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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2405.09653 | Konstantinos Kostaros | Konstantinos Kostaros, Padelis Papadopoulos, George Pappas | Fractal signatures of non-Kerr spacetimes in the shadow of light-ring
bifurcations | 17 pages, 20 figures. Accepted for publication in Physical Review D | Phys. Rev. D 110, 024001 (2024) | 10.1103/PhysRevD.110.024001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Light-ring bifurcations that can occur for prolate non-Kerr compact objects
can leave an indelible signature on SMBH shadows as a fractal sequence of
eyebrow-like formations. These fractal features are the result of two
properties of these spacetimes. The first is that they allow for multiple
escapes for the photons (throats in the effective potential of photon geodesic
motion). The second is that photon geodesics can resonate between different
generalized light-rings related to the escapes, called fundamental photon
orbits, that lead photons to alternate between the different exits either
towards the compact object or infinity. The resulting fractal structures of the
shadow seem to be a generic feature of prolate non-Kerr objects that may be
observable in (accretion-disk)-illuminated compact objects, especially along
equatorial lines of sight, but the best orientation depends on the specific
parameters. Such fractal features if observed in the shadows of singular
supermassive black holes at the centers of galaxies, would be smoking gun
signals of non-Kerr compact objects.
| [
{
"created": "Wed, 15 May 2024 18:43:57 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Jun 2024 19:43:26 GMT",
"version": "v2"
}
] | 2024-07-08 | [
[
"Kostaros",
"Konstantinos",
""
],
[
"Papadopoulos",
"Padelis",
""
],
[
"Pappas",
"George",
""
]
] | Light-ring bifurcations that can occur for prolate non-Kerr compact objects can leave an indelible signature on SMBH shadows as a fractal sequence of eyebrow-like formations. These fractal features are the result of two properties of these spacetimes. The first is that they allow for multiple escapes for the photons (throats in the effective potential of photon geodesic motion). The second is that photon geodesics can resonate between different generalized light-rings related to the escapes, called fundamental photon orbits, that lead photons to alternate between the different exits either towards the compact object or infinity. The resulting fractal structures of the shadow seem to be a generic feature of prolate non-Kerr objects that may be observable in (accretion-disk)-illuminated compact objects, especially along equatorial lines of sight, but the best orientation depends on the specific parameters. Such fractal features if observed in the shadows of singular supermassive black holes at the centers of galaxies, would be smoking gun signals of non-Kerr compact objects. |
gr-qc/0001083 | Beverly K. Berger | Beverly K. Berger and Vincent Moncrief | Exact U(1) symmetric cosmologies with local Mixmaster dynamics | 13 pages, 5 figures, uses RevTeX and psfig | Phys.Rev. D62 (2000) 023509 | 10.1103/PhysRevD.62.023509 | null | gr-qc | null | By applying a standard solution generating technique, we transform an
arbitrary vacuum Mixmaster solution on $S^3 \times {\bf R}$ to a new solution
which is spatially inhomogeneous. We thereby obtain a family of exact,
spatially inhomogeneous, vacuum spacetimes which exhibit Belinskii,
Khalatnikov, and Lifshitz (BKL) oscillatory behavior. The solutions are
constructed explicitly by performing the transformations on numerically
generated, homogeneous Mixmaster solutions. Their behavior is found to be
qualitatively like that seen in previous numerical simulations of generic U(1)
symmetric cosmological spacetimes on $T^3 \times {\bf R}$.
| [
{
"created": "Tue, 25 Jan 2000 23:28:48 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Berger",
"Beverly K.",
""
],
[
"Moncrief",
"Vincent",
""
]
] | By applying a standard solution generating technique, we transform an arbitrary vacuum Mixmaster solution on $S^3 \times {\bf R}$ to a new solution which is spatially inhomogeneous. We thereby obtain a family of exact, spatially inhomogeneous, vacuum spacetimes which exhibit Belinskii, Khalatnikov, and Lifshitz (BKL) oscillatory behavior. The solutions are constructed explicitly by performing the transformations on numerically generated, homogeneous Mixmaster solutions. Their behavior is found to be qualitatively like that seen in previous numerical simulations of generic U(1) symmetric cosmological spacetimes on $T^3 \times {\bf R}$. |
1703.09369 | Daniel R Terno | Valentina Baccetti, Robert B. Mann, and Daniel R. Terno | Horizon avoidance in spherically-symmetric collapse | 4 pages. Comments welcome | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study collapse of evaporating spherically-symmetric thin dust shells and
dust balls assuming that quantum effects are encapsulated in a
spherically-symmetric metric that satisfied mild regularity conditions. The
evaporation may accelerate collapse, but for a generic metric the Schwarzschild
radius is not crossed. Instead the shell (or the layer in the ball of dust) is
always at a certain sub-Planckian distance from it.
| [
{
"created": "Tue, 28 Mar 2017 01:58:22 GMT",
"version": "v1"
}
] | 2017-03-29 | [
[
"Baccetti",
"Valentina",
""
],
[
"Mann",
"Robert B.",
""
],
[
"Terno",
"Daniel R.",
""
]
] | We study collapse of evaporating spherically-symmetric thin dust shells and dust balls assuming that quantum effects are encapsulated in a spherically-symmetric metric that satisfied mild regularity conditions. The evaporation may accelerate collapse, but for a generic metric the Schwarzschild radius is not crossed. Instead the shell (or the layer in the ball of dust) is always at a certain sub-Planckian distance from it. |
2211.06481 | Salvatore Capozziello | Salvatore Capozziello and Nisha Godani | Non-Local Gravity Wormholes | 12 pages, 6 figures, published in Phys. Lett. B | null | 10.1016/j.physletb.2022.137572 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Non-local Gravity in view to obtain stable and traversable
wormhole solutions. In particular, the class of Non-local Integral Kernel
Theories of Gravity, with the inverse d'Alembert operator in the gravitational
action, is taken into account. We obtain constraints for the null energy
condition and derive the field equations. Two special cases for the related
Klein-Gordon equation are assumed: one where the function in the gravitational
action has a linear form and another one with exponential form. In each case,
we take into account two forms for scalar fields and derive the shape
functions. Asymptotic flatness and flaring-out conditions are checked. Energy
conditions and dynamics of the solutions are examined at the throat. The main
result is that non-local gravity contributions allow stability and
traversability of the wormhole without considering any exotic matter.
| [
{
"created": "Fri, 11 Nov 2022 21:08:27 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Nov 2022 10:11:46 GMT",
"version": "v2"
}
] | 2022-11-28 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Godani",
"Nisha",
""
]
] | We consider Non-local Gravity in view to obtain stable and traversable wormhole solutions. In particular, the class of Non-local Integral Kernel Theories of Gravity, with the inverse d'Alembert operator in the gravitational action, is taken into account. We obtain constraints for the null energy condition and derive the field equations. Two special cases for the related Klein-Gordon equation are assumed: one where the function in the gravitational action has a linear form and another one with exponential form. In each case, we take into account two forms for scalar fields and derive the shape functions. Asymptotic flatness and flaring-out conditions are checked. Energy conditions and dynamics of the solutions are examined at the throat. The main result is that non-local gravity contributions allow stability and traversability of the wormhole without considering any exotic matter. |
gr-qc/9408036 | Andrew M. Abrahams | Andrew M. Abrahams, Stuart L. Shapiro, and Saul A. Teukolsky | Calculation of gravitational wave forms from black hole collisions and
disk collapse: Applying perturbation theory to numerical spacetimes | 8 pages (RevTex 3.0 with 7 uuencoded figures) | Phys.Rev. D51 (1995) 4295-4301 | 10.1103/PhysRevD.51.4295 | null | gr-qc | null | Many simulations of gravitational collapse to black holes become inaccurate
before the total emitted gravitational radiation can be determined. The main
difficulty is that a significant component of the radiation is still in the
near-zone, strong field region at the time the simulation breaks down. We show
how to calculate the emitted waveform by matching the numerical simulation to a
perturbation solution when the final state of the system approaches a
Schwarzschild black hole. We apply the technique to two scenarios: the head-on
collision of two black holes, and the collapse of a disk to a black hole. This
is the first reasonably accurate calculation of the radiation generated from
colliding black holes that form from matter collapse.
| [
{
"created": "Tue, 30 Aug 1994 00:42:44 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Abrahams",
"Andrew M.",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] | Many simulations of gravitational collapse to black holes become inaccurate before the total emitted gravitational radiation can be determined. The main difficulty is that a significant component of the radiation is still in the near-zone, strong field region at the time the simulation breaks down. We show how to calculate the emitted waveform by matching the numerical simulation to a perturbation solution when the final state of the system approaches a Schwarzschild black hole. We apply the technique to two scenarios: the head-on collision of two black holes, and the collapse of a disk to a black hole. This is the first reasonably accurate calculation of the radiation generated from colliding black holes that form from matter collapse. |
gr-qc/9405037 | Paul Henry Casper | Bruce Allen, Paul Casper, and Adrian Ottewill | Analytic Results for the Gravitational Radiation from a Class of Cosmic
String Loops | 15 pages, RevTex 3.0, 7 figures available via anonymous ftp from
directory pub/pcasper at alpha1.csd.uwm.edu, WISC-MILW-94-TH-13 | Phys.Rev. D50 (1994) 3703-3712 | 10.1103/PhysRevD.50.3703 | null | gr-qc astro-ph | null | Cosmic string loops are defined by a pair of periodic functions ${\bf a}$ and
${\bf b}$, which trace out unit-length closed curves in three-dimensional
space. We consider a particular class of loops, for which ${\bf a}$ lies along
a line and ${\bf b}$ lies in the plane orthogonal to that line. For this class
of cosmic string loops one may give a simple analytic expression for the power
$\gamma$ radiated in gravitational waves. We evaluate $\gamma$ exactly in
closed form for several special cases: (1) ${\bf b}$ a circle traversed $M$
times; (2) ${\bf b}$ a regular polygon with $N$ sides and interior vertex angle
$\pi-2\pi M/N$; (3) ${\bf b}$ an isosceles triangle with semi-angle $\theta$.
We prove that case (1) with $M=1$ is the absolute minimum of $\gamma$ within
our special class of loops, and identify all the stationary points of $\gamma$
in this class.
| [
{
"created": "Tue, 17 May 1994 19:13:18 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Allen",
"Bruce",
""
],
[
"Casper",
"Paul",
""
],
[
"Ottewill",
"Adrian",
""
]
] | Cosmic string loops are defined by a pair of periodic functions ${\bf a}$ and ${\bf b}$, which trace out unit-length closed curves in three-dimensional space. We consider a particular class of loops, for which ${\bf a}$ lies along a line and ${\bf b}$ lies in the plane orthogonal to that line. For this class of cosmic string loops one may give a simple analytic expression for the power $\gamma$ radiated in gravitational waves. We evaluate $\gamma$ exactly in closed form for several special cases: (1) ${\bf b}$ a circle traversed $M$ times; (2) ${\bf b}$ a regular polygon with $N$ sides and interior vertex angle $\pi-2\pi M/N$; (3) ${\bf b}$ an isosceles triangle with semi-angle $\theta$. We prove that case (1) with $M=1$ is the absolute minimum of $\gamma$ within our special class of loops, and identify all the stationary points of $\gamma$ in this class. |
2307.02557 | Andrea Russo | Isaac Layton, Jonathan Oppenheim, Andrea Russo, Zachary Weller-Davies | The weak field limit of quantum matter back-reacting on classical
spacetime | 42 pages, 1 table, comments welcomed | J. High Energ. Phys. 2023, 163 (2023) | 10.1007/JHEP08(2023)163 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Consistent coupling of quantum and classical degrees of freedom exists so
long as there is both diffusion of the classical degrees of freedom and
decoherence of the quantum system. In this paper, we derive the Newtonian limit
of such classical-quantum (CQ) theories of gravity. Our results are obtained
both via the gauge fixing of the recently proposed path integral theory of CQ
general relativity and via the CQ master equation approach. In each case, we
find the same weak field dynamics. We find that the Newtonian potential
diffuses by an amount lower bounded by the decoherence rate into mass
eigenstates. We also present our results as an unravelled system of stochastic
differential equations for the trajectory of the hybrid classical-quantum state
and provide a series of kernels for constructing figures of merit, which can be
used to rule out part of the parameter space of classical-quantum theories of
gravity by experimentally testing it via the decoherence-diffusion trade-off.
We compare and contrast the weak field limit to previous models of classical
Newtonian gravity coupled to quantum systems. Here, we find that the Newtonian
potential and quantum state change in lock-step, with the flow of time being
stochastic.
| [
{
"created": "Wed, 5 Jul 2023 18:01:06 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Layton",
"Isaac",
""
],
[
"Oppenheim",
"Jonathan",
""
],
[
"Russo",
"Andrea",
""
],
[
"Weller-Davies",
"Zachary",
""
]
] | Consistent coupling of quantum and classical degrees of freedom exists so long as there is both diffusion of the classical degrees of freedom and decoherence of the quantum system. In this paper, we derive the Newtonian limit of such classical-quantum (CQ) theories of gravity. Our results are obtained both via the gauge fixing of the recently proposed path integral theory of CQ general relativity and via the CQ master equation approach. In each case, we find the same weak field dynamics. We find that the Newtonian potential diffuses by an amount lower bounded by the decoherence rate into mass eigenstates. We also present our results as an unravelled system of stochastic differential equations for the trajectory of the hybrid classical-quantum state and provide a series of kernels for constructing figures of merit, which can be used to rule out part of the parameter space of classical-quantum theories of gravity by experimentally testing it via the decoherence-diffusion trade-off. We compare and contrast the weak field limit to previous models of classical Newtonian gravity coupled to quantum systems. Here, we find that the Newtonian potential and quantum state change in lock-step, with the flow of time being stochastic. |
1410.6899 | Matthew J. Lake Dr | Tiberiu Harko and Matthew J. Lake | Bose-Einstein condensate strings | 22 pages, 24 figures. Published version | Phys. Rev. D 91, 045012 (2015) | 10.1103/PhysRevD.91.045012 | null | gr-qc astro-ph.HE cond-mat.other hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the possible existence of gravitationally bound general
relativistic strings consisting of Bose-Einstein condensate (BEC) matter which
is described, in the Newtonian limit, by the zero temperature time-dependent
nonlinear Schr\"odinger equation (the Gross-Pitaevskii equation), with
repulsive interparticle interactions. In the Madelung representation of the
wave function, the quantum dynamics of the condensate can be formulated in
terms of the classical continuity equation and the hydrodynamic Euler
equations. In the case of a condensate with quartic nonlinearity, the
condensates can be described as a gas with two pressure terms, the interaction
pressure, which is proportional to the square of the matter density, and the
quantum pressure, which is without any classical analogue though, when the
number of particles in the system is high enough, the latter may be neglected.
Assuming cylindrical symmetry, we analyze the physical properties of the BEC
strings in both the interaction pressure and quantum pressure dominated limits,
by numerically integrating the gravitational field equations. In this way we
obtain a large class of stable stringlike astrophysical objects, whose basic
parameters (mass density and radius) depend sensitively on the mass and
scattering length of the condensate particle, as well as on the quantum
pressure of the Bose-Einstein gas.
| [
{
"created": "Sat, 25 Oct 2014 09:02:07 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Oct 2014 09:14:56 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Jan 2015 12:15:30 GMT",
"version": "v3"
},
{
"created": "Sun, 27 Sep 2015 12:16:40 GMT",
"version": "v4"
}
] | 2015-09-29 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lake",
"Matthew J.",
""
]
] | We consider the possible existence of gravitationally bound general relativistic strings consisting of Bose-Einstein condensate (BEC) matter which is described, in the Newtonian limit, by the zero temperature time-dependent nonlinear Schr\"odinger equation (the Gross-Pitaevskii equation), with repulsive interparticle interactions. In the Madelung representation of the wave function, the quantum dynamics of the condensate can be formulated in terms of the classical continuity equation and the hydrodynamic Euler equations. In the case of a condensate with quartic nonlinearity, the condensates can be described as a gas with two pressure terms, the interaction pressure, which is proportional to the square of the matter density, and the quantum pressure, which is without any classical analogue though, when the number of particles in the system is high enough, the latter may be neglected. Assuming cylindrical symmetry, we analyze the physical properties of the BEC strings in both the interaction pressure and quantum pressure dominated limits, by numerically integrating the gravitational field equations. In this way we obtain a large class of stable stringlike astrophysical objects, whose basic parameters (mass density and radius) depend sensitively on the mass and scattering length of the condensate particle, as well as on the quantum pressure of the Bose-Einstein gas. |
0809.2452 | David Kubiznak | David Kubiznak | Hidden Symmetries of Higher-Dimensional Rotating Black Holes | PhD Thesis, University of Alberta, September 2008, Advisor: Valeri P.
Frolov, 170 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this thesis we study higher-dimensional rotating black holes. Such black
holes are widely discussed in string theory and brane-world models at present.
We demonstrate that even the most general known Kerr-NUT-(A)dS spacetime,
describing the general rotating higher-dimensional asymptotically (anti) de
Sitter black hole with NUT parameters, is in many aspects similar to its
four-dimensional counterpart. Namely, we show that it admits a fundamental
hidden symmetry associated with the principal conformal Killing-Yano tensor.
Such a tensor generates towers of hidden and explicit symmetries. The tower of
Killing tensors is responsible for the existence of irreducible, quadratic in
momenta, conserved integrals of geodesic motion. These integrals, together with
the integrals corresponding to the tower of explicit symmetries, make geodesic
equations in the Kerr-NUT-(A)dS spacetime completely integrable. We further
demonstrate that in this spacetime the Hamilton-Jacobi, Klein-Gordon, and
stationary string equations allow complete separation of variables and the
problem of finding parallel-propagated frames reduces to the set of the first
order ordinary differential equations. Moreover, we show that the
Kerr-NUT-(A)dS spacetime is the most general Einstein space which possesses all
these properties. We also explicitly derive the most general (off-shell)
canonical metric admitting the principal conformal Killing-Yano tensor and
demonstrate that such a metric is necessarily of the special algebraic type D
of the higher-dimensional algebraic classification. The results presented in
this thesis describe the new and complete picture of the relationship of hidden
symmetries and rotating black holes in higher dimensions.
| [
{
"created": "Mon, 15 Sep 2008 07:30:26 GMT",
"version": "v1"
}
] | 2008-12-15 | [
[
"Kubiznak",
"David",
""
]
] | In this thesis we study higher-dimensional rotating black holes. Such black holes are widely discussed in string theory and brane-world models at present. We demonstrate that even the most general known Kerr-NUT-(A)dS spacetime, describing the general rotating higher-dimensional asymptotically (anti) de Sitter black hole with NUT parameters, is in many aspects similar to its four-dimensional counterpart. Namely, we show that it admits a fundamental hidden symmetry associated with the principal conformal Killing-Yano tensor. Such a tensor generates towers of hidden and explicit symmetries. The tower of Killing tensors is responsible for the existence of irreducible, quadratic in momenta, conserved integrals of geodesic motion. These integrals, together with the integrals corresponding to the tower of explicit symmetries, make geodesic equations in the Kerr-NUT-(A)dS spacetime completely integrable. We further demonstrate that in this spacetime the Hamilton-Jacobi, Klein-Gordon, and stationary string equations allow complete separation of variables and the problem of finding parallel-propagated frames reduces to the set of the first order ordinary differential equations. Moreover, we show that the Kerr-NUT-(A)dS spacetime is the most general Einstein space which possesses all these properties. We also explicitly derive the most general (off-shell) canonical metric admitting the principal conformal Killing-Yano tensor and demonstrate that such a metric is necessarily of the special algebraic type D of the higher-dimensional algebraic classification. The results presented in this thesis describe the new and complete picture of the relationship of hidden symmetries and rotating black holes in higher dimensions. |
1706.09117 | Daiqin Su | Daiqin Su, C. T. Marco Ho, Robert B. Mann and Timothy C. Ralph | Black Hole Squeezers | 19 pages, 3 figures, 1 table. Comments are welcome | Phys. Rev. D 96, 065017 (2017) | 10.1103/PhysRevD.96.065017 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the gravitational quasi-normal modes (QNMs) of a Schwarzschild
black hole play the role of a multimode squeezer that can generate particles.
For a minimally coupled scalar field, the QNMs "squeeze" the initial state of
the scalar field (even for the vacuum) and produce scalar particles. The
maximal squeezing amplitude is inversely proportional to the cube of the
imaginary part of the QNM frequency, implying that the particle generation
efficiency is higher for lower decaying QNMs. Our results show that the
gravitational perturbations can amplify Hawking radiation.
| [
{
"created": "Wed, 28 Jun 2017 03:39:25 GMT",
"version": "v1"
}
] | 2017-10-04 | [
[
"Su",
"Daiqin",
""
],
[
"Ho",
"C. T. Marco",
""
],
[
"Mann",
"Robert B.",
""
],
[
"Ralph",
"Timothy C.",
""
]
] | We show that the gravitational quasi-normal modes (QNMs) of a Schwarzschild black hole play the role of a multimode squeezer that can generate particles. For a minimally coupled scalar field, the QNMs "squeeze" the initial state of the scalar field (even for the vacuum) and produce scalar particles. The maximal squeezing amplitude is inversely proportional to the cube of the imaginary part of the QNM frequency, implying that the particle generation efficiency is higher for lower decaying QNMs. Our results show that the gravitational perturbations can amplify Hawking radiation. |
1301.3205 | Ahmed Youssef | Ahmed Youssef and Dirk Kreimer | Resummation of infrared logarithms in de Sitter space via
Dyson-Schwinger equations: the ladder-rainbow approximation | 4 figures | Phys. Rev. D 89, 124021 (2014) | 10.1103/PhysRevD.89.124021 | MaPhy-AvH/2013-01 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the infrared (large separation) behavior of a massless minimally
coupled scalar quantum field theory with a quartic self interaction in de
Sitter spacetime. We show that the perturbation series in the interaction
strength is singular and secular, i.e. it does not lead to a uniform
approximation of the solution in the infrared region. Only a nonperturbative
resummation can capture the correct infrared behavior. We seek to justify this
picture using the Dyson-Schwinger equations in the ladder-rainbow
approximation. We are able to write down an ordinary differential equation
obeyed by the two-point function and perform its asymptotic analysis. Indeed,
while the perturbative series-truncated at any finite order-is growing in the
infrared, the full nonperturbative sum can be decaying.
| [
{
"created": "Tue, 15 Jan 2013 02:31:23 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Nov 2013 13:56:06 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Aug 2014 13:06:44 GMT",
"version": "v3"
}
] | 2014-08-08 | [
[
"Youssef",
"Ahmed",
""
],
[
"Kreimer",
"Dirk",
""
]
] | We study the infrared (large separation) behavior of a massless minimally coupled scalar quantum field theory with a quartic self interaction in de Sitter spacetime. We show that the perturbation series in the interaction strength is singular and secular, i.e. it does not lead to a uniform approximation of the solution in the infrared region. Only a nonperturbative resummation can capture the correct infrared behavior. We seek to justify this picture using the Dyson-Schwinger equations in the ladder-rainbow approximation. We are able to write down an ordinary differential equation obeyed by the two-point function and perform its asymptotic analysis. Indeed, while the perturbative series-truncated at any finite order-is growing in the infrared, the full nonperturbative sum can be decaying. |
1907.04234 | \"Ozg\"ur Akarsu | Ozgur Akarsu, Alexey Chopovsky, Valerii Shulga, Ezgi Yalcinkaya,
Alexander Zhuk | Weak field limit of higher dimensional massive Brans-Dicke gravity:
Observational constraints | 8 pages, no figures and tables; matches the version published in
Physical Review D | Phys. Rev. D 101, 024004 (2020) | 10.1103/PhysRevD.101.024004 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider higher-dimensional massive Brans-Dicke theory with Ricci-flat
internal space. The background model is perturbed by a massive gravitating
source which is pressureless in the external (our space) but has an arbitrary
equation-of-state parameter $\Omega$ in the internal space. We obtain the exact
solution of the system of linearized equations for the perturbations of the
metric coefficients and scalar field. For a massless scalar field, relying on
the fine-tuning between the Brans-Dicke parameter $\omega$ and $\Omega$, we
demonstrate that (i) the model does not contradict gravitational tests relevant
to the parameterized post-Newtonian parameter $\gamma$, and (ii) the scalar
field is not ghost in the case of nonzero $|\Omega|\sim O(1)$ along with the
natural value $|\omega|\sim O(1)$. In the general case of a massive scalar
field, the metric coefficients acquire the Yukawa correction terms, where the
Yukawa mass scale $m$ is defined by the mass of the scalar field. For the
natural value $\omega\sim O(1)$, the inverse-square-law experiments impose the
following restriction on the lower bound of the mass: $m\gtrsim 10^{-11}\,$GeV.
The experimental constraints on $\gamma$ requires that $\Omega$ must be
extremely close to $-1/2$.
| [
{
"created": "Tue, 9 Jul 2019 15:16:21 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Jan 2020 15:24:08 GMT",
"version": "v2"
}
] | 2020-01-03 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Chopovsky",
"Alexey",
""
],
[
"Shulga",
"Valerii",
""
],
[
"Yalcinkaya",
"Ezgi",
""
],
[
"Zhuk",
"Alexander",
""
]
] | We consider higher-dimensional massive Brans-Dicke theory with Ricci-flat internal space. The background model is perturbed by a massive gravitating source which is pressureless in the external (our space) but has an arbitrary equation-of-state parameter $\Omega$ in the internal space. We obtain the exact solution of the system of linearized equations for the perturbations of the metric coefficients and scalar field. For a massless scalar field, relying on the fine-tuning between the Brans-Dicke parameter $\omega$ and $\Omega$, we demonstrate that (i) the model does not contradict gravitational tests relevant to the parameterized post-Newtonian parameter $\gamma$, and (ii) the scalar field is not ghost in the case of nonzero $|\Omega|\sim O(1)$ along with the natural value $|\omega|\sim O(1)$. In the general case of a massive scalar field, the metric coefficients acquire the Yukawa correction terms, where the Yukawa mass scale $m$ is defined by the mass of the scalar field. For the natural value $\omega\sim O(1)$, the inverse-square-law experiments impose the following restriction on the lower bound of the mass: $m\gtrsim 10^{-11}\,$GeV. The experimental constraints on $\gamma$ requires that $\Omega$ must be extremely close to $-1/2$. |
2304.11833 | Fil Simovic | Pravin Kumar Dahal, Fil Simovic | The Hawking temperature of dynamical black holes via Rindler
transformations | 10 pages, 1 figure. Comments welcome | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | The Vaidya metric serves as a useful model-building tool that captures many
essential features of dynamical and/or evaporating black hole spacetimes.
