of the
differential wave operator. Such a requirement leads to the imposition of a
specific set of boundary conditions at infinity. We employ their scheme in the
particular case of the four-dimensional AdS spacetime and compute the
expectation values of the field squared and the energy-momentum tensor, which
will then bear the effects of those boundary conditions. We are not aware of
any laws of nature constraining us to prescribe the same boundary conditions to
all modes of the wave equation. Thus, we formulate a physical setup in which
one of those modes satisfy a Robin boundary condition, while all others satisfy
the Dirichlet condition. Due to our unusual settings, the resulting
contributions to the fluctuations of the expectation values will not respect
AdS invariance. As a consequence, a back-reaction procedure would yield a
non-maximally symmetric spacetime. Furthermore, we verify the violation of weak
energy condition as a direct consequence of our prescription for dynamics.
| [
{
"created": "Wed, 24 Apr 2019 16:53:46 GMT",
"version": "v1"
}
] | 2020-04-15 | [
[
"Barroso",
"Vitor S.",
""
],
[
"Pitelli",
"J. P. M.",
""
]
] | Initial conditions given on a spacelike, static slice of a non-globally hyperbolic spacetime may not define the fates of classical and quantum fields uniquely. Such lack of global hyperbolicity is a well-known property of the anti-de Sitter solution and led many authors to question how is it possible to develop a quantum field theory on this spacetime. Wald and Ishibashi took a step towards the healing of that causal issue when considering the propagation of scalar fields on AdS. They proposed a systematic procedure to obtain a physically consistent dynamical evolution. Their prescription relies on determining the self-adjoint extensions of the spatial component of the differential wave operator. Such a requirement leads to the imposition of a specific set of boundary conditions at infinity. We employ their scheme in the particular case of the four-dimensional AdS spacetime and compute the expectation values of the field squared and the energy-momentum tensor, which will then bear the effects of those boundary conditions. We are not aware of any laws of nature constraining us to prescribe the same boundary conditions to all modes of the wave equation. Thus, we formulate a physical setup in which one of those modes satisfy a Robin boundary condition, while all others satisfy the Dirichlet condition. Due to our unusual settings, the resulting contributions to the fluctuations of the expectation values will not respect AdS invariance. As a consequence, a back-reaction procedure would yield a non-maximally symmetric spacetime. Furthermore, we verify the violation of weak energy condition as a direct consequence of our prescription for dynamics. |
1209.4503 | Lijing Shao | Lijing Shao, Norbert Wex | New tests of local Lorentz invariance of gravity with small-eccentricity
binary pulsars | 34 pages, 8 figures, 2 tables; accepted by Classical and Quantum
Gravity | Class. Quantum Grav. 29 (2012) 215018 | 10.1088/0264-9381/29/21/215018 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the post-Newtonian parametrization of semi-conservative gravity theories,
local Lorentz invariance (LLI) violation is characterized by two parameters,
alpha_1 and alpha_2. In binary pulsars the isotropic violation of LLI in the
gravitational sector leads to characteristic preferred frame effects (PFEs) in
the orbital dynamics, if the barycenter of the binary is moving relative to the
preferred frame with a velocity w. For small-eccentricity binaries, the effects
induced by alpha_1 and alpha_2 decouple, and can therefore be tested
independently. We use recent timing results of two compact pulsar-white dwarf
binaries with known 3D velocity, PSRs J1012+5307 and J1738+0333, to constrain
PFEs for strongly self-gravitating bodies. We derive a limit |alpha_2| < 1.8e-4
(95% CL), which is the most constraining limit for strongly self-gravitating
systems up to now. Concerning alpha_1, we propose a new, robust method to
constrain this parameter. Our most conservative result, alpha_1 =
-0.4^{+3.7}_{-3.1} e-5 (95% CL) from PSR J1738+0333, constitutes a significant
improvement compared to current most stringent limits obtained both in Solar
system and binary pulsar tests. We also derive corresponding limits for alpha_1
and alpha_2 for a preferred frame that is at rest with respect to our Galaxy,
and preferred frames that locally co-move with the rotation of our Galaxy.
(Abridged)
| [
{
"created": "Thu, 20 Sep 2012 12:09:56 GMT",
"version": "v1"
}
] | 2012-10-18 | [
[
"Shao",
"Lijing",
""
],
[
"Wex",
"Norbert",
""
]
] | In the post-Newtonian parametrization of semi-conservative gravity theories, local Lorentz invariance (LLI) violation is characterized by two parameters, alpha_1 and alpha_2. In binary pulsars the isotropic violation of LLI in the gravitational sector leads to characteristic preferred frame effects (PFEs) in the orbital dynamics, if the barycenter of the binary is moving relative to the preferred frame with a velocity w. For small-eccentricity binaries, the effects induced by alpha_1 and alpha_2 decouple, and can therefore be tested independently. We use recent timing results of two compact pulsar-white dwarf binaries with known 3D velocity, PSRs J1012+5307 and J1738+0333, to constrain PFEs for strongly self-gravitating bodies. We derive a limit |alpha_2| < 1.8e-4 (95% CL), which is the most constraining limit for strongly self-gravitating systems up to now. Concerning alpha_1, we propose a new, robust method to constrain this parameter. Our most conservative result, alpha_1 = -0.4^{+3.7}_{-3.1} e-5 (95% CL) from PSR J1738+0333, constitutes a significant improvement compared to current most stringent limits obtained both in Solar system and binary pulsar tests. We also derive corresponding limits for alpha_1 and alpha_2 for a preferred frame that is at rest with respect to our Galaxy, and preferred frames that locally co-move with the rotation of our Galaxy. (Abridged) |
1608.06553 | Bohdan Novosyadlyj Dr. | R. Neomenko, B. Novosyadlyj | Dynamics of expansion of the Universe in the models with non-minimally
coupled dark energy | 18 pages, 6 figures, published in Kinematics and Physics of Celestial
Bodies (2016) | Kinematics and Physics of Celestial Bodies, 2016, Vol. 32, No. 4,
pp. 157-171 | 10.3103/S088459131604005X | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the dark energy model with barotropic equation of state, which
interacts with dark matter through gravitation and another force, causing the
energy-momentum exchange between them. Both components are described in
approximation of ideal fluids, which are parametrized by density and equation
of state parameters. Three types of interactions between dark components are
considered: the interaction independent from their densities, the one
proportional to density of dark energy and the one proportional to density of
dark matter. The equations which describe the expansion dynamics of homogeneous
and isotropic Universe and evolution of densities of both components for
different values of interaction parameter are obtained on the bases of the
general covariant conservation equations and Einstein's ones. For three kinds
of interactions we show the existence of the range of values of parameters of
dark energy for which the densities of dark components and their sum are
negative. We find the conditions of positivity of density of dark energy and
dark matter. The constraints on the value of parameter of interaction are
derived. The dynamics of expansion of the Universe with these interactions of
dark energy and dark matter is analysed.
| [
{
"created": "Sat, 20 Aug 2016 18:42:07 GMT",
"version": "v1"
}
] | 2016-09-07 | [
[
"Neomenko",
"R.",
""
],
[
"Novosyadlyj",
"B.",
""
]
] | We consider the dark energy model with barotropic equation of state, which interacts with dark matter through gravitation and another force, causing the energy-momentum exchange between them. Both components are described in approximation of ideal fluids, which are parametrized by density and equation of state parameters. Three types of interactions between dark components are considered: the interaction independent from their densities, the one proportional to density of dark energy and the one proportional to density of dark matter. The equations which describe the expansion dynamics of homogeneous and isotropic Universe and evolution of densities of both components for different values of interaction parameter are obtained on the bases of the general covariant conservation equations and Einstein's ones. For three kinds of interactions we show the existence of the range of values of parameters of dark energy for which the densities of dark components and their sum are negative. We find the conditions of positivity of density of dark energy and dark matter. The constraints on the value of parameter of interaction are derived. The dynamics of expansion of the Universe with these interactions of dark energy and dark matter is analysed. |
gr-qc/0411003 | Richard Woodard | L. H. Ford (Tufts University) and R. P. Woodard (University of
Florida) | Stress Tensor Correlators in the Schwinger-Keldysh Formalism | 14 pages, LaTeX 2epsilon, no figures, revised for publication | Class.Quant.Grav. 22 (2005) 1637-1647 | 10.1088/0264-9381/22/9/011 | UFIFT-QG-04-4 | gr-qc hep-ph hep-th | null | We express stress tensor correlators using the Schwinger-Keldysh formalism.
The absence of off-diagonal counterterms in this formalism ensures that the +-
and -+ correlators are free of primitive divergences. We use dimensional
regularization in position space to explicitly check this at one loop order for
a massless scalar on a flat space background. We use the same procedure to show
that the ++ correlator contains the divergences first computed by `t Hooft and
Veltman for the scalar contribution to the graviton self-energy.
| [
{
"created": "Fri, 29 Oct 2004 22:27:32 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Mar 2005 10:04:18 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Ford",
"L. H.",
"",
"Tufts University"
],
[
"Woodard",
"R. P.",
"",
"University of\n Florida"
]
] | We express stress tensor correlators using the Schwinger-Keldysh formalism. The absence of off-diagonal counterterms in this formalism ensures that the +- and -+ correlators are free of primitive divergences. We use dimensional regularization in position space to explicitly check this at one loop order for a massless scalar on a flat space background. We use the same procedure to show that the ++ correlator contains the divergences first computed by `t Hooft and Veltman for the scalar contribution to the graviton self-energy. |
1610.07951 | Nistor Nicolaevici | Nistor Nicolaevici and Attila Farkas | Comment on "Fermion production in a magnetic field in a de Sitter
universe" | 13 pages; no figures; to appear in PRD | null | 10.1103/PhysRevD.95.048501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that the transition probabilities used in a recent perturbative
calculation of pair creation in an external magnetic field in the expanding de
Sitter space with the $in$ and $out$ fermion states defined by the Bunch-Davies
modes [C. Crucean et al., Phys. Rev. D 73 044019 (20016)] are gauge dependent
quantities. We examine the gauge variations of these amplitudes assuming a
decoupling of the interaction at infinite times, which allows to conclude that
the source of the problem lies in the nonoscillatory behavior of the fermion
current in the infinite future.
| [
{
"created": "Tue, 25 Oct 2016 16:26:53 GMT",
"version": "v1"
}
] | 2017-04-05 | [
[
"Nicolaevici",
"Nistor",
""
],
[
"Farkas",
"Attila",
""
]
] | We point out that the transition probabilities used in a recent perturbative calculation of pair creation in an external magnetic field in the expanding de Sitter space with the $in$ and $out$ fermion states defined by the Bunch-Davies modes [C. Crucean et al., Phys. Rev. D 73 044019 (20016)] are gauge dependent quantities. We examine the gauge variations of these amplitudes assuming a decoupling of the interaction at infinite times, which allows to conclude that the source of the problem lies in the nonoscillatory behavior of the fermion current in the infinite future. |
1502.02017 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Wormholes with a barotropic equation of state admitting a one-parameter
group of conformal motions | 8 pages, no figures | Annals of Physics, vol. 355, 115, 2015 | 10.1016/j.aop.2015.02.002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theoretical construction of a traversable wormhole proposed by Morris and
Thorne maintains complete control over the geometry by assigning both the shape
and redshift functions, thereby leaving open the determination of the
stress-energy tensor. This paper examines the effect of introducing the linear
barotropic equation of state $p_r=\omega\rho$ on the theoretical construction.
If either the energy density or the closely related shape function is known,
then the Einstein field equations do not ordinarily yield a finite redshift
function. If, however, the wormhole admits a one-parameter group of conformal
motions, then both the redshift and shape functions exist provided that $\omega
<-1$. In a cosmological setting, the equation of state $p=\omega\rho$, $\omega
<-1$, is associated with phantom dark energy, which is known to support
traversable wormholes.
| [
{
"created": "Fri, 6 Feb 2015 20:34:14 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Aug 2015 15:20:28 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Mar 2016 18:14:18 GMT",
"version": "v3"
},
{
"created": "Fri, 24 Jul 2020 17:06:31 GMT",
"version": "v4"
}
] | 2020-07-27 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | The theoretical construction of a traversable wormhole proposed by Morris and Thorne maintains complete control over the geometry by assigning both the shape and redshift functions, thereby leaving open the determination of the stress-energy tensor. This paper examines the effect of introducing the linear barotropic equation of state $p_r=\omega\rho$ on the theoretical construction. If either the energy density or the closely related shape function is known, then the Einstein field equations do not ordinarily yield a finite redshift function. If, however, the wormhole admits a one-parameter group of conformal motions, then both the redshift and shape functions exist provided that $\omega <-1$. In a cosmological setting, the equation of state $p=\omega\rho$, $\omega <-1$, is associated with phantom dark energy, which is known to support traversable wormholes. |
1412.5527 | Miguel Campiglia | Miguel Campiglia and Madhavan Varadarajan | A quantum kinematics for asymptotically flat spacetimes | 64 pages | null | 10.1088/0264-9381/32/13/135011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a quantum kinematics for asymptotically flat spacetimes based on
the Koslowski-Sahlmann (KS) representation. The KS representation is a
generalization of the representation underlying Loop Quantum Gravity (LQG)
which supports, in addition to the usual LQG operators, the action of
`background exponential operators' which are connection dependent operators
labelled by `background' $su(2)$ electric fields. KS states have, in addition
to the LQG state label corresponding to 1 dimensional excitations of the triad,
a label corresponding to a `background' electric field which describes 3
dimensional excitations of the triad. Asymptotic behaviour in quantum theory is
controlled through asymptotic conditions on the background electric fields
which label the {\em states} and the background electric fields which label the
{\em operators}. Asymptotic conditions on the triad are imposed as conditions
on the background electric field state label while confining the LQG spin net
graph labels to compact sets. We show that KS states can be realised as wave
functions on a quantum configuration space of generalized connections and that
the asymptotic behaviour of each such generalized connection is determined by
that of the background electric fields which label the background exponential
operators. Similar to the spatially compact case, the Gauss Law and
diffeomorphism constraints are then imposed through Group Averaging techniques
to obtain a large sector of gauge invariant states. It is shown that this
sector supports a unitary action of the group of asymptotic rotations and
translations and that, as anticipated by Friedman and Sorkin, for appropriate
spatial topology, this sector contains states which display fermionic behaviour
under $2\pi$ rotations.
| [
{
"created": "Wed, 17 Dec 2014 19:26:45 GMT",
"version": "v1"
}
] | 2015-06-17 | [
[
"Campiglia",
"Miguel",
""
],
[
"Varadarajan",
"Madhavan",
""
]
] | We construct a quantum kinematics for asymptotically flat spacetimes based on the Koslowski-Sahlmann (KS) representation. The KS representation is a generalization of the representation underlying Loop Quantum Gravity (LQG) which supports, in addition to the usual LQG operators, the action of `background exponential operators' which are connection dependent operators labelled by `background' $su(2)$ electric fields. KS states have, in addition to the LQG state label corresponding to 1 dimensional excitations of the triad, a label corresponding to a `background' electric field which describes 3 dimensional excitations of the triad. Asymptotic behaviour in quantum theory is controlled through asymptotic conditions on the background electric fields which label the {\em states} and the background electric fields which label the {\em operators}. Asymptotic conditions on the triad are imposed as conditions on the background electric field state label while confining the LQG spin net graph labels to compact sets. We show that KS states can be realised as wave functions on a quantum configuration space of generalized connections and that the asymptotic behaviour of each such generalized connection is determined by that of the background electric fields which label the background exponential operators. Similar to the spatially compact case, the Gauss Law and diffeomorphism constraints are then imposed through Group Averaging techniques to obtain a large sector of gauge invariant states. It is shown that this sector supports a unitary action of the group of asymptotic rotations and translations and that, as anticipated by Friedman and Sorkin, for appropriate spatial topology, this sector contains states which display fermionic behaviour under $2\pi$ rotations. |
0710.5071 | Wytler Cordeiro dos Santos | Wytler Cordeiro dos Santos | Exponential Metric Fields | Accepted for publication in Astrophysics and Space Science, 17 pages | Astrophys.Space Sci.331:295-307,2011 | 10.1007/s10509-010-0429-4 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Laser Interferometer Space Antenna (LISA) mission will use advanced
technologies to achieve its science goals: the direct detection of
gravitational waves, the observation of signals from compact (small and dense)
stars as they spiral into black holes, the study of the role of massive black
holes in galaxy evolution, the search for gravitational wave emission from the
early Universe. The gravitational red-shift, the advance of the perihelion of
Mercury, deflection of light and the time delay of radar signals are the
classical tests in the first order of General Relativity (GR). However, LISA
can possibly test Einstein's theories in the second order and perhaps, it will
show some particular feature of non-linearity of gravitational interaction. In
the present work we are seeking a method to construct theoretical templates
that limit in the first order the tensorial structure of some metric fields,
thus the non-linear terms are given by exponential functions of gravitational
strength. The Newtonian limit obtained here, in the first order, is equivalent
to GR.
| [
{
"created": "Fri, 26 Oct 2007 18:59:31 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jun 2010 14:15:45 GMT",
"version": "v2"
}
] | 2011-01-17 | [
[
"Santos",
"Wytler Cordeiro dos",
""
]
] | The Laser Interferometer Space Antenna (LISA) mission will use advanced technologies to achieve its science goals: the direct detection of gravitational waves, the observation of signals from compact (small and dense) stars as they spiral into black holes, the study of the role of massive black holes in galaxy evolution, the search for gravitational wave emission from the early Universe. The gravitational red-shift, the advance of the perihelion of Mercury, deflection of light and the time delay of radar signals are the classical tests in the first order of General Relativity (GR). However, LISA can possibly test Einstein's theories in the second order and perhaps, it will show some particular feature of non-linearity of gravitational interaction. In the present work we are seeking a method to construct theoretical templates that limit in the first order the tensorial structure of some metric fields, thus the non-linear terms are given by exponential functions of gravitational strength. The Newtonian limit obtained here, in the first order, is equivalent to GR. |
2204.14231 | Soumya Chakrabarti | Soumya Chakrabarti and Amitabha Lahiri | Scalar-Fermion Interaction as the Driver of Cosmic Acceleration | 15 pages, 15 Figures, In Communication, Comments are Welcome | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that an interacting scalar-fermion distribution can be used to
demonstrate the cosmic acceleration in General Relativity. The interaction is
of Yukawa nature and it drives the fermion density to decay with cosmic time.
The consistency of the model is established through, (a) a generalization of
the Om(z) parameter, the present matter density contrast of the universe, and
(b) a comparison of theoretical results with observational data, using a Markov
Chain Monte Carlo code. A simple model of unified cosmic expansion history is
also discussed. There are more than one instances where the universe goes
through a transition between subsequent epochs with different patterns of
cosmic expansion. These patterns impose some constraints on the scalar-fermion
interaction profile and on the overall cosmological dynamics.
| [
{
"created": "Fri, 29 Apr 2022 17:02:59 GMT",
"version": "v1"
}
] | 2022-05-02 | [
[
"Chakrabarti",
"Soumya",
""
],
[
"Lahiri",
"Amitabha",
""
]
] | We argue that an interacting scalar-fermion distribution can be used to demonstrate the cosmic acceleration in General Relativity. The interaction is of Yukawa nature and it drives the fermion density to decay with cosmic time. The consistency of the model is established through, (a) a generalization of the Om(z) parameter, the present matter density contrast of the universe, and (b) a comparison of theoretical results with observational data, using a Markov Chain Monte Carlo code. A simple model of unified cosmic expansion history is also discussed. There are more than one instances where the universe goes through a transition between subsequent epochs with different patterns of cosmic expansion. These patterns impose some constraints on the scalar-fermion interaction profile and on the overall cosmological dynamics. |
gr-qc/0601007 | Josinaldo Menezes | J. Menezes, P. P. Avelino, C. Santos | Gravitational Effects of Varying Alpha Strings | 8 pages, 2 figures, to be published in Int. Journ. of Mod. Phys. A | Int.J.Mod.Phys.A21:3295-3306,2006 | 10.1142/S0217751X06031430 | null | gr-qc astro-ph hep-th | null | We study spatial variations of the fine-structure constant in the presence of
static straight cosmic strings in the weak-field approximation in Einstein
gravity. We work in the context of a generic Bekenstein-type model and consider
a gauge kinetic function linear in the scalar field. We determine an analytical
form for the scalar field and the string metric at large distances from the
core. We show that the gravitational effects of $\alpha$-varying strings can be
seen as a combination of the gravitational effects of global and local strings.
