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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0611108 | Lars Andersson | Lars Andersson (UM and AEI), Robert Beig (Vienna), Bernd Schmidt (AEI) | Static self-gravitating elastic bodies in Einstein gravity | 29 pages. Updated to conform with published version, typos fixed | Commun.PureAppl.Math.61:988-1023,2008 | 10.1002/cpa.20230 | AEI-2006-084 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that given a stress-free elastic body there exists, for sufficiently
small values of the gravitational constant, a unique static solution of the
Einstein equations coupled to the equations of relativistic elasticity. The
solution constructed is a small deformation of the relaxed configuration. This
result yields the first proof of existence of static solutions of the Einstein
equations without symmetries.
| [
{
"created": "Mon, 20 Nov 2006 21:36:25 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Jan 2009 21:33:05 GMT",
"version": "v2"
}
] | 2009-01-12 | [
[
"Andersson",
"Lars",
"",
"UM and AEI"
],
[
"Beig",
"Robert",
"",
"Vienna"
],
[
"Schmidt",
"Bernd",
"",
"AEI"
]
] | We prove that given a stress-free elastic body there exists, for sufficiently small values of the gravitational constant, a unique static solution of the Einstein equations coupled to the equations of relativistic elasticity. The solution constructed is a small deformation of the relaxed configuration. This result yields the first proof of existence of static solutions of the Einstein equations without symmetries. |
2109.08531 | Carlos Pe\'on-Nieto | Marc Mars and Carlos Pe\'on-Nieto | Classification of Kerr-de Sitter-like spacetimes with conformally flat
$\mathscr{I}$ in all dimensions | 46 pages, 1 figure | null | 10.1103/PhysRevD.105.044027 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using asymptotic characterization results of spacetimes at conformal
infinity, we prove that Kerr-Schild-de Sitter spacetimes are in one-to-one
correspondence with spacetimes in the Kerr-de Sitter-like class with
conformally flat $\mathscr{I}$. Kerr-Schild-de Sitter are spacetimes of
Kerr-Schild form with de Sitter background that solve the $(\Lambda>0)$-vacuum
Einstein equations and admit a smooth conformal compactification sharing
$\mathscr{I}$ with the background metric. Kerr-de Sitter-like metrics with
conformally flat $\mathscr{I}$ are a generalization of the Kerr-de Sitter
metrics, defined originally in four spacetime dimensions and extended here to
all dimensions in terms of their initial data at null infinity. We explicitly
construct all metrics in this class as limits or analytic extensions of Kerr-de
Sitter. The structure of limits is inferred from corresponding limits of the
asymptotic data, which appear to be hard to guess from the spacetime metrics.
| [
{
"created": "Fri, 17 Sep 2021 13:11:44 GMT",
"version": "v1"
}
] | 2022-02-23 | [
[
"Mars",
"Marc",
""
],
[
"Peón-Nieto",
"Carlos",
""
]
] | Using asymptotic characterization results of spacetimes at conformal infinity, we prove that Kerr-Schild-de Sitter spacetimes are in one-to-one correspondence with spacetimes in the Kerr-de Sitter-like class with conformally flat $\mathscr{I}$. Kerr-Schild-de Sitter are spacetimes of Kerr-Schild form with de Sitter background that solve the $(\Lambda>0)$-vacuum Einstein equations and admit a smooth conformal compactification sharing $\mathscr{I}$ with the background metric. Kerr-de Sitter-like metrics with conformally flat $\mathscr{I}$ are a generalization of the Kerr-de Sitter metrics, defined originally in four spacetime dimensions and extended here to all dimensions in terms of their initial data at null infinity. We explicitly construct all metrics in this class as limits or analytic extensions of Kerr-de Sitter. The structure of limits is inferred from corresponding limits of the asymptotic data, which appear to be hard to guess from the spacetime metrics. |
1302.1237 | Stephen McCormick | Stephen McCormick | The Phase Space for the Einstein-Yang-Mills Equations and the First Law
of Black Hole Thermodynamics | 21 pages; references added. v3: typos corrected, minor formatting
changes. To appear in ATMP, 18(4) | Adv. Theor. Math. Phys. 18(4), 799 (2014) | 10.4310/ATMP.2014.v18.n4.a2 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the techniques of Bartnik (2005) to show that the space of solutions
to the Einstein-Yang-Mills constraint equations on an asymptotically at
manifold with one end and zero boundary components, has a Hilbert manifold
structure; the Einstein-Maxwell system can be considered as a special case.
This is equivalent to the property of linearisation stability, which was
studied in depth throughout the 70s. This framework allows us to prove a
conjecture of Sudarsky and Wald (1992), that is, the validity of the first law
of black hole thermodynamics is a suitable condition for stationarity. Since we
work with a single end and no boundary conditions, this is equivalent to
critical points of the ADM mass subject to variations fixing the Yang-Mills
charge corresponding exactly to stationary solutions. The natural extension to
this work is to prove the second conjecture of Sudarsky and Wald, which is the
case where an interior boundary is present; this will be addressed in future
work.
| [
{
"created": "Wed, 6 Feb 2013 00:37:37 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Apr 2013 09:03:54 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Jul 2014 01:16:32 GMT",
"version": "v3"
}
] | 2014-12-02 | [
[
"McCormick",
"Stephen",
""
]
] | We use the techniques of Bartnik (2005) to show that the space of solutions to the Einstein-Yang-Mills constraint equations on an asymptotically at manifold with one end and zero boundary components, has a Hilbert manifold structure; the Einstein-Maxwell system can be considered as a special case. This is equivalent to the property of linearisation stability, which was studied in depth throughout the 70s. This framework allows us to prove a conjecture of Sudarsky and Wald (1992), that is, the validity of the first law of black hole thermodynamics is a suitable condition for stationarity. Since we work with a single end and no boundary conditions, this is equivalent to critical points of the ADM mass subject to variations fixing the Yang-Mills charge corresponding exactly to stationary solutions. The natural extension to this work is to prove the second conjecture of Sudarsky and Wald, which is the case where an interior boundary is present; this will be addressed in future work. |
gr-qc/0202082 | Marcelo Salgado | Marcelo Salgado | On the linear and weak-field limits of scalar-tensor theories of gravity | 12 pages in revtex4-twocolumn format; submitted to Phys.Rev.D | null | null | null | gr-qc | null | The linear approximation of scalar-tensor theories of gravity is obtained in
the physical (Jordan) frame under the 4+0 (covariant) and 3+1 formalisms. Then
the weak-field limit is analyzed and the conditions leading to significant
deviations of the $1/r^{2}$ Newton's law of gravitation are discussed. Finally,
the scalarization effects induced by these theories in extended objects are
confronted within the weak-field limit.
| [
{
"created": "Thu, 21 Feb 2002 21:36:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Salgado",
"Marcelo",
""
]
] | The linear approximation of scalar-tensor theories of gravity is obtained in the physical (Jordan) frame under the 4+0 (covariant) and 3+1 formalisms. Then the weak-field limit is analyzed and the conditions leading to significant deviations of the $1/r^{2}$ Newton's law of gravitation are discussed. Finally, the scalarization effects induced by these theories in extended objects are confronted within the weak-field limit. |
gr-qc/0412135 | John Barrow | Douglas J. Shaw and John D. Barrow | Varying Couplings in Electroweak Theory | 10 pages, no figures | Phys.Rev. D71 (2005) 063525 | 10.1103/PhysRevD.71.063525 | null | gr-qc astro-ph hep-th | null | We extend the theory of Kimberly and Magueijo for the spacetime variation of
the electroweak couplings in the unified Glashow-Salam-Weinberg model of the
electroweak interaction to include quantum corrections. We derive the effective
quantum-corrected dilaton evolution equations in the presence of a background
cosmological matter density that is composed of weakly interacting and
non-weakly-interacting non-relativistic dark-matter components.
| [
{
"created": "Thu, 30 Dec 2004 15:39:21 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Shaw",
"Douglas J.",
""
],
[
"Barrow",
"John D.",
""
]
] | We extend the theory of Kimberly and Magueijo for the spacetime variation of the electroweak couplings in the unified Glashow-Salam-Weinberg model of the electroweak interaction to include quantum corrections. We derive the effective quantum-corrected dilaton evolution equations in the presence of a background cosmological matter density that is composed of weakly interacting and non-weakly-interacting non-relativistic dark-matter components. |
1105.1413 | Juan Pablo Cruz P\'erez | Juan P. Cruz and Jos\'e A. Gonz\'alez | Symmetries without symmetries in Smoothed Particle Hydrodynamics | null | null | null | null | gr-qc physics.comp-ph physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a technique to solve numerically the relativistic Euler's
equations in scenarios with spherical symmetry using the standard Smoothed
Particles Hydrodynamics method in cartesian coordinates. This implementation
allow us to increase the resolution of the simulations in order to obtain
accurate results. We test our implementation studying the evolution of a
perfect fluid in a blast wave configuration in a fixed space-time . The
technique can be easily generalized to axial symmetric problems.
| [
{
"created": "Sat, 7 May 2011 02:59:39 GMT",
"version": "v1"
}
] | 2011-05-10 | [
[
"Cruz",
"Juan P.",
""
],
[
"González",
"José A.",
""
]
] | We introduce a technique to solve numerically the relativistic Euler's equations in scenarios with spherical symmetry using the standard Smoothed Particles Hydrodynamics method in cartesian coordinates. This implementation allow us to increase the resolution of the simulations in order to obtain accurate results. We test our implementation studying the evolution of a perfect fluid in a blast wave configuration in a fixed space-time . The technique can be easily generalized to axial symmetric problems. |
1612.08812 | Ravindra Saraykar Dr. | R.V.Saraykar | Stability and Genericity Aspects of Properties of Space-times in General
Relativity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we review and discuss different aspects of stability and
genericity of some properties of space-times which occur in various contexts in
the General Theory of Relativity. We also give argument supporting the
conclusion that Linearization Stability is a generic property if we restrict
space-times to the class of those which admit compact spacelike constant mean
curvature hypersurfaces.
| [
{
"created": "Wed, 28 Dec 2016 06:55:47 GMT",
"version": "v1"
}
] | 2016-12-30 | [
[
"Saraykar",
"R. V.",
""
]
] | In this article, we review and discuss different aspects of stability and genericity of some properties of space-times which occur in various contexts in the General Theory of Relativity. We also give argument supporting the conclusion that Linearization Stability is a generic property if we restrict space-times to the class of those which admit compact spacelike constant mean curvature hypersurfaces. |
1409.2206 | Wlodzimierz Piechocki | Ewa Czuchry, Nick Kwidzinski, and Wlodzimierz Piechocki | Comparing the dynamics of diagonal and general Bianchi IX spacetime | 25 pages, 2 figures, version including numerical simulations of
dynamics | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make comparison of the dynamics of the diagonal and nondiagonal Bianchi IX
models in the evolution towards the cosmological singularity. Apart from the
original variables, we use the Hubble normalized ones commonly applied in the
examination of the dynamics of homogeneous models. Applying the dynamical
systems method leads to the result that in both cases the continuous space of
critical points is higher dimensional and they are of the nonhyperbolic type.
This is a generic feature of the dynamics of both cases and seems to be
independent on the choice of phase space variables. The topologies of the
corresponding critical spaces are quite different. We conjecture that the
nondiagonal case may carry a new type of chaos different from the one specific
to the usually examined diagonal one.
| [
{
"created": "Mon, 8 Sep 2014 04:59:24 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Oct 2014 11:02:55 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Oct 2015 06:29:31 GMT",
"version": "v3"
},
{
"created": "Sat, 21 Jul 2018 05:14:34 GMT",
"version": "v4"
}
] | 2018-07-24 | [
[
"Czuchry",
"Ewa",
""
],
[
"Kwidzinski",
"Nick",
""
],
[
"Piechocki",
"Wlodzimierz",
""
]
] | We make comparison of the dynamics of the diagonal and nondiagonal Bianchi IX models in the evolution towards the cosmological singularity. Apart from the original variables, we use the Hubble normalized ones commonly applied in the examination of the dynamics of homogeneous models. Applying the dynamical systems method leads to the result that in both cases the continuous space of critical points is higher dimensional and they are of the nonhyperbolic type. This is a generic feature of the dynamics of both cases and seems to be independent on the choice of phase space variables. The topologies of the corresponding critical spaces are quite different. We conjecture that the nondiagonal case may carry a new type of chaos different from the one specific to the usually examined diagonal one. |
1410.4930 | Andronikos Paliathanasis | Andronikos Paliathanasis, Michael Tsamparlis, Spyros Basilakos | Dynamical symmetries and observational constraints in scalar field
cosmology | 20 pages; 4 figures; minor corrections to match with the Phys. Rev.
D. published version | Phys. Rev. D 90, 103524 (2014) | 10.1103/PhysRevD.90.103524 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose to use dynamical symmetries of the field equations, in order to
classify the dark energy models in the context of scalar field (quintessence or
phantom) FLRW cosmologies. Practically, symmetries provide a useful
mathematical tool in physical problems since they can be used to simplify a
given system of differential equations as well as to determine the
integrability of the physical system. The requirement that the field equations
admit dynamical symmetries results in two potentials one of which is the well
known Unified Dark Matter (UDM) potential and another new potential. For each
hyperbolic potential we obtain the corresponding analytic solution of the field
equations. The proposed analysis suggests that the requirement of the contact
symmetry appears to be very competitive to other independent tests used to
probe the functional form of a given potential and thus the associated nature
of dark energy. Finally, in order to test the viability of the above scalar
field models we perform a joint likelihood analysis using some of the latest
cosmological data.
| [
{
"created": "Sat, 18 Oct 2014 09:37:13 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Nov 2014 14:15:32 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Tsamparlis",
"Michael",
""
],
[
"Basilakos",
"Spyros",
""
]
] | We propose to use dynamical symmetries of the field equations, in order to classify the dark energy models in the context of scalar field (quintessence or phantom) FLRW cosmologies. Practically, symmetries provide a useful mathematical tool in physical problems since they can be used to simplify a given system of differential equations as well as to determine the integrability of the physical system. The requirement that the field equations admit dynamical symmetries results in two potentials one of which is the well known Unified Dark Matter (UDM) potential and another new potential. For each hyperbolic potential we obtain the corresponding analytic solution of the field equations. The proposed analysis suggests that the requirement of the contact symmetry appears to be very competitive to other independent tests used to probe the functional form of a given potential and thus the associated nature of dark energy. Finally, in order to test the viability of the above scalar field models we perform a joint likelihood analysis using some of the latest cosmological data. |
1502.00777 | Muhammad Jamil Amir | M. Jamil Amir and M. Yussouf | Kantowski-Sachs Universe Models in $f(T)$ Theory of Gravity | Accepted for publication in IJTP. arXiv admin note: substantial text
overlap with arXiv:1105.6228 by other authors | null | 10.1007/s10773-015-2517-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The $f(T)$ theory is recently proposed to explain the present cosmic
accelerating expansion of the universe. $f(T)$ theory is an extension of
Teleparallel theory of gravity, where $T$ is the torsion scalar. This paper
contains the construction of $f(T)$ models within the Kantowski-Sachs universe.
For this purpose, we use conservation equation and equation of state parameter,
which represents the different phases of the universe. We discuss possible
cases for the matter dominated era, radiation dominated era, present dark
energy phase and their combinations. Particularly, a constant solution has been
obtained which may correspond to the cosmological constant. Further, we
consider two well known $f(T)$ models and derive the equation of state
parameter and discuss the cosmic acceleration. Also, the Hubble parameter and
average scale factor have been evaluated.
| [
{
"created": "Tue, 3 Feb 2015 08:27:45 GMT",
"version": "v1"
}
] | 2015-02-04 | [
[
"Amir",
"M. Jamil",
""
],
[
"Yussouf",
"M.",
""
]
] | The $f(T)$ theory is recently proposed to explain the present cosmic accelerating expansion of the universe. $f(T)$ theory is an extension of Teleparallel theory of gravity, where $T$ is the torsion scalar. This paper contains the construction of $f(T)$ models within the Kantowski-Sachs universe. For this purpose, we use conservation equation and equation of state parameter, which represents the different phases of the universe. We discuss possible cases for the matter dominated era, radiation dominated era, present dark energy phase and their combinations. Particularly, a constant solution has been obtained which may correspond to the cosmological constant. Further, we consider two well known $f(T)$ models and derive the equation of state parameter and discuss the cosmic acceleration. Also, the Hubble parameter and average scale factor have been evaluated. |
1705.08307 | Christian Corda Prof. | Sourav Haldar, Christian Corda, Subenoy Chakraborty | Tunnelling mechanism in non-commutative space with generalized
uncertainty principle and Bohr-like black hole | 17 pages, accepted for publication in the Advances in High Energy
Physics Special Issue "Theoretical and Observational Aspects of Black Holes,
Gravitational Waves, and Space-Time Singularities", Editors: Ozay Gurtug,
Deborah Konkowski and M. Sharif | Advances in High Energy Physics Volume 2018, Article ID 9851598, 9
pages | 10.1155/2018/9851598 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper deals with non-thermal radiation spectrum by tunnelling mechanism
with correction due to the generalized uncertainty principle (GUP) in the
background of non-commutative geometry. Considering the reformulation of the
tunnelling mechanism by Banerjee and Majhi, the Hawking radiation spectrum is
evaluated through the density matrix for the outgoing modes. The GUP corrected
effective temperature and the corresponding GUP corrected effective metric in
non-commutative geometry are determined using Hawking's periodicity arguments.
Thus, we obtain further corrections to the non-strictly thermal black hole (BH)
radiation spectrum which give new final distributions. Then, we show that the
GUP and the non-commutative geometry modify the Bohr-like BH recently discussed
in a series of papers in the literature. In particular, we find the intriguing
result that the famous law of Bekenstein on the area quantization is affected
neither by non-commutative geometry nor by the GUP. This is a clear indication
of the universality of Bekenstein's result. In addition, we find that both the
Bekentsein-Hawking entropy and the total BH entropy to third order
approximation are still functions of the BH quantum level.
| [
{
"created": "Mon, 22 May 2017 12:40:35 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jul 2017 09:01:13 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Feb 2018 09:36:37 GMT",
"version": "v3"
}
] | 2018-05-09 | [
[
"Haldar",
"Sourav",
""
],
[
"Corda",
"Christian",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The paper deals with non-thermal radiation spectrum by tunnelling mechanism with correction due to the generalized uncertainty principle (GUP) in the background of non-commutative geometry. Considering the reformulation of the tunnelling mechanism by Banerjee and Majhi, the Hawking radiation spectrum is evaluated through the density matrix for the outgoing modes. The GUP corrected effective temperature and the corresponding GUP corrected effective metric in non-commutative geometry are determined using Hawking's periodicity arguments. Thus, we obtain further corrections to the non-strictly thermal black hole (BH) radiation spectrum which give new final distributions. Then, we show that the GUP and the non-commutative geometry modify the Bohr-like BH recently discussed in a series of papers in the literature. In particular, we find the intriguing result that the famous law of Bekenstein on the area quantization is affected neither by non-commutative geometry nor by the GUP. This is a clear indication of the universality of Bekenstein's result. In addition, we find that both the Bekentsein-Hawking entropy and the total BH entropy to third order approximation are still functions of the BH quantum level. |
1004.2143 | Alexander Burinskii | Alexander Burinskii | New Aspects of the Problem of the Source of Kerr Spinning Particle | 8 pages, 1 fig., Essay written for Gravity Research Foundation
Competition 2010. | null | null | null | gr-qc hep-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider development of the models of the source of the Kerr-Newman (KN)
solution and new aspects related with the obtained recently field model based
on a domain wall bubble with superconducting interior, arXiv:1003.2928[hep-th].
The internal Higgs field regularizes the KN solution, expelling electromagnetic
field from interior to the boundary of bubble. The KN source forms a
gravitating soliton, interior of which is similar to oscillating solitons
(Q-balls, oscillons), while exterior is consistent with the KN solution. We
obtain that a closed Wilson loop appears on the edge of the bubble, resulting
in quantization of angular momentum of the regularized solutions. A new
holographic interpretation of the mysterious twosheetedness of the Kerr
geometry is given. The KN gravitating soliton with parameters of electron is
discussed.
| [
{
"created": "Tue, 13 Apr 2010 11:01:52 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Burinskii",
"Alexander",
""
]
] | We consider development of the models of the source of the Kerr-Newman (KN) solution and new aspects related with the obtained recently field model based on a domain wall bubble with superconducting interior, arXiv:1003.2928[hep-th]. The internal Higgs field regularizes the KN solution, expelling electromagnetic field from interior to the boundary of bubble. The KN source forms a gravitating soliton, interior of which is similar to oscillating solitons (Q-balls, oscillons), while exterior is consistent with the KN solution. We obtain that a closed Wilson loop appears on the edge of the bubble, resulting in quantization of angular momentum of the regularized solutions. A new holographic interpretation of the mysterious twosheetedness of the Kerr geometry is given. The KN gravitating soliton with parameters of electron is discussed. |
gr-qc/9909006 | Angelo Tartaglia | A. Tartaglia | Detection of the gravitomagnetic clock effect | 14 pages; Latex. To be published on Classical and Quantum Gravity | Class.Quant.Grav.17:783-792,2000 | 10.1088/0264-9381/17/4/304 | null | gr-qc | null | The essence of the gravitomagnetic clock effect is properly defined showing
that its origin is in the topology of world lines with closed space
projections. It is shown that, in weak field approximation and for a
spherically symmetric central body, the loss of synchrony between two clocks
counter-rotating along a circular geodesic is proportional to the angular
momentum of the source of the gravitational field. Numerical estimates are
presented for objects within the solar system. The less unfavorable situation
is found around Jupiter.
| [
{
"created": "Thu, 2 Sep 1999 08:46:23 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Sep 1999 13:18:45 GMT",
"version": "v2"
}
] | 2011-09-13 | [
[
"Tartaglia",
"A.",
""
]
] | The essence of the gravitomagnetic clock effect is properly defined showing that its origin is in the topology of world lines with closed space projections. It is shown that, in weak field approximation and for a spherically symmetric central body, the loss of synchrony between two clocks counter-rotating along a circular geodesic is proportional to the angular momentum of the source of the gravitational field. Numerical estimates are presented for objects within the solar system. The less unfavorable situation is found around Jupiter. |
2006.13287 | Ashkbiz Danehkar PhD | A. Danehkar | Gravitational Fields of the Magnetic-type | 10 pages, 1 figure. This essay received an Honorable Mention in the
2020 Essay Competition of the Gravity Research Foundation | Int.J.Mod.Phys.D29:2043001,2020 | 10.1142/S0218271820430014 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Local conformal symmetry introduces the conformal curvature (Weyl tensor)
that gets split into its (gravito-) electric and magnetic (tensor) parts.
Newtonian tidal forces are expected from the gravitoelectric field, whereas
general-relativistic frame-dragging effects emerge from the gravitomagnetic
field. The symmetric, traceless gravitoelectric and gravitomagnetic tensor
fields can be visualized by their eigenvectors and eigenvalues. In this essay,
we depict the gravitoelectric and gravitomagnetic fields around a slowly
rotating black hole. This suggests that the phenomenon of ultra-fast outflows
observed at the centers of active galaxies may give evidence for the
gravitomagnetic fields of spinning supermassive black holes. We also question
whether the current issues in our contemporary observations might be resolved
by the inclusion of gravitomagnetism on large scales in a perturbed FLRW model.
| [
{
"created": "Tue, 23 Jun 2020 19:35:57 GMT",
"version": "v1"
}
] | 2021-01-05 | [
[
"Danehkar",
"A.",
""
]
] | Local conformal symmetry introduces the conformal curvature (Weyl tensor) that gets split into its (gravito-) electric and magnetic (tensor) parts. Newtonian tidal forces are expected from the gravitoelectric field, whereas general-relativistic frame-dragging effects emerge from the gravitomagnetic field. The symmetric, traceless gravitoelectric and gravitomagnetic tensor fields can be visualized by their eigenvectors and eigenvalues. In this essay, we depict the gravitoelectric and gravitomagnetic fields around a slowly rotating black hole. This suggests that the phenomenon of ultra-fast outflows observed at the centers of active galaxies may give evidence for the gravitomagnetic fields of spinning supermassive black holes. We also question whether the current issues in our contemporary observations might be resolved by the inclusion of gravitomagnetism on large scales in a perturbed FLRW model. |
gr-qc/0110082 | Oliver Henkel | Oliver Henkel | Global Prescribed Mean Curvature foliations in cosmological spacetimes
with matter, Part II | 25 pages, no figures | J.Math.Phys. 43 (2002) 2466-2485 | 10.1063/1.1466883 | AEI-2001-122 | gr-qc | null | This second part is devoted to the investigation of global properties of
Prescribed Mean Curvature (PMC) foliations in cosmological spacetimes with
local $U(1) \times U(1)$ symmetry and matter described by the Vlasov equation.