Working in a semiclassical setting, we show that in the limit of slow
evaporation, a general spherically symmetric metric subject to certain
regularity conditions is uniquely described by a linear ingoing Vaidya metric
in the near-horizon region. This suggests a universal description of the
near-horizon geometry of evaporating black holes in terms of the linear Vaidya
metric. We also demonstrate that the linear Vaidya metric can be brought into
manifestly conformally static form, allowing us to determine the Hawking
temperature associated with the Vaidya background with respect to the conformal
vacuum. Since back-reaction is implicitly accounted for, we conclude that
slowly evaporating black holes are indeed accurately described by quasistatic
sequences of Schwarzschild metrics even when dynamical effects are present.
| [
{
"created": "Mon, 24 Apr 2023 05:44:04 GMT",
"version": "v1"
}
] | 2023-04-25 | [
[
"Dahal",
"Pravin Kumar",
""
],
[
"Simovic",
"Fil",
""
]
] | The Vaidya metric serves as a useful model-building tool that captures many essential features of dynamical and/or evaporating black hole spacetimes. Working in a semiclassical setting, we show that in the limit of slow evaporation, a general spherically symmetric metric subject to certain regularity conditions is uniquely described by a linear ingoing Vaidya metric in the near-horizon region. This suggests a universal description of the near-horizon geometry of evaporating black holes in terms of the linear Vaidya metric. We also demonstrate that the linear Vaidya metric can be brought into manifestly conformally static form, allowing us to determine the Hawking temperature associated with the Vaidya background with respect to the conformal vacuum. Since back-reaction is implicitly accounted for, we conclude that slowly evaporating black holes are indeed accurately described by quasistatic sequences of Schwarzschild metrics even when dynamical effects are present. |
2404.08257 | Eric Ling | Eric Ling | The $C^0$-inextendibility of some spatially flat FLRW spacetimes | 7 pages | null | null | CPH-GEOTOP-DNRF151; CF21-0680 | gr-qc math-ph math.DG math.MP | http://creativecommons.org/licenses/by/4.0/ | Utilizing some of Sbierski's recent $C^0$-inextendibility techniques [13], we
prove the $C^0$-inextendibility of a class of spatially flat FLRW spacetimes
without particle horizons.
| [
{
"created": "Fri, 12 Apr 2024 06:13:33 GMT",
"version": "v1"
}
] | 2024-04-15 | [
[
"Ling",
"Eric",
""
]
] | Utilizing some of Sbierski's recent $C^0$-inextendibility techniques [13], we prove the $C^0$-inextendibility of a class of spatially flat FLRW spacetimes without particle horizons. |
2101.06272 | Surajit Kalita | Surajit Kalita (IISc), T. R. Govindarajan (IMSc) and Banibrata
Mukhopadhyay (IISc) | Super-Chandrasekhar limiting mass white dwarfs as emergent phenomena of
noncommutative squashed fuzzy spheres | 20 pages including 7 figures; text is modified and references are
updated: Accepted for publication in IJMPD | IJMPD, 30, 13 (2021) 2150101 | 10.1142/S0218271821501017 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The indirect evidence for at least a dozen massive white dwarfs violating the
Chandrasekhar mass-limit is considered to be one of the wonderful discoveries
in astronomy for more than a decade. Researchers have already proposed a
diverse amount of models to explain this astounding phenomenon. However, each
of these models always carries some drawbacks. On the other hand,
noncommutative geometry is one of the best replicas of quantum gravity, which
is yet to be proved from observations. Madore introduced the idea of a fuzzy
sphere to describe a formalism of noncommutative geometry. This article shows
that the idea of a squashed fuzzy sphere can self-consistently explain the
super-Chandrasekhar limiting mass white dwarfs. We further show that the
length-scale beyond which the noncommutativity is prominent is an emergent
phenomenon, and there is no prerequisite for an ad-hoc length-scale.
| [
{
"created": "Fri, 15 Jan 2021 19:00:01 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Jul 2021 16:45:15 GMT",
"version": "v2"
}
] | 2021-11-08 | [
[
"Kalita",
"Surajit",
"",
"IISc"
],
[
"Govindarajan",
"T. R.",
"",
"IMSc"
],
[
"Mukhopadhyay",
"Banibrata",
"",
"IISc"
]
] | The indirect evidence for at least a dozen massive white dwarfs violating the Chandrasekhar mass-limit is considered to be one of the wonderful discoveries in astronomy for more than a decade. Researchers have already proposed a diverse amount of models to explain this astounding phenomenon. However, each of these models always carries some drawbacks. On the other hand, noncommutative geometry is one of the best replicas of quantum gravity, which is yet to be proved from observations. Madore introduced the idea of a fuzzy sphere to describe a formalism of noncommutative geometry. This article shows that the idea of a squashed fuzzy sphere can self-consistently explain the super-Chandrasekhar limiting mass white dwarfs. We further show that the length-scale beyond which the noncommutativity is prominent is an emergent phenomenon, and there is no prerequisite for an ad-hoc length-scale. |
gr-qc/9808079 | Nazeem Mustapha | Nazeem Mustapha, Charles Hellaby and G. F. R. Ellis (University of
Cape Town) | Large Scale Inhomogeneity Versus Source Evolution -- Can We Distinguish
Them Observationally? | mn style, mn.sty file included, mn.sty file removed | Mon.Not.Roy.Astron.Soc. 292 (1997) 817-830 | 10.1093/mnras/292.4.817 | null | gr-qc | null | We reconsider the issue of proving large scale spatial homogeneity of the
universe, given isotropic observations about us and the possibility of source
evolution both in numbers and luminosities. Two theorems make precise the
freedom available in constructing cosmological models that will fit the
observations. They make quite clear that homogeneity cannot be proven without
either a fully determinate theory of source evolution, or availability of
distance measures that are independent of source evolution. We contrast this
goal with the standard approach that assumes spatial homogeneity a priori, and
determines source evolution functions on the basis of this assumption.
| [
{
"created": "Fri, 28 Aug 1998 15:42:14 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Mustapha",
"Nazeem",
"",
"University of\n Cape Town"
],
[
"Hellaby",
"Charles",
"",
"University of\n Cape Town"
],
[
"Ellis",
"G. F. R.",
"",
"University of\n Cape Town"
]
] | We reconsider the issue of proving large scale spatial homogeneity of the universe, given isotropic observations about us and the possibility of source evolution both in numbers and luminosities. Two theorems make precise the freedom available in constructing cosmological models that will fit the observations. They make quite clear that homogeneity cannot be proven without either a fully determinate theory of source evolution, or availability of distance measures that are independent of source evolution. We contrast this goal with the standard approach that assumes spatial homogeneity a priori, and determines source evolution functions on the basis of this assumption. |
1612.04387 | Marco Astorino | Marco Astorino | Thermodynamics of Regular Accelerating Black Holes | 17 pages, 2 figures ; v2: extended to fulfil journal requirements,
typos corrected | Phys. Rev. D 95, 064007 (2017) | 10.1103/PhysRevD.95.064007 | UAI-PHY-16/08 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the covariant phase space formalism, we compute the conserved charges
for a solution, describing an accelerating and electrically charged
Reissner-Nordstrom black hole. The metric is regular provided that the
acceleration is driven by an external electric field, in spite of the usual
string of the standard C-metric. The Smarr formula and the first law of black
hole thermodynamics are fulfilled. The resulting mass has the same form of the
Christodoulou-Ruffini mass formula. On the basis of these results, we can
extrapolate the mass and thermodynamics of the rotating C-metric, which
describes a Kerr-Newman-(A)dS black hole accelerated by a pulling string.
| [
{
"created": "Tue, 13 Dec 2016 21:00:47 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Mar 2017 20:43:49 GMT",
"version": "v2"
}
] | 2017-03-17 | [
[
"Astorino",
"Marco",
""
]
] | Using the covariant phase space formalism, we compute the conserved charges for a solution, describing an accelerating and electrically charged Reissner-Nordstrom black hole. The metric is regular provided that the acceleration is driven by an external electric field, in spite of the usual string of the standard C-metric. The Smarr formula and the first law of black hole thermodynamics are fulfilled. The resulting mass has the same form of the Christodoulou-Ruffini mass formula. On the basis of these results, we can extrapolate the mass and thermodynamics of the rotating C-metric, which describes a Kerr-Newman-(A)dS black hole accelerated by a pulling string. |
gr-qc/9909044 | Arbab I. Arbab | Arbab I. Arbab | A linearly Expanding Universe With Variable G and Lambda | A revised version | Spacetime & Substance 1(6) (2001) 39 | null | null | gr-qc | null | We have studied a cosmological model with a cosmological term of the form
$\Lambda=3\alpha\fr{\dot R^2}{R^2}+\bt\fr{\ddot R}{R}+\fr{3\gamma}{R^2} \alpha,
\
\bt \gamma$ are constants. The scale factor (R) is found to vary linearly
with time for both radiation and matter dominated epochs.
The cosmological constant is found to decrease as $t^{-2}$ and the rate of
particle creation is smaller than the Steady State value.
The model gives $\Omega^\Lambda=\fr{1}{3}$ and $\Omega^m=\fr{2}{3}$ in the
present era,
$\Omega^\Lambda=\Omega^m=\fr{1}{2}$ in the radiation era.
The present age of the universe $(\rm t_p$) is found to be $\rm t_p=H_p^{-1}$
, where $\rm H_p$ is the Hubble constant.
The model is free from the main problems of the Standard Model. Since the
scale factor $\rm R\propto t$ during the entire evolution of the universe the
ratio of the cosmological constant at the Planck and present time is
$\rm\fr{\Lambda_{Pl}}{\Lambda_p}=10^{120}$.
This decay law justifies why, today, the cosmological constant is exceedingly
small.
| [
{
"created": "Tue, 14 Sep 1999 20:52:20 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Oct 1999 12:05:52 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Arbab",
"Arbab I.",
""
]
] | We have studied a cosmological model with a cosmological term of the form $\Lambda=3\alpha\fr{\dot R^2}{R^2}+\bt\fr{\ddot R}{R}+\fr{3\gamma}{R^2} \alpha, \ \bt \gamma$ are constants. The scale factor (R) is found to vary linearly with time for both radiation and matter dominated epochs. The cosmological constant is found to decrease as $t^{-2}$ and the rate of particle creation is smaller than the Steady State value. The model gives $\Omega^\Lambda=\fr{1}{3}$ and $\Omega^m=\fr{2}{3}$ in the present era, $\Omega^\Lambda=\Omega^m=\fr{1}{2}$ in the radiation era. The present age of the universe $(\rm t_p$) is found to be $\rm t_p=H_p^{-1}$ , where $\rm H_p$ is the Hubble constant. The model is free from the main problems of the Standard Model. Since the scale factor $\rm R\propto t$ during the entire evolution of the universe the ratio of the cosmological constant at the Planck and present time is $\rm\fr{\Lambda_{Pl}}{\Lambda_p}=10^{120}$. This decay law justifies why, today, the cosmological constant is exceedingly small. |
1808.01941 | Giovanni Otalora | Manuel Gonzalez-Espinoza, Giovanni Otalora, Joel Saavedra, Nelson
Videla | Growth of matter overdensities in non-minimal torsion-matter coupling
theories | 13 pages, 6 figures | Eur. Phys. J. C (2018) 78:799 | 10.1140/epjc/s10052-018-6286-y | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of cosmological perturbations around a homogeneous and
isotropic background in the framework of the non-minimal torsion-matter
coupling extension of $f(T)$ gravity. We are concerned with the effects of the
non-minimal coupling term on the growth of matter overdensities. Under the
quasi-static approximation, we derive the equation which governs the evolution
of matter density perturbations, and it is shown that the effective
gravitational coupling 'constant' acquires an additional contribution due to
the non-minimal matter-torsion coupling term. In this way, this result
generalizes those previously obtained for the growth of matter overdensities in
the case of minimal $f(T)$ gravity. In order to get a feeling of our results we
apply them to the important case of a power-law coupling function, which we
assume to be the responsible for the late-time accelerated expansion in the
dark energy regime. Thereby, analytic solutions for the matter density
perturbation equation in the regime of dark matter dominance and the dark
energy epoch are obtained, along with a complete numerical integration of this
equation. In particular, we show that this model predicts a growth index larger
than those obtained for $\Lambda$CDM model, indicating therefore a smaller
growth rate. Concomitantly, we show that the model at hand is potentially
capable in alleviating the existing $\sigma_{8}$-tension, being that it can
provide us a $f\sigma_{8}$ prediction which is $\sim 4-5$ per cent below the
respective prediction of concordance model.
| [
{
"created": "Mon, 6 Aug 2018 14:47:29 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Oct 2018 23:35:38 GMT",
"version": "v2"
}
] | 2018-10-09 | [
[
"Gonzalez-Espinoza",
"Manuel",
""
],
[
"Otalora",
"Giovanni",
""
],
[
"Saavedra",
"Joel",
""
],
[
"Videla",
"Nelson",
""
]
] | We study the evolution of cosmological perturbations around a homogeneous and isotropic background in the framework of the non-minimal torsion-matter coupling extension of $f(T)$ gravity. We are concerned with the effects of the non-minimal coupling term on the growth of matter overdensities. Under the quasi-static approximation, we derive the equation which governs the evolution of matter density perturbations, and it is shown that the effective gravitational coupling 'constant' acquires an additional contribution due to the non-minimal matter-torsion coupling term. In this way, this result generalizes those previously obtained for the growth of matter overdensities in the case of minimal $f(T)$ gravity. In order to get a feeling of our results we apply them to the important case of a power-law coupling function, which we assume to be the responsible for the late-time accelerated expansion in the dark energy regime. Thereby, analytic solutions for the matter density perturbation equation in the regime of dark matter dominance and the dark energy epoch are obtained, along with a complete numerical integration of this equation. In particular, we show that this model predicts a growth index larger than those obtained for $\Lambda$CDM model, indicating therefore a smaller growth rate. Concomitantly, we show that the model at hand is potentially capable in alleviating the existing $\sigma_{8}$-tension, being that it can provide us a $f\sigma_{8}$ prediction which is $\sim 4-5$ per cent below the respective prediction of concordance model. |
gr-qc/9304007 | null | Dieter R. Brill and Sean A. Hayward | Global Structure of a Black-Hole Cosmos and its Extremes | 11 pages. Diagrams not included | Class.Quant.Grav.11:359-370,1994 | 10.1088/0264-9381/11/2/008 | null | gr-qc | null | We analyze the global structure of a family of Einstein-Maxwell solutions
parametrized by mass, charge and cosmological constant. In a qualitative
classification there are: (i) generic black-hole solutions, describing a
Wheeler wormhole in a closed cosmos of spatial topology $S^2\times S^1$; (ii)
generic naked-singularity solutions, describing a pair of ``point" charges in a
closed cosmos; (iii) extreme black-hole solutions, describing a pair of
``horned" particles in an otherwise closed cosmos; (iv) extreme
naked-singularity solutions, in which a pair of point charges forms and then
evaporates, in a way which is not even weakly censored; and (v) an
ultra-extreme solution. We discuss the properties of the solutions and of
various coordinate systems, and compare with the Kastor-Traschen
multi-black-hole solutions.
| [
{
"created": "Tue, 6 Apr 1993 13:41:27 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Brill",
"Dieter R.",
""
],
[
"Hayward",
"Sean A.",
""
]
] | We analyze the global structure of a family of Einstein-Maxwell solutions parametrized by mass, charge and cosmological constant. In a qualitative classification there are: (i) generic black-hole solutions, describing a Wheeler wormhole in a closed cosmos of spatial topology $S^2\times S^1$; (ii) generic naked-singularity solutions, describing a pair of ``point" charges in a closed cosmos; (iii) extreme black-hole solutions, describing a pair of ``horned" particles in an otherwise closed cosmos; (iv) extreme naked-singularity solutions, in which a pair of point charges forms and then evaporates, in a way which is not even weakly censored; and (v) an ultra-extreme solution. We discuss the properties of the solutions and of various coordinate systems, and compare with the Kastor-Traschen multi-black-hole solutions. |
0711.0243 | Ken-Ichi Nakao | Ken-ichi Nakao, Daisuke Ida, Yasunari Kurita | New instability in relativistic cylindrically symmetric system | 16 pages, no figure | Phys.Rev.D77:044021,2008 | 10.1103/PhysRevD.77.044021 | OCU-PHYS-281, AP-GR-49 | gr-qc | null | We investigate an infinitesimally thin cylindrical shell composed of
counter-rotating dust particles. This system was studied by Apostolatos and
Thorne in terms of the C-energy for a bounded domain. In this paper, we
reanalyze this system by evaluating the C-energy on the future null infinity.
We find that some class of momentarily static and radiation-free initial data
does not settle down into static, equilibrium configurations, and otherwise
infinite amount of the gravitational radiation is emitted to the future null
infinity. Our result implies the existence of an instability in this system. In
the framework of the Newtonian gravity, a cylindrical shell composed of
counter-rotating dust particles can be in a steady state with oscillation by
the gravitational attraction and centrifugal repulsion, and hence a static
state is not necessarily realized as a final state. By contrast, in the
framework of general relativity, the steady oscillating state will be
impossible since the gravitational radiation will carry the energy of the
oscillation to infinity. Thus, this instability has no counterpart in the
Newtonian gravity.
| [
{
"created": "Fri, 2 Nov 2007 04:53:50 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nakao",
"Ken-ichi",
""
],
[
"Ida",
"Daisuke",
""
],
[
"Kurita",
"Yasunari",
""
]
] | We investigate an infinitesimally thin cylindrical shell composed of counter-rotating dust particles. This system was studied by Apostolatos and Thorne in terms of the C-energy for a bounded domain. In this paper, we reanalyze this system by evaluating the C-energy on the future null infinity. We find that some class of momentarily static and radiation-free initial data does not settle down into static, equilibrium configurations, and otherwise infinite amount of the gravitational radiation is emitted to the future null infinity. Our result implies the existence of an instability in this system. In the framework of the Newtonian gravity, a cylindrical shell composed of counter-rotating dust particles can be in a steady state with oscillation by the gravitational attraction and centrifugal repulsion, and hence a static state is not necessarily realized as a final state. By contrast, in the framework of general relativity, the steady oscillating state will be impossible since the gravitational radiation will carry the energy of the oscillation to infinity. Thus, this instability has no counterpart in the Newtonian gravity. |
2006.10827 | Valerio Faraoni | Valerio Faraoni and Genevi\`eve Vachon (Bishop's University) | When Painlev\'e-Gullstrand coordinates fail | 9 pages, no figures, typographical errors corrected. Matches version
accepted in Eur. Phys. J. C | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Painlev\'e-Gullstrand coordinates, a very useful tool in spherical horizon
thermodynamics, fail in anti-de Sitter space and in the inner region of
Reissner-Nordstr\"om. We predict this breakdown to occur in any region
containing negative Misner-Sharp-Hernandez quasilocal mass because of repulsive
gravity stopping the motion of PG observers in radial free fall with zero
initial velocity. PG coordinates break down also in the static Einstein
universe for completely different reasons. The more general Martel-Poisson
family of charts, which normally has PG coordinates as a limit, is reported for
static cosmologies (de Sitter, anti-de Sitter and the static Einstein
universe).
| [
{
"created": "Thu, 18 Jun 2020 19:47:15 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Aug 2020 19:18:44 GMT",
"version": "v2"
}
] | 2020-08-18 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
],
[
"Vachon",
"Geneviève",
"",
"Bishop's University"
]
] | Painlev\'e-Gullstrand coordinates, a very useful tool in spherical horizon thermodynamics, fail in anti-de Sitter space and in the inner region of Reissner-Nordstr\"om. We predict this breakdown to occur in any region containing negative Misner-Sharp-Hernandez quasilocal mass because of repulsive gravity stopping the motion of PG observers in radial free fall with zero initial velocity. PG coordinates break down also in the static Einstein universe for completely different reasons. The more general Martel-Poisson family of charts, which normally has PG coordinates as a limit, is reported for static cosmologies (de Sitter, anti-de Sitter and the static Einstein universe). |
gr-qc/9610074 | Paul Anderson | Paul R. Anderson and Dieter R. Brill | Gravitational Geons Revisited | 18 pages, ReVTeX. To appear in Physical Review D. Significant changes
include more details in the derivations of certain key equations and the
addition of an appendix containing a proof of the existence of a geon
solution to the equations derived by Wheeler. Also a reference has been added
and various minor changes have been made | Phys.Rev.D56:4824-4833,1997 | 10.1103/PhysRevD.56.4824 | null | gr-qc | null | A careful analysis of the gravitational geon solution found by Brill and
Hartle is made. The gravitational wave expansion they used is shown to be
consistent and to result in a gauge invariant wave equation. It also results in
a gauge invariant effective stress-energy tensor for the gravitational waves
provided that a generalized definition of a gauge transformation is used. To
leading order this gauge transformation is the same as the usual one for
gravitational waves. It is shown that the geon solution is a self-consistent
solution to Einstein's equations and that, to leading order, the equations
describing the geometry of the gravitational geon are identical to those
derived by Wheeler for the electromagnetic geon. An appendix provides an
existence proof for geon solutions to these equations.
| [
{
"created": "Thu, 31 Oct 1996 22:41:37 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Sep 1997 21:24:10 GMT",
"version": "v2"
}
] | 2011-09-09 | [
[
"Anderson",
"Paul R.",
""
],
[
"Brill",
"Dieter R.",
""
]
] | A careful analysis of the gravitational geon solution found by Brill and Hartle is made. The gravitational wave expansion they used is shown to be consistent and to result in a gauge invariant wave equation. It also results in a gauge invariant effective stress-energy tensor for the gravitational waves provided that a generalized definition of a gauge transformation is used. To leading order this gauge transformation is the same as the usual one for gravitational waves. It is shown that the geon solution is a self-consistent solution to Einstein's equations and that, to leading order, the equations describing the geometry of the gravitational geon are identical to those derived by Wheeler for the electromagnetic geon. An appendix provides an existence proof for geon solutions to these equations. |
0907.1999 | Natalia Kiriushcheva | N. Kiriushcheva and S.V. Kuzmin | Translational invariance of the Einstein-Cartan action in any dimension | 25 pages, new Section on group properties of transformations is
added, references are added. This version will appear in General Relativity
and Gravitation | Gen.Rel.Grav.42:2613-2631,2010 | 10.1007/s10714-010-1003-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate that from the first order formulation of the Einstein-Cartan
action it is possible to derive the basic differential identity that leads to
translational invariance of the action in the tangent space. The
transformations of fields is written explicitly for both the first and second
order formulations and the group properties of transformations are studied.
