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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1805.10640 | Liwei Ji | Zhoujian Cao, and Pei Fu, and Li-Wei Ji, and Yinhua Xia | Binary black hole simulation with an adaptive finite element method II:
Application of local discontinuous Galerkin method to Einstein equations | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Finite difference method and pseudo-spectral method have been widely used in
the numerical relativity to solve the Einstein equations. As the third major
category method to solve partial differential equations, finite element method
is much less used in numerical relativity. In this paper we design a finite
element algorithm to solve the evolution part of the Einstein equations. This
paper is the second one of a systematic investigation of applying adaptive
finite element method to the Einstein equations, especially aim for binary
compact objects simulations. The first paper of this series has been
contributed to the constrained part of the Einstein equations for initial data.
Since applying finite element method to the Einstein equations is a big
project, we mainly propose the theoretical framework of a finite element
algorithm together with local discontinuous Galerkin method for the Einstein
equations in the current work. In addition, we have tested our algorithm based
on the spherical symmetric spacetime evolution. In order to simplify our
numerical tests, we have reduced the problem to a one-dimensional space problem
by taking the advantage of the spherical symmetry. Our reduced equation system
is a new formalism for spherical symmetric spacetime simulation. Based on our
test results, we find that our finite element method can capture the shock
formation which is introduced by numerical error. In contrast, such shock is
smoothed out by numerical dissipation within the finite difference method. We
suspect this is the part reason for that the accuracy of finite element method
is higher than finite difference method. At the same time kinds of formulation
parameters setting are also discussed.
| [
{
"created": "Sun, 27 May 2018 15:42:32 GMT",
"version": "v1"
}
] | 2018-05-29 | [
[
"Cao",
"Zhoujian",
""
],
[
"Fu",
"Pei",
""
],
[
"Ji",
"Li-Wei",
""
],
[
"Xia",
"Yinhua",
""
]
] | Finite difference method and pseudo-spectral method have been widely used in the numerical relativity to solve the Einstein equations. As the third major category method to solve partial differential equations, finite element method is much less used in numerical relativity. In this paper we design a finite element algorithm to solve the evolution part of the Einstein equations. This paper is the second one of a systematic investigation of applying adaptive finite element method to the Einstein equations, especially aim for binary compact objects simulations. The first paper of this series has been contributed to the constrained part of the Einstein equations for initial data. Since applying finite element method to the Einstein equations is a big project, we mainly propose the theoretical framework of a finite element algorithm together with local discontinuous Galerkin method for the Einstein equations in the current work. In addition, we have tested our algorithm based on the spherical symmetric spacetime evolution. In order to simplify our numerical tests, we have reduced the problem to a one-dimensional space problem by taking the advantage of the spherical symmetry. Our reduced equation system is a new formalism for spherical symmetric spacetime simulation. Based on our test results, we find that our finite element method can capture the shock formation which is introduced by numerical error. In contrast, such shock is smoothed out by numerical dissipation within the finite difference method. We suspect this is the part reason for that the accuracy of finite element method is higher than finite difference method. At the same time kinds of formulation parameters setting are also discussed. |
1105.4057 | Harvey S. Reall | Harvey S. Reall | Algebraically special solutions in higher dimensions | Chapter of a book on higher-dimensional black holes to be published
by Cambridge University Press (editor: G. Horowitz). v2: section 1.4.3
corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An introductory review of algebraic classification of the Weyl tensor and
algebraically special solutions in higher dimensions.
| [
{
"created": "Fri, 20 May 2011 11:02:38 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jun 2011 07:36:28 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Mar 2012 16:08:18 GMT",
"version": "v3"
}
] | 2012-03-13 | [
[
"Reall",
"Harvey S.",
""
]
] | An introductory review of algebraic classification of the Weyl tensor and algebraically special solutions in higher dimensions. |
1706.00026 | Zoe Wyatt | Zoe Wyatt | The Weak Null Condition and Kaluza-Klein Spacetimes | 28 pages, 1 figure | J. Hyperbolic Differ. Equ. Vol 15, No. 02, pp. 219-258 (2018) | 10.1142/S0219891618500091 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we prove the non-linear stability of a system of non-linear
wave equations satisfying the weak null condition. In particular, this includes
the case of the non-linear stability of Minkowski spacetime times a $d$-torus
subject to perturbations depending only on the non-compact coordinates. Our
argument very closely follows the proof of the non-linear stability of
Minkowski spacetime in [Lindblad-Rodnianski-2010].
| [
{
"created": "Wed, 31 May 2017 18:01:04 GMT",
"version": "v1"
}
] | 2019-01-30 | [
[
"Wyatt",
"Zoe",
""
]
] | In this paper we prove the non-linear stability of a system of non-linear wave equations satisfying the weak null condition. In particular, this includes the case of the non-linear stability of Minkowski spacetime times a $d$-torus subject to perturbations depending only on the non-compact coordinates. Our argument very closely follows the proof of the non-linear stability of Minkowski spacetime in [Lindblad-Rodnianski-2010]. |
2104.07889 | Minyong Guo | Haopeng Yan, Minyong Guo and Bin Chen | Observability of Zero-angular-momentum Sources Near Kerr Black Holes | 26 pages, 6 figures. Published in EPJC | null | 10.1140/epjc/s10052-021-09649-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit monochromatic and isotropic photon emissions from the
zero-angular\linebreak-momentum sources (ZAMSs) near a Kerr black hole. We
investigate the escape probability of the photons that can reach to infinity
and study the energy shifts of these escaping photons, which could be expressed
as the functions of the source radius and the black hole spin. We study the
cases for generic source radius and black hole spin, but we pay special
attention to the near-horizon (near-)extremal Kerr ((near-)NHEK) cases. We
reproduce the relevant numerical results using a more efficient method and get
new analytical results for (near-)extremal cases. The main non-trivial results
are: in the NHEK region of a (near-)extremal Kerr black hole, the escape
probability for a ZAMS tends to $\frac{7}{24}\approx 29.17\%$, independent of
the NHEK radius; at the innermost of the photon shell (IPS) in the near-NHEK
region, the escape probability for a ZAMS tends to
\begin{equation}
\frac{5}{12} -\frac{1}{\sqrt{7}} +
\frac{2}{\sqrt{7}\pi}\arctan\frac{1}{\sqrt{7}}\approx12.57\% .
\nonumber
\end{equation} The results show that the photon escape probability remains a
relatively large nonzero value even though the ZAMS is in the deepest region of
a near-horizon throat of a high spin Kerr black hole, as long as the ZAMS is
outside the IPS. The energies of the escaping photons at infinity, however, are
all redshifted but still visible in principle.
| [
{
"created": "Fri, 16 Apr 2021 04:44:36 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Aug 2021 09:32:54 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Dec 2021 10:14:32 GMT",
"version": "v3"
}
] | 2021-12-03 | [
[
"Yan",
"Haopeng",
""
],
[
"Guo",
"Minyong",
""
],
[
"Chen",
"Bin",
""
]
] | We revisit monochromatic and isotropic photon emissions from the zero-angular\linebreak-momentum sources (ZAMSs) near a Kerr black hole. We investigate the escape probability of the photons that can reach to infinity and study the energy shifts of these escaping photons, which could be expressed as the functions of the source radius and the black hole spin. We study the cases for generic source radius and black hole spin, but we pay special attention to the near-horizon (near-)extremal Kerr ((near-)NHEK) cases. We reproduce the relevant numerical results using a more efficient method and get new analytical results for (near-)extremal cases. The main non-trivial results are: in the NHEK region of a (near-)extremal Kerr black hole, the escape probability for a ZAMS tends to $\frac{7}{24}\approx 29.17\%$, independent of the NHEK radius; at the innermost of the photon shell (IPS) in the near-NHEK region, the escape probability for a ZAMS tends to \begin{equation} \frac{5}{12} -\frac{1}{\sqrt{7}} + \frac{2}{\sqrt{7}\pi}\arctan\frac{1}{\sqrt{7}}\approx12.57\% . \nonumber \end{equation} The results show that the photon escape probability remains a relatively large nonzero value even though the ZAMS is in the deepest region of a near-horizon throat of a high spin Kerr black hole, as long as the ZAMS is outside the IPS. The energies of the escaping photons at infinity, however, are all redshifted but still visible in principle. |
0709.0199 | Keisuke Izumi | Keisuke Izumi, Takahiro Tanaka | No de Sitter invariant vacuum in massive gravity theory with ghost | 5 pages | Prog. Theor. Phys. 121 (2009), 419 | 10.1143/PTP.121.419 | KUNS-2092 | gr-qc astro-ph hep-th | null | In this letter we point out that the massive gravity theory with a graviton
ghost mode in de Sitter background cannot possess a de Sitter invariant vacuum
state. In order to avoid a negative norm state, we must associate the creation
operator of the ghost mode with a negative-energy mode function instead of a
positive-energy one as the mode function. Namely, we have to adopt a different
procedure of quantization for a ghost. When a theory has a symmetry mixing a
ghost mode with ordinary non-ghost modes, the choice of a ghost mode is not
unique. However, quantization of a ghost is impossible without specifying a
choice of ghost mode, which breaks the symmetry. For this reason, the vacuum
state cannot respect the symmetry. In the massive gravity theory with a
graviton ghost mode in de Sitter background, the ghost is the helicity-0 mode
of the graviton. This ghost mode is mixed with the other helicity graviton
modes under the action of de Sitter symmetry. Therefore, there is no de Sitter
invariant vacuum in such models. This leads to an interesting possibility that
non-covariant cutoff of the low energy effective theory may naturally arise. As
a result, the instability due to the pair production of a ghost and normal
non-ghost particles gets much milder and that the model may escape from being
rejected.
| [
{
"created": "Mon, 3 Sep 2007 11:55:54 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Sep 2007 10:05:11 GMT",
"version": "v2"
}
] | 2009-03-20 | [
[
"Izumi",
"Keisuke",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | In this letter we point out that the massive gravity theory with a graviton ghost mode in de Sitter background cannot possess a de Sitter invariant vacuum state. In order to avoid a negative norm state, we must associate the creation operator of the ghost mode with a negative-energy mode function instead of a positive-energy one as the mode function. Namely, we have to adopt a different procedure of quantization for a ghost. When a theory has a symmetry mixing a ghost mode with ordinary non-ghost modes, the choice of a ghost mode is not unique. However, quantization of a ghost is impossible without specifying a choice of ghost mode, which breaks the symmetry. For this reason, the vacuum state cannot respect the symmetry. In the massive gravity theory with a graviton ghost mode in de Sitter background, the ghost is the helicity-0 mode of the graviton. This ghost mode is mixed with the other helicity graviton modes under the action of de Sitter symmetry. Therefore, there is no de Sitter invariant vacuum in such models. This leads to an interesting possibility that non-covariant cutoff of the low energy effective theory may naturally arise. As a result, the instability due to the pair production of a ghost and normal non-ghost particles gets much milder and that the model may escape from being rejected. |
gr-qc/0009034 | Gilles Esposito-Farese | G. Esposito-Farese and D. Polarski | Scalar-tensor gravity in an accelerating universe | 37 pages, LaTeX 2.09, REVTeX 3.0, uses epsf.tex to include 6
postscript figures | Phys.Rev. D63 (2001) 063504 | 10.1103/PhysRevD.63.063504 | CPT-2000/PE.4053 | gr-qc astro-ph | null | We consider scalar-tensor theories of gravity in an accelerating universe.
The equations for the background evolution and the perturbations are given in
full generality for any parametrization of the Lagrangian, and we stress that
apparent singularities are sometimes artifacts of a pathological choice of
variables. Adopting a phenomenological viewpoint, i.e., from the observations
back to the theory, we show that the knowledge of the luminosity distance as a
function of redshift up to z ~ (1-2), which is expected in the near future,
severely constrains the viable subclasses of scalar-tensor theories. This is
due to the requirement of positive energy for both the graviton and the scalar
partner. Assuming a particular form for the Hubble diagram, consistent with
present experimental data, we reconstruct the microscopic Lagrangian for
various scalar-tensor models, and find that the most natural ones are obtained
if the universe is (marginally) closed.
| [
{
"created": "Mon, 11 Sep 2000 16:40:25 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Esposito-Farese",
"G.",
""
],
[
"Polarski",
"D.",
""
]
] | We consider scalar-tensor theories of gravity in an accelerating universe. The equations for the background evolution and the perturbations are given in full generality for any parametrization of the Lagrangian, and we stress that apparent singularities are sometimes artifacts of a pathological choice of variables. Adopting a phenomenological viewpoint, i.e., from the observations back to the theory, we show that the knowledge of the luminosity distance as a function of redshift up to z ~ (1-2), which is expected in the near future, severely constrains the viable subclasses of scalar-tensor theories. This is due to the requirement of positive energy for both the graviton and the scalar partner. Assuming a particular form for the Hubble diagram, consistent with present experimental data, we reconstruct the microscopic Lagrangian for various scalar-tensor models, and find that the most natural ones are obtained if the universe is (marginally) closed. |
gr-qc/9505017 | Alan Rendall | Alan D. Rendall | The initial singularity in solutions of the Einstein-Vlasov system of
Bianchi type I | 16 pages | J.Math.Phys.37:438-451,1996 | 10.1063/1.531400 | null | gr-qc | null | The dynamics of solutions of the Einstein-Vlasov system with Bianchi I
symmetry is discussed in the case of massive or massless particles. It is shown
that in the case of massive particles the solutions are asymptotic to isotropic
dust solutions at late times. The initial singularity is more difficult to
analyse. It is shown that the asymptotic behaviour there must be one of a small
set of possibilities but it is not clear whether all of these possibilities are
realized. One solution is exhibited in the case of massless particles which
behaves quite differently near the singularity from any Bianchi I solution with
perfect fluid as matter model. In particular the matter is not dynamically
negligeable near the singularity for this solution.
| [
{
"created": "Mon, 15 May 1995 14:55:15 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Rendall",
"Alan D.",
""
]
] | The dynamics of solutions of the Einstein-Vlasov system with Bianchi I symmetry is discussed in the case of massive or massless particles. It is shown that in the case of massive particles the solutions are asymptotic to isotropic dust solutions at late times. The initial singularity is more difficult to analyse. It is shown that the asymptotic behaviour there must be one of a small set of possibilities but it is not clear whether all of these possibilities are realized. One solution is exhibited in the case of massless particles which behaves quite differently near the singularity from any Bianchi I solution with perfect fluid as matter model. In particular the matter is not dynamically negligeable near the singularity for this solution. |
gr-qc/0005025 | Sergiu Vacaru | Sergiu I. Vacaru | Anholonomic Soliton-Dilaton and Black Hole Solutions in General
Relativity | revtex, twocolumns, 24 pages, version 3 with minor corrections | JHEP 0104:009,2001 | 10.1088/1126-6708/2001/04/009 | null | gr-qc hep-th math-ph math.MP nlin.SI | null | A new method of construction of integral varieties of Einstein equations in
three dimensional (3D) and 4D gravity is presented whereby, under corresponding
redefinition of physical values with respect to anholonomic frames of reference
with associated nonlinear connections, the structure of gravity field equations
is substantially simplified. It is shown that there are 4D solutions of
Einstein equations which are constructed as nonlinear superpositions of soliton
solutions of 2D (pseudo) Euclidean sine-Gordon equations (or of Lorentzian
black holes in Jackiw-Teitelboim dilaton gravity). The Belinski-Zakharov-Meison
solitons for vacuum gravitational field equations are generalized to various
cases of two and three coordinate dependencies, local anisotropy and matter
sources. The general framework of this study is based on investigation of
anholonomic soliton-dilaton black hole structures in general relativity. We
prove that there are possible static and dynamical black hole, black torus and
disk/cylinder like solutions (of non-vacuum gravitational field equations) with
horizons being parametrized by hypersurface equations of rotation ellipsoid,
torus, cylinder and another type configurations. Solutions describing locally
anisotropic variants of the Schwarzschild-- Kerr (black hole), Weyl
(cylindrical symmetry) and Neugebauer--Meinel (disk) solutions with anisotropic
variable masses, distributions of matter and interaction constants are shown to
be contained in Einstein's gravity. It is demonstrated in which manner locally
anisotropic multi-soliton-- dilaton-black hole type solutions can be generated.
| [
{
"created": "Tue, 9 May 2000 09:43:10 GMT",
"version": "v1"
},
{
"created": "Fri, 12 May 2000 13:38:55 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Jun 2000 08:02:11 GMT",
"version": "v3"
}
] | 2010-02-03 | [
[
"Vacaru",
"Sergiu I.",
""
]
] | A new method of construction of integral varieties of Einstein equations in three dimensional (3D) and 4D gravity is presented whereby, under corresponding redefinition of physical values with respect to anholonomic frames of reference with associated nonlinear connections, the structure of gravity field equations is substantially simplified. It is shown that there are 4D solutions of Einstein equations which are constructed as nonlinear superpositions of soliton solutions of 2D (pseudo) Euclidean sine-Gordon equations (or of Lorentzian black holes in Jackiw-Teitelboim dilaton gravity). The Belinski-Zakharov-Meison solitons for vacuum gravitational field equations are generalized to various cases of two and three coordinate dependencies, local anisotropy and matter sources. The general framework of this study is based on investigation of anholonomic soliton-dilaton black hole structures in general relativity. We prove that there are possible static and dynamical black hole, black torus and disk/cylinder like solutions (of non-vacuum gravitational field equations) with horizons being parametrized by hypersurface equations of rotation ellipsoid, torus, cylinder and another type configurations. Solutions describing locally anisotropic variants of the Schwarzschild-- Kerr (black hole), Weyl (cylindrical symmetry) and Neugebauer--Meinel (disk) solutions with anisotropic variable masses, distributions of matter and interaction constants are shown to be contained in Einstein's gravity. It is demonstrated in which manner locally anisotropic multi-soliton-- dilaton-black hole type solutions can be generated. |
1901.08243 | Nikolaos Dimakis | T. Pailas, N. Dimakis, A. Karagiorgos, Petros A. Terzis, G.O.
Papadopoulos and T. Christodoulakis | Classical and quantum analysis of 3D electromagnetic pp-wave spacetime | 27 pages, no figures, updated to match the CQG published version | null | 10.1088/1361-6382/ab2561 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The general classical solution of the 3D electromagnetic pp-wave spacetime
has been obtained. The relevant line element contains an arbitrary essential
function providing an infinite number of in-equivalent geometries as solutions.
A classification is presented based on the symmetry group. To the best of our
knowledge, the solution corresponding to only one of the Classes is known. The
dynamics of some of the Classes was also derived from a minisuperspace
Lagrangian which has been constructed. This Lagrangian contains a degree of
freedom (the lapse) which can be considered either as dynamical or
non-dynamical (indicating a singular or a regular Lagrangian correspondingly).
Surprisingly enough, on the space of classical solutions, an equivalence of
these two points of view can be established. The canonical quantization is then
used in order to quantize the system for both the singular and regular
Hamiltonian. A subsequent interpretation of quantum states is based on a
Bohm-like analysis. The semi-classical trajectories deviate from the classical
only for the regular Hamiltonian and in particular for a superposition of
eigenstates (a Gaussian initial state has been used). Thus, the above mentioned
equivalence is broken at the quantum level. It is noteworthy that the
semi-classical trajectories tend to the classical ones in the limit where the
initial wavepacket is widely spread. Hence, even with this simple superposition
state, the classical solutions are acquired as a limit of the semi-classical.
| [
{
"created": "Thu, 24 Jan 2019 06:00:02 GMT",
"version": "v1"
},
{
"created": "Thu, 30 May 2019 02:47:52 GMT",
"version": "v2"
}
] | 2019-05-31 | [
[
"Pailas",
"T.",
""
],
[
"Dimakis",
"N.",
""
],
[
"Karagiorgos",
"A.",
""
],
[
"Terzis",
"Petros A.",
""
],
[
"Papadopoulos",
"G. O.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | The general classical solution of the 3D electromagnetic pp-wave spacetime has been obtained. The relevant line element contains an arbitrary essential function providing an infinite number of in-equivalent geometries as solutions. A classification is presented based on the symmetry group. To the best of our knowledge, the solution corresponding to only one of the Classes is known. The dynamics of some of the Classes was also derived from a minisuperspace Lagrangian which has been constructed. This Lagrangian contains a degree of freedom (the lapse) which can be considered either as dynamical or non-dynamical (indicating a singular or a regular Lagrangian correspondingly). Surprisingly enough, on the space of classical solutions, an equivalence of these two points of view can be established. The canonical quantization is then used in order to quantize the system for both the singular and regular Hamiltonian. A subsequent interpretation of quantum states is based on a Bohm-like analysis. The semi-classical trajectories deviate from the classical only for the regular Hamiltonian and in particular for a superposition of eigenstates (a Gaussian initial state has been used). Thus, the above mentioned equivalence is broken at the quantum level. It is noteworthy that the semi-classical trajectories tend to the classical ones in the limit where the initial wavepacket is widely spread. Hence, even with this simple superposition state, the classical solutions are acquired as a limit of the semi-classical. |
2209.04358 | Nikolaos Karnesis | Nikolaos Karnesis, Nikolaos Stergioulas, Georgios Pappas, Charis
Anastopoulos, John Antoniadis, Theocharis Apostolatos, Spyros Basilakos,
Kyriakos Destounis, Areti Eleni, Georgios Lukes-Gerakopoulos, Konstantinos N.
Gourgouliatos, Kostas D. Kokkotas, George Kottaras, V K Oikonomou, Theodoros
Papanikolaou, Leandros Perivolaropoulos, Manolis Plionis, Emmanuel N.
Saridakis, Theodoros Sarris, and Elias C. Vagenas, Wolf von Klitzing | The Laser Interferometer Space Antenna mission in Greece White Paper | 11 pages, 2 figures | null | null | null | gr-qc astro-ph.CO astro-ph.GA physics.space-ph | http://creativecommons.org/licenses/by/4.0/ | The Laser Interferometer Space Antenna (LISA) mission, scheduled for launch
in the mid-2030s, is a gravitational wave observatory in space designed to
detect sources emitting in the millihertz band. LISA is an ESA flagship
mission, currently entering the Phase B development phase. It is expected to
help us improve our understanding about our Universe by measuring gravitational
wave sources of different types, with some of the sources being at very high
redshifts $z\sim 20$. On the 23rd of February 2022 we organized the
1$^\mathrm{st}$ {\it LISA in Greece Workshop}. This workshop aimed to inform
the Greek scientific and tech industry community about the possibilities of
participating in LISA science and LISA mission, with the support of the
Hellenic Space Center (HSC). In this white paper, we summarize the outcome of
the workshop, the most important aspect of it being the inclusion of $15$ Greek
researchers to the LISA Consortium, raising our total number to $22$. At the
same time, we present a road-map with the future steps and actions of the Greek
Gravitational Wave community with respect to the future LISA mission.
| [
{
"created": "Fri, 9 Sep 2022 15:44:06 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Sep 2022 10:54:12 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Sep 2022 06:46:13 GMT",
"version": "v3"
},
{
"created": "Thu, 21 Sep 2023 08:41:25 GMT",
"version": "v4"
}
] | 2023-09-22 | [
[
"Karnesis",
"Nikolaos",
""
],
[
"Stergioulas",
"Nikolaos",
""
],
[
"Pappas",
"Georgios",
""
],
[
"Anastopoulos",
"Charis",
""
],
[
"Antoniadis",
"John",
""
],
[
"Apostolatos",
"Theocharis",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Destounis",
"Kyriakos",
""
],
[
"Eleni",
"Areti",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Gourgouliatos",
"Konstantinos N.",
""
],
[
"Kokkotas",
"Kostas D.",
""
],
[
"Kottaras",
"George",
""
],
[
"Oikonomou",
"V K",
""
],
[
"Papanikolaou",
"Theodoros",
""
],
[
"Perivolaropoulos",
"Leandros",
""
],
[
"Plionis",
"Manolis",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Sarris",
"Theodoros",
""
],
[
"Vagenas",
"Elias C.",
""
],
[
"von Klitzing",
"Wolf",
""
]
] | The Laser Interferometer Space Antenna (LISA) mission, scheduled for launch in the mid-2030s, is a gravitational wave observatory in space designed to detect sources emitting in the millihertz band. LISA is an ESA flagship mission, currently entering the Phase B development phase. It is expected to help us improve our understanding about our Universe by measuring gravitational wave sources of different types, with some of the sources being at very high redshifts $z\sim 20$. On the 23rd of February 2022 we organized the 1$^\mathrm{st}$ {\it LISA in Greece Workshop}. This workshop aimed to inform the Greek scientific and tech industry community about the possibilities of participating in LISA science and LISA mission, with the support of the Hellenic Space Center (HSC). In this white paper, we summarize the outcome of the workshop, the most important aspect of it being the inclusion of $15$ Greek researchers to the LISA Consortium, raising our total number to $22$. At the same time, we present a road-map with the future steps and actions of the Greek Gravitational Wave community with respect to the future LISA mission. |
2206.10998 | Hideki Maeda | Takuma Sato, Hideki Maeda, Tomohiro Harada | Conformally Schwarzschild cosmological black holes | 58 pages, 10 figures, 8 tables; v3, this version corrects the
published version according to the corrigendum (2023 Class. Quantum Grav. 40,
079501). The main results remain unchanged | Class. Quant. Grav. 39 (2022) 21, 215011 | 10.1088/1361-6382/ac902f | RUP-22-13 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We thoroughly investigate conformally Schwarzschild spacetimes in different
coordinate systems to seek for physically reasonable models of a cosmological
black hole. We assume that a conformal factor depends only on the time
coordinate and that the spacetime is asymptotically flat
Friedmann-Lema\^{\i}tre-Robertson-Walker universe filled by a perfect fluid
obeying a linear equation state $p=w\rho$ with $w>-1/3$. In this class of
spacetimes, the McClure-Dyer spacetime, constructed in terms of the isotropic
coordinates, and the Thakurta spacetime, constructed in terms of the standard
Schwarzschild coordinates, are identical and do not describe a cosmological
black hole. In contrast, the Sultana-Dyer and Culetu classes of spacetimes,
constructed in terms of the Kerr-Schild and Painlev\'{e}-Gullstrand
coordinates, respectively, describe a cosmological black hole. In the
Sultana-Dyer case, the corresponding matter field in general relativity can be
interpreted as a combination of a homogeneous perfect fluid and an
inhomogeneous null fluid, which is valid everywhere in the spacetime unlike
Sultana and Dyer's interpretation. In the Culetu case, the matter field can be
interpreted as a combination of a homogeneous perfect fluid and an
inhomogeneous anisotropic fluid. However, in both cases, the total
energy-momentum tensor violates all the standard energy conditions at a finite
value of the radial coordinate in late times. As a consequence, the
Sultana-Dyer and Culetu black holes for $-1/3<w\le 1$ cannot describe the
evolution of a primordial black hole after its horizon entry.
| [
{
"created": "Wed, 22 Jun 2022 11:56:25 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Sep 2022 13:24:09 GMT",
"version": "v2"
},
{
"created": "Sun, 12 Mar 2023 07:52:23 GMT",
"version": "v3"
}
] | 2023-03-14 | [
[
"Sato",
"Takuma",
""
],
[
"Maeda",
"Hideki",
""
],
[
"Harada",
"Tomohiro",
""
]
] | We thoroughly investigate conformally Schwarzschild spacetimes in different coordinate systems to seek for physically reasonable models of a cosmological black hole. We assume that a conformal factor depends only on the time coordinate and that the spacetime is asymptotically flat Friedmann-Lema\^{\i}tre-Robertson-Walker universe filled by a perfect fluid obeying a linear equation state $p=w\rho$ with $w>-1/3$. In this class of spacetimes, the McClure-Dyer spacetime, constructed in terms of the isotropic coordinates, and the Thakurta spacetime, constructed in terms of the standard Schwarzschild coordinates, are identical and do not describe a cosmological black hole. In contrast, the Sultana-Dyer and Culetu classes of spacetimes, constructed in terms of the Kerr-Schild and Painlev\'{e}-Gullstrand coordinates, respectively, describe a cosmological black hole. In the Sultana-Dyer case, the corresponding matter field in general relativity can be interpreted as a combination of a homogeneous perfect fluid and an inhomogeneous null fluid, which is valid everywhere in the spacetime unlike Sultana and Dyer's interpretation. In the Culetu case, the matter field can be interpreted as a combination of a homogeneous perfect fluid and an inhomogeneous anisotropic fluid. However, in both cases, the total energy-momentum tensor violates all the standard energy conditions at a finite value of the radial coordinate in late times. As a consequence, the Sultana-Dyer and Culetu black holes for $-1/3<w\le 1$ cannot describe the evolution of a primordial black hole after its horizon entry. |
1411.4599 | David Nichols | \'Eanna \'E. Flanagan, David A. Nichols | Observer dependence of angular momentum in general relativity and its
relationship to the gravitational-wave memory effect | 19 pages, 2 figures. Matches version published in Phys. Rev. D with
errors in Appendix A corrected | Phys. Rev. D 92, 084057 (2015). Erratum: Phys. Rev. D 93 049905
(2016) | 10.1103/PhysRevD.92.084057 10.1103/PhysRevD.93.049905 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We define a procedure by which observers can measure a type of
special-relativistic linear and angular momentum $(P^a, J^{ab})$ at a point in
a curved spacetime using only the spacetime geometry in a neighborhood of that
point. The method is chosen to yield the conventional results in stationary
spacetimes near future null infinity.
