id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1511.05581 | Antoine Klein | Antoine Klein, Enrico Barausse, Alberto Sesana, Antoine Petiteau,
Emanuele Berti, Stanislav Babak, Jonathan Gair, Sofiane Aoudia, Ian Hinder,
Frank Ohme, Barry Wardell | Science with the space-based interferometer eLISA. I: Supermassive black
hole binaries | 28 pages, 13 figures, 7 tables | Phys. Rev. D 93, 024003 (2016) | 10.1103/PhysRevD.93.024003 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare the science capabilities of different eLISA mission designs,
including four-link (two-arm) and six-link (three-arm) configurations with
different arm lengths, low-frequency noise sensitivities and mission durations.
For each of these configurations we consider a few representative massive black
hole formation scenarios. These scenarios are chosen to explore two physical
mechanisms that greatly affect eLISA rates, namely (i) black hole seeding, and
(ii) the delays between the merger of two galaxies and the merger of the black
holes hosted by those galaxies. We assess the eLISA parameter estimation
accuracy using a Fisher matrix analysis with spin-precessing, inspiral-only
waveforms. We quantify the information present in the merger and ringdown by
rescaling the inspiral-only Fisher matrix estimates using the signal-to-noise
ratio from non-precessing inspiral-merger-ringdown phenomenological waveforms,
and from a reduced set of precessing numerical relativity/post-Newtonian hybrid
waveforms. We find that all of the eLISA configurations considered in our study
should detect some massive black hole binaries. However, configurations with
six links and better low-frequency noise will provide much more information on
the origin of black holes at high redshifts and on their accretion history, and
they may allow the identification of electromagnetic counterparts to massive
black hole mergers.
| [
{
"created": "Tue, 17 Nov 2015 21:04:55 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jan 2016 17:42:07 GMT",
"version": "v2"
}
] | 2016-01-13 | [
[
"Klein",
"Antoine",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Sesana",
"Alberto",
""
],
[
"Petiteau",
"Antoine",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Babak",
"Stanislav",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Aoudia",
"Sofiane",
""
],
[
"Hinder",
"Ian",
""
],
[
"Ohme",
"Frank",
""
],
[
"Wardell",
"Barry",
""
]
] | We compare the science capabilities of different eLISA mission designs, including four-link (two-arm) and six-link (three-arm) configurations with different arm lengths, low-frequency noise sensitivities and mission durations. For each of these configurations we consider a few representative massive black hole formation scenarios. These scenarios are chosen to explore two physical mechanisms that greatly affect eLISA rates, namely (i) black hole seeding, and (ii) the delays between the merger of two galaxies and the merger of the black holes hosted by those galaxies. We assess the eLISA parameter estimation accuracy using a Fisher matrix analysis with spin-precessing, inspiral-only waveforms. We quantify the information present in the merger and ringdown by rescaling the inspiral-only Fisher matrix estimates using the signal-to-noise ratio from non-precessing inspiral-merger-ringdown phenomenological waveforms, and from a reduced set of precessing numerical relativity/post-Newtonian hybrid waveforms. We find that all of the eLISA configurations considered in our study should detect some massive black hole binaries. However, configurations with six links and better low-frequency noise will provide much more information on the origin of black holes at high redshifts and on their accretion history, and they may allow the identification of electromagnetic counterparts to massive black hole mergers. |
gr-qc/9510040 | Serge Droz | P. R. Brady, S. Droz, W. Israel and S. M. Morsink | Covariant double-null dynamics: $(2+2)$-splitting of the Einstein
equations | 22 pages, latex, one figure in a separate file | Class.Quant.Grav. 13 (1996) 2211-2230 | 10.1088/0264-9381/13/8/015 | EFI-94-36 | gr-qc hep-th | null | The paper develops a $(2+2)$-imbedding formalism adapted to a double
foliation of spacetime by a net of two intersecting families of lightlike
hypersurfaces. The formalism is two-dimensionally covariant, and leads to
simple, geometrically transparent and tractable expressions for the Einstein
field equations and the Einstein-Hilbert action, and it should find a variety
of applications. It is applied here to elucidate the structure of the
characteristic initial-value problem of general relativity.
| [
{
"created": "Thu, 19 Oct 1995 21:41:54 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Brady",
"P. R.",
""
],
[
"Droz",
"S.",
""
],
[
"Israel",
"W.",
""
],
[
"Morsink",
"S. M.",
""
]
] | The paper develops a $(2+2)$-imbedding formalism adapted to a double foliation of spacetime by a net of two intersecting families of lightlike hypersurfaces. The formalism is two-dimensionally covariant, and leads to simple, geometrically transparent and tractable expressions for the Einstein field equations and the Einstein-Hilbert action, and it should find a variety of applications. It is applied here to elucidate the structure of the characteristic initial-value problem of general relativity. |
gr-qc/0502047 | B. V. Ivanov | Boyko V. Ivanov | On the gravitational field induced by static electromagnetic sources | 18 pages, Revtex4 | null | null | null | gr-qc | null | It is argued that static electromagnetic sources induce
Weyl-Majumdar-Papapetrou solutions for the spacetime metric. The acceleration
in such fields has a term many orders of magnitude stronger than usual
perturbative terms. Two electrostatic and two magnetostatic examples are given.
| [
{
"created": "Thu, 10 Feb 2005 19:18:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ivanov",
"Boyko V.",
""
]
] | It is argued that static electromagnetic sources induce Weyl-Majumdar-Papapetrou solutions for the spacetime metric. The acceleration in such fields has a term many orders of magnitude stronger than usual perturbative terms. Two electrostatic and two magnetostatic examples are given. |
2407.03669 | Shubham Narawade Mr. | Muhammad Azzam Alwan, Tomohiro Inagaki, B. Mishra, S.A. Narawade | Neutron Star in Covariant $f(Q)$ gravity | 27 pages, 24 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Assuming static and spherically symmetric stars with perfect fluid matter, we
used realistic equations of state to study neutron stars in covariant $f(Q)$
gravity. The structure profiles and properties of neutron stars such as mass,
radius and compactness are obtained through numerical methods using quadratic,
exponential, and logarithmic $f(Q)$ models. The results indicate that
nonmetricity affects the interior profile deviations of the star, which in turn
influence the properties of stars, as illustrated in the mass-radius relation
diagram. This effect allows the star to accommodate either more or less matter
compared to GR, resulting in a different total mass. For the quadratic model,
we cannot generate larger masses, whereas the other two models can give
consistent results for both smaller and larger masses of the observed stars. By
tuning model parameters, we obtain $\mathcal{M}-\mathcal{R}$ diagrams that are
compatible with observational constraints from NICER and LIGO.
| [
{
"created": "Thu, 4 Jul 2024 06:33:44 GMT",
"version": "v1"
}
] | 2024-07-08 | [
[
"Alwan",
"Muhammad Azzam",
""
],
[
"Inagaki",
"Tomohiro",
""
],
[
"Mishra",
"B.",
""
],
[
"Narawade",
"S. A.",
""
]
] | Assuming static and spherically symmetric stars with perfect fluid matter, we used realistic equations of state to study neutron stars in covariant $f(Q)$ gravity. The structure profiles and properties of neutron stars such as mass, radius and compactness are obtained through numerical methods using quadratic, exponential, and logarithmic $f(Q)$ models. The results indicate that nonmetricity affects the interior profile deviations of the star, which in turn influence the properties of stars, as illustrated in the mass-radius relation diagram. This effect allows the star to accommodate either more or less matter compared to GR, resulting in a different total mass. For the quadratic model, we cannot generate larger masses, whereas the other two models can give consistent results for both smaller and larger masses of the observed stars. By tuning model parameters, we obtain $\mathcal{M}-\mathcal{R}$ diagrams that are compatible with observational constraints from NICER and LIGO. |
gr-qc/0309016 | Juan A. Valiente-Kroon | Juan A. Valiente Kroon | Does asymptotic simplicity allow for radiation near spatial infinity? | 22 pages, 4 figures. Typos and grammatical mistakes corrected.
Version to appear in Comm. Math. Phys | Commun.Math.Phys. 251 (2004) 211-234 | 10.1007/s00220-004-1174-8 | null | gr-qc | null | A representation of spatial infinity based in the properties of conformal
geodesics is used to obtain asymptotic expansions of the gravitational field
near the region where null infinity touches spatial infinity. These expansions
show that generic time symmetric initial data with an analytic conformal metric
at spatial infinity will give rise to developments with a certain type of
logarithmic singularities at the points where null infinity and spatial
infinity meet. These logarithmic singularities produce a non-smooth null
infinity. The sources of the logarithmic singularities are traced back down to
the initial data. It is shown that is the parts of the initial data responsible
for the non-regular behaviour of the solutions are not present, then the
initial data is static to a certain order. On the basis of these results it is
conjectured that the only time symmetric data sets with developments having a
smooth null infinity are those which are static in a neighbourhood of infinity.
This conjecture generalises a previous conjecture regarding time symmetric,
conformally flat data. The relation of these conjectures to Penrose's proposal
for the description of the asymptotic gravitational field of isolated bodies is
discussed.
| [
{
"created": "Wed, 3 Sep 2003 07:26:46 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Mar 2004 14:42:30 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Kroon",
"Juan A. Valiente",
""
]
] | A representation of spatial infinity based in the properties of conformal geodesics is used to obtain asymptotic expansions of the gravitational field near the region where null infinity touches spatial infinity. These expansions show that generic time symmetric initial data with an analytic conformal metric at spatial infinity will give rise to developments with a certain type of logarithmic singularities at the points where null infinity and spatial infinity meet. These logarithmic singularities produce a non-smooth null infinity. The sources of the logarithmic singularities are traced back down to the initial data. It is shown that is the parts of the initial data responsible for the non-regular behaviour of the solutions are not present, then the initial data is static to a certain order. On the basis of these results it is conjectured that the only time symmetric data sets with developments having a smooth null infinity are those which are static in a neighbourhood of infinity. This conjecture generalises a previous conjecture regarding time symmetric, conformally flat data. The relation of these conjectures to Penrose's proposal for the description of the asymptotic gravitational field of isolated bodies is discussed. |
2111.12109 | Jo\~ao Lu\'is Rosa | Jo\~ao Lu\'is Rosa, Jos\'e P. S. Lemos | Junction conditions for generalized hybrid metric-Palatini gravity with
applications | 26 pages, 3 figures | Phys. Rev. D 104, 124076 (2021) | 10.1103/PhysRevD.104.124076 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The generalized hybrid metric-Palatini gravity is a theory of gravitation
that has an action composed of a Lagrangian $f(R,\cal R)$, where $f$ is a
function of the metric Ricci scalar $R$ and a new Ricci scalar $\cal R$ formed
from a Palatini connection, plus a matter Lagrangian. This theory can be
rewritten by trading the new geometric degrees of freedom of $f(R,\cal R)$ into
two scalar fields, $\varphi$ and $\psi$, yielding an equivalent scalar-tensor
theory. Given a spacetime theory, the next step is to find solutions. To
construct solutions it is often necessary to know the junction conditions
between two regions at a separation hypersurface $\Sigma$, with each region
being an independent solution. The junction conditions for the generalized
hybrid metric-Palatini gravity are found here, in the geometric and in the
scalar-tensor representations, and in addition, for each representation, the
junction conditions for a matching with a thin-shell and for a smooth matching
at $\Sigma$ are worked out. These junction conditions are applied to three
configurations, a star, a quasistar with a black hole, and a wormhole. The star
has a Minkowski interior, a thin shell at the interface with all the energy
conditions being satisfied, and a Schwarzschild exterior with mass $M$, and for
this theory the matching can only be performed at the shell radius given by
$r_\Sigma=\frac{9M}4$, the Buchdahl radius in general relativity. The quasistar
with a black hole has an interior Schwarzschild black hole surrounded by a
thick shell that matches smoothly to a mass $M$ Schwarzschild exterior at the
light ring, and with the energy conditions being satisfied everywhere. The
wormhole has an interior that contains the throat, a thin shell at the
interface, and a Schwarzschild-AdS exterior with mass $M$ and negative
cosmological constant $\Lambda$, with the null energy condition being obeyed.
| [
{
"created": "Tue, 23 Nov 2021 19:02:15 GMT",
"version": "v1"
}
] | 2022-01-07 | [
[
"Rosa",
"João Luís",
""
],
[
"Lemos",
"José P. S.",
""
]
] | The generalized hybrid metric-Palatini gravity is a theory of gravitation that has an action composed of a Lagrangian $f(R,\cal R)$, where $f$ is a function of the metric Ricci scalar $R$ and a new Ricci scalar $\cal R$ formed from a Palatini connection, plus a matter Lagrangian. This theory can be rewritten by trading the new geometric degrees of freedom of $f(R,\cal R)$ into two scalar fields, $\varphi$ and $\psi$, yielding an equivalent scalar-tensor theory. Given a spacetime theory, the next step is to find solutions. To construct solutions it is often necessary to know the junction conditions between two regions at a separation hypersurface $\Sigma$, with each region being an independent solution. The junction conditions for the generalized hybrid metric-Palatini gravity are found here, in the geometric and in the scalar-tensor representations, and in addition, for each representation, the junction conditions for a matching with a thin-shell and for a smooth matching at $\Sigma$ are worked out. These junction conditions are applied to three configurations, a star, a quasistar with a black hole, and a wormhole. The star has a Minkowski interior, a thin shell at the interface with all the energy conditions being satisfied, and a Schwarzschild exterior with mass $M$, and for this theory the matching can only be performed at the shell radius given by $r_\Sigma=\frac{9M}4$, the Buchdahl radius in general relativity. The quasistar with a black hole has an interior Schwarzschild black hole surrounded by a thick shell that matches smoothly to a mass $M$ Schwarzschild exterior at the light ring, and with the energy conditions being satisfied everywhere. The wormhole has an interior that contains the throat, a thin shell at the interface, and a Schwarzschild-AdS exterior with mass $M$ and negative cosmological constant $\Lambda$, with the null energy condition being obeyed. |
2405.07113 | Kun Meng | Kun Meng, Hongsheng Zhang, Xi-Long Fan, Yuan Yong | Distinguish the EMRI and B-EMRI system by gravitational waves | 16 pages, 10 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary stars are as frequency as single stars in the Universe, and at least
70\% of the massive stars located in our Galaxy belong to a binary system. For
the first time we produce the gravitational waveforms for the extreme mass
ratio inspiral systems (EMRIs) of binary stars moving around central
supermassive black hole (SBH). We calculate the orbits of such systems via the
Hamilton-Jacobi approach. To improve accuracy we adopt the quadrupole-octupole
expression of gravitational wave (GW) and consider the contribution of
radiation reaction. Compared to the waveforms of single star, double or
multiple spikes emerge in the waveforms of binary stars. We calculate the
mismatch of the EMRI waveforms of binary stars and those of single stars, and
find the mismatch increases as the binary internal semi-latus rectum
$\tilde{p}$ decreases. According to the distinguishable criterion of two
signals, it's inferred that the two types of waveforms are distinguishable for
small enough $\tilde{p}$. Further, we demonstrate that the most favourable
position to distinguish the waveforms of EMRIs of single star from the
waveforms of EMRIs of binary stars is that revolutions of the binary stars and
the central SBH takes the same direction, i.e., the rotation axis of the binary
is parallel to that of the central SBH.
| [
{
"created": "Sun, 12 May 2024 00:03:59 GMT",
"version": "v1"
}
] | 2024-05-14 | [
[
"Meng",
"Kun",
""
],
[
"Zhang",
"Hongsheng",
""
],
[
"Fan",
"Xi-Long",
""
],
[
"Yong",
"Yuan",
""
]
] | Binary stars are as frequency as single stars in the Universe, and at least 70\% of the massive stars located in our Galaxy belong to a binary system. For the first time we produce the gravitational waveforms for the extreme mass ratio inspiral systems (EMRIs) of binary stars moving around central supermassive black hole (SBH). We calculate the orbits of such systems via the Hamilton-Jacobi approach. To improve accuracy we adopt the quadrupole-octupole expression of gravitational wave (GW) and consider the contribution of radiation reaction. Compared to the waveforms of single star, double or multiple spikes emerge in the waveforms of binary stars. We calculate the mismatch of the EMRI waveforms of binary stars and those of single stars, and find the mismatch increases as the binary internal semi-latus rectum $\tilde{p}$ decreases. According to the distinguishable criterion of two signals, it's inferred that the two types of waveforms are distinguishable for small enough $\tilde{p}$. Further, we demonstrate that the most favourable position to distinguish the waveforms of EMRIs of single star from the waveforms of EMRIs of binary stars is that revolutions of the binary stars and the central SBH takes the same direction, i.e., the rotation axis of the binary is parallel to that of the central SBH. |
2308.10381 | Jose Socorro Garcia | J. Socorro, J. Juan Rosales and L. Toledo Sesma | Anisotropic fractional cosmology: K-essence theory | 26 pages, 8 figures, version to be published in fractal fractionary
journal | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In the particular configuration of the scalar field K-essence in the
Wheeler-DeWitt quantum equation, for some age in the Bianchi type I anisotropic
cosmological model, a fractional differential equation for the scalar field
arises naturally. The order of the fractional differential equation is
$\beta=\frac{2\alpha}{2\alpha - 1}$. This fractional equation belongs to
different intervals, depending on the value of the barotropic parameter; when
$\omega_{X} \in [0,1]$, the order belongs to the interval $1\leq \beta \leq 2$,
and when $\omega_{X}\in[-1,0)$, the order belongs to the interval $0< \beta
\leq 1$. In the quantum scheme, we introduce the factor ordering problem in the
variables $(\Omega,\phi)$ and its corresponding momenta $(\Pi_\Omega,
\Pi_\phi)$, obtaining a linear fractional differential equation with variable
coefficients in the scalar field equation, then the solution is found using a
fractional power series expansion. The corresponding quantum solutions are also
given. We found the classical solution in the usual gauge N obtained in the
Hamiltonian formalism and without a gauge. In the last case, the general
solution is presented in a transformed time $T(\tau)$, however in the dust era
we found a closed solution in the gauge time $\tau$.
Keywords: Fractional derivative, Fractional Quantum Cosmology; K-essence
formalism; Classical and Quantum exact solutions.
| [
{
"created": "Sun, 20 Aug 2023 22:51:32 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Nov 2023 18:48:21 GMT",
"version": "v2"
}
] | 2023-11-09 | [
[
"Socorro",
"J.",
""
],
[
"Rosales",
"J. Juan",
""
],
[
"Sesma",
"L. Toledo",
""
]
] | In the particular configuration of the scalar field K-essence in the Wheeler-DeWitt quantum equation, for some age in the Bianchi type I anisotropic cosmological model, a fractional differential equation for the scalar field arises naturally. The order of the fractional differential equation is $\beta=\frac{2\alpha}{2\alpha - 1}$. This fractional equation belongs to different intervals, depending on the value of the barotropic parameter; when $\omega_{X} \in [0,1]$, the order belongs to the interval $1\leq \beta \leq 2$, and when $\omega_{X}\in[-1,0)$, the order belongs to the interval $0< \beta \leq 1$. In the quantum scheme, we introduce the factor ordering problem in the variables $(\Omega,\phi)$ and its corresponding momenta $(\Pi_\Omega, \Pi_\phi)$, obtaining a linear fractional differential equation with variable coefficients in the scalar field equation, then the solution is found using a fractional power series expansion. The corresponding quantum solutions are also given. We found the classical solution in the usual gauge N obtained in the Hamiltonian formalism and without a gauge. In the last case, the general solution is presented in a transformed time $T(\tau)$, however in the dust era we found a closed solution in the gauge time $\tau$. Keywords: Fractional derivative, Fractional Quantum Cosmology; K-essence formalism; Classical and Quantum exact solutions. |
gr-qc/9805070 | Miguel Navarro | M. Navarro | 2D dilaton gravity made compact | Latex file, no macros, 8 pages | null | null | null | gr-qc | null | We show that the equations of motion of two-dimensional dilaton gravity
conformally coupled to a scalar field can be reduced to a single non-linear
second-order partial differential equation when the coordinates are chosen to
coincide with the two scalar fields, the matter field $f$ and the dilaton
$\phi$, which are present in the theory. This result may help solve and
understand two- and higher-dimensional classical and quantum gravity.
| [
{
"created": "Mon, 18 May 1998 20:28:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Navarro",
"M.",
""
]
] | We show that the equations of motion of two-dimensional dilaton gravity conformally coupled to a scalar field can be reduced to a single non-linear second-order partial differential equation when the coordinates are chosen to coincide with the two scalar fields, the matter field $f$ and the dilaton $\phi$, which are present in the theory. This result may help solve and understand two- and higher-dimensional classical and quantum gravity. |
2007.13761 | Adri\'an del R\'io Vega | Ivan Agullo, Vitor Cardoso, Adrian del Rio, Michele Maggiore, Jorge
Pullin | Potential gravitational-wave signatures of quantum gravity | some comments and clarifications added; published version | Phys. Rev. Lett. 126, 041302 (2021) | 10.1103/PhysRevLett.126.041302 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that gravitational-wave astronomy has the potential to inform us on
quantum aspects of black holes. Based on Bekenstein's quantization, we find
that black hole area discretization could impart observable imprints to the
gravitational-wave signal from a pair of merging black holes, affecting their
absorption properties during inspiral and their late-time relaxation after
merger. In contrast with previous results, we find that black hole rotation,
ubiquitous in astrophysics, improves our ability to probe quantum effects. Our
analysis shows that gravitational-wave echoes and suppressed tidal heating are
signs of new physics from which the fundamental quantum of black hole area can
be measured, and which are within reach of future detectors. Our results also
highlight the need to derive predictions from specific quantum gravity
proposals.
| [
{
"created": "Mon, 27 Jul 2020 18:00:02 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Feb 2021 17:17:18 GMT",
"version": "v2"
}
] | 2021-02-09 | [
[
"Agullo",
"Ivan",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"del Rio",
"Adrian",
""
],
[
"Maggiore",
"Michele",
""
],
[
"Pullin",
"Jorge",
""
]
] | We show that gravitational-wave astronomy has the potential to inform us on quantum aspects of black holes. Based on Bekenstein's quantization, we find that black hole area discretization could impart observable imprints to the gravitational-wave signal from a pair of merging black holes, affecting their absorption properties during inspiral and their late-time relaxation after merger. In contrast with previous results, we find that black hole rotation, ubiquitous in astrophysics, improves our ability to probe quantum effects. Our analysis shows that gravitational-wave echoes and suppressed tidal heating are signs of new physics from which the fundamental quantum of black hole area can be measured, and which are within reach of future detectors. Our results also highlight the need to derive predictions from specific quantum gravity proposals. |
1408.4952 | Andrea Geralico | Donato Bini and Andrea Geralico | Spin-geodesic deviations in the Kerr spacetime | 19 pages, 6 figures; published version | Phys. Rev. D 84, 104012 (2011) | 10.1103/PhysRevD.84.104012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of extended spinning bodies in the Kerr spacetime is
investigated in the pole-dipole particle approximation and under the assumption
that the spin-curvature force only slightly deviates the particle from a
geodesic path. The spin parameter is thus assumed to be very small and the back
reaction on the spacetime geometry neglected. This approach naturally leads to
solve the Mathisson-Papapetrou-Dixon equations linearized in the spin variables
as well as in the deviation vector, with the same initial conditions as for
geodesic motion. General deviations from generic geodesic motion are studied,
generalizing previous results limited to the very special case of an equatorial
circular geodesic as the reference path.
| [
{
"created": "Thu, 21 Aug 2014 10:59:38 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | The dynamics of extended spinning bodies in the Kerr spacetime is investigated in the pole-dipole particle approximation and under the assumption that the spin-curvature force only slightly deviates the particle from a geodesic path. The spin parameter is thus assumed to be very small and the back reaction on the spacetime geometry neglected. This approach naturally leads to solve the Mathisson-Papapetrou-Dixon equations linearized in the spin variables as well as in the deviation vector, with the same initial conditions as for geodesic motion. General deviations from generic geodesic motion are studied, generalizing previous results limited to the very special case of an equatorial circular geodesic as the reference path. |
gr-qc/9408009 | Neil Cornish | Neil Cornish | Analysis of the Non-singular Wyman-Schwarzschild Metric | 14 pages, RevTeX, 6 Figures available on request, UTPT-94-16 | Mod.Phys.Lett. A9 (1994) 3629-3640 | 10.1142/S0217732394003476 | null | gr-qc | null | The analog of the Schwarzschild metric is explored in the context of
Non-Singular Gravity. Analytic results are developed describing redshifts,
curvatures and topological features of the spacetime. All curvatures and
redshifts are finite so there are no Black Holes, no singularities and no
Hawking radiation.
| [
{
"created": "Fri, 5 Aug 1994 01:39:20 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Cornish",
"Neil",
""
]
] | The analog of the Schwarzschild metric is explored in the context of Non-Singular Gravity. Analytic results are developed describing redshifts, curvatures and topological features of the spacetime. All curvatures and redshifts are finite so there are no Black Holes, no singularities and no Hawking radiation. |
0911.1595 | Jeandrew Brink | Jeandrew Brink | Spacetime Encodings IV - The Relationship between Weyl Curvature and
Killing Tensors in Stationary Axisymmetric Vacuum Spacetimes | 15 pages | Phys.Rev.D81:022002,2010 | 10.1103/PhysRevD.81.022002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of obtaining an explicit representation for the fourth invariant
of geodesic motion (generalized Carter constant) of an arbitrary stationary
axisymmetric vacuum spacetime generated from an Ernst Potential is considered.
