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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0911.2189
|
Lorenzo Iorio
|
Lorenzo Iorio
|
Anthropic constraints on the cosmological constant from Sun's motion
through the Milky Way
|
LaTex2e, 3 tables, no figures, 5 pages. Accepted by Monthly Notices
of the Royal Astronomical Society (MNRAS)
|
Mon.Not.Roy.Astron.Soc.403:1469 - 1473,2010
|
10.1111/j.1365-2966.2010.16212.x
| null |
gr-qc astro-ph.GA hep-ph physics.space-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We tentatively look at anthropic constraints on the Cosmological Constant
(CC) \Lambda at galactic scales by investigating its influence on the motion of
the Sun throughout the Milky Way (MW) for -4.5 <= t <=0 Gyr. In particular, we
look at the Galactocentric distance at which the Sun is displaced at the end of
the numerical integration of its equations of motion modified in order to
include the effect of \Lambda as well. Values of it placing our star at its
birth at more than 10 kpc from the Galactic center (GC) are to be considered
implausible, according to the current views on the Galactic Habitable Zone
(GHZ) on the metallicity level needed for stars' formation. Also values
yielding too close approaches to GC should be excluded because of the risks to
life's evolution coming from too much nearby supernovae (SN) explosions and
Gamma Ray Bursts (GRB). We investigate the impact on our results of the
uncertainties on both the MW model's parameters and the Sun's initial
conditions, in particular the Hubble parameter H_0 and the Local Standard Rest
(LSR) speed \Theta_0 accurate at 2% and 6.2% level, respectively. While
H_0=70.1 km s^-1 Mpc^-1, \Theta_0=254 km s^-1 and \Lambda <= 10^-55 cm^-2
locates the place of birth of the Sun at 19.6 kpc from GC, the same values for
H_0 and \Lambda, and \Theta_0^max=270 km s^-1, places it at the plausible
Galactocentric distance of 8.5 kpc. \Lambda = 10^-54 cm^-2 and \Lambda = 10^-53
cm^-2 place the Sun at 10.6 kpc and 18.7 kpc, respectively.
|
[
{
"created": "Wed, 11 Nov 2009 17:32:55 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2009 14:17:22 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Dec 2009 16:57:21 GMT",
"version": "v3"
}
] |
2010-04-08
|
[
[
"Iorio",
"Lorenzo",
""
]
] |
We tentatively look at anthropic constraints on the Cosmological Constant (CC) \Lambda at galactic scales by investigating its influence on the motion of the Sun throughout the Milky Way (MW) for -4.5 <= t <=0 Gyr. In particular, we look at the Galactocentric distance at which the Sun is displaced at the end of the numerical integration of its equations of motion modified in order to include the effect of \Lambda as well. Values of it placing our star at its birth at more than 10 kpc from the Galactic center (GC) are to be considered implausible, according to the current views on the Galactic Habitable Zone (GHZ) on the metallicity level needed for stars' formation. Also values yielding too close approaches to GC should be excluded because of the risks to life's evolution coming from too much nearby supernovae (SN) explosions and Gamma Ray Bursts (GRB). We investigate the impact on our results of the uncertainties on both the MW model's parameters and the Sun's initial conditions, in particular the Hubble parameter H_0 and the Local Standard Rest (LSR) speed \Theta_0 accurate at 2% and 6.2% level, respectively. While H_0=70.1 km s^-1 Mpc^-1, \Theta_0=254 km s^-1 and \Lambda <= 10^-55 cm^-2 locates the place of birth of the Sun at 19.6 kpc from GC, the same values for H_0 and \Lambda, and \Theta_0^max=270 km s^-1, places it at the plausible Galactocentric distance of 8.5 kpc. \Lambda = 10^-54 cm^-2 and \Lambda = 10^-53 cm^-2 place the Sun at 10.6 kpc and 18.7 kpc, respectively.
|
2007.15384
|
Lode Wylleman
|
Lode Wylleman, L. Filipe O. Costa and Jos\'e Nat\'ario
|
Poynting vector, super-Poynting vector, and principal observers in
electromagnetism and general relativity
|
42 pages, 6 figures. Minor improvements, typos corrected, references
added. Matches the final published version
|
Class. Quantum Grav. 38 (2021) 165009
|
10.1088/1361-6382/abfd93
| null |
gr-qc math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In electromagnetism, the concept of Poynting vector as measured by an
observer is well known. A mathematical analogue in general relativity is the
super-Poynting vector of the Weyl tensor. Observers for which the
(super-)Poynting vector vanishes are called principal. When, at a given point,
the electromagnetic field is non-null, or the gravitational field is of
Weyl-Petrov type I or D, principal observers instantaneously passing through
that point always exist. We survey characterizations of such observers and
study their relation to arbitrary observers. In the non-null electromagnetic
case it is known that, given any observer, there is a principal observer which
moves relative to the first in the direction of his Poynting vector. Replacing
Poynting by super-Poynting yields a possible gravitational analogue; we show
that this analogy indeed holds for any observer when the Petrov type is D, but
only for a one-dimensional variety of observers when the Petrov type is I. We
provide algorithms to obtain the principal observers directly from the electric
and magnetic fields (in the electromagnetic case) or electric and magnetic
parts of the Weyl tensor (in the gravitational case) relative to an arbitrary
observer. It is found that in Petrov type D doubly aligned non-null
Einstein-Maxwell fields (which include all classical charged black hole
solutions) the Poynting and super-Poynting vectors are aligned, at each point
and for each observer, and the principal observers coincide. Our results are
illustrated in simple examples.
|
[
{
"created": "Thu, 30 Jul 2020 11:21:51 GMT",
"version": "v1"
},
{
"created": "Thu, 27 May 2021 21:12:22 GMT",
"version": "v2"
}
] |
2021-08-20
|
[
[
"Wylleman",
"Lode",
""
],
[
"Costa",
"L. Filipe O.",
""
],
[
"Natário",
"José",
""
]
] |
In electromagnetism, the concept of Poynting vector as measured by an observer is well known. A mathematical analogue in general relativity is the super-Poynting vector of the Weyl tensor. Observers for which the (super-)Poynting vector vanishes are called principal. When, at a given point, the electromagnetic field is non-null, or the gravitational field is of Weyl-Petrov type I or D, principal observers instantaneously passing through that point always exist. We survey characterizations of such observers and study their relation to arbitrary observers. In the non-null electromagnetic case it is known that, given any observer, there is a principal observer which moves relative to the first in the direction of his Poynting vector. Replacing Poynting by super-Poynting yields a possible gravitational analogue; we show that this analogy indeed holds for any observer when the Petrov type is D, but only for a one-dimensional variety of observers when the Petrov type is I. We provide algorithms to obtain the principal observers directly from the electric and magnetic fields (in the electromagnetic case) or electric and magnetic parts of the Weyl tensor (in the gravitational case) relative to an arbitrary observer. It is found that in Petrov type D doubly aligned non-null Einstein-Maxwell fields (which include all classical charged black hole solutions) the Poynting and super-Poynting vectors are aligned, at each point and for each observer, and the principal observers coincide. Our results are illustrated in simple examples.
|
1504.07519
|
Sumanta Chakraborty
|
Sumanta Chakraborty and Soumitra SenGupta
|
Effective field equation on m-brane embedded in n-dimensional bulk of
Einstein and f(R) gravity
|
v2, Revised, Accepted in EPJC, 35 pages, no figures
|
Eur. Phys. J. C 75, 538 (2015)
|
10.1140/epjc/s10052-015-3768-z
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We have derived effective gravitational field equations on a lower
dimensional hypersurface (known as a brane), placed in a higher dimensional
bulk spacetime for both Einstein and $f(\mathcal{R})$ gravity theories. We have
started our analysis on $n$-dimensional bulk from which the effective field
equations on a $(n-1)$-dimensional brane has been obtained by imposing $Z_{2}$
symmetry. Subsequently, we have arrived at the effective equations in
$(n-2)$-dimensions starting from the effective equations for $(n-1)$
dimensional brane. This analysis has been carried forward and is used to obtain
the effective field equations in $(n-m)$-dimensional brane, embedded in a
$n$-dimensional bulk. Having obtained the effective field equations in Einstein
gravity, we have subsequently generalized the effective field equation in
$(n-m)$-dimensional brane which is embedded the $n$-dimensional bulk spacetime
endowed with $f(\mathcal{R})$ gravity. We have also presented applications of
our results in the context of Einstein and $f(\mathcal{R})$ gravity. In both
the cases we have discussed vacuum static spherically symmetric solutions as
well as solutions in cosmological context. Implications are also discussed.
|
[
{
"created": "Mon, 27 Apr 2015 11:00:36 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Oct 2015 00:55:51 GMT",
"version": "v2"
}
] |
2015-11-24
|
[
[
"Chakraborty",
"Sumanta",
""
],
[
"SenGupta",
"Soumitra",
""
]
] |
We have derived effective gravitational field equations on a lower dimensional hypersurface (known as a brane), placed in a higher dimensional bulk spacetime for both Einstein and $f(\mathcal{R})$ gravity theories. We have started our analysis on $n$-dimensional bulk from which the effective field equations on a $(n-1)$-dimensional brane has been obtained by imposing $Z_{2}$ symmetry. Subsequently, we have arrived at the effective equations in $(n-2)$-dimensions starting from the effective equations for $(n-1)$ dimensional brane. This analysis has been carried forward and is used to obtain the effective field equations in $(n-m)$-dimensional brane, embedded in a $n$-dimensional bulk. Having obtained the effective field equations in Einstein gravity, we have subsequently generalized the effective field equation in $(n-m)$-dimensional brane which is embedded the $n$-dimensional bulk spacetime endowed with $f(\mathcal{R})$ gravity. We have also presented applications of our results in the context of Einstein and $f(\mathcal{R})$ gravity. In both the cases we have discussed vacuum static spherically symmetric solutions as well as solutions in cosmological context. Implications are also discussed.
|
gr-qc/9704013
|
Fotini Markopoulou
|
Fotini Markopoulou
|
Dual formulation of spin network evolution
|
Latex, 20 pages, 16 figures
| null | null | null |
gr-qc
| null |
We illustrate the relationship between spin networks and their dual
representation by labelled triangulations of space in 2+1 and 3+1 dimensions.
We apply this to the recent proposal for causal evolution of spin networks. The
result is labelled spatial triangulations evolving with transition amplitudes
given by labelled spacetime simplices. The formalism is very similar to
simplicial gravity, however, the triangulations represent combinatorics and not
an approximation to the spatial manifold. The distinction between future and
past nodes which can be ordered in causal sets also exists here. Spacelike and
timelike slices can be defined and the foliation is allowed to vary. We clarify
the choice of the two rules in the causal spin network evolution, and the
assumption of trivalent spin networks for 2+1 spacetime dimensions and
four-valent for 3+1. As a direct application, the problem of the exponential
growth of the causal model is remedied. The result is a clear and more rigid
graphical understanding of evolution of combinatorial spin networks, on which
further work can be based.
|
[
{
"created": "Sun, 6 Apr 1997 13:48:04 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Markopoulou",
"Fotini",
""
]
] |
We illustrate the relationship between spin networks and their dual representation by labelled triangulations of space in 2+1 and 3+1 dimensions. We apply this to the recent proposal for causal evolution of spin networks. The result is labelled spatial triangulations evolving with transition amplitudes given by labelled spacetime simplices. The formalism is very similar to simplicial gravity, however, the triangulations represent combinatorics and not an approximation to the spatial manifold. The distinction between future and past nodes which can be ordered in causal sets also exists here. Spacelike and timelike slices can be defined and the foliation is allowed to vary. We clarify the choice of the two rules in the causal spin network evolution, and the assumption of trivalent spin networks for 2+1 spacetime dimensions and four-valent for 3+1. As a direct application, the problem of the exponential growth of the causal model is remedied. The result is a clear and more rigid graphical understanding of evolution of combinatorial spin networks, on which further work can be based.
|
1509.02248
|
Rhondale Tso
|
Rhondale Tso, Michele Zanolin
|
Measuring violations of General Relativity from single gravitational
wave detection by non-spinning binary systems: higher-order asymptotic
analysis
|
15 pages, 9 figures
|
Phys. Rev. D 93, 124033 (2016)
|
10.1103/PhysRevD.93.124033
|
LIGO-P1500144
|
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A frequentist asymptotic expansion method for error estimation is employed
for a network of gravitational wave detectors to assess the amount of
information that can be extracted from gravitational wave observations.
Mathematically we derive lower bounds in the errors that any parameter
estimator will have in the absence of prior knowledge to distinguish between
the post-Einsteinian (ppE) description of coalescing binary systems and that of
general relativity. When such errors are smaller than the parameter value,
there is possibility to detect these violations from GR. A parameter space with
inclusion of dominant dephasing ppE parameters $(\beta, b)$ is used for a study
of first- and second-order (co)variance expansions, focusing on the inspiral
stage of a nonspinning binary system of zero eccentricity detectible through
Adv. LIGO and Adv. Virgo. Our procedure is an improvement of the Cram\'{e}r-Rao
Lower Bound. When Bayesian errors are lower than our bound it means that they
depend critically on the priors. The analysis indicates the possibility of
constraining deviations from GR in inspiral SNR ($\rho \sim 15-17$) regimes
that are achievable in upcoming scientific runs (GW150914 had an inspiral SNR
$\sim 12$). The errors on $\beta$ also increase errors of other parameters such
as the chirp mass $\mathcal{M}$ and symmetric mass ratio $\eta$. Application is
done to existing alternative theories of gravity, which include modified
dispersion relation of the waveform, non-spinning models of quadratic modified
gravity, and dipole gravitational radiation (i.e., Brans-Dicke type)
modifications.
|
[
{
"created": "Tue, 8 Sep 2015 03:47:50 GMT",
"version": "v1"
},
{
"created": "Tue, 24 May 2016 17:25:29 GMT",
"version": "v2"
}
] |
2016-06-22
|
[
[
"Tso",
"Rhondale",
""
],
[
"Zanolin",
"Michele",
""
]
] |
A frequentist asymptotic expansion method for error estimation is employed for a network of gravitational wave detectors to assess the amount of information that can be extracted from gravitational wave observations. Mathematically we derive lower bounds in the errors that any parameter estimator will have in the absence of prior knowledge to distinguish between the post-Einsteinian (ppE) description of coalescing binary systems and that of general relativity. When such errors are smaller than the parameter value, there is possibility to detect these violations from GR. A parameter space with inclusion of dominant dephasing ppE parameters $(\beta, b)$ is used for a study of first- and second-order (co)variance expansions, focusing on the inspiral stage of a nonspinning binary system of zero eccentricity detectible through Adv. LIGO and Adv. Virgo. Our procedure is an improvement of the Cram\'{e}r-Rao Lower Bound. When Bayesian errors are lower than our bound it means that they depend critically on the priors. The analysis indicates the possibility of constraining deviations from GR in inspiral SNR ($\rho \sim 15-17$) regimes that are achievable in upcoming scientific runs (GW150914 had an inspiral SNR $\sim 12$). The errors on $\beta$ also increase errors of other parameters such as the chirp mass $\mathcal{M}$ and symmetric mass ratio $\eta$. Application is done to existing alternative theories of gravity, which include modified dispersion relation of the waveform, non-spinning models of quadratic modified gravity, and dipole gravitational radiation (i.e., Brans-Dicke type) modifications.
|
1705.07082
|
Ivan Agullo
|
Ivan Agullo, Adrian del Rio, and Jose Navarro-Salas
|
Gravity and handedness of photons
|
First Award in the 2017 Essay Competition of the Gravity Research
Foundation
| null |
10.1142/S0218271817420019
|
LSU-REL-190517
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Vacuum fluctuations of quantum fields are altered in presence of a strong
gravitational background, with important physical consequences. We argue that a
non-trivial spacetime geometry can act as an optically active medium for
quantum electromagnetic radiation, in such a way that the state of polarization
of radiation changes in time, even in the absence of electromagnetic sources.
This is a quantum effect, and is a consequence of an anomaly related to the
classical invariance under electric-magnetic duality rotations in Maxwell
theory.
|
[
{
"created": "Fri, 19 May 2017 16:36:54 GMT",
"version": "v1"
}
] |
2017-11-22
|
[
[
"Agullo",
"Ivan",
""
],
[
"del Rio",
"Adrian",
""
],
[
"Navarro-Salas",
"Jose",
""
]
] |
Vacuum fluctuations of quantum fields are altered in presence of a strong gravitational background, with important physical consequences. We argue that a non-trivial spacetime geometry can act as an optically active medium for quantum electromagnetic radiation, in such a way that the state of polarization of radiation changes in time, even in the absence of electromagnetic sources. This is a quantum effect, and is a consequence of an anomaly related to the classical invariance under electric-magnetic duality rotations in Maxwell theory.
|
2203.14969
|
Kimet Jusufi
|
Kimet Jusufi, Mustapha Azreg-A\"inou, Mubasher Jamil, Qiang Wu
|
Equatorial and polar quasinormal modes and quasiperiodic oscillations of
quantum deformed Kerr black hole
|
14 pages, published in Universe
|
Universe 2022, 8(4), 210
|
10.3390/universe8040210
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we focus on the relation between quasinormal modes (QNMs) and a
rotating black hole shadows. As a specific example, we consider the quantum
deformed Kerr black hole obtained via Newman--Janis--Azreg-A\"{\i}nou
algorithm. In particular, using the geometric-optics correspondence between the
parameters of a QNMs and the conserved quantities along geodesics, we show
that, in the eikonal limit, the real part of QNMs is related to the Keplerian
frequency for equatorial orbits. To this end, we explore the typical shadow
radius for the viewing angles, $\theta_0=\pi/2$, and obtained an interesting
relation in the case of viewing angle $\theta_0=0$ (or equivalently
$\theta_0=\pi$). Furthermore we have computed the corresponding equatorial and
polar modes and the thermodynamical stability of the quantum deformed Kerr
black hole. We also investigate other astrophysical applications such as the
quasiperiodic oscillations and the motion of S2 star to constrain the quantum
deforming parameter.
|
[
{
"created": "Mon, 28 Mar 2022 13:12:07 GMT",
"version": "v1"
}
] |
2022-03-30
|
[
[
"Jusufi",
"Kimet",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Wu",
"Qiang",
""
]
] |
In this paper we focus on the relation between quasinormal modes (QNMs) and a rotating black hole shadows. As a specific example, we consider the quantum deformed Kerr black hole obtained via Newman--Janis--Azreg-A\"{\i}nou algorithm. In particular, using the geometric-optics correspondence between the parameters of a QNMs and the conserved quantities along geodesics, we show that, in the eikonal limit, the real part of QNMs is related to the Keplerian frequency for equatorial orbits. To this end, we explore the typical shadow radius for the viewing angles, $\theta_0=\pi/2$, and obtained an interesting relation in the case of viewing angle $\theta_0=0$ (or equivalently $\theta_0=\pi$). Furthermore we have computed the corresponding equatorial and polar modes and the thermodynamical stability of the quantum deformed Kerr black hole. We also investigate other astrophysical applications such as the quasiperiodic oscillations and the motion of S2 star to constrain the quantum deforming parameter.
|
1010.4409
|
Koji Uryu
|
Koji Uryu, Eric Gourgoulhon, Charalampos Markakis
|
Thermodynamics of magnetized binary compact objects
|
21 pages, to appear in PRD
|
Phys.Rev.D82:104054,2010
|
10.1103/PhysRevD.82.104054
|
DPUR-TH-22
|
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Binary systems of compact objects with electromagnetic field are modeled by
helically symmetric Einstein-Maxwell spacetimes with charged and magnetized
perfect fluids. Previously derived thermodynamic laws for helically-symmetric
perfect-fluid spacetimes are extended to include the electromagnetic fields,
and electric currents and charges; the first law is written as a relation
between the change in the asymptotic Noether charge $\dl Q$ and the changes in
the area and electric charge of black holes, and in the vorticity, baryon rest
mass, entropy, charge and magnetic flux of the magnetized fluid. Using the
conservation laws of the circulation of magnetized flow found by Bekenstein and
Oron for the ideal magnetohydrodynamic (MHD) fluid, and also for the flow with
zero conducting current, we show that, for nearby equilibria that conserve the
quantities mentioned above, the relation $\dl Q=0$ is satisfied. We also
discuss a formulation for computing numerical solutions of magnetized binary
compact objects in equilibrium with emphasis on a first integral of the ideal
MHD-Euler equation.
|
[
{
"created": "Thu, 21 Oct 2010 09:58:35 GMT",
"version": "v1"
}
] |
2010-12-23
|
[
[
"Uryu",
"Koji",
""
],
[
"Gourgoulhon",
"Eric",
""
],
[
"Markakis",
"Charalampos",
""
]
] |
Binary systems of compact objects with electromagnetic field are modeled by helically symmetric Einstein-Maxwell spacetimes with charged and magnetized perfect fluids. Previously derived thermodynamic laws for helically-symmetric perfect-fluid spacetimes are extended to include the electromagnetic fields, and electric currents and charges; the first law is written as a relation between the change in the asymptotic Noether charge $\dl Q$ and the changes in the area and electric charge of black holes, and in the vorticity, baryon rest mass, entropy, charge and magnetic flux of the magnetized fluid. Using the conservation laws of the circulation of magnetized flow found by Bekenstein and Oron for the ideal magnetohydrodynamic (MHD) fluid, and also for the flow with zero conducting current, we show that, for nearby equilibria that conserve the quantities mentioned above, the relation $\dl Q=0$ is satisfied. We also discuss a formulation for computing numerical solutions of magnetized binary compact objects in equilibrium with emphasis on a first integral of the ideal MHD-Euler equation.
|
2211.16857
|
Federico De Lillo
|
Federico De Lillo, Jishnu Suresh, Antoine Depasse, Magdalena
Sieniawska, Andrew L. Miller and Giacomo Bruno
|
Probing Ensemble Properties of Vortex-avalanche Pulsar Glitches with a
Stochastic Gravitational-Wave Background Search
|
16 pages, 3 figures, 1 table
| null |
10.1103/PhysRevD.107.102001
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A stochastic gravitational-wave background (SGWB) is expected to be produced
by the superposition of individually undetectable, unresolved
gravitational-wave (GW) signals from cosmological and astrophysical sources.
Such a signal can be searched with dedicated techniques using the data acquired
by a network of ground-based GW detectors. In this work, we consider the
astrophysical SGWB resulting from pulsar glitches, which are sudden increases
in the rotational pulsar frequency, within our Galaxy. More specifically, we
assume glitches to be associated with quantized, superfluid, vortex-avalanches
in the pulsars, and we model the SGWB from the superposition of GW bursts
emitted during the glitching phase. We perform a cross-correlation search for
this SGWB-like signal employing the data from the first three observation runs
of Advanced LIGO and Virgo. Not having found any evidence for a SGWB signal, we
set upper limits on the dimensionless energy density parameter
$\Omega_{\mathrm{gw}}(f)$ for two different power-law SGWBs, corresponding to
two different glitch regimes. We obtain $\Omega_{\mathrm{gw}}(f)\leq 7.5 \times
10^{-10}$ at 25 Hz for a spectral index 5/2, and $\Omega_{\mathrm{gw}}(f)\leq
5.7 \times 10^{-17}$ at 25 Hz for a spectral index 17/2. We then use these
results to set constraints on the average glitch duration and the average
radial motion of the vortices during the glitches for the population of the
glitching Galactic pulsars, as a function of the Galactic glitch rate.
|
[
{
"created": "Wed, 30 Nov 2022 09:59:58 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Apr 2023 11:07:47 GMT",
"version": "v2"
}
] |
2023-05-17
|
[
[
"De Lillo",
"Federico",
""
],
[
"Suresh",
"Jishnu",
""
],
[
"Depasse",
"Antoine",
""
],
[
"Sieniawska",
"Magdalena",
""
],
[
"Miller",
"Andrew L.",
""
],
[
"Bruno",
"Giacomo",
""
]
] |
A stochastic gravitational-wave background (SGWB) is expected to be produced by the superposition of individually undetectable, unresolved gravitational-wave (GW) signals from cosmological and astrophysical sources. Such a signal can be searched with dedicated techniques using the data acquired by a network of ground-based GW detectors. In this work, we consider the astrophysical SGWB resulting from pulsar glitches, which are sudden increases in the rotational pulsar frequency, within our Galaxy. More specifically, we assume glitches to be associated with quantized, superfluid, vortex-avalanches in the pulsars, and we model the SGWB from the superposition of GW bursts emitted during the glitching phase. We perform a cross-correlation search for this SGWB-like signal employing the data from the first three observation runs of Advanced LIGO and Virgo. Not having found any evidence for a SGWB signal, we set upper limits on the dimensionless energy density parameter $\Omega_{\mathrm{gw}}(f)$ for two different power-law SGWBs, corresponding to two different glitch regimes. We obtain $\Omega_{\mathrm{gw}}(f)\leq 7.5 \times 10^{-10}$ at 25 Hz for a spectral index 5/2, and $\Omega_{\mathrm{gw}}(f)\leq 5.7 \times 10^{-17}$ at 25 Hz for a spectral index 17/2. We then use these results to set constraints on the average glitch duration and the average radial motion of the vortices during the glitches for the population of the glitching Galactic pulsars, as a function of the Galactic glitch rate.
|
1809.04715
|
Carmen Li
|
Jerzy Lewandowski, Carmen Li
|
Spacetime near Kerr isolated horizon
|
19 pages
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
The theory of isolated horizon provides a quasi-local framework to study the
spacetime geometry in the neighbourhood of the horizon of a black hole in
equilibrium without any reference to structures far away from the horizon.
While the geometric properties of the Kerr-(A)dS and more general algebraically
special solutions have drawn substantial interest recently in the isolated
horizon formalism, their horizon metrics have never been written down
explicitly in the adapted Bondi-like coordinate system. Following the approach
by Krishnan and assuming that the horizon symmetry extends to certain order in
the bulk, we present in this note a general method to compute the metric
functions order by order radially in Bondi-like coordinates in 4-dimensions
from a small set of intrinsic data -- the connection and the Newman-Penrose
spin coefficient $\pi$ specified on the horizon cross-section. Applying this
general method, we then present the horizon metric of non-extremal Kerr-dS in
Bondi-like coordinates. For the pure Kerr case without a cosmological constant,
we also show explicitly the metric functions to the first order.
|
[
{
"created": "Thu, 13 Sep 2018 00:14:32 GMT",
"version": "v1"
}
] |
2018-09-14
|
[
[
"Lewandowski",
"Jerzy",
""
],
[
"Li",
"Carmen",
""
]
] |
The theory of isolated horizon provides a quasi-local framework to study the spacetime geometry in the neighbourhood of the horizon of a black hole in equilibrium without any reference to structures far away from the horizon. While the geometric properties of the Kerr-(A)dS and more general algebraically special solutions have drawn substantial interest recently in the isolated horizon formalism, their horizon metrics have never been written down explicitly in the adapted Bondi-like coordinate system. Following the approach by Krishnan and assuming that the horizon symmetry extends to certain order in the bulk, we present in this note a general method to compute the metric functions order by order radially in Bondi-like coordinates in 4-dimensions from a small set of intrinsic data -- the connection and the Newman-Penrose spin coefficient $\pi$ specified on the horizon cross-section. Applying this general method, we then present the horizon metric of non-extremal Kerr-dS in Bondi-like coordinates. For the pure Kerr case without a cosmological constant, we also show explicitly the metric functions to the first order.
|
2009.04829
|
Francisco Lobo
|
Roman Korolev, Francisco S. N. Lobo, Sergey V. Sushkov
|
Kinetic gravity braiding wormhole geometries
|
10 pages, 4 figures. V2: 11 pages, section on tidal forces added.
