id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1908.02340 | Salvatore Capozziello | Wladimir-Georges Boskoff and Salvatore Capozziello | Recovering the cosmological constant from affine geometry | 17 pages, to appear in Int. Jou. Geom. Meth. Mod. Phys | null | 10.1142/S0219887819501615 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A gravity theory without masses can be constructed in Minkowski spaces using
a geometric Minkowski potential. The related affine spacelike spheres can be
seen as the regions of the Minkowski spacelike vectors characterized by a
constant Minkowski gravitational potential. These spheres point out, for each
dimension $n \geq 3$, spacetime models, the de Sitter ones, which satisfy
Einstein's field equations in absence of matter. In other words, it is possible
to generate geometrically the cosmological constant. Even if a lot of possible
parameterizations have been proposed, each one highlighting some geometric and
physical properties of the de Sitter space, we present here a new natural
parameterization which reveals the intrinsic geometric nature of cosmological
constant relating it with the invariant affine radius coming from the so called
Minkowski-Tzitzeica surfaces theory.
| [
{
"created": "Tue, 6 Aug 2019 19:33:16 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Aug 2019 10:51:43 GMT",
"version": "v2"
}
] | 2019-10-23 | [
[
"Boskoff",
"Wladimir-Georges",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | A gravity theory without masses can be constructed in Minkowski spaces using a geometric Minkowski potential. The related affine spacelike spheres can be seen as the regions of the Minkowski spacelike vectors characterized by a constant Minkowski gravitational potential. These spheres point out, for each dimension $n \geq 3$, spacetime models, the de Sitter ones, which satisfy Einstein's field equations in absence of matter. In other words, it is possible to generate geometrically the cosmological constant. Even if a lot of possible parameterizations have been proposed, each one highlighting some geometric and physical properties of the de Sitter space, we present here a new natural parameterization which reveals the intrinsic geometric nature of cosmological constant relating it with the invariant affine radius coming from the so called Minkowski-Tzitzeica surfaces theory. |
gr-qc/0501009 | Viktor Czinner | Viktor Czinner, M\'aty\'as Vas\'uth, \'Arp\'ad Luk\'acs and Zolt\'an
Perj\'es | Covariant Linear Perturbations in a Concordance Model | 8 pages | Int.J.Mod.Phys. A20 (2005) 5671-5677 | 10.1142/S0217751X05022378 | null | gr-qc astro-ph | null | We present the complete solution of the first order metric and density
perturbation equations in a spatially flat (K=0), Friedmann-Robertson-Walker
(FRW) universe filled with pressureless ideal fluid, in the presence of
cosmological constant. We use covariant linear perturbation formalism and the
comoving gauge condition to obtain the field and conservation equations. The
solution contains all modes of the perturbations, i.e. scalar, vector and
tensor modes, and we show that our results are in agreement with the Sachs &
Wolfe metric perturbation formalism.
| [
{
"created": "Tue, 4 Jan 2005 18:52:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Czinner",
"Viktor",
""
],
[
"Vasúth",
"Mátyás",
""
],
[
"Lukács",
"Árpád",
""
],
[
"Perjés",
"Zoltán",
""
]
] | We present the complete solution of the first order metric and density perturbation equations in a spatially flat (K=0), Friedmann-Robertson-Walker (FRW) universe filled with pressureless ideal fluid, in the presence of cosmological constant. We use covariant linear perturbation formalism and the comoving gauge condition to obtain the field and conservation equations. The solution contains all modes of the perturbations, i.e. scalar, vector and tensor modes, and we show that our results are in agreement with the Sachs & Wolfe metric perturbation formalism. |
2110.09184 | Marco Danilo Claudio Torri | Marco Danilo Claudio Torri | Quantum gravity phenomenology induced in the propagation of UHECR, a
kinematical solution in Finsler and generalized Finsler spacetime | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that the Universe is opaque to the propagation of
Ultra-High-Energy Cosmic Rays (UHECRs) since these particles dissipate energy
during their propagation interacting with the Cosmic Microwave Background (CMB)
mainly in the so-called GZK cut-off phenomenon. Some experimental evidence
seems to hint at the possibility of a dilation of the GZK predicted opacity
sphere. It is well-known that kinematical perturbations caused by supposed
quantum gravity (QG) effects can modify the foreseen GZK opacity horizon. The
introduction of Lorentz Invariance Violation (LIV) can indeed reduce, in some
cases making negligible, the CMB-UHECRs interaction probability. In this work
we explore the effects induced by modified kinematics in the UHECRs
phenomenology from the QG perspective. We explore the possibility of a
geometrical description of the massive fermions interaction with the supposed
quantum structure of spacetime in order to introduce a Lorentz covariance
modifification. The kinematics is amended modifying the Dispersion Relations
(DRs) of free particles in the context of a covariance-preserving framework.
This spacetime description requires a more general geometry than the usual
Riemannian one, indicating for instance the Finsler construction and the
related generalized Finsler spacetime as ideal candidates. Finally we
investigate the correlation between the magnitude of Lorentz covariance
modification and the attenuation length of the photopion production process
related to the GZK cut-off, demonstrating that the predicted opacity horizon
can be dilated even in the context of a theory that does not require any
privileged reference frame.
| [
{
"created": "Mon, 18 Oct 2021 11:02:07 GMT",
"version": "v1"
}
] | 2021-10-19 | [
[
"Torri",
"Marco Danilo Claudio",
""
]
] | It is well-known that the Universe is opaque to the propagation of Ultra-High-Energy Cosmic Rays (UHECRs) since these particles dissipate energy during their propagation interacting with the Cosmic Microwave Background (CMB) mainly in the so-called GZK cut-off phenomenon. Some experimental evidence seems to hint at the possibility of a dilation of the GZK predicted opacity sphere. It is well-known that kinematical perturbations caused by supposed quantum gravity (QG) effects can modify the foreseen GZK opacity horizon. The introduction of Lorentz Invariance Violation (LIV) can indeed reduce, in some cases making negligible, the CMB-UHECRs interaction probability. In this work we explore the effects induced by modified kinematics in the UHECRs phenomenology from the QG perspective. We explore the possibility of a geometrical description of the massive fermions interaction with the supposed quantum structure of spacetime in order to introduce a Lorentz covariance modifification. The kinematics is amended modifying the Dispersion Relations (DRs) of free particles in the context of a covariance-preserving framework. This spacetime description requires a more general geometry than the usual Riemannian one, indicating for instance the Finsler construction and the related generalized Finsler spacetime as ideal candidates. Finally we investigate the correlation between the magnitude of Lorentz covariance modification and the attenuation length of the photopion production process related to the GZK cut-off, demonstrating that the predicted opacity horizon can be dilated even in the context of a theory that does not require any privileged reference frame. |
2312.17347 | Rog\'erio Capobianco | Rog\'erio Capobianco, Betti Hartmann and Jutta Kunz | Geodesic Motion in a Swirling Universe: The complete set of solutions | 16 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geodesic motion in a space-time describing a swirling universe.
We show that the geodesic equations can be fully decoupled in the
Hamilton-Jacobi formalism leading to an additional constant of motion. The
analytical solutions to the geodesic equations can be given in terms of
elementary and elliptic functions. We also consider a space-time describing a
static black hole immersed in a swirling universe. In this case, full
separation of variables is not possible and the geodesic equations have to be
solved numerically.
| [
{
"created": "Thu, 28 Dec 2023 20:26:47 GMT",
"version": "v1"
}
] | 2024-01-01 | [
[
"Capobianco",
"Rogério",
""
],
[
"Hartmann",
"Betti",
""
],
[
"Kunz",
"Jutta",
""
]
] | We study the geodesic motion in a space-time describing a swirling universe. We show that the geodesic equations can be fully decoupled in the Hamilton-Jacobi formalism leading to an additional constant of motion. The analytical solutions to the geodesic equations can be given in terms of elementary and elliptic functions. We also consider a space-time describing a static black hole immersed in a swirling universe. In this case, full separation of variables is not possible and the geodesic equations have to be solved numerically. |
0909.1280 | Alex Bernardini | Alex E. Bernardini, O. Bertolami | Thermodynamic equilibrium conditions for mass varying particle
structures | 12 pages, 02 figures | Phys.Lett.B684:96-100,2010; Erratum-ibid.B700:389,2011 | 10.1016/j.physletb.2010.01.007 10.1016/j.physletb.2011.04.065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamic equilibrium conditions for compact structures composed by
mass varying particles are discussed assuming that the so-called dynamical mass
behaves like an additional extensive thermodynamic degree of freedom. It then
follows that, such weakly interacting massive particles can form clusters of
non-baryonic matter or even astrophysical objects that, at cosmological scales,
are held together by gravity and by the attractive force mediated by a
background scalar field. The equilibrium conditions for resultant static,
spherically symmetric objects of uniform energy density are derived for the
case where the particles share essential features with the mass varying
mechanism in the context of cosmological scenarios. Physical solutions which
result in stable astrophysical lumps are obtained and discussed.
| [
{
"created": "Mon, 7 Sep 2009 16:45:20 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Nov 2009 02:19:51 GMT",
"version": "v2"
}
] | 2011-06-07 | [
[
"Bernardini",
"Alex E.",
""
],
[
"Bertolami",
"O.",
""
]
] | The thermodynamic equilibrium conditions for compact structures composed by mass varying particles are discussed assuming that the so-called dynamical mass behaves like an additional extensive thermodynamic degree of freedom. It then follows that, such weakly interacting massive particles can form clusters of non-baryonic matter or even astrophysical objects that, at cosmological scales, are held together by gravity and by the attractive force mediated by a background scalar field. The equilibrium conditions for resultant static, spherically symmetric objects of uniform energy density are derived for the case where the particles share essential features with the mass varying mechanism in the context of cosmological scenarios. Physical solutions which result in stable astrophysical lumps are obtained and discussed. |
2110.03547 | Shailesh Kumar | Subhodeep Sarkar, Shailesh Kumar, Srijit Bhattacharjee | Can we detect a supertranslated black hole? | 8 Pages, 4 Figures, text substantially modified, new results added,
to appear in Physical Review D | null | 10.1103/PhysRevD.105.084001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We attempt to address the question of whether standard tests of general
relativity can detect the presence of a black hole carrying a supertranslation
field. In this regard, we study the photon sphere of a dynamical black hole
carrying a supertranslation hair. We find that the dynamics of the photon
sphere is quite subtle and it may offer an opportunity to differentiate a
supertranslated black hole from its bald counterpart. This represents a first
step towards understanding the observational signatures of a supertranslated
dynamical black hole.
| [
{
"created": "Thu, 7 Oct 2021 15:15:45 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Oct 2021 09:03:07 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Oct 2021 08:25:31 GMT",
"version": "v3"
},
{
"created": "Fri, 11 Mar 2022 17:37:22 GMT",
"version": "v4"
}
] | 2022-04-13 | [
[
"Sarkar",
"Subhodeep",
""
],
[
"Kumar",
"Shailesh",
""
],
[
"Bhattacharjee",
"Srijit",
""
]
] | We attempt to address the question of whether standard tests of general relativity can detect the presence of a black hole carrying a supertranslation field. In this regard, we study the photon sphere of a dynamical black hole carrying a supertranslation hair. We find that the dynamics of the photon sphere is quite subtle and it may offer an opportunity to differentiate a supertranslated black hole from its bald counterpart. This represents a first step towards understanding the observational signatures of a supertranslated dynamical black hole. |
0908.4456 | Samuel Collopy | Samuel J. Collopy | Vacuum Structure of Yang-Mills Theory in Curved Spacetime | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The stability of the chromomagnetic Savvidy vacuum in QCD under the influence
of positive Riemannian curvature is studied. The heat traces of the operators
relevant to SO(2) gauge-invariant Yang-Mills fields and Faddeev-Popov ghosts
are calculated on product spaces of S^2 and S^1 \times S^1. It is shown that
the chromomagnetic vacuum with covariantly constant chromomagnetic field is
stable in a certain set of radii and field strengths.
| [
{
"created": "Mon, 31 Aug 2009 05:12:13 GMT",
"version": "v1"
}
] | 2009-09-01 | [
[
"Collopy",
"Samuel J.",
""
]
] | The stability of the chromomagnetic Savvidy vacuum in QCD under the influence of positive Riemannian curvature is studied. The heat traces of the operators relevant to SO(2) gauge-invariant Yang-Mills fields and Faddeev-Popov ghosts are calculated on product spaces of S^2 and S^1 \times S^1. It is shown that the chromomagnetic vacuum with covariantly constant chromomagnetic field is stable in a certain set of radii and field strengths. |
1810.03812 | Maximiliano Isi | Maximiliano Isi, Ling Sun, Richard Brito, and Andrew Melatos | Directed searches for gravitational waves from ultralight bosons | v3: journal version | Phys. Rev. D 99, 084042 (2019) | 10.1103/PhysRevD.99.084042 | LIGO-P1800270 | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave detectors can search for yet-undiscovered ultralight
bosons, including those conjectured to solve problems in particle physics,
high-energy theory and cosmology. Ground-based instruments could probe boson
masses between $10^{-15}$ eV to $10^{-11}$ eV, which are largely inaccessible
to other experiments. In this paper, we explore the prospect of searching for
the continuous gravitational waves generated by boson clouds around known black
holes. We carefully study the predicted waveforms and use the latest-available
numerical results to model signals for different black-hole and boson
parameters. We then demonstrate the suitability of a specific method (hidden
Markov model tracking) to efficiently search for such signals, even when the
source parameters are not perfectly known and allowing for some uncertainty in
theoretical predictions. We empirically study this method's sensitivity and
computational cost in the context of boson signals, finding that it will be
possible to target remnants from compact-binary mergers localized with at least
three instruments. For signals from scalar clouds, we also compute detection
horizons for future detectors (Advanced LIGO, LIGO Voyager, Cosmic Explorer and
the Einstein Telescope). Among other results, we find that, after one year of
observation, an Advanced LIGO detector at design sensitivity could detect these
sources up to over 100 Mpc, while Cosmic Explorer could reach over $10^4$ Mpc.
These projections offer a more complete picture than previous estimates based
on analytic approximations to the signal power or idealized search strategies.
Finally, we discuss specific implications for the followup of compact-binary
coalescences and black holes in x-ray binaries. Along the way, we review the
basic physics of bosons around black holes, in the hope of providing a bridge
between the theory and data-analysis literatures.
| [
{
"created": "Tue, 9 Oct 2018 04:39:45 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Dec 2018 16:23:24 GMT",
"version": "v2"
},
{
"created": "Mon, 6 May 2019 00:18:18 GMT",
"version": "v3"
}
] | 2019-05-07 | [
[
"Isi",
"Maximiliano",
""
],
[
"Sun",
"Ling",
""
],
[
"Brito",
"Richard",
""
],
[
"Melatos",
"Andrew",
""
]
] | Gravitational-wave detectors can search for yet-undiscovered ultralight bosons, including those conjectured to solve problems in particle physics, high-energy theory and cosmology. Ground-based instruments could probe boson masses between $10^{-15}$ eV to $10^{-11}$ eV, which are largely inaccessible to other experiments. In this paper, we explore the prospect of searching for the continuous gravitational waves generated by boson clouds around known black holes. We carefully study the predicted waveforms and use the latest-available numerical results to model signals for different black-hole and boson parameters. We then demonstrate the suitability of a specific method (hidden Markov model tracking) to efficiently search for such signals, even when the source parameters are not perfectly known and allowing for some uncertainty in theoretical predictions. We empirically study this method's sensitivity and computational cost in the context of boson signals, finding that it will be possible to target remnants from compact-binary mergers localized with at least three instruments. For signals from scalar clouds, we also compute detection horizons for future detectors (Advanced LIGO, LIGO Voyager, Cosmic Explorer and the Einstein Telescope). Among other results, we find that, after one year of observation, an Advanced LIGO detector at design sensitivity could detect these sources up to over 100 Mpc, while Cosmic Explorer could reach over $10^4$ Mpc. These projections offer a more complete picture than previous estimates based on analytic approximations to the signal power or idealized search strategies. Finally, we discuss specific implications for the followup of compact-binary coalescences and black holes in x-ray binaries. Along the way, we review the basic physics of bosons around black holes, in the hope of providing a bridge between the theory and data-analysis literatures. |
1708.01482 | Kazufumi Ninomiya | K. Ninomiya, T. Akiyama, M. Hata, M. Hatori, T. Iguri, Y. Ikeda, S.
Inaba, H. Kawamura, R. Kishi, H. Murakami, Y. Nakaya, H. Nishio, N. Ogawa, J.
Onishi, S. Saiba, T. Sakuta, S. Tanaka, R. Tanuma, Y. Totsuka, R. Tsutsui, K.
Watanabe and J. Murata | Short-range test of the universality of gravitational constant $G$ at
the millimeter scale using a digital image sensor | submitted to Class. Quantum Grav | Class. Quantum Grav. 34 185005, 2017 | 10.1088/1361-6382/aa837f | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The composition dependence of gravitational constant $G$ is measured at the
millimeter scale to test the weak equivalence principle, which may be violated
at short range through new Yukawa interactions such as the dilaton exchange
force. A torsion balance on a turning table with two identical tungsten targets
surrounded by two different attractor materials (copper and aluminum) is used
to measure gravitational torque by means of digital measurements of a position
sensor. Values of the ratios $\tilde{G}_{Al-W}/\tilde{G}_{Cu-W} -1$ and
$\tilde{G}_{Cu-W}/G_{N} -1$ were $(0.9 \pm 1.1_{\mathrm{sta}} \pm
4.8_{\mathrm{sys}}) \times 10^{-2}$ and $ (0.2 \pm 0.9_{\mathrm{sta}} \pm
2.1_{\mathrm{sys}}) \times 10^{-2}$ , respectively; these were obtained at a
center to center separation of 1.7 cm and surface to surface separation of 4.5
mm between target and attractor, which is consistent with the universality of
$G$. A weak equivalence principle (WEP) violation parameter of
$\eta_{Al-Cu}(r\sim 1\: \mathrm{cm})=(0.9 \pm 1.1_{\mathrm{sta}} \pm
4.9_{\mathrm{sys}}) \times 10^{-2} $ at the shortest range of around 1 cm was
also obtained.
| [
{
"created": "Fri, 4 Aug 2017 13:12:26 GMT",
"version": "v1"
}
] | 2017-08-25 | [
[
"Ninomiya",
"K.",
""
],
[
"Akiyama",
"T.",
""
],
[
"Hata",
"M.",
""
],
[
"Hatori",
"M.",
""
],
[
"Iguri",
"T.",
""
],
[
"Ikeda",
"Y.",
""
],
[
"Inaba",
"S.",
""
],
[
"Kawamura",
"H.",
""
]... | The composition dependence of gravitational constant $G$ is measured at the millimeter scale to test the weak equivalence principle, which may be violated at short range through new Yukawa interactions such as the dilaton exchange force. A torsion balance on a turning table with two identical tungsten targets surrounded by two different attractor materials (copper and aluminum) is used to measure gravitational torque by means of digital measurements of a position sensor. Values of the ratios $\tilde{G}_{Al-W}/\tilde{G}_{Cu-W} -1$ and $\tilde{G}_{Cu-W}/G_{N} -1$ were $(0.9 \pm 1.1_{\mathrm{sta}} \pm 4.8_{\mathrm{sys}}) \times 10^{-2}$ and $ (0.2 \pm 0.9_{\mathrm{sta}} \pm 2.1_{\mathrm{sys}}) \times 10^{-2}$ , respectively; these were obtained at a center to center separation of 1.7 cm and surface to surface separation of 4.5 mm between target and attractor, which is consistent with the universality of $G$. A weak equivalence principle (WEP) violation parameter of $\eta_{Al-Cu}(r\sim 1\: \mathrm{cm})=(0.9 \pm 1.1_{\mathrm{sta}} \pm 4.9_{\mathrm{sys}}) \times 10^{-2} $ at the shortest range of around 1 cm was also obtained. |
gr-qc/9701063 | N. Redington | N. Redington | Literal Rippling of Spacetime | 4 pages | null | null | null | gr-qc | null | The metric perturbation tensor corresponding to a transverse oscillation of
spacetime is composed of products of cosines. When averaged over many
wavelengths, such a metric may look either Minkowskian or Euclidean at large
scales, depending on the amplitude and wavelength of the oscillation.
| [
{
"created": "Wed, 29 Jan 1997 22:48:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Redington",
"N.",
""
]
] | The metric perturbation tensor corresponding to a transverse oscillation of spacetime is composed of products of cosines. When averaged over many wavelengths, such a metric may look either Minkowskian or Euclidean at large scales, depending on the amplitude and wavelength of the oscillation. |
1711.06206 | Thiago R.P. Caram\^es | J\'ulio C. Fabris, Hermano Velten, Thiago R. P. Caram\^es, Matheus J.
Lazo and Gast\~ao S. F. Frederico | Cosmology from a new non-conservative gravity | 8 pages, 2 figures; version enriched with more discussion, graphs
were improved and new references added. To appear in IJMPD | Int. J. Mod. Phys. D 27, 1841006 (2018) | 10.1142/S0218271818410067 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present a cosmological model arising from a non-conservative
gravitational theory proposed in [PRD 95, 101501(R) (2017)]. The novel feature
where comparing with previous implementations of dissipative effects in gravity
is the possible arising of such phenomena from a least action principle, so
they are of a purely geometric nature. We derive the dynamical equations
describing the behaviour of the cosmic background, considering a single fluid
model composed by pressureles matter, whereas the dark energy is conceived as
an outcome of the "geometric" dissipative process emerging in the model.
Besides, adopting the synchronous gauge we obtain the first-order perturbative
equations which shall describe the evolution of the matter perturbations within
the linear regime.
| [
{
"created": "Thu, 16 Nov 2017 17:24:32 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Nov 2017 19:43:33 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Dec 2017 16:49:46 GMT",
"version": "v3"
}
] | 2018-05-28 | [
[
"Fabris",
"Júlio C.",
""
],
[
"Velten",
"Hermano",
""
],
[
"Caramês",
"Thiago R. P.",
""
],
[
"Lazo",
"Matheus J.",
""
],
[
"Frederico",
"Gastão S. F.",
""
]
] | In this paper we present a cosmological model arising from a non-conservative gravitational theory proposed in [PRD 95, 101501(R) (2017)]. The novel feature where comparing with previous implementations of dissipative effects in gravity is the possible arising of such phenomena from a least action principle, so they are of a purely geometric nature. We derive the dynamical equations describing the behaviour of the cosmic background, considering a single fluid model composed by pressureles matter, whereas the dark energy is conceived as an outcome of the "geometric" dissipative process emerging in the model. Besides, adopting the synchronous gauge we obtain the first-order perturbative equations which shall describe the evolution of the matter perturbations within the linear regime. |
2311.14278 | Tadashi Sasaki | Tadashi Sasaki | Deflection of Light by a Reissner-Nordstr\"om Black Hole and Painlev\'e
VI equation | 20 pages; added 3 references and 1 paragraph for Section 4, corrected
typos in reference list | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider the bending angle of the trajectory of a photon incident from and
deflected to infinity around a Reissner-Nordstr\"om black hole. We treat the
bending angle as a function of the squared reciprocal of the impact parameter
and the squared electric charge of the background normalized by the mass of the
black hole. It is shown that the bending angle satisfies a system of two
inhomogeneous linear partial differential equations with polynomial
coefficients. This system can be understood as an isomonodromic deformation of
the inhomogeneous Picard-Fuchs equation satisfied by the bending angle in the
Schwarzschild spacetime, where the deformation parameter is identified as the
background electric charge. Furthermore, the integrability condition for these
equations is found to be a specific type of the Painlev\'e VI equation that
allows an algebraic solution. We solve the differential equations both at the
weak and strong deflection limits. In the weak deflection limit, the bending
angle is expressed as a power series expansion in terms of the squared
reciprocal of the impact parameter and we obtain the explicit full-order
expression for the coefficients. In the strong deflection limit, we obtain the
asymptotic form of the bending angle that consists of the divergent logarithmic
term and the finite O(1) term supplemented by linear recurrence relations which
enable us to straightforwardly derive higher order coefficients. In deriving
these results, the isomonodromic property of the differential equations plays
an important role. Lastly, we briefly discuss the applicability of our method
to other types of spacetimes such as a spinning black hole.
| [
{
"created": "Fri, 24 Nov 2023 04:49:18 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Dec 2023 07:10:10 GMT",
"version": "v2"
}
] | 2023-12-04 | [
[
"Sasaki",
"Tadashi",
""
]
] | We consider the bending angle of the trajectory of a photon incident from and deflected to infinity around a Reissner-Nordstr\"om black hole. We treat the bending angle as a function of the squared reciprocal of the impact parameter and the squared electric charge of the background normalized by the mass of the black hole. It is shown that the bending angle satisfies a system of two inhomogeneous linear partial differential equations with polynomial coefficients. This system can be understood as an isomonodromic deformation of the inhomogeneous Picard-Fuchs equation satisfied by the bending angle in the Schwarzschild spacetime, where the deformation parameter is identified as the background electric charge. Furthermore, the integrability condition for these equations is found to be a specific type of the Painlev\'e VI equation that allows an algebraic solution. We solve the differential equations both at the weak and strong deflection limits. In the weak deflection limit, the bending angle is expressed as a power series expansion in terms of the squared reciprocal of the impact parameter and we obtain the explicit full-order expression for the coefficients. In the strong deflection limit, we obtain the asymptotic form of the bending angle that consists of the divergent logarithmic term and the finite O(1) term supplemented by linear recurrence relations which enable us to straightforwardly derive higher order coefficients. In deriving these results, the isomonodromic property of the differential equations plays an important role. Lastly, we briefly discuss the applicability of our method to other types of spacetimes such as a spinning black hole. |
gr-qc/9809031 | Jorge Pullin | Jorge Pullin | Matters of Gravity, The newsletter of the APS Topical Group on
Gravitation | 31 pages, html.sty, Jorge Pullin (editor).