The coupling between the non-local curvature content of the spacetime as
encoded in the Weyl tensor, and the existence of a Killing tensor is explored
and a constructive, algebraic test for a fourth order Killing tensor suggested.
The approach used exploits the variables defined for the B\"{a}ckland
transformations to clarify the relationship between Weyl curvature, constants
of geodesic motion, expressed as Killing tensors, and the solution generation
techniques. A new symmetric non-covariant formulation of the Killing equations
is given. This formulation transforms the problem of looking for fourth-order
Killing tensors in 4D into one of looking for four interlocking two-manifolds
admitting fourth-order Killing tensors in 2D.
| [
{
"created": "Mon, 9 Nov 2009 06:43:59 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Brink",
"Jeandrew",
""
]
] | The problem of obtaining an explicit representation for the fourth invariant of geodesic motion (generalized Carter constant) of an arbitrary stationary axisymmetric vacuum spacetime generated from an Ernst Potential is considered. The coupling between the non-local curvature content of the spacetime as encoded in the Weyl tensor, and the existence of a Killing tensor is explored and a constructive, algebraic test for a fourth order Killing tensor suggested. The approach used exploits the variables defined for the B\"{a}ckland transformations to clarify the relationship between Weyl curvature, constants of geodesic motion, expressed as Killing tensors, and the solution generation techniques. A new symmetric non-covariant formulation of the Killing equations is given. This formulation transforms the problem of looking for fourth-order Killing tensors in 4D into one of looking for four interlocking two-manifolds admitting fourth-order Killing tensors in 2D. |
1704.07368 | Guilherme Franzmann | Guilherme Franzmann | Varying fundamental constants: a full covariant approach and
cosmological applications | 10 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We build a minimal extension of General Relativity in which Newton's
gravitational coupling, $G$, the speed of light, $c$, and the cosmological
constant, $\Lambda$, are spacetime variables. This is done while satisfying the
contracted Bianchi identity as well as the local conservation of energy
momentum tensor. A dynamical constraint is derived, which shows that variations
of $G$ and $c$ are coupled to the local matter-energy physical content, while
variation of $\Lambda$ is coupled to the local geometry. This constraint
presents a natural cosmological screening mechanism that brings new perspective
concerning the current observations of a cosmological constant, $\Lambda_0$ in
cosmological observations. We also explore early universe background cosmology
and show that the proposal provides alternatives to obtain an accelerated
expansion, similar to those coming from Varying Speed of Light theories.
| [
{
"created": "Sun, 23 Apr 2017 21:55:13 GMT",
"version": "v1"
}
] | 2017-04-27 | [
[
"Franzmann",
"Guilherme",
""
]
] | We build a minimal extension of General Relativity in which Newton's gravitational coupling, $G$, the speed of light, $c$, and the cosmological constant, $\Lambda$, are spacetime variables. This is done while satisfying the contracted Bianchi identity as well as the local conservation of energy momentum tensor. A dynamical constraint is derived, which shows that variations of $G$ and $c$ are coupled to the local matter-energy physical content, while variation of $\Lambda$ is coupled to the local geometry. This constraint presents a natural cosmological screening mechanism that brings new perspective concerning the current observations of a cosmological constant, $\Lambda_0$ in cosmological observations. We also explore early universe background cosmology and show that the proposal provides alternatives to obtain an accelerated expansion, similar to those coming from Varying Speed of Light theories. |
1605.05816 | Toshiaki Ono | Toshiaki Ono, Tomohito Suzuki, Hideki Asada | Nonradial stability of marginal stable circular orbits in stationary
axisymmetric spacetimes | 6 pages, 3 figures, appendix added, accepted by PRD | Phys. Rev. D 94, 064042 (2016) | 10.1103/PhysRevD.94.064042 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study linear nonradial perturbations and stability of a marginal stable
circular orbit (MSCO) such as the innermost stable circular orbit (ISCO) of a
test particle in stationary axisymmetric spacetimes which possess a reflection
symmetry with respect to the equatorial plane. The proposed approach is applied
to Kerr solution and Majumdar-Papapetrou solution to Einstein equation.
Finally, we reexamine MSCOs for a modified metric of a rapidly spinning black
hole that has been recently proposed by Johannsen and Psaltis [PRD, 83, 124015
(2011)]. We show that, for the Johannsen and Psaltis's model, circular orbits
that are stable against radial perturbations for some parameter region become
unstable against vertical perturbations. This suggests that the last circular
orbit for this model may be larger than the ISCO.
| [
{
"created": "Thu, 19 May 2016 05:45:31 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Sep 2016 02:13:28 GMT",
"version": "v2"
}
] | 2016-09-21 | [
[
"Ono",
"Toshiaki",
""
],
[
"Suzuki",
"Tomohito",
""
],
[
"Asada",
"Hideki",
""
]
] | We study linear nonradial perturbations and stability of a marginal stable circular orbit (MSCO) such as the innermost stable circular orbit (ISCO) of a test particle in stationary axisymmetric spacetimes which possess a reflection symmetry with respect to the equatorial plane. The proposed approach is applied to Kerr solution and Majumdar-Papapetrou solution to Einstein equation. Finally, we reexamine MSCOs for a modified metric of a rapidly spinning black hole that has been recently proposed by Johannsen and Psaltis [PRD, 83, 124015 (2011)]. We show that, for the Johannsen and Psaltis's model, circular orbits that are stable against radial perturbations for some parameter region become unstable against vertical perturbations. This suggests that the last circular orbit for this model may be larger than the ISCO. |
1512.04240 | Kazuhiro Yamamoto | Kazuhiro Yamamoto, Valerio Marra, Viatcheslav Mukhanov, Misao Sasaki | Perturbed Newtonian description of the Lema\^itre model with
non-negligible pressure | 23 pages, 7 figures. Version accepted for publication in JCAP | JCAP03(2016)030 | 10.1088/1475-7516/2016/03/030 | HUPD-1510, YITP-15-113 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the validity of the Newtonian description of cosmological
perturbations using the Lemaitre model, an exact spherically symmetric solution
of Einstein's equation. This problem has been investigated in the past for the
case of a dust fluid. Here, we extend the previous analysis to the more general
case of a fluid with non-negligible pressure, and, for the numerical examples,
we consider the case of radiation (P=\rho/3). We find that, even when the
density contrast has a nonlinear amplitude, the Newtonian description of the
cosmological perturbations using the gravitational potential \psi and the
curvature potential \phi is valid as long as we consider sub-horizon
inhomogeneities. However, the relation \psi+\phi={\cal O}(\phi^2), which holds
for the case of a dust fluid, is not valid for a relativistic fluid and
effective anisotropic stress is generated. This demonstrates the usefulness of
the Lemaitre model which allows us to study in an exact nonlinear fashion the
onset of anisotropic stress in fluids with non-negligible pressure. We show
that this happens when the characteristic scale of the inhomogeneity is smaller
than the sound horizon and that the deviation is caused by the nonlinear effect
of the fluid's fast motion. We also find that \psi+\phi= \max[{\cal
O}(\phi^2),{\cal O}(c_s^2\phi \, \delta)] for an inhomogeneity with density
contrast \delta whose characteristic scale is smaller than the sound horizon,
unless w is close to -1, where w and c_s are the equation of state parameter
and the sound speed of the fluid, respectively. On the other hand, we expect
\psi+\phi={\cal O}(\phi^2) to hold for an inhomogeneity whose characteristic
scale is larger than the sound horizon, unless the amplitude of the
inhomogeneity is large and w is close to -1.
| [
{
"created": "Mon, 14 Dec 2015 10:03:14 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Feb 2016 13:02:37 GMT",
"version": "v2"
}
] | 2016-03-18 | [
[
"Yamamoto",
"Kazuhiro",
""
],
[
"Marra",
"Valerio",
""
],
[
"Mukhanov",
"Viatcheslav",
""
],
[
"Sasaki",
"Misao",
""
]
] | We study the validity of the Newtonian description of cosmological perturbations using the Lemaitre model, an exact spherically symmetric solution of Einstein's equation. This problem has been investigated in the past for the case of a dust fluid. Here, we extend the previous analysis to the more general case of a fluid with non-negligible pressure, and, for the numerical examples, we consider the case of radiation (P=\rho/3). We find that, even when the density contrast has a nonlinear amplitude, the Newtonian description of the cosmological perturbations using the gravitational potential \psi and the curvature potential \phi is valid as long as we consider sub-horizon inhomogeneities. However, the relation \psi+\phi={\cal O}(\phi^2), which holds for the case of a dust fluid, is not valid for a relativistic fluid and effective anisotropic stress is generated. This demonstrates the usefulness of the Lemaitre model which allows us to study in an exact nonlinear fashion the onset of anisotropic stress in fluids with non-negligible pressure. We show that this happens when the characteristic scale of the inhomogeneity is smaller than the sound horizon and that the deviation is caused by the nonlinear effect of the fluid's fast motion. We also find that \psi+\phi= \max[{\cal O}(\phi^2),{\cal O}(c_s^2\phi \, \delta)] for an inhomogeneity with density contrast \delta whose characteristic scale is smaller than the sound horizon, unless w is close to -1, where w and c_s are the equation of state parameter and the sound speed of the fluid, respectively. On the other hand, we expect \psi+\phi={\cal O}(\phi^2) to hold for an inhomogeneity whose characteristic scale is larger than the sound horizon, unless the amplitude of the inhomogeneity is large and w is close to -1. |
1809.08265 | Joao Paulo Manoel Pitelli | S. Carlip, Ricardo A. Mosna, J. P. M. Pitelli | Quantum Fields, Geometric Fluctuations, and the Structure of Spacetime | 5 pages, 5 figures. v3: major revision. The fluctuations of the
stress-energy tensor are now allowed to act independently on different
spacetime patches. The text has been updated accordingly. v4: typos
corrected, final published version | Phys. Rev. D 102, 126018 (2020) | 10.1103/PhysRevD.102.126018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum fluctuations of the vacuum stress-energy tensor are highly
non-Gaussian, and can have unexpectedly large effects on spacetime geometry. In
this paper, we study a two-dimensional dilaton gravity model coupled to a
conformal field, in which the distribution of vacuum fluctuations is well
understood. In this model, the fluctuations of the matter field are responsible
for the fluctuations of the geometry itself. By analyzing the geodesic
deviation in this model, we show that a pencil of massive particles propagating
on this fuzzy spacetime eventually converges and collapses. This is consistent
with our earlier analysis of null geodesics in [Phys. Rev. Lett.\ 107, 021303
(2011)].
| [
{
"created": "Fri, 21 Sep 2018 18:38:49 GMT",
"version": "v1"
},
{
"created": "Sat, 13 Oct 2018 19:39:04 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Oct 2020 11:16:09 GMT",
"version": "v3"
},
{
"created": "Thu, 17 Dec 2020 13:22:44 GMT",
"version": "v4"
}
] | 2020-12-18 | [
[
"Carlip",
"S.",
""
],
[
"Mosna",
"Ricardo A.",
""
],
[
"Pitelli",
"J. P. M.",
""
]
] | Quantum fluctuations of the vacuum stress-energy tensor are highly non-Gaussian, and can have unexpectedly large effects on spacetime geometry. In this paper, we study a two-dimensional dilaton gravity model coupled to a conformal field, in which the distribution of vacuum fluctuations is well understood. In this model, the fluctuations of the matter field are responsible for the fluctuations of the geometry itself. By analyzing the geodesic deviation in this model, we show that a pencil of massive particles propagating on this fuzzy spacetime eventually converges and collapses. This is consistent with our earlier analysis of null geodesics in [Phys. Rev. Lett.\ 107, 021303 (2011)]. |
gr-qc/0106001 | Alexander Feinstein | Alexander Feinstein | Some aspects of pre big bang cosmology | 15 pages, a course given at the Fourth Mexican School on Gravitation
and Mathematical Physics in Huatulco, Mexico | Rev.Mex.Fis.49S1:30-37,2003 | null | null | gr-qc hep-th | null | This is a summary of a course given at the Fourth Mexican School on
Gravitation and Mathematical Physics on some aspects of PBB cosmology. After
introductory remarks the lectures concentrate on some amusing consequences
derived from the symmetries of the string theory with respect to such classical
concepts as isotropy and homogeneity. The extra dimensions and the symmetries
of the M theory are further applied to show that the classical singularities
might be just physically irrelevant. In the final lecture a model universe is
"produced" from "almost nothing" and it is argued that initial plane waves are
thermodynamically natural state for the universe to emerge from.
| [
{
"created": "Fri, 1 Jun 2001 10:37:32 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Feinstein",
"Alexander",
""
]
] | This is a summary of a course given at the Fourth Mexican School on Gravitation and Mathematical Physics on some aspects of PBB cosmology. After introductory remarks the lectures concentrate on some amusing consequences derived from the symmetries of the string theory with respect to such classical concepts as isotropy and homogeneity. The extra dimensions and the symmetries of the M theory are further applied to show that the classical singularities might be just physically irrelevant. In the final lecture a model universe is "produced" from "almost nothing" and it is argued that initial plane waves are thermodynamically natural state for the universe to emerge from. |
gr-qc/9804002 | Leonard Parker | Leonard Parker | Testable Consequences of Curved-Spacetime Renormalization | RevTeX, 7 pages, new title, major revisions, submitted to PRL | null | null | WISC-MILW-98-TH-14 | gr-qc astro-ph hep-th | null | I consider certain renormalization effects in curved spacetime quantum field
theory. In the very early universe these effects resemble those of a
cosmological constant, while in the present universe they give rise to a
significant finite renormalization of the gravitational constant. The relevant
renormalization term and its relation to elementary particle masses was first
found by Parker and Toms in 1985, as a consequence of the ``new partially
summed form'' of the propagator in curved spacetime. The significance of the
term is based on the contribution of massive particles to the vacuum. In the
present universe, this renormalization term appears to account for a large part
or even all of the Newtonian gravitational constant. This conjecture is
testable because it relates the value of Newton's constant to the elementary
particle masses.
| [
{
"created": "Wed, 1 Apr 1998 19:43:17 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Apr 1998 19:17:39 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Parker",
"Leonard",
""
]
] | I consider certain renormalization effects in curved spacetime quantum field theory. In the very early universe these effects resemble those of a cosmological constant, while in the present universe they give rise to a significant finite renormalization of the gravitational constant. The relevant renormalization term and its relation to elementary particle masses was first found by Parker and Toms in 1985, as a consequence of the ``new partially summed form'' of the propagator in curved spacetime. The significance of the term is based on the contribution of massive particles to the vacuum. In the present universe, this renormalization term appears to account for a large part or even all of the Newtonian gravitational constant. This conjecture is testable because it relates the value of Newton's constant to the elementary particle masses. |
2212.01512 | Puxun Wu | Jincheng Wang, Hongwei Yu and Puxun Wu | Cosmological Complexity from initial thermal state | 20 pages, 5 figures | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | The cosmological scalar perturbations should satisfy the thermal distribution
at the beginning of inflation since the cosmic temperature is presumably very
high. In this paper, we investigate, by the Fubini-study method, the effect of
this thermal contribution, which is characterized by a parameter $\kappa_{0}$,
on the evolution of the cosmological complexity $\mathcal{C}_{FS}$ . We find
that when the thermal effect is considered, the Universe would ``decomplex"
firstly with the cosmic expansion after the mode of the scalar perturbations
exiting the horizon in the de Sitter (dS) phase and $\mathcal{C}_{FS}$ has a
minimum about $\pi/4$. If $\mathcal{C}_{FS}$ can reach its minimum during the
dS era, which requires a small $\kappa_0$ or a large e-folding number for a
large $\kappa_0$, it will bounce back to increase, and after the Universe
enters the radiation dominated (RD) phase from the dS one, $\mathcal{C}_{FS}$
will decrease, pass its minimum again, and then increase till the mode reenters
the horizon. For the case of a large enough $\kappa_0$, $\mathcal{C}_{FS}$
decreases but does not reach its minimum during the dS era, and it begins to
increase after the transition from the dS phase to the RD one. When the mode
reenters the horizon during the RD era, the cosmological complexity will
oscillate around about $\kappa_{0}$. These features are different from that of
the initial zero-temperature case, i.e., the cosmological complexity increases
during the dS phase and decreases in the RD era till the mode reenters the
horizon. Our results therefore suggest that the thermal effect changes
qualitatively the evolutionary behavior of the cosmological complexity.
| [
{
"created": "Sat, 3 Dec 2022 02:32:02 GMT",
"version": "v1"
}
] | 2022-12-06 | [
[
"Wang",
"Jincheng",
""
],
[
"Yu",
"Hongwei",
""
],
[
"Wu",
"Puxun",
""
]
] | The cosmological scalar perturbations should satisfy the thermal distribution at the beginning of inflation since the cosmic temperature is presumably very high. In this paper, we investigate, by the Fubini-study method, the effect of this thermal contribution, which is characterized by a parameter $\kappa_{0}$, on the evolution of the cosmological complexity $\mathcal{C}_{FS}$ . We find that when the thermal effect is considered, the Universe would ``decomplex" firstly with the cosmic expansion after the mode of the scalar perturbations exiting the horizon in the de Sitter (dS) phase and $\mathcal{C}_{FS}$ has a minimum about $\pi/4$. If $\mathcal{C}_{FS}$ can reach its minimum during the dS era, which requires a small $\kappa_0$ or a large e-folding number for a large $\kappa_0$, it will bounce back to increase, and after the Universe enters the radiation dominated (RD) phase from the dS one, $\mathcal{C}_{FS}$ will decrease, pass its minimum again, and then increase till the mode reenters the horizon. For the case of a large enough $\kappa_0$, $\mathcal{C}_{FS}$ decreases but does not reach its minimum during the dS era, and it begins to increase after the transition from the dS phase to the RD one. When the mode reenters the horizon during the RD era, the cosmological complexity will oscillate around about $\kappa_{0}$. These features are different from that of the initial zero-temperature case, i.e., the cosmological complexity increases during the dS phase and decreases in the RD era till the mode reenters the horizon. Our results therefore suggest that the thermal effect changes qualitatively the evolutionary behavior of the cosmological complexity. |
1908.02927 | Gihyuk Cho | Gihyuk Cho, Hyung Mok Lee | Analytic Keplerian-type parametrization for general spinning compact
binaries with the leading order spin-orbit interaction | null | null | 10.1103/PhysRevD.100.044046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a fully analytic Keplerian-type parametrization solution to
conservative motion of spinning binary in ADM gauge. This solution is able to
describe three dimensional motion of binaries of arbitrary eccentricity, mass
ratio and initial configuration of spin angular momentum up to the leading
order of post-Newtonian(PN) approximation and a linear order in spin. Based on
our results waveforms can be quickly computed with high accuracy.
| [
{
"created": "Thu, 8 Aug 2019 04:26:33 GMT",
"version": "v1"
}
] | 2019-09-11 | [
[
"Cho",
"Gihyuk",
""
],
[
"Lee",
"Hyung Mok",
""
]
] | We derive a fully analytic Keplerian-type parametrization solution to conservative motion of spinning binary in ADM gauge. This solution is able to describe three dimensional motion of binaries of arbitrary eccentricity, mass ratio and initial configuration of spin angular momentum up to the leading order of post-Newtonian(PN) approximation and a linear order in spin. Based on our results waveforms can be quickly computed with high accuracy. |
2204.06210 | Jainendra Kumar Singh Dr. | J. K. Singh, Shaily and Kazuharu Bamba | Bouncing universe in Gauss-Bonnet gravity | 13 pages, 11 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, a bouncing cosmological scenario is studied in the background
of a flat FLRW model with a specific parametrized hyperbolic form of scale
factor $ a $ in terms of $ t $, where $ \lambda $ is taken as the model
parameter. This model is discussed in $ f(R,G) $ formalism having structured as
$ f(R,G)=R+F(G) $, where $ R $ is Ricci scalar and $ G $ is the Gauss-Bonnet
invariant. The proposed functional form of the Hubble parameter is considered
in such a way that it satisfies the bouncing criteria of the model, which is
free from the initial singularity. The physical consequences of the model are
discussed. In this model, one can see that the EoS parameter crosses the
quintom line $ \omega=-1 $ in the neighborhood of bouncing point $ t\approx0 $,
which is a very strong criterion for a successful bouncing cosmological model.
Finally, we find that all the essential features of the bouncing model are
satisfied successfully.
| [
{
"created": "Wed, 13 Apr 2022 07:32:38 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Apr 2022 15:59:22 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Aug 2022 07:02:11 GMT",
"version": "v3"
},
{
"created": "Wed, 10 Aug 2022 18:35:48 GMT",
"version": "v4"
}
] | 2022-08-12 | [
[
"Singh",
"J. K.",
""
],
[
"Shaily",
"",
""
],
[
"Bamba",
"Kazuharu",
""
]
] | In this paper, a bouncing cosmological scenario is studied in the background of a flat FLRW model with a specific parametrized hyperbolic form of scale factor $ a $ in terms of $ t $, where $ \lambda $ is taken as the model parameter. This model is discussed in $ f(R,G) $ formalism having structured as $ f(R,G)=R+F(G) $, where $ R $ is Ricci scalar and $ G $ is the Gauss-Bonnet invariant. The proposed functional form of the Hubble parameter is considered in such a way that it satisfies the bouncing criteria of the model, which is free from the initial singularity. The physical consequences of the model are discussed. In this model, one can see that the EoS parameter crosses the quintom line $ \omega=-1 $ in the neighborhood of bouncing point $ t\approx0 $, which is a very strong criterion for a successful bouncing cosmological model. Finally, we find that all the essential features of the bouncing model are satisfied successfully. |
2005.12724 | Matthew J. Lake Dr | Matthew J. Lake | Why space could be quantised on a different scale to matter | 5 pages of main text summarising the contents of a talk given at the
4th International Conference on Holography, String Theory and Discrete
Approach, Hanoi, 3rd-8th August 2020, plus an appendix giving technical the
details of the model. No figures. Published version | SciPost Phys. Proc. 4, 014 (2021) | 10.21468/SciPostPhysProc.4.014 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The scale of quantum mechanical effects in matter is set by Planck's
constant, $\hbar$. This represents the quantisation scale for material objects.
