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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2310.15282 | Emmanuel Tassone | Emmanuel A. Tassone and Carlos N. Kozameh | Final velocity and radiated energy in numerical simulations of binary
black holes | 12 pages, 16 figures | Physical Review D 105.4 (2022): 044044 | 10.1103/PhysRevD.105.044044 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The evolution of global binary black holes variables such as energy or linear
momentum are mainly obtained by applying numerical methods near coalescence,
post-Newtonian (PN) expansions, or a combination of both. In this paper, we use
a fully relativistic formalism presented several years ago that only uses
global variables defined at null infinity together with the gravitational
radiation emitted by the source to obtain the time evolution of such variables
for binary black holes (BBH) systems. For that, we use the Rochester catalog
composed of 776 BBHs simulations. We compute the final velocity, radiated
energy, and intrinsic angular momentum predicted by the dynamical equations in
this formalism for nonspinning, aligned and antialigned spins, and several
different precessing configurations. We compare obtained values with reported
values in numerical simulations. As BBHs parameter space is still not
completely covered by numerical simulations, we fit phenomenological formulas
for practical applications to the radiated energy and final velocities
obtained. Also, we compare the fits with reported values. In conclusion, we see
that our formulae and correlations for the variables described in this work are
consistent with those found in the general literature.
| [
{
"created": "Mon, 23 Oct 2023 18:38:59 GMT",
"version": "v1"
}
] | 2023-10-25 | [
[
"Tassone",
"Emmanuel A.",
""
],
[
"Kozameh",
"Carlos N.",
""
]
] | The evolution of global binary black holes variables such as energy or linear momentum are mainly obtained by applying numerical methods near coalescence, post-Newtonian (PN) expansions, or a combination of both. In this paper, we use a fully relativistic formalism presented several years ago that only uses global variables defined at null infinity together with the gravitational radiation emitted by the source to obtain the time evolution of such variables for binary black holes (BBH) systems. For that, we use the Rochester catalog composed of 776 BBHs simulations. We compute the final velocity, radiated energy, and intrinsic angular momentum predicted by the dynamical equations in this formalism for nonspinning, aligned and antialigned spins, and several different precessing configurations. We compare obtained values with reported values in numerical simulations. As BBHs parameter space is still not completely covered by numerical simulations, we fit phenomenological formulas for practical applications to the radiated energy and final velocities obtained. Also, we compare the fits with reported values. In conclusion, we see that our formulae and correlations for the variables described in this work are consistent with those found in the general literature. |
gr-qc/0505025 | Muzaffer Adak | Muzaffer Adak, Mestan Kalay and Ozcan Sert (Pamukkale Unv., Turkey) | Lagrange formulation of the symmetric teleparallel gravity | Corrected typos, Accepted for publication in IJMP-D | Int.J.Mod.Phys. D15 (2006) 619-634 | 10.1142/S0218271806008474 | null | gr-qc | null | We develop a symmetric teleparallel gravity model in a space-time with only
the non-metricity is nonzero, in terms of a Lagrangian quadratic in the
non-metricity tensor. We present a detailed discussion of the variations that
may be used for any gravitational formulation. We seek Schwarzschild-type
solutions because of its observational significance and obtain a class of
solutions that includes Schwarzschild-type, Schwarzschild-de Sitter-type and
Reissner-Nordstr\"{o}m-type solutions for certain values of the parameters. We
also discuss the physical relevance of these solutions.
| [
{
"created": "Thu, 5 May 2005 10:41:26 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Nov 2005 08:25:40 GMT",
"version": "v2"
},
{
"created": "Mon, 6 Feb 2006 08:40:46 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Adak",
"Muzaffer",
"",
"Pamukkale Unv., Turkey"
],
[
"Kalay",
"Mestan",
"",
"Pamukkale Unv., Turkey"
],
[
"Sert",
"Ozcan",
"",
"Pamukkale Unv., Turkey"
]
] | We develop a symmetric teleparallel gravity model in a space-time with only the non-metricity is nonzero, in terms of a Lagrangian quadratic in the non-metricity tensor. We present a detailed discussion of the variations that may be used for any gravitational formulation. We seek Schwarzschild-type solutions because of its observational significance and obtain a class of solutions that includes Schwarzschild-type, Schwarzschild-de Sitter-type and Reissner-Nordstr\"{o}m-type solutions for certain values of the parameters. We also discuss the physical relevance of these solutions. |
2111.10744 | Peng Liu | Cheng-Yong Zhang, Peng Liu, Yunqi Liu, Chao Niu, Bin Wang | Dynamical scalarization in Einstein-Maxwell-dilaton theory | 19 pages, 5 figures | null | 10.1103/PhysRevD.105.024073 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the process of fully nonlinear dynamical scalarization starting from
a charged black hole or a naked singularity in asymptotically flat spacetime in
the Einstein-Maxwell-dilaton theory. Initially the dilaton field is negligible
compared to the gravitational and the Maxwell field. Then the dilaton field
experiences an immediate growth, later it oscillates with damping amplitude and
finally settles down to a finite value. For a hairy black hole develops from an
original Reissner-Nordstr\"om black hole, since the dilaton oscillation and
decay are almost independent of the coupling parameter, unlike the Anti-de
Sitter spacetime it is not easy to distinguish the resulting hairy black hole
from the original asymptotically flat charged hole. For a hairy black hole
evolves from an original naked singularity, the resulting hairy black hole has
rich structures. In the scalarization process, the naked singularity is soon
enveloped by one outer horizon, then another horizon is developed and in the
end a stable hairy black hole forms and two horizons degenerate into one to
protect the singularity. The hairy black hole mass saturates exponentially in
the scalarization.
| [
{
"created": "Sun, 21 Nov 2021 05:43:48 GMT",
"version": "v1"
}
] | 2022-02-09 | [
[
"Zhang",
"Cheng-Yong",
""
],
[
"Liu",
"Peng",
""
],
[
"Liu",
"Yunqi",
""
],
[
"Niu",
"Chao",
""
],
[
"Wang",
"Bin",
""
]
] | We study the process of fully nonlinear dynamical scalarization starting from a charged black hole or a naked singularity in asymptotically flat spacetime in the Einstein-Maxwell-dilaton theory. Initially the dilaton field is negligible compared to the gravitational and the Maxwell field. Then the dilaton field experiences an immediate growth, later it oscillates with damping amplitude and finally settles down to a finite value. For a hairy black hole develops from an original Reissner-Nordstr\"om black hole, since the dilaton oscillation and decay are almost independent of the coupling parameter, unlike the Anti-de Sitter spacetime it is not easy to distinguish the resulting hairy black hole from the original asymptotically flat charged hole. For a hairy black hole evolves from an original naked singularity, the resulting hairy black hole has rich structures. In the scalarization process, the naked singularity is soon enveloped by one outer horizon, then another horizon is developed and in the end a stable hairy black hole forms and two horizons degenerate into one to protect the singularity. The hairy black hole mass saturates exponentially in the scalarization. |
gr-qc/0207072 | Nicola Pinamonti | V. Moretti and N. Pinamonti | Aspects of hidden and manifest SL(2,R) symmetry in 2D near-horizon
black-hole background | 22 pages, 1 figure, latex 2e, some misprint corrected, a reference
and a footnote added | Nucl.Phys. B647 (2002) 131-152 | 10.1016/S0550-3213(02)00940-9 | UTM 624 / UTF 449 | gr-qc hep-th math-ph math.MP | null | The invariance under unitary representations of the conformal group SL(2,R)
of a quantum particle is rigorously investigated in two-dimensional spacetimes
containing Killing horizons using DFF model. The limit of the near-horizon
approximation is considered. If the Killing horizon is bifurcate the conformal
symmetry is hidden, i.e. it does not arise from geometrical spacetime
isometries, but the whole Hilbert space turns out to be an irreducible unitary
representation of SL(2,R) and the time evolution is embodied in the unitary
representation. In this case the symmetry does not depend on the mass of the
particle and, if the representation is faithful, the conformal observable K
shows thermal properties. If the Killing horizon is nonbifurcate the conformal
symmetry is manifest, i.e. it arises from geometrical spacetime isometries. The
SL(2,R) representation which arises from the geometry selects a hidden
conformal representation. Also in that case the Hilbert space is an irreducible
representation of SL(2,R) and the group conformal symmetries embodies the time
evolution with respect to the local Killing time. However no thermal properties
are involved. The conformal observable K gives rise to Killing time evolution
of the quantum state with respect to another global Killing time present in the
manifold. Mathematical proofs about the developed machinery are supplied and
features of the operator H_g = -({d^2}/{dx^2})+ ({g}/{x^2}), with g=-1/4 are
discussed. It is proven that a statement, used in the recent literature, about
the spectrum of self-adjoint extensions of H_g is incorrect.
| [
{
"created": "Thu, 18 Jul 2002 14:42:55 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jul 2002 14:02:27 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Moretti",
"V.",
""
],
[
"Pinamonti",
"N.",
""
]
] | The invariance under unitary representations of the conformal group SL(2,R) of a quantum particle is rigorously investigated in two-dimensional spacetimes containing Killing horizons using DFF model. The limit of the near-horizon approximation is considered. If the Killing horizon is bifurcate the conformal symmetry is hidden, i.e. it does not arise from geometrical spacetime isometries, but the whole Hilbert space turns out to be an irreducible unitary representation of SL(2,R) and the time evolution is embodied in the unitary representation. In this case the symmetry does not depend on the mass of the particle and, if the representation is faithful, the conformal observable K shows thermal properties. If the Killing horizon is nonbifurcate the conformal symmetry is manifest, i.e. it arises from geometrical spacetime isometries. The SL(2,R) representation which arises from the geometry selects a hidden conformal representation. Also in that case the Hilbert space is an irreducible representation of SL(2,R) and the group conformal symmetries embodies the time evolution with respect to the local Killing time. However no thermal properties are involved. The conformal observable K gives rise to Killing time evolution of the quantum state with respect to another global Killing time present in the manifold. Mathematical proofs about the developed machinery are supplied and features of the operator H_g = -({d^2}/{dx^2})+ ({g}/{x^2}), with g=-1/4 are discussed. It is proven that a statement, used in the recent literature, about the spectrum of self-adjoint extensions of H_g is incorrect. |
gr-qc/0606077 | Allan Widom | A. Widom | Concepts of Intertial and Gravitational Mass | LaTeX Format No Figures | null | null | null | gr-qc | null | The general relativistic notion of gravitational and inertial mass is
discussed from the general viewpoint of the tidal forces implicit in the
curvature and the Einstein field equations within ponderable matter. A simple
yet rigorously general derivation is given for the Tolman gravitational mass
viewpoint wherein the computation of gravitational mass requires both a rest
energy contribution (the inertial mass) and a pressure contribution. The
pressure contribution is extremely small under normal conditions which implies
the equality of gravitational and inertial mass to a high degree of accuracy.
However, the pressure contribution is substantial for conformal symmetric
systems such as Maxwell radiation, whose constituent photons are massless.
Implications of the Tolman mass for standard cosmology and standard high energy
particle physics models are briefly explored.
| [
{
"created": "Sat, 17 Jun 2006 17:57:04 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Widom",
"A.",
""
]
] | The general relativistic notion of gravitational and inertial mass is discussed from the general viewpoint of the tidal forces implicit in the curvature and the Einstein field equations within ponderable matter. A simple yet rigorously general derivation is given for the Tolman gravitational mass viewpoint wherein the computation of gravitational mass requires both a rest energy contribution (the inertial mass) and a pressure contribution. The pressure contribution is extremely small under normal conditions which implies the equality of gravitational and inertial mass to a high degree of accuracy. However, the pressure contribution is substantial for conformal symmetric systems such as Maxwell radiation, whose constituent photons are massless. Implications of the Tolman mass for standard cosmology and standard high energy particle physics models are briefly explored. |
2304.13320 | Kanishk Verma | S. Habib Mazharimousavi and Kanishk Verma | Magnetic black hole in Einstein-Dilaton-Square root nonlinear
electrodynamics | Final version accepted for publication in Annals of Physics. 12 pages
1 figure | null | 10.1016/j.aop.2023.169439 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from the most general action in Einstein-Dilaton-Nonlinear
Electrodynamics (NED) theory, we obtain the field equations. We apply the field
equations for the specific NED known as the Liouville type plus a cosmological
constant and solve the field equations. With a pure magnetic field it is shown
that the square root model is the strong field limit of the Born-Infeld NED
theory. In static spherically symmetric spacetime and a magnetic monopole
sitting at the origin, the field equations are exactly solvable provided the
intergation constants of the solution and the theory constants appearing in the
action are linked through two constraints. As it is known such an exact
solution in the absence of dilaton i.e., gravity coupled to square root NED
doesn't exist. Therefore, the presence of the dilaton gives additional freedom
to solve the field equations. The obtained spacetime is singular and
non-asymptotically flat and depending on the free parameters it may be a black
hole or a cosmological object. For the black hole spacetime, we study the
thermal stability of the spacetime and show that the black hole is thermally
stable provided its size is larger than a critical value.
| [
{
"created": "Wed, 26 Apr 2023 06:47:54 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jul 2023 10:03:56 GMT",
"version": "v2"
}
] | 2023-08-15 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Verma",
"Kanishk",
""
]
] | Starting from the most general action in Einstein-Dilaton-Nonlinear Electrodynamics (NED) theory, we obtain the field equations. We apply the field equations for the specific NED known as the Liouville type plus a cosmological constant and solve the field equations. With a pure magnetic field it is shown that the square root model is the strong field limit of the Born-Infeld NED theory. In static spherically symmetric spacetime and a magnetic monopole sitting at the origin, the field equations are exactly solvable provided the intergation constants of the solution and the theory constants appearing in the action are linked through two constraints. As it is known such an exact solution in the absence of dilaton i.e., gravity coupled to square root NED doesn't exist. Therefore, the presence of the dilaton gives additional freedom to solve the field equations. The obtained spacetime is singular and non-asymptotically flat and depending on the free parameters it may be a black hole or a cosmological object. For the black hole spacetime, we study the thermal stability of the spacetime and show that the black hole is thermally stable provided its size is larger than a critical value. |
gr-qc/0101008 | Jerzy Lewandowski | Jerzy Lewandowski, Tomasz Pawlowski (Waszawa) | Geometric Characterizations of the Kerr Isolated Horizon | 11 pages, relevance of the results for the numerical relativity
explained, mistakes corrected | Int.J.Mod.Phys. D11 (2002) 739-746 | 10.1142/S0218271802001986 | null | gr-qc | null | We formulate conditions on the geometry of a non-expanding horizon $\Delta$
which are sufficient for the space-time metric to coincide on $\Delta$ with the
Kerr metric. We introduce an invariant which can be used as a measure of how
different the geometry of a given non-expanding horizon is from the geometry of
the Kerr horizon. Directly, our results concern the space-time metric at $\IH$
at the zeroth and the first orders. Combained with the results of Ashtekar,
Beetle and Lewandowski, our conditions can be used to compare the space-time
geometry at the non-expanding horizon with that of Kerr to every order. The
results should be useful to numerical relativity in analyzing the sense in
which the final black hole horizon produced by a collapse or a merger
approaches the Kerr horizon.
| [
{
"created": "Sun, 31 Dec 2000 20:57:47 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Dec 2001 17:10:43 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Dec 2001 11:00:02 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Lewandowski",
"Jerzy",
"",
"Waszawa"
],
[
"Pawlowski",
"Tomasz",
"",
"Waszawa"
]
] | We formulate conditions on the geometry of a non-expanding horizon $\Delta$ which are sufficient for the space-time metric to coincide on $\Delta$ with the Kerr metric. We introduce an invariant which can be used as a measure of how different the geometry of a given non-expanding horizon is from the geometry of the Kerr horizon. Directly, our results concern the space-time metric at $\IH$ at the zeroth and the first orders. Combained with the results of Ashtekar, Beetle and Lewandowski, our conditions can be used to compare the space-time geometry at the non-expanding horizon with that of Kerr to every order. The results should be useful to numerical relativity in analyzing the sense in which the final black hole horizon produced by a collapse or a merger approaches the Kerr horizon. |
gr-qc/0102082 | Hirayama Tooru | T.Hirayama (Kyoto Sangyo U.) | Bound and Radiation Fields in the Rindler Frame | 30 pages 2 figures | Prog.Theor.Phys. 106 (2001) 71 | 10.1143/PTP.106.71 | null | gr-qc physics.class-ph | null | The energy-momentum tensor of the Li\'enard-Wiechert field is split into
bound and emitted parts in the Rindler frame, by generalizing the reasoning of
Teitelboim applied in the inertial frame. Our analysis proceeds by invoking the
concept of ``energy'' defined with respect to the Killing vector field attached
to the frame. We obtain the radiation formula in the Rindler frame (the Rindler
version of the Larmor formula), and it is found that the radiation power is
proportional to the square of acceleration $\alpha^\mu$ of the charge relative
to the Rindler frame. This result leads us to split the Li\'enard-Wiechert
field into a part II', which is linear in $\alpha^\mu$, and a part I', which is
independent of $\alpha^\mu$. By using these, we split the energy-momentum
tensor into two parts. We find that these are properly interpreted as the
emitted and bound parts of the tensor in the Rindler frame. In our
identification of radiation, a charge radiates neither in the case that the
charge is fixed in the Rindler frame, nor in the case that the charge satisfies
the equation $\alpha^\mu=0$. We then investigate this equation. We consider
four gedanken experiments related to the observer dependence of the concept of
radiation.
| [
{
"created": "Mon, 19 Feb 2001 12:43:58 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Aug 2001 12:35:35 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Hirayama",
"T.",
"",
"Kyoto Sangyo U."
]
] | The energy-momentum tensor of the Li\'enard-Wiechert field is split into bound and emitted parts in the Rindler frame, by generalizing the reasoning of Teitelboim applied in the inertial frame. Our analysis proceeds by invoking the concept of ``energy'' defined with respect to the Killing vector field attached to the frame. We obtain the radiation formula in the Rindler frame (the Rindler version of the Larmor formula), and it is found that the radiation power is proportional to the square of acceleration $\alpha^\mu$ of the charge relative to the Rindler frame. This result leads us to split the Li\'enard-Wiechert field into a part II', which is linear in $\alpha^\mu$, and a part I', which is independent of $\alpha^\mu$. By using these, we split the energy-momentum tensor into two parts. We find that these are properly interpreted as the emitted and bound parts of the tensor in the Rindler frame. In our identification of radiation, a charge radiates neither in the case that the charge is fixed in the Rindler frame, nor in the case that the charge satisfies the equation $\alpha^\mu=0$. We then investigate this equation. We consider four gedanken experiments related to the observer dependence of the concept of radiation. |
2108.08328 | Fabrizio Corelli | Fabrizio Corelli, Taishi Ikeda and Paolo Pani | Challenging the cosmic censorship in Einstein-Maxwell-scalar theory with
numerically simulated gedankenexperiments | 18 pages, 14 figures. Animations and extra material available at
https://web.uniroma1.it/gmunu/ | null | 10.1103/PhysRevD.104.084069 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform extensive nonlinear numerical simulations of the spherical
collapse of (charged) wavepackets onto a charged black hole within
Einstein-Maxwell theory and in Einstein-Maxwell-scalar theory featuring
nonminimal couplings and a spontaneous scalarization mechanism. We confirm that
black holes in full-fledged Einstein-Maxwell theory cannot be overcharged past
extremality and no naked singularities form, in agreement with the cosmic
censorship conjecture. We show that naked singularities do not form even in
Einstein-Maxwell-scalar theory, although it is possible to form scalarized
black holes with charge above the Reissner-Nordstr\"om bound. We argue that
charge and mass extraction due to superradiance at fully nonlinear level is
crucial to bound the charge-to-mass ratio of the final black hole below
extremality. We also discuss some "descalarization" mechanisms for scalarized
black holes induced either by superradiance or by absorption of an
opposite-charged wavepacket; in all cases the final state after descalarization
is a subextremal Reissner-Nordstr\"om black hole.
| [
{
"created": "Wed, 18 Aug 2021 18:06:42 GMT",
"version": "v1"
}
] | 2021-11-03 | [
[
"Corelli",
"Fabrizio",
""
],
[
"Ikeda",
"Taishi",
""
],
[
"Pani",
"Paolo",
""
]
] | We perform extensive nonlinear numerical simulations of the spherical collapse of (charged) wavepackets onto a charged black hole within Einstein-Maxwell theory and in Einstein-Maxwell-scalar theory featuring nonminimal couplings and a spontaneous scalarization mechanism. We confirm that black holes in full-fledged Einstein-Maxwell theory cannot be overcharged past extremality and no naked singularities form, in agreement with the cosmic censorship conjecture. We show that naked singularities do not form even in Einstein-Maxwell-scalar theory, although it is possible to form scalarized black holes with charge above the Reissner-Nordstr\"om bound. We argue that charge and mass extraction due to superradiance at fully nonlinear level is crucial to bound the charge-to-mass ratio of the final black hole below extremality. We also discuss some "descalarization" mechanisms for scalarized black holes induced either by superradiance or by absorption of an opposite-charged wavepacket; in all cases the final state after descalarization is a subextremal Reissner-Nordstr\"om black hole. |
0704.2499 | Clovis Jacinto de Matos | Clovis Jacinto de Matos | Electromagnetic Dark Energy and Gravitoelectrodynamics of
Superconductors | 9 pages | null | null | null | gr-qc | null | It is shown that Beck and Mackey electromagnetic model of dark energy in
superconductors can account for the non-classical inertial properties of
superconductors, which have been conjectured by the author to explain the
Cooper pair's mass excess reported by Cabrera and Tate. A new Einstein-Planck
regime for gravitation in condensed matter is proposed as a natural scale to
host the gravitoelectrodynamic properties of superconductors.
| [
{
"created": "Thu, 19 Apr 2007 10:32:30 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Jul 2007 14:15:19 GMT",
"version": "v2"
},
{
"created": "Fri, 3 Aug 2007 12:38:27 GMT",
"version": "v3"
},
{
"created": "Tue, 7 Aug 2007 14:19:21 GMT",
"version": "v4"
},
{
"created": "Mon, 29 Oct 2007 17:10:22 GMT",
"version": "v5"
}
] | 2007-10-29 | [
[
"de Matos",
"Clovis Jacinto",
""
]
] | It is shown that Beck and Mackey electromagnetic model of dark energy in superconductors can account for the non-classical inertial properties of superconductors, which have been conjectured by the author to explain the Cooper pair's mass excess reported by Cabrera and Tate. A new Einstein-Planck regime for gravitation in condensed matter is proposed as a natural scale to host the gravitoelectrodynamic properties of superconductors. |
2205.12115 | Albert Munyeshyaka Mr | Beatrice Murorunkwere, Fidele Twagirayezu, Albert Munyeshyaka, Joseph
Ntahompagaze, Abraham Ayirwanda | On inflationary parameters in scalar-tensor theories | $27$ pages, $7$ figures | null | 10.1142/S0219887822501456 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The equivalence between $f(R)$ and scalar-tensor theories is revisited, we
consequently explored different $f(R)$ models. After consideration of specific
definition of the scalar field, we derived the potentials $V(\phi)$ for each
$f(R)$ model focusing on the early Universe, mostly the inflation epoch. For a
given potential, we applied the slow-roll approximation approach to each $f(R)$
model and obtained the expressions for the spectral index $n_{s}$ and
tensor-to-scalar ratio $r$. We determined the corresponding numerical values
associated with each of the $f(R)$ models. Our results showed that for certain
choice of parameter space, the values of $n_{s}$ and $r$ are consistent with
the Planck survey results and others produce numerical values that are in the
same range as suggested by Planck data. We further constructed the Klein-Gordon
equations $(KGE)$ of each $f(R)$ model. We found numerical solutions to each
KGE considering different values of free parameters and initial conditions of
each $f(R)$ model. All models showed that the scalar field decreases as time
increases, an indication that there is less content of the scalar field in the
late Universe.
