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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0508062 | Martin Snajdr | Martin Snajdr | Critical Collapse of an Ultrarelativistic Fluid in the $\Gamma\to 1$
Limit | 23 pages, 16 figures, revised version, added new results of
investigation of a supercritical collapse and the existence of naked
singularities in generic gravitational collapse | Class.Quant.Grav. 23 (2006) 3333-3352 | 10.1088/0264-9381/23/10/006 | null | gr-qc | null | In this paper we investigate the critical collapse of an ultrarelativistic
perfect fluid with the equation of state $P=(\Gamma-1)\rho$ in the limit of
$\Gamma\to 1$. We calculate the limiting continuously self similar (CSS)
solution and the limiting scaling exponent by exploiting self-similarity of the
solution. We also solve the complete set of equations governing the
gravitational collapse numerically for $(\Gamma-1) = 10^{-2},...,10^{-6}$ and
compare them with the CSS solutions. We also investigate the supercritical
regime and discuss the hypothesis of naked singularity formation in a generic
gravitational collapse. The numerical calculations make use of advanced methods
such as high resolution shock capturing evolution scheme for the matter
evolution, adaptive mesh refinement, and quadruple precision arithmetic. The
treatment of vacuum is also non standard. We were able to tune the critical
parameter up to 30 significant digits and to calculate the scaling exponents
accurately. The numerical results agree very well with those calculated using
the CSS ansatz. The analysis of the collapse in the supercritical regime
supports the hypothesis of the existence of naked singularities formed during a
generic gravitational collapse.
| [
{
"created": "Tue, 16 Aug 2005 05:30:39 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Feb 2006 06:00:38 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Snajdr",
"Martin",
""
]
] | In this paper we investigate the critical collapse of an ultrarelativistic perfect fluid with the equation of state $P=(\Gamma-1)\rho$ in the limit of $\Gamma\to 1$. We calculate the limiting continuously self similar (CSS) solution and the limiting scaling exponent by exploiting self-similarity of the solution. We also solve the complete set of equations governing the gravitational collapse numerically for $(\Gamma-1) = 10^{-2},...,10^{-6}$ and compare them with the CSS solutions. We also investigate the supercritical regime and discuss the hypothesis of naked singularity formation in a generic gravitational collapse. The numerical calculations make use of advanced methods such as high resolution shock capturing evolution scheme for the matter evolution, adaptive mesh refinement, and quadruple precision arithmetic. The treatment of vacuum is also non standard. We were able to tune the critical parameter up to 30 significant digits and to calculate the scaling exponents accurately. The numerical results agree very well with those calculated using the CSS ansatz. The analysis of the collapse in the supercritical regime supports the hypothesis of the existence of naked singularities formed during a generic gravitational collapse. |
1511.05287 | Titus K Mathew | Athira Sasidharan, Titus K Mathew | Phase space analysis of bulk viscous matter dominated universe | 22 pages and 3 figures | JHEP 1606 (2016) 138 | 10.1007/JHEP06(2016)138 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a Friedmann model of the universe with bulk viscous matter and
radiation as the cosmic components. We study the asymptotic properties in the
equivalent phase space by considering the three cases for the bulk viscous
coefficient as (i) $\zeta = \zeta_{0}$, a constant (ii) $\zeta = \zeta_{0} +
\zeta_{1}\frac{\dot{a}}{a}$, depending on velocity of the expansion of the
universe and (iii) $\zeta = \zeta_{0} + \zeta_{1}\frac{\dot{a}}{a} +
\zeta_{2}\frac{\ddot{a}}{\dot{a}}$, depending both on velocity and acceleration
of the expansion of the universe. It is found that all the three cases predicts
the late acceleration of the universe. However, a conventional realistic
behaviour of the universe, i.e., a universe having an initial radiation
dominated phase and then followed by decelerated matter dominated phase and
then finally evolving to accelerated epoch, is shown only when $\zeta =
\zeta_{0}$, a constant. For the other two cases, it does not show either a
prior conventional radiation dominated phase or a matter dominated phase of the
universe.
| [
{
"created": "Tue, 17 Nov 2015 06:56:59 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Apr 2016 06:04:48 GMT",
"version": "v2"
}
] | 2019-05-13 | [
[
"Sasidharan",
"Athira",
""
],
[
"Mathew",
"Titus K",
""
]
] | We consider a Friedmann model of the universe with bulk viscous matter and radiation as the cosmic components. We study the asymptotic properties in the equivalent phase space by considering the three cases for the bulk viscous coefficient as (i) $\zeta = \zeta_{0}$, a constant (ii) $\zeta = \zeta_{0} + \zeta_{1}\frac{\dot{a}}{a}$, depending on velocity of the expansion of the universe and (iii) $\zeta = \zeta_{0} + \zeta_{1}\frac{\dot{a}}{a} + \zeta_{2}\frac{\ddot{a}}{\dot{a}}$, depending both on velocity and acceleration of the expansion of the universe. It is found that all the three cases predicts the late acceleration of the universe. However, a conventional realistic behaviour of the universe, i.e., a universe having an initial radiation dominated phase and then followed by decelerated matter dominated phase and then finally evolving to accelerated epoch, is shown only when $\zeta = \zeta_{0}$, a constant. For the other two cases, it does not show either a prior conventional radiation dominated phase or a matter dominated phase of the universe. |
2209.05060 | Marie-No\"elle C\'el\'erier | Marie-No\''elle C\'el\'erier (Observatoire de Paris) | Study of stationary rigidly rotating anisotropic cylindrical fluids with
new exact interior solutions of GR. 5. Dust limit and discussion | 8 pages, no figure | null | 10.1063/5.0121183 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The present article is the last in a series of five devoted to the study of
the effect of anisotropic pressure on the gravitationnal impact of a stationary
rigidly rotating cylindrically symmetric fluid with the use of new exact
solutions of General Relativity. In the four first papers in this series, three
kinds of pressures directed each along one of the principal stresses of the
fluid have been considered and new interior solutions of the field equations
have been constructed and analyzed. Here, key results and issues raised in
these previous works are synthesized and some fundamental notions of general
relativity, causality, regularity of Lorentzian manifolds, elementary flatness
in the vicinity of a symmetry axis, singularities, physics of angular deficits,
weak and strong energy conditions, are revisited. Then, a new derivation of the
corresponding dust solution is displayed and shown to correspond indeed to the
Lanczos-van Stockum solution shedding new light to this well-known spacetime.
| [
{
"created": "Mon, 12 Sep 2022 07:39:43 GMT",
"version": "v1"
}
] | 2023-05-24 | [
[
"Célérier",
"Marie-No\\''elle",
"",
"Observatoire de Paris"
]
] | The present article is the last in a series of five devoted to the study of the effect of anisotropic pressure on the gravitationnal impact of a stationary rigidly rotating cylindrically symmetric fluid with the use of new exact solutions of General Relativity. In the four first papers in this series, three kinds of pressures directed each along one of the principal stresses of the fluid have been considered and new interior solutions of the field equations have been constructed and analyzed. Here, key results and issues raised in these previous works are synthesized and some fundamental notions of general relativity, causality, regularity of Lorentzian manifolds, elementary flatness in the vicinity of a symmetry axis, singularities, physics of angular deficits, weak and strong energy conditions, are revisited. Then, a new derivation of the corresponding dust solution is displayed and shown to correspond indeed to the Lanczos-van Stockum solution shedding new light to this well-known spacetime. |
1302.3977 | Isha Pahwa | Isha Pahwa, Debajyoti Choudhury and T. R. Seshadri | Inflation in Higher Dimensional Gauss-Bonnet Cosmology | 11 pages, 7 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Gauss-Bonnet term naturally appears in the action for gravity when one
considers the existence of space time with dimensions more than 1+3. A variety
of inflationary models can be obtained within such a framework, once the scale
factor for the hidden dimension(s) is not constrained to be the same as that of
the visible ones. In particular, the need for an adhoc inflaton field is
eliminated. The phase space has a rich structure with different types of
solutions, both stable and unstable. For a large class of solutions, the scale
factors rapidly approach an asymptotic exponential form. Furthermore,
sufficient inflation can be obtained for only a modest compression of the
hidden world, if the latter is of a sufficiently large dimension.
| [
{
"created": "Sat, 16 Feb 2013 16:43:15 GMT",
"version": "v1"
}
] | 2013-02-19 | [
[
"Pahwa",
"Isha",
""
],
[
"Choudhury",
"Debajyoti",
""
],
[
"Seshadri",
"T. R.",
""
]
] | A Gauss-Bonnet term naturally appears in the action for gravity when one considers the existence of space time with dimensions more than 1+3. A variety of inflationary models can be obtained within such a framework, once the scale factor for the hidden dimension(s) is not constrained to be the same as that of the visible ones. In particular, the need for an adhoc inflaton field is eliminated. The phase space has a rich structure with different types of solutions, both stable and unstable. For a large class of solutions, the scale factors rapidly approach an asymptotic exponential form. Furthermore, sufficient inflation can be obtained for only a modest compression of the hidden world, if the latter is of a sufficiently large dimension. |
gr-qc/0606066 | Jian-Yang Zhu | Jun Ren, Jingyi Zhang, Zheng Zhao | Tunnelling Effect and Hawking Radiation from a Vaidya Black Hole | null | Chin.Phys.Lett. 23 (2006) 2019-2022 | 10.1088/0256-307X/23/8/016 | null | gr-qc | null | In this paper, we extend Parikh' work to the non-stationary black hole. As an
example of the non-stationary black hole, we study the tunnelling effect and
Hawking radiation from a Vaidya black hole whose Bondi mass is identical to its
mass parameter. We view Hawking radiation as a tunnelling process across the
event horizon and calculate the tunnelling probability. We find that the result
is different from Parikh's work because $\frac{dr_{H}}{dv}$ is the function of
Bondi mass m(v).
| [
{
"created": "Thu, 15 Jun 2006 12:50:22 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Ren",
"Jun",
""
],
[
"Zhang",
"Jingyi",
""
],
[
"Zhao",
"Zheng",
""
]
] | In this paper, we extend Parikh' work to the non-stationary black hole. As an example of the non-stationary black hole, we study the tunnelling effect and Hawking radiation from a Vaidya black hole whose Bondi mass is identical to its mass parameter. We view Hawking radiation as a tunnelling process across the event horizon and calculate the tunnelling probability. We find that the result is different from Parikh's work because $\frac{dr_{H}}{dv}$ is the function of Bondi mass m(v). |
2407.08538 | Natalie Williams Ms | Natalie Williams, Patricia Schmidt, Geraint Pratten | PhenomGSF: A phenomenological model of gravitational self-force enhanced
tides in inspiralling binary neutron stars | 25 pages, 14 figures | null | null | LIGO Document P2400286 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves from inspiralling binary neutron stars provide unique
access to ultra-dense nuclear matter and offer the ability to constrain the
currently unknown neutron star equation-of-state through tidal measurements.
This, however, requires the availability of accurate and efficient tidal
waveform models. In this paper we present PhenomGSF, a new phenomenological
tidal phase model for the inspiral of neutron stars in the frequency-domain,
which captures the gravitational self-force informed tidal contributions of the
time-domain effective-one-body model TEOBResumS. PhenomGSF is highly faithful
and computationally efficient, and by choosing a modular approach, it can be
used in conjunction with any frequency-domain binary black hole waveform model
to generate the complete phase for a binary neutron star inspiral. PhenomGSF is
valid for neutron star binaries with unequal masses and mass ratios between 1
and 3, and dimensionless tidal deformabilities up to 5000. Furthermore,
PhenomGSF does not assume universal relations or parameterised
equations-of-state, hence allowing for exotic matter analyses and beyond
standard model physics investigations. We demonstrate the efficacy and accuracy
of our model through comparisons against TEOBResumS, numerical relativity
waveforms and full Bayesian inference, including a reanalysis of the binary
neutron star observation GW170817.
| [
{
"created": "Thu, 11 Jul 2024 14:26:33 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Williams",
"Natalie",
""
],
[
"Schmidt",
"Patricia",
""
],
[
"Pratten",
"Geraint",
""
]
] | Gravitational waves from inspiralling binary neutron stars provide unique access to ultra-dense nuclear matter and offer the ability to constrain the currently unknown neutron star equation-of-state through tidal measurements. This, however, requires the availability of accurate and efficient tidal waveform models. In this paper we present PhenomGSF, a new phenomenological tidal phase model for the inspiral of neutron stars in the frequency-domain, which captures the gravitational self-force informed tidal contributions of the time-domain effective-one-body model TEOBResumS. PhenomGSF is highly faithful and computationally efficient, and by choosing a modular approach, it can be used in conjunction with any frequency-domain binary black hole waveform model to generate the complete phase for a binary neutron star inspiral. PhenomGSF is valid for neutron star binaries with unequal masses and mass ratios between 1 and 3, and dimensionless tidal deformabilities up to 5000. Furthermore, PhenomGSF does not assume universal relations or parameterised equations-of-state, hence allowing for exotic matter analyses and beyond standard model physics investigations. We demonstrate the efficacy and accuracy of our model through comparisons against TEOBResumS, numerical relativity waveforms and full Bayesian inference, including a reanalysis of the binary neutron star observation GW170817. |
gr-qc/9703019 | Chris Chambers | Robert Geroch (Enrico Fermi Institute) | Suggestions For Giving Talks | 4 pages (no figures), Revtex, uses twocolumn.sty and header.sty
(included) | null | null | null | gr-qc | null | This is a latex'd version of Robert Geroch's 1973 notes entitled 'Suggestions
For Giving Talks'.
| [
{
"created": "Fri, 7 Mar 1997 00:09:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Geroch",
"Robert",
"",
"Enrico Fermi Institute"
]
] | This is a latex'd version of Robert Geroch's 1973 notes entitled 'Suggestions For Giving Talks'. |
1501.00331 | Alfredo Sandoval-Villalbazo | A. Sandoval-Villalbazo, A. R. Sagaceta-Mejia, and A. L.
Garcia-Perciante | On the kinetic foundations of Kaluza's magnetohydrodynamics | 13 pages, no figures. Accepted for publication in the Journal of
Non-Equilibrium Thermodynamics | J.Nonequil.Thermo. 40 (2015) 93 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent work has shown the existence of a relativistic effect present in a
single component non-equilibrium fluid, corresponding to a heat flux due to an
electric field. The treatment in that work was limited to a four-dimensional
Minkowksi space-time in which the Boltzmann equation was treated in a special
relativistic approach. The more complete framework of general relativity can be
introduced to kinetic theory in order to describe transport processes
associated to electromagnetic fields. In this context the original Kaluza's
formalism is a promising approach. The present work contains a kinetic theory
basis for Kaluza's magnetohydrodynamics and gives a novel description for the
establishment of thermodynamic forces beyond the special relativistic
description.
| [
{
"created": "Fri, 2 Jan 2015 00:25:55 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Feb 2015 01:37:13 GMT",
"version": "v2"
}
] | 2015-07-30 | [
[
"Sandoval-Villalbazo",
"A.",
""
],
[
"Sagaceta-Mejia",
"A. R.",
""
],
[
"Garcia-Perciante",
"A. L.",
""
]
] | Recent work has shown the existence of a relativistic effect present in a single component non-equilibrium fluid, corresponding to a heat flux due to an electric field. The treatment in that work was limited to a four-dimensional Minkowksi space-time in which the Boltzmann equation was treated in a special relativistic approach. The more complete framework of general relativity can be introduced to kinetic theory in order to describe transport processes associated to electromagnetic fields. In this context the original Kaluza's formalism is a promising approach. The present work contains a kinetic theory basis for Kaluza's magnetohydrodynamics and gives a novel description for the establishment of thermodynamic forces beyond the special relativistic description. |
2009.01623 | Jose Edgar Madriz Aguilar Dr. | Jos\'e Edgar Madriz Aguilar, A. Bernal, M. Montes, J. Zamarripa and E.
Aceves | Non-perturbative gauge invariant scalar fluctuations of the metric in
Higgs inflation from complex geometrical scalar-tensor theory of gravity | 8 pages, no figures. Revised version. arXiv admin note: text overlap
with arXiv:1908.06220 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter we investigate gauge invariant scalar fluctuations of the
metric in a non-perturbative formalism for a Higgs inflationary model recently
introduced in the framework of a geometrical scalar-tensor theory of gravity.
In this scenario the Higgs inflaton field has its origin in the Weyl scalar
field of the background geometry. We found a nearly scale invariance of the
power spectrum for linear scalar fluctuations of the metric. For certain
parameters of the model we obtain values for the scalar spectral index $n_s$
and the scalar to tensor ratio $r$ that fit well with the Planck 2018 results.
Besides we show that in this model the trans-planckian problem can be avoided.
| [
{
"created": "Tue, 1 Sep 2020 23:25:02 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Aug 2021 17:06:46 GMT",
"version": "v2"
}
] | 2021-08-31 | [
[
"Aguilar",
"José Edgar Madriz",
""
],
[
"Bernal",
"A.",
""
],
[
"Montes",
"M.",
""
],
[
"Zamarripa",
"J.",
""
],
[
"Aceves",
"E.",
""
]
] | In this letter we investigate gauge invariant scalar fluctuations of the metric in a non-perturbative formalism for a Higgs inflationary model recently introduced in the framework of a geometrical scalar-tensor theory of gravity. In this scenario the Higgs inflaton field has its origin in the Weyl scalar field of the background geometry. We found a nearly scale invariance of the power spectrum for linear scalar fluctuations of the metric. For certain parameters of the model we obtain values for the scalar spectral index $n_s$ and the scalar to tensor ratio $r$ that fit well with the Planck 2018 results. Besides we show that in this model the trans-planckian problem can be avoided. |
gr-qc/9507024 | Don N. Page | Don N. Page (University of Alberta, Edmonton, Canada) | Sensible Quantum Mechanics: Are Probabilities only in the Mind? | LaTeX, 14 pages, shortened version of quant-ph/9506010 | Int.J.Mod.Phys. D5 (1996) 583-596 | 10.1142/S0218271896000370 | Alberta-Thy-13-95 | gr-qc quant-ph | null | Quantum mechanics may be formulated as {\it Sensible Quantum Mechanics} (SQM)
so that it contains nothing probabilistic except conscious perceptions. Sets of
these perceptions can be deterministically realized with measures given by
expectation values of positive-operator-valued {\it awareness operators}.
Ratios of the measures for these sets of perceptions can be interpreted as
frequency-type probabilities for many actually existing sets. These
probabilities generally cannot be given by the ordinary quantum
``probabilities'' for a single set of alternatives. {\it Probabilism}, or
ascribing probabilities to unconscious aspects of the world, may be seen to be
an {\it aesthemamorphic myth}.
| [
{
"created": "Tue, 11 Jul 1995 23:12:35 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Page",
"Don N.",
"",
"University of Alberta, Edmonton, Canada"
]
] | Quantum mechanics may be formulated as {\it Sensible Quantum Mechanics} (SQM) so that it contains nothing probabilistic except conscious perceptions. Sets of these perceptions can be deterministically realized with measures given by expectation values of positive-operator-valued {\it awareness operators}. Ratios of the measures for these sets of perceptions can be interpreted as frequency-type probabilities for many actually existing sets. These probabilities generally cannot be given by the ordinary quantum ``probabilities'' for a single set of alternatives. {\it Probabilism}, or ascribing probabilities to unconscious aspects of the world, may be seen to be an {\it aesthemamorphic myth}. |
1403.4625 | Sergey Pavluchenko A. | Dmitry Chirkov, Sergey A. Pavluchenko, Alexey Toporensky | Constant volume exponential solutions in Einstein-Gauss-Bonnet flat
anisotropic cosmology with a perfect fluid | 12 pages, 1 figure; matches version accepted to Gen. Rel. Grav | General Relativity and Gravitation 46, 1799 (2014) | 10.1007/s10714-014-1799-7 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the constant volume exponential solutions (i.e.
the solutions with the scale factors change exponentially over time so that the
comoving volume remains the same) in the Einstein-Gauss-Bonnet gravity. We find
conditions for these solutions to exist and show that they are compatible with
any perfect fluid with the equation of state parameter $\omega<1/3$ if the
matter density of the Universe exceeds some critical value. We write down some
exact solutions which generalize ones found in our previous paper for models
with a cosmological constant.
| [
{
"created": "Tue, 18 Mar 2014 21:22:33 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Aug 2014 18:31:41 GMT",
"version": "v2"
}
] | 2014-12-17 | [
[
"Chirkov",
"Dmitry",
""
],
[
"Pavluchenko",
"Sergey A.",
""
],
[
"Toporensky",
"Alexey",
""
]
] | In this paper we investigate the constant volume exponential solutions (i.e. the solutions with the scale factors change exponentially over time so that the comoving volume remains the same) in the Einstein-Gauss-Bonnet gravity. We find conditions for these solutions to exist and show that they are compatible with any perfect fluid with the equation of state parameter $\omega<1/3$ if the matter density of the Universe exceeds some critical value. We write down some exact solutions which generalize ones found in our previous paper for models with a cosmological constant. |
2201.03428 | Roberto Cotesta | Roberto Cotesta | Multipolar gravitational waveforms for spinning binary black holes and
their impact on source characterization | PhD thesis | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the last five years, gravitational-wave astronomy has gone from a purely
theoretical field into a thriving experimental science. Many gravitational-wave
signals, emitted by stellar-mass binary black holes and binary neutron stars,
have been detected, and many more are expected in the future. The observation
of the gravitational-wave signals from these systems, and the characterization
of their sources, heavily relies on the precise models for the emitted
gravitational waveforms. In this thesis, I present an updated version of the
waveform models for spinning binary black holes within the effective-one-body
formalism. The novelty of the waveform models presented in this work is the
inclusion of beyond-quadupolar terms in the waveforms emitted by spinning
binary black holes. I first construct the model in the simplified case of black
holes with spins aligned with the orbital angular momentum of the binary, then
I extend it to the case of generic spin orientations. The measurement of the
source properties of a binary system emitting gravitational waves requires to
compute $\mathcal{O}(10^7-10^9)$ different waveforms. Since the waveform models
mentioned before can require $\mathcal{O}(1-10)$s to generate a single
waveform, they can be difficult to use in data-analysis studies. To overcome
this obstacle, I use the reduced-order-modeling technique to develop a faster
version of the waveform model for black holes with spins aligned to the orbital
angular momentum of the binary. The waveform models developed in this thesis
have been used by the LIGO and Virgo collaborations for the inference of the
source parameters of the gravitational-wave signals detected during the second
and third observing runs (O2 and O3) of the LIGO and Virgo detectors. Here, I
present a study on the source properties of the signals GW170729 and GW190412,
for which I have been directly involved in the analysis.
| [
{
"created": "Mon, 10 Jan 2022 16:20:51 GMT",
"version": "v1"
}
] | 2022-01-11 | [
[
"Cotesta",
"Roberto",
""
]
] | In the last five years, gravitational-wave astronomy has gone from a purely theoretical field into a thriving experimental science. Many gravitational-wave signals, emitted by stellar-mass binary black holes and binary neutron stars, have been detected, and many more are expected in the future. The observation of the gravitational-wave signals from these systems, and the characterization of their sources, heavily relies on the precise models for the emitted gravitational waveforms. In this thesis, I present an updated version of the waveform models for spinning binary black holes within the effective-one-body formalism. The novelty of the waveform models presented in this work is the inclusion of beyond-quadupolar terms in the waveforms emitted by spinning binary black holes. I first construct the model in the simplified case of black holes with spins aligned with the orbital angular momentum of the binary, then I extend it to the case of generic spin orientations. The measurement of the source properties of a binary system emitting gravitational waves requires to compute $\mathcal{O}(10^7-10^9)$ different waveforms. Since the waveform models mentioned before can require $\mathcal{O}(1-10)$s to generate a single waveform, they can be difficult to use in data-analysis studies. To overcome this obstacle, I use the reduced-order-modeling technique to develop a faster version of the waveform model for black holes with spins aligned to the orbital angular momentum of the binary. The waveform models developed in this thesis have been used by the LIGO and Virgo collaborations for the inference of the source parameters of the gravitational-wave signals detected during the second and third observing runs (O2 and O3) of the LIGO and Virgo detectors. Here, I present a study on the source properties of the signals GW170729 and GW190412, for which I have been directly involved in the analysis. |
gr-qc/0112044 | Roberto A. Sussman | Luis G. Cabral-Rosetti, Tonatiuh Matos, Dario Nu\~nez and Roberto A.
