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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0307091 | Bryan Kelleher | Bryan Kelleher (University College Cork) | Scale-invariant gravity: Spacetime recovered | Replaced with final version: minor changes to text | Class.Quant.Grav. 21 (2004) 483-495 | 10.1088/0264-9381/21/2/012 | null | gr-qc | null | The configuration space of general relativity is superspace - the space of
all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued
that the configuration space for gravity should be conformal superspace - the
space of all Riemannian 3-metrics modulo diffeomorphisms and conformal
transformations. Recently a manifestly 3-dimensional theory was constructed
with conformal superspace as the configuration space. Here a fully
4-dimensional action is constructed so as to be invariant under conformal
transformations of the 4-metric using general relativity as a guide. This
action is then decomposed to a (3+1)-dimensional form and from this to its
Jacobi form. The surprising thing is that the new theory turns out to be
precisely the original 3-dimensional theory. The physical data is identified
and used to find the physical representation of the theory. In this
representation the theory is extremely similar to general relativity. The
clarity of the 4-dimensional picture should prove very useful for comparing the
theory with those aspects of general relativity which are usually treated in
the 4-dimensional framework.
| [
{
"created": "Mon, 21 Jul 2003 14:15:28 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Oct 2003 13:54:46 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Jul 2004 11:53:43 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Kelleher",
"Bryan",
"",
"University College Cork"
]
] | The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Recently a manifestly 3-dimensional theory was constructed with conformal superspace as the configuration space. Here a fully 4-dimensional action is constructed so as to be invariant under conformal transformations of the 4-metric using general relativity as a guide. This action is then decomposed to a (3+1)-dimensional form and from this to its Jacobi form. The surprising thing is that the new theory turns out to be precisely the original 3-dimensional theory. The physical data is identified and used to find the physical representation of the theory. In this representation the theory is extremely similar to general relativity. The clarity of the 4-dimensional picture should prove very useful for comparing the theory with those aspects of general relativity which are usually treated in the 4-dimensional framework. |
gr-qc/0104076 | Diego F. Torres | Ernesto Eiroa, Gustavo E. Romero, and Diego F. Torres | Chromaticity effects in microlensing by wormholes | To appear in Modern Physics Letters A, 2001 | Mod.Phys.Lett. A16 (2001) 973-984 | 10.1142/S021773230100398X | null | gr-qc astro-ph | null | Chromaticity effects introduced by the finite source size in microlensing
events by presumed natural wormholes are studied. It is shown that these
effects provide a specific signature that allow to discriminate between
ordinary and negative mass lenses through the spectral analysis of the
microlensing events. Both galactic and extragalactic situations are discussed.
| [
{
"created": "Tue, 24 Apr 2001 11:54:56 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Eiroa",
"Ernesto",
""
],
[
"Romero",
"Gustavo E.",
""
],
[
"Torres",
"Diego F.",
""
]
] | Chromaticity effects introduced by the finite source size in microlensing events by presumed natural wormholes are studied. It is shown that these effects provide a specific signature that allow to discriminate between ordinary and negative mass lenses through the spectral analysis of the microlensing events. Both galactic and extragalactic situations are discussed. |
gr-qc/0602071 | Bahram Mashhoon | C. Chicone and B. Mashhoon | Tidal Dynamics in Kerr Spacetime | 15 pages, 3 figures; v2: slightly expanded version accepted for
publication in CQG | Class.Quant.Grav. 23 (2006) 4021-4033 | 10.1088/0264-9381/23/12/002 | null | gr-qc astro-ph | null | The motion of free nearby test particles relative to a stable equatorial
circular geodesic orbit about a Kerr source is investigated. It is shown that
the nonlinear generalized Jacobi equation can be transformed in this case to an
autonomous form. Tidal dynamics beyond the critical speed c/sqrt(2) is studied.
We show, in particular, that a free test particle vertically launched from the
circular orbit parallel or antiparallel to the Kerr rotation axis is tidally
accelerated if its initial relative speed exceeds c/sqrt(2). Possible
applications of our results to high-energy astrophysics are briefly mentioned.
| [
{
"created": "Sun, 19 Feb 2006 00:11:31 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Apr 2006 21:50:04 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Chicone",
"C.",
""
],
[
"Mashhoon",
"B.",
""
]
] | The motion of free nearby test particles relative to a stable equatorial circular geodesic orbit about a Kerr source is investigated. It is shown that the nonlinear generalized Jacobi equation can be transformed in this case to an autonomous form. Tidal dynamics beyond the critical speed c/sqrt(2) is studied. We show, in particular, that a free test particle vertically launched from the circular orbit parallel or antiparallel to the Kerr rotation axis is tidally accelerated if its initial relative speed exceeds c/sqrt(2). Possible applications of our results to high-energy astrophysics are briefly mentioned. |
1107.3917 | Antonio De Felice | Antonio De Felice, Shinji Tsujikawa | Inflationary non-Gaussianities in the most general second-order
scalar-tensor theories | 17 pages, 1 figure, uses RevTeX. The version to appear in Physical
Review D | Phys.Rev.D84:083504, 2011 | 10.1103/PhysRevD.84.083504 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For very general scalar-field theories in which the equations of motion are
at second-order, we evaluate the three-point correlation function of primordial
scalar perturbations generated during inflation. We show that the shape of
non-Gaussianities is well approximated by the equilateral type. The equilateral
non-linear parameter f_NL^equil is derived on the quasi de Sitter background
where the slow-variation parameters are much smaller than unity. We apply our
formula for f_NL^equil to a number of single-field models of inflation--such as
k-inflation, k-inflation with Galileon terms, potential-driven Galileon
inflation, nonminimal coupling models (including field-derivative coupling
models), and Gauss-Bonnet gravity.
| [
{
"created": "Wed, 20 Jul 2011 08:30:31 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Sep 2011 09:40:13 GMT",
"version": "v2"
}
] | 2011-10-11 | [
[
"De Felice",
"Antonio",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | For very general scalar-field theories in which the equations of motion are at second-order, we evaluate the three-point correlation function of primordial scalar perturbations generated during inflation. We show that the shape of non-Gaussianities is well approximated by the equilateral type. The equilateral non-linear parameter f_NL^equil is derived on the quasi de Sitter background where the slow-variation parameters are much smaller than unity. We apply our formula for f_NL^equil to a number of single-field models of inflation--such as k-inflation, k-inflation with Galileon terms, potential-driven Galileon inflation, nonminimal coupling models (including field-derivative coupling models), and Gauss-Bonnet gravity. |
2306.11531 | Vladimir Khatsymovsky | V.M. Khatsymovsky | On the gravitational diagram technique in the discrete setup | 46 pages, 5 figures, typos corrected, refs added, typical diagrams
added | Int. J. Mod. Phys. A, Volume No. 38, Issue No. 26n27, Article No.
2350143, Year 2023 | 10.1142/S0217751X23501439 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article is in the spirit of our work on the consequences of the Regge
calculus, where some edge length scale arises as an optimal initial point of
the perturbative expansion after functional integration over connection.
Now consider the perturbative expansion itself. To obtain an algorithmizable
diagram technique, we consider the simplest periodic simplicial structure with
a frozen part of the variables ("hypercubic"). After functional integration
over connection, the system is described by the metric $g_{\lambda \mu}$ at the
sites.
We parameterize $g_{\lambda \mu}$ so that the functional measure becomes
Lebesgue. The discrete diagrams are free from ultraviolet divergences and
reproduce (for ordinary, non-Planck external momenta) those continuum
counterparts that are finite. We give the parametrization of $g_{\lambda \mu}$
up to terms, providing, in particular, additional three-graviton and
two-graviton-two-matter vertices, which can give additional one-loop
corrections to the Newtonian potential.
The edge length scale is $\sim \sqrt{ \eta }$, where $\eta$ defines the free
factor $ ( - \det \| g_{\lambda \mu} \| )^{ \eta / 2}$ in the measure and
should be a large parameter to ensure the true action after integration over
connection. We verify the important fact that the perturbative expansion does
not contain increasing powers of $\eta$ if its initial point is chosen close
enough to the maximum point of the measure, thus justifying this choice.
Discrete propagators depend on the Barbero-Immirzi parameter $\gamma$, which
determines the ratio of timelike and spacelike elementary length scales. The
existing estimates of $\gamma$ allow the propagator poles to have real energy
for any (real) spatial momenta.
| [
{
"created": "Tue, 20 Jun 2023 13:35:31 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Dec 2023 15:33:57 GMT",
"version": "v2"
}
] | 2024-01-03 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | This article is in the spirit of our work on the consequences of the Regge calculus, where some edge length scale arises as an optimal initial point of the perturbative expansion after functional integration over connection. Now consider the perturbative expansion itself. To obtain an algorithmizable diagram technique, we consider the simplest periodic simplicial structure with a frozen part of the variables ("hypercubic"). After functional integration over connection, the system is described by the metric $g_{\lambda \mu}$ at the sites. We parameterize $g_{\lambda \mu}$ so that the functional measure becomes Lebesgue. The discrete diagrams are free from ultraviolet divergences and reproduce (for ordinary, non-Planck external momenta) those continuum counterparts that are finite. We give the parametrization of $g_{\lambda \mu}$ up to terms, providing, in particular, additional three-graviton and two-graviton-two-matter vertices, which can give additional one-loop corrections to the Newtonian potential. The edge length scale is $\sim \sqrt{ \eta }$, where $\eta$ defines the free factor $ ( - \det \| g_{\lambda \mu} \| )^{ \eta / 2}$ in the measure and should be a large parameter to ensure the true action after integration over connection. We verify the important fact that the perturbative expansion does not contain increasing powers of $\eta$ if its initial point is chosen close enough to the maximum point of the measure, thus justifying this choice. Discrete propagators depend on the Barbero-Immirzi parameter $\gamma$, which determines the ratio of timelike and spacelike elementary length scales. The existing estimates of $\gamma$ allow the propagator poles to have real energy for any (real) spatial momenta. |
gr-qc/0606084 | Nivaldo Agostinho Lemos | Edesio M. Barboza Jr. and Nivaldo A. Lemos | Does the Big Rip survive quantization? | Ref. [21] added, abstract slightly changed | Gen. Rel. Grav. {\bf 38}, 1609 (2006) | 10.1007/s10714-006-0333-y | null | gr-qc | null | It is known that certain quantum cosmological models present quantum behavior
for large scale factors. Since quantization can suppress past singularities, it
is natural to inquire whether quantum effects can prevent future singularities.
To this end, a Friedmann-Robertson-Walker quantum cosmological model dominated
by a phantom energy fluid is investigated. The classical model displays
accelerated expansion ending in a Big Rip. The quantization is performed in
three different ways, which turn out to lead to the same result, namely there
is a possibility that quantum gravitational effects could not remove the Big
Rip.
| [
{
"created": "Mon, 19 Jun 2006 21:09:45 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Feb 2007 19:50:59 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Barboza",
"Edesio M.",
"Jr."
],
[
"Lemos",
"Nivaldo A.",
""
]
] | It is known that certain quantum cosmological models present quantum behavior for large scale factors. Since quantization can suppress past singularities, it is natural to inquire whether quantum effects can prevent future singularities. To this end, a Friedmann-Robertson-Walker quantum cosmological model dominated by a phantom energy fluid is investigated. The classical model displays accelerated expansion ending in a Big Rip. The quantization is performed in three different ways, which turn out to lead to the same result, namely there is a possibility that quantum gravitational effects could not remove the Big Rip. |
1701.06161 | Daniele Pranzetti | Ramit Dey, Stefano Liberati, Daniele Pranzetti | The black hole quantum atmosphere | 11 pages, 5 figures, minor revision and inclusion of a qualitative
analysis of how to extend our argument to higher dimensions to match the
published version | Phys.Lett. B774 (2017) 308-316 | 10.1016/j.physletb.2017.09.076 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ever since the discovery of black hole evaporation, the region of origin of
the radiated quanta has been a topic of debate. Recently it was argued by
Giddings that the Hawking quanta originate from a region well outside the black
hole horizon by calculating the effective radius of a radiating body via the
Stefan--Boltzmann law. In this paper we try to further explore this issue and
end up corroborating this claim, using both a heuristic argument and a detailed
study of the stress energy tensor. We show that the Hawking quanta originate
from what might be called a quantum atmosphere around the black hole with
energy density and fluxes of particles peaked at about $4M$, running contrary
to the popular belief that these originate from the ultra high energy
excitations very close to the horizon. This long distance origin of Hawking
radiation could have a profound impact on our understanding of the information
and transplanckian problems.
| [
{
"created": "Sun, 22 Jan 2017 13:06:29 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Oct 2017 12:31:18 GMT",
"version": "v2"
}
] | 2017-10-11 | [
[
"Dey",
"Ramit",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Pranzetti",
"Daniele",
""
]
] | Ever since the discovery of black hole evaporation, the region of origin of the radiated quanta has been a topic of debate. Recently it was argued by Giddings that the Hawking quanta originate from a region well outside the black hole horizon by calculating the effective radius of a radiating body via the Stefan--Boltzmann law. In this paper we try to further explore this issue and end up corroborating this claim, using both a heuristic argument and a detailed study of the stress energy tensor. We show that the Hawking quanta originate from what might be called a quantum atmosphere around the black hole with energy density and fluxes of particles peaked at about $4M$, running contrary to the popular belief that these originate from the ultra high energy excitations very close to the horizon. This long distance origin of Hawking radiation could have a profound impact on our understanding of the information and transplanckian problems. |
1312.3539 | Jutta Kunz | Olga Hauser, Rustam Ibadov, Burkhard Kleihaus, Jutta Kunz | Hairy Wormholes and Bartnik-McKinnon Solutions | 25 pages | Phys. Rev. D 89, 064010 (2014) | 10.1103/PhysRevD.89.064010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Lorentzian wormholes supported by a phantom field and threaded by
non-trivial Yang-Mills fields, which may be regarded as hair on the Ellis
wormhole. Like the Bartnik-McKinnon solutions and their associated hairy black
holes, these hairy wormholes form infinite sequences, labeled by the node
number $k$ of their gauge field function. We discuss the throat geometry of
these wormholes, showing that odd-$k$ solutions may exhibit a double-throat,
and evaluate their global charges. We analyze the limiting behavior exhibited
by wormhole solutions as the gravitational coupling becomes large. The even-$k$
solutions approach smoothly the Bartnik-McKinnon solutions with $k/2$ nodes,
while the odd-$k$ solutions develop a singular behavior at the throat in the
limit of large coupling. In the limit of large $k$, on the other hand, an
embedded Abelian wormhole solution is approached, when the throat is large. For
smaller throats the extremal Reissner-Nordstr\"om solution plays a fundamental
role in the limit.
| [
{
"created": "Thu, 12 Dec 2013 16:35:44 GMT",
"version": "v1"
}
] | 2014-03-12 | [
[
"Hauser",
"Olga",
""
],
[
"Ibadov",
"Rustam",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We consider Lorentzian wormholes supported by a phantom field and threaded by non-trivial Yang-Mills fields, which may be regarded as hair on the Ellis wormhole. Like the Bartnik-McKinnon solutions and their associated hairy black holes, these hairy wormholes form infinite sequences, labeled by the node number $k$ of their gauge field function. We discuss the throat geometry of these wormholes, showing that odd-$k$ solutions may exhibit a double-throat, and evaluate their global charges. We analyze the limiting behavior exhibited by wormhole solutions as the gravitational coupling becomes large. The even-$k$ solutions approach smoothly the Bartnik-McKinnon solutions with $k/2$ nodes, while the odd-$k$ solutions develop a singular behavior at the throat in the limit of large coupling. In the limit of large $k$, on the other hand, an embedded Abelian wormhole solution is approached, when the throat is large. For smaller throats the extremal Reissner-Nordstr\"om solution plays a fundamental role in the limit. |
2209.02067 | Mikhail Smolyakov | Vadim Egorov, Mikhail Smolyakov, Igor Volobuev | Doubling of physical states in the quantum scalar field theory for a
remote observer in the Schwarzschild spacetime | 23 pages, 1 figure. v2: major revision of Section 3.3 (more accurate
asymptotics of radial solutions are used), the rest of the text slightly
modified, one reference added. v3: Conclusion expanded, 3 references added,
minor corrections in the rest of the text, typos corrected | Phys. Rev. D 107, 025001 (2023) | 10.1103/PhysRevD.107.025001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the problem of canonical quantization of a free real massive
scalar field in the Schwarzschild spacetime. It is shown that a consistent
procedure of canonical quantization of the field can be carried out without
taking into account the black hole interior, so that in the resulting theory
the canonical commutation relations are satisfied exactly, and the Hamiltonian
has the standard form. However, unlike some papers, in which the expansion of
the quantum field in spherical harmonics is used, here we use an expansion in
scatteringlike states for energies larger than the mass of the field. This
reveals a strange property of the resulting quantum field theory - doubling of
the quantum states, which look as having the same asymptotic momentum to an
observer located far away from the black hole. This purely topological effect
cannot be eliminated by moving away from the black hole.
| [
{
"created": "Mon, 5 Sep 2022 17:26:11 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Oct 2022 21:06:39 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Jan 2023 17:28:20 GMT",
"version": "v3"
}
] | 2023-01-05 | [
[
"Egorov",
"Vadim",
""
],
[
"Smolyakov",
"Mikhail",
""
],
[
"Volobuev",
"Igor",
""
]
] | We discuss the problem of canonical quantization of a free real massive scalar field in the Schwarzschild spacetime. It is shown that a consistent procedure of canonical quantization of the field can be carried out without taking into account the black hole interior, so that in the resulting theory the canonical commutation relations are satisfied exactly, and the Hamiltonian has the standard form. However, unlike some papers, in which the expansion of the quantum field in spherical harmonics is used, here we use an expansion in scatteringlike states for energies larger than the mass of the field. This reveals a strange property of the resulting quantum field theory - doubling of the quantum states, which look as having the same asymptotic momentum to an observer located far away from the black hole. This purely topological effect cannot be eliminated by moving away from the black hole. |
1506.03612 | Remo Garattini | Remo Garattini | Traversable Wormholes in Distorted Gravity | 12 pages, to appear in a special volume of the IJMPD, dedicated to
the VII Black Holes Workshop, Aveiro, Portugal, 18-19 December 2014 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the effects of Distorted Gravity on the traversability of the
wormholes. In particular, we consider configurations which are sustained by
their own gravitational quantum fluctuations. The Ultra-Violet divergences
appearing to one loop are taken under control with the help of a Noncommutative
geometry representation and Gravity's Rainbow. In this context, it will be
shown that for every framework, the self-sustained equation will produce a
Wheeler wormhole, namely a wormhole of Planckian size. This means that, from
the point of view of traversability, the wormhole will be traversable in
principle, but not in practice. To this purpose, in the context of Gravity's
Rainbow we have considered different proposals of rainbow's functions to see if
the smallness of the wormhole is dependent on the chosen form of the rainbow's
function. Unfortunately, we discover that this is not the case and we suggest
that the self-sustained equation can be improved to see if the wormhole radius
can be enlarged or not. Some consequences on topology change are discussed.
| [
{
"created": "Thu, 11 Jun 2015 10:22:24 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Garattini",
"Remo",
""
]
] | We consider the effects of Distorted Gravity on the traversability of the wormholes. In particular, we consider configurations which are sustained by their own gravitational quantum fluctuations. The Ultra-Violet divergences appearing to one loop are taken under control with the help of a Noncommutative geometry representation and Gravity's Rainbow. In this context, it will be shown that for every framework, the self-sustained equation will produce a Wheeler wormhole, namely a wormhole of Planckian size. This means that, from the point of view of traversability, the wormhole will be traversable in principle, but not in practice. To this purpose, in the context of Gravity's Rainbow we have considered different proposals of rainbow's functions to see if the smallness of the wormhole is dependent on the chosen form of the rainbow's function. Unfortunately, we discover that this is not the case and we suggest that the self-sustained equation can be improved to see if the wormhole radius can be enlarged or not. Some consequences on topology change are discussed. |
0907.1193 | Robert Beig | Robert Beig, Gary W.Gibbons, Richard M. Schoen | Gravitating Opposites Attract | 13 pages; slightly amended version, some references added, matches
version to be published in Classical and Quantum Gravity | Class.Quant.Grav.26:225013,2009 | 10.1088/0264-9381/26/22/225013 | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Generalizing previous work by two of us, we prove the non-existence of
certain stationary configurations in General Relativity having a spatial
reflection symmetry across a non-compact surface disjoint from the matter
region. Our results cover cases such that of two symmetrically arranged
rotating bodies with anti-aligned spins in $n+1$ ($n \geq 3$) dimensions, or
two symmetrically arranged static bodies with opposite charges in 3+1
dimensions. They also cover certain symmetric configurations in
(3+1)-dimensional gravity coupled to a collection of scalars and abelian vector
fields, such as arise in supergravity and Kaluza-Klein models. We also treat
the bosonic sector of simple supergravity in 4+1 dimensions.
| [
{
"created": "Tue, 7 Jul 2009 11:14:20 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Oct 2009 14:10:36 GMT",
"version": "v2"
}
] | 2009-11-09 | [
[
"Beig",
"Robert",
""
],
[
"Gibbons",
"Gary W.",
""
],
[
"Schoen",
"Richard M.",
""
]
] | Generalizing previous work by two of us, we prove the non-existence of certain stationary configurations in General Relativity having a spatial reflection symmetry across a non-compact surface disjoint from the matter region. Our results cover cases such that of two symmetrically arranged rotating bodies with anti-aligned spins in $n+1$ ($n \geq 3$) dimensions, or two symmetrically arranged static bodies with opposite charges in 3+1 dimensions. They also cover certain symmetric configurations in (3+1)-dimensional gravity coupled to a collection of scalars and abelian vector fields, such as arise in supergravity and Kaluza-Klein models. We also treat the bosonic sector of simple supergravity in 4+1 dimensions. |
1502.06954 | Hideki Maeda | Hideki Maeda | Unitary evolution of the quantum universe with a Brown-Kuchar dust | 36 pages, 6 figures, 4 tables; v2, revised version; v3, fully revised
version with improved analytical and numerical results, accepted for
publication in Classical and Quantum Gravity | Class.Quant.Grav. 32 (2015) 23, 235023 | 10.1088/0264-9381/32/23/235023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the time evolution of a wave function for the spatially flat
Friedmann-Lemaitre-Robertson-Walker universe governed by the Wheeler-DeWitt
equation in both analytical and numerical methods. We consider a Brown-Kuchar
dust as a matter field in order to introduce a "clock" in quantum cosmology and
adopt the Laplace-Beltrami operator-ordering. The Hamiltonian operator admits
an infinite number of self-adjoint extensions corresponding to a one-parameter
family of boundary conditions at the origin in the minisuperspace. For any
value of the extension parameter in the boundary condition, the evolution of a
wave function is unitary and the classical initial singularity is avoided and
replaced by the big bounce in the quantum system. Exact wave functions show
that the expectation value of the spatial volume of the universe obeys the
classical time evolution in the late time but its variance diverges.
| [
{
"created": "Tue, 24 Feb 2015 20:59:59 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Mar 2015 04:36:29 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Oct 2015 06:44:44 GMT",
"version": "v3"
}
] | 2015-12-14 | [
[
"Maeda",
"Hideki",
""
]
] | We study the time evolution of a wave function for the spatially flat Friedmann-Lemaitre-Robertson-Walker universe governed by the Wheeler-DeWitt equation in both analytical and numerical methods. We consider a Brown-Kuchar dust as a matter field in order to introduce a "clock" in quantum cosmology and adopt the Laplace-Beltrami operator-ordering. The Hamiltonian operator admits an infinite number of self-adjoint extensions corresponding to a one-parameter family of boundary conditions at the origin in the minisuperspace. For any value of the extension parameter in the boundary condition, the evolution of a wave function is unitary and the classical initial singularity is avoided and replaced by the big bounce in the quantum system. Exact wave functions show that the expectation value of the spatial volume of the universe obeys the classical time evolution in the late time but its variance diverges. |
1503.03657 | Hirosuke Kuwabara | H. Kuwabara, T. Yumibayashi and H. Harada | Time dependent Pais-Uhlenbeck oscillator and its decomposition | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Pais-Uhlenbeck(PU) oscillator is the simplest model with higher time
derivatives. Its properties were studied for a long time. In this paper, we
extend the 4th order free PU oscillator to a more non-trivial case, dubbed the
4th order time dependent PU oscillator, which has time dependent frequencies.