| [
{
"created": "Tue, 24 May 2022 14:46:18 GMT",
"version": "v1"
}
] | 2022-09-20 | [
[
"Murorunkwere",
"Beatrice",
""
],
[
"Twagirayezu",
"Fidele",
""
],
[
"Munyeshyaka",
"Albert",
""
],
[
"Ntahompagaze",
"Joseph",
""
],
[
"Ayirwanda",
"Abraham",
""
]
] | The equivalence between $f(R)$ and scalar-tensor theories is revisited, we consequently explored different $f(R)$ models. After consideration of specific definition of the scalar field, we derived the potentials $V(\phi)$ for each $f(R)$ model focusing on the early Universe, mostly the inflation epoch. For a given potential, we applied the slow-roll approximation approach to each $f(R)$ model and obtained the expressions for the spectral index $n_{s}$ and tensor-to-scalar ratio $r$. We determined the corresponding numerical values associated with each of the $f(R)$ models. Our results showed that for certain choice of parameter space, the values of $n_{s}$ and $r$ are consistent with the Planck survey results and others produce numerical values that are in the same range as suggested by Planck data. We further constructed the Klein-Gordon equations $(KGE)$ of each $f(R)$ model. We found numerical solutions to each KGE considering different values of free parameters and initial conditions of each $f(R)$ model. All models showed that the scalar field decreases as time increases, an indication that there is less content of the scalar field in the late Universe. |
1912.08988 | Christopher Pope | M. Cvetic, G.W. Gibbons, C.N. Pope and B.F. Whiting | Positive Energy Functional for Massless Scalars in Rotating Black Hole
Backgrounds of Maximal Ungauged Supergravity | 5 pages, minor corrections and clarifications. Title changed. Version
to appear in Phys. Rev. Lett | Phys. Rev. Lett. 124, 231102 (2020) | 10.1103/PhysRevLett.124.231102 | UPR-1301-T, MI-TH-1943 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We outline a proof of the stability of a massless neutral scalar field $\psi$
in the background of a wide class of four dimensional asymptotically flat
rotating and ``electrically charged'' solutions of supergravity, and the low
energy limit of string theory, known as STU metrics. Despite their complexity,
we find it possible to circumvent the difficulties presented by the existence
of ergo-regions and the related phenomenon of super-radiance in the original
metrics by following a strategy due to Whiting, and passing to an auxiliary
metric admitting an everywhere lightlike Killing field and constructing a
scalar field $\Psi$ (related to a possible unstable mode $\psi$ by a non-local
transformation) which satisfies the massless wave equation with respect to the
auxiliary metric. By contrast with the case for $\psi$, the associated energy
density of $\Psi$ is not only conserved but is also non-negative.
| [
{
"created": "Thu, 19 Dec 2019 02:08:32 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jan 2020 15:14:07 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Jun 2020 13:41:01 GMT",
"version": "v3"
}
] | 2020-07-01 | [
[
"Cvetic",
"M.",
""
],
[
"Gibbons",
"G. W.",
""
],
[
"Pope",
"C. N.",
""
],
[
"Whiting",
"B. F.",
""
]
] | We outline a proof of the stability of a massless neutral scalar field $\psi$ in the background of a wide class of four dimensional asymptotically flat rotating and ``electrically charged'' solutions of supergravity, and the low energy limit of string theory, known as STU metrics. Despite their complexity, we find it possible to circumvent the difficulties presented by the existence of ergo-regions and the related phenomenon of super-radiance in the original metrics by following a strategy due to Whiting, and passing to an auxiliary metric admitting an everywhere lightlike Killing field and constructing a scalar field $\Psi$ (related to a possible unstable mode $\psi$ by a non-local transformation) which satisfies the massless wave equation with respect to the auxiliary metric. By contrast with the case for $\psi$, the associated energy density of $\Psi$ is not only conserved but is also non-negative. |
2301.05243 | Fech Scen Khoo | Bahareh Azad, Jose Luis Bl\'azquez-Salcedo, Fech Scen Khoo, Jutta Kunz | Are slowly rotating Ellis-Bronnikov wormholes stable? | 6 pages, 3 figures; v2: equations added, minor typos corrected,
results unchanged, matches published version | null | 10.1016/j.physletb.2023.138349 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the radial perturbations of Ellis-Bronnikov wormholes
($\mathrm{l}=0$) in a slowly rotating background expanded up to second order in
rotation. We find indications that simple wormhole solutions such as
Ellis-Bronnikov in General Relativity can be stabilized by rotation, thus
favoring a viable traversable wormhole. This opens up the intriguing question
whether the many other wormhole solutions with or without the support of exotic
matter can become linearly mode stable when the wormhole rotates.
| [
{
"created": "Thu, 12 Jan 2023 19:00:04 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Nov 2023 14:36:59 GMT",
"version": "v2"
}
] | 2023-11-27 | [
[
"Azad",
"Bahareh",
""
],
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"Khoo",
"Fech Scen",
""
],
[
"Kunz",
"Jutta",
""
]
] | We investigate the radial perturbations of Ellis-Bronnikov wormholes ($\mathrm{l}=0$) in a slowly rotating background expanded up to second order in rotation. We find indications that simple wormhole solutions such as Ellis-Bronnikov in General Relativity can be stabilized by rotation, thus favoring a viable traversable wormhole. This opens up the intriguing question whether the many other wormhole solutions with or without the support of exotic matter can become linearly mode stable when the wormhole rotates. |
1710.09432 | Carlos Palenzuela | Carlos Palenzuela, Paolo Pani, Miguel Bezares, Vitor Cardoso, Luis
Lehner and Steven Liebling | Gravitational Wave Signatures of Highly Compact Boson Star Binaries | 16 pages, 10 figures | Phys. Rev. D 96, 104058 (2017) | 10.1103/PhysRevD.96.104058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Solitonic boson stars are stable objects made of a complex scalar field with
a compactness that can reach values comparable to that of neutron stars. A
recent study of the collision of identical boson stars produced only
non-rotating boson stars or black holes, suggesting that rotating boson stars
may not form from binary mergers. Here we extend this study to include an
analysis of the gravitational waves radiated during the coalescence of such a
binary, which is crucial to distinguish these events from other binaries with
LIGO and Virgo observations. Our studies reveal that the remnant's
gravitational wave signature is mainly governed by its fundamental frequency as
it settles down to a non-rotating boson star, emitting significant
gravitational radiation during this post-merger state. We calculate how the
waveforms and their post-merger frequencies depend on the compactness of the
initial boson stars and estimate analytically the amount of energy radiated
after the merger.
| [
{
"created": "Wed, 25 Oct 2017 19:39:29 GMT",
"version": "v1"
}
] | 2017-12-06 | [
[
"Palenzuela",
"Carlos",
""
],
[
"Pani",
"Paolo",
""
],
[
"Bezares",
"Miguel",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Lehner",
"Luis",
""
],
[
"Liebling",
"Steven",
""
]
] | Solitonic boson stars are stable objects made of a complex scalar field with a compactness that can reach values comparable to that of neutron stars. A recent study of the collision of identical boson stars produced only non-rotating boson stars or black holes, suggesting that rotating boson stars may not form from binary mergers. Here we extend this study to include an analysis of the gravitational waves radiated during the coalescence of such a binary, which is crucial to distinguish these events from other binaries with LIGO and Virgo observations. Our studies reveal that the remnant's gravitational wave signature is mainly governed by its fundamental frequency as it settles down to a non-rotating boson star, emitting significant gravitational radiation during this post-merger state. We calculate how the waveforms and their post-merger frequencies depend on the compactness of the initial boson stars and estimate analytically the amount of energy radiated after the merger. |
gr-qc/0002051 | Andrzej Woszczyna | Zdzislaw A. Golda, Andrzej Woszczyna | Acoustics of early universe. II. Lifshitz vs. gauge-invariant theories | null | J.Math.Phys. 42 (2001) 856-862 | 10.1063/1.1335557 | null | gr-qc astro-ph math-ph math.MP | null | Appealing to classical methods of order reduction, we reduce the Lifshitz
system to a second order differential equation. We demonstrate its equivalence
to well known gauge-invariant results. For a radiation dominated universe we
express the metric and density corrections in their exact forms and discuss
their acoustic character.
| [
{
"created": "Tue, 15 Feb 2000 11:52:16 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Apr 2000 08:41:29 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Golda",
"Zdzislaw A.",
""
],
[
"Woszczyna",
"Andrzej",
""
]
] | Appealing to classical methods of order reduction, we reduce the Lifshitz system to a second order differential equation. We demonstrate its equivalence to well known gauge-invariant results. For a radiation dominated universe we express the metric and density corrections in their exact forms and discuss their acoustic character. |
gr-qc/0405005 | James W. York Jr. | James W. York | The Initial Value Problem Using Metric and Extrinsic Curvature | 10 pages, to appear in the Proceedings of the Tenth Marcel Grossmann
Meeting on General Relativity | null | 10.1142/9789812704030_0001 | null | gr-qc | null | The initial value problem is introduced after a thorough review of the
essential geometry. The initial value equations are put into elliptic form
using both conformal transformations and a treatment of the extrinsic curvature
introduced recently. This use of the metric and the extrinsic curvature is
manifestly equivalent to the author's conformal thin sandwich formulation.
Therefore, the reformulation of the constraints as an elliptic system by use of
conformal techniques is complete.
| [
{
"created": "Sat, 1 May 2004 19:48:56 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"York",
"James W.",
""
]
] | The initial value problem is introduced after a thorough review of the essential geometry. The initial value equations are put into elliptic form using both conformal transformations and a treatment of the extrinsic curvature introduced recently. This use of the metric and the extrinsic curvature is manifestly equivalent to the author's conformal thin sandwich formulation. Therefore, the reformulation of the constraints as an elliptic system by use of conformal techniques is complete. |
gr-qc/0008035 | Irina Radinschi | I. Radinschi | The Energy of a Dyonic Dilaton Black Hole | 8 pages, no figures | Acta Phys.Slov. 49 (1999) 789-794 | null | null | gr-qc | null | We calculate the energy distribution of a dyonic dilaton black hole by using
the Tolman's energy-momentum complex. All the calculations are performed in
quasi-Cartesian coordinates. The energy distribution of the dyonic dilaton
black hole depends on the mass, electric charge, magnetic charge and asymptotic
value of the dilaton. We get the same result as obtained by Y-Ching Yang,
Ching-Tzung Yeh, Rue-Ron Hsu and Chin-Rong Lee by using the Einstein's
prescription.
| [
{
"created": "Tue, 15 Aug 2000 14:16:56 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Radinschi",
"I.",
""
]
] | We calculate the energy distribution of a dyonic dilaton black hole by using the Tolman's energy-momentum complex. All the calculations are performed in quasi-Cartesian coordinates. The energy distribution of the dyonic dilaton black hole depends on the mass, electric charge, magnetic charge and asymptotic value of the dilaton. We get the same result as obtained by Y-Ching Yang, Ching-Tzung Yeh, Rue-Ron Hsu and Chin-Rong Lee by using the Einstein's prescription. |
2301.05923 | Tong Jiang | Tong Jiang, Yungui Gong, Xuchen Lu | Sky localization of space-based detectors with time-delay interferometry | 24 pages, 8 figures | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accurate sky localization of gravitational wave (GW) sources is an
important scientific goal for space-based GW detectors. Due to the effects of
gravity on three spacecrafts, it is hard to maintain the equality of the arm
length, so the time-delay interferometry (TDI) method is needed to cancel out
the laser frequency noise for space-based GW detectors. By considering the
first-generation TDI combination, we employ the Fisher information matrix to
study the accuracy of sky localizations for future space-based GW detectors and
their combined network. The main difference between future space-based GW
detectors includes the time-changing orientation of the detector plane, the arm
length, the orbital period of spacecrafts and the noise curve. We study the
effects of these factors on the accuracy of source localization at different
frequencies. We find that the amplitude modulation caused by the rotation of
the detector plane can help LISA and Taiji not only to improve the accuracy of
source localization but also to enlarge the sky coverage at frequencies below 1
mHz. As the frequency of monochromatic GWs increases, the Doppler modulation
becomes dominate and the equatorial pattern appears in the sky map. The effect
of arm length on the angular resolution mainly comes from the noise curve and
it is almost the same for both heliocentric and geocentric constellations. The
orbital period of the spacecrafts has little effect on the angular resolutions.
The improvement on the angular resolutions by the network of combined detectors
is small compared with a single detector and the angular resolutions are almost
the same with and without the TDI combination.
| [
{
"created": "Sat, 14 Jan 2023 14:10:15 GMT",
"version": "v1"
}
] | 2023-01-18 | [
[
"Jiang",
"Tong",
""
],
[
"Gong",
"Yungui",
""
],
[
"Lu",
"Xuchen",
""
]
] | The accurate sky localization of gravitational wave (GW) sources is an important scientific goal for space-based GW detectors. Due to the effects of gravity on three spacecrafts, it is hard to maintain the equality of the arm length, so the time-delay interferometry (TDI) method is needed to cancel out the laser frequency noise for space-based GW detectors. By considering the first-generation TDI combination, we employ the Fisher information matrix to study the accuracy of sky localizations for future space-based GW detectors and their combined network. The main difference between future space-based GW detectors includes the time-changing orientation of the detector plane, the arm length, the orbital period of spacecrafts and the noise curve. We study the effects of these factors on the accuracy of source localization at different frequencies. We find that the amplitude modulation caused by the rotation of the detector plane can help LISA and Taiji not only to improve the accuracy of source localization but also to enlarge the sky coverage at frequencies below 1 mHz. As the frequency of monochromatic GWs increases, the Doppler modulation becomes dominate and the equatorial pattern appears in the sky map. The effect of arm length on the angular resolution mainly comes from the noise curve and it is almost the same for both heliocentric and geocentric constellations. The orbital period of the spacecrafts has little effect on the angular resolutions. The improvement on the angular resolutions by the network of combined detectors is small compared with a single detector and the angular resolutions are almost the same with and without the TDI combination. |
2405.00661 | Waleed Sherif | Hanno Sahlmann, Waleed Sherif | Towards quantum gravity with neural networks: Solving quantum Hamilton
constraints of 3d Euclidean gravity in the weak coupling limit | 46 pages, 14 figures | null | null | null | gr-qc hep-th physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider 3-dimensional Euclidean gravity in the weak coupling limit of
Smolin and show that it is BF-theory with $\text{U(1)}^3$ as a Lie group. The
theory is quantised using loop quantum gravity methods. The kinematical degrees
of freedom are truncated, on account of computational feasibility, by fixing a
graph and deforming the algebra of the holonomies to impose a cutoff on the
charge vectors. This leads to a quantum theory related to $\text{U}_q
\text{(1)}^3$ BF-theory. The effect of imposing the cutoff on the charges is
examined. We also implement the quantum volume operator of 3d loop quantum
gravity. Most importantly we compare two constraints for the quantum model
obtained: a master constraint enforcing curvature and Gauss constraint, as well
as a combination of a quantum Hamilton constraint constructed using Thiemann's
strategy and the Gauss master constraint. The two constraints are solved using
the neural network quantum state ansatz, demonstrating its ability to explore
models which are out of reach for exact numerical methods. The solutions spaces
are quantitatively compared and although the forms of the constraints are
radically different, the solutions turn out to have a surprisingly large
overlap. We also investigate the behavior of the quantum volume in solutions to
the constraints.
| [
{
"created": "Wed, 1 May 2024 17:50:06 GMT",
"version": "v1"
}
] | 2024-05-02 | [
[
"Sahlmann",
"Hanno",
""
],
[
"Sherif",
"Waleed",
""
]
] | We consider 3-dimensional Euclidean gravity in the weak coupling limit of Smolin and show that it is BF-theory with $\text{U(1)}^3$ as a Lie group. The theory is quantised using loop quantum gravity methods. The kinematical degrees of freedom are truncated, on account of computational feasibility, by fixing a graph and deforming the algebra of the holonomies to impose a cutoff on the charge vectors. This leads to a quantum theory related to $\text{U}_q \text{(1)}^3$ BF-theory. The effect of imposing the cutoff on the charges is examined. We also implement the quantum volume operator of 3d loop quantum gravity. Most importantly we compare two constraints for the quantum model obtained: a master constraint enforcing curvature and Gauss constraint, as well as a combination of a quantum Hamilton constraint constructed using Thiemann's strategy and the Gauss master constraint. The two constraints are solved using the neural network quantum state ansatz, demonstrating its ability to explore models which are out of reach for exact numerical methods. The solutions spaces are quantitatively compared and although the forms of the constraints are radically different, the solutions turn out to have a surprisingly large overlap. We also investigate the behavior of the quantum volume in solutions to the constraints. |
gr-qc/0002018 | T. P. Singh | T. P. Singh and Cenalo Vaz | Radiation flux and spectrum in the Vaidya collapse model | 10 pages, Latex File | Phys.Lett. B481 (2000) 74-78 | 10.1016/S0370-2693(00)00416-0 | null | gr-qc | null | We consider the quantization of a massless scalar field, using the geometric
optics approximation, in the background spacetime of a collapsing spherical
self-similar Vaidya star, which forms a black hole or a naked singularity. We
show that the outgoing radiation flux of the quantized scalar field diverges on
the Cauchy horizon. The spectrum of the produced scalar partcles is non-thermal
when the background develops a naked singularity. These results are analogous
to those obtained for the scalar quantization on a self-similar dust cloud.
| [
{
"created": "Thu, 3 Feb 2000 16:13:26 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Singh",
"T. P.",
""
],
[
"Vaz",
"Cenalo",
""
]
] | We consider the quantization of a massless scalar field, using the geometric optics approximation, in the background spacetime of a collapsing spherical self-similar Vaidya star, which forms a black hole or a naked singularity. We show that the outgoing radiation flux of the quantized scalar field diverges on the Cauchy horizon. The spectrum of the produced scalar partcles is non-thermal when the background develops a naked singularity. These results are analogous to those obtained for the scalar quantization on a self-similar dust cloud. |
1506.08094 | Jarmo M\"akel\"a Dr. | Jarmo M\"akel\"a | Thermodynamics of Spherically Symmetric Spacetimes in Loop Quantum
Gravity | 26 pages, no figures. Published in the Physical Review D. Comments
welcome | Phys. Rev. D 91, 124050 (2015) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The choice of the area operator in loop quantum gravity is by no means
unique. In addition to the area operator commonly used in loop quantum gravity
there is also an area operator introduced by Krasnov in 1998, which gives
uniformly spaced area spectra for the horizons of spacetime. Using Krasnov's
area operator we consider the thermodynamics of spherically symmetric
spacetimes equipped with horizons in loop quantum gravity. Among other things,
our approach implies, in a pretty simple manner, that every horizon of
spacetime emits thermal radiation and possesses emtropy which, in the natural
units, is one-quarter of its area. When applied to the de Sitter spacetime loop
quantum gravity provides an explanation both to the presence and the smallness
of the cosmological constant.
| [
{
"created": "Thu, 18 Jun 2015 08:12:59 GMT",
"version": "v1"
}
] | 2015-06-29 | [
[
"Mäkelä",
"Jarmo",
""
]
] | The choice of the area operator in loop quantum gravity is by no means unique. In addition to the area operator commonly used in loop quantum gravity there is also an area operator introduced by Krasnov in 1998, which gives uniformly spaced area spectra for the horizons of spacetime. Using Krasnov's area operator we consider the thermodynamics of spherically symmetric spacetimes equipped with horizons in loop quantum gravity. Among other things, our approach implies, in a pretty simple manner, that every horizon of spacetime emits thermal radiation and possesses emtropy which, in the natural units, is one-quarter of its area. When applied to the de Sitter spacetime loop quantum gravity provides an explanation both to the presence and the smallness of the cosmological constant. |
0812.2121 | Ayan Chatterjee | Ayan Chatterjee and Amit Ghosh | Laws of Black Hole Mechanics from Holst Action | References added, Minor Corrections 25 pages 1 fig | Phys.Rev.D80:064036,2009 | 10.1103/PhysRevD.80.064036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formulation of Weak Isolated Horizons (WIH) based on the Isolated Horizon
formulation of black hole horizons is reconsidered. The first part of the paper
deals with the derivation of laws of mechanics of a WIH. While the zeroth law
follows from the WIH boundary conditions, first law depends on the action
chosen. We construct the covariant phase space for a spacetime having an WIH as
inner boundary for the Holst action. This requires the introduction of new
potential functions so that the symplectic structure is foliation independent.