This, combined with the preliminary results from the Hamiltonian formulation
(arXiv:0907.1553 [gr-qc]), allows us to conclude that without any modification,
the Einstein-Cartan action in any dimension higher than two possesses not only
rotational invariance but also a form of \textit{translational invariance in
the tangent space}. We argue that \textit{not} only a complete Hamiltonian
analysis can unambiguously give an answer to the question of what a gauge
symmetry is, but also the pure Lagrangian methods allow us to find the same
gauge symmetry from the \textit{basic} differential identities.
| [
{
"created": "Sun, 12 Jul 2009 03:39:31 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2009 18:24:36 GMT",
"version": "v2"
},
{
"created": "Tue, 18 May 2010 03:58:43 GMT",
"version": "v3"
}
] | 2011-02-21 | [
[
"Kiriushcheva",
"N.",
""
],
[
"Kuzmin",
"S. V.",
""
]
] | We demonstrate that from the first order formulation of the Einstein-Cartan action it is possible to derive the basic differential identity that leads to translational invariance of the action in the tangent space. The transformations of fields is written explicitly for both the first and second order formulations and the group properties of transformations are studied. This, combined with the preliminary results from the Hamiltonian formulation (arXiv:0907.1553 [gr-qc]), allows us to conclude that without any modification, the Einstein-Cartan action in any dimension higher than two possesses not only rotational invariance but also a form of \textit{translational invariance in the tangent space}. We argue that \textit{not} only a complete Hamiltonian analysis can unambiguously give an answer to the question of what a gauge symmetry is, but also the pure Lagrangian methods allow us to find the same gauge symmetry from the \textit{basic} differential identities. |
1808.10757 | Youngsub Yoon | Youngsub Yoon | CMB anisotropy power spectrum of 3-sphere universe for low $l$ | 6 pages, Omega_tot calculated | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the CMB anisotropy power spectrum of a closed universe for large
angle (i.e., low $l$) due to a scale invariant fluctuation of primordial
universe by considering the spherical harmonics for 3-sphere. In particular,
contrary to the wide belief, we show that this consideration affects the CMB
anisotropy power spectrum; instead of constant $l(l+1)C_l$, our consideration
results in the supression for $l=2$, currently explained by the cosmic
variance. As a more concrete proof of our analysis, from the low $l$ CMB
anisotropy data \emph{alone}, we obtained
$\Omega_{\mathrm{tot}}=1.0018^{+0.0031}_{-0.0007}$, which agrees with
$\Omega_{\mathrm{tot}}=1.0023^{+ 0.0056}_{- 0.0054}$ from the previous anlaysis
of WMAP+BAO+$H_0$. Thus, we conclude that our Universe is closed.
| [
{
"created": "Thu, 30 Aug 2018 06:32:21 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2018 13:10:01 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Dec 2020 15:24:05 GMT",
"version": "v3"
},
{
"created": "Tue, 15 Dec 2020 14:14:56 GMT",
"version": "v4"
}
] | 2020-12-16 | [
[
"Yoon",
"Youngsub",
""
]
] | We calculate the CMB anisotropy power spectrum of a closed universe for large angle (i.e., low $l$) due to a scale invariant fluctuation of primordial universe by considering the spherical harmonics for 3-sphere. In particular, contrary to the wide belief, we show that this consideration affects the CMB anisotropy power spectrum; instead of constant $l(l+1)C_l$, our consideration results in the supression for $l=2$, currently explained by the cosmic variance. As a more concrete proof of our analysis, from the low $l$ CMB anisotropy data \emph{alone}, we obtained $\Omega_{\mathrm{tot}}=1.0018^{+0.0031}_{-0.0007}$, which agrees with $\Omega_{\mathrm{tot}}=1.0023^{+ 0.0056}_{- 0.0054}$ from the previous anlaysis of WMAP+BAO+$H_0$. Thus, we conclude that our Universe is closed. |
1805.03781 | Matt Visser | Petarpa Boonserm (Chulalongkorn University), Tritos Ngampitipan
(Chandrakasem Rajabhat University), Alex Simpson (Victoria University of
Wellington), and Matt Visser (Victoria University of Wellington) | The exponential metric represents a traversable wormhole | V1: 25 pages. V2: Still 25 pages. 6 references added. No physics
changes. V3: Still 25 pages. 2 more references added. No physics changes | Phys. Rev. D 98, 084048 (2018) | 10.1103/PhysRevD.98.084048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For various reasons a number of authors have mooted an "exponential form" for
the spacetime metric: \[ ds^2 = - e^{-2m/r} dt^2 + e^{+2m/r}\{dr^2 +
r^2(d\theta^2+\sin^2\theta \, d\phi^2)\}. \] While the weak-field behaviour
matches nicely with weak-field general relativity, and so also automatically
matches nicely with the Newtonian gravity limit, the strong-field behaviour is
markedly different. Proponents of these exponential metrics have very much
focussed on the absence of horizons --- it is certainly clear that this
geometry does not represent a black hole. However, the proponents of these
exponential metrics have failed to note that instead one is dealing with a
traversable wormhole --- with all of the interesting and potentially
problematic features that such an observation raises. If one wishes to replace
all the black hole candidates astronomers have identified with traversable
wormholes, then certainly a careful phenomenological analysis of this quite
radical proposal should be carried out.
| [
{
"created": "Thu, 10 May 2018 01:56:30 GMT",
"version": "v1"
},
{
"created": "Thu, 17 May 2018 07:20:47 GMT",
"version": "v2"
},
{
"created": "Mon, 21 May 2018 07:04:42 GMT",
"version": "v3"
}
] | 2018-11-07 | [
[
"Boonserm",
"Petarpa",
"",
"Chulalongkorn University"
],
[
"Ngampitipan",
"Tritos",
"",
"Chandrakasem Rajabhat University"
],
[
"Simpson",
"Alex",
"",
"Victoria University of\n Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University ... | For various reasons a number of authors have mooted an "exponential form" for the spacetime metric: \[ ds^2 = - e^{-2m/r} dt^2 + e^{+2m/r}\{dr^2 + r^2(d\theta^2+\sin^2\theta \, d\phi^2)\}. \] While the weak-field behaviour matches nicely with weak-field general relativity, and so also automatically matches nicely with the Newtonian gravity limit, the strong-field behaviour is markedly different. Proponents of these exponential metrics have very much focussed on the absence of horizons --- it is certainly clear that this geometry does not represent a black hole. However, the proponents of these exponential metrics have failed to note that instead one is dealing with a traversable wormhole --- with all of the interesting and potentially problematic features that such an observation raises. If one wishes to replace all the black hole candidates astronomers have identified with traversable wormholes, then certainly a careful phenomenological analysis of this quite radical proposal should be carried out. |
1311.3007 | Shahar Hod | Shahar Hod | Purely imaginary polar resonances of rapidly-rotating Kerr black holes | 13 pages | Physical Review D 88, 084018 (2013) | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove the existence of a unique family of non-oscillatory
(purely-imaginary) polar quasinormal resonances of rapidly-rotating Kerr black
holes. These purely imaginary resonances can be expressed in the compact form:
w_n=-i2*pi*T_{BH}*(l+1+n), where T_{BH} is the black-hole temperature, l is the
spheroidal harmonic index of the mode, and n=0,1,2,... is the resonance
parameter. It is shown that our analytical results for the black-hole resonance
spectrum agree with new numerical data that recently appeared in the
literature.
| [
{
"created": "Wed, 13 Nov 2013 03:13:40 GMT",
"version": "v1"
}
] | 2013-11-14 | [
[
"Hod",
"Shahar",
""
]
] | We prove the existence of a unique family of non-oscillatory (purely-imaginary) polar quasinormal resonances of rapidly-rotating Kerr black holes. These purely imaginary resonances can be expressed in the compact form: w_n=-i2*pi*T_{BH}*(l+1+n), where T_{BH} is the black-hole temperature, l is the spheroidal harmonic index of the mode, and n=0,1,2,... is the resonance parameter. It is shown that our analytical results for the black-hole resonance spectrum agree with new numerical data that recently appeared in the literature. |
1808.09589 | Jose Wadih Maluf Dr. | J. W. Maluf, J. F. da Rocha-Neto, S. C. Ulhoa and F. L. Carneiro | The Work-Energy Relation for Particles on Geodesics in the pp-Wave
Spacetimes | 25 pages, 7 figures, published in the JCAP | JCAP03(2019)028 | 10.1088/1475-7516/2019/03/028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A non-linear gravitational wave imparts gravitational acceleration to all
particles that are hit by the wave. We evaluate this acceleration for particles
in the pp-wave space-times, and integrate it numerically along the geodesic
trajectories of the particles during the passage of a burst of gravitational
wave. The time dependence of the wave is given by a Gaussian, so that the
particles are free before and after the passage of the wave. The gravitational
acceleration is understood from the point of view of a flat space-time, which
is the initial and final gravitational field configuration. The integral of the
acceleration along the geodesics is the analogue of the Newtonian concept of
work per unit mass. Surprisingly, it yields almost exactly the variation of the
non-relativistic kinetic energy per unit mass of the free particle. Therefore,
the work-energy relation $\Delta K = \Delta W$ of classical Newtonian physics
also holds for a particle on geodesics in the pp-wave space-times, in a very
good approximation, and explains why the final kinetic energy of the particle
may be smaller or larger than the initial kinetic energy.
| [
{
"created": "Wed, 29 Aug 2018 00:21:56 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Dec 2018 14:28:59 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Mar 2019 16:52:30 GMT",
"version": "v3"
}
] | 2019-03-21 | [
[
"Maluf",
"J. W.",
""
],
[
"da Rocha-Neto",
"J. F.",
""
],
[
"Ulhoa",
"S. C.",
""
],
[
"Carneiro",
"F. L.",
""
]
] | A non-linear gravitational wave imparts gravitational acceleration to all particles that are hit by the wave. We evaluate this acceleration for particles in the pp-wave space-times, and integrate it numerically along the geodesic trajectories of the particles during the passage of a burst of gravitational wave. The time dependence of the wave is given by a Gaussian, so that the particles are free before and after the passage of the wave. The gravitational acceleration is understood from the point of view of a flat space-time, which is the initial and final gravitational field configuration. The integral of the acceleration along the geodesics is the analogue of the Newtonian concept of work per unit mass. Surprisingly, it yields almost exactly the variation of the non-relativistic kinetic energy per unit mass of the free particle. Therefore, the work-energy relation $\Delta K = \Delta W$ of classical Newtonian physics also holds for a particle on geodesics in the pp-wave space-times, in a very good approximation, and explains why the final kinetic energy of the particle may be smaller or larger than the initial kinetic energy. |
1208.1660 | Kourosh Nozari | J. Vahedi, Kourosh Nozari and P. Pedram | Generalized Uncertainty Principle and the Ramsauer-Townsend Effect | 11 pages, 3 figures | Gravitation and Cosmology 18, 211 (2012) | 10.1134/S0202289312030097 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The scattering cross section of electrons in noble gas atoms exhibits a
minimum value at electron energies of approximately 1eV. This is the
Ramsauer-Townsend effect. In this letter, we study the Ramsauer-Townsend effect
in the framework of the Generalized Uncertainty Principle.
| [
{
"created": "Wed, 8 Aug 2012 13:29:16 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Vahedi",
"J.",
""
],
[
"Nozari",
"Kourosh",
""
],
[
"Pedram",
"P.",
""
]
] | The scattering cross section of electrons in noble gas atoms exhibits a minimum value at electron energies of approximately 1eV. This is the Ramsauer-Townsend effect. In this letter, we study the Ramsauer-Townsend effect in the framework of the Generalized Uncertainty Principle. |
1912.06020 | Maciej Maliborski | Piotr T. Chru\'sciel and Maciej Maliborski and Nicol\'as Yunes | The structure of the singular ring in Kerr-like metrics | 27 pages, 8 figures, v2: matches published version | null | 10.1103/PhysRevD.101.104048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kerr geometry is believed to represent the exterior spacetime of
astrophysical black holes. We here re-analyze the geometry of Kerr-like metrics
(Kerr, Kerr-Newman, Kerr-de Sitter, and Kerr-anti de Sitter), paying particular
attention to the region near the singular set. We find that, although the
Kretschmann scalar vanishes at the singular set along a given direction, a
certain combination of curvature invariants diverges regardless of the
direction of approach. We also find that the two-dimensional geometry induced
by the spacetime metric on the orbits of the isometry group also possesses a
singularity regardless of the direction of approach. Likewise, the
two-dimensional geometry in the directions orthogonal to the isometry orbits is
$C^{2}$-divergent, but extends continuously at the singular set as a cone with
opening angle $4\pi$. We conclude by showing that tidal forces lead to infinite
stresses on neighboring geodesics that approach the singular set, destroying
any such observers in finite proper time. Those geodesics that come in from
infinity and do not hit the singular set but approach it are found to need
tremendous energy to get close to the singular set, experiencing an
acceleration transversal to the equatorial plane which grows without bound when
the minimal distance of approach goes to zero. While establishing these
results, we also present an alternative description of some other known
properties, as well as introducing toroidal coordinates that provide a hands-on
description of the double-covering for the geometry near the singular set.
| [
{
"created": "Thu, 12 Dec 2019 15:16:52 GMT",
"version": "v1"
},
{
"created": "Thu, 28 May 2020 11:01:41 GMT",
"version": "v2"
}
] | 2020-05-29 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Maliborski",
"Maciej",
""
],
[
"Yunes",
"Nicolás",
""
]
] | The Kerr geometry is believed to represent the exterior spacetime of astrophysical black holes. We here re-analyze the geometry of Kerr-like metrics (Kerr, Kerr-Newman, Kerr-de Sitter, and Kerr-anti de Sitter), paying particular attention to the region near the singular set. We find that, although the Kretschmann scalar vanishes at the singular set along a given direction, a certain combination of curvature invariants diverges regardless of the direction of approach. We also find that the two-dimensional geometry induced by the spacetime metric on the orbits of the isometry group also possesses a singularity regardless of the direction of approach. Likewise, the two-dimensional geometry in the directions orthogonal to the isometry orbits is $C^{2}$-divergent, but extends continuously at the singular set as a cone with opening angle $4\pi$. We conclude by showing that tidal forces lead to infinite stresses on neighboring geodesics that approach the singular set, destroying any such observers in finite proper time. Those geodesics that come in from infinity and do not hit the singular set but approach it are found to need tremendous energy to get close to the singular set, experiencing an acceleration transversal to the equatorial plane which grows without bound when the minimal distance of approach goes to zero. While establishing these results, we also present an alternative description of some other known properties, as well as introducing toroidal coordinates that provide a hands-on description of the double-covering for the geometry near the singular set. |
2009.00056 | Artur Miroszewski | Artur Miroszewski | Quantum dynamics in Weyl-Heisenberg coherent states | 18 pages, 3 figures; version 2: spelling mistakes corrected,
references updated | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The article explores a new formalism for describing motion in quantum
mechanics. The construction is based on generalized coherent states with
evolving fiducial vector. Weyl-Heisenberg coherent states are utilised to split
quantum systems into `classical' and `quantum' degrees of freedom. The
decomposition is found to be equivalent to quantum mechanics perceived from a
semi-classical frame. The split allows for introduction of a new definition of
classical state and is a convenient starting point for approximate analysis of
quantum dynamics. An example of a meta-stable state is given as a practical
illustration of the introduced concepts.
| [
{
"created": "Mon, 31 Aug 2020 18:47:24 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Sep 2020 08:46:18 GMT",
"version": "v2"
}
] | 2020-09-10 | [
[
"Miroszewski",
"Artur",
""
]
] | The article explores a new formalism for describing motion in quantum mechanics. The construction is based on generalized coherent states with evolving fiducial vector. Weyl-Heisenberg coherent states are utilised to split quantum systems into `classical' and `quantum' degrees of freedom. The decomposition is found to be equivalent to quantum mechanics perceived from a semi-classical frame. The split allows for introduction of a new definition of classical state and is a convenient starting point for approximate analysis of quantum dynamics. An example of a meta-stable state is given as a practical illustration of the introduced concepts. |
1512.03885 | Somenath Chakrabarty | Soma Mitra and Somenath Chakrabarty | Fermat's Principle in Curved Space-time, No Emission from Schwarzschild
Black Holes as Total Internal Reflection and Black Hole Unruh effect | 9 pages, no figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Fermat's principle in curved space-time with stationary type
metric, we have obtained the speed of light as a function of spatial
coordinates and hence the corresponding refractive index. The whole region with
space dependent gravity is divided into a number of overlapping transparent
refracting media with varying refractive index. The refractive index is found
to be increasing with the strength of gravitational field. Hence using the laws
of refraction, we have explained the gravitational bending of light. Further
using the conventional idea of total internal reflection of light while going
from denser to rarer medium, in the present scenario it is the propagation of
light from the region of ultra-strong gravitational field to relatively weaker
gravitational field region, we have proposed an alternative approach for no
emission of any kind of electromagnetic radiation from the surface of a
classical Schwarzschild Black Hole. We have further noticed that for an
observer in a uniformly accelerated frame, analogous to the Unruh radiation,
there can be emission of electromagnetic waves from the event horizon of a
classical black hole. This may be named as "black hole Unruh effect".
| [
{
"created": "Sat, 12 Dec 2015 07:08:39 GMT",
"version": "v1"
}
] | 2015-12-15 | [
[
"Mitra",
"Soma",
""
],
[
"Chakrabarty",
"Somenath",
""
]
] | Using the Fermat's principle in curved space-time with stationary type metric, we have obtained the speed of light as a function of spatial coordinates and hence the corresponding refractive index. The whole region with space dependent gravity is divided into a number of overlapping transparent refracting media with varying refractive index. The refractive index is found to be increasing with the strength of gravitational field. Hence using the laws of refraction, we have explained the gravitational bending of light. Further using the conventional idea of total internal reflection of light while going from denser to rarer medium, in the present scenario it is the propagation of light from the region of ultra-strong gravitational field to relatively weaker gravitational field region, we have proposed an alternative approach for no emission of any kind of electromagnetic radiation from the surface of a classical Schwarzschild Black Hole. We have further noticed that for an observer in a uniformly accelerated frame, analogous to the Unruh radiation, there can be emission of electromagnetic waves from the event horizon of a classical black hole. This may be named as "black hole Unruh effect". |
1103.2388 | Branislav Cvetkovi\'c | M. Blagojevi\'c and B. Cvetkovi\'c | Extra gauge symmetries in BHT gravity | LATEX, 12 pages | JHEP 1103:139,2011 | 10.1007/JHEP03(2011)139 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the canonical structure of the Bergshoeff-Hohm-Townsend massive
gravity, linearized around a maximally symmetric background. At the critical
point in the space of parameters, defined by $\Lambda_0/m^2=-1$, we discover an
extra gauge symmetry, which reflects the existence of the partially massless
mode. The number of the Lagrangian degrees of freedom is found to be 1. We show
that the canonical structure of the theory at the critical point is unstable
under linearization.
| [
{
"created": "Fri, 11 Mar 2011 22:18:12 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Apr 2011 12:10:20 GMT",
"version": "v2"
}
] | 2011-04-05 | [
[
"Blagojević",
"M.",
""
],
[
"Cvetković",
"B.",
""
]
] | We study the canonical structure of the Bergshoeff-Hohm-Townsend massive gravity, linearized around a maximally symmetric background. At the critical point in the space of parameters, defined by $\Lambda_0/m^2=-1$, we discover an extra gauge symmetry, which reflects the existence of the partially massless mode. The number of the Lagrangian degrees of freedom is found to be 1. We show that the canonical structure of the theory at the critical point is unstable under linearization. |
0704.3898 | Gamal Nashed G.L. | Gamal G.L. Nashed and Takeshi Shirafuji | Reissner-Nordstr\"om Spacetime in the Tetrad Theory of Gravitation | 16 pages, Latex | Int.J.Mod.Phys.D16:65,2007 | 10.1142/S0218271807009310 | null | gr-qc | null | We give two classes of spherically symmetric exact solutions of the couple
gravitational and electromagnetic fields with charged source in the tetrad
theory of gravitation. The first solution depends on an arbitrary function
$H({R},t)$. The second solution depends on a constant parameter $\eta$. These
solutions reproduce the same metric, i.e., the Reissner--Nordstr$\ddot{o}$m
metric. If the arbitrary function which characterizes the first solution and
the arbitrary constant of the second solution are set to be zero, then the two
exact solutions will coincide with each other. We then calculate the energy
content associated with these analytic solutions using the superpotential
method. In particular, we examine whether these solutions meet the condition
which M{\o}ller required for a consistent energy-momentum complex: Namely, we
check whether the total four-momentum of an isolated system behaves as a
four-vector under Lorentz transformations. It is then found that the arbitrary
function should decrease faster than $1/\sqrt{R}$ for $R\to \infty$. It is also
shown that the second exact solution meets the M{\o}ller's condition.
| [
{
"created": "Mon, 30 Apr 2007 08:57:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nashed",
"Gamal G. L.",
""
],
[
"Shirafuji",
"Takeshi",
""
]
] | We give two classes of spherically symmetric exact solutions of the couple gravitational and electromagnetic fields with charged source in the tetrad theory of gravitation. The first solution depends on an arbitrary function $H({R},t)$. The second solution depends on a constant parameter $\eta$. These solutions reproduce the same metric, i.e., the Reissner--Nordstr$\ddot{o}$m metric. If the arbitrary function which characterizes the first solution and the arbitrary constant of the second solution are set to be zero, then the two exact solutions will coincide with each other. We then calculate the energy content associated with these analytic solutions using the superpotential method. In particular, we examine whether these solutions meet the condition which M{\o}ller required for a consistent energy-momentum complex: Namely, we check whether the total four-momentum of an isolated system behaves as a four-vector under Lorentz transformations. It is then found that the arbitrary function should decrease faster than $1/\sqrt{R}$ for $R\to \infty$. It is also shown that the second exact solution meets the M{\o}ller's condition. |
1905.04973 | Rang Nitish | R. Nitish, Rohit K. Gupta, Supriya Kar | Perspectives of Perihelion Precession in Torsion Modified Gravity | IJMPD(In Press) | null | null | null | gr-qc astro-ph.EP hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Killing symmetries are revisited in $d$$=$$5$ bulk geometric torsion (GT)
perturbation theory to investigate the perihelion precession. Computation
reveals a non-perturbative (NP) modification to the precession known in General
Relativity (GR). Remarkably the analysis re-assures our proposed holographic
correspondence between a perturbative GT in bulk and a boundary GR coupled to
$B_{2}$$ \wedge $$F_{2}$. In fact the topological correction is sourced by a
non-Newtonian potential in GR and we identify it with an ``electro-gravito''
dipole. Interestingly the dipole correction is shown to possess its origin in a
$4$-form underlying a propagating GT and leads to a NP gravity in $d$$=$$4$.
| [
{
"created": "Mon, 13 May 2019 11:19:59 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jun 2020 06:44:57 GMT",
"version": "v2"
}
] | 2020-06-11 | [
[
"Nitish",
"R.",
""
],
[
"Gupta",
"Rohit K.",
""
],
[
"Kar",
"Supriya",
""
]
] | Killing symmetries are revisited in $d$$=$$5$ bulk geometric torsion (GT) perturbation theory to investigate the perihelion precession. Computation reveals a non-perturbative (NP) modification to the precession known in General Relativity (GR). Remarkably the analysis re-assures our proposed holographic correspondence between a perturbative GT in bulk and a boundary GR coupled to $B_{2}$$ \wedge $$F_{2}$. In fact the topological correction is sourced by a non-Newtonian potential in GR and we identify it with an ``electro-gravito'' dipole. Interestingly the dipole correction is shown to possess its origin in a $4$-form underlying a propagating GT and leads to a NP gravity in $d$$=$$4$. |
1310.7499 | Eric Gourgoulhon | J.-P. Lasota, E. Gourgoulhon, M. Abramowicz, A. Tchekhovskoy, R.
Narayan | Extracting black-hole rotational energy: The generalized Penrose process | 24 pages, 14 figures, version published in Phys. Rev. D | Physical Review D 89, 024041 (2014) | 10.1103/PhysRevD.89.024041 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-sa/3.0/ | In the case involving particles the necessary and sufficient condition for
the Penrose process to extract energy from a rotating black hole is absorption
of particles with negative energies and angular momenta. No torque at the
black-hole horizon occurs. In this article we consider the case of arbitrary
fields or matter described by an unspecified, general energy-momentum tensor
$T_{\mu \nu}$ and show that the necessary and sufficient condition for
extraction of a black hole's rotational energy is analogous to that in the
mechanical Penrose process: absorption of negative energy and negative angular
momentum. We also show that a necessary condition for the Penrose process to
occur is for the Noether current (the conserved energy-momentum density vector)
to be spacelike or past directed (timelike or null) on some part of the
horizon. In the particle case, our general criterion for the occurrence of a
Penrose process reproduces the standard result. In the case of relativistic
jet-producing "magnetically arrested disks" we show that the negative energy
and angular-momentum absorption condition is obeyed when the Blandford-Znajek
mechanism is at work, and hence the high energy extraction efficiency up to
$\sim 300\%$ found in recent numerical simulations of such accretion flows
results from tapping the black hole's rotational energy through the Penrose
process. We show how black-hole rotational energy extraction works in this case
by describing the Penrose process in terms of the Noether current.
| [
{
"created": "Mon, 28 Oct 2013 17:20:25 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Feb 2014 21:24:56 GMT",
"version": "v2"
}
] | 2014-02-04 | [
[
"Lasota",
"J. -P.",
""
],
[
"Gourgoulhon",
"E.",
""
],
[
"Abramowicz",
"M.",
""
],
[
"Tchekhovskoy",
"A.",
""
],
[
"Narayan",
"R.",
""
]
] | In the case involving particles the necessary and sufficient condition for the Penrose process to extract energy from a rotating black hole is absorption of particles with negative energies and angular momenta. No torque at the black-hole horizon occurs. In this article we consider the case of arbitrary fields or matter described by an unspecified, general energy-momentum tensor $T_{\mu \nu}$ and show that the necessary and sufficient condition for extraction of a black hole's rotational energy is analogous to that in the mechanical Penrose process: absorption of negative energy and negative angular momentum. We also show that a necessary condition for the Penrose process to occur is for the Noether current (the conserved energy-momentum density vector) to be spacelike or past directed (timelike or null) on some part of the horizon. In the particle case, our general criterion for the occurrence of a Penrose process reproduces the standard result. In the case of relativistic jet-producing "magnetically arrested disks" we show that the negative energy and angular-momentum absorption condition is obeyed when the Blandford-Znajek mechanism is at work, and hence the high energy extraction efficiency up to $\sim 300\%$ found in recent numerical simulations of such accretion flows results from tapping the black hole's rotational energy through the Penrose process. We show how black-hole rotational energy extraction works in this case by describing the Penrose process in terms of the Noether current. |
1109.1532 | Denitsa Staicova | Plamen Fiziev and Denitsa Staicova | Application of the confluent Heun functions for finding the quasinormal
modes of nonrotating black holes | 5 pages, 1 table, 2 figures. Final version published in Phys. Rev. D | Phys. Rev. D 84, 127502 (2011) | 10.1103/PhysRevD.84.127502 | SU-TH/7-09-2011 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Although finding numerically the quasinormal modes of a nonrotating black
hole is a well-studied question, the physics of the problem is often hidden
behind complicated numerical procedures aimed at avoiding the direct solution
of the spectral system in this case. In this article, we use the exact
analytical solutions of the Regge-Wheeler equation and the Teukolsky radial
equation, written in terms of confluent Heun functions. In both cases, we
obtain the quasinormal modes numerically from spectral condition written in
terms of the Heun functions. The frequencies are compared with ones already
published by Andersson and other authors. A new method of studying the branch
cuts in the solutions is presented -- the epsilon-method. In particular, we
prove that the mode $n=8$ is not algebraically special and find its value with
more than 6 firm figures of precision for the first time. The stability of that
mode is explored using the $\epsilon$ method, and the results show that this
new method provides a natural way of studying the behavior of the modes around
the branch cut points.