We also verify that at large distances to the core the space-time metric is
similar to that of a global string. We study the motion of test particles
approaching from infinity and show that photons are scattered to infinity while
massive particles are trapped in bounded trajectories. We also calculate an
overall limit on the magnitude of the variation of $\alpha$ for a GUT string,
by considering suitable cosmological constraints coming from the Equivalence
Principle.
| [
{
"created": "Tue, 3 Jan 2006 15:22:04 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Menezes",
"J.",
""
],
[
"Avelino",
"P. P.",
""
],
[
"Santos",
"C.",
""
]
] | We study spatial variations of the fine-structure constant in the presence of static straight cosmic strings in the weak-field approximation in Einstein gravity. We work in the context of a generic Bekenstein-type model and consider a gauge kinetic function linear in the scalar field. We determine an analytical form for the scalar field and the string metric at large distances from the core. We show that the gravitational effects of $\alpha$-varying strings can be seen as a combination of the gravitational effects of global and local strings. We also verify that at large distances to the core the space-time metric is similar to that of a global string. We study the motion of test particles approaching from infinity and show that photons are scattered to infinity while massive particles are trapped in bounded trajectories. We also calculate an overall limit on the magnitude of the variation of $\alpha$ for a GUT string, by considering suitable cosmological constraints coming from the Equivalence Principle. |
gr-qc/0204036 | Brien C. Nolan | Brien C. Nolan | Naked singularities in cylindrical collapse of counter-rotating dust
shells | 4 pages, 8 ps figures. To appear in Phys. Rev. D | Phys.Rev. D65 (2002) 104006 | 10.1103/PhysRevD.65.104006 | null | gr-qc | null | Solutions describing the gravitational collapse of asymptotically flat
cylindrical and prolate shells of (null) dust are shown to admit globally naked
singularities.
| [
{
"created": "Tue, 9 Apr 2002 10:57:53 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Nolan",
"Brien C.",
""
]
] | Solutions describing the gravitational collapse of asymptotically flat cylindrical and prolate shells of (null) dust are shown to admit globally naked singularities. |
2101.11124 | Valerio Faraoni | Valerio Faraoni and Farah Atieh | Generalized Fibonacci numbers, cosmological analogies, and an invariant | 5 pages, no figures. Invited paper to appear in Symmetry and Geometry
in Physics, special issue of Symmetry edited by A. Ungar | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Continuous generalizations of the Fibonacci sequence satisfy ODEs that are
formal analogues of the Friedmann equation describing spatially homogeneous and
isotropic cosmology in general relativity. These analogies are presented,
together with their Lagrangian and Hamiltonian formulations and with an
invariant of the Fibonacci sequence.
| [
{
"created": "Tue, 26 Jan 2021 22:47:29 GMT",
"version": "v1"
}
] | 2021-01-28 | [
[
"Faraoni",
"Valerio",
""
],
[
"Atieh",
"Farah",
""
]
] | Continuous generalizations of the Fibonacci sequence satisfy ODEs that are formal analogues of the Friedmann equation describing spatially homogeneous and isotropic cosmology in general relativity. These analogies are presented, together with their Lagrangian and Hamiltonian formulations and with an invariant of the Fibonacci sequence. |
1409.5377 | Andrzej Krasi\'nski | Andrzej Krasi\'nski | Blueshifts in the Lema\^{\i}tre -- Tolman models | 13 pages, 12 figures; axis labels added in all figures, new paragraph
added after (2.16), Ref. 22 updated; no substantial changes | Phys. Rev. D 90, 103525 (2014) | 10.1103/PhysRevD.90.103525 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Lema\^{\i}tre -- Tolman (L--T) models that have nonconstant bang-time
function $t_B(r)$, light emitted close to those points of the Big Bang where
$\dril {t_B} r \neq 0$ is blueshifted at the receiver position. The blueshifted
rays are expected to perturb the temperature of the cosmic microwave background
(CMB) radiation along the lines of sight of the present central observer. It is
shown here that, in a general L--T model, the $t_B(r)$ can be chosen so that
the blueshift-generating region is hidden before the recombination time, where
the L--T model does not apply. The rest of the paper is devoted to
investigating blueshifts in one specific L--T model, called L--T$(t_B)$ -- the
one that duplicates the luminosity distance vs. redshift relation of the
$\Lambda$CDM model using nonconstant $t_B(r)$ alone. The location of the
blueshift-generating region in the L--T$(t_B)$ spacetime is determined.
Profiles of redshift/blueshift along several rays intersecting the past light
cone of the present central observer are calculated. The L--T$(t_B)$ model
matched to Friedmann is considered, and profiles of redshift/blueshift in such
a composite model are calculated. The requirement of invisibility of blueshifts
makes the L--T$(t_B)$ model astrophysically unacceptable if it should apply
back to the recombination time, but does not "rule out" a general L--T model --
it only puts limits on $\dril {t_B} r$.
| [
{
"created": "Thu, 18 Sep 2014 17:10:21 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Nov 2014 13:44:55 GMT",
"version": "v2"
}
] | 2015-02-03 | [
[
"Krasiński",
"Andrzej",
""
]
] | In the Lema\^{\i}tre -- Tolman (L--T) models that have nonconstant bang-time function $t_B(r)$, light emitted close to those points of the Big Bang where $\dril {t_B} r \neq 0$ is blueshifted at the receiver position. The blueshifted rays are expected to perturb the temperature of the cosmic microwave background (CMB) radiation along the lines of sight of the present central observer. It is shown here that, in a general L--T model, the $t_B(r)$ can be chosen so that the blueshift-generating region is hidden before the recombination time, where the L--T model does not apply. The rest of the paper is devoted to investigating blueshifts in one specific L--T model, called L--T$(t_B)$ -- the one that duplicates the luminosity distance vs. redshift relation of the $\Lambda$CDM model using nonconstant $t_B(r)$ alone. The location of the blueshift-generating region in the L--T$(t_B)$ spacetime is determined. Profiles of redshift/blueshift along several rays intersecting the past light cone of the present central observer are calculated. The L--T$(t_B)$ model matched to Friedmann is considered, and profiles of redshift/blueshift in such a composite model are calculated. The requirement of invisibility of blueshifts makes the L--T$(t_B)$ model astrophysically unacceptable if it should apply back to the recombination time, but does not "rule out" a general L--T model -- it only puts limits on $\dril {t_B} r$. |
0811.1430 | Albert V. Minkevich | A. V. Minkevich, A. S. Garkun, V. I. Kudin | Comment on "Torsion Cosmology and Accelerating Universe" | The abstract is changed, some additions and corrections is made | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmological solutions for homogeneous isotropic models in the framework of
the Poincar\'e gauge theory of gravity based on gravitational Lagrangian
adopted in the paper by Kun-Feng Shie, James M. Nester and Hwei-Jang Yo (Phys.
Rev. D \textbf{78}, 023522 (2008)) are discussed. Cosmological solutions for
accelerating Universe obtained in referred paper are compared with
corresponding solutions of standard $\Lambda CDM$-model and also with
cosmological solution obtained by authors of this Comment.
| [
{
"created": "Mon, 10 Nov 2008 09:53:33 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Dec 2008 08:05:49 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Aug 2009 16:15:29 GMT",
"version": "v3"
}
] | 2009-08-28 | [
[
"Minkevich",
"A. V.",
""
],
[
"Garkun",
"A. S.",
""
],
[
"Kudin",
"V. I.",
""
]
] | Cosmological solutions for homogeneous isotropic models in the framework of the Poincar\'e gauge theory of gravity based on gravitational Lagrangian adopted in the paper by Kun-Feng Shie, James M. Nester and Hwei-Jang Yo (Phys. Rev. D \textbf{78}, 023522 (2008)) are discussed. Cosmological solutions for accelerating Universe obtained in referred paper are compared with corresponding solutions of standard $\Lambda CDM$-model and also with cosmological solution obtained by authors of this Comment. |
1105.0047 | Gergely Sz\'ekely | Hajnal Andr\'eka, Istv\'an N\'emeti and Gergely Sz\'ekely | Closed Timelike Curves in Relativistic Computation | 17 pages, 5 figures | Parallel Processing Letters, 22, 1240010 (2012) | 10.1142/S0129626412400105 | null | gr-qc math-ph math.LO math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the possibility of using closed timelike curves
(CTCs) in relativistic hypercomputation. We introduce a wormhole based
hypercomputation scenario which is free from the common worries, such as the
blueshift problem. We also discuss the physical reasonability of our scenario,
and why we cannot simply ignore the possibility of the existence of spacetimes
containing CTCs.
| [
{
"created": "Sat, 30 Apr 2011 05:06:36 GMT",
"version": "v1"
}
] | 2012-11-27 | [
[
"Andréka",
"Hajnal",
""
],
[
"Németi",
"István",
""
],
[
"Székely",
"Gergely",
""
]
] | In this paper, we investigate the possibility of using closed timelike curves (CTCs) in relativistic hypercomputation. We introduce a wormhole based hypercomputation scenario which is free from the common worries, such as the blueshift problem. We also discuss the physical reasonability of our scenario, and why we cannot simply ignore the possibility of the existence of spacetimes containing CTCs. |
gr-qc/0312079 | Jiliang Jing | Jiliang Jing | Dirac quasinormal modes of the Reissner-Nordstr\"om de Sitter black hole | 10 pages, 6 figures, Phys. Rev. D in press | Phys.Rev. D69 (2004) 084009 | 10.1103/PhysRevD.69.084009 | null | gr-qc astro-ph hep-th | null | The quasinormal modes of the Reissner-Nordstr\"om de Sitter black hole for
the massless Dirac fields are studied using the P\"oshl-Teller potential
approximation. We find that the magnitude of the imaginary part of the
quasinormal frequencies decreases as the cosmological constant or the orbital
angular momentum increases, but it increases as the charge or the overtone
number increases. An interesting feature is that the imaginary part is almost
linearly related to the real part as the cosmological constant changes for
fixed charge, and the linearity becomes better as the orbital angular momentum
increases. We also prove exactly that the Dirac quasinormal frequencies are the
same for opposite chirality.
| [
{
"created": "Wed, 17 Dec 2003 15:22:26 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Jing",
"Jiliang",
""
]
] | The quasinormal modes of the Reissner-Nordstr\"om de Sitter black hole for the massless Dirac fields are studied using the P\"oshl-Teller potential approximation. We find that the magnitude of the imaginary part of the quasinormal frequencies decreases as the cosmological constant or the orbital angular momentum increases, but it increases as the charge or the overtone number increases. An interesting feature is that the imaginary part is almost linearly related to the real part as the cosmological constant changes for fixed charge, and the linearity becomes better as the orbital angular momentum increases. We also prove exactly that the Dirac quasinormal frequencies are the same for opposite chirality. |
1112.4903 | Emanuele Berti | Justin Alsing, Emanuele Berti, Clifford M. Will, Helmut Zaglauer | Gravitational radiation from compact binary systems in the massive
Brans-Dicke theory of gravity | 19 pages, 2 figures, 2 tables. Added new Appendix and slightly
rephrased section on Shapiro time delay. Matches version in press in PRD | null | 10.1103/PhysRevD.85.064041 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the equations of motion, the periastron shift, and the
gravitational radiation damping for quasicircular compact binaries in a massive
variant of the Brans-Dicke theory of gravity. We also study the Shapiro time
delay and the Nordtvedt effect in this theory. By comparing with recent
observational data, we put bounds on the two parameters of the theory: the
Brans-Dicke coupling parameter \omega_{BD} and the scalar mass m_s. We find
that the most stringent bounds come from Cassini measurements of the Shapiro
time delay in the Solar System, that yield a lower bound \omega_{BD}>40000 for
scalar masses m_s<2.5x10^{-20} eV, to 95% confidence. In comparison,
observations of the Nordtvedt effect using Lunar Laser Ranging (LLR)
experiments yield \omega_{BD}>1000 for m_s<2.5x10^{-20} eV. Observations of the
orbital period derivative of the quasicircular white dwarf-neutron star binary
PSR J1012+5307 yield \omega_{BD}>1250 for m_s<10^{-20} eV. A first estimate
suggests that bounds comparable to the Shapiro time delay may come from
observations of radiation damping in the eccentric white dwarf-neutron star
binary PSR J1141-6545, but a quantitative prediction requires the extension of
our work to eccentric orbits.
| [
{
"created": "Wed, 21 Dec 2011 01:42:12 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Mar 2012 16:19:49 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Alsing",
"Justin",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Will",
"Clifford M.",
""
],
[
"Zaglauer",
"Helmut",
""
]
] | We derive the equations of motion, the periastron shift, and the gravitational radiation damping for quasicircular compact binaries in a massive variant of the Brans-Dicke theory of gravity. We also study the Shapiro time delay and the Nordtvedt effect in this theory. By comparing with recent observational data, we put bounds on the two parameters of the theory: the Brans-Dicke coupling parameter \omega_{BD} and the scalar mass m_s. We find that the most stringent bounds come from Cassini measurements of the Shapiro time delay in the Solar System, that yield a lower bound \omega_{BD}>40000 for scalar masses m_s<2.5x10^{-20} eV, to 95% confidence. In comparison, observations of the Nordtvedt effect using Lunar Laser Ranging (LLR) experiments yield \omega_{BD}>1000 for m_s<2.5x10^{-20} eV. Observations of the orbital period derivative of the quasicircular white dwarf-neutron star binary PSR J1012+5307 yield \omega_{BD}>1250 for m_s<10^{-20} eV. A first estimate suggests that bounds comparable to the Shapiro time delay may come from observations of radiation damping in the eccentric white dwarf-neutron star binary PSR J1141-6545, but a quantitative prediction requires the extension of our work to eccentric orbits. |
0805.1901 | Francesco Cianfrani dr | F. Cianfrani, G. Montani | Elementary particle interaction from a Kaluza-Klein scheme | 8 pages, Proceedings of the II Stueckelberg workshop | Int.J.Mod.Phys.A23:1182-1189,2008 | 10.1142/S0217751X08040044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss properties of particles and fields in a multi-dimensional
space-time, where the geometrization of gauge interactions can be performed. As
far as spinors are concerned, we outline how the gauge coupling can be
recognized by a proper dependence on extra-coordinates and by the dimensional
reduction procedure. Finally applications to the Electro-Weak model are
presented.
| [
{
"created": "Tue, 13 May 2008 18:45:21 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Cianfrani",
"F.",
""
],
[
"Montani",
"G.",
""
]
] | We discuss properties of particles and fields in a multi-dimensional space-time, where the geometrization of gauge interactions can be performed. As far as spinors are concerned, we outline how the gauge coupling can be recognized by a proper dependence on extra-coordinates and by the dimensional reduction procedure. Finally applications to the Electro-Weak model are presented. |
2001.01460 | Ezgi Yal\c{c}{\i}nkaya | Ezgi Canay, Maxim Eingorn, Alexander Zhuk | Effects of nonlinearity of $f(R)$ gravity and perfect fluid in
Kaluza-Klein models with spherical compactification | v2 (matching the publication in European Physical Journal C) = v1 +
minor changes + new Refs.; 14 pages, no figures | Eur. Phys. J. C 80, 379 (2020) | 10.1140/epjc/s10052-020-7979-6 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effects associated with nonlinearity of $f(R)$ gravity and of
the background perfect fluid manifested in the Kaluza-Klein model with
spherical compactification. The background space-time is perturbed by a massive
gravitating source which is pressureless in the external space but has an
arbitrary equation of state (EoS) parameter in the internal space. As
characteristics of a nonlinear perfect fluid, the squared speeds of sound are
not equal to the background EoS parameters in the external and internal spaces.
In this setting, we find exact solutions to the linearized Einstein equations
for the perturbed metric coefficients. For nonlinear models with
$f^{\prime\prime}(R_0)\neq0$, we show that these coefficients acquire
correction terms in the form of two summed Yukawa potentials and that in the
degenerated case, the solutions are reduced to a single Yukawa potential with
some "corrupted" prefactor (in front of the exponential function), which, in
addition to the standard $1/r$ term, contains a contribution independent of the
three-dimensional distance $r$. In the linear $f''(R)=0$ model, we generalize
the previous studies to the case of an arbitrary nonlinear perfect fluid. We
also investigate the particular case of the nonlinear background perfect fluid
with zero speed of sound in the external space and demonstrate that a
non-trivial solution exists only in the case of $f''(R_0)=0$.
| [
{
"created": "Mon, 6 Jan 2020 10:01:40 GMT",
"version": "v1"
},
{
"created": "Tue, 12 May 2020 14:07:23 GMT",
"version": "v2"
}
] | 2020-05-13 | [
[
"Canay",
"Ezgi",
""
],
[
"Eingorn",
"Maxim",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We study the effects associated with nonlinearity of $f(R)$ gravity and of the background perfect fluid manifested in the Kaluza-Klein model with spherical compactification. The background space-time is perturbed by a massive gravitating source which is pressureless in the external space but has an arbitrary equation of state (EoS) parameter in the internal space. As characteristics of a nonlinear perfect fluid, the squared speeds of sound are not equal to the background EoS parameters in the external and internal spaces. In this setting, we find exact solutions to the linearized Einstein equations for the perturbed metric coefficients. For nonlinear models with $f^{\prime\prime}(R_0)\neq0$, we show that these coefficients acquire correction terms in the form of two summed Yukawa potentials and that in the degenerated case, the solutions are reduced to a single Yukawa potential with some "corrupted" prefactor (in front of the exponential function), which, in addition to the standard $1/r$ term, contains a contribution independent of the three-dimensional distance $r$. In the linear $f''(R)=0$ model, we generalize the previous studies to the case of an arbitrary nonlinear perfect fluid. We also investigate the particular case of the nonlinear background perfect fluid with zero speed of sound in the external space and demonstrate that a non-trivial solution exists only in the case of $f''(R_0)=0$. |
1811.03005 | Olga Sergijenko | O. Sergijenko | 2-field model of dark energy with canonical and non-canonical kinetic
terms | 3 pages, introduction corrected, references added, results and
conclusions unchanged | null | 10.18524/1810-4215.2018.31.144667 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize quintom to include the tachyonic kinetic term along with the
classical one. For such a model we obtain the expressions for energy density
and pressure. For the spatially flat, homogeneous and isotropic Universe with
Friedmann-Robertson-Walker metric of 4-space we derive the equations of motion
for the fields. We discuss in detail the reconstruction of the scalar fields
potential $U(\phi,\xi)$. Such a reconstruction cannot be done unambiguously, so
we consider 3 simplest forms of $U(\phi,\xi)$: the product of $\Phi(\phi)$ and
$\Xi(\xi)$, the sum of $\Phi(\phi)$ and $\Xi(\xi)$ and this sum to the
$\kappa$th power.
| [
{
"created": "Tue, 6 Nov 2018 17:00:07 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Nov 2018 18:15:15 GMT",
"version": "v2"
}
] | 2019-01-09 | [
[
"Sergijenko",
"O.",
""
]
] | We generalize quintom to include the tachyonic kinetic term along with the classical one. For such a model we obtain the expressions for energy density and pressure. For the spatially flat, homogeneous and isotropic Universe with Friedmann-Robertson-Walker metric of 4-space we derive the equations of motion for the fields. We discuss in detail the reconstruction of the scalar fields potential $U(\phi,\xi)$. Such a reconstruction cannot be done unambiguously, so we consider 3 simplest forms of $U(\phi,\xi)$: the product of $\Phi(\phi)$ and $\Xi(\xi)$, the sum of $\Phi(\phi)$ and $\Xi(\xi)$ and this sum to the $\kappa$th power. |
2302.00016 | Carlos A. R. Herdeiro | Carlos A. R. Herdeiro, Eugen Radu | Two Schwarzschild-like black holes balanced by their scalar hair | 22 pages, 8 figures | null | 10.1103/PhysRevD.107.064044 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We show that, unlike vacuum General Relativity, Einstein-scalar theories
allow balanced static, neutral, asymptotically flat, double-black hole
solutions, for scalar field models minimally coupled to gravity, with
appropriate self-interactions. These are scalar hairy versions of the
double-Schwarzschild (or Bach-Weyl) solution, but regular on and outside the
two (topologically spherical) horizons. The balancing repulsive force is
provided by the scalar field. An explicit illustration is presented, using a
Weyl-type construction adapted to numerical solutions, requiring no partial
linearisation, or integrability structure, of the Einstein-scalar equations.