It turns out, that these spacetimes admit a global foliation by PMC surfaces,
as well, but the techniques to achieve this goal are more complex than in the
cases considered in part I.
| [
{
"created": "Thu, 18 Oct 2001 11:34:07 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Henkel",
"Oliver",
""
]
] | This second part is devoted to the investigation of global properties of Prescribed Mean Curvature (PMC) foliations in cosmological spacetimes with local $U(1) \times U(1)$ symmetry and matter described by the Vlasov equation. It turns out, that these spacetimes admit a global foliation by PMC surfaces, as well, but the techniques to achieve this goal are more complex than in the cases considered in part I. |
gr-qc/0404065 | Comelli Denis | D. Comelli, A. Dolgov | Determinant-Gravity: Cosmological implications | revtex format, 5 pages,8 figures,references added | JHEP0411:062,2004 | 10.1088/1126-6708/2004/11/062 | null | gr-qc | null | We analyze the action $\int d^4x \sqrt{\det||{\cal B} g_{\mu\nu}+ {\cal C}
R_{\mu\nu}}||$ as a possible alternative or addition to the Einstein gravity.
Choosing a particular form of ${\cal B}(R)= \sqrt {R}$ we can restore the
Einstein gravity and, if ${\cal B}=m^2$, we obtain the cosmological constant
term. Taking ${\cal B} = m^2 + {\cal B}_1 R$ and expanding the action in $
1/m^2$, we obtain as a leading term the Einstein Lagrangian with a cosmological
constant proportional to $m^4$ and a series of higher order operators. In
general case of non-vanishing ${\cal B}$ and ${\cal C}$ new cosmological
solutions for the Robertson-Walker metric are obtained.
| [
{
"created": "Thu, 15 Apr 2004 09:46:28 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 2004 14:11:54 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Comelli",
"D.",
""
],
[
"Dolgov",
"A.",
""
]
] | We analyze the action $\int d^4x \sqrt{\det||{\cal B} g_{\mu\nu}+ {\cal C} R_{\mu\nu}}||$ as a possible alternative or addition to the Einstein gravity. Choosing a particular form of ${\cal B}(R)= \sqrt {R}$ we can restore the Einstein gravity and, if ${\cal B}=m^2$, we obtain the cosmological constant term. Taking ${\cal B} = m^2 + {\cal B}_1 R$ and expanding the action in $ 1/m^2$, we obtain as a leading term the Einstein Lagrangian with a cosmological constant proportional to $m^4$ and a series of higher order operators. In general case of non-vanishing ${\cal B}$ and ${\cal C}$ new cosmological solutions for the Robertson-Walker metric are obtained. |
gr-qc/9703053 | Jacques Legare | M. A. Clayton (1), L. Demopoulos (2), and J. Legare (2) ((1) CERN
Theory Division, (2) Department of Physics, University of Toronto) | The Initial-Value Problem of Spherically Symmetric Wyman Sector
Nonsymmetric Gravitational Theory | REVTeX 3.0 with epsf macros and AMS symbols, 18 pages, 9 figures | null | null | UTPT-97-04 | gr-qc | null | We cast the four-dimensional field equations of the Nonsymmetric
Gravitational Theory (NGT) into a form appropriate for numerical study. In
doing so, we have restricted ourselves to spherically symmetric spacetimes, and
we have kept only the Wyman sector of the theory. We investigate the
well-posedness of the initial-value problem of NGT for a particular data set
consisting of a pulse in the antisymmetric field on an asymptotically flat
space background. We include some analytic results on the solvability of the
initial-value problem which allow us to place limits on the regions of the
parameter space where the initial-value problem is solvable. These results are
confirmed by numerically solving the constraints.
| [
{
"created": "Thu, 20 Mar 1997 21:42:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Clayton",
"M. A.",
""
],
[
"Demopoulos",
"L.",
""
],
[
"Legare",
"J.",
""
]
] | We cast the four-dimensional field equations of the Nonsymmetric Gravitational Theory (NGT) into a form appropriate for numerical study. In doing so, we have restricted ourselves to spherically symmetric spacetimes, and we have kept only the Wyman sector of the theory. We investigate the well-posedness of the initial-value problem of NGT for a particular data set consisting of a pulse in the antisymmetric field on an asymptotically flat space background. We include some analytic results on the solvability of the initial-value problem which allow us to place limits on the regions of the parameter space where the initial-value problem is solvable. These results are confirmed by numerically solving the constraints. |
2301.03951 | Alejandro Perez | Alejandro Perez, Salvatore Ribisi, Sami Viollet | Modelling quantum particles falling into a black hole: the deep interior
limit | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we construct a solvable toy model of the quantum dynamics of
the interior of a spherical black hole with falling spherical scalar field
excitations. We first argue about how some aspects of the quantum gravity
dynamics of realistic black holes emitting Hawking radiation can be modelled
using Kantowski-Sachs solutions with a massless scalar field when one focuses
on the deep interior region $r\ll M$ (including the singularity). Further, we
show that in the $r\ll M$ regime, and in suitable variables, the KS model
becomes exactly solvable at both the classical and quantum levels. The quantum
dynamics inspired by loop quantum gravity is revisited. We propose a natural
polymer-quantization where the area $a$ of the orbits of the rotation group is
quantized. The polymer (or loop) dynamics is closely related with the
Schroedinger dynamics away from the singularity with a form of continuum limit
naturally emerging from the polymer treatment. The Dirac observable associated
to the mass is quantized and shown to have an infinite degeneracy associated to
the so-called $\epsilon$-sectors. Suitable continuum superpositions of these
are well defined distributions in the fundamental Hilbert space and satisfy the
continuum Schroedinger dynamics.
| [
{
"created": "Tue, 10 Jan 2023 13:16:32 GMT",
"version": "v1"
}
] | 2023-01-11 | [
[
"Perez",
"Alejandro",
""
],
[
"Ribisi",
"Salvatore",
""
],
[
"Viollet",
"Sami",
""
]
] | In this paper we construct a solvable toy model of the quantum dynamics of the interior of a spherical black hole with falling spherical scalar field excitations. We first argue about how some aspects of the quantum gravity dynamics of realistic black holes emitting Hawking radiation can be modelled using Kantowski-Sachs solutions with a massless scalar field when one focuses on the deep interior region $r\ll M$ (including the singularity). Further, we show that in the $r\ll M$ regime, and in suitable variables, the KS model becomes exactly solvable at both the classical and quantum levels. The quantum dynamics inspired by loop quantum gravity is revisited. We propose a natural polymer-quantization where the area $a$ of the orbits of the rotation group is quantized. The polymer (or loop) dynamics is closely related with the Schroedinger dynamics away from the singularity with a form of continuum limit naturally emerging from the polymer treatment. The Dirac observable associated to the mass is quantized and shown to have an infinite degeneracy associated to the so-called $\epsilon$-sectors. Suitable continuum superpositions of these are well defined distributions in the fundamental Hilbert space and satisfy the continuum Schroedinger dynamics. |
1008.2761 | Yosef Zlochower | Marcelo Ponce, Carlos Lousto, Yosef Zlochower | Seeking for toroidal event horizons from initially stationary BH
configurations | 24 pages, 14 figures | Class.Quant.Grav.28:145027,2011 | 10.1088/0264-9381/28/14/145027 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct and evolve non-rotating vacuum initial data with a ring
singularity, based on a simple extension of the standard Brill-Lindquist
multiple black-hole initial data, and search for event horizons with spatial
slices that are toroidal when the ring radius is sufficiently large. While
evolutions of the ring singularity are not numerically feasible for large
radii, we find some evidence, based on configurations of multiple BHs arranged
in a ring, that this configuration leads to singular limit where the horizon
width has zero size, possibly indicating the presence of a naked singularity,
when the radius of the ring is sufficiently large. This is in agreement with
previous studies that have found that there is no apparent horizon surrounding
the ring singularity when the ring's radius is larger than about twice its
mass.
| [
{
"created": "Mon, 16 Aug 2010 20:01:00 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jun 2011 13:54:09 GMT",
"version": "v2"
}
] | 2011-06-24 | [
[
"Ponce",
"Marcelo",
""
],
[
"Lousto",
"Carlos",
""
],
[
"Zlochower",
"Yosef",
""
]
] | We construct and evolve non-rotating vacuum initial data with a ring singularity, based on a simple extension of the standard Brill-Lindquist multiple black-hole initial data, and search for event horizons with spatial slices that are toroidal when the ring radius is sufficiently large. While evolutions of the ring singularity are not numerically feasible for large radii, we find some evidence, based on configurations of multiple BHs arranged in a ring, that this configuration leads to singular limit where the horizon width has zero size, possibly indicating the presence of a naked singularity, when the radius of the ring is sufficiently large. This is in agreement with previous studies that have found that there is no apparent horizon surrounding the ring singularity when the ring's radius is larger than about twice its mass. |
2405.13673 | Don N. Page | Don N. Page | Discrete Orbit Effect Lengthens Merger Times for Inspiraling Binary
Black Holes | 30 pages. arXiv admin note: text overlap with arXiv:2403.10804 | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The inspiral merger time for two black holes captured into a nonrelativistic
bound orbit by gravitational radiation emission has been often calculated by a
formula of Peters that assumes the adiabatic approximation that the changes per
orbit are small. However, initially this is not true for the semimajor axis and
period of most of the initially highly eccentric orbits, which change
significantly during closest approach and much less elsewhere along the orbit.
This effect can make the merger time much longer (using other formulas from
Peters that do not assume the adiabatic approximation) than that calculated by
the adiabatic formula of Peters.
| [
{
"created": "Wed, 22 May 2024 14:16:28 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Jun 2024 05:17:17 GMT",
"version": "v2"
}
] | 2024-06-11 | [
[
"Page",
"Don N.",
""
]
] | The inspiral merger time for two black holes captured into a nonrelativistic bound orbit by gravitational radiation emission has been often calculated by a formula of Peters that assumes the adiabatic approximation that the changes per orbit are small. However, initially this is not true for the semimajor axis and period of most of the initially highly eccentric orbits, which change significantly during closest approach and much less elsewhere along the orbit. This effect can make the merger time much longer (using other formulas from Peters that do not assume the adiabatic approximation) than that calculated by the adiabatic formula of Peters. |
2404.09923 | Gustavo Oleg\'ario Heymans Ms. | G. O. Heymans, G. Scorza, N. F. Svaiter, C. D. Rodr\'iguez-Camargo | The generalized second law in Euclidean Schwarzschild black hole | 12 pages, 2 figures | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/publicdomain/zero/1.0/ | We discuss the Bekenstein generalized entropy of Schwarzschild black hole,
with the contribution of an external matter field affected by degrees of
freedom inside the event horizon. To take into accountthis effect to the
generalized entropy, we use Euclidean functional methods. In the Euclidean
section of the Schwarzschild manifold, we consider an Euclidean quantum
effective model, a scalar theory in the presence of an additive quenched
disorder. The average the Gibbs free energy over the ensemble of possible
configurations of the disorder is obtained by the distributional zeta-function
method. In the series representation for the average free energy with
respective effective actions emerges the generalized Schr\"{o}dinger operators
on Riemannian manifolds. Finally, is presented the generalized entropy density
with the contributions of the black hole geometric entropy and the external
matter fields affected by the internal degrees of freedom. The validity of the
generalized second law using Euclidean functional methods is obtained.
| [
{
"created": "Mon, 15 Apr 2024 16:50:49 GMT",
"version": "v1"
}
] | 2024-04-16 | [
[
"Heymans",
"G. O.",
""
],
[
"Scorza",
"G.",
""
],
[
"Svaiter",
"N. F.",
""
],
[
"Rodríguez-Camargo",
"C. D.",
""
]
] | We discuss the Bekenstein generalized entropy of Schwarzschild black hole, with the contribution of an external matter field affected by degrees of freedom inside the event horizon. To take into accountthis effect to the generalized entropy, we use Euclidean functional methods. In the Euclidean section of the Schwarzschild manifold, we consider an Euclidean quantum effective model, a scalar theory in the presence of an additive quenched disorder. The average the Gibbs free energy over the ensemble of possible configurations of the disorder is obtained by the distributional zeta-function method. In the series representation for the average free energy with respective effective actions emerges the generalized Schr\"{o}dinger operators on Riemannian manifolds. Finally, is presented the generalized entropy density with the contributions of the black hole geometric entropy and the external matter fields affected by the internal degrees of freedom. The validity of the generalized second law using Euclidean functional methods is obtained. |
1107.1267 | P Ajith | P. Ajith | Addressing the spin question in gravitational-wave searches: Waveform
templates for inspiralling compact binaries with nonprecessing spins | 16 pages, 11 figures, More material added, Some changes to clarify
the presentation | Phys. Rev. D 84, 084037 (2011) | 10.1103/PhysRevD.84.084037 | LIGO-P1100075-v5 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents a post-Newtonian (PN) template family of gravitational
waveforms from inspiralling compact binaries with non-precessing spins, where
the spin effects are described by a single "reduced-spin" parameter. This
template family, which reparametrizes all the spin-dependent PN terms in terms
of the leading-order (1.5PN) spin-orbit coupling term \emph{in an approximate
way}, has very high overlaps (fitting factor > 0.99) with non-precessing
binaries with arbitrary mass ratios and spins. We also show that this template
family is "effectual" for the detection of a significant fraction of generic
spinning binaries in the comparable-mass regime (m_2/m_1 <~ 10), providing an
attractive and feasible way of searching for gravitational waves (GWs) from
spinning low-mass binaries. We also show that the secular (non-oscillatory)
spin-dependent effects in the phase evolution (which are taken into account by
the non-precessing templates) are more important than the oscillatory effects
of precession in the comparable-mass (m_1 ~= m_2) regime. Hence the
effectualness of non-spinning templates is particularly poor in this case, as
compared to non-precessing-spin templates. For the case of binary neutron stars
observable by Advanced LIGO, even moderate spins (L . S/m^2 ~= 0.015 - 0.1)
will cause considerable mismatches (~ 3% - 25%) with non-spinning templates.
This is contrary to the expectation that neutron-star spins may not be relevant
for GW detection.
| [
{
"created": "Wed, 6 Jul 2011 22:06:19 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2011 20:13:37 GMT",
"version": "v2"
}
] | 2011-10-20 | [
[
"Ajith",
"P.",
""
]
] | This paper presents a post-Newtonian (PN) template family of gravitational waveforms from inspiralling compact binaries with non-precessing spins, where the spin effects are described by a single "reduced-spin" parameter. This template family, which reparametrizes all the spin-dependent PN terms in terms of the leading-order (1.5PN) spin-orbit coupling term \emph{in an approximate way}, has very high overlaps (fitting factor > 0.99) with non-precessing binaries with arbitrary mass ratios and spins. We also show that this template family is "effectual" for the detection of a significant fraction of generic spinning binaries in the comparable-mass regime (m_2/m_1 <~ 10), providing an attractive and feasible way of searching for gravitational waves (GWs) from spinning low-mass binaries. We also show that the secular (non-oscillatory) spin-dependent effects in the phase evolution (which are taken into account by the non-precessing templates) are more important than the oscillatory effects of precession in the comparable-mass (m_1 ~= m_2) regime. Hence the effectualness of non-spinning templates is particularly poor in this case, as compared to non-precessing-spin templates. For the case of binary neutron stars observable by Advanced LIGO, even moderate spins (L . S/m^2 ~= 0.015 - 0.1) will cause considerable mismatches (~ 3% - 25%) with non-spinning templates. This is contrary to the expectation that neutron-star spins may not be relevant for GW detection. |
2009.13508 | Bayram Tekin | Metin Gurses, Tahsin Cagri Sisman, Bayram Tekin | Comment on "Einstein-Gauss-Bonnet Gravity in 4-Dimensional Space-Time'' | null | Phys. Rev. Lett. 125, 149001 (2020) | 10.1103/PhysRevLett.125.149001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We summarize our proof that the "Einstein-Gauss-Bonnet Gravity in
Four-Dimensional Spacetime" introduced in Phys. Rev. Lett. 124, 081301 (2020)
does not have consistent field equations, as such the theory does not exist.
The proof is given in both the metric and the first order formalisms.
| [
{
"created": "Mon, 28 Sep 2020 17:57:28 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Gurses",
"Metin",
""
],
[
"Sisman",
"Tahsin Cagri",
""
],
[
"Tekin",
"Bayram",
""
]
] | We summarize our proof that the "Einstein-Gauss-Bonnet Gravity in Four-Dimensional Spacetime" introduced in Phys. Rev. Lett. 124, 081301 (2020) does not have consistent field equations, as such the theory does not exist. The proof is given in both the metric and the first order formalisms. |
gr-qc/0006082 | Simonetta Frittelli | Simonetta Frittelli and Roberto Gomez | Ill-posedness in the Einstein equations | 13 pages, 3 figures, accepted for publication in Journal of
Mathematical Physics (to appear August 2000) | J.Math.Phys. 41 (2000) 5535-5549 | 10.1063/1.533423 | null | gr-qc | null | It is shown that the formulation of the Einstein equations widely in use in
numerical relativity, namely, the standard ADM form, as well as some of its
variations (including the most recent conformally-decomposed version), suffers
from a certain but standard type of ill-posedness. Specifically, the norm of
the solution is not bounded by the norm of the initial data irrespective of the
data. A long-running numerical experiment is performed as well, showing that
the type of ill-posedness observed may not be serious in specific practical
applications, as is known from many numerical simulations.
| [
{
"created": "Thu, 22 Jun 2000 17:48:42 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Frittelli",
"Simonetta",
""
],
[
"Gomez",
"Roberto",
""
]
] | It is shown that the formulation of the Einstein equations widely in use in numerical relativity, namely, the standard ADM form, as well as some of its variations (including the most recent conformally-decomposed version), suffers from a certain but standard type of ill-posedness. Specifically, the norm of the solution is not bounded by the norm of the initial data irrespective of the data. A long-running numerical experiment is performed as well, showing that the type of ill-posedness observed may not be serious in specific practical applications, as is known from many numerical simulations. |
gr-qc/9404032 | Martin Rainer | M. Rainer | Resolution of simple singularities yielding particle symmetries in a
space-time | 16 pages, LaTeX | J.Math.Phys.35:646-655,1994 | 10.1063/1.530658 | Univ-Potsdam-MATH-93/07 | gr-qc alg-geom hep-th math.AG | null | A finite subgroup of the conformal group SL(2,C) can be related to invariant
polynomials on a hypersurface in C^3. The latter then carries a simple
singularity, which resolves by a finite iteration of basic cycles of
deprojections. The homological intersection graph of this cycles is the Dynkin
graph of an ADE Lie group. The deformation of the simple singularity
corresponds to ADE symmetry breaking. A 3+1-dimensional topological model of
observation is constructed, transforming consistently under SL(2,C), as an
evolving 3-dimensional system of world tubes, which connect ``possible points
of observation". The existence of an initial singularity for the 4-dimensional
space-time is related to its global topological structure. Associating the
geometry of ADE singularities to the vertex structure of the topological model
puts forward the conjecture on a likewise relation of inner symmetries of
elementary particles to local space-time structure.
| [
{
"created": "Sun, 17 Apr 1994 10:43:16 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Rainer",
"M.",
""
]
] | A finite subgroup of the conformal group SL(2,C) can be related to invariant polynomials on a hypersurface in C^3. The latter then carries a simple singularity, which resolves by a finite iteration of basic cycles of deprojections. The homological intersection graph of this cycles is the Dynkin graph of an ADE Lie group. The deformation of the simple singularity corresponds to ADE symmetry breaking. A 3+1-dimensional topological model of observation is constructed, transforming consistently under SL(2,C), as an evolving 3-dimensional system of world tubes, which connect ``possible points of observation". The existence of an initial singularity for the 4-dimensional space-time is related to its global topological structure. Associating the geometry of ADE singularities to the vertex structure of the topological model puts forward the conjecture on a likewise relation of inner symmetries of elementary particles to local space-time structure. |
gr-qc/0601142 | Lode Wylleman | Lode Wylleman | Anti-Newtonian universes do not exist | 16 pages | Class.Quant.Grav.23:2727-2740,2006 | 10.1063/1.2218261 | null | gr-qc | null | In a paper by Maartens, Lesame and Ellis (Class. Quant. Grav. 15, 1005) it
was shown that irrotational dust solutions with vanishing electric part of the
Weyl tensor are subject to severe integrability conditions and it was
conjectured that the only such solutions are FLRW spacetimes. In their analysis
the possibility of a cosmological constant Lambda was omitted. The conjecture
is proved, irrespective as to whether Lambda is zero or not, and qualitative
differences with the case of vanishing magnetic Weyl curvature are pointed out.
| [
{
"created": "Tue, 31 Jan 2006 17:11:29 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Wylleman",
"Lode",
""
]
] | In a paper by Maartens, Lesame and Ellis (Class. Quant. Grav. 15, 1005) it was shown that irrotational dust solutions with vanishing electric part of the Weyl tensor are subject to severe integrability conditions and it was conjectured that the only such solutions are FLRW spacetimes. In their analysis the possibility of a cosmological constant Lambda was omitted. The conjecture is proved, irrespective as to whether Lambda is zero or not, and qualitative differences with the case of vanishing magnetic Weyl curvature are pointed out. |
gr-qc/9703084 | Sam Drake | S. P. Drake and R. Turolla | The Application of the Newman-Janis Algorithm in Obtaining Interior
Solutions of the Kerr Metric | 11 pages, Latex, 4 postscript figures. To be published in Classical
and Quantum Gravity. Title and abstract are now on the same page | Class.Quant.Grav. 14 (1997) 1883-1897 | 10.1088/0264-9381/14/7/021 | null | gr-qc | null | In this paper we present a class of metrics to be considered as new possible
sources for the Kerr metric. These new solutions are generated by applying the
Newman-Janis algorithm (NJA) to any static spherically symmetric (SSS) ``seed''
metric. The continuity conditions for joining any two of these new metrics is
presented. A specific analysis of the joining of interior solutions to the Kerr
exterior is made. The boundary conditions used are those first developed by
Dormois and Israel. We find that the NJA can be used to generate new physically
allowable interior solutions. These new solutions can be matched smoothly to
the Kerr metric. We present a general method for finding such solutions with
oblate spheroidal boundary surfaces. Finally a trial solution is found and
presented.
| [
{
"created": "Fri, 28 Mar 1997 02:34:37 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Drake",
"S. P.",
""
],
[
"Turolla",
"R.",
""
]
] | In this paper we present a class of metrics to be considered as new possible sources for the Kerr metric. These new solutions are generated by applying the Newman-Janis algorithm (NJA) to any static spherically symmetric (SSS) ``seed'' metric. The continuity conditions for joining any two of these new metrics is presented. A specific analysis of the joining of interior solutions to the Kerr exterior is made. The boundary conditions used are those first developed by Dormois and Israel. We find that the NJA can be used to generate new physically allowable interior solutions. These new solutions can be matched smoothly to the Kerr metric. We present a general method for finding such solutions with oblate spheroidal boundary surfaces. Finally a trial solution is found and presented. |
1505.01353 | Mariam Bouhmadi-Lopez | Imanol Albarran and Mariam Bouhmadi-L\'opez | Quantisation of the holographic Ricci dark energy model | 10 pages, RevTex4-1. Expanded and improved discussion. Version
accepted in JCAP | null | 10.1088/1475-7516/2015/08/051 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While general relativity is an extremely robust theory to describe the
gravitational interaction in our Universe, it is expected to fail close to
singularities like the cosmological ones. On the other hand, it is well known
that some dark energy models might induce future singularities; this can be the
case for example within the setup of the Holographic Ricci Dark Energy model
(HRDE). On this work, we perform a cosmological quantisation of the HRDE model
and obtain under which conditions a cosmic doomsday can be avoided within the
quantum realm. We show as well that this quantum model not only avoid future
singularities but also the past Big Bang.
| [
{
"created": "Wed, 6 May 2015 13:00:14 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Aug 2015 13:57:58 GMT",
"version": "v2"
}
] | 2015-09-09 | [
[
"Albarran",
"Imanol",
""
],
[
"Bouhmadi-López",
"Mariam",
""
]
] | While general relativity is an extremely robust theory to describe the gravitational interaction in our Universe, it is expected to fail close to singularities like the cosmological ones. On the other hand, it is well known that some dark energy models might induce future singularities; this can be the case for example within the setup of the Holographic Ricci Dark Energy model (HRDE). On this work, we perform a cosmological quantisation of the HRDE model and obtain under which conditions a cosmic doomsday can be avoided within the quantum realm. We show as well that this quantum model not only avoid future singularities but also the past Big Bang. |
1804.07415 | Robert A Eisenstein | Robert A. Eisenstein | Numerical Relativity and the Discovery of Gravitational Waves | 14 pages, 6 figures | null | 10.1002/andp.201800348 | P1800055v4 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Solving Einstein's equations precisely for strong-field gravitational systems
is essential to determining the full physics content of gravitational wave
detections. Without these solutions it is not possible to infer precise values
for initial and final-state system parameters. Obtaining these solutions
requires extensive numerical simulations, as Einstein's equations governing
these systems are much too difficult to solve analytically. These difficulties
arise principally from the curved, non-linear nature of spacetime in general
relativity. Developing the numerical capabilities needed to produce reliable,
efficient calculations has required a Herculean 50-year effort involving
hundreds of researchers using sophisticated physical insight, algorithm
development, computational technique and computers that are a billion times
more capable than they were in 1964 when computations were first attempted. My
purpose is to give an accessible overview for non-experts of the major
developments that have made such dramatic progress possible.
| [
{
"created": "Fri, 20 Apr 2018 00:48:04 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Sep 2018 17:58:25 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Mar 2019 20:38:10 GMT",
"version": "v3"
}
] | 2019-09-04 | [
[
"Eisenstein",
"Robert A.",
""
]
] | Solving Einstein's equations precisely for strong-field gravitational systems is essential to determining the full physics content of gravitational wave detections. Without these solutions it is not possible to infer precise values for initial and final-state system parameters. Obtaining these solutions requires extensive numerical simulations, as Einstein's equations governing these systems are much too difficult to solve analytically. These difficulties arise principally from the curved, non-linear nature of spacetime in general relativity. Developing the numerical capabilities needed to produce reliable, efficient calculations has required a Herculean 50-year effort involving hundreds of researchers using sophisticated physical insight, algorithm development, computational technique and computers that are a billion times more capable than they were in 1964 when computations were first attempted. My purpose is to give an accessible overview for non-experts of the major developments that have made such dramatic progress possible. |
gr-qc/0309053 | T. Padmanabhan | T. Padmanabhan, Apoorva Patel | Role of Horizons in Semiclassical Gravity: Entropy and the Area Spectrum | Extends and presents the results of hep-th/0305165 in a broader
context; clarifies some conceptual issues; 24 pages; revtex | null | null | null | gr-qc astro-ph hep-th | null | In any space-time, it is possible to have a family of observers who have
access to only part of the space-time manifold, because of the existence of a
horizon. We demand that \emph{physical theories in a given coordinate system
must be formulated entirely in terms of variables that an observer using that
coordinate system can access}. In the coordinate frame in which these observers
are at rest, the horizon manifests itself as a (coordinate) singularity in the
metric tensor. Regularization of this singularity removes the inaccessible
region, and leads to the following consequences: (a) The non-trivial
topological structure for the effective manifold allows one to obtain the
standard results of quantum field theory in curved space-time. (b) In case of
gravity, this principle requires that the effect of the unobserved degrees of
freedom should reduce to a boundary contribution $A_{\rm boundary}$ to the
gravitational action. When the boundary is a horizon, $A_{\rm boundary}$
reduces to a single, well-defined term proportional to the area of the horizon.
