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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0310033 | Pantelis Apostolopoulos | Pantelis S. Apostolopoulos | On tilted perfect fluid Bianchi type VI$_0$ self-similar models | Latex, 7 pages, no figures; (v2) some clarification comments are
added in the discussion and one reference; (v3) minor corrections in
equations (1), (3) and (19) | Gen.Rel.Grav. 36 (2004) 1939-1945 | 10.1023/B:GERG.0000036051.44778.d8 | null | gr-qc | null | We show that the tilted perfect fluid Bianchi VI$_0$ family of self-similar
models found by Rosquist and Jantzen [K. Rosquist and R. T. Jantzen, \emph{%
Exact power law solutions of the Einstein equations}, 1985 Phys. Lett.
\textbf{107}A 29-32] is the most general class of tilted self-similar models
but the state parameter $\gamma $ lies in the interval $(\frac 65,\frac 32) $.
The model has a four dimensional stable manifold indicating the possibility
that it may be future attractor, at least for the subclass of tilted Bianchi
VI$_0$ models satisfying $n_\alpha ^\alpha =0$ in which it belongs. In addition
the angle of tilt is asymptotically significant at late times suggesting that
for the above subclasses of models the tilt is asymptotically extreme.
| [
{
"created": "Mon, 6 Oct 2003 19:50:04 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Feb 2004 10:09:32 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Aug 2004 08:12:16 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Apostolopoulos",
"Pantelis S.",
""
]
] | We show that the tilted perfect fluid Bianchi VI$_0$ family of self-similar models found by Rosquist and Jantzen [K. Rosquist and R. T. Jantzen, \emph{% Exact power law solutions of the Einstein equations}, 1985 Phys. Lett. \textbf{107}A 29-32] is the most general class of tilted self-similar models but the state parameter $\gamma $ lies in the interval $(\frac 65,\frac 32) $. The model has a four dimensional stable manifold indicating the possibility that it may be future attractor, at least for the subclass of tilted Bianchi VI$_0$ models satisfying $n_\alpha ^\alpha =0$ in which it belongs. In addition the angle of tilt is asymptotically significant at late times suggesting that for the above subclasses of models the tilt is asymptotically extreme. |
gr-qc/0107005 | Dr. Bikash Chandra Paul | Bikash Chandra Paul (North Bengal University) | Inflationary Cosmologies in an Anisotropic Brane World | 15 pages, no figures, LaTeX | Phys.Rev. D64 (2001) 124001 | 10.1103/PhysRevD.64.124001 | null | gr-qc | null | A new cosmological solution of the gravitational field equations in the
generalized Randall-Sundrum model for an anisotropic brane with Bianchi I
geometry and with perfect fluid as matter sources is presented. The matter is
described by a scalar field. The solution admits inflationary era and at a
later epoch the anisotropy of the universe washes out. We obtain two classes of
cosmological scenario, in the first case universe evolves from singularity and
in the second case universe expands without singularity.
| [
{
"created": "Mon, 2 Jul 2001 08:47:24 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Paul",
"Bikash Chandra",
"",
"North Bengal University"
]
] | A new cosmological solution of the gravitational field equations in the generalized Randall-Sundrum model for an anisotropic brane with Bianchi I geometry and with perfect fluid as matter sources is presented. The matter is described by a scalar field. The solution admits inflationary era and at a later epoch the anisotropy of the universe washes out. We obtain two classes of cosmological scenario, in the first case universe evolves from singularity and in the second case universe expands without singularity. |
2206.04943 | Klaas Landsman | Klaas Landsman | Reopening the Hole Argument | 25 pages, considerable revision | null | null | null | gr-qc math-ph math.MP physics.hist-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | This expository paper relates the Hole Argument in general relativity (GR) to
the well-known theorem of Choquet-Bruhat and Geroch (1969) on the existence and
uniqueness of globally hyperbolic solutions to the Einstein field equations.
Like the Earman-Norton (1987) version of the Hole Argument (which is originally
due to Einstein), this theorem exposes the tension beween determinism and some
version of spacetime substantivalism. But it seems less vulnerable to the
campaign by Weatherall (2018) and followers to close the Hole Argument on the
basis of ``mathematical practice'', since the theorem only talks about
isometries and hence does not make the pointwise identifications via
diffeomorphisms that Weatherall objects to. Among other implications of the
theorem for the philosophy of GR, we reconsider Butterfield's (1987)
influential definition of determinism. This should be amended if its goal is to
express the idea that \GR\ is deterministic in the absence of Cauchy horizons,
although its original form does capture the way GR is indeterministic in their
presence! Furthermore, in GR isometries come out as gauge symmetries, as do
Poincar'e transformations in special relativity. Finally, I discuss some
implications of the theorem for the philosophy of science: accepting the
determinism horn still requires a choice between Frege-style abstractionism and
Hilbert-style structuralism; and, within the latter, between structural realism
and empiricist structuralism (which I favour).
| [
{
"created": "Fri, 10 Jun 2022 08:34:05 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Sep 2023 07:36:16 GMT",
"version": "v2"
}
] | 2023-09-06 | [
[
"Landsman",
"Klaas",
""
]
] | This expository paper relates the Hole Argument in general relativity (GR) to the well-known theorem of Choquet-Bruhat and Geroch (1969) on the existence and uniqueness of globally hyperbolic solutions to the Einstein field equations. Like the Earman-Norton (1987) version of the Hole Argument (which is originally due to Einstein), this theorem exposes the tension beween determinism and some version of spacetime substantivalism. But it seems less vulnerable to the campaign by Weatherall (2018) and followers to close the Hole Argument on the basis of ``mathematical practice'', since the theorem only talks about isometries and hence does not make the pointwise identifications via diffeomorphisms that Weatherall objects to. Among other implications of the theorem for the philosophy of GR, we reconsider Butterfield's (1987) influential definition of determinism. This should be amended if its goal is to express the idea that \GR\ is deterministic in the absence of Cauchy horizons, although its original form does capture the way GR is indeterministic in their presence! Furthermore, in GR isometries come out as gauge symmetries, as do Poincar'e transformations in special relativity. Finally, I discuss some implications of the theorem for the philosophy of science: accepting the determinism horn still requires a choice between Frege-style abstractionism and Hilbert-style structuralism; and, within the latter, between structural realism and empiricist structuralism (which I favour). |
2107.02788 | Mar\'ia Jos\'e Bustamante-Rosell | Mar\'ia Jos\'e Bustamante-Rosell, Joel Meyers, Noah Pearson, Cynthia
Trendafilova, Aaron Zimmerman | Gravitational Wave Timing Array | 18 pages, 6 figures, comments welcome. Matches version accepted for
publication in PhysRevD | Physical Review D, vol. 105, no. 4, 2022 | 10.1103/PhysRevD.105.044005 | null | gr-qc astro-ph.CO astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the design of a gravitational wave timing array, a novel scheme
that can be used to search for low-frequency gravitational waves by monitoring
continuous gravitational waves at higher frequencies. We show that observations
of gravitational waves produced by Galactic binaries using a space-based
detector like LISA provide sensitivity in the nanohertz to microhertz band.
While the expected sensitivity of this proposal is not competitive with other
methods, it fills a gap in frequency space around the microhertz regime, which
is above the range probed by current pulsar timing arrays and below the
expected direct frequency coverage of LISA. The low-frequency extension of
sensitivity does not require any experimental design change to space-based
gravitational wave detectors, and can be achieved with the data products that
would already be collected by them.
| [
{
"created": "Tue, 6 Jul 2021 17:57:07 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jul 2022 19:17:54 GMT",
"version": "v2"
}
] | 2022-07-25 | [
[
"Bustamante-Rosell",
"María José",
""
],
[
"Meyers",
"Joel",
""
],
[
"Pearson",
"Noah",
""
],
[
"Trendafilova",
"Cynthia",
""
],
[
"Zimmerman",
"Aaron",
""
]
] | We describe the design of a gravitational wave timing array, a novel scheme that can be used to search for low-frequency gravitational waves by monitoring continuous gravitational waves at higher frequencies. We show that observations of gravitational waves produced by Galactic binaries using a space-based detector like LISA provide sensitivity in the nanohertz to microhertz band. While the expected sensitivity of this proposal is not competitive with other methods, it fills a gap in frequency space around the microhertz regime, which is above the range probed by current pulsar timing arrays and below the expected direct frequency coverage of LISA. The low-frequency extension of sensitivity does not require any experimental design change to space-based gravitational wave detectors, and can be achieved with the data products that would already be collected by them. |
1612.02504 | Soichiro Isoyama | Ryuichi Fujita, Soichiro Isoyama, Alexandre Le Tiec, Hiroyuki Nakano,
Norichika Sago, Takahiro Tanaka | Hamiltonian Formulation of the Conservative Self-Force Dynamics in the
Kerr Geometry | 55 pages, 0 figures, matches the published version | Class. Quantum Grav. 34 134001 (2017) | 10.1088/1361-6382/aa7342 | KUNS-2648,YITP-16-122 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We formulate a Hamiltonian description of the orbital motion of a point
particle in Kerr spacetime for generic (eccentric, inclined) orbits, which
accounts for the effects of the conservative part of the gravitational
self-force. This formulation relies on a description of the particle's motion
as geodesic in a certain smooth effective spacetime, in terms of (generalized)
action-angle variables. Clarifying the role played by the gauge freedom in the
Hamiltonian dynamics, we extract the gauge-invariant information contained in
the conservative self-force. We also propose a possible gauge choice for which
the orbital dynamics can be described by an effective Hamiltonian, written
solely in terms of the action variables. As an application of our Hamiltonian
formulation in this gauge, we derive the conservative self-force correction to
the orbital frequencies of Kerr innermost stable spherical (inclined or
circular) orbits. This gauge choice also allows us to establish a "first law of
mechanics" for black-hole-particle binary systems, at leading order beyond the
test-mass approximation.
| [
{
"created": "Thu, 8 Dec 2016 01:11:13 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2017 20:52:50 GMT",
"version": "v2"
}
] | 2017-06-12 | [
[
"Fujita",
"Ryuichi",
""
],
[
"Isoyama",
"Soichiro",
""
],
[
"Tiec",
"Alexandre Le",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Sago",
"Norichika",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We formulate a Hamiltonian description of the orbital motion of a point particle in Kerr spacetime for generic (eccentric, inclined) orbits, which accounts for the effects of the conservative part of the gravitational self-force. This formulation relies on a description of the particle's motion as geodesic in a certain smooth effective spacetime, in terms of (generalized) action-angle variables. Clarifying the role played by the gauge freedom in the Hamiltonian dynamics, we extract the gauge-invariant information contained in the conservative self-force. We also propose a possible gauge choice for which the orbital dynamics can be described by an effective Hamiltonian, written solely in terms of the action variables. As an application of our Hamiltonian formulation in this gauge, we derive the conservative self-force correction to the orbital frequencies of Kerr innermost stable spherical (inclined or circular) orbits. This gauge choice also allows us to establish a "first law of mechanics" for black-hole-particle binary systems, at leading order beyond the test-mass approximation. |
gr-qc/0410145 | Angelo Tartaglia | Angelo Tartaglia | Space Time Defects as a Source of Curvature and Torsion | Presentation at the Sixth Friedman seminar in Cargese 28/6-3/7/2004.
Submitted for the proceedings of the seminar to appear in the International
Journal of Modern Physics A | Int.J.Mod.Phys. A20 (2005) 2336-2340 | 10.1142/S0217751X05024596 | null | gr-qc | null | Space time is described as a continuum four-dimensional medium similar to
ordinary elastic continua. Exploiting the analogy internal stress states are
considered. The internal ''stress'' is originated by the presence of defects.
The defects are described according to the typical Volterra process. The case
of a point defect in an otherwise isotropic four-dimensional medium is
discussed showing that the resulting metric tensor corresponds to an expanding
(or contracting) universe filled up with a non-zero energy-momentum density.
| [
{
"created": "Thu, 28 Oct 2004 20:59:28 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Tartaglia",
"Angelo",
""
]
] | Space time is described as a continuum four-dimensional medium similar to ordinary elastic continua. Exploiting the analogy internal stress states are considered. The internal ''stress'' is originated by the presence of defects. The defects are described according to the typical Volterra process. The case of a point defect in an otherwise isotropic four-dimensional medium is discussed showing that the resulting metric tensor corresponds to an expanding (or contracting) universe filled up with a non-zero energy-momentum density. |
gr-qc/0406038 | B. S. Sathyaprakash | Edward K. Porter (Cardiff and Paris) and B. S. Sathyaprakash (Cardiff) | Improved gravitational waveforms from spinning black hole binaries | 23 pages, 2 Tables and 18 Figures | Phys.Rev. D71 (2005) 024017 | 10.1103/PhysRevD.71.024017 | null | gr-qc | null | The standard post-Newtonian approximation to gravitational waveforms, called
T-approximants, from non-spinning black hole binaries are known not to be
sufficiently accurate close to the last stable orbit of the system. A new
approximation, called P-approximants, is believed to improve the accuracy of
the waveforms rendering them applicable up to the last stable orbit. In this
study we apply P-approximants to the case of a test-particle in equatorial
orbit around a Kerr black hole parameterized by a spin parameter q that takes
values between -1 and 1. In order to assess the performance of the two
approximants we measure their effectualness (i.e. larger overlaps with the
exact signal), and faithfulness (i.e. smaller biases while measuring the
parameters of the signal) with the exact (numerical) waveforms. We find that in
the case of prograde orbits, that is orbits whose angular momentum is in the
same sense as the spin angular momentum of the black hole, T-approximant
templates obtain an effectualness of ~ 0.99 for spins q < 0.75. For 0.75 < q <
0.95, the effectualness drops to about 0.82. The P-approximants achieve
effectualness of > 0.99 for all spins up to q = 0.95. The bias in the
estimation of parameters is much lower in the case of P-approximants than
T-approximants. We find that P-approximants are both effectual and faithful and
should be more effective than T-approximants as a detection template family
when q>0. For q<0 both T- and P-approximants perform equally well so that
either of them could be used as a detection template family.
| [
{
"created": "Thu, 10 Jun 2004 02:39:35 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Porter",
"Edward K.",
"",
"Cardiff and Paris"
],
[
"Sathyaprakash",
"B. S.",
"",
"Cardiff"
]
] | The standard post-Newtonian approximation to gravitational waveforms, called T-approximants, from non-spinning black hole binaries are known not to be sufficiently accurate close to the last stable orbit of the system. A new approximation, called P-approximants, is believed to improve the accuracy of the waveforms rendering them applicable up to the last stable orbit. In this study we apply P-approximants to the case of a test-particle in equatorial orbit around a Kerr black hole parameterized by a spin parameter q that takes values between -1 and 1. In order to assess the performance of the two approximants we measure their effectualness (i.e. larger overlaps with the exact signal), and faithfulness (i.e. smaller biases while measuring the parameters of the signal) with the exact (numerical) waveforms. We find that in the case of prograde orbits, that is orbits whose angular momentum is in the same sense as the spin angular momentum of the black hole, T-approximant templates obtain an effectualness of ~ 0.99 for spins q < 0.75. For 0.75 < q < 0.95, the effectualness drops to about 0.82. The P-approximants achieve effectualness of > 0.99 for all spins up to q = 0.95. The bias in the estimation of parameters is much lower in the case of P-approximants than T-approximants. We find that P-approximants are both effectual and faithful and should be more effective than T-approximants as a detection template family when q>0. For q<0 both T- and P-approximants perform equally well so that either of them could be used as a detection template family. |
gr-qc/9211025 | Clifford M. Will | Lawrence E. Kidder and Clifford M. Will (Washington University, St.
Louis) and Alan G. Wiseman (Northwestern University, Evanston) | Spin effects in the inspiral of coalescing compact binaries | 12 pages | Phys.Rev.D47:4183-4187,1993 | 10.1103/PhysRevD.47.R4183 | WUGRAV-92-14 | gr-qc | null | We derive the contributions of spin-orbit and spin-spin coupling to the
gravitational radiation from coalescing binary systems of spinning compact
objects. We calculate spin effects in the symmetric, trace-free radiative
multipoles that determine the gravitational waveform, and the rate of energy
loss. Assuming a balance between energy radiated and orbital energy lost, we
determine the spin effects in the evolution of the orbital frequency and
orbital radius. Assuming that a laser interferometric gravitational observatory
can track the gravitational-wave frequency (twice the orbital frequency) as it
sweeps through its sensitive bandwidth between about 10 Hz and one kHz, we
estimate the accuracy with which the spins of the component bodies can be
determined from the gravitational-wave signal.
| [
{
"created": "Thu, 19 Nov 1992 17:25:06 GMT",
"version": "v1"
}
] | 2010-01-06 | [
[
"Kidder",
"Lawrence E.",
"",
"Washington University, St.\n Louis"
],
[
"Will",
"Clifford M.",
"",
"Washington University, St.\n Louis"
],
[
"Wiseman",
"Alan G.",
"",
"Northwestern University, Evanston"
]
] | We derive the contributions of spin-orbit and spin-spin coupling to the gravitational radiation from coalescing binary systems of spinning compact objects. We calculate spin effects in the symmetric, trace-free radiative multipoles that determine the gravitational waveform, and the rate of energy loss. Assuming a balance between energy radiated and orbital energy lost, we determine the spin effects in the evolution of the orbital frequency and orbital radius. Assuming that a laser interferometric gravitational observatory can track the gravitational-wave frequency (twice the orbital frequency) as it sweeps through its sensitive bandwidth between about 10 Hz and one kHz, we estimate the accuracy with which the spins of the component bodies can be determined from the gravitational-wave signal. |
1204.2395 | Vasilis Oikonomou | V. K. Oikonomou | Hidden Supersymmetry in Dirac Fermion Quasinormal Modes of Black Holes | null | null | 10.1142/S0217751X13500577 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We connect the quasinormal modes corresponding to Dirac fermions in various
black holes backgrounds to an N=2 supersymmetric quantum mechanics algebra,
which can be constructed from the radial part of the fermionic solutions of the
Dirac equation. In the massless fermion case, the quasinormal modes are in
bijective correspondence with the zero modes of the fermionic system and this
results to unbroken supersymmetry. The massive case is more evolved but as we
prove, supersymmetry remains unbroken even in this case.
| [
{
"created": "Wed, 11 Apr 2012 10:00:56 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jul 2013 12:06:26 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Oikonomou",
"V. K.",
""
]
] | We connect the quasinormal modes corresponding to Dirac fermions in various black holes backgrounds to an N=2 supersymmetric quantum mechanics algebra, which can be constructed from the radial part of the fermionic solutions of the Dirac equation. In the massless fermion case, the quasinormal modes are in bijective correspondence with the zero modes of the fermionic system and this results to unbroken supersymmetry. The massive case is more evolved but as we prove, supersymmetry remains unbroken even in this case. |
2108.01050 | Belinda Cheeseboro | Belinda D. Cheeseboro and Paul T. Baker | Method for detecting highly-eccentric binaries with a gravitational wave
burst search | null | null | 10.1103/PhysRevD.104.104016 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Detection of gravitational waves (GW) from highly eccentric binary black hole
(BBH) systems can provide insight into their dynamics and formation. To date,
all of the LIGO-Virgo BBH detections have been made using quasi-circular
templates in their initial discovery. However, recent studies have found some
of these systems to be compatible with high eccentricity in the LIGO band,
$e_{10 \textrm{Hz}} > 0.1$, possibly pointing to a population of sources that
are challenging to detect. Current low-latency search methods used with
ground-based GW detector data are not well equipped to detect highly eccentric
sources. Template-based, matched-filter searches require accurate eccentric
waveform models that are computational expensive. Unmodeled burst searches are
designed to detected localized excess power and are unable to identify multiple
isolated bursts, as would originate from a single highly eccentric BBH.
Therefore, we propose a signal-based prior that can be incorporated into an
existing GW burst search to target highly eccentric BBHs. Our eccentric burst
prior is based on the Newtonian burst model described by Loutrel & Yunes
(2017). As a proof of concept, we test our method on simulated data and find
that for intermediate SNR $\sim3-6$ signals using the eccentric burst prior
more effectively localizes GW bursts when compared to a uniform prior.
| [
{
"created": "Mon, 2 Aug 2021 17:15:20 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Sep 2021 18:52:05 GMT",
"version": "v2"
}
] | 2021-11-17 | [
[
"Cheeseboro",
"Belinda D.",
""
],
[
"Baker",
"Paul T.",
""
]
] | Detection of gravitational waves (GW) from highly eccentric binary black hole (BBH) systems can provide insight into their dynamics and formation. To date, all of the LIGO-Virgo BBH detections have been made using quasi-circular templates in their initial discovery. However, recent studies have found some of these systems to be compatible with high eccentricity in the LIGO band, $e_{10 \textrm{Hz}} > 0.1$, possibly pointing to a population of sources that are challenging to detect. Current low-latency search methods used with ground-based GW detector data are not well equipped to detect highly eccentric sources. Template-based, matched-filter searches require accurate eccentric waveform models that are computational expensive. Unmodeled burst searches are designed to detected localized excess power and are unable to identify multiple isolated bursts, as would originate from a single highly eccentric BBH. Therefore, we propose a signal-based prior that can be incorporated into an existing GW burst search to target highly eccentric BBHs. Our eccentric burst prior is based on the Newtonian burst model described by Loutrel & Yunes (2017). As a proof of concept, we test our method on simulated data and find that for intermediate SNR $\sim3-6$ signals using the eccentric burst prior more effectively localizes GW bursts when compared to a uniform prior. |
1209.2815 | Thomas Sch\"onenbach | Thomas Sch\"onenbach, Gunther Caspar, Peter O. Hess, Thomas Boller,
Andreas M\"uller, Mirko Sch\"afer and Walter Greiner | Experimental tests of pseudo-complex General Relativity | submitted for publication to the Monthly Notices of the Royal
Astronomical Society | MNRAS (April 21, 2013) 430 (4): 2999-3009 | 10.1093/mnras/stt108 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on previous publications exploring pseudo-complex General Relativity
(pc-GR) we present a selection of observable consequences of pc-GR and possible
ways to experimentally access them. Whenever possible we compare the results to
Einstein's GR and differences are worked out in detail. We propose experimental
tests to check the predictions of pc-GR for the orbital frequency of test
particles, the gravitational redshift effect and the last stable orbit. We will
show that the orbital frequency of test particles at a given radius in pc-GR is
in general lower compared to standard GR. Also the effect of frame dragging is
modified (weakened) in pc-GR. Concerning the gravitational redshift of a
radiation emitting object we find that it is also lower in pc-GR than in
standard GR. Eventually the classical concept of a last stable orbit has to be
modified in pc-GR.
| [
{
"created": "Thu, 13 Sep 2012 08:35:16 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Dec 2012 10:21:52 GMT",
"version": "v2"
}
] | 2013-04-26 | [
[
"Schönenbach",
"Thomas",
""
],
[
"Caspar",
"Gunther",
""
],
[
"Hess",
"Peter O.",
""
],
[
"Boller",
"Thomas",
""
],
[
"Müller",
"Andreas",
""
],
[
"Schäfer",
"Mirko",
""
],
[
"Greiner",
"Walter",
""
]
] | Based on previous publications exploring pseudo-complex General Relativity (pc-GR) we present a selection of observable consequences of pc-GR and possible ways to experimentally access them. Whenever possible we compare the results to Einstein's GR and differences are worked out in detail. We propose experimental tests to check the predictions of pc-GR for the orbital frequency of test particles, the gravitational redshift effect and the last stable orbit. We will show that the orbital frequency of test particles at a given radius in pc-GR is in general lower compared to standard GR. Also the effect of frame dragging is modified (weakened) in pc-GR. Concerning the gravitational redshift of a radiation emitting object we find that it is also lower in pc-GR than in standard GR. Eventually the classical concept of a last stable orbit has to be modified in pc-GR. |
2311.05525 | I. V. Kanatchikov | Igor V. Kanatchikov and Valery A. Kholodnyi | The Milgromian acceleration and the cosmological constant from
precanonical quantum gravity | 10pp. Based on our presentations at MOND40 (St. Andrews, UK), XL WGMP
(Bialowieza, Poland), EREP 2023 (Bilbao, Spain), Dark Energy (Frascati,
Italy) and POTOR 9th (Krakow, Poland) in June-September 2023 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the Milgromian acceleration of MOND and the cosmological
constant can be understood and quantified as the effects of quantum
fluctuations of spin connection which are described by precanonical quantum
gravity put forward by one of us earlier. We also show that a MOND-like
modification of Newtonian dynamics at small accelerations emerges from this
picture in the non-relativistic approximation.