In this article, we present a simple argument why the quantisation scale for
space, and hence for gravity, may not be equal to $\hbar$. Indeed, assuming a
single quantisation scale for both matter and geometry leads to the `worst
prediction in physics', namely, the huge difference between the observed and
predicted vacuum energies. Conversely, assuming a different quantum of action
for geometry, $\beta \ll \hbar$, allows us to recover the observed density of
the Universe. Thus, by measuring its present-day expansion, we may in principle
determine, empirically, the scale at which the geometric degrees of freedom
should be quantised.
| [
{
"created": "Tue, 26 May 2020 13:51:30 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Sep 2020 12:42:37 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Aug 2021 10:55:53 GMT",
"version": "v3"
}
] | 2021-08-17 | [
[
"Lake",
"Matthew J.",
""
]
] | The scale of quantum mechanical effects in matter is set by Planck's constant, $\hbar$. This represents the quantisation scale for material objects. In this article, we present a simple argument why the quantisation scale for space, and hence for gravity, may not be equal to $\hbar$. Indeed, assuming a single quantisation scale for both matter and geometry leads to the `worst prediction in physics', namely, the huge difference between the observed and predicted vacuum energies. Conversely, assuming a different quantum of action for geometry, $\beta \ll \hbar$, allows us to recover the observed density of the Universe. Thus, by measuring its present-day expansion, we may in principle determine, empirically, the scale at which the geometric degrees of freedom should be quantised. |
gr-qc/0512048 | Daniele Oriti | Daniele Oriti | Quantum gravity as a group field theory: a sketch | jpconf; 8 pages, 9 figures; to appear in the Proceedings of the
Fourth Meeting on Constrained Dynamics and Quantum Gravity, Cala Gonone,
Italy, September 12-16, 2005 | J.Phys.Conf.Ser. 33 (2006) 271-278 | 10.1088/1742-6596/33/1/030 | DAMTP-2005-123 | gr-qc | null | We give a very brief introduction to the group field theory approach to
quantum gravity, a generalisation of matrix models for 2-dimensional quantum
gravity to higher dimension, that has emerged recently from research in spin
foam models.
| [
{
"created": "Wed, 7 Dec 2005 18:42:19 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Oriti",
"Daniele",
""
]
] | We give a very brief introduction to the group field theory approach to quantum gravity, a generalisation of matrix models for 2-dimensional quantum gravity to higher dimension, that has emerged recently from research in spin foam models. |
gr-qc/0606096 | D. F. Mota | A. Balaguera-Antolinez, D. F. Mota and M. Nowakowski | Ellipsoidal configurations in the de Sitter spacetime | 15 pages, 11 figures, published in Class. Quant. Grav. References
added | Class.Quant.Grav. 23 (2006) 4497-4510 | 10.1088/0264-9381/23/13/013 | null | gr-qc | null | The cosmological constant $\Lambda$ modifies certain properties of large
astrophysical rotating configurations with ellipsoidal geometries, provided the
objects are not too compact. Assuming an equilibrium configuration and so using
the tensor virial equation with $\Lambda$ we explore several equilibrium
properties of homogeneous rotating ellipsoids. One shows that the bifurcation
point, which in the oblate case distinguishes the Maclaurin ellipsoid from the
Jacobi ellipsoid, is sensitive to the cosmological constant. Adding to that,
the cosmological constant allows triaxial configurations of equilibrium
rotating the minor axis as solutions of the virial equations. The significance
of the result lies in the fact that minor axis rotation is indeed found in
nature. Being impossible for the oblate case, it is permissible for prolate
geometries, with $\Lambda$ zero and positive. For the triaxial case, however,
an equilibrium solution is found only for non-zero positive $\Lambda$. Finally,
we solve the tensor virial equation for the angular velocity and display
special effects of the cosmological constant there.
| [
{
"created": "Thu, 22 Jun 2006 09:43:23 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jul 2006 07:19:15 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Balaguera-Antolinez",
"A.",
""
],
[
"Mota",
"D. F.",
""
],
[
"Nowakowski",
"M.",
""
]
] | The cosmological constant $\Lambda$ modifies certain properties of large astrophysical rotating configurations with ellipsoidal geometries, provided the objects are not too compact. Assuming an equilibrium configuration and so using the tensor virial equation with $\Lambda$ we explore several equilibrium properties of homogeneous rotating ellipsoids. One shows that the bifurcation point, which in the oblate case distinguishes the Maclaurin ellipsoid from the Jacobi ellipsoid, is sensitive to the cosmological constant. Adding to that, the cosmological constant allows triaxial configurations of equilibrium rotating the minor axis as solutions of the virial equations. The significance of the result lies in the fact that minor axis rotation is indeed found in nature. Being impossible for the oblate case, it is permissible for prolate geometries, with $\Lambda$ zero and positive. For the triaxial case, however, an equilibrium solution is found only for non-zero positive $\Lambda$. Finally, we solve the tensor virial equation for the angular velocity and display special effects of the cosmological constant there. |
1005.4532 | Orlando Luongo | Orlando Luongo, Hernando Quevedo | Toward an invariant definition of repulsive gravity | to appear in the proceedings of MG12, Marcel Grossman Meeting, Paris,
France, 12-18 Jul 2009 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A remarkable property of naked singularities in general relativity is their
repulsive nature. The effects generated by repulsive gravity are usually
investigated by analyzing the trajectories of test particles which move in the
effective potential of a naked singularity. This method is, however, coordinate
and observer dependent. We propose to use the properties of the Riemann tensor
in order to establish in an invariant manner the regions where repulsive
gravity plays a dominant role. In particular, we show that in the case of the
Kerr-Newman singularity and its special subcases the method delivers plausible
results.
| [
{
"created": "Tue, 25 May 2010 11:07:30 GMT",
"version": "v1"
}
] | 2010-05-26 | [
[
"Luongo",
"Orlando",
""
],
[
"Quevedo",
"Hernando",
""
]
] | A remarkable property of naked singularities in general relativity is their repulsive nature. The effects generated by repulsive gravity are usually investigated by analyzing the trajectories of test particles which move in the effective potential of a naked singularity. This method is, however, coordinate and observer dependent. We propose to use the properties of the Riemann tensor in order to establish in an invariant manner the regions where repulsive gravity plays a dominant role. In particular, we show that in the case of the Kerr-Newman singularity and its special subcases the method delivers plausible results. |
2403.15318 | Stefan Strub | Stefan H. Strub, Luigi Ferraioli, C\'edric Schmelzbach, Simon C.
St\"ahler, and Domenico Giardini | Global Analysis of LISA Data with Galactic Binaries and Massive Black
Hole Binaries | 13 pages, 11 figures | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | The Laser Interferometer Space Antenna (LISA) is a planned space-based
observatory to measure gravitational waves in the millihertz frequency band.
This frequency band is expected to be dominated by signals from millions of
Galactic binaries and tens of merging massive black hole binaries. The LISA
Data Challenge 2a is focused on robust signal extraction from a blend of these
two types of gravitational wave signals. Here, we introduce a novel high
performance and cost-effective global fit pipeline extracting and
characterizing galactic binary and massive black hole binary signals and
estimate the noise of the residual. We perform the pipeline in a time-evolving
weekly analysis starting with an observation time of 1 week until we reach a
full year. As expected we detect more galactic binaries and massive black hole
binaries bringing the noise estimate of the residual closer to the instrument
noise with each week of additional observation time. Furthermore, we present a
novel maximum likelihood estimate-based algorithm for extracting multiple
massive black hole binaries. Additionally, we demonstrate a massive black hole
binary signal extraction with a more accurate LISA response, considering higher
harmonic modes, in a noisy data set.
| [
{
"created": "Fri, 22 Mar 2024 16:11:53 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Mar 2024 07:09:35 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Jun 2024 09:28:47 GMT",
"version": "v3"
}
] | 2024-06-04 | [
[
"Strub",
"Stefan H.",
""
],
[
"Ferraioli",
"Luigi",
""
],
[
"Schmelzbach",
"Cédric",
""
],
[
"Stähler",
"Simon C.",
""
],
[
"Giardini",
"Domenico",
""
]
] | The Laser Interferometer Space Antenna (LISA) is a planned space-based observatory to measure gravitational waves in the millihertz frequency band. This frequency band is expected to be dominated by signals from millions of Galactic binaries and tens of merging massive black hole binaries. The LISA Data Challenge 2a is focused on robust signal extraction from a blend of these two types of gravitational wave signals. Here, we introduce a novel high performance and cost-effective global fit pipeline extracting and characterizing galactic binary and massive black hole binary signals and estimate the noise of the residual. We perform the pipeline in a time-evolving weekly analysis starting with an observation time of 1 week until we reach a full year. As expected we detect more galactic binaries and massive black hole binaries bringing the noise estimate of the residual closer to the instrument noise with each week of additional observation time. Furthermore, we present a novel maximum likelihood estimate-based algorithm for extracting multiple massive black hole binaries. Additionally, we demonstrate a massive black hole binary signal extraction with a more accurate LISA response, considering higher harmonic modes, in a noisy data set. |
2403.19162 | Lalit Pathak | Lalit Pathak, Amit Reza, Anand S. Sengupta | Fast and faithful interpolation of numerical relativity surrogate
waveforms using meshfree approximation | 14 pages, 9 figures | null | null | LIGO DCC number: LIGO-P2400089 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several theoretical waveform models have been developed over the years to
capture the gravitational wave emission from the dynamical evolution of compact
binary systems of neutron stars and black holes. As ground-based detectors
improve their sensitivity at low frequencies, the real-time computation of
these waveforms can become computationally expensive, exacerbating the steep
cost of rapidly reconstructing source parameters using Bayesian methods. This
paper describes an efficient numerical algorithm for generating high-fidelity
interpolated compact binary waveforms at an arbitrary point in the signal
manifold by leveraging computational linear algebra techniques such as singular
value decomposition and meshfree approximation. The results are presented for
the time-domain \texttt{NRHybSur3dq8} inspiral-merger-ringdown (IMR) waveform
model that is fine tuned to numerical relativity simulations and parameterized
by the two component-masses and two aligned spins. For demonstration, we target
a specific region of the intrinsic parameter space inspired by the previously
inferred parameters of the \texttt{GW200311\_115853} event -- a binary black
hole system whose merger was recorded by the network of advanced-LIGO and Virgo
detectors during the third observation run. We show that the meshfree
interpolated waveforms can be evaluated in $\sim 2.3$ ms, which is about
$\times 38$ faster than its brute-force (frequency-domain tapered)
implementation in the \textsc{PyCBC} software package at a median accuracy of
$\sim \mathcal{O}(10^{-5})$. The algorithm is computationally efficient and
scales favourably with an increasing number of dimensions of the parameter
space. This technique may find use in rapid parameter estimation and source
reconstruction studies.
| [
{
"created": "Thu, 28 Mar 2024 06:13:54 GMT",
"version": "v1"
}
] | 2024-03-29 | [
[
"Pathak",
"Lalit",
""
],
[
"Reza",
"Amit",
""
],
[
"Sengupta",
"Anand S.",
""
]
] | Several theoretical waveform models have been developed over the years to capture the gravitational wave emission from the dynamical evolution of compact binary systems of neutron stars and black holes. As ground-based detectors improve their sensitivity at low frequencies, the real-time computation of these waveforms can become computationally expensive, exacerbating the steep cost of rapidly reconstructing source parameters using Bayesian methods. This paper describes an efficient numerical algorithm for generating high-fidelity interpolated compact binary waveforms at an arbitrary point in the signal manifold by leveraging computational linear algebra techniques such as singular value decomposition and meshfree approximation. The results are presented for the time-domain \texttt{NRHybSur3dq8} inspiral-merger-ringdown (IMR) waveform model that is fine tuned to numerical relativity simulations and parameterized by the two component-masses and two aligned spins. For demonstration, we target a specific region of the intrinsic parameter space inspired by the previously inferred parameters of the \texttt{GW200311\_115853} event -- a binary black hole system whose merger was recorded by the network of advanced-LIGO and Virgo detectors during the third observation run. We show that the meshfree interpolated waveforms can be evaluated in $\sim 2.3$ ms, which is about $\times 38$ faster than its brute-force (frequency-domain tapered) implementation in the \textsc{PyCBC} software package at a median accuracy of $\sim \mathcal{O}(10^{-5})$. The algorithm is computationally efficient and scales favourably with an increasing number of dimensions of the parameter space. This technique may find use in rapid parameter estimation and source reconstruction studies. |
1111.7192 | Thomas Cailleteau Mr | Thomas Cailleteau, Aurelien Barrau | Gauge invariance in Loop Quantum Cosmology : Hamilton-Jacobi and
Mukhanov-Sasaki equations for scalar perturbations | 16 pages | Phys. Rev. D 85, 123534 (2012) | 10.1103/PhysRevD.85.123534 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gauge invariance of scalar perturbations is studied together with the
associated equations of motion. Extending methods developed in the framework of
hamiltonian General Relativity, the Hamilton-Jacobi equation is investigated
into the details in Loop Quantum Cosmology. The gauge-invariant observables are
built and their equations of motions are reviewed both in Hamiltonian and
Lagrangian approaches. This method is applied to scalar perturbations with
either holonomy or inverse-volume corrections.
| [
{
"created": "Wed, 30 Nov 2011 14:55:50 GMT",
"version": "v1"
}
] | 2012-11-01 | [
[
"Cailleteau",
"Thomas",
""
],
[
"Barrau",
"Aurelien",
""
]
] | Gauge invariance of scalar perturbations is studied together with the associated equations of motion. Extending methods developed in the framework of hamiltonian General Relativity, the Hamilton-Jacobi equation is investigated into the details in Loop Quantum Cosmology. The gauge-invariant observables are built and their equations of motions are reviewed both in Hamiltonian and Lagrangian approaches. This method is applied to scalar perturbations with either holonomy or inverse-volume corrections. |
gr-qc/0306094 | Carl E. Dolby | Carl E. Dolby, Mark D. Goodsell and Stephen F. Gull | The Fermionic Particle Density of Flat 1+1 Dimensional Spacetime seen by
an Arbitrarily Moving Observer | 19 pages, 9 figures | Class.Quant.Grav. 20 (2003) 4861-4876 | 10.1088/0264-9381/20/22/010 | null | gr-qc hep-th | null | A coordinate system is constructed for a general accelerating observer in 1+1
dimensions, and is used to determine the particle density of the massless Dirac
vacuum for that observer. Equations are obtained for the spatial distribution
and frequency distribution of massless fermions seen by this observer, in terms
of the rapidity function of the observer's worldline. Examples that are
considered include the uniformly accelerating observer as a limiting case, but
do not always involve particle horizons. Only the low frequency limit depends
on the possible presence of particle horizons. The rest of the spectrum is
`almost thermal' whenever the observer's acceleration is `almost uniform'.
| [
{
"created": "Fri, 20 Jun 2003 15:24:44 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Dolby",
"Carl E.",
""
],
[
"Goodsell",
"Mark D.",
""
],
[
"Gull",
"Stephen F.",
""
]
] | A coordinate system is constructed for a general accelerating observer in 1+1 dimensions, and is used to determine the particle density of the massless Dirac vacuum for that observer. Equations are obtained for the spatial distribution and frequency distribution of massless fermions seen by this observer, in terms of the rapidity function of the observer's worldline. Examples that are considered include the uniformly accelerating observer as a limiting case, but do not always involve particle horizons. Only the low frequency limit depends on the possible presence of particle horizons. The rest of the spectrum is `almost thermal' whenever the observer's acceleration is `almost uniform'. |
gr-qc/0610086 | Farook Rahaman | F. Rahaman, B.C.Bhui, A Ghosh and R. Mondal | Vacuumless cosmic strings in Einstein Cartan theory | 7 pages, accepted in Fizika B, Reference corrections | FizikaB15:1-8,2006 | null | null | gr-qc | null | The gravitational fields of vacuumless global and gauge strings have been
investigated in the context of Einstein Cartan theory under the weak field
assumption of the field equations. It has been shown that global string and
gauge string can have only repulsive gravitational effect on a test particle.
| [
{
"created": "Tue, 17 Oct 2006 15:44:05 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Oct 2006 10:19:59 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Rahaman",
"F.",
""
],
[
"Bhui",
"B. C.",
""
],
[
"Ghosh",
"A",
""
],
[
"Mondal",
"R.",
""
]
] | The gravitational fields of vacuumless global and gauge strings have been investigated in the context of Einstein Cartan theory under the weak field assumption of the field equations. It has been shown that global string and gauge string can have only repulsive gravitational effect on a test particle. |
2105.13041 | Maurizio Gasperini | G. Fanizza, M. Gasperini, E. Pavone and L. Tedesco | Linearized propagation equations for metric fluctuations in a general
(non-vacuum) background geometry | 17 pages, no figures | JCAP 07 (2021) 021 | 10.1088/1475-7516/2021/07/021 | BA-TH/804-20 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | The linearized dynamical equation for metric perturbations in a fully
general, non-vacuum, background geometry is obtained from the Hamilton
variational principle applied to the action up to second order. We specialize
our results to the case of traceless and transverse metric fluctuations, and we
discuss how the intrinsic properties of the matter stress tensor can affect
(and modify) the process of gravity wave propagation even in most conventional
geometric scenarios, like (for instance) those described by a FLRW metric
background. We provide explicit examples for fluid, scalar field and
electromagnetic field sources.
| [
{
"created": "Thu, 27 May 2021 10:19:39 GMT",
"version": "v1"
}
] | 2021-07-14 | [
[
"Fanizza",
"G.",
""
],
[
"Gasperini",
"M.",
""
],
[
"Pavone",
"E.",
""
],
[
"Tedesco",
"L.",
""
]
] | The linearized dynamical equation for metric perturbations in a fully general, non-vacuum, background geometry is obtained from the Hamilton variational principle applied to the action up to second order. We specialize our results to the case of traceless and transverse metric fluctuations, and we discuss how the intrinsic properties of the matter stress tensor can affect (and modify) the process of gravity wave propagation even in most conventional geometric scenarios, like (for instance) those described by a FLRW metric background. We provide explicit examples for fluid, scalar field and electromagnetic field sources. |
1312.3159 | Alberto Vecchiato | Alberto Vecchiato, Mario Gai, Mario G. Lattanzi, Mariateresa Crosta,
Ugo Becciani and Stefano Bertone | Astrometric tests of General Relativity in the Solar System:
mathematical and computational scenarios | 4 pages, To appear on the proceedings of the International Conference
on Mathematical Modeling in Physical Sciences (IC-MSQUARE) September 1-5,
2013, Prague, Czech Republic | 2014JPhCS.490a2241V | 10.1088/1742-6596/490/1/012241 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the mathematical models available for relativistic astrometry,
discussing the different approaches and their accuracies in the context of the
modern experiments from space like Gaia and GAME, and we show how these models
can be applied to the real world, and their consequences from the mathematical
and numerical point of view, with specific reference to the case of Gaia, whose
launch is due before the end of the year.
| [
{
"created": "Wed, 11 Dec 2013 13:40:19 GMT",
"version": "v1"
}
] | 2014-04-04 | [
[
"Vecchiato",
"Alberto",
""
],
[
"Gai",
"Mario",
""
],
[
"Lattanzi",
"Mario G.",
""
],
[
"Crosta",
"Mariateresa",
""
],
[
"Becciani",
"Ugo",
""
],
[
"Bertone",
"Stefano",
""
]
] | We review the mathematical models available for relativistic astrometry, discussing the different approaches and their accuracies in the context of the modern experiments from space like Gaia and GAME, and we show how these models can be applied to the real world, and their consequences from the mathematical and numerical point of view, with specific reference to the case of Gaia, whose launch is due before the end of the year. |
gr-qc/0306016 | Valerio Bozza | A. Bhadra | Gravitational lensing by a charged black hole of string theory | 6 pages | Phys.Rev. D67 (2003) 103009 | 10.1103/PhysRevD.67.103009 | null | gr-qc astro-ph hep-th | null | We study gravitational lensing by the
Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole of
heterotic string theory and obtain the angular position and magnification of
the relativistic images. Modeling the supermassive central object of the galaxy
as a GMGHS black hole, we estimate the numerical values of different
strong-lensing parameters. We find that there is no significant string effect
present in the lensing observables in the strong-gravity scenario.
| [
{
"created": "Wed, 4 Jun 2003 13:50:23 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bhadra",
"A.",
""
]
] | We study gravitational lensing by the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole of heterotic string theory and obtain the angular position and magnification of the relativistic images. Modeling the supermassive central object of the galaxy as a GMGHS black hole, we estimate the numerical values of different strong-lensing parameters. We find that there is no significant string effect present in the lensing observables in the strong-gravity scenario. |
gr-qc/0206027 | Vladimir Karas | M. Abramowicz, I. Bengtsson, V. Karas, K. Rosquist | Poincare ball embeddings of the optical geometry | 16 pages, 8 figures; CQG accepted | Class.Quant.Grav. 19 (2002) 3963-3976 | 10.1088/0264-9381/19/15/307 | null | gr-qc astro-ph | null | It is shown that optical geometry of the Reissner-Nordstrom exterior metric
can be embedded in a hyperbolic space all the way down to its outer horizon.
The adopted embedding procedure removes a breakdown of flat-space embeddings
which occurs outside the horizon, at and below the Buchdahl-Bondi limit
(R/M=9/4 in the Schwarzschild case). In particular, the horizon can be captured
in the optical geometry embedding diagram. Moreover, by using the compact
Poincare ball representation of the hyperbolic space, the embedding diagram can
cover the whole extent of radius from spatial infinity down to the horizon.
Attention is drawn to advantages of such embeddings in an appropriately curved
space: this approach gives compact embeddings and it distinguishes clearly the
case of an extremal black hole from a non-extremal one in terms of topology of
the embedded horizon.
| [
{
"created": "Mon, 10 Jun 2002 08:16:06 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Abramowicz",
"M.",
""
],
[
"Bengtsson",
"I.",
""
],
[
"Karas",
"V.",
""
],
[
"Rosquist",
"K.",
""
]
] | It is shown that optical geometry of the Reissner-Nordstrom exterior metric can be embedded in a hyperbolic space all the way down to its outer horizon. The adopted embedding procedure removes a breakdown of flat-space embeddings which occurs outside the horizon, at and below the Buchdahl-Bondi limit (R/M=9/4 in the Schwarzschild case). In particular, the horizon can be captured in the optical geometry embedding diagram. Moreover, by using the compact Poincare ball representation of the hyperbolic space, the embedding diagram can cover the whole extent of radius from spatial infinity down to the horizon. Attention is drawn to advantages of such embeddings in an appropriately curved space: this approach gives compact embeddings and it distinguishes clearly the case of an extremal black hole from a non-extremal one in terms of topology of the embedded horizon. |
2202.01835 | H{\aa}kan Andr\'easson | H{\aa}kan Andr\'easson, Markus Kunze | Static solutions to the spherically symmetric Einstein-Vlasov system: a
particle-number-Casimir approach | 41 pages | SIAM J. Math. Anal. 55, 4843-4879 (2023) | 10.1137/22M1522887 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Existence of spherically symmetric solutions to the Einstein-Vlasov system is
well-known. However, it is an open problem whether or not static solutions
arise as minimizers of a variational problem. Apart from being of interest in
its own right, it is the connection to non-linear stability that gives this
topic its importance. This problem was considered in \cite{Wol}, but as has
been pointed out in \cite{AK}, the paper \cite{Wol} contained serious flaws. In
this work we construct static solutions by solving the Euler-Lagrange equation
for the energy density $\rho$ as a fixed point problem. The Euler-Lagrange
equation originates from the particle number-Casimir functional introduced in
\cite{Wol}. We then define a density function $f$ on phase space which induces
the energy density $\rho$ and we show that it constitutes a static solution of
the Einstein-Vlasov system. Hence we settle rigorously parts of what the author
of \cite{Wol} attempted to prove.
| [
{
"created": "Thu, 3 Feb 2022 20:29:48 GMT",
"version": "v1"
}
] | 2024-02-19 | [
[
"Andréasson",
"Håkan",
""
],
[
"Kunze",
"Markus",
""
]
] | Existence of spherically symmetric solutions to the Einstein-Vlasov system is well-known. However, it is an open problem whether or not static solutions arise as minimizers of a variational problem. Apart from being of interest in its own right, it is the connection to non-linear stability that gives this topic its importance. This problem was considered in \cite{Wol}, but as has been pointed out in \cite{AK}, the paper \cite{Wol} contained serious flaws. In this work we construct static solutions by solving the Euler-Lagrange equation for the energy density $\rho$ as a fixed point problem. The Euler-Lagrange equation originates from the particle number-Casimir functional introduced in \cite{Wol}. We then define a density function $f$ on phase space which induces the energy density $\rho$ and we show that it constitutes a static solution of the Einstein-Vlasov system. Hence we settle rigorously parts of what the author of \cite{Wol} attempted to prove. |
gr-qc/9702004 | Raul Abramo | L.R. Abramo, R.H. Brandenberger, V.M. Mukhanov | Back Reaction of Gravitational Perturbations | 3 pages, LaTex using sprocl.sty, to appear in: Proceedings of the
18th Texas Symposium on Relativistic Astrophysics (eds Olinto, Frieman and
Schramm, World Scientific) | null | null | null | gr-qc astro-ph | null | The back reaction of gravitational perturbations in a homogeneous background
is determined by an effective energy-momentum tensor quadratic in the
perturbations. We show that this nonlinear feedback effect is important in the
case of long wavelength scalar perturbations in inflationary universe models.
