id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0105082 | Maurizio Gasperini | M. Gasperini | Dilatonic Interpretation of the Quintessence? | 6 pages, Revtex, four figures included using epsfig. To appear in
Phys. Rev. D | Phys.Rev. D64 (2001) 043510 | 10.1103/PhysRevD.64.043510 | BA-TH/01-409 | gr-qc astro-ph hep-th | null | We discuss the possibility that "quintessential effects", recently displayed
by large scale observations, may be consistently described in the context of
the low-energy string effective action, and we suggest a possible approach to
the problem of the cosmic coincidence based on the link between the strength of
the dilaton couplings and the cosmological state of our Universe.
| [
{
"created": "Wed, 23 May 2001 20:26:28 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Gasperini",
"M.",
""
]
] | We discuss the possibility that "quintessential effects", recently displayed by large scale observations, may be consistently described in the context of the low-energy string effective action, and we suggest a possible approach to the problem of the cosmic coincidence based on the link between the strength of the dilaton couplings and the cosmological state of our Universe. |
2210.04674 | Vitalii Vertogradov | Vitalii Vertogradov | Geodesics for particles with negative energy in Kerr's metric | 8 pages | Gravitation and Cosmology 21(2):171-174 (2015) | 10.1134/S0202289315020115 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | According to Penrose effect, particles with negative energy can exist in the
ergospheres of rotating black holes. We analyze geodesics for such particles
and show that there are no circular and elliptic orbits in the ergosphere of a
rotating black hole. We also show that there are geodesics which begin and
terminate at the singularity and present the conditions under which such
geodesics do not begin and terminate at the singularity.
| [
{
"created": "Mon, 10 Oct 2022 13:25:34 GMT",
"version": "v1"
}
] | 2022-10-11 | [
[
"Vertogradov",
"Vitalii",
""
]
] | According to Penrose effect, particles with negative energy can exist in the ergospheres of rotating black holes. We analyze geodesics for such particles and show that there are no circular and elliptic orbits in the ergosphere of a rotating black hole. We also show that there are geodesics which begin and terminate at the singularity and present the conditions under which such geodesics do not begin and terminate at the singularity. |
1506.03375 | Babak Vakili | M. A. Gorji, K. Nozari and B. Vakili | Polymer quantization versus the Snyder noncommutative space | 14 pages, 1 figure, to appear in CQG | Class. Quantum Grav. 32 (2015) 155007 | 10.1088/0264-9381/32/15/155007 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a noncanonical Hilbert space representation of the polymer quantum
mechanics. It is shown that Heisenberg algebra get some modifications in the
constructed setup from which a generalized uncertainty principle will naturally
come out. Although the extracted physical results are the same as those
obtained from the standard canonical representation, the noncanonical
representation may be notable in view of its possible connection with the
generalized uncertainty theories suggested by string theory. In this regard, by
considering an Snyder-deformed Heisenberg algebra we show that since the
translation group is not deformed it can be identified with a polymer-modified
Heisenberg algebra. In classical level, it is shown the noncanonical Poisson
brackets are related to their canonical counterparts by means of a Darboux
transformation on the corresponding phase space.
| [
{
"created": "Wed, 10 Jun 2015 16:15:03 GMT",
"version": "v1"
}
] | 2015-07-14 | [
[
"Gorji",
"M. A.",
""
],
[
"Nozari",
"K.",
""
],
[
"Vakili",
"B.",
""
]
] | We study a noncanonical Hilbert space representation of the polymer quantum mechanics. It is shown that Heisenberg algebra get some modifications in the constructed setup from which a generalized uncertainty principle will naturally come out. Although the extracted physical results are the same as those obtained from the standard canonical representation, the noncanonical representation may be notable in view of its possible connection with the generalized uncertainty theories suggested by string theory. In this regard, by considering an Snyder-deformed Heisenberg algebra we show that since the translation group is not deformed it can be identified with a polymer-modified Heisenberg algebra. In classical level, it is shown the noncanonical Poisson brackets are related to their canonical counterparts by means of a Darboux transformation on the corresponding phase space. |
1105.2802 | Alfredo Lopez Ortega | A. Lopez-Ortega, I. Vega-Acevedo | Quasinormal frequencies of asymptotically flat two-dimensional black
holes | 12 pages. Accepted for publication in Gen. Rel. and Grav | Gen.Rel.Grav.43:2631-2647,2011 | 10.1007/s10714-011-1185-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss whether the minimally coupled massless Klein-Gordon and Dirac
fields have well defined quasinormal modes in single horizon, asymptotically
flat two-dimensional black holes. To get the result we solve the equations of
motion in the massless limit and we also calculate the effective potentials of
Schrodinger type equations. Furthermore we calculate exactly the quasinormal
frequencies of the Dirac field propagating in the two-dimensional uncharged
Witten black hole. We compare our results on its quasinormal frequencies with
other already published.
| [
{
"created": "Fri, 13 May 2011 18:42:35 GMT",
"version": "v1"
}
] | 2011-09-28 | [
[
"Lopez-Ortega",
"A.",
""
],
[
"Vega-Acevedo",
"I.",
""
]
] | We discuss whether the minimally coupled massless Klein-Gordon and Dirac fields have well defined quasinormal modes in single horizon, asymptotically flat two-dimensional black holes. To get the result we solve the equations of motion in the massless limit and we also calculate the effective potentials of Schrodinger type equations. Furthermore we calculate exactly the quasinormal frequencies of the Dirac field propagating in the two-dimensional uncharged Witten black hole. We compare our results on its quasinormal frequencies with other already published. |
1007.4627 | S Habib Mazharimousavi | S. Habib Mazharimousavi, M. Halilsoy, Z. Amirabi | Higher dimensional thin-shell wormholes in
Einstein-Yang-Mills-Gauss-Bonnet gravity | 9 pages, 6 figures. Dedicated to the memory of Rev. Ibrahim Eken
(1927-2010) of Turkey | Class.Quant.Grav.28:025004,2011 | 10.1088/0264-9381/28/2/025004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present thin-shell wormhole solutions in Einstein-Yang-Mills-Gauss-Bonnet
(EYMGB) theory in higher dimensions d\geq5. Exact black hole solutions are
employed for this purpose where the radius of thin-shell lies outside the event
horizon. For some reasons the cases d=5 and d>5 are treated separately. The
surface energy-momentum of the thin-shell creates surface pressures to resist
against collapse and rendering stable wormholes possible. We test the stability
of the wormholes against spherical perturbations through a linear
energy-pressure relation and plot stability regions. Apart from this restricted
stability we investigate the possibility of normal (i.e. non-exotic) matter
which satisfies the energy conditions. For negative values of the Gauss-Bonnet
(GB) parameter we obtain such physical wormholes.
| [
{
"created": "Tue, 27 Jul 2010 06:11:43 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Aug 2010 16:16:19 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Jan 2011 15:58:40 GMT",
"version": "v3"
}
] | 2011-01-17 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
],
[
"Amirabi",
"Z.",
""
]
] | We present thin-shell wormhole solutions in Einstein-Yang-Mills-Gauss-Bonnet (EYMGB) theory in higher dimensions d\geq5. Exact black hole solutions are employed for this purpose where the radius of thin-shell lies outside the event horizon. For some reasons the cases d=5 and d>5 are treated separately. The surface energy-momentum of the thin-shell creates surface pressures to resist against collapse and rendering stable wormholes possible. We test the stability of the wormholes against spherical perturbations through a linear energy-pressure relation and plot stability regions. Apart from this restricted stability we investigate the possibility of normal (i.e. non-exotic) matter which satisfies the energy conditions. For negative values of the Gauss-Bonnet (GB) parameter we obtain such physical wormholes. |
2009.04386 | Victor Santos | \'Angel Rinc\'on and Victor Santos | Greybody factor and quasinormal modes of Regular Black Holes | Accepted for publication in the European Physical Journal C (EPJ C) | null | 10.1140/epjc/s10052-020-08445-2 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this work, we investigate the quasinormal frequencies of a class of
regular black hole solutions which generalize Bardeen and Hayward spacetimes.
In particular, we analyze scalar, vector and gravitational perturbations of the
black hole both with the semianalytic WKB method and their time-domain
profiles. We analyze in detail the behavior of the spectrum depending on the
parameter $p/q$ of the black hole, the quantum number of angular momentum and
the $s$ number. In addition, we compare our results with the classical solution
valid for $p = q = 1$.
| [
{
"created": "Wed, 9 Sep 2020 16:08:53 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Rincón",
"Ángel",
""
],
[
"Santos",
"Victor",
""
]
] | In this work, we investigate the quasinormal frequencies of a class of regular black hole solutions which generalize Bardeen and Hayward spacetimes. In particular, we analyze scalar, vector and gravitational perturbations of the black hole both with the semianalytic WKB method and their time-domain profiles. We analyze in detail the behavior of the spectrum depending on the parameter $p/q$ of the black hole, the quantum number of angular momentum and the $s$ number. In addition, we compare our results with the classical solution valid for $p = q = 1$. |
gr-qc/9503052 | Vivek Iyer | Vivek Iyer and Robert M. Wald | A comparison of Noether charge and Euclidean methods for Computing the
Entropy of Stationary Black Holes | 29 pages (double-spaced) latex | Phys.Rev. D52 (1995) 4430-4439 | 10.1103/PhysRevD.52.4430 | null | gr-qc hep-th | null | The entropy of stationary black holes has recently been calculated by a
number of different approaches. Here we compare the Noether charge approach
(defined for any diffeomorphism invariant Lagrangian theory) with various
Euclidean methods, specifically, (i) the microcanonical ensemble approach of
Brown and York, (ii) the closely related approach of Ba\~nados, Teitelboim, and
Zanelli which ultimately expresses black hole entropy in terms of the Hilbert
action surface term, (iii) another formula of Ba\~nados, Teitelboim and Zanelli
(also used by Susskind and Uglum) which views black hole entropy as conjugate
to a conical deficit angle, and (iv) the pair creation approach of Garfinkle,
Giddings, and Strominger. All of these approaches have a more restrictive
domain of applicability than the Noether charge approach. Specifically,
approaches (i) and (ii) appear to be restricted to a class of theories
satisfying certain properties listed in section 2; approach (iii) appears to
require the Lagrangian density to be linear in the curvature; and approach (iv)
requires the existence of suitable instanton solutions. However, we show that
within their domains of applicability, all of these approaches yield results in
agreement with the Noether charge approach. In the course of our analysis, we
generalize the definition of Brown and York's quasilocal energy to a much more
general class of diffeomorphism invariant, Lagrangian theories of gravity. In
an appendix, we show that in an arbitrary diffeomorphism invariant theory of
gravity, the ``volume term" in the ``off-shell" Hamiltonian associated with a
time evolution vector field $t^a$ always can be expressed as the spatial
integral of $t^a {\cal C}_a$, where ${\cal C}_a = 0$ are the constraints
associated with the diffeomorphism invariance.
| [
{
"created": "Mon, 27 Mar 1995 20:25:29 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Iyer",
"Vivek",
""
],
[
"Wald",
"Robert M.",
""
]
] | The entropy of stationary black holes has recently been calculated by a number of different approaches. Here we compare the Noether charge approach (defined for any diffeomorphism invariant Lagrangian theory) with various Euclidean methods, specifically, (i) the microcanonical ensemble approach of Brown and York, (ii) the closely related approach of Ba\~nados, Teitelboim, and Zanelli which ultimately expresses black hole entropy in terms of the Hilbert action surface term, (iii) another formula of Ba\~nados, Teitelboim and Zanelli (also used by Susskind and Uglum) which views black hole entropy as conjugate to a conical deficit angle, and (iv) the pair creation approach of Garfinkle, Giddings, and Strominger. All of these approaches have a more restrictive domain of applicability than the Noether charge approach. Specifically, approaches (i) and (ii) appear to be restricted to a class of theories satisfying certain properties listed in section 2; approach (iii) appears to require the Lagrangian density to be linear in the curvature; and approach (iv) requires the existence of suitable instanton solutions. However, we show that within their domains of applicability, all of these approaches yield results in agreement with the Noether charge approach. In the course of our analysis, we generalize the definition of Brown and York's quasilocal energy to a much more general class of diffeomorphism invariant, Lagrangian theories of gravity. In an appendix, we show that in an arbitrary diffeomorphism invariant theory of gravity, the ``volume term" in the ``off-shell" Hamiltonian associated with a time evolution vector field $t^a$ always can be expressed as the spatial integral of $t^a {\cal C}_a$, where ${\cal C}_a = 0$ are the constraints associated with the diffeomorphism invariance. |
1706.07764 | Federico Pasqualotto | Federico Pasqualotto | Nonlinear stability for the Maxwell-Born-Infeld system on a
Schwarzschild background | 116 pages, 5 figures | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we prove small data global existence for solutions to the
Maxwell-Born-Infeld (MBI) system on a fixed Schwarzschild background. This
system has appeared in the context of string theory and can be seen as a
nonlinear model problem for the stability of the background metric itself, due
to its tensorial and quasilinear nature. The MBI system models nonlinear
electromagnetism and does not display birefringence. The key element in our
proof lies in the observation that there exists a first-order differential
transformation which brings solutions of the spin $\pm 1$ Teukolsky equations,
satisfied by the extreme components of the field, into solutions of a "good"
equation (the Fackerell-Ipser Equation). This strategy was established in [F.
Pasqualotto, The spin $\pm 1$ Teukolsky equations and the Maxwell system on
Schwarzschild, Annales Henri Poincar\'e, 20(4):1263-1323, 2019,
arXiv:1612.07244] for the linear Maxwell field on Schwarzschild. We show that
analogous Fackerell-Ipser equations hold for the MBI system on a fixed
Schwarzschild background, which are however nonlinearly coupled. To essentially
decouple these right hand sides, we set up a bootstrap argument. We use the
$r^p$ method of Dafermos and Rodnianski in [M. Dafermos and I. Rodnianski, A
new physical-space approach to decay for the wave equation with applications to
black hole spacetimes, in XVIth International Congress on Mathematical Physics,
Pavel Exner ed., Prague 2009 pp. 421-433, 2009, arXiv:0910.4957] in order to
deduce decay of some null components, and we infer decay for the remaining
quantities by integrating the MBI system as transport equations.
| [
{
"created": "Fri, 23 Jun 2017 16:09:43 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Jul 2019 16:27:53 GMT",
"version": "v2"
}
] | 2019-07-16 | [
[
"Pasqualotto",
"Federico",
""
]
] | In this paper we prove small data global existence for solutions to the Maxwell-Born-Infeld (MBI) system on a fixed Schwarzschild background. This system has appeared in the context of string theory and can be seen as a nonlinear model problem for the stability of the background metric itself, due to its tensorial and quasilinear nature. The MBI system models nonlinear electromagnetism and does not display birefringence. The key element in our proof lies in the observation that there exists a first-order differential transformation which brings solutions of the spin $\pm 1$ Teukolsky equations, satisfied by the extreme components of the field, into solutions of a "good" equation (the Fackerell-Ipser Equation). This strategy was established in [F. Pasqualotto, The spin $\pm 1$ Teukolsky equations and the Maxwell system on Schwarzschild, Annales Henri Poincar\'e, 20(4):1263-1323, 2019, arXiv:1612.07244] for the linear Maxwell field on Schwarzschild. We show that analogous Fackerell-Ipser equations hold for the MBI system on a fixed Schwarzschild background, which are however nonlinearly coupled. To essentially decouple these right hand sides, we set up a bootstrap argument. We use the $r^p$ method of Dafermos and Rodnianski in [M. Dafermos and I. Rodnianski, A new physical-space approach to decay for the wave equation with applications to black hole spacetimes, in XVIth International Congress on Mathematical Physics, Pavel Exner ed., Prague 2009 pp. 421-433, 2009, arXiv:0910.4957] in order to deduce decay of some null components, and we infer decay for the remaining quantities by integrating the MBI system as transport equations. |
2103.11235 | Carlos Maldonado Salazar | Carlos Maldonado and Fernando Mendez | Bi-metric Universe with Matter | null | Phys. Rev. D 103, 123505 (2021) | 10.1103/PhysRevD.103.123505 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the early stage of evolution of a universe with two scale factors
proposed in [1] when matter is present. The scale factors describe two causally
disconnected patches of the universe interacting trough a non-trivial Poisson
bracket structure in the momentum sector characterized by one parameter \kappa.
We studied two scenarios in which one of the patches is always filled with
relativistic matter while the other contains relativistic matter in one case,
and non-relativistic matter in the second case. By solving numerically the set
of equations governing the dynamics, we found that the energy content of one
sector drains to the other and from here it is possible to constraint the
deformation parameter \kappa by imposing that the decay of the energy density
happens, at most, at the Big Bang Nucleosynthesis temperature in order to
return to the usual behavior of radiation. The relation with Non Standard
Cosmologies is also addressed.
| [
{
"created": "Sat, 20 Mar 2021 20:07:20 GMT",
"version": "v1"
}
] | 2021-06-09 | [
[
"Maldonado",
"Carlos",
""
],
[
"Mendez",
"Fernando",
""
]
] | We analyze the early stage of evolution of a universe with two scale factors proposed in [1] when matter is present. The scale factors describe two causally disconnected patches of the universe interacting trough a non-trivial Poisson bracket structure in the momentum sector characterized by one parameter \kappa. We studied two scenarios in which one of the patches is always filled with relativistic matter while the other contains relativistic matter in one case, and non-relativistic matter in the second case. By solving numerically the set of equations governing the dynamics, we found that the energy content of one sector drains to the other and from here it is possible to constraint the deformation parameter \kappa by imposing that the decay of the energy density happens, at most, at the Big Bang Nucleosynthesis temperature in order to return to the usual behavior of radiation. The relation with Non Standard Cosmologies is also addressed. |
2311.07279 | Tieguang Zi | Tieguang Zi, Peng-Cheng Li | Gravitational waves from extreme-mass-ratio inspirals in the
semiclassical gravity spacetime | 11 pages,7 figures,1 table | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | More recently, Fernandes \cite{Fernandes:2023vux} discovered analytic
stationary and axially-symmetric black hole solutions within semiclassical
gravity, driven by the trace anomaly. The study unveils some distinctive
features of these solutions. In this paper, we compute the gravitational waves
emitted from the \ac{EMRI} around these quantum-corrected rotating black holes
using the kludge approximate method. Firstly, we derive the orbital energy,
angular momentum and fundamental frequencies for orbits on the equatorial
plane. We find that, for the gravitational radiation described by quadrupole
formulas, the contribution from the trace anomaly only appears at higher-order
terms in the energy flux when compared with the standard Kerr case. Therefore,
we can compute the EMRI waveforms from the quantum-corrected rotating black
hole using the Kerr fluxes. We assess the differences between the EMRI
waveforms from rotating black holes with and without the trace anomaly by
calculating the dephasing and mismatch. Our results demonstrate that
space-borne gravitational wave detectors can distinguish the EMRI waveform from
the quantum-corrected black holes with a fractional coupling constant of $\sim
10^{-3}$ within one year observation. Finally, we compute the constraint on the
coupling constant using the Fisher information matrix method and find that the
potential constraint on the coupling constant by LISA can be within the error
$\sim 10^{-4}$ in suitable scenarios.
| [
{
"created": "Mon, 13 Nov 2023 12:23:02 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Nov 2023 06:54:54 GMT",
"version": "v2"
}
] | 2023-11-30 | [
[
"Zi",
"Tieguang",
""
],
[
"Li",
"Peng-Cheng",
""
]
] | More recently, Fernandes \cite{Fernandes:2023vux} discovered analytic stationary and axially-symmetric black hole solutions within semiclassical gravity, driven by the trace anomaly. The study unveils some distinctive features of these solutions. In this paper, we compute the gravitational waves emitted from the \ac{EMRI} around these quantum-corrected rotating black holes using the kludge approximate method. Firstly, we derive the orbital energy, angular momentum and fundamental frequencies for orbits on the equatorial plane. We find that, for the gravitational radiation described by quadrupole formulas, the contribution from the trace anomaly only appears at higher-order terms in the energy flux when compared with the standard Kerr case. Therefore, we can compute the EMRI waveforms from the quantum-corrected rotating black hole using the Kerr fluxes. We assess the differences between the EMRI waveforms from rotating black holes with and without the trace anomaly by calculating the dephasing and mismatch. Our results demonstrate that space-borne gravitational wave detectors can distinguish the EMRI waveform from the quantum-corrected black holes with a fractional coupling constant of $\sim 10^{-3}$ within one year observation. Finally, we compute the constraint on the coupling constant using the Fisher information matrix method and find that the potential constraint on the coupling constant by LISA can be within the error $\sim 10^{-4}$ in suitable scenarios. |
2111.10511 | Sanjay Mandal | Sanjay Mandal, P.K. Sahoo | Constraint on the equation of state parameter ($\omega$) in
non-minimally coupled $f(Q)$ gravity | PLB published version | Phys. Lett. B, vol 823 (2021) 136786 | 10.1016/j.physletb.2021.136786 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We study observational constraints on the modified symmetric teleparallel
gravity, the non-metricity $f(Q)$ gravity, which reproduces background
expansion of the universe. For this purpose, we use Hubble measurements,
Baryonic Acoustic Oscillations (BAO), 1048 Pantheon supernovae type Ia data
sample which integrate SuperNova Legacy Survey (SNLS), Sloan Digital Sky Survey
(SDSS), Hubble Space Telescope (HST) survey, Panoramic Survey Telescope and
Rapid Response System (Pan-STARRS1). We confront our cosmological model against
observational samples to set constraints on the parameters using Markov Chain
Monte Carlo (MCMC) methods. We find the equation of state parameter
$\omega=-0.853^{+0.015}_{-0.020}$ and $\omega= -0.796^{+0.049}_{-0.074}$ for
Hubble and Pantheon samples, respectively. As a result, the $f(Q)$ model shows
the quintessence behavior and deviates from $\Lambda$CDM.
| [
{
"created": "Sat, 20 Nov 2021 03:55:32 GMT",
"version": "v1"
}
] | 2021-11-25 | [
[
"Mandal",
"Sanjay",
""
],
[
"Sahoo",
"P. K.",
""
]
] | We study observational constraints on the modified symmetric teleparallel gravity, the non-metricity $f(Q)$ gravity, which reproduces background expansion of the universe. For this purpose, we use Hubble measurements, Baryonic Acoustic Oscillations (BAO), 1048 Pantheon supernovae type Ia data sample which integrate SuperNova Legacy Survey (SNLS), Sloan Digital Sky Survey (SDSS), Hubble Space Telescope (HST) survey, Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1). We confront our cosmological model against observational samples to set constraints on the parameters using Markov Chain Monte Carlo (MCMC) methods. We find the equation of state parameter $\omega=-0.853^{+0.015}_{-0.020}$ and $\omega= -0.796^{+0.049}_{-0.074}$ for Hubble and Pantheon samples, respectively. As a result, the $f(Q)$ model shows the quintessence behavior and deviates from $\Lambda$CDM. |
2105.14679 | Philip D. Mannheim | Philip D. Mannheim | Structure of conformal gravity in the presence of a scale breaking
scalar field | 20 pages, 1 figure. Revised and shortened | null | 10.1007/s10714-022-02982-9 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the structure of conformal gravity in the presence of a c-number,
conformally coupled, long range, macroscopic scalar field. And in the static,
spherically symmetric case discuss two classes of exact exterior solutions, in
one of which the scalar field has a constant value and in the other, which is
due to Brihaye and Verbin, it has a radial dependence. In light of these two
solutions Horne and then Hobson and Lasenby raised the concern that the fitting
of conformal gravity to galactic rotation curves had been misapplied and thus
called the successful fitting of the conformal theory into question. We show
that the analysis of Brihaye and Verbin is not actually general, but is
nonetheless valid in the particular case that they studied. For the analyses of
Horne and of Hobson and Lasenby we show that this macroscopic scalar field is
not related to the mass generation that is required in a conformal theory.