We show that a precise cancellation among various terms leads to the usual
first law for WIH. Subsequently, we show from the same covariant phase space
that for spherical horizons, the topological theory on the inner boundary is a
U(1) Chern-Simons theory.
| [
{
"created": "Thu, 11 Dec 2008 11:03:08 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Feb 2009 07:51:42 GMT",
"version": "v2"
}
] | 2009-11-06 | [
[
"Chatterjee",
"Ayan",
""
],
[
"Ghosh",
"Amit",
""
]
] | The formulation of Weak Isolated Horizons (WIH) based on the Isolated Horizon formulation of black hole horizons is reconsidered. The first part of the paper deals with the derivation of laws of mechanics of a WIH. While the zeroth law follows from the WIH boundary conditions, first law depends on the action chosen. We construct the covariant phase space for a spacetime having an WIH as inner boundary for the Holst action. This requires the introduction of new potential functions so that the symplectic structure is foliation independent. We show that a precise cancellation among various terms leads to the usual first law for WIH. Subsequently, we show from the same covariant phase space that for spherical horizons, the topological theory on the inner boundary is a U(1) Chern-Simons theory. |
1510.06991 | Daniele Pranzetti | Daniele Oriti, Daniele Pranzetti, Lorenzo Sindoni | Horizon entropy from quantum gravity condensates | 6 pages; published version | Phys. Rev. Lett. 116, 211301 (2016) | 10.1103/PhysRevLett.116.211301 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct condensate states encoding the continuum spherically symmetric
quantum geometry of an horizon in full quantum gravity, i.e. without any
classical symmetry reduction, in the group field theory formalism. Tracing over
the bulk degrees of freedom, we show how the resulting reduced density matrix
manifestly exhibits an holographic behavior. We derive a complete orthonormal
basis of eigenstates for the reduced density matrix of the horizon and use it
to compute the horizon entanglement entropy. By imposing consistency with the
horizon boundary conditions and semiclassical thermodynamical properties, we
recover the Bekenstein--Hawking entropy formula for any value of the Immirzi
parameter. Our analysis supports the equivalence between the von Neumann
(entanglement) entropy interpretation and the Boltzmann (statistical) one.
| [
{
"created": "Fri, 23 Oct 2015 16:56:34 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Nov 2015 20:33:47 GMT",
"version": "v2"
},
{
"created": "Thu, 26 May 2016 08:32:21 GMT",
"version": "v3"
}
] | 2016-05-27 | [
[
"Oriti",
"Daniele",
""
],
[
"Pranzetti",
"Daniele",
""
],
[
"Sindoni",
"Lorenzo",
""
]
] | We construct condensate states encoding the continuum spherically symmetric quantum geometry of an horizon in full quantum gravity, i.e. without any classical symmetry reduction, in the group field theory formalism. Tracing over the bulk degrees of freedom, we show how the resulting reduced density matrix manifestly exhibits an holographic behavior. We derive a complete orthonormal basis of eigenstates for the reduced density matrix of the horizon and use it to compute the horizon entanglement entropy. By imposing consistency with the horizon boundary conditions and semiclassical thermodynamical properties, we recover the Bekenstein--Hawking entropy formula for any value of the Immirzi parameter. Our analysis supports the equivalence between the von Neumann (entanglement) entropy interpretation and the Boltzmann (statistical) one. |
gr-qc/0409011 | M. Meyer | S. Deser (Brandeis), R. Jackiw (MIT), S.-Y. Pi (Boston University) | Cotton Blend Gravity $pp$ Waves | 6 pages. Dedicated to Andrzej Staruszkiewicz, a pioneer in d=3
gravity, on his 65th birthday | ActaPhys.Polon.B36:27-34,2005 | null | BRX TH-546; MIT-CTP-3533; BUHEP-04-13 | gr-qc hep-th | null | We study conformal gravity in d=2+1, where the Cotton tensor is equated to
a--necessarily traceless--matter stress tensor, for us that of the improved
scalar field. We first solve this system exactly in the $pp$ wave regime, then
show it to be equivalent to topologically massive gravity.
| [
{
"created": "Thu, 2 Sep 2004 19:02:05 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Deser",
"S.",
"",
"Brandeis"
],
[
"Jackiw",
"R.",
"",
"MIT"
],
[
"Pi",
"S. -Y.",
"",
"Boston University"
]
] | We study conformal gravity in d=2+1, where the Cotton tensor is equated to a--necessarily traceless--matter stress tensor, for us that of the improved scalar field. We first solve this system exactly in the $pp$ wave regime, then show it to be equivalent to topologically massive gravity. |
gr-qc/0211098 | Allemandi Gianluca | G. Allemandi, M. Francaviglia, M. Raiteri | Covariant Charges in Chern-Simons AdS_3 Gravity | 30 pages, no figures. References added | Class.Quant.Grav. 20 (2003) 483-506 | 10.1088/0264-9381/20/3/307 | null | gr-qc hep-th | null | We try to give hereafter an answer to some open questions about the
definition of conserved quantities in Chern-Simons theory, with particular
reference to Chern-Simons AdS_3 Gravity. Our attention is focused on the
problem of global covariance and gauge invariance of the variation of Noether
charges. A theory which satisfies the principle of covariance on each step of
its construction is developed, starting from a gauge invariant Chern-Simons
Lagrangian and using a recipe developed in gr-qc/0110104 and gr-qc/0107074 to
calculate the variation of conserved quantities. The problem to give a
mathematical well-defined expression for the infinitesimal generators of
symmetries is pointed out and it is shown that the generalized Kosmann lift of
spacetime vector fields leads to the expected numerical values for the
conserved quantities when the solution corresponds to the BTZ black hole. The
fist law of black holes mechanics for the BTZ solution is then proved and the
transition between the variation of conserved quantities in Chern-Simons AdS_3
Gravity theory and the variation of conserved quantities in General Relativity
is analysed in detail.
| [
{
"created": "Thu, 28 Nov 2002 11:23:22 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Dec 2002 14:22:56 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Allemandi",
"G.",
""
],
[
"Francaviglia",
"M.",
""
],
[
"Raiteri",
"M.",
""
]
] | We try to give hereafter an answer to some open questions about the definition of conserved quantities in Chern-Simons theory, with particular reference to Chern-Simons AdS_3 Gravity. Our attention is focused on the problem of global covariance and gauge invariance of the variation of Noether charges. A theory which satisfies the principle of covariance on each step of its construction is developed, starting from a gauge invariant Chern-Simons Lagrangian and using a recipe developed in gr-qc/0110104 and gr-qc/0107074 to calculate the variation of conserved quantities. The problem to give a mathematical well-defined expression for the infinitesimal generators of symmetries is pointed out and it is shown that the generalized Kosmann lift of spacetime vector fields leads to the expected numerical values for the conserved quantities when the solution corresponds to the BTZ black hole. The fist law of black holes mechanics for the BTZ solution is then proved and the transition between the variation of conserved quantities in Chern-Simons AdS_3 Gravity theory and the variation of conserved quantities in General Relativity is analysed in detail. |
gr-qc/9503009 | Paulo Rodrigues Lima Vargas Moniz | A.D.Y. Cheng, P.D. D'Eath and P.R.L.V. Moniz (DAMTP-University of
Cambridge) | Quantization of a Friedmann-Robertson-Walker model in N=1 Supergravity
with Gauged Supermatter | 5 pages, Talk at the 1st Mexican School in Gravitation and
mathematical physics, Guanajuato, Mexico, December 12-16 1994 | null | 10.1088/0264-9381/12/6/003 | DAMTP R-94/45c | gr-qc | null | The theory of N = 1 supergravity with gauged supermatter is studied in the
context of a k = + 1 Friedmann minisuperspace model. It is found by imposing
the Lorentz and supersymmetry constraints that there are {\seveni no} physical
states in the particular SU(2) model studied.
| [
{
"created": "Mon, 6 Mar 1995 14:08:49 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Cheng",
"A. D. Y.",
"",
"DAMTP-University of\n Cambridge"
],
[
"D'Eath",
"P. D.",
"",
"DAMTP-University of\n Cambridge"
],
[
"Moniz",
"P. R. L. V.",
"",
"DAMTP-University of\n Cambridge"
]
] | The theory of N = 1 supergravity with gauged supermatter is studied in the context of a k = + 1 Friedmann minisuperspace model. It is found by imposing the Lorentz and supersymmetry constraints that there are {\seveni no} physical states in the particular SU(2) model studied. |
0903.3577 | Jiri Podolsky | Jiri Podolsky, Hedvika Kadlecova | Radiation generated by accelerating and rotating charged black holes in
(anti-)de Sitter space | 24 pages, 18 figures. To appear in Classical and Quantum Gravity | Class.Quant.Grav.26:105007,2009 | 10.1088/0264-9381/26/10/105007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Asymptotic behaviour of gravitational and electromagnetic fields of exact
type D solutions from the large Plebanski-Demianski family of black hole
spacetimes is analyzed. The amplitude and directional structure of radiation is
evaluated in cases when the cosmological constant is non-vanishing, so that the
conformal infinities have either de Sitter-like or anti-de Sitter-like
character. In particular, explicit relations between the parameters that
characterize the sources (that is their mass, electric and magnetic charges,
NUT parameter, rotational parameter, and acceleration) and properties of the
radiation generated by them are presented. The results further elucidate the
physical interpretation of these solutions and may help to understand radiative
characteristics of more general spacetimes than those that are asymptotically
flat.
| [
{
"created": "Fri, 20 Mar 2009 17:39:15 GMT",
"version": "v1"
}
] | 2009-05-18 | [
[
"Podolsky",
"Jiri",
""
],
[
"Kadlecova",
"Hedvika",
""
]
] | Asymptotic behaviour of gravitational and electromagnetic fields of exact type D solutions from the large Plebanski-Demianski family of black hole spacetimes is analyzed. The amplitude and directional structure of radiation is evaluated in cases when the cosmological constant is non-vanishing, so that the conformal infinities have either de Sitter-like or anti-de Sitter-like character. In particular, explicit relations between the parameters that characterize the sources (that is their mass, electric and magnetic charges, NUT parameter, rotational parameter, and acceleration) and properties of the radiation generated by them are presented. The results further elucidate the physical interpretation of these solutions and may help to understand radiative characteristics of more general spacetimes than those that are asymptotically flat. |
1412.2427 | Molin Liu | Molin Liu, Yuling Yang, Jianbo Lv and Lixin Xu | Thermodynamics of Apparent Horizon and Friedmann Equations in Big Bounce
Universe | 15 pages, 2 figures. Accepted by General Relativity and Gravitation | Gen Relativ Gravit (2016) 48:59 | 10.1007/s10714-016-2055-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study a big bounce universe typified by a non-singular big
bounce, as opposed to a singular big bang. This cosmological model can describe
radiation dominated early universe and matter dominated late universe in FRW
model. The connections between thermodynamics and gravity are observed here. In
the early stage of both cold and hot universes, we find there is only one
geometry containing a 4D de Sitter universe with a general state parameter. We
also find the form of the apparent horizon in the early universe strongly
depends on the extra dimension, which suggests that the influence of the extra
dimension could in principle be found in the early universe. Moreover, we show
that in the late stages of both cold and hot universes, the moment when the
apparent horizon begins to bounce keeps essentially in step with the behavior
of the cosmological scalar factor.
| [
{
"created": "Mon, 8 Dec 2014 01:49:12 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Mar 2016 02:45:35 GMT",
"version": "v2"
}
] | 2016-04-15 | [
[
"Liu",
"Molin",
""
],
[
"Yang",
"Yuling",
""
],
[
"Lv",
"Jianbo",
""
],
[
"Xu",
"Lixin",
""
]
] | In this paper, we study a big bounce universe typified by a non-singular big bounce, as opposed to a singular big bang. This cosmological model can describe radiation dominated early universe and matter dominated late universe in FRW model. The connections between thermodynamics and gravity are observed here. In the early stage of both cold and hot universes, we find there is only one geometry containing a 4D de Sitter universe with a general state parameter. We also find the form of the apparent horizon in the early universe strongly depends on the extra dimension, which suggests that the influence of the extra dimension could in principle be found in the early universe. Moreover, we show that in the late stages of both cold and hot universes, the moment when the apparent horizon begins to bounce keeps essentially in step with the behavior of the cosmological scalar factor. |
1104.0819 | Christopher Berry | Christopher P. L. Berry, Jonathan R. Gair | Linearized f(R) Gravity: Gravitational Radiation & Solar System Tests | 19 pages, 1 figure; typos in Sec. VIII. A. corrected | Phys.Rev.D83:104022,2011 | 10.1103/PhysRevD.83.104022 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the linearized form of metric f(R)-gravity, assuming that f(R)
is analytic about R = 0 so it may be expanded as f(R) = R + a_2 R^2/2 + ... .
Gravitational radiation is modified, admitting an extra mode of oscillation,
that of the Ricci scalar. We derive an effective energy-momentum tensor for the
radiation. We also present weak-field metrics for simple sources. These are
distinct from the equivalent Kerr (or Schwarzschild) forms. We apply the
metrics to tests that could constrain f(R). We show that light deflection
experiments cannot distinguish f(R)-gravity from general relativity as both
have an effective post-Newtonian parameter \gamma = 1. We find that planetary
precession rates are enhanced relative to general relativity; from the orbit of
Mercury we derive the bound |a_2| < 1.2 \times 10^18 m^2. Gravitational wave
astronomy may be more useful: considering the phase of a gravitational waveform
we estimate deviations from general relativity could be measurable for an
extreme-mass-ratio inspiral about a 10^6 M_sol black hole if |a_2| > 10^17 m^2,
assuming that the weak-field metric of the black hole coincides with that of a
point mass. However Eot-Wash experiments provide the strictest bound |a_2| < 2
\times 10^-9 m^2. Although the astronomical bounds are weaker, they are still
of interest in the case that the effective form of f(R) is modified in
different regions, perhaps through the chameleon mechanism. Assuming the
laboratory bound is universal, we conclude that the propagating Ricci scalar
mode cannot be excited by astrophysical sources.
| [
{
"created": "Tue, 5 Apr 2011 12:13:15 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Apr 2011 17:22:30 GMT",
"version": "v2"
},
{
"created": "Tue, 17 May 2011 08:40:02 GMT",
"version": "v3"
},
{
"created": "Thu, 29 Mar 2012 17:07:42 GMT",
"version": "v4"
}
] | 2012-03-30 | [
[
"Berry",
"Christopher P. L.",
""
],
[
"Gair",
"Jonathan R.",
""
]
] | We investigate the linearized form of metric f(R)-gravity, assuming that f(R) is analytic about R = 0 so it may be expanded as f(R) = R + a_2 R^2/2 + ... . Gravitational radiation is modified, admitting an extra mode of oscillation, that of the Ricci scalar. We derive an effective energy-momentum tensor for the radiation. We also present weak-field metrics for simple sources. These are distinct from the equivalent Kerr (or Schwarzschild) forms. We apply the metrics to tests that could constrain f(R). We show that light deflection experiments cannot distinguish f(R)-gravity from general relativity as both have an effective post-Newtonian parameter \gamma = 1. We find that planetary precession rates are enhanced relative to general relativity; from the orbit of Mercury we derive the bound |a_2| < 1.2 \times 10^18 m^2. Gravitational wave astronomy may be more useful: considering the phase of a gravitational waveform we estimate deviations from general relativity could be measurable for an extreme-mass-ratio inspiral about a 10^6 M_sol black hole if |a_2| > 10^17 m^2, assuming that the weak-field metric of the black hole coincides with that of a point mass. However Eot-Wash experiments provide the strictest bound |a_2| < 2 \times 10^-9 m^2. Although the astronomical bounds are weaker, they are still of interest in the case that the effective form of f(R) is modified in different regions, perhaps through the chameleon mechanism. Assuming the laboratory bound is universal, we conclude that the propagating Ricci scalar mode cannot be excited by astrophysical sources. |
0909.2741 | Vladimir Dzhunushaliev | Vladimir Dzhunushaliev and Vladimir Folomeev | Spinor brane | errors are corrected | Gen.Rel.Grav.43:1253-1261,2011 | 10.1007/s10714-010-1105-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thick brane model supported by a nonlinear spinor field is constructed.
The different cases with the various values of the cosmological constant
$\Lambda (< = >) 0$ are investigated. It is shown that regular analytical
spinor thick brane solutions with asymptotically Minkowski (at $\Lambda=0$) or
anti-de Sitter spacetimes (at $\Lambda<0$) do exist.
| [
{
"created": "Tue, 15 Sep 2009 08:25:45 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Feb 2010 05:11:36 GMT",
"version": "v2"
}
] | 2011-04-25 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
]
] | The thick brane model supported by a nonlinear spinor field is constructed. The different cases with the various values of the cosmological constant $\Lambda (< = >) 0$ are investigated. It is shown that regular analytical spinor thick brane solutions with asymptotically Minkowski (at $\Lambda=0$) or anti-de Sitter spacetimes (at $\Lambda<0$) do exist. |
2205.15029 | Juan Calderon Bustillo | Juan Calderon Bustillo, Isaac C.F. Wong, Nicolas Sanchis-Gual, Samson
H.W. Leong, Alejandro Torres-Forne, Koustav Chandra, Jose A. Font, Carlos
Herdeiro, Eugen Radu and T.G.F. Li | Gravitational-wave parameter inference with the Newman-Penrose scalar
$\psi_4$ | Version accepted for publication in Physical Review X. 27 pages, 11
Figures, 3 Appendixes | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Detection and parameter inference of gravitational-wave signals \ncor{from
compact mergers} rely on the comparison of the incoming detector strain data
$d(t)$ to waveform templates for the gravitational-wave strain $h(t)$ that
ultimately rely on the resolution of Einstein's equations via numerical
relativity simulations. These, however, commonly output a quantity known as the
Newman-Penrose scalar $\psi_4(t)$ which, under the Bondi gauge, is related to
the gravitational-wave strain by $\psi_4(t)=\mathrm{d}^2h(t) / \mathrm{d}t^2$.
Therefore, obtaining strain templates involves an integration process that
introduces artefacts that need to be treated in a rather manual way. By taking
second-order finite differences on the detector data and inferring the
corresponding background noise distribution, we develop a framework to perform
gravitational-wave data analysis directly using $\psi_4(t)$ templates. We first
demonstrate this formalism, and the impact of integration artefacts in strain
templates, through the recovery of numerically simulated signals from head-on
collisions of Proca stars injected in Advanced LIGO noise. Next, we re-analyse
the event GW190521 under the hypothesis of a Proca-star merger, obtaining
results equivalent to those in Ref.[1], where we used the classical strain
framework. We find, however, that integration errors would strongly impact our
analysis if GW190521 was four times louder. Finally, we show that our framework
fixes significant biases in the interpretation of the high-mass GW trigger
S200114f arising from the usage of strain templates. We remove the need to
obtain strain waveforms from numerical relativity simulations, avoiding the
associated systematic errors.
| [
{
"created": "Mon, 30 May 2022 12:07:16 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jun 2022 12:17:56 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Oct 2023 15:36:20 GMT",
"version": "v3"
}
] | 2023-10-17 | [
[
"Bustillo",
"Juan Calderon",
""
],
[
"Wong",
"Isaac C. F.",
""
],
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Leong",
"Samson H. W.",
""
],
[
"Torres-Forne",
"Alejandro",
""
],
[
"Chandra",
"Koustav",
""
],
[
"Font",
"Jose A.",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
],
[
"Li",
"T. G. F.",
""
]
] | Detection and parameter inference of gravitational-wave signals \ncor{from compact mergers} rely on the comparison of the incoming detector strain data $d(t)$ to waveform templates for the gravitational-wave strain $h(t)$ that ultimately rely on the resolution of Einstein's equations via numerical relativity simulations. These, however, commonly output a quantity known as the Newman-Penrose scalar $\psi_4(t)$ which, under the Bondi gauge, is related to the gravitational-wave strain by $\psi_4(t)=\mathrm{d}^2h(t) / \mathrm{d}t^2$. Therefore, obtaining strain templates involves an integration process that introduces artefacts that need to be treated in a rather manual way. By taking second-order finite differences on the detector data and inferring the corresponding background noise distribution, we develop a framework to perform gravitational-wave data analysis directly using $\psi_4(t)$ templates. We first demonstrate this formalism, and the impact of integration artefacts in strain templates, through the recovery of numerically simulated signals from head-on collisions of Proca stars injected in Advanced LIGO noise. Next, we re-analyse the event GW190521 under the hypothesis of a Proca-star merger, obtaining results equivalent to those in Ref.[1], where we used the classical strain framework. We find, however, that integration errors would strongly impact our analysis if GW190521 was four times louder. Finally, we show that our framework fixes significant biases in the interpretation of the high-mass GW trigger S200114f arising from the usage of strain templates. We remove the need to obtain strain waveforms from numerical relativity simulations, avoiding the associated systematic errors. |
1405.2919 | Michael Grudich | Michael Grudich | Classical gravitational scattering in the relativistic Kepler problem | Undergraduate honours thesis. 74 pages plus source code, 27 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes are an ubiquitous end state of stellar evolution and successfully
explain some of the most extreme physics encountered in astronomical
observations. The Kerr geometry is the known exact solution to Einstein's
equations for a static, eternal black hole within the framework of general
relativity, and hence is of great importance in relativistic astrophysics. An
understanding of the orbital dynamics of test bodies and light rays in the Kerr
spacetime is therefore fundamental to the physics of a black hole. In this
work, the scattering and capturing properties of unbound, "hyperbolic" orbits
in the spacetime are studied. In particular, the differential scattering cross
section and capture cross section are derived over the parameter space of
energies, impact parameters and black hole spin orientation and magnitude. The
problem is then generalized to the motion of two massive objects on a
hyperbolic encounter, and the added effects of gravitational radiation and
finite mass ratio studied within the post-Newtonian formalism.
| [
{
"created": "Mon, 12 May 2014 18:03:27 GMT",
"version": "v1"
}
] | 2014-05-14 | [
[
"Grudich",
"Michael",
""
]
] | Black holes are an ubiquitous end state of stellar evolution and successfully explain some of the most extreme physics encountered in astronomical observations. The Kerr geometry is the known exact solution to Einstein's equations for a static, eternal black hole within the framework of general relativity, and hence is of great importance in relativistic astrophysics. An understanding of the orbital dynamics of test bodies and light rays in the Kerr spacetime is therefore fundamental to the physics of a black hole. In this work, the scattering and capturing properties of unbound, "hyperbolic" orbits in the spacetime are studied. In particular, the differential scattering cross section and capture cross section are derived over the parameter space of energies, impact parameters and black hole spin orientation and magnitude. The problem is then generalized to the motion of two massive objects on a hyperbolic encounter, and the added effects of gravitational radiation and finite mass ratio studied within the post-Newtonian formalism. |
gr-qc/0411051 | Donato Bini | Donato Bini and Robert T. Jantzen | Stationary spacetimes and the Simon tensor | To appear on the Proceedings of the International Conference in Honor
of Y. Choquet-Bruhat, "Analysis, Manifolds, and Geometric Structures in
Physics" Hotel Cala di Mola Porto Azzurro - Isola d'Elba June 24th-26th, 2004 | Nuovo Cim. B119 (2004) 863-873 | 10.1393/ncb/i2004-10183-9 | null | gr-qc | null | For stationary vacuum spacetimes the Bianchi identities of the second kind
equate the Simon tensor to the Simon-Mars tensor, the latter having a clear
geometrical interpretation. The equivalence of these two tensors is broken in
the nonvacuum case by additional source energy-momentum terms, but absorbing
these source terms into a redefinition of the Simon tensor restores the
equality. Explicit examples are discussed for electrovacuum and rigidly
rotating matter fields.
| [
{
"created": "Wed, 10 Nov 2004 08:39:13 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bini",
"Donato",
""
],
[
"Jantzen",
"Robert T.",
""
]
] | For stationary vacuum spacetimes the Bianchi identities of the second kind equate the Simon tensor to the Simon-Mars tensor, the latter having a clear geometrical interpretation. The equivalence of these two tensors is broken in the nonvacuum case by additional source energy-momentum terms, but absorbing these source terms into a redefinition of the Simon tensor restores the equality. Explicit examples are discussed for electrovacuum and rigidly rotating matter fields. |
2306.04832 | Matteo Luca Ruggiero | Matteo Luca Ruggiero | Stationary rotating and axially symmetric dust systems as peculiar
General Relativistic objects | 13 pages; revised to match the version accepted for publication in
JCAP | JCAP02(2024)025 | 10.1088/1475-7516/2024/02/025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study an exact solution of Einstein's equations describing a
self-gravitating system, made of dust, distributed with axial symmetry and in
stationary rotation, and we prove that this type of system has no Newtonian
analogue. In a low-energy limit, its existence depends on the solution of a
Grad-Shafranov equation in vacuum which can be interpreted as a Laplace
equation for the toroidal component of the gravitomagnetic potential; in
particular, in this system the relativistic rotational effects are of the order
of magnitude of Newtonian ones. We therefore argue that this exact solution
should contain singularities and discuss the possible consequences of using
such a system as simplified models for galactic dynamics.
| [
{
"created": "Wed, 7 Jun 2023 23:23:07 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2024 18:56:42 GMT",
"version": "v2"
}
] | 2024-02-22 | [
[
"Ruggiero",
"Matteo Luca",
""
]
] | We study an exact solution of Einstein's equations describing a self-gravitating system, made of dust, distributed with axial symmetry and in stationary rotation, and we prove that this type of system has no Newtonian analogue. In a low-energy limit, its existence depends on the solution of a Grad-Shafranov equation in vacuum which can be interpreted as a Laplace equation for the toroidal component of the gravitomagnetic potential; in particular, in this system the relativistic rotational effects are of the order of magnitude of Newtonian ones. We therefore argue that this exact solution should contain singularities and discuss the possible consequences of using such a system as simplified models for galactic dynamics. |
1905.11443 | Ernesto Contreras | E. Contreras, J. M. Ramirez-Velasquez, \'A. Rinc\'on, G. Panotopoulos
and P. Bargue\~no | Black hole shadow of a rotating polytropic black hole by the
Newman--Janis algorithm without complexification | 9 pages, 2 figures, some references added | Eur. Phys. J. C (2019) 79: 802 | 10.1140/epjc/s10052-019-7309-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, starting from a spherically symmetric polytropic black hole, a
rotating solution is obtained by following the Newman--Janis algorithm without
complexification. Besides studying the horizon, the static conditions and
causality issues of the rotating solution, we obtain and discuss the shape of
its shadow. Some other physical features as the Hawking temperature and
emission rate of the rotating polytropic black hole solution are also
discussed.
