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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1602.02568 | Katy Clough Ms | Katy Clough, Eugene A. Lim | Critical Phenomena in Non-spherically Symmetric Scalar Bubble Collapse | 22 pages, 12 Figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate numerically the critical behaviour which occurs in the
collapse of both spherically symmetric and asymmetric scalar field bubbles with
full general relativity. We use a minimally coupled scalar field subject to a
"double well" interaction potential, with the bubble wall spanning the barrier
between two degenerate minima. We find that the spherically symmetric case
exhibits Type 2 critical behaviour with the critical index consistent with a
value of gamma = 0.37 as expected. In the asymmetric case, we find that again
our results are consistent with a value of gamma = 0.37 for the dominant
unstable mode. We do not see strong evidence of echoing in the solutions, which
could be due to the fact that the coordinates are not well adapted to the
echoing behaviour, or due to being still too far from the critical point to
properly observe the critical solution.
| [
{
"created": "Mon, 8 Feb 2016 13:57:34 GMT",
"version": "v1"
}
] | 2016-02-09 | [
[
"Clough",
"Katy",
""
],
[
"Lim",
"Eugene A.",
""
]
] | We investigate numerically the critical behaviour which occurs in the collapse of both spherically symmetric and asymmetric scalar field bubbles with full general relativity. We use a minimally coupled scalar field subject to a "double well" interaction potential, with the bubble wall spanning the barrier between two degenerate minima. We find that the spherically symmetric case exhibits Type 2 critical behaviour with the critical index consistent with a value of gamma = 0.37 as expected. In the asymmetric case, we find that again our results are consistent with a value of gamma = 0.37 for the dominant unstable mode. We do not see strong evidence of echoing in the solutions, which could be due to the fact that the coordinates are not well adapted to the echoing behaviour, or due to being still too far from the critical point to properly observe the critical solution. |
2109.13031 | Rahul Kumar | Sushant G. Ghosh and Rahul Kumar walia | Rotating black holes in general relativity coupled to nonlinear
electrodynamics | 10 pages and 7 figures. Accepted for publication in Annals of
Physics. arXiv admin note: substantial text overlap with arXiv:2109.08055 | null | 10.1016/j.aop.2021.168619 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find an exact spherically symmetric magnetically charged black hole
solution to general relativity (GR) coupled to nonlinear electrodynamics (NED)
with an appropriate Lagrangian density. In turn, starting with this spherical
black hole as a seed metric, we construct a rotating spacetime, a modification
of Kerr black hole, using the revised Newman-Janis algorithm that depends on
mass, spin, and a NED parameter $g$. We find an exact expression for
thermodynamic quantities of the black holes like the mass, Hawking temperature,
entropy, heat capacity, and free energy expressed in terms of horizon radius,
and they show significant deviations from the Kerr case owing to NED. We also
calculate analytical expressions for effective Komar mass and angular momentum
for the rotating black hole and demonstrate that the Komar conserved quantity
corresponding to the null Killing vector at horizon obeys
$\mathcal{K}_{\chi}=2S_+T_+.$ The radiating counterpart renders a
generalization of Carmeli's spacetime as well as Vaidya's spacetime in the
appropriate limits.
| [
{
"created": "Mon, 27 Sep 2021 13:11:08 GMT",
"version": "v1"
}
] | 2022-01-05 | [
[
"Ghosh",
"Sushant G.",
""
],
[
"walia",
"Rahul Kumar",
""
]
] | We find an exact spherically symmetric magnetically charged black hole solution to general relativity (GR) coupled to nonlinear electrodynamics (NED) with an appropriate Lagrangian density. In turn, starting with this spherical black hole as a seed metric, we construct a rotating spacetime, a modification of Kerr black hole, using the revised Newman-Janis algorithm that depends on mass, spin, and a NED parameter $g$. We find an exact expression for thermodynamic quantities of the black holes like the mass, Hawking temperature, entropy, heat capacity, and free energy expressed in terms of horizon radius, and they show significant deviations from the Kerr case owing to NED. We also calculate analytical expressions for effective Komar mass and angular momentum for the rotating black hole and demonstrate that the Komar conserved quantity corresponding to the null Killing vector at horizon obeys $\mathcal{K}_{\chi}=2S_+T_+.$ The radiating counterpart renders a generalization of Carmeli's spacetime as well as Vaidya's spacetime in the appropriate limits. |
1108.3346 | Saulo Pereira H | S. H. Pereira, J. C. Z. Aguilar and E. C. Rom\~ao | Massless particle creation in a f(R) expanding universe | 14 pages, 2 figures. Expanded and revised version | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present an exact solution to the spectrum of massless
particle creation for a power law expansion of the scale factor of the form
$t^{2n/3}$ for real scalar particles in a flat and matter dominated universe.
Such an evolution follows from a modified theory of gravity of the type
$f(R)=\beta R^n$, and it is showed that the spectrum of created particles is
$\beta$ independent. We find that greater the value of $n$ smaller is the
number of created particles. We study in detail the spectrum of the total
particle number created for $n=1\pm \varepsilon$, with $\varepsilon = 0.1$, a
very small deviation from the standard general relativity case ($n=1$). We find
that such a very small deviation causes a great difference in the total
particle number, of about one order of magnitude as compared to the standard
general relativity. Our calculations are based on the method of instantaneous
Hamiltonian diagonalization, where the vacuum states are defined as those which
minimizes the energy at a particular instant of time. The spectrum of the total
number and total energy of created particles can be determined exactly for any
value of the physical time in a matter dominated universe. We also find that
the main contribution to the total number of particles and total energy comes
from small wavenumbers $k$ and for particles with large values of $k$ the
contribution is very small.
| [
{
"created": "Tue, 16 Aug 2011 20:17:27 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Mar 2012 16:05:29 GMT",
"version": "v2"
},
{
"created": "Sat, 15 Jun 2013 18:15:30 GMT",
"version": "v3"
}
] | 2013-06-18 | [
[
"Pereira",
"S. H.",
""
],
[
"Aguilar",
"J. C. Z.",
""
],
[
"Romão",
"E. C.",
""
]
] | In this paper we present an exact solution to the spectrum of massless particle creation for a power law expansion of the scale factor of the form $t^{2n/3}$ for real scalar particles in a flat and matter dominated universe. Such an evolution follows from a modified theory of gravity of the type $f(R)=\beta R^n$, and it is showed that the spectrum of created particles is $\beta$ independent. We find that greater the value of $n$ smaller is the number of created particles. We study in detail the spectrum of the total particle number created for $n=1\pm \varepsilon$, with $\varepsilon = 0.1$, a very small deviation from the standard general relativity case ($n=1$). We find that such a very small deviation causes a great difference in the total particle number, of about one order of magnitude as compared to the standard general relativity. Our calculations are based on the method of instantaneous Hamiltonian diagonalization, where the vacuum states are defined as those which minimizes the energy at a particular instant of time. The spectrum of the total number and total energy of created particles can be determined exactly for any value of the physical time in a matter dominated universe. We also find that the main contribution to the total number of particles and total energy comes from small wavenumbers $k$ and for particles with large values of $k$ the contribution is very small. |
2310.07540 | Mariia Churilova | Mariia Churilova, Martin Kolo\v{s}, Zden\v{e}k Stuchl\'ik | String loop vibration around Schwarzschild black hole | 13 pages, 9 figures | Eur. Phys. J. C 84, 25 (2024) | 10.1140/epjc/s10052-023-12367-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | String loop vibrations in a central plane of a Schwarzschild black hole are
investigated for various string equations of state. We discuss string loop
stability and derive frequencies of vibrational modes. Using the vibrating
string loop model we fit the quasi-periodic oscillation (QPO) observed in X-ray
signal coming from some compact sources. We demonstrate how the string-loop
parameters are related to the radial and vertical fundamental vibration modes,
and how the vibrational instability can be related to the Q-factor
characterizing the observed QPOs.
| [
{
"created": "Wed, 11 Oct 2023 14:42:57 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jan 2024 16:34:22 GMT",
"version": "v2"
}
] | 2024-01-17 | [
[
"Churilova",
"Mariia",
""
],
[
"Kološ",
"Martin",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | String loop vibrations in a central plane of a Schwarzschild black hole are investigated for various string equations of state. We discuss string loop stability and derive frequencies of vibrational modes. Using the vibrating string loop model we fit the quasi-periodic oscillation (QPO) observed in X-ray signal coming from some compact sources. We demonstrate how the string-loop parameters are related to the radial and vertical fundamental vibration modes, and how the vibrational instability can be related to the Q-factor characterizing the observed QPOs. |
gr-qc/0601085 | Martin Bojowald | Martin Bojowald | Loop Quantum Cosmology | 104 pages, 10 figures; online version, containing 6 movies, available
at http://relativity.livingreviews.org/Articles/lrr-2005-11/ | Living Rev.Rel.8:11,2005 | 10.12942/lrr-2005-11 | AEI-2005-185, IGPG-06/1-6 | gr-qc astro-ph hep-th | null | Quantum gravity is expected to be necessary in order to understand situations
where classical general relativity breaks down. In particular in cosmology one
has to deal with initial singularities, i.e. the fact that the backward
evolution of a classical space-time inevitably comes to an end after a finite
amount of proper time. This presents a breakdown of the classical picture and
requires an extended theory for a meaningful description. Since small length
scales and high curvatures are involved, quantum effects must play a role. Not
only the singularity itself but also the surrounding space-time is then
modified. One particular realization is loop quantum cosmology, an application
of loop quantum gravity to homogeneous systems, which removes classical
singularities. Its implications can be studied at different levels. Main
effects are introduced into effective classical equations which allow to avoid
interpretational problems of quantum theory. They give rise to new kinds of
early universe phenomenology with applications to inflation and cyclic models.
To resolve classical singularities and to understand the structure of geometry
around them, the quantum description is necessary. Classical evolution is then
replaced by a difference equation for a wave function which allows to extend
space-time beyond classical singularities. One main question is how these
homogeneous scenarios are related to full loop quantum gravity, which can be
dealt with at the level of distributional symmetric states. Finally, the new
structure of space-time arising in loop quantum gravity and its application to
cosmology sheds new light on more general issues such as time.
| [
{
"created": "Fri, 20 Jan 2006 15:54:24 GMT",
"version": "v1"
}
] | 2016-10-19 | [
[
"Bojowald",
"Martin",
""
]
] | Quantum gravity is expected to be necessary in order to understand situations where classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e. the fact that the backward evolution of a classical space-time inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding space-time is then modified. One particular realization is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. Main effects are introduced into effective classical equations which allow to avoid interpretational problems of quantum theory. They give rise to new kinds of early universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function which allows to extend space-time beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of space-time arising in loop quantum gravity and its application to cosmology sheds new light on more general issues such as time. |
1303.4832 | Abhishek Majhi | Abhishek Majhi | Energy spectrum of black holes : a new view | version accepted for publication in MPLA | Mod. Phys. Lett. A, 32, 1750002 (2017) | 10.1142/S021773231750002X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Energy of a black hole is usually quantized by invoking some area
quantization scheme after expressing the energy in terms of the horizon area.
However, in this approach one has to quantize the local and asymptotic energy
of the black hole separately and the two results do not manifest any physical
correspondence with each other. Here, as opposed to this practice, we find the
unique energy spectrum of black holes by adopting a top-down approach. The
physical links among the underlying quantum theory, statistical mechanics and
thermodynamics of the black hole horizon play the central role in determining
the energy spectrum. The energy spectrum that we obtain, explicitly reveals the
correspondence between asymptotic and local observations through the presence
of the surface gravity of the horizon as a parameter in the spectrum, rather
than being expressed as a function of area and consequently getting quantized
in the usual approach. Thus, our result presents a new view as far as black
hole energy quantization is concerned. The calculations are performed using the
quantum geometric description of black hole horizons as laid down by loop
quantum gravity.
| [
{
"created": "Wed, 20 Mar 2013 03:52:55 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Nov 2013 04:30:27 GMT",
"version": "v2"
},
{
"created": "Sat, 20 Sep 2014 08:51:09 GMT",
"version": "v3"
},
{
"created": "Tue, 22 Dec 2015 08:03:10 GMT",
"version": "v4"
},
{
"c... | 2017-01-04 | [
[
"Majhi",
"Abhishek",
""
]
] | Energy of a black hole is usually quantized by invoking some area quantization scheme after expressing the energy in terms of the horizon area. However, in this approach one has to quantize the local and asymptotic energy of the black hole separately and the two results do not manifest any physical correspondence with each other. Here, as opposed to this practice, we find the unique energy spectrum of black holes by adopting a top-down approach. The physical links among the underlying quantum theory, statistical mechanics and thermodynamics of the black hole horizon play the central role in determining the energy spectrum. The energy spectrum that we obtain, explicitly reveals the correspondence between asymptotic and local observations through the presence of the surface gravity of the horizon as a parameter in the spectrum, rather than being expressed as a function of area and consequently getting quantized in the usual approach. Thus, our result presents a new view as far as black hole energy quantization is concerned. The calculations are performed using the quantum geometric description of black hole horizons as laid down by loop quantum gravity. |
2405.17161 | Gregoire Pierra | Gr\'egoire Pierra | Gravitational Wave Cosmology: Be Careful of the Black Hole Mass Spectrum | 6 pages, 3 figures, contribution to the 2024 Very High Energy
Phenomena in the Universe session of the 58th Rencontres de Moriond | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Gravitational waves (GWs) from compact binary coalescences (CBCs) offer
insights into the universe expansion. The spectral siren method, used without
electromagnetic counterparts (EMC), infers cosmic expansion (Hubble constant)
by relating detector and source frame masses of black hole (BH) mergers.
However, heuristic mass models (broken power law, power law plus peak,
multipeak) may introduce biases in the Hubble constant estimation, potentially
up to 3 sigma with 2000 detected GW mergers. These biases stem from the models
inability to consider redshift evolution and unexpected mass features. Future
GW cosmology studies should employ adaptable source mass models to address
these issues.
| [
{
"created": "Mon, 27 May 2024 13:34:35 GMT",
"version": "v1"
}
] | 2024-05-28 | [
[
"Pierra",
"Grégoire",
""
]
] | Gravitational waves (GWs) from compact binary coalescences (CBCs) offer insights into the universe expansion. The spectral siren method, used without electromagnetic counterparts (EMC), infers cosmic expansion (Hubble constant) by relating detector and source frame masses of black hole (BH) mergers. However, heuristic mass models (broken power law, power law plus peak, multipeak) may introduce biases in the Hubble constant estimation, potentially up to 3 sigma with 2000 detected GW mergers. These biases stem from the models inability to consider redshift evolution and unexpected mass features. Future GW cosmology studies should employ adaptable source mass models to address these issues. |
0710.1682 | Edmund Schluessel | Edmund Schluessel | Constraining the parameters of binary systems through time-dependent
light deflection | 15 pages, 2 figures, accepted in General Relativity & Gravitation | Gen.Rel.Grav.40:1013-1027,2008 | 10.1007/s10714-007-0588-y | null | gr-qc | null | A theory is derived relating the configuration of the cores of active
galaxies, specifically candidates for presumed super-massive black hole
binaries (SMBHBs), to time-dependent changes in images of those galaxies. Three
deflection quantities, resulting from the monopole term, mass quadrupole term,
and spin dipole term of the core, are examined. The resulting observational
technique is applied to the galaxy 3C66B. This technique is found to under
idealized circumstances surpass the technique proposed by Jenet et al. in
accuracy for constraining the mass of SMBHB candidates, but is exceeded in
accuracy and precision by Jenet's technique under currently-understood likely
conditions. The technique can also under favorable circumstances produce
results measurable by currently-available astronomical interferometry such as
very-long baseline-interferometry (VLBI).
| [
{
"created": "Tue, 9 Oct 2007 08:35:35 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Schluessel",
"Edmund",
""
]
] | A theory is derived relating the configuration of the cores of active galaxies, specifically candidates for presumed super-massive black hole binaries (SMBHBs), to time-dependent changes in images of those galaxies. Three deflection quantities, resulting from the monopole term, mass quadrupole term, and spin dipole term of the core, are examined. The resulting observational technique is applied to the galaxy 3C66B. This technique is found to under idealized circumstances surpass the technique proposed by Jenet et al. in accuracy for constraining the mass of SMBHB candidates, but is exceeded in accuracy and precision by Jenet's technique under currently-understood likely conditions. The technique can also under favorable circumstances produce results measurable by currently-available astronomical interferometry such as very-long baseline-interferometry (VLBI). |
1001.3922 | Naresh Dadhich | N. Dadhich, A. Molina and A. Khugaev | Uniform density static fluid sphere in Einstein-Gauss-Bonnet gravity and
its universality | 5 pages, title and abstract modified, one author added, considerable
improvement in clarity and precision, one reference added, result unchanged.
version to agree with the published paper in Phys. Rev. D | Phys.Rev.D81:104026,2010 | 10.1103/PhysRevD.81.104026 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Newtonian theory, gravity inside a constant density static sphere is
independent of spacetime dimension. Interestingly this general result is also
carried over to Einsteinian as well as higher order Einstein-Gauss-Bonnet
(Lovelock) gravity notwithstanding their nonlinearity. We prove that the
necessary and sufficient condition for universality of Schwarzschild interior
solution describing a uniform density sphere for all $n\geq4$ is that its
density is constant.
| [
{
"created": "Fri, 22 Jan 2010 06:48:33 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jan 2010 11:24:45 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Apr 2010 12:06:34 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Apr 2010 06:11:08 GMT",
"version": "v4"
},
{
"cre... | 2010-05-27 | [
[
"Dadhich",
"N.",
""
],
[
"Molina",
"A.",
""
],
[
"Khugaev",
"A.",
""
]
] | In Newtonian theory, gravity inside a constant density static sphere is independent of spacetime dimension. Interestingly this general result is also carried over to Einsteinian as well as higher order Einstein-Gauss-Bonnet (Lovelock) gravity notwithstanding their nonlinearity. We prove that the necessary and sufficient condition for universality of Schwarzschild interior solution describing a uniform density sphere for all $n\geq4$ is that its density is constant. |
1004.1353 | Pablo Galaviz | Pablo Galaviz, Bernd Bruegmann, Zhoujian Cao | Numerical evolution of multiple black holes with accurate initial data | Published in PRD | Phys.Rev.D82:024005,2010 | 10.1103/PhysRevD.82.024005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present numerical evolutions of three equal-mass black holes using the
moving puncture approach. We calculate puncture initial data for three black
holes solving the constraint equations by means of a high-order multigrid
elliptic solver. Using these initial data, we show the results for three black
hole evolutions with sixth-order waveform convergence. We compare results
obtained with the BAM and AMSS-NCKU codes with previous results. The
approximate analytic solution to the Hamiltonian constraint used in previous
simulations of three black holes leads to different dynamics and waveforms. We
present some numerical experiments showing the evolution of four black holes
and the resulting gravitational waveform.
| [
{
"created": "Thu, 8 Apr 2010 14:47:29 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Dec 2010 18:23:43 GMT",
"version": "v2"
}
] | 2010-12-21 | [
[
"Galaviz",
"Pablo",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Cao",
"Zhoujian",
""
]
] | We present numerical evolutions of three equal-mass black holes using the moving puncture approach. We calculate puncture initial data for three black holes solving the constraint equations by means of a high-order multigrid elliptic solver. Using these initial data, we show the results for three black hole evolutions with sixth-order waveform convergence. We compare results obtained with the BAM and AMSS-NCKU codes with previous results. The approximate analytic solution to the Hamiltonian constraint used in previous simulations of three black holes leads to different dynamics and waveforms. We present some numerical experiments showing the evolution of four black holes and the resulting gravitational waveform. |
gr-qc/9812017 | W. G. Unruh | W. G. Unruh, Moninder Jheeta | Complex Paths and the Hartle Hawking Wave-function for Slow Roll
Cosmologies | 17pp., 2 figures | null | null | null | gr-qc | null | A large set of complex path solutions for the Hartle Hawking semi-classical
wave function are found for an inflationary universe in the "slow roll" regime.
The implication of these for the semi-classical evolution of the universe is
also studied.
| [
{
"created": "Fri, 4 Dec 1998 19:07:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Unruh",
"W. G.",
""
],
[
"Jheeta",
"Moninder",
""
]
] | A large set of complex path solutions for the Hartle Hawking semi-classical wave function are found for an inflationary universe in the "slow roll" regime. The implication of these for the semi-classical evolution of the universe is also studied. |
0810.2602 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | f(R) gravity: successes and challenges | 18 pages, latex. Presented at SIGRAV2008, 18th Congress of the
Italian Society of General Relativity and Gravitation, Cosenza, Italy
September 22-25, 2008 | null | null | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the state of the art of f(R) theories of gravity (in their various
formulations), which have been proposed as an explanation of the cosmic
acceleration alternative to dark energy. The successes of f(R) gravity are
discussed, together with the challenges imposed by minimal criteria for their
viability.
| [
{
"created": "Wed, 15 Oct 2008 05:27:27 GMT",
"version": "v1"
}
] | 2008-10-16 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | We review the state of the art of f(R) theories of gravity (in their various formulations), which have been proposed as an explanation of the cosmic acceleration alternative to dark energy. The successes of f(R) gravity are discussed, together with the challenges imposed by minimal criteria for their viability. |
0708.3768 | Saibal Ray | Saibal Ray, P. C. Ray, Partha Pratim Ghosh, Utpal Mukhopadhyay and
Partha Chowdhury | Scenario of inflationary cosmology from the phenomenological $\Lambda$
models | 12 latex pages with 12 figures; Replaced with the revised version;
Accepeted for `J. Non-lin. Frac. Phen. Sci. Engg.' | Int.J.Theor.Phys.48:2499-2510,2009 | 10.1007/s10773-009-0036-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Choosing the three phenomenological models of the dynamical cosmological term
$\Lambda$, viz., $\Lambda \sim (\dot a/a)^2$, $\Lambda \sim {\ddot a/a}$ and
$\Lambda \sim \rho$ where $a$ is the cosmic scale factor, it has been shown by
the method of numerical analysis that the three models are equivalent for the
flat Universe $k=0$. The evolution plots for dynamical cosmological term
$\Lambda$ vs. time $t$ and also the cosmic scale factor $a$ vs. $t$ are drawn
here for $k=0, +1$. A qualitative analysis has been made from the plots which
supports the idea of inflation and hence expanding Universe.
| [
{
"created": "Tue, 28 Aug 2007 12:27:51 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jun 2008 15:02:33 GMT",
"version": "v2"
}
] | 2009-09-28 | [
[
"Ray",
"Saibal",
""
],
[
"Ray",
"P. C.",
""
],
[
"Ghosh",
"Partha Pratim",
""
],
[
"Mukhopadhyay",
"Utpal",
""
],
[
"Chowdhury",
"Partha",
""
]
] | Choosing the three phenomenological models of the dynamical cosmological term $\Lambda$, viz., $\Lambda \sim (\dot a/a)^2$, $\Lambda \sim {\ddot a/a}$ and $\Lambda \sim \rho$ where $a$ is the cosmic scale factor, it has been shown by the method of numerical analysis that the three models are equivalent for the flat Universe $k=0$. The evolution plots for dynamical cosmological term $\Lambda$ vs. time $t$ and also the cosmic scale factor $a$ vs. $t$ are drawn here for $k=0, +1$. A qualitative analysis has been made from the plots which supports the idea of inflation and hence expanding Universe. |
gr-qc/0108043 | Janna Levin | Janna Levin | Topology and the Cosmic Microwave Background | Hilarioulsy forgot to remove comments to myself in previous version.