http://vishnu.nirvana.phys.psu.edu/mog.html | null | null | MOG-12 | gr-qc | null | Contents:
Editorial
News:
- Topical group news, by Jim Isenberg
- Summer school in gravitational physics opportunity, by Jim Hartle
- Bogart, Bergman and (Al)bert, by Clifford Will and Robert Riemer
- New data-analysis subgroups of the LSC, by Eanna Flanagan
- Marcel Bardon, a man of vision, by Richard Isaacson
Research Briefs:
- Status of the GEO600 project, by Harold Lueck
- A nonperturbative formulation of string theory?, by Gary Horowitz
- TAMA project update, by Seiji Kawamura
- Neohistorical approaches to quantum gravity, by Lee Smolin
- LIGO project update, by David Shoemaker
- Gravitational waves from neutron stars, by Eanna Flanagan
Conference reports
- Perugia meeting, by Joe Kovalik
- Nickel and Dime gravity meeting, by Eric Poisson
- Second international LISA symposium, by Robin Stebbins
- JILA meeting on seismic isolation et al., by Joe Giaime
| [
{
"created": "Mon, 7 Sep 1998 21:51:36 GMT",
"version": "v1"
}
] | 2009-03-10 | [
[
"Pullin",
"Jorge",
""
]
] | Contents: Editorial News: - Topical group news, by Jim Isenberg - Summer school in gravitational physics opportunity, by Jim Hartle - Bogart, Bergman and (Al)bert, by Clifford Will and Robert Riemer - New data-analysis subgroups of the LSC, by Eanna Flanagan - Marcel Bardon, a man of vision, by Richard Isaacson Research Briefs: - Status of the GEO600 project, by Harold Lueck - A nonperturbative formulation of string theory?, by Gary Horowitz - TAMA project update, by Seiji Kawamura - Neohistorical approaches to quantum gravity, by Lee Smolin - LIGO project update, by David Shoemaker - Gravitational waves from neutron stars, by Eanna Flanagan Conference reports - Perugia meeting, by Joe Kovalik - Nickel and Dime gravity meeting, by Eric Poisson - Second international LISA symposium, by Robin Stebbins - JILA meeting on seismic isolation et al., by Joe Giaime |
0705.2034 | Mauricio Bellini | Silvina Paola Gomez Martinez (Mar del Plata University), Lucio Fabio
P. da Silva (Paraiba University), Jose Edgar Madriz Aguilar (Paraiba
University), Mauricio Bellini (Mar del Plata University & CONICET) | Stochastic approach of gravitational waves in presence of a decaying
cosmological parameter from a 5D vacuum theory of gravity | version to be published in Il Nuovo Cimento B | Nuovo Cim.B122:897-907,2007; Nuovo Cim.122B:897-907,2007 | 10.1393/ncb/i2007-10414-7 | null | gr-qc hep-th | null | We develop an stochastic approach to study gravitational waves produced
during the inflationary epoch under the presence of a decaying cosmological
parameter, on a 5D geometrical background which is Riemann flat. We obtain that
the squared tensor metric fluctuations depend strongly on the cosmological
parameter $\Lambda (t)$ and we finally illustrate the formalism with an example
of a decaying $\Lambda(t)$.
| [
{
"created": "Mon, 14 May 2007 21:19:25 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Oct 2007 22:05:06 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Nov 2007 20:39:51 GMT",
"version": "v3"
},
{
"created": "Tue, 11 Dec 2007 16:56:32 GMT",
"version": "v4"
},
{
"c... | 2010-11-15 | [
[
"Martinez",
"Silvina Paola Gomez",
"",
"Mar del Plata University"
],
[
"da Silva",
"Lucio Fabio P.",
"",
"Paraiba University"
],
[
"Aguilar",
"Jose Edgar Madriz",
"",
"Paraiba\n University"
],
[
"Bellini",
"Mauricio",
"",
"Mar del Plata ... | We develop an stochastic approach to study gravitational waves produced during the inflationary epoch under the presence of a decaying cosmological parameter, on a 5D geometrical background which is Riemann flat. We obtain that the squared tensor metric fluctuations depend strongly on the cosmological parameter $\Lambda (t)$ and we finally illustrate the formalism with an example of a decaying $\Lambda(t)$. |
2003.10682 | Jing Ren | Ufuk Aydemir, Bob Holdom, Jing Ren | Not quite black holes as dark matter | 33 pages, 10 figures | Phys. Rev. D 102, 024058 (2020) | 10.1103/PhysRevD.102.024058 | null | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Primordial black holes that survive until the present have been considered as
a dark matter candidate. In this paper we argue that primordial 2-2-hole
remnants provide a more promising and testable option. 2-2-holes arise in
quadratic gravity as a new family of classical solutions for ultracompact
matter distributions and they possess the black hole exterior without an event
horizon. They may serve as the endpoint of gravitational collapse, providing a
resolution for the information loss problem. Intriguing thermodynamic behavior
is found for these objects when sourced by a thermal gas. A large 2-2-hole
radiates with a Hawking-like temperature and exhibits an entropy-area law. At a
late stage, the evaporation slows down and essentially stops as the mass
asymptotically approaches a minimal value. This remnant mass is determined by a
fundamental scale in quadratic gravity. We study the cosmological and
astrophysical implications of having these remnants as dark matter and derive
the corresponding constraints. A distinctive phenomenon associated with remnant
mergers occurs, predicting fluxes of high-energy astrophysical particles due to
the spectacular evaporation of the merger product. Measurements of high-energy
photon and neutrino fluxes could possibly bound the remnant mass to be not far
above the Planck mass. Early-universe physics, on the other hand, requires that
2-2-holes quickly evolve into the remnant state after formation, putting an
upper bound on the formation mass.
| [
{
"created": "Tue, 24 Mar 2020 06:40:10 GMT",
"version": "v1"
}
] | 2020-07-29 | [
[
"Aydemir",
"Ufuk",
""
],
[
"Holdom",
"Bob",
""
],
[
"Ren",
"Jing",
""
]
] | Primordial black holes that survive until the present have been considered as a dark matter candidate. In this paper we argue that primordial 2-2-hole remnants provide a more promising and testable option. 2-2-holes arise in quadratic gravity as a new family of classical solutions for ultracompact matter distributions and they possess the black hole exterior without an event horizon. They may serve as the endpoint of gravitational collapse, providing a resolution for the information loss problem. Intriguing thermodynamic behavior is found for these objects when sourced by a thermal gas. A large 2-2-hole radiates with a Hawking-like temperature and exhibits an entropy-area law. At a late stage, the evaporation slows down and essentially stops as the mass asymptotically approaches a minimal value. This remnant mass is determined by a fundamental scale in quadratic gravity. We study the cosmological and astrophysical implications of having these remnants as dark matter and derive the corresponding constraints. A distinctive phenomenon associated with remnant mergers occurs, predicting fluxes of high-energy astrophysical particles due to the spectacular evaporation of the merger product. Measurements of high-energy photon and neutrino fluxes could possibly bound the remnant mass to be not far above the Planck mass. Early-universe physics, on the other hand, requires that 2-2-holes quickly evolve into the remnant state after formation, putting an upper bound on the formation mass. |
gr-qc/0207076 | Nicola Rossano Bruno | Nicola Rossano Bruno | Group of boost and rotation transformations with two
observer-independent scales | revised version accepted for publication on Phys.Lett.B; one
reference corrected, some physical comments added. 6 pages, RevTex4 | Phys.Lett. B547 (2002) 109-115 | 10.1016/S0370-2693(02)02738-7 | null | gr-qc hep-th | null | I examine the structure of the deformed Lorentz transformations in one of the
recently-proposed schemes with two observer-independent scales. I develop a
technique for the analysis of general combinations of rotations and deformed
boosts. In particular, I verify explicitly that the transformations form group.
| [
{
"created": "Fri, 19 Jul 2002 13:45:21 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Sep 2002 16:45:02 GMT",
"version": "v2"
}
] | 2010-04-05 | [
[
"Bruno",
"Nicola Rossano",
""
]
] | I examine the structure of the deformed Lorentz transformations in one of the recently-proposed schemes with two observer-independent scales. I develop a technique for the analysis of general combinations of rotations and deformed boosts. In particular, I verify explicitly that the transformations form group. |
2310.08758 | Pedro Mario Ca\~nate Casseres | Pedro Ca\~nate | Simple method to generate magnetically charged ultra-static traversable
wormholes without exotic matter in Einstein-scalar-Gauss-Bonnet gravity | Typos corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All the magnetically charged ultrastatic and spherically symmetric spacetime
solutions in the framework of linear/nonlinear electrodynamics, with an
arbitrary electromagnetic Lagrangian density $\mathcal{L}(\mathcal{F})$
depending only of the electromagnetic invariant
$\mathcal{F}\!=\!F_{\alpha\beta}F^{\alpha\beta}\!/4$, minimally coupled to
Einstein-scalar-Gauss-Bonnet gravity [EsGB-$\mathcal{L}(\mathcal{F})$], are
found. We also show that a magnetically charged ultrastatic and spherically
symmetric EsGB-$\mathcal{L}(\mathcal{F})$ solution with invariant $\mathcal{F}$
having a strict global maximum value $\mathcal{F}_{_{0}}$ in the entire domain
of the solution, and such that
$\mathcal{L}_{_{0}}=\mathcal{L}(\mathcal{F}_{_{0}})>0$, can be interpreted as
an ultrastatic wormhole spacetime geometry with throat radius determined by the
scalar charge and the quantity $\mathcal{L}_{_{0}}$. We provide some examples,
including Maxwell's theory of electrodynamics (linear electrodynamics)
$\mathcal{L}_{_{_{\mathrm{LED}}}} \!=\! \mathcal{F}$, producing the magnetic
dual of the purely electric Ellis-Bronnikov EsGB Maxwell wormhole derived in
[P. Ca\~nate, J. Sultana, D. Kazanas, Phys. Rev. D {\bf100}, 064007 (2019)];
and the nonlinear electrodynamics (NLED) models given by Born-Infeld
$\mathcal{L}_{_{_{\mathrm{BI}}}} \!=\! -4\beta^{2} + 4\beta^{2} \sqrt{ 1 +
\mathcal{F}\!/\!(2\beta^{2})~}$, and Euler-Heisenberg in the approximation of
the weak-field limit $\mathcal{L}_{_{_{\mathrm{EH}}}} \!=\!
\mathcal{L}_{_{_{\mathrm{LED}}}} + \gamma \mathcal{F}^{2}\!/2$. With those NLED
models, two novel magnetically charged ultrastatic traversable wormholes (EsGB
Born-Infeld and EsGB Euler-Heisenberg wormholes) are presented as exact
solutions without exotic matter in EsGB-$\mathcal{L}(\mathcal{F})$ gravity.
| [
{
"created": "Thu, 12 Oct 2023 22:55:57 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Dec 2023 16:24:40 GMT",
"version": "v2"
}
] | 2024-01-01 | [
[
"Cañate",
"Pedro",
""
]
] | All the magnetically charged ultrastatic and spherically symmetric spacetime solutions in the framework of linear/nonlinear electrodynamics, with an arbitrary electromagnetic Lagrangian density $\mathcal{L}(\mathcal{F})$ depending only of the electromagnetic invariant $\mathcal{F}\!=\!F_{\alpha\beta}F^{\alpha\beta}\!/4$, minimally coupled to Einstein-scalar-Gauss-Bonnet gravity [EsGB-$\mathcal{L}(\mathcal{F})$], are found. We also show that a magnetically charged ultrastatic and spherically symmetric EsGB-$\mathcal{L}(\mathcal{F})$ solution with invariant $\mathcal{F}$ having a strict global maximum value $\mathcal{F}_{_{0}}$ in the entire domain of the solution, and such that $\mathcal{L}_{_{0}}=\mathcal{L}(\mathcal{F}_{_{0}})>0$, can be interpreted as an ultrastatic wormhole spacetime geometry with throat radius determined by the scalar charge and the quantity $\mathcal{L}_{_{0}}$. We provide some examples, including Maxwell's theory of electrodynamics (linear electrodynamics) $\mathcal{L}_{_{_{\mathrm{LED}}}} \!=\! \mathcal{F}$, producing the magnetic dual of the purely electric Ellis-Bronnikov EsGB Maxwell wormhole derived in [P. Ca\~nate, J. Sultana, D. Kazanas, Phys. Rev. D {\bf100}, 064007 (2019)]; and the nonlinear electrodynamics (NLED) models given by Born-Infeld $\mathcal{L}_{_{_{\mathrm{BI}}}} \!=\! -4\beta^{2} + 4\beta^{2} \sqrt{ 1 + \mathcal{F}\!/\!(2\beta^{2})~}$, and Euler-Heisenberg in the approximation of the weak-field limit $\mathcal{L}_{_{_{\mathrm{EH}}}} \!=\! \mathcal{L}_{_{_{\mathrm{LED}}}} + \gamma \mathcal{F}^{2}\!/2$. With those NLED models, two novel magnetically charged ultrastatic traversable wormholes (EsGB Born-Infeld and EsGB Euler-Heisenberg wormholes) are presented as exact solutions without exotic matter in EsGB-$\mathcal{L}(\mathcal{F})$ gravity. |
2006.09414 | Tiago Fran\c{c}a | Pau Figueras and Tiago Fran\c{c}a | Gravitational Collapse in Cubic Horndeski Theories | 27 pages + 5 appendices (11 pages) + 16 figures. v2: additional
figure added. Updated to match published version | null | 10.1088/1361-6382/abb693 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study spherically symmetric gravitational collapse in cubic Horndeski
theories of gravity. By varying the coupling constants and the initial
amplitude of the scalar field, we determine the region in the space of
couplings and amplitudes for which it is possible to construct global solutions
to the Horndeski theories. Furthermore, we identify the regime of validity of
effective field theory as the sub-region for which a certain weak field
condition remains small at all times. We evolve the initial data using the CCZ4
formulation of the Einstein equations and horizon penetrating coordinates
without assuming spherical symmetry.
| [
{
"created": "Tue, 16 Jun 2020 18:01:01 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2020 20:19:21 GMT",
"version": "v2"
}
] | 2020-12-18 | [
[
"Figueras",
"Pau",
""
],
[
"França",
"Tiago",
""
]
] | We study spherically symmetric gravitational collapse in cubic Horndeski theories of gravity. By varying the coupling constants and the initial amplitude of the scalar field, we determine the region in the space of couplings and amplitudes for which it is possible to construct global solutions to the Horndeski theories. Furthermore, we identify the regime of validity of effective field theory as the sub-region for which a certain weak field condition remains small at all times. We evolve the initial data using the CCZ4 formulation of the Einstein equations and horizon penetrating coordinates without assuming spherical symmetry. |
2310.05823 | Federico De Lillo | Federico De Lillo, Jishnu Suresh | Estimating Astrophysical Population Properties using a multi-component
Stochastic Gravitational-Wave Background Search | 20 pages, 6 figures, 6 tables | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent start of the fourth observing run of the LIGO-Virgo-KAGRA (LVK)
collaboration has reopened the hunt for gravitational-wave (GW) signals, with
one compact-binary-coalescence (CBC) signal expected to be observed every few
days. Among the signals that could be detected for the first time there is the
stochastic gravitational-wave background (SGWB) from the superposition of
unresolvable GW signals that cannot be detected individually. In fact, multiple
SGWBs are likely to arise given the variety of sources, making it crucial to
identify the dominant components and assess their origin. However, most search
methods with ground-based detectors assume the presence of one SGWB component
at a time, which could lead to biased results in estimating its spectral shape
if multiple SGWBs exist. Therefore, a joint estimate of the components is
necessary. In this work, we adapt such an approach and analyse the data from
the first three LVK observing runs, searching for a multi-component isotropic
SGWB. We do not find evidence for any SGWB and establish upper limits on the
dimensionless energy parameter $\Omega_{\rm gw}(f)$ at 25 Hz for five different
power-law spectral indices, $\alpha = 0, \, 2/3,\, 2,\, 3,\, 4$, jointly. For
the spectral indices $\alpha = 2/3,\, 2, \, 4$, corresponding to astrophysical
SGWBs from CBCs, r-mode instabilities in young rotating neutron stars, and
magnetars, we draw further astrophysical implications by constraining the
ensemble parameters $K_{\rm CBC}, \, K_{\rm r-modes}, \, K_{\rm magnetars}$,
defined in the main text.
| [
{
"created": "Mon, 9 Oct 2023 16:08:22 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Mar 2024 08:47:53 GMT",
"version": "v2"
}
] | 2024-03-27 | [
[
"De Lillo",
"Federico",
""
],
[
"Suresh",
"Jishnu",
""
]
] | The recent start of the fourth observing run of the LIGO-Virgo-KAGRA (LVK) collaboration has reopened the hunt for gravitational-wave (GW) signals, with one compact-binary-coalescence (CBC) signal expected to be observed every few days. Among the signals that could be detected for the first time there is the stochastic gravitational-wave background (SGWB) from the superposition of unresolvable GW signals that cannot be detected individually. In fact, multiple SGWBs are likely to arise given the variety of sources, making it crucial to identify the dominant components and assess their origin. However, most search methods with ground-based detectors assume the presence of one SGWB component at a time, which could lead to biased results in estimating its spectral shape if multiple SGWBs exist. Therefore, a joint estimate of the components is necessary. In this work, we adapt such an approach and analyse the data from the first three LVK observing runs, searching for a multi-component isotropic SGWB. We do not find evidence for any SGWB and establish upper limits on the dimensionless energy parameter $\Omega_{\rm gw}(f)$ at 25 Hz for five different power-law spectral indices, $\alpha = 0, \, 2/3,\, 2,\, 3,\, 4$, jointly. For the spectral indices $\alpha = 2/3,\, 2, \, 4$, corresponding to astrophysical SGWBs from CBCs, r-mode instabilities in young rotating neutron stars, and magnetars, we draw further astrophysical implications by constraining the ensemble parameters $K_{\rm CBC}, \, K_{\rm r-modes}, \, K_{\rm magnetars}$, defined in the main text. |
1302.3337 | Sung Won Kim | Sung-Won Kim | Flare-out condition of Morris-Thorne wormhole and finiteness of pressure | null | null | 10.3938/jkps.63.1887 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wormhole is defined as the topological structure with the throat connecting
two asymptotically flat spaces. In order to have and maintain the structure of
the wormhole, there needs the geometrical flare-out condition, i.e., the
minimal size at throat. In the case of Morris-Thorne type wormhole, the
condition is given by the huge surface tension compared to the energy density
times the square of the light speed. In this paper, we re-considered the
flare-out condition for the wormhole with the Einstein equation, checked the
finiteness of the pressure, and investigated its physical meaning.
| [
{
"created": "Thu, 14 Feb 2013 08:19:32 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Kim",
"Sung-Won",
""
]
] | Wormhole is defined as the topological structure with the throat connecting two asymptotically flat spaces. In order to have and maintain the structure of the wormhole, there needs the geometrical flare-out condition, i.e., the minimal size at throat. In the case of Morris-Thorne type wormhole, the condition is given by the huge surface tension compared to the energy density times the square of the light speed. In this paper, we re-considered the flare-out condition for the wormhole with the Einstein equation, checked the finiteness of the pressure, and investigated its physical meaning. |
1405.0229 | Seyed Meraj Mousavi Rasouli | S. M. M. Rasouli, Mehrdad Farhoudi and Paulo Vargas Moniz | Modified Brans-Dicke Theory in Arbitrary Dimensions | 22 pages, 8 figures | Class. Quantum Grav. 31 (2014) 115002 | 10.1088/0264-9381/31/11/115002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within an algebraic framework, used to construct the induced-matter-theory
(IMT) setting, in $(D+1)$-dimensional Brans-Dicke (BD) scenario, we obtain a
modified BD theory (MBDT) in $D$ dimensions. Being more specific, from the
$(D+1)$-dimensional field equations, a $D$--dimensional BD theory, bearing new
features, is extracted by means of a suitable dimensional reduction onto a
hypersurface orthogonal to the extra dimension. In particular, the BD scalar
field in such $D$-dimensional theory has a self-interacting potential, which
can be suitably interpreted as produced by the extra dimension. Subsequently,
as an application to cosmology, we consider an extended spatially flat FLRW
geometry in a $(D+1)$-dimensional space-time. After obtaining the power-law
solutions in the bulk, we proceed to construct the corresponding physics, by
means of the induced MBDT procedure, on the $D$-dimensional hypersurface. We
then contrast the resulted solutions (for different phases of the universe)
with those usually extracted from the conventional GR and BD theories in view
of current ranges for cosmological parameters. We show that the induced perfect
fluid background and the induced scalar potential can be employed, within some
limits, for describing different epochs of the universe. Finally, we comment on
the observational viability of such a model.
| [
{
"created": "Thu, 1 May 2014 17:34:43 GMT",
"version": "v1"
},
{
"created": "Tue, 13 May 2014 14:25:12 GMT",
"version": "v2"
}
] | 2014-05-14 | [
[
"Rasouli",
"S. M. M.",
""
],
[
"Farhoudi",
"Mehrdad",
""
],
[
"Moniz",
"Paulo Vargas",
""
]
] | Within an algebraic framework, used to construct the induced-matter-theory (IMT) setting, in $(D+1)$-dimensional Brans-Dicke (BD) scenario, we obtain a modified BD theory (MBDT) in $D$ dimensions. Being more specific, from the $(D+1)$-dimensional field equations, a $D$--dimensional BD theory, bearing new features, is extracted by means of a suitable dimensional reduction onto a hypersurface orthogonal to the extra dimension. In particular, the BD scalar field in such $D$-dimensional theory has a self-interacting potential, which can be suitably interpreted as produced by the extra dimension. Subsequently, as an application to cosmology, we consider an extended spatially flat FLRW geometry in a $(D+1)$-dimensional space-time. After obtaining the power-law solutions in the bulk, we proceed to construct the corresponding physics, by means of the induced MBDT procedure, on the $D$-dimensional hypersurface. We then contrast the resulted solutions (for different phases of the universe) with those usually extracted from the conventional GR and BD theories in view of current ranges for cosmological parameters. We show that the induced perfect fluid background and the induced scalar potential can be employed, within some limits, for describing different epochs of the universe. Finally, we comment on the observational viability of such a model. |
gr-qc/0111082 | Anjan Ananda Sen | A.A. Sen and S. Sethi (HRI, Allahabad, India) | Quintessence Model With Double Exponential Potential | 6 pages, Revtex Style, four eps figures,some new comments are added
regarding the fitting analysis. Conclusion has been rewritten. Accepted for
publication in Physics Letters B | Phys.Lett. B532 (2002) 159-165 | 10.1016/S0370-2693(02)01547-2 | null | gr-qc astro-ph hep-th | null | We have reinvestigated the quintessence model with minimally coupled scalar
field in the context of recent Supernova observation at $z=1.7$. By assuming
the form of the scale factor which gives both the early time deceleration and
late time acceleration, consistent with the observations, we show that one
needs a double exponential potential. We have also shown that the equation of
state and the behaviour of dark energy density are reasonably consistent with
earlier constraints obtained by different authors. This work shows again the
importance of double exponential potential for a quintessence field.
| [
{
"created": "Sun, 25 Nov 2001 09:47:12 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Mar 2002 18:15:54 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Sen",
"A. A.",
"",
"HRI, Allahabad, India"
],
[
"Sethi",
"S.",
"",
"HRI, Allahabad, India"
]
] | We have reinvestigated the quintessence model with minimally coupled scalar field in the context of recent Supernova observation at $z=1.7$. By assuming the form of the scale factor which gives both the early time deceleration and late time acceleration, consistent with the observations, we show that one needs a double exponential potential. We have also shown that the equation of state and the behaviour of dark energy density are reasonably consistent with earlier constraints obtained by different authors. This work shows again the importance of double exponential potential for a quintessence field. |
gr-qc/0312059 | Roy Maartens | Roy Maartens (Portsmouth) | Brane-world gravity | Corrections, improvements, new references; to appear in Living
Reviews of Relativity; 58 pages, revtex4, 13 figs | Living Rev.Rel.7:7,2004 | 10.12942/lrr-2004-7 | null | gr-qc astro-ph hep-ph hep-th | null | The observable universe could be a 1+3-surface (the "brane") embedded in a
1+3+d-dimensional spacetime (the "bulk"), with standard-model particles and
fields trapped on the brane while gravity is free to access the bulk. At least
one of the d extra spatial dimensions could be very large relative to the
Planck scale, which lowers the fundamental gravity scale, possibly even down to
the electroweak (~ TeV) level. This revolutionary picture arises in the
framework of recent developments in M theory. The 1+10-dimensional M theory
encompasses the known 1+9-dimensional superstring theories, and is widely
considered to be a promising potential route to quantum gravity. General
relativity cannot describe gravity at high enough energies and must be replaced
by a quantum gravity theory, picking up significant corrections as the
fundamental energy scale is approached. At low energies, gravity is localized
at the brane and general relativity is recovered, but at high energies gravity
"leaks" into the bulk, behaving in a truly 1+3+d-dimensional way. This
introduces significant changes to gravitational dynamics and perturbations,
with interesting testable implications for high-energy astrophysics, black
holes and cosmology. Brane-world models offer a phenomenological way to test
some of the novel predictions and corrections to general relativity that are
implied by M theory. This review discusses the geometry, dynamics and
perturbations of simple brane-world models for cosmology and astrophysics,
mainly focusing on warped 5-dimensional brane-worlds based on the
Randall-Sundrum models.
| [
{
"created": "Wed, 10 Dec 2003 15:55:27 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Apr 2004 11:00:56 GMT",
"version": "v2"
}
] | 2016-10-19 | [
[
"Maartens",
"Roy",
"",
"Portsmouth"
]
] | The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+d-dimensional spacetime (the "bulk"), with standard-model particles and fields trapped on the brane while gravity is free to access the bulk. At least one of the d extra spatial dimensions could be very large relative to the Planck scale, which lowers the fundamental gravity scale, possibly even down to the electroweak (~ TeV) level. This revolutionary picture arises in the framework of recent developments in M theory. The 1+10-dimensional M theory encompasses the known 1+9-dimensional superstring theories, and is widely considered to be a promising potential route to quantum gravity. General relativity cannot describe gravity at high enough energies and must be replaced by a quantum gravity theory, picking up significant corrections as the fundamental energy scale is approached. At low energies, gravity is localized at the brane and general relativity is recovered, but at high energies gravity "leaks" into the bulk, behaving in a truly 1+3+d-dimensional way. This introduces significant changes to gravitational dynamics and perturbations, with interesting testable implications for high-energy astrophysics, black holes and cosmology. Brane-world models offer a phenomenological way to test some of the novel predictions and corrections to general relativity that are implied by M theory. This review discusses the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane-worlds based on the Randall-Sundrum models. |
1404.3864 | Vladimir Belinski | Vladimir A. Belinski | On the cosmological singularity | The invited paper for Proceedings of the XIII Marcel Grossmann
Meeting (Stockholm, 2012) by reason of the Marcel Grossmann Award to V.A.