| [
{
"created": "Mon, 27 May 2019 18:43:37 GMT",
"version": "v1"
},
{
"created": "Fri, 31 May 2019 16:05:53 GMT",
"version": "v2"
}
] | 2019-10-23 | [
[
"Contreras",
"E.",
""
],
[
"Ramirez-Velasquez",
"J. M.",
""
],
[
"Rincón",
"Á.",
""
],
[
"Panotopoulos",
"G.",
""
],
[
"Bargueño",
"P.",
""
]
] | In this work, starting from a spherically symmetric polytropic black hole, a rotating solution is obtained by following the Newman--Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we obtain and discuss the shape of its shadow. Some other physical features as the Hawking temperature and emission rate of the rotating polytropic black hole solution are also discussed. |
2107.04504 | Chandrasekhar Bhamidipati | Pavan Kumar Yerra and Chandrasekhar Bhamidipati | Novel relations in massive gravity at Hawking-Page transition | 22 pages, 8 figures | null | 10.1103/PhysRevD.104.104049 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Sign and magnitude of Ruppeiner's curvature $R_N$ is an empirical indicator
of the respective nature and strength of microstructures of a thermodynamic
system. For d-dimensional Schwarzschild black holes in AdS, $R_N$ at the
Hawking-Page (HP) transition point is a universal constant. In this article we
study the nature of $R_N$ at HP transition in a massive gravity theory and show
that its constancy is broken due to the dependence on graviton mass as well as
horizon topology. Although, when the graviton mass reaches a critical value the
HP transition is driven to zero temperature, and $R_N$ at this point again
approaches a universal negative constant, independent of all parameters of the
theory. The geometry of black holes in AdS close to the HP transition point is
also studied via novel near horizon scaling limits, and reveals the emergence
of fully decoupled Rindler spacetimes.
| [
{
"created": "Fri, 9 Jul 2021 15:45:21 GMT",
"version": "v1"
}
] | 2021-12-08 | [
[
"Yerra",
"Pavan Kumar",
""
],
[
"Bhamidipati",
"Chandrasekhar",
""
]
] | Sign and magnitude of Ruppeiner's curvature $R_N$ is an empirical indicator of the respective nature and strength of microstructures of a thermodynamic system. For d-dimensional Schwarzschild black holes in AdS, $R_N$ at the Hawking-Page (HP) transition point is a universal constant. In this article we study the nature of $R_N$ at HP transition in a massive gravity theory and show that its constancy is broken due to the dependence on graviton mass as well as horizon topology. Although, when the graviton mass reaches a critical value the HP transition is driven to zero temperature, and $R_N$ at this point again approaches a universal negative constant, independent of all parameters of the theory. The geometry of black holes in AdS close to the HP transition point is also studied via novel near horizon scaling limits, and reveals the emergence of fully decoupled Rindler spacetimes. |
gr-qc/0104020 | Bernd Bruegmann | Miguel Alcubierre, Bernd Bruegmann, Denis Pollney, Edward Seidel, and
Ryoji Takahashi | Black Hole Excision for Dynamic Black Holes | 5 pages, 7 figures, published version with changes to equation (2) | Phys.Rev.D64:061501,2001 | 10.1103/PhysRevD.64.061501 | AEI-2001-021 | gr-qc | null | We extend previous work on 3D black hole excision to the case of distorted
black holes, with a variety of dynamic gauge conditions that are able to
respond naturally to the spacetime dynamics. We show that the combination of
excision and gauge conditions we use is able to drive highly distorted,
rotating black holes to an almost static state at late times, with well behaved
metric functions, without the need for any special initial conditions or
analytically prescribed gauge functions. Further, we show for the first time
that one can extract accurate waveforms from these simulations, with the full
machinery of excision and dynamic gauge conditions. The evolutions can be
carried out for long times, far exceeding the longevity and accuracy of even
better resolved 2D codes. While traditional 2D codes show errors in quantities
such as apparent horizon mass of over 100% by t = 100M, and crash by t = 150M,
with our new techniques the same systems can be evolved for hundreds of M's in
full 3D with errors of only a few percent.
| [
{
"created": "Thu, 5 Apr 2001 14:23:37 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jul 2002 09:10:10 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Bruegmann",
"Bernd",
""
],
[
"Pollney",
"Denis",
""
],
[
"Seidel",
"Edward",
""
],
[
"Takahashi",
"Ryoji",
""
]
] | We extend previous work on 3D black hole excision to the case of distorted black holes, with a variety of dynamic gauge conditions that are able to respond naturally to the spacetime dynamics. We show that the combination of excision and gauge conditions we use is able to drive highly distorted, rotating black holes to an almost static state at late times, with well behaved metric functions, without the need for any special initial conditions or analytically prescribed gauge functions. Further, we show for the first time that one can extract accurate waveforms from these simulations, with the full machinery of excision and dynamic gauge conditions. The evolutions can be carried out for long times, far exceeding the longevity and accuracy of even better resolved 2D codes. While traditional 2D codes show errors in quantities such as apparent horizon mass of over 100% by t = 100M, and crash by t = 150M, with our new techniques the same systems can be evolved for hundreds of M's in full 3D with errors of only a few percent. |
gr-qc/9911032 | Lars Andersson | Lars Andersson (UM and AEI) | The global existence problem in general relativity | 49 pages, 12 figures, based on talk given at the Arthur L. Besse
Table Ronde de G\'eom\'etrie Pseudo-Riemannienne Globale, Nancy, June 1998.
Major revision, corresponds to published version | "50 years of the Cauchy problem in general relativity", eds.
Chrusciel and Friedrich, Birkhauser, Basel 2004, pp. 71-120 | null | null | gr-qc | null | We survey some known facts and open questions concerning the global
properties of 3+1 dimensional spacetimes containing a compact Cauchy surface.
We consider spacetimes with an $\ell$-dimensional Lie algebra of space-like
Killing fields. For each $\ell \leq 3$, we give some basic results and
conjectures on global existence and cosmic censorship.
| [
{
"created": "Tue, 9 Nov 1999 14:25:00 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Nov 1999 13:28:32 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Feb 2000 08:06:00 GMT",
"version": "v3"
},
{
"created": "Fri, 28 Apr 2006 12:28:17 GMT",
"version": "v4"
}
] | 2009-09-25 | [
[
"Andersson",
"Lars",
"",
"UM and AEI"
]
] | We survey some known facts and open questions concerning the global properties of 3+1 dimensional spacetimes containing a compact Cauchy surface. We consider spacetimes with an $\ell$-dimensional Lie algebra of space-like Killing fields. For each $\ell \leq 3$, we give some basic results and conjectures on global existence and cosmic censorship. |
gr-qc/0207057 | Gennady L. Krasnikov | S. Krasnikov | The quantum inequalities do not forbid spacetime shortcuts | Minor corrections and additions | Phys.Rev. D67 (2003) 104013 | 10.1103/PhysRevD.67.104013 | null | gr-qc | null | A class of spacetimes (comprising the Alcubierre bubble, Krasnikov tube, and
a certain type of wormholes) is considered that admits `superluminal travel' in
a strictly defined sense. Such spacetimes (they are called `shortcuts' in this
paper) were suspected to be impossible because calculations based on `quantum
inequalities' suggest that their existence would involve Planck-scale energy
densities and hence unphysically large values of the `total amount of negative
energy' E_tot. I argue that the spacetimes of this type may not be unphysical
at all. By explicit examples I prove that: 1) the relevant quantum inequality
does not (always) imply large energy densities; 2) large densities may not lead
to large values of E_tot; 3) large E_tot, being physically meaningless in some
relevant situations, does not necessarily exclude shortcuts.
| [
{
"created": "Mon, 15 Jul 2002 22:25:04 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Nov 2002 21:25:08 GMT",
"version": "v2"
},
{
"created": "Mon, 19 May 2003 13:14:26 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Krasnikov",
"S.",
""
]
] | A class of spacetimes (comprising the Alcubierre bubble, Krasnikov tube, and a certain type of wormholes) is considered that admits `superluminal travel' in a strictly defined sense. Such spacetimes (they are called `shortcuts' in this paper) were suspected to be impossible because calculations based on `quantum inequalities' suggest that their existence would involve Planck-scale energy densities and hence unphysically large values of the `total amount of negative energy' E_tot. I argue that the spacetimes of this type may not be unphysical at all. By explicit examples I prove that: 1) the relevant quantum inequality does not (always) imply large energy densities; 2) large densities may not lead to large values of E_tot; 3) large E_tot, being physically meaningless in some relevant situations, does not necessarily exclude shortcuts. |
2111.02805 | Ali \"Ovg\"un Dr. | Yashmitha Kumaran and Ali \"Ovg\"un | Deriving Weak Deflection Angle by Black Holes or Wormholes using
Gauss-Bonnet Theorem | 22 pages. Review Article. Accepted for publication in Turkish Journal
of Physics | Turk J Phys, 45, (2021), 247-267 | 10.3906/fiz-2110-16 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this review, various researches on finding the bending angle of light
deflected by a massive gravitating object which regard the Gauss-Bonnet theorem
as the premise have been revised. Primarily, the Gibbons and Werner method is
studied apropos of the gravitational lensing phenomenon in the weak field
limits. Some exclusive instances are deliberated while calculating the
deflection angle, beginning with the finite-distance corrections on
non-asymptotically flat spacetimes. Effects of plasma medium is then inspected
to observe its contribution to the deflection angle. Finally, the Jacobi metric
is explored as an alternative method, only to arrive at similar results. All of
the cases are probed in three constructs, one as a generic statement of
explanation, one for black holes, and one for wormholes, so as to gain a
perspective on every kind of influence.
| [
{
"created": "Tue, 2 Nov 2021 18:44:27 GMT",
"version": "v1"
}
] | 2021-11-05 | [
[
"Kumaran",
"Yashmitha",
""
],
[
"Övgün",
"Ali",
""
]
] | In this review, various researches on finding the bending angle of light deflected by a massive gravitating object which regard the Gauss-Bonnet theorem as the premise have been revised. Primarily, the Gibbons and Werner method is studied apropos of the gravitational lensing phenomenon in the weak field limits. Some exclusive instances are deliberated while calculating the deflection angle, beginning with the finite-distance corrections on non-asymptotically flat spacetimes. Effects of plasma medium is then inspected to observe its contribution to the deflection angle. Finally, the Jacobi metric is explored as an alternative method, only to arrive at similar results. All of the cases are probed in three constructs, one as a generic statement of explanation, one for black holes, and one for wormholes, so as to gain a perspective on every kind of influence. |
2003.11452 | {\O}yvind Christiansen | {\O}yvind Christiansen, Jose Beltr\'an Jim\'enez, David F. Mota | Charged Black Hole Mergers: Orbit Circularisation and Chirp Mass Bias | 25 pages and 3 figures. For associated code, see
https://github.com/oyvach/matched-filtering-mock-bias | Class. Quantum Grav. 38 (2021) 075017 | 10.1088/1361-6382/abdaf5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the inspiral of black holes carrying U(1) charge that is not
electromagnetic, but corresponds to some dark sector. In the weak-field,
low-velocity regime, the components follow Keplerian orbits. We investigate how
the orbital parameters evolve for dipole-dominated emission and find that the
orbit quickly circularises, though not as efficiently as for a gravitationally
dominated emission. We then regard circular orbits, and look for modifications
in the gravitational waveform from the components carrying small charges.
Taking this into account we populate the waveform with simplified LIGO noise
and put it through a matched filtering procedure where the template bank only
consists of uncharged templates, focusing on the charges' effect on the chirp
mass estimation. We find a consistent overestimation of the `generalised' chirp
mass, and a possible over- and underestimation of the actual chirp mass.
Finally, we briefly consider the effect of such charges on hyperbolic
encounters, finding again a bias arising from interpreting the generalised
chirp mass as the actual chirp mass.
| [
{
"created": "Wed, 25 Mar 2020 15:42:45 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Sep 2020 10:12:56 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jan 2021 09:02:05 GMT",
"version": "v3"
}
] | 2021-03-23 | [
[
"Christiansen",
"Øyvind",
""
],
[
"Jiménez",
"Jose Beltrán",
""
],
[
"Mota",
"David F.",
""
]
] | We consider the inspiral of black holes carrying U(1) charge that is not electromagnetic, but corresponds to some dark sector. In the weak-field, low-velocity regime, the components follow Keplerian orbits. We investigate how the orbital parameters evolve for dipole-dominated emission and find that the orbit quickly circularises, though not as efficiently as for a gravitationally dominated emission. We then regard circular orbits, and look for modifications in the gravitational waveform from the components carrying small charges. Taking this into account we populate the waveform with simplified LIGO noise and put it through a matched filtering procedure where the template bank only consists of uncharged templates, focusing on the charges' effect on the chirp mass estimation. We find a consistent overestimation of the `generalised' chirp mass, and a possible over- and underestimation of the actual chirp mass. Finally, we briefly consider the effect of such charges on hyperbolic encounters, finding again a bias arising from interpreting the generalised chirp mass as the actual chirp mass. |
0906.0005 | Barry Wardell | Adrian C. Ottewill, Barry Wardell | Transport Equation Approach to Calculations of Hadamard Green functions
and non-coincident DeWitt coefficients | 32 pages, 5 figures. Final published version with correction to Eq.
(3.24) | Phys. Rev. D 84, 104039 (2011) | 10.1103/PhysRevD.84.104039 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Building on an insight due to Avramidi, we provide a system of transport
equations for determining key fundamental bi-tensors, including derivatives of
the world-function, \sigma(x,x'), the square root of the Van Vleck determinant,
\Delta^{1/2}(x,x'), and the tail-term, V(x,x'), appearing in the Hadamard form
of the Green function. These bi-tensors are central to a broad range of
problems from radiation reaction to quantum field theory in curved spacetime
and quantum gravity. Their transport equations may be used either in a
semi-recursive approach to determining their covariant Taylor series
expansions, or as the basis of numerical calculations. To illustrate the power
of the semi-recursive approach, we present an implementation in
\textsl{Mathematica} which computes very high order covariant series expansions
of these objects. Using this code, a moderate laptop can, for example,
calculate the coincidence limit a_7(x,x) and V(x,x') to order (\sigma^a)^{20}
in a matter of minutes. Results may be output in either a compact notation or
in xTensor form. In a second application of the approach, we present a scheme
for numerically integrating the transport equations as a system of coupled
ordinary differential equations. As an example application of the scheme, we
integrate along null geodesics to solve for V(x,x') in Nariai and Schwarzschild
spacetimes.
| [
{
"created": "Fri, 29 May 2009 20:04:43 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Nov 2011 17:31:06 GMT",
"version": "v2"
},
{
"created": "Tue, 2 Jul 2013 13:44:44 GMT",
"version": "v3"
},
{
"created": "Fri, 10 Jan 2020 17:43:33 GMT",
"version": "v4"
}
] | 2020-01-13 | [
[
"Ottewill",
"Adrian C.",
""
],
[
"Wardell",
"Barry",
""
]
] | Building on an insight due to Avramidi, we provide a system of transport equations for determining key fundamental bi-tensors, including derivatives of the world-function, \sigma(x,x'), the square root of the Van Vleck determinant, \Delta^{1/2}(x,x'), and the tail-term, V(x,x'), appearing in the Hadamard form of the Green function. These bi-tensors are central to a broad range of problems from radiation reaction to quantum field theory in curved spacetime and quantum gravity. Their transport equations may be used either in a semi-recursive approach to determining their covariant Taylor series expansions, or as the basis of numerical calculations. To illustrate the power of the semi-recursive approach, we present an implementation in \textsl{Mathematica} which computes very high order covariant series expansions of these objects. Using this code, a moderate laptop can, for example, calculate the coincidence limit a_7(x,x) and V(x,x') to order (\sigma^a)^{20} in a matter of minutes. Results may be output in either a compact notation or in xTensor form. In a second application of the approach, we present a scheme for numerically integrating the transport equations as a system of coupled ordinary differential equations. As an example application of the scheme, we integrate along null geodesics to solve for V(x,x') in Nariai and Schwarzschild spacetimes. |
1011.4348 | Zou De Cheng | De-Cheng Zou, Zhan-Ying Yang and Rui-Hong Yue | Thermodynamics of Slowly Rotating Charged Black Holes in anti-de Sitter
Einstein-Gauss-Bonnet Gravity | 9 Pages, submitted to Chin. Phys. Lett | Chin.Phys.Lett.28:020402,2011 | 10.1088/0256-307X/28/2/020402 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using a new approach, we demonstrate analytic expressions for slowly
rotating Gauss-Bonnet charged black holes with negative cosmological constant.
Up to the linear order of the rotating parameter a, the mass, Hawking
temperature and entropy of the charged black holes get no corrections from
rotation.
| [
{
"created": "Fri, 19 Nov 2010 06:10:25 GMT",
"version": "v1"
}
] | 2011-10-04 | [
[
"Zou",
"De-Cheng",
""
],
[
"Yang",
"Zhan-Ying",
""
],
[
"Yue",
"Rui-Hong",
""
]
] | By using a new approach, we demonstrate analytic expressions for slowly rotating Gauss-Bonnet charged black holes with negative cosmological constant. Up to the linear order of the rotating parameter a, the mass, Hawking temperature and entropy of the charged black holes get no corrections from rotation. |
2204.02225 | Peter Woit | Peter Woit | Is Space-time Really Doomed? | Essay written for the Gravity Research Foundation 2022 Awards for
Essays on Gravitation | null | 10.1142/S0218271822420056 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For many years now it has become conventional for theorists to argue that
"space-time is doomed", with the difficulties in finding a quantum theory of
gravity implying the necessity of basing a fundamental theory on something
quite different than usual notions of space-time geometry. But what is this
space-time geometry that is doomed? In this essay we'll explore how our
understanding of four-dimensional geometry has evolved since Einstein, leading
to new ideas about such geometry which may not be doomed at all.
| [
{
"created": "Tue, 5 Apr 2022 13:59:38 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Woit",
"Peter",
""
]
] | For many years now it has become conventional for theorists to argue that "space-time is doomed", with the difficulties in finding a quantum theory of gravity implying the necessity of basing a fundamental theory on something quite different than usual notions of space-time geometry. But what is this space-time geometry that is doomed? In this essay we'll explore how our understanding of four-dimensional geometry has evolved since Einstein, leading to new ideas about such geometry which may not be doomed at all. |
1312.6835 | Kourosh Nozari | M. A. Gorji, Kourosh Nozari and B. Vakili | Polymeric Quantization and Black Hole Thermodynamics | 13 pages, no figures, revised for PLB, title changed | Phys. Lett. B 735 (2014) 62 | 10.1016/j.physletb.2014.06.005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Polymer quantization is a non-standard representation of the quantum
mechanics that inspired by loop quantum gravity. To study the associated
statistical mechanics, one needs to find microstates' energies which are
eigenvalues of the Hamiltonian operator in the polymer framework. But, this is
not an easy task at all since the Hamiltonian takes a nonlinear form in polymer
picture. In this paper, we introduce a semiclassical method in which it is not
necessary to solve the eigenvalue problem. Instead, we work with the classical
Hamiltonian function and the deformed density of states in the polymeric phase
space. Implementing this method, we obtain the canonical partition function for
the polymerized systems and we show that our results are in good agreement with
those arising from full quantum considerations. Using the partition function,
we study the thermodynamics of quantum Schwarzschild black hole and we obtain
corrections to the Bekenstein-Hawking entropy due to loop quantum gravity
effects.
| [
{
"created": "Tue, 24 Dec 2013 15:04:31 GMT",
"version": "v1"
},
{
"created": "Sun, 18 May 2014 15:46:08 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Gorji",
"M. A.",
""
],
[
"Nozari",
"Kourosh",
""
],
[
"Vakili",
"B.",
""
]
] | Polymer quantization is a non-standard representation of the quantum mechanics that inspired by loop quantum gravity. To study the associated statistical mechanics, one needs to find microstates' energies which are eigenvalues of the Hamiltonian operator in the polymer framework. But, this is not an easy task at all since the Hamiltonian takes a nonlinear form in polymer picture. In this paper, we introduce a semiclassical method in which it is not necessary to solve the eigenvalue problem. Instead, we work with the classical Hamiltonian function and the deformed density of states in the polymeric phase space. Implementing this method, we obtain the canonical partition function for the polymerized systems and we show that our results are in good agreement with those arising from full quantum considerations. Using the partition function, we study the thermodynamics of quantum Schwarzschild black hole and we obtain corrections to the Bekenstein-Hawking entropy due to loop quantum gravity effects. |
gr-qc/0202053 | Bayram Tekin | S. Deser | Gauge Invariance with Mass: Higher Spins in Cosmological Spaces | 30 pages, 1 Fig, Expanded version, invited lecture, Francqui
Conference, "Strings and Gravity: Tying the Forces Together", Brussels,
October 2001 | Strings and Gravity (DeBoeck and Larcier, Brussels 2003) | null | BRX TH-498 | gr-qc | null | I review recent work on massive higher (s>1) spins in constant curvature
(deSitter) spaces. Some of the novel properties that emerge are: partial
masslessness and new local gauge invariances, unitarily forbidden ranges of
mass, correlation between fermions/bosons and nagative/positive cosmological
constant Lambda and finally the consistency requirement that in the limit of
infinite spin towers, Lambda must tend to zero.
| [
{
"created": "Thu, 14 Feb 2002 20:56:47 GMT",
"version": "v1"
}
] | 2009-11-19 | [
[
"Deser",
"S.",
""
]
] | I review recent work on massive higher (s>1) spins in constant curvature (deSitter) spaces. Some of the novel properties that emerge are: partial masslessness and new local gauge invariances, unitarily forbidden ranges of mass, correlation between fermions/bosons and nagative/positive cosmological constant Lambda and finally the consistency requirement that in the limit of infinite spin towers, Lambda must tend to zero. |
1312.5428 | Luisa Jaime | Luisa G. Jaime, Leonardo Pati\~no and Marcelo Salgado | Note on the equation of state of geometric dark-energy in f(R) gravity | Submited to Phys. Rev. D | null | 10.1103/PhysRevD.89.084010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We focus on the analysis of three inequivalent equations of state of
geometric dark energy in $f(R)$ cosmology that have been considered in the past
and discuss their differences, advantages and drawbacks.
| [
{
"created": "Thu, 19 Dec 2013 07:38:27 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Jaime",
"Luisa G.",
""
],
[
"Patiño",
"Leonardo",
""
],
[
"Salgado",
"Marcelo",
""
]
] | We focus on the analysis of three inequivalent equations of state of geometric dark energy in $f(R)$ cosmology that have been considered in the past and discuss their differences, advantages and drawbacks. |
1902.01576 | Gilbert Weinstein | Gilbert Weinstein | Harmonic maps with prescribed singularities and applications in general
relativity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper presents a general existence and uniqueness result for harmonic
maps with prescribed singularities into non-positively curved targets, and
surveys a number of applications to general relativity. It is based on a talk
delivered by the author at The 11th Mathematical Society of Japan Seasonal
Institute, The Role of Metrics in the Theory of Partial Differential Equations.
| [
{
"created": "Tue, 5 Feb 2019 07:46:32 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Feb 2019 10:27:06 GMT",
"version": "v2"
}
] | 2019-02-11 | [
[
"Weinstein",
"Gilbert",
""
]
] | This paper presents a general existence and uniqueness result for harmonic maps with prescribed singularities into non-positively curved targets, and surveys a number of applications to general relativity. It is based on a talk delivered by the author at The 11th Mathematical Society of Japan Seasonal Institute, The Role of Metrics in the Theory of Partial Differential Equations. |
1204.5767 | Stanley P. Gudder | Stan Gudder | Causal set approach to discrete quantum gravity | 19 pages, 1 figure | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We begin by describing a sequential growth model in which the universe grows
one element at a time in discrete time steps. At each step, the process has the
form of a causal set and the "completed" universe is given by a path consisting
of a discretely growing chain of causal sets. We then introduce a quantum
dynamics to obtain a quantum sequential growth process (QSGP) which may lead to
a viable model for discrete quantum gravity. A discrete version of Einstein's
field equation is derived and a definition for discrete geodesics is proposed.