We show that this model cannot be decomposed into two harmonic oscillators in
contrast to the original PU oscillator. An interaction is added by the
coordinate transformation of Smilga.
| [
{
"created": "Thu, 12 Mar 2015 10:01:59 GMT",
"version": "v1"
}
] | 2015-03-13 | [
[
"Kuwabara",
"H.",
""
],
[
"Yumibayashi",
"T.",
""
],
[
"Harada",
"H.",
""
]
] | The Pais-Uhlenbeck(PU) oscillator is the simplest model with higher time derivatives. Its properties were studied for a long time. In this paper, we extend the 4th order free PU oscillator to a more non-trivial case, dubbed the 4th order time dependent PU oscillator, which has time dependent frequencies. We show that this model cannot be decomposed into two harmonic oscillators in contrast to the original PU oscillator. An interaction is added by the coordinate transformation of Smilga. |
2205.02499 | Jan Harms | Jan Harms, Ulyana Dupletsa, Biswajit Banerjee, Marica Branchesi, Boris
Goncharov, Andrea Maselli, Ana Carolina Silva Oliveira, Samuele Ronchini,
Jacopo Tissino | GWFish: A simulation software to evaluate parameter-estimation
capabilities of gravitational-wave detector networks | 15 pages, 9 figures | Astronomy and Computing 42, 100671 (2022) | 10.1016/j.ascom.2022.100671 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | An important step in the planning of future gravitational-wave (GW) detectors
and of the networks they will form is the estimation of their detection and
parameter-estimation capabilities, which is the basis of science-case studies.
Several future GW detectors have been proposed or are under development, which
might also operate and observe in parallel. These detectors include
terrestrial, lunar, and space-borne detectors. In this paper, we present
GWFish, a new software to simulate GW detector networks and to calculate
measurement uncertainties based on the Fisher-matrix approximation. GWFish
models the impact of detector motion on PE and makes it possible to analyze
multiband scenarios, i.e., observation of a GW signal by different detectors in
different frequency bands. We showcase a few examples for the Einstein
Telescope (ET) including the sky-localization of binary neutron stars, and ET's
capability to measure the polarization of GWs.
| [
{
"created": "Thu, 5 May 2022 08:22:04 GMT",
"version": "v1"
}
] | 2022-12-21 | [
[
"Harms",
"Jan",
""
],
[
"Dupletsa",
"Ulyana",
""
],
[
"Banerjee",
"Biswajit",
""
],
[
"Branchesi",
"Marica",
""
],
[
"Goncharov",
"Boris",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Oliveira",
"Ana Carolina Silva",
... | An important step in the planning of future gravitational-wave (GW) detectors and of the networks they will form is the estimation of their detection and parameter-estimation capabilities, which is the basis of science-case studies. Several future GW detectors have been proposed or are under development, which might also operate and observe in parallel. These detectors include terrestrial, lunar, and space-borne detectors. In this paper, we present GWFish, a new software to simulate GW detector networks and to calculate measurement uncertainties based on the Fisher-matrix approximation. GWFish models the impact of detector motion on PE and makes it possible to analyze multiband scenarios, i.e., observation of a GW signal by different detectors in different frequency bands. We showcase a few examples for the Einstein Telescope (ET) including the sky-localization of binary neutron stars, and ET's capability to measure the polarization of GWs. |
1401.8191 | Yury F. Pirogov | Yu. F. Pirogov | Scalar graviton as dark matter | 6 pages. Report presented at the Intern. Session-Conference of SNP
DFS RAS "Physics of Fundamental Interactions", Protvino, 5-8 November 2013 | Phys. Atom. Nucl. 78, 528 (2015) | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the report, the theory of unimodular bimode gravity built on principles of
unimodular gauge invariance/relativity and general covariance is exposed.
Besides the massless tensor graviton of General Relativity, the theory includes
an (almost) massless scalar graviton treated as the gravitational dark matter.
A spherically symmetric vacuum solution, describing the coherent
scalar-graviton field for the soft-core dark halos with the asymptotically flat
rotation curves, is demonstrated.
| [
{
"created": "Fri, 31 Jan 2014 15:14:41 GMT",
"version": "v1"
}
] | 2020-01-01 | [
[
"Pirogov",
"Yu. F.",
""
]
] | In the report, the theory of unimodular bimode gravity built on principles of unimodular gauge invariance/relativity and general covariance is exposed. Besides the massless tensor graviton of General Relativity, the theory includes an (almost) massless scalar graviton treated as the gravitational dark matter. A spherically symmetric vacuum solution, describing the coherent scalar-graviton field for the soft-core dark halos with the asymptotically flat rotation curves, is demonstrated. |
gr-qc/9710074 | Hisaaki Shinkai | Hisa-aki Shinkai (Washington Univ., St. Louis) and Gen Yoneda (Waseda
Univ.) | Lorentzian dynamics in the Ashtekar gravity | 3 pages, LaTeX, no figures, Proceedings of the 8th Marcel Grossmann
Meeting, Jerusalem, June 1997 (World Scientific); mprocl.sty is included | null | null | null | gr-qc | null | We examine the advantages of the SO(3)-ADM (Ashtekar) formulation of general
relativity, from the point of following the dynamics of the Lorentzian
spacetime in direction of applying this into numerical relativity. We describe
our strategy how to treat new constraints and reality conditions, together with
a proposal of new variables. We show an example of passing a degenerate point
in flat spacetime numerically by posing `reality recovering' conditions on
spacetime. We also discuss some available advantages in numerical relativity.
| [
{
"created": "Tue, 14 Oct 1997 20:47:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Shinkai",
"Hisa-aki",
"",
"Washington Univ., St. Louis"
],
[
"Yoneda",
"Gen",
"",
"Waseda\n Univ."
]
] | We examine the advantages of the SO(3)-ADM (Ashtekar) formulation of general relativity, from the point of following the dynamics of the Lorentzian spacetime in direction of applying this into numerical relativity. We describe our strategy how to treat new constraints and reality conditions, together with a proposal of new variables. We show an example of passing a degenerate point in flat spacetime numerically by posing `reality recovering' conditions on spacetime. We also discuss some available advantages in numerical relativity. |
gr-qc/0007054 | Stuart Samuel | Stuart Samuel (Columbia University and City College of New York) | The Earliest Phase Transition? | Latex, 10 pages, 1 figure, to appear in Nucl. Phys. B | Nucl.Phys. B585 (2000) 715-721 | 10.1016/S0550-3213(00)00431-4 | CU-TP-934 and CCNY-HEP-00/1 | gr-qc hep-th | null | The question of a phase transition in exiting the Planck epoch of the early
universe is addressed. An order parameter is proposed to help decide the issue,
and estimates are made concerning its behavior. Our analysis is suggestive that
a phase transition occurred.
| [
{
"created": "Fri, 21 Jul 2000 00:33:08 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Samuel",
"Stuart",
"",
"Columbia University and City College of New York"
]
] | The question of a phase transition in exiting the Planck epoch of the early universe is addressed. An order parameter is proposed to help decide the issue, and estimates are made concerning its behavior. Our analysis is suggestive that a phase transition occurred. |
2106.16012 | Lloren\c{c} Espinosa-Portal\'es | Llorenc Espinosa-Portales and Juan Garcia-Bellido | Covariant formulation of non-equilibrium thermodynamics in General
Relativity | 14 pages. Comments and references added. New section dealing with
real fluids added. Matches accepted version by PDU | Physics of the Dark Universe 34 (2021) 100893 | 10.1016/j.dark.2021.100893 | IFT-UAM/CSIC-21-74 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a generally-covariant formulation of non-equilibrium
thermodynamics in General Relativity. We find covariant entropic forces arising
from gradients of the entropy density, and a corresponding non-conservation of
the energy momentum tensor in terms of these forces. We also provide a
Hamiltonian formulation of General Relativity in the context of non-equilibrium
phenomena and write the Raychaudhuri equations for a congruence of geodesics.
We find that a fluid satisfying the strong energy condition could avoid
collapse for a positive and sufficiently large entropic-force contribution. We
then study the forces arising from gradients of the bulk entropy of
hydrodynamical matter, as well as the entropy of boundary terms in the action,
like those of black hole horizons. Finally, we apply the covariant formulation
of non-equilibrium thermodynamics to the expanding universe and obtain the
modified Friedmann equations, with an extra term corresponding to an entropic
force satisfying the second law of thermodynamics.
| [
{
"created": "Wed, 30 Jun 2021 12:20:56 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2021 15:27:56 GMT",
"version": "v2"
}
] | 2021-10-20 | [
[
"Espinosa-Portales",
"Llorenc",
""
],
[
"Garcia-Bellido",
"Juan",
""
]
] | We construct a generally-covariant formulation of non-equilibrium thermodynamics in General Relativity. We find covariant entropic forces arising from gradients of the entropy density, and a corresponding non-conservation of the energy momentum tensor in terms of these forces. We also provide a Hamiltonian formulation of General Relativity in the context of non-equilibrium phenomena and write the Raychaudhuri equations for a congruence of geodesics. We find that a fluid satisfying the strong energy condition could avoid collapse for a positive and sufficiently large entropic-force contribution. We then study the forces arising from gradients of the bulk entropy of hydrodynamical matter, as well as the entropy of boundary terms in the action, like those of black hole horizons. Finally, we apply the covariant formulation of non-equilibrium thermodynamics to the expanding universe and obtain the modified Friedmann equations, with an extra term corresponding to an entropic force satisfying the second law of thermodynamics. |
2408.04408 | BaoYu Tan | Baoyu Tan | Hawking radiation of magnetized particles via tunneling of Bardeen black
hole | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we calculated the emission rate of magnetized particles
passing through the event horizon of the Bardeen black hole by using the
Parikh-Wilczek method. The emission spectrum deviates from the pure thermal
spectrum, but conforms to the unitary principle of quantum mechanics. Our
results support the conservation of information.
| [
{
"created": "Thu, 8 Aug 2024 12:17:04 GMT",
"version": "v1"
}
] | 2024-08-09 | [
[
"Tan",
"Baoyu",
""
]
] | In this paper, we calculated the emission rate of magnetized particles passing through the event horizon of the Bardeen black hole by using the Parikh-Wilczek method. The emission spectrum deviates from the pure thermal spectrum, but conforms to the unitary principle of quantum mechanics. Our results support the conservation of information. |
1106.4318 | Sam Dolan Dr | Sam R. Dolan and Adrian C. Ottewill | Wave Propagation and Quasinormal Mode Excitation on Schwarzschild
Spacetime | 15 pages, 7 figures | Phys.Rev.D84:104002(2011) | 10.1103/PhysRevD.84.104002 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To seek a deeper understanding of wave propagation on the Schwarzschild
spacetime, we investigate the relationship between (i) the lightcone of an
event and its caustics (self-intersections), (ii) the large-$l$ asymptotics of
quasinormal (QN) modes, and (iii) the singular structure of the retarded Green
function (GF) for the scalar field. First, we recall that the GF has a
(partial) representation as a sum over QN modes. Next, we extend a
recently-developed expansion method to obtain asymptotic expressions for QN
wavefunctions and their residues. We employ these asymptotics to show
(approximately) that the QN mode sum is singular on the lightcone, and to
obtain approximations for the GF which are valid close to the lightcone. These
approximations confirm a little-known prediction: the singular part of the GF
undergoes a transition each time the lightcone passes through a caustic,
following a repeating four-fold sequence. We conclude with a discussion of
implications and extensions of this work.
| [
{
"created": "Tue, 21 Jun 2011 20:06:02 GMT",
"version": "v1"
}
] | 2011-11-03 | [
[
"Dolan",
"Sam R.",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | To seek a deeper understanding of wave propagation on the Schwarzschild spacetime, we investigate the relationship between (i) the lightcone of an event and its caustics (self-intersections), (ii) the large-$l$ asymptotics of quasinormal (QN) modes, and (iii) the singular structure of the retarded Green function (GF) for the scalar field. First, we recall that the GF has a (partial) representation as a sum over QN modes. Next, we extend a recently-developed expansion method to obtain asymptotic expressions for QN wavefunctions and their residues. We employ these asymptotics to show (approximately) that the QN mode sum is singular on the lightcone, and to obtain approximations for the GF which are valid close to the lightcone. These approximations confirm a little-known prediction: the singular part of the GF undergoes a transition each time the lightcone passes through a caustic, following a repeating four-fold sequence. We conclude with a discussion of implications and extensions of this work. |
gr-qc/9510049 | Jorge Pullin | Reinaldo Gleiser, Oscar Nicasio, Richard Price, Jorge Pullin | Second order perturbations of a Schwarzschild black hole | 6 pages, RevTeX, no figures, major revision, including several
changes in formulae and presentation | Class.Quant.Grav.13:L117-L124,1996 | 10.1088/0264-9381/13/10/001 | CGQG-96/6-4 | gr-qc astro-ph | null | We study the even-parity $\ell=2$ perturbations of a Schwarzschild black hole
to second order. The Einstein equations can be reduced to a single linear wave
equation with a potential and a source term. The source term is quadratic in
terms of the first order perturbations. This provides a formalism to address
the validity of many first order calculations of interest in astrophysics.
| [
{
"created": "Tue, 24 Oct 1995 22:41:54 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jun 1996 14:54:03 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Gleiser",
"Reinaldo",
""
],
[
"Nicasio",
"Oscar",
""
],
[
"Price",
"Richard",
""
],
[
"Pullin",
"Jorge",
""
]
] | We study the even-parity $\ell=2$ perturbations of a Schwarzschild black hole to second order. The Einstein equations can be reduced to a single linear wave equation with a potential and a source term. The source term is quadratic in terms of the first order perturbations. This provides a formalism to address the validity of many first order calculations of interest in astrophysics. |
gr-qc/0612022 | Lorenzo Iorio | Lorenzo Iorio, Matteo Luca Ruggiero | Constraining models of modified gravity with the double pulsar PSR
J0737-3039A/B system | LaTex2e, World Scientific macros, 10 pages, no figures, 1 table, 27
references. To appear in International Journal of Modern Physics A | Int.J.Mod.Phys.A22:5379-5389,2007 | 10.1142/S0217751X07038001 | null | gr-qc astro-ph nucl-th physics.space-ph | null | In this paper we use Delta P = -1.772341 +/- 13.153788 s between the
phenomenologically determined orbital period P_b of the PSR J0737-3039 double
pulsar system and the purely Keplerian period P^(0)=2\pi\sqrt{a^3/G(m_A+m_B)}
calculated with the system's parameters, determined independently of the third
Kepler law itself, in order to put constraints on some models of modified
gravity (f(R), Yukawa-like fifth force, MOND). The major source of error
affecting Delta P is not the one in the phenomenologically measured period
(\delta P_b=4 10^-6 s), but the systematic uncertainty \delta P^(0) in the
computed Keplerian one due to the relative semimajor axis a mainly caused, in
turn, by the errors in the ratio R of the pulsars' masses and in sin i. We get
|\kappa|< 0.8 10^-26 m^-2 for the parameter that in the f(R) framework is a
measure of the non linearity of the theory, |\alpha|< 5.5 10^-4 for the
fifth-force strength parameter (for \lambda\approx a=0.006 AU). The effects
predicted by the strong-acceleration regime of MOND are far too small to be
constrained with some effectiveness today and in the future as well. In view of
the continuous timing of such an important system, it might happen that in the
near future it will be possible to obtain somewhat tighter constraints.
| [
{
"created": "Mon, 4 Dec 2006 01:38:05 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Dec 2006 10:55:55 GMT",
"version": "v2"
},
{
"created": "Sun, 10 Dec 2006 11:42:57 GMT",
"version": "v3"
},
{
"created": "Mon, 18 Dec 2006 21:25:53 GMT",
"version": "v4"
},
{
"cre... | 2010-10-27 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Ruggiero",
"Matteo Luca",
""
]
] | In this paper we use Delta P = -1.772341 +/- 13.153788 s between the phenomenologically determined orbital period P_b of the PSR J0737-3039 double pulsar system and the purely Keplerian period P^(0)=2\pi\sqrt{a^3/G(m_A+m_B)} calculated with the system's parameters, determined independently of the third Kepler law itself, in order to put constraints on some models of modified gravity (f(R), Yukawa-like fifth force, MOND). The major source of error affecting Delta P is not the one in the phenomenologically measured period (\delta P_b=4 10^-6 s), but the systematic uncertainty \delta P^(0) in the computed Keplerian one due to the relative semimajor axis a mainly caused, in turn, by the errors in the ratio R of the pulsars' masses and in sin i. We get |\kappa|< 0.8 10^-26 m^-2 for the parameter that in the f(R) framework is a measure of the non linearity of the theory, |\alpha|< 5.5 10^-4 for the fifth-force strength parameter (for \lambda\approx a=0.006 AU). The effects predicted by the strong-acceleration regime of MOND are far too small to be constrained with some effectiveness today and in the future as well. In view of the continuous timing of such an important system, it might happen that in the near future it will be possible to obtain somewhat tighter constraints. |
1703.05860 | Andronikos Paliathanasis | Alex Giacomini, Sameerah Jamal, Genly Leon, Andronikos Paliathanasis
and Joel Saavedra | Dynamical Analysis of an Integrable Cubic Galileon Cosmological Model | 25 pages, 6 figures, to appear in Phys. Rev. D | Phys. Rev. D 95, 124060 (2017) | 10.1103/PhysRevD.95.124060 | null | gr-qc hep-th math-ph math.DS math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently a cubic Galileon cosmological model was derived by the assumption
that the field equations are invariant under the action of point
transformations. The cubic Galileon model admits a second conservation law
which means that the field equations form an integrable system. The analysis of
the critical points for this integrable model is the main subject of this work.
To perform the analysis, we work on dimensionless variables different from that
of the Hubble normalization. New critical points are derived while the
gravitational effects which follow from the cubic term are studied.
| [
{
"created": "Fri, 17 Mar 2017 01:04:40 GMT",
"version": "v1"
},
{
"created": "Wed, 31 May 2017 23:55:13 GMT",
"version": "v2"
}
] | 2017-11-28 | [
[
"Giacomini",
"Alex",
""
],
[
"Jamal",
"Sameerah",
""
],
[
"Leon",
"Genly",
""
],
[
"Paliathanasis",
"Andronikos",
""
],
[
"Saavedra",
"Joel",
""
]
] | Recently a cubic Galileon cosmological model was derived by the assumption that the field equations are invariant under the action of point transformations. The cubic Galileon model admits a second conservation law which means that the field equations form an integrable system. The analysis of the critical points for this integrable model is the main subject of this work. To perform the analysis, we work on dimensionless variables different from that of the Hubble normalization. New critical points are derived while the gravitational effects which follow from the cubic term are studied. |
1707.02874 | Andrea Addazi AndAdd | Andrea Addazi | Suppression of Bekenstein-Hawking radiation in $f(T)$-gravity | null | null | 10.1142/S0217751X1850001X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss semiclassical Nariai black holes in the framework of
$f(T)$-gravity. For a diagonal choice of tetrades, stable Nariai metrics can be
found, emitting Bekenstein-Hawking radiation in semiclassical limit. However,
for a non-diagonal choice of tetrades, evaporation and antievaporation
instabilities are turned on. In turn, this causes a back-reaction effect
suppressing the Bekenstein-Hawking radiation. In particular, evaporation
instabilities produce a new radiation -- different by Bekenstein-Hawking
emission -- non-violating unitarity in particle physics sector.
| [
{
"created": "Mon, 10 Jul 2017 14:25:10 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Addazi",
"Andrea",
""
]
] | We discuss semiclassical Nariai black holes in the framework of $f(T)$-gravity. For a diagonal choice of tetrades, stable Nariai metrics can be found, emitting Bekenstein-Hawking radiation in semiclassical limit. However, for a non-diagonal choice of tetrades, evaporation and antievaporation instabilities are turned on. In turn, this causes a back-reaction effect suppressing the Bekenstein-Hawking radiation. In particular, evaporation instabilities produce a new radiation -- different by Bekenstein-Hawking emission -- non-violating unitarity in particle physics sector. |
1111.4962 | Jorge Pullin | Nestor Alvarez, Rodolfo Gambini and Jorge Pullin | A local Hamiltonian for spherically symmetric gravity coupled to a
scalar field | 4 pages, no figures, RevTex, final published version | Phys. Rev. Lett. 108, 051301 (2012) | 10.1103/PhysRevLett.108.051301 | LSU-REL-112111 | gr-qc astro-ph.HE hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a gauge fixing of gravity coupled to a scalar field in spherical
symmetry such that the Hamiltonian is an integral over space of a local
density. Such a formulation had proved elusive over the years. As in any gauge
fixing, it works for a restricted set of initial data. We argue that the set
could be large enough to attempt a quantization the could include the important
case of an evaporating black hole.
| [
{
"created": "Mon, 21 Nov 2011 18:27:11 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Nov 2011 17:13:07 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Feb 2012 13:26:05 GMT",
"version": "v3"
}
] | 2012-02-13 | [
[
"Alvarez",
"Nestor",
""
],
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We present a gauge fixing of gravity coupled to a scalar field in spherical symmetry such that the Hamiltonian is an integral over space of a local density. Such a formulation had proved elusive over the years. As in any gauge fixing, it works for a restricted set of initial data. We argue that the set could be large enough to attempt a quantization the could include the important case of an evaporating black hole. |
0909.1171 | Mark D. Roberts | Mark D. Roberts | Fractional Derivative Cosmology | 11 pages, 2 figures | SOP Transactions on Theoretical Physics1(2014)310 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The degree by which a function can be differentiated need not be restricted
to integer values. Usually most of the field equations of physics are taken to
be second order, curiosity asks what happens if this is only approximately the
case and the field equations are nearly second order. For Robertson-Walker
cosmology there is a simple fractional modification of the Friedman and
conservation equations. In general fractional gravitational equations similar
to Einstein's are hard to define as this requires fractional derivative
geometry. What fractional derivative geometry might entail is briefly looked at
and it turns out that even asking very simple questions in two dimensions leads
to ambiguous or intractable results. A two dimensional line element which
depends on the Gamma-function is looked at.
| [
{
"created": "Mon, 7 Sep 2009 15:55:20 GMT",
"version": "v1"
}
] | 2014-06-23 | [
[
"Roberts",
"Mark D.",
""
]
] | The degree by which a function can be differentiated need not be restricted to integer values. Usually most of the field equations of physics are taken to be second order, curiosity asks what happens if this is only approximately the case and the field equations are nearly second order. For Robertson-Walker cosmology there is a simple fractional modification of the Friedman and conservation equations. In general fractional gravitational equations similar to Einstein's are hard to define as this requires fractional derivative geometry. What fractional derivative geometry might entail is briefly looked at and it turns out that even asking very simple questions in two dimensions leads to ambiguous or intractable results. A two dimensional line element which depends on the Gamma-function is looked at. |
2407.10587 | Pradip Kumar Chattopadhyay Dr. | Debadri Bhattacharjee and Pradip Kumar Chattopadhyay | Charged analogues of a singularity-free anisotropic compact star under
linear $f(Q)$- action | 20 pages, 16 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | This study simulates the characteristics of spherically symmetric,
anisotropic compact stellar bodies with electrical charge within the context of
the $f(Q)$ theory of gravity. Employing the Krori-Barua metric ansatz (K.D.
Krori, J. Barua, J. Phys. A: Math. Gen. 8 (1975) 508) along with a linear form
of $f(Q)$ model, {\it viz.}, $f(Q)=\alpha_{0}+\alpha_{1}Q$, we obtain a
tractable set of exact relativistic solutions of the field equations. A
specific form of charge $(q=q_{0}r^{3})$ is considered here for the present
analysis. Using the data sets of $\rho$ and $p_{r}$ along with the method of
curve fitting, we have obtained the best fit equation of state in the model,
which is incorporated in the numerical solutions of the TOV equations to
determine the maximum mass and radius in this scenario. With increasing charge
intensity $(q_{0})$ from 0.0002 to 0.0006, the maximum mass ranges from
$2.838-2.869~M_{\odot}$, and the corresponding radii range from
$12.0039-12.0822~Km$. Moreover, the predicted radii of some recently observed
pulsars and GW 190814 show that our model also complies with the estimated
radii based on the observational results. Our model is found to satisfy all the
characteristic features, such as behaviour of matter variables, causality
condition, energy constraints and stability criteria, which are pertinent in
the context of a stable stellar configuration to emerge as a viable and
physically acceptable stellar model in the framework of $f(Q)$ gravity.
| [
{
"created": "Mon, 15 Jul 2024 10:08:31 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Jul 2024 09:56:20 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Aug 2024 05:18:08 GMT",
"version": "v3"
}
] | 2024-08-02 | [
[
"Bhattacharjee",
"Debadri",
""
],
[
"Chattopadhyay",
"Pradip Kumar",
""
]
] | This study simulates the characteristics of spherically symmetric, anisotropic compact stellar bodies with electrical charge within the context of the $f(Q)$ theory of gravity. Employing the Krori-Barua metric ansatz (K.D. Krori, J. Barua, J. Phys. A: Math. Gen. 8 (1975) 508) along with a linear form of $f(Q)$ model, {\it viz.}, $f(Q)=\alpha_{0}+\alpha_{1}Q$, we obtain a tractable set of exact relativistic solutions of the field equations. A specific form of charge $(q=q_{0}r^{3})$ is considered here for the present analysis. Using the data sets of $\rho$ and $p_{r}$ along with the method of curve fitting, we have obtained the best fit equation of state in the model, which is incorporated in the numerical solutions of the TOV equations to determine the maximum mass and radius in this scenario. With increasing charge intensity $(q_{0})$ from 0.0002 to 0.0006, the maximum mass ranges from $2.838-2.869~M_{\odot}$, and the corresponding radii range from $12.0039-12.0822~Km$. Moreover, the predicted radii of some recently observed pulsars and GW 190814 show that our model also complies with the estimated radii based on the observational results. Our model is found to satisfy all the characteristic features, such as behaviour of matter variables, causality condition, energy constraints and stability criteria, which are pertinent in the context of a stable stellar configuration to emerge as a viable and physically acceptable stellar model in the framework of $f(Q)$ gravity. |
0707.2726 | Marco Valerio Battisti | Marco Valerio Battisti and Giovanni Montani | Quantum Dynamics of the Taub Universe in a Generalized Uncertainty
Principle framework | 10 pages, 4 figures; v2: section added, to appear on PRD | Phys.Rev.D77:023518,2008 | 10.1103/PhysRevD.77.023518 | null | gr-qc hep-th | null | The implications of a Generalized Uncertainty Principle on the Taub
cosmological model are investigated. The model is studied in the ADM reduction
of the dynamics and therefore a time variable is ruled out. Such a variable is
quantized in a canonical way and the only physical degree of freedom of the
system (related to the Universe anisotropy) is quantized by means of a modified
Heisenberg algebra. The analysis is performed at both classical and quantum
level. In particular, at quantum level, the motion of wave packets is
investigated. The two main results obtained are as follows. i) The classical
singularity is probabilistically suppressed. The Universe exhibits a stationary
behavior and the probability amplitude is peaked in a determinate region. ii)
The GUP wave packets provide the right behavior in the establishment of a
quasi-isotropic configuration for the Universe.
| [
{
"created": "Wed, 18 Jul 2007 14:19:18 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Dec 2007 09:41:46 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Battisti",
"Marco Valerio",
""
],
[
"Montani",
"Giovanni",
""
]
] | The implications of a Generalized Uncertainty Principle on the Taub cosmological model are investigated. The model is studied in the ADM reduction of the dynamics and therefore a time variable is ruled out. Such a variable is quantized in a canonical way and the only physical degree of freedom of the system (related to the Universe anisotropy) is quantized by means of a modified Heisenberg algebra. The analysis is performed at both classical and quantum level. In particular, at quantum level, the motion of wave packets is investigated. The two main results obtained are as follows. i) The classical singularity is probabilistically suppressed. The Universe exhibits a stationary behavior and the probability amplitude is peaked in a determinate region. ii) The GUP wave packets provide the right behavior in the establishment of a quasi-isotropic configuration for the Universe. |
gr-qc/0102052 | Gregory James Stephens | G. J. Stephens and B. L. Hu | Notes on Black Hole Phase Transitions | 9 pages, RevTex, 4 incorporated eps figures, To appear in Int. J.