Sussman | Hydrodynamics of galactic dark matter | LaTeX article style, 16 pages including three figures. Final version
to appear in Classical and Quantum Gravity | Class.Quant.Grav. 19 (2002) 3603-3616 | 10.1088/0264-9381/19/14/303 | null | gr-qc astro-ph hep-ph | null | We consider simple hydrodynamical models of galactic dark matter in which the
galactic halo is a self-gravitating and self-interacting gas that dominates the
dynamics of the galaxy. Modeling this halo as a sphericaly symmetric and static
perfect fluid satisfying the field equations of General Relativity, visible
barionic matter can be treated as ``test particles'' in the geometry of this
field. We show that the assumption of an empirical ``universal rotation curve''
that fits a wide variety of galaxies is compatible, under suitable
approximations, with state variables characteristic of a non-relativistic
Maxwell-Boltzmann gas that becomes an isothermal sphere in the Newtonian limit.
Consistency criteria lead to a minimal bound for particle masses in the range
$30 \hbox{eV} \leq m \leq 60 \hbox{eV}$ and to a constraint between the central
temperature and the particles mass. The allowed mass range includes popular
supersymmetric particle candidates, such as the neutralino, axino and
gravitino, as well as lighter particles ($m\approx$ keV) proposed by numerical
N-body simulations associated with self-interactive CDM and WDM structure
formation theories.
| [
{
"created": "Wed, 19 Dec 2001 00:36:31 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jun 2002 18:38:24 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Cabral-Rosetti",
"Luis G.",
""
],
[
"Matos",
"Tonatiuh",
""
],
[
"Nuñez",
"Dario",
""
],
[
"Sussman",
"Roberto A.",
""
]
] | We consider simple hydrodynamical models of galactic dark matter in which the galactic halo is a self-gravitating and self-interacting gas that dominates the dynamics of the galaxy. Modeling this halo as a sphericaly symmetric and static perfect fluid satisfying the field equations of General Relativity, visible barionic matter can be treated as ``test particles'' in the geometry of this field. We show that the assumption of an empirical ``universal rotation curve'' that fits a wide variety of galaxies is compatible, under suitable approximations, with state variables characteristic of a non-relativistic Maxwell-Boltzmann gas that becomes an isothermal sphere in the Newtonian limit. Consistency criteria lead to a minimal bound for particle masses in the range $30 \hbox{eV} \leq m \leq 60 \hbox{eV}$ and to a constraint between the central temperature and the particles mass. The allowed mass range includes popular supersymmetric particle candidates, such as the neutralino, axino and gravitino, as well as lighter particles ($m\approx$ keV) proposed by numerical N-body simulations associated with self-interactive CDM and WDM structure formation theories. |
2308.15052 | Naomichi Asakawa | Naomichi Asakawa and Yuichiro Sekiguchi | Constraining self-interactions of a massive scalar field using scalar
gravitational waves from stellar core collapse | 16 pages, 16 figures, 1 table | Phys. Rev. D 108, 044060 (2023) | 10.1103/PhysRevD.108.044060 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a comprehensive numerical study of gravitational waves from
stellar core collapse in the massive scalar-tensor theory with the cubic and
quartic self-interactions of the scalar field. We investigate the dependence of
gravitational waves on the self-interaction as well as the mass of the scalar
field and the conformal factor. We find that gravitational-wave spectra show a
systematic difference between the cubic and quartic self-interactions. We also
find that this systematic difference is insensitive to the mass of the scalar
field and the conformal factor. Our results indicate that the type of the
self-interaction could be constrained by observations of gravitational waves
using the future-planned detectors.
| [
{
"created": "Tue, 29 Aug 2023 06:27:20 GMT",
"version": "v1"
}
] | 2023-08-30 | [
[
"Asakawa",
"Naomichi",
""
],
[
"Sekiguchi",
"Yuichiro",
""
]
] | We perform a comprehensive numerical study of gravitational waves from stellar core collapse in the massive scalar-tensor theory with the cubic and quartic self-interactions of the scalar field. We investigate the dependence of gravitational waves on the self-interaction as well as the mass of the scalar field and the conformal factor. We find that gravitational-wave spectra show a systematic difference between the cubic and quartic self-interactions. We also find that this systematic difference is insensitive to the mass of the scalar field and the conformal factor. Our results indicate that the type of the self-interaction could be constrained by observations of gravitational waves using the future-planned detectors. |
1904.11760 | Bibhas Majhi Ranjan | Surojit Dalui, Bibhas Ranjan Majhi, Pankaj Mishra | Induction of chaotic fluctuations in particle dynamics in a uniformly
accelerated frame | Comments added, to appear in Int. J. Mod. Phys. A | Int. J. Mod. Phys. A35 (2020) 2050081 | 10.1142/S0217751X20500815 | null | gr-qc astro-ph.GA hep-th nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ongoing conjecture that the presence of horizon may induce chaos in an
integrable system, is further investigated from the perspective of a uniformly
accelerated frame. Particularly, we build up a model which consists of a
particle (massless and chargeless) trapped in harmonic oscillator in a
uniformly accelerated frame (namely Rindler observer). Here the Rindler frame
provides a Killing horizon without any intrinsic curvature to the system. This
makes the present observations different from previous studies. We observe that
for some particular values of parameters of the system (like acceleration,
energy of the particle), the motion of the particle trapped in harmonic
potential systematically goes from periodic state to the chaotic. This
indicates that the existence of horizon alone, not the intrinsic curvature
(i.e. the gravitational effect) in the background, is sufficient to induce the
chaotic motion in the particle. We believe the present study further enlighten
and balustrade the conjecture.
| [
{
"created": "Fri, 26 Apr 2019 11:03:07 GMT",
"version": "v1"
},
{
"created": "Thu, 14 May 2020 11:30:32 GMT",
"version": "v2"
}
] | 2020-06-17 | [
[
"Dalui",
"Surojit",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
],
[
"Mishra",
"Pankaj",
""
]
] | The ongoing conjecture that the presence of horizon may induce chaos in an integrable system, is further investigated from the perspective of a uniformly accelerated frame. Particularly, we build up a model which consists of a particle (massless and chargeless) trapped in harmonic oscillator in a uniformly accelerated frame (namely Rindler observer). Here the Rindler frame provides a Killing horizon without any intrinsic curvature to the system. This makes the present observations different from previous studies. We observe that for some particular values of parameters of the system (like acceleration, energy of the particle), the motion of the particle trapped in harmonic potential systematically goes from periodic state to the chaotic. This indicates that the existence of horizon alone, not the intrinsic curvature (i.e. the gravitational effect) in the background, is sufficient to induce the chaotic motion in the particle. We believe the present study further enlighten and balustrade the conjecture. |
2007.11239 | Donato Bini | Donato Bini, Thibault Damour, Andrea Geralico | Sixth post-Newtonian nonlocal-in-time dynamics of binary systems | 59 pages, no figures, one ancillary text file | Phys. Rev. D 102, 084047 (2020) | 10.1103/PhysRevD.102.084047 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We complete our previous derivation, at the sixth post-Newtonian (6PN)
accuracy, of the local-in-time dynamics of a gravitationally interacting
two-body system by giving two gauge-invariant characterizations of its
complementary nonlocal-in-time dynamics. On the one hand, we compute the
nonlocal part of the scattering angle for hyberboliclike motions; and, on the
other hand, we compute the nonlocal part of the averaged (Delaunay) Hamiltonian
for ellipticlike motions. The former is computed as a large-angular-momentum
expansion (given here to next-to-next-to-leading order), while the latter is
given as a small-eccentricity expansion (given here to the tenth order). We
note the appearance of $\zeta(3)$ in the nonlocal part of the scattering angle.
The averaged Hamiltonian for ellipticlike motions then yields two more
gauge-invariant observables: the energy and the periastron precession as
functions of orbital frequencies. We point out the existence of a hidden
simplicity in the mass-ratio dependence of the gravitational-wave energy loss
of a two-body system.
| [
{
"created": "Wed, 22 Jul 2020 07:44:42 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Bini",
"Donato",
""
],
[
"Damour",
"Thibault",
""
],
[
"Geralico",
"Andrea",
""
]
] | We complete our previous derivation, at the sixth post-Newtonian (6PN) accuracy, of the local-in-time dynamics of a gravitationally interacting two-body system by giving two gauge-invariant characterizations of its complementary nonlocal-in-time dynamics. On the one hand, we compute the nonlocal part of the scattering angle for hyberboliclike motions; and, on the other hand, we compute the nonlocal part of the averaged (Delaunay) Hamiltonian for ellipticlike motions. The former is computed as a large-angular-momentum expansion (given here to next-to-next-to-leading order), while the latter is given as a small-eccentricity expansion (given here to the tenth order). We note the appearance of $\zeta(3)$ in the nonlocal part of the scattering angle. The averaged Hamiltonian for ellipticlike motions then yields two more gauge-invariant observables: the energy and the periastron precession as functions of orbital frequencies. We point out the existence of a hidden simplicity in the mass-ratio dependence of the gravitational-wave energy loss of a two-body system. |
1301.7609 | Ivan Arraut | Ivan Arraut | Relative locality and relative Co-locality as extensions of the
Generalized Uncertainty Principle | Abstract modified and some small changes done for making the
manuscript more understandable. 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I introduce the spatial curvature effects inside the formalism of Relative
Locality as a non-commutative structure of the momentum space in agreement with
the very well known concepts of Quantum Groups. This gives a natural red-shift
effect in agreement with an extended version of the Generalized Uncertainty
Principle (GUP) and in agreement with the standard notions of curvature inside
General Relativity. I then introduce the concept of Relative Co-locality as a
reinterpretation of the usual notions of spacetime curvature. From this
redefinition, I obtain the momentum space curvature effects as a
non-commutativity in position space. This introduce a natural blue-shift effect
in agreement with the extended version of GUP. Both effects, Relative locality
and Co-locality are dual each other inside the formalism of quantum groups
$SU_q(n)$ symmetric Heisenberg algebras and their q-Bargmann Fock
representations. When Relative locality and Co-locality are introduced, the
q-deformation parameter takes the form $q\approx 1+\sqrt{\frac{\vert p\vert
\vert x\vert}{r_\Lambda m_{pl}}}$ with the spatial curvature effects in
Relative Locality appearing like $\Delta X\approx \frac{\vert
x\vert}{m_{pl}}\Delta P$ and the momentum curvature effects in Relative
Co-locality appearing like $\Delta P\approx \frac{\vert
p\vert}{r_\Lambda}\Delta X$, where $r_\Lambda=\frac{1}{\sqrt{\Lambda}}$ is the
scale defined by the Cosmological Constant $\Lambda$, $m_{pl}$ is the Planck
mass and $\Delta X/\Delta P$ is a scale of position/momentum or time/energy
associated with the event, p and x are the momentum and position of the
observer relative to the event.
| [
{
"created": "Thu, 31 Jan 2013 13:24:32 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Feb 2013 10:14:05 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Jul 2013 10:26:05 GMT",
"version": "v3"
},
{
"created": "Mon, 18 Nov 2013 13:31:02 GMT",
"version": "v4"
}
] | 2013-11-19 | [
[
"Arraut",
"Ivan",
""
]
] | I introduce the spatial curvature effects inside the formalism of Relative Locality as a non-commutative structure of the momentum space in agreement with the very well known concepts of Quantum Groups. This gives a natural red-shift effect in agreement with an extended version of the Generalized Uncertainty Principle (GUP) and in agreement with the standard notions of curvature inside General Relativity. I then introduce the concept of Relative Co-locality as a reinterpretation of the usual notions of spacetime curvature. From this redefinition, I obtain the momentum space curvature effects as a non-commutativity in position space. This introduce a natural blue-shift effect in agreement with the extended version of GUP. Both effects, Relative locality and Co-locality are dual each other inside the formalism of quantum groups $SU_q(n)$ symmetric Heisenberg algebras and their q-Bargmann Fock representations. When Relative locality and Co-locality are introduced, the q-deformation parameter takes the form $q\approx 1+\sqrt{\frac{\vert p\vert \vert x\vert}{r_\Lambda m_{pl}}}$ with the spatial curvature effects in Relative Locality appearing like $\Delta X\approx \frac{\vert x\vert}{m_{pl}}\Delta P$ and the momentum curvature effects in Relative Co-locality appearing like $\Delta P\approx \frac{\vert p\vert}{r_\Lambda}\Delta X$, where $r_\Lambda=\frac{1}{\sqrt{\Lambda}}$ is the scale defined by the Cosmological Constant $\Lambda$, $m_{pl}$ is the Planck mass and $\Delta X/\Delta P$ is a scale of position/momentum or time/energy associated with the event, p and x are the momentum and position of the observer relative to the event. |
gr-qc/9812008 | David Polarski | David Polarski | Primordial Fluctuations from Inflation: a Consistent Histories Approach | LaTeX (7 pages), to appear in Phys. Lett. B | Phys.Lett.B446:53-57,1999 | 10.1016/S0370-2693(98)01533-0 | LMPT 10/98 | gr-qc astro-ph hep-th quant-ph | null | We show how the quantum-to-classical transition of the cosmological
fluctuations produced during an inflationary stage can be described using the
consistent histories approach. We identify the corresponding histories in the
limit of infinite squeezing. To take the decaying mode into account, we propose
an extension to coarse-grained histories.
| [
{
"created": "Wed, 2 Dec 1998 15:25:49 GMT",
"version": "v1"
}
] | 2009-05-20 | [
[
"Polarski",
"David",
""
]
] | We show how the quantum-to-classical transition of the cosmological fluctuations produced during an inflationary stage can be described using the consistent histories approach. We identify the corresponding histories in the limit of infinite squeezing. To take the decaying mode into account, we propose an extension to coarse-grained histories. |
1606.08058 | Bernhard Brehm | Bernhard Brehm | Bianchi VIII and IX vacuum cosmologies: Almost every solution forms
particle horizons and converges to the Mixmaster attractor | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | Bianchi models are posited by the BKL picture to be essential building blocks
towards an understanding of generic cosmological singularities. We study the
behaviour of spatially homogeneous anisotropic vacuum spacetimes of Bianchi
type VIII and IX, as they approach the big bang singularity. It is known since
2001 that generic Bianchi IX spacetimes converge towards the so-called
Mixmaster attractor as time goes towards the singularity. We extend this result
to the case of Bianchi VIII vacuum. The BKL picture suggests that particle
horizons should form, i.e. spatially separate regions should causally decouple.
We prove that this decoupling indeed occurs, for Lebesgue almost every Bianchi
VIII and IX vacuum spacetime.
| [
{
"created": "Sun, 26 Jun 2016 17:31:33 GMT",
"version": "v1"
}
] | 2016-06-28 | [
[
"Brehm",
"Bernhard",
""
]
] | Bianchi models are posited by the BKL picture to be essential building blocks towards an understanding of generic cosmological singularities. We study the behaviour of spatially homogeneous anisotropic vacuum spacetimes of Bianchi type VIII and IX, as they approach the big bang singularity. It is known since 2001 that generic Bianchi IX spacetimes converge towards the so-called Mixmaster attractor as time goes towards the singularity. We extend this result to the case of Bianchi VIII vacuum. The BKL picture suggests that particle horizons should form, i.e. spatially separate regions should causally decouple. We prove that this decoupling indeed occurs, for Lebesgue almost every Bianchi VIII and IX vacuum spacetime. |
1308.0197 | Anil Yadav dr | Ahmad T Ali, Anil Kumar Yadav and S R Mahmoud | Some Plane Symmetric Inhomogeneous Cosmological Models in the
Scalar-Tensor Theory of Gravitation | 12 pages, 1 figures | Astrophys. Space Sci. 349: 539-547 (2014) | 10.1007/s10509-013-1624-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present study deals with the inhomogeneous plane symmetric models in
scalar - tensor theory of gravitation. We used symmetry group analysis method
to solve the field equations analytically. A new class of similarity solutions
have been obtained by considering the inhomogeneous nature of metric potential.
The physical behavior and geometrical aspects of the derived models are also
discussed.
| [
{
"created": "Wed, 31 Jul 2013 16:16:45 GMT",
"version": "v1"
}
] | 2013-12-12 | [
[
"Ali",
"Ahmad T",
""
],
[
"Yadav",
"Anil Kumar",
""
],
[
"Mahmoud",
"S R",
""
]
] | The present study deals with the inhomogeneous plane symmetric models in scalar - tensor theory of gravitation. We used symmetry group analysis method to solve the field equations analytically. A new class of similarity solutions have been obtained by considering the inhomogeneous nature of metric potential. The physical behavior and geometrical aspects of the derived models are also discussed. |
gr-qc/0102084 | S. Antoci | S. Antoci and D.-E. Liebscher | Reconsidering Schwarzschild's original solution | 9 pages, added references and a remark on the norm of the timelike
Killing vector. Accepted for publication by Astronomische Nachrichten | Astron.Nachr. 322 (2001) 137-142 | 10.1002/1521-3994(200107)322:3<137::AID-ASNA137>3.0.CO;2-1 | null | gr-qc astro-ph | null | We analyse the Schwarzschild solution in the context of the historical
development of its present use, and explain the invariant definition of a
singular surface at the Schwarzschild's radius, that can be applied to the
Kerr-Newman solution too.
| [
{
"created": "Mon, 19 Feb 2001 15:28:55 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jul 2001 09:49:47 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Antoci",
"S.",
""
],
[
"Liebscher",
"D. -E.",
""
]
] | We analyse the Schwarzschild solution in the context of the historical development of its present use, and explain the invariant definition of a singular surface at the Schwarzschild's radius, that can be applied to the Kerr-Newman solution too. |
2403.05421 | Claudio Aravena Cap | Claudio Aravena-Plaza, V\'ictor Mu\~noz and Felipe A. Asenjo | Accelerating Airy tensor modes of cosmological gravitational waves | 5 pages, 2 figures. arXiv admin note: text overlap with
arXiv:2304.14222 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | From a classical analysis, it is shown that the nondiffractive accelerating
gravitational Airy wave packets are solutions of Einstein equations for their
linearized tensor modes in a Friedmann-Lema\^itre-Robertson-Walker cosmological
background filled with a perfect fluid, with equations of state $w=1/3$ and
$w=-1/3$. These solutions have finite energy, presenting accelerating behavior
due to the structured spatial form of the wavepacket. This is manifested by
curved trajectories along the wave path. Also, using spectral functions, it is
possible, with these packets, to construct more general, arbitrary wave
packets. All these new solutions bring insights on new forms for gravitational
wave propagation.
| [
{
"created": "Fri, 8 Mar 2024 16:19:33 GMT",
"version": "v1"
}
] | 2024-03-11 | [
[
"Aravena-Plaza",
"Claudio",
""
],
[
"Muñoz",
"Víctor",
""
],
[
"Asenjo",
"Felipe A.",
""
]
] | From a classical analysis, it is shown that the nondiffractive accelerating gravitational Airy wave packets are solutions of Einstein equations for their linearized tensor modes in a Friedmann-Lema\^itre-Robertson-Walker cosmological background filled with a perfect fluid, with equations of state $w=1/3$ and $w=-1/3$. These solutions have finite energy, presenting accelerating behavior due to the structured spatial form of the wavepacket. This is manifested by curved trajectories along the wave path. Also, using spectral functions, it is possible, with these packets, to construct more general, arbitrary wave packets. All these new solutions bring insights on new forms for gravitational wave propagation. |
1509.00492 | Zoltan Keresztes | Zolt\'an Keresztes, L\'aszl\'o \'A. Gergely, Tiberiu Harko, and
Shi-Dong Liang | Cosmological constraints on superconducting dark energy models | 12 pages, 10 figures | Phys. Rev. D 92, 123503 (2015) | 10.1103/PhysRevD.92.123503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider cosmological tests of a scalar-vector-tensor gravitational model,
in which the dark energy is included in the total action through a gauge
invariant, electromagnetic type contribution. The ground state of dark energy,
corresponding to a constant potential $V$ is a Bose-Einstein type condensate
with spontaneously broken U(1) symmetry. In another words dark energy appears
as a massive vector field emerging from a superposition of a massless vector
and a scalar field, the latter corresponding to the Goldstone boson. Two
particular cosmological models, corresponding to pure electric and pure
magnetic type potentials, respectively are confronted with Type IA Supernovae
and Hubble parameter data. In the electric case good fit is obtained along a
narrow inclined stripe in the $\Omega _{m}-\Omega _{V}\,$ parameter plane,
which includes the $\Lambda $CDM limit as the best fit. The other points on
this admissible region represent superconducting dark energy as a sum of a
cosmological constant and a time-evolving contribution. In the magnetic case
the cosmological test selects either i) parameter ranges of the superconducting
dark energy allowing for the standard baryonic plus dark matter or ii) a
unified superconducting dark matter and dark energy model, additionally
including only the baryonic sector.
| [
{
"created": "Tue, 1 Sep 2015 20:22:48 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Dec 2015 23:48:20 GMT",
"version": "v2"
}
] | 2015-12-08 | [
[
"Keresztes",
"Zoltán",
""
],
[
"Gergely",
"László Á.",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Liang",
"Shi-Dong",
""
]
] | We consider cosmological tests of a scalar-vector-tensor gravitational model, in which the dark energy is included in the total action through a gauge invariant, electromagnetic type contribution. The ground state of dark energy, corresponding to a constant potential $V$ is a Bose-Einstein type condensate with spontaneously broken U(1) symmetry. In another words dark energy appears as a massive vector field emerging from a superposition of a massless vector and a scalar field, the latter corresponding to the Goldstone boson. Two particular cosmological models, corresponding to pure electric and pure magnetic type potentials, respectively are confronted with Type IA Supernovae and Hubble parameter data. In the electric case good fit is obtained along a narrow inclined stripe in the $\Omega _{m}-\Omega _{V}\,$ parameter plane, which includes the $\Lambda $CDM limit as the best fit. The other points on this admissible region represent superconducting dark energy as a sum of a cosmological constant and a time-evolving contribution. In the magnetic case the cosmological test selects either i) parameter ranges of the superconducting dark energy allowing for the standard baryonic plus dark matter or ii) a unified superconducting dark matter and dark energy model, additionally including only the baryonic sector. |
0906.2170 | Llu\'is Bel | Ll. Bel, J. Martin-Martin | About the mass problem | Latex, 12 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The concept of {\it active gravitational mass}, its definition and its
relation with the sources of a gravitational field, was clearly established by
Tolman in 1934. On the contrary, and surprisingly in our opinion, the concept
of {\it proper mass} has remained obscure in General relativity. We compare a
new definition to an apparent more obvious one and discuss how each choice
modifies the ratio of active to proper gravitational mass.
| [
{
"created": "Thu, 11 Jun 2009 17:53:06 GMT",
"version": "v1"
}
] | 2009-06-12 | [
[
"Bel",
"Ll.",
""
],
[
"Martin-Martin",
"J.",
""
]
] | The concept of {\it active gravitational mass}, its definition and its relation with the sources of a gravitational field, was clearly established by Tolman in 1934. On the contrary, and surprisingly in our opinion, the concept of {\it proper mass} has remained obscure in General relativity. We compare a new definition to an apparent more obvious one and discuss how each choice modifies the ratio of active to proper gravitational mass. |
1103.3767 | Llu\'is Bel | Ll. Bel | Space and Time models | 11 pages, minor changes, an error in an intermediate step of the
derivation of (40) has been corrected | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive line-element's templates of space-time models with Space models
complying with Helmholtz's Free mobility postulate, and discuss some of the
Time models compatible with them.
| [
{
"created": "Sat, 19 Mar 2011 09:31:58 GMT",
"version": "v1"
},
{
"created": "Sat, 9 Apr 2011 09:30:56 GMT",
"version": "v2"
}
] | 2011-04-12 | [
[
"Bel",
"Ll.",
""
]
] | We derive line-element's templates of space-time models with Space models complying with Helmholtz's Free mobility postulate, and discuss some of the Time models compatible with them. |
1302.2687 | Prado Martin-Moruno | Prado Martin-Moruno (Victoria University of Wellington), Valentina
Baccetti (Victoria University of Wellington), and Matt Visser (Victoria
University of Wellington) | Massive gravity as a limit of bimetric gravity | 3 pages; contribution to the proceedings of the Thirteenth Marcel
Grossmann Meeting, Stockholm University, Sweden, 1-7 July, 2012 | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive gravity may be viewed as a suitable limit of bimetric gravity. The
limiting procedure can lead to an interesting interplay between the
"background" and "foreground" metrics in a cosmological context. The fact that
in bimetric theories one always has two sets of metric equations of motion
continues to have an effect even in the massive gravity limit. Thus, solutions
of bimetric gravity in the limit of vanishing kinetic term are also solutions
of massive gravity, but the contrary statement is not necessarily true.