A type of QSGP called an amplitude process is introduced. An example of an
amplitude process called a complex percolation process is studied. This process
conforms with general principles of causality and covariance. We end with some
detailed quantum measure calculations for a specific percolation constant.
| [
{
"created": "Wed, 25 Apr 2012 20:51:45 GMT",
"version": "v1"
}
] | 2012-04-27 | [
[
"Gudder",
"Stan",
""
]
] | We begin by describing a sequential growth model in which the universe grows one element at a time in discrete time steps. At each step, the process has the form of a causal set and the "completed" universe is given by a path consisting of a discretely growing chain of causal sets. We then introduce a quantum dynamics to obtain a quantum sequential growth process (QSGP) which may lead to a viable model for discrete quantum gravity. A discrete version of Einstein's field equation is derived and a definition for discrete geodesics is proposed. A type of QSGP called an amplitude process is introduced. An example of an amplitude process called a complex percolation process is studied. This process conforms with general principles of causality and covariance. We end with some detailed quantum measure calculations for a specific percolation constant. |
0710.1675 | Rafael Sorkin | Rafael D. Sorkin (Perimeter Institute and Syracuse University) | Is the cosmological "constant" a nonlocal quantum residue of
discreteness of the causal set type? | plainTeX, 13 pages. To appear in the proceedings of the PASCOS-07
Conference, held July, 2007, London, England. Most current version is
available at http://www.physics.syr.edu/~sorkin/some.papers/ (or wherever my
home-page may be) | AIPConf.Proc.957:142-153,2007 | 10.1063/1.2823750 | null | gr-qc astro-ph hep-th | null | The evidence for an accelerating Hubble expansion appears to have confirmed
the heuristic prediction, from causal set theory, of a fluctuating and
``ever-present'' cosmological term in the Einstein equations. A more concrete
phenomenological model incorporating this prediction has been devised and
tested, but it remains incomplete. I will review these developments and also
mention a possible consequence for the dimensionality of spacetime.
| [
{
"created": "Tue, 9 Oct 2007 02:32:48 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sorkin",
"Rafael D.",
"",
"Perimeter Institute and Syracuse University"
]
] | The evidence for an accelerating Hubble expansion appears to have confirmed the heuristic prediction, from causal set theory, of a fluctuating and ``ever-present'' cosmological term in the Einstein equations. A more concrete phenomenological model incorporating this prediction has been devised and tested, but it remains incomplete. I will review these developments and also mention a possible consequence for the dimensionality of spacetime. |
2309.00262 | Deborah Ferguson | Deborah Ferguson, Evelyn Allsup, Surendra Anne, Galina Bouyer, Miguel
Gracia-Linares, Hector Iglesias, Aasim Jan, Pablo Laguna, Jacob Lange, Erick
Martinez, Filippo Meoni, Ryan Nowicki, Deirdre Shoemaker, Blake Steadham, Max
L. Trostel, Bing-Jyun Tsao, and Finny Valorz | Second MAYA Catalog of Binary Black Hole Numerical Relativity Waveforms | 11 pages, 9 figures | null | null | UTWI-32-2023 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical relativity waveforms are a critical resource in the quest to deepen
our understanding of the dynamics of, and gravitational waves emitted from,
merging binary systems. We present 181 new numerical relativity simulations as
the second MAYA catalog of binary black hole waveforms (a sequel to the Georgia
Tech waveform catalog). Most importantly, these include 55 high mass ratio (q
>= 4), 48 precessing, and 92 eccentric (e > 0.01) simulations, including 7
simulations which are both eccentric and precessing. With these significant
additions, this new catalog fills in considerable gaps in existing public
numerical relativity waveform catalogs. The waveforms presented in this catalog
are shown to be convergent and are consistent with current gravitational wave
models. They are available to the public at https://cgp.ph.utexas.edu/waveform.
| [
{
"created": "Fri, 1 Sep 2023 05:40:06 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Sep 2023 18:15:10 GMT",
"version": "v2"
}
] | 2023-09-15 | [
[
"Ferguson",
"Deborah",
""
],
[
"Allsup",
"Evelyn",
""
],
[
"Anne",
"Surendra",
""
],
[
"Bouyer",
"Galina",
""
],
[
"Gracia-Linares",
"Miguel",
""
],
[
"Iglesias",
"Hector",
""
],
[
"Jan",
"Aasim",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Lange",
"Jacob",
""
],
[
"Martinez",
"Erick",
""
],
[
"Meoni",
"Filippo",
""
],
[
"Nowicki",
"Ryan",
""
],
[
"Shoemaker",
"Deirdre",
""
],
[
"Steadham",
"Blake",
""
],
[
"Trostel",
"Max L.",
""
],
[
"Tsao",
"Bing-Jyun",
""
],
[
"Valorz",
"Finny",
""
]
] | Numerical relativity waveforms are a critical resource in the quest to deepen our understanding of the dynamics of, and gravitational waves emitted from, merging binary systems. We present 181 new numerical relativity simulations as the second MAYA catalog of binary black hole waveforms (a sequel to the Georgia Tech waveform catalog). Most importantly, these include 55 high mass ratio (q >= 4), 48 precessing, and 92 eccentric (e > 0.01) simulations, including 7 simulations which are both eccentric and precessing. With these significant additions, this new catalog fills in considerable gaps in existing public numerical relativity waveform catalogs. The waveforms presented in this catalog are shown to be convergent and are consistent with current gravitational wave models. They are available to the public at https://cgp.ph.utexas.edu/waveform. |
2403.16522 | Umananda Dev Goswami | Gayatri Mohan and Umananda Dev Goswami | Galactic dynamics in the presence of scalaron: A perspective from
$\boldsymbol{f(R)}$ gravity | 21 pages, 10 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $f(R)$ modified gravity with the chameleon mechanism as an
alternative approach to address the dark matter issue on the galactic scale.
Metric formalism of $f(R)$ theory is considered in this study. A mathematical
transformation tool called conformal transformation which transforms the action
from Jordan to Einstein frame is employed to simplify the fourth-order modified
field equation and to describe the extra degree of freedom $f_R$ by using a
minimally coupled scalar field (scalaron) showing the chameleonic character.
Then, we examine the viability of a newly introduced $f(R)$ gravity model on
behalf of the chameleonic behavior of the scalaron. The model analyzes this
behavior of the scalaron successfully with the singularity correction. Further,
we consider a test particle (star) in a static, spherically symmetric spacetime
to investigate the importance of the scalaron in galactic dynamics. In the
non-relativistic limit, the rotational velocity equation for the particle with
scalaron contribution is derived. This contribution is found to be model
dependent. We generate the rotation curves using the velocity equation and fit
the predicted curves to observational data of a set of thirty seven sample
galaxies of different categories. The curves are fitted based on two fitting
parameters $M_0$ and $r_c$. The fitting shows good agreement of the prediction
with the observed data.
| [
{
"created": "Mon, 25 Mar 2024 08:05:08 GMT",
"version": "v1"
}
] | 2024-03-26 | [
[
"Mohan",
"Gayatri",
""
],
[
"Goswami",
"Umananda Dev",
""
]
] | We consider $f(R)$ modified gravity with the chameleon mechanism as an alternative approach to address the dark matter issue on the galactic scale. Metric formalism of $f(R)$ theory is considered in this study. A mathematical transformation tool called conformal transformation which transforms the action from Jordan to Einstein frame is employed to simplify the fourth-order modified field equation and to describe the extra degree of freedom $f_R$ by using a minimally coupled scalar field (scalaron) showing the chameleonic character. Then, we examine the viability of a newly introduced $f(R)$ gravity model on behalf of the chameleonic behavior of the scalaron. The model analyzes this behavior of the scalaron successfully with the singularity correction. Further, we consider a test particle (star) in a static, spherically symmetric spacetime to investigate the importance of the scalaron in galactic dynamics. In the non-relativistic limit, the rotational velocity equation for the particle with scalaron contribution is derived. This contribution is found to be model dependent. We generate the rotation curves using the velocity equation and fit the predicted curves to observational data of a set of thirty seven sample galaxies of different categories. The curves are fitted based on two fitting parameters $M_0$ and $r_c$. The fitting shows good agreement of the prediction with the observed data. |
2210.08641 | Bing Tang | Jiayu Xie, Yaxuan Wang, Bing Tang | Chaotic dynamics of string around the Bardeen-AdS black holes surrounded
by quintessence dark energy | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the motion of a ring string in the background of the Bardeen-AdS
black hole surrounded by the quintessence dark energy. The effects of the
magnetic monopole charge, the quintessence state parameter, and the
quintessence normalization parameter on the dynamical behavior of the ring
string are respectively analyzed. Our numerical results show that the chaotic
behavior of string generally becomes stronger with the increase of the
quintessence normalization parameter. In particular, the conditions for the
existence of chaos are distinctly diverse for two different quintessence state
parameters. Furthermore, it is found that the magnetic charge does not
significantly affect the chaotic behavior of the string in a specific range.
| [
{
"created": "Sun, 16 Oct 2022 21:24:16 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Nov 2022 18:22:07 GMT",
"version": "v2"
}
] | 2022-11-16 | [
[
"Xie",
"Jiayu",
""
],
[
"Wang",
"Yaxuan",
""
],
[
"Tang",
"Bing",
""
]
] | We study the motion of a ring string in the background of the Bardeen-AdS black hole surrounded by the quintessence dark energy. The effects of the magnetic monopole charge, the quintessence state parameter, and the quintessence normalization parameter on the dynamical behavior of the ring string are respectively analyzed. Our numerical results show that the chaotic behavior of string generally becomes stronger with the increase of the quintessence normalization parameter. In particular, the conditions for the existence of chaos are distinctly diverse for two different quintessence state parameters. Furthermore, it is found that the magnetic charge does not significantly affect the chaotic behavior of the string in a specific range. |
gr-qc/0304015 | Ingemar Bengtsson | Jan Aman, Ingemar Bengtsson and Narit Pidokrajt | Geometry of black hole thermodynamics | 13 pages, 2 figures | Gen.Rel.Grav.35:1733,2003 | 10.1023/A:1026058111582 | USITP 03-03 | gr-qc | null | The Hessian of the entropy function can be thought of as a metric tensor on
the state space. In the context of thermodynamical fluctuation theory Ruppeiner
has argued that the Riemannian geometry of this metric gives insight into the
underlying statistical mechanical system; the claim is supported by numerous
examples. We study this geometry for some families of black holes. It is flat
for the BTZ and Reissner-Nordstrom black holes, while curvature singularities
occur for the Reissner-Nordstrom-anti-de Sitter and Kerr black holes.
| [
{
"created": "Wed, 2 Apr 2003 18:16:05 GMT",
"version": "v1"
}
] | 2009-01-14 | [
[
"Aman",
"Jan",
""
],
[
"Bengtsson",
"Ingemar",
""
],
[
"Pidokrajt",
"Narit",
""
]
] | The Hessian of the entropy function can be thought of as a metric tensor on the state space. In the context of thermodynamical fluctuation theory Ruppeiner has argued that the Riemannian geometry of this metric gives insight into the underlying statistical mechanical system; the claim is supported by numerous examples. We study this geometry for some families of black holes. It is flat for the BTZ and Reissner-Nordstrom black holes, while curvature singularities occur for the Reissner-Nordstrom-anti-de Sitter and Kerr black holes. |
1904.07876 | Daniele Teresi | Alessandro Strumia, Daniele Teresi | Cosmological constant: relaxation vs multiverse | 15 pages, 3 figures; published version | Phys. Lett. B797 (2019) 134901 | 10.1016/j.physletb.2019.134901 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a scalar field with a bottom-less potential, such as $g^3 \phi$,
finding that cosmologies unavoidably end up with a crunch, late enough to be
compatible with observations if $g \lesssim 1.2 H_0^{2/3} M_{\rm Pl}^{1/3}$. If
rebounces avoid singularities, the multiverse acquires new features; in
particular probabilities avoid some of the usual ambiguities. If rebounces
change the vacuum energy by a small enough amount, this dynamics selects a
small vacuum energy and becomes the most likely source of universes with
anthropically small cosmological constant. Its probability distribution could
avoid the gap by 2 orders of magnitude that seems left by standard anthropic
selection.
| [
{
"created": "Tue, 16 Apr 2019 18:00:03 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 2019 08:44:10 GMT",
"version": "v2"
}
] | 2019-09-09 | [
[
"Strumia",
"Alessandro",
""
],
[
"Teresi",
"Daniele",
""
]
] | We consider a scalar field with a bottom-less potential, such as $g^3 \phi$, finding that cosmologies unavoidably end up with a crunch, late enough to be compatible with observations if $g \lesssim 1.2 H_0^{2/3} M_{\rm Pl}^{1/3}$. If rebounces avoid singularities, the multiverse acquires new features; in particular probabilities avoid some of the usual ambiguities. If rebounces change the vacuum energy by a small enough amount, this dynamics selects a small vacuum energy and becomes the most likely source of universes with anthropically small cosmological constant. Its probability distribution could avoid the gap by 2 orders of magnitude that seems left by standard anthropic selection. |
gr-qc/0702100 | Raymond Chiao Y. | Raymond Y. Chiao | "Millikan oil drops" as quantum transducers between electromagnetic and
gravitational radiation | 31 pages, 4 figures | null | null | null | gr-qc | null | Pairs of Planck-mass-scale drops of superfluid helium coated by electrons
(i.e., "Millikan oil drops"), when levitated in the presence of strong magnetic
fields and at low temperatures, can be efficient quantum transducers between
electromagnetic (EM) and gravitational (GR) radiation. A Hertz-like experiment,
in which EM waves are converted at the source into GR waves, and then
back-converted at the receiver from GR waves back into EM waves, should be
practical to perform. This would open up observations of the gravity-wave
analog of the Cosmic Microwave Background from the extremely early Big Bang,
and also communications directly through the interior of the Earth.
| [
{
"created": "Mon, 19 Feb 2007 18:17:17 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Feb 2007 21:53:39 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Chiao",
"Raymond Y.",
""
]
] | Pairs of Planck-mass-scale drops of superfluid helium coated by electrons (i.e., "Millikan oil drops"), when levitated in the presence of strong magnetic fields and at low temperatures, can be efficient quantum transducers between electromagnetic (EM) and gravitational (GR) radiation. A Hertz-like experiment, in which EM waves are converted at the source into GR waves, and then back-converted at the receiver from GR waves back into EM waves, should be practical to perform. This would open up observations of the gravity-wave analog of the Cosmic Microwave Background from the extremely early Big Bang, and also communications directly through the interior of the Earth. |
1905.09477 | Sunil Kumar Tripathy Dr. | Sunil Kumar Tripathy, Rakesh Kumar Khuntia and Priyabrata Parida | Bouncing cosmology in an Extended Theory of Gravity | 11 pages, 14 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have investigated some bouncing models in the framework of an extended
gravity theory where the usual Ricci scalar in the gravitational action is
replaced by a sum of the Ricci scalar and a term proportional to the trace of
the energy momentum tensor. The dynamical parameters of the model are derived
in most general manner. We considered two bouncing scenarios through an
exponential and a power law scale factor. The non singular bouncing models also
favour a late time cosmic speed up phenomenon. The dynamical behaviour of the
equation of state parameter is studied for the models. It is observed that,
near the bounce, the dynamics is substantially affected by the coupling
parameter of the modified gravity theory as compared to the parameters of the
bouncing scale factors.
| [
{
"created": "Wed, 22 May 2019 04:19:38 GMT",
"version": "v1"
}
] | 2019-05-24 | [
[
"Tripathy",
"Sunil Kumar",
""
],
[
"Khuntia",
"Rakesh Kumar",
""
],
[
"Parida",
"Priyabrata",
""
]
] | We have investigated some bouncing models in the framework of an extended gravity theory where the usual Ricci scalar in the gravitational action is replaced by a sum of the Ricci scalar and a term proportional to the trace of the energy momentum tensor. The dynamical parameters of the model are derived in most general manner. We considered two bouncing scenarios through an exponential and a power law scale factor. The non singular bouncing models also favour a late time cosmic speed up phenomenon. The dynamical behaviour of the equation of state parameter is studied for the models. It is observed that, near the bounce, the dynamics is substantially affected by the coupling parameter of the modified gravity theory as compared to the parameters of the bouncing scale factors. |
gr-qc/0210040 | Valeri V. Kiselev | V.V.Kiselev | Quintessence and black holes | 11 pages, LaTeX file, 1 eps-figure, discussion and references added | Class.Quant.Grav.20:1187-1198,2003 | 10.1088/0264-9381/20/6/310 | null | gr-qc astro-ph hep-ph hep-th | null | We present new static spherically-symmetric exact solutions of Einstein
equations with the quintessential matter surrounding a black hole charged or
not as well as for the case without the black hole. A condition of additivity
and linearity in the energy-momentum tensor is introduced, which allows one to
get correct limits to the known solutions for the electromagnetic static field
implying the relativistic relation between the energy density and pressure, as
well as for the extraordinary case of cosmological constant, i.e. de Sitter
space. We classify the horizons, which evidently reveal themselves in the
static coordinates, and derive the Gibbons-Hawking temperatures. An example of
quintessence with the state parameter w=-2/3 is discussed in detail.
| [
{
"created": "Mon, 14 Oct 2002 10:23:42 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Dec 2002 08:57:49 GMT",
"version": "v2"
},
{
"created": "Fri, 20 Dec 2002 12:13:50 GMT",
"version": "v3"
}
] | 2010-11-19 | [
[
"Kiselev",
"V. V.",
""
]
] | We present new static spherically-symmetric exact solutions of Einstein equations with the quintessential matter surrounding a black hole charged or not as well as for the case without the black hole. A condition of additivity and linearity in the energy-momentum tensor is introduced, which allows one to get correct limits to the known solutions for the electromagnetic static field implying the relativistic relation between the energy density and pressure, as well as for the extraordinary case of cosmological constant, i.e. de Sitter space. We classify the horizons, which evidently reveal themselves in the static coordinates, and derive the Gibbons-Hawking temperatures. An example of quintessence with the state parameter w=-2/3 is discussed in detail. |
gr-qc/0605133 | Saulo Carneiro | Saulo Carneiro | From de Sitter to de Sitter: A non-singular inflationary universe driven
by vacuum | This essay received an "honorable mention" in the 2006 Essay
Competition of the Gravity Research Foundation | Int.J.Mod.Phys.D15:2241-2247,2006 | 10.1142/S0218271806009510 | null | gr-qc astro-ph hep-th | null | A semi-classical analysis of vacuum energy in the expanding spacetime
suggests that the cosmological term decays with time, with a concomitant matter
production. For early times we find, in Planck units, $\Lambda \approx H^4$,
where H is the Hubble parameter. The corresponding cosmological solution has no
initial singularity, existing since an infinite past. During an infinitely long
period we have a quasi-de Sitter, inflationary universe, with $H \approx 1$.
However, at a given time, the expansion undertakes a phase transition, with H
and $\Lambda$ decreasing to nearly zero in a few Planck times, producing a huge
amount of radiation. On the other hand, the late-time scenario is similar to
the standard model, with the radiation phase followed by a dust era, which
tends asymptotically to a de Sitter universe, with vacuum dominating again.
| [
{
"created": "Fri, 26 May 2006 00:15:18 GMT",
"version": "v1"
},
{
"created": "Fri, 26 May 2006 21:02:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Carneiro",
"Saulo",
""
]
] | A semi-classical analysis of vacuum energy in the expanding spacetime suggests that the cosmological term decays with time, with a concomitant matter production. For early times we find, in Planck units, $\Lambda \approx H^4$, where H is the Hubble parameter. The corresponding cosmological solution has no initial singularity, existing since an infinite past. During an infinitely long period we have a quasi-de Sitter, inflationary universe, with $H \approx 1$. However, at a given time, the expansion undertakes a phase transition, with H and $\Lambda$ decreasing to nearly zero in a few Planck times, producing a huge amount of radiation. On the other hand, the late-time scenario is similar to the standard model, with the radiation phase followed by a dust era, which tends asymptotically to a de Sitter universe, with vacuum dominating again. |
1002.2093 | Steven Hergt | Steven Hergt, Jan Steinhoff, Gerhard Schaefer | Reduced Hamiltonian for next-to-leading order Spin-Squared Dynamics of
General Compact Binaries | 11 pages, minor changes to match published version at CQG | Steven Hergt et al 2010 Class. Quantum Grav. 27 135007 | 10.1088/0264-9381/27/13/135007 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the post Newtonian framework the fully reduced Hamiltonian (i.e., with
eliminated spin supplementary condition) for the next-to-leading order
spin-squared dynamics of general compact binaries is presented. The Hamiltonian
is applicable to the spin dynamics of all kinds of binaries with
self-gravitating components like black holes and/or neutron stars taking into
account spin-induced quadrupolar deformation effects in second post-Newtonian
order perturbation theory of Einstein's field equations. The corresponding
equations of motion for spin, position and momentum variables are given in
terms of canonical Poisson brackets. Comparison with a nonreduced potential
calculated within the Effective Field Theory approach is made.
| [
{
"created": "Wed, 10 Feb 2010 13:37:27 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jun 2010 14:46:10 GMT",
"version": "v2"
}
] | 2010-06-04 | [
[
"Hergt",
"Steven",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Schaefer",
"Gerhard",
""
]
] | Within the post Newtonian framework the fully reduced Hamiltonian (i.e., with eliminated spin supplementary condition) for the next-to-leading order spin-squared dynamics of general compact binaries is presented. The Hamiltonian is applicable to the spin dynamics of all kinds of binaries with self-gravitating components like black holes and/or neutron stars taking into account spin-induced quadrupolar deformation effects in second post-Newtonian order perturbation theory of Einstein's field equations. The corresponding equations of motion for spin, position and momentum variables are given in terms of canonical Poisson brackets. Comparison with a nonreduced potential calculated within the Effective Field Theory approach is made. |
1807.04986 | Jake Dunn | Jake Dunn and Claude Warnick | Stability of the Toroidal AdS Schwarzschild Solution in the
Einstein--Klein-Gordon System | 68 pages, 9 figures | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the stability of the toroidal AdS-Schwarzshild black holes as
solutions of the Einstein--Klein-Gordon system, with Dirichlet or Neumann
boundary conditions for the scalar field. Restricting to perturbations that
respect the toroidal symmetry we show both orbital and asymptotic stability for
the full nonlinear problem, for a range of choices of the Klein-Gordon mass.