Theor. Phys | Int.J.Theor.Phys. 40 (2001) 2183-2200 | null | UMDPP-01-034, LA-UR-01-0749 | gr-qc cond-mat hep-th | null | In these notes we present a summary of existing ideas about phase transitions
of black hole spacetimes in semiclassical gravity and offer some thoughts on
three possible scenarios by which these transitions could take place. Our first
theme is ilustrated by a quantum atomic black hole system, generalizing to
finite-temperature a model originally offered by Bekenstein. In this
equilibrium atomic model, the black hole phase transition is realized as the
abrupt excitation of a high energy state, suggesting analogies with the study
of two-level atoms. Our second theme argues that the black hole system shares
similarities with the defect-mediated Kosterlitz-Thouless transition in
condensed matter. These similarities suggest that the black hole phase
transition may be more fully understood by focusing upon the dynamics of black
holes and white holes, the spacetime analogy of vortex and anti-vortex
topological defects. Finally we compare the black hole phase transition to
another transition driven by an exponentially increasing density of states, the
Hagedorn transition first found in hadron physics in the context of dual models
or the old string theory. In modern string theory, the Hagedorn transition is
linked by the Maldacena conjecture to the Hawking-Page black hole phase
transition in Anti-deSitter space, as observed by Witten. Understanding the
dynamics of the Hagedorn transition may thus yield insight into the dynamics of
the black hole phase transition. We argue that characteristics of the Hagedorn
transition are already contained within classical string systems where a
nonperturbative and dynamical analysis is possible.
| [
{
"created": "Mon, 12 Feb 2001 21:15:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Stephens",
"G. J.",
""
],
[
"Hu",
"B. L.",
""
]
] | In these notes we present a summary of existing ideas about phase transitions of black hole spacetimes in semiclassical gravity and offer some thoughts on three possible scenarios by which these transitions could take place. Our first theme is ilustrated by a quantum atomic black hole system, generalizing to finite-temperature a model originally offered by Bekenstein. In this equilibrium atomic model, the black hole phase transition is realized as the abrupt excitation of a high energy state, suggesting analogies with the study of two-level atoms. Our second theme argues that the black hole system shares similarities with the defect-mediated Kosterlitz-Thouless transition in condensed matter. These similarities suggest that the black hole phase transition may be more fully understood by focusing upon the dynamics of black holes and white holes, the spacetime analogy of vortex and anti-vortex topological defects. Finally we compare the black hole phase transition to another transition driven by an exponentially increasing density of states, the Hagedorn transition first found in hadron physics in the context of dual models or the old string theory. In modern string theory, the Hagedorn transition is linked by the Maldacena conjecture to the Hawking-Page black hole phase transition in Anti-deSitter space, as observed by Witten. Understanding the dynamics of the Hagedorn transition may thus yield insight into the dynamics of the black hole phase transition. We argue that characteristics of the Hagedorn transition are already contained within classical string systems where a nonperturbative and dynamical analysis is possible. |
1801.10529 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | The Reconstruction of $f(\phi)R$ and Mimetic Gravity from Viable
Slow-roll Inflation | 28 pages, NPB Accepted | null | 10.1016/j.nuclphysb.2018.01.027 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we extend the bottom-up reconstruction framework of $F(R)$
gravity to other modified gravities, and in particular for $f(\phi)R$ and
mimetic $F(R)$ gravities. We investigate which are the important conditions in
order for the method to work, and we study several viable cosmological
evolutions, focusing on the inflationary era. Particularly, for the $f(\phi)R$
theory case, we specify the functional form of the Hubble rate and of the
scalar-to-tensor ratio as a function of the $e$-foldings number and
accordingly, the rest of the physical quantities and also the slow-roll and the
corresponding observational indices can be calculated. The same method is
applied in the mimetic $F(R)$ gravity case, and in both cases we thoroughly
analyze the resulting free parameter space, in order to show that the viability
of the models presented is guaranteed and secondly that there is a wide range
of values of the free parameters for which the viability of the models occurs.
In addition, the reconstruction method is also studied in the context of
mimetic $F(R)=R$ gravity. As we demonstrate, the resulting theory is viable,
and also in this case, only the scalar-to-tensor ratio needs to be specified,
since the rest follow from this condition. Finally, we discuss in brief how the
reconstruction method could function for other modified gravities.
| [
{
"created": "Wed, 31 Jan 2018 16:29:19 GMT",
"version": "v1"
}
] | 2018-03-14 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | In this work, we extend the bottom-up reconstruction framework of $F(R)$ gravity to other modified gravities, and in particular for $f(\phi)R$ and mimetic $F(R)$ gravities. We investigate which are the important conditions in order for the method to work, and we study several viable cosmological evolutions, focusing on the inflationary era. Particularly, for the $f(\phi)R$ theory case, we specify the functional form of the Hubble rate and of the scalar-to-tensor ratio as a function of the $e$-foldings number and accordingly, the rest of the physical quantities and also the slow-roll and the corresponding observational indices can be calculated. The same method is applied in the mimetic $F(R)$ gravity case, and in both cases we thoroughly analyze the resulting free parameter space, in order to show that the viability of the models presented is guaranteed and secondly that there is a wide range of values of the free parameters for which the viability of the models occurs. In addition, the reconstruction method is also studied in the context of mimetic $F(R)=R$ gravity. As we demonstrate, the resulting theory is viable, and also in this case, only the scalar-to-tensor ratio needs to be specified, since the rest follow from this condition. Finally, we discuss in brief how the reconstruction method could function for other modified gravities. |
2001.00229 | Markus P\"ossel | Markus P\"ossel | The Shapiro time delay and the equivalence principle | 14 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational time delay of light, also called the Shapiro time delay, is
one of the four classical tests of Einstein's theory of general relativity.
This article derives the Newtonian version of the Shapiro time delay from
Einstein's principle of equivalence and the Newtonian description of gravity,
in a manner that is accessible to undergraduate students and advanced
high-school students. The derivation can be used as a pedagogical tool, similar
to the way that simplified derivations of the gravitational deflection of light
are used in teaching about general relativity without making use of the more
advanced mathematical concepts. Next, we compare different general-relativistic
derivations of the Shapiro time delay from the Schwarzschild metric, which
leads to an instructive example for the challenges of formulating the
post-Newtonian limit of Einstein's theory. The article also describes simple
applications of the time delay formula to observations within our solar system,
as well as to binary pulsars.
| [
{
"created": "Tue, 31 Dec 2019 13:52:00 GMT",
"version": "v1"
}
] | 2020-01-03 | [
[
"Pössel",
"Markus",
""
]
] | The gravitational time delay of light, also called the Shapiro time delay, is one of the four classical tests of Einstein's theory of general relativity. This article derives the Newtonian version of the Shapiro time delay from Einstein's principle of equivalence and the Newtonian description of gravity, in a manner that is accessible to undergraduate students and advanced high-school students. The derivation can be used as a pedagogical tool, similar to the way that simplified derivations of the gravitational deflection of light are used in teaching about general relativity without making use of the more advanced mathematical concepts. Next, we compare different general-relativistic derivations of the Shapiro time delay from the Schwarzschild metric, which leads to an instructive example for the challenges of formulating the post-Newtonian limit of Einstein's theory. The article also describes simple applications of the time delay formula to observations within our solar system, as well as to binary pulsars. |
1611.03479 | Ramil Izmailov | Kamal K. Nandi, Ramil N. Izmailov, Almir A. Yanbekov and Azat A.
Shayakhmetov | Ring-down gravitational waves and lensing observables: How far can a
wormhole mimic those of a black hole? | 24 pages, 1 figure | Phys. Rev. D 95, 104011 (2017) | 10.1103/PhysRevD.95.104011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been argued that the recently detected ring-down gravity waveforms
could be indicative only of the presence of light rings in a horizonless
object, such as a surgical Schwarzschild wormhole, with the frequencies
differing drastically from those of the horizon quasinormal mode frequencies
$\omega _{\text{QNM}}$ at late times. While the possibility of such a
horizonless alternative is novel by itself, we show by the example of
Ellis-Bronnikov wormhole that the differences in $\omega _{\text{QNM}}$ in the
eikonal limit (large $l$) need not be drastic. This result will be reached by
exploiting the connection between $\omega _{\text{QNM}}$ and the Bozza strong
field lensing parameters. We shall also show that the lensing observables of
the Ellis-Bronnikov wormhole can also be very close to those of a black hole
(say, SgrA$^{\ast }$ hosted by our galaxy) of the same mass. This situation
indicates that the ring-down frequencies and lensing observables of the
Ellis-Bronnikov wormhole can remarkably mimic those of a black hole. The
constraint on wormhole parameter $\gamma $ imposed by experimental accuracy is
briefly discussed. We also provide independent arguments supporting the
stability of the Ellis-Bronnikov wormhole proven recently.
| [
{
"created": "Tue, 8 Nov 2016 05:43:13 GMT",
"version": "v1"
},
{
"created": "Fri, 19 May 2017 11:18:47 GMT",
"version": "v2"
}
] | 2017-05-22 | [
[
"Nandi",
"Kamal K.",
""
],
[
"Izmailov",
"Ramil N.",
""
],
[
"Yanbekov",
"Almir A.",
""
],
[
"Shayakhmetov",
"Azat A.",
""
]
] | It has been argued that the recently detected ring-down gravity waveforms could be indicative only of the presence of light rings in a horizonless object, such as a surgical Schwarzschild wormhole, with the frequencies differing drastically from those of the horizon quasinormal mode frequencies $\omega _{\text{QNM}}$ at late times. While the possibility of such a horizonless alternative is novel by itself, we show by the example of Ellis-Bronnikov wormhole that the differences in $\omega _{\text{QNM}}$ in the eikonal limit (large $l$) need not be drastic. This result will be reached by exploiting the connection between $\omega _{\text{QNM}}$ and the Bozza strong field lensing parameters. We shall also show that the lensing observables of the Ellis-Bronnikov wormhole can also be very close to those of a black hole (say, SgrA$^{\ast }$ hosted by our galaxy) of the same mass. This situation indicates that the ring-down frequencies and lensing observables of the Ellis-Bronnikov wormhole can remarkably mimic those of a black hole. The constraint on wormhole parameter $\gamma $ imposed by experimental accuracy is briefly discussed. We also provide independent arguments supporting the stability of the Ellis-Bronnikov wormhole proven recently. |
gr-qc/9709063 | null | Dieter R. Brill (University of Maryland) | The Cavendish Experiment in General Relativity | 8 pages, LaTeX. Contribution to Festschrift volume for Engelbert
Schucking | null | null | UMDGR 89-40 | gr-qc | null | Solutions of Einstein's equations are discussed in which the ``gravitational
force" is balanced by an electrical force, and which can serve as models for
the Cavendish experiment.
| [
{
"created": "Wed, 24 Sep 1997 20:25:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Brill",
"Dieter R.",
"",
"University of Maryland"
]
] | Solutions of Einstein's equations are discussed in which the ``gravitational force" is balanced by an electrical force, and which can serve as models for the Cavendish experiment. |
0806.2186 | Celine Cattoen | Celine Cattoen (Victoria University of Wellington), Matt Visser
(Victoria University of Wellington) | Bounding the Hubble flow in terms of the w parameter | 15 pages | JCAP0811:024,2008 | 10.1088/1475-7516/2008/11/024 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The last decade has seen increasing efforts to circumscribe and bound the
cosmological Hubble flow in terms of model-independent constraints on the
cosmological fluid - such as, for instance, the classical energy conditions of
general relativity. Quite a bit can certainly be said in this regard, but much
more refined bounds can be obtained by placing more precise constraints (either
theoretical or observational) on the cosmological fluid. In particular, the use
of the w-parameter (w=p/rho) has become increasingly common as a surrogate for
trying to say something about the cosmological equation of state. Herein we
explore the extent to which a constraint on the w-parameter leads to useful and
nontrivial constraints on the Hubble flow, in terms of constraints on density
rho(z), Hubble parameter H(z), density parameter Omega(z), cosmological
distances d(z), and lookback time T(z). In contrast to other partial results in
the literature, we carry out the computations for arbitrary values of the space
curvature k in [-1,0,+1], equivalently for arbitrary Omega_0 <= 1.
| [
{
"created": "Fri, 13 Jun 2008 05:27:07 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Cattoen",
"Celine",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | The last decade has seen increasing efforts to circumscribe and bound the cosmological Hubble flow in terms of model-independent constraints on the cosmological fluid - such as, for instance, the classical energy conditions of general relativity. Quite a bit can certainly be said in this regard, but much more refined bounds can be obtained by placing more precise constraints (either theoretical or observational) on the cosmological fluid. In particular, the use of the w-parameter (w=p/rho) has become increasingly common as a surrogate for trying to say something about the cosmological equation of state. Herein we explore the extent to which a constraint on the w-parameter leads to useful and nontrivial constraints on the Hubble flow, in terms of constraints on density rho(z), Hubble parameter H(z), density parameter Omega(z), cosmological distances d(z), and lookback time T(z). In contrast to other partial results in the literature, we carry out the computations for arbitrary values of the space curvature k in [-1,0,+1], equivalently for arbitrary Omega_0 <= 1. |
1012.2692 | Mohammad Malekjani | M. Malekjani, A. Khodam-Mohammadi and M. Taji | Cosmological implications of interacting polytropic gas dark energy
model in non-flat universe | 19 pages, 3 figures, accepted by ijtp | International Journal of Theoretical Physics:, Volume 50,
3112-3124, 2011 | 10.1007/s10773-011-0812-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The polytropic gas model is investigated as an interacting dark energy
scenario. The cosmological implications of the model including the evolution of
EoS parameter $w_{\Lambda}$, energy density $\Omega_{\Lambda}$ and deceleration
parameter $q$ are investigated. We show that, depending on the parameter of
model, the interacting polytropic gas can behave as a quintessence or phantom
dark energy. In this model, the phantom divide is crossed from below to up. The
evolution of $q$ in the context of polytropic gas dark energy model represents
the decelerated phase at the early time and accelerated phase later. The
singularity of this model is also discussed. Eventually, we establish the
correspondence between interacting polytropic gas model with tachyon, K-essence
and dilaton scalar fields. The potential and the dynamics of these scalar field
models are reconstructed according to the evolution of interacting polytropic
gas.
| [
{
"created": "Mon, 13 Dec 2010 11:10:19 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Apr 2011 13:10:52 GMT",
"version": "v2"
}
] | 2015-05-20 | [
[
"Malekjani",
"M.",
""
],
[
"Khodam-Mohammadi",
"A.",
""
],
[
"Taji",
"M.",
""
]
] | The polytropic gas model is investigated as an interacting dark energy scenario. The cosmological implications of the model including the evolution of EoS parameter $w_{\Lambda}$, energy density $\Omega_{\Lambda}$ and deceleration parameter $q$ are investigated. We show that, depending on the parameter of model, the interacting polytropic gas can behave as a quintessence or phantom dark energy. In this model, the phantom divide is crossed from below to up. The evolution of $q$ in the context of polytropic gas dark energy model represents the decelerated phase at the early time and accelerated phase later. The singularity of this model is also discussed. Eventually, we establish the correspondence between interacting polytropic gas model with tachyon, K-essence and dilaton scalar fields. The potential and the dynamics of these scalar field models are reconstructed according to the evolution of interacting polytropic gas. |
gr-qc/9410010 | Junichi Iwasaki | Junichi Iwasaki (University of Pittsburgh) | A reformulation of the Ponzano-Regge quantum gravity model in terms of
surfaces | latex 11 pages | null | null | null | gr-qc hep-th | null | We reformulate the Ponzano-Regge quantum gravity model in terms of surfaces
on a 3-dimensional simplex lattice. This formulation (1) has a clear relation
to the loop representation of the canonical quantum general relativity in
3-dimensions, (2) may have a 4-dimensional analogue, in contrast to the 6-j
symbolic formalism of the Ponzano-Regge model, and (3) is purely a theory of
surfaces, in the sense that it does not include any field variables; hence it
is coordinate-free on the surface and background-free in spacetime. We discuss
implications and applications of this formulation.
| [
{
"created": "Mon, 10 Oct 1994 23:49:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Iwasaki",
"Junichi",
"",
"University of Pittsburgh"
]
] | We reformulate the Ponzano-Regge quantum gravity model in terms of surfaces on a 3-dimensional simplex lattice. This formulation (1) has a clear relation to the loop representation of the canonical quantum general relativity in 3-dimensions, (2) may have a 4-dimensional analogue, in contrast to the 6-j symbolic formalism of the Ponzano-Regge model, and (3) is purely a theory of surfaces, in the sense that it does not include any field variables; hence it is coordinate-free on the surface and background-free in spacetime. We discuss implications and applications of this formulation. |
1607.02380 | Karim Noui KN | Jibril Ben Achour, Karim Noui and Alejandro Perez | Analytic continuation of the rotating black hole state counting | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In loop quantum gravity, a spherical black hole can be described in terms of
a Chern-Simons theory on a punctured 2-sphere. The sphere represents the
horizon. The punctures are the edges of spin-networks in the bulk which cross
the horizon and carry quanta of area. One can generalize this construction and
model a rotating black hole by adding an extra puncture colored with the
angular momentum J in the 2-sphere. We compute the entropy of rotating black
holes in this model and study its semi-classical limit. After performing an
analytic continuation which sends the Barbero-Immirzi parameter to +/- i, we
show that the leading order term in the semi-classical expansion of the entropy
reproduces the Bekenstein-Hawking law independently of the value of J.
| [
{
"created": "Fri, 8 Jul 2016 14:28:26 GMT",
"version": "v1"
}
] | 2016-07-11 | [
[
"Achour",
"Jibril Ben",
""
],
[
"Noui",
"Karim",
""
],
[
"Perez",
"Alejandro",
""
]
] | In loop quantum gravity, a spherical black hole can be described in terms of a Chern-Simons theory on a punctured 2-sphere. The sphere represents the horizon. The punctures are the edges of spin-networks in the bulk which cross the horizon and carry quanta of area. One can generalize this construction and model a rotating black hole by adding an extra puncture colored with the angular momentum J in the 2-sphere. We compute the entropy of rotating black holes in this model and study its semi-classical limit. After performing an analytic continuation which sends the Barbero-Immirzi parameter to +/- i, we show that the leading order term in the semi-classical expansion of the entropy reproduces the Bekenstein-Hawking law independently of the value of J. |
2002.06225 | Vassilios Mewes | Vassilios Mewes, Yosef Zlochower, Manuela Campanelli, Thomas W.
Baumgarte, Zachariah B. Etienne, Federico G. Lopez Armengol, Federico
Cipolletta | Numerical relativity in spherical coordinates: A new dynamical spacetime
and general relativistic MHD evolution framework for the Einstein Toolkit | 29 pages, 13 figures, published in Physical Review D | Phys. Rev. D 101, 104007 (2020) | 10.1103/PhysRevD.101.104007 | null | gr-qc astro-ph.HE physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present SphericalNR, a new framework for the publicly available Einstein
Toolkit that numerically solves the Einstein field equations coupled to the
equations of general relativistic magnetohydrodynamics (GRMHD) in a 3+1 split
of spacetime in spherical coordinates without symmetry assumptions. The
spacetime evolution is performed using reference-metric versions of either the
Baumgarte-Shapiro-Shibata-Nakamura equations or the fully covariant and
conformal Z4 system with constraint damping. We have developed a
reference-metric version of the Valencia formulation of GRMHD with a vector
potential method, guaranteeing the absence of magnetic monopoles during the
evolution. In our framework, every dynamical field (both spacetime and matter)
is evolved using its components in an orthonormal basis with respect to the
spherical reference-metric. Furthermore, all geometric information about the
spherical coordinate system is encoded in source terms appearing in the
evolution equations. This allows for the straightforward extension of Cartesian
high-resolution shock-capturing finite volume codes to use spherical
coordinates with our framework. To this end, we have adapted GRHydro, a
Cartesian finite volume GRMHD code already available in the Einstein Toolkit,
to use spherical coordinates. We present the full evolution equations of the
framework, as well as details of its implementation in the Einstein Toolkit. We
validate SphericalNR by demonstrating it passes a variety of challenging code
tests in static and dynamical spacetimes.
| [
{
"created": "Fri, 14 Feb 2020 19:28:53 GMT",
"version": "v1"
},
{
"created": "Tue, 5 May 2020 17:21:29 GMT",
"version": "v2"
}
] | 2020-05-06 | [
[
"Mewes",
"Vassilios",
""
],
[
"Zlochower",
"Yosef",
""
],
[
"Campanelli",
"Manuela",
""
],
[
"Baumgarte",
"Thomas W.",
""
],
[
"Etienne",
"Zachariah B.",
""
],
[
"Armengol",
"Federico G. Lopez",
""
],
[
"Cipolletta... | We present SphericalNR, a new framework for the publicly available Einstein Toolkit that numerically solves the Einstein field equations coupled to the equations of general relativistic magnetohydrodynamics (GRMHD) in a 3+1 split of spacetime in spherical coordinates without symmetry assumptions. The spacetime evolution is performed using reference-metric versions of either the Baumgarte-Shapiro-Shibata-Nakamura equations or the fully covariant and conformal Z4 system with constraint damping. We have developed a reference-metric version of the Valencia formulation of GRMHD with a vector potential method, guaranteeing the absence of magnetic monopoles during the evolution. In our framework, every dynamical field (both spacetime and matter) is evolved using its components in an orthonormal basis with respect to the spherical reference-metric. Furthermore, all geometric information about the spherical coordinate system is encoded in source terms appearing in the evolution equations. This allows for the straightforward extension of Cartesian high-resolution shock-capturing finite volume codes to use spherical coordinates with our framework. To this end, we have adapted GRHydro, a Cartesian finite volume GRMHD code already available in the Einstein Toolkit, to use spherical coordinates. We present the full evolution equations of the framework, as well as details of its implementation in the Einstein Toolkit. We validate SphericalNR by demonstrating it passes a variety of challenging code tests in static and dynamical spacetimes. |
1805.11950 | Mohamed Ould El Hadj | Antoine Folacci and Mohamed Ould El Hadj | Electromagnetic radiation generated by a charged particle plunging into
a Schwarzschild black hole: Multipolar waveforms and ringdowns | v2: Figures 1 and 7 modified. Minor changes in the text to match the
published version | Phys. Rev. D 98, 024021 (2018) | 10.1103/PhysRevD.98.024021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Electromagnetic radiation emitted by a charged particle plunging from
slightly below the innermost stable circular orbit into a Schwarzschild black
hole is examined. Both even- and odd-parity electromagnetic perturbations are
considered. They are described by using gauge invariant master functions and
the regularized multipolar waveforms as well as their unregularized
counterparts constructed from the quasinormal-mode spectrum are obtained for
arbitrary directions of observation and, in particular, outside the orbital
plane of the plunging particle. They are in excellent agreement and the results
especially emphasize the impact of higher harmonics on the distortion of the
waveforms.