Fixing the couplings of the model, the balanced configurationsform a
one-parameter family of solutions, labelled by the proper distance between the
black holes.
| [
{
"created": "Tue, 31 Jan 2023 19:00:01 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] | We show that, unlike vacuum General Relativity, Einstein-scalar theories allow balanced static, neutral, asymptotically flat, double-black hole solutions, for scalar field models minimally coupled to gravity, with appropriate self-interactions. These are scalar hairy versions of the double-Schwarzschild (or Bach-Weyl) solution, but regular on and outside the two (topologically spherical) horizons. The balancing repulsive force is provided by the scalar field. An explicit illustration is presented, using a Weyl-type construction adapted to numerical solutions, requiring no partial linearisation, or integrability structure, of the Einstein-scalar equations. Fixing the couplings of the model, the balanced configurationsform a one-parameter family of solutions, labelled by the proper distance between the black holes. |
gr-qc/0404098 | Won Tae Kim | Won Tae Kim and Edwin J. Son | Wormhole phase in the RST model | v1. REVTeX3, 12 pages and 1 figure; v2. JHEP3, 10 pages and 1 figure,
version published in JHEP | JHEP 0408:006,2004 | 10.1088/1126-6708/2004/08/006 | SOGANG-HEP 312/04 | gr-qc | null | We show that the RST model describing the exactly soluble black hole model
can have a dynamical wormhole solution along with an appropriate boundary
condition. The necessary exotic matter which is usually negative energy density
is remarkably produced by the quantization of the infalling matter fields. Then
the asymptotic geometry in the past is two-dimensional anti-de Sitter(AdS$_2$),
which implies the exotic matter is negative. As time goes on, the wormhole
eventually evolves into the black hole and its Hawking radiation appears. The
throat of the static RST wormhole is lower-bounded but in the presence of
infalling matter it collapses to a black hole.
| [
{
"created": "Thu, 22 Apr 2004 08:58:12 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Sep 2004 00:50:21 GMT",
"version": "v2"
}
] | 2010-02-03 | [
[
"Kim",
"Won Tae",
""
],
[
"Son",
"Edwin J.",
""
]
] | We show that the RST model describing the exactly soluble black hole model can have a dynamical wormhole solution along with an appropriate boundary condition. The necessary exotic matter which is usually negative energy density is remarkably produced by the quantization of the infalling matter fields. Then the asymptotic geometry in the past is two-dimensional anti-de Sitter(AdS$_2$), which implies the exotic matter is negative. As time goes on, the wormhole eventually evolves into the black hole and its Hawking radiation appears. The throat of the static RST wormhole is lower-bounded but in the presence of infalling matter it collapses to a black hole. |
1312.6871 | David Garfinkle | Lydia Bieri and David Garfinkle | A perturbative and gauge invariant treatment of gravitational wave
memory | Typos corrected. Discussion extended | Phys. Rev. D 89, 084039 (2014) | 10.1103/PhysRevD.89.084039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a perturbative treatment of gravitational wave memory. The
coordinate invariance of Einstein's equations leads to a type of gauge
invariance in perturbation theory. As with any gauge invariant theory, results
are more clear when expressed in terms of manifestly gauge invariant
quantities. Therefore we derive all our results from the perturbed Weyl tensor
rather than the perturbed metric. We derive gravitational wave memory for the
Einstein equations coupled to a general energy-momentum tensor that reaches
null infinity.
| [
{
"created": "Tue, 24 Dec 2013 18:49:48 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Apr 2014 15:01:25 GMT",
"version": "v2"
}
] | 2014-04-23 | [
[
"Bieri",
"Lydia",
""
],
[
"Garfinkle",
"David",
""
]
] | We present a perturbative treatment of gravitational wave memory. The coordinate invariance of Einstein's equations leads to a type of gauge invariance in perturbation theory. As with any gauge invariant theory, results are more clear when expressed in terms of manifestly gauge invariant quantities. Therefore we derive all our results from the perturbed Weyl tensor rather than the perturbed metric. We derive gravitational wave memory for the Einstein equations coupled to a general energy-momentum tensor that reaches null infinity. |
gr-qc/0412044 | Lorenzo Iorio | Lorenzo Iorio | The challenge to reliably measure the general relativistic
Lense-Thirring effect with a few percent accuracy | LaTeX2e, no figures, no tables, 12 pages, 35 references | Proceedings of the Joint CHAMP/GRACE Science Meeting,
GeoForschungsZentrum, Potsdam, July 6-8, 2004.
http://www-app2.gfz-potsdam.de/pb1/JCG/ | null | null | gr-qc astro-ph physics.geo-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we critically analyze the so far performed and proposed tests
for measuring the general relativistic Lense-Thirring effect in the
gravitational field of the Earth with some of the existing accurately tracked
artificial satellites. The impact of the 2nd generation GRACE-only
EIGEN-GRACE02S Earth gravity model and of the 1st CHAMP+GRACE+terrestrial
gravity combined EIGEN-CG01C Earth gravity model is discussed. The role of the
proposed LARES is discussed as well.
| [
{
"created": "Thu, 9 Dec 2004 23:52:25 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Dec 2004 20:18:33 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Dec 2004 00:06:19 GMT",
"version": "v3"
},
{
"created": "Thu, 30 Dec 2004 18:57:10 GMT",
"version": "v4"
},
{
"cr... | 2012-07-31 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper we critically analyze the so far performed and proposed tests for measuring the general relativistic Lense-Thirring effect in the gravitational field of the Earth with some of the existing accurately tracked artificial satellites. The impact of the 2nd generation GRACE-only EIGEN-GRACE02S Earth gravity model and of the 1st CHAMP+GRACE+terrestrial gravity combined EIGEN-CG01C Earth gravity model is discussed. The role of the proposed LARES is discussed as well. |
gr-qc/0610127 | Jose M. M. Senovilla | Jos\'e M. M. Senovilla | A singularity theorem based on spatial averages | Corrections made in the main theorem and related places. 16 pages, no
figures. Invited contribution to the Pramana special issue, dedicated to A K
Raychaudhuri, on "the Raychaudhuri Equation and its Role in Modern Cosmology"
(Edited by Naresh Dadhich, Pankaj Joshi and Probir Roy). Final version to be
published | Pramana69:31-48,2007 | 10.1007/s12043-007-0109-2 | null | gr-qc | null | Inspired by Raychaudhuri's work, and using the equation named after him as a
basic ingredient, a new singularity theorem is proved. Open non-rotating
everywhere expanding universes with non-vanishing spatial average of the matter
variables are severely geodesically incomplete to the past. Another way of
stating the result is that, under the same conditions, any singularity-free
model must have a vanishing spatial average of the energy density (and other
physical variables). This is very satisfactory and provides a clear decisive
difference between singular and non-singular cosmologies.
| [
{
"created": "Thu, 26 Oct 2006 16:28:05 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Mar 2007 11:05:58 GMT",
"version": "v2"
},
{
"created": "Sun, 6 May 2007 11:53:50 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Senovilla",
"José M. M.",
""
]
] | Inspired by Raychaudhuri's work, and using the equation named after him as a basic ingredient, a new singularity theorem is proved. Open non-rotating everywhere expanding universes with non-vanishing spatial average of the matter variables are severely geodesically incomplete to the past. Another way of stating the result is that, under the same conditions, any singularity-free model must have a vanishing spatial average of the energy density (and other physical variables). This is very satisfactory and provides a clear decisive difference between singular and non-singular cosmologies. |
1601.05795 | Sourav Dutta | Sourav Dutta and Subenoy Chakraborty | A study of phantom scalar field cosmology using Lie and Noether
symmetries | 14 pages, 9 figures, accepted for publication in Int. J. Mod. Phys. D
(2016) | null | 10.1142/S0218271816500516 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper deals with phantom scalar field cosmology in Einstein gravity. At
first using Lie symmetry, the coupling function to the kinetic term and the
potential function of the scalar field and the equation of state parameter of
the matter field are determined and a simple solution is obtained.
Subsequently, Noether symmetry is imposed on the Lagrangian of the system. The
symmetry vector is obtained and the potential takes a very general form from
which potential using Lie Symmetry can be obtained as a particular case. Then
we choose a point transformation $(a,\phi)\rightarrow(u,v)$ such that one of
the transformed variables (say u) is a cyclic for the Lagrangian. Using
conserved charge (corresponding to the cyclic coordinate) and the constant of
motion, solutions are obtained.
| [
{
"created": "Thu, 21 Jan 2016 10:41:05 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Mar 2016 07:21:44 GMT",
"version": "v2"
}
] | 2016-04-27 | [
[
"Dutta",
"Sourav",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The paper deals with phantom scalar field cosmology in Einstein gravity. At first using Lie symmetry, the coupling function to the kinetic term and the potential function of the scalar field and the equation of state parameter of the matter field are determined and a simple solution is obtained. Subsequently, Noether symmetry is imposed on the Lagrangian of the system. The symmetry vector is obtained and the potential takes a very general form from which potential using Lie Symmetry can be obtained as a particular case. Then we choose a point transformation $(a,\phi)\rightarrow(u,v)$ such that one of the transformed variables (say u) is a cyclic for the Lagrangian. Using conserved charge (corresponding to the cyclic coordinate) and the constant of motion, solutions are obtained. |
gr-qc/0410007 | Graham Woan | The LIGO Scientific Collaboration: B. Abbott, et al, and M. Kramer and
A.G. Lyne | Limits on gravitational wave emission from selected pulsars using LIGO
data | 6 pages, 2 figures | Phys.Rev.Lett.94:181103,2005 | 10.1103/PhysRevLett.94.181103 | LIGO-P040008-A-Z | gr-qc astro-ph | null | We place direct upper limits on the amplitude of gravitational waves from 28
isolated radio pulsars by a coherent multi-detector analysis of the data
collected during the second science run of the LIGO interferometric detectors.
These are the first direct upper limits for 26 of the 28 pulsars. We use
coordinated radio observations for the first time to build radio-guided phase
templates for the expected gravitational wave signals. The unprecedented
sensitivity of the detectors allow us to set strain upper limits as low as a
few times $10^{-24}$. These strain limits translate into limits on the
equatorial ellipticities of the pulsars, which are smaller than $10^{-5}$ for
the four closest pulsars.
| [
{
"created": "Fri, 1 Oct 2004 20:01:22 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jan 2005 15:51:09 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"The LIGO Scientific Collaboration",
"",
""
],
[
"Abbott",
"B.",
""
],
[
"Kramer",
"M.",
""
],
[
"Lyne",
"A. G.",
""
]
] | We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multi-detector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational wave signals. The unprecedented sensitivity of the detectors allow us to set strain upper limits as low as a few times $10^{-24}$. These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than $10^{-5}$ for the four closest pulsars. |
gr-qc/0009021 | Carlo Rovelli | Alejandro Perez and Carlo Rovelli | Spin foam model for Lorentzian General Relativity | 8 pages, 1 figure | Phys.Rev.D63:041501,2001 | 10.1103/PhysRevD.63.041501 | null | gr-qc | null | We present a spin foam formulation of Lorentzian quantum General Relativity.
The theory is based on a simple generalization of an Euclidean model defined in
terms of a field theory over a group. Its vertex amplitude turns out to be the
one recently introduced by Barrett and Crane. As in the case of its Euclidean
relatives, the model fully implements the desired sum over 2-complexes which
encodes the local degrees of freedom of the theory.
| [
{
"created": "Thu, 7 Sep 2000 12:14:38 GMT",
"version": "v1"
}
] | 2009-12-31 | [
[
"Perez",
"Alejandro",
""
],
[
"Rovelli",
"Carlo",
""
]
] | We present a spin foam formulation of Lorentzian quantum General Relativity. The theory is based on a simple generalization of an Euclidean model defined in terms of a field theory over a group. Its vertex amplitude turns out to be the one recently introduced by Barrett and Crane. As in the case of its Euclidean relatives, the model fully implements the desired sum over 2-complexes which encodes the local degrees of freedom of the theory. |
2202.09251 | Di Wu | Di Wu, Shuang-Qing Wu | Consistent mass formulas for the four-dimensional dyonic NUT-charged
spacetimes | 12 pages, no figure, revtex 4-1.cls, to appear in PRD. Companion to
1909.07776 | Phys. Rev. D 105, 124013 (2022) | 10.1103/PhysRevD.105.124013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In our previous work, a novel idea that the NUT charge can be thought of as a
thermodynamical multi-hair has been advocated to describe perfectly the
thermodynamical character of the generic four-dimensional Taub-NUT spacetimes.
According to this scheme, the Komar mass M, the gravito-magnetic charge and/or
the dual (magnetic) mass N, together with a new secondary hair J_N=MN, namely,
a Kerr-like conserved angular momentum, enter into the standard forms of the
first law and Bekenstein-Smarr mass formula. Distinguished from other recent
attempts, our consistent thermodynamic differential and integral mass formulae
are both obtainable from a meaningful Christodoulou-Ruffini-type squared mass
formula of almost all of the four-dimensional NUT-charged spacetimes. As an
excellent consequence, the famous Bekenstein-Hawking one-quarter area-entropy
relation can be naturally restored not only in the Lorentzian sector and but
also in the Euclidian counterpart of the generic Taub-NUT-type spacetimes
without imposing any constraint condition. However, only purely
electric-charged cases in the four-dimensional Einstein-Maxwell gravity theory
with a NUT charge have been addressed there. In this paper, we shall follow the
simple, systematic way proposed in that article to further investigate the
dyonic NUT-charged case. It is shown that the standard thermodynamic relations
continue to hold true provided that no new secondary charge is added, however,
the so-obtained electrostatic and magneto-static potentials are not coincident
with those computed via the standard method. To rectify this inconsistence, a
simple strategy is provided by further introducing two additional secondary
hairs: Q_N=QN and P_N=PN, together with their thermodynamical conjugate
potentials, so that the first law and Bekenstein-Smarr mass formula are still
satisfied.
| [
{
"created": "Fri, 18 Feb 2022 15:27:52 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Apr 2022 03:34:02 GMT",
"version": "v2"
},
{
"created": "Thu, 26 May 2022 02:39:49 GMT",
"version": "v3"
}
] | 2022-06-08 | [
[
"Wu",
"Di",
""
],
[
"Wu",
"Shuang-Qing",
""
]
] | In our previous work, a novel idea that the NUT charge can be thought of as a thermodynamical multi-hair has been advocated to describe perfectly the thermodynamical character of the generic four-dimensional Taub-NUT spacetimes. According to this scheme, the Komar mass M, the gravito-magnetic charge and/or the dual (magnetic) mass N, together with a new secondary hair J_N=MN, namely, a Kerr-like conserved angular momentum, enter into the standard forms of the first law and Bekenstein-Smarr mass formula. Distinguished from other recent attempts, our consistent thermodynamic differential and integral mass formulae are both obtainable from a meaningful Christodoulou-Ruffini-type squared mass formula of almost all of the four-dimensional NUT-charged spacetimes. As an excellent consequence, the famous Bekenstein-Hawking one-quarter area-entropy relation can be naturally restored not only in the Lorentzian sector and but also in the Euclidian counterpart of the generic Taub-NUT-type spacetimes without imposing any constraint condition. However, only purely electric-charged cases in the four-dimensional Einstein-Maxwell gravity theory with a NUT charge have been addressed there. In this paper, we shall follow the simple, systematic way proposed in that article to further investigate the dyonic NUT-charged case. It is shown that the standard thermodynamic relations continue to hold true provided that no new secondary charge is added, however, the so-obtained electrostatic and magneto-static potentials are not coincident with those computed via the standard method. To rectify this inconsistence, a simple strategy is provided by further introducing two additional secondary hairs: Q_N=QN and P_N=PN, together with their thermodynamical conjugate potentials, so that the first law and Bekenstein-Smarr mass formula are still satisfied. |
2211.12056 | Yu-Xiao Liu | Yu-Qi Dong, Yu-Qiang Liu, Yu-Xiao Liu | Constraining Palatini-Horndeski theory with gravitational waves after
GW170817 | 23 pages, no figure | Eur.Phys.J.C 83 (2023) 8, 702 | 10.1140/epjc/s10052-023-11861-9 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the possible parameter space of
Palatini-Horndeski theory with gravitational waves in a spatially flat
Universe. We find that if the theory satisfies the following condition: in any
spatially flat cosmological background, the tensor gravitational wave speed is
the speed of light $c$, then only $S = \int d^4x \sqrt{-g}
\big[K(\phi,X)-G_{3}(\phi,X){\tilde{\Box}}\phi+G_{4}(\phi)\tilde{R}\big]$ is
left as the possible action in Palatini-Horndeski theory.
| [
{
"created": "Tue, 22 Nov 2022 07:04:43 GMT",
"version": "v1"
}
] | 2024-02-21 | [
[
"Dong",
"Yu-Qi",
""
],
[
"Liu",
"Yu-Qiang",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | In this paper, we investigate the possible parameter space of Palatini-Horndeski theory with gravitational waves in a spatially flat Universe. We find that if the theory satisfies the following condition: in any spatially flat cosmological background, the tensor gravitational wave speed is the speed of light $c$, then only $S = \int d^4x \sqrt{-g} \big[K(\phi,X)-G_{3}(\phi,X){\tilde{\Box}}\phi+G_{4}(\phi)\tilde{R}\big]$ is left as the possible action in Palatini-Horndeski theory. |
1403.6286 | Oleg Zaslavskii | O. B. Zaslavskii | Ultrahigh energy particle collisions near the black hole horizon in the
strong magnetic field | 6 pages | Mod. Phys. Lett. A, 29, 1450112 (2014) | 10.1142/S0217732314501120 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider collision between two charged (or charged and neutral) particles
near the black hole horizon in the strong magnetic field B. It is shown that
there exists a strip near the horizon within which collision of any two such
particles leads to ultrahigh energy in the centre of mass frame. The results
apply to generic (not necessarily vacuum) black holes.
| [
{
"created": "Tue, 25 Mar 2014 10:39:57 GMT",
"version": "v1"
}
] | 2014-07-09 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We consider collision between two charged (or charged and neutral) particles near the black hole horizon in the strong magnetic field B. It is shown that there exists a strip near the horizon within which collision of any two such particles leads to ultrahigh energy in the centre of mass frame. The results apply to generic (not necessarily vacuum) black holes. |
1211.5310 | Jian-Yang Zhu | Xiao-Jun Yue and Jian-Yang Zhu | Power spectrum and anisotropy of super inflation in loop quantum
cosmology | 12 pages,4 figures,Published version | Phys. Rev. D 87, 063518 (2013) | 10.1103/PhysRevD.87.063518 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the scalar mode of perturbation of super inflation in the
version of loop quantum cosmology in which the gauge invariant holonomy
corrections are considered. Given a background solution, we calculate the power
spectrum of the perturbation in the classical and LQC conditions. Then we
compute the anisotropy originated from the perturbation. It is found that in
the presence of the gauge invariant holonomy corrections the power spectrum is
exponentially blue and the anisotropy also grows exponentially in the epoch of
super inflation.
| [
{
"created": "Thu, 22 Nov 2012 15:29:51 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Mar 2013 04:24:14 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Yue",
"Xiao-Jun",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | We investigate the scalar mode of perturbation of super inflation in the version of loop quantum cosmology in which the gauge invariant holonomy corrections are considered. Given a background solution, we calculate the power spectrum of the perturbation in the classical and LQC conditions. Then we compute the anisotropy originated from the perturbation. It is found that in the presence of the gauge invariant holonomy corrections the power spectrum is exponentially blue and the anisotropy also grows exponentially in the epoch of super inflation. |
1304.3607 | Nicola Tamanini | Tomi S. Koivisto and Nicola Tamanini | Ghosts in pure and hybrid formalisms of gravity theories: a unified
analysis | 9 pages | null | 10.1103/PhysRevD.87.104030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the first order formalism of gravitational theories, the spacetime
connection is considered as an independent variable to vary together with the
metric. However, the metric still generates its Levi-Civita connection that
turns out to determine the geodesics of matter. Recently, "hybrid" gravity
theories have been introduced by constructing actions involving both the
independent Palatini connection and the metric Levi-Civita connection. In this
study a method is developed to analyse the field content of such theories, in
particular to determine whether the propagating degrees of freedom are ghosts
or tachyons. New types of second, fourth and sixth order derivative gravity
theories are investigated and the so called f(X) theories are singled out as a
viable class of "hybrid" extensions of General Relativity.
| [
{
"created": "Fri, 12 Apr 2013 11:33:46 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Koivisto",
"Tomi S.",
""
],
[
"Tamanini",
"Nicola",
""
]
] | In the first order formalism of gravitational theories, the spacetime connection is considered as an independent variable to vary together with the metric. However, the metric still generates its Levi-Civita connection that turns out to determine the geodesics of matter. Recently, "hybrid" gravity theories have been introduced by constructing actions involving both the independent Palatini connection and the metric Levi-Civita connection. In this study a method is developed to analyse the field content of such theories, in particular to determine whether the propagating degrees of freedom are ghosts or tachyons. New types of second, fourth and sixth order derivative gravity theories are investigated and the so called f(X) theories are singled out as a viable class of "hybrid" extensions of General Relativity. |
2301.08322 | Alexander Dolgov | E. Arbuzova, A. Dolgov, K. Dutta, R. Rangarajan | Gravitational Baryogenesis: Problems and Possible Resolution | 11 pages, no figures, presented at $6^{th}$ International Conference
on Particle Physics and Astrophysics (ICCPA-2022)}. arXiv admin note: text
overlap with arXiv:1808.08577 | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | The coupling of baryonic current to the derivative of the curvature scalar,
$R$, inherent to gravitational baryogenesis (GBG), leads to a fourth order
differential equation of motion for $R$ instead of the algebraic one of General
Relativity (GR). The fourth-order differential equation is generically
unstable. We consider a possible mechanism of stabilization of GBG by
modification of gravity, introducing an $R^2$-term into the canonical action of
GR.