Rather, not just in conformal gravity, but also in standard Einstein gravity,
the presence of such a long range scalar field would lead to test particles
whose masses would be of the same order as the masses of the galaxies around
which they orbit. Since particle masses are not at all of this form, such
macroscopic fields cannot be responsible for mass generation; and the existence
of any such mass-generating scalar fields can be excluded, consistent with
there actually being no known massless scalar particles in nature. Instead,
mass generation has to be due to c-number vacuum expectation values of q-number
fields. Such expectation values are microscopic not macroscopic and only vary
within particle interiors, giving particles an extended, baglike structure, as
needed for localization in a conformal theory. And being purely internal they
have no effect on galactic orbits, to thus leave the good conformal gravity
fitting to galactic rotation curves intact.
| [
{
"created": "Mon, 31 May 2021 02:40:59 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Nov 2021 00:56:38 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Jan 2022 16:04:24 GMT",
"version": "v3"
}
] | 2022-09-14 | [
[
"Mannheim",
"Philip D.",
""
]
] | We revisit the structure of conformal gravity in the presence of a c-number, conformally coupled, long range, macroscopic scalar field. And in the static, spherically symmetric case discuss two classes of exact exterior solutions, in one of which the scalar field has a constant value and in the other, which is due to Brihaye and Verbin, it has a radial dependence. In light of these two solutions Horne and then Hobson and Lasenby raised the concern that the fitting of conformal gravity to galactic rotation curves had been misapplied and thus called the successful fitting of the conformal theory into question. We show that the analysis of Brihaye and Verbin is not actually general, but is nonetheless valid in the particular case that they studied. For the analyses of Horne and of Hobson and Lasenby we show that this macroscopic scalar field is not related to the mass generation that is required in a conformal theory. Rather, not just in conformal gravity, but also in standard Einstein gravity, the presence of such a long range scalar field would lead to test particles whose masses would be of the same order as the masses of the galaxies around which they orbit. Since particle masses are not at all of this form, such macroscopic fields cannot be responsible for mass generation; and the existence of any such mass-generating scalar fields can be excluded, consistent with there actually being no known massless scalar particles in nature. Instead, mass generation has to be due to c-number vacuum expectation values of q-number fields. Such expectation values are microscopic not macroscopic and only vary within particle interiors, giving particles an extended, baglike structure, as needed for localization in a conformal theory. And being purely internal they have no effect on galactic orbits, to thus leave the good conformal gravity fitting to galactic rotation curves intact. |
1801.07289 | Jarrod Williams | J. A. Valiente Kroon and J. L. Williams | A perturbative approach to the construction of initial data on compact
manifolds | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the implementation, to the case of compact manifolds, of the
perturbative method of Friedrich-Butscher for the construction of solutions to
the vaccum Einstein constraint equations. This method is of a perturbative
nature and exploits the properties of the extended constraint equations ---a
larger system of equations whose solutions imply a solution to the Einstein
constraints. The method is applied to the construction of nonlinear
perturbations of constant mean curvature initial data of constant negative
sectional curvature. We prove the existence of a neighbourhood of solutions to
the constraint equations around such initial data, with particular components
of the extrinsic curvature and electric/magnetic parts of the spacetime Weyl
curvature prescribed as free data. The space of such free data is parametrised
explicitly.
| [
{
"created": "Mon, 22 Jan 2018 19:37:32 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jun 2018 22:04:59 GMT",
"version": "v2"
},
{
"created": "Sat, 15 Jun 2019 10:49:29 GMT",
"version": "v3"
}
] | 2019-06-18 | [
[
"Kroon",
"J. A. Valiente",
""
],
[
"Williams",
"J. L.",
""
]
] | We discuss the implementation, to the case of compact manifolds, of the perturbative method of Friedrich-Butscher for the construction of solutions to the vaccum Einstein constraint equations. This method is of a perturbative nature and exploits the properties of the extended constraint equations ---a larger system of equations whose solutions imply a solution to the Einstein constraints. The method is applied to the construction of nonlinear perturbations of constant mean curvature initial data of constant negative sectional curvature. We prove the existence of a neighbourhood of solutions to the constraint equations around such initial data, with particular components of the extrinsic curvature and electric/magnetic parts of the spacetime Weyl curvature prescribed as free data. The space of such free data is parametrised explicitly. |
1910.07506 | Francisco Jos\'e Maldonado Torralba | Jose Beltr\'an Jim\'enez and Francisco Jos\'e Maldonado Torralba | Revisiting the Stability of Quadratic Poincar\'e Gauge Gravity | 25 pages, 1 figure. More insight on the bi-scalar theory has been
added, including its possible extensions and the coupling with fermions. A
clarifying footnote on the Holst term has been introduced. Extended
discussion. It matches the version published in EPJC | Eur.Phys.J.C 80 (2020) 7, 611 | 10.1140/epjc/s10052-020-8163-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Poincar\'e gauge theories provide an approach to gravity based on the gauging
of the Poincar\'e group, whose homogeneous part generates curvature while the
translational sector gives rise to torsion. In this note we revisit the
stability of the widely studied quadratic theories within this framework. We
analyse the presence of ghosts without fixing any background by obtaining the
relevant interactions in an exact post-Riemannian expansion. We find that the
axial sector of the theory exhibits ghostly couplings to the graviton sector
that render the theory unstable. Remarkably, imposing the absence of these
pathological couplings results in a theory where either the axial sector or the
torsion trace becomes a ghost. We conclude that imposing ghost-freedom
generically leads to a non-dynamical torsion. We analyse however two special
choices of parameters that allow a dynamical scalar in the torsion and obtain
the corresponding effective action where the dynamics of the scalar is
apparent. These special cases are shown to be equivalent to a generalised
Brans-Dicke theory and a Holst Lagrangian with a dynamical Barbero-Immirzi
pseudoscalar field respectively. The two sectors can co-exist giving a
bi-scalar theory. Finally, we discuss how the ghost nature of the vector sector
can be avoided by including additional dimension four operators.
| [
{
"created": "Wed, 16 Oct 2019 17:48:15 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Dec 2020 10:24:41 GMT",
"version": "v2"
}
] | 2020-12-16 | [
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Torralba",
"Francisco José Maldonado",
""
]
] | Poincar\'e gauge theories provide an approach to gravity based on the gauging of the Poincar\'e group, whose homogeneous part generates curvature while the translational sector gives rise to torsion. In this note we revisit the stability of the widely studied quadratic theories within this framework. We analyse the presence of ghosts without fixing any background by obtaining the relevant interactions in an exact post-Riemannian expansion. We find that the axial sector of the theory exhibits ghostly couplings to the graviton sector that render the theory unstable. Remarkably, imposing the absence of these pathological couplings results in a theory where either the axial sector or the torsion trace becomes a ghost. We conclude that imposing ghost-freedom generically leads to a non-dynamical torsion. We analyse however two special choices of parameters that allow a dynamical scalar in the torsion and obtain the corresponding effective action where the dynamics of the scalar is apparent. These special cases are shown to be equivalent to a generalised Brans-Dicke theory and a Holst Lagrangian with a dynamical Barbero-Immirzi pseudoscalar field respectively. The two sectors can co-exist giving a bi-scalar theory. Finally, we discuss how the ghost nature of the vector sector can be avoided by including additional dimension four operators. |
2003.13434 | Sebasti\'an Bahamonde Dr | Sebastian Bahamonde, Mihai Marciu, Sergei D. Odintsov, Prabir Rudra | String-inspired Teleparallel Cosmology | 18 pages. Matches published version in NPB | Nucl.Phys. B 962 (2020), 115238 | 10.1016/j.nuclphysb.2020.115238 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper represents an attempt for a very generic string inspired
theory of gravitation, based on a stringy action in the teleparallel gravity
which includes a specific functional which depends on the scalar field and its
kinetic energy, as well as the torsion and boundary terms, embedding also
possible effects from the teleparallel Gauss--Bonnet invariants. We focus our
study on FLRW cosmology. After we deduce the cosmological equations for the
associated generic theory of gravitation, we focus on string inspired couplings
which are studied by considering different analytical techniques. The first
analytical technique is based on the linear stability theory, by introducing
proper dimensionless variables which enables us to study the structure of the
phase space and the associated physical effects. In this case, we have obtained
different cosmological solutions which correspond to matter and dark energy
dominated solutions, achieving a possible transition between matter and dark
energy dominated epochs. For each type of cosmological solutions, we have
discussed the corresponding physical features, attaining viable constraints for
the coupling constants due to dynamical effects. The dynamical study of the
physical features included also a numerical analysis by fine--tuning the
initial conditions deep into the matter era, obtaining possible trajectories
for the effective equation of state for specific coupling functions.
| [
{
"created": "Mon, 30 Mar 2020 13:01:00 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Mar 2020 15:47:36 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Nov 2020 22:44:31 GMT",
"version": "v3"
}
] | 2020-11-26 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Marciu",
"Mihai",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Rudra",
"Prabir",
""
]
] | The present paper represents an attempt for a very generic string inspired theory of gravitation, based on a stringy action in the teleparallel gravity which includes a specific functional which depends on the scalar field and its kinetic energy, as well as the torsion and boundary terms, embedding also possible effects from the teleparallel Gauss--Bonnet invariants. We focus our study on FLRW cosmology. After we deduce the cosmological equations for the associated generic theory of gravitation, we focus on string inspired couplings which are studied by considering different analytical techniques. The first analytical technique is based on the linear stability theory, by introducing proper dimensionless variables which enables us to study the structure of the phase space and the associated physical effects. In this case, we have obtained different cosmological solutions which correspond to matter and dark energy dominated solutions, achieving a possible transition between matter and dark energy dominated epochs. For each type of cosmological solutions, we have discussed the corresponding physical features, attaining viable constraints for the coupling constants due to dynamical effects. The dynamical study of the physical features included also a numerical analysis by fine--tuning the initial conditions deep into the matter era, obtaining possible trajectories for the effective equation of state for specific coupling functions. |
2307.11051 | Alvaro Duenas-Vidal | \'Alvaro Duenas-Vidal, Jorge Segovia | Quantum dynamics for massless particles in Brinkmann spacetimes | 29 pages, 2 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In Classical Dynamics, Eisenhart lift connects the dynamics of null geodesics
in a Brinkmann spacetime with a continuous family of Hamiltonian systems by
means of a suitable projection. In this work we explore the possibility of
building a model for quantum dynamics of massless particles propagating inside
a Brinkmann spacetime from the Einsenhart lift. As a result, we describe
spatial tunneling between regions classically disconnected for certain class of
null geodesics because of curvature. Also we describe entangled states arising
from observers who have a limited access to the whole Brinkmann space. Finally
we explore the possibility to find a quantum field theory behind these quantum
phenomena.
| [
{
"created": "Thu, 20 Jul 2023 17:32:02 GMT",
"version": "v1"
}
] | 2023-07-21 | [
[
"Duenas-Vidal",
"Álvaro",
""
],
[
"Segovia",
"Jorge",
""
]
] | In Classical Dynamics, Eisenhart lift connects the dynamics of null geodesics in a Brinkmann spacetime with a continuous family of Hamiltonian systems by means of a suitable projection. In this work we explore the possibility of building a model for quantum dynamics of massless particles propagating inside a Brinkmann spacetime from the Einsenhart lift. As a result, we describe spatial tunneling between regions classically disconnected for certain class of null geodesics because of curvature. Also we describe entangled states arising from observers who have a limited access to the whole Brinkmann space. Finally we explore the possibility to find a quantum field theory behind these quantum phenomena. |
1004.3035 | Sanjay Jhingan | S. Jhingan, I. H. Dwivedi and S. Barve | Depletion of energy from Naked Singular regions during gravitational
collapse | 5 pages, 1 EPS figure, revised version accepted for publication in
PRD | Phys.Rev.D84:024001,2011 | 10.1103/PhysRevD.84.024001 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A distinguishable and observable physical property of Naked Singular Regions
of the spacetime formed during a gravitational collapse has important
implications for both experimental and theoretical relativity. We examine here
whether energy can escape physically from naked singular regions to reach
either a local or a distant observer within the framework of general
relativity. We find that in case of imploding null dust collapse scenarios
field outgoing singular null geodesics including the cauchy horizon can be
immersed between two Vaidya spacetimes as null boundary layers with non
vanishing positive energy density. Thus energy can transported from the naked
singularity to either a local or a distant observer. And example illustrating
that similar considerations can be applied to dust models is given.
| [
{
"created": "Sun, 18 Apr 2010 16:02:20 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2011 16:43:33 GMT",
"version": "v2"
}
] | 2011-08-08 | [
[
"Jhingan",
"S.",
""
],
[
"Dwivedi",
"I. H.",
""
],
[
"Barve",
"S.",
""
]
] | A distinguishable and observable physical property of Naked Singular Regions of the spacetime formed during a gravitational collapse has important implications for both experimental and theoretical relativity. We examine here whether energy can escape physically from naked singular regions to reach either a local or a distant observer within the framework of general relativity. We find that in case of imploding null dust collapse scenarios field outgoing singular null geodesics including the cauchy horizon can be immersed between two Vaidya spacetimes as null boundary layers with non vanishing positive energy density. Thus energy can transported from the naked singularity to either a local or a distant observer. And example illustrating that similar considerations can be applied to dust models is given. |
2311.14569 | Vesselin G. Gueorguiev | Vesselin G. Gueorguiev and Andre Maeder | The Scale Invariant Vacuum Paradigm: Main Results and Current Progress
Review (Part II) | 27 pages, 7 figures, 2 tables | Symmetry 2024, 16 (6), 657 | 10.3390/sym16060657 | null | gr-qc astro-ph.CO astro-ph.GA physics.plasm-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a summary of the main results within the Scale Invariant Vacuum
(SIV) paradigm based on the Weyl Integrable Geometry (WIG) as an extension to
the standard Einstein General Relativity (EGR). After a brief review of the
mathematical framework, where we also highlight the connection between the
weak-field SIV equations and the notion of un-proper time parametrization
within the reparametrization paradigm, we continue with the main results
related to early Universe; that is, applications to inflation, Big Bang
Nucleosynthesis, and the growth of the density fluctuations within the SIV. In
the late time Universe the applications of the SIV paradigm are related to
scale-invariant dynamics of galaxies, MOND, dark matter, and the dwarf
spheroidals where one can find MOND to be a peculiar case of the SIV theory.
Finally, within the recent time epoch, we highlight that some of the change in
the length-of-the-day (LOD), about 0.92 cm/yr, can be accounted for by SIV
effects in the Earth-Moon system.
| [
{
"created": "Fri, 24 Nov 2023 15:58:30 GMT",
"version": "v1"
}
] | 2024-06-03 | [
[
"Gueorguiev",
"Vesselin G.",
""
],
[
"Maeder",
"Andre",
""
]
] | We present a summary of the main results within the Scale Invariant Vacuum (SIV) paradigm based on the Weyl Integrable Geometry (WIG) as an extension to the standard Einstein General Relativity (EGR). After a brief review of the mathematical framework, where we also highlight the connection between the weak-field SIV equations and the notion of un-proper time parametrization within the reparametrization paradigm, we continue with the main results related to early Universe; that is, applications to inflation, Big Bang Nucleosynthesis, and the growth of the density fluctuations within the SIV. In the late time Universe the applications of the SIV paradigm are related to scale-invariant dynamics of galaxies, MOND, dark matter, and the dwarf spheroidals where one can find MOND to be a peculiar case of the SIV theory. Finally, within the recent time epoch, we highlight that some of the change in the length-of-the-day (LOD), about 0.92 cm/yr, can be accounted for by SIV effects in the Earth-Moon system. |
2302.12352 | Jose Miguel Ladino | Jose Miguel Ladino, Carlos Andr\'es del Valle and Eduard Larra\~naga | Motion of Spinning Particles around Black Holes | 14 pages, 2 figures | A Guide to Black Holes, ed. by Kenath Arun (Nova Science
Publishers, New York, 2022), pp. 79-96 | 10.52305/JOLT6397 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The motion of spinning particles around compact objects, for example a
rotating stellar object moving around a supermassive black hole, is described
by differential equations that are, in general, non-integrable. In this work,
we present a computational code that integrates the equations of motion of a
spinning particle moving in the equatorial plane of a spherically symmetric
spacetime and gives a visual representation of its trajectory. This code is
open source, freely available and modular, so that users may extend its
application not only to the Schwarzschild metric, but also to other
backgrounds.
| [
{
"created": "Thu, 23 Feb 2023 22:15:39 GMT",
"version": "v1"
}
] | 2023-02-27 | [
[
"Ladino",
"Jose Miguel",
""
],
[
"del Valle",
"Carlos Andrés",
""
],
[
"Larrañaga",
"Eduard",
""
]
] | The motion of spinning particles around compact objects, for example a rotating stellar object moving around a supermassive black hole, is described by differential equations that are, in general, non-integrable. In this work, we present a computational code that integrates the equations of motion of a spinning particle moving in the equatorial plane of a spherically symmetric spacetime and gives a visual representation of its trajectory. This code is open source, freely available and modular, so that users may extend its application not only to the Schwarzschild metric, but also to other backgrounds. |
2109.02947 | Spiros Cotsakis | Spiros Cotsakis | Primordial synchronization of Mixmaster spatial points | 6 pages, uses special world scientific style; invited talk in the
16th Marcel-Grossmann virtual Conference, parallel session EU2 | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review recent work on the possibility of primordial synchronization of
different Mixmaster regions in generic inhomogeneous spacetime. It is shown
that inhomogeneous domains undergoing chaotic oscillations may synchronize
themselves exponentially fast and proceed in perfect symphony asymptotically in
the past direction. Implications of this result for the structure and evolution
of an early phase of the universe are briefly discussed.
| [
{
"created": "Tue, 7 Sep 2021 09:03:38 GMT",
"version": "v1"
}
] | 2021-09-08 | [
[
"Cotsakis",
"Spiros",
""
]
] | We review recent work on the possibility of primordial synchronization of different Mixmaster regions in generic inhomogeneous spacetime. It is shown that inhomogeneous domains undergoing chaotic oscillations may synchronize themselves exponentially fast and proceed in perfect symphony asymptotically in the past direction. Implications of this result for the structure and evolution of an early phase of the universe are briefly discussed. |
gr-qc/9403024 | Luis Oxman | M. Kruczenski, L.E. Oxman and M. Zaldarriaga | Large Squeezing Behavior of Cosmological Entropy Generation | 19 pages (LaTeX) | Class.Quant.Grav.11:2317-2330,1994 | 10.1088/0264-9381/11/9/013 | null | gr-qc | null | We consider the generation of entropy when particle pairs are created at a
cosmological level. Making a reduction via the particle number basis, we
compute the classical limit for the entropy generation due to the evolution of
the matter field fluctuations (squeeze transformation), obtaining that it is
linear in the squeeze parameter for a general class of initial states. We also
discuss the dependence of the generated entropy on the coarse graining
criteria.
| [
{
"created": "Fri, 11 Mar 1994 21:40:06 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Kruczenski",
"M.",
""
],
[
"Oxman",
"L. E.",
""
],
[
"Zaldarriaga",
"M.",
""
]
] | We consider the generation of entropy when particle pairs are created at a cosmological level. Making a reduction via the particle number basis, we compute the classical limit for the entropy generation due to the evolution of the matter field fluctuations (squeeze transformation), obtaining that it is linear in the squeeze parameter for a general class of initial states. We also discuss the dependence of the generated entropy on the coarse graining criteria. |
2301.02930 | Dongxue Qu | Muxin Han, Hongguang Liu, Dongxue Qu | Complex critical points in Lorentzian spinfoam quantum gravity:
4-simplex amplitude and effective dynamics on double-$\Delta_3$ complex | 29 pages, 15 figures | null | 10.1103/PhysRevD.108.026010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The complex critical points are analyzed in the 4-dimensional Lorentzian
Engle-Pereira-Rovelli-Livine (EPRL) spinfoam model in the large-$j$ regime. For
the 4-simplex amplitude, taking into account the complex critical point
generalizes the large-$j$ asymptotics to the situation with non-Regge boundary
data and relates to the twisted geometry. For generic simplicial complexes, we
present a general procedure to derive the effective theory of Regge geometries
from the spinfoam amplitude in the large-$j$ regime by using the complex
critical points. The effective theory is analyzed in detail for the spinfoam
amplitude on the double-$\Delta_3$ simplicial complex. We numerically compute
the effective action and the solution of the effective equation of motion on
the double-$\Delta_3$ complex. The effective theory reproduces the classical
Regge gravity when the Barbero-Immirzi parameter $\gamma$ is small.
| [
{
"created": "Sat, 7 Jan 2023 20:16:37 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Feb 2023 17:11:53 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Jul 2023 03:24:34 GMT",
"version": "v3"
}
] | 2023-08-02 | [
[
"Han",
"Muxin",
""
],
[
"Liu",
"Hongguang",
""
],
[
"Qu",
"Dongxue",
""
]
] | The complex critical points are analyzed in the 4-dimensional Lorentzian Engle-Pereira-Rovelli-Livine (EPRL) spinfoam model in the large-$j$ regime. For the 4-simplex amplitude, taking into account the complex critical point generalizes the large-$j$ asymptotics to the situation with non-Regge boundary data and relates to the twisted geometry. For generic simplicial complexes, we present a general procedure to derive the effective theory of Regge geometries from the spinfoam amplitude in the large-$j$ regime by using the complex critical points. The effective theory is analyzed in detail for the spinfoam amplitude on the double-$\Delta_3$ simplicial complex. We numerically compute the effective action and the solution of the effective equation of motion on the double-$\Delta_3$ complex. The effective theory reproduces the classical Regge gravity when the Barbero-Immirzi parameter $\gamma$ is small. |
2102.11547 | Rainer Verch | Fiona Kurpicz, Nicola Pinamonti, Rainer Verch | Temperature and entropy-area relation of quantum matter near spherically
symmetric outer trapping horizons | latex2e, 44 pages, 1 Figure. v2: Typos removed, minor errors
corrected, references added. This version matches the journal publication in
Lett. Math. Phys. up to formatting | Letters in Mathematical Physics 111 (2021) No 110 (open access) | 10.1007/s11005-021-01445-7 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We consider spherically symmetric spacetimes with an outer trapping horizon.
Such spacetimes are generalizations of spherically symmetric black hole
spacetimes where the central mass can vary with time, like in black hole
collapse or black hole evaporation. These spacetimes possess in general no
timelike Killing vector field, but admit a Kodama vector field which provides a
replacement. Spherically symmetric spacelike cross-sections of the outer
trapping horizon define in- and outgoing lightlike congruences. We investigate
a scaling limit of Hadamard 2-point functions of a quantum field on the
spacetime onto the ingoing lightlike congruence. The scaling limit 2-point
function has a universal form and a thermal spectrum with respect to the
time-parameter of the Kodama flow, where the inverse temperature is related to
the surface gravity of the horizon cross-section in the same way as in the
Hawking effect for an asymptotically static black hole. Similarly, the
tunneling probability in the scaling limit between in- and outgoing Fourier
modes with respect to the the Kodama time shows a thermal distribution with the
same inverse temperature, determined by the surface gravity. This can be seen
as a local counterpart of the Hawking effect for a dynamical horizon in the
scaling limit. The scaling limit 2-point function as well as the 2-point
functions of coherent states of the scaling-limit-theory have relative
entropies behaving proportional to the cross-sectional horizon area. Thereby,
we establish a local counterpart, and microscopic interpretation in the setting
of quantum field theory on curved spacetimes, of the dynamical laws of outer
trapping horizons, derived by Hayward and others in generalizing the laws of
black hole dynamics originally shown for stationary black holes by Bardeen,
Carter and Hawking. (Extended abstract in the article.)
| [
{
"created": "Tue, 23 Feb 2021 08:30:10 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Aug 2021 15:55:19 GMT",
"version": "v2"
}
] | 2021-08-17 | [
[
"Kurpicz",
"Fiona",
""
],
[
"Pinamonti",
"Nicola",
""
],
[
"Verch",
"Rainer",
""
]
] | We consider spherically symmetric spacetimes with an outer trapping horizon. Such spacetimes are generalizations of spherically symmetric black hole spacetimes where the central mass can vary with time, like in black hole collapse or black hole evaporation. These spacetimes possess in general no timelike Killing vector field, but admit a Kodama vector field which provides a replacement. Spherically symmetric spacelike cross-sections of the outer trapping horizon define in- and outgoing lightlike congruences. We investigate a scaling limit of Hadamard 2-point functions of a quantum field on the spacetime onto the ingoing lightlike congruence. The scaling limit 2-point function has a universal form and a thermal spectrum with respect to the time-parameter of the Kodama flow, where the inverse temperature is related to the surface gravity of the horizon cross-section in the same way as in the Hawking effect for an asymptotically static black hole. Similarly, the tunneling probability in the scaling limit between in- and outgoing Fourier modes with respect to the the Kodama time shows a thermal distribution with the same inverse temperature, determined by the surface gravity. This can be seen as a local counterpart of the Hawking effect for a dynamical horizon in the scaling limit. The scaling limit 2-point function as well as the 2-point functions of coherent states of the scaling-limit-theory have relative entropies behaving proportional to the cross-sectional horizon area. Thereby, we establish a local counterpart, and microscopic interpretation in the setting of quantum field theory on curved spacetimes, of the dynamical laws of outer trapping horizons, derived by Hayward and others in generalizing the laws of black hole dynamics originally shown for stationary black holes by Bardeen, Carter and Hawking. (Extended abstract in the article.) |
1201.1590 | Jan Ambjorn | J. Ambjorn, A. T. Goerlich, J. Jurkiewicz and H.-G. Zhang | Pseudo-topological transitions in 2D gravity models coupled to massless
scalar fields | 19 pages, many figures | null | 10.1016/j.nuclphysb.2012.05.024 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the geometries generated by two-dimensional causal dynamical
triangulations (CDT) coupled to $d$ massless scalar fields. Using methods
similar to those used to study four-dimensional CDT we show that there exists a
$c=1$ "barrier", analogous to the $c=1$ barrier encountered in non-critical
string theory, only the CDT transition is easier to be detected numerically.