| [
{
"created": "Wed, 30 May 2018 13:40:15 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Jul 2018 19:19:49 GMT",
"version": "v2"
}
] | 2018-07-16 | [
[
"Folacci",
"Antoine",
""
],
[
"Hadj",
"Mohamed Ould El",
""
]
] | Electromagnetic radiation emitted by a charged particle plunging from slightly below the innermost stable circular orbit into a Schwarzschild black hole is examined. Both even- and odd-parity electromagnetic perturbations are considered. They are described by using gauge invariant master functions and the regularized multipolar waveforms as well as their unregularized counterparts constructed from the quasinormal-mode spectrum are obtained for arbitrary directions of observation and, in particular, outside the orbital plane of the plunging particle. They are in excellent agreement and the results especially emphasize the impact of higher harmonics on the distortion of the waveforms. |
1804.00643 | Ali \"Ovg\"un Dr. | Kimet Jusufi, Ali \"Ovg\"un, Joel Saavedra, P. A. Gonz\'alez and Yerko
V\'asquez | Deflection of light by rotating regular black holes using the
Gauss-Bonnet theorem | 19 pages and 5 figures. Accepted for publication in Physical Review D | Phys. Rev. D 97, 124024 (2018) | 10.1103/PhysRevD.97.124024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the weak gravitational lensing in the spacetime of
rotating regular black hole geometries such as Ayon-Beato-Garc\'ia (ABG),
Bardeen, and Hayward black holes. We calculate the deflection angle of light
using the Gauss-Bonnet theorem (GBT) and show that the deflection of light can
be viewed as a partially topological effect in which the deflection angle can
be calculated by considering a domain outside of the light ray applied to the
black hole optical geometries. Then, we demonstrate also the deflection angle
via the geodesics formalism for these black holes to verify our results and
explore the differences with the Kerr solution. These black holes have in
addition to the total mass and rotation parameter, different parameters as
electric charge, magnetic charge, and deviation parameter. Newsworthy, we find
that the deflection of light has correction terms coming from these parameters
which generalizes the Kerr deflection angle.
| [
{
"created": "Mon, 2 Apr 2018 17:42:10 GMT",
"version": "v1"
},
{
"created": "Mon, 28 May 2018 02:15:11 GMT",
"version": "v2"
}
] | 2018-06-12 | [
[
"Jusufi",
"Kimet",
""
],
[
"Övgün",
"Ali",
""
],
[
"Saavedra",
"Joel",
""
],
[
"González",
"P. A.",
""
],
[
"Vásquez",
"Yerko",
""
]
] | In this paper, we study the weak gravitational lensing in the spacetime of rotating regular black hole geometries such as Ayon-Beato-Garc\'ia (ABG), Bardeen, and Hayward black holes. We calculate the deflection angle of light using the Gauss-Bonnet theorem (GBT) and show that the deflection of light can be viewed as a partially topological effect in which the deflection angle can be calculated by considering a domain outside of the light ray applied to the black hole optical geometries. Then, we demonstrate also the deflection angle via the geodesics formalism for these black holes to verify our results and explore the differences with the Kerr solution. These black holes have in addition to the total mass and rotation parameter, different parameters as electric charge, magnetic charge, and deviation parameter. Newsworthy, we find that the deflection of light has correction terms coming from these parameters which generalizes the Kerr deflection angle. |
2403.16363 | Tomoya Tachinami | Tomoya Tachinami and Yuuiti Sendouda | Non-relativistic stellar structure in the Fierz--Pauli theory and
generic linear massive gravity | 17 pages, 9 figures | null | null | null | gr-qc astro-ph.HE astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the structure of static spherical stars composed of non-relativistic
matter in linear massive gravity with or without the Fierz-Pauli (FP) tuning.
Adopting a polytropic equation of state, we construct master differential
equations for the stellar profile function, which is fourth order in the FP
theory or sixth order in generic non-FP theories, where the difference in the
differential order reflects the presence of a ghost spin-0 graviton in the
latter. In both cases, even when the spin-0 ghost is present, we find exact
solutions with finite radius for the polytropic indices n = 0 and 1. Analyzing
the dependences of the stellar radius, mass, and Yukawa charge on the graviton
masses, we observe that a discontinuous behavior arises in the massless limit
of the FP theory similarly to the van Dam-Veltman-Zakharov discontinuity, while
it is absent in non-FP theories. We discuss rough observational constraints on
the graviton masses.
| [
{
"created": "Mon, 25 Mar 2024 01:58:39 GMT",
"version": "v1"
}
] | 2024-03-26 | [
[
"Tachinami",
"Tomoya",
""
],
[
"Sendouda",
"Yuuiti",
""
]
] | We study the structure of static spherical stars composed of non-relativistic matter in linear massive gravity with or without the Fierz-Pauli (FP) tuning. Adopting a polytropic equation of state, we construct master differential equations for the stellar profile function, which is fourth order in the FP theory or sixth order in generic non-FP theories, where the difference in the differential order reflects the presence of a ghost spin-0 graviton in the latter. In both cases, even when the spin-0 ghost is present, we find exact solutions with finite radius for the polytropic indices n = 0 and 1. Analyzing the dependences of the stellar radius, mass, and Yukawa charge on the graviton masses, we observe that a discontinuous behavior arises in the massless limit of the FP theory similarly to the van Dam-Veltman-Zakharov discontinuity, while it is absent in non-FP theories. We discuss rough observational constraints on the graviton masses. |
1801.00834 | James Edholm | James Edholm | Revealing Infinite Derivative Gravity's true potential: The weak-field
limit around de Sitter backgrounds | 6 pages | Phys. Rev. D 97, 064011 (2018) | 10.1103/PhysRevD.97.064011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity is known to produce singularities in the potential
generated by a point source. Our universe can be modelled as a de Sitter (dS)
metric and we show that ghost-free Infinite Derivative Gravity (IDG) produces a
non-singular potential around a dS background, while returning to the GR
prediction at large distances. We also show that although there are an
apparently infinite number of coefficients in the theory, only a finite number
actually affect the predictions.
By writing the linearised equations of motion in a simplified form, we find
that at distances below the Hubble length scale, the difference between the IDG
potential around a flat background and around a de Sitter background is
negligible.
| [
{
"created": "Tue, 2 Jan 2018 20:59:57 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jan 2018 15:34:56 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Feb 2018 11:38:31 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Feb 2018 13:51:28 GMT",
"version": "v4"
},
{
"creat... | 2018-04-06 | [
[
"Edholm",
"James",
""
]
] | General Relativity is known to produce singularities in the potential generated by a point source. Our universe can be modelled as a de Sitter (dS) metric and we show that ghost-free Infinite Derivative Gravity (IDG) produces a non-singular potential around a dS background, while returning to the GR prediction at large distances. We also show that although there are an apparently infinite number of coefficients in the theory, only a finite number actually affect the predictions. By writing the linearised equations of motion in a simplified form, we find that at distances below the Hubble length scale, the difference between the IDG potential around a flat background and around a de Sitter background is negligible. |
2008.04957 | Sander M. Vermeulen | Sander M Vermeulen, Lorenzo Aiello, Aldo Ejlli, William L Griffiths,
Alasdair L James, Katherine L Dooley, Hartmut Grote | An Experiment for Observing Quantum Gravity Phenomena using Twin
Table-Top 3D Interferometers | Accepted for publication in Classical and Quantum Gravity | null | 10.1088/1361-6382/abe757 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories of quantum gravity based on the holographic principle predict the
existence of quantum fluctuations of distance measurements that accumulate and
exhibit correlations over macroscopic distances. This paper models an expected
signal due to this phenomenology, and details the design and estimated
sensitivity of co-located twin table-top 3D interferometers being built to
measure or constrain it. The experiment is estimated to be sensitive to
displacements $\sim10^{-19}\,\rm{m}/\sqrt{\rm{Hz}}$ in a frequency band between
1 and 250 MHz, surpassing previous experiments and enabling the possible
observation of quantum gravity phenomena. The experiment will also be sensitive
to MHz gravitational waves and various dark matter candidates.
| [
{
"created": "Tue, 11 Aug 2020 18:43:59 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Feb 2021 11:19:42 GMT",
"version": "v2"
}
] | 2021-02-19 | [
[
"Vermeulen",
"Sander M",
""
],
[
"Aiello",
"Lorenzo",
""
],
[
"Ejlli",
"Aldo",
""
],
[
"Griffiths",
"William L",
""
],
[
"James",
"Alasdair L",
""
],
[
"Dooley",
"Katherine L",
""
],
[
"Grote",
"Hartmut",
"... | Theories of quantum gravity based on the holographic principle predict the existence of quantum fluctuations of distance measurements that accumulate and exhibit correlations over macroscopic distances. This paper models an expected signal due to this phenomenology, and details the design and estimated sensitivity of co-located twin table-top 3D interferometers being built to measure or constrain it. The experiment is estimated to be sensitive to displacements $\sim10^{-19}\,\rm{m}/\sqrt{\rm{Hz}}$ in a frequency band between 1 and 250 MHz, surpassing previous experiments and enabling the possible observation of quantum gravity phenomena. The experiment will also be sensitive to MHz gravitational waves and various dark matter candidates. |
gr-qc/0310034 | Yi Pan | Yi Pan, Alessandra Buonanno, Yanbei Chen, and Michele Vallisneri | A physical template family for gravitational waves from precessing
binaries of spinning compact objects: Application to single-spin binaries | 27 pages, 11 figures; reference added for Sec. 6, typos corrected;
small corrections to GW flux terms as per Blanchet et al., PRD 71,
129902(E)-129904(E) (2005) | Phys.Rev.D69:104017,2004; Erratum-ibid.D74:029905,2006 | 10.1103/PhysRevD.69.104017 10.1103/PhysRevD.74.029905 | null | gr-qc | null | The detection of the gravitational waves (GWs) emitted by precessing binaries
of spinning compact objects is complicated by the large number of parameters
(such as the magnitudes and initial directions of the spins, and the position
and orientation of the binary with respect to the detector) that are required
to model accurately the precession-induced modulations of the GW signal. In
this paper we describe a fast matched-filtering search scheme for precessing
binaries, and we adopt the physical template family proposed by Buonanno, Chen,
and Vallisneri [Phys.Rev.D 67, 104025 (2003)] for ground-based interferometers.
This family provides essentially exact waveforms, written directly in terms of
the physical parameters, for binaries with a single significant spin, and for
which the observed GW signal is emitted during the phase of adiabatic inspiral
(for LIGO-I and VIRGO, this corresponds to a total mass M < 15Msun). We show
how the detection statistic can be maximized automatically over all the
parameters (including the position and orientation of the binary with respect
to the detector), except four (the two masses, the magnitude of the single
spin, and the opening angle between the spin and the orbital angular momentum),
so the template bank used in the search is only four-dimensional; this
technique is relevant also to the searches for GW from extreme--mass-ratio
inspirals and supermassive blackhole inspirals to be performed using the
space-borne detector LISA. Using the LIGO-I design sensitivity, we compute the
detection threshold (~10) required for a false-alarm probability of
10^(-3)/year, and the number of templates (~76,000) required for a minimum
match of 0.97, for the mass range (m1,m2)=[7,12]Msun*[1,3]Msun.
| [
{
"created": "Mon, 6 Oct 2003 20:56:58 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Nov 2003 15:16:37 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Jul 2006 15:34:43 GMT",
"version": "v3"
}
] | 2014-11-17 | [
[
"Pan",
"Yi",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Vallisneri",
"Michele",
""
]
] | The detection of the gravitational waves (GWs) emitted by precessing binaries of spinning compact objects is complicated by the large number of parameters (such as the magnitudes and initial directions of the spins, and the position and orientation of the binary with respect to the detector) that are required to model accurately the precession-induced modulations of the GW signal. In this paper we describe a fast matched-filtering search scheme for precessing binaries, and we adopt the physical template family proposed by Buonanno, Chen, and Vallisneri [Phys.Rev.D 67, 104025 (2003)] for ground-based interferometers. This family provides essentially exact waveforms, written directly in terms of the physical parameters, for binaries with a single significant spin, and for which the observed GW signal is emitted during the phase of adiabatic inspiral (for LIGO-I and VIRGO, this corresponds to a total mass M < 15Msun). We show how the detection statistic can be maximized automatically over all the parameters (including the position and orientation of the binary with respect to the detector), except four (the two masses, the magnitude of the single spin, and the opening angle between the spin and the orbital angular momentum), so the template bank used in the search is only four-dimensional; this technique is relevant also to the searches for GW from extreme--mass-ratio inspirals and supermassive blackhole inspirals to be performed using the space-borne detector LISA. Using the LIGO-I design sensitivity, we compute the detection threshold (~10) required for a false-alarm probability of 10^(-3)/year, and the number of templates (~76,000) required for a minimum match of 0.97, for the mass range (m1,m2)=[7,12]Msun*[1,3]Msun. |
1611.10198 | Carlos Augusto Romero Filho | R. Avalos, F. Dahia and C. Romero | A note on the problem of proper time in Weyl space-time | 19 pages and 3 figures | Avalos, R., Dahia, F. & Romero, C. Found Phys (2018) 48: 253 | 10.1007/s10701-017-0134-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the question of whether or not a general Weyl structure is a
suitable mathematical model of space-time. This is an issue that has been in
debate since Weyl formulated his unified field theory for the first time. We do
not present the discussion from the point of view of a particular unification
theory, but instead from a more general standpoint, in which the viability of
such a structure as a model of space-time is investigated. Our starting point
is the well known axiomatic approach to space-time given by Elhers, Pirani and
Schild (EPS). In this framework, we carry out an exhaustive analysis of what is
required for a consistent definition for proper time and show that such a
definition leads to the prediction of the so-called "second clock effect". We
take the view that if, based on experience, we were to reject space-time models
predicting this effect, this could be incorporated as the last axiom in the EPS
approach. Finally, we provide a proof that, in this case, we are led to a Weyl
integrable space-time (WIST) as the most general structure that would be
suitable to model space-time.
| [
{
"created": "Wed, 30 Nov 2016 15:00:21 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Apr 2018 02:32:21 GMT",
"version": "v2"
}
] | 2018-04-09 | [
[
"Avalos",
"R.",
""
],
[
"Dahia",
"F.",
""
],
[
"Romero",
"C.",
""
]
] | We discuss the question of whether or not a general Weyl structure is a suitable mathematical model of space-time. This is an issue that has been in debate since Weyl formulated his unified field theory for the first time. We do not present the discussion from the point of view of a particular unification theory, but instead from a more general standpoint, in which the viability of such a structure as a model of space-time is investigated. Our starting point is the well known axiomatic approach to space-time given by Elhers, Pirani and Schild (EPS). In this framework, we carry out an exhaustive analysis of what is required for a consistent definition for proper time and show that such a definition leads to the prediction of the so-called "second clock effect". We take the view that if, based on experience, we were to reject space-time models predicting this effect, this could be incorporated as the last axiom in the EPS approach. Finally, we provide a proof that, in this case, we are led to a Weyl integrable space-time (WIST) as the most general structure that would be suitable to model space-time. |
2307.05181 | Yong Tang | Yan Cao, Yong Tang | Signatures of Ultralight Bosons in Compact Binary Inspiral and Outspiral | 17 pages, 10 figures | Phys.Rev.D 108 (2023) 12, 123017 | 10.1103/PhysRevD.108.123017 | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | Ultralight bosons are well-motivated particles from various physical and
cosmological theories, and can be spontaneously produced during the
superradiant process, forming a dense hydrogen-like cloud around the spinning
black hole. After the growth saturates, the cloud slowly depletes its mass
through gravitational-wave emission. In this work we study the orbit dynamics
of a binary system containing such a gravitational atom saturated in various
spin-0,1,2 superradiant states, taking into account both the effects of
dynamical friction and the cloud mass depletion. We estimate the significance
of mass depletion, finding that although dynamical friction could dominate the
inspiral phase, it typically does not affect the outspiral phase driven by the
mass depletion. Focusing on the large orbit radius, we investigate the
condition to observe the outspiral, and the detectability of the cloud via
pulsar-timing signal in the case of black hole-pulsar binary.
| [
{
"created": "Tue, 11 Jul 2023 11:33:51 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jan 2024 08:26:38 GMT",
"version": "v2"
}
] | 2024-01-04 | [
[
"Cao",
"Yan",
""
],
[
"Tang",
"Yong",
""
]
] | Ultralight bosons are well-motivated particles from various physical and cosmological theories, and can be spontaneously produced during the superradiant process, forming a dense hydrogen-like cloud around the spinning black hole. After the growth saturates, the cloud slowly depletes its mass through gravitational-wave emission. In this work we study the orbit dynamics of a binary system containing such a gravitational atom saturated in various spin-0,1,2 superradiant states, taking into account both the effects of dynamical friction and the cloud mass depletion. We estimate the significance of mass depletion, finding that although dynamical friction could dominate the inspiral phase, it typically does not affect the outspiral phase driven by the mass depletion. Focusing on the large orbit radius, we investigate the condition to observe the outspiral, and the detectability of the cloud via pulsar-timing signal in the case of black hole-pulsar binary. |
2112.10430 | Muhammad Zaeem-Ul-Haq Bhatti | M. Z. Bhatti, Z. Yousaf, F. Hussain | Study of Generalized Lema\^{\i}tre-Tolman-Bondi Spacetime in Palatini
$f(R)$ Gravity | 21 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper aims to analyze the generalization of Lema\^{\i}tre-Tolman-Bondi
(LTB) spacetime for dissipative dust under the influence of Palatini $f(R)$
gravity. We explore the modified field equations, kinematical variables, and
mass function in this scenario. We construct Bianchi identities using
conservation and differential equations for shear, expansion, and curvature
scalar in the background of Palatini $f(R)$ gravity. We calculated the scalar
functions coming from the orthogonal decomposition of the Riemann tensor in
this framework. These scalar functions known as structure scalars have been
explored for LTB spacetime using modified field equations. The symmetric
properties of LTB spacetime have been discussed using two subcases. We found
that generalized LTB spacetime has properties comparable with LTB and obtained
structure scalars in both cases which have a similar dependence on a material
profile even in Palatini gravity.
| [
{
"created": "Mon, 20 Dec 2021 10:19:38 GMT",
"version": "v1"
}
] | 2021-12-21 | [
[
"Bhatti",
"M. Z.",
""
],
[
"Yousaf",
"Z.",
""
],
[
"Hussain",
"F.",
""
]
] | This paper aims to analyze the generalization of Lema\^{\i}tre-Tolman-Bondi (LTB) spacetime for dissipative dust under the influence of Palatini $f(R)$ gravity. We explore the modified field equations, kinematical variables, and mass function in this scenario. We construct Bianchi identities using conservation and differential equations for shear, expansion, and curvature scalar in the background of Palatini $f(R)$ gravity. We calculated the scalar functions coming from the orthogonal decomposition of the Riemann tensor in this framework. These scalar functions known as structure scalars have been explored for LTB spacetime using modified field equations. The symmetric properties of LTB spacetime have been discussed using two subcases. We found that generalized LTB spacetime has properties comparable with LTB and obtained structure scalars in both cases which have a similar dependence on a material profile even in Palatini gravity. |
2211.02958 | Luther Rinehart | Luther Rinehart | Radiation from an accelerating charge in a family of Rindler frames | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The generalization of the Larmor radiation formula in gravitational fields
and with accelerating observers was obtained by Hirayama and others. We verify
a special case of their result by explicit computation using a family of
displaced Rindler frames. We discuss the role of observer-dependence of energy
and simultaneity. We also include a discussion of conservation laws in
spacetimes equipped with a Killing vector and a time function.
| [
{
"created": "Sat, 5 Nov 2022 18:36:26 GMT",
"version": "v1"
}
] | 2022-11-08 | [
[
"Rinehart",
"Luther",
""
]
] | The generalization of the Larmor radiation formula in gravitational fields and with accelerating observers was obtained by Hirayama and others. We verify a special case of their result by explicit computation using a family of displaced Rindler frames. We discuss the role of observer-dependence of energy and simultaneity. We also include a discussion of conservation laws in spacetimes equipped with a Killing vector and a time function. |
1508.06543 | Andronikos Paliathanasis | Andronikos Paliathanasis, Supriya Pan and Souvik Pramanik | Scalar field cosmology modified by the Generalized Uncertainty Principle | 12 pages; 3 figures; discussion improved; new references; accepted
for publication by CQG | Class. Quantum Grav. 32 245006 (2015) | 10.1088/0264-9381/32/24/245006 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider quintessence scalar field cosmology in which the Lagrangian of
the scalar field is modified by the Generalized Uncertainty Principle. We show
that the perturbation terms which arise from the deformed algebra are
equivalent with the existence of a second scalar field, where the two fields
interact in the kinetic part. Moreover, we consider a spatially flat
Friedmann-Lema\^{\i}tre-Robertson-Walker spacetime (FLRW), and we derive the
gravitational field equations. We show that the modified equation of state
parameter $w_{GUP}$ can cross the phantom divide line; that is $w_{GUP}<-1$.
Furthermore, we derive the field equations in the dimensionless parameters, the
dynamical system which arises is a singular perturbation system in which we
study the existence of the fixed points in the slow manifold. Finally, we
perform numerical simulations for some well known models and we show that for
these models with the specific initial conditions, the parameter $w_{GUP}$
crosses the phantom barrier.
| [
{
"created": "Mon, 24 Aug 2015 08:27:46 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Oct 2015 22:37:32 GMT",
"version": "v2"
}
] | 2015-12-03 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Pan",
"Supriya",
""
],
[
"Pramanik",
"Souvik",
""
]
] | We consider quintessence scalar field cosmology in which the Lagrangian of the scalar field is modified by the Generalized Uncertainty Principle. We show that the perturbation terms which arise from the deformed algebra are equivalent with the existence of a second scalar field, where the two fields interact in the kinetic part. Moreover, we consider a spatially flat Friedmann-Lema\^{\i}tre-Robertson-Walker spacetime (FLRW), and we derive the gravitational field equations. We show that the modified equation of state parameter $w_{GUP}$ can cross the phantom divide line; that is $w_{GUP}<-1$. Furthermore, we derive the field equations in the dimensionless parameters, the dynamical system which arises is a singular perturbation system in which we study the existence of the fixed points in the slow manifold. Finally, we perform numerical simulations for some well known models and we show that for these models with the specific initial conditions, the parameter $w_{GUP}$ crosses the phantom barrier. |
1712.02129 | J. W. van Holten | T. de Beer and J.W. van Holten | Chaplygin gas halos | 18 pages, 9 figures; vs: references added | null | null | Nikhef/2017-062 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unification of dark matter and dark energy as short- and long-range
manifestations of a single cosmological substance is possible in models
described by the generalized Chaplygin gas equation of state. We show it admits
halo-like structures and discuss their density profiles, the resulting
space-time geometry and the rotational velocity profiles expected in these
models.
| [
{
"created": "Wed, 6 Dec 2017 11:03:48 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Dec 2017 21:56:45 GMT",
"version": "v2"
}
] | 2017-12-20 | [
[
"de Beer",
"T.",
""
],
[
"van Holten",
"J. W.",
""
]
] | Unification of dark matter and dark energy as short- and long-range manifestations of a single cosmological substance is possible in models described by the generalized Chaplygin gas equation of state. We show it admits halo-like structures and discuss their density profiles, the resulting space-time geometry and the rotational velocity profiles expected in these models. |
1606.02646 | Vojtech Pravda | Vojtech Pravda, Alena Pravdova, Jiri Podolsky, Robert Svarc | Exact solutions to quadratic gravity | 13 pages, matches the published version | Phys. Rev. D 95, 084025 (2017) | 10.1103/PhysRevD.95.084025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Since all Einstein spacetimes are vacuum solutions to quadratic gravity in
four dimensions, in this paper we study various aspects of non-Einstein vacuum
solutions to this theory. Most such known solutions are of traceless Ricci and
Petrov type N with a constant Ricci scalar. Thus we assume the Ricci scalar to
be constant which leads to a substantial simplification of the field equations.
We prove that a vacuum solution to quadratic gravity with traceless Ricci
tensor of type N and aligned Weyl tensor of any Petrov type is necessarily a
Kundt spacetime. This will considerably simplify the search for new
non-Einstein solutions. Similarly, a vacuum solution to quadratic gravity with
traceless Ricci type III and aligned Weyl tensor of Petrov type II or more
special is again necessarily a Kundt spacetime.