Belinski and I.M. Khalatnikov | Inter. Journ. Modern Phys. D, vol.23, p.1430016 (2014) | 10.1142/S021827181430016X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The long story of the oscillatory approach to the initial cosmological
singularity and its more recent incarnation in multidimensional universe models
is told.
| [
{
"created": "Tue, 15 Apr 2014 10:37:36 GMT",
"version": "v1"
}
] | 2014-09-18 | [
[
"Belinski",
"Vladimir A.",
""
]
] | The long story of the oscillatory approach to the initial cosmological singularity and its more recent incarnation in multidimensional universe models is told. |
0907.3975 | Mark Fisher | Robert A. Bartnik, Mark Fisher, Todd A. Oliynyk | Static Spherically Symmetric Solutions of the SO(5) Einstein Yang-Mills
Equations | 11 pages, 5 figures, 1 table | J.Math.Phys.51:032504,2010 | 10.1063/1.3309500 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Globally regular (ie. asymptotically flat and regular interior), spherically
symmetric and localised ("particle-like") solutions of the coupled Einstein
Yang-Mills (EYM) equations with gauge group SU(2) have been known for more than
20 years, yet their properties are still not well understood. Spherically
symmetric Yang--Mills fields are classified by a choice of isotropy generator
and SO(5) is distinguished as the simplest model with a \emph{non-Abelian}
residual (little) group, $SU(2)\times U(1)$, and which admits globally regular
particle-like solutions. We exhibit an algebraic gauge condition which
normalises the residual gauge freedom to a finite number of discrete
symmetries. This generalises the well-known reduction to the real magnetic
potential $w(r,t)$ in the original SU(2) YM model. Reformulating using gauge
invariant polynomials dramatically simplifies the system and makes numerical
search techniques feasible. We find three families of embedded SU(2) EYM
equations within the SO(5) system, one of which was first detected only within
the gauge-invariant polynomial reduced system. Numerical solutions representing
mixtures of the three SU(2) sub-systems are found, classified by a pair of
positive integers.
| [
{
"created": "Thu, 23 Jul 2009 03:04:25 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Bartnik",
"Robert A.",
""
],
[
"Fisher",
"Mark",
""
],
[
"Oliynyk",
"Todd A.",
""
]
] | Globally regular (ie. asymptotically flat and regular interior), spherically symmetric and localised ("particle-like") solutions of the coupled Einstein Yang-Mills (EYM) equations with gauge group SU(2) have been known for more than 20 years, yet their properties are still not well understood. Spherically symmetric Yang--Mills fields are classified by a choice of isotropy generator and SO(5) is distinguished as the simplest model with a \emph{non-Abelian} residual (little) group, $SU(2)\times U(1)$, and which admits globally regular particle-like solutions. We exhibit an algebraic gauge condition which normalises the residual gauge freedom to a finite number of discrete symmetries. This generalises the well-known reduction to the real magnetic potential $w(r,t)$ in the original SU(2) YM model. Reformulating using gauge invariant polynomials dramatically simplifies the system and makes numerical search techniques feasible. We find three families of embedded SU(2) EYM equations within the SO(5) system, one of which was first detected only within the gauge-invariant polynomial reduced system. Numerical solutions representing mixtures of the three SU(2) sub-systems are found, classified by a pair of positive integers. |
1706.02969 | Tim Dietrich | Tim Dietrich, Sebastiano Bernuzzi, Wolfgang Tichy | Closed-form tidal approximants for binary neutron star gravitational
waveforms constructed from high-resolution numerical relativity simulations | null | Phys. Rev. D 96, 121501 (2017) | 10.1103/PhysRevD.96.121501 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct closed-form gravitational waveforms (GWs) with tidal effects for
the coalescence and merger of binary neutron stars. The method relies on a new
set of eccentricity-reduced and high-resolution numerical relativity (NR)
simulations and is composed of three steps. First, tidal contributions to the
GW phase are extracted from the time-domain NR data. Second, those
contributions are employed to fix high-order coefficients in an effective and
resummed post-Newtonian expression. Third, frequency-domain tidal approximants
are built using the stationary phase approximation. Our tidal approximants are
valid from the low frequencies to the strong-field regime and up to merger.
They can be analytically added to any binary black hole GW model to obtain a
binary neutron star waveform, either in the time or in the frequency domain.
This work provides simple, flexible, and accurate models ready to be used in
both searches and parameter estimation of binary neutron star events.
| [
{
"created": "Fri, 9 Jun 2017 14:23:36 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jul 2018 08:27:25 GMT",
"version": "v2"
}
] | 2018-07-06 | [
[
"Dietrich",
"Tim",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Tichy",
"Wolfgang",
""
]
] | We construct closed-form gravitational waveforms (GWs) with tidal effects for the coalescence and merger of binary neutron stars. The method relies on a new set of eccentricity-reduced and high-resolution numerical relativity (NR) simulations and is composed of three steps. First, tidal contributions to the GW phase are extracted from the time-domain NR data. Second, those contributions are employed to fix high-order coefficients in an effective and resummed post-Newtonian expression. Third, frequency-domain tidal approximants are built using the stationary phase approximation. Our tidal approximants are valid from the low frequencies to the strong-field regime and up to merger. They can be analytically added to any binary black hole GW model to obtain a binary neutron star waveform, either in the time or in the frequency domain. This work provides simple, flexible, and accurate models ready to be used in both searches and parameter estimation of binary neutron star events. |
2301.12801 | Andrea Palessandro | Andrea Palessandro and Tony Rothman | Autocatalysis of Graviton Production via the Gertsenshtein Effect for
the Yang-Mills Field | 11 pages, no figures. V2: Largely as version one. Units changed to
conform to previous paper. Results unchanged but a few lines regarding
relationship to Higgs mechanism and neutrino oscillations rewritten. V3:
Ansatz slightly modified. Four-current introduced to satisfy constraint
equations. Results unchanged. Version accepted for publication in PDU | Phys. Dark Univ. 42 (2023) 101341 | 10.1016/j.dark.2023.101341 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | As shown by Gertsenshtein in 1961, an external magnetic field can couple
electromagnetic to gravitational waves, giving rise to oscillations between
them. Viewed as a quantum process, the magnetic field has catalyzed the mixing
of photon and graviton states. We show that the self-interaction terms of the
Yang-Mills SU(2) field can take the place of the external magnetic field and
autocatalyze the mixing of Yang-Mills bosons and gravitons. In the process,
rotational symmetry is broken and the Yang-Mills boson acquires a mass.
| [
{
"created": "Mon, 30 Jan 2023 11:51:12 GMT",
"version": "v1"
},
{
"created": "Sun, 14 May 2023 09:39:39 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Sep 2023 13:23:09 GMT",
"version": "v3"
}
] | 2023-10-06 | [
[
"Palessandro",
"Andrea",
""
],
[
"Rothman",
"Tony",
""
]
] | As shown by Gertsenshtein in 1961, an external magnetic field can couple electromagnetic to gravitational waves, giving rise to oscillations between them. Viewed as a quantum process, the magnetic field has catalyzed the mixing of photon and graviton states. We show that the self-interaction terms of the Yang-Mills SU(2) field can take the place of the external magnetic field and autocatalyze the mixing of Yang-Mills bosons and gravitons. In the process, rotational symmetry is broken and the Yang-Mills boson acquires a mass. |
gr-qc/0007083 | Mauricio Bellini | Mauricio Bellini (Universidad Nacional de Mar del Plata) | Warm inflation and scalar perturbations of the metric | 10 pages, no figures, to be published in General Rel. and Gravitation | Gen.Rel.Grav.33:127-143,2001 | 10.1023/A:1002053121300 | null | gr-qc | null | A second-order expansion for the quantum fluctuations of the matter field was
considered in the framework of the warm inflation scenario. The friction and
Hubble parameters were expended by means of a semiclassical approach. The
fluctuations of the Hubble parameter generates fluctuations of the metric.
These metric fluctuations produce an effective term of curvature. The power
spectrum for the metric fluctuations can be calculated on the infrared sector.
| [
{
"created": "Mon, 31 Jul 2000 13:55:30 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jan 2001 16:59:20 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Bellini",
"Mauricio",
"",
"Universidad Nacional de Mar del Plata"
]
] | A second-order expansion for the quantum fluctuations of the matter field was considered in the framework of the warm inflation scenario. The friction and Hubble parameters were expended by means of a semiclassical approach. The fluctuations of the Hubble parameter generates fluctuations of the metric. These metric fluctuations produce an effective term of curvature. The power spectrum for the metric fluctuations can be calculated on the infrared sector. |
0807.0448 | Dan Vollick | Dan N. Vollick | Homogeneous and isotropic cosmologies with nonlinear electromagnetic
radiation | 8 pages, change of title plus minor changes | Phys.Rev.D78:063524,2008 | 10.1103/PhysRevD.78.063524 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I examine cosmological models that contain a stochastic
background of nonlinear electromagnetic radiation. I show that for Born-Infeld
electrodynamics the equation of state parameter, $w=P/\rho$, remains close to
1/3 throughout the evolution of the universe if $E^2=B^2$ in the late universe
to a high degree of accuracy.
Theories with electromagnetic Lagrangians of the form $L=-{1/4}F^2+\alpha
F^4$ have recently been studied in magnetic universes, where the electric field
vanishes. It was shown that the $F^4$ term can produce a bounce in the early
universe, avoiding an initial singularity. Here I show that the inclusion of an
electric field, with $E^2\simeq B^2$ in the late universe, eliminates the
bounce and the universe "begins" in an initial singularity.
I also examine theories with Lagrangians of the form $L=-{1/4}F^2-\mu^8/F^2$,
which have been shown to produce a period of late time accelerated expansion in
magnetic universes. I show that, if an electric field is introduced, the
accelerated phase will only occur if $E^2<3B^2$.
| [
{
"created": "Wed, 2 Jul 2008 20:42:11 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Nov 2008 23:55:33 GMT",
"version": "v2"
}
] | 2008-12-18 | [
[
"Vollick",
"Dan N.",
""
]
] | In this paper I examine cosmological models that contain a stochastic background of nonlinear electromagnetic radiation. I show that for Born-Infeld electrodynamics the equation of state parameter, $w=P/\rho$, remains close to 1/3 throughout the evolution of the universe if $E^2=B^2$ in the late universe to a high degree of accuracy. Theories with electromagnetic Lagrangians of the form $L=-{1/4}F^2+\alpha F^4$ have recently been studied in magnetic universes, where the electric field vanishes. It was shown that the $F^4$ term can produce a bounce in the early universe, avoiding an initial singularity. Here I show that the inclusion of an electric field, with $E^2\simeq B^2$ in the late universe, eliminates the bounce and the universe "begins" in an initial singularity. I also examine theories with Lagrangians of the form $L=-{1/4}F^2-\mu^8/F^2$, which have been shown to produce a period of late time accelerated expansion in magnetic universes. I show that, if an electric field is introduced, the accelerated phase will only occur if $E^2<3B^2$. |
1905.05628 | Robert J. Scherrer | John Kehayias and Robert J. Scherrer | A new generic evolution for $k$-essence dark energy with $w \approx -1$ | 7 pages, 2 figures, discussion and references added | Phys. Rev. D 100, 023525 (2019) | 10.1103/PhysRevD.100.023525 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reexamine $k$-essence dark energy models with a scalar field $\phi$ and a
factorized Lagrangian, $\mathcal L = V(\phi)F(X)$, with $X = \frac{1}{2}
\nabla_\mu \phi \nabla^\mu \phi.$ A value of the equation of state parameter,
$w$, near $-1$ requires either $X \approx 0$ or $dF/dX \approx 0$. Previous
work showed that thawing models with $X \approx 0$ evolve along a set of unique
trajectories for $w(a)$, while those with $dF/dX \approx 0$ can result in a
variety of different forms for $w(a)$. We show that if $dV/d\phi$ is small and
$(1/V)(dV/d\phi)$ is roughly constant, then the latter models also converge
toward a single unique set of behaviors for $w(a)$, different from those with
$X \approx 0$. We derive the functional form for $w(a)$ in this case, determine
the conditions on $V(\phi)$ for which it applies, and present observational
constraints on this new class of models. We note that $k$-essence models with
$dF/dX \approx 0$ correspond to a dark energy sound speed $c_s^2 \approx 0$.
| [
{
"created": "Tue, 14 May 2019 14:14:15 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jun 2019 18:23:37 GMT",
"version": "v2"
}
] | 2019-07-24 | [
[
"Kehayias",
"John",
""
],
[
"Scherrer",
"Robert J.",
""
]
] | We reexamine $k$-essence dark energy models with a scalar field $\phi$ and a factorized Lagrangian, $\mathcal L = V(\phi)F(X)$, with $X = \frac{1}{2} \nabla_\mu \phi \nabla^\mu \phi.$ A value of the equation of state parameter, $w$, near $-1$ requires either $X \approx 0$ or $dF/dX \approx 0$. Previous work showed that thawing models with $X \approx 0$ evolve along a set of unique trajectories for $w(a)$, while those with $dF/dX \approx 0$ can result in a variety of different forms for $w(a)$. We show that if $dV/d\phi$ is small and $(1/V)(dV/d\phi)$ is roughly constant, then the latter models also converge toward a single unique set of behaviors for $w(a)$, different from those with $X \approx 0$. We derive the functional form for $w(a)$ in this case, determine the conditions on $V(\phi)$ for which it applies, and present observational constraints on this new class of models. We note that $k$-essence models with $dF/dX \approx 0$ correspond to a dark energy sound speed $c_s^2 \approx 0$. |
1006.2202 | Kohkichi Konno | Kohkichi Konno, Toyoki Matsuyama, Satoshi Tanda | Effects of Chern-Simons Corrections on Conserved Quantities of
Relativistic Fluid | 12 pages, Accepted for publication in Modern Physics Letters A | Mod.Phys.Lett.A25:2655-2666,2010 | 10.1142/S0217732310033876 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider relativistic fluid flow under Chern-Simons modified Maxwell
theory and under Chern-Simons modified gravity theory. We take account of the
effects of Chern-Simons corrections on the quantities of fluid flow that are
conserved without the Chern-Simons corrections. We find that the conservations
of several quantities are generally broken by the Chern-Simons corrections.
| [
{
"created": "Fri, 11 Jun 2010 05:37:14 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Konno",
"Kohkichi",
""
],
[
"Matsuyama",
"Toyoki",
""
],
[
"Tanda",
"Satoshi",
""
]
] | We consider relativistic fluid flow under Chern-Simons modified Maxwell theory and under Chern-Simons modified gravity theory. We take account of the effects of Chern-Simons corrections on the quantities of fluid flow that are conserved without the Chern-Simons corrections. We find that the conservations of several quantities are generally broken by the Chern-Simons corrections. |
gr-qc/0602085 | Marcin Jankiewicz | Marcin Jankiewicz, Anjan A. Sen | Black Holes and Generalized Scalar Field | 8 pages, LaTeX with elsart style | null | null | null | gr-qc | null | We study the possibility of occurrence of scalar hair with a non-canonical
kinetic term for a static, spherically symmetric asymptotically flat black hole
spacetime. We first obtain a general equation for this purpose and then
consider various examples for the kinetic term $F(X)$ with
$X=-{1\over{2}}\partial^{\mu}\phi\partial_{\mu}\phi$. Our study shows that for
a tachyon field with a positive potential, which naturally arises in open
string theory, asymptotically flat a static black hole solution does not exist.
| [
{
"created": "Tue, 21 Feb 2006 20:15:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Jankiewicz",
"Marcin",
""
],
[
"Sen",
"Anjan A.",
""
]
] | We study the possibility of occurrence of scalar hair with a non-canonical kinetic term for a static, spherically symmetric asymptotically flat black hole spacetime. We first obtain a general equation for this purpose and then consider various examples for the kinetic term $F(X)$ with $X=-{1\over{2}}\partial^{\mu}\phi\partial_{\mu}\phi$. Our study shows that for a tachyon field with a positive potential, which naturally arises in open string theory, asymptotically flat a static black hole solution does not exist. |
1408.3534 | Kazunari Eda | Kazunari Eda, Yousuke Itoh, Sachiko Kuroyanagi, Joseph Silk | Gravitational waves as a probe of dark matter mini-spikes | 19 pages, 8 figures | Phys. Rev. D 91, 044045 (2015) | 10.1103/PhysRevD.91.044045 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent studies show that an intermediate mass black hole (IMBH) may develop a
dark matter (DM) mini-halo according to some BH formation scenarios. We
consider a binary system composed of an IMBH surrounded by a DM mini-spike and
a stellar mass object orbiting around the IMBH. The binary evolves due to
gravitational pull and dynamical friction from the DM mini-spike and
back-reaction from its gravitational wave (GW) radiation which can be detected
by future space-borne GW experiments such as eLISA/NGO. We consider a single
power-law model for the DM mini-spike which is assumed to consist of
non-annihilating DM particles and demonstrate that an eLISA/NGO detection of GW
from such a binary enables us to measure the DM mini-spike parameters very
accurately. For instance, in our reference case originally advocated by Zhao
and Silk (2005) and Bertone et al. (2005), we could determine the power-law
index $\alpha$ of the DM mini-spike radial profile with a 1 $\sigma$ relative
error of $\pm 5\times 10^{-6}$ for a GW signal with signal-to-noise-ratio 10
and assuming a 5 year observation with eLISA. We also investigate how
accurately the DM parameters can be determined for various DM parameters and
the masses of the IMBH-stellar mass object binary surrounded by a DM
mini-spike. We find that we can determine the power-law index $\alpha$ at 10 %
level even for a slightly flatter radial distribution of $\alpha \sim 1.7$.
| [
{
"created": "Fri, 15 Aug 2014 13:34:55 GMT",
"version": "v1"
}
] | 2015-03-05 | [
[
"Eda",
"Kazunari",
""
],
[
"Itoh",
"Yousuke",
""
],
[
"Kuroyanagi",
"Sachiko",
""
],
[
"Silk",
"Joseph",
""
]
] | Recent studies show that an intermediate mass black hole (IMBH) may develop a dark matter (DM) mini-halo according to some BH formation scenarios. We consider a binary system composed of an IMBH surrounded by a DM mini-spike and a stellar mass object orbiting around the IMBH. The binary evolves due to gravitational pull and dynamical friction from the DM mini-spike and back-reaction from its gravitational wave (GW) radiation which can be detected by future space-borne GW experiments such as eLISA/NGO. We consider a single power-law model for the DM mini-spike which is assumed to consist of non-annihilating DM particles and demonstrate that an eLISA/NGO detection of GW from such a binary enables us to measure the DM mini-spike parameters very accurately. For instance, in our reference case originally advocated by Zhao and Silk (2005) and Bertone et al. (2005), we could determine the power-law index $\alpha$ of the DM mini-spike radial profile with a 1 $\sigma$ relative error of $\pm 5\times 10^{-6}$ for a GW signal with signal-to-noise-ratio 10 and assuming a 5 year observation with eLISA. We also investigate how accurately the DM parameters can be determined for various DM parameters and the masses of the IMBH-stellar mass object binary surrounded by a DM mini-spike. We find that we can determine the power-law index $\alpha$ at 10 % level even for a slightly flatter radial distribution of $\alpha \sim 1.7$. |
1501.03478 | Zeeshan Yousaf | M. Sharif and Z. Yousaf | Energy Density Inhomogeneities with Polynomial $f(R)$ Cosmology | references are updated | Astrophys. Space Sci. 352(2014)321 | 10.1007/s10509-014-1913-z | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the effects of polynomial $f(R)$ model on the
stability of homogeneous energy density in self-gravitating spherical stellar
object. For this purpose, we construct couple of evolution equations which
relate the Weyl tensor with matter parameters. We explore different factors
responsible for density inhomogeneities with non-dissipative dust, isotropic as
well as anisotropic fluids and dissipative dust cloud. We find that shear,
pressure, dissipative parameters and $f(R)$ terms affect the existence of
inhomogeneous energy density.
| [
{
"created": "Fri, 15 Aug 2014 03:40:53 GMT",
"version": "v1"
}
] | 2016-03-14 | [
[
"Sharif",
"M.",
""
],
[
"Yousaf",
"Z.",
""
]
] | In this paper, we study the effects of polynomial $f(R)$ model on the stability of homogeneous energy density in self-gravitating spherical stellar object. For this purpose, we construct couple of evolution equations which relate the Weyl tensor with matter parameters. We explore different factors responsible for density inhomogeneities with non-dissipative dust, isotropic as well as anisotropic fluids and dissipative dust cloud. We find that shear, pressure, dissipative parameters and $f(R)$ terms affect the existence of inhomogeneous energy density. |
1708.05621 | B\'eatrice Bonga | B\'eatrice Bonga, Jeffrey S. Hazboun | Power radiated by a binary system in a de Sitter Universe | 15 pages, 4 figures, accepted for publication in PRD | null | 10.1103/PhysRevD.96.064018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves emitted by high redshift sources propagate through
various epochs of the Universe including the current era of measurable,
accelerated expansion. Historically, the calculation of gravitational wave
power on cosmological backgrounds is based on various simplifications,
including a $1/r$-expansion and the use of an algebraic projection to retrieve
the radiative degrees of freedom. On a de Sitter spacetime, recent work has
demonstrated that many of these calculational techniques and approximations do
not apply. Here we calculate the power emitted by a binary system on a de
Sitter background using techniques tailored to de Sitter spacetime. The common
expression for the power radiated by this source in an FLRW spacetime,
calculated using far wave-zone techniques, gives the same expression as the
late time expansion specialized to the de Sitter background in the
high-frequency approximation.
| [
{
"created": "Fri, 18 Aug 2017 14:09:13 GMT",
"version": "v1"
}
] | 2017-10-11 | [
[
"Bonga",
"Béatrice",
""
],
[
"Hazboun",
"Jeffrey S.",
""
]
] | Gravitational waves emitted by high redshift sources propagate through various epochs of the Universe including the current era of measurable, accelerated expansion. Historically, the calculation of gravitational wave power on cosmological backgrounds is based on various simplifications, including a $1/r$-expansion and the use of an algebraic projection to retrieve the radiative degrees of freedom. On a de Sitter spacetime, recent work has demonstrated that many of these calculational techniques and approximations do not apply. Here we calculate the power emitted by a binary system on a de Sitter background using techniques tailored to de Sitter spacetime. The common expression for the power radiated by this source in an FLRW spacetime, calculated using far wave-zone techniques, gives the same expression as the late time expansion specialized to the de Sitter background in the high-frequency approximation. |
2209.01955 | Gaoping Long | Gaoping Long, Xiangdong Zhang | On the gauge reduction with respect to simplicity constraint in all
dimensional loop quantum gravity | null | null | 10.1103/PhysRevD.107.046022 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this paper, we are going to discuss the gauge reduction with respect to
the simplicity constraint in both classical and quantum theory of all
dimensional loop quantum gravity. With the gauge reduction with respect to
edge-simplicity constraint being proceeded and the anomalous vertex simplicity
constraint being imposed weakly in holonomy-flux phase space, the simplicity
reduced holonomy can be established. However, we find that the simplicity
reduced holonomy can not capture the degrees of freedom of intrinsic curvature,
which leads that it fails to construct a correct scalar constraint operator in
all dimensional LQG following the standard strategy. To tackle this problem, we
establish a new type of holonomy corresponding to the simplicity reduced
connection, which captures the degrees of freedom of both intrinsic and
extrinsic curvature properly. Based on this new type of holonomy, we propose
three new strategies to construct the scalar constraint operators, which serve
as valuable candidates to study the dynamics of all dimensional LQG in the
future.
| [
{
"created": "Mon, 5 Sep 2022 13:20:08 GMT",
"version": "v1"
}
] | 2023-03-08 | [
[
"Long",
"Gaoping",
""
],
[
"Zhang",
"Xiangdong",
""
]
] | In this paper, we are going to discuss the gauge reduction with respect to the simplicity constraint in both classical and quantum theory of all dimensional loop quantum gravity. With the gauge reduction with respect to edge-simplicity constraint being proceeded and the anomalous vertex simplicity constraint being imposed weakly in holonomy-flux phase space, the simplicity reduced holonomy can be established. However, we find that the simplicity reduced holonomy can not capture the degrees of freedom of intrinsic curvature, which leads that it fails to construct a correct scalar constraint operator in all dimensional LQG following the standard strategy. To tackle this problem, we establish a new type of holonomy corresponding to the simplicity reduced connection, which captures the degrees of freedom of both intrinsic and extrinsic curvature properly. Based on this new type of holonomy, we propose three new strategies to construct the scalar constraint operators, which serve as valuable candidates to study the dynamics of all dimensional LQG in the future. |
1409.2687 | Chayan Ranjit | Chayan Ranjit, Ujjal Debnath | Reconstruction of Einstein-Aether Gravity from other Modified Gravity
Models | 13 pages, 10 figure, Accepted in The European Physical Journal - Plus | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly describe the modified Friedmann equations for Einstein-Aether
gravity theory and we find the effective density and pressure. The purpose of
our present work is to reconstruction of Einstein-Aether Gravity from other
modified gravities like $f(T)$, $f(R)$, $f(G)$, $f(R,T)$ and $f(R,G)$ and check
its viability. The scale factor is chosen in power law form. The free function
$F(K)$ for Einstein-Aether gravity (where $K$ is proportional to $H^{2}$) have
been found in terms for $K$ by the correspondence between Einstein-Aether
gravity and other modified gravities and the nature of $F(K)$ vs $K$ have been
shown graphically for every cases. Finally, we analyzed the stability of each
reconstructed Einstein-Aether gravity model.
| [
{
"created": "Mon, 8 Sep 2014 07:57:40 GMT",
"version": "v1"
}
] | 2014-09-10 | [
[
"Ranjit",
"Chayan",
""
],
[
"Debnath",
"Ujjal",
""
]
] | We briefly describe the modified Friedmann equations for Einstein-Aether gravity theory and we find the effective density and pressure. The purpose of our present work is to reconstruction of Einstein-Aether Gravity from other modified gravities like $f(T)$, $f(R)$, $f(G)$, $f(R,T)$ and $f(R,G)$ and check its viability. The scale factor is chosen in power law form. The free function $F(K)$ for Einstein-Aether gravity (where $K$ is proportional to $H^{2}$) have been found in terms for $K$ by the correspondence between Einstein-Aether gravity and other modified gravities and the nature of $F(K)$ vs $K$ have been shown graphically for every cases. Finally, we analyzed the stability of each reconstructed Einstein-Aether gravity model. |
1701.05824 | Parampreet Singh | Peter Diener, Anton Joe, Miguel Megevand, Parampreet Singh | Numerical simulations of loop quantum Bianchi-I spacetimes | Discussion of results expanded. Two figures added. To appear in the
focus issue on Applications of Loop Quantum Gravity to Cosmology in CQG | Class. Quantum Grav. 34 094004 (2017) | 10.1088/1361-6382/aa68b5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Due to the numerical complexities of studying evolution in an anisotropic
quantum spacetime, in comparison to the isotropic models, the physics of loop
quantized anisotropic models has remained largely unexplored. In particular,
robustness of bounce and the validity of effective dynamics have so far not
been established. Our analysis fills these gaps for the case of vacuum
Bianchi-I spacetime. To efficiently solve the quantum Hamiltonian constraint we
perform an implementation of the Cactus framework which is conventionally used
for applications in numerical relativity. Using high performance computing,
numerical simulations for a large number of initial states with a wide variety
of fluctuations are performed. Big bang singularity is found to be replaced by
anisotropic bounces for all the cases. We find that for initial states which
are sharply peaked at the late times in the classical regime and bounce at a
mean volume much greater than the Planck volume, effective dynamics is an
excellent approximation to the underlying quantum dynamics. Departures of the
effective dynamics from the quantum evolution appear for the states probing
deep Planck volumes. A detailed analysis of the behavior of this departure
reveals a non-monotonic and subtle dependence on fluctuations of the initial
states. We find that effective dynamics in almost all of the cases
underestimates the volume and hence overestimates the curvature at the bounce,
a result in synergy with earlier findings in isotropic case. The expansion and
shear scalars are found to be bounded throughout the evolution.