We also explore the extent to which spatially separated observers can compare
the values of angular momentum that they measure and find consistent results.
We define a generalization of parallel transport along curves which gives a
prescription for transporting values of angular momentum along curves that
yields the correct result in special relativity. If observers use this
prescription, then they will find that the angular momenta they measure are
observer dependent, because of the effects of spacetime curvature. The observer
dependence can be quantified by a kind of generalized holonomy. We show that
bursts of gravitational waves with memory generically give rise to a nontrivial
generalized holonomy: there is, in this context, a close relation between the
observer dependence of angular momentum and the gravitational-wave memory
effect.
| [
{
"created": "Mon, 17 Nov 2014 19:21:43 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jul 2015 17:45:05 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Oct 2015 18:42:02 GMT",
"version": "v3"
},
{
"created": "Mon, 1 Feb 2016 23:48:02 GMT",
"version": "v4"
}
] | 2016-06-08 | [
[
"Flanagan",
"Éanna É.",
""
],
[
"Nichols",
"David A.",
""
]
] | We define a procedure by which observers can measure a type of special-relativistic linear and angular momentum $(P^a, J^{ab})$ at a point in a curved spacetime using only the spacetime geometry in a neighborhood of that point. The method is chosen to yield the conventional results in stationary spacetimes near future null infinity. We also explore the extent to which spatially separated observers can compare the values of angular momentum that they measure and find consistent results. We define a generalization of parallel transport along curves which gives a prescription for transporting values of angular momentum along curves that yields the correct result in special relativity. If observers use this prescription, then they will find that the angular momenta they measure are observer dependent, because of the effects of spacetime curvature. The observer dependence can be quantified by a kind of generalized holonomy. We show that bursts of gravitational waves with memory generically give rise to a nontrivial generalized holonomy: there is, in this context, a close relation between the observer dependence of angular momentum and the gravitational-wave memory effect. |
gr-qc/0702099 | Andrea Passamonti | Andrea Passamonti, Nikolaos Stergioulas, Alessandro Nagar | Gravitational Waves from Nonlinear Couplings of Radial and Polar
Nonradial Modes in Relativistic Stars | 12 pages, 7 figures, ReVTeX 4.0, submitted to Phys. Rev. D | Phys.Rev.D75:084038,2007 | 10.1103/PhysRevD.75.084038 | null | gr-qc astro-ph | null | The post-bounce oscillations of newly-born relativistic stars are expected to
lead to gravitational-wave emission through the excitation of nonradial
oscillation modes. At the same time, the star is oscillating in its radial
modes, with a central density variation that can reach several percent.
Nonlinear couplings between radial oscillations and polar nonradial modes lead
to the appearance of combination frequencies (sums and differences of the
linear mode frequencies). We study such combination frequencies using a
gauge-invariant perturbative formalism, which includes bilinear coupling terms
between different oscillation modes. For typical values of the energy stored in
each mode we find that gravitational waves emitted at combination frequencies
could become detectable in galactic core-collapse supernovae with advanced
interferometric or wide-band resonant detectors.
| [
{
"created": "Sat, 17 Feb 2007 17:39:05 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Passamonti",
"Andrea",
""
],
[
"Stergioulas",
"Nikolaos",
""
],
[
"Nagar",
"Alessandro",
""
]
] | The post-bounce oscillations of newly-born relativistic stars are expected to lead to gravitational-wave emission through the excitation of nonradial oscillation modes. At the same time, the star is oscillating in its radial modes, with a central density variation that can reach several percent. Nonlinear couplings between radial oscillations and polar nonradial modes lead to the appearance of combination frequencies (sums and differences of the linear mode frequencies). We study such combination frequencies using a gauge-invariant perturbative formalism, which includes bilinear coupling terms between different oscillation modes. For typical values of the energy stored in each mode we find that gravitational waves emitted at combination frequencies could become detectable in galactic core-collapse supernovae with advanced interferometric or wide-band resonant detectors. |
gr-qc/0612062 | Lau Loi So | Lau Loi So and James M. Nester | On source coupling and the teleparallel equivalent to GR | 5 pages | Proceedings of the tenth Marcel Grossman meeting on general
relativity 2003, p.1498. | null | null | gr-qc | null | Alternatives to the usual general relativity (GR) Riemannian framework
include Riemann-Cartan and teleparallel geometry. The ``teleparallel equivalent
of GR" (TEGR, aka GR${}_{||}$) has certain virtues, however there have been
allegations of serious source coupling limitations. Now it is quite
straightforward to show that the coupled dynamical field equations of
Einstein's GR with any source can be accurately represented in terms of any
other connection, in particular teleparallel geometry. Using an argument
similar to one used long ago to show the "effective equivalence" between GR and
the Einstein-Cartan theory, we construct the teleparallel action which is
equivalent to a given Riemanian one; thereby finding the ``effectively
equivalent" coupling principle for all sources, including spinors. No auxiliary
field is required. Can one decide which is the real "physical" geometry?
Invoking the minimal coupling principle may give a unique answer.
| [
{
"created": "Mon, 11 Dec 2006 12:11:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"So",
"Lau Loi",
""
],
[
"Nester",
"James M.",
""
]
] | Alternatives to the usual general relativity (GR) Riemannian framework include Riemann-Cartan and teleparallel geometry. The ``teleparallel equivalent of GR" (TEGR, aka GR${}_{||}$) has certain virtues, however there have been allegations of serious source coupling limitations. Now it is quite straightforward to show that the coupled dynamical field equations of Einstein's GR with any source can be accurately represented in terms of any other connection, in particular teleparallel geometry. Using an argument similar to one used long ago to show the "effective equivalence" between GR and the Einstein-Cartan theory, we construct the teleparallel action which is equivalent to a given Riemanian one; thereby finding the ``effectively equivalent" coupling principle for all sources, including spinors. No auxiliary field is required. Can one decide which is the real "physical" geometry? Invoking the minimal coupling principle may give a unique answer. |
0802.0788 | Sini R | Sini R, Nijo Varghese, V. C. Kuriakose | Quasi-normal modes of spherically symmetric black hole spacetimes with
cosmic string in a Dirac field | 16 pages, 16 figures, title, abstract and content in section 2
changed | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dirac equation for a general black hole metric having a cosmic string is
derived. The quasi-normal mode frequencies for Schwarzschild, RN extremal, SdS
and near extremal SdS black hole space-times with cosmic string perturbed by a
massless Dirac field are obtained using WKB approximation and found that in all
these cases, decay is less in black holes having cosmic string compared to
black holes with out string.
| [
{
"created": "Wed, 6 Feb 2008 13:16:29 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Sep 2008 12:27:30 GMT",
"version": "v2"
}
] | 2008-09-02 | [
[
"R",
"Sini",
""
],
[
"Varghese",
"Nijo",
""
],
[
"Kuriakose",
"V. C.",
""
]
] | Dirac equation for a general black hole metric having a cosmic string is derived. The quasi-normal mode frequencies for Schwarzschild, RN extremal, SdS and near extremal SdS black hole space-times with cosmic string perturbed by a massless Dirac field are obtained using WKB approximation and found that in all these cases, decay is less in black holes having cosmic string compared to black holes with out string. |
0901.4674 | Jurjen Koksma | Jurjen F. Koksma (Utrecht University), Tomislav Prokopec (Utrecht
University) | Fermion Propagator in Cosmological Spaces with Constant Deceleration | 18 pages, 1 figure, published version | Class.Quant.Grav.26:125003,2009 | 10.1088/0264-9381/26/12/125003 | ITP-UU-09/01, SPIN-09/01 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the fermion propagator in FLRW spacetimes with constant
deceleration $q=\epsilon-1$, $\epsilon=-\dot{H}/H^{2}$ for excited states. For
fermions whose mass is generated by a scalar field through a Yukawa coupling
$m=g_{\mathrm{\scriptscriptstyle{Y}}} \phi$, we assume $\phi \propto H$. We
first solve for the mode functions by splitting the spinor into a direct
product of helicity and chirality spinors. We also allow for non-vacuum states.
We normalise the spinors using a consistent canonical quantisation and by
requiring orthogonality of particle and anti-particle spinors. We apply our
propagator to calculate the one loop effective action and renormalise using
dimensional regularisation. Since the Hubble parameter is now treated
dynamically, this paves the way to study the dynamical backreaction of fermions
on the background spacetime.
| [
{
"created": "Thu, 29 Jan 2009 13:17:58 GMT",
"version": "v1"
},
{
"created": "Thu, 7 May 2009 17:03:21 GMT",
"version": "v2"
}
] | 2010-01-15 | [
[
"Koksma",
"Jurjen F.",
"",
"Utrecht University"
],
[
"Prokopec",
"Tomislav",
"",
"Utrecht\n University"
]
] | We calculate the fermion propagator in FLRW spacetimes with constant deceleration $q=\epsilon-1$, $\epsilon=-\dot{H}/H^{2}$ for excited states. For fermions whose mass is generated by a scalar field through a Yukawa coupling $m=g_{\mathrm{\scriptscriptstyle{Y}}} \phi$, we assume $\phi \propto H$. We first solve for the mode functions by splitting the spinor into a direct product of helicity and chirality spinors. We also allow for non-vacuum states. We normalise the spinors using a consistent canonical quantisation and by requiring orthogonality of particle and anti-particle spinors. We apply our propagator to calculate the one loop effective action and renormalise using dimensional regularisation. Since the Hubble parameter is now treated dynamically, this paves the way to study the dynamical backreaction of fermions on the background spacetime. |
gr-qc/0105054 | Elisa Di Pietro | Elisa Di Pietro | Scale factor duality in quintessence models ? | 10 pages, 3 figures, submitted to Mod.Phys.Lett.A | null | null | null | gr-qc astro-ph | null | We consider several kinds of quintessence models in the framework of scale
factor duality. We show that this symmetry exists only for a very small number
of quintessence potentials. We then apply the duality transformations found to
several analytical solutions. It turns out that, in some cases, the presence of
the potential allows a smooth connection between the pre- and the post-Big Bang
phases. This may be a first step toward the resolution of the singularity
problem.
| [
{
"created": "Wed, 16 May 2001 09:07:36 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Di Pietro",
"Elisa",
""
]
] | We consider several kinds of quintessence models in the framework of scale factor duality. We show that this symmetry exists only for a very small number of quintessence potentials. We then apply the duality transformations found to several analytical solutions. It turns out that, in some cases, the presence of the potential allows a smooth connection between the pre- and the post-Big Bang phases. This may be a first step toward the resolution of the singularity problem. |
gr-qc/9811010 | Garcia | L.C.Garcia de Andrade | On the non-minimal coupling of Riemann-flat Klein-Gordon | 5 pages, Latex | null | null | null | gr-qc | null | On the non-minimal coupling of Riemann-flat Klein-Gordon Fields to Space-time
torsion} The energy spectrum of Klein-Gordon particles is obtained via the
non-minimal coupling of Klein-Gordon fields to Cartan torsion in the
approximation of Riemann-flatness and constant torsion.When the mass squared is
proportional to torsion coupling constant it is shown that the splitting of
energy does not occur.I consider that only the vector part of torsion does not
vanish and that it is constant.A torsion Hamiltonian operator is
constructed.The spectrum of Klein-Gordon fields is continuos.
| [
{
"created": "Tue, 3 Nov 1998 22:24:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | On the non-minimal coupling of Riemann-flat Klein-Gordon Fields to Space-time torsion} The energy spectrum of Klein-Gordon particles is obtained via the non-minimal coupling of Klein-Gordon fields to Cartan torsion in the approximation of Riemann-flatness and constant torsion.When the mass squared is proportional to torsion coupling constant it is shown that the splitting of energy does not occur.I consider that only the vector part of torsion does not vanish and that it is constant.A torsion Hamiltonian operator is constructed.The spectrum of Klein-Gordon fields is continuos. |
2304.07364 | Silas Vilhena | S. G. Vilhena, M. Dutra, O. Louren\c{c}o, P. J. Pompeia | Dark matter effects in modified teleparallel gravity | 8 pages, 2 figures | Phys. Rev. D. 108, 104051 (2023) | 10.1103/PhysRevD.108.104051 | null | gr-qc astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work investigates dark matter (DM) effects in compact objects in
modified teleparallel gravity (MTG) in which a modification of Teleparallel
Equivalent to General Relativity is used. We applied a tetrad to the modified
field equations where a set of relations is found. The conservation equation
allows us to rewrite our Tolman-Oppenheimer-Volkoff equations with an effective
gravitational coupling constant. As input to these new equations, we use a
relativistic mean-field (RMF) model with dark matter content included, obtained
from a Lagrangian density with both, hadronic and dark particle degrees of
freedom, as well as the Higgs boson, used as a mediator in both sectors of the
theory. Through numerical calculations, we analyze the mass-radius diagrams
obtained from different parametrizations of the RMF-DM model, generated by
assuming different values of the dark particle Fermi momentum and running the
free parameter coming from the MTG. Our results show that it is possible for
the system simultaneously support more DM content, and be compatible with
recent astrophysical data provided by LIGO and Virgo Collaboration, as well as
by NASA's Neutron star Interior Composition Explorer (NICER).
| [
{
"created": "Fri, 14 Apr 2023 19:49:29 GMT",
"version": "v1"
}
] | 2023-11-30 | [
[
"Vilhena",
"S. G.",
""
],
[
"Dutra",
"M.",
""
],
[
"Lourenço",
"O.",
""
],
[
"Pompeia",
"P. J.",
""
]
] | This work investigates dark matter (DM) effects in compact objects in modified teleparallel gravity (MTG) in which a modification of Teleparallel Equivalent to General Relativity is used. We applied a tetrad to the modified field equations where a set of relations is found. The conservation equation allows us to rewrite our Tolman-Oppenheimer-Volkoff equations with an effective gravitational coupling constant. As input to these new equations, we use a relativistic mean-field (RMF) model with dark matter content included, obtained from a Lagrangian density with both, hadronic and dark particle degrees of freedom, as well as the Higgs boson, used as a mediator in both sectors of the theory. Through numerical calculations, we analyze the mass-radius diagrams obtained from different parametrizations of the RMF-DM model, generated by assuming different values of the dark particle Fermi momentum and running the free parameter coming from the MTG. Our results show that it is possible for the system simultaneously support more DM content, and be compatible with recent astrophysical data provided by LIGO and Virgo Collaboration, as well as by NASA's Neutron star Interior Composition Explorer (NICER). |
1412.2054 | Giulia Gubitosi | Michele Arzano, Giulia Gubitosi, Joao Magueijo, Giovanni
Amelino-Camelia | Planck-scale phenomenology with anti-de Sitter momentum space | null | Phys. Rev. D 92, 024028 (2015) | 10.1103/PhysRevD.92.024028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the anti-de Sitter (AdS) counterpart to the well studied de
Sitter (dS) model for energy-momentum space, viz "$\kappa$-momentum space"
space (with a structure based on the properties of the $\kappa$-Poincar\'e Hopf
algebra). On the basis of previous preliminary results one might expect the two
models to be "dual": dS exhibiting an invariant maximal spatial momentum but
unbounded energy, AdS a maximal energy but unbounded momentum. If that were the
case AdS momentum space could be used to implement a principle of maximal
Planck-scale energy, just as several studies use dS momentum space to postulate
of maximal Planck-scale spatial momentum. However several unexpected features
are uncovered in this paper, which limit the scope of the expected duality, and
interestingly they take different forms in different coordinatizations of AdS
momentum space. "Cosmological" AdS coordinates mimic the dS construction used
for $\kappa$-momentum space, and produce a Carrol limit in the ultraviolet.
However, unlike the $\kappa$-momentum space, the boundary of the covered patch
breaks Lorentz invariance, thereby introducing a preferred frame. In
"horospherical" coordinates we achieve full consistency with frame independence
as far as boost transformations are concerned, but find that rotational
symmetry is broken, leading to an anisotropic model for the speed of light.
Finally, in "static" coordinates we find a way of deforming relativistic
transformations that successfully enforces frame invariance and isotropy, and
produces a Carrol limit in the ultraviolet. However, the phenomenological
implications appear to be too weak for any realistic chance of detection. Our
results are also relevant for a long-standing debate on whether or not
coordinate redefinitions in momentum space lead to physically equivalent
theories: our three proposals are evidently physically inequivalent (abridged)
| [
{
"created": "Fri, 5 Dec 2014 16:43:54 GMT",
"version": "v1"
}
] | 2015-07-22 | [
[
"Arzano",
"Michele",
""
],
[
"Gubitosi",
"Giulia",
""
],
[
"Magueijo",
"Joao",
""
],
[
"Amelino-Camelia",
"Giovanni",
""
]
] | We investigate the anti-de Sitter (AdS) counterpart to the well studied de Sitter (dS) model for energy-momentum space, viz "$\kappa$-momentum space" space (with a structure based on the properties of the $\kappa$-Poincar\'e Hopf algebra). On the basis of previous preliminary results one might expect the two models to be "dual": dS exhibiting an invariant maximal spatial momentum but unbounded energy, AdS a maximal energy but unbounded momentum. If that were the case AdS momentum space could be used to implement a principle of maximal Planck-scale energy, just as several studies use dS momentum space to postulate of maximal Planck-scale spatial momentum. However several unexpected features are uncovered in this paper, which limit the scope of the expected duality, and interestingly they take different forms in different coordinatizations of AdS momentum space. "Cosmological" AdS coordinates mimic the dS construction used for $\kappa$-momentum space, and produce a Carrol limit in the ultraviolet. However, unlike the $\kappa$-momentum space, the boundary of the covered patch breaks Lorentz invariance, thereby introducing a preferred frame. In "horospherical" coordinates we achieve full consistency with frame independence as far as boost transformations are concerned, but find that rotational symmetry is broken, leading to an anisotropic model for the speed of light. Finally, in "static" coordinates we find a way of deforming relativistic transformations that successfully enforces frame invariance and isotropy, and produces a Carrol limit in the ultraviolet. However, the phenomenological implications appear to be too weak for any realistic chance of detection. Our results are also relevant for a long-standing debate on whether or not coordinate redefinitions in momentum space lead to physically equivalent theories: our three proposals are evidently physically inequivalent (abridged) |
gr-qc/0001062 | Patrice Hello | T. Pradier, N. Arnaud, M.-A. Bizouard, F. Cavalier, M. Davier and P.
Hello | About the detection of gravitational wave bursts | 5 pages, proceedings of GWDAW99 (Roma, Dec. 1999), to appear in Int.
J. Mod. Phys. D | Int.J.Mod.Phys. D9 (2000) 309-314 | 10.1142/S0218271800000335 | null | gr-qc | null | Several filtering methods for the detection of gravitational wave bursts in
interferometric detectors are presented. These are simple and fast methods
which can act as online triggers. All methods are compared to matched filtering
with the help of a figure of merit based on the detection of supernovae signals
simulated by Zwerger and Muller.
| [
{
"created": "Fri, 21 Jan 2000 09:14:52 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Pradier",
"T.",
""
],
[
"Arnaud",
"N.",
""
],
[
"Bizouard",
"M. -A.",
""
],
[
"Cavalier",
"F.",
""
],
[
"Davier",
"M.",
""
],
[
"Hello",
"P.",
""
]
] | Several filtering methods for the detection of gravitational wave bursts in interferometric detectors are presented. These are simple and fast methods which can act as online triggers. All methods are compared to matched filtering with the help of a figure of merit based on the detection of supernovae signals simulated by Zwerger and Muller. |
1306.5633 | Wei Zhang | Yi Ling, Chao Niu, Yu Tian, Xiao-Ning Wu and Wei Zhang | The Petrov-like boundary condition at finite cutoff surface in
Gravity/Fluid duality | 17 pages, no figures, published in PRD | Phys. Rev. D 90, 043525 (2014) | 10.1103/PhysRevD.90.043525 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Previously it has been shown that imposing a Petrov-like boundary condition
on a hypersurface may reduce the Einstein equation to the incompressible
Navier-Stokes equation, but all these correspondences are established in the
near horizon limit. In this note, we remark that this strategy can be extended
to an arbitrary finite cutoff surface which is spatially flat, and the
Navier-Stokes equation is obtained by employing a non-relativistic
long-wavelength limit.
| [
{
"created": "Mon, 24 Jun 2013 14:01:58 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Sep 2013 14:06:51 GMT",
"version": "v2"
},
{
"created": "Sun, 24 Aug 2014 15:23:58 GMT",
"version": "v3"
}
] | 2014-08-27 | [
[
"Ling",
"Yi",
""
],
[
"Niu",
"Chao",
""
],
[
"Tian",
"Yu",
""
],
[
"Wu",
"Xiao-Ning",
""
],
[
"Zhang",
"Wei",
""
]
] | Previously it has been shown that imposing a Petrov-like boundary condition on a hypersurface may reduce the Einstein equation to the incompressible Navier-Stokes equation, but all these correspondences are established in the near horizon limit. In this note, we remark that this strategy can be extended to an arbitrary finite cutoff surface which is spatially flat, and the Navier-Stokes equation is obtained by employing a non-relativistic long-wavelength limit. |
2101.09168 | Faizuddin Ahmed | Faizuddin Ahmed | Linear confinement of generalized KG-oscillator with a uniform magnetic
field in Kaluza-Klein theory and Aharonov-Bohm effect | 23 pages, accepted in Scientific Reports journal. arXiv admin note:
text overlap with arXiv:2008.04745 | Sci. Rep. 11, 1742 (2021) | 10.1038/s41598-021-81273-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we solve generalized KG-oscillator interacts with a uniform
magnetic field in five-dimensional space-time background produced by
topological defects under a linear confining potential using the Kaluza-Klein
theory. We solve this equation and analyze an analogue of the Aharonov-Bohm
effect for bound states. We observe that the energy levels for each radial mode
depends on the global parameters characterizing the space-time, the confining
potential, and the magnetic field which shows a quantum effect
| [
{
"created": "Thu, 21 Jan 2021 11:53:11 GMT",
"version": "v1"
}
] | 2021-01-25 | [
[
"Ahmed",
"Faizuddin",
""
]
] | In this paper, we solve generalized KG-oscillator interacts with a uniform magnetic field in five-dimensional space-time background produced by topological defects under a linear confining potential using the Kaluza-Klein theory. We solve this equation and analyze an analogue of the Aharonov-Bohm effect for bound states. We observe that the energy levels for each radial mode depends on the global parameters characterizing the space-time, the confining potential, and the magnetic field which shows a quantum effect |
1301.1479 | Sunil Maharaj | A. M. Msomi, K. S Govinder, S. D. Maharaj | Applications of Lie Symmetries to Higher Dimensional Gravitating Fluid | 10 pages, To appear in Int. J. Theor. Phys. arXiv admin note: text
overlap with arXiv:1212.6655 | Int. J. Theor. Phys. 51: 1290-1299, 2012 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a radiating shear-free spherically symmetric metric in higher
dimensions. Several new solutions to the Einstein's equations are found
systematically using the method of Lie analysis of differential equations.