| [
{
"created": "Tue, 12 Feb 2013 02:48:21 GMT",
"version": "v1"
}
] | 2013-02-13 | [
[
"Martin-Moruno",
"Prado",
"",
"Victoria University of Wellington"
],
[
"Baccetti",
"Valentina",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria\n University of Wellington"
]
] | Massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure can lead to an interesting interplay between the "background" and "foreground" metrics in a cosmological context. The fact that in bimetric theories one always has two sets of metric equations of motion continues to have an effect even in the massive gravity limit. Thus, solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true. |
1604.01663 | Aur\'elien Hees | C. Le Poncin-Lafitte and A. Hees and S. lambert | Lorentz symmetry and Very Long Baseline Interferometry | 5 pages, 3 figures, version accepted for publication | Phys. Rev. D 94, 125030 (2016) | 10.1103/PhysRevD.94.125030 | null | gr-qc astro-ph.EP hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lorentz symmetry violations can be described by an effective field theory
framework that contains both General Relativity and the Standard Model of
particle physics called the Standard-Model extension (SME). Recently, post-fit
analysis of Gravity Probe B and binary pulsars lead to an upper limit at the
$10^{-4}$ level on the time-time coefficient $\bar s^{TT}$ of the pure-gravity
sector of the minimal SME. In this work, we derive the observable of Very Long
Baseline Interferometry (VLBI) in SME and then we implement it into a real data
analysis code of geodetic VLBI observations. Analyzing all available
observations recorded since 1979, we compare estimates of $\bar s^{TT}$ and
errors obtained with various analysis schemes, including global estimations
over several time spans and with various Sun elongation cut-off angles, and
with analysis of radio source coordinate time series. We obtain a constraint on
$\bar s^{TT}=(-5\pm 8)\times 10^{-5}$, directly fitted to the observations and
improving by a factor 5 previous post-fit analysis estimates.
| [
{
"created": "Wed, 6 Apr 2016 15:39:54 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Dec 2016 15:42:36 GMT",
"version": "v2"
}
] | 2017-01-04 | [
[
"Poncin-Lafitte",
"C. Le",
""
],
[
"Hees",
"A.",
""
],
[
"lambert",
"S.",
""
]
] | Lorentz symmetry violations can be described by an effective field theory framework that contains both General Relativity and the Standard Model of particle physics called the Standard-Model extension (SME). Recently, post-fit analysis of Gravity Probe B and binary pulsars lead to an upper limit at the $10^{-4}$ level on the time-time coefficient $\bar s^{TT}$ of the pure-gravity sector of the minimal SME. In this work, we derive the observable of Very Long Baseline Interferometry (VLBI) in SME and then we implement it into a real data analysis code of geodetic VLBI observations. Analyzing all available observations recorded since 1979, we compare estimates of $\bar s^{TT}$ and errors obtained with various analysis schemes, including global estimations over several time spans and with various Sun elongation cut-off angles, and with analysis of radio source coordinate time series. We obtain a constraint on $\bar s^{TT}=(-5\pm 8)\times 10^{-5}$, directly fitted to the observations and improving by a factor 5 previous post-fit analysis estimates. |
gr-qc/0304046 | Ruth Lazkoz | J.M. Aguirregabiria and Ruth Lazkoz | Anisotropic brane cosmologies with exponential potentials | 11 pages, 1 figure | Int.J.Mod.Phys. D13 (2004) 539-554 | 10.1142/S0218271804003846 | null | gr-qc | null | We study Bianchi I type brane cosmologies with scalar matter self-interacting
through combinations of exponential potentials. Such models correspond in some
cases to inflationary universes. We discuss the conditions for accelerated
expansion to occur, and pay particular attention to the influence of extra
dimensions and anisotropy. Our results show that the associated effects evolve
in such a way that they become negligible in the late time limit, those related
to the anisotropy disappearing earlier. This study focuses mainly on single
field models, but we also consider a generalization yielding models with
multiple non-interacting fields and examine its features briefly. We conclude
that in the brane scenario, as happens in general relativity, an increase in
the number of fields assists inflation.
| [
{
"created": "Fri, 11 Apr 2003 08:02:40 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Mar 2004 18:13:24 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Aguirregabiria",
"J. M.",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | We study Bianchi I type brane cosmologies with scalar matter self-interacting through combinations of exponential potentials. Such models correspond in some cases to inflationary universes. We discuss the conditions for accelerated expansion to occur, and pay particular attention to the influence of extra dimensions and anisotropy. Our results show that the associated effects evolve in such a way that they become negligible in the late time limit, those related to the anisotropy disappearing earlier. This study focuses mainly on single field models, but we also consider a generalization yielding models with multiple non-interacting fields and examine its features briefly. We conclude that in the brane scenario, as happens in general relativity, an increase in the number of fields assists inflation. |
gr-qc/0204032 | Sanjeev S. Seahra | Sanjeev S. Seahra | The Dynamics of Test Particles and Pointlike Gyroscopes in the Brane
World and Other 5D Models | 13 pages, 2 figures, in press in Phys. Rev. D | Phys.Rev. D65 (2002) 124004 | 10.1103/PhysRevD.65.124004 | null | gr-qc | null | We study the dynamics of test particles and pointlike gyroscopes in 5D
manifolds like those used in the Randall-Sundrum brane world and non-compact
Kaluza-Klein models. Our analysis is based on a covariant foliation of the
manifold using 3+1 dimensional spacetime slices orthogonal to the extra
dimension, and is hence similar to the ADM 3+1 split in ordinary general
relativity. We derive gauge invariant equations of motion for freely-falling
test particles in the 5D and 4D affine parameterizations and contrast these
results with previous work concerning the so-called ``fifth force''. Motivated
by the conjectured localization of matter fields on a 3-brane, we derive the
form of the classical non-gravitational force required to confine particles to
a 4D hypersurface and show that the resulting trajectories are geometrically
identical to the spacetime geodesics of Einstein's theory. We then discuss the
issue of determining the 5D dynamics of a torque-free spinning body in the
point-dipole approximation, and then perform a covariant (3+1)+1 decomposition
of the relevant formulae (i.e. the 5D Fermi-Walker transport equation) for the
cases of freely-falling and hypersurface-confined point gyroscopes. In both
cases, the 4D spin tensor is seen to be subject to an anomalous torque. We
solve the spin equations for a gyroscope confined to a single spacetime section
in a simple 5D cosmological model and observe a cosmological variation of the
magnitude and orientation of the 4D spin.
| [
{
"created": "Mon, 8 Apr 2002 01:19:25 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Seahra",
"Sanjeev S.",
""
]
] | We study the dynamics of test particles and pointlike gyroscopes in 5D manifolds like those used in the Randall-Sundrum brane world and non-compact Kaluza-Klein models. Our analysis is based on a covariant foliation of the manifold using 3+1 dimensional spacetime slices orthogonal to the extra dimension, and is hence similar to the ADM 3+1 split in ordinary general relativity. We derive gauge invariant equations of motion for freely-falling test particles in the 5D and 4D affine parameterizations and contrast these results with previous work concerning the so-called ``fifth force''. Motivated by the conjectured localization of matter fields on a 3-brane, we derive the form of the classical non-gravitational force required to confine particles to a 4D hypersurface and show that the resulting trajectories are geometrically identical to the spacetime geodesics of Einstein's theory. We then discuss the issue of determining the 5D dynamics of a torque-free spinning body in the point-dipole approximation, and then perform a covariant (3+1)+1 decomposition of the relevant formulae (i.e. the 5D Fermi-Walker transport equation) for the cases of freely-falling and hypersurface-confined point gyroscopes. In both cases, the 4D spin tensor is seen to be subject to an anomalous torque. We solve the spin equations for a gyroscope confined to a single spacetime section in a simple 5D cosmological model and observe a cosmological variation of the magnitude and orientation of the 4D spin. |
gr-qc/9405025 | null | Jose P. Mimoso and David Wands | Massless Fileds in Scalar-Tensor Cosmologies | 24 pages (5 figures available on request from
dwands@star.susx.ac.uk), LaTeX with REVTeX macros, SUSSEX-AST-94/4-1 | Phys.Rev.D51:477-489,1995 | 10.1103/PhysRevD.51.477 | null | gr-qc | null | We derive exact Friedmann--Robertson--Walker cosmological solutions in
general scalar--tensor gravity theories, including Brans--Dicke gravity, for
stiff matter or radiation. These correspond to the long or short wavelength
modes respectively of massless scalar fields. If present, the long wavelength
modes of such fields would be expected to dominate the energy density of the
universe at early times and thus these models provide an insight into the
classical behaviour of these scalar--tensor cosmologies near an initial
singularity, or bounce. The particularly simple exact solutions also provide a
useful example of the possible evolution of the Brans--Dicke (or dilaton)
field, $\phi$, and the Brans--Dicke parameter, $\omega(\phi)$, at late times in
spatially curved as well as flat universes. We also discuss the corresponding
solutions in the conformally related Einstein metric.
| [
{
"created": "Tue, 10 May 1994 15:53:00 GMT",
"version": "v1"
}
] | 2011-08-11 | [
[
"Mimoso",
"Jose P.",
""
],
[
"Wands",
"David",
""
]
] | We derive exact Friedmann--Robertson--Walker cosmological solutions in general scalar--tensor gravity theories, including Brans--Dicke gravity, for stiff matter or radiation. These correspond to the long or short wavelength modes respectively of massless scalar fields. If present, the long wavelength modes of such fields would be expected to dominate the energy density of the universe at early times and thus these models provide an insight into the classical behaviour of these scalar--tensor cosmologies near an initial singularity, or bounce. The particularly simple exact solutions also provide a useful example of the possible evolution of the Brans--Dicke (or dilaton) field, $\phi$, and the Brans--Dicke parameter, $\omega(\phi)$, at late times in spatially curved as well as flat universes. We also discuss the corresponding solutions in the conformally related Einstein metric. |
1209.2015 | S Habib Mazharimousavi | S. Habib Mazharimousavi and M. Halilsoy | Necessary conditions for having wormholes in f(R) gravity | 7 pages, 1 figure | Mod. Phys. Lett. A, 31, 1650203 (2016); Mod. Phys. Lett. A, 31,
1650192 (2016) | 10.1142/S0217732316501923 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a generic $f(R)$ which admits a polynomial expansion of at least third
order (i.e. $\frac{d^{3}f}{dR^{3}}\neq 0$) we find the near-throat wormhole
solution. Necessary conditions for the existence of wormholes in such $f(R)$
theories are derived for both zero and non-zero matter sources. A particular
choice of energy-momentum reveals that the wormhole geometry satisfies the weak
energy condition (WEC). For a range of parameters even the strong energy
condition (SEC) is shown to be satisfied.
| [
{
"created": "Fri, 7 Sep 2012 14:06:25 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Sep 2012 08:01:51 GMT",
"version": "v2"
}
] | 2016-11-15 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | For a generic $f(R)$ which admits a polynomial expansion of at least third order (i.e. $\frac{d^{3}f}{dR^{3}}\neq 0$) we find the near-throat wormhole solution. Necessary conditions for the existence of wormholes in such $f(R)$ theories are derived for both zero and non-zero matter sources. A particular choice of energy-momentum reveals that the wormhole geometry satisfies the weak energy condition (WEC). For a range of parameters even the strong energy condition (SEC) is shown to be satisfied. |
1410.5736 | Yuri Pavlov | A. A. Grib, Yu. V. Pavlov | Are black holes totally black? | 6 pages, 1 figure | Gravitation and Cosmology 21 (2015), 13-18 | 10.1134/S0202289315010065 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Geodesic completeness needs existence near the horizon of the black hole of
"white hole" geodesics coming from the region inside of the horizon. Here we
give the classification of all such geodesics with the energies $E/m \le 1$ for
the Schwarzschild and Kerr's black hole. The collisions of particles moving
along the "white hole" geodesics with those moving along "black hole" geodesics
are considered. Formulas for the increase of the energy of collision in the
centre of mass frame are obtained and the possibility of observation of high
energy particles arriving from the black hole to the Earth is discussed.
| [
{
"created": "Tue, 21 Oct 2014 16:42:16 GMT",
"version": "v1"
}
] | 2015-03-10 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | Geodesic completeness needs existence near the horizon of the black hole of "white hole" geodesics coming from the region inside of the horizon. Here we give the classification of all such geodesics with the energies $E/m \le 1$ for the Schwarzschild and Kerr's black hole. The collisions of particles moving along the "white hole" geodesics with those moving along "black hole" geodesics are considered. Formulas for the increase of the energy of collision in the centre of mass frame are obtained and the possibility of observation of high energy particles arriving from the black hole to the Earth is discussed. |
gr-qc/0307104 | Jose' P. S. Lemos | Vitor Cardoso, Jose' P. S. Lemos, Shijun Yoshida | Electromagnetic radiation from collisions at almost the speed of light:
an extremely relativistic charged particle falling into a Schwarzschild black
hole | 6 pages, 2 figures | Phys.Rev. D68 (2003) 084011 | 10.1103/PhysRevD.68.084011 | null | gr-qc astro-ph hep-ph hep-th | null | We investigate the electromagnetic radiation released during the high energy
collision of a charged point particle with a four-dimensional Schwarzschild
black hole. We show that the spectra is flat, and well described by a classical
calculation. We also compare the total electromagnetic and gravitational
energies emitted, and find that the former is supressed in relation to the
latter for very high energies. These results could apply to the astrophysical
world in the case charged stars and small charged black holes are out there
colliding into large black holes, and to a very high energy collision
experiment in a four-dimensional world. In this latter scenario the calculation
is to be used for the moments just after the black hole formation, when the
collision of charged debris with the newly formed black hole is certainly
expected. Since the calculation is four-dimensional, it does not directly apply
to Tev-scale gravity black holes, as these inhabit a world of six to eleven
dimensions, although our results should qualitatively hold when extrapolated
with some care to higher dimensions.
| [
{
"created": "Wed, 23 Jul 2003 22:24:58 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Cardoso",
"Vitor",
""
],
[
"Lemos",
"Jose' P. S.",
""
],
[
"Yoshida",
"Shijun",
""
]
] | We investigate the electromagnetic radiation released during the high energy collision of a charged point particle with a four-dimensional Schwarzschild black hole. We show that the spectra is flat, and well described by a classical calculation. We also compare the total electromagnetic and gravitational energies emitted, and find that the former is supressed in relation to the latter for very high energies. These results could apply to the astrophysical world in the case charged stars and small charged black holes are out there colliding into large black holes, and to a very high energy collision experiment in a four-dimensional world. In this latter scenario the calculation is to be used for the moments just after the black hole formation, when the collision of charged debris with the newly formed black hole is certainly expected. Since the calculation is four-dimensional, it does not directly apply to Tev-scale gravity black holes, as these inhabit a world of six to eleven dimensions, although our results should qualitatively hold when extrapolated with some care to higher dimensions. |
2011.04550 | Beatriz Elizaga Navascu\'es | Jer\'onimo Cortez, Beatriz Elizaga Navascu\'es, Guillermo A. Mena
Marug\'an, Santiago Prado, and Jos\'e M. Velhinho | Uniqueness Criteria for the Fock Quantization of Dirac Fields and
Applications in Hybrid Loop Quantum Cosmology | 48 pages | Universe 2020, 6(12), 241 | 10.3390/universe6120241 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In generic curved spacetimes, the unavailability of a natural choice of
vacuum state introduces a serious ambiguity in the Fock quantization of fields.
In this review, we study the case of fermions described by a Dirac field in
several cosmological spacetimes, and present recent results about
well-motivated criteria that ensure the uniqueness in the selection of a vacuum
up to unitary transformations. These criteria are based on two requirements.
First, the invariance of the vacuum under the symmetries of the Dirac equations
in the considered spacetime. Second, the unitary implementability of the
Heisenberg dynamics of the annihilation and creation operators when the curved
spacetime is treated as a fixed background. This last requirement not only
permits the uniqueness of the Fock quantization but, remarkably, it also
determines an essentially unique splitting between the phase space variables
assigned to the background and the fermionic annihilation and creation
variables. We first consider Dirac fields in cosmological spacetimes of 2+1
dimensions and then discuss the more relevant case of 3+1 dimensions. We use
this analysis to investigate the hybrid loop quantization of a flat
Friedmann-Lema\^itre-Robertson-Walker background cosmology coupled to a
perturbative Dirac field. Among the Fock quantizations for the fermionic
perturbations allowed by our criteria, we further restrict the choice of vacuum
by demanding a finite fermionic backreaction and, moreover, by diagonalizing
the fermionic contribution to the total Hamiltonian in the asymptotic limit of
large wave numbers of the Dirac modes. Finally, we argue in support of the
uniquess of the vacuum state selected by the extension of this diagonalization
condition beyond the ultraviolet regime, proving that it picks out the standard
Poincar\'e and Bunch-Davies vacua for fixed flat and de Sitter background
spacetimes, respectively.
| [
{
"created": "Mon, 9 Nov 2020 16:49:19 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jun 2021 06:08:40 GMT",
"version": "v2"
}
] | 2021-06-02 | [
[
"Cortez",
"Jerónimo",
""
],
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Prado",
"Santiago",
""
],
[
"Velhinho",
"José M.",
""
]
] | In generic curved spacetimes, the unavailability of a natural choice of vacuum state introduces a serious ambiguity in the Fock quantization of fields. In this review, we study the case of fermions described by a Dirac field in several cosmological spacetimes, and present recent results about well-motivated criteria that ensure the uniqueness in the selection of a vacuum up to unitary transformations. These criteria are based on two requirements. First, the invariance of the vacuum under the symmetries of the Dirac equations in the considered spacetime. Second, the unitary implementability of the Heisenberg dynamics of the annihilation and creation operators when the curved spacetime is treated as a fixed background. This last requirement not only permits the uniqueness of the Fock quantization but, remarkably, it also determines an essentially unique splitting between the phase space variables assigned to the background and the fermionic annihilation and creation variables. We first consider Dirac fields in cosmological spacetimes of 2+1 dimensions and then discuss the more relevant case of 3+1 dimensions. We use this analysis to investigate the hybrid loop quantization of a flat Friedmann-Lema\^itre-Robertson-Walker background cosmology coupled to a perturbative Dirac field. Among the Fock quantizations for the fermionic perturbations allowed by our criteria, we further restrict the choice of vacuum by demanding a finite fermionic backreaction and, moreover, by diagonalizing the fermionic contribution to the total Hamiltonian in the asymptotic limit of large wave numbers of the Dirac modes. Finally, we argue in support of the uniquess of the vacuum state selected by the extension of this diagonalization condition beyond the ultraviolet regime, proving that it picks out the standard Poincar\'e and Bunch-Davies vacua for fixed flat and de Sitter background spacetimes, respectively. |
1206.0728 | Dennis Bessada | Dennis Bessada | Non-Gaussian signatures of Tachyacoustic Cosmology | Some comments and references added. Matches the version published in
JCAP | null | 10.1088/1475-7516/2012/09/018 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I investigate non-Gaussian signatures in the context of tachyacoustic
cosmology, that is, a noninflationary model with superluminal speed of sound. I
calculate the full non-Gaussian amplitude $\mathcal{A}$, its size $f_{\rm NL}$,
and corresponding shapes for a red-tilted spectrum of primordial scalar
perturbations. Specifically, for cuscuton-like models I show that $f_{\rm
NL}\sim {\cal O}(1)$, and the shape of its non-Gaussian amplitude peaks for
both equilateral and local configurations, the latter being dominant. These
results, albeit similar, are quantitatively distinct from the corresponding
ones obtained by Magueijo {\it{et. al}} in the context of superluminal bimetric
models.
| [
{
"created": "Sat, 2 Jun 2012 19:58:52 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Sep 2012 02:06:52 GMT",
"version": "v2"
}
] | 2015-06-05 | [
[
"Bessada",
"Dennis",
""
]
] | I investigate non-Gaussian signatures in the context of tachyacoustic cosmology, that is, a noninflationary model with superluminal speed of sound. I calculate the full non-Gaussian amplitude $\mathcal{A}$, its size $f_{\rm NL}$, and corresponding shapes for a red-tilted spectrum of primordial scalar perturbations. Specifically, for cuscuton-like models I show that $f_{\rm NL}\sim {\cal O}(1)$, and the shape of its non-Gaussian amplitude peaks for both equilateral and local configurations, the latter being dominant. These results, albeit similar, are quantitatively distinct from the corresponding ones obtained by Magueijo {\it{et. al}} in the context of superluminal bimetric models. |
2105.05666 | Rolando Gaitan Deveras RGD | Rolando Gaitan and Yessica Dominguez | Elements of the Metric-Affine Gravity I: Aspects of F(R) theories
reductions and the Topologically Massive Gravity | 42 pages, 1 figure | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Some classical aspects of Metric-Affine Gravity are reviewed in the context
of the $F^{(n)}(R)$ type models (polynomials of degree $n$ in the Riemann
tensor) and the topologically massive gravity. At the non-perturbative level,
we explore the consistency of the field equations when the $F^{(n)}(R)$ models
are reduced to a Riemann-Christoffel (RCh) space-time, either via a
Riemann-Cartan (RC) space or via an Einstein-Weyl (EW) space. It is well known
for the case $F^{(1)}(R)=R$ that any path or reduction "classes" via RC or EW,
leads to the same field equations with the exception of the $F^{(n)}(R)$
theories for $n>1$. We verify that this discrepancy can be solved by imposing
non-metricity and torsion constraints. In particular, we explore the case
$F^{(2)}(R)$ for the interest in expected physical solutions as those of
conformally flat class. On the other hand, the symmetries of the topologically
massive gravity are reviewed, as the physical content in RC and EW scenarios.
The appearance of a non-linearly modified selfdual model in RC and existence of
many non-unitary degrees of freedom in EW with the suggestion of a modified
model for a massive gravity which cure the unphysical propagations, shall be
discussed.
| [
{
"created": "Wed, 12 May 2021 13:56:13 GMT",
"version": "v1"
}
] | 2021-05-13 | [
[
"Gaitan",
"Rolando",
""
],
[
"Dominguez",
"Yessica",
""
]
] | Some classical aspects of Metric-Affine Gravity are reviewed in the context of the $F^{(n)}(R)$ type models (polynomials of degree $n$ in the Riemann tensor) and the topologically massive gravity. At the non-perturbative level, we explore the consistency of the field equations when the $F^{(n)}(R)$ models are reduced to a Riemann-Christoffel (RCh) space-time, either via a Riemann-Cartan (RC) space or via an Einstein-Weyl (EW) space. It is well known for the case $F^{(1)}(R)=R$ that any path or reduction "classes" via RC or EW, leads to the same field equations with the exception of the $F^{(n)}(R)$ theories for $n>1$. We verify that this discrepancy can be solved by imposing non-metricity and torsion constraints. In particular, we explore the case $F^{(2)}(R)$ for the interest in expected physical solutions as those of conformally flat class. On the other hand, the symmetries of the topologically massive gravity are reviewed, as the physical content in RC and EW scenarios. The appearance of a non-linearly modified selfdual model in RC and existence of many non-unitary degrees of freedom in EW with the suggestion of a modified model for a massive gravity which cure the unphysical propagations, shall be discussed. |
2402.05049 | Soichiro Isoyama | Paul Ramond and Soichiro Isoyama | Symplectic mechanics of relativistic spinning compact bodies II.:
Canonical formalism in the Schwarzschild spacetime | 69 pages, 3 figures, 2 tables. V2: minor revisions before submission
to PRD. added references | null | null | null | gr-qc nlin.SI | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work constitutes the second part of a series of studies that aim to
utilise tools from Hamiltonian mechanics to investigate the motion of an
extended body in general relativity. The first part of this work [Refs. [1, 2]]
constructed a ten-dimensional, covariant Hamiltonian framework encompassing all
the linear-in-spin corrections to the geodesic motion in arbitrary spacetime.