For $d\leq 1$ we observe time-translation invariance and geometries entirely
governed by quantum fluctuations around the uniform toroidal topology put in by
hand. For $d>1$ the effective average geometry is no longer toroidal but
"semiclassical" and spherical with Hausdorff dimension $d_H = 3$. In the $d>1$
sector we study the time dependence of the semiclassical spatial volume
distribution and show that the observed behavior is described an effective
mini-superspace action analogous to the actions found in the de Sitter phase of
three- and four-dimensional pure CDT simulations and in the three-dimensional
CDT-like Ho\v{r}ava-Lifshitz models.
| [
{
"created": "Sat, 7 Jan 2012 23:50:01 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Ambjorn",
"J.",
""
],
[
"Goerlich",
"A. T.",
""
],
[
"Jurkiewicz",
"J.",
""
],
[
"Zhang",
"H. -G.",
""
]
] | We study the geometries generated by two-dimensional causal dynamical triangulations (CDT) coupled to $d$ massless scalar fields. Using methods similar to those used to study four-dimensional CDT we show that there exists a $c=1$ "barrier", analogous to the $c=1$ barrier encountered in non-critical string theory, only the CDT transition is easier to be detected numerically. For $d\leq 1$ we observe time-translation invariance and geometries entirely governed by quantum fluctuations around the uniform toroidal topology put in by hand. For $d>1$ the effective average geometry is no longer toroidal but "semiclassical" and spherical with Hausdorff dimension $d_H = 3$. In the $d>1$ sector we study the time dependence of the semiclassical spatial volume distribution and show that the observed behavior is described an effective mini-superspace action analogous to the actions found in the de Sitter phase of three- and four-dimensional pure CDT simulations and in the three-dimensional CDT-like Ho\v{r}ava-Lifshitz models. |
1911.00372 | Hemwati Nandan | Prateek Sharma, Hemwati Nandan, Radouane Gannouji, Rashmi Uniyal and
Amare Abebe | Deflection of Light by a Rotating Black Hole Surrounded by
"Quintessence" | null | International Journal of Modern Physics A (2020) 2050155 | 10.1142/S0217751X20501559 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a detailed analysis of a rotating black hole surrounded by
"quintessence". This solution represents a fluid with a constant equation of
state, $w$, which can for example describe an effective warm dark matter fluid
around a black hole. We clarify the conditions for the existence of such a
solution and study its structure by analyzing the existence of horizons as well
as the extremal case. We show that the deflection angle produced by the black
hole depends on the parameters $(c,w)$ which need to obey the condition $cw<0$
because of the weak energy condition, where $c$ is an additional parameter
describing the hair of the black hole. In this context, we found that for
$w\simeq 0.1$ (consistent with warm dark matter) and $c<0$, the deviation angle
is larger than that in the Kerr spacetime for direct and retrograde orbits. We
also derive an exact solution in the case of $w=-1/3$.
| [
{
"created": "Fri, 1 Nov 2019 13:37:51 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Oct 2020 09:48:14 GMT",
"version": "v2"
}
] | 2020-10-06 | [
[
"Sharma",
"Prateek",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Gannouji",
"Radouane",
""
],
[
"Uniyal",
"Rashmi",
""
],
[
"Abebe",
"Amare",
""
]
] | We present a detailed analysis of a rotating black hole surrounded by "quintessence". This solution represents a fluid with a constant equation of state, $w$, which can for example describe an effective warm dark matter fluid around a black hole. We clarify the conditions for the existence of such a solution and study its structure by analyzing the existence of horizons as well as the extremal case. We show that the deflection angle produced by the black hole depends on the parameters $(c,w)$ which need to obey the condition $cw<0$ because of the weak energy condition, where $c$ is an additional parameter describing the hair of the black hole. In this context, we found that for $w\simeq 0.1$ (consistent with warm dark matter) and $c<0$, the deviation angle is larger than that in the Kerr spacetime for direct and retrograde orbits. We also derive an exact solution in the case of $w=-1/3$. |
1502.04907 | Gabriel Bengochea | Gabriel Leon, Gabriel R. Bengochea | Emergence of inflationary perturbations in the CSL model | 14 pages. Final version. To be published in EPJC | Eur. Phys. J. C 76 (2016) 29 | 10.1140/epjc/s10052-015-3860-4 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inflationary paradigm is the most successful model that explains the
observed spectrum of primordial perturbations. However, the precise emergence
of such inhomogeneities and the quantum-to-classical transition of the
perturbations has not yet reached a consensus among the community. The
Continuous Spontaneous Localization model (CSL), in the cosmological context,
might be used to provide a solution to the mentioned issues by considering a
dynamical reduction of the wave function. The CSL model has been applied to the
inflationary universe before and different conclusions have been obtained. In
this letter, we use a different approach to implement the CSL model during
inflation. In particular, in addition to accounting for the
quantum-to-classical transition, we use the CSL model to generate the
primordial perturbations, that is, the dynamical evolution provided by the CSL
model is responsible for the transition from a homogeneous and isotropic
initial state to a final one lacking such symmetries. Our approach leads to
results that can be clearly distinguished from preceding works. Specifically,
the scalar and tensor power spectra are not time-dependent, and retains the
amplification mechanism of the CSL model. Moreover, our framework depends only
on one parameter (the CSL parameter) and its value is consistent with
cosmological and laboratory observations.
| [
{
"created": "Tue, 17 Feb 2015 14:40:47 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Oct 2015 19:16:19 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Jan 2016 14:43:52 GMT",
"version": "v3"
}
] | 2016-01-26 | [
[
"Leon",
"Gabriel",
""
],
[
"Bengochea",
"Gabriel R.",
""
]
] | The inflationary paradigm is the most successful model that explains the observed spectrum of primordial perturbations. However, the precise emergence of such inhomogeneities and the quantum-to-classical transition of the perturbations has not yet reached a consensus among the community. The Continuous Spontaneous Localization model (CSL), in the cosmological context, might be used to provide a solution to the mentioned issues by considering a dynamical reduction of the wave function. The CSL model has been applied to the inflationary universe before and different conclusions have been obtained. In this letter, we use a different approach to implement the CSL model during inflation. In particular, in addition to accounting for the quantum-to-classical transition, we use the CSL model to generate the primordial perturbations, that is, the dynamical evolution provided by the CSL model is responsible for the transition from a homogeneous and isotropic initial state to a final one lacking such symmetries. Our approach leads to results that can be clearly distinguished from preceding works. Specifically, the scalar and tensor power spectra are not time-dependent, and retains the amplification mechanism of the CSL model. Moreover, our framework depends only on one parameter (the CSL parameter) and its value is consistent with cosmological and laboratory observations. |
1012.3090 | Shrirang S. Deshingkar | Shrirang S. Deshingkar | On physical insignificance of null naked singularities | 11 pages, 1 figure | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study collapse of a general matter in a most general
spacetime i.e., a spacetime with any matter and without (assuming) any
symmetry. We show that the energy is completely trapped inside the null
singularity and therefore they cannot be experimentally observed. This most
general result implies, there is no physical significance of the null naked
singularities irrespective of their existence. This conclusion strongly
supports the essence of cosmic censorship hypothesis.
| [
{
"created": "Tue, 14 Dec 2010 16:54:29 GMT",
"version": "v1"
}
] | 2010-12-15 | [
[
"Deshingkar",
"Shrirang S.",
""
]
] | In this work we study collapse of a general matter in a most general spacetime i.e., a spacetime with any matter and without (assuming) any symmetry. We show that the energy is completely trapped inside the null singularity and therefore they cannot be experimentally observed. This most general result implies, there is no physical significance of the null naked singularities irrespective of their existence. This conclusion strongly supports the essence of cosmic censorship hypothesis. |
1106.6269 | Alexey Krugly | Alexey L. Krugly | Discrete mechanics: a sequential growth dynamics for causal sets that is
based on binary alternatives | 23 pages, 13 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of approaches to quantum gravity is different models of a discrete
pregeometry. An example of a discrete pregeometry on a microscopic scale is
introduced. This is the particular case of a causal set. The causal set is a
locally finite partially ordered set. The dynamics of this model is a
stochastic sequential growth dynamics. New elements of causal set are added one
by one. The probability of this addition of a new element depends on the
structure of existed causal set. The particular case of the dynamics is
considered. This dynamics is based on binary alternatives. Each directed path
is considered as a sequence of outcomes of binary alternatives. The
probabilities of a stochastic sequential growth have quadratic dependence on
these paths.
| [
{
"created": "Wed, 11 May 2011 06:14:54 GMT",
"version": "v1"
}
] | 2011-07-01 | [
[
"Krugly",
"Alexey L.",
""
]
] | One of approaches to quantum gravity is different models of a discrete pregeometry. An example of a discrete pregeometry on a microscopic scale is introduced. This is the particular case of a causal set. The causal set is a locally finite partially ordered set. The dynamics of this model is a stochastic sequential growth dynamics. New elements of causal set are added one by one. The probability of this addition of a new element depends on the structure of existed causal set. The particular case of the dynamics is considered. This dynamics is based on binary alternatives. Each directed path is considered as a sequence of outcomes of binary alternatives. The probabilities of a stochastic sequential growth have quadratic dependence on these paths. |
2309.07952 | Sebastian Baum | Sebastian Baum, Zachary Bogorad, Peter W. Graham | Gravitational Wave Measurement in the Mid-Band with Atom Interferometers | 45+15 pages, many figures. Code available at
github.com/sbaum90/AIMforGW. v2: updated to match the published version | JCAP05(2024)027 | 10.1088/1475-7516/2024/05/027 | TTK-23-24 | gr-qc astro-ph.CO astro-ph.IM hep-ph physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational Waves (GWs) have been detected in the $\sim$100 Hz and nHz
bands, but most of the gravitational spectrum remains unobserved. A variety of
detector concepts have been proposed to expand the range of observable
frequencies. In this work, we study the capability of GW detectors in the
``mid-band'', the $\sim$30 mHz -- 10 Hz range between LISA and LIGO, to measure
the signals from and constrain the properties of ${\sim}$1 -- 100 $M_\odot$
compact binaries. We focus on atom-interferometer-based detectors. We describe
a Fisher matrix code, AIMforGW, which we created to evaluate their
capabilities, and present numerical results for two benchmarks: terrestrial
km-scale detectors, and satellite-borne detectors in medium Earth orbit.
Mid-band GW detectors are particularly well-suited to pinpointing the location
of GW sources on the sky. We demonstrate that a satellite-borne detector could
achieve sub-degree sky localization for any detectable source with chirp mass
$\mathcal{M}_c \lesssim 50 M_\odot$. We also compare different detector
configurations, including different locations of terrestrial detectors and
various choices of the orbit of a satellite-borne detector. As we show, a
network of only two terrestrial single-baseline detectors or one
single-baseline satellite-borne detector would each provide close-to-uniform
sky-coverage, with signal-to-noise ratios varying by less than a factor of two
across the entire sky. We hope that this work contributes to the efforts of the
GW community to assess the merits of different detector proposals.
| [
{
"created": "Thu, 14 Sep 2023 18:00:00 GMT",
"version": "v1"
},
{
"created": "Thu, 2 May 2024 15:25:33 GMT",
"version": "v2"
}
] | 2024-05-03 | [
[
"Baum",
"Sebastian",
""
],
[
"Bogorad",
"Zachary",
""
],
[
"Graham",
"Peter W.",
""
]
] | Gravitational Waves (GWs) have been detected in the $\sim$100 Hz and nHz bands, but most of the gravitational spectrum remains unobserved. A variety of detector concepts have been proposed to expand the range of observable frequencies. In this work, we study the capability of GW detectors in the ``mid-band'', the $\sim$30 mHz -- 10 Hz range between LISA and LIGO, to measure the signals from and constrain the properties of ${\sim}$1 -- 100 $M_\odot$ compact binaries. We focus on atom-interferometer-based detectors. We describe a Fisher matrix code, AIMforGW, which we created to evaluate their capabilities, and present numerical results for two benchmarks: terrestrial km-scale detectors, and satellite-borne detectors in medium Earth orbit. Mid-band GW detectors are particularly well-suited to pinpointing the location of GW sources on the sky. We demonstrate that a satellite-borne detector could achieve sub-degree sky localization for any detectable source with chirp mass $\mathcal{M}_c \lesssim 50 M_\odot$. We also compare different detector configurations, including different locations of terrestrial detectors and various choices of the orbit of a satellite-borne detector. As we show, a network of only two terrestrial single-baseline detectors or one single-baseline satellite-borne detector would each provide close-to-uniform sky-coverage, with signal-to-noise ratios varying by less than a factor of two across the entire sky. We hope that this work contributes to the efforts of the GW community to assess the merits of different detector proposals. |
1403.7756 | Michael Coughlin | Michael Coughlin, Jan Harms, Nelson Christensen, Vladimir Dergachev,
Riccardo DeSalvo, Shivaraj Kandhasamy, Vuk Mandic | Wiener filtering with a seismic underground array at the Sanford
Underground Research Facility | null | null | 10.1088/0264-9381/31/21/215003 | null | gr-qc astro-ph.IM physics.geo-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A seismic array has been deployed at the Sanford Underground Research
Facility in the former Homestake mine, South Dakota, to study the underground
seismic environment. This includes exploring the advantages of constructing a
third-generation gravitational-wave detector underground. A major noise source
for these detectors would be Newtonian noise, which is induced by fluctuations
in the local gravitational field. The hope is that a combination of a low-noise
seismic environment and coherent noise subtraction using seismometers in the
vicinity of the detector could suppress the Newtonian noise to below the
projected noise floor for future gravitational-wave detectors. In this paper,
we use Wiener filtering techniques to subtract coherent noise in a seismic
array in the frequency band 0.05 -- 1\,Hz. This achieves more than an order of
magnitude noise cancellation over a majority of this band. We show how this
subtraction would benefit proposed future low-frequency gravitational wave
detectors. The variation in the Wiener filter coefficients over the course of
the day, including how local activities impact the filter, is analyzed. We also
study the variation in coefficients over the course of a month, showing the
stability of the filter with time. How varying the filter order affects the
subtraction performance is also explored. It is shown that optimizing filter
order can significantly improve subtraction of seismic noise, which gives hope
for future gravitational-wave detectors to address Newtonian noise.
| [
{
"created": "Sun, 30 Mar 2014 13:29:33 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jun 2014 09:31:44 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Aug 2014 20:38:53 GMT",
"version": "v3"
}
] | 2015-06-19 | [
[
"Coughlin",
"Michael",
""
],
[
"Harms",
"Jan",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Dergachev",
"Vladimir",
""
],
[
"DeSalvo",
"Riccardo",
""
],
[
"Kandhasamy",
"Shivaraj",
""
],
[
"Mandic",
"Vuk",
""
... | A seismic array has been deployed at the Sanford Underground Research Facility in the former Homestake mine, South Dakota, to study the underground seismic environment. This includes exploring the advantages of constructing a third-generation gravitational-wave detector underground. A major noise source for these detectors would be Newtonian noise, which is induced by fluctuations in the local gravitational field. The hope is that a combination of a low-noise seismic environment and coherent noise subtraction using seismometers in the vicinity of the detector could suppress the Newtonian noise to below the projected noise floor for future gravitational-wave detectors. In this paper, we use Wiener filtering techniques to subtract coherent noise in a seismic array in the frequency band 0.05 -- 1\,Hz. This achieves more than an order of magnitude noise cancellation over a majority of this band. We show how this subtraction would benefit proposed future low-frequency gravitational wave detectors. The variation in the Wiener filter coefficients over the course of the day, including how local activities impact the filter, is analyzed. We also study the variation in coefficients over the course of a month, showing the stability of the filter with time. How varying the filter order affects the subtraction performance is also explored. It is shown that optimizing filter order can significantly improve subtraction of seismic noise, which gives hope for future gravitational-wave detectors to address Newtonian noise. |
2108.10185 | Malsawmtluangi N | N. Malsawmtluangi | Analytical study of classic models of Hybrid Inflation | 10 pages, 10 figures | J. Phys. Commun. 5 (2021) 085016 | 10.1088/2399-6528/ac1f75 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We study the classic hybrid inflation model in its original and modified
forms and show the shape of the inflationary potentials and analyze the amount
of primordial gravitational waves each model predicts. We compare the resulting
EE-mode and BB-mode power spectrum with the data from the joint BICEP2/Keck and
Planck collaboration to check the viability of each model.
| [
{
"created": "Fri, 20 Aug 2021 08:18:56 GMT",
"version": "v1"
}
] | 2021-09-01 | [
[
"Malsawmtluangi",
"N.",
""
]
] | We study the classic hybrid inflation model in its original and modified forms and show the shape of the inflationary potentials and analyze the amount of primordial gravitational waves each model predicts. We compare the resulting EE-mode and BB-mode power spectrum with the data from the joint BICEP2/Keck and Planck collaboration to check the viability of each model. |
gr-qc/0007057 | Lorenzo Iorio | Lorenzo Iorio | Satellite non-gravitational orbital perturbations and the detection of
the gravitomagnetic clock effect | LaTex2e, 12 pages, no figures, no tables. Reference added | Class.Quant.Grav.18:4303-4310,2001 | 10.1088/0264-9381/18/20/309 | null | gr-qc astro-ph physics.geo-ph physics.space-ph | null | The general relativistic gravitomagnetic clock effect consists in the fact
that two massive test bodies orbiting a central spinning mass in its equatorial
plane along two identical circular trajectories, but in opposite directions,
take different times in describing a full revolution with respect to an
asymptotically inertial observer. In the field of the Earth such time shift
amounts to 10^{-7} s. Detecting it by means of a space based mission with
artificial satellites is a very demanding task because there are severe
constraints on the precision with which the radial and azimuthal positions of a
satellite must be known: delta r= 10^{-2} cm and delta phi= 10^{-2}
milliarcseconds per revolution. In this paper we assess if the systematic
errors induced by various non-gravitational perturbations allow to meet such
stringent requirements. A couple of identical, passive laser-ranged satellites
of LAGEOS type with their spins aligned with the Earth's one is considered. It
turns out that all the non vanishing non-gravitational perturbations induce
systematic errors in r and phi within the required constraints for a reasonable
assumption of the mismodeling in some satellite's and Earth's parameters and/or
by using dense satellites with small area-to-mass ratio. However, the error in
the Earth's GM is by far the largest source of uncertainty in the azimuthal
location which is affected at a level of 1.2 milliarcseconds per revolution.
| [
{
"created": "Fri, 21 Jul 2000 16:23:39 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jun 2001 15:46:10 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Jul 2001 23:30:15 GMT",
"version": "v3"
},
{
"created": "Tue, 7 Aug 2001 14:11:40 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Iorio",
"Lorenzo",
""
]
] | The general relativistic gravitomagnetic clock effect consists in the fact that two massive test bodies orbiting a central spinning mass in its equatorial plane along two identical circular trajectories, but in opposite directions, take different times in describing a full revolution with respect to an asymptotically inertial observer. In the field of the Earth such time shift amounts to 10^{-7} s. Detecting it by means of a space based mission with artificial satellites is a very demanding task because there are severe constraints on the precision with which the radial and azimuthal positions of a satellite must be known: delta r= 10^{-2} cm and delta phi= 10^{-2} milliarcseconds per revolution. In this paper we assess if the systematic errors induced by various non-gravitational perturbations allow to meet such stringent requirements. A couple of identical, passive laser-ranged satellites of LAGEOS type with their spins aligned with the Earth's one is considered. It turns out that all the non vanishing non-gravitational perturbations induce systematic errors in r and phi within the required constraints for a reasonable assumption of the mismodeling in some satellite's and Earth's parameters and/or by using dense satellites with small area-to-mass ratio. However, the error in the Earth's GM is by far the largest source of uncertainty in the azimuthal location which is affected at a level of 1.2 milliarcseconds per revolution. |
2206.08608 | Zi-Yu Tang | Zi-Yu Tang, Xiao-Mei Kuang, Bin Wang, and Wei-Liang Qian | The length of a compact extra dimension from black hole shadow | 4 pages, 2 figures, to be published in Science Bulletin as a short
communication | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Plenty of efforts have been made to explore the black string and its
instability, but the fate of the black strings with fewer extra dimensions is
still inconclusive. Now starting from the 5D uniform black string, we show that
the EHT observations of M87* and SgrA* can not only rule out the black string
with an infinite extra dimension, but also constrain the length of a compact
extra dimension, which is much smaller than the critical length given from the
Gregory-Laflamme (GL) instability. Our findings support the hypothesis that the
extra dimension is compact avoiding the GL instability.
| [
{
"created": "Fri, 17 Jun 2022 08:08:37 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Nov 2022 09:56:56 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Nov 2022 08:57:05 GMT",
"version": "v3"
}
] | 2022-11-11 | [
[
"Tang",
"Zi-Yu",
""
],
[
"Kuang",
"Xiao-Mei",
""
],
[
"Wang",
"Bin",
""
],
[
"Qian",
"Wei-Liang",
""
]
] | Plenty of efforts have been made to explore the black string and its instability, but the fate of the black strings with fewer extra dimensions is still inconclusive. Now starting from the 5D uniform black string, we show that the EHT observations of M87* and SgrA* can not only rule out the black string with an infinite extra dimension, but also constrain the length of a compact extra dimension, which is much smaller than the critical length given from the Gregory-Laflamme (GL) instability. Our findings support the hypothesis that the extra dimension is compact avoiding the GL instability. |
1510.08159 | Aaron Zimmerman | Aaron Zimmerman, Huan Yang, Fan Zhang, David A. Nichols, Emanuele
Berti, Yanbei Chen | Reply to "On the branching of quasinormal resonances of near-extremal
Kerr black holes" by Shahar Hod | 4 pages, 3 figures, reply to arXiv:1510.05604 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a study of the quasinormal mode frequencies of nearly extremal black
holes, we pointed out a bifurcation of the mode spectrum into modes with finite
decay and modes with vanishing decay in the extremal limit. We provided
analytic and semi-analytic results identifying which families of modes
bifurcated, and when modes with finite decay rates exist when approaching the
extremal limit. In a recent note (arXiv:1510.05604), Hod suggests that
additional modes asymptote to finite decay at extremely high spin parameter,
based on past work by Detweiler. We search for these suggested modes and find
no evidence of their existence. In addition, we point out an inconsistency in
the derivation of the proposed modes, which further indicates that these damped
modes do not exist.
| [
{
"created": "Wed, 28 Oct 2015 01:51:20 GMT",
"version": "v1"
}
] | 2015-10-29 | [
[
"Zimmerman",
"Aaron",
""
],
[
"Yang",
"Huan",
""
],
[
"Zhang",
"Fan",
""
],
[
"Nichols",
"David A.",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Chen",
"Yanbei",
""
]
] | In a study of the quasinormal mode frequencies of nearly extremal black holes, we pointed out a bifurcation of the mode spectrum into modes with finite decay and modes with vanishing decay in the extremal limit. We provided analytic and semi-analytic results identifying which families of modes bifurcated, and when modes with finite decay rates exist when approaching the extremal limit. In a recent note (arXiv:1510.05604), Hod suggests that additional modes asymptote to finite decay at extremely high spin parameter, based on past work by Detweiler. We search for these suggested modes and find no evidence of their existence. In addition, we point out an inconsistency in the derivation of the proposed modes, which further indicates that these damped modes do not exist. |
gr-qc/0505057 | Martin Bojowald | Martin Bojowald | Elements of Loop Quantum Cosmology | 30 pages, 4 figures, Chapter contributed to "100 Years of Relativity
- Space-time Structure: Einstein and Beyond", Ed. A. Ashtekar (World
Scientific) | null | null | AEI-2005-025 | gr-qc astro-ph hep-th | null | The expansion of our universe, when followed backward in time, implies that
it emerged from a phase of huge density, the big bang. These stages are so
extreme that classical general relativity combined with matter theories is not
able to describe them properly, and one has to refer to quantum gravity. A
complete quantization of gravity has not yet been developed, but there are many
results about key properties to be expected. When applied to cosmology, a
consistent picture of the early universe arises which is free of the classical
pathologies and has implications for the generation of structure which are
potentially observable in the near future.
| [
{
"created": "Thu, 12 May 2005 08:50:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bojowald",
"Martin",
""
]
] | The expansion of our universe, when followed backward in time, implies that it emerged from a phase of huge density, the big bang. These stages are so extreme that classical general relativity combined with matter theories is not able to describe them properly, and one has to refer to quantum gravity. A complete quantization of gravity has not yet been developed, but there are many results about key properties to be expected. When applied to cosmology, a consistent picture of the early universe arises which is free of the classical pathologies and has implications for the generation of structure which are potentially observable in the near future. |
1607.02736 | Suprit Singh | Suprit Singh | From Quantum to Classical in the Sky | Contribution to the Festschrift in honor of Prof. T. Padmanabhan on
the occassion of his 60th birthday. Extending the results of arXiv:1308.4976
to tensor perturbations. Title from my poster presented at ICTP Summer School
on Cosmology, June 2016 | Fundam.Theor.Phys. 187 (2017) pp 397-409 | 10.1007/978-3-319-51700-1_24 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inflation has by-far set itself as one of the prime ideas in the current
cosmological models that seemingly has an answer for every observed phenomenon
in cosmology. More importantly, it serves as a bridge between the early quantum
fluctuations and the present-day classical structures. Although the transition
from quantum to classical is still not completely understood till date, there
are two assumptions made in the inflationary paradigm in this regard:
(i) the modes (metric perturbations or fluctuations) behave classically once
they are well outside the Hubble radius and,
(ii) once they become classical they stay classical and hence can be
described by standard perturbation theory after they re-enter the Hubble
radius.
We critically examine these assumptions for the tensor modes of (linear)
metric perturbations in a toy three stage universe with (i) inflation, (ii)
radiation-dominated and (iii) late-time accelerated phases. The
quantum-to-classical transition for these modes is evident from the evolution
of Wigner function in phase space and its peaking on the classical trajectory.
However, a better approach to quantify the degree of classicality and study its
evolution was given by Mahajan and Padmanabhan [1] using a classicality
parameter constructed from the parameters of the Wigner function. We study the
evolution of the classicality parameter across the three phases and it turns
out that the first assumption holds true, there is emergence of classicality on
Hubble exit, however the latter assumption of "once classical, always
classical" seems to lie on a shaky ground.
| [
{
"created": "Sun, 10 Jul 2016 12:04:50 GMT",
"version": "v1"
}
] | 2017-04-18 | [
[
"Singh",
"Suprit",
""
]
] | Inflation has by-far set itself as one of the prime ideas in the current cosmological models that seemingly has an answer for every observed phenomenon in cosmology. More importantly, it serves as a bridge between the early quantum fluctuations and the present-day classical structures. Although the transition from quantum to classical is still not completely understood till date, there are two assumptions made in the inflationary paradigm in this regard: (i) the modes (metric perturbations or fluctuations) behave classically once they are well outside the Hubble radius and, (ii) once they become classical they stay classical and hence can be described by standard perturbation theory after they re-enter the Hubble radius. We critically examine these assumptions for the tensor modes of (linear) metric perturbations in a toy three stage universe with (i) inflation, (ii) radiation-dominated and (iii) late-time accelerated phases. The quantum-to-classical transition for these modes is evident from the evolution of Wigner function in phase space and its peaking on the classical trajectory. However, a better approach to quantify the degree of classicality and study its evolution was given by Mahajan and Padmanabhan [1] using a classicality parameter constructed from the parameters of the Wigner function. We study the evolution of the classicality parameter across the three phases and it turns out that the first assumption holds true, there is emergence of classicality on Hubble exit, however the latter assumption of "once classical, always classical" seems to lie on a shaky ground. |
1205.1427 | Claus Gerhardt | Claus Gerhardt | The quantization of gravity in globally hyperbolic spacetimes | 26 pages, v4: some minor typos corrected, to appear in ATMP 2013 | Adv. Theor. Math. Phys. 17 (6), 1347 - 1391 (2013) | 10.4310/ATMP.2013.v17.n6.a5 | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the ADM approach to obtain a Hamiltonian description of the
Einstein-Hilbert action. In doing so we add four new ingredients: (i) We
eliminate the diffeomorphism constraints. (ii) We replace the densities $\sqrt
g$ by a function $\f(x,g_{ij})$ with the help of a fixed metric $\chi$ such
that the Lagrangian and hence the Hamiltonian are functions. (iii) We consider
the Lagrangian to be defined in a fiber bundle with base space $\so$ and fibers
F(x) which can be treated as Lorentzian manifolds equipped with the
Wheeler-DeWitt metric. It turns out that the fibers are globally hyperbolic.