Using the five Lie point symmetries of the fundamental field equation, we
obtain either an implicit solution or we can reduce the governing equations to
a Riccati equation. We show that known solutions of the Einstein equations can
produce infinite families of new solutions. Earlier results in four dimensions
are shown to be special cases of our generalised results.
| [
{
"created": "Tue, 8 Jan 2013 10:39:53 GMT",
"version": "v1"
}
] | 2013-01-09 | [
[
"Msomi",
"A. M.",
""
],
[
"Govinder",
"K. S",
""
],
[
"Maharaj",
"S. D.",
""
]
] | We consider a radiating shear-free spherically symmetric metric in higher dimensions. Several new solutions to the Einstein's equations are found systematically using the method of Lie analysis of differential equations. Using the five Lie point symmetries of the fundamental field equation, we obtain either an implicit solution or we can reduce the governing equations to a Riccati equation. We show that known solutions of the Einstein equations can produce infinite families of new solutions. Earlier results in four dimensions are shown to be special cases of our generalised results. |
2408.01863 | Biswajit Deb | Biswajit Deb, Atri Deshamukhya | Slow-roll Hilltop Inflation in $f(\phi,T)$ gravity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Over the last four decades, a number of modified gravity theories have been
proposed to study cosmological phenomena as they can provide solutions for some
of the shortcomings of Einstein's gravity in explaining early and late time
accelerations of the observed Universe, the existence of dark matter,
singularities at center of Black holes etc. The theoretical and observational
challenges faced by the $\Lambda$CDM model also point towards the necessity for
looking beyond General Relativity. In this direction, recently $f(\phi, T)$
gravity has been proposed in literature where the non-minimal coupling of the
scalar field $\phi$ with the trace of energy-momentum tensor $T$ has been
introduced in the Einstein-Hilbert action. Considering the Hilltop potential,
we have studied the slow-roll inflation in the framework of $f(\phi, T)$
gravity. It is found that Hilltop inflationary models in $f(\phi, T)$ gravity
are viable when seen in the light of latest Planck data.
| [
{
"created": "Sat, 3 Aug 2024 20:53:02 GMT",
"version": "v1"
}
] | 2024-08-06 | [
[
"Deb",
"Biswajit",
""
],
[
"Deshamukhya",
"Atri",
""
]
] | Over the last four decades, a number of modified gravity theories have been proposed to study cosmological phenomena as they can provide solutions for some of the shortcomings of Einstein's gravity in explaining early and late time accelerations of the observed Universe, the existence of dark matter, singularities at center of Black holes etc. The theoretical and observational challenges faced by the $\Lambda$CDM model also point towards the necessity for looking beyond General Relativity. In this direction, recently $f(\phi, T)$ gravity has been proposed in literature where the non-minimal coupling of the scalar field $\phi$ with the trace of energy-momentum tensor $T$ has been introduced in the Einstein-Hilbert action. Considering the Hilltop potential, we have studied the slow-roll inflation in the framework of $f(\phi, T)$ gravity. It is found that Hilltop inflationary models in $f(\phi, T)$ gravity are viable when seen in the light of latest Planck data. |
2110.05953 | Ding Jia | Ding Jia | Complex, Lorentzian, and Euclidean simplicial quantum gravity: numerical
methods and physical prospects | matches well published version | Class. Quantum Grav. 39, 065002 (2022) | 10.1088/1361-6382/ac4b04 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Evaluating gravitational path integrals in the Lorentzian has been a
long-standing challenge due to the numerical sign problem. We show that this
challenge can be overcome in simplicial quantum gravity. By deforming the
integration contour into the complex, the sign fluctuations can be suppressed,
for instance using the holomorphic gradient flow algorithm. Working through
simple models, we show that this algorithm enables efficient Monte Carlo
simulations for Lorentzian simplicial quantum gravity.
In order to allow complex deformations of the integration contour, we provide
a manifestly holomorphic formula for Lorentzian simplicial gravity. This leads
to a complex version of simplicial gravity that generalizes the Euclidean and
Lorentzian cases. Outside the context of numerical computation, complex
simplicial gravity is also relevant to studies of singularity resolving
processes with complex semi-classical solutions. Along the way, we prove a
complex version of the Gauss-Bonnet theorem, which may be of independent
interest.
| [
{
"created": "Mon, 11 Oct 2021 02:35:37 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2021 15:17:18 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Mar 2022 20:52:56 GMT",
"version": "v3"
}
] | 2022-03-03 | [
[
"Jia",
"Ding",
""
]
] | Evaluating gravitational path integrals in the Lorentzian has been a long-standing challenge due to the numerical sign problem. We show that this challenge can be overcome in simplicial quantum gravity. By deforming the integration contour into the complex, the sign fluctuations can be suppressed, for instance using the holomorphic gradient flow algorithm. Working through simple models, we show that this algorithm enables efficient Monte Carlo simulations for Lorentzian simplicial quantum gravity. In order to allow complex deformations of the integration contour, we provide a manifestly holomorphic formula for Lorentzian simplicial gravity. This leads to a complex version of simplicial gravity that generalizes the Euclidean and Lorentzian cases. Outside the context of numerical computation, complex simplicial gravity is also relevant to studies of singularity resolving processes with complex semi-classical solutions. Along the way, we prove a complex version of the Gauss-Bonnet theorem, which may be of independent interest. |
2203.04081 | Iver Brevik | I. Brevik and A. V. Timoshkin | Holographic representation of the unified early and late universe via a
viscous dark fluid | 6 pages, minor changes in the references; to appear in Int. J. Geom.
Meth. Mod. Phys | Int. J. Geom. Meth. Mod. Phys. 19, 2250113 (2022) | 10.1142/S0219887822501134 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this article we apply the holographic principle for describing in a
unifying way the early and the late-time universe, when the general equation of
state contains a bulk viscosity. We use the idea of a generalized cut-off
holographic dark energy introduced by Nojiri and Odintsov (2006,2017), and
study the evolution of the universe when the equation of state has two
power-law asymptotes. Analytical expressions for the infrared cut-offs in terms
of the particle horizon are obtained. The energy conservation laws as derived
from the holographic point of view, are given for various forms of the
thermodynamic parameters and for various forms of the bulk viscosity. As a
result, we obtain a unifying description of the early and the late-time
universe in the presence of a viscous holographic fluid.
| [
{
"created": "Tue, 8 Mar 2022 13:52:47 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Apr 2022 18:52:02 GMT",
"version": "v2"
}
] | 2022-06-24 | [
[
"Brevik",
"I.",
""
],
[
"Timoshkin",
"A. V.",
""
]
] | In this article we apply the holographic principle for describing in a unifying way the early and the late-time universe, when the general equation of state contains a bulk viscosity. We use the idea of a generalized cut-off holographic dark energy introduced by Nojiri and Odintsov (2006,2017), and study the evolution of the universe when the equation of state has two power-law asymptotes. Analytical expressions for the infrared cut-offs in terms of the particle horizon are obtained. The energy conservation laws as derived from the holographic point of view, are given for various forms of the thermodynamic parameters and for various forms of the bulk viscosity. As a result, we obtain a unifying description of the early and the late-time universe in the presence of a viscous holographic fluid. |
2407.12328 | Ran Chen | Ran Chen, Zhao Li, Yin-Jie Li, Yi-Ying Wang, Rui Niu, Wen Zhao, and
Yi-Zhong Fan | Forecast Analysis of Astrophysical Stochastic Gravitational Wave
Background beyond general relativity: A Case Study on Brans-Dicke Gravity | 26 pages, 6 figures, and 2 tables | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar-tensor gravity, exemplified by Brans-Dicke (BD) gravity, introduces
additional scalar polarization modes that contribute scalar radiation alongside
tensor modes. We conduct a comprehensive analysis of how gravitational wave
generation and propagation effects under Brans-Dicke gravity are encoded into
the astrophysical stochastic gravitational wave background (AGWB). We perform
end-to-end analyses of realistic populations of simulated coalescing binary
systems to generate AGWB mock data with third-generation gravitational wave
detectors and conducted a complete Bayesian analysis for the first time. We
find the uncertainties in the population properties of binary black holes (BBH)
significantly affect the ability to constrain BD gravity. Under the most
favorable conditions, the upper limit may suggest $\omega_{\rm BD} > 816$.
Furthermore, we explore the detectability of potential scalar backgrounds
arising from binary neutron star (BNS) mergers, setting upper limits on scalar
backgrounds expected to be two orders of magnitude lower than the total
background contributed by both BBH and BNS in one year of observational data.
We conclude that for ambiguous populations, employing waveform matching with
individual sources provides a more robust approach to constrain Brans-Dicke
gravity. However, the future detection of a potential scalar background within
the AGWB could provide significant support for gravity theories beyond General
Relativity.
| [
{
"created": "Wed, 17 Jul 2024 06:07:03 GMT",
"version": "v1"
}
] | 2024-07-18 | [
[
"Chen",
"Ran",
""
],
[
"Li",
"Zhao",
""
],
[
"Li",
"Yin-Jie",
""
],
[
"Wang",
"Yi-Ying",
""
],
[
"Niu",
"Rui",
""
],
[
"Zhao",
"Wen",
""
],
[
"Fan",
"Yi-Zhong",
""
]
] | Scalar-tensor gravity, exemplified by Brans-Dicke (BD) gravity, introduces additional scalar polarization modes that contribute scalar radiation alongside tensor modes. We conduct a comprehensive analysis of how gravitational wave generation and propagation effects under Brans-Dicke gravity are encoded into the astrophysical stochastic gravitational wave background (AGWB). We perform end-to-end analyses of realistic populations of simulated coalescing binary systems to generate AGWB mock data with third-generation gravitational wave detectors and conducted a complete Bayesian analysis for the first time. We find the uncertainties in the population properties of binary black holes (BBH) significantly affect the ability to constrain BD gravity. Under the most favorable conditions, the upper limit may suggest $\omega_{\rm BD} > 816$. Furthermore, we explore the detectability of potential scalar backgrounds arising from binary neutron star (BNS) mergers, setting upper limits on scalar backgrounds expected to be two orders of magnitude lower than the total background contributed by both BBH and BNS in one year of observational data. We conclude that for ambiguous populations, employing waveform matching with individual sources provides a more robust approach to constrain Brans-Dicke gravity. However, the future detection of a potential scalar background within the AGWB could provide significant support for gravity theories beyond General Relativity. |
2408.07864 | Jacob Taylor | Jacob A. Taylor, Rand Burnette, Bence B\'ecsy, Neil J. Cornish | Fast wavelet basis search for generic gravitational wave bursts in
Pulsar Timing Array data | 13 pages, 7 figures, submitted to PRD | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As we move into an era of more sensitive pulsar timing array data sets, we
may be able to resolve individual gravitational wave sources from the
stochastic gravitational wave background. While some of these sources, like
orbiting massive black hole binaries, have well-defined waveform models, there
could also be signals present with unknown morphology. This motivates the
search for generic gravitational-wave bursts in a signal-agnostic way. However,
these searches are computationally prohibitive due to the expansive parameter
space. In this paper we present QuickBurst, an algorithm with a re-defined
likelihood that lets us expedite Markov chain Monte Carlo sampling for a subset
of the signal parameters by avoiding repeated calculations of costly inner
products. This results in an overall speedup factor of $\sim$200 on realistic
simulated datasets, which is sufficient to make generic gravitational-wave
burst searches feasible on current and growing pulsar timing array datasets.
| [
{
"created": "Thu, 15 Aug 2024 00:23:03 GMT",
"version": "v1"
}
] | 2024-08-16 | [
[
"Taylor",
"Jacob A.",
""
],
[
"Burnette",
"Rand",
""
],
[
"Bécsy",
"Bence",
""
],
[
"Cornish",
"Neil J.",
""
]
] | As we move into an era of more sensitive pulsar timing array data sets, we may be able to resolve individual gravitational wave sources from the stochastic gravitational wave background. While some of these sources, like orbiting massive black hole binaries, have well-defined waveform models, there could also be signals present with unknown morphology. This motivates the search for generic gravitational-wave bursts in a signal-agnostic way. However, these searches are computationally prohibitive due to the expansive parameter space. In this paper we present QuickBurst, an algorithm with a re-defined likelihood that lets us expedite Markov chain Monte Carlo sampling for a subset of the signal parameters by avoiding repeated calculations of costly inner products. This results in an overall speedup factor of $\sim$200 on realistic simulated datasets, which is sufficient to make generic gravitational-wave burst searches feasible on current and growing pulsar timing array datasets. |
1703.09057 | William Cunningham | William Cunningham, Konstantin Zuev, and Dmitri Krioukov | Navigability of Random Geometric Graphs in the Universe and Other
Spacetimes | 15 pages, 10 figures | Sci. Rep. 7, 8699 (2017) | 10.1038/s41598-017-08872-4 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Random geometric graphs in hyperbolic spaces explain many common structural
and dynamical properties of real networks, yet they fail to predict the correct
values of the exponents of power-law degree distributions observed in real
networks. In that respect, random geometric graphs in asymptotically de Sitter
spacetimes, such as the Lorentzian spacetime of our accelerating universe, are
more attractive as their predictions are more consistent with observations in
real networks. Yet another important property of hyperbolic graphs is their
navigability, and it remains unclear if de Sitter graphs are as navigable as
hyperbolic ones. Here we study the navigability of random geometric graphs in
three Lorentzian manifolds corresponding to universes filled only with dark
energy (de Sitter spacetime), only with matter, and with a mixture of dark
energy and matter as in our universe. We find that these graphs are navigable
only in the manifolds with dark energy. This result implies that, in terms of
navigability, random geometric graphs in asymptotically de Sitter spacetimes
are as good as random hyperbolic graphs. It also establishes a connection
between the presence of dark energy and navigability of the discretized causal
structure of spacetime, which provides a basis for a different approach to the
dark energy problem in cosmology.
| [
{
"created": "Thu, 16 Mar 2017 18:18:05 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Oct 2017 13:44:22 GMT",
"version": "v2"
}
] | 2017-11-15 | [
[
"Cunningham",
"William",
""
],
[
"Zuev",
"Konstantin",
""
],
[
"Krioukov",
"Dmitri",
""
]
] | Random geometric graphs in hyperbolic spaces explain many common structural and dynamical properties of real networks, yet they fail to predict the correct values of the exponents of power-law degree distributions observed in real networks. In that respect, random geometric graphs in asymptotically de Sitter spacetimes, such as the Lorentzian spacetime of our accelerating universe, are more attractive as their predictions are more consistent with observations in real networks. Yet another important property of hyperbolic graphs is their navigability, and it remains unclear if de Sitter graphs are as navigable as hyperbolic ones. Here we study the navigability of random geometric graphs in three Lorentzian manifolds corresponding to universes filled only with dark energy (de Sitter spacetime), only with matter, and with a mixture of dark energy and matter as in our universe. We find that these graphs are navigable only in the manifolds with dark energy. This result implies that, in terms of navigability, random geometric graphs in asymptotically de Sitter spacetimes are as good as random hyperbolic graphs. It also establishes a connection between the presence of dark energy and navigability of the discretized causal structure of spacetime, which provides a basis for a different approach to the dark energy problem in cosmology. |
1508.01825 | Cecilia Chirenti | Cecilia Chirenti and Manuela G. Rodrigues | Effect of a variable cosmological constant on black hole quasinormal
modes | 6 pages, 2 figures, v2: final version accepted for publication in
Phys.Rev.D | Phys. Rev. D 92, 084051 (2015) | 10.1103/PhysRevD.92.084051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many different cosmological models have been proposed to address the
cosmological constant problem and the coincidence problem. We compare here four
different models that can be used to describe an effective (time-dependent)
cosmological constant $\Lambda(z)$. A numerical analysis of the $\Lambda(z)$
evolution obtained for each model shows that it can be used for distinguishing
between all four models. We calculate next the $\omega(\Lambda)$ frequencies
for quasinormal modes of gravitational perturbations of Schwarzschild-de Sitter
black holes at different redshifts. Considering that the variation of $\Lambda$
happens on cosmological timescales, the combined $\omega(\Lambda(z))$ could be
used in principle to track the evolution of the cosmological constant. We
quantify the resulting minute frequency shift in the quasinormal mode
frequencies and show that the relative frequency shift grows as $M^2$. However,
even in a most optimistic scenario with an extremely high mass supermassive
black hole there is no prospect for the detection of this effect.
| [
{
"created": "Fri, 7 Aug 2015 21:44:23 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Oct 2015 17:03:09 GMT",
"version": "v2"
}
] | 2015-10-28 | [
[
"Chirenti",
"Cecilia",
""
],
[
"Rodrigues",
"Manuela G.",
""
]
] | Many different cosmological models have been proposed to address the cosmological constant problem and the coincidence problem. We compare here four different models that can be used to describe an effective (time-dependent) cosmological constant $\Lambda(z)$. A numerical analysis of the $\Lambda(z)$ evolution obtained for each model shows that it can be used for distinguishing between all four models. We calculate next the $\omega(\Lambda)$ frequencies for quasinormal modes of gravitational perturbations of Schwarzschild-de Sitter black holes at different redshifts. Considering that the variation of $\Lambda$ happens on cosmological timescales, the combined $\omega(\Lambda(z))$ could be used in principle to track the evolution of the cosmological constant. We quantify the resulting minute frequency shift in the quasinormal mode frequencies and show that the relative frequency shift grows as $M^2$. However, even in a most optimistic scenario with an extremely high mass supermassive black hole there is no prospect for the detection of this effect. |
2403.11864 | Franz Hinterleitner | F. Hinterleitner | Symmetry-reduced Loop Quantum Gravity: Plane Waves, Flat Space and the
Hamiltonian Constraint | 34 pages, 1 figure | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Loop quantum gravity methods are applied to a symmetry-reduced model with
homogeneity in two dimensions, derived from a Gowdy model [5,6]. The conditions
for propagation of unidirectional plane gravitational waves at exactly the
speed of light are set up in form of null Killing equations in terms of
Ashtekar variables and imposed as operators on quantum states of the system.
Due to the effective one-dimensionality, holonomies and holonomy operators
appear as simple phase factors. In correspondence, state functions might be
considered as U(1) elements with the usual inner product. Under the assumption
of equal spacing of the eigenvalues of geometrical quantities the solutions are
not normalizable in this sense. With decreasing spacing for growing
eigenvalues, as introduced for example in [11], the situation becomes worse.
Taking over the inner product from the genuine gauge group SU(2) of LQG renders
the obtained states normalizable, nevertheless fluctuations of geometrical
quantities remain divergent. In consequence, the solutions of the Killing
conditions are modified, which means allowing for small fluctuations of the
propagation speed, i. e. dispersion of gravitational waves. Vacuum fluctuations
of Minkowski space are sketched. Finally the same methods are applied to the
Hamiltonian constraint with the same result concerning normalizability. With
such a modification also the constraint is not exactly satisfied any more,
which indicates the necessary presence of some kind of interacting matter.
| [
{
"created": "Mon, 18 Mar 2024 15:17:44 GMT",
"version": "v1"
}
] | 2024-03-19 | [
[
"Hinterleitner",
"F.",
""
]
] | Loop quantum gravity methods are applied to a symmetry-reduced model with homogeneity in two dimensions, derived from a Gowdy model [5,6]. The conditions for propagation of unidirectional plane gravitational waves at exactly the speed of light are set up in form of null Killing equations in terms of Ashtekar variables and imposed as operators on quantum states of the system. Due to the effective one-dimensionality, holonomies and holonomy operators appear as simple phase factors. In correspondence, state functions might be considered as U(1) elements with the usual inner product. Under the assumption of equal spacing of the eigenvalues of geometrical quantities the solutions are not normalizable in this sense. With decreasing spacing for growing eigenvalues, as introduced for example in [11], the situation becomes worse. Taking over the inner product from the genuine gauge group SU(2) of LQG renders the obtained states normalizable, nevertheless fluctuations of geometrical quantities remain divergent. In consequence, the solutions of the Killing conditions are modified, which means allowing for small fluctuations of the propagation speed, i. e. dispersion of gravitational waves. Vacuum fluctuations of Minkowski space are sketched. Finally the same methods are applied to the Hamiltonian constraint with the same result concerning normalizability. With such a modification also the constraint is not exactly satisfied any more, which indicates the necessary presence of some kind of interacting matter. |
gr-qc/9610031 | Ghanashyam Date | G. Date | On a Static Solution to Einstein Equations with incoming and outgoing
radiation | 20 pages, latex, needs psfig.tex macro. An appendix is added
discussing more general situations and matching conditions. Accepted for
publication in General Relativity and Gravitation | Gen.Rel.Grav.29:953,1997 | 10.1023/A:1018864423958 | IMSc-96/09/28 | gr-qc | null | Einstein equations with $T_{\mu\nu} = k_\mu k_\nu + \ell_\mu \ell_\nu$ where
$k, \ell$ are null are considered with spherical symmetry and staticity. The
solution has naked singularity and is not asymptotically flat. However, it may
be interpreted as an envelope for any static spherical body making it more
massive. Such an interpretation and some of its implications are detailed.
| [
{
"created": "Tue, 15 Oct 1996 15:00:36 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Feb 1997 06:15:11 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Date",
"G.",
""
]
] | Einstein equations with $T_{\mu\nu} = k_\mu k_\nu + \ell_\mu \ell_\nu$ where $k, \ell$ are null are considered with spherical symmetry and staticity. The solution has naked singularity and is not asymptotically flat. However, it may be interpreted as an envelope for any static spherical body making it more massive. Such an interpretation and some of its implications are detailed. |
gr-qc/9706030 | Fabio Scardigli | Fabio Scardigli (Dep. of Phys., Univ. of Milano, Italy) | Black Hole Entropy: a spacetime foam approach | 23 pages, no figures, postscript file gzipped,to be published in
Classical and Quantum Gravity, July 1997 | Class.Quant.Grav. 14 (1997) 1781-1793 | 10.1088/0264-9381/14/7/014 | null | gr-qc hep-th | null | The spacetime foam structure is reviewed briefly (topogical fluctuations and
virtual black hole possibility; equation of state of the foam). A model of
space foam at the surface of the event horizon is introduced. The model is
applied to the calculus of the number of states of a black hole, of its entropy
and of other thermodynamical properties. A formula for the number of microholes
on the surface of the event horizon is derived. Thermodynamical properties of
the event horizon are extended to thermodynamical properties of the space. On
the basis of the previous results, the possibility of micro black holes
creation by the Unruh Effect is investigated.
| [
{
"created": "Wed, 11 Jun 1997 17:44:00 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Scardigli",
"Fabio",
"",
"Dep. of Phys., Univ. of Milano, Italy"
]
] | The spacetime foam structure is reviewed briefly (topogical fluctuations and virtual black hole possibility; equation of state of the foam). A model of space foam at the surface of the event horizon is introduced. The model is applied to the calculus of the number of states of a black hole, of its entropy and of other thermodynamical properties. A formula for the number of microholes on the surface of the event horizon is derived. Thermodynamical properties of the event horizon are extended to thermodynamical properties of the space. On the basis of the previous results, the possibility of micro black holes creation by the Unruh Effect is investigated. |
gr-qc/0506049 | Muhammad Sharif | M. Sharif | Symmetries of Locally Rotationally Symmetric Models | 12 pages, accepted for publication in Int. J. of Mod. Phys. D | Int.J.Mod.Phys. D14 (2005) 1675-1684 | 10.1142/S0218271805007322 | null | gr-qc | null | Matter collineations of locally rotationally symmetric spacetimes are
considered. These are investigated when the energy-momentum tensor is
degenerate. We know that the degenerate case provides infinite dimensional
matter collineations in most of the cases. However, an interesting case arises
where we obtain proper matter collineations. We also solve the constraint
equations for a particular case to obtain some cosmological models.
| [
{
"created": "Wed, 8 Jun 2005 08:54:01 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sharif",
"M.",
""
]
] | Matter collineations of locally rotationally symmetric spacetimes are considered. These are investigated when the energy-momentum tensor is degenerate. We know that the degenerate case provides infinite dimensional matter collineations in most of the cases. However, an interesting case arises where we obtain proper matter collineations. We also solve the constraint equations for a particular case to obtain some cosmological models. |
gr-qc/0009066 | Guido Pizzella | P. Astone, M. Bassan, P. Bonifazi, P. Carelli, E. Coccia, S.D'Antonio,
V. Fafone, G.Federici, A. Marini, G. Mazzitelli, Y. Minenkov, I. Modena, G.
Modestino, A. Moleti, G. V. Pallottino, V. Pampaloni, G. Pizzella,
L.Quintieri, F. Ronga, R. Terenzi, M. Visco, L. Votano | Energetic Cosmic Rays observed by the resonant gravitational wave
detector NAUTILUS | Submitted to Phys. Letters B | Phys.Lett.B499:16-22,2001 | 10.1016/S0370-2693(01)00026-0 | Frascati Report LNF-00/023 (P 19 Sep 2000) | gr-qc astro-ph | null | Cosmic ray showers interacting with the resonant mass gravitational wave
antenna NAUTILUS have been detected. The experimental results show large
signals at a rate much greater than expected. The largest signal corresponds to
an energy release in NAUTILUS of 87 TeV. We remark that a resonant mass
gravitational wave detector used as particle detector has characteristics
different from the usual particle detectors, and it could detect new features
of cosmic rays. Among several possibilities, one can invoke unexpected
behaviour of superconducting Aluminium as particle detector, producing enhanced
signals, the excitation of non-elastic modes with large energy release or
anomalies in cosmic rays (for instance, the showers might include exotic
particles as nuclearites or Q-balls). Suggestions for explaining these
observations are solicited.
| [
{
"created": "Tue, 19 Sep 2000 08:04:10 GMT",
"version": "v1"
}
] | 2011-08-17 | [
[
"Astone",
"P.",
""
],
[
"Bassan",
"M.",
""
],
[
"Bonifazi",
"P.",
""
],
[
"Carelli",
"P.",
""
],
[
"Coccia",
"E.",
""
],
[
"D'Antonio",
"S.",
""
],
[
"Fafone",
"V.",
""
],
[
"Federici",
"G.",
""
],
[
"Marini",
"A.",
""
],
[
"Mazzitelli",
"G.",
""
],
[
"Minenkov",
"Y.",
""
],
[
"Modena",
"I.",
""
],
[
"Modestino",
"G.",
""
],
[
"Moleti",
"A.",
""
],
[
"Pallottino",
"G. V.",
""
],
[
"Pampaloni",
"V.",
""
],
[
"Pizzella",
"G.",
""
],
[
"Quintieri",
"L.",
""
],
[
"Ronga",
"F.",
""
],
[
"Terenzi",
"R.",
""
],
[
"Visco",
"M.",
""
],
[
"Votano",
"L.",
""
]
] | Cosmic ray showers interacting with the resonant mass gravitational wave antenna NAUTILUS have been detected. The experimental results show large signals at a rate much greater than expected. The largest signal corresponds to an energy release in NAUTILUS of 87 TeV. We remark that a resonant mass gravitational wave detector used as particle detector has characteristics different from the usual particle detectors, and it could detect new features of cosmic rays. Among several possibilities, one can invoke unexpected behaviour of superconducting Aluminium as particle detector, producing enhanced signals, the excitation of non-elastic modes with large energy release or anomalies in cosmic rays (for instance, the showers might include exotic particles as nuclearites or Q-balls). Suggestions for explaining these observations are solicited. |
1908.09469 | Timothy Budd | Jerome Barkley, Timothy Budd | Precision measurements of Hausdorff dimensions in two-dimensional
quantum gravity | 26 pages, 15 figures | Class. Quantum Grav. 36 (2019) 244001 | 10.1088/1361-6382/ab4f21 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two-dimensional quantum gravity, defined either via scaling limits of random
discrete surfaces or via Liouville quantum gravity, is known to possess a
geometry that is genuinely fractal with a Hausdorff dimension equal to 4.