| [
{
"created": "Fri, 20 Jan 2017 15:23:46 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Mar 2017 23:54:18 GMT",
"version": "v2"
}
] | 2017-04-14 | [
[
"Diener",
"Peter",
""
],
[
"Joe",
"Anton",
""
],
[
"Megevand",
"Miguel",
""
],
[
"Singh",
"Parampreet",
""
]
] | Due to the numerical complexities of studying evolution in an anisotropic quantum spacetime, in comparison to the isotropic models, the physics of loop quantized anisotropic models has remained largely unexplored. In particular, robustness of bounce and the validity of effective dynamics have so far not been established. Our analysis fills these gaps for the case of vacuum Bianchi-I spacetime. To efficiently solve the quantum Hamiltonian constraint we perform an implementation of the Cactus framework which is conventionally used for applications in numerical relativity. Using high performance computing, numerical simulations for a large number of initial states with a wide variety of fluctuations are performed. Big bang singularity is found to be replaced by anisotropic bounces for all the cases. We find that for initial states which are sharply peaked at the late times in the classical regime and bounce at a mean volume much greater than the Planck volume, effective dynamics is an excellent approximation to the underlying quantum dynamics. Departures of the effective dynamics from the quantum evolution appear for the states probing deep Planck volumes. A detailed analysis of the behavior of this departure reveals a non-monotonic and subtle dependence on fluctuations of the initial states. We find that effective dynamics in almost all of the cases underestimates the volume and hence overestimates the curvature at the bounce, a result in synergy with earlier findings in isotropic case. The expansion and shear scalars are found to be bounded throughout the evolution. |
1507.01720 | Guillaume Faye | Luc Blanchet, Guillaume Faye, Bernard F. Whiting | High-order comparisons between post-Newtonian and perturbative self
forces | 6 pages; contribution to the proceedings of the 50th Rencontres de
Moriond, "Gravitation: 100 years after GR" | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent numerical and analytic computations based on the self-force (SF)
formalism in general relativity showed that half-integral post-Newtonian (PN)
terms, i.e. terms involving odd powers of 1/c, arise in the redshift factor of
small mass-ratio black-hole binaries on exact circular orbits. Although those
contributions might seem puzzling at first sight for conservative systems that
are invariant under time-reversal, they are in fact associated with the
so-called non-linear tail-of-tail effect. We shall describe here how the
next-to-next-to-leading order contributions beyond the first half-integral
5.5PN conservative effect (i.e. up to order 7.5PN included) have been obtained
by means of the standard PN formalism applied to binary systems of point-like
objects. The resulting redshift factor in the small mass-ratio limit fully
agrees with that of the SF approach.
| [
{
"created": "Tue, 7 Jul 2015 09:20:53 GMT",
"version": "v1"
}
] | 2015-07-08 | [
[
"Blanchet",
"Luc",
""
],
[
"Faye",
"Guillaume",
""
],
[
"Whiting",
"Bernard F.",
""
]
] | Recent numerical and analytic computations based on the self-force (SF) formalism in general relativity showed that half-integral post-Newtonian (PN) terms, i.e. terms involving odd powers of 1/c, arise in the redshift factor of small mass-ratio black-hole binaries on exact circular orbits. Although those contributions might seem puzzling at first sight for conservative systems that are invariant under time-reversal, they are in fact associated with the so-called non-linear tail-of-tail effect. We shall describe here how the next-to-next-to-leading order contributions beyond the first half-integral 5.5PN conservative effect (i.e. up to order 7.5PN included) have been obtained by means of the standard PN formalism applied to binary systems of point-like objects. The resulting redshift factor in the small mass-ratio limit fully agrees with that of the SF approach. |
2309.06914 | Massimo Giovannini | Massimo Giovannini | Relic gravitons and pulsar timing arrays: a theoretical viewpoint | 40 pages, 15 included figures; comments added and corrected typos to
match the version in press | Eur.Phys.J.C 84 (2024) 2, 67 | 10.1140/epjc/s10052-024-12419-z | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | During the last three years the pulsar timing arrays reported a series of
repeated evidences of gravitational radiation (with stochastically distributed
Fourier amplitudes) at a benchmark frequency of the order of $30$ nHz and
characterized by spectral energy densities (in critical units) ranging between
$10^{-8}$ and $10^{-9}$. While it is still unclear whether or not these effects
are just a consequence of the pristine variation of the space-time curvature,
the nature of the underlying physical processes would suggest that the spectral
energy density of the relic gravitons in the nHz domain may only depend on the
evolution of the comoving horizon at late, intermediate and early times. Along
this systematic perspective we first consider the most conventional option,
namely a post-inflationary modification of the expansion rate. Given the
present constraints on the relic graviton backgrounds, we then show that such a
late-time effect is unable to produce the desired hump in the nHz region. We
then analyze a modified exit of the relevant wavelengths as it may happen when
the gravitons inherit an effective refractive index from the interactions with
the geometry. A relatively short inflationary phase leads, in this case, to an
excess in the nHz region even if the observational data coming from competing
experiments do not pin down exactly the same regions in the parameter space. We
finally examine an early stage of increasing curvature and argue that it is not
compatible with the observed spectral energy density unless the wavelengths
crossing the comoving horizon at early times reenter in a decelerated stage not
dominated by radiation.
| [
{
"created": "Wed, 13 Sep 2023 12:24:22 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Jan 2024 15:36:54 GMT",
"version": "v2"
}
] | 2024-01-24 | [
[
"Giovannini",
"Massimo",
""
]
] | During the last three years the pulsar timing arrays reported a series of repeated evidences of gravitational radiation (with stochastically distributed Fourier amplitudes) at a benchmark frequency of the order of $30$ nHz and characterized by spectral energy densities (in critical units) ranging between $10^{-8}$ and $10^{-9}$. While it is still unclear whether or not these effects are just a consequence of the pristine variation of the space-time curvature, the nature of the underlying physical processes would suggest that the spectral energy density of the relic gravitons in the nHz domain may only depend on the evolution of the comoving horizon at late, intermediate and early times. Along this systematic perspective we first consider the most conventional option, namely a post-inflationary modification of the expansion rate. Given the present constraints on the relic graviton backgrounds, we then show that such a late-time effect is unable to produce the desired hump in the nHz region. We then analyze a modified exit of the relevant wavelengths as it may happen when the gravitons inherit an effective refractive index from the interactions with the geometry. A relatively short inflationary phase leads, in this case, to an excess in the nHz region even if the observational data coming from competing experiments do not pin down exactly the same regions in the parameter space. We finally examine an early stage of increasing curvature and argue that it is not compatible with the observed spectral energy density unless the wavelengths crossing the comoving horizon at early times reenter in a decelerated stage not dominated by radiation. |
gr-qc/0405017 | Vladimir Dzhunushaliev | V. Dzhunushaliev | Wormhole solutions in 5D Kaluza-Klein theory as string-like objects | 29 pages, 10 figures | Horizons in World Physics, vol. 247, New Developments in Quantum
Cosmology Research, p. 113-139, ed. A. Reimer, (Nova Science Publishers, New
York, 2005) | null | null | gr-qc hep-th | null | The detailed numerical and analytical approximate analysis of wormhole-like
solutions in 5D Kaluza-Klein gravity is given. It is shown that some part of
these solutions with $E \approx H, E>H$ relation between electric $E$ and
magnetic $H$ fields can be considered as a superthin and superlong
gravitational flux tube filled with electric and magnetic fields, namely
$\Delta-$strings. The solution behaviour near hypersurface $ds^2=0$ and the
model of electric charge on the basis of $\Delta-$string are discussed. The
comparison of the properties of $\Delta-$string and ordinary string in string
theory is carried out. Some arguments are given that fermionic degrees of
freedom can be build in on the $\Delta-$string. These degrees of freedom are
connected with quantum wormholes of spacetime foam. It is shown that the
natural theory for these spinor fields is supergravity.
| [
{
"created": "Wed, 5 May 2004 01:37:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dzhunushaliev",
"V.",
""
]
] | The detailed numerical and analytical approximate analysis of wormhole-like solutions in 5D Kaluza-Klein gravity is given. It is shown that some part of these solutions with $E \approx H, E>H$ relation between electric $E$ and magnetic $H$ fields can be considered as a superthin and superlong gravitational flux tube filled with electric and magnetic fields, namely $\Delta-$strings. The solution behaviour near hypersurface $ds^2=0$ and the model of electric charge on the basis of $\Delta-$string are discussed. The comparison of the properties of $\Delta-$string and ordinary string in string theory is carried out. Some arguments are given that fermionic degrees of freedom can be build in on the $\Delta-$string. These degrees of freedom are connected with quantum wormholes of spacetime foam. It is shown that the natural theory for these spinor fields is supergravity. |
gr-qc/0406100 | Etera R. Livine | Florian Girelli, Etera R. Livine, Daniele Oriti | Deformed Special Relativity as an effective flat limit of quantum
gravity | 18 pages, RevTex4, 2 figures | Nucl.Phys. B708 (2005) 411-433 | 10.1016/j.nuclphysb.2004.11.026 | null | gr-qc hep-th | null | We argue that a (slightly) curved space-time probed with a finite resolution,
equivalently a finite minimal length, is effectively described by a flat
non-commutative space-time. More precisely, a small cosmological constant (so a
constant curvature) leads the kappa-deformed Poincar\'e flat space-time of
deformed special relativity (DSR) theories. This point of view eventually helps
understanding some puzzling features of DSR. It also explains how DSR can be
considered as an effective flat (low energy) limit of a (true) quantum gravity
theory. This point of view leads us to consider a possible generalization of
DSR to arbitrary curvature in momentum space and to speculate about a possible
formulation of an effective quantum gravity model in these terms. It also leads
us to suggest a {\it doubly deformed special relativity} framework for
describing particle kinematics in an effective low energy description of
quantum gravity.
| [
{
"created": "Thu, 24 Jun 2004 15:00:03 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Girelli",
"Florian",
""
],
[
"Livine",
"Etera R.",
""
],
[
"Oriti",
"Daniele",
""
]
] | We argue that a (slightly) curved space-time probed with a finite resolution, equivalently a finite minimal length, is effectively described by a flat non-commutative space-time. More precisely, a small cosmological constant (so a constant curvature) leads the kappa-deformed Poincar\'e flat space-time of deformed special relativity (DSR) theories. This point of view eventually helps understanding some puzzling features of DSR. It also explains how DSR can be considered as an effective flat (low energy) limit of a (true) quantum gravity theory. This point of view leads us to consider a possible generalization of DSR to arbitrary curvature in momentum space and to speculate about a possible formulation of an effective quantum gravity model in these terms. It also leads us to suggest a {\it doubly deformed special relativity} framework for describing particle kinematics in an effective low energy description of quantum gravity. |
2308.12713 | Enrico Junior Schioppa | Luca Abrahao, Francesco Coradeschi, Antonia Micol Frassino, Thiago
Guerreiro, Jennifer Rittenhouse West and Enrico Junior Schioppa | The quantum optics of gravitational waves | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | By utilizing quantum optics techniques, we examine the characteristics of a
quantum gravitational wave (GW) signature at interferometers. In particular, we
study the problem by analyzing the equations of motion of a GW interacting with
an idealized interferometer. Using this method, we reconstruct the classical GW
signal from a representation of the quantum version of an almost classical
monochromatic wave (a single-mode coherent state), then we discuss the
experimental signatures of some specific, more general quantum states. We
calculate the observables that could be used at future interferometers to probe
possible quantum states carried by the gravitational waves.
| [
{
"created": "Thu, 24 Aug 2023 11:17:47 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Aug 2023 12:29:24 GMT",
"version": "v2"
}
] | 2023-08-28 | [
[
"Abrahao",
"Luca",
""
],
[
"Coradeschi",
"Francesco",
""
],
[
"Frassino",
"Antonia Micol",
""
],
[
"Guerreiro",
"Thiago",
""
],
[
"West",
"Jennifer Rittenhouse",
""
],
[
"Schioppa",
"Enrico Junior",
""
]
] | By utilizing quantum optics techniques, we examine the characteristics of a quantum gravitational wave (GW) signature at interferometers. In particular, we study the problem by analyzing the equations of motion of a GW interacting with an idealized interferometer. Using this method, we reconstruct the classical GW signal from a representation of the quantum version of an almost classical monochromatic wave (a single-mode coherent state), then we discuss the experimental signatures of some specific, more general quantum states. We calculate the observables that could be used at future interferometers to probe possible quantum states carried by the gravitational waves. |
gr-qc/0311061 | David Vitali | David Vitali, Michele Punturo, Stefano Mancini, Paolo Amico, Paolo
Tombesi | Noise reduction in gravitational wave interferometers using feedback | 12 pages, 2 figures, in print in the Special Issue of J. Opt. B on
Fluctuations and Noise in Photonics and Quantum Optics | J.Opt.B Quant.Semiclass.Opt. 6 (2004) S691-S697 | 10.1088/1464-4266/6/8/010 | null | gr-qc quant-ph | null | We show that the quantum locking scheme recently proposed by Courty {\it et
al.} [Phys. Rev. Lett. {\bf 90}, 083601 (2003)] for the reduction of back
action noise is able to significantly improve the sensitivity of the next
generation of gravitational wave interferometers.
| [
{
"created": "Wed, 19 Nov 2003 10:20:28 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Feb 2004 10:01:12 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Vitali",
"David",
""
],
[
"Punturo",
"Michele",
""
],
[
"Mancini",
"Stefano",
""
],
[
"Amico",
"Paolo",
""
],
[
"Tombesi",
"Paolo",
""
]
] | We show that the quantum locking scheme recently proposed by Courty {\it et al.} [Phys. Rev. Lett. {\bf 90}, 083601 (2003)] for the reduction of back action noise is able to significantly improve the sensitivity of the next generation of gravitational wave interferometers. |
gr-qc/0008049 | Paola Zizzi | P. A. Zizzi | Quantum Computation toward Quantum Gravity | 11 pages. Contributed to XIII International Congress on Mathematical
Physics (ICMP 2000), London, England, 17-22 Jul 2000. Typos corrected.
Accepted for publication in General Relativity and Gravitation | Gen.Rel.Grav. 33 (2001) 1305-1318 | 10.1023/A:1012053424024 | null | gr-qc hep-th quant-ph | null | The aim of this paper is to enlight the emerging relevance of Quantum
Information Theory in the field of Quantum Gravity. As it was suggested by J.
A. Wheeler, information theory must play a relevant role in understanding the
foundations of Quantum Mechanics (the "It from bit" proposal). Here we suggest
that quantum information must play a relevant role in Quantum Gravity (the "It
from qubit" proposal). The conjecture is that Quantum Gravity, the theory which
will reconcile Quantum Mechanics with General Relativity, can be formulated in
terms of quantum bits of information (qubits) stored in space at the Planck
scale. This conjecture is based on the following arguments: a) The holographic
principle, b) The loop quantum gravity approach and spin networks, c) Quantum
geometry and black hole entropy. Here we present the quantum version of the
holographic principle by considering each pixel of area of an event horizon as
a qubit. This is possible if the horizon is pierced by spin networks' edges of
spin 1\2, in the superposed state of spin "up" and spin "down".
| [
{
"created": "Mon, 21 Aug 2000 11:28:51 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Sep 2000 07:48:06 GMT",
"version": "v2"
},
{
"created": "Sun, 25 Feb 2001 14:26:04 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Zizzi",
"P. A.",
""
]
] | The aim of this paper is to enlight the emerging relevance of Quantum Information Theory in the field of Quantum Gravity. As it was suggested by J. A. Wheeler, information theory must play a relevant role in understanding the foundations of Quantum Mechanics (the "It from bit" proposal). Here we suggest that quantum information must play a relevant role in Quantum Gravity (the "It from qubit" proposal). The conjecture is that Quantum Gravity, the theory which will reconcile Quantum Mechanics with General Relativity, can be formulated in terms of quantum bits of information (qubits) stored in space at the Planck scale. This conjecture is based on the following arguments: a) The holographic principle, b) The loop quantum gravity approach and spin networks, c) Quantum geometry and black hole entropy. Here we present the quantum version of the holographic principle by considering each pixel of area of an event horizon as a qubit. This is possible if the horizon is pierced by spin networks' edges of spin 1\2, in the superposed state of spin "up" and spin "down". |
1104.4546 | Francesco Cianfrani dr | Francesco Cianfrani, Giovanni Montani | Implications of the gauge-fixing in Loop Quantum Cosmology | 7 pages, accepted for publication in Physical Review D | Phys. Rev. D, 85. 024027(2012) | 10.1103/PhysRevD.85.024027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The restriction to invariant connections in a Friedmann-Robertson-Walker
space-time is discussed via the analysis of the Dirac brackets associated with
the corresponding gauge fixing. This analysis allows us to establish the proper
correspondence between reduced and un-reduced variables. In this respect, it is
outlined how the holonomy-flux algebra coincides with the one of Loop Quantum
Gravity if edges are parallel to simplicial vectors and the quantization of the
model is performed via standard techniques by restricting admissible paths.
Within this scheme, the discretization of the area spectrum is emphasized.
Then, the role of the diffeomorphisms generator in reduced phase-space is
investigated and it is clarified how it implements homogeneity on quantum
states, which are defined over cubical knots. Finally, the perspectives for a
consistent dynamical treatment are discussed.
| [
{
"created": "Sat, 23 Apr 2011 10:52:52 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Nov 2011 14:04:43 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Jan 2012 15:36:44 GMT",
"version": "v3"
}
] | 2015-05-27 | [
[
"Cianfrani",
"Francesco",
""
],
[
"Montani",
"Giovanni",
""
]
] | The restriction to invariant connections in a Friedmann-Robertson-Walker space-time is discussed via the analysis of the Dirac brackets associated with the corresponding gauge fixing. This analysis allows us to establish the proper correspondence between reduced and un-reduced variables. In this respect, it is outlined how the holonomy-flux algebra coincides with the one of Loop Quantum Gravity if edges are parallel to simplicial vectors and the quantization of the model is performed via standard techniques by restricting admissible paths. Within this scheme, the discretization of the area spectrum is emphasized. Then, the role of the diffeomorphisms generator in reduced phase-space is investigated and it is clarified how it implements homogeneity on quantum states, which are defined over cubical knots. Finally, the perspectives for a consistent dynamical treatment are discussed. |
2011.01213 | Leong Khim Wong | Philippe Brax, Anne-Christine Davis, Scott Melville, Leong Khim Wong | Spin precession as a new window into disformal scalar fields | 22 pages + an appendix, 3 figures. v2: Version accepted for
publication. Typos in Table 1, Eq. (3.21), and Eq. (3.26) have been corrected | JCAP 03 (2021) 001 | 10.1088/1475-7516/2021/03/001 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We launch a first investigation into how a light scalar field coupled both
conformally and disformally to matter influences the evolution of spinning
point-like bodies. Working directly at the level of the equations of motion, we
derive novel spin-orbit and spin-spin effects accurate to leading order in a
nonrelativistic and weak-field expansion. Crucially, unlike the
spin-independent effects induced by the disformal coupling, which have been
shown to vanish in circular binaries due to rotational symmetry, the
spin-dependent effects we study here persist even in the limit of zero
eccentricity, and so provide a new and qualitatively distinct way of probing
these kinds of interactions. To illustrate their potential, we confront our
predictions with spin-precession measurements from the Gravity Probe B
experiment and find that the resulting constraint improves upon existing bounds
from perihelion precession by over 5 orders of magnitude. Our results therefore
establish spin effects as a promising window into the disformally coupled dark
sector.
| [
{
"created": "Mon, 2 Nov 2020 18:58:02 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Mar 2021 16:00:03 GMT",
"version": "v2"
}
] | 2021-03-09 | [
[
"Brax",
"Philippe",
""
],
[
"Davis",
"Anne-Christine",
""
],
[
"Melville",
"Scott",
""
],
[
"Wong",
"Leong Khim",
""
]
] | We launch a first investigation into how a light scalar field coupled both conformally and disformally to matter influences the evolution of spinning point-like bodies. Working directly at the level of the equations of motion, we derive novel spin-orbit and spin-spin effects accurate to leading order in a nonrelativistic and weak-field expansion. Crucially, unlike the spin-independent effects induced by the disformal coupling, which have been shown to vanish in circular binaries due to rotational symmetry, the spin-dependent effects we study here persist even in the limit of zero eccentricity, and so provide a new and qualitatively distinct way of probing these kinds of interactions. To illustrate their potential, we confront our predictions with spin-precession measurements from the Gravity Probe B experiment and find that the resulting constraint improves upon existing bounds from perihelion precession by over 5 orders of magnitude. Our results therefore establish spin effects as a promising window into the disformally coupled dark sector. |
0810.4848 | C\'esar Henrique Lenzi CHL | C.H. Lenzi, M. Malheiro, R. M. Marinho, C. Provid\^encia and G. F.
Marranghello | Determination of the neutron star mass-radii relation using narrow-band
gravitational wave detector | 10 pages and 3 figures | J.Phys.Conf.Ser.154:012039,2009 | 10.1088/1742-6596/154/1/012039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct detection of gravitational waves will provide valuable
astrophysical information about many celestial objects. The most promising
sources of gravitational waves are neutron stars and black holes. These objects
emit waves in a very wide spectrum of frequencies determined by their
quasi-normal modes oscillations. In this work we are concerned with the
information we can extract from f and p$_I$-modes when a candidate leaves its
signature in the resonant mass detectors ALLEGRO, EXPLORER, NAUTILUS, MiniGrail
and SCHENBERG. Using the empirical equations, that relate the gravitational
wave frequency and damping time with the mass and radii of the source, we have
calculated the radii of the stars for a given interval of masses $M$ in the
range of frequencies that include the bandwidth of all resonant mass detectors.
With these values we obtain diagrams of mass-radii for different frequencies
that allowed to determine the better candidates to future detection taking in
account the compactness of the source. Finally, to determine which are the
models of compact stars that emit gravitational waves in the frequency band of
the mass resonant detectors, we compare the mass-radii diagrams obtained by
different neutron stars sequences from several relativistic hadronic equations
of state (GM1, GM3, TM1, NL3) and quark matter equations of state (NJL, MTI bag
model). We verify that quark stars obtained from MIT bag model with bag
constant equal to 170 MeV and quark of matter in color-superconductivity phase
are the best candidates for mass resonant detectors.
| [
{
"created": "Mon, 27 Oct 2008 15:41:56 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Oct 2008 12:40:59 GMT",
"version": "v2"
},
{
"created": "Fri, 19 Dec 2008 15:39:05 GMT",
"version": "v3"
},
{
"created": "Wed, 21 Jan 2009 20:40:19 GMT",
"version": "v4"
}
] | 2010-04-21 | [
[
"Lenzi",
"C. H.",
""
],
[
"Malheiro",
"M.",
""
],
[
"Marinho",
"R. M.",
""
],
[
"Providência",
"C.",
""
],
[
"Marranghello",
"G. F.",
""
]
] | The direct detection of gravitational waves will provide valuable astrophysical information about many celestial objects. The most promising sources of gravitational waves are neutron stars and black holes. These objects emit waves in a very wide spectrum of frequencies determined by their quasi-normal modes oscillations. In this work we are concerned with the information we can extract from f and p$_I$-modes when a candidate leaves its signature in the resonant mass detectors ALLEGRO, EXPLORER, NAUTILUS, MiniGrail and SCHENBERG. Using the empirical equations, that relate the gravitational wave frequency and damping time with the mass and radii of the source, we have calculated the radii of the stars for a given interval of masses $M$ in the range of frequencies that include the bandwidth of all resonant mass detectors. With these values we obtain diagrams of mass-radii for different frequencies that allowed to determine the better candidates to future detection taking in account the compactness of the source. Finally, to determine which are the models of compact stars that emit gravitational waves in the frequency band of the mass resonant detectors, we compare the mass-radii diagrams obtained by different neutron stars sequences from several relativistic hadronic equations of state (GM1, GM3, TM1, NL3) and quark matter equations of state (NJL, MTI bag model). We verify that quark stars obtained from MIT bag model with bag constant equal to 170 MeV and quark of matter in color-superconductivity phase are the best candidates for mass resonant detectors. |
0902.4318 | Eduard Masso | Eduard Masso (Univ. Autonoma Barcelona) | The Weight of Vacuum Fluctuations | 7 pages. v2 with a comment added and some typos fixed. It matches
article to be published in Phys. Lett. B | Phys.Lett.B679:433-435,2009 | 10.1016/j.physletb.2009.08.007 | UAB-FT-663 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the gravitational properties of Lamb shift energies. Using
available experimental data we show that these energies have a standard
gravitational behavior at the level of $\sim 10^{-5}$. We are motivated by the
point of view that Lamb shift energies may be interpreted as a consequence of
vacuum fluctuations of the electromagnetic field. If this is the case, our
result is a test of the gravitational properties of quantum fluctuations. The
result is of interest in relation to the problem of the zero-point energy
contribution to the cosmological constant. Indeed, the problem presupposes that
the zero-point energy gravitates as all other forms of energy, and this
supposition is what we test.
| [
{
"created": "Wed, 25 Feb 2009 08:56:14 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Aug 2009 12:41:56 GMT",
"version": "v2"
}
] | 2009-09-28 | [
[
"Masso",
"Eduard",
"",
"Univ. Autonoma Barcelona"
]
] | We examine the gravitational properties of Lamb shift energies. Using available experimental data we show that these energies have a standard gravitational behavior at the level of $\sim 10^{-5}$. We are motivated by the point of view that Lamb shift energies may be interpreted as a consequence of vacuum fluctuations of the electromagnetic field. If this is the case, our result is a test of the gravitational properties of quantum fluctuations. The result is of interest in relation to the problem of the zero-point energy contribution to the cosmological constant. Indeed, the problem presupposes that the zero-point energy gravitates as all other forms of energy, and this supposition is what we test. |
gr-qc/0410061 | Masayuki Tanimoto | Masayuki Tanimoto | Scalar fields on SL(2,R) and H^2 x R geometric spacetimes and linear
perturbations | 23 pages, no figures, to be published in Class. Quant. Gravit | Class.Quant.Grav.21:5355-5374,2004 | 10.1088/0264-9381/21/23/005 | null | gr-qc hep-th | null | Using appropriate harmonics, we study the future asymptotic behavior of
massless scalar fields on a class of cosmological vacuum spacetimes. The
spatial manifold is assumed to be a circle bundle over a higher genus surface
with a locally homogeneous metric. Such a manifold corresponds to the
SL(2,R)-geometry (Bianchi VIII type) or the H^2 x R-geometry (Bianchi III
type). After a technical preparation including an introduction of suitable
harmonics for the circle-fibered Bianchi VIII to separate variables, we derive
systems of ordinary differential equations for the scalar field. We present
future asymptotic solutions for these equations in a special case, and find
that there is a close similarity with those on the circle-fibered Bianchi III
spacetime. We discuss implications of this similarity, especially to
(gravitational) linear perturbations. We also point out that this similarity
can be explained by the "fiber term dominated behavior" of the two models.