Using the form of this boundary term, it is possible to obtain the full
gravitational action in the semiclassical limit. (c) This boundary term must
have a quantized spectrum with uniform spacing, $\Delta
A_{boundary}=2\pi\hbar$, in the semiclassical limit. This, in turn, yields the
following results for semiclassical gravity: (i) The area of any one-way
membrane is quantized. (ii) The information hidden by a one-way membrane
amounts to an entropy, which is always one-fourth of the area of the membrane
in the leading order. (iii) In static space-times, the action for gravity can
be given a purely thermodynamic interpretation and the Einstein equations have
a formal similarity to laws of thermodynamics.
| [
{
"created": "Tue, 9 Sep 2003 15:20:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Padmanabhan",
"T.",
""
],
[
"Patel",
"Apoorva",
""
]
] | In any space-time, it is possible to have a family of observers who have access to only part of the space-time manifold, because of the existence of a horizon. We demand that \emph{physical theories in a given coordinate system must be formulated entirely in terms of variables that an observer using that coordinate system can access}. In the coordinate frame in which these observers are at rest, the horizon manifests itself as a (coordinate) singularity in the metric tensor. Regularization of this singularity removes the inaccessible region, and leads to the following consequences: (a) The non-trivial topological structure for the effective manifold allows one to obtain the standard results of quantum field theory in curved space-time. (b) In case of gravity, this principle requires that the effect of the unobserved degrees of freedom should reduce to a boundary contribution $A_{\rm boundary}$ to the gravitational action. When the boundary is a horizon, $A_{\rm boundary}$ reduces to a single, well-defined term proportional to the area of the horizon. Using the form of this boundary term, it is possible to obtain the full gravitational action in the semiclassical limit. (c) This boundary term must have a quantized spectrum with uniform spacing, $\Delta A_{boundary}=2\pi\hbar$, in the semiclassical limit. This, in turn, yields the following results for semiclassical gravity: (i) The area of any one-way membrane is quantized. (ii) The information hidden by a one-way membrane amounts to an entropy, which is always one-fourth of the area of the membrane in the leading order. (iii) In static space-times, the action for gravity can be given a purely thermodynamic interpretation and the Einstein equations have a formal similarity to laws of thermodynamics. |
2112.07336 | Liang-Bi Wu | Li-Ming Cao and Liang-Bi Wu | A Note on the Strong Hyperbolicity of $f(R)$ Gravity with Dynamical
Shifts | revtex, 12 pages, no figures | null | 10.1103/PhysRevD.105.124062 | ICTS-USTC/PCFT-21-47 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The well-posedness of the gravitational equations of $f(R)$ gravity are
studied in this paper. Three formulations of the $f(R)$ gravity with dynamical
shifts (which are all based on the Arnowitt-Deser-Misner (ADM) formalism of the
equations) are investigated. These three formulations are all proved to be
strongly hyperbolic by pseudodifferential reduction. The first one is the
Baumagarte-Shapiro-Shibata-Nakamura (BSSN) formulation with the so-called
"hyperbolic $K$-driver" condition and the "hyperbolic Gamma driver" condition.
The second one is the ADM formulation with modified harmonic gauge conditions.
We find that the equations are not strong hyperbolic in traditional Z4
formulation for $f(R)$ gravity. So, in the third formulation, we improve the Z4
formulation, and show these equations are strong hyperbolic with modified
harmonic gauge conditions.
| [
{
"created": "Tue, 14 Dec 2021 12:46:50 GMT",
"version": "v1"
}
] | 2022-07-13 | [
[
"Cao",
"Li-Ming",
""
],
[
"Wu",
"Liang-Bi",
""
]
] | The well-posedness of the gravitational equations of $f(R)$ gravity are studied in this paper. Three formulations of the $f(R)$ gravity with dynamical shifts (which are all based on the Arnowitt-Deser-Misner (ADM) formalism of the equations) are investigated. These three formulations are all proved to be strongly hyperbolic by pseudodifferential reduction. The first one is the Baumagarte-Shapiro-Shibata-Nakamura (BSSN) formulation with the so-called "hyperbolic $K$-driver" condition and the "hyperbolic Gamma driver" condition. The second one is the ADM formulation with modified harmonic gauge conditions. We find that the equations are not strong hyperbolic in traditional Z4 formulation for $f(R)$ gravity. So, in the third formulation, we improve the Z4 formulation, and show these equations are strong hyperbolic with modified harmonic gauge conditions. |
2003.02286 | Carlos O. Lousto | James Healy, Carlos O. Lousto, Nicole Rosato | Adapted gauge to a quasilocal measure of the black holes recoil | 14 pages, 9 figures | Phys. Rev. D 102, 024040 (2020) | 10.1103/PhysRevD.102.024040 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore different gauge choices in the moving puncture formulation in
order to improve the accuracy of a linear momentum measure evaluated on the
horizon of the remnant black hole produced by the merger of a binary. In
particular, motivated by constant values studies, we design a gauge via a
variable shift parameter $m\eta(\vec{r}(t))$ such that it takes a low
asymptotic (and at the orbiting punctures) value, while about the standard
value of 2 at the final hole horizon. This choice then follows the remnant
black hole as it moves due to its net recoil velocity. We find that this choice
keeps the accuracy of the binary evolution and, once the asymptotic value of
the parameter $m\eta$ is chosen about or below 1.0, it produces more accurate
results for the recoil velocity than the corresponding evaluation of the
radiated linear momentum at infinity, for typical numerical resolutions. We
also find that the choice of the $\partial_t$-gauge (at our working
resolutions) is more accurate in this regard of computing recoil velocities
than the $\partial_0$-gauge. Detailed studies of an unequal mass
$q=m_1/m_2=1/3$ nonspinning binary are provided and then verified for other
mass ratios $(q=1/2,1/5)$ and spinning $(q=1)$ binary black hole mergers.
| [
{
"created": "Wed, 4 Mar 2020 19:03:14 GMT",
"version": "v1"
},
{
"created": "Tue, 5 May 2020 19:02:34 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Jun 2020 15:25:23 GMT",
"version": "v3"
}
] | 2020-07-22 | [
[
"Healy",
"James",
""
],
[
"Lousto",
"Carlos O.",
""
],
[
"Rosato",
"Nicole",
""
]
] | We explore different gauge choices in the moving puncture formulation in order to improve the accuracy of a linear momentum measure evaluated on the horizon of the remnant black hole produced by the merger of a binary. In particular, motivated by constant values studies, we design a gauge via a variable shift parameter $m\eta(\vec{r}(t))$ such that it takes a low asymptotic (and at the orbiting punctures) value, while about the standard value of 2 at the final hole horizon. This choice then follows the remnant black hole as it moves due to its net recoil velocity. We find that this choice keeps the accuracy of the binary evolution and, once the asymptotic value of the parameter $m\eta$ is chosen about or below 1.0, it produces more accurate results for the recoil velocity than the corresponding evaluation of the radiated linear momentum at infinity, for typical numerical resolutions. We also find that the choice of the $\partial_t$-gauge (at our working resolutions) is more accurate in this regard of computing recoil velocities than the $\partial_0$-gauge. Detailed studies of an unequal mass $q=m_1/m_2=1/3$ nonspinning binary are provided and then verified for other mass ratios $(q=1/2,1/5)$ and spinning $(q=1)$ binary black hole mergers. |
2112.02126 | Piotr T. Chru\'sciel | Piotr T. Chrusciel | Quo Vadis, Mathematical General Relativity? | 8 pages, 1 Table, talk at the Oberwolfach workshop on Mathematical
Aspects of General Relativity, August 29 - September 4, 2021, to appear in
the Proceedings | null | null | null | gr-qc math.DG | http://creativecommons.org/licenses/by-nc-sa/4.0/ | A review of selected topics in mathematical general relativity
| [
{
"created": "Thu, 2 Dec 2021 16:03:40 GMT",
"version": "v1"
}
] | 2021-12-07 | [
[
"Chrusciel",
"Piotr T.",
""
]
] | A review of selected topics in mathematical general relativity |
gr-qc/9501039 | David Graham Wands | Jose P. Mimoso and David Wands | Anisotropic Scalar-Tensor Cosmologies | 30 pages, LaTeX, four uuencoded postscript figures | Phys.Rev. D52 (1995) 5612-5627 | 10.1103/PhysRevD.52.5612 | SUSSEX-AST-95/1-2 | gr-qc | null | We examine homogeneous but anisotropic cosmologies in scalar-tensor gravity
theories, including Brans-Dicke gravity. We present a method for deriving
solutions for any isotropic perfect fluid with a barotropic equation of state
($p\propto\rho$) in a spatially flat (Bianchi type~I) cosmology. These models
approach an isotropic, general relativistic solution as the expansion becomes
dominated by the barotropic fluid. All models that approach general relativity
isotropize except for the case of a maximally stiff fluid. For stiff fluid or
radiation or in vacuum we are able to give solutions for arbitrary
scalar-tensor theories in a number of anisotropic Bianchi and Kantowski-Sachs
metrics. We show how this approach can also be used to derive solutions from
the low-energy string effective action. We discuss the nature, and possibly
avoidance of, the initial singularity where both shear and non-Einstein
behavior is important.
| [
{
"created": "Fri, 27 Jan 1995 17:10:05 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Mimoso",
"Jose P.",
""
],
[
"Wands",
"David",
""
]
] | We examine homogeneous but anisotropic cosmologies in scalar-tensor gravity theories, including Brans-Dicke gravity. We present a method for deriving solutions for any isotropic perfect fluid with a barotropic equation of state ($p\propto\rho$) in a spatially flat (Bianchi type~I) cosmology. These models approach an isotropic, general relativistic solution as the expansion becomes dominated by the barotropic fluid. All models that approach general relativity isotropize except for the case of a maximally stiff fluid. For stiff fluid or radiation or in vacuum we are able to give solutions for arbitrary scalar-tensor theories in a number of anisotropic Bianchi and Kantowski-Sachs metrics. We show how this approach can also be used to derive solutions from the low-energy string effective action. We discuss the nature, and possibly avoidance of, the initial singularity where both shear and non-Einstein behavior is important. |
1004.2906 | Roberto Chan | R. Chan, M.F.A. da Silva, Jaime F. Villas da Rocha | Dynamical Evolution of an Unstable Gravastar with Zero Mass | 8 pages, 10 figures, to appear in Astrophysics and Space Science | Astrophys. Spa. Sci. 337, 185-191, 2012 | 10.1007/s10509-011-0858-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the conventional gravastar model, that is, an object constituted by two
components where one of them is a massive infinitely thin shell and the other
one is a de Sitter interior spacetime, we physically interpret a solution
characterized by a zero Schwarzschild mass. No stable gravastar is formed and
it collapses without forming an event horizon, originating what we call a
massive non-gravitational object. The most surprise here is that the collapse
occurs with an exterior de Sitter vacuum spacetime. This creates an object
which does not interact gravitationally with an outside test particle and it
may evolve to a point-like topological defect.
| [
{
"created": "Fri, 16 Apr 2010 19:06:48 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Sep 2011 13:35:16 GMT",
"version": "v2"
}
] | 2012-10-30 | [
[
"Chan",
"R.",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"da Rocha",
"Jaime F. Villas",
""
]
] | Using the conventional gravastar model, that is, an object constituted by two components where one of them is a massive infinitely thin shell and the other one is a de Sitter interior spacetime, we physically interpret a solution characterized by a zero Schwarzschild mass. No stable gravastar is formed and it collapses without forming an event horizon, originating what we call a massive non-gravitational object. The most surprise here is that the collapse occurs with an exterior de Sitter vacuum spacetime. This creates an object which does not interact gravitationally with an outside test particle and it may evolve to a point-like topological defect. |
gr-qc/0203097 | Metin Gurses | Metin Gurses (Bilkent University) and Ozgur Sarioglu (METU) | Accelerated Charge Kerr-Schild Metrics in D-Dimensions | Title changed, added references, corrected typos, added a section. To
be published in Classical and Quantum Gravity | Class.Quant.Grav. 19 (2002) 4249-4262; Erratum-ibid. 20 (2003)
1413-1414 | 10.1088/0264-9381/19/16/302 | null | gr-qc hep-th | null | We consider the D dimensional Einstein Maxwell theory with a null fluid in
the Kerr-Schild Geometry. We obtain a complete set of differential conditions
that are necessary for finding solutions. We examine the case of vanishing
pressure and cosmological constant in detail. For this specific case, we give
the metric, the electromagnetic vector potential and the fluid energy density.
This is, in fact, the generalization of the well known Bonnor-Vaidya solution
to arbitrary D dimensions. We show that due to the acceleration of charged
sources, there is an energy flux in $D \ge 4$ dimensions and we give the
explicit form of this energy flux formula.
| [
{
"created": "Wed, 27 Mar 2002 12:04:40 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jul 2002 14:01:58 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Jul 2002 06:50:54 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Gurses",
"Metin",
"",
"Bilkent University"
],
[
"Sarioglu",
"Ozgur",
"",
"METU"
]
] | We consider the D dimensional Einstein Maxwell theory with a null fluid in the Kerr-Schild Geometry. We obtain a complete set of differential conditions that are necessary for finding solutions. We examine the case of vanishing pressure and cosmological constant in detail. For this specific case, we give the metric, the electromagnetic vector potential and the fluid energy density. This is, in fact, the generalization of the well known Bonnor-Vaidya solution to arbitrary D dimensions. We show that due to the acceleration of charged sources, there is an energy flux in $D \ge 4$ dimensions and we give the explicit form of this energy flux formula. |
gr-qc/0507041 | Lorenzo Iorio | Lorenzo Iorio | First preliminary tests of the general relativistic gravitomagnetic
field of the Sun and new constraints on a Yukawa-like fifth force from
planetary data | LaTex, 22 pages, 1 figure, 5 tables, 62 references. To appear in
Planetary and Space Science | Planet.SpaceSci.55:1290-1298,2007 | 10.1016/j.pss.2007.04.001 | null | gr-qc astro-ph hep-ph physics.space-ph | null | The general relativistic Lense-Thirring precessions of the perihelia of the
inner planets of the Solar System are about 10^-3 arcseconds per century.
Recent improvements in planetary orbit determination may yield the first
observational evidence of such a tiny effect. Indeed, corrections to the known
perihelion rates of -0.0036 +/- 0.0050, -0.0002 +/- 0.0004 and 0.0001 +/-
0.0005 arcseconds per century were recently estimated by E.V. Pitjeva for
Mercury, the Earth and Mars, respectively, on the basis of the EPM2004
ephemerides and a set of more than 317,000 observations of various kinds. The
predicted relativistic Lense-Thirring precessions for these planets are
-0.0020, -0.0001 and -3 10^-5 arcseconds per century, respectively and are
compatible with the determined perihelia corrections. The relativistic
predictions fit better than the zero-effect hypothesis, especially if a
suitable linear combination of the perihelia of Mercury and the Earth, which a
priori cancels out any possible bias due to the solar quadrupole mass moment,
is considered. However, the experimental errors are still large. Also the
latest data for Mercury processed independently by Fienga et al. with the INPOP
ephemerides yield preliminary insights about the existence of the solar
Lense-Thirring effect. The data from the forthcoming planetary mission
BepiColombo will improve our knowledge of the orbital motion of this planet
and, consequently, the precision of the measurement of the Lense-Thirring
effect. As a by-product of the present analysis, it is also possible to
constrain the strength of a Yukawa-like fifth force to a 10^-12-10^-13 level at
scales of about one Astronomical Unit (10^11 m).
| [
{
"created": "Sat, 9 Jul 2005 08:10:46 GMT",
"version": "v1"
},
{
"created": "Fri, 19 May 2006 15:43:42 GMT",
"version": "v10"
},
{
"created": "Tue, 27 Mar 2007 20:26:51 GMT",
"version": "v11"
},
{
"created": "Sat, 21 Apr 2007 13:46:36 GMT",
"version": "v12"
},
{
"created": "Mon, 18 Jul 2005 13:54:43 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Aug 2005 15:11:50 GMT",
"version": "v3"
},
{
"created": "Sat, 20 Aug 2005 23:02:23 GMT",
"version": "v4"
},
{
"created": "Sun, 25 Sep 2005 14:10:33 GMT",
"version": "v5"
},
{
"created": "Fri, 7 Oct 2005 12:51:12 GMT",
"version": "v6"
},
{
"created": "Wed, 12 Oct 2005 11:35:18 GMT",
"version": "v7"
},
{
"created": "Tue, 8 Nov 2005 17:30:23 GMT",
"version": "v8"
},
{
"created": "Sun, 11 Dec 2005 00:31:40 GMT",
"version": "v9"
}
] | 2008-11-26 | [
[
"Iorio",
"Lorenzo",
""
]
] | The general relativistic Lense-Thirring precessions of the perihelia of the inner planets of the Solar System are about 10^-3 arcseconds per century. Recent improvements in planetary orbit determination may yield the first observational evidence of such a tiny effect. Indeed, corrections to the known perihelion rates of -0.0036 +/- 0.0050, -0.0002 +/- 0.0004 and 0.0001 +/- 0.0005 arcseconds per century were recently estimated by E.V. Pitjeva for Mercury, the Earth and Mars, respectively, on the basis of the EPM2004 ephemerides and a set of more than 317,000 observations of various kinds. The predicted relativistic Lense-Thirring precessions for these planets are -0.0020, -0.0001 and -3 10^-5 arcseconds per century, respectively and are compatible with the determined perihelia corrections. The relativistic predictions fit better than the zero-effect hypothesis, especially if a suitable linear combination of the perihelia of Mercury and the Earth, which a priori cancels out any possible bias due to the solar quadrupole mass moment, is considered. However, the experimental errors are still large. Also the latest data for Mercury processed independently by Fienga et al. with the INPOP ephemerides yield preliminary insights about the existence of the solar Lense-Thirring effect. The data from the forthcoming planetary mission BepiColombo will improve our knowledge of the orbital motion of this planet and, consequently, the precision of the measurement of the Lense-Thirring effect. As a by-product of the present analysis, it is also possible to constrain the strength of a Yukawa-like fifth force to a 10^-12-10^-13 level at scales of about one Astronomical Unit (10^11 m). |
0710.4260 | Kjell Rosquist | Kjell Rosquist, Tomas Bylund, Lars Samuelsson | Carter's constant revealed | Minor changes to match published version | Int.J.Mod.Phys.D18:429-434,2009 | 10.1142/S0218271809014546 | NORDITA 2007-31 | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new formulation of Carter's constant for geodesic motion in Kerr black
holes is given. It is shown that Carter's constant corresponds to the total
angular momentum plus a precisely defined part which is quadratic in the linear
momenta. The characterization is exact in the weak field limit obtained by
letting the gravitational constant go to zero. It is suggested that the new
form can be useful in current studies of the dynamics of extreme mass ratio
inspiral (EMRI) systems emitting gravitational radiation.
| [
{
"created": "Tue, 23 Oct 2007 10:56:11 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Oct 2007 12:25:27 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Mar 2009 12:26:40 GMT",
"version": "v3"
}
] | 2009-05-12 | [
[
"Rosquist",
"Kjell",
""
],
[
"Bylund",
"Tomas",
""
],
[
"Samuelsson",
"Lars",
""
]
] | A new formulation of Carter's constant for geodesic motion in Kerr black holes is given. It is shown that Carter's constant corresponds to the total angular momentum plus a precisely defined part which is quadratic in the linear momenta. The characterization is exact in the weak field limit obtained by letting the gravitational constant go to zero. It is suggested that the new form can be useful in current studies of the dynamics of extreme mass ratio inspiral (EMRI) systems emitting gravitational radiation. |
gr-qc/9706058 | Gerard 't Hooft | G. 't Hooft | The self-screening Hawking atmosphere | 19 pages, plain TeX, 5 figures PostScript. The author was made aware
of further references to older work, in view of which modifications were made
in order to avoid too much overlap. A discussion is added on the case
$\kappa=1$ | Nucl.Phys.Proc.Suppl. 68 (1998) 174-184 | 10.1016/S0920-5632(98)00151-0 | THU-97/14 | gr-qc | null | A model is proposed in which the Hawking particles emitted by a black hole
are treated as an envelope of matter that obeys an equation of state, and acts
as a source in Einstein's equations. This is a crude but interesting way to
accommodate for the back reaction. For large black holes, the solution can be
given analytically, if the equation of state is $p=\kappa\rho$, with
$0<\kappa<1$. The solution exhibits a singularity at the origin. If we assume
$N$ free particle types, we can use a Hartree-Fock procedure to compute the
contribution of one such field to the entropy, and the result scales as
expected as $1/N$. A slight mismatch is found that could be attributed to
quantum corrections to Einstein's equations, but can also be made to disappear
when $\k$ is set equal to one. The case $\kappa=1$ is further analysed.
| [
{
"created": "Thu, 19 Jun 1997 07:53:55 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Aug 1997 15:19:01 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Hooft",
"G. 't",
""
]
] | A model is proposed in which the Hawking particles emitted by a black hole are treated as an envelope of matter that obeys an equation of state, and acts as a source in Einstein's equations. This is a crude but interesting way to accommodate for the back reaction. For large black holes, the solution can be given analytically, if the equation of state is $p=\kappa\rho$, with $0<\kappa<1$. The solution exhibits a singularity at the origin. If we assume $N$ free particle types, we can use a Hartree-Fock procedure to compute the contribution of one such field to the entropy, and the result scales as expected as $1/N$. A slight mismatch is found that could be attributed to quantum corrections to Einstein's equations, but can also be made to disappear when $\k$ is set equal to one. The case $\kappa=1$ is further analysed. |
1707.03021 | Vitor Cardoso | Vitor Cardoso, Paolo Pani | The observational evidence for horizons: from echoes to precision
gravitational-wave physics | Expanded version of a "Perspectives" article submitted to Nature
Astronomy arXiv:1709.01525; Superseded by arXiv:1904.05363 (invited Review
article for Living Reviews in Relativity) | Nat.Astron. 1 (2017) 586-591 | 10.1038/s41550-017-0225-y | null | gr-qc astro-ph.HE hep-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of black holes and of spacetime singularities is a fundamental
issue in science. Despite this, observations supporting their existence are
scarce, and their interpretation unclear. We overview how strong a case for
black holes has been made in the last few decades, and how well observations
adjust to this paradigm. Unsurprisingly, we conclude that observational
evidence for black holes is impossible to come by. However, just like Popper's
black swan, alternatives can be ruled out or confirmed to exist with a single
observation. These observations are within reach. In the next few years and
decades, we will enter the era of precision gravitational-wave physics with
more sensitive detectors. Just as accelerators require larger and larger
energies to probe smaller and smaller scales, more sensitive gravitational-wave
detectors will be probing regions closer and closer to the horizon, potentially
reaching Planck scales and beyond. What may be there, lurking?
| [
{
"created": "Mon, 10 Jul 2017 18:56:24 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jul 2017 12:54:02 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Sep 2017 06:07:23 GMT",
"version": "v3"
},
{
"created": "Sun, 8 Oct 2017 07:51:00 GMT",
"version": "v4"
},
{
"created": "Fri, 12 Apr 2019 05:01:20 GMT",
"version": "v5"
}
] | 2019-04-15 | [
[
"Cardoso",
"Vitor",
""
],
[
"Pani",
"Paolo",
""
]
] | The existence of black holes and of spacetime singularities is a fundamental issue in science. Despite this, observations supporting their existence are scarce, and their interpretation unclear. We overview how strong a case for black holes has been made in the last few decades, and how well observations adjust to this paradigm. Unsurprisingly, we conclude that observational evidence for black holes is impossible to come by. However, just like Popper's black swan, alternatives can be ruled out or confirmed to exist with a single observation. These observations are within reach. In the next few years and decades, we will enter the era of precision gravitational-wave physics with more sensitive detectors. Just as accelerators require larger and larger energies to probe smaller and smaller scales, more sensitive gravitational-wave detectors will be probing regions closer and closer to the horizon, potentially reaching Planck scales and beyond. What may be there, lurking? |
2011.08680 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou, F.P. Fronimos | Canonical Scalar Field Inflation with String and $R^2$-Corrections | AoP Accepted-Abstract is reduced due to arXiv limitations | null | 10.1016/j.aop.2020.168359 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Assuming that a scalar field controls the inflationary era, we examine the
combined effects of string and $f(R)$ gravity corrections on the inflationary
dynamics of canonical scalar field inflation, imposing the constraint that the
speed of the primordial gravitational waves is equal to that of light's.
