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1912.03897 | Waleed El Hanafy | G.G.L. Nashed, W. El Hanafy, S.D. Odintsov and V.K. Oikonomou | Thermodynamical correspondence of $f(R)$ gravity in Jordan and Einstein
frames | LaTeX2e (revtex4-1): 22 pages, 7 figures | Int. J. Mod. Phys. D, Vol. 29, No. 10, 1750154 (2020) | 10.1142/S021827182050090X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thermodynamical aspects of $f(R)$ gravity in the Jordan and the
Einstein frame, and we investigate the corresponding equivalence of the
thermodynamical quantities in the two frames. We examine static spherically
symmetric black hole solutions with constant Ricci scalar curvature $R$, and as
we demonstrate, the thermodynamical quantities in the two frames are
equivalent. However, for the case of black holes with non-constant scalar
curvature $R$, the thermodynamical equivalence of the two frames is no longer
valid. In addition, we examine cosmological solutions with non-trivial
curvatures and as we demonstrate the thermodynamical quantities in both frames
are not equivalent. In conclusion, although $f(R)$ gravity and its
corresponding scalar-tensor theory are mathematically equivalent, at least for
conformal invariant quantities, the two frames are not thermodynamically
equivalent at a quantitative level, in terms of several physical quantities.
| [
{
"created": "Mon, 9 Dec 2019 08:30:07 GMT",
"version": "v1"
}
] | 2020-08-19 | [
[
"Nashed",
"G. G. L.",
""
],
[
"Hanafy",
"W. El",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We study the thermodynamical aspects of $f(R)$ gravity in the Jordan and the Einstein frame, and we investigate the corresponding equivalence of the thermodynamical quantities in the two frames. We examine static spherically symmetric black hole solutions with constant Ricci scalar curvature $R$, and as we demonstrate, the thermodynamical quantities in the two frames are equivalent. However, for the case of black holes with non-constant scalar curvature $R$, the thermodynamical equivalence of the two frames is no longer valid. In addition, we examine cosmological solutions with non-trivial curvatures and as we demonstrate the thermodynamical quantities in both frames are not equivalent. In conclusion, although $f(R)$ gravity and its corresponding scalar-tensor theory are mathematically equivalent, at least for conformal invariant quantities, the two frames are not thermodynamically equivalent at a quantitative level, in terms of several physical quantities. |
2401.14116 | Marek Rogatko | Marek Rogatko | Uniqueness of photon sphere for Reissner-Nordstr\"om electric-magnetic
system | 22 pages, RevTex, to be published in Phys.Rev.D15 | null | 10.1103/PhysRevD.109.024056 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Uniqueness of static, asymptotically flat, non-extremal {\it photon sphere}
in Einstein-Maxwell spacetime with electric and magnetic charges has been
proved. Using conformal positive energy theorem, as well as, the positive mass
theorem and adequate conformal transformations, we envisage the two alternative
ways of proving that the exterior region of a certain radius of the studied
static {\it photon sphere}, is characterized by ADM mass, electric and magnetic
charges.
| [
{
"created": "Thu, 25 Jan 2024 11:53:32 GMT",
"version": "v1"
}
] | 2024-03-05 | [
[
"Rogatko",
"Marek",
""
]
] | Uniqueness of static, asymptotically flat, non-extremal {\it photon sphere} in Einstein-Maxwell spacetime with electric and magnetic charges has been proved. Using conformal positive energy theorem, as well as, the positive mass theorem and adequate conformal transformations, we envisage the two alternative ways of proving that the exterior region of a certain radius of the studied static {\it photon sphere}, is characterized by ADM mass, electric and magnetic charges. |
2210.04588 | Vincent Boudart | Vincent Boudart | A convolutional neural network to distinguish glitches from minute-long
gravitational wave transients | 12 pages, 15 figures | null | 10.1103/PhysRevD.107.024007 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Gravitational wave bursts are transient signals distinct from compact binary
mergers that arise from a wide variety of astrophysical phenomena. Because most
of these phenomena are poorly modeled, the use of traditional search methods
such as matched filtering is excluded. Bursts include short ($<$10 seconds) and
long (from 10 to a few hundreds of seconds) duration signals for which the
detection is constrained by environmental and instrumental transient noises
called glitches. Glitches contaminate burst searches, reducing the amount of
useful data and limiting the sensitivity of current algorithms. It is therefore
of primordial importance to locate and distinguish them from potential burst
signals. In this paper, we propose to train a convolutional neural network to
detect glitches in the time-frequency space of the cross-correlated LIGO noise.
We show that our network is retrieving more than 95$\%$ of the glitches while
being trained only on a subset of the existing glitch classes highlighting the
sensitivity of the network to completely new glitch classes.
| [
{
"created": "Mon, 10 Oct 2022 11:49:26 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Oct 2022 08:26:52 GMT",
"version": "v2"
}
] | 2023-01-18 | [
[
"Boudart",
"Vincent",
""
]
] | Gravitational wave bursts are transient signals distinct from compact binary mergers that arise from a wide variety of astrophysical phenomena. Because most of these phenomena are poorly modeled, the use of traditional search methods such as matched filtering is excluded. Bursts include short ($<$10 seconds) and long (from 10 to a few hundreds of seconds) duration signals for which the detection is constrained by environmental and instrumental transient noises called glitches. Glitches contaminate burst searches, reducing the amount of useful data and limiting the sensitivity of current algorithms. It is therefore of primordial importance to locate and distinguish them from potential burst signals. In this paper, we propose to train a convolutional neural network to detect glitches in the time-frequency space of the cross-correlated LIGO noise. We show that our network is retrieving more than 95$\%$ of the glitches while being trained only on a subset of the existing glitch classes highlighting the sensitivity of the network to completely new glitch classes. |
1303.5944 | Jacques Smulevici | Gustav Holzegel and Jacques Smulevici | Quasimodes and a Lower Bound on the Uniform Energy Decay Rate for
Kerr-AdS Spacetimes | null | Anal. PDE 7 (2014) 1057-1090 | 10.2140/apde.2014.7.1057 | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct quasimodes for the Klein-Gordon equation on the black hole
exterior of Kerr-Anti-de Sitter (Kerr-AdS) spacetimes. Such quasi-modes are
associated with time-periodic approximate solutions of the Klein Gordon
equation and provide natural candidates to probe the decay of solutions on
these backgrounds. They are constructed as the solutions of a semi-classical
non-linear eigenvalue problem arising after separation of variables, with the
(inverse of the) angular momentum playing the role of the semi-classical
parameter. Our construction results in exponentially small errors in the
semi-classical parameter. This implies that general solutions to the Klein
Gordon equation on Kerr-AdS cannot decay faster than logarithmically. The
latter result completes previous work by the authors, where a logarithmic decay
rate was established as an upper bound.
| [
{
"created": "Sun, 24 Mar 2013 12:54:54 GMT",
"version": "v1"
}
] | 2016-01-20 | [
[
"Holzegel",
"Gustav",
""
],
[
"Smulevici",
"Jacques",
""
]
] | We construct quasimodes for the Klein-Gordon equation on the black hole exterior of Kerr-Anti-de Sitter (Kerr-AdS) spacetimes. Such quasi-modes are associated with time-periodic approximate solutions of the Klein Gordon equation and provide natural candidates to probe the decay of solutions on these backgrounds. They are constructed as the solutions of a semi-classical non-linear eigenvalue problem arising after separation of variables, with the (inverse of the) angular momentum playing the role of the semi-classical parameter. Our construction results in exponentially small errors in the semi-classical parameter. This implies that general solutions to the Klein Gordon equation on Kerr-AdS cannot decay faster than logarithmically. The latter result completes previous work by the authors, where a logarithmic decay rate was established as an upper bound. |
1612.07865 | Baocheng Zhang | Baocheng Zhang and Li You | Infinite Volume of Noncommutative Black Hole Wrapped by Finite Surface | null | Physics Letter B 765, 226 (2017) | 10.1016/j.physletb.2016.12.027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The volume of a black hole under noncommutative spacetime background is found
to be infinite, in contradiction with the surface area of a black hole, or its
Bekenstein-Hawking (BH) entropy, which is well-known to be finite. Our result
rules out the possibility of interpreting the entropy of a black hole by
counting the number of modes wrapped inside its surface if the final
evaporation stage can be properly treated. It implies the statistical
interpretation for the BH entropy can be independent of the volume, provided
spacetime is noncommutative. The effect of radiation back reaction is found to
be small and doesn't influence the above conclusion.
| [
{
"created": "Fri, 23 Dec 2016 03:58:18 GMT",
"version": "v1"
}
] | 2016-12-26 | [
[
"Zhang",
"Baocheng",
""
],
[
"You",
"Li",
""
]
] | The volume of a black hole under noncommutative spacetime background is found to be infinite, in contradiction with the surface area of a black hole, or its Bekenstein-Hawking (BH) entropy, which is well-known to be finite. Our result rules out the possibility of interpreting the entropy of a black hole by counting the number of modes wrapped inside its surface if the final evaporation stage can be properly treated. It implies the statistical interpretation for the BH entropy can be independent of the volume, provided spacetime is noncommutative. The effect of radiation back reaction is found to be small and doesn't influence the above conclusion. |
gr-qc/9908011 | Abel Camacho Quintana | A. Camacho (Astrophysikalisches Institut Potsdam) and A.
Camacho-Galvan (DEP-FI-UNAM) | Time emergence by self-measurement in a quantum anisotropic universe | 19 pages, accepted in Nuovo Cimento B | Nuovo Cim. B114 (1999) 923-938 | null | null | gr-qc quant-ph | null | We begin this work calculating Halliwell's propagator in the case of a
Mixmaster universe with small anisotropy. Afterwards in the context of the
Decoherence Model we introduce in our system terms that comprise the
self-measurement of the universe of this model by higher multipoles of matter.
Analyzing self-measurement with the Restricted Path Integral Formalism we
obtain Halliwell's modified propagator and find that a gauge invariant physical
time emerges as consequence of this process. The conditions leading to
Wheeler-DeWitt dynamics are also obtained. The comparison of our results with
those of the isotropic case will enable us to conclude that the number of
conditions to be satisfied in order to have Halliwell's regime is in the
anisotropic situation bigger than in an isotropic universe. We obtain also in
terms of the parameters of the measurement process an expression for the
threshold in time beyond which the scale factors of this model are meaningless.
| [
{
"created": "Tue, 3 Aug 1999 15:57:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Camacho",
"A.",
"",
"Astrophysikalisches Institut Potsdam"
],
[
"Camacho-Galvan",
"A.",
"",
"DEP-FI-UNAM"
]
] | We begin this work calculating Halliwell's propagator in the case of a Mixmaster universe with small anisotropy. Afterwards in the context of the Decoherence Model we introduce in our system terms that comprise the self-measurement of the universe of this model by higher multipoles of matter. Analyzing self-measurement with the Restricted Path Integral Formalism we obtain Halliwell's modified propagator and find that a gauge invariant physical time emerges as consequence of this process. The conditions leading to Wheeler-DeWitt dynamics are also obtained. The comparison of our results with those of the isotropic case will enable us to conclude that the number of conditions to be satisfied in order to have Halliwell's regime is in the anisotropic situation bigger than in an isotropic universe. We obtain also in terms of the parameters of the measurement process an expression for the threshold in time beyond which the scale factors of this model are meaningless. |
gr-qc/0302059 | Andrzej Okolow | Andrzej Okolow and Jerzy Lewandowski | Diffeomorphism covariant representations of the holonomy-flux
star-algebra | 37 pages, no figures, LaTeX2e, to be published in Class. Quant. Grav;
typos corrected, minor clarifying remarks | Class.Quant.Grav. 20 (2003) 3543-3568 | 10.1088/0264-9381/20/16/302 | null | gr-qc | null | Recently, Sahlmann proposed a new, algebraic point of view on the loop
quantization. He brought up the issue of a star-algebra underlying that
framework, studied the algebra consisting of the fluxes and holonomies and
characterized its representations. We define the diffeomorphism covariance of a
representation of the Sahlmann algebra and study the diffeomorphism covariant
representations. We prove they are all given by Sahlmann's decomposition into
the cyclic representations of the sub-algebra of the holonomies by using a
single state only. The state corresponds to the natural measure defined on the
space of the generalized connections. This result is a generalization of
Sahlmann's result concerning the U(1) case.
| [
{
"created": "Fri, 14 Feb 2003 18:03:58 GMT",
"version": "v1"
},
{
"created": "Sun, 22 Jun 2003 23:20:39 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Jun 2003 16:54:30 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Okolow",
"Andrzej",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | Recently, Sahlmann proposed a new, algebraic point of view on the loop quantization. He brought up the issue of a star-algebra underlying that framework, studied the algebra consisting of the fluxes and holonomies and characterized its representations. We define the diffeomorphism covariance of a representation of the Sahlmann algebra and study the diffeomorphism covariant representations. We prove they are all given by Sahlmann's decomposition into the cyclic representations of the sub-algebra of the holonomies by using a single state only. The state corresponds to the natural measure defined on the space of the generalized connections. This result is a generalization of Sahlmann's result concerning the U(1) case. |
gr-qc/0503102 | Brihaye Yves | Yves Brihaye (Universite de Mons-Hainaut, Belgium) and Betti Hartmann
(IUB, Germany) | Deformed black strings in 5-dimensional Einstein-Yang-Mills theory | 8 Revtex pages; 4 eps figures; references added | Class.Quant.Grav. 22 (2005) 5145-5156 | 10.1088/0264-9381/22/23/014 | null | gr-qc hep-th | null | We construct the first examples of deformed non-abelian black strings in a
5-dimensional Einstein-Yang-Mills model. Assuming all fields to be independent
of the extra coordinate, we construct deformed black strings, which in the
4-dimensional picture correspond to axially symmetric non-abelian black holes
in gravity-dilaton theory. These solutions thus have deformed S^2 x R horizon
topology. We study fundamental properties of the black strings and find that
for all choices of the gravitational coupling two branches of solutions exist.
The limiting behaviour of the second branch of solutions however depends
strongly on the choice of the gravitational coupling.
| [
{
"created": "Wed, 23 Mar 2005 17:08:36 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Apr 2005 14:47:19 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Apr 2005 09:56:15 GMT",
"version": "v3"
},
{
"created": "Fri, 14 Oct 2005 08:11:32 GMT",
"version": "v4"
}
] | 2009-11-11 | [
[
"Brihaye",
"Yves",
"",
"Universite de Mons-Hainaut, Belgium"
],
[
"Hartmann",
"Betti",
"",
"IUB, Germany"
]
] | We construct the first examples of deformed non-abelian black strings in a 5-dimensional Einstein-Yang-Mills model. Assuming all fields to be independent of the extra coordinate, we construct deformed black strings, which in the 4-dimensional picture correspond to axially symmetric non-abelian black holes in gravity-dilaton theory. These solutions thus have deformed S^2 x R horizon topology. We study fundamental properties of the black strings and find that for all choices of the gravitational coupling two branches of solutions exist. The limiting behaviour of the second branch of solutions however depends strongly on the choice of the gravitational coupling. |
1407.5033 | Alessandro Nagar | Alessandro Nagar, Enno Harms, Sebastiano Bernuzzi and An{\i}l
Zengino\u{g}lu | The antikick strikes back: recoil velocities for nearly-extremal binary
black hole mergers in the test-mass limit | 9 pages, 6 figures, submitted to Phys. Rev. D | null | 10.1103/PhysRevD.90.124086 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves emitted from a generic binary black-hole merger carry
away linear momentum anisotropically, resulting in a gravitational recoil, or
"kick", of the center of mass. For certain merger configurations the time
evolution of the magnitude of the kick velocity has a local maximum followed by
a sudden drop. Perturbative studies of this "antikick" in a limited range of
black hole spins have found that the antikick decreases for retrograde orbits
as a function of negative spin. We analyze this problem using a recently
developed code to evolve gravitational perturbations from a point-particle in
Kerr spacetime driven by an effective-one-body resummed radiation reaction
force at linear order in the mass ratio $\nu\ll 1$. Extending previous studies
to nearly-extremal negative spins, we find that the well-known decrease of the
antikick is overturned and, instead of approaching zero, the antikick increases
again to reach $\Delta v/(c\nu^{2})=3.37\times10^{-3}$ for dimensionless spin
$\hat{a}=-0.9999$. The corresponding final kick velocity is
$v_{end}/(c\nu^{2})=0.076$. This result is connected to the nonadiabatic
character of the emission of linear momentum during the plunge. We interpret it
analytically by means of the quality factor of the flux to capture
quantitatively the main properties of the kick velocity. The use of such
quality factor of the flux does not require trajectories nor horizon curvature
distributions and should therefore be useful both in perturbation theory and
numerical relativity.
| [
{
"created": "Fri, 18 Jul 2014 15:20:52 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Nagar",
"Alessandro",
""
],
[
"Harms",
"Enno",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Zenginoğlu",
"Anıl",
""
]
] | Gravitational waves emitted from a generic binary black-hole merger carry away linear momentum anisotropically, resulting in a gravitational recoil, or "kick", of the center of mass. For certain merger configurations the time evolution of the magnitude of the kick velocity has a local maximum followed by a sudden drop. Perturbative studies of this "antikick" in a limited range of black hole spins have found that the antikick decreases for retrograde orbits as a function of negative spin. We analyze this problem using a recently developed code to evolve gravitational perturbations from a point-particle in Kerr spacetime driven by an effective-one-body resummed radiation reaction force at linear order in the mass ratio $\nu\ll 1$. Extending previous studies to nearly-extremal negative spins, we find that the well-known decrease of the antikick is overturned and, instead of approaching zero, the antikick increases again to reach $\Delta v/(c\nu^{2})=3.37\times10^{-3}$ for dimensionless spin $\hat{a}=-0.9999$. The corresponding final kick velocity is $v_{end}/(c\nu^{2})=0.076$. This result is connected to the nonadiabatic character of the emission of linear momentum during the plunge. We interpret it analytically by means of the quality factor of the flux to capture quantitatively the main properties of the kick velocity. The use of such quality factor of the flux does not require trajectories nor horizon curvature distributions and should therefore be useful both in perturbation theory and numerical relativity. |
gr-qc/0203062 | Amritanshu Shukla | G S Khadekar, Bavana Butey (Department of Mathematics, Nagpur
University, Nagpur) | Bimetric Gravitation and Cosmology in Five Dimension | Latex 8 pages, no figure | null | null | null | gr-qc | null | Lee. et.al. (1976) analysed the bimetric theory with the help of
parameterized post Newtonian (PPN) formalism. They found that the post
Newtonian limit of the theory is identical with that of general theory of
relativity except for their PPN parameter $\alpha_{2}$, on the basis of
cosmological considerations. In the present paper it is pointed out that
feasibility of such considerations are doubtful in five dimensional bimetric
theory of relativity. As the universe is unique and is governed by physical
laws, many different cosmologies are possible. Examples are given for some
possible cosmological models, which are different, that those of Lee. et.al.
This work is an extension in five dimension of a similar one obtained earlier
by Rosen (1977) for four dimensional space-time.
| [
{
"created": "Tue, 19 Mar 2002 03:48:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Khadekar",
"G S",
"",
"Department of Mathematics, Nagpur\n University, Nagpur"
],
[
"Butey",
"Bavana",
"",
"Department of Mathematics, Nagpur\n University, Nagpur"
]
] | Lee. et.al. (1976) analysed the bimetric theory with the help of parameterized post Newtonian (PPN) formalism. They found that the post Newtonian limit of the theory is identical with that of general theory of relativity except for their PPN parameter $\alpha_{2}$, on the basis of cosmological considerations. In the present paper it is pointed out that feasibility of such considerations are doubtful in five dimensional bimetric theory of relativity. As the universe is unique and is governed by physical laws, many different cosmologies are possible. Examples are given for some possible cosmological models, which are different, that those of Lee. et.al. This work is an extension in five dimension of a similar one obtained earlier by Rosen (1977) for four dimensional space-time. |
1902.10726 | Pedro Gir\~ao | Jo\~ao L. Costa and Pedro M. Gir\~ao | Higher Order Linear Stability and Instability of Reissner-Nordstr\"om's
Cauchy Horizon | 22 pages, 2 figures | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider smooth solutions of the wave equation, on a fixed black hole
region of a subextremal Reissner-Nordstr\"om (asymptotically flat, de Sitter or
anti-de Sitter) spacetime, whose restrictions to the event horizon have compact
support. We provide criteria, in terms of surface gravities, for the waves to
remain in $C^l$, $l\geq 1$, up to and including the Cauchy horizon. We also
provide sufficient conditions for the blow up of solutions in $C^1$ and $H^1$.
| [
{
"created": "Wed, 27 Feb 2019 19:00:14 GMT",
"version": "v1"
}
] | 2019-03-01 | [
[
"Costa",
"João L.",
""
],
[
"Girão",
"Pedro M.",
""
]
] | We consider smooth solutions of the wave equation, on a fixed black hole region of a subextremal Reissner-Nordstr\"om (asymptotically flat, de Sitter or anti-de Sitter) spacetime, whose restrictions to the event horizon have compact support. We provide criteria, in terms of surface gravities, for the waves to remain in $C^l$, $l\geq 1$, up to and including the Cauchy horizon. We also provide sufficient conditions for the blow up of solutions in $C^1$ and $H^1$. |
gr-qc/0008032 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | The large cosmological constant approximation to classical and quantum
gravity: model examples | 21 pages, RevTex, 2 figures with epsfig | Class.Quant.Grav. 17 (2000) 4515-4540 | 10.1088/0264-9381/17/21/311 | CGPG-00/8-3 | gr-qc hep-th | null | We have recently introduced an approach for studying perturbatively classical
and quantum canonical general relativity. The perturbative technique appears to
preserve many of the attractive features of the non-perturbative quantization
approach based on Ashtekar's new variables and spin networks. With this
approach one can find perturbatively classical observables (quantities that
have vanishing Poisson brackets with the constraints) and quantum states
(states that are annihilated by the quantum constraints). The relative ease
with which the technique appears to deal with these traditionally hard problems
opens several questions about how relevant the results produced can possibly
be. Among the questions is the issue of how useful are results for large values
of the cosmological constant and how the approach can deal with several
pathologies that are expected to be present in the canonical approach to
quantum gravity. With the aim of clarifying these points, and to make our
construction as explicit as possible, we study its application in several
simple models. We consider Bianchi cosmologies, the asymmetric top, the coupled
harmonic oscillators with constant energy density and a simple quantum
mechanical system with two Hamiltonian constraints. We find that the technique
satisfactorily deals with the pathologies of these models and offers promise
for finding (at least some) results even for small values of the cosmological
constant. Finally, we briefly sketch how the method would operate in the full
four dimensional quantum general relativity case.
| [
{
"created": "Mon, 14 Aug 2000 20:26:10 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Aug 2000 13:14:37 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We have recently introduced an approach for studying perturbatively classical and quantum canonical general relativity. The perturbative technique appears to preserve many of the attractive features of the non-perturbative quantization approach based on Ashtekar's new variables and spin networks. With this approach one can find perturbatively classical observables (quantities that have vanishing Poisson brackets with the constraints) and quantum states (states that are annihilated by the quantum constraints). The relative ease with which the technique appears to deal with these traditionally hard problems opens several questions about how relevant the results produced can possibly be. Among the questions is the issue of how useful are results for large values of the cosmological constant and how the approach can deal with several pathologies that are expected to be present in the canonical approach to quantum gravity. With the aim of clarifying these points, and to make our construction as explicit as possible, we study its application in several simple models. We consider Bianchi cosmologies, the asymmetric top, the coupled harmonic oscillators with constant energy density and a simple quantum mechanical system with two Hamiltonian constraints. We find that the technique satisfactorily deals with the pathologies of these models and offers promise for finding (at least some) results even for small values of the cosmological constant. Finally, we briefly sketch how the method would operate in the full four dimensional quantum general relativity case. |
gr-qc/9912091 | Luca Lusanna | Luca Lusanna (INFN, Firenze) | Tetrad Gravity and Dirac's Observables | 11 pages, Revtex file | Nucl.Phys.Proc.Suppl. 88 (2000) 301-307 | 10.1016/S0920-5632(00)00790-8 | null | gr-qc astro-ph hep-th | null | Talk given at the Conference ``Constrained Dynamics and Quantum Gravity 99'',
Villasimius (Sardinia, Italy), September 13-17, 1999
| [
{
"created": "Tue, 21 Dec 1999 14:52:34 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Lusanna",
"Luca",
"",
"INFN, Firenze"
]
] | Talk given at the Conference ``Constrained Dynamics and Quantum Gravity 99'', Villasimius (Sardinia, Italy), September 13-17, 1999 |
gr-qc/0010039 | Vladimir Zhelnorovich | V.A.Zhelnorovich | General exact solution of the Einstein-Dirac equations with the
cosmological constant in homogeneous space | 12 pages, RevTex, minor correction | J.Exp.Theor.Phys. 98 (2004) 619-628; Zh.Eksp.Teor.Fiz. 125 (2004)
707-716 | 10.1134/1.1757661 | null | gr-qc | null | The general exact solution of the Einstein-Dirac equations with cosmological
constant in the homogeneous Riemannian space of the Bianchi 1 type is obtained.
| [
{
"created": "Tue, 10 Oct 2000 15:15:35 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Oct 2000 19:38:06 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Zhelnorovich",
"V. A.",
""
]
] | The general exact solution of the Einstein-Dirac equations with cosmological constant in the homogeneous Riemannian space of the Bianchi 1 type is obtained. |
2209.02698 | Grigory Volovik | G.E. Volovik | Painleve-Gullstrand coordinates for Schwarzschild-de Sitter spacetime | 6 pages, no figures | null | 10.1016/j.aop.2023.169219 | null | gr-qc cond-mat.other | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Painleve-Gullstrand coordinates are extended to describe the black hole
in the cosmological environment: the Schwarzschild-de-Sitter black hole, which
has two horizons. The extension is made using the Arnowitt-Deser-Misner
formalism. In this extension, which describes the metric in the whole range of
radial coordinates $0<r < \infty$, there is the point $r=r_0$ at which the
shift function (velocity) changes sign. At this point the observer is at rest,
while the observers at $r<r_0$ are free falling to the black hole and the
observers at $r>r_0$ are free falling towards the cosmological horizon. The
existence of the stationary observer allows to determine the temperature of
Hawking radiation, which is in agreement with R. Bousso and S.W. Hawking, Phys.