| [
{
"created": "Thu, 14 Oct 2004 13:27:30 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Tanimoto",
"Masayuki",
""
]
] | Using appropriate harmonics, we study the future asymptotic behavior of massless scalar fields on a class of cosmological vacuum spacetimes. The spatial manifold is assumed to be a circle bundle over a higher genus surface with a locally homogeneous metric. Such a manifold corresponds to the SL(2,R)-geometry (Bianchi VIII type) or the H^2 x R-geometry (Bianchi III type). After a technical preparation including an introduction of suitable harmonics for the circle-fibered Bianchi VIII to separate variables, we derive systems of ordinary differential equations for the scalar field. We present future asymptotic solutions for these equations in a special case, and find that there is a close similarity with those on the circle-fibered Bianchi III spacetime. We discuss implications of this similarity, especially to (gravitational) linear perturbations. We also point out that this similarity can be explained by the "fiber term dominated behavior" of the two models. |
gr-qc/0306019 | Claus Lammerzahl | Giovanni Amelino-Camelia and Claus Lammerzahl | Quantum-gravity-motivated Lorentz-symmetry tests with laser
interferometers | 17 pages, 3 figures | Class.Quant.Grav.21:899-916,2004 | 10.1088/0264-9381/21/4/010 | null | gr-qc astro-ph hep-ph hep-th | null | We consider the implications for laser interferometry of the
quantum-gravity-motivated modifications in the laws of particle propagation,
which are presently being considered in attempts to explain puzzling
observations of ultra-high-energy cosmic rays. We show that there are
interferometric setups in which the Planck-scale effect on propagation leads to
a characteristic signature. A naive estimate is encouraging with respect to the
possibility of achieving Planck-scale sensitivity, but we also point out some
severe technological challenges which would have to be overcome in order to
achieve this sensitivity.
| [
{
"created": "Wed, 4 Jun 2003 17:28:43 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Lammerzahl",
"Claus",
""
]
] | We consider the implications for laser interferometry of the quantum-gravity-motivated modifications in the laws of particle propagation, which are presently being considered in attempts to explain puzzling observations of ultra-high-energy cosmic rays. We show that there are interferometric setups in which the Planck-scale effect on propagation leads to a characteristic signature. A naive estimate is encouraging with respect to the possibility of achieving Planck-scale sensitivity, but we also point out some severe technological challenges which would have to be overcome in order to achieve this sensitivity. |
gr-qc/9705039 | Yuri N. Obukhov | Yu.N. Obukhov, E.J. Vlachynsky, W. Esser, and F.W. Hehl | Irreducible decompositions in metric-affine gravity models | 27 pages, RevTex | null | null | null | gr-qc | null | The irreducible decomposition technique is applied to the study of classical
models of metric-affine gravity (MAG). The dynamics of the gravitational field
is described by a 12-parameter Lagrangian encompassing a Hilbert-Einstein term,
torsion and nonmetricity square terms, and one quadratic curvature piece that
is built up from Weyl's segmental curvature. Matter is represented by a
hyperfluid, a continuous medium the elements of which possess classical
momentum and hypermomentum. With the help of irreducible decompositions, we are
able to express torsion and traceless nonmetricity explicitly in terms of the
spin and the shear current of the hyperfluid. Thereby the field equations
reduce to an effective Einstein theory describing a metric coupled to the Weyl
1-form (a Proca-type vector field) and to a spin fluid. We demonstrate that a
triplet of torsion and nonmetricity 1-forms describes the general and unique
vacuum solution of the field equations of MAG. Finally, we study homogeneous
cosmologies with an hyperfluid. We find that the hypermomentum affects
significantly the cosmological evolution at very early stages. However, unlike
spin, shear does not prevent the formation of a cosmological singularity.
| [
{
"created": "Wed, 14 May 1997 14:27:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Obukhov",
"Yu. N.",
""
],
[
"Vlachynsky",
"E. J.",
""
],
[
"Esser",
"W.",
""
],
[
"Hehl",
"F. W.",
""
]
] | The irreducible decomposition technique is applied to the study of classical models of metric-affine gravity (MAG). The dynamics of the gravitational field is described by a 12-parameter Lagrangian encompassing a Hilbert-Einstein term, torsion and nonmetricity square terms, and one quadratic curvature piece that is built up from Weyl's segmental curvature. Matter is represented by a hyperfluid, a continuous medium the elements of which possess classical momentum and hypermomentum. With the help of irreducible decompositions, we are able to express torsion and traceless nonmetricity explicitly in terms of the spin and the shear current of the hyperfluid. Thereby the field equations reduce to an effective Einstein theory describing a metric coupled to the Weyl 1-form (a Proca-type vector field) and to a spin fluid. We demonstrate that a triplet of torsion and nonmetricity 1-forms describes the general and unique vacuum solution of the field equations of MAG. Finally, we study homogeneous cosmologies with an hyperfluid. We find that the hypermomentum affects significantly the cosmological evolution at very early stages. However, unlike spin, shear does not prevent the formation of a cosmological singularity. |
0812.3532 | Jian-Yang Zhu | Li-Fang Li and Jian-Yang Zhu | Averaged null energy condition in Loop Quantum Cosmology | 5 pages | Phys.Rev.D79:044011,2009 | 10.1103/PhysRevD.79.044011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wormhole and time machine are very interesting objects in general relativity.
However, they need exotic matters which are impossible in classical level to
support them. But if we introduce the quantum effects of gravity into the
stress-energy tensor, these peculiar objects can be constructed
self-consistently. Fortunately, loop quantum cosmology (LQC) has the potential
to serve as a bridge connecting the classical theory and quantum gravity.
Therefore it provides a simple way for the study of quantum effect in the
semiclassical case. As is well known, loop quantum cosmology is very successful
to deal with the behavior of early universe. In the early stage, if taken the
quantum effect into consideration, inflation is natural because of the
violation of every kind of local energy conditions. Similar to the inflationary
universe, the violation of the averaged null energy condition is the necessary
condition for the traversable wormholes. In this paper, we investigate the
averaged null energy condition in LQC in the framework of effective
Hamiltonian, and find out that LQC do violate the averaged null energy
condition in the massless scalar field coupled model.
| [
{
"created": "Thu, 18 Dec 2008 13:27:51 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Li",
"Li-Fang",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | Wormhole and time machine are very interesting objects in general relativity. However, they need exotic matters which are impossible in classical level to support them. But if we introduce the quantum effects of gravity into the stress-energy tensor, these peculiar objects can be constructed self-consistently. Fortunately, loop quantum cosmology (LQC) has the potential to serve as a bridge connecting the classical theory and quantum gravity. Therefore it provides a simple way for the study of quantum effect in the semiclassical case. As is well known, loop quantum cosmology is very successful to deal with the behavior of early universe. In the early stage, if taken the quantum effect into consideration, inflation is natural because of the violation of every kind of local energy conditions. Similar to the inflationary universe, the violation of the averaged null energy condition is the necessary condition for the traversable wormholes. In this paper, we investigate the averaged null energy condition in LQC in the framework of effective Hamiltonian, and find out that LQC do violate the averaged null energy condition in the massless scalar field coupled model. |
2007.03255 | Morteza Rafiee | Seyed Ali Hosseini Mansoori, Morteza Rafiee, Shao-Wen Wei | Universal criticality of thermodynamic curvatures for charged AdS black
holes | 18 pages, 3 figures, 3 tables, Accepted by PRD | Phys. Rev. D 102, 124066 (2020) | 10.1103/PhysRevD.102.124066 | null | gr-qc cond-mat.stat-mech hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we analytically study the critical exponents and universal
amplitudes of the thermodynamic curvatures such as the intrinsic and extrinsic
curvature at the critical point of the small-large black hole phase transition
for the charged AdS black holes. At the critical point, it is found that the
normalized intrinsic curvature $R_N$ and extrinsic curvature $K_N$ has critical
exponents 2 and 1, respectively. Based on them, the universal amplitudes
$R_Nt^2$ and $K_Nt$ are calculated with the temperature parameter $t=T/T_c-1$
where $T_c$ the critical value of the temperature. Near the critical point, we
find that the critical amplitude of $R_Nt^2$ and $K_Nt$ is $-\frac{1}{2}$ when
$t\rightarrow0^+$, whereas $R_Nt^2\approx -\frac{1}{8}$ and
$K_Nt\approx-\frac{1}{4}$ in the limit $t\rightarrow0^-$. These results not
only hold for the four dimensional charged AdS black hole, but also for the
higher dimensional cases. Therefore, such universal properties will cast new
insight into the thermodynamic geometries and black hole phase transitions.
| [
{
"created": "Tue, 7 Jul 2020 07:51:01 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jul 2020 06:22:08 GMT",
"version": "v2"
},
{
"created": "Mon, 21 Dec 2020 06:39:22 GMT",
"version": "v3"
}
] | 2021-01-04 | [
[
"Mansoori",
"Seyed Ali Hosseini",
""
],
[
"Rafiee",
"Morteza",
""
],
[
"Wei",
"Shao-Wen",
""
]
] | In this paper, we analytically study the critical exponents and universal amplitudes of the thermodynamic curvatures such as the intrinsic and extrinsic curvature at the critical point of the small-large black hole phase transition for the charged AdS black holes. At the critical point, it is found that the normalized intrinsic curvature $R_N$ and extrinsic curvature $K_N$ has critical exponents 2 and 1, respectively. Based on them, the universal amplitudes $R_Nt^2$ and $K_Nt$ are calculated with the temperature parameter $t=T/T_c-1$ where $T_c$ the critical value of the temperature. Near the critical point, we find that the critical amplitude of $R_Nt^2$ and $K_Nt$ is $-\frac{1}{2}$ when $t\rightarrow0^+$, whereas $R_Nt^2\approx -\frac{1}{8}$ and $K_Nt\approx-\frac{1}{4}$ in the limit $t\rightarrow0^-$. These results not only hold for the four dimensional charged AdS black hole, but also for the higher dimensional cases. Therefore, such universal properties will cast new insight into the thermodynamic geometries and black hole phase transitions. |
1908.04445 | Marcelo E. Rubio | A. L. Garcia-Perciante, Marcelo E. Rubio and Oscar A. Reula | Generic instabilities in the relativistic Chapman-Enskog heat conduction
law | 9 pages, 2 figures, refs added | JSP (2020) | 10.1007/s10955-020-02578-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the well-posedness of the Cauchy problem corresponding to the
relativistic fluid equations, when coupled with the heat-flux constitutive
relation arising within the relativistic Chapman-Enskog procedure. The
resulting system of equations is shown to be non hyperbolic, by considering
general perturbations over the whole set of equations written with respect to a
generic time direction. The obtained eigenvalues are not purely imaginary and
their real part grows without bound as the wave-number increases. Unlike
Eckart's theory, this instability is not present when the time direction is
aligned with the fluid's direction. However, since in general the fluid
velocity is not surface-forming, the instability can only be avoided in the
particular case where no rotation is present.
| [
{
"created": "Tue, 13 Aug 2019 00:46:04 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Nov 2019 02:52:40 GMT",
"version": "v2"
}
] | 2020-06-11 | [
[
"Garcia-Perciante",
"A. L.",
""
],
[
"Rubio",
"Marcelo E.",
""
],
[
"Reula",
"Oscar A.",
""
]
] | We address the well-posedness of the Cauchy problem corresponding to the relativistic fluid equations, when coupled with the heat-flux constitutive relation arising within the relativistic Chapman-Enskog procedure. The resulting system of equations is shown to be non hyperbolic, by considering general perturbations over the whole set of equations written with respect to a generic time direction. The obtained eigenvalues are not purely imaginary and their real part grows without bound as the wave-number increases. Unlike Eckart's theory, this instability is not present when the time direction is aligned with the fluid's direction. However, since in general the fluid velocity is not surface-forming, the instability can only be avoided in the particular case where no rotation is present. |
2009.13242 | A. Yu. Petrov | J. R. Nascimento, A. Yu. Petrov, P. Porf\'irio, A. F. Santos | G\"{o}del-type Solutions in Cubic Galileon Gravity | 16 pages | Phys. Rev. D 102, 104064 (2020) | 10.1103/PhysRevD.102.104064 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the homogeneous in space and time (ST-homogeneous) G\"{o}del-type
metrics within the cubic galileon theory, a particular class of generalized
galileon theories. We check the consistency of such spacetimes for a physically
well-motivated matter content, namely, a perfect fluid and an electromagnetic
field. In this scenario, we find that the admissible solutions impose
constraints on the constant couplings ($c_{i}$'s) of the cubic galileon theory
to ensure the consistency. Also, we show the existence of a vacuum completely
causal solution.
| [
{
"created": "Mon, 28 Sep 2020 12:17:12 GMT",
"version": "v1"
}
] | 2020-11-26 | [
[
"Nascimento",
"J. R.",
""
],
[
"Petrov",
"A. Yu.",
""
],
[
"Porfírio",
"P.",
""
],
[
"Santos",
"A. F.",
""
]
] | We address the homogeneous in space and time (ST-homogeneous) G\"{o}del-type metrics within the cubic galileon theory, a particular class of generalized galileon theories. We check the consistency of such spacetimes for a physically well-motivated matter content, namely, a perfect fluid and an electromagnetic field. In this scenario, we find that the admissible solutions impose constraints on the constant couplings ($c_{i}$'s) of the cubic galileon theory to ensure the consistency. Also, we show the existence of a vacuum completely causal solution. |
gr-qc/0507039 | J. A. R. Cembranos | J. A. R. Cembranos | The Newtonian limit at intermediate energies | 4 pages, REVTeX 4; minor typos corrected, one reference added | Phys.Rev.D73:064029,2006 | 10.1103/PhysRevD.73.064029 | UCI-TR-2005-30 | gr-qc | null | We study the metric solutions for the gravitational equations in Modified
Gravity Models (MGMs). In models with negative powers of the scalar curvature,
we show that the Newtonian Limit (NL) is well defined as a limit at
intermediate energies, in contrast with the usual low energy interpretation.
Indeed, we show that the gravitational interaction is modified at low densities
or low curvatures.
| [
{
"created": "Sat, 9 Jul 2005 18:20:43 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jul 2005 18:29:12 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Cembranos",
"J. A. R.",
""
]
] | We study the metric solutions for the gravitational equations in Modified Gravity Models (MGMs). In models with negative powers of the scalar curvature, we show that the Newtonian Limit (NL) is well defined as a limit at intermediate energies, in contrast with the usual low energy interpretation. Indeed, we show that the gravitational interaction is modified at low densities or low curvatures. |
1709.08413 | Ramil Izmailov N | R.Kh. Karimov, R.N. Izmailov, A.A. Potapov and K.K. Nandi | Terrestrial Sagnac delay constraining modified gravity models | 18 pages, 3 figures | Gen. Relativ. Gravit. 50 (2018) 44 | 10.1007/s10714-018-2365-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified gravity theories include $f(\mathbf{R})-$gravity models that are
usually constrained by the cosmological evolutionary scenario. However, it has
been recently shown that they can also be constrained by the signatures of
accretion disk around constant Ricci curvature Kerr-$f(\mathbf{R}_{0})$ stellar
sized black holes. Our aim here is to use another experimental fact, viz., the
terrestrial Sagnac delay to constrain the parameters of specific
$f(\mathbf{R})-$gravity prescriptions. We shall assume that a
Kerr-$f(\mathbf{R}_{0})$ solution asymptotically describes Earth's weak gravity
near its surface. In this spacetime, we shall study oppositely directed light
beams from source/observer moving on non-geodesic and geodesic circular
trajectories and calculate the time gap, when the beams re-unite. We obtain the
\textit{exact }time gap called Sagnac delay in both cases and expand it to show
how the flat space value is corrected by the Ricci curvature, the mass and the
spin of the gravitating source. Under the assumption that the magnitude of
corrections are of the order of residual uncertainties in the delay
measurement, we derive the allowed intervals for Ricci curvature. We conclude
that the terrestrial Sagnac delay can be used to constrain the parameters of
specific $f(\mathbf{R})$ prescriptions. Despite using the weak field gravity
near Earth's surface, it turns out that the model parameter ranges still remain
the same as those obtained from the strong field accretion disk phenomenon.
| [
{
"created": "Mon, 25 Sep 2017 10:15:08 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Apr 2018 10:16:25 GMT",
"version": "v2"
}
] | 2018-04-03 | [
[
"Karimov",
"R. Kh.",
""
],
[
"Izmailov",
"R. N.",
""
],
[
"Potapov",
"A. A.",
""
],
[
"Nandi",
"K. K.",
""
]
] | Modified gravity theories include $f(\mathbf{R})-$gravity models that are usually constrained by the cosmological evolutionary scenario. However, it has been recently shown that they can also be constrained by the signatures of accretion disk around constant Ricci curvature Kerr-$f(\mathbf{R}_{0})$ stellar sized black holes. Our aim here is to use another experimental fact, viz., the terrestrial Sagnac delay to constrain the parameters of specific $f(\mathbf{R})-$gravity prescriptions. We shall assume that a Kerr-$f(\mathbf{R}_{0})$ solution asymptotically describes Earth's weak gravity near its surface. In this spacetime, we shall study oppositely directed light beams from source/observer moving on non-geodesic and geodesic circular trajectories and calculate the time gap, when the beams re-unite. We obtain the \textit{exact }time gap called Sagnac delay in both cases and expand it to show how the flat space value is corrected by the Ricci curvature, the mass and the spin of the gravitating source. Under the assumption that the magnitude of corrections are of the order of residual uncertainties in the delay measurement, we derive the allowed intervals for Ricci curvature. We conclude that the terrestrial Sagnac delay can be used to constrain the parameters of specific $f(\mathbf{R})$ prescriptions. Despite using the weak field gravity near Earth's surface, it turns out that the model parameter ranges still remain the same as those obtained from the strong field accretion disk phenomenon. |
1811.00072 | Daniel Charbul\'ak | Zden\v{e}k Stuchl\'ik, Daniel Charbul\'ak and Jan Schee | Light escape cones in local reference frames of Kerr-de Sitter black
hole spacetimes and related black hole shadows | 58 pages, 136 figures | The European Physical Journal C, 78(3):180, Mar 2018 | 10.1140/epjc/s10052-018-5578-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the light escape cones of isotropic spot sources of radiation
residing in special classes of reference frames in the Kerr-de Sitter (KdS)
black hole spacetimes, namely, in the fundamental class of 'non-geodesic'
locally non-rotating reference frames (LNRFs), and two classes of 'geodesic'
frames, the radial geodesic frames (RGFs), both falling and escaping, and the
frames related to the circular geodesic orbits (CGFs). We compare the cones
constructed in a given position for the LNRFs, RGFs, and CGFs. We have shown
that the photons locally counter-rotating relative to LNRFs with positive
impact parameter and negative covariant energy are confined to the ergosphere
region. Finally, we demonstrate that the light escaping cones govern the
shadows of black holes located in front of a radiating screen, as seen by the
observers in the considered frames. For shadows related to distant static
observers the LNRFs are relevant.
| [
{
"created": "Wed, 31 Oct 2018 19:14:53 GMT",
"version": "v1"
}
] | 2018-11-02 | [
[
"Stuchlík",
"Zdeněk",
""
],
[
"Charbulák",
"Daniel",
""
],
[
"Schee",
"Jan",
""
]
] | We construct the light escape cones of isotropic spot sources of radiation residing in special classes of reference frames in the Kerr-de Sitter (KdS) black hole spacetimes, namely, in the fundamental class of 'non-geodesic' locally non-rotating reference frames (LNRFs), and two classes of 'geodesic' frames, the radial geodesic frames (RGFs), both falling and escaping, and the frames related to the circular geodesic orbits (CGFs). We compare the cones constructed in a given position for the LNRFs, RGFs, and CGFs. We have shown that the photons locally counter-rotating relative to LNRFs with positive impact parameter and negative covariant energy are confined to the ergosphere region. Finally, we demonstrate that the light escaping cones govern the shadows of black holes located in front of a radiating screen, as seen by the observers in the considered frames. For shadows related to distant static observers the LNRFs are relevant. |
gr-qc/0108003 | Oliver Henkel | Oliver Henkel | Local Prescribed Mean Curvature foliations in cosmological spacetimes | 23 pages, no figures | null | 10.1063/1.1466882 | null | gr-qc | null | A theorem about local in time existence of spacelike foliations with
prescribed mean curvature in cosmological spacetimes will be proved. The time
function of the foliation is geometrically defined and fixes the diffeomorphism
invariance inherent in general foliations of spacetimes. Moreover, in contrast
to the situation of the more special constant mean curvature foliations, which
play an important role in the global analysis of spacetimes, this theorem
overcomes the existence problem arising from topological restrictions for
surfaces of constant mean curvature.
| [
{
"created": "Wed, 1 Aug 2001 16:36:12 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Henkel",
"Oliver",
""
]
] | A theorem about local in time existence of spacelike foliations with prescribed mean curvature in cosmological spacetimes will be proved. The time function of the foliation is geometrically defined and fixes the diffeomorphism invariance inherent in general foliations of spacetimes. Moreover, in contrast to the situation of the more special constant mean curvature foliations, which play an important role in the global analysis of spacetimes, this theorem overcomes the existence problem arising from topological restrictions for surfaces of constant mean curvature. |
2209.02176 | Kazufumi Takahashi | Kazufumi Takahashi, Masato Minamitsuji, Hayato Motohashi | Generalized disformal Horndeski theories: cosmological perturbations and
consistent matter coupling | 23 pages, 2 figures | PTEP 2023, 013E01 (2023) | 10.1093/ptep/ptac161 | YITP-22-89 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Invertible disformal transformations are a useful tool to investigate
ghost-free scalar-tensor theories. By performing a higher-derivative
generalization of the invertible disformal transformation on Horndeski
theories, we construct a novel class of ghost-free scalar-tensor theories,
which we dub generalized disformal Horndeski theories. Specifically, these
theories lie beyond the quadratic/cubic DHOST class. We explore cosmological
perturbations to identify a subclass where gravitational waves propagate at the
speed of light and clarify the conditions for the absence of ghost/gradient
instabilities for tensor and scalar perturbations. We also investigate the
conditions under which a matter field can be consistently coupled to these
theories without introducing unwanted extra degrees of freedom.
| [
{
"created": "Tue, 6 Sep 2022 01:46:50 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jan 2023 11:02:03 GMT",
"version": "v2"
}
] | 2023-01-16 | [
[
"Takahashi",
"Kazufumi",
""
],
[
"Minamitsuji",
"Masato",
""
],
[
"Motohashi",
"Hayato",
""
]
] | Invertible disformal transformations are a useful tool to investigate ghost-free scalar-tensor theories. By performing a higher-derivative generalization of the invertible disformal transformation on Horndeski theories, we construct a novel class of ghost-free scalar-tensor theories, which we dub generalized disformal Horndeski theories. Specifically, these theories lie beyond the quadratic/cubic DHOST class. We explore cosmological perturbations to identify a subclass where gravitational waves propagate at the speed of light and clarify the conditions for the absence of ghost/gradient instabilities for tensor and scalar perturbations. We also investigate the conditions under which a matter field can be consistently coupled to these theories without introducing unwanted extra degrees of freedom. |
gr-qc/9604008 | Matt Visser | Matt Visser (Washington University) | Gravitational vacuum polarization II: Energy conditions in the Boulware
vacuum | 8 pages, ReV_TeX | Phys.Rev.D54:5116-5122,1996 | 10.1103/PhysRevD.54.5116 | null | gr-qc hep-th | null | I show that in the Boulware vacuum (1) all standard (point-wise and averaged)
energy conditions are violated throughout the exterior region---all the way
from spatial infinity down to the event horizon, and (2) outside the event
horizon the standard point-wise energy conditions are violated in a maximal
manner: they are violated at all points and for all null/timelike vectors. (The
region inside the event horizon is considerably messier, and of dubious
physical relevance. Nevertheless the standard point-wise energy conditions also
seem to be violated even inside the event horizon.) This is rather different
from the case of the Hartle--Hawking vacuum, wherein violations of the energy
conditions were confined to the region inside the unstable photon orbit. These
calculations are for the quantum stress-energy tensor corresponding to a
conformally-coupled massless scalar field in the Boulware vacuum. I work in the
test-field limit, restrict attention to the Schwarzschild geometry, and invoke
a mixture of analytical and numerical techniques. This *suggests* that general
self-consistent solutions of semiclassical quantum gravity might *not* satisfy
the energy conditions, and may in fact for certain quantum fields and certain
quantum states violate *all* the energy conditions.
| [
{
"created": "Wed, 3 Apr 1996 01:31:02 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Visser",
"Matt",
"",
"Washington University"
]
] | I show that in the Boulware vacuum (1) all standard (point-wise and averaged) energy conditions are violated throughout the exterior region---all the way from spatial infinity down to the event horizon, and (2) outside the event horizon the standard point-wise energy conditions are violated in a maximal manner: they are violated at all points and for all null/timelike vectors. (The region inside the event horizon is considerably messier, and of dubious physical relevance. Nevertheless the standard point-wise energy conditions also seem to be violated even inside the event horizon.) This is rather different from the case of the Hartle--Hawking vacuum, wherein violations of the energy conditions were confined to the region inside the unstable photon orbit. These calculations are for the quantum stress-energy tensor corresponding to a conformally-coupled massless scalar field in the Boulware vacuum. I work in the test-field limit, restrict attention to the Schwarzschild geometry, and invoke a mixture of analytical and numerical techniques. This *suggests* that general self-consistent solutions of semiclassical quantum gravity might *not* satisfy the energy conditions, and may in fact for certain quantum fields and certain quantum states violate *all* the energy conditions. |
2303.04813 | Behzad Eslam Panah | A. Bagheri Tudeshki, G. H. Bordbar, and B. Eslam Panah | Effect of massive graviton on dark energy star structure | 17 pages, 10 figures, 4 tables | Phys. Dark Universe. 42 (2023) 101354 | 10.1016/j.dark.2023.101354 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence of massive gravitons in the field of massive gravity is
considered as an important factor in investigating the structure of compact
objects. Hence, we are encouraged to study the dark energy star structure in
the Vegh's massive gravity. We consider that the equation of state governing
the inner spacetime of the star is the extended Chaplygin gas, and then using
this equation of state, we numerically solve the Tolman-Oppenheimer-Volkoff
(TOV) equation in massive gravity. In the following, assuming different values
of free parameters defined in massive gravity, we calculate the properties of
dark energy star such as radial pressure, transverse pressure, anisotropy
parameter, and other characteristics. Then, after obtaining the maximum mass
and its corresponding radius, we compute redshift and compactness. The obtained
results show that for this model of dark energy star, the maximum mass and its
corresponding radius depend on the massive gravity's free parameters and
anisotropy parameter. These results are consistent with the observational data,
and cover the lower mass gap. We also demonstrate that all energy conditions
are satisfied for this model, and in the presence of anisotropy, the dark
energy star is potentially unstable.
| [
{
"created": "Wed, 8 Mar 2023 07:43:17 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Oct 2023 08:06:48 GMT",
"version": "v2"
}
] | 2023-10-17 | [
[
"Tudeshki",
"A. Bagheri",
""
],
[
"Bordbar",
"G. H.",
""
],
[
"Panah",
"B. Eslam",
""
]
] | The presence of massive gravitons in the field of massive gravity is considered as an important factor in investigating the structure of compact objects. Hence, we are encouraged to study the dark energy star structure in the Vegh's massive gravity. We consider that the equation of state governing the inner spacetime of the star is the extended Chaplygin gas, and then using this equation of state, we numerically solve the Tolman-Oppenheimer-Volkoff (TOV) equation in massive gravity. In the following, assuming different values of free parameters defined in massive gravity, we calculate the properties of dark energy star such as radial pressure, transverse pressure, anisotropy parameter, and other characteristics. Then, after obtaining the maximum mass and its corresponding radius, we compute redshift and compactness. The obtained results show that for this model of dark energy star, the maximum mass and its corresponding radius depend on the massive gravity's free parameters and anisotropy parameter. These results are consistent with the observational data, and cover the lower mass gap. We also demonstrate that all energy conditions are satisfied for this model, and in the presence of anisotropy, the dark energy star is potentially unstable. |
1303.1807 | Ezra Newman | Ezra T. Newman | On Integrating the Left-Flat Vacuum Einstein Equations | the mislabeling of equations has been fixed | null | 10.1088/0264-9381/31/1/015013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering the spin-coefficient version of the left-flat vacuum Einstein
equations, all but one of the fifty equations can be explicitly integrated via
the introduction of five spin-weight s=-2 complex potentials. The final
equation is a non-linear wave equation for the last of the potentials.