We also show how to solve an old problem concerning the gauge dependence of the
effective energy-momentum tensor of perturbations.
| [
{
"created": "Sat, 1 Feb 1997 21:37:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Abramo",
"L. R.",
""
],
[
"Brandenberger",
"R. H.",
""
],
[
"Mukhanov",
"V. M.",
""
]
] | The back reaction of gravitational perturbations in a homogeneous background is determined by an effective energy-momentum tensor quadratic in the perturbations. We show that this nonlinear feedback effect is important in the case of long wavelength scalar perturbations in inflationary universe models. We also show how to solve an old problem concerning the gauge dependence of the effective energy-momentum tensor of perturbations. |
1412.8660 | Ilia Musco | John C. Miller and Ilia Musco | Causal horizons and topics in structure formation | 12 pages, 2 figures, To appear in Proceedings of the RAGtime meetings
2008-2014, Opava, Czech Republic; S. Hledik and Z. Stuchlik, editors | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a write-up of a talk given at the Opava RAGtime meeting in 2011, but
it has been updated to include some subsequent related developments. The talk
focused on discussion of some aspects of black hole and cosmological horizons
under rather general circumstances, and on two different topics related to
formation of cosmological structures at different epochs of the universe:
virialization of cold dark matter during standard structure formation in the
matter-dominated era, and primordial black hole formation during the radiative
era.
| [
{
"created": "Tue, 30 Dec 2014 15:37:06 GMT",
"version": "v1"
}
] | 2014-12-31 | [
[
"Miller",
"John C.",
""
],
[
"Musco",
"Ilia",
""
]
] | This is a write-up of a talk given at the Opava RAGtime meeting in 2011, but it has been updated to include some subsequent related developments. The talk focused on discussion of some aspects of black hole and cosmological horizons under rather general circumstances, and on two different topics related to formation of cosmological structures at different epochs of the universe: virialization of cold dark matter during standard structure formation in the matter-dominated era, and primordial black hole formation during the radiative era. |
gr-qc/9709056 | David Scialom | Philippe Jetzer and David Scialom | On the Stability of Real Scalar Boson Stars | 3 pages, latex, no figures | null | null | null | gr-qc | null | We discuss spherically symmetric static solutions of the
Einstein-Klein-Gordon equations for a real scalar field with a mass and a
quartic self-interaction term. As for the massless case the solutions have a
naked singularity at the origin. However, linear stability analysis shows that
these solutions as well as the massless ones are dynamically unstable.
| [
{
"created": "Mon, 22 Sep 1997 15:50:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Jetzer",
"Philippe",
""
],
[
"Scialom",
"David",
""
]
] | We discuss spherically symmetric static solutions of the Einstein-Klein-Gordon equations for a real scalar field with a mass and a quartic self-interaction term. As for the massless case the solutions have a naked singularity at the origin. However, linear stability analysis shows that these solutions as well as the massless ones are dynamically unstable. |
1706.07421 | N\'estor Ortiz | Juan Cayuso, N\'estor Ortiz, and Luis Lehner | Fixing extensions to General Relativity in the non-linear regime | 26 pages, 10 figures. Matches published version | Phys. Rev. D 96, 084043 (2017) | 10.1103/PhysRevD.96.084043 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The question of what gravitational theory could supersede General Relativity
has been central in theoretical physics for decades. Many disparate
alternatives have been proposed motivated by cosmology, quantum gravity and
phenomenological angles, and have been subjected to tests derived from
cosmological, solar system and pulsar observations typically restricted to
linearized regimes. Gravitational waves from compact binaries provide new
opportunities to probe these theories in the strongly gravitating/highly
dynamical regimes. To this end however, a reliable understanding of the
dynamics in such a regime is required. Unfortunately, most of these theories
fail to define well posed initial value problems, which prevents at face value
from meeting such challenge. In this work, we introduce a consistent program
able to remedy this situation. This program is inspired in the approach to
"fixing" viscous relativistic hydrodynamics introduced by Israel and Stewart in
the late 70's. We illustrate how to implement this approach to control
undesirable effects of higher order derivatives in gravity theories and argue
how the modified system still captures the true dynamics of the putative
underlying theories in 3+1 dimensions. We sketch the implementation of this
idea in a couple of effective theories of gravity, one in the context of
Non-commutative geometry, and one in the context of Chern-Simons modified
General Relativity.
| [
{
"created": "Thu, 22 Jun 2017 17:53:09 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jun 2017 21:34:54 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Nov 2017 00:49:58 GMT",
"version": "v3"
}
] | 2017-11-13 | [
[
"Cayuso",
"Juan",
""
],
[
"Ortiz",
"Néstor",
""
],
[
"Lehner",
"Luis",
""
]
] | The question of what gravitational theory could supersede General Relativity has been central in theoretical physics for decades. Many disparate alternatives have been proposed motivated by cosmology, quantum gravity and phenomenological angles, and have been subjected to tests derived from cosmological, solar system and pulsar observations typically restricted to linearized regimes. Gravitational waves from compact binaries provide new opportunities to probe these theories in the strongly gravitating/highly dynamical regimes. To this end however, a reliable understanding of the dynamics in such a regime is required. Unfortunately, most of these theories fail to define well posed initial value problems, which prevents at face value from meeting such challenge. In this work, we introduce a consistent program able to remedy this situation. This program is inspired in the approach to "fixing" viscous relativistic hydrodynamics introduced by Israel and Stewart in the late 70's. We illustrate how to implement this approach to control undesirable effects of higher order derivatives in gravity theories and argue how the modified system still captures the true dynamics of the putative underlying theories in 3+1 dimensions. We sketch the implementation of this idea in a couple of effective theories of gravity, one in the context of Non-commutative geometry, and one in the context of Chern-Simons modified General Relativity. |
1704.04444 | Kostiantyn Ropotenko | Kostiantyn Ropotenko | Fast scrambling as Brownian motion in a fluid with negative viscosity | 7 pages, Essay written for the Gravity Research Foundation 2017
Awards for Essays on Gravitation | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the fast scrambling of information in a black hole can be
viewed as Brownian motion of information in a fluid with negative viscosity
(and negative temperature). It is argued that a non-local character of the fast
scrambling is only an illusion; the stretched horizon with negative viscosity
is an amplifying medium that mimics non-locality and superluminal
communication.
| [
{
"created": "Thu, 13 Apr 2017 16:18:41 GMT",
"version": "v1"
}
] | 2017-04-17 | [
[
"Ropotenko",
"Kostiantyn",
""
]
] | It is shown that the fast scrambling of information in a black hole can be viewed as Brownian motion of information in a fluid with negative viscosity (and negative temperature). It is argued that a non-local character of the fast scrambling is only an illusion; the stretched horizon with negative viscosity is an amplifying medium that mimics non-locality and superluminal communication. |
1802.06062 | Jos\'e Francisco da Rocha-Neto J. F. | J. F. da Rocha-Neto, B. R. Morais | Gravitational Pressure, apparent horizon and thermodynamics of FLRW
universe in the teleparallel gravity | 20 pages, no figures | General Relativity and Gravitation 2018 | 10.1007/s10714-018-2350-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of the teleparallel equivalent of general relativity the
concept of gravitational pressure and gravitational energy-momentum arisen in a
natural way. In the case of a Friedmann-Lemaitre-Robertson-Walker space FLRW we
obtain the total energy contained inside the apparent horizon and the radial
pressure over the apparent horizon area. We use these definitions to written a
thermodynamics relation $T_{A}dS_{A} = dE_{A}+P_{A}dV_{A}$ at the apparent
horizon, where $E_{A}$ is the total energy inside the apparent horizon, $V_{A}$
is the areal volume of the apparent horizon, $P_{A}$ is the radial pressure
over the apparent horizon area, $S_{A}$ is the entropy which can be assumed as
one quarter of the apparent horizon area only for a non stationary apparent
horizon. We identify $T_{A}$ as the temperature at the surface of the apparent
horizon. We shown that for all expanding accelerated FLRW model of universe the
radial pressure is positive.
| [
{
"created": "Fri, 16 Feb 2018 18:27:37 GMT",
"version": "v1"
}
] | 2018-02-19 | [
[
"da Rocha-Neto",
"J. F.",
""
],
[
"Morais",
"B. R.",
""
]
] | In the context of the teleparallel equivalent of general relativity the concept of gravitational pressure and gravitational energy-momentum arisen in a natural way. In the case of a Friedmann-Lemaitre-Robertson-Walker space FLRW we obtain the total energy contained inside the apparent horizon and the radial pressure over the apparent horizon area. We use these definitions to written a thermodynamics relation $T_{A}dS_{A} = dE_{A}+P_{A}dV_{A}$ at the apparent horizon, where $E_{A}$ is the total energy inside the apparent horizon, $V_{A}$ is the areal volume of the apparent horizon, $P_{A}$ is the radial pressure over the apparent horizon area, $S_{A}$ is the entropy which can be assumed as one quarter of the apparent horizon area only for a non stationary apparent horizon. We identify $T_{A}$ as the temperature at the surface of the apparent horizon. We shown that for all expanding accelerated FLRW model of universe the radial pressure is positive. |
2308.05132 | Rabia Saleem | Xin-Yun Hu, M. Israr Aslam, Rabia Saleem and Xiao-Xiong Zeng | Holographic Einstein Rings of an AdS Black Hole in Massive Gravity | 15 pages, 14 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | In the context of holography, the Einstein ring of an AdS black hole (BH) in
massive gravity (MG) is depicted. An oscillating Gaussian source on one side of
the AdS boundary propagates in bulk, and we impose a response function to
explain it. Using a wave optics imaging system, we obtain the optical
appearance of the Einstein ring. Our research reveals that the ring can change
into a luminosity-deformed ring or light spots depending on the variation of
parameters and observational positions. When observers are positioned at the
north pole, the holographic profiles always appear as a ring with concentric
stripe surroundings, and a bright ring appears at the location of the photon
sphere of the BH. These findings are consistent with the radius of the photon
sphere of the BH, which is calculated in geometrical optics. Our study
contributes to a better understanding of the analytical studies of holographic
theory, which can be used to evaluate different types of BHs for a fixed wave
source and optical system.
| [
{
"created": "Wed, 9 Aug 2023 13:00:56 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Aug 2023 12:11:24 GMT",
"version": "v2"
}
] | 2023-08-22 | [
[
"Hu",
"Xin-Yun",
""
],
[
"Aslam",
"M. Israr",
""
],
[
"Saleem",
"Rabia",
""
],
[
"Zeng",
"Xiao-Xiong",
""
]
] | In the context of holography, the Einstein ring of an AdS black hole (BH) in massive gravity (MG) is depicted. An oscillating Gaussian source on one side of the AdS boundary propagates in bulk, and we impose a response function to explain it. Using a wave optics imaging system, we obtain the optical appearance of the Einstein ring. Our research reveals that the ring can change into a luminosity-deformed ring or light spots depending on the variation of parameters and observational positions. When observers are positioned at the north pole, the holographic profiles always appear as a ring with concentric stripe surroundings, and a bright ring appears at the location of the photon sphere of the BH. These findings are consistent with the radius of the photon sphere of the BH, which is calculated in geometrical optics. Our study contributes to a better understanding of the analytical studies of holographic theory, which can be used to evaluate different types of BHs for a fixed wave source and optical system. |
2007.03769 | Sam Patrick | Sam Patrick, Silke Weinfurtner | Superradiance in dispersive black hole analogues | 22 pages, 11 figures | Phys. Rev. D 102, 084041 (2020) | 10.1103/PhysRevD.102.084041 | null | gr-qc physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Wave equations containing spatial derivatives which are higher than second
order arise naturally in the context of condensed matter systems. The solutions
of such equations contain more than two modes and consequently, the range of
possible interactions between the different modes is significantly enhanced
compared to the two mode case. We develop a framework for analysing the
different mode interactions based on the classical turning points of the
dispersion relation. We then apply this framework to the scattering of deep
water gravity waves with a draining bathtub vortex, a system which constitutes
the analogue of a rotating black hole in the non-dispersive limit. In
particular, we show that the different scattering outcomes are controlled by
the light-ring frequencies, a concept routinely applied in black hole physics,
and two new frequencies which are related to the strength of dispersion. We
find that the frequency range in which the reflected wave is superradiantly
amplified appears as a simple modification to the non-dispersive case. However,
the condition to observe this amplification is complicated by the fact that a
superradiant mode can be reflected back into the system by scattering with one
of the additional modes. We provide estimates for the reflection coefficients
in the full dispersive regime.
| [
{
"created": "Tue, 7 Jul 2020 20:05:36 GMT",
"version": "v1"
}
] | 2020-10-28 | [
[
"Patrick",
"Sam",
""
],
[
"Weinfurtner",
"Silke",
""
]
] | Wave equations containing spatial derivatives which are higher than second order arise naturally in the context of condensed matter systems. The solutions of such equations contain more than two modes and consequently, the range of possible interactions between the different modes is significantly enhanced compared to the two mode case. We develop a framework for analysing the different mode interactions based on the classical turning points of the dispersion relation. We then apply this framework to the scattering of deep water gravity waves with a draining bathtub vortex, a system which constitutes the analogue of a rotating black hole in the non-dispersive limit. In particular, we show that the different scattering outcomes are controlled by the light-ring frequencies, a concept routinely applied in black hole physics, and two new frequencies which are related to the strength of dispersion. We find that the frequency range in which the reflected wave is superradiantly amplified appears as a simple modification to the non-dispersive case. However, the condition to observe this amplification is complicated by the fact that a superradiant mode can be reflected back into the system by scattering with one of the additional modes. We provide estimates for the reflection coefficients in the full dispersive regime. |
0911.1589 | Jeandrew Brink | Jeandrew Brink | Spacetime Encodings III - Second Order Killing Tensors | 9 pages | Phys.Rev.D81:022001,2010 | 10.1103/PhysRevD.81.022001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper explores the Petrov type D, stationary axisymmetric vacuum (SAV)
spacetimes that were found by Carter to have separable Hamilton-Jacobi
equations, and thus admit a second-order Killing tensor. The derivation of the
spacetimes presented in this paper borrows from ideas about dynamical systems,
and illustrates concepts that can be generalized to higher- order Killing
tensors. The relationship between the components of the Killing equations and
metric functions are given explicitly. The origin of the four separable
coordinate systems found by Carter is explained and classified in terms of the
analytic structure associated with the Killing equations. A geometric picture
of what the orbital invariants may represent is built. Requiring that a SAV
spacetime admits a second-order Killing tensor is very restrictive, selecting
very few candidates from the group of all possible SAV spacetimes. This
restriction arises due to the fact that the consistency conditions associated
with the Killing equations require that the field variables obey a second-order
differential equation, as opposed to a fourth-order differential equation that
imposes the weaker condition that the spacetime be SAV. This paper introduces
ideas that could lead to the explicit computation of more general orbital
invariants in the form of higher-order Killing Tensors.
| [
{
"created": "Mon, 9 Nov 2009 05:42:17 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Brink",
"Jeandrew",
""
]
] | This paper explores the Petrov type D, stationary axisymmetric vacuum (SAV) spacetimes that were found by Carter to have separable Hamilton-Jacobi equations, and thus admit a second-order Killing tensor. The derivation of the spacetimes presented in this paper borrows from ideas about dynamical systems, and illustrates concepts that can be generalized to higher- order Killing tensors. The relationship between the components of the Killing equations and metric functions are given explicitly. The origin of the four separable coordinate systems found by Carter is explained and classified in terms of the analytic structure associated with the Killing equations. A geometric picture of what the orbital invariants may represent is built. Requiring that a SAV spacetime admits a second-order Killing tensor is very restrictive, selecting very few candidates from the group of all possible SAV spacetimes. This restriction arises due to the fact that the consistency conditions associated with the Killing equations require that the field variables obey a second-order differential equation, as opposed to a fourth-order differential equation that imposes the weaker condition that the spacetime be SAV. This paper introduces ideas that could lead to the explicit computation of more general orbital invariants in the form of higher-order Killing Tensors. |
1509.00590 | Sergey Yu. Vernov | A.Yu. Kamenshchik, E.O. Pozdeeva, A. Tronconi, G. Venturi, S.Yu.
Vernov | Interdependence between integrable cosmological models with minimal and
non-minimal coupling | 15 pages, v2: figures and references added, accepted for publication
in CQG | Class. Quantum Grav. 33 (2016) 015004 | 10.1088/0264-9381/33/1/015004 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the relation between exact solutions of cosmological models
having minimally and non-minimally coupled scalar fields. This is done for a
particular class of solvable models which, in the Einstein frame, have
potentials depending on hyperbolic functions and in the Jordan frame, where the
non-minimal coupling is conformal, possess a relatively simple dynamics. We
show that a particular model in this class can be generalized to the cases of
closed and open Friedmann universes and still exhibits a simple dynamics.
Further we illustrate the conditions for the existences of bounces in some
sub-classes of the set of integrable models we have considered.
| [
{
"created": "Wed, 2 Sep 2015 07:41:55 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2015 18:53:45 GMT",
"version": "v2"
}
] | 2015-12-15 | [
[
"Kamenshchik",
"A. Yu.",
""
],
[
"Pozdeeva",
"E. O.",
""
],
[
"Tronconi",
"A.",
""
],
[
"Venturi",
"G.",
""
],
[
"Vernov",
"S. Yu.",
""
]
] | We consider the relation between exact solutions of cosmological models having minimally and non-minimally coupled scalar fields. This is done for a particular class of solvable models which, in the Einstein frame, have potentials depending on hyperbolic functions and in the Jordan frame, where the non-minimal coupling is conformal, possess a relatively simple dynamics. We show that a particular model in this class can be generalized to the cases of closed and open Friedmann universes and still exhibits a simple dynamics. Further we illustrate the conditions for the existences of bounces in some sub-classes of the set of integrable models we have considered. |
gr-qc/0204040 | Varun Sahni | Yuri Shtanov and Varun Sahni | New Cosmological Singularities in Braneworld Models | 11 pages, 3 figures. Slight change in title to match version accepted
for publication in Class. Quant. Grav. (Lett.) | Class.Quant.Grav.19:L101-L107,2002 | 10.1088/0264-9381/19/11/102 | null | gr-qc astro-ph hep-ph hep-th | null | Higher-dimensional braneworld models which contain both bulk and brane
curvature terms in the action admit cosmological singularities of rather
unusual form and nature. These `quiescent' singularities, which can occur both
during the contracting as well as the expanding phase, are characterised by the
fact that while the matter density and Hubble parameter remain finite, all
higher derivatives of the scale factor ($\stackrel{..}{a}$, $\stackrel{...}{a}$
etc.) diverge as the cosmological singularity is approached. The singularities
are the result of the embedding of the (3+1)-dimensional brane in the bulk and
can exist even in an empty homogeneous and isotropic (FRW) universe. The
possibility that the present universe may expand into a singular state is
discussed.
| [
{
"created": "Thu, 11 Apr 2002 07:29:02 GMT",
"version": "v1"
},
{
"created": "Thu, 2 May 2002 17:43:32 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Shtanov",
"Yuri",
""
],
[
"Sahni",
"Varun",
""
]
] | Higher-dimensional braneworld models which contain both bulk and brane curvature terms in the action admit cosmological singularities of rather unusual form and nature. These `quiescent' singularities, which can occur both during the contracting as well as the expanding phase, are characterised by the fact that while the matter density and Hubble parameter remain finite, all higher derivatives of the scale factor ($\stackrel{..}{a}$, $\stackrel{...}{a}$ etc.) diverge as the cosmological singularity is approached. The singularities are the result of the embedding of the (3+1)-dimensional brane in the bulk and can exist even in an empty homogeneous and isotropic (FRW) universe. The possibility that the present universe may expand into a singular state is discussed. |
0909.2717 | Masoud Alimohammadi | M. Alimohammadi and H. Behnamian | Remarks on generalized scalar-tensor models of dark energy | 20 pages, 5 figures, typos corrected, reference added | Phys.Rev.D80:063008,2009 | 10.1103/PhysRevD.80.063008 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The generalized scalar-tensor models with Lagrangian
$F(\phi,R)-U(\phi)(\nabla\phi)^2$ are considered. It is shown that the
phantom-divide-line crossing and the deceleration to acceleration transition
generally occurr in these models. Two specific examples, the coupled
quintessence model and the Brans-Dicke model are considered. For the first
example, it is shown that for the models with $\xi>3/16$, the $\omega=-1$
transition exists. This is verified numerically for some special cases. For the
Brans-Dicke model, it is shown that the transition does not occur, a result
which can be verified by using the exact solution of this model. Finally the
contribution of quantum effects on these phenomena is investigated. It is shown
that for some special cases where the $\omega=-1$ transition is classically
forbidden, the quantum effects can induce transition. The $\xi=1/6$ of coupled
quintessence model is an example of this. The quantum effects are described via
the account of conformal anomaly.
| [
{
"created": "Tue, 15 Sep 2009 06:06:37 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Sep 2009 10:21:33 GMT",
"version": "v2"
}
] | 2010-04-30 | [
[
"Alimohammadi",
"M.",
""
],
[
"Behnamian",
"H.",
""
]
] | The generalized scalar-tensor models with Lagrangian $F(\phi,R)-U(\phi)(\nabla\phi)^2$ are considered. It is shown that the phantom-divide-line crossing and the deceleration to acceleration transition generally occurr in these models. Two specific examples, the coupled quintessence model and the Brans-Dicke model are considered. For the first example, it is shown that for the models with $\xi>3/16$, the $\omega=-1$ transition exists. This is verified numerically for some special cases. For the Brans-Dicke model, it is shown that the transition does not occur, a result which can be verified by using the exact solution of this model. Finally the contribution of quantum effects on these phenomena is investigated. It is shown that for some special cases where the $\omega=-1$ transition is classically forbidden, the quantum effects can induce transition. The $\xi=1/6$ of coupled quintessence model is an example of this. The quantum effects are described via the account of conformal anomaly. |
gr-qc/9207011 | Sai Iyer | Sai Iyer and A R Prasanna | Centrifugal force in Kerr geometry | 6 pages, LateX macros | null | 10.1088/0264-9381/10/1/003 | PRL-TH-92/33 | gr-qc | null | We have obtained the correct expression for the centrifugal force acting on a
particle at the equatorial circumference of a rotating body in the locally
non-rotating frame of the Kerr geometry. Using this expression for the
equilibrium of an element on the surface of a slowly rotating Maclaurin
spheroid, we obtain the expression for the ellipticity (as discussed earlier by
Abramowicz and Miller) and determine the radius at which the ellipticity is
maximum.
| [
{
"created": "Fri, 31 Jul 1992 16:09:17 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Iyer",
"Sai",
""
],
[
"Prasanna",
"A R",
""
]
] | We have obtained the correct expression for the centrifugal force acting on a particle at the equatorial circumference of a rotating body in the locally non-rotating frame of the Kerr geometry. Using this expression for the equilibrium of an element on the surface of a slowly rotating Maclaurin spheroid, we obtain the expression for the ellipticity (as discussed earlier by Abramowicz and Miller) and determine the radius at which the ellipticity is maximum. |
1706.01879 | Lorenzo Sebastiani | E. Elizalde, S.D. Odintsov, L.Sebastiani, R.Myrzakulov | Beyond-one-loop quantum gravity action yielding both inflation and
late-time acceleration | 20 pages, to appear in NPB | null | 10.1016/j.nuclphysb.2017.06.003 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A unified description of early-time inflation with the current cosmic
acceleration is achieved by means of a new theory that uses a quadratic model
of gravity, with the inclusion of an exponential $F(R)$-gravity contribution
for dark energy. High-curvature corrections of the theory come from
higher-derivative quantum gravity and yield an effective action that goes
beyond the one-loop approximation. It is shown that, in this theory, viable
inflation emerges in a natural way, leading to a spectral index and
tensor-to-scalar ratio that are in perfect agreement with the most reliable
Planck results. At low energy, late-time accelerated expansion takes place. As
exponential gravity, for dark energy, must be stabilized during the matter and
radiation eras, we introduce a curing term in order to avoid nonphysical
singularities in the effective equation of state parameter. The results of our
analysis are confirmed by accurate numerical simulations, which show that our
model does fit the most recent cosmological data for dark energy very
precisely.
| [
{
"created": "Tue, 6 Jun 2017 12:55:27 GMT",
"version": "v1"
}
] | 2017-06-28 | [
[
"Elizalde",
"E.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Sebastiani",
"L.",
""
],
[
"Myrzakulov",
"R.",
""
]
] | A unified description of early-time inflation with the current cosmic acceleration is achieved by means of a new theory that uses a quadratic model of gravity, with the inclusion of an exponential $F(R)$-gravity contribution for dark energy. High-curvature corrections of the theory come from higher-derivative quantum gravity and yield an effective action that goes beyond the one-loop approximation. It is shown that, in this theory, viable inflation emerges in a natural way, leading to a spectral index and tensor-to-scalar ratio that are in perfect agreement with the most reliable Planck results. At low energy, late-time accelerated expansion takes place. As exponential gravity, for dark energy, must be stabilized during the matter and radiation eras, we introduce a curing term in order to avoid nonphysical singularities in the effective equation of state parameter. The results of our analysis are confirmed by accurate numerical simulations, which show that our model does fit the most recent cosmological data for dark energy very precisely. |
2309.05643 | Christian J. Kr\"uger | Christian J. Kr\"uger, Sebastian H. V\"olkel | Rapidly rotating neutron stars: Universal relations and EOS inference | 17 pages, 14 figures | Phys. Rev. D108, 124056 (2023) | 10.1103/PhysRevD.108.124056 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide accurate universal relations that allow to estimate the moment of
inertia $I$ and the ratio of kinetic to gravitational binding energy $T/W$ of
uniformly rotating neutron stars from the knowledge of mass, radius, and moment
of inertia of an associated non-rotating neutron star. Based on these, several
other fluid quantities can be estimated as well. Astrophysical neutron stars
rotate to varying degrees, and, although rotational effects may be neglected in
some cases, not modeling them will inevitably introduce bias when performing
parameter estimation. This is especially important for future, high-precision
measurements coming from electromagnetic and gravitational wave observations.