Particularly, we study the inflationary dynamics of an Einstein-Gauss-Bonnet
gravity in the presence of $\alpha R^2$ corrections, where $\alpha$ is a free
coupling parameter. As it was the case in the pure Einstein-Gauss-Bonnet
gravity, the realization that the gravitational waves propagate through
spacetime with the velocity of light, imposes the constraint that the
Gauss-Bonnet coupling function $\xi(\phi)$ obeys the differential equation
$\ddot\xi=H\dot\xi$, where $H$ is the Hubble rate. Subsequently, a relation for
the time derivative of the scalar field is extracted which implies that the
scalar functions of the model, which are the Gauss-Bonnet coupling and the
scalar potential, are interconnected and simply designating one of them
specifies the other immediately. In this framework, it is useful to freely
designate $\xi(\phi)$ and extract the corresponding scalar potential from the
equations of motion but the opposite is still feasible. We demonstrate that the
model can produce a viable inflationary phenomenology and for a wide range of
the free parameters. Also, a mentionable issue is that when the coupling
parameter $\alpha$ of the $R^2$ correction term is $\alpha<10^{-3}$ in Planck
Units, the $R^2$ term is practically negligible and one obtains the same
equations of motion as in the pure Einstein-Gauss-Bonnet theory, however the
dynamics still change, since now the time derivative of $\frac{\partial
f}{\partial R}$ is nonzero.
| [
{
"created": "Tue, 17 Nov 2020 14:56:28 GMT",
"version": "v1"
}
] | 2020-12-30 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
],
[
"Fronimos",
"F. P.",
""
]
] | Assuming that a scalar field controls the inflationary era, we examine the combined effects of string and $f(R)$ gravity corrections on the inflationary dynamics of canonical scalar field inflation, imposing the constraint that the speed of the primordial gravitational waves is equal to that of light's. Particularly, we study the inflationary dynamics of an Einstein-Gauss-Bonnet gravity in the presence of $\alpha R^2$ corrections, where $\alpha$ is a free coupling parameter. As it was the case in the pure Einstein-Gauss-Bonnet gravity, the realization that the gravitational waves propagate through spacetime with the velocity of light, imposes the constraint that the Gauss-Bonnet coupling function $\xi(\phi)$ obeys the differential equation $\ddot\xi=H\dot\xi$, where $H$ is the Hubble rate. Subsequently, a relation for the time derivative of the scalar field is extracted which implies that the scalar functions of the model, which are the Gauss-Bonnet coupling and the scalar potential, are interconnected and simply designating one of them specifies the other immediately. In this framework, it is useful to freely designate $\xi(\phi)$ and extract the corresponding scalar potential from the equations of motion but the opposite is still feasible. We demonstrate that the model can produce a viable inflationary phenomenology and for a wide range of the free parameters. Also, a mentionable issue is that when the coupling parameter $\alpha$ of the $R^2$ correction term is $\alpha<10^{-3}$ in Planck Units, the $R^2$ term is practically negligible and one obtains the same equations of motion as in the pure Einstein-Gauss-Bonnet theory, however the dynamics still change, since now the time derivative of $\frac{\partial f}{\partial R}$ is nonzero. |
gr-qc/0511047 | Shahar Hod | Shahar Hod | Quasinormal Spectrum and Quantization of Charged Black Holes | 4 pages | Class.Quant.Grav. 23 (2006) L23-L28 | 10.1088/0264-9381/23/4/L01 | null | gr-qc | null | Black-hole quasinormal modes have been the subject of much recent attention,
with the hope that these oscillation frequencies may shed some light on the
elusive theory of quantum gravity. We study {\it analytically} the asymptotic
quasinormal spectrum of a {\it charged} scalar field in the (charged)
Reissner-Nordstr\"om spacetime. We find an analytic expression for these
black-hole resonances in terms of the black-hole physical parameters: its
Bekenstein-Hawking temperature $T_{BH}$, and its electric potential $\Phi$. We
discuss the applicability of the results in the context of black-hole
quantization. In particular, we show that according to Bohr's correspondence
principle, the asymptotic resonance corresponds to a fundamental area unit
$\Delta A=4\hbar\ln2$.
| [
{
"created": "Wed, 9 Nov 2005 19:38:31 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Hod",
"Shahar",
""
]
] | Black-hole quasinormal modes have been the subject of much recent attention, with the hope that these oscillation frequencies may shed some light on the elusive theory of quantum gravity. We study {\it analytically} the asymptotic quasinormal spectrum of a {\it charged} scalar field in the (charged) Reissner-Nordstr\"om spacetime. We find an analytic expression for these black-hole resonances in terms of the black-hole physical parameters: its Bekenstein-Hawking temperature $T_{BH}$, and its electric potential $\Phi$. We discuss the applicability of the results in the context of black-hole quantization. In particular, we show that according to Bohr's correspondence principle, the asymptotic resonance corresponds to a fundamental area unit $\Delta A=4\hbar\ln2$. |
1903.07029 | Sang Pyo Kim | Sang Pyo Kim (Kunsan Nat'l Univ.) | Simulation of Quantum Universe | LaTex, 8 pages, no figure; DICE 2017, Italy, September 17-21, 2018 | null | 10.1088/1742-6596/1275/1/012057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum simulation provides quantum systems under study with analogous
controllable quantum systems and has wide applications from condensed-matter
physics to high energy physics and to cosmology. The quantum system of a
homogeneous and isotropic field in the Friedmann-Robertson-Walker universe can
be simulated by a charge in an electrically modulated ion trap. The quantum
states of these time-dependent oscillators are constructed by quantum
invariants. Further, we propose simulation of quantum
Friedmann-Robertson-Walker universe with a minimal massive scalar field by a
charged scalar field in a homogeneous, time-dependent, magnetic field in
quantum electrodynamics and investigate the Cauchy problem of how the wave
functions evolve.
| [
{
"created": "Sun, 17 Mar 2019 05:27:02 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Kim",
"Sang Pyo",
"",
"Kunsan Nat'l Univ."
]
] | Quantum simulation provides quantum systems under study with analogous controllable quantum systems and has wide applications from condensed-matter physics to high energy physics and to cosmology. The quantum system of a homogeneous and isotropic field in the Friedmann-Robertson-Walker universe can be simulated by a charge in an electrically modulated ion trap. The quantum states of these time-dependent oscillators are constructed by quantum invariants. Further, we propose simulation of quantum Friedmann-Robertson-Walker universe with a minimal massive scalar field by a charged scalar field in a homogeneous, time-dependent, magnetic field in quantum electrodynamics and investigate the Cauchy problem of how the wave functions evolve. |
gr-qc/9609034 | Lee Smolin | Lee Smolin | The classical limit and the form of the hamiltonian constraint in
nonperturbative quantum gravity | Latex, 37 pages, no figures | null | null | CGPG-96/94 | gr-qc hep-th | null | It is argued that some approaches to non-perturbative quantum general
relativity lack a sensible continuum limit that reproduces general relativity.
The basic problem is that generic physical states lack long ranged
correlations, because the form of the state allows a division into spatial
regions, such that no change in the physical state in one region can be
measured by observables restricted to another. These disconnected regions have
generically finite expectation value of physical volume, which means that the
theory has no long ranged correlations or massless particles. One consequence
of this is that the $ADM$ energy is unbounded from below, at least when that is
defined with respect to a natural notion of quantum asymptotic flatness and a
corresponding definition of an operator that measures $E_{ADM}$ (which is given
here). These problems occur in Thiemann's new formulation of quantum gravity.
Related issues arise in some other approaches such as that of Borissov, Rovelli
and Smolin. A new approach to the Hamiltonian constraint, which may avoid the
problem of the lack of long ranged correlations, is proposed.
| [
{
"created": "Thu, 12 Sep 1996 20:56:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Smolin",
"Lee",
""
]
] | It is argued that some approaches to non-perturbative quantum general relativity lack a sensible continuum limit that reproduces general relativity. The basic problem is that generic physical states lack long ranged correlations, because the form of the state allows a division into spatial regions, such that no change in the physical state in one region can be measured by observables restricted to another. These disconnected regions have generically finite expectation value of physical volume, which means that the theory has no long ranged correlations or massless particles. One consequence of this is that the $ADM$ energy is unbounded from below, at least when that is defined with respect to a natural notion of quantum asymptotic flatness and a corresponding definition of an operator that measures $E_{ADM}$ (which is given here). These problems occur in Thiemann's new formulation of quantum gravity. Related issues arise in some other approaches such as that of Borissov, Rovelli and Smolin. A new approach to the Hamiltonian constraint, which may avoid the problem of the lack of long ranged correlations, is proposed. |
gr-qc/9907050 | Patricio S. Letelier | Patricio S. Letelier | Exact General Relativistic Disks with Magnetic Fields | 21 pages, 11 figures, uses package graphics, accepted in PRD | Phys.Rev. D60 (1999) 104042 | 10.1103/PhysRevD.60.104042 | null | gr-qc astro-ph | null | The well-known ``displace, cut, and reflect'' method used to generate cold
disks from given solutions of Einstein equations is extended to solutions of
Einstein-Maxwell equations. Four exact solutions of the these last equations
are used to construct models of hot disks with surface density, azimuthal
pressure, and azimuthal current. The solutions are closely related to Kerr,
Taub-NUT, Lynden-Bell-Pinault and to a one-soliton solution. We find that the
presence of the magnetic field can change in a nontrivial way the different
properties of the disks. In particular, the pure general relativistic
instability studied by Bicak, Lynden-Bell and Katz [Phys. Rev. D47, 4334, 1993]
can be enhanced or cured by different distributions of currents inside the
disk. These currents, outside the disk, generate a variety of axial symmetric
magnetic fields. As far as we know these are the first models of hot disks
studied in the context of general relativity.
| [
{
"created": "Tue, 13 Jul 1999 17:15:34 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Letelier",
"Patricio S.",
""
]
] | The well-known ``displace, cut, and reflect'' method used to generate cold disks from given solutions of Einstein equations is extended to solutions of Einstein-Maxwell equations. Four exact solutions of the these last equations are used to construct models of hot disks with surface density, azimuthal pressure, and azimuthal current. The solutions are closely related to Kerr, Taub-NUT, Lynden-Bell-Pinault and to a one-soliton solution. We find that the presence of the magnetic field can change in a nontrivial way the different properties of the disks. In particular, the pure general relativistic instability studied by Bicak, Lynden-Bell and Katz [Phys. Rev. D47, 4334, 1993] can be enhanced or cured by different distributions of currents inside the disk. These currents, outside the disk, generate a variety of axial symmetric magnetic fields. As far as we know these are the first models of hot disks studied in the context of general relativity. |
gr-qc/0407008 | Sukanta Bose | Aaron Rogan and Sukanta Bose (Washington State University) | Optimal statistic for detecting gravitational wave signals from binary
inspirals with LISA | 22 pages, 15 eps figures, Latex, uses iopart style/class files. Based
on talk given at the 8th Gravitational Wave Data Analysis Workshop,
Milwaukee, USA, December 17-20, 2003. Accepted for publication in Class.
Quant. Grav | Class.Quant.Grav. 21 (2004) S1607-S1624 | 10.1088/0264-9381/21/20/004 | null | gr-qc astro-ph | null | A binary compact object early in its inspiral phase will be picked up by its
nearly monochromatic gravitational radiation by LISA. But even this innocuous
appearing candidate poses interesting detection challenges. The data that will
be scanned for such sources will be a set of three functions of LISA's twelve
data streams obtained through time-delay interferometry, which is necessary to
cancel the noise contributions from laser-frequency fluctuations and
optical-bench motions to these data streams. We call these three functions
pseudo-detectors. The sensitivity of any pseudo-detector to a given sky
position is a function of LISA's orbital position. Moreover, at a given point
in LISA's orbit, each pseudo-detector has a different sensitivity to the same
sky position. In this work, we obtain the optimal statistic for detecting
gravitational wave signals, such as from compact binaries early in their
inspiral stage, in LISA data. We also present how the sensitivity of LISA,
defined by this optimal statistic, varies as a function of sky position and
LISA's orbital location. Finally, we show how a real-time search for inspiral
signals can be implemented on the LISA data by constructing a bank of templates
in the sky positions.
| [
{
"created": "Fri, 2 Jul 2004 00:38:27 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Rogan",
"Aaron",
"",
"Washington State University"
],
[
"Bose",
"Sukanta",
"",
"Washington State University"
]
] | A binary compact object early in its inspiral phase will be picked up by its nearly monochromatic gravitational radiation by LISA. But even this innocuous appearing candidate poses interesting detection challenges. The data that will be scanned for such sources will be a set of three functions of LISA's twelve data streams obtained through time-delay interferometry, which is necessary to cancel the noise contributions from laser-frequency fluctuations and optical-bench motions to these data streams. We call these three functions pseudo-detectors. The sensitivity of any pseudo-detector to a given sky position is a function of LISA's orbital position. Moreover, at a given point in LISA's orbit, each pseudo-detector has a different sensitivity to the same sky position. In this work, we obtain the optimal statistic for detecting gravitational wave signals, such as from compact binaries early in their inspiral stage, in LISA data. We also present how the sensitivity of LISA, defined by this optimal statistic, varies as a function of sky position and LISA's orbital location. Finally, we show how a real-time search for inspiral signals can be implemented on the LISA data by constructing a bank of templates in the sky positions. |
0802.1561 | David Mattingly | David Mattingly | Have we tested Lorentz invariance enough? | 17 pages, Talk given at 'From Quantum to Emergent Gravity: Theory and
Phenomenology', SISSA, June 2007 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by ideas from quantum gravity, Lorentz invariance has undergone
many stringent tests over the past decade and passed every one. Since there is
no conclusive reason from quantum gravity that the symmetry \textit{must} be
violated at some point we should ask the questions: a) are the existing tests
sufficient that the symmetry is already likely exact at the Planck scale? b)
Are further tests simply blind searches for new physics without reasonable
expectation of a positive signal? Here we argue that the existing tests are not
quite sufficient and describe some theoretically interesting areas of existing
parameterizations for Lorentz violation in the infrared that are not yet ruled
out but are accessible (or almost accessible) by current experiments. We
illustrate this point using a vector field model for Lorentz violation
containing operators up to mass dimension six and analyzing how terrestrial
experiments, neutrino observatories, and Auger results on ultra-high energy
cosmic rays limit this model.
| [
{
"created": "Tue, 12 Feb 2008 03:33:17 GMT",
"version": "v1"
}
] | 2008-02-13 | [
[
"Mattingly",
"David",
""
]
] | Motivated by ideas from quantum gravity, Lorentz invariance has undergone many stringent tests over the past decade and passed every one. Since there is no conclusive reason from quantum gravity that the symmetry \textit{must} be violated at some point we should ask the questions: a) are the existing tests sufficient that the symmetry is already likely exact at the Planck scale? b) Are further tests simply blind searches for new physics without reasonable expectation of a positive signal? Here we argue that the existing tests are not quite sufficient and describe some theoretically interesting areas of existing parameterizations for Lorentz violation in the infrared that are not yet ruled out but are accessible (or almost accessible) by current experiments. We illustrate this point using a vector field model for Lorentz violation containing operators up to mass dimension six and analyzing how terrestrial experiments, neutrino observatories, and Auger results on ultra-high energy cosmic rays limit this model. |
1501.05848 | Astrid Eichhorn | Astrid Eichhorn | The Renormalization Group flow of unimodular f(R) gravity | 17 pages, 2 figures; new version with some clarifications, identical
to version to appear in JHEP | null | 10.1007/JHEP04(2015)096 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unimodular gravity is classically equivalent to General Relativity. This
equivalence extends to actions which are functions of the curvature scalar. At
the quantum level, the dynamics could differ. Most importantly, the
cosmological constant is not a coupling in the unimodular action, providing a
new vantage point from which to address the cosmological constant fine-tuning
problem. Here, a quantum theory based on the asymptotic safety scenario is
studied, and evidence for an interacting fixed point in unimodular f(R) gravity
is found. We study the fixed point and its properties, and also discuss the
compatibility of unimodular asymptotic safety with dynamical matter, finding
evidence for its compatibility with the matter degrees of freedom of the
Standard Model.
| [
{
"created": "Fri, 23 Jan 2015 15:59:30 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Apr 2015 09:18:37 GMT",
"version": "v2"
}
] | 2015-05-20 | [
[
"Eichhorn",
"Astrid",
""
]
] | Unimodular gravity is classically equivalent to General Relativity. This equivalence extends to actions which are functions of the curvature scalar. At the quantum level, the dynamics could differ. Most importantly, the cosmological constant is not a coupling in the unimodular action, providing a new vantage point from which to address the cosmological constant fine-tuning problem. Here, a quantum theory based on the asymptotic safety scenario is studied, and evidence for an interacting fixed point in unimodular f(R) gravity is found. We study the fixed point and its properties, and also discuss the compatibility of unimodular asymptotic safety with dynamical matter, finding evidence for its compatibility with the matter degrees of freedom of the Standard Model. |
gr-qc/0311004 | Ghanashyam Date | Martin Bojowald, Ghanashyam Date and Kevin Vandersloot | Homogeneous Loop Quantum Cosmology: The Role of the Spin Connection | revtex4, 36 pages, 10 figures. In version 2 the introduction is
expanded, section III E is added and a paragraph on relevance of results is
added in the conclusions. Refs updated, results unchanged. To appear in
Class. Quant. Gravity | Class.Quant.Grav.21:1253-1278,2004 | 10.1088/0264-9381/21/4/034 | IMSc/2003/04/06, CGPG-03/10-5, AEI-2003-085 | gr-qc hep-th | null | Homogeneous cosmological models with non-vanishing intrinsic curvature
require a special treatment when they are quantized with loop quantum
cosmological methods. Guidance from the full theory which is lost in this
context can be replaced by two criteria for an acceptable quantization,
admissibility of a continuum approximation and local stability. A quantization
of the corresponding Hamiltonian constraints is presented and shown to lead to
a locally stable, non-singular evolution compatible with almost classical
behavior at large volume. As an application, the Bianchi IX model and its
modified behavior close to its classical singularity is explored.
| [
{
"created": "Mon, 3 Nov 2003 07:17:08 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jan 2004 12:35:30 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bojowald",
"Martin",
""
],
[
"Date",
"Ghanashyam",
""
],
[
"Vandersloot",
"Kevin",
""
]
] | Homogeneous cosmological models with non-vanishing intrinsic curvature require a special treatment when they are quantized with loop quantum cosmological methods. Guidance from the full theory which is lost in this context can be replaced by two criteria for an acceptable quantization, admissibility of a continuum approximation and local stability. A quantization of the corresponding Hamiltonian constraints is presented and shown to lead to a locally stable, non-singular evolution compatible with almost classical behavior at large volume. As an application, the Bianchi IX model and its modified behavior close to its classical singularity is explored. |
1911.03213 | Julio Arrechea | Julio Arrechea, Carlos Barcel\'o, Ra\'ul Carballo-Rubio, Luis J. Garay | Schwarzschild geometry counterpart in semiclassical gravity | 22 pages, 4 figures, v2: references and minor changes added to match
published version | Phys. Rev. D 101, 064059 (2020) | 10.1103/PhysRevD.101.064059 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the effects of vacuum polarization on vacuum static
spherically-symmetric spacetimes. We start from the Polyakov approximation to
the renormalized stress-energy tensor (RSET) of a minimally coupled massless
scalar field. This RSET is not regular at $r=0$, so we define a regularized
version of the Polyakov RSET. Using this Regularized RSET, and under the
previous symmetry assumptions, we find all the solutions to the semiclassical
field equations in vacuum. The resulting counterpart to the Schwarzschild
classical geometry substitutes the presence of an event horizon by a wormhole
throat that connects an external asymptotically flat region with an internal
asymptotic region possessing a naked singularity: there are no semiclassical
vacuum solutions with well-defined Cauchy surfaces. We also show that the
Regularized Polyakov RSET allows for wormhole geometries of arbitrarily small
throat radius. This analysis paves the way to future investigations of proper
stellar configurations with an internal non-vacuum region.
| [
{
"created": "Fri, 8 Nov 2019 12:23:27 GMT",
"version": "v1"
},
{
"created": "Wed, 6 May 2020 23:11:04 GMT",
"version": "v2"
}
] | 2020-05-08 | [
[
"Arrechea",
"Julio",
""
],
[
"Barceló",
"Carlos",
""
],
[
"Carballo-Rubio",
"Raúl",
""
],
[
"Garay",
"Luis J.",
""
]
] | We investigate the effects of vacuum polarization on vacuum static spherically-symmetric spacetimes. We start from the Polyakov approximation to the renormalized stress-energy tensor (RSET) of a minimally coupled massless scalar field. This RSET is not regular at $r=0$, so we define a regularized version of the Polyakov RSET. Using this Regularized RSET, and under the previous symmetry assumptions, we find all the solutions to the semiclassical field equations in vacuum. The resulting counterpart to the Schwarzschild classical geometry substitutes the presence of an event horizon by a wormhole throat that connects an external asymptotically flat region with an internal asymptotic region possessing a naked singularity: there are no semiclassical vacuum solutions with well-defined Cauchy surfaces. We also show that the Regularized Polyakov RSET allows for wormhole geometries of arbitrarily small throat radius. This analysis paves the way to future investigations of proper stellar configurations with an internal non-vacuum region. |
gr-qc/0104040 | Lee Samuel Finn | Lee Samuel Finn and Albert Lazzarini | Modulating the experimental signature of a stochastic gravitational wave
backgroun | 20 pages, including 5 in-lined figures. Submitted to PRD | Phys.Rev.D64:082002,2001 | 10.1103/PhysRevD.64.082002 | null | gr-qc | null | Detecting a stationary, stochastic gravitational wave signal is complicated
by impossibility of observing the detector noise independently of the signal.