This framework was proven to be integrable in the Schwarzschild and Kerr
spacetimes, specifically. The present work translates this abstract
integrability result into tangible applications for linear-in-spin Hamiltonian
dynamics of a compact object in a Schwarzschild spacetime. In particular, a
canonical system of coordinates is constructed explicitly, which exploits the
spherical symmetry of the Schwarzschild spacetime. These coordinates are based
on a relativistic generalization of the classical Andoyer variables of
Newtonian rigid body motion. This canonical setup allows us to derive
ready-to-use formulae for action-angle coordinates and gauge-invariant
Hamiltonian frequencies, which automatically include all linear-in-spin
effects. No external parameters or ad hoc choices are necessary, and the
framework can be used to find complete solutions by quadrature of generic
(bound or unbound), linear-in-spin orbits, including orbital inclination,
precession and eccentricity, as well as spin precession. The efficacy of the
formalism is demonstrated here in the context of circular orbits with arbitrary
spin and orbital precession, with the results validated against known results
in the literature.
| [
{
"created": "Wed, 7 Feb 2024 17:41:44 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2024 04:09:36 GMT",
"version": "v2"
}
] | 2024-05-07 | [
[
"Ramond",
"Paul",
""
],
[
"Isoyama",
"Soichiro",
""
]
] | This work constitutes the second part of a series of studies that aim to utilise tools from Hamiltonian mechanics to investigate the motion of an extended body in general relativity. The first part of this work [Refs. [1, 2]] constructed a ten-dimensional, covariant Hamiltonian framework encompassing all the linear-in-spin corrections to the geodesic motion in arbitrary spacetime. This framework was proven to be integrable in the Schwarzschild and Kerr spacetimes, specifically. The present work translates this abstract integrability result into tangible applications for linear-in-spin Hamiltonian dynamics of a compact object in a Schwarzschild spacetime. In particular, a canonical system of coordinates is constructed explicitly, which exploits the spherical symmetry of the Schwarzschild spacetime. These coordinates are based on a relativistic generalization of the classical Andoyer variables of Newtonian rigid body motion. This canonical setup allows us to derive ready-to-use formulae for action-angle coordinates and gauge-invariant Hamiltonian frequencies, which automatically include all linear-in-spin effects. No external parameters or ad hoc choices are necessary, and the framework can be used to find complete solutions by quadrature of generic (bound or unbound), linear-in-spin orbits, including orbital inclination, precession and eccentricity, as well as spin precession. The efficacy of the formalism is demonstrated here in the context of circular orbits with arbitrary spin and orbital precession, with the results validated against known results in the literature. |
2408.05668 | Shin'ichi Nojiri | Shin'ichi Nojiri and Sergei D. Odintsov | Improving Mimetic Gravity with Non-trivial Scalar Potential: Cosmology,
Black Holes, Shadow and Photon Sphere | LaTeX, 32 pages, no figure | null | null | KEK-TH-2645, KEK-Cosmo-0353 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is not easy to treat the spacetime with horizon(s) in the standard mimetic
gravity. The solution to this problem has been presented in Phys.~Lett.~B 830
(2022), 137140, where it was suggested to modify the Lagrange multiplier
constraint.
In this paper, by using the improved formulation, we investigate the
cosmology and black holes in mimetic gravity with scalar potential and in the
scalar mimetic $F(R)$ gravity. The inflationary era and dark energy epoch for
the above theories are presented as specific examples from the general
reconstruction scheme which permits to realise any universe expansion history
via the choice of the corresponding scalar potential or function $F(R)$. Two
black hole solutions including the Schwarzschild and Hayward ones are
constructed. The shadow and the radius of the photon sphere for the above black
holes are found. The explicit confrontation of the black hole shadow radius
with the observational bounds from M87$^*$ and Sgr A$^*$ objects is done. It is
demonstrated that they do not conflict with Event Horizon Telescope
observations.
| [
{
"created": "Sun, 11 Aug 2024 01:15:39 GMT",
"version": "v1"
}
] | 2024-08-13 | [
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | It is not easy to treat the spacetime with horizon(s) in the standard mimetic gravity. The solution to this problem has been presented in Phys.~Lett.~B 830 (2022), 137140, where it was suggested to modify the Lagrange multiplier constraint. In this paper, by using the improved formulation, we investigate the cosmology and black holes in mimetic gravity with scalar potential and in the scalar mimetic $F(R)$ gravity. The inflationary era and dark energy epoch for the above theories are presented as specific examples from the general reconstruction scheme which permits to realise any universe expansion history via the choice of the corresponding scalar potential or function $F(R)$. Two black hole solutions including the Schwarzschild and Hayward ones are constructed. The shadow and the radius of the photon sphere for the above black holes are found. The explicit confrontation of the black hole shadow radius with the observational bounds from M87$^*$ and Sgr A$^*$ objects is done. It is demonstrated that they do not conflict with Event Horizon Telescope observations. |
gr-qc/0307100 | Nicolas Arnaud | Nicolas Arnaud, Matteo Barsuglia, Marie-Anne Bizouard, Violette
Brisson, Fabien Cavalier, Michel Davier, Patrice Hello, Stephane
Kreckelbergh, Edward K. Porter | Coincidence and coherent data analysis methods for gravitational wave
bursts in a network of interferometric detectors | Spelling mistake corrected in one author's name | Phys.Rev. D68 (2003) 102001 | 10.1103/PhysRevD.68.102001 | null | gr-qc | null | Network data analysis methods are the only way to properly separate real
gravitational wave (GW) transient events from detector noise. They can be
divided into two generic classes: the coincidence method and the coherent
analysis. The former uses lists of selected events provided by each
interferometer belonging to the network and tries to correlate them in time to
identify a physical signal. Instead of this binary treatment of detector
outputs (signal present or absent), the latter method involves first the
merging of the interferometer data and looks for a common pattern, consistent
with an assumed GW waveform and a given source location in the sky. The
thresholds are only applied later, to validate or not the hypothesis made. As
coherent algorithms use a more complete information than coincidence methods,
they are expected to provide better detection performances, but at a higher
computational cost. An efficient filter must yield a good compromise between a
low false alarm rate (hence triggering on data at a manageable rate) and a high
detection efficiency. Therefore, the comparison of the two approaches is
achieved using so-called Receiving Operating Characteristics (ROC), giving the
relationship between the false alarm rate and the detection efficiency for a
given method. This paper investigates this question via Monte-Carlo
simulations, using the network model developed in a previous article.
| [
{
"created": "Wed, 23 Jul 2003 16:08:06 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Sep 2003 11:32:11 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Sep 2003 12:17:25 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Arnaud",
"Nicolas",
""
],
[
"Barsuglia",
"Matteo",
""
],
[
"Bizouard",
"Marie-Anne",
""
],
[
"Brisson",
"Violette",
""
],
[
"Cavalier",
"Fabien",
""
],
[
"Davier",
"Michel",
""
],
[
"Hello",
"Patrice",
""
... | Network data analysis methods are the only way to properly separate real gravitational wave (GW) transient events from detector noise. They can be divided into two generic classes: the coincidence method and the coherent analysis. The former uses lists of selected events provided by each interferometer belonging to the network and tries to correlate them in time to identify a physical signal. Instead of this binary treatment of detector outputs (signal present or absent), the latter method involves first the merging of the interferometer data and looks for a common pattern, consistent with an assumed GW waveform and a given source location in the sky. The thresholds are only applied later, to validate or not the hypothesis made. As coherent algorithms use a more complete information than coincidence methods, they are expected to provide better detection performances, but at a higher computational cost. An efficient filter must yield a good compromise between a low false alarm rate (hence triggering on data at a manageable rate) and a high detection efficiency. Therefore, the comparison of the two approaches is achieved using so-called Receiving Operating Characteristics (ROC), giving the relationship between the false alarm rate and the detection efficiency for a given method. This paper investigates this question via Monte-Carlo simulations, using the network model developed in a previous article. |
1111.3858 | Mubasher Jamil | Ujjal Debnath, Surajit Chattopadhyay, Ibrar Hussain, Mubasher Jamil,
Ratbay Myrzakulov | Generalized Second Law of Thermodynamics for FRW Cosmology with
Power-Law Entropy Correction | 10 pages | Eur. Phys. J. C (2012) 72:1875 | 10.1140/epjc/s10052-012-1875-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have considered the power law correction of entropy on the
horizon. If the flat FRW Universe is filled with the n components fluid with
interactions, the GSL of thermodynamics for apparent and event horizons have
been investigated for equilibrium and non-equilibrium cases. If we consider a
small perturbation around the de Sitter space-time, the general conditions of
the validity of GSL have been found. Also if a phantom dominated Universe has a
polelike type scale factor, the validity of GSL has also been analyzed. Further
we have obtained constraints on the power-law parameter {\alpha} in the phantom
and quintessence dominated regimes. Finally we obtain conditions under which
GSL breaks down in a cosmological background.
| [
{
"created": "Tue, 15 Nov 2011 08:26:58 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jan 2012 04:50:38 GMT",
"version": "v2"
},
{
"created": "Thu, 23 Feb 2012 11:02:07 GMT",
"version": "v3"
}
] | 2012-07-03 | [
[
"Debnath",
"Ujjal",
""
],
[
"Chattopadhyay",
"Surajit",
""
],
[
"Hussain",
"Ibrar",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In this work, we have considered the power law correction of entropy on the horizon. If the flat FRW Universe is filled with the n components fluid with interactions, the GSL of thermodynamics for apparent and event horizons have been investigated for equilibrium and non-equilibrium cases. If we consider a small perturbation around the de Sitter space-time, the general conditions of the validity of GSL have been found. Also if a phantom dominated Universe has a polelike type scale factor, the validity of GSL has also been analyzed. Further we have obtained constraints on the power-law parameter {\alpha} in the phantom and quintessence dominated regimes. Finally we obtain conditions under which GSL breaks down in a cosmological background. |
gr-qc/0101005 | Valery Gavrilov | V.R. Gavrilov and V.N. Melnikov | X-fluid and viscous fluid in D-dimensional anisotropic integrable
cosmology | 11 pages, Latex 2.09 | null | null | null | gr-qc | null | D-dimensional cosmological model describing the evolution of a perfect fluid
with negative pressure (x-fluid) and a fluid possessing both shear and bulk
viscosity in n Ricci-flat spaces is investigated. The second equations of state
are chosen in some special form of metric dependence of the shear and bulk
viscosity coefficients. The equations of motion are integrated and the
dynamical properties of the exact solutions are studied. It is shown the
possibility to resolve the cosmic coincidence problem when the x-fluid plays
role of quintessence and the viscous fluid is used as cold dark matter.
| [
{
"created": "Sat, 30 Dec 2000 17:09:59 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Mar 2001 21:00:59 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Gavrilov",
"V. R.",
""
],
[
"Melnikov",
"V. N.",
""
]
] | D-dimensional cosmological model describing the evolution of a perfect fluid with negative pressure (x-fluid) and a fluid possessing both shear and bulk viscosity in n Ricci-flat spaces is investigated. The second equations of state are chosen in some special form of metric dependence of the shear and bulk viscosity coefficients. The equations of motion are integrated and the dynamical properties of the exact solutions are studied. It is shown the possibility to resolve the cosmic coincidence problem when the x-fluid plays role of quintessence and the viscous fluid is used as cold dark matter. |
2208.07324 | Serguei Krasnikov | Serguei Krasnikov | A causality preserving evolution of a pair of strings | More details | Universe 8 (2022) 640 | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | As shown by Gott, a pair of straight cosmic strings moving in opposite
directions, when they have suitable speed and impact parameter, produce closed
timelike curves.
I argue in this paper that there always is a not-so-frightening alternative:
the Universe may prefer to produce a certain (surprisingly simple and
absolutely mild) singularity instead.
| [
{
"created": "Mon, 15 Aug 2022 16:42:21 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Dec 2022 16:03:26 GMT",
"version": "v2"
}
] | 2022-12-02 | [
[
"Krasnikov",
"Serguei",
""
]
] | As shown by Gott, a pair of straight cosmic strings moving in opposite directions, when they have suitable speed and impact parameter, produce closed timelike curves. I argue in this paper that there always is a not-so-frightening alternative: the Universe may prefer to produce a certain (surprisingly simple and absolutely mild) singularity instead. |
1307.1097 | Henrique de Andrade Gomes | Henrique Gomes | A construction principle for ADM-type theories in maximal slicing gauge | 14 pages, updated references, matches version submitted to Phys. Rev.
D | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The differing concepts of time in general relativity and quantum mechanics
are widely accused as the main culprits in our persistent failure in finding a
complete theory of quantum gravity. Here we address this issue by constructing
ADM-type theories \emph{in a particular time gauge} directly from first
principles. The principles are expressed as conditions on phase space
constraints: we search for two sets of spatially covariant constraints, which
generate symmetries (are first class) and gauge-fix each other leaving two
propagating degrees of freedom.
One of the sets is the Weyl generator tr$(\pi)$, and the other is a
one-parameter family containing the ADM scalar constraint $\lambda R-
\beta(\pi^{ab}\pi_{ab}+(\mbox{tr}(\pi))^2/2))$. The two sets of constraints can
be seen as defining ADM-type theories with a maximal slicing gauge-fixing. This
work provides an independent, first principles derivation of ADM gravity.
The principles above are motivated by a heuristic argument relying in the
relation between symmetry doubling and exact renormalization arguments for
quantum gravity, aside from compatibility with the spatial diffeomorphisms. As
a by-product, these results address one of the most popular criticisms of Shape
Dynamics: its construction starts off from the ADM Hamiltonian formulation.
The present work severs this dependence: the set of constraints yield reduced
phase space theories that can be naturally represented by either Shape Dynamics
or ADM. More precisely, the resulting theories can be naturally "unfixed" to
encompass either spatial Weyl invariance (the symmetry of Shape Dynamics) or
refoliation symmetry (ADM).
| [
{
"created": "Wed, 3 Jul 2013 18:05:57 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jul 2013 18:37:27 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Oct 2013 08:18:50 GMT",
"version": "v3"
}
] | 2013-10-08 | [
[
"Gomes",
"Henrique",
""
]
] | The differing concepts of time in general relativity and quantum mechanics are widely accused as the main culprits in our persistent failure in finding a complete theory of quantum gravity. Here we address this issue by constructing ADM-type theories \emph{in a particular time gauge} directly from first principles. The principles are expressed as conditions on phase space constraints: we search for two sets of spatially covariant constraints, which generate symmetries (are first class) and gauge-fix each other leaving two propagating degrees of freedom. One of the sets is the Weyl generator tr$(\pi)$, and the other is a one-parameter family containing the ADM scalar constraint $\lambda R- \beta(\pi^{ab}\pi_{ab}+(\mbox{tr}(\pi))^2/2))$. The two sets of constraints can be seen as defining ADM-type theories with a maximal slicing gauge-fixing. This work provides an independent, first principles derivation of ADM gravity. The principles above are motivated by a heuristic argument relying in the relation between symmetry doubling and exact renormalization arguments for quantum gravity, aside from compatibility with the spatial diffeomorphisms. As a by-product, these results address one of the most popular criticisms of Shape Dynamics: its construction starts off from the ADM Hamiltonian formulation. The present work severs this dependence: the set of constraints yield reduced phase space theories that can be naturally represented by either Shape Dynamics or ADM. More precisely, the resulting theories can be naturally "unfixed" to encompass either spatial Weyl invariance (the symmetry of Shape Dynamics) or refoliation symmetry (ADM). |
0904.1272 | Dario Zappala | M. Consoli | Ultraweak excitations of the quantum vacuum as physical models of
gravity | 30 pages, no figures, accepted by Classical and Quantum Gravity | Class.Quant.Grav.26:225008,2009 | 10.1088/0264-9381/26/22/225008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been argued by several authors that the space-time curvature observed
in gravitational fields, and the same idea of forms of physical equivalence
different from the Lorentz group, might emerge from the dynamical properties of
the physical flat-space vacuum in a suitable hydrodynamic limit. To explore
this idea, one could start by representing the physical vacuum as a Bose
condensate of elementary quanta and look for vacuum excitations that, on a
coarse grained scale, resemble the Newtonian potential. In this way, it is
relatively easy to match the weak-field limit of classical General Relativity
or of some of its possible variants. The idea that Bose condensates can provide
various forms of gravitational dynamics is not new. Here, I want to emphasize
some genuine quantum field theoretical aspects that can help to understand i)
why infinitesimally weak, 1/r interactions can indeed arise from the same
physical vacuum of electroweak and strong interactions and ii) why, on a
coarse-grained scale, their dynamical effects can be re-absorbed into an
effective curved metric structure.
| [
{
"created": "Wed, 8 Apr 2009 07:22:05 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Sep 2009 09:52:44 GMT",
"version": "v2"
}
] | 2009-11-19 | [
[
"Consoli",
"M.",
""
]
] | It has been argued by several authors that the space-time curvature observed in gravitational fields, and the same idea of forms of physical equivalence different from the Lorentz group, might emerge from the dynamical properties of the physical flat-space vacuum in a suitable hydrodynamic limit. To explore this idea, one could start by representing the physical vacuum as a Bose condensate of elementary quanta and look for vacuum excitations that, on a coarse grained scale, resemble the Newtonian potential. In this way, it is relatively easy to match the weak-field limit of classical General Relativity or of some of its possible variants. The idea that Bose condensates can provide various forms of gravitational dynamics is not new. Here, I want to emphasize some genuine quantum field theoretical aspects that can help to understand i) why infinitesimally weak, 1/r interactions can indeed arise from the same physical vacuum of electroweak and strong interactions and ii) why, on a coarse-grained scale, their dynamical effects can be re-absorbed into an effective curved metric structure. |
1103.1220 | Suat Dengiz | Suat Dengiz | 3+1 Orthogonal and Conformal Decomposition of the Einstein Equation and
the ADM Formalism for General Relativity | M. Sc. Thesis, 88 pages, 6 figures | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, two particular orthogonal and conformal decompositions of the
3+1 dimensional Einstein equation and Arnowitt-Deser-Misner (ADM) formalism for
general relativity are obtained. In order to do these, the 3+1 foliation of the
four-dimensional spacetime, the fundamental conformal transformations and the
Hamiltonian form of general relativity that leads to the ADM formalism, defined
for the conserved quantities of the hypersurfaces of the globally-hyperbolic
asymptotically flat spacetimes, are reconstructed. All the calculations up to
chapter 7 are just a review.
We propose a method in chapter 7 which gives an interesting relation between
the Cotton (Conformal) soliton and the static vacuum solutions. The formulation
that we introduce can be extended to find the gradient Cotton soliton and the
solutions of Topologically Massive Gravity (TMG) as well as the gradient Ricci
soliton.
| [
{
"created": "Mon, 7 Mar 2011 09:45:40 GMT",
"version": "v1"
}
] | 2011-03-08 | [
[
"Dengiz",
"Suat",
""
]
] | In this work, two particular orthogonal and conformal decompositions of the 3+1 dimensional Einstein equation and Arnowitt-Deser-Misner (ADM) formalism for general relativity are obtained. In order to do these, the 3+1 foliation of the four-dimensional spacetime, the fundamental conformal transformations and the Hamiltonian form of general relativity that leads to the ADM formalism, defined for the conserved quantities of the hypersurfaces of the globally-hyperbolic asymptotically flat spacetimes, are reconstructed. All the calculations up to chapter 7 are just a review. We propose a method in chapter 7 which gives an interesting relation between the Cotton (Conformal) soliton and the static vacuum solutions. The formulation that we introduce can be extended to find the gradient Cotton soliton and the solutions of Topologically Massive Gravity (TMG) as well as the gradient Ricci soliton. |
1411.4057 | Laszlo Arpad Gergely | L\'aszl\'o \'Arp\'ad Gergely, Zolt\'an Keresztes | Spinning compact binary dynamics and chameleon orbits | to be published in Phys. Rev. D, 19 pages, 3 figure panels | Phys. Rev. D 91, 024012 (2015) | 10.1103/PhysRevD.91.024012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the conservative evolution of spinning compact binaries to second
post-Newtonian (2PN) order accuracy, with leading order spin-orbit, spin-spin
and mass quadrupole-monopole contributions included. As a main result we derive
a closed system of first order differential equations in a compact form, for a
set of dimensionless variables encompassing both orbital elements and spin
angles. These evolutions are constrained by conservation laws holding at 2PN
order. As required by the generic theory of constrained dynamical systems we
perform a consistency check and prove that the constraints are preserved by the
evolution. We apply the formalism to show the existence of chameleon orbits,
whose local, orbital parameters evolve from elliptic (in the Newtonian sense)
near pericenter, towards hyperbolic at large distances. This behavior is
consistent with the picture that General Relativity predicts stronger gravity
at short distances than Newtonian theory does.
| [
{
"created": "Fri, 14 Nov 2014 21:07:48 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Dec 2014 07:19:48 GMT",
"version": "v2"
}
] | 2015-05-04 | [
[
"Gergely",
"László Árpád",
""
],
[
"Keresztes",
"Zoltán",
""
]
] | We analyse the conservative evolution of spinning compact binaries to second post-Newtonian (2PN) order accuracy, with leading order spin-orbit, spin-spin and mass quadrupole-monopole contributions included. As a main result we derive a closed system of first order differential equations in a compact form, for a set of dimensionless variables encompassing both orbital elements and spin angles. These evolutions are constrained by conservation laws holding at 2PN order. As required by the generic theory of constrained dynamical systems we perform a consistency check and prove that the constraints are preserved by the evolution. We apply the formalism to show the existence of chameleon orbits, whose local, orbital parameters evolve from elliptic (in the Newtonian sense) near pericenter, towards hyperbolic at large distances. This behavior is consistent with the picture that General Relativity predicts stronger gravity at short distances than Newtonian theory does. |
2407.00174 | Marius Adrian Oancea | Abraham I. Harte, Thomas B. Mieling, Marius A. Oancea, Florian
Steininger | Gravitational wave memory and its effects on particles and fields | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave memory is said to arise when a gravitational wave burst
produces changes in a physical system that persist even after that wave has
passed. This paper analyzes gravitational wave bursts in plane wave spacetimes,
deriving memory effects on timelike and null geodesics, massless scalar fields,
and massless spinning particles whose motion is described by the spin Hall
equations. All associated memory effects are found to be characterized by four
``memory tensors,'' three of which are independent. These tensors form a
scattering matrix for the transverse components of geodesics. However, unlike
for the ``classical'' memory effect involving initially comoving pairs of
timelike geodesics, one of our results is that memory effects for null
geodesics can have strong longitudinal components. When considering massless
particles with spin, we solve the spin Hall equations analytically by showing
that there exists a conservation law associated with each conformal Killing
vector field. These solutions depend only on the same four memory tensors that
control geodesic scattering. For massless scalar fields, we show that given any
solution in flat spacetime, a weak-field solution in a plane wave spacetime can
be generated just by differentiation. Precisely which derivatives are involved
depend on the same four memory tensors. These effects are illustrated for
scalar plane waves and higher-order Gaussian beams. Furthermore, we also
present a numerical comparison between the dynamics of localized wave packets
carrying angular momentum and the spin Hall equations.
| [
{
"created": "Fri, 28 Jun 2024 18:23:32 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jul 2024 17:12:08 GMT",
"version": "v2"
}
] | 2024-07-23 | [
[
"Harte",
"Abraham I.",
""
],
[
"Mieling",
"Thomas B.",
""
],
[
"Oancea",
"Marius A.",
""
],
[
"Steininger",
"Florian",
""
]
] | Gravitational wave memory is said to arise when a gravitational wave burst produces changes in a physical system that persist even after that wave has passed. This paper analyzes gravitational wave bursts in plane wave spacetimes, deriving memory effects on timelike and null geodesics, massless scalar fields, and massless spinning particles whose motion is described by the spin Hall equations. All associated memory effects are found to be characterized by four ``memory tensors,'' three of which are independent. These tensors form a scattering matrix for the transverse components of geodesics. However, unlike for the ``classical'' memory effect involving initially comoving pairs of timelike geodesics, one of our results is that memory effects for null geodesics can have strong longitudinal components. When considering massless particles with spin, we solve the spin Hall equations analytically by showing that there exists a conservation law associated with each conformal Killing vector field. These solutions depend only on the same four memory tensors that control geodesic scattering. For massless scalar fields, we show that given any solution in flat spacetime, a weak-field solution in a plane wave spacetime can be generated just by differentiation. Precisely which derivatives are involved depend on the same four memory tensors. These effects are illustrated for scalar plane waves and higher-order Gaussian beams. Furthermore, we also present a numerical comparison between the dynamics of localized wave packets carrying angular momentum and the spin Hall equations. |
1412.1955 | Marco Frasca | Marco Frasca | Hawking radiation and interacting fields | 12 pages, 1 figure. Fixed some LaTeX and added references. Accepted
for publication in European Physical Journal Plus | Eur. Phys. J. Plus (2017) 132: 467 | 10.1140/epjp/i2017-11732-1 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation is generally derived using a non-interacting field theory.
