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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1708.01969 | Katsuki Aoki | Katsuki Aoki and Shinji Mukohyama | Massive graviton dark matter with environment dependent mass: A natural
explanation of the dark matter-baryon ratio | 13 pages, 6 figures; v2: references added, published version | Phys. Rev. D 96, 104039 (2017) | 10.1103/PhysRevD.96.104039 | YITP-17-81, IPMU17-0106, WU-AP/1703/17 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a scenario that can naturally explain the observed dark
matter-baryon ratio in the context of bimetric theory with a chameleon field.
We introduce two additional gravitational degrees of freedom, the massive
graviton and the chameleon field, corresponding to dark matter and dark energy,
respectively. The chameleon field is assumed to be non-minimally coupled to
dark matter, i.e., the massive graviton, through the graviton mass terms. We
find that the dark matter-baryon ratio is dynamically adjusted to the observed
value due to the energy transfer by the chameleon field. As a result, the model
can explain the observed dark matter-baryon ratio independently from the
initial abundance of them.
| [
{
"created": "Mon, 7 Aug 2017 02:34:44 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Dec 2017 05:51:37 GMT",
"version": "v2"
}
] | 2017-12-18 | [
[
"Aoki",
"Katsuki",
""
],
[
"Mukohyama",
"Shinji",
""
]
] | We propose a scenario that can naturally explain the observed dark matter-baryon ratio in the context of bimetric theory with a chameleon field. We introduce two additional gravitational degrees of freedom, the massive graviton and the chameleon field, corresponding to dark matter and dark energy, respectively. The chameleon field is assumed to be non-minimally coupled to dark matter, i.e., the massive graviton, through the graviton mass terms. We find that the dark matter-baryon ratio is dynamically adjusted to the observed value due to the energy transfer by the chameleon field. As a result, the model can explain the observed dark matter-baryon ratio independently from the initial abundance of them. |
1506.04148 | Shahar Hod | Shahar Hod | Eigenvalue spectrum of the spheroidal harmonics: A uniform asymptotic
analysis | 5 pages | Physics Letters B 746, 365 (2015) | 10.1016/j.physletb.2015.05.036 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spheroidal harmonics $S_{lm}(\theta;c)$ have attracted the attention of
both physicists and mathematicians over the years. These special functions play
a central role in the mathematical description of diverse physical phenomena,
including black-hole perturbation theory and wave scattering by nonspherical
objects. The asymptotic eigenvalues $\{A_{lm}(c)\}$ of these functions have
been determined by many authors. However, it should be emphasized that all
previous asymptotic analyzes were restricted either to the regime $m\to\infty$
with a fixed value of $c$, or to the complementary regime $|c|\to\infty$ with a
fixed value of $m$. A fuller understanding of the asymptotic behavior of the
eigenvalue spectrum requires an analysis which is asymptotically uniform in
both $m$ and $c$. In this paper we analyze the asymptotic eigenvalue spectrum
of these important functions in the double limit $m\to\infty$ and
$|c|\to\infty$ with a fixed $m/c$ ratio.
| [
{
"created": "Fri, 12 Jun 2015 20:00:31 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Hod",
"Shahar",
""
]
] | The spheroidal harmonics $S_{lm}(\theta;c)$ have attracted the attention of both physicists and mathematicians over the years. These special functions play a central role in the mathematical description of diverse physical phenomena, including black-hole perturbation theory and wave scattering by nonspherical objects. The asymptotic eigenvalues $\{A_{lm}(c)\}$ of these functions have been determined by many authors. However, it should be emphasized that all previous asymptotic analyzes were restricted either to the regime $m\to\infty$ with a fixed value of $c$, or to the complementary regime $|c|\to\infty$ with a fixed value of $m$. A fuller understanding of the asymptotic behavior of the eigenvalue spectrum requires an analysis which is asymptotically uniform in both $m$ and $c$. In this paper we analyze the asymptotic eigenvalue spectrum of these important functions in the double limit $m\to\infty$ and $|c|\to\infty$ with a fixed $m/c$ ratio. |
gr-qc/0407092 | Aleks Kleyn | Aleks Kleyn | Tidal Force in Metric-Affine Gravity | English text - 8 pages; Russian text - 9 pages | Global Journals of Science Frontier Research A, volume 13, issue
1, pages 39 - 55, 2013 | null | null | gr-qc | null | Generalization of an idea may lead to very interesting result. Learning how
torsion influences on tidal force reveals similarity between tidal equation for
geodesic and the Killing equation of second type.
The relationship between tidal acceleration, curvature and torsion gives an
opportunity to measure torsion.
| [
{
"created": "Sat, 24 Jul 2004 03:12:48 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Mar 2008 17:28:52 GMT",
"version": "v2"
}
] | 2013-02-14 | [
[
"Kleyn",
"Aleks",
""
]
] | Generalization of an idea may lead to very interesting result. Learning how torsion influences on tidal force reveals similarity between tidal equation for geodesic and the Killing equation of second type. The relationship between tidal acceleration, curvature and torsion gives an opportunity to measure torsion. |
0801.1334 | Jonathan Feng | Jonathan L. Feng | Collider Physics and Cosmology | 14 pages, plenary talk presented at the 18th International Conference
on General Relativity and Gravitation (GRG18) and the 7th Edoardo Amaldi
Conference on Gravitational Waves (Amaldi7), Sydney, Australia, 8-14 July
2007; published version | Class.Quant.Grav.25:114003,2008 | 10.1088/0264-9381/25/11/114003 | UCI-TR-2008-2 | gr-qc astro-ph.CO hep-ex | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the coming year, the Large Hadron Collider will begin colliding protons at
energies nearly an order of magnitude beyond the current frontier. The LHC
will, of course, provide unprecedented opportunities to discover new particle
physics. Less well-known, however, is that the LHC may also provide insights
about gravity and the early universe. I review some of these connections,
focusing on the topics of dark matter and dark energy, and highlight
outstanding prospects for breakthroughs at the interface of particle physics
and cosmology.
| [
{
"created": "Tue, 8 Jan 2008 23:36:03 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Jul 2008 18:25:17 GMT",
"version": "v2"
}
] | 2009-08-12 | [
[
"Feng",
"Jonathan L.",
""
]
] | In the coming year, the Large Hadron Collider will begin colliding protons at energies nearly an order of magnitude beyond the current frontier. The LHC will, of course, provide unprecedented opportunities to discover new particle physics. Less well-known, however, is that the LHC may also provide insights about gravity and the early universe. I review some of these connections, focusing on the topics of dark matter and dark energy, and highlight outstanding prospects for breakthroughs at the interface of particle physics and cosmology. |
1212.1103 | Stefanos Aretakis | Stefanos Aretakis | A note on instabilities of extremal black holes under scalar
perturbations from afar | 14 pages, 8 figures | Class. Quantum Grav. 30 (2013) 095010 | 10.1088/0264-9381/30/9/095010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In previous work of the author it was shown that instabilities of solutions
to the wave equation develop asymptotically along the event horizon of extremal
Kerr provided a certain expression H of the initial data is non-trivial on the
horizon. In this note we remove this restriction by showing that instabilities
develop even from initial data supported arbitrarily far away from the horizon
(for which, in particular, H=0). The latter instabilities concern one order
higher derivatives compared to the case where H is non-zero. The result also
applies to extremal Reissner-Nordstrom. This note was motivated by numerical
analysis of Lucietti, Murata, Reall and Tanahashi.
| [
{
"created": "Wed, 5 Dec 2012 17:19:07 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Apr 2013 20:28:33 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Aretakis",
"Stefanos",
""
]
] | In previous work of the author it was shown that instabilities of solutions to the wave equation develop asymptotically along the event horizon of extremal Kerr provided a certain expression H of the initial data is non-trivial on the horizon. In this note we remove this restriction by showing that instabilities develop even from initial data supported arbitrarily far away from the horizon (for which, in particular, H=0). The latter instabilities concern one order higher derivatives compared to the case where H is non-zero. The result also applies to extremal Reissner-Nordstrom. This note was motivated by numerical analysis of Lucietti, Murata, Reall and Tanahashi. |
1802.04438 | Marcus Khuri | Jaroslaw S. Jaracz, Marcus A. Khuri | Bekenstein Bounds, Penrose Inequalities, and Black Hole Formation | 10 pages | Phys. Rev. D 97, 124026 (2018) | 10.1103/PhysRevD.97.124026 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A universal geometric inequality for bodies relating energy, size, angular
momentum, and charge is naturally implied by Bekenstein's entropy bounds. We
establish versions of this inequality for axisymmetric bodies satisfying
appropriate energy conditions, thus lending credence to the most general form
of Bekenstein's bound. Similar techniques are then used to prove a Penrose-like
inequality in which the ADM energy is bounded from below in terms of horizon
area, angular momentum, and charge. Lastly, new criteria for the formation of
black holes is presented involving concentration of angular momentum, charge,
and nonelectromagnetic matter energy.
| [
{
"created": "Tue, 13 Feb 2018 02:23:09 GMT",
"version": "v1"
}
] | 2018-06-20 | [
[
"Jaracz",
"Jaroslaw S.",
""
],
[
"Khuri",
"Marcus A.",
""
]
] | A universal geometric inequality for bodies relating energy, size, angular momentum, and charge is naturally implied by Bekenstein's entropy bounds. We establish versions of this inequality for axisymmetric bodies satisfying appropriate energy conditions, thus lending credence to the most general form of Bekenstein's bound. Similar techniques are then used to prove a Penrose-like inequality in which the ADM energy is bounded from below in terms of horizon area, angular momentum, and charge. Lastly, new criteria for the formation of black holes is presented involving concentration of angular momentum, charge, and nonelectromagnetic matter energy. |
1407.7246 | Ivica Smoli\'c | Benjamin Mesi\'c, Ivica Smoli\'c | Symmetry Inheritance and Jebsen-Birkhoff Theorem | 9 pages; v2: several comments and references added | null | null | ZTF-EP-14-11 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the Jebsen-Birkhoff theorem is valid for vacuum solutions to
Einstein's equation, as well as some of its generalizations. Using symmetry
inheritance properties we investigate in detail the additional constraints that
fields have to satisfy in order to allow the Jebsen-Birkhoff theorem in the
non-vacuum cases of a wide class of gravitational field equations.
| [
{
"created": "Sun, 27 Jul 2014 15:28:45 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Aug 2014 20:01:42 GMT",
"version": "v2"
}
] | 2014-08-20 | [
[
"Mesić",
"Benjamin",
""
],
[
"Smolić",
"Ivica",
""
]
] | It is known that the Jebsen-Birkhoff theorem is valid for vacuum solutions to Einstein's equation, as well as some of its generalizations. Using symmetry inheritance properties we investigate in detail the additional constraints that fields have to satisfy in order to allow the Jebsen-Birkhoff theorem in the non-vacuum cases of a wide class of gravitational field equations. |
1807.11875 | Fil Simovic | Fil Simovic and Robert. B. Mann | Critical Phenomena of Charged de Sitter Black Holes in Cavities | 19 pages, 7 figures | null | 10.1088/1361-6382/aaf445 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | We examine the thermodynamic behaviour of four-dimensional charged and
uncharged de Sitter black holes enclosed in an isothermal cavity, in the
extended phase space where the cosmological constant is treated as a
thermodynamic pressure. We demonstrate the presence of a novel
pressure-dependent phase transition in a compact region of phase space that
does not appear in asymptotically anti-de Sitter black holes, and find a highly
non-linear equation of state that does not lead to the usual interpretation of
a van der Waals fluid.
| [
{
"created": "Tue, 31 Jul 2018 15:38:51 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Simovic",
"Fil",
""
],
[
"Mann",
"Robert. B.",
""
]
] | We examine the thermodynamic behaviour of four-dimensional charged and uncharged de Sitter black holes enclosed in an isothermal cavity, in the extended phase space where the cosmological constant is treated as a thermodynamic pressure. We demonstrate the presence of a novel pressure-dependent phase transition in a compact region of phase space that does not appear in asymptotically anti-de Sitter black holes, and find a highly non-linear equation of state that does not lead to the usual interpretation of a van der Waals fluid. |
1506.01676 | Ahmad Sheykhi | S. Ghaffari, M. H. Dehghani, A. Sheykhi | Holographic dark energy in the DGP braneworld with GO cutoff | 13 pages | Phys Rev D 89 (2014) 123009 | 10.1103/PhysRevD.89.123009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the holographic dark energy (HDE) model in the framework of DGP
braneworld with Granda-Oliveros infrared (IR) cutoff, $L=(\alpha \dot{H}+\beta
H^2)^{-1/2}$. With this choice for IR cutoff, we are able to derive evolution
of the cosmological parameters such as the equation of state and the
deceleration parameters, $w$ and $q$, as the functions of the redshift
parameter $z$. As far as we know, most previous models of HDE presented in the
literatures, do not gives analytically $\omega=\omega(z)$ and $q=q(z)$. We plot
the evolution of these parameters versus $z$ and discuss that the results are
compatible with the recent observations. With suitably choosing the parameters,
this model can exhibit a transition from deceleration to the acceleration
around $z\approx 0.6$. Then, we suggest a correspondence between the
quintessence and tachyon scalar fields and HDE in the framework of DGP
braneworld. This correspondence allows us to reconstruct the evolution of the
scalar fields and the scalar potentials. We also investigate stability of the
presented model by calculating the squared sound speed, $v^2_s$, whose sign
determines the stability of the model. Our study shows that $v^2_s$ could be
positive provided the parameters of the model are chosen suitably. In
particular, for $\alpha>1$, $\beta>0$, and $\alpha<1$, $\beta<0$, we have
$v^2_s>0$ during the history of the universe, and so the stable dark energy
dominated universe can be achieved. This is in contrast to the HDE in standard
cosmology, which is unstable against background perturbations and so cannot
lead to a stable dark energy dominated universe.
| [
{
"created": "Wed, 15 Apr 2015 17:23:25 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Ghaffari",
"S.",
""
],
[
"Dehghani",
"M. H.",
""
],
[
"Sheykhi",
"A.",
""
]
] | We consider the holographic dark energy (HDE) model in the framework of DGP braneworld with Granda-Oliveros infrared (IR) cutoff, $L=(\alpha \dot{H}+\beta H^2)^{-1/2}$. With this choice for IR cutoff, we are able to derive evolution of the cosmological parameters such as the equation of state and the deceleration parameters, $w$ and $q$, as the functions of the redshift parameter $z$. As far as we know, most previous models of HDE presented in the literatures, do not gives analytically $\omega=\omega(z)$ and $q=q(z)$. We plot the evolution of these parameters versus $z$ and discuss that the results are compatible with the recent observations. With suitably choosing the parameters, this model can exhibit a transition from deceleration to the acceleration around $z\approx 0.6$. Then, we suggest a correspondence between the quintessence and tachyon scalar fields and HDE in the framework of DGP braneworld. This correspondence allows us to reconstruct the evolution of the scalar fields and the scalar potentials. We also investigate stability of the presented model by calculating the squared sound speed, $v^2_s$, whose sign determines the stability of the model. Our study shows that $v^2_s$ could be positive provided the parameters of the model are chosen suitably. In particular, for $\alpha>1$, $\beta>0$, and $\alpha<1$, $\beta<0$, we have $v^2_s>0$ during the history of the universe, and so the stable dark energy dominated universe can be achieved. This is in contrast to the HDE in standard cosmology, which is unstable against background perturbations and so cannot lead to a stable dark energy dominated universe. |
1106.1021 | Yi Pan | Yi Pan, Alessandra Buonanno, Michael Boyle, Luisa T. Buchman, Lawrence
E. Kidder, Harald P. Pfeiffer, Mark A. Scheel | Inspiral-merger-ringdown multipolar waveforms of nonspinning black-hole
binaries using the effective-one-body formalism | 26 pages, 25 figures, published Phys. Rev. D version | null | 10.1103/PhysRevD.84.124052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calibrate an effective-one-body (EOB) model to numerical-relativity
simulations of mass ratios 1, 2, 3, 4, and 6, by maximizing phase and amplitude
agreement of the leading (2,2) mode and of the subleading modes (2,1), (3,3),
(4,4) and (5,5). Aligning the calibrated EOB waveforms and the numerical
waveforms at low frequency, the phase difference of the (2,2) mode between
model and numerical simulation remains below 0.1 rad throughout the evolution
for all mass ratios considered. The fractional amplitude difference at peak
amplitude of the (2,2) mode is 2% and grows to 12% during the ringdown. Using
the Advanced LIGO noise curve we study the effectualness and measurement
accuracy of the EOB model, and stress the relevance of modeling the
higher-order modes for parameter estimation. We find that the effectualness,
measured by the mismatch, between the EOB and numerical-relativity
polarizations which include only the (2,2) mode is smaller than 0.2% for
binaries with total mass 20-200 Msun and mass ratios 1, 2, 3, 4, and 6. When
numerical-relativity polarizations contain the strongest seven modes, and
stellar-mass black holes with masses less than 50Msun are considered, the
mismatch for mass ratio 6 (1) can be as high as 5% (0.2%) when only the EOB
(2,2) mode is included, and an upper bound of the mismatch is 0.5% (0.07%) when
all the four subleading EOB modes calibrated in this paper are taken into
account. For binaries with intermediate-mass black holes with masses greater
than 50Msun the mismatches are larger. We also determine for which
signal-to-noise ratios the EOB model developed here can be used to measure
binary parameters with systematic biases smaller than statistical errors due to
detector noise.
| [
{
"created": "Mon, 6 Jun 2011 11:19:50 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Mar 2012 23:33:06 GMT",
"version": "v2"
}
] | 2013-05-29 | [
[
"Pan",
"Yi",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Boyle",
"Michael",
""
],
[
"Buchman",
"Luisa T.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
... | We calibrate an effective-one-body (EOB) model to numerical-relativity simulations of mass ratios 1, 2, 3, 4, and 6, by maximizing phase and amplitude agreement of the leading (2,2) mode and of the subleading modes (2,1), (3,3), (4,4) and (5,5). Aligning the calibrated EOB waveforms and the numerical waveforms at low frequency, the phase difference of the (2,2) mode between model and numerical simulation remains below 0.1 rad throughout the evolution for all mass ratios considered. The fractional amplitude difference at peak amplitude of the (2,2) mode is 2% and grows to 12% during the ringdown. Using the Advanced LIGO noise curve we study the effectualness and measurement accuracy of the EOB model, and stress the relevance of modeling the higher-order modes for parameter estimation. We find that the effectualness, measured by the mismatch, between the EOB and numerical-relativity polarizations which include only the (2,2) mode is smaller than 0.2% for binaries with total mass 20-200 Msun and mass ratios 1, 2, 3, 4, and 6. When numerical-relativity polarizations contain the strongest seven modes, and stellar-mass black holes with masses less than 50Msun are considered, the mismatch for mass ratio 6 (1) can be as high as 5% (0.2%) when only the EOB (2,2) mode is included, and an upper bound of the mismatch is 0.5% (0.07%) when all the four subleading EOB modes calibrated in this paper are taken into account. For binaries with intermediate-mass black holes with masses greater than 50Msun the mismatches are larger. We also determine for which signal-to-noise ratios the EOB model developed here can be used to measure binary parameters with systematic biases smaller than statistical errors due to detector noise. |
1911.02143 | Yosuke Mishima | Yosuke Mishima, Tsutomu Kobayashi | Revisiting slow-roll dynamics and the tensor tilt in general
single-field inflation | 7 pages + appendix, 2 figures, v2: Matches published version in PRD,
references added | Phys. Rev. D 101, 043536 (2020) | 10.1103/PhysRevD.101.043536 | RUP-19-30 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the possibility of a blue-tilted gravitational wave spectrum from
potential-driven slow-roll inflation in the Horndeski theory. In Kamada et al.
(2012), it was claimed that a blue gravitational wave spectrum cannot be
obtained from stable potential-driven slow-roll inflation within the Horndeski
framework. However, it has been demonstrated that the spectrum of primordial
gravitational waves can be blue in inflation with the Gauss-Bonnet term, where
the potential term is dominant and slow-roll conditions as well as the
stability conditions are satisfied. To fill in this gap, we clarify where the
discrepancy is coming from. We extend the formulation of Kamada et al. (2012)
and show that a blue gravitational wave spectrum can certainly be generated
from stable slow-roll inflation if some of the conditions previously imposed on
the form of the free functions in the Lagrangian are relaxed.
| [
{
"created": "Tue, 5 Nov 2019 23:43:41 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Feb 2020 16:48:55 GMT",
"version": "v2"
}
] | 2020-03-02 | [
[
"Mishima",
"Yosuke",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] | We explore the possibility of a blue-tilted gravitational wave spectrum from potential-driven slow-roll inflation in the Horndeski theory. In Kamada et al. (2012), it was claimed that a blue gravitational wave spectrum cannot be obtained from stable potential-driven slow-roll inflation within the Horndeski framework. However, it has been demonstrated that the spectrum of primordial gravitational waves can be blue in inflation with the Gauss-Bonnet term, where the potential term is dominant and slow-roll conditions as well as the stability conditions are satisfied. To fill in this gap, we clarify where the discrepancy is coming from. We extend the formulation of Kamada et al. (2012) and show that a blue gravitational wave spectrum can certainly be generated from stable slow-roll inflation if some of the conditions previously imposed on the form of the free functions in the Lagrangian are relaxed. |
1607.04252 | Mich\`ele Levi | Mich\`ele Levi, Jan Steinhoff | Complete conservative dynamics for inspiralling compact binaries with
spins at the fourth post-Newtonian order | 23 pages, published | JCAP 2109 (2021) 029 | 10.1088/1475-7516/2021/09/029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we complete the spin-dependent conservative dynamics of
inspiralling compact binaries at the fourth post-Newtonian order, and in
particular the derivation of the next-to-next-to-leading order spin-squared
interaction potential. We derive the physical equations of motion of the
position and the spin from a direct variation of the action. Further, we derive
the quadratic-in-spin Hamiltonians, as well as their expressions in the
center-of-mass frame. We construct the conserved integrals of motion, which
form the Poincar\'e algebra. This construction provided a consistency check for
the validity of our result, which is crucial in particular in the current
absence of another independent derivation of the next-to-next-to-leading order
spin-squared interaction. Finally, we provide here the complete gauge-invariant
relations among the binding energy, angular momentum, and orbital frequency of
an inspiralling binary with generic compact spinning components to the fourth
post-Newtonian order. These high post-Newtonian orders, in particular taking
into account the spins of the binary constituents, will enable to gain more
accurate information on the constituents from even more sensitive
gravitational-wave detections to come.
| [
{
"created": "Thu, 14 Jul 2016 19:19:16 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Sep 2021 16:23:54 GMT",
"version": "v2"
}
] | 2021-09-23 | [
[
"Levi",
"Michèle",
""
],
[
"Steinhoff",
"Jan",
""
]
] | In this work we complete the spin-dependent conservative dynamics of inspiralling compact binaries at the fourth post-Newtonian order, and in particular the derivation of the next-to-next-to-leading order spin-squared interaction potential. We derive the physical equations of motion of the position and the spin from a direct variation of the action. Further, we derive the quadratic-in-spin Hamiltonians, as well as their expressions in the center-of-mass frame. We construct the conserved integrals of motion, which form the Poincar\'e algebra. This construction provided a consistency check for the validity of our result, which is crucial in particular in the current absence of another independent derivation of the next-to-next-to-leading order spin-squared interaction. Finally, we provide here the complete gauge-invariant relations among the binding energy, angular momentum, and orbital frequency of an inspiralling binary with generic compact spinning components to the fourth post-Newtonian order. These high post-Newtonian orders, in particular taking into account the spins of the binary constituents, will enable to gain more accurate information on the constituents from even more sensitive gravitational-wave detections to come. |
1504.02433 | Yeinzon Rodriguez Garcia Dr. | Jose F. Rodriguez (1), Yeinzon Rodriguez (1,2) ((1) Universidad
Industrial de Santander, (2) Universidad Antonio Narino) | Analysis of Vector-Inflation Models Using Dynamical Systems | LaTeX file in elsarticle style, 4 pages, 1 figure. To be published in
Nuclear Physics B Proceedings Supplement as the proceedings of the Tenth
Latin American Symposium on High Energy Physics (Medellin - Colombia,
24th-28th November, 2014) | Nucl.Part.Phys.Proc. 267-269: 257-259, 2015 | 10.1016/j.nuclphysbps.2015.10.115 | PI/UAN-2015-582FT | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze two possible vector-field models using the techniques of dynamical
systems. The first model involves a U(1)-vector field and the second a triad of
SU(2)-vector fields. Both models include a gauge-fixing term and a power-law
potential. A dynamical system is formulated and it is found that one of the
critical points, for each model, corresponds to inflation, the origin of these
critical points being the respective gauge-fixing terms. The conditions for the
existence of an inflationary era which lasts for at least 60 efolds are
studied.
| [
{
"created": "Tue, 7 Apr 2015 20:57:11 GMT",
"version": "v1"
}
] | 2015-12-11 | [
[
"Rodriguez",
"Jose F.",
""
],
[
"Rodriguez",
"Yeinzon",
""
]
] | We analyze two possible vector-field models using the techniques of dynamical systems. The first model involves a U(1)-vector field and the second a triad of SU(2)-vector fields. Both models include a gauge-fixing term and a power-law potential. A dynamical system is formulated and it is found that one of the critical points, for each model, corresponds to inflation, the origin of these critical points being the respective gauge-fixing terms. The conditions for the existence of an inflationary era which lasts for at least 60 efolds are studied. |
2309.08645 | Chiranjeeb Singha | Chiranjeeb Singha, Pritam Nanda, Pabitra Tripathy | Hawking temperature of black holes with multiple horizons | 16 pages, accepted for publication in General Relativity and
Gravitation | null | 10.1007/s10714-023-03154-z | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | There are several well-established methods for computing thermodynamics in
single-horizon spacetimes. However, understanding thermodynamics becomes
particularly important when dealing with spacetimes with multiple horizons.