It is shown that this mechanism allows for stabilization of GBG with bosonic
and fermionic baryon currents. We have established the region of the model
parameters leading to stabilization of $R$. Still, the standard cosmology would
be noticeably modified.
| [
{
"created": "Thu, 19 Jan 2023 21:25:08 GMT",
"version": "v1"
}
] | 2023-01-23 | [
[
"Arbuzova",
"E.",
""
],
[
"Dolgov",
"A.",
""
],
[
"Dutta",
"K.",
""
],
[
"Rangarajan",
"R.",
""
]
] | The coupling of baryonic current to the derivative of the curvature scalar, $R$, inherent to gravitational baryogenesis (GBG), leads to a fourth order differential equation of motion for $R$ instead of the algebraic one of General Relativity (GR). The fourth-order differential equation is generically unstable. We consider a possible mechanism of stabilization of GBG by modification of gravity, introducing an $R^2$-term into the canonical action of GR. It is shown that this mechanism allows for stabilization of GBG with bosonic and fermionic baryon currents. We have established the region of the model parameters leading to stabilization of $R$. Still, the standard cosmology would be noticeably modified. |
2202.12241 | Chun Hing Jackie Liu | Jackie C.H. Liu | A quintessence dynamical dark energy model from ratio gravity | 7 pages, 2 figures, Accepted for publication in EPJC | Eur. Phys. J. C (2022) 82:165 | 10.1140/epjc/s10052-022-10134-1 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Based on the work of ratio gravity developed in 2018, which postulates the
deformation of the cross ratio to associate with the physical model of gravity,
we develop a mechanism to generate dynamical dark energy - a quintessence field
coupled with gravity. Such model causes the dark energy behaving differently in
early and late time universe. In the radiation-dominated-era and
matter-dominated-era, the related analytical solutions of the quintessence
field have an interesting property - starting as a constant field, then
oscillating as the universe expands. By Markov Chain Monte Carlo search of the
parameter space with the local measurement (Type Ia supernovae) in the Bayesian
framework, the probed range of {H_0} (within 1{\sigma}) overlaps the {H_0}
value inferred from Planck CMB dataset by {\Lambda}CDM model.
| [
{
"created": "Tue, 22 Feb 2022 11:45:07 GMT",
"version": "v1"
}
] | 2022-02-25 | [
[
"Liu",
"Jackie C. H.",
""
]
] | Based on the work of ratio gravity developed in 2018, which postulates the deformation of the cross ratio to associate with the physical model of gravity, we develop a mechanism to generate dynamical dark energy - a quintessence field coupled with gravity. Such model causes the dark energy behaving differently in early and late time universe. In the radiation-dominated-era and matter-dominated-era, the related analytical solutions of the quintessence field have an interesting property - starting as a constant field, then oscillating as the universe expands. By Markov Chain Monte Carlo search of the parameter space with the local measurement (Type Ia supernovae) in the Bayesian framework, the probed range of {H_0} (within 1{\sigma}) overlaps the {H_0} value inferred from Planck CMB dataset by {\Lambda}CDM model. |
1603.07744 | Parthapratim Pradhan | Parthapratim Pradhan | Mass Independent Area (or Entropy) and Thermodynamic Volume Products in
Conformal Gravity | Accepted in MPLA | Modern Physics Letters A, Vol. 32 (2017) 1750090 | 10.1142/S0217732317500900 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate the thermodynamic properties of conformal gravity
in four dimensions. We compute the \emph{area(or entropy) functional} relation
for this black hole. We consider both de-Sitter (dS) and anti de-Sitter (AdS)
cases. We derive the \emph{Cosmic-Censorship-Inequality} which is an important
relation in general relativity that relates the total mass of a spacetime to
the area of all the black hole horizons. Local thermodynamic stability is
studied by computing the specific heat. The second order phase transition
occurs at a certain condition. Various type of second order phase structure has
been given for various values of $a$ and the cosmological constant $\Lambda$ in
the Appendix. When $a=0$, one obtains the result of Schwarzschild-dS and
Schwarzschild-AdS cases. In the limit $aM<<1$, one obtains the result of
Grumiller space-time. Where $a$ is non-trivial Rindler parameter or Rindler
acceleration and $M$ is the mass parameter. The \emph{thermodynamic volume
functional} relation is derived in the \emph{extended phase space}, where the
cosmological constant treated as a thermodynamic pressure and its conjugate
variable as a thermodynamic volume. The \emph{mass-independent} area (or
entropy) functional relation and thermodynamic volume functional relation that
we have derived could turn out to be a \emph{universal} quantity.
| [
{
"created": "Thu, 24 Mar 2016 20:37:14 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Apr 2017 14:59:03 GMT",
"version": "v2"
}
] | 2017-05-02 | [
[
"Pradhan",
"Parthapratim",
""
]
] | In this work we investigate the thermodynamic properties of conformal gravity in four dimensions. We compute the \emph{area(or entropy) functional} relation for this black hole. We consider both de-Sitter (dS) and anti de-Sitter (AdS) cases. We derive the \emph{Cosmic-Censorship-Inequality} which is an important relation in general relativity that relates the total mass of a spacetime to the area of all the black hole horizons. Local thermodynamic stability is studied by computing the specific heat. The second order phase transition occurs at a certain condition. Various type of second order phase structure has been given for various values of $a$ and the cosmological constant $\Lambda$ in the Appendix. When $a=0$, one obtains the result of Schwarzschild-dS and Schwarzschild-AdS cases. In the limit $aM<<1$, one obtains the result of Grumiller space-time. Where $a$ is non-trivial Rindler parameter or Rindler acceleration and $M$ is the mass parameter. The \emph{thermodynamic volume functional} relation is derived in the \emph{extended phase space}, where the cosmological constant treated as a thermodynamic pressure and its conjugate variable as a thermodynamic volume. The \emph{mass-independent} area (or entropy) functional relation and thermodynamic volume functional relation that we have derived could turn out to be a \emph{universal} quantity. |
1606.00702 | Sudipto Roy | Sudipto Roy | Time Evolution of the Matter Content of the Expanding Universe in the
Framework of Brans-Dicke Gravity | 23 pages, 16 figures, 1 table and 54 equations in the present
version. Changes made to the older version: 1)Some errors have been
corrected, 2) Three figures have been corrected and their interpretations
have been modified, 3) New references have been added, 4) Some explanations
have been re-written | Research in Astronomy and Astrophysics (RAA), Vol. 19, No. 4,
61(14pp), 2019 | 10.1088/1674-4527/19/4/61 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A cosmological model has been constructed in the framework of Brans-Dicke
(BD) gravity, based on an inter-conversion between matter and dark energy, for
a spatially flat universe in the era of pressureless dust. To account for the
non-conservartion of the matter content, a function of time f(t) has been
arbitrarily put into the expression of the density of matter. By definition,
f(t) is proportional to the matter content of the universe. Using suitable
ansazes for scale factor and scalar field, the functional form of f(t) has been
determined from the BD field equations. The scale factor has been so chosen
that it would cause a signature flip of the deceleration parameter with time.
The function f(t) decreases monotonically with time, indicating a
transformation of matter into dark energy. Time dependence of the proportions
of matter and dark energy of the universe has been determined. The effect of
non-conservation of the matter content upon various cosmological parameters has
been explored in the present study. Two models of matter-energy interaction
have been proposed and f(t) has been expressed as a function of their
interaction term. The dark energy equation-of-state (EoS) parameter has been
expressed and analyzed in terms of f(t).
| [
{
"created": "Thu, 26 May 2016 20:37:23 GMT",
"version": "v1"
},
{
"created": "Sun, 22 Jul 2018 04:51:28 GMT",
"version": "v2"
},
{
"created": "Tue, 28 Apr 2020 08:58:39 GMT",
"version": "v3"
}
] | 2020-05-01 | [
[
"Roy",
"Sudipto",
""
]
] | A cosmological model has been constructed in the framework of Brans-Dicke (BD) gravity, based on an inter-conversion between matter and dark energy, for a spatially flat universe in the era of pressureless dust. To account for the non-conservartion of the matter content, a function of time f(t) has been arbitrarily put into the expression of the density of matter. By definition, f(t) is proportional to the matter content of the universe. Using suitable ansazes for scale factor and scalar field, the functional form of f(t) has been determined from the BD field equations. The scale factor has been so chosen that it would cause a signature flip of the deceleration parameter with time. The function f(t) decreases monotonically with time, indicating a transformation of matter into dark energy. Time dependence of the proportions of matter and dark energy of the universe has been determined. The effect of non-conservation of the matter content upon various cosmological parameters has been explored in the present study. Two models of matter-energy interaction have been proposed and f(t) has been expressed as a function of their interaction term. The dark energy equation-of-state (EoS) parameter has been expressed and analyzed in terms of f(t). |
1405.3257 | Horace W. Crater | Horace W. Crater, Luca Lusanna | Non-Inertial Frames in Minkowski Space-Time, Accelerated either
Mathematical or Dynamical Observers and Comments on Non-Inertial Relativistic
Quantum Mechanics | null | null | 10.1142/S0219887814500868 | null | gr-qc hep-th physics.class-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After a review of the existing theory of non-inertial frames and mathematical
observers in Minkowski space-time we give the explicit expression of a family
of such frames obtained from the inertial ones by means of point-dependent
Lorentz transformations as suggested by the locality principle. These
non-inertial frames have non-Euclidean 3-spaces and contain the differentially
rotating ones in Euclidean 3-spaces as a subcase. Then we discuss how to
replace mathematical accelerated observers with dynamical ones (their
world-lines belong to interacting particles in an isolated system) and of how
to define Unruh-DeWitt detectors without using mathematical Rindler uniformly
accelerated observers. Also some comments are done on the transition from
relativistic classical mechanics to relativistic quantum mechanics in
non-inertial frames.
| [
{
"created": "Fri, 9 May 2014 20:10:03 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Crater",
"Horace W.",
""
],
[
"Lusanna",
"Luca",
""
]
] | After a review of the existing theory of non-inertial frames and mathematical observers in Minkowski space-time we give the explicit expression of a family of such frames obtained from the inertial ones by means of point-dependent Lorentz transformations as suggested by the locality principle. These non-inertial frames have non-Euclidean 3-spaces and contain the differentially rotating ones in Euclidean 3-spaces as a subcase. Then we discuss how to replace mathematical accelerated observers with dynamical ones (their world-lines belong to interacting particles in an isolated system) and of how to define Unruh-DeWitt detectors without using mathematical Rindler uniformly accelerated observers. Also some comments are done on the transition from relativistic classical mechanics to relativistic quantum mechanics in non-inertial frames. |
1703.03344 | Burkhard Kleihaus | Christian Hoffmann (1 and 2), Theodora Ioannidou (3), Sarah Kahlen
(1), Burkhard Kleihaus (1) and Jutta Kunz (1) ((1) University of Oldenburg,
Germany, (2) University of Massachusetts, Amherst, USA (3) Aristotle
University of Thessaloniki, Greece) | Spontaneous Symmetry Breaking in Wormholes Spacetimes with Matter | 21 pages, 8 figures | Phys. Rev. D 95, 084010 (2017) | 10.1103/PhysRevD.95.084010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When bosonic matter in the form of a complex scalar field is added to Ellis
wormholes, the phenomenon of spontaneous symmetry breaking is observed.
Symmetric solutions possess full reflection symmetry with respect to the radial
coordinate of the two asymptotically flat spacetime regions connected by the
wormhole, whereas asymmetric solutions do not possess this symmetry. Depending
on the size of the throat, at bifurcation points pairs of asymmetric solutions
arise from or merge with the symmetric solutions. These asymmetric solutions
are energetically favoured. When the backreaction of the boson field is taken
into account, this phenomenon is retained. Moreover, in a certain region of the
solution space both symmetric and asymmetric solutions exhibit a transition
from single throat to double throat configurations.
| [
{
"created": "Thu, 9 Mar 2017 17:04:19 GMT",
"version": "v1"
}
] | 2017-04-12 | [
[
"Hoffmann",
"Christian",
"",
"1 and 2"
],
[
"Ioannidou",
"Theodora",
""
],
[
"Kahlen",
"Sarah",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | When bosonic matter in the form of a complex scalar field is added to Ellis wormholes, the phenomenon of spontaneous symmetry breaking is observed. Symmetric solutions possess full reflection symmetry with respect to the radial coordinate of the two asymptotically flat spacetime regions connected by the wormhole, whereas asymmetric solutions do not possess this symmetry. Depending on the size of the throat, at bifurcation points pairs of asymmetric solutions arise from or merge with the symmetric solutions. These asymmetric solutions are energetically favoured. When the backreaction of the boson field is taken into account, this phenomenon is retained. Moreover, in a certain region of the solution space both symmetric and asymmetric solutions exhibit a transition from single throat to double throat configurations. |
2106.00605 | Brendan O'Brien | Brendan O'Brien, Marek Szczepanczyk, V. Gayathri, Imre Bartos,
Gabriele Vedovato, Giovanni Prodi, Guenakh Mitselmakher, Sergey Klimenko | Detection of LIGO-Virgo binary black holes in the pair-instability mass
gap | 10 pages, 6 figures, 2 tables | Phys. Rev. D 104, 082003 (2021) | 10.1103/PhysRevD.104.082003 | LIGO-P2100128 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By probing the population of binary black hole (BBH) mergers detected by
LIGO-Virgo, we can infer properties about the underlying black hole formation
channels. A mechanism known as pair-instability (PI) supernova is expected to
prevent the formation of black holes from stellar collapse with mass greater
than $\sim 40-65\,M_\odot$ and less than $\sim 120\,M_\odot$. Any BBH merger
detected by LIGO-Virgo with a component black hole in this gap, known as the PI
mass gap, likely originated from an alternative formation channel. Here, we
firmly establish GW190521 as an outlier to the stellar-mass BBH population if
the PI mass gap begins at or below $65\, M_{\odot}$. In addition, for a PI
lower boundary of $40-50\, M_{\odot}$, we find it unlikely that the remaining
distribution of detected BBH events, excluding GW190521, is consistent with the
stellar-mass population.
| [
{
"created": "Tue, 1 Jun 2021 16:15:39 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Jun 2021 15:56:29 GMT",
"version": "v2"
}
] | 2021-10-13 | [
[
"O'Brien",
"Brendan",
""
],
[
"Szczepanczyk",
"Marek",
""
],
[
"Gayathri",
"V.",
""
],
[
"Bartos",
"Imre",
""
],
[
"Vedovato",
"Gabriele",
""
],
[
"Prodi",
"Giovanni",
""
],
[
"Mitselmakher",
"Guenakh",
""
... | By probing the population of binary black hole (BBH) mergers detected by LIGO-Virgo, we can infer properties about the underlying black hole formation channels. A mechanism known as pair-instability (PI) supernova is expected to prevent the formation of black holes from stellar collapse with mass greater than $\sim 40-65\,M_\odot$ and less than $\sim 120\,M_\odot$. Any BBH merger detected by LIGO-Virgo with a component black hole in this gap, known as the PI mass gap, likely originated from an alternative formation channel. Here, we firmly establish GW190521 as an outlier to the stellar-mass BBH population if the PI mass gap begins at or below $65\, M_{\odot}$. In addition, for a PI lower boundary of $40-50\, M_{\odot}$, we find it unlikely that the remaining distribution of detected BBH events, excluding GW190521, is consistent with the stellar-mass population. |
2006.04818 | Carlos O. Lousto | Carlos O. Lousto and James Healy | Exploring the small mass ratio binary black hole merger via Zeno's
dichotomy approach | 6 pages, 4 figures | Phys. Rev. Lett. 125, 191102 (2020) | 10.1103/PhysRevLett.125.191102 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a sequence of binary black hole simulations with increasingly
small mass ratios, reaching to a 128:1 binary that displays 13 orbits before
merger. Based on a detailed convergence study of the $q=m_1/m_2=1/15$
nonspinning case, we apply additional mesh refinements levels around the
smaller hole horizon to reach successively the $q=1/32$, $q=1/64$, and
$q=1/128$ cases. Roughly a linear computational resources scaling with $1/q$ is
observed on 8-nodes simulations. We compute the remnant properties of the
merger: final mass, spin, and recoil velocity, finding precise consistency
between horizon and radiation measures. We also compute the gravitational
waveforms: its peak frequency, amplitude, and luminosity. We compare those
values with predictions of the corresponding phenomenological formulas,
reproducing the particle limit within 2%, and we then use the new results to
improve their fitting coefficients.
| [
{
"created": "Mon, 8 Jun 2020 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Sep 2020 16:52:05 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Oct 2020 13:25:04 GMT",
"version": "v3"
}
] | 2020-11-11 | [
[
"Lousto",
"Carlos O.",
""
],
[
"Healy",
"James",
""
]
] | We perform a sequence of binary black hole simulations with increasingly small mass ratios, reaching to a 128:1 binary that displays 13 orbits before merger. Based on a detailed convergence study of the $q=m_1/m_2=1/15$ nonspinning case, we apply additional mesh refinements levels around the smaller hole horizon to reach successively the $q=1/32$, $q=1/64$, and $q=1/128$ cases. Roughly a linear computational resources scaling with $1/q$ is observed on 8-nodes simulations. We compute the remnant properties of the merger: final mass, spin, and recoil velocity, finding precise consistency between horizon and radiation measures. We also compute the gravitational waveforms: its peak frequency, amplitude, and luminosity. We compare those values with predictions of the corresponding phenomenological formulas, reproducing the particle limit within 2%, and we then use the new results to improve their fitting coefficients. |
2306.08547 | Mustafa Saeed | Mustafa Saeed and Viqar Husain | Ising-like models on Euclidean black holes | 13 pages, 8 figures, 1 table | Class. Quantum Grav. 41 015002 (2024) | 10.1088/1361-6382/ad0b9a | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study spin models on Euclidean black hole backgrounds. These resemble the
Ising model, but are inhomogeneous with two parameters, the black hole mass and
the cosmological constant. We use Monte-Carlo methods to study macroscopic
properties of these systems for Schwarzschild and anti-deSitter black holes in
four and five dimensions for spin-1/2 and spin-1. We find in every case that
increasing the black hole mass causes the spins to undergo a second order phase
transition from disorder to order and that the phase transition occurs at
sub-Planckian black hole mass.
| [
{
"created": "Wed, 14 Jun 2023 14:46:42 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Saeed",
"Mustafa",
""
],
[
"Husain",
"Viqar",
""
]
] | We study spin models on Euclidean black hole backgrounds. These resemble the Ising model, but are inhomogeneous with two parameters, the black hole mass and the cosmological constant. We use Monte-Carlo methods to study macroscopic properties of these systems for Schwarzschild and anti-deSitter black holes in four and five dimensions for spin-1/2 and spin-1. We find in every case that increasing the black hole mass causes the spins to undergo a second order phase transition from disorder to order and that the phase transition occurs at sub-Planckian black hole mass. |
gr-qc/9405063 | Susan M. Scott | Susan M. Scott and Peter Szekeres | The abstract boundary---a new approach to singularities of manifolds | 40 pages (amslatex) + 5 uuencoded figures (A postscript version is
also available on http://einstein.anu.edu.au/), CMA Maths. Research Report
No. MRR028-94 | J.Geom.Phys.13:223-253,1994 | 10.1016/0393-0440(94)90032-9 | null | gr-qc | null | A new scheme is proposed for dealing with the problem of singularities in
General Relativity. The proposal is, however, much more general than this. It
can be used to deal with manifolds of any dimension which are endowed with
nothing more than an affine connection, and requires a family \calc\ of curves
satisfying a {\em bounded parameter property} to be specified at the outset.
All affinely parametrised geodesics are usually included in this family, but
different choices of family \calc\ will in general lead to different
singularity structures. Our key notion is the {\em abstract boundary\/} or {\em
$a$-boundary\/} of a manifold, which is defined for any manifold \calm\ and is
independent of both the affine connection and the chosen family \calc\ of
curves. The $a$-boundary is made up of equivalence classes of boundary points
of \calm\ in all possible open embeddings. It is shown that for a
pseudo-Riemannian manifold $(\calm,g)$ with a specified family \calc\ of
curves, the abstract boundary points can then be split up into four main
categories---regular, points at infinity, unapproachable points and
singularities. Precise definitions are also provided for the notions of a {\em
removable singularity} and a {\em directional singularity}. The
pseudo-Riemannian manifold will be said to be singularity-free if its abstract
boundary contains no singularities. The scheme passes a number of tests
required of any theory of singularities. For instance, it is shown that all
compact manifolds are singularity-free, irrespective of the metric and chosen
family \calc.
| [
{
"created": "Thu, 26 May 1994 20:38:55 GMT",
"version": "v1"
}
] | 2010-12-03 | [
[
"Scott",
"Susan M.",
""
],
[
"Szekeres",
"Peter",
""
]
] | A new scheme is proposed for dealing with the problem of singularities in General Relativity. The proposal is, however, much more general than this. It can be used to deal with manifolds of any dimension which are endowed with nothing more than an affine connection, and requires a family \calc\ of curves satisfying a {\em bounded parameter property} to be specified at the outset. All affinely parametrised geodesics are usually included in this family, but different choices of family \calc\ will in general lead to different singularity structures. Our key notion is the {\em abstract boundary\/} or {\em $a$-boundary\/} of a manifold, which is defined for any manifold \calm\ and is independent of both the affine connection and the chosen family \calc\ of curves. The $a$-boundary is made up of equivalence classes of boundary points of \calm\ in all possible open embeddings. It is shown that for a pseudo-Riemannian manifold $(\calm,g)$ with a specified family \calc\ of curves, the abstract boundary points can then be split up into four main categories---regular, points at infinity, unapproachable points and singularities. Precise definitions are also provided for the notions of a {\em removable singularity} and a {\em directional singularity}. The pseudo-Riemannian manifold will be said to be singularity-free if its abstract boundary contains no singularities. The scheme passes a number of tests required of any theory of singularities. For instance, it is shown that all compact manifolds are singularity-free, irrespective of the metric and chosen family \calc. |
2011.00945 | Yannick Herfray | Yannick Herfray and Carlos Scarinci | Einstein gravity as a gauge theory for the conformal group | 18 pages, no figures. This is the version accepted for publication in
Classical and Quantum Gravity | Class. Quantum Grav. 39 025011 (2022) | 10.1088/1361-6382/ac3e53 | null | gr-qc hep-th math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity in dimension $n = p + q$ can be formulated as a gauge
theory for the conformal group $SO(p+1,q+1)$, along with an additional field
reducing the structure group down to the Poincar\'e group $ISO(p,q)$. In this
paper, we propose a new variational principle for Einstein geometry which
realizes this fact. Importantly, as opposed to previous treatments in the
literature, our action functional gives first order field equations and does
not require supplementary constraints on gauge fields, such as
torsion-freeness.
Our approach is based on the "first order formulation" of conformal tractor
geometry. Accordingly, it provides a straightforward variational derivation of
the tractor version of the Einstein equation. To achieve this, we review the
standard theory of tractor geometry with a gauge theory perspective, defining
the tractor bundle a priori in terms of an abstract principal bundle and
providing an identification with the standard conformal tractor bundle via a
dynamical soldering form. This can also be seen as a generalization of the so
called Cartan-Palatini formulation of General Relativity in which the
"internal" orthogonal group $SO(p,q)$ is extended to an appropriate parabolic
subgroup $P\subset SO(p+1,q+1)$ of the conformal group.
| [
{
"created": "Mon, 2 Nov 2020 12:59:09 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2022 07:57:32 GMT",
"version": "v2"
}
] | 2022-04-01 | [
[
"Herfray",
"Yannick",
""
],
[
"Scarinci",
"Carlos",
""
]
] | General Relativity in dimension $n = p + q$ can be formulated as a gauge theory for the conformal group $SO(p+1,q+1)$, along with an additional field reducing the structure group down to the Poincar\'e group $ISO(p,q)$. In this paper, we propose a new variational principle for Einstein geometry which realizes this fact. Importantly, as opposed to previous treatments in the literature, our action functional gives first order field equations and does not require supplementary constraints on gauge fields, such as torsion-freeness. Our approach is based on the "first order formulation" of conformal tractor geometry. Accordingly, it provides a straightforward variational derivation of the tractor version of the Einstein equation. To achieve this, we review the standard theory of tractor geometry with a gauge theory perspective, defining the tractor bundle a priori in terms of an abstract principal bundle and providing an identification with the standard conformal tractor bundle via a dynamical soldering form. This can also be seen as a generalization of the so called Cartan-Palatini formulation of General Relativity in which the "internal" orthogonal group $SO(p,q)$ is extended to an appropriate parabolic subgroup $P\subset SO(p+1,q+1)$ of the conformal group. |
1311.4912 | Sergei Kopeikin | Sergei M. Kopeikin (University of Missouri, USA) | Einstein's equivalence principle in cosmology | 52 pages, no figures, references added | null | null | null | gr-qc astro-ph.CO physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study physical consequences of the Einstein equivalence principle (EEP)
for a Hubble observer in FLRW universe. We introduce the local inertial
coordinates with the help of a special conformal transformation. The local
inertial metric is Minkowski-flat and materialized by a congruence of time-like
geodesics of static observers. The static observers are equipped with the ideal
clocks measuring the proper time that is synchronized with the clocks of the
Hubble observer. The local inertial metric is used for physical measurements of
spacetime intervals with the ideal clocks and rulers. The special conformal
transformation preserves null geodesics but does not keep invariant time-like
geodesics. Moreover, it makes the rate of the local time coordinate dependent
on velocity of the particle which makes impossible to rich the uniform
parameterization of the world lines of static observers and light geodesics
with a single parameter - they differ by the conformal factor of FLRW metric.