Reference added. Submitted to Physics Reports | Phys.Rept.365:251-333,2002 | 10.1016/S0370-1573(02)00018-2 | null | gr-qc astro-ph | null | Nature abhors an infinity. The limits of general relativity are often
signaled by infinities: infinite curvature as in the center of a black hole,
the infinite energy of the singular big bang. We might be inclined to add an
infinite universe to the list of intolerable infinities. Theories that move
beyond general relativity naturally treat space as finite. In this review we
discuss the mathematics of finite spaces and our aspirations to observe the
finite extent of the universe in the cosmic background radiation.
| [
{
"created": "Thu, 16 Aug 2001 20:48:09 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Aug 2001 13:01:54 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Levin",
"Janna",
""
]
] | Nature abhors an infinity. The limits of general relativity are often signaled by infinities: infinite curvature as in the center of a black hole, the infinite energy of the singular big bang. We might be inclined to add an infinite universe to the list of intolerable infinities. Theories that move beyond general relativity naturally treat space as finite. In this review we discuss the mathematics of finite spaces and our aspirations to observe the finite extent of the universe in the cosmic background radiation. |
1905.00826 | Vasilis Oikonomou | V.K. Oikonomou | The Classical and Loop Quantum Cosmology Phase Space of Interacting Dark
Energy and Superfluid Dark Matter | PRD Accepted | null | 10.1103/PhysRevD.99.104042 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study in detail the phase space of a cosmological system
consisting of two coupled fluids, namely a dark energy fluid coupled with a
superfluid dark matter fluid. The dark matter fluid is assumed to have a
superfluid equation of state, hence it is not pressureless and our aim is to
find the impact of this non-trivial equation of state on the phase space of the
coupled system. We shall use two theoretical contexts, namely that of classical
cosmology and that of loop quantum cosmology. In the classical case, we
investigated the existence and stability of fixed points, and as we will show,
no de Sitter fixed points occur, however matter and radiation domination fixed
points occur, which are hyperbolic and unstable. We also show that there exist
limited sets of initial conditions for which singular solutions occur in the
phase space. With regard to the loop quantum cosmology case, we demonstrate
that stable de Sitter fixed points exist, for some values of the free
parameters of the theory, and interestingly enough, for the same values,
singular solutions corresponding to general sets of initial conditions occur.
To our knowledge this feature does not occur so frequently in loop quantum
cosmological frameworks. We also demonstrate that non-singular solutions
corresponding to a general set of initial conditions occur, however these occur
when the dark matter superfluid has negative pressure, so it is a rather
physically unappealing situation.
| [
{
"created": "Thu, 2 May 2019 16:01:10 GMT",
"version": "v1"
}
] | 2019-05-29 | [
[
"Oikonomou",
"V. K.",
""
]
] | In this paper we study in detail the phase space of a cosmological system consisting of two coupled fluids, namely a dark energy fluid coupled with a superfluid dark matter fluid. The dark matter fluid is assumed to have a superfluid equation of state, hence it is not pressureless and our aim is to find the impact of this non-trivial equation of state on the phase space of the coupled system. We shall use two theoretical contexts, namely that of classical cosmology and that of loop quantum cosmology. In the classical case, we investigated the existence and stability of fixed points, and as we will show, no de Sitter fixed points occur, however matter and radiation domination fixed points occur, which are hyperbolic and unstable. We also show that there exist limited sets of initial conditions for which singular solutions occur in the phase space. With regard to the loop quantum cosmology case, we demonstrate that stable de Sitter fixed points exist, for some values of the free parameters of the theory, and interestingly enough, for the same values, singular solutions corresponding to general sets of initial conditions occur. To our knowledge this feature does not occur so frequently in loop quantum cosmological frameworks. We also demonstrate that non-singular solutions corresponding to a general set of initial conditions occur, however these occur when the dark matter superfluid has negative pressure, so it is a rather physically unappealing situation. |
gr-qc/9906075 | David Polarski | D. Polarski | Direct Detection of Primordial Gravitational Waves in a BSI Inflationary
Model | to appear in Phys. Lett. B, (uses LaTeX, 10 pages) | Phys.Lett. B458 (1999) 13-18 | 10.1016/S0370-2693(99)00570-5 | null | gr-qc astro-ph hep-ph | null | We investigate the possibility for a direct detection by future space
interferometers of the stochastic gravitational wave (GW) background generated
during the inflationary stage in a class of viable $\Lambda$CDM BSI models. At
frequencies around $10^{-3}$Hz, maximal values $\Omega_{gw}(\nu)\sim 3\times
10^{-15}$ are found, an improvement of about one order of magnitude compared to
single-field, slow-roll inflationary models. This is presumably not sufficient
in order to be probed in the near future.
| [
{
"created": "Thu, 17 Jun 1999 14:38:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Polarski",
"D.",
""
]
] | We investigate the possibility for a direct detection by future space interferometers of the stochastic gravitational wave (GW) background generated during the inflationary stage in a class of viable $\Lambda$CDM BSI models. At frequencies around $10^{-3}$Hz, maximal values $\Omega_{gw}(\nu)\sim 3\times 10^{-15}$ are found, an improvement of about one order of magnitude compared to single-field, slow-roll inflationary models. This is presumably not sufficient in order to be probed in the near future. |
0905.2984 | Riccardo Sturani | R. Terenzi, R. Sturani | Wavelet entropy filter and cross-correlation of gravitational wave data | 10 pages, 6 figures. Proceeding of the GWDAW-13 conference | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method for enhancing the cross-correlation of gravitational wave
signals eventually present in data streams containing otherwise uncorrelated
noise. Such method makes use of the wavelet decomposition to cast the
cross-correlation time series in time-frequency space. Then an entropy
criterion is applied to identify the best time frequency resolution, i.e. the
resolution allowing to concentrate the signal in the smallest number of wavelet
coefficients. By keeping only the coefficients above a certain threshold, it is
possible to reconstruct a cross-correlation time series where the effect of
common signal is stronger. We tested our method against signals injected over
two data streams of uncorrelated white noise.
| [
{
"created": "Mon, 18 May 2009 21:23:55 GMT",
"version": "v1"
},
{
"created": "Thu, 28 May 2009 17:54:52 GMT",
"version": "v2"
}
] | 2009-05-28 | [
[
"Terenzi",
"R.",
""
],
[
"Sturani",
"R.",
""
]
] | We present a method for enhancing the cross-correlation of gravitational wave signals eventually present in data streams containing otherwise uncorrelated noise. Such method makes use of the wavelet decomposition to cast the cross-correlation time series in time-frequency space. Then an entropy criterion is applied to identify the best time frequency resolution, i.e. the resolution allowing to concentrate the signal in the smallest number of wavelet coefficients. By keeping only the coefficients above a certain threshold, it is possible to reconstruct a cross-correlation time series where the effect of common signal is stronger. We tested our method against signals injected over two data streams of uncorrelated white noise. |
1603.06504 | Christof Wetterich | C. Wetterich | Quantum correlations for the metric | extended discussion of off-shell propagator and mode functions, new
references, 38 pages | Phys. Rev. D 95, 123525 (2017) | 10.1103/PhysRevD.95.123525 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the correlation function for the metric for homogeneous and
isotropic cosmologies. The exact propagator equation determines the correlation
function as the inverse of the second functional derivative of the quantum
effective action. This formulation relates the metric correlation function
employed in quantum gravity computations to cosmological observables as the
graviton power spectrum. In the Einstein-Hilbert approximation for the
effective action the on-shell graviton correlation function can be obtained
equivalently from a product of mode functions which solve the linearized
Einstein equations. In contrast, the product of mode functions, often employed
in the context of cosmology, does not yield the correlation function for the
vector and scalar components of the metric fluctuations. We divide the metric
fluctuations into "physical fluctuations", which couple to a conserved energy
momentum tensor, and gauge fluctuations. On the subspace of physical metric
fluctuations the relation to physical sources becomes invertible, such that the
effective action and its relation to correlation functions no longer needs to
involve a gauge fixing term. The physical metric fluctuations have a similar
status as the Bardeen potentials, while being formulated in a covariant way. We
compute the effective action for the physical metric fluctuations for
geometries corresponding to realistic cosmologies.
| [
{
"created": "Mon, 21 Mar 2016 17:22:52 GMT",
"version": "v1"
},
{
"created": "Mon, 29 May 2017 12:20:50 GMT",
"version": "v2"
}
] | 2017-06-28 | [
[
"Wetterich",
"C.",
""
]
] | We discuss the correlation function for the metric for homogeneous and isotropic cosmologies. The exact propagator equation determines the correlation function as the inverse of the second functional derivative of the quantum effective action. This formulation relates the metric correlation function employed in quantum gravity computations to cosmological observables as the graviton power spectrum. In the Einstein-Hilbert approximation for the effective action the on-shell graviton correlation function can be obtained equivalently from a product of mode functions which solve the linearized Einstein equations. In contrast, the product of mode functions, often employed in the context of cosmology, does not yield the correlation function for the vector and scalar components of the metric fluctuations. We divide the metric fluctuations into "physical fluctuations", which couple to a conserved energy momentum tensor, and gauge fluctuations. On the subspace of physical metric fluctuations the relation to physical sources becomes invertible, such that the effective action and its relation to correlation functions no longer needs to involve a gauge fixing term. The physical metric fluctuations have a similar status as the Bardeen potentials, while being formulated in a covariant way. We compute the effective action for the physical metric fluctuations for geometries corresponding to realistic cosmologies. |
2208.04949 | Rituparna Mandal | Sunandan Gangopadhyay, Rituparna Mandal, Amitabha Lahiri | Bianchi-I cosmology in quantum gravity | 4 pages, Contribution to the proceedings of XXIV DAE-BRNS High Energy
Physics Symposium 2020 | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The exact renormalization group flow equations for gravity lead to quantum
corrections of Newton's constant and cosmological constant. Using this we
investigate the Bianchi-I cosmological model at late times. In particular, we
obtain the scale factors in different directions, and observe that they
eventually evolve into Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe
for radiation. However, for stiff matter the universe shows a Kasner like
behaviour. The presentation is based on our work published in
\cite{Mandal:2019xlg}.
| [
{
"created": "Tue, 9 Aug 2022 05:46:08 GMT",
"version": "v1"
}
] | 2022-08-11 | [
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Mandal",
"Rituparna",
""
],
[
"Lahiri",
"Amitabha",
""
]
] | The exact renormalization group flow equations for gravity lead to quantum corrections of Newton's constant and cosmological constant. Using this we investigate the Bianchi-I cosmological model at late times. In particular, we obtain the scale factors in different directions, and observe that they eventually evolve into Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe for radiation. However, for stiff matter the universe shows a Kasner like behaviour. The presentation is based on our work published in \cite{Mandal:2019xlg}. |
gr-qc/9411063 | Jerose Martin | Marcus Kriele and Jerome Martin | Black holes, cosmological singularities and change of signature | 14pages, Latex, no figure | Class.Quant.Grav.12:503-512,1995 | 10.1088/0264-9381/12/2/019 | null | gr-qc | null | There exists a widespread belief that signature type change could be used to
avoid spacetime singularities. We show that signature change cannot be utilised
to this end unless the Einstein equation is abandoned at the suface of
signature type change. We also discuss how to solve the initial value problem
and show to which extent smooth and discontinuous signature changing solutions
are equivalent.
| [
{
"created": "Fri, 25 Nov 1994 12:58:00 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Kriele",
"Marcus",
""
],
[
"Martin",
"Jerome",
""
]
] | There exists a widespread belief that signature type change could be used to avoid spacetime singularities. We show that signature change cannot be utilised to this end unless the Einstein equation is abandoned at the suface of signature type change. We also discuss how to solve the initial value problem and show to which extent smooth and discontinuous signature changing solutions are equivalent. |
2007.15717 | Maximilian Koegler | Bruno Hoegl, Stefan Hofmann, Maximilian Koegler | Physics in precision-dependent normal neighborhoods | 21 pages, 4 figures, minor spelling change, agrees with publication
in Physical Review D | Phys. Rev. D 102, 084065 (2020) | 10.1103/PhysRevD.102.084065 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a procedure to determine the size and shape of normal
neighborhoods in any spacetimes and their dependence on the precision of the
measurements performed by arbitrary observers. As an example, we consider the
Schwarzschild geometry in Riemann and Fermi normal coordinates and determine
the size and shape of normal neighborhoods in the vicinity of the event
horizon. Depending on the observers, normal neighborhoods extend to the event
horizon and even beyond into the black hole interior. It is shown that the
causal structure supported by normal neighborhoods across an event horizon is
consistent with general relativity. In particular, normal neighborhoods
reaching over an event horizon are void of the Schwarzschild coordinate
singularity. In addition, we introduce a new variant of normal coordinates
which we call Fermi normal coordinates around a point, unifying features of
Riemann and Fermi normal coordinates, and analyze their neighborhoods.
| [
{
"created": "Thu, 30 Jul 2020 20:00:23 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Oct 2020 19:59:09 GMT",
"version": "v2"
}
] | 2020-11-02 | [
[
"Hoegl",
"Bruno",
""
],
[
"Hofmann",
"Stefan",
""
],
[
"Koegler",
"Maximilian",
""
]
] | We introduce a procedure to determine the size and shape of normal neighborhoods in any spacetimes and their dependence on the precision of the measurements performed by arbitrary observers. As an example, we consider the Schwarzschild geometry in Riemann and Fermi normal coordinates and determine the size and shape of normal neighborhoods in the vicinity of the event horizon. Depending on the observers, normal neighborhoods extend to the event horizon and even beyond into the black hole interior. It is shown that the causal structure supported by normal neighborhoods across an event horizon is consistent with general relativity. In particular, normal neighborhoods reaching over an event horizon are void of the Schwarzschild coordinate singularity. In addition, we introduce a new variant of normal coordinates which we call Fermi normal coordinates around a point, unifying features of Riemann and Fermi normal coordinates, and analyze their neighborhoods. |
1009.5042 | Matyas Vasuth | J\'anos Maj\'ar, P\'eter Forg\'acs, and M\'aty\'as Vas\'uth | Gravitational waves from binaries on unbound orbits | 27 pages, 10 figures, to appear in Phys. Rev. D | Phys.Rev.D82:064041,2010 | 10.1103/PhysRevD.82.064041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A generalized true anomaly-type parametrization, convenient to describe both
bound and open orbits of a two-body system in general relativity is introduced.
A complete description of the time evolution of both the radial and of the
angular equations of a binary system taking into account the first order
post-newtonian (1PN) is given. The gravitational radiation field emitted by the
system is computed in the 1PN approximation including higher multipole moments
beyond the standard quadrupole term. The gravitational waveforms in the time
domain are explicitly given up to the 1PN order for unbound orbits, but the
results are also illustrated on binaries on elliptic orbits with special
attention given to the effects of eccentricity.
| [
{
"created": "Sat, 25 Sep 2010 23:25:41 GMT",
"version": "v1"
}
] | 2010-10-05 | [
[
"Majár",
"János",
""
],
[
"Forgács",
"Péter",
""
],
[
"Vasúth",
"Mátyás",
""
]
] | A generalized true anomaly-type parametrization, convenient to describe both bound and open orbits of a two-body system in general relativity is introduced. A complete description of the time evolution of both the radial and of the angular equations of a binary system taking into account the first order post-newtonian (1PN) is given. The gravitational radiation field emitted by the system is computed in the 1PN approximation including higher multipole moments beyond the standard quadrupole term. The gravitational waveforms in the time domain are explicitly given up to the 1PN order for unbound orbits, but the results are also illustrated on binaries on elliptic orbits with special attention given to the effects of eccentricity. |
0708.3470 | Andri Gretarsson | Andri M. Gretarsson, Erika D'Ambrosio, Valery Frolov, Brian O'Reilly,
Peter K. Fritschel | Effects of mode degeneracy in the LIGO Livingston Observatory recycling
cavity | Eight pages in two-column format. Six color figures. To be published
JOSA B | null | 10.1364/JOSAB.24.002821 | null | gr-qc | null | We analyze the electromagnetic fields in a Pound-Drever-Hall locked,
marginally unstable, Fabry-Perot cavity as a function of small changes in the
cavity length during resonance. More specifically, we compare the results of a
detailed numerical model with the behavior of the recycling cavity of the Laser
Interferometer Gravitational-wave Observatory (LIGO) detector that is located
in Livingston, Louisiana. In the interferometer's normal mode of operation, the
recycling cavity is stabilized by inducing a thermal lens in the cavity mirrors
with an external CO2 laser. During the study described here, this thermal
compensation system was not operating, causing the cavity to be marginally
optically unstable and cavity modes to become degenerate. In contrast to stable
optical cavities, the modal content of the resonating beam in the uncompensated
recycling cavity is significantly altered by very small cavity length changes.
This modifies the error signals used to control the cavity length in such a way
that the zero crossing point is no longer the point of maximum power in the
cavity nor is it the point where the input beam mode in the cavity is
maximized.
| [
{
"created": "Sun, 26 Aug 2007 08:10:26 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Gretarsson",
"Andri M.",
""
],
[
"D'Ambrosio",
"Erika",
""
],
[
"Frolov",
"Valery",
""
],
[
"O'Reilly",
"Brian",
""
],
[
"Fritschel",
"Peter K.",
""
]
] | We analyze the electromagnetic fields in a Pound-Drever-Hall locked, marginally unstable, Fabry-Perot cavity as a function of small changes in the cavity length during resonance. More specifically, we compare the results of a detailed numerical model with the behavior of the recycling cavity of the Laser Interferometer Gravitational-wave Observatory (LIGO) detector that is located in Livingston, Louisiana. In the interferometer's normal mode of operation, the recycling cavity is stabilized by inducing a thermal lens in the cavity mirrors with an external CO2 laser. During the study described here, this thermal compensation system was not operating, causing the cavity to be marginally optically unstable and cavity modes to become degenerate. In contrast to stable optical cavities, the modal content of the resonating beam in the uncompensated recycling cavity is significantly altered by very small cavity length changes. This modifies the error signals used to control the cavity length in such a way that the zero crossing point is no longer the point of maximum power in the cavity nor is it the point where the input beam mode in the cavity is maximized. |
2001.06490 | Mohammadtaher Safarzadeh | Mohammadtaher Safarzadeh, Will M. Farr, Enrico Ramirez-Ruiz | A trend in the effective spin distribution of LIGO binary black holes
with mass | Accepted for publication in ApJ main journal | null | 10.3847/1538-4357/ab80be | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary black holes (BBHs) detected by gravitational wave (GW) observations
could be broadly divided into two formation channels: those formed through
field binary evolution and those assembled dynamically in dense stellar
systems. Each of these formation channels, and their sub-channels, populate a
distinct region in the effective spin-mass ($\chi_{\rm eff}-M$) plane.
Depending on the branching ratio of different channels, an ensemble of BBHs
could show a trend in this plane. Here we fit a mass-dependent distribution for
$\chi_{\rm eff}$ to the GWTC-1 BBHs from the first and second observing runs of
Advanced LIGO and Advanced Virgo. We find a negative correlation between mass
and the mean effective spin ($\bar{\chi}_{\mathrm{eff}}$), and positive
correlation with its dispersion ($\sigma_{\chi_\mathrm{eff}}$) at 75\% and 80\%
confidence. This trend is robust against the choice of mass variable, but most
pronounced when the mass variable is taken to be the chirp mass of the binary.
The result is consistent with significant contributions from both dynamically
assembled and field binaries in the GWTC-1 catalog. The upcoming LIGO O3a data
release will critically test this interpretation.
| [
{
"created": "Fri, 17 Jan 2020 19:00:00 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Mar 2020 13:11:52 GMT",
"version": "v2"
}
] | 2020-05-20 | [
[
"Safarzadeh",
"Mohammadtaher",
""
],
[
"Farr",
"Will M.",
""
],
[
"Ramirez-Ruiz",
"Enrico",
""
]
] | Binary black holes (BBHs) detected by gravitational wave (GW) observations could be broadly divided into two formation channels: those formed through field binary evolution and those assembled dynamically in dense stellar systems. Each of these formation channels, and their sub-channels, populate a distinct region in the effective spin-mass ($\chi_{\rm eff}-M$) plane. Depending on the branching ratio of different channels, an ensemble of BBHs could show a trend in this plane. Here we fit a mass-dependent distribution for $\chi_{\rm eff}$ to the GWTC-1 BBHs from the first and second observing runs of Advanced LIGO and Advanced Virgo. We find a negative correlation between mass and the mean effective spin ($\bar{\chi}_{\mathrm{eff}}$), and positive correlation with its dispersion ($\sigma_{\chi_\mathrm{eff}}$) at 75\% and 80\% confidence. This trend is robust against the choice of mass variable, but most pronounced when the mass variable is taken to be the chirp mass of the binary. The result is consistent with significant contributions from both dynamically assembled and field binaries in the GWTC-1 catalog. The upcoming LIGO O3a data release will critically test this interpretation. |
gr-qc/0008026 | Kip S. Thorne | H.J. Kimble (1), Yuri Levin (1,2), Andrey B. Matsko (3), Kip S. Thorne
(1), and Sergey P. Vyatchanin (4) ((1) California Institute of Technology,
(2) University of California, Berkeley, (3) Texas A&M University, (4) Moscow
State University) | Conversion of conventional gravitational-wave interferometers into QND
interferometers by modifying their input and/or output optics | Submitted to Physical Review D; RevTeX manuscript with 16 figures;
prints to 33 pages in Physical Review double column format. Minor revisions
have been made in response to referee report | Phys.Rev. D65 (2002) 022002 | 10.1103/PhysRevD.65.022002 | null | gr-qc quant-ph | null | The LIGO-II gravitational-wave interferometers (ca. 2006--2008) are designed
to have sensitivities at about the standard quantum limit (SQL) near 100 Hz.
This paper describes and analyzes possible designs for subsequent, LIGO-III
interferometers that can beat the SQL. These designs are identical to a
conventional broad-band interferometer (without signal recycling), except for
new input and/or output optics. Three designs are analyzed: (i) a
"squeezed-input interferometer" (conceived by Unruh based on earlier work of
Caves) in which squeezed vacuum with frequency-dependent (FD) squeeze angle is
injected into the interferometer's dark port; (ii) a "variational-output"
interferometer (conceived in a different form by Vyatchanin, Matsko and
Zubova), in which homodyne detection with FD homodyne phase is performed on the
output light; and (iii) a "squeezed-variational interferometer" with squeezed
input and FD-homodyne output. It is shown that the FD squeezed-input light can
be produced by sending ordinary squeezed light through two successive
Fabry-Perot filter cavities before injection into the interferometer, and
FD-homodyne detection can be achieved by sending the output light through two
filter cavities before ordinary homodyne detection. With anticipated technology
and with laser powers comparable to that planned for LIGO-II, these
interferometers can beat the amplitude SQL by factors in the range from 3 to 5,
corresponding to event rate increases between ~30 and ~100 over the rate for a
SQL-limited interferometer.
| [
{
"created": "Fri, 11 Aug 2000 06:07:43 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2001 06:03:20 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Kimble",
"H. J.",
""
],
[
"Levin",
"Yuri",
""
],
[
"Matsko",
"Andrey B.",
""
],
[
"Thorne",
"Kip S.",
""
],
[
"Vyatchanin",
"Sergey P.",
""
]
] | The LIGO-II gravitational-wave interferometers (ca. 2006--2008) are designed to have sensitivities at about the standard quantum limit (SQL) near 100 Hz. This paper describes and analyzes possible designs for subsequent, LIGO-III interferometers that can beat the SQL. These designs are identical to a conventional broad-band interferometer (without signal recycling), except for new input and/or output optics. Three designs are analyzed: (i) a "squeezed-input interferometer" (conceived by Unruh based on earlier work of Caves) in which squeezed vacuum with frequency-dependent (FD) squeeze angle is injected into the interferometer's dark port; (ii) a "variational-output" interferometer (conceived in a different form by Vyatchanin, Matsko and Zubova), in which homodyne detection with FD homodyne phase is performed on the output light; and (iii) a "squeezed-variational interferometer" with squeezed input and FD-homodyne output. It is shown that the FD squeezed-input light can be produced by sending ordinary squeezed light through two successive Fabry-Perot filter cavities before injection into the interferometer, and FD-homodyne detection can be achieved by sending the output light through two filter cavities before ordinary homodyne detection. With anticipated technology and with laser powers comparable to that planned for LIGO-II, these interferometers can beat the amplitude SQL by factors in the range from 3 to 5, corresponding to event rate increases between ~30 and ~100 over the rate for a SQL-limited interferometer. |
0805.1947 | Henrik Zinkernagel | Svend Erik Rugh and Henrik Zinkernagel | On the physical basis of cosmic time | 44 pages. Submitted to Studies in History and Philosophy of Modern
Physics | Stud.Hist.Philos.Mod.Phys.40:1-19,2009 | 10.1016/j.shpsb.2008.06.001 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this manuscript we initiate a systematic examination of the physical basis
for the time concept in cosmology. We discuss and defend the idea that the
physical basis of the time concept is necessarily related to physical processes
which could conceivably take place among the material constituents available in
the universe. It is common practice to link the concept of cosmic time with a
space-time metric set up to describe the universe at large scales, and then
define a cosmic time $t$ as what is measured by a comoving standard clock. We
want to examine, however, the physical basis for setting up a comoving
reference frame and, in particular, what could be meant by a standard clock.