The solutions we construct with Neumann boundary conditions have a Hawking mass
which diverges towards infinity, reflecting the infinite energy of the
Klein-Gordon field for perturbations satisfying these boundary conditions.
| [
{
"created": "Fri, 13 Jul 2018 09:42:04 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Nov 2018 17:50:15 GMT",
"version": "v2"
}
] | 2018-11-13 | [
[
"Dunn",
"Jake",
""
],
[
"Warnick",
"Claude",
""
]
] | We consider the stability of the toroidal AdS-Schwarzshild black holes as solutions of the Einstein--Klein-Gordon system, with Dirichlet or Neumann boundary conditions for the scalar field. Restricting to perturbations that respect the toroidal symmetry we show both orbital and asymptotic stability for the full nonlinear problem, for a range of choices of the Klein-Gordon mass. The solutions we construct with Neumann boundary conditions have a Hawking mass which diverges towards infinity, reflecting the infinite energy of the Klein-Gordon field for perturbations satisfying these boundary conditions. |
2004.02411 | Pedro Bargueno | F. D. Villalba, P. Bargueno, A. F. Vargas and E. Contreras | Newman-Penrose scalars and black hole equations of state | 11 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore the connections between Newman-Penrose scalars,
including the Penrose-Rindler $\mathcal{K}$-curvature, with the equation of
state of asymptotically Anti-de Sitter Reissner-Nordstr\"om black holes. After
briefly reviewing the equation of state for these black holes from the point of
view of both the Extended Phase Space and the Horizon Thermodynamics
approaches, a geometric splitting is given for such an equation in terms of the
non vanishing Newman-Penrose scalars which define the $\mathcal{K}$-curvature
at the horizon. From this splitting, a possible thermodynamical interpretation
is developed for such scalars in the context of the black hole thermodynamics
approaches initially discussed. Afterwards, the square root of the Bel-Robinson
tensor is employed to propose conditions at the horizons in terms of pressures
or energy densities, which can be understood as alternative thermodynamical
definitions of these surfaces.
| [
{
"created": "Mon, 6 Apr 2020 06:02:36 GMT",
"version": "v1"
}
] | 2020-04-07 | [
[
"Villalba",
"F. D.",
""
],
[
"Bargueno",
"P.",
""
],
[
"Vargas",
"A. F.",
""
],
[
"Contreras",
"E.",
""
]
] | In this work we explore the connections between Newman-Penrose scalars, including the Penrose-Rindler $\mathcal{K}$-curvature, with the equation of state of asymptotically Anti-de Sitter Reissner-Nordstr\"om black holes. After briefly reviewing the equation of state for these black holes from the point of view of both the Extended Phase Space and the Horizon Thermodynamics approaches, a geometric splitting is given for such an equation in terms of the non vanishing Newman-Penrose scalars which define the $\mathcal{K}$-curvature at the horizon. From this splitting, a possible thermodynamical interpretation is developed for such scalars in the context of the black hole thermodynamics approaches initially discussed. Afterwards, the square root of the Bel-Robinson tensor is employed to propose conditions at the horizons in terms of pressures or energy densities, which can be understood as alternative thermodynamical definitions of these surfaces. |
0811.4155 | Catherine Meusburger | C. Meusburger | Cosmological measurements, time and observables in (2+1)-dimensional
gravity | 38 pages, 11 eps figures, typos corrected, references updated | Class.Quant.Grav.26:055006,2009 | 10.1088/0264-9381/26/5/055006 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the relation between measurements and the physical observables
for vacuum spacetimes with compact spatial surfaces in (2+1)-gravity with
vanishing cosmological constant. By considering an observer who emits lightrays
that return to him at a later time, we obtain explicit expressions for several
measurable quantities as functions on the physical phase space of the theory:
the eigentime elapsed between the emission of a lightray and its return to the
observer, the angles between the directions into which the light has to be
emitted to return to the observer and the relative frequencies of the lightrays
at their emission and return. This provides a framework in which conceptual
questions about time, observables and measurements can be addressed. We analyse
the properties of these measurements and their geometrical interpretation and
show how they allow an observer to determine the values of the Wilson loop
observables that parametrise the physical phase space of (2+1)-gravity. We
discuss the role of time in the theory and demonstrate that the specification
of an observer with respect to the spacetime's geometry amounts to a gauge
fixing procedure yielding Dirac observables.
| [
{
"created": "Tue, 25 Nov 2008 18:36:41 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Feb 2009 06:46:05 GMT",
"version": "v2"
}
] | 2009-02-16 | [
[
"Meusburger",
"C.",
""
]
] | We investigate the relation between measurements and the physical observables for vacuum spacetimes with compact spatial surfaces in (2+1)-gravity with vanishing cosmological constant. By considering an observer who emits lightrays that return to him at a later time, we obtain explicit expressions for several measurable quantities as functions on the physical phase space of the theory: the eigentime elapsed between the emission of a lightray and its return to the observer, the angles between the directions into which the light has to be emitted to return to the observer and the relative frequencies of the lightrays at their emission and return. This provides a framework in which conceptual questions about time, observables and measurements can be addressed. We analyse the properties of these measurements and their geometrical interpretation and show how they allow an observer to determine the values of the Wilson loop observables that parametrise the physical phase space of (2+1)-gravity. We discuss the role of time in the theory and demonstrate that the specification of an observer with respect to the spacetime's geometry amounts to a gauge fixing procedure yielding Dirac observables. |
1512.05284 | Remo Garattini | Remo Garattini | The Distorted Wheeler-DeWitt Equation | 6 pages. Contribution to the proceedings of "The Fourtheenth Marcel
Grossmann Meeting on General Relativity", University of Rome "La Sapienza",
Rome, July 12-18, 2015, based on a talk delivered at the EU1 parallel session | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Wheeler-DeWitt Equation represents a tool to study Quantum Gravity and
Quantum Cosmology. Its solution in a very general context is, of course,
impossible. To this purpose we consider some distortions of General Relativity
like Gravity's Rainbow, Varying Speed of Light Cosmology, Generalized
Uncertainty Principle deformations and Ho\v{r}ava-Lifshitz gravity which could
allow the calculation of some observables like the cosmological constant. For
simplicity we consider only the Mini-Superspace approach related to a
Friedmann-Lema\^itre-Robertson-Walker space-time.
| [
{
"created": "Tue, 15 Dec 2015 12:35:45 GMT",
"version": "v1"
}
] | 2015-12-21 | [
[
"Garattini",
"Remo",
""
]
] | The Wheeler-DeWitt Equation represents a tool to study Quantum Gravity and Quantum Cosmology. Its solution in a very general context is, of course, impossible. To this purpose we consider some distortions of General Relativity like Gravity's Rainbow, Varying Speed of Light Cosmology, Generalized Uncertainty Principle deformations and Ho\v{r}ava-Lifshitz gravity which could allow the calculation of some observables like the cosmological constant. For simplicity we consider only the Mini-Superspace approach related to a Friedmann-Lema\^itre-Robertson-Walker space-time. |
1309.0777 | Hal Haggard | Goffredo Chirco, Hal M. Haggard and Carlo Rovelli | Coupling and thermal equilibrium in general-covariant systems | 8 pages, 3 figures | Phys. Rev. D 88, 084027 (2013) | 10.1103/PhysRevD.88.084027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A fully general-covariant formulation of statistical mechanics is still
lacking. We take a step toward this theory by studying the meaning of
statistical equilibrium for coupled, parametrized systems. We discuss how to
couple parametrized systems. We express the thermalization hypothesis in a
general-covariant context. This takes the form of vanishing of information
flux. An interesting relation emerges between thermal equilibrium and gauge.
| [
{
"created": "Tue, 3 Sep 2013 18:54:19 GMT",
"version": "v1"
}
] | 2013-10-30 | [
[
"Chirco",
"Goffredo",
""
],
[
"Haggard",
"Hal M.",
""
],
[
"Rovelli",
"Carlo",
""
]
] | A fully general-covariant formulation of statistical mechanics is still lacking. We take a step toward this theory by studying the meaning of statistical equilibrium for coupled, parametrized systems. We discuss how to couple parametrized systems. We express the thermalization hypothesis in a general-covariant context. This takes the form of vanishing of information flux. An interesting relation emerges between thermal equilibrium and gauge. |
2212.00203 | Xiangdong Zhang | Xiangdong Zhang and Yongge Ma | Realization of Dirac quantization in loop quantum gravity | 6 pages | Phys. Lett. B 847 (2023) 138297 | 10.1016/j.physletb.2023.138297 | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | The system of gravity coupled to the non-rotational dust field is studied at
both classical and quantum levels. The scalar constraint of the system can be
written in the form of a true physical Hamiltonian with respect to the dust
time. In the framework of loop quantum gravity, the scalar constraint is
promoted to a well-defined operator in a suitable Hilbert space of the coupled
system, such that the physical Hamiltonian becomes a symmetric operator. By the
deparametrized form, a general expression of the solutions to the quantum
scalar constraint is obtained, and the observables on the space of solutions
can be constructed. Moreover, the Dirac quantization procedure can be fully
carried out in loop quantum gravity by this system.
| [
{
"created": "Thu, 1 Dec 2022 01:16:47 GMT",
"version": "v1"
}
] | 2023-11-15 | [
[
"Zhang",
"Xiangdong",
""
],
[
"Ma",
"Yongge",
""
]
] | The system of gravity coupled to the non-rotational dust field is studied at both classical and quantum levels. The scalar constraint of the system can be written in the form of a true physical Hamiltonian with respect to the dust time. In the framework of loop quantum gravity, the scalar constraint is promoted to a well-defined operator in a suitable Hilbert space of the coupled system, such that the physical Hamiltonian becomes a symmetric operator. By the deparametrized form, a general expression of the solutions to the quantum scalar constraint is obtained, and the observables on the space of solutions can be constructed. Moreover, the Dirac quantization procedure can be fully carried out in loop quantum gravity by this system. |
2209.03390 | Antoni Ramos-Buades | Antoni Ramos-Buades, Maarten van de Meent, Harald P. Pfeiffer, Hannes
R. R\"uter, Mark A. Scheel, Michael Boyle, Lawrence E. Kidder | Eccentric binary black holes: Comparing numerical relativity and small
mass-ratio perturbation theory | null | null | 10.1103/PhysRevD.106.124040 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The modelling of unequal mass binary black hole systems is of high importance
to detect and estimate parameters from these systems. Numerical relativity (NR)
is well suited to study systems with comparable component masses, $m_1\sim
m_2$, whereas small mass ratio (SMR) perturbation theory applies to binaries
where $q=m_2/m_1<< 1$. This work investigates the applicability for NR and SMR
as a function of mass ratio for eccentric non-spinning binary black holes. We
produce $52$ NR simulations with mass ratios between $1:10$ and $1:1$ and
initial eccentricities up to $0.7$. From these we extract quantities like
gravitational wave energy and angular momentum fluxes and periastron advance,
and assess their accuracy. To facilitate comparison, we develop tools to map
between NR and SMR inspiral evolutions of eccentric binary black holes. We
derive post-Newtonian accurate relations between different definitions of
eccentricity. Based on these analyses, we introduce a new definition of
eccentricity based on the (2,2)-mode of the gravitational radiation, which
reduces to the Newtonian definition of eccentricity in the Newtonian limit.
From the comparison between NR simulations and SMR results, we quantify the
unknown next-to-leading order SMR contributions to the gravitational energy and
angular momentum fluxes, and periastron advance. We show that in the comparable
mass regime these contributions are subdominant and higher order SMR
contributions are negligible.
| [
{
"created": "Wed, 7 Sep 2022 18:01:23 GMT",
"version": "v1"
}
] | 2023-01-11 | [
[
"Ramos-Buades",
"Antoni",
""
],
[
"van de Meent",
"Maarten",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Rüter",
"Hannes R.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Boyle",
"Michael",
""
],
[
"Kidder",
"Lawrence E.",
""
]
] | The modelling of unequal mass binary black hole systems is of high importance to detect and estimate parameters from these systems. Numerical relativity (NR) is well suited to study systems with comparable component masses, $m_1\sim m_2$, whereas small mass ratio (SMR) perturbation theory applies to binaries where $q=m_2/m_1<< 1$. This work investigates the applicability for NR and SMR as a function of mass ratio for eccentric non-spinning binary black holes. We produce $52$ NR simulations with mass ratios between $1:10$ and $1:1$ and initial eccentricities up to $0.7$. From these we extract quantities like gravitational wave energy and angular momentum fluxes and periastron advance, and assess their accuracy. To facilitate comparison, we develop tools to map between NR and SMR inspiral evolutions of eccentric binary black holes. We derive post-Newtonian accurate relations between different definitions of eccentricity. Based on these analyses, we introduce a new definition of eccentricity based on the (2,2)-mode of the gravitational radiation, which reduces to the Newtonian definition of eccentricity in the Newtonian limit. From the comparison between NR simulations and SMR results, we quantify the unknown next-to-leading order SMR contributions to the gravitational energy and angular momentum fluxes, and periastron advance. We show that in the comparable mass regime these contributions are subdominant and higher order SMR contributions are negligible. |
1908.05680 | Abhik Kumar Sanyal Dr. | Abhik Kumar Sanyal and Chandramouli Sarkar | The role of cosmological constant in f(R, G) gravity | 12 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein-Hilbert action is supplemented by Gauss-Bonnet squared term, its
phase-space structure is constructed and canonical quantization is performed.
Resolution of a contradiction that emerges in the process, requires the
presence of other fields at least in the form of vacuum energy-density,
commonly known as the cosmological constant. This reveals the very importance
of the presence of other fields at least in the form of cosmological constant,
in the very early universe.
| [
{
"created": "Thu, 15 Aug 2019 15:11:23 GMT",
"version": "v1"
}
] | 2019-08-19 | [
[
"Sanyal",
"Abhik Kumar",
""
],
[
"Sarkar",
"Chandramouli",
""
]
] | Einstein-Hilbert action is supplemented by Gauss-Bonnet squared term, its phase-space structure is constructed and canonical quantization is performed. Resolution of a contradiction that emerges in the process, requires the presence of other fields at least in the form of vacuum energy-density, commonly known as the cosmological constant. This reveals the very importance of the presence of other fields at least in the form of cosmological constant, in the very early universe. |
2010.02018 | Andrea Antonelli | Andrea Antonelli, Chris Kavanagh, Mohammed Khalil, Jan Steinhoff,
Justin Vines | Gravitational spin-orbit and aligned spin$_1$-spin$_2$ couplings through
third-subleading post-Newtonian orders | 29 pages, 2 figures, supplemental material; v2: added references | Phys. Rev. D 102, 124024 (2020) | 10.1103/PhysRevD.102.124024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The study of scattering encounters continues to provide new insights into the
general relativistic two-body problem. The local-in-time conservative dynamics
of an aligned-spin binary, for both unbound and bound orbits, is fully encoded
in the gauge-invariant scattering-angle function, which is most naturally
expressed in a post-Minkowskian (PM) expansion, and which exhibits a remarkably
simple dependence on the masses of the two bodies (in terms of appropriate
geometric variables). This dependence links the PM and small-mass-ratio
approximations, allowing gravitational self-force results to determine new
post-Newtonian (PN) information to all orders in the mass ratio. In this paper,
we exploit this interplay between relativistic scattering and self-force theory
to obtain the third-subleading (4.5PN) spin-orbit dynamics for generic spins,
and the third-subleading (5PN) spin$_1$-spin$_2$ dynamics for aligned spins. We
further implement these novel PN results in an effective-one-body framework,
and demonstrate the improvement in accuracy by comparing against
numerical-relativity simulations.
| [
{
"created": "Fri, 2 Oct 2020 14:05:37 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Oct 2020 09:41:16 GMT",
"version": "v2"
}
] | 2021-01-04 | [
[
"Antonelli",
"Andrea",
""
],
[
"Kavanagh",
"Chris",
""
],
[
"Khalil",
"Mohammed",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Vines",
"Justin",
""
]
] | The study of scattering encounters continues to provide new insights into the general relativistic two-body problem. The local-in-time conservative dynamics of an aligned-spin binary, for both unbound and bound orbits, is fully encoded in the gauge-invariant scattering-angle function, which is most naturally expressed in a post-Minkowskian (PM) expansion, and which exhibits a remarkably simple dependence on the masses of the two bodies (in terms of appropriate geometric variables). This dependence links the PM and small-mass-ratio approximations, allowing gravitational self-force results to determine new post-Newtonian (PN) information to all orders in the mass ratio. In this paper, we exploit this interplay between relativistic scattering and self-force theory to obtain the third-subleading (4.5PN) spin-orbit dynamics for generic spins, and the third-subleading (5PN) spin$_1$-spin$_2$ dynamics for aligned spins. We further implement these novel PN results in an effective-one-body framework, and demonstrate the improvement in accuracy by comparing against numerical-relativity simulations. |
2304.06472 | Shouvik Sadhukhan Mr | Alokananda Kar and Shouvik Sadhukhan | Binary Interaction with Multiple Fluid Type Cosmology Under Modified
Gravity Frame | 8 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present chapter, we have established multiple fluid cosmological
models under interaction scenarios. the interaction model we have established
is a binary type of interaction scenario where three types of fluids are bound
with interaction. We have incorporated variable gravitational constant and
variable cosmological constant. The whole work has proceeded with modified
gravity geometry where the modified effect over Einstein's gravity act like a
variable cosmological constant.
| [
{
"created": "Tue, 4 Apr 2023 08:02:41 GMT",
"version": "v1"
}
] | 2023-04-14 | [
[
"Kar",
"Alokananda",
""
],
[
"Sadhukhan",
"Shouvik",
""
]
] | In the present chapter, we have established multiple fluid cosmological models under interaction scenarios. the interaction model we have established is a binary type of interaction scenario where three types of fluids are bound with interaction. We have incorporated variable gravitational constant and variable cosmological constant. The whole work has proceeded with modified gravity geometry where the modified effect over Einstein's gravity act like a variable cosmological constant. |
1711.09625 | Kimet Jusufi | Kimet Jusufi | Hawking Radiation in the Spacetime of White Holes | Ref. [50] added, version published in General Relativity and
Gravitation | Gen. Relativ. Gravit. 50, 84 (2018) | 10.1007/s10714-018-2406-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A white hole (WH) is a time-reversed black hole (BH) solution in General
relativity with a spacetime region to which cannot be entered from the outside.
Recently they have been proposed as a possible solution to the information loss
problem [Haggard and Rovelli, 2015]. In particular it has been argued that the
quantization of the gravitational field may prevent a BH from collapsing
entirely with an exponential decay law associated to the
black-hole-to-white-hole (BHWH) tunneling scenario [Barcelo, Carballo, and
Garay, 2017]. During this period of BHWH transition the Hawking radiation
should take place. Taking this possibility into account, we utilize the
Hamilton-Jacobi and Parkih-Wilczek methods to study the Hawking radiation
viewed as a quantum tunneling effect to calculate the tunneling rate of vector
particles tunneling inside (outside) the horizon of a WH (BH), respectively. We
show that there is a Hawking radiation associated to a WH spacetime equal to
the BH Hawking temperature when viewed from the outside region of the WH
geometry. In the framework of Parkih-Wilczek method, surprisingly, we show that
Hawking temperature is affected by the initial radial distance at which the
gravitational collapse starts.
| [
{
"created": "Mon, 27 Nov 2017 11:23:59 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jun 2018 17:34:59 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Jun 2018 16:41:11 GMT",
"version": "v3"
}
] | 2018-06-22 | [
[
"Jusufi",
"Kimet",
""
]
] | A white hole (WH) is a time-reversed black hole (BH) solution in General relativity with a spacetime region to which cannot be entered from the outside. Recently they have been proposed as a possible solution to the information loss problem [Haggard and Rovelli, 2015]. In particular it has been argued that the quantization of the gravitational field may prevent a BH from collapsing entirely with an exponential decay law associated to the black-hole-to-white-hole (BHWH) tunneling scenario [Barcelo, Carballo, and Garay, 2017]. During this period of BHWH transition the Hawking radiation should take place. Taking this possibility into account, we utilize the Hamilton-Jacobi and Parkih-Wilczek methods to study the Hawking radiation viewed as a quantum tunneling effect to calculate the tunneling rate of vector particles tunneling inside (outside) the horizon of a WH (BH), respectively. We show that there is a Hawking radiation associated to a WH spacetime equal to the BH Hawking temperature when viewed from the outside region of the WH geometry. In the framework of Parkih-Wilczek method, surprisingly, we show that Hawking temperature is affected by the initial radial distance at which the gravitational collapse starts. |
0709.3286 | Vladimir Strokov N. | V. Strokov, S. Repin | Perihelion precession and deflection of light in gravitational field of
wormholes | 8 pages, no figures, submitted to Grav. and Cosm | null | null | null | gr-qc astro-ph | null | Quite exotic relativistic objects known as wormholes are hypothetical
candidates for central machine of active galactic nuclei as well as black
holes. We find the magnitude of the perihelion precession and the deflection of
light in gravitational field of a wormhole and compare them with those for a
black hole. The impact parameter is taken to be much larger than the wormhole
throat size. We show that the relative difference between results for a black
hole and a wormhole may be significant and amount to tens of percent.
| [
{
"created": "Thu, 20 Sep 2007 19:43:06 GMT",
"version": "v1"
}
] | 2007-09-24 | [
[
"Strokov",
"V.",
""
],
[
"Repin",
"S.",
""
]
] | Quite exotic relativistic objects known as wormholes are hypothetical candidates for central machine of active galactic nuclei as well as black holes. We find the magnitude of the perihelion precession and the deflection of light in gravitational field of a wormhole and compare them with those for a black hole. The impact parameter is taken to be much larger than the wormhole throat size. We show that the relative difference between results for a black hole and a wormhole may be significant and amount to tens of percent. |
2405.12074 | Ahmad Al-Badawi | Ahmad Al-Badawi | Quazinormal modes and greybody factor of black hole surrounded by a
quintessence in the S-V-T modified gravity as well as shadow | null | Phys. Scr. 99 (2024) 065002 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this study is to investigate the quasinormal modes (QNMs),
greybody factors (GFs) and shadows in a plasma of a black hole (BH) surrounded
by an exotic fluid of quintessence type in a scalar-vector-tensor modified
gravity. The effects of a quintessence scalar field and the modified gravity
(MOG) field on the QNM, GF, and shadow are examined. Using the sixth-order WKB
approach, we investigate the QNMs of massless scalar and electromagnetic
perturbations. Our findings show that as the quintessence and the MOG parameter
($\epsilon$ and $\alpha$) increase, the oscillation frequencies decrease
significantly. Gravitational wave damping, on the other hand, decreases with
increasing $\epsilon$ and $\alpha$. In addition, we obtain an analytical
solution for the transmission coefficients (GF) and demonstrate that more
thermal radiation reaches the observer at spatial infinity as both the
$\epsilon$ and $\alpha$ parameters increase. We also investigate the effect of
the plasma background on the BH shadow and show that as the plasma background
parameter increases, the shadow radius slightly shrinks. Nevertheless, the
shadow radius increases as $\alpha$ and $\epsilon$ increase. Particularly
intriguing is the fact that increasing $\epsilon$ has a greater impact on the
shadow radius than increasing $\alpha$, indicating that the quintessence
parameter has a greater impact than the MOG parameter.