It tells us that the metric on the light cone is not Minkowski-flat but depends
on the scale factor of FLRW universe and it can be interpreted as a weak
violation of EEP for photons. The importance of this violation for
gravitational physics is that some of local experiments conducted with
freely-propagating electromagnetic waves may be sensitive to the Hubble
expansion. We show that the Hubble constant H can be measured within the solar
system by means of high-precision spacecraft Doppler tracking as a blue shift
of frequency of radio waves circulating in the Earth-spacecraft radio link. We
also analyze the behavior of the standing wave in a microwave resonator and
show that the standing wave is insensitive to the Hubble expansion.
| [
{
"created": "Tue, 19 Nov 2013 22:38:44 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Nov 2013 04:40:21 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Feb 2014 15:44:33 GMT",
"version": "v3"
}
] | 2014-02-19 | [
[
"Kopeikin",
"Sergei M.",
"",
"University of Missouri, USA"
]
] | We study physical consequences of the Einstein equivalence principle (EEP) for a Hubble observer in FLRW universe. We introduce the local inertial coordinates with the help of a special conformal transformation. The local inertial metric is Minkowski-flat and materialized by a congruence of time-like geodesics of static observers. The static observers are equipped with the ideal clocks measuring the proper time that is synchronized with the clocks of the Hubble observer. The local inertial metric is used for physical measurements of spacetime intervals with the ideal clocks and rulers. The special conformal transformation preserves null geodesics but does not keep invariant time-like geodesics. Moreover, it makes the rate of the local time coordinate dependent on velocity of the particle which makes impossible to rich the uniform parameterization of the world lines of static observers and light geodesics with a single parameter - they differ by the conformal factor of FLRW metric. It tells us that the metric on the light cone is not Minkowski-flat but depends on the scale factor of FLRW universe and it can be interpreted as a weak violation of EEP for photons. The importance of this violation for gravitational physics is that some of local experiments conducted with freely-propagating electromagnetic waves may be sensitive to the Hubble expansion. We show that the Hubble constant H can be measured within the solar system by means of high-precision spacecraft Doppler tracking as a blue shift of frequency of radio waves circulating in the Earth-spacecraft radio link. We also analyze the behavior of the standing wave in a microwave resonator and show that the standing wave is insensitive to the Hubble expansion. |
gr-qc/0201005 | Angelo Tartaglia | A. Tartaglia | Angular momentum effects in weak gravitational fields | LATEX, 8 pages | Europhys.Lett.57:167-173,2002 | 10.1209/epl/i2002-00334-5 | null | gr-qc | null | It is shown that, contrary to what is normally expected, it is possible to
have angular momentum effects on the geometry of space time at the laboratory
scale, much bigger than the purely Newtonian effects. This is due to the fact
that the ratio between the angular momentum of a body and its mass, expressed
as a length, is easily greater than the mass itself, again expressed as a
length.
| [
{
"created": "Wed, 2 Jan 2002 18:10:36 GMT",
"version": "v1"
}
] | 2010-12-17 | [
[
"Tartaglia",
"A.",
""
]
] | It is shown that, contrary to what is normally expected, it is possible to have angular momentum effects on the geometry of space time at the laboratory scale, much bigger than the purely Newtonian effects. This is due to the fact that the ratio between the angular momentum of a body and its mass, expressed as a length, is easily greater than the mass itself, again expressed as a length. |
1608.07589 | Sylvia Zhu | Sylvia J. Zhu, Maria Alessandra Papa, Heinz-Bernd Eggenstein, Reinhard
Prix, Karl Wette, Bruce Allen, Oliver Bock, David Keitel, Badri Krishnan,
Bernd Machenschalk, Miroslav Shaltev, Xavier Siemens | An Einstein@home search for continuous gravitational waves from
Cassiopeia A | 29 pages, 7 figures, 3 tables | Phys. Rev. D 94, 082008 (2016) | 10.1103/PhysRevD.94.082008 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report the results of a directed search for continuous gravitational-wave
emission in a broad frequency range (between 50 and 1000 Hz) from the central
compact object of the supernova remnant Cassiopeia A (Cas A). The data comes
from the sixth science run of LIGO and the search is performed on the volunteer
distributed computing network Einstein@Home. We find no significant signal
candidate, and set the most constraining upper limits to date on the
gravitational-wave emission from Cas A, which beat the indirect age-based upper
limit across the entire search range. At around 170 Hz (the most sensitive
frequency range), we set 90% confidence upper limits on the gravitational wave
amplitude $h_0$ of $\sim\!\!~2.9\times 10^{-25}$, roughly twice as constraining
as the upper limits from previous searches on Cas A. The upper limits can also
be expressed as constraints on the ellipticity of Cas A; with a few reasonable
assumptions, we show that at gravitational-wave frequencies greater than
300~Hz, we can exclude an ellipticity of $\gtrsim\!\!~10^{-5}$.
| [
{
"created": "Fri, 26 Aug 2016 20:10:15 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Sep 2016 08:50:44 GMT",
"version": "v2"
}
] | 2016-11-02 | [
[
"Zhu",
"Sylvia J.",
""
],
[
"Papa",
"Maria Alessandra",
""
],
[
"Eggenstein",
"Heinz-Bernd",
""
],
[
"Prix",
"Reinhard",
""
],
[
"Wette",
"Karl",
""
],
[
"Allen",
"Bruce",
""
],
[
"Bock",
"Oliver",
""
],
... | We report the results of a directed search for continuous gravitational-wave emission in a broad frequency range (between 50 and 1000 Hz) from the central compact object of the supernova remnant Cassiopeia A (Cas A). The data comes from the sixth science run of LIGO and the search is performed on the volunteer distributed computing network Einstein@Home. We find no significant signal candidate, and set the most constraining upper limits to date on the gravitational-wave emission from Cas A, which beat the indirect age-based upper limit across the entire search range. At around 170 Hz (the most sensitive frequency range), we set 90% confidence upper limits on the gravitational wave amplitude $h_0$ of $\sim\!\!~2.9\times 10^{-25}$, roughly twice as constraining as the upper limits from previous searches on Cas A. The upper limits can also be expressed as constraints on the ellipticity of Cas A; with a few reasonable assumptions, we show that at gravitational-wave frequencies greater than 300~Hz, we can exclude an ellipticity of $\gtrsim\!\!~10^{-5}$. |
gr-qc/9310008 | null | G. Lifschytz and M. Ortiz | Scalar field quantization on the 2+1 dimensional black hole background | CTP 2243, 24 pages, RevTex. (The backreaction section is extended,
and some confusing notation has been changed) | Phys.Rev.D49:1929-1943,1994 | 10.1103/PhysRevD.49.1929 | null | gr-qc hep-th | null | The quantization of a massless conformally coupled scalar field on the 2+1
dimensional Anti de Sitter black hole background is presented. The Green's
function is calculated, using the fact that the black hole is Anti de Sitter
space with points identified, and taking into account the fact that the black
hole spacetime is not globally hyperbolic. It is shown that the Green's
function calculated in this way is the Hartle-Hawking Green's function. The
Green's function is used to compute $\langle T^\mu_\nu \rangle$, which is
regular on the black hole horizon, and diverges at the singularity. A particle
detector response function outside the horizon is also calculated and shown to
be a fermi type distribution. The back-reaction from $\langle T_{\mu\nu}
\rangle$ is calculated exactly and is shown to give rise to a curvature
singularity at $r=0$ and to shift the horizon outwards. For $M=0$ a horizon
develops, shielding the singularity. Some speculations about the endpoint of
evaporation are discussed.
| [
{
"created": "Mon, 4 Oct 1993 13:46:34 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Oct 1993 13:58:25 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Nov 1993 19:19:37 GMT",
"version": "v3"
}
] | 2009-09-25 | [
[
"Lifschytz",
"G.",
""
],
[
"Ortiz",
"M.",
""
]
] | The quantization of a massless conformally coupled scalar field on the 2+1 dimensional Anti de Sitter black hole background is presented. The Green's function is calculated, using the fact that the black hole is Anti de Sitter space with points identified, and taking into account the fact that the black hole spacetime is not globally hyperbolic. It is shown that the Green's function calculated in this way is the Hartle-Hawking Green's function. The Green's function is used to compute $\langle T^\mu_\nu \rangle$, which is regular on the black hole horizon, and diverges at the singularity. A particle detector response function outside the horizon is also calculated and shown to be a fermi type distribution. The back-reaction from $\langle T_{\mu\nu} \rangle$ is calculated exactly and is shown to give rise to a curvature singularity at $r=0$ and to shift the horizon outwards. For $M=0$ a horizon develops, shielding the singularity. Some speculations about the endpoint of evaporation are discussed. |
gr-qc/0507104 | Olga Babourova Valer'evna | Olga V. Babourova | Modified Friedmann-Leme\^{\i}tre equation for dilaton-spin dark matter
in Weyl-Cartan space | LaTex, 6 pages, no figures, gc.sty is used | Grav.Cosmol.10:121-126,2004 | null | null | gr-qc astro-ph | null | It is proposed to consider dark matter as a perfect dilaton-spin fluid (with
particles endowed with intrinsic spin and dilaton charge) in the framework of a
gravitational theory with a Weyl-Cartan geometrical structure. The modified
Friedmann-Lema\^{\i}tre equation (with a cosmological term) is obtained for the
homogeneous and isotropic Universe filled with the dilaton-spin dark matter. On
the basis of this equation, we develop a nonsingular cosmological model
starting from an inflation-like stage (for super-stiff equation of state),
passing radiation-dominated and matter-dominated decelerating stages and
turning into a post-Friedmann accelerating era.
| [
{
"created": "Mon, 25 Jul 2005 10:24:30 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Babourova",
"Olga V.",
""
]
] | It is proposed to consider dark matter as a perfect dilaton-spin fluid (with particles endowed with intrinsic spin and dilaton charge) in the framework of a gravitational theory with a Weyl-Cartan geometrical structure. The modified Friedmann-Lema\^{\i}tre equation (with a cosmological term) is obtained for the homogeneous and isotropic Universe filled with the dilaton-spin dark matter. On the basis of this equation, we develop a nonsingular cosmological model starting from an inflation-like stage (for super-stiff equation of state), passing radiation-dominated and matter-dominated decelerating stages and turning into a post-Friedmann accelerating era. |
0707.4552 | Farook Rahaman | F. Rahaman, M. Sarker and M. Kalam | Wormhole and C-field: Revisited | 10 pages and 5 figures, Submitted to Nuovo Cimento B after minor
revisions | Nuovo Cim.B122:389-396,2007 | 10.1393/ncb/i2007-10372-0 | null | gr-qc | null | Recently, Rahaman et al [ Nuovo.Cim 119B, 1115(2004)] have shown that the
static spherically symmetric solutions in presence of C-field give rise to
wormhole geometry. We highlight some of the characteristics of this wormhole,
which have not been considered in the previous study.
| [
{
"created": "Tue, 31 Jul 2007 07:47:40 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Rahaman",
"F.",
""
],
[
"Sarker",
"M.",
""
],
[
"Kalam",
"M.",
""
]
] | Recently, Rahaman et al [ Nuovo.Cim 119B, 1115(2004)] have shown that the static spherically symmetric solutions in presence of C-field give rise to wormhole geometry. We highlight some of the characteristics of this wormhole, which have not been considered in the previous study. |
1704.08373 | Thomas Callister | Thomas Callister, A. Sylvia Biscoveanu, Nelson Christensen,
Maximiliano Isi, Andrew Matas, Olivier Minazzoli, Tania Regimbau, Mairi
Sakellariadou, Jay Tasson, and Eric Thrane | Polarization-based Tests of Gravity with the Stochastic
Gravitational-Wave Background | 24 pages, 20 figures; Accepted by PRX. This version includes major
changes in response to referee comments and corrects an error in Eq. E2 | Phys. Rev. X 7, 041058 (2017) | 10.1103/PhysRevX.7.041058 | LIGO DCC# P1700059; KCL report number KCL-PH-TH/2017-25 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct observation of gravitational waves with Advanced LIGO and Advanced
Virgo offers novel opportunities to test general relativity in strong-field,
highly dynamical regimes. One such opportunity is the measurement of
gravitational-wave polarizations. While general relativity predicts only two
tensor gravitational-wave polarizations, general metric theories of gravity
allow for up to four additional vector and scalar modes. The detection of these
alternative polarizations would represent a clear violation of general
relativity. The LIGO-Virgo detection of the binary black hole merger GW170814
has recently offered the first direct constraints on the polarization of
gravitational waves. The current generation of ground-based detectors, however,
is limited in its ability to sensitively determine the polarization content of
transient gravitational-wave signals. Observation of the stochastic
gravitational-wave background, in contrast, offers a means of directly
measuring generic gravitational-wave polarizations. The stochastic background,
arising from the superposition of many individually unresolvable
gravitational-wave signals, may be detectable by Advanced LIGO at
design-sensitivity. In this paper, we present a Bayesian method with which to
detect and characterize the polarization of the stochastic background. We
explore prospects for estimating parameters of the background, and quantify the
limits that Advanced LIGO can place on vector and scalar polarizations in the
absence of a detection. Finally, we investigate how the introduction of new
terrestrial detectors like Advanced Virgo aid in our ability to detect or
constrain alternative polarizations in the stochastic background. We find that,
although the addition of Advanced Virgo does not notably improve detection
prospects, it may dramatically improve our ability to estimate the parameters
of backgrounds of mixed polarization.
| [
{
"created": "Wed, 26 Apr 2017 22:55:16 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Oct 2017 17:22:09 GMT",
"version": "v2"
}
] | 2017-12-13 | [
[
"Callister",
"Thomas",
""
],
[
"Biscoveanu",
"A. Sylvia",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Isi",
"Maximiliano",
""
],
[
"Matas",
"Andrew",
""
],
[
"Minazzoli",
"Olivier",
""
],
[
"Regimbau",
"Tania",
... | The direct observation of gravitational waves with Advanced LIGO and Advanced Virgo offers novel opportunities to test general relativity in strong-field, highly dynamical regimes. One such opportunity is the measurement of gravitational-wave polarizations. While general relativity predicts only two tensor gravitational-wave polarizations, general metric theories of gravity allow for up to four additional vector and scalar modes. The detection of these alternative polarizations would represent a clear violation of general relativity. The LIGO-Virgo detection of the binary black hole merger GW170814 has recently offered the first direct constraints on the polarization of gravitational waves. The current generation of ground-based detectors, however, is limited in its ability to sensitively determine the polarization content of transient gravitational-wave signals. Observation of the stochastic gravitational-wave background, in contrast, offers a means of directly measuring generic gravitational-wave polarizations. The stochastic background, arising from the superposition of many individually unresolvable gravitational-wave signals, may be detectable by Advanced LIGO at design-sensitivity. In this paper, we present a Bayesian method with which to detect and characterize the polarization of the stochastic background. We explore prospects for estimating parameters of the background, and quantify the limits that Advanced LIGO can place on vector and scalar polarizations in the absence of a detection. Finally, we investigate how the introduction of new terrestrial detectors like Advanced Virgo aid in our ability to detect or constrain alternative polarizations in the stochastic background. We find that, although the addition of Advanced Virgo does not notably improve detection prospects, it may dramatically improve our ability to estimate the parameters of backgrounds of mixed polarization. |
0705.1756 | Christian Boehmer | C. G. Boehmer, T. Harko | On Einstein clusters as galactic dark matter halos | MNRAS LaTeX, 7 pages, accepted by MNRAS; reference added | Mon.Not.Roy.Astron.Soc.379:393-398,2007 | 10.1111/j.1365-2966.2007.11977.x | null | gr-qc astro-ph | null | We consider global and gravitational lensing properties of the recently
suggested Einstein clusters of WIMPs as galactic dark matter halos. Being
tangential pressure dominated, Einstein clusters are strongly anisotropic
systems which can describe any galactic rotation curve by specifying the
anisotropy. Due to this property, Einstein clusters may be considered as dark
matter candidates. We analyse the stability of the Einstein clusters against
both radial and non-radial pulsations, and we show that the Einstein clusters
are dynamically stable. With the use of the Buchdahl type inequalities for
anisotropic bodies, we derive upper limits on the velocity of the particles
defining the cluster. These limits are consistent with those obtained from
stability considerations. The study of light deflection shows that the
gravitational lensing effect is slightly smaller for the Einstein clusters, as
compared to the singular isothermal density sphere model for dark matter.
Therefore lensing observations may discriminate, at least in principle, between
Einstein cluster and other dark matter models.
| [
{
"created": "Sat, 12 May 2007 09:55:12 GMT",
"version": "v1"
},
{
"created": "Thu, 24 May 2007 22:16:12 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Boehmer",
"C. G.",
""
],
[
"Harko",
"T.",
""
]
] | We consider global and gravitational lensing properties of the recently suggested Einstein clusters of WIMPs as galactic dark matter halos. Being tangential pressure dominated, Einstein clusters are strongly anisotropic systems which can describe any galactic rotation curve by specifying the anisotropy. Due to this property, Einstein clusters may be considered as dark matter candidates. We analyse the stability of the Einstein clusters against both radial and non-radial pulsations, and we show that the Einstein clusters are dynamically stable. With the use of the Buchdahl type inequalities for anisotropic bodies, we derive upper limits on the velocity of the particles defining the cluster. These limits are consistent with those obtained from stability considerations. The study of light deflection shows that the gravitational lensing effect is slightly smaller for the Einstein clusters, as compared to the singular isothermal density sphere model for dark matter. Therefore lensing observations may discriminate, at least in principle, between Einstein cluster and other dark matter models. |
1110.2006 | Stefanos Aretakis | Stefanos Aretakis | Decay of Axisymmetric Solutions of the Wave Equation on Extreme Kerr
Backgrounds | 47 pages, 17 figures | J. Functional Analysis, 263 (2012), 2770-2831 | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Cauchy problem for the wave equation on extreme Kerr backgrounds
under axisymmetry. Specifically, we consider regular axisymmetric initial data
prescribed on a Cauchy hypersurface S which connects the future event horizon
with spacelike or null infinity, and we solve the linear wave equation on the
domain of dependence of S. We show that the spacetime integral of an
energy-type density is bounded by the initial conserved flux corresponding to
the stationary Killing field T, and we derive boundedness of the non-degenerate
energy flux corresponding to a globally timelike vector field N. Finally, we
prove uniform pointwise boundedness and power-law decay for solutions to the
wave equation. Our estimates hold up to and including the event horizon. We
remark that these results do not yield decay for the derivatives transversal to
the horizon, and this is suggestive that these derivatives may satisfy
instability properties analogous to those shown in our previous work on extreme
Reissner-Nordstrom backgrounds.
| [
{
"created": "Mon, 10 Oct 2011 11:16:10 GMT",
"version": "v1"
}
] | 2012-10-17 | [
[
"Aretakis",
"Stefanos",
""
]
] | We study the Cauchy problem for the wave equation on extreme Kerr backgrounds under axisymmetry. Specifically, we consider regular axisymmetric initial data prescribed on a Cauchy hypersurface S which connects the future event horizon with spacelike or null infinity, and we solve the linear wave equation on the domain of dependence of S. We show that the spacetime integral of an energy-type density is bounded by the initial conserved flux corresponding to the stationary Killing field T, and we derive boundedness of the non-degenerate energy flux corresponding to a globally timelike vector field N. Finally, we prove uniform pointwise boundedness and power-law decay for solutions to the wave equation. Our estimates hold up to and including the event horizon. We remark that these results do not yield decay for the derivatives transversal to the horizon, and this is suggestive that these derivatives may satisfy instability properties analogous to those shown in our previous work on extreme Reissner-Nordstrom backgrounds. |
gr-qc/0306103 | Michael B. Mensky | Michael B. Mensky | Universal approach to gravitational thermal effects | 8 pages, LATEX | Phys.Lett. A314 (2003) 169-176 | 10.1016/S0375-9601(03)00801-6 | null | gr-qc hep-th | null | A universal scheme for describing gravitational thermal effects is developed
as a generalization of Unruh effect. Quasi-Rindler (QR) coordinates are
constructed in an arbitrary curved space-time in such a way that the imaginary
QR time be periodical. The observer at rest in QR coordinates should experience
a thermal effect. Application to de Sitter space-time is considered.