Matches published version
|
Phys. Rev. D 102, 104016 (2020)
|
10.1103/PhysRevD.102.104016
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
An interesting class of scalar-tensor models, denoted by kinetic gravity
braiding (KGB), has recently been proposed. These models contain interactions
of the second derivatives of the scalar field that do not lead to additional
degrees of freedom and exhibit peculiar features, such as an essential mixing
of the scalar $\phi$ and tensor kinetic $X$ terms. In this work, we consider
the possibility that wormhole geometries are sustained by the KGB theory. More
specifically, we present the full gravitational field equations in a static and
spherically symmetric traversable wormhole background, and outline the general
constraints at the wormhole throat, imposed by the flaring-out conditions.
Furthermore, we present a plethora of analytical and numerical wormhole
solutions by considering particular choices of the KGB factors. The analysis
explicitly demonstrates that the KGB theory exhibits a rich structure of
wormhole geometries, ranging from asymptotically flat solutions to
asymptotically anti-de Sitter spacetimes.
|
[
{
"created": "Thu, 10 Sep 2020 13:04:40 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Nov 2020 21:01:41 GMT",
"version": "v2"
}
] |
2020-11-11
|
[
[
"Korolev",
"Roman",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Sushkov",
"Sergey V.",
""
]
] |
An interesting class of scalar-tensor models, denoted by kinetic gravity braiding (KGB), has recently been proposed. These models contain interactions of the second derivatives of the scalar field that do not lead to additional degrees of freedom and exhibit peculiar features, such as an essential mixing of the scalar $\phi$ and tensor kinetic $X$ terms. In this work, we consider the possibility that wormhole geometries are sustained by the KGB theory. More specifically, we present the full gravitational field equations in a static and spherically symmetric traversable wormhole background, and outline the general constraints at the wormhole throat, imposed by the flaring-out conditions. Furthermore, we present a plethora of analytical and numerical wormhole solutions by considering particular choices of the KGB factors. The analysis explicitly demonstrates that the KGB theory exhibits a rich structure of wormhole geometries, ranging from asymptotically flat solutions to asymptotically anti-de Sitter spacetimes.
|
2106.05104
|
Shubhen Biswas
|
Shubhen Biswas
|
Modified gravity over the linearized metric perturbation for two body
dynamics
| null | null | null | null |
gr-qc astro-ph.GA
|
http://creativecommons.org/licenses/by/4.0/
|
In this paper Modified gravity is studied over the linearized metric
perturbation in post-Minkowskian theory. This is a different aspect for two
body dynamics without taking usual self force originated from the radiative
backscattering of gravitational waves. The new multiplicative approach to
determine the background metric of curved space-time for two different massive
sources is computed in post-Newtonian theory. The theoretical result is checked
for galactic flat rotation curve and is very good agreement with 249 kilometer
per second solar rotational speed.
|
[
{
"created": "Wed, 9 Jun 2021 14:29:11 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jul 2021 04:32:40 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Mar 2023 09:06:04 GMT",
"version": "v3"
}
] |
2023-03-22
|
[
[
"Biswas",
"Shubhen",
""
]
] |
In this paper Modified gravity is studied over the linearized metric perturbation in post-Minkowskian theory. This is a different aspect for two body dynamics without taking usual self force originated from the radiative backscattering of gravitational waves. The new multiplicative approach to determine the background metric of curved space-time for two different massive sources is computed in post-Newtonian theory. The theoretical result is checked for galactic flat rotation curve and is very good agreement with 249 kilometer per second solar rotational speed.
|
1109.6722
|
Tomohiro Harada
|
Tomohiro Harada and Masashi Kimura
|
Collision of an object in the transition from adiabatic inspiral to
plunge around a Kerr black hole
|
18 pages, no figure, accepted for publication in Physical Review D,
typos corrected
|
Phys.Rev.D84:124032,2011
|
10.1103/PhysRevD.84.124032
|
RUP-11-2, YITP-11-75
|
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
An inspiralling object of mass $\mu$ around a Kerr black hole of mass $M (\gg
\mu)$ experiences a continuous transition near the innermost stable circular
orbit from adiabatic inspiral to plunge into the horizon as gravitational
radiation extracts its energy and angular momentum. We investigate the
collision of such an object with a generic counterpart around a Kerr black
hole. We find that the angular momentum of the object is fine-tuned through
gravitational radiation and that the high-velocity collision of the object with
a generic counterpart naturally occurs around a nearly maximally rotating black
hole. We also find that the centre-of-mass energy can be far beyond the Planck
energy for dark matter particles colliding around a stellar mass black hole and
as high as $10^{58}$ erg for stellar mass compact objects colliding around a
supermassive black hole, where the present transition formalism is well
justified. Therefore, rapidly rotating black holes can accelerate objects
inspiralling around them to energy high enough to be of great physical
interest.
|
[
{
"created": "Fri, 30 Sep 2011 06:04:50 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Nov 2011 01:16:58 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Dec 2011 21:22:46 GMT",
"version": "v3"
}
] |
2015-05-30
|
[
[
"Harada",
"Tomohiro",
""
],
[
"Kimura",
"Masashi",
""
]
] |
An inspiralling object of mass $\mu$ around a Kerr black hole of mass $M (\gg \mu)$ experiences a continuous transition near the innermost stable circular orbit from adiabatic inspiral to plunge into the horizon as gravitational radiation extracts its energy and angular momentum. We investigate the collision of such an object with a generic counterpart around a Kerr black hole. We find that the angular momentum of the object is fine-tuned through gravitational radiation and that the high-velocity collision of the object with a generic counterpart naturally occurs around a nearly maximally rotating black hole. We also find that the centre-of-mass energy can be far beyond the Planck energy for dark matter particles colliding around a stellar mass black hole and as high as $10^{58}$ erg for stellar mass compact objects colliding around a supermassive black hole, where the present transition formalism is well justified. Therefore, rapidly rotating black holes can accelerate objects inspiralling around them to energy high enough to be of great physical interest.
|
2012.14049
|
Alan Coley
|
A. A. Coley
|
Persistence in black hole lattice cosmological models
| null |
Class. Quant. Grav. 37, 245002 (2020)
|
10.1088/1361-6382/abbf31
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Dynamical solutions for an evolving multiple network of black holes near a
cosmological bounce dominated by a scalar field are investigated. In
particular, we consider the class of black hole lattice models in a
hyperspherical cosmology, and we focus on the special case of eight
regularly-spaced black holes with equal masses when the model parameter $\kappa
> 1$. We first derive exact time evolving solutions of instantaneously-static
models, by utilizing perturbative solutions of the constraint equations that
can then be used to develop exact 4D dynamical solutions of the Einstein field
equations. We use the notion of a geometric horizon, which can be characterized
by curvature invariants, to determine the black hole horizon. We explicitly
compute the invariants for the exact dynamical models obtained. As an
application, we discuss whether black holes can persist in such a universe that
collapses and then subsequently bounces into a new expansionary phase. We find
evidence that in the physical models under investigation (and particularly for
$\kappa > 1$) the individual black holes do not merge before nor at the bounce,
so that consequently black holes can indeed persist through the bounce.
|
[
{
"created": "Mon, 28 Dec 2020 01:11:36 GMT",
"version": "v1"
}
] |
2021-01-06
|
[
[
"Coley",
"A. A.",
""
]
] |
Dynamical solutions for an evolving multiple network of black holes near a cosmological bounce dominated by a scalar field are investigated. In particular, we consider the class of black hole lattice models in a hyperspherical cosmology, and we focus on the special case of eight regularly-spaced black holes with equal masses when the model parameter $\kappa > 1$. We first derive exact time evolving solutions of instantaneously-static models, by utilizing perturbative solutions of the constraint equations that can then be used to develop exact 4D dynamical solutions of the Einstein field equations. We use the notion of a geometric horizon, which can be characterized by curvature invariants, to determine the black hole horizon. We explicitly compute the invariants for the exact dynamical models obtained. As an application, we discuss whether black holes can persist in such a universe that collapses and then subsequently bounces into a new expansionary phase. We find evidence that in the physical models under investigation (and particularly for $\kappa > 1$) the individual black holes do not merge before nor at the bounce, so that consequently black holes can indeed persist through the bounce.
|
gr-qc/9403047
| null |
L.Diosi, N.Gisin, J.J.Halliwell and I.G.Percival
|
Decoherent Histories and Quantum State Diffusion
|
11 pages (plain Tex), Imperial College preprint 93-94/25
|
Phys.Rev.Lett. 74 (1995) 203-207
|
10.1103/PhysRevLett.74.203
| null |
gr-qc cond-mat hep-th
| null |
We demonstrate a close connection between the decoherent histories (DH)
approach to quantum mechanics and the quantum state diffusion (QSD) picture,
for open quantum systems described by a master equation of Lindblad form. The
(physically unique) set of variables that localize in the QSD picture also
define an approximately decoherent set of histories in the DH approach. The
degree of localization is related to the degree of decoherence, and the
probabilities for histories prescribed by each approach are essentially the
same.
|
[
{
"created": "Sat, 26 Mar 1994 15:20:28 GMT",
"version": "v1"
}
] |
2009-10-22
|
[
[
"Diosi",
"L.",
""
],
[
"Gisin",
"N.",
""
],
[
"Halliwell",
"J. J.",
""
],
[
"Percival",
"I. G.",
""
]
] |
We demonstrate a close connection between the decoherent histories (DH) approach to quantum mechanics and the quantum state diffusion (QSD) picture, for open quantum systems described by a master equation of Lindblad form. The (physically unique) set of variables that localize in the QSD picture also define an approximately decoherent set of histories in the DH approach. The degree of localization is related to the degree of decoherence, and the probabilities for histories prescribed by each approach are essentially the same.
|
1010.0549
|
Nijo Varghese Mr.
|
Nijo Varghese and V C Kuriakose
|
Evolution of electromagnetic and Dirac perturbations around a black hole
in Horava gravity
|
The article was fully rewritten, references added, to appear in MPLA
|
Mod.Phys.Lett.A26:1645-1656,2011
|
10.1142/S0217732311035936
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The evolution of electromagnetic and Dirac perturbations in the spacetime
geometry of Kehagias-Sfetsos(KS) black hole in the deformed Horava-Lifshitz(HL)
gravity is investigated and the associated quasinormal modes are evaluated
using time domain integration and WKB methods. We find a considerable deviation
in the nature of field evolution in HL theory from that in the Schwarzschild
spacetime and QNMs region extends over a longer time in HL theory before the
power-law tail decay begins. The dependence of the field evolution on the HL
parameter $\alpha$ are studied. In the time domain picture we find that the
length of QNM region increases with $\alpha$. But the late time decay of field
follows the same power-law tail behavior as in the case of Schwarzschild black
hole.
|
[
{
"created": "Mon, 4 Oct 2010 11:38:38 GMT",
"version": "v1"
},
{
"created": "Mon, 16 May 2011 09:14:56 GMT",
"version": "v2"
}
] |
2015-03-17
|
[
[
"Varghese",
"Nijo",
""
],
[
"Kuriakose",
"V C",
""
]
] |
The evolution of electromagnetic and Dirac perturbations in the spacetime geometry of Kehagias-Sfetsos(KS) black hole in the deformed Horava-Lifshitz(HL) gravity is investigated and the associated quasinormal modes are evaluated using time domain integration and WKB methods. We find a considerable deviation in the nature of field evolution in HL theory from that in the Schwarzschild spacetime and QNMs region extends over a longer time in HL theory before the power-law tail decay begins. The dependence of the field evolution on the HL parameter $\alpha$ are studied. In the time domain picture we find that the length of QNM region increases with $\alpha$. But the late time decay of field follows the same power-law tail behavior as in the case of Schwarzschild black hole.
|
1006.2451
|
Etera R. Livine
|
Enrique F. Borja, Jacobo Diaz-Polo, I\~naki Garay, Etera R. Livine
|
Dynamics for a 2-vertex Quantum Gravity Model
|
28 pages, v2: typos corrected
|
Class.Quant.Grav.27:235010,2010
|
10.1088/0264-9381/27/23/235010
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We use the recently introduced U(N) framework for loop quantum gravity to
study the dynamics of spin network states on the simplest class of graphs: two
vertices linked with an arbitrary number N of edges. Such graphs represent two
regions, in and out, separated by a boundary surface. We study the algebraic
structure of the Hilbert space of spin networks from the U(N) perspective. In
particular, we describe the algebra of operators acting on that space and
discuss their relation to the standard holonomy operator of loop quantum
gravity. Furthermore, we show that it is possible to make the restriction to
the isotropic/homogeneous sector of the model by imposing the invariance under
a global U(N) symmetry. We then propose a U(N) invariant Hamiltonian operator
and study the induced dynamics. Finally, we explore the analogies between this
model and loop quantum cosmology and sketch some possible generalizations of
it.
|
[
{
"created": "Sat, 12 Jun 2010 10:00:24 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jun 2010 14:26:33 GMT",
"version": "v2"
}
] |
2011-03-28
|
[
[
"Borja",
"Enrique F.",
""
],
[
"Diaz-Polo",
"Jacobo",
""
],
[
"Garay",
"Iñaki",
""
],
[
"Livine",
"Etera R.",
""
]
] |
We use the recently introduced U(N) framework for loop quantum gravity to study the dynamics of spin network states on the simplest class of graphs: two vertices linked with an arbitrary number N of edges. Such graphs represent two regions, in and out, separated by a boundary surface. We study the algebraic structure of the Hilbert space of spin networks from the U(N) perspective. In particular, we describe the algebra of operators acting on that space and discuss their relation to the standard holonomy operator of loop quantum gravity. Furthermore, we show that it is possible to make the restriction to the isotropic/homogeneous sector of the model by imposing the invariance under a global U(N) symmetry. We then propose a U(N) invariant Hamiltonian operator and study the induced dynamics. Finally, we explore the analogies between this model and loop quantum cosmology and sketch some possible generalizations of it.
|
1701.03446
|
George E. A. Matsas Professor
|
Gabriel Cozzella, Andre G. S. Landulfo, George E. A. Matsas, and
Daniel A. T. Vanzella
|
Proposal for observing the Unruh effect with classical electrodynamics
|
Same as published version except for minor stylistic differences. 7
pages and 2 figures, including Supplemental Material. Title distinct from the
original one to comply with editorial request. Overall, original and
published versions are the same
|
Phys. Rev. Lett. 118, 161102 (2017)
|
10.1103/PhysRevLett.118.161102
| null |
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Unruh effect -- according to which linearly accelerated observers with
proper acceleration a= constant in the (no-particle) vacuum state of inertial
observers experience a thermal bath of particles with temperature $T_U = a
\hbar / (2 \pi k_B c)$ -- has just completed its 40$^{th}$ anniversary. A
'direct' experimental confirmation of the Unruh effect has been seen with
concern because the linear acceleration needed to reach a temperature $1 K$ is
of order $10^{20} m/s^2$. Although the Unruh effect can be rigorously
considered as well tested as free quantum field theory itself, it would be
satisfying to observe some lab phenomenon which could evidence its existence.
Here, we propose a simple experiment reachable under present technology whose
result may be directly interpreted in terms of the Unruh thermal bath. Then,
instead of waiting for experimentalists to perform the experiment, we use
standard classical electrodynamics to anticipate its output and show that it
reveals the presence of a thermal bath with temperature $T_U$ in the
accelerated frame. Unless one is willing to question the validity of classical
electrodynamics, this must be seen as a virtual observation of the Unruh
effect. Regardless of doubts still raised by some voices, the Unruh effect
lives among us.
|
[
{
"created": "Thu, 12 Jan 2017 18:30:31 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Apr 2017 19:32:05 GMT",
"version": "v2"
}
] |
2017-04-26
|
[
[
"Cozzella",
"Gabriel",
""
],
[
"Landulfo",
"Andre G. S.",
""
],
[
"Matsas",
"George E. A.",
""
],
[
"Vanzella",
"Daniel A. T.",
""
]
] |
The Unruh effect -- according to which linearly accelerated observers with proper acceleration a= constant in the (no-particle) vacuum state of inertial observers experience a thermal bath of particles with temperature $T_U = a \hbar / (2 \pi k_B c)$ -- has just completed its 40$^{th}$ anniversary. A 'direct' experimental confirmation of the Unruh effect has been seen with concern because the linear acceleration needed to reach a temperature $1 K$ is of order $10^{20} m/s^2$. Although the Unruh effect can be rigorously considered as well tested as free quantum field theory itself, it would be satisfying to observe some lab phenomenon which could evidence its existence. Here, we propose a simple experiment reachable under present technology whose result may be directly interpreted in terms of the Unruh thermal bath. Then, instead of waiting for experimentalists to perform the experiment, we use standard classical electrodynamics to anticipate its output and show that it reveals the presence of a thermal bath with temperature $T_U$ in the accelerated frame. Unless one is willing to question the validity of classical electrodynamics, this must be seen as a virtual observation of the Unruh effect. Regardless of doubts still raised by some voices, the Unruh effect lives among us.
|
1611.00076
|
Adam Rogers
|
Adam Rogers
|
Gravitational lensing by compact objects within plasma
|
8 pages, 2 figures. Summary of an invited parallel session talk given
in the GL3 session at the 14th Marcel Grossmann meeting, University of Rome
"La Sapienza", Rome, July 12-18, 2015. For more details, see A. Rogers, 2015,
MNRAS, 451, 1, 17-25
| null | null | null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Frequency-dependent gravitational lens effects are found for trajectories of
electromagnetic rays passing through a distribution of plasma near a massive
object. Ray propagation through plasma adds extra terms to the equations of
motion that depend on the plasma refractive index. For low-frequency rays these
refractive effects can dominate, turning the gravitational lens into a mirror.
While light rays behave like particles with an effective mass given by the
plasma frequency in a medium with constant density, an inhomogeneous plasma
introduces more complicated behavior even for the spherically symmetric case.
As a physical example, the pulse profile of a compact object sheathed in a
dense plasma is examined, which introduces dramatic frequency-dependent shifts
from the behavior in vacuum.
|
[
{
"created": "Mon, 31 Oct 2016 23:03:12 GMT",
"version": "v1"
}
] |
2016-11-02
|
[
[
"Rogers",
"Adam",
""
]
] |
Frequency-dependent gravitational lens effects are found for trajectories of electromagnetic rays passing through a distribution of plasma near a massive object. Ray propagation through plasma adds extra terms to the equations of motion that depend on the plasma refractive index. For low-frequency rays these refractive effects can dominate, turning the gravitational lens into a mirror. While light rays behave like particles with an effective mass given by the plasma frequency in a medium with constant density, an inhomogeneous plasma introduces more complicated behavior even for the spherically symmetric case. As a physical example, the pulse profile of a compact object sheathed in a dense plasma is examined, which introduces dramatic frequency-dependent shifts from the behavior in vacuum.
|
gr-qc/0511124
|
Matej Pavsic
|
Matej Pavsic
|
Spin Gauge Theory of Gravity in Clifford Space
|
9 pages, talk presented at the QG05 conference, 12-16 September 2005,
Cala Gonone, Italy
|
J.Phys.Conf.Ser.33:422-427,2006
|
10.1088/1742-6596/33/1/053
| null |
gr-qc
| null |
A theory in which 16-dimensional curved Clifford space (C-space) provides a
realization of Kaluza-Klein theory is investigated. No extra dimensions of
spacetime are needed: "extra dimensions" are in C-space. We explore the spin
gauge theory in C-space and show that the generalized spin connection contains
the usual 4-dimensional gravity and Yang-Mills fields of the U(1)xSU(2)xSU(3)
gauge group. The representation space for the latter group is provided by
16-component generalized spinors composed of four usual 4-component spinors,
defined geometrically as the members of four independent minimal left ideals of
Clifford algebra.
|
[
{
"created": "Wed, 23 Nov 2005 11:46:57 GMT",
"version": "v1"
}
] |
2011-08-17
|
[
[
"Pavsic",
"Matej",
""
]
] |
A theory in which 16-dimensional curved Clifford space (C-space) provides a realization of Kaluza-Klein theory is investigated. No extra dimensions of spacetime are needed: "extra dimensions" are in C-space. We explore the spin gauge theory in C-space and show that the generalized spin connection contains the usual 4-dimensional gravity and Yang-Mills fields of the U(1)xSU(2)xSU(3) gauge group. The representation space for the latter group is provided by 16-component generalized spinors composed of four usual 4-component spinors, defined geometrically as the members of four independent minimal left ideals of Clifford algebra.
|
1509.01835
|
Kaushik Bhattacharya
|
Kaushik Bhattacharya, Saikat Chakrabarty
|
Intricacies of Cosmological bounce in polynomial metric $f(R)$ gravity
for flat FLRW spacetime
|
28 pages, latex file, 6 figures. The new file has minor changes. The
present manuscript is accepted for publication in JCAP
| null |
10.1088/1475-7516/2016/02/030
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we present the techniques for computing cosmological bounces in
polynomial $f(R)$ theories, whose order is more than two, for spatially flat
FLRW spacetime. In these cases the conformally connected Einstein frame shows
up multiple scalar potentials predicting various possibilities of cosmological
evolution in the Jordan frame where the $f(R)$ theory lives. We present a
reasonable way in which one can associate the various possible potentials in
the Einstein frame, for cubic $f(R)$ gravity, to the cosmological development
in the Jordan frame. The issue concerning the energy conditions in $f(R)$
theories is presented. We also point out the very important relationships
between the conformal transformations connecting the Jordan frame and the
Einstein frame and the various instabilities of $f(R)$ theory. All the
calculations are done for cubic $f(R)$ gravity but we hope the results are
sufficiently general for higher order polynomial gravity.
|
[
{
"created": "Sun, 6 Sep 2015 17:41:27 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jan 2016 10:09:52 GMT",
"version": "v2"
}
] |
2016-02-17
|
[
[
"Bhattacharya",
"Kaushik",
""
],
[
"Chakrabarty",
"Saikat",
""
]
] |
In this paper we present the techniques for computing cosmological bounces in polynomial $f(R)$ theories, whose order is more than two, for spatially flat FLRW spacetime. In these cases the conformally connected Einstein frame shows up multiple scalar potentials predicting various possibilities of cosmological evolution in the Jordan frame where the $f(R)$ theory lives. We present a reasonable way in which one can associate the various possible potentials in the Einstein frame, for cubic $f(R)$ gravity, to the cosmological development in the Jordan frame. The issue concerning the energy conditions in $f(R)$ theories is presented. We also point out the very important relationships between the conformal transformations connecting the Jordan frame and the Einstein frame and the various instabilities of $f(R)$ theory. All the calculations are done for cubic $f(R)$ gravity but we hope the results are sufficiently general for higher order polynomial gravity.
|
gr-qc/0701160
|
Nurettin Pirin \c{c} \c{c}io \u{g}lu
|
Nurettin Pirin\c{c}\c{c}io\~glu, and Ilker Sert
|
Differences between scalar field and scalar density solutions
|
8 pages, no figures
| null |
10.1139/p11-146
| null |
gr-qc
| null |
We explore differences between scalar field, and scalar density solutions by
using Robertson-Walker (RW) metric, and also a non-relativistic Hamiltonian is
derived for a scalar density field in the post-Newtonian approximation. The
results are compared with those of scalar field. The expanding universe in RW
metric, and post-Newtonian solution of Klein-Gordon equation are separately
discussed.
|
[
{
"created": "Mon, 29 Jan 2007 14:53:33 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Pirinççioglu",
"Nurettin",
""
],
[
"Sert",
"Ilker",
""
]
] |
We explore differences between scalar field, and scalar density solutions by using Robertson-Walker (RW) metric, and also a non-relativistic Hamiltonian is derived for a scalar density field in the post-Newtonian approximation. The results are compared with those of scalar field. The expanding universe in RW metric, and post-Newtonian solution of Klein-Gordon equation are separately discussed.
|
gr-qc/9903046
|
Sergey V. Sushkov
|
Sergey V. Sushkov
|
Completeness principle and quantum field theory on nonglobally
hyperbolic spacetimes
|
revtex, Submitted to Phys. Rev. D
|
Grav.Cosmol. 9 (2003) 249-255
| null | null |
gr-qc
| null |
We analyse in details the problems which one faces trying to quantize a
scalar field on the spacelike cylinder being the simple example of a spacetime
with closed timelike curves. Our analysis brings to light the fact that the
usual set of positive and negative frequency solutions of the field equation
turns out to be incomplete. The consequence of this fact is that the usual
formulation of quantum field theory breaks down on such a spacetime. We
postulate the completeness principle and build on its basis the modified
quantization procedure. As an example, the Hadamard function and $<\phi^2>$ for
the scalar field on the spacelike cylinder are calculated. It is shown that the
``naive'' method of images gives the same results of calculation.
|
[
{
"created": "Sat, 13 Mar 1999 10:01:28 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Sushkov",
"Sergey V.",
""
]
] |
We analyse in details the problems which one faces trying to quantize a scalar field on the spacelike cylinder being the simple example of a spacetime with closed timelike curves. Our analysis brings to light the fact that the usual set of positive and negative frequency solutions of the field equation turns out to be incomplete. The consequence of this fact is that the usual formulation of quantum field theory breaks down on such a spacetime. We postulate the completeness principle and build on its basis the modified quantization procedure. As an example, the Hadamard function and $<\phi^2>$ for the scalar field on the spacelike cylinder are calculated. It is shown that the ``naive'' method of images gives the same results of calculation.
|
1605.05217
|
Stephen Adler
|
Stephen L. Adler
|
A frame-dependent gravitational effective action mimics a cosmological
constant, but modifies the black hole horizon
|
Latex, 5 pages. First Award Essay in the 2016 Gravity Research
Foundation essay competition. To be published in International Journal of
Modern Physics D
|
Int. J. Mod. Phys. D 25, 1643001 (2016)
|
10.1142/S021827181643001X
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A frame dependent effective action motivated by the postulates of three-space
general coordinate invariance and Weyl scaling invariance exactly mimics a
cosmological constant in Robertson-Walker spacetimes. However, in a static
spherically symmetric Schwarzschild-like geometry it modifies the black hole
horizon structure within microscopic distances of the nominal horizon, in such
a way that $g_{00}$ never vanishes. This could have important implications for
the black hole "information paradox".
|
[
{
"created": "Tue, 17 May 2016 15:49:52 GMT",
"version": "v1"
}
] |
2018-06-05
|
[
[
"Adler",
"Stephen L.",
""
]
] |
A frame dependent effective action motivated by the postulates of three-space general coordinate invariance and Weyl scaling invariance exactly mimics a cosmological constant in Robertson-Walker spacetimes. However, in a static spherically symmetric Schwarzschild-like geometry it modifies the black hole horizon structure within microscopic distances of the nominal horizon, in such a way that $g_{00}$ never vanishes. This could have important implications for the black hole "information paradox".