(iv) The Hamiltonian operator $H$ is a normally hyperbolic operator in the
bundle acting only in the fibers and the Wheeler-DeWitt equation $Hu=0$ is a
hyperbolic equation in the bundle. Since the corresponding Cauchy problem can
be solved for arbitrary smooth data with compact support, we then apply the
standard techniques of QFT which can be naturally modified to work in the
bundle.
| [
{
"created": "Mon, 7 May 2012 15:22:48 GMT",
"version": "v1"
},
{
"created": "Thu, 17 May 2012 17:50:01 GMT",
"version": "v2"
},
{
"created": "Sun, 17 Jun 2012 13:33:13 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Feb 2013 19:38:48 GMT",
"version": "v4"
}
] | 2014-05-01 | [
[
"Gerhardt",
"Claus",
""
]
] | We apply the ADM approach to obtain a Hamiltonian description of the Einstein-Hilbert action. In doing so we add four new ingredients: (i) We eliminate the diffeomorphism constraints. (ii) We replace the densities $\sqrt g$ by a function $\f(x,g_{ij})$ with the help of a fixed metric $\chi$ such that the Lagrangian and hence the Hamiltonian are functions. (iii) We consider the Lagrangian to be defined in a fiber bundle with base space $\so$ and fibers F(x) which can be treated as Lorentzian manifolds equipped with the Wheeler-DeWitt metric. It turns out that the fibers are globally hyperbolic. (iv) The Hamiltonian operator $H$ is a normally hyperbolic operator in the bundle acting only in the fibers and the Wheeler-DeWitt equation $Hu=0$ is a hyperbolic equation in the bundle. Since the corresponding Cauchy problem can be solved for arbitrary smooth data with compact support, we then apply the standard techniques of QFT which can be naturally modified to work in the bundle. |
1302.6956 | Jong-Ping Hsu | Jong-Ping Hsu | Experimental Tests on Yang-Mills Gravity with Accurate Measurements of
the Deflection of Light | 7 pages. To be published in The European Physical Journal - Plus
(2013) | Eur. Phys. J. Plus (2013) 128: 31 | 10.1140/epjp/i2013-133031-3 | null | gr-qc hep-th physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the geometric-optics limit, Yang-Mills gravity with space-time
translational gauge symmetry predicts $\D \phi =7Gm/(2R) \approx 1.53''$ for
the deflection of a light ray by the sun. The result, which is about 12%
smaller than that in the conventional theory, is consistent with experiments
involving optical frequencies that had an accuracy of 10-20%.
| [
{
"created": "Wed, 27 Feb 2013 18:50:59 GMT",
"version": "v1"
}
] | 2014-02-26 | [
[
"Hsu",
"Jong-Ping",
""
]
] | In the geometric-optics limit, Yang-Mills gravity with space-time translational gauge symmetry predicts $\D \phi =7Gm/(2R) \approx 1.53''$ for the deflection of a light ray by the sun. The result, which is about 12% smaller than that in the conventional theory, is consistent with experiments involving optical frequencies that had an accuracy of 10-20%. |
1701.06668 | Eavan Gleeson | Eavan Gleeson | Linear Instability of the Reissner-Nordstr\"om Cauchy Horizon | Submitted as MSc thesis, University of Cambridge, 2016 | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work studies solutions of the scalar wave equation \[\Box_g\phi=0\] on a
fixed subextremal Reissner-Nordstr\"{o}m spacetime with non-vanishing charge
$q$ and mass $M$. In a recent paper, Luk and Oh established that generic smooth
and compactly supported initial data on a Cauchy hypersurface lead to solutions
which are singular in the $W^{1,2}_{loc}$ sense near the Cauchy horizon in the
black hole interior, and it follows easily that they are also singular in the
$W^{1,p}_{loc}$ sense for $p>2$. On the other hand, the work of Franzen shows
that such solutions are non-singular near the Cauchy horizon in the
$W^{1,1}_{loc}$ sense. Motivated by these results, we investigate the strength
of the singularity at the Cauchy horizon. We identify a sufficient condition on
the black hole interior (which holds for the full subextremal parameter range
$0<|q|<M$) ensuring $W^{1,p}_{loc}$ blow up near the Cauchy horizon of
solutions arising from generic smooth and compactly supported data for every
$1<p<2$. We moreover prove that provided the spacetime parameters satisfy
$\frac{2\sqrt e}{e+1}<\frac{|q|}{M}<1$, we in fact have $W^{1,p}_{loc}$ blow up
near the Cauchy horizon for such solutions for every $1<p<2$. This shows that
the singularity is even stronger than was implied by the work of Luk and Oh for
this restricted parameter range.
| [
{
"created": "Mon, 23 Jan 2017 22:57:46 GMT",
"version": "v1"
}
] | 2017-01-25 | [
[
"Gleeson",
"Eavan",
""
]
] | This work studies solutions of the scalar wave equation \[\Box_g\phi=0\] on a fixed subextremal Reissner-Nordstr\"{o}m spacetime with non-vanishing charge $q$ and mass $M$. In a recent paper, Luk and Oh established that generic smooth and compactly supported initial data on a Cauchy hypersurface lead to solutions which are singular in the $W^{1,2}_{loc}$ sense near the Cauchy horizon in the black hole interior, and it follows easily that they are also singular in the $W^{1,p}_{loc}$ sense for $p>2$. On the other hand, the work of Franzen shows that such solutions are non-singular near the Cauchy horizon in the $W^{1,1}_{loc}$ sense. Motivated by these results, we investigate the strength of the singularity at the Cauchy horizon. We identify a sufficient condition on the black hole interior (which holds for the full subextremal parameter range $0<|q|<M$) ensuring $W^{1,p}_{loc}$ blow up near the Cauchy horizon of solutions arising from generic smooth and compactly supported data for every $1<p<2$. We moreover prove that provided the spacetime parameters satisfy $\frac{2\sqrt e}{e+1}<\frac{|q|}{M}<1$, we in fact have $W^{1,p}_{loc}$ blow up near the Cauchy horizon for such solutions for every $1<p<2$. This shows that the singularity is even stronger than was implied by the work of Luk and Oh for this restricted parameter range. |
gr-qc/9602020 | Victor Berezin | V.A.Berezin | Quantum Black Hole Model and Hawking's Radiation | LaTeX file | Phys.Rev.D55:2139-2151,1997 | 10.1103/PhysRevD.55.2139 | Preprint INR-0916/Febr 1996 | gr-qc | null | The black hole model with a self-gravitating charged spherical symmetric dust
thin shell as a source is considered. The Schroedinger-type equation for such a
model is derived. This equation appeared to be a finite differences equation. A
theory of such an equation is developed and general solution is found and
investigated in details. The discrete spectrum of the bound state energy levels
is obtained. All the eigenvalues appeared to be infinitely degenerate. The
ground state wave functions are evaluated explicitly. The quantum black hole
states are selected and investigated. It is shown that the obtained black hole
mass spectrum is compatible with the existence of Hawking's radiation in the
limit of low temperatures both for large and nearly extreme Reissner-Nordstrom
black holes. The above mentioned infinite degeneracy of the mass (energy)
eigenvalues may appeared helpful in resolving the well known information
paradox in the black hole physics.
| [
{
"created": "Mon, 12 Feb 1996 12:03:06 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Berezin",
"V. A.",
""
]
] | The black hole model with a self-gravitating charged spherical symmetric dust thin shell as a source is considered. The Schroedinger-type equation for such a model is derived. This equation appeared to be a finite differences equation. A theory of such an equation is developed and general solution is found and investigated in details. The discrete spectrum of the bound state energy levels is obtained. All the eigenvalues appeared to be infinitely degenerate. The ground state wave functions are evaluated explicitly. The quantum black hole states are selected and investigated. It is shown that the obtained black hole mass spectrum is compatible with the existence of Hawking's radiation in the limit of low temperatures both for large and nearly extreme Reissner-Nordstrom black holes. The above mentioned infinite degeneracy of the mass (energy) eigenvalues may appeared helpful in resolving the well known information paradox in the black hole physics. |
gr-qc/9603034 | Fodor Gyula | G. Fodor, K. Nakamura, Y. Oshiro and A. Tomimatsu | Surface gravity in dynamical spherically symmetric spacetimes | 35 pages, revtex, 3 figures included using epsf | Phys.Rev.D54:3882-3891,1996 | 10.1103/PhysRevD.54.3882 | DPNU-96-20 | gr-qc | null | A definition of surface gravity at the apparent horizon of dynamical
spherically symmetric spacetimes is proposed. It is based on a unique foliation
by ingoing null hypersurfaces. The function parametrizing the hypersurfaces can
be interpreted as the phase of a light wave uniformly emitted by some far-away
static observer. The definition gives back the accepted value of surface
gravity in the static case by virtue of its nonlocal character. Although the
definition is motivated by the behavior of outgoing null rays, it turns out
that there is a simple connection between the generalized surface gravity, the
acceleration of any radially moving observer, and the observed frequency change
of the infalling light signal. In particular, this gives a practical and simple
method of how any geodesic observer can determine surface gravity by measuring
only the redshift of the infalling light wave. The surface gravity can be
expressed as an integral of matter field quantities along an ingoing null line,
which shows that it is a continuous function along the apparent horizon. A
formula for the area change of the apparent horizon is presented, and the
possibility of thermodynamical interpretation is discussed. Finally, concrete
expressions of surface gravity are given for a number of four-dimensional and
two-dimensional dynamical black hole solutions.
| [
{
"created": "Fri, 22 Mar 1996 07:54:48 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Fodor",
"G.",
""
],
[
"Nakamura",
"K.",
""
],
[
"Oshiro",
"Y.",
""
],
[
"Tomimatsu",
"A.",
""
]
] | A definition of surface gravity at the apparent horizon of dynamical spherically symmetric spacetimes is proposed. It is based on a unique foliation by ingoing null hypersurfaces. The function parametrizing the hypersurfaces can be interpreted as the phase of a light wave uniformly emitted by some far-away static observer. The definition gives back the accepted value of surface gravity in the static case by virtue of its nonlocal character. Although the definition is motivated by the behavior of outgoing null rays, it turns out that there is a simple connection between the generalized surface gravity, the acceleration of any radially moving observer, and the observed frequency change of the infalling light signal. In particular, this gives a practical and simple method of how any geodesic observer can determine surface gravity by measuring only the redshift of the infalling light wave. The surface gravity can be expressed as an integral of matter field quantities along an ingoing null line, which shows that it is a continuous function along the apparent horizon. A formula for the area change of the apparent horizon is presented, and the possibility of thermodynamical interpretation is discussed. Finally, concrete expressions of surface gravity are given for a number of four-dimensional and two-dimensional dynamical black hole solutions. |
gr-qc/9705019 | Thomas Thiemann | Thomas Thiemann | QSD V : Quantum Gravity as the Natural Regulator of Matter Quantum Field
Theories | 34p, LATEX | Class.Quant.Grav. 15 (1998) 1281-1314 | 10.1088/0264-9381/15/5/012 | HUTMP-96/B-357 | gr-qc hep-th | null | It is an old speculation in physics that, once the gravitational field is
successfully quantized, it should serve as the natural regulator of infrared
and ultraviolet singularities that plague quantum field theories in a
background metric. We demonstrate that this idea is implemented in a precise
sense within the framework of four-dimensional canonical Lorentzian quantum
gravity in the continuum. Specifically, we show that the Hamiltonian of the
standard model supports a representation in which finite linear combinations of
Wilson loop functionals around closed loops, as well as along open lines with
fermionic and Higgs field insertions at the end points are densely defined
operators. This Hamiltonian, surprisingly, does not suffer from any
singularities, it is completely finite without renormalization. This property
is shared by string theory. In contrast to string theory, however, we are
dealing with a particular phase of the standard model coupled to gravity which
is entirely non-perturbatively defined and second quantized.
| [
{
"created": "Sat, 10 May 1997 00:14:50 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Thiemann",
"Thomas",
""
]
] | It is an old speculation in physics that, once the gravitational field is successfully quantized, it should serve as the natural regulator of infrared and ultraviolet singularities that plague quantum field theories in a background metric. We demonstrate that this idea is implemented in a precise sense within the framework of four-dimensional canonical Lorentzian quantum gravity in the continuum. Specifically, we show that the Hamiltonian of the standard model supports a representation in which finite linear combinations of Wilson loop functionals around closed loops, as well as along open lines with fermionic and Higgs field insertions at the end points are densely defined operators. This Hamiltonian, surprisingly, does not suffer from any singularities, it is completely finite without renormalization. This property is shared by string theory. In contrast to string theory, however, we are dealing with a particular phase of the standard model coupled to gravity which is entirely non-perturbatively defined and second quantized. |
0709.0539 | David Mattingly | David Mattingly | Causal sets and conservation laws in tests of Lorentz symmetry | 8 pages, matches version published in PRD | Phys.Rev.D77:125021,2008 | 10.1103/PhysRevD.77.125021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many of the most important astrophysical tests of Lorentz symmetry also
assume that energy-momentum of the observed particles is exactly conserved. In
the causal set approach to quantum gravity a particular kind of Lorentz
symmetry holds but energy-momentum conservation may be violated. We show that
incorrectly assuming exact conservation can give rise to a spurious signal of
Lorentz symmetry violation for a causal set. However, the size of this spurious
signal is much smaller than can be currently detected and hence astrophysical
Lorentz symmetry tests as currently performed are safe from causal set induced
violations of energy-momentum conservation.
| [
{
"created": "Tue, 4 Sep 2007 20:32:55 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jun 2008 01:14:00 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mattingly",
"David",
""
]
] | Many of the most important astrophysical tests of Lorentz symmetry also assume that energy-momentum of the observed particles is exactly conserved. In the causal set approach to quantum gravity a particular kind of Lorentz symmetry holds but energy-momentum conservation may be violated. We show that incorrectly assuming exact conservation can give rise to a spurious signal of Lorentz symmetry violation for a causal set. However, the size of this spurious signal is much smaller than can be currently detected and hence astrophysical Lorentz symmetry tests as currently performed are safe from causal set induced violations of energy-momentum conservation. |
2008.13425 | Parthasarathi Majumdar | Parthasarathi Majumdar and Anarya Ray | Holographic Bound on Area of Compact Binary Merger Remnant | 8 pages Revtex with three figures in .png format | Phys. Rev. D 104, 044036 (2021) | 10.1103/PhysRevD.104.044036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using concomitantly the Generalized Second Law of black hole thermodynamics
and the holographic Bekenstein entropy bound embellished by Loop Quantum
Gravity corrections to quantum black hole entropy, we show that the boundary
cross sectional area of the postmerger remnant formed from the compact binary
merger in gravitational wave detection experiments like GW150914, is bounded
from below. This lower bound is more general than the bound from application of
the classical area theorem for black holes, since it does not depend on whether
the inspiralling compact binary pair or the postmerger remnant consists of
black holes or other exotic compact objects. The derivation of the bound
entails an estimate of the entropy of the gravitational waves emitted during
the binary merger which adapts to gravitational waves an extant formalism
proposed originally for particle ensembles. The results for the minimal
cross-sectional area of the merger remnant due to binary compact mergers
observed recently by the LIGO-VIRGO collaboration are discussed. While accurate
measurement of the mass of the remnant for the BNS merger GW170817 remains a
challenge, we provide a proof of principle that for BNS mergers our lower bound
on the cross-sectional area of the remnant provides an alternative approach to
probe the validity of neutron star Equations of State, independent of the
measurements of the tidal deformabilities of the components.
| [
{
"created": "Mon, 31 Aug 2020 08:31:45 GMT",
"version": "v1"
},
{
"created": "Mon, 3 May 2021 10:50:10 GMT",
"version": "v2"
}
] | 2021-08-25 | [
[
"Majumdar",
"Parthasarathi",
""
],
[
"Ray",
"Anarya",
""
]
] | Using concomitantly the Generalized Second Law of black hole thermodynamics and the holographic Bekenstein entropy bound embellished by Loop Quantum Gravity corrections to quantum black hole entropy, we show that the boundary cross sectional area of the postmerger remnant formed from the compact binary merger in gravitational wave detection experiments like GW150914, is bounded from below. This lower bound is more general than the bound from application of the classical area theorem for black holes, since it does not depend on whether the inspiralling compact binary pair or the postmerger remnant consists of black holes or other exotic compact objects. The derivation of the bound entails an estimate of the entropy of the gravitational waves emitted during the binary merger which adapts to gravitational waves an extant formalism proposed originally for particle ensembles. The results for the minimal cross-sectional area of the merger remnant due to binary compact mergers observed recently by the LIGO-VIRGO collaboration are discussed. While accurate measurement of the mass of the remnant for the BNS merger GW170817 remains a challenge, we provide a proof of principle that for BNS mergers our lower bound on the cross-sectional area of the remnant provides an alternative approach to probe the validity of neutron star Equations of State, independent of the measurements of the tidal deformabilities of the components. |
1802.03502 | Xun Xue | Jiayin Shen and Xun Xue | Large Scale Lorentz Violation Gravity and Dark Energy | 13 pages,6 figures,1 table | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accelerating expansion of universe can be described by the non-zero
cosmological constant or the dark energy. However, the origin of the dark
energy remains a mystery of modern physics. The local Lorentz invariance is the
most exact symmetry of the Nature on the one hand, but all quantum gravity
theories predict Lorentz violation on the other hand. The local Lorentz
violation induced by the quantum gravity at the very early universe may be
transformed into large scale by inflation. Combining the low-$l$ anomalies of
the CMB spectrum, we propose that the local Lorentz invariance may be broken at
the large scale. We construct the effective gravity at the cosmic scale with a
local $SO(3)$ symmetry. The theory exhibits non-trivial contortion distribution
even with scalar matter source. The FRW like solution of the theory is analyzed
and the contortion distribution contributes a dark energy like effect which is
responsible for the accelerating expansion of the universe. It reveals that the
dark energy may be the remnants of quantum gravity in this sense.
| [
{
"created": "Sat, 10 Feb 2018 02:13:42 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Feb 2018 17:32:46 GMT",
"version": "v2"
},
{
"created": "Sat, 13 Oct 2018 17:37:54 GMT",
"version": "v3"
}
] | 2018-10-16 | [
[
"Shen",
"Jiayin",
""
],
[
"Xue",
"Xun",
""
]
] | The accelerating expansion of universe can be described by the non-zero cosmological constant or the dark energy. However, the origin of the dark energy remains a mystery of modern physics. The local Lorentz invariance is the most exact symmetry of the Nature on the one hand, but all quantum gravity theories predict Lorentz violation on the other hand. The local Lorentz violation induced by the quantum gravity at the very early universe may be transformed into large scale by inflation. Combining the low-$l$ anomalies of the CMB spectrum, we propose that the local Lorentz invariance may be broken at the large scale. We construct the effective gravity at the cosmic scale with a local $SO(3)$ symmetry. The theory exhibits non-trivial contortion distribution even with scalar matter source. The FRW like solution of the theory is analyzed and the contortion distribution contributes a dark energy like effect which is responsible for the accelerating expansion of the universe. It reveals that the dark energy may be the remnants of quantum gravity in this sense. |
1004.2734 | Matt Visser | Bethan Cropp (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | General polarization modes for the Rosen gravitational wave | V1: 12 pages, no figures. V2: still 12 pages, reformatted. Minor
technical edits, discussion of Riemann tensor added, two references added, no
significant physics changes. This version accepted for publication in
Classical and Quantum Gravity | Class.Quant.Grav.27:165022,2010 | 10.1088/0264-9381/27/16/165022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Strong-field gravitational plane waves are often represented in either the
Rosen or Brinkmann forms. While these two metric ansatze are related by a
coordinate transformation, so that they should describe essentially the same
physics, they rather puzzlingly seem to treat polarization states quite
differently. Both ansatze deal equally well with + and X linear polarizations,
but there is a qualitative difference in they way they deal with circular,
elliptic, and more general polarization states. In this article we will develop
a general formalism for dealing with arbitrary polarization states in the Rosen
form of the gravitational wave metric, representing an arbitrary polarization
by a trajectory in a suitably defined two dimensional hyperbolic plane.
| [
{
"created": "Thu, 15 Apr 2010 23:07:32 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jun 2010 23:38:40 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Cropp",
"Bethan",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Strong-field gravitational plane waves are often represented in either the Rosen or Brinkmann forms. While these two metric ansatze are related by a coordinate transformation, so that they should describe essentially the same physics, they rather puzzlingly seem to treat polarization states quite differently. Both ansatze deal equally well with + and X linear polarizations, but there is a qualitative difference in they way they deal with circular, elliptic, and more general polarization states. In this article we will develop a general formalism for dealing with arbitrary polarization states in the Rosen form of the gravitational wave metric, representing an arbitrary polarization by a trajectory in a suitably defined two dimensional hyperbolic plane. |
1906.11779 | Oscar Lasso Andino | Marcos Arga\~naraz and Oscar Lasso Andino | Dynamics in wormhole spacetimes: a Jacobi metric approach | null | Class. Quantum Grav. 38 045004 (2021) | 10.1088/1361-6382/abcf86 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article deals with the study of the dynamics of particles in different
wormhole geometries. Using the Jacobi metric approach we study the geodesic
motion on the Morris-Thorne wormhole. We found the only stable circular orbit
located at the throat. We show that the Gaussian curvature of the Jacobi metric
is directly related with the wormhole flare-out condition. We provide a simple
test for determining the existence of a throat in a spacetime by using the
Gaussian curvature of the associated Jacobi metric only. We discuss about the
trajectories in the Kepler problem in a wormhole background. Finally, we
discuss about the restrictions over the stress-energy tensor imposed by the
existence of elliptic orbits in the Kepler problem.
| [
{
"created": "Thu, 27 Jun 2019 16:39:00 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Oct 2019 17:25:48 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Dec 2020 19:18:22 GMT",
"version": "v3"
}
] | 2021-01-01 | [
[
"Argañaraz",
"Marcos",
""
],
[
"Andino",
"Oscar Lasso",
""
]
] | This article deals with the study of the dynamics of particles in different wormhole geometries. Using the Jacobi metric approach we study the geodesic motion on the Morris-Thorne wormhole. We found the only stable circular orbit located at the throat. We show that the Gaussian curvature of the Jacobi metric is directly related with the wormhole flare-out condition. We provide a simple test for determining the existence of a throat in a spacetime by using the Gaussian curvature of the associated Jacobi metric only. We discuss about the trajectories in the Kepler problem in a wormhole background. Finally, we discuss about the restrictions over the stress-energy tensor imposed by the existence of elliptic orbits in the Kepler problem. |
1609.05915 | M\'arton T\'apai | M\'arton T\'apai, Zolt\'an Keresztes, L\'aszl\'o \'Arp\'ad Gergely | Secular precessing compact binary dynamics, spin and orbital angular
momentum flip-flops | 24 pages, 10 figure panels, figure resolution downscaled for arXiv
version, LIGO document P1600207 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the conservative secular evolution of precessing compact binaries
to second post-Newtonian order accuracy, with leading-order spin-orbit,
spin-spin and mass quadrupole-monopole contributions included. The emerging
closed system of first-order differential equations evolves the pairs of polar
and azimuthal angles of the spin and orbital angular momentum vectors together
with the periastron angle. In contrast with the instantaneous dynamics, the
secular dynamics is autonomous. This secular dynamics reliably characterizes
the system over timescales starting from a few times the radial period to
several precessional periods, but less than the radiation reaction timescale.
We numerically compare the instantaneous and secular evolutions and estimate
the number of periods for which dissipation has no significant effect, e.g. the
conservative timescale. We apply the analytic equations to study the spin
flip-flop effect, recently found by numerical relativity methods. Our
investigations show that the effect does not generalize beyond its original
parameter settings, although we reveal distinct configurations exhibiting one
half flip-flops. In addition, we find a flip-flopping evolution of the orbital
angular momentum vector, which ventures from one pole to another through
several precessional periods. This is a new effect, occurring for mass ratios
much less than one.
| [
{
"created": "Mon, 19 Sep 2016 20:01:04 GMT",
"version": "v1"
}
] | 2016-09-21 | [
[
"Tápai",
"Márton",
""
],
[
"Keresztes",
"Zoltán",
""
],
[
"Gergely",
"László Árpád",
""
]
] | We derive the conservative secular evolution of precessing compact binaries to second post-Newtonian order accuracy, with leading-order spin-orbit, spin-spin and mass quadrupole-monopole contributions included. The emerging closed system of first-order differential equations evolves the pairs of polar and azimuthal angles of the spin and orbital angular momentum vectors together with the periastron angle. In contrast with the instantaneous dynamics, the secular dynamics is autonomous. This secular dynamics reliably characterizes the system over timescales starting from a few times the radial period to several precessional periods, but less than the radiation reaction timescale. We numerically compare the instantaneous and secular evolutions and estimate the number of periods for which dissipation has no significant effect, e.g. the conservative timescale. We apply the analytic equations to study the spin flip-flop effect, recently found by numerical relativity methods. Our investigations show that the effect does not generalize beyond its original parameter settings, although we reveal distinct configurations exhibiting one half flip-flops. In addition, we find a flip-flopping evolution of the orbital angular momentum vector, which ventures from one pole to another through several precessional periods. This is a new effect, occurring for mass ratios much less than one. |
2004.08362 | Pedro Fernandes | Pedro G. S. Fernandes, Pedro Carrilho, Timothy Clifton, David J.