For this purpose we introduce the concept of a `core' of a clock (which, for a
standard clock in cosmology, is a scale-setting physical process) and we ask if
such a core can--in principle--be found in the available physics contemplated
in the various `stages' of the early universe. We find that a first problem
arises above the quark-gluon phase transition (which roughly occurs when the
cosmological model is extrapolated back to $\sim 10^{-5}$ seconds) where there
might be no bound systems left, and the concept of a physical length scale to a
certain extent disappears. A more serious problem appears above the electroweak
phase transition believed to occur at $\sim 10^{-11}$ seconds. At this point
the property of mass (almost) disappears and it becomes difficult to identify a
physical basis for concepts like length scale, energy scale and temperature --
which are all intimately linked to the concept of time in modern cosmology.
This situation suggests that the concept of a time scale in `very early'
universe cosmology lacks a physical basis or, at least, that the time scale
will have to be based on speculative new physics.
| [
{
"created": "Tue, 13 May 2008 22:29:44 GMT",
"version": "v1"
}
] | 2009-02-23 | [
[
"Rugh",
"Svend Erik",
""
],
[
"Zinkernagel",
"Henrik",
""
]
] | In this manuscript we initiate a systematic examination of the physical basis for the time concept in cosmology. We discuss and defend the idea that the physical basis of the time concept is necessarily related to physical processes which could conceivably take place among the material constituents available in the universe. It is common practice to link the concept of cosmic time with a space-time metric set up to describe the universe at large scales, and then define a cosmic time $t$ as what is measured by a comoving standard clock. We want to examine, however, the physical basis for setting up a comoving reference frame and, in particular, what could be meant by a standard clock. For this purpose we introduce the concept of a `core' of a clock (which, for a standard clock in cosmology, is a scale-setting physical process) and we ask if such a core can--in principle--be found in the available physics contemplated in the various `stages' of the early universe. We find that a first problem arises above the quark-gluon phase transition (which roughly occurs when the cosmological model is extrapolated back to $\sim 10^{-5}$ seconds) where there might be no bound systems left, and the concept of a physical length scale to a certain extent disappears. A more serious problem appears above the electroweak phase transition believed to occur at $\sim 10^{-11}$ seconds. At this point the property of mass (almost) disappears and it becomes difficult to identify a physical basis for concepts like length scale, energy scale and temperature -- which are all intimately linked to the concept of time in modern cosmology. This situation suggests that the concept of a time scale in `very early' universe cosmology lacks a physical basis or, at least, that the time scale will have to be based on speculative new physics. |
gr-qc/9904017 | Wai-Mo Suen | E. S. C. Ching, P. T. Leung, W. M. Suen, S. S. Tong and K. Young | Waves in Open Systems: Eigenfunction Expansions | Review of Modern Physics, 70, 1545, 1998 | Rev.Mod.Phys.70:1545,1998 | 10.1103/RevModPhys.70.1545 | null | gr-qc | null | An open system is not conservative because energy can escape to the outside.
An open system by itself is thus not conservative. As a result, the
time-evolution operator is not hermitian in the usual sense and the
eigenfunctions (factorized solutions in space and time) are no longer normal
modes but quasinormal modes (QNMs) whose frequencies $\omega$ are complex. QNM
analysis has been a powerful tool for investigating open systems. Previous
studies have been mostly system specific, and use a few QNMs to provide
approximate descriptions. Here we review recent developments which aim at a
unifying treatment. The formulation leads to a mathematical structure in close
analogy to that in conservative, hermitian systems. Many of the mathematical
tools for the latter can hence be transcribed. Emphasis is placed on those
cases in which the QNMs form a complete set for outgoing wavefunctions, so that
in principle all the QNMs together give an exact description of the dynamics.
Applications to optics in microspheres and to gravitational waves from black
holes are reviewed, and directions for further development are outlined.
| [
{
"created": "Tue, 6 Apr 1999 17:27:16 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ching",
"E. S. C.",
""
],
[
"Leung",
"P. T.",
""
],
[
"Suen",
"W. M.",
""
],
[
"Tong",
"S. S.",
""
],
[
"Young",
"K.",
""
]
] | An open system is not conservative because energy can escape to the outside. An open system by itself is thus not conservative. As a result, the time-evolution operator is not hermitian in the usual sense and the eigenfunctions (factorized solutions in space and time) are no longer normal modes but quasinormal modes (QNMs) whose frequencies $\omega$ are complex. QNM analysis has been a powerful tool for investigating open systems. Previous studies have been mostly system specific, and use a few QNMs to provide approximate descriptions. Here we review recent developments which aim at a unifying treatment. The formulation leads to a mathematical structure in close analogy to that in conservative, hermitian systems. Many of the mathematical tools for the latter can hence be transcribed. Emphasis is placed on those cases in which the QNMs form a complete set for outgoing wavefunctions, so that in principle all the QNMs together give an exact description of the dynamics. Applications to optics in microspheres and to gravitational waves from black holes are reviewed, and directions for further development are outlined. |
1107.3445 | Lorenzo Iorio | Lorenzo Iorio | Orbital effects of the time-dependent component of the Pioneer anomaly | LaTex2e, 7 pages, no figures, 1 table, 23 references. Version
matching the one at press in Modern Physics Letters A (MPLA) | Mod.Phys.Lett.A 27:1250071,2012 | 10.1142/S021773231250071X | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We work out the impact that the recently determined time-dependent component
of the Pioneer Anomaly (PA), interpreted as an additional exotic acceleration
of gravitational origin with respect to the well known PA-like constant one,
may have on the orbital motions of some planets of the solar system. By
assuming that it points towards the Sun, it turns out that both the semi-major
axis a and the eccentricity e of the orbit of a test particle experience
secular variations. For Saturn and Uranus, for which modern data records cover
at least one full orbital revolution, such predicted anomalies are up to 2-3
orders of magnitude larger than the present-day accuracies in empirical
determinations their orbital parameters from the usual orbit determination
procedures in which the PA was not modeled. Given the predicted huge sizes of
such hypothetical signatures, it is unlikely that their absence from the
presently available processed data can be attributable to an "absorption" for
them in the estimated parameters caused by the fact that they were not
explicitly modeled. The magnitude of a constant PA-type acceleration at 9.5 au
cannot be larger than 9 10^-15 m s^-2 according to the latest observational
results for the perihelion precession of Saturn.
| [
{
"created": "Mon, 18 Jul 2011 14:15:50 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Aug 2011 13:59:42 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Sep 2011 07:45:08 GMT",
"version": "v3"
},
{
"created": "Wed, 7 Mar 2012 10:08:58 GMT",
"version": "v4"
},
{
"cre... | 2012-04-18 | [
[
"Iorio",
"Lorenzo",
""
]
] | We work out the impact that the recently determined time-dependent component of the Pioneer Anomaly (PA), interpreted as an additional exotic acceleration of gravitational origin with respect to the well known PA-like constant one, may have on the orbital motions of some planets of the solar system. By assuming that it points towards the Sun, it turns out that both the semi-major axis a and the eccentricity e of the orbit of a test particle experience secular variations. For Saturn and Uranus, for which modern data records cover at least one full orbital revolution, such predicted anomalies are up to 2-3 orders of magnitude larger than the present-day accuracies in empirical determinations their orbital parameters from the usual orbit determination procedures in which the PA was not modeled. Given the predicted huge sizes of such hypothetical signatures, it is unlikely that their absence from the presently available processed data can be attributable to an "absorption" for them in the estimated parameters caused by the fact that they were not explicitly modeled. The magnitude of a constant PA-type acceleration at 9.5 au cannot be larger than 9 10^-15 m s^-2 according to the latest observational results for the perihelion precession of Saturn. |
gr-qc/0011014 | Bahram Mashhoon | Bahram Mashhoon | Gravitoelectromagnetism | LaTeX file, no figures, 12 pages, Plenary talk given at EREs2000
(Valladolid, Spain, 6-9 September 2000); to be published in Proc. Spanish
Relativity Meeting, edited by J.-F. Pascual-S\'anchez, L. Flor\'ia, A. San
Miguel, and F. Vicente (World Scientific, 2001) | null | 10.1142/9789812810021_0009 | UMC-00-1 | gr-qc | null | Gravitoelectromagnetism is briefly reviewed and some recent developments in
this topic are discussed. The stress-energy content of the
gravitoelectromagnetic field is described from different standpoints. In
particular, the gravitational Poynting flux is analyzed and it is shown that
there exists a steady flow of gravitational energy circulating around a
rotating mass.
| [
{
"created": "Fri, 3 Nov 2000 23:23:17 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Mashhoon",
"Bahram",
""
]
] | Gravitoelectromagnetism is briefly reviewed and some recent developments in this topic are discussed. The stress-energy content of the gravitoelectromagnetic field is described from different standpoints. In particular, the gravitational Poynting flux is analyzed and it is shown that there exists a steady flow of gravitational energy circulating around a rotating mass. |
1812.00956 | Justin Vines | Justin Vines, Jan Steinhoff, Alessandra Buonanno | Spinning-black-hole scattering and the test-black-hole limit at second
post-Minkowskian order | v2: corrected misstatements in Sec. IV.C regarding the amount of
residual gauge freedom within quasi-isotropic gauges for aligned-spin
canonical Hamiltonians; no changes in any results or conclusions; improved
discussion in Sections III-VI | Phys. Rev. D 99, 064054 (2019) | 10.1103/PhysRevD.99.064054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the gravitational scattering of two black holes (BHs) treated at
the leading order in the weak-field, or post-Minkowskian (PM), approximation to
General Relativity has been shown to map bijectively onto a simpler effectively
one-body process: the scattering of a test BH in a stationary BH spacetime.
Here, for BH spins aligned with the orbital angular momentum, we propose a
simple extension of that mapping to 2PM order. We provide evidence for the
validity and utility of this 2PM mapping by demonstrating its compatibility
with all known analytical results for the conservative local-in-time dynamics
of binary BHs in the post-Newtonian (weak-field and slow-motion) approximation
and, separately, in the test-BH limit. Our result could be employed in the
construction of improved effective-one-body models for the conservative
dynamics of inspiraling spinning binary BHs.
| [
{
"created": "Mon, 3 Dec 2018 18:27:02 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Sep 2019 16:53:50 GMT",
"version": "v2"
}
] | 2019-09-11 | [
[
"Vines",
"Justin",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | Recently, the gravitational scattering of two black holes (BHs) treated at the leading order in the weak-field, or post-Minkowskian (PM), approximation to General Relativity has been shown to map bijectively onto a simpler effectively one-body process: the scattering of a test BH in a stationary BH spacetime. Here, for BH spins aligned with the orbital angular momentum, we propose a simple extension of that mapping to 2PM order. We provide evidence for the validity and utility of this 2PM mapping by demonstrating its compatibility with all known analytical results for the conservative local-in-time dynamics of binary BHs in the post-Newtonian (weak-field and slow-motion) approximation and, separately, in the test-BH limit. Our result could be employed in the construction of improved effective-one-body models for the conservative dynamics of inspiraling spinning binary BHs. |
0812.4383 | Andrzej Borowiec | A. Borowiec (Wroclaw U., JINR Dubna) | From Dark Energy to Dark Matter via Non-Minimal Coupling | 6 pages in revtex, contribution to the special volume "Problems of
Modern Cosmology", TSPU publishing - in press | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Toy cosmological models based on non-minimal coupling between gravity and
scalar dilaton-like field are presented in the framework of Palatini formalism.
They have the following property: preceding to a given cosmological epoch is a
dark energy epoch with an accelerated expansion. The next (future) epoch
becomes dominated by some kind of dark matter.
| [
{
"created": "Tue, 23 Dec 2008 12:43:30 GMT",
"version": "v1"
}
] | 2008-12-24 | [
[
"Borowiec",
"A.",
"",
"Wroclaw U., JINR Dubna"
]
] | Toy cosmological models based on non-minimal coupling between gravity and scalar dilaton-like field are presented in the framework of Palatini formalism. They have the following property: preceding to a given cosmological epoch is a dark energy epoch with an accelerated expansion. The next (future) epoch becomes dominated by some kind of dark matter. |
gr-qc/0205121 | D. V. Ahluwalia | D. V. Ahluwalia (Zacateacs) | Interface of Gravitational and Quantum Realms | Invited talk, First IUCAA Meeting on the Interafce of Gravitational
and Quantum Realms | Mod.Phys.Lett.A17:1135,2002 | 10.1142/S021773230200765X | null | gr-qc | null | The talk centers around the question: Can general-relativistic description of
physical reality be considered complete? On the way I argue how -- unknown to
many a physicists, even today -- the ``forty orders of magnitude argument''
against quantum gravity phenomenology was defeated more than a quarter of a
century ago, and how we now stand at the possible verge of detecting a signal
for the spacetime foam, and studying the gravitationally-modified wave particle
duality using superconducting quantum interference devices.
| [
{
"created": "Wed, 29 May 2002 18:23:32 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ahluwalia",
"D. V.",
"",
"Zacateacs"
]
] | The talk centers around the question: Can general-relativistic description of physical reality be considered complete? On the way I argue how -- unknown to many a physicists, even today -- the ``forty orders of magnitude argument'' against quantum gravity phenomenology was defeated more than a quarter of a century ago, and how we now stand at the possible verge of detecting a signal for the spacetime foam, and studying the gravitationally-modified wave particle duality using superconducting quantum interference devices. |
1306.5932 | Zhengxiang Li | Zhengxiang Li, Kai Liao, Puxun Wu, Hongwei Yu, and Zong-Hong Zhu | Probing modified gravity theories with the Sandage-Loeb test | 18 pages, 6 figures, typos corrected and three references added, to
be published in Phys. Rev. D | Physical Review D 88, 023003 (2013) | 10.1103/PhysRevD.88.023003 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we quantify the ability of a future measurement of the
Sandage-Loeb test signal from the Cosmic-Dynamic-Experiment-like spectrograph
to constrain some popular modified gravity theories including DGP brane-world
scenario, $f(R)$ modified gravity and $f(T)$ gravity theory. We find that the
Sandage-Loeb test measurements are able to break degeneracies between model
parameters markedly and thus greatly improve cosmological constraints for all
concerned modified gravity theories when combined with the latest observations
of CMB--shift parameter. However, they yield almost the same degeneracy
directions between model parameters as that from the distance ratio data
derived from the latest observations of the cosmic microwave background and
baryonic acoustic oscillations (CMB/BAO). Moreover, for the $f(R)$ modified
gravity, the Sandage-Loeb test could provide completely different bounded
regions in model parameters space as compared to CMB/BAO and thus supplement
strong complementary constraints.
| [
{
"created": "Tue, 25 Jun 2013 12:11:35 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Jul 2013 02:48:14 GMT",
"version": "v2"
}
] | 2013-07-16 | [
[
"Li",
"Zhengxiang",
""
],
[
"Liao",
"Kai",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | In this paper, we quantify the ability of a future measurement of the Sandage-Loeb test signal from the Cosmic-Dynamic-Experiment-like spectrograph to constrain some popular modified gravity theories including DGP brane-world scenario, $f(R)$ modified gravity and $f(T)$ gravity theory. We find that the Sandage-Loeb test measurements are able to break degeneracies between model parameters markedly and thus greatly improve cosmological constraints for all concerned modified gravity theories when combined with the latest observations of CMB--shift parameter. However, they yield almost the same degeneracy directions between model parameters as that from the distance ratio data derived from the latest observations of the cosmic microwave background and baryonic acoustic oscillations (CMB/BAO). Moreover, for the $f(R)$ modified gravity, the Sandage-Loeb test could provide completely different bounded regions in model parameters space as compared to CMB/BAO and thus supplement strong complementary constraints. |
1404.6226 | Sergey Yu. Vernov | Maria A. Skugoreva, Alexey V. Toporensky, Sergey Yu. Vernov | Global stability analysis for cosmological models with non-minimally
coupled scalar fields | 21 pages, 9 figures, v2: references added, accepted for publication
in PRD | Phys. Rev. D 90, 064044 (2014) | 10.1103/PhysRevD.90.064044 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore dynamics of cosmological models with a nonminimally coupled scalar
field evolving on a spatially flat Friedmann-Lemaitre-Robertson-Walker
background. We consider cosmological models including the Hilbert-Einstein
curvature term and the $N$ degree monomial of the scalar field nonminimally
coupled to gravity. The potential of the scalar field is the $n$ degree
monomial or polynomial. We describe several qualitatively different types of
dynamics depending on values of power indices $N$ and $n$. We identify that
three main possible pictures correspond to $n<N$, $N<n<2N$ and $n>2N$ cases.
Some special features connected with the important cases of $N=n$ (including
the quadratic potential with quadratic coupling) and $n=2N$ (which shares its
asymptotics with the potential of the Higgs-driven inflation) are described
separately. A global qualitative analysis allows us to cover the most
interesting cases of small $N$ and $n$ by a limiting number of phase-space
diagrams. The influence of the cosmological constant to the global features of
dynamics is also studied.
| [
{
"created": "Thu, 24 Apr 2014 19:01:44 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Sep 2014 07:35:04 GMT",
"version": "v2"
}
] | 2014-10-01 | [
[
"Skugoreva",
"Maria A.",
""
],
[
"Toporensky",
"Alexey V.",
""
],
[
"Vernov",
"Sergey Yu.",
""
]
] | We explore dynamics of cosmological models with a nonminimally coupled scalar field evolving on a spatially flat Friedmann-Lemaitre-Robertson-Walker background. We consider cosmological models including the Hilbert-Einstein curvature term and the $N$ degree monomial of the scalar field nonminimally coupled to gravity. The potential of the scalar field is the $n$ degree monomial or polynomial. We describe several qualitatively different types of dynamics depending on values of power indices $N$ and $n$. We identify that three main possible pictures correspond to $n<N$, $N<n<2N$ and $n>2N$ cases. Some special features connected with the important cases of $N=n$ (including the quadratic potential with quadratic coupling) and $n=2N$ (which shares its asymptotics with the potential of the Higgs-driven inflation) are described separately. A global qualitative analysis allows us to cover the most interesting cases of small $N$ and $n$ by a limiting number of phase-space diagrams. The influence of the cosmological constant to the global features of dynamics is also studied. |
2205.01350 | Sanjar Shaymatov | Sanjar Shaymatov, Naresh Dadhich | Extending the weak cosmic censorship conjecture to the charged Buchdahl
star by employing the gedanken experiments | 17 pages, no figures. Updated to match with the published version | JCAP 06 (2023) 010 | 10.1088/1475-7516/2023/06/010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we wish to investigate the weak cosmic censorship conjecture
(WCCC) for the non black hole object, Buchdahl star and test its validity. It
turns out that the extremal limit for the star is over-extremal for black hole,
$Q^2/M^2 \leq 9/8 >1$; i.e., it could have $9/8 \geq Q^2/M^2 > 1$. By carrying
out both linear and non-linear perturbations, we establish the same result for
the Buchdahl star as well. That is, as for black hole it could be overcharged
at the linear perturbation while the result is overturned when the non-linear
perturbations are included. Thus WCCC is always obeyed by the Buchdahl star.
| [
{
"created": "Tue, 3 May 2022 07:21:36 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Jun 2023 11:22:28 GMT",
"version": "v2"
}
] | 2023-06-14 | [
[
"Shaymatov",
"Sanjar",
""
],
[
"Dadhich",
"Naresh",
""
]
] | In this paper, we wish to investigate the weak cosmic censorship conjecture (WCCC) for the non black hole object, Buchdahl star and test its validity. It turns out that the extremal limit for the star is over-extremal for black hole, $Q^2/M^2 \leq 9/8 >1$; i.e., it could have $9/8 \geq Q^2/M^2 > 1$. By carrying out both linear and non-linear perturbations, we establish the same result for the Buchdahl star as well. That is, as for black hole it could be overcharged at the linear perturbation while the result is overturned when the non-linear perturbations are included. Thus WCCC is always obeyed by the Buchdahl star. |
2004.01233 | Kirill Bronnikov | K.A. Bronnikov | On variations of $G$ in the geometric scalar theory of gravity | 7 two-column pages, no figures. A few references added | Euro Phys. J. C 80, 434 (2020) | 10.1140/epjc/s10052-020-8012-9 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the possible variability of the effective Newtonian gravitational
constant $G_{\rm N}$ in space and time in the framework of the geometric scalar
theory of gravity suggested by M. Novello et al. [JCAP 06, 014 (2013); arXiv:
1212.0770]. Spatial variations of $G_{\rm N}$ in the Solar system are shown to
have orders of magnitude detectable by modern instruments. As to variations of
$G_{\rm N}$ with cosmological time, it is shown (at least for the particular
formulation of the theory discussed in the original paper and the corresponding
cosmological models) that these variations are more rapid than is allowed by
observations.
| [
{
"created": "Thu, 2 Apr 2020 19:22:24 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Apr 2020 15:43:46 GMT",
"version": "v2"
}
] | 2020-10-20 | [
[
"Bronnikov",
"K. A.",
""
]
] | We analyze the possible variability of the effective Newtonian gravitational constant $G_{\rm N}$ in space and time in the framework of the geometric scalar theory of gravity suggested by M. Novello et al. [JCAP 06, 014 (2013); arXiv: 1212.0770]. Spatial variations of $G_{\rm N}$ in the Solar system are shown to have orders of magnitude detectable by modern instruments. As to variations of $G_{\rm N}$ with cosmological time, it is shown (at least for the particular formulation of the theory discussed in the original paper and the corresponding cosmological models) that these variations are more rapid than is allowed by observations. |
0807.1832 | Tekin Dereli | M. Adak, T. Dereli | String-Inspired Chern-Simons Modified Gravity In 4-Dimensions | To appear in the European Physics Journal C | Eur. Phys. J. C 72 (2012) 1979 | 10.1140/epjc/s10052-012-1979-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Chern-Simons modified gravity models in 4-dimensions are shown to be special
cases of low energy effective string models to first order in the string
constant.
| [
{
"created": "Fri, 11 Jul 2008 12:10:31 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jan 2010 09:29:04 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Apr 2012 05:54:18 GMT",
"version": "v3"
}
] | 2012-05-01 | [
[
"Adak",
"M.",
""
],
[
"Dereli",
"T.",
""
]
] | Chern-Simons modified gravity models in 4-dimensions are shown to be special cases of low energy effective string models to first order in the string constant. |
gr-qc/9610012 | Ali Mostafazadeh | Ali Mostafazadeh | Two-Component Formulation of the Wheeler-DeWitt Equation | Substantially improved version. Some new observations and nine
figures are added. An explicit example is worked out | J.Math.Phys. 39 (1998) 4499-4512 | 10.1063/1.532522 | University of Alberta preprint no: Thy 36-96 | gr-qc hep-th | null | The Wheeler-DeWitt equation for the minimally coupled
FRW-massive-scalar-field minisuperspace is written as a two-component
Schr\"odinger equation with an explicitly `time'-dependent Hamiltonian. This
reduces the solution of the Wheeler-DeWitt equation to the eigenvalue problem
for a non-relativistic one-dimensional harmonic oscillator and an infinite
series of trivial algebraic equations whose iterative solution is easily found.