Coupling gravity to a statistical system at criticality changes the fractal
properties of the geometry in a way that depends on the central charge of the
critical system. Establishing the dependence of the Hausdorff dimension on this
central charge $c$ has been an important open problem in physics and
mathematics in the past decades. All simulation data produced thus far has
supported a formula put forward by Watabiki in the nineties. However, recent
rigorous bounds on the Hausdorff dimension in Liouville quantum gravity show
that Watabiki's formula cannot be correct when $c$ approaches $-\infty$. Based
on simulations of discrete surfaces encoded by random planar maps and a
numerical implementation of Liouville quantum gravity, we obtain new
finite-size scaling estimates of the Hausdorff dimension that are in clear
contradiction with Watabiki's formula for all simulated values of $c\in
(-\infty,0)$. Instead, the most reliable data in the range $c\in [-12.5, 0)$ is
in very good agreement with an alternative formula that was recently suggested
by Ding and Gwynne. The estimates for $c\in(-\infty,-12.5)$ display a negative
deviation from the latter formula, but the scaling is seen to be less accurate
in this regime.
| [
{
"created": "Mon, 26 Aug 2019 04:51:46 GMT",
"version": "v1"
}
] | 2020-02-05 | [
[
"Barkley",
"Jerome",
""
],
[
"Budd",
"Timothy",
""
]
] | Two-dimensional quantum gravity, defined either via scaling limits of random discrete surfaces or via Liouville quantum gravity, is known to possess a geometry that is genuinely fractal with a Hausdorff dimension equal to 4. Coupling gravity to a statistical system at criticality changes the fractal properties of the geometry in a way that depends on the central charge of the critical system. Establishing the dependence of the Hausdorff dimension on this central charge $c$ has been an important open problem in physics and mathematics in the past decades. All simulation data produced thus far has supported a formula put forward by Watabiki in the nineties. However, recent rigorous bounds on the Hausdorff dimension in Liouville quantum gravity show that Watabiki's formula cannot be correct when $c$ approaches $-\infty$. Based on simulations of discrete surfaces encoded by random planar maps and a numerical implementation of Liouville quantum gravity, we obtain new finite-size scaling estimates of the Hausdorff dimension that are in clear contradiction with Watabiki's formula for all simulated values of $c\in (-\infty,0)$. Instead, the most reliable data in the range $c\in [-12.5, 0)$ is in very good agreement with an alternative formula that was recently suggested by Ding and Gwynne. The estimates for $c\in(-\infty,-12.5)$ display a negative deviation from the latter formula, but the scaling is seen to be less accurate in this regime. |
1712.07855 | Abdulla Al Mamon | Abdulla Al Mamon | A new parametrization for dark energy density and future deceleration | 6 pages, 3 figures, title has been changed, references added, revised
version accepted for publication in MPLA | null | 10.1142/S0217732318501134 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have proposed a general dark energy density parametrization
to study the evolution of the universe. We have also constrained the model
parameters using the combination of Type Ia supernova (SNIa), baryonic acoustic
oscillations (BAO), cosmic microwave background radiation (CMB) and
observational $H(z)$ datasets. For the $H(z)$ dataset, we have used the direct
observations of the Hubble rate, from the radial BAO size and the cosmic
chronometer methods. Our result indicates that the SNIa+$H(z)$+BAO/CMB dataset
does not favour the $\Lambda$CDM model at more than $2\sigma$ confidence level.
Furthermore, we have also measured the percentage deviation in the evolution of
the normalized Hubble parameter for the present model compared to a
$\Lambda$CDM model, and the corresponding deviation is found to be $4-5\%$ at
low redshifts ($z\sim 0.5$). Finally, we have also investigated whether the
deceleration parameter $q$ may have more than one transition during the
evolution of the universe. The present model shows a transient accelerating
phase, in which the universe was decelerated in the past and is presently
accelerating, but will return to a decelerating phase in the near future. This
result is in great contrast to the $\Lambda$CDM scenario, which predicts that
the cosmic acceleration must remain forever.
| [
{
"created": "Thu, 21 Dec 2017 10:11:58 GMT",
"version": "v1"
},
{
"created": "Wed, 23 May 2018 09:52:36 GMT",
"version": "v2"
}
] | 2018-07-25 | [
[
"Mamon",
"Abdulla Al",
""
]
] | In this work, we have proposed a general dark energy density parametrization to study the evolution of the universe. We have also constrained the model parameters using the combination of Type Ia supernova (SNIa), baryonic acoustic oscillations (BAO), cosmic microwave background radiation (CMB) and observational $H(z)$ datasets. For the $H(z)$ dataset, we have used the direct observations of the Hubble rate, from the radial BAO size and the cosmic chronometer methods. Our result indicates that the SNIa+$H(z)$+BAO/CMB dataset does not favour the $\Lambda$CDM model at more than $2\sigma$ confidence level. Furthermore, we have also measured the percentage deviation in the evolution of the normalized Hubble parameter for the present model compared to a $\Lambda$CDM model, and the corresponding deviation is found to be $4-5\%$ at low redshifts ($z\sim 0.5$). Finally, we have also investigated whether the deceleration parameter $q$ may have more than one transition during the evolution of the universe. The present model shows a transient accelerating phase, in which the universe was decelerated in the past and is presently accelerating, but will return to a decelerating phase in the near future. This result is in great contrast to the $\Lambda$CDM scenario, which predicts that the cosmic acceleration must remain forever. |
2009.01213 | Jeremy Sakstein | Jeremy Sakstein, Djuna Croon, Samuel D. McDermott, Maria C. Straight,
Eric J. Baxter | Beyond the Standard Model Explanations of GW190521 | Four pages, one figure. Comments welcome | Phys. Rev. Lett. 125, 261105 (2020) | 10.1103/PhysRevLett.125.261105 | FERMILAB-PUB-20-461-T | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LIGO/Virgo collaboration has recently announced the detection of a heavy
binary black hole merger, with component masses that cannot be explained by
standard stellar structure theory. In this letter we propose several
explanations based on models of new physics, including new light particle
losses, modified gravity, large extra dimensions, and a small magnetic moment
of the neutrino. Each of these affect the physics of the pair-instability
differently, leading to novel mechanisms for forming black holes inside the
black hole mass gap.
| [
{
"created": "Wed, 2 Sep 2020 17:38:53 GMT",
"version": "v1"
}
] | 2021-01-04 | [
[
"Sakstein",
"Jeremy",
""
],
[
"Croon",
"Djuna",
""
],
[
"McDermott",
"Samuel D.",
""
],
[
"Straight",
"Maria C.",
""
],
[
"Baxter",
"Eric J.",
""
]
] | The LIGO/Virgo collaboration has recently announced the detection of a heavy binary black hole merger, with component masses that cannot be explained by standard stellar structure theory. In this letter we propose several explanations based on models of new physics, including new light particle losses, modified gravity, large extra dimensions, and a small magnetic moment of the neutrino. Each of these affect the physics of the pair-instability differently, leading to novel mechanisms for forming black holes inside the black hole mass gap. |
2404.06979 | Loris Del Grosso | Emanuele Berti, Valerio De Luca, Loris Del Grosso, Paolo Pani | Tidal Love numbers and approximate universal relations for fermion
soliton stars | 15 pages, 4 figures. v2: new figure added, matches version accepted
in PRD | Phys. Rev. D 109, 124008 (2024) | 10.1103/PhysRevD.109.124008 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fermion soliton stars are a consistent model of exotic compact objects which
involve a nonlinear interaction between a real scalar field and fermions
through a Yukawa term. This interaction results in an effective fermion mass
that depends upon the vacuum structure in the scalar potential. In this work we
investigate the tidal deformations of fermion soliton stars and compute the
corresponding tidal Love numbers for different model parameters. Furthermore,
we discuss the existence of approximate universal relations for the electric
and magnetic tidal deformabilities of these stars, and compare them with other
solutions of general relativity, such as neutron stars or boson stars. These
relations for fermion soliton stars are less universal than for neutron stars,
but they are sufficiently different from the ordinary neutron star case that a
measurement of the electric and magnetic tidal Love numbers (as potentially
achievable by next-generation gravitational wave detectors) can be used to
disentangle these families of compact objects. Finally, we discuss the
conditions for tidal disruption of fermion soliton stars in a binary system and
estimate the detectability of the electromagnetic signal associated with such
tidal disruption events.
| [
{
"created": "Wed, 10 Apr 2024 12:49:31 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jun 2024 08:07:15 GMT",
"version": "v2"
}
] | 2024-06-07 | [
[
"Berti",
"Emanuele",
""
],
[
"De Luca",
"Valerio",
""
],
[
"Del Grosso",
"Loris",
""
],
[
"Pani",
"Paolo",
""
]
] | Fermion soliton stars are a consistent model of exotic compact objects which involve a nonlinear interaction between a real scalar field and fermions through a Yukawa term. This interaction results in an effective fermion mass that depends upon the vacuum structure in the scalar potential. In this work we investigate the tidal deformations of fermion soliton stars and compute the corresponding tidal Love numbers for different model parameters. Furthermore, we discuss the existence of approximate universal relations for the electric and magnetic tidal deformabilities of these stars, and compare them with other solutions of general relativity, such as neutron stars or boson stars. These relations for fermion soliton stars are less universal than for neutron stars, but they are sufficiently different from the ordinary neutron star case that a measurement of the electric and magnetic tidal Love numbers (as potentially achievable by next-generation gravitational wave detectors) can be used to disentangle these families of compact objects. Finally, we discuss the conditions for tidal disruption of fermion soliton stars in a binary system and estimate the detectability of the electromagnetic signal associated with such tidal disruption events. |
2203.07066 | B\'eatrice Bonga | Ivan Agullo, B\'eatrice Bonga, Patricia Ribes Metidieri | Does inflation squeeze cosmological perturbations? | 19 pages + 8 pages as appendices | null | 10.1088/1475-7516/2022/09/032 | null | gr-qc astro-ph.CO hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | There seems to exist agreement about the fact that inflation squeezes the
quantum state of cosmological perturbations and entangles modes with
wavenumbers $\vec k$ and $-\vec k$. Paradoxically, this result has been used to
justify both the classicality as well as the quantumness of the primordial
perturbations at the end of inflation. We reexamine this question and point out
that the definition of two-mode squeezing of the modes $\vec k$ and $-\vec k$
used in previous work rests on choices that are only justified for systems with
time-independent Hamiltonians and finitely many degrees of freedom. We argue
that for quantum fields propagating on generic time-dependent
Friedmann-Lema\^itre-Robertson-Walker backgrounds, the notion of squeezed
states is subject to ambiguities, which go hand in hand with the ambiguity in
the definition of particles. In other words, we argue that the question "does
the cosmic expansion squeeze and entangle modes with wavenumbers $\vec k$ and
$-\vec k$?" contains the same ambiguity as the question "does the cosmic
expansion create particles?". When additional symmetries are present, like in
the (quasi) de Sitter-like spacetimes used in inflationary models, one can
resolve the ambiguities, and we find that the answer to the question in the
title turns out to be in the negative. We further argue that this fact does not
make the state of cosmological perturbations any less quantum, at least when
deviations from Gaussianity can be neglected.
| [
{
"created": "Mon, 14 Mar 2022 13:02:46 GMT",
"version": "v1"
}
] | 2022-09-21 | [
[
"Agullo",
"Ivan",
""
],
[
"Bonga",
"Béatrice",
""
],
[
"Metidieri",
"Patricia Ribes",
""
]
] | There seems to exist agreement about the fact that inflation squeezes the quantum state of cosmological perturbations and entangles modes with wavenumbers $\vec k$ and $-\vec k$. Paradoxically, this result has been used to justify both the classicality as well as the quantumness of the primordial perturbations at the end of inflation. We reexamine this question and point out that the definition of two-mode squeezing of the modes $\vec k$ and $-\vec k$ used in previous work rests on choices that are only justified for systems with time-independent Hamiltonians and finitely many degrees of freedom. We argue that for quantum fields propagating on generic time-dependent Friedmann-Lema\^itre-Robertson-Walker backgrounds, the notion of squeezed states is subject to ambiguities, which go hand in hand with the ambiguity in the definition of particles. In other words, we argue that the question "does the cosmic expansion squeeze and entangle modes with wavenumbers $\vec k$ and $-\vec k$?" contains the same ambiguity as the question "does the cosmic expansion create particles?". When additional symmetries are present, like in the (quasi) de Sitter-like spacetimes used in inflationary models, one can resolve the ambiguities, and we find that the answer to the question in the title turns out to be in the negative. We further argue that this fact does not make the state of cosmological perturbations any less quantum, at least when deviations from Gaussianity can be neglected. |
gr-qc/9812025 | Robert D. Klauber | Robert D. Klauber | Relativistically Rotating Frames and Non-time-orthogonality | 4 pages, no figures. Brief overview of more extensive article
published in Found. Phys. Lett. 11 (5) 405, Oct 98. Rev includes both LaTeX
and HTML files | Am.J.Phys. 67 (1999) 158-159 | 10.1119/1.19213 | null | gr-qc | null | This paper is a brief overview of a more extensive article recently published
in Found. Phys. Lett. [2]. Apparent disagreement with experiment as well as
internal inconsistencies found in the traditional analysis of relativistically
rotating frames/disks are summarized. As one example, a point p at 0 degrees on
the circumference of a rotating disk does not, according to the standard
theory, exist at the same moment in time as the same point p at 360 degrees.
This and other problems with the standard theory are completely resolved by a
novel analysis that directly addresses, apparently for the first time, the
non-time-orthogonal nature of rotating frames. Though ultimately consonant with
the special and general theories of relativity, due to non-time-orthogonality,
the analysis predicts several peculiar (i.e., not traditionally relativistic)
results. For example, the local circumferential speed of light is not invariant
(thereby agreeing with the Sagnac experiment), and no Lorentz contraction
exists along the disk rim. Other experimental results, including time dilation,
mass-energy dependence on speed, and what has heretofore been considered a
"spurious" signal in the most accurate Michelson-Morley experiment performed to
date, are accurately predicted. Further, the widely accepted postulate for the
equivalence of co-moving inertial and non-inertial rods, used liberally with
prior rotating frame analyses, is shown to be invalid for non-time-orthogonal
frames. This understanding of the ramifications of non-time-orthogonality
resolves paradoxes inherent in the traditional theory.
| [
{
"created": "Mon, 7 Dec 1998 16:09:21 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Jan 1999 18:05:20 GMT",
"version": "v2"
},
{
"created": "Fri, 1 Jun 2001 21:28:51 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Klauber",
"Robert D.",
""
]
] | This paper is a brief overview of a more extensive article recently published in Found. Phys. Lett. [2]. Apparent disagreement with experiment as well as internal inconsistencies found in the traditional analysis of relativistically rotating frames/disks are summarized. As one example, a point p at 0 degrees on the circumference of a rotating disk does not, according to the standard theory, exist at the same moment in time as the same point p at 360 degrees. This and other problems with the standard theory are completely resolved by a novel analysis that directly addresses, apparently for the first time, the non-time-orthogonal nature of rotating frames. Though ultimately consonant with the special and general theories of relativity, due to non-time-orthogonality, the analysis predicts several peculiar (i.e., not traditionally relativistic) results. For example, the local circumferential speed of light is not invariant (thereby agreeing with the Sagnac experiment), and no Lorentz contraction exists along the disk rim. Other experimental results, including time dilation, mass-energy dependence on speed, and what has heretofore been considered a "spurious" signal in the most accurate Michelson-Morley experiment performed to date, are accurately predicted. Further, the widely accepted postulate for the equivalence of co-moving inertial and non-inertial rods, used liberally with prior rotating frame analyses, is shown to be invalid for non-time-orthogonal frames. This understanding of the ramifications of non-time-orthogonality resolves paradoxes inherent in the traditional theory. |
1412.0944 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig and Vance D. Gladney | Revisiting galactic rotation curves given a noncommutative-geometry
background | 7 pages, 3 figures | Journal of Modern Physics, vol. 5, 1931-1937 (2014) | 10.4236/jmp.2014.517187 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was shown earlier by Rahaman et al. that a noncommutative-geometry
background can account for galactic rotation curves without the need for dark
matter. The smearing effect that characterizes noncommutative geometry is
described by means of a Gaussian distribution intended to replace the Dirac
delta function. The purpose of this paper is two-fold: (1) to account for the
galactic rotation curves in a more transparent and intuitively more appealing
way by replacing the Gaussian function by the simpler Lorentzian distribution
proposed by Nozari and Mehdipour and (2) to show that the smearing effect is
both a necessary and sufficient condition for meeting the stability criterion.
| [
{
"created": "Tue, 2 Dec 2014 15:32:31 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Kuhfittig",
"Peter K. F.",
""
],
[
"Gladney",
"Vance D.",
""
]
] | It was shown earlier by Rahaman et al. that a noncommutative-geometry background can account for galactic rotation curves without the need for dark matter. The smearing effect that characterizes noncommutative geometry is described by means of a Gaussian distribution intended to replace the Dirac delta function. The purpose of this paper is two-fold: (1) to account for the galactic rotation curves in a more transparent and intuitively more appealing way by replacing the Gaussian function by the simpler Lorentzian distribution proposed by Nozari and Mehdipour and (2) to show that the smearing effect is both a necessary and sufficient condition for meeting the stability criterion. |
1304.2833 | Miguel Socolovsky | M. Socolovsky | Rindler Space and Unruh Effect | 31 pages, 13 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the geometry of the Rindler space induced by hyperbolic motion in
special relativity, and its applications to the calculation of the Unruh effect
in flat spacetime, and to the Hawking temperature of the Schwarzschild black
hole.
| [
{
"created": "Wed, 10 Apr 2013 03:11:46 GMT",
"version": "v1"
},
{
"created": "Mon, 20 May 2013 21:06:55 GMT",
"version": "v2"
}
] | 2013-05-22 | [
[
"Socolovsky",
"M.",
""
]
] | We review the geometry of the Rindler space induced by hyperbolic motion in special relativity, and its applications to the calculation of the Unruh effect in flat spacetime, and to the Hawking temperature of the Schwarzschild black hole. |
1807.06048 | Guillem Dom\`enech | Guillem Dom\`enech, Shinji Mukohyama, Ryo Namba and Vassilis
Papadopoulos | Vector disformal transformation of generalized Proca theory | null | Phys. Rev. D 98, 064037 (2018) | 10.1103/PhysRevD.98.064037 | YITP-18-55, IPMU18-0092 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the GW170817/GRB170817A constraint on the deviation of the speed
of gravitational waves from that of photons, we study disformal transformations
of the metric in the context of the generalized Proca theory. The constraint
restricts the form of the gravity Lagrangian, the way the electromagnetism
couples to the gravity sector on cosmological backgrounds, or in general a
combination of both. Since different ways of coupling matter to gravity are
typically related to each other by disformal transformations, it is important
to understand how the structure of the generalized Proca Lagrangian changes
under disformal transformations. For disformal transformations with constant
coefficients we provide the complete transformation rule of the Lagrangian. We
find that additional terms, which were considered as beyond generalized Proca
in the literature, are generated by the transformations. Once these additional
terms are included, on the other hand, the structure of the gravity Lagrangian
is preserved under the transformations. We then derive the transformation rules
for the sound speeds of the scalar, vector and tensor perturbations on a
homogeneous and isotropic background. We explicitly show that they transform
following the natural expectation of metric transformations, that is, according
to the transformation of the background lightcone structure. We end by arguing
that inhomogeneities due to structures in the universe, e.g. dark matter halos,
generically changes the speed of gravitational waves from its cosmological
value. We give a rough estimate of the effect of inhomogeneities and find that
the fine-tuning should not depend on the background or that the fine-tuned
theory has to be further fine-tuned to pass the tight constraint.
| [
{
"created": "Mon, 16 Jul 2018 18:25:15 GMT",
"version": "v1"
}
] | 2018-09-26 | [
[
"Domènech",
"Guillem",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Namba",
"Ryo",
""
],
[
"Papadopoulos",
"Vassilis",
""
]
] | Motivated by the GW170817/GRB170817A constraint on the deviation of the speed of gravitational waves from that of photons, we study disformal transformations of the metric in the context of the generalized Proca theory. The constraint restricts the form of the gravity Lagrangian, the way the electromagnetism couples to the gravity sector on cosmological backgrounds, or in general a combination of both. Since different ways of coupling matter to gravity are typically related to each other by disformal transformations, it is important to understand how the structure of the generalized Proca Lagrangian changes under disformal transformations. For disformal transformations with constant coefficients we provide the complete transformation rule of the Lagrangian. We find that additional terms, which were considered as beyond generalized Proca in the literature, are generated by the transformations. Once these additional terms are included, on the other hand, the structure of the gravity Lagrangian is preserved under the transformations. We then derive the transformation rules for the sound speeds of the scalar, vector and tensor perturbations on a homogeneous and isotropic background. We explicitly show that they transform following the natural expectation of metric transformations, that is, according to the transformation of the background lightcone structure. We end by arguing that inhomogeneities due to structures in the universe, e.g. dark matter halos, generically changes the speed of gravitational waves from its cosmological value. We give a rough estimate of the effect of inhomogeneities and find that the fine-tuning should not depend on the background or that the fine-tuned theory has to be further fine-tuned to pass the tight constraint. |
2106.10553 | Massimo Tinto | Massimo Tinto, Sanjeev Dhurandhar, Prasanna Joshi | Reply to the Bayle {\it et al.} gr-qc document dated June 7, 2021} | 5 pages, no figures | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the two issues raised by Bayle, Vallisneri, Babak, and Petiteau
(in their gr-qc document arXiv:2106.03976) about our matrix formulation of
Time-Delay Interferometry (TDI) (arXiv:2105.02054) \cite{TDJ21}. In so doing we
explain and quantify our concerns about the results derived by Vallisneri,
Bayle, Babak and Petiteau \cite{Vallisneri2020} by applying their data
processing technique (named TDI-$\infty$) to the two heterodyne measurements
made by a two-arm space-based GW interferometer. First we show that the
solutions identified by the TDI-$\infty$ algorithm derived by Vallisneri,
Bayle, Babak and Petiteau \cite{Vallisneri2020} {\underbar {do}} depend on the
boundary-conditions selected for the two-way Doppler data. We prove this by
adopting the (non-physical) boundary conditions used by Vallisneri {\it et al.}
and deriving the corresponding analytic expression for a laser-noise-canceling
combination. We show it to be characterized by a number of Doppler measurement
terms that grows with the observation time and works for any time-dependent
time delays. We then prove that, for a constant-arm-length interferometer whose
two-way light times are equal to twice and three-times the sampling time, the
solutions identified by TDI-$\infty$ are linear combinations of the TDI
variable $X$. In the second part of this document we address the concern
expressed by Bayle {\it et al.} regarding our matrix formulation of TDI when
the two-way light-times are constant but not equal to integer multiples of the
sampling time. We mathematically prove the homomorphism between the delay
operators and their matrix representation \cite{TDJ21} holds in general. By
sequentially applying two order-$m$ Fractional-Delay (FD) Lagrange filters of
delays $l_1$, $l_2$ we find its result to be equal to applying an order-$m$ FD
Lagrange filter of delay $l_1 + l_2$.
| [
{
"created": "Sat, 19 Jun 2021 18:44:16 GMT",
"version": "v1"
}
] | 2021-08-24 | [
[
"Tinto",
"Massimo",
""
],
[
"Dhurandhar",
"Sanjeev",
""
],
[
"Joshi",
"Prasanna",
""
]
] | We address the two issues raised by Bayle, Vallisneri, Babak, and Petiteau (in their gr-qc document arXiv:2106.03976) about our matrix formulation of Time-Delay Interferometry (TDI) (arXiv:2105.02054) \cite{TDJ21}. In so doing we explain and quantify our concerns about the results derived by Vallisneri, Bayle, Babak and Petiteau \cite{Vallisneri2020} by applying their data processing technique (named TDI-$\infty$) to the two heterodyne measurements made by a two-arm space-based GW interferometer. First we show that the solutions identified by the TDI-$\infty$ algorithm derived by Vallisneri, Bayle, Babak and Petiteau \cite{Vallisneri2020} {\underbar {do}} depend on the boundary-conditions selected for the two-way Doppler data. We prove this by adopting the (non-physical) boundary conditions used by Vallisneri {\it et al.} and deriving the corresponding analytic expression for a laser-noise-canceling combination. We show it to be characterized by a number of Doppler measurement terms that grows with the observation time and works for any time-dependent time delays. We then prove that, for a constant-arm-length interferometer whose two-way light times are equal to twice and three-times the sampling time, the solutions identified by TDI-$\infty$ are linear combinations of the TDI variable $X$. In the second part of this document we address the concern expressed by Bayle {\it et al.} regarding our matrix formulation of TDI when the two-way light-times are constant but not equal to integer multiples of the sampling time. We mathematically prove the homomorphism between the delay operators and their matrix representation \cite{TDJ21} holds in general. By sequentially applying two order-$m$ Fractional-Delay (FD) Lagrange filters of delays $l_1$, $l_2$ we find its result to be equal to applying an order-$m$ FD Lagrange filter of delay $l_1 + l_2$. |
1909.13796 | Francisco Fern\'andez-\'Alvarez | Francisco Fern\'andez-\'Alvarez and Jos\'e M. M. Senovilla | A novel characterisation of gravitational radiation in asymptotically
flat space-times | 10 pages, acknowledgments added | Phys. Rev. D 101, 024060 (2020) | 10.1103/PhysRevD.101.024060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A novel criterion to determine the presence of gravitational radiation
arriving to, or departing from, null infinity of any weakly
asymptotically-simple space-time with vanishing cosmological constant is given.