Multiple horizons raise questions about the existence of a global temperature
for such spacetimes. Recent studies highlight the significant role played by
the contribution of all the horizons in determining Hawking temperature. Here
we explore the Hawking temperature of a rotating and charged black hole in four
spacetime dimensions and a rotating BTZ black hole. We also find that each
horizon of those black holes contributes to the Hawking temperature. The
effective Hawking temperature for a four-dimensional rotating and charged black
hole depends only on its mass. This temperature is the same as the Hawking
temperature of a Schwarzschild black hole. In contrast, the effective Hawking
temperature depends on the black hole mass and angular momentum for a rotating
BTZ hole.
| [
{
"created": "Fri, 15 Sep 2023 09:29:15 GMT",
"version": "v1"
}
] | 2023-09-29 | [
[
"Singha",
"Chiranjeeb",
""
],
[
"Nanda",
"Pritam",
""
],
[
"Tripathy",
"Pabitra",
""
]
] | There are several well-established methods for computing thermodynamics in single-horizon spacetimes. However, understanding thermodynamics becomes particularly important when dealing with spacetimes with multiple horizons. Multiple horizons raise questions about the existence of a global temperature for such spacetimes. Recent studies highlight the significant role played by the contribution of all the horizons in determining Hawking temperature. Here we explore the Hawking temperature of a rotating and charged black hole in four spacetime dimensions and a rotating BTZ black hole. We also find that each horizon of those black holes contributes to the Hawking temperature. The effective Hawking temperature for a four-dimensional rotating and charged black hole depends only on its mass. This temperature is the same as the Hawking temperature of a Schwarzschild black hole. In contrast, the effective Hawking temperature depends on the black hole mass and angular momentum for a rotating BTZ hole. |
0904.0568 | Francesco Cianfrani dr | Giovanni Montani, Nakia Carlevaro, Francesco Cianfrani and Valentino
Lacquaniti | Perspectives in Cosmology, Gravitation and Multidimensions | 9 pages, Proceedings of The 3rd Stueckelberg Workshop on Relativistic
Field Theories | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent developments from the activity of the CGM Group are discussed.
Cosmological implications of fundamental approaches to quantization of gravity
are presented in order to fix the main issues as well as perspectives for
future investigations. Particular attention will be devoted to the classical
and quantum features of the generic inhomogeneous Universe, to the role of
reference frame in quantum gravity, and eventually to phenomenological features
related with the Kaluza-Klein framework.
| [
{
"created": "Fri, 3 Apr 2009 13:05:58 GMT",
"version": "v1"
}
] | 2009-04-06 | [
[
"Montani",
"Giovanni",
""
],
[
"Carlevaro",
"Nakia",
""
],
[
"Cianfrani",
"Francesco",
""
],
[
"Lacquaniti",
"Valentino",
""
]
] | Recent developments from the activity of the CGM Group are discussed. Cosmological implications of fundamental approaches to quantization of gravity are presented in order to fix the main issues as well as perspectives for future investigations. Particular attention will be devoted to the classical and quantum features of the generic inhomogeneous Universe, to the role of reference frame in quantum gravity, and eventually to phenomenological features related with the Kaluza-Klein framework. |
1807.04727 | Philippe Landry | Philippe Landry and Bharat Kumar | Constraints on the moment of inertia of PSR J0737-3039A from GW170817 | 8 pages, 4 figures; matches the published version | null | 10.3847/2041-8213/aaee76 | null | gr-qc astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Continued observation of PSR J0737-3039, the double pulsar, is expected to
yield a precise determination of its primary component's moment of inertia in
the next few years. Since the moment of inertia depends sensitively on the
neutron star's internal structure, such a measurement will constrain the
equation of state of ultra-dense matter, which is believed to be universal.
Independent equation-of-state constraints have already been established by the
gravitational-wave measurement of the neutron-star tidal deformability in
GW170817. Here, using well-known universal relations among neutron star
observables, we translate the reported 90%-credible bounds on tidal
deformability into a direct constraint, $I_{\star} = 1.15^{+0.38}_{-0.24}
\times 10^{45} \text{ g cm}^2$, on the moment of inertia of PSR J0737-3039A.
Should a future astrophysical measurement of $I_{\star}$ disagree with this
prediction, it could indicate a breakdown in the universality of the
neutron-star equation of state.
| [
{
"created": "Thu, 12 Jul 2018 17:05:44 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Oct 2018 15:36:23 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Mar 2019 07:42:58 GMT",
"version": "v3"
}
] | 2019-03-13 | [
[
"Landry",
"Philippe",
""
],
[
"Kumar",
"Bharat",
""
]
] | Continued observation of PSR J0737-3039, the double pulsar, is expected to yield a precise determination of its primary component's moment of inertia in the next few years. Since the moment of inertia depends sensitively on the neutron star's internal structure, such a measurement will constrain the equation of state of ultra-dense matter, which is believed to be universal. Independent equation-of-state constraints have already been established by the gravitational-wave measurement of the neutron-star tidal deformability in GW170817. Here, using well-known universal relations among neutron star observables, we translate the reported 90%-credible bounds on tidal deformability into a direct constraint, $I_{\star} = 1.15^{+0.38}_{-0.24} \times 10^{45} \text{ g cm}^2$, on the moment of inertia of PSR J0737-3039A. Should a future astrophysical measurement of $I_{\star}$ disagree with this prediction, it could indicate a breakdown in the universality of the neutron-star equation of state. |
1404.7039 | Thomas Linz | Thomas M. Linz, John L. Friedman, Alan G. Wiseman | Self force on an accelerated particle | 54 pages, 1 figure | Phys. Rev. D 90, 024064, 2014 | 10.1103/PhysRevD.90.024064 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the singular field of an accelerated point particle (scalar
charge, electric charge or small gravitating mass) moving on an accelerated
(non-geodesic) trajectory in a generic background spacetime. Using a mode-sum
regularization scheme, we obtain explicit expressions for the self-force
regularization parameters. In the electromagnetic and gravitational case, we
use a Lorenz gauge. This work extends the work of Barack and Ori [1] who
demonstrated that the regularization parameters for a point particle in
geodesic motion in a Schwarzschild spacetime can be described solely by the
leading and subleading terms in the mode-sum (commonly known as the $A$ and $B$
terms) and that all terms of higher order in $\ell$ vanish upon summation
(later they showed the same behavior for geodesic motion in Kerr [2], [3]). We
demonstrate that these properties are universal to point particles moving
through any smooth spacetime along arbitrary (accelerated) trajectories. Our
renormalization scheme is based on, but not identical to, the Quinn-Wald
axioms. As we develop our approach, we review and extend work showing that that
different definitions of the singular field used in the literature are
equivalent to our approach. Because our approach does not assume geodesic
motion of the perturbing particle, we are able use our mode-sum formalism to
explicitly recover a well-known result: The self-force on static scalar charges
near a Schwarzschild black hole vanishes.
| [
{
"created": "Mon, 28 Apr 2014 16:17:52 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Linz",
"Thomas M.",
""
],
[
"Friedman",
"John L.",
""
],
[
"Wiseman",
"Alan G.",
""
]
] | We calculate the singular field of an accelerated point particle (scalar charge, electric charge or small gravitating mass) moving on an accelerated (non-geodesic) trajectory in a generic background spacetime. Using a mode-sum regularization scheme, we obtain explicit expressions for the self-force regularization parameters. In the electromagnetic and gravitational case, we use a Lorenz gauge. This work extends the work of Barack and Ori [1] who demonstrated that the regularization parameters for a point particle in geodesic motion in a Schwarzschild spacetime can be described solely by the leading and subleading terms in the mode-sum (commonly known as the $A$ and $B$ terms) and that all terms of higher order in $\ell$ vanish upon summation (later they showed the same behavior for geodesic motion in Kerr [2], [3]). We demonstrate that these properties are universal to point particles moving through any smooth spacetime along arbitrary (accelerated) trajectories. Our renormalization scheme is based on, but not identical to, the Quinn-Wald axioms. As we develop our approach, we review and extend work showing that that different definitions of the singular field used in the literature are equivalent to our approach. Because our approach does not assume geodesic motion of the perturbing particle, we are able use our mode-sum formalism to explicitly recover a well-known result: The self-force on static scalar charges near a Schwarzschild black hole vanishes. |
gr-qc/9906037 | Jan Sladkowski | Jan Sladkowski (Univ. of Silesia) | Strongly gravitating empty spaces | null | null | null | null | gr-qc astro-ph hep-th | null | We use various results concerning isometry groups of Riemannian and
pseudo-Riemannian manifolds to prove that there are spaces on which
differential structure can act as a source of gravitational force (Brans
conjecture). The result is important for the analysis of the possible physical
meaning of differential calculus. Possible astrophysical consequences are
discussed.
| [
{
"created": "Fri, 11 Jun 1999 09:12:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sladkowski",
"Jan",
"",
"Univ. of Silesia"
]
] | We use various results concerning isometry groups of Riemannian and pseudo-Riemannian manifolds to prove that there are spaces on which differential structure can act as a source of gravitational force (Brans conjecture). The result is important for the analysis of the possible physical meaning of differential calculus. Possible astrophysical consequences are discussed. |
1902.11242 | Piero Nicolini | Piero Nicolini, Euro Spallucci, Michael F. Wondrak | Quantum Corrected Black Holes from String T-Duality | 7 pages, 6 figures; v2 6 pages, 3 figures, in press on Phys. Lett. B | Physics Letters B 797 (2019) 134888 | 10.1016/j.physletb.2019.134888 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present some stringy corrections to black hole spacetimes
emerging from string T-duality. As a first step, we derive the static Newtonian
potential by exploiting the relation between the T-duality and the path
integral duality. We show that the intrinsic non-perturbative nature of stringy
corrections introduce an ultraviolet cutoff known as zero-point length in the
path integral duality literature. As a result, the static potential is found to
be regular. We use this result to derive a consistent black hole metric for the
spherically symmetric, electrically neutral case. It turns out that the new
spacetime is regular and is formally equivalent to the Bardeen metric, apart
from a different ultraviolet regulator. On the thermodynamics side, the Hawking
temperature admits a maximum before a cooling down phase towards a
thermodynamically stable end of the black hole evaporation process. The
findings support the idea of universality of quantum black holes.
| [
{
"created": "Thu, 28 Feb 2019 17:44:00 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Aug 2019 19:27:20 GMT",
"version": "v2"
}
] | 2019-09-10 | [
[
"Nicolini",
"Piero",
""
],
[
"Spallucci",
"Euro",
""
],
[
"Wondrak",
"Michael F.",
""
]
] | In this paper we present some stringy corrections to black hole spacetimes emerging from string T-duality. As a first step, we derive the static Newtonian potential by exploiting the relation between the T-duality and the path integral duality. We show that the intrinsic non-perturbative nature of stringy corrections introduce an ultraviolet cutoff known as zero-point length in the path integral duality literature. As a result, the static potential is found to be regular. We use this result to derive a consistent black hole metric for the spherically symmetric, electrically neutral case. It turns out that the new spacetime is regular and is formally equivalent to the Bardeen metric, apart from a different ultraviolet regulator. On the thermodynamics side, the Hawking temperature admits a maximum before a cooling down phase towards a thermodynamically stable end of the black hole evaporation process. The findings support the idea of universality of quantum black holes. |
2103.12752 | Alex Davey | Alex Davey, Oscar J. C. Dias, Paul Rodgers | Phase diagram of the charged black hole bomb system | 36 pages, 12 figures | null | 10.1007/JHEP05(2021)189 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find the phase diagram of solutions of the charged black hole bomb system.
In particular, we find the static hairy black holes of Einstein-Maxwell-Scalar
theory confined in a Minkowski box. We impose boundary conditions such that the
scalar field vanishes at and outside a cavity of constant radius. These hairy
black holes are asymptotically flat with a scalar condensate floating above the
horizon. We identify four critical scalar charges which mark significant
changes in the qualitative features of the phase diagram. When they coexist,
hairy black holes always have higher entropy than the Reissner-Nordstr\"om
black hole with the same quasilocal mass and charge. So hairy black holes are
natural candidates for the endpoint of the superradiant/near-horizon
instabilities of the black hole bomb system. We also relate hairy black holes
to the boson stars of the theory. When it has a zero horizon radius limit, the
hairy black hole family terminates on the boson star family. Finally, we find
the Israel surface tensor of the box required to confine the scalar condensate
and that it can obey suitable energy conditions.
| [
{
"created": "Tue, 23 Mar 2021 18:00:02 GMT",
"version": "v1"
}
] | 2023-01-11 | [
[
"Davey",
"Alex",
""
],
[
"Dias",
"Oscar J. C.",
""
],
[
"Rodgers",
"Paul",
""
]
] | We find the phase diagram of solutions of the charged black hole bomb system. In particular, we find the static hairy black holes of Einstein-Maxwell-Scalar theory confined in a Minkowski box. We impose boundary conditions such that the scalar field vanishes at and outside a cavity of constant radius. These hairy black holes are asymptotically flat with a scalar condensate floating above the horizon. We identify four critical scalar charges which mark significant changes in the qualitative features of the phase diagram. When they coexist, hairy black holes always have higher entropy than the Reissner-Nordstr\"om black hole with the same quasilocal mass and charge. So hairy black holes are natural candidates for the endpoint of the superradiant/near-horizon instabilities of the black hole bomb system. We also relate hairy black holes to the boson stars of the theory. When it has a zero horizon radius limit, the hairy black hole family terminates on the boson star family. Finally, we find the Israel surface tensor of the box required to confine the scalar condensate and that it can obey suitable energy conditions. |
1510.01211 | Marcony Silva Cunha | C. R. Muniz, G. Alencar, M. S. Cunha, R. R. Landim and R.N. Costa
Filho | Dependence of the Black-body Force on Spacetime Geometry and Topology | 8 pages, 5 figures. Revised version | Euro.Phys.Lett. 117,6, (2017) | 10.1209/0295-5075/117/60001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we compute the corrections to the black-body force (BBF)
potential due to spacetime geometry and topology. This recently discovered
attractive force on neutral atoms is caused by the thermal radiation emitted
from black bodies and here we investigate it in relativistic gravitational
systems with spherical and cylindrical symmetries. For some astrophysical
objects we find that the corrected black-body potential is greater than the
flat case, showing that this kind of correction can be quite relevant when
curved spaces are considered. Then we consider four cases: The Schwarzschild
spacetime, the global monopole, the non-relativistic infinity cylinder and the
static cosmic string. For the spherically symmetric case of a massive body, we
find that two corrections appear: One due to the gravitational modification of
the temperature and the other due to the modification of the solid angle
subtended by the atom. We apply the found results to a typical neutron star and
to the Sun. For the global monopole, the modification in the black-body
potential is of topological nature and it is due to the central solid angle
deficit that occurs in the spacetime generated by that object. In the
cylindrical case, which is locally flat, no gravitational correction to the
temperature exists, as in the global monopole case. However, we find the
curious fact that the BBF depends on the topology of the spacetime through the
modification of the azimuthal angle and therefore of the solid angle. For the
static cosmic string we find that the force is null for the zero thickness
case.
| [
{
"created": "Mon, 5 Oct 2015 16:23:18 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jun 2016 18:01:30 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Apr 2017 13:38:01 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Dec 2017 06:37:47 GMT",
"version": "v4"
}
] | 2017-12-18 | [
[
"Muniz",
"C. R.",
""
],
[
"Alencar",
"G.",
""
],
[
"Cunha",
"M. S.",
""
],
[
"Landim",
"R. R.",
""
],
[
"Filho",
"R. N. Costa",
""
]
] | In this paper we compute the corrections to the black-body force (BBF) potential due to spacetime geometry and topology. This recently discovered attractive force on neutral atoms is caused by the thermal radiation emitted from black bodies and here we investigate it in relativistic gravitational systems with spherical and cylindrical symmetries. For some astrophysical objects we find that the corrected black-body potential is greater than the flat case, showing that this kind of correction can be quite relevant when curved spaces are considered. Then we consider four cases: The Schwarzschild spacetime, the global monopole, the non-relativistic infinity cylinder and the static cosmic string. For the spherically symmetric case of a massive body, we find that two corrections appear: One due to the gravitational modification of the temperature and the other due to the modification of the solid angle subtended by the atom. We apply the found results to a typical neutron star and to the Sun. For the global monopole, the modification in the black-body potential is of topological nature and it is due to the central solid angle deficit that occurs in the spacetime generated by that object. In the cylindrical case, which is locally flat, no gravitational correction to the temperature exists, as in the global monopole case. However, we find the curious fact that the BBF depends on the topology of the spacetime through the modification of the azimuthal angle and therefore of the solid angle. For the static cosmic string we find that the force is null for the zero thickness case. |
2012.08551 | Vojtech Pravda | Vojtech Pravda, Alena Pravdova, Jiri Podolsky, Robert Svarc | Black holes and other spherical solutions in quadratic gravity with a
cosmological constant | 68 pages, matches the published version + contains the table of
contents | Phys. Rev. D 103, 064049 (2021) | 10.1103/PhysRevD.103.064049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study static spherically symmetric solutions to the vacuum field equations
of quadratic gravity in the presence of a cosmological constant $\Lambda$.
Motivated by the trace no-hair theorem, we assume the Ricci scalar to be
constant throughout a spacetime. Furthermore, we employ the conformal-to-Kundt
metric ansatz that is valid for all static spherically symmetric spacetimes and
leads to a considerable simplification of the field equations. We arrive at a
set of two ordinary differential equations and study its solutions using the
Frobenius-like approach of (infinite) power series expansions. While the
indicial equations considerably restrict the set of possible leading powers,
careful analysis of higher-order terms is necessary to establish the existence
of the corresponding classes of solutions. We thus obtain various non-Einstein
generalizations of the Schwarzschild, (anti-)de Sitter [or (A)dS for short],
Nariai, and Pleba\'{n}ski-Hacyan spacetimes. Interestingly, some classes of
solutions allow for an arbitrary value of $\Lambda$, while other classes admit
only discrete values of $\Lambda$. For most of these classes, we give recurrent
formulas for all series coefficients. We determine which classes contain the
Schwarzschild-(A)dS black hole as a special case and briefly discuss the
physical interpretation of the spacetimes. In the discussion of physical
properties, we naturally focus on the generalization of the Schwarzschild-(A)dS
black hole, namely the Schwarzschild-Bach-(A)dS black hole, which possesses one
additional Bach parameter. We also study its basic thermodynamical properties
and observable effects on test particles caused by the presence of the Bach
tensor. This work is a considerable extension of our letter [Phys. Rev. Lett.,
121, 231104, 2018].
| [
{
"created": "Tue, 15 Dec 2020 19:03:18 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Mar 2021 18:37:12 GMT",
"version": "v2"
}
] | 2021-03-26 | [
[
"Pravda",
"Vojtech",
""
],
[
"Pravdova",
"Alena",
""
],
[
"Podolsky",
"Jiri",
""
],
[
"Svarc",
"Robert",
""
]
] | We study static spherically symmetric solutions to the vacuum field equations of quadratic gravity in the presence of a cosmological constant $\Lambda$. Motivated by the trace no-hair theorem, we assume the Ricci scalar to be constant throughout a spacetime. Furthermore, we employ the conformal-to-Kundt metric ansatz that is valid for all static spherically symmetric spacetimes and leads to a considerable simplification of the field equations. We arrive at a set of two ordinary differential equations and study its solutions using the Frobenius-like approach of (infinite) power series expansions. While the indicial equations considerably restrict the set of possible leading powers, careful analysis of higher-order terms is necessary to establish the existence of the corresponding classes of solutions. We thus obtain various non-Einstein generalizations of the Schwarzschild, (anti-)de Sitter [or (A)dS for short], Nariai, and Pleba\'{n}ski-Hacyan spacetimes. Interestingly, some classes of solutions allow for an arbitrary value of $\Lambda$, while other classes admit only discrete values of $\Lambda$. For most of these classes, we give recurrent formulas for all series coefficients. We determine which classes contain the Schwarzschild-(A)dS black hole as a special case and briefly discuss the physical interpretation of the spacetimes. In the discussion of physical properties, we naturally focus on the generalization of the Schwarzschild-(A)dS black hole, namely the Schwarzschild-Bach-(A)dS black hole, which possesses one additional Bach parameter. We also study its basic thermodynamical properties and observable effects on test particles caused by the presence of the Bach tensor. This work is a considerable extension of our letter [Phys. Rev. Lett., 121, 231104, 2018]. |
gr-qc/0605106 | Akihiro Ishibashi | Stefan Hollands, Akihiro Ishibashi, and Robert M. Wald | A Higher Dimensional Stationary Rotating Black Hole Must be Axisymmetric | 24 pages, no figures, v2: footnotes and references added, v3:
numerous minor revisions | Commun.Math.Phys.271:699-722,2007 | 10.1007/s00220-007-0216-4 | null | gr-qc hep-th | null | A key result in the proof of black hole uniqueness in 4-dimensions is that a
stationary black hole that is ``rotating''--i.e., is such that the stationary
Killing field is not everywhere normal to the horizon--must be axisymmetric.
The proof of this result in 4-dimensions relies on the fact that the orbits of
the stationary Killing field on the horizon have the property that they must
return to the same null geodesic generator of the horizon after a certain
period, $P$. This latter property follows, in turn, from the fact that the
cross-sections of the horizon are two-dimensional spheres. However, in
spacetimes of dimension greater than 4, it is no longer true that the orbits of
the stationary Killing field on the horizon must return to the same null
geodesic generator. In this paper, we prove that, nevertheless, a higher
dimensional stationary black hole that is rotating must be axisymmetric. No
assumptions are made concerning the topology of the horizon cross-sections
other than that they are compact. However, we assume that the horizon is
non-degenerate and, as in the 4-dimensional proof, that the spacetime is
analytic.
| [
{
"created": "Fri, 19 May 2006 19:43:21 GMT",
"version": "v1"
},
{
"created": "Tue, 30 May 2006 20:29:49 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Aug 2006 21:19:48 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Hollands",
"Stefan",
""
],
[
"Ishibashi",
"Akihiro",
""
],
[
"Wald",
"Robert M.",
""
]
] | A key result in the proof of black hole uniqueness in 4-dimensions is that a stationary black hole that is ``rotating''--i.e., is such that the stationary Killing field is not everywhere normal to the horizon--must be axisymmetric. The proof of this result in 4-dimensions relies on the fact that the orbits of the stationary Killing field on the horizon have the property that they must return to the same null geodesic generator of the horizon after a certain period, $P$. This latter property follows, in turn, from the fact that the cross-sections of the horizon are two-dimensional spheres. However, in spacetimes of dimension greater than 4, it is no longer true that the orbits of the stationary Killing field on the horizon must return to the same null geodesic generator. In this paper, we prove that, nevertheless, a higher dimensional stationary black hole that is rotating must be axisymmetric. No assumptions are made concerning the topology of the horizon cross-sections other than that they are compact. However, we assume that the horizon is non-degenerate and, as in the 4-dimensional proof, that the spacetime is analytic. |
1909.00269 | Joseph Romano | Joseph D. Romano | Searches for stochastic gravitational-wave backgrounds | Lectures for the 2018 Les Houches Summer School on Gravitational
Waves (55 pages; 31 figures). Fixed some minor typos in a few equations | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | These lecture notes provide a brief introduction to methods used to search
for a stochastic background of gravitational radiation -- a superposition of
gravitational-wave signals that are either too weak or too numerous to
individually detect. The focus of these notes is on relevant data analysis
techniques, not on the particular astrophysical or cosmological sources that
are responsible for producing the background. The lecture notes are divided
into two main parts: (i) an overview, consisting of a description of different
types of gravitational-wave backgrounds and an introduction to the method of
cross-correlating data from multiple detectors, which can be used to extract
the signal from the noise; (ii) details, extending the previous discussion to
non-trivial detector response, non-trivial overlap functions, and a recently
proposed Bayesian method to search for the gravitational-wave background
produced by stellar-mass binary black hole mergers throughout the universe.
Suggested exercises for the reader are given throughout the text, and compiled
in an appendix.
| [
{
"created": "Sat, 31 Aug 2019 19:36:17 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jul 2023 17:26:55 GMT",
"version": "v2"
}
] | 2023-07-07 | [
[
"Romano",
"Joseph D.",
""
]
] | These lecture notes provide a brief introduction to methods used to search for a stochastic background of gravitational radiation -- a superposition of gravitational-wave signals that are either too weak or too numerous to individually detect. The focus of these notes is on relevant data analysis techniques, not on the particular astrophysical or cosmological sources that are responsible for producing the background. The lecture notes are divided into two main parts: (i) an overview, consisting of a description of different types of gravitational-wave backgrounds and an introduction to the method of cross-correlating data from multiple detectors, which can be used to extract the signal from the noise; (ii) details, extending the previous discussion to non-trivial detector response, non-trivial overlap functions, and a recently proposed Bayesian method to search for the gravitational-wave background produced by stellar-mass binary black hole mergers throughout the universe. Suggested exercises for the reader are given throughout the text, and compiled in an appendix. |
0811.1011 | Emanuele Berti | K. G. Arun, Stas Babak, Emanuele Berti, Neil Cornish, Curt Cutler,
Jonathan Gair, Scott A. Hughes, Bala R. Iyer, Ryan N. Lang, Ilya Mandel,
Edward K. Porter, Bangalore S. Sathyaprakash, Siddhartha Sinha, Alicia M.