One consequence is that we require at least two detectors to observe the
signal, which will be apparent in the cross-correlation of the detector
outputs. A corollary is that there remains a systematic error, associated with
the possible presence of correlated instrumental noise, in any observation
aimed at estimating or limiting a stochastic gravitational wave signal. Here we
describe a method of identifying this systematic error by varying the
orientation of one of the detectors, leading to separate and independent
modulations of the signal and noise contribution to the cross-correlation. Our
method can be applied to measurements of a stochastic gravitational wave
background by the ALLEGRO/LIGO Livingston Observatory detector pair. We explore
-- in the context of this detector pair -- how this new measurement technique
is insensitive to a cross-correlated detector noise component that can confound
a conventional measurement.
| [
{
"created": "Fri, 13 Apr 2001 22:58:12 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Finn",
"Lee Samuel",
""
],
[
"Lazzarini",
"Albert",
""
]
] | Detecting a stationary, stochastic gravitational wave signal is complicated by impossibility of observing the detector noise independently of the signal. One consequence is that we require at least two detectors to observe the signal, which will be apparent in the cross-correlation of the detector outputs. A corollary is that there remains a systematic error, associated with the possible presence of correlated instrumental noise, in any observation aimed at estimating or limiting a stochastic gravitational wave signal. Here we describe a method of identifying this systematic error by varying the orientation of one of the detectors, leading to separate and independent modulations of the signal and noise contribution to the cross-correlation. Our method can be applied to measurements of a stochastic gravitational wave background by the ALLEGRO/LIGO Livingston Observatory detector pair. We explore -- in the context of this detector pair -- how this new measurement technique is insensitive to a cross-correlated detector noise component that can confound a conventional measurement. |
1510.06245 | Alvin Chua | Alvin J. K. Chua, Jonathan R. Gair | Improved analytic extreme-mass-ratio inspiral model for scoping out
eLISA data analysis | 8 pages, 2 figures, accepted for publication as Fast Track
Communication in Classical and Quantum Gravity | Class. Quantum Grav. 32, 232002 (2015) | 10.1088/0264-9381/32/23/232002 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The space-based gravitational-wave detector eLISA has been selected as the
ESA L3 mission, and the mission design will be finalised by the end of this
decade. To prepare for mission formulation over the next few years, several
outstanding and urgent questions in data analysis will be addressed using mock
data challenges, informed by instrument measurements from the LISA Pathfinder
satellite launching at the end of 2015. These data challenges will require
accurate and computationally affordable waveform models for anticipated sources
such as the extreme-mass-ratio inspirals (EMRIs) of stellar-mass compact
objects into massive black holes. Previous data challenges have made use of the
well-known analytic EMRI waveforms of Barack and Cutler, which are extremely
quick to generate but dephase relative to more accurate waveforms within hours,
due to their mismatched radial, polar and azimuthal frequencies. In this paper,
we describe an augmented Barack-Cutler model that uses a frequency map to the
correct Kerr frequencies, along with updated evolution equations and a simple
fit to a more accurate model. The augmented waveforms stay in phase for months
and may be generated with virtually no additional computational cost.
| [
{
"created": "Wed, 21 Oct 2015 13:32:10 GMT",
"version": "v1"
}
] | 2015-11-10 | [
[
"Chua",
"Alvin J. K.",
""
],
[
"Gair",
"Jonathan R.",
""
]
] | The space-based gravitational-wave detector eLISA has been selected as the ESA L3 mission, and the mission design will be finalised by the end of this decade. To prepare for mission formulation over the next few years, several outstanding and urgent questions in data analysis will be addressed using mock data challenges, informed by instrument measurements from the LISA Pathfinder satellite launching at the end of 2015. These data challenges will require accurate and computationally affordable waveform models for anticipated sources such as the extreme-mass-ratio inspirals (EMRIs) of stellar-mass compact objects into massive black holes. Previous data challenges have made use of the well-known analytic EMRI waveforms of Barack and Cutler, which are extremely quick to generate but dephase relative to more accurate waveforms within hours, due to their mismatched radial, polar and azimuthal frequencies. In this paper, we describe an augmented Barack-Cutler model that uses a frequency map to the correct Kerr frequencies, along with updated evolution equations and a simple fit to a more accurate model. The augmented waveforms stay in phase for months and may be generated with virtually no additional computational cost. |
gr-qc/0002042 | Michael Bradley | M Berg, M Bradley | Are Simple Real Pole Solutions Physical? | 13 pages, 3 figures | Phys.Scripta 62 (2000) 17-22 | 10.1238/Physica.Regular.062a00017 | null | gr-qc | null | We consider exact solutions generated by the inverse scattering technique,
also known as the soliton transformation. In particular, we study the class of
simple real pole solutions. For quite some time, those solutions have been
considered interesting as models of cosmological shock waves. A coordinate
singularity on the wave fronts was removed by a transformation which induces a
null fluid with negative energy density on the wave front. This null fluid is
usually seen as another coordinate artifact, since there seems to be a general
belief that that this kind of solution can be seen as the real pole limit of
the smooth solution generated with a pair of complex conjugate poles in the
transformation. We perform this limit explicitly, and find that the belief is
unfounded: two coalescing complex conjugate poles cannot yield a solution with
one real pole. Instead, the two complex conjugate poles go to a different
limit, what we call a ``pole on a pole''. The limiting procedure is not unique;
it is sensitive to how quickly some parameters approach zero. We also show that
there exists no improved coordinate transformation which would remove the
negative energy density. We conclude that negative energy is an intrinsic part
of this class of solutions.
| [
{
"created": "Fri, 11 Feb 2000 18:17:55 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Berg",
"M",
""
],
[
"Bradley",
"M",
""
]
] | We consider exact solutions generated by the inverse scattering technique, also known as the soliton transformation. In particular, we study the class of simple real pole solutions. For quite some time, those solutions have been considered interesting as models of cosmological shock waves. A coordinate singularity on the wave fronts was removed by a transformation which induces a null fluid with negative energy density on the wave front. This null fluid is usually seen as another coordinate artifact, since there seems to be a general belief that that this kind of solution can be seen as the real pole limit of the smooth solution generated with a pair of complex conjugate poles in the transformation. We perform this limit explicitly, and find that the belief is unfounded: two coalescing complex conjugate poles cannot yield a solution with one real pole. Instead, the two complex conjugate poles go to a different limit, what we call a ``pole on a pole''. The limiting procedure is not unique; it is sensitive to how quickly some parameters approach zero. We also show that there exists no improved coordinate transformation which would remove the negative energy density. We conclude that negative energy is an intrinsic part of this class of solutions. |
gr-qc/0011003 | Shahar Hod | Shahar Hod and Tsvi Piran | Cosmic Censorship: The Role of Quantum Gravity | 7 pages. This essay received the Second Prize from the Gravity
Research Foundation 2000 | Gen.Rel.Grav. 32 (2000) 2333-2338 | 10.1023/A:1002098800227 | null | gr-qc astro-ph hep-th quant-ph | null | The cosmic censorship hypothesis introduced by Penrose thirty years ago is
still one of the most important open questions in {\it classical} general
relativity. In this essay we put forward the idea that cosmic censorship is
intrinsically a {\it quantum gravity} phenomena. To that end we construct a
gedanken experiment in which cosmic censorship is violated within the purely
{\it classical} framework of general relativity. We prove, however, that {\it
quantum} effects restore the validity of the conjecture. This suggests that
classical general relativity is inconsistent and that cosmic censorship might
be enforced only by a quantum theory of gravity.
| [
{
"created": "Wed, 1 Nov 2000 08:44:22 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Hod",
"Shahar",
""
],
[
"Piran",
"Tsvi",
""
]
] | The cosmic censorship hypothesis introduced by Penrose thirty years ago is still one of the most important open questions in {\it classical} general relativity. In this essay we put forward the idea that cosmic censorship is intrinsically a {\it quantum gravity} phenomena. To that end we construct a gedanken experiment in which cosmic censorship is violated within the purely {\it classical} framework of general relativity. We prove, however, that {\it quantum} effects restore the validity of the conjecture. This suggests that classical general relativity is inconsistent and that cosmic censorship might be enforced only by a quantum theory of gravity. |
gr-qc/0201081 | Lorenzo Iorio | Lorenzo Iorio | Constraints to a Yukawa gravitational potential from laser data to
LAGEOS satellites | LaTex, no figures, no tables. To appear in Physics Letters A | Phys.Lett. A298 (2002) 315-318 | 10.1016/S0375-9601(02)00580-7 | null | gr-qc astro-ph hep-ph physics.space-ph | null | In this paper we investigate the possibility of constraining the hypothesis
of a fifth force at the length scale of two Earth's radii by investigating the
effects of a Yukawa gravitational potential on the orbits of the laser--ranged
LAGEOS satellites. The existing constraints on the Yukawa coupling $\alpha$,
obtained by fitting the LAGEOS orbit, are of the order of | \alpha | <
10^{-5}-10^{-8} for distances of the order of 10^9 cm. Here we show that with a
suitable combination of the orbital residuals of the perigee \omega of LAGEOS
II and the nodes \Omega of LAGEOS II and LAGEOS it should be possible to
constrain \alpha at a level of 4 X 10^{-12} or less. Various sources of
systematic errors are accounted for, as well. Their total impact amounts to 1 X
10^{-11} during an observational time span of 5 years. In the near future, when
the new data on the terrestrial gravitational field will be available from the
CHAMP and GRACE missions, these limits will be further improved. The use of the
proposed LARES laser--ranged satellite would yield an experimental accuracy in
constraining \alpha of the order of 1 X 10^{-12}.
| [
{
"created": "Thu, 24 Jan 2002 14:09:34 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Apr 2002 14:18:47 GMT",
"version": "v2"
}
] | 2007-11-12 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper we investigate the possibility of constraining the hypothesis of a fifth force at the length scale of two Earth's radii by investigating the effects of a Yukawa gravitational potential on the orbits of the laser--ranged LAGEOS satellites. The existing constraints on the Yukawa coupling $\alpha$, obtained by fitting the LAGEOS orbit, are of the order of | \alpha | < 10^{-5}-10^{-8} for distances of the order of 10^9 cm. Here we show that with a suitable combination of the orbital residuals of the perigee \omega of LAGEOS II and the nodes \Omega of LAGEOS II and LAGEOS it should be possible to constrain \alpha at a level of 4 X 10^{-12} or less. Various sources of systematic errors are accounted for, as well. Their total impact amounts to 1 X 10^{-11} during an observational time span of 5 years. In the near future, when the new data on the terrestrial gravitational field will be available from the CHAMP and GRACE missions, these limits will be further improved. The use of the proposed LARES laser--ranged satellite would yield an experimental accuracy in constraining \alpha of the order of 1 X 10^{-12}. |
2310.08438 | Lisa Valerie Drummond | Lisa V. Drummond, Philip Lynch, Alexandra G. Hanselman, Devin R.
Becker, Scott A. Hughes | Extreme mass-ratio inspiral and waveforms for a spinning body into a
Kerr black hole via osculating geodesics and near-identity transformations | 38 pages, including 17 pages of Appendices, 13 figures. Submitted to
Physics Review D. This posting and submission supersedes arXiv:2305.08919, in
response to helpful critical referee feedback | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Understanding the orbits of spinning bodies in curved spacetime is important
for modeling binary black hole systems with small mass ratios. At zeroth order
in mass ratio, the smaller body moves on a geodesic. Post-geodesic effects are
needed to model the system accurately. One very important post-geodesic effect
is the gravitational self-force, which describes the small body's interaction
with its own contribution to a binary's spacetime. Another post-geodesic
effect, the spin-curvature force, is due to the smaller body's spin coupling to
spacetime curvature. In this paper, we combine the leading orbit-averaged
backreaction of point-particle gravitational-wave emission with the
spin-curvature force to construct the worldline and gravitational waveform for
a spinning body spiraling into a Kerr black hole. We use an osculating geodesic
integrator, which treats the worldline as evolution through a sequence of
geodesic orbits, as well as near-identity transformations, which eliminate
dependence on orbital phases, allowing for fast computation of inspirals. The
resulting inspirals and waveforms include all critical dynamical effects which
govern such systems (orbit and precession frequencies, inspiral, strong-field
gravitational-wave amplitudes), and as such form an effective first model for
the inspiral of spinning bodies into Kerr black holes. We emphasize that our
present calculation is not self consistent, since we neglect effects which
enter at the same order as effects we include. However, our analysis
demonstrates that the impact of spin-curvature forces can be incorporated into
EMRI waveform tools with relative ease. The calculation is sufficiently modular
that it should not be difficult to include neglected post-geodesic effects as
efficient tools for computing them become available. (Abridged)
| [
{
"created": "Thu, 12 Oct 2023 16:02:10 GMT",
"version": "v1"
}
] | 2023-10-13 | [
[
"Drummond",
"Lisa V.",
""
],
[
"Lynch",
"Philip",
""
],
[
"Hanselman",
"Alexandra G.",
""
],
[
"Becker",
"Devin R.",
""
],
[
"Hughes",
"Scott A.",
""
]
] | Understanding the orbits of spinning bodies in curved spacetime is important for modeling binary black hole systems with small mass ratios. At zeroth order in mass ratio, the smaller body moves on a geodesic. Post-geodesic effects are needed to model the system accurately. One very important post-geodesic effect is the gravitational self-force, which describes the small body's interaction with its own contribution to a binary's spacetime. Another post-geodesic effect, the spin-curvature force, is due to the smaller body's spin coupling to spacetime curvature. In this paper, we combine the leading orbit-averaged backreaction of point-particle gravitational-wave emission with the spin-curvature force to construct the worldline and gravitational waveform for a spinning body spiraling into a Kerr black hole. We use an osculating geodesic integrator, which treats the worldline as evolution through a sequence of geodesic orbits, as well as near-identity transformations, which eliminate dependence on orbital phases, allowing for fast computation of inspirals. The resulting inspirals and waveforms include all critical dynamical effects which govern such systems (orbit and precession frequencies, inspiral, strong-field gravitational-wave amplitudes), and as such form an effective first model for the inspiral of spinning bodies into Kerr black holes. We emphasize that our present calculation is not self consistent, since we neglect effects which enter at the same order as effects we include. However, our analysis demonstrates that the impact of spin-curvature forces can be incorporated into EMRI waveform tools with relative ease. The calculation is sufficiently modular that it should not be difficult to include neglected post-geodesic effects as efficient tools for computing them become available. (Abridged) |
0810.5336 | Evan Ochsner | K.G. Arun, Alessandra Buonanno, Guillaume Faye, Evan Ochsner | Higher-order spin effects in the amplitude and phase of gravitational
waveforms emitted by inspiraling compact binaries: Ready-to-use gravitational
waveforms | 43 pages, 10 Postscript figures. submitted to Physical Review D.
Includes corrections due to errata | Phys.Rev.D79:104023,2009; Erratum-ibid.D84:049901,2011 | 10.1103/PhysRevD.79.104023 10.1103/PhysRevD.84.049901 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide ready-to-use time-domain gravitational waveforms for spinning
compact binaries with precession effects through 1.5PN order in amplitude and
compute their mode decomposition using spin-weighted -2 spherical harmonics. In
the presence of precession, the gravitational-wave modes (l,m) contain
harmonics originating from combinations of the orbital frequency and precession
frequencies. We find that the gravitational radiation from binary systems with
large mass asymmetry and large inclination angle can be distributed among
several modes. For example, during the last stages of inspiral, for some
maximally spinning configurations, the amplitude of the (2,0) and (2,1) modes
can be comparable to the amplitude of the (2,2) mode. If the mass ratio is not
too extreme, the l=3 and l=4 modes are generally one or two orders of magnitude
smaller than the l = 2 modes. Restricting ourselves to spinning, non-precessing
compact binaries, we apply the stationary-phase approximation and derive the
frequency-domain gravitational waveforms including spin-orbit and spin(1)-
spin(2) effects through 1.5PN and 2PN order respectively in amplitude, and
2.5PN order in phase. Since spin effects in the amplitude through 2PN order
affect only the first and second harmonics of the orbital phase, they do not
extend the mass reach of gravitational-wave detectors. However, they can
interfere with other harmonics and lower or raise the signal-to-noise ratio
depending on the spin orientation. These ready-to-use waveforms could be
employed in the data-analysis of the spinning, inspiraling binaries as well as
in comparison studies at the interface between analytical and numerical
relativity.
| [
{
"created": "Wed, 29 Oct 2008 19:07:37 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jul 2011 16:19:53 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Jul 2011 22:19:16 GMT",
"version": "v3"
}
] | 2015-03-13 | [
[
"Arun",
"K. G.",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Faye",
"Guillaume",
""
],
[
"Ochsner",
"Evan",
""
]
] | We provide ready-to-use time-domain gravitational waveforms for spinning compact binaries with precession effects through 1.5PN order in amplitude and compute their mode decomposition using spin-weighted -2 spherical harmonics. In the presence of precession, the gravitational-wave modes (l,m) contain harmonics originating from combinations of the orbital frequency and precession frequencies. We find that the gravitational radiation from binary systems with large mass asymmetry and large inclination angle can be distributed among several modes. For example, during the last stages of inspiral, for some maximally spinning configurations, the amplitude of the (2,0) and (2,1) modes can be comparable to the amplitude of the (2,2) mode. If the mass ratio is not too extreme, the l=3 and l=4 modes are generally one or two orders of magnitude smaller than the l = 2 modes. Restricting ourselves to spinning, non-precessing compact binaries, we apply the stationary-phase approximation and derive the frequency-domain gravitational waveforms including spin-orbit and spin(1)- spin(2) effects through 1.5PN and 2PN order respectively in amplitude, and 2.5PN order in phase. Since spin effects in the amplitude through 2PN order affect only the first and second harmonics of the orbital phase, they do not extend the mass reach of gravitational-wave detectors. However, they can interfere with other harmonics and lower or raise the signal-to-noise ratio depending on the spin orientation. These ready-to-use waveforms could be employed in the data-analysis of the spinning, inspiraling binaries as well as in comparison studies at the interface between analytical and numerical relativity. |
gr-qc/9612008 | Martin Xavier | X. Martin and A. Vilenkin (Tufts University) | Gravitational radiation from monopoles connected by strings | 18 pages, RevTex and 2 postscript figures. Submitted to Phys. Rev. D | Phys.Rev.D55:6054-6060,1997 | 10.1103/PhysRevD.55.6054 | null | gr-qc | null | Monopole-antimonopole pairs connected by strings can be formed as topological
defects in a sequence of cosmological phase transitions. Such hybrid defects
typically decay early in the history of the universe but can still generate an
observable background of gravitational waves. We study the spectrum of
gravitational radiation from these objects both analytically and numerically,
concentrating on the simplest case of an oscillating pair connected by a
straight string.
| [
{
"created": "Mon, 2 Dec 1996 23:02:08 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Martin",
"X.",
"",
"Tufts University"
],
[
"Vilenkin",
"A.",
"",
"Tufts University"
]
] | Monopole-antimonopole pairs connected by strings can be formed as topological defects in a sequence of cosmological phase transitions. Such hybrid defects typically decay early in the history of the universe but can still generate an observable background of gravitational waves. We study the spectrum of gravitational radiation from these objects both analytically and numerically, concentrating on the simplest case of an oscillating pair connected by a straight string. |
gr-qc/0210021 | Francesco Belgiorno | F.Belgiorno | Quasi-Homogeneous Thermodynamics and Black Holes | 39 pages, uses RevteX. Published version (minor changes w.r.t. the
original one) | J.Math.Phys. 44 (2003) 1089-1128 | 10.1063/1.1542922 | null | gr-qc | null | We propose a generalized thermodynamics in which quasi-homogeneity of the
thermodynamic potentials plays a fundamental role. This thermodynamic formalism
arises from a generalization of the approach presented in paper [1], and it is
based on the requirement that quasi-homogeneity is a non-trivial symmetry for
the Pfaffian form $\delta Q_{rev}$. It is shown that quasi-homogeneous
thermodynamics fits the thermodynamic features of at least some
self-gravitating systems. We analyze how quasi-homogeneous thermodynamics is
suggested by black hole thermodynamics. Then, some existing results involving
self-gravitating systems are also shortly discussed in the light of this
thermodynamic framework. The consequences of the lack of extensivity are also
recalled. We show that generalized Gibbs-Duhem equations arise as a consequence
of quasi-homogeneity of the thermodynamic potentials. An heuristic link between
this generalized thermodynamic formalism and the thermodynamic limit is also
discussed.
| [
{
"created": "Mon, 7 Oct 2002 15:29:59 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Dec 2005 13:42:35 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Belgiorno",
"F.",
""
]
] | We propose a generalized thermodynamics in which quasi-homogeneity of the thermodynamic potentials plays a fundamental role. This thermodynamic formalism arises from a generalization of the approach presented in paper [1], and it is based on the requirement that quasi-homogeneity is a non-trivial symmetry for the Pfaffian form $\delta Q_{rev}$. It is shown that quasi-homogeneous thermodynamics fits the thermodynamic features of at least some self-gravitating systems. We analyze how quasi-homogeneous thermodynamics is suggested by black hole thermodynamics. Then, some existing results involving self-gravitating systems are also shortly discussed in the light of this thermodynamic framework. The consequences of the lack of extensivity are also recalled. We show that generalized Gibbs-Duhem equations arise as a consequence of quasi-homogeneity of the thermodynamic potentials. An heuristic link between this generalized thermodynamic formalism and the thermodynamic limit is also discussed. |
1506.04382 | Muhammed Amir | Sushant G. Ghosh, Muhammed Amir | Horizon structure of rotating Bardeen black hole and particle
acceleration | 12 pages, 11 figures, 4 tables, few changes and references added,
accepted in EPJC | null | 10.1140/epjc/s10052-015-3786-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the horizon structure and ergosphere in a rotating Bardeen
regular black hole, which has an additional parameter ($g$) due to magnetic
charge, apart from mass ($M$) and rotation parameter ($a$). Interestingly, for
each value of parameter $g$, there exist a critical rotation parameter
($a=a_{E}$), which corresponds to an extremal black hole with degenerate
horizons, while for $a<a_{E}$ describes a non-extremal black hole with two
horizons, and no black hole for $a>a_{E}$. We find that the extremal value
$a_E$ is also influenced by the parameter $g$ and so is the ergosphere. While
the value of $a_E$ remarkably decreases when compared with the Kerr black hole,
the ergosphere becomes more thick with increase in $g$. We also study collision
of two equal mass particle near the horizon of this black hole, and explicitly
bring out the effect of parameter $g$. The center-of-mass energy ($E_{CM}$) not
only depends on rotation parameter $a$, but also on parameter $g$. It is
demonstrated that the $E_{CM}$ could be arbitrary high in the extremal cases
when one of the colliding particle has critical angular momentum, thereby
suggesting that the rotating Bardeen regular black hole can act as a particle
accelerator.
| [
{
"created": "Sun, 14 Jun 2015 11:32:11 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Sep 2015 13:47:17 GMT",
"version": "v2"
},
{
"created": "Sun, 8 Nov 2015 13:30:29 GMT",
"version": "v3"
}
] | 2016-01-20 | [
[
"Ghosh",
"Sushant G.",
""
],
[
"Amir",
"Muhammed",
""
]
] | We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter ($g$) due to magnetic charge, apart from mass ($M$) and rotation parameter ($a$). Interestingly, for each value of parameter $g$, there exist a critical rotation parameter ($a=a_{E}$), which corresponds to an extremal black hole with degenerate horizons, while for $a<a_{E}$ describes a non-extremal black hole with two horizons, and no black hole for $a>a_{E}$. We find that the extremal value $a_E$ is also influenced by the parameter $g$ and so is the ergosphere. While the value of $a_E$ remarkably decreases when compared with the Kerr black hole, the ergosphere becomes more thick with increase in $g$. We also study collision of two equal mass particle near the horizon of this black hole, and explicitly bring out the effect of parameter $g$. The center-of-mass energy ($E_{CM}$) not only depends on rotation parameter $a$, but also on parameter $g$. It is demonstrated that the $E_{CM}$ could be arbitrary high in the extremal cases when one of the colliding particle has critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator. |
2010.16183 | Hemwati Nandan | Shubham Kala, Hemwati Nandan, Prateek Sharma | Deflection of Light Around a Rotating BTZ Black Hole | null | Modern Physics Letters A 2050323 (2020) | 10.1142/S021773232050323X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a detailed study of gravitational lensing around a rotating BTZ
black hole in (2+1) dimensional gravity. The study of orbits for massless test
particle around this BH spacetime is performed to describe the nature of
cosmological constant in lower dimensions. We study the effect of cosmological
constant on the photon orbit in view of other critical parameters. The bending
angle of light is studied in view of different values of cosmological constant
for direct and retrograde motion of test particles. It is being observed that
the bending angle slightly decreases as the value of cosmological constant
increases in the negative region.
| [
{
"created": "Fri, 30 Oct 2020 10:39:45 GMT",
"version": "v1"
}
] | 2020-11-02 | [
[
"Kala",
"Shubham",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Sharma",
"Prateek",
""
]
] | We present a detailed study of gravitational lensing around a rotating BTZ black hole in (2+1) dimensional gravity. The study of orbits for massless test particle around this BH spacetime is performed to describe the nature of cosmological constant in lower dimensions. We study the effect of cosmological constant on the photon orbit in view of other critical parameters. The bending angle of light is studied in view of different values of cosmological constant for direct and retrograde motion of test particles. It is being observed that the bending angle slightly decreases as the value of cosmological constant increases in the negative region. |
gr-qc/0004024 | Dumitru Baleanu | Dumitru Baleanu, Ayse Karasu | Lax Tensors, Killing Tensors and Geometric Duality | 9 pages LATEX | Mod.Phys.Lett. A14 (1999) 2597 | 10.1142/S0217732399002716 | null | gr-qc | null | The solution of the Lax tensor equations in the case
$L_{\alpha\beta\gamma}=-L_{\beta\alpha\gamma}$ was analyzed. The Lax tensors on
the dual metrics were investigated. We classified all two dimensional metrics
having the symmetric Lax tensor $L_{\alpha\beta\gamma}$. The Lax tensors of the
flat space, Rindler system and its dual were found.
| [
{
"created": "Sat, 8 Apr 2000 18:16:17 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Baleanu",
"Dumitru",
""
],
[
"Karasu",
"Ayse",
""
]
] | The solution of the Lax tensor equations in the case $L_{\alpha\beta\gamma}=-L_{\beta\alpha\gamma}$ was analyzed. The Lax tensors on the dual metrics were investigated. We classified all two dimensional metrics having the symmetric Lax tensor $L_{\alpha\beta\gamma}$. The Lax tensors of the flat space, Rindler system and its dual were found. |
1710.10599 | T. Damour | Thibault Damour | High-energy gravitational scattering and the general relativistic
two-body problem | 25 pages, 5 figures | Phys. Rev. D 97, 044038 (2018) | 10.1103/PhysRevD.97.044038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A technique for translating the classical scattering function of two
gravitationally interacting bodies into a corresponding (effective one-body)
Hamiltonian description has been recently introduced [Phys.\ Rev.\ D {\bf 94},
104015 (2016)]. Using this technique, we derive, for the first time, to
second-order in Newton's constant (i.e. one classical loop) the Hamiltonian of
two point masses having an arbitrary (possibly relativistic) relative velocity.