Some time ago, Leahy and Unruh showed that, in two dimensions with a
Schwarzschild geometry, a scalar field theory with a quartic interaction gets
the coupling switched off near the horizon of the black hole. This would imply
that interaction has no effect on Hawking radiation and free theory for
particles can be used. Recently, a set of exact classical solutions for the
quartic scalar field theory has been obtained. These solutions display a
massive dispersion relation even if the starting theory is massless. When one
considers the corresponding quantum field theory, this mass gap becomes a tower
of massive excitations and, at the leading order, the theory is trivial. We
apply these results to Hawking radiation for a Kerr geometry and prove that the
Leahy-Unruh effect is at work. Approaching the horizon the scalar field theory
has the mass gap going to zero. We devise a technique to study the interacting
scalar theory very near the horizon increasing the coupling. As these solutions
are represented by a Fourier series of plane waves, Hawking radiation can be
immediately obtained with well-known techniques. These results open a question
about the behavior of the Standard Model of particles very near the horizon of
a black hole where the interactions turn out to be switched off and the
electroweak symmetry could be restored.
| [
{
"created": "Fri, 5 Dec 2014 11:14:22 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Dec 2014 16:34:35 GMT",
"version": "v2"
},
{
"created": "Sun, 15 Oct 2017 14:05:33 GMT",
"version": "v3"
}
] | 2017-11-06 | [
[
"Frasca",
"Marco",
""
]
] | Hawking radiation is generally derived using a non-interacting field theory. Some time ago, Leahy and Unruh showed that, in two dimensions with a Schwarzschild geometry, a scalar field theory with a quartic interaction gets the coupling switched off near the horizon of the black hole. This would imply that interaction has no effect on Hawking radiation and free theory for particles can be used. Recently, a set of exact classical solutions for the quartic scalar field theory has been obtained. These solutions display a massive dispersion relation even if the starting theory is massless. When one considers the corresponding quantum field theory, this mass gap becomes a tower of massive excitations and, at the leading order, the theory is trivial. We apply these results to Hawking radiation for a Kerr geometry and prove that the Leahy-Unruh effect is at work. Approaching the horizon the scalar field theory has the mass gap going to zero. We devise a technique to study the interacting scalar theory very near the horizon increasing the coupling. As these solutions are represented by a Fourier series of plane waves, Hawking radiation can be immediately obtained with well-known techniques. These results open a question about the behavior of the Standard Model of particles very near the horizon of a black hole where the interactions turn out to be switched off and the electroweak symmetry could be restored. |
gr-qc/9801086 | Lior M. Burko | Amos Ori | Null weak singularities in plane-symmetric spacetimes | 17 pages, 2 PostScript figures, to appear in Phys. Rev. D | Phys.Rev. D57 (1998) 4745-4753 | 10.1103/PhysRevD.57.4745 | null | gr-qc | null | We construct a new class of plane-symmetric solutions possessing a curvature
singularity which is null and weak, like the spacetime singularity at the
Cauchy horizon of spinning (or charged) black holes. We then analyse the
stability of this singularity using a rigorous non-perturbative method. We find
that within the framework of (linearly-polarized) plane-symmetric spacetimes
this type of null weak singularity is locally stable. Generically, the
singularity is also scalar-curvature. These observations support the new
picture of the null weak singularity inside spinning (or charged) black holes,
which is so far established primarily on the perturbative approach.
| [
{
"created": "Mon, 26 Jan 1998 10:45:19 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Ori",
"Amos",
""
]
] | We construct a new class of plane-symmetric solutions possessing a curvature singularity which is null and weak, like the spacetime singularity at the Cauchy horizon of spinning (or charged) black holes. We then analyse the stability of this singularity using a rigorous non-perturbative method. We find that within the framework of (linearly-polarized) plane-symmetric spacetimes this type of null weak singularity is locally stable. Generically, the singularity is also scalar-curvature. These observations support the new picture of the null weak singularity inside spinning (or charged) black holes, which is so far established primarily on the perturbative approach. |
gr-qc/0511133 | Bin Wang | Bin Wang | Perturbations around black holes | 14 pages, 4 figures, Invited plenary talk given in the Conference
"100 Years of Relativity", Sao Paulo, Brazil, August 2005 | Braz.J.Phys. 35 (2005) 1029-1037 | null | null | gr-qc | null | Perturbations around black holes have been an intriguing topic in the last
few decades. They are particularly important today, since they relate to the
gravitational wave observations which may provide the unique fingerprint of
black holes' existence. Besides the astrophysical interest, theoretically
perturbations around black holes can be used as testing grounds to examine the
proposed AdS/CFT and dS/CFT correspondence.
| [
{
"created": "Thu, 24 Nov 2005 15:31:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wang",
"Bin",
""
]
] | Perturbations around black holes have been an intriguing topic in the last few decades. They are particularly important today, since they relate to the gravitational wave observations which may provide the unique fingerprint of black holes' existence. Besides the astrophysical interest, theoretically perturbations around black holes can be used as testing grounds to examine the proposed AdS/CFT and dS/CFT correspondence. |
gr-qc/9802005 | Bruce Bassett | G. F. R. Ellis and D. M. Solomons (UCT) | Caustics of Compensated Spherical Lens Models | 21 pages, 5 ps figures, epsf | Class.Quant.Grav. 15 (1998) 2381-2396 | 10.1088/0264-9381/15/8/017 | null | gr-qc astro-ph | null | We consider compensated spherical lens models and the caustic surfaces they
create in the past light cone. Examination of cusp and crossover angles
associated with particular source and lens redshifts gives explicit lensing
models that confirm previous claims that area distances can differ by
substantial factors from angular diameter distances even when averaged over
large angular scales. `Shrinking' in apparent sizes occurs, typically by a
factor of 3 for a single spherical lens, on the scale of the cusp caused by the
lens; summing over many lenses will still leave a residual effect.
| [
{
"created": "Tue, 3 Feb 1998 00:18:55 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Ellis",
"G. F. R.",
"",
"UCT"
],
[
"Solomons",
"D. M.",
"",
"UCT"
]
] | We consider compensated spherical lens models and the caustic surfaces they create in the past light cone. Examination of cusp and crossover angles associated with particular source and lens redshifts gives explicit lensing models that confirm previous claims that area distances can differ by substantial factors from angular diameter distances even when averaged over large angular scales. `Shrinking' in apparent sizes occurs, typically by a factor of 3 for a single spherical lens, on the scale of the cusp caused by the lens; summing over many lenses will still leave a residual effect. |
gr-qc/9410040 | null | Piotr T. Chru\'sciel, Alan D. Rendall | Strong cosmic censorship in vacuum space--times with compact, locally
homogeneous Cauchy surfaces | Latex, 38 pages | Annals Phys. 242 (1995) 349-385 | 10.1006/aphy.1995.1084 | null | gr-qc | null | We consider the question of strong cosmic censorship in spatially compact,
spatially locally homogeneous vacuum models. We show in particular that strong
cosmic censorship holds in Bianchi IX vacuum space--times with spherical
spatial topology.
| [
{
"created": "Fri, 28 Oct 1994 13:53:48 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Oct 1994 18:15:13 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Rendall",
"Alan D.",
""
]
] | We consider the question of strong cosmic censorship in spatially compact, spatially locally homogeneous vacuum models. We show in particular that strong cosmic censorship holds in Bianchi IX vacuum space--times with spherical spatial topology. |
0912.4744 | Sean McWilliams | Sean T. McWilliams | Constraining the braneworld with gravitational wave observations | 4 pages, replaced with version published in Phys. Rev. Lett. | Phys.Rev.Lett.104:141601,2010 | 10.1103/PhysRevLett.104.141601 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some braneworld models may have observable consequences that, if detected,
would validate a requisite element of string theory. In the infinite
Randall-Sundrum model (RS2), the AdS radius of curvature, L, of the extra
dimension supports a single bound state of the massless graviton on the brane,
thereby reproducing Newtonian gravity in the weak-field limit. However, using
the AdS/CFT correspondence, it has been suggested that one possible consequence
of RS2 is an enormous increase in Hawking radiation emitted by black holes. We
utilize this possibility to derive two novel methods for constraining L via
gravitational wave measurements. We show that the EMRI event rate detected by
LISA can constrain L at the ~1 micron level for optimal cases, while the
observation of a single galactic black hole binary with LISA results in an
optimal constraint of L <= 5 microns.
| [
{
"created": "Wed, 23 Dec 2009 21:52:50 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Apr 2010 19:22:01 GMT",
"version": "v2"
}
] | 2010-04-21 | [
[
"McWilliams",
"Sean T.",
""
]
] | Some braneworld models may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model (RS2), the AdS radius of curvature, L, of the extra dimension supports a single bound state of the massless graviton on the brane, thereby reproducing Newtonian gravity in the weak-field limit. However, using the AdS/CFT correspondence, it has been suggested that one possible consequence of RS2 is an enormous increase in Hawking radiation emitted by black holes. We utilize this possibility to derive two novel methods for constraining L via gravitational wave measurements. We show that the EMRI event rate detected by LISA can constrain L at the ~1 micron level for optimal cases, while the observation of a single galactic black hole binary with LISA results in an optimal constraint of L <= 5 microns. |
2405.12987 | Ivan Arraut Dr. | Ivan Arraut | Reply to the "Comment on The Tully-Fisher law and dark matter effects
derived via modified symmetries by I. Arraut" | 4 pages; reply to arXiv:2402.00081 | 2024 EPL 147 19002 | 10.1209/0295-5075/ad6180 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been claimed in \cite{1}, that the idea proposed in \cite{2} has
certain mistakes based on arguments of energy conditions and others.
Additionally, some of the key arguments of the paper are criticized. Here we
demonstrate that the results obtained in \cite{2} are correct and that there is
no violation of any energy condition. The statements claimed in \cite{1} are
based on three things: 1). Misinterpretation of the metric solution. 2).
Language issues related to the physical quantities obtained in \cite{1}, where
the authors make wrong interpretations about certain results over the geometry
proposed in \cite{2}. 3). Non-rigorous evaluations of the vacuum condition
defined via the result over the Ricci tensor $R_{\mu\nu}=0$
| [
{
"created": "Tue, 2 Apr 2024 10:38:30 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Arraut",
"Ivan",
""
]
] | It has been claimed in \cite{1}, that the idea proposed in \cite{2} has certain mistakes based on arguments of energy conditions and others. Additionally, some of the key arguments of the paper are criticized. Here we demonstrate that the results obtained in \cite{2} are correct and that there is no violation of any energy condition. The statements claimed in \cite{1} are based on three things: 1). Misinterpretation of the metric solution. 2). Language issues related to the physical quantities obtained in \cite{1}, where the authors make wrong interpretations about certain results over the geometry proposed in \cite{2}. 3). Non-rigorous evaluations of the vacuum condition defined via the result over the Ricci tensor $R_{\mu\nu}=0$ |
2405.08895 | Ali Kaya | Ali Kaya | Time Evolution in Canonical Quantum Gravity is Trivial | 9 pages, v2: comments and references added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Wheeler-DeWitt equation does not describe any explicit time evolution of
the wave function, and somehow related to this issue, there is no natural way
of defining an invariant inner product that provides a viable probability
interpretation. We show that both of these difficulties are solved in a
covariant canonical formulation of general relativity where the configuration
space is extended by introducing the embedding coordinates as dynamical
variables. The formalism describes the evolution of the wave function from one
spacelike slice to another, but as in the case of spatial diffeomorphisms this
is simply implemented by a coordinate change in the wave function. We
demonstrate how the time equation disappears after gauge fixing that removes
the embedding coordinates. These findings indicate that the time evolution is
trivial in a background independent formulation of quantum gravity.
| [
{
"created": "Tue, 14 May 2024 18:13:02 GMT",
"version": "v1"
},
{
"created": "Tue, 28 May 2024 14:17:11 GMT",
"version": "v2"
}
] | 2024-05-29 | [
[
"Kaya",
"Ali",
""
]
] | The Wheeler-DeWitt equation does not describe any explicit time evolution of the wave function, and somehow related to this issue, there is no natural way of defining an invariant inner product that provides a viable probability interpretation. We show that both of these difficulties are solved in a covariant canonical formulation of general relativity where the configuration space is extended by introducing the embedding coordinates as dynamical variables. The formalism describes the evolution of the wave function from one spacelike slice to another, but as in the case of spatial diffeomorphisms this is simply implemented by a coordinate change in the wave function. We demonstrate how the time equation disappears after gauge fixing that removes the embedding coordinates. These findings indicate that the time evolution is trivial in a background independent formulation of quantum gravity. |
1202.1905 | Deniz Olgu Devecioglu | Gokhan Alkac, Deniz Olgu Devecioglu | Covariant Symplectic Structure and Conserved Charges of New Massive
Gravity | 18 pages, No figures, RevTEX4.1; ver 2: minor corrections, version
accepted for publication in Physical Review D | Phys.RevD.85:064048,2012 | 10.1103/PhysRevD.85.064048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the symplectic current obtained from the boundary term, which
arises in the first variation of a local diffeomorphism invariant action, is
covariantly conserved for any gravity theory described by that action.
Therefore, a Poincare invariant 2-form can be constructed on the phase space,
which is shown to be closed without reference to a specific theory. Finally, we
show that one can obtain a charge expression for gravity theories in various
dimensions, which plays the role of the Abbott-Deser-Tekin (ADT) charge for
spacetimes with non-constant curvature backgrounds, by using the diffeomorphism
invariance of the symplectic 2-form. As an example, we calculate the conserved
charges of some solutions of New Massive Gravity (NMG) and compare the results
with the previous works.
| [
{
"created": "Thu, 9 Feb 2012 08:04:16 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Apr 2012 12:29:58 GMT",
"version": "v2"
}
] | 2012-04-13 | [
[
"Alkac",
"Gokhan",
""
],
[
"Devecioglu",
"Deniz Olgu",
""
]
] | We show that the symplectic current obtained from the boundary term, which arises in the first variation of a local diffeomorphism invariant action, is covariantly conserved for any gravity theory described by that action. Therefore, a Poincare invariant 2-form can be constructed on the phase space, which is shown to be closed without reference to a specific theory. Finally, we show that one can obtain a charge expression for gravity theories in various dimensions, which plays the role of the Abbott-Deser-Tekin (ADT) charge for spacetimes with non-constant curvature backgrounds, by using the diffeomorphism invariance of the symplectic 2-form. As an example, we calculate the conserved charges of some solutions of New Massive Gravity (NMG) and compare the results with the previous works. |
2306.10273 | Gamal G.L. Nashed | G.G.L. Nashed | The effect of $f(R,T)$ modified gravity on mass and radius of pulsar
HerX1 | 22 pages, 10 figures, 3 tables | The Astrophysical Journal, 950:129 (2023) | 10.3847/1538-4357/acd182 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Recent findings from the Neutron Star Interior Composition Explorer (NICER)
have opened up opportunities to investigate the potential coupling between
matter and geometry, along with its resulting physical implications.
Millisecond pulsars serve as an ideal subject for conducting such tests and
examining these phenomena. We apply the field equations of modified gravity,
$f(R, T)=R+\alpha\, T$ to a spherically symmetric spacetime, where $R$ is the
Ricci scalar, $\alpha$ is a dimensional parameter, and $T$ is the matter of the
geometry. Five unknown functions are present in the output system of
differential equations, which consists of three equations. To close the system,
we make explicit assumptions about the anisotropy and the radial metric
potential, $g_{rr}$. We then solve the output differential equations and derive
the explicit forms of the components of the energy-momentum tensor, namely,
density, radial, and tangential pressures.
| [
{
"created": "Sat, 17 Jun 2023 06:38:22 GMT",
"version": "v1"
}
] | 2023-06-21 | [
[
"Nashed",
"G. G. L.",
""
]
] | Recent findings from the Neutron Star Interior Composition Explorer (NICER) have opened up opportunities to investigate the potential coupling between matter and geometry, along with its resulting physical implications. Millisecond pulsars serve as an ideal subject for conducting such tests and examining these phenomena. We apply the field equations of modified gravity, $f(R, T)=R+\alpha\, T$ to a spherically symmetric spacetime, where $R$ is the Ricci scalar, $\alpha$ is a dimensional parameter, and $T$ is the matter of the geometry. Five unknown functions are present in the output system of differential equations, which consists of three equations. To close the system, we make explicit assumptions about the anisotropy and the radial metric potential, $g_{rr}$. We then solve the output differential equations and derive the explicit forms of the components of the energy-momentum tensor, namely, density, radial, and tangential pressures. |
2010.09918 | P. M. Petryakova | P. M. Petryakova | Dynamics of a homogeneous and isotropic space in pure cubic f(R) gravity | null | Physics 2021, 3(2), 379-385 | 10.3390/physics3020027 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We consider a possible ways of the dynamics of a homogeneous and isotropic
space described by the FLRW metric in the framework of cubic f(R) gravity in
the absence of matter. This article points an method for limiting the
parameters of extended gravity models. We propose and develop a method for f(R)
gravity models based on the dynamics of metrics for various model parameters in
the simplest example. The influence of parameters and initial conditions on
further dynamics are discussed. The parameters can be limited by 1) slow growth
of space, 2) instability, 3) divergence with the inflationary scenario.
| [
{
"created": "Mon, 19 Oct 2020 23:32:56 GMT",
"version": "v1"
},
{
"created": "Wed, 5 May 2021 16:17:06 GMT",
"version": "v2"
}
] | 2023-04-20 | [
[
"Petryakova",
"P. M.",
""
]
] | We consider a possible ways of the dynamics of a homogeneous and isotropic space described by the FLRW metric in the framework of cubic f(R) gravity in the absence of matter. This article points an method for limiting the parameters of extended gravity models. We propose and develop a method for f(R) gravity models based on the dynamics of metrics for various model parameters in the simplest example. The influence of parameters and initial conditions on further dynamics are discussed. The parameters can be limited by 1) slow growth of space, 2) instability, 3) divergence with the inflationary scenario. |
2302.12524 | Leandros Perivolaropoulos | L. Perivolaropoulos, I. Antoniou and D. Papadopoulos | Probing dark fluids and modified gravity with gravitational lensing | 9 pages, 4 Figures, 2 Tables. Published in MNRAS. The Mathematica
files used for the construction of Fig. 2 and 3 may be downloaded from
https://github.com/leandros11/lensing1 | null | 10.1093/mnras/stad1882 | null | gr-qc astro-ph.CO physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize the Rindler-Ishak (2007) result for the lensing deflection
angle in a SdS spacetime, to the case of a general spherically symmetric fluid
beyond the cosmological constant. We thus derive an analytic expression to
first post-Newtonian order for the lensing deflection angle in a general static
spherically symmetric metric of the form $ ds^2 = f(r)dt^{2}
-\frac{dr^{2}}{f(r)}-r^{2}(d\theta ^2 +\sin ^2 \theta d\phi ^2)$ with $f(r) = 1
- \frac{2m}{r}-\sum_{i} b_i\; r_0^{-q_i}\; \left( \frac{r_0}{r}\right)^{q_i}$
where $r_0$ is the lensing impact parameter, $b_i\ll r_0^{q_i}$, $m$ is the
mass of the lens and $q_i$ are real arbitrary constants related to the
properties of the fluid that surrounds the lens or to modified gravity. This is
a generalization of the well known Kiselev black hole metric. The approximate
analytic expression of the deflection angle is verified by an exact numerical
derivation and in special cases it reduces to results of previous studies. The
density and pressure of the spherically symmetric fluid that induces this
metric is derived in terms of the constants $b_i$. The Kiselev case of a
Schwarzschild metric perturbed by a general spherically symmetric dark fluid
(eg vacuum energy) is studied in some detail and consistency with the special
case of Rindler Ishak result is found for the case of a cosmological constant
background. Observational data of the Einstein radii from distant clusters of
galaxies lead to observational constraints on the constants $b_i$ and through
them on the density and pressure of dark fluids, field theories or modified
gravity theories that could induce this metric.
| [
{
"created": "Fri, 24 Feb 2023 09:17:11 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Mar 2023 08:57:49 GMT",
"version": "v2"
},
{
"created": "Sat, 24 Jun 2023 14:57:10 GMT",
"version": "v3"
}
] | 2023-06-28 | [
[
"Perivolaropoulos",
"L.",
""
],
[
"Antoniou",
"I.",
""
],
[
"Papadopoulos",
"D.",
""
]
] | We generalize the Rindler-Ishak (2007) result for the lensing deflection angle in a SdS spacetime, to the case of a general spherically symmetric fluid beyond the cosmological constant. We thus derive an analytic expression to first post-Newtonian order for the lensing deflection angle in a general static spherically symmetric metric of the form $ ds^2 = f(r)dt^{2} -\frac{dr^{2}}{f(r)}-r^{2}(d\theta ^2 +\sin ^2 \theta d\phi ^2)$ with $f(r) = 1 - \frac{2m}{r}-\sum_{i} b_i\; r_0^{-q_i}\; \left( \frac{r_0}{r}\right)^{q_i}$ where $r_0$ is the lensing impact parameter, $b_i\ll r_0^{q_i}$, $m$ is the mass of the lens and $q_i$ are real arbitrary constants related to the properties of the fluid that surrounds the lens or to modified gravity. This is a generalization of the well known Kiselev black hole metric. The approximate analytic expression of the deflection angle is verified by an exact numerical derivation and in special cases it reduces to results of previous studies. The density and pressure of the spherically symmetric fluid that induces this metric is derived in terms of the constants $b_i$. The Kiselev case of a Schwarzschild metric perturbed by a general spherically symmetric dark fluid (eg vacuum energy) is studied in some detail and consistency with the special case of Rindler Ishak result is found for the case of a cosmological constant background. Observational data of the Einstein radii from distant clusters of galaxies lead to observational constraints on the constants $b_i$ and through them on the density and pressure of dark fluids, field theories or modified gravity theories that could induce this metric. |
1503.02956 | Kirill Bronnikov | K.A. Bronnikov and P.A. Korolyov | Magnetic wormholes and black universes with invisible ghosts | 9 pages, 5 figures | Grav. Cosmol. 21 (2), 157-165 (2015) | 10.1134/S0202289315020024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct explicit examples of globally regular static, spherically
symmetric solutions in general relativity with scalar and electromagnetic
fields describing traversable wormholes with flat and AdS asymptotics and
regular black holes, in particular, black universes. (A black universe is a
regular black hole with an expanding, asymptotically isotropic space-time
beyond the horizon.) The existence of such objects requires invoking scalars
with negative kinetic energy ("phantoms", or "ghosts"), which are not observed
under usual physical conditions. To account for that, the so-called "trapped
ghosts" were previously introduced, i.e., scalars whose kinetic energy is only
negative in a restricted strong-field region of space-time and positive outside
it. This approach leads to certain problems, including instability (as is
illustrated here by derivation of an effective potential for spherical
pertubations of such systems). In this paper, we use for model construction
what we call "invisible ghosts", i.e., phantom scalar fields sufficiently
rapidly decaying in the weak-field region. The resulting configurations contain
different numbers of Killing horizons, from zero to four.
| [
{
"created": "Tue, 10 Mar 2015 15:41:12 GMT",
"version": "v1"
}
] | 2015-09-07 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Korolyov",
"P. A.",
""
]
] | We construct explicit examples of globally regular static, spherically symmetric solutions in general relativity with scalar and electromagnetic fields describing traversable wormholes with flat and AdS asymptotics and regular black holes, in particular, black universes. (A black universe is a regular black hole with an expanding, asymptotically isotropic space-time beyond the horizon.) The existence of such objects requires invoking scalars with negative kinetic energy ("phantoms", or "ghosts"), which are not observed under usual physical conditions. To account for that, the so-called "trapped ghosts" were previously introduced, i.e., scalars whose kinetic energy is only negative in a restricted strong-field region of space-time and positive outside it. This approach leads to certain problems, including instability (as is illustrated here by derivation of an effective potential for spherical pertubations of such systems). In this paper, we use for model construction what we call "invisible ghosts", i.e., phantom scalar fields sufficiently rapidly decaying in the weak-field region. The resulting configurations contain different numbers of Killing horizons, from zero to four. |
gr-qc/0108017 | Boris Grobov | Elena V. Palesheva | Ghost spinors, shadow electrons and the Deutsch Multiverse | 8 pages, LaTeX2e | null | null | null | gr-qc | null | In this article a new solution of the Einstein-Dirac's equations is
presented. There are ghost spinors, i.e. the stress-energy tensor is equal to
zero and the current of these fields is non-zero vector. Last the ghost
neutrino was found. These ghost spinors and shadow particles of Deutsch are
identified. And in result the ghost spinors have a physical interpretation and
solutions of the field equations for shadow electrons as another shadow
particles are found.
| [
{
"created": "Sun, 5 Aug 2001 15:39:49 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Oct 2001 18:25:54 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Palesheva",
"Elena V.",
""
]
] | In this article a new solution of the Einstein-Dirac's equations is presented. There are ghost spinors, i.e. the stress-energy tensor is equal to zero and the current of these fields is non-zero vector. Last the ghost neutrino was found. These ghost spinors and shadow particles of Deutsch are identified. And in result the ghost spinors have a physical interpretation and solutions of the field equations for shadow electrons as another shadow particles are found. |
1005.2927 | Simone Speziale | Carlo Rovelli, Simone Speziale | On the geometry of loop quantum gravity on a graph | 6 pages, 1 figure. v2: some typos corrected, references updated | Phys.Rev.D82:044018,2010 | 10.1103/PhysRevD.82.044018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the meaning of geometrical constructions associated to loop
quantum gravity states on a graph. In particular, we discuss the "twisted
geometries" and derive a simple relation between these and Regge geometries.