| [
{
"created": "Thu, 9 Nov 2023 17:11:24 GMT",
"version": "v1"
}
] | 2023-11-10 | [
[
"Kanatchikov",
"Igor V.",
""
],
[
"Kholodnyi",
"Valery A.",
""
]
] | We show that the Milgromian acceleration of MOND and the cosmological constant can be understood and quantified as the effects of quantum fluctuations of spin connection which are described by precanonical quantum gravity put forward by one of us earlier. We also show that a MOND-like modification of Newtonian dynamics at small accelerations emerges from this picture in the non-relativistic approximation. |
2312.05438 | David Radice | Alireza Rashti and Maitraya Bhattacharyya and David Radice and Boris
Daszuta and William Cook and Sebastiano Bernuzzi | Adaptive mesh refinement in binary black holes simulations | 23 pages, 7 figures. Matches the version accepted on Classical and
Quantum Gravity | Class. Quantum Grav. 41 095001 (2024) | 10.1088/1361-6382/ad36a5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss refinement criteria for the Berger-Rigoutsos (block-based)
refinement algorithm in our numerical relativity code GR-Athena++ in the
context of binary black hole merger simulations. We compare three different
strategies: the "box-in-box" approach, the "sphere-in-sphere" approach and a
local criterion for refinement based on the estimation of truncation error of
the finite difference scheme. We extract and compare gravitational waveforms
using the three different mesh refinement methods and compare their accuracy
against a calibration waveform and demonstrate that the sphere-in-sphere
approach provides the best strategy overall when considering computational cost
and the waveform accuracy. Ultimately, we demonstrate the capability of each
mesh refinement method in accurately simulating gravitational waves from binary
black hole systems -- a crucial aspect for their application in next-generation
detectors. We quantify the mismatch achievable with the different strategies by
extrapolating the gravitational wave mismatch to higher resolution.
| [
{
"created": "Sat, 9 Dec 2023 02:05:22 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Mar 2024 16:54:16 GMT",
"version": "v2"
}
] | 2024-04-29 | [
[
"Rashti",
"Alireza",
""
],
[
"Bhattacharyya",
"Maitraya",
""
],
[
"Radice",
"David",
""
],
[
"Daszuta",
"Boris",
""
],
[
"Cook",
"William",
""
],
[
"Bernuzzi",
"Sebastiano",
""
]
] | We discuss refinement criteria for the Berger-Rigoutsos (block-based) refinement algorithm in our numerical relativity code GR-Athena++ in the context of binary black hole merger simulations. We compare three different strategies: the "box-in-box" approach, the "sphere-in-sphere" approach and a local criterion for refinement based on the estimation of truncation error of the finite difference scheme. We extract and compare gravitational waveforms using the three different mesh refinement methods and compare their accuracy against a calibration waveform and demonstrate that the sphere-in-sphere approach provides the best strategy overall when considering computational cost and the waveform accuracy. Ultimately, we demonstrate the capability of each mesh refinement method in accurately simulating gravitational waves from binary black hole systems -- a crucial aspect for their application in next-generation detectors. We quantify the mismatch achievable with the different strategies by extrapolating the gravitational wave mismatch to higher resolution. |
gr-qc/0410135 | Nathalie Deruelle | Nathalie Deruelle and Joseph Katz | On the mass of a Kerr-anti-de Sitter spacetime in D dimensions | minor changes; accepted by CQG | Class.Quant.Grav. 22 (2005) 421-424 | 10.1088/0264-9381/22/2/013 | null | gr-qc hep-th | null | We show how to compute the mass of a Kerr-anti-de Sitter spacetime with
respect to the anti-de Sitter background in any dimension, using a
superpotential which has been derived from standard Noether identities. The
calculation takes no account of the source of the curvature and confirms
results obtained for black holes via the first law of thermodynamics.
| [
{
"created": "Thu, 28 Oct 2004 01:12:26 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Nov 2004 05:01:06 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Deruelle",
"Nathalie",
""
],
[
"Katz",
"Joseph",
""
]
] | We show how to compute the mass of a Kerr-anti-de Sitter spacetime with respect to the anti-de Sitter background in any dimension, using a superpotential which has been derived from standard Noether identities. The calculation takes no account of the source of the curvature and confirms results obtained for black holes via the first law of thermodynamics. |
gr-qc/0609021 | D. Bar | D. Bar | Double-slit interference pattern from single-slit screen and its
gravitational analogues | 51 pages, 12 Figures five of them contain two subfigures and thus the
number of figures is 17, 1 Table. Some minor changes introduced, especially,
in the references | Int.J.Theor.Phys.46:2626-2657,2007 | 10.1007/s10773-007-9377-3 | null | gr-qc | null | The double slit experiment (DSE) is known as an important cornerstone in the
foundations of physical theories such as Quantum Mechanics and Special
Relativity. A large number of different variants of it were designed and
performed over the years. We perform and discuss here a new verion with the
somewhat unexpected results of obtaining interference pattern from single-slit
screen. This outcome, which shows that the routes of the photons through the
array were changed, leads one to discuss it, using the equivalence principle,
in terms of geodesics mechanics. We show using either the Brill's version of
the canonical formulation of general relativity or the linearized version of it
that one may find corresponding and analogous situations in the framework of
general relativity.
| [
{
"created": "Thu, 7 Sep 2006 01:54:15 GMT",
"version": "v1"
},
{
"created": "Fri, 2 May 2008 21:18:51 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bar",
"D.",
""
]
] | The double slit experiment (DSE) is known as an important cornerstone in the foundations of physical theories such as Quantum Mechanics and Special Relativity. A large number of different variants of it were designed and performed over the years. We perform and discuss here a new verion with the somewhat unexpected results of obtaining interference pattern from single-slit screen. This outcome, which shows that the routes of the photons through the array were changed, leads one to discuss it, using the equivalence principle, in terms of geodesics mechanics. We show using either the Brill's version of the canonical formulation of general relativity or the linearized version of it that one may find corresponding and analogous situations in the framework of general relativity. |
2312.12087 | F Shojai | Reza Saadati and Fatimah Shojai | Geodetic precession and shadow of quantum extended black holes | 9 pages | Class. Quantum Grav. 41 015032, 2024 | 10.1088/1361-6382/ad13c3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the circular motion of massive and massless particles in a recently
proposed quantum-corrected Schwarzschild black hole in loop quantum gravity.
This solution is supposed to introduce small but non-zero quantum corrections
in the low curvature limit. In this paper, we confine our attention to the
shadow of the black hole and the geodetic precession of a freely falling
gyroscope in a circular orbit. Despite the mathematical complexity of the
metric, our results are exact and show that the black hole shadow decreases
slightly in this solution while the quantum corrections introduce a non-trivial
term in the geodetic precession frequency of the gyroscope.
| [
{
"created": "Tue, 19 Dec 2023 12:07:10 GMT",
"version": "v1"
}
] | 2023-12-20 | [
[
"Saadati",
"Reza",
""
],
[
"Shojai",
"Fatimah",
""
]
] | We study the circular motion of massive and massless particles in a recently proposed quantum-corrected Schwarzschild black hole in loop quantum gravity. This solution is supposed to introduce small but non-zero quantum corrections in the low curvature limit. In this paper, we confine our attention to the shadow of the black hole and the geodetic precession of a freely falling gyroscope in a circular orbit. Despite the mathematical complexity of the metric, our results are exact and show that the black hole shadow decreases slightly in this solution while the quantum corrections introduce a non-trivial term in the geodetic precession frequency of the gyroscope. |
1601.06083 | Cosima Breu | Cosima Breu and Luciano Rezzolla | Maximum mass, moment of inertia and compactness of relativistic stars | v2 matches version published on MNRAS | null | 10.1093/mnras/stw575 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A number of recent works have highlighted that it is possible to express the
properties of general-relativistic stellar equilibrium configurations in terms
of functions that do not depend on the specific equation of state employed to
describe matter at nuclear densities. These functions are normally referred to
as "universal relations" and have been found to apply, within limits, both to
static or stationary isolated stars, as well as to fully dynamical and merging
binary systems. Further extending the idea that universal relations can be
valid also away from stability, we show that a universal relation is exhibited
also by equilibrium solutions that are not stable. In particular, the mass of
rotating configurations on the turning-point line shows a universal behaviour
when expressed in terms of the normalised Keplerian angular momentum. In turn,
this allows us to compute the maximum mass allowed by uniform rotation,
M_{max}, simply in terms of the maximum mass of the nonrotating configuration,
M_{TOV}, finding that M_{max} ~ (1.203 +- 0.022) M_{TOV} for all the equations
of state we have considered. We further show that a universal relation can be
found between the dimensionless moment of inertia and the stellar compactness.
Although this relation is not surprising as it involves two quantities that
have been shown to exhibit universal behaviour with other stellar properties,
our parameterisation represents a refinement over a similar relation by
Lattimer and Schutz (2005), where a different normalisation was used, and could
provide an accurate tool to constrain the equation of state of nuclear matter
when measurements of the moment of inertia become available.
| [
{
"created": "Fri, 22 Jan 2016 17:39:26 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Apr 2016 19:42:35 GMT",
"version": "v2"
}
] | 2016-04-12 | [
[
"Breu",
"Cosima",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | A number of recent works have highlighted that it is possible to express the properties of general-relativistic stellar equilibrium configurations in terms of functions that do not depend on the specific equation of state employed to describe matter at nuclear densities. These functions are normally referred to as "universal relations" and have been found to apply, within limits, both to static or stationary isolated stars, as well as to fully dynamical and merging binary systems. Further extending the idea that universal relations can be valid also away from stability, we show that a universal relation is exhibited also by equilibrium solutions that are not stable. In particular, the mass of rotating configurations on the turning-point line shows a universal behaviour when expressed in terms of the normalised Keplerian angular momentum. In turn, this allows us to compute the maximum mass allowed by uniform rotation, M_{max}, simply in terms of the maximum mass of the nonrotating configuration, M_{TOV}, finding that M_{max} ~ (1.203 +- 0.022) M_{TOV} for all the equations of state we have considered. We further show that a universal relation can be found between the dimensionless moment of inertia and the stellar compactness. Although this relation is not surprising as it involves two quantities that have been shown to exhibit universal behaviour with other stellar properties, our parameterisation represents a refinement over a similar relation by Lattimer and Schutz (2005), where a different normalisation was used, and could provide an accurate tool to constrain the equation of state of nuclear matter when measurements of the moment of inertia become available. |
gr-qc/9809017 | Nora Breton | Nora Breton (CINVESTAV--IPN), Alberto Garcia (CINVESTAV--IPN), Alfredo
Macias (UAM-Iztapalapa) and Gustavo Y\'a\~nez (CINVESTAV--IPN) | Class of colliding plane waves in terms of Jacobi functions | 25 pages, Latex, uses revtex macros | J.Math.Phys. 39 (1998) 6051-6065 | 10.1063/1.532627 | null | gr-qc | null | We present a general class of noncolinear colliding wave solutions of the
Einstein-Maxwell equations given in terms of fourth order polynomials, which in
turn can be expressed through Jacobi functions depending on generalized
advanced and retarded time coordinates. The solutions are characterized by six
free parameters. The parameters can be chosen in such a way to avoid the
generic focusing singularity
| [
{
"created": "Thu, 3 Sep 1998 18:34:08 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Breton",
"Nora",
"",
"CINVESTAV--IPN"
],
[
"Garcia",
"Alberto",
"",
"CINVESTAV--IPN"
],
[
"Macias",
"Alfredo",
"",
"UAM-Iztapalapa"
],
[
"Yáñez",
"Gustavo",
"",
"CINVESTAV--IPN"
]
] | We present a general class of noncolinear colliding wave solutions of the Einstein-Maxwell equations given in terms of fourth order polynomials, which in turn can be expressed through Jacobi functions depending on generalized advanced and retarded time coordinates. The solutions are characterized by six free parameters. The parameters can be chosen in such a way to avoid the generic focusing singularity |
gr-qc/9803065 | Gary Gibbons | G W Gibbons | Quantum Gravity/String/M-theory/ as we approach the 3rd Millennium | This is the text of my plenary lecture, aimed at a non-expert
audience, given at GR15, Pune, India, December 1997. 22 pages Latex file with
two figures and using crckapb.sty style file | null | null | null | gr-qc hep-th | null | I review some recent progress in String/M-theory
| [
{
"created": "Wed, 18 Mar 1998 16:07:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gibbons",
"G W",
""
]
] | I review some recent progress in String/M-theory |
2307.06405 | Mohit Raj Sah Mr. | Mohit Raj Sah and Suvodip Mukherjee | Non-Stationary Astrophysical Stochastic Gravitational-Wave Background: A
New Probe to the High Redshift Population of Binary Black Holes | 14 pages, 13 figures. Accepted for publication in MNRAS | null | null | null | gr-qc astro-ph.CO astro-ph.HE | http://creativecommons.org/licenses/by-nc-nd/4.0/ | The astrophysical Stochastic Gravitational Wave Background (SGWB) originates
from the mergers of compact binary objects that are otherwise undetected as
individual events, along with other sources such as supernovae, magnetars, etc.
The individual GW signal is time-varying over a time scale that depends on the
chirp mass of the coalescing binaries. Another timescale that plays a role is
the timescale at which the sources repeat, which depends on the merger rate.
The combined effect of these two leads to a breakdown of the time-translation
symmetry of the observed SGWB and a correlation between different frequency
modes in the signal covariance matrix of the SGWB. Using an ensemble of SGWB
due to binary black hole coalescence, calculated using simulations of different
black hole mass distributions and merger rates, we show how the structure of
the signal covariance matrix varies. This structure in the signal covariance
matrix brings additional information about the sources on top of the power
spectrum. We show that there is a significant improvement in the Figure of
Merit by using this additional information in comparison to only power spectrum
estimation for the LIGO-Virgo-KAGRA (LVK) network of detectors with the design
sensitivity noise with two years of observation. The inclusion of the
off-diagonal correlation in the covariance of the SGWB in the data analysis
pipelines will be beneficial in the quest for the SGWB signal in LVK frequency
bands as well as in lower frequencies and in getting an insight into its
origin.
| [
{
"created": "Wed, 12 Jul 2023 18:41:52 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Oct 2023 13:56:33 GMT",
"version": "v2"
}
] | 2023-11-01 | [
[
"Sah",
"Mohit Raj",
""
],
[
"Mukherjee",
"Suvodip",
""
]
] | The astrophysical Stochastic Gravitational Wave Background (SGWB) originates from the mergers of compact binary objects that are otherwise undetected as individual events, along with other sources such as supernovae, magnetars, etc. The individual GW signal is time-varying over a time scale that depends on the chirp mass of the coalescing binaries. Another timescale that plays a role is the timescale at which the sources repeat, which depends on the merger rate. The combined effect of these two leads to a breakdown of the time-translation symmetry of the observed SGWB and a correlation between different frequency modes in the signal covariance matrix of the SGWB. Using an ensemble of SGWB due to binary black hole coalescence, calculated using simulations of different black hole mass distributions and merger rates, we show how the structure of the signal covariance matrix varies. This structure in the signal covariance matrix brings additional information about the sources on top of the power spectrum. We show that there is a significant improvement in the Figure of Merit by using this additional information in comparison to only power spectrum estimation for the LIGO-Virgo-KAGRA (LVK) network of detectors with the design sensitivity noise with two years of observation. The inclusion of the off-diagonal correlation in the covariance of the SGWB in the data analysis pipelines will be beneficial in the quest for the SGWB signal in LVK frequency bands as well as in lower frequencies and in getting an insight into its origin. |
2105.06650 | Matt Visser | Aden Jowsey (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Reconsidering maximum luminosity | 11 Pages. This essay was awarded an honourable mention in the 2021
Gravity Research Foundation essay contest | International Journal of Modern Physics D 30 # 14 (2021) 2142026 | 10.1142/S0218271821420268 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The suggestion that there is a maximum luminosity (maximum power) in nature
has a long and somewhat convoluted history. Though this idea is commonly
attributed to Freeman Dyson, he was actually much more circumspect in his
views. What is certainly true is that dimensional analysis shows that the speed
of light and Newton's constant of gravitation can be combined to define a
quantity P_* = c^5/G_N with the dimensions of luminosity (equivalently, power).
Then in any physical situation we must have P_{physical} =$\wp$ P_*, where the
quantity $\wp$ is some dimensionless function of dimensionless parameters. This
has lead some authors to suggest a maximum luminosity/maximum power conjecture.
Working within the framework of standard general relativity, we will re-assess
this conjecture, paying particular attention to the extent to which various
examples and counter-examples are physically reasonable. We focus specifically
on Vaidya spacetimes, and on an evaporating version of Schwarzschild's constant
density star. For both of these spacetimes luminosity can be arbitrarily large.
We argue that any luminosity bound must depend on delicate internal features of
the radiating object.
| [
{
"created": "Fri, 14 May 2021 05:30:55 GMT",
"version": "v1"
}
] | 2022-01-11 | [
[
"Jowsey",
"Aden",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | The suggestion that there is a maximum luminosity (maximum power) in nature has a long and somewhat convoluted history. Though this idea is commonly attributed to Freeman Dyson, he was actually much more circumspect in his views. What is certainly true is that dimensional analysis shows that the speed of light and Newton's constant of gravitation can be combined to define a quantity P_* = c^5/G_N with the dimensions of luminosity (equivalently, power). Then in any physical situation we must have P_{physical} =$\wp$ P_*, where the quantity $\wp$ is some dimensionless function of dimensionless parameters. This has lead some authors to suggest a maximum luminosity/maximum power conjecture. Working within the framework of standard general relativity, we will re-assess this conjecture, paying particular attention to the extent to which various examples and counter-examples are physically reasonable. We focus specifically on Vaidya spacetimes, and on an evaporating version of Schwarzschild's constant density star. For both of these spacetimes luminosity can be arbitrarily large. We argue that any luminosity bound must depend on delicate internal features of the radiating object. |
0710.0277 | Guillermo A. Mena Marugan | Alejandro Corichi, Jeronimo Cortez, Guillermo A. Mena Marugan, Jose M.
Velhinho | Quantum Gowdy $T^3$ Model: Schrodinger Representation with Unitary
Dynamics | 21 pages, version accepted for publication in Physical Review D | Phys.Rev.D76:124031,2007 | 10.1103/PhysRevD.76.124031 | null | gr-qc | null | The linearly polarized Gowdy $T^3$ model is paradigmatic for studying
technical and conceptual issues in the quest for a quantum theory of gravity
since, after a suitable and almost complete gauge fixing, it becomes an exactly
soluble midisuperspace model. Recently, a new quantization of the model,
possessing desired features such as a unitary implementation of the gauge group
and of the time evolution, has been put forward and proven to be essentially
unique. An appropriate setting for making contact with other approaches to
canonical quantum gravity is provided by the Schr\"odinger representation,
where states are functionals on the configuration space of the theory. Here we
construct this functional description, analyze the time evolution in this
context and show that it is also unitary when restricted to physical states,
i.e. states which are solutions to the remaining constraint of the theory.
| [
{
"created": "Mon, 1 Oct 2007 12:30:06 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Nov 2007 16:46:51 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Corichi",
"Alejandro",
""
],
[
"Cortez",
"Jeronimo",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Velhinho",
"Jose M.",
""
]
] | The linearly polarized Gowdy $T^3$ model is paradigmatic for studying technical and conceptual issues in the quest for a quantum theory of gravity since, after a suitable and almost complete gauge fixing, it becomes an exactly soluble midisuperspace model. Recently, a new quantization of the model, possessing desired features such as a unitary implementation of the gauge group and of the time evolution, has been put forward and proven to be essentially unique. An appropriate setting for making contact with other approaches to canonical quantum gravity is provided by the Schr\"odinger representation, where states are functionals on the configuration space of the theory. Here we construct this functional description, analyze the time evolution in this context and show that it is also unitary when restricted to physical states, i.e. states which are solutions to the remaining constraint of the theory. |
0906.5562 | Viqar Husain | Viqar Husain | Time, vacuum energy, and the cosmological constant | 5 pages. Honorable mention, Gravity Research Foundation Essay Awards
(2009) | Int.J.Mod.Phys.D18:2265-2268,2009 | 10.1142/S0218271809015928 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a link between the cosmological constant problem and the problem
of time in quantum gravity. This arises by examining the relationship between
the cosmological constant and vacuum energy in light of non-perturbative
formulations of quantum gravity.
| [
{
"created": "Tue, 30 Jun 2009 15:21:58 GMT",
"version": "v1"
}
] | 2010-03-12 | [
[
"Husain",
"Viqar",
""
]
] | We describe a link between the cosmological constant problem and the problem of time in quantum gravity. This arises by examining the relationship between the cosmological constant and vacuum energy in light of non-perturbative formulations of quantum gravity. |
1402.6950 | Aur\'elien Hees | A. Hees, W. M. Folkner, R. A. Jacobson, R. S. Park | Constraints on MOND theory from radio tracking data of the Cassini
spacecraft | 9 pages, 7 figures, version accepted in Phys. Rev. D | Phys. Rev. D 89, 102002, 2014 | 10.1103/PhysRevD.89.102002 | null | gr-qc astro-ph.EP astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The MOdified Newtonian Dynamics (MOND) is an attempt to modify the
gravitation theory to solve the Dark Matter problem. This phenomenology is very
successful at the galactic level. The main effect produced by MOND in the Solar
System is called the External Field Effect parametrized by the parameter $Q_2$.
We have used 9 years of Cassini range and Doppler measurements to constrain
$Q_2$. Our estimate of this parameter based on Cassini data is given by $Q_2=(3
\pm 3)\times 10^{-27} \ \rm{s^{-2}}$ which shows no deviation from General
Relativity and excludes a large part of the relativistic MOND theories. This
limit can also be interpreted as a limit on a external tidal potential acting
on the Solar System coming from the internal mass of our galaxy (including Dark
Matter) or from a new hypothetical body.
| [
{
"created": "Thu, 27 Feb 2014 16:06:20 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Apr 2014 19:33:17 GMT",
"version": "v2"
}
] | 2014-05-14 | [
[
"Hees",
"A.",
""
],
[
"Folkner",
"W. M.",
""
],
[
"Jacobson",
"R. A.",
""
],
[
"Park",
"R. S.",
""
]
] | The MOdified Newtonian Dynamics (MOND) is an attempt to modify the gravitation theory to solve the Dark Matter problem. This phenomenology is very successful at the galactic level. The main effect produced by MOND in the Solar System is called the External Field Effect parametrized by the parameter $Q_2$. We have used 9 years of Cassini range and Doppler measurements to constrain $Q_2$. Our estimate of this parameter based on Cassini data is given by $Q_2=(3 \pm 3)\times 10^{-27} \ \rm{s^{-2}}$ which shows no deviation from General Relativity and excludes a large part of the relativistic MOND theories. This limit can also be interpreted as a limit on a external tidal potential acting on the Solar System coming from the internal mass of our galaxy (including Dark Matter) or from a new hypothetical body. |
2405.05750 | Hassan Firouzjahi | Hassan Firouzjahi | Quantum Fluctuations in the Interior of Black Holes and Backreactions | v2:minor revisions, matches journal version | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the propagation of the quantum field perturbations in the interior
of the Schwarzschild black hole. The interior of the black hole is like an
anisotropic cosmological background which expands in one extended direction
while contracting in azimuthal directions. Solving the quantum mode functions
approximately, we calculate the expectation values of physical quantities such
as the energy density $\langle \rho \rangle$ and pressure $\langle P\rangle$ as
measured by an observer in the interior of the black hole. We employ a
combination of the $\zeta$ function regularization and dimensional
regularization schemes to regularize the UV divergences in the energy momentum
tensor associated to these quantum perturbations. By solving the Einstein field
equations, we calculate the quantum backreactions induced in the background
geometry. We speculate that the effects of quantum fluctuations in the interior
of the black hole can be measured by the exterior observer.
| [
{
"created": "Thu, 9 May 2024 13:14:42 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jun 2024 09:15:55 GMT",
"version": "v2"
}
] | 2024-06-28 | [
[
"Firouzjahi",
"Hassan",
""
]
] | We study the propagation of the quantum field perturbations in the interior of the Schwarzschild black hole. The interior of the black hole is like an anisotropic cosmological background which expands in one extended direction while contracting in azimuthal directions. Solving the quantum mode functions approximately, we calculate the expectation values of physical quantities such as the energy density $\langle \rho \rangle$ and pressure $\langle P\rangle$ as measured by an observer in the interior of the black hole. We employ a combination of the $\zeta$ function regularization and dimensional regularization schemes to regularize the UV divergences in the energy momentum tensor associated to these quantum perturbations. By solving the Einstein field equations, we calculate the quantum backreactions induced in the background geometry. We speculate that the effects of quantum fluctuations in the interior of the black hole can be measured by the exterior observer. |
0906.4524 | Alejandro Perez | Lihui Liu, Merced Montesinos, Alejandro Perez | A topological limit of gravity admitting an SU(2) connection formulation | Appendix added where moldels leading to boundary degrees of freedom
are constructed. This version will appear in PRD. | Phys.Rev.D81:064033,2010 | 10.1103/PhysRevD.81.064033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Hamiltonian formulation of the generally covariant theory
defined by the Lagrangian 4-form L=e_I e_J F^{IJ}(\omega) where e^I is a tetrad
field and F^{IJ} is the curvature of a Lorentz connection \omega^{IJ}. This
theory can be thought of as the limit of the Holst action for gravity for the
Newton constant G goes to infinity and Immirzi parameter goes to zero, while
keeping their product fixed. This theory has for a long time been conjectured
to be topological. We prove this statement both in the covariant phase space
formulation as well as in the standard Dirac formulation. In the time gauge,
the unconstrained phase space of theory admits an SU(2) connection formulation
which makes it isomorphic to the unconstrained phase space of gravity in terms
of Ashtekar-Barbero variables. Among possible physical applications, we argue
that the quantization of this topological theory might shed new light on the
nature of the degrees of freedom that are responsible for black entropy in loop
quantum gravity.
| [
{
"created": "Wed, 24 Jun 2009 17:16:22 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Mar 2010 17:34:42 GMT",
"version": "v2"
}
] | 2015-03-13 | [
[
"Liu",
"Lihui",
""
],
[
"Montesinos",
"Merced",
""
],
[
"Perez",
"Alejandro",
""
]
] | We study the Hamiltonian formulation of the generally covariant theory defined by the Lagrangian 4-form L=e_I e_J F^{IJ}(\omega) where e^I is a tetrad field and F^{IJ} is the curvature of a Lorentz connection \omega^{IJ}. This theory can be thought of as the limit of the Holst action for gravity for the Newton constant G goes to infinity and Immirzi parameter goes to zero, while keeping their product fixed. This theory has for a long time been conjectured to be topological. We prove this statement both in the covariant phase space formulation as well as in the standard Dirac formulation. In the time gauge, the unconstrained phase space of theory admits an SU(2) connection formulation which makes it isomorphic to the unconstrained phase space of gravity in terms of Ashtekar-Barbero variables. Among possible physical applications, we argue that the quantization of this topological theory might shed new light on the nature of the degrees of freedom that are responsible for black entropy in loop quantum gravity. |
1801.07724 | Christian Pfeifer | Norman G\"urlebeck and Christian Pfeifer | Observers' measurements in premetric electrodynamics I: Time and radar
length | 18 pages, updated to journal version, typos corrected, discussion
extended | Phys. Rev. D 97, 084043 (2018) | 10.1103/PhysRevD.97.084043 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The description of an observer's measurement in general relativity and the
standard model of particle physics is closely related to the spacetime metric.