The resulting (second post-Minkowskian) Hamiltonian is found to have a tame
high-energy structure which we relate both to gravitational self-force studies
of large mass-ratio binary systems, and to the ultra high-energy quantum
scattering results of Amati, Ciafaloni and Veneziano. We derive several
consequences of our second post-Minkowskian Hamiltonian: (i) the need to use
special phase-space gauges to get a tame high-energy limit; and (ii)
predictions about a (rest-mass independent) linear Regge trajectory behavior of
high-angular-momenta, high-energy circular orbits. Ways of testing these
predictions by dedicated numerical simulations are indicated. We finally
indicate a way to connect our classical results to the quantum gravitational
scattering amplitude of two particles, and we urge amplitude experts to use
their novel techniques to compute the 2-loop scattering amplitude of scalar
masses, from which one could deduce the third post-Minkowskian effective
one-body Hamiltonian.
| [
{
"created": "Sun, 29 Oct 2017 12:16:27 GMT",
"version": "v1"
}
] | 2018-03-07 | [
[
"Damour",
"Thibault",
""
]
] | A technique for translating the classical scattering function of two gravitationally interacting bodies into a corresponding (effective one-body) Hamiltonian description has been recently introduced [Phys.\ Rev.\ D {\bf 94}, 104015 (2016)]. Using this technique, we derive, for the first time, to second-order in Newton's constant (i.e. one classical loop) the Hamiltonian of two point masses having an arbitrary (possibly relativistic) relative velocity. The resulting (second post-Minkowskian) Hamiltonian is found to have a tame high-energy structure which we relate both to gravitational self-force studies of large mass-ratio binary systems, and to the ultra high-energy quantum scattering results of Amati, Ciafaloni and Veneziano. We derive several consequences of our second post-Minkowskian Hamiltonian: (i) the need to use special phase-space gauges to get a tame high-energy limit; and (ii) predictions about a (rest-mass independent) linear Regge trajectory behavior of high-angular-momenta, high-energy circular orbits. Ways of testing these predictions by dedicated numerical simulations are indicated. We finally indicate a way to connect our classical results to the quantum gravitational scattering amplitude of two particles, and we urge amplitude experts to use their novel techniques to compute the 2-loop scattering amplitude of scalar masses, from which one could deduce the third post-Minkowskian effective one-body Hamiltonian. |
1703.09214 | Francesco De Martini | Francesco De Martini | The Higgs field and the resolution of the Cosmological Constant Paradox
in the Weyl geometrical Universe | Philosophical Transactions A of the Royal Society (2017) | null | 10.1098/rsta.2016.0388 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard electroweak theory of leptons and the conformal groups of
spacetime Weyl's transformations are at the core of a general relativistic,
conformally covariant scalar tensor theory aimed at the resolution of the most
intriguing enigma of modern Physics: the cosmological constant paradox
(hereafter: Lambda paradox. A Higgs mechanism within a spontaneous symmetry
breaking process offers formal connections, via an effective potential V(eff),
between some relevant properties of the elementary particles and the dark
energy content of the Universe. The nonintegrable application of the Weyl's
geometry leads to a Proca equation accounting for the dynamics of a
vector-meson proposed as an optimum candidate for Dark Matter. The average
vacuum-energy density in the Universe and the "cosmological constant" are
evaluated on the basis of the recent experimental data of the PLANCK Mission.
The resolution of the paradox is found for all exponential inflationary
potentials and is consistent with the experimental data. The result of the
theory: Lambda=6|V(eff)|shows that the paradox is determined by the algebraic
mismatch between two large counteracting functions of the scalar field
contributing to V(eff). The critical stability of the Universe is discussed.
| [
{
"created": "Sat, 25 Mar 2017 17:01:57 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Apr 2017 14:10:55 GMT",
"version": "v2"
},
{
"created": "Fri, 5 May 2017 19:27:39 GMT",
"version": "v3"
},
{
"created": "Sun, 3 Sep 2017 19:50:16 GMT",
"version": "v4"
},
{
"created": "Thu, 19 Oct 2017 10:28:12 GMT",
"version": "v5"
},
{
"created": "Sun, 3 Dec 2017 14:53:35 GMT",
"version": "v6"
},
{
"created": "Mon, 1 Jan 2018 17:46:16 GMT",
"version": "v7"
},
{
"created": "Mon, 29 Jan 2018 16:05:15 GMT",
"version": "v8"
},
{
"created": "Mon, 26 Feb 2018 16:38:44 GMT",
"version": "v9"
}
] | 2018-02-27 | [
[
"De Martini",
"Francesco",
""
]
] | The standard electroweak theory of leptons and the conformal groups of spacetime Weyl's transformations are at the core of a general relativistic, conformally covariant scalar tensor theory aimed at the resolution of the most intriguing enigma of modern Physics: the cosmological constant paradox (hereafter: Lambda paradox. A Higgs mechanism within a spontaneous symmetry breaking process offers formal connections, via an effective potential V(eff), between some relevant properties of the elementary particles and the dark energy content of the Universe. The nonintegrable application of the Weyl's geometry leads to a Proca equation accounting for the dynamics of a vector-meson proposed as an optimum candidate for Dark Matter. The average vacuum-energy density in the Universe and the "cosmological constant" are evaluated on the basis of the recent experimental data of the PLANCK Mission. The resolution of the paradox is found for all exponential inflationary potentials and is consistent with the experimental data. The result of the theory: Lambda=6|V(eff)|shows that the paradox is determined by the algebraic mismatch between two large counteracting functions of the scalar field contributing to V(eff). The critical stability of the Universe is discussed. |
gr-qc/0611066 | Kazuhiro Yamamoto | Hidenori Nomura, Misao Sasaki, Kazuhiro Yamamoto | Classical and quantum radiation from a moving charge in an expanding
universe | 16 pages, JCAP in press | JCAP 0611:013,2006 | 10.1088/1475-7516/2006/11/013 | HUPD-0613, YITP-06-60 | gr-qc | null | We investigate photon emission from a moving particle in an expanding
universe. This process is analogous to the radiation from an accelerated charge
in the classical electromagnetic theory. Using the framework of quantum field
theory in curved spacetime, we demonstrate that the Wentzel-Kramers-Brillouin
(WKB) approximation leads to the Larmor formula for the rate of the radiation
energy from a moving charge in an expanding universe. Using exactly solvable
models in a radiation-dominated universe and in a Milne universe, we examine
the validity of the WKB formula. It is shown that the quantum effect suppresses
the radiation energy in comparison with the WKB formula.
| [
{
"created": "Mon, 13 Nov 2006 09:16:21 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Nov 2006 07:10:20 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Nomura",
"Hidenori",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Yamamoto",
"Kazuhiro",
""
]
] | We investigate photon emission from a moving particle in an expanding universe. This process is analogous to the radiation from an accelerated charge in the classical electromagnetic theory. Using the framework of quantum field theory in curved spacetime, we demonstrate that the Wentzel-Kramers-Brillouin (WKB) approximation leads to the Larmor formula for the rate of the radiation energy from a moving charge in an expanding universe. Using exactly solvable models in a radiation-dominated universe and in a Milne universe, we examine the validity of the WKB formula. It is shown that the quantum effect suppresses the radiation energy in comparison with the WKB formula. |
0905.2974 | Sam Dolan Dr | Sam Dolan and Jonathan Gair | The massive Dirac field on a rotating black hole spacetime: Angular
solutions | 22 pages, 6 figures. Minor corrections, to match published version | Class.Quant.Grav.26:175020,2009 | 10.1088/0264-9381/26/17/175020 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The massive Dirac equation on a Kerr-Newman background may be solved by the
method of separation of variables. The radial and angular equations are coupled
via an angular eigenvalue, which is determined from the Chandrasekhar-Page (CP)
equation. Obtaining accurate angular eigenvalues is a key step in studying
scattering, absorption and emission of the fermionic field.
Here we introduce a new method for finding solutions of the CP equation.
First, we introduce a novel representation for the spin-half spherical
harmonics. Next, we decompose the angular solutions of the CP equation (the
mass-dependent spin-half spheroidal harmonics) in the spherical basis. The
method yields a three-term recurrence relation which may be solved numerically
via continued-fraction methods, or perturbatively to obtain a series expansion
for the eigenvalues. In the case $\mu = \pm \omega$ (where $\omega$ and $\mu$
are the frequency and mass of the fermion) we obtain eigenvalues and
eigenfunctions in closed form. We study the eigenvalue spectrum, and the zeros
of the maximally co-rotating mode.
We compare our results with previous studies, and uncover and correct some
errors in the literature. We provide series expansions, tables of eigenvalues
and numerical fits across a wide parameter range, and present plots of a
selection of eigenfunctions. It is hoped this study will be a useful resource
for all researchers interested in the Dirac equation on a rotating black hole
background.
| [
{
"created": "Mon, 18 May 2009 20:15:34 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2009 01:30:18 GMT",
"version": "v2"
}
] | 2010-03-25 | [
[
"Dolan",
"Sam",
""
],
[
"Gair",
"Jonathan",
""
]
] | The massive Dirac equation on a Kerr-Newman background may be solved by the method of separation of variables. The radial and angular equations are coupled via an angular eigenvalue, which is determined from the Chandrasekhar-Page (CP) equation. Obtaining accurate angular eigenvalues is a key step in studying scattering, absorption and emission of the fermionic field. Here we introduce a new method for finding solutions of the CP equation. First, we introduce a novel representation for the spin-half spherical harmonics. Next, we decompose the angular solutions of the CP equation (the mass-dependent spin-half spheroidal harmonics) in the spherical basis. The method yields a three-term recurrence relation which may be solved numerically via continued-fraction methods, or perturbatively to obtain a series expansion for the eigenvalues. In the case $\mu = \pm \omega$ (where $\omega$ and $\mu$ are the frequency and mass of the fermion) we obtain eigenvalues and eigenfunctions in closed form. We study the eigenvalue spectrum, and the zeros of the maximally co-rotating mode. We compare our results with previous studies, and uncover and correct some errors in the literature. We provide series expansions, tables of eigenvalues and numerical fits across a wide parameter range, and present plots of a selection of eigenfunctions. It is hoped this study will be a useful resource for all researchers interested in the Dirac equation on a rotating black hole background. |
2010.15019 | Rio Saitou | Rio Saitou and Hiromi Saida | Light deflection in Observation: Angle differences between two null
geodesics on the de Sitter spacetime with multi-lensing objects | 9 pages, 2 figures, Affiliation and e-mail addresses are just added | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive angle differences between two null geodesics, propagating from
light sources to an observer, on the de Sitter spacetime with multi-lensing
objects. Assuming the lensing objects are mass monopoles on the de Sitter
background, we derive the metric tensor by solving the Einstein equation
perturbatively. On that spacetime, we solve a null geodesic parametrized by the
coordinate time. Using the null geodesics, we define the angle differences in a
coordinate invariant way. We take in the relativistic effects up to the first
order of perturbation and clarify the magnitude of approximation errors. We
find that the rest observer, who sees the isotropic cosmic space, implicitly
observes the effect of the cosmological constant on the angle differences
through the positions of the light sources. As a practical application, we
regard the massive black hole at our galactic center (Sgr A*) and the solar
system as the lensing objects, further a star and a flare around Sgr A* as the
light sources. We write the angle differences between these light sources using
their spatial coordinates. We find that deflections by Sgr A* remain in the
angle differences while deflections by the solar system cancel out up to the
first order of perturbation. The deflections by Sgr A* amounts around 10
microarcseconds, which is detectable in the near future observations.
| [
{
"created": "Wed, 28 Oct 2020 14:52:04 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Oct 2020 10:42:52 GMT",
"version": "v2"
}
] | 2020-10-30 | [
[
"Saitou",
"Rio",
""
],
[
"Saida",
"Hiromi",
""
]
] | We derive angle differences between two null geodesics, propagating from light sources to an observer, on the de Sitter spacetime with multi-lensing objects. Assuming the lensing objects are mass monopoles on the de Sitter background, we derive the metric tensor by solving the Einstein equation perturbatively. On that spacetime, we solve a null geodesic parametrized by the coordinate time. Using the null geodesics, we define the angle differences in a coordinate invariant way. We take in the relativistic effects up to the first order of perturbation and clarify the magnitude of approximation errors. We find that the rest observer, who sees the isotropic cosmic space, implicitly observes the effect of the cosmological constant on the angle differences through the positions of the light sources. As a practical application, we regard the massive black hole at our galactic center (Sgr A*) and the solar system as the lensing objects, further a star and a flare around Sgr A* as the light sources. We write the angle differences between these light sources using their spatial coordinates. We find that deflections by Sgr A* remain in the angle differences while deflections by the solar system cancel out up to the first order of perturbation. The deflections by Sgr A* amounts around 10 microarcseconds, which is detectable in the near future observations. |
1107.5650 | Thomas M\"uller | Thomas M\"uller and Daniel Weiskopf | Detailed study of null and time-like geodesics in the Alcubierre Warp
spacetime | null | null | 10.1007/s10714-011-1289-0 | null | gr-qc physics.pop-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Alcubierre warp spacetime yields a fascinating chance for comfortable
interstellar travel between arbitrary distant places without the time dilation
effect as in special relativistic flights. Even though the warp spacetime needs
exotic matter for its construction and is thus far from being physically
feasible, it offers a rich playground for studying geodesics in the general
theory of relativity. This paper is addressed to graduate students who have
finished a first course in general relativity to give them a deeper inside in
the calculation of non-affinely parametrized null and time-like geodesics and a
straightforward approach to determine the gravitational lensing effect due to
curved spacetime by means of the Jacobi equation. Both topics are necessary for
a thorough discussion of the visual effects as observed by a traveller inside
the warp bubble or a person looking from outside. The visual effects of the
traveller can be reproduced with an interactive Java application.
| [
{
"created": "Thu, 28 Jul 2011 08:59:51 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Müller",
"Thomas",
""
],
[
"Weiskopf",
"Daniel",
""
]
] | The Alcubierre warp spacetime yields a fascinating chance for comfortable interstellar travel between arbitrary distant places without the time dilation effect as in special relativistic flights. Even though the warp spacetime needs exotic matter for its construction and is thus far from being physically feasible, it offers a rich playground for studying geodesics in the general theory of relativity. This paper is addressed to graduate students who have finished a first course in general relativity to give them a deeper inside in the calculation of non-affinely parametrized null and time-like geodesics and a straightforward approach to determine the gravitational lensing effect due to curved spacetime by means of the Jacobi equation. Both topics are necessary for a thorough discussion of the visual effects as observed by a traveller inside the warp bubble or a person looking from outside. The visual effects of the traveller can be reproduced with an interactive Java application. |
gr-qc/9710109 | Clement Gerard | Gerard Clement | From Schwarzschild to Kerr: Generating spinning Einstein-maxwell fields
from static fields | 8 pages, Latex | Phys.Rev. D57 (1998) 4885-4889 | 10.1103/PhysRevD.57.4885 | DF-UFES 002/97 | gr-qc hep-th | null | The Kerr solution is generated from the Schwarzschild solution by a simple
combination of real global coordinate transformations and of invariance
transformations acting on the space of stationary solutions of the
Einstein-Maxwell equations. The same transformation can be used to generate a
spinning field configuration from any static axisymmetric configuration. We
illustrate this by generating from the continuous family of Voorhees--Zipoy
vacuum solutions a family of solutions endowed with mass, angular momentum,
dipole magnetic moment and quadrupole electric moment.
| [
{
"created": "Thu, 23 Oct 1997 18:52:54 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Clement",
"Gerard",
""
]
] | The Kerr solution is generated from the Schwarzschild solution by a simple combination of real global coordinate transformations and of invariance transformations acting on the space of stationary solutions of the Einstein-Maxwell equations. The same transformation can be used to generate a spinning field configuration from any static axisymmetric configuration. We illustrate this by generating from the continuous family of Voorhees--Zipoy vacuum solutions a family of solutions endowed with mass, angular momentum, dipole magnetic moment and quadrupole electric moment. |
gr-qc/0601015 | Ignazio Ciufolini | Ignazio Ciufolini and Erricos Pavlis | On the Measurement of the Lense-Thirring effect Using the Nodes of the
LAGEOS Satellites in reply to "On the reliability of the so-far performed
tests for measuring the Lense-Thirring effect with the LAGEOS satellites" by
L. Iorio | Added: the precise references to the the ArXiv papers of L. Iorio:
gr-qc/0411024 v9 19 Apr 2005 and gr-qc/0411084 v5 19 Apr 2005, explicitly
containing his proposal to use the mean anomaly | New Astron. 10 (2005) 636-651 | 10.1016/j.newast.2005.04.003 | null | gr-qc | null | In this paper, we provide a detailed description of our recent analysis and
determination of the frame-dragging effect obtained using the nodes of the
satellites LAGEOS and LAGEOS 2, in reply to the paper "On the reliability of
the so-far performed tests for measuring the Lense-Thirring effect with the
LAGEOS satellites" by L. Iorio
| [
{
"created": "Wed, 4 Jan 2006 19:22:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ciufolini",
"Ignazio",
""
],
[
"Pavlis",
"Erricos",
""
]
] | In this paper, we provide a detailed description of our recent analysis and determination of the frame-dragging effect obtained using the nodes of the satellites LAGEOS and LAGEOS 2, in reply to the paper "On the reliability of the so-far performed tests for measuring the Lense-Thirring effect with the LAGEOS satellites" by L. Iorio |
gr-qc/0203052 | Johannes Ruoff | Johannes Ruoff, Adamantios Stavridis, Kostas D. Kokkotas | Inertial modes of slowly rotating relativistic stars in the Cowling
approximation | 18 pages, 4 figures, MNRAS typesetting | Mon.Not.Roy.Astron.Soc.339:1170,2003 | 10.1046/j.1365-8711.2003.06267.x | null | gr-qc astro-ph | null | We study oscillations of slowly rotating relativistic barotropic as well as
non-barotropic polytropic stars in the Cowling approximation, including first
order rotational corrections. By taking into account the coupling between the
polar and axial equations, we find that, in contrast to previous results, the
$m=2$ $r$ modes are essentially unaffected by the continuous spectrum and exist
even for very relativistic stellar models. We perform our calculations both in
the time and frequency domain. In order to numerically solve the infinite
system of coupled equations, we truncate it at some value $l_{\rm max}$.
Although the time dependent equations can be numerically evolved without any
problems, the eigenvalue equations possess a singular structure, which is
related to the existence of a continuous spectrum. This prevents the numerical
computation of an eigenmode if its eigenfrequency falls inside the continuous
spectrum. The properties of the latter depend strongly on the cut-off value
$l_{\rm max}$ and it can consist of several either disconnected or overlapping
patches, which are the broader the more relativistic the stellar model is. By
discussing the dependence of the continuous spectrum as a function of both the
cut-off value $l_{\rm max}$ and the compactness $M/R$, we demonstrate how it
affects the inertial modes. Through the time evolutions we are able to show
that some of the inertial modes can actually exist inside the continuous
spectrum, but some cannot. For more compact and therefore more relativistic
stellar models, the width of the continuous spectrum strongly increases and as
a consequence, some of the inertial modes, which exist in less relativistic
stars, disappear.
| [
{
"created": "Thu, 14 Mar 2002 15:46:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ruoff",
"Johannes",
""
],
[
"Stavridis",
"Adamantios",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | We study oscillations of slowly rotating relativistic barotropic as well as non-barotropic polytropic stars in the Cowling approximation, including first order rotational corrections. By taking into account the coupling between the polar and axial equations, we find that, in contrast to previous results, the $m=2$ $r$ modes are essentially unaffected by the continuous spectrum and exist even for very relativistic stellar models. We perform our calculations both in the time and frequency domain. In order to numerically solve the infinite system of coupled equations, we truncate it at some value $l_{\rm max}$. Although the time dependent equations can be numerically evolved without any problems, the eigenvalue equations possess a singular structure, which is related to the existence of a continuous spectrum. This prevents the numerical computation of an eigenmode if its eigenfrequency falls inside the continuous spectrum. The properties of the latter depend strongly on the cut-off value $l_{\rm max}$ and it can consist of several either disconnected or overlapping patches, which are the broader the more relativistic the stellar model is. By discussing the dependence of the continuous spectrum as a function of both the cut-off value $l_{\rm max}$ and the compactness $M/R$, we demonstrate how it affects the inertial modes. Through the time evolutions we are able to show that some of the inertial modes can actually exist inside the continuous spectrum, but some cannot. For more compact and therefore more relativistic stellar models, the width of the continuous spectrum strongly increases and as a consequence, some of the inertial modes, which exist in less relativistic stars, disappear. |
gr-qc/9704025 | Vitorio Alberto De Lorenci | M. Novello and V. A. De Lorenci | The Binary Pulsar Is Not the Ultimate Test for the Theory of Gravity | 14 pages, LaTex, no figures | null | null | CBPF-NF-025/97 | gr-qc | null | General relativity can be formulated either as in its original geometrical
version (Einstein, 1915) or as a field theory (Feynman, 1962). In the Feynman
presentation of Einstein theory an hypothesis concerning the interaction of
gravity to gravity, which was hidden in the original version, becomes explicit.
This is nothing but the assumed extension of the validity of the equivalence
principle not only for matter-gravity interaction, but also for
gravity-gravity. Recently we have presented a field theory of gravity (from
here on called the NDL theory) which does not contain such a hypothesis. We
have shown that, for this theory, both the cosmological structure and the PPN
approximation for the solar tests are satisfied.
The proposal of this paper is to go one step further and to show that NDL
theory is able to solve the problem of radiation emission by a binary pulsar in
the same degree of accuracy as it was done in the GR theory. In the
post-Newtonian order of approximation we show that the quadrupole formula of
this theory is equal to the corresponding one in general relativity. Thus, the
unique actual observable distinction of these theories concerns the velocity of
gravitational waves, which becomes then the true ultimate test for gravity
theory.
| [
{
"created": "Tue, 8 Apr 1997 19:48:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Novello",
"M.",
""
],
[
"De Lorenci",
"V. A.",
""
]
] | General relativity can be formulated either as in its original geometrical version (Einstein, 1915) or as a field theory (Feynman, 1962). In the Feynman presentation of Einstein theory an hypothesis concerning the interaction of gravity to gravity, which was hidden in the original version, becomes explicit. This is nothing but the assumed extension of the validity of the equivalence principle not only for matter-gravity interaction, but also for gravity-gravity. Recently we have presented a field theory of gravity (from here on called the NDL theory) which does not contain such a hypothesis. We have shown that, for this theory, both the cosmological structure and the PPN approximation for the solar tests are satisfied. The proposal of this paper is to go one step further and to show that NDL theory is able to solve the problem of radiation emission by a binary pulsar in the same degree of accuracy as it was done in the GR theory. In the post-Newtonian order of approximation we show that the quadrupole formula of this theory is equal to the corresponding one in general relativity. Thus, the unique actual observable distinction of these theories concerns the velocity of gravitational waves, which becomes then the true ultimate test for gravity theory. |
1110.1223 | Georgios Kraniotis | G. V. Kraniotis | Exact deflection of a Neutral-Tachyon in the Kerr's Gravitational field | 8 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve in closed analytic form space-like geodesic equations in the Kerr
gravitational field. Such geodesic equations describe the motion of neutral
tachyons (faster than light particles) in the Kerr spacetime. More specifically
we derive the closed form solution for the deflection angle of a neutral
tachyon on an equatorial orbit in Kerr spacetime. The solution is expressed
elegantly in terms of Lauricella's hypergeometric function F_{D}.We applied our
results to three cases: first, for the calculation of the deflection angle of a
neutral tachyon on an equatorial trajectory in the gravitational field of a
Kerr black hole. Subsequently, we applied our exact solutions to compute the
deflection angle of equatorial spacelike geodesics in the gravitational fields
of Sun and Earth assuming the Kerr spacetime geometry.
| [
{
"created": "Thu, 6 Oct 2011 11:04:11 GMT",
"version": "v1"
}
] | 2011-10-13 | [
[
"Kraniotis",
"G. V.",
""
]
] | We solve in closed analytic form space-like geodesic equations in the Kerr gravitational field. Such geodesic equations describe the motion of neutral tachyons (faster than light particles) in the Kerr spacetime. More specifically we derive the closed form solution for the deflection angle of a neutral tachyon on an equatorial orbit in Kerr spacetime. The solution is expressed elegantly in terms of Lauricella's hypergeometric function F_{D}.We applied our results to three cases: first, for the calculation of the deflection angle of a neutral tachyon on an equatorial trajectory in the gravitational field of a Kerr black hole. Subsequently, we applied our exact solutions to compute the deflection angle of equatorial spacelike geodesics in the gravitational fields of Sun and Earth assuming the Kerr spacetime geometry. |
1507.05878 | Kalin Staykov | Kalin Staykov, K. Yavuz Ek\c{s}i, Stoytcho S. Yazadjiev, M. Metehan
T\"urko\u{g}lu, A. Sava\c{s} Arapo\u{g}lu | Moment of inertia of neutron star crust in alternative and modified
theories of gravity | 8 pages, 3 figures, v2 matches version published on Phys. Rev. D | Phys. Rev. D 94, 024056 (2016) | 10.1103/PhysRevD.94.024056 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The glitch activity of young pulsars arises from the exchange of angular
momentum between the crust and the interior of the star. Recently, it was
inferred that the moment of inertia of the crust of a neutron star is not
sufficient to explain the observed glitches. Such estimates are presumed in the
Einstein's general relativity in describing the hydrostatic equilibrium of
neutron stars. The crust of the neutron star has a space-time curvature of 14
orders of magnitude larger than that probed in solar system tests. This makes
gravity the weakest constrained physics input in the crust related processes.