The quantities involved are geometric, of tidal nature, with good gauge
behaviour and univocally defined at null infinity. The relationship with the
classical characterisation using the News tensor is analysed in detail. A new
balance law at infinity is presented, which may be useful to define `radiation
states'.
| [
{
"created": "Mon, 30 Sep 2019 15:48:20 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jan 2020 10:10:09 GMT",
"version": "v2"
}
] | 2020-02-04 | [
[
"Fernández-Álvarez",
"Francisco",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | A novel criterion to determine the presence of gravitational radiation arriving to, or departing from, null infinity of any weakly asymptotically-simple space-time with vanishing cosmological constant is given. The quantities involved are geometric, of tidal nature, with good gauge behaviour and univocally defined at null infinity. The relationship with the classical characterisation using the News tensor is analysed in detail. A new balance law at infinity is presented, which may be useful to define `radiation states'. |
gr-qc/0412130 | Ivan L. Zhogin | I. L. Zhogin | Old and new research on the Absolute Parallelism theory | PhD thesis (with a preface and some fresh comments); published by the
Lambert publishing (LAP) ISBN 978-3-8383-8876-2; 104 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Compatible equations, Singularities of solutions, Topological charges and
quasi-charges.
PhD thesis (translated frorm Russian).
The book shows the sights of Absolute Parallelism (AP), and contains useful
information on the problem of singularities, compatibility theory, homotopy
groups (also relative and k-ad), topological quasi-charge groups and their
morphisms. AP is a single (frame) field theory proposed by Einstein some 80
years ago; it embraces symmetries of both Special and General Relativity.
The compatibility theory, if applied to the cases when the frame matrix
degenerates, gives a covariant test on singularities of solutions. This gives a
single variant (missed in Einstein-Mayer's list of compatible equations), the
unique 5D equation (nothing, nor D, can be changed), which solutions are free
of emerging singularities. SO4-symmetrical nonstationary solutions give rise to
a cosmological model (relativistic surfing; anti-Milne model in FRW framework)
with a specific reduction of the extra-dimension.
Topological classification of localized field configurations, combinatorics
of topological quasi-charges (quanta), is discussed in an attempt to imagine
the Standard Model (and quantum theory itself; and, perhaps, to make some
qualitative predictions, like the absence of spin zero elementary quanta).
| [
{
"created": "Fri, 31 Dec 2004 18:22:25 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2010 15:21:58 GMT",
"version": "v2"
}
] | 2010-10-20 | [
[
"Zhogin",
"I. L.",
""
]
] | Compatible equations, Singularities of solutions, Topological charges and quasi-charges. PhD thesis (translated frorm Russian). The book shows the sights of Absolute Parallelism (AP), and contains useful information on the problem of singularities, compatibility theory, homotopy groups (also relative and k-ad), topological quasi-charge groups and their morphisms. AP is a single (frame) field theory proposed by Einstein some 80 years ago; it embraces symmetries of both Special and General Relativity. The compatibility theory, if applied to the cases when the frame matrix degenerates, gives a covariant test on singularities of solutions. This gives a single variant (missed in Einstein-Mayer's list of compatible equations), the unique 5D equation (nothing, nor D, can be changed), which solutions are free of emerging singularities. SO4-symmetrical nonstationary solutions give rise to a cosmological model (relativistic surfing; anti-Milne model in FRW framework) with a specific reduction of the extra-dimension. Topological classification of localized field configurations, combinatorics of topological quasi-charges (quanta), is discussed in an attempt to imagine the Standard Model (and quantum theory itself; and, perhaps, to make some qualitative predictions, like the absence of spin zero elementary quanta). |
1810.04885 | Yu-Tong Wang | Yu-Tong Wang, Jun Zhang, Yun-Song Piao | Primordial gravastar from inflation | 10 pages, 4 figures | null | 10.1016/j.physletb.2019.06.036 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dS bubbles can nucleate spontaneously during inflation, and will be
stretched by the cosmological expansion to astrophysical scale. We report on a
novel phenomenon that such a bubble might develop into a gravastar (an
ultra-compact object with a dS core) after inflation, which witnessed the
occurrence of inflation and would survive till today. It is pointed out that if
a primordial gravastar was involved in one of the LIGO/Virgo gravitational wave
(GW) events, the post-merger object could be a gravastar that will eventually
collapse into a black hole. As a result, the late-time GW ringdown waveform
will exhibit a series of "echoes" with intervals increasing with time.
| [
{
"created": "Thu, 11 Oct 2018 08:15:36 GMT",
"version": "v1"
}
] | 2019-06-26 | [
[
"Wang",
"Yu-Tong",
""
],
[
"Zhang",
"Jun",
""
],
[
"Piao",
"Yun-Song",
""
]
] | The dS bubbles can nucleate spontaneously during inflation, and will be stretched by the cosmological expansion to astrophysical scale. We report on a novel phenomenon that such a bubble might develop into a gravastar (an ultra-compact object with a dS core) after inflation, which witnessed the occurrence of inflation and would survive till today. It is pointed out that if a primordial gravastar was involved in one of the LIGO/Virgo gravitational wave (GW) events, the post-merger object could be a gravastar that will eventually collapse into a black hole. As a result, the late-time GW ringdown waveform will exhibit a series of "echoes" with intervals increasing with time. |
gr-qc/0610065 | Dimitry Leites | Yu.E. Gliklikh, P.S. Zykov | A two-point boundary value problem on a Lorentz manifold arising in A.
Poltorak's concept of reference frame | 11 pages | null | 10.2991/jnmp.2007.14.3.7 | null | gr-qc | null | In A. Poltorak's concept, the reference frame in General Relativity is a
certain manifold equipped with a connection. The question under consideration
here is whether it is possible to join two events in the space-time by a
time-like geodesic if they are joined by a geodesic of the reference frame
connection that has a time-like initial vector. This question is interpreted as
whether an event belongs to the proper future of another event in the
space-time in case it is so in the reference frame. For reference frames of two
special types some geometric conditions are found under which the answer is
positive.
| [
{
"created": "Thu, 12 Oct 2006 12:33:34 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Gliklikh",
"Yu. E.",
""
],
[
"Zykov",
"P. S.",
""
]
] | In A. Poltorak's concept, the reference frame in General Relativity is a certain manifold equipped with a connection. The question under consideration here is whether it is possible to join two events in the space-time by a time-like geodesic if they are joined by a geodesic of the reference frame connection that has a time-like initial vector. This question is interpreted as whether an event belongs to the proper future of another event in the space-time in case it is so in the reference frame. For reference frames of two special types some geometric conditions are found under which the answer is positive. |
2104.05644 | Cristian Erices | Cristian Erices, Pantelis Filis and Eleftherios Papantonopoulos | Hairy Black Holes in Disformal Scalar-Tensor Gravity Theories | null | Phys. Rev. D 104, 024031 (2021) | 10.1103/PhysRevD.104.024031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the no-hair theorem for scalar-tensor theories with bi-metric
structure can be evaded. We find that hairy black hole solutions in the
presence of an electric charge admit AdS, flat or dS asymptotics with
spherical, flat, or hyperbolic base manifolds. Spherically symmetric,
asymptotically flat black holes and asymptotically AdS configurations with any
horizon topology are compatible with a regular scalar field on and outside the
event horizon. The latter presents a rich thermodynamic behavior induced by the
disformal factor that enters as a coupling parameter in the theory. In the
grand canonical ensemble, there is an interplay of stability and first-order
phase transitions between thermal AdS, the hairy black hole, and the
Reissner-Nordstr\"om-AdS black hole, whose thermodynamic phase space resembles
a solid-liquid-gas system, with an electric potential playing the role of
pressure. In close analogy, there is a triple point where the three phases
coexist, being equally probable.
| [
{
"created": "Mon, 12 Apr 2021 17:10:23 GMT",
"version": "v1"
},
{
"created": "Sun, 16 May 2021 21:51:19 GMT",
"version": "v2"
}
] | 2021-07-21 | [
[
"Erices",
"Cristian",
""
],
[
"Filis",
"Pantelis",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
]
] | We show that the no-hair theorem for scalar-tensor theories with bi-metric structure can be evaded. We find that hairy black hole solutions in the presence of an electric charge admit AdS, flat or dS asymptotics with spherical, flat, or hyperbolic base manifolds. Spherically symmetric, asymptotically flat black holes and asymptotically AdS configurations with any horizon topology are compatible with a regular scalar field on and outside the event horizon. The latter presents a rich thermodynamic behavior induced by the disformal factor that enters as a coupling parameter in the theory. In the grand canonical ensemble, there is an interplay of stability and first-order phase transitions between thermal AdS, the hairy black hole, and the Reissner-Nordstr\"om-AdS black hole, whose thermodynamic phase space resembles a solid-liquid-gas system, with an electric potential playing the role of pressure. In close analogy, there is a triple point where the three phases coexist, being equally probable. |
1808.06582 | Vojtech Witzany | Vojt\v{e}ch Witzany, Jan Steinhoff, and Georgios Lukes-Gerakopoulos | Hamiltonians and canonical coordinates for spinning particles in curved
space-time | 37 pages, 2 figures. Accepted at CQG | 2019 Class. Quantum Grav. 36 075003 | 10.1088/1361-6382/ab002f | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spin-curvature coupling as captured by the so-called
Mathisson-Papapetrou-Dixon (MPD) equations is the leading order effect of the
finite size of a rapidly rotating compact astrophysical object moving in a
curved background. It is also a next-to-leading order effect in the phase of
gravitational waves emitted by extreme-mass-ratio inspirals (EMRIs), which are
expected to become observable by the LISA space mission. Additionally,
exploring the Hamiltonian formalism for spinning bodies is important for the
construction of the so-called Effective-One-Body waveform models that should
eventually cover all mass ratios.
The MPD equations require supplementary conditions determining the frame in
which the moments of the body are computed. We review various choices of these
supplementary spin conditions and their properties. Then, we give Hamiltonians
either in proper-time or coordinate-time parametrization for the
Tulczyjew-Dixon, Mathisson-Pirani, and Kyrian-Semer\'ak conditions. Finally, we
also give canonical phase-space coordinates parametrizing the spin tensor. We
demonstrate the usefulness of the canonical coordinates for symplectic
integration by constructing Poincar\'e surfaces of section for spinning bodies
moving in the equatorial plane in Schwarzschild space-time. We observe the
motion to be essentially regular for EMRI-ranges of the spin, but for larger
values the Poincar\'e surfaces of section exhibit the typical structure of a
weakly chaotic system. A possible future application of the numerical
integration method is the inclusion of spin effects in EMRIs at the precision
requirements of LISA.
| [
{
"created": "Mon, 20 Aug 2018 17:42:00 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Jan 2019 12:18:16 GMT",
"version": "v2"
}
] | 2019-03-01 | [
[
"Witzany",
"Vojtěch",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
]
] | The spin-curvature coupling as captured by the so-called Mathisson-Papapetrou-Dixon (MPD) equations is the leading order effect of the finite size of a rapidly rotating compact astrophysical object moving in a curved background. It is also a next-to-leading order effect in the phase of gravitational waves emitted by extreme-mass-ratio inspirals (EMRIs), which are expected to become observable by the LISA space mission. Additionally, exploring the Hamiltonian formalism for spinning bodies is important for the construction of the so-called Effective-One-Body waveform models that should eventually cover all mass ratios. The MPD equations require supplementary conditions determining the frame in which the moments of the body are computed. We review various choices of these supplementary spin conditions and their properties. Then, we give Hamiltonians either in proper-time or coordinate-time parametrization for the Tulczyjew-Dixon, Mathisson-Pirani, and Kyrian-Semer\'ak conditions. Finally, we also give canonical phase-space coordinates parametrizing the spin tensor. We demonstrate the usefulness of the canonical coordinates for symplectic integration by constructing Poincar\'e surfaces of section for spinning bodies moving in the equatorial plane in Schwarzschild space-time. We observe the motion to be essentially regular for EMRI-ranges of the spin, but for larger values the Poincar\'e surfaces of section exhibit the typical structure of a weakly chaotic system. A possible future application of the numerical integration method is the inclusion of spin effects in EMRIs at the precision requirements of LISA. |
2001.00599 | Mostafizur Rahman | Mostafizur Rahman, Soumodeep Mitra and Sumanta Chakraborty | Strong cosmic censorship conjecture with NUT charge and conformal
coupling | v2, minor revision, 47 pages, 4 figures, published in Class. Quant.
Grav | Class. Quantum Grav. 37, 195004 (2020) | 10.1088/1361-6382/aba17d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Strong cosmic censorship conjecture is central to the deterministic nature of
general relativity, since it asserts that given any generic initial data on a
spacelike hypersurface, the future can be uniquely predicted. However, recently
it has been found that for charged black holes in asymptotically de Sitter
spacetimes, the metric and massless scalar fields can be extended beyond the
Cauchy horizon. This spells doom on the strong cosmic censorship conjecture,
which prohibits precisely this scenario. In this work we try to understand the
genericness of the above situation by studying the effect of NUT charge and
conformally coupled scalar field on the violation of strong cosmic censorship
conjecture for charged asymptotically de Sitter black holes. We have shown that
even in the presence of the NUT charge and a conformally coupled scalar field
strong cosmic censorship conjecture in indeed violated for such black holes
with Cauchy horizon. Moreover, the presence of conformal coupling makes the
situation even worse, in the sense that the scalar field is extendible across
the Cauchy horizon as a $C^{1}$ function. On the other hand, the strong cosmic
censorship conjecture is respected for conformally coupled scalar field in
rotating black hole spacetimes with NUT charge. This reinforces the belief that
possibly for astrophysical black holes, strong cosmic censorship conjecture is
respected, irrespective of the nature of the scalar field.
| [
{
"created": "Thu, 2 Jan 2020 19:16:32 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Sep 2020 09:14:34 GMT",
"version": "v2"
}
] | 2020-09-22 | [
[
"Rahman",
"Mostafizur",
""
],
[
"Mitra",
"Soumodeep",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] | Strong cosmic censorship conjecture is central to the deterministic nature of general relativity, since it asserts that given any generic initial data on a spacelike hypersurface, the future can be uniquely predicted. However, recently it has been found that for charged black holes in asymptotically de Sitter spacetimes, the metric and massless scalar fields can be extended beyond the Cauchy horizon. This spells doom on the strong cosmic censorship conjecture, which prohibits precisely this scenario. In this work we try to understand the genericness of the above situation by studying the effect of NUT charge and conformally coupled scalar field on the violation of strong cosmic censorship conjecture for charged asymptotically de Sitter black holes. We have shown that even in the presence of the NUT charge and a conformally coupled scalar field strong cosmic censorship conjecture in indeed violated for such black holes with Cauchy horizon. Moreover, the presence of conformal coupling makes the situation even worse, in the sense that the scalar field is extendible across the Cauchy horizon as a $C^{1}$ function. On the other hand, the strong cosmic censorship conjecture is respected for conformally coupled scalar field in rotating black hole spacetimes with NUT charge. This reinforces the belief that possibly for astrophysical black holes, strong cosmic censorship conjecture is respected, irrespective of the nature of the scalar field. |
gr-qc/9703086 | 3 | Donald E. Neville | Total intrinsic spin for plane gravity waves | 14 pages; LaTex | Phys.Rev.D56:3485-3489,1997 | 10.1103/PhysRevD.56.3485 | TU-328-97 | gr-qc | null | A quantity which measures total intrinsic spin along the z axis is
constructed for planar gravity (fields dependent on z and t only), in both the
Ashtekar complex connection formalism and in geometrodynamics. The total spin
is conserved but (surprisingly) is not a surface term. This constant of the
motion coincides with one of four observables previously discovered by Husain
and Smolin. Two more of those observables can be interpreted physically as
raising and lowering operators for total spin.
| [
{
"created": "Fri, 28 Mar 1997 18:52:12 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Neville",
"Donald E.",
""
]
] | A quantity which measures total intrinsic spin along the z axis is constructed for planar gravity (fields dependent on z and t only), in both the Ashtekar complex connection formalism and in geometrodynamics. The total spin is conserved but (surprisingly) is not a surface term. This constant of the motion coincides with one of four observables previously discovered by Husain and Smolin. Two more of those observables can be interpreted physically as raising and lowering operators for total spin. |
1208.2934 | Maciej Maliborski | Maciej Maliborski | Instability of Flat Space Enclosed in a Cavity | 4 pages, 7 figures; Revised version, consistent with published paper | Phys. Rev. Lett. 109, 221101 (2012) | 10.1103/PhysRevLett.109.221101 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a spherically symmetric self-gravitating massless scalar field
enclosed inside a timelike worldtube $R\times S^3$ with a perfectly reflecting
wall. Numerical evidence is given that arbitrarily small generic initial data
evolve into a black hole.
| [
{
"created": "Tue, 14 Aug 2012 17:59:48 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Jan 2013 17:11:44 GMT",
"version": "v2"
}
] | 2013-01-22 | [
[
"Maliborski",
"Maciej",
""
]
] | We consider a spherically symmetric self-gravitating massless scalar field enclosed inside a timelike worldtube $R\times S^3$ with a perfectly reflecting wall. Numerical evidence is given that arbitrarily small generic initial data evolve into a black hole. |
1209.0213 | Sergio Dain | Sergio Dain and Gustavo Dotti | The wave equation on the extreme Reissner-Nordstr\"om black hole | Minor corrections | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the scalar wave equation on the open exterior region of an extreme
Reissner-Nordstr\"om black hole and prove that, given compactly supported data
on a Cauchy surface orthogonal to the timelike Killing vector field, the
solution, together with its $(t,s,\theta,\phi)$ derivatives of arbitrary order,
$s$ a tortoise radial coordinate, is bounded by a constant that depends only on
the initial data. Our technique does not allow to study transverse derivatives
at the horizon, which is outside the coordinate patch that we use. However,
using previous results that show that second and higher transverse derivatives
at the horizon of a generic solution grow unbounded along horizon generators,
we show that any such a divergence, if present, would be milder for solutions
with compact initial data.
| [
{
"created": "Sun, 2 Sep 2012 20:48:27 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Oct 2012 22:41:40 GMT",
"version": "v2"
},
{
"created": "Wed, 24 Oct 2012 18:14:55 GMT",
"version": "v3"
},
{
"created": "Fri, 1 Feb 2013 14:12:09 GMT",
"version": "v4"
}
] | 2013-02-04 | [
[
"Dain",
"Sergio",
""
],
[
"Dotti",
"Gustavo",
""
]
] | We study the scalar wave equation on the open exterior region of an extreme Reissner-Nordstr\"om black hole and prove that, given compactly supported data on a Cauchy surface orthogonal to the timelike Killing vector field, the solution, together with its $(t,s,\theta,\phi)$ derivatives of arbitrary order, $s$ a tortoise radial coordinate, is bounded by a constant that depends only on the initial data. Our technique does not allow to study transverse derivatives at the horizon, which is outside the coordinate patch that we use. However, using previous results that show that second and higher transverse derivatives at the horizon of a generic solution grow unbounded along horizon generators, we show that any such a divergence, if present, would be milder for solutions with compact initial data. |
1909.11661 | S. I. Kruglov | S. I. Kruglov | Dyonic black holes in framework of Born--Infeld-type electrodynamics | 17 pages, 6 figures | Gen.Rel.Grav. 51 (2019) no.9, 121 | 10.1007/s10714-019-2603-5 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dyonic black hole solutions with spherically symmetric configurations within
general relativity are investigated where the source of the gravitational field
is Born - Infeld-type electrodynamics. Corrections to Coulomb's law and
Reissner - Nordstrom solutions are obtained. From principles of causality and
unitarity we find the restriction on electric and magnetic fields. The Hawking
temperature and the heat capacity of black holes are obtained. At some event
horizons second-order phase transitions take place.
| [
{
"created": "Wed, 25 Sep 2019 14:55:30 GMT",
"version": "v1"
}
] | 2019-09-30 | [
[
"Kruglov",
"S. I.",
""
]
] | Dyonic black hole solutions with spherically symmetric configurations within general relativity are investigated where the source of the gravitational field is Born - Infeld-type electrodynamics. Corrections to Coulomb's law and Reissner - Nordstrom solutions are obtained. From principles of causality and unitarity we find the restriction on electric and magnetic fields. The Hawking temperature and the heat capacity of black holes are obtained. At some event horizons second-order phase transitions take place. |
2311.13268 | Ignazio Ciufolini | Ignazio Ciufolini, Claudio Paris, Erricos C. Pavlis, John Ries,
Richard Matzner, Antonio Paolozzi, Emiliano Ortore, Giuseppe Bianco,
Magdalena Kuzmicz-Cieslak, Vahe Gurzadyan, Roger Penrose | First results of the LARES 2 space experiment to test the general theory
of relativity | 11 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | The LAGEOS 3 (today LARES 2) space experiment was proposed in the eighties by
the Physics Department and by the Center of Space Research (CSR) of the
University of Texas (UT) at Austin and by the Italian Space Agency (ASI) to
test and accurately measure frame-dragging, with the strong support of John
Archibald Wheeler, director of the Center for Theoretical Physics of UT Austin.
Frame-dragging is an intriguing phenomenon predicted by Einstein's theory of
general relativity which has fundamental implications in high energy
astrophysics and in the generation of gravitational waves by spinning black
holes. LAGEOS 3 was reproposed in 2016 to the Italian Space Agency and to the
European Space Agency as a technologically much improved version of LAGEOS 3
under the name LARES 2 (LAres RElativity Satellite 2) and then successfully
launched in 2022 with the new launch vehicle VEGA C of ASI, ESA and AVIO.
Today, after almost forty years since the original proposal, we report the
first results of the LARES 2 space experiment to test general relativity. The
results are in complete agreement with the predictions of Einstein's
gravitational theory. Whereas previous results already confirmed the
frame-dragging prediction, the conceptual relative simplicity of the LARES 2
experiment with respect to the previous tests with the LARES and LAGEOS
satellites provides a significant advance in the field of tests of general
relativity.
| [
{
"created": "Wed, 22 Nov 2023 09:38:49 GMT",
"version": "v1"
}
] | 2023-11-23 | [
[
"Ciufolini",
"Ignazio",
""
],
[
"Paris",
"Claudio",
""
],
[
"Pavlis",
"Erricos C.",
""
],
[
"Ries",
"John",
""
],
[
"Matzner",
"Richard",
""
],
[
"Paolozzi",
"Antonio",
""
],
[
"Ortore",
"Emiliano",
""
],
[
"Bianco",
"Giuseppe",
""
],
[
"Kuzmicz-Cieslak",
"Magdalena",
""
],
[
"Gurzadyan",
"Vahe",
""
],
[
"Penrose",
"Roger",
""
]
] | The LAGEOS 3 (today LARES 2) space experiment was proposed in the eighties by the Physics Department and by the Center of Space Research (CSR) of the University of Texas (UT) at Austin and by the Italian Space Agency (ASI) to test and accurately measure frame-dragging, with the strong support of John Archibald Wheeler, director of the Center for Theoretical Physics of UT Austin. Frame-dragging is an intriguing phenomenon predicted by Einstein's theory of general relativity which has fundamental implications in high energy astrophysics and in the generation of gravitational waves by spinning black holes. LAGEOS 3 was reproposed in 2016 to the Italian Space Agency and to the European Space Agency as a technologically much improved version of LAGEOS 3 under the name LARES 2 (LAres RElativity Satellite 2) and then successfully launched in 2022 with the new launch vehicle VEGA C of ASI, ESA and AVIO. Today, after almost forty years since the original proposal, we report the first results of the LARES 2 space experiment to test general relativity. The results are in complete agreement with the predictions of Einstein's gravitational theory. Whereas previous results already confirmed the frame-dragging prediction, the conceptual relative simplicity of the LARES 2 experiment with respect to the previous tests with the LARES and LAGEOS satellites provides a significant advance in the field of tests of general relativity. |
1509.01878 | Erik Curiel | Erik Curiel | Measure, Topology and Probabilistic Reasoning in Cosmology | 26 pages | null | null | null | gr-qc math-ph math.MP physics.data-an physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I explain the difficulty of making various concepts of and relating to
probability precise, rigorous and physically significant when attempting to
apply them in reasoning about objects (e.g., spacetimes) living in
infinite-dimensional spaces, working through many examples from cosmology. I
focus on the relation of topological to measure-theoretic notions of and
relating to probability, how they diverge in unpleasant ways in the
infinite-dimensional case, and are difficult to work with on their own as well
in that context. Even in cases where an appropriate family of spacetimes is
finite-dimensional, however, and so admits a measure of the relevant sort, it
is always the case that the family is not a compact topological space, and so
does not admit a physically significant, well behaved probability measure.