|
2402.09044
|
Sudipta Sarkar
|
Soham Acharya, Sudipta Sarkar
|
Non-existence of short hairs for static black holes
|
7 pages
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The black hole no-short hair theorem establishes a universal lower bound on
the extension of hairs outside any 4-dimensional spherically symmetric black
hole solutions. We generalise this theorem beyond spherical symmetry,
specifically for static, axisymmetric hairy black hole solutions and prove that
the ``hairosphere'' must extend beyond the radial extent of the innermost light
ring.
|
[
{
"created": "Wed, 14 Feb 2024 09:39:04 GMT",
"version": "v1"
}
] |
2024-02-15
|
[
[
"Acharya",
"Soham",
""
],
[
"Sarkar",
"Sudipta",
""
]
] |
The black hole no-short hair theorem establishes a universal lower bound on the extension of hairs outside any 4-dimensional spherically symmetric black hole solutions. We generalise this theorem beyond spherical symmetry, specifically for static, axisymmetric hairy black hole solutions and prove that the ``hairosphere'' must extend beyond the radial extent of the innermost light ring.
|
2004.06434
|
Jose Luis Jaramillo
|
Jos\'e Luis Jaramillo, Rodrigo Panosso Macedo and Lamis Al Sheikh
|
Pseudospectrum and black hole quasi-normal mode (in)stability
|
40 pages, 17 figures + 4 Appendices
|
Phys. Rev. X 11, 031003 (2021)
|
10.1103/PhysRevX.11.031003
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the stability of quasinormal modes (QNM) in asymptotically flat
black hole spacetimes by means of a pseudospectrum analysis. The construction
of the Schwarzschild QNM pseudospectrum reveals the following: (i) the
stability of the slowest-decaying QNM under perturbations respecting the
asymptotic structure, reassessing the instability of the fundamental QNM
discussed by Nollert [H. P. Nollert, About the Significance of Quasinormal
Modes of Black Holes, Phys. Rev. D 53, 4397 (1996)] as an "infrared" effect;
(ii) the instability of all overtones under small-scale ("ultraviolet")
perturbations of sufficiently high frequency, which migrate towards universal
QNM branches along pseudospectra boundaries, shedding light on Nollert's
pioneer work and Nollert and Price's analysis [H. P. Nollert and R. H. Price,
Quantifying Excitations of Quasinormal Mode Systems, J. Math. Phys. (N.Y.) 40,
980 (1999)]. Methodologically, a compactified hyperboloidal approach to QNMs is
adopted to cast QNMs in terms of the spectral problem of a non-self-adjoint
operator. In this setting, spectral (in)stability is naturally addressed
through the pseudospectrum notion that we construct numerically via Chebyshev
spectral methods and foster in gravitational physics. After illustrating the
approach with the P\"oschl-Teller potential, we address the Schwarzschild black
hole case, where QNM (in)stabilities are physically relevant in the context of
black hole spectroscopy in gravitational-wave physics and, conceivably, as
probes into fundamental high-frequency spacetime fluctuations at the Planck
scale.
|
[
{
"created": "Tue, 14 Apr 2020 11:48:35 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2020 16:45:46 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Jan 2021 19:50:06 GMT",
"version": "v3"
},
{
"created": "Tue, 14 Sep 2021 16:37:22 GMT",
"version": "v4"
}
] |
2021-09-15
|
[
[
"Jaramillo",
"José Luis",
""
],
[
"Macedo",
"Rodrigo Panosso",
""
],
[
"Sheikh",
"Lamis Al",
""
]
] |
We study the stability of quasinormal modes (QNM) in asymptotically flat black hole spacetimes by means of a pseudospectrum analysis. The construction of the Schwarzschild QNM pseudospectrum reveals the following: (i) the stability of the slowest-decaying QNM under perturbations respecting the asymptotic structure, reassessing the instability of the fundamental QNM discussed by Nollert [H. P. Nollert, About the Significance of Quasinormal Modes of Black Holes, Phys. Rev. D 53, 4397 (1996)] as an "infrared" effect; (ii) the instability of all overtones under small-scale ("ultraviolet") perturbations of sufficiently high frequency, which migrate towards universal QNM branches along pseudospectra boundaries, shedding light on Nollert's pioneer work and Nollert and Price's analysis [H. P. Nollert and R. H. Price, Quantifying Excitations of Quasinormal Mode Systems, J. Math. Phys. (N.Y.) 40, 980 (1999)]. Methodologically, a compactified hyperboloidal approach to QNMs is adopted to cast QNMs in terms of the spectral problem of a non-self-adjoint operator. In this setting, spectral (in)stability is naturally addressed through the pseudospectrum notion that we construct numerically via Chebyshev spectral methods and foster in gravitational physics. After illustrating the approach with the P\"oschl-Teller potential, we address the Schwarzschild black hole case, where QNM (in)stabilities are physically relevant in the context of black hole spectroscopy in gravitational-wave physics and, conceivably, as probes into fundamental high-frequency spacetime fluctuations at the Planck scale.
|
1501.04568
|
Jorge Bellor\'in
|
Jorge Bellorin, Alvaro Restuccia and Adrian Sotomayor
|
Wormholes in Horava gravity with cosmological constant
|
30 pages, 7 figures. Version 3: Changes in presentation with the same
results
|
International Journal of Modern Physics D25 (2016) 1650016
|
10.1142/S0218271816500164
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
By combining analytical and numerical methods we find that the solutions of
the complete Horava theory with negative cosmological constant that satisfy the
conditions of staticity, spherical symmetry and vanishing of the shift function
are two kinds of geometry: (i) a wormhole-like solution with two sides joined
by a throat and (ii) a single side with a naked singularity at the origin. We
study the second-order effective action. We consider the case when the coupling
constant of the (partial ln N)^2 term, which is the unique deviation from
general relativity in the effective action, is small. At one side the wormhole
acquires a kind of deformed AdS asymptotia and at the other side there is an
asymptotic essential singularity. The deformation of AdS essentially means that
the lapse function N diverges asymptotically a bit faster than AdS. This can
also be interpreted as an anisotropic Lifshitz scaling that the solutions
acquire asymptotically.
|
[
{
"created": "Mon, 19 Jan 2015 17:34:01 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jun 2015 17:24:32 GMT",
"version": "v2"
},
{
"created": "Tue, 3 Nov 2015 21:50:02 GMT",
"version": "v3"
}
] |
2015-11-05
|
[
[
"Bellorin",
"Jorge",
""
],
[
"Restuccia",
"Alvaro",
""
],
[
"Sotomayor",
"Adrian",
""
]
] |
By combining analytical and numerical methods we find that the solutions of the complete Horava theory with negative cosmological constant that satisfy the conditions of staticity, spherical symmetry and vanishing of the shift function are two kinds of geometry: (i) a wormhole-like solution with two sides joined by a throat and (ii) a single side with a naked singularity at the origin. We study the second-order effective action. We consider the case when the coupling constant of the (partial ln N)^2 term, which is the unique deviation from general relativity in the effective action, is small. At one side the wormhole acquires a kind of deformed AdS asymptotia and at the other side there is an asymptotic essential singularity. The deformation of AdS essentially means that the lapse function N diverges asymptotically a bit faster than AdS. This can also be interpreted as an anisotropic Lifshitz scaling that the solutions acquire asymptotically.
|
1408.6929
|
Nobuyuki Sakai
|
Nobuyuki Sakai, Hiromi Saida, Takashi Tamaki
|
Gravastar Shadows
|
9 pages, 11 figures
| null |
10.1103/PhysRevD.90.104013
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Direct observation of black holes is one of the grand challenges in
astronomy. If there are super-compact objects which possess unstable circular
orbits of photons, however, it may be difficult to distinguish them from black
holes by observing photons. As a model of super-compact objects, we consider a
gravastar (gravitational-vacuum-star) which was originally proposed by Mazur
and Mottola. For definiteness, we adopt a spherical thin-shell model of a
gravastar developed by Visser and Wiltshire, which connects interior de-Sitter
geometry and exterior Schwarzschild geometry. We find that unstable circular
orbits of photons can appear around the gravastar. Then, we investigate the
optical images of the gravastar possessing unstable circular orbits, with
assuming the optically transparent surface of it and two types of optical
sources behind the gravastar: (i) an infinite optical plane and (ii) a
companion star. The main feature of the image of (i) is that a bright disk and
a dark thick ring surrounding the disk appear in the center of the region which
would be completely dark if the compact object was not the gravastar but
Schwarzschild black hole. Also in the case (ii), a small disk and arcs around
the disk appear in the region which would be completely dark for the lensing
image by Schwarzschild black hole. Because characteristic images appear inside
the gravastar in both cases, we could tell the difference between a black hole
and a gravastar with high-resolution VLBI observations near future.
|
[
{
"created": "Fri, 29 Aug 2014 06:18:30 GMT",
"version": "v1"
}
] |
2015-06-22
|
[
[
"Sakai",
"Nobuyuki",
""
],
[
"Saida",
"Hiromi",
""
],
[
"Tamaki",
"Takashi",
""
]
] |
Direct observation of black holes is one of the grand challenges in astronomy. If there are super-compact objects which possess unstable circular orbits of photons, however, it may be difficult to distinguish them from black holes by observing photons. As a model of super-compact objects, we consider a gravastar (gravitational-vacuum-star) which was originally proposed by Mazur and Mottola. For definiteness, we adopt a spherical thin-shell model of a gravastar developed by Visser and Wiltshire, which connects interior de-Sitter geometry and exterior Schwarzschild geometry. We find that unstable circular orbits of photons can appear around the gravastar. Then, we investigate the optical images of the gravastar possessing unstable circular orbits, with assuming the optically transparent surface of it and two types of optical sources behind the gravastar: (i) an infinite optical plane and (ii) a companion star. The main feature of the image of (i) is that a bright disk and a dark thick ring surrounding the disk appear in the center of the region which would be completely dark if the compact object was not the gravastar but Schwarzschild black hole. Also in the case (ii), a small disk and arcs around the disk appear in the region which would be completely dark for the lensing image by Schwarzschild black hole. Because characteristic images appear inside the gravastar in both cases, we could tell the difference between a black hole and a gravastar with high-resolution VLBI observations near future.
|
2006.01562
|
John Barrow
|
John D. Barrow
|
A conjecture about the general cosmological solution of Einstein's
equations
|
7 pages, no figures, added analysis
|
Phys. Rev. D 102, 024017 (2020)
|
10.1103/PhysRevD.102.024017
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We introduce consideration of a new factor, synchronisation of spacetime
Mixmaster oscillations, that may play a simplifying role in understanding the
nature of the general inhomogeneous cosmological solution to Einstein's
equations. We conjecture that, on approach to a singularity, the interaction of
spacetime Mixmaster oscillations in different regions of an inhomogeneous
universe can produce a synchronisation of these oscillations through a coupling
to their mean field in the way first demonstrated by the Kuramoto coupled
oscillator model.
|
[
{
"created": "Tue, 2 Jun 2020 12:33:04 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jun 2020 10:50:15 GMT",
"version": "v2"
}
] |
2020-07-15
|
[
[
"Barrow",
"John D.",
""
]
] |
We introduce consideration of a new factor, synchronisation of spacetime Mixmaster oscillations, that may play a simplifying role in understanding the nature of the general inhomogeneous cosmological solution to Einstein's equations. We conjecture that, on approach to a singularity, the interaction of spacetime Mixmaster oscillations in different regions of an inhomogeneous universe can produce a synchronisation of these oscillations through a coupling to their mean field in the way first demonstrated by the Kuramoto coupled oscillator model.
|
1705.07034
|
Carlos O. Lousto
|
James Healy, Carlos O. Lousto, Yosef Zlochower
|
The nonspinning binary black hole merger scenario revisited
|
8 pages, 4 figures
|
Phys. Rev. D 96, 024031 (2017)
|
10.1103/PhysRevD.96.024031
| null |
gr-qc astro-ph.CO astro-ph.GA astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present the results of 14 simulations of nonspinning black hole binaries
with mass ratios $q=m_1/m_2$ in the range $1/100\leq q\leq1$. For each of these
simulations we perform three runs at increasing resolution to assess the finite
difference errors and to extrapolate the results to infinite resolution. For
$q\geq 1/6$, we follow the evolution of the binary typically for the last ten
orbits prior to merger. By fitting the results of these simulations, we
accurately model the peak luminosity, peak waveform frequency and amplitude,
and the recoil of the remnant hole for unequal mass nonspinning binaries. We
verify the accuracy of these new models and compare them to previously existing
empirical formulas. These new fits provide a basis for a hierarchical approach
to produce more accurate remnant formulas in the generic precessing case. They
also provide input to gravitational waveform modeling.
|
[
{
"created": "Fri, 19 May 2017 14:51:53 GMT",
"version": "v1"
}
] |
2017-07-26
|
[
[
"Healy",
"James",
""
],
[
"Lousto",
"Carlos O.",
""
],
[
"Zlochower",
"Yosef",
""
]
] |
We present the results of 14 simulations of nonspinning black hole binaries with mass ratios $q=m_1/m_2$ in the range $1/100\leq q\leq1$. For each of these simulations we perform three runs at increasing resolution to assess the finite difference errors and to extrapolate the results to infinite resolution. For $q\geq 1/6$, we follow the evolution of the binary typically for the last ten orbits prior to merger. By fitting the results of these simulations, we accurately model the peak luminosity, peak waveform frequency and amplitude, and the recoil of the remnant hole for unequal mass nonspinning binaries. We verify the accuracy of these new models and compare them to previously existing empirical formulas. These new fits provide a basis for a hierarchical approach to produce more accurate remnant formulas in the generic precessing case. They also provide input to gravitational waveform modeling.
|
0812.3752
|
Mihaela Chirvasa
|
M. Chirvasa, S. Husa
|
Finite Difference Methods for Second Order in Space, First Order in Time
Hyperbolic Systems and the Linear Shifted Wave Equation as a Model Problem in
Numerical Relativity
|
36 pages, 10 figures
|
J. Comput. Phys. (2010)
|
10.1016/j.jcp.2009.12.016
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Motivated by the problem of solving the Einstein equations, we discuss high
order finite difference discretizations of first order in time, second order in
space hyperbolic systems.Particular attention is paid to the case when first
order derivatives that can be identified with advection terms are approximated
with non-centered finite difference operators.We first derive general
properties of these discrete operators, then we extend a known result on
numerical stability for such systems to general order of accuracy.As an
application we analyze the shifted wave equation, including the behavior of the
numerical phase and group speeds at different orders of approximations. Special
attention is paid to when the use of off-centered schemes improves the accuracy
over the centered schemes.
|
[
{
"created": "Fri, 19 Dec 2008 14:00:49 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Jan 2010 11:11:40 GMT",
"version": "v2"
}
] |
2010-01-18
|
[
[
"Chirvasa",
"M.",
""
],
[
"Husa",
"S.",
""
]
] |
Motivated by the problem of solving the Einstein equations, we discuss high order finite difference discretizations of first order in time, second order in space hyperbolic systems.Particular attention is paid to the case when first order derivatives that can be identified with advection terms are approximated with non-centered finite difference operators.We first derive general properties of these discrete operators, then we extend a known result on numerical stability for such systems to general order of accuracy.As an application we analyze the shifted wave equation, including the behavior of the numerical phase and group speeds at different orders of approximations. Special attention is paid to when the use of off-centered schemes improves the accuracy over the centered schemes.
|
0904.0184
|
Abhay Ashtekar
|
Abhay Ashtekar
|
Some surprising implications of background independence in canonical
quantum gravity
|
To appear in the special issue of General Relativity and Gravitation,
dedicated to the memory of Professor Juergen Ehlers. 16 pages
|
Gen.Rel.Grav.41:1927-1943,2009
|
10.1007/s10714-009-0802-1
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
There is a precise sense in which the requirement of background independence
suffices to uniquely select the kinematics of loop quantum gravity (LQG).
Specifically, the fundamental kinematic algebra of LQG admits a unique
diffeomorphism invariant state. Although this result has been established
rigorously, it comes as a surprise to researchers working with other approaches
to quantum gravity. The goal of this article is to explain the underlying
reasons in a pedagogical fashion using geometrodynamics, keeping the
technicalities at their minimum. This discussion will bring out the
surprisingly powerful role played by diffeomorphism invariance (and covariance)
in non-perturbative, canonical quantum gravity.
|
[
{
"created": "Wed, 1 Apr 2009 15:24:49 GMT",
"version": "v1"
}
] |
2010-03-12
|
[
[
"Ashtekar",
"Abhay",
""
]
] |
There is a precise sense in which the requirement of background independence suffices to uniquely select the kinematics of loop quantum gravity (LQG). Specifically, the fundamental kinematic algebra of LQG admits a unique diffeomorphism invariant state. Although this result has been established rigorously, it comes as a surprise to researchers working with other approaches to quantum gravity. The goal of this article is to explain the underlying reasons in a pedagogical fashion using geometrodynamics, keeping the technicalities at their minimum. This discussion will bring out the surprisingly powerful role played by diffeomorphism invariance (and covariance) in non-perturbative, canonical quantum gravity.
|
1108.3994
|
Jan Weenink
|
Jan Weenink and Tomislav Prokopec
|
On decoherence of cosmological perturbations and stochastic inflation
|
21 pages, 1 figure, prepared for submission to JCAP
| null | null | null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
By making a suitable generalization of the Starobinsky stochastic inflation,
we propose a classical phase space formulation of stochastic inflation which
may be used for a quantitative study of decoherence of cosmological
perturbations during inflation. The precise knowledge of how much cosmological
perturbations have decohered is essential to the understanding of acoustic
oscillations of cosmological microwave background (CMB) photons. In order to
show how the method works, we provide the relevant equations for a
self-interacting inflaton field. For pedagogical reasons and to provide a link
to the field theoretical case, we consider the quantum stochastic harmonic
oscillator.
|
[
{
"created": "Fri, 19 Aug 2011 16:12:26 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jan 2012 14:56:00 GMT",
"version": "v2"
}
] |
2012-01-04
|
[
[
"Weenink",
"Jan",
""
],
[
"Prokopec",
"Tomislav",
""
]
] |
By making a suitable generalization of the Starobinsky stochastic inflation, we propose a classical phase space formulation of stochastic inflation which may be used for a quantitative study of decoherence of cosmological perturbations during inflation. The precise knowledge of how much cosmological perturbations have decohered is essential to the understanding of acoustic oscillations of cosmological microwave background (CMB) photons. In order to show how the method works, we provide the relevant equations for a self-interacting inflaton field. For pedagogical reasons and to provide a link to the field theoretical case, we consider the quantum stochastic harmonic oscillator.
|
2210.06608
|
G. Alencar
|
J. Furtado and G. Alencar
|
BTZ Black-bounce to Traversable Wormhole
|
Accepted for publication in Universe
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we study the charged and uncharged BTZ counterpart of the
Black-Bounce proposed by Simpson and Visser recently. For the uncharged case,
we find that the temperature is not modified by the bounce parameter. We also
find that the wormhole side of the solution must always be supported by exotic
matter over the throat. For the charged case we find that the thermodynamics is
changed and the bounce parameter controls a phase transition, affecting the
sign of the heat capacity and therefore the stability of the system. For the
uncharged case, we find that there are no stable orbits for both massive and
massless incoming particles while stable orbits are present for the charged
case and the bounce parameter affects the points of stability.
|
[
{
"created": "Wed, 12 Oct 2022 22:12:50 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Nov 2022 12:41:46 GMT",
"version": "v2"
}
] |
2022-11-24
|
[
[
"Furtado",
"J.",
""
],
[
"Alencar",
"G.",
""
]
] |
In this paper, we study the charged and uncharged BTZ counterpart of the Black-Bounce proposed by Simpson and Visser recently. For the uncharged case, we find that the temperature is not modified by the bounce parameter. We also find that the wormhole side of the solution must always be supported by exotic matter over the throat. For the charged case we find that the thermodynamics is changed and the bounce parameter controls a phase transition, affecting the sign of the heat capacity and therefore the stability of the system. For the uncharged case, we find that there are no stable orbits for both massive and massless incoming particles while stable orbits are present for the charged case and the bounce parameter affects the points of stability.
|
1410.2631
|
Piotr Bizon
|
Piotr Bizo\'n, Andrzej Rostworowski
|
Comment on "Holographic Thermalization, stability of AdS, and the
Fermi-Pasta-Ulam-Tsingou paradox" by V. Balasubramanian et al
|
1 page
|
Phys. Rev. Lett. 115, 049101 (2015)
|
10.1103/PhysRevLett.115.049101
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We comment upon a numerical computation in a recent paper by Balasubramanian,
Buchel, Green, Lehner, and Liebling.
|
[
{
"created": "Thu, 9 Oct 2014 21:21:23 GMT",
"version": "v1"
}
] |
2016-12-07
|
[
[
"Bizoń",
"Piotr",
""
],
[
"Rostworowski",
"Andrzej",
""
]
] |
We comment upon a numerical computation in a recent paper by Balasubramanian, Buchel, Green, Lehner, and Liebling.
|
gr-qc/9405048
|
Carlos O. Lousto
|
C. O. Lousto
|
The Emergence of an Effective two - dimensional Quantum Description from
the study of Critical Phenomena in Black Holes
|
Plain TeX, 16 pages, preprint UAB-FT-340 (Fifth Price from the
Gravity Research Foundation 1994)
|
Phys.Rev.D51:1733-1740,1995
|
10.1103/PhysRevD.51.1733
| null |
gr-qc astro-ph hep-th
| null |
We study the occurrence of critical phenomena in four - dimensional, rotating
and charged black holes, derive the critical exponents and show that they
fulfill the scaling laws. Correlation functions critical exponents and
Renormalization Group considerations assign an effective (spatial) dimension,
$d=2$, to the system. The two - dimensional Gaussian approximation to critical
systems is shown to reproduce all the black hole's critical exponents. Higher
order corrections (which are always relevant) are discussed. Identifying the
two - dimensional surface with the event horizon and noting that generalization
of scaling leads to conformal invariance and then to string theory, we arrive
to 't Hooft's string interpretation of black holes. From this, a model for
dealing with a coarse grained black hole quantization is proposed. We also give
simple arguments that lead to a rough quantization of the black hole mass in
units of the Planck mass, i. e. $M\simeq{1\over\sqrt{2}}M_{pl} \sqrt{l}$ with a
$l$ positive integer and then, from this result, to the proportionality between
quantum entropy and area.
|
[
{
"created": "Sun, 22 May 1994 19:32:34 GMT",
"version": "v1"
},
{
"created": "Wed, 25 May 1994 12:39:33 GMT",
"version": "v2"
}
] |
2011-07-19
|
[
[
"Lousto",
"C. O.",
""
]
] |
We study the occurrence of critical phenomena in four - dimensional, rotating and charged black holes, derive the critical exponents and show that they fulfill the scaling laws. Correlation functions critical exponents and Renormalization Group considerations assign an effective (spatial) dimension, $d=2$, to the system. The two - dimensional Gaussian approximation to critical systems is shown to reproduce all the black hole's critical exponents. Higher order corrections (which are always relevant) are discussed. Identifying the two - dimensional surface with the event horizon and noting that generalization of scaling leads to conformal invariance and then to string theory, we arrive to 't Hooft's string interpretation of black holes. From this, a model for dealing with a coarse grained black hole quantization is proposed. We also give simple arguments that lead to a rough quantization of the black hole mass in units of the Planck mass, i. e. $M\simeq{1\over\sqrt{2}}M_{pl} \sqrt{l}$ with a $l$ positive integer and then, from this result, to the proportionality between quantum entropy and area.
|
1111.1801
|
Xin-Zhou Li
|
Xi-Chen Ao and Xin-Zhou Li
|
de Sitter Gauge Theory of Gravity: An Alternative Torsion Cosmology
|
11pages, 5 figures
|
JCAP 1110:039,2011
|
10.1088/1475-7516/2011/10/039
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A new cosmological model based on the de Sitter gauge theory (dSGT) is
studied in this paper. By some transformations, we find, in the dust universe,
the cosmological equations of dSGT could form an autonomous system. We conduct
dynamics analysis to this system, and find 9 critical points, among which there
exist one positive attractor and one negative attractor. The positive attractor
shows us that our universe will enter a exponential expansion phase in the end,
which is similar to the conclusion of $\Lambda$CDM. We also carry out some
numerical calculations, which confirms the conclusion of dynamics analysis.