| [
{
"created": "Mon, 20 May 2024 14:42:28 GMT",
"version": "v1"
}
] | 2024-05-21 | [
[
"Al-Badawi",
"Ahmad",
""
]
] | The purpose of this study is to investigate the quasinormal modes (QNMs), greybody factors (GFs) and shadows in a plasma of a black hole (BH) surrounded by an exotic fluid of quintessence type in a scalar-vector-tensor modified gravity. The effects of a quintessence scalar field and the modified gravity (MOG) field on the QNM, GF, and shadow are examined. Using the sixth-order WKB approach, we investigate the QNMs of massless scalar and electromagnetic perturbations. Our findings show that as the quintessence and the MOG parameter ($\epsilon$ and $\alpha$) increase, the oscillation frequencies decrease significantly. Gravitational wave damping, on the other hand, decreases with increasing $\epsilon$ and $\alpha$. In addition, we obtain an analytical solution for the transmission coefficients (GF) and demonstrate that more thermal radiation reaches the observer at spatial infinity as both the $\epsilon$ and $\alpha$ parameters increase. We also investigate the effect of the plasma background on the BH shadow and show that as the plasma background parameter increases, the shadow radius slightly shrinks. Nevertheless, the shadow radius increases as $\alpha$ and $\epsilon$ increase. Particularly intriguing is the fact that increasing $\epsilon$ has a greater impact on the shadow radius than increasing $\alpha$, indicating that the quintessence parameter has a greater impact than the MOG parameter. |
1812.01331 | Kimet Jusufi | Muhammad Rizwan, Mubasher Jamil, Kimet Jusufi | Distinguishing a Kerr-like black hole and a naked singularity in perfect
fluid dark matter via precession frequencies | 17 pages, 12 figures, 1 table. Version published in Physical Review D | Phys. Rev. D 99, 024050 (2019) | 10.1103/PhysRevD.99.024050 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a Kerr-like black hole and naked singularity in perfect fluid dark
matter (PFDM). The critical value of spin parameter $a_c$ is presented to
differentiate the black hole from naked singularity. It is seen that for any
fixed value of dark matter parameter $\alpha$ the rotating object is black hole
if $a\leq a_c$ and naked singularity if $a>a_c$. Also for $-2\leq\alpha<2/3$
the size of the black hole horizons decrease whereas for $2/3<\alpha$ it
increases. We also study spin precession frequency of a test gyroscope attached
to stationary observer to differentiate a black hole from naked singularity in
perfect fluid dark matter. For the black hole, spin precession frequency blows
up as the observer reaches the central object while for naked singularity it
remains finite except at the ring singularity. Moreover, we study
Lense-Thirring precession for a Kerr-like black hole and geodetic precession
for Schwarzschild black hole in perfect fluid dark matter. To this end, we have
calculated the Kepler frequency (KF), the vertical epicyclic frequency (VEF),
and the nodal plane precession frequency (NPPF). Our results show that, the
PFDM parameter $\alpha$ significantly affects those frequencies. This
difference can be used by astrophysical observations in the near future to shed
some light on the nature of dark matter.
| [
{
"created": "Tue, 4 Dec 2018 11:01:20 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jan 2019 15:26:53 GMT",
"version": "v2"
}
] | 2019-02-01 | [
[
"Rizwan",
"Muhammad",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Jusufi",
"Kimet",
""
]
] | We study a Kerr-like black hole and naked singularity in perfect fluid dark matter (PFDM). The critical value of spin parameter $a_c$ is presented to differentiate the black hole from naked singularity. It is seen that for any fixed value of dark matter parameter $\alpha$ the rotating object is black hole if $a\leq a_c$ and naked singularity if $a>a_c$. Also for $-2\leq\alpha<2/3$ the size of the black hole horizons decrease whereas for $2/3<\alpha$ it increases. We also study spin precession frequency of a test gyroscope attached to stationary observer to differentiate a black hole from naked singularity in perfect fluid dark matter. For the black hole, spin precession frequency blows up as the observer reaches the central object while for naked singularity it remains finite except at the ring singularity. Moreover, we study Lense-Thirring precession for a Kerr-like black hole and geodetic precession for Schwarzschild black hole in perfect fluid dark matter. To this end, we have calculated the Kepler frequency (KF), the vertical epicyclic frequency (VEF), and the nodal plane precession frequency (NPPF). Our results show that, the PFDM parameter $\alpha$ significantly affects those frequencies. This difference can be used by astrophysical observations in the near future to shed some light on the nature of dark matter. |
1403.3858 | Filipe Mena | Irene Brito, M. F. A. da Silva, Filipe C. Mena and N. O. Santos | Geodesics dynamics in the Linet-Tian spacetime with Lambda<0 | 25 pages, 13 figures | General Relativity and Gravitation, 46 (2014) 1681 (23 pages) | 10.1007/s10714-014-1681-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the geodesics' kinematics and dynamics in the Linet-Tian
metric with Lambda<0 and compare with the results for the Levi-Civita metric,
when Lambda=0. This is used to derive new stability results about the
geodesics' dynamics in static vacuum cylindrically symmetric spacetimes with
respect to the introduction of Lambda<0. In particular, we find that increasing
|Lambda| always increases the minimum and maximum radial distances to the axis
of any spatially confined planar null geodesic. Furthermore, we show that, in
some cases, the inclusion of any Lambda<0 breaks the geodesics' orbit
confinement of the Lambda=0 metric, for both planar and non-planar null
geodesics, which are therefore unstable. Using the full system of geodesics'
equations, we provide numerical examples which illustrate our results.
| [
{
"created": "Sat, 15 Mar 2014 23:11:33 GMT",
"version": "v1"
}
] | 2014-03-18 | [
[
"Brito",
"Irene",
""
],
[
"da Silva",
"M. F. A.",
""
],
[
"Mena",
"Filipe C.",
""
],
[
"Santos",
"N. O.",
""
]
] | We investigate the geodesics' kinematics and dynamics in the Linet-Tian metric with Lambda<0 and compare with the results for the Levi-Civita metric, when Lambda=0. This is used to derive new stability results about the geodesics' dynamics in static vacuum cylindrically symmetric spacetimes with respect to the introduction of Lambda<0. In particular, we find that increasing |Lambda| always increases the minimum and maximum radial distances to the axis of any spatially confined planar null geodesic. Furthermore, we show that, in some cases, the inclusion of any Lambda<0 breaks the geodesics' orbit confinement of the Lambda=0 metric, for both planar and non-planar null geodesics, which are therefore unstable. Using the full system of geodesics' equations, we provide numerical examples which illustrate our results. |
gr-qc/0509099 | Cherubini Christian | Christian Cherubini, Simonetta Filippi | Using FEMLAB for Gravitational problems: numerical simulations for all | 6 pages, 18 eps figures, RevTeX style | J.Korean Phys.Soc. 49 (2006) S829-S834 | null | null | gr-qc | null | We discuss the possibility to solve Modern Numerical Relativity problems
using finite element methods (FEM). Adopting a "user friendly" software for
handling totally general systems of nonlinear partial differential equations,
FEMLAB, we model and numerically solve in a short time a Gowdy vacuum
spacetime, representing an inhomogeneous cosmology. Results agree perfectly
with existing simulations in the recent literature based not of FEMs but on
finite differences methods. Possible applications for non relativistic
Astrophysics, General Relativity, elementary particle physics and more general
theories of gravitation like EMDA and branes are discussed.
| [
{
"created": "Mon, 26 Sep 2005 09:55:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cherubini",
"Christian",
""
],
[
"Filippi",
"Simonetta",
""
]
] | We discuss the possibility to solve Modern Numerical Relativity problems using finite element methods (FEM). Adopting a "user friendly" software for handling totally general systems of nonlinear partial differential equations, FEMLAB, we model and numerically solve in a short time a Gowdy vacuum spacetime, representing an inhomogeneous cosmology. Results agree perfectly with existing simulations in the recent literature based not of FEMs but on finite differences methods. Possible applications for non relativistic Astrophysics, General Relativity, elementary particle physics and more general theories of gravitation like EMDA and branes are discussed. |
2205.08261 | Yorgo Senikoglu | Tekin Dereli, Ozay Gurtug, Mustafa Halilsoy, Yorgo Senikoglu | Neutrino Fields in a Sandwich Gravitational Wave Background | Accepted Version to appear in Class.Quant.Grav | null | 10.1088/1361-6382/ac9bc6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Sandwich gravitational waves are given globally in terms of step functions at
the boundaries. Linearized Einstein-Weyl equations are solved exactly in this
background in Rosen coordinates. Depending on the geometry and composition of
the sandwich wave, the neutrino's energy-momentum redistributes itself. At the
test field level, since the background will not change, the neutrino's energy
density in particular will show variations between positive and negative
extrema when crossing the sandwich wave. This may reveal facts about the weakly
interacting neutrinos in cosmology.
| [
{
"created": "Tue, 17 May 2022 12:02:14 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Oct 2022 13:40:29 GMT",
"version": "v2"
}
] | 2022-11-23 | [
[
"Dereli",
"Tekin",
""
],
[
"Gurtug",
"Ozay",
""
],
[
"Halilsoy",
"Mustafa",
""
],
[
"Senikoglu",
"Yorgo",
""
]
] | Sandwich gravitational waves are given globally in terms of step functions at the boundaries. Linearized Einstein-Weyl equations are solved exactly in this background in Rosen coordinates. Depending on the geometry and composition of the sandwich wave, the neutrino's energy-momentum redistributes itself. At the test field level, since the background will not change, the neutrino's energy density in particular will show variations between positive and negative extrema when crossing the sandwich wave. This may reveal facts about the weakly interacting neutrinos in cosmology. |
1905.00600 | Gang Wang | Gang Wang, Dongfeng Gao, Wei-Tou Ni, Jin Wang and Mingsheng Zhan | Orbit Design for Space Atom-Interferometer AIGSO | 14 pages, 8 figures, accepted by IJMPD | International Journal of Physics D Vol. 29 (2020) 1940004 | 10.1142/S0218271819400042 | null | gr-qc physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Atom Interferometric Gravitational-wave (GW) Space Observatory (AIGSO) is a
mission concept mainly aimed at the middle-frequency (0.1 Hz - 10 Hz) GW
detection. AIGSO proposes to have three spacecraft in linear formation with
extension of 10 km. The three spacecraft need to maintain 5 km + 5 km constant
arm-length formation. In this study, we address the issue of orbit design and
thruster requirement. The acceleration to maintain the formation can be
designed to be less than 30 pm/s$^2$ and the thruster requirement is in the 30
nN range. Application to other arm-length-maintaining missions is also
discussed.
| [
{
"created": "Thu, 2 May 2019 07:44:30 GMT",
"version": "v1"
}
] | 2020-07-14 | [
[
"Wang",
"Gang",
""
],
[
"Gao",
"Dongfeng",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Wang",
"Jin",
""
],
[
"Zhan",
"Mingsheng",
""
]
] | Atom Interferometric Gravitational-wave (GW) Space Observatory (AIGSO) is a mission concept mainly aimed at the middle-frequency (0.1 Hz - 10 Hz) GW detection. AIGSO proposes to have three spacecraft in linear formation with extension of 10 km. The three spacecraft need to maintain 5 km + 5 km constant arm-length formation. In this study, we address the issue of orbit design and thruster requirement. The acceleration to maintain the formation can be designed to be less than 30 pm/s$^2$ and the thruster requirement is in the 30 nN range. Application to other arm-length-maintaining missions is also discussed. |
1502.06458 | Yafet Sanchez Sanchez | Yafet Sanchez Sanchez | Regularity of curve integrable spacetimes | 28 pages, 1 figure | General Relativity and Gravitation 47, 80 (2015) | 10.1007/s10714-015-1922-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The idea of defining a gravitational singularity as an obstruction to the
dynamical evolution of a test field (described by a PDE) rather than the
dynamical evolution of a particle (described by a geodesics) is explored. In
particular, the concept of field regularity is introduced which serves to
describe the well-posedness of the local initial value problem for a given
field.In particular this is applied to (classical) scalar fields in the class
of curve integrable spacetimes to show that the classical singularities do not
interrupt the well-posedness of the wave equation.
| [
{
"created": "Mon, 23 Feb 2015 15:11:41 GMT",
"version": "v1"
},
{
"created": "Fri, 1 May 2015 11:15:57 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Jun 2015 09:25:38 GMT",
"version": "v3"
}
] | 2015-06-23 | [
[
"Sanchez",
"Yafet Sanchez",
""
]
] | The idea of defining a gravitational singularity as an obstruction to the dynamical evolution of a test field (described by a PDE) rather than the dynamical evolution of a particle (described by a geodesics) is explored. In particular, the concept of field regularity is introduced which serves to describe the well-posedness of the local initial value problem for a given field.In particular this is applied to (classical) scalar fields in the class of curve integrable spacetimes to show that the classical singularities do not interrupt the well-posedness of the wave equation. |
2001.07945 | Diego S\'aez-Chill\'on G\'omez | Sergei D. Odintsov, Diego Saez-Chillon Gomez and German S. Sharov | Testing the equation of state for viscous dark energy | 13 pages, 3 figures. To be published in PRD | Phys. Rev. D 101, 044010 (2020) | 10.1103/PhysRevD.101.044010 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some cosmological scenarios with bulk viscosity for the dark energy fluid are
considered. Based on some considerations related to hydrodynamics, two
different equations of state for dark energy are assumed, leading to power-law
and logarithmic effective corrections to the pressure. The models are tested
with the latest astronomical data from Type Ia supernovae (Pantheon sample),
measurements of the Hubble parameter $H(z)$,
Baryon Acoustic Oscillations and Cosmic Microwave Background radiation. In
comparison with $\Lambda$CDM model, some different results are obtained and
their viability is discussed. The power-law model shows some modest results,
achieved under negative values of bulk viscosity, while the logarithmic
scenario provide good fits in comparison to $\Lambda$CDM model.
| [
{
"created": "Wed, 22 Jan 2020 10:28:08 GMT",
"version": "v1"
}
] | 2020-02-07 | [
[
"Odintsov",
"Sergei D.",
""
],
[
"Gomez",
"Diego Saez-Chillon",
""
],
[
"Sharov",
"German S.",
""
]
] | Some cosmological scenarios with bulk viscosity for the dark energy fluid are considered. Based on some considerations related to hydrodynamics, two different equations of state for dark energy are assumed, leading to power-law and logarithmic effective corrections to the pressure. The models are tested with the latest astronomical data from Type Ia supernovae (Pantheon sample), measurements of the Hubble parameter $H(z)$, Baryon Acoustic Oscillations and Cosmic Microwave Background radiation. In comparison with $\Lambda$CDM model, some different results are obtained and their viability is discussed. The power-law model shows some modest results, achieved under negative values of bulk viscosity, while the logarithmic scenario provide good fits in comparison to $\Lambda$CDM model. |
1508.02001 | Fabio Briscese | F. Briscese, E. R. Bezerra de Mello, A. Yu. Petrov, V. B. Bezerra | One-loop effective potential in nonlocal scalar field models | null | Phys. Rev. D 92, 104026 (2015) | 10.1103/PhysRevD.92.104026 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we apply the usual perturbative methodology to evaluate the
one-loop effective potential in a nonlocal scalar field theory. We find that
the effect induced by the nonlocaliity of the theory is always very small and
we discuss the consequences of this result. In particular we argue that,
looking at one-loop corrections for matter fields, it is not possible to find
signals of the nonlocality of the theory in cosmological observables since,
even during inflation when energies are very high, nonlocality-induced
corrections are expected to be very small.
| [
{
"created": "Sun, 9 Aug 2015 09:11:31 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Nov 2015 21:58:12 GMT",
"version": "v2"
}
] | 2015-11-18 | [
[
"Briscese",
"F.",
""
],
[
"de Mello",
"E. R. Bezerra",
""
],
[
"Petrov",
"A. Yu.",
""
],
[
"Bezerra",
"V. B.",
""
]
] | In this paper we apply the usual perturbative methodology to evaluate the one-loop effective potential in a nonlocal scalar field theory. We find that the effect induced by the nonlocaliity of the theory is always very small and we discuss the consequences of this result. In particular we argue that, looking at one-loop corrections for matter fields, it is not possible to find signals of the nonlocality of the theory in cosmological observables since, even during inflation when energies are very high, nonlocality-induced corrections are expected to be very small. |
1704.02990 | Anzhong Wang | Kai Lin, Shinji Mukohyama, Anzhong Wang, and Tao Zhu | No static black hole hairs in gravitational theories of gravity with
broken Lorentz invariance | revtex4, 4 figures and no table. A version to appear in Phys. Rev. D | Phys. Rev. D 95, 124053 (2017) | 10.1103/PhysRevD.95.124053 | YITP-17-36, IPMU17-0056 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we revisit the issue of static hairs of black holes in
gravitational theories with broken Lorentz invariance in the case that the
speed $c_{\phi}$ of the khronon field becomes infinitely large, $c_{\phi} =
\infty$, for which the sound horizon of the khronon field coincides with the
universal horizon, and the boundary conditions at the sound horizon reduce to
those given normally at the universal horizons. As a result, less boundary
conditions are present in this extreme case in comparison with the case
$c_{\phi} = $ finite. Then, it would be expected that static hairs might exist.
However, we show analytically that even in this case static hairs still cannot
exist, based on a decoupling limit analysis. We also consider the cases in
which $c_{\phi}$ is finite but with $c_{\phi} \gg 1$, and obtain the same
conclusion.
| [
{
"created": "Mon, 10 Apr 2017 18:00:18 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jun 2017 01:30:58 GMT",
"version": "v2"
}
] | 2017-07-05 | [
[
"Lin",
"Kai",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Wang",
"Anzhong",
""
],
[
"Zhu",
"Tao",
""
]
] | In this paper, we revisit the issue of static hairs of black holes in gravitational theories with broken Lorentz invariance in the case that the speed $c_{\phi}$ of the khronon field becomes infinitely large, $c_{\phi} = \infty$, for which the sound horizon of the khronon field coincides with the universal horizon, and the boundary conditions at the sound horizon reduce to those given normally at the universal horizons. As a result, less boundary conditions are present in this extreme case in comparison with the case $c_{\phi} = $ finite. Then, it would be expected that static hairs might exist. However, we show analytically that even in this case static hairs still cannot exist, based on a decoupling limit analysis. We also consider the cases in which $c_{\phi}$ is finite but with $c_{\phi} \gg 1$, and obtain the same conclusion. |
2206.04085 | Christopher Munna | Christopher Munna, Charles R. Evans | Post-Newtonian expansion of the spin-precession invariant for
eccentric-orbit non-spinning extreme-mass-ratio inspirals to 9PN and $e^{16}$ | 23 pages, 2 figures | null | 10.1103/PhysRevD.106.044058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the eccentricity dependence of the high-order post-Newtonian
(PN) expansion of the spin-precession invariant $\psi$ for eccentric-orbit
extreme-mass-ratio inspirals with a Schwarzschild primary. The series is
calculated in first-order black hole perturbation theory through direct
analytic expansion of solutions in the Regge-Wheeler-Zerilli formalism, using a
code written in \textsc{Mathematica}. Modes with small values of $l$ are found
via the Mano-Suzuki-Takasugi (MST) analytic function expansion formalism for
solutions to the Regge-Wheeler equation. Large-$l$ solutions are found by
applying a PN expansion ansatz to the Regge-Wheeler equation. Previous work has
given $\psi$ to 9.5PN order and to order $e^2$ (i.e., the near circular orbit
limit). We calculate the expansion to 9PN but to $e^{16}$ in eccentricity. It
proves possible to find a few terms that have closed-form expressions, all of
which are associated with logarithmic terms in the PN expansion. We also
compare the numerical evaluation of our PN expansion to prior numerical
calculations of $\psi$ in close orbits to assess its radius of convergence. We
find that the series is not as rapidly convergent as the one for the redshift
invariant at $r \simeq 10M$ but still yielding $\sim 1\%$ accuracy for
eccentricities $e \lesssim 0.25$.
| [
{
"created": "Wed, 8 Jun 2022 18:00:05 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Munna",
"Christopher",
""
],
[
"Evans",
"Charles R.",
""
]
] | We calculate the eccentricity dependence of the high-order post-Newtonian (PN) expansion of the spin-precession invariant $\psi$ for eccentric-orbit extreme-mass-ratio inspirals with a Schwarzschild primary. The series is calculated in first-order black hole perturbation theory through direct analytic expansion of solutions in the Regge-Wheeler-Zerilli formalism, using a code written in \textsc{Mathematica}. Modes with small values of $l$ are found via the Mano-Suzuki-Takasugi (MST) analytic function expansion formalism for solutions to the Regge-Wheeler equation. Large-$l$ solutions are found by applying a PN expansion ansatz to the Regge-Wheeler equation. Previous work has given $\psi$ to 9.5PN order and to order $e^2$ (i.e., the near circular orbit limit). We calculate the expansion to 9PN but to $e^{16}$ in eccentricity. It proves possible to find a few terms that have closed-form expressions, all of which are associated with logarithmic terms in the PN expansion. We also compare the numerical evaluation of our PN expansion to prior numerical calculations of $\psi$ in close orbits to assess its radius of convergence. We find that the series is not as rapidly convergent as the one for the redshift invariant at $r \simeq 10M$ but still yielding $\sim 1\%$ accuracy for eccentricities $e \lesssim 0.25$. |
1707.00984 | Alexandros Karam | Alexandros Karam, Thomas Pappas, Kyriakos Tamvakis | Frame-dependence of higher-order inflationary observables in
scalar-tensor theories | Title changed per journal request, typos fixed, a few comments and
references added, to appear in PRD | Phys. Rev. D 96, 064036 (2017) | 10.1103/PhysRevD.96.064036 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of scalar-tensor theories of gravity we compute the
third-order corrected spectral indices in the slow-roll approximation. The
calculation is carried out by employing the Green's function method for scalar
and tensor perturbations in both the Einstein and Jordan frames. Then, using
the interrelations between the Hubble slow-roll parameters in the two frames we
find that the frames are equivalent up to third order. Since the Hubble
slow-roll parameters are related to the potential slow-roll parameters, we
express the observables in terms of the latter which are manifestly invariant.