| [
{
"created": "Wed, 7 Sep 2011 18:33:59 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2011 21:04:55 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Dec 2011 21:42:15 GMT",
"version": "v3"
}
] | 2011-12-26 | [
[
"Fiziev",
"Plamen",
""
],
[
"Staicova",
"Denitsa",
""
]
] | Although finding numerically the quasinormal modes of a nonrotating black hole is a well-studied question, the physics of the problem is often hidden behind complicated numerical procedures aimed at avoiding the direct solution of the spectral system in this case. In this article, we use the exact analytical solutions of the Regge-Wheeler equation and the Teukolsky radial equation, written in terms of confluent Heun functions. In both cases, we obtain the quasinormal modes numerically from spectral condition written in terms of the Heun functions. The frequencies are compared with ones already published by Andersson and other authors. A new method of studying the branch cuts in the solutions is presented -- the epsilon-method. In particular, we prove that the mode $n=8$ is not algebraically special and find its value with more than 6 firm figures of precision for the first time. The stability of that mode is explored using the $\epsilon$ method, and the results show that this new method provides a natural way of studying the behavior of the modes around the branch cut points. |
1307.6793 | Alejandro Bohe | Sylvain Marsat, Alejandro Bohe, Luc Blanchet, Alessandra Buonanno | Next-to-leading tail-induced spin-orbit effects in the gravitational
radiation flux of compact binaries | 22 pages, 1 figure; replaced to match the published version, two
references added | Class. Quantum Grav. 31 (2014) 025023 | 10.1088/0264-9381/31/2/025023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The imprint of non-linearities in the propagation of gravitational waves ---
the tail effect --- is responsible for new spin contributions to the energy
flux and orbital phasing of spinning black hole binaries. The spin-orbit
(linear in spin) contribution to this effect is currently known at leading
post-Newtonian order, namely 3PN for maximally spinning black holes on
quasi-circular orbits. In the present work, we generalize these tail-originated
spin-orbit terms to the next-to-leading 4PN order. This requires in particular
extending previous results on the dynamical evolution of precessing compact
binaries. We show that the tails represent the only spin-orbit terms at that
order for quasi-circular orbits, and we find perfect agreement with the known
result for a test particle around a Kerr black hole, computed by perturbation
theory. The BH-horizon absorption terms have to be added to the PN result
computed here. Our work completes the knowledge of the spin-orbit effects to
the phasing of compact binaries up to the 4PN order, and will allow the
building of more faithful PN templates for the inspiral phase of black hole
binaries, improving the capabilities of ground-based and space-based
gravitational wave detectors.
| [
{
"created": "Thu, 25 Jul 2013 15:30:58 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 2013 17:20:04 GMT",
"version": "v2"
}
] | 2013-12-24 | [
[
"Marsat",
"Sylvain",
""
],
[
"Bohe",
"Alejandro",
""
],
[
"Blanchet",
"Luc",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | The imprint of non-linearities in the propagation of gravitational waves --- the tail effect --- is responsible for new spin contributions to the energy flux and orbital phasing of spinning black hole binaries. The spin-orbit (linear in spin) contribution to this effect is currently known at leading post-Newtonian order, namely 3PN for maximally spinning black holes on quasi-circular orbits. In the present work, we generalize these tail-originated spin-orbit terms to the next-to-leading 4PN order. This requires in particular extending previous results on the dynamical evolution of precessing compact binaries. We show that the tails represent the only spin-orbit terms at that order for quasi-circular orbits, and we find perfect agreement with the known result for a test particle around a Kerr black hole, computed by perturbation theory. The BH-horizon absorption terms have to be added to the PN result computed here. Our work completes the knowledge of the spin-orbit effects to the phasing of compact binaries up to the 4PN order, and will allow the building of more faithful PN templates for the inspiral phase of black hole binaries, improving the capabilities of ground-based and space-based gravitational wave detectors. |
2406.00351 | Debojit Paul ` | Debojit Paul and Sanjeev Kalita | Solar system consistency of $f(R)$ gravity theory and its MOND
equivalence | 8 pages, 7 figures, 4 tables, Comments are welcomed | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since last two decades $f(R)$ gravity theory has been extensively used as a
serious alternative of general relativity to mimic the effects of dark energy.
The theory presents a Yukawa correction to Newtonian gravitational potential,
acting as a fifth force of Nature. Generally speaking, this new force is
mediated by a scalar field known as scalaron. It affects orbital dynamics of
test bodies around a central mass. When the scalaron becomes extremely massive
$f(R)$ gravity reduces to Newtonian theory in the weak field limit. In this
paper we test $f(R)$ gravity theory in the Solar system by constraining
scalaron mass through existing measurements of perihelion shift of planets,
Cassini's measurement of the Parameterised Post Newtonian parameter and
measurement of the Brans-Dicke coupling constant. We calculate acceleration due
to gravity in the theory for planets, Trans Neptunian Objects (TNOs), Centaurs,
Scattered Disk Objects (SDOs) and Oort cloud objects and compare it with the
values predicted by Newtonian and Modified Newtonian Dynamics (MOND). It is
found that the theory reproduces to MOND like acceleration in the outer Solar
system ($r_p \sim 2000$ au - $36000$ au) for available interpolating functions
of the MOND paradigm. From its MOND equivalence we constrain the parameters of
the theory. Our results are consistent with existing constraints on the theory
arising from the environment of the Galactic Centre black hole.
| [
{
"created": "Sat, 1 Jun 2024 08:05:20 GMT",
"version": "v1"
}
] | 2024-06-04 | [
[
"Paul",
"Debojit",
""
],
[
"Kalita",
"Sanjeev",
""
]
] | Since last two decades $f(R)$ gravity theory has been extensively used as a serious alternative of general relativity to mimic the effects of dark energy. The theory presents a Yukawa correction to Newtonian gravitational potential, acting as a fifth force of Nature. Generally speaking, this new force is mediated by a scalar field known as scalaron. It affects orbital dynamics of test bodies around a central mass. When the scalaron becomes extremely massive $f(R)$ gravity reduces to Newtonian theory in the weak field limit. In this paper we test $f(R)$ gravity theory in the Solar system by constraining scalaron mass through existing measurements of perihelion shift of planets, Cassini's measurement of the Parameterised Post Newtonian parameter and measurement of the Brans-Dicke coupling constant. We calculate acceleration due to gravity in the theory for planets, Trans Neptunian Objects (TNOs), Centaurs, Scattered Disk Objects (SDOs) and Oort cloud objects and compare it with the values predicted by Newtonian and Modified Newtonian Dynamics (MOND). It is found that the theory reproduces to MOND like acceleration in the outer Solar system ($r_p \sim 2000$ au - $36000$ au) for available interpolating functions of the MOND paradigm. From its MOND equivalence we constrain the parameters of the theory. Our results are consistent with existing constraints on the theory arising from the environment of the Galactic Centre black hole. |
1711.01643 | Ignacio Salazar | Nicolas Grandi, Ignacio Salazar Landea | Scalar Hair Around Charged Black Holes in Einstein-Gauss-Bonnet Gravity | 22 pages, 7 figures. v2: Improved discussion. Improved section IV.
PRD refereed version | Phys. Rev. D 97, 044042 (2018) | 10.1103/PhysRevD.97.044042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore charged black hole solutions in Einstein-Gauss-Bonnet gravity in
five dimensions, with a charged scalar hair. We interpret such hairy black
holes as the final state of the superradiant instability previously reported
for this system. We explore the relation of the hairy black hole solutions with
the non-backreacting quasibound states and scalar clouds, as well as with the
boson star solutions.
| [
{
"created": "Sun, 5 Nov 2017 19:09:49 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Feb 2018 18:06:54 GMT",
"version": "v2"
}
] | 2018-03-07 | [
[
"Grandi",
"Nicolas",
""
],
[
"Landea",
"Ignacio Salazar",
""
]
] | We explore charged black hole solutions in Einstein-Gauss-Bonnet gravity in five dimensions, with a charged scalar hair. We interpret such hairy black holes as the final state of the superradiant instability previously reported for this system. We explore the relation of the hairy black hole solutions with the non-backreacting quasibound states and scalar clouds, as well as with the boson star solutions. |
gr-qc/9807012 | Zloshchastiev Konstantin | Konstantin G. Zloshchastiev | Extended particle models based on hollow singular hypersurfaces in
general relativity: Classical and quantum aspects of charged textures | I try to unitarily answer both the question "Can sub-lepton/hadron
matter be of topological nature" and "What is the origin of cosmic textures
and pre-lepton-hadron phase in the early Universe"; slightly shortened
version (v2) was published in IJMPD | Int.J.Mod.Phys. D8 (1999) 165-176 | 10.1142/S0218271899000158 | null | gr-qc hep-ph hep-th | null | In present paper we construct classical and quantum models of an extended
charged particle. One shows that consecutive modelling can be based on the
hollow thin-wall charged texture (in the hydrodynamical approach of a perfect
fluid) which acquires gravitational mass due to Einstein-Maxwell interaction.
We demonstrate that such a model has equilibrium states at the radius equal to
the established classical radius of a charged particle. Also we consider
quantum aspects of the theory and obtain the (internal) Dirac sea conception in
a natural way. Besides, the phenomenological unification on the mass level of
the two families of elementary particles, charged pions and electrons and
positrons, evidently arises as the effect induced by classical and quantum
gravity prior to Standard Model.
Finally, in the cosmological connection our model proposes the answer on the
important question, what are the real sources of texture matter. Besides, the
texture hypothesis means that in the early Universe the topological texture
foam phase existed before the lepton-hadron one.
| [
{
"created": "Mon, 6 Jul 1998 15:02:58 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 1999 04:05:20 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Sep 1999 07:51:28 GMT",
"version": "v3"
},
{
"created": "Mon, 4 Oct 1999 13:08:15 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Zloshchastiev",
"Konstantin G.",
""
]
] | In present paper we construct classical and quantum models of an extended charged particle. One shows that consecutive modelling can be based on the hollow thin-wall charged texture (in the hydrodynamical approach of a perfect fluid) which acquires gravitational mass due to Einstein-Maxwell interaction. We demonstrate that such a model has equilibrium states at the radius equal to the established classical radius of a charged particle. Also we consider quantum aspects of the theory and obtain the (internal) Dirac sea conception in a natural way. Besides, the phenomenological unification on the mass level of the two families of elementary particles, charged pions and electrons and positrons, evidently arises as the effect induced by classical and quantum gravity prior to Standard Model. Finally, in the cosmological connection our model proposes the answer on the important question, what are the real sources of texture matter. Besides, the texture hypothesis means that in the early Universe the topological texture foam phase existed before the lepton-hadron one. |
2105.09166 | Francisco Fernández-Ãlvarez | Francisco Fern\'andez-\'Alvarez and Jos\'e M. M. Senovilla | Asymptotic Structure with vanishing cosmological constant | 45 pages, first of two papers, minor corrections, accepted version
for publication | Class. Quant. Grav. 39 165011 2022 | 10.1088/1361-6382/ac387e | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the first of two papers devoted to the asymptotic structure of
space-time in the presence of a non-negative cosmological constant $\Lambda$.
This first paper is concerned with the case of $\Lambda =0$. Our approach is
fully based on the tidal nature of the gravitational field and therefore on the
`tidal energies' built with the Weyl curvature. In particular, we use the
(radiant) asymptotic supermomenta computed from the rescaled Weyl tensor at
infinity to provide a novel characterisation of radiation escaping from, or
entering into, the space-time. Our new criterion is easy to implement and shown
to be fully equivalent to the classical one based on the news tensor. One of
its virtues is that its formulation can be easily adapted to the case with
$\Lambda>0$ covered in the second paper. We derive the general
energy-momentum-loss formulae including the matter terms and all factors
associated to the choices of arbitrary foliation and of super-translation. We
also revisit and present a full reformulation of the traditional peeling
behaviour with a neat geometrical construction that leads, in particular, to an
asymptotic alignment of the supermomenta in accordance with the radiation
criterion.
| [
{
"created": "Wed, 19 May 2021 14:36:12 GMT",
"version": "v1"
},
{
"created": "Thu, 20 May 2021 15:53:28 GMT",
"version": "v2"
},
{
"created": "Mon, 21 Jun 2021 14:31:14 GMT",
"version": "v3"
},
{
"created": "Tue, 23 Nov 2021 19:40:44 GMT",
"version": "v4"
}
] | 2022-08-23 | [
[
"Fernández-Álvarez",
"Francisco",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | This is the first of two papers devoted to the asymptotic structure of space-time in the presence of a non-negative cosmological constant $\Lambda$. This first paper is concerned with the case of $\Lambda =0$. Our approach is fully based on the tidal nature of the gravitational field and therefore on the `tidal energies' built with the Weyl curvature. In particular, we use the (radiant) asymptotic supermomenta computed from the rescaled Weyl tensor at infinity to provide a novel characterisation of radiation escaping from, or entering into, the space-time. Our new criterion is easy to implement and shown to be fully equivalent to the classical one based on the news tensor. One of its virtues is that its formulation can be easily adapted to the case with $\Lambda>0$ covered in the second paper. We derive the general energy-momentum-loss formulae including the matter terms and all factors associated to the choices of arbitrary foliation and of super-translation. We also revisit and present a full reformulation of the traditional peeling behaviour with a neat geometrical construction that leads, in particular, to an asymptotic alignment of the supermomenta in accordance with the radiation criterion. |
2209.09620 | Joseph Johnson PhD | Joseph E. Johnson | Riemannian Geometry Framed as a Generalized Lie Algebra to Incorporate
General Relativity with Quantum Theory 1 | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper reframes Riemannian geometry as a generalized Lie algebra allowing
the equations of both RG and then General Relativity to be expressed as
commutation relations among fundamental operators. We begin with an Abelian Lie
algebra of n operators, X, whose simultaneous eigenvalues, y, define a real
n-dimensional space. Then with n new operators defined as independent
functions, we define contravariant and covariant tensors in terms of their
eigenvalues, on a Hilbert space representation. We then define n additional
operators, D, whose exponential map is to translate X as defined by a
noncommutative algebra of operators (observables) where the structure constants
are shown to be the metric functions of the X operators thus allowing for
spatial curvature resulting in a noncommutativity among the D operators. The D
operators then have a Hilbert space position-diagonal representation as
generalized differential operators plus an arbitrary vector function A(X),
which, with the metric, written as a commutator, can express the Christoffel
symbols, and the Riemann, Ricci and other tensors as commutators in this
representation. Traditional RG and GR are obtained in a position diagonal
representation of this noncommutative algebra of 2n+1 operators. We seek to
provide a more general framework for RG to support an integration of GR, QT,
and the SM by generalizing Lie algebras as described.
| [
{
"created": "Fri, 16 Sep 2022 21:13:58 GMT",
"version": "v1"
}
] | 2022-09-21 | [
[
"Johnson",
"Joseph E.",
""
]
] | This paper reframes Riemannian geometry as a generalized Lie algebra allowing the equations of both RG and then General Relativity to be expressed as commutation relations among fundamental operators. We begin with an Abelian Lie algebra of n operators, X, whose simultaneous eigenvalues, y, define a real n-dimensional space. Then with n new operators defined as independent functions, we define contravariant and covariant tensors in terms of their eigenvalues, on a Hilbert space representation. We then define n additional operators, D, whose exponential map is to translate X as defined by a noncommutative algebra of operators (observables) where the structure constants are shown to be the metric functions of the X operators thus allowing for spatial curvature resulting in a noncommutativity among the D operators. The D operators then have a Hilbert space position-diagonal representation as generalized differential operators plus an arbitrary vector function A(X), which, with the metric, written as a commutator, can express the Christoffel symbols, and the Riemann, Ricci and other tensors as commutators in this representation. Traditional RG and GR are obtained in a position diagonal representation of this noncommutative algebra of 2n+1 operators. We seek to provide a more general framework for RG to support an integration of GR, QT, and the SM by generalizing Lie algebras as described. |
gr-qc/9910096 | Gerard Clement | Gerard Clement | Generating rotating fields in general relativity | 8 pages, talk presented at the 10th Russian Gravitational Conference
(Vladimir, June 1999) | Grav.Cosmol. 5 (1999) 281-284 | null | null | gr-qc hep-th | null | I present a new method to generate rotating solutions of the Einstein-Maxwell
equations from static solutions, give several examples of its application, and
discuss its general properties.
| [
{
"created": "Tue, 26 Oct 1999 12:47:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Clement",
"Gerard",
""
]
] | I present a new method to generate rotating solutions of the Einstein-Maxwell equations from static solutions, give several examples of its application, and discuss its general properties. |
gr-qc/9610003 | null | Pedro F. Gonzalez-Diaz (IMAFF, Madrid, Spain) | On the black-hole kink | 20 pages, LaTex, to appear in Int. J. Mod. Phys. D | Int.J.Mod.Phys. D6 (1997) 57-68 | 10.1142/S0218271897000054 | IMAFF-RCA-96-05 | gr-qc | null | By allowing the light cones to tip over on hypersurfaces according to the
conservation laws of an one-kink in static, Schwarzschild black hole metric, we
show that in the quantum regime there also exist instantons whose finite
imaginary action gives the probability of occurrence of the kink metric
corresponding to single chargeless, nonrotating black hole taking place in
pairs, the holes of each pair being joined on an interior surface, beyond the
horizon.
| [
{
"created": "Tue, 1 Oct 1996 17:39:34 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Gonzalez-Diaz",
"Pedro F.",
"",
"IMAFF, Madrid, Spain"
]
] | By allowing the light cones to tip over on hypersurfaces according to the conservation laws of an one-kink in static, Schwarzschild black hole metric, we show that in the quantum regime there also exist instantons whose finite imaginary action gives the probability of occurrence of the kink metric corresponding to single chargeless, nonrotating black hole taking place in pairs, the holes of each pair being joined on an interior surface, beyond the horizon. |
2201.02543 | Zhenwei Lyu | Zhenwei Lyu and Nan Jiang and Kent Yagi | Constraints on Einstein-dilaton-Gauss-Bonnet gravity from Black
Hole-Neutron Star Gravitational Wave Events | 12 pages, 5 figures | Phys. Rev. D 105, 064001 (2022), Erratum Phys. Rev. D 106, 069901
(2022) | 10.1103/PhysRevD.105.064001 | LIGO-P2100466 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Recent gravitational wave observations allow us to probe gravity in the
strong and dynamical field regime. In this paper, we focus on testing
Einstein-dilaton Gauss-Bonnet gravity which is motivated by string theory. In
particular, we use two new neutron star black hole binaries (GW200105 and
GW200115). We also consider GW190814 which is consistent with both a binary
black hole and a neutron star black hole binary. Adopting the leading
post-Newtonian correction and carrying out a Bayesian Markov-chain Monte Carlo
analyses, we derive the 90\% credible upper bound on the coupling constant of
the theory as $\sqrt{\alpha_{GB}} \lesssim 1.33\,\rm km$, whose consistency is
checked with an independent Fisher analysis. This bound is stronger than the
bound obtained in previous literature by combining selected binary black hole
events in GWTC-1 and GWTC-2 catalogs. We also derive a combined bound of
$\sqrt{\alpha_{GB}} \lesssim 1.18\,\rm km$ by stacking GW200105, GW200115,
GW190814, and selected binary black hole events. In order to check the validity
of the effect of higher post-Newtonian terms, we derive corrections to the
waveform phase up to second post Newtonian order by mapping results in
scalar-tensor theories to Einstein-dilaton Gauss-Bonnet gravity. We find that
such higher-order terms improve the bounds by $14.5\%$ for GW200105 and $6.9\%$
for GW200115 respectively.
| [
{
"created": "Fri, 7 Jan 2022 17:02:57 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Feb 2022 17:36:53 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Sep 2022 13:38:36 GMT",
"version": "v3"
},
{
"created": "Wed, 24 May 2023 17:09:47 GMT",
"version": "v4"
},
{
"cre... | 2023-08-03 | [
[
"Lyu",
"Zhenwei",
""
],
[
"Jiang",
"Nan",
""
],
[
"Yagi",
"Kent",
""
]
] | Recent gravitational wave observations allow us to probe gravity in the strong and dynamical field regime. In this paper, we focus on testing Einstein-dilaton Gauss-Bonnet gravity which is motivated by string theory. In particular, we use two new neutron star black hole binaries (GW200105 and GW200115). We also consider GW190814 which is consistent with both a binary black hole and a neutron star black hole binary. Adopting the leading post-Newtonian correction and carrying out a Bayesian Markov-chain Monte Carlo analyses, we derive the 90\% credible upper bound on the coupling constant of the theory as $\sqrt{\alpha_{GB}} \lesssim 1.33\,\rm km$, whose consistency is checked with an independent Fisher analysis. This bound is stronger than the bound obtained in previous literature by combining selected binary black hole events in GWTC-1 and GWTC-2 catalogs. We also derive a combined bound of $\sqrt{\alpha_{GB}} \lesssim 1.18\,\rm km$ by stacking GW200105, GW200115, GW190814, and selected binary black hole events. In order to check the validity of the effect of higher post-Newtonian terms, we derive corrections to the waveform phase up to second post Newtonian order by mapping results in scalar-tensor theories to Einstein-dilaton Gauss-Bonnet gravity. We find that such higher-order terms improve the bounds by $14.5\%$ for GW200105 and $6.9\%$ for GW200115 respectively. |
2312.03487 | Alexey Nenashev | A. V. Nenashev and S. D. Baranovskii | How to detect the spacetime curvature without rulers and clocks. II.
Three-dimensional spacetime | This is paper #2 in a series; paper #1 is arXiv:2302.12209 | null | null | null | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | We have generalized the results of the previous work [arXiv:2302.12209] to
the case of three-dimensional (3D) spacetime with two spatial and one temporal
coordinates. We have found that the flat Minkowski 3D spacetime is
"well-stitched", which means that it possesses a structure described by 24
causal relations between 12 events. We have proved that a 3D spacetime is
"well-stitched" if and only if it is conformally flat. The concept of a
"well-stitched" spacetime does not rely on metrical information about lengths,
times, etc., and does not belong to the metric geometry, but rather to geometry
of incidence. We therefore have "translated" an important concept of a
conformally-flat spacetime from the "metric" language of Riemannian geometry to
the "non-metric" language of the geometry of incidence. The results of this
paper provide a tool for detecting the curvature of the 3D spacetime on the
basis of causal relations only, without any measurement instruments like rulers
and clocks, provided that the spacetime is not conformally flat.
| [
{
"created": "Wed, 6 Dec 2023 13:30:32 GMT",
"version": "v1"
}
] | 2023-12-07 | [
[
"Nenashev",
"A. V.",
""
],
[
"Baranovskii",
"S. D.",
""
]
] | We have generalized the results of the previous work [arXiv:2302.12209] to the case of three-dimensional (3D) spacetime with two spatial and one temporal coordinates. We have found that the flat Minkowski 3D spacetime is "well-stitched", which means that it possesses a structure described by 24 causal relations between 12 events. We have proved that a 3D spacetime is "well-stitched" if and only if it is conformally flat. The concept of a "well-stitched" spacetime does not rely on metrical information about lengths, times, etc., and does not belong to the metric geometry, but rather to geometry of incidence. We therefore have "translated" an important concept of a conformally-flat spacetime from the "metric" language of Riemannian geometry to the "non-metric" language of the geometry of incidence. The results of this paper provide a tool for detecting the curvature of the 3D spacetime on the basis of causal relations only, without any measurement instruments like rulers and clocks, provided that the spacetime is not conformally flat. |
2401.15435 | Yangting Liu Dr. | Yangting Liu | Research on the application of loop quantum theory model in black hole
quantum information | 43pages,15figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An important reason why it is currently difficult to unify relativity theory
and quantum theory is the quantum information paradox. The information
engulfment pointed out by general relativity violates the principles of quantum
mechanics. An important reason why the industry does not have a clear
understanding of this phenomenon is the current lack of a theoretically
solvable cosmological model. Based on the complete model of loop quantum
theory, this article solves different levels of Hamiltonian constraint models
and simulates black hole information transfer dynamics, especially at extreme
points, from analytical results to step-by-step quantum corrections, and
attempts to compare the performance of different physical models in simulating
quantum Advantages during information transmission. Our study shows that even
second-order expansions are sufficient to distinguish differences in dynamics
at the black hole extremes, but to truly identify a model that has the
potential to describe quantum information transfer mechanisms and is
significantly different from other models, the theoretical analytical solution
should at least extend to Level three and above. In addition, the research
results such as computational simulation methods and related conclusions cited
and improved in this article can provide certain theoretical support and new
insights for the research prospects of general relativity loop quantum
cosmology and the intersection of quantum information and quantum fields.
| [
{
"created": "Sat, 27 Jan 2024 15:06:14 GMT",
"version": "v1"
}
] | 2024-01-30 | [
[
"Liu",
"Yangting",
""
]
] | An important reason why it is currently difficult to unify relativity theory and quantum theory is the quantum information paradox. The information engulfment pointed out by general relativity violates the principles of quantum mechanics. An important reason why the industry does not have a clear understanding of this phenomenon is the current lack of a theoretically solvable cosmological model. Based on the complete model of loop quantum theory, this article solves different levels of Hamiltonian constraint models and simulates black hole information transfer dynamics, especially at extreme points, from analytical results to step-by-step quantum corrections, and attempts to compare the performance of different physical models in simulating quantum Advantages during information transmission. Our study shows that even second-order expansions are sufficient to distinguish differences in dynamics at the black hole extremes, but to truly identify a model that has the potential to describe quantum information transfer mechanisms and is significantly different from other models, the theoretical analytical solution should at least extend to Level three and above. In addition, the research results such as computational simulation methods and related conclusions cited and improved in this article can provide certain theoretical support and new insights for the research prospects of general relativity loop quantum cosmology and the intersection of quantum information and quantum fields. |
1311.7409 | Joanna Ja{\l}mu\.zna | Joanna Ja{\l}mu\.zna | Three-dimensional gravity and instability of $\text{AdS}_{3}$ | 21 pages, 6 figures | null | 10.5506/APhysPolB.44.2603 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is an extended version of my lecture at the LIII Cracow School of
Theoretical Physics in Zakopane in which I presented the results of joint work
with Piotr Bizo\'n concerning (in)stability of the three-dimensional anti-de
Sitter spacetime.
| [
{
"created": "Thu, 28 Nov 2013 19:51:45 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Jałmużna",
"Joanna",
""
]
] | This is an extended version of my lecture at the LIII Cracow School of Theoretical Physics in Zakopane in which I presented the results of joint work with Piotr Bizo\'n concerning (in)stability of the three-dimensional anti-de Sitter spacetime. |
0808.2299 | Mikhail V. Gorbatenko | M.V.Gorbatenko, T.M.Gorbatenko | Dirac particle in gravitation field | 13 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Being considered is the motion of Dirac particle in gravitational field,
described by Kerr solution. It is proved, that evolution of the wave function
is determined by Hermitian Hamiltonian, if the concomitant reference frame is
involved.
| [
{
"created": "Sun, 17 Aug 2008 16:46:56 GMT",
"version": "v1"
}
] | 2008-08-19 | [
[
"Gorbatenko",
"M. V.",
""
],
[
"Gorbatenko",
"T. M.",
""
]
] | Being considered is the motion of Dirac particle in gravitational field, described by Kerr solution. It is proved, that evolution of the wave function is determined by Hermitian Hamiltonian, if the concomitant reference frame is involved. |
1806.00620 | Saheb Soroushfar | Saheb Soroushfar and Maryam Afrooz | Analytical solutions of the geodesic equation in the space-time of a
black hole surrounded by perfect fluid in Rastall theory | 25 pages, 46 figures, 7 tables | Indian J Phys (2021) | 10.1007/s12648-020-01971-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the geodesic motion of massive and massless
test particles in the vicinity of a black hole space-time surrounded by perfect
fluid (quintessence, dust, radiation, cosmological constant and phantom) in
Rastall theory. We obtain the full set of analytical solutions of the geodesic
equation of motion in the space-time of this black hole. For all cases of
perfect fluid, we consider some different values of Rastall coupling constant
$k\lambda$ so that the equations of motion have integer powers of $\tilde{r}$
and also can be solved analytically. These analytical solutions are presented
in the form of elliptic and also hyperelliptic functions. In addition, using
obtained analytical solution and also figures of effective potential and
$L-E^2$ diagrams, we plot some examples of possibles orbits. moreover we use of
the angular momentum, conserved energy, electrical charge and also Rastall
parameter, to classify the different types of the possible gained orbits.