Finally, we fit the model parameter and initial values to the Union 2 SNIa
dataset, present the confidence contour of parameters and obtain the best-fit
values of parameters of dSGT.
|
[
{
"created": "Tue, 8 Nov 2011 04:43:34 GMT",
"version": "v1"
}
] |
2011-11-09
|
[
[
"Ao",
"Xi-Chen",
""
],
[
"Li",
"Xin-Zhou",
""
]
] |
A new cosmological model based on the de Sitter gauge theory (dSGT) is studied in this paper. By some transformations, we find, in the dust universe, the cosmological equations of dSGT could form an autonomous system. We conduct dynamics analysis to this system, and find 9 critical points, among which there exist one positive attractor and one negative attractor. The positive attractor shows us that our universe will enter a exponential expansion phase in the end, which is similar to the conclusion of $\Lambda$CDM. We also carry out some numerical calculations, which confirms the conclusion of dynamics analysis. Finally, we fit the model parameter and initial values to the Union 2 SNIa dataset, present the confidence contour of parameters and obtain the best-fit values of parameters of dSGT.
|
0901.0964
|
Herbert Hamber
|
Herbert W. Hamber
|
Quantum Gravity on the Lattice
|
63 pages, 12 figures
|
Gen.Rel.Grav.41:817-876,2009
|
10.1007/s10714-009-0769-y
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
I review the lattice approach to quantum gravity, and how it relates to the
non-trivial ultraviolet fixed point scenario of the continuum theory. After a
brief introduction covering the general problem of ultraviolet divergences in
gravity and other non-renormalizable theories, I cover the general methods and
goals of the lattice approach. An underlying theme is the attempt at
establishing connections between the continuum renormalization group results,
which are mainly based on diagrammatic perturbation theory, and the recent
lattice results, which apply to the strong gravity regime and are inherently
non-perturbative. A second theme in this review is the ever-present natural
correspondence between infrared methods of strongly coupled non-abelian gauge
theories on the one hand, and the low energy approach to quantum gravity based
on the renormalization group and universality of critical behavior on the
other. Towards the end of the review I discuss possible observational
consequences of path integral quantum gravity, as derived from the non-trivial
ultraviolet fixed point scenario. I argue that the theoretical framework
naturally leads to considering a weakly scale-dependent Newton's costant, with
a scaling violation parameter related to the observed scaled cosmological
constant (and not, as naively expected, to the Planck length).
|
[
{
"created": "Thu, 8 Jan 2009 02:30:06 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jan 2009 20:57:59 GMT",
"version": "v2"
}
] |
2009-04-17
|
[
[
"Hamber",
"Herbert W.",
""
]
] |
I review the lattice approach to quantum gravity, and how it relates to the non-trivial ultraviolet fixed point scenario of the continuum theory. After a brief introduction covering the general problem of ultraviolet divergences in gravity and other non-renormalizable theories, I cover the general methods and goals of the lattice approach. An underlying theme is the attempt at establishing connections between the continuum renormalization group results, which are mainly based on diagrammatic perturbation theory, and the recent lattice results, which apply to the strong gravity regime and are inherently non-perturbative. A second theme in this review is the ever-present natural correspondence between infrared methods of strongly coupled non-abelian gauge theories on the one hand, and the low energy approach to quantum gravity based on the renormalization group and universality of critical behavior on the other. Towards the end of the review I discuss possible observational consequences of path integral quantum gravity, as derived from the non-trivial ultraviolet fixed point scenario. I argue that the theoretical framework naturally leads to considering a weakly scale-dependent Newton's costant, with a scaling violation parameter related to the observed scaled cosmological constant (and not, as naively expected, to the Planck length).
|
2403.12731
|
Shunsei Yamamura
|
Shunsei Yamamura, Hirotaka Yuzurihara, Takahiro Yamamoto, Takashi
Uchiyama
|
Extension of the characterization method for non-Gaussianity in
gravitational wave detector with statistical hypothesis test
|
18 pages, 11 figures
| null | null | null |
gr-qc astro-ph.IM
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In gravitational wave astronomy, non-Gaussian noise, such as scattered light
noise disturbs stable interferometer operation, limiting the interferometer's
sensitivity, and reducing the reliability of the analyses. In scattered light
noise, the non-Gaussian noise dominates the sensitivity in a low frequency
range of less than a few hundred Hz, which is sensitive to gravitational waves
from compact binary coalescence. This non-Gaussian noise prevents reliable
parameter estimation, since several analysis methods are optimized only for
Gaussian noise. Therefore, identifying data contaminated by non-Gaussian noise
is important. In this work, we extended the conventional method to evaluate
non-Gaussian noise, Rayleigh statistic, by using a statistical hypothesis test
to determine a threshold for non-Gaussian noise. First, we estimated the
distribution of the Rayleigh statistic against Gaussian noise, called the
background distribution, and validated that our extension serves as the
hypothetical test. Moreover, we investigated the detection efficiency by
assuming two non-Gaussian noise models. For example, for the model with strong
scattered light noise, the true positive rate was always above 0.7 when the
significance level was 0.05. The results showed that our extension can
contribute to an initial detection of non-Gaussian noise and lead to further
investigation of the origin of the non-Gaussian noise.
|
[
{
"created": "Tue, 19 Mar 2024 13:46:59 GMT",
"version": "v1"
}
] |
2024-03-20
|
[
[
"Yamamura",
"Shunsei",
""
],
[
"Yuzurihara",
"Hirotaka",
""
],
[
"Yamamoto",
"Takahiro",
""
],
[
"Uchiyama",
"Takashi",
""
]
] |
In gravitational wave astronomy, non-Gaussian noise, such as scattered light noise disturbs stable interferometer operation, limiting the interferometer's sensitivity, and reducing the reliability of the analyses. In scattered light noise, the non-Gaussian noise dominates the sensitivity in a low frequency range of less than a few hundred Hz, which is sensitive to gravitational waves from compact binary coalescence. This non-Gaussian noise prevents reliable parameter estimation, since several analysis methods are optimized only for Gaussian noise. Therefore, identifying data contaminated by non-Gaussian noise is important. In this work, we extended the conventional method to evaluate non-Gaussian noise, Rayleigh statistic, by using a statistical hypothesis test to determine a threshold for non-Gaussian noise. First, we estimated the distribution of the Rayleigh statistic against Gaussian noise, called the background distribution, and validated that our extension serves as the hypothetical test. Moreover, we investigated the detection efficiency by assuming two non-Gaussian noise models. For example, for the model with strong scattered light noise, the true positive rate was always above 0.7 when the significance level was 0.05. The results showed that our extension can contribute to an initial detection of non-Gaussian noise and lead to further investigation of the origin of the non-Gaussian noise.
|
gr-qc/0012013
|
Ronald W. Hellings
|
Ronald W. Hellings (Jet Propulsion Laboratory)
|
Elimination of Clock Jitter Noise in Spaceborn Laser Interferometers
|
20 pages, 5 figures
|
Phys.Rev. D64 (2001) 022002
|
10.1103/PhysRevD.64.022002
| null |
gr-qc
| null |
Space gravitational wave detectors employing laser interferometry between
free-flying spacecraft differ in many ways from their laboratory counterparts.
Among these differences is the fact that, in space, the end-masses will be
moving relative to each other. This creates a problem by inducing a Doppler
shift between the incoming and outgoing frequencies. The resulting beat
frequency is so high that its phase cannot be read to sufficient accuracy when
referenced to state-of-the-art space-qualified clocks. This is the problem that
is addressed in this paper. We introduce a set of time-domain algorithms in
which the effects of clock jitter are exactly canceled. The method employs the
two-color laser approach that has been previously proposed, but avoids the
singularities that arise in the previous frequency-domain algorithms. In
addition, several practical aspects of the laser and clock noise cancellation
schemes are addressed.
|
[
{
"created": "Mon, 4 Dec 2000 21:04:32 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Dec 2000 00:47:21 GMT",
"version": "v2"
}
] |
2009-10-31
|
[
[
"Hellings",
"Ronald W.",
"",
"Jet Propulsion Laboratory"
]
] |
Space gravitational wave detectors employing laser interferometry between free-flying spacecraft differ in many ways from their laboratory counterparts. Among these differences is the fact that, in space, the end-masses will be moving relative to each other. This creates a problem by inducing a Doppler shift between the incoming and outgoing frequencies. The resulting beat frequency is so high that its phase cannot be read to sufficient accuracy when referenced to state-of-the-art space-qualified clocks. This is the problem that is addressed in this paper. We introduce a set of time-domain algorithms in which the effects of clock jitter are exactly canceled. The method employs the two-color laser approach that has been previously proposed, but avoids the singularities that arise in the previous frequency-domain algorithms. In addition, several practical aspects of the laser and clock noise cancellation schemes are addressed.
|
gr-qc/0304027
|
Achilles D. Speliotopoulos
|
Raymond Y. Chiao and Achilles D. Speliotopoulos
|
Quantum Interference to Measure Spacetime Curvature: A Proposed
Experiment at the Intersection of Quantum Mechanics and General Relativity
|
7 pages LaTeXed with RevTeX 4.0, 2 figures. Submitted to the 2003
Gravity Research Foundation Essay Contest
|
Int.J.Mod.Phys.D12:1627-1632,2003
|
10.1142/S0218271803003943
| null |
gr-qc
| null |
An experiment in Low Earth Orbit (LEO) is proposed to measure components of
the Riemann curvature tensor using atom interferometry. We show that the
difference in the quantum phase $\Delta\phi$ of an atom that can travel along
two intersecting geodesics is given by $mR_{0i0j}/\hbar$ times the spacetime
volume contained within the geodesics. Our expression for $\Delta\phi$ also
holds for gravitational waves in the long wavelength limit.
|
[
{
"created": "Sun, 6 Apr 2003 03:41:18 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Apr 2003 21:54:30 GMT",
"version": "v2"
}
] |
2011-09-13
|
[
[
"Chiao",
"Raymond Y.",
""
],
[
"Speliotopoulos",
"Achilles D.",
""
]
] |
An experiment in Low Earth Orbit (LEO) is proposed to measure components of the Riemann curvature tensor using atom interferometry. We show that the difference in the quantum phase $\Delta\phi$ of an atom that can travel along two intersecting geodesics is given by $mR_{0i0j}/\hbar$ times the spacetime volume contained within the geodesics. Our expression for $\Delta\phi$ also holds for gravitational waves in the long wavelength limit.
|
1904.05762
|
David Benisty
|
Fotios K. Anagnostopoulos, David Benisty, Spyros Basilakos, Eduardo I.
Guendelman
|
Dark energy and dark matter unification from dynamical space time:
observational constraints and cosmological implications
|
Small modifications, BBN constraint
|
JCAP 06 (2019) 003
|
10.1088/1475-7516/2019/06/003
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A recently proposed Dynamical Space-time Cosmology (DSC) that unifies dark
energy and dark matter is studied. The general action of this scenario includes
a Lagrange multiplier, which is coupled to the energy momentum tensor and a
scalar field which is different from quintessence. First for various types of
potentials we implement a critical point analysis and we find solutions which
lead to cosmic acceleration and under certain conditions to stable late-time
attractors. Then the DSC cosmology is confronted with the latest cosmological
data from low-redshift probes, namely measurements of the Hubble parameter and
standard candles (Pantheon SnIa, Quasi-stellar objects). Performing an overall
likelihood analysis and using the appropriate information criteria we find that
the explored DSC models are in very good agreement with the data. We also find
that one of the DSC models shows a small but non-zero deviation from $\Lambda$
cosmology, nevertheless the confidence level is close to $\sim 1.5\sigma$.
|
[
{
"created": "Thu, 11 Apr 2019 15:18:02 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2019 13:27:22 GMT",
"version": "v2"
}
] |
2019-06-10
|
[
[
"Anagnostopoulos",
"Fotios K.",
""
],
[
"Benisty",
"David",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Guendelman",
"Eduardo I.",
""
]
] |
A recently proposed Dynamical Space-time Cosmology (DSC) that unifies dark energy and dark matter is studied. The general action of this scenario includes a Lagrange multiplier, which is coupled to the energy momentum tensor and a scalar field which is different from quintessence. First for various types of potentials we implement a critical point analysis and we find solutions which lead to cosmic acceleration and under certain conditions to stable late-time attractors. Then the DSC cosmology is confronted with the latest cosmological data from low-redshift probes, namely measurements of the Hubble parameter and standard candles (Pantheon SnIa, Quasi-stellar objects). Performing an overall likelihood analysis and using the appropriate information criteria we find that the explored DSC models are in very good agreement with the data. We also find that one of the DSC models shows a small but non-zero deviation from $\Lambda$ cosmology, nevertheless the confidence level is close to $\sim 1.5\sigma$.
|
1606.05265
|
Etienne Baffou
|
E. H. Baffou, I. G. Salako, M. J. S. Houndjo
|
Viscous Generalized Chaplygin Gas Interacting with f(R,T) gravity
|
10 pages and 5 figures
|
International Journal of Geometric Methods in Modern Physics, 2017
|
10.1142/S0219887817500517
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we study in Friedmann-Robertson-Walker universe the
interaction between the viscous generalized Chaplygin gas with $f(R,T)$
gravity, which is an arbitrary function of the Ricci scalar $R$ and the trace
$T$ of the energy-momentum tensor. Assuming that the contents of universe is
dominated by a generalized Chaplygin gas and dark energy, we obtained the
modified Friedmann equations and also the time dependent energy density and
pressure of dark energy due to the shear and bulk viscosities for three
interacting models depending on an input parameter $Q$. Within the simple form
of scale factor (power-law), we discuss the graphical representation of dark
energy density parameter and investigate the shear and bulk viscosities effects
on the accelerating expansion of the universe for each interacting model.
|
[
{
"created": "Wed, 15 Jun 2016 09:23:54 GMT",
"version": "v1"
}
] |
2017-05-11
|
[
[
"Baffou",
"E. H.",
""
],
[
"Salako",
"I. G.",
""
],
[
"Houndjo",
"M. J. S.",
""
]
] |
In this paper, we study in Friedmann-Robertson-Walker universe the interaction between the viscous generalized Chaplygin gas with $f(R,T)$ gravity, which is an arbitrary function of the Ricci scalar $R$ and the trace $T$ of the energy-momentum tensor. Assuming that the contents of universe is dominated by a generalized Chaplygin gas and dark energy, we obtained the modified Friedmann equations and also the time dependent energy density and pressure of dark energy due to the shear and bulk viscosities for three interacting models depending on an input parameter $Q$. Within the simple form of scale factor (power-law), we discuss the graphical representation of dark energy density parameter and investigate the shear and bulk viscosities effects on the accelerating expansion of the universe for each interacting model.
|
1810.05001
|
Hossein Shenavar
|
Hossein Shenavar and Kurosh Javidan
|
A Modified Dynamical Model of Cosmology I. Theory
|
The model is discussed in more details. Data analysis of the model
will be presented in future. Includes 48 pages and 9 figures
|
Universe 2020, 6(1), 1
|
10.3390/universe6010001
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Wheeler (1964) had formulated Mach's principle as the boundary condition for
general relativistic field equations. Here, we use this idea and develop a
modified dynamical model of cosmology based on imposing Neumann boundary
condition on cosmological perturbation equations. Then, it is shown that a new
term appears in the equation of motion, which leads to a modified Poisson
equation. In addition, a modified Hubble parameter is derived due to the
presence of the new term. Moreover, it is proved that, without a cosmological
constant, such a model has a late time-accelerated expansion with an equation
of state converging to $w < -1$. Also, the luminosity distance in the present
model is shown to differ from that of the $\Lambda CDM$ model at high
redshifts. Furthermore, it is found that the adiabatic sound speed squared is
positive in radiation-dominated era and then converges to zero at later times.
Theoretical implications of the Neumann boundary condition have been discussed,
and it is shown that, by fixing the value of the conjugate momentum (under
certain conditions), one could derive a similar version of modified dynamics.
In a future work, we will confine the free parameters of the Neumann model
based on hype Ia Supernovae, Hubble parameter data, and the age of the oldest
stars.
|
[
{
"created": "Thu, 11 Oct 2018 13:15:05 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jun 2019 16:31:43 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Jan 2020 08:03:54 GMT",
"version": "v3"
}
] |
2020-01-16
|
[
[
"Shenavar",
"Hossein",
""
],
[
"Javidan",
"Kurosh",
""
]
] |
Wheeler (1964) had formulated Mach's principle as the boundary condition for general relativistic field equations. Here, we use this idea and develop a modified dynamical model of cosmology based on imposing Neumann boundary condition on cosmological perturbation equations. Then, it is shown that a new term appears in the equation of motion, which leads to a modified Poisson equation. In addition, a modified Hubble parameter is derived due to the presence of the new term. Moreover, it is proved that, without a cosmological constant, such a model has a late time-accelerated expansion with an equation of state converging to $w < -1$. Also, the luminosity distance in the present model is shown to differ from that of the $\Lambda CDM$ model at high redshifts. Furthermore, it is found that the adiabatic sound speed squared is positive in radiation-dominated era and then converges to zero at later times. Theoretical implications of the Neumann boundary condition have been discussed, and it is shown that, by fixing the value of the conjugate momentum (under certain conditions), one could derive a similar version of modified dynamics. In a future work, we will confine the free parameters of the Neumann model based on hype Ia Supernovae, Hubble parameter data, and the age of the oldest stars.
|
1707.07125
|
Sushant Ghosh Prof
|
Balendra Pratap Singh and Sushant G. Ghosh
|
Shadow of Schwarzschild-Tangherlini black holes
|
16 pages, 5 figures, 1 table
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the shadow cast by the H$D$ Schwarzschild-Tangherlini black hole,
and analytically calculate the influence of extra dimensions on the shadow of a
black hole. A black hole casts a shadow as an optical appearance because of its
strong gravitational field which is known to be a dark zone covered by a circle
for a Schwarzschild black hole. We demonstrate that the null geodesic equation
can be integrated by Hamilton-Jacobi approach, which enables us to investigate
the shadow cast by the H$D$ Schwarzschild-Tangherlini black holes.
Interestingly, it turns out that, for fixed values of the mass parameter, the
shadow in H$D$ spacetimes are smaller when compared with 4$D$ Schwarzschild
black hole. Further, the shadows of H$D$ Schwarzschild-Tangherlini black holes
are concentric circles with a radius of the circle decreases with increase in
$D$. We visualize the photon regions and the shadows in various dimensions for
different values of the parameters, and the energy emission rates are is also
investigated. Our results, in the limit $D=4$, reduced exactly to
\emph{vis-$\grave{a}$-vis} Schwarzschild black hole case.
|
[
{
"created": "Sat, 22 Jul 2017 09:15:31 GMT",
"version": "v1"
}
] |
2017-07-25
|
[
[
"Singh",
"Balendra Pratap",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] |
We study the shadow cast by the H$D$ Schwarzschild-Tangherlini black hole, and analytically calculate the influence of extra dimensions on the shadow of a black hole. A black hole casts a shadow as an optical appearance because of its strong gravitational field which is known to be a dark zone covered by a circle for a Schwarzschild black hole. We demonstrate that the null geodesic equation can be integrated by Hamilton-Jacobi approach, which enables us to investigate the shadow cast by the H$D$ Schwarzschild-Tangherlini black holes. Interestingly, it turns out that, for fixed values of the mass parameter, the shadow in H$D$ spacetimes are smaller when compared with 4$D$ Schwarzschild black hole. Further, the shadows of H$D$ Schwarzschild-Tangherlini black holes are concentric circles with a radius of the circle decreases with increase in $D$. We visualize the photon regions and the shadows in various dimensions for different values of the parameters, and the energy emission rates are is also investigated. Our results, in the limit $D=4$, reduced exactly to \emph{vis-$\grave{a}$-vis} Schwarzschild black hole case.
|
gr-qc/0010025
|
Daniel Sforza
|
Rafael Ferraro and Daniel M. Sforza
|
Operator ordering for generally covariant systems
|
4 pages. Talk given at the Third Conference on "Constrained Dynamics
and Quantum Gravity" held in Sardinia (Italy), September 1999. Journal
reference:Nucl. Phys. B (Proc. Suppl.) 88 (2000) 322-325
|
Nucl.Phys.Proc.Suppl. 88 (2000) 322-325
|
10.1016/S0920-5632(00)00794-5
| null |
gr-qc
| null |
The constraint operators belonging to a generally covariant system are found
out within the framework of the BRST formalism. The result embraces quadratic
Hamiltonian constraints whose potential can be factorized as a never null
function times a gauge invariant function. The building of the inner product
between physical states is analyzed for systems featuring either intrinsic or
extrinsic time.
|
[
{
"created": "Fri, 6 Oct 2000 21:46:41 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Ferraro",
"Rafael",
""
],
[
"Sforza",
"Daniel M.",
""
]
] |
The constraint operators belonging to a generally covariant system are found out within the framework of the BRST formalism. The result embraces quadratic Hamiltonian constraints whose potential can be factorized as a never null function times a gauge invariant function. The building of the inner product between physical states is analyzed for systems featuring either intrinsic or extrinsic time.
|
1512.00655
|
K Haris
|
K Haris, Archana Pai
|
Study of statistical properties of hybrid statistic in coherent
multi-detector compact binary coalescences Search
|
Published in Phys. Rev. D
|
Phys. Rev. D 93, 102002 (2016)
|
10.1103/PhysRevD.93.102002
|
LIGO laboratory document number LIGO-P1500221
|
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this article, we revisit the problem of coherent multi-detector search of
gravitational wave from compact binary coalescence with Neutron stars and Black
Holes using advanced interferometers like LIGO-Virgo. Based on the loss of
optimal multi-detector signal-to-noise ratio (SNR), we construct a hybrid
statistic as a best of maximum-likelihood-ratio(MLR) statistic tuned for
face-on and face-off binaries. The statistical properties of the hybrid
statistic is studied. The performance of this hybrid statistic is compared with
that of the coherent MLR statistic for generic inclination angles. Owing to the
single synthetic data stream, the hybrid statistic gives low false alarms
compared to the multi-detector MLR statistic and small fractional loss in the
optimum SNR for a large range of binary inclinations. We have demonstrated that
for a LIGO-Virgo network and binary inclination, \epsilon < 70 deg. and
\epsilon > 110 deg., the hybrid statistic captures more than 98% of network
optimum matched filter SNR with low false alarm rate. The Monte-Carlo exercise
with two distributions of incoming inclination angles namely, U[cos(\epsilon)]
and more realistic distribution proposed by B. F. Schutz are performed with
hybrid statistic and gave ~5% and ~7% higher detection probability respectively
compared to the two stream multi-detector MLR statistic for a fixed false alarm
probability of 10^-5.
|
[
{
"created": "Wed, 2 Dec 2015 11:37:22 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Mar 2017 18:32:28 GMT",
"version": "v2"
}
] |
2017-03-17
|
[
[
"Haris",
"K",
""
],
[
"Pai",
"Archana",
""
]
] |
In this article, we revisit the problem of coherent multi-detector search of gravitational wave from compact binary coalescence with Neutron stars and Black Holes using advanced interferometers like LIGO-Virgo. Based on the loss of optimal multi-detector signal-to-noise ratio (SNR), we construct a hybrid statistic as a best of maximum-likelihood-ratio(MLR) statistic tuned for face-on and face-off binaries. The statistical properties of the hybrid statistic is studied. The performance of this hybrid statistic is compared with that of the coherent MLR statistic for generic inclination angles. Owing to the single synthetic data stream, the hybrid statistic gives low false alarms compared to the multi-detector MLR statistic and small fractional loss in the optimum SNR for a large range of binary inclinations. We have demonstrated that for a LIGO-Virgo network and binary inclination, \epsilon < 70 deg. and \epsilon > 110 deg., the hybrid statistic captures more than 98% of network optimum matched filter SNR with low false alarm rate. The Monte-Carlo exercise with two distributions of incoming inclination angles namely, U[cos(\epsilon)] and more realistic distribution proposed by B. F. Schutz are performed with hybrid statistic and gave ~5% and ~7% higher detection probability respectively compared to the two stream multi-detector MLR statistic for a fixed false alarm probability of 10^-5.
|
1608.08705
|
Yu-Xiao Liu
|
Yu-Peng Zhang, Bao-Min Gu, Shao-Wen Wei, Jie Yang, Yu-Xiao Liu
|
Charged spinning black holes as accelerators of spinning particles
|
10 pages, 11 figures, Superluminal region in the parameter space
discussed, to be published in PRD
|
Phys. Rev. D 94, 124017 (2016)
|
10.1103/PhysRevD.94.124017
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is well known that some black holes can act as accelerators for particles
without spin. Recently, there are some works considering collision of two
spinning particles in the background of Schwarzschild and Kerr black holes and
it was shown that {the center-of-mass energy of the test particles is related
to the spin}. In this paper we extend the results to some more general cases.
We consider Kerr-Newman black holes as accelerators for spinning particles. We
derive the center-of-mass energy of the spinning particles and use numerical
method to investigate how the center-of-mass energy is affected by the
properties of the black holes and spinning particles.
|
[
{
"created": "Wed, 31 Aug 2016 02:09:06 GMT",
"version": "v1"
},
{
"created": "Sat, 17 Sep 2016 02:12:55 GMT",
"version": "v2"
},
{
"created": "Tue, 29 Nov 2016 01:04:59 GMT",
"version": "v3"
}
] |
2016-12-21
|
[
[
"Zhang",
"Yu-Peng",
""
],
[
"Gu",
"Bao-Min",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Yang",
"Jie",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] |
It is well known that some black holes can act as accelerators for particles without spin. Recently, there are some works considering collision of two spinning particles in the background of Schwarzschild and Kerr black holes and it was shown that {the center-of-mass energy of the test particles is related to the spin}. In this paper we extend the results to some more general cases. We consider Kerr-Newman black holes as accelerators for spinning particles. We derive the center-of-mass energy of the spinning particles and use numerical method to investigate how the center-of-mass energy is affected by the properties of the black holes and spinning particles.
|
gr-qc/0503097
|
Leonard Susskind
|
Leonard Susskind
|
Wormholes and Time Travel? Not Likely
|
5 pages, remark added about time delay in identification. Reference
added
| null | null | null |
gr-qc astro-ph hep-th
| null |
Wormholes have been advanced as both a method for circumventing the
limitations of the speed of light as well as a means for building a time
machine (to travel to the past). Thus it is argued that General Relativity may
allow both of these possibilities. In this note I argue that traversable
wormholes connecting otherwise causally disconnected regions, violate two of
the most fundamental principles physics, namely local energy conservation and
the energy-time uncertainty principle.
|
[
{
"created": "Wed, 23 Mar 2005 02:10:21 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Mar 2005 04:02:05 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Apr 2005 19:54:25 GMT",
"version": "v3"
}
] |
2007-05-23
|
[
[
"Susskind",
"Leonard",
""
]
] |
Wormholes have been advanced as both a method for circumventing the limitations of the speed of light as well as a means for building a time machine (to travel to the past). Thus it is argued that General Relativity may allow both of these possibilities. In this note I argue that traversable wormholes connecting otherwise causally disconnected regions, violate two of the most fundamental principles physics, namely local energy conservation and the energy-time uncertainty principle.
|
gr-qc/0511152
|
Alicia M. Sintes
|
Alicia M Sintes (for the LIGO Scientific Collaboration)
|
Recent results on the search for continuous sources with LIGO and GEO600
|
TAUP2005 Proceedings to be published in Journal of Physics:
Conference Series
|
J.Phys.Conf.Ser. 39 (2006) 36-38
|
10.1088/1742-6596/39/1/008
| null |
gr-qc
| null |
An overview of the searches for continuous gravitational wave signals in LIGO
and GEO 600 performed on different recent science runs and results are
presented. This includes both searching for gravitational waves from known
pulsars as well as blind searches over a wide parameter space.
|
[
{
"created": "Tue, 29 Nov 2005 14:51:50 GMT",
"version": "v1"
}
] |
2009-11-11
|
[
[
"Sintes",
"Alicia M",
"",
"for the LIGO Scientific Collaboration"
]
] |
An overview of the searches for continuous gravitational wave signals in LIGO and GEO 600 performed on different recent science runs and results are presented. This includes both searching for gravitational waves from known pulsars as well as blind searches over a wide parameter space.
|
gr-qc/9710027
|
William Pezzaglia . D.
|
William M. Pezzaglia (Physics Dept., Santa Clara Univ.)
|
Physical Applications of a Generalized Clifford Calculus (Papapetrou
equations and Metamorphic Curvature)
|
12 pages, LaTeX, no figures, Summary of talk given in the Analysis of
Dirac Operators section at the meeting of the International Society for
Analysis, its Applications and Computation, Univ. of Delaware June 1997
| null | null |
clf-alg/pezz9701
|
gr-qc dg-ga math-ph math.DG math.MP
| null |
A generalized Clifford manifold is proposed in which there are coordinates
not only for the basis vector generators, but for each element of the Clifford
group, including the identity scalar. These new quantities are physically
interpreted to represent internal structure of matter (e.g. classical or
quantum spin). The generalized Dirac operator must now include differentiation
with respect to these higher order geometric coordinates. In a Riemann space,
where the magnitude and rank of geometric objects are preserved under
displacement, these new terms modify the geodesics. One possible physical
interpretation is natural coupling of the classical spin to linear motion,
providing a new derivation of the Papapetrou equations. A generalized curvature
is proposed for the Clifford manifold in which the connection does not preserve
the rank of a multivector under parallel transport, e.g. a vector may be
``rotated'' into a scalar.
|
[
{
"created": "Fri, 3 Oct 1997 22:37:51 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Pezzaglia",
"William M.",
"",
"Physics Dept., Santa Clara Univ."