We calculate the ratio of the crustal to the total moment of inertia of neutron
stars in the scalar-tensor theory of gravity and the non-perturbative $f({\cal
R})={\cal R}+ a {\cal R}^2$ gravity. We find for the former that the crust to
core ratio of the moment of inertia does not change significantly from what is
inferred in general relativity. For the latter we find that the ratio increases
significantly from what is inferred in general relativity in the case of high
mass objects. Our results suggest that the glitch activity of pulsars may be
used to probe gravity models, although the gravity models explored in this work
are not appropriate candidates.
| [
{
"created": "Tue, 21 Jul 2015 15:44:53 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Aug 2016 12:43:51 GMT",
"version": "v2"
}
] | 2016-08-02 | [
[
"Staykov",
"Kalin",
""
],
[
"Ekşi",
"K. Yavuz",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
],
[
"Türkoğlu",
"M. Metehan",
""
],
[
"Arapoğlu",
"A. Savaş",
""
]
] | The glitch activity of young pulsars arises from the exchange of angular momentum between the crust and the interior of the star. Recently, it was inferred that the moment of inertia of the crust of a neutron star is not sufficient to explain the observed glitches. Such estimates are presumed in the Einstein's general relativity in describing the hydrostatic equilibrium of neutron stars. The crust of the neutron star has a space-time curvature of 14 orders of magnitude larger than that probed in solar system tests. This makes gravity the weakest constrained physics input in the crust related processes. We calculate the ratio of the crustal to the total moment of inertia of neutron stars in the scalar-tensor theory of gravity and the non-perturbative $f({\cal R})={\cal R}+ a {\cal R}^2$ gravity. We find for the former that the crust to core ratio of the moment of inertia does not change significantly from what is inferred in general relativity. For the latter we find that the ratio increases significantly from what is inferred in general relativity in the case of high mass objects. Our results suggest that the glitch activity of pulsars may be used to probe gravity models, although the gravity models explored in this work are not appropriate candidates. |
gr-qc/0610155 | Marc-Thierry Jaekel | Marc-Thierry Jaekel (LPTENS), Serge Reynaud (LKB - Jussieu) | Radar ranging and Doppler tracking in post-Einsteinian metric theories
of gravity | 15 pages | Class.Quant.Grav. 23 (2006) 7561 | 10.1088/0264-9381/23/24/025 | null | gr-qc | null | The study of post-Einsteinian metric extensions of general relativity (GR),
which preserve the metric interpretation of gravity while considering metrics
which may differ from that predicted by GR, is pushed one step further. We give
a complete description of radar ranging and Doppler tracking in terms of the
time delay affecting an electromagnetic signal travelling between the Earth and
a remote probe. Results of previous publications concerning the Pioneer anomaly
are corrected and an annually modulated anomaly is predicted besides the
secular anomaly. Their correlation is shown to play an important role when
extracting reliable information from Pioneer observations. The formalism
developed here provides a basis for a quantitative analysis of the Pioneer
data, in order to assess whether extended metric theories can be the
appropriate description of gravity in the solar system.
| [
{
"created": "Mon, 30 Oct 2006 19:25:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Jaekel",
"Marc-Thierry",
"",
"LPTENS"
],
[
"Reynaud",
"Serge",
"",
"LKB - Jussieu"
]
] | The study of post-Einsteinian metric extensions of general relativity (GR), which preserve the metric interpretation of gravity while considering metrics which may differ from that predicted by GR, is pushed one step further. We give a complete description of radar ranging and Doppler tracking in terms of the time delay affecting an electromagnetic signal travelling between the Earth and a remote probe. Results of previous publications concerning the Pioneer anomaly are corrected and an annually modulated anomaly is predicted besides the secular anomaly. Their correlation is shown to play an important role when extracting reliable information from Pioneer observations. The formalism developed here provides a basis for a quantitative analysis of the Pioneer data, in order to assess whether extended metric theories can be the appropriate description of gravity in the solar system. |
1612.05725 | Xinhe Meng | Deng Wang, Xin-He Meng | Wormholes from cosmological reconstruction based on Gaussian processes | null | Phys.Dark Univ. 16 (2017) 81-86 | 10.1016/j.dark.2017.04.006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the model-independent traversable wormholes from cosmological
reconstruction based on Gaussian processes (GP). Using a combination of Union
2.1 SNe Ia data, the latest observational Hubble parameter data and recent
Planck's shift parameter, we find that our GP method can give a tighter
constraint on the normalized comoving distance, its derivatives and the dark
energy equation of state than the previous work \cite{1}. Subsequently, two
specific traversable wormhole solutions are obtained, i.e., the cases of a
constant redshift function and a linear shape function. We find that, with
decreasing cosmic acceleration, the traversal velocity $v$ of the former case
increases and the amounts of exotic matter $I_V$ of the latter case decreases.
| [
{
"created": "Sat, 17 Dec 2016 09:27:51 GMT",
"version": "v1"
}
] | 2017-05-30 | [
[
"Wang",
"Deng",
""
],
[
"Meng",
"Xin-He",
""
]
] | We study the model-independent traversable wormholes from cosmological reconstruction based on Gaussian processes (GP). Using a combination of Union 2.1 SNe Ia data, the latest observational Hubble parameter data and recent Planck's shift parameter, we find that our GP method can give a tighter constraint on the normalized comoving distance, its derivatives and the dark energy equation of state than the previous work \cite{1}. Subsequently, two specific traversable wormhole solutions are obtained, i.e., the cases of a constant redshift function and a linear shape function. We find that, with decreasing cosmic acceleration, the traversal velocity $v$ of the former case increases and the amounts of exotic matter $I_V$ of the latter case decreases. |
1809.05329 | Yan Peng | Yan Peng | Hair formation in the background of noncommutative reflecting stars | 12 pages, 4 figures | Nuclear Physics B 938 (2019) 143-153 | 10.1016/j.nuclphysb.2018.11.008 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate scalar condensations around noncommutative compact reflecting
stars. We find that the neutral noncommutative reflecting star cannot support
the existence of scalar field hairs. In the charged noncommutative reflecting
star spacetime, we provide upper bounds for star radii. Above the bound, scalar
fields cannot exist outside the star. In contrast, when the star radius is
below the bound, we show that the scalar field can condense. We also obtain the
largest radii of scalar hairy reflecting stars.
| [
{
"created": "Fri, 14 Sep 2018 09:48:49 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Nov 2018 13:42:24 GMT",
"version": "v2"
}
] | 2018-11-20 | [
[
"Peng",
"Yan",
""
]
] | We investigate scalar condensations around noncommutative compact reflecting stars. We find that the neutral noncommutative reflecting star cannot support the existence of scalar field hairs. In the charged noncommutative reflecting star spacetime, we provide upper bounds for star radii. Above the bound, scalar fields cannot exist outside the star. In contrast, when the star radius is below the bound, we show that the scalar field can condense. We also obtain the largest radii of scalar hairy reflecting stars. |
1607.02316 | Vartika Gupta | Daksh Lohiya and Vartika Gupta | Non - Topological Solitons in a Non-minimally Coupled Scalar Field
Induced Gravity Theory | 27 pages, 2 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Properties of soliton stars that could be expected to naturally arise out of
a first order phase transition in non-minimally coupled scalar-field-induced
gravity theories are investigated. Of particular interest are configurations,
similar to Lee-Wick stars, with vanishing effective gravitational constant in
the interiors.
| [
{
"created": "Fri, 8 Jul 2016 11:12:50 GMT",
"version": "v1"
}
] | 2016-07-11 | [
[
"Lohiya",
"Daksh",
""
],
[
"Gupta",
"Vartika",
""
]
] | Properties of soliton stars that could be expected to naturally arise out of a first order phase transition in non-minimally coupled scalar-field-induced gravity theories are investigated. Of particular interest are configurations, similar to Lee-Wick stars, with vanishing effective gravitational constant in the interiors. |
gr-qc/9802040 | Konstantinov Mikhail | M. Yu. Konstantinov | Causality properties of topologically nontrivial space-time models | 7 pages, LaTeX; Talk presented at the International School-Seminar
"Problems of Theoretical Cosmology", Ulyanovsk, September 1--7, 1997 | Grav.Cosmol.3:299-304,1997 | null | RGS-VNIIMS-002/98 | gr-qc | null | Some problems of the space-time causal structure are discussed using models
with traversable wormholes. For this purpose the conditions of traversable
wormhole matching with the exterior space-time are considered in detail and a
mixed boundary problem for the Einstein equations is formulated and analyzed.
The influence of these matching conditions on the space-time properties and
causal structure is analyzed. These conditions have a non-dynamical nature and
cannot be determined by any physical process. So, the causality violation
cannot be a result of dynamical evolution of some initial hypersurface. It is
also shown that the same conditions which determine the wormhole joining with
the outer space provide the self-consistency of solutions and the absence of
paradoxes in the case of causality violation.
| [
{
"created": "Tue, 17 Feb 1998 14:19:05 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Konstantinov",
"M. Yu.",
""
]
] | Some problems of the space-time causal structure are discussed using models with traversable wormholes. For this purpose the conditions of traversable wormhole matching with the exterior space-time are considered in detail and a mixed boundary problem for the Einstein equations is formulated and analyzed. The influence of these matching conditions on the space-time properties and causal structure is analyzed. These conditions have a non-dynamical nature and cannot be determined by any physical process. So, the causality violation cannot be a result of dynamical evolution of some initial hypersurface. It is also shown that the same conditions which determine the wormhole joining with the outer space provide the self-consistency of solutions and the absence of paradoxes in the case of causality violation. |
gr-qc/0406004 | Robert Carroll | Robert Carroll | Gravity and the quantum potential | Latex, 30 pages, Remark added | null | null | null | gr-qc | null | We review some material connecting gravity and the quantum potential and
provide a few new observations.
| [
{
"created": "Wed, 2 Jun 2004 12:00:40 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jun 2004 23:33:53 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Carroll",
"Robert",
""
]
] | We review some material connecting gravity and the quantum potential and provide a few new observations. |
1512.01317 | Taeyoon Moon | Yun Soo Myung, Taeyoon Moon, and Young-Jai Park | Einstein-singleton theory and its power spectra in de Sitter inflation | 1+15 pages, 3 figures, version to appear in Int. J. Mod. Phys. D | null | 10.1142/S0218271816501078 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Einstein-singleton theory during de Sitter inflation since it
provides a way of degenerate fourth-order scalar theory. We obtain an exact
solution expressed in terms of the exponential-integral function by solving the
degenerate fourth-order scalar equation in de Sitter spacetime. Furthermore, we
find that its power spectrum blows negatively up in the superhorizon limit,
while it is negatively scale-invariant in the subhorizon limit. This suggests
that the Einstein-singleton theory contains the ghost-instability and thus, it
is not suitable for developing a slow-roll inflation model.
| [
{
"created": "Fri, 4 Dec 2015 05:03:11 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Jun 2016 03:17:24 GMT",
"version": "v2"
}
] | 2017-01-25 | [
[
"Myung",
"Yun Soo",
""
],
[
"Moon",
"Taeyoon",
""
],
[
"Park",
"Young-Jai",
""
]
] | We study the Einstein-singleton theory during de Sitter inflation since it provides a way of degenerate fourth-order scalar theory. We obtain an exact solution expressed in terms of the exponential-integral function by solving the degenerate fourth-order scalar equation in de Sitter spacetime. Furthermore, we find that its power spectrum blows negatively up in the superhorizon limit, while it is negatively scale-invariant in the subhorizon limit. This suggests that the Einstein-singleton theory contains the ghost-instability and thus, it is not suitable for developing a slow-roll inflation model. |
1503.07437 | Abril Su\'arez | Abril Su\'arez and Pierre-Henri Chavanis | Hydrodynamic representation of the Klein-Gordon-Einstein equations in
the weak field limit: I. General formalism and perturbations analysis | 29 pages, 11 figures | Phys. Rev. D 92, 023510 (2015) | 10.1103/PhysRevD.92.023510 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a generalization of the Madelung transformation, we derive the
hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak
field limit. We consider a complex self-interacting scalar field with a
$\lambda|\varphi|^4$ potential. We study the evolution of the homogeneous
background in the fluid representation and derive the linearized equations
describing the evolution of small perturbations in a static and in an expanding
universe. We compare the results with simplified models in which the
gravitational potential is introduced by hand in the Klein-Gordon equation, and
assumed to satisfy a (generalized) Poisson equation. We study the evolution of
the perturbations in the matter era using the nonrelativistic limit of our
formalism. Perturbations whose wavelength is below the Jeans length oscillate
in time while pertubations whose wavelength is above the Jeans length grow
linearly with the scale factor as in the cold dark matter model. The growth of
perturbations in the scalar field model is substantially faster than in the
cold dark matter model. When the wavelength of the pertubations approaches the
cosmological horizon (Hubble length), a relativistic treatment is mandatory. In
that case, we find that relativistic effects attenuate or even prevent the
growth of pertubations. This paper exposes the general formalism and provides
illustrations in simple cases. Other applications of our formalism will be
considered in companion papers.
| [
{
"created": "Tue, 24 Mar 2015 14:23:54 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Dec 2015 15:24:25 GMT",
"version": "v2"
}
] | 2015-12-09 | [
[
"Suárez",
"Abril",
""
],
[
"Chavanis",
"Pierre-Henri",
""
]
] | Using a generalization of the Madelung transformation, we derive the hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit. We consider a complex self-interacting scalar field with a $\lambda|\varphi|^4$ potential. We study the evolution of the homogeneous background in the fluid representation and derive the linearized equations describing the evolution of small perturbations in a static and in an expanding universe. We compare the results with simplified models in which the gravitational potential is introduced by hand in the Klein-Gordon equation, and assumed to satisfy a (generalized) Poisson equation. We study the evolution of the perturbations in the matter era using the nonrelativistic limit of our formalism. Perturbations whose wavelength is below the Jeans length oscillate in time while pertubations whose wavelength is above the Jeans length grow linearly with the scale factor as in the cold dark matter model. The growth of perturbations in the scalar field model is substantially faster than in the cold dark matter model. When the wavelength of the pertubations approaches the cosmological horizon (Hubble length), a relativistic treatment is mandatory. In that case, we find that relativistic effects attenuate or even prevent the growth of pertubations. This paper exposes the general formalism and provides illustrations in simple cases. Other applications of our formalism will be considered in companion papers. |
1712.09903 | Roberto Percacci | R. Percacci | Unimodular quantum gravity and the cosmological constant | Prepared for the proceedings of the workshop "Black holes,
gravitational waves and spacetime singularities", held at the Vatican
Observatory, Castel Gandolfo (Rome) May 9 - 12, 2017 | null | 10.1007/s10701-018-0189-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the one-loop effective action of unimodular gravity is the
same as that of ordinary gravity, restricted to unimodular metrics. The only
difference is in the treatment of the global scale degree of freedom and of the
cosmological term. A constant vacuum energy does not gravitate, addressing one
aspect of the cosmological constant problem.
| [
{
"created": "Thu, 28 Dec 2017 15:39:52 GMT",
"version": "v1"
}
] | 2018-08-01 | [
[
"Percacci",
"R.",
""
]
] | It is shown that the one-loop effective action of unimodular gravity is the same as that of ordinary gravity, restricted to unimodular metrics. The only difference is in the treatment of the global scale degree of freedom and of the cosmological term. A constant vacuum energy does not gravitate, addressing one aspect of the cosmological constant problem. |
1401.5397 | Hor\'acio Santana Vieira | H. S. Vieira, V. B. Bezerra, C. R. Muniz | Exact solutions of the Klein-Gordon equation in the Kerr-Newman
background and Hawking radiation | 25 pages | Annals of Physics 350 (2014) 14-28 | 10.1016/j.aop.2014.07.011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work considers the influence of the gravitational field produced by a
charged and rotating black hole (Kerr-Newman spacetime) on a charged massive
scalar field. We obtain exact solutions of both angular and radial parts of the
Klein-Gordon equation in this spacetime, which are given in terms of the
confluent Heun functions. From the radial solution, we obtain the exact wave
solutions near the exterior horizon of the black hole, and discuss the Hawking
radiation of charged massive scalar particles.
| [
{
"created": "Tue, 21 Jan 2014 17:35:11 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Feb 2014 22:16:01 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Apr 2014 21:05:48 GMT",
"version": "v3"
},
{
"created": "Thu, 31 Jul 2014 14:08:43 GMT",
"version": "v4"
}
] | 2014-08-01 | [
[
"Vieira",
"H. S.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Muniz",
"C. R.",
""
]
] | This work considers the influence of the gravitational field produced by a charged and rotating black hole (Kerr-Newman spacetime) on a charged massive scalar field. We obtain exact solutions of both angular and radial parts of the Klein-Gordon equation in this spacetime, which are given in terms of the confluent Heun functions. From the radial solution, we obtain the exact wave solutions near the exterior horizon of the black hole, and discuss the Hawking radiation of charged massive scalar particles. |
2308.07299 | Leonardo Giuliano Trombetta | Juan Manuel Armaleo, Sebastian Bahamonde, Georg Trenkler, Leonardo G.
Trombetta | Symmetric Teleparallel Gauss-Bonnet Gravity and its Extensions | 23 pages | Phys.Rev.D 108, 104019 (2023) | 10.1103/PhysRevD.108.104019 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Teleparallel theories assume that curvature is vanishing in which
case gravity can be solely represented by torsion and/or nonmetricity. Using
differential form language, we express the Riemannian Gauss-Bonnet invariant
concisely in terms of two General Teleparallel Gauss-Bonnet invariants, a bulk
and a boundary one. Both terms are boundary terms in four dimensions. We also
find that the split is not unique and present two possible alternatives. In the
absence of nonmetricity our expressions coincide with the well-known Metric
Teleparallel Gauss-Bonnet invariants for one of the splits. Next, we focus on
the description where only nonmetricity is present and show some examples in
different spacetimes. We finish our discussion by formulating novel modified
Symmetric Teleparallel theories constructed with our new scalars.
| [
{
"created": "Mon, 14 Aug 2023 17:36:53 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Nov 2023 18:12:11 GMT",
"version": "v2"
}
] | 2023-11-13 | [
[
"Armaleo",
"Juan Manuel",
""
],
[
"Bahamonde",
"Sebastian",
""
],
[
"Trenkler",
"Georg",
""
],
[
"Trombetta",
"Leonardo G.",
""
]
] | General Teleparallel theories assume that curvature is vanishing in which case gravity can be solely represented by torsion and/or nonmetricity. Using differential form language, we express the Riemannian Gauss-Bonnet invariant concisely in terms of two General Teleparallel Gauss-Bonnet invariants, a bulk and a boundary one. Both terms are boundary terms in four dimensions. We also find that the split is not unique and present two possible alternatives. In the absence of nonmetricity our expressions coincide with the well-known Metric Teleparallel Gauss-Bonnet invariants for one of the splits. Next, we focus on the description where only nonmetricity is present and show some examples in different spacetimes. We finish our discussion by formulating novel modified Symmetric Teleparallel theories constructed with our new scalars. |
1911.03736 | Wei-Chen Lin | Wei-Chen Lin, William H. Kinney | Trans-Planckian Censorship and $k$-inflation | 9 pages, 4 figures. (V3: The version accepted by PRD. With a major
revision and figures replaced.) | Phys. Rev. D 101, 123534 (2020) | 10.1103/PhysRevD.101.123534 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a more general version of the Trans-Planckian Censorship
Conjecture (TCC) which can apply to models of inflation with varying speed of
sound. We find that inflation models with $c_S < 1$ are in general more
strongly constrained by censorship of trans-Planckian modes than canonical
inflation models, with the upper bound on the tensor/scalar ratio reduced by as
much as three orders of magnitude for sound speeds consistent with bounds from
data. In particular, models which satisfy the TCC, and therefore the de Sitter
Swampland Conjecture, can still violate the more general condition for
non-classicality of trans-Planckian modes. As a concrete example, we apply the
constraint to Dirac-Born-Infeld inflation models motivated by string theory.
| [
{
"created": "Sat, 9 Nov 2019 17:02:46 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Nov 2019 17:04:12 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Jun 2020 16:34:23 GMT",
"version": "v3"
}
] | 2020-07-08 | [
[
"Lin",
"Wei-Chen",
""
],
[
"Kinney",
"William H.",
""
]
] | We propose a more general version of the Trans-Planckian Censorship Conjecture (TCC) which can apply to models of inflation with varying speed of sound. We find that inflation models with $c_S < 1$ are in general more strongly constrained by censorship of trans-Planckian modes than canonical inflation models, with the upper bound on the tensor/scalar ratio reduced by as much as three orders of magnitude for sound speeds consistent with bounds from data. In particular, models which satisfy the TCC, and therefore the de Sitter Swampland Conjecture, can still violate the more general condition for non-classicality of trans-Planckian modes. As a concrete example, we apply the constraint to Dirac-Born-Infeld inflation models motivated by string theory. |
1806.00648 | Javier Olmedo | Abhay Ashtekar, Javier Olmedo and Parampreet Singh | Quantum Transfiguration of Kruskal Black Holes | 5 pages, 1 figure, minor changes, version to appear in PRL | Phys. Rev. Lett. 121, 241301 (2018) | 10.1103/PhysRevLett.121.241301 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new effective description of macroscopic Kruskal black holes
that incorporates corrections due to quantum geometry effects of loop quantum
gravity. It encompasses both the `interior' region that contains classical
singularities and the `exterior' asymptotic region. Singularities are naturally
resolved by the quantum geometry effects of loop quantum gravity, and the
resulting quantum extension of the full Kruskal space-time is free of all the
known limitations of previous investigations [1-11] of the Schwarzschild
interior. We compare and contrast our results with these investigations and
also with the expectations based on the AdS/CFT duality [12].
| [
{
"created": "Sat, 2 Jun 2018 15:01:34 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Nov 2018 20:17:33 GMT",
"version": "v2"
}
] | 2018-12-19 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Olmedo",
"Javier",
""
],
[
"Singh",
"Parampreet",
""
]
] | We present a new effective description of macroscopic Kruskal black holes that incorporates corrections due to quantum geometry effects of loop quantum gravity. It encompasses both the `interior' region that contains classical singularities and the `exterior' asymptotic region. Singularities are naturally resolved by the quantum geometry effects of loop quantum gravity, and the resulting quantum extension of the full Kruskal space-time is free of all the known limitations of previous investigations [1-11] of the Schwarzschild interior. We compare and contrast our results with these investigations and also with the expectations based on the AdS/CFT duality [12]. |
gr-qc/9706071 | Wang Anzhong | M.F.A. da Silva, Anzhong Wang, and N.O. Santos | On the sources of static plane symmetric vacuum space-times | null | Phys.Lett.A244:462-466,1998 | 10.1016/S0375-9601(98)00355-7 | null | gr-qc | null | The static vacuum plane spacetimes are considered, which have two non-trivial
solutions: The Taub solution and the Rindler solution. Imposed reflection
symmetry, we find that the source for the Taub solution does not satisfy any
energy conditions, which is consistent with previous studies, while the source
for the Rindler solution satisfies the weak and strong energy conditions (but
not the dominant one). It is argued that the counterpart of the Einstein theory
to the gravitational field of a massive Newtonian plane should be described by
the Rindler solution, which represents also a uniform gravitational field.
| [
{
"created": "Mon, 23 Jun 1997 20:06:20 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"da Silva",
"M. F. A.",
""
],
[
"Wang",
"Anzhong",
""
],
[
"Santos",
"N. O.",
""
]
] | The static vacuum plane spacetimes are considered, which have two non-trivial solutions: The Taub solution and the Rindler solution. Imposed reflection symmetry, we find that the source for the Taub solution does not satisfy any energy conditions, which is consistent with previous studies, while the source for the Rindler solution satisfies the weak and strong energy conditions (but not the dominant one). It is argued that the counterpart of the Einstein theory to the gravitational field of a massive Newtonian plane should be described by the Rindler solution, which represents also a uniform gravitational field. |
1610.09181 | Norbert Klein | Norbert Klein | Are gravitational constant measurement discrepancies linked to galaxy
rotation curves ? | 9 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:1504.07622 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The discrepancies between recently reported experimental values of the
gravitational constant were analysed within an inertia interpretation of MOND
theory. According to this scenario the relative gravitational acceleration
between a test mass and an array of source masses determines the magnitude of
post Newtonian corrections at small magnitudes of acceleration. The analysis
was applied to one of the most advanced recent Cavendish-type experiment which
revealed an experimental value for the gravitational constant of 180 ppm above
the current CODATA value with more than five standard deviations significance.