Moreover, we show that when Rastall field structure constant becomes zero
($N=0$) our results are consistent with the analysis of a Reissner-Nordstr\"om
black hole, however when both Rastall geometric parameter and electric charge
vanish $(N=Q=0)$, the metric and results are same as analysis of a
Schwarzschild black hole.
| [
{
"created": "Sat, 2 Jun 2018 11:16:17 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jun 2019 09:33:30 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Mar 2020 04:34:34 GMT",
"version": "v3"
}
] | 2021-02-15 | [
[
"Soroushfar",
"Saheb",
""
],
[
"Afrooz",
"Maryam",
""
]
] | In this paper, we investigate the geodesic motion of massive and massless test particles in the vicinity of a black hole space-time surrounded by perfect fluid (quintessence, dust, radiation, cosmological constant and phantom) in Rastall theory. We obtain the full set of analytical solutions of the geodesic equation of motion in the space-time of this black hole. For all cases of perfect fluid, we consider some different values of Rastall coupling constant $k\lambda$ so that the equations of motion have integer powers of $\tilde{r}$ and also can be solved analytically. These analytical solutions are presented in the form of elliptic and also hyperelliptic functions. In addition, using obtained analytical solution and also figures of effective potential and $L-E^2$ diagrams, we plot some examples of possibles orbits. moreover we use of the angular momentum, conserved energy, electrical charge and also Rastall parameter, to classify the different types of the possible gained orbits. Moreover, we show that when Rastall field structure constant becomes zero ($N=0$) our results are consistent with the analysis of a Reissner-Nordstr\"om black hole, however when both Rastall geometric parameter and electric charge vanish $(N=Q=0)$, the metric and results are same as analysis of a Schwarzschild black hole. |
2004.10139 | Diego S\'aez-Chill\'on G\'omez | Ismael Ayuso and Diego S\'aez-Chill\'on G\'omez | Extremal cosmological black holes in Horndeski gravity and the
anti-evaporation regime | 15 pages, version published | Universe 2020, 6(11), 210 | 10.3390/universe6110210 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extremal cosmological black holes are analysed in the framework of the most
general second order scalar-tensor theory, the~so-called Horndeski gravity.
Such~extremal black holes are a particular case of Schwarzschild-De Sitter
black holes that arises when the black hole horizon and the cosmological one
coincide. Such~metric is induced by a particular value of the effective
cosmological constant and is known as Nariai spacetime. The~existence of this
type of solutions is studied when considering the Horndeski Lagrangian and its
stability is analysed, where the so-called anti-evaporation regime is studied.
Contrary to other frameworks, the~radius of the horizon remains stable for some
cases of the Horndeski Lagrangian when considering perturbations at linear
order.
| [
{
"created": "Tue, 21 Apr 2020 16:29:33 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Nov 2020 20:30:30 GMT",
"version": "v2"
}
] | 2020-11-19 | [
[
"Ayuso",
"Ismael",
""
],
[
"Gómez",
"Diego Sáez-Chillón",
""
]
] | Extremal cosmological black holes are analysed in the framework of the most general second order scalar-tensor theory, the~so-called Horndeski gravity. Such~extremal black holes are a particular case of Schwarzschild-De Sitter black holes that arises when the black hole horizon and the cosmological one coincide. Such~metric is induced by a particular value of the effective cosmological constant and is known as Nariai spacetime. The~existence of this type of solutions is studied when considering the Horndeski Lagrangian and its stability is analysed, where the so-called anti-evaporation regime is studied. Contrary to other frameworks, the~radius of the horizon remains stable for some cases of the Horndeski Lagrangian when considering perturbations at linear order. |
1402.2481 | Antoine Folacci | Yves Decanini, Antoine Folacci and Mohamed Ould El Hadj | Resonant excitation of black holes by massive bosonic fields and giant
ringings | v1 : We extend to massive bosonic fields our work concerning resonant
excitation of BHs in massive gravity arXiv:1401.0321[gr-qc]. v2 : Minor
changes to match the published version | Phys. Rev. D 89, 084066 (2014) | 10.1103/PhysRevD.89.084066 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the massive scalar field, the Proca field and the Fierz-Pauli
field in the Schwarzschild spacetime and we focus more particularly on their
long-lived quasinormal modes. We show numerically that the associated
excitation factors have a strong resonant behavior and we confirm this result
analytically from semiclassical considerations based on the properties of the
unstable circular geodesics on which a massive particle can orbit the black
hole. The conspiracy of (i) the long-lived behavior of the quasinormal modes
and (ii) the resonant behavior of their excitation factors induces intrinsic
giant ringings, i.e., ringings of a huge amplitude. Such ringings, which are
moreover slowly decaying, are directly constructed from the retarded Green
function. If we describe the source of the black hole perturbation by an
initial value problem with Gaussian initial data, i.e., if we consider the
excitation of the black hole from an extrinsic point of view, we can show that
these extraordinary ringings are still present. This suggests that physically
realistic sources of perturbations should generate giant and slowly decaying
ringings and that their existence could be used to constrain ultralight bosonic
field theory interacting with black holes.
| [
{
"created": "Tue, 11 Feb 2014 13:07:54 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Mar 2014 15:15:11 GMT",
"version": "v2"
}
] | 2014-04-23 | [
[
"Decanini",
"Yves",
""
],
[
"Folacci",
"Antoine",
""
],
[
"Hadj",
"Mohamed Ould El",
""
]
] | We consider the massive scalar field, the Proca field and the Fierz-Pauli field in the Schwarzschild spacetime and we focus more particularly on their long-lived quasinormal modes. We show numerically that the associated excitation factors have a strong resonant behavior and we confirm this result analytically from semiclassical considerations based on the properties of the unstable circular geodesics on which a massive particle can orbit the black hole. The conspiracy of (i) the long-lived behavior of the quasinormal modes and (ii) the resonant behavior of their excitation factors induces intrinsic giant ringings, i.e., ringings of a huge amplitude. Such ringings, which are moreover slowly decaying, are directly constructed from the retarded Green function. If we describe the source of the black hole perturbation by an initial value problem with Gaussian initial data, i.e., if we consider the excitation of the black hole from an extrinsic point of view, we can show that these extraordinary ringings are still present. This suggests that physically realistic sources of perturbations should generate giant and slowly decaying ringings and that their existence could be used to constrain ultralight bosonic field theory interacting with black holes. |
2404.15203 | Ayesha Almas | Adnan Malik, Amjad Hussain, M. Farasat Shamir, Ayesha Almas | Impact of Ricci Inverse Gravity on Hybrid Star Model | 21 pages, 9 figures, Submitted for publication | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The objective of our current study is to explore novel aspects of a
stationary anisotropic relativistic hybrid compact star that consists of quark
matter (QM) in its core and ordinary baryonic matter (OBM) in its crust. This
study has been done by adopting separate equations of states (EoSs) for quark
matter and baryonic matter. The MIT bag model equation of state
$p_{q}=\frac{1}{3}(\rho_{q}-4B)$ has been used to demonstrate a correlation
between the density and pressure of weird quark matter in the interior of the
star. In addition, we present a simple linear equation of state
$p_{r}=\beta_{1}\rho-\beta$ that links radial pressure and matter density for
OBM. The stellar model was formulated within the context of
$f(\mathcal{R},\mathcal{A})$ gravity, utilizing a linear correlation between
Ricci tensor $\mathcal{R}$ and anticurvature scaler $\mathcal{A}$.To solve the
field equations of this novel alternative gravity, we employ the Krori and
Barua approach to the metric potentials. The validity of our suggested model is
assessed using the graphical approach, while ensuring that the conditions are
physically feasible. Our focus is specifically on the tiny celestial object
known as LMC X-4 [$\text{M} =
(1.04^{+0.09}_{-0.09})M_{\odot};\text{R}=8.301^{+0.2}_{-0.2}\text{km}$], which
we consider a viable candidate for a strange quark star. We want to clarify the
model's physical validity by examining a variety of physical assessments,
including dynamical equilibrium, energy conditions, compactness factor, mass
function, and surface redshift. The resulting outcome confirms the authenticity
of the hybrid star model under analysis.
| [
{
"created": "Tue, 23 Apr 2024 16:37:19 GMT",
"version": "v1"
}
] | 2024-04-24 | [
[
"Malik",
"Adnan",
""
],
[
"Hussain",
"Amjad",
""
],
[
"Shamir",
"M. Farasat",
""
],
[
"Almas",
"Ayesha",
""
]
] | The objective of our current study is to explore novel aspects of a stationary anisotropic relativistic hybrid compact star that consists of quark matter (QM) in its core and ordinary baryonic matter (OBM) in its crust. This study has been done by adopting separate equations of states (EoSs) for quark matter and baryonic matter. The MIT bag model equation of state $p_{q}=\frac{1}{3}(\rho_{q}-4B)$ has been used to demonstrate a correlation between the density and pressure of weird quark matter in the interior of the star. In addition, we present a simple linear equation of state $p_{r}=\beta_{1}\rho-\beta$ that links radial pressure and matter density for OBM. The stellar model was formulated within the context of $f(\mathcal{R},\mathcal{A})$ gravity, utilizing a linear correlation between Ricci tensor $\mathcal{R}$ and anticurvature scaler $\mathcal{A}$.To solve the field equations of this novel alternative gravity, we employ the Krori and Barua approach to the metric potentials. The validity of our suggested model is assessed using the graphical approach, while ensuring that the conditions are physically feasible. Our focus is specifically on the tiny celestial object known as LMC X-4 [$\text{M} = (1.04^{+0.09}_{-0.09})M_{\odot};\text{R}=8.301^{+0.2}_{-0.2}\text{km}$], which we consider a viable candidate for a strange quark star. We want to clarify the model's physical validity by examining a variety of physical assessments, including dynamical equilibrium, energy conditions, compactness factor, mass function, and surface redshift. The resulting outcome confirms the authenticity of the hybrid star model under analysis. |
2003.13591 | Jonathan Luk | Grigorios Fournodavlos, Jonathan Luk | Asymptotically Kasner-like singularities | 57 pages; minor corrections | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove existence, uniqueness and regularity of solutions to the Einstein
vacuum equations taking the form $${^{(4)}g} = -dt^2 + \sum_{i,j = 1}^3
a_{ij}t^{2p_{\max\{i,j\}}}\, \mathrm{d} x^i\, \mathrm{d} x^j$$ on $(0,T]_t
\times \mathbb T^3_x$, where $a_{ij}(t,x)$ and $p_i(x)$ are regular functions
without symmetry or analyticity assumptions. These metrics are singular and
asymptotically Kasner-like as $t\to 0^+$. These solutions are expected to be
highly non-generic, and our construction can be viewed as solving a singular
initial value problem with Fuchsian-type analysis where the data are posed on
the "singular hypersurface" $\{ t = 0\}$. This is the first such result without
imposing symmetry or analyticity.
To carry out the analysis, we study the problem in a synchronized coordinate
system. In particular, we introduce a novel way to perform (weighted) energy
estimates in such a coordinate system based on estimating the second
fundamental forms of the constant-$t$ hypersurfaces.
| [
{
"created": "Mon, 30 Mar 2020 16:18:22 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2022 16:45:17 GMT",
"version": "v2"
}
] | 2022-05-18 | [
[
"Fournodavlos",
"Grigorios",
""
],
[
"Luk",
"Jonathan",
""
]
] | We prove existence, uniqueness and regularity of solutions to the Einstein vacuum equations taking the form $${^{(4)}g} = -dt^2 + \sum_{i,j = 1}^3 a_{ij}t^{2p_{\max\{i,j\}}}\, \mathrm{d} x^i\, \mathrm{d} x^j$$ on $(0,T]_t \times \mathbb T^3_x$, where $a_{ij}(t,x)$ and $p_i(x)$ are regular functions without symmetry or analyticity assumptions. These metrics are singular and asymptotically Kasner-like as $t\to 0^+$. These solutions are expected to be highly non-generic, and our construction can be viewed as solving a singular initial value problem with Fuchsian-type analysis where the data are posed on the "singular hypersurface" $\{ t = 0\}$. This is the first such result without imposing symmetry or analyticity. To carry out the analysis, we study the problem in a synchronized coordinate system. In particular, we introduce a novel way to perform (weighted) energy estimates in such a coordinate system based on estimating the second fundamental forms of the constant-$t$ hypersurfaces. |
0708.2984 | Nils Andersson | B. Haskell, N. Andersson, D. I. Jones and L. Samuelsson | Are neutron stars with crystalline colour superconducting cores
interesting for the LIGO experiment? | published as Physical Review Letters, vol. 99, Issue 23, id. 231101 | null | 10.1103/PhysRevLett.99.231101 | null | gr-qc astro-ph | null | We estimate the maximal deformation that can be sustained by a rotating
neutron star with a crystalline colour superconducting quark core. Our results
suggest that current gravitational-wave data from LIGO have already reached the
level where a detection would have been possible over a wide range of the
poorly constrained QCD parameters. This leads to the non-trivial conclusion
that compact objects \emph{do not} contain maximally strained colour
crystalline cores drawn from this range of parameter space. We discuss the
uncertainties associated with our simple model and how it can be improved in
the future.
| [
{
"created": "Wed, 22 Aug 2007 10:16:36 GMT",
"version": "v1"
},
{
"created": "Fri, 16 May 2008 14:54:30 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Haskell",
"B.",
""
],
[
"Andersson",
"N.",
""
],
[
"Jones",
"D. I.",
""
],
[
"Samuelsson",
"L.",
""
]
] | We estimate the maximal deformation that can be sustained by a rotating neutron star with a crystalline colour superconducting quark core. Our results suggest that current gravitational-wave data from LIGO have already reached the level where a detection would have been possible over a wide range of the poorly constrained QCD parameters. This leads to the non-trivial conclusion that compact objects \emph{do not} contain maximally strained colour crystalline cores drawn from this range of parameter space. We discuss the uncertainties associated with our simple model and how it can be improved in the future. |
2207.02771 | Michele Mancarella | Francesco Iacovelli, Michele Mancarella, Stefano Foffa, Michele
Maggiore | Forecasting the detection capabilities of third-generation
gravitational-wave detectors using $\texttt{GWFAST}$ | 43 + 12 pages, 24 + 5 Figures, $\texttt{GWFAST}$ available at
https://github.com/CosmoStatGW/gwfast, $\texttt{WF4Py}$ available at
https://github.com/CosmoStatGW/WF4Py. v3: resubmitted to APJ, minor changes
in results, Appendix C added | null | 10.3847/1538-4357/ac9cd4 | null | gr-qc astro-ph.CO astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We introduce $\texttt{GWFAST}$, a novel Fisher-matrix code for
gravitational-wave studies, tuned toward third-generation gravitational-wave
detectors such as Einstein Telescope (ET) and Cosmic Explorer (CE). We use it
to perform a comprehensive study of the capabilities of ET alone, and of a
network made by ET and two CE detectors, as well as to provide forecasts for
the forthcoming O4 run of the LVK collaboration. We consider binary neutron
stars, binary black holes and neutron star-black hole binaries, and compute
basic metrics such as the distribution of signal-to-noise ratio (SNR), the
accuracy in the reconstruction of various parameters (including distance, sky
localization, masses, spins and, for neutron stars, tidal deformabilities), and
the redshift distribution of the detections for different thresholds in SNR and
different levels of accuracy in localization and distance measurement. We
examine the expected distribution and properties of `golden events', with
especially large values of the SNR. We also pay special attention to the
dependence of the results on astrophysical uncertainties and on various
technical details (such as choice of waveforms, or the threshold in SNR), and
we compare with other Fisher codes in the literature. In a companion paper we
discuss the technical aspects of the code. Together with this paper, we
publicly release the code $\texttt{GWFAST}$ at
https://github.com/CosmoStatGW/gwfast, and the library $\texttt{WF4Py}$
implementing state-of-the-art gravitational-wave waveforms in pure
$\texttt{Python}$ at https://github.com/CosmoStatGW/WF4Py.
| [
{
"created": "Wed, 6 Jul 2022 16:04:23 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jul 2022 15:56:23 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Sep 2022 14:05:06 GMT",
"version": "v3"
}
] | 2023-01-02 | [
[
"Iacovelli",
"Francesco",
""
],
[
"Mancarella",
"Michele",
""
],
[
"Foffa",
"Stefano",
""
],
[
"Maggiore",
"Michele",
""
]
] | We introduce $\texttt{GWFAST}$, a novel Fisher-matrix code for gravitational-wave studies, tuned toward third-generation gravitational-wave detectors such as Einstein Telescope (ET) and Cosmic Explorer (CE). We use it to perform a comprehensive study of the capabilities of ET alone, and of a network made by ET and two CE detectors, as well as to provide forecasts for the forthcoming O4 run of the LVK collaboration. We consider binary neutron stars, binary black holes and neutron star-black hole binaries, and compute basic metrics such as the distribution of signal-to-noise ratio (SNR), the accuracy in the reconstruction of various parameters (including distance, sky localization, masses, spins and, for neutron stars, tidal deformabilities), and the redshift distribution of the detections for different thresholds in SNR and different levels of accuracy in localization and distance measurement. We examine the expected distribution and properties of `golden events', with especially large values of the SNR. We also pay special attention to the dependence of the results on astrophysical uncertainties and on various technical details (such as choice of waveforms, or the threshold in SNR), and we compare with other Fisher codes in the literature. In a companion paper we discuss the technical aspects of the code. Together with this paper, we publicly release the code $\texttt{GWFAST}$ at https://github.com/CosmoStatGW/gwfast, and the library $\texttt{WF4Py}$ implementing state-of-the-art gravitational-wave waveforms in pure $\texttt{Python}$ at https://github.com/CosmoStatGW/WF4Py. |
2003.00455 | Miguel Angel Javaloyes | Antonio Bernal, Miguel \'Angel Javaloyes, Miguel S\'anchez | Foundations of Finsler spacetimes from the Observers' Viewpoint | v2: 47 pages, new section 5.2.5, added seven references and minor
changes | Universe 2020, 6(4), 55 | 10.3390/universe6040055 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Physical foundations for relativistic spacetimes are revisited, in order to
check at what extent Finsler spacetimes lie in their framework. Arguments based
on inertial observers (as in the foundations of Special Relativity and
Classical Mechanics) are shown to correspond with a double linear approximation
in the measurement of space and time. While General Relativity appears by
dropping the first linearization, Finsler spacetimes appear by dropping the
second one. The classical Ehlers-Pirani-Schild approach is carefully discussed
and shown to be compatible with the Lorentz-Finsler case.
The precise mathematical definition of Finsler spacetime is discussed by
using the {\em space of observers}. Special care is taken in some issues such
as: the fact that a Lorentz-Finsler metric would be physically measurable only
on the causal directions for a cone structure, the implications for models of
spacetimes of some apparently innocuous hypotheses on differentiability, or the
possibilities of measurement of a varying speed of light.
| [
{
"created": "Sun, 1 Mar 2020 10:04:01 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Apr 2020 17:16:55 GMT",
"version": "v2"
}
] | 2020-04-21 | [
[
"Bernal",
"Antonio",
""
],
[
"Javaloyes",
"Miguel Ángel",
""
],
[
"Sánchez",
"Miguel",
""
]
] | Physical foundations for relativistic spacetimes are revisited, in order to check at what extent Finsler spacetimes lie in their framework. Arguments based on inertial observers (as in the foundations of Special Relativity and Classical Mechanics) are shown to correspond with a double linear approximation in the measurement of space and time. While General Relativity appears by dropping the first linearization, Finsler spacetimes appear by dropping the second one. The classical Ehlers-Pirani-Schild approach is carefully discussed and shown to be compatible with the Lorentz-Finsler case. The precise mathematical definition of Finsler spacetime is discussed by using the {\em space of observers}. Special care is taken in some issues such as: the fact that a Lorentz-Finsler metric would be physically measurable only on the causal directions for a cone structure, the implications for models of spacetimes of some apparently innocuous hypotheses on differentiability, or the possibilities of measurement of a varying speed of light. |
gr-qc/0311079 | Adam Szereszewski | Adam Szereszewski, Jacek Tafel | From 2-Dimensional Surfaces to Cosmological Solutions | 12 pages, no figures, LaTeX2e, to be published in Class. Quant. Grav | Gen.Rel.Grav. 37 (2005) 257-269 | 10.1007/s10714-005-0016-0 | null | gr-qc | null | We construct perfect fluid metrics corresponding to spacelike surfaces
invariant under a 1-dimensional group of isometries in 3-dimensional Minkowski
space. Under additional assumptions we obtain new cosmological solutions of
Bianchi type II, VI_0 and VII_0. The solutions depend on an arbitrary function
of time, which can be specified in order to satisfy an equation of state.
| [
{
"created": "Mon, 24 Nov 2003 13:22:14 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Szereszewski",
"Adam",
""
],
[
"Tafel",
"Jacek",
""
]
] | We construct perfect fluid metrics corresponding to spacelike surfaces invariant under a 1-dimensional group of isometries in 3-dimensional Minkowski space. Under additional assumptions we obtain new cosmological solutions of Bianchi type II, VI_0 and VII_0. The solutions depend on an arbitrary function of time, which can be specified in order to satisfy an equation of state. |
gr-qc/0204012 | Chiao | Raymond Y. Chiao | Superconductors as quantum transducers and antennas for gravitational
and electromagnetic radiation | 21 pages, 3 figures, abbreviated writeup of my March 23, 2002 Wheeler
Symposium lecture, and book chapter for Wheeler Festschrift; submitted to PRD | null | null | null | gr-qc | null | Superconductors will be considered as macroscopic quantum gravitational
antennas and transducers, which can directly convert upon reflection a beam of
quadrupolar electromagnetic radiation into gravitational radiation, and vice
versa, and thus serve as practical laboratory sources and receivers of
microwave and other radio-frequency gravitational waves. An estimate of the
transducer conversion efficiency on the order of unity comes out of the
Ginzburg-Landau theory for an extreme type II, dissipationless superconductor
with minimal coupling to weak gravitational and electromagnetic radiation
fields, whose frequency is smaller than the BCS gap frequency, thus satisfying
the quantum adiabatic theorem. The concept of ``the impedance of free space for
gravitational plane waves'' is introduced, and leads to a natural
impedance-matching process, in which the two kinds of radiation fields are
impedance-matched to each other around a hundred coherence lengths beneath the
surface of the superconductor. A simple, Hertz-like experiment has been
performed to test these ideas, and preliminary results will be reported. (PACS
nos.: 03.65.Ud, 04.30.Db, 04.30.Nk, 04.80.Nn, 74.60-w, 74.72.Bk)
| [
{
"created": "Tue, 2 Apr 2002 21:20:03 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Apr 2002 22:32:09 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Jul 2002 19:57:02 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Chiao",
"Raymond Y.",
""
]
] | Superconductors will be considered as macroscopic quantum gravitational antennas and transducers, which can directly convert upon reflection a beam of quadrupolar electromagnetic radiation into gravitational radiation, and vice versa, and thus serve as practical laboratory sources and receivers of microwave and other radio-frequency gravitational waves. An estimate of the transducer conversion efficiency on the order of unity comes out of the Ginzburg-Landau theory for an extreme type II, dissipationless superconductor with minimal coupling to weak gravitational and electromagnetic radiation fields, whose frequency is smaller than the BCS gap frequency, thus satisfying the quantum adiabatic theorem. The concept of ``the impedance of free space for gravitational plane waves'' is introduced, and leads to a natural impedance-matching process, in which the two kinds of radiation fields are impedance-matched to each other around a hundred coherence lengths beneath the surface of the superconductor. A simple, Hertz-like experiment has been performed to test these ideas, and preliminary results will be reported. (PACS nos.: 03.65.Ud, 04.30.Db, 04.30.Nk, 04.80.Nn, 74.60-w, 74.72.Bk) |
gr-qc/0006031 | Yasusada Nambu | Yasusada Nambu | Renormalization Group Approach to Cosmological Back Reaction Problems | 18 pages, revtex, to appear in Phys. Rev. D | Phys.Rev. D62 (2000) 104010 | 10.1103/PhysRevD.62.104010 | DPNU-00-10 | gr-qc astro-ph | null | We investigated the back reaction of cosmological perturbations on the
evolution of the universe using the second order perturbation of the Einstein's
equation. To incorporate the back reaction effect due to the inhomogeneity into
the framework of the cosmological perturbation, we used the renormalization
group method. The second order zero mode solution which appears by the
non-linearities of the Einstein's equation is regarded as a secular term of the
perturbative expansion, we renormalized a constant of integration contained in
the background solution and absorbed the secular term to this constant. For a
dust dominated universe, using the second order gauge invariant quantity, we
derived the renormalization group equation which determines the effective
dynamics of the Friedman-Robertson-Walker universe with the back reaction
effect in a gauge invariant manner. We obtained the solution of the
renormalization group equation and found that perturbations of the scalar mode
and the long wavelength tensor mode works as positive spatial curvature, and
the short wavelength tensor mode as radiation fluid.