]
] |
A generalized Clifford manifold is proposed in which there are coordinates not only for the basis vector generators, but for each element of the Clifford group, including the identity scalar. These new quantities are physically interpreted to represent internal structure of matter (e.g. classical or quantum spin). The generalized Dirac operator must now include differentiation with respect to these higher order geometric coordinates. In a Riemann space, where the magnitude and rank of geometric objects are preserved under displacement, these new terms modify the geodesics. One possible physical interpretation is natural coupling of the classical spin to linear motion, providing a new derivation of the Papapetrou equations. A generalized curvature is proposed for the Clifford manifold in which the connection does not preserve the rank of a multivector under parallel transport, e.g. a vector may be ``rotated'' into a scalar.
|
2102.06550
|
Ahmad Sheykhi
|
Ahmad Sheykhi
|
Barrow Entropy Corrections to Friedmann Equations
|
8 pages, two columns, new version
|
Phys. Rev. D 103, 123503 (2021)
|
10.1103/PhysRevD.103.123503
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Inspired by the Covid-$19$ virus structure, Barrow argued that
quantum-gravitational effects may introduce intricate, fractal features on the
black hole horizon [Phys. Lett. B {\bf808} (2020) 135643]. In this viewpoint,
black hole entropy no longer obeys the area law and instead it can be given by
$S\sim A^{1+\delta/2}$, where the exponent $\delta$ ranges $0\leq\delta\leq1$,
and indicates the amount of the quantum-gravitational deformation effects.
Based on this, and using the deep connection between gravity and
thermodynamics, we disclose the effects of the Barrow entropy on the
cosmological equations. For this purpose, we start from the first law of
thermodynamics, $dE=TdS+WdV$, on the apparent horizon of the
Friedmann-Robertson-Walker (FRW) Universe, and derive the corresponding
modified Friedmann equations by assuming the entropy associated with the
apparent horizon has the form of Barrow entropy. We also examine the validity
of the generalized second law of thermodynamics for the Universe enclosed by
the apparent horizon. Finally, we employ the emergence scenario of gravity and
extract the modified Friedmann equation in the presence of Barrow entropy which
coincide with one obtained from the first law of thermodynamics. When
$\delta=0$, the results of standard cosmology are deduced.
|
[
{
"created": "Thu, 11 Feb 2021 18:44:59 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Feb 2021 13:18:30 GMT",
"version": "v2"
},
{
"created": "Sun, 28 Feb 2021 07:13:21 GMT",
"version": "v3"
}
] |
2021-06-09
|
[
[
"Sheykhi",
"Ahmad",
""
]
] |
Inspired by the Covid-$19$ virus structure, Barrow argued that quantum-gravitational effects may introduce intricate, fractal features on the black hole horizon [Phys. Lett. B {\bf808} (2020) 135643]. In this viewpoint, black hole entropy no longer obeys the area law and instead it can be given by $S\sim A^{1+\delta/2}$, where the exponent $\delta$ ranges $0\leq\delta\leq1$, and indicates the amount of the quantum-gravitational deformation effects. Based on this, and using the deep connection between gravity and thermodynamics, we disclose the effects of the Barrow entropy on the cosmological equations. For this purpose, we start from the first law of thermodynamics, $dE=TdS+WdV$, on the apparent horizon of the Friedmann-Robertson-Walker (FRW) Universe, and derive the corresponding modified Friedmann equations by assuming the entropy associated with the apparent horizon has the form of Barrow entropy. We also examine the validity of the generalized second law of thermodynamics for the Universe enclosed by the apparent horizon. Finally, we employ the emergence scenario of gravity and extract the modified Friedmann equation in the presence of Barrow entropy which coincide with one obtained from the first law of thermodynamics. When $\delta=0$, the results of standard cosmology are deduced.
|
gr-qc/9609035
| null |
Vladimir S. Mashkevich (Institute of Physics, Kiev)
|
Indeterministic Quantum Gravity IV. The Cosmic-length Universe and the
Problem of the Missing Dark Matter
|
7 pages, LATEX 2.09
| null | null | null |
gr-qc astro-ph
| null |
This paper is a sequel of the series of papers [gr-qc/9409010, gr-qc/9505034,
gr-qc/9603022], being an immediate continuation and development of the latter
of them. In the Friedmann universe, the equation $\Omega_0=2q_0$ holds
($\Omega$ is density parameter, $q$ is deceleration parameter, and subscript 0
indicates present-day values), which gives rise to the problem of the missing
matter as observational data give $\Omega_0<2q_0$. In the cosmic-length
universe, $\Omega_0=2q_0- L/R_0^3H_0^2$ ($R_0$ is the radius of the universe,
$H_0$ is Hubble constant), which lifts the problem. The cosmic length, $L=const
\approx 1/H_0$, is the infimum of the set of maximal radii of a closed
universe.
|
[
{
"created": "Fri, 13 Sep 1996 09:37:08 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Mashkevich",
"Vladimir S.",
"",
"Institute of Physics, Kiev"
]
] |
This paper is a sequel of the series of papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022], being an immediate continuation and development of the latter of them. In the Friedmann universe, the equation $\Omega_0=2q_0$ holds ($\Omega$ is density parameter, $q$ is deceleration parameter, and subscript 0 indicates present-day values), which gives rise to the problem of the missing matter as observational data give $\Omega_0<2q_0$. In the cosmic-length universe, $\Omega_0=2q_0- L/R_0^3H_0^2$ ($R_0$ is the radius of the universe, $H_0$ is Hubble constant), which lifts the problem. The cosmic length, $L=const \approx 1/H_0$, is the infimum of the set of maximal radii of a closed universe.
|
1706.09175
|
Yasusada Nambu
|
Shingo Kukita and Yasusada Nambu
|
Entanglement dynamics in de Sitter spacetime
|
16 pages, accepted version in Class. Quantum Gravity
| null |
10.1088/1361-6382/aa8e31
| null |
gr-qc quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We apply the master equation with dynamical coarse graining approximation to
a pair of detectors interacting with a scalar field. By solving the master
equation numerically, we investigate evolution of negativity between comoving
detectors in de Sitter space. For the massless conformal scalar field, it is
found that a pair of detectors can perceive entanglement beyond the Hubble
horizon scale if the initial separation of detectors is sufficiently small. At
the same time, violation of the Bell-CHSH inequality on the super horizon scale
is also detected. For the massless minimal scalar field, on the other hand, the
entanglement decays within Hubble time scale owing to the quantum noise caused
by particle creations in de Sitter space and the entanglement on the super
horizon scale cannot be detected.
|
[
{
"created": "Wed, 28 Jun 2017 09:00:51 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Oct 2017 01:08:15 GMT",
"version": "v2"
}
] |
2017-12-06
|
[
[
"Kukita",
"Shingo",
""
],
[
"Nambu",
"Yasusada",
""
]
] |
We apply the master equation with dynamical coarse graining approximation to a pair of detectors interacting with a scalar field. By solving the master equation numerically, we investigate evolution of negativity between comoving detectors in de Sitter space. For the massless conformal scalar field, it is found that a pair of detectors can perceive entanglement beyond the Hubble horizon scale if the initial separation of detectors is sufficiently small. At the same time, violation of the Bell-CHSH inequality on the super horizon scale is also detected. For the massless minimal scalar field, on the other hand, the entanglement decays within Hubble time scale owing to the quantum noise caused by particle creations in de Sitter space and the entanglement on the super horizon scale cannot be detected.
|
gr-qc/0010050
|
John W. Barrett
|
John W. Barrett
|
State sum models for quantum gravity
|
amslatex, 7 pages, ICMP conference talk
| null | null | null |
gr-qc
| null |
This paper reviews the construction of quantum field theory on a
4-dimensional spacetime by combinatorial methods, and discusses the recent
developments in the direction of a combinatorial construction of quantum
gravity.
|
[
{
"created": "Thu, 12 Oct 2000 22:08:30 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Barrett",
"John W.",
""
]
] |
This paper reviews the construction of quantum field theory on a 4-dimensional spacetime by combinatorial methods, and discusses the recent developments in the direction of a combinatorial construction of quantum gravity.
|
1412.4475
|
Yoshiaki Ohkuwa
|
Yoshiaki Ohkuwa, Yasuo Ezawa
|
On the canonical formalism of $f(R)$-type gravity using Lie derivatives
|
11 pages, no figures, Version accepted for publication in Eur. Phys.
J. Plus
|
Eur. Phys. J. Plus (2015) 130: 77
|
10.1140/epjp/i2015-15077-5
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a canonical formalism of the $f(R)$-type gravity using the Lie
derivatives instead of the time derivatives by refining the formalism of our
group. The previous formalism is a direct generalization of the Ostrogradski's
formalism. However the use of the Lie derivatives was not sufficient in that
Lie derivatives and time derivatives are used in a mixed way, so that the
expressions are somewhat complicated. In this paper, we use the Lie derivatives
and foliation structure of the spacetime thoroughly, which makes the procedure
and the expressions far more concise.
|
[
{
"created": "Mon, 15 Dec 2014 07:13:39 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Dec 2014 00:51:43 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Jun 2015 08:45:25 GMT",
"version": "v3"
}
] |
2015-06-26
|
[
[
"Ohkuwa",
"Yoshiaki",
""
],
[
"Ezawa",
"Yasuo",
""
]
] |
We present a canonical formalism of the $f(R)$-type gravity using the Lie derivatives instead of the time derivatives by refining the formalism of our group. The previous formalism is a direct generalization of the Ostrogradski's formalism. However the use of the Lie derivatives was not sufficient in that Lie derivatives and time derivatives are used in a mixed way, so that the expressions are somewhat complicated. In this paper, we use the Lie derivatives and foliation structure of the spacetime thoroughly, which makes the procedure and the expressions far more concise.
|
1007.3820
|
Xin Li
|
Xin Li and Zhe Chang
|
Reply to Sergiu I. Vacaru's "Critical remarks on Finsler modifications
of gravity and cosmology by Zhe Chang and Xin Li"
| null | null | null | null |
gr-qc math-ph math.MP
|
http://creativecommons.org/licenses/by/3.0/
|
This is our reply to "Critical remarks on Finslerian modifications of gravity
and cosmology by Zhe Chang and Xin Li", Sergiu I. Vacaru, Phys. Lett. B 690
(2010) 224. It is pointed out that the Finslerian modifications of gravity and
cosmology (Zhe Chang and Xin Li, Phys. Lett. B 676 (2009) 173; {\it ibid} 668
(2008) 453) is a suggestion on the generalization of Einstein's gravity and
cosmology, but not a proof for theorems in geometry. False or true of the
theory should be tested by experiments or observations. We show that the
arguments of Sergiu I. Vacaru were based a wrong logic. A personal claim can
not be used to prove any other theory be wrong. To get the claim: {\it "we may
construct more "standard" physical Finsler classical/quantum gravity theories
for metric compatible connections like the Cartan d-connection"}, Sergiu I.
Vacaru should complete a consistent presentation at least. We suggest Sergiu I.
Vacaru to make some predictions on gravity and cosmoligy using his {\it
"standard" physical Finsler classical/quantum gravity theories} as we did, and
compare them with astronomical observations. By the way, we should say that it
is still really far from a theory of quantum gravity.
|
[
{
"created": "Thu, 22 Jul 2010 08:08:32 GMT",
"version": "v1"
}
] |
2010-07-23
|
[
[
"Li",
"Xin",
""
],
[
"Chang",
"Zhe",
""
]
] |
This is our reply to "Critical remarks on Finslerian modifications of gravity and cosmology by Zhe Chang and Xin Li", Sergiu I. Vacaru, Phys. Lett. B 690 (2010) 224. It is pointed out that the Finslerian modifications of gravity and cosmology (Zhe Chang and Xin Li, Phys. Lett. B 676 (2009) 173; {\it ibid} 668 (2008) 453) is a suggestion on the generalization of Einstein's gravity and cosmology, but not a proof for theorems in geometry. False or true of the theory should be tested by experiments or observations. We show that the arguments of Sergiu I. Vacaru were based a wrong logic. A personal claim can not be used to prove any other theory be wrong. To get the claim: {\it "we may construct more "standard" physical Finsler classical/quantum gravity theories for metric compatible connections like the Cartan d-connection"}, Sergiu I. Vacaru should complete a consistent presentation at least. We suggest Sergiu I. Vacaru to make some predictions on gravity and cosmoligy using his {\it "standard" physical Finsler classical/quantum gravity theories} as we did, and compare them with astronomical observations. By the way, we should say that it is still really far from a theory of quantum gravity.
|
1402.6285
|
Larry Ford
|
C. H. G. Bessa, V. A. De Lorenci and L. H. Ford
|
An Analog Model for Light Propagation in Semiclassical Gravity
|
12 pages, 2 figures
|
Phys. Rev. D 90, 024036 (2014)
|
10.1103/PhysRevD.90.024036
| null |
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We treat a model based upon nonlinear optics for the semiclassical
gravitational effects of quantum fields upon light propagation. Our model uses
a nonlinear material with a nonzero third order polarizability. Here a probe
light pulse satisfies a wave equation containing the expectation value of the
squared electric field. This expectation value depends upon the presence of
lower frequency quanta, the background field, and modifies the effective index
of refraction, and hence the speed of the probe pulse. If the mean squared
electric field is positive, then the pulse is slowed, which is analogous to the
gravitational effects of ordinary matter. Such matter satisfies the null energy
condition and produce gravitational lensing and time delay. If the mean squared
field is negative, then the pulse has a higher speed than in the absence of the
background field. This is analogous to the gravitational effects of exotic
matter, such as stress tensor expectation values with locally negative energy
densities, which lead to repulsive gravitational effects, such as defocussing
and time advance. We give some estimates of the magnitude of the effects in our
model, and find that they may be large enough to be observable. We also briefly
discuss the possibility that the mean squared electric field could be produced
by the Casimir vacuum near a reflecting boundary.
|
[
{
"created": "Tue, 25 Feb 2014 19:26:18 GMT",
"version": "v1"
}
] |
2014-07-23
|
[
[
"Bessa",
"C. H. G.",
""
],
[
"De Lorenci",
"V. A.",
""
],
[
"Ford",
"L. H.",
""
]
] |
We treat a model based upon nonlinear optics for the semiclassical gravitational effects of quantum fields upon light propagation. Our model uses a nonlinear material with a nonzero third order polarizability. Here a probe light pulse satisfies a wave equation containing the expectation value of the squared electric field. This expectation value depends upon the presence of lower frequency quanta, the background field, and modifies the effective index of refraction, and hence the speed of the probe pulse. If the mean squared electric field is positive, then the pulse is slowed, which is analogous to the gravitational effects of ordinary matter. Such matter satisfies the null energy condition and produce gravitational lensing and time delay. If the mean squared field is negative, then the pulse has a higher speed than in the absence of the background field. This is analogous to the gravitational effects of exotic matter, such as stress tensor expectation values with locally negative energy densities, which lead to repulsive gravitational effects, such as defocussing and time advance. We give some estimates of the magnitude of the effects in our model, and find that they may be large enough to be observable. We also briefly discuss the possibility that the mean squared electric field could be produced by the Casimir vacuum near a reflecting boundary.
|
2010.13071
|
Liu Zhao
|
Shaofan Liu and Liu Zhao
|
Work and work-energy theorem in curved spacetime
|
21 pages. v3: Title changed and significant amendments involved
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The definitions of gravitational work as well as work done by the total
external force on a massive probe particle moving in generic spacetime
backgrounds are proposed. These definitions are given in the form of scalar
integrals and thus, are independent of coordinate choices. However, the
dependence on the choice of observer field is essential and inevitable. The
definitions are checked in the case of Minkowski, Schwarzschild,
Reisner-Nordstr\"om and Kerr-Newman spacetimes and agreements with Newtonian
mechanical definitions are verified in the slow motion or the far field limit.
|
[
{
"created": "Sun, 25 Oct 2020 09:02:09 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Oct 2020 01:49:17 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Nov 2021 15:52:51 GMT",
"version": "v3"
}
] |
2021-11-17
|
[
[
"Liu",
"Shaofan",
""
],
[
"Zhao",
"Liu",
""
]
] |
The definitions of gravitational work as well as work done by the total external force on a massive probe particle moving in generic spacetime backgrounds are proposed. These definitions are given in the form of scalar integrals and thus, are independent of coordinate choices. However, the dependence on the choice of observer field is essential and inevitable. The definitions are checked in the case of Minkowski, Schwarzschild, Reisner-Nordstr\"om and Kerr-Newman spacetimes and agreements with Newtonian mechanical definitions are verified in the slow motion or the far field limit.
|
1811.01625
|
Zhu Yi
|
Zhu Yi and Yungui Gong
|
Gauss-Bonnet inflation and swampland
|
11 pages, 2 figures
| null | null | null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The two swampland criteria are generically in tension with the single field
slow-roll inflation because the first swampland criterion requires small tensor
to scalar ratio while the second swampland criterion requires large tensor to
scalar ratio. The challenge to the single field slow-roll inflation imposed by
the swampland criteria can be avoided by modifying the relationship between the
tensor to scalar ratio and the slow-roll parameter. We show that the
Gauss-Bonnet inflation with the coupling function inversely proportional to the
potential overcomes the challenge by adding a constant factor in the
relationship between the tensor to scalar ratio and the slow-roll parameter.
For the Gauss-Bonnet inflation, while the swampland criteria are satisfied, the
slow-roll conditions are also fulfilled, so the scalar spectral tilt and the
tensor to scalar ratio are consistent with the observations. We use the
potentials for chaotic inflation and the E-model as examples to show that the
models pass all the constraints. The swampland criteria may imply Gauss-Bonnet
coupling.
|
[
{
"created": "Mon, 5 Nov 2018 11:46:16 GMT",
"version": "v1"
}
] |
2018-11-06
|
[
[
"Yi",
"Zhu",
""
],
[
"Gong",
"Yungui",
""
]
] |
The two swampland criteria are generically in tension with the single field slow-roll inflation because the first swampland criterion requires small tensor to scalar ratio while the second swampland criterion requires large tensor to scalar ratio. The challenge to the single field slow-roll inflation imposed by the swampland criteria can be avoided by modifying the relationship between the tensor to scalar ratio and the slow-roll parameter. We show that the Gauss-Bonnet inflation with the coupling function inversely proportional to the potential overcomes the challenge by adding a constant factor in the relationship between the tensor to scalar ratio and the slow-roll parameter. For the Gauss-Bonnet inflation, while the swampland criteria are satisfied, the slow-roll conditions are also fulfilled, so the scalar spectral tilt and the tensor to scalar ratio are consistent with the observations. We use the potentials for chaotic inflation and the E-model as examples to show that the models pass all the constraints. The swampland criteria may imply Gauss-Bonnet coupling.
|
gr-qc/0610025
|
Mattias Marklund
|
G. Brodin, D. Eriksson, M. Marklund
|
Graviton mediated photon-photon scattering in general relativity
|
5 pages, 3 figures
|
Phys.Rev.D74:124028,2006
|
10.1103/PhysRevD.74.124028
| null |
gr-qc hep-ph
| null |
In this paper we consider photon-photon scattering due to self-induced
gravitational perturbations on a Minkowski background. We focus on four-wave
interaction between plane waves with weakly space and time dependent
amplitudes, since interaction involving a fewer number of waves is excluded by
energy-momentum conservation. The Einstein-Maxwell system is solved
perturbatively to third order in the field amplitudes and the coupling
coefficients are found for arbitrary polarizations in the center of mass
system. Comparisons with calculations based on quantum field theoretical
methods are made, and the small discrepances are explained.
|
[
{
"created": "Fri, 6 Oct 2006 14:30:55 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Brodin",
"G.",
""
],
[
"Eriksson",
"D.",
""
],
[
"Marklund",
"M.",
""
]
] |
In this paper we consider photon-photon scattering due to self-induced gravitational perturbations on a Minkowski background. We focus on four-wave interaction between plane waves with weakly space and time dependent amplitudes, since interaction involving a fewer number of waves is excluded by energy-momentum conservation. The Einstein-Maxwell system is solved perturbatively to third order in the field amplitudes and the coupling coefficients are found for arbitrary polarizations in the center of mass system. Comparisons with calculations based on quantum field theoretical methods are made, and the small discrepances are explained.
|
gr-qc/0503008
|
Chul-Moon Yoo
|
Chul-Moon Yoo, Ken-ichi Nakao, Daisuke Ida
|
Hoop Conjecture in Five-dimensios -Violation of Cosmic Censorship-
|
23 pages, 7 figures, PRD accepted version
|
Phys.Rev. D71 (2005) 104014
|
10.1103/PhysRevD.71.104014
|
OCU-PHYS-227, AP-GR-23
|
gr-qc
| null |
We study the condition of black hole formation in five-dimensional
space-time. We analytically solve the constraint equations of five-dimensional
Einstein equations for momentarily static and conformally flat initial data of
a spheroidal mass. We numerically search for an apparent horizon in various
initial hypersurfaces and find both necessary and sufficient conditions for the
horizon formation in terms of inequalities relating a geometric quantity and a
mass defined in an appropriate manner. In the case of infinitely thin spheroid,
our results suggest a possibility of naked singularity formation by the spindle
gravitational collapse in five-dimensional space-time.
|
[
{
"created": "Wed, 2 Mar 2005 03:54:21 GMT",
"version": "v1"
},
{
"created": "Fri, 13 May 2005 05:36:05 GMT",
"version": "v2"
}
] |
2009-11-11
|
[
[
"Yoo",
"Chul-Moon",
""
],
[
"Nakao",
"Ken-ichi",
""
],
[
"Ida",
"Daisuke",
""
]
] |
We study the condition of black hole formation in five-dimensional space-time. We analytically solve the constraint equations of five-dimensional Einstein equations for momentarily static and conformally flat initial data of a spheroidal mass. We numerically search for an apparent horizon in various initial hypersurfaces and find both necessary and sufficient conditions for the horizon formation in terms of inequalities relating a geometric quantity and a mass defined in an appropriate manner. In the case of infinitely thin spheroid, our results suggest a possibility of naked singularity formation by the spindle gravitational collapse in five-dimensional space-time.
|
2010.07472
|
V. G. Gurzadyan
|
A.Stepanian, Sh.Khlghatyan, V.G. Gurzadyan
|
Lense-Thirring precession and gravito-gyromagnetic ratio
|
Eur. Phys. Journal C (Lett), in press, 6 pages
|
Eur. Phys. Journal C, 80, 1011 (2020)
|
10.1140/epjc/s10052-020-08560-0
| null |
gr-qc astro-ph.IM
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The geodesics of bound spherical orbits i.e. of orbits performing
Lense-Thirring precession, are obtained in the case of the $\Lambda$-term
within gravito-electromagnetic formalism. It is shown that the presence of the
$\Lambda$-term in the equations of gravity leads to both relativistic and
non-relativistic corrections in the equations of motion. The contribution of
the $\Lambda$-term in the Lense-Thirring precession is interpreted as an
additional relativistic correction and the gravito-gyromagnetic ratio is
defined.
|
[
{
"created": "Thu, 15 Oct 2020 02:27:13 GMT",
"version": "v1"
}
] |
2020-11-18
|
[
[
"Stepanian",
"A.",
""
],
[
"Khlghatyan",
"Sh.",
""
],
[
"Gurzadyan",
"V. G.",
""
]
] |
The geodesics of bound spherical orbits i.e. of orbits performing Lense-Thirring precession, are obtained in the case of the $\Lambda$-term within gravito-electromagnetic formalism. It is shown that the presence of the $\Lambda$-term in the equations of gravity leads to both relativistic and non-relativistic corrections in the equations of motion. The contribution of the $\Lambda$-term in the Lense-Thirring precession is interpreted as an additional relativistic correction and the gravito-gyromagnetic ratio is defined.
|
1804.05840
|
Mordehai Milgrom
|
Mordehai Milgrom
|
MOND from a brane-world picture
|
17 pages, 1 Figure. Added a figure describing the schematics of the
brane dynamics. To appear in Jacob Bekenstein Memorial Volume: The
Conservative Revolutionary (World Scientific)
| null | null | null |
gr-qc astro-ph.CO astro-ph.GA hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
I describe a heuristic model where MOND dynamics emerge in a universe viewed
as a nearly spherical brane embedded in a higher-dimensional flat space. The
brane, described by $\xi(\Omega)$, is of density $\sigma$ ($\xi$ and $\Omega$
are the radial and angular coordinates in the embedding space). The brane and
matter -- confined to the brane and of density $\rho(\Omega)\ll\sigma$ -- are
coupled to a potential $\varepsilon(\xi)$. I restrict myself to shallow
perturbations, $\xi(\Omega)=\ell_0+\zeta(\Omega)$, $|\zeta|\ll\ell_0$. A
balanced brane implies $\hat a_0\equiv\varepsilon'(\ell_0)\sim T/\sigma\ell_0$,
$T$ is the brane tension, yielding for the velocity of small brane
perturbations $c^2\sim T/\sigma\sim \ell_0\hat a_0$. But, $\hat a_0$ plays the
role of the MOND acceleration constant in local gravitational dynamics; so
$\hat a_0\sim c^2/\ell_0$. What we, in the brane, perceive as the gravitational
potential is $\phi\equiv\varepsilon[\xi(\Omega)]\approx \phi_0+\hat a_0\zeta$.