The proposed universal relations facilitate computationally cheap EOS inference
codes that permit the inclusion of observations of rotating neutron stars. To
demonstrate this, we deploy them into a recent Bayesian framework for equation
of state parameter estimation that is now valid for arbitrary, uniform
rotation. Our inference results are robust up to around percent level precision
for the generated neutron star observations, consisting of the mass, equatorial
radius, rotation rate, as well as co- and counter-rotating $f$-mode
frequencies, that enter the framework as data.
| [
{
"created": "Mon, 11 Sep 2023 17:33:38 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jan 2024 22:33:48 GMT",
"version": "v2"
}
] | 2024-01-17 | [
[
"Krüger",
"Christian J.",
""
],
[
"Völkel",
"Sebastian H.",
""
]
] | We provide accurate universal relations that allow to estimate the moment of inertia $I$ and the ratio of kinetic to gravitational binding energy $T/W$ of uniformly rotating neutron stars from the knowledge of mass, radius, and moment of inertia of an associated non-rotating neutron star. Based on these, several other fluid quantities can be estimated as well. Astrophysical neutron stars rotate to varying degrees, and, although rotational effects may be neglected in some cases, not modeling them will inevitably introduce bias when performing parameter estimation. This is especially important for future, high-precision measurements coming from electromagnetic and gravitational wave observations. The proposed universal relations facilitate computationally cheap EOS inference codes that permit the inclusion of observations of rotating neutron stars. To demonstrate this, we deploy them into a recent Bayesian framework for equation of state parameter estimation that is now valid for arbitrary, uniform rotation. Our inference results are robust up to around percent level precision for the generated neutron star observations, consisting of the mass, equatorial radius, rotation rate, as well as co- and counter-rotating $f$-mode frequencies, that enter the framework as data. |
0903.4724 | Xin-Zhou Li | Xin-zhou Li, Chang-bo Sun and Ping Xi | Statefinder diagnostic in a torsion cosmology | 18 pages, 15 figures, accepted paper in JCAP | JCAP 0904:015,2009 | 10.1088/1475-7516/2009/04/015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the statefinder diagnostic to the torsion cosmology, in which an
accounting for the accelerated universe is considered in term of a
Riemann-Cartan geometry: dynamic scalar torsion. We find that there are some
typical characteristic of the evolution of statefinder parameters for the
torsion cosmology that can be distinguished from the other cosmological models.
Furthermore, we also show that statefinder diagnostic has a direct bearing on
the critical points. The statefinder diagnostic divides the torsion parameter
$a_1$ into differential ranges, which is in keeping with the requirement of
dynamical analysis. In addition, we fit the scalar torsion model to ESSENCE
supernovae data and give the best fit values of the model parameters.
| [
{
"created": "Fri, 27 Mar 2009 01:46:14 GMT",
"version": "v1"
}
] | 2011-03-31 | [
[
"Li",
"Xin-zhou",
""
],
[
"Sun",
"Chang-bo",
""
],
[
"Xi",
"Ping",
""
]
] | We apply the statefinder diagnostic to the torsion cosmology, in which an accounting for the accelerated universe is considered in term of a Riemann-Cartan geometry: dynamic scalar torsion. We find that there are some typical characteristic of the evolution of statefinder parameters for the torsion cosmology that can be distinguished from the other cosmological models. Furthermore, we also show that statefinder diagnostic has a direct bearing on the critical points. The statefinder diagnostic divides the torsion parameter $a_1$ into differential ranges, which is in keeping with the requirement of dynamical analysis. In addition, we fit the scalar torsion model to ESSENCE supernovae data and give the best fit values of the model parameters. |
0803.3849 | Myungseok Yoon | Wontae Kim, Hyeonjoon Shin, and Myungseok Yoon | Anomaly and Hawking radiation from regular black holes | 14 pages, 4 figures | J.Korean Phys.Soc. 53 (2008) 1791-1796 | 10.3938/jkps.53.1791 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Hawking radiation from two regular black holes, the minimal
model and the noncommutative black hole. The flux of Hawking radiation is
derived by applying the anomaly cancellation method proposed by Robinson and
Wilczek. Two regular black holes have the same radiation pattern except for the
detailed expression for the Hawking temperature. The resulting flux of the
energy-momentum tensor is shown to be precisely the same with the thermal flux
from each regular black hole at the Hawking temperature.
| [
{
"created": "Thu, 27 Mar 2008 00:53:54 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Kim",
"Wontae",
""
],
[
"Shin",
"Hyeonjoon",
""
],
[
"Yoon",
"Myungseok",
""
]
] | We consider the Hawking radiation from two regular black holes, the minimal model and the noncommutative black hole. The flux of Hawking radiation is derived by applying the anomaly cancellation method proposed by Robinson and Wilczek. Two regular black holes have the same radiation pattern except for the detailed expression for the Hawking temperature. The resulting flux of the energy-momentum tensor is shown to be precisely the same with the thermal flux from each regular black hole at the Hawking temperature. |
1312.4529 | William East | William E. East, Fethi M. Ramazano\u{g}lu, and Frans Pretorius | Black Hole Superradiance in Dynamical Spacetime | 5 pages, 4 figures; revised to match PRD version | Phys. Rev. D 89, 061503 (2014) | 10.1103/PhysRevD.89.061503 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the superradiant scattering of gravitational waves by a nearly
extremal black hole (dimensionless spin $a=0.99$) by numerically solving the
full Einstein field equations, thus including backreaction effects. This allows
us to study the dynamics of the black hole as it loses energy and angular
momentum during the scattering process. To explore the nonlinear phase of the
interaction, we consider gravitational wave packets with initial energies up to
$10%$ of the mass of the black hole. We find that as the incident wave energy
increases, the amplification of the scattered waves, as well as the energy
extraction efficiency from the black hole, is reduced. During the interaction
the apparent horizon geometry undergoes sizable nonaxisymmetric oscillations.
The largest amplitude excitations occur when the peak frequency of the incident
wave packet is above where superradiance occurs, but close to the dominant
quasinormal mode frequency of the black hole.
| [
{
"created": "Mon, 16 Dec 2013 21:00:00 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Mar 2014 21:50:16 GMT",
"version": "v2"
}
] | 2014-03-26 | [
[
"East",
"William E.",
""
],
[
"Ramazanoğlu",
"Fethi M.",
""
],
[
"Pretorius",
"Frans",
""
]
] | We study the superradiant scattering of gravitational waves by a nearly extremal black hole (dimensionless spin $a=0.99$) by numerically solving the full Einstein field equations, thus including backreaction effects. This allows us to study the dynamics of the black hole as it loses energy and angular momentum during the scattering process. To explore the nonlinear phase of the interaction, we consider gravitational wave packets with initial energies up to $10%$ of the mass of the black hole. We find that as the incident wave energy increases, the amplification of the scattered waves, as well as the energy extraction efficiency from the black hole, is reduced. During the interaction the apparent horizon geometry undergoes sizable nonaxisymmetric oscillations. The largest amplitude excitations occur when the peak frequency of the incident wave packet is above where superradiance occurs, but close to the dominant quasinormal mode frequency of the black hole. |
gr-qc/9611048 | Marco `BRONI` Bruni | M. Bruni, S. Matarrese, S. Mollerach, and S. Sonego | On Relativistic Perturbations of Second and Higher Order | 6 pages, latex, with special style included, Proceedings of the 12th
Italian Conference on General Relativity and Gravitational Physics | null | null | IC/96/224, SISSA--162/96/A | gr-qc astro-ph | null | We present the results of a study of the gauge dependence of spacetime
perturbations. In particular, we consider gauge invariance in general, we give
a generating formula for gauge transformations to an arbitrary order n, and
explicit transformation rules at second order.
| [
{
"created": "Wed, 20 Nov 1996 11:26:14 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bruni",
"M.",
""
],
[
"Matarrese",
"S.",
""
],
[
"Mollerach",
"S.",
""
],
[
"Sonego",
"S.",
""
]
] | We present the results of a study of the gauge dependence of spacetime perturbations. In particular, we consider gauge invariance in general, we give a generating formula for gauge transformations to an arbitrary order n, and explicit transformation rules at second order. |
0708.0490 | Luca Lusanna | Luca Lusanna (INFN, Firenze) | The Chrono-Geometrical Structure of General Relativity and Clock
Synchronization | 13 pages, Talk at the First Colloquium Scientific and Fundamental
Aspects of the Galileo Programme, Toulouse 1-4 October 2007 | null | null | null | gr-qc | null | After a review of the chrono-geometrical structure of special relativity,
where the definition of the instantaneous 3-space is based on the
observer-dependent convention for the synchronization of distant clocks, it is
shown that in a class of models of general relativity the instantaneous 3-space
and the associated clock synchronization convention are dynamically determined
by Einstein's equations. This theoretical framework is necessary to understand
the relativistic effects around the Earth, to be tested with the ACES mission
of ESA, and the implications for metrology induced by the accuracy of the new
generation of atomic clocks.
| [
{
"created": "Fri, 3 Aug 2007 10:50:48 GMT",
"version": "v1"
}
] | 2007-08-06 | [
[
"Lusanna",
"Luca",
"",
"INFN, Firenze"
]
] | After a review of the chrono-geometrical structure of special relativity, where the definition of the instantaneous 3-space is based on the observer-dependent convention for the synchronization of distant clocks, it is shown that in a class of models of general relativity the instantaneous 3-space and the associated clock synchronization convention are dynamically determined by Einstein's equations. This theoretical framework is necessary to understand the relativistic effects around the Earth, to be tested with the ACES mission of ESA, and the implications for metrology induced by the accuracy of the new generation of atomic clocks. |
gr-qc/0411031 | Thomas Thiemann | Thomas Thiemann | Reduced Phase Space Quantization and Dirac Observables | 18 pages, no figures | Class.Quant.Grav. 23 (2006) 1163-1180 | 10.1088/0264-9381/23/4/006 | AEI-2004-103 | gr-qc | null | In her recent work, Dittrich generalized Rovelli's idea of partial
observables to construct Dirac observables for constrained systems to the
general case of an arbitrary first class constraint algebra with structure
functions rather than structure constants. Here we use this framework and
propose a new way for how to implement explicitly a reduced phase space
quantization of a given system, at least in principle, without the need to
compute the gauge equivalence classes. The degree of practicality of this
programme depends on the choice of the partial observables involved. The
(multi-fingered) time evolution was shown to correspond to an automorphism on
the set of Dirac observables so generated and interesting representations of
the latter will be those for which a suitable preferred subgroup is realized
unitarily. We sketch how such a programme might look like for General
Relativity. We also observe that the ideas by Dittrich can be used in order to
generate constraints equivalent to those of the Hamiltonian constraints for
General Relativity such that they are spatially diffeomorphism invariant. This
has the important consequence that one can now quantize the new Hamiltonian
constraints on the partially reduced Hilbert space of spatially diffeomorphism
invariant states, just as for the recently proposed Master constraint
programme.
| [
{
"created": "Sat, 6 Nov 2004 19:08:06 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Thiemann",
"Thomas",
""
]
] | In her recent work, Dittrich generalized Rovelli's idea of partial observables to construct Dirac observables for constrained systems to the general case of an arbitrary first class constraint algebra with structure functions rather than structure constants. Here we use this framework and propose a new way for how to implement explicitly a reduced phase space quantization of a given system, at least in principle, without the need to compute the gauge equivalence classes. The degree of practicality of this programme depends on the choice of the partial observables involved. The (multi-fingered) time evolution was shown to correspond to an automorphism on the set of Dirac observables so generated and interesting representations of the latter will be those for which a suitable preferred subgroup is realized unitarily. We sketch how such a programme might look like for General Relativity. We also observe that the ideas by Dittrich can be used in order to generate constraints equivalent to those of the Hamiltonian constraints for General Relativity such that they are spatially diffeomorphism invariant. This has the important consequence that one can now quantize the new Hamiltonian constraints on the partially reduced Hilbert space of spatially diffeomorphism invariant states, just as for the recently proposed Master constraint programme. |
gr-qc/0504005 | Christian Heinicke | Christian Heinicke, Peter Baekler, Friedrich W. Hehl | Einstein-aether theory, violation of Lorentz invariance, and
metric-affine gravity | Revtex4, 38 pages, 1 figure | Phys.Rev.D72:025012,2005 | 10.1103/PhysRevD.72.025012 | null | gr-qc hep-th | null | We show that the Einstein-aether theory of Jacobson and Mattingly (J&M) can
be understood in the framework of the metric-affine (gauge theory of) gravity
(MAG). We achieve this by relating the aether vector field of J&M to certain
post-Riemannian nonmetricity pieces contained in an independent linear
connection of spacetime. Then, for the aether, a corresponding geometrical
curvature-square Lagrangian with a massive piece can be formulated
straightforwardly. We find an exact spherically symmetric solution of our
model.
| [
{
"created": "Fri, 1 Apr 2005 16:58:14 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Heinicke",
"Christian",
""
],
[
"Baekler",
"Peter",
""
],
[
"Hehl",
"Friedrich W.",
""
]
] | We show that the Einstein-aether theory of Jacobson and Mattingly (J&M) can be understood in the framework of the metric-affine (gauge theory of) gravity (MAG). We achieve this by relating the aether vector field of J&M to certain post-Riemannian nonmetricity pieces contained in an independent linear connection of spacetime. Then, for the aether, a corresponding geometrical curvature-square Lagrangian with a massive piece can be formulated straightforwardly. We find an exact spherically symmetric solution of our model. |
1909.01129 | Michael Good | Michael R. R. Good, Eric V. Linder, Frank Wilczek | Remnant-free Moving Mirror Model for Black Hole Radiation Field | 5 pages, 5 figures | Phys. Rev. D 101, 025012 (2020) | 10.1103/PhysRevD.101.025012 | MIT-CTP/5144 | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the flow of energy and entropy emitted by a class of moving mirror
trajectories which provide models for the radiation fields produced by black
hole evaporation. The mirror radiation fields provide natural, concrete
examples of processes that follow thermal distributions for long periods,
accompanied by transients which are brief and carry little net energy, yet they
ultimately represent pure quantum states. A burst of negative energy flux is a
generic feature of these fields, but it need not be prominent.
| [
{
"created": "Fri, 30 Aug 2019 04:00:54 GMT",
"version": "v1"
}
] | 2020-02-04 | [
[
"Good",
"Michael R. R.",
""
],
[
"Linder",
"Eric V.",
""
],
[
"Wilczek",
"Frank",
""
]
] | We analyze the flow of energy and entropy emitted by a class of moving mirror trajectories which provide models for the radiation fields produced by black hole evaporation. The mirror radiation fields provide natural, concrete examples of processes that follow thermal distributions for long periods, accompanied by transients which are brief and carry little net energy, yet they ultimately represent pure quantum states. A burst of negative energy flux is a generic feature of these fields, but it need not be prominent. |
1105.0667 | Jorge Pullin | Rodolfo Gambini, Jorge Pullin, Saeed Rastgoo | Quantum scalar field in quantum gravity: the propagator and Lorentz
invariance in the spherically symmetric case | Dedicated to Josh Goldberg, to appear in special issue of Gen. Rel.
Grav., 14 pages RevTex. We expanded the section on Lorentz invariance | Gen. Rel. Grav. 43 3569-3592 (2011) | 10.1007/s10714-011-1252-0 | LSU-REL-050311 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We recently studied gravity coupled to a scalar field in spherical symmetry
using loop quantum gravity techniques. Since there are local degrees of freedom
one faces the "problem of dynamics". We attack it using the "uniform
discretization technique". We find the quantum state that minimizes the value
of the master constraint for the case of weak fields and curvatures. The state
has the form of a direct product of Gaussians for the gravitational variables
times a modified Fock state for the scalar field. In this paper we do three
things. First, we verify that the previous state also yields a small value of
the master constraint when one polymerizes the scalar field in addition to the
gravitational variables. We then study the propagators for the polymerized
scalar field in flat space-time using the previously considered ground state in
the low energy limit. We discuss the issue of the Lorentz invariance of the
whole approach. We note that if one uses real clocks to describe the system,
Lorentz invariance violations are small. We discuss the implications of these
results in the light of Horava's Gravity at the Lifshitz point and of the
argument about potential large Lorentz violations in interacting field theories
of Collins et. al.
| [
{
"created": "Tue, 3 May 2011 19:55:48 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Jul 2011 18:26:36 GMT",
"version": "v2"
}
] | 2012-02-13 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
],
[
"Rastgoo",
"Saeed",
""
]
] | We recently studied gravity coupled to a scalar field in spherical symmetry using loop quantum gravity techniques. Since there are local degrees of freedom one faces the "problem of dynamics". We attack it using the "uniform discretization technique". We find the quantum state that minimizes the value of the master constraint for the case of weak fields and curvatures. The state has the form of a direct product of Gaussians for the gravitational variables times a modified Fock state for the scalar field. In this paper we do three things. First, we verify that the previous state also yields a small value of the master constraint when one polymerizes the scalar field in addition to the gravitational variables. We then study the propagators for the polymerized scalar field in flat space-time using the previously considered ground state in the low energy limit. We discuss the issue of the Lorentz invariance of the whole approach. We note that if one uses real clocks to describe the system, Lorentz invariance violations are small. We discuss the implications of these results in the light of Horava's Gravity at the Lifshitz point and of the argument about potential large Lorentz violations in interacting field theories of Collins et. al. |
2109.10336 | Quentin Vigneron | Quentin Vigneron | Is backreaction in cosmology a relativistic effect? On the need for an
extension of Newton's theory to non-Euclidean topologies | Accepted for publication in Physical Review D | null | 10.1103/PhysRevD.105.043524 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Cosmological backreaction corresponds to the effect of inhomogeneities of
structure on the global expansion of the Universe. The main question
surrounding this phenomenon is whether or not it is important enough to lead to
measurable effects on the scale factor evolution eventually explaining its
acceleration or the Hubble tension. One of the most important result on this
subject is the Buchert-Ehlers theorem (Buchert \& Ehlers, 1997) stating that
backreaction is exactly zero when calculated using Newton's theory of
gravitation, which may not be the case in general relativity. It is generally
said that this result implies that backreaction is a purely relativistic
effect. We will show that this is not necessarily the case, in the sense that
this implication does not apply to a universe which is still well described by
Newton's theory on small scales but has a non-Euclidean topology. The theorem
should therefore be generalised to account for such a scenario. In a heuristic
calculation where we construct a theory which is locally Newtonian but defined
on a non-Euclidean topology, we show that backreaction is non-zero, meaning
that it might be non-relativistic depending on the topological class of our
Universe. However, that construction is not unique and remains to be justified
from a non-relativistic limit of general relativity.
| [
{
"created": "Tue, 21 Sep 2021 17:44:05 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jan 2022 14:25:10 GMT",
"version": "v2"
}
] | 2022-03-02 | [
[
"Vigneron",
"Quentin",
""
]
] | Cosmological backreaction corresponds to the effect of inhomogeneities of structure on the global expansion of the Universe. The main question surrounding this phenomenon is whether or not it is important enough to lead to measurable effects on the scale factor evolution eventually explaining its acceleration or the Hubble tension. One of the most important result on this subject is the Buchert-Ehlers theorem (Buchert \& Ehlers, 1997) stating that backreaction is exactly zero when calculated using Newton's theory of gravitation, which may not be the case in general relativity. It is generally said that this result implies that backreaction is a purely relativistic effect. We will show that this is not necessarily the case, in the sense that this implication does not apply to a universe which is still well described by Newton's theory on small scales but has a non-Euclidean topology. The theorem should therefore be generalised to account for such a scenario. In a heuristic calculation where we construct a theory which is locally Newtonian but defined on a non-Euclidean topology, we show that backreaction is non-zero, meaning that it might be non-relativistic depending on the topological class of our Universe. However, that construction is not unique and remains to be justified from a non-relativistic limit of general relativity. |
2106.01297 | Fay Dowker | Fay Dowker and Jeremy Butterfield | Recovering General Relativity from a Planck scale discrete theory of
quantum gravity | 47 pages, 2 figures | null | null | null | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An argument is presented that if a theory of quantum gravity is physically
discrete at the Planck scale and the theory recovers General Relativity as an
approximation, then, at the current stage of our knowledge, causal sets must
arise within the theory, even if they are not its basis.
We show in particular that an apparent alternative to causal sets, viz. a
certain sort of discrete Lorentzian simplicial complex, cannot recover General
Relativistic spacetimes in the appropriately unique way. For it cannot
discriminate between Minkowski spacetime and a spacetime with a certain sort of
gravitational wave burst.
| [
{
"created": "Wed, 2 Jun 2021 17:06:34 GMT",
"version": "v1"
}
] | 2021-06-03 | [
[
"Dowker",
"Fay",
""
],
[
"Butterfield",
"Jeremy",
""
]
] | An argument is presented that if a theory of quantum gravity is physically discrete at the Planck scale and the theory recovers General Relativity as an approximation, then, at the current stage of our knowledge, causal sets must arise within the theory, even if they are not its basis. We show in particular that an apparent alternative to causal sets, viz. a certain sort of discrete Lorentzian simplicial complex, cannot recover General Relativistic spacetimes in the appropriately unique way. For it cannot discriminate between Minkowski spacetime and a spacetime with a certain sort of gravitational wave burst. |
1409.7977 | Benjamin Schulz | Benjamin Schulz | Review on the quantization of gravity | 100 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a review article on quantum gravity. In section 1, the Penrose
singularity theorem is proven. In section 2, the covariant quantization
approach of gravity is reviewed. In section 3, an article by Hawking is
reviewed that shows the gravitational path integral at one loop level to be
dominated by contributions from some kind of virtual gravitational instantons.
In section 4, the canonical, non-perturbative quantization approach is
reviewed. In section 5, arguments from Hawking are mentioned which show the
gravitational path integral to be an approximate solution of the Wheeler deWitt
equation. In section 6, the black hole entropy is derived in various ways.