Then we study the general role of conformal transformations in constructing
vacuum solutions to quadratic gravity. We find that such solutions can be
obtained by solving one non-linear partial differential equation for a
conformal factor on any Einstein spacetime or, more generally, on any
background with vanishing Bach tensor. In particular, we show that all
geometries conformal to Kundt are either Kundt or Robinson-Trautman, and we
provide some explicit Kundt and Robinson-Trautman solutions to quadratic
gravity by solving the above mentioned equation on certain Kundt backgrounds.
| [
{
"created": "Wed, 8 Jun 2016 17:31:00 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Dec 2016 16:19:42 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Apr 2017 13:31:41 GMT",
"version": "v3"
}
] | 2017-04-25 | [
[
"Pravda",
"Vojtech",
""
],
[
"Pravdova",
"Alena",
""
],
[
"Podolsky",
"Jiri",
""
],
[
"Svarc",
"Robert",
""
]
] | Since all Einstein spacetimes are vacuum solutions to quadratic gravity in four dimensions, in this paper we study various aspects of non-Einstein vacuum solutions to this theory. Most such known solutions are of traceless Ricci and Petrov type N with a constant Ricci scalar. Thus we assume the Ricci scalar to be constant which leads to a substantial simplification of the field equations. We prove that a vacuum solution to quadratic gravity with traceless Ricci tensor of type N and aligned Weyl tensor of any Petrov type is necessarily a Kundt spacetime. This will considerably simplify the search for new non-Einstein solutions. Similarly, a vacuum solution to quadratic gravity with traceless Ricci type III and aligned Weyl tensor of Petrov type II or more special is again necessarily a Kundt spacetime. Then we study the general role of conformal transformations in constructing vacuum solutions to quadratic gravity. We find that such solutions can be obtained by solving one non-linear partial differential equation for a conformal factor on any Einstein spacetime or, more generally, on any background with vanishing Bach tensor. In particular, we show that all geometries conformal to Kundt are either Kundt or Robinson-Trautman, and we provide some explicit Kundt and Robinson-Trautman solutions to quadratic gravity by solving the above mentioned equation on certain Kundt backgrounds. |
1410.4479 | Javier Olmedo | Rodolfo Gambini, Javier Olmedo, Jorge Pullin | Casimir effect in a quantum space-time | 4 pages | null | 10.1088/0264-9381/32/11/115002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply quantum field theory in quantum space-time techniques to study the
Casimir effect for large spherical shells. As background we use the recently
constructed exact quantum solution for spherically symmetric vacuum space-time
in loop quantum gravity. All calculations are finite and one recovers the usual
results without the need of regularization or renormalization. This is an
example of how loop quantum gravity provides a natural resolution to the
infinities of quantum field theories.
| [
{
"created": "Thu, 16 Oct 2014 16:07:00 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Olmedo",
"Javier",
""
],
[
"Pullin",
"Jorge",
""
]
] | We apply quantum field theory in quantum space-time techniques to study the Casimir effect for large spherical shells. As background we use the recently constructed exact quantum solution for spherically symmetric vacuum space-time in loop quantum gravity. All calculations are finite and one recovers the usual results without the need of regularization or renormalization. This is an example of how loop quantum gravity provides a natural resolution to the infinities of quantum field theories. |
1907.05516 | Rafael Nunes | Rocco D'Agostino, Rafael C. Nunes | Probing observational bounds on scalar-tensor theories from standard
sirens | 12 pages, 8 figures, 1 table. Matches the version published in PRD | Phys. Rev. D 100, 044041 (2019) | 10.1103/PhysRevD.100.044041 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Standard sirens are the gravitational wave (GW) analog of the astronomical
standard candles, and can provide powerful information about the dynamics of
the Universe. In this work, we simulate a catalog with 1000 standard siren
events from binary neutron star mergers, within the sensitivity predicted for
the third generation of the ground GW detector called Einstein telescope. After
correctly modifying the propagation of GWs as input to generate the catalog, we
apply our mock data set on scalar-tensor theories where the speed of GW
propagation is equal to the speed of light. As a first application, we find new
observational bounds on the running of the Planck mass, when considering
appropriate values within the stability condition of the theory, and we discuss
some consequences on the amplitude of the running of the Planck mass. In the
second part, we combine our simulated standard sirens catalog with other
geometric cosmological tests (Supernovae Ia and cosmic chronometers
measurements) to constrain the Hu-Sawicki $f(R)$ gravity model. We thus find
new and non-null deviations from the standard $\Lambda$CDM model, showing that
in the future the $f(R)$ gravity can be tested up to 95\% confidence level. The
results obtained here show that the statistical accuracy achievable by future
ground based GW observations, mainly with the ET detector (and planed detectors
with a similar sensitivity), can provide strong observational bounds on
modified gravity theories.
| [
{
"created": "Thu, 11 Jul 2019 22:55:10 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Aug 2019 12:18:35 GMT",
"version": "v2"
}
] | 2019-08-26 | [
[
"D'Agostino",
"Rocco",
""
],
[
"Nunes",
"Rafael C.",
""
]
] | Standard sirens are the gravitational wave (GW) analog of the astronomical standard candles, and can provide powerful information about the dynamics of the Universe. In this work, we simulate a catalog with 1000 standard siren events from binary neutron star mergers, within the sensitivity predicted for the third generation of the ground GW detector called Einstein telescope. After correctly modifying the propagation of GWs as input to generate the catalog, we apply our mock data set on scalar-tensor theories where the speed of GW propagation is equal to the speed of light. As a first application, we find new observational bounds on the running of the Planck mass, when considering appropriate values within the stability condition of the theory, and we discuss some consequences on the amplitude of the running of the Planck mass. In the second part, we combine our simulated standard sirens catalog with other geometric cosmological tests (Supernovae Ia and cosmic chronometers measurements) to constrain the Hu-Sawicki $f(R)$ gravity model. We thus find new and non-null deviations from the standard $\Lambda$CDM model, showing that in the future the $f(R)$ gravity can be tested up to 95\% confidence level. The results obtained here show that the statistical accuracy achievable by future ground based GW observations, mainly with the ET detector (and planed detectors with a similar sensitivity), can provide strong observational bounds on modified gravity theories. |
1910.14197 | Yun-Cherng Lin | Yun-Cherng Lin, Michael P. Hobson, Anthony N. Lasenby | Power-counting renormalizable, ghost-and-tachyon-free Poincar\'e gauge
theories | 10 pages | Phys. Rev. D 101, 064038 (2020) | 10.1103/PhysRevD.101.064038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present 48 further examples, in addition to the 10 identified in [1], of
ghost-and-tachyon-free critical cases of parity-conserving Poincar\'e gauge
theories of gravity (PGT$^+$) that are also power-counting renormalizable
(PCR). This is achieved by extending the range of critical cases considered. Of
the new PCR theories, seven have 2 massless degrees of freedom (d.o.f.) in
propagating modes and a massive $0^-$ or $2^-$ mode, eight have only 2 massless
d.o.f., and 33 have only massive mode(s). We also clarify the treatment of
nonpropagating modes in determining whether a theory is PCR.
| [
{
"created": "Thu, 31 Oct 2019 01:01:34 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Apr 2020 16:19:32 GMT",
"version": "v2"
}
] | 2020-04-24 | [
[
"Lin",
"Yun-Cherng",
""
],
[
"Hobson",
"Michael P.",
""
],
[
"Lasenby",
"Anthony N.",
""
]
] | We present 48 further examples, in addition to the 10 identified in [1], of ghost-and-tachyon-free critical cases of parity-conserving Poincar\'e gauge theories of gravity (PGT$^+$) that are also power-counting renormalizable (PCR). This is achieved by extending the range of critical cases considered. Of the new PCR theories, seven have 2 massless degrees of freedom (d.o.f.) in propagating modes and a massive $0^-$ or $2^-$ mode, eight have only 2 massless d.o.f., and 33 have only massive mode(s). We also clarify the treatment of nonpropagating modes in determining whether a theory is PCR. |
1812.05635 | Massimo Giovannini | Massimo Giovannini | Polarized backgrounds of relic gravitons | 11 pages | Phys. Rev. D 99, 083501 (2019) | 10.1103/PhysRevD.99.083501 | CERN-TH-2018-215 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The polarizations of the tensor modes of the geometry evolving in
cosmological backgrounds are treated as the components of a bispinor whose
dynamics follows from an appropriate gauge-invariant action. This novel
framework bears a close analogy with the (optical) Jones calculus and leads to
a compact classification of the various interactions able to polarize the relic
gravitons.
| [
{
"created": "Thu, 13 Dec 2018 19:07:32 GMT",
"version": "v1"
}
] | 2019-04-10 | [
[
"Giovannini",
"Massimo",
""
]
] | The polarizations of the tensor modes of the geometry evolving in cosmological backgrounds are treated as the components of a bispinor whose dynamics follows from an appropriate gauge-invariant action. This novel framework bears a close analogy with the (optical) Jones calculus and leads to a compact classification of the various interactions able to polarize the relic gravitons. |
1408.5306 | Christian Pfeifer | Christian Pfeifer | Radar orthogonality and radar length in Finsler and metric spacetime
geometry | 18 pages, 7 figures, axes label in figures corrected, journal
references added | Phys. Rev. D 90, 064052 (2014) | 10.1103/PhysRevD.90.064052 | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The radar experiment connects the geometry of spacetime with an observers
measurement of spatial length. We investigate the radar experiment on Finsler
spacetimes which leads to a general definition of radar orthogonality and radar
length. The directions radar orthogonal to an observer form the spatial equal
time surface an observer experiences and the radar length is the physical
length the observer associates to spatial objects. We demonstrate these
concepts on a forth order polynomial Finsler spacetime geometry which may
emerge from area metric or pre-metric linear electrodynamics or in quantum
gravity phenomenology. In an explicit generalisation of Minkowski spacetime
geometry we derive the deviation from the euclidean spatial length measure in
an observers rest frame explicitly.
| [
{
"created": "Fri, 22 Aug 2014 14:42:15 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Aug 2014 08:02:10 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Oct 2014 07:43:41 GMT",
"version": "v3"
}
] | 2014-10-08 | [
[
"Pfeifer",
"Christian",
""
]
] | The radar experiment connects the geometry of spacetime with an observers measurement of spatial length. We investigate the radar experiment on Finsler spacetimes which leads to a general definition of radar orthogonality and radar length. The directions radar orthogonal to an observer form the spatial equal time surface an observer experiences and the radar length is the physical length the observer associates to spatial objects. We demonstrate these concepts on a forth order polynomial Finsler spacetime geometry which may emerge from area metric or pre-metric linear electrodynamics or in quantum gravity phenomenology. In an explicit generalisation of Minkowski spacetime geometry we derive the deviation from the euclidean spatial length measure in an observers rest frame explicitly. |
2203.16892 | Sanasam Surendra Singh | Chingtham Sonia, S. Surendra Singh | Dynamical systems of cosmological models for different possibilities of
$G$ and $\rho_{\Lambda}$ | 43 pages, 20 figures | null | 10.1140/epjc/s10052-022-10826-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper deals with the dynamics of spatially flat
Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model with a time
varying cosmological constant $\Lambda$ where $\Lambda$ evolves with the cosmic
time (t) through the Hubble parameter (H). We consider that the model dynamics
has a reflection symmetry $H \rightarrow -H $ with $\Lambda(H)$ expressed in
the form of Taylor series with respect to H. Dynamical systems for three
different cases based on the possibilities of gravitational constant G and the
vacuum energy density $\rho_{\Lambda}$ have been analysed. In Case I, both G
and $\rho_{\Lambda}$ are taken to be constant. We analyse stability of the
system by using the notion of spectral radius, behavior of perturbation along
each of the axis with respect to cosmic time and Poincare sphere. In Case II,
we have dynamical system analysis for G=constant and $\rho_{\Lambda} \neq $
constant where we study stability by using the concept of spectral radius and
perturbation function. In Case III, we take $G \neq$ constant and
$\rho_{\Lambda} \neq$ constant where we introduce a new set of variables to set
up the corresponding dynamical system. We find out the fixed points of the
system and analyse the stability from different directions: by analysing
behaviour of the perturbation along each of the axis, Center Manifold Theory
and stability at infinity using Poincare sphere respectively. Phase plots and
perturbation plots have been presented. We deeply study the cosmological
scenario with respect to the fixed points obtained and analyse the late time
behavior of the Universe. Our model agrees with the fact that the Universe is
in the epoch of accelerated expansion. The EOS parameter $\omega_{eff}$, total
energy density $\Omega_{tt}$ are also evaluated at the fixed points for each of
the three cases and these values are in agreement with the observational values
in [1].
| [
{
"created": "Thu, 31 Mar 2022 09:00:33 GMT",
"version": "v1"
}
] | 2022-10-19 | [
[
"Sonia",
"Chingtham",
""
],
[
"Singh",
"S. Surendra",
""
]
] | The present paper deals with the dynamics of spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model with a time varying cosmological constant $\Lambda$ where $\Lambda$ evolves with the cosmic time (t) through the Hubble parameter (H). We consider that the model dynamics has a reflection symmetry $H \rightarrow -H $ with $\Lambda(H)$ expressed in the form of Taylor series with respect to H. Dynamical systems for three different cases based on the possibilities of gravitational constant G and the vacuum energy density $\rho_{\Lambda}$ have been analysed. In Case I, both G and $\rho_{\Lambda}$ are taken to be constant. We analyse stability of the system by using the notion of spectral radius, behavior of perturbation along each of the axis with respect to cosmic time and Poincare sphere. In Case II, we have dynamical system analysis for G=constant and $\rho_{\Lambda} \neq $ constant where we study stability by using the concept of spectral radius and perturbation function. In Case III, we take $G \neq$ constant and $\rho_{\Lambda} \neq$ constant where we introduce a new set of variables to set up the corresponding dynamical system. We find out the fixed points of the system and analyse the stability from different directions: by analysing behaviour of the perturbation along each of the axis, Center Manifold Theory and stability at infinity using Poincare sphere respectively. Phase plots and perturbation plots have been presented. We deeply study the cosmological scenario with respect to the fixed points obtained and analyse the late time behavior of the Universe. Our model agrees with the fact that the Universe is in the epoch of accelerated expansion. The EOS parameter $\omega_{eff}$, total energy density $\Omega_{tt}$ are also evaluated at the fixed points for each of the three cases and these values are in agreement with the observational values in [1]. |
1510.00301 | Filip Hejda | Filip Hejda and Ji\v{r}\'i Bi\v{c}\'ak | Black Holes and Magnetic Fields | Published in WDS'14 Proceedings of Contributed Papers - Physics (eds.
J. \v{S}afr\'ankov\'a and J. Pavl\r{u}), 48-55, MATFYZPRESS, Prague, 2014.
ISBN 978-80-7378-276-4 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly summarise the basic properties of spacetimes representing
rotating, charged black holes in strong axisymmetric magnetic fields. We
concentrate on extremal cases, for which the horizon surface gravity vanishes.
We investigate their properties by finding simpler spacetimes that exhibit
their geometries near degenerate horizons. Employing the simpler geometries
obtained by near-horizon limiting description we analyse the Meissner effect of
magnetic field expulsion from extremal black holes.
| [
{
"created": "Thu, 1 Oct 2015 16:27:48 GMT",
"version": "v1"
}
] | 2015-10-02 | [
[
"Hejda",
"Filip",
""
],
[
"Bičák",
"Jiří",
""
]
] | We briefly summarise the basic properties of spacetimes representing rotating, charged black holes in strong axisymmetric magnetic fields. We concentrate on extremal cases, for which the horizon surface gravity vanishes. We investigate their properties by finding simpler spacetimes that exhibit their geometries near degenerate horizons. Employing the simpler geometries obtained by near-horizon limiting description we analyse the Meissner effect of magnetic field expulsion from extremal black holes. |
2307.11158 | Christopher Munna | Christopher Munna | High-order post-Newtonian expansion of the generalized redshift
invariant for eccentric-orbit, equatorial extreme-mass-ratio inspirals with a
spinning primary | 23 pages, 2 figures | null | 10.1103/PhysRevD.108.084012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive new terms in the post-Newtonian (PN) expansion of the generalized
redshift invariant $\langle u^t \rangle_\tau$ for a small body in eccentric,
equatorial orbit about a massive Kerr black hole. The series is computed
analytically using the Teukolsky formalism for first-order black hole
perturbation theory (BHPT), along with the CCK method for metric reconstruction
using the Hertz potential in ingoing radiation gauge. Modal contributions with
small values of $l$ are derived via the semi-analytic solution of
Mano-Suzuki-Takasugi (MST), while the remaining values of $l$ to infinity are
determined via direct expansion of the Teukolsky equation. Each PN order is
calculated as a series in eccentricity $e$ but kept exact in the primary black
hole's spin parameter $a$. In total, the PN terms are expanded to $e^{16}$
through 6PN relative order, and separately to $e^{10}$ through 8PN relative
order. Upon grouping eccentricity coefficients by spin dependence, we find that
many resulting component terms can be simplified to closed-form functions of
eccentricity, in close analogy to corresponding terms derived previously in the
Schwarzschild limit. We use numerical calculations to compare convergence of
the full series to its Schwarzschild counterpart and discuss implications for
gravitational wave analysis.
| [
{
"created": "Thu, 20 Jul 2023 18:00:04 GMT",
"version": "v1"
}
] | 2023-11-09 | [
[
"Munna",
"Christopher",
""
]
] | We derive new terms in the post-Newtonian (PN) expansion of the generalized redshift invariant $\langle u^t \rangle_\tau$ for a small body in eccentric, equatorial orbit about a massive Kerr black hole. The series is computed analytically using the Teukolsky formalism for first-order black hole perturbation theory (BHPT), along with the CCK method for metric reconstruction using the Hertz potential in ingoing radiation gauge. Modal contributions with small values of $l$ are derived via the semi-analytic solution of Mano-Suzuki-Takasugi (MST), while the remaining values of $l$ to infinity are determined via direct expansion of the Teukolsky equation. Each PN order is calculated as a series in eccentricity $e$ but kept exact in the primary black hole's spin parameter $a$. In total, the PN terms are expanded to $e^{16}$ through 6PN relative order, and separately to $e^{10}$ through 8PN relative order. Upon grouping eccentricity coefficients by spin dependence, we find that many resulting component terms can be simplified to closed-form functions of eccentricity, in close analogy to corresponding terms derived previously in the Schwarzschild limit. We use numerical calculations to compare convergence of the full series to its Schwarzschild counterpart and discuss implications for gravitational wave analysis. |
gr-qc/0312092 | Alexander Gorbatsievich | A.A. Blinkouski, A.K. Gorbatsievich | Some cosmological consequences of the five-dimensional Projective
Unified Field Theory | LaTeX, 12 pages, 1 figure | Grav.Cosmol.7:286-292,2001 | null | null | gr-qc | null | The classical observational cosmological tests (Hubble diagram, count of
sources, etc.) are considered for a homogeneous and isotropic model of the
Universe in the framework of the five-dimensional Projective Unified Field
Theory in which gravitation is described by both space-time curvature and some
hypothetical scalar field (sigma-field). It is shown that the presence of the
sigma-field can essentially affect conclusions obtained from the cosmological
tests. The surface brightness-redshift relation can be used as a critical test
for sigma-field effects. It seems reasonable to say that the available
experimental data testify that the sigma-field decreases with time. It is
concluded that the spatial curvature is positive or negative depending on
whether the mass density is larger or smaller than some critical parameter
which is smaller than the critical density and can even take negative values.
It is shown that the increase in the number of the observational cosmological
parameters as compared to the standard Friedmann model can essentially
facilitate coordination of the existing observational data.
| [
{
"created": "Fri, 19 Dec 2003 20:27:30 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Dec 2003 20:19:13 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Blinkouski",
"A. A.",
""
],
[
"Gorbatsievich",
"A. K.",
""
]
] | The classical observational cosmological tests (Hubble diagram, count of sources, etc.) are considered for a homogeneous and isotropic model of the Universe in the framework of the five-dimensional Projective Unified Field Theory in which gravitation is described by both space-time curvature and some hypothetical scalar field (sigma-field). It is shown that the presence of the sigma-field can essentially affect conclusions obtained from the cosmological tests. The surface brightness-redshift relation can be used as a critical test for sigma-field effects. It seems reasonable to say that the available experimental data testify that the sigma-field decreases with time. It is concluded that the spatial curvature is positive or negative depending on whether the mass density is larger or smaller than some critical parameter which is smaller than the critical density and can even take negative values. It is shown that the increase in the number of the observational cosmological parameters as compared to the standard Friedmann model can essentially facilitate coordination of the existing observational data. |
gr-qc/0401104 | Pedro Marronetti | P. Marronetti and S. L. Shapiro | Numerical Models of Spin-Orbital Coupling in Neutron Star Binaries | 4 pages, 3 figures. Submitted to the Proceedings of the "X Marcel
Grossmann Meeting on General Relativity" in Rio de Janeiro, Brazil, July
20-26 (2003) | null | 10.1142/9789812704030_0107 | null | gr-qc astro-ph | null | We present a new numerical scheme for solving the initial value problem for
quasiequilibrium binary neutron stars allowing for arbitrary spins. We
construct sequences of circular-orbit binaries of varying separation, keeping
the rest mass and circulation constant along each sequence. The spin angular
frequency of the stars is shown to vary along the sequence, a result that can
be derived analytically in the PPN limit. This spin effect, in addition to
leaving an imprint on the gravitational waveform emitted during binary
inspiral, is measurable in the electromagnetic signal if one of the stars is a
pulsar visible from Earth.
| [
{
"created": "Mon, 26 Jan 2004 21:24:59 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Marronetti",
"P.",
""
],
[
"Shapiro",
"S. L.",
""
]
] | We present a new numerical scheme for solving the initial value problem for quasiequilibrium binary neutron stars allowing for arbitrary spins. We construct sequences of circular-orbit binaries of varying separation, keeping the rest mass and circulation constant along each sequence. The spin angular frequency of the stars is shown to vary along the sequence, a result that can be derived analytically in the PPN limit. This spin effect, in addition to leaving an imprint on the gravitational waveform emitted during binary inspiral, is measurable in the electromagnetic signal if one of the stars is a pulsar visible from Earth. |
1505.06790 | Adam Rogers | Adam Rogers | Frequency-dependent effects of gravitational lensing within plasma | 10 pages, 6 figures | Monthly Notices of the Royal Astronomical Society, 2015, 451 (1):
4536-4544 | 10.1093/mnras/stv903 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The interaction between refraction from a distribution of inhomogeneous
plasma and gravitational lensing introduces novel effects to the paths of light
rays passing by a massive object. The plasma contributes additional terms to
the equations of motion, and the resulting ray trajectories are
frequency-dependent. Lensing phenomena and circular orbits are investigated for
plasma density distributions $N \propto 1/r^h$ with $h \geq 0$ in the
Schwarzschild space-time. For rays passing by the mass near the plasma
frequency refractive effects can dominate, effectively turning the
gravitational lens into a mirror. We obtain the turning points, circular orbit
radii, and angular momentum for general $h$. Previous results have shown that
light rays behave like massive particles with an effective mass given by the
plasma frequency for a constant density $h=0$. We study the behaviour for
general $h$ and show that when $h=2$ the plasma term acts like an additional
contribution to the angular momentum of the passing ray. When $h=3$ the
potential and radii of circular orbits are analogous to those found in studies
of massless scalar fields on the Schwarzschild background. As a physically
motivated example we study the pulse profiles of a compact object with
antipodal hotspots sheathed in a dense plasma, which shows dramatic
frequency-dependent shifts from the behaviour in vacuum. Finally, we consider
the potential observability and applications of such frequency-dependent plasma
effects in general relativity for several types of neutron star.
| [
{
"created": "Tue, 26 May 2015 02:03:41 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Rogers",
"Adam",
""
]
] | The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions $N \propto 1/r^h$ with $h \geq 0$ in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens into a mirror. We obtain the turning points, circular orbit radii, and angular momentum for general $h$. Previous results have shown that light rays behave like massive particles with an effective mass given by the plasma frequency for a constant density $h=0$. We study the behaviour for general $h$ and show that when $h=2$ the plasma term acts like an additional contribution to the angular momentum of the passing ray. When $h=3$ the potential and radii of circular orbits are analogous to those found in studies of massless scalar fields on the Schwarzschild background. As a physically motivated example we study the pulse profiles of a compact object with antipodal hotspots sheathed in a dense plasma, which shows dramatic frequency-dependent shifts from the behaviour in vacuum. Finally, we consider the potential observability and applications of such frequency-dependent plasma effects in general relativity for several types of neutron star. |
gr-qc/9906060 | Iver H. Brevik | I. Brevik | Self-Screening Hawking Atmosphere in the Presence of a Bulk Viscosity | 12 pages, LaTeX, no figures, minor extensions of the discussion. To
appear in PRD | Phys.Rev.D61:124017,2000 | 10.1103/PhysRevD.61.124017 | null | gr-qc | null | The recent theory of 't Hooft [ Nucl. Phys. Suppl. {\bf 68}, 174 (1998)]
models the black hole as a system endowed with an envelope of matter that obeys
an equation of state in the form $ p=(\gamma -1)\rho$, and acts as a source in
Einstein's equations. The present paper generalizes the 't Hooft theory so as
to take into account a bulk viscosity $\zeta$ in the fluid. It is shown that
even a slight positive value of $\zeta$ will suffice to yield complete
agreement with the Hawking formula for the entropy of the black hole, if the
value of the constant $\gamma$ takes a value that is slightly less than 4/3.