Rev. D 54, 6312 (1996). It is the red-shifted modification of the conventional
Hawking temperature determined by the gravity at the horizon. We also consider
the Painlev\'e-Gullstrand coordinates and their extension for such
configurations as Schwarzschild-de-Sitter white hole, where the sign of the
shift function is everywhere positive; the black hole in the environment of the
contracting de Sitter spacetime, where the sign of the shift function is
everywhere negative; and the white hole in the contracting de Sitter spacetime,
where the shift velocity changes sign at $r=r_0$.
| [
{
"created": "Mon, 5 Sep 2022 10:33:23 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2022 15:17:16 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Sep 2022 14:02:11 GMT",
"version": "v3"
},
{
"created": "Mon, 7 Nov 2022 19:19:30 GMT",
"version": "v4"
},
{
"cre... | 2023-01-25 | [
[
"Volovik",
"G. E.",
""
]
] | The Painleve-Gullstrand coordinates are extended to describe the black hole in the cosmological environment: the Schwarzschild-de-Sitter black hole, which has two horizons. The extension is made using the Arnowitt-Deser-Misner formalism. In this extension, which describes the metric in the whole range of radial coordinates $0<r < \infty$, there is the point $r=r_0$ at which the shift function (velocity) changes sign. At this point the observer is at rest, while the observers at $r<r_0$ are free falling to the black hole and the observers at $r>r_0$ are free falling towards the cosmological horizon. The existence of the stationary observer allows to determine the temperature of Hawking radiation, which is in agreement with R. Bousso and S.W. Hawking, Phys. Rev. D 54, 6312 (1996). It is the red-shifted modification of the conventional Hawking temperature determined by the gravity at the horizon. We also consider the Painlev\'e-Gullstrand coordinates and their extension for such configurations as Schwarzschild-de-Sitter white hole, where the sign of the shift function is everywhere positive; the black hole in the environment of the contracting de Sitter spacetime, where the sign of the shift function is everywhere negative; and the white hole in the contracting de Sitter spacetime, where the shift velocity changes sign at $r=r_0$. |
0710.5613 | Dario Zappala | M. Consoli, E. Costanzo | Flat-space picture of gravity vs. General Relativity: a precision test
for present ether-drift experiments | 23 pages, 7 tables, no figures | null | null | null | gr-qc | null | Modern ether-drift experiments in vacuum could in principle detect the tiny
refractive index that, in a flat-space picture of gravity, is appropriate for
an apparatus placed on the Earth's surface. In this picture, in fact, if there
were a preferred reference frame, light on the Earth would exhibit a slight
anisotropy with definite quantitative differences from General Relativity. By
re-analyzing the data published by two modern experiments with rotating optical
resonators, and concentrating on the part of the signal that should be free of
spurious systematic effects, we have found evidences that would support the
flat-space scenario.
| [
{
"created": "Tue, 30 Oct 2007 11:29:10 GMT",
"version": "v1"
}
] | 2007-10-31 | [
[
"Consoli",
"M.",
""
],
[
"Costanzo",
"E.",
""
]
] | Modern ether-drift experiments in vacuum could in principle detect the tiny refractive index that, in a flat-space picture of gravity, is appropriate for an apparatus placed on the Earth's surface. In this picture, in fact, if there were a preferred reference frame, light on the Earth would exhibit a slight anisotropy with definite quantitative differences from General Relativity. By re-analyzing the data published by two modern experiments with rotating optical resonators, and concentrating on the part of the signal that should be free of spurious systematic effects, we have found evidences that would support the flat-space scenario. |
1906.03624 | Jun Peng | Luca Buoninfante, Anupam Mazumdar, Jun Peng | Nonlocality amplifies echoes | 4 pages + 3 figures | Phys. Rev. D 100, 104059 (2019) | 10.1103/PhysRevD.100.104059 | null | gr-qc cond-mat.other hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we will provide smoking-gun signatures of nonlocal interactions
while studying reflection and transmission of waves bouncing through two Dirac
delta potentials. In particular, we will show that the transmission of waves is
less damped compared to the local case, due to the fact that nonlocality
weakens the interaction. As a consequence the echoes are amplified. These
signatures can be potentially detectable in the context of gravitational waves,
where two Dirac delta potentials can mimic the two potential barriers at the
surface and at the photon sphere of an ultra compact object, or, at the two
photon spheres of a wormhole, experiencing nonlocal interactions.
| [
{
"created": "Sun, 9 Jun 2019 12:11:17 GMT",
"version": "v1"
}
] | 2019-12-04 | [
[
"Buoninfante",
"Luca",
""
],
[
"Mazumdar",
"Anupam",
""
],
[
"Peng",
"Jun",
""
]
] | In this paper we will provide smoking-gun signatures of nonlocal interactions while studying reflection and transmission of waves bouncing through two Dirac delta potentials. In particular, we will show that the transmission of waves is less damped compared to the local case, due to the fact that nonlocality weakens the interaction. As a consequence the echoes are amplified. These signatures can be potentially detectable in the context of gravitational waves, where two Dirac delta potentials can mimic the two potential barriers at the surface and at the photon sphere of an ultra compact object, or, at the two photon spheres of a wormhole, experiencing nonlocal interactions. |
0810.0447 | Francesco Cianfrani dr | Francesco Cianfrani, Giovanni Montani | Dirac equations in curved space-time versus Papapetrou spinning
particles | 6 pages, 1 figure, accepted for publication in Europhysics Letters | Europhys.Lett.84:30008,2008 | 10.1209/0295-5075/84/30008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find out classical particles, starting from Dirac quantum fields on a
curved space-time, by an eikonal approximation and a localization hypothesis
for amplitudes. We recover the results by Mathisson-Papapetrou, hence
establishing a fundamental correspondence between the coupling of classical and
quantum spinning particles with the gravitational field.
| [
{
"created": "Thu, 2 Oct 2008 15:30:06 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Cianfrani",
"Francesco",
""
],
[
"Montani",
"Giovanni",
""
]
] | We find out classical particles, starting from Dirac quantum fields on a curved space-time, by an eikonal approximation and a localization hypothesis for amplitudes. We recover the results by Mathisson-Papapetrou, hence establishing a fundamental correspondence between the coupling of classical and quantum spinning particles with the gravitational field. |
1607.06095 | Alan Kostelecky | Cheng-Gang Shao, Yu-Jie Tan, Wen-Hai Tan, Shan-Qing Yang, Jun Luo,
Michael Edmund Tobar, Quentin G. Bailey, J.C. Long, E. Weisman, Rui Xu, Alan
Kostelecky | Combined search for Lorentz violation in short-range gravity | 5 pages two-column REVTeX, accepted for publication in Physical
Review Letters | Phys.Rev.Lett.117:071102,2016 | 10.1103/PhysRevLett.117.071102 | null | gr-qc hep-ex hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Short-range experiments testing the gravitational inverse-square law at the
submillimeter scale offer uniquely sensitive probes of Lorentz invariance. A
combined analysis of results from the short-range gravity experiments
HUST-2015, HUST-2011, IU-2012, and IU-2002 permits the first independent
measurements of the 14 nonrelativistic coefficients for Lorentz violation in
the pure-gravity sector at the level of $10^{-9}$ m$^2$, improving by an order
of magnitude the sensitivity to numerous types of Lorentz violation involving
quadratic curvature derivatives and curvature couplings.
| [
{
"created": "Wed, 20 Jul 2016 20:00:07 GMT",
"version": "v1"
}
] | 2016-11-08 | [
[
"Shao",
"Cheng-Gang",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Tan",
"Wen-Hai",
""
],
[
"Yang",
"Shan-Qing",
""
],
[
"Luo",
"Jun",
""
],
[
"Tobar",
"Michael Edmund",
""
],
[
"Bailey",
"Quentin G.",
""
],
[
... | Short-range experiments testing the gravitational inverse-square law at the submillimeter scale offer uniquely sensitive probes of Lorentz invariance. A combined analysis of results from the short-range gravity experiments HUST-2015, HUST-2011, IU-2012, and IU-2002 permits the first independent measurements of the 14 nonrelativistic coefficients for Lorentz violation in the pure-gravity sector at the level of $10^{-9}$ m$^2$, improving by an order of magnitude the sensitivity to numerous types of Lorentz violation involving quadratic curvature derivatives and curvature couplings. |
1810.11816 | Carlo Pagani | Maximilian Becker, Carlo Pagani | Geometric operators in the asymptotic safety scenario for quantum
gravity | 31 pages | Phys. Rev. D 99, 066002 (2019) | 10.1103/PhysRevD.99.066002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider geometric operators, such as the geodesic length and the volume
of hypersurfaces, in the context of the Asymptotic Safety scenario for quantum
gravity. We discuss the role of these operators from the Asymptotic Safety
perspective, and compute their anomalous dimensions within the Einstein-Hilbert
truncation. We also discuss certain subtleties arising in the definition of
such geometric operators. Our results hint to an effective dimensional
reduction of the considered geometric operators.
| [
{
"created": "Sun, 28 Oct 2018 14:11:38 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Apr 2019 08:30:12 GMT",
"version": "v2"
}
] | 2019-04-16 | [
[
"Becker",
"Maximilian",
""
],
[
"Pagani",
"Carlo",
""
]
] | We consider geometric operators, such as the geodesic length and the volume of hypersurfaces, in the context of the Asymptotic Safety scenario for quantum gravity. We discuss the role of these operators from the Asymptotic Safety perspective, and compute their anomalous dimensions within the Einstein-Hilbert truncation. We also discuss certain subtleties arising in the definition of such geometric operators. Our results hint to an effective dimensional reduction of the considered geometric operators. |
1708.04646 | Pablo Anglada | Pablo Anglada | Penrose-like inequality with angular momentum for minimal surfaces | null | Class. Quantum Grav. 35(4), 2018, 045018 | 10.1088/1361-6382/aaa0a6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In axially symmetric spacetimes the Penrose inequality can be strengthened to
include angular momentum. We prove a version of this inequality for minimal
surfaces, more precisely, a lower bound for the ADM mass in terms of the area
of a minimal surface, the angular momentum and a particular measure of the
surface size. We consider axially symmetric and asymptotically flat initial
data, and use the monotonicity of the Geroch quasi-local energy on 2-surfaces
along the inverse mean curvature flow.
| [
{
"created": "Tue, 15 Aug 2017 18:55:16 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jan 2018 12:33:50 GMT",
"version": "v2"
}
] | 2018-01-26 | [
[
"Anglada",
"Pablo",
""
]
] | In axially symmetric spacetimes the Penrose inequality can be strengthened to include angular momentum. We prove a version of this inequality for minimal surfaces, more precisely, a lower bound for the ADM mass in terms of the area of a minimal surface, the angular momentum and a particular measure of the surface size. We consider axially symmetric and asymptotically flat initial data, and use the monotonicity of the Geroch quasi-local energy on 2-surfaces along the inverse mean curvature flow. |
1109.2804 | Sijie Gao | Sijie Gao | A general maximum entropy principle for self-gravitating perfect fluid | 13 pages, no figure. The arguments have been improved so that the
assumption p=p(\rho) is no longer needed | Phys.Rev.D 84, 104023 (2011); Phys. Rev. D 85, 027503 (2012) | 10.1103/PhysRevD.84.104023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a self-gravitating system consisting of perfect fluid with
spherical symmetry. Using the general expression of entropy density, we
extremize the total entropy $S$ under the constraint that the total number of
particles is fixed. We show that extrema of $S$ coincides precisely with the
relativistic Tolman-Oppenheimer-Volkoff (TOV) equation of hydrostatic
equilibrium. Furthermore, we apply the maximum entropy principle to a charged
perfect fluid and derive the generalized TOV equation. Our work provides a
strong evidence for the fundamental relationship between general relativity and
ordinary thermodynamics.
| [
{
"created": "Tue, 13 Sep 2011 14:42:50 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Oct 2011 05:09:30 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Jan 2012 11:10:47 GMT",
"version": "v3"
}
] | 2015-05-30 | [
[
"Gao",
"Sijie",
""
]
] | We consider a self-gravitating system consisting of perfect fluid with spherical symmetry. Using the general expression of entropy density, we extremize the total entropy $S$ under the constraint that the total number of particles is fixed. We show that extrema of $S$ coincides precisely with the relativistic Tolman-Oppenheimer-Volkoff (TOV) equation of hydrostatic equilibrium. Furthermore, we apply the maximum entropy principle to a charged perfect fluid and derive the generalized TOV equation. Our work provides a strong evidence for the fundamental relationship between general relativity and ordinary thermodynamics. |
1809.03579 | Behnam Pourhassan | Sudhaker Upadhyay, Behnam Pourhassan, and Salvatore Capozziello | Thermodynamics and phase transitions of galactic clustering in
higher-order Modified Gravity | Accepted for publication in IJMPD | Int. J. Mod. Phys. D 28 (2019) 1950027 | 10.1142/S0218271819500275 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thermodynamics of galactic clustering under the higher-order
corrected Newtonian dynamics. The clustering of galaxies is considered as a
gravitational phase transition. In order to study the effects of higher-order
correction to the thermodynamics of gravitational system, we compute more exact
equations of state. Moreover, we investigate the corrected probability
distribution function for such gravitating system. A relation between order
parameter and the critical temperature is also established.
| [
{
"created": "Tue, 11 Sep 2018 06:04:57 GMT",
"version": "v1"
}
] | 2019-01-23 | [
[
"Upadhyay",
"Sudhaker",
""
],
[
"Pourhassan",
"Behnam",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | We study the thermodynamics of galactic clustering under the higher-order corrected Newtonian dynamics. The clustering of galaxies is considered as a gravitational phase transition. In order to study the effects of higher-order correction to the thermodynamics of gravitational system, we compute more exact equations of state. Moreover, we investigate the corrected probability distribution function for such gravitating system. A relation between order parameter and the critical temperature is also established. |
2308.11595 | Mostafa Bousder Dr. | M. Bousder, A.Riadsolh, M El Belkacemi and H. Ez-Zahraouy | Cosmic acceleration in Lovelock quantum gravity | 18 pages, 2 figures | Volume 458, Part 1, November 2023, 169441 | 10.1016/j.aop.2023.169441 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | This paper introduces novel solutions for inflation and late-time cosmic
acceleration within the framework of quantum Lovelock gravity, utilizing
Friedmann equations. Furthermore, we demonstrate the hypergeometric states of
cosmic acceleration through the Schr\"{o}dinger stationary equation. A physical
interpretation is proposed, whereby the rescaled Lovelock couplings represent a
topological mass that characterizes the Lovelock branch. This research holds
the potential for an extension into the quantum description. Predictions for
the spectral tilt and tensor-to-scalar ratio are depicted through plotted
curves. By utilizing the rescaled Hubble parameter, the spectral index is
determined in terms of the number of e-folds.
| [
{
"created": "Mon, 21 Aug 2023 12:23:29 GMT",
"version": "v1"
}
] | 2023-08-23 | [
[
"Bousder",
"M.",
""
],
[
"Riadsolh",
"A.",
""
],
[
"Belkacemi",
"M El",
""
],
[
"Ez-Zahraouy",
"H.",
""
]
] | This paper introduces novel solutions for inflation and late-time cosmic acceleration within the framework of quantum Lovelock gravity, utilizing Friedmann equations. Furthermore, we demonstrate the hypergeometric states of cosmic acceleration through the Schr\"{o}dinger stationary equation. A physical interpretation is proposed, whereby the rescaled Lovelock couplings represent a topological mass that characterizes the Lovelock branch. This research holds the potential for an extension into the quantum description. Predictions for the spectral tilt and tensor-to-scalar ratio are depicted through plotted curves. By utilizing the rescaled Hubble parameter, the spectral index is determined in terms of the number of e-folds. |
1512.00032 | Yu Chen | Yu Chen | Gravitational multi-soliton solutions on flat space | 68 pages, 5 figures, LaTeX; v2: published version | Phys. Rev. D 93, 044021 (2016) | 10.1103/PhysRevD.93.044021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known that, for even n, the n-soliton solution on the Minkowski
seed, constructed using the inverse-scattering method (ISM) of Belinski and
Zakharov (BZ), is the multi-Kerr-NUT solution. We show that, for odd n, the
natural seed to use is the Euclidean space with two manifest translational
symmetries, and the n-soliton solution is the accelerating multi-Kerr-NUT
solution. We thus define the n-soliton solution on flat space for any positive
integer n. It admits both Lorentzian and Euclidean sections. In the latter
section, we find that a number, say m, of solitons can be eliminated in a
non-trivial way by appropriately fixing their corresponding so-called BZ
parameters. The resulting solutions, which may split into separate classes, are
collectively denoted as [n-m]-soliton solutions on flat space. We then carry
out a systematic study of the n- and [n-m]-soliton solutions on flat space.
This includes, in particular, an explicit presentation of their ISM
construction, an analysis of their local geometries, and a classification of
all separate classes of solutions they form. We also show how even-soliton
solutions on the seeds of the collinearly centred Gibbons-Hawking and Taub-NUT
arise from these solutions.
| [
{
"created": "Mon, 30 Nov 2015 21:08:01 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 2016 02:45:59 GMT",
"version": "v2"
}
] | 2016-02-17 | [
[
"Chen",
"Yu",
""
]
] | It is well known that, for even n, the n-soliton solution on the Minkowski seed, constructed using the inverse-scattering method (ISM) of Belinski and Zakharov (BZ), is the multi-Kerr-NUT solution. We show that, for odd n, the natural seed to use is the Euclidean space with two manifest translational symmetries, and the n-soliton solution is the accelerating multi-Kerr-NUT solution. We thus define the n-soliton solution on flat space for any positive integer n. It admits both Lorentzian and Euclidean sections. In the latter section, we find that a number, say m, of solitons can be eliminated in a non-trivial way by appropriately fixing their corresponding so-called BZ parameters. The resulting solutions, which may split into separate classes, are collectively denoted as [n-m]-soliton solutions on flat space. We then carry out a systematic study of the n- and [n-m]-soliton solutions on flat space. This includes, in particular, an explicit presentation of their ISM construction, an analysis of their local geometries, and a classification of all separate classes of solutions they form. We also show how even-soliton solutions on the seeds of the collinearly centred Gibbons-Hawking and Taub-NUT arise from these solutions. |
2208.02077 | Lucas Gardai Collodel | Daniela D. Doneva, Lucas G. Collodel and Stoytcho S. Yazadjiev | Spontaneous nonlinear scalarization of Kerr black holes | null | null | 10.1103/PhysRevD.106.104027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As it became well known in the past years, Einstein-scalar-Gauss-Bonnet
(EsGB) theories evade no-hair theorems and allow for scalarized compact objects
including black holes (BH). The coupling function that defines the theory is
the main character in the process and nature of scalarization. With the right
choice, the theory becomes an extension of general relativity (GR) in the sense
any solution to the GR field equations remains a solution in the EsGB theory,
but it can destabilize if a certain threshold value of the spacetime curvature
is exceeded. Thus BHs can spontaneously scalarized. The most studied driving
mechanism to this phenomenon is a tachyonic instability due to an effective
negative squared mass for the scalar field. However, even when the coupling is
chosen such that this mass is zero, higher order terms with respect to the
scalar field can lead to what is coined nonlinear scalarization. In this paper
we investigate how Kerr BHs spontaneously scalarize by evolving the scalar
field on a fixed background via solving the nonlinear Klein-Gordon equation. We
consider two different coupling functions with higher order terms, one that
yields a non-zero effective mass and another that does not. We sweep through
the Kerr parameter space in its mass and spin and obtain the scalar charge by
the end of the evolution when the field settles in an equilibrium stationary
state. When there is no tachyonic instability present, there is no probe limit
in which the BH scalarizes with zero charge, i.e. there is a gap between bald
and hairy BHs and they only connect when the mass goes to zero together with
the charge.