Problems of a different but still deeply troubling sort plague arguments about
likelihood in that context, which I also discuss. I conclude that most standard
forms of argument used in cosmology to estimate the likelihood of the
occurrence of various properties or behaviors of spacetimes have serious
mathematical, physical and conceptual problems.
| [
{
"created": "Mon, 7 Sep 2015 01:22:29 GMT",
"version": "v1"
}
] | 2015-09-08 | [
[
"Curiel",
"Erik",
""
]
] | I explain the difficulty of making various concepts of and relating to probability precise, rigorous and physically significant when attempting to apply them in reasoning about objects (e.g., spacetimes) living in infinite-dimensional spaces, working through many examples from cosmology. I focus on the relation of topological to measure-theoretic notions of and relating to probability, how they diverge in unpleasant ways in the infinite-dimensional case, and are difficult to work with on their own as well in that context. Even in cases where an appropriate family of spacetimes is finite-dimensional, however, and so admits a measure of the relevant sort, it is always the case that the family is not a compact topological space, and so does not admit a physically significant, well behaved probability measure. Problems of a different but still deeply troubling sort plague arguments about likelihood in that context, which I also discuss. I conclude that most standard forms of argument used in cosmology to estimate the likelihood of the occurrence of various properties or behaviors of spacetimes have serious mathematical, physical and conceptual problems. |
1508.05375 | Yurii Ignat'ev | Yurii Ignat'ev | Instability Model of the Universe with De Sitter Beginning | 13 pages, 5 references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The physical instability of the Universe model with de Sitter beginning is
proved in this article. 1. It is shown that even a small addition of
ultrarelativistic matter turns the de Sitter Universe into the Universe with
finite past. 2. Constant solution of equation of model with constant scalar
field is shown to be instable. 3. It is also shown that lateral gravitational
perturbations of such model make it instable near of cosmological singularity.
The conclusion is made that de Sitter stage of the Universe evolution most
likely should be preceded by the ultrarelativistic stage.
| [
{
"created": "Fri, 21 Aug 2015 19:25:41 GMT",
"version": "v1"
}
] | 2015-08-24 | [
[
"Ignat'ev",
"Yurii",
""
]
] | The physical instability of the Universe model with de Sitter beginning is proved in this article. 1. It is shown that even a small addition of ultrarelativistic matter turns the de Sitter Universe into the Universe with finite past. 2. Constant solution of equation of model with constant scalar field is shown to be instable. 3. It is also shown that lateral gravitational perturbations of such model make it instable near of cosmological singularity. The conclusion is made that de Sitter stage of the Universe evolution most likely should be preceded by the ultrarelativistic stage. |
gr-qc/9712015 | Jeeva S. Anandan | Jeeva S. Anandan | Classical and Quantum Physical Geometry | 31 pages, tex, 1 figure. Published in Potentiality, Entanglement and
Passion-at-a-distance - Quantum Mechanical Studies for Abner Shimony, vol. 2,
edited by R. S. Cohen, M. Horne and J. Stachel, (Kluwer, Dordrecht, Holland
1997), p. 31-52 | null | null | null | gr-qc hep-th | null | The task of quantizing gravity is compared with Einstein's relativization of
gravity. The philosophical and physical foundations of general relativity are
briefly reviewed. The Ehlers-Pirani-Schild scheme of operationally determining
the geometry of space-time, using freely falling classical particle
trajectories, is done using operations in an infinitesimal neighborhood around
each point. The study of the free fall of a quantum wave suggests a quantum
principle of equivalence. The principle of general covariance is clarified. The
sign change of a Fermion field when rotated by $2\pi$ radians is used to argue
for a quantum mechanical modification of space-time, which leads naturally to
supersymmetry. A novel effect in quantum gravity due to the author is used to
extend Einstein's hole argument to quantum gravity. This suggests a quantum
principle of general covariance, according to which the fundamental laws of
physics should be covariant under `quantum diffeomorphisms'. This heuristic
principle implies that space-time points have no invariant meaning in quantum
gravity.
| [
{
"created": "Tue, 2 Dec 1997 21:49:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Anandan",
"Jeeva S.",
""
]
] | The task of quantizing gravity is compared with Einstein's relativization of gravity. The philosophical and physical foundations of general relativity are briefly reviewed. The Ehlers-Pirani-Schild scheme of operationally determining the geometry of space-time, using freely falling classical particle trajectories, is done using operations in an infinitesimal neighborhood around each point. The study of the free fall of a quantum wave suggests a quantum principle of equivalence. The principle of general covariance is clarified. The sign change of a Fermion field when rotated by $2\pi$ radians is used to argue for a quantum mechanical modification of space-time, which leads naturally to supersymmetry. A novel effect in quantum gravity due to the author is used to extend Einstein's hole argument to quantum gravity. This suggests a quantum principle of general covariance, according to which the fundamental laws of physics should be covariant under `quantum diffeomorphisms'. This heuristic principle implies that space-time points have no invariant meaning in quantum gravity. |
gr-qc/0101067 | Pinto Innocenzo M. | R.P. Croce, Th. Demma, V. Pierro, I.M. Pinto | Tanaka-Tagoshi Parametrization of post-1PN Spin-Free Gravitational Wave
Chirps: Equispaced and Cardinal Interpolated Lattices For First Generation
Interferometric Antennas | 9 pages, 8 figures, 3 tables, accepted for publication in Phys. Rev.
D | Phys.Rev.D64:042005,2001 | 10.1103/PhysRevD.64.042005 | null | gr-qc | null | The spin-free binary-inspiral parameter-space introduced by Tanaka and
Tagoshi to construct a uniformly-spaced lattice of templates at (and possibly
beyond) $2.5PN$ order is shown to work for all first generation interferometric
gravitational wave antennas. This allows to extend the minimum-redundant
cardinal interpolation techniques of the correlator bank developed by the
Authors to the highest available order PN templates. The total number of 2PN
templates to be computed for a minimal match $\Gamma=0.97$ is reduced by a
factor 4, as in the 1PN case.
| [
{
"created": "Wed, 17 Jan 2001 11:12:21 GMT",
"version": "v1"
},
{
"created": "Fri, 11 May 2001 14:10:08 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Jun 2001 20:51:30 GMT",
"version": "v3"
}
] | 2011-04-12 | [
[
"Croce",
"R. P.",
""
],
[
"Demma",
"Th.",
""
],
[
"Pierro",
"V.",
""
],
[
"Pinto",
"I. M.",
""
]
] | The spin-free binary-inspiral parameter-space introduced by Tanaka and Tagoshi to construct a uniformly-spaced lattice of templates at (and possibly beyond) $2.5PN$ order is shown to work for all first generation interferometric gravitational wave antennas. This allows to extend the minimum-redundant cardinal interpolation techniques of the correlator bank developed by the Authors to the highest available order PN templates. The total number of 2PN templates to be computed for a minimal match $\Gamma=0.97$ is reduced by a factor 4, as in the 1PN case. |
2311.03423 | Dr. Goutam Manna | Bivash Majumder, Maxim Khlopov, Saibal Ray and Goutam Manna | Geodesic structure of generalized Vaidya spacetime through the K-essence | 19 pages, 21 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This article investigates on the radial and non-radial geodesic structures of
the generalized K-essence Vaidya spacetime. Within the framework of K-essence
geometry, it is important to note that the metric does not possess conformal
equivalence to the conventional gravitational metric. This study employs a
non-canonical action of the Dirac-Born-Infeld kind. In this work, we categorize
the generalized K-essence Vaidya mass function into two distinct forms. Both
the forms of the mass functions have been extensively utilized to analyze the
radial and non-radial time-like or null geodesics in great details inside the
comoving plane. Indications of the existence of wormhole can be noted during
the extreme phases of spacetime, particularly in relation to black holes and
white holes, which resemble the Einstein-Rosen bridge. In addition, we have
also detected the distinctive indication of the quantum tunneling phenomenon
around the central singularity.
| [
{
"created": "Mon, 6 Nov 2023 16:22:09 GMT",
"version": "v1"
}
] | 2023-11-08 | [
[
"Majumder",
"Bivash",
""
],
[
"Khlopov",
"Maxim",
""
],
[
"Ray",
"Saibal",
""
],
[
"Manna",
"Goutam",
""
]
] | This article investigates on the radial and non-radial geodesic structures of the generalized K-essence Vaidya spacetime. Within the framework of K-essence geometry, it is important to note that the metric does not possess conformal equivalence to the conventional gravitational metric. This study employs a non-canonical action of the Dirac-Born-Infeld kind. In this work, we categorize the generalized K-essence Vaidya mass function into two distinct forms. Both the forms of the mass functions have been extensively utilized to analyze the radial and non-radial time-like or null geodesics in great details inside the comoving plane. Indications of the existence of wormhole can be noted during the extreme phases of spacetime, particularly in relation to black holes and white holes, which resemble the Einstein-Rosen bridge. In addition, we have also detected the distinctive indication of the quantum tunneling phenomenon around the central singularity. |
gr-qc/9405008 | null | Peter Dunsby and Marco Bruni | Conserved Quantities in Perturbed Inflationary Universes | 17 Pages, LaTeX | Int.J.Mod.Phys.D3:443-459,1994 | 10.1142/S0218271894000629 | UCT Preprint 94/5 | gr-qc | null | Given that observations seem to favour a \index{density parameter}
$\Omega_0<1$, corresponding to an open universe, we consider gauge\hs invariant
perturbations of non\hs flat Robertson\hs Walker universes filled with a
general imperfect fluid which can also be taken to represent a scalar field.
Our aim is to set up the equations that govern the evolution of the density
perturbations $\Delta$ so that it can be determined through a {\it first order
differential equation} with a quantity $\kk$ which is conserved at any length
scale, even in non\hs flat universe models, acting as a source term. The
quantity $\kk$ generalizes other variables that are conserved in specific cases
(for example at large scales in a flat universe) and is useful to connect
different epochs in the evolution of density perturbations via a transfer
function. We show that the problem of finding a conserved $\kk$ can be reduced
to determining two auxiliary variables $X$ and $Y$, and illustrate the method
with two simple examples.
| [
{
"created": "Wed, 4 May 1994 16:11:16 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Dunsby",
"Peter",
""
],
[
"Bruni",
"Marco",
""
]
] | Given that observations seem to favour a \index{density parameter} $\Omega_0<1$, corresponding to an open universe, we consider gauge\hs invariant perturbations of non\hs flat Robertson\hs Walker universes filled with a general imperfect fluid which can also be taken to represent a scalar field. Our aim is to set up the equations that govern the evolution of the density perturbations $\Delta$ so that it can be determined through a {\it first order differential equation} with a quantity $\kk$ which is conserved at any length scale, even in non\hs flat universe models, acting as a source term. The quantity $\kk$ generalizes other variables that are conserved in specific cases (for example at large scales in a flat universe) and is useful to connect different epochs in the evolution of density perturbations via a transfer function. We show that the problem of finding a conserved $\kk$ can be reduced to determining two auxiliary variables $X$ and $Y$, and illustrate the method with two simple examples. |
2203.10868 | Ya-Peng Hu | Haximjan Abdusattar, Shi-Bei Kong, Yihao Yin and Ya-Peng Hu | The Hawking-Page-like Phase Transition from FRW Spacetime to McVittie
Black Hole | 12 pages, 4 figures | null | 10.1088/1475-7516/2022/08/060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the thermodynamics especially the
Hawking-Page-like phase transition of the McVittie space-time. We formulate the
first law of thermodynamics for the McVittie black hole, and find that the work
density $W$ of the perfect fluid plays the role of the thermodynamic pressure,
i.e. $P$:=$-W$. We also construct the thermodynamic equation of state for the
McVittie black hole. Most importantly, by analysing the Gibbs free energy, we
find that the Hawking-Page-like phase transition from FRW spacetime to McVittie
black hole is possible in the case $P>0$.
| [
{
"created": "Mon, 21 Mar 2022 10:41:59 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Abdusattar",
"Haximjan",
""
],
[
"Kong",
"Shi-Bei",
""
],
[
"Yin",
"Yihao",
""
],
[
"Hu",
"Ya-Peng",
""
]
] | In this paper, we investigate the thermodynamics especially the Hawking-Page-like phase transition of the McVittie space-time. We formulate the first law of thermodynamics for the McVittie black hole, and find that the work density $W$ of the perfect fluid plays the role of the thermodynamic pressure, i.e. $P$:=$-W$. We also construct the thermodynamic equation of state for the McVittie black hole. Most importantly, by analysing the Gibbs free energy, we find that the Hawking-Page-like phase transition from FRW spacetime to McVittie black hole is possible in the case $P>0$. |
2102.03221 | Po-Ning Chen | Po-Ning Chen, Jordan Keller, Mu-Tao Wang, Ye-Kai Wang, and Shing-Tung
Yau | Evolution of angular momentum and center of mass at null infinity | 40 pages, references added and typos corrected | null | 10.1007/s00220-021-04053-7 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study how conserved quantities such as angular momentum and center of mass
evolve with respect to the retarded time at null infinity, which is described
in terms of a Bondi-Sachs coordinate system. These evolution formulae
complement the classical Bondi mass loss formula for gravitational radiation.
They are further expressed in terms of the potentials of the shear and news
tensors. The consequences that follow from these formulae are (1)
Supertranslation invariance of the fluxes of the CWY conserved quantities. (2)
A conservation law of angular momentum \`a la Christodoulou. (3) A duality
paradigm for null infinity. In particular, the supertranslation invariance
distinguishes the CWY angular momentum and center of mass from the classical
definitions.
| [
{
"created": "Fri, 5 Feb 2021 15:12:23 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Feb 2021 20:14:34 GMT",
"version": "v2"
}
] | 2021-04-28 | [
[
"Chen",
"Po-Ning",
""
],
[
"Keller",
"Jordan",
""
],
[
"Wang",
"Mu-Tao",
""
],
[
"Wang",
"Ye-Kai",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | We study how conserved quantities such as angular momentum and center of mass evolve with respect to the retarded time at null infinity, which is described in terms of a Bondi-Sachs coordinate system. These evolution formulae complement the classical Bondi mass loss formula for gravitational radiation. They are further expressed in terms of the potentials of the shear and news tensors. The consequences that follow from these formulae are (1) Supertranslation invariance of the fluxes of the CWY conserved quantities. (2) A conservation law of angular momentum \`a la Christodoulou. (3) A duality paradigm for null infinity. In particular, the supertranslation invariance distinguishes the CWY angular momentum and center of mass from the classical definitions. |
1901.05902 | Halston Lim | Halston Lim, Gaurav Khanna, Anuj Apte, and Scott A. Hughes | Exciting black hole modes via misaligned coalescences: II. The mode
content of late-time coalescence waveforms | 21 pages, 20 figures. This update matches text in published version | Phys. Rev. D 100, 084032 (2019) | 10.1103/PhysRevD.100.084032 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using inspiral and plunge trajectories we construct with a generalized
Ori-Thorne algorithm, we use a time-domain black hole perturbation theory code
to compute the corresponding gravitational waves. The last cycles of these
waveforms are a superposition of Kerr quasinormal modes. In this paper, we
examine how the modes' excitations vary as a function of source parameters,
such as the larger black hole's spin and the geometry of the smaller body's
inspiral and plunge. We find that the mixture of quasinormal modes that
characterize the final gravitational waves from a coalescence is entirely
determined by the spin $a$ of the larger black hole, an angle $I$ which
characterizes the misalignment of the orbital plane from the black hole's spin
axis, a second angle $\theta_{\rm fin}$ which describes the location at which
the small body crosses the black hole's event horizon, and the direction
sgn$(\dot\theta_{\rm fin})$ of the body's final motion. If these
large-mass-ratio results hold at less extreme mass ratios, then measuring
multiple ringdown modes of binary black hole coalescence gravitational waves
may provide important information about the source's binary properties, such as
the misalignment of the orbit's angular momentum with black hole spin. This may
be particularly useful for large mass binaries, for which the early inspiral
waves are out of the detectors' most sensitive band.
| [
{
"created": "Thu, 17 Jan 2019 17:04:19 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Nov 2019 16:52:12 GMT",
"version": "v2"
}
] | 2019-11-18 | [
[
"Lim",
"Halston",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Apte",
"Anuj",
""
],
[
"Hughes",
"Scott A.",
""
]
] | Using inspiral and plunge trajectories we construct with a generalized Ori-Thorne algorithm, we use a time-domain black hole perturbation theory code to compute the corresponding gravitational waves. The last cycles of these waveforms are a superposition of Kerr quasinormal modes. In this paper, we examine how the modes' excitations vary as a function of source parameters, such as the larger black hole's spin and the geometry of the smaller body's inspiral and plunge. We find that the mixture of quasinormal modes that characterize the final gravitational waves from a coalescence is entirely determined by the spin $a$ of the larger black hole, an angle $I$ which characterizes the misalignment of the orbital plane from the black hole's spin axis, a second angle $\theta_{\rm fin}$ which describes the location at which the small body crosses the black hole's event horizon, and the direction sgn$(\dot\theta_{\rm fin})$ of the body's final motion. If these large-mass-ratio results hold at less extreme mass ratios, then measuring multiple ringdown modes of binary black hole coalescence gravitational waves may provide important information about the source's binary properties, such as the misalignment of the orbit's angular momentum with black hole spin. This may be particularly useful for large mass binaries, for which the early inspiral waves are out of the detectors' most sensitive band. |
2301.12133 | Tiberiu Harko | Zahra Haghani, Tiberiu Harko, Shahab Shahidi | The first variation of the matter energy-momentum tensor with respect to
the metric, and its implications on modified gravity theories | 9 pages, 4 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first order variation of the matter energy-momentum tensor $T_{\mu \nu}$
with respect to the metric tensor $g^{\alpha \beta}$ plays an important role in
modified gravity theories with geometry-matter coupling, and in particular in
the $f(R,T)$ modified gravity theory. We obtain the expression of the variation
$\delta T_{\mu \nu}/\delta g^{\alpha \beta}$ for the baryonic matter described
by an equation given in a parametric form, with the basic thermodynamic
variables represented by the particle number density, and by the specific
entropy, respectively. The first variation of the matter energy-momentum tensor
turns out to be independent on the matter Lagrangian, and can be expressed in
terms of the pressure, the energy-momentum tensor itself, and the matter fluid
four-velocity. We apply the obtained results for the case of the $f(R,T)$
gravity theory, where $R$ is the Ricci scalar, and $T$ is the trace of the
matter energy-momentum tensor, which thus becomes a unique theory, also
independent on the choice of the matter Lagrangian. A simple cosmological
model, in which the Hilbert-Einstein Lagrangian is generalized through the
addition of a term proportional to $T^n$ is considered in detail, and it is
shown that it gives a very good description of the observational values of the
Hubble parameter up to a redshift of $z\approx 2.5$.
| [
{
"created": "Sat, 28 Jan 2023 09:03:21 GMT",
"version": "v1"
},
{
"created": "Sun, 14 May 2023 12:01:59 GMT",
"version": "v2"
}
] | 2023-05-16 | [
[
"Haghani",
"Zahra",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Shahidi",
"Shahab",
""
]
] | The first order variation of the matter energy-momentum tensor $T_{\mu \nu}$ with respect to the metric tensor $g^{\alpha \beta}$ plays an important role in modified gravity theories with geometry-matter coupling, and in particular in the $f(R,T)$ modified gravity theory. We obtain the expression of the variation $\delta T_{\mu \nu}/\delta g^{\alpha \beta}$ for the baryonic matter described by an equation given in a parametric form, with the basic thermodynamic variables represented by the particle number density, and by the specific entropy, respectively. The first variation of the matter energy-momentum tensor turns out to be independent on the matter Lagrangian, and can be expressed in terms of the pressure, the energy-momentum tensor itself, and the matter fluid four-velocity. We apply the obtained results for the case of the $f(R,T)$ gravity theory, where $R$ is the Ricci scalar, and $T$ is the trace of the matter energy-momentum tensor, which thus becomes a unique theory, also independent on the choice of the matter Lagrangian. A simple cosmological model, in which the Hilbert-Einstein Lagrangian is generalized through the addition of a term proportional to $T^n$ is considered in detail, and it is shown that it gives a very good description of the observational values of the Hubble parameter up to a redshift of $z\approx 2.5$. |
1911.02892 | Elena V. Arbuzova | Elena Arbuzova | Instabilities in modified theories of gravity | 21 pages, 6 figures. Talk presented at the conference "Multifrequency
Behaviour of High Energy Cosmic Sources - XIII - MULTIF2019", 3-8 June 2019,
Palermo, Italy | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The review is devoted to consideration of possible observational consequences
of modified gravity theories, suggested for explanation of the contemporary
accelerated expansion of the universe. The major attention is paid to
F(R)-models. It is shown that in systems with rising energy density high
frequency and large amplitude oscillations of the curvature scalar, R(t), are
induced. These oscillations lead to the production of elementary particles,
which may be observed in the spectra of energetic cosmic rays. In the
background of such oscillating solutions gravitation repulsion between
finite-size objects becomes possible. Since the Lagrangian is a non-linear
function of curvature, equations of motion become of higher (4th) order and
exhibit very rich pattern of new physical effects. In particular, the evolution
of density perturbations is strongly different from that in General Relativity,
amplified due to both parametric resonance and anti-friction phenomena.
| [
{
"created": "Thu, 7 Nov 2019 13:27:59 GMT",
"version": "v1"
}
] | 2019-11-11 | [
[
"Arbuzova",
"Elena",
""
]
] | The review is devoted to consideration of possible observational consequences of modified gravity theories, suggested for explanation of the contemporary accelerated expansion of the universe. The major attention is paid to F(R)-models. It is shown that in systems with rising energy density high frequency and large amplitude oscillations of the curvature scalar, R(t), are induced. These oscillations lead to the production of elementary particles, which may be observed in the spectra of energetic cosmic rays. In the background of such oscillating solutions gravitation repulsion between finite-size objects becomes possible. Since the Lagrangian is a non-linear function of curvature, equations of motion become of higher (4th) order and exhibit very rich pattern of new physical effects. In particular, the evolution of density perturbations is strongly different from that in General Relativity, amplified due to both parametric resonance and anti-friction phenomena. |
1403.0083 | Yu-Xiao Liu | Xiao-Long Du, Ke Yang, Xin-He Meng, Yu-Xiao Liu | Large Scale Structure Formation in Eddington-inspired Born-Infeld
Gravity | 11 pages, 3 figures, improved version to be published in Phys. Rev. D | Phys. Rev. D 90, 044054 (2014) | 10.1103/PhysRevD.90.044054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the large scale structure formation in Eddington-inspired
Born-Infeld (EiBI) gravity. It is found that the linear growth of scalar
perturbations in EiBI gravity deviates from that in general relativity for
modes with large wave numbers ($k$), but the deviation is largely suppressed
with the expansion of the Universe. We investigate the integrated Sachs-Wolfe
effect in EiBI gravity, and find that its effect on the angular power spectrum
of the anisotropy of the cosmic microwave background (CMB) is almost the same
as that in the Lambda-cold dark matter ($\Lambda$CDM) model. We further
calculate the linear matter power spectrum in EiBI gravity and compare it with
that in the $\Lambda$CDM model. Deviation is found on small scales ($k\gtrsim
0.1 h$ Mpc$^{-1}$), which can be tested in the future by observations from
galaxy surveys.
| [
{
"created": "Sat, 1 Mar 2014 13:28:47 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Aug 2014 14:06:24 GMT",
"version": "v2"
}
] | 2014-09-23 | [
[
"Du",
"Xiao-Long",
""
],
[
"Yang",
"Ke",
""
],
[
"Meng",
"Xin-He",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | We study the large scale structure formation in Eddington-inspired Born-Infeld (EiBI) gravity. It is found that the linear growth of scalar perturbations in EiBI gravity deviates from that in general relativity for modes with large wave numbers ($k$), but the deviation is largely suppressed with the expansion of the Universe. We investigate the integrated Sachs-Wolfe effect in EiBI gravity, and find that its effect on the angular power spectrum of the anisotropy of the cosmic microwave background (CMB) is almost the same as that in the Lambda-cold dark matter ($\Lambda$CDM) model. We further calculate the linear matter power spectrum in EiBI gravity and compare it with that in the $\Lambda$CDM model. Deviation is found on small scales ($k\gtrsim 0.1 h$ Mpc$^{-1}$), which can be tested in the future by observations from galaxy surveys. |
0708.2488 | Rickard Jonsson | Rickard Jonsson | An intuitive approach to inertial forces and the centrifugal force
paradox in general relativity | 14 pages, 21 figures | Am.J.Phys.74:905-916,2006 | 10.1119/1.2198880 | null | gr-qc | null | As the velocity of a rocket in a circular orbit near a black hole increases,
the outwardly directed rocket thrust must increase to keep the rocket in its
orbit. This feature might appear paradoxical from a Newtonian viewpoint, but we
show that it follows naturally from the equivalence principle together with
special relativity and a few general features of black holes. We also derive a
general relativistic formalism of inertial forces for reference frames with
acceleration and rotation. The resulting equation relates the real experienced
forces to the time derivative of the speed and the spatial curvature of the
particle trajectory relative to the reference frame. We show that an observer
who follows the path taken by a free (geodesic) photon will experience a force
perpendicular to the direction of motion that is independent of the observers
velocity. We apply our approach to resolve the submarine paradox, which regards
whether a submerged submarine in a balanced state of rest will sink or float
when given a horizontal velocity if we take relativistic effects into account.