Solutions to this equation determine solutions for the entire system. Solutions
for several special cases are obtained
| [
{
"created": "Thu, 7 Mar 2013 20:41:48 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2013 15:27:35 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Newman",
"Ezra T.",
""
]
] | Considering the spin-coefficient version of the left-flat vacuum Einstein equations, all but one of the fifty equations can be explicitly integrated via the introduction of five spin-weight s=-2 complex potentials. The final equation is a non-linear wave equation for the last of the potentials. Solutions to this equation determine solutions for the entire system. Solutions for several special cases are obtained |
1211.1557 | Carlos Augusto Romero Filho | J. B. Fonseca-Neto, C. Romero and S. P. G. Martinez | Scalar torsion and a new symmetry of general relativity | 28 pages. arXiv admin note: text overlap with arXiv:1201.1469 | null | 10.1007/s10714-013-1553-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reformulate the general theory of relativity in the language of
Riemann-Cartan geometry. We start from the assumption that the space-time can
be described as a non-Riemannian manifold, which, in addition to the metric
field, is endowed with torsion. In this new framework, the gravitational field
is represented not only by the metric, but also by the torsion, which is
completely determined by a geometric scalar field. We show that in this
formulation general relativity has a new kind of invariance, whose invariance
group consists of a set of conformal and gauge transformations, called Cartan
transformations. These involve both the metric tensor and the torsion vector
field, and are similar to the well known Weyl gauge transformations. By making
use of the concept of Cartan gauges, we show that, under Cartan
transformations, the new formalism leads to different pictures of the same
gravitational phenomena. We show that in an arbitrary Cartan gauge general
relativity has the form of a scalar-tensor theory. In this approach, the
Riemann-Cartan geometry appears as the natural geometrical setting of the
general relativity theory when the latter is viewed in an arbitrary Cartan
gauge. We illustrate this fact by looking at the one of the classical tests of
general relativity theory, namely the gravitational spectral shift. Finally, we
extend the concept of space-time symmetry to the more general case of
Riemann-Cartan space-times endowed with scalar torsion. As an example, we
obtain the conservation laws for auto-parallel motion in a static spherically
symmetric vacuum space-time in a Cartan gauge, whose orbits are identical to
Schwarzschild orbits in general relativity.
| [
{
"created": "Wed, 7 Nov 2012 14:20:48 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Fonseca-Neto",
"J. B.",
""
],
[
"Romero",
"C.",
""
],
[
"Martinez",
"S. P. G.",
""
]
] | We reformulate the general theory of relativity in the language of Riemann-Cartan geometry. We start from the assumption that the space-time can be described as a non-Riemannian manifold, which, in addition to the metric field, is endowed with torsion. In this new framework, the gravitational field is represented not only by the metric, but also by the torsion, which is completely determined by a geometric scalar field. We show that in this formulation general relativity has a new kind of invariance, whose invariance group consists of a set of conformal and gauge transformations, called Cartan transformations. These involve both the metric tensor and the torsion vector field, and are similar to the well known Weyl gauge transformations. By making use of the concept of Cartan gauges, we show that, under Cartan transformations, the new formalism leads to different pictures of the same gravitational phenomena. We show that in an arbitrary Cartan gauge general relativity has the form of a scalar-tensor theory. In this approach, the Riemann-Cartan geometry appears as the natural geometrical setting of the general relativity theory when the latter is viewed in an arbitrary Cartan gauge. We illustrate this fact by looking at the one of the classical tests of general relativity theory, namely the gravitational spectral shift. Finally, we extend the concept of space-time symmetry to the more general case of Riemann-Cartan space-times endowed with scalar torsion. As an example, we obtain the conservation laws for auto-parallel motion in a static spherically symmetric vacuum space-time in a Cartan gauge, whose orbits are identical to Schwarzschild orbits in general relativity. |
2407.13867 | James T. Wheeler | James T. Wheeler | Nonmetricity and Poincare gauge gravity | 11 pages plus citations | null | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by-sa/4.0/ | We show that in a spacetime geometry with general connection, there exist
field redefinitions that replace the mixed-symmetry nonmetricity of the
asymmetric connection with the sum of torsion and the field strength of special
conformal transformations of a Lorentzian connection. In contrast to general
relativity, generic action functionals give different results for metric versus
Palatini-style variations. We consider some of the resulting issues in
Poincar\`e gauge theory, where it is natural to vary both the solder form and
the spin connection, and where the action may differ from the Einstein-Hilbert
case. Independent variation may introduce nonmetricity as well as torsion.
Appending the defining equation of nonmetricity to the Maurer-Cartan equations
of the Poincar\`e Lie algebra, we show that the mixed symmetry components of
nonmetricity can be absorbed into an altered torsion tensor, restoring local
Lorentz symmetry and metric compatibility while including quadratic terms in
the redefined curvature. In order to recover the original torsion and nonmetric
fields, we replace the definition of nonmetricity by an additional structure
equation. We show that the maximal Lie algebra compatible with the enlarged set
is isomorphic to the conformal Lie algebra. Therefore, in a Lorentzian
conformal geometry the sum of torsion and the field strength of special
conformal transformations is given by the mixed symmetry nonmetricity of an
equivalent asymmetric system.
| [
{
"created": "Thu, 18 Jul 2024 19:25:17 GMT",
"version": "v1"
}
] | 2024-07-22 | [
[
"Wheeler",
"James T.",
""
]
] | We show that in a spacetime geometry with general connection, there exist field redefinitions that replace the mixed-symmetry nonmetricity of the asymmetric connection with the sum of torsion and the field strength of special conformal transformations of a Lorentzian connection. In contrast to general relativity, generic action functionals give different results for metric versus Palatini-style variations. We consider some of the resulting issues in Poincar\`e gauge theory, where it is natural to vary both the solder form and the spin connection, and where the action may differ from the Einstein-Hilbert case. Independent variation may introduce nonmetricity as well as torsion. Appending the defining equation of nonmetricity to the Maurer-Cartan equations of the Poincar\`e Lie algebra, we show that the mixed symmetry components of nonmetricity can be absorbed into an altered torsion tensor, restoring local Lorentz symmetry and metric compatibility while including quadratic terms in the redefined curvature. In order to recover the original torsion and nonmetric fields, we replace the definition of nonmetricity by an additional structure equation. We show that the maximal Lie algebra compatible with the enlarged set is isomorphic to the conformal Lie algebra. Therefore, in a Lorentzian conformal geometry the sum of torsion and the field strength of special conformal transformations is given by the mixed symmetry nonmetricity of an equivalent asymmetric system. |
1701.07700 | Manuel Hohmann | Manuel Hohmann | Post-Newtonian parameter $\gamma$ and the deflection of light in
ghost-free massive bimetric gravity | 36 pages, 1 figure; journal version | Phys. Rev. D 95, 124049 (2017) | 10.1103/PhysRevD.95.124049 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the parametrized post-Newtonian (PPN) limit of ghost-free massive
bimetric gravity with two mutually non-interacting matter sectors coupled to
the two metrics. Making use of a gauge-invariant differential decomposition of
the metric perturbations, we solve the field equations up to the linear PPN
order for a static, point-like mass source. From the result we derive the PPN
parameter $\gamma$ for spherically symmetric systems, which describes the
gravitational deflection of light by visible matter. By a comparison to its
value measured in the solar system we obtain bounds on the parameters of the
theory. We further discuss the deflection of light by dark matter and find an
agreement with the observed light deflection by galaxies. We finally speculate
about a possible explanation for the observed distribution of dark matter in
galactic mergers such as Abell 520 and Abell 3827.
| [
{
"created": "Thu, 26 Jan 2017 13:52:16 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jul 2017 20:15:33 GMT",
"version": "v2"
}
] | 2017-07-14 | [
[
"Hohmann",
"Manuel",
""
]
] | We consider the parametrized post-Newtonian (PPN) limit of ghost-free massive bimetric gravity with two mutually non-interacting matter sectors coupled to the two metrics. Making use of a gauge-invariant differential decomposition of the metric perturbations, we solve the field equations up to the linear PPN order for a static, point-like mass source. From the result we derive the PPN parameter $\gamma$ for spherically symmetric systems, which describes the gravitational deflection of light by visible matter. By a comparison to its value measured in the solar system we obtain bounds on the parameters of the theory. We further discuss the deflection of light by dark matter and find an agreement with the observed light deflection by galaxies. We finally speculate about a possible explanation for the observed distribution of dark matter in galactic mergers such as Abell 520 and Abell 3827. |
0805.3834 | Hwei-Jang Yo | Kun-Feng Shie, James M. Nester, Hwei-Jang Yo | Torsion Cosmology and the Accelerating Universe | 16 pages, 4 figures, accepted by PRD | Phys.Rev.D78:023522,2008 | 10.1103/PhysRevD.78.023522 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Investigations of the dynamic modes of the Poincare gauge theory of gravity
found only two good propagating torsion modes; they are effectively a scalar
and a pseudoscalar. Cosmology affords a natural situation where one might see
observational effects of these modes. Here we consider only the ``scalar
torsion'' mode. This mode has certain distinctive and interesting qualities. In
particular this type of torsion does not interact directly with any known
matter and it allows a critical non-zero value for the affine scalar curvature.
Via numerical evolution of the coupled nonlinear equations we show that this
mode can contribute an oscillating aspect to the expansion rate of the
Universe. From the examination of specific cases of the parameters and initial
conditions we show that for suitable ranges of the parameters the dynamic
``scalar torsion'' model can display features similar to those of the presently
observed accelerating universe.
| [
{
"created": "Sun, 25 May 2008 15:25:34 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Shie",
"Kun-Feng",
""
],
[
"Nester",
"James M.",
""
],
[
"Yo",
"Hwei-Jang",
""
]
] | Investigations of the dynamic modes of the Poincare gauge theory of gravity found only two good propagating torsion modes; they are effectively a scalar and a pseudoscalar. Cosmology affords a natural situation where one might see observational effects of these modes. Here we consider only the ``scalar torsion'' mode. This mode has certain distinctive and interesting qualities. In particular this type of torsion does not interact directly with any known matter and it allows a critical non-zero value for the affine scalar curvature. Via numerical evolution of the coupled nonlinear equations we show that this mode can contribute an oscillating aspect to the expansion rate of the Universe. From the examination of specific cases of the parameters and initial conditions we show that for suitable ranges of the parameters the dynamic ``scalar torsion'' model can display features similar to those of the presently observed accelerating universe. |
1701.07804 | Andrzej Rostworowski | Andrzej Rostworowski | Higher order perturbations of Anti-de Sitter space and time-periodic
solutions of vacuum Einstein equations | 16 pages, v2: minor changes / corrections in text and equations; in
particular missing $\theta$ dependence in eqs. (110,111,114,117,120) added
(thanks to Gyula Fodor for pointing it out!), misprints in eqs. (28,55)
corrected, implicit limits in the integrals in eqs. (71-73,77-81,95-97) made
explicit, misplaced Lorentz indices in eqs. (17-19) lowered, 2 references
added | Phys. Rev. D 95, 124043 (2017) | 10.1103/PhysRevD.95.124043 | CERN-TH-2017-023 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the problem of stability of Anti-de Sitter (AdS) spacetime, we
discuss nonlinear gravitational perturbations of maximally symmetric solutions
of vacuum Einstein equations in general and the case of AdS in particular. We
present the evidence that, similarly to the self-gravitating scalar field at
spherical symmetry, the negative cosmological constant allows for the existence
of globally regular, asymptotically AdS, time-periodic solutions of vacuum
Einstein equations whose frequencies bifurcate from linear eigenfrequencies of
AdS. Interestingly, our preliminary results indicate that the number of one
parameter families of time-periodic solutions bifurcating from a given
eigenfrequency equals the multiplicity of this eigenfrequency.
| [
{
"created": "Thu, 26 Jan 2017 18:22:53 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2017 10:27:44 GMT",
"version": "v2"
}
] | 2017-07-05 | [
[
"Rostworowski",
"Andrzej",
""
]
] | Motivated by the problem of stability of Anti-de Sitter (AdS) spacetime, we discuss nonlinear gravitational perturbations of maximally symmetric solutions of vacuum Einstein equations in general and the case of AdS in particular. We present the evidence that, similarly to the self-gravitating scalar field at spherical symmetry, the negative cosmological constant allows for the existence of globally regular, asymptotically AdS, time-periodic solutions of vacuum Einstein equations whose frequencies bifurcate from linear eigenfrequencies of AdS. Interestingly, our preliminary results indicate that the number of one parameter families of time-periodic solutions bifurcating from a given eigenfrequency equals the multiplicity of this eigenfrequency. |
1405.4967 | Dawood Kothawala Dr. | Dawood Kothawala, T. Padmanabhan | Grin of the Cheshire cat: Entropy density of spacetime as a relic from
quantum gravity | v3: minor corrections; matches version accepted in Phys. Rev. D | Phys. Rev. D 90, 124060 (2014) | 10.1103/PhysRevD.90.124060 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is considerable evidence to suggest that the field equations of gravity
have the same status as, say, the equations describing an emergent phenomenon
like elasticity. In fact, it is possible to derive the field equations from a
thermodynamic variational principle in which a set of normalized vector fields
are varied rather than the metric. We show that this variational principle can
arise as a low energy ($L_P = (G\hbar/c^3)^{1/2} \to 0$) relic of a plausible
nonperturbative effect of quantum gravity, viz. the existence of a
zero-point-length in the spacetime. Our result is nonperturbative in the
following sense: If we modify the geodesic distance in a spacetime by
introducing a zero-point-length, to incorporate some effects of quantum
gravity, and take the limit $L_P \to 0$ of the Ricci scalar of the modified
metric, we end up getting a nontrivial, leading order ($L_P$ - independent)
term. \textit{This term is identical to the expression for entropy density of
spacetime used previously in the emergent gravity approach.} This reconfirms
the idea that the microscopic degrees of freedom of the spacetime, when
properly described in the full theory, could lead to an effective description
of geometry in terms of a thermodynamic variational principle. This is
conceptually similar to the emergence of thermodynamics from mechanics of, say,
molecules. The approach also has important implications for cosmological
constant which are briefly discussed.
| [
{
"created": "Tue, 20 May 2014 06:46:19 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jun 2014 18:54:25 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Dec 2014 06:21:32 GMT",
"version": "v3"
}
] | 2014-12-24 | [
[
"Kothawala",
"Dawood",
""
],
[
"Padmanabhan",
"T.",
""
]
] | There is considerable evidence to suggest that the field equations of gravity have the same status as, say, the equations describing an emergent phenomenon like elasticity. In fact, it is possible to derive the field equations from a thermodynamic variational principle in which a set of normalized vector fields are varied rather than the metric. We show that this variational principle can arise as a low energy ($L_P = (G\hbar/c^3)^{1/2} \to 0$) relic of a plausible nonperturbative effect of quantum gravity, viz. the existence of a zero-point-length in the spacetime. Our result is nonperturbative in the following sense: If we modify the geodesic distance in a spacetime by introducing a zero-point-length, to incorporate some effects of quantum gravity, and take the limit $L_P \to 0$ of the Ricci scalar of the modified metric, we end up getting a nontrivial, leading order ($L_P$ - independent) term. \textit{This term is identical to the expression for entropy density of spacetime used previously in the emergent gravity approach.} This reconfirms the idea that the microscopic degrees of freedom of the spacetime, when properly described in the full theory, could lead to an effective description of geometry in terms of a thermodynamic variational principle. This is conceptually similar to the emergence of thermodynamics from mechanics of, say, molecules. The approach also has important implications for cosmological constant which are briefly discussed. |
2203.11671 | Zhong-Wen Feng | Zhong-Wen Feng, Xia Zhou, Shi-Qi Zhou | Higher-order generalized uncertainty principle applied to gravitational
baryogenesis | 16 pages, 1 figure | Journal of Cosmology and Astroparticle Physics, 2022, 06: 022 | 10.1088/1475-7516/2022/06/022 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The gravitational baryogenesis plays an important role in the study of the
baryon asymmetry. However, the original mechanism of gravitational baryogenesis
in the radiation dominated era leads to the asymmetry factor $\eta$ is equal to
zero, which indicates this mechanism may not generate a sufficient baryon
asymmetry for the standard cosmological model. In this manuscript, we
investigate the gravitational baryogenesis for the generation of baryon
asymmetry in the early Universe by using an new higher-order generalized
uncertainty principle (GUP). It is demonstrated that the entropy and Friedman
equation of the Universe deviate from the original cases due to the effect of
the higher-order GUP. Those modifications break the thermal equilibrium of the
Universe and in turn produces a non-zero asymmetry factor $\eta $. In
particular, our results satisfy all three Sakharov conditions, which indicates
that the scheme of explaining baryon asymmetry in the framework of higher-order
GUP is feasible. In addition, confronting our theoretical results with the
observational results, we constraint the GUP parameter $\beta_0$, whose bound
between $8.4 \times {10^{10}} \sim 1.1 \times {10^{13}}$.
| [
{
"created": "Mon, 21 Mar 2022 11:59:48 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Mar 2022 11:21:18 GMT",
"version": "v2"
},
{
"created": "Sat, 9 Jul 2022 08:54:36 GMT",
"version": "v3"
}
] | 2022-07-12 | [
[
"Feng",
"Zhong-Wen",
""
],
[
"Zhou",
"Xia",
""
],
[
"Zhou",
"Shi-Qi",
""
]
] | The gravitational baryogenesis plays an important role in the study of the baryon asymmetry. However, the original mechanism of gravitational baryogenesis in the radiation dominated era leads to the asymmetry factor $\eta$ is equal to zero, which indicates this mechanism may not generate a sufficient baryon asymmetry for the standard cosmological model. In this manuscript, we investigate the gravitational baryogenesis for the generation of baryon asymmetry in the early Universe by using an new higher-order generalized uncertainty principle (GUP). It is demonstrated that the entropy and Friedman equation of the Universe deviate from the original cases due to the effect of the higher-order GUP. Those modifications break the thermal equilibrium of the Universe and in turn produces a non-zero asymmetry factor $\eta $. In particular, our results satisfy all three Sakharov conditions, which indicates that the scheme of explaining baryon asymmetry in the framework of higher-order GUP is feasible. In addition, confronting our theoretical results with the observational results, we constraint the GUP parameter $\beta_0$, whose bound between $8.4 \times {10^{10}} \sim 1.1 \times {10^{13}}$. |
1103.0731 | Steffen Gielen | Steffen Gielen | Geometric Aspects of Gauge and Spacetime Symmetries | Ph.D. Thesis, University of Cambridge (Supervisor: Prof. Gary W.
Gibbons), 180 pages, 3 figures; originally submitted in October 2010 | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate several problems in relativity and particle physics where
symmetries play a central role; in all cases geometric properties of Lie groups
and their quotients are related to physical effects. The first part is
concerned with symmetries in gravity. We apply the theory of Lie group
deformations to isometry groups of exact solutions in general relativity,
relating the algebraic properties of these groups to physical properties of the
spacetimes. We then make group deformation local, generalising deformed special
relativity (DSR) by describing gravity as a gauge theory of the de Sitter
group. We find that in our construction Minkowski space has a connection with
torsion; physical effects of torsion seem to rule out the proposed framework as
a viable theory. A third chapter discusses a formulation of gravity as a
topological BF theory with added linear constraints that reduce the symmetries
of the topological theory to those of general relativity. We discretise our
constructions and compare to a similar construction by Plebanski which uses
quadratic constraints. In the second part we study CP violation in the
electroweak sector of the standard model and certain extensions of it. We
quantify fine-tuning in the observed magnitude of CP violation by determining a
natural measure on the space of CKM matrices, a double quotient of SU(3),
introducing different possible choices and comparing their predictions for CP
violation. While one generically faces a fine-tuning problem, in the standard
model the problem is removed by a measure that incorporates the observed quark
masses, which suggests a close relation between a mass hierarchy and
suppression of CP violation. Going beyond the standard model by adding a
left-right symmetry spoils the result, leaving us to conclude that such
additional symmetries appear less natural.
| [
{
"created": "Thu, 3 Mar 2011 16:53:52 GMT",
"version": "v1"
}
] | 2011-03-04 | [
[
"Gielen",
"Steffen",
""
]
] | We investigate several problems in relativity and particle physics where symmetries play a central role; in all cases geometric properties of Lie groups and their quotients are related to physical effects. The first part is concerned with symmetries in gravity. We apply the theory of Lie group deformations to isometry groups of exact solutions in general relativity, relating the algebraic properties of these groups to physical properties of the spacetimes. We then make group deformation local, generalising deformed special relativity (DSR) by describing gravity as a gauge theory of the de Sitter group. We find that in our construction Minkowski space has a connection with torsion; physical effects of torsion seem to rule out the proposed framework as a viable theory. A third chapter discusses a formulation of gravity as a topological BF theory with added linear constraints that reduce the symmetries of the topological theory to those of general relativity. We discretise our constructions and compare to a similar construction by Plebanski which uses quadratic constraints. In the second part we study CP violation in the electroweak sector of the standard model and certain extensions of it. We quantify fine-tuning in the observed magnitude of CP violation by determining a natural measure on the space of CKM matrices, a double quotient of SU(3), introducing different possible choices and comparing their predictions for CP violation. While one generically faces a fine-tuning problem, in the standard model the problem is removed by a measure that incorporates the observed quark masses, which suggests a close relation between a mass hierarchy and suppression of CP violation. Going beyond the standard model by adding a left-right symmetry spoils the result, leaving us to conclude that such additional symmetries appear less natural. |
0808.1971 | Claudio Perini | Emanuele Alesci, Eugenio Bianchi, Elena Magliaro, Claudio Perini | Intertwiner dynamics in the flipped vertex | 12 pages, 7 figures | Class.Quant.Grav.26:185003,2009 | 10.1088/0264-9381/26/18/185003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue the semiclassical analysis, started in a previous paper, of the
intertwiner sector of the flipped vertex spinfoam model. We use independently
both a semi-analytical and a purely numerical approach, finding the correct
behavior of wave packet propagation and physical expectation values. In the
end, we show preliminary results about correlation functions.
| [
{
"created": "Thu, 14 Aug 2008 15:24:52 GMT",
"version": "v1"
}
] | 2009-09-28 | [
[
"Alesci",
"Emanuele",
""
],
[
"Bianchi",
"Eugenio",
""
],
[
"Magliaro",
"Elena",
""
],
[
"Perini",
"Claudio",
""
]
] | We continue the semiclassical analysis, started in a previous paper, of the intertwiner sector of the flipped vertex spinfoam model. We use independently both a semi-analytical and a purely numerical approach, finding the correct behavior of wave packet propagation and physical expectation values. In the end, we show preliminary results about correlation functions. |
2212.13745 | Philippe G. LeFloch | Philippe G. LeFloch, Filipe C. Mena, and The-Cang Nguyen | Global evolution in spherical symmetry for self-gravitating massive
fields | 43 pages | null | null | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | We are interested in the global dynamics of a massive scalar field evolving
under its own gravitational field and, in this paper, we study spherically
symmetric solutions to Einstein's field equations coupled with a Klein-Gordon
equation with quadratic potential. For the initial value problem we establish a
global existence theory when initial data are prescribed on a future light cone
with vertex at the center of symmetry. A suitably generalized solution in Bondi
coordinates is sought which has low regularity and possibly large but finite
Bondi mass. A similar result was established first by Christodoulou for
massless fields. In order to deal with massive fields, we must overcome several
challenges and significantly modify Christodoulou's original method. First of
all, we formulate the Einstein-Klein-Gordon system in spherical symmetry as a
non-local and nonlinear hyperbolic equation and, by carefully investigating the
global dynamical behavior of the massive field, we establish various estimates
concerning the Einstein operator, the Hawking mass, and the Bondi mass,
including positivity and monotonicity properties. Importantly, in addition to a
regularization at the center of symmetry we find it necessary to also introduce
a regularization at null infinity. We also establish new energy and decay
estimates for, both, regularized and generalized solutions.
| [
{
"created": "Wed, 28 Dec 2022 08:43:39 GMT",
"version": "v1"
}
] | 2022-12-29 | [
[
"LeFloch",
"Philippe G.",
""
],
[
"Mena",
"Filipe C.",
""
],
[
"Nguyen",
"The-Cang",
""
]
] | We are interested in the global dynamics of a massive scalar field evolving under its own gravitational field and, in this paper, we study spherically symmetric solutions to Einstein's field equations coupled with a Klein-Gordon equation with quadratic potential. For the initial value problem we establish a global existence theory when initial data are prescribed on a future light cone with vertex at the center of symmetry. A suitably generalized solution in Bondi coordinates is sought which has low regularity and possibly large but finite Bondi mass. A similar result was established first by Christodoulou for massless fields. In order to deal with massive fields, we must overcome several challenges and significantly modify Christodoulou's original method. First of all, we formulate the Einstein-Klein-Gordon system in spherical symmetry as a non-local and nonlinear hyperbolic equation and, by carefully investigating the global dynamical behavior of the massive field, we establish various estimates concerning the Einstein operator, the Hawking mass, and the Bondi mass, including positivity and monotonicity properties. Importantly, in addition to a regularization at the center of symmetry we find it necessary to also introduce a regularization at null infinity. We also establish new energy and decay estimates for, both, regularized and generalized solutions. |
0710.4299 | Roh Suan Tung | Roh-Suan Tung | Stationary untrapped boundary conditions in general relativity | 11 pages, improved discussion section, a reference added, accepted
for publication in Classical and Quantum Gravity | Class.Quant.Grav.25:085005,2008 | 10.1088/0264-9381/25/8/085005 | null | gr-qc | null | A class of boundary conditions for canonical general relativity are proposed
and studied at the quasi-local level. It is shown that for untrapped or
marginal surfaces, fixing the area element on the 2-surface (rather than the
induced 2-metric) and the angular momentum surface density is enough to have a
functionally differentiable Hamiltonian, thus providing definition of conserved
quantities for the quasi-local regions. If on the boundary the evolution vector
normal to the 2-surface is chosen to be proportional to the dual expansion
vector, we obtain a generalization of the Hawking energy associated with a
generalized Kodama vector. This vector plays the role for the stationary
untrapped boundary conditions which the stationary Killing vector plays for
stationary black holes. When the dual expansion vector is null, the boundary
conditions reduce to the ones given by the non-expanding horizons and the null
trapping horizons.