| [
{
"created": "Wed, 3 Aug 2022 13:57:49 GMT",
"version": "v1"
}
] | 2022-11-23 | [
[
"Doneva",
"Daniela D.",
""
],
[
"Collodel",
"Lucas G.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | As it became well known in the past years, Einstein-scalar-Gauss-Bonnet (EsGB) theories evade no-hair theorems and allow for scalarized compact objects including black holes (BH). The coupling function that defines the theory is the main character in the process and nature of scalarization. With the right choice, the theory becomes an extension of general relativity (GR) in the sense any solution to the GR field equations remains a solution in the EsGB theory, but it can destabilize if a certain threshold value of the spacetime curvature is exceeded. Thus BHs can spontaneously scalarized. The most studied driving mechanism to this phenomenon is a tachyonic instability due to an effective negative squared mass for the scalar field. However, even when the coupling is chosen such that this mass is zero, higher order terms with respect to the scalar field can lead to what is coined nonlinear scalarization. In this paper we investigate how Kerr BHs spontaneously scalarize by evolving the scalar field on a fixed background via solving the nonlinear Klein-Gordon equation. We consider two different coupling functions with higher order terms, one that yields a non-zero effective mass and another that does not. We sweep through the Kerr parameter space in its mass and spin and obtain the scalar charge by the end of the evolution when the field settles in an equilibrium stationary state. When there is no tachyonic instability present, there is no probe limit in which the BH scalarizes with zero charge, i.e. there is a gap between bald and hairy BHs and they only connect when the mass goes to zero together with the charge. |
1803.01817 | Papantonopoulos Eleftherios | Stella Kiorpelidi, Konstantinos Ntrekis and Eleftherios
Papantonopoulos | Superradiance Effect of a Black Hole Immersed in an Expanding Universe | 14 pages, 13 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We studied the superradiance effect of a charge black hole immersed in an
expanding Universe. We considered a test massive charged scalar field scattered
off the horizon of the charge McVittie black hole. We carried out a detailed
analysis of the electric energy extracted from the horizon of McVittie black
hole in two different epochs of the expansion of the Universe, the dust
dominated and radiation dominated epochs. We found that we have the
superradiance effect in both epochs of the expansion of the Universe. Our study
also provides evidence that we have extraction of energy from the horizon of
the neutral McVittie black hole.
| [
{
"created": "Mon, 5 Mar 2018 18:24:28 GMT",
"version": "v1"
}
] | 2018-03-06 | [
[
"Kiorpelidi",
"Stella",
""
],
[
"Ntrekis",
"Konstantinos",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | We studied the superradiance effect of a charge black hole immersed in an expanding Universe. We considered a test massive charged scalar field scattered off the horizon of the charge McVittie black hole. We carried out a detailed analysis of the electric energy extracted from the horizon of McVittie black hole in two different epochs of the expansion of the Universe, the dust dominated and radiation dominated epochs. We found that we have the superradiance effect in both epochs of the expansion of the Universe. Our study also provides evidence that we have extraction of energy from the horizon of the neutral McVittie black hole. |
1507.02394 | Pankaj Jain | Pankaj Jain, Gopal Kashyap and Subhadip Mitra | Non-relativistic matter and Dark energy in a quantum conformal model | 12 pages | Astropart.Phys. 75 (2016) 64-71 | 10.1016/j.astropartphys.2015.11.003 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a generalization of the standard model which respects quantum
conformal invariance. This model leads to identically zero vacuum energy. We
show how non-relativistic matter and dark energy arises in this model. Hence
the model is shown to be consistent with observations.
| [
{
"created": "Thu, 9 Jul 2015 07:13:07 GMT",
"version": "v1"
}
] | 2019-12-09 | [
[
"Jain",
"Pankaj",
""
],
[
"Kashyap",
"Gopal",
""
],
[
"Mitra",
"Subhadip",
""
]
] | We consider a generalization of the standard model which respects quantum conformal invariance. This model leads to identically zero vacuum energy. We show how non-relativistic matter and dark energy arises in this model. Hence the model is shown to be consistent with observations. |
1602.04306 | Sourav Bhattacharya | Sourav Bhattacharya | Rotating Killing horizons in generic $F(R)$ gravity theories | v2, 14pp; added references, discussions and clarifications, improved
presentation; accepted in GRG | Gen Relativ Gravit (2016) 48: 128 | 10.1007/s10714-016-2119-1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss various properties of rotating Killing horizons in generic $F(R)$
theories of gravity in dimension four for spacetimes endowed with two commuting
Killing vector fields. Assuming there is no curvature singularity anywhere on
or outside the horizon, we construct a suitable $(3+1)$-foliation. We show that
similar to Einstein's gravity, we must have $T_{ab}k^ak^b=0$ on the Killing
horizon, where $k^a$ is a null geodesic tangent to the horizon. For
axisymmetric spacetimes, the effective gravitational coupling
$\sim\,F'^{-1}(R)$ should usually depend upon the polar coordinate and hence
need not necessarily be a constant on the Killing horizon. We prove that the
surface gravity of such a Killing horizon must be a constant, irrespective of
whether $F'(R)$ is a constant there or not. We next apply these results to
investigate some further basic features. In particular, we show that any hairy
solution for the real massive vector field in such theories is clearly ruled
out, as long as the potential of the scalar field generated in the
corresponding Einstein's frame is a positive definite quantity.
| [
{
"created": "Sat, 13 Feb 2016 08:54:22 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Aug 2016 05:25:29 GMT",
"version": "v2"
}
] | 2016-09-06 | [
[
"Bhattacharya",
"Sourav",
""
]
] | We discuss various properties of rotating Killing horizons in generic $F(R)$ theories of gravity in dimension four for spacetimes endowed with two commuting Killing vector fields. Assuming there is no curvature singularity anywhere on or outside the horizon, we construct a suitable $(3+1)$-foliation. We show that similar to Einstein's gravity, we must have $T_{ab}k^ak^b=0$ on the Killing horizon, where $k^a$ is a null geodesic tangent to the horizon. For axisymmetric spacetimes, the effective gravitational coupling $\sim\,F'^{-1}(R)$ should usually depend upon the polar coordinate and hence need not necessarily be a constant on the Killing horizon. We prove that the surface gravity of such a Killing horizon must be a constant, irrespective of whether $F'(R)$ is a constant there or not. We next apply these results to investigate some further basic features. In particular, we show that any hairy solution for the real massive vector field in such theories is clearly ruled out, as long as the potential of the scalar field generated in the corresponding Einstein's frame is a positive definite quantity. |
1301.1588 | Richard Petti | Richard James Petti | Derivation of Einstein Cartan theory from General Relativity | 44 pages, 1 table, 63 equations, 3 figures, 93 lines of computer
algebra, 37 references, 7 Appendices. This version Adds a post-publication
note the responds to some commentaries about the paper | null | 10.1142/S0219887821500833 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work derives the elements of classical Einstein Cartan theory (EC) from
classical general relativity (GR) in two ways. (I) Derive discrete versions of
torsion (translational holonomy) and the spin torsion field equation of EC from
one Kerr solution in GR. (II) Derive the field equations of EC as the continuum
limit of a distribution of many Kerr masses in classical GR. The convergence
computations employ epsilon delta arguments, and are not as rigorous as
convergence in Sobolev norm. Inequality constraints needed for convergence
restrict the limits from continuing to an infinitesimal length scale. EC
enables modeling exchange of intrinsic and orbital angular momentum, which GR
cannot do. Derivation of EC from GR strengthens the case for EC and for new
physics derived from EC.
| [
{
"created": "Tue, 8 Jan 2013 16:45:27 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Aug 2014 14:17:08 GMT",
"version": "v10"
},
{
"created": "Tue, 30 Sep 2014 19:16:48 GMT",
"version": "v11"
},
{
"created": "Sat, 18 Oct 2014 22:05:32 GMT",
"version": "v12"
},
{
... | 2022-05-31 | [
[
"Petti",
"Richard James",
""
]
] | This work derives the elements of classical Einstein Cartan theory (EC) from classical general relativity (GR) in two ways. (I) Derive discrete versions of torsion (translational holonomy) and the spin torsion field equation of EC from one Kerr solution in GR. (II) Derive the field equations of EC as the continuum limit of a distribution of many Kerr masses in classical GR. The convergence computations employ epsilon delta arguments, and are not as rigorous as convergence in Sobolev norm. Inequality constraints needed for convergence restrict the limits from continuing to an infinitesimal length scale. EC enables modeling exchange of intrinsic and orbital angular momentum, which GR cannot do. Derivation of EC from GR strengthens the case for EC and for new physics derived from EC. |
1102.4824 | Massimo Tinto | Marcio Eduardo da Silva Alves, Massimo Tinto | Pulsar Timing Sensitivities to Gravitational Waves from Relativistic
Metric Theories of Gravity | 11 pages, 2 figures. Submitted to Phys. Rev. D | null | 10.1103/PhysRevD.83.123529 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Pulsar timing experiments aimed at the detection of gravitational radiation
have been performed for decades now. With the forthcoming construction of large
arrays capable of tracking multiple millisecond pulsars, it is very likely we
will be able to make the first detection of gravitational radiation in the
nano-Hertz band, and test Einstein's theory of relativity by measuring the
polarization components of the detected signals. Since a gravitational wave
predicted by the most general relativistic metric theory of gravity accounts
for {\it six} polarization modes (the usual two Einstein's tensor polarizations
as well as two vector and two scalar wave components), we have estimated the
single-antenna sensitivities to these six polarizations. We find pulsar timing
experiments to be significantly more sensitive, over their entire observational
frequency band ($\approx 10^{-9} - 10^{-6}$ Hz), to scalar-longitudinal and
vector waves than to scalar-transverse and tensor waves. At $10^{-7}$ Hz and
with pulsars at a distance of $1$ kpc, for instance, we estimate an average
sensitivity to scalar-longitudinal waves that is more than two orders of
magnitude better than the sensitivity to tensor waves. Our results imply that a
direct detection of gravitational radiation by pulsar timing will result into a
test of the theory of general relativity that is more stringent than that based
on monitoring the decay of the orbital period of a binary system.
| [
{
"created": "Wed, 23 Feb 2011 19:29:00 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Alves",
"Marcio Eduardo da Silva",
""
],
[
"Tinto",
"Massimo",
""
]
] | Pulsar timing experiments aimed at the detection of gravitational radiation have been performed for decades now. With the forthcoming construction of large arrays capable of tracking multiple millisecond pulsars, it is very likely we will be able to make the first detection of gravitational radiation in the nano-Hertz band, and test Einstein's theory of relativity by measuring the polarization components of the detected signals. Since a gravitational wave predicted by the most general relativistic metric theory of gravity accounts for {\it six} polarization modes (the usual two Einstein's tensor polarizations as well as two vector and two scalar wave components), we have estimated the single-antenna sensitivities to these six polarizations. We find pulsar timing experiments to be significantly more sensitive, over their entire observational frequency band ($\approx 10^{-9} - 10^{-6}$ Hz), to scalar-longitudinal and vector waves than to scalar-transverse and tensor waves. At $10^{-7}$ Hz and with pulsars at a distance of $1$ kpc, for instance, we estimate an average sensitivity to scalar-longitudinal waves that is more than two orders of magnitude better than the sensitivity to tensor waves. Our results imply that a direct detection of gravitational radiation by pulsar timing will result into a test of the theory of general relativity that is more stringent than that based on monitoring the decay of the orbital period of a binary system. |
1107.1540 | Gianluca Calcagni | Martin Bojowald, Gianluca Calcagni, Shinji Tsujikawa | Observational test of inflation in loop quantum cosmology | 1+37 pages, 6 figures, 1 table. v2: minor improvements in the text,
references added | JCAP11(2011)046 | 10.1088/1475-7516/2011/11/046 | AEI-2011-042 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study in detail the power spectra of scalar and tensor perturbations
generated during inflation in loop quantum cosmology (LQC). After clarifying in
a novel quantitative way how inverse-volume corrections arise in inhomogeneous
settings, we show that they can generate large running spectral indices, which
generally lead to an enhancement of power at large scales. We provide explicit
formulae for the scalar/tensor power spectra under the slow-roll approximation,
by taking into account corrections of order higher than the runnings. Via a
standard analysis, we place observational bounds on the inverse-volume quantum
correction \delta ~ a^{- \sigma} (\sigma >0, $a$ is the scale factor) and the
slow-roll parameter \epsilon_V for power-law potentials as well as exponential
potentials by using the data of WMAP 7yr combined with other observations. We
derive the constraints on \delta for two pivot wavenumbers k_0 for several
values of \delta. The quadratic potential can be compatible with the data even
in the presence of the LQC corrections, but the quartic potential is in tension
with observations. We also find that the upper bounds on \delta (k_0) for given
\sigma and k_0 are insensitive to the choice of the inflaton potentials.
| [
{
"created": "Fri, 8 Jul 2011 00:21:52 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Nov 2011 14:38:39 GMT",
"version": "v2"
}
] | 2015-03-19 | [
[
"Bojowald",
"Martin",
""
],
[
"Calcagni",
"Gianluca",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | We study in detail the power spectra of scalar and tensor perturbations generated during inflation in loop quantum cosmology (LQC). After clarifying in a novel quantitative way how inverse-volume corrections arise in inhomogeneous settings, we show that they can generate large running spectral indices, which generally lead to an enhancement of power at large scales. We provide explicit formulae for the scalar/tensor power spectra under the slow-roll approximation, by taking into account corrections of order higher than the runnings. Via a standard analysis, we place observational bounds on the inverse-volume quantum correction \delta ~ a^{- \sigma} (\sigma >0, $a$ is the scale factor) and the slow-roll parameter \epsilon_V for power-law potentials as well as exponential potentials by using the data of WMAP 7yr combined with other observations. We derive the constraints on \delta for two pivot wavenumbers k_0 for several values of \delta. The quadratic potential can be compatible with the data even in the presence of the LQC corrections, but the quartic potential is in tension with observations. We also find that the upper bounds on \delta (k_0) for given \sigma and k_0 are insensitive to the choice of the inflaton potentials. |
1309.7296 | Luca Maccione | Stefano Liberati (SISSA and INFN, Trieste) and Luca Maccione (LMU and
MPP, Munich) | Astrophysical constraints on Planck scale dissipative phenomena | 5 pages, 1 figure. v2: Minor revisions. Accepted for publication in
Phys. Rev. Lett | Phys. Rev. Lett. 112, 151301 (2014) | 10.1103/PhysRevLett.112.151301 | LMU-ASC 67/13; MPP-2013-272 | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The emergence of a classical spacetime from any quantum gravity model is
still a subtle and only partially understood issue. If indeed spacetime is
arising as some sort of large scale condensate of more fundamental objects then
it is natural to expect that matter, being a collective excitations of the
spacetime constituents, will present modified kinematics at sufficiently high
energies. We consider here the phenomenology of the dissipative effects
necessarily arising in such a picture. Adopting dissipative hydrodynamics as a
general framework for the description of the energy exchange between collective
excitations and the spacetime fundamental degrees of freedom, we discuss how
rates of energy loss for elementary particles can be derived from dispersion
relations and used to provide strong constraints on the base of current
astrophysical observations of high energy particles.
| [
{
"created": "Fri, 27 Sep 2013 16:56:55 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Mar 2014 17:30:24 GMT",
"version": "v2"
}
] | 2014-04-24 | [
[
"Liberati",
"Stefano",
"",
"SISSA and INFN, Trieste"
],
[
"Maccione",
"Luca",
"",
"LMU and\n MPP, Munich"
]
] | The emergence of a classical spacetime from any quantum gravity model is still a subtle and only partially understood issue. If indeed spacetime is arising as some sort of large scale condensate of more fundamental objects then it is natural to expect that matter, being a collective excitations of the spacetime constituents, will present modified kinematics at sufficiently high energies. We consider here the phenomenology of the dissipative effects necessarily arising in such a picture. Adopting dissipative hydrodynamics as a general framework for the description of the energy exchange between collective excitations and the spacetime fundamental degrees of freedom, we discuss how rates of energy loss for elementary particles can be derived from dispersion relations and used to provide strong constraints on the base of current astrophysical observations of high energy particles. |
gr-qc/0402055 | Oliver Preuss | S.K. Solanki (1), O.Preuss (1), M.P. Haugan (2), A. Gandorfer (1,3),
H. P. Povel (3), P. Steiner (3), K. Stucki (3), P. N. Bernasconi (4), D.
Soltau (5), ((1) Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau,
Germany; (2) Purdue University, West Lafayette Indiana USA; (3) Institute of
Astronomy, ETH-Zentrum Zuerich, Switzerland; (4) Space Department, John
Hopkins University, USA; (5) Kiepenheuer-Institut fuer Sonnenphysik,
Freiburg, Germany) | Solar constraints on new couplings between electromagnetism and gravity | Accepted for publication in Phys.Rev. D | Phys.Rev. D69 (2004) 062001 | 10.1103/PhysRevD.69.062001 | null | gr-qc astro-ph | null | The unification of quantum field theory and general relativity is a
fundamental goal of modern physics. In many cases, theoretical efforts to
achieve this goal introduce auxiliary gravitational fields, ones in addition to
the familiar symmetric second-rank tensor potential of general relativity, and
lead to nonmetric theories because of direct couplings between these auxiliary
fields and matter. Here, we consider an example of a metric-affine gauge theory
of gravity in which torsion couples nonminimally to the electromagnetic field.
This coupling causes a phase difference to accumulate between different
polarization states of light as they propagate through the metric-affine
gravitational field. Solar spectropolarimetric observations are reported and
used to set strong constraints on the relevant coupling constant k: k^2 < (2.5
km)^2.
| [
{
"created": "Thu, 12 Feb 2004 15:24:44 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Solanki",
"S. K.",
""
],
[
"Preuss",
"O.",
""
],
[
"Haugan",
"M. P.",
""
],
[
"Gandorfer",
"A.",
""
],
[
"Povel",
"H. P.",
""
],
[
"Steiner",
"P.",
""
],
[
"Stucki",
"K.",
""
],
[
"Bernasconi",
... | The unification of quantum field theory and general relativity is a fundamental goal of modern physics. In many cases, theoretical efforts to achieve this goal introduce auxiliary gravitational fields, ones in addition to the familiar symmetric second-rank tensor potential of general relativity, and lead to nonmetric theories because of direct couplings between these auxiliary fields and matter. Here, we consider an example of a metric-affine gauge theory of gravity in which torsion couples nonminimally to the electromagnetic field. This coupling causes a phase difference to accumulate between different polarization states of light as they propagate through the metric-affine gravitational field. Solar spectropolarimetric observations are reported and used to set strong constraints on the relevant coupling constant k: k^2 < (2.5 km)^2. |
gr-qc/9708022 | Carlos O. Lousto | Carlos O. Lousto and Richard H. Price (Univ. Utah) | Improved initial data for black hole collisions | 10 pages, REVTEX, 14 PS figs | Phys.Rev. D57 (1998) 1073-1083 | 10.1103/PhysRevD.57.1073 | null | gr-qc hep-th | null | Numerical relativity codes now being developed will evolve initial data
representing colliding black holes at a relatively late stage in the collision.
The choice of initial data used for code development has been made on the basis
of mathematical definitiveness and usefulness for computational implementation.
By using the ``particle limit'' (the limit of an extreme ratio of masses of
colliding holes) we recently showed that the standard choice is not a good
representation of astrophysically generated initial data. Here we show that,
for the particle limit, there is a very simple alternative choice that appears
to give excellent results. That choice, ``convective'' initial data is, roughly
speaking, equivalent to the start of a time sequence of parameterized solutions
of the Hamiltonian constraint; for a particle in circular orbit, it is the
initial data of the steady state solution on any hypersurface. The
implementation of related schemes for equal mass holes is discussed.
| [
{
"created": "Mon, 11 Aug 1997 23:10:36 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Lousto",
"Carlos O.",
"",
"Univ. Utah"
],
[
"Price",
"Richard H.",
"",
"Univ. Utah"
]
] | Numerical relativity codes now being developed will evolve initial data representing colliding black holes at a relatively late stage in the collision. The choice of initial data used for code development has been made on the basis of mathematical definitiveness and usefulness for computational implementation. By using the ``particle limit'' (the limit of an extreme ratio of masses of colliding holes) we recently showed that the standard choice is not a good representation of astrophysically generated initial data. Here we show that, for the particle limit, there is a very simple alternative choice that appears to give excellent results. That choice, ``convective'' initial data is, roughly speaking, equivalent to the start of a time sequence of parameterized solutions of the Hamiltonian constraint; for a particle in circular orbit, it is the initial data of the steady state solution on any hypersurface. The implementation of related schemes for equal mass holes is discussed. |
gr-qc/0401009 | Deborah A. Konkowski | D.A. Konkowski, T.M. Helliwell and C. Wieland | Quantum singularity of Levi-Civita spacetimes | null | Class.Quant.Grav. 21 (2004) 265-272 | 10.1088/0264-9381/21/1/018 | null | gr-qc | null | Quantum singularities in general relativistic spacetimes are determined by
the behavior of quantum test particles. A static spacetime is quantum
mechanically singular if the spatial portion of the wave operator is not
essentially self-adjoint. Here Weyl's limit point-limit circle criterion is
used to determine whether a wave operator is essentially self-adjoint. This
test is then applied to scalar wave packets in Levi-Civita spacetimes to help
elucidate the physical properties of the spacetimes in terms of their metric
parameters.
| [
{
"created": "Sun, 4 Jan 2004 00:16:07 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Konkowski",
"D. A.",
""
],
[
"Helliwell",
"T. M.",
""
],
[
"Wieland",
"C.",
""
]
] | Quantum singularities in general relativistic spacetimes are determined by the behavior of quantum test particles. A static spacetime is quantum mechanically singular if the spatial portion of the wave operator is not essentially self-adjoint. Here Weyl's limit point-limit circle criterion is used to determine whether a wave operator is essentially self-adjoint. This test is then applied to scalar wave packets in Levi-Civita spacetimes to help elucidate the physical properties of the spacetimes in terms of their metric parameters. |
2312.17563 | ChengGang Shao | Li-Jie Xin, Jun-Qi Guo, Cheng-Gang Shao | Energy transfer in the collision of two scalar wave packets in spherical
symmetry | null | null | 10.1103/PhysRevD.108.124071 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the collisions of two scalar wave packets in the asymptotically flat
spacetime and asymptotically anti-de Sitter spacetime in spherical symmetry. An
energy transfer formula is obtained, $y=Cm_{i}m_{o}/r$, where $y$ is the
transferred energy in the collisions of the two wave packets, $m_i$ and $m_o$
are the Misner-Sharp energies for the ingoing and outgoing wave packets,
respectively, $r$ is the areal radius and collision place, and $C=1.873$ and
$C=1.875$ for the asymptotically flat spacetime and asymptotically anti-de
Sitter spacetime circumstances, respectively. The formula is universal,
independent of the initial profiles of the scalar fields.
| [
{
"created": "Fri, 29 Dec 2023 11:11:40 GMT",
"version": "v1"
}
] | 2024-01-01 | [
[
"Xin",
"Li-Jie",
""
],
[
"Guo",
"Jun-Qi",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] | We study the collisions of two scalar wave packets in the asymptotically flat spacetime and asymptotically anti-de Sitter spacetime in spherical symmetry. An energy transfer formula is obtained, $y=Cm_{i}m_{o}/r$, where $y$ is the transferred energy in the collisions of the two wave packets, $m_i$ and $m_o$ are the Misner-Sharp energies for the ingoing and outgoing wave packets, respectively, $r$ is the areal radius and collision place, and $C=1.873$ and $C=1.875$ for the asymptotically flat spacetime and asymptotically anti-de Sitter spacetime circumstances, respectively. The formula is universal, independent of the initial profiles of the scalar fields. |
1005.2922 | Nicholas Taylor | Nicholas W. Taylor, Lawrence E. Kidder, Saul A. Teukolsky | Spectral methods for the wave equation in second-order form | 16 pages, 5 figures | Phys.Rev.D82:024037,2010 | 10.1103/PhysRevD.82.024037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Current spectral simulations of Einstein's equations require writing the
equations in first-order form, potentially introducing instabilities and
inefficiencies. We present a new penalty method for pseudo-spectral evolutions
of second order in space wave equations. The penalties are constructed as
functions of Legendre polynomials and are added to the equations of motion
everywhere, not only on the boundaries. Using energy methods, we prove
semi-discrete stability of the new method for the scalar wave equation in flat
space and show how it can be applied to the scalar wave on a curved background.