Section 6.1 uses the gravitational path integral for this calculation. Section
6.2 shows how the black hole entropy can be derived from canonical quantum
gravity. In section 7.1, arguments from Dvali and Gomez who claim that gravity
can be quantized in a way which would be in some sense self-complete are
critically assessed. In section 7.2 a model from Dvali and Gomez for the
description of quantum mechanical black holes is critically assessed and
compared with the standard quantization methods of gravity.
| [
{
"created": "Mon, 29 Sep 2014 01:24:05 GMT",
"version": "v1"
}
] | 2014-09-30 | [
[
"Schulz",
"Benjamin",
""
]
] | This is a review article on quantum gravity. In section 1, the Penrose singularity theorem is proven. In section 2, the covariant quantization approach of gravity is reviewed. In section 3, an article by Hawking is reviewed that shows the gravitational path integral at one loop level to be dominated by contributions from some kind of virtual gravitational instantons. In section 4, the canonical, non-perturbative quantization approach is reviewed. In section 5, arguments from Hawking are mentioned which show the gravitational path integral to be an approximate solution of the Wheeler deWitt equation. In section 6, the black hole entropy is derived in various ways. Section 6.1 uses the gravitational path integral for this calculation. Section 6.2 shows how the black hole entropy can be derived from canonical quantum gravity. In section 7.1, arguments from Dvali and Gomez who claim that gravity can be quantized in a way which would be in some sense self-complete are critically assessed. In section 7.2 a model from Dvali and Gomez for the description of quantum mechanical black holes is critically assessed and compared with the standard quantization methods of gravity. |
gr-qc/0510016 | Harald P. Pfeiffer | Harald P. Pfeiffer | Initial data for black hole evolutions | Ph.D. thesis, Cornell University, 2003 | null | null | null | gr-qc | null | We discuss the initial value problem of general relativity in its recently
unified Lagrangian and Hamiltonian pictures and present a multi-domain
pseudo-spectral collocation method to solve the resulting coupled nonlinear
partial differential equations. Using this code, we explore several approaches
to construct initial data sets containing one or two black holes: We compute
quasi-circular orbits for spinning equal mass black holes and unequal mass
(nonspinning) black holes using the effective potential method with Bowen-York
extrinsic curvature. We compare initial data sets resulting from different
decompositions, and from different choices of the conformal metric with each
other. Furthermore, we use the quasi-equilibrium method to construct initial
data for single black holes and for binary black holes in quasi-circular
orbits. We investigate these binary black hole data sets and examine the limits
of large mass-ratio and wide separation. Finally, we propose a new method for
constructing spacetimes with superposed gravitational waves of possibly very
large amplitude.
| [
{
"created": "Tue, 4 Oct 2005 18:40:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pfeiffer",
"Harald P.",
""
]
] | We discuss the initial value problem of general relativity in its recently unified Lagrangian and Hamiltonian pictures and present a multi-domain pseudo-spectral collocation method to solve the resulting coupled nonlinear partial differential equations. Using this code, we explore several approaches to construct initial data sets containing one or two black holes: We compute quasi-circular orbits for spinning equal mass black holes and unequal mass (nonspinning) black holes using the effective potential method with Bowen-York extrinsic curvature. We compare initial data sets resulting from different decompositions, and from different choices of the conformal metric with each other. Furthermore, we use the quasi-equilibrium method to construct initial data for single black holes and for binary black holes in quasi-circular orbits. We investigate these binary black hole data sets and examine the limits of large mass-ratio and wide separation. Finally, we propose a new method for constructing spacetimes with superposed gravitational waves of possibly very large amplitude. |
1506.01664 | Alexandre Filippov | Alexandre T. Filippov | On solving dynamical equations in general homogeneous isotropic
cosmologies with scalaron | New version: 33 pages instead 32; revised and extended Abstract,
Sections 4.3, 5; edited Section 1, changed a few titles; corrected misprints | null | 10.1134/S0040577916070072 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study general dynamical equations describing homogeneous isotropic
cosmologies coupled to a scalaron $\psi$. For flat cosmologies ($k=0$), we
analyze in detail the gauge-independent equation describing the differential,
$\chi(\alpha)\equiv\psi^\prime(\alpha)$, of the map of the metric $\alpha$ to
the scalaron field $\psi$, which is the main mathematical characteristic
locally defining a `portrait' of a cosmology in `$\alpha$-version'. In the
`$\psi$-version', a similar equation for the differential of the inverse map,
$\bar{\chi}(\psi)\equiv \chi^{-1}(\alpha)$, can be solved asymptotically or for
some `integrable' scalaron potentials $v(\psi)$. In the flat case,
$\bar{\chi}(\psi)$ and $\chi(\alpha)$ satisfy the first-order differential
equations depending only on the logarithmic derivative of the potential. Once
we know a general analytic solution for one of these $\chi$-functions, we can
explicitly derive all characteristics of the cosmological model. In the
$\alpha$-version, the whole dynamical system is integrable for $k\neq 0$ and
with any `$\alpha$-potential', $\bar{v}(\alpha)\equiv v[\psi(\alpha)]$,
replacing $v(\psi)$. There is no a priori relation between the two potentials
before deriving $\chi$ or $\bar{\chi}$, which implicitly depend on the
potential itself, but relations between the two pictures can be found by
asymptotic expansions or by inflationary perturbation theory. Explicit
applications of the results to a more rigorous treatment of the chaotic
inflation models and to their comparison with the ekpyrotic-bouncing ones are
outlined in the frame of our `$\alpha$-formulation' of isotropic scalaron
cosmologies. In particular, we establish an inflationary perturbation expansion
for $\chi$. When all the conditions for inflation are satisfied and $\chi$
obeys a certain boundary (initial) condition, we get the standard inflationary
parameters, with higher-order corrections.
| [
{
"created": "Thu, 4 Jun 2015 17:35:53 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Sep 2015 16:11:27 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Oct 2015 18:14:36 GMT",
"version": "v3"
}
] | 2016-08-24 | [
[
"Filippov",
"Alexandre T.",
""
]
] | We study general dynamical equations describing homogeneous isotropic cosmologies coupled to a scalaron $\psi$. For flat cosmologies ($k=0$), we analyze in detail the gauge-independent equation describing the differential, $\chi(\alpha)\equiv\psi^\prime(\alpha)$, of the map of the metric $\alpha$ to the scalaron field $\psi$, which is the main mathematical characteristic locally defining a `portrait' of a cosmology in `$\alpha$-version'. In the `$\psi$-version', a similar equation for the differential of the inverse map, $\bar{\chi}(\psi)\equiv \chi^{-1}(\alpha)$, can be solved asymptotically or for some `integrable' scalaron potentials $v(\psi)$. In the flat case, $\bar{\chi}(\psi)$ and $\chi(\alpha)$ satisfy the first-order differential equations depending only on the logarithmic derivative of the potential. Once we know a general analytic solution for one of these $\chi$-functions, we can explicitly derive all characteristics of the cosmological model. In the $\alpha$-version, the whole dynamical system is integrable for $k\neq 0$ and with any `$\alpha$-potential', $\bar{v}(\alpha)\equiv v[\psi(\alpha)]$, replacing $v(\psi)$. There is no a priori relation between the two potentials before deriving $\chi$ or $\bar{\chi}$, which implicitly depend on the potential itself, but relations between the two pictures can be found by asymptotic expansions or by inflationary perturbation theory. Explicit applications of the results to a more rigorous treatment of the chaotic inflation models and to their comparison with the ekpyrotic-bouncing ones are outlined in the frame of our `$\alpha$-formulation' of isotropic scalaron cosmologies. In particular, we establish an inflationary perturbation expansion for $\chi$. When all the conditions for inflation are satisfied and $\chi$ obeys a certain boundary (initial) condition, we get the standard inflationary parameters, with higher-order corrections. |
0906.2655 | Stefan Hild | Stefan Hild, Simon Chelkowski, Andreas Freise, Janyce Franc, Nazario
Morgado, Raffaele Flaminio and Riccardo DeSalvo | A Xylophone Configuration for a third Generation Gravitational Wave
Detector | null | Class.Quant.Grav.27:015003,2010 | 10.1088/0264-9381/27/1/015003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Achieving the demanding sensitivity and bandwidth, envisaged for third
generation gravitational wave (GW) observatories, is extremely challenging with
a single broadband interferometer. Very high optical powers (Megawatts) are
required to reduce the quantum noise contribution at high frequencies, while
the interferometer mirrors have to be cooled to cryogenic temperatures in order
to reduce thermal noise sources at low frequencies. To resolve this potential
conflict of cryogenic test masses with high thermal load, we present a
conceptual design for a 2-band xylophone configuration for a third generation
GW observatory, composed of a high-power, high-frequency interferometer and a
cryogenic low-power, low-frequency instrument. Featuring inspiral ranges of
3200Mpc and 38000Mpc for binary neutron stars and binary black holes
coalesences, respectively, we find that the potential sensitivity of xylophone
configurations can be significantly wider and better than what is possible in a
single broadband interferometer.
| [
{
"created": "Mon, 15 Jun 2009 10:45:33 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jul 2009 15:09:43 GMT",
"version": "v2"
}
] | 2010-01-06 | [
[
"Hild",
"Stefan",
""
],
[
"Chelkowski",
"Simon",
""
],
[
"Freise",
"Andreas",
""
],
[
"Franc",
"Janyce",
""
],
[
"Morgado",
"Nazario",
""
],
[
"Flaminio",
"Raffaele",
""
],
[
"DeSalvo",
"Riccardo",
""
]
] | Achieving the demanding sensitivity and bandwidth, envisaged for third generation gravitational wave (GW) observatories, is extremely challenging with a single broadband interferometer. Very high optical powers (Megawatts) are required to reduce the quantum noise contribution at high frequencies, while the interferometer mirrors have to be cooled to cryogenic temperatures in order to reduce thermal noise sources at low frequencies. To resolve this potential conflict of cryogenic test masses with high thermal load, we present a conceptual design for a 2-band xylophone configuration for a third generation GW observatory, composed of a high-power, high-frequency interferometer and a cryogenic low-power, low-frequency instrument. Featuring inspiral ranges of 3200Mpc and 38000Mpc for binary neutron stars and binary black holes coalesences, respectively, we find that the potential sensitivity of xylophone configurations can be significantly wider and better than what is possible in a single broadband interferometer. |
0711.1284 | Carlo Rovelli | Emanuele Alesci, Carlo Rovelli | The complete LQG propagator: II. Asymptotic behavior of the vertex | 16 pages | Phys.Rev.D77:044024,2008 | 10.1103/PhysRevD.77.044024 | null | gr-qc | null | In a previous article we have show that there are difficulties in obtaining
the correct graviton propagator from the loop-quantum-gravity dynamics defined
by the Barrett-Crane vertex amplitude. Here we show that a vertex amplitude
that depends nontrivially on the intertwiners can yield the correct propagator.
We give an explicit example of asymptotic behavior of a vertex amplitude that
gives the correct full graviton propagator in the large distance limit.
| [
{
"created": "Thu, 8 Nov 2007 14:45:43 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Alesci",
"Emanuele",
""
],
[
"Rovelli",
"Carlo",
""
]
] | In a previous article we have show that there are difficulties in obtaining the correct graviton propagator from the loop-quantum-gravity dynamics defined by the Barrett-Crane vertex amplitude. Here we show that a vertex amplitude that depends nontrivially on the intertwiners can yield the correct propagator. We give an explicit example of asymptotic behavior of a vertex amplitude that gives the correct full graviton propagator in the large distance limit. |
gr-qc/0509068 | Stephane Fay | Stephane Fay | Properties of homogeneous cosmologies in scalar tensor theories | 40 pages, 6 figures, chapter of book | Frontiers in field theory, Nova publishers, 2005 | null | null | gr-qc | null | We study the isotropisation of the homogeneous but anisotropic Bianchi class
A models in presence of a minimally coupled and massive scalar field with or
without a perfect fluid. To this end, we use the Hamiltonian formalism of
Arnowitt, Deser and Misner(ADM) and the dynamical systems analysis methods. Our
results allow to define three kinds of isotropisation called class 1, 2 and 3.
We have specifically studied the class 1 and obtained some general constraints
on scalar-tensor theories which are necessary conditions for isotropisation.
The asymptotical behaviors of the metric functions and potential in the
neighborhood of isotropy have also been determined when the isotropic state is
reached sufficiently quickly. We show that the scalar field responsible for
isotropisation may be quintessent and that the presence of curvature favor a
late times acceleration and quintessence. Some applications are made with the
well known exponential law potential by using our theoretical results but also
by help of numerical analysis. The isotropisation process with a power law
potential is also explored. We think this work represents a framework able to
guide some future researches on the isotropisation of homogeneous models in
scalar-tensor theories and we argue by discussing briefly about some recent
results we have obtained in presence of a non minimally coupled scalar field or
several scalar fields.
| [
{
"created": "Fri, 16 Sep 2005 15:15:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fay",
"Stephane",
""
]
] | We study the isotropisation of the homogeneous but anisotropic Bianchi class A models in presence of a minimally coupled and massive scalar field with or without a perfect fluid. To this end, we use the Hamiltonian formalism of Arnowitt, Deser and Misner(ADM) and the dynamical systems analysis methods. Our results allow to define three kinds of isotropisation called class 1, 2 and 3. We have specifically studied the class 1 and obtained some general constraints on scalar-tensor theories which are necessary conditions for isotropisation. The asymptotical behaviors of the metric functions and potential in the neighborhood of isotropy have also been determined when the isotropic state is reached sufficiently quickly. We show that the scalar field responsible for isotropisation may be quintessent and that the presence of curvature favor a late times acceleration and quintessence. Some applications are made with the well known exponential law potential by using our theoretical results but also by help of numerical analysis. The isotropisation process with a power law potential is also explored. We think this work represents a framework able to guide some future researches on the isotropisation of homogeneous models in scalar-tensor theories and we argue by discussing briefly about some recent results we have obtained in presence of a non minimally coupled scalar field or several scalar fields. |
1005.1097 | John D. Swain | John Swain | Black Holes and the Strong CP Problem | Small corrections/additions made plus added references and discussion
of theta terms for electromagnetism and gravity in topologically more
complicated spacetimes | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The strong CP problem is that SU(3) gauge field instantons naturally induce a
CP violating term in the QCD Lagrangian which is constrained by experiment to
be very small for no obvious reason. We show that this problem disappears if
one assumes the existence of at least one black hole somewhere in the universe.
The argument is reminiscent of Dirac's argument for the quantization of charge,
in which the existence of one monople anywhere in the universe suffices to
require the quantization of electric charge everywhere.
| [
{
"created": "Thu, 6 May 2010 22:35:11 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jun 2010 01:00:47 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Swain",
"John",
""
]
] | The strong CP problem is that SU(3) gauge field instantons naturally induce a CP violating term in the QCD Lagrangian which is constrained by experiment to be very small for no obvious reason. We show that this problem disappears if one assumes the existence of at least one black hole somewhere in the universe. The argument is reminiscent of Dirac's argument for the quantization of charge, in which the existence of one monople anywhere in the universe suffices to require the quantization of electric charge everywhere. |
2011.13198 | Joseph Ntahompagaze | Joseph Ntahompagaze, Shambel Sahlu, Amare Abebe and Manasse R. Mbonye | On multifluid perturbations in scalar-tensor cosmology | Accepted for International Journal of Modern Physics D | null | 10.1142/S0218271820501205 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper the scalar-tensor theory is applied to the study of
perturbations in a multi-fluid universe, using the 1+3 covariant approach. Both
scalar and harmonic decompositions are instituted on the perturbation
equations. In particular, as an application, we study perturbations on a
background FRW cosmology consisting of both radiation and dust in the presence
of a scalar field. We consider both radiation-dominated and dust-dominated
epochs, respectively, and study the results. During the analysis, quasi-static
approximation is instituted. It is observed that the fluctuations of the energy
density decrease with increasing redshift, for different values of $n$ of a
power law $R^{n}$ model
| [
{
"created": "Thu, 26 Nov 2020 09:48:24 GMT",
"version": "v1"
}
] | 2020-11-30 | [
[
"Ntahompagaze",
"Joseph",
""
],
[
"Sahlu",
"Shambel",
""
],
[
"Abebe",
"Amare",
""
],
[
"Mbonye",
"Manasse R.",
""
]
] | In this paper the scalar-tensor theory is applied to the study of perturbations in a multi-fluid universe, using the 1+3 covariant approach. Both scalar and harmonic decompositions are instituted on the perturbation equations. In particular, as an application, we study perturbations on a background FRW cosmology consisting of both radiation and dust in the presence of a scalar field. We consider both radiation-dominated and dust-dominated epochs, respectively, and study the results. During the analysis, quasi-static approximation is instituted. It is observed that the fluctuations of the energy density decrease with increasing redshift, for different values of $n$ of a power law $R^{n}$ model |
2009.11410 | Maria Skugoreva | Maria A. Skugoreva, Alexey V. Toporensky | Bouncing solutions in $f(T)$ gravity | 11 pages, 5 figures, v3: some corrections, published version | Eur. Phys. J. C 80 (2020) no. 11, 1054 | 10.1140/epjc/s10052-020-08638-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider certain aspects of cosmological dynamics of a spatially curved
Universe in $f(T)$ gravity. Local analysis allows us to find conditions for
bounces and for static solutions; these conditions appear to be in general less
restrictive than in general relativity. We also provide a global analysis of
the corresponding cosmological dynamics in the cases when bounces and static
configurations exist, by constructing phase diagrams. These diagrams indicate
that the fate of a big contracting Universe is not altered significantly when
bounces become possible, since they appear to be inaccessible by a sufficiently
big Universe.
| [
{
"created": "Wed, 23 Sep 2020 22:41:01 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Oct 2020 01:01:30 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Jun 2021 20:34:07 GMT",
"version": "v3"
}
] | 2021-06-10 | [
[
"Skugoreva",
"Maria A.",
""
],
[
"Toporensky",
"Alexey V.",
""
]
] | We consider certain aspects of cosmological dynamics of a spatially curved Universe in $f(T)$ gravity. Local analysis allows us to find conditions for bounces and for static solutions; these conditions appear to be in general less restrictive than in general relativity. We also provide a global analysis of the corresponding cosmological dynamics in the cases when bounces and static configurations exist, by constructing phase diagrams. These diagrams indicate that the fate of a big contracting Universe is not altered significantly when bounces become possible, since they appear to be inaccessible by a sufficiently big Universe. |
gr-qc/0009096 | Roberto Scipioni | Roberto Mignani (University of Rome III) Roberto Scipioni (University
of British Columbia) | On the solutions of the Cartan equation in Metric Affine Gravity | To appear in General Relativity and Gravitation | Gen.Rel.Grav. 33 (2001) 683-711 | 10.1023/A:1010222015861 | null | gr-qc | null | In the Tucker-Wang approach to Metric Affine gravity we review some
particular solutions of the Cartan equation for the non-riemannian part of the
connection. As application we show how a quite general non Riemannian model
gives a Proca type equation for the trace of the nonmetricity 1-forms Q.
| [
{
"created": "Thu, 28 Sep 2000 17:17:52 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Mignani",
"Roberto",
"",
"University of Rome III"
],
[
"Scipioni",
"Roberto",
"",
"University\n of British Columbia"
]
] | In the Tucker-Wang approach to Metric Affine gravity we review some particular solutions of the Cartan equation for the non-riemannian part of the connection. As application we show how a quite general non Riemannian model gives a Proca type equation for the trace of the nonmetricity 1-forms Q. |
gr-qc/0507048 | Dario Zappala | C. M. L. de Aragao, M. Consoli, A. Grillo | Extra dimensions, preferred frames and ether-drift experiments | 15 pages, Latex, no figures | null | null | null | gr-qc astro-ph hep-ph | null | Models with extra space-time dimensions produce, tipically, a 4D effective
theory whose vacuum is not exactly Lorentz invariant but can be considered a
physical medium whose refractive index is determined by the gravitational
field. This leads to a version of relativity with a preferred frame and to look
for experimental tests with the new generation of ether-drift experiments using
rotating cryogenic optical resonators. Considering various types of cosmic
motion, we formulate precise predictions for the modulations of the signal
induced by the Earth's rotation and its orbital revolution around the Sun. We
also compare with recent experimental results that might represent the first
modern experimental evidence for a preferred frame.
| [
{
"created": "Tue, 12 Jul 2005 08:41:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Aragao",
"C. M. L.",
""
],
[
"Consoli",
"M.",
""
],
[
"Grillo",
"A.",
""
]
] | Models with extra space-time dimensions produce, tipically, a 4D effective theory whose vacuum is not exactly Lorentz invariant but can be considered a physical medium whose refractive index is determined by the gravitational field. This leads to a version of relativity with a preferred frame and to look for experimental tests with the new generation of ether-drift experiments using rotating cryogenic optical resonators. Considering various types of cosmic motion, we formulate precise predictions for the modulations of the signal induced by the Earth's rotation and its orbital revolution around the Sun. We also compare with recent experimental results that might represent the first modern experimental evidence for a preferred frame. |
0804.3852 | Farook Rahaman | F.Rahaman, M.Kalam and K. A. Rahman | Conical thin shell wormhole from global monopole: A theoretical
construction | Some chages have been done | Acta Phys.Polon.B40:1575-1590,2009 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By applying 'Darmois-Israel formalism', we establish a new class of thin
shell wormhole in the context of global monopole resulting from the breaking of
a global O(3) symmetry. Since global monopole is asymptotically conical (no
longer asymptotically flat), we call it as conical thin shell wormhole.
Different characteristics of this conical thin shell wormhole, namely, time
evolution of the throat, stability, total amount of exotic matter have been
discussed.
| [
{
"created": "Thu, 24 Apr 2008 06:57:19 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Nov 2008 11:24:53 GMT",
"version": "v2"
}
] | 2009-07-24 | [
[
"Rahaman",
"F.",
""
],
[
"Kalam",
"M.",
""
],
[
"Rahman",
"K. A.",
""
]
] | By applying 'Darmois-Israel formalism', we establish a new class of thin shell wormhole in the context of global monopole resulting from the breaking of a global O(3) symmetry. Since global monopole is asymptotically conical (no longer asymptotically flat), we call it as conical thin shell wormhole. Different characteristics of this conical thin shell wormhole, namely, time evolution of the throat, stability, total amount of exotic matter have been discussed. |
1212.4810 | Francois Foucart | Francois Foucart, M. Brett Deaton, Matthew D. Duez, Lawrence E.
Kidder, Ilana MacDonald, Christian D. Ott, Harald P. Pfeiffer, Mark A.
Scheel, Bela Szilagyi, and Saul A. Teukolsky | Black hole-neutron star mergers at realistic mass ratios: Equation of
state and spin orientation effects | 25 pages, 16 Figures, updated to match published version | Phys. Rev. D 87, 084006 (2013) | 10.1103/PhysRevD.87.084006 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole-neutron star mergers resulting in the disruption of the neutron
star and the formation of an accretion disk and/or the ejection of unbound
material are prime candidates for the joint detection of gravitational-wave and
electromagnetic signals when the next generation of gravitational-wave
detectors comes online. However, the disruption of the neutron star and the
properties of the post-merger remnant are very sensitive to the parameters of
the binary. In this paper, we study the impact of the radius of the neutron
star and the alignment of the black hole spin for systems within the range of
mass ratio currently deemed most likely for field binaries (M_BH ~ 7 M_NS) and
for black hole spins large enough for the neutron star to disrupt (J/M^2=0.9).