Mulryne | Derivation of Regularized Field Equations for the Einstein-Gauss-Bonnet
Theory in Four Dimensions | 6 pages + 2 pages with references; V2: Published in Physical Review D | Phys. Rev. D 102, 024025 (2020) | 10.1103/PhysRevD.102.024025 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a regularization procedure for the novel Einstein-Gauss-Bonnet
theory of gravity, which produces a set of field equations that can be written
in closed form in four dimensions. Our method consists of introducing a counter
term into the action, and does not rely on the embedding or compactification of
any higher-dimensional spaces. This counterterm is sufficient to cancel the
divergence in the action that would otherwise occur, and exactly reproduces the
trace of the field equations of the original formulation of the theory. All
other field equations display an extra scalar gravitational degree of freedom
in the gravitational sector, in keeping with the requirements of Lovelock's
theorem. We discuss issues concerning the equivalence between our new
regularized theory and the original.
| [
{
"created": "Fri, 17 Apr 2020 17:36:55 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jul 2020 15:39:03 GMT",
"version": "v2"
}
] | 2020-07-07 | [
[
"Fernandes",
"Pedro G. S.",
""
],
[
"Carrilho",
"Pedro",
""
],
[
"Clifton",
"Timothy",
""
],
[
"Mulryne",
"David J.",
""
]
] | We propose a regularization procedure for the novel Einstein-Gauss-Bonnet theory of gravity, which produces a set of field equations that can be written in closed form in four dimensions. Our method consists of introducing a counter term into the action, and does not rely on the embedding or compactification of any higher-dimensional spaces. This counterterm is sufficient to cancel the divergence in the action that would otherwise occur, and exactly reproduces the trace of the field equations of the original formulation of the theory. All other field equations display an extra scalar gravitational degree of freedom in the gravitational sector, in keeping with the requirements of Lovelock's theorem. We discuss issues concerning the equivalence between our new regularized theory and the original. |
1908.03337 | Mohammad Mehrafarin | Mansoureh Hoseini and Mohammad Mehrafarin | Cosmological Birefringence and the Geometric Phase of Photons | To appear in Phys. Lett. B., 2019 | Phys. Lett. B 797 (2019) 134841 | 10.1016/j.physletb.2019.134841 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Regarding axion electrodynamics in the background flat FRW universe, we show
that cosmological birefringence arises from an adiabatic noncyclic geometric
phase that appears in the quantum state of photons because of their interaction
with the axion field. We also show that the axion electrodynamics is equivalent
to standard electrodynamics in time-dependent bi-isotropic magnetoelectric
Tellegen media, which serves as an analogue system that can simulate
cosmological birefringence.
| [
{
"created": "Fri, 9 Aug 2019 07:02:43 GMT",
"version": "v1"
}
] | 2019-08-19 | [
[
"Hoseini",
"Mansoureh",
""
],
[
"Mehrafarin",
"Mohammad",
""
]
] | Regarding axion electrodynamics in the background flat FRW universe, we show that cosmological birefringence arises from an adiabatic noncyclic geometric phase that appears in the quantum state of photons because of their interaction with the axion field. We also show that the axion electrodynamics is equivalent to standard electrodynamics in time-dependent bi-isotropic magnetoelectric Tellegen media, which serves as an analogue system that can simulate cosmological birefringence. |
1710.05891 | Huan Yang | Huan Yang, William E. East, Luis Lehner | Can we distinguish low mass black holes in neutron star binaries? | 7 pages, 3 figures, fig 2 updated to fix an error in the previous
version | The Astrophysical Journal 856, 110, 2018 | 10.3847/1538-4357/aab2b0 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of gravitational waves from coalescing binary neutron stars
represents another milestone in gravitational-wave astronomy. However, since
LIGO is currently not as sensitive to the merger/ringdown part of the waveform,
the possibility that such signals are produced by a black hole-neutron star
binary can not be easily ruled out without appealing to assumptions about the
underlying compact object populations. We review a few astrophysical channels
that might produce black holes below 3 $M_{\odot}$ (roughly the upper bound on
the maximum mass of a neutron star), as well as existing constraints for these
channels. We show that, due to the uncertainty in the neutron star equation of
state, it is difficult to distinguish gravitational waves from a binary neutron
star system, from those of a black hole-neutron star system with the same
component masses, assuming Advanced LIGO sensitivity. This degeneracy can be
broken by accumulating statistics from many events to better constrain the
equation of state, or by third-generation detectors with higher sensitivity to
the late spiral to post-merger signal. We also discuss the possible differences
in electromagnetic counterparts between binary neutron star and low mass black
hole-neutron star mergers, arguing that it will be challenging to definitively
distinguish the two without better understanding of the underlying
astrophysical processes.
| [
{
"created": "Mon, 16 Oct 2017 17:44:34 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Aug 2018 14:48:30 GMT",
"version": "v2"
},
{
"created": "Thu, 29 Nov 2018 19:57:57 GMT",
"version": "v3"
}
] | 2018-12-03 | [
[
"Yang",
"Huan",
""
],
[
"East",
"William E.",
""
],
[
"Lehner",
"Luis",
""
]
] | The detection of gravitational waves from coalescing binary neutron stars represents another milestone in gravitational-wave astronomy. However, since LIGO is currently not as sensitive to the merger/ringdown part of the waveform, the possibility that such signals are produced by a black hole-neutron star binary can not be easily ruled out without appealing to assumptions about the underlying compact object populations. We review a few astrophysical channels that might produce black holes below 3 $M_{\odot}$ (roughly the upper bound on the maximum mass of a neutron star), as well as existing constraints for these channels. We show that, due to the uncertainty in the neutron star equation of state, it is difficult to distinguish gravitational waves from a binary neutron star system, from those of a black hole-neutron star system with the same component masses, assuming Advanced LIGO sensitivity. This degeneracy can be broken by accumulating statistics from many events to better constrain the equation of state, or by third-generation detectors with higher sensitivity to the late spiral to post-merger signal. We also discuss the possible differences in electromagnetic counterparts between binary neutron star and low mass black hole-neutron star mergers, arguing that it will be challenging to definitively distinguish the two without better understanding of the underlying astrophysical processes. |
2307.12102 | Tatyana P. Shestakova | R. I. Ayala O\~na, M. B. Kalmykov, D. P. Kislyakova and T. P.
Shestakova | The semiclassical limit of quantum gravity and the problem of time | 18 pages, no figure, to be published in Int. J. Mod. Phys. D | null | 10.1142/S0218271823400035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The question about the appearance of time in the semiclassical limit of
quantum gravity continues to be discussed in the literature. It is believed
that a temporal Schrodinger equation for matter fields on the background of a
classical gravitational field must be true. To obtain this equation, the Born -
Oppenheimer approximation for gravity is used. However, the origin of time in
this equation is different in works of various authors. For example, in the
papers of Kiefer and his collaborators, time is a parameter along a classical
trajectory of gravitational field; in the works of Montani and his
collaborators the origin of time is introducing the Kuchar - Torre reference
fluid; in the extended phase space approach the origin of time is the
consequence of existing of the observer in a fixed reference frame. We discuss
and compare these approaches. To make the calculations transparent, we
illustrate them with a model of a closed isotropic universe. In each approach,
one obtains some Schrodinger equation for matter fields with quantum
gravitational corrections, but the form of the equation and the corrections
depend on additional assumptions which are rather arbitrary. None of the
approaches can explain how time had appeared in the Early Universe, since it is
supposed that classical gravity and, therefore, classical spacetime had already
come into being.
| [
{
"created": "Sat, 22 Jul 2023 15:23:31 GMT",
"version": "v1"
}
] | 2023-07-25 | [
[
"Oña",
"R. I. Ayala",
""
],
[
"Kalmykov",
"M. B.",
""
],
[
"Kislyakova",
"D. P.",
""
],
[
"Shestakova",
"T. P.",
""
]
] | The question about the appearance of time in the semiclassical limit of quantum gravity continues to be discussed in the literature. It is believed that a temporal Schrodinger equation for matter fields on the background of a classical gravitational field must be true. To obtain this equation, the Born - Oppenheimer approximation for gravity is used. However, the origin of time in this equation is different in works of various authors. For example, in the papers of Kiefer and his collaborators, time is a parameter along a classical trajectory of gravitational field; in the works of Montani and his collaborators the origin of time is introducing the Kuchar - Torre reference fluid; in the extended phase space approach the origin of time is the consequence of existing of the observer in a fixed reference frame. We discuss and compare these approaches. To make the calculations transparent, we illustrate them with a model of a closed isotropic universe. In each approach, one obtains some Schrodinger equation for matter fields with quantum gravitational corrections, but the form of the equation and the corrections depend on additional assumptions which are rather arbitrary. None of the approaches can explain how time had appeared in the Early Universe, since it is supposed that classical gravity and, therefore, classical spacetime had already come into being. |
2303.13840 | Rebecca Briffa Ms | Rebecca Briffa, Celia Escamilla-Rivera, Jackson Levi Said, Jurgen
Mifsud | Constraints on $f(T)$ Cosmology with Pantheon+ | null | Monthly Notices of the Royal Astronomical Society 552 (2023)
6024-6034 | 10.1093/mnras/stad1384 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | $f(T)$ cosmology has shown promise in explaining aspects of cosmic evolution.
In this work, we analyze constraints on leading models of $f(T)$ gravity in the
context of the recently released Pantheon+ data set, together with comparisons
with previous releases. We also consider other late-time data sets including
cosmic chronometers and baryonic acoustic oscillation data. Our main result is
that we find that the different $f(T)$ models under investigation connect to a
variety of Hubble constant, which may help alleviate the cosmic tension on this
parameter.
| [
{
"created": "Fri, 24 Mar 2023 07:25:31 GMT",
"version": "v1"
}
] | 2023-05-22 | [
[
"Briffa",
"Rebecca",
""
],
[
"Escamilla-Rivera",
"Celia",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Mifsud",
"Jurgen",
""
]
] | $f(T)$ cosmology has shown promise in explaining aspects of cosmic evolution. In this work, we analyze constraints on leading models of $f(T)$ gravity in the context of the recently released Pantheon+ data set, together with comparisons with previous releases. We also consider other late-time data sets including cosmic chronometers and baryonic acoustic oscillation data. Our main result is that we find that the different $f(T)$ models under investigation connect to a variety of Hubble constant, which may help alleviate the cosmic tension on this parameter. |
gr-qc/9710010 | Matt Visser | Matt Visser (Washington University) | Energy conditions and galaxy formation | Three pages, uses mprocl.sty To appear in the proceedings of the
Eighth Marcel Grossmann Conference on General Relativity. (Jerusalem, Israel,
June 1997) [Minor typo fixed in references.] | null | 10.1126/science.276.5309.88 | null | gr-qc astro-ph | null | This note summarizes a model-independent analysis of the age of the universe
problem that trades off precision in favour of robustness: The energy
conditions of Einstein gravity are designed to extract as much information as
possible from classical general relativity without specifying a particular
equation of state. This is particularly useful in a cosmological setting, where
the equation of state for the cosmological fluid is extremely uncertain. The
strong energy condition (SEC) provides a simple and robust bound on the
behaviour of the look-back time as a function of red-shift. Observation
suggests that the SEC may be violated sometime between the epoch of galaxy
formation and the present.
| [
{
"created": "Thu, 2 Oct 1997 04:29:44 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Oct 1997 01:52:22 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Visser",
"Matt",
"",
"Washington University"
]
] | This note summarizes a model-independent analysis of the age of the universe problem that trades off precision in favour of robustness: The energy conditions of Einstein gravity are designed to extract as much information as possible from classical general relativity without specifying a particular equation of state. This is particularly useful in a cosmological setting, where the equation of state for the cosmological fluid is extremely uncertain. The strong energy condition (SEC) provides a simple and robust bound on the behaviour of the look-back time as a function of red-shift. Observation suggests that the SEC may be violated sometime between the epoch of galaxy formation and the present. |
2102.02713 | Scott A. Hughes | Scott A. Hughes, Niels Warburton, Gaurav Khanna, Alvin J. K. Chua, and
Michael L. Katz | Adiabatic waveforms for extreme mass-ratio inspirals via multivoice
decomposition in time and frequency | 31 pages, 17 figures. Update: corrected a sign error in a term in Eq.
(B5). This factor was correct in the related code, it was purely a typo in
the manuscript. An erratum to PRD has been submitted. Many thanks to Angelica
Albertini for bringing this error to our attention. Update 2: corrected a
missing factor of $m$ in Eq. (3.30) | Phys. Rev. D 103, 104014 (2021) | 10.1103/PhysRevD.103.104014 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute adiabatic waveforms for extreme mass-ratio inspirals (EMRIs) by
"stitching" together a long inspiral waveform from a sequence of waveform
snapshots, each of which corresponds to a particular geodesic orbit. We show
that the complicated total waveform can be regarded as a sum of "voices." Each
voice evolves in a simple way on long timescales, a property which can be
exploited to efficiently produce waveform models that faithfully encode the
properties of EMRI systems. We look at examples for a range of different
orbital geometries: spherical orbits, equatorial eccentric orbits, and one
example of generic (inclined and eccentric) orbits. To our knowledge, this is
the first calculation of a generic EMRI waveform that uses strong-field
radiation reaction. We examine waveforms in both the time and frequency
domains. Although EMRIs evolve slowly enough that the stationary phase
approximation (SPA) to the Fourier transform is valid, the SPA calculation must
be done to higher order for some voices, since their instantaneous frequency
can change from chirping forward ($\dot f > 0$) to chirping backward ($\dot f <
0$). The approach we develop can eventually be extended to more complete EMRI
waveform models, for example to include effects neglected by the adiabatic
approximation such as the conservative self force and spin-curvature coupling.
| [
{
"created": "Thu, 4 Feb 2021 16:12:22 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Apr 2021 15:10:51 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Jun 2021 15:46:27 GMT",
"version": "v3"
},
{
"created": "Fri, 24 Mar 2023 12:25:39 GMT",
"version": "v4"
},
{
"cr... | 2024-04-01 | [
[
"Hughes",
"Scott A.",
""
],
[
"Warburton",
"Niels",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Chua",
"Alvin J. K.",
""
],
[
"Katz",
"Michael L.",
""
]
] | We compute adiabatic waveforms for extreme mass-ratio inspirals (EMRIs) by "stitching" together a long inspiral waveform from a sequence of waveform snapshots, each of which corresponds to a particular geodesic orbit. We show that the complicated total waveform can be regarded as a sum of "voices." Each voice evolves in a simple way on long timescales, a property which can be exploited to efficiently produce waveform models that faithfully encode the properties of EMRI systems. We look at examples for a range of different orbital geometries: spherical orbits, equatorial eccentric orbits, and one example of generic (inclined and eccentric) orbits. To our knowledge, this is the first calculation of a generic EMRI waveform that uses strong-field radiation reaction. We examine waveforms in both the time and frequency domains. Although EMRIs evolve slowly enough that the stationary phase approximation (SPA) to the Fourier transform is valid, the SPA calculation must be done to higher order for some voices, since their instantaneous frequency can change from chirping forward ($\dot f > 0$) to chirping backward ($\dot f < 0$). The approach we develop can eventually be extended to more complete EMRI waveform models, for example to include effects neglected by the adiabatic approximation such as the conservative self force and spin-curvature coupling. |
2109.12670 | Kirill Bronnikov | Kirill A. Bronnikov, Pavel E. Kashargin, Sergey V. Sushkov | Magnetized dusty black holes and wormholes | 17 pages, 5 figures. Some comments and references added, matching to
the published version, as well as other minor corrections | Universe 7, 419 (2021) | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the generalized Tolman solution of general relativity, describing
the evolution of a spherical dust cloud in the presence of an external electric
or magnetic field. The solution contains three arbitrary functions $f(R)$,
$F(R)$ and $\tau_0(R)$, where $R$ is a radial coordinate in the comoving
reference frame. The solution splits into three branches corresponding to
hyperbolic ($f >0$), parabolic ($f=0$) and elliptic ($f < 0$) types of motion.
In such models, we study the possible existence of wormhole throats defined as
spheres of minimum radius at a fixed time instant, and prove the existence of
throats in the elliptic branch under certain conditions imposed on the
arbitrary functions. It is further shown that the normal to a throat is a
timelike vector (except for the instant of maximum expansion, when this vector
is null), hence a throat is in general located in a T-region of space-time.
Thus if such a dust cloud is placed between two empty (Reissner-Nordstr\"om or
Schwarzschild) space-time regions, the whole configuration is a black hole
rather than a wormhole. However, dust clouds with throats can be inscribed into
closed isotropic cosmological models filled with dust to form wormholes which
exist for a finite period of time and experience expansion and contraction
together with the corresponding cosmology. Explicit examples and numerical
estimates are presented. The possible traversability of wormhole-like evolving
dust layers is established by a numerical study of radial null geodesics.
| [
{
"created": "Sun, 26 Sep 2021 18:28:25 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Nov 2021 15:58:08 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Nov 2021 15:12:05 GMT",
"version": "v3"
}
] | 2021-11-18 | [
[
"Bronnikov",
"Kirill A.",
""
],
[
"Kashargin",
"Pavel E.",
""
],
[
"Sushkov",
"Sergey V.",
""
]
] | We consider the generalized Tolman solution of general relativity, describing the evolution of a spherical dust cloud in the presence of an external electric or magnetic field. The solution contains three arbitrary functions $f(R)$, $F(R)$ and $\tau_0(R)$, where $R$ is a radial coordinate in the comoving reference frame. The solution splits into three branches corresponding to hyperbolic ($f >0$), parabolic ($f=0$) and elliptic ($f < 0$) types of motion. In such models, we study the possible existence of wormhole throats defined as spheres of minimum radius at a fixed time instant, and prove the existence of throats in the elliptic branch under certain conditions imposed on the arbitrary functions. It is further shown that the normal to a throat is a timelike vector (except for the instant of maximum expansion, when this vector is null), hence a throat is in general located in a T-region of space-time. Thus if such a dust cloud is placed between two empty (Reissner-Nordstr\"om or Schwarzschild) space-time regions, the whole configuration is a black hole rather than a wormhole. However, dust clouds with throats can be inscribed into closed isotropic cosmological models filled with dust to form wormholes which exist for a finite period of time and experience expansion and contraction together with the corresponding cosmology. Explicit examples and numerical estimates are presented. The possible traversability of wormhole-like evolving dust layers is established by a numerical study of radial null geodesics. |
0804.1174 | Mu-Tao Wang | Mu-Tao Wang and Shing-Tung Yau | Quasilocal mass in general relativity | 10 pages, editorial changes made to comply with journal's page limit,
to appear in Physical Review Letters | Phys.Rev.Lett.102:021101,2009 | 10.1103/PhysRevLett.102.021101 | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There have been many attempts to define the notion of quasilocal mass for a
spacelike 2-surface in spacetime by the Hamilton-Jacobi analysis. The essential
difficulty in this approach is to identify the right choice of the background
configuration to be subtracted from the physical Hamiltonian. Quasilocal mass
should be nonnegative for surfaces in general spacetime and zero for surfaces
in flat spacetime. In this letter, we propose a new definition of
gauge-independent quasilocal mass and prove that it has the desired properties.
| [
{
"created": "Tue, 8 Apr 2008 02:35:12 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jul 2008 10:49:49 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Dec 2008 16:32:44 GMT",
"version": "v3"
}
] | 2009-02-23 | [
[
"Wang",
"Mu-Tao",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | There have been many attempts to define the notion of quasilocal mass for a spacelike 2-surface in spacetime by the Hamilton-Jacobi analysis. The essential difficulty in this approach is to identify the right choice of the background configuration to be subtracted from the physical Hamiltonian. Quasilocal mass should be nonnegative for surfaces in general spacetime and zero for surfaces in flat spacetime. In this letter, we propose a new definition of gauge-independent quasilocal mass and prove that it has the desired properties. |
gr-qc/9801064 | Toporenskij A. V. | A.Yu.Kamenshchik, I.M.Khalatnikov, A.V.Toporensky | Simplest cosmological model with the scalar field | 24 pages with 2 gif figures and 4 eps figures, mprocl.sty, To appear
in International Journal of Modern Physics D | Int.J.Mod.Phys. D6 (1997) 673-692 | 10.1142/S0218271897000418 | null | gr-qc | null | We investigate the simplest cosmological model with the massive real scalar
non-interacting inflaton field minimally coupled to gravity. The classification
of trajectories in closed minisuperspace Friedmann-Robertson-Walker model is
presented.The fractal nature of a set of infinitely bounced trajectories is
discussed. The results of numerical calculations are compared with those
obtained byperturbative analytical calculations around the exactly solvable
minisuperspace cosmological model with massless scalar field.
| [
{
"created": "Tue, 20 Jan 1998 15:13:47 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Kamenshchik",
"A. Yu.",
""
],
[
"Khalatnikov",
"I. M.",
""
],
[
"Toporensky",
"A. V.",
""
]
] | We investigate the simplest cosmological model with the massive real scalar non-interacting inflaton field minimally coupled to gravity. The classification of trajectories in closed minisuperspace Friedmann-Robertson-Walker model is presented.The fractal nature of a set of infinitely bounced trajectories is discussed. The results of numerical calculations are compared with those obtained byperturbative analytical calculations around the exactly solvable minisuperspace cosmological model with massless scalar field. |
1512.08166 | Argha Banerjee | Argha Banerjee | Inflation in Brane World Gravity | 53 pages (in English), 13 figures. M.Sc. thesis submitted to
Presidency University on May, 2015 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the inflationary dynamics in Brane World gravity and look for
observational signatures of any deviation from the standard General Relativity
based results of Cosmological Perturbation Theory. We first review the standard
paradigm of General Relativity based inflationary dynamics and cosmological
perturbation theory and then go on to review Brane World gravity. Finally we
look at the high energy corrections for some chosen models and compare the
results with the Planck and WMAP (9 year) data. Then we make a summary of our
results and point out certain interesting features of Brane World gravity based
calculations and infer it's implications on Brane World gravity itself.
| [
{
"created": "Sun, 27 Dec 2015 03:04:35 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Dec 2015 02:48:08 GMT",
"version": "v2"
}
] | 2015-12-31 | [
[
"Banerjee",
"Argha",
""
]
] | We study the inflationary dynamics in Brane World gravity and look for observational signatures of any deviation from the standard General Relativity based results of Cosmological Perturbation Theory. We first review the standard paradigm of General Relativity based inflationary dynamics and cosmological perturbation theory and then go on to review Brane World gravity. Finally we look at the high energy corrections for some chosen models and compare the results with the Planck and WMAP (9 year) data. Then we make a summary of our results and point out certain interesting features of Brane World gravity based calculations and infer it's implications on Brane World gravity itself. |
1504.02423 | Andrea Pelissetto | A. Pelissetto and M. Testa | Getting the Lorentz transformations without requiring an invariant speed | 4 pages, 1 figure | American Journal of Physics 83 (2015) 338-340 | 10.1119/1.4901453 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The structure of the Lorentz transformations follows purely from the absence
of privileged inertial reference frames and the group structure (closure under
composition) of the transformations---two assumptions that are simple and
physically necessary. The existence of an invariant speed is \textit{not} a
necessary assumption, and in fact is a consequence of the principle of
relativity (though the finite value of this speed must, of course, be obtained
from experiment). Von Ignatowsky derived this result in 1911, but it is still
not widely known and is absent from most textbooks. Here we present a
completely elementary proof of the result, suitable for use in an introductory
course in special relativity.
| [
{
"created": "Wed, 8 Apr 2015 11:13:44 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Pelissetto",
"A.",
""
],
[
"Testa",
"M.",
""
]
] | The structure of the Lorentz transformations follows purely from the absence of privileged inertial reference frames and the group structure (closure under composition) of the transformations---two assumptions that are simple and physically necessary. The existence of an invariant speed is \textit{not} a necessary assumption, and in fact is a consequence of the principle of relativity (though the finite value of this speed must, of course, be obtained from experiment). Von Ignatowsky derived this result in 1911, but it is still not widely known and is absent from most textbooks. Here we present a completely elementary proof of the result, suitable for use in an introductory course in special relativity. |
1304.1878 | Lorenzo Sebastiani | Guido Cognola, Ratbay Myrzakulov, Lorenzo Sebastiani and Sergio
Zerbini | Einstein gravity with Gauss-Bonnet entropic corrections | 11 pages, published version | Phys. Rev. D, v. 88, N2, 024006 (2013) | 10.1103/PhysRevD.88.024006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A toy model of Einstein gravity with a Gauss-Bonnet classically "entropic"
term mimicking a quantum correction is considered. The static black hole
solution due to Tomozawa is found and generalized with the inclusion of non
trivial horizon topology, and its entropy evaluated deriving the first law by
equations of motion. As a result the Bekenstein-Hawking area law turns to be
corrected by a logarithmic area term. A Misner-Sharp expression for the mass of
black hole is found. Within a Friedmann-Lema\^itre-Robertson-Walker (FLRW)
cosmological setting, the model is used in order to derive modified Friedmann
equations. Such new equations are shown to reproduce the first law with the
same formal entropy and quasi local energy of the static case, but here within
a FLRW space-time interpreted as a dynamical cosmological black hole. A
detailed analysis of cosmological solutions is presented, and it is shown that
the presence of the correction term provides regular solutions and interesting
phases of acceleration and decelerations, as well as, with negligible matter,
exact de Sitter solutions.
| [
{
"created": "Sat, 6 Apr 2013 11:36:59 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Jun 2013 04:07:04 GMT",
"version": "v2"
}
] | 2013-10-15 | [
[
"Cognola",
"Guido",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Sebastiani",
"Lorenzo",
""
],
[
"Zerbini",
"Sergio",
""
]
] | A toy model of Einstein gravity with a Gauss-Bonnet classically "entropic" term mimicking a quantum correction is considered. The static black hole solution due to Tomozawa is found and generalized with the inclusion of non trivial horizon topology, and its entropy evaluated deriving the first law by equations of motion. As a result the Bekenstein-Hawking area law turns to be corrected by a logarithmic area term. A Misner-Sharp expression for the mass of black hole is found. Within a Friedmann-Lema\^itre-Robertson-Walker (FLRW) cosmological setting, the model is used in order to derive modified Friedmann equations. Such new equations are shown to reproduce the first law with the same formal entropy and quasi local energy of the static case, but here within a FLRW space-time interpreted as a dynamical cosmological black hole. A detailed analysis of cosmological solutions is presented, and it is shown that the presence of the correction term provides regular solutions and interesting phases of acceleration and decelerations, as well as, with negligible matter, exact de Sitter solutions. |
gr-qc/0102098 | Laurent Freidel | Laurent Freidel | A Ponzano-Regge model of Lorentzian 3-Dimensional gravity | 7 pages, Talk presented at Villasimius 1999, constraint dynamics and
quantum gravity conference | Nucl.Phys.Proc.Suppl. 88 (2000) 237-240 | 10.1016/S0920-5632(00)00775-1 | null | gr-qc | null | We present the construction of the partition function of 3-dimensional
gravity in the Lorentzian regime as a state sum model over a triangulation.