In order to understand and interpret measurements, which test the metric
structure of the spacetime, like the classical Michelson-Morley, Ives-Stilwell,
Kennedy-Thorndike experiments or frequency comparison experiments in general,
it is necessary to describe them in theories, which go beyond the Lorentzian
metric structure. However, this requires a description of an observer's
measurement without relying on a metric. We provide such a description of an
observer's measurement of the fundamental quantities time and length derived
from a premetric perturbation of Maxwell's electrodynamics and a discussion on
how these measurements influence classical relativistic observables like time
dilation and length contraction. Most importantly, we find that the
modification of electrodynamics influences the measurements at two instances:
the propagation of light is altered as well as the observer's proper time
normalization. When interpreting the results of a specific experiment, both
effects cannot be disentangled, in general, and have to be taken into account.
| [
{
"created": "Tue, 23 Jan 2018 19:00:08 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Apr 2018 06:36:09 GMT",
"version": "v2"
}
] | 2018-04-27 | [
[
"Gürlebeck",
"Norman",
""
],
[
"Pfeifer",
"Christian",
""
]
] | The description of an observer's measurement in general relativity and the standard model of particle physics is closely related to the spacetime metric. In order to understand and interpret measurements, which test the metric structure of the spacetime, like the classical Michelson-Morley, Ives-Stilwell, Kennedy-Thorndike experiments or frequency comparison experiments in general, it is necessary to describe them in theories, which go beyond the Lorentzian metric structure. However, this requires a description of an observer's measurement without relying on a metric. We provide such a description of an observer's measurement of the fundamental quantities time and length derived from a premetric perturbation of Maxwell's electrodynamics and a discussion on how these measurements influence classical relativistic observables like time dilation and length contraction. Most importantly, we find that the modification of electrodynamics influences the measurements at two instances: the propagation of light is altered as well as the observer's proper time normalization. When interpreting the results of a specific experiment, both effects cannot be disentangled, in general, and have to be taken into account. |
gr-qc/9902060 | Maurizio Gasperini | M. Gasperini | Inflation and initial conditions in the pre-big bang scenario | 4 pages, Latex, one figure. Many references added. The text has been
improved in many points. To appear in Phys. Rev. D | Phys.Rev. D61 (2000) 087301 | 10.1103/PhysRevD.61.087301 | BA-TH/99-332 | gr-qc hep-th | null | The pre-big bang scenario describes the evolution of the Universe from an
initial state approaching the flat, cold, empty, string perturbative vacuum.
The choice of such an initial state is suggested by the present state of our
Universe if we accept that the cosmological evolution is (at least partially)
duality-symmetric. Recently, the initial conditions of the pre-big bang
scenario have been criticized as they introduce large dimensionless parameters
allowing the Universe to be "exponentially large from the very beginning". We
agree that a set of initial parameters (such as the initial homogeneity scale,
the initial entropy) larger than those determined by the initial horizon scale,
H^{-1}, would be somewhat unnatural to start with. However, in the pre-big bang
scenario, the initial parameters are all bounded by the size of the initial
horizon. The basic question thus becomes: is a maximal homogeneity scale of
order H^{-1} necessarily unnatural if the initial curvature is small and,
consequently, H^{-1} is very large in Planck (or string) units? In the
impossibility of experimental information one could exclude "a priori", for
large horizons, the maximal homogeneity scale H^{-1} as a natural initial
condition. In the pre-big bang scenario, however, pre-Planckian initial
conditions are not necessarily washed out by inflation and are accessible (in
principle) to observational tests, so that their naturalness could be also
analyzed with a Bayesan approach, in terms of "a posteriori" probabilities.
| [
{
"created": "Fri, 19 Feb 1999 18:13:55 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Feb 1999 14:57:05 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Mar 1999 14:34:04 GMT",
"version": "v3"
},
{
"created": "Tue, 16 Nov 1999 18:43:48 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Gasperini",
"M.",
""
]
] | The pre-big bang scenario describes the evolution of the Universe from an initial state approaching the flat, cold, empty, string perturbative vacuum. The choice of such an initial state is suggested by the present state of our Universe if we accept that the cosmological evolution is (at least partially) duality-symmetric. Recently, the initial conditions of the pre-big bang scenario have been criticized as they introduce large dimensionless parameters allowing the Universe to be "exponentially large from the very beginning". We agree that a set of initial parameters (such as the initial homogeneity scale, the initial entropy) larger than those determined by the initial horizon scale, H^{-1}, would be somewhat unnatural to start with. However, in the pre-big bang scenario, the initial parameters are all bounded by the size of the initial horizon. The basic question thus becomes: is a maximal homogeneity scale of order H^{-1} necessarily unnatural if the initial curvature is small and, consequently, H^{-1} is very large in Planck (or string) units? In the impossibility of experimental information one could exclude "a priori", for large horizons, the maximal homogeneity scale H^{-1} as a natural initial condition. In the pre-big bang scenario, however, pre-Planckian initial conditions are not necessarily washed out by inflation and are accessible (in principle) to observational tests, so that their naturalness could be also analyzed with a Bayesan approach, in terms of "a posteriori" probabilities. |
1701.00607 | Taketo Ariki | Taketo Ariki | Self-consistent hyperfluid | Some typos corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hyperfluid model is reconstructed on the basis of its action free from any
external constraints, regarding the hyperfluid as a self-consistent classical
field. Intrinsic hypermomentum is no more a given variable, but arises purely
from the diffeomorphism covariance of the dynamical field, which allows the
hypermomentum to be exchanged via fundamental interactions of various classes;
fluid-fluid interactions, SU(n)-gauge coupling with non-minimal interaction,
and coupling with the metric-affine gravity are all successfully formulated in
the classical regime.
| [
{
"created": "Tue, 3 Jan 2017 09:14:19 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Jan 2017 14:47:57 GMT",
"version": "v2"
},
{
"created": "Sat, 5 Aug 2017 06:13:49 GMT",
"version": "v3"
}
] | 2017-08-08 | [
[
"Ariki",
"Taketo",
""
]
] | Hyperfluid model is reconstructed on the basis of its action free from any external constraints, regarding the hyperfluid as a self-consistent classical field. Intrinsic hypermomentum is no more a given variable, but arises purely from the diffeomorphism covariance of the dynamical field, which allows the hypermomentum to be exchanged via fundamental interactions of various classes; fluid-fluid interactions, SU(n)-gauge coupling with non-minimal interaction, and coupling with the metric-affine gravity are all successfully formulated in the classical regime. |
gr-qc/9608024 | Bahman K. Darian | B. K. Darian and H. P. Kunzle | Axially Symmetric Bianchi I Yang-Mills Cosmology as a Dynamical System | 18 pages, 6 Postscript figures, uses amsmath,amssymb,epsfig,verbatim,
to appear in CQG | Class.Quant.Grav. 13 (1996) 2651 | 10.1088/0264-9381/13/10/005 | Alberta Thy 21-96 | gr-qc chao-dyn nlin.CD | null | We construct the most general form of axially symmetric SU(2)-Yang-Mills
fields in Bianchi cosmologies. The dynamical evolution of axially symmetric YM
fields in Bianchi I model is compared with the dynamical evolution of the
electromagnetic field in Bianchi I and the fully isotropic YM field in
Friedmann-Robertson-Walker cosmologies. The stochastic properties of axially
symmetric Bianchi I-Einstein-Yang-Mills systems are compared with those of
axially symmetric YM fields in flat space. After numerical computation of
Liapunov exponents in synchronous (cosmological) time, it is shown that the
Bianchi I-EYM system has milder stochastic properties than the corresponding
flat YM system. The Liapunov exponent is non-vanishing in conformal time.
| [
{
"created": "Fri, 9 Aug 1996 20:21:14 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Darian",
"B. K.",
""
],
[
"Kunzle",
"H. P.",
""
]
] | We construct the most general form of axially symmetric SU(2)-Yang-Mills fields in Bianchi cosmologies. The dynamical evolution of axially symmetric YM fields in Bianchi I model is compared with the dynamical evolution of the electromagnetic field in Bianchi I and the fully isotropic YM field in Friedmann-Robertson-Walker cosmologies. The stochastic properties of axially symmetric Bianchi I-Einstein-Yang-Mills systems are compared with those of axially symmetric YM fields in flat space. After numerical computation of Liapunov exponents in synchronous (cosmological) time, it is shown that the Bianchi I-EYM system has milder stochastic properties than the corresponding flat YM system. The Liapunov exponent is non-vanishing in conformal time. |
2405.09151 | Ran Li | Ran Li, Jin Wang | Thermodynamics and kinetics of state switching for the asymptotically
flat black hole in a cavity | null | null | null | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose that the thermodynamics and the kinetics of state switching for
the asymptotically flat black hole enclosed by a cavity can be studied in terms
of the free energy landscape formalism. The generalized free energy for the
black hole enclosed by a cavity in the canonical ensemble is derived by using
the York's approach, where the temperature on the cavity and the charges inside
the cavity are kept as the fixed parameters. By quantifying the corresponding
free energy landscape, we obtain the phase diagrams for the black hole in
cavity, which reveal a Hawking-Page type transition for the uncharged black
hole and a Van der Waals type transition for the charged black hole. We further
assume that the dynamics of black hole state switching is mutually determined
by the gradient force and the stochastic force arising from the free energy
landscape and the thermal noises respectively. We then derive a recurrence
relation for the $n$-momentum of the first passage time distribution function,
which enables the calculation of the kinetic times characterized by the mean
first passage time and its relative fluctuation. Our analysis illustrates that
the kinetics of black hole state switching is determined by the ensemble
temperature and the barrier height on the free energy landscape.
| [
{
"created": "Wed, 15 May 2024 07:31:15 GMT",
"version": "v1"
}
] | 2024-05-16 | [
[
"Li",
"Ran",
""
],
[
"Wang",
"Jin",
""
]
] | We propose that the thermodynamics and the kinetics of state switching for the asymptotically flat black hole enclosed by a cavity can be studied in terms of the free energy landscape formalism. The generalized free energy for the black hole enclosed by a cavity in the canonical ensemble is derived by using the York's approach, where the temperature on the cavity and the charges inside the cavity are kept as the fixed parameters. By quantifying the corresponding free energy landscape, we obtain the phase diagrams for the black hole in cavity, which reveal a Hawking-Page type transition for the uncharged black hole and a Van der Waals type transition for the charged black hole. We further assume that the dynamics of black hole state switching is mutually determined by the gradient force and the stochastic force arising from the free energy landscape and the thermal noises respectively. We then derive a recurrence relation for the $n$-momentum of the first passage time distribution function, which enables the calculation of the kinetic times characterized by the mean first passage time and its relative fluctuation. Our analysis illustrates that the kinetics of black hole state switching is determined by the ensemble temperature and the barrier height on the free energy landscape. |
2206.11367 | Claus Gerhardt | Claus Gerhardt | A unified quantization of gravity and other fundamental forces of nature | 32 pages, v3: This is the published version. arXiv admin note: text
overlap with arXiv:1301.6101, arXiv:2104.08084 | Universe 8 (2022), no.8, 404 | 10.3390/universe8080404 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We quantize the interaction of gravity with Yang-Mills and spinor fields,
hence offering a quantum theory incorporating all four fundamental forces of
nature. Let us\ann{as} abbreviate the spatial Hamilton functions of the
Standard Model by $H_{SM}$ and the Hamilton function of gravity by $H_G$.
Working in a fiber bundle $E$ with base space $\socc=\R[n]$, where the fiber
elements are Riemannian metrics, we can express the Hamilton functions in the
form $H_G+H_{SM}=H_G+t^{-\frac23}\tilde H_{SM}$ if $n=3$, where $\tilde H_{SM}$
depends on metrics $\s_{ij}$ satisfying $\det{\s_{ij}}=1$. In the quantization
process, we quantize $H_G$ for general $\s_{ij}$ but $\tilde H_{SM}$ only for
$\s_{ij}=\de_{ij}$ by the usual methods of QFT. Let $v$ \resp $\psi$ be the
spatial eigendistributions of the respective Hamilton operators, then, the
solutions $u$ of the Wheeler-DeWitt equation are given by $u=wv\psi$, where $w$
satisfies an ODE and $u$ is evaluated at $(t,\de_{ij})$ in the fibers.
| [
{
"created": "Sat, 18 Jun 2022 16:18:25 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Jun 2022 10:43:08 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Aug 2022 16:55:38 GMT",
"version": "v3"
}
] | 2022-08-02 | [
[
"Gerhardt",
"Claus",
""
]
] | We quantize the interaction of gravity with Yang-Mills and spinor fields, hence offering a quantum theory incorporating all four fundamental forces of nature. Let us\ann{as} abbreviate the spatial Hamilton functions of the Standard Model by $H_{SM}$ and the Hamilton function of gravity by $H_G$. Working in a fiber bundle $E$ with base space $\socc=\R[n]$, where the fiber elements are Riemannian metrics, we can express the Hamilton functions in the form $H_G+H_{SM}=H_G+t^{-\frac23}\tilde H_{SM}$ if $n=3$, where $\tilde H_{SM}$ depends on metrics $\s_{ij}$ satisfying $\det{\s_{ij}}=1$. In the quantization process, we quantize $H_G$ for general $\s_{ij}$ but $\tilde H_{SM}$ only for $\s_{ij}=\de_{ij}$ by the usual methods of QFT. Let $v$ \resp $\psi$ be the spatial eigendistributions of the respective Hamilton operators, then, the solutions $u$ of the Wheeler-DeWitt equation are given by $u=wv\psi$, where $w$ satisfies an ODE and $u$ is evaluated at $(t,\de_{ij})$ in the fibers. |
gr-qc/9809035 | Masahiro Hotta | Masahiro Hotta | Asymptotic Isometry and Two Dimensional Anti-de Sitter Gravity | 22 pages, No Figures | null | null | TU-553 | gr-qc | null | We analyze canonical asymptotic isometry of two dimensional AdS dilaton
gravity in detail.
| [
{
"created": "Wed, 9 Sep 1998 07:33:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hotta",
"Masahiro",
""
]
] | We analyze canonical asymptotic isometry of two dimensional AdS dilaton gravity in detail. |
gr-qc/0402011 | Xinhe Meng | Xin-He Meng, Peng Wang (Nankai U.) | $R^2$ corrections to the cosmological dynamics of inflation in the
Palatini formulation | 11 pages, no figures. Accepted by Class.Quant.Grav.v2:References
added | Class.Quant.Grav. 21 (2004) 2029-2036 | 10.1088/0264-9381/21/8/008 | null | gr-qc | null | We investigate the corrections to the inflationary cosmological dynamics due
to a $R^2$ term in the Palatini formulation which may arise as quantum
corrections to the effective Lagrangian in early universe. We found that the
standard Friedmann equation will not be changed when the scalar field is in the
potential energy dominated era. However, in the kinetic energy dominated era,
the standard Friedmann equation will be modified and in the case of closed and
flat universe, the Modified Friedmann equation will automatically require that
the initial kinetic energy density of the scalar field must be in sub-Planckian
scale.
| [
{
"created": "Tue, 3 Feb 2004 05:15:16 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Feb 2004 04:39:34 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Meng",
"Xin-He",
"",
"Nankai U."
],
[
"Wang",
"Peng",
"",
"Nankai U."
]
] | We investigate the corrections to the inflationary cosmological dynamics due to a $R^2$ term in the Palatini formulation which may arise as quantum corrections to the effective Lagrangian in early universe. We found that the standard Friedmann equation will not be changed when the scalar field is in the potential energy dominated era. However, in the kinetic energy dominated era, the standard Friedmann equation will be modified and in the case of closed and flat universe, the Modified Friedmann equation will automatically require that the initial kinetic energy density of the scalar field must be in sub-Planckian scale. |
1309.5699 | Juhua Chen | Hai Huang, Juhua Chen, Yongjiu Wang | Distribution of Entropy of Bardeen Regular Black Hole with Corrected
State Density | 11 pages, 11 figures, 1 table. Int. J. Theor. Phys. 2013 | Int J Theor Phys (2014) 53:249 | 10.1007/s10773-013-1803-0 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | We consider corrections to all orders in the Planck length on the quantum
state density, and calculate the statistical entropy of the scalar field on the
background of the Bardeen regular black hole numerically. We obtain the
distribution of entropy which is inside the horizon of black hole and the
contribution of the vicinity of horizon takes a great part of the whole
entropy.
| [
{
"created": "Mon, 23 Sep 2013 06:08:21 GMT",
"version": "v1"
}
] | 2014-08-28 | [
[
"Huang",
"Hai",
""
],
[
"Chen",
"Juhua",
""
],
[
"Wang",
"Yongjiu",
""
]
] | We consider corrections to all orders in the Planck length on the quantum state density, and calculate the statistical entropy of the scalar field on the background of the Bardeen regular black hole numerically. We obtain the distribution of entropy which is inside the horizon of black hole and the contribution of the vicinity of horizon takes a great part of the whole entropy. |
gr-qc/0405132 | Lukas Saul | Lukas A. Saul | The Dynamic Space of General Relativity in Second Atomization | 17 pages, 0 figures. To appear in NovaPublishers "Progress in General
Relativity and Quantum Cosmology Research" | General Relativity Research Trends, Horizons in World Physics vol.
249. Albert Reimer, ed.; pp. 153-172, 2005 | null | null | gr-qc | null | The notion that the geometry of our space-time is not only a static
background but can be physically dynamic is well established in general
relativity. Geometry can be described as shaped by the presence of matter,
where such shaping manifests itself as gravitational force. We consider here
probabilistic or atomistic models of such space-time, in which the active
geometry emerges from a statistical distribution of 'atoms'. Such atoms are not
to be confused with their chemical counterparts, however the shift of
perspective obtained in analyzing a gas via its molecules rather than its bulk
properties is analogous to this "second atomization". In this atomization,
space-time itself (i.e. the meter and the second) is effectively atomized, so
the atoms themselves must exist in a 'subspace'.
Here we build a simple model of such a space-time from the ground up,
establishing a route for more complete theories, and enabling a review of
recent work. We first introduce the motivation behind statistical
interpretations and atomism, and look at applications to the realm of dynamic
space-time theories. We then consider models of kinetic media in subspace
compatible with our understanding of light. From the equations governing the
propagation of light in subspace we can build a metric geometry, describing the
dynamic and physical space-time of general relativity. Finally, implications of
the theory on current frontiers of general relativity including cosmology,
black holes, and quantum gravity are discussed.
| [
{
"created": "Wed, 26 May 2004 18:03:24 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Aug 2005 19:36:13 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Saul",
"Lukas A.",
""
]
] | The notion that the geometry of our space-time is not only a static background but can be physically dynamic is well established in general relativity. Geometry can be described as shaped by the presence of matter, where such shaping manifests itself as gravitational force. We consider here probabilistic or atomistic models of such space-time, in which the active geometry emerges from a statistical distribution of 'atoms'. Such atoms are not to be confused with their chemical counterparts, however the shift of perspective obtained in analyzing a gas via its molecules rather than its bulk properties is analogous to this "second atomization". In this atomization, space-time itself (i.e. the meter and the second) is effectively atomized, so the atoms themselves must exist in a 'subspace'. Here we build a simple model of such a space-time from the ground up, establishing a route for more complete theories, and enabling a review of recent work. We first introduce the motivation behind statistical interpretations and atomism, and look at applications to the realm of dynamic space-time theories. We then consider models of kinetic media in subspace compatible with our understanding of light. From the equations governing the propagation of light in subspace we can build a metric geometry, describing the dynamic and physical space-time of general relativity. Finally, implications of the theory on current frontiers of general relativity including cosmology, black holes, and quantum gravity are discussed. |
gr-qc/9506052 | null | L.H. Ford and Thomas A. Roman | Averaged Energy Conditions and Evaporating Black Holes | Sections 2.1 and 2.2 have been revised and some erroneous statements
corrected. The main conclusions and the figures are unchanged. 27 pp, plain
Latex, 3 figures available upon request | Phys.Rev. D53 (1996) 1988-2000 | 10.1103/PhysRevD.53.1988 | MIT-CTP-2446 and TUTP 95-1 | gr-qc hep-th | null | In this paper the averaged weak (AWEC) and averaged null (ANEC) energy
conditions, together with uncertainty principle-type restrictions on negative
energy (``quantum inequalities''), are examined in the context of evaporating
black hole backgrounds in both two and four dimensions. In particular,
integrals over only half-geodesics are studied. We determine the regions of the
spacetime in which the averaged energy conditions are violated. In all cases
where these conditions fail, there appear to be quantum inequalities which
bound the magnitude and extent of the negative energy, and hence the degree of
the violation. The possible relevance of these results for the validity of
singularity theorems in evaporating black hole spacetimes is discussed.
| [
{
"created": "Fri, 23 Jun 1995 22:39:30 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Dec 1995 02:35:37 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Ford",
"L. H.",
""
],
[
"Roman",
"Thomas A.",
""
]
] | In this paper the averaged weak (AWEC) and averaged null (ANEC) energy conditions, together with uncertainty principle-type restrictions on negative energy (``quantum inequalities''), are examined in the context of evaporating black hole backgrounds in both two and four dimensions. In particular, integrals over only half-geodesics are studied. We determine the regions of the spacetime in which the averaged energy conditions are violated. In all cases where these conditions fail, there appear to be quantum inequalities which bound the magnitude and extent of the negative energy, and hence the degree of the violation. The possible relevance of these results for the validity of singularity theorems in evaporating black hole spacetimes is discussed. |
gr-qc/9904053 | Yasusada Nambu | Yasusada Nambu and Yoshiyuki Y. Yamaguchi | Renormalization of Long-wavelength Solution of Einstein Equation | 12 pages, 1 figure, typeset by REVTeX | Phys.Rev. D60 (1999) 104011 | 10.1103/PhysRevD.60.104011 | DPNU-99-09 | gr-qc astro-ph nlin.PS patt-sol | null | Using the renormalization group method, we improved the first order solution
of the long-wavelength expansion of the Einstein equation. By assuming that the
renormalization group transformation has the property of Lie group, we can
regularize the secular divergence caused by the spatial gradient terms and
absorb it to the background seed metric. The solution of the renormalization
group equation shows that the renormalized metric describes the behavior of
gravitational collapse in the expanding universe qualitatively well.
| [
{
"created": "Wed, 21 Apr 1999 09:03:40 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Nambu",
"Yasusada",
""
],
[
"Yamaguchi",
"Yoshiyuki Y.",
""
]
] | Using the renormalization group method, we improved the first order solution of the long-wavelength expansion of the Einstein equation. By assuming that the renormalization group transformation has the property of Lie group, we can regularize the secular divergence caused by the spatial gradient terms and absorb it to the background seed metric. The solution of the renormalization group equation shows that the renormalized metric describes the behavior of gravitational collapse in the expanding universe qualitatively well. |
1011.0843 | Valentin Gladush | Valentin D. Gladush and Marina V. Galadgyi | Some peculiarities of motion of neutral and charged test particles in
the field of a spherically symmetric charged object in General Relativity | 15 pages, 9 figures | Gen.Rel.Grav.43:1347-1363,2011 | 10.1007/s10714-010-1119-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose the method of investigation of radial motions for charged and
neutral test particles in the Reissner-Nordstr\"{o}m field by means of mass
potential. In this context we analyze special features of interaction of
charges and their motions in General Relativity and construct the radial motion
classification. For test particles and a central source with charges $q$ and
$Q$, respectively, the conditions of attraction (when $qQ>0$) and repulsion
(when $qQ<0$) are obtained. The conditions of motionless test particle states
with respect to the central source are investigated and, in addition, stability
conditions for such static equilibrium states are found. It is shown that
stable states are possible only for the bound states of weakly charged
particles in the field of a naked singularity. Frequencies of small
oscillations of test particles near their equilibrium positions are also found.
| [
{
"created": "Wed, 3 Nov 2010 10:43:58 GMT",
"version": "v1"
}
] | 2011-04-22 | [
[
"Gladush",
"Valentin D.",
""
],
[
"Galadgyi",
"Marina V.",
""
]
] | We propose the method of investigation of radial motions for charged and neutral test particles in the Reissner-Nordstr\"{o}m field by means of mass potential. In this context we analyze special features of interaction of charges and their motions in General Relativity and construct the radial motion classification. For test particles and a central source with charges $q$ and $Q$, respectively, the conditions of attraction (when $qQ>0$) and repulsion (when $qQ<0$) are obtained. The conditions of motionless test particle states with respect to the central source are investigated and, in addition, stability conditions for such static equilibrium states are found. It is shown that stable states are possible only for the bound states of weakly charged particles in the field of a naked singularity. Frequencies of small oscillations of test particles near their equilibrium positions are also found. |
1508.01052 | Ali Bleybel Dr. | Ali Bleybel and Abdallah Zaiour | A general theorem on temporal foliation of causal sets | null | Found Phys (2018) 48: 456 | 10.1007/s10701-018-0157-0 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show a general theorem of existence of temporal foliations in a general
causal set, under mild constraints. Then we study automorphisms of infinite
causal sets (which satisfy further requirements) and show that they fall under
one of two types:
1) Automorphims that induce automorphisms of spacelike hypersurfaces in some
given foliation (i.e. spacelike automorphisms), or
2) Translation in time.