A remarkable agreement between this discrepancy and the acceleration anomalies
inherent of galaxy rotation curves was found by a consistent extrapolation
within the framework of MOND. This surprising result suggests that the two
anomalies on totally different length scales may originate from the same
underlying physics.
| [
{
"created": "Fri, 28 Oct 2016 12:05:58 GMT",
"version": "v1"
}
] | 2016-10-31 | [
[
"Klein",
"Norbert",
""
]
] | The discrepancies between recently reported experimental values of the gravitational constant were analysed within an inertia interpretation of MOND theory. According to this scenario the relative gravitational acceleration between a test mass and an array of source masses determines the magnitude of post Newtonian corrections at small magnitudes of acceleration. The analysis was applied to one of the most advanced recent Cavendish-type experiment which revealed an experimental value for the gravitational constant of 180 ppm above the current CODATA value with more than five standard deviations significance. A remarkable agreement between this discrepancy and the acceleration anomalies inherent of galaxy rotation curves was found by a consistent extrapolation within the framework of MOND. This surprising result suggests that the two anomalies on totally different length scales may originate from the same underlying physics. |
2405.12928 | Peter Horvathy | P.-M. Zhang (SYSU, Zhuhai) and P. A. Horvathy (Tours) | Displacement within velocity effect in gravitational wave memory | 29 pages, 21 figures, with Appendix contributed by J. Balog | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Particles initially at rest hit by a passing sandwich gravitational wave
exhibit, in general, thevelocity memory effect (VM): they fly apart with
constant velocity. For specific values of the wave parameters their motion can
however become pure displacement (DM) as suggested by Zel'dovich and Polnarev.
For such a ``miraculous'' value, the particle trajectory is composed of an
integer number of (approximate) standing half-waves. Our statements are
illustrated numerically by a Gaussian, and analytically by the P\"oschl-Teller
profiles.
| [
{
"created": "Tue, 21 May 2024 16:53:07 GMT",
"version": "v1"
},
{
"created": "Tue, 28 May 2024 16:44:57 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Jul 2024 12:33:37 GMT",
"version": "v3"
}
] | 2024-07-09 | [
[
"Zhang",
"P. -M.",
"",
"SYSU, Zhuhai"
],
[
"Horvathy",
"P. A.",
"",
"Tours"
]
] | Particles initially at rest hit by a passing sandwich gravitational wave exhibit, in general, thevelocity memory effect (VM): they fly apart with constant velocity. For specific values of the wave parameters their motion can however become pure displacement (DM) as suggested by Zel'dovich and Polnarev. For such a ``miraculous'' value, the particle trajectory is composed of an integer number of (approximate) standing half-waves. Our statements are illustrated numerically by a Gaussian, and analytically by the P\"oschl-Teller profiles. |
gr-qc/9511052 | Eric Hirschmann | Eric W. Hirschmann, Douglas M. Eardley | Criticality and Bifurcation in the Gravitational Collapse of a
Self-Coupled Scalar Field | 18 pages; one figure, uuencoded postscript; figure is also available
at http://www.physics.ucsb.edu/people/eric_hirschmann | Phys.Rev.D56:4696-4705,1997 | 10.1103/PhysRevD.56.4696 | NSF-ITP-95-154 | gr-qc | null | We examine the gravitational collapse of a non-linear sigma model in
spherical symmetry. There exists a family of continuously self-similar
solutions parameterized by the coupling constant of the theory. These solutions
are calculated together with the critical exponents for black hole formation of
these collapse models. We also find that the sequence of solutions exhibits a
Hopf-type bifurcation as the continuously self-similar solutions become
unstable to perturbations away from self-similarity.
| [
{
"created": "Sat, 18 Nov 1995 00:06:56 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Hirschmann",
"Eric W.",
""
],
[
"Eardley",
"Douglas M.",
""
]
] | We examine the gravitational collapse of a non-linear sigma model in spherical symmetry. There exists a family of continuously self-similar solutions parameterized by the coupling constant of the theory. These solutions are calculated together with the critical exponents for black hole formation of these collapse models. We also find that the sequence of solutions exhibits a Hopf-type bifurcation as the continuously self-similar solutions become unstable to perturbations away from self-similarity. |
2008.11022 | Farook Rahaman | Monimala Mondal, Parthapratim Pradhan, Farook Rahaman and Indrani
Karar | Geodesic stability and Quasi normal modes via Lyapunov exponent for
Hayward Black Hole | To appear in Mod.Phys.Lett.A, 19 pages and 6 figures | null | 10.1142/S0217732320502491 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive proper-time Lyapunov exponent $(\lambda_{p})$ and coordinate-time
Lyapunov exponent $(\lambda_{c})$ for a regular Hayward class of black hole.
The proper-time corresponds to $\tau$ and the coordinate time corresponds to
$t$. Where $t$ is measured by the asymptotic observers both for for Hayward
black hole and for special case of Schwarzschild black hole.
We compute their ratio as $\frac{\lambda_{p}}{\lambda_{c}} =
\frac{(r_{\sigma}^{3} + 2 l^{2} m )}{\sqrt{(r_{\sigma}^{2} + 2 l^{2} m )^{3}- 3
m r_{\sigma}^{5}}}$ for time-like geodesics. In the limit of $l=0$ that means
for Schwarzschild black hole this ratio reduces to
$\frac{\lambda_{p}}{\lambda_{c}} = \sqrt{\frac{r_{\sigma}}{(r_{\sigma}-3 m)}}$.
Using Lyponuov exponent, we investigate the stability and instability of
equatorial circular geodesics. By evaluating the Lyapunov exponent, which is
the inverse of the instability time-scale, we show that, in the eikonal limit,
the real and imaginary parts of quasi-normal modes~(QNMs) is specified by the
frequency and instability time scale of the null circular geodesics.
Furthermore, we discuss the unstable photon sphere and radius of shadow for
this class of black hole.
| [
{
"created": "Sun, 23 Aug 2020 14:44:23 GMT",
"version": "v1"
}
] | 2020-08-26 | [
[
"Mondal",
"Monimala",
""
],
[
"Pradhan",
"Parthapratim",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Karar",
"Indrani",
""
]
] | We derive proper-time Lyapunov exponent $(\lambda_{p})$ and coordinate-time Lyapunov exponent $(\lambda_{c})$ for a regular Hayward class of black hole. The proper-time corresponds to $\tau$ and the coordinate time corresponds to $t$. Where $t$ is measured by the asymptotic observers both for for Hayward black hole and for special case of Schwarzschild black hole. We compute their ratio as $\frac{\lambda_{p}}{\lambda_{c}} = \frac{(r_{\sigma}^{3} + 2 l^{2} m )}{\sqrt{(r_{\sigma}^{2} + 2 l^{2} m )^{3}- 3 m r_{\sigma}^{5}}}$ for time-like geodesics. In the limit of $l=0$ that means for Schwarzschild black hole this ratio reduces to $\frac{\lambda_{p}}{\lambda_{c}} = \sqrt{\frac{r_{\sigma}}{(r_{\sigma}-3 m)}}$. Using Lyponuov exponent, we investigate the stability and instability of equatorial circular geodesics. By evaluating the Lyapunov exponent, which is the inverse of the instability time-scale, we show that, in the eikonal limit, the real and imaginary parts of quasi-normal modes~(QNMs) is specified by the frequency and instability time scale of the null circular geodesics. Furthermore, we discuss the unstable photon sphere and radius of shadow for this class of black hole. |
0706.0923 | Milton Ruiz | Milton Ruiz, Miguel Alcubierre, Dario Nunez | Regularization of spherical and axisymmetric evolution codes in
numerical relativity | 11 pages, 9 figures. Several changes. Main corrections are in eqs.
(2.12) and (5.14). Accepted in Gen. Rel. Grav | Gen.Rel.Grav.40:159-182,2008 | 10.1007/s10714-007-0522-3 | null | gr-qc | null | Several interesting astrophysical phenomena are symmetric with respect to the
rotation axis, like the head-on collision of compact bodies, the collapse
and/or accretion of fields with a large variety of geometries, or some forms of
gravitational waves. Most current numerical relativity codes, however, can not
take advantage of these symmetries due to the fact that singularities in the
adapted coordinates, either at the origin or at the axis of symmetry, rapidly
cause the simulation to crash. Because of this regularity problem it has become
common practice to use full-blown Cartesian three-dimensional codes to simulate
axi-symmetric systems. In this work we follow a recent idea idea of Rinne and
Stewart and present a simple procedure to regularize the equations both in
spherical and axi-symmetric spaces. We explicitly show the regularity of the
evolution equations, describe the corresponding numerical code, and present
several examples clearly showing the regularity of our evolutions.
| [
{
"created": "Wed, 6 Jun 2007 21:49:26 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Sep 2007 22:40:53 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Ruiz",
"Milton",
""
],
[
"Alcubierre",
"Miguel",
""
],
[
"Nunez",
"Dario",
""
]
] | Several interesting astrophysical phenomena are symmetric with respect to the rotation axis, like the head-on collision of compact bodies, the collapse and/or accretion of fields with a large variety of geometries, or some forms of gravitational waves. Most current numerical relativity codes, however, can not take advantage of these symmetries due to the fact that singularities in the adapted coordinates, either at the origin or at the axis of symmetry, rapidly cause the simulation to crash. Because of this regularity problem it has become common practice to use full-blown Cartesian three-dimensional codes to simulate axi-symmetric systems. In this work we follow a recent idea idea of Rinne and Stewart and present a simple procedure to regularize the equations both in spherical and axi-symmetric spaces. We explicitly show the regularity of the evolution equations, describe the corresponding numerical code, and present several examples clearly showing the regularity of our evolutions. |
0708.3037 | Eric Poisson | Adam Pound and Eric Poisson | Multi-scale analysis of the electromagnetic self-force in a weak
gravitational field | 17 pages, 6 figures, final version to be published in Physical Review
D | Phys.Rev.D77:044012,2008 | 10.1103/PhysRevD.77.044012 | null | gr-qc | null | We examine the motion of a charged particle in a weak gravitational field. In
addition to the Newtonian gravity exerted by a large central body, the particle
is subjected to an electromagnetic self-force that contains both a conservative
piece and a radiation-reaction piece. This toy problem shares many of the
features of the strong-field gravitational self-force problem, and it is
sufficiently simple that it can be solved exactly with numerical methods, and
approximately with analytical methods. We submit the equations of motion to a
multi-scale analysis, and we examine the roles of the conservative and
radiation-reaction pieces of the self-force. We show that the
radiation-reaction force drives secular changes in the orbit's semilatus rectum
and eccentricity, while the conservative force drives a secular regression of
the periapsis and affects the orbital time function; neglect of the
conservative term can hence give rise to an important phasing error. We next
examine what might be required in the formulation of a reliable adiabatic
approximation for the orbital evolution; this would capture all secular changes
in the orbit and discard all irrelevant oscillations. We conclude that such an
approximation would be very difficult to formulate without prior knowledge of
the exact solution.
| [
{
"created": "Wed, 22 Aug 2007 15:24:58 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Dec 2007 20:49:14 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Pound",
"Adam",
""
],
[
"Poisson",
"Eric",
""
]
] | We examine the motion of a charged particle in a weak gravitational field. In addition to the Newtonian gravity exerted by a large central body, the particle is subjected to an electromagnetic self-force that contains both a conservative piece and a radiation-reaction piece. This toy problem shares many of the features of the strong-field gravitational self-force problem, and it is sufficiently simple that it can be solved exactly with numerical methods, and approximately with analytical methods. We submit the equations of motion to a multi-scale analysis, and we examine the roles of the conservative and radiation-reaction pieces of the self-force. We show that the radiation-reaction force drives secular changes in the orbit's semilatus rectum and eccentricity, while the conservative force drives a secular regression of the periapsis and affects the orbital time function; neglect of the conservative term can hence give rise to an important phasing error. We next examine what might be required in the formulation of a reliable adiabatic approximation for the orbital evolution; this would capture all secular changes in the orbit and discard all irrelevant oscillations. We conclude that such an approximation would be very difficult to formulate without prior knowledge of the exact solution. |
1105.6153 | Qiyuan Pan | Qiyuan Pan, Jiliang Jing and Bin Wang | Analytical investigation of the phase transition between holographic
insulator and superconductor in Gauss-Bonnet gravity | 18 pages, 1 figure, 3 tables | JHEP 11 (2011) 088 | 10.1007/JHEP11(2011)088 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We employ the variational method for the Sturm-Liouville eigenvalue problem
to analytically study the phase transition between the holographic insulator
and superconductor in the Gauss-Bonnet gravity. By investigating the s-wave and
p-wave holographic insulator/superconductor models, we find that this analytic
method is more effective to obtain the analytic results on the condensation and
the critical phenomena in the AdS soliton background in Gauss-Bonnet gravity.
Our analytic result can be used to back up the numerical computations in the
AdS soliton with Gauss-Bonnet correction.
| [
{
"created": "Tue, 31 May 2011 03:04:49 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Nov 2011 06:47:26 GMT",
"version": "v2"
}
] | 2011-11-22 | [
[
"Pan",
"Qiyuan",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Wang",
"Bin",
""
]
] | We employ the variational method for the Sturm-Liouville eigenvalue problem to analytically study the phase transition between the holographic insulator and superconductor in the Gauss-Bonnet gravity. By investigating the s-wave and p-wave holographic insulator/superconductor models, we find that this analytic method is more effective to obtain the analytic results on the condensation and the critical phenomena in the AdS soliton background in Gauss-Bonnet gravity. Our analytic result can be used to back up the numerical computations in the AdS soliton with Gauss-Bonnet correction. |
2105.08936 | Masato Minamitsuji | Masato Minamitsuji | Black holes in the quadratic-order extended vector-tensor theories | 15 pages | Classical and Quantum Gravity 38,105011 (2021) | 10.1088/1361-6382/abed62 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the static and spherically black hole solutions in the
quadratic-order extended vector-tensor theories without suffering from the
Ostrogradsky instabilities, which include the quartic-order
(beyond-)generalized Proca theories as the subclass. We start from the most
general action of the vector-tensor theories constructed with up to the
quadratic-order terms of the first-order covariant derivatives of the vector
field, and derive the Euler-Lagrange equations for the metric and vector field
variables in the static and spherically symmetric backgrounds. We then
substitute the spacetime metric functions of the Schwarzschild,
Schwarzschild-de Sitter/ anti-de Sitter, Reissner-Nordstr\"{o}m-type, and
Reissner-Nordstr\"{o}m-de Sitter/ anti-de Sitter-type solutions and the vector
field with the constant spacetime norm into the Euler-Lagrange equations, and
obtain the conditions for the existence of these black hole solutions. These
solutions are classified into the two cases 1) the solutions with the vanishing
vector field strength; the stealth Schwarzschild and the Schwarzschild de
Sitter/ anti- de Sitter solutions, and 2) those with the nonvanishing vector
field strength; the charged stealth Schwarzschild and the charged Schwarzschild
de Sitter/ anti- de Sitter solutions, in the case that the tuning relation
among the coupling functions is satisfied. In the latter case, if this tuning
relation is violated, the solution becomes the Reissner-Nordstr\"{o}m-type
solution. We show that the conditions for the existence of these solutions are
compatible with the degeneracy conditions for the Class-A theories, and recover
the black hole solutions in the generalized Proca theories as the particular
cases.
| [
{
"created": "Wed, 19 May 2021 05:54:40 GMT",
"version": "v1"
}
] | 2021-05-20 | [
[
"Minamitsuji",
"Masato",
""
]
] | We investigate the static and spherically black hole solutions in the quadratic-order extended vector-tensor theories without suffering from the Ostrogradsky instabilities, which include the quartic-order (beyond-)generalized Proca theories as the subclass. We start from the most general action of the vector-tensor theories constructed with up to the quadratic-order terms of the first-order covariant derivatives of the vector field, and derive the Euler-Lagrange equations for the metric and vector field variables in the static and spherically symmetric backgrounds. We then substitute the spacetime metric functions of the Schwarzschild, Schwarzschild-de Sitter/ anti-de Sitter, Reissner-Nordstr\"{o}m-type, and Reissner-Nordstr\"{o}m-de Sitter/ anti-de Sitter-type solutions and the vector field with the constant spacetime norm into the Euler-Lagrange equations, and obtain the conditions for the existence of these black hole solutions. These solutions are classified into the two cases 1) the solutions with the vanishing vector field strength; the stealth Schwarzschild and the Schwarzschild de Sitter/ anti- de Sitter solutions, and 2) those with the nonvanishing vector field strength; the charged stealth Schwarzschild and the charged Schwarzschild de Sitter/ anti- de Sitter solutions, in the case that the tuning relation among the coupling functions is satisfied. In the latter case, if this tuning relation is violated, the solution becomes the Reissner-Nordstr\"{o}m-type solution. We show that the conditions for the existence of these solutions are compatible with the degeneracy conditions for the Class-A theories, and recover the black hole solutions in the generalized Proca theories as the particular cases. |
1401.5898 | Sanjit Mitra | Nairwita Mazumder, Sanjit Mitra and Sanjeev Dhurandhar | Astrophysical motivation for directed searches for a stochastic
gravitational wave background | 13 pages, 2 figures, 3 tables. Matched the published version | Phys. Rev. D 89, 084076 (2014) | 10.1103/PhysRevD.89.084076 | IUCAA-02/14, LIGO-P1300223 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nearby universe is expected to create an anisotropic stochastic
gravitational wave background (SGWB). Different algorithms have been developed
and implemented to search for isotropic and anisotropic SGWB. The aim of this
paper is to quantify the advantage of an optimal anisotropic search,
specifically comparing a point source with an isotropic background. Clusters of
galaxies appear as point sources to a network of ground based laser
interferometric detectors. The optimal search strategy for these sources is a
"directed radiometer search". We show that the flux of SGWB created by the
millisecond pulsars in the Virgo cluster produces a significantly stronger
signal than the nearly isotropic background of unresolved sources of the same
kind. We compute their strain power spectra for different cosmologies and
distribution of population over redshifts. We conclude that a localised source,
like the Virgo cluster, can be resolved from the isotropic background with very
high significance using the directed search algorithm. For backgrounds
dominated by nearby sources, up to redshift of about 3, we show that the
directed search for a localised source can have signal to noise ratio more than
that for the all sky integrated isotropic search.
| [
{
"created": "Thu, 23 Jan 2014 09:15:30 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jan 2014 04:58:06 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Apr 2014 09:17:33 GMT",
"version": "v3"
}
] | 2014-05-07 | [
[
"Mazumder",
"Nairwita",
""
],
[
"Mitra",
"Sanjit",
""
],
[
"Dhurandhar",
"Sanjeev",
""
]
] | The nearby universe is expected to create an anisotropic stochastic gravitational wave background (SGWB). Different algorithms have been developed and implemented to search for isotropic and anisotropic SGWB. The aim of this paper is to quantify the advantage of an optimal anisotropic search, specifically comparing a point source with an isotropic background. Clusters of galaxies appear as point sources to a network of ground based laser interferometric detectors. The optimal search strategy for these sources is a "directed radiometer search". We show that the flux of SGWB created by the millisecond pulsars in the Virgo cluster produces a significantly stronger signal than the nearly isotropic background of unresolved sources of the same kind. We compute their strain power spectra for different cosmologies and distribution of population over redshifts. We conclude that a localised source, like the Virgo cluster, can be resolved from the isotropic background with very high significance using the directed search algorithm. For backgrounds dominated by nearby sources, up to redshift of about 3, we show that the directed search for a localised source can have signal to noise ratio more than that for the all sky integrated isotropic search. |
2009.12846 | Yu-Xiao Liu | Wen-Bin Feng, Si-Jiang Yang, Qin Tan, Jie Yang, Yu-Xiao Liu | Overcharging a Reissner-Nordstr\"om Taub-NUT regular black hole | 22 pages, 3 figures | Sci.China Phys.Mech.Astron. 64 (2021) 6, 260411 | 10.1007/s11433-020-1659-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The destruction of a regular black hole event horizon might provide us the
possibility to access regions inside black hole event horizon. This paper
investigates the possibility of overcharging a charged Taub-NUT regular black
hole via the scattering of a charged field and the absorption of a charged
particle. For the charged scalar field scattering, both the near-extremal and
extremal charged Taub-NUT regular black holes cannot be overcharged. For the
test charged particle absorption, the result shows that the event horizon of
the extremal charged Taub-NUT regular black hole still exists while the event
horizon of the near-extremal one can be destroyed. However, if the charge and
energy cross the event horizon in a continuous path, the near-extremal charged
Taub-NUT regular black hole might not be overcharged.
| [
{
"created": "Sun, 27 Sep 2020 13:54:39 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Nov 2020 02:20:52 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Apr 2022 03:19:48 GMT",
"version": "v3"
}
] | 2022-04-29 | [
[
"Feng",
"Wen-Bin",
""
],
[
"Yang",
"Si-Jiang",
""
],
[
"Tan",
"Qin",
""
],
[
"Yang",
"Jie",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | The destruction of a regular black hole event horizon might provide us the possibility to access regions inside black hole event horizon. This paper investigates the possibility of overcharging a charged Taub-NUT regular black hole via the scattering of a charged field and the absorption of a charged particle. For the charged scalar field scattering, both the near-extremal and extremal charged Taub-NUT regular black holes cannot be overcharged. For the test charged particle absorption, the result shows that the event horizon of the extremal charged Taub-NUT regular black hole still exists while the event horizon of the near-extremal one can be destroyed. However, if the charge and energy cross the event horizon in a continuous path, the near-extremal charged Taub-NUT regular black hole might not be overcharged. |
1601.08106 | Moritz Reintjes | Moritz Reintjes | A note on incompressibility of relativistic fluids and the instantaneity
of their pressures | 7 pages. Version 2: Improved wording and presentation | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a natural notion of incompressibility for fluids governed by the
relativistic Euler equations on a fixed background spacetime, and show that the
resulting equations reduce to the incompressible Euler equations in the
classical limit as $c\rightarrow \infty$. As our main result, we prove that the
fluid pressure of solutions of these incompressible "relativistic" Euler
equations satisfies an elliptic equation on each of the hypersurfaces
orthogonal to the fluid four-velocity, which indicates infinite speed of
propagation.
| [
{
"created": "Fri, 29 Jan 2016 13:53:45 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jun 2017 11:33:20 GMT",
"version": "v2"
}
] | 2017-06-15 | [
[
"Reintjes",
"Moritz",
""
]
] | We introduce a natural notion of incompressibility for fluids governed by the relativistic Euler equations on a fixed background spacetime, and show that the resulting equations reduce to the incompressible Euler equations in the classical limit as $c\rightarrow \infty$. As our main result, we prove that the fluid pressure of solutions of these incompressible "relativistic" Euler equations satisfies an elliptic equation on each of the hypersurfaces orthogonal to the fluid four-velocity, which indicates infinite speed of propagation. |
1412.5531 | Miguel Campiglia | Miguel Campiglia | Note on the phase space of asymptotically flat gravity in
Ashtekar-Barbero variables | 18 pages | null | 10.1088/0264-9381/32/14/145011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the canonical phase space of asymptotically flat gravity in
Ashtekar-Barbero variables. We show that the Gauss constraint multiplier must
fall off slower than previously considered in order to recover ADM phase space.
The generators of the asymptotic Poincare group are derived within the
Ashtekar-Barbero phase space without reference to the ADM generators. The
resulting expressions are shown to agree, modulo Gauss constraint terms, with
those obtained from the ADM generators. A payoff of this procedure is a new
expression for the generator of asymptotic rotations which is polynomial in the
triad and hence better suited for quantum theory. Our treatment complements
earlier description by Thiemann in the context of self-dual variables.
| [
{
"created": "Wed, 17 Dec 2014 19:31:13 GMT",
"version": "v1"
}
] | 2015-08-06 | [
[
"Campiglia",
"Miguel",
""
]
] | We describe the canonical phase space of asymptotically flat gravity in Ashtekar-Barbero variables. We show that the Gauss constraint multiplier must fall off slower than previously considered in order to recover ADM phase space. The generators of the asymptotic Poincare group are derived within the Ashtekar-Barbero phase space without reference to the ADM generators. The resulting expressions are shown to agree, modulo Gauss constraint terms, with those obtained from the ADM generators. A payoff of this procedure is a new expression for the generator of asymptotic rotations which is polynomial in the triad and hence better suited for quantum theory. Our treatment complements earlier description by Thiemann in the context of self-dual variables. |
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