This generalize the work of Ponzano and Regge to the case of Lorentzian
signature.
| [
{
"created": "Thu, 22 Feb 2001 15:54:46 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Freidel",
"Laurent",
""
]
] | We present the construction of the partition function of 3-dimensional gravity in the Lorentzian regime as a state sum model over a triangulation. This generalize the work of Ponzano and Regge to the case of Lorentzian signature. |
1807.06268 | Dao-Jun Liu | Yang Huang, Yi-Ping Dong and Dao-Jun Liu | Revisiting the shadow of a black hole in the presence of a plasma | 16 pages, 8 figures, published in Int. J. Mod. Phys. D | null | 10.1142/S0218271818501146 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the photon's motion around a black hole in the presence of a plasma
whose density is a function of the radius coordinate by a renewed ray-tracing
algorithm and investigate the influence of the plasma on the shadow of the
black hole. The presence of plasma affects not only the size but also the shape
of black hole shadow. Furthermore, the influence of plasma on trajectories of
photons depends on the frequency of photon. For the high-frequency photons, the
influence is negligible, on the contrary, the trajectories of low-frequency
photons is affected significantly by the plasma. Interestingly, it is also
found that the black hole image would take on a multi-ring structure due to the
presence of plasma.
| [
{
"created": "Tue, 17 Jul 2018 08:06:30 GMT",
"version": "v1"
}
] | 2018-07-18 | [
[
"Huang",
"Yang",
""
],
[
"Dong",
"Yi-Ping",
""
],
[
"Liu",
"Dao-Jun",
""
]
] | We study the photon's motion around a black hole in the presence of a plasma whose density is a function of the radius coordinate by a renewed ray-tracing algorithm and investigate the influence of the plasma on the shadow of the black hole. The presence of plasma affects not only the size but also the shape of black hole shadow. Furthermore, the influence of plasma on trajectories of photons depends on the frequency of photon. For the high-frequency photons, the influence is negligible, on the contrary, the trajectories of low-frequency photons is affected significantly by the plasma. Interestingly, it is also found that the black hole image would take on a multi-ring structure due to the presence of plasma. |
1007.2768 | Jonathan Engle | Christopher Beetle, Jonathan Engle | Generic isolated horizons in loop quantum gravity | 13 pages | Class.Quant.Grav.27:235024,2010 | 10.1088/0264-9381/27/23/235024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Isolated horizons model equilibrium states of classical black holes. A
detailed quantization, starting from a classical phase space restricted to
spherically symmetric horizons, exists in the literature and has since been
extended to axisymmetry. This paper extends the quantum theory to horizons of
arbitrary shape. Surprisingly, the Hilbert space obtained by quantizing the
full phase space of \textit{all} generic horizons with a fixed area is
identical to that originally found in spherical symmetry. The entropy of a
large horizon remains one quarter its area, with the Barbero-Immirzi parameter
retaining its value from symmetric analyses. These results suggest a
reinterpretation of the intrinsic quantum geometry of the horizon surface.
| [
{
"created": "Fri, 16 Jul 2010 13:15:03 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Beetle",
"Christopher",
""
],
[
"Engle",
"Jonathan",
""
]
] | Isolated horizons model equilibrium states of classical black holes. A detailed quantization, starting from a classical phase space restricted to spherically symmetric horizons, exists in the literature and has since been extended to axisymmetry. This paper extends the quantum theory to horizons of arbitrary shape. Surprisingly, the Hilbert space obtained by quantizing the full phase space of \textit{all} generic horizons with a fixed area is identical to that originally found in spherical symmetry. The entropy of a large horizon remains one quarter its area, with the Barbero-Immirzi parameter retaining its value from symmetric analyses. These results suggest a reinterpretation of the intrinsic quantum geometry of the horizon surface. |
1005.5296 | Edward Porter | Edward K. Porter and Alberto Sesana | Eccentric Massive Black Hole Binaries in LISA I : The Detection
Capabilities of Circular Templates | Revtex, 21 pages, 12 figures. Submitted to PRD | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the major assumptions in the search for gravitational wave signatures
from massive and supermassive black hole binaries with LISA, is that these
systems will have circularized before entering the LISA bandwidth. Current
astrophysical simulations now suggest that systems could have a non-negligible
eccentricity in the LISA band, and an important level of eccentricity in the
Pulsar Timing regime. In this work, we use a set of source catalogues from
astrophysically motivated models of massive black hole binary formation and
assume a one year LISA mission lifetime. Depending on the model in question,
the initial eccentricities in the final year of the inspiral can be as high as
0.6 for high mass seeds and 0.8 for low mass seeds. We show that restricted
post-Newtonian circular templates are extremely inefficient in recovering
eccentric binaries, with median optimal signal to noise ratio recoveries of
approximately 10% for all models considered. This coupled with extremely large
errors in parameter recovery from individual Markov chain Monte Carlo's
demonstrate quite clearly that even to search for binaries with initial
eccentricities as low as $10^{-4}$, we will require eccentric templates for
LISA data analysis.
| [
{
"created": "Fri, 28 May 2010 14:14:48 GMT",
"version": "v1"
}
] | 2010-05-31 | [
[
"Porter",
"Edward K.",
""
],
[
"Sesana",
"Alberto",
""
]
] | One of the major assumptions in the search for gravitational wave signatures from massive and supermassive black hole binaries with LISA, is that these systems will have circularized before entering the LISA bandwidth. Current astrophysical simulations now suggest that systems could have a non-negligible eccentricity in the LISA band, and an important level of eccentricity in the Pulsar Timing regime. In this work, we use a set of source catalogues from astrophysically motivated models of massive black hole binary formation and assume a one year LISA mission lifetime. Depending on the model in question, the initial eccentricities in the final year of the inspiral can be as high as 0.6 for high mass seeds and 0.8 for low mass seeds. We show that restricted post-Newtonian circular templates are extremely inefficient in recovering eccentric binaries, with median optimal signal to noise ratio recoveries of approximately 10% for all models considered. This coupled with extremely large errors in parameter recovery from individual Markov chain Monte Carlo's demonstrate quite clearly that even to search for binaries with initial eccentricities as low as $10^{-4}$, we will require eccentric templates for LISA data analysis. |
0903.5225 | Maurice Dupre | Maurice J. Dupr\'e | The Fully Covariant Energy Momentum Stress Tensor For Gravity and the
Einstein Equation in General Relativity | preprint | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a fully covariant energy momentum stress tensor for the gravitational
field which is easily physically motivated, and which leads to a very general
derivation of the Einstein equation for gravity. We do not need to assume any
property of the surce matter fields' energy momentum stress tensor other than
symmetry. We give a physical motivation for this choice using laser light
pressure. As a consequence of our derivation, the energy momentum stress tensor
for the total source matter and fields must be divergence free, when spacetime
is 4 dimensional. Moreoverr, if the total source matter fields are assumed to
be divergence free, then either spacetime is dimension 4 or the spacetime has
constant scalar curvature.
| [
{
"created": "Mon, 30 Mar 2009 13:53:46 GMT",
"version": "v1"
}
] | 2009-03-31 | [
[
"Dupré",
"Maurice J.",
""
]
] | We give a fully covariant energy momentum stress tensor for the gravitational field which is easily physically motivated, and which leads to a very general derivation of the Einstein equation for gravity. We do not need to assume any property of the surce matter fields' energy momentum stress tensor other than symmetry. We give a physical motivation for this choice using laser light pressure. As a consequence of our derivation, the energy momentum stress tensor for the total source matter and fields must be divergence free, when spacetime is 4 dimensional. Moreoverr, if the total source matter fields are assumed to be divergence free, then either spacetime is dimension 4 or the spacetime has constant scalar curvature. |
2010.02753 | Prabir Rudra | Chayan Ranjit (Egra S.S.B. College), Prabir Rudra (Asutosh College),
Sujata Kundu (Narula Instt. of Tech.) | Constraints on Energy Momentum Squared Gravity from cosmic chronometers
and Supernovae Type Ia data | 22 pages, 18 figures | Annals of Physics, Volume 428 (2021) 168432 | 10.1016/j.aop.2021.168432 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we perform an observational data analysis on the energy momentum
squared gravity model. Possible solutions for matter density are obtained from
the model and their cosmological implications are studied. Some recent
observational data is used to constrain model parameters using statistical
techniques. We have used the cosmic chronometer and SNe Type-Ia Riess (292)
$H(z)-z$ data-sets in our study. Along with the data-sets we have also used
baryon acoustic oscillation (BAO) peak parameter and cosmic microwave
background (CMB) peak parameter to obtain bounds on the model parameters. Joint
analysis of the data with the above mentioned parameters have been performed to
obtain better results. For the statistical analysis we have used the
minimization technique of the $\chi^{2}$ statistic. Using this tool we have
constrained the free parameters of the model. Confidence contours have been
generated for the predicted values of the free parameters at the $66\%$, $90\%$
and $99\%$ confidence levels. Finally we have compared our analysis with the
union2 data sample presented by Amanullah et al.,2010 and the recently
published Pantheon data sample. Finally a multi-component model is investigated
by adding dust to a general cosmological fluid with equation of state $w=-1/3$.
The density parameters were studied and their values were found to comply with
the observational results.
| [
{
"created": "Sun, 4 Oct 2020 14:21:34 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Mar 2021 17:14:35 GMT",
"version": "v2"
}
] | 2021-03-25 | [
[
"Ranjit",
"Chayan",
"",
"Egra S.S.B. College"
],
[
"Rudra",
"Prabir",
"",
"Asutosh College"
],
[
"Kundu",
"Sujata",
"",
"Narula Instt. of Tech."
]
] | In this work we perform an observational data analysis on the energy momentum squared gravity model. Possible solutions for matter density are obtained from the model and their cosmological implications are studied. Some recent observational data is used to constrain model parameters using statistical techniques. We have used the cosmic chronometer and SNe Type-Ia Riess (292) $H(z)-z$ data-sets in our study. Along with the data-sets we have also used baryon acoustic oscillation (BAO) peak parameter and cosmic microwave background (CMB) peak parameter to obtain bounds on the model parameters. Joint analysis of the data with the above mentioned parameters have been performed to obtain better results. For the statistical analysis we have used the minimization technique of the $\chi^{2}$ statistic. Using this tool we have constrained the free parameters of the model. Confidence contours have been generated for the predicted values of the free parameters at the $66\%$, $90\%$ and $99\%$ confidence levels. Finally we have compared our analysis with the union2 data sample presented by Amanullah et al.,2010 and the recently published Pantheon data sample. Finally a multi-component model is investigated by adding dust to a general cosmological fluid with equation of state $w=-1/3$. The density parameters were studied and their values were found to comply with the observational results. |
2407.08241 | Zhen-Ming Xu | Zhen-Ming Xu, Pan-Pan Zhang, Bin Wu, Xing Zhang | Thermodynamic bounce effect in quantum BTZ black hole | 8 pages, 3 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A novel thermodynamic phenomenon has been observed in the quantum
Ba\~{n}ados-Teitelboim-Zanelli (qBTZ) black hole, utilizing generalized free
energy and Kramer escape rate. This phenomenon also reveals the unique property
of the quantum black hole. The stochastic thermal motion of various
thermodynamic states within the black hole system induces phase transitions,
under the influence of generalized free energy which obtained by extending
Maxwell's construction. Through the analysis of Kramer escape rate, it is
discovered that the qBTZ black hole thermodynamic system exhibits a bounce
effect. Furthermore, the overall thermodynamic picture of the qBTZ black hole
has been obtained under different quantum backreactions.
| [
{
"created": "Thu, 11 Jul 2024 07:38:09 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Xu",
"Zhen-Ming",
""
],
[
"Zhang",
"Pan-Pan",
""
],
[
"Wu",
"Bin",
""
],
[
"Zhang",
"Xing",
""
]
] | A novel thermodynamic phenomenon has been observed in the quantum Ba\~{n}ados-Teitelboim-Zanelli (qBTZ) black hole, utilizing generalized free energy and Kramer escape rate. This phenomenon also reveals the unique property of the quantum black hole. The stochastic thermal motion of various thermodynamic states within the black hole system induces phase transitions, under the influence of generalized free energy which obtained by extending Maxwell's construction. Through the analysis of Kramer escape rate, it is discovered that the qBTZ black hole thermodynamic system exhibits a bounce effect. Furthermore, the overall thermodynamic picture of the qBTZ black hole has been obtained under different quantum backreactions. |
2210.01852 | Abhishek Joshi | Abhishek V. Joshi, Shawn G. Rosofsky, Roland Haas and E. A. Huerta | Numerical relativity higher order gravitational waveforms of eccentric,
spinning, non-precessing binary black hole mergers | 13 pages, 5 figures, updated manuscript with added waveform
comparisons to TEOBResumS. accepted in Phys. Rev. D | Phys. Rev. D 107, 064038 (2023) | 10.1103/PhysRevD.107.064038 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We use the open source, community-driven, numerical relativity software, the
Einstein Toolkit to study the physics of eccentric, spinning, nonprecessing
binary black hole mergers with mass-ratios $q=\{2, 4, 6\}$, individual
dimensionless spin parameters $\chi_{1z}=\pm0.6$, $\chi_{2z}=\pm0.3$, that
include higher order gravitational wave modes $\ell\leq4$, except for memory
modes. Assuming stellar mass binary black hole mergers that may be detectable
by the advanced LIGO detectors, we find that including modes up to $\ell=4$
increases the signal-to-noise of compact binaries between $3.5\%$ to $35\%$,
compared to signals that only include the $\ell=|m|=2$ mode. We use two
waveform models, TEOBResumS and SEOBNRE, which incorporate spin and
eccentricity corrections in the waveform dynamics, to quantify the orbital
eccentricity of our numerical relativity catalog in a gauge-invariant manner
through fitting factor calculations. Our findings indicate that the inclusion
of higher order wave modes has a measurable effect in the recovery of
moderately and highly eccentric black hole mergers, and thus it is essential to
develop waveform models and signal processing tools that accurately describe
the physics of these astrophysical sources.
| [
{
"created": "Tue, 4 Oct 2022 18:43:09 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Mar 2023 08:20:54 GMT",
"version": "v2"
}
] | 2023-03-22 | [
[
"Joshi",
"Abhishek V.",
""
],
[
"Rosofsky",
"Shawn G.",
""
],
[
"Haas",
"Roland",
""
],
[
"Huerta",
"E. A.",
""
]
] | We use the open source, community-driven, numerical relativity software, the Einstein Toolkit to study the physics of eccentric, spinning, nonprecessing binary black hole mergers with mass-ratios $q=\{2, 4, 6\}$, individual dimensionless spin parameters $\chi_{1z}=\pm0.6$, $\chi_{2z}=\pm0.3$, that include higher order gravitational wave modes $\ell\leq4$, except for memory modes. Assuming stellar mass binary black hole mergers that may be detectable by the advanced LIGO detectors, we find that including modes up to $\ell=4$ increases the signal-to-noise of compact binaries between $3.5\%$ to $35\%$, compared to signals that only include the $\ell=|m|=2$ mode. We use two waveform models, TEOBResumS and SEOBNRE, which incorporate spin and eccentricity corrections in the waveform dynamics, to quantify the orbital eccentricity of our numerical relativity catalog in a gauge-invariant manner through fitting factor calculations. Our findings indicate that the inclusion of higher order wave modes has a measurable effect in the recovery of moderately and highly eccentric black hole mergers, and thus it is essential to develop waveform models and signal processing tools that accurately describe the physics of these astrophysical sources. |
2206.14006 | Teagan Clarke | Teagan A. Clarke, Isobel M. Romero-Shaw, Paul D. Lasky, Eric Thrane | Gravitational-wave inference for eccentric binaries: the argument of
periapsis | 7 pages, 4 figures. Accepted in MNRAS | null | 10.1093/mnras/stac2965 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves from binary black hole mergers have allowed us to
directly observe stellar-mass black hole binaries for the first time, and
therefore explore their formation channels. One of the ways to infer how a
binary system is assembled is by measuring the system's orbital eccentricity.
Current methods of parameter estimation do not include all physical effects of
eccentric systems such as spin-induced precession, higher-order modes, and the
initial argument of periapsis: an angle describing the orientation of the
orbital ellipse. We explore how varying the argument of periapsis changes
gravitational waveforms and study its effect on the inference of astrophysical
parameters. We use the eccentric spin-aligned waveforms TEOBResumS and SEOBNRE
to measure the change in the waveforms as the argument of periapsis is changed.
We find that the argument of periapsis could already be impacting analyses
performed with TEOBResumS. However, it is likely to be well-resolvable in the
foreseeable future only for the loudest events observed by LIGO--Virgo--KAGRA.
The systematic error in previous, low-eccentricity analyses that have not
considered the argument of periapsis is likely to be small.
| [
{
"created": "Tue, 28 Jun 2022 13:47:40 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2022 03:21:15 GMT",
"version": "v2"
}
] | 2022-10-26 | [
[
"Clarke",
"Teagan A.",
""
],
[
"Romero-Shaw",
"Isobel M.",
""
],
[
"Lasky",
"Paul D.",
""
],
[
"Thrane",
"Eric",
""
]
] | Gravitational waves from binary black hole mergers have allowed us to directly observe stellar-mass black hole binaries for the first time, and therefore explore their formation channels. One of the ways to infer how a binary system is assembled is by measuring the system's orbital eccentricity. Current methods of parameter estimation do not include all physical effects of eccentric systems such as spin-induced precession, higher-order modes, and the initial argument of periapsis: an angle describing the orientation of the orbital ellipse. We explore how varying the argument of periapsis changes gravitational waveforms and study its effect on the inference of astrophysical parameters. We use the eccentric spin-aligned waveforms TEOBResumS and SEOBNRE to measure the change in the waveforms as the argument of periapsis is changed. We find that the argument of periapsis could already be impacting analyses performed with TEOBResumS. However, it is likely to be well-resolvable in the foreseeable future only for the loudest events observed by LIGO--Virgo--KAGRA. The systematic error in previous, low-eccentricity analyses that have not considered the argument of periapsis is likely to be small. |
1502.01622 | Alberto Enciso | Alberto Enciso and Niky Kamran | Determining an asymptotically AdS spacetime from data on its conformal
boundary | 6 pages | null | 10.1007/s10714-015-1974-5 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An outstanding question lying at the core of the AdS/CFT correspondence in
string theory is the holographic prescription problem for Einstein metrics,
which asserts that one can slightly perturb the conformal geometry at infinity
of the anti-de Sitter space and still obtain an asymptotically anti-de Sitter
spacetime that satisfies the Einstein equations with a negative cosmological
constant. The purpose of this paper is to address this question by providing a
precise quantitative statement of the real-time holographic principle for
Einstein spacetimes, to outline its proof and to discuss its physical
implications.
| [
{
"created": "Thu, 5 Feb 2015 16:17:29 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Sep 2015 08:03:49 GMT",
"version": "v2"
}
] | 2015-12-09 | [
[
"Enciso",
"Alberto",
""
],
[
"Kamran",
"Niky",
""
]
] | An outstanding question lying at the core of the AdS/CFT correspondence in string theory is the holographic prescription problem for Einstein metrics, which asserts that one can slightly perturb the conformal geometry at infinity of the anti-de Sitter space and still obtain an asymptotically anti-de Sitter spacetime that satisfies the Einstein equations with a negative cosmological constant. The purpose of this paper is to address this question by providing a precise quantitative statement of the real-time holographic principle for Einstein spacetimes, to outline its proof and to discuss its physical implications. |
0809.2422 | Vladimir S. Manko | V.S. Manko, E.D. Rodchenko, E. Ruiz and B.I. Sadovnikov | Exact solution for the simplest binary system of Kerr black holes | 9 pages, 1 figure, typos corrected, a footnote on p.6 extended | Phys.Rev.D78:124014,2008 | 10.1103/PhysRevD.78.124014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The full metric describing two counter-rotating identical Kerr black holes
separated by a massless strut is derived in the explicit analytical form. It
contains three arbitrary parameters which are the Komar mass M, Komar angular
momentum per unit mass a of one of the black holes (the other has the same mass
and equal but opposite angular momentum) and the coordinate distance R between
the centers of the horizons. In the limit of extreme black holes, the metric
becomes a special member of the Kinnersly-Chitre five-parameter family of
vacuum solutions generalizing the Tomimatsu-Sato delta=2 spacetime, and we
present the complete set of metrical fields defining this limit.
| [
{
"created": "Sun, 14 Sep 2008 22:00:22 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Oct 2008 12:59:39 GMT",
"version": "v2"
}
] | 2008-12-30 | [
[
"Manko",
"V. S.",
""
],
[
"Rodchenko",
"E. D.",
""
],
[
"Ruiz",
"E.",
""
],
[
"Sadovnikov",
"B. I.",
""
]
] | The full metric describing two counter-rotating identical Kerr black holes separated by a massless strut is derived in the explicit analytical form. It contains three arbitrary parameters which are the Komar mass M, Komar angular momentum per unit mass a of one of the black holes (the other has the same mass and equal but opposite angular momentum) and the coordinate distance R between the centers of the horizons. In the limit of extreme black holes, the metric becomes a special member of the Kinnersly-Chitre five-parameter family of vacuum solutions generalizing the Tomimatsu-Sato delta=2 spacetime, and we present the complete set of metrical fields defining this limit. |
1902.08200 | Kartik Prabhu | Kartik Prabhu | Conservation of asymptotic charges from past to future null infinity:
Supermomentum in general relativity | v2: corrected formula for epsilon in Eqs. A.4E and A.9 v1: (published
version in JHEP) 49 pages, 2 figures. arXiv admin note: substantial text
overlap with arXiv:1808.07863 | JHEP 03 (2019) 148 | 10.1007/JHEP03(2019)148 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the BMS-supertranslations and their associated supermomenta on
past null infinity can be related to those on future null infinity, proving the
conjecture of Strominger for a class of spacetimes which are
asymptotically-flat in the sense of Ashtekar and Hansen. Using a cylindrical
3-manifold of both null and spatial directions of approach towards spatial
infinity, we impose appropriate regularity conditions on the Weyl tensor near
spatial infinity along null directions. The asymptotic Einstein equations on
this 3-manifold and the regularity conditions imply that the relevant Weyl
tensor components on past null infinity are antipodally matched to those on
future null infinity. The subalgebra of totally fluxless supertranslations near
spatial infinity provides a natural isomorphism between the
BMS-supertranslations on past and future null infinity. This proves that the
flux of the supermomenta is conserved from past to future null infinity in a
classical gravitational scattering process provided additional suitable
conditions are satisfied at the timelike infinities.
| [
{
"created": "Thu, 21 Feb 2019 17:55:53 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Mar 2019 19:38:30 GMT",
"version": "v2"
}
] | 2019-04-02 | [
[
"Prabhu",
"Kartik",
""
]
] | We show that the BMS-supertranslations and their associated supermomenta on past null infinity can be related to those on future null infinity, proving the conjecture of Strominger for a class of spacetimes which are asymptotically-flat in the sense of Ashtekar and Hansen. Using a cylindrical 3-manifold of both null and spatial directions of approach towards spatial infinity, we impose appropriate regularity conditions on the Weyl tensor near spatial infinity along null directions. The asymptotic Einstein equations on this 3-manifold and the regularity conditions imply that the relevant Weyl tensor components on past null infinity are antipodally matched to those on future null infinity. The subalgebra of totally fluxless supertranslations near spatial infinity provides a natural isomorphism between the BMS-supertranslations on past and future null infinity. This proves that the flux of the supermomenta is conserved from past to future null infinity in a classical gravitational scattering process provided additional suitable conditions are satisfied at the timelike infinities. |
gr-qc/0411070 | John Barrow | John D. Barrow and Christos G. Tsagas (DAMTP) | Structure and stability of the Lukash plane-wave spacetime | Revised version, references added. To appear in Class. Quantum Grav | Class.Quant.Grav. 22 (2005) 825-840 | 10.1088/0264-9381/22/5/005 | null | gr-qc astro-ph hep-th | null | We study the vacuum, plane-wave Bianchi $VII{}_{h}$ spacetimes described by
the Lukash metric. Combining covariant with orthonormal frame techniques, we
describe these models in terms of their irreducible kinematical and geometrical
quantities. This covariant description is used to study analytically the
response of the Lukash spacetime to linear perturbations. We find that the
stability of the vacuum solution depends crucially on the background shear
anisotropy. The stronger the deviation from the Hubble expansion, the more
likely the overall linear instability of the model. Our analysis addresses
rotational, shear and Weyl curvature perturbations and identifies conditions
sufficient for the linear growth of these distortions.
| [
{
"created": "Mon, 15 Nov 2004 17:52:34 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Feb 2005 17:03:58 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Barrow",
"John D.",
"",
"DAMTP"
],
[
"Tsagas",
"Christos G.",
"",
"DAMTP"
]
] | We study the vacuum, plane-wave Bianchi $VII{}_{h}$ spacetimes described by the Lukash metric. Combining covariant with orthonormal frame techniques, we describe these models in terms of their irreducible kinematical and geometrical quantities. This covariant description is used to study analytically the response of the Lukash spacetime to linear perturbations. We find that the stability of the vacuum solution depends crucially on the background shear anisotropy. The stronger the deviation from the Hubble expansion, the more likely the overall linear instability of the model. Our analysis addresses rotational, shear and Weyl curvature perturbations and identifies conditions sufficient for the linear growth of these distortions. |
1601.01460 | Grant J. Mathews | InSaeng Suh, Grant J. Mathews, J. Reese Haywood, N. Q. Lan | Review of Conformally Flat Approximation for Binary Neutron Star Initial
Conditions | 22 pages, 12 figures, revised as per referee recommendations | null | 10.1155/2017/6127031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spatially conformally flat approximation (CFA) is a viable method to
deduce initial conditions for the subsequent evolution of binary neutron stars
employing the full Einstein equations. Here we review the status of the
original formulation of the CFA for the general relativistic hydrodynamic
initial conditions of binary neutron stars. We illustrate the stability of the
conformally flat condition on the hydrodynamics by numerically evolving ~100
quasi-circular orbits. We illustrate the use of this approximation for orbiting
neutron stars in the quasi-circular orbit approximation to demonstrate the
equation of state dependence of these initial conditions and how they might
affect the emergent gravitational wave frequency as the stars approach the
innermost stable circular orbit.
| [
{
"created": "Thu, 7 Jan 2016 09:46:30 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Mar 2016 17:37:12 GMT",
"version": "v2"
}
] | 2017-01-18 | [
[
"Suh",
"InSaeng",
""
],
[
"Mathews",
"Grant J.",
""
],
[
"Haywood",
"J. Reese",
""
],
[
"Lan",
"N. Q.",
""
]
] | The spatially conformally flat approximation (CFA) is a viable method to deduce initial conditions for the subsequent evolution of binary neutron stars employing the full Einstein equations. Here we review the status of the original formulation of the CFA for the general relativistic hydrodynamic initial conditions of binary neutron stars. We illustrate the stability of the conformally flat condition on the hydrodynamics by numerically evolving ~100 quasi-circular orbits. We illustrate the use of this approximation for orbiting neutron stars in the quasi-circular orbit approximation to demonstrate the equation of state dependence of these initial conditions and how they might affect the emergent gravitational wave frequency as the stars approach the innermost stable circular orbit. |
2310.13946 | Daniel Jampolski | Daniel Jampolski, Luciano Rezzolla | Nested solutions of gravitational condensate stars | 26 pages, 12 figures; matches published version in Class.Quant.Grav | Classical and Quantum Gravity, Volume 41, Number 6, 2024 | 10.1088/1361-6382/ad2317 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes are normally and naturally associated to the end-point of
gravitational collapse. Yet, alternatives have been proposed and a particularly
interesting one is that of gravitational condensate stars, or gravastars. We
here revisit the gravastar model and increase the degree of speculation by
considering new solutions that are inspired by the original model of gravastars
with anisotropic pressure, but also offer surprising new features. In
particular, we show that it is possible to nest two gravastars into each other
and obtain a new solution of the Einstein equations. Since each gravastar
essentially behaves as a distinct self-gravitating equilibrium, a large and
rich space of parameters exists for the construction of nested gravastars. In
addition, we show that these nested-gravastar solutions can be extended to an
arbitrarily large number of shells, with a prescription specified in terms of
simple recursive relations. Although these ultra-compact objects are admittedly
very exotic, some of the solutions found, provide an interesting alternative to
a black hole by having a singularity-free origin, a full matter interior, a
time-like matter surface, and a compactness $\mathcal{C}\to (1/2)^{-}$.