These results might be useful for quantization of the aforementioned causal
sets.
| [
{
"created": "Wed, 5 Aug 2015 12:34:23 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Oct 2020 14:47:06 GMT",
"version": "v2"
}
] | 2020-10-02 | [
[
"Bleybel",
"Ali",
""
],
[
"Zaiour",
"Abdallah",
""
]
] | We show a general theorem of existence of temporal foliations in a general causal set, under mild constraints. Then we study automorphisms of infinite causal sets (which satisfy further requirements) and show that they fall under one of two types: 1) Automorphims that induce automorphisms of spacelike hypersurfaces in some given foliation (i.e. spacelike automorphisms), or 2) Translation in time. These results might be useful for quantization of the aforementioned causal sets. |
gr-qc/0509019 | Slava G. Turyshev | Juergen Mueller, James G. Williams, Slava G. Turyshev, and Peter J.
Shelus | Potential Capabilities of Lunar Laser Ranging for Geodesy and Relativity | 7 pages, 7 figures, 2 tables. Talk given at `Dynamic Planet 2005:
Monitoring and Understanding a Dynamic Planet with Geodetic and Oceanographic
Tools,'' a Joint Assembly of International Associations: IAG, IAPSO and IABO,
Cairns, Australia, 22-26 August 2005 | "Dynamic Planet", P. Tregoning, C. Rizos (eds.), IAG Symposia
(Springer) 130, 903-909 (2006) | null | null | gr-qc | null | Lunar Laser Ranging (LLR), which has been carried out for more than 35 years,
is used to determine many parameters within the Earth-Moon system. This
includes coordinates of terrestrial ranging stations and that of lunar
retro-reflectors, as well as lunar orbit, gravity field, and its tidal
acceleration. LLR data analysis also performs a number of gravitational physics
experiments such as test of the equivalence principle, search for time
variation of the gravitational constant, and determines value of several metric
gravity parameters. These gravitational physics parameters cause both secular
and periodic effects on the lunar orbit that are detectable with LLR.
Furthermore, LLR contributes to the determination of Earth orientation
parameters (EOP) such as nutation, precession (including relativistic
precession), polar motion, and UT1. The corresponding LLR EOP series is three
decades long. LLR can be used for the realization of both the terrestrial and
selenocentric reference frames. The realization of a dynamically defined
inertial reference frame, in contrast to the kinematically realized frame of
VLBI, offers new possibilities for mutual cross-checking and confirmation.
Finally, LLR also investigates the processes related to the Moon's interior
dynamics. Here, we review the LLR technique focusing on its impact on Geodesy
and Relativity. We discuss the modern observational accuracy and the level of
existing LLR modeling. We present the near-term objectives and emphasize
improvements needed to fully utilize the scientific potential of LLR.
| [
{
"created": "Tue, 6 Sep 2005 19:09:54 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Dec 2005 01:14:21 GMT",
"version": "v2"
}
] | 2009-09-29 | [
[
"Mueller",
"Juergen",
""
],
[
"Williams",
"James G.",
""
],
[
"Turyshev",
"Slava G.",
""
],
[
"Shelus",
"Peter J.",
""
]
] | Lunar Laser Ranging (LLR), which has been carried out for more than 35 years, is used to determine many parameters within the Earth-Moon system. This includes coordinates of terrestrial ranging stations and that of lunar retro-reflectors, as well as lunar orbit, gravity field, and its tidal acceleration. LLR data analysis also performs a number of gravitational physics experiments such as test of the equivalence principle, search for time variation of the gravitational constant, and determines value of several metric gravity parameters. These gravitational physics parameters cause both secular and periodic effects on the lunar orbit that are detectable with LLR. Furthermore, LLR contributes to the determination of Earth orientation parameters (EOP) such as nutation, precession (including relativistic precession), polar motion, and UT1. The corresponding LLR EOP series is three decades long. LLR can be used for the realization of both the terrestrial and selenocentric reference frames. The realization of a dynamically defined inertial reference frame, in contrast to the kinematically realized frame of VLBI, offers new possibilities for mutual cross-checking and confirmation. Finally, LLR also investigates the processes related to the Moon's interior dynamics. Here, we review the LLR technique focusing on its impact on Geodesy and Relativity. We discuss the modern observational accuracy and the level of existing LLR modeling. We present the near-term objectives and emphasize improvements needed to fully utilize the scientific potential of LLR. |
gr-qc/0310079 | Hajime Sotani | Hajime Sotani, Kazunori Kohri and Tomohiro Harada | Restricting quark matter models by gravitational wave observation | To appear in Phys. Rev. D | Phys.Rev. D69 (2004) 084008 | 10.1103/PhysRevD.69.084008 | WU-AP/175/03, OU-TAP 220 | gr-qc astro-ph hep-ph | null | We consider the possibilities for obtaining information about the equation of
state for quark matter by using future direct observational data on
gravitational waves. We study the nonradial oscillations of both fluid and
spacetime modes of pure quark stars. If we observe the $f$ and the lowest
$w_{\rm II}$ modes from quark stars, by using the simultaneously obtained
radiation radius we can constrain the bag constant $B$ with reasonable
accuracy, independently of the $s$ quark mass.
| [
{
"created": "Thu, 16 Oct 2003 10:22:23 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Feb 2004 14:09:24 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Sotani",
"Hajime",
""
],
[
"Kohri",
"Kazunori",
""
],
[
"Harada",
"Tomohiro",
""
]
] | We consider the possibilities for obtaining information about the equation of state for quark matter by using future direct observational data on gravitational waves. We study the nonradial oscillations of both fluid and spacetime modes of pure quark stars. If we observe the $f$ and the lowest $w_{\rm II}$ modes from quark stars, by using the simultaneously obtained radiation radius we can constrain the bag constant $B$ with reasonable accuracy, independently of the $s$ quark mass. |
gr-qc/9611047 | Osamu Iguchi | Osamu Iguchi and Hideki Ishihara | Onset of inflation in inhomogeneous cosmology | 22 pages including 12 eps figures, RevTex | Phys.Rev. D56 (1997) 3216-3224 | 10.1103/PhysRevD.56.3216 | TIT/HEP-326/COSMO-71 | gr-qc | null | We study how the initial inhomogeneities of the universe affect the onset of
inflation in the closed universe. We consider the model of a chaotic inflation
which is driven by a massive scalar field. In order to construct an
inhomogeneous universe model, we use the long wavelength approximation ( the
gradient expansion method ). We show the condition of the inhomogeneities for
the universe to enter the inflationary phase.
| [
{
"created": "Wed, 20 Nov 1996 08:33:10 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Iguchi",
"Osamu",
""
],
[
"Ishihara",
"Hideki",
""
]
] | We study how the initial inhomogeneities of the universe affect the onset of inflation in the closed universe. We consider the model of a chaotic inflation which is driven by a massive scalar field. In order to construct an inhomogeneous universe model, we use the long wavelength approximation ( the gradient expansion method ). We show the condition of the inhomogeneities for the universe to enter the inflationary phase. |
2109.09466 | Ugur Camci | Ugur Camci | On Dark Matter As A Geometric Effect in the Galactic Halo | 11 pages, 2, tables, 2 figures; Matches published version in
Astrophysics and Space Science | Astrophys. Space. Sci.366, 91 (2021) | 10.1007/s10509-021-03997-5 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We obtain more straightforwardly some features of dark matter distribution in
the halos of galaxies by considering the spherically symmetric space-time,
which satisfies the flat rotational curve condition, and the geometric equation
of state resulting from the modified gravity theory. In order to measure the
equation of state for dark matter in the galactic halo, we provide a general
formalism taking into account the modified $f(X)$ gravity theories. Here,
$f(X)$ is a general function of $X \in \{ R, \mathcal{G}, T \}$, where $R,
\mathcal{G}$ and $T$ are the Ricci scalar, the Gauss-Bonnet scalar and the
torsion scalar, respectively. These theories yield that the flat rotation
curves appear as a consequence of the additional geometric structure
accommodated by those of modified gravity theories. Constructing a geometric
equation of state $w_{_X} \equiv p_{_X} / \rho_{_X}$ and inspiring by some
values of the equation of state for the ordinary matter, we infer some
properties of dark matter in galactic halos of galaxies.
| [
{
"created": "Fri, 17 Sep 2021 10:52:34 GMT",
"version": "v1"
}
] | 2021-09-21 | [
[
"Camci",
"Ugur",
""
]
] | We obtain more straightforwardly some features of dark matter distribution in the halos of galaxies by considering the spherically symmetric space-time, which satisfies the flat rotational curve condition, and the geometric equation of state resulting from the modified gravity theory. In order to measure the equation of state for dark matter in the galactic halo, we provide a general formalism taking into account the modified $f(X)$ gravity theories. Here, $f(X)$ is a general function of $X \in \{ R, \mathcal{G}, T \}$, where $R, \mathcal{G}$ and $T$ are the Ricci scalar, the Gauss-Bonnet scalar and the torsion scalar, respectively. These theories yield that the flat rotation curves appear as a consequence of the additional geometric structure accommodated by those of modified gravity theories. Constructing a geometric equation of state $w_{_X} \equiv p_{_X} / \rho_{_X}$ and inspiring by some values of the equation of state for the ordinary matter, we infer some properties of dark matter in galactic halos of galaxies. |
1301.4618 | Ken-Ichi Nakao | Ken-ichi Nakao, Masashi Kimura, Mandar Patil, Pankaj S. Joshi | Ultra-high energy collision with neither black hole nor naked
singularity | 27 pages, 1 figure. Equation (B36) in the 1st version of the
manuscript is incorrect, and thus we have corrected it. The result becomes
different from the original one, but the conclusion that the ultra-high
energy collision of particles is possible is unchanged | null | 10.1103/PhysRevD.87.104033 | OCU-PHYS-379, AP-GR-104, YITP-12-101 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the collision between two concentric spherical thin shells. The
inner shell is charged, whereas the outer one is either neutral or charged. In
the situation we consider, the charge of the inner shell is larger than its
gravitational mass, and the inside of it is empty and regular. Hence the domain
just outside it is described by the overcharged Reissner-Nordstrom geometry
whereas the inside of it is Minkowski. First, the inner shell starts to shrink
form infinity with finite kinetic energy, and then the outer shell starts to
shrink from infinity with vanishing kinetic energy. The inner shell bounces on
the potential wall and collides with the ingoing outer shell. The energy of
collision between these shells at "their center of mass frame" does not exceed
the total energy of the system. By contrast, by virtue of the very large gamma
factor of the relative velocity of the shells, the energy of collision between
two of the constituent particles of these shells at their center of mass frame
can be much larger than the Planck scale. This result suggests that the black
hole or naked singularity is not necessary for ultra-high energy collision of
particles.
| [
{
"created": "Sun, 20 Jan 2013 01:05:52 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Mar 2013 23:16:31 GMT",
"version": "v2"
}
] | 2013-05-29 | [
[
"Nakao",
"Ken-ichi",
""
],
[
"Kimura",
"Masashi",
""
],
[
"Patil",
"Mandar",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | We explore the collision between two concentric spherical thin shells. The inner shell is charged, whereas the outer one is either neutral or charged. In the situation we consider, the charge of the inner shell is larger than its gravitational mass, and the inside of it is empty and regular. Hence the domain just outside it is described by the overcharged Reissner-Nordstrom geometry whereas the inside of it is Minkowski. First, the inner shell starts to shrink form infinity with finite kinetic energy, and then the outer shell starts to shrink from infinity with vanishing kinetic energy. The inner shell bounces on the potential wall and collides with the ingoing outer shell. The energy of collision between these shells at "their center of mass frame" does not exceed the total energy of the system. By contrast, by virtue of the very large gamma factor of the relative velocity of the shells, the energy of collision between two of the constituent particles of these shells at their center of mass frame can be much larger than the Planck scale. This result suggests that the black hole or naked singularity is not necessary for ultra-high energy collision of particles. |
0811.1446 | Diego Pavon | Diego Pavon and Anjan A. Sen | The Interaction Rate in Holographic Models of Dark Energy | 8 pages, 2 figures. Key words: cosmology, holography, late
accelerated expansion, dark energy. To appear in the Proceedings of the
Spanish Relativity Meeting held in Salamanca (Spain) in September 2008. Uses
AIP style | AIP Conf.Proc.1122:156-163,2009 | 10.1063/1.3141240 | null | gr-qc astro-ph hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observational data from supernovae type Ia, baryon acoustic oscillations, gas
mass fraction in galaxy clusters, and the growth factor are used to reconstruct
the the interaction rate of the holographic dark energy model recently proposed
by Zimdahl and Pav\'{o}n [1] in the redshift interval $0 < z < 1.8$. It shows a
reasonable behavior as it increases with expansion from a small or vanishing
value in the far past and begins decreasing at recent times. This suggests that
the equation of state parameter of dark energy does not cross the phantom
divide line.
| [
{
"created": "Mon, 10 Nov 2008 11:10:52 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Pavon",
"Diego",
""
],
[
"Sen",
"Anjan A.",
""
]
] | Observational data from supernovae type Ia, baryon acoustic oscillations, gas mass fraction in galaxy clusters, and the growth factor are used to reconstruct the the interaction rate of the holographic dark energy model recently proposed by Zimdahl and Pav\'{o}n [1] in the redshift interval $0 < z < 1.8$. It shows a reasonable behavior as it increases with expansion from a small or vanishing value in the far past and begins decreasing at recent times. This suggests that the equation of state parameter of dark energy does not cross the phantom divide line. |
1902.00400 | Alex Giacomini | Fabrizio Canfora, Nikolaos Dimakis, Alex Giacomini, Andronikos
Paliathanasis | Bianchi IX cosmologies in the Einstein-Skyrme system in a sector with
non-trivial topological charge | LaTeX, 31 pages. Accepted for publication in Physical Review D | Phys. Rev. D 99, 044035 (2019) | 10.1103/PhysRevD.99.044035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of the most general Bianchi IX cosmology with three time
dependent scale factors for the Einstein-Skyrme system is analyzed. For the
Skyrmion, a generalized hedgehog ansatz with unit baryon charge is introduced.
The most remarkable feature of this ansatz is that, in the above topologically
non-trivial sector with unit topological charge, the Skyrme field equations are
identically satisfied on any Bianchi IX metric. We will show that due to this
feature the complete set of coupled Einstein-Skyrme field equations can be
deduced from a suitable minisuperspace Lagrangian. The latter allows to perform
a systematic study of the integrability properties of the Einstein-Skyrme
system for the Bianchi IX cosmology. Moreover, some analytic and algebraic
solutions for the Einstein-Skyrme model are derived. Another remarkable
consequence of the present formalism is that it is possible to derive the
Wheeler de-Witt equation for the Bianchi IX metric in the Einstein-Skyrme
cosmology in which all the effects of the Skyrmion are encoded in an effective
potential of the minisuperspace Lagrangian.
| [
{
"created": "Fri, 1 Feb 2019 15:25:44 GMT",
"version": "v1"
}
] | 2019-03-06 | [
[
"Canfora",
"Fabrizio",
""
],
[
"Dimakis",
"Nikolaos",
""
],
[
"Giacomini",
"Alex",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | The dynamics of the most general Bianchi IX cosmology with three time dependent scale factors for the Einstein-Skyrme system is analyzed. For the Skyrmion, a generalized hedgehog ansatz with unit baryon charge is introduced. The most remarkable feature of this ansatz is that, in the above topologically non-trivial sector with unit topological charge, the Skyrme field equations are identically satisfied on any Bianchi IX metric. We will show that due to this feature the complete set of coupled Einstein-Skyrme field equations can be deduced from a suitable minisuperspace Lagrangian. The latter allows to perform a systematic study of the integrability properties of the Einstein-Skyrme system for the Bianchi IX cosmology. Moreover, some analytic and algebraic solutions for the Einstein-Skyrme model are derived. Another remarkable consequence of the present formalism is that it is possible to derive the Wheeler de-Witt equation for the Bianchi IX metric in the Einstein-Skyrme cosmology in which all the effects of the Skyrmion are encoded in an effective potential of the minisuperspace Lagrangian. |
1501.00107 | Ilya Kirnos Vasilyevich | Ilya V. Kirnos | Some Cosmological Solutions in an Arbitrary Order of Lovelock Gravity | 5 pages | Gravitation and Cosmology, 2012, Vol. 18, No. 4, pp. 259-261 | 10.1134/S0202289312040068 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Lovelock theory of gravity that assumes a nonlinearity of the
field equations in the second-order derivatives of the metric. We prove the
opportunity of obtaining cosmological solutions without isotropization in the
presence of matter in the form of a perfect fluid, which is necessary for
invisibility of extra dimensions that inevitably emerge in the Lovelock theory.
In particular, the Jacobs solution has been generalized to an arbitrary order
of the theory, and in the third order, an anisotropic exponential solution has
been found.
| [
{
"created": "Wed, 31 Dec 2014 10:49:19 GMT",
"version": "v1"
}
] | 2015-01-05 | [
[
"Kirnos",
"Ilya V.",
""
]
] | We consider the Lovelock theory of gravity that assumes a nonlinearity of the field equations in the second-order derivatives of the metric. We prove the opportunity of obtaining cosmological solutions without isotropization in the presence of matter in the form of a perfect fluid, which is necessary for invisibility of extra dimensions that inevitably emerge in the Lovelock theory. In particular, the Jacobs solution has been generalized to an arbitrary order of the theory, and in the third order, an anisotropic exponential solution has been found. |
2009.05016 | Carlo Rovelli | Fabio D'Ambrosio, Marios Christodoulou, Pierre Martin-Dussaud, Carlo
Rovelli, Farshid Soltani | The End of a Black Hole's Evaporation -- Part I | 11 pages, 10 figures | Phys. Rev. D 103, 106014 (2021) | 10.1103/PhysRevD.103.106014 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | At the end of Hawking evaporation, the horizon of a black hole enters a
physical region where quantum gravity cannot be neglected. The physics of this
region has not been much explored. We characterise its physics and introduce a
technique to study it.
| [
{
"created": "Thu, 10 Sep 2020 17:31:16 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Feb 2021 21:38:04 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"D'Ambrosio",
"Fabio",
""
],
[
"Christodoulou",
"Marios",
""
],
[
"Martin-Dussaud",
"Pierre",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Soltani",
"Farshid",
""
]
] | At the end of Hawking evaporation, the horizon of a black hole enters a physical region where quantum gravity cannot be neglected. The physics of this region has not been much explored. We characterise its physics and introduce a technique to study it. |
gr-qc/0512067 | J. Ponce de Leon | J. Ponce de Leon | Extra symmetry in the field equations in 5D with spatial spherical
symmetry | Typos corrected. Accepted for publication in Classical and Quantum
Gravity | Class.Quant.Grav.23:3043-3052,2006 | 10.1088/0264-9381/23/9/017 | null | gr-qc | null | We point out that the field equations in 5D, with spatial spherical symmetry,
possess an extra symmetry that leaves them invariant. This symmetry corresponds
to certain simultaneous interchange of coordinates and metric coefficients. As
a consequence a single solution in 5D can generate very different scenarios in
4D, ranging from static configurations to cosmological situations. A new
perspective emanates from our work. Namely, that different astrophysical and
cosmological scenarios in 4D might correspond to the same physics in 5D. We
present explicit examples that illustrate this point of view.
| [
{
"created": "Mon, 12 Dec 2005 07:15:04 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Mar 2006 15:48:27 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"de Leon",
"J. Ponce",
""
]
] | We point out that the field equations in 5D, with spatial spherical symmetry, possess an extra symmetry that leaves them invariant. This symmetry corresponds to certain simultaneous interchange of coordinates and metric coefficients. As a consequence a single solution in 5D can generate very different scenarios in 4D, ranging from static configurations to cosmological situations. A new perspective emanates from our work. Namely, that different astrophysical and cosmological scenarios in 4D might correspond to the same physics in 5D. We present explicit examples that illustrate this point of view. |
2210.07257 | Parampreet Singh | A. Meenakshi McNamara, Sahil Saini, Parampreet Singh | On a novel relationship between shear and energy density at the bounce
in non-singular Bianchi-I spacetimes | 24 pages, 12 figures. A figure added to discuss cigar like approach
in ekpyrotic model. Published version in Phys. Rev. D | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In classical Bianchi-I spacetimes, underlying conditions for what dictates
the singularity structure - whether it is anisotropic shear or energy density,
can be easily determined from the generalized Friedmann equation. However, in
non-singular bouncing anisotropic models these insights are difficult to obtain
in the quantum gravity regime where the singularity is resolved at a
non-vanishing mean volume which can be large compared to the Planck volume,
depending on the initial conditions. Such non-singular models may also lack a
generalized Friedmann equation making the task even more difficult. We address
this problem in an effective spacetime description of loop quantum cosmology
(LQC) where energy density and anisotropic shear are universally bounded due to
quantum geometry effects, but a generalized Friedmann equation has been
difficult to derive due to the underlying complexity. Performing extensive
numerical simulations of effective Hamiltonian dynamics, we bring to light a
surprising, seemingly universal relationship between energy density and
anisotropic shear at the bounce in LQC. For a variety of initial conditions for
a massless scalar field, an inflationary potential, and two types of ekpyrotic
potentials we find that the values of energy density and the anisotropic shear
at the quantum bounce follow a novel parabolic relationship which reveals some
surprising results about the anisotropic nature of the bounce, such as the
maximum value of the anisotropic shear at the bounce is reached when the energy
density reaches approximately half of its maximum allowed value. The
relationship we find can prove very useful for developing our understanding of
the degree of anisotropy of the bounce, isotropization of the post-bounce
universe, and discovering the modified generalized Friedmann equation in
Bianchi-I models with quantum gravity corrections.