The solution of these equations yields a mode expansion of the solution of the
original Wheeler-DeWitt equation. Further analysis of the mode expansion shows
that in general the solutions of the Wheeler-DeWitt equation for this model are
doubly graded, i.e., every solution is a superposition of two definite-parity
solutions. Moreover, it is shown that the mode expansion of both even and
odd-parity solutions is always infinite. It may be terminated artificially to
construct approximate solutions. This is demonstrated by working out an
explicit example which turns out to satisfy DeWitt's boundary condition at
initial singularity.
| [
{
"created": "Wed, 9 Oct 1996 20:06:44 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Oct 1996 02:34:11 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Jan 1997 23:52:13 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Mostafazadeh",
"Ali",
""
]
] | The Wheeler-DeWitt equation for the minimally coupled FRW-massive-scalar-field minisuperspace is written as a two-component Schr\"odinger equation with an explicitly `time'-dependent Hamiltonian. This reduces the solution of the Wheeler-DeWitt equation to the eigenvalue problem for a non-relativistic one-dimensional harmonic oscillator and an infinite series of trivial algebraic equations whose iterative solution is easily found. The solution of these equations yields a mode expansion of the solution of the original Wheeler-DeWitt equation. Further analysis of the mode expansion shows that in general the solutions of the Wheeler-DeWitt equation for this model are doubly graded, i.e., every solution is a superposition of two definite-parity solutions. Moreover, it is shown that the mode expansion of both even and odd-parity solutions is always infinite. It may be terminated artificially to construct approximate solutions. This is demonstrated by working out an explicit example which turns out to satisfy DeWitt's boundary condition at initial singularity. |
1603.07756 | Sean Leavey | S. S. Leavey, S. L. Danilishin, A. Gl\"afke, B. W. Barr, A. S. Bell,
C. Gr\"af, J.-S. Hennig, E. A. Houston, S. H. Huttner, H. L\"uck, D.
Pascucci, K. Somiya, B. Sorazu, A. Spencer, S. Steinlechner, K. A. Strain, J.
Wright, T. Zhang, S. Hild | Control of a velocity-sensitive audio-band quantum non-demolition
interferometer | null | null | null | null | gr-qc astro-ph.IM quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Sagnac speed meter interferometer topology can potentially provide
enhanced sensitivity to gravitational waves in the audio-band compared to
equivalent Michelson interferometers. A challenge with the Sagnac speed meter
interferometer arises from the intrinsic lack of sensitivity at low frequencies
where the velocity-proportional signal is smaller than the noise associated
with the sensing of the signal. Using as an example the on-going
proof-of-concept Sagnac speed meter experiment in Glasgow, we quantify the
problem and present a solution involving the extraction of a small
displacement-proportional signal. This displacement signal can be combined with
the existing velocity signal to enhance low frequency sensitivity, and we
derive optimal filters to accomplish this for different signal strengths. We
show that the extraction of the displacement signal for low frequency control
purposes can be performed without reducing significantly the quantum
non-demolition character of this type of interferometer.
| [
{
"created": "Thu, 24 Mar 2016 21:05:17 GMT",
"version": "v1"
}
] | 2016-03-28 | [
[
"Leavey",
"S. S.",
""
],
[
"Danilishin",
"S. L.",
""
],
[
"Gläfke",
"A.",
""
],
[
"Barr",
"B. W.",
""
],
[
"Bell",
"A. S.",
""
],
[
"Gräf",
"C.",
""
],
[
"Hennig",
"J. -S.",
""
],
[
"Houston",
"... | The Sagnac speed meter interferometer topology can potentially provide enhanced sensitivity to gravitational waves in the audio-band compared to equivalent Michelson interferometers. A challenge with the Sagnac speed meter interferometer arises from the intrinsic lack of sensitivity at low frequencies where the velocity-proportional signal is smaller than the noise associated with the sensing of the signal. Using as an example the on-going proof-of-concept Sagnac speed meter experiment in Glasgow, we quantify the problem and present a solution involving the extraction of a small displacement-proportional signal. This displacement signal can be combined with the existing velocity signal to enhance low frequency sensitivity, and we derive optimal filters to accomplish this for different signal strengths. We show that the extraction of the displacement signal for low frequency control purposes can be performed without reducing significantly the quantum non-demolition character of this type of interferometer. |
2111.13900 | Polina Dyadina | P. I. Dyadina, S. P. Labazova | On Shapiro time delay in massive scalar-tensor theories | 10 pages, submitted to JCAP | JCAP 01(2022)029 | 10.1088/1475-7516/2022/01/029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of determining the post-Newtonian parameter $\gamma$ in massive
scalar-tensor theories is considered. We demonstrate equivalent correspondence
between the post-Newtonian parameter $\gamma$ and the parameter appearing in
the equation of null geodysic in massive scalar-tensor theories. We show that
massive scalar-tensor theories can be distinguished from general relativity
based on the predictions of Shapiro time delay. All calculations are presented
using hybrid metric-Palatini f(R)-gravity as an example. The expression for
Shapiro time delay in hybrid f(R)-gravity is obtained for the first time.
| [
{
"created": "Sat, 27 Nov 2021 13:59:01 GMT",
"version": "v1"
}
] | 2022-02-03 | [
[
"Dyadina",
"P. I.",
""
],
[
"Labazova",
"S. P.",
""
]
] | The problem of determining the post-Newtonian parameter $\gamma$ in massive scalar-tensor theories is considered. We demonstrate equivalent correspondence between the post-Newtonian parameter $\gamma$ and the parameter appearing in the equation of null geodysic in massive scalar-tensor theories. We show that massive scalar-tensor theories can be distinguished from general relativity based on the predictions of Shapiro time delay. All calculations are presented using hybrid metric-Palatini f(R)-gravity as an example. The expression for Shapiro time delay in hybrid f(R)-gravity is obtained for the first time. |
1603.05404 | Ellery Ames | Ellery Ames, H{\aa}kan Andr\'easson, Anders Logg | On Axisymmetric and Stationary Solutions of the Self-Gravitating Vlasov
System | 24 pages | Classical and Quantum Gravity 33(15):155008, 2016 | 10.1088/0264-9381/33/15/155008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Axisymmetric and stationary solutions are constructed to the Einstein--Vlasov
and Vlasov--Poisson systems. These solutions are constructed numerically, using
finite element methods and a fixed-point iteration in which the total mass is
fixed at each step. A variety of axisymmetric stationary solutions are
exhibited, including solutions with toroidal, disk-like, spindle-like, and
composite spatial density configurations, as are solutions with non-vanishing
net angular momentum. In the case of toroidal solutions, we show for the first
time, solutions of the Einstein--Vlasov system which contain ergoregions.
| [
{
"created": "Thu, 17 Mar 2016 09:39:41 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Apr 2018 15:29:41 GMT",
"version": "v2"
}
] | 2018-04-11 | [
[
"Ames",
"Ellery",
""
],
[
"Andréasson",
"Håkan",
""
],
[
"Logg",
"Anders",
""
]
] | Axisymmetric and stationary solutions are constructed to the Einstein--Vlasov and Vlasov--Poisson systems. These solutions are constructed numerically, using finite element methods and a fixed-point iteration in which the total mass is fixed at each step. A variety of axisymmetric stationary solutions are exhibited, including solutions with toroidal, disk-like, spindle-like, and composite spatial density configurations, as are solutions with non-vanishing net angular momentum. In the case of toroidal solutions, we show for the first time, solutions of the Einstein--Vlasov system which contain ergoregions. |
gr-qc/9907064 | Zc | Zhong Chao Wu (BNU & Uct) | Quantum Creation of Topological Black Hole | Report-no change only | Mod.Phys.Lett. A15 (2000) 1589 | 10.1142/S0217732300001857 | uct-cosmology-99/02 | gr-qc astro-ph hep-th | null | The constrained instanton method is used to study quantum creation of a
vacuum or charged topological black hole. At the $WKB$ level, the relative
creation probability is the exponential of a quarter sum of the horizon areas
associated with the seed instanton.
| [
{
"created": "Tue, 20 Jul 1999 19:25:36 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Jul 1999 10:20:53 GMT",
"version": "v2"
},
{
"created": "Thu, 29 Jul 1999 08:15:49 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Wu",
"Zhong Chao",
"",
"BNU & Uct"
]
] | The constrained instanton method is used to study quantum creation of a vacuum or charged topological black hole. At the $WKB$ level, the relative creation probability is the exponential of a quarter sum of the horizon areas associated with the seed instanton. |
1506.09116 | Davide Gerosa | Davide Gerosa, Michael Kesden, Richard O'Shaughnessy, Antoine Klein,
Emanuele Berti, Ulrich Sperhake, Daniele Trifir\`o | Precessional instability in binary black holes with aligned spins | Accepted for publication in PRL. Animations available at
http://davidegerosa.com/spinprecession/ | Phys. Rev. Lett. 115, 141102 (2015) | 10.1103/PhysRevLett.115.141102 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary black holes on quasicircular orbits with spins aligned with their
orbital angular momentum have been testbeds for analytic and numerical
relativity for decades, not least because symmetry ensures that such
configurations are equilibrium solutions to the spin-precession equations. In
this work, we show that these solutions can be unstable when the spin of the
higher-mass black hole is aligned with the orbital angular momentum and the
spin of the lower-mass black hole is anti-aligned. Spins in these
configurations are unstable to precession to large misalignment when the binary
separation $r$ is between the values $r_{\rm ud\pm}= (\sqrt{\chi_1} \pm \sqrt{q
\chi_2})^4 (1-q)^{-2} M$, where $M$ is the total mass, $q \equiv m_2/m_1$ is
the mass ratio, and $\chi_1$ ($\chi_2$) is the dimensionless spin of the more
(less) massive black hole. This instability exists for a wide range of spin
magnitudes and mass ratios and can occur in the strong-field regime near
merger. We describe the origin and nature of the instability using recently
developed analytical techniques to characterize fully generic spin precession.
This instability provides a channel to circumvent astrophysical spin alignment
at large binary separations, allowing significant spin precession prior to
merger affecting both gravitational-wave and electromagnetic signatures of
stellar-mass and supermassive binary black holes.
| [
{
"created": "Tue, 30 Jun 2015 15:23:29 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Oct 2015 08:53:28 GMT",
"version": "v2"
}
] | 2015-10-06 | [
[
"Gerosa",
"Davide",
""
],
[
"Kesden",
"Michael",
""
],
[
"O'Shaughnessy",
"Richard",
""
],
[
"Klein",
"Antoine",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Trifirò",
"Daniele",
""
... | Binary black holes on quasicircular orbits with spins aligned with their orbital angular momentum have been testbeds for analytic and numerical relativity for decades, not least because symmetry ensures that such configurations are equilibrium solutions to the spin-precession equations. In this work, we show that these solutions can be unstable when the spin of the higher-mass black hole is aligned with the orbital angular momentum and the spin of the lower-mass black hole is anti-aligned. Spins in these configurations are unstable to precession to large misalignment when the binary separation $r$ is between the values $r_{\rm ud\pm}= (\sqrt{\chi_1} \pm \sqrt{q \chi_2})^4 (1-q)^{-2} M$, where $M$ is the total mass, $q \equiv m_2/m_1$ is the mass ratio, and $\chi_1$ ($\chi_2$) is the dimensionless spin of the more (less) massive black hole. This instability exists for a wide range of spin magnitudes and mass ratios and can occur in the strong-field regime near merger. We describe the origin and nature of the instability using recently developed analytical techniques to characterize fully generic spin precession. This instability provides a channel to circumvent astrophysical spin alignment at large binary separations, allowing significant spin precession prior to merger affecting both gravitational-wave and electromagnetic signatures of stellar-mass and supermassive binary black holes. |
1903.10682 | Dieter Van den Bleeken | Dieter Van den Bleeken | Torsional Newton-Cartan gravity and strong gravitational fields | Proceedings of talk at Fifteenth Marcel Grossmann Meeting. 6p | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review how the large $c$ expansion of General Relativity leads to an
effective theory in the form of Twistless Torsional Newton-Cartan gravity. We
show how this is a strong field expansion around the static sector of General
Relativity and illustrate this through two examples.
| [
{
"created": "Tue, 26 Mar 2019 05:29:05 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Bleeken",
"Dieter Van den",
""
]
] | We review how the large $c$ expansion of General Relativity leads to an effective theory in the form of Twistless Torsional Newton-Cartan gravity. We show how this is a strong field expansion around the static sector of General Relativity and illustrate this through two examples. |
gr-qc/0504059 | Florian Conrady | Florian Conrady (CPT, Marseille & Potsdam, Max Planck Inst.) | Geometric spin foams, Yang-Mills theory and background-independent
models | 28 pages, 27 diagrams, typos corrected | null | null | AEI-2005-090 | gr-qc hep-th | null | We review the dual transformation from pure lattice gauge theory to spin foam
models with an emphasis on a geometric viewpoint. This allows us to give a
simple dual formulation of SU(N) Yang-Mills theory, where spin foam surfaces
are weighted with the exponentiated area. In the case of gravity, we introduce
a symmetry condition which demands that the amplitude of an individual spin
foam depends only on its geometric properties and not on the lattice on which
it is defined. For models that have this property, we define a new sum over
abstract spin foams that is independent of any choice of lattice or
triangulation. We show that a version of the Barrett-Crane model satisfies our
symmetry requirement.
| [
{
"created": "Wed, 13 Apr 2005 14:49:06 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Apr 2005 09:50:22 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Conrady",
"Florian",
"",
"CPT, Marseille & Potsdam, Max Planck Inst."
]
] | We review the dual transformation from pure lattice gauge theory to spin foam models with an emphasis on a geometric viewpoint. This allows us to give a simple dual formulation of SU(N) Yang-Mills theory, where spin foam surfaces are weighted with the exponentiated area. In the case of gravity, we introduce a symmetry condition which demands that the amplitude of an individual spin foam depends only on its geometric properties and not on the lattice on which it is defined. For models that have this property, we define a new sum over abstract spin foams that is independent of any choice of lattice or triangulation. We show that a version of the Barrett-Crane model satisfies our symmetry requirement. |
2108.05445 | Andrea Geralico | Donato Bini, Andrea Geralico | Higher-order tail contributions to the energy and angular momentum
fluxes in a two-body scattering process | 14 pages, 1 figure (2 eps files), revtex macros used; v2: Eq. (4.14)
corrected | null | 10.1103/PhysRevD.104.104020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The need for more and more accurate gravitational wave templates requires
taking into account all possible contributions to the emission of gravitational
radiation from a binary system. Therefore, working within a
multipolar-post-Minkowskian framework to describe the gravitational wave field
in terms of the source multipole moments, the dominant instantaneous effects
should be supplemented by hereditary contributions arising from nonlinear
interactions between the multipoles. The latter effects are referred to as
tails being described in terms of integrals depending on the past history of
the source. We compute higher-order tail (i.e., tail-of-tail and tail-squared)
contributions to both energy and angular momentum fluxes and their averaged
values along hyperboliclike orbits at the leading post-Newtonian approximation,
using harmonic coordinates and working in the Fourier domain. Due to the
increasing level of accuracy recently achieved in the determination of the
scattering angle in a two-body system by several complementary approaches, the
knowledge of these terms will provide useful information to compare results
from different formalisms.
| [
{
"created": "Wed, 11 Aug 2021 21:06:41 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Mar 2022 10:29:27 GMT",
"version": "v2"
}
] | 2022-03-17 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | The need for more and more accurate gravitational wave templates requires taking into account all possible contributions to the emission of gravitational radiation from a binary system. Therefore, working within a multipolar-post-Minkowskian framework to describe the gravitational wave field in terms of the source multipole moments, the dominant instantaneous effects should be supplemented by hereditary contributions arising from nonlinear interactions between the multipoles. The latter effects are referred to as tails being described in terms of integrals depending on the past history of the source. We compute higher-order tail (i.e., tail-of-tail and tail-squared) contributions to both energy and angular momentum fluxes and their averaged values along hyperboliclike orbits at the leading post-Newtonian approximation, using harmonic coordinates and working in the Fourier domain. Due to the increasing level of accuracy recently achieved in the determination of the scattering angle in a two-body system by several complementary approaches, the knowledge of these terms will provide useful information to compare results from different formalisms. |
1503.02326 | Valerio Faraoni | Valerio Faraoni, Marianne Lapierre-Leonard, Angus Prain | Do Newtonian large-scale structure simulations fail to include
relativistic effects? | 7 pages | Phys. Rev. D 92, 023511 (2015) | 10.1103/PhysRevD.92.023511 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Newtonian simulations describing the formation of large-scale structures
do not include relativistic effects. A new approach to this problem is
proposed, which consists of splitting the Hawking-Hayward quasi-local energy of
a closed spacelike 2-surface into a "Newtonian" part due to local perturbations
and a "relativistic" part due to the cosmology. It is found that the Newtonian
part dominates over the relativistic one as time evolves, lending support to
the validity of Newtonian simulations.
| [
{
"created": "Sun, 8 Mar 2015 21:35:04 GMT",
"version": "v1"
}
] | 2015-07-15 | [
[
"Faraoni",
"Valerio",
""
],
[
"Lapierre-Leonard",
"Marianne",
""
],
[
"Prain",
"Angus",
""
]
] | The Newtonian simulations describing the formation of large-scale structures do not include relativistic effects. A new approach to this problem is proposed, which consists of splitting the Hawking-Hayward quasi-local energy of a closed spacelike 2-surface into a "Newtonian" part due to local perturbations and a "relativistic" part due to the cosmology. It is found that the Newtonian part dominates over the relativistic one as time evolves, lending support to the validity of Newtonian simulations. |
0906.2921 | Sergey S. Kokarev | Sergey S. Kokarev | Are different geometries really that different? | 13 pages, 2 figures, talk that will be presented at PIRT-2009, July
(Russia), one misprint is removed, formulation of the theorem is made more
clear | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here is presented a concept of centrogeometry which can be seen as a
combination of the concept of point-like observer with an idea of
Poincar\'{e}'s that different geometries are principally equivalent. As it is
to be shown later, all centrogeometries are obtained from each other by general
deformation (i.e. active coordinate transformations). Isometries of
centrogeometries are equivalent to those of the Euclidean centrogeometry as
described by common diffeomorphisms of the Euclidean spheres. There are
discussed physical aspects of centrogeometry in the context of chronogeometry,
mechanics and cosmology.
| [
{
"created": "Tue, 16 Jun 2009 13:03:55 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Nov 2009 11:15:08 GMT",
"version": "v2"
}
] | 2009-11-09 | [
[
"Kokarev",
"Sergey S.",
""
]
] | Here is presented a concept of centrogeometry which can be seen as a combination of the concept of point-like observer with an idea of Poincar\'{e}'s that different geometries are principally equivalent. As it is to be shown later, all centrogeometries are obtained from each other by general deformation (i.e. active coordinate transformations). Isometries of centrogeometries are equivalent to those of the Euclidean centrogeometry as described by common diffeomorphisms of the Euclidean spheres. There are discussed physical aspects of centrogeometry in the context of chronogeometry, mechanics and cosmology. |
1412.8123 | Parthapratim Pradhan | Parthapratim Pradhan | Circular Geodesics in Tidal Charged Black Hole | Version accepted in IJGMMP | Int. J. Geom. Methods Mod. Phys. Vol. 14 (2018) 185011 (26 pages) | 10.1142/S0219887818500111 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the existence and stability criteria for circular geodesics of
spherically symmetric tidal charged black hole~(BH). We investigate in details
the equatorial causal geodesics of the tidal charged BH in comparison with
spherically symmetric Reissner-Nordstr\"{o}m BH spacetime. We particularly
focused on both the null circular geodesics and time-like circular geodesics.
Using the effective potential diagram, we have compared the geodesic structure
between two spacetimes. We have derived the ISCO~(innermost stable circular
orbit), MBCO~(marginally bound circular orbit) and CPO~(circular photon orbit)
for both the space-times. Moreover, we have derived the \emph{quasi-normal
modes~(QNM) frequency} in the \emph{eikonal limit} for both the spacetimes via
Lyapunov exponent. In the Appendix section, we have shown that a spherically
symmetric tidal-charged BH can act as particle accelerators with ultra-high
center-of-mass~(CM) energy in the limiting case of \emph{maximal BH tidal
charge~($q$)} and it is possible when two neutral particles are colliding near
the horizon.
| [
{
"created": "Sun, 28 Dec 2014 07:26:39 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Sep 2017 16:40:23 GMT",
"version": "v2"
}
] | 2017-09-26 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We study the existence and stability criteria for circular geodesics of spherically symmetric tidal charged black hole~(BH). We investigate in details the equatorial causal geodesics of the tidal charged BH in comparison with spherically symmetric Reissner-Nordstr\"{o}m BH spacetime. We particularly focused on both the null circular geodesics and time-like circular geodesics. Using the effective potential diagram, we have compared the geodesic structure between two spacetimes. We have derived the ISCO~(innermost stable circular orbit), MBCO~(marginally bound circular orbit) and CPO~(circular photon orbit) for both the space-times. Moreover, we have derived the \emph{quasi-normal modes~(QNM) frequency} in the \emph{eikonal limit} for both the spacetimes via Lyapunov exponent. In the Appendix section, we have shown that a spherically symmetric tidal-charged BH can act as particle accelerators with ultra-high center-of-mass~(CM) energy in the limiting case of \emph{maximal BH tidal charge~($q$)} and it is possible when two neutral particles are colliding near the horizon. |
1601.01662 | Ali Masoumi | Ali Masoumi and Alexander Vilenkin | Vacuum statistics and stability in axionic landscapes | 37 pages, 19 figures. (References and one paragraph added. ) | null | 10.1088/1475-7516/2016/03/054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate vacuum statistics and stability in random axionic landscapes.
For this purpose we developed an algorithm for a quick evaluation of the
tunneling action, which in most cases is accurate within 10%. We find that
stability of a vacuum is strongly correlated with its energy density, with
lifetime rapidly growing as the energy density is decreased. The probability
$P(B)$ for a vacuum to have a tunneling action $B$ greater than a given value
declines as a slow power law in $B$. This is in sharp contrast with the studies
of random quartic potentials, which found a fast exponential decline of $P(B)$.