| [
{
"created": "Mon, 17 May 2010 14:11:29 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Aug 2010 14:35:50 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Rovelli",
"Carlo",
""
],
[
"Speziale",
"Simone",
""
]
] | We discuss the meaning of geometrical constructions associated to loop quantum gravity states on a graph. In particular, we discuss the "twisted geometries" and derive a simple relation between these and Regge geometries. |
gr-qc/0401055 | Giovanni Imponente | Giovanni Imponente and Giovanni Montani | General Aspects of the de Sitter phase | 30 pages with cimento.cls, no figures, to appear on "Il Nuovo Cimento
B" | Nuovo Cim.B120:1085-1114,2005 | 10.1393/ncb/i2005-10142-0 | null | gr-qc astro-ph | null | We present a detailed discussion of the inflationary scenario in the context
of inhomogeneous cosmologies. After a review of the fundamental features
characterizing the inflationary model, as referred to a homogeneous and
isotropic Universe, we develop a generalization in view of including small
inhomogeneous corrections in the theory. A second step in our discussion is
devoted to show that the inflationary scenario provides a valuable dynamical
``bridge'' between a generic Kasner-like regime and a homogeneous and isotropic
Universe in the horizon scale. This result is achieved by solving the
Hamilton-Jacobi equation for a Bianchi IX model in the presence of a
cosmological space-dependent term. In this respect, we construct a
quasi-isotropic inflationary solution based on the expansion of the Einstein
equations up to first-two orders of approximation, in which the isotropy of the
Universe is due to the dominance of the scalar field kinetic term; the first
order of approximation corresponds to the inhomogeneous corrections and is
driven by the matter evolution. We show how such a quasi-isotropic solution
contains a certain freedom in fixing the space functions involved in the
problem. The main physical issue of this analysis corresponds to outline the
impossibility for the classical origin of density perturbations, due to the
exponential decay of the matter term during the de Sitter phase.
| [
{
"created": "Tue, 13 Jan 2004 12:05:38 GMT",
"version": "v1"
}
] | 2010-11-11 | [
[
"Imponente",
"Giovanni",
""
],
[
"Montani",
"Giovanni",
""
]
] | We present a detailed discussion of the inflationary scenario in the context of inhomogeneous cosmologies. After a review of the fundamental features characterizing the inflationary model, as referred to a homogeneous and isotropic Universe, we develop a generalization in view of including small inhomogeneous corrections in the theory. A second step in our discussion is devoted to show that the inflationary scenario provides a valuable dynamical ``bridge'' between a generic Kasner-like regime and a homogeneous and isotropic Universe in the horizon scale. This result is achieved by solving the Hamilton-Jacobi equation for a Bianchi IX model in the presence of a cosmological space-dependent term. In this respect, we construct a quasi-isotropic inflationary solution based on the expansion of the Einstein equations up to first-two orders of approximation, in which the isotropy of the Universe is due to the dominance of the scalar field kinetic term; the first order of approximation corresponds to the inhomogeneous corrections and is driven by the matter evolution. We show how such a quasi-isotropic solution contains a certain freedom in fixing the space functions involved in the problem. The main physical issue of this analysis corresponds to outline the impossibility for the classical origin of density perturbations, due to the exponential decay of the matter term during the de Sitter phase. |
gr-qc/0401030 | Claudio Benedito Silva Furtado | A. M. de M. Carvalho, Fernando Moraes, Claudio Furtado | The self-energy of a charged particle in the presence of a topological
defect distribution | 12 pages, Revtex4, two figures,to appear in Int. Joun. Mod. Phys. A | Int.J.Mod.Phys. A19 (2004) 2113-2122 | 10.1142/S0217751X04018373 | null | gr-qc | null | In this work we study a charged particle in the presence of both a continuous
distribution of disclinations and a continuous distribution of edge
dislocations in the framework of the geometrical theory of defects. We obtain
the self-energy for a single charge both in the internal and external regions
of either distribution. For both distributions the result outside the defect
distribution is the self-energy that a single charge experiments in the
presence of a single defect.
| [
{
"created": "Fri, 9 Jan 2004 11:32:21 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Carvalho",
"A. M. de M.",
""
],
[
"Moraes",
"Fernando",
""
],
[
"Furtado",
"Claudio",
""
]
] | In this work we study a charged particle in the presence of both a continuous distribution of disclinations and a continuous distribution of edge dislocations in the framework of the geometrical theory of defects. We obtain the self-energy for a single charge both in the internal and external regions of either distribution. For both distributions the result outside the defect distribution is the self-energy that a single charge experiments in the presence of a single defect. |
1106.2054 | Jonathan Ziprick | C. Danielle Leonard, Jonathan Ziprick, Gabor Kunstatter and Robert B.
Mann | Gravitational collapse of K-essence Matter in Painlev\'{e}-Gullstrand
coordinates | 14 pages, 8 figures | null | 10.1007/JHEP10(2011)028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We conduct numerical simulations in Painlev\'{e}-Gullstrand coordinates of a
variety of K-essence-type scalar fields under spherically symmetric
gravitational collapse. We write down generic conditions on the K-essence
lagrangian that can be used to determine whether superluminality and Cauchy
breakdown are possible. Consistent with these conditions, for specific choices
of K-essence-type fields we verify the presence of superluminality during
collapse, while for other type we do not. We also demonstrate that certain
choices of K-essence scalar fields present issues under gravitational collapse
in Painlev\'{e}-Gullstrand coordinates, such as a breakdown of the Cauchy
problem.
| [
{
"created": "Fri, 10 Jun 2011 13:46:24 GMT",
"version": "v1"
}
] | 2012-05-15 | [
[
"Leonard",
"C. Danielle",
""
],
[
"Ziprick",
"Jonathan",
""
],
[
"Kunstatter",
"Gabor",
""
],
[
"Mann",
"Robert B.",
""
]
] | We conduct numerical simulations in Painlev\'{e}-Gullstrand coordinates of a variety of K-essence-type scalar fields under spherically symmetric gravitational collapse. We write down generic conditions on the K-essence lagrangian that can be used to determine whether superluminality and Cauchy breakdown are possible. Consistent with these conditions, for specific choices of K-essence-type fields we verify the presence of superluminality during collapse, while for other type we do not. We also demonstrate that certain choices of K-essence scalar fields present issues under gravitational collapse in Painlev\'{e}-Gullstrand coordinates, such as a breakdown of the Cauchy problem. |
gr-qc/0011039 | Steven Detweiler | Steven Detweiler | Radiation reaction and the self-force for a point mass in general
relativity | 4 pages, RevTex | Phys.Rev.Lett.86:1931-1934,2001 | 10.1103/PhysRevLett.86.1931 | null | gr-qc | null | A point particle of mass m moving on a geodesic creates a perturbation h, of
the spacetime metric g, that diverges at the particle. Simple expressions are
given for the singular m/r part of h and its quadrupole distortion caused by
the spacetime. Subtracting these from h leaves a remainder h^R that is C^1. The
self-force on the particle from its own gravitational field corrects the
worldline at O(m) to be a geodesic of g+h^R. For the case that the particle is
a small non-rotating black hole, an approximate solution to the Einstein
equations is given with error of O(m^2) as m approaches 0.
| [
{
"created": "Sat, 11 Nov 2000 17:55:22 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Detweiler",
"Steven",
""
]
] | A point particle of mass m moving on a geodesic creates a perturbation h, of the spacetime metric g, that diverges at the particle. Simple expressions are given for the singular m/r part of h and its quadrupole distortion caused by the spacetime. Subtracting these from h leaves a remainder h^R that is C^1. The self-force on the particle from its own gravitational field corrects the worldline at O(m) to be a geodesic of g+h^R. For the case that the particle is a small non-rotating black hole, an approximate solution to the Einstein equations is given with error of O(m^2) as m approaches 0. |
2101.01549 | Muhammad Sharif | M. Sharif and Amal Majid | Complexity of Dynamical Sphere in Self-interacting Brans-Dicke Gravity | 19 pages, no figure | Eur. Phys. J. C 80(2020)1185 | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | This paper aims to derive a definition of complexity for a dynamic spherical
system in the background of self-interacting Brans-Dicke gravity. We measure
complexity of the structure in terms of inhomogeneous energy density,
anisotropic pressure and massive scalar field. For this purpose, we formulate
structure scalars by orthogonally splitting the Riemann tensor. We show that
self-gravitating models collapsing homologously follow the simplest mode of
evolution. Furthermore, we demonstrate the effect of scalar field on the
complexity and evolution of non-dissipative as well as dissipative systems. The
criteria under which the system deviates from the initial state of zero
complexity is also discussed. It is concluded that complexity of the sphere
increases in self-interacting Brans-Dicke gravity because the homologous model
is not shear-free.
| [
{
"created": "Fri, 1 Jan 2021 05:50:45 GMT",
"version": "v1"
}
] | 2021-01-06 | [
[
"Sharif",
"M.",
""
],
[
"Majid",
"Amal",
""
]
] | This paper aims to derive a definition of complexity for a dynamic spherical system in the background of self-interacting Brans-Dicke gravity. We measure complexity of the structure in terms of inhomogeneous energy density, anisotropic pressure and massive scalar field. For this purpose, we formulate structure scalars by orthogonally splitting the Riemann tensor. We show that self-gravitating models collapsing homologously follow the simplest mode of evolution. Furthermore, we demonstrate the effect of scalar field on the complexity and evolution of non-dissipative as well as dissipative systems. The criteria under which the system deviates from the initial state of zero complexity is also discussed. It is concluded that complexity of the sphere increases in self-interacting Brans-Dicke gravity because the homologous model is not shear-free. |
1903.06037 | Arman Stepanian | A. Stepanian | On the invalidity of "negative mass" description of the dark sector | "Mod. Phys. Lett. A, in press" | Mod. Phys.Lett. A, 34, 1975002 (2019) | 10.1142/S0217732319750026 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the concept of "negative mass" introduced by Farnes (2018)
to describe the dark sector within a unifying theory with the negative
cosmological constant contradicts both the essence of the General Relativity
and the available observational data. A viable model with modified weak-field
General Relativity is mentioned.
| [
{
"created": "Wed, 13 Mar 2019 14:45:09 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Jun 2019 15:01:18 GMT",
"version": "v2"
}
] | 2020-09-02 | [
[
"Stepanian",
"A.",
""
]
] | It is shown that the concept of "negative mass" introduced by Farnes (2018) to describe the dark sector within a unifying theory with the negative cosmological constant contradicts both the essence of the General Relativity and the available observational data. A viable model with modified weak-field General Relativity is mentioned. |
gr-qc/9210018 | Wai Suen | Wai-Mo Suen | Self-Consistence of Semi-Classical Gravity | 12 pages | null | null | WUGRAV-92-12 | gr-qc | null | Simon argued that the semi-classical theory of gravity, unless with some of
its solutions excluded, is unacceptable for reasons of both self-consistency
and experiment, and that it has to be replaced by a constrained semi-classical
theory. We examined whether the evidence is conclusive.
| [
{
"created": "Wed, 28 Oct 1992 23:14:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Suen",
"Wai-Mo",
""
]
] | Simon argued that the semi-classical theory of gravity, unless with some of its solutions excluded, is unacceptable for reasons of both self-consistency and experiment, and that it has to be replaced by a constrained semi-classical theory. We examined whether the evidence is conclusive. |
2103.13086 | Shinta Kasuya | Shinta Kasuya, Masataka Kobayashi | Throat effects on shadows of Kerr-like wormholes | 8 pages, 19 figures, matches to published version | Phys. Rev. D 103, 104050 (2021) | 10.1103/PhysRevD.103.104050 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit to investigate shadows cast by Kerr-like wormholes. The boundary
of the shadow is determined by unstable circular photon orbits. We find that,
in certain parameter regions, the orbit is located at the throat of the
Kerr-like wormhole, which was not considered in the literature. In these cases,
the existence of the throat alters the shape of the shadow significantly, and
makes it possible for us to differentiate it from that of a Kerr black hole.
| [
{
"created": "Wed, 24 Mar 2021 11:00:54 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Apr 2021 09:48:38 GMT",
"version": "v2"
},
{
"created": "Thu, 27 May 2021 07:15:14 GMT",
"version": "v3"
}
] | 2021-05-28 | [
[
"Kasuya",
"Shinta",
""
],
[
"Kobayashi",
"Masataka",
""
]
] | We revisit to investigate shadows cast by Kerr-like wormholes. The boundary of the shadow is determined by unstable circular photon orbits. We find that, in certain parameter regions, the orbit is located at the throat of the Kerr-like wormhole, which was not considered in the literature. In these cases, the existence of the throat alters the shape of the shadow significantly, and makes it possible for us to differentiate it from that of a Kerr black hole. |
2210.16143 | Guo-Chin Liu | Guo-Chin Liu and Kin-Wang Ng | Overlap reduction functions for a polarized stochastic
gravitational-wave background in the Einstein Telescope-Cosmic Explorer and
the LISA-Taiji networks | Accepted in PRD | null | 10.1103/PhysRevD.107.104040 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | The detection of gravitational waves from the coalescences of binary compact
stars by current interferometry experiments has opened up a new era of
gravitational-wave astrophysics and cosmology. The search for a stochastic
gravitational-wave background is underway by correlating signals from a pair of
detectors in the detector network formed by the LIGO, Virgo, and KAGRA. In a
previous work, we have developed a method based on spherical harmonic expansion
to calculate the overlap reduction functions of the LIGO-Virgo-KAGRA network
for a polarized stochastic gravitational-wave background. In this work, we will
apply the method to calculate the overlap reduction functions of
third-generation detectors such as a ground-based network linking the Einstein
Telescope, the Cosmic Explorer, and the LISA-Taiji joint space mission.
| [
{
"created": "Fri, 28 Oct 2022 14:13:28 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Jun 2023 00:57:28 GMT",
"version": "v2"
}
] | 2023-06-06 | [
[
"Liu",
"Guo-Chin",
""
],
[
"Ng",
"Kin-Wang",
""
]
] | The detection of gravitational waves from the coalescences of binary compact stars by current interferometry experiments has opened up a new era of gravitational-wave astrophysics and cosmology. The search for a stochastic gravitational-wave background is underway by correlating signals from a pair of detectors in the detector network formed by the LIGO, Virgo, and KAGRA. In a previous work, we have developed a method based on spherical harmonic expansion to calculate the overlap reduction functions of the LIGO-Virgo-KAGRA network for a polarized stochastic gravitational-wave background. In this work, we will apply the method to calculate the overlap reduction functions of third-generation detectors such as a ground-based network linking the Einstein Telescope, the Cosmic Explorer, and the LISA-Taiji joint space mission. |
gr-qc/0303082 | Antonio Padilla | Antonio Padilla | Surface terms and the Gauss-Bonnet Hamiltonian | Version to appear in Classical and Quantum Gravity. Note that this
version is 8 pages shorter than version 1, making it more suitable for the
journal. Anyone wishing more calculational detail should refer to version 1.
Some references have also been added | Class.Quant.Grav. 20 (2003) 3129-3150 | 10.1088/0264-9381/20/14/315 | null | gr-qc hep-th | null | We derive the gravitational Hamiltonian starting from the Gauss-Bonnet
action, keeping track of all surface terms. This is done using the language of
orthonormal frames and forms to keep things as tidy as possible. The surface
terms in the Hamiltonian give a remarkably simple expression for the total
energy of a spacetime. This expression is consistent with energy expressions
found in hep-th/0212292. However, we can apply our results whatever the choice
of background and whatever the symmetries of the spacetime.
| [
{
"created": "Thu, 20 Mar 2003 17:55:36 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jun 2003 15:55:24 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Padilla",
"Antonio",
""
]
] | We derive the gravitational Hamiltonian starting from the Gauss-Bonnet action, keeping track of all surface terms. This is done using the language of orthonormal frames and forms to keep things as tidy as possible. The surface terms in the Hamiltonian give a remarkably simple expression for the total energy of a spacetime. This expression is consistent with energy expressions found in hep-th/0212292. However, we can apply our results whatever the choice of background and whatever the symmetries of the spacetime. |
2207.08471 | Javier Relancio | J.J. Relancio | Relativistic deformed kinematics: from flat to curved spacetimes | 34 pages, 1 figure | International Journal of Geometric Methods in Modern Physics
Vol.19 No. 9 (2022), 2230004 | 10.1142/S0219887822300045 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Doubly special relativity has been studied for the last twenty years as a way
to go beyond the special relativistic kinematics, trying to capture residual
effects of a quantum gravity theory. In particular, in doubly special
relativity the Einstenian relativity principle is generalized, adding to the
speed of light another relativistic invariant, the Planck energy. There are
several papers in the literature showing a connection between this deformed
kinematics and a curved momentum space. Here we review how such kinematics can
be derived from geometrical ingredients in a rigorous way, and how they can be
generalized when regarding a curved spacetime. For the last aim, it is
mandatory to consider a particular geometry for all phase-space variables, the
so-called generalized Hamilton spaces. This construction allows us to define a
spacetime in these theories, which in fact depends on the momenta. Then,
starting from such a momentum dependent metric, we also revise several concepts
of general relativity, with the final aim of establishing a self-consistent
geometrical structure from which quantum gravity phenomenology can be explored.
| [
{
"created": "Mon, 18 Jul 2022 09:48:00 GMT",
"version": "v1"
}
] | 2022-07-19 | [
[
"Relancio",
"J. J.",
""
]
] | Doubly special relativity has been studied for the last twenty years as a way to go beyond the special relativistic kinematics, trying to capture residual effects of a quantum gravity theory. In particular, in doubly special relativity the Einstenian relativity principle is generalized, adding to the speed of light another relativistic invariant, the Planck energy. There are several papers in the literature showing a connection between this deformed kinematics and a curved momentum space. Here we review how such kinematics can be derived from geometrical ingredients in a rigorous way, and how they can be generalized when regarding a curved spacetime. For the last aim, it is mandatory to consider a particular geometry for all phase-space variables, the so-called generalized Hamilton spaces. This construction allows us to define a spacetime in these theories, which in fact depends on the momenta. Then, starting from such a momentum dependent metric, we also revise several concepts of general relativity, with the final aim of establishing a self-consistent geometrical structure from which quantum gravity phenomenology can be explored. |
2310.16031 | Adri\`a Delhom | Adri\`a Delhom, Killian Guerrero, Paula Calizaya, K\'evin Falque,
Alberto Bramati, Anthony J. Brady, Maxime J. Jacquet and Ivan Agullo | Entanglement from superradiance and rotating quantum fluids of light | Updated to match published version. 13 pages with 10 figures (main
body of the article) + 11 pages (references + appendices with two extra
figures and a table with numerical data) | null | 10.1103/PhysRevD.109.105024 | null | gr-qc cond-mat.quant-gas hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | The amplification of radiation by superradiance is a universal phenomenon
observed in numerous physical systems. We demonstrate that superradiant
scattering generates entanglement for different input states, including
coherent states, thereby establishing the inherently quantum nature of this
phenomenon. To put these concepts to the test, we propose a novel approach to
create horizonless ergoregions, which are nonetheless dynamically stable thanks
to the dissipative dynamics of a polaritonic fluid of light. We numerically
simulate the system to demonstrate the creation of a stable ergoregion.
Subsequently, we investigate rotational superradiance within this system, with
a primary focus on entanglement generation and the possibilities for its
enhancement using current techniques. Our methods permit the investigation of
quantum emission by rotational superradiance in state-of-the-art experiments,
in which the input state can be controlled at will.
| [
{
"created": "Tue, 24 Oct 2023 17:46:24 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Feb 2024 19:40:35 GMT",
"version": "v2"
},
{
"created": "Wed, 29 May 2024 09:41:50 GMT",
"version": "v3"
}
] | 2024-05-30 | [
[
"Delhom",
"Adrià",
""
],
[
"Guerrero",
"Killian",
""
],
[
"Calizaya",
"Paula",
""
],
[
"Falque",
"Kévin",
""
],
[
"Bramati",
"Alberto",
""
],
[
"Brady",
"Anthony J.",
""
],
[
"Jacquet",
"Maxime J.",
""
],... | The amplification of radiation by superradiance is a universal phenomenon observed in numerous physical systems. We demonstrate that superradiant scattering generates entanglement for different input states, including coherent states, thereby establishing the inherently quantum nature of this phenomenon. To put these concepts to the test, we propose a novel approach to create horizonless ergoregions, which are nonetheless dynamically stable thanks to the dissipative dynamics of a polaritonic fluid of light. We numerically simulate the system to demonstrate the creation of a stable ergoregion. Subsequently, we investigate rotational superradiance within this system, with a primary focus on entanglement generation and the possibilities for its enhancement using current techniques. Our methods permit the investigation of quantum emission by rotational superradiance in state-of-the-art experiments, in which the input state can be controlled at will. |
2407.00767 | Yin-Da Guo | Yin-Da Guo, Nayun Jia, Shou-Shan Bao, Hong Zhang, Xin Zhang | The evolution and detection of vector superradiant instabilities | 23 pages, 15 figures | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | Ultralight vectors can extract energy and angular momentum from a Kerr black
hole (BH) due to superradiant instability, resulting in the formation of a
BH-condensate system. In this work, we carefully investigate the evolution of
this system numerically with multiple superradiant modes. Simple formulas are
obtained to estimate important timescales, maximum masses of different modes,
as well as the BH mass and spin at various times. Due to the coexistence of
modes with small frequency differences, the BH-condensate system emits
gravitational waves with a unique beat signature, which could be directly
observed by current and projected interferometers. Besides, the current BH
spin-mass data from the binary BH merger events already excludes the vector
mass in the range $5\times 10^{-15}\ \mathrm{eV} <\mu< 9\times 10^{-12}\
\mathrm{eV}$.
| [
{
"created": "Sun, 30 Jun 2024 17:05:23 GMT",
"version": "v1"
}
] | 2024-07-02 | [
[
"Guo",
"Yin-Da",
""
],
[
"Jia",
"Nayun",
""
],
[
"Bao",
"Shou-Shan",
""
],
[
"Zhang",
"Hong",
""
],
[
"Zhang",
"Xin",
""
]
] | Ultralight vectors can extract energy and angular momentum from a Kerr black hole (BH) due to superradiant instability, resulting in the formation of a BH-condensate system. In this work, we carefully investigate the evolution of this system numerically with multiple superradiant modes. Simple formulas are obtained to estimate important timescales, maximum masses of different modes, as well as the BH mass and spin at various times. Due to the coexistence of modes with small frequency differences, the BH-condensate system emits gravitational waves with a unique beat signature, which could be directly observed by current and projected interferometers. Besides, the current BH spin-mass data from the binary BH merger events already excludes the vector mass in the range $5\times 10^{-15}\ \mathrm{eV} <\mu< 9\times 10^{-12}\ \mathrm{eV}$. |
2212.10725 | Kallol Dey | Kallol Dey, Enrico Barausse and Soumen Basak | Measuring deviations from the Kerr geometry with black hole ringdown | 15 pages, 6 figures, matches version published in PRD | Phys. Rev. D 108 (2023) 2, 024064 | 10.1103/PhysRevD.108.024064 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes in General Relativity are famously characterized by two "hairs"
only, the mass and the spin of the Kerr spacetime. Theories extending General
Relativity, however, allow in principle for additional black hole charges,
which will generally modify the multipole structure of the Kerr solution. Here,
we show that gravitational wave observations of the post-merger ringdown signal
from black hole binaries may permit measuring these additional "hairs". We do
so by considering spacetime geometries differing from the Kerr one at the level
of the quadrupole moment, and computing the differences of their quasinormal
mode frequencies from the Kerr ones in the eikonal limit. We then perform a
Bayesian analysis with current and future gravitational wave data and compute
posterior constraints for the quadrupole deviation away from Kerr. We find that
the inclusion of higher modes, which are potentially observable by future
detectors, will allow for constraining deviations from the Kerr quadrupole at
percent level.