| [
{
"created": "Fri, 9 Jun 2000 00:48:57 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Nambu",
"Yasusada",
""
]
] | We investigated the back reaction of cosmological perturbations on the evolution of the universe using the second order perturbation of the Einstein's equation. To incorporate the back reaction effect due to the inhomogeneity into the framework of the cosmological perturbation, we used the renormalization group method. The second order zero mode solution which appears by the non-linearities of the Einstein's equation is regarded as a secular term of the perturbative expansion, we renormalized a constant of integration contained in the background solution and absorbed the secular term to this constant. For a dust dominated universe, using the second order gauge invariant quantity, we derived the renormalization group equation which determines the effective dynamics of the Friedman-Robertson-Walker universe with the back reaction effect in a gauge invariant manner. We obtained the solution of the renormalization group equation and found that perturbations of the scalar mode and the long wavelength tensor mode works as positive spatial curvature, and the short wavelength tensor mode as radiation fluid. |
gr-qc/0610068 | George Sparling | George A.J. Sparling | Spacetime is spinorial; new dimensions are timelike | 9 pages; the stripped down version | null | null | null | gr-qc | null | A new theory of fundamental physics is presented; it predicts that the new
dimensions that may be observed by the Large Hadron Collider are timelike.
| [
{
"created": "Fri, 13 Oct 2006 03:35:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sparling",
"George A. J.",
""
]
] | A new theory of fundamental physics is presented; it predicts that the new dimensions that may be observed by the Large Hadron Collider are timelike. |
gr-qc/9304028 | null | Gerhard Rein | Static solutions of the spherically symmetric Vlasov-Einstein system | 20 pages, Latex, report # 1 | null | 10.1017/S0305004100072303 | null | gr-qc | null | The Vlasov-Einstein system describes the evolution of an ensemble of
particles (such as stars in a galaxy, galaxies in a galaxy cluster etc.)
interacting only by the gravitational field which they create collectively and
which obeys Einstein's field equations. The matter distribution is described by
the Vlasov or Liouville equation for a collisionless gas. Recent investigations
seem to indicate that such a matter model is particularly suited in a general
relativistic setting and may avoid the formation of naked singularities, as
opposed to other matter models. In the present note we consider the
Vlasov-Einstein system in a spherically symmetric setting and prove the
existence of static solutions which are asymptotically flat and have finite
total mass and finite extension of the matter. Among these there are smooth,
singularity-free solutions, which have a regular center and may have isotropic
or anisotropic pressure, and solutions, which have a Schwarzschild-singularity
at the center. The paper extends previous work, where smooth, globally defined
solutions with regular center and isotropic pressure were considered.
| [
{
"created": "Tue, 20 Apr 1993 10:19:06 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Rein",
"Gerhard",
""
]
] | The Vlasov-Einstein system describes the evolution of an ensemble of particles (such as stars in a galaxy, galaxies in a galaxy cluster etc.) interacting only by the gravitational field which they create collectively and which obeys Einstein's field equations. The matter distribution is described by the Vlasov or Liouville equation for a collisionless gas. Recent investigations seem to indicate that such a matter model is particularly suited in a general relativistic setting and may avoid the formation of naked singularities, as opposed to other matter models. In the present note we consider the Vlasov-Einstein system in a spherically symmetric setting and prove the existence of static solutions which are asymptotically flat and have finite total mass and finite extension of the matter. Among these there are smooth, singularity-free solutions, which have a regular center and may have isotropic or anisotropic pressure, and solutions, which have a Schwarzschild-singularity at the center. The paper extends previous work, where smooth, globally defined solutions with regular center and isotropic pressure were considered. |
2204.13044 | Ningchen Bai | Ningchen Bai, Aoyun He, Jun Tao | Microstructure of Charged AdS Black Hole with Minimal Length Effects | 29 pages, 10 figures | null | 10.1088/1674-1137/ac8e53 | CTP-SCU/2022005 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, the microstructure of charged AdS black holes under minimal
length effects is investigated. We study the thermodynamics of black holes in
the extended phase space, where the cosmological constant is regarded as the
thermodynamic pressure. The modified Hawking temperature and phase transition
are obtained based on the generalized uncertainty principle (GUP). Then, using
thermodynamic geometry, we show that the microstructure of black holes can be
determined by the ratio of GUP parameter to charge. For a small ratio, the
black hole exhibits the typical RN-AdS microstructure with van der Waals phase
transition and repulsive/attractive interactions. As the ratio increases, the
reentrant phase transition takes place, and both the repulsion-attraction
coexisted black hole and the attraction dominated black hole can be found in
this case. For a large ratio, the black hole behaves like a Schwarzchild-AdS
black hole in which neither phase transition nor repulsive interaction exists.
These results suggest that the GUP effect will reduce the repulsive interaction
presented by the charged AdS black hole, which can also be qualitatively
understood from the perspective of black hole molecules.
| [
{
"created": "Wed, 27 Apr 2022 16:36:57 GMT",
"version": "v1"
},
{
"created": "Wed, 11 May 2022 15:51:17 GMT",
"version": "v2"
}
] | 2022-12-14 | [
[
"Bai",
"Ningchen",
""
],
[
"He",
"Aoyun",
""
],
[
"Tao",
"Jun",
""
]
] | In this work, the microstructure of charged AdS black holes under minimal length effects is investigated. We study the thermodynamics of black holes in the extended phase space, where the cosmological constant is regarded as the thermodynamic pressure. The modified Hawking temperature and phase transition are obtained based on the generalized uncertainty principle (GUP). Then, using thermodynamic geometry, we show that the microstructure of black holes can be determined by the ratio of GUP parameter to charge. For a small ratio, the black hole exhibits the typical RN-AdS microstructure with van der Waals phase transition and repulsive/attractive interactions. As the ratio increases, the reentrant phase transition takes place, and both the repulsion-attraction coexisted black hole and the attraction dominated black hole can be found in this case. For a large ratio, the black hole behaves like a Schwarzchild-AdS black hole in which neither phase transition nor repulsive interaction exists. These results suggest that the GUP effect will reduce the repulsive interaction presented by the charged AdS black hole, which can also be qualitatively understood from the perspective of black hole molecules. |
gr-qc/9702032 | Cai Rong-gen | Rong-Gen Cai, Zhi-Jiang Lu and Yuan-Zhong Zhang (ITP, Beijing, China) | Critical behavior in 2+1 dimensional black holes | RevTex, 9 pages, nofigure | Phys.Rev.D55:853-860,1997 | 10.1103/PhysRevD.55.853 | null | gr-qc | null | The critical behavior and phase transition in the 2+1 dimensional Ba\~nados,
Teitelboim, and Zanelli (BTZ) black holes are discussed. By calculating the
equilibrium thermodynamic fluctuations in the microcanonical ensemble,
canonical ensemble, and grand canonical ensemble, respectively, we find that
the extremal spinning BTZ black hole is a critical point, some critical
exponents satisfy the scaling laws of the ``first kind'', and the scaling laws
related to the correlation length suggest that the effective spatial dimension
of extremal black holes is one, which is in agreement with the argument that
the extremal black holes are the Bogomol'nyi saturated string states. In
addition, we find that the massless BTZ black hole is a critical point of
spinless BTZ black holes.
| [
{
"created": "Tue, 18 Feb 1997 09:49:48 GMT",
"version": "v1"
}
] | 2019-08-17 | [
[
"Cai",
"Rong-Gen",
"",
"ITP, Beijing, China"
],
[
"Lu",
"Zhi-Jiang",
"",
"ITP, Beijing, China"
],
[
"Zhang",
"Yuan-Zhong",
"",
"ITP, Beijing, China"
]
] | The critical behavior and phase transition in the 2+1 dimensional Ba\~nados, Teitelboim, and Zanelli (BTZ) black holes are discussed. By calculating the equilibrium thermodynamic fluctuations in the microcanonical ensemble, canonical ensemble, and grand canonical ensemble, respectively, we find that the extremal spinning BTZ black hole is a critical point, some critical exponents satisfy the scaling laws of the ``first kind'', and the scaling laws related to the correlation length suggest that the effective spatial dimension of extremal black holes is one, which is in agreement with the argument that the extremal black holes are the Bogomol'nyi saturated string states. In addition, we find that the massless BTZ black hole is a critical point of spinless BTZ black holes. |
gr-qc/9302034 | null | M.C. Bento, O. Bertolami, P.V. Moniz, J.M. Mourao and P.M. S\'a | On the Cosmology of Massive Vector Fields with SO(3) Global Symmetry | 19 pages, plain tex, DF/IST-3/92 and DFFCUL 03-5/1992 | Class.Quant.Grav.10:285-298,1993 | 10.1088/0264-9381/10/2/010 | null | gr-qc | null | A relevant reference ([14]) has been added.
| [
{
"created": "Tue, 23 Feb 1993 19:48:44 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Mar 1993 11:22:17 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Bento",
"M. C.",
""
],
[
"Bertolami",
"O.",
""
],
[
"Moniz",
"P. V.",
""
],
[
"Mourao",
"J. M.",
""
],
[
"Sá",
"P. M.",
""
]
] | A relevant reference ([14]) has been added. |
2007.11567 | Richard Woodard | A. Sivasankaran and R. P. Woodard | Inflaton Effective Potential from Fermions for General $\epsilon$ | 25 pages, 9 figures, uses LaTeX2e. Version 2 (32 pages, 11 figures)
substantially revised to provide a detailed comparison between the effective
potential and the classical potential, and to explain the tendency for smooth
potentials to favor high reheat temperatures | Phys. Rev. D 103, 125013 (2021) | 10.1103/PhysRevD.103.125013 | UFIFT-QG-20-04 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We accurately approximate the contribution of a Yukawa-coupled fermion to the
inflaton effective potential for inflationary geometries with a general first
slow roll parameter $\epsilon(t)$. For $\epsilon = 0$ our final result agrees
with the famous computation of Candelas and Raine done long ago on de Sitter
background, and both computations degenerate to the result of Coleman and
Weinberg in the flat space limit. Our result contains a small part that depends
nonlocally on the inflationary geometry. Even in the numerically larger local
part, very little of the $\epsilon$ dependence takes the form of Ricci scalars.
We discuss the implications of these corrections for inflation.
| [
{
"created": "Wed, 22 Jul 2020 17:44:48 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Jun 2021 17:09:00 GMT",
"version": "v2"
}
] | 2021-06-30 | [
[
"Sivasankaran",
"A.",
""
],
[
"Woodard",
"R. P.",
""
]
] | We accurately approximate the contribution of a Yukawa-coupled fermion to the inflaton effective potential for inflationary geometries with a general first slow roll parameter $\epsilon(t)$. For $\epsilon = 0$ our final result agrees with the famous computation of Candelas and Raine done long ago on de Sitter background, and both computations degenerate to the result of Coleman and Weinberg in the flat space limit. Our result contains a small part that depends nonlocally on the inflationary geometry. Even in the numerically larger local part, very little of the $\epsilon$ dependence takes the form of Ricci scalars. We discuss the implications of these corrections for inflation. |
1606.06242 | Julio Cesar Fabris | K.A. Bronnikov, J.C. Fabris, O.F. Piattella, E.C. Santos | Static, spherically symmetric solutions with a scalar field in Rastall
gravity | Latex file, 18 pages. To fit published version | Gen.Rel.Grav. 48 (2016) no.12, 162 | 10.1007/s10714-016-2152-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Rastall's theory belongs to the class of non-conservative theories of
gravity. In vacuum, the only non-trivial static, spherically symmetric solution
is the Schwarzschild one, except in a very special case. When a canonical
scalar field is coupled to the gravity sector in this theory, new exact
solutions appear for some values of the Rastall parameter $a$. Some of these
solutions describe the same space-time geometry as the recently found solutions
in the $k$-essence theory with a power function for the kinetic term of the
scalar field. There is a large class of solutions (in particular, those
describing wormholes and regular black holes) whose geometry coincides with
that of solutions of GR coupled to scalar fields with nontrivial
self-interaction potentials; the form of these potentials, however, depends on
the Rastall parameter $a$. We also note that all solutions of GR with a zero
trace of the energy-momentum tensor, including black-hole and wormhole ones,
may be re-interpreted as solutions of Rastall's theory.
| [
{
"created": "Mon, 20 Jun 2016 18:50:48 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Mar 2017 19:25:28 GMT",
"version": "v2"
}
] | 2017-03-03 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Piattella",
"O. F.",
""
],
[
"Santos",
"E. C.",
""
]
] | Rastall's theory belongs to the class of non-conservative theories of gravity. In vacuum, the only non-trivial static, spherically symmetric solution is the Schwarzschild one, except in a very special case. When a canonical scalar field is coupled to the gravity sector in this theory, new exact solutions appear for some values of the Rastall parameter $a$. Some of these solutions describe the same space-time geometry as the recently found solutions in the $k$-essence theory with a power function for the kinetic term of the scalar field. There is a large class of solutions (in particular, those describing wormholes and regular black holes) whose geometry coincides with that of solutions of GR coupled to scalar fields with nontrivial self-interaction potentials; the form of these potentials, however, depends on the Rastall parameter $a$. We also note that all solutions of GR with a zero trace of the energy-momentum tensor, including black-hole and wormhole ones, may be re-interpreted as solutions of Rastall's theory. |
gr-qc/9708021 | Dmitry Kalinin | D. A. Kalinin (Kazan State University) | Large Quantum mechanics in curved space and quantization of polynomial
Hamiltonians | 15 pages, LaTeX | null | null | KSU-GRG-97-12 | gr-qc | null | The quantization of a single particle without spin in an appropriate curved
space-time is considered. The Hamilton formalism on reduced space for a
particle in a curved space-time is constructed and the main aspects of
quantization scheme are developed. These investigations are applied to
quantization of the particle Hamiltonian in an appropriate curved space-time.
As an example the energy eigenvalues in Einstein universe are calculated. In
the last sections o the paper approximation for small values of momenta of the
results previously obtained is considered as well as quantization of polynomial
Hamiltonians of general type is discussed.
| [
{
"created": "Mon, 11 Aug 1997 11:09:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kalinin",
"D. A.",
"",
"Kazan State University"
]
] | The quantization of a single particle without spin in an appropriate curved space-time is considered. The Hamilton formalism on reduced space for a particle in a curved space-time is constructed and the main aspects of quantization scheme are developed. These investigations are applied to quantization of the particle Hamiltonian in an appropriate curved space-time. As an example the energy eigenvalues in Einstein universe are calculated. In the last sections o the paper approximation for small values of momenta of the results previously obtained is considered as well as quantization of polynomial Hamiltonians of general type is discussed. |
2212.03573 | Jaiyul Yoo | Jaiyul Yoo (Z\"urich) | Incompatibility of Standard Galaxy Bias Models in General Relativity | 16 pages, 1 figure, published in JCAP | JCAP 10 (2023) 054 | 10.1088/1475-7516/2023/10/054 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | The standard model for galaxy bias is built in a Newtonian framework, and
several attempts have been made in the past to put it in a relativistic
framework. The focus of past works was, however, to use the same Newtonian
formulation, but to provide its interpretation in a relativistic framework by
either fixing a gauge condition or transforming to a local coordinate system.
Here we demonstrate that these reverse-engineered approaches do not respect the
diffeomorphism symmetry in general relativity, and we need to develop a
covariant model of galaxy bias that is diffeomorphism compatible. We consider a
simple toy model for galaxy bias and discuss the impact for measuring the
primordial non-Gaussianity.
| [
{
"created": "Wed, 7 Dec 2022 11:19:32 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Apr 2023 10:52:38 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Oct 2023 18:05:38 GMT",
"version": "v3"
}
] | 2023-10-23 | [
[
"Yoo",
"Jaiyul",
"",
"Zürich"
]
] | The standard model for galaxy bias is built in a Newtonian framework, and several attempts have been made in the past to put it in a relativistic framework. The focus of past works was, however, to use the same Newtonian formulation, but to provide its interpretation in a relativistic framework by either fixing a gauge condition or transforming to a local coordinate system. Here we demonstrate that these reverse-engineered approaches do not respect the diffeomorphism symmetry in general relativity, and we need to develop a covariant model of galaxy bias that is diffeomorphism compatible. We consider a simple toy model for galaxy bias and discuss the impact for measuring the primordial non-Gaussianity. |
1503.00354 | Atsushi Nishizawa | Atsushi Nishizawa and Naoki Seto | Search for an emission line of a gravitational wave background | 5 pages, 3 figures | Phys. Rev. D 91, 122001 (2015) | 10.1103/PhysRevD.91.122001 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the light of the history of researches on electromagnetic wave spectrum, a
sharp emission line of gravitational-wave background (GWB) would be an
interesting observational target. Here we study an efficient method to detect a
line GWB by correlating data of multiple ground-based detectors. We find that
the width of frequency bin for coarse graining is a critical parameter, and the
commonly-used value 0.25 Hz is far from optimal, decreasing the signal-to-noise
ratio by up to a factor of seven. By reanalyzing the existing data with a
smaller bin width, we might detect a precious line signal from the early
universe.
| [
{
"created": "Sun, 1 Mar 2015 21:14:46 GMT",
"version": "v1"
}
] | 2015-06-10 | [
[
"Nishizawa",
"Atsushi",
""
],
[
"Seto",
"Naoki",
""
]
] | In the light of the history of researches on electromagnetic wave spectrum, a sharp emission line of gravitational-wave background (GWB) would be an interesting observational target. Here we study an efficient method to detect a line GWB by correlating data of multiple ground-based detectors. We find that the width of frequency bin for coarse graining is a critical parameter, and the commonly-used value 0.25 Hz is far from optimal, decreasing the signal-to-noise ratio by up to a factor of seven. By reanalyzing the existing data with a smaller bin width, we might detect a precious line signal from the early universe. |
2307.06778 | Diego Rubiera-Garcia | Lu\'is F. Dias da Silva, Francisco S. N. Lobo, Gonzalo J. Olmo, Diego
Rubiera-Garcia | Photon rings as tests for alternative spherically symmetric geometries
with thin accretion disks | 17 pages, 58 figures/images; v2: many comments and additions, version
accepted for publication in Physical Review D | Phys. Rev. D 108, 084055 (2023) | 10.1103/PhysRevD.108.084055 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The imaging by the Event Horizon Telescope (EHT) of the supermassive central
objects at the heart of the M87 and Milky Way (Sgr A$^\star$) galaxies, has
marked the first step into peering at the photon rings and central brightness
depression that characterize the optical appearance of black holes surrounded
by an accretion disk. Recently, Vagnozzi et. al. [S.~Vagnozzi, \textit{et al.}
arXiv:2205.07787 [gr-qc]] used the claim by the EHT that the size of the {\it
shadow} of Sgr A$^\star$ can be inferred by calibrated measurements of the
bright ring enclosing it, to constrain a large number of spherically symmetric
space-time geometries. In this work we use this result to study some features
of the first and second photon rings of a restricted pool of such geometries in
thin accretion disk settings. The emission profile of the latter is described
by calling upon three analytic samples belonging to the family introduced by
Gralla, Lupsasca and Marrone, in order to characterize such photon rings using
the Lyapunov exponent of nearly bound orbits and discuss its correlation with
the luminosity extinction rate between the first and second photon rings. We
finally elaborate on the chances of using such photon rings as observational
discriminators of alternative black hole geometries using very long baseline
interferometry.
| [
{
"created": "Thu, 13 Jul 2023 14:36:29 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Oct 2023 10:30:23 GMT",
"version": "v2"
}
] | 2023-11-17 | [
[
"da Silva",
"Luís F. Dias",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"Diego",
""
]
] | The imaging by the Event Horizon Telescope (EHT) of the supermassive central objects at the heart of the M87 and Milky Way (Sgr A$^\star$) galaxies, has marked the first step into peering at the photon rings and central brightness depression that characterize the optical appearance of black holes surrounded by an accretion disk. Recently, Vagnozzi et. al. [S.~Vagnozzi, \textit{et al.} arXiv:2205.07787 [gr-qc]] used the claim by the EHT that the size of the {\it shadow} of Sgr A$^\star$ can be inferred by calibrated measurements of the bright ring enclosing it, to constrain a large number of spherically symmetric space-time geometries. In this work we use this result to study some features of the first and second photon rings of a restricted pool of such geometries in thin accretion disk settings. The emission profile of the latter is described by calling upon three analytic samples belonging to the family introduced by Gralla, Lupsasca and Marrone, in order to characterize such photon rings using the Lyapunov exponent of nearly bound orbits and discuss its correlation with the luminosity extinction rate between the first and second photon rings. We finally elaborate on the chances of using such photon rings as observational discriminators of alternative black hole geometries using very long baseline interferometry. |
gr-qc/9901027 | Dong Hyun Park | Dong Hyun Park and Seung-ho Yang | Geodesic Motions in 2+1 Dimensional Charged Black Holes | 13pages | Gen.Rel.Grav. 31 (1999) 1343-1353 | 10.1023/A:1026733026282 | null | gr-qc | null | We study the geodesic motions of a test particle around 2+1 dimensional
charged black holes. We obtain a class of exact geodesic motions for the
massless test particle when the ratio of its energy and angular momentum is
given by square root of cosmological constant. The other geodesic motions for
both massless and massive test particles are analyzed by use of numerical
method.
| [
{
"created": "Sun, 10 Jan 1999 03:21:04 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Park",
"Dong Hyun",
""
],
[
"Yang",
"Seung-ho",
""
]
] | We study the geodesic motions of a test particle around 2+1 dimensional charged black holes. We obtain a class of exact geodesic motions for the massless test particle when the ratio of its energy and angular momentum is given by square root of cosmological constant. The other geodesic motions for both massless and massive test particles are analyzed by use of numerical method. |
2404.09274 | Morgan Lynch | Morgan H. Lynch | Analysis of the CERN-NA63 radiation reaction data set, assuming the
Rindler bath is composed of microscopic black holes | 8 pages, 9 figures. Accepted for publication at Phys. Rev. D.
Original title changed by editor | null | 10.1103/PhysRevD.109.105009 | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In this manuscript we examine the Unruh-thermalized CERN-NA63 radiation
reaction data set from the point of view of a diphoton Rindler bath. Under the
assumption that these Hawking-Unruh diphoton pairs are microscopic
trans-Planckian black holes, we find the resultant heat capacity describes the
measured energy spectrum and is thus a dual description of the data set. Then,
employing an n-dimensional Stefan-Boltzmann analysis, we find the power
radiated by a black hole in the standard 3+1 spacetime dimensions in complete
agreement with the data. Finally, we utilize this power spectrum to directly
measure Newtons constant of gravitation.
| [
{
"created": "Sun, 14 Apr 2024 14:32:55 GMT",
"version": "v1"
},
{
"created": "Tue, 7 May 2024 11:13:41 GMT",
"version": "v2"
}
] | 2024-05-08 | [
[
"Lynch",
"Morgan H.",
""
]
] | In this manuscript we examine the Unruh-thermalized CERN-NA63 radiation reaction data set from the point of view of a diphoton Rindler bath. Under the assumption that these Hawking-Unruh diphoton pairs are microscopic trans-Planckian black holes, we find the resultant heat capacity describes the measured energy spectrum and is thus a dual description of the data set. Then, employing an n-dimensional Stefan-Boltzmann analysis, we find the power radiated by a black hole in the standard 3+1 spacetime dimensions in complete agreement with the data. Finally, we utilize this power spectrum to directly measure Newtons constant of gravitation. |
2012.01840 | Daniil Krichevskiy | S. Alexeyev and D.Krichevskiy | Inflationary solutions in the simplest gravity model with conformal
symmetry | null | Physics of Particles and Nuclei Letters, Vol 18, No 2 (2021) | 10.1134/S1547477121020035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a model of gravity with conformal symmetry appearing in the
simplest extension of General Relativity with the Poincar\'e algebra terms. The
nonlinear realization of symmetry causes the existence of five scalar fields.