Aspects of MOND that may emerge naturally as geometrical properties are: a. The
special role of acceleration in MOND, and why it is an acceleration, $a_0$,
that marks the transition from the standard dynamics much above $a_0$ to
scale-invariant dynamics much below $a_0$. b. The intriguing connection of
$a_0$ with cosmology. c. The Newtonian limit corresponds to local departure
$|\zeta|\ll\ell_0$; i.e., $\phi-\phi_0\sim a_0\zeta\ll a_0\ell_0\sim c^2$ -
whereas relativity enters when $|\zeta|\not\ll\ell_0$. The model also opens new
vistas for extension, e.g., it points to possible dependence of $a_0$ on
$\phi$, and to $a_0$ losing its status and meaning altogether in the
relativistic regime. The required global balance of the brane might solve the
`old' cosmological-constant problem. I discuss possible connections with the
nearly-de-Sitter nature of our Universe. (Abridged.)
|
[
{
"created": "Mon, 16 Apr 2018 12:35:16 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Mar 2019 11:32:47 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Jul 2019 12:40:51 GMT",
"version": "v3"
}
] |
2019-07-30
|
[
[
"Milgrom",
"Mordehai",
""
]
] |
I describe a heuristic model where MOND dynamics emerge in a universe viewed as a nearly spherical brane embedded in a higher-dimensional flat space. The brane, described by $\xi(\Omega)$, is of density $\sigma$ ($\xi$ and $\Omega$ are the radial and angular coordinates in the embedding space). The brane and matter -- confined to the brane and of density $\rho(\Omega)\ll\sigma$ -- are coupled to a potential $\varepsilon(\xi)$. I restrict myself to shallow perturbations, $\xi(\Omega)=\ell_0+\zeta(\Omega)$, $|\zeta|\ll\ell_0$. A balanced brane implies $\hat a_0\equiv\varepsilon'(\ell_0)\sim T/\sigma\ell_0$, $T$ is the brane tension, yielding for the velocity of small brane perturbations $c^2\sim T/\sigma\sim \ell_0\hat a_0$. But, $\hat a_0$ plays the role of the MOND acceleration constant in local gravitational dynamics; so $\hat a_0\sim c^2/\ell_0$. What we, in the brane, perceive as the gravitational potential is $\phi\equiv\varepsilon[\xi(\Omega)]\approx \phi_0+\hat a_0\zeta$. Aspects of MOND that may emerge naturally as geometrical properties are: a. The special role of acceleration in MOND, and why it is an acceleration, $a_0$, that marks the transition from the standard dynamics much above $a_0$ to scale-invariant dynamics much below $a_0$. b. The intriguing connection of $a_0$ with cosmology. c. The Newtonian limit corresponds to local departure $|\zeta|\ll\ell_0$; i.e., $\phi-\phi_0\sim a_0\zeta\ll a_0\ell_0\sim c^2$ - whereas relativity enters when $|\zeta|\not\ll\ell_0$. The model also opens new vistas for extension, e.g., it points to possible dependence of $a_0$ on $\phi$, and to $a_0$ losing its status and meaning altogether in the relativistic regime. The required global balance of the brane might solve the `old' cosmological-constant problem. I discuss possible connections with the nearly-de-Sitter nature of our Universe. (Abridged.)
|
gr-qc/9904081
|
George Bogoslovsky
|
G.Yu. Bogoslovsky, H.F. Goenner
|
Finslerian spaces possessing local relativistic symmetry
|
32 pages, 1 table, 4 figures, latex
|
Gen.Rel.Grav. 31 (1999) 1565-1603
|
10.1023/A:1026786505326
|
Preprint NPI MSU -- 99-10/568
|
gr-qc astro-ph hep-th
| null |
It is shown that the problem of a possible violation of the Lorentz
transformations at Lorentz factors $\gamma >5\times 10^{10} ,$ indicated by the
situation which has developed in the physics of ultra-high energy cosmic rays
(the absence of the GZK cutoff), has a nontrivial solution. Its essence
consists in the discovery of the so-called generalized Lorentz transformations
which seem to correctly link the inertial reference frames at any values of
$\gamma .$ Like the usual Lorentz transformations, the generalized ones are
linear, possess group properties and lead to the Einstein law of addition of
3-velocities. However, their geometric meaning turns out to be different: they
serve as relativistic symmetry transformations of a flat anisotropic Finslerian
event space rather than of Minkowski space. Consideration is given to two types
of Finsler spaces which generalize locally isotropic Riemannian space-time of
relativity theory, e. g. Finsler spaces with a partially and entirely broken
local 3D isotropy. The investigation advances arguments for the corresponding
generalization of the theory of fundamental interactions and for a specific
search for physical effects due to local anisotropy of space-time.
|
[
{
"created": "Fri, 30 Apr 1999 11:19:50 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Bogoslovsky",
"G. Yu.",
""
],
[
"Goenner",
"H. F.",
""
]
] |
It is shown that the problem of a possible violation of the Lorentz transformations at Lorentz factors $\gamma >5\times 10^{10} ,$ indicated by the situation which has developed in the physics of ultra-high energy cosmic rays (the absence of the GZK cutoff), has a nontrivial solution. Its essence consists in the discovery of the so-called generalized Lorentz transformations which seem to correctly link the inertial reference frames at any values of $\gamma .$ Like the usual Lorentz transformations, the generalized ones are linear, possess group properties and lead to the Einstein law of addition of 3-velocities. However, their geometric meaning turns out to be different: they serve as relativistic symmetry transformations of a flat anisotropic Finslerian event space rather than of Minkowski space. Consideration is given to two types of Finsler spaces which generalize locally isotropic Riemannian space-time of relativity theory, e. g. Finsler spaces with a partially and entirely broken local 3D isotropy. The investigation advances arguments for the corresponding generalization of the theory of fundamental interactions and for a specific search for physical effects due to local anisotropy of space-time.
|
1809.03109
|
Mohammed M. Khalil
|
Mohammed Khalil, Noah Sennett, Jan Steinhoff, Justin Vines, Alessandra
Buonanno
|
Hairy binary black holes in Einstein-Maxwell-dilaton theory and their
effective-one-body description
|
36 pages, 12 figures, updated to match published version
|
Phys. Rev. D 98, 104010 (2018)
|
10.1103/PhysRevD.98.104010
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In General Relativity and many modified theories of gravity, isolated black
holes (BHs) cannot source massless scalar fields. Einstein-Maxwell-dilaton
(EMd) theory is an exception: through couplings both to electromagnetism and
(non-minimally) to gravity, a massless scalar field can be generated by an
electrically charged BH. In this work, we analytically model the dynamics of
binaries comprised of such scalar-charged ("hairy") BHs. While BHs are not
expected to have substantial electric charge within the Standard Model of
particle physics, nearly-extremally charged BHs could occur in models of
minicharged dark matter and dark photons. We begin by studying the test-body
limit for a binary BH in EMd theory, and we argue that only very compact
binaries of nearly-extremally charged BHs can manifest non-perturbative
phenomena similar to those found in certain scalar-tensor theories. Then, we
use the post-Newtonian approximation to study the dynamics of binary BHs with
arbitrary mass ratios. We derive the equations governing the conservative and
dissipative sectors of the dynamics at next-to-leading order, use our results
to compute the Fourier-domain gravitational waveform in the stationary-phase
approximation, and compute the number of useful cycles measurable by the
Advanced LIGO detector. Finally, we construct two effective-one-body (EOB)
Hamiltonians for binary BHs in EMd theory: one that reproduces the exact
test-body limit and another whose construction more closely resembles similar
models in General Relativity, and thus could be more easily integrated into
existing EOB waveform models used in the data analysis of gravitational-wave
events by the LIGO and Virgo collaborations.
|
[
{
"created": "Mon, 3 Sep 2018 16:07:05 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Nov 2018 18:35:56 GMT",
"version": "v2"
}
] |
2018-11-15
|
[
[
"Khalil",
"Mohammed",
""
],
[
"Sennett",
"Noah",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Vines",
"Justin",
""
],
[
"Buonanno",
"Alessandra",
""
]
] |
In General Relativity and many modified theories of gravity, isolated black holes (BHs) cannot source massless scalar fields. Einstein-Maxwell-dilaton (EMd) theory is an exception: through couplings both to electromagnetism and (non-minimally) to gravity, a massless scalar field can be generated by an electrically charged BH. In this work, we analytically model the dynamics of binaries comprised of such scalar-charged ("hairy") BHs. While BHs are not expected to have substantial electric charge within the Standard Model of particle physics, nearly-extremally charged BHs could occur in models of minicharged dark matter and dark photons. We begin by studying the test-body limit for a binary BH in EMd theory, and we argue that only very compact binaries of nearly-extremally charged BHs can manifest non-perturbative phenomena similar to those found in certain scalar-tensor theories. Then, we use the post-Newtonian approximation to study the dynamics of binary BHs with arbitrary mass ratios. We derive the equations governing the conservative and dissipative sectors of the dynamics at next-to-leading order, use our results to compute the Fourier-domain gravitational waveform in the stationary-phase approximation, and compute the number of useful cycles measurable by the Advanced LIGO detector. Finally, we construct two effective-one-body (EOB) Hamiltonians for binary BHs in EMd theory: one that reproduces the exact test-body limit and another whose construction more closely resembles similar models in General Relativity, and thus could be more easily integrated into existing EOB waveform models used in the data analysis of gravitational-wave events by the LIGO and Virgo collaborations.
|
gr-qc/0201062
|
Carlos Lousto
|
S.Dain (AEI), C.O.Lousto (AEI-UTBrownsville), and R.Takahashi
(TAC-Copenhagen)
|
New conformally flat initial data for spinning black holes
|
6 pages, 4 figures, RevTeX 4
|
Phys.Rev. D65 (2002) 104038
|
10.1103/PhysRevD.65.104038
|
AEI-2002-009
|
gr-qc
| null |
We obtain an explicit solution of the momentum constraint for conformally
flat, maximal slicing, initial data which gives an alternative to the purely
longitudinal extrinsic curvature of Bowen and York. The new solution is
related, in a precise form, with the extrinsic curvature of a Kerr slice. We
study these new initial data representing spinning black holes by numerically
solving the Hamiltonian constraint. They have the following features: i)
Contain less radiation, for all allowed values of the rotation parameter, than
the corresponding single spinning Bowen-York black hole. ii) The maximum
rotation parameter $J/m^2$ reached by this solution is higher than that of the
purely longitudinal solution allowing thus to describe holes closer to a
maximally rotating Kerr one. We discuss the physical interpretation of these
properties and their relation with the weak cosmic censorship conjecture.
Finally, we generalize the data for multiple black holes using the ``puncture''
and isometric formulations.
|
[
{
"created": "Fri, 18 Jan 2002 17:24:37 GMT",
"version": "v1"
}
] |
2009-11-07
|
[
[
"Dain",
"S.",
"",
"AEI"
],
[
"Lousto",
"C. O.",
"",
"AEI-UTBrownsville"
],
[
"Takahashi",
"R.",
"",
"TAC-Copenhagen"
]
] |
We obtain an explicit solution of the momentum constraint for conformally flat, maximal slicing, initial data which gives an alternative to the purely longitudinal extrinsic curvature of Bowen and York. The new solution is related, in a precise form, with the extrinsic curvature of a Kerr slice. We study these new initial data representing spinning black holes by numerically solving the Hamiltonian constraint. They have the following features: i) Contain less radiation, for all allowed values of the rotation parameter, than the corresponding single spinning Bowen-York black hole. ii) The maximum rotation parameter $J/m^2$ reached by this solution is higher than that of the purely longitudinal solution allowing thus to describe holes closer to a maximally rotating Kerr one. We discuss the physical interpretation of these properties and their relation with the weak cosmic censorship conjecture. Finally, we generalize the data for multiple black holes using the ``puncture'' and isometric formulations.
|
1807.09699
|
Igor Khavkine
|
Igor Khavkine
|
IDEAL characterization of higher dimensional spherically symmetric black
holes
|
v2: 16 pages, close to published version; v1: 15 pages
|
Class. Quantum Grav. 36 (2019) 045001
|
10.1088/1361-6382/aafcf1
| null |
gr-qc math-ph math.MP
|
http://creativecommons.org/licenses/by/4.0/
|
In general relativity, an IDEAL (Intrinsic, Deductive, Explicit, ALgorithmic)
characterization of a reference spacetime metric $g_0$ consists of a set of
tensorial equations $T[g]=0$, constructed covariantly out of the metric $g$,
its Riemann curvature and their derivatives, that are satisfied if and only if
$g$ is locally isometric to the reference spacetime metric $g_0$. We give the
first IDEAL characterization of generalized Schwarzschild-Tangherlini
spacetimes, which consist of $\Lambda$-vacuum extensions of higher dimensional
spherically symmetric black holes, as well as their versions where spheres are
replaced by flat or hyperbolic spaces. The standard Schwarzschild black hole
has been previously characterized in the work of Ferrando and S\'aez, but using
methods highly specific to $4$ dimensions. Specialized to $4$ dimensions, our
result provides an independent, alternative characterization. We also give a
proof of a version of Birkhoff's theorem that is applicable also on
neighborhoods of horizon and horizon bifurcation points, which is necessary for
our arguments.
|
[
{
"created": "Wed, 25 Jul 2018 16:24:41 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Sep 2019 09:41:08 GMT",
"version": "v2"
}
] |
2019-09-20
|
[
[
"Khavkine",
"Igor",
""
]
] |
In general relativity, an IDEAL (Intrinsic, Deductive, Explicit, ALgorithmic) characterization of a reference spacetime metric $g_0$ consists of a set of tensorial equations $T[g]=0$, constructed covariantly out of the metric $g$, its Riemann curvature and their derivatives, that are satisfied if and only if $g$ is locally isometric to the reference spacetime metric $g_0$. We give the first IDEAL characterization of generalized Schwarzschild-Tangherlini spacetimes, which consist of $\Lambda$-vacuum extensions of higher dimensional spherically symmetric black holes, as well as their versions where spheres are replaced by flat or hyperbolic spaces. The standard Schwarzschild black hole has been previously characterized in the work of Ferrando and S\'aez, but using methods highly specific to $4$ dimensions. Specialized to $4$ dimensions, our result provides an independent, alternative characterization. We also give a proof of a version of Birkhoff's theorem that is applicable also on neighborhoods of horizon and horizon bifurcation points, which is necessary for our arguments.
|
1605.01037
|
Salvatore Vitale
|
Salvatore Vitale
|
Multi-band gravitational-wave astronomy: parameter estimation and tests
of general relativity with space and ground-based detectors
| null |
Phys. Rev. Lett. 117, 051102 (2016)
|
10.1103/PhysRevLett.117.051102
|
LIGO P1600138
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
With the discovery of the black hole binary (BBH) coalescence GW150914 the
era of gravitational-wave (GW) astronomy has started. It has recently been
shown that BBH with masses comparable to or higher than GW150914 would be
visible in the eLISA band a few years before they finally merge in the band of
ground-based detectors. This would allow for pre-merger electromagnetic alerts,
dramatically increasing the chances of a joint detection, if BBH are indeed
luminous in the electromagnetic band. In this paper we explore a quite
different aspect of multi-band GW astronomy, and verify if, and to what extent,
measurement of masses and sky position with eLISA could improve parameter
estimation and tests of general relativity with ground-based detectors. We
generate a catalog of 200 BBH and find that having prior information from eLISA
can reduce the uncertainty in the measurement of source distance and primary
black hole spin by up to factor of 2 in ground-based GW detectors. The
component masses estimate from eLISA will not be refined by the ground based
detectors, whereas joint analysis will yield precise characterization of the
newly formed black hole and improve consistency tests of general relativity.
|
[
{
"created": "Tue, 3 May 2016 19:32:09 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jun 2016 03:44:26 GMT",
"version": "v2"
}
] |
2017-03-02
|
[
[
"Vitale",
"Salvatore",
""
]
] |
With the discovery of the black hole binary (BBH) coalescence GW150914 the era of gravitational-wave (GW) astronomy has started. It has recently been shown that BBH with masses comparable to or higher than GW150914 would be visible in the eLISA band a few years before they finally merge in the band of ground-based detectors. This would allow for pre-merger electromagnetic alerts, dramatically increasing the chances of a joint detection, if BBH are indeed luminous in the electromagnetic band. In this paper we explore a quite different aspect of multi-band GW astronomy, and verify if, and to what extent, measurement of masses and sky position with eLISA could improve parameter estimation and tests of general relativity with ground-based detectors. We generate a catalog of 200 BBH and find that having prior information from eLISA can reduce the uncertainty in the measurement of source distance and primary black hole spin by up to factor of 2 in ground-based GW detectors. The component masses estimate from eLISA will not be refined by the ground based detectors, whereas joint analysis will yield precise characterization of the newly formed black hole and improve consistency tests of general relativity.
|
gr-qc/0510128
|
Jos\'e Cleriston Campos de Souza Mr
|
J. C. C. Souza, A. Saa
|
Phase space solutions in scalar-tensor cosmological models
|
revtex, 2 pages, 4 eps figures, to appear in Brazilian Journal of
Physics (proceedings of the Conference 100 Years of Relativity, Sao Paulo,
Brazil, August 2005)
|
Braz.J.Phys. 35 (2005) 1041-1043
| null | null |
gr-qc
| null |
An analysis of the solutions for the field equations of generalized
scalar-tensor theories of gravitation is performed through the study of the
geometry of the phase space and the stability of the solutions, with special
interest in the Brans-Dicke model. Particularly, we believe to be possible to
find suitable forms of the Brans-Dicke parameter omega and potential V of the
scalar field, using the dynamical systems approach, in such a way that they can
be fitted in the present observed scenario of the Universe.
|
[
{
"created": "Mon, 31 Oct 2005 17:50:55 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Souza",
"J. C. C.",
""
],
[
"Saa",
"A.",
""
]
] |
An analysis of the solutions for the field equations of generalized scalar-tensor theories of gravitation is performed through the study of the geometry of the phase space and the stability of the solutions, with special interest in the Brans-Dicke model. Particularly, we believe to be possible to find suitable forms of the Brans-Dicke parameter omega and potential V of the scalar field, using the dynamical systems approach, in such a way that they can be fitted in the present observed scenario of the Universe.
|
2007.00227
|
Alana Carolina Lima Dos Santos
|
A. C. L. Santos, C. R. Muniz and L. T. Oliveira
|
Casimir Effect in a Schwarzschild-Like Wormhole Spacetime
|
15 pages, 2 figures
| null |
10.1142/S0218271821500322
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
In this paper, we investigate the role of gravito-inertial effects on the
Casimir energy of a massless scalar field confined between two parallel plates
orbiting a static and zero tidal Schwarzschild-like wormhole, at zero
temperature. Firstly, we obtain the metric in isotropic coordinates, finding
the allowed angular velocities and the circular orbit radii for a material
particle as well as for the photon. Following, we compute the changes induced
by both gravity and rotation of the plates in the energy density of the quantum
vacuum fluctuations associated to the scalar field, in the zero tidal
approximation inside the cavity. Finally, the Casimir energy obtained for some
these wormholes are graphically compared between themselves and also with those
ones related to an Ellis wormhole as well as to a Schwarzschild black hole.
With this, the gravito-inertial effects on the quantum vacuum fluctuations
analyzed in this work allow to recognize and identify both the geometry and
topology of the spacetime associated to each one of these objects.
|
[
{
"created": "Wed, 1 Jul 2020 04:28:07 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Jul 2020 11:59:26 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Feb 2021 23:23:28 GMT",
"version": "v3"
}
] |
2021-03-02
|
[
[
"Santos",
"A. C. L.",
""
],
[
"Muniz",
"C. R.",
""
],
[
"Oliveira",
"L. T.",
""
]
] |
In this paper, we investigate the role of gravito-inertial effects on the Casimir energy of a massless scalar field confined between two parallel plates orbiting a static and zero tidal Schwarzschild-like wormhole, at zero temperature. Firstly, we obtain the metric in isotropic coordinates, finding the allowed angular velocities and the circular orbit radii for a material particle as well as for the photon. Following, we compute the changes induced by both gravity and rotation of the plates in the energy density of the quantum vacuum fluctuations associated to the scalar field, in the zero tidal approximation inside the cavity. Finally, the Casimir energy obtained for some these wormholes are graphically compared between themselves and also with those ones related to an Ellis wormhole as well as to a Schwarzschild black hole. With this, the gravito-inertial effects on the quantum vacuum fluctuations analyzed in this work allow to recognize and identify both the geometry and topology of the spacetime associated to each one of these objects.
|
gr-qc/0106065
|
Christodoulakis Theodosios
|
T. Christodoulakis, T. Gakis, G.O. Papadopoulos
|
Conditional Symmetries and the Quantization of Bianchi Type I Vacuum
Cosmologies with and without Cosmological Constant
|
LaTeX, 13 Pages
|
Class.Quant.Grav.19:1013-1026,2002
|
10.1088/0264-9381/19/6/301
|
UA/NPPS-5-2001
|
gr-qc
| null |
In this work, the quantization of the most general Bianchi Type I geometry,
with and without a cosmological constant, is considered. In the spirit of
identifying and subsequently removing as many gauge degrees of freedom as
possible, a reduction of the initial 6--dimensional configuration space is
presented. This reduction is achieved by imposing as additional conditions on
the wave function, the quantum version of the --linear in momenta-- classical
integrals of motion (conditional symmetries). The vector fields inferred from
these integrals induce, through their integral curves, motions in the
configuration space which can be identified to the action of the automorphism
group of Type I, i.e. $GL(3,\Re)$. Thus, a wave function depending on one
degree of freedom, namely the determinant of the scale factor matrix, is found.
A measure for constructing the Hilbert space is proposed. This measure respects
the above mentioned symmetries, and is also invariant under the classical
property of covariance under arbitrary scalings of the Hamiltonian (quadratic
constraint).
|
[
{
"created": "Thu, 21 Jun 2001 10:13:52 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Nov 2001 12:48:20 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Dec 2001 10:49:53 GMT",
"version": "v3"
}
] |
2008-11-26
|
[
[
"Christodoulakis",
"T.",
""
],
[
"Gakis",
"T.",
""
],
[
"Papadopoulos",
"G. O.",
""
]
] |
In this work, the quantization of the most general Bianchi Type I geometry, with and without a cosmological constant, is considered. In the spirit of identifying and subsequently removing as many gauge degrees of freedom as possible, a reduction of the initial 6--dimensional configuration space is presented. This reduction is achieved by imposing as additional conditions on the wave function, the quantum version of the --linear in momenta-- classical integrals of motion (conditional symmetries). The vector fields inferred from these integrals induce, through their integral curves, motions in the configuration space which can be identified to the action of the automorphism group of Type I, i.e. $GL(3,\Re)$. Thus, a wave function depending on one degree of freedom, namely the determinant of the scale factor matrix, is found. A measure for constructing the Hilbert space is proposed. This measure respects the above mentioned symmetries, and is also invariant under the classical property of covariance under arbitrary scalings of the Hamiltonian (quadratic constraint).
|
1308.3659
|
Walter Simon
|
David Fajman and Walter Simon
|
Area inequalities for stable marginally outer trapped surfaces in
Einstein-Maxwell-dilaton theory
|
minor changes to v2
|
Adv. Theor. Math. Phys. 18, 687-707 (2014)
| null |
UWThPh-2013-18
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We prove area inequalities for stable marginally outer trapped surfaces in
Einstein-Maxwell-dilaton theory. Our inspiration comes on the one hand from a
corresponding upper bound for the area in terms of the charges obtained
recently by Dain, Jaramillo and Reiris [1] in the pure Einstein-Maxwell case
without symmetries, and on the other hand from Yazadjiev's inequality [2] in
the axially symmetric Einstein-Maxwell-dilaton case. The common issue in these
proofs and in the present one is a functional ${\mathscr W}$ of the matter
fields for which the stability condition readily yields an {\it upper} bound.
On the other hand, the step which crucially depends on whether or not a dilaton
field is present is to obtain a {\it lower} bound for ${\mathscr W}$ as well.
We obtain the latter by first setting up a variational principle for ${\mathscr
W}$ with respect to the dilaton field $\phi$, then by proving existence of a
minimizer $\psi$ as solution of the corresponding Euler-Lagrange equations and
finally by estimating ${\mathscr W}(\psi)$. In the special case that the normal
components of the electric and magnetic fields are proportional we obtain the
area bound $A \ge 8\pi P Q$ in terms of the electric and magnetic charges. In
the generic case our results are less explicit but imply rigorous
`perturbation' results for the above inequality. All our inequalities are
saturated for a 2-parameter family of static, extreme solutions found by
Gibbons [3]. Via the Bekenstein-Hawking relation $A = 4S$ our results give
positive lower bounds for the entropy $S$ which are particularly interesting in
the Einstein-Maxwell-dilaton case.
|
[
{
"created": "Fri, 16 Aug 2013 16:02:28 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Aug 2013 12:05:56 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Oct 2014 12:31:29 GMT",
"version": "v3"
}
] |
2015-09-01
|
[
[
"Fajman",
"David",
""
],
[
"Simon",
"Walter",
""
]
] |
We prove area inequalities for stable marginally outer trapped surfaces in Einstein-Maxwell-dilaton theory. Our inspiration comes on the one hand from a corresponding upper bound for the area in terms of the charges obtained recently by Dain, Jaramillo and Reiris [1] in the pure Einstein-Maxwell case without symmetries, and on the other hand from Yazadjiev's inequality [2] in the axially symmetric Einstein-Maxwell-dilaton case. The common issue in these proofs and in the present one is a functional ${\mathscr W}$ of the matter fields for which the stability condition readily yields an {\it upper} bound. On the other hand, the step which crucially depends on whether or not a dilaton field is present is to obtain a {\it lower} bound for ${\mathscr W}$ as well. We obtain the latter by first setting up a variational principle for ${\mathscr W}$ with respect to the dilaton field $\phi$, then by proving existence of a minimizer $\psi$ as solution of the corresponding Euler-Lagrange equations and finally by estimating ${\mathscr W}(\psi)$. In the special case that the normal components of the electric and magnetic fields are proportional we obtain the area bound $A \ge 8\pi P Q$ in terms of the electric and magnetic charges. In the generic case our results are less explicit but imply rigorous `perturbation' results for the above inequality. All our inequalities are saturated for a 2-parameter family of static, extreme solutions found by Gibbons [3]. Via the Bekenstein-Hawking relation $A = 4S$ our results give positive lower bounds for the entropy $S$ which are particularly interesting in the Einstein-Maxwell-dilaton case.
|
0812.3200
|
Laurent Freidel
|
Laurent Freidel
|
Modified gravity without new degrees of freedom
|
19 pages
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We show that the new type of "non-metric" gravity theories introduced
independently by Bengtsson and Krasnov can in fact be reexpressed explicitely
as a metrical theory coupled to an auxiliary field. We unravel why such
theories possess only one propagating graviton by looking at the quadratic
perturbation around a fixed solution. And we give a general construction
principle with a new class of example of such modified gravity theories still
possessing only two propagating degrees of freedom.
|
[
{
"created": "Wed, 17 Dec 2008 03:33:22 GMT",
"version": "v1"
}
] |
2008-12-18
|
[
[
"Freidel",
"Laurent",
""
]
] |
We show that the new type of "non-metric" gravity theories introduced independently by Bengtsson and Krasnov can in fact be reexpressed explicitely as a metrical theory coupled to an auxiliary field. We unravel why such theories possess only one propagating graviton by looking at the quadratic perturbation around a fixed solution. And we give a general construction principle with a new class of example of such modified gravity theories still possessing only two propagating degrees of freedom.
|
gr-qc/0405120
|
Valery Gavrilov
|
J.-M. Alimi, V. R. Gavrilov and V. N. Melnikov
|
Multicomponent perfect fluid with variable parameters in n Ricci-flat
spaces
|
12 pages
|
J.Korean Phys.Soc. 45 (2004) S148-S154
| null | null |
gr-qc
| null |
D-dimensional cosmological model describing the evolution of a multicomponent
perfect fluid with variable barotropic parameters in n Ricci-flat spaces is
investigated. The equations of motion are integrated for the case, when each
component possesses an isotropic pressure with respect to all spaces. Exact
solutions are presented in the Kasner-like form. Some explicit examples are
given: 4-dimensional model with an isotropic accelerated expansion at late
times and (4+d)-dimensional model describing a compactification of extra
dimensions.
|
[
{
"created": "Mon, 24 May 2004 05:39:50 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Alimi",
"J. -M.",
""
],
[
"Gavrilov",
"V. R.",
""
],
[
"Melnikov",
"V. N.",
""
]
] |
D-dimensional cosmological model describing the evolution of a multicomponent perfect fluid with variable barotropic parameters in n Ricci-flat spaces is investigated. The equations of motion are integrated for the case, when each component possesses an isotropic pressure with respect to all spaces. Exact solutions are presented in the Kasner-like form. Some explicit examples are given: 4-dimensional model with an isotropic accelerated expansion at late times and (4+d)-dimensional model describing a compactification of extra dimensions.