The value $\gamma=4/3$ corresponds to a radiation fluid.
| [
{
"created": "Wed, 16 Jun 1999 11:43:33 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Mar 2000 16:19:40 GMT",
"version": "v2"
}
] | 2009-01-14 | [
[
"Brevik",
"I.",
""
]
] | The recent theory of 't Hooft [ Nucl. Phys. Suppl. {\bf 68}, 174 (1998)] models the black hole as a system endowed with an envelope of matter that obeys an equation of state in the form $ p=(\gamma -1)\rho$, and acts as a source in Einstein's equations. The present paper generalizes the 't Hooft theory so as to take into account a bulk viscosity $\zeta$ in the fluid. It is shown that even a slight positive value of $\zeta$ will suffice to yield complete agreement with the Hawking formula for the entropy of the black hole, if the value of the constant $\gamma$ takes a value that is slightly less than 4/3. The value $\gamma=4/3$ corresponds to a radiation fluid. |
1212.2208 | Mark Israelit | Mark Israelit | Nowadays cosmology with the Weyl-Dirac approach | arXiv admin note: substantial text overlap with arXiv:1008.0767,
arXiv:1212.2025 In this new version the following changes are made: 1. The
terms perturbated/perturbation are deleted as not appropriate. 2. The new
title "Cosmology with the Weyl-Dirac approach." 3. In Sec-s 7-8 are corrected
and added some formulae. 4. The list of references is reorganized | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some problems of cosmology: the big bang singularity, the origin of
conventional matter, of dark matter and of dark energy may be successfully
described and treated in the framework of the Weyl-Dirac theory. This theory,
being a minimal expansion of Einstein's GRT, contains in addition to the metric
tensor\g, the Weyl connection vector \w and the Dirac gauge function\beta. From
these geometrically based quantities one obtains the behavior of our universe.
The Weyl connection vector \w existing in microcells creates dark matter
particles, weylons. In the very early universe \beta creates matter, whereas in
the present dust period \beta forms dark energy, the latter causing cosmic
acceleration. Around a massive body the - dark energy form a ball-like
concentration having negative mass and negative pressure. These \beta-balls
cause an additional acceleration of the expanding universe. The Weyl-Dirac
theory is a classical geometrically based framework appropriate for describing
and searching cosmology.
| [
{
"created": "Mon, 10 Dec 2012 15:05:04 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Aug 2013 12:58:39 GMT",
"version": "v2"
}
] | 2013-08-07 | [
[
"Israelit",
"Mark",
""
]
] | Some problems of cosmology: the big bang singularity, the origin of conventional matter, of dark matter and of dark energy may be successfully described and treated in the framework of the Weyl-Dirac theory. This theory, being a minimal expansion of Einstein's GRT, contains in addition to the metric tensor\g, the Weyl connection vector \w and the Dirac gauge function\beta. From these geometrically based quantities one obtains the behavior of our universe. The Weyl connection vector \w existing in microcells creates dark matter particles, weylons. In the very early universe \beta creates matter, whereas in the present dust period \beta forms dark energy, the latter causing cosmic acceleration. Around a massive body the - dark energy form a ball-like concentration having negative mass and negative pressure. These \beta-balls cause an additional acceleration of the expanding universe. The Weyl-Dirac theory is a classical geometrically based framework appropriate for describing and searching cosmology. |
2002.01174 | Piotr T. Chru\'sciel | Robert Beig, Piotr T. Chru\'sciel | On linearised vacuum constraint equations on Einstein manifolds | Minor rewordings, version should be identical to the published one | null | 10.1088/1361-6382/ab81cc | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show how to parameterise solutions of the general relativistic vector
constraint equation on Einstein manifolds by unconstrained potentials. We
provide a similar construction for the trace-free part of tensors satisfying
the linearised scalar constraint. Previous work of ours has provided similar
different constructions for solutions of the linearized constraints in the case
where the cosmological constant $\Lambda$ is zero. We use our new potentials to
show that one can shield linearised gravitational fields using linearised
gravitational fields without imposing the TT gauge (as done in previous work),
for any value of $\Lambda \in \mathbb{R}$.
| [
{
"created": "Tue, 4 Feb 2020 09:09:05 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Feb 2020 11:00:21 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Apr 2020 13:41:47 GMT",
"version": "v3"
},
{
"created": "Tue, 21 Apr 2020 18:01:08 GMT",
"version": "v4"
}
] | 2020-12-02 | [
[
"Beig",
"Robert",
""
],
[
"Chruściel",
"Piotr T.",
""
]
] | We show how to parameterise solutions of the general relativistic vector constraint equation on Einstein manifolds by unconstrained potentials. We provide a similar construction for the trace-free part of tensors satisfying the linearised scalar constraint. Previous work of ours has provided similar different constructions for solutions of the linearized constraints in the case where the cosmological constant $\Lambda$ is zero. We use our new potentials to show that one can shield linearised gravitational fields using linearised gravitational fields without imposing the TT gauge (as done in previous work), for any value of $\Lambda \in \mathbb{R}$. |
gr-qc/0504018 | Leonid Grishchuk P | L. P. Grishchuk | Relic Gravitational Waves and Cosmology | 36 pages including 8 figures; expanded version of a talk at the
international conference `Zeldovich-90', Moscow, December 2004;
http://hea.iki.rssi.ru/Z-90; v.2: additional formulas and explanations in
response to remarks of anonymous referee; v.3: extra details about 'scalar'
perturbations and T/S ratio, scheduled to appear in Uspekhi Fiz. Nauk v.176
(2006); v.4: matches published paper: Physics-Uspekhi, 48(12) 1235-1247
(2005) [Russian version: Uspekhi Fiz. Nauk, 175(12) 1289-1303 (2005)] | Phys.Usp.48:1235-1247,2005 | 10.1070/PU2005v048n12ABEH005795 | null | gr-qc astro-ph hep-ph hep-th | null | This is an expanded version of my talk given at the international conference
"Zeldovich-90". I start with a brief recollection of interactions with
Zeldovich in the context of the study of relic gravitational waves. I then
summarise the principles and early results on the quantum-mechanical generation
of cosmological perturbations. The expected amplitudes of relic gravitational
waves are different in different frequency windows, and therefore the
techniques and prospects of their detection are different. One section of the
paper describes the present state of efforts in direct detection of relic
gravitational waves. Another section is devoted to indirect detection via the
anisotropy and polarisation measurements of the cosmic microwave background
radiation (CMB). It is emphasized throughout the paper that the conclusions on
the existence and expected amount of relic gravitational waves are based on a
solid theoretical foundation and the best available cosmological observations.
I also explain in great detail what went wrong with the so-called `inflationary
gravitational waves', whose amount is predicted by inflationary theorists to be
negligibly small, thus depriving them of any observational significance.
| [
{
"created": "Tue, 5 Apr 2005 16:11:52 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jul 2005 15:55:49 GMT",
"version": "v2"
},
{
"created": "Sun, 13 Nov 2005 11:36:56 GMT",
"version": "v3"
},
{
"created": "Sun, 5 Mar 2006 14:32:07 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Grishchuk",
"L. P.",
""
]
] | This is an expanded version of my talk given at the international conference "Zeldovich-90". I start with a brief recollection of interactions with Zeldovich in the context of the study of relic gravitational waves. I then summarise the principles and early results on the quantum-mechanical generation of cosmological perturbations. The expected amplitudes of relic gravitational waves are different in different frequency windows, and therefore the techniques and prospects of their detection are different. One section of the paper describes the present state of efforts in direct detection of relic gravitational waves. Another section is devoted to indirect detection via the anisotropy and polarisation measurements of the cosmic microwave background radiation (CMB). It is emphasized throughout the paper that the conclusions on the existence and expected amount of relic gravitational waves are based on a solid theoretical foundation and the best available cosmological observations. I also explain in great detail what went wrong with the so-called `inflationary gravitational waves', whose amount is predicted by inflationary theorists to be negligibly small, thus depriving them of any observational significance. |
1904.11945 | Miguel Cruz | Miguel Cruz, Samuel Lepe and Gerardo Morales-Navarrete | A thermodynamics revision of Rastall gravity | 11 pages, 2 figures, accepted version in CQG | Class. Quantum Grav. 36, 225007 (2019) | 10.1088/1361-6382/ab45ab | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study some aspects of the Rastall gravity, being the
thermodynamics consistency of the model the core of this paper, for this
purpose we will consider the dynamical equations of Rastall model in a flat
FLRW geometry. Under a holographic description can be seen that this scenario
for gravity contributes to the energy density of the fluid with an extra term
that can be related to the deceleration parameter, providing a way to estimate
the value of the Rastall parameter, termed as $\xi \lambda$, at present time.
By adopting a specific Ansatz for the $\xi \lambda$ term it is possible to
determine that the behaviour of the Hubble parameter in Rastall gravity has a
similar aspect to the $\Lambda$CDM model at late times, but at thermodynamics
level differs from the standard cosmology since the adiabatic behaviour for the
entropy depends on the value of the parameter state, $\omega$. However, the
entropy has a positive growth and simultaneously its convexity condition can be
guaranteed; when other contributions are considered such as matter production
and chemical potential, the adiabatic expansion can not be achieved, but the
theory keeps its thermodynamics consistency. The chemical potential seems to
have an interesting role since at effective level we could have a cosmological
constant or phantom expansion in the model.
| [
{
"created": "Fri, 26 Apr 2019 17:23:52 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jun 2019 18:42:10 GMT",
"version": "v2"
},
{
"created": "Fri, 18 Oct 2019 18:34:21 GMT",
"version": "v3"
}
] | 2019-10-22 | [
[
"Cruz",
"Miguel",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Morales-Navarrete",
"Gerardo",
""
]
] | In this work we study some aspects of the Rastall gravity, being the thermodynamics consistency of the model the core of this paper, for this purpose we will consider the dynamical equations of Rastall model in a flat FLRW geometry. Under a holographic description can be seen that this scenario for gravity contributes to the energy density of the fluid with an extra term that can be related to the deceleration parameter, providing a way to estimate the value of the Rastall parameter, termed as $\xi \lambda$, at present time. By adopting a specific Ansatz for the $\xi \lambda$ term it is possible to determine that the behaviour of the Hubble parameter in Rastall gravity has a similar aspect to the $\Lambda$CDM model at late times, but at thermodynamics level differs from the standard cosmology since the adiabatic behaviour for the entropy depends on the value of the parameter state, $\omega$. However, the entropy has a positive growth and simultaneously its convexity condition can be guaranteed; when other contributions are considered such as matter production and chemical potential, the adiabatic expansion can not be achieved, but the theory keeps its thermodynamics consistency. The chemical potential seems to have an interesting role since at effective level we could have a cosmological constant or phantom expansion in the model. |
gr-qc/0010011 | Alessandra Buonanno | Alessandra Buonanno and Yanbei Chen | Optical noise correlations and beating the standard quantum limit in
advanced gravitational-wave detectors | 12 pages, 2 figures; minor changes, some references added | Class.Quant.Grav.18:L95-L101,2001 | 10.1088/0264-9381/18/15/102 | GRP/00/549 | gr-qc quant-ph | null | The uncertainty principle, applied naively to the test masses of a
laser-interferometer gravitational-wave detector, produces a Standard Quantum
Limit (SQL) on the interferometer's sensitivity. It has long been thought that
beating this SQL would require a radical redesign of interferometers. However,
we show that LIGO-II interferometers, currently planned for 2006, can beat the
SQL by as much as a factor two over a bandwidth \Delta f \sim f, if their
thermal noise can be pushed low enough. This is due to dynamical correlations
between photon shot noise and radiation-pressure noise, produced by the LIGO-II
signal-recycling mirror.
| [
{
"created": "Wed, 4 Oct 2000 04:45:56 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jul 2001 21:18:52 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Buonanno",
"Alessandra",
""
],
[
"Chen",
"Yanbei",
""
]
] | The uncertainty principle, applied naively to the test masses of a laser-interferometer gravitational-wave detector, produces a Standard Quantum Limit (SQL) on the interferometer's sensitivity. It has long been thought that beating this SQL would require a radical redesign of interferometers. However, we show that LIGO-II interferometers, currently planned for 2006, can beat the SQL by as much as a factor two over a bandwidth \Delta f \sim f, if their thermal noise can be pushed low enough. This is due to dynamical correlations between photon shot noise and radiation-pressure noise, produced by the LIGO-II signal-recycling mirror. |
2004.00907 | B. V. Ivanov | B.V. Ivanov | Linear and Riccati equations in generating functions for stellar models
in general relativity | accepted for publication in Eur. Phys. J. Plus | Eur. Phys. J. Plus 135 (2020) 377 | 10.1140/epjp/s13360-020-00380-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the expressions for the tangential pressure, the anisotropy
factor and the radial pressure in the Einstein equations may serve as
generating functions for stellar models. The latter can incorporate an equation
of state when the expression for the energy density is also used. Other
generating functions are based on the condition for the existence of conformal
motion (conformal flatness in particular) and the Karmarkar condition for
embedding class one metrics. In all these cases the equations are linear first
order differential equations for one of the metric components and Riccati
equations for the other. The latter may be always transformed into second order
homogenous linear differential equations. These conclusions are illustrated by
numerous particular examples from the study of stellar models.
| [
{
"created": "Thu, 2 Apr 2020 09:53:48 GMT",
"version": "v1"
}
] | 2020-04-30 | [
[
"Ivanov",
"B. V.",
""
]
] | It is shown that the expressions for the tangential pressure, the anisotropy factor and the radial pressure in the Einstein equations may serve as generating functions for stellar models. The latter can incorporate an equation of state when the expression for the energy density is also used. Other generating functions are based on the condition for the existence of conformal motion (conformal flatness in particular) and the Karmarkar condition for embedding class one metrics. In all these cases the equations are linear first order differential equations for one of the metric components and Riccati equations for the other. The latter may be always transformed into second order homogenous linear differential equations. These conclusions are illustrated by numerous particular examples from the study of stellar models. |
1810.09322 | Fabio Biancalana | Charles W. Robson, Leone Di Mauro Villari and Fabio Biancalana | On the Topological Nature of the Hawking Temperature of Black Holes | Updated version with more relevant references | Phys. Rev. D 99, 044042 (2019) | 10.1103/PhysRevD.99.044042 | null | gr-qc nlin.PS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we determine that the Hawking temperature of black holes
possesses a purely topological nature. We find a very simple but powerful
formula, based on a topological invariant known as the Euler characteristic,
which is able to provide the exact Hawking temperature of any two-dimensional
black hole -- and in fact of any metric that can be dimensionally reduced to
two dimensions -- in any given coordinate system, introducing a covariant way
to determine the temperature only using virtually trivial computations. We
apply the topological temperature formula to several known black hole systems
as well as to the Hawking emission of solitons of integrable equations.
| [
{
"created": "Mon, 22 Oct 2018 14:44:59 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Oct 2018 13:03:06 GMT",
"version": "v2"
}
] | 2019-02-27 | [
[
"Robson",
"Charles W.",
""
],
[
"Villari",
"Leone Di Mauro",
""
],
[
"Biancalana",
"Fabio",
""
]
] | In this work we determine that the Hawking temperature of black holes possesses a purely topological nature. We find a very simple but powerful formula, based on a topological invariant known as the Euler characteristic, which is able to provide the exact Hawking temperature of any two-dimensional black hole -- and in fact of any metric that can be dimensionally reduced to two dimensions -- in any given coordinate system, introducing a covariant way to determine the temperature only using virtually trivial computations. We apply the topological temperature formula to several known black hole systems as well as to the Hawking emission of solitons of integrable equations. |
gr-qc/9303017 | null | Vanda Silveira and M.D. Maia (Universidade de Brasilia) | Topologica Defects and Corrections to the Nambu Action | UNB.FIS.FM-002/92, Marcos@FNAL, 12 pages, Latex | Phys.Lett.A174:280-284,1993 | 10.1016/0375-9601(93)90138-P | null | gr-qc | null | The effective action of a (1+2)-dimensional defect is obtained as an
expansion in powers of the thickness.Considering non-straight solutions as the
zero order term, the corrections to the Nambu action are found to depend on the
curvature scalar and on the gaussian curvature .
| [
{
"created": "Thu, 11 Mar 1993 22:53:08 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Silveira",
"Vanda",
"",
"Universidade de Brasilia"
],
[
"Maia",
"M. D.",
"",
"Universidade de Brasilia"
]
] | The effective action of a (1+2)-dimensional defect is obtained as an expansion in powers of the thickness.Considering non-straight solutions as the zero order term, the corrections to the Nambu action are found to depend on the curvature scalar and on the gaussian curvature . |
1005.2046 | Antoine Klein | Antoine Klein, Philippe Jetzer | Spin effects in the phasing of gravitational waves from binaries on
eccentric orbits | 7 pages, 1 figure; Accepted for publication in Phys. Rev. D | Phys.Rev.D81:124001,2010 | 10.1103/PhysRevD.81.124001 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute here the spin-orbit and spin-spin couplings needed for an accurate
computation of the phasing of gravitational waves emitted by comparable-mass
binaries on eccentric orbits at the second post-Newtonian (PN) order. We use a
quasi-Keplerian parametrization of the orbit free of divergencies in the zero
eccentricity limit. We find that spin-spin couplings induce a residual
eccentricity for coalescing binaries at 2PN, of the order of
$10^{-4}$-$10^{-3}$ for supermassive black hole binaries in the LISA band.
Spin-orbit precession also induces a non-trivial pattern in the evolution of
the eccentricity, which could help to reduce the errors on the determination of
the eccentricity and spins in a gravitational wave measurement.
| [
{
"created": "Wed, 12 May 2010 10:58:47 GMT",
"version": "v1"
}
] | 2015-03-17 | [
[
"Klein",
"Antoine",
""
],
[
"Jetzer",
"Philippe",
""
]
] | We compute here the spin-orbit and spin-spin couplings needed for an accurate computation of the phasing of gravitational waves emitted by comparable-mass binaries on eccentric orbits at the second post-Newtonian (PN) order. We use a quasi-Keplerian parametrization of the orbit free of divergencies in the zero eccentricity limit. We find that spin-spin couplings induce a residual eccentricity for coalescing binaries at 2PN, of the order of $10^{-4}$-$10^{-3}$ for supermassive black hole binaries in the LISA band. Spin-orbit precession also induces a non-trivial pattern in the evolution of the eccentricity, which could help to reduce the errors on the determination of the eccentricity and spins in a gravitational wave measurement. |
gr-qc/0208087 | Carlos Palenzuela | C. Bona, T. Ledvinka and C. Palenzuela | A 3+1 covariant suite of Numerical Relativity Evolution Systems | null | Phys.Rev.D66:084013,2002 | 10.1103/PhysRevD.66.084013 | null | gr-qc | null | A suite of three evolution systems is presented in the framework of the 3+1
formalism. The first one is of second order in space derivatives and has the
same causal structure of the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) system
for a suitable choice of parameters. The second one is the standard first order
version of the first one and has the same causal structure of the Bona-Masso
system for a given parameter choice. The third one is obtained from the second
one by reducing the space of variables in such a way that the only modes that
propagate with zero characteristic speed are the trivial ones. This last system
has the same structure of the ones recently presented by Kidder, Scheel and
Teukolski: the correspondence between both sets of parameters is explicitly
given. The fact that the suite started with a system in which all the dynamical
variables behave as tensors (contrary to what happens with BSSN system) allows
one to keep the same parametrization when passing from one system to the next
in the suite. The direct relationship between each parameter and a particular
characteristic speed, which is quite evident in the second and the third
systems, is a direct consequence of the manifest 3+1 covariance of the
approach.
| [
{
"created": "Wed, 28 Aug 2002 15:23:42 GMT",
"version": "v1"
}
] | 2010-05-19 | [
[
"Bona",
"C.",
""
],
[
"Ledvinka",
"T.",
""
],
[
"Palenzuela",
"C.",
""
]
] | A suite of three evolution systems is presented in the framework of the 3+1 formalism. The first one is of second order in space derivatives and has the same causal structure of the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) system for a suitable choice of parameters. The second one is the standard first order version of the first one and has the same causal structure of the Bona-Masso system for a given parameter choice. The third one is obtained from the second one by reducing the space of variables in such a way that the only modes that propagate with zero characteristic speed are the trivial ones. This last system has the same structure of the ones recently presented by Kidder, Scheel and Teukolski: the correspondence between both sets of parameters is explicitly given. The fact that the suite started with a system in which all the dynamical variables behave as tensors (contrary to what happens with BSSN system) allows one to keep the same parametrization when passing from one system to the next in the suite. The direct relationship between each parameter and a particular characteristic speed, which is quite evident in the second and the third systems, is a direct consequence of the manifest 3+1 covariance of the approach. |
2111.01298 | Marcelo Byrro Ribeiro | Osvaldo L. Santos-Pereira, Everton M. C. Abreu, Marcelo B. Ribeiro | Warp drive dynamic solutions considering different fluid sources | 16 pages, 4 tables, LaTeX. To appear in the Proceedings of the 16th
Marcel Grossmann Meeting (July 5-10, 2021) | Proc. 16th Marcel Grossmann Meeting on General Relativity (5-10
July 2021) - Part A; R. Ruffini & G. Vereshchagin (eds), pp. 840-855.
Singapore: World Scientific, (2023) | 10.1142/9789811269776_0066 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Alcubierre proposed in 1994 that the well known special relativistic
limitation that particles cannot travel with velocities bigger than the light
speed can be bypassed when such trips are considered globally within specific
general relativistic frameworks. Although initial results indicated this
scenario as being unphysical, since it would seem to require negative
mass-energy density, recent theoretical analyses suggest that such an
unphysical situation may not always be necessarily true. In this paper we
review some solutions of the Einstein equations using the original Alcubierre
warp drive metric endowed with various matter-energy sources, namely dust,
perfect fluid, anisotropic fluid, and perfect fluid with a cosmological
constant. A connection of some of these solutions featuring shock waves
described by the Burgers equation is also shown.
| [
{
"created": "Mon, 1 Nov 2021 23:47:50 GMT",
"version": "v1"
}
] | 2023-01-31 | [
[
"Santos-Pereira",
"Osvaldo L.",
""
],
[
"Abreu",
"Everton M. C.",
""
],
[
"Ribeiro",
"Marcelo B.",
""
]
] | Alcubierre proposed in 1994 that the well known special relativistic limitation that particles cannot travel with velocities bigger than the light speed can be bypassed when such trips are considered globally within specific general relativistic frameworks. Although initial results indicated this scenario as being unphysical, since it would seem to require negative mass-energy density, recent theoretical analyses suggest that such an unphysical situation may not always be necessarily true. In this paper we review some solutions of the Einstein equations using the original Alcubierre warp drive metric endowed with various matter-energy sources, namely dust, perfect fluid, anisotropic fluid, and perfect fluid with a cosmological constant. A connection of some of these solutions featuring shock waves described by the Burgers equation is also shown. |
1512.09259 | Dragoljub Dimitrijevic | Dragoljub D. Dimitrijevic, Goran S. Djordjevic and Milan Milosevic | Classicalization and Quantization of Tachyon-like Matter on
(non)Archimedean Spaces | null | Romanian Reports in Physics, Volume 68, Number 1, 2016 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a class of tachyon-like potentials, inspired by string theory,
D-brane dynamics and cosmology in the context of classical and quantum
mechanics. Motivated by the trans-Plankcian problem in the very early stage of
cosmological evolution of the Universe, we consider the theoretical role of
DBI-type tachyon scalar field, defined over the field of real as well as
$p$-adic numbers, i.e. archemedean and nonarchimedean spaces. To simplify the
equation of motion for the scalar field, canonical transformations are defined
and engaged. The corresponding quantum propagators in the Feynman path integral
approach on real and nonarchimedean spaces are calculated and discussed, as are
possibilities for a quantum adelic generalization and its application.
| [
{
"created": "Thu, 31 Dec 2015 11:17:40 GMT",
"version": "v1"
}
] | 2016-01-01 | [
[
"Dimitrijevic",
"Dragoljub D.",
""
],
[
"Djordjevic",
"Goran S.",
""
],
[
"Milosevic",
"Milan",
""
]
] | We consider a class of tachyon-like potentials, inspired by string theory, D-brane dynamics and cosmology in the context of classical and quantum mechanics. Motivated by the trans-Plankcian problem in the very early stage of cosmological evolution of the Universe, we consider the theoretical role of DBI-type tachyon scalar field, defined over the field of real as well as $p$-adic numbers, i.e. archemedean and nonarchimedean spaces. To simplify the equation of motion for the scalar field, canonical transformations are defined and engaged. The corresponding quantum propagators in the Feynman path integral approach on real and nonarchimedean spaces are calculated and discussed, as are possibilities for a quantum adelic generalization and its application. |
2204.01015 | Salvatore Capozziello | Salvatore Capozziello and Rocco D'Agostino | Model-independent reconstruction of $f(Q)$ non-metric gravity | 6 pages, 2 figures, accepted for publication in Physics Letters B | null | 10.1016/j.physletb.2022.137229 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider gravity mediated by non-metricity, with vanishing curvature and
torsion. The gravitational action, including an arbitrary function of the
non-metric scalar, is investigated in view of characterizing the dark energy
effects. In particular, we present a method to reconstruct the $f(Q)$ action
without resorting to \emph{a priori} assumptions on the cosmological model. To
this purpose, we adopt a method based on rational Pad\'e approximations, which
provides a stable behaviour of the cosmographic series at high redshifts,
alleviating the convergence issues proper of the standard approach. We thus
describe how to reconstruct $f(Q)$ through a numerical inversion procedure
based on the current observational bounds on cosmographic parameters. Our
analysis suggests that the best approximation for describing the accelerated
expansion of the universe is represented by a scenario with $f(Q)=\alpha+\beta
Q^{n}$. Finally, possible deviations from the standard $\Lambda$CDM model are
discussed.