Sintes, Miquel Trias, Chris Van Den Broeck, Marta Volonteri | Massive Black Hole Binary Inspirals: Results from the LISA Parameter
Estimation Taskforce | 14 pages, 2 figures, 5 tables, minor changes to match version to be
published in the proceedings of the 7th LISA Symposium. For more information
see the Taskforce's wiki at http://www.tapir.caltech.edu/dokuwiki/lisape:home | Class.Quant.Grav.26:094027,2009 | 10.1088/0264-9381/26/9/094027 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LISA Parameter Estimation (LISAPE) Taskforce was formed in September 2007
to provide the LISA Project with vetted codes, source distribution models, and
results related to parameter estimation. The Taskforce's goal is to be able to
quickly calculate the impact of any mission design changes on LISA's science
capabilities, based on reasonable estimates of the distribution of
astrophysical sources in the universe. This paper describes our Taskforce's
work on massive black-hole binaries (MBHBs). Given present uncertainties in the
formation history of MBHBs, we adopt four different population models, based on
(i) whether the initial black-hole seeds are small or large, and (ii) whether
accretion is efficient or inefficient at spinning up the holes. We compare four
largely independent codes for calculating LISA's parameter-estimation
capabilities. All codes are based on the Fisher-matrix approximation, but in
the past they used somewhat different signal models, source parametrizations
and noise curves. We show that once these differences are removed, the four
codes give results in extremely close agreement with each other. Using a code
that includes both spin precession and higher harmonics in the
gravitational-wave signal, we carry out Monte Carlo simulations and determine
the number of events that can be detected and accurately localized in our four
population models.
| [
{
"created": "Thu, 6 Nov 2008 18:43:45 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Mar 2009 04:42:59 GMT",
"version": "v2"
}
] | 2014-11-18 | [
[
"Arun",
"K. G.",
""
],
[
"Babak",
"Stas",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Cornish",
"Neil",
""
],
[
"Cutler",
"Curt",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Hughes",
"Scott A.",
""
],
[
"Iyer",
... | The LISA Parameter Estimation (LISAPE) Taskforce was formed in September 2007 to provide the LISA Project with vetted codes, source distribution models, and results related to parameter estimation. The Taskforce's goal is to be able to quickly calculate the impact of any mission design changes on LISA's science capabilities, based on reasonable estimates of the distribution of astrophysical sources in the universe. This paper describes our Taskforce's work on massive black-hole binaries (MBHBs). Given present uncertainties in the formation history of MBHBs, we adopt four different population models, based on (i) whether the initial black-hole seeds are small or large, and (ii) whether accretion is efficient or inefficient at spinning up the holes. We compare four largely independent codes for calculating LISA's parameter-estimation capabilities. All codes are based on the Fisher-matrix approximation, but in the past they used somewhat different signal models, source parametrizations and noise curves. We show that once these differences are removed, the four codes give results in extremely close agreement with each other. Using a code that includes both spin precession and higher harmonics in the gravitational-wave signal, we carry out Monte Carlo simulations and determine the number of events that can be detected and accurately localized in our four population models. |
gr-qc/0403058 | Robert Beig | Robert Beig and Werner Krammer | Bowen-York Tensors | 12 pages, Contribution to CQG Special Issue "A Spacetime Safari:
Essays in Honour of Vincent Moncrief" | Class.Quant.Grav. 21 (2004) S73-S79 | 10.1088/0264-9381/21/3/005 | null | gr-qc | null | There is derived, for a conformally flat three-space, a family of linear
second-order partial differential operators which send vectors into tracefree,
symmetric two-tensors. These maps, which are parametrized by conformal Killing
vectors on the three-space, are such that the divergence of the resulting
tensor field depends only on the divergence of the original vector field. In
particular these maps send source-free electric fields into TT-tensors.
Moreover, if the original vector field is the Coulomb field on
$\mathbb{R}^3\backslash \lbrace0\rbrace$, the resulting tensor fields on
$\mathbb{R}^3\backslash \lbrace0\rbrace$ are nothing but the family of
TT-tensors originally written down by Bowen and York.
| [
{
"created": "Sun, 14 Mar 2004 10:33:45 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Beig",
"Robert",
""
],
[
"Krammer",
"Werner",
""
]
] | There is derived, for a conformally flat three-space, a family of linear second-order partial differential operators which send vectors into tracefree, symmetric two-tensors. These maps, which are parametrized by conformal Killing vectors on the three-space, are such that the divergence of the resulting tensor field depends only on the divergence of the original vector field. In particular these maps send source-free electric fields into TT-tensors. Moreover, if the original vector field is the Coulomb field on $\mathbb{R}^3\backslash \lbrace0\rbrace$, the resulting tensor fields on $\mathbb{R}^3\backslash \lbrace0\rbrace$ are nothing but the family of TT-tensors originally written down by Bowen and York. |
gr-qc/0102021 | Kyriakopoulos E. | E. Kyriakopoulos | B\"{a}cklund Transformations of Einstein's Field Equations for the
Interior of a Uniformly Rotating Stationary Axisymmetric Perfect Fluid | null | null | null | null | gr-qc | null | Clairin's method of obtaining B\"{a}cklund transformations is applied to
Einstein's field equations for the interior of a uniformly rotating stationary
axisymmetric perfect fluid. It is shown that for arbitrary pressure $p$ and
mass density $\mu$ the method does not give non-trivial B\"{a}cklund
transformations, while if $\mu + 3p =0$ it gives the transformation of Ehlers.
| [
{
"created": "Tue, 6 Feb 2001 09:55:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kyriakopoulos",
"E.",
""
]
] | Clairin's method of obtaining B\"{a}cklund transformations is applied to Einstein's field equations for the interior of a uniformly rotating stationary axisymmetric perfect fluid. It is shown that for arbitrary pressure $p$ and mass density $\mu$ the method does not give non-trivial B\"{a}cklund transformations, while if $\mu + 3p =0$ it gives the transformation of Ehlers. |
gr-qc/9905024 | Riuji Mochizuki | Riuji Mochizuki and Takayuki Suga | Energy Conservation and the Unruh Effect | null | null | null | null | gr-qc | null | In this paper it is explicitly demonstrated that the energy conservation law
is kept when a detector uniformly accelerated in the Minkowski vacuum is
excited and emits a particle. This fact had been hidden in conventional
approaches in which detectors were considered to be forced on trajectories. To
lift the veil we suggest a detector model written in terms of the Minkowski
coordinates. In this model the Hamiltonian of the detector involves a classical
potential term instead of the detector's fixed trajectory. The transition rate
agrees with the corresponding conventional one in the limit of an infinite mass
detector though even then the recoil remains.
| [
{
"created": "Fri, 7 May 1999 04:48:56 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Aug 1999 01:39:39 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Mochizuki",
"Riuji",
""
],
[
"Suga",
"Takayuki",
""
]
] | In this paper it is explicitly demonstrated that the energy conservation law is kept when a detector uniformly accelerated in the Minkowski vacuum is excited and emits a particle. This fact had been hidden in conventional approaches in which detectors were considered to be forced on trajectories. To lift the veil we suggest a detector model written in terms of the Minkowski coordinates. In this model the Hamiltonian of the detector involves a classical potential term instead of the detector's fixed trajectory. The transition rate agrees with the corresponding conventional one in the limit of an infinite mass detector though even then the recoil remains. |
1505.06390 | James Isenberg | James Isenberg | On Strong Cosmic Censorship | Accepted for publication in Surveys in Differential Geometry, Volume
20 | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For almost half of the one hundred year history of Einstein's theory of
general relativity, Strong Cosmic Censorship has been one of its most
intriguing conjectures. The SCC conjecture addresses the issue of the nature of
the singularities found in most solutions of Einstein's gravitational field
equations: Are such singularities generically characterized by unbounded
curvature? Is the existence of a Cauchy horizon (and the accompanying
extensions into spacetime regions in which determinism fails) an unstable
feature of solutions of Einstein's equations? In this short review article,
after briefly commenting on the history of the SCC conjecture, we survey some
of the progress made in research directed either toward supporting SCC or
toward uncovering some of its weaknesses. We focus in particular on model
versions of SCC which have been proven for restricted families of spacetimes
(e.g., the Gowdy spacetimes), and the role played by the generic presence of
Asymptotically Velocity Term Dominated behavior in these solutions. We also
note recent work on spacetimes containing weak null singularities, and their
relevance for the SCC conjecture.
| [
{
"created": "Sun, 24 May 2015 00:44:55 GMT",
"version": "v1"
}
] | 2015-05-26 | [
[
"Isenberg",
"James",
""
]
] | For almost half of the one hundred year history of Einstein's theory of general relativity, Strong Cosmic Censorship has been one of its most intriguing conjectures. The SCC conjecture addresses the issue of the nature of the singularities found in most solutions of Einstein's gravitational field equations: Are such singularities generically characterized by unbounded curvature? Is the existence of a Cauchy horizon (and the accompanying extensions into spacetime regions in which determinism fails) an unstable feature of solutions of Einstein's equations? In this short review article, after briefly commenting on the history of the SCC conjecture, we survey some of the progress made in research directed either toward supporting SCC or toward uncovering some of its weaknesses. We focus in particular on model versions of SCC which have been proven for restricted families of spacetimes (e.g., the Gowdy spacetimes), and the role played by the generic presence of Asymptotically Velocity Term Dominated behavior in these solutions. We also note recent work on spacetimes containing weak null singularities, and their relevance for the SCC conjecture. |
2311.03890 | Akira Taniguchi | Sugumi Kanno, Jiro Soda, and Akira Taniguchi | Search for high-frequency gravitational waves with Rydberg atoms | 24 pages, 6 figures | null | null | KOBE-COSMO-23-10 | gr-qc hep-ph hep-th physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose high-frequency gravitational wave (GW) detectors with Rydberg
atoms. Rydberg atoms are sensitive detectors of electric fields. By setting up
a constant magnetic field, a weak electric field is generated upon the arrival
of GWs. The weak electric field signal is then detected by an
electromagnetically induced transparency (EIT) in the system of the Rydberg
atoms. Recently, the sensitivity of the Rydberg atoms is further improved by
combining superheterodyne detection method. Hence, even the weak signal
generated by the GWs turns out to be detectable. We calculate the amplitude of
Rabi frequency of the Rydberg atoms induced by the GWs and show that the
sensitivity of the Rydberg atoms becomes maximum when the size of the Rydberg
atoms is close to the wavelength of GWs. As an example, we evaluate the
sensitivity of the GW detector with Rubidium Rydberg atoms and find that the
detector can probe GWs with a frequency 26.4 GHz and an amplitude approximately
around $10^{20}$. We argue that the sensitivity can be further enhanced by
exploiting entangled atoms.
| [
{
"created": "Tue, 7 Nov 2023 11:10:02 GMT",
"version": "v1"
}
] | 2023-11-08 | [
[
"Kanno",
"Sugumi",
""
],
[
"Soda",
"Jiro",
""
],
[
"Taniguchi",
"Akira",
""
]
] | We propose high-frequency gravitational wave (GW) detectors with Rydberg atoms. Rydberg atoms are sensitive detectors of electric fields. By setting up a constant magnetic field, a weak electric field is generated upon the arrival of GWs. The weak electric field signal is then detected by an electromagnetically induced transparency (EIT) in the system of the Rydberg atoms. Recently, the sensitivity of the Rydberg atoms is further improved by combining superheterodyne detection method. Hence, even the weak signal generated by the GWs turns out to be detectable. We calculate the amplitude of Rabi frequency of the Rydberg atoms induced by the GWs and show that the sensitivity of the Rydberg atoms becomes maximum when the size of the Rydberg atoms is close to the wavelength of GWs. As an example, we evaluate the sensitivity of the GW detector with Rubidium Rydberg atoms and find that the detector can probe GWs with a frequency 26.4 GHz and an amplitude approximately around $10^{20}$. We argue that the sensitivity can be further enhanced by exploiting entangled atoms. |
1811.03006 | Phongpichit Channuie | Khamphee Karwan (Naresuan U.), Phongpichit Channuie (Walailak U.) | Generalized Conformal Transformation and Inflationary Attractors | v2: 6 figures, version published in Phys. Rev. D | Phys. Rev. D 100, 023514 (2019) | 10.1103/PhysRevD.100.023514 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the inflationary attractors in models of inflation inspired
from general conformal transformation of general scalar-tensor theories to the
Einstein frame. The coefficient of the conformal transformation in our study
depends on both the scalar field and its kinetic term. Therefore the relevant
scalar-tensor theories display the subset of the class I of the degenerate
higher-order scalar-tensor theories in which both the scalar field and its
kinetic term can non-minimally couple to gravity. We find that if the conformal
coefficient $\Omega$ takes a multiplicative form such that $\Omega \equiv
w(\phi)W(X)$ where $X$ is the kinetic term of the field $\phi$, the theoretical
predictions of the proposed model can have usual universal attractor
independent of any functions of $W(X)$. For the case where $\Omega$ takes an
additive form, such that $\Omega \equiv w(\phi) + k(\phi) \Xi(X)$, we find that
there are new $\xi$ attractors in addition to the universal ones. We analyze
the inflationary observables of these models and compare them to the latest
constraints from the Planck collaboration. We find that the observable
quantities associated to these new $\xi$ attractors do not satisfy the
constraints from Planck data at a strong coupling limit.
| [
{
"created": "Tue, 6 Nov 2018 12:57:55 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jul 2019 13:58:49 GMT",
"version": "v2"
}
] | 2019-07-31 | [
[
"Karwan",
"Khamphee",
"",
"Naresuan U."
],
[
"Channuie",
"Phongpichit",
"",
"Walailak U."
]
] | We investigate the inflationary attractors in models of inflation inspired from general conformal transformation of general scalar-tensor theories to the Einstein frame. The coefficient of the conformal transformation in our study depends on both the scalar field and its kinetic term. Therefore the relevant scalar-tensor theories display the subset of the class I of the degenerate higher-order scalar-tensor theories in which both the scalar field and its kinetic term can non-minimally couple to gravity. We find that if the conformal coefficient $\Omega$ takes a multiplicative form such that $\Omega \equiv w(\phi)W(X)$ where $X$ is the kinetic term of the field $\phi$, the theoretical predictions of the proposed model can have usual universal attractor independent of any functions of $W(X)$. For the case where $\Omega$ takes an additive form, such that $\Omega \equiv w(\phi) + k(\phi) \Xi(X)$, we find that there are new $\xi$ attractors in addition to the universal ones. We analyze the inflationary observables of these models and compare them to the latest constraints from the Planck collaboration. We find that the observable quantities associated to these new $\xi$ attractors do not satisfy the constraints from Planck data at a strong coupling limit. |
0807.2574 | Gonzalo Garc\'ia-Reyes | Gonzalo Garc\'ia-Reyes and Guillermo A. Gonz\'alez | Rotating relativistic thin disks as sources of charged and magnetized
Kerr-NUT spacetimes | 21 pages, 4 figures, Latex | Int. J. Mod. Phys. D, Vol. 18, No. 9 (2009), pags. 1461-1481 | 10.1142/S0218271809015205 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A family of models of counterrotating and rotating relativistic thin discs of
infinite extension based on a charged and magnetized Kerr-NUT metric are
constructed using the well-known "displace, cut and reflect" method extended to
solutions of vacuum Einstein-Maxwell equations. The metric considered has as
limiting cases a charged and magnetized Taub-NUT solution and the well known
Kerr-Newman solutions. We show that for Kerr-Newman fields the eigenvalues of
the energy-momentum tensor of the disc are for all the values of the parameters
real quantities so that these discs do not present heat flow in any case,
whereas for charged and magnetized Kerr-NUT and Taub-NUT fields we find always
regions with heat flow. We also find a general constraint over the
counterrotating tangential velocities needed to cast the surface
energy-momentum tensor of the disc as the superposition of two counterrotating
charged dust fluids. We show that, in general, it is not possible to take the
two counterrotating fluids as circulating along electrogeodesics nor take the
two counterrotating tangential velocities as equal and opposite.
| [
{
"created": "Wed, 16 Jul 2008 15:14:21 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jul 2008 15:18:57 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Mar 2009 15:46:18 GMT",
"version": "v3"
},
{
"created": "Tue, 3 Mar 2009 14:01:01 GMT",
"version": "v4"
},
{
"cre... | 2015-05-13 | [
[
"García-Reyes",
"Gonzalo",
""
],
[
"González",
"Guillermo A.",
""
]
] | A family of models of counterrotating and rotating relativistic thin discs of infinite extension based on a charged and magnetized Kerr-NUT metric are constructed using the well-known "displace, cut and reflect" method extended to solutions of vacuum Einstein-Maxwell equations. The metric considered has as limiting cases a charged and magnetized Taub-NUT solution and the well known Kerr-Newman solutions. We show that for Kerr-Newman fields the eigenvalues of the energy-momentum tensor of the disc are for all the values of the parameters real quantities so that these discs do not present heat flow in any case, whereas for charged and magnetized Kerr-NUT and Taub-NUT fields we find always regions with heat flow. We also find a general constraint over the counterrotating tangential velocities needed to cast the surface energy-momentum tensor of the disc as the superposition of two counterrotating charged dust fluids. We show that, in general, it is not possible to take the two counterrotating fluids as circulating along electrogeodesics nor take the two counterrotating tangential velocities as equal and opposite. |
2301.10278 | Tiberiu Harko | Amine Bouali, Himanshu Chaudhary, Rattanasak Hama, Tiberiu Harko,
Sorin V. Sabau, Marco San Mart\'in | Cosmological tests of the osculating Barthel-Kropina dark energy model | 23 pages, 16 figures, accepted for publication in EPJC | null | 10.1140/epjc/s10052-023-11265-9 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We further investigate the dark energy model based on the Finsler geometry
inspired osculating Barthel-Kropina cosmology. The Barthel-Kropina cosmological
approach is based on the introduction of a Barthel connection in an osculating
Finsler geometry, with the connection having the property that it is the
Levi-Civita connection of a Riemannian metric. From the generalized Friedmann
equations of the Barthel-Kropina model, obtained by assuming that the
background Riemannian metric is of the Friedmann-Lemaitre-Robertson-Walker
type, an effective geometric dark energy component can be generated, with the
effective, geometric type pressure, satisfying a linear barotropic type
equation of state. The cosmological tests, and comparisons with observational
data of this dark energy model are considered in detail. To constrain the
Barthel-Kropina model parameters, and the parameter of the equation of state,
we use 57 Hubble data points, and the Pantheon Supernovae Type Ia data sample.
The st statistical analysis is performed by using Markov Chain Monte Carlo
(MCMC) simulations. A detailed comparison with the standard $\Lambda$CDM model
is also performed, with the Akaike information criterion (AIC), and the
Bayesian information criterion (BIC) used as the two model selection tools. The
statefinder diagnostics consisting of jerk and snap parameters, and the $Om(z)$
diagnostics are also considered for the comparative study of the
Barthel-Kropina and $\Lambda$CDM cosmologies. Our results indicate that the
Barthel-Kropina dark energy model gives a good description of the observational
data, and thus it can be considered a viable alternative of the $\Lambda$CDM
model.
| [
{
"created": "Tue, 24 Jan 2023 19:25:07 GMT",
"version": "v1"
}
] | 2023-02-22 | [
[
"Bouali",
"Amine",
""
],
[
"Chaudhary",
"Himanshu",
""
],
[
"Hama",
"Rattanasak",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Sabau",
"Sorin V.",
""
],
[
"Martín",
"Marco San",
""
]
] | We further investigate the dark energy model based on the Finsler geometry inspired osculating Barthel-Kropina cosmology. The Barthel-Kropina cosmological approach is based on the introduction of a Barthel connection in an osculating Finsler geometry, with the connection having the property that it is the Levi-Civita connection of a Riemannian metric. From the generalized Friedmann equations of the Barthel-Kropina model, obtained by assuming that the background Riemannian metric is of the Friedmann-Lemaitre-Robertson-Walker type, an effective geometric dark energy component can be generated, with the effective, geometric type pressure, satisfying a linear barotropic type equation of state. The cosmological tests, and comparisons with observational data of this dark energy model are considered in detail. To constrain the Barthel-Kropina model parameters, and the parameter of the equation of state, we use 57 Hubble data points, and the Pantheon Supernovae Type Ia data sample. The st statistical analysis is performed by using Markov Chain Monte Carlo (MCMC) simulations. A detailed comparison with the standard $\Lambda$CDM model is also performed, with the Akaike information criterion (AIC), and the Bayesian information criterion (BIC) used as the two model selection tools. The statefinder diagnostics consisting of jerk and snap parameters, and the $Om(z)$ diagnostics are also considered for the comparative study of the Barthel-Kropina and $\Lambda$CDM cosmologies. Our results indicate that the Barthel-Kropina dark energy model gives a good description of the observational data, and thus it can be considered a viable alternative of the $\Lambda$CDM model. |
2303.16789 | Dipanjan Dey | Dipanjan Dey, N. T. Layden, A. A. Coley, Pankaj S. Joshi | The equilibrium condition in gravitational collapse and its application
to a cosmological scenario | 20 pages, 7 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We discuss the equilibrium conditions of the gravitational collapse of a
spherically symmetric matter cloud. We analyze the spinor structure of a
general collapsing space-time and redefine the equilibrium conditions by using
Cartan scalars. We qualitatively investigate the equilibrium configuration of a
two-fluid system consisting of a dust-like fluid and a fluid with a negative
equation of state. We use our results to investigate certain cosmological
scenarios where dark energy can cluster inside the over-dense regions of dark
matter and together reaches a stable configuration. We compare the outcomes of
our work with existing work where the virialization technique is used to
stabilize the two-fluid system.
| [
{
"created": "Wed, 29 Mar 2023 15:26:09 GMT",
"version": "v1"
}
] | 2023-03-30 | [
[
"Dey",
"Dipanjan",
""
],
[
"Layden",
"N. T.",
""
],
[
"Coley",
"A. A.",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | We discuss the equilibrium conditions of the gravitational collapse of a spherically symmetric matter cloud. We analyze the spinor structure of a general collapsing space-time and redefine the equilibrium conditions by using Cartan scalars. We qualitatively investigate the equilibrium configuration of a two-fluid system consisting of a dust-like fluid and a fluid with a negative equation of state. We use our results to investigate certain cosmological scenarios where dark energy can cluster inside the over-dense regions of dark matter and together reaches a stable configuration. We compare the outcomes of our work with existing work where the virialization technique is used to stabilize the two-fluid system. |
2302.12485 | Christoph Schiller | Christoph Schiller | From the Bronshtein cube of limits to the degrees of freedom of
relativistic quantum gravity | Essay written for the Gravity Research Foundation 2023 Awards for
Essays on Gravitation; one figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | It is argued that the quadruple gravitational constant 4G can be seen as a
fundamental limit of nature. The limit holds across all gravitational systems
and distinguishes bound from unbound systems. Including the maximum force
c^4/4G allows extending the Bronshtein cube of physical theories to a cube of
limits. Every theory of physics refining Galilean physics - universal
gravitation, special relativity, general relativity, quantum theory and quantum
field theory - is defined by one fundamental limit. As a result, also
relativistic quantum gravity is defined by a limit: the minimum length in
nature. The minimum length is used to deduce the Planck-scale structure of
space. Numerous options are eliminated. Then, the minimum length is used to
deduce the main properties of the common constituents that make up space and
particles.
| [
{
"created": "Fri, 24 Feb 2023 06:58:27 GMT",
"version": "v1"
}
] | 2023-02-27 | [
[
"Schiller",
"Christoph",
""
]
] | It is argued that the quadruple gravitational constant 4G can be seen as a fundamental limit of nature. The limit holds across all gravitational systems and distinguishes bound from unbound systems. Including the maximum force c^4/4G allows extending the Bronshtein cube of physical theories to a cube of limits. Every theory of physics refining Galilean physics - universal gravitation, special relativity, general relativity, quantum theory and quantum field theory - is defined by one fundamental limit. As a result, also relativistic quantum gravity is defined by a limit: the minimum length in nature. The minimum length is used to deduce the Planck-scale structure of space. Numerous options are eliminated. Then, the minimum length is used to deduce the main properties of the common constituents that make up space and particles. |
gr-qc/0002092 | Martin O'Loughlin | Martin O'Loughlin | Boundary actions in Ponzano-Regge discretization, Quantum groups and
AdS(3) | 27 pages, 7 figures. Equations corrected and reference added. To
appear in ATMP | Adv.Theor.Math.Phys. 6 (2003) 795-826 | null | SPIN-2000/04 | gr-qc hep-th | null | Boundary actions for three-dimensional quantum gravity in the discretized
formalism of Ponzano-Regge are studied with a view towards understanding the
boundary degrees of freedom. These degrees of freedom postulated in the
holography hypothesis are supposed to be characteristic of quantum gravity
theories. In particular it is expected that some of these degrees of freedom
reside on black hole horizons. This paper is a study of these ideas in the
context of a theory of quantum gravity that requires no additional structure
such as supersymmetry or special gravitational backgrounds. Lorentzian as well
as Euclidean regimes are examined. Some surprising relationships to Liouville
theory and string theory in AdS(3) are found.