| [
{
"created": "Wed, 21 Dec 2022 02:40:23 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Aug 2023 08:57:18 GMT",
"version": "v2"
}
] | 2023-08-08 | [
[
"Dey",
"Kallol",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Basak",
"Soumen",
""
]
] | Black holes in General Relativity are famously characterized by two "hairs" only, the mass and the spin of the Kerr spacetime. Theories extending General Relativity, however, allow in principle for additional black hole charges, which will generally modify the multipole structure of the Kerr solution. Here, we show that gravitational wave observations of the post-merger ringdown signal from black hole binaries may permit measuring these additional "hairs". We do so by considering spacetime geometries differing from the Kerr one at the level of the quadrupole moment, and computing the differences of their quasinormal mode frequencies from the Kerr ones in the eikonal limit. We then perform a Bayesian analysis with current and future gravitational wave data and compute posterior constraints for the quadrupole deviation away from Kerr. We find that the inclusion of higher modes, which are potentially observable by future detectors, will allow for constraining deviations from the Kerr quadrupole at percent level. |
1609.09243 | Rakesh Kabir | R. Kabir, A. Mukherjee, D. Lohiya | Reheating constraints on K\"ahler Moduli Inflation | 10 pages, 6 figures; v(2) submitted to PLB. arXiv admin note: text
overlap with arXiv:1502.04673, arXiv:1602.07427 by other authors | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The end of inflation is connected to the standard cosmological scenario
through reheating. During reheating, the inflaton oscillates around the minimum
of the potential and thus decays into the daughter particles that populate the
Universe at later times. Using cosmological evolution for observable CMB scales
from the time of Hubble crossing to the present time, we translate the
constraint on the spectral index $n_s$ from Planck data to the constraint on
the reheating scenario in the context of K\"ahler Moduli Inflation. In
addition, we extend the de-facto analysis generally done only for the pivot
scale to all the observable scales which crossed the Hubble radius during
inflation. We study how the maximum number of e-folds varies for different
scales, and the effect of the equation of state and potential parameters.
| [
{
"created": "Thu, 29 Sep 2016 08:01:56 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Oct 2016 06:43:11 GMT",
"version": "v2"
}
] | 2016-10-19 | [
[
"Kabir",
"R.",
""
],
[
"Mukherjee",
"A.",
""
],
[
"Lohiya",
"D.",
""
]
] | The end of inflation is connected to the standard cosmological scenario through reheating. During reheating, the inflaton oscillates around the minimum of the potential and thus decays into the daughter particles that populate the Universe at later times. Using cosmological evolution for observable CMB scales from the time of Hubble crossing to the present time, we translate the constraint on the spectral index $n_s$ from Planck data to the constraint on the reheating scenario in the context of K\"ahler Moduli Inflation. In addition, we extend the de-facto analysis generally done only for the pivot scale to all the observable scales which crossed the Hubble radius during inflation. We study how the maximum number of e-folds varies for different scales, and the effect of the equation of state and potential parameters. |
1805.12558 | Anne Franzen | Artur Alho, Grigorios Fournodavlos and Anne T. Franzen | The wave equation near flat Friedmann-Lema\^itre-Robertson-Walker and
Kasner Big Bang singularities | 14 pages, 1 figure | null | null | null | gr-qc astro-ph.CO math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the wave equation, $\square_g\psi=0$, in fixed flat
Friedmann-Lema\^itre-Robertson-Walker and Kasner spacetimes with topology
$\mathbb{R}_+\times\mathbb{T}^3$. We obtain generic blow up results for
solutions to the wave equation towards the Big Bang singularity in both
backgrounds. In particular, we characterize open sets of initial data
prescribed at a spacelike hypersurface close to the singularity, which give
rise to solutions that blow up in an open set of the Big Bang hypersurface
$\{t=0\}$. The initial data sets are characterized by the condition that the
Neumann data should dominate, in an appropriate $L^2$-sense, up to two spatial
derivatives of the Dirichlet data. For these initial configurations, the
$L^2(\mathbb{T}^3)$ norms of the solutions blow up towards the Big Bang
hypersurfaces of FLRW and Kasner with inverse polynomial and logarithmic rates
respectively. Our method is based on deriving suitably weighted energy
estimates in physical space. No symmetries of solutions are assumed.
| [
{
"created": "Thu, 31 May 2018 16:55:59 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Jun 2018 09:36:10 GMT",
"version": "v2"
}
] | 2018-06-04 | [
[
"Alho",
"Artur",
""
],
[
"Fournodavlos",
"Grigorios",
""
],
[
"Franzen",
"Anne T.",
""
]
] | We consider the wave equation, $\square_g\psi=0$, in fixed flat Friedmann-Lema\^itre-Robertson-Walker and Kasner spacetimes with topology $\mathbb{R}_+\times\mathbb{T}^3$. We obtain generic blow up results for solutions to the wave equation towards the Big Bang singularity in both backgrounds. In particular, we characterize open sets of initial data prescribed at a spacelike hypersurface close to the singularity, which give rise to solutions that blow up in an open set of the Big Bang hypersurface $\{t=0\}$. The initial data sets are characterized by the condition that the Neumann data should dominate, in an appropriate $L^2$-sense, up to two spatial derivatives of the Dirichlet data. For these initial configurations, the $L^2(\mathbb{T}^3)$ norms of the solutions blow up towards the Big Bang hypersurfaces of FLRW and Kasner with inverse polynomial and logarithmic rates respectively. Our method is based on deriving suitably weighted energy estimates in physical space. No symmetries of solutions are assumed. |
gr-qc/0308054 | L. K. Chavda | L.K.Chavda and Abhijit L.Chavda | Dark matter and stable bound states of primordial black holes | 13 pages,2tables,for wider circulation,PDF | Class.Quant.Grav. 19 (2002) 2927 | 10.1088/0264-9381/19/11/311 | null | gr-qc astro-ph astro-ph.CO | null | We present three reasons for the formation of gravitational bound states of
primordial black holes,called holeums,in the early universe.Using Newtonian
gravity and nonrelativistic quantum mechanics we find a purely quantum
mechanical mass-dependant exclusion property for the nonoverlap of the
constituent black holes in a holeum.This ensures that the holeum occupies space
just like ordinary matter.A holeum emits only gravitational radiation whose
spectrum is an exact analogue of that of a hydrogen atom. A part of this
spectrum lies in the region accessible to the detectors being built.The holeums
would form haloes around the galaxies and would be an important component of
the dark matter in the universe today.They may also be the constituents of the
invisible domain walls in the universe.
| [
{
"created": "Sun, 17 Aug 2003 16:05:54 GMT",
"version": "v1"
}
] | 2014-02-11 | [
[
"Chavda",
"L. K.",
""
],
[
"Chavda",
"Abhijit L.",
""
]
] | We present three reasons for the formation of gravitational bound states of primordial black holes,called holeums,in the early universe.Using Newtonian gravity and nonrelativistic quantum mechanics we find a purely quantum mechanical mass-dependant exclusion property for the nonoverlap of the constituent black holes in a holeum.This ensures that the holeum occupies space just like ordinary matter.A holeum emits only gravitational radiation whose spectrum is an exact analogue of that of a hydrogen atom. A part of this spectrum lies in the region accessible to the detectors being built.The holeums would form haloes around the galaxies and would be an important component of the dark matter in the universe today.They may also be the constituents of the invisible domain walls in the universe. |
2301.12455 | Jonathan Gorard | Jonathan Gorard, Julia Dannemann-Freitag | Axiomatic Quantum Field Theory in Discrete Spacetime via Multiway Causal
Structure: The Case of Entanglement Entropies | 93 pages, 30 figures | null | null | null | gr-qc cs.DM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The causal set and Wolfram model approaches to discrete quantum gravity both
permit the formulation of a manifestly covariant notion of entanglement entropy
for quantum fields. In the causal set case, this is given by a construction
(due to Sorkin and Johnston) of a 2-point correlation function for a Gaussian
scalar field from causal set Feynman propagators and Pauli-Jordan functions,
from which an eigendecomposition, and hence an entanglement entropy, can be
computed. In the Wolfram model case, it is given instead in terms of the
Fubini-Study metric on branchial graphs, whose tensor product structure is
inherited functorially from that of finite-dimensional Hilbert spaces. In both
cases, the entanglement entropies in question are most naturally defined over
an extended spacetime region (hence the manifest covariance), in contrast to
the generically non-covariant definitions over single spacelike hypersurfaces
common to most continuum quantum field theories. In this article, we show how
an axiomatic field theory for a free, massless scalar field (obeying the
appropriate bosonic commutation relations) may be rigorously constructed over
multiway causal graphs: a combinatorial structure sufficiently general as to
encompass both causal sets and Wolfram model evolutions as special cases. We
proceed to show numerically that the entanglement entropies computed using both
the Sorkin-Johnston approach and the branchial graph approach are monotonically
related for a large class of Wolfram model evolution rules. We also prove a
special case of this monotonic relationship using a recent geometrical
entanglement monotone proposed by Cocchiarella et al.
| [
{
"created": "Sun, 29 Jan 2023 14:37:30 GMT",
"version": "v1"
}
] | 2023-01-31 | [
[
"Gorard",
"Jonathan",
""
],
[
"Dannemann-Freitag",
"Julia",
""
]
] | The causal set and Wolfram model approaches to discrete quantum gravity both permit the formulation of a manifestly covariant notion of entanglement entropy for quantum fields. In the causal set case, this is given by a construction (due to Sorkin and Johnston) of a 2-point correlation function for a Gaussian scalar field from causal set Feynman propagators and Pauli-Jordan functions, from which an eigendecomposition, and hence an entanglement entropy, can be computed. In the Wolfram model case, it is given instead in terms of the Fubini-Study metric on branchial graphs, whose tensor product structure is inherited functorially from that of finite-dimensional Hilbert spaces. In both cases, the entanglement entropies in question are most naturally defined over an extended spacetime region (hence the manifest covariance), in contrast to the generically non-covariant definitions over single spacelike hypersurfaces common to most continuum quantum field theories. In this article, we show how an axiomatic field theory for a free, massless scalar field (obeying the appropriate bosonic commutation relations) may be rigorously constructed over multiway causal graphs: a combinatorial structure sufficiently general as to encompass both causal sets and Wolfram model evolutions as special cases. We proceed to show numerically that the entanglement entropies computed using both the Sorkin-Johnston approach and the branchial graph approach are monotonically related for a large class of Wolfram model evolution rules. We also prove a special case of this monotonic relationship using a recent geometrical entanglement monotone proposed by Cocchiarella et al. |
gr-qc/0512139 | Matt Visser | Stefano Liberati (SISSA/ISAS and INFN, Trieste), Matt Visser (Victoria
University of Wellington, New Zealand), Silke Weinfurtner (Victoria
University of Wellington, New Zealand) | Naturalness in emergent spacetime | V1:4 pages, revtex4; V2: slight changes in title, presentation, and
conclusions. This version to appear in Physical Review Letters | Phys.Rev.Lett. 96 (2006) 151301 | 10.1103/PhysRevLett.96.151301 | null | gr-qc | null | Effective field theories (EFTs) have been widely used as a framework in order
to place constraints on the Planck suppressed Lorentz violations predicted by
various models of quantum gravity. There are however technical problems in the
EFT framework when it comes to ensuring that small Lorentz violations remain
small -- this is the essence of the "naturalness" problem. Herein we present an
"emergent" space-time model, based on the "analogue gravity'' programme, by
investigating a specific condensed-matter system that is in principle capable
of simulating the salient features of an EFT framework with Lorentz violations.
Specifically, we consider the class of two-component BECs subject to
laser-induced transitions between the components, and we show that this model
is an example for Lorentz invariance violation due to ultraviolet physics.
Furthermore our model explicitly avoids the "naturalness problem", and makes
specific suggestions regarding how to construct a physically reasonable quantum
gravity phenomenology.
| [
{
"created": "Thu, 22 Dec 2005 21:36:59 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Mar 2006 00:07:39 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Liberati",
"Stefano",
"",
"SISSA/ISAS and INFN, Trieste"
],
[
"Visser",
"Matt",
"",
"Victoria\n University of Wellington, New Zealand"
],
[
"Weinfurtner",
"Silke",
"",
"Victoria\n University of Wellington, New Zealand"
]
] | Effective field theories (EFTs) have been widely used as a framework in order to place constraints on the Planck suppressed Lorentz violations predicted by various models of quantum gravity. There are however technical problems in the EFT framework when it comes to ensuring that small Lorentz violations remain small -- this is the essence of the "naturalness" problem. Herein we present an "emergent" space-time model, based on the "analogue gravity'' programme, by investigating a specific condensed-matter system that is in principle capable of simulating the salient features of an EFT framework with Lorentz violations. Specifically, we consider the class of two-component BECs subject to laser-induced transitions between the components, and we show that this model is an example for Lorentz invariance violation due to ultraviolet physics. Furthermore our model explicitly avoids the "naturalness problem", and makes specific suggestions regarding how to construct a physically reasonable quantum gravity phenomenology. |
gr-qc/9605036 | Robin W. Tucker | T Dereli, J Schray, Robin W Tucker | Finite Action Yang-Mills Solutions on the Group Manifold | 10 pages LaTeX (REVTeX3.0, No Figures), To appear in J. Physics A:
Mathematical and General | J.Phys.A29:5001-5005,1996 | 10.1088/0305-4470/29/16/021 | null | gr-qc | null | We demonstrate that the left (and right) invariant Maurer-Cartan forms for
any semi-simple Lie group enable one to construct solutions of the Yang-Mills
equations on the group manifold equipped with the natural Cartan-Killing
metric. For the unitary unimodular groups the Yang-Mills action integral is
finite for such solutions. This is explicitly exhibited for the case of
$SU(3)$.
| [
{
"created": "Fri, 17 May 1996 13:06:08 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Dereli",
"T",
""
],
[
"Schray",
"J",
""
],
[
"Tucker",
"Robin W",
""
]
] | We demonstrate that the left (and right) invariant Maurer-Cartan forms for any semi-simple Lie group enable one to construct solutions of the Yang-Mills equations on the group manifold equipped with the natural Cartan-Killing metric. For the unitary unimodular groups the Yang-Mills action integral is finite for such solutions. This is explicitly exhibited for the case of $SU(3)$. |
1507.06727 | Qing-Yu Cai | Dongshan He, Dongfeng Gao and Qing-yu Cai | Dynamical interpretation of the wavefunction of the universe | null | Phys. Lett. B 748, 361-365 (2015) | 10.1016/j.physletb.2015.07.029 | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the physical meaning of the wavefunction of the
universe. With the continuity equation derived from the Wheeler-DeWitt (WDW)
equation in the minisuperspace model, we show that the quantity
$\rho(a)=|\psi(a)|^2$ for the universe is inversely proportional to the Hubble
parameter of the universe. Thus, $\rho(a)$ represents the probability density
of the universe staying in the state $a$ during its evolution, which we call
the dynamical interpretation of the wavefunction of the universe. We
demonstrate that the dynamical interpretation can predict the evolution laws of
the universe in the classical limit as those given by the Friedmann equation.
Furthermore, we show that the value of the operator ordering factor $p$ in the
WDW equation can be determined to be $p=-2$.
| [
{
"created": "Fri, 24 Jul 2015 02:26:19 GMT",
"version": "v1"
}
] | 2015-07-27 | [
[
"He",
"Dongshan",
""
],
[
"Gao",
"Dongfeng",
""
],
[
"Cai",
"Qing-yu",
""
]
] | In this paper, we study the physical meaning of the wavefunction of the universe. With the continuity equation derived from the Wheeler-DeWitt (WDW) equation in the minisuperspace model, we show that the quantity $\rho(a)=|\psi(a)|^2$ for the universe is inversely proportional to the Hubble parameter of the universe. Thus, $\rho(a)$ represents the probability density of the universe staying in the state $a$ during its evolution, which we call the dynamical interpretation of the wavefunction of the universe. We demonstrate that the dynamical interpretation can predict the evolution laws of the universe in the classical limit as those given by the Friedmann equation. Furthermore, we show that the value of the operator ordering factor $p$ in the WDW equation can be determined to be $p=-2$. |
2401.13972 | Umber Sheikh | Wasib Ali and Umber Sheikh | Charged Strange Star Model with Stringy Quark Matter in Rainbow Gravity | 17 pages, 18 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This study deals with the formation and evolution of a strange star in the
Krori Barua Rainbow spacetime from collapsing charged stringy quark matter. The
dynamical variables are explored from the field equations, taking into account
the effects of particle's energy on the mass density, pressure, and string
tension. The electric field is also computed using the MIT Bag model. The real
time data of SAX J1808.4-3658 is used to analyzed the physical properties
including gradients, energy conditions, anisotropy, stability, Tolman
Oppenheimer Volkoff equation, mass function, compactness, and red-shift. The
graphical analysis has been made according to both the theories of rainbow
gravity and general relativity. The energy conditions and anisotropy are found
to be satisfied, indicating the physical existence of suggested model. Tolman
Oppenheimer Volkoff equation is satisfied indicating equilibrium of forces and
stability of the compact object. Overall, our model is consistent with the
observational information of SAX J1808.4-3658.
| [
{
"created": "Thu, 25 Jan 2024 06:07:22 GMT",
"version": "v1"
}
] | 2024-01-26 | [
[
"Ali",
"Wasib",
""
],
[
"Sheikh",
"Umber",
""
]
] | This study deals with the formation and evolution of a strange star in the Krori Barua Rainbow spacetime from collapsing charged stringy quark matter. The dynamical variables are explored from the field equations, taking into account the effects of particle's energy on the mass density, pressure, and string tension. The electric field is also computed using the MIT Bag model. The real time data of SAX J1808.4-3658 is used to analyzed the physical properties including gradients, energy conditions, anisotropy, stability, Tolman Oppenheimer Volkoff equation, mass function, compactness, and red-shift. The graphical analysis has been made according to both the theories of rainbow gravity and general relativity. The energy conditions and anisotropy are found to be satisfied, indicating the physical existence of suggested model. Tolman Oppenheimer Volkoff equation is satisfied indicating equilibrium of forces and stability of the compact object. Overall, our model is consistent with the observational information of SAX J1808.4-3658. |
1709.02768 | Anna M. Nobili | Anna M. Nobili and Alberto Anselmi | Relevance of the weak equivalence principle and experiments to test it:
lessons from the past and improvements expected in space | To appear: Physics Letters A, special issue in memory of Professor
Vladimir Braginsky, 2017. Available online:
http://dx.doi.org/10.1016/j.physleta.2017.09.027 | null | 10.1016/j.physleta.2017.09.027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tests of the Weak Equivalence Principle (WEP) probe the foundations of
physics. Ever since Galileo in the early 1600s, WEP tests have attracted some
of the best experimentalists of any time. Progress has come in bursts, each
stimulated by the introduction of a new technique: the torsion balance, signal
modulation by Earth rotation, the rotating torsion balance. Tests for various
materials in the field of the Earth and the Sun have found no violation to the
level of about 1 part in 1e13. A different technique, Lunar Laser Ranging
(LLR), has reached comparable precision. Today, both laboratory tests and LLR
have reached a point when improving by a factor of 10 is extremely hard. The
promise of another quantum leap in precision rests on experiments performed in
low Earth orbit. The Microscope satellite, launched in April 2016 and currently
taking data, aims to test WEP in the field of Earth to 1e-15, a 100-fold
improvement possible thanks to a driving signal in orbit almost 500 times
stronger than for torsion balances on ground. The `Galileo Galilei' (GG)
experiment, by combining the advantages of space with those of the rotating
torsion balance, aims at a WEP test 100 times more precise than Microscope, to
1e-17. A quantitative comparison of the key issues in the two experiments is
presented, along with recent experimental measurements relevant for GG. Early
results from Microscope, reported at a conference in March 2017, show
measurement performance close to the expectations and confirm the key role of
rotation with the advantage (unique to space) of rotating the whole spacecraft.
Any non-null result from Microscope would be a major discovery and call for
urgent confirmation; with 100 times better precision GG could settle the matter
and provide a deeper probe of the foundations of physics.
| [
{
"created": "Fri, 8 Sep 2017 16:38:41 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Oct 2017 16:38:06 GMT",
"version": "v2"
}
] | 2018-08-01 | [
[
"Nobili",
"Anna M.",
""
],
[
"Anselmi",
"Alberto",
""
]
] | Tests of the Weak Equivalence Principle (WEP) probe the foundations of physics. Ever since Galileo in the early 1600s, WEP tests have attracted some of the best experimentalists of any time. Progress has come in bursts, each stimulated by the introduction of a new technique: the torsion balance, signal modulation by Earth rotation, the rotating torsion balance. Tests for various materials in the field of the Earth and the Sun have found no violation to the level of about 1 part in 1e13. A different technique, Lunar Laser Ranging (LLR), has reached comparable precision. Today, both laboratory tests and LLR have reached a point when improving by a factor of 10 is extremely hard. The promise of another quantum leap in precision rests on experiments performed in low Earth orbit. The Microscope satellite, launched in April 2016 and currently taking data, aims to test WEP in the field of Earth to 1e-15, a 100-fold improvement possible thanks to a driving signal in orbit almost 500 times stronger than for torsion balances on ground. The `Galileo Galilei' (GG) experiment, by combining the advantages of space with those of the rotating torsion balance, aims at a WEP test 100 times more precise than Microscope, to 1e-17. A quantitative comparison of the key issues in the two experiments is presented, along with recent experimental measurements relevant for GG. Early results from Microscope, reported at a conference in March 2017, show measurement performance close to the expectations and confirm the key role of rotation with the advantage (unique to space) of rotating the whole spacecraft. Any non-null result from Microscope would be a major discovery and call for urgent confirmation; with 100 times better precision GG could settle the matter and provide a deeper probe of the foundations of physics. |
1209.1701 | Jan Weenink | Tomislav Prokopec and Jan Weenink | Uniqueness of the gauge invariant action for cosmological perturbations | 27 pages | null | 10.1088/1475-7516/2012/12/031 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In second order perturbation theory different definitions are known of gauge
invariant perturbations in single field inflationary models. Consequently the
corresponding gauge invariant cubic actions do not have the same form. Here we
show that the cubic action for one choice of gauge invariant variables is
unique in the following sense: the action for any other, non-linearly related
variable can be brought to the same bulk action, plus additional boundary
terms. These boundary terms correspond to the choice of hypersurface and
generate extra, disconnected contributions to the bispectrum. We also discuss
uniqueness of the action with respect to conformal frames. When expressed in
terms of the gauge invariant curvature perturbation on uniform field
hypersurfaces the action for cosmological perturbations has a unique form,
independent of the original Einstein or Jordan frame. Crucial is that the gauge
invariant comoving curvature perturbation is frame independent, which makes it
extremely helpful in showing the quantum equivalence of the two frames, and
therefore in calculating quantum effects in nonminimally coupled theories such
as Higss inflation.
| [
{
"created": "Sat, 8 Sep 2012 10:21:44 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Prokopec",
"Tomislav",
""
],
[
"Weenink",
"Jan",
""
]
] | In second order perturbation theory different definitions are known of gauge invariant perturbations in single field inflationary models. Consequently the corresponding gauge invariant cubic actions do not have the same form. Here we show that the cubic action for one choice of gauge invariant variables is unique in the following sense: the action for any other, non-linearly related variable can be brought to the same bulk action, plus additional boundary terms. These boundary terms correspond to the choice of hypersurface and generate extra, disconnected contributions to the bispectrum. We also discuss uniqueness of the action with respect to conformal frames. When expressed in terms of the gauge invariant curvature perturbation on uniform field hypersurfaces the action for cosmological perturbations has a unique form, independent of the original Einstein or Jordan frame. Crucial is that the gauge invariant comoving curvature perturbation is frame independent, which makes it extremely helpful in showing the quantum equivalence of the two frames, and therefore in calculating quantum effects in nonminimally coupled theories such as Higss inflation. |
2102.12805 | Reinoud Slagter | Reinoud Jan Slagter | New Evidence of the Azimuthal Alignment of Quasars Spin vector in the
LQG U1.28, U1.27, U1.11, Cosmologically Explained | Second version. No major changes. Feedback welcome. 3 figures 3 pages | null | 10.1016/j.newast.2022.101797 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | There is observational evidence that the spin axes of quasars in large quasar
groups are correlated over hundreds of Mpc. This is found in the radio sector
as well as in the optical range. There is not yet a satisfactory explanation of
this "spooky" alignment. This alignment cannot be explained by mutual
interaction at the time that quasars manifest themselves optically. A
cosmological explanation could be possible by the formation of superconducting
vortices (cosmic strings) in the early universe, just after the
symmetry-breaking phase of the universe. We gathered from the NASA/IPAC and
SIMBAD extragalactic databases the right ascension, declination, inclination,
position angle and eccentricity of the host galaxies of 3 large quasar groups
in order to obtain the azimuthal and polar angle of the spin vectors. The
alignment of the azimuthal angle of the spin vectors of quasars in their host
galaxy is confirmed in the large quasar group U1.27 and compared with two other
groups in the vicinity, i.e., U1.11 and U1.28, investigated by Clowes2013. It
is well possible that the azimuthal angle alignment fits the predicted
azimuthal angle dependency in the theoretical model of the formation of general
relativistic superconducting vortices, where the initial axial symmetry is
broken just after the symmetry breaking of the scalar-gauge field.