We find that: (i) In this regime, the merger is particularly sensitive to the
radius of the neutron star, with remnant masses varying from 0.3M_NS to 0.1M_NS
for changes of only 2 km in the NS radius; (ii) 0.01-0.05M_sun of unbound
material can be ejected with kinetic energy >10^51 ergs, a significant increase
compared to low mass ratio, low spin binaries. This ejecta could power
detectable optical and radio afterglows. (iii) Only a small fraction (<3%) of
the Advanced LIGO events in this parameter range have gravitational-wave
signals which could offer constraints on the equation of state of the neutron
star. (iv) A misaligned black hole spin works against disk formation, with less
neutron star material remaining outside of the black hole after merger, and a
larger fraction of that material remaining in the tidal tail instead of the
forming accretion disk. (v) Large kicks (v>300 km/s) can be given to the final
black hole as a result of a precessing BHNS merger, when the disruption of the
neutron star occurs just outside or within the innermost stable spherical
orbit.
| [
{
"created": "Wed, 19 Dec 2012 20:08:25 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Apr 2013 14:51:21 GMT",
"version": "v2"
}
] | 2013-04-19 | [
[
"Foucart",
"Francois",
""
],
[
"Deaton",
"M. Brett",
""
],
[
"Duez",
"Matthew D.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"MacDonald",
"Ilana",
""
],
[
"Ott",
"Christian D.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | Black hole-neutron star mergers resulting in the disruption of the neutron star and the formation of an accretion disk and/or the ejection of unbound material are prime candidates for the joint detection of gravitational-wave and electromagnetic signals when the next generation of gravitational-wave detectors comes online. However, the disruption of the neutron star and the properties of the post-merger remnant are very sensitive to the parameters of the binary. In this paper, we study the impact of the radius of the neutron star and the alignment of the black hole spin for systems within the range of mass ratio currently deemed most likely for field binaries (M_BH ~ 7 M_NS) and for black hole spins large enough for the neutron star to disrupt (J/M^2=0.9). We find that: (i) In this regime, the merger is particularly sensitive to the radius of the neutron star, with remnant masses varying from 0.3M_NS to 0.1M_NS for changes of only 2 km in the NS radius; (ii) 0.01-0.05M_sun of unbound material can be ejected with kinetic energy >10^51 ergs, a significant increase compared to low mass ratio, low spin binaries. This ejecta could power detectable optical and radio afterglows. (iii) Only a small fraction (<3%) of the Advanced LIGO events in this parameter range have gravitational-wave signals which could offer constraints on the equation of state of the neutron star. (iv) A misaligned black hole spin works against disk formation, with less neutron star material remaining outside of the black hole after merger, and a larger fraction of that material remaining in the tidal tail instead of the forming accretion disk. (v) Large kicks (v>300 km/s) can be given to the final black hole as a result of a precessing BHNS merger, when the disruption of the neutron star occurs just outside or within the innermost stable spherical orbit. |
1702.08187 | Angela D. V. Di Virgilio dr | Angela D. V. Di Virgilio, Wei-Tou Ni, Wei-Tou Ni, Sperello di Serego
Alighieri, Hung-Yi Pu, Sheau-shi Pan | Observational and Experimental Gravity | 1 figure, Second LeCosPa Simposium, December 2015, Taipei Taiwan | Everything about Gravity, World Scientific, pp. 341-346, 2016 | 10.1142/9789813203952_0044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We indicate the progress of experimental gravity, present an outlook in this
field, and summarise the Observational/Experimental Parallel Session together
with a related plenary talk on gravitational waves of the 2nd LeCosPA
Symposium.
| [
{
"created": "Mon, 27 Feb 2017 08:34:35 GMT",
"version": "v1"
}
] | 2017-02-28 | [
[
"Di Virgilio",
"Angela D. V.",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Alighieri",
"Sperello di Serego",
""
],
[
"Pu",
"Hung-Yi",
""
],
[
"Pan",
"Sheau-shi",
""
]
] | We indicate the progress of experimental gravity, present an outlook in this field, and summarise the Observational/Experimental Parallel Session together with a related plenary talk on gravitational waves of the 2nd LeCosPA Symposium. |
2309.00205 | Mohammad Bagher Jahani Poshteh | Amjad Ashoorioon, Mohammad Bagher Jahani Poshteh, Robert B. Mann | Measuring black hole spin through gravitational lensing of pulsars | 6 pages, 1 figure | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We put forward a new procedure for measuring the spin of a black hole with
unprecedented accuracy based on gravitational lensing of millisecond pulsars.
The deflection angle of light increases by increasing the rotation parameter.
For primary and secondary images the angular positions are larger for rotating
black holes by an amount of the order of microarcseconds. Also, the
differential time delay for the case of a rotating black hole is larger than
that for the non-rotating case and the difference could be as large as a few
seconds. We show that this quantity could help us achieve an extremely precise
measurement of the black hole spin, much more accurate than the current and
near future achievable estimation of black hole spin through other methods.
| [
{
"created": "Fri, 1 Sep 2023 01:48:07 GMT",
"version": "v1"
}
] | 2023-09-04 | [
[
"Ashoorioon",
"Amjad",
""
],
[
"Poshteh",
"Mohammad Bagher Jahani",
""
],
[
"Mann",
"Robert B.",
""
]
] | We put forward a new procedure for measuring the spin of a black hole with unprecedented accuracy based on gravitational lensing of millisecond pulsars. The deflection angle of light increases by increasing the rotation parameter. For primary and secondary images the angular positions are larger for rotating black holes by an amount of the order of microarcseconds. Also, the differential time delay for the case of a rotating black hole is larger than that for the non-rotating case and the difference could be as large as a few seconds. We show that this quantity could help us achieve an extremely precise measurement of the black hole spin, much more accurate than the current and near future achievable estimation of black hole spin through other methods. |
1107.2633 | Francesca Vidotto | Francesca Vidotto | Many-nodes/many-links spinfoam: the homogeneous and isotropic case | 8 pages, 4 figures | Class.QuantumGrav.28:245005,2011 | 10.1088/0264-9381/28/24/245005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I compute the Lorentzian EPRL/FK/KKL spinfoam vertex amplitude for regular
graphs, with an arbitrary number of links and nodes, and coherent states peaked
on a homogeneous and isotropic geometry. This form of the amplitude can be
applied for example to a dipole with an arbitrary number of links or to the
4-simplex given by the compete graph on 5 nodes. All the resulting amplitudes
have the same support, independently of the graph used, in the large j (large
volume) limit. This implies that they all yield the Friedmann equation: I show
this in the presence of the cosmological constant. This result indicates that
in the semiclassical limit quantum corrections in spinfoam cosmology do not
come from just refining the graph, but rather from relaxing the large j limit.
| [
{
"created": "Wed, 13 Jul 2011 19:18:34 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jul 2011 14:57:46 GMT",
"version": "v2"
},
{
"created": "Thu, 13 Oct 2011 11:47:34 GMT",
"version": "v3"
}
] | 2012-05-22 | [
[
"Vidotto",
"Francesca",
""
]
] | I compute the Lorentzian EPRL/FK/KKL spinfoam vertex amplitude for regular graphs, with an arbitrary number of links and nodes, and coherent states peaked on a homogeneous and isotropic geometry. This form of the amplitude can be applied for example to a dipole with an arbitrary number of links or to the 4-simplex given by the compete graph on 5 nodes. All the resulting amplitudes have the same support, independently of the graph used, in the large j (large volume) limit. This implies that they all yield the Friedmann equation: I show this in the presence of the cosmological constant. This result indicates that in the semiclassical limit quantum corrections in spinfoam cosmology do not come from just refining the graph, but rather from relaxing the large j limit. |
0906.2617 | Israel Quiros | Israel Quiros, Tame Gonzalez, Dania Gonzalez, Yunelsy Napoles, Ricardo
Garcia-Salcedo and Claudia Moreno | Study Of Tachyon Dynamics For Broad Classes of Potentials | 13 pages, latex, 4 eps figures. Title changed, authors added,
motivation rewritten, discussion improved, references added. To match the
published version | Class.Quant.Grav.27:215021,2010 | 10.1088/0264-9381/27/21/215021 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate in detail the asymptotic properties of tachyon cosmology for a
broad class of self-interaction potentials. The present approach relies in an
appropriate re-definition of the tachyon field, which, in conjunction with a
method formerly applied in the bibliography in a different context, allows to
generalize the dynamical systems study of tachyon cosmology to a wider class of
self-interaction potentials beyond the (inverse) square-law one. It is revealed
that independent of the functional form of the potential, the matter-dominated
solution and the ultra-relativistic (also matter-dominated) solution, are
always associated with equilibrium points in the phase space of the tachyon
models. The latter is always the past attractor, while the former is a saddle
critical point. For inverse power-law potentials $V\propto\phi^{-2\lambda}$ the
late-time attractor is always the de Sitter solution, while for sinh-like
potentials $V\propto\sinh^{-\alpha}(\lambda\phi)$, depending on the region of
parameter space, the late-time attractor can be either the inflationary
tachyon-dominated solution or the matter-scaling (also inflationary) phase. In
general, for most part of known quintessential potentials, the late-time
dynamics will be associated either with de Sitter inflation, or with
matter-scaling, or with scalar field-dominated solutions.
| [
{
"created": "Mon, 15 Jun 2009 12:45:21 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Dec 2009 20:04:07 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Apr 2010 14:45:36 GMT",
"version": "v3"
},
{
"created": "Tue, 12 Oct 2010 20:03:57 GMT",
"version": "v4"
}
] | 2011-03-28 | [
[
"Quiros",
"Israel",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"Gonzalez",
"Dania",
""
],
[
"Napoles",
"Yunelsy",
""
],
[
"Garcia-Salcedo",
"Ricardo",
""
],
[
"Moreno",
"Claudia",
""
]
] | We investigate in detail the asymptotic properties of tachyon cosmology for a broad class of self-interaction potentials. The present approach relies in an appropriate re-definition of the tachyon field, which, in conjunction with a method formerly applied in the bibliography in a different context, allows to generalize the dynamical systems study of tachyon cosmology to a wider class of self-interaction potentials beyond the (inverse) square-law one. It is revealed that independent of the functional form of the potential, the matter-dominated solution and the ultra-relativistic (also matter-dominated) solution, are always associated with equilibrium points in the phase space of the tachyon models. The latter is always the past attractor, while the former is a saddle critical point. For inverse power-law potentials $V\propto\phi^{-2\lambda}$ the late-time attractor is always the de Sitter solution, while for sinh-like potentials $V\propto\sinh^{-\alpha}(\lambda\phi)$, depending on the region of parameter space, the late-time attractor can be either the inflationary tachyon-dominated solution or the matter-scaling (also inflationary) phase. In general, for most part of known quintessential potentials, the late-time dynamics will be associated either with de Sitter inflation, or with matter-scaling, or with scalar field-dominated solutions. |
2212.11798 | Marc Mars | Piotr T. Chru\'sciel and Marc Mars | Analyticity of stationary spacetimes from maximal hypersurfaces | 11 pages, no figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The standard method of proving analyticity of stationary vacuum metrics
invokes the quotient-space version of Einstein equations. We verify that the
same conclusion can be obtained using the KID equations on maximal surfaces.
| [
{
"created": "Thu, 22 Dec 2022 15:27:59 GMT",
"version": "v1"
}
] | 2022-12-23 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Mars",
"Marc",
""
]
] | The standard method of proving analyticity of stationary vacuum metrics invokes the quotient-space version of Einstein equations. We verify that the same conclusion can be obtained using the KID equations on maximal surfaces. |
1812.00384 | Wan Cong Ms | Niloofar Abbasvandi, Wan Cong, David Kubiznak, Robert B. Mann | Snapping swallowtails in accelerating black hole thermodynamics | 18 pages, 8 figures. Accepted for publication in Classical and
Quantum Gravity | null | 10.1088/1361-6382/ab129f | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamic behaviour of a charged and accelerating AdS black hole is
studied in the context of extended phase space with variable cosmological
constant. When compared to the charged AdS black hole without acceleration, a
remarkable new feature of `snapping swallowtails' appears. Namely, for any
black hole with charge $Q$ and any string tension $\mu$ causing the
acceleration of the black hole, there exists a transition pressure
$P_t=3\mu^2/(8\pi Q^2)$ at which the standard swallowtail `snaps', causing the
branch of low temperature black holes to completely disappear, leading to a
pressure induced zeroth order phase transition between small and large black
holes. For intermediate values of the string tension, we also observe a
reentrant phase transition, as the small black hole changes to a large one and
then back to small, as the pressure decreases, crossing the coexistence line of
the two phases several times. We also find a new class of `mini-entropic' black
holes, whose isoperimetric ratio becomes unbounded in a certain region of
parameter space.
| [
{
"created": "Sun, 2 Dec 2018 13:03:06 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Mar 2019 00:52:20 GMT",
"version": "v2"
}
] | 2019-05-22 | [
[
"Abbasvandi",
"Niloofar",
""
],
[
"Cong",
"Wan",
""
],
[
"Kubiznak",
"David",
""
],
[
"Mann",
"Robert B.",
""
]
] | The thermodynamic behaviour of a charged and accelerating AdS black hole is studied in the context of extended phase space with variable cosmological constant. When compared to the charged AdS black hole without acceleration, a remarkable new feature of `snapping swallowtails' appears. Namely, for any black hole with charge $Q$ and any string tension $\mu$ causing the acceleration of the black hole, there exists a transition pressure $P_t=3\mu^2/(8\pi Q^2)$ at which the standard swallowtail `snaps', causing the branch of low temperature black holes to completely disappear, leading to a pressure induced zeroth order phase transition between small and large black holes. For intermediate values of the string tension, we also observe a reentrant phase transition, as the small black hole changes to a large one and then back to small, as the pressure decreases, crossing the coexistence line of the two phases several times. We also find a new class of `mini-entropic' black holes, whose isoperimetric ratio becomes unbounded in a certain region of parameter space. |
1701.06900 | Tahir Hussain | Tahir Hussain, Sumaira Saleem Akhtar and Fawad Khan | Classification of LRS Bianchi type I Spacetimes via Conformal Ricci
Collineations | 24 pages | null | 10.1142/S0219887818500068 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present a complete classification of Locally Rotationally
Symmetric (LRS) Bianchi type I spacetimes according to their Conformal Ricci
Collineations (CRCs). When the Ricci tensor is non-degenerate, a general form
of the vector field generating CRCs is found, subject to some integrability
conditions. Solving the integrability conditions in different cases, it is
found that the LRS Bianchi type I spacetimes admit 7, 10, 11 or 15- dimensional
Lie algebra of CRCs for the choice of non-degenerate Ricci tensor. Moreover, it
is found that these spacetimes admit infinite number of CRCs when the Ricci
tensor is degenerate. Some examples of perfect fluid LRS Bianchi type I
spacetime metrics are provided admitting non trivial CRCs.
| [
{
"created": "Thu, 19 Jan 2017 11:58:08 GMT",
"version": "v1"
}
] | 2018-01-10 | [
[
"Hussain",
"Tahir",
""
],
[
"Akhtar",
"Sumaira Saleem",
""
],
[
"Khan",
"Fawad",
""
]
] | In this paper, we present a complete classification of Locally Rotationally Symmetric (LRS) Bianchi type I spacetimes according to their Conformal Ricci Collineations (CRCs). When the Ricci tensor is non-degenerate, a general form of the vector field generating CRCs is found, subject to some integrability conditions. Solving the integrability conditions in different cases, it is found that the LRS Bianchi type I spacetimes admit 7, 10, 11 or 15- dimensional Lie algebra of CRCs for the choice of non-degenerate Ricci tensor. Moreover, it is found that these spacetimes admit infinite number of CRCs when the Ricci tensor is degenerate. Some examples of perfect fluid LRS Bianchi type I spacetime metrics are provided admitting non trivial CRCs. |
1412.6837 | Giulio D'Odorico | Alessandro Codello and Giulio D'Odorico | Scaling and Renormalization in two dimensional Quantum Gravity | 39 pages | Phys. Rev. D 92, 024026 (2015) | 10.1103/PhysRevD.92.024026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study scaling and renormalization in two dimensional quantum gravity in a
covariant framework. After reviewing the definition of a proper path integral
measure, we use scaling arguments to rederive the KPZ relations, the fractal
dimension of the theory and the scaling of the reparametrization-invariant two
point function. Then we compute the scaling exponents entering in this
relations by means of the functional RG. We show that a key ingredient to
obtain the correct results already known from Liouville theory is the use of
the exponential parametrization for metric fluctuations. We also show that with
this parametrization we can recover the correct finite part of the effective
action as the $\epsilon \to 0$ continuation of gravity in $d=2+\epsilon$
dimensions.
| [
{
"created": "Sun, 21 Dec 2014 21:34:33 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Feb 2015 20:09:07 GMT",
"version": "v2"
}
] | 2015-07-22 | [
[
"Codello",
"Alessandro",
""
],
[
"D'Odorico",
"Giulio",
""
]
] | We study scaling and renormalization in two dimensional quantum gravity in a covariant framework. After reviewing the definition of a proper path integral measure, we use scaling arguments to rederive the KPZ relations, the fractal dimension of the theory and the scaling of the reparametrization-invariant two point function. Then we compute the scaling exponents entering in this relations by means of the functional RG. We show that a key ingredient to obtain the correct results already known from Liouville theory is the use of the exponential parametrization for metric fluctuations. We also show that with this parametrization we can recover the correct finite part of the effective action as the $\epsilon \to 0$ continuation of gravity in $d=2+\epsilon$ dimensions. |
1605.01271 | Rogerio Cavalcanti Teixeira | R. T. Cavalcanti, A. Goncalves da Silva and Roldao da Rocha | Strong Deflection Limit Lensing Effects in the Minimal Geometric
Deformation and Casadio-Fabbri-Mazzacurati Solutions | null | Class. Quantum Grav. 33 (2016) 215007 | 10.1088/0264-9381/33/21/215007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we apply the strong deflection limit approach to investigate
the gravitational lensing phenomena beyond general relativity. This is
accomplished by considering the lensing effects related to black hole solutions
that emerge out of the domain of Einstein gravity, namely, the ones acquired
from the method of geometric deformation and the Casadio-Fabbri-Mazzacurati
brane-world black holes. The lensing observables, for those brane-world black
hole metrics, are compared with the standard ones for the Schwarzschild case.
We prove that brane-world black holes could have significantly different
observational signatures, compared to the Schwarzschild black hole, with terms
containing the post-Newtonian parameter, for the case of the
Casadio-Fabbri-Mazzacurati, and terms with variable brane-world tension, for
the method of geometric deformation.
| [
{
"created": "Tue, 3 May 2016 00:44:39 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Oct 2016 17:38:22 GMT",
"version": "v2"
}
] | 2016-10-13 | [
[
"Cavalcanti",
"R. T.",
""
],
[
"da Silva",
"A. Goncalves",
""
],
[
"da Rocha",
"Roldao",
""
]
] | In this paper we apply the strong deflection limit approach to investigate the gravitational lensing phenomena beyond general relativity. This is accomplished by considering the lensing effects related to black hole solutions that emerge out of the domain of Einstein gravity, namely, the ones acquired from the method of geometric deformation and the Casadio-Fabbri-Mazzacurati brane-world black holes. The lensing observables, for those brane-world black hole metrics, are compared with the standard ones for the Schwarzschild case. We prove that brane-world black holes could have significantly different observational signatures, compared to the Schwarzschild black hole, with terms containing the post-Newtonian parameter, for the case of the Casadio-Fabbri-Mazzacurati, and terms with variable brane-world tension, for the method of geometric deformation. |
1005.2205 | Peter Dunsby | Peter K. S. Dunsby, Emilio Elizalde, Rituparno Goswami, Sergei
Odintsov and Diego Saez-Gomez | On the LCDM Universe in f(R) gravity | 7 pages, accepted for publication in PRD | Phys.Rev.D82:023519,2010 | 10.1103/PhysRevD.82.023519 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several different explicit reconstructions of f(R) gravity are obtained from
the background FRW expansion history. It is shown that the only theory whose
Lagrangian is a simple function of the Ricci scalar R, that admits an exact
LCDM expansion history is standard General Relativity with a positive
cosmological constant and the only way to obtain this behaviour of the scale
factor for more general functions of R is to add additional degrees of freedom
to the matter sector.
| [
{
"created": "Wed, 12 May 2010 20:52:46 GMT",
"version": "v1"
},
{
"created": "Mon, 17 May 2010 19:29:28 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Jul 2010 13:59:28 GMT",
"version": "v3"
}
] | 2014-11-21 | [
[
"Dunsby",
"Peter K. S.",
""
],
[
"Elizalde",
"Emilio",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Odintsov",
"Sergei",
""
],
[
"Saez-Gomez",
"Diego",
""
]
] | Several different explicit reconstructions of f(R) gravity are obtained from the background FRW expansion history. It is shown that the only theory whose Lagrangian is a simple function of the Ricci scalar R, that admits an exact LCDM expansion history is standard General Relativity with a positive cosmological constant and the only way to obtain this behaviour of the scale factor for more general functions of R is to add additional degrees of freedom to the matter sector. |
1611.06025 | Wei-Tou Ni | Wei-Tou Ni | Solar-system tests of the relativistic gravity | 30 pages, 3 tables, Chapter 8 in One Hundred Years of General
Relativity: From Genesis and Empirical Foundations to Gravitational Waves,
Cosmology and Quantum Gravity, ed. W.-T. Ni (World Scientific, Singapore,
2016); matches the published version of IJMPD. This article is an 11-year
update of the solar-system tests part of arXiv:gr-qc/0504116 on Empirical
Foundations of Relativistic Gravity | International Journal of Modern Physics D, Vol. 25, No. 14 (2016)
1630003 (36 pages) | 10.1142/S0218271816300032 | null | gr-qc astro-ph.EP astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1859, Le Verrier discovered the Mercury perihelion advance anomaly. This
anomaly turned out to be the first relativistic-gravity effect observed. During
the 157 years to 2016, the precisions and accuracies of laboratory and space
experiments, and of astrophysical and cosmological observations on relativistic
gravity have been improved by 3-4 orders of magnitude. The improvements have
been mainly from optical observations at first followed by radio observations.
The achievements for the past 50 years are from radio Doppler tracking and
radio ranging together with lunar laser ranging. At the present, the radio
observations and lunar laser ranging experiments are similar in the accuracy of
testing relativistic gravity. We review and summarize the present status of
solar-system tests of relativistic gravity. With planetary laser ranging,
spacecraft laser ranging and interferometric laser ranging (laser Doppler
ranging) together with the development of drag-free technology, the optical
observations will improve the accuracies by another 3-4 orders of magnitude in
both the equivalence principle tests and solar-system dynamics tests of
relativistic gravity. Clock tests and atomic interferometry tests of
relativistic gravity will reach an ever-increasing precision. These will give
crucial clues in both experimental and theoretical aspects of gravity, and may
lead to answers to some profound issues in gravity and cosmology.
| [
{
"created": "Fri, 18 Nov 2016 10:00:55 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Dec 2016 07:47:27 GMT",
"version": "v2"
}
] | 2016-12-28 | [
[
"Ni",
"Wei-Tou",
""
]
] | In 1859, Le Verrier discovered the Mercury perihelion advance anomaly. This anomaly turned out to be the first relativistic-gravity effect observed. During the 157 years to 2016, the precisions and accuracies of laboratory and space experiments, and of astrophysical and cosmological observations on relativistic gravity have been improved by 3-4 orders of magnitude. The improvements have been mainly from optical observations at first followed by radio observations. The achievements for the past 50 years are from radio Doppler tracking and radio ranging together with lunar laser ranging. At the present, the radio observations and lunar laser ranging experiments are similar in the accuracy of testing relativistic gravity. We review and summarize the present status of solar-system tests of relativistic gravity. With planetary laser ranging, spacecraft laser ranging and interferometric laser ranging (laser Doppler ranging) together with the development of drag-free technology, the optical observations will improve the accuracies by another 3-4 orders of magnitude in both the equivalence principle tests and solar-system dynamics tests of relativistic gravity. Clock tests and atomic interferometry tests of relativistic gravity will reach an ever-increasing precision. These will give crucial clues in both experimental and theoretical aspects of gravity, and may lead to answers to some profound issues in gravity and cosmology. |
1002.1172 | Martin Reiris | Martin Reiris | Stationary solutions and asymptotic flatness I | The original submission was revised and divided in two: Stationary
solutions and asymptotic flatness I & Stationary solutions and asymptotic
flatness II | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article and its sequel we discuss the asymptotic structure of
space-times representing isolated bodies in General Relativity. Such
space-times are usually required to be asymptotically flat (AF), and thus to
have a prescribed type of asymptotic. Despite all the "reasonable" that the
requirement is, it seems to be against the spirit of General Relativity where
the global structure of the space-time should be also considered as a variable.