Numerical results demonstrating stability and convergence for multi-domain
second-order scalar wave evolutions are also presented. This work provides a
foundation for treating Einstein's equations directly in second-order form by
spectral methods.
| [
{
"created": "Mon, 17 May 2010 13:47:07 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Taylor",
"Nicholas W.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | Current spectral simulations of Einstein's equations require writing the equations in first-order form, potentially introducing instabilities and inefficiencies. We present a new penalty method for pseudo-spectral evolutions of second order in space wave equations. The penalties are constructed as functions of Legendre polynomials and are added to the equations of motion everywhere, not only on the boundaries. Using energy methods, we prove semi-discrete stability of the new method for the scalar wave equation in flat space and show how it can be applied to the scalar wave on a curved background. Numerical results demonstrating stability and convergence for multi-domain second-order scalar wave evolutions are also presented. This work provides a foundation for treating Einstein's equations directly in second-order form by spectral methods. |
gr-qc/0210087 | Tiberiu Harko | M. K. Mak, T. Harko | Brans-Dicke cosmology with a scalar field potential | 6 pages, 4 figures | Europhys.Lett. 60 (2002) 155-161 | 10.1209/epl/i2002-00664-2 | null | gr-qc | null | Three solutions of the Brans-Dicke theory with a self-interacting quartic
potential and perfect fluid distribution are presented for a spatially flat
geometry. The physical behavior is consistent with the recent cosmological
scenario favored by type Ia supernova observations, indicating an accelerated
expansion of the Universe.
| [
{
"created": "Fri, 25 Oct 2002 07:51:59 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Mak",
"M. K.",
""
],
[
"Harko",
"T.",
""
]
] | Three solutions of the Brans-Dicke theory with a self-interacting quartic potential and perfect fluid distribution are presented for a spatially flat geometry. The physical behavior is consistent with the recent cosmological scenario favored by type Ia supernova observations, indicating an accelerated expansion of the Universe. |
1307.8338 | Walter Del Pozzo | Walter Del Pozzo, Tjonnie G.F. Li, Michalis Agathos, Chris Van Den
Broeck, Salvatore Vitale | Demonstrating the feasibility of probing the neutron star equation of
state with second-generation gravitational wave detectors | 5 pages, 2 figures, accepted for publication on Phys. Rev. Lett | null | 10.1103/PhysRevLett.111.071101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fisher matrix and related studies have suggested that with second-generation
gravitational wave detectors, it may be possible to infer the equation of state
of neutron stars using tidal effects in binary inspiral. Here we present the
first fully Bayesian investigation of this problem. We simulate a realistic
data analysis setting by performing a series of numerical experiments of binary
neutron star signals hidden in detector noise, assuming the projected final
design sensitivity of the Advanced LIGO- Virgo network. With an astrophysical
distribution of events (in particular, uniform in co-moving volume), we find
that only a few tens of detections will be required to arrive at strong
constraints, even for some of the softest equations of state in the literature.
Thus, direct gravitational wave detection will provide a unique probe of
neutron star structure.
| [
{
"created": "Wed, 31 Jul 2013 14:46:12 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Del Pozzo",
"Walter",
""
],
[
"Li",
"Tjonnie G. F.",
""
],
[
"Agathos",
"Michalis",
""
],
[
"Broeck",
"Chris Van Den",
""
],
[
"Vitale",
"Salvatore",
""
]
] | Fisher matrix and related studies have suggested that with second-generation gravitational wave detectors, it may be possible to infer the equation of state of neutron stars using tidal effects in binary inspiral. Here we present the first fully Bayesian investigation of this problem. We simulate a realistic data analysis setting by performing a series of numerical experiments of binary neutron star signals hidden in detector noise, assuming the projected final design sensitivity of the Advanced LIGO- Virgo network. With an astrophysical distribution of events (in particular, uniform in co-moving volume), we find that only a few tens of detections will be required to arrive at strong constraints, even for some of the softest equations of state in the literature. Thus, direct gravitational wave detection will provide a unique probe of neutron star structure. |
1612.00713 | Lisa Glaser | Lisa Glaser | Scaling behaviour in random non-commutative geometries | 16 pages, 16 figures (v2: updated after review) | J. Phys. A: Math. Theor. 50 275201 (2017) | 10.1088/1751-8121/aa7424 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Random non-commutative geometries are a novel approach to taking a
non-perturbative path integral over geometries. They were introduced in
arxiv.org/abs/1510.01377, where a first examination was performed. During this
examination we found that some geometries show indications of a phase
transition. In this article we explore this phase transition further for
geometries of type $(1,1)$, $(2,0)$, and $(1,3)$. We determine the pseudo
critical points of these geometries and explore how some of the observables
scale with the system size. We also undertake first steps towards understanding
the critical behaviour through correlations and in determining critical
exponents of the system.
| [
{
"created": "Fri, 2 Dec 2016 15:47:21 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jun 2017 11:20:40 GMT",
"version": "v2"
}
] | 2017-06-14 | [
[
"Glaser",
"Lisa",
""
]
] | Random non-commutative geometries are a novel approach to taking a non-perturbative path integral over geometries. They were introduced in arxiv.org/abs/1510.01377, where a first examination was performed. During this examination we found that some geometries show indications of a phase transition. In this article we explore this phase transition further for geometries of type $(1,1)$, $(2,0)$, and $(1,3)$. We determine the pseudo critical points of these geometries and explore how some of the observables scale with the system size. We also undertake first steps towards understanding the critical behaviour through correlations and in determining critical exponents of the system. |
1807.05970 | Ian Durham | Ian T. Durham | Global ontologies for relativistic quantum systems and quantum field
theory | Cleaned up sections in response to reviewer comments; added
discussion of Lorentz invariance and determinism; removed section on fermion
doubling; added acknowledgement of funding sources | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Epistemic models of nature prove to be problematic in many settings,
particularly in those in which measurement procedures are ill-defined. By
contrast, in ontological models of nature, measurement results are independent
of the procedure used to obtain them. Quantum mechanics, as a model of nature,
is notoriously ambiguous in this regard. If we assume that all measurement
results can be expressed in terms of pointer readings, then any useful ontology
would need to unambiguously specify the positions of things. But the positions
of pointers are ill-defined in many relativistic and cosmological settings. One
potential solution to this problem presents itself in the solutions to the
Wheeler-DeWitt equation as developed by Hartle and Hawking. In this article we
introduce such a model in which these solutions to the Wheeler-DeWitt equation
serve as the ontology of the model. We then show that, for any model that
admits these solutions as beables, the global preservation of Lorentz
invariance is incompatible with global determinism. However, we also show that
an Everett-like interpretation that allows for all possible mappings of the
matter field to the geometry and for all possible foliations of these mappings
as being equally real, might solve this problem.
| [
{
"created": "Mon, 16 Jul 2018 17:06:51 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Aug 2018 19:27:45 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Dec 2018 22:37:17 GMT",
"version": "v3"
}
] | 2018-12-06 | [
[
"Durham",
"Ian T.",
""
]
] | Epistemic models of nature prove to be problematic in many settings, particularly in those in which measurement procedures are ill-defined. By contrast, in ontological models of nature, measurement results are independent of the procedure used to obtain them. Quantum mechanics, as a model of nature, is notoriously ambiguous in this regard. If we assume that all measurement results can be expressed in terms of pointer readings, then any useful ontology would need to unambiguously specify the positions of things. But the positions of pointers are ill-defined in many relativistic and cosmological settings. One potential solution to this problem presents itself in the solutions to the Wheeler-DeWitt equation as developed by Hartle and Hawking. In this article we introduce such a model in which these solutions to the Wheeler-DeWitt equation serve as the ontology of the model. We then show that, for any model that admits these solutions as beables, the global preservation of Lorentz invariance is incompatible with global determinism. However, we also show that an Everett-like interpretation that allows for all possible mappings of the matter field to the geometry and for all possible foliations of these mappings as being equally real, might solve this problem. |
1008.2165 | David Jennings | David Jennings | On the response of a particle detector in Anti-de Sitter spacetime | 13 pages, no figures, accepted for publication in Class. Quantum Grav | Class.Quant.Grav.27:205005,2010 | 10.1088/0264-9381/27/20/205005 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the vacuum response of a particle detector in Anti-de Sitter
spacetime, and in particular analyze how spacetime features such as curvature
and dimensionality affect the response spectrum of an accelerated detector. We
calculate useful limits on Wightman functions, analyze the dynamics of the
detector in terms of vacuum fluctuations and radiation reactions, and discuss
the thermalization process for the detector. We also present a generalization
of the GEMS approach and obtain the Gibbons-Hawking temperature of de Sitter
spacetime as an embedded Unruh temperature in a curved Anti-de Sitter
spacetime.
| [
{
"created": "Thu, 12 Aug 2010 17:19:20 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Jennings",
"David",
""
]
] | We consider the vacuum response of a particle detector in Anti-de Sitter spacetime, and in particular analyze how spacetime features such as curvature and dimensionality affect the response spectrum of an accelerated detector. We calculate useful limits on Wightman functions, analyze the dynamics of the detector in terms of vacuum fluctuations and radiation reactions, and discuss the thermalization process for the detector. We also present a generalization of the GEMS approach and obtain the Gibbons-Hawking temperature of de Sitter spacetime as an embedded Unruh temperature in a curved Anti-de Sitter spacetime. |
1707.03741 | Cristiano Germani | Cristiano Germani and Prado Martin-Moruno | Tracking our Universe to de Sitter by a Horndeski scalar | 14 pages, v2: comment on frames added. Conclusions unchanged, version
accepted for publication in Physics of the Dark Universe | Physics of the Dark Universe 18C (2017) pp. 1-5 | null | ICCUB-17-014 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Assuming both that our Universe is evolving into a de Sitter space and a
vanishing cosmological constant, leaves only the option that the observed
acceleration is provided by a "kinetic" energy of a scalar field. From an
effective field theory point of view, the absence of Ostrogradsky instabilities
restricts the choice to shift-symmetric Horndeski theories. Within these
theories, we find the conditions for the existence of a de Sitter critical
point in a universe filled by matter, radiation and a Horndeski scalar.
Moreover, we show that this point is a universal attractor and we provide the
tracking trajectory. Therefore, if a de Sitter fixed point exists within these
models, our Universe will eventually evolve into a de Sitter space. As an
example, we have discussed the case of the combined Galileon-Slotheon system,
in which the Galileon is kinetically non-minimal coupled to the Einstein
tensor. Interestingly, we have also found that the tracker trajectory of this
system does not follow previous literature assumptions.
| [
{
"created": "Wed, 12 Jul 2017 14:37:27 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Sep 2017 13:15:42 GMT",
"version": "v2"
}
] | 2017-09-26 | [
[
"Germani",
"Cristiano",
""
],
[
"Martin-Moruno",
"Prado",
""
]
] | Assuming both that our Universe is evolving into a de Sitter space and a vanishing cosmological constant, leaves only the option that the observed acceleration is provided by a "kinetic" energy of a scalar field. From an effective field theory point of view, the absence of Ostrogradsky instabilities restricts the choice to shift-symmetric Horndeski theories. Within these theories, we find the conditions for the existence of a de Sitter critical point in a universe filled by matter, radiation and a Horndeski scalar. Moreover, we show that this point is a universal attractor and we provide the tracking trajectory. Therefore, if a de Sitter fixed point exists within these models, our Universe will eventually evolve into a de Sitter space. As an example, we have discussed the case of the combined Galileon-Slotheon system, in which the Galileon is kinetically non-minimal coupled to the Einstein tensor. Interestingly, we have also found that the tracker trajectory of this system does not follow previous literature assumptions. |
2001.00011 | Pardyumn Kumar Sahoo | Koijam Manihar Singh, Sanjay Mandal, Longjam Parbati Devi, P.K. Sahoo | Dark Energy and Modified Scale Covariant Theory of Gravitation | 12 pages, 12 figures, Accepted version in New Astronomy | New Astron. 77 (2020) 101353 | 10.1016/j.newast.2019.101353 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Taking up four model universes we study the behaviour and contribution of
dark energy to the accelerated expansion of the universe, in the modified scale
covariant theory of gravitation. Here, it is seen that though this modified
theory may be a cause of the accelerated expansion it cannot totally outcast
the contribution of dark energy in causing the accelerated expansion. In one
case the dark energy is found to be the sole cause of the accelerated
expansion. The dark energy contained in these models come out to be of the
$\Lambda$CDM type and quintessence type comparable to the modern observations.
Some of the models originated with a big bang, the dark energy being prevalent
inside the universe before the evolution of this era. One of the models
predicts big rip singularity, though at a very distant future. It is
interestingly found that the interaction between the dark energy and the other
part of the universe containing different matters is enticed and enhanced by
the gauge function $\phi(t)$ here.
| [
{
"created": "Mon, 30 Dec 2019 08:44:04 GMT",
"version": "v1"
}
] | 2020-01-28 | [
[
"Singh",
"Koijam Manihar",
""
],
[
"Mandal",
"Sanjay",
""
],
[
"Devi",
"Longjam Parbati",
""
],
[
"Sahoo",
"P. K.",
""
]
] | Taking up four model universes we study the behaviour and contribution of dark energy to the accelerated expansion of the universe, in the modified scale covariant theory of gravitation. Here, it is seen that though this modified theory may be a cause of the accelerated expansion it cannot totally outcast the contribution of dark energy in causing the accelerated expansion. In one case the dark energy is found to be the sole cause of the accelerated expansion. The dark energy contained in these models come out to be of the $\Lambda$CDM type and quintessence type comparable to the modern observations. Some of the models originated with a big bang, the dark energy being prevalent inside the universe before the evolution of this era. One of the models predicts big rip singularity, though at a very distant future. It is interestingly found that the interaction between the dark energy and the other part of the universe containing different matters is enticed and enhanced by the gauge function $\phi(t)$ here. |
1304.2291 | Giovanni Marozzi Dr. | Giovanni Marozzi, Gian Paolo Vacca | Gauge invariant backreaction in general single field models of inflation | 5 pages, no figures. Minor corrections made and typos corrected.
Version accepted for publication in PRD | Phys. Rev. D 88, 027302 (2013) | 10.1103/PhysRevD.88.027302 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a general single field inflationary model we consider the effects of long
wavelength scalar fluctuations on the effective expansion rate and equation of
state seen by a class of free falling observers, using a physical gauge
invariant formulation. In a previous work we showed that for a free massive
inflaton no backreaction is observed within some constraints. In this paper we
extend the validity of our previous results to the case of an arbitrary
self-interacting inflation potential, working to second order in cosmological
perturbation theory and to all order in slow-roll approximation. For these
general inflationary models, we also show the equivalence of the free falling
observers to the ones comoving with the inflaton field.
| [
{
"created": "Mon, 8 Apr 2013 18:17:56 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2013 16:55:46 GMT",
"version": "v2"
}
] | 2013-08-06 | [
[
"Marozzi",
"Giovanni",
""
],
[
"Vacca",
"Gian Paolo",
""
]
] | In a general single field inflationary model we consider the effects of long wavelength scalar fluctuations on the effective expansion rate and equation of state seen by a class of free falling observers, using a physical gauge invariant formulation. In a previous work we showed that for a free massive inflaton no backreaction is observed within some constraints. In this paper we extend the validity of our previous results to the case of an arbitrary self-interacting inflation potential, working to second order in cosmological perturbation theory and to all order in slow-roll approximation. For these general inflationary models, we also show the equivalence of the free falling observers to the ones comoving with the inflaton field. |
2208.14119 | Giulia Gubitosi | Michele Arzano, Vittorio D'Esposito, Giulia Gubitosi | Fundamental decoherence from quantum spacetime | v2 matches the version accepted for publication in Communications
Physics | null | null | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We show that quantum properties of spacetime, encoded by noncommutativity at
the Planck scale, lead to a generalized time evolution of quantum systems in
which pure states can evolve into mixed states. Specifically, a decoherence
mechanism is obtained in the form of a Lindblad-like time evolution for the
density operator when the action of time translations generator is deformed by
the effects of spacetime noncommutativity. The decoherence time for the
evolution of a free particle is used to show that the Planck mass is the
maximum allowed mass for elementary quantum systems.
| [
{
"created": "Tue, 30 Aug 2022 10:06:21 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jan 2023 18:27:53 GMT",
"version": "v2"
}
] | 2023-01-27 | [
[
"Arzano",
"Michele",
""
],
[
"D'Esposito",
"Vittorio",
""
],
[
"Gubitosi",
"Giulia",
""
]
] | We show that quantum properties of spacetime, encoded by noncommutativity at the Planck scale, lead to a generalized time evolution of quantum systems in which pure states can evolve into mixed states. Specifically, a decoherence mechanism is obtained in the form of a Lindblad-like time evolution for the density operator when the action of time translations generator is deformed by the effects of spacetime noncommutativity. The decoherence time for the evolution of a free particle is used to show that the Planck mass is the maximum allowed mass for elementary quantum systems. |
1703.09811 | Arvin Ravanpak | Arvin Ravanpak, Hossein Farajollahi, Golnaz Farpoor Fadakar | Normal DGP in varying speed of light cosmology | null | Res. Astron. Astrophys., 17 (2017) 26 | 10.1088/1674-4527/17/3/26 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The varying speed of light (VSL) has been used in cosmological models in
which the physical constants vary over time. On the other hand, the Dvali,
Gabadadze and Porrati (DGP) brane world model, especially its normal branch has
been extensively discussed to justify the current cosmic acceleration. In this
article we show that the normal branch of DGP in VSL cosmology leads to a
self-accelerating behavior and therefore can interpret cosmic acceleration.
Applying statefinder diagnostics demonstrate that our result slightly deviates
{\Lambda}CDM model.
| [
{
"created": "Tue, 28 Mar 2017 21:35:01 GMT",
"version": "v1"
}
] | 2017-04-05 | [
[
"Ravanpak",
"Arvin",
""
],
[
"Farajollahi",
"Hossein",
""
],
[
"Fadakar",
"Golnaz Farpoor",
""
]
] | The varying speed of light (VSL) has been used in cosmological models in which the physical constants vary over time. On the other hand, the Dvali, Gabadadze and Porrati (DGP) brane world model, especially its normal branch has been extensively discussed to justify the current cosmic acceleration. In this article we show that the normal branch of DGP in VSL cosmology leads to a self-accelerating behavior and therefore can interpret cosmic acceleration. Applying statefinder diagnostics demonstrate that our result slightly deviates {\Lambda}CDM model. |
0907.2253 | Luis Herrera | L. Herrera, N.O. Santos | Collapsing Spheres Satisfying An "Euclidean Condition" | 1o pages, Latex. Title changed and text shortened to fit the version
to appear in Gen.Rel.Grav. | Gen.Rel.Grav.42:2383-2391,2010 | 10.1007/s10714-010-0986-4 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the general properties of fluid spheres satisfying the heuristic
assumption that their areas and proper radius are equal (the Euclidean
condition). Dissipative and non-dissipative models are considered. In the
latter case, all models are necessarily geodesic and a subclass of the
Lemaitre-Tolman-Bondi solution is obtained. In the dissipative case solutions
are non-geodesic and are characterized by the fact that all non-gravitational
forces acting on any fluid element produces a radial three-acceleration
independent on its inertial mass.
| [
{
"created": "Mon, 13 Jul 2009 20:11:35 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Apr 2010 09:12:35 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Herrera",
"L.",
""
],
[
"Santos",
"N. O.",
""
]
] | We study the general properties of fluid spheres satisfying the heuristic assumption that their areas and proper radius are equal (the Euclidean condition). Dissipative and non-dissipative models are considered. In the latter case, all models are necessarily geodesic and a subclass of the Lemaitre-Tolman-Bondi solution is obtained. In the dissipative case solutions are non-geodesic and are characterized by the fact that all non-gravitational forces acting on any fluid element produces a radial three-acceleration independent on its inertial mass. |
0809.2916 | M. D. Maia | M. D. Maia, S. S. e Almeida Silva, F. S. Carvalho | Quaternion-Loop Quantum Gravity | 5 pages, latex, no figures. Improved pdf. To appear in the
Foundations of Physics | Found.Phys.39:1273-1279,2009 | 10.1007/s10701-009-9350-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the Riemannian curvature of the 3-dimensional hypersurfaces
in space-time, described by the Wilson loop integral, can be represented by a
quaternion quantum operator induced by the SU(2) gauge potential, thus
providing a justification for quaternion quantum gravity at the Tev energy
scale.
| [
{
"created": "Wed, 17 Sep 2008 12:12:37 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Dec 2008 12:04:04 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Sep 2009 17:39:42 GMT",
"version": "v3"
}
] | 2009-11-05 | [
[
"Maia",
"M. D.",
""
],
[
"Silva",
"S. S. e Almeida",
""
],
[
"Carvalho",
"F. S.",
""
]
] | It is shown that the Riemannian curvature of the 3-dimensional hypersurfaces in space-time, described by the Wilson loop integral, can be represented by a quaternion quantum operator induced by the SU(2) gauge potential, thus providing a justification for quaternion quantum gravity at the Tev energy scale. |
1405.0504 | Scott A. Hughes | Scott A. Hughes | Gravitational wave astronomy and cosmology | 11 pages. Proceedings writeup of a talk given at the 2013 Topics in
Astroparticle and Underground Physics (TAUP) conference | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first direct observation of gravitational waves' action upon matter has
recently been reported by the BICEP2 experiment. Advanced ground-based
gravitational-wave detectors are being installed. They will soon be
commissioned, and then begin searches for high-frequency gravitational waves at
a sensitivity level that is widely expected to reach events involving compact
objects like stellar mass black holes and neutron stars. Pulsar timing arrays
continue to improve the bounds on gravitational waves at nanohertz frequencies,
and may detect a signal on roughly the same timescale as ground-based
detectors. The science case for space-based interferometers targeting
millihertz sources is very strong. The decade of gravitational-wave discovery
is poised to begin. In this writeup of a talk given at the 2013 TAUP
conference, we will briefly review the physics of gravitational waves and
gravitational-wave detectors, and then discuss the promise of these
measurements for making cosmological measurements in the near future.
| [
{
"created": "Fri, 2 May 2014 20:23:47 GMT",
"version": "v1"
}
] | 2014-05-06 | [
[
"Hughes",
"Scott A.",
""
]
] | The first direct observation of gravitational waves' action upon matter has recently been reported by the BICEP2 experiment. Advanced ground-based gravitational-wave detectors are being installed. They will soon be commissioned, and then begin searches for high-frequency gravitational waves at a sensitivity level that is widely expected to reach events involving compact objects like stellar mass black holes and neutron stars. Pulsar timing arrays continue to improve the bounds on gravitational waves at nanohertz frequencies, and may detect a signal on roughly the same timescale as ground-based detectors. The science case for space-based interferometers targeting millihertz sources is very strong. The decade of gravitational-wave discovery is poised to begin. In this writeup of a talk given at the 2013 TAUP conference, we will briefly review the physics of gravitational waves and gravitational-wave detectors, and then discuss the promise of these measurements for making cosmological measurements in the near future. |
2406.17018 | Marina De Amicis Ms. | Marina De Amicis, Simone Albanesi, Gregorio Carullo | Inspiral-inherited ringdown tails | 27 pages, 18 figures | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the late-time relaxation of a perturbed Schwarzschild black hole,
driven by a source term representing an infalling particle in generic orbits.