| [
{
"created": "Sun, 3 Apr 2022 07:29:54 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Jun 2022 10:54:49 GMT",
"version": "v2"
}
] | 2022-07-13 | [
[
"Capozziello",
"Salvatore",
""
],
[
"D'Agostino",
"Rocco",
""
]
] | We consider gravity mediated by non-metricity, with vanishing curvature and torsion. The gravitational action, including an arbitrary function of the non-metric scalar, is investigated in view of characterizing the dark energy effects. In particular, we present a method to reconstruct the $f(Q)$ action without resorting to \emph{a priori} assumptions on the cosmological model. To this purpose, we adopt a method based on rational Pad\'e approximations, which provides a stable behaviour of the cosmographic series at high redshifts, alleviating the convergence issues proper of the standard approach. We thus describe how to reconstruct $f(Q)$ through a numerical inversion procedure based on the current observational bounds on cosmographic parameters. Our analysis suggests that the best approximation for describing the accelerated expansion of the universe is represented by a scenario with $f(Q)=\alpha+\beta Q^{n}$. Finally, possible deviations from the standard $\Lambda$CDM model are discussed. |
2003.04304 | Gabriele Gionti S.J. | Gabriele Gionti, S.J | Canonical Analysis of Brans-Dicke Theory Addresses Hamiltonian
Inequivalence between Jordan and Einstein Frames | Revised version PRD accepted. 8 pages, Article, latex. Detailed
calculations added. Typo corrected | Phys. Rev. D 103, 024022 (2021) | 10.1103/PhysRevD.103.024022 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Jordan and Einstein frame are studied under the light of Hamiltonian
formalism. Dirac's constraint theory for Hamiltonian systems is applied to
Brans-Dicke theory in the Jordan Frame. In both Jordan and Einstein frame,
Brans-Dicke theory has four secondary first class constraints and their
constraint algebra is closed. We show, contrary to what is generally believed,
the Weyl (conformal) transformation, between the two frames, is not a canonical
transformation, in the sense of Hamiltonian formalism. This addresses quantum
mechanical inequivalence as well. A canonical transformation is shown.
| [
{
"created": "Fri, 6 Mar 2020 19:18:23 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Mar 2020 12:04:14 GMT",
"version": "v2"
},
{
"created": "Wed, 30 Sep 2020 15:03:59 GMT",
"version": "v3"
},
{
"created": "Mon, 23 Nov 2020 08:47:45 GMT",
"version": "v4"
},
{
"cr... | 2021-01-20 | [
[
"Gionti",
"Gabriele",
""
],
[
"J",
"S.",
""
]
] | Jordan and Einstein frame are studied under the light of Hamiltonian formalism. Dirac's constraint theory for Hamiltonian systems is applied to Brans-Dicke theory in the Jordan Frame. In both Jordan and Einstein frame, Brans-Dicke theory has four secondary first class constraints and their constraint algebra is closed. We show, contrary to what is generally believed, the Weyl (conformal) transformation, between the two frames, is not a canonical transformation, in the sense of Hamiltonian formalism. This addresses quantum mechanical inequivalence as well. A canonical transformation is shown. |
1502.05905 | Alfred Molina | J. Mart\'in, A. Molina and E. Ruiz | Perturbation theory and harmonic gauge propagation in general
relativity, a particular example | 19 pages, 0 figures | null | 10.1007/s10714-015-1947-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study how the changes of coordinates between the class of harmonic
coordinates affect the analitycal solutions of Einstein's equations and we
apply it to an analytical approach for stationary and axisymmetric solutions of
Einstein equation used by the authors \cite{cmmr}, \cite{cugmmr} to solve the
problem of a self-gravitating rigidly rotating perfect fluid compact source.
| [
{
"created": "Fri, 20 Feb 2015 15:34:18 GMT",
"version": "v1"
}
] | 2015-09-23 | [
[
"Martín",
"J.",
""
],
[
"Molina",
"A.",
""
],
[
"Ruiz",
"E.",
""
]
] | We study how the changes of coordinates between the class of harmonic coordinates affect the analitycal solutions of Einstein's equations and we apply it to an analytical approach for stationary and axisymmetric solutions of Einstein equation used by the authors \cite{cmmr}, \cite{cugmmr} to solve the problem of a self-gravitating rigidly rotating perfect fluid compact source. |
2302.12158 | Andrea Miani | Andrea Miani, Claudia Lazzaro, Giovanni Andrea Prodi, Shubhanshu
Tiwari, Marco Drago, Edoardo Milotti, Gabriele Vedovato | Constraints on the amplitude of gravitational wave echoes from black
hole ring-down using minimal assumptions | 16 pages, 11 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravitational wave echoes may appear following a compact binary coalescence
if the remnant is an "exotic compact object" (ECO). ECOs are proposed
alternatives to the black holes of Einstein's general relativity theory and are
predicted to possess reflective boundaries. This work reports a search for
gravitational wave transients (GWTs) of generic morphology occurring shortly
after (<1s) binary black hole (BBH) mergers, therefore targeting all
gravitational wave echo models. We investigated the times after the ringdown
for the higher signal-to-noise ratio BBHs within the public catalog GWTC-3 by
the LIGO-Virgo-KAGRA collaborations (LVK). Our search is based on the
coherentWaveBurst pipeline, widely used in generic searches for GWTs by the
LVK, and deploys new methods to enhance its detection performances at low
signal-to-noise ratios. We employ Monte Carlo simulations for estimating the
detection efficiency of the search and determining the statistical significance
of candidates. We find no evidence of previously undetected GWTs and our
loudest candidates are morphologically consistent with known instrumental noise
disturbances. Finally, we set upper limits on the amplitude of GW echoes for
single BBH mergers.
| [
{
"created": "Thu, 23 Feb 2023 16:43:25 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jul 2023 11:07:56 GMT",
"version": "v2"
}
] | 2023-07-07 | [
[
"Miani",
"Andrea",
""
],
[
"Lazzaro",
"Claudia",
""
],
[
"Prodi",
"Giovanni Andrea",
""
],
[
"Tiwari",
"Shubhanshu",
""
],
[
"Drago",
"Marco",
""
],
[
"Milotti",
"Edoardo",
""
],
[
"Vedovato",
"Gabriele",
"... | Gravitational wave echoes may appear following a compact binary coalescence if the remnant is an "exotic compact object" (ECO). ECOs are proposed alternatives to the black holes of Einstein's general relativity theory and are predicted to possess reflective boundaries. This work reports a search for gravitational wave transients (GWTs) of generic morphology occurring shortly after (<1s) binary black hole (BBH) mergers, therefore targeting all gravitational wave echo models. We investigated the times after the ringdown for the higher signal-to-noise ratio BBHs within the public catalog GWTC-3 by the LIGO-Virgo-KAGRA collaborations (LVK). Our search is based on the coherentWaveBurst pipeline, widely used in generic searches for GWTs by the LVK, and deploys new methods to enhance its detection performances at low signal-to-noise ratios. We employ Monte Carlo simulations for estimating the detection efficiency of the search and determining the statistical significance of candidates. We find no evidence of previously undetected GWTs and our loudest candidates are morphologically consistent with known instrumental noise disturbances. Finally, we set upper limits on the amplitude of GW echoes for single BBH mergers. |
1611.07586 | Amare Abebe | Amare Abebe, Peter K.S. Dunsby, Deon Solomons | Integrability conditions of quasi-Newtonian cosmologies in modified
gravity | 13 pages, no figures | Int. J. Mod. Phys. D Vol. 26 (2017) 1750054 | 10.1142/S0218271817500547 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the integrability conditions of a class of shear-free
perfect-fluid cosmological models within the framework of anisotropic fluid
sources, applying our results to f(R) dark energy models. Generalising earlier
general relativistic results for time-like geodesics, we extend the potential
and acceleration terms of the quasi-Newtonian formulation of integrable dust
cosmological models about a linearized Friedmann-Lemaitre-Robertson-Walker
background and derive the equations that describe their dynamical evolutions.
We show that in general, models with an anisotropic fluid source are not
consistent, but because of the particular form the anisotropic stress takes in
f(R) gravity, the general integrability conditions, in this case, are
satisfied.
| [
{
"created": "Wed, 23 Nov 2016 00:03:52 GMT",
"version": "v1"
}
] | 2016-11-24 | [
[
"Abebe",
"Amare",
""
],
[
"Dunsby",
"Peter K. S.",
""
],
[
"Solomons",
"Deon",
""
]
] | We investigate the integrability conditions of a class of shear-free perfect-fluid cosmological models within the framework of anisotropic fluid sources, applying our results to f(R) dark energy models. Generalising earlier general relativistic results for time-like geodesics, we extend the potential and acceleration terms of the quasi-Newtonian formulation of integrable dust cosmological models about a linearized Friedmann-Lemaitre-Robertson-Walker background and derive the equations that describe their dynamical evolutions. We show that in general, models with an anisotropic fluid source are not consistent, but because of the particular form the anisotropic stress takes in f(R) gravity, the general integrability conditions, in this case, are satisfied. |
1711.09891 | Saumya Ghosh | Saumya Ghosh, Sunandan Gangopadhyay, Prasanta K. Panigrahi | Scalar-metric quantum cosmology with Chaplygin gas and perfect fluid | 8 pages LateX | null | 10.1140/epjc/s10052-018-5521-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider the flat FRW cosmology with a scalar field coupled
with the metric along with generalized Chaplygin gas and perfect fluid
comprising the matter sector. We use the Schutz's formalism to deal with the
generalized Chaplygin gas sector. The full theory is then quantized canonically
using the Wheeler-DeWitt Hamiltonian formalism. We then solve the WD equation
with appropriate boundary conditions. Then by defining a proper completeness
relation for the self-adjointness of the WD equation we arrive at the wave
packet for the universe. It is observed that the peak in the probability
density gets affected due to both fluids in the matter sector, namely, the
Chaplygin gas and perfect fluid.
| [
{
"created": "Mon, 27 Nov 2017 10:33:38 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Ghosh",
"Saumya",
""
],
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Panigrahi",
"Prasanta K.",
""
]
] | In this paper we consider the flat FRW cosmology with a scalar field coupled with the metric along with generalized Chaplygin gas and perfect fluid comprising the matter sector. We use the Schutz's formalism to deal with the generalized Chaplygin gas sector. The full theory is then quantized canonically using the Wheeler-DeWitt Hamiltonian formalism. We then solve the WD equation with appropriate boundary conditions. Then by defining a proper completeness relation for the self-adjointness of the WD equation we arrive at the wave packet for the universe. It is observed that the peak in the probability density gets affected due to both fluids in the matter sector, namely, the Chaplygin gas and perfect fluid. |
1605.09286 | Emanuele Berti | Emanuele Berti, Alberto Sesana, Enrico Barausse, Vitor Cardoso,
Krzysztof Belczynski | Spectroscopy of Kerr black holes with Earth- and space-based
interferometers | 3 figures; small changes to match version published in Physical
Review Letters | Phys. Rev. Lett. 117, 101102 (2016) | 10.1103/PhysRevLett.117.101102 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We estimate the potential of present and future interferometric
gravitational-wave detectors to test the Kerr nature of black holes through
"gravitational spectroscopy," i.e. the measurement of multiple quasinormal mode
frequencies from the remnant of a black hole merger. Using population synthesis
models of the formation and evolution of stellar-mass black hole binaries, we
find that Voyager-class interferometers will be necessary to perform these
tests. Gravitational spectroscopy in the local Universe may become routine with
the Einstein Telescope, but a 40-km facility like Cosmic Explorer is necessary
to go beyond $z\sim 3$. In contrast, eLISA-like detectors should carry out a
few - or even hundreds - of these tests every year, depending on uncertainties
in massive black hole formation models. Many space-based spectroscopical
measurements will occur at high redshift, testing the strong gravity dynamics
of Kerr black holes in domains where cosmological corrections to general
relativity (if they occur in nature) must be significant.
| [
{
"created": "Mon, 30 May 2016 15:42:15 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2016 00:06:22 GMT",
"version": "v2"
}
] | 2016-09-07 | [
[
"Berti",
"Emanuele",
""
],
[
"Sesana",
"Alberto",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Belczynski",
"Krzysztof",
""
]
] | We estimate the potential of present and future interferometric gravitational-wave detectors to test the Kerr nature of black holes through "gravitational spectroscopy," i.e. the measurement of multiple quasinormal mode frequencies from the remnant of a black hole merger. Using population synthesis models of the formation and evolution of stellar-mass black hole binaries, we find that Voyager-class interferometers will be necessary to perform these tests. Gravitational spectroscopy in the local Universe may become routine with the Einstein Telescope, but a 40-km facility like Cosmic Explorer is necessary to go beyond $z\sim 3$. In contrast, eLISA-like detectors should carry out a few - or even hundreds - of these tests every year, depending on uncertainties in massive black hole formation models. Many space-based spectroscopical measurements will occur at high redshift, testing the strong gravity dynamics of Kerr black holes in domains where cosmological corrections to general relativity (if they occur in nature) must be significant. |
gr-qc/9610073 | null | Alexandr K. Guts, Egor B. Grinkevich | Toposes in General Theory of Relativity | 13 pages, LATEX, email guts@univer.omsk.su, grinkev@univer.omsk.su | null | null | null | gr-qc | null | We study in this paper different topos-theoretical approaches to the problem
of construction of General Theory of Relativity. In general case the resulting
space-time theory will be non-classical, different from that of the usual
Einstein theory of space-time. This is a new theory of space-time, created in a
purely logical manner. Four possibitities are investigated: axiomatic approach
to causal theory of space-time, the smooth toposes as a models of Theory of
Relativity, Synthetic Theory of Relativity, and space-time as Grothendieck
topos.
| [
{
"created": "Thu, 31 Oct 1996 14:18:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Guts",
"Alexandr K.",
""
],
[
"Grinkevich",
"Egor B.",
""
]
] | We study in this paper different topos-theoretical approaches to the problem of construction of General Theory of Relativity. In general case the resulting space-time theory will be non-classical, different from that of the usual Einstein theory of space-time. This is a new theory of space-time, created in a purely logical manner. Four possibitities are investigated: axiomatic approach to causal theory of space-time, the smooth toposes as a models of Theory of Relativity, Synthetic Theory of Relativity, and space-time as Grothendieck topos. |
1801.06392 | Mart\'in G. Richarte MR | G.M.Kremer, M.G. Richarte, F. Teston | Jeans Instability in a Universe with Dissipation | 17pp, 5 figures.Phys. Rev. D 97, 023515 (2018) | null | 10.1103/PhysRevD.97.023515 | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of Jeans gravitational instability is investigated for static and
expanding universes within the context of the five and thirteen field theories
which account for viscous and thermal effects. For the five-field theory a
general dispersion relation has been derived with the help of relevant
linearized perturbation equations, showing that the shear viscosity parameter
alters the propagating modes for large and small wavelengths. The behavior of
density and temperature contrasts are analyzed for the hard-sphere model in
detail. In the small wavelengths regime, increasing the amount of shear
viscosity into the system forces the harmonic perturbations to damp faster,
however, in the opposite limit larger values of shear viscosity lead to smaller
values of density and temperature contrasts. For the hyperbolic case, the
dispersion relation becomes a polynomial in the frequency with two orders
higher in relation to the five-field theory, indicating that the effects
associated with the shear viscosity and heat flux are non-trivial. The profile
of Jeans mass in terms of the temperature and number density is explored by
contrasting with several data of molecular clouds. Regarding the dynamical
evolution of the density, temperature, stress and heat flux contrasts for a
universe dominated by pressureless matter, we obtain also damped harmonic waves
for small wavelengths. In the case of large wavelengths, the density and
temperature contrasts grow with time (due to the Jeans mechanism) while the
stress and heat flux contrasts heavily decay with time.
| [
{
"created": "Fri, 19 Jan 2018 13:14:51 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jan 2018 14:10:30 GMT",
"version": "v2"
}
] | 2018-01-23 | [
[
"Kremer",
"G. M.",
""
],
[
"Richarte",
"M. G.",
""
],
[
"Teston",
"F.",
""
]
] | The problem of Jeans gravitational instability is investigated for static and expanding universes within the context of the five and thirteen field theories which account for viscous and thermal effects. For the five-field theory a general dispersion relation has been derived with the help of relevant linearized perturbation equations, showing that the shear viscosity parameter alters the propagating modes for large and small wavelengths. The behavior of density and temperature contrasts are analyzed for the hard-sphere model in detail. In the small wavelengths regime, increasing the amount of shear viscosity into the system forces the harmonic perturbations to damp faster, however, in the opposite limit larger values of shear viscosity lead to smaller values of density and temperature contrasts. For the hyperbolic case, the dispersion relation becomes a polynomial in the frequency with two orders higher in relation to the five-field theory, indicating that the effects associated with the shear viscosity and heat flux are non-trivial. The profile of Jeans mass in terms of the temperature and number density is explored by contrasting with several data of molecular clouds. Regarding the dynamical evolution of the density, temperature, stress and heat flux contrasts for a universe dominated by pressureless matter, we obtain also damped harmonic waves for small wavelengths. In the case of large wavelengths, the density and temperature contrasts grow with time (due to the Jeans mechanism) while the stress and heat flux contrasts heavily decay with time. |
1607.02315 | Jose Luis Hernandez-Pastora | J.L. Hernandez-Pastora, L. Herrera and J. Martin | Axially symmetric static sources of gravitational field | 17 pages, 13 figures and 3 tables, typos corrected, published in CQG:
Class. Quantum Grav. 33, 235005, (2016) | null | 10.1088/0264-9381/33/23/235005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general procedure to find static and axially symmetric, interior solutions
to the Einstein equations is presented. All the so obtained solutions, verify
the energy conditions for a wide range of values of the parameters, and match
smoothly to some exterior solution of the Weyl family, thereby representing
globally regular models describing non spherical sources of gravitational
field. In the spherically symmetric limit, all our models converge to the well
known incompressible perfect fluid solution.The key stone of our approach is
based on an ansatz allowing to define the interior metric in terms of the
exterior metric functions evaluated at the boundary source. Some particular
sources are obtained, and the physical variables of the energy-momentum tensor
are calculated explicitly, as well as the geometry of the source in terms of
the relativistic multipole moments. The total mass of different configurations
is also calculated, it is shown to be equal to the monopole of the exterior
solution.
| [
{
"created": "Fri, 8 Jul 2016 11:10:01 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Oct 2016 06:46:10 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Nov 2016 08:01:33 GMT",
"version": "v3"
}
] | 2016-11-07 | [
[
"Hernandez-Pastora",
"J. L.",
""
],
[
"Herrera",
"L.",
""
],
[
"Martin",
"J.",
""
]
] | A general procedure to find static and axially symmetric, interior solutions to the Einstein equations is presented. All the so obtained solutions, verify the energy conditions for a wide range of values of the parameters, and match smoothly to some exterior solution of the Weyl family, thereby representing globally regular models describing non spherical sources of gravitational field. In the spherically symmetric limit, all our models converge to the well known incompressible perfect fluid solution.The key stone of our approach is based on an ansatz allowing to define the interior metric in terms of the exterior metric functions evaluated at the boundary source. Some particular sources are obtained, and the physical variables of the energy-momentum tensor are calculated explicitly, as well as the geometry of the source in terms of the relativistic multipole moments. The total mass of different configurations is also calculated, it is shown to be equal to the monopole of the exterior solution. |
1805.10650 | Helei Liu | B. Eslam Panah and H.L. Liu | White dwarfs in de Rham-Gabadadze-Tolley like massive gravity | 13 pages, 7 figures and 4 tables | Phys. Rev. D 99, 104074 (2019) | 10.1103/PhysRevD.99.104074 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of possible massive white dwarfs more than the Chandrasekhar
limit ($1.45M_{\odot }$, in which $M_{\odot }$ is mass of the sun) is a
challenging topic. In this regard and motivated by the important effect of
massive graviton on the structure of white dwarfs we study the white dwarfs in
Vegh's massive gravity which is known as one of theories of de Rham, Gabadadze
and Tolley (dRGT) like massive gravity. First, we consider the modified
Tolman-Oppenheimer-Volkoff equation in this theory of massive gravity and solve
it numerically by using the Chandrasekhar's equation of state. Our results show
that the maximum mass of white dwarfs in massive gravity can be more than the
Chandrasekhar limit ($M>1.45M_{\odot }$ ), and this result imposes some
constraints on parameters of massive gravity. Then, we investigate the effects
of various parameters on other properties of the white dwarfs such as
mass-radius relation, mass-central density relation, Schwarzschild radius,
average density and Kretschmann scalar. Next, we study dynamical stability
condition for super-Chandrasekhar white dwarfs and show that these massive
compact objects enjoy dynamical stability. Finally, in order to have a better
insight, we compare the super-Chandrasekhar white dwarfs with the obtained
massive neutron stars in dRGT like massive theory of gravity.
| [
{
"created": "Sun, 27 May 2018 16:41:52 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Oct 2018 15:29:37 GMT",
"version": "v2"
},
{
"created": "Tue, 30 Oct 2018 09:37:44 GMT",
"version": "v3"
},
{
"created": "Thu, 30 May 2019 17:09:19 GMT",
"version": "v4"
},
{
"c... | 2019-06-05 | [
[
"Panah",
"B. Eslam",
""
],
[
"Liu",
"H. L.",
""
]
] | The existence of possible massive white dwarfs more than the Chandrasekhar limit ($1.45M_{\odot }$, in which $M_{\odot }$ is mass of the sun) is a challenging topic. In this regard and motivated by the important effect of massive graviton on the structure of white dwarfs we study the white dwarfs in Vegh's massive gravity which is known as one of theories of de Rham, Gabadadze and Tolley (dRGT) like massive gravity. First, we consider the modified Tolman-Oppenheimer-Volkoff equation in this theory of massive gravity and solve it numerically by using the Chandrasekhar's equation of state. Our results show that the maximum mass of white dwarfs in massive gravity can be more than the Chandrasekhar limit ($M>1.45M_{\odot }$ ), and this result imposes some constraints on parameters of massive gravity. Then, we investigate the effects of various parameters on other properties of the white dwarfs such as mass-radius relation, mass-central density relation, Schwarzschild radius, average density and Kretschmann scalar. Next, we study dynamical stability condition for super-Chandrasekhar white dwarfs and show that these massive compact objects enjoy dynamical stability. Finally, in order to have a better insight, we compare the super-Chandrasekhar white dwarfs with the obtained massive neutron stars in dRGT like massive theory of gravity. |
1405.0667 | Behnam Pourhassan | B. Pourhassan, E.O. Kahya | FRW cosmology with the extended Chaplygin gas | 20 pages | Advances in High Energy PhysicsVolume 2014 (2014) Article ID
231452 | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we propose extended Chaplygin gas equation of state for which
it recovers barotropic fluid with quadratic equation of state. We use numerical
method to investigate the behavior of some cosmological parameters such as
scale factor, Hubble expansion parameter, energy density and deceleration
parameter. We also discuss about the resulting effective equation of state
parameter. Using density perturbations we investigate the stability of the
theory.
| [
{
"created": "Sun, 4 May 2014 09:00:52 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Aug 2014 07:15:30 GMT",
"version": "v2"
}
] | 2014-09-17 | [
[
"Pourhassan",
"B.",
""
],
[
"Kahya",
"E. O.",
""
]
] | In this paper, we propose extended Chaplygin gas equation of state for which it recovers barotropic fluid with quadratic equation of state. We use numerical method to investigate the behavior of some cosmological parameters such as scale factor, Hubble expansion parameter, energy density and deceleration parameter. We also discuss about the resulting effective equation of state parameter. Using density perturbations we investigate the stability of the theory. |
2306.09181 | Seyed Ali Hosseini Mansoori | Seyed Ali Hosseini Mansoori, Fereshteh Felegary, Mahmood Roshan, Ozgur
Akarsu, Mohammad Sami | $\mathbb{T}^{2}$- inflation: Sourced by energy-momentum squared gravity | 25 pages, 4 figures, and 2 tables, added discussion, accepted by
Physics of the Dark Universe | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we examine chaotic inflation within the context of the
energy-momentum squared gravity (EMSG) focusing on the energy-momentum powered
gravity (EMPG) that incorporates the functional $f(\mathbb{T}^2)\propto
(\mathbb{T}^2)^{\beta}$ in the Einstein-Hilbert action, in which $\beta$ is a
constant and $\mathbb{T}^2\equiv T_{\mu \nu}T^{\mu \nu}$ where $T_{\mu \nu}$ is
the energy-momentum tensor, which we consider to represent a single scalar
field with a power-law potential. We demonstrate that the presence of EMSG
terms allows the single-field monomial chaotic inflationary models to fall
within current observational constraints, which are otherwise disfavored by
Planck and BICEP/Keck findings. We show that the use of a non-canonical
Lagrangian with chaotic potential in EMSG can lead to significantly larger
values of the non-Gaussianity parameter, $f_{\rm Nl}^{\rm equi}$ whereas EMSG
framework with canonical Lagrangian gives rise to results similar to those of
the standard single-field model.