| [
{
"created": "Mon, 28 Feb 2000 14:59:26 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Nov 2002 16:39:57 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Dec 2003 01:14:50 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"O'Loughlin",
"Martin",
""
]
] | Boundary actions for three-dimensional quantum gravity in the discretized formalism of Ponzano-Regge are studied with a view towards understanding the boundary degrees of freedom. These degrees of freedom postulated in the holography hypothesis are supposed to be characteristic of quantum gravity theories. In particular it is expected that some of these degrees of freedom reside on black hole horizons. This paper is a study of these ideas in the context of a theory of quantum gravity that requires no additional structure such as supersymmetry or special gravitational backgrounds. Lorentzian as well as Euclidean regimes are examined. Some surprising relationships to Liouville theory and string theory in AdS(3) are found. |
0909.0563 | Michele Vallisneri | Gian Mario Manca and Michele Vallisneri | Cover art: issues in the metric-guided and metric-less placement of
random and stochastic template banks | RevTeX4, 21 pages, 9 PDF figures | Phys.Rev.D81:024004,2010 | 10.1103/PhysRevD.81.024004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The efficient placement of signal templates in source-parameter space is a
crucial requisite for exhaustive matched-filtering searches of modeled
gravitational-wave sources. Unfortunately, the current placement algorithms
based on regular parameter-space meshes are difficult to generalize beyond
simple signal models with few parameters. Various authors have suggested that a
general, flexible, yet efficient alternative can be found in randomized
placement strategies such as random placement and stochastic placement, which
enhances random placement by selectively rejecting templates that are too close
to others. In this article we explore several theoretical and practical issues
in randomized placement: the size and performance of the resulting template
banks; the effects of parameter-space boundaries; the use of quasi-random (self
avoiding) number sequences; most important, the implementation of these
algorithms in curved signal manifolds with and without the use of a Riemannian
signal metric, which may be difficult to obtain. Specifically, we show how the
metric can be replaced with a discrete triangulation-based representation of
local geometry. We argue that the broad class of randomized placement
algorithms offers a promising answer to many search problems, but that the
specific choice of a scheme and its implementation details will still need to
be fine-tuned separately for each problem.
| [
{
"created": "Thu, 3 Sep 2009 02:20:45 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jan 2010 03:52:13 GMT",
"version": "v2"
}
] | 2010-01-15 | [
[
"Manca",
"Gian Mario",
""
],
[
"Vallisneri",
"Michele",
""
]
] | The efficient placement of signal templates in source-parameter space is a crucial requisite for exhaustive matched-filtering searches of modeled gravitational-wave sources. Unfortunately, the current placement algorithms based on regular parameter-space meshes are difficult to generalize beyond simple signal models with few parameters. Various authors have suggested that a general, flexible, yet efficient alternative can be found in randomized placement strategies such as random placement and stochastic placement, which enhances random placement by selectively rejecting templates that are too close to others. In this article we explore several theoretical and practical issues in randomized placement: the size and performance of the resulting template banks; the effects of parameter-space boundaries; the use of quasi-random (self avoiding) number sequences; most important, the implementation of these algorithms in curved signal manifolds with and without the use of a Riemannian signal metric, which may be difficult to obtain. Specifically, we show how the metric can be replaced with a discrete triangulation-based representation of local geometry. We argue that the broad class of randomized placement algorithms offers a promising answer to many search problems, but that the specific choice of a scheme and its implementation details will still need to be fine-tuned separately for each problem. |
2103.02104 | \.I \c{C}a\u{g}r{\i} \.I\c{s}eri | Levent Akant, \.I. \c{C}a\u{g}r{\i} \.I\c{s}eri and \.Ibrahim Semiz | Estimation of attenuation of gravitational waves by Bose-Einstein
condensate dark matter halos using Bogoliubov-de Gennes theory | Additional references, corrected typos | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a gravitational plane wave passing through a galactic dark matter
halo composed of weakly self-interacting, self-gravitating, Bose-Einstein
condensate of ultralight particles. Treating the gravitational wave as a time
dependent perturbation, we study energy transfer between the gravitational wave
and the Bose-Einstein condensate by applying linear response theory to a
non-uniform condensate described by the Bogoliubov-de Gennes theory, and
compute the fractional loss in gravitational wave energy. We apply our results
to investigate the extent to which this loss effects the estimation of the
distance between the gravitational wave source and the earth. We show that the
effect is negligible.
| [
{
"created": "Wed, 3 Mar 2021 00:57:59 GMT",
"version": "v1"
},
{
"created": "Sat, 15 May 2021 19:12:50 GMT",
"version": "v2"
}
] | 2021-05-18 | [
[
"Akant",
"Levent",
""
],
[
"İşeri",
"İ. Çağrı",
""
],
[
"Semiz",
"İbrahim",
""
]
] | We consider a gravitational plane wave passing through a galactic dark matter halo composed of weakly self-interacting, self-gravitating, Bose-Einstein condensate of ultralight particles. Treating the gravitational wave as a time dependent perturbation, we study energy transfer between the gravitational wave and the Bose-Einstein condensate by applying linear response theory to a non-uniform condensate described by the Bogoliubov-de Gennes theory, and compute the fractional loss in gravitational wave energy. We apply our results to investigate the extent to which this loss effects the estimation of the distance between the gravitational wave source and the earth. We show that the effect is negligible. |
gr-qc/0607112 | Roald Sosnovskiy | Roald Sosnovskiy | The gravitational field energy density for symmetrical and asymmetrical
systems | 5 pages; corrected | null | null | null | gr-qc | null | The relativistic theory of gravitation has the considerable difficulties by
description of the gravitational field energy. Pseudotensor t00 in the some
cases cannot be interpreted as energy density of the gravitational field. In
[1] the approach was proposed, which allow to express the energy density of
such a field through the components of a metric tensor. This approach based on
the consideration of the isothermal compression of the layer consisted of the
incoherent matter. It was employ to the cylindrically and spherically
symmetrical static gravitational field. In presented paper the approach is
developed.
| [
{
"created": "Tue, 25 Jul 2006 16:58:41 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jan 2007 17:16:32 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Mar 2007 14:26:29 GMT",
"version": "v3"
},
{
"created": "Fri, 22 Jun 2007 11:10:21 GMT",
"version": "v4"
}
] | 2007-06-22 | [
[
"Sosnovskiy",
"Roald",
""
]
] | The relativistic theory of gravitation has the considerable difficulties by description of the gravitational field energy. Pseudotensor t00 in the some cases cannot be interpreted as energy density of the gravitational field. In [1] the approach was proposed, which allow to express the energy density of such a field through the components of a metric tensor. This approach based on the consideration of the isothermal compression of the layer consisted of the incoherent matter. It was employ to the cylindrically and spherically symmetrical static gravitational field. In presented paper the approach is developed. |
1407.7814 | Gabriel Catren | Gabriel Catren | Geometrical Foundations of Cartan Gauge Gravity | 24 pages | null | 10.1142/S0219887815300020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the theory of Cartan connections to analyze the geometrical structures
underpinning the gauge-theoretical descriptions of the gravitational
interaction. According to the theory of Cartan connections, the spin connection
$\omega$ and the soldering form $\theta$ that define the fundamental variables
of the Palatini formulation of general relativity can be understood as
different components of a single field, namely a Cartan connection
$A=\omega+\theta$. In order to stress both the similarities and the differences
between the notions of Ehresmann connection and Cartan connection, we explain
in detail how a Cartan geometry $(P_{H}\rightarrow M, A)$ can be obtained from
a $G$-principal bundle $P_{G}\rightarrow M$ endowed with an Ehresmann
connection (being the Lorentz group $H$ a subgroup of $G$) by means of a bundle
reduction mechanism. We claim that this reduction must be understood as a
partial gauge fixing of the local gauge symmetries of $P_{G}$, i.e. as a gauge
fixing that leaves "unbroken" the local Lorentz invariance. We then argue that
the "broken" part of the symmetry--that is the internal local translational
invariance--is implicitly preserved by the invariance under the external
diffeomorphisms of $M$.
| [
{
"created": "Mon, 28 Jul 2014 18:17:37 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Catren",
"Gabriel",
""
]
] | We use the theory of Cartan connections to analyze the geometrical structures underpinning the gauge-theoretical descriptions of the gravitational interaction. According to the theory of Cartan connections, the spin connection $\omega$ and the soldering form $\theta$ that define the fundamental variables of the Palatini formulation of general relativity can be understood as different components of a single field, namely a Cartan connection $A=\omega+\theta$. In order to stress both the similarities and the differences between the notions of Ehresmann connection and Cartan connection, we explain in detail how a Cartan geometry $(P_{H}\rightarrow M, A)$ can be obtained from a $G$-principal bundle $P_{G}\rightarrow M$ endowed with an Ehresmann connection (being the Lorentz group $H$ a subgroup of $G$) by means of a bundle reduction mechanism. We claim that this reduction must be understood as a partial gauge fixing of the local gauge symmetries of $P_{G}$, i.e. as a gauge fixing that leaves "unbroken" the local Lorentz invariance. We then argue that the "broken" part of the symmetry--that is the internal local translational invariance--is implicitly preserved by the invariance under the external diffeomorphisms of $M$. |
gr-qc/0010021 | J. Ibanez | A. Di Prisco, L. Herrera and J. Ibanez | Qualitative analysis of dissipative cosmologies | 10 pages, 5 figures, RevTex. To appear in PRD | Phys.Rev.D63:023501,2001 | 10.1103/PhysRevD.63.023501 | null | gr-qc astro-ph | null | The evolution of an homogeneous and isotropic dissipative fluid is analyzed
using dynamical systems techniques. The dissipation is driven by bulk viscous
pressure and the truncated Israel-Stewart theory is used. Although almost all
solutions inflate, we show that only few of them can be considered as physical
solutions since the dominant energy condition is not satisfied.
| [
{
"created": "Fri, 6 Oct 2000 07:56:42 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Di Prisco",
"A.",
""
],
[
"Herrera",
"L.",
""
],
[
"Ibanez",
"J.",
""
]
] | The evolution of an homogeneous and isotropic dissipative fluid is analyzed using dynamical systems techniques. The dissipation is driven by bulk viscous pressure and the truncated Israel-Stewart theory is used. Although almost all solutions inflate, we show that only few of them can be considered as physical solutions since the dominant energy condition is not satisfied. |
2205.12994 | Dirk Heumann | Dirk Heumann and Dimitrios Psaltis | Identifying the Event Horizons of Parametrically Deformed Black-Hole
Metrics | null | null | 10.1103/PhysRevD.107.044015 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Recent advancements in observational techniques have led to new tests of the
general relativistic predictions for black-hole spacetimes in the strong-field
regime. One of the key ingredients for several tests is a metric that allows
for deviations from the Kerr solution but remains free of pathologies outside
its event horizon. Existing metrics that have been used in the literature often
do not satisfy the null convergence condition that is necessary to apply the
strong rigidity theorem and would have allowed us to calculate the location of
the event horizon by identifying it with an appropriate Killing horizon. This
has led earlier calculations of event horizons of parametrically deformed
metrics to either follow numerical techniques or simply search heuristically
for coordinate singularities. We show that several of these metrics, almost by
construction, are circular. We can, therefore, use the weak rigidity and
Carter's rotosurface theorem and calculate algebraically the locations of their
event horizons, without relying on expansions or numerical techniques. We apply
this approach to a number of parametrically deformed metrics, calculate the
locations of their event horizons, and place constraints on the deviation
parameters such that the metrics remain regular outside their horizons. We show
that calculating the angular velocity of the horizon and the effective gravity
there offers new insights into the observational signatures of deformed
metrics, such as the sizes and shapes of the predicted black-hole shadows.
| [
{
"created": "Wed, 25 May 2022 18:04:56 GMT",
"version": "v1"
}
] | 2023-02-22 | [
[
"Heumann",
"Dirk",
""
],
[
"Psaltis",
"Dimitrios",
""
]
] | Recent advancements in observational techniques have led to new tests of the general relativistic predictions for black-hole spacetimes in the strong-field regime. One of the key ingredients for several tests is a metric that allows for deviations from the Kerr solution but remains free of pathologies outside its event horizon. Existing metrics that have been used in the literature often do not satisfy the null convergence condition that is necessary to apply the strong rigidity theorem and would have allowed us to calculate the location of the event horizon by identifying it with an appropriate Killing horizon. This has led earlier calculations of event horizons of parametrically deformed metrics to either follow numerical techniques or simply search heuristically for coordinate singularities. We show that several of these metrics, almost by construction, are circular. We can, therefore, use the weak rigidity and Carter's rotosurface theorem and calculate algebraically the locations of their event horizons, without relying on expansions or numerical techniques. We apply this approach to a number of parametrically deformed metrics, calculate the locations of their event horizons, and place constraints on the deviation parameters such that the metrics remain regular outside their horizons. We show that calculating the angular velocity of the horizon and the effective gravity there offers new insights into the observational signatures of deformed metrics, such as the sizes and shapes of the predicted black-hole shadows. |
gr-qc/0202100 | Farid Ya. Khalili | S.L.Danilishin, F.Ya.Khalili | Stroboscopic Variation Measurement | 13 pages, 2 figures drawn in TeX and 2 figures in postscript,
misprint corrected | Phys.Lett. A300 (2002) 547-558 | 10.1016/S0375-9601(02)00903-9 | null | gr-qc | null | A new procedure of the linear position measurement which allows to obtain
sensitivity better than the Standard Quantum Limit and close to the Energetic
Quantum Limit is proposed and analyzed in details. Proposed method is based on
the principles of stroboscopic quantum measurement and variation quantum
measurement and allows to avoid main disadvantages of both these procedures.
This method can be considered as a good candidate for use as a local position
meter in the ``intracavity'' topologies of the laser gravitational-wave
antennae.
| [
{
"created": "Thu, 28 Feb 2002 14:17:06 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Mar 2002 10:34:59 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Mar 2002 12:09:46 GMT",
"version": "v3"
},
{
"created": "Thu, 20 Jun 2002 08:32:15 GMT",
"version": "v4"
}
] | 2015-06-25 | [
[
"Danilishin",
"S. L.",
""
],
[
"Khalili",
"F. Ya.",
""
]
] | A new procedure of the linear position measurement which allows to obtain sensitivity better than the Standard Quantum Limit and close to the Energetic Quantum Limit is proposed and analyzed in details. Proposed method is based on the principles of stroboscopic quantum measurement and variation quantum measurement and allows to avoid main disadvantages of both these procedures. This method can be considered as a good candidate for use as a local position meter in the ``intracavity'' topologies of the laser gravitational-wave antennae. |
1304.7924 | Seyen Kouwn | Seoktae Koh, Seyen Kouwn, O-Kab Kwon, and Phillial Oh | Cosmological Perturbations of a Quartet of Scalar Fields with a
Spatially Constant Gradient | 26 pages, 1 figure, minor corrections, references are added,
published version | null | 10.1103/PhysRevD.88.043523 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the linear perturbations for the single scalar field inflation
model interacting with an additional triad of scalar fields. The background
solutions of the three additional scalar fields depend on spatial coordinates
with a constant gradient $\alpha$ and the ensuing evolution preserves the
homogeneity of the cosmological principle. After we discuss the properties of
background evolution including an exact solution for the exponential-type
potential, we investigate the linear perturbations of the scalar and tensor
modes in the background of the slow-roll inflation. In our model with small
$\alpha$, the comoving wavenumber has {\it a lower bound} $\sim \alpha M_{\rm
P}$ to have well-defined initial quantum states. We find that cosmological
quantities, for instance, the power spectrums and spectral indices of the
comoving curvature and isocurvature perturbations, and the running of the
spectral indices have small corrections depending on {\it the lower bound}.
Similar behaviors happen for the tensor perturbation with the same lower bound.
| [
{
"created": "Tue, 30 Apr 2013 09:10:22 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Aug 2013 16:15:37 GMT",
"version": "v2"
}
] | 2013-09-04 | [
[
"Koh",
"Seoktae",
""
],
[
"Kouwn",
"Seyen",
""
],
[
"Kwon",
"O-Kab",
""
],
[
"Oh",
"Phillial",
""
]
] | We consider the linear perturbations for the single scalar field inflation model interacting with an additional triad of scalar fields. The background solutions of the three additional scalar fields depend on spatial coordinates with a constant gradient $\alpha$ and the ensuing evolution preserves the homogeneity of the cosmological principle. After we discuss the properties of background evolution including an exact solution for the exponential-type potential, we investigate the linear perturbations of the scalar and tensor modes in the background of the slow-roll inflation. In our model with small $\alpha$, the comoving wavenumber has {\it a lower bound} $\sim \alpha M_{\rm P}$ to have well-defined initial quantum states. We find that cosmological quantities, for instance, the power spectrums and spectral indices of the comoving curvature and isocurvature perturbations, and the running of the spectral indices have small corrections depending on {\it the lower bound}. Similar behaviors happen for the tensor perturbation with the same lower bound. |
gr-qc/0207094 | J. Frauendiener | J. Frauendiener and Matthias Hein | Numerical evolution of axisymmetric, isolated systems in General
Relativity | 10 pages, 8 figures, uses revtex4, replaced with revised version | Phys.Rev. D66 (2002) 124004 | 10.1103/PhysRevD.66.124004 | null | gr-qc | null | We describe in this article a new code for evolving axisymmetric isolated
systems in general relativity. Such systems are described by asymptotically
flat space-times which have the property that they admit a conformal extension.
We are working directly in the extended `conformal' manifold and solve
numerically Friedrich's conformal field equations, which state that Einstein's
equations hold in the physical space-time. Because of the compactness of the
conformal space-time the entire space-time can be calculated on a finite
numerical grid. We describe in detail the numerical scheme, especially the
treatment of the axisymmetry and the boundary.
| [
{
"created": "Wed, 24 Jul 2002 14:39:09 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jul 2002 10:01:37 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Frauendiener",
"J.",
""
],
[
"Hein",
"Matthias",
""
]
] | We describe in this article a new code for evolving axisymmetric isolated systems in general relativity. Such systems are described by asymptotically flat space-times which have the property that they admit a conformal extension. We are working directly in the extended `conformal' manifold and solve numerically Friedrich's conformal field equations, which state that Einstein's equations hold in the physical space-time. Because of the compactness of the conformal space-time the entire space-time can be calculated on a finite numerical grid. We describe in detail the numerical scheme, especially the treatment of the axisymmetry and the boundary. |
2311.12896 | Hassan Hassanabadi prof. | Salvatore Capozziello, Soroush Zare, and Hassan Hassanabadi | Testing bumblebee gravity with global monopoles in a dark matter spike
by EHT observations from M87 and Sgr A | null | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate supermassive black holes (SMBH), surrounded by a dark matter
(DM) spike, that can be found at the centers of Milky Way and M87 galaxies and
are accompanied by a specific kind of topological defect. The investigation is
developed within the framework of Bumblebee Gravity (BG) with a global monopole
(GM). The power-law density profile, describing the DM spike, is expected to
follow a power-law distribution starting from a few times the BH horizon radius
and extending outward to an external radius Rsp. We determine the normalization
parameter, \r{ho}0, for the density profile to ensure its compatibility with
both the galaxy total mass and the enclosed DM mass within the radius of
influence of Sagittarius A (Sgr A) and M87 SMBHs, approximately of order 105Rs.
Our main objective is to assess how the background arising from spontaneous
Lorentz symmetry (LS) breaking and the presence of a GM influence the
properties of the Kerr BH within the region affected by the spike. The scarcity
of non-rotating and rotating BH models embedded in a DM spike and subject to BG
and GM (BGGM) effects significantly hinders the progress in testing BGGM
through observations. To address this issue, we initiate our investigation by
considering a spherically symmetric static BH with BGGM properties as the seed
metric. From there, we construct a non-rotating spacetime with a DM spike
(similar to the Schwarzschild spacetime), leading to the emergence of the
BGGM-motivated Schwarzschild-like BH (BGMSLBH). To construct the BGMSLBH
spacetime, we employ two different methods: one involves solving the modified
Tolman-Oppenheimer-Volkoff (TOV) equations, while the other entails solving the
modified Einstein field equations. In the latter approach, we consider the
energy-momentum tensor incorporating the contributions of DM spike and BH
counterpart of the BGGM.
| [
{
"created": "Tue, 21 Nov 2023 08:28:17 GMT",
"version": "v1"
}
] | 2023-11-23 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Zare",
"Soroush",
""
],
[
"Hassanabadi",
"Hassan",
""
]
] | We investigate supermassive black holes (SMBH), surrounded by a dark matter (DM) spike, that can be found at the centers of Milky Way and M87 galaxies and are accompanied by a specific kind of topological defect. The investigation is developed within the framework of Bumblebee Gravity (BG) with a global monopole (GM). The power-law density profile, describing the DM spike, is expected to follow a power-law distribution starting from a few times the BH horizon radius and extending outward to an external radius Rsp. We determine the normalization parameter, \r{ho}0, for the density profile to ensure its compatibility with both the galaxy total mass and the enclosed DM mass within the radius of influence of Sagittarius A (Sgr A) and M87 SMBHs, approximately of order 105Rs. Our main objective is to assess how the background arising from spontaneous Lorentz symmetry (LS) breaking and the presence of a GM influence the properties of the Kerr BH within the region affected by the spike. The scarcity of non-rotating and rotating BH models embedded in a DM spike and subject to BG and GM (BGGM) effects significantly hinders the progress in testing BGGM through observations. To address this issue, we initiate our investigation by considering a spherically symmetric static BH with BGGM properties as the seed metric. From there, we construct a non-rotating spacetime with a DM spike (similar to the Schwarzschild spacetime), leading to the emergence of the BGGM-motivated Schwarzschild-like BH (BGMSLBH). To construct the BGMSLBH spacetime, we employ two different methods: one involves solving the modified Tolman-Oppenheimer-Volkoff (TOV) equations, while the other entails solving the modified Einstein field equations. In the latter approach, we consider the energy-momentum tensor incorporating the contributions of DM spike and BH counterpart of the BGGM. |
1901.01416 | SangChul Yoon | SangChul Yoon | From Lagrangian to Hamiltonian formulations of the Palatini action | 12 pages, completion of previous works, arXiv:1706.07301 and
arXiv:1805.01996 | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We work on the Lagrangian and the Hamiltonian formulations of the Palatini
action. In the Lagrangian formulation, we find that we need to assume the
metric compatibility and the torsion zero or to assume the tetrad compatibility
to describe General Relativity. In the Hamiltonian formulation, we obtain the
Einstein's equations only with assuming the tetrad compatibility. The
Hamiltonian from assuming the metric compatibility and the torsion zero should
be used to quantize General Relativity.
| [
{
"created": "Sat, 5 Jan 2019 13:52:12 GMT",
"version": "v1"
}
] | 2019-01-08 | [
[
"Yoon",
"SangChul",
""
]
] | We work on the Lagrangian and the Hamiltonian formulations of the Palatini action. In the Lagrangian formulation, we find that we need to assume the metric compatibility and the torsion zero or to assume the tetrad compatibility to describe General Relativity. In the Hamiltonian formulation, we obtain the Einstein's equations only with assuming the tetrad compatibility. The Hamiltonian from assuming the metric compatibility and the torsion zero should be used to quantize General Relativity. |
1504.04592 | Volker Schlue | Spyros Alexakis and Volker Schlue | Non-existence of time-periodic vacuum spacetimes | 50 pages, 3 figures | J. Differential Geom. 108(1): 1-62 (2018) | 10.4310/jdg/1513998029 | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that smooth asymptotically flat solutions to the Einstein vacuum
equations which are assumed to be periodic in time, are in fact stationary in a
neighborhood of infinity. Our result applies under physically relevant
regularity assumptions purely at the level of the initial data. In particular,
our work removes the assumption of analyticity up to null infinity in [Bicak,
Scholtz, and Tod; 2010]. The proof relies on extending a suitably constructed
"candidate" Killing vector field from null infinity, via Carleman-type
estimates obtained in [Alexakis, Schlue, Shao; 2013].
| [
{
"created": "Fri, 17 Apr 2015 17:52:51 GMT",
"version": "v1"
}
] | 2021-08-16 | [
[
"Alexakis",
"Spyros",
""
],
[
"Schlue",
"Volker",
""
]
] | We prove that smooth asymptotically flat solutions to the Einstein vacuum equations which are assumed to be periodic in time, are in fact stationary in a neighborhood of infinity. Our result applies under physically relevant regularity assumptions purely at the level of the initial data. In particular, our work removes the assumption of analyticity up to null infinity in [Bicak, Scholtz, and Tod; 2010]. The proof relies on extending a suitably constructed "candidate" Killing vector field from null infinity, via Carleman-type estimates obtained in [Alexakis, Schlue, Shao; 2013]. |
2406.09431 | Farruh Atamurotov | Yovqochev Pahlavon, Farruh Atamurotov, Kimet Jusufi, Mubasher Jamil,
Ahmadjon Abdujabbarov | Effect of magnetized plasma on shadow and gravitational lensing of a
Reissner-Nordstr\"om black hole | 18 pages, 15 figures, To appear in Physics of the Dark Universe.
arXiv admin note: substantial text overlap with arXiv:2109.08150 | Physics of the Dark Universe 45 (2024) 101543 | 10.1016/j.dark.2024.101543 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the influence of the axion-plasmon on the optical properties of
the charged black hole and show how the axion-plasmon coupling modifies the
motion of photons around the charged black hole. We then explore in details
observational effects such as the black hole shadow, the gravitational
deflection angle, Einstein rings and shadow images obtained by radially
infalling gas on a black hole within a plasma medium. An important finding is
that the intensity of the electromagnetic radiation increases with the increase
of charge and the size of the black hole shadow decreases with increase of the
electric charge for a fixed axion-plasmon coupling values when observed from
sufficiently large distance. Overall, for a constant value of charge the
optical appearance of the black hole shadow depends on the surrounding plasma
model and the largest shadow radius if found for the case of no plasma, while
the smallest shadow radius is found for the case of homogeneous plasma.
| [
{
"created": "Sat, 1 Jun 2024 13:06:17 GMT",
"version": "v1"
}
] | 2024-06-21 | [
[
"Pahlavon",
"Yovqochev",
""
],
[
"Atamurotov",
"Farruh",
""
],
[
"Jusufi",
"Kimet",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
]
] | We explore the influence of the axion-plasmon on the optical properties of the charged black hole and show how the axion-plasmon coupling modifies the motion of photons around the charged black hole. We then explore in details observational effects such as the black hole shadow, the gravitational deflection angle, Einstein rings and shadow images obtained by radially infalling gas on a black hole within a plasma medium. An important finding is that the intensity of the electromagnetic radiation increases with the increase of charge and the size of the black hole shadow decreases with increase of the electric charge for a fixed axion-plasmon coupling values when observed from sufficiently large distance. Overall, for a constant value of charge the optical appearance of the black hole shadow depends on the surrounding plasma model and the largest shadow radius if found for the case of no plasma, while the smallest shadow radius is found for the case of homogeneous plasma. |
gr-qc/0701129 | J. Ponce de Leon | J. Ponce de Leon | Exterior spacetime for stellar models in 5-dimensional Kaluza-Klein
gravity | Typos corrected. Accepted for publication in Classical and Quantum
Gravity | Class.Quant.Grav.24:1755-1774,2007 | 10.1088/0264-9381/24/7/006 | null | gr-qc | null | It is well-known that Birkhoff's theorem is no longer valid in theories with
more than four dimensions. Thus, in these theories the effective 4-dimensional
picture allows the existence of different possible, non-Schwarzschild,
scenarios for the description of the spacetime outside of a spherical star,
contrary to general relativity in 4D. We investigate the exterior spacetime of
a spherically symmetric star in the context of Kaluza-Klein gravity. We take a
well-known family of static spherically symmetric solutions of the Einstein
equations in an empty five-dimensional universe, and analyze possible stellar
exteriors that are conformal to the metric induced on four-dimensional
hypersurfaces orthogonal to the extra dimension. All these exteriors are
continuously matched with the interior of the star. Then, without making any
assumptions about the interior solution, we prove the following statement: the
condition that in the weak-field limit we recover the usual Newtonian physics
singles out an unique exterior. This exterior is "similar" to Scharzschild
vacuum in the sense that it has no effect on gravitational interactions.