| [
{
"created": "Tue, 23 Oct 2007 18:55:11 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Feb 2008 07:58:42 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Tung",
"Roh-Suan",
""
]
] | A class of boundary conditions for canonical general relativity are proposed and studied at the quasi-local level. It is shown that for untrapped or marginal surfaces, fixing the area element on the 2-surface (rather than the induced 2-metric) and the angular momentum surface density is enough to have a functionally differentiable Hamiltonian, thus providing definition of conserved quantities for the quasi-local regions. If on the boundary the evolution vector normal to the 2-surface is chosen to be proportional to the dual expansion vector, we obtain a generalization of the Hawking energy associated with a generalized Kodama vector. This vector plays the role for the stationary untrapped boundary conditions which the stationary Killing vector plays for stationary black holes. When the dual expansion vector is null, the boundary conditions reduce to the ones given by the non-expanding horizons and the null trapping horizons. |
gr-qc/9511047 | null | M. Farhoudi | Classical Trace Anomaly | Version 2: 21 pages, TeX file (using phyzzx.tex), added new section
and references. Version 3: Just replaced Abstract | Int.J.Mod.Phys. D14 (2005) 1233 | 10.1142/S0218271805006730 | QMW-PH-95-41 | gr-qc hep-th | null | We seek an analogy of the mathematical form of the alternative form of
Einstein's field equations for Lovelock's field equations. We find that the
price for this analogy is to accept the existence of the trace anomaly of the
energy-momentum tensor even in classical treatments. As an example, we take
this analogy to any generic second order Lagrangian and exactly derive the
trace anomaly relation suggested by Duff. This indicates that an intrinsic
reason for the existence of such a relation should perhaps be, classically,
somehow related to the covariance of the form of Einstein's equations.
| [
{
"created": "Thu, 16 Nov 1995 20:24:57 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Sep 2005 18:02:45 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Nov 2005 08:41:45 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Farhoudi",
"M.",
""
]
] | We seek an analogy of the mathematical form of the alternative form of Einstein's field equations for Lovelock's field equations. We find that the price for this analogy is to accept the existence of the trace anomaly of the energy-momentum tensor even in classical treatments. As an example, we take this analogy to any generic second order Lagrangian and exactly derive the trace anomaly relation suggested by Duff. This indicates that an intrinsic reason for the existence of such a relation should perhaps be, classically, somehow related to the covariance of the form of Einstein's equations. |
1110.1941 | Mercedes Martin-Benito | M Mart\'in-Benito, L J Garay, G A Mena Marug\'an, and E. Wilson-Ewing | Loop quantum cosmology of the Bianchi I model: complete quantization | 4 pages, Proceedings of Loops'11, Madrid, to appear in Journal of
Physics: Conference Series (JPCS) | J.Phys.Conf.Ser.360:012031,2012 | 10.1088/1742-6596/360/1/012031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We complete the canonical quantization of the vacuum Bianchi I model within
the improved dynamics scheme of loop quantum cosmology, characterizing the
Hilbert structure of the physical states and providing a complete set of
observables acting on them. In order to achieve this task, it has been
essential to determine the structure of the separable superselection sectors
that arise owing to the polymeric quantization, and to prove that the initial
value problem obtained when regarding the Hamiltonian constraint as an
evolution equation, interpreting the volume as the evolution parameter, is
well-posed.
| [
{
"created": "Mon, 10 Oct 2011 06:53:55 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Martín-Benito",
"M",
""
],
[
"Garay",
"L J",
""
],
[
"Marugán",
"G A Mena",
""
],
[
"Wilson-Ewing",
"E.",
""
]
] | We complete the canonical quantization of the vacuum Bianchi I model within the improved dynamics scheme of loop quantum cosmology, characterizing the Hilbert structure of the physical states and providing a complete set of observables acting on them. In order to achieve this task, it has been essential to determine the structure of the separable superselection sectors that arise owing to the polymeric quantization, and to prove that the initial value problem obtained when regarding the Hamiltonian constraint as an evolution equation, interpreting the volume as the evolution parameter, is well-posed. |
gr-qc/0309020 | Matteo Luca Ruggiero | Matteo Luca Ruggiero | The Relative Space: Space Measurements on a Rotating Platform | 14 pages, 2 EPS figures, LaTeX, to appear in the European Journal of
Physics | Eur.J.Phys.24:563-573,2003 | 10.1088/0143-0807/24/6/002 | null | gr-qc | null | We introduce here the concept of relative space, an extended 3-space which is
recognized as the only space having an operational meaning in the study of the
space geometry of a rotating disk. Accordingly, we illustrate how space
measurements are performed in the relative space, and we show that an old-aged
puzzling problem, that is the Ehrenfest's paradox, is explained in this purely
relativistic context. Furthermore, we illustrate the kinematical origin of the
tangential dilation which is responsible for the solution of the Ehrenfest's
paradox.
| [
{
"created": "Wed, 3 Sep 2003 13:45:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ruggiero",
"Matteo Luca",
""
]
] | We introduce here the concept of relative space, an extended 3-space which is recognized as the only space having an operational meaning in the study of the space geometry of a rotating disk. Accordingly, we illustrate how space measurements are performed in the relative space, and we show that an old-aged puzzling problem, that is the Ehrenfest's paradox, is explained in this purely relativistic context. Furthermore, we illustrate the kinematical origin of the tangential dilation which is responsible for the solution of the Ehrenfest's paradox. |
1001.0444 | Kourosh Nozari | Kourosh Nozari and M. Shoukrani | Nonminimal Inflation on the Randall-Sundrum II Brane with Induced
Gravity | 15 pages, 5 figures | Mod.Phys.Lett.A24:3205-3217,2009 | 10.1142/S0217732309031132 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study an inflation model that inflaton field is non-minimally coupled to
the induced scalar curvature on the Randall-Sundrum (RS) II brane. We
investigate the effects of the non-minimal coupling on the inflationary
dynamics of this braneworld model. Our study shows that the number of e-folds
decreases by increasing the value of the non-minimal coupling. We compare our
model parameters with the minimal case and also with recent observational data.
In comparison with recent observation, we obtain a constraint on the values
that the non-minimal coupling attains.
| [
{
"created": "Mon, 4 Jan 2010 05:51:20 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Nozari",
"Kourosh",
""
],
[
"Shoukrani",
"M.",
""
]
] | We study an inflation model that inflaton field is non-minimally coupled to the induced scalar curvature on the Randall-Sundrum (RS) II brane. We investigate the effects of the non-minimal coupling on the inflationary dynamics of this braneworld model. Our study shows that the number of e-folds decreases by increasing the value of the non-minimal coupling. We compare our model parameters with the minimal case and also with recent observational data. In comparison with recent observation, we obtain a constraint on the values that the non-minimal coupling attains. |
1910.01088 | David Vasak | David Vasak, Johannes Kirsch and Juergen Struckmeier | Dark energy and inflation invoked in CCGG by locally contorted
space-time | Correction of sign errors, Eqs. (18-20), with no impact on results.
23 pages + 3 appendices, 38 figures, 2 tables | The European Physical Journal Plus 2020 | 10.1140/epjp/s13360-020-00415-7 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological implications of the Covariant Canonical Gauge Theory of
Gravity (CCGG) are investigated. We deduce that, in a metric compatible
geometry, the requirement of covariant conservation of matter invokes torsion
of space-time. In the Friedman model this leads to a scalar field built from
contortion and the metric with the property of dark energy, which transforms
the cosmological constant to a time-dependent function. Moreover, the
quadratic, scale invariant Riemann-Cartan term in the CCGG Lagrangian endows
space-time with kinetic energy, and in the field equations adds a geometrical
curvature correction to Einstein gravity. Applying in the Friedman model the
standard $\Lambda$CDM parameter set, those equations yield a cosmological field
depending just on one additional, dimensionless ``deformation'' parameter of
the theory that determines the strength of the quadratic term, viz. the
deviation from the Einstein-Hilbert ansatz. Moreover, the apparent curvature of
the universe differs from the actual curvature parameter of the metric. The
numerical analysis in that parameter space yields three cosmology types: (I) A
bounce universe starting off from a finite scale followed by a steady
inflation, (II) a singular Big Bang universe undergoing a secondary
inflation-deceleration phase, and (III) a solution similar to standard
cosmology but with a different temporal profile. The common feature of all
scenarios is the graceful exit to the current dark energy era. The value of the
deformation parameter can be deduced by comparing theoretical calculations with
observations, namely with the SNeIa Hubble diagram and the deceleration
parameter. That comparison implies a considerable admixture of scale invariant
quadratic gravity to Einstein gravity. This theory also sheds new light on the
resolution of the cosmological constant problem and of the Hubble tension.
| [
{
"created": "Wed, 2 Oct 2019 17:08:47 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Feb 2020 12:09:34 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Nov 2023 15:30:29 GMT",
"version": "v3"
}
] | 2023-11-27 | [
[
"Vasak",
"David",
""
],
[
"Kirsch",
"Johannes",
""
],
[
"Struckmeier",
"Juergen",
""
]
] | The cosmological implications of the Covariant Canonical Gauge Theory of Gravity (CCGG) are investigated. We deduce that, in a metric compatible geometry, the requirement of covariant conservation of matter invokes torsion of space-time. In the Friedman model this leads to a scalar field built from contortion and the metric with the property of dark energy, which transforms the cosmological constant to a time-dependent function. Moreover, the quadratic, scale invariant Riemann-Cartan term in the CCGG Lagrangian endows space-time with kinetic energy, and in the field equations adds a geometrical curvature correction to Einstein gravity. Applying in the Friedman model the standard $\Lambda$CDM parameter set, those equations yield a cosmological field depending just on one additional, dimensionless ``deformation'' parameter of the theory that determines the strength of the quadratic term, viz. the deviation from the Einstein-Hilbert ansatz. Moreover, the apparent curvature of the universe differs from the actual curvature parameter of the metric. The numerical analysis in that parameter space yields three cosmology types: (I) A bounce universe starting off from a finite scale followed by a steady inflation, (II) a singular Big Bang universe undergoing a secondary inflation-deceleration phase, and (III) a solution similar to standard cosmology but with a different temporal profile. The common feature of all scenarios is the graceful exit to the current dark energy era. The value of the deformation parameter can be deduced by comparing theoretical calculations with observations, namely with the SNeIa Hubble diagram and the deceleration parameter. That comparison implies a considerable admixture of scale invariant quadratic gravity to Einstein gravity. This theory also sheds new light on the resolution of the cosmological constant problem and of the Hubble tension. |
2312.11659 | Justin Ripley | Justin L. Ripley and Abhishek Hegade K.R. and Rohit S. Chandramouli
and and Nicolas Yunes | First constraint on the dissipative tidal deformability of neutron stars | 7 pages, 4 figures; edits in response to referee comments | null | 10.1038/s41550-024-02323-7 | null | gr-qc astro-ph.HE nucl-ex nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational waves (GWs) emitted by neutron star binaries probe the
physics of matter at supra nuclear densities. During the late inspiral, tidal
deformations raised on each star by the gravitational field of its companion
depend crucially on the star's internal properties. The misalignment of a
star's tidal bulge with its companion's gravitational field encodes the
strength of internal dissipative processes, which imprint onto the phase of the
gravitational waves emitted. We here analyze GW data from the GW170817 (binary
neutron star) event detected by LIGO and Virgo and find the first constraint on
the dissipative tidal deformability of a neutron star. From this constraint,
\emph{assuming} a temperature profile for each star in the binary, we obtain an
order of magnitude bound on the averaged bulk ($\zeta$) and shear ($\eta$)
viscosity of each star during the inspiral.: $\zeta \lesssim 10^{31}
\mathrm{g}\;\mathrm{cm}^{-1}\mathrm{s}^{-1}$ and $\eta \lesssim 10^{28}
\mathrm{g}\;\mathrm{cm}^{-1}\mathrm{s}^{-1} $. We forecast that these bounds
could be improved by two orders of magnitude with third-generation detectors,
like Cosmic Explorer, using inspiral data. These constraints already inform
nuclear physics models and motivate further theoretical work to better
understand the interplay between viscosity and temperature in the late inspiral
of neutron stars.
| [
{
"created": "Mon, 18 Dec 2023 19:13:05 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jun 2024 22:24:00 GMT",
"version": "v2"
}
] | 2024-07-22 | [
[
"Ripley",
"Justin L.",
""
],
[
"R.",
"Abhishek Hegade K.",
""
],
[
"Chandramouli",
"Rohit S.",
""
],
[
"Yunes",
"and Nicolas",
""
]
] | The gravitational waves (GWs) emitted by neutron star binaries probe the physics of matter at supra nuclear densities. During the late inspiral, tidal deformations raised on each star by the gravitational field of its companion depend crucially on the star's internal properties. The misalignment of a star's tidal bulge with its companion's gravitational field encodes the strength of internal dissipative processes, which imprint onto the phase of the gravitational waves emitted. We here analyze GW data from the GW170817 (binary neutron star) event detected by LIGO and Virgo and find the first constraint on the dissipative tidal deformability of a neutron star. From this constraint, \emph{assuming} a temperature profile for each star in the binary, we obtain an order of magnitude bound on the averaged bulk ($\zeta$) and shear ($\eta$) viscosity of each star during the inspiral.: $\zeta \lesssim 10^{31} \mathrm{g}\;\mathrm{cm}^{-1}\mathrm{s}^{-1}$ and $\eta \lesssim 10^{28} \mathrm{g}\;\mathrm{cm}^{-1}\mathrm{s}^{-1} $. We forecast that these bounds could be improved by two orders of magnitude with third-generation detectors, like Cosmic Explorer, using inspiral data. These constraints already inform nuclear physics models and motivate further theoretical work to better understand the interplay between viscosity and temperature in the late inspiral of neutron stars. |
1309.4049 | Jutta Kunz | Jutta Kunz | Black Holes in Higher Dimensions (Black Strings and Black Rings) | Summary of session BH1 at MG13 in Stockholm, 14 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main focus of this session was the presentation of new higher-dimensional
black hole solutions, including black rings, black strings, and multi black
holes, and the study of their properties. Besides new asymptotically flat and
locally asymptotically flat black objects also new black holes with anti-de
Sitter asymptotics were reported. The studies of their properties included the
investigation of their stability, their thermodynamics, their analyticity and
their existence. Furthermore, the geodesics in such higher-dimensional
space-times were investigated.
| [
{
"created": "Mon, 16 Sep 2013 17:49:58 GMT",
"version": "v1"
}
] | 2013-09-17 | [
[
"Kunz",
"Jutta",
""
]
] | The main focus of this session was the presentation of new higher-dimensional black hole solutions, including black rings, black strings, and multi black holes, and the study of their properties. Besides new asymptotically flat and locally asymptotically flat black objects also new black holes with anti-de Sitter asymptotics were reported. The studies of their properties included the investigation of their stability, their thermodynamics, their analyticity and their existence. Furthermore, the geodesics in such higher-dimensional space-times were investigated. |
2310.19037 | Julio Cesar Fabris | J\'ulio C. Fabris, Mahamadou Hamani Daouda, Hermano Velten | Spherically Symmetric Configurations in Unimodular Gravity | 12 pages, latex file | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Unimodular gravity (UG) is considered, under many aspects, equivalent to
General Relativity (GR), even if the theory is invariant under a more
restricted diffeomorphic class of transformations. We discuss the conditions
for the equivalence between the two formulations by applying the UG to the
static and spherically symmetric configurations being the energy-momentum
tensor sourced by a scalar field or by the electromagnetic field. We argue that
the equivalence between UG and GR may be broken when analyzing the stability of
the solutions at perturbative level.
| [
{
"created": "Sun, 29 Oct 2023 15:04:06 GMT",
"version": "v1"
}
] | 2023-10-31 | [
[
"Fabris",
"Júlio C.",
""
],
[
"Daouda",
"Mahamadou Hamani",
""
],
[
"Velten",
"Hermano",
""
]
] | Unimodular gravity (UG) is considered, under many aspects, equivalent to General Relativity (GR), even if the theory is invariant under a more restricted diffeomorphic class of transformations. We discuss the conditions for the equivalence between the two formulations by applying the UG to the static and spherically symmetric configurations being the energy-momentum tensor sourced by a scalar field or by the electromagnetic field. We argue that the equivalence between UG and GR may be broken when analyzing the stability of the solutions at perturbative level. |
2207.07193 | Oleksii Sokoliuk | Oleksii Sokoliuk, Subhrat Praharaj, Alexander Baransky and P. K. Sahoo | Accretion flows around exotic tidal wormholes I. Ray-tracing | 18 pages, 14 figures, revision submitted to A&A | A&A 665, A139 (2022) | 10.1051/0004-6361/202244358 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | This paper investigates the various spherically symmetric wormhole solutions
in the presence of tidal forces and applies numerous methods, such as test
particle orbital dynamics, ray-tracing and microlensing. We make the
theoretical predictions on the test particle orbital motion around the tidal
wormholes with the use of normalized by $\mathcal{L}^2$ effective potential. In
order to obtain the ray-tracing images (of both geometrically thin and thick
accretion disks, relativistic jets), we properly modify the open source
$\texttt{GYOTO}$ code with python interface. We applied this techniques to
probe the accretion flows nearby the Schwarzschild-like and charged
Reissner-N\"ordstrom (RS) wormholes (we assumed both charged RS wormhole and
special case with the vanishing electromagnetic charge, namely
Damour-Solodukhin (DS) wormhole). It was shown that the photon sphere for
Schwarzschild-like wormhole presents for both thin and thick accretion disks
and even for the vanishing tidal forces. Moreover, it was observed that
$r_{\mathrm{ph}}\to\infty$ as $\alpha\to\infty$, which constraints $\alpha$
parameter to be sufficiently small and positive in order to respect the EHT
observations. On the other hand, for the case of RS wormhole, photon sphere
radius shrinks as $\Lambda\to\infty$, as it was predicted by the effective
potential. In addition to the accretion disks, we as well probe the
relativistic jets around two wormhole solutions of our consideration. Finally,
with the help of star bulb microlensing, we approximate the radius of the
wormhole shadow and as we found out, for Schild WH, $R_{\mathrm{Sh}}\approx
r_0$ for ZTF and grows linearly with $\alpha$. On the contrary, shadow radius
for charged wormholes slowly decreases with the growing trend of DS parameter
$\Lambda$.
| [
{
"created": "Thu, 30 Jun 2022 15:47:18 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jul 2022 10:51:45 GMT",
"version": "v2"
}
] | 2022-09-21 | [
[
"Sokoliuk",
"Oleksii",
""
],
[
"Praharaj",
"Subhrat",
""
],
[
"Baransky",
"Alexander",
""
],
[
"Sahoo",
"P. K.",
""
]
] | This paper investigates the various spherically symmetric wormhole solutions in the presence of tidal forces and applies numerous methods, such as test particle orbital dynamics, ray-tracing and microlensing. We make the theoretical predictions on the test particle orbital motion around the tidal wormholes with the use of normalized by $\mathcal{L}^2$ effective potential. In order to obtain the ray-tracing images (of both geometrically thin and thick accretion disks, relativistic jets), we properly modify the open source $\texttt{GYOTO}$ code with python interface. We applied this techniques to probe the accretion flows nearby the Schwarzschild-like and charged Reissner-N\"ordstrom (RS) wormholes (we assumed both charged RS wormhole and special case with the vanishing electromagnetic charge, namely Damour-Solodukhin (DS) wormhole). It was shown that the photon sphere for Schwarzschild-like wormhole presents for both thin and thick accretion disks and even for the vanishing tidal forces. Moreover, it was observed that $r_{\mathrm{ph}}\to\infty$ as $\alpha\to\infty$, which constraints $\alpha$ parameter to be sufficiently small and positive in order to respect the EHT observations. On the other hand, for the case of RS wormhole, photon sphere radius shrinks as $\Lambda\to\infty$, as it was predicted by the effective potential. In addition to the accretion disks, we as well probe the relativistic jets around two wormhole solutions of our consideration. Finally, with the help of star bulb microlensing, we approximate the radius of the wormhole shadow and as we found out, for Schild WH, $R_{\mathrm{Sh}}\approx r_0$ for ZTF and grows linearly with $\alpha$. On the contrary, shadow radius for charged wormholes slowly decreases with the growing trend of DS parameter $\Lambda$. |
1503.04775 | Alan Coley | A. Coley | On the Action, Topology and Geometric Invariants in Quantum Gravity | Based on recent talk | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The action in general relativity (GR), which is an integral over the manifold
plus an integral over the boundary, is a global object and is only well defined
when the topology is fixed. Therefore, to use the action in GR and in most
approaches to quantum gravity (QG) based on a covariant Lorentzian action,
there needs to exist a prefered (global) timelike vector, and hence a global
topology $R \times S^3$, for it to make sense. This is especially true in the
Hamiltonian formulation of QG. Therefore, in order to do canonical
quantization, we need to know the topology, appropriate boundary conditions and
(in an open manifold) the conditions at infinity, which affects the fundamental
geometrical scalar invariants of the spacetime (and especially those which may
occur in the QG action).
| [
{
"created": "Mon, 16 Mar 2015 19:17:27 GMT",
"version": "v1"
}
] | 2015-03-17 | [
[
"Coley",
"A.",
""
]
] | The action in general relativity (GR), which is an integral over the manifold plus an integral over the boundary, is a global object and is only well defined when the topology is fixed. Therefore, to use the action in GR and in most approaches to quantum gravity (QG) based on a covariant Lorentzian action, there needs to exist a prefered (global) timelike vector, and hence a global topology $R \times S^3$, for it to make sense. This is especially true in the Hamiltonian formulation of QG. Therefore, in order to do canonical quantization, we need to know the topology, appropriate boundary conditions and (in an open manifold) the conditions at infinity, which affects the fundamental geometrical scalar invariants of the spacetime (and especially those which may occur in the QG action). |
2204.06633 | Jean-Baptiste Bayle | Michael L. Katz, Jean-Baptiste Bayle, Alvin J. K. Chua, Michele
Vallisneri | Assessing the data-analysis impact of LISA orbit approximations using a
GPU-accelerated response model | 15 pages, 7 figures, 2 tables | Phys. Rev. D 106, 103001 (2022) | 10.1103/PhysRevD.106.103001 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The analysis of gravitational wave (GW) datasets is based on the comparison
of measured time series with theoretical templates of the detector's response
to a variety of source parameters. For LISA, the main scientific observables
will be the so-called time-delay interferometry (TDI) combinations, which
suppress the otherwise overwhelming laser noise. Computing the TDI response to
GW involves projecting the GW polarizations onto the LISA constellation arms,
and then combining projections delayed by a multiple of the light propagation
time along the arms. Both computations are difficult to perform efficiently for
generic LISA orbits and GW signals. Various approximations are currently used
in practice, e.g., assuming constant and equal armlengths, which yields
analytical TDI expressions. In this article, we present 'fastlisaresponse', a
new efficient GPU-accelerated code that implements the generic TDI response to
GWs in the time domain. We use it to characterize the parameter-estimation bias
incurred by analyzing loud Galactic-binary signals using the equal-armlength
approximation. We conclude that equal-armlength parameter-estimation codes
should be upgraded to the generic response if they are to achieve optimal
accuracy for high (but reasonable) SNR sources within the actual LISA data.
| [
{
"created": "Wed, 13 Apr 2022 20:53:00 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Apr 2022 13:18:44 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Sep 2022 07:54:11 GMT",
"version": "v3"
}
] | 2022-11-02 | [
[
"Katz",
"Michael L.",
""
],
[
"Bayle",
"Jean-Baptiste",
""
],
[
"Chua",
"Alvin J. K.",
""
],
[
"Vallisneri",
"Michele",
""
]
] | The analysis of gravitational wave (GW) datasets is based on the comparison of measured time series with theoretical templates of the detector's response to a variety of source parameters. For LISA, the main scientific observables will be the so-called time-delay interferometry (TDI) combinations, which suppress the otherwise overwhelming laser noise. Computing the TDI response to GW involves projecting the GW polarizations onto the LISA constellation arms, and then combining projections delayed by a multiple of the light propagation time along the arms. Both computations are difficult to perform efficiently for generic LISA orbits and GW signals. Various approximations are currently used in practice, e.g., assuming constant and equal armlengths, which yields analytical TDI expressions. In this article, we present 'fastlisaresponse', a new efficient GPU-accelerated code that implements the generic TDI response to GWs in the time domain. We use it to characterize the parameter-estimation bias incurred by analyzing loud Galactic-binary signals using the equal-armlength approximation. We conclude that equal-armlength parameter-estimation codes should be upgraded to the generic response if they are to achieve optimal accuracy for high (but reasonable) SNR sources within the actual LISA data. |
2011.02524 | Cesar Daniel Peralta Gonzalez | C. D. Peralta | Study of General Relativity and $f(R)$ Modified Gravity with
Cosmological Constant for Einstein and Jordan Frames | Phd thesis (2020) | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This thesis investigates a toy model for inflation in a class of modified
theories of gravity in the metric formalism. Instead of the standard procedure
-- assuming a non-linear Lagrangian $f(R)$ in the Jordan frame -- we start from
a simple {\phi}^2 potential in the Einstein frame and investigate the
corresponding $f(R)$ in the former picture. Such approach yields plenty of new
pieces of information, namely a self-terminating inflationary solution with a
linear Lagrangian, a robust criterion for stability of such theories, a
dynamical effective potential for the Ricci scalar $R$, the addition of an
ad-hoc Cosmological Constant in the Einstein frame leads to a Thermodynamical
interpretation of this physical system, which allows further insight on its
(meta)stability and evolution.
| [
{
"created": "Wed, 4 Nov 2020 20:14:17 GMT",
"version": "v1"
}
] | 2020-11-06 | [
[
"Peralta",
"C. D.",
""
]
] | This thesis investigates a toy model for inflation in a class of modified theories of gravity in the metric formalism. Instead of the standard procedure -- assuming a non-linear Lagrangian $f(R)$ in the Jordan frame -- we start from a simple {\phi}^2 potential in the Einstein frame and investigate the corresponding $f(R)$ in the former picture. Such approach yields plenty of new pieces of information, namely a self-terminating inflationary solution with a linear Lagrangian, a robust criterion for stability of such theories, a dynamical effective potential for the Ricci scalar $R$, the addition of an ad-hoc Cosmological Constant in the Einstein frame leads to a Thermodynamical interpretation of this physical system, which allows further insight on its (meta)stability and evolution. |
2107.10341 | Iver Brevik | I. Brevik, K. Myrzakulov, A. V. Timoshkin and A. Zhadyranova | Viscous coupled fluids in terms of a log-corrected equation of state | 15 pages latex, author list corrected. To appear in Int. J. Geom.