We consider quasi-circular and eccentric binaries, dynamical captures and
radial infalls, with orbital dynamics driven by an highly accurate analytical
radiation reaction. After reviewing the description of the late-time behaviour
as an integral over the whole inspiral history, we derive an analytical
expression exactly reproducing the slow relaxation observed in our numerical
evolutions, obtained with a hyperboloidal compactified grid, for a given
particle trajectory. We find this signal to be a superposition of an infinite
number of power-laws, the slowest decaying term being Price's law. Next, we use
our model to explain the several orders-of-magnitude enhancement of tail terms
for binaries in non-circular orbits, shedding light on recent unexpected
results obtained in numerical evolutions. In particular, we show the dominant
terms controlling the enhancement to be activated when the particle is far from
the BH, with small tangential and radial velocities soon before the plunge. As
we corroborate with semi-analytical calculations, this implies that for large
eccentricities the tail amplitude can be correctly extracted even when starting
to evolve only from the last apastron before merger. We discuss the
implications of these findings on the extraction of late-time tail terms in
non-linear evolutions, and possible observational consequences. We also briefly
comment on the scattering scenario, and on the connection with the soft
graviton theorem.
| [
{
"created": "Mon, 24 Jun 2024 18:00:02 GMT",
"version": "v1"
}
] | 2024-06-26 | [
[
"De Amicis",
"Marina",
""
],
[
"Albanesi",
"Simone",
""
],
[
"Carullo",
"Gregorio",
""
]
] | We study the late-time relaxation of a perturbed Schwarzschild black hole, driven by a source term representing an infalling particle in generic orbits. We consider quasi-circular and eccentric binaries, dynamical captures and radial infalls, with orbital dynamics driven by an highly accurate analytical radiation reaction. After reviewing the description of the late-time behaviour as an integral over the whole inspiral history, we derive an analytical expression exactly reproducing the slow relaxation observed in our numerical evolutions, obtained with a hyperboloidal compactified grid, for a given particle trajectory. We find this signal to be a superposition of an infinite number of power-laws, the slowest decaying term being Price's law. Next, we use our model to explain the several orders-of-magnitude enhancement of tail terms for binaries in non-circular orbits, shedding light on recent unexpected results obtained in numerical evolutions. In particular, we show the dominant terms controlling the enhancement to be activated when the particle is far from the BH, with small tangential and radial velocities soon before the plunge. As we corroborate with semi-analytical calculations, this implies that for large eccentricities the tail amplitude can be correctly extracted even when starting to evolve only from the last apastron before merger. We discuss the implications of these findings on the extraction of late-time tail terms in non-linear evolutions, and possible observational consequences. We also briefly comment on the scattering scenario, and on the connection with the soft graviton theorem. |
1602.02413 | Kent Yagi | Kent Yagi and Leo C. Stein | Black Hole Based Tests of General Relativity | 95 pages, 11 figures; a nomenclature for the braneworld BH conjecture
corrected, references added and updated; Invited review article to the Focus
Issue on "Black holes and fundamental fields" published in Classical and
Quantum Gravity | Class. Quantum Grav. 33 054001 (2016) | 10.1088/0264-9381/33/5/054001 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity has passed all solar system experiments and neutron star
based tests, such as binary pulsar observations, with flying colors. A more
exotic arena for testing general relativity is in systems that contain one or
more black holes. Black holes are the most compact objects in the universe,
providing probes of the strongest-possible gravitational fields. We are
motivated to study strong-field gravity since many theories give large
deviations from general relativity only at large field strengths, while
recovering the weak-field behavior. In this article, we review how one can
probe general relativity and various alternative theories of gravity by using
electromagnetic waves from a black hole with an accretion disk, and
gravitational waves from black hole binaries. We first review model-independent
ways of testing gravity with electromagnetic/gravitational waves from a black
hole system. We then focus on selected examples of theories that extend general
relativity in rather simple ways. Some important characteristics of general
relativity include (but are not limited to) (i) only tensor gravitational
degrees of freedom, (ii) the graviton is massless, (iii) no quadratic or higher
curvatures in the action, and (iv) the theory is 4 dimensional. Altering a
characteristic leads to a different extension of general relativity: (i)
scalar-tensor theories, (ii) massive gravity theories, (iii) quadratic gravity,
and (iv) theories with large extra dimensions. Within each theory, we describe
black hole solutions, their properties, and current and projected constraints
on each theory using black hole-based tests of gravity. We close this review by
listing some of the open problems in model-independent tests and within each
specific theory.
| [
{
"created": "Sun, 7 Feb 2016 19:33:09 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Feb 2016 18:36:51 GMT",
"version": "v2"
}
] | 2016-02-19 | [
[
"Yagi",
"Kent",
""
],
[
"Stein",
"Leo C.",
""
]
] | General relativity has passed all solar system experiments and neutron star based tests, such as binary pulsar observations, with flying colors. A more exotic arena for testing general relativity is in systems that contain one or more black holes. Black holes are the most compact objects in the universe, providing probes of the strongest-possible gravitational fields. We are motivated to study strong-field gravity since many theories give large deviations from general relativity only at large field strengths, while recovering the weak-field behavior. In this article, we review how one can probe general relativity and various alternative theories of gravity by using electromagnetic waves from a black hole with an accretion disk, and gravitational waves from black hole binaries. We first review model-independent ways of testing gravity with electromagnetic/gravitational waves from a black hole system. We then focus on selected examples of theories that extend general relativity in rather simple ways. Some important characteristics of general relativity include (but are not limited to) (i) only tensor gravitational degrees of freedom, (ii) the graviton is massless, (iii) no quadratic or higher curvatures in the action, and (iv) the theory is 4 dimensional. Altering a characteristic leads to a different extension of general relativity: (i) scalar-tensor theories, (ii) massive gravity theories, (iii) quadratic gravity, and (iv) theories with large extra dimensions. Within each theory, we describe black hole solutions, their properties, and current and projected constraints on each theory using black hole-based tests of gravity. We close this review by listing some of the open problems in model-independent tests and within each specific theory. |
1609.05129 | Michael Cole | Michael J. Cole, Juan A. Valiente Kroon | A geometric invariant characterising initial data for the Kerr-Newman
spacetime | 34 pages | null | 10.1007/s00023-017-0606-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the construction of a geometric invariant characterising initial
data for the Kerr-Newman spacetime. This geometric invariant vanishes if and
only if the initial data set corresponds to exact Kerr-Newman initial data, and
so characterises this type of data. We first illustrate the characterisation of
the Kerr-Newman spacetime in terms of Killing spinors. The space spinor
formalism is then used to obtain a set of four independent conditions on an
initial Cauchy hypersurface that guarantee the existence of a Killing spinor on
the development of the initial data. Following a similar analysis in the vacuum
case, we study the properties of solutions to the approximate Killing spinor
equation and use them to construct the geometric invariant.
| [
{
"created": "Fri, 16 Sep 2016 16:41:30 GMT",
"version": "v1"
}
] | 2018-03-28 | [
[
"Cole",
"Michael J.",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | We describe the construction of a geometric invariant characterising initial data for the Kerr-Newman spacetime. This geometric invariant vanishes if and only if the initial data set corresponds to exact Kerr-Newman initial data, and so characterises this type of data. We first illustrate the characterisation of the Kerr-Newman spacetime in terms of Killing spinors. The space spinor formalism is then used to obtain a set of four independent conditions on an initial Cauchy hypersurface that guarantee the existence of a Killing spinor on the development of the initial data. Following a similar analysis in the vacuum case, we study the properties of solutions to the approximate Killing spinor equation and use them to construct the geometric invariant. |
1406.6107 | Soon-Tae Hong | Soon-Tae Hong | Higher dimensional flat embedding of Taub-NUT-AdS spacetime | 8 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a global flat embedding structure of a Taub-NUT-AdS spacetime to
yield a (6+5)-dimensional novel global embedding Minkowski spacetime. We also
investigate Taub-NUT, Schwarzschild-AdS and Schwarzschild limits of the global
embedding by exploiting parameter reduction scheme. In particular, we observe
in the vanishing monopole strength limit of the Taub-NUT-AdS that the parameter
reduction is not smoothly applicable to the Schwarzschild-AdS, due to the
presence of imaginary roots of its lapse function associated with event
horizon. Moreover, reductions from the Taub-NUT-AdS and Schwarzschild-AdS to
Taub-NUT and Schwarzschild, respectively, are successfully performed. Finally,
we construct the global embedding Minkowski spacetimes for the patches inside
the event horizons of the Taub-NUT-AdS and its extended manifolds.
| [
{
"created": "Mon, 23 Jun 2014 23:27:24 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Feb 2016 07:21:58 GMT",
"version": "v2"
}
] | 2016-02-19 | [
[
"Hong",
"Soon-Tae",
""
]
] | We construct a global flat embedding structure of a Taub-NUT-AdS spacetime to yield a (6+5)-dimensional novel global embedding Minkowski spacetime. We also investigate Taub-NUT, Schwarzschild-AdS and Schwarzschild limits of the global embedding by exploiting parameter reduction scheme. In particular, we observe in the vanishing monopole strength limit of the Taub-NUT-AdS that the parameter reduction is not smoothly applicable to the Schwarzschild-AdS, due to the presence of imaginary roots of its lapse function associated with event horizon. Moreover, reductions from the Taub-NUT-AdS and Schwarzschild-AdS to Taub-NUT and Schwarzschild, respectively, are successfully performed. Finally, we construct the global embedding Minkowski spacetimes for the patches inside the event horizons of the Taub-NUT-AdS and its extended manifolds. |
gr-qc/0504007 | James R. Bogan | James R. Bogan | Induced Matter Theory & Heisenberg-like Uncertainty Relations | null | null | null | null | gr-qc | null | We show that a differential variant of the Heisenberg uncertainty relations
emerges naturally from induced matter theory, as a sum of line elements in both
momentum and Minkowski spaces.
| [
{
"created": "Fri, 1 Apr 2005 23:02:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bogan",
"James R.",
""
]
] | We show that a differential variant of the Heisenberg uncertainty relations emerges naturally from induced matter theory, as a sum of line elements in both momentum and Minkowski spaces. |
gr-qc/0302090 | Hanno Sahlmann | Hanno Sahlmann and Thomas Thiemann | On the superselection theory of the Weyl algebra for diffeomorphism
invariant quantum gauge theories | 31 pages, no figures. v2: Instructive second method of proof
supplemented | null | null | AEI-2003-025, PI-2003-001, CGPG-03/2-1, ESI-1284 | gr-qc hep-th math-ph math.MP | null | Much of the work in loop quantum gravity and quantum geometry rests on a
mathematically rigorous integration theory on spaces of distributional
connections. Most notably, a diffeomorphism invariant representation of the
algebra of basic observables of the theory, the Ashtekar-Lewandowski
representation, has been constructed. This representation is singled out by its
mathematical elegance, and up to now, no other diffeomorphism invariant
representation has been constructed. This raises the question whether it is
unique in a precise sense.
In the present article we take steps towards answering this question. Our
main result is that upon imposing relatively mild additional assumptions, the
AL-representation is indeed unique.
As an important tool which is also interesting in its own right, we introduce
a C*-algebra which is very similar to the Weyl algebra used in the canonical
quantization of free quantum field theories.
| [
{
"created": "Fri, 21 Feb 2003 20:31:58 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Feb 2003 18:57:50 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Sahlmann",
"Hanno",
""
],
[
"Thiemann",
"Thomas",
""
]
] | Much of the work in loop quantum gravity and quantum geometry rests on a mathematically rigorous integration theory on spaces of distributional connections. Most notably, a diffeomorphism invariant representation of the algebra of basic observables of the theory, the Ashtekar-Lewandowski representation, has been constructed. This representation is singled out by its mathematical elegance, and up to now, no other diffeomorphism invariant representation has been constructed. This raises the question whether it is unique in a precise sense. In the present article we take steps towards answering this question. Our main result is that upon imposing relatively mild additional assumptions, the AL-representation is indeed unique. As an important tool which is also interesting in its own right, we introduce a C*-algebra which is very similar to the Weyl algebra used in the canonical quantization of free quantum field theories. |
1803.08683 | Sabine Hossenfelder | Sabine Hossenfelder, Tobias Mistele | The Redshift-Dependence of Radial Acceleration: Modified Gravity versus
Particle Dark Matter | 7 pages, 4 figures | null | 10.1142/S0218271818470107 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified Newtonian Dynamics has one free parameter and requires an
interpolation function to recover the normal Newtonian limit. We here show that
this interpolation function is unnecessary in a recently proposed covariant
completion of Erik Verlinde's emergent gravity, and that Verlinde's approach
moreover fixes the function's one free parameter. The so-derived correlation
between the observed acceleration (inferred from rotation curves) and the
gravitational acceleration due to merely the baryonic matter fits well with
data. We then argue that the redshift-dependence of galactic rotation curves
could offer a way to tell apart different versions of modified gravity from
particle dark matter.
| [
{
"created": "Fri, 23 Mar 2018 08:18:40 GMT",
"version": "v1"
}
] | 2018-11-14 | [
[
"Hossenfelder",
"Sabine",
""
],
[
"Mistele",
"Tobias",
""
]
] | Modified Newtonian Dynamics has one free parameter and requires an interpolation function to recover the normal Newtonian limit. We here show that this interpolation function is unnecessary in a recently proposed covariant completion of Erik Verlinde's emergent gravity, and that Verlinde's approach moreover fixes the function's one free parameter. The so-derived correlation between the observed acceleration (inferred from rotation curves) and the gravitational acceleration due to merely the baryonic matter fits well with data. We then argue that the redshift-dependence of galactic rotation curves could offer a way to tell apart different versions of modified gravity from particle dark matter. |
1508.07439 | Yong-Wan Kim | Yong-Wan Kim, Young-Jai Park | Local free-fall Temperature of modified Schwarzschild black hole in
rainbow spacetime | 12 pages, 4 figures, version to appear in MPLA | Mod. Phys. Lett. A, Vol. 31, No. 17 (2016) 1650106 | 10.1142/S0217732316501066 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain a (5+1)-dimensional global flat embedding of modified Schwarzschild
black hole in rainbow gravity. We show that local free-fall temperature in
rainbow gravity, which depends on different energy $\omega$ of a test particle,
is finite at the event horizon for a freely falling observer, while local
temperature is divergent at the event horizon for a fiducial observer.
Moreover, these temperatures in rainbow gravity satisfy similar relations to
those of the Schwarzschild black hole except overall factor $g(\omega)$, which
plays a key role of rainbow functions in this embedding approach.
| [
{
"created": "Sat, 29 Aug 2015 11:47:59 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Sep 2015 07:19:41 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Apr 2016 05:27:20 GMT",
"version": "v3"
}
] | 2016-06-06 | [
[
"Kim",
"Yong-Wan",
""
],
[
"Park",
"Young-Jai",
""
]
] | We obtain a (5+1)-dimensional global flat embedding of modified Schwarzschild black hole in rainbow gravity. We show that local free-fall temperature in rainbow gravity, which depends on different energy $\omega$ of a test particle, is finite at the event horizon for a freely falling observer, while local temperature is divergent at the event horizon for a fiducial observer. Moreover, these temperatures in rainbow gravity satisfy similar relations to those of the Schwarzschild black hole except overall factor $g(\omega)$, which plays a key role of rainbow functions in this embedding approach. |
gr-qc/9811089 | Eric Gourgoulhon | S. Bonazzola, E. Gourgoulhon and J.-A. Marck (DARC, CNRS, Observatoire
de Paris) | Spectral methods in general relativistic astrophysics | 51 pages, elsart (Elsevier Preprint), 19 PostScript figures,
submitted to Journal of Computational & Applied Mathematics | J.Comput.Appl.Math. 109 (1999) 433 | null | null | gr-qc astro-ph physics.comp-ph | null | We present spectral methods developed in our group to solve three-dimensional
partial differential equations. The emphasis is put on equations arising from
astrophysical problems in the framework of general relativity.
| [
{
"created": "Thu, 26 Nov 1998 16:27:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bonazzola",
"S.",
"",
"DARC, CNRS, Observatoire\n de Paris"
],
[
"Gourgoulhon",
"E.",
"",
"DARC, CNRS, Observatoire\n de Paris"
],
[
"Marck",
"J. -A.",
"",
"DARC, CNRS, Observatoire\n de Paris"
]
] | We present spectral methods developed in our group to solve three-dimensional partial differential equations. The emphasis is put on equations arising from astrophysical problems in the framework of general relativity. |
gr-qc/9804054 | Eric Gourgoulhon | Eric Gourgoulhon (DARC, CNRS, Observatoire de Paris, France) | Relations between three formalisms for irrotational binary neutron stars
in general relativity | 5 pages, REVTeX, submitted as a brief report to Physical Review D | null | null | null | gr-qc astro-ph | null | Various formalisms proposed recently for irrotational binary systems in
general relativity are compared and explicit relations between them are
exhibited. It is notably shown that the formalisms of (i) Teukolsky, (ii)
Shibata and (iii) Bonazzola et al. (as corrected by Asada) are equivalent, i.e.
yield exactly the same solution, although the former two are simpler than the
latter one.
| [
{
"created": "Wed, 22 Apr 1998 14:31:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gourgoulhon",
"Eric",
"",
"DARC, CNRS, Observatoire de Paris, France"
]
] | Various formalisms proposed recently for irrotational binary systems in general relativity are compared and explicit relations between them are exhibited. It is notably shown that the formalisms of (i) Teukolsky, (ii) Shibata and (iii) Bonazzola et al. (as corrected by Asada) are equivalent, i.e. yield exactly the same solution, although the former two are simpler than the latter one. |
2203.05398 | Gabriele Barca | Gabriele Barca, Eleonora Giovannetti and Giovanni Montani | PQM and the GUP: Implications of Lattice Dynamics and Minimal
Uncertainties in Quantum Mechanics and Cosmology | Contribution to the 2022 Gravitation session of the 56th Rencontres
de Moriond. Proceedings available at https://doi.org/10.58027/1e1n-7973 | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare two alternative representations of quantum mechanics: Polymer
Quantum Mechanics (PQM), which presents features similar to Loop Quantum
Gravity and Loop Quantum Cosmology, and the Generalized Uncertainty Principle
(GUP) representation, that through a modified Algebra yields an alternative
uncertainty principle similar to those derived in String Theories and Brane
Cosmology. These formalisms can be recast to apparently look similar, but while
the GUP yields an absolute minimal uncertainty on position, PQM implements some
kind of ultraviolet cut-off through a lattice and does not have a minimal
uncertainty. Then we implement them on the anisotropic Bianchi I model in
Misner-like variables on a semiclassical level: PQM always implies a removal of
the singularities, while the GUP fails to do so, highlighting once again how
the two representations are fundamentally incompatible.
| [
{
"created": "Thu, 10 Mar 2022 14:42:04 GMT",
"version": "v1"
}
] | 2023-05-01 | [
[
"Barca",
"Gabriele",
""
],
[
"Giovannetti",
"Eleonora",
""
],
[
"Montani",
"Giovanni",
""
]
] | We compare two alternative representations of quantum mechanics: Polymer Quantum Mechanics (PQM), which presents features similar to Loop Quantum Gravity and Loop Quantum Cosmology, and the Generalized Uncertainty Principle (GUP) representation, that through a modified Algebra yields an alternative uncertainty principle similar to those derived in String Theories and Brane Cosmology. These formalisms can be recast to apparently look similar, but while the GUP yields an absolute minimal uncertainty on position, PQM implements some kind of ultraviolet cut-off through a lattice and does not have a minimal uncertainty. Then we implement them on the anisotropic Bianchi I model in Misner-like variables on a semiclassical level: PQM always implies a removal of the singularities, while the GUP fails to do so, highlighting once again how the two representations are fundamentally incompatible. |
1307.6694 | Salvatore Capozziello | Michael Tsamparlis, Andronikos Paliathanasis, Spyros Basilakos, and
Salvatore Capozziello | Conformally related metrics and Lagrangians and their physical
interpretation in cosmology | 13 pages, to appear in Gen. Rel. Grav | null | 10.1007/s10714-013-1575-0 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conformally related metrics and Lagrangians are considered in the context of
scalar-tensor gravity cosmology. After the discussion of the problem, we pose a
lemma in which we show that the field equations of two conformally related
Lagrangians are also conformally related if and only if the corresponding
Hamiltonian vanishes. Then we prove that to every non-minimally coupled scalar
field, we may associate a unique minimally coupled scalar field in a
conformally related space with an appropriate potential. The latter result
implies that the field equations of a non-minimally coupled scalar field are
the same at the conformal level with the field equations of the minimally
coupled scalar field. This fact is relevant in order to select physical
variables among conformally equivalent systems. Finally, we find that the above
propositions can be extended to a general Riemannian space of n-dimensions.
| [
{
"created": "Thu, 25 Jul 2013 10:52:46 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Tsamparlis",
"Michael",
""
],
[
"Paliathanasis",
"Andronikos",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | Conformally related metrics and Lagrangians are considered in the context of scalar-tensor gravity cosmology. After the discussion of the problem, we pose a lemma in which we show that the field equations of two conformally related Lagrangians are also conformally related if and only if the corresponding Hamiltonian vanishes. Then we prove that to every non-minimally coupled scalar field, we may associate a unique minimally coupled scalar field in a conformally related space with an appropriate potential. The latter result implies that the field equations of a non-minimally coupled scalar field are the same at the conformal level with the field equations of the minimally coupled scalar field. This fact is relevant in order to select physical variables among conformally equivalent systems. Finally, we find that the above propositions can be extended to a general Riemannian space of n-dimensions. |
0908.2074 | Ilya Gurwich | Ilya Gurwich and Aharon Davidson | Artifact Dark Matter from Unified Brane Gravity | 6 pages, no figures. Prepared for Identification of dark matter 2008,
Stockholm, Sweden, August 18-22, 2008 | PoS IDM2008:094,2008 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Adopting Dirac's brane variation prescription, the energy-momentum tensor of
a brane gets supplemented by a geometrical (embedding originated) dark
component. While the masslessness of the graviton is preserved, and the Newton
force law is recovered, the corresponding Newton constant is necessarily lower
than the one which governs FRW cosmology. This has the potential to puzzle out
cosmological dark matter, a subsequent conjecture concerning galactic dark
matter follows.
| [
{
"created": "Fri, 14 Aug 2009 14:30:06 GMT",
"version": "v1"
}
] | 2010-02-17 | [
[
"Gurwich",
"Ilya",
""
],
[
"Davidson",
"Aharon",
""
]
] | Adopting Dirac's brane variation prescription, the energy-momentum tensor of a brane gets supplemented by a geometrical (embedding originated) dark component. While the masslessness of the graviton is preserved, and the Newton force law is recovered, the corresponding Newton constant is necessarily lower than the one which governs FRW cosmology. This has the potential to puzzle out cosmological dark matter, a subsequent conjecture concerning galactic dark matter follows. |
1605.01669 | Istvan Racz | Istv\'an R\'acz | A simple method of constructing binary black hole initial data | Substantial simplification of the main argument. Supplemental
material available at http://www.kfki.hu/~iracz/SM-BH-data.pdf | Astronomy Reports, 62(12), 953-958 (2018) | 10.1134/S1063772918120302 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By applying a parabolic-hyperbolic formulation of the constraints and
superposing Kerr-Schild black holes, a simple method is introduced to
initialize time evolution of binary systems. As the input parameters are
essentially the same as those used in the post-Newtonian (PN) setup the
proposed method interrelates various physical expressions applied in PN and in
fully relativistic formulations. The global ADM charges are also determined by
the input parameters, and no use of boundary conditions in the strong field
regime is made.
| [
{
"created": "Thu, 5 May 2016 17:48:00 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Aug 2016 16:38:16 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Aug 2016 15:09:21 GMT",
"version": "v3"
},
{
"created": "Fri, 6 Jan 2017 12:48:13 GMT",
"version": "v4"
}
] | 2019-01-07 | [
[
"Rácz",
"István",
""
]
] | By applying a parabolic-hyperbolic formulation of the constraints and superposing Kerr-Schild black holes, a simple method is introduced to initialize time evolution of binary systems. As the input parameters are essentially the same as those used in the post-Newtonian (PN) setup the proposed method interrelates various physical expressions applied in PN and in fully relativistic formulations. The global ADM charges are also determined by the input parameters, and no use of boundary conditions in the strong field regime is made. |
2310.19722 | Robert Seeger | Hanno Sahlmann and Robert Seeger | Revisiting loop quantum gravity with selfdual variables: Hilbert space
and first reality condition | 29 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the quantization of gravity as an SL(2,C) gauge theory in terms
of Ashtekar's selfdual variables and reality conditions for the spatial metric
(RCI) and its evolution (RCII). We start from a holomorphic phase space
formulation. It is then natural to push for a quantization in terms of
holomorphic wave functions. Thus we consider holomorphic cylindrical wave
functions over SL(2,C) connections. We use an overall phase ambiguity of the
complex selfdual action to obtain Poisson brackets that mirror those of the
real theory. We then show that there is a representation of the corresponding
canonical commutation relations the space of holomorphic cylindrical functions.