However, it is more realistic because instead of being absolutely empty, it is
consistent with the existence of quantum zero-point fields. We also examine the
question of how would the deviation from the Schwarzschild vacuum exterior
affect the parameters of a neutron star. In the context of a model star of
uniform density, we show that the general relativity upper limit M/R < 4/9 is
significantly increased as we go away from the Schwarzschild vacuum exterior.
We find that, in principle, the compactness limit of a star can be larger than
1/2, without being a black hole. The generality of our approach is also
discussed.
| [
{
"created": "Wed, 24 Jan 2007 12:10:59 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2007 17:24:45 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"de Leon",
"J. Ponce",
""
]
] | It is well-known that Birkhoff's theorem is no longer valid in theories with more than four dimensions. Thus, in these theories the effective 4-dimensional picture allows the existence of different possible, non-Schwarzschild, scenarios for the description of the spacetime outside of a spherical star, contrary to general relativity in 4D. We investigate the exterior spacetime of a spherically symmetric star in the context of Kaluza-Klein gravity. We take a well-known family of static spherically symmetric solutions of the Einstein equations in an empty five-dimensional universe, and analyze possible stellar exteriors that are conformal to the metric induced on four-dimensional hypersurfaces orthogonal to the extra dimension. All these exteriors are continuously matched with the interior of the star. Then, without making any assumptions about the interior solution, we prove the following statement: the condition that in the weak-field limit we recover the usual Newtonian physics singles out an unique exterior. This exterior is "similar" to Scharzschild vacuum in the sense that it has no effect on gravitational interactions. However, it is more realistic because instead of being absolutely empty, it is consistent with the existence of quantum zero-point fields. We also examine the question of how would the deviation from the Schwarzschild vacuum exterior affect the parameters of a neutron star. In the context of a model star of uniform density, we show that the general relativity upper limit M/R < 4/9 is significantly increased as we go away from the Schwarzschild vacuum exterior. We find that, in principle, the compactness limit of a star can be larger than 1/2, without being a black hole. The generality of our approach is also discussed. |
1111.1383 | Xin Li | Xin Li and Zhe Chang | Gravitational wave in Lorentz violating gravity | major corrections, 8 pages, 1 figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | By making use of the weak gravitational field approximation, we obtain a
linearized solution of the gravitational vacuum field equation in an
anisotropic spacetime. The plane-wave solution and dispersion relation of
gravitational wave is presented explicitly. There is possibility that the speed
of gravitational wave is larger than the speed of light and the casuality still
holds. We show that the energy-momentum of gravitational wave in the
ansiotropic spacetime is still well defined and conserved.
| [
{
"created": "Sun, 6 Nov 2011 08:02:54 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Apr 2012 09:53:40 GMT",
"version": "v2"
}
] | 2012-04-03 | [
[
"Li",
"Xin",
""
],
[
"Chang",
"Zhe",
""
]
] | By making use of the weak gravitational field approximation, we obtain a linearized solution of the gravitational vacuum field equation in an anisotropic spacetime. The plane-wave solution and dispersion relation of gravitational wave is presented explicitly. There is possibility that the speed of gravitational wave is larger than the speed of light and the casuality still holds. We show that the energy-momentum of gravitational wave in the ansiotropic spacetime is still well defined and conserved. |
gr-qc/0204024 | Efrain Rojas | Ruben Cordero and Efrain Rojas | Generalized Chiral Membrane Dynamics | 8 pages, to appear in Proceedings of the 4th Mexican School on
Gravitation and Mathematical Physics, Huatulco Oax, Mexico, December 2000 | Rev.Mex.Fis. 49S1 (2003) 44-48 | null | null | gr-qc | null | We develop the dynamics of the chiral superconducting membranes(with null
current) in an alternative geometrical approach. Besides of this, we show the
equivalence of the resulting description to the one known Dirac-Nambu-Goto
(DNG) case. Integrability for chiral string model is obtained using a proposed
light-cone gauge. In a similar way, domain walls are integrated by means of a
simple ansatz.
| [
{
"created": "Fri, 5 Apr 2002 04:11:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cordero",
"Ruben",
""
],
[
"Rojas",
"Efrain",
""
]
] | We develop the dynamics of the chiral superconducting membranes(with null current) in an alternative geometrical approach. Besides of this, we show the equivalence of the resulting description to the one known Dirac-Nambu-Goto (DNG) case. Integrability for chiral string model is obtained using a proposed light-cone gauge. In a similar way, domain walls are integrated by means of a simple ansatz. |
2111.12650 | Philippe G. LeFloch | Philippe G. LeFloch | Gravitational singularities, scattering maps for bouncing, and
structure-preserving algorithms | 15 pages | null | null | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | This note emphasizes the role of multi-scale wave structures and junction
conditions in many fields of physics, from the dynamics of fluids with
non-convex equations of state to the study of gravitational singularities and
bouncing cosmologies in general relativity. Concerning the definition and
construction of bouncing spacetimes, we review the recent proposal in
collaboration with B. Le Floch and G. Veneziano based on the notion of
singularity scattering maps. We also present recent numerical investigations of
small-scale phenomena arising in compressible fluid flows on FRLW or Kasner
geometries for which we developed structure-preserving algorithms.
| [
{
"created": "Wed, 24 Nov 2021 17:30:57 GMT",
"version": "v1"
}
] | 2021-11-25 | [
[
"LeFloch",
"Philippe G.",
""
]
] | This note emphasizes the role of multi-scale wave structures and junction conditions in many fields of physics, from the dynamics of fluids with non-convex equations of state to the study of gravitational singularities and bouncing cosmologies in general relativity. Concerning the definition and construction of bouncing spacetimes, we review the recent proposal in collaboration with B. Le Floch and G. Veneziano based on the notion of singularity scattering maps. We also present recent numerical investigations of small-scale phenomena arising in compressible fluid flows on FRLW or Kasner geometries for which we developed structure-preserving algorithms. |
gr-qc/0009065 | Vikram Soni | Vikram Soni (National Physical Laboratory, New Delhi, India) | Planck Scale Physics of the Single Particle Schr\"{o}dinger Equation
with Gravitational Self-Interaction | 16 pages, Revtex, No figure, Submitted to Physics Letters A | Pramana 59:375-384,2002 | 10.1007/s12043-002-0130-4 | null | gr-qc | null | We consider the modification of a single particle Schr\"{o}dinger equation by
the inclusion of an additional gravitational self-potential term which follows
from the prescription that the' mass-density'that enters this term is given by
$m |\psi (\vec {r},t)|^2$, where $\psi (\vec {r}, t)$ is the wavefunction and
$m$ is the mass of the particle. This leads to a nonlinear equation, the '
Newton Schrodinger' equation, which has been found to possess stationary
self-bound solutions, whose energy can be determined exactly using an
asymptotic method. We find that such a particle strongly violates superposition
and becomes a black hole as its mass approaches the Planck mass.
| [
{
"created": "Tue, 19 Sep 2000 07:27:07 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Soni",
"Vikram",
"",
"National Physical Laboratory, New Delhi, India"
]
] | We consider the modification of a single particle Schr\"{o}dinger equation by the inclusion of an additional gravitational self-potential term which follows from the prescription that the' mass-density'that enters this term is given by $m |\psi (\vec {r},t)|^2$, where $\psi (\vec {r}, t)$ is the wavefunction and $m$ is the mass of the particle. This leads to a nonlinear equation, the ' Newton Schrodinger' equation, which has been found to possess stationary self-bound solutions, whose energy can be determined exactly using an asymptotic method. We find that such a particle strongly violates superposition and becomes a black hole as its mass approaches the Planck mass. |
2301.12509 | Giuseppe Gaetano Luciano Dr | Giuseppe Gaetano Luciano | Constraining Barrow entropy-based Cosmology with power-law inflation | 10 pages, 2 labeled figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study the inflationary era of the Universe in a modified cosmological
scenario based on the gravity-thermodynamics conjecture with Barrow entropy
instead of the usual Bekenstein-Hawking one. The former arises from the effort
to account for quantum gravitational effects on the horizon surface of black
holes and, in a broader sense, of the Universe. First, we extract modified
Friedmann equations from the first law of thermodynamics applied to the
apparent horizon of a Friedmann- Robertson-Walker Universe in (n +
1)-dimensions. Assuming a power-law behavior for the scalar inflaton field, we
then investigate how the inflationary dynamics is affected in Barrow
cosmological setup. We find that the inflationary era may phenomenologically
consist of the slow-roll phase, while Barrow entropy is incompatible with
kinetic inflation. By demanding observationally consistency of the scalar
spectral index and tensor-to-scalar ratio with recent Planck data, we finally
constrain Barrow exponent to $\Delta\lesssim10^{-4}$.
| [
{
"created": "Sun, 29 Jan 2023 18:31:04 GMT",
"version": "v1"
}
] | 2023-01-31 | [
[
"Luciano",
"Giuseppe Gaetano",
""
]
] | We study the inflationary era of the Universe in a modified cosmological scenario based on the gravity-thermodynamics conjecture with Barrow entropy instead of the usual Bekenstein-Hawking one. The former arises from the effort to account for quantum gravitational effects on the horizon surface of black holes and, in a broader sense, of the Universe. First, we extract modified Friedmann equations from the first law of thermodynamics applied to the apparent horizon of a Friedmann- Robertson-Walker Universe in (n + 1)-dimensions. Assuming a power-law behavior for the scalar inflaton field, we then investigate how the inflationary dynamics is affected in Barrow cosmological setup. We find that the inflationary era may phenomenologically consist of the slow-roll phase, while Barrow entropy is incompatible with kinetic inflation. By demanding observationally consistency of the scalar spectral index and tensor-to-scalar ratio with recent Planck data, we finally constrain Barrow exponent to $\Delta\lesssim10^{-4}$. |
2208.08676 | Philippe G. LeFloch | Philippe G. LeFloch and Yue Ma | Einstein-Klein-Gordon spacetimes in the harmonic near-Minkowski regime | 32 pages. arXiv admin note: text overlap with arXiv:1712.10045 | null | null | null | gr-qc math.AP | http://creativecommons.org/licenses/by/4.0/ | We study the initial value problem for the Einstein-Klein-Gordon system and
establish the global nonlinear stability of massive matter in the
near-Minkowski regime when the initial geometry is a perturbation of an
asymptotically flat, spacelike hypersurface in Minkowski spacetime and the
metric enjoys the harmonic decay 1/r (in term of a suitable distance function r
at spatial infinity). Our analysis encompasses matter fields that have small
energy norm and solely enjoys a slow decay at spacelike infinity. Our proof is
based on the Euclidean-hyperboloidal foliation method recently introduced by
the authors, and distinguishes between the decay along asymptotically
hyperbolic slices and the decay along asymptotically Euclidean slices. We
carefully analyze the decay of metric component at the harmonic level 1/r,
especially the metric component in the direction of the light cone. In presence
of such a slow-decaying matter field, we establish a global existence theory
for the Einstein equations expressed as a coupled system of nonlinear wave and
Klein-Gordon equations.
| [
{
"created": "Thu, 18 Aug 2022 07:23:57 GMT",
"version": "v1"
}
] | 2022-11-15 | [
[
"LeFloch",
"Philippe G.",
""
],
[
"Ma",
"Yue",
""
]
] | We study the initial value problem for the Einstein-Klein-Gordon system and establish the global nonlinear stability of massive matter in the near-Minkowski regime when the initial geometry is a perturbation of an asymptotically flat, spacelike hypersurface in Minkowski spacetime and the metric enjoys the harmonic decay 1/r (in term of a suitable distance function r at spatial infinity). Our analysis encompasses matter fields that have small energy norm and solely enjoys a slow decay at spacelike infinity. Our proof is based on the Euclidean-hyperboloidal foliation method recently introduced by the authors, and distinguishes between the decay along asymptotically hyperbolic slices and the decay along asymptotically Euclidean slices. We carefully analyze the decay of metric component at the harmonic level 1/r, especially the metric component in the direction of the light cone. In presence of such a slow-decaying matter field, we establish a global existence theory for the Einstein equations expressed as a coupled system of nonlinear wave and Klein-Gordon equations. |
1806.05047 | Marco Cariglia Dr | M. Cariglia, G. W. Gibbons | L\'evy-Leblond fermions on the wormhole | 15 pages, 3 figures. V2 references added | null | null | null | gr-qc cond-mat.mes-hall hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a simple model of entanglement generated by geometry, studying
non-relativistic massive L\'evy-Leblond fermions in the $1+2$ geometry of a
Bronnikov-Ellis wormhole. The model is equivalent to that of relativistic
massless Dirac fermions in $1+3$ dimensions, where one spatial direction is
flat. The effect of the wormhole is to generate quantum states that, far from
the throat, are approximated by entangled particles on two flat, separated
spacetime regions. An appealing feature of the model is that it has a condensed
matter analogue, the regime of intermediate energies for two planes of bilayer
graphene linked by a bilayer carbon nanotube. Therefore we expect that it might
be possible to realize in the laboratory the entangled states studied here. We
argue that generalisations of our solvable model which preserve the topology
will have similar quantum behaviour.
| [
{
"created": "Tue, 12 Jun 2018 05:51:47 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jun 2018 12:33:05 GMT",
"version": "v2"
}
] | 2018-06-28 | [
[
"Cariglia",
"M.",
""
],
[
"Gibbons",
"G. W.",
""
]
] | We propose a simple model of entanglement generated by geometry, studying non-relativistic massive L\'evy-Leblond fermions in the $1+2$ geometry of a Bronnikov-Ellis wormhole. The model is equivalent to that of relativistic massless Dirac fermions in $1+3$ dimensions, where one spatial direction is flat. The effect of the wormhole is to generate quantum states that, far from the throat, are approximated by entangled particles on two flat, separated spacetime regions. An appealing feature of the model is that it has a condensed matter analogue, the regime of intermediate energies for two planes of bilayer graphene linked by a bilayer carbon nanotube. Therefore we expect that it might be possible to realize in the laboratory the entangled states studied here. We argue that generalisations of our solvable model which preserve the topology will have similar quantum behaviour. |
2310.20625 | Gregorio Carullo | Gregorio Carullo, Roberto Cotesta, Emanuele Berti, Vitor Cardoso | Reply to Comment on "Analysis of Ringdown Overtones in GW150914" | 3 pages, 1 figure. Unabridged version of the shorter (due to format
constraints) Reply published in Phys. Rev. Lett | Phys. Rev. Lett. 131, 169002 (2023) | 10.1103/PhysRevLett.131.169002 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this Reply we include the corrections suggested in the Comment [Phys. Rev.
Lett. 131, 169001]. We show that their impact on our results is small, and that
the overall conclusion of the Article [Phys. Rev. Lett. 129, 111102] are
robust. As pointed out in the Article, it is crucial to account for the
statistical uncertainty in the ringdown starting time, neglected in most
previous studies. This uncertainty is ~40 times larger than the systematic
shift induced by the software bug mentioned in the Comment. The remaining
discrepancies between the Comment and the Article can be attributed to
additional differences in the setup, notably the sampling rate and the noise
estimation method (in the Article the latter was chosen to mimic the original
methods of [Phys. Rev. Lett. 123, 111102]). Beyond data analysis
considerations, the physics of the problem cannot be ignored. As shown in
[arXiv:2302.03050], a model consisting of a sum of constant-amplitude overtones
starting at the peak of the waveform introduces uncontrolled systematic
uncertainties in the measurement due to dynamical and strong-field effects.
These theoretical considerations imply that studies based on such models cannot
be interpreted as black hole spectroscopy tests.
| [
{
"created": "Tue, 31 Oct 2023 16:57:13 GMT",
"version": "v1"
}
] | 2023-11-01 | [
[
"Carullo",
"Gregorio",
""
],
[
"Cotesta",
"Roberto",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
]
] | In this Reply we include the corrections suggested in the Comment [Phys. Rev. Lett. 131, 169001]. We show that their impact on our results is small, and that the overall conclusion of the Article [Phys. Rev. Lett. 129, 111102] are robust. As pointed out in the Article, it is crucial to account for the statistical uncertainty in the ringdown starting time, neglected in most previous studies. This uncertainty is ~40 times larger than the systematic shift induced by the software bug mentioned in the Comment. The remaining discrepancies between the Comment and the Article can be attributed to additional differences in the setup, notably the sampling rate and the noise estimation method (in the Article the latter was chosen to mimic the original methods of [Phys. Rev. Lett. 123, 111102]). Beyond data analysis considerations, the physics of the problem cannot be ignored. As shown in [arXiv:2302.03050], a model consisting of a sum of constant-amplitude overtones starting at the peak of the waveform introduces uncontrolled systematic uncertainties in the measurement due to dynamical and strong-field effects. These theoretical considerations imply that studies based on such models cannot be interpreted as black hole spectroscopy tests. |
2204.02875 | Jos\'e Eliel Camargo Molina | Jos\'e Eliel Camargo-Molina and Arttu Rajantie | Phase transitions in de Sitter: The stochastic formalism | 7 pages, 6 figures | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The stochastic spectral expansion method offers a simple framework for
calculations in de Sitter spacetimes. We show how to extend its reach to
metastable vacuum states, both in the case when the potential is bounded from
below, and when it is unbounded from below and therefore no stable vacuum state
exists. In both cases, the decay rate of the metastable vacuum is given by the
lowest non-zero eigenvalue associated to the Fokker-Planck equation. We show
how the corresponding eigenfunction determines the field probability
distribution which can be used to compute correlation functions and other
observables in the metastable vacuum state.
| [
{
"created": "Wed, 6 Apr 2022 14:44:47 GMT",
"version": "v1"
}
] | 2022-04-07 | [
[
"Camargo-Molina",
"José Eliel",
""
],
[
"Rajantie",
"Arttu",
""
]
] | The stochastic spectral expansion method offers a simple framework for calculations in de Sitter spacetimes. We show how to extend its reach to metastable vacuum states, both in the case when the potential is bounded from below, and when it is unbounded from below and therefore no stable vacuum state exists. In both cases, the decay rate of the metastable vacuum is given by the lowest non-zero eigenvalue associated to the Fokker-Planck equation. We show how the corresponding eigenfunction determines the field probability distribution which can be used to compute correlation functions and other observables in the metastable vacuum state. |
1404.0299 | Fatimah Shojai | F. Shojai and A. Shojai | An f(R) model for dark matter: rotation curves and gravitational lensing | null | General Relativity and Gravitation, 46, 4, 1704, 2014 | 10.1007/s10714-014-1704-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There should be two ways to describe the flat rotation curves of galaxies and
cluster of galaxies. Either one can introduce a dark matter component for the
matter filling the halo, or by modifying the gravity theory and give the flat
rotation curve a geometrical nature. Here we adopt an f(R) model suitable for
describing the effect. After matching the solution with the exterior solution,
the effective density, radial and tangential pressures are obtained. Then the
energy conditions and lensing effect is investigated.
| [
{
"created": "Tue, 1 Apr 2014 16:19:51 GMT",
"version": "v1"
}
] | 2014-04-02 | [
[
"Shojai",
"F.",
""
],
[
"Shojai",
"A.",
""
]
] | There should be two ways to describe the flat rotation curves of galaxies and cluster of galaxies. Either one can introduce a dark matter component for the matter filling the halo, or by modifying the gravity theory and give the flat rotation curve a geometrical nature. Here we adopt an f(R) model suitable for describing the effect. After matching the solution with the exterior solution, the effective density, radial and tangential pressures are obtained. Then the energy conditions and lensing effect is investigated. |
gr-qc/0101013 | Monica Pierri | M. Pierri | Probing Quantum General Relativity Through Exactly Soluble
Midi-Superspaces II: Polarized Gowdy Models | 20 pages, latex | Int.J.Mod.Phys. D11 (2002) 135 | 10.1142/S0218271802001779 | null | gr-qc | null | Canonical quantization of the polarized Gowdy midi-superspace with a 3-torus
spatial topology is carried out. As in an earlier work on the Einstein-Rosen
cylindrical waves, symmetry reduction is used to cast the original problem in
4-dimensional space-times to a 3-dimensional setting. To our knowledge, this is
the first complete, systematic treatment of the Gowdy model in the
geometrodynamical setting.
| [
{
"created": "Tue, 2 Jan 2001 16:50:08 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Pierri",
"M.",
""
]
] | Canonical quantization of the polarized Gowdy midi-superspace with a 3-torus spatial topology is carried out. As in an earlier work on the Einstein-Rosen cylindrical waves, symmetry reduction is used to cast the original problem in 4-dimensional space-times to a 3-dimensional setting. To our knowledge, this is the first complete, systematic treatment of the Gowdy model in the geometrodynamical setting. |
gr-qc/9409023 | Hadi Salehi Kermani | Hadi Salehi | Evaporating Black Holes And An Entropic Scale-Hierarchy | 7 pages, Latex, (ISTPM) IPM-94-055 | null | null | null | gr-qc | null | It is argued that a characteristic length may be associated with the entropic
state of a spherically symmetric black hole in the cosmological context. This
length is much smaller than the Schwarzschild-radius of a black hole and may
act as a regulator of arbitrarily high frequencies apparently entering the
usual derivation of Hawking's radiation.
| [
{
"created": "Mon, 12 Sep 1994 16:40:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Salehi",
"Hadi",
""
]
] | It is argued that a characteristic length may be associated with the entropic state of a spherically symmetric black hole in the cosmological context. This length is much smaller than the Schwarzschild-radius of a black hole and may act as a regulator of arbitrarily high frequencies apparently entering the usual derivation of Hawking's radiation. |
gr-qc/9305017 | Kristin Schleich | John L. Friedman, Kristin Schleich, and Donald M. Witt | Topological Censorship | 12 pages, REVTEX; 1 postscript figure in a separate uuencoded file.
Our earlier version (PRL 71, 1486 (1993)) contained a secondary result,
mistakenly attributed to Schoen and Yau, regarding ``passive topological
censorship'' of a certain class of topologies. As Gregory Burnett has pointed
out (gr-qc/9504012), this secondary result is false. The main topological
censorship theorem is unaffected by the error | Phys.Rev.Lett. 71 (1993) 1486-1489; Erratum-ibid. 75 (1995) 1872 | 10.1103/PhysRevLett.75.1872 | null | gr-qc | null | All three-manifolds are known to occur as Cauchy surfaces of asymptotically
flat vacuum spacetimes and of spacetimes with positive-energy sources. We prove
here the conjecture that general relativity does not allow an observer to probe
the topology of spacetime: any topological structure collapses too quickly to
allow light to traverse it. More precisely, in a globally hyperbolic,
asymptotically flat spacetime satisfying the null energy condition, every
causal curve from $\scri^-$ to ${\scri}^+$ is homotopic to a topologically
trivial curve from $\scri^-$ to ${\scri}^+$. (If the Poincar\'e conjecture is
false, the theorem does not prevent one from probing fake 3-spheres).
| [
{
"created": "Sun, 23 May 1993 21:09:00 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jun 1995 05:21:58 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Friedman",
"John L.",
""
],
[
"Schleich",
"Kristin",
""
],
[
"Witt",
"Donald M.",
""
]
] | All three-manifolds are known to occur as Cauchy surfaces of asymptotically flat vacuum spacetimes and of spacetimes with positive-energy sources. We prove here the conjecture that general relativity does not allow an observer to probe the topology of spacetime: any topological structure collapses too quickly to allow light to traverse it. More precisely, in a globally hyperbolic, asymptotically flat spacetime satisfying the null energy condition, every causal curve from $\scri^-$ to ${\scri}^+$ is homotopic to a topologically trivial curve from $\scri^-$ to ${\scri}^+$. (If the Poincar\'e conjecture is false, the theorem does not prevent one from probing fake 3-spheres). |
2009.04460 | Murli Manohar Verma Dr. | Ajay Sharma and Murli Manohar Verma | Constraining $f(R)$ model through spectral indices and reheating
temperature | 14 pages, 13 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a form of $ f(R) = {R^{1+\delta}}/{R_c^{\delta}}$ and study
the viability of the model for inflation in the Jordan and the Einstein frames.