It is shown here that, even eliminating from the definition any a priori
reference or assumption about the asymptotic, the space-times of isolated
bodies are unavoidably and a posteriori AF. In precise terms, between the two
articles it is proved that any vacuum strictly stationary space-time end whose
(quotient) manifold is diffeomorphic to R^3 minus a ball and whose Killing
field has its norm bounded away from zero is necessarily AF with
Schwarzschidian fall off. The "excised" ball would contain (if any) the actual
material body, but this information or any other is not necessary to reach the
conclusion. Physical and mathematical implications are also discussed.
| [
{
"created": "Fri, 5 Feb 2010 09:52:47 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Nov 2011 19:56:13 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Oct 2013 14:49:47 GMT",
"version": "v3"
}
] | 2013-10-02 | [
[
"Reiris",
"Martin",
""
]
] | In this article and its sequel we discuss the asymptotic structure of space-times representing isolated bodies in General Relativity. Such space-times are usually required to be asymptotically flat (AF), and thus to have a prescribed type of asymptotic. Despite all the "reasonable" that the requirement is, it seems to be against the spirit of General Relativity where the global structure of the space-time should be also considered as a variable. It is shown here that, even eliminating from the definition any a priori reference or assumption about the asymptotic, the space-times of isolated bodies are unavoidably and a posteriori AF. In precise terms, between the two articles it is proved that any vacuum strictly stationary space-time end whose (quotient) manifold is diffeomorphic to R^3 minus a ball and whose Killing field has its norm bounded away from zero is necessarily AF with Schwarzschidian fall off. The "excised" ball would contain (if any) the actual material body, but this information or any other is not necessary to reach the conclusion. Physical and mathematical implications are also discussed. |
1907.01269 | Prado Martin-Moruno | Prado Mart\'in-Moruno, Matt Visser | The type III stress-energy tensor: Ugly Duckling of the Hawking-Ellis
classification | V3: 6 references added, some clarifications included, changes in
notation, no physics changes, matches published version. V2: 1 reference
added. V1: 23 pages | null | 10.1088/1361-6382/ab56f6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present some advances in the understanding of type III stress-energy
tensors as per the Hawking-Ellis classification. Type I and type II naturally
appear in classical situations, and can also describe semiclassical effects.
Type IV often shows up in semiclassical gravity. Type III is much more subtle.
We focus our attention on type III$_0$ stress-energy tensors, which capture the
essence ("essential core") of type III. Reflecting on known purely
phenomenological examples, ("gyratons"), we are able to generalize the geometry
generated by those type III$_0$ stress-energy tensors. Moreover, we also
succeed in extending work by Griffiths based on massless Weyl spinors by
finding a fundamental classical bosonic Lagrangian description of these type
III$_0$ stress-energy tensors. To the best of our knowledge this is the first
time in the literature that a consistent classical bosonic Lagrangian
formulation for type III$_0$ stress-energy has been found.
| [
{
"created": "Tue, 2 Jul 2019 10:01:24 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jul 2019 07:24:03 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Nov 2019 10:11:54 GMT",
"version": "v3"
}
] | 2019-11-14 | [
[
"Martín-Moruno",
"Prado",
""
],
[
"Visser",
"Matt",
""
]
] | We present some advances in the understanding of type III stress-energy tensors as per the Hawking-Ellis classification. Type I and type II naturally appear in classical situations, and can also describe semiclassical effects. Type IV often shows up in semiclassical gravity. Type III is much more subtle. We focus our attention on type III$_0$ stress-energy tensors, which capture the essence ("essential core") of type III. Reflecting on known purely phenomenological examples, ("gyratons"), we are able to generalize the geometry generated by those type III$_0$ stress-energy tensors. Moreover, we also succeed in extending work by Griffiths based on massless Weyl spinors by finding a fundamental classical bosonic Lagrangian description of these type III$_0$ stress-energy tensors. To the best of our knowledge this is the first time in the literature that a consistent classical bosonic Lagrangian formulation for type III$_0$ stress-energy has been found. |
gr-qc/0301046 | Dzhunushaliev Vladimir | V. Dzhunushaliev | $\Delta-$string - a hybrid between wormhole and string | 5 pages, LATEX | Gen.Rel.Grav. 35 (2003) 1481-1488 | 10.1023/A:1024542903983 | null | gr-qc hep-th | null | The flux tube solutions in 5D Kaluza-Klein theory can be considered as a
string-like object - $\Delta-$string. The initial 5D metric can be reduced to
some inner degrees of freedom living on the $\Delta-$string. The propagation of
electromagnetic waves through the $\Delta-$string is considered. It is shown
that the difference between $\Delta$ and ordinary strings are connected with
the fact that for the $\Delta-$string such limitations as critical dimensions
are missing.
| [
{
"created": "Tue, 14 Jan 2003 04:19:13 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Dzhunushaliev",
"V.",
""
]
] | The flux tube solutions in 5D Kaluza-Klein theory can be considered as a string-like object - $\Delta-$string. The initial 5D metric can be reduced to some inner degrees of freedom living on the $\Delta-$string. The propagation of electromagnetic waves through the $\Delta-$string is considered. It is shown that the difference between $\Delta$ and ordinary strings are connected with the fact that for the $\Delta-$string such limitations as critical dimensions are missing. |
0707.0368 | Salvatore Capozziello | S. Capozziello, Ch. Corda, M De Laurentis | Stochastic background of relic scalar gravitational waves from
scalar-tensor gravity | 7 pages, 1 figure | Mod.Phys.Lett.A22:2647-2655,2007 | 10.1142/S021773230702573X | null | gr-qc | null | A stochastic background of relic gravitational waves is achieved by the so
called adiabatically-amplified zero-point fluctuations process derived from
early inflation. In principle, it provides a distinctive spectrum of relic
gravitational waves. In the framework of scalar-tensor gravity, we discuss the
scalar modes of gravitational waves and the primordial production of this
scalar component which is generated beside tensorial one. We discuss also the
upper limit for such a relic scalar component with respect to the WMAP
constraints.
| [
{
"created": "Tue, 3 Jul 2007 09:11:09 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Capozziello",
"S.",
""
],
[
"Corda",
"Ch.",
""
],
[
"De Laurentis",
"M",
""
]
] | A stochastic background of relic gravitational waves is achieved by the so called adiabatically-amplified zero-point fluctuations process derived from early inflation. In principle, it provides a distinctive spectrum of relic gravitational waves. In the framework of scalar-tensor gravity, we discuss the scalar modes of gravitational waves and the primordial production of this scalar component which is generated beside tensorial one. We discuss also the upper limit for such a relic scalar component with respect to the WMAP constraints. |
1311.7137 | Carlos Molina Mendes | C. Molina | Deformations of the vacuum solutions of general relativity subjected to
linear constraints | 4 pages | Phys. Rev. D 88, 127501 (2013) | 10.1103/PhysRevD.88.127501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of deforming geometries is particularly important in the context
of constructing new exact solutions of Einstein's equation. This issue often
appears when extensions of the general relativity are treated, for instance in
brane world scenarios. In this paper we investigate spacetimes in which the
energy-momentum tensor obeys a linear constraint. Extensions of the usual
vacuum and electrovacuum solutions of general relativity are derived and an
exact solution is presented. The classes of geometries obtained include a wide
variety of compact objects, among them black holes and wormholes. The general
metric derived in this work generalizes several solutions already published in
the literature. Perturbations around the exact solution are also considered.
| [
{
"created": "Wed, 27 Nov 2013 12:15:13 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Apr 2014 21:27:24 GMT",
"version": "v2"
}
] | 2014-04-11 | [
[
"Molina",
"C.",
""
]
] | The problem of deforming geometries is particularly important in the context of constructing new exact solutions of Einstein's equation. This issue often appears when extensions of the general relativity are treated, for instance in brane world scenarios. In this paper we investigate spacetimes in which the energy-momentum tensor obeys a linear constraint. Extensions of the usual vacuum and electrovacuum solutions of general relativity are derived and an exact solution is presented. The classes of geometries obtained include a wide variety of compact objects, among them black holes and wormholes. The general metric derived in this work generalizes several solutions already published in the literature. Perturbations around the exact solution are also considered. |
1904.05112 | Oliver J. Tattersall | Oliver J. Tattersall, Pedro G. Ferreira | Forecasts for Low Spin Black Hole Spectroscopy in Horndeski Gravity | Updated to match published version | Phys. Rev. D 99, 104082 (2019) | 10.1103/PhysRevD.99.104082 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the prospect of using black hole spectroscopy to constrain the
parameters of Horndeski gravity through observations of gravitational waves
from perturbed black holes. We study the gravitational waves emitted during
ringdown from black holes without hair in Horndeski gravity, demonstrating the
qualitative differences between such emission in General Relativity and
Horndeski theory. In particular, Quasi-Normal Mode frequencies associated with
the scalar field spectrum can appear in the emitted gravitational radiation.
Analytic expressions for error estimates for both the black hole and Horndeski
parameters are calculated using a Fisher Matrix approach, with constraints on
the `effective mass' of the Horndeski scalar field of order $\sim
10^{-17}$eV$c^{-2}$ or tighter being shown to be achievable in some scenarios.
Estimates for the minimum signal-noise-ratio required to observe such a signal
are also presented.
| [
{
"created": "Wed, 10 Apr 2019 11:30:39 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2019 12:47:37 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Jun 2019 11:59:11 GMT",
"version": "v3"
}
] | 2019-06-18 | [
[
"Tattersall",
"Oliver J.",
""
],
[
"Ferreira",
"Pedro G.",
""
]
] | We investigate the prospect of using black hole spectroscopy to constrain the parameters of Horndeski gravity through observations of gravitational waves from perturbed black holes. We study the gravitational waves emitted during ringdown from black holes without hair in Horndeski gravity, demonstrating the qualitative differences between such emission in General Relativity and Horndeski theory. In particular, Quasi-Normal Mode frequencies associated with the scalar field spectrum can appear in the emitted gravitational radiation. Analytic expressions for error estimates for both the black hole and Horndeski parameters are calculated using a Fisher Matrix approach, with constraints on the `effective mass' of the Horndeski scalar field of order $\sim 10^{-17}$eV$c^{-2}$ or tighter being shown to be achievable in some scenarios. Estimates for the minimum signal-noise-ratio required to observe such a signal are also presented. |
1507.02306 | Carlos Hidalgo | Roberto A. Sussman and I. Delgado Gaspar and Juan Carlos Hidalgo | Coarse-grained description of cosmic structure from Szekeres models | V3: Discussion of the expansion eigenvalues and of the Zeldovich
approximation added. Figures modified accordingly. References updated.
Version accepted for publication in JCAP | null | 10.1088/1475-7516/2016/03/012 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the full dynamical freedom of the well known Szekeres models
allows for the description of elaborated 3--dimensional networks of cold dark
matter structures (over--densities and/or density voids) undergoing "pancake"
collapse. By reducing Einstein's field equations to a set of evolution
equations, which themselves reduce in the linear limit to evolution equations
for linear perturbations, we determine the dynamics of such structures, with
the spatial comoving location of each structure uniquely specified by standard
early Universe initial conditions. By means of a representative example we
examine in detail the density contrast, the Hubble flow and peculiar velocities
of structures that evolved, from linear initial data at the last scattering
surface, to fully non--linear 10--20 Mpc. scale configurations today. To
motivate further research, we provide a qualitative discussion on the
connection of Szekeres models with linear perturbations and the pancake
collapse of the Zeldovich approximation. This type of structure modelling
provides a coarse grained -- but fully relativistic non--linear and
non--perturbative -- description of evolving large scale cosmic structures
before their virialisation, and as such it has an enormous potential for
applications in cosmological research.
| [
{
"created": "Wed, 8 Jul 2015 20:46:43 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Nov 2015 19:22:35 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Feb 2016 23:43:54 GMT",
"version": "v3"
}
] | 2016-03-23 | [
[
"Sussman",
"Roberto A.",
""
],
[
"Gaspar",
"I. Delgado",
""
],
[
"Hidalgo",
"Juan Carlos",
""
]
] | We show that the full dynamical freedom of the well known Szekeres models allows for the description of elaborated 3--dimensional networks of cold dark matter structures (over--densities and/or density voids) undergoing "pancake" collapse. By reducing Einstein's field equations to a set of evolution equations, which themselves reduce in the linear limit to evolution equations for linear perturbations, we determine the dynamics of such structures, with the spatial comoving location of each structure uniquely specified by standard early Universe initial conditions. By means of a representative example we examine in detail the density contrast, the Hubble flow and peculiar velocities of structures that evolved, from linear initial data at the last scattering surface, to fully non--linear 10--20 Mpc. scale configurations today. To motivate further research, we provide a qualitative discussion on the connection of Szekeres models with linear perturbations and the pancake collapse of the Zeldovich approximation. This type of structure modelling provides a coarse grained -- but fully relativistic non--linear and non--perturbative -- description of evolving large scale cosmic structures before their virialisation, and as such it has an enormous potential for applications in cosmological research. |
2205.12531 | Hee-Suk Cho | Hee-Suk Cho | Systematic bias due to eccentricity in parameter estimation for merging
binary neutron stars | 16 pages, 18 figures, version published in PRD | Phys. Rev. D 105, 124022 (2022) | 10.1103/PhysRevD.105.124022 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the impact of eccentricity on gravitational-wave parameter
estimation for binary neutron star systems. For signals with small eccentricity
injected into the advanced LIGO sensitivity, we perform Bayesian parameter
estimation using the circular waveform model and show how the recovered
parameters can be biased from their true values, focusing on the intrinsic
parameters the chirp mass ($M_c$), the symmetric mass ratio ($\eta$), and the
tidal deformability ($\tilde{\lambda}$). By comparing the results between the
Bayesian and the analytic Fisher-Cutler-Vallisneri (FCV) methods, we obtain the
valid criteria for the FCV approach. Employing the FCV method and using the
realistic population of binary neutron star sources distributed in the
$m_1$-$m_2$-$e_0$ space, where $e_0$ indicates the eccentricity at 10Hz, we
calculate the measurement errors ($\sigma_{\theta}$) and the systematic biases
($\Delta \theta/\sigma_{\theta}$) and obtain their generalized distributions in
the range of $0 \leq e_0 \leq 0.025$. We find that for all of the three
parameters, the biases increase with increasing $e_0$, and this increase is
faster for larger $e_0$. The bias is mainly dependent on the value of $e_0$ and
weakly dependent on the component masses, and thus the distribution shows a
narrow band in the $e_0$-$\Delta \theta/\sigma_{\theta}$ plane. We present
various posterior examples to illustrate our new findings, such as the
bimodality of posteriors. In particular, we give a specific injection-recovery
example to demonstrate the importance of including eccentricity in parameter
estimation to avoid incorrect predictions of the neutron star equation of
state.
| [
{
"created": "Wed, 25 May 2022 06:55:59 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jun 2022 14:48:19 GMT",
"version": "v2"
}
] | 2022-06-13 | [
[
"Cho",
"Hee-Suk",
""
]
] | We study the impact of eccentricity on gravitational-wave parameter estimation for binary neutron star systems. For signals with small eccentricity injected into the advanced LIGO sensitivity, we perform Bayesian parameter estimation using the circular waveform model and show how the recovered parameters can be biased from their true values, focusing on the intrinsic parameters the chirp mass ($M_c$), the symmetric mass ratio ($\eta$), and the tidal deformability ($\tilde{\lambda}$). By comparing the results between the Bayesian and the analytic Fisher-Cutler-Vallisneri (FCV) methods, we obtain the valid criteria for the FCV approach. Employing the FCV method and using the realistic population of binary neutron star sources distributed in the $m_1$-$m_2$-$e_0$ space, where $e_0$ indicates the eccentricity at 10Hz, we calculate the measurement errors ($\sigma_{\theta}$) and the systematic biases ($\Delta \theta/\sigma_{\theta}$) and obtain their generalized distributions in the range of $0 \leq e_0 \leq 0.025$. We find that for all of the three parameters, the biases increase with increasing $e_0$, and this increase is faster for larger $e_0$. The bias is mainly dependent on the value of $e_0$ and weakly dependent on the component masses, and thus the distribution shows a narrow band in the $e_0$-$\Delta \theta/\sigma_{\theta}$ plane. We present various posterior examples to illustrate our new findings, such as the bimodality of posteriors. In particular, we give a specific injection-recovery example to demonstrate the importance of including eccentricity in parameter estimation to avoid incorrect predictions of the neutron star equation of state. |
gr-qc/0012037 | Christian Heinicke | Christian Heinicke | The Einstein 3-form G_a and its equivalent 1-form L_a in Riemann-Cartan
space | LaTeX, 13 Pages. To appear in Gen. Rel. Grav | Gen.Rel.Grav. 33 (2001) 1115-1130 | 10.1023/A:1010236517022 | null | gr-qc | null | The definition of the Einstein 3-form G_a is motivated by means of the
contracted 2nd Bianchi identity. This definition involves at first the complete
curvature 2-form. The 1-form L_a is defined via G_a = L^b \wedge #(o_b \wedge
o_a). Here # denotes the Hodge-star, o_a the coframe, and \wedge the exterior
product. The L_a is equivalent to the Einstein 3-form and represents a certain
contraction of the curvature 2-form. A variational formula of Salgado on
quadratic invariants of the L_a 1-form is discussed, generalized, and put into
proper perspective.
| [
{
"created": "Mon, 11 Dec 2000 12:37:31 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Heinicke",
"Christian",
""
]
] | The definition of the Einstein 3-form G_a is motivated by means of the contracted 2nd Bianchi identity. This definition involves at first the complete curvature 2-form. The 1-form L_a is defined via G_a = L^b \wedge #(o_b \wedge o_a). Here # denotes the Hodge-star, o_a the coframe, and \wedge the exterior product. The L_a is equivalent to the Einstein 3-form and represents a certain contraction of the curvature 2-form. A variational formula of Salgado on quadratic invariants of the L_a 1-form is discussed, generalized, and put into proper perspective. |
2305.07742 | Tobias Mistele | Tobias Mistele | A new scale in the quasi-static limit of Aether Scalar Tensor Theory | 16 pages, 6 figures; accepted for publication in PRD | null | null | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the aims of Aether Scalar Tensor Theory (AeST) is to reproduce the
successes of Modified Newtonian Dynamics (MOND) on galactic scales. Indeed, the
quasi-static limit of AeST achieves precisely this, assuming that the vector
field $\vec{A}$ vanishes and that the so-called ghost condensate can be
neglected. The effects of the ghost condensate were investigated in detail in
previous studies. Here, we focus on the assumption of a vanishing vector field.
We argue that this assumption is not always justified and show how to correctly
take into account the vector field, finding that the quasi-static limit depends
on a model parameter $m_\times$. In the limit $m_\times \to 0$, one recovers
the quasi-static limit with a vanishing vector field. In particular, one finds
a two-field version of MOND. In the opposite limit, $m_\times \to \infty$, one
finds a single-field version of MOND. We show that, in practice, much of the
phenomenology of the quasi-static limit depends only very little on the value
of $m_\times$. Still, for some observational tests, such as those involving
wide binaries, $m_\times$ has percent-level effects that may be important.
| [
{
"created": "Fri, 12 May 2023 19:55:45 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Jun 2023 18:51:35 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Jun 2024 16:22:15 GMT",
"version": "v3"
}
] | 2024-06-24 | [
[
"Mistele",
"Tobias",
""
]
] | One of the aims of Aether Scalar Tensor Theory (AeST) is to reproduce the successes of Modified Newtonian Dynamics (MOND) on galactic scales. Indeed, the quasi-static limit of AeST achieves precisely this, assuming that the vector field $\vec{A}$ vanishes and that the so-called ghost condensate can be neglected. The effects of the ghost condensate were investigated in detail in previous studies. Here, we focus on the assumption of a vanishing vector field. We argue that this assumption is not always justified and show how to correctly take into account the vector field, finding that the quasi-static limit depends on a model parameter $m_\times$. In the limit $m_\times \to 0$, one recovers the quasi-static limit with a vanishing vector field. In particular, one finds a two-field version of MOND. In the opposite limit, $m_\times \to \infty$, one finds a single-field version of MOND. We show that, in practice, much of the phenomenology of the quasi-static limit depends only very little on the value of $m_\times$. Still, for some observational tests, such as those involving wide binaries, $m_\times$ has percent-level effects that may be important. |
0802.3629 | Sigbjorn Hervik | A. Coley and S. Hervik | Bianchi models with vorticity: The type III bifurcation | 12 pages | Class. Quantum Grav. 25 (2008) 198001 | 10.1088/0264-9381/25/19/198001 | null | gr-qc astro-ph math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the late-time behaviour of tilted perfect fluid Bianchi type III
models using a dynamical systems approach. We consider models with dust, and
perfect fluids stiffer than dust, and eludicate the late-time behaviour by
studying the centre manifold which dominates the behaviour of the model at late
times. In the dust case, this centre manifold is 3-dimensional and can be
considered as a double bifurcation as the 2 parameters ($h$ and $\gamma$) of
the type VI$_h$ model are varied. We calculate the decay rates and show that
for dust or stiffer the models approach a vacuum spacetime, however, it does so
rather slowly: $\rho/H^2\sim 1/\ln t$.
| [
{
"created": "Mon, 25 Feb 2008 14:21:36 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Coley",
"A.",
""
],
[
"Hervik",
"S.",
""
]
] | We study the late-time behaviour of tilted perfect fluid Bianchi type III models using a dynamical systems approach. We consider models with dust, and perfect fluids stiffer than dust, and eludicate the late-time behaviour by studying the centre manifold which dominates the behaviour of the model at late times. In the dust case, this centre manifold is 3-dimensional and can be considered as a double bifurcation as the 2 parameters ($h$ and $\gamma$) of the type VI$_h$ model are varied. We calculate the decay rates and show that for dust or stiffer the models approach a vacuum spacetime, however, it does so rather slowly: $\rho/H^2\sim 1/\ln t$. |
gr-qc/9810063 | Ram Brustein | Ram Brustein | Production and Detection of Cosmic Gravitational Wave Background in
String Cosmology | 21 pages, 3 figures, Revtex. Invited paper to appear in the special
issue of the Journal of Chaos, Solitons and Fractals on "Superstrings, M, F,
S... Theory", eds. C. Castro and M.S. El Naschie | null | 10.1016/S0960-0779(98)00196-9 | BGU-PH-98/06 | gr-qc astro-ph | null | String cosmology models predict a cosmic background of gravitational waves
produced during a period of dilaton-driven inflation. I describe the
background, present astrophysical and cosmological bounds on it, and discuss in
some detail how it may be possible to detect it with large operating and
planned gravitational wave detectors. The possible use of smaller detectors is
outlined.
| [
{
"created": "Tue, 20 Oct 1998 13:48:26 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Brustein",
"Ram",
""
]
] | String cosmology models predict a cosmic background of gravitational waves produced during a period of dilaton-driven inflation. I describe the background, present astrophysical and cosmological bounds on it, and discuss in some detail how it may be possible to detect it with large operating and planned gravitational wave detectors. The possible use of smaller detectors is outlined. |
1404.0898 | Marta Campigotto | M.Campigotto, L.Fatibene | Gauge Natural Formulation of Conformal Theory of Gravity | 13 pages, calculations added, matches published version on Annals of
Physics | Annals of Physics, Volume 354, 328 (2015) | 10.1016/j.aop.2014.12.026 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider conformal gravity as a gauge natural theory. We study its
conservation laws and superpotentials. We also consider the Mannheim and
Kazanas spherically symmetric vacuum solution and discuss conserved quantities
associated to conformal and diffeomorphism symmetries.
| [
{
"created": "Thu, 3 Apr 2014 13:19:22 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Feb 2015 14:19:47 GMT",
"version": "v2"
}
] | 2015-02-10 | [
[
"Campigotto",
"M.",
""
],
[
"Fatibene",
"L.",
""
]
] | We consider conformal gravity as a gauge natural theory. We study its conservation laws and superpotentials. We also consider the Mannheim and Kazanas spherically symmetric vacuum solution and discuss conserved quantities associated to conformal and diffeomorphism symmetries. |
1003.2476 | Paul Wesson | Paul S. Wesson | The Scalar Field Of 5D Gravity And The Higgs Field Of 4D Particle
Physics: A Possible Connection | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main results are reviewed of relating the scalar field of noncompactified
Kaluza-Klein gravity to the Higgs field of particle physics. The embedding of
4D spacetime in a 5D manifold can result in a variable cosmological 'constant'
and particle masses tiny compared to the Planck value.
| [
{
"created": "Fri, 12 Mar 2010 04:50:00 GMT",
"version": "v1"
}
] | 2010-03-15 | [
[
"Wesson",
"Paul S.",
""
]
] | The main results are reviewed of relating the scalar field of noncompactified Kaluza-Klein gravity to the Higgs field of particle physics. The embedding of 4D spacetime in a 5D manifold can result in a variable cosmological 'constant' and particle masses tiny compared to the Planck value. |
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