We describe a class of cylindrically consistent measures that implements RCI.
We show that spin networks with SU(2) intertwiners form a basis for gauge
invariant states. They are still mutually orthogonal, but the normalisation is
different than for the Ashtekar-Lewandowski measure for SU(2). We do not
consider RCII in the present article. Work on RCII is ongoing and will be
presented elsewhere.
| [
{
"created": "Mon, 30 Oct 2023 16:50:16 GMT",
"version": "v1"
}
] | 2023-10-31 | [
[
"Sahlmann",
"Hanno",
""
],
[
"Seeger",
"Robert",
""
]
] | We consider the quantization of gravity as an SL(2,C) gauge theory in terms of Ashtekar's selfdual variables and reality conditions for the spatial metric (RCI) and its evolution (RCII). We start from a holomorphic phase space formulation. It is then natural to push for a quantization in terms of holomorphic wave functions. Thus we consider holomorphic cylindrical wave functions over SL(2,C) connections. We use an overall phase ambiguity of the complex selfdual action to obtain Poisson brackets that mirror those of the real theory. We then show that there is a representation of the corresponding canonical commutation relations the space of holomorphic cylindrical functions. We describe a class of cylindrically consistent measures that implements RCI. We show that spin networks with SU(2) intertwiners form a basis for gauge invariant states. They are still mutually orthogonal, but the normalisation is different than for the Ashtekar-Lewandowski measure for SU(2). We do not consider RCII in the present article. Work on RCII is ongoing and will be presented elsewhere. |
gr-qc/0203009 | Sawa Manoff | Sawa Manoff | Local criteria for the existence of an accelerated frame of reference | 6 pages, LaTeX | null | null | null | gr-qc | null | A local criteria for the existence of an accelerated frame of reference is
found. An accelerated frame of reference could exist in all regions where a
non-null (non-isotropic) vector field does not degenerate in a null (isotropic)
vector field.
| [
{
"created": "Mon, 4 Mar 2002 08:46:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Manoff",
"Sawa",
""
]
] | A local criteria for the existence of an accelerated frame of reference is found. An accelerated frame of reference could exist in all regions where a non-null (non-isotropic) vector field does not degenerate in a null (isotropic) vector field. |
2107.12875 | Edgar Gasperin | Edgar Gasperin and Juan A. Valiente Kroon | Staticity and regularity for zero rest-mass fields near spatial infinity
on flat spacetime | 21 pages | null | 10.1088/1361-6382/ac37ce | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Linear zero-rest-mass fields generically develop logarithmic singularities at
the critical sets where spatial infinity meets null infinity. Friedrich's
representation of spatial infinity is ideally suited to study this phenomenon.
These logarithmic singularities are an obstruction to the smoothness of the
zero-rest-mass field at null infinity and, in particular, to peeling. In the
case of the spin-2 field it has been shown that these logarithmic singularities
can be precluded if the initial data for the field satisfies a certain
regularity condition involving the vanishing, at spatial infinity, of a certain
spinor (the linearised Cotton spinor) and its totally symmetrised derivatives.
In this article we investigate the relation between this regularity condition
and the staticity of the spin-2 field. It is shown that while any static spin-2
field satisfies the regularity condition, not every solution satisfying the
regularity condition is static. This result is in contrast with what happens in
the case of General Relativity where staticity in a neighbourhood of spatial
infinity and the smoothness of the field at future and past null infinities are
much more closely related.
| [
{
"created": "Tue, 27 Jul 2021 15:17:50 GMT",
"version": "v1"
}
] | 2021-12-22 | [
[
"Gasperin",
"Edgar",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | Linear zero-rest-mass fields generically develop logarithmic singularities at the critical sets where spatial infinity meets null infinity. Friedrich's representation of spatial infinity is ideally suited to study this phenomenon. These logarithmic singularities are an obstruction to the smoothness of the zero-rest-mass field at null infinity and, in particular, to peeling. In the case of the spin-2 field it has been shown that these logarithmic singularities can be precluded if the initial data for the field satisfies a certain regularity condition involving the vanishing, at spatial infinity, of a certain spinor (the linearised Cotton spinor) and its totally symmetrised derivatives. In this article we investigate the relation between this regularity condition and the staticity of the spin-2 field. It is shown that while any static spin-2 field satisfies the regularity condition, not every solution satisfying the regularity condition is static. This result is in contrast with what happens in the case of General Relativity where staticity in a neighbourhood of spatial infinity and the smoothness of the field at future and past null infinities are much more closely related. |
0707.0042 | Karthik Shankar | Karthik Shankar and Bernard F. Whiting | Self force of a static electric charge near a Schwarzschild Star | 11 pages, 2 figures | Phys.Rev.D76:124027,2007 | 10.1103/PhysRevD.76.124027 | null | gr-qc | null | When a charge is held static near a constant density spherical star, it
experiences a self-force which is significantly different from the force it
would experience when placed near a black hole of the same mass. In this paper,
an expression for the self-force (as measured by a locally inertial observer)
is given %explicitly calculated for an insulating Schwarzschild star, and the
result is explicitly computed for the extreme density case, which has a
singularity at its center. The force is found to be repulsive. A similar
calculation of the self-force is also performed for a conducting star. This
calculation is valid for any static, spherically conducting star, since the
result is independent of the interior metric. When the charge is placed very
close to the conducting star, the force is found to be attractive but when the
charge is placed beyond a certain distance (2.95M for a conducting star of
radius 2.25M), the force is found to be repulsive. When the charge is placed
very far from the star (be it conducting or insulating), the charge experiences
the same repulsive force it would experience when placed in the spacetime of a
black hole with the same mass as the star.
| [
{
"created": "Sat, 30 Jun 2007 04:38:30 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Nov 2007 12:57:22 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Shankar",
"Karthik",
""
],
[
"Whiting",
"Bernard F.",
""
]
] | When a charge is held static near a constant density spherical star, it experiences a self-force which is significantly different from the force it would experience when placed near a black hole of the same mass. In this paper, an expression for the self-force (as measured by a locally inertial observer) is given %explicitly calculated for an insulating Schwarzschild star, and the result is explicitly computed for the extreme density case, which has a singularity at its center. The force is found to be repulsive. A similar calculation of the self-force is also performed for a conducting star. This calculation is valid for any static, spherically conducting star, since the result is independent of the interior metric. When the charge is placed very close to the conducting star, the force is found to be attractive but when the charge is placed beyond a certain distance (2.95M for a conducting star of radius 2.25M), the force is found to be repulsive. When the charge is placed very far from the star (be it conducting or insulating), the charge experiences the same repulsive force it would experience when placed in the spacetime of a black hole with the same mass as the star. |
1912.07401 | I. V. Kanatchikov | I.V. Kanatchikov | On the precanonical structure of the Schr\"odinger wave functional in
curved space-time | 8 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The functional Schr\"odinger equation in curved space-time is derived from
the manifestly covariant precanonical Schr\"odinger equation. The Schr\"odinger
wave functional is expressed as the trace of the multidimensional product
integral of precanonical wave function restricted to a field configuration. The
functional Schr\"odinger representation of QFT in curved space-time appears as
a singular limiting case of a formulation based on precanonical quantization,
which leads to a hypercomplex generalization of quantum formalism in field
theory.
| [
{
"created": "Mon, 16 Dec 2019 14:27:44 GMT",
"version": "v1"
}
] | 2019-12-17 | [
[
"Kanatchikov",
"I. V.",
""
]
] | The functional Schr\"odinger equation in curved space-time is derived from the manifestly covariant precanonical Schr\"odinger equation. The Schr\"odinger wave functional is expressed as the trace of the multidimensional product integral of precanonical wave function restricted to a field configuration. The functional Schr\"odinger representation of QFT in curved space-time appears as a singular limiting case of a formulation based on precanonical quantization, which leads to a hypercomplex generalization of quantum formalism in field theory. |
1703.04426 | Pac\^ome Delva Dr. | P. Delva, J. Lodewyck, S. Bilicki, E. Bookjans, G. Vallet, R. Le
Targat, P.-E. Pottie, C. Guerlin, F. Meynadier, C. Le Poncin-Lafitte, O.
Lopez, A. Amy-Klein, W.-K. Lee, N. Quintin, C. Lisdat, A. Al-Masoudi, S.
D\"orscher, C. Grebing, G. Grosche, A. Kuhl, S. Raupach, U. Sterr, I. R.
Hill, R. Hobson, W. Bowden, J. Kronj\"ager, G. Marra, A. Rolland, F. N.
Baynes, H. S. Margolis and P. Gill | Test of special relativity using a fiber network of optical clocks | 6 pages, 3 figures, published in Phys. Rev. L | Phys. Rev. Lett. 118, 221102 (2017) | 10.1103/PhysRevLett.118.221102 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Phase compensated optical fiber links enable high accuracy atomic clocks
separated by thousands of kilometers to be compared with unprecedented
statistical resolution. By searching for a daily variation of the frequency
difference between four strontium optical lattice clocks in different locations
throughout Europe connected by such links, we improve upon previous tests of
time dilation predicted by special relativity. We obtain a constraint on the
Robertson--Mansouri--Sexl parameter $|\alpha|\lesssim 1.1 \times10^{-8}$
quantifying a violation of time dilation, thus improving by a factor of around
two the best known constraint obtained with Ives--Stilwell type experiments,
and by two orders of magnitude the best constraint obtained by comparing atomic
clocks. This work is the first of a new generation of tests of fundamental
physics using optical clocks and fiber links. As clocks improve, and as fiber
links are routinely operated, we expect that the tests initiated in this paper
will improve by orders of magnitude in the near future.
| [
{
"created": "Mon, 13 Mar 2017 14:54:02 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Jun 2017 12:33:02 GMT",
"version": "v2"
}
] | 2017-06-13 | [
[
"Delva",
"P.",
""
],
[
"Lodewyck",
"J.",
""
],
[
"Bilicki",
"S.",
""
],
[
"Bookjans",
"E.",
""
],
[
"Vallet",
"G.",
""
],
[
"Targat",
"R. Le",
""
],
[
"Pottie",
"P. -E.",
""
],
[
"Guerlin",
"C."... | Phase compensated optical fiber links enable high accuracy atomic clocks separated by thousands of kilometers to be compared with unprecedented statistical resolution. By searching for a daily variation of the frequency difference between four strontium optical lattice clocks in different locations throughout Europe connected by such links, we improve upon previous tests of time dilation predicted by special relativity. We obtain a constraint on the Robertson--Mansouri--Sexl parameter $|\alpha|\lesssim 1.1 \times10^{-8}$ quantifying a violation of time dilation, thus improving by a factor of around two the best known constraint obtained with Ives--Stilwell type experiments, and by two orders of magnitude the best constraint obtained by comparing atomic clocks. This work is the first of a new generation of tests of fundamental physics using optical clocks and fiber links. As clocks improve, and as fiber links are routinely operated, we expect that the tests initiated in this paper will improve by orders of magnitude in the near future. |
2012.11209 | Sebastian Murk | Sebastian Murk, Daniel R. Terno | Spherically symmetric black holes in metric gravity | 13 pages. Published version. Comments welcome! | Phys. Rev. D 104, 064048 (2021) | 10.1103/PhysRevD.104.064048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of black holes is one of the key predictions of general
relativity (GR) and therefore a basic consistency test for modified theories of
gravity. In the case of spherical symmetry in GR the existence of an apparent
horizon and its regularity is consistent with only two distinct classes of
physical black holes. Here we derive constraints that any self-consistent
modified theory of gravity must satisfy to be compatible with their existence.
We analyze their properties and illustrate characteristic features using the
Starobinsky model. Both of the GR solutions can be regarded as zeroth-order
terms in perturbative solutions of this model. We also show how to construct
nonperturbative solutions without a well-defined GR limit.
| [
{
"created": "Mon, 21 Dec 2020 09:44:02 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Feb 2021 05:30:05 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Sep 2021 09:45:14 GMT",
"version": "v3"
}
] | 2021-09-22 | [
[
"Murk",
"Sebastian",
""
],
[
"Terno",
"Daniel R.",
""
]
] | The existence of black holes is one of the key predictions of general relativity (GR) and therefore a basic consistency test for modified theories of gravity. In the case of spherical symmetry in GR the existence of an apparent horizon and its regularity is consistent with only two distinct classes of physical black holes. Here we derive constraints that any self-consistent modified theory of gravity must satisfy to be compatible with their existence. We analyze their properties and illustrate characteristic features using the Starobinsky model. Both of the GR solutions can be regarded as zeroth-order terms in perturbative solutions of this model. We also show how to construct nonperturbative solutions without a well-defined GR limit. |
2208.12849 | Christopher Berry | J. Glanzer, S. Banagiri, S. B. Coughlin, S. Soni, M. Zevin, C. P. L.
Berry, O. Patane, S. Bahaadini, N. Rohani, K. Crowston, V. Kalogera, C.
{\O}sterlund and A. Katsaggelos | Data quality up to the third observing run of Advanced LIGO: Gravity Spy
glitch classifications | 33 pages (including bibliography), 11 figures, 3 tables, 1 appendix;
updated to match version to be published in Classical & Quantum Gravity; data
release available from https://doi.org/10.5281/zenodo.5649211 | Classical & Quantum Gravity; 40(6):065004(28); 2023 | 10.1088/1361-6382/acb633 | LIGO-P2200238 | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Understanding the noise in gravitational-wave detectors is central to
detecting and interpreting gravitational-wave signals. Glitches are transient,
non-Gaussian noise features that can have a range of environmental and
instrumental origins. The Gravity Spy project uses a machine-learning algorithm
to classify glitches based upon their time-frequency morphology. The resulting
set of classified glitches can be used as input to detector-characterisation
investigations of how to mitigate glitches, or data-analysis studies of how to
ameliorate the impact of glitches. Here we present the results of the Gravity
Spy analysis of data up to the end of the third observing run of Advanced LIGO.
We classify 233981 glitches from LIGO Hanford and 379805 glitches from LIGO
Livingston into morphological classes. We find that the distribution of
glitches differs between the two LIGO sites. This highlights the potential need
for studies of data quality to be individually tailored to each
gravitational-wave observatory.
| [
{
"created": "Fri, 26 Aug 2022 19:24:19 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Feb 2023 11:13:36 GMT",
"version": "v2"
}
] | 2023-02-23 | [
[
"Glanzer",
"J.",
""
],
[
"Banagiri",
"S.",
""
],
[
"Coughlin",
"S. B.",
""
],
[
"Soni",
"S.",
""
],
[
"Zevin",
"M.",
""
],
[
"Berry",
"C. P. L.",
""
],
[
"Patane",
"O.",
""
],
[
"Bahaadini",
"S.... | Understanding the noise in gravitational-wave detectors is central to detecting and interpreting gravitational-wave signals. Glitches are transient, non-Gaussian noise features that can have a range of environmental and instrumental origins. The Gravity Spy project uses a machine-learning algorithm to classify glitches based upon their time-frequency morphology. The resulting set of classified glitches can be used as input to detector-characterisation investigations of how to mitigate glitches, or data-analysis studies of how to ameliorate the impact of glitches. Here we present the results of the Gravity Spy analysis of data up to the end of the third observing run of Advanced LIGO. We classify 233981 glitches from LIGO Hanford and 379805 glitches from LIGO Livingston into morphological classes. We find that the distribution of glitches differs between the two LIGO sites. This highlights the potential need for studies of data quality to be individually tailored to each gravitational-wave observatory. |
1809.00785 | Ernesto Contreras | E. Contreras and P. Bargue\~no | Scale--dependent Hayward black hole and the generalized uncertainty
principle | 5 pages. References added. Accepted in Mod. Phys. Lett. A | Modern Physics Letters A Vol. 33, No. 32 (2018) 1850184 | 10.1142/S0217732318501845 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present a technique to obtain bounds on the generalized
uncertainty principle deformation parameter by using an improved Schwarzschild
solution represented by the Hayward metric in the context of scale--dependent
gravity. Specifically, this deformation parameter can be interpreted in terms
of a running parameter which controls the deviation from the standard
Einstein--Hilbert action in the scale--dependent scenario.
| [
{
"created": "Tue, 4 Sep 2018 03:32:00 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Sep 2018 00:36:42 GMT",
"version": "v2"
}
] | 2018-10-01 | [
[
"Contreras",
"E.",
""
],
[
"Bargueño",
"P.",
""
]
] | In this work we present a technique to obtain bounds on the generalized uncertainty principle deformation parameter by using an improved Schwarzschild solution represented by the Hayward metric in the context of scale--dependent gravity. Specifically, this deformation parameter can be interpreted in terms of a running parameter which controls the deviation from the standard Einstein--Hilbert action in the scale--dependent scenario. |
gr-qc/0212100 | Victor Berezin | Victor Berezin (Inst. Nucl. Res. Russ. Acad. Sci., Moscow) | What can we learn studying quantum black holes? | 65 pp.,11 Figs. To be published in Int.Journ.Mod.Phys.A as a review
article | null | null | null | gr-qc | null | In this paper we try to answer the main question: what is a quantum black
hole?
| [
{
"created": "Tue, 24 Dec 2002 12:31:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Berezin",
"Victor",
"",
"Inst. Nucl. Res. Russ. Acad. Sci., Moscow"
]
] | In this paper we try to answer the main question: what is a quantum black hole? |
1206.6559 | Seth Lloyd | Seth Lloyd | The quantum geometric limit | 13 pages, LaTeX. This version updated with figures. arXiv admin note:
substantial text overlap with arXiv:quant-ph/0505064 | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Einstein's gedankenexperiment for measuring space and time, an ensemble of
clocks moving through curved spacetime measures geometry by sending signals
back and forth, as in the global positioning system (GPS). Combining well-known
quantum limits to measurement with the requirement that the energy density of
clocks and signals be be no greater than the black hole density leads to the
quantum geometric limit: the total number of ticks of clocks and clicks of
detectors that can be contained in a four volume of spacetime of radius r and
temporal extent t is less than or equal to rt/\pi l_P t_P, where l_P, t_P are
the Planck length and time. The quantum geometric limit suggests that each
event or `op' that takes place in a four-volume of spacetime is associated with
a Planck-scale area. This paper shows that the quantum geometric limit can be
used to derive general relativity: if each quantum event is associated with a
Planck-scale area removed from two-dimensional surfaces in the volume in which
the event takes place, then Einstein's equations must hold.
| [
{
"created": "Thu, 28 Jun 2012 03:53:03 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Jun 2012 16:10:02 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Jul 2012 22:05:23 GMT",
"version": "v3"
},
{
"created": "Wed, 17 Oct 2012 19:42:26 GMT",
"version": "v4"
}
] | 2012-10-18 | [
[
"Lloyd",
"Seth",
""
]
] | In Einstein's gedankenexperiment for measuring space and time, an ensemble of clocks moving through curved spacetime measures geometry by sending signals back and forth, as in the global positioning system (GPS). Combining well-known quantum limits to measurement with the requirement that the energy density of clocks and signals be be no greater than the black hole density leads to the quantum geometric limit: the total number of ticks of clocks and clicks of detectors that can be contained in a four volume of spacetime of radius r and temporal extent t is less than or equal to rt/\pi l_P t_P, where l_P, t_P are the Planck length and time. The quantum geometric limit suggests that each event or `op' that takes place in a four-volume of spacetime is associated with a Planck-scale area. This paper shows that the quantum geometric limit can be used to derive general relativity: if each quantum event is associated with a Planck-scale area removed from two-dimensional surfaces in the volume in which the event takes place, then Einstein's equations must hold. |
0805.2811 | Francesco Cianfrani dr | F. Cianfrani, G. Montani | The role of the time gauge in the 2nd order formalism | 4 pages, Proceedings of the II Stueckelberg Workshop | Int.J.Mod.Phys.A23:1214-1217,2008 | 10.1142/S0217751X08040081 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a canonical quantization of gravity in a second-order formulation,
taking as configuration variables those describing a 4-bein, not adapted to the
space-time splitting. We outline how, neither if we fix the Lorentz frame
before quantizing, nor if we perform no gauge fixing at all, is invariance
under boost transformations affected by the quantization.
| [
{
"created": "Mon, 19 May 2008 08:22:38 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Cianfrani",
"F.",
""
],
[
"Montani",
"G.",
""
]
] | We perform a canonical quantization of gravity in a second-order formulation, taking as configuration variables those describing a 4-bein, not adapted to the space-time splitting. We outline how, neither if we fix the Lorentz frame before quantizing, nor if we perform no gauge fixing at all, is invariance under boost transformations affected by the quantization. |
gr-qc/0405144 | Christodoulakis Theodosios | T. Christodoulakis, G.O. Papadopoulos | Space Time Covariance of Canonical Quantization of Gravity: A (formal)
general result and the (rigorous) explicit case of 2+1 Quantum Cosmology | 28 pages, LaTeX2e | null | null | null | gr-qc | null | A general classical theorem is presented according to which all invariant
relations among the space time metric scalars, when turned into functions on
the Phase Space of full Pure Gravity (using the Canonical Equations of motion),
become weakly vanishing functions of the Quadratic and Linear Constraints. The
implication of this result is that (formal) Dirac consistency of the Quantum
Operator Constraints (annihilating the wave Function) suffices to guarantee
space time covariance f the ensuing quantum theory: An ordering for each
invariant relation will always exist such that the emanating operator has an
eigenvalue identical to the classical value. The example of 2+1 Quantum
Cosmology is explicitly considered: The four possible ``Cosmological
Solutions'' --two for pure Einstein's equations plus two more when a $\Lambda$
term is present- are exhibited and the corresponding models are quantized. The
invariant relations describing the geometries are explicitly calculated and
promoted to operators whose eigenvalues are their corresponding classical
values.