| [
{
"created": "Thu, 15 Jun 2023 15:02:26 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Oct 2023 04:31:35 GMT",
"version": "v2"
}
] | 2023-10-20 | [
[
"Mansoori",
"Seyed Ali Hosseini",
""
],
[
"Felegary",
"Fereshteh",
""
],
[
"Roshan",
"Mahmood",
""
],
[
"Akarsu",
"Ozgur",
""
],
[
"Sami",
"Mohammad",
""
]
] | In this paper, we examine chaotic inflation within the context of the energy-momentum squared gravity (EMSG) focusing on the energy-momentum powered gravity (EMPG) that incorporates the functional $f(\mathbb{T}^2)\propto (\mathbb{T}^2)^{\beta}$ in the Einstein-Hilbert action, in which $\beta$ is a constant and $\mathbb{T}^2\equiv T_{\mu \nu}T^{\mu \nu}$ where $T_{\mu \nu}$ is the energy-momentum tensor, which we consider to represent a single scalar field with a power-law potential. We demonstrate that the presence of EMSG terms allows the single-field monomial chaotic inflationary models to fall within current observational constraints, which are otherwise disfavored by Planck and BICEP/Keck findings. We show that the use of a non-canonical Lagrangian with chaotic potential in EMSG can lead to significantly larger values of the non-Gaussianity parameter, $f_{\rm Nl}^{\rm equi}$ whereas EMSG framework with canonical Lagrangian gives rise to results similar to those of the standard single-field model. |
2009.10212 | Bangalore Sathyaprakash | B.F. Schutz and B.S. Sathyaprakash | Self-calibration of Networks of Gravitational Wave Detectors | 14 pages including references | null | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | As LIGO and Virgo are upgraded, improving calibration systems to keep pace
with the anticipated signal-to-noise enhancements will be challenging. We
explore here a calibration method that uses astronomical signals, namely
inspiral signals from compact-object binaries, and we show that it can in
principle enable calibration at the sub-1\% accuracy levels needed for future
gravitational wave science. We show how ensembles of these transient events can
be used to measure the calibration errors of individual detectors in a network
of three or more comparably sensitive instruments. As with telescopes, relative
calibration of gravitational-wave detectors using detected events is easier to
achieve than absolute calibration, which in principle would still need to be
done with a hardware method for at least one detector at one frequency. Our
proposed method uses the so-called null streams, the signal-free linear
combinations of the outputs of the detectors that exist in any network with
three or more differently oriented detectors. Signals do not appear in the null
stream if the signal amplitude in the detector output is faithful to that of
the real signal. Frequency-dependent calibration errors and relative
calibration and timing errors between detectors leave a residual in the null
stream. The amount of residual from each detector depends on the source
direction. We adapt the method of matched filtering to the problem of
extracting the calibration error of each detector from this residual. This
requires combining linearly the filter outputs of a sufficient number of
detected signals, and in principle it can achieve any desired accuracy in a
long enough observation run. We anticipate that A+ detector networks, expected
in 5 years, could employ this method to check anticipated hardware calibration
accuracies.
| [
{
"created": "Mon, 21 Sep 2020 23:05:39 GMT",
"version": "v1"
}
] | 2020-09-23 | [
[
"Schutz",
"B. F.",
""
],
[
"Sathyaprakash",
"B. S.",
""
]
] | As LIGO and Virgo are upgraded, improving calibration systems to keep pace with the anticipated signal-to-noise enhancements will be challenging. We explore here a calibration method that uses astronomical signals, namely inspiral signals from compact-object binaries, and we show that it can in principle enable calibration at the sub-1\% accuracy levels needed for future gravitational wave science. We show how ensembles of these transient events can be used to measure the calibration errors of individual detectors in a network of three or more comparably sensitive instruments. As with telescopes, relative calibration of gravitational-wave detectors using detected events is easier to achieve than absolute calibration, which in principle would still need to be done with a hardware method for at least one detector at one frequency. Our proposed method uses the so-called null streams, the signal-free linear combinations of the outputs of the detectors that exist in any network with three or more differently oriented detectors. Signals do not appear in the null stream if the signal amplitude in the detector output is faithful to that of the real signal. Frequency-dependent calibration errors and relative calibration and timing errors between detectors leave a residual in the null stream. The amount of residual from each detector depends on the source direction. We adapt the method of matched filtering to the problem of extracting the calibration error of each detector from this residual. This requires combining linearly the filter outputs of a sufficient number of detected signals, and in principle it can achieve any desired accuracy in a long enough observation run. We anticipate that A+ detector networks, expected in 5 years, could employ this method to check anticipated hardware calibration accuracies. |
gr-qc/0310043 | Vladimir Ivashchuk | H. Dehnen and V.D. Ivashchuk | On spherically symmetric solutions with horizon in model with
multicomponent anisotropic fluid | 16 pages, no figures | J.Math.Phys.45:4726-4736,2004 | 10.1063/1.1812357 | IGC-PFUR-09/2003 | gr-qc astro-ph hep-th | null | A family of spherically symmetric solutions in the model with m-component
anisotropic fluid is considered. The metric of the solution depends on
parameters q_s, s = 1,...,m, relating radial pressures and the densities and
contains (n -1)m parameters corresponding to Ricci-flat "internal space"
metrics and obeying certain m(m-1)/2 ("orthogonality") relations. For q_s = 1
(for all s) and certian equations of state (p_i^s = \pm \rho^s) the metric
coincides with the metric of intersecting black brane solution in the model
with antisymmetric forms. A family of solutions with (regular) horizon
corresponding to natural numbers q_s = 1,2,... is singled out. Certain examples
of "generalized simulation" of intersecting M-branes in D=11 supergravity are
considered. The post-Newtonian parameters \beta and \gamma corresponding to the
4-dimensional section of the metric are calculated.
| [
{
"created": "Tue, 7 Oct 2003 16:12:46 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Dehnen",
"H.",
""
],
[
"Ivashchuk",
"V. D.",
""
]
] | A family of spherically symmetric solutions in the model with m-component anisotropic fluid is considered. The metric of the solution depends on parameters q_s, s = 1,...,m, relating radial pressures and the densities and contains (n -1)m parameters corresponding to Ricci-flat "internal space" metrics and obeying certain m(m-1)/2 ("orthogonality") relations. For q_s = 1 (for all s) and certian equations of state (p_i^s = \pm \rho^s) the metric coincides with the metric of intersecting black brane solution in the model with antisymmetric forms. A family of solutions with (regular) horizon corresponding to natural numbers q_s = 1,2,... is singled out. Certain examples of "generalized simulation" of intersecting M-branes in D=11 supergravity are considered. The post-Newtonian parameters \beta and \gamma corresponding to the 4-dimensional section of the metric are calculated. |
gr-qc/0110109 | Bahram Mashhoon | C. Chicone and B. Mashhoon | Acceleration-induced nonlocality: kinetic memory versus dynamic memory | LaTeX file, 6 PS figures, 34 pages | Annalen Phys. 11 (2002) 309-332 | 10.1002/1521-3889(200204)11:4<309::AID-ANDP309>3.0.CO;2-A | null | gr-qc | null | The characteristics of the memory of accelerated motion in Minkowski
spacetime are discussed within the framework of the nonlocal theory of
accelerated observers. Two types of memory are distinguished: kinetic and
dynamic. We show that only kinetic memory is acceptable, since dynamic memory
leads to divergences for nonuniform accelerated motion.
| [
{
"created": "Wed, 24 Oct 2001 22:07:26 GMT",
"version": "v1"
}
] | 2017-09-27 | [
[
"Chicone",
"C.",
""
],
[
"Mashhoon",
"B.",
""
]
] | The characteristics of the memory of accelerated motion in Minkowski spacetime are discussed within the framework of the nonlocal theory of accelerated observers. Two types of memory are distinguished: kinetic and dynamic. We show that only kinetic memory is acceptable, since dynamic memory leads to divergences for nonuniform accelerated motion. |
1707.09289 | Tanguy Marchand | Tanguy Marchand, Laura Bernard, Luc Blanchet, Guillaume Faye | Ambiguity-Free Completion of the Equations of Motion of Compact Binary
Systems at the Fourth Post-Newtonian Order | 6 pages | Phys. Rev. D 97, 044023 (2018) | 10.1103/PhysRevD.97.044023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first complete (i.e., ambiguity-free) derivation of the
equations of motion of two non-spinning compact objects up to the 4PN order,
based on the Fokker action of point particles in harmonic coordinates. The last
ambiguity parameter is determined from first principle, by resorting to a
matching between the near zone and far zone fields, and a consistent
computation of the 4PN tail effect in d dimensions. Dimensional regularization
is used throughout for treating IR divergences appearing at 4PN order, as well
as UV divergences due to the model of point particles describing compact
objects.
| [
{
"created": "Fri, 28 Jul 2017 15:46:55 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Mar 2018 15:56:56 GMT",
"version": "v2"
}
] | 2018-03-12 | [
[
"Marchand",
"Tanguy",
""
],
[
"Bernard",
"Laura",
""
],
[
"Blanchet",
"Luc",
""
],
[
"Faye",
"Guillaume",
""
]
] | We present the first complete (i.e., ambiguity-free) derivation of the equations of motion of two non-spinning compact objects up to the 4PN order, based on the Fokker action of point particles in harmonic coordinates. The last ambiguity parameter is determined from first principle, by resorting to a matching between the near zone and far zone fields, and a consistent computation of the 4PN tail effect in d dimensions. Dimensional regularization is used throughout for treating IR divergences appearing at 4PN order, as well as UV divergences due to the model of point particles describing compact objects. |
1708.04857 | Abhik Kumar Sanyal Dr. | Abhik Kumar Sanyal and Subhra Debnath | Thermodynamics of irreversible particle creation phenomena and its
cosmological consequence | 28 pages, 3 figures, To appear in 'CFD Technics and Thermo-Mechanics
Applications', Springer, Chapter - N0 | Sanyal A.K., Debnath S. (2018) Thermodynamics of Irreversible
Particle Creation Phenomena and Its Cosmological Consequence. In: Driss Z.,
Necib B., Zhang HC. (eds) Thermo-Mechanics Applications and Engineering
Technology pp 171-198. Springer, Cham | 10.1007/978-3-319-70957-4_8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The study of particle creation phenomena at the expense of the gravitational
field is of great research interest. It might solve the cosmological puzzle
single-handedly, without the need for either dark energy or the modified theory
of gravity. In the early universe, following graceful exit from inflationary
phase, it serves the purpose of reheating the cold universe, which gave way to
the hot Big-Bang model. In the late universe, it led to late time cosmic
acceleration, without affecting stand-ard Big-Bang-Nucleosynthesis (BBN),
Cosmic Microwave Background Radiation (CMBR), or Structure Formation. In this
chapter, we briefly review the present status of cosmic evolution, develop the
thermodynamics for irreversible particle creation phenomena and study its
consequences at the early as well as in the late universe.
| [
{
"created": "Wed, 16 Aug 2017 12:27:42 GMT",
"version": "v1"
}
] | 2018-06-26 | [
[
"Sanyal",
"Abhik Kumar",
""
],
[
"Debnath",
"Subhra",
""
]
] | The study of particle creation phenomena at the expense of the gravitational field is of great research interest. It might solve the cosmological puzzle single-handedly, without the need for either dark energy or the modified theory of gravity. In the early universe, following graceful exit from inflationary phase, it serves the purpose of reheating the cold universe, which gave way to the hot Big-Bang model. In the late universe, it led to late time cosmic acceleration, without affecting stand-ard Big-Bang-Nucleosynthesis (BBN), Cosmic Microwave Background Radiation (CMBR), or Structure Formation. In this chapter, we briefly review the present status of cosmic evolution, develop the thermodynamics for irreversible particle creation phenomena and study its consequences at the early as well as in the late universe. |
gr-qc/0608083 | Farook Rahaman | F. Rahaman, N. Begum, G. Bag, B. C. Bhui | Cosmological models with negative constant deceleration parameter in
Lyra geometry | 8 pages | Astrophys.Space Sci. 299 (2005) 211-218 | 10.1007/s10509-005-5943-4 | null | gr-qc | null | Bermann [ Nuovo Cimento B (1983), 74, 182 ] presented a law of variation of
Hubble parameter that yields constant deceleration parameter models of the
Universe. In this paper, we study some cosmological models with negative
constant deceleration parameter within the framework of Lyra geometry.
| [
{
"created": "Thu, 17 Aug 2006 11:30:42 GMT",
"version": "v1"
}
] | 2016-04-26 | [
[
"Rahaman",
"F.",
""
],
[
"Begum",
"N.",
""
],
[
"Bag",
"G.",
""
],
[
"Bhui",
"B. C.",
""
]
] | Bermann [ Nuovo Cimento B (1983), 74, 182 ] presented a law of variation of Hubble parameter that yields constant deceleration parameter models of the Universe. In this paper, we study some cosmological models with negative constant deceleration parameter within the framework of Lyra geometry. |
0812.4063 | Salvatore Capozziello | S. Capozziello, M. De Laurentis, F. Garufi, and L. Milano | Relativistic orbits with gravitomagnetic corrections | 16 pages, 5 figures | Phys.Scripta 79:025901,2009 | 10.1088/0031-8949/79/02/025901 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Corrections to the relativistic orbits are studied considering higher order
approximations induced by gravitomagnetic effects. We discuss in details how
such corrections come out taking into account magnetic components in the weak
field limit of gravitational field and then the theory of orbits is developed
starting from the Newtonian one, the lowest order in the approximation.
Finally, the orbital structure and the stability conditions are discussed
giving numerical examples. Beside the standard periastron corrections of
General Relativity, a new nutation effect is due to the c^{-3} corrections. The
transition to a chaotic behavior strictly depends on the initial conditions.
The orbital phase space portrait is discussed.
| [
{
"created": "Sat, 20 Dec 2008 14:12:07 GMT",
"version": "v1"
}
] | 2009-03-12 | [
[
"Capozziello",
"S.",
""
],
[
"De Laurentis",
"M.",
""
],
[
"Garufi",
"F.",
""
],
[
"Milano",
"L.",
""
]
] | Corrections to the relativistic orbits are studied considering higher order approximations induced by gravitomagnetic effects. We discuss in details how such corrections come out taking into account magnetic components in the weak field limit of gravitational field and then the theory of orbits is developed starting from the Newtonian one, the lowest order in the approximation. Finally, the orbital structure and the stability conditions are discussed giving numerical examples. Beside the standard periastron corrections of General Relativity, a new nutation effect is due to the c^{-3} corrections. The transition to a chaotic behavior strictly depends on the initial conditions. The orbital phase space portrait is discussed. |
2011.02938 | Kent Yagi | Zack Carson and Kent Yagi | Testing General Relativity with Gravitational Waves | v1: Submitted as a chapter in "Handbook of Gravitational Wave
Astronomy" (Eds. C. Bambi, S. Katsanevas and K. Kokkotas; Springer Singapore,
2021). The maximum number of allowed references is used; v2, v3: minor
corrections to refs | null | 10.1007/978-981-15-4702-7_41-1 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave sources offer us unique testbeds for probing strong-field,
dynamical and nonlinear aspects of gravity. In this chapter, we give a brief
overview of the current status and future prospects of testing General
Relativity with gravitational waves. In particular, we focus on three
theory-agnostic tests (parameterized tests, inspiral-merger-ringdown
consistency tests, and gravitational-wave propagation tests) and explain how
one can apply such tests to example modified theories of gravity. We conclude
by giving some open questions that need to be resolved to carry out more
accurate tests of gravity with gravitational waves.
| [
{
"created": "Thu, 5 Nov 2020 16:04:49 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jan 2021 23:45:52 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Nov 2021 23:59:27 GMT",
"version": "v3"
}
] | 2021-11-15 | [
[
"Carson",
"Zack",
""
],
[
"Yagi",
"Kent",
""
]
] | Gravitational-wave sources offer us unique testbeds for probing strong-field, dynamical and nonlinear aspects of gravity. In this chapter, we give a brief overview of the current status and future prospects of testing General Relativity with gravitational waves. In particular, we focus on three theory-agnostic tests (parameterized tests, inspiral-merger-ringdown consistency tests, and gravitational-wave propagation tests) and explain how one can apply such tests to example modified theories of gravity. We conclude by giving some open questions that need to be resolved to carry out more accurate tests of gravity with gravitational waves. |
2110.09033 | Jin Qiao | Jin Qiao, Tao Zhu, Guoliang Li, Wen Zhao | Post-Newtonian parameters of ghost-free parity-violating gravities | 20 pages, 1 figure | JCAP 04(2022)054 | 10.1088/1475-7516/2022/04/054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the slow-motion and weak-field approximation of the general
ghost-free parity-violating (PV) theory of gravity in the parametrized
post-Newtonian (PPN) framework and derive the perturbative field equations,
which are modified by the PV terms of this theory. The complete PPN parameters
are obtained by solving the perturbative field equations. We find that all the
PPN parameters are exactly the same as those in general relativity, except for
an extra parameter $\kappa$, which is caused by the new curl-type term in the
gravitomagnetic sector of the metric in this theory. We calculate the
precession effects of gyroscopes in this theory and constrain the model
parameters by the observations of the Gravity Probe B experiment.
| [
{
"created": "Mon, 18 Oct 2021 06:11:01 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jan 2022 02:06:51 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Apr 2022 06:42:36 GMT",
"version": "v3"
}
] | 2022-05-04 | [
[
"Qiao",
"Jin",
""
],
[
"Zhu",
"Tao",
""
],
[
"Li",
"Guoliang",
""
],
[
"Zhao",
"Wen",
""
]
] | We investigate the slow-motion and weak-field approximation of the general ghost-free parity-violating (PV) theory of gravity in the parametrized post-Newtonian (PPN) framework and derive the perturbative field equations, which are modified by the PV terms of this theory. The complete PPN parameters are obtained by solving the perturbative field equations. We find that all the PPN parameters are exactly the same as those in general relativity, except for an extra parameter $\kappa$, which is caused by the new curl-type term in the gravitomagnetic sector of the metric in this theory. We calculate the precession effects of gyroscopes in this theory and constrain the model parameters by the observations of the Gravity Probe B experiment. |
2401.16814 | Phongpichit Channuie | Piyachat Panyasiripan (Walailak U.), Narakorn Kaewkhao (Prince Songkla
U.), Phongpichit Channuie (Walailak U.), Ali \"Ovg\"un (Eastern Mediterranean
U.) | Traversable Wormholes in Minimally Geometrical Deformed Trace-Free
Gravity using Gravitational Decoupling | v1: 24 pages, many figures | Nucl. Phys. B 1004 (2024) 116563 | 10.1016/j.nuclphysb.2024.116563 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work, we investigate wormhole solutions through the utilization of
gravitational decoupling, employing the Minimal Geometric Deformation (MGD)
procedure within the framework of Trace-Free Gravity. We base our investigation
on static and spherically symmetric Morris-Thorne traversable wormholes,
considering both constant and variable equation of state parameters. We derive
the field equations and extract the shape function for each scenario. Moreover,
we explore the gravitational decoupling technique and examine various forms of
energy density for both a smeared and particle-like gravitational source,
encompassing the realm of noncommutative geometry and a statically charged
fluid. We also examinethe wormhole geometry through the utilization of
embedding diagrams. Through our analysis, we uncover a violation of the Null
Energy Condition (NEC). To conclude, we employ the Gauss-Bonnet theorem to
determine the weak deflection angle for the wormhole configurations.
| [
{
"created": "Tue, 30 Jan 2024 08:28:18 GMT",
"version": "v1"
}
] | 2024-05-17 | [
[
"Panyasiripan",
"Piyachat",
"",
"Walailak U."
],
[
"Kaewkhao",
"Narakorn",
"",
"Prince Songkla\n U."
],
[
"Channuie",
"Phongpichit",
"",
"Walailak U."
],
[
"Övgün",
"Ali",
"",
"Eastern Mediterranean\n U."
]
] | In this work, we investigate wormhole solutions through the utilization of gravitational decoupling, employing the Minimal Geometric Deformation (MGD) procedure within the framework of Trace-Free Gravity. We base our investigation on static and spherically symmetric Morris-Thorne traversable wormholes, considering both constant and variable equation of state parameters. We derive the field equations and extract the shape function for each scenario. Moreover, we explore the gravitational decoupling technique and examine various forms of energy density for both a smeared and particle-like gravitational source, encompassing the realm of noncommutative geometry and a statically charged fluid. We also examinethe wormhole geometry through the utilization of embedding diagrams. Through our analysis, we uncover a violation of the Null Energy Condition (NEC). To conclude, we employ the Gauss-Bonnet theorem to determine the weak deflection angle for the wormhole configurations. |
gr-qc/0502039 | Clifford M. Will | Clifford M. Will (Institut d'Astrophysique de Paris and Washington
University) | Post-Newtonian gravitational radiation and equations of motion via
direct integration of the relaxed Einstein equations. III. Radiation reaction
for binary systems with spinning bodies | 19 pages, small corrections, equivalent to published version | Phys.Rev. D71 (2005) 084027 | 10.1103/PhysRevD.71.084027 | null | gr-qc | null | Using post-Newtonian equations of motion for fluid bodies that include
radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c)^5]
and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for
binary systems with spinning bodies. In particular we determine the effects of
radiation-reaction coupled to spin-orbit effects on the two-body equations of
motion, and on the evolution of the spins. For a suitable definition of spin,
we reproduce the standard equations of motion and spin-precession at the first
post-Newtonian order. At 3.5PN order, we determine the spin-orbit induced
reaction effects on the orbital motion, but we find that radiation damping has
no effect on either the magnitude or the direction of the spins. Using the
equations of motion, we find that the loss of total energy and total angular
momentum induced by spin-orbit effects precisely balances the radiative flux of
those quantities calculated by Kidder et al. The equations of motion may be
useful for evolving inspiraling orbits of compact spinning binaries.
| [
{
"created": "Wed, 9 Feb 2005 20:19:52 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Apr 2005 19:51:26 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Will",
"Clifford M.",
"",
"Institut d'Astrophysique de Paris and Washington\n University"
]
] | Using post-Newtonian equations of motion for fluid bodies that include radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c)^5] and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for binary systems with spinning bodies. In particular we determine the effects of radiation-reaction coupled to spin-orbit effects on the two-body equations of motion, and on the evolution of the spins. For a suitable definition of spin, we reproduce the standard equations of motion and spin-precession at the first post-Newtonian order. At 3.5PN order, we determine the spin-orbit induced reaction effects on the orbital motion, but we find that radiation damping has no effect on either the magnitude or the direction of the spins. Using the equations of motion, we find that the loss of total energy and total angular momentum induced by spin-orbit effects precisely balances the radiative flux of those quantities calculated by Kidder et al. The equations of motion may be useful for evolving inspiraling orbits of compact spinning binaries. |
gr-qc/9912077 | Konstantina Savvidou | Ntina Savvidou, Charis Anastopoulos | Histories quantisation of parameterised systems: I. Development of a
general algorithm | 34 pages, Latex | Class.Quant.Grav. 17 (2000) 2463-2490 | 10.1088/0264-9381/17/13/301 | null | gr-qc quant-ph | null | We develop a new algorithm for the quantisation of systems with first-class
constraints. Our approach lies within the (History Projection Operator)
continuous-time histories quantisation programme. In particular, the
Hamiltonian treatment (either classical or quantum) of parameterised systems is
characterised by the loss of the notion of time in the space of true degrees of
freedom (i.e. the `problem of time'). The novel temporal structure of the HPO
theory (two laws of time transformation that distinguish between the temporal
logical structure and the dynamics) persists after the imposition of the
constraints, hence the problem of time does not arise. We expound the algorithm
for both the classical and quantum cases and apply it to simple models.
| [
{
"created": "Fri, 17 Dec 1999 21:40:52 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Savvidou",
"Ntina",
""
],
[
"Anastopoulos",
"Charis",
""
]
] | We develop a new algorithm for the quantisation of systems with first-class constraints. Our approach lies within the (History Projection Operator) continuous-time histories quantisation programme. In particular, the Hamiltonian treatment (either classical or quantum) of parameterised systems is characterised by the loss of the notion of time in the space of true degrees of freedom (i.e. the `problem of time'). The novel temporal structure of the HPO theory (two laws of time transformation that distinguish between the temporal logical structure and the dynamics) persists after the imposition of the constraints, hence the problem of time does not arise. We expound the algorithm for both the classical and quantum cases and apply it to simple models. |
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