| [
{
"created": "Mon, 23 Jun 2003 05:01:49 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Mensky",
"Michael B.",
""
]
] | A universal scheme for describing gravitational thermal effects is developed as a generalization of Unruh effect. Quasi-Rindler (QR) coordinates are constructed in an arbitrary curved space-time in such a way that the imaginary QR time be periodical. The observer at rest in QR coordinates should experience a thermal effect. Application to de Sitter space-time is considered. |
2306.13593 | Reginald Christian Bernardo | Reginald Christian Bernardo and Kin-Wang Ng | Testing gravity with cosmic variance-limited pulsar timing array
correlations | 5 1/2 pages + refs + supp, 4 figures, v4: to appear in PRD Letters,
our codes
https://github.com/reggiebernardo/PTAfast/tree/main/app3_cvlimitedgravity | Phys. Rev. D 109, L101502 (2024) | 10.1103/PhysRevD.109.L101502 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nanohertz stochastic gravitational wave background (SGWB) is an excellent
early universe laboratory for testing the fundamental properties of gravity. In
this letter, we elucidate on the full potential of pulsar timing array (PTA) by
utilizing cosmic variance-limited, or rather experimental noise-free,
correlation measurements to understand the SGWB and by extension gravity. We
show that measurements of the angular power spectrum play a pivotal role in the
PTA precision era for scientific inferencing. In particular, we illustrate that
cosmic variance-limited measurements of the first few power spectrum multipoles
enable us to clearly set apart general relativity from alternative theories of
gravity. This ultimately conveys that PTAs can be most ambitious for testing
gravity in the nanohertz GW regime by zeroing in on the power spectrum.
| [
{
"created": "Fri, 23 Jun 2023 16:33:18 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Jul 2023 06:59:36 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Apr 2024 10:14:38 GMT",
"version": "v3"
},
{
"created": "Wed, 22 May 2024 04:21:03 GMT",
"version": "v4"
}
] | 2024-05-24 | [
[
"Bernardo",
"Reginald Christian",
""
],
[
"Ng",
"Kin-Wang",
""
]
] | The nanohertz stochastic gravitational wave background (SGWB) is an excellent early universe laboratory for testing the fundamental properties of gravity. In this letter, we elucidate on the full potential of pulsar timing array (PTA) by utilizing cosmic variance-limited, or rather experimental noise-free, correlation measurements to understand the SGWB and by extension gravity. We show that measurements of the angular power spectrum play a pivotal role in the PTA precision era for scientific inferencing. In particular, we illustrate that cosmic variance-limited measurements of the first few power spectrum multipoles enable us to clearly set apart general relativity from alternative theories of gravity. This ultimately conveys that PTAs can be most ambitious for testing gravity in the nanohertz GW regime by zeroing in on the power spectrum. |
0904.1741 | Jose' P. S. Lemos | Jos\'e P. S. Lemos, Oleg B. Zaslavskii | Entropy of quasiblack holes | 20 pages, no figures. We thank the editors and referees A, B, and C
of Physical Review Letters and Physical Review D for helping in the
improvement of this paper. | Phys.Rev.D81:064012,2010 | 10.1103/PhysRevD.81.064012 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We trace the origin of the black hole entropy S replacing a black hole by a
quasiblack hole. Let the boundary of a static body approach its own
gravitational radius, in such a way that a quasihorizon forms. We show that if
the body is thermal with the temperature taking the Hawking value at the
quasihorizon limit, it follows, in the nonextremal case, from the first law of
thermodynamics that the entropy approaches the Bekenstein-Hawking value S=A/4.
In this setup, the key role is played by the surface stresses on the
quasihorizon and one finds that the entropy comes from the quasihorizon
surface. Any distribution of matter inside the surface leads to the same
universal value for the entropy in the quasihorizon limit. This can be of some
help in the understanding of black hole entropy. Other similarities between
black holes and quasiblack holes, such as the mass formulas for both objects
had been found previously. We also discuss the entropy for extremal quasiblack
holes, a more subtle issue.
| [
{
"created": "Fri, 10 Apr 2009 20:04:51 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Mar 2010 20:21:27 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Lemos",
"José P. S.",
""
],
[
"Zaslavskii",
"Oleg B.",
""
]
] | We trace the origin of the black hole entropy S replacing a black hole by a quasiblack hole. Let the boundary of a static body approach its own gravitational radius, in such a way that a quasihorizon forms. We show that if the body is thermal with the temperature taking the Hawking value at the quasihorizon limit, it follows, in the nonextremal case, from the first law of thermodynamics that the entropy approaches the Bekenstein-Hawking value S=A/4. In this setup, the key role is played by the surface stresses on the quasihorizon and one finds that the entropy comes from the quasihorizon surface. Any distribution of matter inside the surface leads to the same universal value for the entropy in the quasihorizon limit. This can be of some help in the understanding of black hole entropy. Other similarities between black holes and quasiblack holes, such as the mass formulas for both objects had been found previously. We also discuss the entropy for extremal quasiblack holes, a more subtle issue. |
0911.1403 | T. Padmanabhan | T. Padmanabhan | A Physical Interpretation of Gravitational Field Equations | Based on the Plenary talk given at the International Conference on
`Invisible Universe', 29 June- 3 July, 2009 Paris; to appear in the
Proceedings; 2 figures; 16 pages | AIP Conf.Proc.1241:93-108,2010 | 10.1063/1.3462738 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is possible to provide a thermodynamic interpretation for the field
equations in any diffeomorphism invariant theory of gravity. This insight, in
turn, leads us to the possibility of deriving the gravitational field equations
from another variational principle without using the metric as a dynamical
variable. I review this approach and discuss its implications.
| [
{
"created": "Sat, 7 Nov 2009 09:56:50 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Padmanabhan",
"T.",
""
]
] | It is possible to provide a thermodynamic interpretation for the field equations in any diffeomorphism invariant theory of gravity. This insight, in turn, leads us to the possibility of deriving the gravitational field equations from another variational principle without using the metric as a dynamical variable. I review this approach and discuss its implications. |
0905.2476 | Pavel Krtous | Hedvika Kadlecova, Andrei Zelnikov, Pavel Krtous, Jiri Podolsky | Gyratons on direct-product spacetimes | 22 pages, no figures, contains some material not included in the
journal version | Phys.Rev.D80:024004,2009 | 10.1103/PhysRevD.80.024004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present and analyze exact gyraton and nonexpanding gravitational wave
solutions of algebraic type II on backgrounds which are a direct-product of two
2-spaces of constant curvature, or more general type D spacetimes. This family
of electro-vacuum background spacetimes contains the Nariai, anti-Nariai and
Plebanski-Hacyan universes, conformally flat Bertotti-Robinson and Minkowski
spaces. The gyraton solutions are given in a simple Kundt metric form. They
belong to the recently discussed class of spacetimes with constant scalar
invariants (CSI) of the curvature tensor. We show that the Einstein equations
reduce to a set of linear equations on the transverse 2-space which can be
explicitly solved using the Green functions.
| [
{
"created": "Fri, 15 May 2009 06:42:52 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jun 2009 10:03:16 GMT",
"version": "v2"
}
] | 2009-08-11 | [
[
"Kadlecova",
"Hedvika",
""
],
[
"Zelnikov",
"Andrei",
""
],
[
"Krtous",
"Pavel",
""
],
[
"Podolsky",
"Jiri",
""
]
] | We present and analyze exact gyraton and nonexpanding gravitational wave solutions of algebraic type II on backgrounds which are a direct-product of two 2-spaces of constant curvature, or more general type D spacetimes. This family of electro-vacuum background spacetimes contains the Nariai, anti-Nariai and Plebanski-Hacyan universes, conformally flat Bertotti-Robinson and Minkowski spaces. The gyraton solutions are given in a simple Kundt metric form. They belong to the recently discussed class of spacetimes with constant scalar invariants (CSI) of the curvature tensor. We show that the Einstein equations reduce to a set of linear equations on the transverse 2-space which can be explicitly solved using the Green functions. |
1910.10423 | Anirban Chatterjee | Abhijit Bandyopadhyay and Anirban Chatterjee | Time-dependent diffusive interactions between dark matter and dark
energy in the context of $k-$essence cosmology | 14 pages, 7 figures; Accepted for publication in Research in
Astronomy and Astrophysics | RAA 2021 Vol.21 No.1, 2 (10pp) | 10.1088/1674-4527/21/1/2 | null | gr-qc astro-ph.CO | http://creativecommons.org/publicdomain/zero/1.0/ | We investigated the scenario of time-dependent diffusive interaction between
dark matter and dark energy and showed that such a model can be accommodated
within the observations of luminosity distance - redshift data in Supernova Ia
(SNe Ia) observations. We obtain constrains on different relevant parameters of
this model from the observational data. We consider a homogeneous scalar field
$\phi(t)$ driven by a $k-$essence Lagrangian of the from $L = V(\phi)F(X)$ with
constant potential $V(\phi) = V$, to describe the dynamics of dark energy in
this model. Using the temporal behaviour of the FRW scale factor, the equation
of state and total energy density of the dark fluid, extracted from the
analysis of SNe Ia (JLA) data, we have obtained the time-dependence of the
$k-$essence scalar field and also reconstructed form of the function $F(X)$ in
the $k-$essence Lagrangian.
| [
{
"created": "Wed, 23 Oct 2019 09:17:51 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jun 2020 18:59:04 GMT",
"version": "v2"
}
] | 2021-01-11 | [
[
"Bandyopadhyay",
"Abhijit",
""
],
[
"Chatterjee",
"Anirban",
""
]
] | We investigated the scenario of time-dependent diffusive interaction between dark matter and dark energy and showed that such a model can be accommodated within the observations of luminosity distance - redshift data in Supernova Ia (SNe Ia) observations. We obtain constrains on different relevant parameters of this model from the observational data. We consider a homogeneous scalar field $\phi(t)$ driven by a $k-$essence Lagrangian of the from $L = V(\phi)F(X)$ with constant potential $V(\phi) = V$, to describe the dynamics of dark energy in this model. Using the temporal behaviour of the FRW scale factor, the equation of state and total energy density of the dark fluid, extracted from the analysis of SNe Ia (JLA) data, we have obtained the time-dependence of the $k-$essence scalar field and also reconstructed form of the function $F(X)$ in the $k-$essence Lagrangian. |
2105.10803 | Grigoris Panotopoulos | Grigoris Panotopoulos and \'Angel Rinc\'on | Growth of structures and redshift-space distortion data in
scale-dependent gravity | 10 pages, 1 table, 4 figures, accepted in EPJ Plus | Eur. Phys. J. Plus 136, 622 (2021) | 10.1140/epjp/s13360-021-01583-w | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study is devoted to the implications of scale-dependent gravity in
Cosmology. Redshift-space distortion data indicate that there is a tension
between $\Lambda$CDM and available observations as far as the value of the rms
density fluctuation, $\sigma_8$, is concerned. It has been pointed out that
this tension may be alleviated in alternative theories in which gravity is
weaker at red-shift $z \sim 1$. We study the evolution of density perturbations
for non-relativistic matter on top of a spatially flat FLRW Universe, and we
compute the combination $A=f \sigma_8$ in the framework of scale-dependent
gravity, where both Newton's constant and the cosmological constant are allowed
to vary with time. Upon comparison between available observational data
(supernovae data as well as redshift-space distortion data) and theoretical
predictions of the model, we determine the numerical value of $\sigma_8$ that
best fits the data.
| [
{
"created": "Sat, 22 May 2021 20:08:59 GMT",
"version": "v1"
}
] | 2021-06-08 | [
[
"Panotopoulos",
"Grigoris",
""
],
[
"Rincón",
"Ángel",
""
]
] | This study is devoted to the implications of scale-dependent gravity in Cosmology. Redshift-space distortion data indicate that there is a tension between $\Lambda$CDM and available observations as far as the value of the rms density fluctuation, $\sigma_8$, is concerned. It has been pointed out that this tension may be alleviated in alternative theories in which gravity is weaker at red-shift $z \sim 1$. We study the evolution of density perturbations for non-relativistic matter on top of a spatially flat FLRW Universe, and we compute the combination $A=f \sigma_8$ in the framework of scale-dependent gravity, where both Newton's constant and the cosmological constant are allowed to vary with time. Upon comparison between available observational data (supernovae data as well as redshift-space distortion data) and theoretical predictions of the model, we determine the numerical value of $\sigma_8$ that best fits the data. |
gr-qc/0201091 | Sergio Dain | Sergio Dain and Gabriel Nagy | Initial data for fluid bodies in general relativity | 38 pages, LaTeX 2e, no figures. Accepted for publication in Phys.
Rev. D | Phys.Rev.D65:084020,2002 | 10.1103/PhysRevD.65.084020 | AEI-2001-137 | gr-qc | null | We show that there exist asymptotically flat almost-smooth initial data for
Einstein-perfect fluid's equation that represent an isolated liquid-type body.
By liquid-type body we mean that the fluid energy density has compact support
and takes a strictly positive constant value at its boundary. By almost-smooth
we mean that all initial data fields are smooth everywhere on the initial
hypersurface except at the body boundary, where tangential derivatives of any
order are continuous at that boundary.
PACS: 04.20.Ex, 04.40.Nr, 02.30.Jr
| [
{
"created": "Tue, 29 Jan 2002 14:45:47 GMT",
"version": "v1"
}
] | 2011-04-21 | [
[
"Dain",
"Sergio",
""
],
[
"Nagy",
"Gabriel",
""
]
] | We show that there exist asymptotically flat almost-smooth initial data for Einstein-perfect fluid's equation that represent an isolated liquid-type body. By liquid-type body we mean that the fluid energy density has compact support and takes a strictly positive constant value at its boundary. By almost-smooth we mean that all initial data fields are smooth everywhere on the initial hypersurface except at the body boundary, where tangential derivatives of any order are continuous at that boundary. PACS: 04.20.Ex, 04.40.Nr, 02.30.Jr |
gr-qc/9606078 | Eric Poisson | Eric Poisson | Gravitational radiation from infall into a black hole: Regularization of
the Teukolsky equation | ReVTeX, 23 pages | Phys.Rev.D55:639-649,1997 | 10.1103/PhysRevD.55.639 | null | gr-qc | null | The Teukolsky equation has long been known to lead to divergent integrals
when it is used to calculate the gravitational radiation emitted when a test
mass falls into a black hole from infinity. Two methods have been used in the
past to remove those divergent integrals. In the first, integrations by parts
are carried out, and the infinite boundary terms are simply discarded. In the
second, the Teukolsky equation is transformed into another equation which does
not lead to divergent integrals. The purpose of this paper is to show that
there is nothing intrinsically wrong with the Teukolsky equation when dealing
with non-compact source terms, and that the divergent integrals result simply
from an incorrect choice of Green's function. In this paper, regularization of
the Teukolsky equation is carried out in an entirely natural way which does not
involve modifying the equation.
| [
{
"created": "Thu, 27 Jun 1996 18:40:31 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Poisson",
"Eric",
""
]
] | The Teukolsky equation has long been known to lead to divergent integrals when it is used to calculate the gravitational radiation emitted when a test mass falls into a black hole from infinity. Two methods have been used in the past to remove those divergent integrals. In the first, integrations by parts are carried out, and the infinite boundary terms are simply discarded. In the second, the Teukolsky equation is transformed into another equation which does not lead to divergent integrals. The purpose of this paper is to show that there is nothing intrinsically wrong with the Teukolsky equation when dealing with non-compact source terms, and that the divergent integrals result simply from an incorrect choice of Green's function. In this paper, regularization of the Teukolsky equation is carried out in an entirely natural way which does not involve modifying the equation. |
gr-qc/9501031 | Marcos Duarte Maia | M.D. Maia and E. M. Monte (Universidade de Brasilia) | The Signature Problem for Embedded Space-times | 13 pages, Latex | null | null | UnB.FM.M.-001.95 | gr-qc | null | The compatibility between the general relativity and the mathematical
property that the space-times are embedded manifolds are further examined. In
particular we study the uniqueness of the signature of the embedding space for
a given space-time. The interpretation of the twisting vector as a gauge
potential is also implemented.
| [
{
"created": "Wed, 25 Jan 1995 14:41:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Maia",
"M. D.",
"",
"Universidade de Brasilia"
],
[
"Monte",
"E. M.",
"",
"Universidade de Brasilia"
]
] | The compatibility between the general relativity and the mathematical property that the space-times are embedded manifolds are further examined. In particular we study the uniqueness of the signature of the embedding space for a given space-time. The interpretation of the twisting vector as a gauge potential is also implemented. |
2007.13011 | Mehedi Kalam | Sajahan Molla, Bidisha Ghosh, Mehedi Kalam | Does Dark Matter admixed pulsar exist ? | 10 pages, 17 figures, Accepted in EPJ Plus | Eur.Phys.J.Plus 135, 362 (2020) | 10.1140/epjp/s13360-020-00364-1 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have considered a twofluid model assuming that the pulsars
are made of ordinary matter admixed with dark matter.Contribution of dark
matter comes from the fitting of the rotation curves of the SPARC sample of
galaxies[95]. For this we have investigated the dark matter based on the
Singular Isothermal Sphere (SIS) dark matter density profile in the galactic
halo region. Considering this twofluid model, we have studied the physical
features of the pulsars present in different galaxy in details. Here, we
compute the probable radii, compactness (u) and surface red-shift (Zs) of the
four pulsars namely : PSR J1748-2021B in NGC 6440B galaxy, PSR J1911-5958A in
NGC 6752 galaxy, PSR B1802-07 in NGC 6539 galaxy and PSR J1750-37A in NGC 6441
galaxy.
| [
{
"created": "Sat, 25 Jul 2020 21:19:41 GMT",
"version": "v1"
}
] | 2020-07-28 | [
[
"Molla",
"Sajahan",
""
],
[
"Ghosh",
"Bidisha",
""
],
[
"Kalam",
"Mehedi",
""
]
] | In this paper, we have considered a twofluid model assuming that the pulsars are made of ordinary matter admixed with dark matter.Contribution of dark matter comes from the fitting of the rotation curves of the SPARC sample of galaxies[95]. For this we have investigated the dark matter based on the Singular Isothermal Sphere (SIS) dark matter density profile in the galactic halo region. Considering this twofluid model, we have studied the physical features of the pulsars present in different galaxy in details. Here, we compute the probable radii, compactness (u) and surface red-shift (Zs) of the four pulsars namely : PSR J1748-2021B in NGC 6440B galaxy, PSR J1911-5958A in NGC 6752 galaxy, PSR B1802-07 in NGC 6539 galaxy and PSR J1750-37A in NGC 6441 galaxy. |
1411.3192 | Sharmanthie Fernando | Sharmanthie Fernando, Scott Meadows, and Kevon Reis | Null trajectories and bending of light in charged black holes with
quintessence | 18 figures and 26 pages, some text is removed from the earlier
version but the results remain the same. Accepted to be published in
International Journal of Theoretical Physics | Int. Jour. Theo. Phys. 54, 3634 ( 2015) | 10.1007/s10773-015-2601-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied null geodesics of the charged black hole surrounded by
quintessence. Quintessence is a candidate for dark energy and is represented by
a scalar field. Here, we have done a detailed study of the photon trajectories.