| [
{
"created": "Sat, 29 May 2004 11:55:21 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Jul 2005 12:14:31 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Christodoulakis",
"T.",
""
],
[
"Papadopoulos",
"G. O.",
""
]
] | A general classical theorem is presented according to which all invariant relations among the space time metric scalars, when turned into functions on the Phase Space of full Pure Gravity (using the Canonical Equations of motion), become weakly vanishing functions of the Quadratic and Linear Constraints. The implication of this result is that (formal) Dirac consistency of the Quantum Operator Constraints (annihilating the wave Function) suffices to guarantee space time covariance f the ensuing quantum theory: An ordering for each invariant relation will always exist such that the emanating operator has an eigenvalue identical to the classical value. The example of 2+1 Quantum Cosmology is explicitly considered: The four possible ``Cosmological Solutions'' --two for pure Einstein's equations plus two more when a $\Lambda$ term is present- are exhibited and the corresponding models are quantized. The invariant relations describing the geometries are explicitly calculated and promoted to operators whose eigenvalues are their corresponding classical values. |
0709.2743 | Hyung Won Lee | Kyoung Yee Kim, Hyung Won Lee and Yun Soo Myung | Instability of agegraphic dark energy models | 15 pages 4 figures | Phys.Lett.B660:118-124,2008 | 10.1016/j.physletb.2007.12.045 | INJE-TP-07-09 | gr-qc | null | We investigate the agegraphic dark energy models which were recently proposed
to explain the dark energy-dominated universe. For this purpose, we calculate
their equation of states and squared speeds of sound. We find that the squared
speed for agegraphic dark energy is always negative. This means that the
perfect fluid for agegraphic dark energy is classically unstable. Furthermore,
it is shown that the new agegraphic dark energy model could describe the matter
(radiation)-dominated universe in the far past only when the parameter $n$ is
chosen to be $n>n_c$, where the critical values are determined to be
$n_c=2.6878(2.5137752)$ numerically. It seems that the new agegraphic dark
energy model is no better than the holographic dark energy model for the
description of the dark energy-dominated universe, even though it resolves the
causality problem.
| [
{
"created": "Tue, 18 Sep 2007 03:14:56 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kim",
"Kyoung Yee",
""
],
[
"Lee",
"Hyung Won",
""
],
[
"Myung",
"Yun Soo",
""
]
] | We investigate the agegraphic dark energy models which were recently proposed to explain the dark energy-dominated universe. For this purpose, we calculate their equation of states and squared speeds of sound. We find that the squared speed for agegraphic dark energy is always negative. This means that the perfect fluid for agegraphic dark energy is classically unstable. Furthermore, it is shown that the new agegraphic dark energy model could describe the matter (radiation)-dominated universe in the far past only when the parameter $n$ is chosen to be $n>n_c$, where the critical values are determined to be $n_c=2.6878(2.5137752)$ numerically. It seems that the new agegraphic dark energy model is no better than the holographic dark energy model for the description of the dark energy-dominated universe, even though it resolves the causality problem. |
1607.06159 | Friedrich W. Hehl | Friedrich W. Hehl (Cologne), Yakov Itin (Jerusalem), Yuri N. Obukhov
(Moscow) | On Kottler's path: origin and evolution of the premetric program in
gravity and in electrodynamics | 72 pages latex with 6 figures; based on an invited talk given at the
Annual Meeting of the German Physical Society (DPG) in Berlin on 20 March
2015, Working Group on Philosophy of Physics (AGPhil); a short version will
be submitted to IJMPD | null | 10.1142/S0218271816400162 | null | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1922, Kottler put forward the program to remove the gravitational
potential, the metric of spacetime, from the fundamental equations in physics
as far as possible. He successfully applied this idea to Newton's
gravitostatics and to Maxwell's electrodynamics, where Kottler recast the field
equations in premetric form and specified a metric-dependent constitutive law.
We will discuss the basics of the premetric approach and some of its beautiful
consequences, like the division of universal constants into two classes. We
show that classical electrodynamics can be developed without a metric quite
straightforwardly: the Maxwell equations, together with a local and linear
response law for electromagnetic media, admit a consistent premetric
formulation. Kottler's program succeeds here without provisos. In Kottler's
approach to gravity, making the theory relativistic, two premetric
quasi-Maxwellian field equations arise, but their field variables, if
interpreted in terms of general relativity, do depend on the metric. However,
one can hope to bring the Kottler idea to work by using the teleparallelism
equivalent of general relativity, where the gravitational potential, the
coframe, can be chosen in a premetric way.
| [
{
"created": "Thu, 21 Jul 2016 00:14:35 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Hehl",
"Friedrich W.",
"",
"Cologne"
],
[
"Itin",
"Yakov",
"",
"Jerusalem"
],
[
"Obukhov",
"Yuri N.",
"",
"Moscow"
]
] | In 1922, Kottler put forward the program to remove the gravitational potential, the metric of spacetime, from the fundamental equations in physics as far as possible. He successfully applied this idea to Newton's gravitostatics and to Maxwell's electrodynamics, where Kottler recast the field equations in premetric form and specified a metric-dependent constitutive law. We will discuss the basics of the premetric approach and some of its beautiful consequences, like the division of universal constants into two classes. We show that classical electrodynamics can be developed without a metric quite straightforwardly: the Maxwell equations, together with a local and linear response law for electromagnetic media, admit a consistent premetric formulation. Kottler's program succeeds here without provisos. In Kottler's approach to gravity, making the theory relativistic, two premetric quasi-Maxwellian field equations arise, but their field variables, if interpreted in terms of general relativity, do depend on the metric. However, one can hope to bring the Kottler idea to work by using the teleparallelism equivalent of general relativity, where the gravitational potential, the coframe, can be chosen in a premetric way. |
1009.3897 | Swastik Bhattacharya | Swastik Bhattacharya and Pankaj S. Joshi | Trapped surfaces and horizons in static massless scalar field spacetimes | Revtex, 6 pages, No figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider here the existence and structure of trapped surfaces, horizons
and singularities in spherically symmetric static massless scalar field
spacetimes. Earlier studies have shown that there exists no event horizon in
such spacetimes if the scalar field is asymptotically flat. We extend this
result here to show that this is true in general for spherically symmetric
static massless scalar field spacetimes, whether the scalar field is
asymptotically flat or not. Other general properties and certain important
features of these models are also discussed.
| [
{
"created": "Mon, 20 Sep 2010 17:36:29 GMT",
"version": "v1"
}
] | 2010-09-21 | [
[
"Bhattacharya",
"Swastik",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | We consider here the existence and structure of trapped surfaces, horizons and singularities in spherically symmetric static massless scalar field spacetimes. Earlier studies have shown that there exists no event horizon in such spacetimes if the scalar field is asymptotically flat. We extend this result here to show that this is true in general for spherically symmetric static massless scalar field spacetimes, whether the scalar field is asymptotically flat or not. Other general properties and certain important features of these models are also discussed. |
0805.0208 | Alok Laddha | Alok Laddha, Madhavan Varadarajan | Polymer Parametrised Field Theory | 44 pages, no figures | Phys.Rev.D78:044008,2008 | 10.1103/PhysRevD.78.044008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Free scalar field theory on 2 dimensional flat spacetime, cast in
diffeomorphism invariant guise by treating the inertial coordinates of the
spacetime as dynamical variables, is quantized using LQG type `polymer'
representations for the matter field and the inertial variables. The quantum
constraints are solved via group averaging techniques and, analogous to the
case of spatial geometry in LQG, the smooth (flat) spacetime geometry is
replaced by a discrete quantum structure. An overcomplete set of Dirac
observables, consisting of (a) (exponentials of) the standard free scalar field
creation- annihilation modes and (b) canonical transformations corresponding to
conformal isometries, are represented as operators on the physical Hilbert
space. None of these constructions suffer from any of the `triangulation'
dependent choices which arise in treatments of LQG. In contrast to the standard
Fock quantization, the non- Fock nature of the representation ensures that the
algebra of conformal isometries as well as that of spacetime diffeomorphisms
are represented in an anomaly free manner. Semiclassical states can be analysed
at the gauge invariant level. It is shown that `physical weaves' necessarily
underly such states and that such states display semiclassicality with respect
to, at most, a countable subset of the (uncountably large) set of observables
of type (a). The model thus offers a fertile testing ground for proposed
definitions of quantum dynamics as well as semiclassical states in LQG.
| [
{
"created": "Fri, 2 May 2008 11:03:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Laddha",
"Alok",
""
],
[
"Varadarajan",
"Madhavan",
""
]
] | Free scalar field theory on 2 dimensional flat spacetime, cast in diffeomorphism invariant guise by treating the inertial coordinates of the spacetime as dynamical variables, is quantized using LQG type `polymer' representations for the matter field and the inertial variables. The quantum constraints are solved via group averaging techniques and, analogous to the case of spatial geometry in LQG, the smooth (flat) spacetime geometry is replaced by a discrete quantum structure. An overcomplete set of Dirac observables, consisting of (a) (exponentials of) the standard free scalar field creation- annihilation modes and (b) canonical transformations corresponding to conformal isometries, are represented as operators on the physical Hilbert space. None of these constructions suffer from any of the `triangulation' dependent choices which arise in treatments of LQG. In contrast to the standard Fock quantization, the non- Fock nature of the representation ensures that the algebra of conformal isometries as well as that of spacetime diffeomorphisms are represented in an anomaly free manner. Semiclassical states can be analysed at the gauge invariant level. It is shown that `physical weaves' necessarily underly such states and that such states display semiclassicality with respect to, at most, a countable subset of the (uncountably large) set of observables of type (a). The model thus offers a fertile testing ground for proposed definitions of quantum dynamics as well as semiclassical states in LQG. |
1405.5455 | Yaser Tavakoli | Yaser Tavakoli | Astrophysical and cosmological doomsdays | PhD thesis 2013 (148 pages). It contains material first presented in
arXiv:1105.0445, arXiv:1303.6157, arXiv:1308.4953 and arXiv:0911.1428
[gr-qc]. arXiv admin note: text overlap with arXiv:gr-qc/0301045,
arXiv:gr-qc/0506129, arXiv:gr-qc/0702144 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this dissertation we study two well known gravitational scenarios in which
singularities may appear; the final state of gravitational collapse and the
late time evolution of the universe. In the first scenario, we study a
spherically symmetric space-time whose matter content includes a tachyon scalar
field and a barotropic fluid. By employing a dynamical system analysis, we find
classical solutions corresponding to a naked singularity or a black hole
formation. We then investigate, in a semiclassical manner, loop quantum gravity
induced effects on the fate of the classical singularities. By employing an
inverse triad correction, we identify a subset which corresponds to an outward
flux of energy, thus avoiding either a naked singularity or a black hole
formation. Within a holonomy correction, we obtain the semiclassical
counterpart of our (classical) general relativistic collapse in which,
classical singularity is resolved and replaced by a bounce. In addition, we
find a threshold scale for non-singular black hole formation. In the second
scenario, we employ several models of dark energy to investigate the status of
the late time cosmological singularities. In the first one we consider a DGP
brane-world model with a GB term being provided for the bulk action; a phantom
matter is present on the brane as dark energy component. It is shown that a
combination of IR and UV modifications to general relativity replaces a big rip
by a sudden singularity at late times. The second model we cosnider is the
generalized running vacuum energy (GRVE) model. The Friedmann equation of the
GRVE model looks much similar to the one of a holographic Ricci dark energy
(HRDE) model. Despite the analogy between these two models, it turns out that
one of them, a GRVE, is singularity-free in the future while the other, the
HRDE, is not, which can hit, for example, a big rip singularity.
| [
{
"created": "Wed, 21 May 2014 15:25:16 GMT",
"version": "v1"
}
] | 2014-05-22 | [
[
"Tavakoli",
"Yaser",
""
]
] | In this dissertation we study two well known gravitational scenarios in which singularities may appear; the final state of gravitational collapse and the late time evolution of the universe. In the first scenario, we study a spherically symmetric space-time whose matter content includes a tachyon scalar field and a barotropic fluid. By employing a dynamical system analysis, we find classical solutions corresponding to a naked singularity or a black hole formation. We then investigate, in a semiclassical manner, loop quantum gravity induced effects on the fate of the classical singularities. By employing an inverse triad correction, we identify a subset which corresponds to an outward flux of energy, thus avoiding either a naked singularity or a black hole formation. Within a holonomy correction, we obtain the semiclassical counterpart of our (classical) general relativistic collapse in which, classical singularity is resolved and replaced by a bounce. In addition, we find a threshold scale for non-singular black hole formation. In the second scenario, we employ several models of dark energy to investigate the status of the late time cosmological singularities. In the first one we consider a DGP brane-world model with a GB term being provided for the bulk action; a phantom matter is present on the brane as dark energy component. It is shown that a combination of IR and UV modifications to general relativity replaces a big rip by a sudden singularity at late times. The second model we cosnider is the generalized running vacuum energy (GRVE) model. The Friedmann equation of the GRVE model looks much similar to the one of a holographic Ricci dark energy (HRDE) model. Despite the analogy between these two models, it turns out that one of them, a GRVE, is singularity-free in the future while the other, the HRDE, is not, which can hit, for example, a big rip singularity. |
2111.04161 | Marcelo J. Reboucas | N.A. Lemos, M.J. Reboucas | Orientability of space from electromagnetic quantum fluctuations | 11 pages, 2 figures, to appear in the Proceedings of the 16th Marcell
Grossman Meeting | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Whether the space where we live is a globally orientable manifold $M_3$, and
whether the local laws of physics require that $M_3$ be equipped with a
canonical orientation, are among the unsettled questions in cosmology and
quantum field theory. It is often assumed that a test for spatial orientability
requires a global journey across the whole $3-$space. Since such a global
expedition is not feasible, theoretical arguments are usually offered to
support the choice of time orientation for the spacetime manifold $M_4$, and
space orientation for $M_3$. Theoretical arguments can certainly be used, but
one would expect that the ultimate answer to the orientability question should
rely on observations or local experiments, or can come from a topological
fundamental theory in physics. In a recent paper we have argued that it is
potentially possible to locally access the $3-$space orientability of Minkowski
spacetime through effects involving 'point-like charged particles' under
quantum electromagnetic fluctuations. Specifically, we studied the stochastic
motions of a charged particle and an electric dipole subjected to these
fluctuations in Minkowski spacetime, with either an orientable or a
non-orientable $3-$space topology, and derived expressions for a statistical
orientability indicator in these two flat topologically inequivalent manifolds.
For the dipole we found that a characteristic inversion pattern exhibited by
the curves of the orientability indicator is a signature of non-orientability,
making it possible to locally probe the orientability of the $3-$space. Here,
to shed some additional light on the spatial orientability, we briefly review
these results, and also discuss some of its features and consequences. The
results might open the way to a conceivable experiment involving quantum
fluctuations to look into the spatial orientability of Minkowski empty
spacetime.
| [
{
"created": "Sun, 7 Nov 2021 19:37:55 GMT",
"version": "v1"
}
] | 2021-11-09 | [
[
"Lemos",
"N. A.",
""
],
[
"Reboucas",
"M. J.",
""
]
] | Whether the space where we live is a globally orientable manifold $M_3$, and whether the local laws of physics require that $M_3$ be equipped with a canonical orientation, are among the unsettled questions in cosmology and quantum field theory. It is often assumed that a test for spatial orientability requires a global journey across the whole $3-$space. Since such a global expedition is not feasible, theoretical arguments are usually offered to support the choice of time orientation for the spacetime manifold $M_4$, and space orientation for $M_3$. Theoretical arguments can certainly be used, but one would expect that the ultimate answer to the orientability question should rely on observations or local experiments, or can come from a topological fundamental theory in physics. In a recent paper we have argued that it is potentially possible to locally access the $3-$space orientability of Minkowski spacetime through effects involving 'point-like charged particles' under quantum electromagnetic fluctuations. Specifically, we studied the stochastic motions of a charged particle and an electric dipole subjected to these fluctuations in Minkowski spacetime, with either an orientable or a non-orientable $3-$space topology, and derived expressions for a statistical orientability indicator in these two flat topologically inequivalent manifolds. For the dipole we found that a characteristic inversion pattern exhibited by the curves of the orientability indicator is a signature of non-orientability, making it possible to locally probe the orientability of the $3-$space. Here, to shed some additional light on the spatial orientability, we briefly review these results, and also discuss some of its features and consequences. The results might open the way to a conceivable experiment involving quantum fluctuations to look into the spatial orientability of Minkowski empty spacetime. |
1311.3263 | Murli Manohar Verma | Murli Manohar Verma and Shankar Dayal Pathak | Cosmic expansion driven by real scalar field for different forms of
potential | 5 pages, no figures | Astrophys. Space Sci., 350, (2014),381 | 10.1007/s10509-013-1736-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the expansion of the universe in the FRLW model assuming that the
source of dark energy is either tachyonic scalar field or quintessence. The
tachyonic scalar field with exponential and power-law potential (function of
homogeneous scalar field $\phi$) both gives exponential expansion of the
universe. It is found that this behaviour is not distinguishable from the
quintessence with respect to these potentials.
| [
{
"created": "Tue, 12 Nov 2013 20:27:56 GMT",
"version": "v1"
}
] | 2015-08-11 | [
[
"Verma",
"Murli Manohar",
""
],
[
"Pathak",
"Shankar Dayal",
""
]
] | We discuss the expansion of the universe in the FRLW model assuming that the source of dark energy is either tachyonic scalar field or quintessence. The tachyonic scalar field with exponential and power-law potential (function of homogeneous scalar field $\phi$) both gives exponential expansion of the universe. It is found that this behaviour is not distinguishable from the quintessence with respect to these potentials. |
1902.04781 | Chiranjeeb Singha | Golam Mortuza Hossain, Chiranjeeb Singha | New coordinates for a simpler canonical derivation of the Hawking effect | 6 pages, 1 figure, revtex4 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to achieve a Hamiltonian-based canonical derivation of the Hawking
effect, one usually faces multiple hurdles. Firstly, the spacetime foliation
using Schwarzschild time does not lead to hyper-surfaces which are always
spacelike. Secondly, the null coordinates which are frequently used in
covariant approach, do not lead to a true matter Hamiltonian. Recently, an
exact canonical derivation was presented using the so-called near-null
coordinates. However, there too one faces the difficulty of having to deal with
non-vanishing matter diffeomorphism generator as the spatial decomposition
involves a non-zero shift vector. Here we introduce a new set of coordinates
which allows one to perform an exact canonical derivation of Hawking effect
without having to deal with matter diffeomorphism generator.
| [
{
"created": "Wed, 13 Feb 2019 08:28:32 GMT",
"version": "v1"
}
] | 2019-02-14 | [
[
"Hossain",
"Golam Mortuza",
""
],
[
"Singha",
"Chiranjeeb",
""
]
] | In order to achieve a Hamiltonian-based canonical derivation of the Hawking effect, one usually faces multiple hurdles. Firstly, the spacetime foliation using Schwarzschild time does not lead to hyper-surfaces which are always spacelike. Secondly, the null coordinates which are frequently used in covariant approach, do not lead to a true matter Hamiltonian. Recently, an exact canonical derivation was presented using the so-called near-null coordinates. However, there too one faces the difficulty of having to deal with non-vanishing matter diffeomorphism generator as the spatial decomposition involves a non-zero shift vector. Here we introduce a new set of coordinates which allows one to perform an exact canonical derivation of Hawking effect without having to deal with matter diffeomorphism generator. |
gr-qc/9802024 | Marco Caldarelli | Marco M. Caldarelli | Quantum implementation of the cosmic censorship conjecture for toroidal
black holes | 12 pages, RevTeX, no figures, corrected typos | Phys.Rev. D58 (1998) 064008 | 10.1103/PhysRevD.58.064008 | null | gr-qc | null | We consider some aspects of quantum field theory of a conformally coupled
scalar field on the singular background obtained in the massless limit of a
class of toroidal black holes. The stress-tensor and its back-reaction on the
metric are computed using the point-splitting regularization, in the cases of
transparent, Neumann and Dirichlet boundary conditions. We find that the
quantum fluctuations generate an event horizon which hides the singularity. The
resulting object can be interpreted as a long lived remnant. We discuss the
relevance of this result in the context of the cosmic censorship conjecture,
and in connection to the end-point of the quantum evaporation process.
| [
{
"created": "Tue, 10 Feb 1998 18:25:37 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Feb 1998 18:50:08 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Sep 1998 17:49:42 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Caldarelli",
"Marco M.",
""
]
] | We consider some aspects of quantum field theory of a conformally coupled scalar field on the singular background obtained in the massless limit of a class of toroidal black holes. The stress-tensor and its back-reaction on the metric are computed using the point-splitting regularization, in the cases of transparent, Neumann and Dirichlet boundary conditions. We find that the quantum fluctuations generate an event horizon which hides the singularity. The resulting object can be interpreted as a long lived remnant. We discuss the relevance of this result in the context of the cosmic censorship conjecture, and in connection to the end-point of the quantum evaporation process. |
gr-qc/0606027 | Christian Fronsdal | Christian Fronsdal | Ideal Stars and General Relativity | 26 pages, 7 figures | Gen.Rel.Grav.39:1971-2000,2007 | 10.1007/s10714-007-0496-1 | UCLA/06/TEP15 | gr-qc | null | We study a system of differential equations that governs the distribution of
matter in the theory of General Relativity. The new element in this paper is
the use of a dynamical action principle that includes all the degrees of
freedom, matter as well as metric. The matter lagrangian defines a relativistic
version of non-viscous, isentropic hydrodynamics. The matter fields are a
scalar density and a velocity potential; the conventional, four-vector velocity
field is replaced by the gradient of the potential and its scale is fixed by
one of the eulerian equations of motion, an innovation that significantly
affects the imposition of boundary conditions. If the density is integrable at
infinity, then the metric approaches the Schwarzschild metric at large
distances. There are stars without boundary and with finite total mass; the
metric shows rapid variation in the neighbourhood of the Schwarzschild radius
and there is a very small core where a singularity indicates that the gas laws
break down. For stars with boundary there emerges a new, critical relation
between the radius and the gravitational mass, a consequence of the stronger
boundary conditions. Tentative applications are suggested, to certain Red
Giants, and to neutron stars, but the investigation reported here was limited
to polytropic equations of state. Comparison with the results of Oppenheimer
and Volkoff on neutron cores shows a close agreement of numerical results.