This model is further analysed by using the power spectrum indices of the
inflation and the reheating temperature. During the inflationary evolution, the
model predicts a value of $\delta$ parameter very close to one ($\delta=0.98$),
while the reheating temperature $T_{re} \sim 10^{17}$ GeV at $\delta=0.98$ is
consistent with the standard approach to inflation and observations. We
calculate the slow roll parameters for the minimally coupled scalar field
within the framework of our model. It is found that the values of the scalar
spectral index and tensor-to-scalar ratio are very close to the recent
observational data, including those released by Planck 2018. We also show that
the Jordan and the Einstein frames are equivalent when $\delta \sim 1 $ by
using the scalar spectral index, tensor-to-scalar ratio and reheating
temperature.
| [
{
"created": "Wed, 9 Sep 2020 10:20:22 GMT",
"version": "v1"
}
] | 2020-09-11 | [
[
"Sharma",
"Ajay",
""
],
[
"Verma",
"Murli Manohar",
""
]
] | We investigate a form of $ f(R) = {R^{1+\delta}}/{R_c^{\delta}}$ and study the viability of the model for inflation in the Jordan and the Einstein frames. This model is further analysed by using the power spectrum indices of the inflation and the reheating temperature. During the inflationary evolution, the model predicts a value of $\delta$ parameter very close to one ($\delta=0.98$), while the reheating temperature $T_{re} \sim 10^{17}$ GeV at $\delta=0.98$ is consistent with the standard approach to inflation and observations. We calculate the slow roll parameters for the minimally coupled scalar field within the framework of our model. It is found that the values of the scalar spectral index and tensor-to-scalar ratio are very close to the recent observational data, including those released by Planck 2018. We also show that the Jordan and the Einstein frames are equivalent when $\delta \sim 1 $ by using the scalar spectral index, tensor-to-scalar ratio and reheating temperature. |
gr-qc/0703076 | Roldao da Rocha | Roldao da Rocha and J. G. Pereira | The quadratic spinor Lagrangian, axial torsion current, and
generalizations | 9 pages, RevTeX, to be published in Int.J.Mod.Phys.D (2007) | Int.J.Mod.Phys.D16:1653-1667,2007 | 10.1142/S0218271807010900 | null | gr-qc | null | We show that the Einstein-Hilbert, the Einstein-Palatini, and the Holst
actions can be derived from the Quadratic Spinor Lagrangian (QSL), when the
three classes of Dirac spinor fields, under Lounesto spinor field
classification, are considered. To each one of these classes, there corresponds
a unique kind of action for a covariant gravity theory. In other words, it is
shown to exist a one-to-one correspondence between the three classes of
non-equivalent solutions of the Dirac equation, and Einstein-Hilbert,
Einstein-Palatini, and Holst actions. Furthermore, it arises naturally, from
Lounesto spinor field classification, that any other class of spinor field
(Weyl, Majorana, flagpole, or flag-dipole spinor fields) yields a trivial
(zero) QSL, up to a boundary term. To investigate this boundary term we do not
impose any constraint on the Dirac spinor field, and consequently we obtain new
terms in the boundary component of the QSL. In the particular case of a
teleparallel connection, an axial torsion 1-form current density is obtained.
New terms are also obtained in the corresponding Hamiltonian formalism. We then
discuss how these new terms could shed new light on more general
investigations.
| [
{
"created": "Tue, 13 Mar 2007 20:53:58 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"da Rocha",
"Roldao",
""
],
[
"Pereira",
"J. G.",
""
]
] | We show that the Einstein-Hilbert, the Einstein-Palatini, and the Holst actions can be derived from the Quadratic Spinor Lagrangian (QSL), when the three classes of Dirac spinor fields, under Lounesto spinor field classification, are considered. To each one of these classes, there corresponds a unique kind of action for a covariant gravity theory. In other words, it is shown to exist a one-to-one correspondence between the three classes of non-equivalent solutions of the Dirac equation, and Einstein-Hilbert, Einstein-Palatini, and Holst actions. Furthermore, it arises naturally, from Lounesto spinor field classification, that any other class of spinor field (Weyl, Majorana, flagpole, or flag-dipole spinor fields) yields a trivial (zero) QSL, up to a boundary term. To investigate this boundary term we do not impose any constraint on the Dirac spinor field, and consequently we obtain new terms in the boundary component of the QSL. In the particular case of a teleparallel connection, an axial torsion 1-form current density is obtained. New terms are also obtained in the corresponding Hamiltonian formalism. We then discuss how these new terms could shed new light on more general investigations. |
1609.02841 | Luis Herrera | L. Herrera, A. Di Prisco, J. Ospino, J. Carot | Earliest stages of the non-equilibrium in axially symmetric,
self-gravitating, dissipative fluids | 13 pages Latex. To appear in Phys. Rev. D. Typos corrected | Phys. Rev. D94, 064072, (2016) | 10.1103/PhysRevD.94.064072 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report a study on axially and reflection symmetric dissipative fluids,
just after its departure from hydrostatic and thermal equilibrium, at the
smallest time scale at which the first signs of dynamic evolution appear. Such
a time scale is smaller than the thermal relaxation time, the thermal
adjustment time and the hydrostatic time. It is obtained that the onset of
non--equilibrium will critically depend on a single function directly related
to the time derivative of the vorticity. Among all fluid variables (at the time
scale under consideration), only the tetrad component of the anisotropic tensor
in the subspace orthogonal to the four--velocity and the Killing vector of
axial symmetry, shows signs of dynamic evolution. Also, the first step toward a
dissipative regime begins with a non--vanishing time derivative of the heat
flux component along the meridional direction. The magnetic part of the Weyl
tensor vanishes (not so its time derivative), indicating that the emission of
gravitational radiation will occur at later times. Finally, the decreasing of
the effective inertial mass density, associated to thermal effects, is clearly
illustrated.
| [
{
"created": "Fri, 9 Sep 2016 15:51:55 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Sep 2016 15:10:41 GMT",
"version": "v2"
}
] | 2016-10-12 | [
[
"Herrera",
"L.",
""
],
[
"Di Prisco",
"A.",
""
],
[
"Ospino",
"J.",
""
],
[
"Carot",
"J.",
""
]
] | We report a study on axially and reflection symmetric dissipative fluids, just after its departure from hydrostatic and thermal equilibrium, at the smallest time scale at which the first signs of dynamic evolution appear. Such a time scale is smaller than the thermal relaxation time, the thermal adjustment time and the hydrostatic time. It is obtained that the onset of non--equilibrium will critically depend on a single function directly related to the time derivative of the vorticity. Among all fluid variables (at the time scale under consideration), only the tetrad component of the anisotropic tensor in the subspace orthogonal to the four--velocity and the Killing vector of axial symmetry, shows signs of dynamic evolution. Also, the first step toward a dissipative regime begins with a non--vanishing time derivative of the heat flux component along the meridional direction. The magnetic part of the Weyl tensor vanishes (not so its time derivative), indicating that the emission of gravitational radiation will occur at later times. Finally, the decreasing of the effective inertial mass density, associated to thermal effects, is clearly illustrated. |
2312.14603 | M Blagojevi\'c | Milutin Blagojevi\'c and James M. Nester | From the Lorentz invariant to the coframe form of $f(T)$ gravity | null | null | null | LaTeX, 21 pages | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the Lorentz invariant $f(T)$ gravity, defined by the
coframe-connection-multiplier form of the Lagrangian, can be gauge-fixed to the
pure coframe form. After clarifying basic aspects of the problem in the
Lagrangian formalism, a more detailed analysis of this gauge equivalence is
given relying on the Dirac Hamiltonian approach.
| [
{
"created": "Fri, 22 Dec 2023 10:58:26 GMT",
"version": "v1"
}
] | 2023-12-25 | [
[
"Blagojević",
"Milutin",
""
],
[
"Nester",
"James M.",
""
]
] | It is shown that the Lorentz invariant $f(T)$ gravity, defined by the coframe-connection-multiplier form of the Lagrangian, can be gauge-fixed to the pure coframe form. After clarifying basic aspects of the problem in the Lagrangian formalism, a more detailed analysis of this gauge equivalence is given relying on the Dirac Hamiltonian approach. |
1412.3827 | Alex Va\~n\'o-Vi\~nuales | Alex Va\~n\'o-Vi\~nuales, Sascha Husa and David Hilditch | Spherical symmetry as a test case for unconstrained hyperboloidal
evolution | 30 pages, 7 figures | Class. Quantum Grav. 32 (2015) 175010 | 10.1088/0264-9381/32/17/175010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the hyperboloidal initial value problem in numerical relativity,
motivated by the goal to evolve radiating compact objects such as black hole
binaries with a numerical grid that includes null infinity. Unconstrained
evolution schemes promise optimal efficiency, but are difficult to regularize
at null infinity, where the compactified Einstein equations are formally
singular. In this work we treat the spherically symmetry case, which already
poses nontrivial problems and constitutes an important first step. We have
carried out stable numerical evolutions with the generalized BSSN and Z4
equations coupled to a scalar field. The crucial ingredients have been to find
an appropriate evolution equation for the lapse function and to adapt
constraint damping terms to handle null infinity.
| [
{
"created": "Thu, 11 Dec 2014 21:20:39 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Sep 2015 16:55:01 GMT",
"version": "v2"
}
] | 2015-09-07 | [
[
"Vañó-Viñuales",
"Alex",
""
],
[
"Husa",
"Sascha",
""
],
[
"Hilditch",
"David",
""
]
] | We consider the hyperboloidal initial value problem in numerical relativity, motivated by the goal to evolve radiating compact objects such as black hole binaries with a numerical grid that includes null infinity. Unconstrained evolution schemes promise optimal efficiency, but are difficult to regularize at null infinity, where the compactified Einstein equations are formally singular. In this work we treat the spherically symmetry case, which already poses nontrivial problems and constitutes an important first step. We have carried out stable numerical evolutions with the generalized BSSN and Z4 equations coupled to a scalar field. The crucial ingredients have been to find an appropriate evolution equation for the lapse function and to adapt constraint damping terms to handle null infinity. |
gr-qc/0208042 | Tekin Dereli | M. Adak (Pamukkale Univ., Denizli, Turkey), T. Dereli (Koc Univ.,
Istanbul, Turkey), L.H. Ryder (Univ. of Kent, Canterbury, UK) | Dirac equation in spacetimes with torsion and non-metricity | 12 pages LATEX file, no figures, to appear in Int. J. Mod. Phys. D | Int.J.Mod.Phys. D12 (2003) 145-156 | 10.1142/S0218271803002445 | null | gr-qc | null | Dirac equation is written in a non-Riemannian spacetime with torsion and
non-metricity by lifting the connection from the tangent bundle to the spinor
bundle over spacetime. Foldy-Wouthuysen transformation of the Dirac equation in
a Schwarzschild background spacetime is considered and it is shown that both
the torsion and non-metricity couples to the momentum and spin of a massive,
spinning particle. However, the effects are small to be observationally
significant.
| [
{
"created": "Fri, 16 Aug 2002 10:26:45 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Adak",
"M.",
"",
"Pamukkale Univ., Denizli, Turkey"
],
[
"Dereli",
"T.",
"",
"Koc Univ.,\n Istanbul, Turkey"
],
[
"Ryder",
"L. H.",
"",
"Univ. of Kent, Canterbury, UK"
]
] | Dirac equation is written in a non-Riemannian spacetime with torsion and non-metricity by lifting the connection from the tangent bundle to the spinor bundle over spacetime. Foldy-Wouthuysen transformation of the Dirac equation in a Schwarzschild background spacetime is considered and it is shown that both the torsion and non-metricity couples to the momentum and spin of a massive, spinning particle. However, the effects are small to be observationally significant. |
1510.05172 | Adam Pound | Adam Pound | Second-order perturbation theory: problems on large scales | 25 pages. Submitted to PRD | Phys. Rev. D 92, 104047 (2015) | 10.1103/PhysRevD.92.104047 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general-relativistic perturbation theory, a point mass accelerates away
from geodesic motion due to its gravitational self-force. Because the
self-force is small, one can often approximate the motion as geodesic. However,
it is well known that self-force effects accumulate over time, making the
geodesic approximation fail on long timescales. It is less well known that this
failure at large times translates to a failure at large distances as well. At
second perturbative order, two large-distance pathologies arise: spurious
secular growth and infrared-divergent retarded integrals. Both stand in the way
of practical computations of second-order self-force effects.
Utilizing a simple flat-space scalar toy model, I develop methods to overcome
these obstacles. The secular growth is tamed with a multiscale expansion that
captures the system's slow evolution. The divergent integrals are eliminated by
matching to the correct retarded solution at large distances. I also show how
to extract conservative self-force effects by taking local-in-time "snapshots"
of the global solution. These methods are readily adaptable to the physically
relevant case of a point mass orbiting a black hole.
| [
{
"created": "Sat, 17 Oct 2015 22:05:18 GMT",
"version": "v1"
}
] | 2016-08-23 | [
[
"Pound",
"Adam",
""
]
] | In general-relativistic perturbation theory, a point mass accelerates away from geodesic motion due to its gravitational self-force. Because the self-force is small, one can often approximate the motion as geodesic. However, it is well known that self-force effects accumulate over time, making the geodesic approximation fail on long timescales. It is less well known that this failure at large times translates to a failure at large distances as well. At second perturbative order, two large-distance pathologies arise: spurious secular growth and infrared-divergent retarded integrals. Both stand in the way of practical computations of second-order self-force effects. Utilizing a simple flat-space scalar toy model, I develop methods to overcome these obstacles. The secular growth is tamed with a multiscale expansion that captures the system's slow evolution. The divergent integrals are eliminated by matching to the correct retarded solution at large distances. I also show how to extract conservative self-force effects by taking local-in-time "snapshots" of the global solution. These methods are readily adaptable to the physically relevant case of a point mass orbiting a black hole. |
1402.1967 | Ikjyot Singh Kohli | Ikjyot Singh Kohli and Michael C. Haslam | The Dynamics of a Two-Fluid Bianchi Type I Universe | null | null | null | null | gr-qc astro-ph.CO math-ph math.CA math.DS math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a dynamical systems approach based on the method of orthonormal frames
to study the dynamics of a two-fluid, non-tilted Bianchi Type I cosmological
model. In our model, one of the fluids is a fluid with bulk viscosity, while
the other fluid assumes the role of a cosmological constant and represents
nonnegative vacuum energy. We begin by completing a detailed fixed-points
analysis of the system which gives information about the local sinks, sources
and saddles. We then proceeded to analyze the global features of the dynamical
system by using topological methods by finding the $\alpha$- and $\omega$-limit
sets. The fixed points found are a flat FLRW universe, an Einstein-de Sitter
universe, a de Sitter universe, a mixed FLRW universe with both vacuum and
non-vacuum energy, and a Kasner universe. We then find conditions for which
each equilibrium point was a saddle, sink, or source, and attempt to describe
the global and past asymptotic behaviour of the model with respect to each
fixed point. The flat FLRW universe solution we found with both vacuum and
non-vacuum energy is clearly of primary importance with respect to modelling
the present-day universe. In particular, we show that this equilibrium point is
a local sink and a saddle of the dynamical system, so there are orbits that
approach this equilibrium point in the future. Therefore, there exists a time
period for which our cosmological model will isotropize and be compatible with
present-day observations of a high degree of isotropy of the cosmic microwave
background in addition to the existence of both vacuum and non-vacuum energy.
| [
{
"created": "Sun, 9 Feb 2014 17:27:48 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Jul 2015 22:46:16 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Oct 2015 23:20:04 GMT",
"version": "v3"
}
] | 2015-10-22 | [
[
"Kohli",
"Ikjyot Singh",
""
],
[
"Haslam",
"Michael C.",
""
]
] | We use a dynamical systems approach based on the method of orthonormal frames to study the dynamics of a two-fluid, non-tilted Bianchi Type I cosmological model. In our model, one of the fluids is a fluid with bulk viscosity, while the other fluid assumes the role of a cosmological constant and represents nonnegative vacuum energy. We begin by completing a detailed fixed-points analysis of the system which gives information about the local sinks, sources and saddles. We then proceeded to analyze the global features of the dynamical system by using topological methods by finding the $\alpha$- and $\omega$-limit sets. The fixed points found are a flat FLRW universe, an Einstein-de Sitter universe, a de Sitter universe, a mixed FLRW universe with both vacuum and non-vacuum energy, and a Kasner universe. We then find conditions for which each equilibrium point was a saddle, sink, or source, and attempt to describe the global and past asymptotic behaviour of the model with respect to each fixed point. The flat FLRW universe solution we found with both vacuum and non-vacuum energy is clearly of primary importance with respect to modelling the present-day universe. In particular, we show that this equilibrium point is a local sink and a saddle of the dynamical system, so there are orbits that approach this equilibrium point in the future. Therefore, there exists a time period for which our cosmological model will isotropize and be compatible with present-day observations of a high degree of isotropy of the cosmic microwave background in addition to the existence of both vacuum and non-vacuum energy. |
gr-qc/9812094 | Mohammad Nouri-Zonoz | Mohammad Nouri-Zonoz and Donald Lynden-Bell | Gravomagnetic Lensing by NUT Space | 29 pages including 15 figures, MNRAS format | Mon. Not. R. Astron. Soc. 292, (1997) | null | null | gr-qc | null | Using the fact that the null geodesics in NUT space lie on spatial cones, we
consider the gravomagnetic lens effect on light rays passing a NUT deflector.
We show that this effect changes the observed shape, size and orientation of a
source. Compared to the Schwarzschild lens, there is an extra shear (a
differential twist around the lens axis) due to the gravomagnetic field which
shears the shape of the source. Gravomagnetic monopoles can thus be recognized
by the spirality that they produce in the lensing pattern. All the results
obtained in this case (magnification factor, orientation of images,
multiplicity of images, etc.) depend on $Q$, the strength of the gravomagnetic
monopole represented by NUT metric. One recovers the results of the usual
Schwarzschild lens effect by putting this factor equal to zero.
| [
{
"created": "Wed, 30 Dec 1998 17:57:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nouri-Zonoz",
"Mohammad",
""
],
[
"Lynden-Bell",
"Donald",
""
]
] | Using the fact that the null geodesics in NUT space lie on spatial cones, we consider the gravomagnetic lens effect on light rays passing a NUT deflector. We show that this effect changes the observed shape, size and orientation of a source. Compared to the Schwarzschild lens, there is an extra shear (a differential twist around the lens axis) due to the gravomagnetic field which shears the shape of the source. Gravomagnetic monopoles can thus be recognized by the spirality that they produce in the lensing pattern. All the results obtained in this case (magnification factor, orientation of images, multiplicity of images, etc.) depend on $Q$, the strength of the gravomagnetic monopole represented by NUT metric. One recovers the results of the usual Schwarzschild lens effect by putting this factor equal to zero. |
2003.04264 | Vasilis Oikonomou | E. Elizalde, S.D. Odintsov, V.K. Oikonomou, Tanmoy Paul | Extended matter bounce scenario in ghost free $f(R,\mathcal{G})$ gravity
compatible with GW170817 | NPB Accepted | null | 10.1016/j.nuclphysb.2020.114984 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of a ghost free $f(R,\mathcal{G})$ model, an extended matter
bounce scenario is studied where the form of the scale factor is given by $a(t)
= (a_0t^2 + 1)^n$. The ghost free character of the model is ensured by the
presence of a Lagrange multiplier, as developed in \cite{Nojiri:2018ouv}. The
conditions under which, in this model, the speed of gravitational waves becomes
equal to the speed of light (equal to one, in natural units), thus becoming
compatible with the striking event GW170817, is investigated. It is shown that
this happens for a class of Gauss-Bonnet (GB) coupling functions ($h(t)$) which
satisfies a constraint equation of the form $\ddot{h} = \dot{h}H$, with $H$ the
Hubble parameter. This constraint is then imposed on the ghost free
$f(R,\mathcal{G})$ gravity theory to be consistent with the GW170817 event,
subsequently, the corresponding non-singular bouncing cosmology with the
aforementioned scale factor is extensively studied. The forms of the coupling
function and Lagrange multiplier in the "low curvature limit" of the theory are
reconstructed, yielding a viable approximation for $n < 1/2$. Correspondingly,
by solving the cosmological perturbation equation, the main observable
quantities, namely the spectral index, tensor to scalar ratio, and the running
index are determined and confronted with the latest Planck 2018 data.
Consistency with the data is proven for those parametric regimes that which
correspond to $n < 1/2$. This makes the low curvature approximation a viable
one for calculating the scalar and tensor power spectra.
| [
{
"created": "Mon, 9 Mar 2020 17:10:16 GMT",
"version": "v1"
}
] | 2020-04-22 | [
[
"Elizalde",
"E.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
],
[
"Paul",
"Tanmoy",
""
]
] | In the context of a ghost free $f(R,\mathcal{G})$ model, an extended matter bounce scenario is studied where the form of the scale factor is given by $a(t) = (a_0t^2 + 1)^n$. The ghost free character of the model is ensured by the presence of a Lagrange multiplier, as developed in \cite{Nojiri:2018ouv}. The conditions under which, in this model, the speed of gravitational waves becomes equal to the speed of light (equal to one, in natural units), thus becoming compatible with the striking event GW170817, is investigated. It is shown that this happens for a class of Gauss-Bonnet (GB) coupling functions ($h(t)$) which satisfies a constraint equation of the form $\ddot{h} = \dot{h}H$, with $H$ the Hubble parameter. This constraint is then imposed on the ghost free $f(R,\mathcal{G})$ gravity theory to be consistent with the GW170817 event, subsequently, the corresponding non-singular bouncing cosmology with the aforementioned scale factor is extensively studied. The forms of the coupling function and Lagrange multiplier in the "low curvature limit" of the theory are reconstructed, yielding a viable approximation for $n < 1/2$. Correspondingly, by solving the cosmological perturbation equation, the main observable quantities, namely the spectral index, tensor to scalar ratio, and the running index are determined and confronted with the latest Planck 2018 data. Consistency with the data is proven for those parametric regimes that which correspond to $n < 1/2$. This makes the low curvature approximation a viable one for calculating the scalar and tensor power spectra. |
2010.05910 | Vasilisa Nikiforova | Vasilisa Nikiforova | Black holes in the long-range limit of torsion bigravity | null | null | 10.1103/PhysRevD.102.124007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue the study of spherically symmetric black hole solutions in
torsion bigravity, a class of Einstein-Cartan-type gravity theories involving,
besides a metric, a massive propagating torsion field. In the infinite-range
limit, these theories admit asymptotically flat black hole solutions related to
the presence of attractive fixed points in the asymptotic radial evolution of
the metric and the torsion. We discuss these fixed points, and the way they are
approached at large radii. Several phenomenological aspects of asymptotically
flat torsion-hairy black holes are discussed: (i) location of the light ring
and of the shadow; (ii) correction to the redshift of orbiting stars; and (iii)
modification of the periastron precession of orbiting stars. By comparing the
observable properties of torsion-hairy black holes to existing observational
data on supermassive black holes obtained by the Event Horizon Telescope
collaboration, and by the GRAVITY collaboration, we derive constraints on the
theory parameters of torsion bigravity. The strongest constraint is found to
come from the recent measurement of the periastron precession of the star S2
orbiting the Galactic-center massive black hole [Astron. Astrophys. 636, L5
(2020)], and to be a thousand times more stringent than solar-system
gravitational tests.
| [
{
"created": "Mon, 12 Oct 2020 16:40:00 GMT",
"version": "v1"
}
] | 2020-12-09 | [
[
"Nikiforova",
"Vasilisa",
""
]
] | We continue the study of spherically symmetric black hole solutions in torsion bigravity, a class of Einstein-Cartan-type gravity theories involving, besides a metric, a massive propagating torsion field. In the infinite-range limit, these theories admit asymptotically flat black hole solutions related to the presence of attractive fixed points in the asymptotic radial evolution of the metric and the torsion. We discuss these fixed points, and the way they are approached at large radii. Several phenomenological aspects of asymptotically flat torsion-hairy black holes are discussed: (i) location of the light ring and of the shadow; (ii) correction to the redshift of orbiting stars; and (iii) modification of the periastron precession of orbiting stars. By comparing the observable properties of torsion-hairy black holes to existing observational data on supermassive black holes obtained by the Event Horizon Telescope collaboration, and by the GRAVITY collaboration, we derive constraints on the theory parameters of torsion bigravity. The strongest constraint is found to come from the recent measurement of the periastron precession of the star S2 orbiting the Galactic-center massive black hole [Astron. Astrophys. 636, L5 (2020)], and to be a thousand times more stringent than solar-system gravitational tests. |
2210.03950 | Xuefeng Zhang | Yi-De Jing, Lu Zheng, Shutao Yang, Xuefeng Zhang, Lingfeng Lu, Binbin
Tang, and Wei Su | Plasma noise in TianQin time delay interferometry | 12 pages, 15 figures, accepted by Phys. Rev. D | Phys. Rev. D 106, 082006 (2022) | 10.1103/PhysRevD.106.082006 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | TianQin is a proposed geocentric space-based gravitational wave observatory
mission, which requires time-delay interferometry (TDI) to cancel laser
frequency noise. With high demands for precision, solar-wind plasma environment
at $\sim 10^5$ km above the Earth may constitute a non-negligible noise source
to laser interferometric measurements between satellites, as charged particles
perturb the refractivity along light paths. In this paper, we first assess the
plasma noises along single links from space-weather models and numerical
orbits, and analyze the time and frequency domain characteristics.