| [
{
"created": "Thu, 13 Oct 2022 18:00:06 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Dec 2022 12:02:56 GMT",
"version": "v2"
}
] | 2022-12-29 | [
[
"McNamara",
"A. Meenakshi",
""
],
[
"Saini",
"Sahil",
""
],
[
"Singh",
"Parampreet",
""
]
] | In classical Bianchi-I spacetimes, underlying conditions for what dictates the singularity structure - whether it is anisotropic shear or energy density, can be easily determined from the generalized Friedmann equation. However, in non-singular bouncing anisotropic models these insights are difficult to obtain in the quantum gravity regime where the singularity is resolved at a non-vanishing mean volume which can be large compared to the Planck volume, depending on the initial conditions. Such non-singular models may also lack a generalized Friedmann equation making the task even more difficult. We address this problem in an effective spacetime description of loop quantum cosmology (LQC) where energy density and anisotropic shear are universally bounded due to quantum geometry effects, but a generalized Friedmann equation has been difficult to derive due to the underlying complexity. Performing extensive numerical simulations of effective Hamiltonian dynamics, we bring to light a surprising, seemingly universal relationship between energy density and anisotropic shear at the bounce in LQC. For a variety of initial conditions for a massless scalar field, an inflationary potential, and two types of ekpyrotic potentials we find that the values of energy density and the anisotropic shear at the quantum bounce follow a novel parabolic relationship which reveals some surprising results about the anisotropic nature of the bounce, such as the maximum value of the anisotropic shear at the bounce is reached when the energy density reaches approximately half of its maximum allowed value. The relationship we find can prove very useful for developing our understanding of the degree of anisotropy of the bounce, isotropization of the post-bounce universe, and discovering the modified generalized Friedmann equation in Bianchi-I models with quantum gravity corrections. |
0710.0301 | Jose Geraldo Pereira | H. I. Arcos and J. G. Pereira | Spacetime: Arena or Reality? | Chapter in the book "Relativity and the Dimensionality of the World",
Springer series "Fundamental Theories of Physics", Vol. 153 (2007). Volume
Editor: Vesselin Petkov | null | 10.1007/978-1-4020-6318-3_12 | null | gr-qc hep-th | null | For small values of the mass (in relation to the angular momentum and
electric charge), the Kerr-Newman (KN) solution of Einstein equation reduces to
a naked singularity of circular shape. By considering the Hawking and Ellis
extended interpretation of the KN spacetime, as well as Wheeler's idea of
"charge without charge", the non-trivial topological structure of the extended
KN spatial section is found to represent gravitational states with
half-integral angular momentum. As a consequence, it can be consistently
interpreted as a model for the electron-positron system, in which the concepts
of mass, charge and spin emerge from the spacetime geometry. According to this
model, therefore, instead of a simple arena, spacetime must have a concrete
existence, being responsible -- through its highly non-trivial topological
structures -- for the building blocks of (at least some of) the existing matter
in the universe.
| [
{
"created": "Mon, 1 Oct 2007 14:01:09 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Arcos",
"H. I.",
""
],
[
"Pereira",
"J. G.",
""
]
] | For small values of the mass (in relation to the angular momentum and electric charge), the Kerr-Newman (KN) solution of Einstein equation reduces to a naked singularity of circular shape. By considering the Hawking and Ellis extended interpretation of the KN spacetime, as well as Wheeler's idea of "charge without charge", the non-trivial topological structure of the extended KN spatial section is found to represent gravitational states with half-integral angular momentum. As a consequence, it can be consistently interpreted as a model for the electron-positron system, in which the concepts of mass, charge and spin emerge from the spacetime geometry. According to this model, therefore, instead of a simple arena, spacetime must have a concrete existence, being responsible -- through its highly non-trivial topological structures -- for the building blocks of (at least some of) the existing matter in the universe. |
2406.00579 | Jieci Wang | Wentao Liu, Di Wu, Xiongjun Fang, Jiliang Jing, Jieci Wang | Kerr-MOG-(A)dS black hole and its shadow in scalar-tensor-vector gravity
theory | 13 pages, 32 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The scalar-tensor-vector gravity (STVG) theory has attracted significant
interest due to its ability to effectively address the issue of galaxy rotation
curves and clusters of galaxies without considering the influence of dark
matter. In this paper, we construct rotating black hole solutions with a
cosmological constant in the STVG theory (i.e., Kerr-MOG-(A)dS black hole
solutions), where the import of a gravitational charge as a source modifies the
gravitational constant, determined by $ G=G_{\text{N}}(1+\alpha) $. For
Kerr-MOG-dS spacetime, the observer is situated at a specific location within
the domain of outer communication, rather than being located infinitely far
away. Since black hole shadows are shaped by light propagation in spacetime,
the interaction between the MOG parameter and the cosmological constant is
expected to produce novel effects on these shadows. As the cosmological
constant $\Lambda$ increases, the apparent size of the black hole shadow
decreases. Additionally, the shadow expands with an increase in the MOG
parameter $\alpha$, reaching a maximum at a certain value, and its shape
becomes more rounded under an arbitrary rotation parameter, which leads to
degeneracy between different black hole parameters. However, by employing
numerical ray-tracing techniques, we have found that gravitational lensing and
the frame-dragging effect effectively distinguish this degeneracy. Our work
contributes to a deeper understanding of black holes in modified gravity, their
observational signatures, and constraints.
| [
{
"created": "Sun, 2 Jun 2024 00:05:35 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jun 2024 08:03:27 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Jul 2024 11:43:28 GMT",
"version": "v3"
}
] | 2024-07-19 | [
[
"Liu",
"Wentao",
""
],
[
"Wu",
"Di",
""
],
[
"Fang",
"Xiongjun",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Wang",
"Jieci",
""
]
] | The scalar-tensor-vector gravity (STVG) theory has attracted significant interest due to its ability to effectively address the issue of galaxy rotation curves and clusters of galaxies without considering the influence of dark matter. In this paper, we construct rotating black hole solutions with a cosmological constant in the STVG theory (i.e., Kerr-MOG-(A)dS black hole solutions), where the import of a gravitational charge as a source modifies the gravitational constant, determined by $ G=G_{\text{N}}(1+\alpha) $. For Kerr-MOG-dS spacetime, the observer is situated at a specific location within the domain of outer communication, rather than being located infinitely far away. Since black hole shadows are shaped by light propagation in spacetime, the interaction between the MOG parameter and the cosmological constant is expected to produce novel effects on these shadows. As the cosmological constant $\Lambda$ increases, the apparent size of the black hole shadow decreases. Additionally, the shadow expands with an increase in the MOG parameter $\alpha$, reaching a maximum at a certain value, and its shape becomes more rounded under an arbitrary rotation parameter, which leads to degeneracy between different black hole parameters. However, by employing numerical ray-tracing techniques, we have found that gravitational lensing and the frame-dragging effect effectively distinguish this degeneracy. Our work contributes to a deeper understanding of black holes in modified gravity, their observational signatures, and constraints. |
gr-qc/0504085 | Clifford M. Will | Clifford M. Will | Special Relativity: A Centenary Perspective | 24 pages, 4 figures, to be published in the proceedings of the 2005
Seminaire Poincare held in Paris, 09 April 2005 | Einstein, 1905-2005: Poincare Seminar 2005, ed. T. Damour, O.
Darrigol, B. Duplantier and V. Rivasseau (Birkhauser, Basel 2006), pp. 33-58 | 10.1007/3-7643-7436-5_2 | null | gr-qc | null | This article is a partly pedagogical, partly historical and partly technical
review of special relativity and its experimental foundations, in honor of the
centenary of Einstein's annus mirabilis.
| [
{
"created": "Tue, 19 Apr 2005 16:10:03 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Will",
"Clifford M.",
""
]
] | This article is a partly pedagogical, partly historical and partly technical review of special relativity and its experimental foundations, in honor of the centenary of Einstein's annus mirabilis. |
0907.2788 | Vincenzo Branchina | Vincenzo Branchina, Marco Di Liberto, Ivano Lodato | Dark energy and Josephson junctions | 9 pages, no figures | JCAP 0908:011,2009 | 10.1088/1475-7516/2009/08/011 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been recently claimed that dark energy can be (and has been) observed
in laboratory experiments by measuring the power spectrum $S_I(\omega)$ of the
noise current in a resistively shunted Josephson junction and that in new
dedicated experiments, which will soon test a higher frequency range,
$S_I(\omega)$ should show a deviation from the linear rising observed in the
lower frequency region because higher frequencies should not contribute to dark
energy. Based on previous work on theoretical aspects of the
fluctuation-dissipation theorem, we carefully investigate these issues and show
that these claims are based on a misunderstanding of the physical origin of the
spectral function $S_I(\omega)$. According to our analysis, dark energy has
never been (and will never be) observed in Josephson junctions experiments. We
also predict that no deviation from the linear rising behavior of $S_I(\omega)$
will be observed in forthcoming experiments. Our findings provide new (we
believe definite) arguments which strongly support previous criticisms.
| [
{
"created": "Thu, 16 Jul 2009 09:09:21 GMT",
"version": "v1"
}
] | 2009-09-01 | [
[
"Branchina",
"Vincenzo",
""
],
[
"Di Liberto",
"Marco",
""
],
[
"Lodato",
"Ivano",
""
]
] | It has been recently claimed that dark energy can be (and has been) observed in laboratory experiments by measuring the power spectrum $S_I(\omega)$ of the noise current in a resistively shunted Josephson junction and that in new dedicated experiments, which will soon test a higher frequency range, $S_I(\omega)$ should show a deviation from the linear rising observed in the lower frequency region because higher frequencies should not contribute to dark energy. Based on previous work on theoretical aspects of the fluctuation-dissipation theorem, we carefully investigate these issues and show that these claims are based on a misunderstanding of the physical origin of the spectral function $S_I(\omega)$. According to our analysis, dark energy has never been (and will never be) observed in Josephson junctions experiments. We also predict that no deviation from the linear rising behavior of $S_I(\omega)$ will be observed in forthcoming experiments. Our findings provide new (we believe definite) arguments which strongly support previous criticisms. |
gr-qc/0212085 | Joan Ferrando | J.J. Ferrando (U. de Val\`encia), J.A. S\'aez (U. de Val\`encia) | A Rainich-like approach to the Killing-Yano tensors | 19 pages, 0 figures | Gen. Rel. Grav. 35 (2002) 1191 | 10.1023/A:1024493607191 | null | gr-qc | null | The Rainich problem for the Killing-Yano tensors posed by Collinson
\cite{col} is solved. In intermediate steps, we first obtain the necessary and
sufficient conditions for a 2+2 almost-product structure to determine the
principal 2--planes of a skew-symmetric Killing-Yano tensor and then we give
the additional conditions on a symmetric Killing tensor for it to be the square
of a Killing-Yano tensor.We also analyze a similar problem for the conformal
Killing-Yano and the conformal Killing tensors. Our results show that, in both
cases, the principal 2--planes define a maxwellian structure. The associated
Maxwell fields are obtained and we outline how this approach is of interest in
studying the spacetimes that admit these kind of first integrals of the
geodesic equation.
| [
{
"created": "Fri, 20 Dec 2002 14:44:30 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jan 2003 18:06:11 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Ferrando",
"J. J.",
"",
"U. de València"
],
[
"Sáez",
"J. A.",
"",
"U. de València"
]
] | The Rainich problem for the Killing-Yano tensors posed by Collinson \cite{col} is solved. In intermediate steps, we first obtain the necessary and sufficient conditions for a 2+2 almost-product structure to determine the principal 2--planes of a skew-symmetric Killing-Yano tensor and then we give the additional conditions on a symmetric Killing tensor for it to be the square of a Killing-Yano tensor.We also analyze a similar problem for the conformal Killing-Yano and the conformal Killing tensors. Our results show that, in both cases, the principal 2--planes define a maxwellian structure. The associated Maxwell fields are obtained and we outline how this approach is of interest in studying the spacetimes that admit these kind of first integrals of the geodesic equation. |
1001.4053 | Vladimir Ivashchuk | V. D. Ivashchuk | On analogues of black brane solutions in the model with multicomponent
anisotropic fluid | 8 pages, Latex, references and several equations and examples are
added, typos are eliminated | Phys.Lett.B693:399-403,2010 | 10.1016/j.physletb.2010.08.060 | IGC-PFUR/22-01-10 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A family of spherically symmetric solutions with horizon in the model with
m-component anisotropic fluid is presented. The metrics are defined on a
manifold that contains a product of n-1 Ricci-flat "internal" spaces. The
equation of state for any s-th component is defined by a vector U^s belonging
to R^{n + 1}. The solutions are governed by moduli functions H_s obeying
non-linear differential equations with certain boundary conditions imposed. A
simulation of black brane solutions in the model with antisymmetric forms is
considered. An example of solution imitating M_2-M_5 configuration (in D =11
supergravity) corresponding to Lie algebra A_2 is presented.
| [
{
"created": "Fri, 22 Jan 2010 18:07:19 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Apr 2010 11:14:28 GMT",
"version": "v2"
}
] | 2011-04-20 | [
[
"Ivashchuk",
"V. D.",
""
]
] | A family of spherically symmetric solutions with horizon in the model with m-component anisotropic fluid is presented. The metrics are defined on a manifold that contains a product of n-1 Ricci-flat "internal" spaces. The equation of state for any s-th component is defined by a vector U^s belonging to R^{n + 1}. The solutions are governed by moduli functions H_s obeying non-linear differential equations with certain boundary conditions imposed. A simulation of black brane solutions in the model with antisymmetric forms is considered. An example of solution imitating M_2-M_5 configuration (in D =11 supergravity) corresponding to Lie algebra A_2 is presented. |
2309.15439 | Stefano Viaggiu | Stefano Viaggiu | A new class of anisotropic rotating fluids and some throat-like sources
for Kerr metric as examples | Version published on IJMPD, references 34 and 46 corrected | Internation Journal of Modern Physics D, Vol. 32 No 03, 2350008
(2023) | 10.1142/S0218271823500086 | null | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the increasing interest in finding physically viable rotating
sources, we present a new class of anisotropic rotating solutions. The
energy-momentum tensor compatible with the metric is composed of anisotropic
matter with a non-vanishing energy flow around the symmetry axis and vanishing
viscosity. The new class of solutions can be used to find new possible sources
for the Kerr metric, to obtain new regular black hole solutions and to study
galaxies with a central rotating black hole and an halo of dark matter. As an
example, we obtain a 5-parameter class of solutions representing a two-way
traversable wormhole smoothly matched to the Kerr one and satisfying all energy
conditions outside the wormhole for a wide range of parameters, in particular
for compact objects. Finally, with a simple modification of the aforementioned
solution, we obtain a source for Kerr metric with a throat geometry,
non-representing a two-way traversable wormhole and satisfying all energy
conditions.
| [
{
"created": "Wed, 27 Sep 2023 06:59:50 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Oct 2023 19:11:22 GMT",
"version": "v2"
}
] | 2023-10-10 | [
[
"Viaggiu",
"Stefano",
""
]
] | Motivated by the increasing interest in finding physically viable rotating sources, we present a new class of anisotropic rotating solutions. The energy-momentum tensor compatible with the metric is composed of anisotropic matter with a non-vanishing energy flow around the symmetry axis and vanishing viscosity. The new class of solutions can be used to find new possible sources for the Kerr metric, to obtain new regular black hole solutions and to study galaxies with a central rotating black hole and an halo of dark matter. As an example, we obtain a 5-parameter class of solutions representing a two-way traversable wormhole smoothly matched to the Kerr one and satisfying all energy conditions outside the wormhole for a wide range of parameters, in particular for compact objects. Finally, with a simple modification of the aforementioned solution, we obtain a source for Kerr metric with a throat geometry, non-representing a two-way traversable wormhole and satisfying all energy conditions. |
2407.19363 | Bruno Alexandre | Bruno Alexandre | Higgs Mechanism for the Ashtekar Self-Dual Connection | 6 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We introduce the Higgs mechanism for the self-dual spin connection (also
known as the Ashtekar connection), using the Pleba\'{n}ski formulation of
gravity. We develop our formalism within the framework of the chiral action and
derive the equations of motion of the theory. One particular test model is
explored: since anisotropy is an intrinsic property of the theory, a modified
version of the spatially flat Bianchi I model with two different scale factors
is considered. We apply our formalism and derive the Friedmann equations which
regulate the scale factors and the Higgs field. We also present a Proca-like
term for the connection, which when reduced to minisuperspace with a positive
$\Lambda$ yields a De Sitter universe with the solution scaled by a constant
that depends on the mass of the gauge fields. We finally investigate the effect
of these mass terms on gravitational waves and find that the wave equation
remains unchanged relatively to GR; however the Weyl tensor is scaled by a
constant which depends on the mass of the connection components.
| [
{
"created": "Sun, 28 Jul 2024 02:06:29 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Alexandre",
"Bruno",
""
]
] | We introduce the Higgs mechanism for the self-dual spin connection (also known as the Ashtekar connection), using the Pleba\'{n}ski formulation of gravity. We develop our formalism within the framework of the chiral action and derive the equations of motion of the theory. One particular test model is explored: since anisotropy is an intrinsic property of the theory, a modified version of the spatially flat Bianchi I model with two different scale factors is considered. We apply our formalism and derive the Friedmann equations which regulate the scale factors and the Higgs field. We also present a Proca-like term for the connection, which when reduced to minisuperspace with a positive $\Lambda$ yields a De Sitter universe with the solution scaled by a constant that depends on the mass of the gauge fields. We finally investigate the effect of these mass terms on gravitational waves and find that the wave equation remains unchanged relatively to GR; however the Weyl tensor is scaled by a constant which depends on the mass of the connection components. |
2211.11755 | Salvatore Mignemi | S. Meljanac and S. Mignemi | Noncommutative Yang model and its generalizations | 11 pages; version published on Journal of Mathematical Physics | null | 10.1063/5.0135492 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Long time ago, C.N. Yang proposed a model of noncommutative spacetime that
generalized the Snyder model to a curved background. In this paper we review
his proposal and the generalizations that have been suggested during the years.
In particular, we discuss the most general algebras that contain as subalgebras
both de Sitter and Snyder algebras, preserving Lorentz invariance, and are
generated by a two-parameter deformation of the canonical Heisenberg algebra.
We also define their realizations on quantum phase space, giving explicit
examples, both exact and in terms of a perturbative expansion in the
deformation parameters.
| [
{
"created": "Sun, 20 Nov 2022 18:20:08 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Feb 2023 11:23:52 GMT",
"version": "v2"
}
] | 2023-03-08 | [
[
"Meljanac",
"S.",
""
],
[
"Mignemi",
"S.",
""
]
] | Long time ago, C.N. Yang proposed a model of noncommutative spacetime that generalized the Snyder model to a curved background. In this paper we review his proposal and the generalizations that have been suggested during the years. In particular, we discuss the most general algebras that contain as subalgebras both de Sitter and Snyder algebras, preserving Lorentz invariance, and are generated by a two-parameter deformation of the canonical Heisenberg algebra. We also define their realizations on quantum phase space, giving explicit examples, both exact and in terms of a perturbative expansion in the deformation parameters. |
1902.01705 | Telem Ibungochouba Singh | Y.Kenedy Meitei, T. Ibungochouba Singh, I. Ablu Meitei | Quantization of horizon area of Kerr-Newman-de Sitter black hole | Accepted in Chinese Physics Letters | null | 10.1088/0256-307X/36/3/030401 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the adiabatic invariant action and applying Bohr-Sommerfeld
quantization rule and first law of black hole thermodynamics a study of
quantization of entropy and horizon area of Kerr-Newman-de Sitter black hole is
carried out. The same entropy spectrum is obtained in two different coordinate
systems. It is also observed that the spacing of the entropy spectrum is
independent of the black hole parameters and also the corresponding quantum of
horizon area is in agreement with the results of Bekenstein.
| [
{
"created": "Sat, 2 Feb 2019 07:57:42 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Meitei",
"Y. Kenedy",
""
],
[
"Singh",
"T. Ibungochouba",
""
],
[
"Meitei",
"I. Ablu",
""
]
] | Using the adiabatic invariant action and applying Bohr-Sommerfeld quantization rule and first law of black hole thermodynamics a study of quantization of entropy and horizon area of Kerr-Newman-de Sitter black hole is carried out. The same entropy spectrum is obtained in two different coordinate systems. It is also observed that the spacing of the entropy spectrum is independent of the black hole parameters and also the corresponding quantum of horizon area is in agreement with the results of Bekenstein. |
1011.1538 | Farook Rahaman | F. Rahaman, Peter K. F. Kuhfittig, K. Chakraborty, A. A. Usmani and
Saibal Ray | Galactic rotation curves inspired by a noncommutative-geometry
background | 12 pages, 3 figures. Published in Gen.Rel.Grav. 44 (2012) 905-916 | Gen.Rel.Grav. 44 (2012) 905-916 | 10.1007/s10714-011-1320-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper discusses the observed at rotation curves of galaxies in the
context of noncommutative geometry. The energy density of such a geometry is
diffused throughout a region due to the uncertainty encoded in the coordinate
commutator. This intrinsic property appears to be sufficient for producing
stable circular orbits, as well as attractive gravity, without the need for
dark matter.
| [
{
"created": "Sat, 6 Nov 2010 05:41:21 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Sep 2012 18:10:22 GMT",
"version": "v2"
}
] | 2016-11-25 | [
[
"Rahaman",
"F.",
""
],
[
"Kuhfittig",
"Peter K. F.",
""
],
[
"Chakraborty",
"K.",
""
],
[
"Usmani",
"A. A.",
""
],
[
"Ray",
"Saibal",
""
]
] | This paper discusses the observed at rotation curves of galaxies in the context of noncommutative geometry. The energy density of such a geometry is diffused throughout a region due to the uncertainty encoded in the coordinate commutator. This intrinsic property appears to be sufficient for producing stable circular orbits, as well as attractive gravity, without the need for dark matter. |
1010.0241 | Mauro Cattani | M.Cattani | The Schwarzschild geometry and the black holes | 20 pages 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we analyze the predictions of the Einstein gravitation theory
(EGT) on black holes in the framework of the Schwarzschild geometry that is
defined in the vacuum around a spherically symmetric mass distribution, without
charge, not in rotation. The Eddington and Kruskal metrics have been also taken
unto account and the topological connections named wormholes have been
analyzed. This article was written to graduate and postgraduate students of
Physics.
| [
{
"created": "Fri, 1 Oct 2010 19:23:31 GMT",
"version": "v1"
}
] | 2010-10-04 | [
[
"Cattani",
"M.",
""
]
] | In this article we analyze the predictions of the Einstein gravitation theory (EGT) on black holes in the framework of the Schwarzschild geometry that is defined in the vacuum around a spherically symmetric mass distribution, without charge, not in rotation. The Eddington and Kruskal metrics have been also taken unto account and the topological connections named wormholes have been analyzed. This article was written to graduate and postgraduate students of Physics. |
1702.06024 | Ricardo Landim | Ricardo C. G. Landim | Dark Sector Cosmology | 96 pages, PhD thesis (University of Sao Paulo) | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dark side of the universe is mysterious and its nature is still unknown.
In fact, this poses perhaps as the biggest challenge in the modern cosmology.