However, in the model the boundary of the star is fixed uniquely by the
required matching of the interior metric to the external Schwarzschild metric,
which is not the case in the traditional approach.
| [
{
"created": "Tue, 6 Jun 2006 18:47:16 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Fronsdal",
"Christian",
""
]
] | We study a system of differential equations that governs the distribution of matter in the theory of General Relativity. The new element in this paper is the use of a dynamical action principle that includes all the degrees of freedom, matter as well as metric. The matter lagrangian defines a relativistic version of non-viscous, isentropic hydrodynamics. The matter fields are a scalar density and a velocity potential; the conventional, four-vector velocity field is replaced by the gradient of the potential and its scale is fixed by one of the eulerian equations of motion, an innovation that significantly affects the imposition of boundary conditions. If the density is integrable at infinity, then the metric approaches the Schwarzschild metric at large distances. There are stars without boundary and with finite total mass; the metric shows rapid variation in the neighbourhood of the Schwarzschild radius and there is a very small core where a singularity indicates that the gas laws break down. For stars with boundary there emerges a new, critical relation between the radius and the gravitational mass, a consequence of the stronger boundary conditions. Tentative applications are suggested, to certain Red Giants, and to neutron stars, but the investigation reported here was limited to polytropic equations of state. Comparison with the results of Oppenheimer and Volkoff on neutron cores shows a close agreement of numerical results. However, in the model the boundary of the star is fixed uniquely by the required matching of the interior metric to the external Schwarzschild metric, which is not the case in the traditional approach. |
2104.10119 | Charles Dalang | Charles Dalang, Giulia Cusin, Macarena Lagos | Polarization distortions of lensed gravitational waves | 18 pages, 5 figures, added Appendix C | null | 10.1103/PhysRevD.105.024005 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity (GR), gravitational waves (GWs) propagate the
well-known plus and cross polarization modes which are the signature of a
massless spin-2 field. However, diffraction of GWs caused by intervening
objects along the line of sight can cause the apparent rise of additional
polarizations due to GW-curvature interactions. In this paper, we continue the
analysis by two of the authors of the present article, on lensing of
gravitational waves beyond geometric optics. In particular, we calculate the
lensing effect caused by a point-like lens, in the regime where its
Schwarzschild radius $R_s$ is much smaller than the wavelength $\lambda$ of the
signal, itself smaller than the impact parameter $b$. In this case, the
curvature of spacetime induces distortions in the polarization of the wave such
that effective scalar and vector polarizations may appear. We find that the
amplitude of these apparent non-GR polarizations is suppressed by a factor
$R_s\lambda/b^2$ with respect to the amplitude of the GR-like tensor modes. We
estimate the probability to develop these extra polarization modes for a nearly
monochromatic GW in the Pulsar Timing Arrays band traveling through a
distribution of galaxies.
| [
{
"created": "Tue, 20 Apr 2021 17:03:48 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Nov 2021 17:41:16 GMT",
"version": "v2"
}
] | 2022-01-12 | [
[
"Dalang",
"Charles",
""
],
[
"Cusin",
"Giulia",
""
],
[
"Lagos",
"Macarena",
""
]
] | In general relativity (GR), gravitational waves (GWs) propagate the well-known plus and cross polarization modes which are the signature of a massless spin-2 field. However, diffraction of GWs caused by intervening objects along the line of sight can cause the apparent rise of additional polarizations due to GW-curvature interactions. In this paper, we continue the analysis by two of the authors of the present article, on lensing of gravitational waves beyond geometric optics. In particular, we calculate the lensing effect caused by a point-like lens, in the regime where its Schwarzschild radius $R_s$ is much smaller than the wavelength $\lambda$ of the signal, itself smaller than the impact parameter $b$. In this case, the curvature of spacetime induces distortions in the polarization of the wave such that effective scalar and vector polarizations may appear. We find that the amplitude of these apparent non-GR polarizations is suppressed by a factor $R_s\lambda/b^2$ with respect to the amplitude of the GR-like tensor modes. We estimate the probability to develop these extra polarization modes for a nearly monochromatic GW in the Pulsar Timing Arrays band traveling through a distribution of galaxies. |
1608.05716 | Edgar Gasperin | Edgar Gasperin, Juan Antonio Valiente Kroon | Zero rest-mass fields and the Newman-Penrose constants on flat space | 36 pages. Updated version. Main results changed | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Zero rest-mass fields of spin 1 (the electromagnetic field) and spin 2
propagating on flat space and their corresponding Newman-Penrose (NP) constants
are studied near spatial infinity. The aim of this analysis is to clarify the
correspondence between data for these fields on a spacelike hypersurface and
the value of their corresponding NP constants at future and past null infinity.
To do so, Friedrich's framework of the cylinder at spatial infinity is employed
to show that, expanding the initial data in terms spherical harmonics and
powers of the geodesic spatial distance $\rho$ to spatial infinity, the NP
constants correspond to the data for the second highest possible spherical
harmonic at fixed order in $\rho$. In addition, it is shown that for generic
initial data within the class considered in this article, there is no natural
correspondence between the NP constants at future and past null infinity ---for
both the Maxwell and spin-2 field. However, if the initial data is
time-symmetric then the NP constants at future and past null infinity have the
same information.
| [
{
"created": "Fri, 19 Aug 2016 20:00:08 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Oct 2020 08:58:55 GMT",
"version": "v2"
}
] | 2020-10-23 | [
[
"Gasperin",
"Edgar",
""
],
[
"Kroon",
"Juan Antonio Valiente",
""
]
] | Zero rest-mass fields of spin 1 (the electromagnetic field) and spin 2 propagating on flat space and their corresponding Newman-Penrose (NP) constants are studied near spatial infinity. The aim of this analysis is to clarify the correspondence between data for these fields on a spacelike hypersurface and the value of their corresponding NP constants at future and past null infinity. To do so, Friedrich's framework of the cylinder at spatial infinity is employed to show that, expanding the initial data in terms spherical harmonics and powers of the geodesic spatial distance $\rho$ to spatial infinity, the NP constants correspond to the data for the second highest possible spherical harmonic at fixed order in $\rho$. In addition, it is shown that for generic initial data within the class considered in this article, there is no natural correspondence between the NP constants at future and past null infinity ---for both the Maxwell and spin-2 field. However, if the initial data is time-symmetric then the NP constants at future and past null infinity have the same information. |
1910.09580 | Karan Jani | Karan Jani, Abraham Loeb | Global Stellar Budget for LIGO Black Holes | null | null | 10.3847/2041-8213/ab6854 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The binary black hole mergers observed by LIGO-Virgo gravitational-wave
detectors pose two major challenges: (i) how to produce these massive black
holes from stellar processes; and (ii) how to bring them close enough to merge
within the age of the universe? We derive a fundamental constraint relating the
binary separation and the available stellar budget in the universe to produce
the observed black hole mergers. We find that $\lesssim 14\%$ of the entire
budget contributes to the observed merger rate of $(30 + 30)~\mathrm{M}_\odot$
black holes, if the separation is around the diameter of their progenitor
stars. Furthermore, the upgraded LIGO detector and third-generation
gravitational-wave detectors are not expected to find stellar-mass black hole
mergers at high redshifts. From LIGO's strong constraints on the mergers of
black holes in the pair-instability mass-gap ($60-120~\mathrm{M}_\odot$), we
find that $\lesssim 0.8\%$ of all massive stars contribute to a remnant black
hole population in this gap. Our derived separation$-$budget constraint
provides a robust framework for testing the formation scenarios of stellar
binary black holes.
| [
{
"created": "Mon, 21 Oct 2019 18:13:28 GMT",
"version": "v1"
}
] | 2020-02-12 | [
[
"Jani",
"Karan",
""
],
[
"Loeb",
"Abraham",
""
]
] | The binary black hole mergers observed by LIGO-Virgo gravitational-wave detectors pose two major challenges: (i) how to produce these massive black holes from stellar processes; and (ii) how to bring them close enough to merge within the age of the universe? We derive a fundamental constraint relating the binary separation and the available stellar budget in the universe to produce the observed black hole mergers. We find that $\lesssim 14\%$ of the entire budget contributes to the observed merger rate of $(30 + 30)~\mathrm{M}_\odot$ black holes, if the separation is around the diameter of their progenitor stars. Furthermore, the upgraded LIGO detector and third-generation gravitational-wave detectors are not expected to find stellar-mass black hole mergers at high redshifts. From LIGO's strong constraints on the mergers of black holes in the pair-instability mass-gap ($60-120~\mathrm{M}_\odot$), we find that $\lesssim 0.8\%$ of all massive stars contribute to a remnant black hole population in this gap. Our derived separation$-$budget constraint provides a robust framework for testing the formation scenarios of stellar binary black holes. |
2008.01433 | Paul R. Anderson | Richard A. Dudley, Alessandro Fabbri, Paul R. Anderson, and Roberto
Balbinot | Correlations between a Hawking particle and its partner in a 1+1D
Bose-Einstein condensate analog black hole | Some changes and corrections in the text, cosmetic changes in two
figures, one reference added, Phys. Rev. D version, 24 pages, 8 figures | Phys. Rev. D 102, 105005 (2020) | 10.1103/PhysRevD.102.105005 | null | gr-qc cond-mat.quant-gas hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Fourier transform of the density-density correlation function in a
Bose-Einstein condensate (BEC) analog black hole is a useful tool to
investigate correlations between the Hawking particles and their partners. It
can be expressed in terms of $\langle
^{\text{out}}\hat{a}_{\text{up}}^{\text{ext}}\
^{\text{out}}\hat{a}_{\text{up}}^{\text{int}} \rangle$, where
$^{\text{out}}\hat{a}_{\text{up}}^{\text{ext}}$ is the annihilation operator
for the Hawking particle and $^{\text{out}}\hat{a}_{\text{up}}^{\text{int}} $
is the corresponding one for the partner. This basic quantity is calculated for
three different models for the BEC flow. It is shown that in each model the
inclusion of the effective potential in the mode equations makes a significant
difference. Furthermore, particle production induced by this effective
potential in the interior of the black hole is studied for each model and shown
to be nonthermal. An interesting peak that is related to the particle
production and is present in some models is discussed.
| [
{
"created": "Tue, 4 Aug 2020 09:37:09 GMT",
"version": "v1"
},
{
"created": "Mon, 17 May 2021 20:00:52 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"Dudley",
"Richard A.",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Anderson",
"Paul R.",
""
],
[
"Balbinot",
"Roberto",
""
]
] | The Fourier transform of the density-density correlation function in a Bose-Einstein condensate (BEC) analog black hole is a useful tool to investigate correlations between the Hawking particles and their partners. It can be expressed in terms of $\langle ^{\text{out}}\hat{a}_{\text{up}}^{\text{ext}}\ ^{\text{out}}\hat{a}_{\text{up}}^{\text{int}} \rangle$, where $^{\text{out}}\hat{a}_{\text{up}}^{\text{ext}}$ is the annihilation operator for the Hawking particle and $^{\text{out}}\hat{a}_{\text{up}}^{\text{int}} $ is the corresponding one for the partner. This basic quantity is calculated for three different models for the BEC flow. It is shown that in each model the inclusion of the effective potential in the mode equations makes a significant difference. Furthermore, particle production induced by this effective potential in the interior of the black hole is studied for each model and shown to be nonthermal. An interesting peak that is related to the particle production and is present in some models is discussed. |
1306.0972 | Stefan Ballmer | Stefan W. Ballmer, David J. Ottaway | A New Class of Optical Beams for Large Baseline Interferometric
Gravitational Wave Detectors | null | null | 10.1103/PhysRevD.88.062004 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A folded resonant Fabry-Perot cavity has the potential to significantly
reduce the impact of coating thermal noise on the performance of kilometer
scale gravitational wave detectors. When constructed using only spherical
mirror surfaces it is possible to utilize the extremely robust $TEM_{00}$ mode
optical mode. In this paper we investigate the potential thermal noise
improvements that can be achieved for third generation gravitational wave
detectors using realistic constraints. Comparing the previously proposed beam
configurations such as e.g. higher order Laguerre-Gauss modes, we find that
similar or better thermal noise improvement factors can be achieved, while
avoiding degeneracy issues associated with those beams.
| [
{
"created": "Wed, 5 Jun 2013 03:36:48 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jun 2013 03:11:02 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Jun 2013 00:39:26 GMT",
"version": "v3"
},
{
"created": "Mon, 2 Sep 2013 03:56:33 GMT",
"version": "v4"
}
] | 2013-10-02 | [
[
"Ballmer",
"Stefan W.",
""
],
[
"Ottaway",
"David J.",
""
]
] | A folded resonant Fabry-Perot cavity has the potential to significantly reduce the impact of coating thermal noise on the performance of kilometer scale gravitational wave detectors. When constructed using only spherical mirror surfaces it is possible to utilize the extremely robust $TEM_{00}$ mode optical mode. In this paper we investigate the potential thermal noise improvements that can be achieved for third generation gravitational wave detectors using realistic constraints. Comparing the previously proposed beam configurations such as e.g. higher order Laguerre-Gauss modes, we find that similar or better thermal noise improvement factors can be achieved, while avoiding degeneracy issues associated with those beams. |
0707.2829 | Yongli Ping | Yongli Ping, Lixin Xu, Hongya Liu | Correspondence Between DGP Brane Cosmology and 5D Ricci-flat Cosmology | 8 pages, 1 figure, accepted by MPLA, added reference | Mod.Phys.Lett.A23:695-702,2008 | 10.1142/S0217732308024079 | null | gr-qc | null | We discuss the correspondence between the DGP brane cosmology and 5D
Ricci-flat cosmology by letting their metrics equal each other. By this
correspondence, a specific geometrical property of the arbitrary integral
constant I in DGP metric is given and it is related to the curvature of 5D
bulk. At the same time, the relation of arbitrary functions $\mu$ and $\nu$ in
a class of Ricci-flat solutions is obtained from DGP brane metric.
| [
{
"created": "Thu, 19 Jul 2007 02:13:58 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jul 2007 01:34:01 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Ping",
"Yongli",
""
],
[
"Xu",
"Lixin",
""
],
[
"Liu",
"Hongya",
""
]
] | We discuss the correspondence between the DGP brane cosmology and 5D Ricci-flat cosmology by letting their metrics equal each other. By this correspondence, a specific geometrical property of the arbitrary integral constant I in DGP metric is given and it is related to the curvature of 5D bulk. At the same time, the relation of arbitrary functions $\mu$ and $\nu$ in a class of Ricci-flat solutions is obtained from DGP brane metric. |
gr-qc/0210046 | Ozay Gurtug | O.Gurtug and M.Halilsoy | Failure of a Stability Conjecture in General Relativity | 8 Pages. Accepted for publication in Nuovo Cimento B | Nuovo Cim.B117:493-499,2002 | null | null | gr-qc | null | By employing an exact back-reaction geometry, Helliwell-Konkowski stability
conjecture is shown to fail. This happens when a test null dust is inserted to
the interaction region of cross-polarized Bell-Szekeres spacetime.
| [
{
"created": "Tue, 15 Oct 2002 11:02:29 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Gurtug",
"O.",
""
],
[
"Halilsoy",
"M.",
""
]
] | By employing an exact back-reaction geometry, Helliwell-Konkowski stability conjecture is shown to fail. This happens when a test null dust is inserted to the interaction region of cross-polarized Bell-Szekeres spacetime. |
gr-qc/0601108 | Ralf Schutzhold | Friedemann Queisser, Michael Uhlmann, and Ralf Sch\"utzhold | Signatures of Planck-scale interactions in the cosmic microwave
background? | 4 pages | Class.Quant.Grav.24:1375-1384,2007 | 10.1088/0264-9381/24/6/001 | null | gr-qc | null | Based on a rather general low-energy effective action (interacting quantum
fields in classical curved space-times), we calculate potential signatures of
new physics (such as quantum gravity) at ultra-high energies (presumably the
Planck scale) in the anisotropies of the cosmic microwave background. These
Planck-scale interactions create non-Gaussian contributions, where special
emphasis is laid on the three-point function as the most promising observable,
which also allows the discrimination between models violating and those obeying
Lorentz invariance. PACS: 98.80.Cq, 04.62.+v, 98.70.Vc, 98.80.Qc.
| [
{
"created": "Wed, 25 Jan 2006 15:37:55 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Queisser",
"Friedemann",
""
],
[
"Uhlmann",
"Michael",
""
],
[
"Schützhold",
"Ralf",
""
]
] | Based on a rather general low-energy effective action (interacting quantum fields in classical curved space-times), we calculate potential signatures of new physics (such as quantum gravity) at ultra-high energies (presumably the Planck scale) in the anisotropies of the cosmic microwave background. These Planck-scale interactions create non-Gaussian contributions, where special emphasis is laid on the three-point function as the most promising observable, which also allows the discrimination between models violating and those obeying Lorentz invariance. PACS: 98.80.Cq, 04.62.+v, 98.70.Vc, 98.80.Qc. |
1409.2696 | David Keitel | David Keitel, Reinhard Prix | Line-robust statistics for continuous gravitational waves: safety in the
case of unequal detector sensitivities | 21 pages, 11 figures, updated to match published version | Class. Quantum Grav. 32 (2015) 035004 | 10.1088/0264-9381/32/3/035004 | LIGO-P1400161; AEI-2014-039 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The multi-detector F-statistic is close to optimal for detecting continuous
gravitational waves (CWs) in Gaussian noise. However, it is susceptible to
false alarms from instrumental artefacts, for example quasi-monochromatic
disturbances ('lines'), which resemble a CW signal more than Gaussian noise. In
a recent paper [Keitel et al 2014, PRD 89 064023], a Bayesian model selection
approach was used to derive line-robust detection statistics for CW signals,
generalising both the F-statistic and the F-statistic consistency veto
technique and yielding improved performance in line-affected data. Here we
investigate a generalisation of the assumptions made in that paper: if a CW
analysis uses data from two or more detectors with very different
sensitivities, the line-robust statistics could be less effective. We
investigate the boundaries within which they are still safe to use, in
comparison with the F-statistic. Tests using synthetic draws show that the
optimally-tuned version of the original line-robust statistic remains safe in
most cases of practical interest. We also explore a simple idea on further
improving the detection power and safety of these statistics, which we however
find to be of limited practical use.
| [
{
"created": "Tue, 9 Sep 2014 11:45:19 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jan 2015 11:46:07 GMT",
"version": "v2"
}
] | 2015-01-19 | [
[
"Keitel",
"David",
""
],
[
"Prix",
"Reinhard",
""
]
] | The multi-detector F-statistic is close to optimal for detecting continuous gravitational waves (CWs) in Gaussian noise. However, it is susceptible to false alarms from instrumental artefacts, for example quasi-monochromatic disturbances ('lines'), which resemble a CW signal more than Gaussian noise. In a recent paper [Keitel et al 2014, PRD 89 064023], a Bayesian model selection approach was used to derive line-robust detection statistics for CW signals, generalising both the F-statistic and the F-statistic consistency veto technique and yielding improved performance in line-affected data. Here we investigate a generalisation of the assumptions made in that paper: if a CW analysis uses data from two or more detectors with very different sensitivities, the line-robust statistics could be less effective. We investigate the boundaries within which they are still safe to use, in comparison with the F-statistic. Tests using synthetic draws show that the optimally-tuned version of the original line-robust statistic remains safe in most cases of practical interest. We also explore a simple idea on further improving the detection power and safety of these statistics, which we however find to be of limited practical use. |
1604.01001 | Ali Mozaffari | Ali Mozaffari | Testing General Free Functions in Preferred Scale Theories | 8 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Building on previous work, we explore the parameter space of general free
functions in non-relativistic modified gravity theories motivated by k-essence
and other scalar-tensor theories. Using a few proposed tests, we aim to update
Solar System based constraints on these ideas in line with previous theories
and suggest their utility in constraining modification to GR, potentially even
being able to test k-essence type theories.
| [
{
"created": "Mon, 4 Apr 2016 19:49:02 GMT",
"version": "v1"
}
] | 2016-04-05 | [
[
"Mozaffari",
"Ali",
""
]
] | Building on previous work, we explore the parameter space of general free functions in non-relativistic modified gravity theories motivated by k-essence and other scalar-tensor theories. Using a few proposed tests, we aim to update Solar System based constraints on these ideas in line with previous theories and suggest their utility in constraining modification to GR, potentially even being able to test k-essence type theories. |
2111.15027 | Roman Berens | Prakruth Adari, Roman Berens, Janna Levin | Charging up Boosted Black Holes | 23 pages, 12 figures v2: added references v3: added subsection 3.1.1,
replaced grainy figures in section 3.1, edited language | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Contrary to a prevailing assumption that black holes would swiftly discharge,
we argue that black holes can charge preferentially when boosted through an
ambient magnetic field. Though the details are very different, the preference
for charge is related to the precipitation of the Wald charge on a spinning
black hole in an ambient magnetic field. The gravito-electrodynamics upstage
naive arguments about screening electric fields in determining the value of the
charge accrued. Charged test particles, which build up the black hole charge,
exhibit chaotic behavior as evidenced by fractal basin boundaries between
dynamical regions. Charged, boosted black holes will generate their own
electromagnetic fields and thereby their own luminous signatures, even if they
are initially bare. We therefore add boosted black holes to the growing list of
potentially observable black hole signatures, alongside black hole batteries
and black hole pulsars. The implications should be relevant for supermassive
black holes that are boosted relative to a galactic magnetic field as well as
black holes merging with magnetized neutron stars.
| [
{
"created": "Mon, 29 Nov 2021 23:53:55 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Dec 2021 07:13:29 GMT",
"version": "v2"
},
{
"created": "Sun, 4 Dec 2022 07:39:42 GMT",
"version": "v3"
}
] | 2022-12-06 | [
[
"Adari",
"Prakruth",
""
],
[
"Berens",
"Roman",
""
],
[
"Levin",
"Janna",
""
]
] | Contrary to a prevailing assumption that black holes would swiftly discharge, we argue that black holes can charge preferentially when boosted through an ambient magnetic field. Though the details are very different, the preference for charge is related to the precipitation of the Wald charge on a spinning black hole in an ambient magnetic field. The gravito-electrodynamics upstage naive arguments about screening electric fields in determining the value of the charge accrued. Charged test particles, which build up the black hole charge, exhibit chaotic behavior as evidenced by fractal basin boundaries between dynamical regions. Charged, boosted black holes will generate their own electromagnetic fields and thereby their own luminous signatures, even if they are initially bare. We therefore add boosted black holes to the growing list of potentially observable black hole signatures, alongside black hole batteries and black hole pulsars. The implications should be relevant for supermassive black holes that are boosted relative to a galactic magnetic field as well as black holes merging with magnetized neutron stars. |
1402.4859 | Huan Yang | Huan Yang, Aaron Zimmerman, Luis Lehner | Turbulent Black Holes | 5+3 pages, 2 figures, corrected an error in the treatment of the
driving mode; example and figures changed, discussion added | Phys. Rev. Lett. 114, 081101 (2015) | 10.1103/PhysRevLett.114.081101 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that rapidly-spinning black holes can display turbulent gravitational
behavior which is mediated by a new type of parametric instability. This
instability transfers energy from higher temporal and azimuthal spatial
frequencies to lower frequencies--- a phenomenon reminiscent of the inverse
energy cascade displayed by 2+1-dimensional turbulent fluids. Our finding
reveals a path towards gravitational turbulence for perturbations of
rapidly-spinning black holes, and provides the first evidence for gravitational
turbulence in an asymptotically flat spacetime. Interestingly, this finding
predicts observable gravitational wave signatures from such phenomena in black
hole binaries with high spins and gives a gravitational description of
turbulence relevant to the fluid-gravity duality.
| [
{
"created": "Thu, 20 Feb 2014 01:16:45 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Mar 2014 05:44:47 GMT",
"version": "v2"
}
] | 2015-03-05 | [
[
"Yang",
"Huan",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Lehner",
"Luis",
""
]
] | We show that rapidly-spinning black holes can display turbulent gravitational behavior which is mediated by a new type of parametric instability. This instability transfers energy from higher temporal and azimuthal spatial frequencies to lower frequencies--- a phenomenon reminiscent of the inverse energy cascade displayed by 2+1-dimensional turbulent fluids. Our finding reveals a path towards gravitational turbulence for perturbations of rapidly-spinning black holes, and provides the first evidence for gravitational turbulence in an asymptotically flat spacetime. Interestingly, this finding predicts observable gravitational wave signatures from such phenomena in black hole binaries with high spins and gives a gravitational description of turbulence relevant to the fluid-gravity duality. |
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