|
2001.08750
|
Alexandru Lupsasca
|
Elizabeth Himwich, Michael D. Johnson, Alexandru Lupsasca, Andrew
Strominger
|
Universal Polarimetric Signatures of the Black Hole Photon Ring
|
13 pages, 4 figures
|
Phys. Rev. D 101, 084020 (2020)
|
10.1103/PhysRevD.101.084020
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Black hole images present an annular region of enhanced brightness. In the
absence of propagation effects, this "photon ring" has universal features that
are completely governed by general relativity and independent of the details of
the emission. Here, we show that the polarimetric image of a black hole also
displays universal properties. In particular, the photon ring exhibits a
self-similar pattern of polarization that encodes the black hole spin. We
explore the corresponding universal polarimetric signatures of the photon ring
on long interferometric baselines, and propose a method for measuring the black
hole spin using a sparse interferometric array. These signatures could enable
spin measurements of the supermassive black hole in M87, as well as precision
tests of general relativity in the strong field regime, via a future extension
of the Event Horizon Telescope to space.
|
[
{
"created": "Thu, 23 Jan 2020 19:00:00 GMT",
"version": "v1"
}
] |
2020-04-15
|
[
[
"Himwich",
"Elizabeth",
""
],
[
"Johnson",
"Michael D.",
""
],
[
"Lupsasca",
"Alexandru",
""
],
[
"Strominger",
"Andrew",
""
]
] |
Black hole images present an annular region of enhanced brightness. In the absence of propagation effects, this "photon ring" has universal features that are completely governed by general relativity and independent of the details of the emission. Here, we show that the polarimetric image of a black hole also displays universal properties. In particular, the photon ring exhibits a self-similar pattern of polarization that encodes the black hole spin. We explore the corresponding universal polarimetric signatures of the photon ring on long interferometric baselines, and propose a method for measuring the black hole spin using a sparse interferometric array. These signatures could enable spin measurements of the supermassive black hole in M87, as well as precision tests of general relativity in the strong field regime, via a future extension of the Event Horizon Telescope to space.
|
gr-qc/0407058
|
Evgeny Sorkin
|
Barak Kol and Evgeny Sorkin
|
On Black-Brane Instability In an Arbitrary Dimension
|
1+14 pages, 2 eps figures. Replaced with the published version
|
Class.Quant.Grav.21:4793-4804,2004
|
10.1088/0264-9381/21/21/003
| null |
gr-qc hep-th
| null |
The black-hole black-string system is known to exhibit critical dimensions
and therefore it is interesting to vary the spacetime dimension $D$, treating
it as a parameter of the system. We derive the large $D$ asymptotics of the
critical, i.e. marginally stable, string following an earlier numerical
analysis. For a background with an arbitrary compactification manifold we give
an expression for the critical mass of a corresponding black brane. This
expression is completely explicit for ${\bf T}^n$, the $n$ dimensional torus of
an arbitrary shape. An indication is given that by employing a higher
dimensional torus, rather than a single compact dimension, the total critical
dimension above which the nature of the black-brane black-hole phase transition
changes from sudden to smooth could be as low as $D\leq 11$.
|
[
{
"created": "Thu, 15 Jul 2004 18:20:26 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Nov 2004 07:31:55 GMT",
"version": "v2"
}
] |
2010-11-19
|
[
[
"Kol",
"Barak",
""
],
[
"Sorkin",
"Evgeny",
""
]
] |
The black-hole black-string system is known to exhibit critical dimensions and therefore it is interesting to vary the spacetime dimension $D$, treating it as a parameter of the system. We derive the large $D$ asymptotics of the critical, i.e. marginally stable, string following an earlier numerical analysis. For a background with an arbitrary compactification manifold we give an expression for the critical mass of a corresponding black brane. This expression is completely explicit for ${\bf T}^n$, the $n$ dimensional torus of an arbitrary shape. An indication is given that by employing a higher dimensional torus, rather than a single compact dimension, the total critical dimension above which the nature of the black-brane black-hole phase transition changes from sudden to smooth could be as low as $D\leq 11$.
|
2405.03902
|
Lucas C\'eleri
|
Marcos L. W. Basso, Jonas Maziero and Lucas Chibebe C\'eleri
|
Quantum fluctuation theorem in a curved spacetime
| null | null | null | null |
gr-qc quant-ph
|
http://creativecommons.org/licenses/by/4.0/
|
The interplay between thermodynamics, general relativity and quantum
mechanics has long intrigued researchers. Recently, important advances have
been obtained in thermodynamics, mainly regarding its application to the
quantum domain through fluctuation theorems. In this letter, we apply Fermi
normal coordinates to report a fully general relativistic detailed quantum
fluctuation theorem based on the two point measurement scheme. We demonstrate
how the spacetime curvature can produce entropy in a localized quantum system
moving in a general spacetime. The example of a quantum harmonic oscillator
living in an expanding universe is presented. This result implies that entropy
production is strongly observer dependent and deeply connects the arrow of time
with the causal structure of the spacetime.
|
[
{
"created": "Mon, 6 May 2024 23:16:50 GMT",
"version": "v1"
}
] |
2024-05-08
|
[
[
"Basso",
"Marcos L. W.",
""
],
[
"Maziero",
"Jonas",
""
],
[
"Céleri",
"Lucas Chibebe",
""
]
] |
The interplay between thermodynamics, general relativity and quantum mechanics has long intrigued researchers. Recently, important advances have been obtained in thermodynamics, mainly regarding its application to the quantum domain through fluctuation theorems. In this letter, we apply Fermi normal coordinates to report a fully general relativistic detailed quantum fluctuation theorem based on the two point measurement scheme. We demonstrate how the spacetime curvature can produce entropy in a localized quantum system moving in a general spacetime. The example of a quantum harmonic oscillator living in an expanding universe is presented. This result implies that entropy production is strongly observer dependent and deeply connects the arrow of time with the causal structure of the spacetime.
|
2210.01833
|
Pedro V. P. Cunha
|
P. Cunha, C. Herdeiro, E. Radu, Ya. Shnir
|
Two boson stars in equilibrium
|
22 pages, 8 figures; Some data can be found in
http://gravitation.web.ua.pt/node/4065
| null |
10.1103/PhysRevD.106.124039
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We construct and explore the solution space of two non-spinning, mini-boson
stars in equilibrium, in fully non-linear General Relativity (GR), minimally
coupled to a free, massive, complex scalar field. The equilibrium is due to the
balance between the (long range) gravitational attraction and the (short-range)
scalar mediated repulsion, the latter enabled by a $\pi$ relative phase.
Gravity is \textit{mandatory}; it is shown no similar solutions exist in flat
spacetime, replacing gravity by non-linear scalar interactions. We study the
variation of the proper distance between the stars with their mass (or
oscillation frequency), showing it can be qualitatively captured by a simple
analytic model that features the two competing interactions. Finally, we
discuss some physical properties of the solutions, including their
gravitational lensing.
|
[
{
"created": "Tue, 4 Oct 2022 18:06:21 GMT",
"version": "v1"
}
] |
2023-01-11
|
[
[
"Cunha",
"P.",
""
],
[
"Herdeiro",
"C.",
""
],
[
"Radu",
"E.",
""
],
[
"Shnir",
"Ya.",
""
]
] |
We construct and explore the solution space of two non-spinning, mini-boson stars in equilibrium, in fully non-linear General Relativity (GR), minimally coupled to a free, massive, complex scalar field. The equilibrium is due to the balance between the (long range) gravitational attraction and the (short-range) scalar mediated repulsion, the latter enabled by a $\pi$ relative phase. Gravity is \textit{mandatory}; it is shown no similar solutions exist in flat spacetime, replacing gravity by non-linear scalar interactions. We study the variation of the proper distance between the stars with their mass (or oscillation frequency), showing it can be qualitatively captured by a simple analytic model that features the two competing interactions. Finally, we discuss some physical properties of the solutions, including their gravitational lensing.
|
1908.06050
|
Archisman Ghosh
|
Rachel Gray, Ignacio Maga\~na Hernandez, Hong Qi, Ankan Sur, Patrick
R. Brady, Hsin-Yu Chen, Will M. Farr, Maya Fishbach, Jonathan R. Gair,
Archisman Ghosh, Daniel E. Holz, Simone Mastrogiovanni, Christopher
Messenger, Dani\`ele A. Steer, John Veitch
|
Cosmological Inference using Gravitational Wave Standard Sirens: A Mock
Data Challenge
|
19 pages, 8 figures
|
Phys. Rev. D 101, 122001 (2020)
|
10.1103/PhysRevD.101.122001
|
LIGO-P1900017
|
gr-qc astro-ph.CO astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The observation of binary neutron star merger GW170817, along with its
optical counterpart, provided the first constraint on the Hubble constant $H_0$
using gravitational wave standard sirens. When no counterpart is identified, a
galaxy catalog can be used to provide the necessary redshift information.
However, the true host might not be contained in a catalog which is not
complete out to the limit of gravitational-wave detectability. These
electromagnetic and gravitational-wave selection effects must be accounted for.
We describe and implement a method to estimate $H_0$ using both the counterpart
and the galaxy catalog standard siren methods. We perform a series of mock data
analyses using binary neutron star mergers to confirm our ability to recover an
unbiased estimate of $H_0$. Our simulations used a simplified universe with no
redshift uncertainties or galaxy clustering, but with different
magnitude-limited catalogs and assumed host galaxy properties, to test our
treatment of both selection effects. We explore how the incompleteness of
catalogs affects the final measurement of $H_0$, as well as the effect of
weighting each galaxy's likelihood of being a host by its luminosity. In our
most realistic simulation, where the simulated catalog is about three times
denser than the density of galaxies in the local universe, we find that a 4.4\%
measurement precision can be reached using galaxy catalogs with 50\%
completeness and $\sim 250$ binary neutron star detections with sensitivity
similar to that of Advanced LIGO's second observing run.
|
[
{
"created": "Fri, 16 Aug 2019 16:30:53 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Aug 2019 16:45:59 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Oct 2019 17:57:23 GMT",
"version": "v3"
},
{
"created": "Fri, 12 Jun 2020 17:10:36 GMT",
"version": "v4"
}
] |
2020-06-15
|
[
[
"Gray",
"Rachel",
""
],
[
"Hernandez",
"Ignacio Magaña",
""
],
[
"Qi",
"Hong",
""
],
[
"Sur",
"Ankan",
""
],
[
"Brady",
"Patrick R.",
""
],
[
"Chen",
"Hsin-Yu",
""
],
[
"Farr",
"Will M.",
""
],
[
"Fishbach",
"Maya",
""
],
[
"Gair",
"Jonathan R.",
""
],
[
"Ghosh",
"Archisman",
""
],
[
"Holz",
"Daniel E.",
""
],
[
"Mastrogiovanni",
"Simone",
""
],
[
"Messenger",
"Christopher",
""
],
[
"Steer",
"Danièle A.",
""
],
[
"Veitch",
"John",
""
]
] |
The observation of binary neutron star merger GW170817, along with its optical counterpart, provided the first constraint on the Hubble constant $H_0$ using gravitational wave standard sirens. When no counterpart is identified, a galaxy catalog can be used to provide the necessary redshift information. However, the true host might not be contained in a catalog which is not complete out to the limit of gravitational-wave detectability. These electromagnetic and gravitational-wave selection effects must be accounted for. We describe and implement a method to estimate $H_0$ using both the counterpart and the galaxy catalog standard siren methods. We perform a series of mock data analyses using binary neutron star mergers to confirm our ability to recover an unbiased estimate of $H_0$. Our simulations used a simplified universe with no redshift uncertainties or galaxy clustering, but with different magnitude-limited catalogs and assumed host galaxy properties, to test our treatment of both selection effects. We explore how the incompleteness of catalogs affects the final measurement of $H_0$, as well as the effect of weighting each galaxy's likelihood of being a host by its luminosity. In our most realistic simulation, where the simulated catalog is about three times denser than the density of galaxies in the local universe, we find that a 4.4\% measurement precision can be reached using galaxy catalogs with 50\% completeness and $\sim 250$ binary neutron star detections with sensitivity similar to that of Advanced LIGO's second observing run.
|
gr-qc/9912050
|
Jose M. M. Senovilla
|
J. M. M. Senovilla
|
Applications of Super-Energy Tensors
|
10 pages, no figures, LaTeX. Contribution to appear in the
Proceedings of the Spanish Relativity Meeting ERE-99
| null | null | null |
gr-qc
| null |
In this contribution I intend to give a summary of the new relevant results
obtained by using the general superenergy tensors. After a quick review of the
definition and properties of these tensors, several of their mathematical and
physical applications are presented. In particular, their interest and
usefulness is mentioned or explicitly analyzed in 1) the study of causal
propagation of general fields; 2) the existence of an infinite number of
conserved quantities in Ricci-flat spacetimes; 3) the different gravitational
theories, such as Einstein's General Relativity or, say, $n=11$ supergravity;
4) the appearance of some scalars possibly related to entropy or quality
factors; 5) the possibility of superenergy exchange between different physical
fields and the appearance of mixed conserved currents.
|
[
{
"created": "Mon, 13 Dec 1999 20:03:51 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Senovilla",
"J. M. M.",
""
]
] |
In this contribution I intend to give a summary of the new relevant results obtained by using the general superenergy tensors. After a quick review of the definition and properties of these tensors, several of their mathematical and physical applications are presented. In particular, their interest and usefulness is mentioned or explicitly analyzed in 1) the study of causal propagation of general fields; 2) the existence of an infinite number of conserved quantities in Ricci-flat spacetimes; 3) the different gravitational theories, such as Einstein's General Relativity or, say, $n=11$ supergravity; 4) the appearance of some scalars possibly related to entropy or quality factors; 5) the possibility of superenergy exchange between different physical fields and the appearance of mixed conserved currents.
|
2308.12990
|
Shahar Hod
|
Shahar Hod
|
Analytic study of the Maxwell electromagnetic invariant in spinning and
charged Kerr-Newman black-hole spacetimes
|
20 pages
|
Journal of High Energy Physics 09, 140 (2023)
| null | null |
gr-qc astro-ph.HE hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
The Maxwell invariant plays a fundamental role in the mathematical
description of electromagnetic fields in charged spacetimes. We present a
detailed {\it analytical} study of the physical and mathematical properties of
the Maxwell electromagnetic invariant ${\cal F}_{\text{KN}}(r,\theta;M,a,Q)$
which characterizes the Kerr-Newman black-hole spacetime. It is proved that,
for all Kerr-Newman black-hole spacetimes, the spin and charge dependent
minimum value of the Maxwell electromagnetic invariant is attained on the
equator of the black-hole surface. Interestingly, we reveal the physically
important fact that Kerr-Newman spacetimes are characterized by two critical
values of the dimensionless rotation parameter ${\hat a}\equiv a/r_+$, ${\hat
a}^{-}_{\text{crit}}=\sqrt{3-2\sqrt{2}}$ and ${\hat a}^{+}_{\text{crit}}=
\sqrt{5-2\sqrt{5}}$, which mark the boundaries between three qualitatively
different spatial functional behaviors of the Maxwell electromagnetic
invariant: (i) Kerr-Newman black holes in the slow-rotation ${\hat a}<{\hat
a}^{-}_{\text{crit}}$ regime are characterized by negative definite Maxwell
electromagnetic invariants that increase monotonically towards spatial
infinity, (ii) for black holes in the intermediate spin regime ${\hat
a}^{-}_{\text{crit}}\leq {\hat a}\leq{\hat a}^{+}_{\text{crit}}$, the positive
global maximum of the Kerr-Newman Maxwell electromagnetic invariant is located
at the black-hole poles, and (iii) Kerr-Newman black holes in the
super-critical regime ${\hat a}>{\hat a}^{+}_{\text{crit}}$ are characterized
by a non-monotonic spatial behavior of the Maxwell electromagnetic invariant
along the black-hole horizon with a spin and charge dependent global maximum
whose polar angular location is characterized by the dimensionless functional
relation ${\hat a}^2\cdot(\cos^2\theta)_{\text{max}}=5-2\sqrt{5}$.
|
[
{
"created": "Thu, 24 Aug 2023 18:00:02 GMT",
"version": "v1"
}
] |
2023-09-27
|
[
[
"Hod",
"Shahar",
""
]
] |
The Maxwell invariant plays a fundamental role in the mathematical description of electromagnetic fields in charged spacetimes. We present a detailed {\it analytical} study of the physical and mathematical properties of the Maxwell electromagnetic invariant ${\cal F}_{\text{KN}}(r,\theta;M,a,Q)$ which characterizes the Kerr-Newman black-hole spacetime. It is proved that, for all Kerr-Newman black-hole spacetimes, the spin and charge dependent minimum value of the Maxwell electromagnetic invariant is attained on the equator of the black-hole surface. Interestingly, we reveal the physically important fact that Kerr-Newman spacetimes are characterized by two critical values of the dimensionless rotation parameter ${\hat a}\equiv a/r_+$, ${\hat a}^{-}_{\text{crit}}=\sqrt{3-2\sqrt{2}}$ and ${\hat a}^{+}_{\text{crit}}= \sqrt{5-2\sqrt{5}}$, which mark the boundaries between three qualitatively different spatial functional behaviors of the Maxwell electromagnetic invariant: (i) Kerr-Newman black holes in the slow-rotation ${\hat a}<{\hat a}^{-}_{\text{crit}}$ regime are characterized by negative definite Maxwell electromagnetic invariants that increase monotonically towards spatial infinity, (ii) for black holes in the intermediate spin regime ${\hat a}^{-}_{\text{crit}}\leq {\hat a}\leq{\hat a}^{+}_{\text{crit}}$, the positive global maximum of the Kerr-Newman Maxwell electromagnetic invariant is located at the black-hole poles, and (iii) Kerr-Newman black holes in the super-critical regime ${\hat a}>{\hat a}^{+}_{\text{crit}}$ are characterized by a non-monotonic spatial behavior of the Maxwell electromagnetic invariant along the black-hole horizon with a spin and charge dependent global maximum whose polar angular location is characterized by the dimensionless functional relation ${\hat a}^2\cdot(\cos^2\theta)_{\text{max}}=5-2\sqrt{5}$.
|
0806.4640
|
Florian Conrady
|
Florian Conrady and Laurent Freidel (Perimeter Inst. Theor. Phys.)
|
Path integral representation of spin foam models of 4d gravity
|
29 pages, 6 figures
|
Class.Quant.Grav.25:245010,2008
|
10.1088/0264-9381/25/24/245010
|
PI-QG-84
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We give a unified description of all recent spin foam models introduced by
Engle, Livine, Pereira and Rovelli (ELPR) and by Freidel and Krasnov (FK). We
show that the FK models are, for all values of the Immirzi parameter,
equivalent to path integrals of a discrete theory and we provide an explicit
formula for the associated actions. We discuss the relation between the FK and
ELPR models and also study the corresponding boundary states. For general
Immirzi parameter, these are given by Alexandrov's and Livine's SO(4) projected
states. For 0 <= gamma < 1, the states can be restricted to SU(2) spin
networks.
|
[
{
"created": "Sat, 28 Jun 2008 01:42:19 GMT",
"version": "v1"
}
] |
2008-12-18
|
[
[
"Conrady",
"Florian",
"",
"Perimeter Inst. Theor. Phys."
],
[
"Freidel",
"Laurent",
"",
"Perimeter Inst. Theor. Phys."
]
] |
We give a unified description of all recent spin foam models introduced by Engle, Livine, Pereira and Rovelli (ELPR) and by Freidel and Krasnov (FK). We show that the FK models are, for all values of the Immirzi parameter, equivalent to path integrals of a discrete theory and we provide an explicit formula for the associated actions. We discuss the relation between the FK and ELPR models and also study the corresponding boundary states. For general Immirzi parameter, these are given by Alexandrov's and Livine's SO(4) projected states. For 0 <= gamma < 1, the states can be restricted to SU(2) spin networks.
|
2207.13369
|
Priti Gupta
|
Priti Gupta, Takafumi Kakehi, Takahiro Tanaka
|
Resonant jumps induced by stationary tidal perturbation: a two-for-one
deal
|
9 pages, 1 figure, submitted to Class. Quantum Grav
| null |
10.1088/1361-6382/aca1a3
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Extreme-mass-ratio inspirals (EMRIs) are promising target sources for
space-based interferometers such as LISA, Taiji, and Tianqin. Depending on the
astrophysical environment, such as close perturbers or an accretion disk, EMRI
orbital evolution may deviate from the predictions of general relativity in
vacuum. In particular, we focus on the resonance jumps, i.e., the changes of
the conserved quantities induced by a stationary perturbation to the background
Kerr geometry. Using Hamiltonian formulation, we provide a closed relation
between the jump in Carter constant and that in the axial component of angular
momentum. It is also shown that the obtained relation is consistent with the
fitting formulae computed for the tidal resonance in previous works.
|
[
{
"created": "Wed, 27 Jul 2022 08:50:12 GMT",
"version": "v1"
}
] |
2022-11-30
|
[
[
"Gupta",
"Priti",
""
],
[
"Kakehi",
"Takafumi",
""
],
[
"Tanaka",
"Takahiro",
""
]
] |
Extreme-mass-ratio inspirals (EMRIs) are promising target sources for space-based interferometers such as LISA, Taiji, and Tianqin. Depending on the astrophysical environment, such as close perturbers or an accretion disk, EMRI orbital evolution may deviate from the predictions of general relativity in vacuum. In particular, we focus on the resonance jumps, i.e., the changes of the conserved quantities induced by a stationary perturbation to the background Kerr geometry. Using Hamiltonian formulation, we provide a closed relation between the jump in Carter constant and that in the axial component of angular momentum. It is also shown that the obtained relation is consistent with the fitting formulae computed for the tidal resonance in previous works.
|
1201.2247
|
Colin Cunliff
|
Colin Cunliff
|
Conformal fluctuations do not establish a minimum length
| null |
Class. Quant. Grav. 29 (2012) 207001
|
10.1088/0264-9381/29/20/207001
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper corrects an earlier work suggesting that the quantum expectation
value of the proper length is bounded from below by the Planck length. The
original calculation examined fluctuations of the conformal factor of
Einstein-Hilbert gravity. However, in Einstein-Hilbert gravity, the conformal
factor is not a dynamical field subject to fluctuations. This paper performs
the same calculation using the trace anomaly-induced effective action for the
conformal factor and finds that, while conformal fluctuations modify the
short-distance behavior of the interval, the interval still approaches zero in
the coincidence limit.
|
[
{
"created": "Wed, 11 Jan 2012 05:55:54 GMT",
"version": "v1"
}
] |
2013-01-04
|
[
[
"Cunliff",
"Colin",
""
]
] |
This paper corrects an earlier work suggesting that the quantum expectation value of the proper length is bounded from below by the Planck length. The original calculation examined fluctuations of the conformal factor of Einstein-Hilbert gravity. However, in Einstein-Hilbert gravity, the conformal factor is not a dynamical field subject to fluctuations. This paper performs the same calculation using the trace anomaly-induced effective action for the conformal factor and finds that, while conformal fluctuations modify the short-distance behavior of the interval, the interval still approaches zero in the coincidence limit.
|
1804.02989
|
Mohammad Malekjani
|
I. A. Akhlaghi, M. Malekjani, S. Basilakos and H. Haghi
|
Model selection and constraints from Holographic dark energy scenarios
|
13 Pages, 7 Figures and 9 Tables. Accepted in MNRAS
|
MNRAS 477(3), 3659 (2018)
|
10.1093/mnras/sty903
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this study we combine the expansion and the growth data in order to
investigate the ability of the three most popular holographic dark energy
models, namely event future horizon, Ricci scale and Granda-Oliveros IR
cutoffs, to fit the data. Using a standard $\chi^2$ minimization method we
place tight constraints on the free parameters of the models. Based on the
values of the Akaike and Bayesian information criteria we find that two out of
three holographic dark energy models are disfavored by the data, because they
predict a non-negligible amount of dark energy density at early enough times.