Our results suggest that the total number of relatively stable vacua (say, with
$B> 100$) grows exponentially with the number of fields $N$ and can get
extremely large for $N\gtrsim 100$. The problem with this kind of model is that
the stable vacua are concentrated near the absolute minimum of the potential,
so the observed value of the cosmological constant cannot be explained without
fine-tuning. To address this difficulty, we consider a modification of the
model, where the axions acquire a quadratic mass term, due to their mixing with
4-form fields. This results in a larger landscape with a much broader
distribution of vacuum energies. The number of relatively stable vacua in such
models can still be extremely large.
| [
{
"created": "Thu, 7 Jan 2016 20:46:41 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Jan 2016 02:04:50 GMT",
"version": "v2"
}
] | 2016-04-13 | [
[
"Masoumi",
"Ali",
""
],
[
"Vilenkin",
"Alexander",
""
]
] | We investigate vacuum statistics and stability in random axionic landscapes. For this purpose we developed an algorithm for a quick evaluation of the tunneling action, which in most cases is accurate within 10%. We find that stability of a vacuum is strongly correlated with its energy density, with lifetime rapidly growing as the energy density is decreased. The probability $P(B)$ for a vacuum to have a tunneling action $B$ greater than a given value declines as a slow power law in $B$. This is in sharp contrast with the studies of random quartic potentials, which found a fast exponential decline of $P(B)$. Our results suggest that the total number of relatively stable vacua (say, with $B> 100$) grows exponentially with the number of fields $N$ and can get extremely large for $N\gtrsim 100$. The problem with this kind of model is that the stable vacua are concentrated near the absolute minimum of the potential, so the observed value of the cosmological constant cannot be explained without fine-tuning. To address this difficulty, we consider a modification of the model, where the axions acquire a quadratic mass term, due to their mixing with 4-form fields. This results in a larger landscape with a much broader distribution of vacuum energies. The number of relatively stable vacua in such models can still be extremely large. |
0904.2008 | Leonid V. Verozub | Leonid Verozub | Space-Based Gravity Detector for a Space Laboratory | 4 pages, 4 figures, | Class.Quant.Grav.17:2455-2458,2000 | 10.1088/0264-9381/17/12/317 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A space-based superconducting gravitational low-frequency wave detector is
considered. Sensitivity of the detector is sufficient to use the detector as a
partner of other contemporary low-frequency detectors like LIGO and LISA. This
device can also be very useful for experimental study of other effects
predicted by theories of gravitation.
| [
{
"created": "Mon, 13 Apr 2009 20:18:39 GMT",
"version": "v1"
}
] | 2009-04-21 | [
[
"Verozub",
"Leonid",
""
]
] | A space-based superconducting gravitational low-frequency wave detector is considered. Sensitivity of the detector is sufficient to use the detector as a partner of other contemporary low-frequency detectors like LIGO and LISA. This device can also be very useful for experimental study of other effects predicted by theories of gravitation. |
1711.10943 | Edward Wilson-Ewing | Edward Wilson-Ewing | The loop quantum cosmology bounce as a Kasner transition | 28 pages. v2: Minor clarifications, references added | Class.Quant.Grav. 35 (2018) 065005 | 10.1088/1361-6382/aaab8b | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the Bianchi type I space-time (vacuum or with a massless scalar field),
the loop quantum cosmology bounce can be viewed as a rapid transition between
two classical solutions, with a simple transformation rule relating the Kasner
exponents of the two epochs. This transformation rule can be extended to other
Bianchi space-times under the assumption that during the loop quantum cosmology
bounce the contribution of the spatial curvature to the Hamiltonian constraint
is negligible compared to the kinetic terms. For the vacuum Bianchi type IX
space-time there are transformation rules for how each of the parameters
characterizing the Kasner epochs change during the bounce. This provides a
quantum gravity extension to the Mixmaster dynamics of general relativity, and
may have interesting implications for the Belinski-Khalatnikov-Lifshitz
conjecture.
| [
{
"created": "Wed, 29 Nov 2017 16:25:27 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Feb 2018 14:32:52 GMT",
"version": "v2"
}
] | 2018-03-14 | [
[
"Wilson-Ewing",
"Edward",
""
]
] | For the Bianchi type I space-time (vacuum or with a massless scalar field), the loop quantum cosmology bounce can be viewed as a rapid transition between two classical solutions, with a simple transformation rule relating the Kasner exponents of the two epochs. This transformation rule can be extended to other Bianchi space-times under the assumption that during the loop quantum cosmology bounce the contribution of the spatial curvature to the Hamiltonian constraint is negligible compared to the kinetic terms. For the vacuum Bianchi type IX space-time there are transformation rules for how each of the parameters characterizing the Kasner epochs change during the bounce. This provides a quantum gravity extension to the Mixmaster dynamics of general relativity, and may have interesting implications for the Belinski-Khalatnikov-Lifshitz conjecture. |
gr-qc/0506040 | Valerio Bozza | V. Bozza, G. Veneziano | Regular two-component bouncing cosmologies and perturbations therein | 19 pages, 9 figures | JCAP 0509:007,2005 | 10.1088/1475-7516/2005/09/007 | null | gr-qc hep-th | null | We present a full investigation of scalar perturbations in a rather generic
model for a regular bouncing universe, where the bounce is triggered by an
effective perfect fluid with negative energy density. Long before and after the
bounce the universe is dominated by a source with positive energy density,
which may be a perfect fluid, a scalar field, or any other source with an
intrinsic isocurvature perturbation. Within this framework, we present an
analytical method to accurately estimate the spectrum of large-scale scalar
perturbations until their reentry, long after the bounce. We also propose a
simple way to identify non-singular gauge-invariant variables through the
bounce and present the results of extensive numerical tests in several possible
realizations of the scenario. In no case do we find that the spectrum of the
pre-bounce growing mode of the Bardeen potential can be transferred to a
post-bounce constant mode.
| [
{
"created": "Tue, 7 Jun 2005 07:53:16 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Sep 2005 16:20:53 GMT",
"version": "v2"
}
] | 2009-07-09 | [
[
"Bozza",
"V.",
""
],
[
"Veneziano",
"G.",
""
]
] | We present a full investigation of scalar perturbations in a rather generic model for a regular bouncing universe, where the bounce is triggered by an effective perfect fluid with negative energy density. Long before and after the bounce the universe is dominated by a source with positive energy density, which may be a perfect fluid, a scalar field, or any other source with an intrinsic isocurvature perturbation. Within this framework, we present an analytical method to accurately estimate the spectrum of large-scale scalar perturbations until their reentry, long after the bounce. We also propose a simple way to identify non-singular gauge-invariant variables through the bounce and present the results of extensive numerical tests in several possible realizations of the scenario. In no case do we find that the spectrum of the pre-bounce growing mode of the Bardeen potential can be transferred to a post-bounce constant mode. |
2310.16796 | Hong-Bo Jin | Pan Guo, Hong-Bo Jin, Cong-Feng Qiao and Yue-Liang Wu | Sky location of Galactic white dwarf binaries in space-based
gravitational wave detection | 22 pages, 15 figures | Results in Physics, 2024 | 10.1016/j.rinp.2024.107607 | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | Quickly localizing the identified white dwarf (WD) binaries is the basic
requirement for the space-based gravitational wave (GW) detection. In fact, the
amplitude of GW signals are modulated by the periodic motion of GW detectors on
the solar orbit. The intensity of the observed signals is enhanced according to
the observation time beyond a year to enhance a high signal to noise ratio
(SNR). As data gap exists, the completeness of the data observed for a long
time depends on filling gaps in the data. Actually, in a year period, the GW
sources have a best observation orbit position of GW detectors, where the
detector response intensity of GW is maximum. Thus, the best positions, where
the direction of GW source is perpendicular to the detection arms, can be
searched for the verified GW sources of the sky map to enhance SNR too. For the
three arms response intensity of the GW signals changing more clearly with the
location of the GW sources relative to the detector, the noises and the
suppression of noise by time delay interferometer are ignored. In the four
chosen sources, the two verification WD binaries: J0806 and V407 Vul are
observed at the best orbit positions by TAIJI for the short time of 2 and 3
days respectively. The intensities of those GWs are above the values of the
TAIJI sensitivity curve, significantly. Compared with a single detector, the
network of two detectors does not significantly improve the accuracy of
location of the verification binaries. These results imply that the searching
of GW signals and parameter estimation of GW sources from the experimental data
of the space-based mission do not ignore the orbit positions relevant to GW
sources.
| [
{
"created": "Wed, 25 Oct 2023 17:25:08 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Mar 2024 00:34:39 GMT",
"version": "v2"
}
] | 2024-04-01 | [
[
"Guo",
"Pan",
""
],
[
"Jin",
"Hong-Bo",
""
],
[
"Qiao",
"Cong-Feng",
""
],
[
"Wu",
"Yue-Liang",
""
]
] | Quickly localizing the identified white dwarf (WD) binaries is the basic requirement for the space-based gravitational wave (GW) detection. In fact, the amplitude of GW signals are modulated by the periodic motion of GW detectors on the solar orbit. The intensity of the observed signals is enhanced according to the observation time beyond a year to enhance a high signal to noise ratio (SNR). As data gap exists, the completeness of the data observed for a long time depends on filling gaps in the data. Actually, in a year period, the GW sources have a best observation orbit position of GW detectors, where the detector response intensity of GW is maximum. Thus, the best positions, where the direction of GW source is perpendicular to the detection arms, can be searched for the verified GW sources of the sky map to enhance SNR too. For the three arms response intensity of the GW signals changing more clearly with the location of the GW sources relative to the detector, the noises and the suppression of noise by time delay interferometer are ignored. In the four chosen sources, the two verification WD binaries: J0806 and V407 Vul are observed at the best orbit positions by TAIJI for the short time of 2 and 3 days respectively. The intensities of those GWs are above the values of the TAIJI sensitivity curve, significantly. Compared with a single detector, the network of two detectors does not significantly improve the accuracy of location of the verification binaries. These results imply that the searching of GW signals and parameter estimation of GW sources from the experimental data of the space-based mission do not ignore the orbit positions relevant to GW sources. |
1903.06067 | Paul Tod | Ho Lee, Ernesto Nungesser and Paul Tod | The massless Einstein-Boltzmann system with a conformal-gauge
singularity in an FLRW background | 26 pages, no figures; this revised version is as accepted by CQG | null | 10.1088/1361-6382/ab5f41 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain finite-time existence for the massless Boltzmann equation, with a
range of soft cross-sections, in an FLRW background with data given at the
initial singularity. In the case of positive cosmological constant we obtain
long-time existence in proper-time for small data as a corollary.
| [
{
"created": "Thu, 14 Mar 2019 15:16:20 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Dec 2019 16:03:24 GMT",
"version": "v2"
}
] | 2020-01-29 | [
[
"Lee",
"Ho",
""
],
[
"Nungesser",
"Ernesto",
""
],
[
"Tod",
"Paul",
""
]
] | We obtain finite-time existence for the massless Boltzmann equation, with a range of soft cross-sections, in an FLRW background with data given at the initial singularity. In the case of positive cosmological constant we obtain long-time existence in proper-time for small data as a corollary. |
2210.14025 | Stephanie Brown | Stephanie M. Brown | Tidal Deformability of Neutron Stars in Scalar-Tensor Theories of
Gravity | Accepted to APJ | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves from compact binary coalescences are valuable for testing
theories of gravity in the strong field regime. By measuring neutron star tidal
deformability using gravitational waves from binary neutron stars, stringent
constraints were placed on the equation of state of matter at extreme
densities. Tidal Love numbers in alternative theories of gravity may differ
significantly from their general relativistic counterparts. Understanding
exactly how the tidal Love numbers change will enable scientists to untangle
physics beyond general relativity from the uncertainty in the equation of state
measurement. In this work, we explicitly calculate the fully relativistic $l
\geq 2$ tidal love numbers for neutron stars in scalar-tensor theories of
gravitation. We use several realistic equations of state to explore how the
mass, radius, and tidal deformability relations differ from those of general
relativity. We find that tidal Love numbers and tidal deformabilities can
differ significantly from those in general relativity in certain regimes. The
electric tidal deformability can differ by $\sim 200\%$, and the magnetic tidal
deformability differs by $\sim 300 \%$. These deviations occur at large
compactnesses ($C = M/r \gtrsim 0.2$) and vary slightly depending on the
equation of state. This difference suggests that using the tidal Love numbers
from general relativity could lead to significant errors in tests of general
relativity using the gravitational waves from binary neutron star and
neutron-star--black-hole mergers.
| [
{
"created": "Tue, 25 Oct 2022 13:58:30 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Sep 2023 17:13:18 GMT",
"version": "v2"
}
] | 2023-09-25 | [
[
"Brown",
"Stephanie M.",
""
]
] | Gravitational waves from compact binary coalescences are valuable for testing theories of gravity in the strong field regime. By measuring neutron star tidal deformability using gravitational waves from binary neutron stars, stringent constraints were placed on the equation of state of matter at extreme densities. Tidal Love numbers in alternative theories of gravity may differ significantly from their general relativistic counterparts. Understanding exactly how the tidal Love numbers change will enable scientists to untangle physics beyond general relativity from the uncertainty in the equation of state measurement. In this work, we explicitly calculate the fully relativistic $l \geq 2$ tidal love numbers for neutron stars in scalar-tensor theories of gravitation. We use several realistic equations of state to explore how the mass, radius, and tidal deformability relations differ from those of general relativity. We find that tidal Love numbers and tidal deformabilities can differ significantly from those in general relativity in certain regimes. The electric tidal deformability can differ by $\sim 200\%$, and the magnetic tidal deformability differs by $\sim 300 \%$. These deviations occur at large compactnesses ($C = M/r \gtrsim 0.2$) and vary slightly depending on the equation of state. This difference suggests that using the tidal Love numbers from general relativity could lead to significant errors in tests of general relativity using the gravitational waves from binary neutron star and neutron-star--black-hole mergers. |
gr-qc/9701013 | Joy Christian | Joy Christian (Perimeter and Oxford) | Exactly Soluble Sector of Quantum Gravity | 83 pages (TeX). A note is added on the early work of a remarkable
Soviet physicist called Bronstein, especially on his insightful contribution
to "the cube of theories" (Fig. 1) -- see "Note Added to Proof" on pages 71
and 72, together with the new references [59] and [61] | Phys.Rev.D56:4844-4877,1997 | 10.1103/PhysRevD.56.4844 | null | gr-qc hep-th quant-ph | null | Cartan's spacetime reformulation of the Newtonian theory of gravity is a
generally-covariant Galilean-relativistic limit-form of Einstein's theory of
gravity known as the Newton-Cartan theory. According to this theory, space is
flat, time is absolute with instantaneous causal influences, and the degenerate
`metric' structure of spacetime remains fixed with two mutually orthogonal
non-dynamical metrics, one spatial and the other temporal. The spacetime
according to this theory is, nevertheless, curved, duly respecting the
principle of equivalence, and the non-metric gravitational connection-field is
dynamical in the sense that it is determined by matter distributions. Here,
this generally-covariant but Galilean-relativistic theory of gravity with a
possible non-zero cosmological constant, viewed as a parameterized gauge theory
of a gravitational vector-potential minimally coupled to a complex
Schroedinger-field (bosonic or fermionic), is successfully cast -- for the
first time -- into a manifestly covariant Lagrangian form. Then, exploiting the
fact that Newton-Cartan spacetime is intrinsically globally-hyperbolic with a
fixed causal structure, the theory is recast both into a constraint-free
Hamiltonian form in 3+1-dimensions and into a manifestly covariant reduced
phase-space form with non-degenerate symplectic structure in 4-dimensions.
Next, this Newton-Cartan-Schroedinger system is non-perturbatively quantized
using the standard C*-algebraic technique combined with the geometric procedure
of manifestly covariant phase-space quantization. The ensuing unitary quantum
field theory of Newtonian gravity coupled to Galilean-relativistic matter is
not only generally-covariant, but also exactly soluble.
| [
{
"created": "Thu, 9 Jan 1997 15:55:42 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jul 1997 11:57:25 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Oct 1997 18:32:13 GMT",
"version": "v3"
},
{
"created": "Mon, 7 Nov 2005 21:09:09 GMT",
"version": "v4"
}
] | 2011-09-09 | [
[
"Christian",
"Joy",
"",
"Perimeter and Oxford"
]
] | Cartan's spacetime reformulation of the Newtonian theory of gravity is a generally-covariant Galilean-relativistic limit-form of Einstein's theory of gravity known as the Newton-Cartan theory. According to this theory, space is flat, time is absolute with instantaneous causal influences, and the degenerate `metric' structure of spacetime remains fixed with two mutually orthogonal non-dynamical metrics, one spatial and the other temporal. The spacetime according to this theory is, nevertheless, curved, duly respecting the principle of equivalence, and the non-metric gravitational connection-field is dynamical in the sense that it is determined by matter distributions. Here, this generally-covariant but Galilean-relativistic theory of gravity with a possible non-zero cosmological constant, viewed as a parameterized gauge theory of a gravitational vector-potential minimally coupled to a complex Schroedinger-field (bosonic or fermionic), is successfully cast -- for the first time -- into a manifestly covariant Lagrangian form. Then, exploiting the fact that Newton-Cartan spacetime is intrinsically globally-hyperbolic with a fixed causal structure, the theory is recast both into a constraint-free Hamiltonian form in 3+1-dimensions and into a manifestly covariant reduced phase-space form with non-degenerate symplectic structure in 4-dimensions. Next, this Newton-Cartan-Schroedinger system is non-perturbatively quantized using the standard C*-algebraic technique combined with the geometric procedure of manifestly covariant phase-space quantization. The ensuing unitary quantum field theory of Newtonian gravity coupled to Galilean-relativistic matter is not only generally-covariant, but also exactly soluble. |
gr-qc/0110045 | J. Daniel Christensen | J. Daniel Christensen and Greg Egan | An efficient algorithm for the Riemannian 10j symbols | 9 pages, 5 postscript figures. This is the version that is to appear
in Classical and Quantum Gravity. See also http://jdc.math.uwo.ca/spin-foams | Class.Quant.Grav. 19 (2002) 1185-1194 | 10.1088/0264-9381/19/6/310 | null | gr-qc | null | The 10j symbol is a spin network that appears in the partition function for
the Barrett-Crane model of Riemannian quantum gravity. Elementary methods of
calculating the 10j symbol require order(j^9) or more operations and order(j^2)
or more space, where j is the average spin. We present an algorithm that
computes the 10j symbol using order(j^5) operations and order(j^2) space, and a
variant that uses order(j^6) operations and a constant amount of space. An
implementation has been made available on the web.
| [
{
"created": "Tue, 9 Oct 2001 01:31:46 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2001 01:36:26 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Jan 2002 18:42:28 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Christensen",
"J. Daniel",
""
],
[
"Egan",
"Greg",
""
]
] | The 10j symbol is a spin network that appears in the partition function for the Barrett-Crane model of Riemannian quantum gravity. Elementary methods of calculating the 10j symbol require order(j^9) or more operations and order(j^2) or more space, where j is the average spin. We present an algorithm that computes the 10j symbol using order(j^5) operations and order(j^2) space, and a variant that uses order(j^6) operations and a constant amount of space. An implementation has been made available on the web. |
1807.01998 | Jean-Marie Vigoureux | Jean-Marie Vigoureux | Quantum Theory and Special Relativity: when are physical properties
attributed jointly to the system and to the context in which it is studied? | 11 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Alexia Auff\`eves and Philippe Grangier proposed to modify the quantum
ontology by requiring that physical properties are attributed jointly to the
system and to the context in which it is embedded. Comparing the formal
structures of Quantum Theory and of Special Relativity may suggest a basis for
such an interpretation of quantum theory.
| [
{
"created": "Wed, 4 Jul 2018 16:55:30 GMT",
"version": "v1"
}
] | 2018-07-06 | [
[
"Vigoureux",
"Jean-Marie",
""
]
] | Alexia Auff\`eves and Philippe Grangier proposed to modify the quantum ontology by requiring that physical properties are attributed jointly to the system and to the context in which it is embedded. Comparing the formal structures of Quantum Theory and of Special Relativity may suggest a basis for such an interpretation of quantum theory. |
0912.0459 | L\'aszl\'o \'A Gergely | L\'aszl\'o \'Arp\'ad Gergely | Spinning compact binary inspiral: Independent variables and dynamically
preserved spin configurations | 13 pages, 2 figures, subsection IV.A improved, published version | Phys.Rev.D81:084025,2010 | 10.1103/PhysRevD.81.084025 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish the set of independent variables suitable to monitor the
complicated evolution of the spinning compact binary during the inspiral. Our
approach is valid up to the second post-Newtonian order, including leading
order spin-orbit, spin-spin and mass quadrupol-mass monopole effects, for
generic (noncircular, nonspherical) orbits. Then we analyze the conservative
spin dynamics in terms of these variables. We prove that the only binary black
hole configuration allowing for spin precessions with equal angular velocities
about a common intantaneous axis roughly aligned to the normal of the
osculating orbit, is the equal mass and parallel (aligned or antialigned) spin
configuration. This analytic result puts limitations on what particular
configurations can be selected in numerical investigations of compact binary
evolutions, even in those including only the last orbits of the inspiral.
| [
{
"created": "Wed, 2 Dec 2009 16:37:16 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Feb 2010 10:51:06 GMT",
"version": "v2"
},
{
"created": "Tue, 11 May 2010 05:34:01 GMT",
"version": "v3"
}
] | 2010-05-12 | [
[
"Gergely",
"László Árpád",
""
]
] | We establish the set of independent variables suitable to monitor the complicated evolution of the spinning compact binary during the inspiral. Our approach is valid up to the second post-Newtonian order, including leading order spin-orbit, spin-spin and mass quadrupol-mass monopole effects, for generic (noncircular, nonspherical) orbits. Then we analyze the conservative spin dynamics in terms of these variables. We prove that the only binary black hole configuration allowing for spin precessions with equal angular velocities about a common intantaneous axis roughly aligned to the normal of the osculating orbit, is the equal mass and parallel (aligned or antialigned) spin configuration. This analytic result puts limitations on what particular configurations can be selected in numerical investigations of compact binary evolutions, even in those including only the last orbits of the inspiral. |
2102.13556 | Jan Henryk Kwapisz | Jan Chojnacki and Jan H. Kwapisz | Finite Action Principle and Horava-Lifshitz Gravity: early universe,
black holes and wormholes | Matches the version accepted in PRD, one minor mistake corrected | null | 10.1103/PhysRevD.104.103504 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | The destructive interference of the neighbouring field configurations with
infinite classical action in the gravitational path integral approach serves as
a dynamical mechanism resolving the black hole singularity problem. It also
provides an isotropic and homogeneous early universe without the need of
inflation. In this work, we elaborate on the finite action in the framework of
Horava-Lifshitz gravity -- a ghost-free QFT. Assuming the mixmaster chaotic
solutions in the projectable H-L theory, we show that the beginning of the
universe is homogeneous and isotropic. Furthermore, we show that the H-L
gravity action selects only the regular black-hole spacetimes. We also comment
on possibility of traversable wormholes in theories with higher curvature
invariants.
| [
{
"created": "Fri, 26 Feb 2021 15:50:27 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Mar 2021 14:22:22 GMT",
"version": "v2"
},
{
"created": "Mon, 31 May 2021 17:21:48 GMT",
"version": "v3"
},
{
"created": "Thu, 10 Jun 2021 10:26:11 GMT",
"version": "v4"
},
{
"cr... | 2021-11-17 | [
[
"Chojnacki",
"Jan",
""
],
[
"Kwapisz",
"Jan H.",
""
]
] | The destructive interference of the neighbouring field configurations with infinite classical action in the gravitational path integral approach serves as a dynamical mechanism resolving the black hole singularity problem. It also provides an isotropic and homogeneous early universe without the need of inflation. In this work, we elaborate on the finite action in the framework of Horava-Lifshitz gravity -- a ghost-free QFT. Assuming the mixmaster chaotic solutions in the projectable H-L theory, we show that the beginning of the universe is homogeneous and isotropic. Furthermore, we show that the H-L gravity action selects only the regular black-hole spacetimes. We also comment on possibility of traversable wormholes in theories with higher curvature invariants. |
gr-qc/0207069 | Jose A. Gonzalez | Daniel Sudarsky and Jose Antonio Gonzalez | On Black Hole Scalar Hair in Asymptotically Anti de Sitter Spacetimes | 12 pages. Published version | Phys.Rev.D67:024038,2003 | 10.1103/PhysRevD.67.024038 | null | gr-qc | null | The unexpected discovery of hairy black hole solutions in theories with
scalar fields simply by considering asymptotically Anti de-Sitter, rather than
asymptotically flat, boundary conditions is analyzed in a way that exhibits in
a clear manner the differences between the two situations.