We extend earlier treatments of this topic to include spherical oceans and show
that for the case of the Earth the submarine floats upward if we take the
curvature of the ocean into account.
| [
{
"created": "Sat, 18 Aug 2007 14:01:47 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Jonsson",
"Rickard",
""
]
] | As the velocity of a rocket in a circular orbit near a black hole increases, the outwardly directed rocket thrust must increase to keep the rocket in its orbit. This feature might appear paradoxical from a Newtonian viewpoint, but we show that it follows naturally from the equivalence principle together with special relativity and a few general features of black holes. We also derive a general relativistic formalism of inertial forces for reference frames with acceleration and rotation. The resulting equation relates the real experienced forces to the time derivative of the speed and the spatial curvature of the particle trajectory relative to the reference frame. We show that an observer who follows the path taken by a free (geodesic) photon will experience a force perpendicular to the direction of motion that is independent of the observers velocity. We apply our approach to resolve the submarine paradox, which regards whether a submerged submarine in a balanced state of rest will sink or float when given a horizontal velocity if we take relativistic effects into account. We extend earlier treatments of this topic to include spherical oceans and show that for the case of the Earth the submarine floats upward if we take the curvature of the ocean into account. |
2109.01660 | Jos\'e Pedro Pinto Vieira | J. P. P. Vieira | The Universe as a driven quantum system: Unbounded heating in cyclic
cosmologies | null | null | null | null | gr-qc astro-ph.CO cond-mat.stat-mech quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamiltonian of an evolving Universe is shown to be formally equivalent to
that of a driven quantum system, whose driving follows from the temporal
dependence of the spacetime metric. This analogy allows insights from the field
of driven quantum systems to be applied to cosmological settings. In
particular, it is shown that periodic cyclic cosmologies are generically
prohibited (except under certain limiting constraints) due to their
correspondence with periodically-driven quantum systems (which are typically
expected to experience unbounded heating in the infinite future). This result
highlights how future work on non-periodically-driven quantum systems is
required to fully describe the dynamics of more general cyclic cosmologies (for
which a qualitative picture is briefly discussed).
| [
{
"created": "Thu, 2 Sep 2021 15:29:37 GMT",
"version": "v1"
}
] | 2021-09-07 | [
[
"Vieira",
"J. P. P.",
""
]
] | The Hamiltonian of an evolving Universe is shown to be formally equivalent to that of a driven quantum system, whose driving follows from the temporal dependence of the spacetime metric. This analogy allows insights from the field of driven quantum systems to be applied to cosmological settings. In particular, it is shown that periodic cyclic cosmologies are generically prohibited (except under certain limiting constraints) due to their correspondence with periodically-driven quantum systems (which are typically expected to experience unbounded heating in the infinite future). This result highlights how future work on non-periodically-driven quantum systems is required to fully describe the dynamics of more general cyclic cosmologies (for which a qualitative picture is briefly discussed). |
2301.08646 | Alice Boldrin | Alice Boldrin | The Gauge issue and the Hamiltonian theory of cosmological perturbations | Presented at the 8th Conference of the Polish Society on Relativity | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a general formalism for the Hamiltonian description of
perturbation theory around any spatially homogeneous spacetime. We employ and
refine the Dirac method for constrained systems, which is very well-suited to
cosmological perturbations. This approach includes a discussion of the
gauge-invariant dynamics of perturbations as well as an analysis of gauge
transformations, gauge-fixing, partial gauge-fixing and spacetime
reconstruction. We will introduce the Kucha\v{r} parametrization of the
kinematical phase space as a convenient tool for studying the gauge
transformations. The key element of this approach is the reconstruction of
spacetime based on gauge-fixing conditions.
| [
{
"created": "Fri, 20 Jan 2023 15:51:47 GMT",
"version": "v1"
}
] | 2023-01-23 | [
[
"Boldrin",
"Alice",
""
]
] | We present a general formalism for the Hamiltonian description of perturbation theory around any spatially homogeneous spacetime. We employ and refine the Dirac method for constrained systems, which is very well-suited to cosmological perturbations. This approach includes a discussion of the gauge-invariant dynamics of perturbations as well as an analysis of gauge transformations, gauge-fixing, partial gauge-fixing and spacetime reconstruction. We will introduce the Kucha\v{r} parametrization of the kinematical phase space as a convenient tool for studying the gauge transformations. The key element of this approach is the reconstruction of spacetime based on gauge-fixing conditions. |
1505.02882 | George Pappas Dr | George Pappas and Thomas P. Sotiriou | Geodesic properties in terms of multipole moments in scalar-tensor
theories of gravity | 16 pages | MNRAS 453, 2862-2876 (2015) | 10.1093/mnras/stv1819 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formalism for describing a metric and the corresponding scalar in terms
of multipole moments has recently been developed for scalar-tensor theories. We
take advantage of this formalism in order to obtain expressions for the
observables that characterise geodesics in terms of the moments. These
expressions provide some insight into how the structure of a scalarized compact
object affects observables. They can also be used to understand how deviations
from general relativity are imprinted on the observables.
| [
{
"created": "Tue, 12 May 2015 06:16:08 GMT",
"version": "v1"
}
] | 2015-09-07 | [
[
"Pappas",
"George",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | The formalism for describing a metric and the corresponding scalar in terms of multipole moments has recently been developed for scalar-tensor theories. We take advantage of this formalism in order to obtain expressions for the observables that characterise geodesics in terms of the moments. These expressions provide some insight into how the structure of a scalarized compact object affects observables. They can also be used to understand how deviations from general relativity are imprinted on the observables. |
1311.0087 | Sourav Bhattacharya | Sourav Bhattacharya and Hideki Maeda | Can a black hole with conformal scalar hair rotate? | v3, 4pp; added references and discussions, modifications in
presentation and the interpretation of the result; accepted in Phys. Rev. D
as brief report | Phys. Rev. D 89, 087501 (2014) | 10.1103/PhysRevD.89.087501 | RUP-13-14, CECS-PHY-13/08 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that, under the separability assumption for the metric, the
slow-rotation approximation for the Bocharova-Bronnikov-Melnikov-Bekenstein
black hole in general relativity with a conformally coupled scalar field does
not work outside the event horizon. Suggestions indicated by our present
analysis towards a fully rotating black hole solution are discussed.
| [
{
"created": "Fri, 1 Nov 2013 04:43:06 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Nov 2013 10:13:50 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Mar 2014 05:45:21 GMT",
"version": "v3"
}
] | 2014-04-23 | [
[
"Bhattacharya",
"Sourav",
""
],
[
"Maeda",
"Hideki",
""
]
] | It is shown that, under the separability assumption for the metric, the slow-rotation approximation for the Bocharova-Bronnikov-Melnikov-Bekenstein black hole in general relativity with a conformally coupled scalar field does not work outside the event horizon. Suggestions indicated by our present analysis towards a fully rotating black hole solution are discussed. |
2207.13531 | Angela Borchers | Angela Borchers, Frank Ohme | Inconsistent black hole kick estimates from gravitational-wave models | 31 pages, 17 figures | Class. Quantum Grav. 40 095008 (2023) | 10.1088/1361-6382/acc5da | LIGO-P2200225 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The accuracy of gravitational-wave models of compact binaries has
traditionally been addressed by the mismatch between the model and
numerical-relativity simulations. This is a measure of the overall agreement
between the two waveforms. However, the largest modelling error typically
appears in the strong-field merger regime and may affect subdominant signal
harmonics more strongly. These inaccuracies are often not well characterised by
the mismatch. We explore the use of a complementary, physically motivated tool
to investigate the accuracy of gravitational-wave harmonics in waveform models:
the remnant's recoil, or kick velocity. Asymmetric binary mergers produce
remnants with significant recoil, encoded by subtle imprints in the
gravitational-wave signal. The kick estimate is highly sensitive to the
intrinsic inaccuracies of the modelled gravitational-wave harmonics during the
strongly relativistic merger regime. Here we investigate the accuracy of the
higher harmonics in four state-of-the-art waveform models of binary black
holes. We find that the SEOBNRv4HM_ROM, IMRPhenomHM, IMRPhenomXHM and
NRHybSur3dq8 models are not consistent in their kick predictions. Our results
enable us to identify regions in the parameter space where the models require
further improvement and support the use of the kick estimate to investigate
waveform systematics. We discuss how numerical-relativity kick estimates could
be used to calibrate waveform models further, proposing the first steps towards
kick-based gravitational-wave tuning.
| [
{
"created": "Wed, 27 Jul 2022 14:03:29 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Oct 2022 15:27:09 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Apr 2023 12:25:49 GMT",
"version": "v3"
}
] | 2023-04-25 | [
[
"Borchers",
"Angela",
""
],
[
"Ohme",
"Frank",
""
]
] | The accuracy of gravitational-wave models of compact binaries has traditionally been addressed by the mismatch between the model and numerical-relativity simulations. This is a measure of the overall agreement between the two waveforms. However, the largest modelling error typically appears in the strong-field merger regime and may affect subdominant signal harmonics more strongly. These inaccuracies are often not well characterised by the mismatch. We explore the use of a complementary, physically motivated tool to investigate the accuracy of gravitational-wave harmonics in waveform models: the remnant's recoil, or kick velocity. Asymmetric binary mergers produce remnants with significant recoil, encoded by subtle imprints in the gravitational-wave signal. The kick estimate is highly sensitive to the intrinsic inaccuracies of the modelled gravitational-wave harmonics during the strongly relativistic merger regime. Here we investigate the accuracy of the higher harmonics in four state-of-the-art waveform models of binary black holes. We find that the SEOBNRv4HM_ROM, IMRPhenomHM, IMRPhenomXHM and NRHybSur3dq8 models are not consistent in their kick predictions. Our results enable us to identify regions in the parameter space where the models require further improvement and support the use of the kick estimate to investigate waveform systematics. We discuss how numerical-relativity kick estimates could be used to calibrate waveform models further, proposing the first steps towards kick-based gravitational-wave tuning. |
gr-qc/9808078 | Sheng Li | Sheng Li and Yishi Duan | The Bifurcation of the Topological Structure in the Sunspot's Electric
Topological Current with Locally Gauge-invariant Maxwell-Chern-Simons Term | 13 page, revtex | Astrophys.Space Sci. 268 (1999) 455-468 | 10.1023/A:1002083106965 | null | gr-qc | null | The topological structure of the electric topological current of the locally
gauge invariant Maxwell-Chern-Simons Model and its bifurcation is studied. The
electric topological charge is quantized in term of winding number. The Hopf
indices and Brouwer degree labeled the local topological structure of the
electric topological current. Using $\Phi $-mapping method and implicity
theory, the electric topological current is found generating or annihilating at
the limit points and splitting or merging at the bifurcate points. The total
electric charge holds invariant during the evolution.
| [
{
"created": "Fri, 28 Aug 1998 03:20:00 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Oct 1998 06:15:11 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Li",
"Sheng",
""
],
[
"Duan",
"Yishi",
""
]
] | The topological structure of the electric topological current of the locally gauge invariant Maxwell-Chern-Simons Model and its bifurcation is studied. The electric topological charge is quantized in term of winding number. The Hopf indices and Brouwer degree labeled the local topological structure of the electric topological current. Using $\Phi $-mapping method and implicity theory, the electric topological current is found generating or annihilating at the limit points and splitting or merging at the bifurcate points. The total electric charge holds invariant during the evolution. |
2112.13701 | Branislav Cvetkovi\'c | Branislav Cvetkovi\'c and Dejan Simi\'c | Memory effect of the pp waves with torsion | LaTeX, 12 pages, 6 figures. arXiv admin note: substantial text
overlap with arXiv:1702.04367; v2 minor revisions | Eur. Phys. J. C (2022) 82:127 | 10.1140/epjc/s10052-022-10081-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the motion of test particles in the spacetime of the plane-fronted
(pp) waves with torsion in four-dimensions. We conclude that there is a
velocity memory effect in the direction of advanced time and along radial
direction, while we have rotation of particles in angular direction. The
velocity memory effect in the aforementioned directions is severely affected by
the value of the tordion mass and probably it is not observable. A very
interesting, probably observable effect, stems from the rotation, which is
insensitive to the tordion mass.
| [
{
"created": "Thu, 23 Dec 2021 15:16:33 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Feb 2022 20:44:18 GMT",
"version": "v2"
}
] | 2022-02-23 | [
[
"Cvetković",
"Branislav",
""
],
[
"Simić",
"Dejan",
""
]
] | We analyze the motion of test particles in the spacetime of the plane-fronted (pp) waves with torsion in four-dimensions. We conclude that there is a velocity memory effect in the direction of advanced time and along radial direction, while we have rotation of particles in angular direction. The velocity memory effect in the aforementioned directions is severely affected by the value of the tordion mass and probably it is not observable. A very interesting, probably observable effect, stems from the rotation, which is insensitive to the tordion mass. |
1106.1103 | Andreas Thurn | Norbert Bodendorfer, Thomas Thiemann, Andreas Thurn | Towards Loop Quantum Supergravity (LQSG) | 9 pages. v2: minor improvements in presentation, virtually identical
to published version | Phys. Lett. B 711: 205-211 (2012) | 10.1016/j.physletb.2012.04.003 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Should nature be supersymmetric, then it will be described by Quantum
Supergravity at least in some energy regimes. The currently most advanced
description of Quantum Supergravity and beyond is Superstring Theory/M-Theory
in 10/11 dimensions. String Theory is a top-to-bottom approach to Quantum
Supergravity in that it postulates a new object, the string, from which
classical Supergravity emerges as a low energy limit. On the other hand, one
may try more traditional bottom-to-top routes and apply the techniques of
Quantum Field Theory. Loop Quantum Gravity (LQG) is a manifestly background
independent and non-perturbative approach to the quantisation of classical
General Relativity, however, so far mostly without supersymmetry. The main
obstacle to the extension of the techniques of LQG to the quantisation of
higher dimensional Supergravity is that LQG rests on a specific connection
formulation of General Relativity which exists only in D+1 = 4 dimensions. In
this Letter we introduce a new connection formulation of General Relativity
which exists in all space-time dimensions. We show that all LQG techniques
developed in D+1 = 4 can be transferred to the new variables in all dimensions
and describe how they can be generalised to the new types of fields that appear
in Supergravity theories as compared to standard matter, specifically
Rarita-Schwinger and p-form gauge fields.
| [
{
"created": "Mon, 6 Jun 2011 15:57:19 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jun 2012 07:45:59 GMT",
"version": "v2"
}
] | 2012-06-13 | [
[
"Bodendorfer",
"Norbert",
""
],
[
"Thiemann",
"Thomas",
""
],
[
"Thurn",
"Andreas",
""
]
] | Should nature be supersymmetric, then it will be described by Quantum Supergravity at least in some energy regimes. The currently most advanced description of Quantum Supergravity and beyond is Superstring Theory/M-Theory in 10/11 dimensions. String Theory is a top-to-bottom approach to Quantum Supergravity in that it postulates a new object, the string, from which classical Supergravity emerges as a low energy limit. On the other hand, one may try more traditional bottom-to-top routes and apply the techniques of Quantum Field Theory. Loop Quantum Gravity (LQG) is a manifestly background independent and non-perturbative approach to the quantisation of classical General Relativity, however, so far mostly without supersymmetry. The main obstacle to the extension of the techniques of LQG to the quantisation of higher dimensional Supergravity is that LQG rests on a specific connection formulation of General Relativity which exists only in D+1 = 4 dimensions. In this Letter we introduce a new connection formulation of General Relativity which exists in all space-time dimensions. We show that all LQG techniques developed in D+1 = 4 can be transferred to the new variables in all dimensions and describe how they can be generalised to the new types of fields that appear in Supergravity theories as compared to standard matter, specifically Rarita-Schwinger and p-form gauge fields. |
gr-qc/0411068 | Miguel Lorente | M. Lorente | Discrete quantum gravity: the Lorentz invariant weight for the
Barrett-Crane model | LaTex, 6 pages. Communication presented to the XXV international
Colloquium on Group Theoretical Methods in Physics, Cocoyoc, Mexico August
2004. To be published by IOP Publishers | null | null | null | gr-qc | null | In a recent paper [1] we have constructed the spin and tensor representations
of SO(4) from which the invariant weight can be derived for the Barrett-Crane
model in quantum gravity. By analogy with the SO(4) group, we present the
complexified Clebsch-Gordan coefficients in order to construct the
Biedenharn-Dolginov function for the SO(3,1) group and the spherical function
as the Lorentz invariant weight of the model.
| [
{
"created": "Sun, 14 Nov 2004 22:41:06 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Lorente",
"M.",
""
]
] | In a recent paper [1] we have constructed the spin and tensor representations of SO(4) from which the invariant weight can be derived for the Barrett-Crane model in quantum gravity. By analogy with the SO(4) group, we present the complexified Clebsch-Gordan coefficients in order to construct the Biedenharn-Dolginov function for the SO(3,1) group and the spherical function as the Lorentz invariant weight of the model. |
1707.06079 | Martin Taylor | Hans Lindblad, Martin Taylor | Global stability of Minkowski space for the Einstein--Vlasov system in
the harmonic gauge | null | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Minkowski space is shown to be globally stable as a solution to the massive
Einstein--Vlasov system. The proof is based on a harmonic gauge in which the
equations reduce to a system of quasilinear wave equations for the metric,
satisfying the weak null condition, coupled to a transport equation for the
Vlasov particle distribution function. Central to the proof is a collection of
vector fields used to control the particle distribution function, a function of
both spacetime and momentum variables. The vector fields are derived using a
general procedure, are adapted to the geometry of the solution and reduce to
the generators of the symmetries of Minkowski space when restricted to acting
on spacetime functions. Moreover, when specialising to the case of vacuum, the
proof provides a simplification of previous stability works.
| [
{
"created": "Wed, 19 Jul 2017 13:29:37 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Nov 2017 17:54:34 GMT",
"version": "v2"
}
] | 2017-11-07 | [
[
"Lindblad",
"Hans",
""
],
[
"Taylor",
"Martin",
""
]
] | Minkowski space is shown to be globally stable as a solution to the massive Einstein--Vlasov system. The proof is based on a harmonic gauge in which the equations reduce to a system of quasilinear wave equations for the metric, satisfying the weak null condition, coupled to a transport equation for the Vlasov particle distribution function. Central to the proof is a collection of vector fields used to control the particle distribution function, a function of both spacetime and momentum variables. The vector fields are derived using a general procedure, are adapted to the geometry of the solution and reduce to the generators of the symmetries of Minkowski space when restricted to acting on spacetime functions. Moreover, when specialising to the case of vacuum, the proof provides a simplification of previous stability works. |
0906.3680 | Zhao Ren | Li Huaifan, Zhang Shengli, Wu Yueqin, Zhang Lichun and Zhao Ren | Hawking radiation of Kerr-Newman-de Sitter black hole | 8 pages | Eur.Phys.J.C63:133-138,2009 | 10.1140/epjc/s10052-009-1085-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the classical Damour-Ruffini method and discuss Hawking radiation
in Kerr-Newman-de Sitter(KNdS) black hole. Under the condition that the total
energy, angular momentum and charge of spacetime are conserved, taking the
reaction of the radiation of the particle to the spacetime and the relation
between the black hole event horizon and the cosmological horizon into
consideration, we derive the black hole radiation spectrum. The radiation
spectrum is no longer a pure thermal one. It is related to the change of the
Bekenstein-Hawking entropy corresponding the black hole event horizon and the
cosmological horizon. It is consistent with an underlying unitary theory.
| [
{
"created": "Fri, 19 Jun 2009 14:21:27 GMT",
"version": "v1"
}
] | 2010-02-22 | [
[
"Huaifan",
"Li",
""
],
[
"Shengli",
"Zhang",
""
],
[
"Yueqin",
"Wu",
""
],
[
"Lichun",
"Zhang",
""
],
[
"Ren",
"Zhao",
""
]
] | We extend the classical Damour-Ruffini method and discuss Hawking radiation in Kerr-Newman-de Sitter(KNdS) black hole. Under the condition that the total energy, angular momentum and charge of spacetime are conserved, taking the reaction of the radiation of the particle to the spacetime and the relation between the black hole event horizon and the cosmological horizon into consideration, we derive the black hole radiation spectrum. The radiation spectrum is no longer a pure thermal one. It is related to the change of the Bekenstein-Hawking entropy corresponding the black hole event horizon and the cosmological horizon. It is consistent with an underlying unitary theory. |
1503.05147 | Alexey Toporensky | A.V. Toporensky and S.B. Popov (Sternberg Astronomical Institute,
Russia) | Cosmological redshift, recession velocities and acceleration measures in
FRW cosmologies | 24 pages with 10 eps figures and 1 table, typos corrected, matches
published version | Astron. and Astrophys. Trans. v. 29, pp. 65 - 88 (2015) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this methodological note we discuss several topics related to
interpretation of some basic cosmological principles. We demonstrate that one
of the key points is the usage of synchronous reference frames. The
Friedmann-Robertson-Walker one is the most known example of them. We describe
how different quantities behave in this frame. Special attention is paid to
potentially observable parameters. We discuss different variants for choosing
measures of velocity and acceleration representing the Hubble flow, and present
illustrative calculations of apparent acceleration in flat $\Lambda CDM$ model
for various epochs. We generalize description of the "tethered" galaxies
problem for different velocity measures and equations of state, and illustrate
time behavior of velocities and redshifts in the $\Lambda CDM$ model.
| [
{
"created": "Tue, 17 Mar 2015 18:14:45 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Nov 2015 11:27:01 GMT",
"version": "v2"
}
] | 2015-11-20 | [
[
"Toporensky",
"A. V.",
"",
"Sternberg Astronomical Institute,\n Russia"
],
[
"Popov",
"S. B.",
"",
"Sternberg Astronomical Institute,\n Russia"
]
] | In this methodological note we discuss several topics related to interpretation of some basic cosmological principles. We demonstrate that one of the key points is the usage of synchronous reference frames. The Friedmann-Robertson-Walker one is the most known example of them. We describe how different quantities behave in this frame. Special attention is paid to potentially observable parameters. We discuss different variants for choosing measures of velocity and acceleration representing the Hubble flow, and present illustrative calculations of apparent acceleration in flat $\Lambda CDM$ model for various epochs. We generalize description of the "tethered" galaxies problem for different velocity measures and equations of state, and illustrate time behavior of velocities and redshifts in the $\Lambda CDM$ model. |
2010.05173 | Shambel Sahlu Akalu | Shambel Sahlu, Heba Sami, Anna-Mia Swart and Thato Tsabone, Maye
Elmardi and Amare Abebe | Perturbations in a Chaplygin gas Cosmology | SAIP2019 Proceedings, SA Institute of Physics 6 pages, 7 figures | SAIP2019 Proceedings, | null | ISBN: 978-0-620-88875-2 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the perturbations of a cosmic multi-fluid medium
consisting of radiation, dust and a Chaplygin gas. To do so, we follow the 1 +
3 covariant formalism and derive the evolution equations of the fluctuations in
the energy density for each species of fluid in the multi-fluid system. The
solutions to these coupled systems of equations are then computed in both
short-wavelength and long-wavelength modes. Our preliminary results suggest
that unlike most dark energy models that discourage large-scale structure
formation due to the rapid cosmological expansion (which gives little time for
fluctuations to coalesce), the Chaplygin-gas model supports the formation of
cosmic structures. This is manifested in the solutions of the perturbation
equations which show the growth of density fluctuations over time.
| [
{
"created": "Sun, 11 Oct 2020 05:55:33 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Oct 2020 19:11:33 GMT",
"version": "v2"
}
] | 2020-10-27 | [
[
"Sahlu",
"Shambel",
""
],
[
"Sami",
"Heba",
""
],
[
"Swart",
"Anna-Mia",
""
],
[
"Tsabone",
"Thato",
""
],
[
"Elmardi",
"Maye",
""
],
[
"Abebe",
"Amare",
""
]
] | In this paper we study the perturbations of a cosmic multi-fluid medium consisting of radiation, dust and a Chaplygin gas. To do so, we follow the 1 + 3 covariant formalism and derive the evolution equations of the fluctuations in the energy density for each species of fluid in the multi-fluid system. The solutions to these coupled systems of equations are then computed in both short-wavelength and long-wavelength modes. Our preliminary results suggest that unlike most dark energy models that discourage large-scale structure formation due to the rapid cosmological expansion (which gives little time for fluctuations to coalesce), the Chaplygin-gas model supports the formation of cosmic structures. This is manifested in the solutions of the perturbation equations which show the growth of density fluctuations over time. |
gr-qc/0202013 | Choquet-Bruhat | Yvonne Choquet-Bruhat and James W. York | Constraints and evolution in cosmology | To appear in the proceedings of the first Aegean summer school in
General Relativity, S. Cotsakis ed. Springer Lecture Notes in Physics | Lect.Notes Phys. 592 (2002) 29-58 | null | null | gr-qc | null | We review some old and new results about strict and non strict hyperbolic
formulations of the Einstein equations.
| [
{
"created": "Tue, 5 Feb 2002 19:41:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Choquet-Bruhat",
"Yvonne",
""
],
[
"York",
"James W.",
""
]
] | We review some old and new results about strict and non strict hyperbolic formulations of the Einstein equations. |
1607.03394 | Maxim Eingorn | Maxim Eingorn, Claus Kiefer, Alexander Zhuk | Scalar and vector perturbations in a universe with discrete and
continuous matter sources | 17 pages, no figures | JCAP 09 (2016) 032 | 10.1088/1475-7516/2016/09/032 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a universe filled with dust-like matter in the form of discrete
inhomogeneities (e.g., galaxies and their groups and clusters) and two sets of
perfect fluids with linear and nonlinear equations of state, respectively. The
background spacetime geometry is defined by the FLRW metric. In the weak
gravitational field limit, we develop the first-order scalar and vector
cosmological perturbation theory. Our approach works at all cosmological scales
(i.e. sub-horizon and super-horizon ones) and incorporates linear and nonlinear
effects with respect to energy density fluctuations. We demonstrate that the
scalar perturbation (i.e. the gravitational potential) as well as the vector
perturbation can be split into individual contributions from each matter
source. Each of these contributions satisfies its own equation. The
velocity-independent parts of the individual gravitational potentials are
characterized by a finite time-dependent Yukawa interaction range being the
same for each individual contribution. We also obtain the exact form of the
gravitational potential and vector perturbation related to the discrete matter
sources. The self-consistency of our approach is thoroughly checked. The
derived equations can form the theoretical basis for numerical simulations for
a wide class of cosmological models.
| [
{
"created": "Tue, 5 Jul 2016 17:38:26 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Sep 2016 21:33:29 GMT",
"version": "v2"
}
] | 2016-09-21 | [
[
"Eingorn",
"Maxim",
""
],
[
"Kiefer",
"Claus",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We study a universe filled with dust-like matter in the form of discrete inhomogeneities (e.g., galaxies and their groups and clusters) and two sets of perfect fluids with linear and nonlinear equations of state, respectively. The background spacetime geometry is defined by the FLRW metric. In the weak gravitational field limit, we develop the first-order scalar and vector cosmological perturbation theory. Our approach works at all cosmological scales (i.e. sub-horizon and super-horizon ones) and incorporates linear and nonlinear effects with respect to energy density fluctuations. We demonstrate that the scalar perturbation (i.e. the gravitational potential) as well as the vector perturbation can be split into individual contributions from each matter source. Each of these contributions satisfies its own equation. The velocity-independent parts of the individual gravitational potentials are characterized by a finite time-dependent Yukawa interaction range being the same for each individual contribution. We also obtain the exact form of the gravitational potential and vector perturbation related to the discrete matter sources. The self-consistency of our approach is thoroughly checked. The derived equations can form the theoretical basis for numerical simulations for a wide class of cosmological models. |
2002.10833 | Javier Relancio | J.J. Relancio, S. Liberati | Phenomenological consequences of a geometry in the cotangent bundle | 19 pages, 3 figures | Phys. Rev. D 101, 064062 (2020) | 10.1103/PhysRevD.101.064062 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A deformed relativistic kinematics can be understood within a geometrical
framework through a maximally symmetric momentum space. However, when
considering this kind of approach, usually one works in a flat spacetime and in
a curved momentum space. In this paper, we will discuss a possible
generalization to take into account both curvatures and some possible
observable effects. We will first explain how to construct a metric in the
cotangent bundle in order to have a curved spacetime with a nontrivial geometry
in momentum space and the relationship with an action in phase space
characterized by a deformed Casimir. Then, we will study within this proposal
two different space-time geometries. In the Friedmann-Robertson-Walker
universe, we will see the modifications in the geodesics (redshift, luminosity
distance and geodesic expansion) due to a momentum dependence of the metric in
the cotangent bundle. Also, we will see that when the spacetime considered is a
Schwarzschild black hole, one still has a common horizon for particles with
different energies, differently from a Lorentz invariance violation case.