The exact solutions for the trajectories are obtained in terms of the
Jacobi-elliptic integrals for all possible energy and angular momentum of the
photons. We have also studied the bending angle using the Rindler and Ishak
method.
| [
{
"created": "Wed, 12 Nov 2014 14:57:32 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jun 2015 16:54:43 GMT",
"version": "v2"
}
] | 2015-09-17 | [
[
"Fernando",
"Sharmanthie",
""
],
[
"Meadows",
"Scott",
""
],
[
"Reis",
"Kevon",
""
]
] | We have studied null geodesics of the charged black hole surrounded by quintessence. Quintessence is a candidate for dark energy and is represented by a scalar field. Here, we have done a detailed study of the photon trajectories. The exact solutions for the trajectories are obtained in terms of the Jacobi-elliptic integrals for all possible energy and angular momentum of the photons. We have also studied the bending angle using the Rindler and Ishak method. |
2206.08234 | Kyungmin Kim | Kyungmin Kim, Joongoo Lee, Otto A. Hannuksela, Tjonnie G. F. Li | Deep Learning-based Search for Microlensing Signature from Binary Black
Hole Events in GWTC-1 and -2 | 14 pages, 7 figures, 4 tables, Accepted by Astrophys. J | ApJ 938 (2022) 2, 157 | 10.3847/1538-4357/ac92f3 | LIGO-P2200006 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We present the result of the first deep learning-based search for the
signature of microlensing in gravitational waves. This search seeks the
signature induced by lenses with masses between $10^3M_\odot$--$10^5M_\odot$
from spectrograms of the binary black hole events in the first and second
gravitational-wave transient catalogs. We use a deep learning model trained
with spectrograms of simulated noisy gravitational-wave signals to classify the
events into two classes, lensed or unlensed. We introduce ensemble learning and
a majority voting-based consistency test for the predictions of ensemble
learners. The classification scheme of this search primarily classifies one
event, GW190707_093326, into the lensed class. To verify the primary
classification of this event, we also examine the median probability to the
lensed class and observe the resulting value, $0.984^{+0.012}_{-0.342}$, agrees
with an empirical criterion $>\!0.6$ for claiming the detection of a lensed
signal. However, the uncertainty of the estimated $p$-value for the median
probability and error, ranging from 0 to 0.1, convinces us GW190707_093326 is
less likely a lensed event because it includes $p\!\geq\!0.05$ where the
unlensed hypothesis is true. Therefore, we conclude our search finds no
significant evidence of microlensing signature from the evaluated binary black
hole events.
| [
{
"created": "Thu, 16 Jun 2022 14:59:36 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Sep 2022 07:10:00 GMT",
"version": "v2"
}
] | 2022-10-25 | [
[
"Kim",
"Kyungmin",
""
],
[
"Lee",
"Joongoo",
""
],
[
"Hannuksela",
"Otto A.",
""
],
[
"Li",
"Tjonnie G. F.",
""
]
] | We present the result of the first deep learning-based search for the signature of microlensing in gravitational waves. This search seeks the signature induced by lenses with masses between $10^3M_\odot$--$10^5M_\odot$ from spectrograms of the binary black hole events in the first and second gravitational-wave transient catalogs. We use a deep learning model trained with spectrograms of simulated noisy gravitational-wave signals to classify the events into two classes, lensed or unlensed. We introduce ensemble learning and a majority voting-based consistency test for the predictions of ensemble learners. The classification scheme of this search primarily classifies one event, GW190707_093326, into the lensed class. To verify the primary classification of this event, we also examine the median probability to the lensed class and observe the resulting value, $0.984^{+0.012}_{-0.342}$, agrees with an empirical criterion $>\!0.6$ for claiming the detection of a lensed signal. However, the uncertainty of the estimated $p$-value for the median probability and error, ranging from 0 to 0.1, convinces us GW190707_093326 is less likely a lensed event because it includes $p\!\geq\!0.05$ where the unlensed hypothesis is true. Therefore, we conclude our search finds no significant evidence of microlensing signature from the evaluated binary black hole events. |
1805.02767 | Pavel Friedrich | Pavel Friedrich, Tomislav Prokopec | Kinetic theory and classical limit for real scalar quantum field in
curved space-time | This version matches the one accepted for publication in Physical
Review D | Phys. Rev. D 98, 025010 (2018) | 10.1103/PhysRevD.98.025010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from a real scalar quantum field theory with quartic
self-interactions and non-minimal coupling to classical gravity, we define four
equal-time, spatially covariant phase-space operators through a Wigner
transformation of spatially translated canonical operators within a 3+1
decomposition. A subset of these operators can be interpreted as fluctuating
particle densities in phase-space whenever the quantum state of the system
allows for a classical limit. We come to this conclusion by expressing
hydrodynamic variables through the expectation values of these operators and
moreover, by deriving the dynamics of the expectation values within a spatial
gradient expansion and a 1-loop approximation which subsequently yields the
Vlasov equation with a self-mass correction as a limit. We keep an arbitrary
classical metric in the 3+1 decomposition which is assumed to be determined
semi-classically. Our formalism allows to systematically study the transition
from quantum field theory in curved space-time to classical particle physics
for this minimal model of self-interacting, gravitating matter. As an
application we show how to include relativistic and self-interaction
corrections to existing dark matter models in a kinetic description by taking
into account the gravitational slip, vector perturbations and tensor
perturbations.
| [
{
"created": "Mon, 7 May 2018 22:09:01 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jun 2018 12:53:44 GMT",
"version": "v2"
}
] | 2018-07-17 | [
[
"Friedrich",
"Pavel",
""
],
[
"Prokopec",
"Tomislav",
""
]
] | Starting from a real scalar quantum field theory with quartic self-interactions and non-minimal coupling to classical gravity, we define four equal-time, spatially covariant phase-space operators through a Wigner transformation of spatially translated canonical operators within a 3+1 decomposition. A subset of these operators can be interpreted as fluctuating particle densities in phase-space whenever the quantum state of the system allows for a classical limit. We come to this conclusion by expressing hydrodynamic variables through the expectation values of these operators and moreover, by deriving the dynamics of the expectation values within a spatial gradient expansion and a 1-loop approximation which subsequently yields the Vlasov equation with a self-mass correction as a limit. We keep an arbitrary classical metric in the 3+1 decomposition which is assumed to be determined semi-classically. Our formalism allows to systematically study the transition from quantum field theory in curved space-time to classical particle physics for this minimal model of self-interacting, gravitating matter. As an application we show how to include relativistic and self-interaction corrections to existing dark matter models in a kinetic description by taking into account the gravitational slip, vector perturbations and tensor perturbations. |
gr-qc/0302103 | Michael Hartl | Michael D. Hartl | A survey of spinning test particle orbits in Kerr spacetime | Submitted to Phys. Rev. D. Follow-up to gr-qc/0210042. Figures are
low-resolution in order to satisfy archive size constraints; a
high-resolution version is available at http://www.michaelhartl.com/papers/ | Phys.Rev. D67 (2003) 104023 | 10.1103/PhysRevD.67.104023 | null | gr-qc | null | We investigate the dynamics of the Papapetrou equations in Kerr spacetime.
These equations provide a model for the motion of a relativistic spinning test
particle orbiting a rotating (Kerr) black hole. We perform a thorough parameter
space search for signs of chaotic dynamics by calculating the Lyapunov
exponents for a large variety of initial conditions. We find that the
Papapetrou equations admit many chaotic solutions, with the strongest chaos
occurring in the case of eccentric orbits with pericenters close to the limit
of stability against plunge into a maximally spinning Kerr black hole. Despite
the presence of these chaotic solutions, we show that physically realistic
solutions to the Papapetrou equations are not chaotic; in all cases, the
chaotic solutions either do not correspond to realistic astrophysical systems,
or involve a breakdown of the test-particle approximation leading to the
Papapetrou equations (or both). As a result, the gravitational radiation from
bodies spiraling into much more massive black holes (as detectable, for
example, by LISA, the Laser Interferometer Space Antenna) should not exhibit
any signs of chaos.
| [
{
"created": "Tue, 25 Feb 2003 22:19:16 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Hartl",
"Michael D.",
""
]
] | We investigate the dynamics of the Papapetrou equations in Kerr spacetime. These equations provide a model for the motion of a relativistic spinning test particle orbiting a rotating (Kerr) black hole. We perform a thorough parameter space search for signs of chaotic dynamics by calculating the Lyapunov exponents for a large variety of initial conditions. We find that the Papapetrou equations admit many chaotic solutions, with the strongest chaos occurring in the case of eccentric orbits with pericenters close to the limit of stability against plunge into a maximally spinning Kerr black hole. Despite the presence of these chaotic solutions, we show that physically realistic solutions to the Papapetrou equations are not chaotic; in all cases, the chaotic solutions either do not correspond to realistic astrophysical systems, or involve a breakdown of the test-particle approximation leading to the Papapetrou equations (or both). As a result, the gravitational radiation from bodies spiraling into much more massive black holes (as detectable, for example, by LISA, the Laser Interferometer Space Antenna) should not exhibit any signs of chaos. |
1306.3886 | Lorenzo Iorio | Lorenzo Iorio | Modified theories of gravity with nonminimal coupling and orbital
particle dynamics | LaTex2e, 18 pages, 1 table, 2 figures, 29 references. Accepted for
publication in Classical and Quantum Gravity | Class. Quant. Gravit..31:085003,2014 | 10.1088/0264-9381/31/8/085003 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a non-rotating, massive test particle acted upon by a
"pressure"-type, non-geodesic acceleration arising from a certain general class
of gravitational theories with nonminimal coupling between the matter and the
metric. The resulting orbital perturbations for a two-body system are
investigated both analytically and numerically. Among the other long-term
effects, a secular increase of the two-body relative distance occurs. In
principle, it may yield a physical mechanism for the steady recession of the
Earth from the Sun recently proposed to explain the Faint Young Sun Paradox in
the Archean eon. At present, the theorists have not yet derived explicit
expressions for some of the key parameters of the model, such as the integrated
"charge" $\xi$, depending on the matter distribution of the system, and the
4-vector $K^{\mu}=\{K^0,\boldsymbol{K}\}$ connected with the nonminimal
function $F$. Thus, we phenomenologically treat them as free parameters, and
preliminarily infer some indications on their admissible values according to
the most recent Solar System's planetary ephemerides. From the latest
determinations of the corrections $\Delta\dot\varpi$ to the standard perihelion
precessions, estimated by the astronomers who produced the EPM2011 ephemerides
without modeling the theory considered here, we preliminarily obtain $|\xi
K|\lesssim 0.1$ kg s$^{-1}$ for Mars. From guesses on what could be the current
bounds on the secular rates of change of the planetary semimajor axes, we get
$|\xi K^0|\lesssim 1249$ kg s$^{-1}$ for Mars. More effective constraints could
be posed by reprocessing the same planetary data sets with dedicated dynamical
models including the effects studied here, and explicitly estimating the
associated parameters. COBE and GP-B terrestrial satellites yield $|\xi
K|\lesssim 2\times 10^{-4}$ kg s$^{-1}$ and $|\xi K_0|\lesssim 2\times
10^{-10}$ kg s$^{-1}$.
| [
{
"created": "Mon, 17 Jun 2013 15:08:04 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jun 2013 14:58:39 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Sep 2013 06:10:18 GMT",
"version": "v3"
},
{
"created": "Thu, 19 Sep 2013 19:10:34 GMT",
"version": "v4"
},
{
"c... | 2014-03-26 | [
[
"Iorio",
"Lorenzo",
""
]
] | We consider a non-rotating, massive test particle acted upon by a "pressure"-type, non-geodesic acceleration arising from a certain general class of gravitational theories with nonminimal coupling between the matter and the metric. The resulting orbital perturbations for a two-body system are investigated both analytically and numerically. Among the other long-term effects, a secular increase of the two-body relative distance occurs. In principle, it may yield a physical mechanism for the steady recession of the Earth from the Sun recently proposed to explain the Faint Young Sun Paradox in the Archean eon. At present, the theorists have not yet derived explicit expressions for some of the key parameters of the model, such as the integrated "charge" $\xi$, depending on the matter distribution of the system, and the 4-vector $K^{\mu}=\{K^0,\boldsymbol{K}\}$ connected with the nonminimal function $F$. Thus, we phenomenologically treat them as free parameters, and preliminarily infer some indications on their admissible values according to the most recent Solar System's planetary ephemerides. From the latest determinations of the corrections $\Delta\dot\varpi$ to the standard perihelion precessions, estimated by the astronomers who produced the EPM2011 ephemerides without modeling the theory considered here, we preliminarily obtain $|\xi K|\lesssim 0.1$ kg s$^{-1}$ for Mars. From guesses on what could be the current bounds on the secular rates of change of the planetary semimajor axes, we get $|\xi K^0|\lesssim 1249$ kg s$^{-1}$ for Mars. More effective constraints could be posed by reprocessing the same planetary data sets with dedicated dynamical models including the effects studied here, and explicitly estimating the associated parameters. COBE and GP-B terrestrial satellites yield $|\xi K|\lesssim 2\times 10^{-4}$ kg s$^{-1}$ and $|\xi K_0|\lesssim 2\times 10^{-10}$ kg s$^{-1}$. |
2102.11888 | Dejan Gajic | Yannis Angelopoulos and Stefanos Aretakis and Dejan Gajic | Price's law and precise late-time asymptotics for subextremal
Reissner-Nordstr\"om black holes | 65 pages, 2 figures | null | 10.1007/s00023-023-01328-8 | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | In this paper, we prove precise late-time asymptotics for solutions to the
wave equation supported on angular frequencies greater or equal to $\ell$ on
the domain of outer communications of subextremal Reissner-Nordstr\"om
spacetimes up to and including the event horizon. Our asymptotics yield, in
particular, sharp upper and lower decay rates which are consistent with Price's
law on such backgrounds. We present a theory for inverting the time operator
and derive an explicit representation of the leading-order asymptotic
coefficient in terms of the Newman-Penrose charges at null infinity associated
with the time integrals. Our method is based on purely physical space
techniques. For each angular frequency $\ell$ we establish a sharp hierarchy of
$r$-weighted radially commuted estimates with length $2\ell+5$. We complement
this hierarchy with a novel hierarchy of weighted elliptic estimates of length
$\ell+1$.
| [
{
"created": "Tue, 23 Feb 2021 19:00:06 GMT",
"version": "v1"
}
] | 2023-08-09 | [
[
"Angelopoulos",
"Yannis",
""
],
[
"Aretakis",
"Stefanos",
""
],
[
"Gajic",
"Dejan",
""
]
] | In this paper, we prove precise late-time asymptotics for solutions to the wave equation supported on angular frequencies greater or equal to $\ell$ on the domain of outer communications of subextremal Reissner-Nordstr\"om spacetimes up to and including the event horizon. Our asymptotics yield, in particular, sharp upper and lower decay rates which are consistent with Price's law on such backgrounds. We present a theory for inverting the time operator and derive an explicit representation of the leading-order asymptotic coefficient in terms of the Newman-Penrose charges at null infinity associated with the time integrals. Our method is based on purely physical space techniques. For each angular frequency $\ell$ we establish a sharp hierarchy of $r$-weighted radially commuted estimates with length $2\ell+5$. We complement this hierarchy with a novel hierarchy of weighted elliptic estimates of length $\ell+1$. |
1911.08062 | Yun Soo Myung | De-Cheng Zou, Yun Soo Myung | Scalar hairy black holes in Einstein-Maxwell-conformally coupled scalar
theory | 19 pages, 5 figures, version to appear in PLB | null | 10.1016/j.physletb.2020.135332 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain scalar hairy black holes from Einstein-Maxwell-conformally coupled
scalar (EMCS) theory with the scalar coupling parameter $\alpha$ to the Maxwell
term. In case of $\alpha=0$, the $\alpha=0$ EMCS theory provides constant
(charged) scalar hairy black hole and charged BBMB
(Bocharova-Bronnikov-Melnikov-Bekenstein) black hole where the former is stable
against full perturbations, while the latter remains unstable because it
belongs to an extremal black hole. It is noted that for $\alpha\not=0$, the
unstable Reissner-Nordstr\"{o}m black holes without scalar hair imply infinite
branches of $n=0(\alpha \ge 8.019),1(\alpha \ge 40.84),2(\alpha \ge
99.89),\cdots$ scalarized charged black holes. In addition, for $\alpha>0$, we
develop a single branch of scalarized charged black hole solutions inspired by
the constant scalar hairy black hole. Finally, we obtain the numerical charged
BBMB black hole solution from the $\alpha=0$ EMCS theory.
| [
{
"created": "Tue, 19 Nov 2019 02:56:56 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Feb 2020 23:06:03 GMT",
"version": "v2"
}
] | 2020-03-04 | [
[
"Zou",
"De-Cheng",
""
],
[
"Myung",
"Yun Soo",
""
]
] | We obtain scalar hairy black holes from Einstein-Maxwell-conformally coupled scalar (EMCS) theory with the scalar coupling parameter $\alpha$ to the Maxwell term. In case of $\alpha=0$, the $\alpha=0$ EMCS theory provides constant (charged) scalar hairy black hole and charged BBMB (Bocharova-Bronnikov-Melnikov-Bekenstein) black hole where the former is stable against full perturbations, while the latter remains unstable because it belongs to an extremal black hole. It is noted that for $\alpha\not=0$, the unstable Reissner-Nordstr\"{o}m black holes without scalar hair imply infinite branches of $n=0(\alpha \ge 8.019),1(\alpha \ge 40.84),2(\alpha \ge 99.89),\cdots$ scalarized charged black holes. In addition, for $\alpha>0$, we develop a single branch of scalarized charged black hole solutions inspired by the constant scalar hairy black hole. Finally, we obtain the numerical charged BBMB black hole solution from the $\alpha=0$ EMCS theory. |
1405.4288 | Sam Cormack | Stephon Alexander, Sam Cormack, Antonino Marcian\`o, Nicol\'as Yunes | Gravitational-Wave Mediated Preheating | 6 pages, 2 figures | Phys. Lett. B 743, 82--86 (2015) | 10.1016/j.physletb.2015.02.018 | NSF-KITP-14-047 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new preheating mechanism through the coupling of the
gravitational field to both the inflaton and matter fields, without direct
inflaton-matter couplings. The inflaton transfers power to the matter fields
through interactions with gravitational waves, which are exponentially enhanced
due to an inflation-graviton coupling. One such coupling is the product of the
inflaton to the Pontryagin density, as in dynamical Chern-Simons gravity. The
energy scales involved are constrained by requiring that preheating happens
fast during matter domination.
| [
{
"created": "Fri, 16 May 2014 20:00:01 GMT",
"version": "v1"
},
{
"created": "Thu, 7 May 2015 20:53:19 GMT",
"version": "v2"
}
] | 2015-05-11 | [
[
"Alexander",
"Stephon",
""
],
[
"Cormack",
"Sam",
""
],
[
"Marcianò",
"Antonino",
""
],
[
"Yunes",
"Nicolás",
""
]
] | We propose a new preheating mechanism through the coupling of the gravitational field to both the inflaton and matter fields, without direct inflaton-matter couplings. The inflaton transfers power to the matter fields through interactions with gravitational waves, which are exponentially enhanced due to an inflation-graviton coupling. One such coupling is the product of the inflaton to the Pontryagin density, as in dynamical Chern-Simons gravity. The energy scales involved are constrained by requiring that preheating happens fast during matter domination. |
2305.02098 | Gerhard Rein | Gerhard Rein | Stability and instability results for equilibria of a (relativistic)
self-gravitating collisionless gas -- A review | 71 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review stability and instability results for self-gravitating matter
distributions, where the matter model is a collisionless gas as described by
the Vlasov equation. The focus is on the general relativistic situation, i.e.,
on steady states of the Einstein-Vlasov system and their stability properties.
In order to put things into perspective we include the Vlasov-Poisson system
and the relativistic Vlasov-Poisson system into the discussion.
| [
{
"created": "Wed, 3 May 2023 13:04:52 GMT",
"version": "v1"
}
] | 2023-05-04 | [
[
"Rein",
"Gerhard",
""
]
] | We review stability and instability results for self-gravitating matter distributions, where the matter model is a collisionless gas as described by the Vlasov equation. The focus is on the general relativistic situation, i.e., on steady states of the Einstein-Vlasov system and their stability properties. In order to put things into perspective we include the Vlasov-Poisson system and the relativistic Vlasov-Poisson system into the discussion. |
1904.12675 | Faizuddin Ahmed | Faizuddin Ahmed | Axial symmetry Type N space-time with a naked curvature singularity and
Closed Time-like Curves | Typos corrected, accepted for publication in Gravitation and
Cosmology | Grav. and Cosmo. Vol. 26, Issue 2, 136 (2020) | 10.1134/S0202289320020024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A family of type N exact solution of the Einstein's field equations, regular
everywhere except on the symmetry axis where it possesses a naked curvature
singularity, is present. The stress-energy tensor is of the anisotropic fluid
coupled with pure radiation field satisfy the different energy conditions and
the physical parameters diverge $r \rightarrow 0$. The space-time admitting a
non-expanding, non-twisting, and shear-free geodesic null congruence and
belongs to a special class of type N Kundt metrics. The space-time is
geodesically complete along the radiation direction in the constant $z$-planes
and exhibits geometrically different properties from the known pp-waves. The
present family of solution admits closed time-like curves (CTC) which appear
after a certain instant of time and the space-time is a four-dimensional
generalization of the Misner space metric in curved space-time.
| [
{
"created": "Fri, 26 Apr 2019 08:23:39 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2019 06:50:51 GMT",
"version": "v2"
},
{
"created": "Fri, 14 Feb 2020 05:30:55 GMT",
"version": "v3"
}
] | 2020-04-14 | [
[
"Ahmed",
"Faizuddin",
""
]
] | A family of type N exact solution of the Einstein's field equations, regular everywhere except on the symmetry axis where it possesses a naked curvature singularity, is present. The stress-energy tensor is of the anisotropic fluid coupled with pure radiation field satisfy the different energy conditions and the physical parameters diverge $r \rightarrow 0$. The space-time admitting a non-expanding, non-twisting, and shear-free geodesic null congruence and belongs to a special class of type N Kundt metrics. The space-time is geodesically complete along the radiation direction in the constant $z$-planes and exhibits geometrically different properties from the known pp-waves. The present family of solution admits closed time-like curves (CTC) which appear after a certain instant of time and the space-time is a four-dimensional generalization of the Misner space metric in curved space-time. |
2210.02130 | Seema Satin | Seema Satin | Correspondences between scalar field and fluid fluctuations in curved
spacetime | null | null | 10.1142/S0218271823500244 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A correspondence between scalar field fluctuations and generalized
fluctuations in a hydrodynamic approximation of fields is obtained. The results
presented here are of interest to field-fluid correspondences and form part of
theoretical foundations in this area. The intention for such developments is to
explore sub-hydro range mesoscopic physics for the relativistic fluids in
curved spacetime. The fluid correspondences fall in the classical domain and
can replace the quantum fields and fluctuations for scales around the
hydrodynamic limits.The present article extends our earlier results with a more
elaborate physical insight towards the quantum fluids and retention of partial
quantum nature in a stochastic description in bulk of the fluids. This also
accounts for non-thermal effects along with thermal and quantum fluctuations
for the fields in the hydro limit. Hence the expressions presented here are
very general in nature for various applications. The further scope of research
that such developments give is discussed in the concluding section.
| [
{
"created": "Wed, 5 Oct 2022 10:31:58 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Dec 2022 04:29:57 GMT",
"version": "v2"
}
] | 2023-05-03 | [
[
"Satin",
"Seema",
""
]
] | A correspondence between scalar field fluctuations and generalized fluctuations in a hydrodynamic approximation of fields is obtained. The results presented here are of interest to field-fluid correspondences and form part of theoretical foundations in this area. The intention for such developments is to explore sub-hydro range mesoscopic physics for the relativistic fluids in curved spacetime. The fluid correspondences fall in the classical domain and can replace the quantum fields and fluctuations for scales around the hydrodynamic limits.The present article extends our earlier results with a more elaborate physical insight towards the quantum fluids and retention of partial quantum nature in a stochastic description in bulk of the fluids. This also accounts for non-thermal effects along with thermal and quantum fluctuations for the fields in the hydro limit. Hence the expressions presented here are very general in nature for various applications. The further scope of research that such developments give is discussed in the concluding section. |
2407.20512 | Zhen-Ming Xu | Chen Ma, Pan-Pan Zhang, Bin Wu, Zhen-Ming Xu | The Kramers escape rate of phase transitions for the 6-dimensional
Gauss-Bonnet AdS black hole with triple phases | 10 pages, 4 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, we obtain specific picture of the phase transitions for the
6-dimensional Gauss-Bonnet Anti-de Sitter (AdS) black hole with triple phases,
using the generalized free energy we constructed and Kramers escape rate in
stochastic motion. There are six possible phase transition processes between
the three different stable states (small, medium, and large black hole states).