Therefore it looks desirable to use them for driving the inflation at the
earliest stages of the Universe evolution. It is shown that the evolution of
the scale factor doesn't imply accelerated expansion so that there are no
inflationary solutions in this model. To drive inflation a more complicated
model induced by extension of the Poincare algebra is required.
| [
{
"created": "Thu, 3 Dec 2020 11:21:10 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Nov 2021 19:14:23 GMT",
"version": "v2"
}
] | 2021-11-18 | [
[
"Alexeyev",
"S.",
""
],
[
"Krichevskiy",
"D.",
""
]
] | We discuss a model of gravity with conformal symmetry appearing in the simplest extension of General Relativity with the Poincar\'e algebra terms. The nonlinear realization of symmetry causes the existence of five scalar fields. Therefore it looks desirable to use them for driving the inflation at the earliest stages of the Universe evolution. It is shown that the evolution of the scale factor doesn't imply accelerated expansion so that there are no inflationary solutions in this model. To drive inflation a more complicated model induced by extension of the Poincare algebra is required. |
1007.1517 | Sun ChengYi | Cheng-Yi Sun | Weak Gravity Conjecture and Holographic Dark Energy Model with
Interaction and Spatial Curvature | 14 pages, 7 figures, typographical errors are corrected; conclusin is
unchanged | null | 10.1088/0253-6102/56/1/33 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the paper, we apply the weak gravity conjecture to the holographic
quintessence model of dark energy. Three different holographic dark energy
models are considered: without the interaction in the non-flat universe; with
interaction in the flat universe; with interaction in the non-flat universe. We
find that only in the models with the spatial curvature and interaction term
proportional to the energy density of matter, it is possible for the weak
gravity conjecture to be satisfied.
| [
{
"created": "Fri, 9 Jul 2010 07:24:48 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Sep 2010 13:42:58 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Dec 2010 08:26:54 GMT",
"version": "v3"
}
] | 2015-05-19 | [
[
"Sun",
"Cheng-Yi",
""
]
] | In the paper, we apply the weak gravity conjecture to the holographic quintessence model of dark energy. Three different holographic dark energy models are considered: without the interaction in the non-flat universe; with interaction in the flat universe; with interaction in the non-flat universe. We find that only in the models with the spatial curvature and interaction term proportional to the energy density of matter, it is possible for the weak gravity conjecture to be satisfied. |
2001.10277 | Dennis Hansen | Dennis Hansen, Jelle Hartong and Niels A. Obers | Non-Relativistic Gravity and its Coupling to Matter | 101 pages (78 main text), Nordita preprint number 2020-008 | null | 10.1007/JHEP06(2020)145 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the non-relativistic expansion of general relativity coupled to
matter. This is done by expanding the metric and matter fields analytically in
powers of $1/c^2$ where $c$ is the speed of light. In order to perform this
expansion it is shown to be very convenient to rewrite general relativity in
terms of a timelike vielbein and a spatial metric. This expansion can be
performed covariantly and off shell. We study the expansion of the
Einstein-Hilbert action up to next-to-next-to-leading order. We couple this to
different forms of matter: point particles, perfect fluids, scalar fields
(including an off-shell derivation of the Schr\"odinger-Newton equation) and
electrodynamics (both its electric and magnetic limits). We find that the role
of matter is crucial in order to understand the properties of the Newton-Cartan
geometry that emerges from the expansion of the metric. It turns out to be the
matter that decides what type of clock form is allowed, i.e. whether we have
absolute time or a global foliation of constant time hypersurfaces. We end by
studying a variety of solutions of non-relativistic gravity coupled to perfect
fluids. This includes the Schwarzschild geometry, the
Tolman-Oppenheimer-Volkoff solution for a fluid star, the FLRW cosmological
solutions and anti-de Sitter spacetimes.
| [
{
"created": "Tue, 28 Jan 2020 11:47:30 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Apr 2020 16:10:19 GMT",
"version": "v2"
}
] | 2020-07-15 | [
[
"Hansen",
"Dennis",
""
],
[
"Hartong",
"Jelle",
""
],
[
"Obers",
"Niels A.",
""
]
] | We study the non-relativistic expansion of general relativity coupled to matter. This is done by expanding the metric and matter fields analytically in powers of $1/c^2$ where $c$ is the speed of light. In order to perform this expansion it is shown to be very convenient to rewrite general relativity in terms of a timelike vielbein and a spatial metric. This expansion can be performed covariantly and off shell. We study the expansion of the Einstein-Hilbert action up to next-to-next-to-leading order. We couple this to different forms of matter: point particles, perfect fluids, scalar fields (including an off-shell derivation of the Schr\"odinger-Newton equation) and electrodynamics (both its electric and magnetic limits). We find that the role of matter is crucial in order to understand the properties of the Newton-Cartan geometry that emerges from the expansion of the metric. It turns out to be the matter that decides what type of clock form is allowed, i.e. whether we have absolute time or a global foliation of constant time hypersurfaces. We end by studying a variety of solutions of non-relativistic gravity coupled to perfect fluids. This includes the Schwarzschild geometry, the Tolman-Oppenheimer-Volkoff solution for a fluid star, the FLRW cosmological solutions and anti-de Sitter spacetimes. |
2007.15119 | Valerio Bozza | Valerio Bozza, Silvia Pietroni and Chiara Melchiorre | Caustics in gravitational lensing by mixed binary systems | 25 pages, 18 figures, in press on Universe, special issue
Gravitational Lensing and Optical Geometry: A Centennial Perspective | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate binary lenses with $1/r^n$ potentials in the asymmetric case
with two lenses with different indexes $n$ and $m$. These kinds of potentials
have been widely used in several contexts, ranging from galaxies with halos
described by different power laws to lensing by wormholes or exotic matter. In
this paper, we present a complete atlas of critical curves and caustics for
mixed binaries, starting from the equal-strength case, and then exploring
unequal-strength systems. We also calculate the transitions between all
different topology regimes. Finally we find some useful analytic approximations
for the wide binary case and for the extreme unequal-strength case.
| [
{
"created": "Wed, 29 Jul 2020 21:26:47 GMT",
"version": "v1"
}
] | 2020-07-31 | [
[
"Bozza",
"Valerio",
""
],
[
"Pietroni",
"Silvia",
""
],
[
"Melchiorre",
"Chiara",
""
]
] | We investigate binary lenses with $1/r^n$ potentials in the asymmetric case with two lenses with different indexes $n$ and $m$. These kinds of potentials have been widely used in several contexts, ranging from galaxies with halos described by different power laws to lensing by wormholes or exotic matter. In this paper, we present a complete atlas of critical curves and caustics for mixed binaries, starting from the equal-strength case, and then exploring unequal-strength systems. We also calculate the transitions between all different topology regimes. Finally we find some useful analytic approximations for the wide binary case and for the extreme unequal-strength case. |
2306.12201 | Surojit Dalui | Deeshani Mitra, Surojit Dalui, Subir Ghosh and Arpan Krishna Mitra | Acoustic Kerr Metric in Analogue Gravity | 7 pages, no figure | null | null | null | gr-qc hep-th physics.flu-dyn quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper is based on a previous work (involving two of the present
authors) where a generalized fluid dynamical model was proposed. The underlying
symplectic structure of the Lagrangian discrete degrees of freedom obeyed a
Non-Commutative algebra, generated by Berry curvature correction. In an Euler
(or Hamiltonian) framework, this is manifested as an extended algebra between
the fluid variables, leading to the extended fluid model. Here we study the
dynamics of sonic fluctuations that live in this effective analogue gravity
spacetime. Interestingly enough, the effective metric resembles that of a
spinning Black Hole; the spin is induced by the underlying Non-Commutative
structure. The effective mass and spin parameters of the Black Hole, in terms
of fluid parameters, are also identified. The connection of our model with
anomalous Hall systems may lead to observable signatures of the analogue black
hole in physical systems.
| [
{
"created": "Wed, 21 Jun 2023 11:51:20 GMT",
"version": "v1"
}
] | 2023-06-23 | [
[
"Mitra",
"Deeshani",
""
],
[
"Dalui",
"Surojit",
""
],
[
"Ghosh",
"Subir",
""
],
[
"Mitra",
"Arpan Krishna",
""
]
] | The present paper is based on a previous work (involving two of the present authors) where a generalized fluid dynamical model was proposed. The underlying symplectic structure of the Lagrangian discrete degrees of freedom obeyed a Non-Commutative algebra, generated by Berry curvature correction. In an Euler (or Hamiltonian) framework, this is manifested as an extended algebra between the fluid variables, leading to the extended fluid model. Here we study the dynamics of sonic fluctuations that live in this effective analogue gravity spacetime. Interestingly enough, the effective metric resembles that of a spinning Black Hole; the spin is induced by the underlying Non-Commutative structure. The effective mass and spin parameters of the Black Hole, in terms of fluid parameters, are also identified. The connection of our model with anomalous Hall systems may lead to observable signatures of the analogue black hole in physical systems. |
2304.05031 | Ganesh Subramaniam | Ganesh Subramaniam, Avik De, Tee-How Loo, Yong Kheng Goh | Energy condition bounds on $f(Q)$ model parameters in a curved FLRW
universe | Accepted for publication in Physics of the Dark Universe | Physics of the Dark Universe Volume 41, August 2023, 101243 | 10.1016/j.dark.2023.101243 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this exclusive study of the modified $f(Q)$ theory of gravity in the open
and closed type Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe model, we
impose some constraints from the classical energy conditions. The viable range
of parameter $\beta$ for two different $f(Q)$ models, $f(Q)=Q+\beta Q^2$ and
$f(Q)=Q+\beta\sqrt{-Q}$, are analyzed in details and the related cosmological
implications are discussed. Violation of effective strong energy condition is
resulting into late-time acceleration of the Universe. Present observational
values of Hubble parameter and deceleration parameter are used to constrain the
parameters.
| [
{
"created": "Tue, 11 Apr 2023 07:39:05 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Apr 2023 13:32:34 GMT",
"version": "v2"
}
] | 2023-06-07 | [
[
"Subramaniam",
"Ganesh",
""
],
[
"De",
"Avik",
""
],
[
"Loo",
"Tee-How",
""
],
[
"Goh",
"Yong Kheng",
""
]
] | In this exclusive study of the modified $f(Q)$ theory of gravity in the open and closed type Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe model, we impose some constraints from the classical energy conditions. The viable range of parameter $\beta$ for two different $f(Q)$ models, $f(Q)=Q+\beta Q^2$ and $f(Q)=Q+\beta\sqrt{-Q}$, are analyzed in details and the related cosmological implications are discussed. Violation of effective strong energy condition is resulting into late-time acceleration of the Universe. Present observational values of Hubble parameter and deceleration parameter are used to constrain the parameters. |
gr-qc/0404045 | Belinch\'on Jos\'e Antonio | Jos\'e Antonio Belinch\'on and Indrajit Chakrabarty | Full Causal Bulk Viscous Cosmologies with time-varying Constants | 28 pages, RevTeX4 | Int.J.Mod.Phys.D12:861-883,2003 | 10.1142/S0218271803003402 | null | gr-qc | null | We study the evolution of a flat Friedmann-Robertson-Walker Universe, filled
with a bulk viscous cosmological fluid, in the presence of time varying
``constants''. The dimensional analysis of the model suggests a proportionality
between the bulk viscous pressure of the dissipative fluid and the energy
density. On using this assumption and with the choice of the standard equations
of state for the bulk viscosity coefficient, temperature and relaxation time,
the general solution of the field equations can be obtained, with all physical
parameters having a power-law time dependence. The symmetry analysis of this
model, performed by using Lie group techniques, confirms the unicity of the
solution for this functional form of the bulk viscous pressure. In order to
find another possible solution we relax the hypotheses assuming a concrete
functional dependence for the ``constants''.
| [
{
"created": "Fri, 9 Apr 2004 16:59:00 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Belinchón",
"José Antonio",
""
],
[
"Chakrabarty",
"Indrajit",
""
]
] | We study the evolution of a flat Friedmann-Robertson-Walker Universe, filled with a bulk viscous cosmological fluid, in the presence of time varying ``constants''. The dimensional analysis of the model suggests a proportionality between the bulk viscous pressure of the dissipative fluid and the energy density. On using this assumption and with the choice of the standard equations of state for the bulk viscosity coefficient, temperature and relaxation time, the general solution of the field equations can be obtained, with all physical parameters having a power-law time dependence. The symmetry analysis of this model, performed by using Lie group techniques, confirms the unicity of the solution for this functional form of the bulk viscous pressure. In order to find another possible solution we relax the hypotheses assuming a concrete functional dependence for the ``constants''. |
1003.1159 | David Kaiser | David I. Kaiser | Conformal Transformations with Multiple Scalar Fields | 17 pages, no figures. References added to match published version. | Phys.Rev.D81:084044,2010 | 10.1103/PhysRevD.81.084044 | MIT-CTP 4125 | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many interesting models incorporate scalar fields with non-minimal couplings
to the spacetime Ricci curvature scalar. As is well known, if only one scalar
field is non-minimally coupled, then one may perform a conformal transformation
to a new frame in which both the gravitational portion of the Lagrangian and
the kinetic term for the (rescaled) scalar field assume canonical form. We
examine under what conditions the gravitational and kinetic terms in the
Lagrangian may be brought into canonical form when more than one scalar field
has non-minimal coupling. A particular class of two-field models admits such a
transformation, but models with more than two non-minimally coupled fields in
general do not.
| [
{
"created": "Thu, 4 Mar 2010 22:56:05 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Apr 2010 02:26:52 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Kaiser",
"David I.",
""
]
] | Many interesting models incorporate scalar fields with non-minimal couplings to the spacetime Ricci curvature scalar. As is well known, if only one scalar field is non-minimally coupled, then one may perform a conformal transformation to a new frame in which both the gravitational portion of the Lagrangian and the kinetic term for the (rescaled) scalar field assume canonical form. We examine under what conditions the gravitational and kinetic terms in the Lagrangian may be brought into canonical form when more than one scalar field has non-minimal coupling. A particular class of two-field models admits such a transformation, but models with more than two non-minimally coupled fields in general do not. |
2303.14513 | Soumya Jana | Soumya Jana, Sayan Kar | Shadows in dyonic Kerr-Sen black holes | 28 pages, 9 figures, published version | Phys. Rev. D 108, 044008 (2023) | 10.1103/PhysRevD.108.044008 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Black holes with dyonic charges in Einstein-Maxwell-dilaton-axion
supergravity theory are revisited in the context of black hole shadows. We
consider static as well as rotating (namely the dyonic Kerr-Sen) black holes.
The matter stress-energy tensor components, sourced by the Maxwell, axion and
dilaton fields satisfy the standard energy conditions. The analytical
expressions for the horizon and the shadow radius of the static spacetimes
demonstrate their dependence on $P^2+Q^2$ ($P$, $Q$ the magnetic and electric
charges, respectively) and the mass parameter $M$. The shadow radius lies in
the range $2M <R_{shadow}<3\sqrt{3} M$ and there is no stable photon orbit
outside the horizon. Further, shadows cast by the rotating dyonic Kerr-Sen
black holes are also studied and compared graphically with their Kerr-Newman
and Kerr-Sen counterparts. Deviation of the shadow boundary is prominent with
the variation of the magnetic charge, for the relatively slowly rotating dyonic
Kerr-Sen spacetimes. We test any possible presence of a magnetic monopole
charge in the backdrop of recent EHT observations for the supermassive black
holes M87$^*$ and Sgr A$^*$. Deviation from circularity of the shadow boundary
($\Delta C$) and deviation of the average shadow radius from the Schwarzschild
shadow radius (quantified as the fractional deviation parameter $\delta$) are
the two observables used here. Observational bound on $\Delta C$ (available
only for M87$^*$) is satisfied for all theoretically allowed regions of
parameter space and thus cannot constrain the parameters. The observational
bound on $\delta$ available for Sgr A$^*$ translates into an upper limit on any
possible magnetic monopole charge linked to Sgr A$^*$ and is given as
$P\lesssim 0.873\, M$. Such a constraint on $P$ is however expected to be far
more stringent for other astrophysical tests.
| [
{
"created": "Sat, 25 Mar 2023 16:38:08 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Apr 2023 15:49:57 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Aug 2023 16:31:44 GMT",
"version": "v3"
}
] | 2023-08-08 | [
[
"Jana",
"Soumya",
""
],
[
"Kar",
"Sayan",
""
]
] | Black holes with dyonic charges in Einstein-Maxwell-dilaton-axion supergravity theory are revisited in the context of black hole shadows. We consider static as well as rotating (namely the dyonic Kerr-Sen) black holes. The matter stress-energy tensor components, sourced by the Maxwell, axion and dilaton fields satisfy the standard energy conditions. The analytical expressions for the horizon and the shadow radius of the static spacetimes demonstrate their dependence on $P^2+Q^2$ ($P$, $Q$ the magnetic and electric charges, respectively) and the mass parameter $M$. The shadow radius lies in the range $2M <R_{shadow}<3\sqrt{3} M$ and there is no stable photon orbit outside the horizon. Further, shadows cast by the rotating dyonic Kerr-Sen black holes are also studied and compared graphically with their Kerr-Newman and Kerr-Sen counterparts. Deviation of the shadow boundary is prominent with the variation of the magnetic charge, for the relatively slowly rotating dyonic Kerr-Sen spacetimes. We test any possible presence of a magnetic monopole charge in the backdrop of recent EHT observations for the supermassive black holes M87$^*$ and Sgr A$^*$. Deviation from circularity of the shadow boundary ($\Delta C$) and deviation of the average shadow radius from the Schwarzschild shadow radius (quantified as the fractional deviation parameter $\delta$) are the two observables used here. Observational bound on $\Delta C$ (available only for M87$^*$) is satisfied for all theoretically allowed regions of parameter space and thus cannot constrain the parameters. The observational bound on $\delta$ available for Sgr A$^*$ translates into an upper limit on any possible magnetic monopole charge linked to Sgr A$^*$ and is given as $P\lesssim 0.873\, M$. Such a constraint on $P$ is however expected to be far more stringent for other astrophysical tests. |
gr-qc/0505081 | Carlo Rovelli | Alejandro Perez, Carlo Rovelli | Physical effects of the Immirzi parameter | 3 pages. Substantial revision from the first version | Phys.Rev. D73 (2006) 044013 | 10.1103/PhysRevD.73.044013 | null | gr-qc astro-ph hep-ph hep-th | null | The Immirzi parameter is a constant appearing in the general relativity
action used as a starting point for the loop quantization of gravity. The
parameter is commonly believed not to show up in the equations of motion,
because it appears in front of a term in the action that vanishes on shell. We
show that in the presence of fermions, instead, the Immirzi term in the action
does not vanish on shell, and the Immirzi parameter does appear in the
equations of motion. It determines the coupling constant of a four-fermion
interaction. Therefore the Immirzi parameter leads to effects that are
observable in principle, even independently from nonperturbative quantum
gravity.
| [
{
"created": "Tue, 17 May 2005 18:25:00 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Aug 2005 14:22:23 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Perez",
"Alejandro",
""
],
[
"Rovelli",
"Carlo",
""
]
] | The Immirzi parameter is a constant appearing in the general relativity action used as a starting point for the loop quantization of gravity. The parameter is commonly believed not to show up in the equations of motion, because it appears in front of a term in the action that vanishes on shell. We show that in the presence of fermions, instead, the Immirzi term in the action does not vanish on shell, and the Immirzi parameter does appear in the equations of motion. It determines the coupling constant of a four-fermion interaction. Therefore the Immirzi parameter leads to effects that are observable in principle, even independently from nonperturbative quantum gravity. |
1901.10959 | Sandeep Aashish | Sandeep Aashish, Abhilash Padhy, Sukanta Panda | Avoiding instabilities in antisymmetric tensor field driven inflation | 14 pages; Sec. III rewritten, with new and improved calculations for
gradient stability analysis; matches published version | Eur. Phys. J. C (2019) 79: 784 | 10.1140/epjc/s10052-019-7308-0 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Models of inflation with antisymmetric tensor studied in the past are plagued
with ghost instability even in an unperturbed FRW background. We show that it
is possible to avoid ghosts in an unperturbed FRW background by considering the
most general kinetic term for antisymmetric tensor field. The kinetic part
acquires a new gauge symmetry violating term whose effect on perturbed modes is
to prevent the appearance of nondynamical modes, and thus avoid ghosts. For
completeness, we perform a check for gradient instability and derive the
conditions for perturbations to be free of gradient instability.
| [
{
"created": "Wed, 30 Jan 2019 17:19:05 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Sep 2019 06:34:54 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Sep 2019 09:12:07 GMT",
"version": "v3"
}
] | 2019-09-25 | [
[
"Aashish",
"Sandeep",
""
],
[
"Padhy",
"Abhilash",
""
],
[
"Panda",
"Sukanta",
""
]
] | Models of inflation with antisymmetric tensor studied in the past are plagued with ghost instability even in an unperturbed FRW background. We show that it is possible to avoid ghosts in an unperturbed FRW background by considering the most general kinetic term for antisymmetric tensor field. The kinetic part acquires a new gauge symmetry violating term whose effect on perturbed modes is to prevent the appearance of nondynamical modes, and thus avoid ghosts. For completeness, we perform a check for gradient instability and derive the conditions for perturbations to be free of gradient instability. |
1308.5927 | Yury Eroshenko | V.I. Dokuchaev, Yu.N. Eroshenko | Stationary Solutions of the Dirac Equation in the Gravitational Field of
a Charged Black Hole | 6 pages, 1 figure | Journal of Experimental and Theoretical Physics 117, 72 (2013) | 10.1134/S1063776113080049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A stationary solution of the Dirac equation in the metric of a
Reissner-Nordstrom black hole has been found. Only one stationary regular state
outside the black hole event horizon and only one stationary regular state
below the Cauchy horizon are shown to exist. The normalization integral of the
wave functions diverges on both horizons if the black hole is non-extremal.
This means that the solution found can be only the asymptotic limit of a
nonstationary solution. In contrast, in the case of an extremal black hole, the
normalization integral is finite and the stationary regular solution is
physically self-consistent. The existence of quantum levels below the Cauchy
horizon can affect the final stage of Hawking black hole evaporation and opens
up the fundamental possibility of investigating the internal structure of black
holes using quantum tunneling between external and internal states.
| [
{
"created": "Tue, 27 Aug 2013 17:01:27 GMT",
"version": "v1"
}
] | 2013-08-28 | [
[
"Dokuchaev",
"V. I.",
""
],
[
"Eroshenko",
"Yu. N.",
""
]
] | A stationary solution of the Dirac equation in the metric of a Reissner-Nordstrom black hole has been found. Only one stationary regular state outside the black hole event horizon and only one stationary regular state below the Cauchy horizon are shown to exist. The normalization integral of the wave functions diverges on both horizons if the black hole is non-extremal. This means that the solution found can be only the asymptotic limit of a nonstationary solution. In contrast, in the case of an extremal black hole, the normalization integral is finite and the stationary regular solution is physically self-consistent. The existence of quantum levels below the Cauchy horizon can affect the final stage of Hawking black hole evaporation and opens up the fundamental possibility of investigating the internal structure of black holes using quantum tunneling between external and internal states. |
1810.09034 | Luis L\'opez | L. A. Lopez and Valeria Hinojosa | Quasinormal modes of Charged Regular Black Hole | arXiv admin note: text overlap with arXiv:1607.02476 | Canadian Journal of Physics 2020 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quasinormal modes (QNMs) of a regular black hole with charge are
calculated in the eikonal approximation. In the eikonal limit the QNMs of black
hole are determined by the parameters of the unstable circular null geodesics.