It is shown that the trivial Schwarzschild Anti de Sitter becomes unstable in
some of these situations, and the possible relevance of this fact for the
ADS/CFT conjecture is pointed out.
| [
{
"created": "Thu, 18 Jul 2002 01:12:33 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Mar 2003 22:57:23 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Sudarsky",
"Daniel",
""
],
[
"Gonzalez",
"Jose Antonio",
""
]
] | The unexpected discovery of hairy black hole solutions in theories with scalar fields simply by considering asymptotically Anti de-Sitter, rather than asymptotically flat, boundary conditions is analyzed in a way that exhibits in a clear manner the differences between the two situations. It is shown that the trivial Schwarzschild Anti de Sitter becomes unstable in some of these situations, and the possible relevance of this fact for the ADS/CFT conjecture is pointed out. |
1205.1216 | Md. Rahman Atiqur | M. Atiqur Rahman, M. Ilias Hossain | Hawking Radiation of Schwarzschild-de Sitter Black Hole by
Hamilton-Jacobi method | 9 page. arXiv admin note: text overlap with arXiv:1205.1390 | Phys. Lett. B 712 (2012) 1-5 | 10.1016/j.physletb.2012.04.049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the Hawking radiation of Schwarzschild-de Sitter (SdS) black
hole by massive particles tunneling method. We consider the spacetime
background to be dynamical, incorporate the self-gravitation effect of the
emitted particles and show that the tunneling rate is related to the change of
Bekenstein-Hawking entropy and the derived emission spectrum deviates from the
pure thermal spectrum when energy and angular momentum are conserved. Our
result is also in accordance with Parikh and Wilczek\rq s opinion and gives a
correction to the Hawking radiation of SdS black hole.
| [
{
"created": "Sun, 6 May 2012 13:19:34 GMT",
"version": "v1"
},
{
"created": "Sun, 13 May 2012 07:51:51 GMT",
"version": "v2"
}
] | 2012-06-01 | [
[
"Rahman",
"M. Atiqur",
""
],
[
"Hossain",
"M. Ilias",
""
]
] | We investigate the Hawking radiation of Schwarzschild-de Sitter (SdS) black hole by massive particles tunneling method. We consider the spacetime background to be dynamical, incorporate the self-gravitation effect of the emitted particles and show that the tunneling rate is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum when energy and angular momentum are conserved. Our result is also in accordance with Parikh and Wilczek\rq s opinion and gives a correction to the Hawking radiation of SdS black hole. |
0809.0811 | Jiliang Jing | Qiyuan Pan, Jiliang Jing | Hawking radiation, Entanglement and Teleportation in background of an
asymptotically flat static black hole | 17 pages, 3 figures, to be published in Physical Review D | Phys.Rev.D78:065015,2008 | 10.1103/PhysRevD.78.065015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effect of the Hawking temperature on the entanglement and teleportation
for the scalar field in a most general, static and asymptotically flat black
hole with spherical symmetry has been investigated. It is shown that the same
"initial entanglement" for the state parameter $\alpha$ and its "normalized
partners" $\sqrt{1-\alpha^{2}}$ will be degraded by the Hawking effect with
increasing Hawking temperature along two different trajectories except for the
maximally entangled state. In the infinite Hawking temperature limit,
corresponding to the case of the black hole evaporating completely, the state
has no longer distillable entanglement for any $\alpha$. It is interesting to
note that the mutual information in this limit equals to just half of the
"initially mutual information". It has also been demonstrated that the fidelity
of teleportation decreases as the Hawking temperature increases, which just
indicates the degradation of entanglement.
| [
{
"created": "Thu, 4 Sep 2008 13:37:18 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Sep 2008 01:10:09 GMT",
"version": "v2"
}
] | 2009-02-20 | [
[
"Pan",
"Qiyuan",
""
],
[
"Jing",
"Jiliang",
""
]
] | The effect of the Hawking temperature on the entanglement and teleportation for the scalar field in a most general, static and asymptotically flat black hole with spherical symmetry has been investigated. It is shown that the same "initial entanglement" for the state parameter $\alpha$ and its "normalized partners" $\sqrt{1-\alpha^{2}}$ will be degraded by the Hawking effect with increasing Hawking temperature along two different trajectories except for the maximally entangled state. In the infinite Hawking temperature limit, corresponding to the case of the black hole evaporating completely, the state has no longer distillable entanglement for any $\alpha$. It is interesting to note that the mutual information in this limit equals to just half of the "initially mutual information". It has also been demonstrated that the fidelity of teleportation decreases as the Hawking temperature increases, which just indicates the degradation of entanglement. |
gr-qc/0506069 | Claudio Dappiaggi | C. Dappiaggi (Pavia U.), V. Moretti (Trento U.), N. Pinamonti (Trento
U.) | Rigorous steps towards holography in asymptotically flat spacetimes | 62 pages, amslatex, xy package; revised section 2 and the
conclusions; corrected some typos; added some references; accepted for
pubblication on Rev. Math. Phys | Rev.Math.Phys. 18 (2006) 349-416 | 10.1142/S0129055X0600270X | FNT-T/2005-05, UTM 683 | gr-qc hep-th math-ph math.MP | null | Scalar QFT on the boundary $\Im^+$ at null infinity of a general
asymptotically flat 4D spacetime is constructed using the algebraic approach
based on Weyl algebra associated to a BMS-invariant symplectic form. The
constructed theory is invariant under a suitable unitary representation of the
BMS group with manifest meaning when the fields are interpreted as suitable
extensions to $\Im^+$ of massless minimally coupled fields propagating in the
bulk. The analysis of the found unitary BMS representation proves that such a
field on $\Im^+$ coincides with the natural wave function constructed out of
the unitary BMS irreducible representation induced from the little group
$\Delta$, the semidirect product between SO(2) and the two dimensional
translational group. The result proposes a natural criterion to solve the long
standing problem of the topology of BMS group. Indeed the found natural
correspondence of quantum field theories holds only if the BMS group is
equipped with the nuclear topology rejecting instead the Hilbert one.
Eventually some theorems towards a holographic description on $\Im^+$ of QFT in
the bulk are established at level of $C^*$ algebras of fields for strongly
asymptotically predictable spacetimes. It is proved that preservation of a
certain symplectic form implies the existence of an injective $*$-homomorphism
from the Weyl algebra of fields of the bulk into that associated with the
boundary $\Im^+$. Those results are, in particular, applied to 4D Minkowski
spacetime where a nice interplay between Poincar\'e invariance in the bulk and
BMS invariance on the boundary at $\Im^+$ is established at level of QFT. It
arises that the $*$-homomorphism admits unitary implementation and Minkowski
vacuum is mapped into the BMS invariant vacuum on $\Im^+$.
| [
{
"created": "Sat, 11 Jun 2005 13:28:26 GMT",
"version": "v1"
},
{
"created": "Thu, 18 May 2006 19:42:36 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Dappiaggi",
"C.",
"",
"Pavia U."
],
[
"Moretti",
"V.",
"",
"Trento U."
],
[
"Pinamonti",
"N.",
"",
"Trento\n U."
]
] | Scalar QFT on the boundary $\Im^+$ at null infinity of a general asymptotically flat 4D spacetime is constructed using the algebraic approach based on Weyl algebra associated to a BMS-invariant symplectic form. The constructed theory is invariant under a suitable unitary representation of the BMS group with manifest meaning when the fields are interpreted as suitable extensions to $\Im^+$ of massless minimally coupled fields propagating in the bulk. The analysis of the found unitary BMS representation proves that such a field on $\Im^+$ coincides with the natural wave function constructed out of the unitary BMS irreducible representation induced from the little group $\Delta$, the semidirect product between SO(2) and the two dimensional translational group. The result proposes a natural criterion to solve the long standing problem of the topology of BMS group. Indeed the found natural correspondence of quantum field theories holds only if the BMS group is equipped with the nuclear topology rejecting instead the Hilbert one. Eventually some theorems towards a holographic description on $\Im^+$ of QFT in the bulk are established at level of $C^*$ algebras of fields for strongly asymptotically predictable spacetimes. It is proved that preservation of a certain symplectic form implies the existence of an injective $*$-homomorphism from the Weyl algebra of fields of the bulk into that associated with the boundary $\Im^+$. Those results are, in particular, applied to 4D Minkowski spacetime where a nice interplay between Poincar\'e invariance in the bulk and BMS invariance on the boundary at $\Im^+$ is established at level of QFT. It arises that the $*$-homomorphism admits unitary implementation and Minkowski vacuum is mapped into the BMS invariant vacuum on $\Im^+$. |
1405.5085 | Eolo Di Casola | Eolo Di Casola and Stefano Liberati and Sebastiano Sonego | Between quantum and classical gravity: Is there a mesoscopic spacetime? | 7 pages, no figures | Found. Phys. 45 (2), 171 (2015) | 10.1007/s10701-014-9859-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Between the microscopic domain ruled by quantum gravity, and the macroscopic
scales described by general relativity, there might be an intermediate,
"mesoscopic" regime, where spacetime can still be approximately treated as a
differentiable pseudo-Riemannian manifold, with small corrections of quantum
gravitational origin. We argue that, unless one accepts to give up the
relativity principle, either such a regime does not exist at all (hence, the
quantum-to-classical transition is sharp), or the only mesoscopic, tiny
corrections conceivable are on the behaviour of physical fields, rather than on
the geometric structures.
| [
{
"created": "Tue, 20 May 2014 14:00:52 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Mar 2015 18:19:51 GMT",
"version": "v2"
}
] | 2015-03-19 | [
[
"Di Casola",
"Eolo",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Sonego",
"Sebastiano",
""
]
] | Between the microscopic domain ruled by quantum gravity, and the macroscopic scales described by general relativity, there might be an intermediate, "mesoscopic" regime, where spacetime can still be approximately treated as a differentiable pseudo-Riemannian manifold, with small corrections of quantum gravitational origin. We argue that, unless one accepts to give up the relativity principle, either such a regime does not exist at all (hence, the quantum-to-classical transition is sharp), or the only mesoscopic, tiny corrections conceivable are on the behaviour of physical fields, rather than on the geometric structures. |
1902.03485 | Saken Toktarbay | Medeu Abishev, Farida Belissarova, Kuantay Boshkayev, Hernando
Quevedo, Saken Toktarbay, Aizhan Mansurova and Aray Muratkhan | Approximate perfect fluid solutions with quadrupole moment | null | International Journal of Modern Physics DVol. 30, No. 13, 2150096
(2021) | 10.1142/S0218271821500966 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the interior Einstein's equations in the case of a static,
axially symmetric, perfect fluid source. We present a particular line element
that is specially suitable for the investigation of this type of interior
gravitational fields. Assuming that the deviation from spherically symmetry is
small, we linearize the corresponding field equations and find several classes
of vacuum and perfect fluid solutions. We find physically meaninful spacetimes
by imposing appropriate matching conditions.
| [
{
"created": "Sat, 9 Feb 2019 20:38:09 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2022 17:44:53 GMT",
"version": "v2"
}
] | 2022-03-29 | [
[
"Abishev",
"Medeu",
""
],
[
"Belissarova",
"Farida",
""
],
[
"Boshkayev",
"Kuantay",
""
],
[
"Quevedo",
"Hernando",
""
],
[
"Toktarbay",
"Saken",
""
],
[
"Mansurova",
"Aizhan",
""
],
[
"Muratkhan",
"Aray",
... | We investigate the interior Einstein's equations in the case of a static, axially symmetric, perfect fluid source. We present a particular line element that is specially suitable for the investigation of this type of interior gravitational fields. Assuming that the deviation from spherically symmetry is small, we linearize the corresponding field equations and find several classes of vacuum and perfect fluid solutions. We find physically meaninful spacetimes by imposing appropriate matching conditions. |
2102.12921 | Snehasish Bhattacharjee | Snehasish Bhattacharjee | BBN Constraints on $f(Q,T)$ Gravity | null | International Journal of Modern Physics A, 37, 06, 2250017 (2022) | 10.1142/S0217751X22500178 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | $f(Q,T)$ gravity is a novel extension of the symmetric teleparallel gravity
where the Lagrangian $L$ is represented through an arbitrary function of the
nonmetricity $Q$ and the trace of the energy-momentum tensor $T$ \cite{fqt}. In
this work, we have constrained a widely used $f(Q,T)$ gravity model of the form
$f(Q,T) = Q^{n+1} + m T$ from the primordial abundances of the light elements
to understand its viability in Cosmology. We report that the $f(Q,T)$ gravity
model can elegantly explain the observed abundances of Helium and Deuterium
while the Lithium problem persists. From the constraint on the expansion factor
in the range $0.9425 \lesssim Z \lesssim1.1525$, we report strict constraints
on the parameters $m$ and $n$ in the range $-1.13 \lesssim n \lesssim -1.08$
and $-5.86 \lesssim m \lesssim12.52$ respectively.
| [
{
"created": "Thu, 25 Feb 2021 15:20:49 GMT",
"version": "v1"
}
] | 2022-03-23 | [
[
"Bhattacharjee",
"Snehasish",
""
]
] | $f(Q,T)$ gravity is a novel extension of the symmetric teleparallel gravity where the Lagrangian $L$ is represented through an arbitrary function of the nonmetricity $Q$ and the trace of the energy-momentum tensor $T$ \cite{fqt}. In this work, we have constrained a widely used $f(Q,T)$ gravity model of the form $f(Q,T) = Q^{n+1} + m T$ from the primordial abundances of the light elements to understand its viability in Cosmology. We report that the $f(Q,T)$ gravity model can elegantly explain the observed abundances of Helium and Deuterium while the Lithium problem persists. From the constraint on the expansion factor in the range $0.9425 \lesssim Z \lesssim1.1525$, we report strict constraints on the parameters $m$ and $n$ in the range $-1.13 \lesssim n \lesssim -1.08$ and $-5.86 \lesssim m \lesssim12.52$ respectively. |
0901.2750 | Parampreet Singh | Parampreet Singh | Are loop quantum cosmos never singular? | 20 pages, IOP style. Minor revision. Typos corrected and 1 figure
replaced. To appear in Classical & Quantum Gravity | Class.Quant.Grav.26:125005,2009 | 10.1088/0264-9381/26/12/125005 | PI-QG-100 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A unified treatment of all known types of singularities for flat, isotropic
and homogeneous spacetimes in the framework of loop quantum cosmology (LQC) is
presented. These include bangs, crunches and all future singularities. Using
effective spacetime description we perform a model independent general analysis
of the properties of curvature, behavior of geodesics and strength of
singularities. For illustration purposes a phenomenological model based
analysis is also performed. We show that all values of the scale factor at
which a strong singularity may occur are excluded from the effective loop
quantum spacetime. Further, if the evolution leads to either a vanishing or
divergent scale factor then the loop quantum universe is asymptotically
deSitter in that regime. We also show that there exist a class of sudden
extremal events, which includes a recently discussed possibility, for which the
curvature or its derivatives will always diverge. Such events however turn out
to be harmless weak curvature singularities beyond which geodesics can be
extended. Our results point towards a generic resolution of physical
singularities in LQC.
| [
{
"created": "Mon, 19 Jan 2009 15:59:33 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Apr 2009 15:58:39 GMT",
"version": "v2"
}
] | 2009-07-18 | [
[
"Singh",
"Parampreet",
""
]
] | A unified treatment of all known types of singularities for flat, isotropic and homogeneous spacetimes in the framework of loop quantum cosmology (LQC) is presented. These include bangs, crunches and all future singularities. Using effective spacetime description we perform a model independent general analysis of the properties of curvature, behavior of geodesics and strength of singularities. For illustration purposes a phenomenological model based analysis is also performed. We show that all values of the scale factor at which a strong singularity may occur are excluded from the effective loop quantum spacetime. Further, if the evolution leads to either a vanishing or divergent scale factor then the loop quantum universe is asymptotically deSitter in that regime. We also show that there exist a class of sudden extremal events, which includes a recently discussed possibility, for which the curvature or its derivatives will always diverge. Such events however turn out to be harmless weak curvature singularities beyond which geodesics can be extended. Our results point towards a generic resolution of physical singularities in LQC. |
0809.2453 | Dmitry I. Podolsky | Dmitry I. Podolsky | Dynamical renormalization group methods in theory of eternal inflation | 11 pages; invited mini-review for Grav.Cosm | Grav.Cosmol.15:69-74,2009 | 10.1134/S0202289309010174 | HIP-2008-29/TH | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamics of eternal inflation on the landscape admits description in terms of
the Martin-Siggia-Rose (MSR) effective field theory that is in one-to-one
correspondence with vacuum dynamics equations. On those sectors of the
landscape, where transport properties of the probability measure for eternal
inflation are important, renormalization group fixed points of the MSR
effective action determine late time behavior of the probability measure. I
argue that these RG fixed points may be relevant for the solution of the gauge
invariance problem for eternal inflation.
| [
{
"created": "Mon, 15 Sep 2008 08:28:16 GMT",
"version": "v1"
}
] | 2009-03-19 | [
[
"Podolsky",
"Dmitry I.",
""
]
] | Dynamics of eternal inflation on the landscape admits description in terms of the Martin-Siggia-Rose (MSR) effective field theory that is in one-to-one correspondence with vacuum dynamics equations. On those sectors of the landscape, where transport properties of the probability measure for eternal inflation are important, renormalization group fixed points of the MSR effective action determine late time behavior of the probability measure. I argue that these RG fixed points may be relevant for the solution of the gauge invariance problem for eternal inflation. |
1801.05031 | Grigoris Panotopoulos | Ilidio Lopes and Grigoris Panotopoulos | Dark matter admixed strange quark stars in the Starobinsky model | 7 pages, two-column revtex, 6 figures, minor changes. arXiv admin
note: text overlap with arXiv:1801.03387 | null | 10.1103/PhysRevD.97.024030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The properties of dark matter admixed strange quark stars are investigated in
the Starobinsky model of modified gravity. For quark matter we assume the MIT
bag model, while self-interacting dark matter inside the star is modelled as a
Bose-Einstein condensate with a polytropic equation of state. We numerically
integrate the structure equations in the Einstein frame adopting the two-fluid
formalism treating the curvature correction term non-perturbatively. Our
findings show that strange quark stars (in agreement with current observational
constraints) with the highest masses are equally affected by dark matter and
modified gravity.
| [
{
"created": "Fri, 12 Jan 2018 11:25:56 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jan 2018 16:59:39 GMT",
"version": "v2"
}
] | 2018-02-14 | [
[
"Lopes",
"Ilidio",
""
],
[
"Panotopoulos",
"Grigoris",
""
]
] | The properties of dark matter admixed strange quark stars are investigated in the Starobinsky model of modified gravity. For quark matter we assume the MIT bag model, while self-interacting dark matter inside the star is modelled as a Bose-Einstein condensate with a polytropic equation of state. We numerically integrate the structure equations in the Einstein frame adopting the two-fluid formalism treating the curvature correction term non-perturbatively. Our findings show that strange quark stars (in agreement with current observational constraints) with the highest masses are equally affected by dark matter and modified gravity. |
2402.11663 | Dimitris Moustos | Dimitris Moustos, Charis Anastopoulos | Gravity-mediated decoherence | 7 pages | Phys. Rev. D 110, 024022 (2024) | 10.1103/PhysRevD.110.024022 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A small quantum system within the gravitational field of a massive body will
be entangled with the quantum degrees of freedom of the latter. Hence, the
massive body acts as an environment, and it induces non-unitary dynamics,
noise, and decoherence to the quantum system. It is impossible to shield
systems on Earth from this gravity-mediated decoherence, which could severely
affect all experiments with macroscopic quantum systems. We undertake a
first-principles analysis of this effect, by deriving the corresponding open
system dynamics. We find that near-future quantum experiments are not affected,
but there is a strong decoherence effect at the human scale. The decoherence
time for a superposition of two localized states of a human with an one meter
separation is of the order of one second.
| [
{
"created": "Sun, 18 Feb 2024 17:44:35 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jul 2024 16:40:21 GMT",
"version": "v2"
}
] | 2024-07-10 | [
[
"Moustos",
"Dimitris",
""
],
[
"Anastopoulos",
"Charis",
""
]
] | A small quantum system within the gravitational field of a massive body will be entangled with the quantum degrees of freedom of the latter. Hence, the massive body acts as an environment, and it induces non-unitary dynamics, noise, and decoherence to the quantum system. It is impossible to shield systems on Earth from this gravity-mediated decoherence, which could severely affect all experiments with macroscopic quantum systems. We undertake a first-principles analysis of this effect, by deriving the corresponding open system dynamics. We find that near-future quantum experiments are not affected, but there is a strong decoherence effect at the human scale. The decoherence time for a superposition of two localized states of a human with an one meter separation is of the order of one second. |
gr-qc/0402093 | Richard J. Drociuk | Richard J. Drociuk | On the Closed Form Solution for the Geodesics in SdS Space | null | null | null | null | gr-qc | null | The closed form solution for the geodesics of classical particles in SdS
space are obtained in terms of hyperelliptic modular functions and multiple
hypergeometric functions. The closed form solution for the five roots of the
fifth degree polynomial are found giving the branch places on the genus two
Riemann surface. The `Inversion Problem', for the genus two hyperelliptic
integral is solved in a closed form. Thus a couple of mathematical problems
that have been around for a couple of centuries are solved. The solution is
important in astrophysical applications of measuring the cosmological constant.
| [
{
"created": "Mon, 23 Feb 2004 05:07:05 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Jun 2004 21:03:55 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Jun 2004 20:50:56 GMT",
"version": "v3"
},
{
"created": "Thu, 15 Jul 2004 19:29:34 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Drociuk",
"Richard J.",
""
]
] | The closed form solution for the geodesics of classical particles in SdS space are obtained in terms of hyperelliptic modular functions and multiple hypergeometric functions. The closed form solution for the five roots of the fifth degree polynomial are found giving the branch places on the genus two Riemann surface. The `Inversion Problem', for the genus two hyperelliptic integral is solved in a closed form. Thus a couple of mathematical problems that have been around for a couple of centuries are solved. The solution is important in astrophysical applications of measuring the cosmological constant. |
1908.06004 | Hang Yu | Kevin A. Kuns, Hang Yu, Yanbei Chen, Rana X Adhikari | Astrophysics and cosmology with a decihertz gravitational-wave detector:
TianGO | 20 pages (including references), 13 figures | Phys. Rev. D 102, 043001 (2020) | 10.1103/PhysRevD.102.043001 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the astrophysical science case for a space-based, decihertz
gravitational-wave (GW) detector. We particularly highlight an ability to infer
a source's sky location, both when combined with a network of ground-based
detectors to form a long triangulation baseline, and by itself for the early
warning of merger events. Such an accurate location measurement is the key for
using GW signals as standard sirens for constraining the Hubble constant. This
kind of detector also opens up the possibility to test type Ia supernovae
progenitor hypotheses by constraining the merger rates of white dwarf binaries
with both super- and sub-Chandrasekhar masses separately. We will discuss other
scientific outcomes that can be delivered, including the constraint of
structure formation in the early Universe, the search for intermediate-mass
black holes, the precise determination of black hole spins, the probe of binary
systems' orbital eccentricity evolution, and the detection of tertiary masses
around merging binaries.