The two components of the dark sector (dark matter and dark energy) correspond
today to around ninety five percent of the universe. The simplest dark energy
candidate is a cosmological constant. However, this attempt presents a huge
discrepancy of 120 orders of magnitude between the theoretical prediction and
the observed data. Such a huge disparity motivates physicists to look into a
more sophisticated models. This can be done either looking for a deeper
understanding of where the cosmological constant comes from, if one wants to
derive it from first principles, or considering other possibilities for
accelerated expansion, such as modifications of general relativity, additional
matter fields and so on. Still regarding a dynamical dark energy, there may
exist a possibility of interaction between dark energy and dark matter, since
their densities are comparable and, depending on the coupling used, the
interaction can also alleviate the issue of why dark energy and matter
densities are of the same order today. Phenomenological models have been widely
explored in the literature. On the other hand, field theory models that aim a
consistent description of the dark energy/dark matter interaction are still
few. In this thesis, we explore either a scalar or a vector field as a dark
energy candidate in several different approaches, taking into account a
possible interaction between the two components of the dark sector. This thesis
is based on the following papers: 1611.00428, 1605.03550, 1509.04980,
1508.07248, 1507.00902 and 1505.03243. The author also collaborated in the
works 1607.03506 and 1605.05264.
| [
{
"created": "Fri, 17 Feb 2017 13:12:56 GMT",
"version": "v1"
}
] | 2017-02-21 | [
[
"Landim",
"Ricardo C. G.",
""
]
] | The dark side of the universe is mysterious and its nature is still unknown. In fact, this poses perhaps as the biggest challenge in the modern cosmology. The two components of the dark sector (dark matter and dark energy) correspond today to around ninety five percent of the universe. The simplest dark energy candidate is a cosmological constant. However, this attempt presents a huge discrepancy of 120 orders of magnitude between the theoretical prediction and the observed data. Such a huge disparity motivates physicists to look into a more sophisticated models. This can be done either looking for a deeper understanding of where the cosmological constant comes from, if one wants to derive it from first principles, or considering other possibilities for accelerated expansion, such as modifications of general relativity, additional matter fields and so on. Still regarding a dynamical dark energy, there may exist a possibility of interaction between dark energy and dark matter, since their densities are comparable and, depending on the coupling used, the interaction can also alleviate the issue of why dark energy and matter densities are of the same order today. Phenomenological models have been widely explored in the literature. On the other hand, field theory models that aim a consistent description of the dark energy/dark matter interaction are still few. In this thesis, we explore either a scalar or a vector field as a dark energy candidate in several different approaches, taking into account a possible interaction between the two components of the dark sector. This thesis is based on the following papers: 1611.00428, 1605.03550, 1509.04980, 1508.07248, 1507.00902 and 1505.03243. The author also collaborated in the works 1607.03506 and 1605.05264. |
2212.08441 | Rafael Robson Lino dos Santos | Astrid Eichhorn, Rafael R. Lino dos Santos and Fabian Wagner | Shift-symmetric Horndeski gravity in the asymptotic-safety paradigm | 26 pages, 7 figures; references added, text matches the published
version | JCAP 02 (2023) 052 | 10.1088/1475-7516/2023/02/052 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Horndeski gravity is a popular contender for a phenomenological model of
dynamical dark energy, and as such subject to observational constraints. In
this work, we ask whether Horndeski gravity can be more than a phenomenological
model and instead become a fundamental theory, which extends towards high
energy scales and includes quantum effects. We find that within the
asymptotic-safety paradigm, an ultraviolet completion of a simple class of
models of Horndeski gravity is achievable, but places strong constraints on the
couplings of the theory. These constraints are not compatible with dynamical
dark energy. Further, we find a similar result in an effective-field theory
approach to this class of models of Horndeski gravity: under the assumption
that there is no new strongly-coupled physics below the Planck scale, quantum
gravity fluctuations force the Horndeski couplings to be too small to achieve
an explanation of dynamical dark energy.
| [
{
"created": "Fri, 16 Dec 2022 12:40:54 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Mar 2023 13:00:07 GMT",
"version": "v2"
}
] | 2023-03-22 | [
[
"Eichhorn",
"Astrid",
""
],
[
"Santos",
"Rafael R. Lino dos",
""
],
[
"Wagner",
"Fabian",
""
]
] | Horndeski gravity is a popular contender for a phenomenological model of dynamical dark energy, and as such subject to observational constraints. In this work, we ask whether Horndeski gravity can be more than a phenomenological model and instead become a fundamental theory, which extends towards high energy scales and includes quantum effects. We find that within the asymptotic-safety paradigm, an ultraviolet completion of a simple class of models of Horndeski gravity is achievable, but places strong constraints on the couplings of the theory. These constraints are not compatible with dynamical dark energy. Further, we find a similar result in an effective-field theory approach to this class of models of Horndeski gravity: under the assumption that there is no new strongly-coupled physics below the Planck scale, quantum gravity fluctuations force the Horndeski couplings to be too small to achieve an explanation of dynamical dark energy. |
1512.07097 | Nikolay Koshelev Anatolievich | N.A. Koshelev | Effective dark matter fluid with higher derivative corrections | v3: 20 pages, 2 figures, clarified several points, in section 4 added
discussion on the sensitivity of the effective dark matter fluid to various
h.d. corrections, results unchanged | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effective field theory for hydrodynamics allows to write the action
functional for fluid. In this paper, some simplest possible higher derivative
terms in the fluid action and the cosmological consequences of their presence
are considered. Particular attention is given to dark matter, modelled as a
dust with higher derivative corrections. We study the conditions of absence of
singularities in the solutions of the background and perturbed equations and
investigate the evolution of perturbations in two simple models of matter
dominated Universe. There is a range of parameters describing the higher
derivative terms, in which the short-wavelength perturbations of dark matter
are suppressed and the dark matter can be seen as fairly homogeneous on a
sufficiently small scale.
| [
{
"created": "Tue, 22 Dec 2015 14:16:52 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jan 2016 18:40:53 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Apr 2016 10:23:15 GMT",
"version": "v3"
}
] | 2016-04-21 | [
[
"Koshelev",
"N. A.",
""
]
] | The effective field theory for hydrodynamics allows to write the action functional for fluid. In this paper, some simplest possible higher derivative terms in the fluid action and the cosmological consequences of their presence are considered. Particular attention is given to dark matter, modelled as a dust with higher derivative corrections. We study the conditions of absence of singularities in the solutions of the background and perturbed equations and investigate the evolution of perturbations in two simple models of matter dominated Universe. There is a range of parameters describing the higher derivative terms, in which the short-wavelength perturbations of dark matter are suppressed and the dark matter can be seen as fairly homogeneous on a sufficiently small scale. |
2006.01462 | Vittorio De Falco Dr | Vittorio De Falco | New approaches to the general relativistic Poynting-Robertson effect | 12 pages, 5 figures, accepted on the 1st of June 2020 on Emerging
Science Journal | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Objectives: A systematic study on the general relativistic Poynting-Robertson
effect has been developed so far by introducing different complementary
approaches, which can be mainly divided in two kinds: (1) improving the
theoretical assessments and model in its simple aspects, and (2) extracting
mathematical and physical information from such system with the aim to extend
methods or results to other similar physical systems of analogue structure.
Methods/Analysis: We use these theoretical approaches: relativity of observer
splitting formalism; Lagrangian formalism and Rayleigh potential with a new
integration method; Lyapunov theory os stability.
Findings: We determined the three-dimensional formulation of the general
relativistic Poynting-Robertson effect model. We determine the analytical form
of the Rayleigh potential and discuss its implications. We prove that the
critical hypersurfaces (regions where there is a balance between gravitational
and radiation forces) are stable configurations.
Novelty /Improvement: Our new contributions are: to have introduced the
three-dimensional description; to have determined the general relativistic
Rayleigh potential for the first time in the General Relativity literature; to
have provided an alternative, general and more elegant proof of the stability
of the critical hypersurfaces.
| [
{
"created": "Tue, 2 Jun 2020 09:02:30 GMT",
"version": "v1"
}
] | 2020-06-03 | [
[
"De Falco",
"Vittorio",
""
]
] | Objectives: A systematic study on the general relativistic Poynting-Robertson effect has been developed so far by introducing different complementary approaches, which can be mainly divided in two kinds: (1) improving the theoretical assessments and model in its simple aspects, and (2) extracting mathematical and physical information from such system with the aim to extend methods or results to other similar physical systems of analogue structure. Methods/Analysis: We use these theoretical approaches: relativity of observer splitting formalism; Lagrangian formalism and Rayleigh potential with a new integration method; Lyapunov theory os stability. Findings: We determined the three-dimensional formulation of the general relativistic Poynting-Robertson effect model. We determine the analytical form of the Rayleigh potential and discuss its implications. We prove that the critical hypersurfaces (regions where there is a balance between gravitational and radiation forces) are stable configurations. Novelty /Improvement: Our new contributions are: to have introduced the three-dimensional description; to have determined the general relativistic Rayleigh potential for the first time in the General Relativity literature; to have provided an alternative, general and more elegant proof of the stability of the critical hypersurfaces. |
1004.0804 | Deepak Baskaran Dr. | D. Baskaran, L. P. Grishchuk and W. Zhao | Primordial Gravitational Waves and Cosmic Microwave Background Radiation | A summary of presentations delivered at the OC1 parallel session
"Primordial Gravitational Waves and the CMB" of the 12th Marcel Grossmann
Meeting on General Relativity (Paris, 12-18 July 2009). To be published in
the Proceedings of the MG12. 18 pages, 8 (colour) figures. | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a summary of presentations delivered at the OC1 parallel session
"Primordial Gravitational Waves and the CMB" of the 12th Marcel Grossmann
meeting in Paris, July 2009. The reports and discussions demonstrated
significant progress that was achieved in theory and observations. It appears
that the existing data provide some indications of the presence of
gravitational wave contribution to the CMB anisotropies, while ongoing and
planned observational efforts are likely to convert these indications into more
confident statements about the actual detection.
| [
{
"created": "Tue, 6 Apr 2010 09:09:42 GMT",
"version": "v1"
}
] | 2015-03-14 | [
[
"Baskaran",
"D.",
""
],
[
"Grishchuk",
"L. P.",
""
],
[
"Zhao",
"W.",
""
]
] | This is a summary of presentations delivered at the OC1 parallel session "Primordial Gravitational Waves and the CMB" of the 12th Marcel Grossmann meeting in Paris, July 2009. The reports and discussions demonstrated significant progress that was achieved in theory and observations. It appears that the existing data provide some indications of the presence of gravitational wave contribution to the CMB anisotropies, while ongoing and planned observational efforts are likely to convert these indications into more confident statements about the actual detection. |
2101.08960 | Alberto Molgado | Jasel Berra-Montiel, Alberto Molgado, and Angel Rodr\'iguez-L\'opez | A review on geometric formulations for classical field theory: the
Bonzom-Livine model for gravity | 55 pages, no figures | null | 10.1088/1361-6382/abf711 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the study of physical models associated with General Relativity,
we review some finite-dimensional, geometric and covariant formulations that
allow us to characterize in a simple manner the symmetries for classical field
theory by implementing an appropriate fibre-bundle structure, either at the
Lagrangian, the multisymplectic or the polysymplectic levels. In particular, we
are able to formulate Noether's theorems by means of the covariant momentum
maps and to systematically introduce a covariant Poisson-Hamiltonian framework.
Also, by focusing on the space plus time decomposition for a generic classical
field theory and its relation to these geometric formulations, we are able to
successfully recover the gauge content and the true local degrees of freedom
for the theory. In order to illustrate the relevance of these geometric
frameworks, we center our attention to the analysis of a model for
$3$-dimensional theory of General Relativity that involves an arbitrary
Immirzi-like parameter. At the Lagrangian level, we reproduce the field
equations of the system which for this model turn out to be equivalent to the
vanishing torsion condition and the Einstein equations. We also concentrate on
the analysis of the gauge symmetries of the system in order to obtain the
Lagrangian covariant momentum map associated with the theory and, consequently,
its corresponding Noether currents. Next, we aim our attention to describing
how the gauge symmetries of the model yield covariant canonical transformations
on the covariant multimomenta phase-space, thus giving rise to the existence of
a covariant momentum map. Besides, we analyze the physical system under
consideration within the De Donder-Weyl canonical theory implemented at the
polysymplectic level, thus establishing a relation from the covariant momentum
map to the conserved currents of the theory.
| [
{
"created": "Fri, 22 Jan 2021 06:03:36 GMT",
"version": "v1"
}
] | 2021-07-07 | [
[
"Berra-Montiel",
"Jasel",
""
],
[
"Molgado",
"Alberto",
""
],
[
"Rodríguez-López",
"Angel",
""
]
] | Motivated by the study of physical models associated with General Relativity, we review some finite-dimensional, geometric and covariant formulations that allow us to characterize in a simple manner the symmetries for classical field theory by implementing an appropriate fibre-bundle structure, either at the Lagrangian, the multisymplectic or the polysymplectic levels. In particular, we are able to formulate Noether's theorems by means of the covariant momentum maps and to systematically introduce a covariant Poisson-Hamiltonian framework. Also, by focusing on the space plus time decomposition for a generic classical field theory and its relation to these geometric formulations, we are able to successfully recover the gauge content and the true local degrees of freedom for the theory. In order to illustrate the relevance of these geometric frameworks, we center our attention to the analysis of a model for $3$-dimensional theory of General Relativity that involves an arbitrary Immirzi-like parameter. At the Lagrangian level, we reproduce the field equations of the system which for this model turn out to be equivalent to the vanishing torsion condition and the Einstein equations. We also concentrate on the analysis of the gauge symmetries of the system in order to obtain the Lagrangian covariant momentum map associated with the theory and, consequently, its corresponding Noether currents. Next, we aim our attention to describing how the gauge symmetries of the model yield covariant canonical transformations on the covariant multimomenta phase-space, thus giving rise to the existence of a covariant momentum map. Besides, we analyze the physical system under consideration within the De Donder-Weyl canonical theory implemented at the polysymplectic level, thus establishing a relation from the covariant momentum map to the conserved currents of the theory. |
2005.06515 | Tomasz Smo{\l}ka | Jacek Jezierski and Tomasz Smo{\l}ka | Quasi-local instantaneous charges asymptotics at spatial infinity | 27 pages. arXiv admin note: substantial text overlap with
arXiv:1903.06907 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The article aims to analyze a construction of charges (conserved quantities)
for the gravity field in the (3+1) decomposition. The construction is based on
(3+1) splitting of conformal Yano--Killing (CYK) two-form. The splitting leads
to charges, defined on Cauchy surface, which are combined from components of
Weyl tensor and conformal Killing vector. The relations between the conserved
quantities and its classical ADM counterparts are revisited. Asymptotic
behavior of the conserved quantities is described. The charges are analyzed for
a particular choice of initial data, among others, Bowen -- York spinning black
hole.
| [
{
"created": "Tue, 12 May 2020 07:59:30 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Mar 2022 10:03:56 GMT",
"version": "v2"
}
] | 2022-03-15 | [
[
"Jezierski",
"Jacek",
""
],
[
"Smołka",
"Tomasz",
""
]
] | The article aims to analyze a construction of charges (conserved quantities) for the gravity field in the (3+1) decomposition. The construction is based on (3+1) splitting of conformal Yano--Killing (CYK) two-form. The splitting leads to charges, defined on Cauchy surface, which are combined from components of Weyl tensor and conformal Killing vector. The relations between the conserved quantities and its classical ADM counterparts are revisited. Asymptotic behavior of the conserved quantities is described. The charges are analyzed for a particular choice of initial data, among others, Bowen -- York spinning black hole. |
1809.05392 | Albert Kotvytskiy | Albert Kotvytskiy, Semen Bronza and Svatoslav Vovk | Estimating the number of solutions equation of N-point gravitational
lens algebraic geometry methods | 5 pages | null | null | null | gr-qc astro-ph.CO math.AG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the main problems in the study of system of equations of the
gravitational lens, is the computation of coordinates from the known position
of the source. In the process of computing finds the solution of equations with
two unknowns. The difficulty lies in the fact that, in general, is not known
constructive or analytical algorithm for solving systems of polynomial
equations In this connection, use numerical methods like the method of tracing.
For the N-point gravitational lenses have a system of polynomial equations.
Systems Research is advisable to start with an assessment of the number of
solutions. This can be done by methods of algebraic geometry.
| [
{
"created": "Sun, 2 Sep 2018 16:13:45 GMT",
"version": "v1"
}
] | 2018-09-28 | [
[
"Kotvytskiy",
"Albert",
""
],
[
"Bronza",
"Semen",
""
],
[
"Vovk",
"Svatoslav",
""
]
] | One of the main problems in the study of system of equations of the gravitational lens, is the computation of coordinates from the known position of the source. In the process of computing finds the solution of equations with two unknowns. The difficulty lies in the fact that, in general, is not known constructive or analytical algorithm for solving systems of polynomial equations In this connection, use numerical methods like the method of tracing. For the N-point gravitational lenses have a system of polynomial equations. Systems Research is advisable to start with an assessment of the number of solutions. This can be done by methods of algebraic geometry. |
1102.4965 | Wei-Tou Ni | S. V. Dhurandhar, W.-T. Ni, and G. Wang | Numerical simulation of time delay interferometry for a LISA-like
mission with the simplification of having only one interferometer | 16 pages, 5 figures, version to appear in Advances in Space Research
reflecting the change from LISA to eLISA | null | 10.1016/j.asr.2012.09.017 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to attain the requisite sensitivity for LISA, laser frequency noise
must be suppressed below the secondary noises such as the optical path noise,
acceleration noise etc. In a previous paper (Dhurandhar et al., Class. Quantum
Grav., 27, 135013, 2010), we have found a large family of second-generation
analytic solutions of time delay interferometry with one arm dysfunctional, and
we also estimated the laser noise due to residual time-delay semi-analytically
from orbit perturbations due to Earth. Since other planets and solar-system
bodies also perturb the orbits of LISA spacecraft and affect the time delay
interferometry (TDI), we simulate the time delay numerically in this paper for
all solutions with the generation number n \leq 3. We have worked out a set of
3-year optimized mission orbits of LISA spacecraft starting at January 1, 2021
using the CGC2.7 ephemeris framework. We then use this numerical solution to
calculate the residual optical path differences in the second-generation
solutions of our previous paper, and compare with the semi-analytic error
estimate. The accuracy of this calculation is better than 1 cm (or 30 ps). The
maximum path length difference, for all configuration calculated, is below 1 m
(3 ns). This is well below the limit under which the laser frequency noise is
required to be suppressed. The numerical simulation in this paper can be
applied to other space-borne interferometers for gravitational wave detection
with the simplification of having only one interferometer.
| [
{
"created": "Thu, 24 Feb 2011 11:35:00 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Sep 2012 09:40:15 GMT",
"version": "v2"
}
] | 2012-10-25 | [
[
"Dhurandhar",
"S. V.",
""
],
[
"Ni",
"W. -T.",
""
],
[
"Wang",
"G.",
""
]
] | In order to attain the requisite sensitivity for LISA, laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. In a previous paper (Dhurandhar et al., Class. Quantum Grav., 27, 135013, 2010), we have found a large family of second-generation analytic solutions of time delay interferometry with one arm dysfunctional, and we also estimated the laser noise due to residual time-delay semi-analytically from orbit perturbations due to Earth. Since other planets and solar-system bodies also perturb the orbits of LISA spacecraft and affect the time delay interferometry (TDI), we simulate the time delay numerically in this paper for all solutions with the generation number n \leq 3. We have worked out a set of 3-year optimized mission orbits of LISA spacecraft starting at January 1, 2021 using the CGC2.7 ephemeris framework. We then use this numerical solution to calculate the residual optical path differences in the second-generation solutions of our previous paper, and compare with the semi-analytic error estimate. The accuracy of this calculation is better than 1 cm (or 30 ps). The maximum path length difference, for all configuration calculated, is below 1 m (3 ns). This is well below the limit under which the laser frequency noise is required to be suppressed. The numerical simulation in this paper can be applied to other space-borne interferometers for gravitational wave detection with the simplification of having only one interferometer. |
gr-qc/9909005 | Richard Price | A. Garat and R. H. Price (U. of Utah) | Gauge invariant formalism for second order perturbations of
Schwarzschild spacetimes | 18 pages, no figures | Phys.Rev. D61 (2000) 044006 | 10.1103/PhysRevD.61.044006 | null | gr-qc | null | The ``close limit,'' a method based on perturbations of Schwarzschild
spacetime, has proved to be a very useful tool for finding approximate
solutions to models of black hole collisions. Calculations carried out with
second order perturbation theory have been shown to give the limits of
applicability of the method without the need for comparison with numerical
relativity results. Those second order calculations have been carried out in a
fixed coordinate gauge, a method that entails conceptual and computational
difficulties. Here we demonstrate a gauge invariant approach to such
calculations. For a specific set of models (requiring head on collisions and
quadrupole dominance of both the first and second order perturbations), we give
a self contained gauge invariant formalism. Specifically, we give (i) wave
equations and sources for first and second order gauge invariant wave
functions; (ii) the prescription for finding Cauchy data for those equations
from initial values of the first and second fundamental forms on an initial
hypersurface; (iii) the formula for computing the gravitational wave power from
the evolved first and second order wave functions.
| [
{
"created": "Wed, 1 Sep 1999 20:46:50 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Garat",
"A.",
"",
"U. of Utah"
],
[
"Price",
"R. H.",
"",
"U. of Utah"
]
] | The ``close limit,'' a method based on perturbations of Schwarzschild spacetime, has proved to be a very useful tool for finding approximate solutions to models of black hole collisions. Calculations carried out with second order perturbation theory have been shown to give the limits of applicability of the method without the need for comparison with numerical relativity results. Those second order calculations have been carried out in a fixed coordinate gauge, a method that entails conceptual and computational difficulties. Here we demonstrate a gauge invariant approach to such calculations. For a specific set of models (requiring head on collisions and quadrupole dominance of both the first and second order perturbations), we give a self contained gauge invariant formalism. Specifically, we give (i) wave equations and sources for first and second order gauge invariant wave functions; (ii) the prescription for finding Cauchy data for those equations from initial values of the first and second fundamental forms on an initial hypersurface; (iii) the formula for computing the gravitational wave power from the evolved first and second order wave functions. |
1401.0741 | Jose Wadih Maluf Dr. | J. W. Maluf | Repulsive gravity near naked singularities and point massive particles | 14 pages, no figures, referenced added, published in the General
Relativity and Gravitation Journal | null | 10.1007/s10714-014-1734-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the existence of repulsive gravitational acceleration near
naked singularities. The investigation is carried out by means of the
acceleration tensor, which is a coordinate invariant object. We find that the
gravitational acceleration is repulsive in the vicinity of the origin in the
Reissner-Nordstr{\o}m and in the Kerr space-times, and attractive at large
distances in the expected Newtonian way. We further address the space-time of a
point massive particle, which also exhibits repulsive effects near the origin.
| [
{
"created": "Fri, 3 Jan 2014 22:07:47 GMT",
"version": "v1"
},
{
"created": "Mon, 5 May 2014 23:15:40 GMT",
"version": "v2"
}
] | 2014-05-07 | [
[
"Maluf",
"J. W.",
""
]
] | We investigate the existence of repulsive gravitational acceleration near naked singularities. The investigation is carried out by means of the acceleration tensor, which is a coordinate invariant object. We find that the gravitational acceleration is repulsive in the vicinity of the origin in the Reissner-Nordstr{\o}m and in the Kerr space-times, and attractive at large distances in the expected Newtonian way. We further address the space-time of a point massive particle, which also exhibits repulsive effects near the origin. |
gr-qc/0408097 | Syksy Rasanen | Syksy Rasanen | Backreaction in the Lemaitre-Tolman-Bondi model | 11 pages, JCAP-style. v2: Published version. One added reference, no
major changes | JCAP0411:010,2004 | 10.1088/1475-7516/2004/11/010 | null | gr-qc astro-ph hep-th | null | We study backreaction analytically using the parabolic Lemaitre-Tolman-Bondi
universe as a toy model. We calculate the average expansion rate and energy
density on two different hypersurfaces and compare the results. We also
consider the Hubble law and find that backreaction slows down the expansion if
measured with proper time, but speeds it up if measured with energy density.
| [
{
"created": "Tue, 31 Aug 2004 19:55:19 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Dec 2004 15:20:41 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Rasanen",
"Syksy",
""
]
] | We study backreaction analytically using the parabolic Lemaitre-Tolman-Bondi universe as a toy model. We calculate the average expansion rate and energy density on two different hypersurfaces and compare the results. We also consider the Hubble law and find that backreaction slows down the expansion if measured with proper time, but speeds it up if measured with energy density. |
gr-qc/0410122 | Massimo Tinto | Massimo Tinto, Michele Vallisneri, J.W. Armstrong | TDIR: Time-Delay Interferometric Ranging for Space-Borne
Gravitational-Wave Detectors | 5 pages, 2 figures | Phys.Rev. D71 (2005) 041101 | 10.1103/PhysRevD.71.041101 | null | gr-qc | null | Space-borne interferometric gravitational-wave detectors, sensitive in the
low-frequency (mHz) band, will fly in the next decade. In these detectors, the
spacecraft-to-spacecraft light-travel times will necessarily be unequal and
time-varying, and (because of aberration) will have different values on up- and
down-links. In such unequal-armlength interferometers, laser phase noise will
be canceled by taking linear combinations of the laser-phase observables
measured between pairs of spacecraft, appropriately time-shifted by the light
propagation times along the corresponding arms. This procedure, known as
time-delay interferometry (TDI), requires an accurate knowledge of the
light-time delays as functions of time. Here we propose a high-accuracy
technique to estimate these time delays and study its use in the context of the
Laser Interferometer Space Antenna (LISA) mission. We refer to this ranging
technique, which relies on the TDI combinations themselves, as Time-Delay
Interferometric Ranging (TDIR). For every TDI combination, we show that, by
minimizing the rms power in that combination (averaged over integration times
$\sim 10^4$ s) with respect to the time-delay parameters, we obtain estimates
of the time delays accurate enough to cancel laser noise to a level well below
the secondary noises. Thus TDIR allows the implementation of TDI without the
use of dedicated inter-spacecraft ranging systems, with a potential
simplification of the LISA design. In this paper we define the TDIR procedure
formally, and we characterize its expected performance via simulations with the
\textit{Synthetic LISA} software package.