| [
{
"created": "Thu, 25 Feb 2021 12:08:39 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jun 2021 15:44:17 GMT",
"version": "v2"
}
] | 2022-03-14 | [
[
"Slagter",
"Reinoud Jan",
""
]
] | There is observational evidence that the spin axes of quasars in large quasar groups are correlated over hundreds of Mpc. This is found in the radio sector as well as in the optical range. There is not yet a satisfactory explanation of this "spooky" alignment. This alignment cannot be explained by mutual interaction at the time that quasars manifest themselves optically. A cosmological explanation could be possible by the formation of superconducting vortices (cosmic strings) in the early universe, just after the symmetry-breaking phase of the universe. We gathered from the NASA/IPAC and SIMBAD extragalactic databases the right ascension, declination, inclination, position angle and eccentricity of the host galaxies of 3 large quasar groups in order to obtain the azimuthal and polar angle of the spin vectors. The alignment of the azimuthal angle of the spin vectors of quasars in their host galaxy is confirmed in the large quasar group U1.27 and compared with two other groups in the vicinity, i.e., U1.11 and U1.28, investigated by Clowes2013. It is well possible that the azimuthal angle alignment fits the predicted azimuthal angle dependency in the theoretical model of the formation of general relativistic superconducting vortices, where the initial axial symmetry is broken just after the symmetry breaking of the scalar-gauge field. |
1504.04610 | Giorgio Papini | Giorgio Papini | Perspectives on gravity-induced radiative processes in astrophysics | 8 pages, one figure. arXiv admin note: substantial text overlap with
arXiv:1007.4834 | Galaxies 2015, 3, 72-83 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Single-vertex Feynman diagrams represent the dominant contribution to
physical processes, but are frequently forbidden kinematically. This is changed
when the particles involved propagate in a gravitational background and acquire
an effective mass. Procedures are introduced that allow the calculation of
lowest order diagrams, their corresponding transition probabilities, emission
powers and spectra to all orders in the metric deviation, for particles of any
spin propagating in gravitational fields described by any metric. Physical
properties of the "space-time medium" are also discussed. It is shown in
particular that a small dissipation term in the particle wave equations can
trigger a strong back-reaction that introduces resonances in the radiative
process and affects the resulting gravitational background.
| [
{
"created": "Fri, 17 Apr 2015 19:16:37 GMT",
"version": "v1"
}
] | 2015-04-20 | [
[
"Papini",
"Giorgio",
""
]
] | Single-vertex Feynman diagrams represent the dominant contribution to physical processes, but are frequently forbidden kinematically. This is changed when the particles involved propagate in a gravitational background and acquire an effective mass. Procedures are introduced that allow the calculation of lowest order diagrams, their corresponding transition probabilities, emission powers and spectra to all orders in the metric deviation, for particles of any spin propagating in gravitational fields described by any metric. Physical properties of the "space-time medium" are also discussed. It is shown in particular that a small dissipation term in the particle wave equations can trigger a strong back-reaction that introduces resonances in the radiative process and affects the resulting gravitational background. |
2001.04367 | Dipanjan Dey | Karim Mosani, Dipanjan Dey, Pankaj S. Joshi | Strong curvature naked singularities in spherically symmetric perfect
fluid collapse | 8 pages | Phys. Rev. D 101, 044052 (2020) | 10.1103/PhysRevD.101.044052 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate here the locally naked singularity formed due to a spherically
symmetric inhomogeneous collapsing cloud having non-zero isotropic pressure, in
terms of its strength. Sufficient condition provided by Clarke and Krolak for
it to be Tipler strong has been used to restrict the parameters that represent
the non-linear relation between the physical radius and the radial coordinate
of the outgoing radial null geodesic at the singular center. Studying end state
of a collapsing cloud requires information about the dynamics of collapse,
which is unknown in a general scenario. Hence we study small perturbations to
the mass profile for inhomogeneous dust, which is possible using the formalism
developed here. This perturbed mass profile, in turn, gives rise to non-zero
pressure. We show the existence of a non-zero measure set of initial data
giving rise to such strong curvature naked singularity.
| [
{
"created": "Mon, 13 Jan 2020 16:01:15 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Mar 2020 05:07:49 GMT",
"version": "v2"
}
] | 2020-03-04 | [
[
"Mosani",
"Karim",
""
],
[
"Dey",
"Dipanjan",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | We investigate here the locally naked singularity formed due to a spherically symmetric inhomogeneous collapsing cloud having non-zero isotropic pressure, in terms of its strength. Sufficient condition provided by Clarke and Krolak for it to be Tipler strong has been used to restrict the parameters that represent the non-linear relation between the physical radius and the radial coordinate of the outgoing radial null geodesic at the singular center. Studying end state of a collapsing cloud requires information about the dynamics of collapse, which is unknown in a general scenario. Hence we study small perturbations to the mass profile for inhomogeneous dust, which is possible using the formalism developed here. This perturbed mass profile, in turn, gives rise to non-zero pressure. We show the existence of a non-zero measure set of initial data giving rise to such strong curvature naked singularity. |
gr-qc/0703127 | Hirotaka Yoshino | Hirotaka Yoshino, Andrei Zelnikov, Valeri P. Frolov | Apparent horizon formation in the head-on collision of gyratons | 44 pages, 21 figures, published version | Phys.Rev.D75:124005,2007 | 10.1103/PhysRevD.75.124005 | Alberta-Thy-01-07 | gr-qc hep-ph hep-th | null | The gyraton model describes a gravitational field of an object moving with
the velocity of light which has finite energy and spin distributed during some
finite time interval $L$. A gyraton may be considered as a classical toy model
for a quantum wave packet of high-energy particles with spin. In this paper we
study a head-on collision of two gyratons and black hole formation in this
process. The goal of this study is to understand the role of the gravitational
spin-spin interaction in the process of mini-black-hole formation in particle
collisions. To simplify the problem we consider several gyraton models with
special profiles of the energy and spin density distribution. For these models
we study the apparent horizon (AH) formation on the future edge of a spacetime
region before interaction. We demonstrate that the AH forms only if the energy
duration and the spin are smaller than some critical values, while the length
of the spin distribution should be at least of the order of the system
gravitational radius. We also study gravitational spin-spin interaction in the
head-on collision of two gyratons under the assumption that the values of
gyraton spins are small. We demonstrate that the metric in the interaction
region for such gyratons depends on the relative helicities of incoming
gyratons, and the collision of gyratons with oppositely directed spins allows
the AH formation in a larger parameter region than in the collision of the
gyratons with the same direction of spins. Some applications of the obtained
results to the mini-black-hole production at the Large Hadron Collider in TeV
gravity scenarios are briefly discussed.
| [
{
"created": "Mon, 26 Mar 2007 20:37:41 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Apr 2007 04:35:26 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Jun 2007 21:12:04 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Yoshino",
"Hirotaka",
""
],
[
"Zelnikov",
"Andrei",
""
],
[
"Frolov",
"Valeri P.",
""
]
] | The gyraton model describes a gravitational field of an object moving with the velocity of light which has finite energy and spin distributed during some finite time interval $L$. A gyraton may be considered as a classical toy model for a quantum wave packet of high-energy particles with spin. In this paper we study a head-on collision of two gyratons and black hole formation in this process. The goal of this study is to understand the role of the gravitational spin-spin interaction in the process of mini-black-hole formation in particle collisions. To simplify the problem we consider several gyraton models with special profiles of the energy and spin density distribution. For these models we study the apparent horizon (AH) formation on the future edge of a spacetime region before interaction. We demonstrate that the AH forms only if the energy duration and the spin are smaller than some critical values, while the length of the spin distribution should be at least of the order of the system gravitational radius. We also study gravitational spin-spin interaction in the head-on collision of two gyratons under the assumption that the values of gyraton spins are small. We demonstrate that the metric in the interaction region for such gyratons depends on the relative helicities of incoming gyratons, and the collision of gyratons with oppositely directed spins allows the AH formation in a larger parameter region than in the collision of the gyratons with the same direction of spins. Some applications of the obtained results to the mini-black-hole production at the Large Hadron Collider in TeV gravity scenarios are briefly discussed. |
gr-qc/9901047 | Matt Visser | Matt Visser (Washington University) | Acoustic black holes | 10 pages, uses Springer-Verlag macro package. To appear in the
Proceedings of the 1998 Peniscola Summer School on Particle Physics and
Cosmology. (Springer-Verlag) | null | null | null | gr-qc | null | Acoustic propagation in a moving fluid provides a conceptually clean and
powerful analogy for understanding black hole physics. As a teaching tool, the
analogy is useful for introducing students to both General Relativity and fluid
mechanics. As a research tool, the analogy helps clarify what aspects of the
physics are kinematics and what aspects are dynamics. In particular, Hawking
radiation is a purely kinematical effect, whereas black hole entropy is
intrinsically dynamical. Finally, I discuss the fact that with present
technology acoustic Hawking radiation is almost experimentally testable.
| [
{
"created": "Sat, 16 Jan 1999 01:47:03 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Visser",
"Matt",
"",
"Washington University"
]
] | Acoustic propagation in a moving fluid provides a conceptually clean and powerful analogy for understanding black hole physics. As a teaching tool, the analogy is useful for introducing students to both General Relativity and fluid mechanics. As a research tool, the analogy helps clarify what aspects of the physics are kinematics and what aspects are dynamics. In particular, Hawking radiation is a purely kinematical effect, whereas black hole entropy is intrinsically dynamical. Finally, I discuss the fact that with present technology acoustic Hawking radiation is almost experimentally testable. |
1302.5628 | Miquel Nofrarias | M. Nofrarias, F. Gibert, N. Karnesis, A.F. Garcia, M. Hewitson, G.
Heinzel, K. Danzmann | Subtraction of temperature induced phase noise in the LISA frequency
band | 8 pages, 6 figures | null | 10.1103/PhysRevD.87.102003 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Temperature fluctuations are expected to be one of the limiting factors for
gravitational wave detectors in the very low frequency range. Here we report
the characterisation of this noise source in the LISA Pathfinder optical bench
and propose a method to remove its contribution from the data. Our results show
that temperature fluctuations are indeed limiting our measurement below one
millihertz, and that their subtraction leads to a factor 5.6 (15 dB) reduction
in the noise level at the lower end of the LISA measurement band 10^{-4} Hz,
which increases to 20.2 (26 dB) at even lower frequencies, i.e., 1.5x10^{-5}
Hz. The method presented here can be applied to the subtraction of other noise
sources in gravitational wave detectors in the general situation where multiple
sensors are used to characterise the noise source.
| [
{
"created": "Fri, 22 Feb 2013 16:12:44 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jun 2013 10:20:21 GMT",
"version": "v2"
}
] | 2013-06-20 | [
[
"Nofrarias",
"M.",
""
],
[
"Gibert",
"F.",
""
],
[
"Karnesis",
"N.",
""
],
[
"Garcia",
"A. F.",
""
],
[
"Hewitson",
"M.",
""
],
[
"Heinzel",
"G.",
""
],
[
"Danzmann",
"K.",
""
]
] | Temperature fluctuations are expected to be one of the limiting factors for gravitational wave detectors in the very low frequency range. Here we report the characterisation of this noise source in the LISA Pathfinder optical bench and propose a method to remove its contribution from the data. Our results show that temperature fluctuations are indeed limiting our measurement below one millihertz, and that their subtraction leads to a factor 5.6 (15 dB) reduction in the noise level at the lower end of the LISA measurement band 10^{-4} Hz, which increases to 20.2 (26 dB) at even lower frequencies, i.e., 1.5x10^{-5} Hz. The method presented here can be applied to the subtraction of other noise sources in gravitational wave detectors in the general situation where multiple sensors are used to characterise the noise source. |
1111.3737 | Frank Ohme | Frank Ohme | Analytical meets numerical relativity - status of complete gravitational
waveform models for binary black holes | 13 pages, 2 figures, 1 table, NRDA2011/Amaldi 9 proceedings;
published version with extended discussion of accuracy requirements and a new
figure 2 | 2012 Class. Quantum Grav. 29 124002 | 10.1088/0264-9381/29/12/124002 | AEI-2011-090 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Models of gravitational waveforms from coalescing black-hole binaries play a
crucial role in the efforts to detect and interpret the signatures of those
binaries in the data of large-scale interferometers. Here we summarize recent
models that combine information both from analytical approximations and
numerical relativity. We briefly lay out and compare the strategies employed to
build such complete models and we recapitulate the errors associated with
various aspects of the modelling process.
| [
{
"created": "Wed, 16 Nov 2011 09:33:35 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Feb 2012 14:51:46 GMT",
"version": "v2"
}
] | 2015-03-19 | [
[
"Ohme",
"Frank",
""
]
] | Models of gravitational waveforms from coalescing black-hole binaries play a crucial role in the efforts to detect and interpret the signatures of those binaries in the data of large-scale interferometers. Here we summarize recent models that combine information both from analytical approximations and numerical relativity. We briefly lay out and compare the strategies employed to build such complete models and we recapitulate the errors associated with various aspects of the modelling process. |
gr-qc/9704067 | Max welling | M. Welling (Utrecht University) | Winding Solutions for the two Particle System in 2+1 Gravity | 15 pages Latex, 4 eps figures | Class.Quant.Grav. 15 (1998) 613-626 | 10.1088/0264-9381/15/3/012 | THU-97/10 | gr-qc | null | Using a PASCAL program to follow the evolution of two gravitating particles
in 2+1 dimensions we find solutions in which the particles wind around one
another indefinitely. As their center of mass moves `tachyonic' they form a
Gott-pair. To avoid unphysical boundary conditions we consider a large but
closed universe. After the particles have evolved for some time their momenta
have grown very large. In this limit we quantize the model and find that both
the relevant configuration variable and its conjugate momentum become discrete.
| [
{
"created": "Thu, 24 Apr 1997 13:36:11 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Welling",
"M.",
"",
"Utrecht University"
]
] | Using a PASCAL program to follow the evolution of two gravitating particles in 2+1 dimensions we find solutions in which the particles wind around one another indefinitely. As their center of mass moves `tachyonic' they form a Gott-pair. To avoid unphysical boundary conditions we consider a large but closed universe. After the particles have evolved for some time their momenta have grown very large. In this limit we quantize the model and find that both the relevant configuration variable and its conjugate momentum become discrete. |
1502.04679 | Florent Michel | Florent Michel, Renaud Parentani | Non-linear effects in time-dependent transonic flows: An analysis of
analogue black hole stability | 25 pages, 16 figures. Final version published in PRA | Phys. Rev. A 91, 053603 (2015) | 10.1103/PhysRevA.91.053603 | LPT-Orsay-15-13 | gr-qc cond-mat.quant-gas nlin.PS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study solutions of the one-dimensional Gross-Pitaevskii equation to better
understand dynamical instabilities occurring in flowing atomic condensates.
Whereas transonic stationary flows can be fully described in simple terms,
time-dependent flows exhibit a wide variety of behaviors. When the sound speed
is crossed once, we observe that flows analogous to black holes obey something
similar to the so-called no hair theorem since their late time profile is
stationary and uniquely fixed by parameters entering the Hamiltonian and
conserved quantities. For flows analogous to white holes, at late time one
finds a macroscopic undulation in the supersonic side which has either a fixed
amplitude, or a widely varying one signaling a quasi periodic emission of
solitons on the subsonic side. When considering flows which cross the sound
speed twice, we observe various scenarios which can be understood from the
above behaviors, and from the hierarchy of the growth rates of the dynamical
instabilities characterizing such flows.
| [
{
"created": "Mon, 16 Feb 2015 19:43:28 GMT",
"version": "v1"
},
{
"created": "Sat, 9 May 2015 16:45:35 GMT",
"version": "v2"
}
] | 2015-05-12 | [
[
"Michel",
"Florent",
""
],
[
"Parentani",
"Renaud",
""
]
] | We study solutions of the one-dimensional Gross-Pitaevskii equation to better understand dynamical instabilities occurring in flowing atomic condensates. Whereas transonic stationary flows can be fully described in simple terms, time-dependent flows exhibit a wide variety of behaviors. When the sound speed is crossed once, we observe that flows analogous to black holes obey something similar to the so-called no hair theorem since their late time profile is stationary and uniquely fixed by parameters entering the Hamiltonian and conserved quantities. For flows analogous to white holes, at late time one finds a macroscopic undulation in the supersonic side which has either a fixed amplitude, or a widely varying one signaling a quasi periodic emission of solitons on the subsonic side. When considering flows which cross the sound speed twice, we observe various scenarios which can be understood from the above behaviors, and from the hierarchy of the growth rates of the dynamical instabilities characterizing such flows. |
gr-qc/9608061 | Lior M. Burko | Lior M. Burko | Comment on the Roberts solution for the spherically-symmetric
Einstein-scalar field equations | 3 pages, RevTeX | Gen.Rel.Grav.29:259,1997 | 10.1023/A:1010200430550 | null | gr-qc | null | We critically examine the Roberts homothetic solution for the spherically
symmetric Einstein-scalar field equations in double null coordinates, and show
that the Roberts solution indeed solves the field equations only for one
non-trivial case. We generalize this solution and discuss its relations with
other known exact solutions.
| [
{
"created": "Mon, 26 Aug 1996 11:37:38 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Burko",
"Lior M.",
""
]
] | We critically examine the Roberts homothetic solution for the spherically symmetric Einstein-scalar field equations in double null coordinates, and show that the Roberts solution indeed solves the field equations only for one non-trivial case. We generalize this solution and discuss its relations with other known exact solutions. |
2306.06576 | Huan Yang | Zhen Pan, Huan Yang, Laura Bernard, B\'eatrice Bonga | Resonant dynamics of extreme mass-ratio inspirals in a perturbed Kerr
spacetime | 22 pages, 17 figures | Phys. Rev. D 108,104026 (2023) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extreme mass-ratio inspirals (EMRI) are one of the most sensitive probes of
black hole spacetimes with gravitational wave measurements. In this work, we
systematically analyze the dynamics of an EMRI system near orbital resonances,
assuming the background spacetime is weakly perturbed from Kerr. Using the
action-angle formalism, we have derived an effective resonant Hamiltonian that
describes the dynamics of the resonant degree of freedom, for the case that the
EMRI motion across the resonance regime. This effective resonant Hamiltonian
can also be used to derive the condition that the trajectory enters/exits a
resonant island and the permanent change of action variables across the
resonance with the gravitational wave radiation turned on. The orbital chaos,
on the other hand, generally leads to transitions between different branches of
rotational orbits with finite changes of the action variables. These findings
are demonstrated with numerical orbital evolutions that are mapped into
representations using action-angle variables. This study is one part of the
program of understanding EMRI dynamics in a generic perturbed Kerr spacetime,
which paves the way of using EMRIs to precisely measure the black hole
spacetime.
| [
{
"created": "Sun, 11 Jun 2023 03:44:49 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Jul 2023 01:59:30 GMT",
"version": "v2"
}
] | 2023-11-15 | [
[
"Pan",
"Zhen",
""
],
[
"Yang",
"Huan",
""
],
[
"Bernard",
"Laura",
""
],
[
"Bonga",
"Béatrice",
""
]
] | Extreme mass-ratio inspirals (EMRI) are one of the most sensitive probes of black hole spacetimes with gravitational wave measurements. In this work, we systematically analyze the dynamics of an EMRI system near orbital resonances, assuming the background spacetime is weakly perturbed from Kerr. Using the action-angle formalism, we have derived an effective resonant Hamiltonian that describes the dynamics of the resonant degree of freedom, for the case that the EMRI motion across the resonance regime. This effective resonant Hamiltonian can also be used to derive the condition that the trajectory enters/exits a resonant island and the permanent change of action variables across the resonance with the gravitational wave radiation turned on. The orbital chaos, on the other hand, generally leads to transitions between different branches of rotational orbits with finite changes of the action variables. These findings are demonstrated with numerical orbital evolutions that are mapped into representations using action-angle variables. This study is one part of the program of understanding EMRI dynamics in a generic perturbed Kerr spacetime, which paves the way of using EMRIs to precisely measure the black hole spacetime. |
1612.08661 | Sunny Vagnozzi | L. Sebastiani, S. Vagnozzi, R. Myrzakulov | Mimetic gravity: a review of recent developments and applications to
cosmology and astrophysics | 68 pages, invited review to appear in Advances in High Energy Physics | Adv. High Energy Phys. 2017 (2017) 3156915 | 10.1155/2017/3156915 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mimetic gravity is a Weyl-symmetric extension of General Relativity, related
to the latter by a singular disformal transformation, wherein the appearance of
a dust-like perfect fluid can mimic cold dark matter at a cosmological level.
Within this framework, it is possible to provide an unified geometrical
explanation for dark matter, the late-time acceleration, and inflation, making
it a very attractive theory. In this review, we summarize the main aspects of
mimetic gravity, as well as extensions of the minimal formulation of the model.
We devote particular focus to the reconstruction technique, which allows the
realization of any desired expansionary history of the Universe by an accurate
choice of potential, or other functions defined within the theory (as in the
case of mimetic $f(R)$ gravity). We briefly discuss cosmological perturbation
theory within mimetic gravity. As a case study within which we apply the
concepts previously discussed, we study a mimetic Ho\v{r}ava-like theory, of
which we explore solutions and cosmological perturbations in detail. Finally,
we conclude the review by discussing static spherically symmetric solutions
within mimetic gravity, and apply our findings to the problem of galactic
rotation curves. Our review provides an introduction to mimetic gravity, as
well as a concise but self-contained summary of recent findings, progresses,
open questions, and outlooks on future research directions.
| [
{
"created": "Tue, 27 Dec 2016 15:44:39 GMT",
"version": "v1"
}
] | 2017-03-03 | [
[
"Sebastiani",
"L.",
""
],
[
"Vagnozzi",
"S.",
""
],
[
"Myrzakulov",
"R.",
""
]
] | Mimetic gravity is a Weyl-symmetric extension of General Relativity, related to the latter by a singular disformal transformation, wherein the appearance of a dust-like perfect fluid can mimic cold dark matter at a cosmological level. Within this framework, it is possible to provide an unified geometrical explanation for dark matter, the late-time acceleration, and inflation, making it a very attractive theory. In this review, we summarize the main aspects of mimetic gravity, as well as extensions of the minimal formulation of the model. We devote particular focus to the reconstruction technique, which allows the realization of any desired expansionary history of the Universe by an accurate choice of potential, or other functions defined within the theory (as in the case of mimetic $f(R)$ gravity). We briefly discuss cosmological perturbation theory within mimetic gravity. As a case study within which we apply the concepts previously discussed, we study a mimetic Ho\v{r}ava-like theory, of which we explore solutions and cosmological perturbations in detail. Finally, we conclude the review by discussing static spherically symmetric solutions within mimetic gravity, and apply our findings to the problem of galactic rotation curves. Our review provides an introduction to mimetic gravity, as well as a concise but self-contained summary of recent findings, progresses, open questions, and outlooks on future research directions. |
gr-qc/9711042 | R. Garcia | H.F.Dowker, R.S.Garcia | A handlebody calculus for topology change | Latex, 32 pages, 7 figures | Class.Quant.Grav. 15 (1998) 1859-1879 | 10.1088/0264-9381/15/7/005 | Imperial/TP/97-98/11 | gr-qc | null | We consider certain interesting processes in quantum gravity which involve a
change of spatial topology. We use Morse theory and the machinery of
handlebodies to characterise topology changes as suggested by Sorkin. Our
results support the view that that the pair production of Kaluza-Klein
monopoles and the nucleation of various higher dimensional objects are allowed
transitions with non-zero amplitude.
| [
{
"created": "Wed, 12 Nov 1997 17:26:25 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Dowker",
"H. F.",
""
],
[
"Garcia",
"R. S.",
""
]
] | We consider certain interesting processes in quantum gravity which involve a change of spatial topology. We use Morse theory and the machinery of handlebodies to characterise topology changes as suggested by Sorkin. Our results support the view that that the pair production of Kaluza-Klein monopoles and the nucleation of various higher dimensional objects are allowed transitions with non-zero amplitude. |
gr-qc/9810002 | Takeshi Chiba | Takeshi Chiba | Resolving the singularity of the Hawking-Turok type instanton | minor changes, 8 pages, to be published in Phys.Lett.B | Phys.Lett. B442 (1998) 59-62 | 10.1016/S0370-2693(98)01273-8 | null | gr-qc astro-ph | null | We point out that the singular instanton of Hawking-Turok type, in which the
singularity occurs due to the divergence of a massless scalar field, can be
generated by Euclideanized regular $p$-brane solutions in string (or M-) theory
upon compactification to four dimensions.
| [
{
"created": "Thu, 1 Oct 1998 13:22:26 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Nov 1998 07:03:34 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Chiba",
"Takeshi",
""
]
] | We point out that the singular instanton of Hawking-Turok type, in which the singularity occurs due to the divergence of a massless scalar field, can be generated by Euclideanized regular $p$-brane solutions in string (or M-) theory upon compactification to four dimensions. |
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