| [
{
"created": "Fri, 16 Aug 2019 15:12:40 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jun 2020 17:10:16 GMT",
"version": "v2"
}
] | 2020-08-12 | [
[
"Kuns",
"Kevin A.",
""
],
[
"Yu",
"Hang",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Adhikari",
"Rana X",
""
]
] | We present the astrophysical science case for a space-based, decihertz gravitational-wave (GW) detector. We particularly highlight an ability to infer a source's sky location, both when combined with a network of ground-based detectors to form a long triangulation baseline, and by itself for the early warning of merger events. Such an accurate location measurement is the key for using GW signals as standard sirens for constraining the Hubble constant. This kind of detector also opens up the possibility to test type Ia supernovae progenitor hypotheses by constraining the merger rates of white dwarf binaries with both super- and sub-Chandrasekhar masses separately. We will discuss other scientific outcomes that can be delivered, including the constraint of structure formation in the early Universe, the search for intermediate-mass black holes, the precise determination of black hole spins, the probe of binary systems' orbital eccentricity evolution, and the detection of tertiary masses around merging binaries. |
gr-qc/9605028 | Hagen Kleinert | H. Kleinert and A. Pelster | Autoparallels From a New Action Principle | Paper in src. Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html Read paper directly
with Netscape under
http://www.physik.fu-berlin.de/~kleinert/kleiner_re243/preprint.html | Gen.Rel.Grav. 31 (1999) 1439 | 10.1023/A:1026701613987 | null | gr-qc | null | We present a simpler and more powerful version of the recently-discovered
action principle for the motion of a spinless point particle in spacetimes with
curvature and torsion. The surprising feature of the new principle is that an
action involving only the metric can produce an equation of motion with a
torsion force, thus changing geodesics to autoparallels. This additional
torsion force arises from a noncommutativity of variations with parameter
derivatives of the paths due to the closure failure of parallelograms in the
presence of torsion
| [
{
"created": "Thu, 16 May 1996 07:57:03 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Oct 1999 08:08:36 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Kleinert",
"H.",
""
],
[
"Pelster",
"A.",
""
]
] | We present a simpler and more powerful version of the recently-discovered action principle for the motion of a spinless point particle in spacetimes with curvature and torsion. The surprising feature of the new principle is that an action involving only the metric can produce an equation of motion with a torsion force, thus changing geodesics to autoparallels. This additional torsion force arises from a noncommutativity of variations with parameter derivatives of the paths due to the closure failure of parallelograms in the presence of torsion |
1208.6261 | Aharon Davidson | Aharon Davidson and Ben Yellin | Schwarzschild Mass Uncertainty | 5 two-column pages; v.2,3: Slight modifications (title and abstract
included) | Gen. Rel. Grav. 46, 1662 (2014) | 10.1007/s10714-013-1662-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Applying Dirac's procedure to $r$-dependent constrained systems, we derive a
reduced total Hamiltonian, resembling an upside down harmonic oscillator, which
generates the Schwarzschild solution in the mini super-spacetime. Associated
with the now $r$-dependent Schrodinger equation is a tower of localized
Guth-Pi-Barton wave packets, orthonormal and non-singular, admitting equally
spaced average-'energy' levels. Our approach is characterized by a universal
quantum mechanical uncertainty structure which enters the game already at the
flat spacetime level, and accompanies the massive Schwarzschild sector for any
arbitrary mean mass. The average black hole horizon surface area is linearly
quantized.
| [
{
"created": "Thu, 30 Aug 2012 18:45:43 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Sep 2012 05:48:58 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Dec 2013 20:18:31 GMT",
"version": "v3"
}
] | 2014-02-03 | [
[
"Davidson",
"Aharon",
""
],
[
"Yellin",
"Ben",
""
]
] | Applying Dirac's procedure to $r$-dependent constrained systems, we derive a reduced total Hamiltonian, resembling an upside down harmonic oscillator, which generates the Schwarzschild solution in the mini super-spacetime. Associated with the now $r$-dependent Schrodinger equation is a tower of localized Guth-Pi-Barton wave packets, orthonormal and non-singular, admitting equally spaced average-'energy' levels. Our approach is characterized by a universal quantum mechanical uncertainty structure which enters the game already at the flat spacetime level, and accompanies the massive Schwarzschild sector for any arbitrary mean mass. The average black hole horizon surface area is linearly quantized. |
1804.03331 | Q. H. Liu | Q. H. Liu, Q. Li, T. G. Liu, X .Wang | Gravitational major-axis contraction of Mercury's elliptical orbit | 5 pages, major revision | null | 10.1142/S0217732319501591 | null | gr-qc physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The local curvature of the space produced by the Sun causes not only the
perihelion precession of Mercury's elliptical orbit, but also the variations of
the whole orbit, in comparison with those predicted by the Newtonian theory of
gravitation. Calculations show that the gravitational major-axis contraction of
the Mercury's elliptical orbit is 1.3 kilometers which can be confirmed by the
present astronomical distance measurement technology.
| [
{
"created": "Tue, 10 Apr 2018 03:42:38 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Feb 2019 09:29:41 GMT",
"version": "v2"
}
] | 2019-07-17 | [
[
"Liu",
"Q. H.",
""
],
[
"Li",
"Q.",
""
],
[
"Liu",
"T. G.",
""
],
[
"Wang",
"X .",
""
]
] | The local curvature of the space produced by the Sun causes not only the perihelion precession of Mercury's elliptical orbit, but also the variations of the whole orbit, in comparison with those predicted by the Newtonian theory of gravitation. Calculations show that the gravitational major-axis contraction of the Mercury's elliptical orbit is 1.3 kilometers which can be confirmed by the present astronomical distance measurement technology. |
1805.07385 | Yuri Obukhov | Yuri N. Obukhov | Poincar\'e gauge gravity: An overview | 29 pages, Revtex, contribution to the Proceedings of the
International Conference "Geometric Foundations of Gravity" (Tartu, Estonia,
August 28-September 1, 2017) | null | 10.1142/S0219887818400054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the basics and the current status of the Poincar\'e gauge theory of
gravity. The general dynamical scheme of Poincar\'e gauge gravity (PG) is
formulated, and its physical consequences are outlined. In particular, we
discuss exact solutions with and without torsion, highlight the cosmological
aspects, and consider the probing of the spacetime geometry.
| [
{
"created": "Fri, 18 May 2018 18:34:46 GMT",
"version": "v1"
}
] | 2018-12-05 | [
[
"Obukhov",
"Yuri N.",
""
]
] | We review the basics and the current status of the Poincar\'e gauge theory of gravity. The general dynamical scheme of Poincar\'e gauge gravity (PG) is formulated, and its physical consequences are outlined. In particular, we discuss exact solutions with and without torsion, highlight the cosmological aspects, and consider the probing of the spacetime geometry. |
2107.11660 | Mario Martinez Dr. | Alba Romero-Rodriguez, Mario Martinez, Oriol Pujol\`as, Mairi
Sakellariadou, Ville Vaskonen | Search for a scalar induced stochastic gravitational wave background in
the third LIGO-Virgo observing run | 5 pages, 2 tables, 2 figures | null | 10.1103/PhysRevLett.128.051301 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Formation of primordial black holes from inflationary fluctuations is
accompanied by a scalar induced gravitational wave background. We perform a
Bayesian search of such background in the data from Advanced LIGO and Virgo's
first, second and third observing runs, parametrizing the peak in the curvature
power spectrum by a log-normal distribution. The search shows no evidence for
such a background. We place 95\% confidence level upper limits on the
integrated power of the curvature power spectrum peak which, for a narrow
width, reaches down to $0.02$ at $10^{17}\,{\rm Mpc}^{-1}$. The resulting
constraints are stronger than those arising from BBN or CMB observations. In
addition, we find that LIGO and Virgo, at its design sensitivity, and the
Einstein Telescope can compete with the constraints related to the abundance of
the formed primordial black holes.
| [
{
"created": "Sat, 24 Jul 2021 17:43:20 GMT",
"version": "v1"
}
] | 2022-02-16 | [
[
"Romero-Rodriguez",
"Alba",
""
],
[
"Martinez",
"Mario",
""
],
[
"Pujolàs",
"Oriol",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Vaskonen",
"Ville",
""
]
] | Formation of primordial black holes from inflationary fluctuations is accompanied by a scalar induced gravitational wave background. We perform a Bayesian search of such background in the data from Advanced LIGO and Virgo's first, second and third observing runs, parametrizing the peak in the curvature power spectrum by a log-normal distribution. The search shows no evidence for such a background. We place 95\% confidence level upper limits on the integrated power of the curvature power spectrum peak which, for a narrow width, reaches down to $0.02$ at $10^{17}\,{\rm Mpc}^{-1}$. The resulting constraints are stronger than those arising from BBN or CMB observations. In addition, we find that LIGO and Virgo, at its design sensitivity, and the Einstein Telescope can compete with the constraints related to the abundance of the formed primordial black holes. |
1207.4500 | Norman G\"urlebeck | Norman G\"urlebeck | Source integrals for multipole moments in static and axially symmetric
spacetimes | 16 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we derive source integrals for multipole moments in axially
symmetric and static spacetimes. The multipole moments can be read off the
asymptotics of the metric close to spatial infinity in a hypersurface, which is
orthogonal to the timelike Killing vector. Whereas for the evaluation of the
source integrals the geometry needs to be known in a compact region of this
hypersurface, which encloses all source, i.e. matter as well as singularities.
The source integrals can be written either as volume integrals over such a
region or in quasi-local form as integrals over the surface of that region.
| [
{
"created": "Wed, 18 Jul 2012 20:37:14 GMT",
"version": "v1"
}
] | 2012-07-20 | [
[
"Gürlebeck",
"Norman",
""
]
] | In this article, we derive source integrals for multipole moments in axially symmetric and static spacetimes. The multipole moments can be read off the asymptotics of the metric close to spatial infinity in a hypersurface, which is orthogonal to the timelike Killing vector. Whereas for the evaluation of the source integrals the geometry needs to be known in a compact region of this hypersurface, which encloses all source, i.e. matter as well as singularities. The source integrals can be written either as volume integrals over such a region or in quasi-local form as integrals over the surface of that region. |
2307.05576 | Athira Sasidharan | Athira Sasidharan, Titus K Mathew | Constraining the bulk viscous coefficients in a viscous universe with
cosmological constant | 12 pages 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider dissipative effects in $\Lambda$CDM model, i.e., we
consider a universe with cosmological constant having viscous matter. We assume
the most general form for bulk viscous coefficient,
$\zeta=\zeta_{0}+\zeta_{1}\frac{\dot{a}}{a}+\zeta_{2}\frac{\ddot{a}}{\dot{a}}$
and obtained various constrains for $\zeta$'s . We also studied the background
study of the model with $\zeta=\zeta_{0}$ and
$\zeta=\zeta_{1}\frac{\dot{a}}{a}$. Extracted the value of $\zeta_1$ using the
Pantheon data and also obtained its thermodynamic evolution and the age.
| [
{
"created": "Mon, 10 Jul 2023 12:19:06 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Aug 2024 12:52:44 GMT",
"version": "v2"
}
] | 2024-08-14 | [
[
"Sasidharan",
"Athira",
""
],
[
"Mathew",
"Titus K",
""
]
] | In this paper we consider dissipative effects in $\Lambda$CDM model, i.e., we consider a universe with cosmological constant having viscous matter. We assume the most general form for bulk viscous coefficient, $\zeta=\zeta_{0}+\zeta_{1}\frac{\dot{a}}{a}+\zeta_{2}\frac{\ddot{a}}{\dot{a}}$ and obtained various constrains for $\zeta$'s . We also studied the background study of the model with $\zeta=\zeta_{0}$ and $\zeta=\zeta_{1}\frac{\dot{a}}{a}$. Extracted the value of $\zeta_1$ using the Pantheon data and also obtained its thermodynamic evolution and the age. |
gr-qc/0004067 | Lucan | Miroslav Sukenik, Jozef Sima and Julius Vanko | Compatibility of the expansive nondecelerative universe model with the
Newton gravitational theory and the general theory of relativity | 2 pages, LaTex | null | null | SS-00-03 | gr-qc | null | Applying the Vaidya metrics in the model of Expansive Nondecelerative
Universe (ENU) leads to compatibility of the ENU model both with the classic
Newton gravitational theory and the general theory of relativity in weak fields
| [
{
"created": "Thu, 20 Apr 2000 07:58:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sukenik",
"Miroslav",
""
],
[
"Sima",
"Jozef",
""
],
[
"Vanko",
"Julius",
""
]
] | Applying the Vaidya metrics in the model of Expansive Nondecelerative Universe (ENU) leads to compatibility of the ENU model both with the classic Newton gravitational theory and the general theory of relativity in weak fields |
1703.05783 | Slava G. Turyshev | Slava G. Turyshev | Wave-theoretical description of the solar gravitational lens | 5 pages | Phys. Rev. D 95, 084041 (2017) | 10.1103/PhysRevD.95.084041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the propagation of electromagnetic (EM) waves in the
post-Newtonian approximation of the general theory of relativity. We consider
diffraction of EM waves in the static gravitational field of a massive
monopole. We develop a wave-theoretical description of the solar gravitational
lens (SGL) and show that with its enormous magnifying power of $\sim 10^{11}$
(for $\lambda=1~\mu$m) and angular resolution of $\lesssim 10^{-10}$ arcsec,
the SGL may be used for direct megapixel imaging of an exoplanet.
| [
{
"created": "Thu, 16 Mar 2017 18:16:00 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Apr 2017 17:00:21 GMT",
"version": "v2"
}
] | 2017-04-25 | [
[
"Turyshev",
"Slava G.",
""
]
] | We discuss the propagation of electromagnetic (EM) waves in the post-Newtonian approximation of the general theory of relativity. We consider diffraction of EM waves in the static gravitational field of a massive monopole. We develop a wave-theoretical description of the solar gravitational lens (SGL) and show that with its enormous magnifying power of $\sim 10^{11}$ (for $\lambda=1~\mu$m) and angular resolution of $\lesssim 10^{-10}$ arcsec, the SGL may be used for direct megapixel imaging of an exoplanet. |
1405.0729 | Abdul Jawad | Abdul Jawad, Antonio Pasqua and Surajit Chattopadhyay | Holographic reconstruction of $f(G)$ Gravity for scale factors
pertaining to Emergent, Logamediate and Intermediate scenarios | 12 pages, 9 figures | Eur. Phys. J. Plus 128(2013)156 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we reconstruct the holographic dark energy in the framework of
$f(G)$ modified theory of gravity, where $G$ is Gauss-Bonnet invariant. In this
context, we choose the infrared cut-off as Granda-Oliveros cut-off which is
proportional to the Hubble parameter $H$ and its first derivative with respect
to the cosmic time $t$. We reconstruct $f(G)$ model with the inclusion of HDE
and three well-known forms of the scale factor $a(t)$, i.e. the emergent, the
logamediate and the intermediate scale factors. The reconstructed model as well
as equation of state parameter are discussed numerically with the help of
graphical representation to explore the accelerated expansion of the universe.
Moreover, the stability of the models incorporating all the scale factors is
checked through squared speed of sound $v_s^2$.
| [
{
"created": "Sun, 4 May 2014 18:43:27 GMT",
"version": "v1"
}
] | 2014-05-06 | [
[
"Jawad",
"Abdul",
""
],
[
"Pasqua",
"Antonio",
""
],
[
"Chattopadhyay",
"Surajit",
""
]
] | In this paper, we reconstruct the holographic dark energy in the framework of $f(G)$ modified theory of gravity, where $G$ is Gauss-Bonnet invariant. In this context, we choose the infrared cut-off as Granda-Oliveros cut-off which is proportional to the Hubble parameter $H$ and its first derivative with respect to the cosmic time $t$. We reconstruct $f(G)$ model with the inclusion of HDE and three well-known forms of the scale factor $a(t)$, i.e. the emergent, the logamediate and the intermediate scale factors. The reconstructed model as well as equation of state parameter are discussed numerically with the help of graphical representation to explore the accelerated expansion of the universe. Moreover, the stability of the models incorporating all the scale factors is checked through squared speed of sound $v_s^2$. |
gr-qc/0611021 | Jean-Philippe Bruneton | Jean-Philippe Bruneton | The two-body problem: analytical results in a toy-model of relativistic
gravity | 7 Figures, To appear in the proceedings of Albert Einstein's Century
International Conference, Paris, France, 18-22 July | null | 10.1063/1.2399624 | null | gr-qc | null | The two body problem in a scalar theory of gravity is investigated. We focus
on the closest theory to General Relativity (GR), namely Nordstr\"om's theory
of gravity (1913). The gravitational field can be exactly solved for any
configuration of point-particles. We then derive the exact equations of motion
of two inspiraling bodies including the exact self-forces terms. We prove that
there is no innermost circular orbit (ICO) in the exact theory whereas we find
(order-dependent) ICOs if post-Newtonian (PN) truncations are used. We
construct a solution of the two body problem in an iterative (non-PN) way,
which can be viewed as a series in powers of $(v/c)^{5}$. Besides this rapid
convergence, each order also provides non-perturbative information. Starting
from a circular Newtonian-like orbit, the first iteration already yields the
4.5 PN radiation reaction. These results not only shed light on some
non-perturbative effects of relativistic gravity, but may also be useful to
test numerical codes.
| [
{
"created": "Fri, 3 Nov 2006 18:34:19 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Bruneton",
"Jean-Philippe",
""
]
] | The two body problem in a scalar theory of gravity is investigated. We focus on the closest theory to General Relativity (GR), namely Nordstr\"om's theory of gravity (1913). The gravitational field can be exactly solved for any configuration of point-particles. We then derive the exact equations of motion of two inspiraling bodies including the exact self-forces terms. We prove that there is no innermost circular orbit (ICO) in the exact theory whereas we find (order-dependent) ICOs if post-Newtonian (PN) truncations are used. We construct a solution of the two body problem in an iterative (non-PN) way, which can be viewed as a series in powers of $(v/c)^{5}$. Besides this rapid convergence, each order also provides non-perturbative information. Starting from a circular Newtonian-like orbit, the first iteration already yields the 4.5 PN radiation reaction. These results not only shed light on some non-perturbative effects of relativistic gravity, but may also be useful to test numerical codes. |
1703.07921 | Rashmi Uniyal | Ravi Shankar Kuniyal, Rashmi Uniyal, Anindya Biswas, Hemwati Nandan
and K. D. Purohit | Null Geodesics and Red-Blue Shifts of Photons Emitted from Geodesic
Particles Around a Non-Commutative Black Hole Spacetime | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the geodesic motion of massless test particles in the
background of a noncommutative geometry inspired Schwarzschild black hole. The
behaviour of effective potential is analysed in the equatorial plane and the
possible motions of massless particles (i.e. photons) for different values of
impact parameter are discussed accordingly. We have also calculated the
frequency shift of photons in this spacetime. Further, the mass parameter of a
non-commutative inspired Schwarzschild black hole is computed in terms of the
measurable redshift of photons emitted by massive particles moving along
circular geodesics in equatorial plane. It is observed that the the
gravitational field of a non-commutative inspired Schwarzschild black hole is
more attractive than the Schwarzschild black hole in General Relativity.
| [
{
"created": "Thu, 23 Mar 2017 03:50:47 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Mar 2017 08:28:56 GMT",
"version": "v2"
}
] | 2017-03-28 | [
[
"Kuniyal",
"Ravi Shankar",
""
],
[
"Uniyal",
"Rashmi",
""
],
[
"Biswas",
"Anindya",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Purohit",
"K. D.",
""
]
] | We investigate the geodesic motion of massless test particles in the background of a noncommutative geometry inspired Schwarzschild black hole. The behaviour of effective potential is analysed in the equatorial plane and the possible motions of massless particles (i.e. photons) for different values of impact parameter are discussed accordingly. We have also calculated the frequency shift of photons in this spacetime. Further, the mass parameter of a non-commutative inspired Schwarzschild black hole is computed in terms of the measurable redshift of photons emitted by massive particles moving along circular geodesics in equatorial plane. It is observed that the the gravitational field of a non-commutative inspired Schwarzschild black hole is more attractive than the Schwarzschild black hole in General Relativity. |
gr-qc/0505121 | Saulo Carneiro | Saulo Carneiro | The cosmic coincidence in Brans-Dicke cosmologies | This essay received an "honorable mention" in the 2005 Essay
Competition of the Gravity Research Foundation | Int.J.Mod.Phys.D14:2201-2206,2005 | 10.1142/S021827180500784X | null | gr-qc astro-ph | null | Among the suggested solutions to the cosmological constant problem, we find
the idea of a dynamic vacuum, with an energy density decaying with the universe
expansion. We investigate the possibility of a variation in the gravitational
constant as well, induced, at the cosmological scale, by the vacuum decay. We
consider an effective Brans-Dicke theory in the spatially flat FLRW spacetime,
finding late time solutions characterized by a constant ratio between the
matter and vacuum energy densities. By using the observed limits for the
universe age, we fix the only free parameter of our solutions, obtaining a
relative matter density in the range 0.25-0.4. In particular, for Ht = 1 we
obtain a relative matter density equals to 1/3. This constitutes a possible
explanation for another problem related to the cosmological term, the cosmic
coincidence problem.
| [
{
"created": "Mon, 23 May 2005 21:41:51 GMT",
"version": "v1"
}
] | 2011-08-17 | [
[
"Carneiro",
"Saulo",
""
]
] | Among the suggested solutions to the cosmological constant problem, we find the idea of a dynamic vacuum, with an energy density decaying with the universe expansion. We investigate the possibility of a variation in the gravitational constant as well, induced, at the cosmological scale, by the vacuum decay. We consider an effective Brans-Dicke theory in the spatially flat FLRW spacetime, finding late time solutions characterized by a constant ratio between the matter and vacuum energy densities. By using the observed limits for the universe age, we fix the only free parameter of our solutions, obtaining a relative matter density in the range 0.25-0.4. In particular, for Ht = 1 we obtain a relative matter density equals to 1/3. This constitutes a possible explanation for another problem related to the cosmological term, the cosmic coincidence problem. |
1309.2581 | Curt Cutler | Curt Cutler, Sarah Burke-Spolaor, Michele Vallisneri, Joseph Lazio and
Walid Majid | The Gravitational-Wave Discovery Space of Pulsar Timing Arrays | 12 pages, 1 figure, submitted to PRD | Phys. Rev. D 89, 042003 (2014) | 10.1103/PhysRevD.89.042003 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent years have seen a burgeoning interest in using pulsar timing arrays
(PTAs) as gravitational-wave (GW) detectors. To date, that interest has focused
mainly on three particularly promising source types: supermassive--black-hole
binaries, cosmic strings, and the stochastic background from early-Universe
phase transitions. In this paper, by contrast, our aim is to investigate the
PTA potential for discovering unanticipated sources. We derive significant
constraints on the available discovery space based solely on energetic and
statistical considerations: we show that a PTA detection of GWs at frequencies
above ~3.e-5 Hz would either be an extraordinary coincidence or violate
"cherished beliefs;" we show that for PTAs GW memory can be more detectable
than direct GWs, and that, as we consider events at ever higher redshift, the
memory effect increasingly dominates an event's total signal-to-noise ratio.
The paper includes also a simple analysis of the effects of pulsar red noise in
PTA searches, and a demonstration that the effects of periodic GWs in the 10^-8
-- 10^-4.5 Hz band would not be degenerate with small errors in standard pulsar
parameters (except in a few narrow bands).
| [
{
"created": "Tue, 10 Sep 2013 17:22:32 GMT",
"version": "v1"
}
] | 2014-02-26 | [
[
"Cutler",
"Curt",
""
],
[
"Burke-Spolaor",
"Sarah",
""
],
[
"Vallisneri",
"Michele",
""
],
[
"Lazio",
"Joseph",
""
],
[
"Majid",
"Walid",
""
]
] | Recent years have seen a burgeoning interest in using pulsar timing arrays (PTAs) as gravitational-wave (GW) detectors. To date, that interest has focused mainly on three particularly promising source types: supermassive--black-hole binaries, cosmic strings, and the stochastic background from early-Universe phase transitions. In this paper, by contrast, our aim is to investigate the PTA potential for discovering unanticipated sources. We derive significant constraints on the available discovery space based solely on energetic and statistical considerations: we show that a PTA detection of GWs at frequencies above ~3.e-5 Hz would either be an extraordinary coincidence or violate "cherished beliefs;" we show that for PTAs GW memory can be more detectable than direct GWs, and that, as we consider events at ever higher redshift, the memory effect increasingly dominates an event's total signal-to-noise ratio. The paper includes also a simple analysis of the effects of pulsar red noise in PTA searches, and a demonstration that the effects of periodic GWs in the 10^-8 -- 10^-4.5 Hz band would not be degenerate with small errors in standard pulsar parameters (except in a few narrow bands). |
1507.03993 | Sam Dolan Dr | Lu\'is C. B. Crispino, Sam R. Dolan, Atsushi Higuchi and Ednilton S.
de Oliveira | Scattering from charged black holes and supergravity | 5 pages, 1 figure | Phys. Rev. D 92, 084056 (2015) | 10.1103/PhysRevD.92.084056 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The scattering cross sections of the unpolarized electromagnetic and
gravitational waves are shown to be equal for the extreme Reissner-Nordstr\"om
black hole using $N=2$ supergravity. The conversion cross sections between the
unpolarized electromagnetic and gravitational waves are also shown to coincide.