Meth. Mod. Phys | Int. J. Geom. Meth. Mod. Phys. (2021) 2150198 | 10.1142/S021988782150198X | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider a class of cosmological fluids that possess properties analogous
to those of crystalline solids undergoing isotropic deformations. Our research
is based on a modified log-corrected power-law equation of state in the
presence of a bulk viscosity. This formalism represents a class of so-called
logotropic fluids, and allows explaining an accelerating late-time universe. In
order to obtain a more detailed picture of its evolution, we add in our model a
coupling of the log-corrected power-law fluid to dark matter, and study various
interacting forms between them. We solve the system of equations for a modified
log-power-law fluid coupled to dark matter, and obtain expressions for the
log-corrected power-law energy density, and the energy density for dark matter.
A comparative analysis is made with the model of a nonviscous log-corrected
power-law fluid without interaction with dark matter.
| [
{
"created": "Wed, 21 Jul 2021 20:11:44 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Aug 2021 13:50:13 GMT",
"version": "v2"
}
] | 2021-08-23 | [
[
"Brevik",
"I.",
""
],
[
"Myrzakulov",
"K.",
""
],
[
"Timoshkin",
"A. V.",
""
],
[
"Zhadyranova",
"A.",
""
]
] | We consider a class of cosmological fluids that possess properties analogous to those of crystalline solids undergoing isotropic deformations. Our research is based on a modified log-corrected power-law equation of state in the presence of a bulk viscosity. This formalism represents a class of so-called logotropic fluids, and allows explaining an accelerating late-time universe. In order to obtain a more detailed picture of its evolution, we add in our model a coupling of the log-corrected power-law fluid to dark matter, and study various interacting forms between them. We solve the system of equations for a modified log-power-law fluid coupled to dark matter, and obtain expressions for the log-corrected power-law energy density, and the energy density for dark matter. A comparative analysis is made with the model of a nonviscous log-corrected power-law fluid without interaction with dark matter. |
gr-qc/9707026 | Paul Anderson | Paul R. Anderson and Courtney D. Mull | Constraints on Black Holes in Classical and Semiclassical Theories of
Gravity | 7 pages, ReVTeX | null | null | null | gr-qc | null | Constraints on the geometry of a static spherically symmetric black hole are
obtained by requiring the spacetime curvature to be analytic at the event
horizon. For a zero temperature black hole further constraints are obtained by
also requiring that the semiclassical trace equation be satisfied when
conformally invariant fields are present. It is found that zero temperature
black holes whose sizes lie within a certain range do not exist. The range
depends on the numbers and types of conformally invariant quantized fields that
are present.
| [
{
"created": "Fri, 11 Jul 1997 13:59:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Anderson",
"Paul R.",
""
],
[
"Mull",
"Courtney D.",
""
]
] | Constraints on the geometry of a static spherically symmetric black hole are obtained by requiring the spacetime curvature to be analytic at the event horizon. For a zero temperature black hole further constraints are obtained by also requiring that the semiclassical trace equation be satisfied when conformally invariant fields are present. It is found that zero temperature black holes whose sizes lie within a certain range do not exist. The range depends on the numbers and types of conformally invariant quantized fields that are present. |
2202.01900 | Miko{\l}aj Myszkowski Mr | Miko{\l}aj Myszkowski | Atom interferometers and a small-scale test of general relativity | 28 pages, 6 figures | null | 10.1007/s10714-022-03012-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since the first appearance of general relativity in 1916, various experiments
have been conducted to test the theory. Due to the weakness of the interactions
involved, all of the documented tests were carried out in a gravitational field
generated by objects of an astronomical scale. We propose an idea for an
experiment that could detect purely general-relativistic effects in a
lab-generated gravitational field. It is shown that a set of dense
rapidly-revolving cylinders produce a frame-dragging effect substantial enough
to be two orders of magnitude away from the observable range of the next
generation of atomic interferometers. The metric tensor due to a uniform
rotating axisymmetric body in the weak-field limit is calculated and the phase
shift formula for the interferometer is derived. This article is meant to
demonstrate feasibility of the concept and stimulate further research into the
field of low-scale experiments in general relativity. It is by no means a fully
developed experiment proposal.
| [
{
"created": "Thu, 3 Feb 2022 23:04:19 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Feb 2022 11:15:52 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Apr 2022 19:21:39 GMT",
"version": "v3"
},
{
"created": "Fri, 16 Sep 2022 11:40:28 GMT",
"version": "v4"
}
] | 2022-11-30 | [
[
"Myszkowski",
"Mikołaj",
""
]
] | Since the first appearance of general relativity in 1916, various experiments have been conducted to test the theory. Due to the weakness of the interactions involved, all of the documented tests were carried out in a gravitational field generated by objects of an astronomical scale. We propose an idea for an experiment that could detect purely general-relativistic effects in a lab-generated gravitational field. It is shown that a set of dense rapidly-revolving cylinders produce a frame-dragging effect substantial enough to be two orders of magnitude away from the observable range of the next generation of atomic interferometers. The metric tensor due to a uniform rotating axisymmetric body in the weak-field limit is calculated and the phase shift formula for the interferometer is derived. This article is meant to demonstrate feasibility of the concept and stimulate further research into the field of low-scale experiments in general relativity. It is by no means a fully developed experiment proposal. |
gr-qc/0103109 | Nina Jansen | Nina Jansen, Peter Diener, Alexei Khokhlov, Igor Novikov | Local and global properties of conformally flat initial data for black
hole collisions | null | Class.Quant.Grav. 20 (2003) 51-74 | 10.1088/0264-9381/20/1/304 | null | gr-qc | null | We study physical properties of conformal initial value data for single and
binary black hole configurations obtained using conformal-imaging and
conformal-puncture methods. We investigate how the total mass M_tot of a
dataset with two black holes depends on the configuration of linear or angular
momentum and separation of the holes. The asymptotic behavior of M_tot with
increasing separation allows us to make conclusions about an unphysical
``junk'' gravitation field introduced in the solutions by the conformal
approaches. We also calculate the spatial distribution of scalar invariants of
the Riemann tensor which determine the gravitational tidal forces. For single
black hole configurations, these are compared to known analytical solutions.
Spatial distribution of the invariants allows us to make certain conclusions
about the local distribution of the additional field in the numerical datasets.
| [
{
"created": "Thu, 29 Mar 2001 10:28:34 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Jansen",
"Nina",
""
],
[
"Diener",
"Peter",
""
],
[
"Khokhlov",
"Alexei",
""
],
[
"Novikov",
"Igor",
""
]
] | We study physical properties of conformal initial value data for single and binary black hole configurations obtained using conformal-imaging and conformal-puncture methods. We investigate how the total mass M_tot of a dataset with two black holes depends on the configuration of linear or angular momentum and separation of the holes. The asymptotic behavior of M_tot with increasing separation allows us to make conclusions about an unphysical ``junk'' gravitation field introduced in the solutions by the conformal approaches. We also calculate the spatial distribution of scalar invariants of the Riemann tensor which determine the gravitational tidal forces. For single black hole configurations, these are compared to known analytical solutions. Spatial distribution of the invariants allows us to make certain conclusions about the local distribution of the additional field in the numerical datasets. |
1909.10382 | Sam S. C. Wong | Lam Hui, Daniel Kabat and Sam S. C. Wong | Quasinormal modes, echoes and the causal structure of the Green's
function | 23 pages, 5 figures | null | 10.1088/1475-7516/2019/12/020 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasinormal modes describe the return to equilibrium of a perturbed system,
in particular the ringdown phase of a black hole merger. But as
globally-defined quantities, the quasinormal spectrum can be highly sensitive
to global structure, including distant small perturbations to the potential. In
what sense are quasinormal modes a property of the resulting black hole? We
explore this question for the linearized perturbation equation with two
potentials having disjoint bounded support. We give a composition law for the
Wronskian that determines the quasinormal frequencies of the combined system.
We show that over short time scales the evolution is governed by the
quasinormal frequencies of the individual potentials, while the sensitivity to
global structure can be understood in terms of echoes. We introduce an echo
expansion of the Green's function and show that, as expected on general
grounds, at any finite time causality limits the number of echoes that can
contribute. We illustrate our results with the soluble example of a pair of
$\delta$-function potentials. We explicate the causal structure of the Green's
function, demonstrating under what conditions two very different quasinormal
spectra give rise to very similar ringdown waveforms.
| [
{
"created": "Mon, 23 Sep 2019 14:20:30 GMT",
"version": "v1"
}
] | 2019-12-18 | [
[
"Hui",
"Lam",
""
],
[
"Kabat",
"Daniel",
""
],
[
"Wong",
"Sam S. C.",
""
]
] | Quasinormal modes describe the return to equilibrium of a perturbed system, in particular the ringdown phase of a black hole merger. But as globally-defined quantities, the quasinormal spectrum can be highly sensitive to global structure, including distant small perturbations to the potential. In what sense are quasinormal modes a property of the resulting black hole? We explore this question for the linearized perturbation equation with two potentials having disjoint bounded support. We give a composition law for the Wronskian that determines the quasinormal frequencies of the combined system. We show that over short time scales the evolution is governed by the quasinormal frequencies of the individual potentials, while the sensitivity to global structure can be understood in terms of echoes. We introduce an echo expansion of the Green's function and show that, as expected on general grounds, at any finite time causality limits the number of echoes that can contribute. We illustrate our results with the soluble example of a pair of $\delta$-function potentials. We explicate the causal structure of the Green's function, demonstrating under what conditions two very different quasinormal spectra give rise to very similar ringdown waveforms. |
2405.11334 | Rubens R. S. Oliveira | R. R. S. Oliveira | Dirac fermions in a spinning conical G\"odel-type spacetime | 14 pages, 6 figures. arXiv admin note: text overlap with
arXiv:2402.15720 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we determine the relativistic and nonrelativistic energy
levels for Dirac fermions in a spinning conical G\"odel-type spacetime in
$(2+1)$-dimensions, where we work with the curved Dirac equation in polar
coordinates and we use the tetrads formalism. Solving a second-order
differential equation for the two components of the Dirac spinor, we obtain a
generalized Laguerre equation, and the relativistic energy levels of the
fermion and antifermion, where such levels are quantized in terms of the radial
and total magnetic quantum numbers $n$ and $m_j$, and explicitly depends on the
spin parameter $s$ (describes the ``spin''), spinorial parameter $u$ (describes
the two components of the spinor), curvature and rotation parameters $\alpha$
and $\beta$ (describes the conical curvature and the angular momentum of the
spinning cosmic string), and on the vorticity parameter $\Omega$ (describes the
G\"odel-type spacetime). In particular, the quantization is a direct result of
the existence of $\Omega$ (i.e., $\Omega$ acts as a kind of ``external field or
potential''). We see that for $m_j>0$, the energy levels do not depend on $s$
and $u$; however, depend on $n$, $m_j$, $\alpha$, and $\beta$. In this case,
$\alpha$ breaks the degeneracy of the energy levels and such levels can
increase infinitely in the limit $\frac{4\Omega\beta}{\alpha}\to 1$. Already
for $m_j<0$, we see that the energy levels depends on $s$, $u$ and $n$;
however, it no longer depends on $m_j$, $\alpha$ and $\beta$. In this case, it
is as if the fermion ``lives only in a flat G\"odel-type spacetime''. Besides,
we also study the low-energy or nonrelativistic limit of the system. In both
cases (relativistic and nonrelativistic), we graphically analyze the behavior
of energy levels as a function of $\Omega$, $\alpha$, and $\beta$ for three
different values of $n$ (ground state and the first two excited states).
| [
{
"created": "Sat, 18 May 2024 16:46:27 GMT",
"version": "v1"
}
] | 2024-05-21 | [
[
"Oliveira",
"R. R. S.",
""
]
] | In this paper, we determine the relativistic and nonrelativistic energy levels for Dirac fermions in a spinning conical G\"odel-type spacetime in $(2+1)$-dimensions, where we work with the curved Dirac equation in polar coordinates and we use the tetrads formalism. Solving a second-order differential equation for the two components of the Dirac spinor, we obtain a generalized Laguerre equation, and the relativistic energy levels of the fermion and antifermion, where such levels are quantized in terms of the radial and total magnetic quantum numbers $n$ and $m_j$, and explicitly depends on the spin parameter $s$ (describes the ``spin''), spinorial parameter $u$ (describes the two components of the spinor), curvature and rotation parameters $\alpha$ and $\beta$ (describes the conical curvature and the angular momentum of the spinning cosmic string), and on the vorticity parameter $\Omega$ (describes the G\"odel-type spacetime). In particular, the quantization is a direct result of the existence of $\Omega$ (i.e., $\Omega$ acts as a kind of ``external field or potential''). We see that for $m_j>0$, the energy levels do not depend on $s$ and $u$; however, depend on $n$, $m_j$, $\alpha$, and $\beta$. In this case, $\alpha$ breaks the degeneracy of the energy levels and such levels can increase infinitely in the limit $\frac{4\Omega\beta}{\alpha}\to 1$. Already for $m_j<0$, we see that the energy levels depends on $s$, $u$ and $n$; however, it no longer depends on $m_j$, $\alpha$ and $\beta$. In this case, it is as if the fermion ``lives only in a flat G\"odel-type spacetime''. Besides, we also study the low-energy or nonrelativistic limit of the system. In both cases (relativistic and nonrelativistic), we graphically analyze the behavior of energy levels as a function of $\Omega$, $\alpha$, and $\beta$ for three different values of $n$ (ground state and the first two excited states). |
2209.12455 | Jing-Bo Wang | Jingbo Wang | The topological entanglement entropy of black holes in loop quantum
gravity | This paper will be extended by the paper 2303.15760 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Topological order (long-range entanglement) play important role in modern
condensed matter physics. In this paper, we will show that the four dimensional
black hole can also have topological order, by showing that the topological
entanglement entropy is non-zero. The properties of the topological order show
that the large diffeomorphisms will act as symmetry (not gauge) transformation
on the physical states. More importantly, the long-range entanglement will make
the Hawking radiation pure.
| [
{
"created": "Mon, 26 Sep 2022 06:52:43 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Dec 2023 07:59:46 GMT",
"version": "v2"
}
] | 2023-12-06 | [
[
"Wang",
"Jingbo",
""
]
] | Topological order (long-range entanglement) play important role in modern condensed matter physics. In this paper, we will show that the four dimensional black hole can also have topological order, by showing that the topological entanglement entropy is non-zero. The properties of the topological order show that the large diffeomorphisms will act as symmetry (not gauge) transformation on the physical states. More importantly, the long-range entanglement will make the Hawking radiation pure. |
2204.11810 | Giovanni Camelio | Giovanni Camelio, Lorenzo Gavassino, Marco Antonelli, Sebastiano
Bernuzzi, Brynmor Haskell | Simulating bulk viscosity in neutron stars. II. Evolution in spherical
symmetry | 23 pages, 16 figures, 3 appendices, 5 tables. Code published on
zenodo with DOI:10.5281/zenodo.6478022 | Phys. Rev. D 107, 103032 (2023) | 10.1103/PhysRevD.107.103032 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Out-of-equilibrium reactions between different particle species are the main
processes contributing to bulk viscosity in neutron stars. In this work, we
numerically compare three different approaches to the modeling of bulk
viscosity: the multi-component fluid with reacting particle species and two
bulk stress formalism based on the M\"uller-Israel-Stewart theory, namely the
Hiscock-Lindblom and the Maxwell-Cattaneo models, whose flux-conservative
formulation in radial gauge-polar slicing coordinates and spherical symmetry is
derived in a companion paper. To our knowledge, this is the first time that a
neutron star is simulated with the complete Hiscock-Lindblom model of bulk
viscosity. We find that the Hiscock-Lindblom and Maxwell-Cattaneo models are
good approximations of the multi-component fluid for small perturbations and
when the non-equilibrium equation of state of the fluid depends on only one
independent particle fraction. For more than one independent particle fraction
and for large perturbations, the bulk stress approximation is still valid but
less accurate. In addition, we include the energy loss due to the luminosity of
the reactions in the bulk stress formulation. We find that the energy loss due
to bulk viscosity has a larger effect on the dynamics than the bulk stress or
the variation in particle composition per se. The new one-dimensional,
general-relativistic hydrodynamic code developed for this work, hydro-bulk-1D,
is publicly available.
| [
{
"created": "Mon, 25 Apr 2022 17:36:13 GMT",
"version": "v1"
},
{
"created": "Fri, 19 May 2023 18:28:06 GMT",
"version": "v2"
}
] | 2023-05-23 | [
[
"Camelio",
"Giovanni",
""
],
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Haskell",
"Brynmor",
""
]
] | Out-of-equilibrium reactions between different particle species are the main processes contributing to bulk viscosity in neutron stars. In this work, we numerically compare three different approaches to the modeling of bulk viscosity: the multi-component fluid with reacting particle species and two bulk stress formalism based on the M\"uller-Israel-Stewart theory, namely the Hiscock-Lindblom and the Maxwell-Cattaneo models, whose flux-conservative formulation in radial gauge-polar slicing coordinates and spherical symmetry is derived in a companion paper. To our knowledge, this is the first time that a neutron star is simulated with the complete Hiscock-Lindblom model of bulk viscosity. We find that the Hiscock-Lindblom and Maxwell-Cattaneo models are good approximations of the multi-component fluid for small perturbations and when the non-equilibrium equation of state of the fluid depends on only one independent particle fraction. For more than one independent particle fraction and for large perturbations, the bulk stress approximation is still valid but less accurate. In addition, we include the energy loss due to the luminosity of the reactions in the bulk stress formulation. We find that the energy loss due to bulk viscosity has a larger effect on the dynamics than the bulk stress or the variation in particle composition per se. The new one-dimensional, general-relativistic hydrodynamic code developed for this work, hydro-bulk-1D, is publicly available. |
1410.4190 | Alejandro Cardenas Avendano | Carlos A. Benavides, Alejandro Cardenas-Avendano, Alexis Larranaga | Gravitational lensing in the strong field limit for Kar's metric | v3: 18 pages, 5 figures, references and an Appendix added | International Journal of Theoretical Physics Volume 55, Issue 4 ,
pp 2219-2236, 2016 | 10.1007/s10773-015-2861-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we calculate the strong field limit deflection angle for a
light ray passing near a scalar charged spherically symmetric object, described
by a metric which comes from the low-energy limit of heterotic string theory.
Then, we compare the expansion parameters of our results with those obtained in
the Einstein's canonical frame, obtained by a conformal transformation, and we
show that, at least at first order, the results do not agree.
| [
{
"created": "Wed, 15 Oct 2014 17:19:36 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Oct 2014 04:44:36 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Oct 2015 01:15:50 GMT",
"version": "v3"
}
] | 2016-03-15 | [
[
"Benavides",
"Carlos A.",
""
],
[
"Cardenas-Avendano",
"Alejandro",
""
],
[
"Larranaga",
"Alexis",
""
]
] | In this paper we calculate the strong field limit deflection angle for a light ray passing near a scalar charged spherically symmetric object, described by a metric which comes from the low-energy limit of heterotic string theory. Then, we compare the expansion parameters of our results with those obtained in the Einstein's canonical frame, obtained by a conformal transformation, and we show that, at least at first order, the results do not agree. |
2012.10184 | Eric Poisson | Eric Poisson | Compact body in a tidal environment: New types of relativistic Love
numbers, and a post-Newtonian operational definition for tidally induced
multipole moments | 62 pages, 1 figure. New appendix. This version matches the published
article | Phys. Rev. D 103, 064023 (2021) | 10.1103/PhysRevD.103.064023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the tidal deformation of a nonrotating compact body (material body
or black hole) in general relativity. The body's exterior metric is calculated
in a simultaneous expansion in powers of the ratio between the distance to the
body and three distinct length scales: the radius of curvature of the external
spacetime in which the body is inserted, the scale of spatial inhomogeneity of
the curvature, and the scale of temporal variation. The metric is valid in the
body's immediate neighborhood, which excludes the external matter responsible
for the tidal environment. The body's tidal response is encapsulated in four
types of relativistic Love numbers: $k_\ell$, the familiar Love number that
measures the linear response to a static tidal field, $p_\ell$, which measures
the quadratic response to the tidal field, $\dot{k}_\ell$ and $\ddot{k}_\ell$,
associated with first and second time derivatives of the tidal field,
respectively. The Love numbers acquire an operational meaning through the
definition of tidally induced multipole moments. Previously proposed
definitions for the moments suffer from ambiguities associated with the
subtraction of a "pure tidal field" from the full metric. A robust operational
definition is proposed here. It relies on inserting the body's local metric
within a global metric constructed in post-Newtonian theory; the global metric
includes the external matter responsible for the tidal environment. When viewed
in the post-Newtonian spacetime, the compact body appears as a skeletonized
object with a specific multipole structure. The tidally induced multipole
moments provide a description of this structure. They manifest themselves, for
example, in the body's tidal acceleration, which is nonlinear in the tidal
field. At leading order in the tidal interaction, the acceleration is
proportional to the $k_2$ Love number as calculated in full general relativity.
| [
{
"created": "Fri, 18 Dec 2020 12:07:08 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Mar 2021 18:39:48 GMT",
"version": "v2"
}
] | 2021-03-24 | [
[
"Poisson",
"Eric",
""
]
] | We examine the tidal deformation of a nonrotating compact body (material body or black hole) in general relativity. The body's exterior metric is calculated in a simultaneous expansion in powers of the ratio between the distance to the body and three distinct length scales: the radius of curvature of the external spacetime in which the body is inserted, the scale of spatial inhomogeneity of the curvature, and the scale of temporal variation. The metric is valid in the body's immediate neighborhood, which excludes the external matter responsible for the tidal environment. The body's tidal response is encapsulated in four types of relativistic Love numbers: $k_\ell$, the familiar Love number that measures the linear response to a static tidal field, $p_\ell$, which measures the quadratic response to the tidal field, $\dot{k}_\ell$ and $\ddot{k}_\ell$, associated with first and second time derivatives of the tidal field, respectively. The Love numbers acquire an operational meaning through the definition of tidally induced multipole moments. Previously proposed definitions for the moments suffer from ambiguities associated with the subtraction of a "pure tidal field" from the full metric. A robust operational definition is proposed here. It relies on inserting the body's local metric within a global metric constructed in post-Newtonian theory; the global metric includes the external matter responsible for the tidal environment. When viewed in the post-Newtonian spacetime, the compact body appears as a skeletonized object with a specific multipole structure. The tidally induced multipole moments provide a description of this structure. They manifest themselves, for example, in the body's tidal acceleration, which is nonlinear in the tidal field. At leading order in the tidal interaction, the acceleration is proportional to the $k_2$ Love number as calculated in full general relativity. |
2210.00133 | Marko Vojinovic | Nikola Paunkovic and Marko Vojinovic | Equivalence Principle in Classical and Quantum Gravity | v2: published version, 7+6 pages | Universe 8, 598 (2022) | 10.3390/universe8110598 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a general overview of various flavors of the equivalence principle in
classical and quantum physics, with special emphasis on the so-called weak
equivalence principle, and contrast its validity in mechanics versus field
theory. We also discuss its generalisation to a theory of quantum gravity. Our
analysis suggests that only the strong equivalence principle can be considered
fundamental enough to be generalised to a quantum gravity context, since all
other flavors of equivalence principle hold only approximately already at the
classical level.
| [
{
"created": "Fri, 30 Sep 2022 23:10:49 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Nov 2022 02:14:20 GMT",
"version": "v2"
}
] | 2022-11-15 | [
[
"Paunkovic",
"Nikola",
""
],
[
"Vojinovic",
"Marko",
""
]
] | We give a general overview of various flavors of the equivalence principle in classical and quantum physics, with special emphasis on the so-called weak equivalence principle, and contrast its validity in mechanics versus field theory. We also discuss its generalisation to a theory of quantum gravity. Our analysis suggests that only the strong equivalence principle can be considered fundamental enough to be generalised to a quantum gravity context, since all other flavors of equivalence principle hold only approximately already at the classical level. |
gr-qc/0309030 | Christos G. Tsagas | John D. Barrow (DAMTP), Christos G. Tsagas (UCT/DAMTP) | Godel brane | Revised version, to match paper published in Phys. Rev. D | Phys.Rev. D69 (2004) 064007 | 10.1103/PhysRevD.69.064007 | null | gr-qc astro-ph hep-th | null | We consider the brane-world generalisation of the Godel universe and analyse
its dynamical interaction with the bulk. The exact homogeneity of the standard
Godel spacetime no longer holds, unless the bulk is also static. We show how
the anisotropy of the Godel-type brane is dictated by that of the bulk and find
that the converse is also true. This determines the precise evolution of the
nonlocal anisotropic stresses, without any phenomenological assumptions, and
leads to a self-consistent closed set of equations for the evolution of the
Godel brane. We also examine the causality of the Godel brane and show that the
presence of the bulk cannot prevent the appearance of closed timelike curves.
| [
{
"created": "Fri, 5 Sep 2003 10:22:26 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Dec 2003 18:14:34 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Mar 2004 17:18:48 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Barrow",
"John D.",
"",
"DAMTP"
],
[
"Tsagas",
"Christos G.",
"",
"UCT/DAMTP"
]
] | We consider the brane-world generalisation of the Godel universe and analyse its dynamical interaction with the bulk. The exact homogeneity of the standard Godel spacetime no longer holds, unless the bulk is also static. We show how the anisotropy of the Godel-type brane is dictated by that of the bulk and find that the converse is also true. This determines the precise evolution of the nonlocal anisotropic stresses, without any phenomenological assumptions, and leads to a self-consistent closed set of equations for the evolution of the Godel brane. We also examine the causality of the Godel brane and show that the presence of the bulk cannot prevent the appearance of closed timelike curves. |
gr-qc/0512047 | Claus Kiefer | Claus Kiefer, Jakob Mueller-Hill, Cenalo Vaz | Classical and quantum LTB model for the non-marginal case | 23 pages, no figures, typos corrected | Phys.Rev.D73:044025,2006 | 10.1103/PhysRevD.73.044025 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the classical and quantum treatment of the Lemaitre-Tolman-Bondi
(LTB) model to the non-marginal case (defined by the fact that the shells of
the dust cloud start with a non-vanishing velocity at infinity). We present the
classical canonical formalism and address with particular care the boundary
terms in the action. We give the general relation between dust time and Killing
time. Employing a lattice regularization, we then derive and discuss for
particular factor orderings exact solutions to all quantum constraints.
| [
{
"created": "Wed, 7 Dec 2005 16:28:06 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Oct 2009 09:17:34 GMT",
"version": "v2"
}
] | 2009-10-05 | [
[
"Kiefer",
"Claus",
""
],
[
"Mueller-Hill",
"Jakob",
""
],
[
"Vaz",
"Cenalo",
""
]
] | We extend the classical and quantum treatment of the Lemaitre-Tolman-Bondi (LTB) model to the non-marginal case (defined by the fact that the shells of the dust cloud start with a non-vanishing velocity at infinity). We present the classical canonical formalism and address with particular care the boundary terms in the action. We give the general relation between dust time and Killing time. Employing a lattice regularization, we then derive and discuss for particular factor orderings exact solutions to all quantum constraints. |
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