During these phase transitions, there are two key temperatures. One is the
temperature at which the medium black hole state emerges, and the other is the
temperature at which the small black hole state annihilates. Meanwhile, two
dynamic equilibrium processes are formed. One is a dynamic equilibrium of the
transition from the medium black hole state to the large black hole state and
the transition from the small black hole state to the medium black hole state.
The other is a dynamic equilibrium of the transition from the small black hole
state to the medium black hole state and the transition from the medium black
hole state to the small black hole state.
| [
{
"created": "Tue, 30 Jul 2024 03:10:26 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Ma",
"Chen",
""
],
[
"Zhang",
"Pan-Pan",
""
],
[
"Wu",
"Bin",
""
],
[
"Xu",
"Zhen-Ming",
""
]
] | In this study, we obtain specific picture of the phase transitions for the 6-dimensional Gauss-Bonnet Anti-de Sitter (AdS) black hole with triple phases, using the generalized free energy we constructed and Kramers escape rate in stochastic motion. There are six possible phase transition processes between the three different stable states (small, medium, and large black hole states). During these phase transitions, there are two key temperatures. One is the temperature at which the medium black hole state emerges, and the other is the temperature at which the small black hole state annihilates. Meanwhile, two dynamic equilibrium processes are formed. One is a dynamic equilibrium of the transition from the medium black hole state to the large black hole state and the transition from the small black hole state to the medium black hole state. The other is a dynamic equilibrium of the transition from the small black hole state to the medium black hole state and the transition from the medium black hole state to the small black hole state. |
0804.3955 | Sergey Tarabrin | Sergey P. Tarabrin and Sergey P. Vyatchanin | Displacement-noise-free gravitational-wave detection with a single
Fabry-Perot cavity: a toy model | 16 pages, 5 figures; extended discussion of basic mechanism of noise
cancelation moved to new Sec. II (with new figure), added discussion of laser
noise cancelation in Sec. VI D (with new figure) | Phys.Lett.A372:6801-6812,2008 | 10.1016/j.physleta.2008.09.055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a detuned Fabry-Perot cavity, pumped through both the mirrors, as
\textit{a toy model} of the gravitational-wave (GW) detector partially free
from displacement noise of the test masses. It is demonstrated that the noise
of cavity mirrors can be eliminated, but the one of lasers and detectors
cannot. The isolation of the GW signal from displacement noise of the mirrors
is achieved in a proper linear combination of the cavity output signals. The
construction of such a linear combination is possible due to the difference
between the reflected and transmitted output signals of detuned cavity. We
demonstrate that in low-frequency region the obtained displacement-noise-free
response signal is much stronger than the $f^3_{\textrm{gw}}$-limited
sensitivity of displacement-noise-free interferometers recently proposed by S.
Kawamura and Y. Chen. However, the loss of the resonant gain in the noise
cancelation procedure results is the sensitivity limitation of our toy model by
displacement noise of lasers and detectors.
| [
{
"created": "Thu, 24 Apr 2008 17:37:45 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Nov 2008 08:11:19 GMT",
"version": "v2"
}
] | 2008-12-18 | [
[
"Tarabrin",
"Sergey P.",
""
],
[
"Vyatchanin",
"Sergey P.",
""
]
] | We propose a detuned Fabry-Perot cavity, pumped through both the mirrors, as \textit{a toy model} of the gravitational-wave (GW) detector partially free from displacement noise of the test masses. It is demonstrated that the noise of cavity mirrors can be eliminated, but the one of lasers and detectors cannot. The isolation of the GW signal from displacement noise of the mirrors is achieved in a proper linear combination of the cavity output signals. The construction of such a linear combination is possible due to the difference between the reflected and transmitted output signals of detuned cavity. We demonstrate that in low-frequency region the obtained displacement-noise-free response signal is much stronger than the $f^3_{\textrm{gw}}$-limited sensitivity of displacement-noise-free interferometers recently proposed by S. Kawamura and Y. Chen. However, the loss of the resonant gain in the noise cancelation procedure results is the sensitivity limitation of our toy model by displacement noise of lasers and detectors. |
2404.02940 | Kharanshu N. Solanki Mr. | Kharanshu N. Solanki, Karim Mosani, Omkar Deshpande and Pankaj S.
Joshi | Tipler Naked Singularities in $N$ Dimensions | Final version (accepted in Class. Quant. Grav.) | null | 10.1088/1361-6382/ad6115 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | A spacetime singularity, identified by the existence of incomplete causal
geodesics in the spacetime, is called a (Tipler) strong curvature singularity
if the volume form acting on independent Jacobi fields along causal geodesics
vanishes in the approach of the singularity. It is called naked if at least one
of these causal geodesics is past incomplete. Here, we study the formation of
strong curvature naked singularities arising from spherically symmetric
gravitational collapse of general type-I matter fields in an arbitrarily finite
number of dimensions. In the spirit of Joshi and Dwivedi [26], and Goswami and
Joshi [31], we first construct regular initial data in terms of matter
variables and geometric quantities, subject to the dominant and null energy
conditions. Using this initial data, we derive two distinct (but not mutually
exclusive) conditions, which we call the positive root condition (PRC) and the
simple positive root condition (SPRC), that serve as necessary and sufficient
conditions, respectively, for the existence of naked singularities. In doing
so, we generalize the results of [26] and [31]. We further restrict the PRC and
the SPRC by imposing the curvature growth condition (CGC) of Clarke and Krolak
[24] on all causal curves that satisfy the causal convergence condition. The
CGC gives a sufficient condition for the naked singularities implying the PRC
and implied by the SPRC, to be of strong curvature type; thereby also implying
the inextendibility of the spacetime. Using the CGC, we extend the results of
[28] (that hold for dimension $N=4$) to the case $N=5$, showing that strong
curvature naked singularities can occur in this case. However, for the case
$N\geq6$, we show that past-incomplete causal curves that identify naked
singularities do not satisfy the CGC. These results shed light on the validity
of the cosmic censorship conjectures in arbitrary dimensions.
| [
{
"created": "Wed, 3 Apr 2024 11:02:45 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Apr 2024 03:08:19 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Apr 2024 12:31:15 GMT",
"version": "v3"
},
{
"created": "Tue, 16 Apr 2024 22:02:13 GMT",
"version": "v4"
},
{
"cre... | 2024-07-15 | [
[
"Solanki",
"Kharanshu N.",
""
],
[
"Mosani",
"Karim",
""
],
[
"Deshpande",
"Omkar",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | A spacetime singularity, identified by the existence of incomplete causal geodesics in the spacetime, is called a (Tipler) strong curvature singularity if the volume form acting on independent Jacobi fields along causal geodesics vanishes in the approach of the singularity. It is called naked if at least one of these causal geodesics is past incomplete. Here, we study the formation of strong curvature naked singularities arising from spherically symmetric gravitational collapse of general type-I matter fields in an arbitrarily finite number of dimensions. In the spirit of Joshi and Dwivedi [26], and Goswami and Joshi [31], we first construct regular initial data in terms of matter variables and geometric quantities, subject to the dominant and null energy conditions. Using this initial data, we derive two distinct (but not mutually exclusive) conditions, which we call the positive root condition (PRC) and the simple positive root condition (SPRC), that serve as necessary and sufficient conditions, respectively, for the existence of naked singularities. In doing so, we generalize the results of [26] and [31]. We further restrict the PRC and the SPRC by imposing the curvature growth condition (CGC) of Clarke and Krolak [24] on all causal curves that satisfy the causal convergence condition. The CGC gives a sufficient condition for the naked singularities implying the PRC and implied by the SPRC, to be of strong curvature type; thereby also implying the inextendibility of the spacetime. Using the CGC, we extend the results of [28] (that hold for dimension $N=4$) to the case $N=5$, showing that strong curvature naked singularities can occur in this case. However, for the case $N\geq6$, we show that past-incomplete causal curves that identify naked singularities do not satisfy the CGC. These results shed light on the validity of the cosmic censorship conjectures in arbitrary dimensions. |
gr-qc/0212060 | null | K.Ghosh | Entropy of Scalar Field in 3+1 Dimensional Reissner-Nordstrom de Sitter
Black Hole Background | Latex,15 pages; a few discussions added, a new reference added | null | null | null | gr-qc | null | We consider the thermodynamics of minimally coupled massive scalar field in
3+1 dimensional constant curvature black hole background. The brick wall model
of 't Hooft is used. When Schwarzschild like coordinates are used it is found
that two radial brick wall cut-off parameters are required to regularize the
solution. Free energy of the scalar field is obtained through counting of
states using the WKB approximation. It is found that the free energy and the
entropy are divergent in both the cut-off parameters.
| [
{
"created": "Fri, 13 Dec 2002 11:29:30 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Mar 2004 13:34:57 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Ghosh",
"K.",
""
]
] | We consider the thermodynamics of minimally coupled massive scalar field in 3+1 dimensional constant curvature black hole background. The brick wall model of 't Hooft is used. When Schwarzschild like coordinates are used it is found that two radial brick wall cut-off parameters are required to regularize the solution. Free energy of the scalar field is obtained through counting of states using the WKB approximation. It is found that the free energy and the entropy are divergent in both the cut-off parameters. |
1308.6565 | Luis Granda | L. N. Granda | Natural scaling for dark energy | 18 pages, 8 figures | null | 10.1142/S0217732313501174 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a dark energy density based on the Gauss-Bonnet 4-dimensional
invariant and its modification. This model avoids the necessity of introducing
the black hole limit to define the holographic density, since it can be
considered as a non-saturated regime. This allows to describe the dark energy
with an equation of state and Hubble parameter behaving in a way that can be
adjusted very well to recent observations. The model presents quintom behavior
without any future finite-time singularities.
| [
{
"created": "Thu, 29 Aug 2013 19:15:49 GMT",
"version": "v1"
}
] | 2013-08-30 | [
[
"Granda",
"L. N.",
""
]
] | We propose a dark energy density based on the Gauss-Bonnet 4-dimensional invariant and its modification. This model avoids the necessity of introducing the black hole limit to define the holographic density, since it can be considered as a non-saturated regime. This allows to describe the dark energy with an equation of state and Hubble parameter behaving in a way that can be adjusted very well to recent observations. The model presents quintom behavior without any future finite-time singularities. |
gr-qc/9511019 | Ugo Moschella | J. Bros and U. Moschella | Two-point Functions and Quantum Fields in de Sitter Universe | 51 p, uuencoded, LaTex, epsf, 2 figures included | Rev.Math.Phys. 8 (1996) 327-392 | 10.1142/S0129055X96000123 | Saclay preprint SPhT 94/160, to appear in Rev. Math. Phys | gr-qc | null | We present a theory of general two-point functions and of generalized free
fields in d-dimensional de Sitter space-time which closely parallels the
corresponding minkowskian theory. The usual spectral condition is now replaced
by a certain geodesic spectral condition, equivalent to a precise thermal
characterization of the corresponding ``vacuum''states. Our method is based on
the geometry of the complex de Sitter space-time and on the introduction of a
class of holomorphic functions on this manifold, called perikernels, which
reproduce mutatis mutandis the structural properties of the two-point
correlation functions of the minkowskian quantum field theory. The theory
contains as basic elementary case the linear massive field models in their
``preferred'' representation. The latter are described by the introduction of
de Sitter plane waves in their tube domains which lead to a new integral
representation of the two-point functions and to a Fourier-Laplace type
transformation on the hyperboloid. The Hilbert space structure of these
theories is then analysed by using this transformation. In particular we show
the Reeh-Schlieder property. For general two-point functions, a substitute to
the Wick rotation is defined both in complex space-time and in the complex mass
variable, and substantial results concerning the derivation of Kallen-Lehmann
type representation are obtained.
| [
{
"created": "Mon, 6 Nov 1995 12:06:08 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Bros",
"J.",
""
],
[
"Moschella",
"U.",
""
]
] | We present a theory of general two-point functions and of generalized free fields in d-dimensional de Sitter space-time which closely parallels the corresponding minkowskian theory. The usual spectral condition is now replaced by a certain geodesic spectral condition, equivalent to a precise thermal characterization of the corresponding ``vacuum''states. Our method is based on the geometry of the complex de Sitter space-time and on the introduction of a class of holomorphic functions on this manifold, called perikernels, which reproduce mutatis mutandis the structural properties of the two-point correlation functions of the minkowskian quantum field theory. The theory contains as basic elementary case the linear massive field models in their ``preferred'' representation. The latter are described by the introduction of de Sitter plane waves in their tube domains which lead to a new integral representation of the two-point functions and to a Fourier-Laplace type transformation on the hyperboloid. The Hilbert space structure of these theories is then analysed by using this transformation. In particular we show the Reeh-Schlieder property. For general two-point functions, a substitute to the Wick rotation is defined both in complex space-time and in the complex mass variable, and substantial results concerning the derivation of Kallen-Lehmann type representation are obtained. |
1606.03383 | Vladimir Shevchenko | Vladimir Shevchenko, Efim Shevrin | Archimedes Force on Casimir Apparatus | 13 pages, 1 figure | null | 10.1142/S0217732316501662 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address a problem of Casimir apparatus in dense medium and weak
gravitational field. The falling of the apparatus has to be governed by the
equivalence principle, with proper account for contributions to the weight of
the apparatus from its material part and from distorted quantum fields. We
discuss general expression for the corresponding force in metric with
cylindrical symmetry. By way of example we compute explicit expression for
Archimedes force, acting on the Casimir apparatus of finite size, immersed into
thermal bath of free scalar field. It is shown that besides universal term,
proportional to the volume of the apparatus, there are non-universal quantum
corrections, depending on the boundary conditions.
| [
{
"created": "Thu, 9 Jun 2016 16:30:23 GMT",
"version": "v1"
}
] | 2016-09-21 | [
[
"Shevchenko",
"Vladimir",
""
],
[
"Shevrin",
"Efim",
""
]
] | We address a problem of Casimir apparatus in dense medium and weak gravitational field. The falling of the apparatus has to be governed by the equivalence principle, with proper account for contributions to the weight of the apparatus from its material part and from distorted quantum fields. We discuss general expression for the corresponding force in metric with cylindrical symmetry. By way of example we compute explicit expression for Archimedes force, acting on the Casimir apparatus of finite size, immersed into thermal bath of free scalar field. It is shown that besides universal term, proportional to the volume of the apparatus, there are non-universal quantum corrections, depending on the boundary conditions. |
gr-qc/0203071 | Sergio Dain | Osvaldo M. Moreschi and Sergio Dain | Estimates of the total gravitation radiation in the head-on black hole
collision | 10 pages, 2 figures, LaTeX2e | Phys.Rev.D53:1745-1749,1996 | 10.1103/PhysRevD.53.R1745 | null | gr-qc | null | We report on calculations of the total gravitational energy radiated in the
head-on black hole collision, where we use the geometry of the
Robinson-Trautman metrics.
| [
{
"created": "Thu, 21 Mar 2002 15:49:50 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Moreschi",
"Osvaldo M.",
""
],
[
"Dain",
"Sergio",
""
]
] | We report on calculations of the total gravitational energy radiated in the head-on black hole collision, where we use the geometry of the Robinson-Trautman metrics. |
2208.04473 | Hussain Gohar | Ilim \c{C}imdiker, Mariusz P. Dabrowski and Hussain Gohar | Equilibrium Temperature for Black Holes with Nonextensive Entropy | 19 pages, some sections merged, accepted for publication in Eur.
Phys. J. C | Eur. Phys. J. C (2023) 83:169 | 10.1140/epjc/s10052-023-11317-0 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Hawking temperature has been widely utilised in the literature as the
temperature that corresponds to various nonextensive entropies. In this study,
we analyze the compatibility of the Hawking temperature with the nonextensive
entropies. We demonstrate that, for every nonextensive entropy, one may define
an effective temperature (which we call equilibrium temperature) by utilizing
the equilibrium condition, and that there is always an additive equilibrium
entropy associated with this effective temperature. Except for Bekenstein
entropy, we show that Hawking temperature is thermodynamically inconsistent
with other nonextensive entropies. We focus on the equilibrium requirement for
the Tsallis-Cirto black hole entropy and demonstrate that the
Bekenstein-Hawking entropy is the related equilibrium entropy, and the Hawking
temperature is the associated equilibrium temperature for the Tsallis-Cirto
black hole entropy.
| [
{
"created": "Tue, 9 Aug 2022 00:23:09 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Feb 2023 17:55:38 GMT",
"version": "v2"
}
] | 2023-02-24 | [
[
"Çimdiker",
"Ilim",
""
],
[
"Dabrowski",
"Mariusz P.",
""
],
[
"Gohar",
"Hussain",
""
]
] | Hawking temperature has been widely utilised in the literature as the temperature that corresponds to various nonextensive entropies. In this study, we analyze the compatibility of the Hawking temperature with the nonextensive entropies. We demonstrate that, for every nonextensive entropy, one may define an effective temperature (which we call equilibrium temperature) by utilizing the equilibrium condition, and that there is always an additive equilibrium entropy associated with this effective temperature. Except for Bekenstein entropy, we show that Hawking temperature is thermodynamically inconsistent with other nonextensive entropies. We focus on the equilibrium requirement for the Tsallis-Cirto black hole entropy and demonstrate that the Bekenstein-Hawking entropy is the related equilibrium entropy, and the Hawking temperature is the associated equilibrium temperature for the Tsallis-Cirto black hole entropy. |
1705.07694 | Puxun Wu | Puxun Wu, Jiawei Hu and Hongwei Yu | Interaction between two gravitationally polarizable objects induced by
thermal bath of gravitons | 11 pages. Accepted by PRD | null | 10.1103/PhysRevD.95.104057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quadrupole-quadrupole interaction between a pair of gravitationally
polarizable objects induced by vacuum fluctuations of the quantum linearized
gravitational field is first obtained with a relatively simple method, which is
then used to investigate the contribution of thermal fluctuations of a bath of
gravitons to the interaction at temperature $T$. Our result shows that, in the
high temperature limit, the contribution of thermal fluctuations dominates over
that of vacuum fluctuations and the interaction potential behaves like $T/
r^{10} $, where $r$ is the separation between the objects, and in the low
temperature limit, the contribution of thermal fluctuations is proportional to
$T^{10}/r$, which only provides a small correction to the interaction induced
by zero-point fluctuations.
| [
{
"created": "Mon, 22 May 2017 12:31:06 GMT",
"version": "v1"
}
] | 2017-06-28 | [
[
"Wu",
"Puxun",
""
],
[
"Hu",
"Jiawei",
""
],
[
"Yu",
"Hongwei",
""
]
] | The quadrupole-quadrupole interaction between a pair of gravitationally polarizable objects induced by vacuum fluctuations of the quantum linearized gravitational field is first obtained with a relatively simple method, which is then used to investigate the contribution of thermal fluctuations of a bath of gravitons to the interaction at temperature $T$. Our result shows that, in the high temperature limit, the contribution of thermal fluctuations dominates over that of vacuum fluctuations and the interaction potential behaves like $T/ r^{10} $, where $r$ is the separation between the objects, and in the low temperature limit, the contribution of thermal fluctuations is proportional to $T^{10}/r$, which only provides a small correction to the interaction induced by zero-point fluctuations. |
0808.4002 | Alessandro Nagar | Luca Baiotti, Sebastiano Bernuzzi, Giovanni Corvino, Roberto De
Pietri, Alessandro Nagar | Gravitational-Wave Extraction from Neutron Star Oscillations: comparing
linear and nonlinear techniques | 27 pages, 18 figures. Published in Phys. Rev. D | Phys.Rev.D79:024002,2009 | 10.1103/PhysRevD.79.024002 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main aim of this study is the comparison of gravitational waveforms
obtained from numerical simulations which employ different numerical evolution
approaches and different wave-extraction techniques. For this purpose, we
evolve an oscillating, non-rotating polytropic neutron-star model with two
different approaches: a full nonlinear relativistic simulation (in three
dimensions) and a linear simulation based on perturbation theory. The
extraction of the gravitational-wave signal is performed with three methods:
The gauge-invariant curvature-perturbation theory based on the Newman-Penrose
scalar $\psi_4$; The gauge-invariant Regge-Wheeler-Zerilli-Moncrief
metric-perturbation theory of a Schwarzschild space-time; Some generalization
of the quadrupole emission formula.
| [
{
"created": "Thu, 28 Aug 2008 21:47:58 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Sep 2008 08:37:41 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Mar 2009 13:37:35 GMT",
"version": "v3"
}
] | 2009-03-11 | [
[
"Baiotti",
"Luca",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Corvino",
"Giovanni",
""
],
[
"De Pietri",
"Roberto",
""
],
[
"Nagar",
"Alessandro",
""
]
] | The main aim of this study is the comparison of gravitational waveforms obtained from numerical simulations which employ different numerical evolution approaches and different wave-extraction techniques. For this purpose, we evolve an oscillating, non-rotating polytropic neutron-star model with two different approaches: a full nonlinear relativistic simulation (in three dimensions) and a linear simulation based on perturbation theory. The extraction of the gravitational-wave signal is performed with three methods: The gauge-invariant curvature-perturbation theory based on the Newman-Penrose scalar $\psi_4$; The gauge-invariant Regge-Wheeler-Zerilli-Moncrief metric-perturbation theory of a Schwarzschild space-time; Some generalization of the quadrupole emission formula. |
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