The gravitational and electromagnetic scattering cross sections are computed
numerically for Reissner-Nordstr\"om black holes for several charge-to-mass
ratios and the coincidence between the two scattering cross sections for the
extremal case is confirmed.
| [
{
"created": "Tue, 14 Jul 2015 20:00:30 GMT",
"version": "v1"
}
] | 2015-11-04 | [
[
"Crispino",
"Luís C. B.",
""
],
[
"Dolan",
"Sam R.",
""
],
[
"Higuchi",
"Atsushi",
""
],
[
"de Oliveira",
"Ednilton S.",
""
]
] | The scattering cross sections of the unpolarized electromagnetic and gravitational waves are shown to be equal for the extreme Reissner-Nordstr\"om black hole using $N=2$ supergravity. The conversion cross sections between the unpolarized electromagnetic and gravitational waves are also shown to coincide. The gravitational and electromagnetic scattering cross sections are computed numerically for Reissner-Nordstr\"om black holes for several charge-to-mass ratios and the coincidence between the two scattering cross sections for the extremal case is confirmed. |
gr-qc/9909094 | null | Pedro F. Gonzalez-Diaz (IMAFF, CSIC, Madrid) | Generalized De Sitter Space | 10 pages, RevTex, to appear in Phys. Rev. D | Phys.Rev. D61 (2000) 024019 | 10.1103/PhysRevD.61.024019 | IMAFF-RCA-99-05 | gr-qc | null | This paper deals with some two-parameter solutions to the spherically
symmetric, vacuum Einstein equations which, we argue, are more general than de
Sitter solution. The global structure of one such spacetimes and its extension
to the multiply connected case have also been investigated. By using a
six-dimensional Minkowskian embedding as its maximal extension, we check that
the thermal properties of the considered solution in such an embedding space
are the same as those derived by the usual Euclidean method. The stability of
the generalized de Sitter space containing a black hole has been investigated
as well by introducing perturbations of the Ginsparg-Perry type in first order
approximation. It has been obtained that such a space perdures against the
effects of these perturbations.
| [
{
"created": "Thu, 30 Sep 1999 17:14:30 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gonzalez-Diaz",
"Pedro F.",
"",
"IMAFF, CSIC, Madrid"
]
] | This paper deals with some two-parameter solutions to the spherically symmetric, vacuum Einstein equations which, we argue, are more general than de Sitter solution. The global structure of one such spacetimes and its extension to the multiply connected case have also been investigated. By using a six-dimensional Minkowskian embedding as its maximal extension, we check that the thermal properties of the considered solution in such an embedding space are the same as those derived by the usual Euclidean method. The stability of the generalized de Sitter space containing a black hole has been investigated as well by introducing perturbations of the Ginsparg-Perry type in first order approximation. It has been obtained that such a space perdures against the effects of these perturbations. |
1101.3655 | Tiberiu Harko | T. Harko | Evolution of cosmological perturbations in Bose-Einstein condensate dark
matter | 11 pages, 4 figures, accepted for publication in MNRAS | Mon.Not.Roy.Astron.Soc.413: 3095-3104,2011 | 10.1111/j.1365-2966.2011.18386.x | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the global cosmological evolution and the evolution of the
density contrast in the Bose-Einstein condensate dark matter model, in the
framework of a Post-Newtonian cosmological approach. In the Bose-Einstein
model, dark matter can be described as a non-relativistic, Newtonian
gravitational condensate, whose density and pressure are related by a
barotropic equation of state. For a condensate with quartic non-linearity, the
equation of state is polytropic with index $n=1$. The basic equation describing
the evolution of the perturbations of the Bose-Einstein condensate is obtained,
and its solution is studied by using both analytical and numerical methods. The
global cosmological evolution as well as the evolution of the perturbations of
the condensate dark matter shows significant differences with respect to the
pressureless dark matter model, considered in the framework of standard
cosmology. Therefore the presence of condensate dark matter could have modified
drastically the cosmological evolution of the early universe, as well as the
large scale structure formation process.
| [
{
"created": "Wed, 19 Jan 2011 10:36:11 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Feb 2011 04:20:49 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Harko",
"T.",
""
]
] | We consider the global cosmological evolution and the evolution of the density contrast in the Bose-Einstein condensate dark matter model, in the framework of a Post-Newtonian cosmological approach. In the Bose-Einstein model, dark matter can be described as a non-relativistic, Newtonian gravitational condensate, whose density and pressure are related by a barotropic equation of state. For a condensate with quartic non-linearity, the equation of state is polytropic with index $n=1$. The basic equation describing the evolution of the perturbations of the Bose-Einstein condensate is obtained, and its solution is studied by using both analytical and numerical methods. The global cosmological evolution as well as the evolution of the perturbations of the condensate dark matter shows significant differences with respect to the pressureless dark matter model, considered in the framework of standard cosmology. Therefore the presence of condensate dark matter could have modified drastically the cosmological evolution of the early universe, as well as the large scale structure formation process. |
1312.5646 | Jeff Hnybida | Bianca Dittrich and Jeff Hnybida | Ising Model from Intertwiners | null | null | null | null | gr-qc cond-mat.stat-mech hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin networks appear in a number of areas, for instance in lattice gauge
theories and in quantum gravity. They describe the contraction of intertwiners
according to the underlying network. We show that a certain generating function
of intertwiner contractions leads to the partition function of the 2d Ising
model. This implies that the intertwiner model possesses a second order phase
transition, thus leading to a continuum limit with propagating degrees of
freedom.
| [
{
"created": "Thu, 19 Dec 2013 17:13:11 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Dec 2013 20:14:15 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Nov 2015 15:58:51 GMT",
"version": "v3"
}
] | 2015-11-24 | [
[
"Dittrich",
"Bianca",
""
],
[
"Hnybida",
"Jeff",
""
]
] | Spin networks appear in a number of areas, for instance in lattice gauge theories and in quantum gravity. They describe the contraction of intertwiners according to the underlying network. We show that a certain generating function of intertwiner contractions leads to the partition function of the 2d Ising model. This implies that the intertwiner model possesses a second order phase transition, thus leading to a continuum limit with propagating degrees of freedom. |
1712.02778 | Mikjel Thorsrud | Mikjel Thorsrud | Balancing Anisotropic Curvature with Gauge Fields in a Class of
Shear-Free Cosmological Models | 33 pages, see pages 4-7 for summary of main results. V3: matches
published version, cites V2 for more details and discussion | Class. Quantum Grav. 35 (2018) 095011 | 10.1088/1361-6382/aab65a | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a complete list of general relativistic shear-free solutions in a
class of anisotropic, spatially homogeneous and orthogonal cosmological models
containing a collection of $n$ independent $p$-form gauge fields, where
$p\in\{0,1,2,3\}$, in addition to standard $\Lambda$CDM matter fields modelled
as perfect fluids. Here a (collection of) gauge field(s) balances anisotropic
spatial curvature on the right-hand side of the shear propagation equation. The
result is a class of solutions dynamically equivalent to standard FLRW
cosmologies, with an effective curvature constant $K_{\rm{eff}}$ that depends
both on spatial curvature and the energy density of the gauge field(s). In the
case of a single gauge field ($n=1$) we show that the only spacetimes that
admit such solutions are the LRS Bianchi type III, Bianchi type VI$_0$ and
Kantowski-Sachs metric, which are dynamically equivalent to open
($K_{\rm{eff}}<0$), flat ($K_{\rm{eff}}=0$) and closed ($K_{\rm{eff}}>0$) FLRW
models, respectively. With a collection of gauge fields ($n>1$) also Bianchi
type II admits a shear-free solution ($K_{\rm{eff}}>0$). We identify the LRS
Bianchi type III solution to be the unique shear-free solution with a gauge
field Hamiltonian bounded from below in the entire class of models.
| [
{
"created": "Thu, 7 Dec 2017 18:53:34 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Mar 2018 21:22:52 GMT",
"version": "v2"
},
{
"created": "Sun, 8 Apr 2018 16:24:49 GMT",
"version": "v3"
}
] | 2018-04-10 | [
[
"Thorsrud",
"Mikjel",
""
]
] | We present a complete list of general relativistic shear-free solutions in a class of anisotropic, spatially homogeneous and orthogonal cosmological models containing a collection of $n$ independent $p$-form gauge fields, where $p\in\{0,1,2,3\}$, in addition to standard $\Lambda$CDM matter fields modelled as perfect fluids. Here a (collection of) gauge field(s) balances anisotropic spatial curvature on the right-hand side of the shear propagation equation. The result is a class of solutions dynamically equivalent to standard FLRW cosmologies, with an effective curvature constant $K_{\rm{eff}}$ that depends both on spatial curvature and the energy density of the gauge field(s). In the case of a single gauge field ($n=1$) we show that the only spacetimes that admit such solutions are the LRS Bianchi type III, Bianchi type VI$_0$ and Kantowski-Sachs metric, which are dynamically equivalent to open ($K_{\rm{eff}}<0$), flat ($K_{\rm{eff}}=0$) and closed ($K_{\rm{eff}}>0$) FLRW models, respectively. With a collection of gauge fields ($n>1$) also Bianchi type II admits a shear-free solution ($K_{\rm{eff}}>0$). We identify the LRS Bianchi type III solution to be the unique shear-free solution with a gauge field Hamiltonian bounded from below in the entire class of models. |
1312.1011 | Lap-Ming Lin | Y.-H. Sham, L.-M. Lin, P. T. Leung | Testing universal relations of neutron stars with a nonlinear
matter-gravity coupling theory | Minor changes to match the published version | Astrophys.J.781,66,2014 | 10.1088/0004-637X/781/2/66 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Due to our ignorance of the equation of state (EOS) beyond nuclear density,
there is still no unique theoretical model for neutron stars (NSs). It is
therefore surprising that universal EOS-independent relations connecting
different physical quantities of neutron stars can exist. Lau et al. [ApJ, 714,
1234 (2010)] found that the frequency of the $f$-mode oscillation, the mass,
and the moment of inertia are connected by universal relations. More recently,
Yagi and Yunes [Science, 341, 365 (2013)] discovered the I-Love-Q universal
relations among the mass, the moment of inertia, the Love number, and the
quadrupole moment. In this paper, we study these universal relations in the
Eddington-inspired Born-Infeld (EiBI) gravity. This theory differs from general
relativity (GR) significantly only at high densities due to the nonlinear
coupling between matter and gravity. It thus provides us an ideal case to test
how robust the universal relations of NSs are with respect to the change of the
gravity theory. Thanks to the apparent EOS formulation of EiBI gravity
developed recently by Delsate and Steinhoff [Phys. Rev. Lett., 109, 021101
(2012)], we are able to study the universal relations in EiBI gravity using the
same techniques as those in GR. We find that the universal relations in EiBI
gravity are essentially the same as those in GR. Our work shows that, within
the currently viable coupling constant, there exists at least one modified
gravity theory that is indistinguishable from GR in view of the unexpected
universal relations.
| [
{
"created": "Wed, 4 Dec 2013 03:20:37 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jan 2014 07:56:43 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Sham",
"Y. -H.",
""
],
[
"Lin",
"L. -M.",
""
],
[
"Leung",
"P. T.",
""
]
] | Due to our ignorance of the equation of state (EOS) beyond nuclear density, there is still no unique theoretical model for neutron stars (NSs). It is therefore surprising that universal EOS-independent relations connecting different physical quantities of neutron stars can exist. Lau et al. [ApJ, 714, 1234 (2010)] found that the frequency of the $f$-mode oscillation, the mass, and the moment of inertia are connected by universal relations. More recently, Yagi and Yunes [Science, 341, 365 (2013)] discovered the I-Love-Q universal relations among the mass, the moment of inertia, the Love number, and the quadrupole moment. In this paper, we study these universal relations in the Eddington-inspired Born-Infeld (EiBI) gravity. This theory differs from general relativity (GR) significantly only at high densities due to the nonlinear coupling between matter and gravity. It thus provides us an ideal case to test how robust the universal relations of NSs are with respect to the change of the gravity theory. Thanks to the apparent EOS formulation of EiBI gravity developed recently by Delsate and Steinhoff [Phys. Rev. Lett., 109, 021101 (2012)], we are able to study the universal relations in EiBI gravity using the same techniques as those in GR. We find that the universal relations in EiBI gravity are essentially the same as those in GR. Our work shows that, within the currently viable coupling constant, there exists at least one modified gravity theory that is indistinguishable from GR in view of the unexpected universal relations. |
1303.6402 | Hyeong-Chan Kim | Hyeong-Chan Kim | A new variable in scalar cosmology with exponential potential | 7pages, 1figure | J.Korean Phys.Soc. 63 (2013) 1675-1680 | 10.3938/jkps.63.1675 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new way describing the solution of the Einstein-scalar field
theory with exponential potential $V\propto e^{\sqrt{6}\beta \phi/M_{Pl}}$ in
spatially flat Friedmann-Robertson-Walker space-time. We introduced a new time
variable, $L$, which may vary in $[-1,1]$. The new time represents the state of
the universe clearly because the equation of state at a given time takes the
simple form, $w= -1+ 2L^2$. The universe will inflate when $|L|<1/\sqrt{3}$.
For $\beta\leq 1$, the universe ends with its evolution at $L=\beta$. This
implies that the equation of state at the end of the universe is nothing but
$w=-1+2\beta^2$. For $\beta \geq 1$, the universe ends at L=1, where the
equation of state of the universe is one. On the other hand, the universe
always begins with $w=1$ at $L=\pm 1$.
| [
{
"created": "Tue, 26 Mar 2013 08:01:56 GMT",
"version": "v1"
}
] | 2013-12-10 | [
[
"Kim",
"Hyeong-Chan",
""
]
] | We present a new way describing the solution of the Einstein-scalar field theory with exponential potential $V\propto e^{\sqrt{6}\beta \phi/M_{Pl}}$ in spatially flat Friedmann-Robertson-Walker space-time. We introduced a new time variable, $L$, which may vary in $[-1,1]$. The new time represents the state of the universe clearly because the equation of state at a given time takes the simple form, $w= -1+ 2L^2$. The universe will inflate when $|L|<1/\sqrt{3}$. For $\beta\leq 1$, the universe ends with its evolution at $L=\beta$. This implies that the equation of state at the end of the universe is nothing but $w=-1+2\beta^2$. For $\beta \geq 1$, the universe ends at L=1, where the equation of state of the universe is one. On the other hand, the universe always begins with $w=1$ at $L=\pm 1$. |
1905.12433 | Mohit Sharma | Mohit Kumar Sharma, Kairat Myrzakulov, Mudhahir Al Ajmi | Curvaton: Perturbations and reheating | Accepted for publication in MPLA | null | 10.1142/S0217732320502594 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study chaotic and runaway potential inflationary models in the curvaton
scenario. In particular, we address the issue of large tensor-to-scalar ratio
and red-tilted spectrum in chaotic models and reheating in runaway model in the
light of latest Planck results. We show that curvaton can easily circumvent
these problems and is well applicable to both type of models. For chaotic
models, the observable non-Gaussianity put strong constraints on the decay
epoch of curvaton as well as on its field value around the horizon exit.
Besides, it can also explain the observed red-tilt in the spectrum as a
consequence of its negative mass-squared value. As for the runaway inflationary
models, curvaton by sudden decay into the background radiation provides an
efficient reheating mechanism, whereas the inflaton rolls down from its
potential and enters into the kinetic regime. To this effect, we consider the
generalized exponential potential and obtain the allowed parametric space for
model parameters. From the estimates on inflaton parameters, we constrained the
curvaton mass and then the reheating temperature. We constrained the latter for
both dominating and sub-dominating case and show that it agrees with the
nucleosynthesis constraint.
| [
{
"created": "Wed, 29 May 2019 13:31:56 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jun 2019 16:09:17 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Aug 2020 06:36:16 GMT",
"version": "v3"
}
] | 2020-08-27 | [
[
"Sharma",
"Mohit Kumar",
""
],
[
"Myrzakulov",
"Kairat",
""
],
[
"Ajmi",
"Mudhahir Al",
""
]
] | We study chaotic and runaway potential inflationary models in the curvaton scenario. In particular, we address the issue of large tensor-to-scalar ratio and red-tilted spectrum in chaotic models and reheating in runaway model in the light of latest Planck results. We show that curvaton can easily circumvent these problems and is well applicable to both type of models. For chaotic models, the observable non-Gaussianity put strong constraints on the decay epoch of curvaton as well as on its field value around the horizon exit. Besides, it can also explain the observed red-tilt in the spectrum as a consequence of its negative mass-squared value. As for the runaway inflationary models, curvaton by sudden decay into the background radiation provides an efficient reheating mechanism, whereas the inflaton rolls down from its potential and enters into the kinetic regime. To this effect, we consider the generalized exponential potential and obtain the allowed parametric space for model parameters. From the estimates on inflaton parameters, we constrained the curvaton mass and then the reheating temperature. We constrained the latter for both dominating and sub-dominating case and show that it agrees with the nucleosynthesis constraint. |
1509.02903 | Ott Vilson | Piret Kuusk, Laur Jarv and Ott Vilson | Invariant quantities in the multiscalar-tensor theories of gravitation | 11 pages, references added and updated, a few typos corrected | Int. J. Mod. Phys. A 31, 1641003 (2016) | 10.1142/S0217751X16410037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of the current paper is to study the multiscalar-tensor theories of
gravity without derivative couplings. We construct a few basic objects that are
invariant under a Weyl rescaling of the metric and transform covariantly when
the scalar fields are redefined. We introduce rules to construct further such
objects and put forward a scheme that allows to express the results obtained
either in the Einstein frame or in the Jordan frame as general ones. These so
called translation rules are used to show that the parametrized post-Newtonian
approximation results obtained in the aforementioned two frames indeed are the
same if expressed in a general frame.
| [
{
"created": "Wed, 9 Sep 2015 19:43:53 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jan 2016 14:34:25 GMT",
"version": "v2"
}
] | 2016-01-25 | [
[
"Kuusk",
"Piret",
""
],
[
"Jarv",
"Laur",
""
],
[
"Vilson",
"Ott",
""
]
] | The aim of the current paper is to study the multiscalar-tensor theories of gravity without derivative couplings. We construct a few basic objects that are invariant under a Weyl rescaling of the metric and transform covariantly when the scalar fields are redefined. We introduce rules to construct further such objects and put forward a scheme that allows to express the results obtained either in the Einstein frame or in the Jordan frame as general ones. These so called translation rules are used to show that the parametrized post-Newtonian approximation results obtained in the aforementioned two frames indeed are the same if expressed in a general frame. |
2203.16399 | Folkert Kuipers | Folkert Kuipers | Spacetime Stochasticity and Second Order Geometry | 6 pages; contribution to the proceedings of the 14th international
workshop on Lie Theory and its Applications in Physics (LT-14) | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the Schwartz-Meyer second order geometry framework and its
relevance to theories of quantum gravity that incorporate a notion of spacetime
stochasticity or quantum foam. We illustrate the framework in the context of
Nelson's stochastic quantization.
| [
{
"created": "Wed, 30 Mar 2022 15:27:49 GMT",
"version": "v1"
}
] | 2022-03-31 | [
[
"Kuipers",
"Folkert",
""
]
] | We discuss the Schwartz-Meyer second order geometry framework and its relevance to theories of quantum gravity that incorporate a notion of spacetime stochasticity or quantum foam. We illustrate the framework in the context of Nelson's stochastic quantization. |
2003.03742 | Sergey Paston | A.D. Kapustin, M.V. Ioffe, S.A. Paston | Explicit isometric embeddings of collapsing dust ball | LaTeX, 18 pages | Class. Quantum Grav. 37 (2020) 075019 | 10.1088/1361-6382/ab74f8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The work is devoted to the search for explicit isometric embeddings of a
metric corresponding to the collapse of spherically symmetric matter with the
formation of a black hole. Two approaches are considered: in the first, the
embedding is constructed for the whole manifold at once; in the second, the
idea of a junction of solutions, obtained separately for areas inside and
outside the dust ball, is used. In the framework of the first approach, a
global smooth embedding in 7D space with a signature (2 + 5) was constructed.
It corresponds to the formation of the horizon as a result of matter falling
from infinity. The second approach generally leads to an embedding in 7D space
with the signature (1 + 6). This embedding corresponds to the case when matter
flies out of a white hole with the disappearance of its horizon, after which
the radius of the dust ball reaches its maximum, and then a collapse occurs
with the formation of the horizon of a black hole. The embedding obtained is
not smooth everywhere --- it contains a kink on the edge of the dust ball, and
{also, it is} not quite global. In the particular case, when the maximum radius
of the dust ball coincides with the radius of the horizon, it is possible to
construct a global smooth embedding in a flat 6D space with a signature (1 +
5).
| [
{
"created": "Sun, 8 Mar 2020 08:24:25 GMT",
"version": "v1"
}
] | 2020-03-10 | [
[
"Kapustin",
"A. D.",
""
],
[
"Ioffe",
"M. V.",
""
],
[
"Paston",
"S. A.",
""
]
] | The work is devoted to the search for explicit isometric embeddings of a metric corresponding to the collapse of spherically symmetric matter with the formation of a black hole. Two approaches are considered: in the first, the embedding is constructed for the whole manifold at once; in the second, the idea of a junction of solutions, obtained separately for areas inside and outside the dust ball, is used. In the framework of the first approach, a global smooth embedding in 7D space with a signature (2 + 5) was constructed. It corresponds to the formation of the horizon as a result of matter falling from infinity. The second approach generally leads to an embedding in 7D space with the signature (1 + 6). This embedding corresponds to the case when matter flies out of a white hole with the disappearance of its horizon, after which the radius of the dust ball reaches its maximum, and then a collapse occurs with the formation of the horizon of a black hole. The embedding obtained is not smooth everywhere --- it contains a kink on the edge of the dust ball, and {also, it is} not quite global. In the particular case, when the maximum radius of the dust ball coincides with the radius of the horizon, it is possible to construct a global smooth embedding in a flat 6D space with a signature (1 + 5). |
1906.02498 | Pawan Joshi | pawan Joshi, Sukanta Panda | Higher Derivative Theory For Curvature Term Coupling With Scalar Field | 3 pages, No figure, Presented at XXIII DAE-BRNS High Energy Physics
Symposium | Springer Proc. Phys. 2021 | 10.1007/978-981-33-4408-2_128 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Higher order derivative theories, generally suffer from instabilities, known
as Ostrogradsky instabilities. This issue can be resolved by removing any
existing degeneracy present in such theories. We consider a model involving at
most second order derivatives of scalar field non-minimally coupled to
curvature terms. Here we perform (3+1) decomposition of Lagrangian to separate
second order time derivative form the rest. This is useful to check the
degeneracy hidden in the Lagrangian will help us to find conditions under which
Ostrogradsky instability do not appear. In our case, we find no such non
trivial conditions which can stop the appearance of the Ostrogradsky ghost.
| [
{
"created": "Thu, 6 Jun 2019 09:46:00 GMT",
"version": "v1"
}
] | 2022-03-21 | [
[
"Joshi",
"pawan",
""
],
[
"Panda",
"Sukanta",
""
]
] | Higher order derivative theories, generally suffer from instabilities, known as Ostrogradsky instabilities. This issue can be resolved by removing any existing degeneracy present in such theories. We consider a model involving at most second order derivatives of scalar field non-minimally coupled to curvature terms. Here we perform (3+1) decomposition of Lagrangian to separate second order time derivative form the rest. This is useful to check the degeneracy hidden in the Lagrangian will help us to find conditions under which Ostrogradsky instability do not appear. In our case, we find no such non trivial conditions which can stop the appearance of the Ostrogradsky ghost. |
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