The behaviors of QNMs are compared with QNMs of Reisner-Nordstr\"{o}m black
hole, it is done by fixing some of the parameters that characterize the black
holes and varying another. We observed that the parameter that is related one
effective cosmological constant at small distances , determines the behaviors
of the QNMs of regular black hole with charge.
| [
{
"created": "Sun, 21 Oct 2018 22:22:07 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jul 2019 17:56:59 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Aug 2020 16:03:47 GMT",
"version": "v3"
}
] | 2020-08-20 | [
[
"Lopez",
"L. A.",
""
],
[
"Hinojosa",
"Valeria",
""
]
] | The quasinormal modes (QNMs) of a regular black hole with charge are calculated in the eikonal approximation. In the eikonal limit the QNMs of black hole are determined by the parameters of the unstable circular null geodesics. The behaviors of QNMs are compared with QNMs of Reisner-Nordstr\"{o}m black hole, it is done by fixing some of the parameters that characterize the black holes and varying another. We observed that the parameter that is related one effective cosmological constant at small distances , determines the behaviors of the QNMs of regular black hole with charge. |
2108.13379 | Sung-Jin Oh | Jonathan Luk and Sung-Jin Oh | Global nonlinear stability of large dispersive solutions to the Einstein
equations | 94 pages, 1 figure; v2: minor typos fixed | null | 10.1007/s00023-021-01148-8 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the monumental result of Christodoulou-Klainerman on the global
nonlinear stability of the Minkowski spacetime to the global nonlinear
stability of a class of large dispersive spacetimes. More precisely, we show
that any regular future causally geodesically complete, asymptotically flat
solution to the Einstein-scalar field system which approaches the Minkowski
spacetime sufficiently fast for large times is future globally nonlinearly
stable. Combining our main theorem with results of Luk-Oh, Luk-Oh-Yang and
Kilgore, we prove that a class of large data spherically symmetric dispersive
solutions to the Einstein-scalar field system are globally nonlinearly stable
with respect to small non-spherically symmetric perturbations. This in
particular gives the first construction of an open set of large asymptotically
flat initial data for which the solutions to the Einstein-scalar field system
are future causally geodesically complete.
| [
{
"created": "Mon, 30 Aug 2021 17:01:38 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Dec 2021 00:17:45 GMT",
"version": "v2"
}
] | 2022-06-29 | [
[
"Luk",
"Jonathan",
""
],
[
"Oh",
"Sung-Jin",
""
]
] | We extend the monumental result of Christodoulou-Klainerman on the global nonlinear stability of the Minkowski spacetime to the global nonlinear stability of a class of large dispersive spacetimes. More precisely, we show that any regular future causally geodesically complete, asymptotically flat solution to the Einstein-scalar field system which approaches the Minkowski spacetime sufficiently fast for large times is future globally nonlinearly stable. Combining our main theorem with results of Luk-Oh, Luk-Oh-Yang and Kilgore, we prove that a class of large data spherically symmetric dispersive solutions to the Einstein-scalar field system are globally nonlinearly stable with respect to small non-spherically symmetric perturbations. This in particular gives the first construction of an open set of large asymptotically flat initial data for which the solutions to the Einstein-scalar field system are future causally geodesically complete. |
1210.4719 | Yoshiaki Ohkuwa | Yoshiaki Ohkuwa, Yasuo Ezawa | Third quantization of $f(R)$-type gravity II - General $f(R)$ case - | 9 pages. Subtitle and a reference are added with some minor changes.
arXiv admin note: text overlap with arXiv:1203.1361 | Class. Quantum Grav. 30 (2013) 235015 | 10.1088/0264-9381/30/23/235015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the previous paper we examined the third quantization of the $f(R)$-type
gravity and studied the Heisenberg uncertainty relation of the universe in the
example of $f(R)=R^2$. In this work the Heisenberg uncertainty relation of the
universe is investigated in the general $f(R)$-type gravity where tachyonic
states are avoided. It is shown that, at late times namely the scale factor of
the universe is large, the spacetime becomes classical, and, at early times
namely the scale factor of the universe is small, the quantum effects dominate.
| [
{
"created": "Wed, 10 Oct 2012 01:54:21 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Oct 2012 08:27:57 GMT",
"version": "v2"
}
] | 2019-04-30 | [
[
"Ohkuwa",
"Yoshiaki",
""
],
[
"Ezawa",
"Yasuo",
""
]
] | In the previous paper we examined the third quantization of the $f(R)$-type gravity and studied the Heisenberg uncertainty relation of the universe in the example of $f(R)=R^2$. In this work the Heisenberg uncertainty relation of the universe is investigated in the general $f(R)$-type gravity where tachyonic states are avoided. It is shown that, at late times namely the scale factor of the universe is large, the spacetime becomes classical, and, at early times namely the scale factor of the universe is small, the quantum effects dominate. |
2209.13471 | Shokoufe Faraji | Shokoufe Faraji, Audrey Trova | Oscillation properties of relativistic tori in the vicinity of a
distorted deformed compact object | null | null | 10.1093/mnras/stad2209 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies the oscillation properties of relativistic,
non-self-gravitating tori in the background of a distorted deformed compact
object. This work concentrates on the static and axially symmetric metric
containing two quadrupole parameters; relating to the central object and the
external fields. This metric may associate the observable effects to these
parameters as dynamical degrees of freedom. The astrophysical motivation for
choosing such a field is the possibility of constituting a reasonable model for
an actual scenario occurring in the vicinity of compact objects. This paper
aims to investigate the radial epicyclic frequency in a perfect fluid disk and
not a test particle scenario via a local analysis. To achieve this goal, we
employ the vertically integrated technique to able to treat the equation
analytically. The tori are also modelled with Keplerian and non-Keplerian
distributions of specific angular momentum, and we discuss the dependence of
oscillation properties on the variable of the model related to angular momentum
distribution and quadrupoles. In the present contribution, we further explore
these properties with the possibility of relating oscillatory frequencies to
some high-frequency quasi-periodic oscillations models and observed data.
| [
{
"created": "Tue, 6 Sep 2022 17:45:41 GMT",
"version": "v1"
}
] | 2023-08-02 | [
[
"Faraji",
"Shokoufe",
""
],
[
"Trova",
"Audrey",
""
]
] | This paper studies the oscillation properties of relativistic, non-self-gravitating tori in the background of a distorted deformed compact object. This work concentrates on the static and axially symmetric metric containing two quadrupole parameters; relating to the central object and the external fields. This metric may associate the observable effects to these parameters as dynamical degrees of freedom. The astrophysical motivation for choosing such a field is the possibility of constituting a reasonable model for an actual scenario occurring in the vicinity of compact objects. This paper aims to investigate the radial epicyclic frequency in a perfect fluid disk and not a test particle scenario via a local analysis. To achieve this goal, we employ the vertically integrated technique to able to treat the equation analytically. The tori are also modelled with Keplerian and non-Keplerian distributions of specific angular momentum, and we discuss the dependence of oscillation properties on the variable of the model related to angular momentum distribution and quadrupoles. In the present contribution, we further explore these properties with the possibility of relating oscillatory frequencies to some high-frequency quasi-periodic oscillations models and observed data. |
0904.0469 | Fred Cooperstock I | F.I. Cooperstock and M.J. Dupre | Covariant energy-momentum and an uncertainty principle for general
relativity | 11 pages, new material added | Annals of Physics 339, 531-541, 2013 | 10.1016/j.aop.2013.08.009 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | We introduce a naturally-defined totally invariant spacetime energy
expression for general relativity incorporating the contribution from gravity.
The extension links seamlessly to the action integral for the gravitational
field. The demand that the general expression for arbitrary systems reduces to
the Tolman integral in the case of stationary bounded distributions, leads to
the matter-localized Ricci integral for energy-momentum in support of the
energy localization hypothesis. The role of the observer is addressed and as an
extension of the special relativistic case, the field of observers comoving
with the matter is seen to compute the intrinsic global energy of a system. The
new localized energy supports the Bonnor claim that the Szekeres collapsing
dust solutions are energy-conserving. It is suggested that in the extreme of
strong gravity, the Heisenberg Uncertainty Principle be generalized in terms of
spacetime energy-momentum.
| [
{
"created": "Thu, 2 Apr 2009 21:00:27 GMT",
"version": "v1"
},
{
"created": "Wed, 19 May 2010 18:43:52 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Oct 2014 16:30:30 GMT",
"version": "v3"
}
] | 2015-05-13 | [
[
"Cooperstock",
"F. I.",
""
],
[
"Dupre",
"M. J.",
""
]
] | We introduce a naturally-defined totally invariant spacetime energy expression for general relativity incorporating the contribution from gravity. The extension links seamlessly to the action integral for the gravitational field. The demand that the general expression for arbitrary systems reduces to the Tolman integral in the case of stationary bounded distributions, leads to the matter-localized Ricci integral for energy-momentum in support of the energy localization hypothesis. The role of the observer is addressed and as an extension of the special relativistic case, the field of observers comoving with the matter is seen to compute the intrinsic global energy of a system. The new localized energy supports the Bonnor claim that the Szekeres collapsing dust solutions are energy-conserving. It is suggested that in the extreme of strong gravity, the Heisenberg Uncertainty Principle be generalized in terms of spacetime energy-momentum. |
2303.16664 | Hamza Boumaza | Hamza Boumaza | Axial and polar stability of neutron stars in scalar-tensor theories
with disformal coupling | Added references and appendix, corrected typos, Revised section 2 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we study the radial and non-radial perturbative
stability of neutron stars in which the matter is disformally coupled to the
metric. First, we derive the gravitational and the fluid equations of the
neutron star in a static and spherically symmetric background. Then, we
calculate the second-order expansion of the action that describes the dynamics
of both axial and polar modes. From the resulting expressions, we derive the
conditions to avoid gradient and ghost instabilities at the center of the star
and at spatial infinity. In addition, a numerical analysis is performed to
investigate the stability of a particular model with a constant disformal
function denoted as $\Lambda$ in the whole space time. We found that the chosen
model is stable against the gradient instability in a small range of the
constant $\Lambda$.
| [
{
"created": "Wed, 29 Mar 2023 13:14:50 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Aug 2023 19:32:00 GMT",
"version": "v2"
}
] | 2023-08-08 | [
[
"Boumaza",
"Hamza",
""
]
] | In the present work, we study the radial and non-radial perturbative stability of neutron stars in which the matter is disformally coupled to the metric. First, we derive the gravitational and the fluid equations of the neutron star in a static and spherically symmetric background. Then, we calculate the second-order expansion of the action that describes the dynamics of both axial and polar modes. From the resulting expressions, we derive the conditions to avoid gradient and ghost instabilities at the center of the star and at spatial infinity. In addition, a numerical analysis is performed to investigate the stability of a particular model with a constant disformal function denoted as $\Lambda$ in the whole space time. We found that the chosen model is stable against the gradient instability in a small range of the constant $\Lambda$. |
2210.17135 | PanPan Wang | Pan-Pan Wang, Wei-Liang Qian, Han-Zhong Wu, Yu-Jie Tan, and Cheng-Gang
Shao | Arm locking in conjunction with time-delay interferometry | null | null | 10.1103/PhysRevD.106.104042 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A crucial challenge to the ongoing endeavor of spaceborne gravitational wave
(GW) detection resides in the laser phase noise, typically 7 to 8 orders of
magnitude above the inevitable noise. The arm locking technique was proposed to
suppress the noise in pre-stabilized laser beams. Based on the feedback control
theory, it is implemented by appropriate design of the signal routing
architecture, particularly the controllers' transfer functions. Theoretically
and experimentally, the technique has been demonstrated to be capable of
suppressing the laser phase noise by approximately 2-4 orders of magnitude
while taking into account various aspects such as the gain and distribution of
nulls in the Bode plot and the laser frequency pulling associated with the
Doppler frequency subtraction. Consequently, the resultant noise floor is
composed of the sources attributed to the clock jitter, optical bench motion,
test mass fluctuations, shot-noise phase fluctuations at the photodetectors,
whereas the magnitudes of these noises largely remain unchanged during the
process. Besides, the original GW signals are deformed through the arm-locking
control loop and therefore bear specific features governed by the associated
arm-locking scheme. Nonetheless, the remaining laser phase noise from the
arm-locking feedback routing settles within the capability threshold of the
time-delay interferometry (TDI). In this regard, it is generally understood
that the output of arm locking furnishes the input of TDI, through which the
residual noise is further reduced to the desired level at a post-processing
stage. In this work, we investigate the specific schemes regarding how the arm
locking output is processed further by the TDI algorithm. Specific forms of the
TDI combinations are derived in accordance with suppressed laser phase noise
and deformed signals of GW.
| [
{
"created": "Mon, 31 Oct 2022 08:35:20 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Wang",
"Pan-Pan",
""
],
[
"Qian",
"Wei-Liang",
""
],
[
"Wu",
"Han-Zhong",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] | A crucial challenge to the ongoing endeavor of spaceborne gravitational wave (GW) detection resides in the laser phase noise, typically 7 to 8 orders of magnitude above the inevitable noise. The arm locking technique was proposed to suppress the noise in pre-stabilized laser beams. Based on the feedback control theory, it is implemented by appropriate design of the signal routing architecture, particularly the controllers' transfer functions. Theoretically and experimentally, the technique has been demonstrated to be capable of suppressing the laser phase noise by approximately 2-4 orders of magnitude while taking into account various aspects such as the gain and distribution of nulls in the Bode plot and the laser frequency pulling associated with the Doppler frequency subtraction. Consequently, the resultant noise floor is composed of the sources attributed to the clock jitter, optical bench motion, test mass fluctuations, shot-noise phase fluctuations at the photodetectors, whereas the magnitudes of these noises largely remain unchanged during the process. Besides, the original GW signals are deformed through the arm-locking control loop and therefore bear specific features governed by the associated arm-locking scheme. Nonetheless, the remaining laser phase noise from the arm-locking feedback routing settles within the capability threshold of the time-delay interferometry (TDI). In this regard, it is generally understood that the output of arm locking furnishes the input of TDI, through which the residual noise is further reduced to the desired level at a post-processing stage. In this work, we investigate the specific schemes regarding how the arm locking output is processed further by the TDI algorithm. Specific forms of the TDI combinations are derived in accordance with suppressed laser phase noise and deformed signals of GW. |
2310.04883 | Celso de Camargo Barros Jr. | L. G. Barbosa and C. C. Barros Jr | Scalar bosons in Bonnor-Melvin-$\Lambda$ universe: Exact solution,
Landau levels and Coulomb-like potential | 16 pages, 10 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work we study spin-0 particles in a spacetime which structure is
determined by a homogeneous magnetic field and a cosmological constant. For
this purpose we take into account a framework based on the Bonnor-Melvin
solution with the inclusion of the cosmological constant. We write the
Klein-Gordon equation, solve it and determine the Landau levels. The effect of
a scalar potential is also considered.
| [
{
"created": "Sat, 7 Oct 2023 17:46:55 GMT",
"version": "v1"
}
] | 2023-10-10 | [
[
"Barbosa",
"L. G.",
""
],
[
"Barros",
"C. C.",
"Jr"
]
] | In this work we study spin-0 particles in a spacetime which structure is determined by a homogeneous magnetic field and a cosmological constant. For this purpose we take into account a framework based on the Bonnor-Melvin solution with the inclusion of the cosmological constant. We write the Klein-Gordon equation, solve it and determine the Landau levels. The effect of a scalar potential is also considered. |
1705.01277 | Hernando Quevedo | Hernando Quevedo | Can spacetime curvature be used in future navigation systems? | Prepared for the Proceedings of the Conference "Relativistic Geodesy:
Foundations and Applications", March 2016, Bad Honnef (Germany) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that the curvature generated by a gravitational field can be used to
calculate the corresponding metric which determines the trajectories of freely
falling test particles. To this end, we present a method to compute the metric
from a given curvature tensor. We use Petrov's classification to handle the
structure and properties of the curvature tensor, and Cartan's structure
equations in an orthonormal tetrad to investigate the differential equations
that relate the curvature with the metric. The second structure equation is
integrated to obtain the explicit expression for the connection $1-$form from
which the components of the orthonormal tetrad are obtained by using the first
structure equation. This opens the possibility of using the curvature of
astrophysical objects like the Earth to determine the position of freely
falling satellites that are used in modern navigation systems.
| [
{
"created": "Wed, 3 May 2017 07:17:23 GMT",
"version": "v1"
}
] | 2017-05-04 | [
[
"Quevedo",
"Hernando",
""
]
] | We argue that the curvature generated by a gravitational field can be used to calculate the corresponding metric which determines the trajectories of freely falling test particles. To this end, we present a method to compute the metric from a given curvature tensor. We use Petrov's classification to handle the structure and properties of the curvature tensor, and Cartan's structure equations in an orthonormal tetrad to investigate the differential equations that relate the curvature with the metric. The second structure equation is integrated to obtain the explicit expression for the connection $1-$form from which the components of the orthonormal tetrad are obtained by using the first structure equation. This opens the possibility of using the curvature of astrophysical objects like the Earth to determine the position of freely falling satellites that are used in modern navigation systems. |
0709.2628 | Muhammad Sharif | M. Sharif and Umber Sheikh | Isothermal Plasma Waves in Gravitomagnetic Planar Analogue | 28 pages, 6 figures, accepted for publication Class. Quantum Grav | Class.Quant.Grav.24:5495-5514,2007 | 10.1088/0264-9381/24/22/013 | null | gr-qc astro-ph | null | We investigate the wave properties of the Kerr black hole with isothermal
plasma using 3+1 ADM formalism. The corresponding Fourier analyzed perturbed
GRMHD equations are used to obtain the dispersion relations. These relations
lead to the real values of the components of wave vector $\textbf{k}$ which are
used to evaluate the quantities like phase and group velocities etc. These have
been discussed graphically in the neighborhood of the pair production region.
The results obtained verify the conclusion of Mackay et al. according to which
rotation of a black hole is required for negative phase velocity propagation.
| [
{
"created": "Sat, 15 Sep 2007 06:11:39 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sharif",
"M.",
""
],
[
"Sheikh",
"Umber",
""
]
] | We investigate the wave properties of the Kerr black hole with isothermal plasma using 3+1 ADM formalism. The corresponding Fourier analyzed perturbed GRMHD equations are used to obtain the dispersion relations. These relations lead to the real values of the components of wave vector $\textbf{k}$ which are used to evaluate the quantities like phase and group velocities etc. These have been discussed graphically in the neighborhood of the pair production region. The results obtained verify the conclusion of Mackay et al. according to which rotation of a black hole is required for negative phase velocity propagation. |
1901.04640 | Gil de Oliveira-Neto | G. Oliveira-Neto, L. G. Martins, G. A. Monerat and E. V. Corr\^ea
Silva | Quantum cosmology of a Ho\v{r}ava-Lifshitz model coupled to radiation | 33 pages and 15 figures. Few modifications in the text and new
references added. Submitted to IJMPD | null | 10.1142/S021827181950130X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper, we canonically quantize an homogeneous and isotropic
Ho\v{r}ava-Lifshitz cosmological model, with constant positive spatial sections
and coupled to radiation. We consider the projectable version of that
gravitational theory without the detailed balance condition. We use the ADM
formalism to write the gravitational Hamiltonian of the model and the Schutz
variational formalism to write the perfect fluid Hamiltonian. We find the
Wheeler-DeWitt equation for the model, which depends on several parameters. We
study the case in which parameter values are chosen so that the solutions to
the Wheeler-DeWitt equation are bounded. Initially, we solve it using the {\it
Many Worlds} interpretation. Using wavepackets computed with the solutions to
the Wheeler-DeWitt equation, we obtain the scalar factor expected value
$\left<a\right>$. We show that this quantity oscillates between finite maximum
and minimum values and never vanishes. Such result indicates that the model is
free from singularities, at the quantum level. We reinforce this indication by
showing that by subtracting one standard deviation unit from the expected value
$\left<a\right>$, the latter remains positive. Then, we use the {\it
DeBroglie-Bohm} interpretation. Initially, we compute the Bohm's trajectories
for the scale factor and show that they never vanish. Then, we show that each
trajectory agrees with the corresponding $\left<a\right>$. Finally, we compute
the quantum potential, which helps understanding why the scale factor never
vanishes.
| [
{
"created": "Tue, 15 Jan 2019 02:49:38 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Jan 2019 13:26:01 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Apr 2019 21:48:21 GMT",
"version": "v3"
}
] | 2019-08-07 | [
[
"Oliveira-Neto",
"G.",
""
],
[
"Martins",
"L. G.",
""
],
[
"Monerat",
"G. A.",
""
],
[
"Silva",
"E. V. Corrêa",
""
]
] | In the present paper, we canonically quantize an homogeneous and isotropic Ho\v{r}ava-Lifshitz cosmological model, with constant positive spatial sections and coupled to radiation. We consider the projectable version of that gravitational theory without the detailed balance condition. We use the ADM formalism to write the gravitational Hamiltonian of the model and the Schutz variational formalism to write the perfect fluid Hamiltonian. We find the Wheeler-DeWitt equation for the model, which depends on several parameters. We study the case in which parameter values are chosen so that the solutions to the Wheeler-DeWitt equation are bounded. Initially, we solve it using the {\it Many Worlds} interpretation. Using wavepackets computed with the solutions to the Wheeler-DeWitt equation, we obtain the scalar factor expected value $\left<a\right>$. We show that this quantity oscillates between finite maximum and minimum values and never vanishes. Such result indicates that the model is free from singularities, at the quantum level. We reinforce this indication by showing that by subtracting one standard deviation unit from the expected value $\left<a\right>$, the latter remains positive. Then, we use the {\it DeBroglie-Bohm} interpretation. Initially, we compute the Bohm's trajectories for the scale factor and show that they never vanish. Then, we show that each trajectory agrees with the corresponding $\left<a\right>$. Finally, we compute the quantum potential, which helps understanding why the scale factor never vanishes. |
1801.08872 | Juliano Neves | R. V. Maluf, Juliano C. S. Neves | Bardeen regular black hole as a quantum-corrected Schwarzschild black
hole | 5 pages. V2 with minor changes. This article is a consequence of
arXiv:1801.02661. Published in International Journal of Modern Physics D | Int. J. Mod. Phys. D 28, 1950048 (2019) | 10.1142/S0218271819500482 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bardeen regular black hole is commonly considered as a solution of general
relativity coupled to a nonlinear electrodynamics. In this paper, it is shown
that the Bardeen solution may be interpreted as a quantum-corrected
Schwarzschild black hole. This new interpretation is obtained by means of a
generalized uncertainty principle applied to the Hawking temperature. Moreover,
using the regular black hole of Bardeen, it is possible to evaluate the quantum
gravity parameter of the generalized uncertainty principle or, assuming the
recent upper bounds for such a parameter, to verify an enormous discrepancy
between a cosmological constant and that measured by recent cosmological
observations $(\sim 10^{120})$.
| [
{
"created": "Fri, 26 Jan 2018 18:53:58 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Dec 2018 13:42:59 GMT",
"version": "v2"
}
] | 2018-12-06 | [
[
"Maluf",
"R. V.",
""
],
[
"Neves",
"Juliano C. S.",
""
]
] | Bardeen regular black hole is commonly considered as a solution of general relativity coupled to a nonlinear electrodynamics. In this paper, it is shown that the Bardeen solution may be interpreted as a quantum-corrected Schwarzschild black hole. This new interpretation is obtained by means of a generalized uncertainty principle applied to the Hawking temperature. Moreover, using the regular black hole of Bardeen, it is possible to evaluate the quantum gravity parameter of the generalized uncertainty principle or, assuming the recent upper bounds for such a parameter, to verify an enormous discrepancy between a cosmological constant and that measured by recent cosmological observations $(\sim 10^{120})$. |
2311.18640 | Qianyun Yun | Qianyun Yun, Wen-Biao Han, Yi-Yang Guo, He Wang, and Minghui Du | The detection, extraction and parameter estimation of extreme-mass-ratio
inspirals with deep learning | 6 pages, 5 figures | null | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | One of the primary goals of space-borne gravitational wave detectors is to
detect and analyze extreme-mass-ratio inspirals (EMRIs). This endeavor presents
a significant challenge due to the complex and lengthy EMRI signals, further
compounded by their inherently faint nature. In this letter, we introduce a
2-layer Convolutional Neural Network (CNN) approach to detect EMRI signals for
space-borne detectors, achieving a true positive rate (TPR) of 96.9 % at a 1 %
false positive rate (FPR) for signal-to-noise ratio (SNR) from 50 to 100.
Especially, the key intrinsic parameters of EMRIs such as mass and spin of the
supermassive black hole (SMBH) and the initial eccentricity of the orbit can be
inferred directly by employing a VGG network. The mass and spin of the SMBH can
be determined at 99 % and 92 % respectively. This will greatly reduce the
parameter spaces and computing cost for the following Bayesian parameter
estimation. Our model also has a low dependency on the accuracy of the waveform
model. This study underscores the potential of deep learning methods in EMRI
data analysis, enabling the rapid detection of EMRI signals and efficient
parameter estimation .
| [
{
"created": "Thu, 30 Nov 2023 15:46:44 GMT",
"version": "v1"
}
] | 2023-12-01 | [
[
"Yun",
"Qianyun",
""
],
[
"Han",
"Wen-Biao",
""
],
[
"Guo",
"Yi-Yang",
""
],
[
"Wang",
"He",
""
],
[
"Du",
"Minghui",
""
]
] | One of the primary goals of space-borne gravitational wave detectors is to detect and analyze extreme-mass-ratio inspirals (EMRIs). This endeavor presents a significant challenge due to the complex and lengthy EMRI signals, further compounded by their inherently faint nature. In this letter, we introduce a 2-layer Convolutional Neural Network (CNN) approach to detect EMRI signals for space-borne detectors, achieving a true positive rate (TPR) of 96.9 % at a 1 % false positive rate (FPR) for signal-to-noise ratio (SNR) from 50 to 100. Especially, the key intrinsic parameters of EMRIs such as mass and spin of the supermassive black hole (SMBH) and the initial eccentricity of the orbit can be inferred directly by employing a VGG network. The mass and spin of the SMBH can be determined at 99 % and 92 % respectively. This will greatly reduce the parameter spaces and computing cost for the following Bayesian parameter estimation. Our model also has a low dependency on the accuracy of the waveform model. This study underscores the potential of deep learning methods in EMRI data analysis, enabling the rapid detection of EMRI signals and efficient parameter estimation . |
1103.1127 | Mike Stannett | Mike Stannett | Computation and Spacetime Structure | 10 pages, 2 figures. Submitted to Physics & Computation 2011, Turku,
Finland | null | null | null | gr-qc cs.CC | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the relationship between computation and spacetime structure,
focussing on the role of closed timelike curves (CTCs) in promoting
computational speedup. We note first that CTC traversal can be interpreted in
two distinct ways, depending on ones understanding of spacetime. Focussing on
one interpretation leads us to develop a toy universe in which no CTC can be
traversed more than once, whence no computational speedup is possible.
Focussing on the second (and more standard) interpretation leads to the
surprising conclusion that CTCs act as perfect information repositories: just
as black holes have entropy, so do CTCs. If we also assume that P is not equal
to NP, we find that all observers agree that, even if unbounded time travel
existed in their youth, this capability eventually vanishes as they grow older.
Thus the computational assumption "P is not NP" is also an assumption
concerning cosmological structure.
| [
{
"created": "Sun, 6 Mar 2011 14:34:28 GMT",
"version": "v1"
}
] | 2011-03-08 | [
[
"Stannett",
"Mike",
""
]
] | We investigate the relationship between computation and spacetime structure, focussing on the role of closed timelike curves (CTCs) in promoting computational speedup. We note first that CTC traversal can be interpreted in two distinct ways, depending on ones understanding of spacetime. Focussing on one interpretation leads us to develop a toy universe in which no CTC can be traversed more than once, whence no computational speedup is possible. Focussing on the second (and more standard) interpretation leads to the surprising conclusion that CTCs act as perfect information repositories: just as black holes have entropy, so do CTCs. If we also assume that P is not equal to NP, we find that all observers agree that, even if unbounded time travel existed in their youth, this capability eventually vanishes as they grow older. Thus the computational assumption "P is not NP" is also an assumption concerning cosmological structure. |
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