However, the surface gravity computed as the peeling off of null geodesics is
energy dependent.
| [
{
"created": "Tue, 25 Feb 2020 12:45:19 GMT",
"version": "v1"
}
] | 2020-04-01 | [
[
"Relancio",
"J. J.",
""
],
[
"Liberati",
"S.",
""
]
] | A deformed relativistic kinematics can be understood within a geometrical framework through a maximally symmetric momentum space. However, when considering this kind of approach, usually one works in a flat spacetime and in a curved momentum space. In this paper, we will discuss a possible generalization to take into account both curvatures and some possible observable effects. We will first explain how to construct a metric in the cotangent bundle in order to have a curved spacetime with a nontrivial geometry in momentum space and the relationship with an action in phase space characterized by a deformed Casimir. Then, we will study within this proposal two different space-time geometries. In the Friedmann-Robertson-Walker universe, we will see the modifications in the geodesics (redshift, luminosity distance and geodesic expansion) due to a momentum dependence of the metric in the cotangent bundle. Also, we will see that when the spacetime considered is a Schwarzschild black hole, one still has a common horizon for particles with different energies, differently from a Lorentz invariance violation case. However, the surface gravity computed as the peeling off of null geodesics is energy dependent. |
gr-qc/0409060 | Vladimir Dzhunushaliev | Vladimir Dzhunushaliev | Pure quantum freezing of the 5$^{th}$ dimension | grammar errors are corrected | Int.J.Mod.Phys. D14 (2005) 1293 | 10.1142/S0218271805007395 | null | gr-qc hep-th | null | It is shown that superthin and superlong gravitational flux tube solutions in
the 5D Kaluza-Klein gravity have the region $(\approx l_{Pl})$ where the metric
signature changes from $\{+,-,-,-,- \}$ to $\{-,-,-,-,+ \}$. Such change is too
quickly from one of the paradigms of quantum gravity which tells that the
Planck length is the minimal length in the nature and consequently the physical
quantities can not change very quickly in the course of this length. For
avoiding such dynamic it is supposed that a pure quantum freezing of the
dynamic of the $5^{th}$ dimension takes place. As the continuation of the flux
tube metric in the longitudinal direction the Reissner-Nordstr\"om metric is
proposed. In the consequence of such construction one can avoid the appearance
of a point-like singularity in the extremal Reissner-Nordstr\"om solution.
| [
{
"created": "Wed, 15 Sep 2004 11:12:20 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Oct 2004 07:21:17 GMT",
"version": "v2"
},
{
"created": "Fri, 13 May 2005 11:59:25 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Dzhunushaliev",
"Vladimir",
""
]
] | It is shown that superthin and superlong gravitational flux tube solutions in the 5D Kaluza-Klein gravity have the region $(\approx l_{Pl})$ where the metric signature changes from $\{+,-,-,-,- \}$ to $\{-,-,-,-,+ \}$. Such change is too quickly from one of the paradigms of quantum gravity which tells that the Planck length is the minimal length in the nature and consequently the physical quantities can not change very quickly in the course of this length. For avoiding such dynamic it is supposed that a pure quantum freezing of the dynamic of the $5^{th}$ dimension takes place. As the continuation of the flux tube metric in the longitudinal direction the Reissner-Nordstr\"om metric is proposed. In the consequence of such construction one can avoid the appearance of a point-like singularity in the extremal Reissner-Nordstr\"om solution. |
1905.09370 | Bob Holdom | Randy S. Conklin and Bob Holdom | Gravitational Wave "Echo" Spectra | 17 pages, 6 figures | Phys. Rev. D 100, 124030 (2019) | 10.1103/PhysRevD.100.124030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Exotic compact objects may resemble black holes very closely while remaining
horizonless. They may be distinguished from black holes because they
effectively give rise to a resonant cavity for the propagation of low frequency
gravity waves. In a Green's function approach, the resonance structure appears
in a transfer function. The transfer function in turn is modulated by an
initial-condition-dependent source integral to obtain the observed spectrum. We
find that the source integral displays universal factors that tend to enhance
low and negative frequencies, and this increases the complexity of the
waveforms in the time domain. These waveforms also display a significant
sensitivity to initial conditions. For these reasons a standard matched-filter
search strategy is difficult. In contrast, the sharp and evenly spaced
resonance spectrum presents a much more robust signal to target. It persists
even in the absence of simple echoes. We also describe an additional
two-component structure of this resonance pattern.
| [
{
"created": "Wed, 22 May 2019 21:19:03 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Sep 2019 16:32:36 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Dec 2019 20:04:18 GMT",
"version": "v3"
}
] | 2019-12-18 | [
[
"Conklin",
"Randy S.",
""
],
[
"Holdom",
"Bob",
""
]
] | Exotic compact objects may resemble black holes very closely while remaining horizonless. They may be distinguished from black holes because they effectively give rise to a resonant cavity for the propagation of low frequency gravity waves. In a Green's function approach, the resonance structure appears in a transfer function. The transfer function in turn is modulated by an initial-condition-dependent source integral to obtain the observed spectrum. We find that the source integral displays universal factors that tend to enhance low and negative frequencies, and this increases the complexity of the waveforms in the time domain. These waveforms also display a significant sensitivity to initial conditions. For these reasons a standard matched-filter search strategy is difficult. In contrast, the sharp and evenly spaced resonance spectrum presents a much more robust signal to target. It persists even in the absence of simple echoes. We also describe an additional two-component structure of this resonance pattern. |
2012.12914 | Abhishek Chowdhuri | Abhishek Chowdhuri, Arpan Bhattacharyya | Shadow analysis for rotating black holes in the presence of plasma for
an expanding universe | 27 pages, 6 figures, 2 tables, shadow plots and discussion regarding
distortion parameter updated, references added, version to appear in Physical
Review D | Phys. Rev. D 104, 064039 (2021) | 10.1103/PhysRevD.104.064039 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the structure of shadow for a Kerr-de Sitter black hole with a
non-magnetized, pressureless plasma surrounding it. Specific plasma
distributions are considered to separate the Hamilton-Jacobi equation and find
the photon regions. An analytic formula describing the boundary curve of the
shadow for such a black hole in an expanding universe for an observer at any
finite point outside the horizon is derived. We observe deviations which are
further explored by calculating the curvature radius at a particular point for
such structures in the presence and absence of plasma and calculate the
diameter of the shadow.
| [
{
"created": "Wed, 23 Dec 2020 19:03:16 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Jul 2021 17:43:10 GMT",
"version": "v2"
},
{
"created": "Sun, 29 Aug 2021 16:32:07 GMT",
"version": "v3"
}
] | 2021-09-16 | [
[
"Chowdhuri",
"Abhishek",
""
],
[
"Bhattacharyya",
"Arpan",
""
]
] | We explore the structure of shadow for a Kerr-de Sitter black hole with a non-magnetized, pressureless plasma surrounding it. Specific plasma distributions are considered to separate the Hamilton-Jacobi equation and find the photon regions. An analytic formula describing the boundary curve of the shadow for such a black hole in an expanding universe for an observer at any finite point outside the horizon is derived. We observe deviations which are further explored by calculating the curvature radius at a particular point for such structures in the presence and absence of plasma and calculate the diameter of the shadow. |
gr-qc/9712039 | Dan Selaru | D. Selaru, I. Dobrescu | On the PPN 1+2 Body Problem | 6 pages | null | null | null | gr-qc | null | A particulare case of the three-body problem, in the PPN formalism, is
presented. The Hamiltonian function is obtained and the problem is reduced to a
perturbed two-body one.
| [
{
"created": "Mon, 8 Dec 1997 15:23:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Selaru",
"D.",
""
],
[
"Dobrescu",
"I.",
""
]
] | A particulare case of the three-body problem, in the PPN formalism, is presented. The Hamiltonian function is obtained and the problem is reduced to a perturbed two-body one. |
2311.11148 | Celso de Camargo Barros Jr. | L. G. Barbosa and C. C. Barros Jr | Klein-Gordon oscillator subject to a Coulomb-type potential in
Bonnor-Melvin universe with a cosmological constant | 9 pages, 2 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work we study spin-0 particles described by the Klein-Gordon
oscillator formalism in a spacetime which structure is determined by a
homogeneous magnetic field and a cosmological constant. For this purpose we
take into account a framework based on the Bonnor-Melvin solution with the
inclusion of the cosmological constant. We write the Klein-Gordon equation and
the effect of a scalar potential is also considered.
| [
{
"created": "Sat, 18 Nov 2023 19:11:32 GMT",
"version": "v1"
}
] | 2023-11-21 | [
[
"Barbosa",
"L. G.",
""
],
[
"Barros",
"C. C.",
"Jr"
]
] | In this work we study spin-0 particles described by the Klein-Gordon oscillator formalism in a spacetime which structure is determined by a homogeneous magnetic field and a cosmological constant. For this purpose we take into account a framework based on the Bonnor-Melvin solution with the inclusion of the cosmological constant. We write the Klein-Gordon equation and the effect of a scalar potential is also considered. |
2309.04871 | Milko Estrada | R. Aros, Milko Estrada | A study about black hole solutions with nonconstant transversal
curvature and its conserved charges in Lovelock gravity | accepted in Phys.Rev.D | Phys. Rev. D 109 (2024), 104044 | 10.1103/PhysRevD.109.104044 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, the analysis of some new static black hole solutions of
Lovelock gravity with nonconstant curvature transverse section is presented. It
will be shown that the finiteness of the charges and the action principle rely
on the existence of constraints on the geometry of the transverse sections.
Finally, in this context, some new sound solutions with nonconstant curvature
transverse sections that deviate from the previously known geometries are
discussed.
| [
{
"created": "Sat, 9 Sep 2023 20:15:32 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Oct 2023 11:40:01 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Apr 2024 19:30:23 GMT",
"version": "v3"
}
] | 2024-05-15 | [
[
"Aros",
"R.",
""
],
[
"Estrada",
"Milko",
""
]
] | In this work, the analysis of some new static black hole solutions of Lovelock gravity with nonconstant curvature transverse section is presented. It will be shown that the finiteness of the charges and the action principle rely on the existence of constraints on the geometry of the transverse sections. Finally, in this context, some new sound solutions with nonconstant curvature transverse sections that deviate from the previously known geometries are discussed. |
1712.02297 | Yen Chin Ong | Yen Chin Ong, S. Sedigheh Hashemi, Rui An, Bin Wang | Stephani Cosmology: Entropically Viable But Observationally Challenged | Discussion on observational constraints elaborated. Version accepted
by EPJC | Eur. Phys. J. C 78 (2018) 405 | 10.1140/epjc/s10052-018-5866-1 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inhomogeneous cosmological models such as the Stephani universes could, in
principle, provide an explanation for the observed accelerated expansion of the
Universe. Working with a concrete, popular model of the Stephani cosmology --
the Stephani-Dabrowski model, we found that it is entropically viable. We also
comment on the energy conditions and the two-sheeted geometry of the spacetime.
However, similar to the LTB models, despite satisfying the holographic
principle, Stephani cosmology has difficulty satisfying all the constraints
from observations.
| [
{
"created": "Wed, 6 Dec 2017 17:23:49 GMT",
"version": "v1"
},
{
"created": "Thu, 31 May 2018 12:40:56 GMT",
"version": "v2"
}
] | 2018-06-01 | [
[
"Ong",
"Yen Chin",
""
],
[
"Hashemi",
"S. Sedigheh",
""
],
[
"An",
"Rui",
""
],
[
"Wang",
"Bin",
""
]
] | Inhomogeneous cosmological models such as the Stephani universes could, in principle, provide an explanation for the observed accelerated expansion of the Universe. Working with a concrete, popular model of the Stephani cosmology -- the Stephani-Dabrowski model, we found that it is entropically viable. We also comment on the energy conditions and the two-sheeted geometry of the spacetime. However, similar to the LTB models, despite satisfying the holographic principle, Stephani cosmology has difficulty satisfying all the constraints from observations. |
1905.09832 | Marcus H\"og{\aa}s | Marcus H\"og{\aa}s, Mikica Kocic, Francesco Torsello, Edvard
M\"ortsell | Generalized Vaidya solutions in bimetric gravity | 15 pages, 2 figures. Updates in v2: changed title of the paper, added
appendix on the Fierz-Pauli mass, removed all occurences of "bare
cosmological constant" in the text and changed the comparison between
bimetric gravity and GR accordingly, updated references, corrected typo in
eq. (2.6b) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, the endpoint of spherically symmetric gravitational
collapse is a Schwarzschild--[(A)dS] black hole. In bimetric gravity, it has
been speculated that a static end state must also be Schwarzschild--[(A)dS]. To
this end, we present a set of exact solutions, including collapsing massless
dust particles. For these, the speculation is confirmed.
| [
{
"created": "Thu, 23 May 2019 18:00:01 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jun 2020 09:56:05 GMT",
"version": "v2"
}
] | 2020-06-09 | [
[
"Högås",
"Marcus",
""
],
[
"Kocic",
"Mikica",
""
],
[
"Torsello",
"Francesco",
""
],
[
"Mörtsell",
"Edvard",
""
]
] | In general relativity, the endpoint of spherically symmetric gravitational collapse is a Schwarzschild--[(A)dS] black hole. In bimetric gravity, it has been speculated that a static end state must also be Schwarzschild--[(A)dS]. To this end, we present a set of exact solutions, including collapsing massless dust particles. For these, the speculation is confirmed. |
1308.4832 | Nelson Merino | Laura Andrianopoli, Nelson Merino, Felip Nadal, Mario Trigiante | General properties of the expansion methods of Lie algebras | 2 figures | J. Phys. A: Math. Theor. 46 (2013) 365204 (33pp) | 10.1088/1751-8113/46/36/365204 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The study of the relation between Lie algebras and groups, and especially the
derivation of new algebras from them, is a problem of great interest in
mathematics and physics, because finding a new Lie group from an already known
one also means that a new physical theory can be obtained from a known one. One
of the procedures that allow to do so is called expansion of Lie algebras, and
has been recently used in different physical applications - particularly in
gauge theories of gravity. Here we report on further developments of this
method, required to understand in a deeper way their consequences in physical
theories. We have found theorems related to the preservation of some properties
of the algebras under expansions that can be used as criteria and, more
specifically, as necessary conditions to know if two arbitrary Lie algebras can
be related by the some expansion mechanism. Formal aspects, such as the Cartan
decomposition of the expanded algebras, are also discussed. Finally, an
instructive example that allows to check explicitly all our theoretical results
is also provided.
| [
{
"created": "Thu, 22 Aug 2013 11:43:00 GMT",
"version": "v1"
}
] | 2013-08-23 | [
[
"Andrianopoli",
"Laura",
""
],
[
"Merino",
"Nelson",
""
],
[
"Nadal",
"Felip",
""
],
[
"Trigiante",
"Mario",
""
]
] | The study of the relation between Lie algebras and groups, and especially the derivation of new algebras from them, is a problem of great interest in mathematics and physics, because finding a new Lie group from an already known one also means that a new physical theory can be obtained from a known one. One of the procedures that allow to do so is called expansion of Lie algebras, and has been recently used in different physical applications - particularly in gauge theories of gravity. Here we report on further developments of this method, required to understand in a deeper way their consequences in physical theories. We have found theorems related to the preservation of some properties of the algebras under expansions that can be used as criteria and, more specifically, as necessary conditions to know if two arbitrary Lie algebras can be related by the some expansion mechanism. Formal aspects, such as the Cartan decomposition of the expanded algebras, are also discussed. Finally, an instructive example that allows to check explicitly all our theoretical results is also provided. |
2407.06553 | Dan-Dan Lian | Wei-Si Qiu and Dan-Dan Lian and Peng-Ming Zhang | Gravitational orbital Hall effect of vortex light in Lense-Thirring
metric | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Vortex light, characterized by an intrinsic orbital angular momentum (OAM)
aligned with its propagation direction, is described through vortex
electromagnetic waves. Similar to the gravitational spin Hall effect (SHE),
vortex light is expected to exhibit intrinsic OAM-dependent trajectories and
deviations from the null geodesic plane when propagating through a
gravitational field, a phenomenon termed the gravitational orbital Hall effect
(OHE). In this work, we model the vortex light as vortex Laguerre-Gaussian
electromagnetic wave packets and analyze its motion by solving covariant
Maxwell equations within the Lense-Thirring metric. Our findings reveal that
the trajectory of vortex light with an intrinsic OAM deviates from the null
geodesic in two ways. It deviates both perpendicular to, and within, the null
geodesic plane. This behavior contrasts with the gravitational SHE, where
spin-polarized light primarily deviates perpendicular to the null geodesic
plane. Moreover, the relationship between the deviation and intrinsic OAM
differs significantly from that between the deviation and spin. These results
suggest a unique interaction between intrinsic OAM and gravity, distinct from
the spin-gravity coupling, indicating that the gravitational OHE of light might
not be precisely predicted by merely substituting spin with intrinsic OAM in
the gravitational SHE of light.
| [
{
"created": "Tue, 9 Jul 2024 05:18:30 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Aug 2024 08:24:26 GMT",
"version": "v2"
}
] | 2024-08-12 | [
[
"Qiu",
"Wei-Si",
""
],
[
"Lian",
"Dan-Dan",
""
],
[
"Zhang",
"Peng-Ming",
""
]
] | Vortex light, characterized by an intrinsic orbital angular momentum (OAM) aligned with its propagation direction, is described through vortex electromagnetic waves. Similar to the gravitational spin Hall effect (SHE), vortex light is expected to exhibit intrinsic OAM-dependent trajectories and deviations from the null geodesic plane when propagating through a gravitational field, a phenomenon termed the gravitational orbital Hall effect (OHE). In this work, we model the vortex light as vortex Laguerre-Gaussian electromagnetic wave packets and analyze its motion by solving covariant Maxwell equations within the Lense-Thirring metric. Our findings reveal that the trajectory of vortex light with an intrinsic OAM deviates from the null geodesic in two ways. It deviates both perpendicular to, and within, the null geodesic plane. This behavior contrasts with the gravitational SHE, where spin-polarized light primarily deviates perpendicular to the null geodesic plane. Moreover, the relationship between the deviation and intrinsic OAM differs significantly from that between the deviation and spin. These results suggest a unique interaction between intrinsic OAM and gravity, distinct from the spin-gravity coupling, indicating that the gravitational OHE of light might not be precisely predicted by merely substituting spin with intrinsic OAM in the gravitational SHE of light. |
0808.0239 | Albert V. Minkevich | A. V. Minkevich | To theory of gravitational interaction | 10 pages | Acta Phys. Polon. B40:229-239,2009 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some principal problems of general relativity theory and attempts of their
solution are discussed. The Poincare gauge theory of gravity as natural
generalization of Einsteinian gravitation theory is considered. The changes of
gravitational interaction in the frame of this theory leading to the solution
of principal problems of general relativity theory are analyzed.
| [
{
"created": "Sat, 2 Aug 2008 08:03:11 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Aug 2008 17:50:10 GMT",
"version": "v2"
}
] | 2014-11-18 | [
[
"Minkevich",
"A. V.",
""
]
] | Some principal problems of general relativity theory and attempts of their solution are discussed. The Poincare gauge theory of gravity as natural generalization of Einsteinian gravitation theory is considered. The changes of gravitational interaction in the frame of this theory leading to the solution of principal problems of general relativity theory are analyzed. |
gr-qc/0210037 | Thomas Buchert | Thomas Buchert and Mauro Carfora | Regional averaging and scaling in relativistic cosmology | LateX, IOPstyle, 48 pages, 11 figures; matches published version in
C.Q.G | Class.Quant.Grav.19:6109-6145,2002 | 10.1088/0264-9381/19/23/314 | null | gr-qc astro-ph hep-ph hep-th | null | Averaged inhomogeneous cosmologies lie at the forefront of interest, since
cosmological parameters like the rate of expansion or the mass density are to
be considered as volume-averaged quantities and only these can be compared with
observations. For this reason the relevant parameters are intrinsically
scale-dependent and one wishes to control this dependence without restricting
the cosmological model by unphysical assumptions. In the latter respect we
contrast our way to approach the averaging problem in relativistic cosmology
with shortcomings of averaged Newtonian models. Explicitly, we investigate the
scale-dependence of Eulerian volume averages of scalar functions on Riemannian
three-manifolds. We propose a complementary view of a Lagrangian smoothing of
(tensorial) variables as opposed to their Eulerian averaging on spatial
domains. This program is realized with the help of a global Ricci deformation
flow for the metric. We explain rigorously the origin of the Ricci flow which,
on heuristic grounds, has already been suggested as a possible candidate for
smoothing the initial data set for cosmological spacetimes. The smoothing of
geometry implies a renormalization of averaged spatial variables. We discuss
the results in terms of effective cosmological parameters that would be
assigned to the smoothed cosmological spacetime.
| [
{
"created": "Fri, 11 Oct 2002 18:55:30 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Nov 2002 16:23:40 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Buchert",
"Thomas",
""
],
[
"Carfora",
"Mauro",
""
]
] | Averaged inhomogeneous cosmologies lie at the forefront of interest, since cosmological parameters like the rate of expansion or the mass density are to be considered as volume-averaged quantities and only these can be compared with observations. For this reason the relevant parameters are intrinsically scale-dependent and one wishes to control this dependence without restricting the cosmological model by unphysical assumptions. In the latter respect we contrast our way to approach the averaging problem in relativistic cosmology with shortcomings of averaged Newtonian models. Explicitly, we investigate the scale-dependence of Eulerian volume averages of scalar functions on Riemannian three-manifolds. We propose a complementary view of a Lagrangian smoothing of (tensorial) variables as opposed to their Eulerian averaging on spatial domains. This program is realized with the help of a global Ricci deformation flow for the metric. We explain rigorously the origin of the Ricci flow which, on heuristic grounds, has already been suggested as a possible candidate for smoothing the initial data set for cosmological spacetimes. The smoothing of geometry implies a renormalization of averaged spatial variables. We discuss the results in terms of effective cosmological parameters that would be assigned to the smoothed cosmological spacetime. |
1208.3165 | Lee Hodgkinson | Lee Hodgkinson and Jorma Louko | Unruh-DeWitt detector on the BTZ black hole | 8 pages 4 figures. Talk given talk given by L.H. at "Relativity and
Gravitation:100 Years after Einstein in Prague", Prague, 25 June -- 29 June
2012 | null | null | NSF-KITP-12-149 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine an Unruh-DeWitt particle detector coupled to a scalar field in
three-dimensional curved spacetime, within first-order perturbation theory. We
first obtain a causal and manifestly regular expression for the instantaneous
transition rate in an arbitrary Hadamard state. We then specialise to the
Ba\~nados-Teitelboim-Zanelli black hole and to a massless conformally coupled
field in the Hartle-Hawking vacuum. A co-rotating detector responds thermally
in the expected local Hawking temperature, while a freely-falling detector
shows no evidence of thermality in regimes that we are able to probe, not even
far from the horizon. The boundary condition at the asymptotically anti-de
Sitter infinity has a significant effect on the transition rate.
| [
{
"created": "Wed, 15 Aug 2012 17:37:13 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"Hodgkinson",
"Lee",
""
],
[
"Louko",
"Jorma",
""
]
] | We examine an Unruh-DeWitt particle detector coupled to a scalar field in three-dimensional curved spacetime, within first-order perturbation theory. We first obtain a causal and manifestly regular expression for the instantaneous transition rate in an arbitrary Hadamard state. We then specialise to the Ba\~nados-Teitelboim-Zanelli black hole and to a massless conformally coupled field in the Hartle-Hawking vacuum. A co-rotating detector responds thermally in the expected local Hawking temperature, while a freely-falling detector shows no evidence of thermality in regimes that we are able to probe, not even far from the horizon. The boundary condition at the asymptotically anti-de Sitter infinity has a significant effect on the transition rate. |
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