| [
{
"created": "Mon, 25 Oct 2004 21:37:15 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Tinto",
"Massimo",
""
],
[
"Vallisneri",
"Michele",
""
],
[
"Armstrong",
"J. W.",
""
]
] | Space-borne interferometric gravitational-wave detectors, sensitive in the low-frequency (mHz) band, will fly in the next decade. In these detectors, the spacecraft-to-spacecraft light-travel times will necessarily be unequal and time-varying, and (because of aberration) will have different values on up- and down-links. In such unequal-armlength interferometers, laser phase noise will be canceled by taking linear combinations of the laser-phase observables measured between pairs of spacecraft, appropriately time-shifted by the light propagation times along the corresponding arms. This procedure, known as time-delay interferometry (TDI), requires an accurate knowledge of the light-time delays as functions of time. Here we propose a high-accuracy technique to estimate these time delays and study its use in the context of the Laser Interferometer Space Antenna (LISA) mission. We refer to this ranging technique, which relies on the TDI combinations themselves, as Time-Delay Interferometric Ranging (TDIR). For every TDI combination, we show that, by minimizing the rms power in that combination (averaged over integration times $\sim 10^4$ s) with respect to the time-delay parameters, we obtain estimates of the time delays accurate enough to cancel laser noise to a level well below the secondary noises. Thus TDIR allows the implementation of TDI without the use of dedicated inter-spacecraft ranging systems, with a potential simplification of the LISA design. In this paper we define the TDIR procedure formally, and we characterize its expected performance via simulations with the \textit{Synthetic LISA} software package. |
1907.01050 | Carlos Alfonso Conde Ocazionez | Carlos Conde, Cristian Galvis and Eduard Larra\~naga | On the properties of a Static and a Stationary Charged Black Hole in
$f(R)$ Gravity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper, Nashed and Capozziello presented a new class of charged,
spherically symmetric black hole solutions of $f(R)$ gravity with an asymptotic
flat or (anti-)de Sitter behavior. These metrics depend on a dimensional
parameter $\alpha$ and are interesting because they cannot reduce to general
relativity solutions. In this paper, we present a corrected study of their
physical and thermodynamic properties and generalize these solutions to obtain
a new set of stationary, axisymmetric black holes in the $f(R)$ scenario. Some
of our results show that the entropy is always positive within the allowed
values of parameter $\alpha$ and due to the well behaved quantities such as the
Gibbs free energy, we conclude that there is no such a phase transition as
discussed in the work of Nashed and Capozziello. We also study the geodesics in
these spacetimes and particularly, the stability of the circular orbits to
obtain the radius of the Innermost Stable Circular Orbit.
| [
{
"created": "Mon, 1 Jul 2019 20:15:21 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Sep 2020 14:29:04 GMT",
"version": "v2"
}
] | 2020-09-30 | [
[
"Conde",
"Carlos",
""
],
[
"Galvis",
"Cristian",
""
],
[
"Larrañaga",
"Eduard",
""
]
] | In a recent paper, Nashed and Capozziello presented a new class of charged, spherically symmetric black hole solutions of $f(R)$ gravity with an asymptotic flat or (anti-)de Sitter behavior. These metrics depend on a dimensional parameter $\alpha$ and are interesting because they cannot reduce to general relativity solutions. In this paper, we present a corrected study of their physical and thermodynamic properties and generalize these solutions to obtain a new set of stationary, axisymmetric black holes in the $f(R)$ scenario. Some of our results show that the entropy is always positive within the allowed values of parameter $\alpha$ and due to the well behaved quantities such as the Gibbs free energy, we conclude that there is no such a phase transition as discussed in the work of Nashed and Capozziello. We also study the geodesics in these spacetimes and particularly, the stability of the circular orbits to obtain the radius of the Innermost Stable Circular Orbit. |
1709.02264 | Maxim Eingorn | Maxim Eingorn | Cosmological law of universal gravitation | essay on aspects of screening in the context of equations of motion;
preprint of an article published in International Journal of Modern Physics D
[copyright World Scientific Publishing Company],
http://www.worldscientific.com/worldscinet/ijmpd; comments welcome | Int. J. Mod. Phys. D 26, 1750121 (2017) | 10.1142/S0218271817501218 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Without exceeding the limits of the conventional $\Lambda$CDM paradigm, we
argue for Yukawa law of interparticle interaction as the law of gravitation in
the real expanding inhomogeneous Universe. It covers the whole space and comes
up to take place of Newtonian gravity, which is restricted exclusively to
sub-horizon distances. The large-scale screening of gravitational interaction
between every two nonrelativistic massive particles is ensured by the
homogeneous cosmological background (specifically, by the nonzero average rest
mass density of nonrelativistic matter). We take advantage of the uniform
matter distribution case (i.e. the homogeneous Universe limit) to demonstrate
superiority of Yukawa gravity. Attention is also devoted to the concrete
particular case of inhomogeneity.
| [
{
"created": "Thu, 7 Sep 2017 14:15:38 GMT",
"version": "v1"
}
] | 2017-09-08 | [
[
"Eingorn",
"Maxim",
""
]
] | Without exceeding the limits of the conventional $\Lambda$CDM paradigm, we argue for Yukawa law of interparticle interaction as the law of gravitation in the real expanding inhomogeneous Universe. It covers the whole space and comes up to take place of Newtonian gravity, which is restricted exclusively to sub-horizon distances. The large-scale screening of gravitational interaction between every two nonrelativistic massive particles is ensured by the homogeneous cosmological background (specifically, by the nonzero average rest mass density of nonrelativistic matter). We take advantage of the uniform matter distribution case (i.e. the homogeneous Universe limit) to demonstrate superiority of Yukawa gravity. Attention is also devoted to the concrete particular case of inhomogeneity. |
1305.5674 | Simone Balmelli | Simone Balmelli and Philippe Jetzer | Effective-one-body Hamiltonian with next-to-leading order spin-spin
coupling for two nonprecessing black holes with aligned spins | 15 pages, 5 figures. Submitted to Phys. Rev. D | Phys. Rev. D 87 (2013) 124036; Erratum: Phys. Rev. D 90 (2014)
089905(E) | 10.1103/PhysRevD.87.124036 10.1103/PhysRevD.90.089905 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The canonical Arnowitt-Deser-Misner (ADM) Hamiltonian with next-to-leading
order spin-spin coupling [J. Steinhoff, S. Hergt, and G. Sch\"afer] is
converted into the EOB formalism of T. Damour, P. Jaranowski, and G. Sch\"afer
for the special case of spinning black hole binaries whose spins are aligned
with the angular momentum. In particular, we propose to include the new terms
by adding a dynamical term of next-to-leading order to the Kerr parameter
squared entering the effective metric. The modified EOB Hamiltonian
consistently reduces to the Kerr Hamiltonian as the mass ratio tends to zero;
moreover, it predicts the existence of an Innermost Stable Circular Orbit. We
also derive, for the general case of arbitrarily oriented spins but in the
vanishing mass-ratio limit, a coordinate transformation that maps the
next-to-leading order spin-spin contribution of the ADM Hamiltonian to the EOB
Hamiltonian.
| [
{
"created": "Fri, 24 May 2013 09:58:38 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2013 14:27:27 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Feb 2015 21:00:15 GMT",
"version": "v3"
}
] | 2015-02-06 | [
[
"Balmelli",
"Simone",
""
],
[
"Jetzer",
"Philippe",
""
]
] | The canonical Arnowitt-Deser-Misner (ADM) Hamiltonian with next-to-leading order spin-spin coupling [J. Steinhoff, S. Hergt, and G. Sch\"afer] is converted into the EOB formalism of T. Damour, P. Jaranowski, and G. Sch\"afer for the special case of spinning black hole binaries whose spins are aligned with the angular momentum. In particular, we propose to include the new terms by adding a dynamical term of next-to-leading order to the Kerr parameter squared entering the effective metric. The modified EOB Hamiltonian consistently reduces to the Kerr Hamiltonian as the mass ratio tends to zero; moreover, it predicts the existence of an Innermost Stable Circular Orbit. We also derive, for the general case of arbitrarily oriented spins but in the vanishing mass-ratio limit, a coordinate transformation that maps the next-to-leading order spin-spin contribution of the ADM Hamiltonian to the EOB Hamiltonian. |
0707.2819 | Dirk Puetzfeld | Dirk Puetzfeld, Yuri N. Obukhov | Propagation equations for deformable test bodies with microstructure in
extended theories of gravity | 27 pages, 1 figure, matches published version including the erratum
in Phys. Rev. D 79 (2009) 069902(E) | Phys.Rev.D76:084025,2007; Erratum-ibid.D79:069902,2009 | 10.1103/PhysRevD.76.084025 10.1103/PhysRevD.79.069902 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the equations of motion in metric-affine gravity by making use of
the conservation laws obtained from Noether's theorem. The results are given in
the form of propagation equations for the multipole decomposition of the matter
sources in metric-affine gravity, i.e., the canonical energy-momentum current
and the hypermomentum current. In particular, the propagation equations allow
for a derivation of the equations of motion of test particles in this
generalized gravity theory, and allow for direct identification of the
couplings between the matter currents and the gauge gravitational field
strengths of the theory, namely, the curvature, the torsion, and the
nonmetricity. We demonstrate that the possible non-Riemannian spacetime
geometry can only be detected with the help of the test bodies that are formed
of matter with microstructure. Ordinary gravitating matter, i.e., matter
without microscopic internal degrees of freedom, can probe only the Riemannian
spacetime geometry. Thereby, we generalize previous results of general
relativity and Poincare gauge theory.
| [
{
"created": "Wed, 18 Jul 2007 23:42:43 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Nov 2007 13:37:34 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Mar 2009 10:56:27 GMT",
"version": "v3"
}
] | 2014-11-18 | [
[
"Puetzfeld",
"Dirk",
""
],
[
"Obukhov",
"Yuri N.",
""
]
] | We derive the equations of motion in metric-affine gravity by making use of the conservation laws obtained from Noether's theorem. The results are given in the form of propagation equations for the multipole decomposition of the matter sources in metric-affine gravity, i.e., the canonical energy-momentum current and the hypermomentum current. In particular, the propagation equations allow for a derivation of the equations of motion of test particles in this generalized gravity theory, and allow for direct identification of the couplings between the matter currents and the gauge gravitational field strengths of the theory, namely, the curvature, the torsion, and the nonmetricity. We demonstrate that the possible non-Riemannian spacetime geometry can only be detected with the help of the test bodies that are formed of matter with microstructure. Ordinary gravitating matter, i.e., matter without microscopic internal degrees of freedom, can probe only the Riemannian spacetime geometry. Thereby, we generalize previous results of general relativity and Poincare gauge theory. |
2006.02177 | Malcolm MacCallum | Malcolm A.H. MacCallum | Totally symmetrized spinors and null rotation invariance | Text revised after refereeing. This version accepted in Classical and
Quantum Gravity and now available online under CC BY 3.0 licence | Class. Quant. Grav. 37, 195011 (2020) | 10.1088/1361-6382/aba844 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the existing implementations of the Cartan-Karlhede procedure for
characterization and classification of spacetimes, a prominent r\^ole is played
by multi-index two-component spinors symmetrized over both types of index. This
paper considers the conditions for, and detection of, null rotational
invariance of such spinors, and corrects a previous discussion.
| [
{
"created": "Wed, 3 Jun 2020 11:27:36 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jul 2020 08:03:47 GMT",
"version": "v2"
}
] | 2021-06-03 | [
[
"MacCallum",
"Malcolm A. H.",
""
]
] | In the existing implementations of the Cartan-Karlhede procedure for characterization and classification of spacetimes, a prominent r\^ole is played by multi-index two-component spinors symmetrized over both types of index. This paper considers the conditions for, and detection of, null rotational invariance of such spinors, and corrects a previous discussion. |
2311.01595 | Sepideh Bakhoda | Sepideh Bakhoda | Boundary conditions for Ashtekar-Barbero variables in the context of
asymptotically flat spacetimes which lead to supertranslations at spatial
infinity | 35 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This paper delves into the exploration of suitable boundary conditions for
the asymptotically flat scenario of general relativity presented in terms of
Ashtekar-Barbero variables. While the standard parity conditions have been
extensively studied in \cite{Thiemann, Campiglia}, it turns out that they fail
to produce non-trivial supertranslations at spatial infinity. We propose new
parity conditions for the Ashtekar-Barbero variables that do yield non-trivial
supertranslation charges at spatial infinity. We compare our findings with
those presented in \cite{Henneaux} and demonstrate that the new boundary
conditions ensure the finiteness of the symplectic structure. Moreover, when
embarking on the quest for appropriate parity conditions, it is essential to
ensure that the selected parities remain invariant under hypersurface
deformations. Given that working with Ashtekar-Barbero variables provides more
asymptotic structure as compared to the ADM variables, it is shown that by
fixing the Lagrange multiplier corresponding to the Gauss constraint, the
invariance of certain parity conditions can be guaranteed.
| [
{
"created": "Thu, 2 Nov 2023 21:00:25 GMT",
"version": "v1"
}
] | 2023-11-06 | [
[
"Bakhoda",
"Sepideh",
""
]
] | This paper delves into the exploration of suitable boundary conditions for the asymptotically flat scenario of general relativity presented in terms of Ashtekar-Barbero variables. While the standard parity conditions have been extensively studied in \cite{Thiemann, Campiglia}, it turns out that they fail to produce non-trivial supertranslations at spatial infinity. We propose new parity conditions for the Ashtekar-Barbero variables that do yield non-trivial supertranslation charges at spatial infinity. We compare our findings with those presented in \cite{Henneaux} and demonstrate that the new boundary conditions ensure the finiteness of the symplectic structure. Moreover, when embarking on the quest for appropriate parity conditions, it is essential to ensure that the selected parities remain invariant under hypersurface deformations. Given that working with Ashtekar-Barbero variables provides more asymptotic structure as compared to the ADM variables, it is shown that by fixing the Lagrange multiplier corresponding to the Gauss constraint, the invariance of certain parity conditions can be guaranteed. |
2401.00277 | Alessandro Santoni | Benjamin Koch, Enrique Mu\~noz, Alessandro Santoni | Ultracold Neutrons in the Low Curvature Limit: Remarks on the
post-Newtonian effects | null | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Ultracold neutrons are great experimental tools to explore the gravitational
interaction in the regime of quantized states. From a theoretical perspective,
starting from a Dirac equation in curved spacetime, we applied a perturbative
scheme to systematically derive the non-relativistic Schr\"odinger equation
that governs the evolution of the neutron's wave function in the Earth's
gravitational field. At the lowest order, this procedure reproduces a
Schr\"odinger system affected by a linear Newtonian potential, but corrections
due to both curvature and relativistic effects are present. Here, we argue that
one should be very careful when going one step further in the perturbative
expansion. Proceeding methodically with the help of the Foldy-Wouthuysen
transformation and a formal post-Newtonian $c^{-2}-$expansion, we derive the
non-relativistic Hamiltonian for a generic static spacetime. By employing Fermi
coordinates within this framework, we calculate the next-to-leading order
corrections to the neutron's energy spectrum. Finally, we evaluate them for
typical experimental configurations, such as that of qBOUNCE, and note that,
while the current precision for observations of ultracold neutrons may not yet
enable to probe them, they could still be relevant in the future or in
alternative circumstances.
| [
{
"created": "Sat, 30 Dec 2023 16:45:56 GMT",
"version": "v1"
}
] | 2024-01-02 | [
[
"Koch",
"Benjamin",
""
],
[
"Muñoz",
"Enrique",
""
],
[
"Santoni",
"Alessandro",
""
]
] | Ultracold neutrons are great experimental tools to explore the gravitational interaction in the regime of quantized states. From a theoretical perspective, starting from a Dirac equation in curved spacetime, we applied a perturbative scheme to systematically derive the non-relativistic Schr\"odinger equation that governs the evolution of the neutron's wave function in the Earth's gravitational field. At the lowest order, this procedure reproduces a Schr\"odinger system affected by a linear Newtonian potential, but corrections due to both curvature and relativistic effects are present. Here, we argue that one should be very careful when going one step further in the perturbative expansion. Proceeding methodically with the help of the Foldy-Wouthuysen transformation and a formal post-Newtonian $c^{-2}-$expansion, we derive the non-relativistic Hamiltonian for a generic static spacetime. By employing Fermi coordinates within this framework, we calculate the next-to-leading order corrections to the neutron's energy spectrum. Finally, we evaluate them for typical experimental configurations, such as that of qBOUNCE, and note that, while the current precision for observations of ultracold neutrons may not yet enable to probe them, they could still be relevant in the future or in alternative circumstances. |
gr-qc/0603098 | Chandrasekher Mukku Prof. | Bindu A.Bambah, K.V.S.Shiv Chaitanya and C.Mukku | Baryon Asymmetry, Inflation and Squeezed States | 21 pages, 2 figures | AnnalsPhys.322:849-865,2007 | 10.1016/j.aop.2006.08.005 | null | gr-qc hep-ph hep-th | null | We use the general formalism of squeezed rotated states to calculate baryon
asymmetry in the wake of inflation through parametric amplification. We base
our analysis on a B and CP violating Lagrangian in an isotropically expanding
universe. The B and CP violating terms originate from the coupling of complex
fields with non-zero baryon number to a complex background inflaton field. We
show that a differential amplification of particle and anti-particle modes
gives rise to baryon asymmetry.
| [
{
"created": "Fri, 24 Mar 2006 15:00:45 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bambah",
"Bindu A.",
""
],
[
"Chaitanya",
"K. V. S. Shiv",
""
],
[
"Mukku",
"C.",
""
]
] | We use the general formalism of squeezed rotated states to calculate baryon asymmetry in the wake of inflation through parametric amplification. We base our analysis on a B and CP violating Lagrangian in an isotropically expanding universe. The B and CP violating terms originate from the coupling of complex fields with non-zero baryon number to a complex background inflaton field. We show that a differential amplification of particle and anti-particle modes gives rise to baryon asymmetry. |
gr-qc/0409118 | Roberto Casadio | G.L. Alberghi, R. Casadio and G.Venturi | Thermodynamics of a collapsing shell in an expanding Universe | 9 pages, 2 figures, accepted for publication in Phys. Lett. B | Phys.Lett.B602:8-13,2004 | 10.1016/j.physletb.2004.09.063 | null | gr-qc | null | We describe the quasi-static collapse of a radiating, spherical shell of
matter in de Sitter space-time using a thermodynamical formalism. It is found
that the specific heat at constant area and other thermodynamical quantities
exhibit singularities related to phase transitions during the collapse.
| [
{
"created": "Thu, 30 Sep 2004 08:59:13 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Alberghi",
"G. L.",
""
],
[
"Casadio",
"R.",
""
],
[
"Venturi",
"G.",
""
]
] | We describe the quasi-static collapse of a radiating, spherical shell of matter in de Sitter space-time using a thermodynamical formalism. It is found that the specific heat at constant area and other thermodynamical quantities exhibit singularities related to phase transitions during the collapse. |
1001.4029 | Philipp Hoehn | Philipp A Hoehn and Susan M Scott | Conformal formulation of cosmological futures | 3 pages, to appear in the proceedings of the 12th Marcel Grossmann
Meeting, Paris, July 2009 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We summarise the new conformal framework of an Anisotropic Future Endless
Universe and an Anisotropic Future Singularity. Both new definitions are
motivated by, but not restricted to quiescent cosmology and the Weyl curvature
hypothesis, which previously only possessed a framework for a classical initial
state of the universe, namely the Isotropic Singularity. Some of the features
of the framework are briefly discussed.
| [
{
"created": "Fri, 22 Jan 2010 15:45:39 GMT",
"version": "v1"
}
] | 2010-01-25 | [
[
"Hoehn",
"Philipp A",
""
],
[
"Scott",
"Susan M",
""
]
] | We summarise the new conformal framework of an Anisotropic Future Endless Universe and an Anisotropic Future Singularity. Both new definitions are motivated by, but not restricted to quiescent cosmology and the Weyl curvature hypothesis, which previously only possessed a framework for a classical initial state of the universe, namely the Isotropic Singularity. Some of the features of the framework are briefly discussed. |
1812.07490 | Luc Blanchet | Luc Blanchet | Analytic Approximations in GR and Gravitational Waves | 24 pages, 2 figures, based on a plenary talk given at the Fifteenth
Marcel Grossmann Meeting on recent developments in General Relativity (MG15),
Rome, July 2018, added references | null | 10.1142/S0218271819300118 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analytic approximation methods in general relativity play a very important
role when analyzing the gravitational wave signals recently discovered by the
LIGO and Virgo detectors. In this contribution, we present the state-of-the-art
and some recent developments in the famous post-Newtonian (PN) or slow-motion
approximation, which has successfully computed the equations of motion and the
early inspiral phase of compact binary systems. We discuss also some
interesting interfaces between the PN and the gravitational self-force (GSF)
approach based on black-hole perturbation theory, and between PN and the
post-Minkowskian (PM) approximation, namely a non-linearity expansion valid for
weak field and possibly fast-moving sources.
| [
{
"created": "Tue, 18 Dec 2018 17:17:52 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Dec 2018 18:23:10 GMT",
"version": "v2"
}
] | 2019-05-22 | [
[
"Blanchet",
"Luc",
""
]
] | Analytic approximation methods in general relativity play a very important role when analyzing the gravitational wave signals recently discovered by the LIGO and Virgo detectors. In this contribution, we present the state-of-the-art and some recent developments in the famous post-Newtonian (PN) or slow-motion approximation, which has successfully computed the equations of motion and the early inspiral phase of compact binary systems. We discuss also some interesting interfaces between the PN and the gravitational self-force (GSF) approach based on black-hole perturbation theory, and between PN and the post-Minkowskian (PM) approximation, namely a non-linearity expansion valid for weak field and possibly fast-moving sources. |
2107.10129 | Amanda Guerrieri | Amanda Guerrieri and Rodrigo F. Sobreiro | Carroll limit of four-dimensional gravity theories in the first order
formalism | 22 pages; 1 figure | null | 10.1088/1361-6382/ac345f | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the ultra-relativistic limit of a class of four dimensional
gravity theories, known as Lovelock-Cartan gravities, in the first order
formalism. First, we review the well known limit of the Einstein-Hilbert
action. A very useful scale symmetry involving the vierbeins and the boost
connection is presented. Moreover, we explore the field equations in order to
find formal solutions. Some remarkable results are obtained: Riemann and
Weitzenb\"ock like manifolds are discussed; Birkhoff's theorem is verified for
the torsionless case; an explicit solution with non-trivial geometry is
discussed; A quite general solution in the presence of matter is obtained.