Although the growth rate data are relatively consistent with the holographic
dark energy models which are based on Ricci scale and Granda-Oliveros IR
cutoffs, the combined analysis provides strong indications against these
models. Finally, we find that the model for which the holographic dark energy
is related with the future horizon is consistent with the combined
observational data.
|
[
{
"created": "Thu, 5 Apr 2018 18:36:03 GMT",
"version": "v1"
}
] |
2018-06-19
|
[
[
"Akhlaghi",
"I. A.",
""
],
[
"Malekjani",
"M.",
""
],
[
"Basilakos",
"S.",
""
],
[
"Haghi",
"H.",
""
]
] |
In this study we combine the expansion and the growth data in order to investigate the ability of the three most popular holographic dark energy models, namely event future horizon, Ricci scale and Granda-Oliveros IR cutoffs, to fit the data. Using a standard $\chi^2$ minimization method we place tight constraints on the free parameters of the models. Based on the values of the Akaike and Bayesian information criteria we find that two out of three holographic dark energy models are disfavored by the data, because they predict a non-negligible amount of dark energy density at early enough times. Although the growth rate data are relatively consistent with the holographic dark energy models which are based on Ricci scale and Granda-Oliveros IR cutoffs, the combined analysis provides strong indications against these models. Finally, we find that the model for which the holographic dark energy is related with the future horizon is consistent with the combined observational data.
|
1402.6026
|
Diego Carranza Diego Carranza
|
D.A. Carranza and S. Mendoza
|
Modified Newtonian Dynamics as an entropic force
|
6 pages. Accepted for publication in Journal of Modern Physics (JMP)
|
Journal of Modern Physics, 2015, 6, 786-793
|
10.4236/jmp.2015.66084
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Under natural assumptions on the thermodynamic properties of space and time
with the holographic principle we reproduce a MOND-like behaviour of gravity on
particular scales of mass and length, where Newtonian gravity requires a
modification or extension if no dark matter component is introduced in the
description of gravitational phenomena. The result is directly obtained with
the assumption that a fundamental constant of nature with dimensions of
acceleration needs to be introduced into gravitational interactions. This in
turn allows for modifications or extensions of the equipartion law and/or the
holographic principle. In other words, MOND-like phenomenology can be
reproduced when appropriate generalised concepts at the thermodynamical level
of space and/or at the holographic principle are introduced. Thermodynamical
modifications are reflected in extensions to the equipartition law which occur
when the temperature of the system drops below a critical value, equals to
Unruh's temperature evaluated at the acceleration constant scale introduced for
the description of the gravitational phenomena. Our calculations extend the
ones by Verlinde (2011) in which Newtonian gravity is shown to be an emergent
phenomenon, and together with it reinforces the idea that gravity at all scales
is emergent.
|
[
{
"created": "Tue, 25 Feb 2014 00:45:13 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jun 2014 19:43:22 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Jun 2015 05:05:42 GMT",
"version": "v3"
},
{
"created": "Wed, 14 Oct 2015 20:53:08 GMT",
"version": "v4"
}
] |
2015-10-16
|
[
[
"Carranza",
"D. A.",
""
],
[
"Mendoza",
"S.",
""
]
] |
Under natural assumptions on the thermodynamic properties of space and time with the holographic principle we reproduce a MOND-like behaviour of gravity on particular scales of mass and length, where Newtonian gravity requires a modification or extension if no dark matter component is introduced in the description of gravitational phenomena. The result is directly obtained with the assumption that a fundamental constant of nature with dimensions of acceleration needs to be introduced into gravitational interactions. This in turn allows for modifications or extensions of the equipartion law and/or the holographic principle. In other words, MOND-like phenomenology can be reproduced when appropriate generalised concepts at the thermodynamical level of space and/or at the holographic principle are introduced. Thermodynamical modifications are reflected in extensions to the equipartition law which occur when the temperature of the system drops below a critical value, equals to Unruh's temperature evaluated at the acceleration constant scale introduced for the description of the gravitational phenomena. Our calculations extend the ones by Verlinde (2011) in which Newtonian gravity is shown to be an emergent phenomenon, and together with it reinforces the idea that gravity at all scales is emergent.
|
2207.08004
|
Paul Halpern
|
Hootan Amani and Paul Halpern
|
Energy conditions in a modified Brans-Dicke theory
|
20 pages, 5 figures
|
General Relativity and Gravitation 54, 64 (2022)
|
10.1007/s10714-022-02950-3
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We consider a modified version of Brans-Dicke theory (MBDT) in four
dimensions obtained by applying the induced matter method of Wesson to a 5D
generalized Brans-Dicke theory. In 5D the model consists of pure vacuum, with
no self-interacting potential, except for a scalar field. Constraining the 5D
geometry to be a generalization of the anisotropic Bianchi type I universe
model first studied by Kasner, we derive the induced energy-momentum. We
discuss the energy conditions and their bounds in the MBDT with such an induced
imperfect fluid, with an eye toward a realistic model of the present-day
universe, and consider the large-scale behavior of that spatially homogeneous
and anisotropic model. We discuss how the energy conditions would be satisfied
or violated in the context of MBDT, with the aim of providing a feasible
description of the universe in the current era.
|
[
{
"created": "Sat, 16 Jul 2022 19:32:47 GMT",
"version": "v1"
}
] |
2022-07-19
|
[
[
"Amani",
"Hootan",
""
],
[
"Halpern",
"Paul",
""
]
] |
We consider a modified version of Brans-Dicke theory (MBDT) in four dimensions obtained by applying the induced matter method of Wesson to a 5D generalized Brans-Dicke theory. In 5D the model consists of pure vacuum, with no self-interacting potential, except for a scalar field. Constraining the 5D geometry to be a generalization of the anisotropic Bianchi type I universe model first studied by Kasner, we derive the induced energy-momentum. We discuss the energy conditions and their bounds in the MBDT with such an induced imperfect fluid, with an eye toward a realistic model of the present-day universe, and consider the large-scale behavior of that spatially homogeneous and anisotropic model. We discuss how the energy conditions would be satisfied or violated in the context of MBDT, with the aim of providing a feasible description of the universe in the current era.
|
gr-qc/0012034
|
Ronald W. Hellings
|
Ronald W. Hellings
|
Data Processing for LISA's Laser Interferometer Tracking System (LITS)
|
5 pages, Proceedings of the Third LISA Symposium (Golm, Germany,
2000)
|
Class.Quant.Grav. 18 (2001) 4075-4080
|
10.1088/0264-9381/18/19/315
| null |
gr-qc
| null |
The purpose of this paper is twofold. First, we will present recent results
on the data processing for LISA, including algorithms for elimination of clock
jitter noise and discussion of the generation of the data averages that will
eventually need to be telemetered to the ground. Second, we will argue, based
partly on these results, that a laser interferometer tracking system (LITS)
that employs independent lasers in each spacecraft is preferable for reasons of
simplicity to that in which the lasers in two of the spacecraft are locked to
the incoming beam from the third.
|
[
{
"created": "Fri, 8 Dec 2000 23:54:20 GMT",
"version": "v1"
}
] |
2016-08-31
|
[
[
"Hellings",
"Ronald W.",
""
]
] |
The purpose of this paper is twofold. First, we will present recent results on the data processing for LISA, including algorithms for elimination of clock jitter noise and discussion of the generation of the data averages that will eventually need to be telemetered to the ground. Second, we will argue, based partly on these results, that a laser interferometer tracking system (LITS) that employs independent lasers in each spacecraft is preferable for reasons of simplicity to that in which the lasers in two of the spacecraft are locked to the incoming beam from the third.
|
1203.3454
|
Bahram Mashhoon
|
D. Bini, C. Chicone, B. Mashhoon
|
Spacetime Splitting, Admissible Coordinates and Causality
|
25 pages, 3 figures; v2: minor typos corrected, accepted for
publication in Phys. Rev. D
|
Phys.Rev.D85:104020,2012
|
10.1103/PhysRevD.85.104020
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
To confront relativity theory with observation, it is necessary to split
spacetime into its temporal and spatial components. The (1+3) timelike
threading approach involves restrictions on the gravitational potentials
$(g_{\mu \nu})$, while the (3+1) spacelike slicing approach involves
restrictions on $(g^{\mu \nu})$. These latter coordinate conditions protect
chronology within any such coordinate patch. While the threading coordinate
conditions can be naturally integrated into the structure of Lorentzian
geometry and constitute the standard coordinate conditions in general
relativity, this circumstance does not extend to the slicing coordinate
conditions. We explore the influence of chronology violation on wave motion. In
particular, we consider the propagation of radiation parallel to the rotation
axis of stationary G\"odel-type universes characterized by parameters $\eta >
0$ and $\lambda > 0$ such that for $\eta < 1$ ($\eta >1$) chronology is
protected (violated). We show that in the WKB approximation such waves can
freely propagate only when chronology is protected.
|
[
{
"created": "Thu, 15 Mar 2012 19:46:33 GMT",
"version": "v1"
},
{
"created": "Wed, 9 May 2012 21:59:19 GMT",
"version": "v2"
}
] |
2013-05-30
|
[
[
"Bini",
"D.",
""
],
[
"Chicone",
"C.",
""
],
[
"Mashhoon",
"B.",
""
]
] |
To confront relativity theory with observation, it is necessary to split spacetime into its temporal and spatial components. The (1+3) timelike threading approach involves restrictions on the gravitational potentials $(g_{\mu \nu})$, while the (3+1) spacelike slicing approach involves restrictions on $(g^{\mu \nu})$. These latter coordinate conditions protect chronology within any such coordinate patch. While the threading coordinate conditions can be naturally integrated into the structure of Lorentzian geometry and constitute the standard coordinate conditions in general relativity, this circumstance does not extend to the slicing coordinate conditions. We explore the influence of chronology violation on wave motion. In particular, we consider the propagation of radiation parallel to the rotation axis of stationary G\"odel-type universes characterized by parameters $\eta > 0$ and $\lambda > 0$ such that for $\eta < 1$ ($\eta >1$) chronology is protected (violated). We show that in the WKB approximation such waves can freely propagate only when chronology is protected.
|
gr-qc/0507035
|
Etienne Takou
|
Etienne Takou and Norbert Noutchegueme
|
Global existence of solutions for the relativistic Boltzmann equation on
the flat Robertson-Walker space-time for arbitrarily large intial data
| null | null | null | null |
gr-qc
| null |
We prove a global result in time for the initial value problem for the
relativistic Boltzmann equation on the flat Robertson-Walker sapace time, in
the functional framework appropriate to the coupling with Einstein's equations.
We had nowhere to restrict the size of the initial data which can hence be
taken arbitrarily large.
|
[
{
"created": "Fri, 8 Jul 2005 08:36:14 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Mar 2006 10:38:54 GMT",
"version": "v2"
}
] |
2007-05-23
|
[
[
"Takou",
"Etienne",
""
],
[
"Noutchegueme",
"Norbert",
""
]
] |
We prove a global result in time for the initial value problem for the relativistic Boltzmann equation on the flat Robertson-Walker sapace time, in the functional framework appropriate to the coupling with Einstein's equations. We had nowhere to restrict the size of the initial data which can hence be taken arbitrarily large.
|
1710.01815
|
Andr\'es Ace\~na
|
Andr\'es Ace\~na, Ericson L\'opez and Mario Llerena
|
Isoperimetric surfaces and area-angular momentum inequality in a
rotating black hole in New Massive Gravity
|
9 pages, no figures
|
Phys. Rev. D 97, 064043 (2018)
|
10.1103/PhysRevD.97.064043
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the existence and stability of isoperimetric surfaces in a family of
rotating black holes in New Massive Gravity. We show that the stability of such
surfaces is determined by the sign of the hair parameter. We use the
isoperimetric surfaces to find a geometric inequality between the area and the
angular momentum of the black hole, conjecturing geometric inequalities for
more general black holes.
|
[
{
"created": "Wed, 4 Oct 2017 21:41:26 GMT",
"version": "v1"
}
] |
2018-04-04
|
[
[
"Aceña",
"Andrés",
""
],
[
"López",
"Ericson",
""
],
[
"Llerena",
"Mario",
""
]
] |
We study the existence and stability of isoperimetric surfaces in a family of rotating black holes in New Massive Gravity. We show that the stability of such surfaces is determined by the sign of the hair parameter. We use the isoperimetric surfaces to find a geometric inequality between the area and the angular momentum of the black hole, conjecturing geometric inequalities for more general black holes.
|
2307.02084
|
ChengGang Shao
|
Cai-Ying Shao, Yu Hu, Cheng-Gang Shao
|
Parameter estimation for Einstein-dilaton-Gauss-Bonnet gravity with
ringdown signals
|
to be published in Chinese Physics C
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Future space-based gravitational-wave detectors will detect gravitational
waves with high sensitivity in the millihertz frequency band, which provides
more opportunities to test theories of gravity than ground-based ones. The
study of quasinormal modes (QNMs) and their application to testing gravity
theories have been an important aspect in the field of gravitational physics.
In this study, we investigate the capability of future space-based
gravitational wave detectors such as LISA, TaiJi, and TianQin to constrain the
dimensionless deviating parameter for Einstein-dilaton-Gauss-Bonnet (EdGB)
gravity with ringdown signals from the merger of binary black holes. The
ringdown signal is modeled by the two strongest QNMs in EdGB gravity. Taking
into account time-delay interferometry, we calculate the signal-to-noise ratio
(SNR) of different space-based detectors for ringdown signals to analyze their
capabilities. The Fisher information matrix is employed to analyze the accuracy
of parameter estimation, with particular focus on the dimensionless deviating
parameter for EdGB gravity. The impact of the parameters of gravitational wave
sources on the estimation accuracy of the dimensionless deviating parameter has
also been studied. We find that the constraint ability of EdGB gravity is
limited because the uncertainty of the dimensionless deviating parameter
increases with the decrease of the dimensionless deviating parameter. LISA and
TaiJi has more advantages to constrain the dimensionless deviating parameter to
a more accurate level for the massive black hole, while TianQin is more
suitable for less massive black holes. Bayesian inference method is used to
perform parameter estimation on simulated data, which verifies the reliability
of the conclusion.
|
[
{
"created": "Wed, 5 Jul 2023 07:47:33 GMT",
"version": "v1"
}
] |
2023-07-06
|
[
[
"Shao",
"Cai-Ying",
""
],
[
"Hu",
"Yu",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] |
Future space-based gravitational-wave detectors will detect gravitational waves with high sensitivity in the millihertz frequency band, which provides more opportunities to test theories of gravity than ground-based ones. The study of quasinormal modes (QNMs) and their application to testing gravity theories have been an important aspect in the field of gravitational physics. In this study, we investigate the capability of future space-based gravitational wave detectors such as LISA, TaiJi, and TianQin to constrain the dimensionless deviating parameter for Einstein-dilaton-Gauss-Bonnet (EdGB) gravity with ringdown signals from the merger of binary black holes. The ringdown signal is modeled by the two strongest QNMs in EdGB gravity. Taking into account time-delay interferometry, we calculate the signal-to-noise ratio (SNR) of different space-based detectors for ringdown signals to analyze their capabilities. The Fisher information matrix is employed to analyze the accuracy of parameter estimation, with particular focus on the dimensionless deviating parameter for EdGB gravity. The impact of the parameters of gravitational wave sources on the estimation accuracy of the dimensionless deviating parameter has also been studied. We find that the constraint ability of EdGB gravity is limited because the uncertainty of the dimensionless deviating parameter increases with the decrease of the dimensionless deviating parameter. LISA and TaiJi has more advantages to constrain the dimensionless deviating parameter to a more accurate level for the massive black hole, while TianQin is more suitable for less massive black holes. Bayesian inference method is used to perform parameter estimation on simulated data, which verifies the reliability of the conclusion.
|
1008.4061
|
Luke Butcher
|
Luke M. Butcher, Michael Hobson, Anthony Lasenby
|
Localizing the Energy and Momentum of Linear Gravity
|
20 pages, 3 figures, published in Phys. Rev. D
|
Phys.Rev.D82:104040,2010
|
10.1103/PhysRevD.82.104040
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A framework is developed which quantifies the local exchange of energy and
momentum between matter and the linearized gravitational field. We derive the
unique gravitational energy-momentum tensor consistent with this description,
and find that this tensor only exists in the harmonic gauge. Consequently,
nearly all the gauge freedom of our framework is naturally and unavoidably
removed. The gravitational energy-momentum tensor is then shown to have two
exceptional properties: (a) it is gauge-invariant for gravitational
plane-waves, (b) for arbitrary transverse-traceless fields, the energy-density
is never negative, and the energy-flux is never spacelike. We analyse in detail
the local gauge invariant energy-momentum transferred between the gravitational
field and an infinitesimal point-source, and show that these invariants depend
only on the transverse-traceless components of the field. As a result, we are
led to a natural gauge-fixing program which at last renders the energy-momentum
of the linear gravitational field completely unambiguous, and additionally
ensures that gravitational energy is never negative nor flows faster than
light. Finally, we calculate the energy-momentum content of gravitational
plane-waves, the linearized Schwarzschild spacetime (extending to arbitrary
static linear spacetimes) and the gravitational radiation outside two compact
sources: a vibrating rod, and an equal-mass binary.
|
[
{
"created": "Tue, 24 Aug 2010 14:55:05 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Nov 2010 16:16:02 GMT",
"version": "v2"
}
] |
2010-11-26
|
[
[
"Butcher",
"Luke M.",
""
],
[
"Hobson",
"Michael",
""
],
[
"Lasenby",
"Anthony",
""
]
] |
A framework is developed which quantifies the local exchange of energy and momentum between matter and the linearized gravitational field. We derive the unique gravitational energy-momentum tensor consistent with this description, and find that this tensor only exists in the harmonic gauge. Consequently, nearly all the gauge freedom of our framework is naturally and unavoidably removed. The gravitational energy-momentum tensor is then shown to have two exceptional properties: (a) it is gauge-invariant for gravitational plane-waves, (b) for arbitrary transverse-traceless fields, the energy-density is never negative, and the energy-flux is never spacelike. We analyse in detail the local gauge invariant energy-momentum transferred between the gravitational field and an infinitesimal point-source, and show that these invariants depend only on the transverse-traceless components of the field. As a result, we are led to a natural gauge-fixing program which at last renders the energy-momentum of the linear gravitational field completely unambiguous, and additionally ensures that gravitational energy is never negative nor flows faster than light. Finally, we calculate the energy-momentum content of gravitational plane-waves, the linearized Schwarzschild spacetime (extending to arbitrary static linear spacetimes) and the gravitational radiation outside two compact sources: a vibrating rod, and an equal-mass binary.
|
0902.1127
|
Pablo Laguna
|
Tanja Bode, Pablo Laguna, Deirdre M. Shoemaker, Ian Hinder, Frank
Herrmann, Birjoo Vaishnav
|
Binary black hole evolutions of approximate puncture initial data
| null |
Phys.Rev.D80:024008,2009
|
10.1103/PhysRevD.80.024008
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Approximate solutions to the Einstein field equations are a valuable tool to
investigate gravitational phenomena. An important aspect of any approximation
is to investigate and quantify its regime of validity. We present a study that
evaluates the effects that approximate puncture initial data, based on
"skeleton" solutions to the Einstein constraints as proposed by Faye et al.
[PRD 69, 124029 (2004)], have on numerical evolutions. Using data analysis
tools, we assess the effectiveness of these constraint-violating initial data
and show that the matches of waveforms from skeleton data with the
corresponding waveforms from constraint-satisfying initial data are > 0.97 when
the total mass of the binary is > 40M(solar). In addition, we demonstrate that
the differences between the skeleton and the constraint-satisfying initial data
evolutions, and thus waveforms, are due to negative Hamiltonian constraint
violations present in the skeleton initial data located in the vicinity of the
punctures. During the evolution, the skeleton data develops both Hamiltonian
and momentum constraint violations that decay with time, with the binary system
relaxing to a constraint-satisfying solution with black holes of smaller mass
and thus different dynamics.
|
[
{
"created": "Fri, 6 Feb 2009 16:09:48 GMT",
"version": "v1"
}
] |
2009-09-02
|
[
[
"Bode",
"Tanja",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Shoemaker",
"Deirdre M.",
""
],
[
"Hinder",
"Ian",
""
],
[
"Herrmann",
"Frank",
""
],
[
"Vaishnav",
"Birjoo",
""
]
] |
Approximate solutions to the Einstein field equations are a valuable tool to investigate gravitational phenomena. An important aspect of any approximation is to investigate and quantify its regime of validity. We present a study that evaluates the effects that approximate puncture initial data, based on "skeleton" solutions to the Einstein constraints as proposed by Faye et al. [PRD 69, 124029 (2004)], have on numerical evolutions. Using data analysis tools, we assess the effectiveness of these constraint-violating initial data and show that the matches of waveforms from skeleton data with the corresponding waveforms from constraint-satisfying initial data are > 0.97 when the total mass of the binary is > 40M(solar). In addition, we demonstrate that the differences between the skeleton and the constraint-satisfying initial data evolutions, and thus waveforms, are due to negative Hamiltonian constraint violations present in the skeleton initial data located in the vicinity of the punctures. During the evolution, the skeleton data develops both Hamiltonian and momentum constraint violations that decay with time, with the binary system relaxing to a constraint-satisfying solution with black holes of smaller mass and thus different dynamics.
|
gr-qc/0011055
|
Akihiro Ishibashi
|
Gary W. Gibbons and Akihiro Ishibashi
|
Convex Functions and Spacetime Geometry
|
26 pages, latex, 7 figures, improved version. some claims removed,
references added
|
Class.Quant.Grav.18:4607-4628,2001
|
10.1088/0264-9381/18/21/314
|
YITP-00-54, DAMTP-2000-116
|
gr-qc hep-th math.DG
| null |
Convexity and convex functions play an important role in theoretical physics.
To initiate a study of the possible uses of convex functions in General
Relativity, we discuss the consequences of a spacetime $(M,g_{\mu \nu})$ or an
initial data set $(\Sigma, h_{ij}, K_{ij})$ admitting a suitably defined convex
function. We show how the existence of a convex function on a spacetime places
restrictions on the properties of the spacetime geometry.
|
[
{
"created": "Wed, 15 Nov 2000 19:47:20 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Sep 2001 14:23:21 GMT",
"version": "v2"
}
] |
2009-10-07
|
[
[
"Gibbons",
"Gary W.",
""
],
[
"Ishibashi",
"Akihiro",
""
]
] |
Convexity and convex functions play an important role in theoretical physics. To initiate a study of the possible uses of convex functions in General Relativity, we discuss the consequences of a spacetime $(M,g_{\mu \nu})$ or an initial data set $(\Sigma, h_{ij}, K_{ij})$ admitting a suitably defined convex function. We show how the existence of a convex function on a spacetime places restrictions on the properties of the spacetime geometry.
|
2108.12103
|
Puskar Mondal
|
Vincent Moncrief, Puskar Mondal
|
Einstein flow with matter sources: stability and convergence
|
20 pages. arXiv admin note: text overlap with arXiv:1903.00323,
arXiv:1911.01233
| null |
10.1098/rsta.2021.0190
| null |
gr-qc astro-ph.CO math-ph math.DG math.MP
|
http://creativecommons.org/licenses/by/4.0/
|
Two recent articles \cite{ashtekar2015general, moncrief2019could} suggested
an interesting dynamical mechanism within the framework of the vacuum Einstein
flow (or Einstein-$\Lambda$ flow if a positive cosmological constant $\Lambda$
is included) which suggests that many closed (compact without boundary)
manifolds that do not support homogeneous and isotropic metrics \textit{at all}
will nevertheless evolve to be asymptotically compatible with the observed
approximate homogeneity and isotropy of the physical universe. These studies
however did not include matter sources. Therefore the aim of the present study
is to include suitable matter sources and investigate whether one is able to
draw a similar conclusion.
|
[
{
"created": "Fri, 27 Aug 2021 03:09:36 GMT",
"version": "v1"
}
] |
2022-03-23
|
[
[
"Moncrief",
"Vincent",
""
],
[
"Mondal",
"Puskar",
""
]
] |
Two recent articles \cite{ashtekar2015general, moncrief2019could} suggested an interesting dynamical mechanism within the framework of the vacuum Einstein flow (or Einstein-$\Lambda$ flow if a positive cosmological constant $\Lambda$ is included) which suggests that many closed (compact without boundary) manifolds that do not support homogeneous and isotropic metrics \textit{at all} will nevertheless evolve to be asymptotically compatible with the observed approximate homogeneity and isotropy of the physical universe. These studies however did not include matter sources. Therefore the aim of the present study is to include suitable matter sources and investigate whether one is able to draw a similar conclusion.
|
2212.00529
|
Swagat Saurav Mishra
|
Siddharth S. Bhatt, Swagat S. Mishra, Soumen Basak, Surya N. Sahoo
|
Numerical simulations of inflationary dynamics: slow roll and beyond
|
40 pages, 19 figures, GitHub link to codes provided in the paper,
revised version
| null | null | null |
gr-qc astro-ph.CO hep-ph hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
Numerical simulations of the inflationary dynamics are presented here for a
single canonical scalar field minimally coupled to gravity. We spell out the
basic equations governing the inflationary dynamics in terms of cosmic time $t$
and define a set of dimensionless variables convenient for numerical analysis.
We then provide a link to our simple numerical Python code on GitHub that can
be used to simulate the background dynamics as well as the evolution of linear
perturbations during inflation. The code computes both scalar and tensor power
spectra for a given inflaton potential $V(\phi)$. We discuss a concrete
algorithm to use the code for various purposes, especially for computing the
enhanced scalar power spectrum in the context of Primordial Black Holes and
scalar-induced Gravitational Waves. We also compare the efficiency of different
variables used in the literature to compute the scalar fluctuations. We intend
to extend the framework to simulate the dynamics of a number of different
quantities, including the computation of scalar-induced second-order tensor
power spectrum in the near future.
|
[
{
"created": "Thu, 1 Dec 2022 14:36:04 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Feb 2024 04:10:02 GMT",
"version": "v2"
}
] |
2024-02-21
|
[
[
"Bhatt",
"Siddharth S.",
""
],
[
"Mishra",
"Swagat S.",
""
],
[
"Basak",
"Soumen",
""
],
[
"Sahoo",
"Surya N.",
""
]
] |
Numerical simulations of the inflationary dynamics are presented here for a single canonical scalar field minimally coupled to gravity. We spell out the basic equations governing the inflationary dynamics in terms of cosmic time $t$ and define a set of dimensionless variables convenient for numerical analysis. We then provide a link to our simple numerical Python code on GitHub that can be used to simulate the background dynamics as well as the evolution of linear perturbations during inflation. The code computes both scalar and tensor power spectra for a given inflaton potential $V(\phi)$. We discuss a concrete algorithm to use the code for various purposes, especially for computing the enhanced scalar power spectrum in the context of Primordial Black Holes and scalar-induced Gravitational Waves. We also compare the efficiency of different variables used in the literature to compute the scalar fluctuations. We intend to extend the framework to simulate the dynamics of a number of different quantities, including the computation of scalar-induced second-order tensor power spectrum in the near future.
|
gr-qc/0108056
|
Maurice H. P. M. van Putten
|
Maurice H.P.M. van Putten
|
Past and future gauge in numerical relativity
|
To appear in Class Quantum Grav, Lett
|
Class.Quant.Grav.19:L31-L36,2002
|
10.1088/0264-9381/19/6/101
| null |
gr-qc
| null |
Numerical relativity describes a discrete initial value problem for general
relativity. A choice of gauge involves slicing space-time into space-like
hypersurfaces. This introduces past and future gauge relative to the
hypersurface of present time. Here, we propose solving the discretized Einstein
equations with a choice of gauge in the future and a dynamical gauge in the
past. The method is illustrated on a polarized Gowdy wave.
|
[
{
"created": "Thu, 23 Aug 2001 16:13:43 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2002 23:38:23 GMT",
"version": "v2"
}
] |
2010-04-06
|
[
[
"van Putten",
"Maurice H. P. M.",
""
]
] |
Numerical relativity describes a discrete initial value problem for general relativity. A choice of gauge involves slicing space-time into space-like hypersurfaces. This introduces past and future gauge relative to the hypersurface of present time. Here, we propose solving the discretized Einstein equations with a choice of gauge in the future and a dynamical gauge in the past. The method is illustrated on a polarized Gowdy wave.
|
2012.02375
|
Yun Soo Myung
|
Yun Soo Myung, De-Cheng Zou
|
Onset of rotating scalarized black holes in Einstein-Chern-Simons-Scalar
theory
|
12 pages, 3 figures
| null |
10.1016/j.physletb.2021.136081
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We perform the stability analysis of the Kerr black hole in the
Einstein-Chern-Simons-Scalar theory with quadratic scalar coupling. For
positive coupling parameter ($\alpha>0$), we introduce the (2+1)-dimensional
hyperboloidal foliation method to show that the Kerr black hole is unstable
against scalar-mode perturbation. In case of $\alpha<0$, it is shown that the
Kerr black hole is unstable without any $\alpha$-independent bound on the
rotation parameter $a$ when using the the hyperboloidal foliation method. The
disappearance of the $a$-bound is confirmed analytically by implementing the
(1+1)-dimensional linearized scalar equation.
|
[
{
"created": "Fri, 4 Dec 2020 02:57:30 GMT",
"version": "v1"
}
] |
2021-01-20
|
[
[
"Myung",
"Yun Soo",
""
],
[
"Zou",
"De-Cheng",
""
]
] |
We perform the stability analysis of the Kerr black hole in the Einstein-Chern-Simons-Scalar theory with quadratic scalar coupling. For positive coupling parameter ($\alpha>0$), we introduce the (2+1)-dimensional hyperboloidal foliation method to show that the Kerr black hole is unstable against scalar-mode perturbation. In case of $\alpha<0$, it is shown that the Kerr black hole is unstable without any $\alpha$-independent bound on the rotation parameter $a$ when using the the hyperboloidal foliation method. The disappearance of the $a$-bound is confirmed analytically by implementing the (1+1)-dimensional linearized scalar equation.
|
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