| [
{
"created": "Sat, 21 Oct 2023 09:00:00 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Feb 2024 01:00:00 GMT",
"version": "v2"
}
] | 2024-02-20 | [
[
"Jampolski",
"Daniel",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | Black holes are normally and naturally associated to the end-point of gravitational collapse. Yet, alternatives have been proposed and a particularly interesting one is that of gravitational condensate stars, or gravastars. We here revisit the gravastar model and increase the degree of speculation by considering new solutions that are inspired by the original model of gravastars with anisotropic pressure, but also offer surprising new features. In particular, we show that it is possible to nest two gravastars into each other and obtain a new solution of the Einstein equations. Since each gravastar essentially behaves as a distinct self-gravitating equilibrium, a large and rich space of parameters exists for the construction of nested gravastars. In addition, we show that these nested-gravastar solutions can be extended to an arbitrarily large number of shells, with a prescription specified in terms of simple recursive relations. Although these ultra-compact objects are admittedly very exotic, some of the solutions found, provide an interesting alternative to a black hole by having a singularity-free origin, a full matter interior, a time-like matter surface, and a compactness $\mathcal{C}\to (1/2)^{-}$. |
1602.04766 | Stoytcho Yazadjiev | Stoytcho S. Yazadjiev, Daniela D. Doneva and Dimitar Popchev | Slowly rotating neutron stars in scalar-tensor theories with a massive
scalar field | 12 pages, 4 figures | Phys. Rev. D 93, 084038 (2016) | 10.1103/PhysRevD.93.084038 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the scalar-tensor theories with a massive scalar field the coupling
constants, and the coupling functions in general, which are observationally
allowed, can differ significantly from those in the massless case. This fact
naturally implies that the scalar-tensor neutron stars with a massive scalar
field can have rather different structure and properties in comparison with
their counterparts in the massless case and in general relativity. In the
present paper we study slowly rotating neutron stars in scalar-tensor theories
with a massive gravitational scalar. Two examples of scalar-tensor theories are
examined - the first example is the massive Brans-Dicke theory and the second
one is a massive scalar-tensor theory indistinguishable from general relativity
in the weak field limit. In the later case we study the effect of the scalar
field mass on the spontaneous scalarization of neutron stars. Our numerical
results show that the inclusion of a mass term for the scalar field indeed
changes the picture drastically compared to the massless case. It turns out
that mass, radius and moment of inertia for neutron stars in massive
scalar-tensor theories can differ drastically from the pure general
relativistic solutions if sufficiently large masses of the scalar field are
considered.
| [
{
"created": "Mon, 15 Feb 2016 18:54:07 GMT",
"version": "v1"
}
] | 2016-04-27 | [
[
"Yazadjiev",
"Stoytcho S.",
""
],
[
"Doneva",
"Daniela D.",
""
],
[
"Popchev",
"Dimitar",
""
]
] | In the scalar-tensor theories with a massive scalar field the coupling constants, and the coupling functions in general, which are observationally allowed, can differ significantly from those in the massless case. This fact naturally implies that the scalar-tensor neutron stars with a massive scalar field can have rather different structure and properties in comparison with their counterparts in the massless case and in general relativity. In the present paper we study slowly rotating neutron stars in scalar-tensor theories with a massive gravitational scalar. Two examples of scalar-tensor theories are examined - the first example is the massive Brans-Dicke theory and the second one is a massive scalar-tensor theory indistinguishable from general relativity in the weak field limit. In the later case we study the effect of the scalar field mass on the spontaneous scalarization of neutron stars. Our numerical results show that the inclusion of a mass term for the scalar field indeed changes the picture drastically compared to the massless case. It turns out that mass, radius and moment of inertia for neutron stars in massive scalar-tensor theories can differ drastically from the pure general relativistic solutions if sufficiently large masses of the scalar field are considered. |
gr-qc/9805058 | Devis Iellici | Devis Iellici (Univ. of Trento and INFN) | Aspects and applications of quantum field theory on spaces with conical
singularities | LaTeX, 146 pages, 2 eps figures included. Ph.D. dissertation | null | null | null | gr-qc hep-th | null | One-loop effects for quantum fields living on manifolds containing conical
singularities are investigated in the context of cosmic string background and
of finite-temperature theory in the Rindler wedge or outside the horizon of a
Schwarzschild black-hole.
| [
{
"created": "Thu, 14 May 1998 15:15:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Iellici",
"Devis",
"",
"Univ. of Trento and INFN"
]
] | One-loop effects for quantum fields living on manifolds containing conical singularities are investigated in the context of cosmic string background and of finite-temperature theory in the Rindler wedge or outside the horizon of a Schwarzschild black-hole. |
1811.09232 | Soumi De | Soumi De, Christopher M. Biwer, Collin D. Capano, Alexander H. Nitz,
Duncan A. Brown | Posterior samples of the parameters of binary black holes from Advanced
LIGO, Virgo's second observing run | 15 pages, 4 figures | Scientific Data 6, 81 (2019) | 10.1038/s41597-019-0086-6 | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | This paper presents a parameter estimation analysis of the seven binary black
hole mergers---GW170104, GW170608, GW170729, GW170809, GW170814, GW170818, and
GW170823---detected during the second observing run of the Advanced LIGO and
Virgo observatories using the gravitational-wave open data. We describe the
methodology for parameter estimation of compact binaries using
gravitational-wave data, and we present the posterior distributions of the
inferred astrophysical parameters. We release our samples of the posterior
probability density function with tutorials on using and replicating our
results presented in this paper.
| [
{
"created": "Thu, 22 Nov 2018 16:44:53 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Mar 2019 00:40:52 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Jun 2019 23:46:38 GMT",
"version": "v3"
}
] | 2019-06-05 | [
[
"De",
"Soumi",
""
],
[
"Biwer",
"Christopher M.",
""
],
[
"Capano",
"Collin D.",
""
],
[
"Nitz",
"Alexander H.",
""
],
[
"Brown",
"Duncan A.",
""
]
] | This paper presents a parameter estimation analysis of the seven binary black hole mergers---GW170104, GW170608, GW170729, GW170809, GW170814, GW170818, and GW170823---detected during the second observing run of the Advanced LIGO and Virgo observatories using the gravitational-wave open data. We describe the methodology for parameter estimation of compact binaries using gravitational-wave data, and we present the posterior distributions of the inferred astrophysical parameters. We release our samples of the posterior probability density function with tutorials on using and replicating our results presented in this paper. |
2310.01005 | David Izabel | David Izabel | Analogy of space time as un elastic medium -- Can we establish a thermal
expansion coefficient of space from the cosmological constant Lambda? | 33 pages, 3 figures | International Journal of modern Physic D 24 september 2023 | 10.1142/S0218271823500918 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper advances the state of the art by extending the study of the
analogy between the spacetime fabric and elasticity.As no prior work exists
about a potential spacetime thermal expansion coeff Lambda, we explore the
analogy of GR with the elasticity theory by considering the cosmological
constant Lambda as an additional space curvature of the space frame due to a
thermal gradient coming from the cosmic web and the cold vacuum and we propose
((AlphaxDeltaT)/e)^2=(1/Ro)^2=Lambda with Ro being the curvature radius of the
space fabric.It follows from this analogy and from the supposed space model
consisting of thin sheets of Planck thickness Lp curved by this thermal
gradient DeltaT a possible thermal expansion coefficient of the equivalent
elastic medium modeling the space AlphaS=(LpxLambda^(1/2))/DeltaT of the order
of Alphas(QFT)=1.16x10-6 K-1.As space-time and not only space must be
considered in GR, this paper also proposes an innovative approach which
consists in introducing into the interval ds^2 of special relativity a temp
effect T,(entropy variations correlated with time laps, based on temperature
variations affecting always physically the clocks) based on different thermal
expansion coefficients for space and time with for the flow of time
t:cxt/cxnxtau=(kBxt)/nxhxDeltaT=AlphatxDeltaT.With T=10^6 K, n=1, the associate
time interval is 4.8x10^-17s and Alphat=1.0x10^-6K^-1.The consequence of these
hypothesis is that dark energy potentially becomes a thermal space-time
curvature ((AlphafxT)/Lp)^2 with f equal to s or t depending of the
temperature, the thermal entropy variation of the universe, the Planck
thickness and time, that increases since the Bigbang, depending on thermal
expansion coefficients for space-time Alphas and Alphat as a function
respectively of Lambda, kB/hxt, in opposition to space-time curvature gravity
due to mass/energy density as described in GR.
| [
{
"created": "Mon, 2 Oct 2023 09:01:18 GMT",
"version": "v1"
}
] | 2023-10-03 | [
[
"Izabel",
"David",
""
]
] | This paper advances the state of the art by extending the study of the analogy between the spacetime fabric and elasticity.As no prior work exists about a potential spacetime thermal expansion coeff Lambda, we explore the analogy of GR with the elasticity theory by considering the cosmological constant Lambda as an additional space curvature of the space frame due to a thermal gradient coming from the cosmic web and the cold vacuum and we propose ((AlphaxDeltaT)/e)^2=(1/Ro)^2=Lambda with Ro being the curvature radius of the space fabric.It follows from this analogy and from the supposed space model consisting of thin sheets of Planck thickness Lp curved by this thermal gradient DeltaT a possible thermal expansion coefficient of the equivalent elastic medium modeling the space AlphaS=(LpxLambda^(1/2))/DeltaT of the order of Alphas(QFT)=1.16x10-6 K-1.As space-time and not only space must be considered in GR, this paper also proposes an innovative approach which consists in introducing into the interval ds^2 of special relativity a temp effect T,(entropy variations correlated with time laps, based on temperature variations affecting always physically the clocks) based on different thermal expansion coefficients for space and time with for the flow of time t:cxt/cxnxtau=(kBxt)/nxhxDeltaT=AlphatxDeltaT.With T=10^6 K, n=1, the associate time interval is 4.8x10^-17s and Alphat=1.0x10^-6K^-1.The consequence of these hypothesis is that dark energy potentially becomes a thermal space-time curvature ((AlphafxT)/Lp)^2 with f equal to s or t depending of the temperature, the thermal entropy variation of the universe, the Planck thickness and time, that increases since the Bigbang, depending on thermal expansion coefficients for space-time Alphas and Alphat as a function respectively of Lambda, kB/hxt, in opposition to space-time curvature gravity due to mass/energy density as described in GR. |
2304.01265 | Paolo Pani | Oscar J. C. Dias and Giuseppe Lingetti and Paolo Pani and Jorge E.
Santos | Black hole superradiant instability for massive spin-2 fields | 5+3 pages, 2+1 figures v2: extended appendix with numerical details.
Matches PRD version | Phys. Rev. D 108, L041502 (2023) | 10.1103/PhysRevD.108.L041502 | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Due to coherent superradiant amplification, massive bosonic fields can
trigger an instability in spinning black holes, tapping their energy and
angular momentum and forming macroscopic Bose-Einstein condensates around them.
This phenomenon produces gaps in the mass-spin distribution of astrophysical
black holes, a continuous gravitational-wave signal emitted by the condensate,
and several environmental effects relevant for gravitational-wave astronomy and
radio images of black holes. While the spectrum of superradiantly unstable mode
is known in great detail for massive scalar (spin-0) and vector (spin-1)
perturbations, so far only approximated results were derived for the case of
massive tensor (spin-2) fields, due to the nonseparability of the field
equations. Here, solving a system of ten elliptic partial differential
equations, we close this program and compute the spectrum of the most unstable
modes of a massive spin-2 field for generic black-hole spin and boson mass,
beyond the hydrogenic approximation and including the unique dipole mode that
dominates the instability in the spin-2 case. We find that the instability
timescale for this mode is orders of magnitude shorter than for any other
superradiant mode, yielding much stronger constraints on massive spin-2 fields.
These results pave the way for phenomenological studies aimed at constraining
beyond Standard Model scenarios, ultralight dark matter candidates, and
extensions to General Relativity using gravitational-wave and electromagnetic
observations, and have implications for the phase diagram of vacuum solutions
of higher-dimensional gravity.
| [
{
"created": "Mon, 3 Apr 2023 18:00:56 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Sep 2023 08:51:50 GMT",
"version": "v2"
}
] | 2023-09-22 | [
[
"Dias",
"Oscar J. C.",
""
],
[
"Lingetti",
"Giuseppe",
""
],
[
"Pani",
"Paolo",
""
],
[
"Santos",
"Jorge E.",
""
]
] | Due to coherent superradiant amplification, massive bosonic fields can trigger an instability in spinning black holes, tapping their energy and angular momentum and forming macroscopic Bose-Einstein condensates around them. This phenomenon produces gaps in the mass-spin distribution of astrophysical black holes, a continuous gravitational-wave signal emitted by the condensate, and several environmental effects relevant for gravitational-wave astronomy and radio images of black holes. While the spectrum of superradiantly unstable mode is known in great detail for massive scalar (spin-0) and vector (spin-1) perturbations, so far only approximated results were derived for the case of massive tensor (spin-2) fields, due to the nonseparability of the field equations. Here, solving a system of ten elliptic partial differential equations, we close this program and compute the spectrum of the most unstable modes of a massive spin-2 field for generic black-hole spin and boson mass, beyond the hydrogenic approximation and including the unique dipole mode that dominates the instability in the spin-2 case. We find that the instability timescale for this mode is orders of magnitude shorter than for any other superradiant mode, yielding much stronger constraints on massive spin-2 fields. These results pave the way for phenomenological studies aimed at constraining beyond Standard Model scenarios, ultralight dark matter candidates, and extensions to General Relativity using gravitational-wave and electromagnetic observations, and have implications for the phase diagram of vacuum solutions of higher-dimensional gravity. |
0812.2428 | Valeria Kagramanova | Eva Hackmann, Valeria Kagramanova, Jutta Kunz and Claus Laemmerzahl | Analytic solutions of the geodesic equation in higher dimensional static
spherically symmetric space-times | accepted for publication in PRD | Phys.Rev.D78:124018,2008; Erratum-ibid.79:029901,2009 | 10.1103/PhysRevD.78.124018 10.1103/PhysRevD.79.029901 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The complete analytical solutions of the geodesic equation of massive test
particles in higher dimensional Schwarzschild, Schwarzschild-(anti)de Sitter,
Reissner-Nordstroem and Reissner-Nordstroem-(anti)de Sitter space--times are
presented. Using the Jacobi inversion problem restricted to the theta divisor
the explicit solution is given in terms of Kleinian sigma functions. The
derived orbits depend on the structure of the roots of the characteristic
polynomials which depend on the particle's energy and angular momentum, on the
mass and the charge of the gravitational source, and the cosmological constant.
We discuss the general structure of the orbits and show that due to the
specific dimension-independent form of the angular momentum and the
cosmological force a rich variety of orbits can emerge only in four and five
dimensions. We present explicit analytical solutions for orbits up to 11
dimensions. A particular feature of Reissner--Nordstroem space-times is that
bound and escape orbits traverse through different universes.
| [
{
"created": "Fri, 12 Dec 2008 16:59:07 GMT",
"version": "v1"
}
] | 2009-04-23 | [
[
"Hackmann",
"Eva",
""
],
[
"Kagramanova",
"Valeria",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Laemmerzahl",
"Claus",
""
]
] | The complete analytical solutions of the geodesic equation of massive test particles in higher dimensional Schwarzschild, Schwarzschild-(anti)de Sitter, Reissner-Nordstroem and Reissner-Nordstroem-(anti)de Sitter space--times are presented. Using the Jacobi inversion problem restricted to the theta divisor the explicit solution is given in terms of Kleinian sigma functions. The derived orbits depend on the structure of the roots of the characteristic polynomials which depend on the particle's energy and angular momentum, on the mass and the charge of the gravitational source, and the cosmological constant. We discuss the general structure of the orbits and show that due to the specific dimension-independent form of the angular momentum and the cosmological force a rich variety of orbits can emerge only in four and five dimensions. We present explicit analytical solutions for orbits up to 11 dimensions. A particular feature of Reissner--Nordstroem space-times is that bound and escape orbits traverse through different universes. |
2408.02762 | Tousif Islam | Tousif Islam, Gaurav Khanna and Scott E. Field | Adding higher-order spherical harmonics in non-spinning eccentric binary
black hole merger waveform models | 14 pages, 11 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | gwNRHME is a recently developed framework that seamlessly converts a
multi-modal (i.e with several spherical harmonic modes) quasi-circular waveform
into multi-modal eccentric waveform if the quadrupolar eccentric waveform is
known. Here, we employ the gwNRHME framework to combine a multi-modal
quasi-circular waveform model NRHybSur3dq8 and quadrupolar non-spinning
eccentric waveform model EccentricIMR to construct multi-modal non-spinning
eccentric model NRHybSur3dq8-gwNRHME. Using a total of 35 eccentric numerical
relativity (NR) simulations obtained from the SXS and RIT catalogs, we
demonstrate that NRHybSur3dq8-gwNRHME model predictions agree well with NR
(with typical relative $L_2$ errors of ~0.01 for the dominant quadrupolar mode)
for mass ratios $ 1 \leq q \leq 4$ and eccentricities up to ~0.2 measured about
10 cycles before the merger. To demonstrate the modularity of the gwNRHME
framework, we further combine EccentricIMR with BHPTNRSur1dq1e4 model and
develop a non-spinning eccentric models named BHPTNRSur1dq1e4-gwNRHME. Finally,
we develop a different variant of these models by replacing EccentricIMR with
EccentricTD. Both the gwNRHME framework and associated models are available
through the gwModels package.
| [
{
"created": "Mon, 5 Aug 2024 18:26:04 GMT",
"version": "v1"
}
] | 2024-08-07 | [
[
"Islam",
"Tousif",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Field",
"Scott E.",
""
]
] | gwNRHME is a recently developed framework that seamlessly converts a multi-modal (i.e with several spherical harmonic modes) quasi-circular waveform into multi-modal eccentric waveform if the quadrupolar eccentric waveform is known. Here, we employ the gwNRHME framework to combine a multi-modal quasi-circular waveform model NRHybSur3dq8 and quadrupolar non-spinning eccentric waveform model EccentricIMR to construct multi-modal non-spinning eccentric model NRHybSur3dq8-gwNRHME. Using a total of 35 eccentric numerical relativity (NR) simulations obtained from the SXS and RIT catalogs, we demonstrate that NRHybSur3dq8-gwNRHME model predictions agree well with NR (with typical relative $L_2$ errors of ~0.01 for the dominant quadrupolar mode) for mass ratios $ 1 \leq q \leq 4$ and eccentricities up to ~0.2 measured about 10 cycles before the merger. To demonstrate the modularity of the gwNRHME framework, we further combine EccentricIMR with BHPTNRSur1dq1e4 model and develop a non-spinning eccentric models named BHPTNRSur1dq1e4-gwNRHME. Finally, we develop a different variant of these models by replacing EccentricIMR with EccentricTD. Both the gwNRHME framework and associated models are available through the gwModels package. |
2408.07166 | Pedro A S\'anchez | Pedro A. S\'anchez | Kundt Gravitational Waves Coupled with a Non-Noetherian Conformal Scalar
Field | null | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Type N spacetimes of the Kundt class are presented as solutions to the
Einstein's equations sourced by a real scalar field whose equation of motion is
conformally invariant and that generalizes the standard conformal scalar field.
The specific spacetimes considered model gravitational waves with uniform and
totally geodesic wave fronts, propagating in a maximally symmetric background,
and are characterized by the value of their constant scalar curvature and by
the so-called wave profile function. All subclasses of such spacetimes are
analyzed. It is shown that the scalar field solutions generically divide into
two branches, of which one has a strikingly different behavior from that of the
standard conformal case. The scalar field contributes to the equation satisfied
by the wave profile function by adding new singular terms. Closed form and mode
solutions for the wave profile function are found for different scenarios. The
resulting energy-momentum tensor has a null eigenvector, but is more general
than the pure radiation type usually coupled with this kind of spacetimes.
| [
{
"created": "Tue, 13 Aug 2024 19:11:54 GMT",
"version": "v1"
}
] | 2024-08-15 | [
[
"Sánchez",
"Pedro A.",
""
]
] | Type N spacetimes of the Kundt class are presented as solutions to the Einstein's equations sourced by a real scalar field whose equation of motion is conformally invariant and that generalizes the standard conformal scalar field. The specific spacetimes considered model gravitational waves with uniform and totally geodesic wave fronts, propagating in a maximally symmetric background, and are characterized by the value of their constant scalar curvature and by the so-called wave profile function. All subclasses of such spacetimes are analyzed. It is shown that the scalar field solutions generically divide into two branches, of which one has a strikingly different behavior from that of the standard conformal case. The scalar field contributes to the equation satisfied by the wave profile function by adding new singular terms. Closed form and mode solutions for the wave profile function are found for different scenarios. The resulting energy-momentum tensor has a null eigenvector, but is more general than the pure radiation type usually coupled with this kind of spacetimes. |
2202.02221 | Oleksii Sokoliuk | Oleksii Sokoliuk, Alexander Baransky and Praduymn Kumar Sahoo | Non-singular T-K axion stars with/without the dynamical bosonic field in
the presence of negative $\Lambda$ term | 19 pages, 10 figures | Physics of the Dark Universe, 35 (2022) 100972 | 10.1016/j.dark.2022.100972 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present work authors derive exact solutions for the relativistic
compact stars in the presence of two fields axion (Dante's Inferno model) and
with/without the complex scalar field (with the quartic self-interaction)
coupled to gravity. The matter source is assumed as the perfect fluid one, and
we also use barotropic/MIT bag EoS to derive energy density and
anisotropic/isotropic pressures from Einstein Field Equations (EFE's). For
simplicity, as the metric potentials we use Tolman-Kuchowicz metric potentials,
which are non-singular and physically acceptable. Unknown variables for the T-K
metric potentials were derived from the junction conditions. To examine the
redshift function, adiabatic index and energy, causality conditions we used
such compact stars as PSR J1416-223, PSR J1903+32, 4U 1820-30, Cen X-3, EXO
1785-248, SAX J1808.4365.
| [
{
"created": "Thu, 3 Feb 2022 08:27:16 GMT",
"version": "v1"
}
] | 2022-02-07 | [
[
"Sokoliuk",
"Oleksii",
""
],
[
"Baransky",
"Alexander",
""
],
[
"Sahoo",
"Praduymn Kumar",
""
]
] | In the present work authors derive exact solutions for the relativistic compact stars in the presence of two fields axion (Dante's Inferno model) and with/without the complex scalar field (with the quartic self-interaction) coupled to gravity. The matter source is assumed as the perfect fluid one, and we also use barotropic/MIT bag EoS to derive energy density and anisotropic/isotropic pressures from Einstein Field Equations (EFE's). For simplicity, as the metric potentials we use Tolman-Kuchowicz metric potentials, which are non-singular and physically acceptable. Unknown variables for the T-K metric potentials were derived from the junction conditions. To examine the redshift function, adiabatic index and energy, causality conditions we used such compact stars as PSR J1416-223, PSR J1903+32, 4U 1820-30, Cen X-3, EXO 1785-248, SAX J1808.4365. |
2102.06399 | Shuxun Tian | S. X. Tian and Zong-Hong Zhu | Early dark energy in $k$-essence | 5 pages, 2 figures, published in Phys. Rev. D | Phys. Rev. D 103, 043518 (2021) | 10.1103/PhysRevD.103.043518 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Early dark energy (EDE) that becomes subdominant around the epoch of
matter-radiation equality can be used to ease the Hubble tension. However,
there is a theoretical problem that why the energy scale of EDE is in
coincidence with that of matter-radiation equality when their physics are
completely unrelated. Sakstein and Trodden [Phys. Rev. Lett. 124, 161301
(2020)] proposed a mechanism to solve this coincidence problem with
$\mathcal{O}({\rm eV})$-mass neutrino. In this paper, in order to solve the
coincidence problem, we propose a new scenario for EDE, in which the onset and
ending of EDE are triggered by the radiation-matter transition. The specific
example we study is a $k$-essence model. The cosmic evolution equations can be
recast into a two-dimensional dynamical system and its main properties are
analyzed. Our results suggest that $k$-essence seems unable to realize the new
scenario for EDE. However, an EDE model with different scenario is realized in
$k$-essence. In this model, the ending of EDE can be triggered by the
radiation-matter transition while the onset depends on the initial conditions
of the scalar field. Therefore, the obtained model can only be used to solve
half of the coincidence problem. The full resolution in the framework of our
initial proposed scenario is worthy of more research.
| [
{
"created": "Fri, 12 Feb 2021 08:57:19 GMT",
"version": "v1"
}
] | 2021-02-15 | [
[
"Tian",
"S. X.",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] | Early dark energy (EDE) that becomes subdominant around the epoch of matter-radiation equality can be used to ease the Hubble tension. However, there is a theoretical problem that why the energy scale of EDE is in coincidence with that of matter-radiation equality when their physics are completely unrelated. Sakstein and Trodden [Phys. Rev. Lett. 124, 161301 (2020)] proposed a mechanism to solve this coincidence problem with $\mathcal{O}({\rm eV})$-mass neutrino. In this paper, in order to solve the coincidence problem, we propose a new scenario for EDE, in which the onset and ending of EDE are triggered by the radiation-matter transition. The specific example we study is a $k$-essence model. The cosmic evolution equations can be recast into a two-dimensional dynamical system and its main properties are analyzed. Our results suggest that $k$-essence seems unable to realize the new scenario for EDE. However, an EDE model with different scenario is realized in $k$-essence. In this model, the ending of EDE can be triggered by the radiation-matter transition while the onset depends on the initial conditions of the scalar field. Therefore, the obtained model can only be used to solve half of the coincidence problem. The full resolution in the framework of our initial proposed scenario is worthy of more research. |
0710.3150 | Tao Luo | Tao Luo, Joel Smoller | Nonlinear Dynamical Stability of Newtonian Rotating White Dwarfs and
Supermassive Stars | null | Comm. Math. Physics, 284(2008) no.2, 425-457 | 10.1007/s00220-008-0569-3 | null | gr-qc math-ph math.MP | null | We prove general nonlinear stability and existence theorems for rotating star
solutions which are axi-symmetric steady-state solutions of the compressible
isentropic Euler-Poisson equations in 3 spatial dimensions. We apply our
results to rotating and non-rotating white dwarf, and rotating high density
supermassive (extreme relativistic) stars, stars which are in convective
equilibrium and have uniform chemical composition. This paper is a continuation
of our earlier work ([28]).