Particularly, to capture the plasma noise in the entire measurement band of
$10^{-4} - 1$ Hz, we have performed additional space-weather
magnetohydrodynamic simulations in finer spatial and temporal resolutions and
utilized Kolmogorov spectra in high-frequency data generation. Then we evaluate
the residual plasma noises of the first- and second-generation TDI
combinations. Both analytical and numerical estimations have shown that under
normal solar conditions the plasma noise after TDI is less than the secondary
noise requirement. Moreover, TDI is shown to exhibit moderate suppression on
the plasma noise below $\sim 10^{-2}$ Hz due to noise correlation between
different arms, when compared with the secondary noise before and after TDI.
| [
{
"created": "Sat, 8 Oct 2022 07:36:15 GMT",
"version": "v1"
}
] | 2022-12-26 | [
[
"Jing",
"Yi-De",
""
],
[
"Zheng",
"Lu",
""
],
[
"Yang",
"Shutao",
""
],
[
"Zhang",
"Xuefeng",
""
],
[
"Lu",
"Lingfeng",
""
],
[
"Tang",
"Binbin",
""
],
[
"Su",
"Wei",
""
]
] | TianQin is a proposed geocentric space-based gravitational wave observatory mission, which requires time-delay interferometry (TDI) to cancel laser frequency noise. With high demands for precision, solar-wind plasma environment at $\sim 10^5$ km above the Earth may constitute a non-negligible noise source to laser interferometric measurements between satellites, as charged particles perturb the refractivity along light paths. In this paper, we first assess the plasma noises along single links from space-weather models and numerical orbits, and analyze the time and frequency domain characteristics. Particularly, to capture the plasma noise in the entire measurement band of $10^{-4} - 1$ Hz, we have performed additional space-weather magnetohydrodynamic simulations in finer spatial and temporal resolutions and utilized Kolmogorov spectra in high-frequency data generation. Then we evaluate the residual plasma noises of the first- and second-generation TDI combinations. Both analytical and numerical estimations have shown that under normal solar conditions the plasma noise after TDI is less than the secondary noise requirement. Moreover, TDI is shown to exhibit moderate suppression on the plasma noise below $\sim 10^{-2}$ Hz due to noise correlation between different arms, when compared with the secondary noise before and after TDI. |
1301.2081 | Paul R. Anderson | Paul R. Anderson, Roberto Balbinot, Alessandro Fabbri and Renaud
Parentani | Hawking radiation correlations in Bose Einstein condensates using
quantum field theory in curved space | minor changes, references added, 38 pages, 14 figures | Phys. Rev. D87, 124018 (2013) | 10.1103/PhysRevD.87.124018 | null | gr-qc cond-mat.quant-gas hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The density density correlation function is computed for the Bogoliubov
pseudoparticles created in a Bose-Einstein condensate undergoing a black hole
flow. On the basis of the gravitational analogy, the method used relies only on
quantum field theory in curved spacetime techniques. A comparison with the
results obtained by ab initio full condensed matter calculations is given,
confirming the validity of the approximation used provided the profile of the
flow varies smoothly on scales compared to the condensate healing length.
| [
{
"created": "Thu, 10 Jan 2013 10:57:29 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jan 2013 16:45:56 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Anderson",
"Paul R.",
""
],
[
"Balbinot",
"Roberto",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Parentani",
"Renaud",
""
]
] | The density density correlation function is computed for the Bogoliubov pseudoparticles created in a Bose-Einstein condensate undergoing a black hole flow. On the basis of the gravitational analogy, the method used relies only on quantum field theory in curved spacetime techniques. A comparison with the results obtained by ab initio full condensed matter calculations is given, confirming the validity of the approximation used provided the profile of the flow varies smoothly on scales compared to the condensate healing length. |
1408.2729 | Adam D. Helfer | Adam D. Helfer | Fermions and gravitational gyrotropy | To appear in PRD. Considerably expanded from the earlier version;
numerical results for effects on the CMB are given. The only substantive
correction to the earlier version is to the overall sign of the effect. 21
pages, 4 figures | Phys. Rev. D 94, 124011 (2016) | 10.1103/PhysRevD.94.124011 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In conventional general relativity without torsion, high-frequency
gravitational waves couple to the chiral number density of spin one-half
quanta: the polarization of the waves is rotated by $2\pi N_5 {\ell_{\rm
Pl}^2}$, where $N_5$ is the chiral column density and $\ell_{\rm Pl}$ is the
Planck length. This means that if a primordial distribution of gravitational
waves with E-E or B-B correlations passed through a chiral density of fermions
in the very early Universe, an E-B correlation will be generated. This in turn
will give rise to E-B and T-B correlations in the cosmic microwave background
(CMB). Less obviously but more primitively, the condition Albrecht called
"cosmic coherence" would be violated, changing the restrictions on the class of
admissible cosmological gravitational waves. This altered class of waves would,
generally speaking, probe earlier physics than do the conventional waves; their
effects on the CMB would be most pronounced for low ($\lesssim 100$)
multipoles. Rough estimates indicate that if the tensor-to-scalar ratio is less
than about $10^{-2}$, it will be hard to constrain a spatially homogeneous
primordial $N_5$ by present data.
| [
{
"created": "Tue, 12 Aug 2014 14:48:01 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Nov 2016 21:27:12 GMT",
"version": "v2"
}
] | 2016-12-14 | [
[
"Helfer",
"Adam D.",
""
]
] | In conventional general relativity without torsion, high-frequency gravitational waves couple to the chiral number density of spin one-half quanta: the polarization of the waves is rotated by $2\pi N_5 {\ell_{\rm Pl}^2}$, where $N_5$ is the chiral column density and $\ell_{\rm Pl}$ is the Planck length. This means that if a primordial distribution of gravitational waves with E-E or B-B correlations passed through a chiral density of fermions in the very early Universe, an E-B correlation will be generated. This in turn will give rise to E-B and T-B correlations in the cosmic microwave background (CMB). Less obviously but more primitively, the condition Albrecht called "cosmic coherence" would be violated, changing the restrictions on the class of admissible cosmological gravitational waves. This altered class of waves would, generally speaking, probe earlier physics than do the conventional waves; their effects on the CMB would be most pronounced for low ($\lesssim 100$) multipoles. Rough estimates indicate that if the tensor-to-scalar ratio is less than about $10^{-2}$, it will be hard to constrain a spatially homogeneous primordial $N_5$ by present data. |
2209.10197 | Kornel Sailer Dr. | S. Nagy, K. Sailer | Interpolation formulas for asymptotically safe cosmology | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Simple interpolation formulas are proposed for the description of the
renormalization group (RG) scale dependences of the gravitational couplings in
the framework of the 2-parameters Einstein-Hilbert (EH) theory of gravity and
applied to a simple, analytically solvable, spatially homogeneous and
isotropic, spatially flat model universe. The analytical solution is found in
two schemes incorporating different methods of the determination of the
conversion rule $k(t)$ of the RG scale $k$ to the cosmological time $t$. In the
case of the discussed model these schemes turn out to yield identical
cosmological evolution. Explicit analytical formulas are found for the
conversion rule $k(t)$ as well as for the characteristic time scales $t_G$ and
$t_\Lambda>t_G$ corresponding to the dynamical energy scales $k_G$ and
$k_\Lambda$, respectively, arising form the RG analysis of the EH theory. It is
shown that there exists a model-dependent time scale $t_d$ ($t_G\le
t_d<t_\Lambda$) at which the accelerating expansion changes to the decelerating
one. It is shown that the evolution runs from a well-identified cosmological
fixed point to another one. As a by-product we show that the entropy of the
system decreases monotonically in the interval $0<t\le t_\Lambda$ due to the
quantum effects.
| [
{
"created": "Wed, 21 Sep 2022 08:48:26 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Nov 2022 06:50:26 GMT",
"version": "v2"
}
] | 2022-11-28 | [
[
"Nagy",
"S.",
""
],
[
"Sailer",
"K.",
""
]
] | Simple interpolation formulas are proposed for the description of the renormalization group (RG) scale dependences of the gravitational couplings in the framework of the 2-parameters Einstein-Hilbert (EH) theory of gravity and applied to a simple, analytically solvable, spatially homogeneous and isotropic, spatially flat model universe. The analytical solution is found in two schemes incorporating different methods of the determination of the conversion rule $k(t)$ of the RG scale $k$ to the cosmological time $t$. In the case of the discussed model these schemes turn out to yield identical cosmological evolution. Explicit analytical formulas are found for the conversion rule $k(t)$ as well as for the characteristic time scales $t_G$ and $t_\Lambda>t_G$ corresponding to the dynamical energy scales $k_G$ and $k_\Lambda$, respectively, arising form the RG analysis of the EH theory. It is shown that there exists a model-dependent time scale $t_d$ ($t_G\le t_d<t_\Lambda$) at which the accelerating expansion changes to the decelerating one. It is shown that the evolution runs from a well-identified cosmological fixed point to another one. As a by-product we show that the entropy of the system decreases monotonically in the interval $0<t\le t_\Lambda$ due to the quantum effects. |
1303.7219 | Frans Klinkhamer | F.R. Klinkhamer, C. Rahmede | A nonsingular spacetime defect | 20 pages, v8: published version | Phys. Rev. D 89, 084064 (2014) | 10.1103/PhysRevD.89.084064 | KA-TP-07-2013 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A nonsingular localized static classical solution is constructed for standard
Einstein gravity coupled to an $SO(3)\times SO(3)$ chiral model of scalars
(Skyrme model). This solution corresponds to a spacetime defect and its
construction proceeds in three steps. First, an \textit{Ansatz} is presented
for a solution with nonsimply connected topology of the spacetime manifold.
Second, an exact vacuum solution of the reduced field equations is obtained.
Third, matter fields are included and a particular exact solution of the
reduced field equations is found. The latter solution has a diverging total
energy, but its existence at least demonstrates that a nonsingular defect-type
solution having nonsimply connected topology is possible with nontrivial matter
fields.
| [
{
"created": "Thu, 28 Mar 2013 19:32:57 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Apr 2013 18:45:44 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Apr 2013 17:22:40 GMT",
"version": "v3"
},
{
"created": "Mon, 8 Apr 2013 17:56:07 GMT",
"version": "v4"
},
{
"crea... | 2015-06-15 | [
[
"Klinkhamer",
"F. R.",
""
],
[
"Rahmede",
"C.",
""
]
] | A nonsingular localized static classical solution is constructed for standard Einstein gravity coupled to an $SO(3)\times SO(3)$ chiral model of scalars (Skyrme model). This solution corresponds to a spacetime defect and its construction proceeds in three steps. First, an \textit{Ansatz} is presented for a solution with nonsimply connected topology of the spacetime manifold. Second, an exact vacuum solution of the reduced field equations is obtained. Third, matter fields are included and a particular exact solution of the reduced field equations is found. The latter solution has a diverging total energy, but its existence at least demonstrates that a nonsingular defect-type solution having nonsimply connected topology is possible with nontrivial matter fields. |
1611.06701 | Bibhas Majhi Ranjan | Rabin Banerjee, Bibhas Ranjan Majhi, Saurav Samanta | Thermogeometric phase transition in a unified framework | Minor changes, to appear in Phys. Lett. B | Phys. Lett. B767 (2017) 25 - 28 | 10.1016/j.physletb.2017.01.040 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using geomterothermodynamics (GTD), we investigate the phase transition of
black hole in a metric independent way. We show that for any black hole,
curvature scalar (of equilibrium state space geometry) is singular at the point
where specific heat diverges. Previously such a result could only be shown by
taking specific examples on a case by case basis. A different type of phase
transition, where inverse specific heat diverges, is also studied within this
framework. We show that in the latter case, metric (of equilibrium state space
geometry) is singular instead of curvature scalar. Since a metric singularity
may be a coordinate artifact, we propose that GTD indicates that it is the
singularity of specific heat and not inverse specific heat which indicates a
phase transition of black holes.
| [
{
"created": "Mon, 21 Nov 2016 09:49:35 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jan 2017 06:56:15 GMT",
"version": "v2"
}
] | 2017-02-03 | [
[
"Banerjee",
"Rabin",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
],
[
"Samanta",
"Saurav",
""
]
] | Using geomterothermodynamics (GTD), we investigate the phase transition of black hole in a metric independent way. We show that for any black hole, curvature scalar (of equilibrium state space geometry) is singular at the point where specific heat diverges. Previously such a result could only be shown by taking specific examples on a case by case basis. A different type of phase transition, where inverse specific heat diverges, is also studied within this framework. We show that in the latter case, metric (of equilibrium state space geometry) is singular instead of curvature scalar. Since a metric singularity may be a coordinate artifact, we propose that GTD indicates that it is the singularity of specific heat and not inverse specific heat which indicates a phase transition of black holes. |
2305.02768 | Chiranjeeb Singha | Shauvik Biswas, Chiranjeeb Singha | Looking for static interior solutions of Buchdahl star with $p_r=0,
p_t=k\rho$ in general relativity and pure Lovelock theories | 10 pages, Comments are welcome | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We find static fluid solutions of Einstein and pure Lovelock equations with
$p_r=0$, $p_t=k\rho$, which could be possible models for the interior of a
Buchdahl-like star. Buchdahl star is a limiting stellar configuration without a
horizon whose formation does not need any exotic matter.
| [
{
"created": "Thu, 4 May 2023 12:14:09 GMT",
"version": "v1"
}
] | 2023-05-05 | [
[
"Biswas",
"Shauvik",
""
],
[
"Singha",
"Chiranjeeb",
""
]
] | We find static fluid solutions of Einstein and pure Lovelock equations with $p_r=0$, $p_t=k\rho$, which could be possible models for the interior of a Buchdahl-like star. Buchdahl star is a limiting stellar configuration without a horizon whose formation does not need any exotic matter. |
1512.03239 | Andronikos Paliathanasis | Andronikos Paliathanasis | $f(R)$-gravity from Killing Tensors | 20 pages, 4 figures, minor corrections, to appear in Classical and
Quantum Gravity | null | 10.1088/0264-9381/33/7/075012 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $f\left(R\right) $-gravity in a
Friedmann-Lema\^itre-Robertson-Walker spacetime with zero spatial curvature. We
apply the Killing tensors of the minisuperspace in order to specify the
functional form of $f\left(R\right) $ and the field equations to be invariant
under Lie-B\"acklund transformations which are linear in the momentum (contact
symmetries). Consequently, the field equations to admit quadratic conservation
laws given by Noether's Theorem. We find three new integrable $f\left(R\right)
$ models, for which with the application of the conservation laws we reduce the
field equations to a system of two first-order ordinary differential equations.
For each model we study the evolution of the cosmological fluid. Where we find
that for the one integrable model the cosmological fluid has an equation of
state parameter, in which in the latter there is a linear behavior in terms of
the scale factor which describes the Chevallier, Polarski and Linder (CPL)
parametric dark energy model.
| [
{
"created": "Thu, 10 Dec 2015 12:59:56 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jan 2016 12:31:32 GMT",
"version": "v2"
}
] | 2016-03-23 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | We consider $f\left(R\right) $-gravity in a Friedmann-Lema\^itre-Robertson-Walker spacetime with zero spatial curvature. We apply the Killing tensors of the minisuperspace in order to specify the functional form of $f\left(R\right) $ and the field equations to be invariant under Lie-B\"acklund transformations which are linear in the momentum (contact symmetries). Consequently, the field equations to admit quadratic conservation laws given by Noether's Theorem. We find three new integrable $f\left(R\right) $ models, for which with the application of the conservation laws we reduce the field equations to a system of two first-order ordinary differential equations. For each model we study the evolution of the cosmological fluid. Where we find that for the one integrable model the cosmological fluid has an equation of state parameter, in which in the latter there is a linear behavior in terms of the scale factor which describes the Chevallier, Polarski and Linder (CPL) parametric dark energy model. |
1105.1974 | Mauricio Bellini | Mauricio Bellini (IFIMAR - Mar del Plata University and CONICET) | Super exponential inflation from a dynamical foliation of a 5D vacuum
state | Final version, to be published in Phys. Lett. B | null | 10.1016/j.physletb.2011.06.071 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce super exponential inflation ($\omega < -1$) from a 5D
Riemann-flat canonical metric on which we make a dynamical foliation. The
resulting metric describes a super accelerated expansion for the early universe
well-known as super exponential inflation that, for very large times, tends to
an asymptotic de Sitter (vacuum dominated) expansion. The scalar field
fluctuations are analyzed. The important result here obtained is that the
spectral index for energy density fluctuations is not scale invariant, and for
cosmological scales becomes $n_s(k<k_*) \simeq 1$. However, for astrophysical
scales this spectrum changes to negative values $n_s(k>k_*) <0 $.
| [
{
"created": "Tue, 10 May 2011 15:27:25 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2011 12:54:54 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Jun 2011 22:26:04 GMT",
"version": "v3"
},
{
"created": "Mon, 15 Aug 2011 16:13:53 GMT",
"version": "v4"
}
] | 2015-05-28 | [
[
"Bellini",
"Mauricio",
"",
"IFIMAR - Mar del Plata University and CONICET"
]
] | We introduce super exponential inflation ($\omega < -1$) from a 5D Riemann-flat canonical metric on which we make a dynamical foliation. The resulting metric describes a super accelerated expansion for the early universe well-known as super exponential inflation that, for very large times, tends to an asymptotic de Sitter (vacuum dominated) expansion. The scalar field fluctuations are analyzed. The important result here obtained is that the spectral index for energy density fluctuations is not scale invariant, and for cosmological scales becomes $n_s(k<k_*) \simeq 1$. However, for astrophysical scales this spectrum changes to negative values $n_s(k>k_*) <0 $. |
2005.00001 | Naouel Boulkaboul | Naouel Boulkaboul | Can Gibbons-Hawking Radiation and Inflation Arise Due to Spacetime
Quanta? | typos corrected, results unchanged | Physics of the Dark Universe 29C (2020) 100553 | 10.1016/j.dark.2020.100553 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, we provide an alternatively reformulated interpretation of
Gibbons-Hawking radiation as well as inflation. By using a spacetime
quantization procedure, proposed recently by L.C. C\'eleri et al., in anti-de
Sitter space we show that Gibbons-Hawking radiation is an intrinsic property of
the concerned space, that arises due to the existence of a scalar field whose
quanta "carry" a length $l$ (i.e. the radius of the hyperboloid curvature).
Furthermore, within the context of Tsallis q-framework, we propose an
inflationary model that depends on the non-extensive parameter $q$. The main
source of such an inflation is the same scalar field mentioned before. Being
constrained by the observational data, the q-parameter along with the rest of
the model's parameters has been used to estimate the time at which inflation
ends as well as the reheating temperature. The latter is found to be related to
Gibbons-Hawking temperature. Thus, the present model offers an alternative
perspective regarding the nature of the cosmic background radiation (CMB).
| [
{
"created": "Thu, 30 Apr 2020 23:30:29 GMT",
"version": "v1"
},
{
"created": "Thu, 7 May 2020 17:12:14 GMT",
"version": "v2"
}
] | 2020-05-08 | [
[
"Boulkaboul",
"Naouel",
""
]
] | In this study, we provide an alternatively reformulated interpretation of Gibbons-Hawking radiation as well as inflation. By using a spacetime quantization procedure, proposed recently by L.C. C\'eleri et al., in anti-de Sitter space we show that Gibbons-Hawking radiation is an intrinsic property of the concerned space, that arises due to the existence of a scalar field whose quanta "carry" a length $l$ (i.e. the radius of the hyperboloid curvature). Furthermore, within the context of Tsallis q-framework, we propose an inflationary model that depends on the non-extensive parameter $q$. The main source of such an inflation is the same scalar field mentioned before. Being constrained by the observational data, the q-parameter along with the rest of the model's parameters has been used to estimate the time at which inflation ends as well as the reheating temperature. The latter is found to be related to Gibbons-Hawking temperature. Thus, the present model offers an alternative perspective regarding the nature of the cosmic background radiation (CMB). |
1110.6274 | Valeri Frolov P | Valeri P. Frolov | Weakly magnetized black holes as particle accelerators | 7 pages, 5 figures | null | 10.1103/PhysRevD.85.024020 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study collision of particles in the vicinity of a horizon of a weakly
magnetized non-rotating black hole. In the presence of the magnetic field
innermost stable circular orbits (ISCO) of charged particles can be located
close to the horizon. We demonstrate that for a collision of two particles, one
of which is charged and revolving at ISCO and the other is neutral and falling
from infinity, the maximal collision energy can be high in the limit of strong
magnetic field. This effect has some similarity with the recently discussed
effect of high center-of-mass energy for collision of particles in extremely
rotating black holes. We also demonstrate that for `realistic' astrophysical
black holes their ability to play the role of `accelerators' is in fact quite
restricted.
| [
{
"created": "Fri, 28 Oct 2011 08:20:22 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Nov 2011 08:55:55 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Dec 2011 08:29:22 GMT",
"version": "v3"
}
] | 2015-06-03 | [
[
"Frolov",
"Valeri P.",
""
]
] | We study collision of particles in the vicinity of a horizon of a weakly magnetized non-rotating black hole. In the presence of the magnetic field innermost stable circular orbits (ISCO) of charged particles can be located close to the horizon. We demonstrate that for a collision of two particles, one of which is charged and revolving at ISCO and the other is neutral and falling from infinity, the maximal collision energy can be high in the limit of strong magnetic field. This effect has some similarity with the recently discussed effect of high center-of-mass energy for collision of particles in extremely rotating black holes. We also demonstrate that for `realistic' astrophysical black holes their ability to play the role of `accelerators' is in fact quite restricted. |
gr-qc/0211094 | Vitor Cardoso | Vitor Cardoso, Jos\'e P. S. Lemos | Gravitational Radiation from the radial infall of highly relativistic
point particles into Kerr black holes | 15 pages, REVTEX4. Some comments and references added | Phys.Rev.D67:084005,2003 | 10.1103/PhysRevD.67.084005 | null | gr-qc astro-ph hep-ph hep-th | null | In this paper, we consider the gravitational radiation generated by the
collision of highly relativistic particles with rotating Kerr black holes. We
use the Sasaki-Nakamura formalism to compute the waveform, energy spectra and
total energy radiated during this process. We show that the gravitational
spectrum for high-energy collisions has definite characteristic universal
features, which are independent of the spin of the colliding objects. We also
discuss possible connections between these results and the black hole-black
hole collision at the speed of light process. With these results at hand, we
predict that during the high speed collision of a non-rotating hole with a
rotating one, about 35% of the total energy can get converted into
gravitational waves. Thus, if one is able to produce black holes at the Large
Hadron Collider, as much as 35% of the partons' energy should be emitted during
the so called balding phase. This energy will be missing, since we don't have
gravitational wave detectors able to measure such amplitudes. The collision at
the speed of light between one rotating black hole and a non-rotating one or
two rotating black holes turns out to be the most efficient gravitational wave
generator in the Universe.
| [
{
"created": "Wed, 27 Nov 2002 13:41:07 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jan 2003 13:46:14 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Cardoso",
"Vitor",
""
],
[
"Lemos",
"José P. S.",
""
]
] | In this paper, we consider the gravitational radiation generated by the collision of highly relativistic particles with rotating Kerr black holes. We use the Sasaki-Nakamura formalism to compute the waveform, energy spectra and total energy radiated during this process. We show that the gravitational spectrum for high-energy collisions has definite characteristic universal features, which are independent of the spin of the colliding objects. We also discuss possible connections between these results and the black hole-black hole collision at the speed of light process. With these results at hand, we predict that during the high speed collision of a non-rotating hole with a rotating one, about 35% of the total energy can get converted into gravitational waves. Thus, if one is able to produce black holes at the Large Hadron Collider, as much as 35% of the partons' energy should be emitted during the so called balding phase. This energy will be missing, since we don't have gravitational wave detectors able to measure such amplitudes. The collision at the speed of light between one rotating black hole and a non-rotating one or two rotating black holes turns out to be the most efficient gravitational wave generator in the Universe. |
gr-qc/0506015 | Neil J. Cornish | Jeff Crowder and Neil J. Cornish | Beyond LISA: Exploring Future Gravitational Wave Missions | 9 pages, 10 figures, published version | Phys.Rev. D72 (2005) 083005 | 10.1103/PhysRevD.72.083005 | null | gr-qc | null | The Advanced Laser Interferometer Antenna (ALIA) and the Big Bang Observer
(BBO) have been proposed as follow on missions to the Laser Interferometer
Space Antenna (LISA). Here we study the capabilities of these observatories,
and how they relate to the science goals of the missions. We find that the
Advanced Laser Interferometer Antenna in Stereo (ALIAS), our proposed extension
to the ALIA mission, will go considerably further toward meeting ALIA's main
scientific goal of studying intermediate mass black holes. We also compare the
capabilities of LISA to a related extension of the LISA mission, the Laser
Interferometer Space Antenna in Stereo (LISAS). Additionally, we find that the
initial deployment phase of the BBO would be sufficient to address the BBO's
key scientific goal of detecting the Gravitational Wave Background, while still
providing detailed information about foreground sources.
| [
{
"created": "Fri, 3 Jun 2005 16:46:52 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jun 2005 04:35:37 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Oct 2005 19:04:42 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Crowder",
"Jeff",
""
],
[
"Cornish",
"Neil J.",
""
]
] | The Advanced Laser Interferometer Antenna (ALIA) and the Big Bang Observer (BBO) have been proposed as follow on missions to the Laser Interferometer Space Antenna (LISA). Here we study the capabilities of these observatories, and how they relate to the science goals of the missions. We find that the Advanced Laser Interferometer Antenna in Stereo (ALIAS), our proposed extension to the ALIA mission, will go considerably further toward meeting ALIA's main scientific goal of studying intermediate mass black holes. We also compare the capabilities of LISA to a related extension of the LISA mission, the Laser Interferometer Space Antenna in Stereo (LISAS). Additionally, we find that the initial deployment phase of the BBO would be sufficient to address the BBO's key scientific goal of detecting the Gravitational Wave Background, while still providing detailed information about foreground sources. |
2309.14912 | Andreu Maso-Ferrando | Andreu Mas\'o-Ferrando, Nicolas Sanchis-Gual, Jos\'e A. Font, Gonzalo
J. Olmo | Numerical evolutions of boson stars in Palatini $f(\mathcal{R})$ gravity | null | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We investigate the time evolution of spherically symmetric boson stars in
Palatini $f(\mathcal{R})$ gravity through Numerical Relativity computations.