Latter, we consider the ultra-relativistic limit of the more general
Lovelock-Cartan gravity. The previously scale symmetry is also discussed. The
field equations are studied in vacuum and in the presence of matter. In
comparison with the Einstein-Hilbert case, a few relevant results are found:
Birkhoff's theorem is also verified for the torsionless case; A quite general
solution in the presence of matter is obtained. This solution generalizes the
previous case; Riemann and Weitzenb\"ock like manifolds are derived in the same
lines of the Einstein-Hilbert case.
| [
{
"created": "Wed, 21 Jul 2021 14:51:50 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Aug 2021 18:17:08 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Oct 2021 00:23:42 GMT",
"version": "v3"
}
] | 2021-12-08 | [
[
"Guerrieri",
"Amanda",
""
],
[
"Sobreiro",
"Rodrigo F.",
""
]
] | We explore the ultra-relativistic limit of a class of four dimensional gravity theories, known as Lovelock-Cartan gravities, in the first order formalism. First, we review the well known limit of the Einstein-Hilbert action. A very useful scale symmetry involving the vierbeins and the boost connection is presented. Moreover, we explore the field equations in order to find formal solutions. Some remarkable results are obtained: Riemann and Weitzenb\"ock like manifolds are discussed; Birkhoff's theorem is verified for the torsionless case; an explicit solution with non-trivial geometry is discussed; A quite general solution in the presence of matter is obtained. Latter, we consider the ultra-relativistic limit of the more general Lovelock-Cartan gravity. The previously scale symmetry is also discussed. The field equations are studied in vacuum and in the presence of matter. In comparison with the Einstein-Hilbert case, a few relevant results are found: Birkhoff's theorem is also verified for the torsionless case; A quite general solution in the presence of matter is obtained. This solution generalizes the previous case; Riemann and Weitzenb\"ock like manifolds are derived in the same lines of the Einstein-Hilbert case. |
gr-qc/0203011 | Barbachoux | C.Barbachoux, J.Gariel, G.Marcilhacy, N.O.Santos | Reduction of the effective mass of the Reissner-Nordstrom spacetime | accepted in Int.J.Mod.Phys. D some changes have been performed and
the bibliography had been enlarged | null | 10.1142/S0218271802002311 | null | gr-qc | null | We derive the Teixeira, Wolk and Som method, for obtaining electrostatic
solutions from given vacuum solutions, in its inverse form. Then we use it to
obtain the geometrical mass $M_S$ in the Schwarzschild spacetime, and we find
$M_S^2=M^2-Q^2$, where $M$ and $Q$ are, respectively, the mass and charge
parameters of the Reissner-Nordstr\"om spacetime. We compare $M_S$ to the
corresponding active gravitational mass and mass function.
| [
{
"created": "Mon, 4 Mar 2002 09:20:59 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jun 2002 15:11:43 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Barbachoux",
"C.",
""
],
[
"Gariel",
"J.",
""
],
[
"Marcilhacy",
"G.",
""
],
[
"Santos",
"N. O.",
""
]
] | We derive the Teixeira, Wolk and Som method, for obtaining electrostatic solutions from given vacuum solutions, in its inverse form. Then we use it to obtain the geometrical mass $M_S$ in the Schwarzschild spacetime, and we find $M_S^2=M^2-Q^2$, where $M$ and $Q$ are, respectively, the mass and charge parameters of the Reissner-Nordstr\"om spacetime. We compare $M_S$ to the corresponding active gravitational mass and mass function. |
0705.3128 | Bijan Saha | Bijan Saha and Victor Rikhvitsky | Anisotropic cosmological models with spinor field and viscous fluid in
presence of a $\Lambda$ term: qualitative solutions | 12 pages, 3 Tables, 12 Figures | J.Phys.A40 (2007) 14011 - 14028 | 10.1088/1751-8113/40/46/013 | null | gr-qc | null | The study of a self-consistent system of nonlinear spinor and Bianchi type I
gravitational fields in presence of a viscous fluid and $\Lambda$ term with the
spinor field nonlinearity being some arbitrary functions of the invariants $I$
an $J$ constructed from bilinear spinor forms $S$ and $P$, generates a
multi-parametric system of ordinary differential equations
\cite{saharrp,grqcnlsp}. A qualitative analysis of the system in question has
been thoroughly carried out. A complete qualitative classification of the mode
of evolution of the universe given by the corresponding dynamic system has been
illustrated.
| [
{
"created": "Tue, 22 May 2007 09:57:57 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Saha",
"Bijan",
""
],
[
"Rikhvitsky",
"Victor",
""
]
] | The study of a self-consistent system of nonlinear spinor and Bianchi type I gravitational fields in presence of a viscous fluid and $\Lambda$ term with the spinor field nonlinearity being some arbitrary functions of the invariants $I$ an $J$ constructed from bilinear spinor forms $S$ and $P$, generates a multi-parametric system of ordinary differential equations \cite{saharrp,grqcnlsp}. A qualitative analysis of the system in question has been thoroughly carried out. A complete qualitative classification of the mode of evolution of the universe given by the corresponding dynamic system has been illustrated. |
1302.0687 | Alexey Golovnev | Alexey Golovnev | ADM analysis and massive gravity | 6 pages; 7th Mathematical Physics Meeting: Summer School and
Conference on Modern Mathematical Physics; minor changes | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a contribution to the Proceedings of the 7th Mathematical Physics
Meeting: Summer School and Conference on Modern Mathematical Physics, held in
Belgrade 09 -- 19 September 2012.
We give an easily accessible introduction to the ADM decomposition of the
curvature components. After that we review the basic problems associated with
attempts of constructing a viable massive gravity theory. And finally, we
present the metric formulations of ghost-free massive gravity models, and
comment on existence problem of the matrix square root.
| [
{
"created": "Mon, 4 Feb 2013 13:56:47 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Feb 2013 09:57:38 GMT",
"version": "v2"
},
{
"created": "Fri, 22 Mar 2013 13:55:51 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Mar 2013 12:48:06 GMT",
"version": "v4"
}
] | 2013-03-27 | [
[
"Golovnev",
"Alexey",
""
]
] | This is a contribution to the Proceedings of the 7th Mathematical Physics Meeting: Summer School and Conference on Modern Mathematical Physics, held in Belgrade 09 -- 19 September 2012. We give an easily accessible introduction to the ADM decomposition of the curvature components. After that we review the basic problems associated with attempts of constructing a viable massive gravity theory. And finally, we present the metric formulations of ghost-free massive gravity models, and comment on existence problem of the matrix square root. |
2107.08641 | Homa Shababi | Mohamed Moussa, Homa Shababi, Anisur Rahaman, Ujjal Kumar Dey | Minimal length, maximal momentum and stochastic gravitational waves
spectrum generated from cosmological QCD phase transition | 11 pages, 7 figures | Physics Letters B 820 (2021) 136488 | 10.1016/j.physletb.2021.136488 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate thoroughly the temporal evolution of the universe temperature
as a function of the Hubble parameter associated with the Stochastic
Gravitational Wave (SGW), that formed at the cosmological QCD phase transition
epoch to the current epoch, within the Generalized Uncertainty Principle (GUP)
framework. Here we use GUP version which provide constraints on the minimum
measurable length and the maximum observable momentum, that characterized by a
free parameter $\alpha$. We study the effect of this parameter on the SGW
background. We show that the effect can slightly enhance the SGW frequency in
the lower frequency regime which might be important in the detection of SGW in
the future GW detection facilities.
| [
{
"created": "Mon, 19 Jul 2021 06:45:05 GMT",
"version": "v1"
}
] | 2021-07-20 | [
[
"Moussa",
"Mohamed",
""
],
[
"Shababi",
"Homa",
""
],
[
"Rahaman",
"Anisur",
""
],
[
"Dey",
"Ujjal Kumar",
""
]
] | We investigate thoroughly the temporal evolution of the universe temperature as a function of the Hubble parameter associated with the Stochastic Gravitational Wave (SGW), that formed at the cosmological QCD phase transition epoch to the current epoch, within the Generalized Uncertainty Principle (GUP) framework. Here we use GUP version which provide constraints on the minimum measurable length and the maximum observable momentum, that characterized by a free parameter $\alpha$. We study the effect of this parameter on the SGW background. We show that the effect can slightly enhance the SGW frequency in the lower frequency regime which might be important in the detection of SGW in the future GW detection facilities. |
1706.05097 | Richard Brito | Richard Brito, Shrobana Ghosh, Enrico Barausse, Emanuele Berti, Vitor
Cardoso, Irina Dvorkin, Antoine Klein, Paolo Pani | Stochastic and resolvable gravitational waves from ultralight bosons | 6 pages, 4 Figures; v2: small changes to match version published in
Physical Review Letters | Phys. Rev. Lett. 119, 131101 (2017) | 10.1103/PhysRevLett.119.131101 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ultralight scalar fields around spinning black holes can trigger superradiant
instabilities, forming a long-lived bosonic condensate outside the horizon. We
use numerical solutions of the perturbed field equations and astrophysical
models of massive and stellar-mass black hole populations to compute, for the
first time, the stochastic gravitational-wave background from these sources. In
optimistic scenarios the background is observable by Advanced LIGO and LISA for
field masses $m_s$ in the range $\sim [2\times 10^{-13}, 10^{-12}]\,{\rm eV}$
and $\sim 5\times[ 10^{-19}, 10^{-16}]\,{\rm eV}$, respectively, and it can
affect the detectability of resolvable sources. Our estimates suggest that an
analysis of the stochastic background limits from LIGO O1 might already be used
to marginally exclude axions with mass $\sim 10^{-12.5}{\rm eV}$. Semicoherent
searches with Advanced LIGO (LISA) should detect $\sim 15~(5)$ to $200~(40)$
resolvable sources for scalar field masses $3\times 10^{-13}$ ($10^{-17}$) eV.
LISA measurements of massive BH spins could either rule out bosons in the range
$\sim [10^{-18}, 2\times 10^{-13}]$ eV, or measure $m_s$ with ten percent
accuracy in the range $\sim[10^{-17}, 10^{-13}]$ eV.
| [
{
"created": "Thu, 15 Jun 2017 21:37:32 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Oct 2017 14:27:37 GMT",
"version": "v2"
}
] | 2017-10-05 | [
[
"Brito",
"Richard",
""
],
[
"Ghosh",
"Shrobana",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Dvorkin",
"Irina",
""
],
[
"Klein",
"Antoine",
""
],
[
... | Ultralight scalar fields around spinning black holes can trigger superradiant instabilities, forming a long-lived bosonic condensate outside the horizon. We use numerical solutions of the perturbed field equations and astrophysical models of massive and stellar-mass black hole populations to compute, for the first time, the stochastic gravitational-wave background from these sources. In optimistic scenarios the background is observable by Advanced LIGO and LISA for field masses $m_s$ in the range $\sim [2\times 10^{-13}, 10^{-12}]\,{\rm eV}$ and $\sim 5\times[ 10^{-19}, 10^{-16}]\,{\rm eV}$, respectively, and it can affect the detectability of resolvable sources. Our estimates suggest that an analysis of the stochastic background limits from LIGO O1 might already be used to marginally exclude axions with mass $\sim 10^{-12.5}{\rm eV}$. Semicoherent searches with Advanced LIGO (LISA) should detect $\sim 15~(5)$ to $200~(40)$ resolvable sources for scalar field masses $3\times 10^{-13}$ ($10^{-17}$) eV. LISA measurements of massive BH spins could either rule out bosons in the range $\sim [10^{-18}, 2\times 10^{-13}]$ eV, or measure $m_s$ with ten percent accuracy in the range $\sim[10^{-17}, 10^{-13}]$ eV. |
gr-qc/0111034 | Guillermo A. Mena Marugan | Guillermo A. Mena Marugan and Saulo Carneiro | Holography and the large number hypothesis | 4 pages, version accepted for publication in Phys. Rev. D | Phys.Rev. D65 (2002) 087303 | 10.1103/PhysRevD.65.087303 | null | gr-qc astro-ph | null | Dirac's large number hypothesis is motivated by certain scaling
transformations that relate the parameters of macro and microphysics. We show
that these relations can actually be explained in terms of the holographic $N$
bound conjectured by Bousso and a series of purely cosmological observations,
namely, that our universe is spatially homogeneous, isotropic, and flat to a
high degree of approximation and that the cosmological constant dominates the
energy density at present.
| [
{
"created": "Mon, 12 Nov 2001 17:27:22 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Feb 2002 16:53:26 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Carneiro",
"Saulo",
""
]
] | Dirac's large number hypothesis is motivated by certain scaling transformations that relate the parameters of macro and microphysics. We show that these relations can actually be explained in terms of the holographic $N$ bound conjectured by Bousso and a series of purely cosmological observations, namely, that our universe is spatially homogeneous, isotropic, and flat to a high degree of approximation and that the cosmological constant dominates the energy density at present. |
0906.0023 | Holger Pletsch | Holger J. Pletsch, Bruce Allen | Exploiting Large-Scale Correlations to Detect Continuous Gravitational
Waves | 4 pages, 2 figures | Phys.Rev.Lett.103:181102,2009 | 10.1103/PhysRevLett.103.181102 | LIGO-P0900048, AEI-2009-051 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Fully coherent searches (over realistic ranges of parameter space and
year-long observation times) for unknown sources of continuous gravitational
waves are computationally prohibitive. Less expensive hierarchical searches
divide the data into shorter segments which are analyzed coherently, then
detection statistics from different segments are combined incoherently. The
novel method presented here solves the long-standing problem of how best to do
the incoherent combination. The optimal solution exploits large-scale
parameter-space correlations in the coherent detection statistic. Application
to simulated data shows dramatic sensitivity improvements compared with
previously available (ad hoc) methods, increasing the spatial volume probed by
more than 2 orders of magnitude at lower computational cost.
| [
{
"created": "Sun, 31 May 2009 21:23:53 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Oct 2009 15:27:21 GMT",
"version": "v2"
}
] | 2009-10-27 | [
[
"Pletsch",
"Holger J.",
""
],
[
"Allen",
"Bruce",
""
]
] | Fully coherent searches (over realistic ranges of parameter space and year-long observation times) for unknown sources of continuous gravitational waves are computationally prohibitive. Less expensive hierarchical searches divide the data into shorter segments which are analyzed coherently, then detection statistics from different segments are combined incoherently. The novel method presented here solves the long-standing problem of how best to do the incoherent combination. The optimal solution exploits large-scale parameter-space correlations in the coherent detection statistic. Application to simulated data shows dramatic sensitivity improvements compared with previously available (ad hoc) methods, increasing the spatial volume probed by more than 2 orders of magnitude at lower computational cost. |
2004.00356 | Alkiviadis Triantafyllopoulos | Alkiviadis Triantafyllopoulos, Emmanuel Kapsabelis and Panayiotis
Stavrinos | Gravitational Field on the Lorentz Tangent Bundle: Generalized Paths and
Field Equations | 13 pages. arXiv admin note: text overlap with arXiv:2006.05913 | Eur. Phys. J. Plus 135 (2020) 557 | 10.1140/epjp/s13360-020-00570-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the dynamics of gravitational field and particles in a
generalized framework of a Lorentz tangent bundle. By variating an appropriate
action for each case, we obtain generalized forms of paths and generalized
field equations for a Sasaki type metric. We show that Stokes theorem is
modified with respect to general relativity due to local anisotropy and the
presence of a nonlinear connection which induces an adapted basis in our space.
| [
{
"created": "Wed, 1 Apr 2020 11:53:58 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jul 2020 17:23:42 GMT",
"version": "v2"
}
] | 2020-07-23 | [
[
"Triantafyllopoulos",
"Alkiviadis",
""
],
[
"Kapsabelis",
"Emmanuel",
""
],
[
"Stavrinos",
"Panayiotis",
""
]
] | We investigate the dynamics of gravitational field and particles in a generalized framework of a Lorentz tangent bundle. By variating an appropriate action for each case, we obtain generalized forms of paths and generalized field equations for a Sasaki type metric. We show that Stokes theorem is modified with respect to general relativity due to local anisotropy and the presence of a nonlinear connection which induces an adapted basis in our space. |
1709.02265 | Luis Herrera | L. Herrera and A. Di Prisco | Self-similarity in static axially symmetric relativistic fluids | 34 pages latex. Published in Int. J. Mod. Phys. D | Int. J. Mod. Phys.D27,1750176, (2018) | 10.1142/S0218271817501760 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We carry on a general study on axially symmetric, static fluids admitting a
conformal Killing vector (CKV). The physical relevance of this kind of symmetry
is emphasized. Next, we investigate all possible consequences derived from the
imposition of such a symmetry. Special attention is paid to the problem of
symmetry inheritance. Several families of solutions endowed with a CKV are
exhibited.
| [
{
"created": "Thu, 7 Sep 2017 14:18:41 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jan 2018 08:18:23 GMT",
"version": "v2"
}
] | 2018-01-10 | [
[
"Herrera",
"L.",
""
],
[
"Di Prisco",
"A.",
""
]
] | We carry on a general study on axially symmetric, static fluids admitting a conformal Killing vector (CKV). The physical relevance of this kind of symmetry is emphasized. Next, we investigate all possible consequences derived from the imposition of such a symmetry. Special attention is paid to the problem of symmetry inheritance. Several families of solutions endowed with a CKV are exhibited. |
2101.07763 | Godwill Mbiti Kanyolo PhD | Godwill Mbiti Kanyolo and Titus Masese | Reproducing the asymptotic behaviour of galaxy rotation curves by a
novel constraint in general relativity | 13 pages, 1 figure | null | null | null | gr-qc astro-ph.GA cond-mat.other | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cold dark matter paradigm has been posited as the standard explanation
for the non-Keplerian behavior of galaxy rotation curves, where for galaxies
satisfying the Tully-Fisher relation, the mass of the dark matter halo from a
large class of universal dark matter profiles ought to roughly increase
linearly with radial distance at large distances, $m(r) \sim r/nG$ ($G$ is the
gravitational constant and $n$ is a dimensionless parameter which depends on
the amount of baryonic matter $M$ within the galaxy). Despite numerous advances
in modeling galaxy formation and evolution, a scientific consensus on the
origin of the observed dependence of the dimensionless parameter $n =
(GMa_{0})^{-1/2}$ on the mass of baryonic matter $M$ within the galaxy (the
Tully-Fisher relation), and the connection of the cosmological constant
$\Lambda$ to the parameter $a_{0} \sim (\Lambda/3)^{1/2}$ remains elusive.
Here, we show that Einstein Field Equations can be remolded into
$\nabla_{\nu}\mathcal{K}^{\nu}_{\,\,\mu} = 8\pi
GM\Psi^{*}\mathcal{D}_{\mu}\Psi$, where $\mathcal{K}_{\mu\nu}$ is a complex
Hermitian tensor, $\mathcal{D}_{\mu}$ is a covariant derivative and $\Psi$ is a
complex-valued function. This avails a novel constraint,
$\nabla_{\mu}\nabla_{\nu}\mathcal{K}^{\mu\nu} = 0$ not necessarily available in
Einstein's General Relativity. In the weak-field regime, we can readily
reproduce the Tully-Fisher relation using the usual charge-less pressure-less
fluid. Moreover, our approach is equivalent to a Ginzburg-Landau theory of $n$
bosons, where the order parameter is normalized as $\int_{0}^{1/a_{0}} dr\,4\pi
r^2\Psi^*\Psi = n$ and $1/a_{0} \sim (\Lambda/3)^{-1/2}$ is the cut-off length
scale comparable to the size of the de Sitter universe. Our investigations
provide a framework that reproduces the mass-asymptotic speed relation in
galaxies within the cold dark matter paradigm.
| [
{
"created": "Tue, 19 Jan 2021 18:16:30 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Feb 2021 14:53:30 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Apr 2021 11:25:46 GMT",
"version": "v3"
},
{
"created": "Sun, 30 May 2021 18:03:08 GMT",
"version": "v4"
},
{
"cre... | 2021-09-08 | [
[
"Kanyolo",
"Godwill Mbiti",
""
],
[
"Masese",
"Titus",
""
]
] | The cold dark matter paradigm has been posited as the standard explanation for the non-Keplerian behavior of galaxy rotation curves, where for galaxies satisfying the Tully-Fisher relation, the mass of the dark matter halo from a large class of universal dark matter profiles ought to roughly increase linearly with radial distance at large distances, $m(r) \sim r/nG$ ($G$ is the gravitational constant and $n$ is a dimensionless parameter which depends on the amount of baryonic matter $M$ within the galaxy). Despite numerous advances in modeling galaxy formation and evolution, a scientific consensus on the origin of the observed dependence of the dimensionless parameter $n = (GMa_{0})^{-1/2}$ on the mass of baryonic matter $M$ within the galaxy (the Tully-Fisher relation), and the connection of the cosmological constant $\Lambda$ to the parameter $a_{0} \sim (\Lambda/3)^{1/2}$ remains elusive. Here, we show that Einstein Field Equations can be remolded into $\nabla_{\nu}\mathcal{K}^{\nu}_{\,\,\mu} = 8\pi GM\Psi^{*}\mathcal{D}_{\mu}\Psi$, where $\mathcal{K}_{\mu\nu}$ is a complex Hermitian tensor, $\mathcal{D}_{\mu}$ is a covariant derivative and $\Psi$ is a complex-valued function. This avails a novel constraint, $\nabla_{\mu}\nabla_{\nu}\mathcal{K}^{\mu\nu} = 0$ not necessarily available in Einstein's General Relativity. In the weak-field regime, we can readily reproduce the Tully-Fisher relation using the usual charge-less pressure-less fluid. Moreover, our approach is equivalent to a Ginzburg-Landau theory of $n$ bosons, where the order parameter is normalized as $\int_{0}^{1/a_{0}} dr\,4\pi r^2\Psi^*\Psi = n$ and $1/a_{0} \sim (\Lambda/3)^{-1/2}$ is the cut-off length scale comparable to the size of the de Sitter universe. Our investigations provide a framework that reproduces the mass-asymptotic speed relation in galaxies within the cold dark matter paradigm. |
1901.00767 | Shin'ichi Nojiri | Iver Brevik and Shin'ichi Nojiri | Gravitational Waves in the Presence of Viscosity | Version to appear in IJMPD. LaTeX 14 pages | null | 10.1142/S0218271819501335 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze gravitational waves propagating in an isotropic cosmic fluid
endowed with a bulk viscosity $\zeta$ and a shear viscosity $\eta$, assuming
these coefficients to vary with fluid density $\rho$ as $\rho^\lambda$, with
$\lambda=1/2$ favored by experimental evidence. We give the general governing
equation for the gravitational waves, and focus thereafter on two examples. The
first concerns waves in the very late universe, close to the Big Rip, where the
fate of the comic fluid is dependent highly on the values of the parameters.
Our second example considers the very early universe, the lepton era; the
motivation for this choice being that the microscopical bulk viscosity as
calculated from statistical mechanics is then at maximum. We find that the
gravitational waves on such an underlying medium are damped, having a decay
constant equal to the inverse of the conformal Hubble parameter. Our results
turn out to be in good agreement with other viscosity-based approaches.
| [
{
"created": "Tue, 1 Jan 2019 05:19:32 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Apr 2019 18:09:14 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Jul 2019 09:41:31 GMT",
"version": "v3"
}
] | 2019-07-16 | [
[
"Brevik",
"Iver",
""
],
[
"Nojiri",
"Shin'ichi",
""
]
] | We analyze gravitational waves propagating in an isotropic cosmic fluid endowed with a bulk viscosity $\zeta$ and a shear viscosity $\eta$, assuming these coefficients to vary with fluid density $\rho$ as $\rho^\lambda$, with $\lambda=1/2$ favored by experimental evidence. We give the general governing equation for the gravitational waves, and focus thereafter on two examples. The first concerns waves in the very late universe, close to the Big Rip, where the fate of the comic fluid is dependent highly on the values of the parameters. Our second example considers the very early universe, the lepton era; the motivation for this choice being that the microscopical bulk viscosity as calculated from statistical mechanics is then at maximum. We find that the gravitational waves on such an underlying medium are damped, having a decay constant equal to the inverse of the conformal Hubble parameter. Our results turn out to be in good agreement with other viscosity-based approaches. |
1705.10775 | Alexey Chopovsky | Alexander Zhuk, Alexey Chopovsky, Seyed Hossein Fakhr, Valerii Shulga,
Han Wei | Weak-field limit of Kaluza-Klein models with spherically symmetric
static scalar field: observational constraints | 7 pages, no figures | Eur. Phys. J. C (2017) 77: 721 | 10.1140/epjc/s10052-017-5311-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a multidimensional Kaluza-Klein model with Ricci-flat internal space, we
study the gravitational field in the weak-field limit. This field is created by
two coupled sources. First, this is a point-like massive body which has a
dust-like equation of state in the external space and an arbitrary parameter
$\Omega$ of equation of state in the internal space. The second source is a
static spherically symmetric massive scalar field centered at the origin where
the point-like massive body is. The found perturbed metric coefficients are
used to calculate the parameterized post-Newtonian (PPN) parameter $\gamma$. We
define under which conditions $\gamma$ can be very close to unity in accordance
with the relativistic gravitational tests in the Solar system. This can take
place for both massive or massless scalar fields. For example, to have $\gamma
\approx 1$ in the Solar system, the mass of scalar field should be $\mu \gtrsim
5.05\times 10^{-49}$g $\sim 2.83\times 10^{-16}$eV. In all cases, we arrive at
the same conclusion that to be in agreement with the relativistic gravitational
tests, the gravitating mass should have tension: $\Omega=-1/2$.
| [
{
"created": "Tue, 30 May 2017 17:54:33 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Nov 2017 16:48:31 GMT",
"version": "v2"
}
] | 2017-11-03 | [
[
"Zhuk",
"Alexander",
""
],
[
"Chopovsky",
"Alexey",
""
],
[
"Fakhr",
"Seyed Hossein",
""
],
[
"Shulga",
"Valerii",
""
],
[
"Wei",
"Han",
""
]
] | In a multidimensional Kaluza-Klein model with Ricci-flat internal space, we study the gravitational field in the weak-field limit. This field is created by two coupled sources. First, this is a point-like massive body which has a dust-like equation of state in the external space and an arbitrary parameter $\Omega$ of equation of state in the internal space. The second source is a static spherically symmetric massive scalar field centered at the origin where the point-like massive body is. The found perturbed metric coefficients are used to calculate the parameterized post-Newtonian (PPN) parameter $\gamma$. We define under which conditions $\gamma$ can be very close to unity in accordance with the relativistic gravitational tests in the Solar system. This can take place for both massive or massless scalar fields. For example, to have $\gamma \approx 1$ in the Solar system, the mass of scalar field should be $\mu \gtrsim 5.05\times 10^{-49}$g $\sim 2.83\times 10^{-16}$eV. In all cases, we arrive at the same conclusion that to be in agreement with the relativistic gravitational tests, the gravitating mass should have tension: $\Omega=-1/2$. |
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