| [
{
"created": "Tue, 16 Oct 2007 18:39:48 GMT",
"version": "v1"
}
] | 2014-08-04 | [
[
"Luo",
"Tao",
""
],
[
"Smoller",
"Joel",
""
]
] | We prove general nonlinear stability and existence theorems for rotating star solutions which are axi-symmetric steady-state solutions of the compressible isentropic Euler-Poisson equations in 3 spatial dimensions. We apply our results to rotating and non-rotating white dwarf, and rotating high density supermassive (extreme relativistic) stars, stars which are in convective equilibrium and have uniform chemical composition. This paper is a continuation of our earlier work ([28]). |
2210.06166 | Siddheshwar Kadam | S.A. Kadam, B.Mishra, Jackson Levi Said | Noether Symmetries in $f(T,T_G)$ Cosmology | 12 pages | Physica Scripta, 98, 4, 2023 | 10.1088/1402-4896/acc0ac | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All degrees of freedom related to the torsion scalar can be explored by
analysing, the $f(T,T_G)$ gravity formalism where, $T$ is a torsion scalar and
$T_G$ is the teleparallel counterpart of the Gauss-Bonnet topological invariant
term. The well-known Noether symmetry approach is a useful tool for selecting
models that are motivated at a fundamental level and determining the exact
solution to a given Lagrangian, hence we explore Noether symmetry approach in
$f(T,T_G)$ gravity formalism with three different forms of $f(T,T_G)$ and study
how to establish nontrivial Noether vector form for each one of them. We extend
the analysis made in \cite{capozziello2016noether} for the form
$f(T,T_{G})=b_{0}T_{G}^{k}+t_{0}T^{m}$ and discussed the symmetry for this
model with linear teleparallel equivalent of the Gauss-Bonnet term, followed by
the study of two models containing exponential form of the teleparallel
equivalent of the Gauss-Bonnet term. We have shown that all three cases will
allow us to obtain non-trivial Noether vector which will play an important role
to obtain the exact solutions for the cosmological equations.
| [
{
"created": "Tue, 11 Oct 2022 11:37:54 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Mar 2023 10:47:33 GMT",
"version": "v2"
}
] | 2023-03-27 | [
[
"Kadam",
"S. A.",
""
],
[
"Mishra",
"B.",
""
],
[
"Said",
"Jackson Levi",
""
]
] | All degrees of freedom related to the torsion scalar can be explored by analysing, the $f(T,T_G)$ gravity formalism where, $T$ is a torsion scalar and $T_G$ is the teleparallel counterpart of the Gauss-Bonnet topological invariant term. The well-known Noether symmetry approach is a useful tool for selecting models that are motivated at a fundamental level and determining the exact solution to a given Lagrangian, hence we explore Noether symmetry approach in $f(T,T_G)$ gravity formalism with three different forms of $f(T,T_G)$ and study how to establish nontrivial Noether vector form for each one of them. We extend the analysis made in \cite{capozziello2016noether} for the form $f(T,T_{G})=b_{0}T_{G}^{k}+t_{0}T^{m}$ and discussed the symmetry for this model with linear teleparallel equivalent of the Gauss-Bonnet term, followed by the study of two models containing exponential form of the teleparallel equivalent of the Gauss-Bonnet term. We have shown that all three cases will allow us to obtain non-trivial Noether vector which will play an important role to obtain the exact solutions for the cosmological equations. |
1106.1632 | Stephen R. Lau | Stephen R. Lau and Richard H. Price | Sparse spectral-tau method for the three-dimensional helically reduced
wave equation on two-center domains | 37 pages, 3 figures, 12 tables | null | 10.1016/j.jcp.2012.07.006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a multidomain spectral-tau method for solving the
three-dimensional helically reduced wave equation on the type of two-center
domain that arises when modeling compact binary objects in astrophysical
applications. A global two-center domain may arise as the union of Cartesian
blocks, cylindrical shells, and inner and outer spherical shells. For each such
subdomain, our key objective is to realize certain (differential and
multiplication) physical-space operators as matrices acting on the
corresponding set of modal coefficients. We achieve sparse banded realizations
through the integration "preconditioning" of Coutsias, Hagstrom, Hesthaven, and
Torres. Since ours is the first three-dimensional multidomain implementation of
the technique, we focus on the issue of convergence for the global solver, here
the alternating Schwarz method accelerated by GMRES. Our methods may prove
relevant for numerical solution of other mixed-type or elliptic problems, and
in particular for the generation of initial data in general relativity.
| [
{
"created": "Wed, 8 Jun 2011 19:40:13 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Lau",
"Stephen R.",
""
],
[
"Price",
"Richard H.",
""
]
] | We describe a multidomain spectral-tau method for solving the three-dimensional helically reduced wave equation on the type of two-center domain that arises when modeling compact binary objects in astrophysical applications. A global two-center domain may arise as the union of Cartesian blocks, cylindrical shells, and inner and outer spherical shells. For each such subdomain, our key objective is to realize certain (differential and multiplication) physical-space operators as matrices acting on the corresponding set of modal coefficients. We achieve sparse banded realizations through the integration "preconditioning" of Coutsias, Hagstrom, Hesthaven, and Torres. Since ours is the first three-dimensional multidomain implementation of the technique, we focus on the issue of convergence for the global solver, here the alternating Schwarz method accelerated by GMRES. Our methods may prove relevant for numerical solution of other mixed-type or elliptic problems, and in particular for the generation of initial data in general relativity. |
gr-qc/0209004 | Abel Camacho Quintana | Abel Camacho (Instituto Nacional de Investigaciones Nucleares) | Decoherence and bare mass induced by nonconformal metric fluctuations | 10 pages, accepted in General Relativity and Gravitation | Gen.Rel.Grav. 35 (2003) 319-325 | 10.1023/A:1022349328278 | null | gr-qc | null | The effects, upon the Klein--Gordon field, of nonconformal stochastic metric
fluctuations, are analyzed. It will be shown that these fluctuations allow us
to consider an effective mass, i.e., the mass detected in a laboratory is not
the parameter appearing in the Klein--Gordon equation, but a function of this
parameter and of the fluctuations of the metric. In other words, in analogy to
the case of a nonrelativistic electron in interaction with a quantized
electromagnetic field, we may speak of a bare mass, where the observed mass
shows a dependence upon the stochastic terms included in the metric.
Afterwards, we prove, resorting to the influence functional, that the
energy--momentum tensor of the Klein--Gordon field inherites this stochastic
behavior, and that this feature provokes decoherence upon a particle immersed
in the region where this tensor is present.
| [
{
"created": "Mon, 2 Sep 2002 13:56:13 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Camacho",
"Abel",
"",
"Instituto Nacional de Investigaciones Nucleares"
]
] | The effects, upon the Klein--Gordon field, of nonconformal stochastic metric fluctuations, are analyzed. It will be shown that these fluctuations allow us to consider an effective mass, i.e., the mass detected in a laboratory is not the parameter appearing in the Klein--Gordon equation, but a function of this parameter and of the fluctuations of the metric. In other words, in analogy to the case of a nonrelativistic electron in interaction with a quantized electromagnetic field, we may speak of a bare mass, where the observed mass shows a dependence upon the stochastic terms included in the metric. Afterwards, we prove, resorting to the influence functional, that the energy--momentum tensor of the Klein--Gordon field inherites this stochastic behavior, and that this feature provokes decoherence upon a particle immersed in the region where this tensor is present. |
1206.3772 | Eric Poisson | Marc Casals, Eric Poisson, and Ian Vega | Regularization of static self-forces | 23 pages, no figures | null | 10.1103/PhysRevD.86.064033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Various regularization methods have been used to compute the self-force
acting on a static particle in a static, curved spacetime. Many of these are
based on Hadamard's two-point function in three dimensions. On the other hand,
the regularization method that enjoys the best justification is that of
Detweiler and Whiting, which is based on a four-dimensional Green's function.
We establish the connection between these methods and find that they are all
equivalent, in the sense that they all lead to the same static self-force. For
general static spacetimes, we compute local expansions of the Green's functions
on which the various regularization methods are based. We find that these agree
up to a certain high order, and conjecture that they might be equal to all
orders. We show that this equivalence is exact in the case of ultrastatic
spacetimes. Finally, our computations are exploited to provide regularization
parameters for a static particle in a general static and spherically-symmetric
spacetime.
| [
{
"created": "Sun, 17 Jun 2012 17:41:15 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Casals",
"Marc",
""
],
[
"Poisson",
"Eric",
""
],
[
"Vega",
"Ian",
""
]
] | Various regularization methods have been used to compute the self-force acting on a static particle in a static, curved spacetime. Many of these are based on Hadamard's two-point function in three dimensions. On the other hand, the regularization method that enjoys the best justification is that of Detweiler and Whiting, which is based on a four-dimensional Green's function. We establish the connection between these methods and find that they are all equivalent, in the sense that they all lead to the same static self-force. For general static spacetimes, we compute local expansions of the Green's functions on which the various regularization methods are based. We find that these agree up to a certain high order, and conjecture that they might be equal to all orders. We show that this equivalence is exact in the case of ultrastatic spacetimes. Finally, our computations are exploited to provide regularization parameters for a static particle in a general static and spherically-symmetric spacetime. |
2208.03011 | Vittorio De Falco Dr | Salvatore Capozziello, Vittorio De Falco, Carmen Ferrara | Comparing Equivalent Gravities: common features and differences | 30 pages, 6 figures | null | 10.1140/epjc/s10052-022-10823-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss equivalent representations of gravity in the framework of
metric-affine geometries pointing out basic concepts from where these theories
stem out. In particular, we take into account tetrads and spin connection to
describe the so called {\it Geometric Trinity of Gravity}. Specifically, we
consider General Relativity, constructed upon the metric tensor and based on
the curvature $R$; Teleparallel Equivalent of General Relativity, formulated in
terms of torsion $T$ and relying on tetrads and spin connection; Symmetric
Teleparallel Equivalent of General Relativity, built up on non-metricity $Q$,
constructed from metric tensor and affine connection. General Relativity is
formulated as a geometric theory of gravity based on metric, whereas
teleparallel approaches configure as gauge theories, where gauge choices permit
not only to simplify calculations, but also to give deep insight into the basic
concepts of gravitational field. In particular, we point out how foundation
principles of General Relativity (i.e the Equivalence Principle and the General
Covariance) can be seen from the teleparallel point of view. These theories are
dynamically equivalent and this feature can be demonstrated under three
different standards: (1) the variational method; (2) the field equations; (3)
the solutions.
| [
{
"created": "Fri, 5 Aug 2022 06:58:34 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Dec 2022 10:08:33 GMT",
"version": "v2"
}
] | 2022-12-06 | [
[
"Capozziello",
"Salvatore",
""
],
[
"De Falco",
"Vittorio",
""
],
[
"Ferrara",
"Carmen",
""
]
] | We discuss equivalent representations of gravity in the framework of metric-affine geometries pointing out basic concepts from where these theories stem out. In particular, we take into account tetrads and spin connection to describe the so called {\it Geometric Trinity of Gravity}. Specifically, we consider General Relativity, constructed upon the metric tensor and based on the curvature $R$; Teleparallel Equivalent of General Relativity, formulated in terms of torsion $T$ and relying on tetrads and spin connection; Symmetric Teleparallel Equivalent of General Relativity, built up on non-metricity $Q$, constructed from metric tensor and affine connection. General Relativity is formulated as a geometric theory of gravity based on metric, whereas teleparallel approaches configure as gauge theories, where gauge choices permit not only to simplify calculations, but also to give deep insight into the basic concepts of gravitational field. In particular, we point out how foundation principles of General Relativity (i.e the Equivalence Principle and the General Covariance) can be seen from the teleparallel point of view. These theories are dynamically equivalent and this feature can be demonstrated under three different standards: (1) the variational method; (2) the field equations; (3) the solutions. |
2308.13261 | Alexander Florian Jercher | Alexander F. Jercher, Luca Marchetti, Andreas G. A. Pithis | Scalar Cosmological Perturbations from Quantum Entanglement within
Lorentzian Quantum Gravity | 44 + 18 pages, 6 figures | Phys.Rev.D 109 (2024) 6 | 10.1103/PhysRevD.109.066021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the dynamics of (isotropic) scalar perturbations from the
mean-field hydrodynamics of full Lorentzian quantum gravity, as described by a
two-sector (timelike and spacelike) Barrett-Crane group field theory (GFT)
model. The rich causal structure of this model allows us to consistently
implement in the quantum theory the causal properties of a physical Lorentzian
reference frame composed of four minimally coupled, massless, and free scalar
fields. Using this frame, we are able to effectively construct relational
observables that are used to recover macroscopic cosmological quantities. In
particular, small isotropic scalar inhomogeneities emerge as a result of
(relational) nearest-neighbor two-body entanglement between degrees of freedom
of the underlying quantum gravity theory. The dynamical equations we obtain for
geometric and matter perturbations show agreement with those of classical
general relativity in the long-wavelength, super-horizon limit. In general,
deviations become important for sub-horizon modes, which seem to be naturally
associated with a trans-Planckian regime in our physical reference frame. We
argue that these trans-Planckian corrections are quantum gravitational in
nature. However, we explicitly show that for some physically interesting
solutions these quantum gravity effects can be quite small, leading to a very
good agreement with the classical GR behavior.
| [
{
"created": "Fri, 25 Aug 2023 09:25:40 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Mar 2024 21:13:06 GMT",
"version": "v2"
}
] | 2024-04-02 | [
[
"Jercher",
"Alexander F.",
""
],
[
"Marchetti",
"Luca",
""
],
[
"Pithis",
"Andreas G. A.",
""
]
] | We derive the dynamics of (isotropic) scalar perturbations from the mean-field hydrodynamics of full Lorentzian quantum gravity, as described by a two-sector (timelike and spacelike) Barrett-Crane group field theory (GFT) model. The rich causal structure of this model allows us to consistently implement in the quantum theory the causal properties of a physical Lorentzian reference frame composed of four minimally coupled, massless, and free scalar fields. Using this frame, we are able to effectively construct relational observables that are used to recover macroscopic cosmological quantities. In particular, small isotropic scalar inhomogeneities emerge as a result of (relational) nearest-neighbor two-body entanglement between degrees of freedom of the underlying quantum gravity theory. The dynamical equations we obtain for geometric and matter perturbations show agreement with those of classical general relativity in the long-wavelength, super-horizon limit. In general, deviations become important for sub-horizon modes, which seem to be naturally associated with a trans-Planckian regime in our physical reference frame. We argue that these trans-Planckian corrections are quantum gravitational in nature. However, we explicitly show that for some physically interesting solutions these quantum gravity effects can be quite small, leading to a very good agreement with the classical GR behavior. |
2308.01815 | Marie-No\"elle C\'el\'erier | M.-N. C\'el\'erier | Interior spacetimes sourced by stationary differentially rotating
irrotational cylindrical fluids. IV. Radial pressure | overlap with 2312.09263 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent series of papers new exact analytical solutions of the field
equations of General Relativity representing interior spacetimes sourced by
stationary rigidly rotating cylinders of fluids with various equations of state
have been displayed. This work is currently extended to the cases of
differentially rotating irrotational fluids. The results are presented in a new
series of papers considering, in turn, a perfect fluid source, as well as the
three anisotropic pressure cases already studied in the rigidly rotating
configuration. Here, we analyze the case of a fluid with radially directed
pressure. Four classes of solutions are identified from the field equations.
Among them, class I and III are fully integrated, and their mathematical and
physical properties are studied, which implies a ruling out of class III for
lack of proper metric signature. For each of the two other classes, a set of
simplified differential equation is displayed so as to ease their possible
further numerical integration. Finally, a comparison with the corresponding
rigidly rotating fluid solution is provided.
| [
{
"created": "Thu, 3 Aug 2023 15:24:52 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jul 2024 15:29:34 GMT",
"version": "v2"
}
] | 2024-07-08 | [
[
"Célérier",
"M. -N.",
""
]
] | In a recent series of papers new exact analytical solutions of the field equations of General Relativity representing interior spacetimes sourced by stationary rigidly rotating cylinders of fluids with various equations of state have been displayed. This work is currently extended to the cases of differentially rotating irrotational fluids. The results are presented in a new series of papers considering, in turn, a perfect fluid source, as well as the three anisotropic pressure cases already studied in the rigidly rotating configuration. Here, we analyze the case of a fluid with radially directed pressure. Four classes of solutions are identified from the field equations. Among them, class I and III are fully integrated, and their mathematical and physical properties are studied, which implies a ruling out of class III for lack of proper metric signature. For each of the two other classes, a set of simplified differential equation is displayed so as to ease their possible further numerical integration. Finally, a comparison with the corresponding rigidly rotating fluid solution is provided. |
2305.04829 | Sudipta Das | Sudipta Das | Ideal Gas Thermodynamics with an Invariant Energy Scale | 11 pages, 3 figures, submitted to journal for consideration | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A viable approach towards Quantum Gravity is the Doubly Special Relativity
(DSR) framework in which an observer-independent finite energy upper bound (or
a finite smallest length scale) appears quite naturally. In this work, we have
studied the thermodynamic properties of an ideal gas in a specific DSR
framework, known as the Magueijo-Smolin (MS) Model. We use the fact that DSR
can be considered as nonlinear representation of Lorentz Group. Subsequently,
various thermodynamic parameters of ideal gas have been derived in this
modified framework to compare the corresponding deviations from the usual
scenario due to the presence of the invariant energy (length) scale.
| [
{
"created": "Mon, 8 May 2023 16:25:58 GMT",
"version": "v1"
},
{
"created": "Thu, 18 May 2023 14:57:25 GMT",
"version": "v2"
}
] | 2023-05-19 | [
[
"Das",
"Sudipta",
""
]
] | A viable approach towards Quantum Gravity is the Doubly Special Relativity (DSR) framework in which an observer-independent finite energy upper bound (or a finite smallest length scale) appears quite naturally. In this work, we have studied the thermodynamic properties of an ideal gas in a specific DSR framework, known as the Magueijo-Smolin (MS) Model. We use the fact that DSR can be considered as nonlinear representation of Lorentz Group. Subsequently, various thermodynamic parameters of ideal gas have been derived in this modified framework to compare the corresponding deviations from the usual scenario due to the presence of the invariant energy (length) scale. |
gr-qc/9811012 | Hongsu Kim | Hongsu Kim | New Black Hole Solutions in Brans-Dicke Theory of Gravity | 20 pages, no figure, Revtex, version to appear in Phys. Rev. D | Phys.Rev. D60 (1999) 024001 | 10.1103/PhysRevD.60.024001 | null | gr-qc astro-ph hep-th | null | Existence check of non-trivial, stationary axisymmetric black hole solutions
in Brans-Dicke theory of gravity in different direction from those of Penrose,
Thorne and Dykla, and Hawking is performed. Namely, working directly with the
known explicit spacetime solutions in Brans-Dicke theory, it is found that
non-trivial Kerr-Newman-type black hole solutions different from general
relativistic solutions could occur for the generic Brans-Dicke parameter values
-5/2\leq \omega <-3/2. Finally, issues like whether these new black holes carry
scalar hair and can really arise in nature and if they can, what the associated
physical implications would be are discussed carefully.
| [
{
"created": "Wed, 4 Nov 1998 07:23:17 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Nov 1998 03:06:06 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Mar 1999 00:51:16 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Kim",
"Hongsu",
""
]
] | Existence check of non-trivial, stationary axisymmetric black hole solutions in Brans-Dicke theory of gravity in different direction from those of Penrose, Thorne and Dykla, and Hawking is performed. Namely, working directly with the known explicit spacetime solutions in Brans-Dicke theory, it is found that non-trivial Kerr-Newman-type black hole solutions different from general relativistic solutions could occur for the generic Brans-Dicke parameter values -5/2\leq \omega <-3/2. Finally, issues like whether these new black holes carry scalar hair and can really arise in nature and if they can, what the associated physical implications would be are discussed carefully. |
1706.05673 | Javier Olmedo | Daniel Mart\'in de Blas, Javier Olmedo and Tomasz Paw{\l}owski | Loop quantization of the Gowdy model with local rotational symmetry | 19 pages, 1 fig | Phys. Rev. D 96, 106016 (2017) | 10.1103/PhysRevD.96.106016 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a full quantization of the vacuum Gowdy model with local
rotational symmetry. We consider a redefinition of the constraints where the
Hamiltonian Poisson-commutes with itself. We then apply the canonical
quantization program of loop quantum gravity within an improved dynamics
scheme. We identify the exact solutions of the constraints and the physical
observables, and we construct the physical Hilbert space. It is remarkable that
quantum spacetimes are free of singularities. New quantum observables naturally
arising in the treatment partially codify the discretization of the geometry.
The preliminary analysis of the asymptotic future/past of the evolution
indicates that the existing Abelianization technique needs further refinement.
| [
{
"created": "Sun, 18 Jun 2017 15:47:27 GMT",
"version": "v1"
}
] | 2017-12-06 | [
[
"de Blas",
"Daniel Martín",
""
],
[
"Olmedo",
"Javier",
""
],
[
"Pawłowski",
"Tomasz",
""
]
] | We provide a full quantization of the vacuum Gowdy model with local rotational symmetry. We consider a redefinition of the constraints where the Hamiltonian Poisson-commutes with itself. We then apply the canonical quantization program of loop quantum gravity within an improved dynamics scheme. We identify the exact solutions of the constraints and the physical observables, and we construct the physical Hilbert space. It is remarkable that quantum spacetimes are free of singularities. New quantum observables naturally arising in the treatment partially codify the discretization of the geometry. The preliminary analysis of the asymptotic future/past of the evolution indicates that the existing Abelianization technique needs further refinement. |
gr-qc/0511125 | Muhammad Sharif | M. Sharif | Matter Inheritance Symmetries of Spherically Symmetric Static Spacetimes | 15 pages, accepted for publication in Int. J. of Mod. Phys. A | Int.J.Mod.Phys.A21:2645-2657,2006 | 10.1142/S0217751X06029430 | null | gr-qc | null | In this paper we discuss matter inheritance collineations by giving a
complete classification of spherically symmetric static spacetimes by their
matter inheritance symmetries. It is shown that when the energy-momentum tensor
is degenerate, most of the cases yield infinite dimensional matter inheriting
symmetries. It is worth mentioning here that two cases provide finite
dimensional matter inheriting vectors even for the degenerate case. The
non-degenerate case provides finite dimensional matter inheriting symmetries.
We obtain different constraints on the energy-momentum tensor in each case. It
is interesting to note that if the inheriting factor vanishes, matter
inheriting collineations reduce to be matter collineations already available in
the literature. This idea of matter inheritance collineations turn out to be
the same as homotheties and conformal Killing vectors are for the metric
tensor.
| [
{
"created": "Wed, 23 Nov 2005 10:30:07 GMT",
"version": "v1"
}
] | 2010-11-05 | [
[
"Sharif",
"M.",
""
]
] | In this paper we discuss matter inheritance collineations by giving a complete classification of spherically symmetric static spacetimes by their matter inheritance symmetries. It is shown that when the energy-momentum tensor is degenerate, most of the cases yield infinite dimensional matter inheriting symmetries. It is worth mentioning here that two cases provide finite dimensional matter inheriting vectors even for the degenerate case. The non-degenerate case provides finite dimensional matter inheriting symmetries. We obtain different constraints on the energy-momentum tensor in each case. It is interesting to note that if the inheriting factor vanishes, matter inheriting collineations reduce to be matter collineations already available in the literature. This idea of matter inheritance collineations turn out to be the same as homotheties and conformal Killing vectors are for the metric tensor. |
1504.01251 | Ifra Noureen | Ifra Noureen, M. Zubair, A.A. Bhatti, G. Abbas | Shearfree Condition and dynamical Instability in $f(R,T)$ gravity | 16 pages | Eur. Phys. J. C (2015) 75: 323 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The implications of shearfree condition on instability range of anisotropic
fluid in $f(R,T)$ are studied in this manuscript. A viable $f(R, T)$ model is
chosen to arrive at stability criterion, where $R$ is Ricci scalar and $T$ is
the trace of energy momentum tensor. The evolution of spherical star is
explored by employing perturbation scheme on modified field equations and
contracted Bianchi identities in $f(R, T)$. The effect of imposed shearfree
condition on collapse equation and adiabatic index $\Gamma$ is studied in
Newtonian and post-Newtonian regimes.
| [
{
"created": "Mon, 6 Apr 2015 10:11:40 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jul 2015 11:34:44 GMT",
"version": "v2"
}
] | 2015-07-29 | [
[
"Noureen",
"Ifra",
""
],
[
"Zubair",
"M.",
""
],
[
"Bhatti",
"A. A.",
""
],
[
"Abbas",
"G.",
""
]
] | The implications of shearfree condition on instability range of anisotropic fluid in $f(R,T)$ are studied in this manuscript. A viable $f(R, T)$ model is chosen to arrive at stability criterion, where $R$ is Ricci scalar and $T$ is the trace of energy momentum tensor. The evolution of spherical star is explored by employing perturbation scheme on modified field equations and contracted Bianchi identities in $f(R, T)$. The effect of imposed shearfree condition on collapse equation and adiabatic index $\Gamma$ is studied in Newtonian and post-Newtonian regimes. |
0807.0439 | Tomislav Prokopec | Tomas Janssen, Shun-Pei Miao, Tomislav Prokopec (ITP, Utrecht
University) | Graviton one-loop effective action and inflationary dynamics | 25 pages, 3 figures | null | null | ITP-UU-80/45, SPIN-08/32 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the one-loop effective action due to gravitons in a FLRW
background with constant epsilon=-(dH/dt)/H^2. By expanding around epsilon=0
(corresponding to an expansion around de Sitter space), we can study how the
deviation from de Sitter space effects the quantum corrected Friedmann
equations. We find that, at zeroth order in epsilon, one-loop effects induce
only a finite shift in the coupling constants. At linear order in epsilon there
is however a divergent contribution to the equations of motion. This
contribution leads to a nontrivial term in the renormalized equations that
depends logarithmically on H and thus cannot be absorbed in local counterterms.
We find that deviations due to this term are unobservably small. Our study
shows that quantum effects in quasi de Sitter space can be fundamentally
different then in de Sitter space, albeit in the case under consideration the
effect is unobservably small.
| [
{
"created": "Wed, 2 Jul 2008 20:31:43 GMT",
"version": "v1"
}
] | 2008-07-04 | [
[
"Janssen",
"Tomas",
"",
"ITP, Utrecht\n University"
],
[
"Miao",
"Shun-Pei",
"",
"ITP, Utrecht\n University"
],
[
"Prokopec",
"Tomislav",
"",
"ITP, Utrecht\n University"
]
] | We consider the one-loop effective action due to gravitons in a FLRW background with constant epsilon=-(dH/dt)/H^2. By expanding around epsilon=0 (corresponding to an expansion around de Sitter space), we can study how the deviation from de Sitter space effects the quantum corrected Friedmann equations. We find that, at zeroth order in epsilon, one-loop effects induce only a finite shift in the coupling constants. At linear order in epsilon there is however a divergent contribution to the equations of motion. This contribution leads to a nontrivial term in the renormalized equations that depends logarithmically on H and thus cannot be absorbed in local counterterms. We find that deviations due to this term are unobservably small. Our study shows that quantum effects in quasi de Sitter space can be fundamentally different then in de Sitter space, albeit in the case under consideration the effect is unobservably small. |
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