Employing a novel approach that establishes a correspondence between modified
gravity with scalar matter and General Relativity with modified scalar matter,
we are able to use the techniques of Numerical Relativity to simulate these
systems. Specifically, we focus on the quadratic theory
$f(\mathcal{R})=\mathcal{R}+\xi\mathcal{R}^2$ and compare the obtained
solutions with those in General Relativity, exploring both positive and
negative values of the coupling parameter $\xi$. Our findings reveal that boson
stars in Palatini $f(\mathcal{R})$ gravity exhibit both stable and unstable
evolutions. The latter give rise to three distinct scenarios: migration towards
a stable configuration, complete dispersion, and gravitational collapse leading
to the formation of a baby universe structure.
| [
{
"created": "Tue, 26 Sep 2023 13:14:26 GMT",
"version": "v1"
}
] | 2023-09-27 | [
[
"Masó-Ferrando",
"Andreu",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Font",
"José A.",
""
],
[
"Olmo",
"Gonzalo J.",
""
]
] | We investigate the time evolution of spherically symmetric boson stars in Palatini $f(\mathcal{R})$ gravity through Numerical Relativity computations. Employing a novel approach that establishes a correspondence between modified gravity with scalar matter and General Relativity with modified scalar matter, we are able to use the techniques of Numerical Relativity to simulate these systems. Specifically, we focus on the quadratic theory $f(\mathcal{R})=\mathcal{R}+\xi\mathcal{R}^2$ and compare the obtained solutions with those in General Relativity, exploring both positive and negative values of the coupling parameter $\xi$. Our findings reveal that boson stars in Palatini $f(\mathcal{R})$ gravity exhibit both stable and unstable evolutions. The latter give rise to three distinct scenarios: migration towards a stable configuration, complete dispersion, and gravitational collapse leading to the formation of a baby universe structure. |
1812.01620 | Richard Brito | Shrobana Ghosh, Emanuele Berti, Richard Brito and Mauricio Richartz | Follow-up signals from superradiant instabilities of black hole merger
remnants | v1:10 pages, 8 figures, 2 tables; v2: matches published version | Phys. Rev. D 99, 104030 (2019) | 10.1103/PhysRevD.99.104030 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Superradiant instabilities can trigger the formation of bosonic clouds around
rotating black holes. If the bosonic field growth is sufficiently fast, these
clouds could form shortly after a binary black hole merger. Such clouds are
continuous sources of gravitational waves whose detection (or lack thereof) can
probe the existence of ultralight bosons (such as axion-like particles) and
their properties. Motivated by the binary black hole mergers seen by Advanced
LIGO so far, we investigate in detail the parameter space that can be probed
with continuous gravitational wave signals from ultralight scalar field clouds
around black hole merger remnants with particular focus on future ground-based
detectors (A+, Voyager and Cosmic Explorer). We also study the impact that the
confusion noise from a putative stochastic gravitational-wave background from
unresolved sources would have on such searches and we estimate, under different
astrophysical priors, the number of binary black-hole merger events that could
lead to an observable post-merger signal. Under our most optimistic
assumptions, Cosmic Explorer could detect dozens of post-merger signals.
| [
{
"created": "Tue, 4 Dec 2018 19:00:08 GMT",
"version": "v1"
},
{
"created": "Sat, 25 May 2019 08:26:39 GMT",
"version": "v2"
}
] | 2019-05-28 | [
[
"Ghosh",
"Shrobana",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Brito",
"Richard",
""
],
[
"Richartz",
"Mauricio",
""
]
] | Superradiant instabilities can trigger the formation of bosonic clouds around rotating black holes. If the bosonic field growth is sufficiently fast, these clouds could form shortly after a binary black hole merger. Such clouds are continuous sources of gravitational waves whose detection (or lack thereof) can probe the existence of ultralight bosons (such as axion-like particles) and their properties. Motivated by the binary black hole mergers seen by Advanced LIGO so far, we investigate in detail the parameter space that can be probed with continuous gravitational wave signals from ultralight scalar field clouds around black hole merger remnants with particular focus on future ground-based detectors (A+, Voyager and Cosmic Explorer). We also study the impact that the confusion noise from a putative stochastic gravitational-wave background from unresolved sources would have on such searches and we estimate, under different astrophysical priors, the number of binary black-hole merger events that could lead to an observable post-merger signal. Under our most optimistic assumptions, Cosmic Explorer could detect dozens of post-merger signals. |
gr-qc/9910115 | Horacio Casini | H. Casini and R. Montemayor | Covariant description for superfluids in gravitational fields | 22 pages, no figures | null | null | null | gr-qc | null | In this paper we develop a formalism to describe a superfluid in a
gravitational background. This formalism is based on a covariant generalization
of the field description for a superconductor in terms of a U(1) spontaneous
symmetry breaking. We study the stability of the solutions for a vortexless
fluid and the force acting on vortices in the fluid, which is a generalization
of the well-known flat space-time Magnus force. To clarify the development we
include the explicit discussion of two particular cases, one of them of
astrophysical interest.
| [
{
"created": "Mon, 1 Nov 1999 17:26:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Casini",
"H.",
""
],
[
"Montemayor",
"R.",
""
]
] | In this paper we develop a formalism to describe a superfluid in a gravitational background. This formalism is based on a covariant generalization of the field description for a superconductor in terms of a U(1) spontaneous symmetry breaking. We study the stability of the solutions for a vortexless fluid and the force acting on vortices in the fluid, which is a generalization of the well-known flat space-time Magnus force. To clarify the development we include the explicit discussion of two particular cases, one of them of astrophysical interest. |
gr-qc/9605009 | George Emanuel Avraam Matsas | George E.A. Matsas | Rindler and Minkowski particles relationship revisited | To appear in Physics Letters B, 9 pages, LATEX, no-figures | Phys.Lett. B380 (1996) 24-28 | 10.1016/0370-2693(96)00493-5 | null | gr-qc | null | We show that the emission of a Minkowski particle by a general class of
scalar sources as described by inertial observers corresponds to either the
emission or the absorption of a Rindler particle as described by uniformly
accelerated observers. Our results are discussed in connection with the current
controversy whether uniformly accelerated detectors radiate.
| [
{
"created": "Sun, 5 May 1996 22:20:03 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Matsas",
"George E. A.",
""
]
] | We show that the emission of a Minkowski particle by a general class of scalar sources as described by inertial observers corresponds to either the emission or the absorption of a Rindler particle as described by uniformly accelerated observers. Our results are discussed in connection with the current controversy whether uniformly accelerated detectors radiate. |
2006.11889 | Angel Rincon | Angel Rincon and Grigoris Panotopoulos | Quasinormal modes of an improved Schwarzschild black hole | v2: 11 pages, 6 figures, 4 tables. Published in Physics of the Dark
Universe, reference added | Physics of the Dark Universe, ISSN: 2212-6864, Vol: 30, Year:
2020, Page: 100639 | 10.1016/j.dark.2020.100639 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the quasinormal frequencies for scalar and electromagnetic
perturbations of an improved Schwarzschild geometry in the framework of
asymptotically safe gravity, which is one of the approaches to quantum gravity.
Adopting the widely used WKB semi-classical approximation, we investigate the
impact on the spectrum of the angular degree, the overtone number as well as
the black hole mass. We summarize our numerical results in tables, and for
better visualization, we show them graphically as well. All modes are found to
be stable. Finally, we compare our numerical results with those corresponding
to the classical Schwarzschild solution as well as to the results obtained
using a different approach. Our findings show that i) a different cut-off
identification does not affect the spectra significantly, and ii) for
hypothetical objects with masses comparable to the Planck mass, the difference
in the numerical values between the modes of the classical solution and the
modes of the improved solution studied here is of the order of a few per cent.
On the contrary, for realistic, astrophysical BHs no difference in the
frequencies is observed.
| [
{
"created": "Sun, 21 Jun 2020 19:42:11 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jul 2020 21:29:17 GMT",
"version": "v2"
}
] | 2020-07-03 | [
[
"Rincon",
"Angel",
""
],
[
"Panotopoulos",
"Grigoris",
""
]
] | We compute the quasinormal frequencies for scalar and electromagnetic perturbations of an improved Schwarzschild geometry in the framework of asymptotically safe gravity, which is one of the approaches to quantum gravity. Adopting the widely used WKB semi-classical approximation, we investigate the impact on the spectrum of the angular degree, the overtone number as well as the black hole mass. We summarize our numerical results in tables, and for better visualization, we show them graphically as well. All modes are found to be stable. Finally, we compare our numerical results with those corresponding to the classical Schwarzschild solution as well as to the results obtained using a different approach. Our findings show that i) a different cut-off identification does not affect the spectra significantly, and ii) for hypothetical objects with masses comparable to the Planck mass, the difference in the numerical values between the modes of the classical solution and the modes of the improved solution studied here is of the order of a few per cent. On the contrary, for realistic, astrophysical BHs no difference in the frequencies is observed. |
gr-qc/0611055 | Ilya Lvovich Shapiro | Ilya L. Shapiro (UFJF, Brazil), Joan Sola (University of Barcelona) | Cosmological Constant Problems and Renormalization Group | 12 pages, LaTeX, based on the on the talk at IRGAC-2006 (Barcelona,
July 11-15, 2006), misprints corrected, comment on anthropic approach
modified, some references added, accepted in Journal of Physics A | J.Phys.A40:6583-6593,2007 | 10.1088/1751-8113/40/25/S03 | DF-UFJF/01-2006 | gr-qc | null | The Cosmological Constant Problem emerges when Quantum Field Theory is
applied to the gravitational theory, due to the enormous magnitude of the
induced energy of the vacuum. The unique known solution of this problem
involves an extremely precise fine-tuning of the vacuum counterpart. We review
a few of the existing approaches to this problem based on the account of the
quantum (loop) effects and pay special attention to the ones involving the
renormalization group.
| [
{
"created": "Wed, 8 Nov 2006 22:19:48 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jan 2007 18:55:10 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Shapiro",
"Ilya L.",
"",
"UFJF, Brazil"
],
[
"Sola",
"Joan",
"",
"University of Barcelona"
]
] | The Cosmological Constant Problem emerges when Quantum Field Theory is applied to the gravitational theory, due to the enormous magnitude of the induced energy of the vacuum. The unique known solution of this problem involves an extremely precise fine-tuning of the vacuum counterpart. We review a few of the existing approaches to this problem based on the account of the quantum (loop) effects and pay special attention to the ones involving the renormalization group. |
0912.4563 | David Wiltshire | David L. Wiltshire | From time to timescape - Einstein's unfinished revolution | 13 pages, 3 figures; A runner-up in the 2008 FQXi Essay Contest on
the Nature of Time; Int. J. Mod. Phys. D 18, in press | Int.J.Mod.Phys.D18:2121-2134,2009 | 10.1142/S0218271809016193 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I argue that Einstein overlooked an important aspect of the relativity of
time in never quite realizing his quest to embody Mach's principle in his
theory of gravity. As a step towards that goal, I broaden the Strong
Equivalence Principle to a new principle of physics, the Cosmological
Equivalence Principle, to account for the role of the evolving average regional
density of the universe in the synchronisation of clocks and the relative
calibration of inertial frames. In a universe dominated by voids of the size
observed in large-scale structure surveys, the density contrasts of expanding
regions are strong enough that a relative deceleration of the background
between voids and the environment of galaxies, typically of order 10^{-10}
m/s^2, must be accounted for. As a result one finds a universe whose present
age varies by billions of years according to the position of the observer: a
timescape. This model universe is observationally viable: it passes three
critical independent tests, and makes additional predictions. Dark energy is
revealed as a mis-identification of gravitational energy gradients and the
resulting variance in clock rates. Understanding the biggest mystery in
cosmology therefore involves a paradigm shift, but in an unexpected direction:
the conceptual understanding of time and energy in Einstein's own theory is
incomplete.
| [
{
"created": "Wed, 23 Dec 2009 08:55:56 GMT",
"version": "v1"
}
] | 2010-04-21 | [
[
"Wiltshire",
"David L.",
""
]
] | I argue that Einstein overlooked an important aspect of the relativity of time in never quite realizing his quest to embody Mach's principle in his theory of gravity. As a step towards that goal, I broaden the Strong Equivalence Principle to a new principle of physics, the Cosmological Equivalence Principle, to account for the role of the evolving average regional density of the universe in the synchronisation of clocks and the relative calibration of inertial frames. In a universe dominated by voids of the size observed in large-scale structure surveys, the density contrasts of expanding regions are strong enough that a relative deceleration of the background between voids and the environment of galaxies, typically of order 10^{-10} m/s^2, must be accounted for. As a result one finds a universe whose present age varies by billions of years according to the position of the observer: a timescape. This model universe is observationally viable: it passes three critical independent tests, and makes additional predictions. Dark energy is revealed as a mis-identification of gravitational energy gradients and the resulting variance in clock rates. Understanding the biggest mystery in cosmology therefore involves a paradigm shift, but in an unexpected direction: the conceptual understanding of time and energy in Einstein's own theory is incomplete. |
2107.02562 | Horacio Santana Vieira | H. S. Vieira, V. B. Bezerra and C. R. Muniz | Instability of the charged massive scalar field on the Kerr-Newman black
hole spacetime | 29 pages, 8 figures | Eur. Phys. J. C 82, 932 (2022) | 10.1140/epjc/s10052-022-10908-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the quasibound states of charged massive scalar fields in the
Kerr-Newman black hole spacetime by using a new approach recently developed,
which uses the polynomial conditions of the Heun functions. We calculate the
resonant frequencies related to the spectrum of quasibound states, as well as
its corresponding angular and radial wave eigenfunctions. We also analyze the
instability of the system. These results are particularized to the cases of
Schwarzschild and Kerr black holes. Additionally, we compare our analytical
results with the numerical ones known in the literature. Finally, we apply the
obtained results to compute the characteristic times of growth and decay of
bosonic particles around a supermassive black hole situated at the center of
the M87 galaxy.
| [
{
"created": "Tue, 6 Jul 2021 12:04:05 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Oct 2022 13:21:46 GMT",
"version": "v2"
}
] | 2022-10-24 | [
[
"Vieira",
"H. S.",
""
],
[
"Bezerra",
"V. B.",
""
],
[
"Muniz",
"C. R.",
""
]
] | We investigate the quasibound states of charged massive scalar fields in the Kerr-Newman black hole spacetime by using a new approach recently developed, which uses the polynomial conditions of the Heun functions. We calculate the resonant frequencies related to the spectrum of quasibound states, as well as its corresponding angular and radial wave eigenfunctions. We also analyze the instability of the system. These results are particularized to the cases of Schwarzschild and Kerr black holes. Additionally, we compare our analytical results with the numerical ones known in the literature. Finally, we apply the obtained results to compute the characteristic times of growth and decay of bosonic particles around a supermassive black hole situated at the center of the M87 galaxy. |
1508.03832 | Tiberiu Harko | Piyabut Burikham, Krai Cheamsawat, Tiberiu Harko, Matthew J. Lake | The minimum mass of a spherically symmetric object in $D$-dimensions,
and its implications for the mass hierarchy problem | 16 pages, one figure; Section IV extended; references added; accepted
for publication in EPJC | Eur. Phys. J. C (2015) 75:442 | 10.1140/epjc/s10052-015-3673-5 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of both a minimum mass and a minimum density in nature, in the
presence of a positive cosmological constant, is one of the most intriguing
results in classical general relativity. These results follow rigorously from
the Buchdahl inequalities in four dimensional de Sitter space. In this work, we
obtain the generalized Buchdahl inequalities in arbitrary space-time dimensions
with $\Lambda \neq 0$ and consider both the de Sitter and anti-de Sitter cases.
The dependence on $D$, the number of space-time dimensions, of the minimum and
maximum masses for stable spherical objects is explicitly obtained. The
analysis is then extended to the case of dark energy satisfying an arbitrary
linear barotropic equation of state. The Jeans instability of barotropic dark
energy is also investigated, for arbitrary $D$, in the framework of a simple
Newtonian model with and without viscous dissipation, and we determine the
dispersion relation describing the dark energy$-$matter condensation process,
along with estimates of the corresponding Jeans mass (and radius). Finally, the
quantum mechanical implications of mass limits are investigated, and we show
that the existence of a minimum mass scale naturally leads to a model in which
dark energy is composed of a `sea' of quantum particles, each with an effective
mass proportional to $\Lambda^{1/4}$.
| [
{
"created": "Sun, 16 Aug 2015 15:00:41 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Sep 2015 18:30:59 GMT",
"version": "v2"
}
] | 2015-11-30 | [
[
"Burikham",
"Piyabut",
""
],
[
"Cheamsawat",
"Krai",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Lake",
"Matthew J.",
""
]
] | The existence of both a minimum mass and a minimum density in nature, in the presence of a positive cosmological constant, is one of the most intriguing results in classical general relativity. These results follow rigorously from the Buchdahl inequalities in four dimensional de Sitter space. In this work, we obtain the generalized Buchdahl inequalities in arbitrary space-time dimensions with $\Lambda \neq 0$ and consider both the de Sitter and anti-de Sitter cases. The dependence on $D$, the number of space-time dimensions, of the minimum and maximum masses for stable spherical objects is explicitly obtained. The analysis is then extended to the case of dark energy satisfying an arbitrary linear barotropic equation of state. The Jeans instability of barotropic dark energy is also investigated, for arbitrary $D$, in the framework of a simple Newtonian model with and without viscous dissipation, and we determine the dispersion relation describing the dark energy$-$matter condensation process, along with estimates of the corresponding Jeans mass (and radius). Finally, the quantum mechanical implications of mass limits are investigated, and we show that the existence of a minimum mass scale naturally leads to a model in which dark energy is composed of a `sea' of quantum particles, each with an effective mass proportional to $\Lambda^{1/4}$. |
1807.03802 | Dejan Gajic | Yannis Angelopoulos and Stefanos Aretakis and Dejan Gajic | Late-time asymptotics for the wave equation on extremal
Reissner-Nordstr\"om backgrounds | 87 pages, 10 figures; version accepted for publication | Advances in Mathematics 375, 107363 (2020) | 10.1016/j.aim.2020.107363 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the precise late-time asymptotics for solutions to the wave
equation on extremal Reissner-Nordstr\"om black holes and explicitly express
the leading-order coefficients in terms of the initial data. Our method is
based on purely physical space techniques. We derive novel weighted energy
hierarchies and develop a singular time inversion theory, which allow us to
uncover the subtle contribution of both the near-horizon and near-infinity
regions to the precise asymptotics. We introduce a new horizon charge and
provide applications pertaining to the interior dynamics of extremal black
holes. Our work confirms, and in some cases extends, the numerical and
heuristic analysis of Lucietti-Murata-Reall-Tanahashi, Ori-Sela and
Blaksley-Burko.
| [
{
"created": "Tue, 10 Jul 2018 18:03:53 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Feb 2021 17:24:50 GMT",
"version": "v2"
}
] | 2021-02-25 | [
[
"Angelopoulos",
"Yannis",
""
],
[
"Aretakis",
"Stefanos",
""
],
[
"Gajic",
"Dejan",
""
]
] | We derive the precise late-time asymptotics for solutions to the wave equation on extremal Reissner-Nordstr\"om black holes and explicitly express the leading-order coefficients in terms of the initial data. Our method is based on purely physical space techniques. We derive novel weighted energy hierarchies and develop a singular time inversion theory, which allow us to uncover the subtle contribution of both the near-horizon and near-infinity regions to the precise asymptotics. We introduce a new horizon charge and provide applications pertaining to the interior dynamics of extremal black holes. Our work confirms, and in some cases extends, the numerical and heuristic analysis of Lucietti-Murata-Reall-Tanahashi, Ori-Sela and Blaksley-Burko. |
gr-qc/0109072 | Jacques L. Rubin | Jacques L. Rubin | Pfaff systems theory and the unifications of gravitation and
electromagnetism | 29 pages, 25 references, no figures, submitted in May 2001 to J.
Geom. Phys | null | null | Preprint INLN 2001/14 | gr-qc | null | We show in the framework of Pfaff systems theory, the functional dependences
of the general analytic solutions of a suitable system of involutive
differential equations describing the differences between the analytic
solutions of the conformal and "Poincar\'e" Lie equations. Then we ascribe to
the infinitesimal variations of the parametrizing functionals some physical
meanings as the electromagnetic and gravitation potentials. We also deduce
their corresponding fields of interactions together with the differential
equations they must satisfy. Then we discuss on various possible physical
interpretations.
| [
{
"created": "Thu, 20 Sep 2001 10:26:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rubin",
"Jacques L.",
""
]
] | We show in the framework of Pfaff systems theory, the functional dependences of the general analytic solutions of a suitable system of involutive differential equations describing the differences between the analytic solutions of the conformal and "Poincar\'e" Lie equations. Then we ascribe to the infinitesimal variations of the parametrizing functionals some physical meanings as the electromagnetic and gravitation potentials. We also deduce their corresponding fields of interactions together with the differential equations they must satisfy. Then we discuss on various possible physical interpretations. |
2403.18446 | Emir Syahreza Fadhilla | Emir Syahreza Fadhilla, Bobby Eka Gunara, Agus Suroso, Ardian Nata
Atmaja | Cosmic Inflation From Fluctuating Baby-Skyrme Brane | 14 pages, 3 figures, single column format, the analysis of dynamical
system are revised for both high and low energy cases, accepted in Annals of
Physics | null | 10.1016/j.aop.2024.169766 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we explore the inflationary dynamics induced by small
fluctuations on the Skyrme brane, characterized by a time-dependent
perturbative function $\tilde{\phi}$. In the low-energy regime, the model
successfully reproduces standard inflation, with a potential term dictated by
the Skyrmion at the brane. Gravity localization is achieved at the brane, and
the lowest energy scale is established at the asymptotic boundary. The model
demonstrates the capability to emulate standard inflation dynamics, resembling
$\tilde{\phi}^4$ potential characteristics under certain conditions. At higher
energy levels, the behaviour of $\tilde{\phi}$ is contingent upon the Skyrme
term coupling constant $\lambda$, influencing reheating phases. The wave-like
nature of fluctuations allows for energy transfer, resulting in a possibly
lower reheating temperature. We also discuss the prospect of $\lambda$ changing
sign during inflation, presenting a non-standard coupling dependent on the
matter field.
| [
{
"created": "Wed, 27 Mar 2024 11:05:26 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Aug 2024 08:25:17 GMT",
"version": "v2"
}
] | 2024-08-15 | [
[
"Fadhilla",
"Emir Syahreza",
""
],
[
"Gunara",
"Bobby Eka",
""
],
[
"Suroso",
"Agus",
""
],
[
"Atmaja",
"Ardian Nata",
""
]
] | In this work, we explore the inflationary dynamics induced by small fluctuations on the Skyrme brane, characterized by a time-dependent perturbative function $\tilde{\phi}$. In the low-energy regime, the model successfully reproduces standard inflation, with a potential term dictated by the Skyrmion at the brane. Gravity localization is achieved at the brane, and the lowest energy scale is established at the asymptotic boundary. The model demonstrates the capability to emulate standard inflation dynamics, resembling $\tilde{\phi}^4$ potential characteristics under certain conditions. At higher energy levels, the behaviour of $\tilde{\phi}$ is contingent upon the Skyrme term coupling constant $\lambda$, influencing reheating phases. The wave-like nature of fluctuations allows for energy transfer, resulting in a possibly lower reheating temperature. We also discuss the prospect of $\lambda$ changing sign during inflation, presenting a non-standard coupling dependent on the matter field. |
2309.06333 | Elliot Nash | Steffen Gielen and Elliot Nash | Unimodular Pleba\'{n}ski Gravity | 11 pages | Class. Quant. Grav. 41 (2024) 085009 | 10.1088/1361-6382/ad3277 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new action principles for unimodular gravity, defined in the
chiral Pleba\'{n}ski formulation based on (complex) two-forms and a complex
${\rm SO}(3)$ connection. In these theories, just as in their analogues in the
metric formulation, the cosmological constant does not take a prescribed value
but is an integration constant whose value can differ between different
(classical) solutions. We discuss some subtleties when identifying Lorentzian
solutions in the generally complex theory, and show how these theories can be
reduced to a ``pure connection'' form similar to Krasnov's pure connection
formalism for general relativity.
| [
{
"created": "Tue, 12 Sep 2023 15:49:18 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jan 2024 14:56:31 GMT",
"version": "v2"
}
] | 2024-03-29 | [
[
"Gielen",
"Steffen",
""
],
[
"Nash",
"Elliot",
""
]
] | We present new action principles for unimodular gravity, defined in the chiral Pleba\'{n}ski formulation based on (complex) two-forms and a complex ${\rm SO}(3)$ connection. In these theories, just as in their analogues in the metric formulation, the cosmological constant does not take a prescribed value but is an integration constant whose value can differ between different (classical) solutions. We discuss some subtleties when identifying Lorentzian solutions in the generally complex theory, and show how these theories can be reduced to a ``pure connection'' form similar to Krasnov's pure connection formalism for general relativity. |
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