Nevertheless, the same inflaton excursion leads to different predictions in the
two frames since the definition of the number of e-folds differs. To illustrate
this effect we consider a nonminimal inflationary model and find that the
difference in the predictions grows with the nonminimal coupling and it can
actually be larger than the difference between the first and third order
results for the observables. Finally, we demonstrate the effect of various
end-of-inflation conditions on the observables. These effects will become
important for the analyses of inflationary models in view of the improved
sensitivity of future experiments.
| [
{
"created": "Sun, 2 Jul 2017 17:07:28 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Sep 2017 18:40:32 GMT",
"version": "v2"
}
] | 2017-09-27 | [
[
"Karam",
"Alexandros",
""
],
[
"Pappas",
"Thomas",
""
],
[
"Tamvakis",
"Kyriakos",
""
]
] | In the context of scalar-tensor theories of gravity we compute the third-order corrected spectral indices in the slow-roll approximation. The calculation is carried out by employing the Green's function method for scalar and tensor perturbations in both the Einstein and Jordan frames. Then, using the interrelations between the Hubble slow-roll parameters in the two frames we find that the frames are equivalent up to third order. Since the Hubble slow-roll parameters are related to the potential slow-roll parameters, we express the observables in terms of the latter which are manifestly invariant. Nevertheless, the same inflaton excursion leads to different predictions in the two frames since the definition of the number of e-folds differs. To illustrate this effect we consider a nonminimal inflationary model and find that the difference in the predictions grows with the nonminimal coupling and it can actually be larger than the difference between the first and third order results for the observables. Finally, we demonstrate the effect of various end-of-inflation conditions on the observables. These effects will become important for the analyses of inflationary models in view of the improved sensitivity of future experiments. |
1809.10729 | Merced Montesinos | Merced Montesinos, Diego Gonzalez, Mariano Celada | The gauge symmetries of first-order general relativity with matter
fields | It matches published version | Class.Quant.Grav.35:205005,2018 | 10.1088/1361-6382/aae10d | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In $n$-dimensional spacetimes ($n>3$), there exists an internal gauge
symmetry of the Palatini action with a cosmological constant that is the
natural generalization of the so-called "local translations" of
three-dimensional general relativity. We report the extension of this symmetry
to include the minimal coupling of Yang-Mills and fermion fields to the
Palatini action with a cosmological constant. We show that, as in the case of
three-dimensional local translations, the extended symmetry depends on the
energy-momentum tensor of the corresponding matter field and, for fermions, it
contains an additional term that in four dimensions is proportional to the
axial fermion current. We also report the extension of the analog of this
internal gauge symmetry for the Holst action with a cosmological constant by
incorporating minimally coupled scalar and Yang-Mills fields, as well as a
non-minimally coupled fermion field. In the last case, the extended symmetry is
affected by both the Immirzi parameter and the energy-momentum tensor and, for
fermions, it also depends on the axial fermion current.
| [
{
"created": "Thu, 27 Sep 2018 19:07:59 GMT",
"version": "v1"
}
] | 2018-11-21 | [
[
"Montesinos",
"Merced",
""
],
[
"Gonzalez",
"Diego",
""
],
[
"Celada",
"Mariano",
""
]
] | In $n$-dimensional spacetimes ($n>3$), there exists an internal gauge symmetry of the Palatini action with a cosmological constant that is the natural generalization of the so-called "local translations" of three-dimensional general relativity. We report the extension of this symmetry to include the minimal coupling of Yang-Mills and fermion fields to the Palatini action with a cosmological constant. We show that, as in the case of three-dimensional local translations, the extended symmetry depends on the energy-momentum tensor of the corresponding matter field and, for fermions, it contains an additional term that in four dimensions is proportional to the axial fermion current. We also report the extension of the analog of this internal gauge symmetry for the Holst action with a cosmological constant by incorporating minimally coupled scalar and Yang-Mills fields, as well as a non-minimally coupled fermion field. In the last case, the extended symmetry is affected by both the Immirzi parameter and the energy-momentum tensor and, for fermions, it also depends on the axial fermion current. |
2402.08307 | Andr\'es M\'inguez-S\'anchez | Guillermo A. Mena Marug\'an and Andr\'es M\'inguez-S\'anchez | Axial perturbations in Kantowski-Sachs spacetimes and hybrid quantum
cosmology | 18 pages | Phys. Rev. D 109, 106009 (2024) | 10.1103/PhysRevD.109.106009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, there has been a growing interest in investigating homogeneous but
anisotropic spacetimes owing to their relation with nonrotating, uncharged
black hole interiors. We present a description of axial perturbations for a
massless scalar field minimally coupled to this geometry. We truncate the
action at the quadratic perturbative order and tailor our analysis to compact
spatial sections. Perturbations are described in terms of perturbative gauge
invariants, linear perturbative constraints, and their canonically conjugate
variables. The entire set, encompassing perturbations and homogeneous degrees
of freedom, is consolidated into a canonical one. We employ a hybrid approach
to quantize this system, integrating a quantum representation of the
homogeneous sector using Loop Quantum Cosmology techniques with a conventional
field quantization of the perturbations.
| [
{
"created": "Tue, 13 Feb 2024 09:09:26 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jun 2024 09:42:49 GMT",
"version": "v2"
}
] | 2024-06-24 | [
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Mínguez-Sánchez",
"Andrés",
""
]
] | Recently, there has been a growing interest in investigating homogeneous but anisotropic spacetimes owing to their relation with nonrotating, uncharged black hole interiors. We present a description of axial perturbations for a massless scalar field minimally coupled to this geometry. We truncate the action at the quadratic perturbative order and tailor our analysis to compact spatial sections. Perturbations are described in terms of perturbative gauge invariants, linear perturbative constraints, and their canonically conjugate variables. The entire set, encompassing perturbations and homogeneous degrees of freedom, is consolidated into a canonical one. We employ a hybrid approach to quantize this system, integrating a quantum representation of the homogeneous sector using Loop Quantum Cosmology techniques with a conventional field quantization of the perturbations. |
1312.3622 | Shuang-Yong Zhou | Thomas P. Sotiriou and Shuang-Yong Zhou | Black hole hair in generalized scalar-tensor gravity | 4+1 pages, PRL version | Phys. Rev. Lett. 112, 251102 (2014) | 10.1103/PhysRevLett.112.251102 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The most general action for a scalar field coupled to gravity that leads to
second order field equations for both the metric and the scalar --- Horndeski's
theory --- is considered, with the extra assumption that the scalar satisfies
shift symmetry. We show that in such theories the scalar field is forced to
have a nontrivial configuration in black hole spacetimes, unless one carefully
tunes away a linear coupling with the Gauss--Bonnet invariant. Hence, black
holes for generic theories in this class will have hair. This contradicts a
recent no-hair theorem, which seems to have overlooked the presence of this
coupling.
| [
{
"created": "Thu, 12 Dec 2013 20:51:42 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Aug 2014 23:05:09 GMT",
"version": "v2"
}
] | 2014-08-13 | [
[
"Sotiriou",
"Thomas P.",
""
],
[
"Zhou",
"Shuang-Yong",
""
]
] | The most general action for a scalar field coupled to gravity that leads to second order field equations for both the metric and the scalar --- Horndeski's theory --- is considered, with the extra assumption that the scalar satisfies shift symmetry. We show that in such theories the scalar field is forced to have a nontrivial configuration in black hole spacetimes, unless one carefully tunes away a linear coupling with the Gauss--Bonnet invariant. Hence, black holes for generic theories in this class will have hair. This contradicts a recent no-hair theorem, which seems to have overlooked the presence of this coupling. |
gr-qc/0212127 | Yuri Goncharov | A. A. Bytsenko (Departamento de Fisica, Universidade Estadual de
Londrina, Londrina-Parana, Brazil) and Yu. P. Goncharov (Sankt-Petersburg
State Polytechnical Unversity) | Dirac Monopoles and Hawking radiation in Kottler spacetime | 11 pages, LaTeX with using the ijmpa1.sty file from the package of
World Scientific Publishing Co | Int.J.Mod.Phys. A17 (2002) 4947-4957 | 10.1142/S0217751X02012168 | null | gr-qc | null | The natural extension of Schwarzschild metric to the case of nonzero
cosmological constant $\Lambda$ known as the Kottler metric is considered and
it is discussed under what circumstances the given metric could describe the
Schwarzschild black hole immersed in a medium with nonzero energy density.
Under the latter situation such an object might carry topologically
inequivalent configurations of various fields. The given possibility is
analysed for complex scalar field and it is shown that the mentioned
configurations might be tied with natural presence of Dirac monopoles on black
hole under consideration. In turn, this could markedly modify the Hawking
radiation process.
| [
{
"created": "Tue, 31 Dec 2002 11:05:53 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Bytsenko",
"A. A.",
"",
"Departamento de Fisica, Universidade Estadual de\n Londrina, Londrina-Parana, Brazil"
],
[
"Goncharov",
"Yu. P.",
"",
"Sankt-Petersburg\n State Polytechnical Unversity"
]
] | The natural extension of Schwarzschild metric to the case of nonzero cosmological constant $\Lambda$ known as the Kottler metric is considered and it is discussed under what circumstances the given metric could describe the Schwarzschild black hole immersed in a medium with nonzero energy density. Under the latter situation such an object might carry topologically inequivalent configurations of various fields. The given possibility is analysed for complex scalar field and it is shown that the mentioned configurations might be tied with natural presence of Dirac monopoles on black hole under consideration. In turn, this could markedly modify the Hawking radiation process. |
1105.4709 | Mikhail Gorbatenko | M.V. Gorbatenko, V.P. Neznamov | Atoms and Forces of Interaction Between Elementary Particles in the
Expanding Universe | 12 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The earlier developed algorithm for constructing a self-conjugate Hamiltonian
in the \eta-representation for Dirac particles interacting with a general
gravitational field is extended to the case of electromagnetic fields. This
Hamiltonian is applied to the case when the gravitational field describes the
spatially flat Friedmann model, and the electromagnetic field is the Coulomb
potential extended to the case of this model. The analysis of atomic systems
and electromagnetic forces of interaction under the conditions of spatially
flat expansion of the universe has demonstrated that the system of atomic
levels does not change with cosmological time. Spectral lines of atoms in the
spatially flat Friedmann model are identical at different points of
cosmological time. In this case the redshift is stipulated entirely by the
growth of wavelength of photons at movement in the expending universe. At the
same time force of interaction between elementary particles can change with
expansion of the universe.
| [
{
"created": "Tue, 24 May 2011 08:36:18 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Nov 2011 07:22:29 GMT",
"version": "v2"
}
] | 2011-11-07 | [
[
"Gorbatenko",
"M. V.",
""
],
[
"Neznamov",
"V. P.",
""
]
] | The earlier developed algorithm for constructing a self-conjugate Hamiltonian in the \eta-representation for Dirac particles interacting with a general gravitational field is extended to the case of electromagnetic fields. This Hamiltonian is applied to the case when the gravitational field describes the spatially flat Friedmann model, and the electromagnetic field is the Coulomb potential extended to the case of this model. The analysis of atomic systems and electromagnetic forces of interaction under the conditions of spatially flat expansion of the universe has demonstrated that the system of atomic levels does not change with cosmological time. Spectral lines of atoms in the spatially flat Friedmann model are identical at different points of cosmological time. In this case the redshift is stipulated entirely by the growth of wavelength of photons at movement in the expending universe. At the same time force of interaction between elementary particles can change with expansion of the universe. |
1209.4374 | Abhay Ashtekar | Abhay Ashtekar and Miguel Campiglia | On the Uniqueness of Kinematics of Loop Quantum Cosmology | 9 pages | Class. Quantum Grav. 29, 242001 (2012) | 10.1088/0264-9381/29/24/242001 | GC-12/09/03 | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The holonomy-flux algebra $\A$ of loop quantum gravity is known to admit a
natural representation that is uniquely singled out by the requirement of
covariance under spatial diffeomorphisms. In the cosmological context, the
requirement of spatial homogeneity naturally reduces $\A$ to a much smaller
algebra, $\A_{\rm Red}$, used in loop quantum cosmology. In Bianchi I models,
it is shown that the requirement of covariance under \emph{residual}
diffeomorphism symmetries again uniquely selects the representation of $\A_{\rm
Red}$ that has been commonly used. We discuss the close parallel between the
two uniqueness results and also point out a difference.
| [
{
"created": "Wed, 19 Sep 2012 21:16:38 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Campiglia",
"Miguel",
""
]
] | The holonomy-flux algebra $\A$ of loop quantum gravity is known to admit a natural representation that is uniquely singled out by the requirement of covariance under spatial diffeomorphisms. In the cosmological context, the requirement of spatial homogeneity naturally reduces $\A$ to a much smaller algebra, $\A_{\rm Red}$, used in loop quantum cosmology. In Bianchi I models, it is shown that the requirement of covariance under \emph{residual} diffeomorphism symmetries again uniquely selects the representation of $\A_{\rm Red}$ that has been commonly used. We discuss the close parallel between the two uniqueness results and also point out a difference. |
gr-qc/9807064 | K. Srinivasan | K. Srinivasan and T. Padmanabhan | Facets of Tunneling: Particle production in external fields | 22 pages, Revtex file | null | null | IUCAA Preprint No: 29/98 | gr-qc hep-th | null | This paper presents a critical review of particle production in an uniform
electric field and Schwarzchild-like spacetimes. Both problems can be reduced
to solving an effective one-dimensional Schrodinger equation with a potential
barrier. In the electric field case, the potential is that of an inverted
oscillator -x^2 while in the case of Schwarchild-like spacetimes, the potential
is of the form -1/x^2 near the horizon. The transmission and reflection
coefficients can easily be obtained for both potentials. To describe particle
production, these coefficients have to be suitably interpreted. In the case of
the electric field, the standard Bogoliubov coefficients can be identified and
the standard gauge invariant result is recovered. However, for
Schwarzchild-like spacetimes, such a tunnelling interpretation appears to be
invalid. The Bogoliubov coefficients cannot be determined by using an
identification process similar to that invoked in the case of the electric
field. The reason for such a discrepancy appears to be that, in the tunnelling
method, the effective potential near the horizon is singular and symmetric. We
also provide a new and simple semi-classical method of obtaining Hawking's
result in the (t,r) co-ordinate system of the usual standard Schwarzchild
metric. We give a prescription whereby the singularity at the horizon can be
regularised with Hawking's result being recovered. This regularisation
prescription contains a fundamental asymmetry that renders both sides of the
horizon dissimilar. Finally, we attempt to interpret particle production by the
electric field as a tunnelling process between the two sectors of the Rindler
metric.
| [
{
"created": "Thu, 23 Jul 1998 06:40:49 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Srinivasan",
"K.",
""
],
[
"Padmanabhan",
"T.",
""
]
] | This paper presents a critical review of particle production in an uniform electric field and Schwarzchild-like spacetimes. Both problems can be reduced to solving an effective one-dimensional Schrodinger equation with a potential barrier. In the electric field case, the potential is that of an inverted oscillator -x^2 while in the case of Schwarchild-like spacetimes, the potential is of the form -1/x^2 near the horizon. The transmission and reflection coefficients can easily be obtained for both potentials. To describe particle production, these coefficients have to be suitably interpreted. In the case of the electric field, the standard Bogoliubov coefficients can be identified and the standard gauge invariant result is recovered. However, for Schwarzchild-like spacetimes, such a tunnelling interpretation appears to be invalid. The Bogoliubov coefficients cannot be determined by using an identification process similar to that invoked in the case of the electric field. The reason for such a discrepancy appears to be that, in the tunnelling method, the effective potential near the horizon is singular and symmetric. We also provide a new and simple semi-classical method of obtaining Hawking's result in the (t,r) co-ordinate system of the usual standard Schwarzchild metric. We give a prescription whereby the singularity at the horizon can be regularised with Hawking's result being recovered. This regularisation prescription contains a fundamental asymmetry that renders both sides of the horizon dissimilar. Finally, we attempt to interpret particle production by the electric field as a tunnelling process between the two sectors of the Rindler metric. |
1612.06504 | Abhik Kumar Sanyal Dr. | Abhik Kumar Sanyal | Enlightening the dark universe | 21 pages, 13 figures, The lecture given on "One day seminar on
Einstein and his contributions in Physics and Cosmology to celebrate 100
years of General Theory of Relativity" organized by " Calcutta Institute of
Theoretical Physics in collaboration with Department of Mathematics, St.
Xavier's College, Kolkata" on 28th. March, 2015, Indian Journal of
Theoretical Physics, Vol 62, Nos. 3,4, 2014. ISSN: 0019-5693. arXiv admin
note: text overlap with arXiv:astro-ph/0005003 by other authors without
attribution | Indian Journal of Theoretical Physics, 62, 211-262 (2014) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lot of avenues, the black hole, the wormhole, the dark matter, the dark
energy etc. have been opened since the advent of General Theory of Relativity
in 1915. Cosmology, the physics of creation and evolution of the universe,
which was once thought to be beyond human perseverance, has now become a rich
science of highest importance. However, the theory of gravitation, the oldest
known interaction, is still not well understood. In the process of unveiling
the evolutionary history of the universe, we shall explore some facts that
suggest General Theory of Relativity is not the complete theory of gravitation.
| [
{
"created": "Tue, 20 Dec 2016 04:53:49 GMT",
"version": "v1"
}
] | 2017-07-18 | [
[
"Sanyal",
"Abhik Kumar",
""
]
] | Lot of avenues, the black hole, the wormhole, the dark matter, the dark energy etc. have been opened since the advent of General Theory of Relativity in 1915. Cosmology, the physics of creation and evolution of the universe, which was once thought to be beyond human perseverance, has now become a rich science of highest importance. However, the theory of gravitation, the oldest known interaction, is still not well understood. In the process of unveiling the evolutionary history of the universe, we shall explore some facts that suggest General Theory of Relativity is not the complete theory of gravitation. |
1401.0368 | Yuri Pavlov | A. A. Grib, Yu. V. Pavlov | High energy particles with negative and positive energies in the
vicinity of black holes | 12 pages, no figures. arXiv admin note: substantial text overlap with
arXiv:1301.0698, arXiv:1304.7360 | AIP Conf. Proc. 1606, (2014) 11-18 | 10.1063/1.4891112 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that the energy in the centre of mass frame of two colliding
particles in free fall at any point of the ergosphere of the rotating black
hole can grow without limit for fixed energy values of particles on infinity.
The effect takes place for large negative values of the angular momentum of one
of the particles. It occurs that the geodesics with negative energy in
equatorial plane of rotating black holes cannot originate or terminate inside
the ergosphere. Their length is always finite and this leads to conclusion that
they must originate and terminate inside the gravitational radius of the
ergosphere. The energy in the centre of mass frame of one particle falling into
the gravitational radius and the other arriving from the area inside it is
growing without limit on the horizon.
| [
{
"created": "Thu, 2 Jan 2014 05:53:38 GMT",
"version": "v1"
}
] | 2014-09-16 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | It is shown that the energy in the centre of mass frame of two colliding particles in free fall at any point of the ergosphere of the rotating black hole can grow without limit for fixed energy values of particles on infinity. The effect takes place for large negative values of the angular momentum of one of the particles. It occurs that the geodesics with negative energy in equatorial plane of rotating black holes cannot originate or terminate inside the ergosphere. Their length is always finite and this leads to conclusion that they must originate and terminate inside the gravitational radius of the ergosphere. The energy in the centre of mass frame of one particle falling into the gravitational radius and the other arriving from the area inside it is growing without limit on the horizon. |
2207.10085 | Surajit Mandal | Surajit Mandal, Sudhaker Upadhyay, Yerlan Myrzakulov, Gulmira
Yergaliyeva | Shadow of the $5D$ Reissner-Nordstr\"om AdS Black Hole | 23 pages, 19 captioned figures | International Journal of Modern Physics A 38 (2023) 2350047 | 10.1142/S0217751X23500471 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We discuss the shadow cast by the charged Reissner-Nordstr\"om (RN) AdS black
hole. With the help of Killing equation and Hamilton-Jacobi equation, we
calculate the geodesic equations for null particle. With the help of geodesics
of null particle, we then determine the celestial coordinates ($\alpha$,
$\beta$) and the shadow radius of the RN AdS black hole. We present a graphical
analysis of the black hole shadow and find that shadow is a perfectly dark
circle. The impacts of charge and cosmological constant of the RN AdS black
hole on the radius of shadow are also presented. In this connection, radius of
the shadow is a decreasing function of the charge. Furthermore, we study the
effects of plasma medium on the RN AdS black hole shadow. Here, we find that
radius of circular shadow increases with increasing plasma parameter. In
addition, we also discuss the energy emission rate of RN AdS black hole. The
effects of parameters like charge, cosmological constant and plasma parameter
on energy emission rate are analyzed graphically.
| [
{
"created": "Wed, 20 Jul 2022 15:41:05 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Aug 2022 13:24:48 GMT",
"version": "v2"
}
] | 2023-07-06 | [
[
"Mandal",
"Surajit",
""
],
[
"Upadhyay",
"Sudhaker",
""
],
[
"Myrzakulov",
"Yerlan",
""
],
[
"Yergaliyeva",
"Gulmira",
""
]
] | We discuss the shadow cast by the charged Reissner-Nordstr\"om (RN) AdS black hole. With the help of Killing equation and Hamilton-Jacobi equation, we calculate the geodesic equations for null particle. With the help of geodesics of null particle, we then determine the celestial coordinates ($\alpha$, $\beta$) and the shadow radius of the RN AdS black hole. We present a graphical analysis of the black hole shadow and find that shadow is a perfectly dark circle. The impacts of charge and cosmological constant of the RN AdS black hole on the radius of shadow are also presented. In this connection, radius of the shadow is a decreasing function of the charge. Furthermore, we study the effects of plasma medium on the RN AdS black hole shadow. Here, we find that radius of circular shadow increases with increasing plasma parameter. In addition, we also discuss the energy emission rate of RN AdS black hole. The effects of parameters like charge, cosmological constant and plasma parameter on energy emission rate are analyzed graphically. |
2011.12533 | Suparna Roychowdhury Dr. | Shounak De, Suparna Roychowdhury, Roopkatha Banerjee | Beyond-Newtonian dynamics of a planar circular restricted three-body
problem with Kerr-like primaries | 19 pages, 11 figures; Accepted for publication in MNRAS | null | 10.1093/mnras/staa3733 | null | gr-qc astro-ph.HE nlin.CD | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The dynamics of the planar circular restricted three-body problem with
Kerr-like primaries in the context of a beyond-Newtonian approximation is
studied. The beyond-Newtonian potential is developed by using the
Fodor-Hoenselaers-Perj\'es procedure. An expansion in the Kerr potential is
performed and terms up-to the first non-Newtonian contribution of both the mass
and spin effects are included. With this potential, a model for a test particle
of infinitesimal mass orbiting in the equatorial plane of the two primaries is
examined. The introduction of a parameter, $\epsilon$, allows examination of
the system as it transitions from the Newtonian to the beyond-Newtonian regime.
The evolution and stability of the fixed points of the system as a function of
the parameter $\epsilon$ is also studied. The dynamics of the particle is
studied using the Poincar\'e map of section and the Maximal Lyapunov Exponent
as indicators of chaos. Intermediate values of $\epsilon$ seem to be the most
chaotic for the two cases of primary mass-ratios ($=0.001,0.5$) examined. The
amount of chaos in the system remains higher than the Newtonian system as well
as for the planar circular restricted three-body problem with
Schwarzschild-like primaries for all non-zero values of $\epsilon$.
| [
{
"created": "Wed, 25 Nov 2020 06:09:26 GMT",
"version": "v1"
}
] | 2020-12-09 | [
[
"De",
"Shounak",
""
],
[
"Roychowdhury",
"Suparna",
""
],
[
"Banerjee",
"Roopkatha",
""
]
] | The dynamics of the planar circular restricted three-body problem with Kerr-like primaries in the context of a beyond-Newtonian approximation is studied. The beyond-Newtonian potential is developed by using the Fodor-Hoenselaers-Perj\'es procedure. An expansion in the Kerr potential is performed and terms up-to the first non-Newtonian contribution of both the mass and spin effects are included. With this potential, a model for a test particle of infinitesimal mass orbiting in the equatorial plane of the two primaries is examined. The introduction of a parameter, $\epsilon$, allows examination of the system as it transitions from the Newtonian to the beyond-Newtonian regime. The evolution and stability of the fixed points of the system as a function of the parameter $\epsilon$ is also studied. The dynamics of the particle is studied using the Poincar\'e map of section and the Maximal Lyapunov Exponent as indicators of chaos. Intermediate values of $\epsilon$ seem to be the most chaotic for the two cases of primary mass-ratios ($=0.001,0.5$) examined. The amount of chaos in the system remains higher than the Newtonian system as well as for the planar circular restricted three-body problem with Schwarzschild-like primaries for all non-zero values of $\epsilon$. |
0911.2971 | Shahram Jalalzadeh | S. M. M. Rasouli, A. F. Bahrehbakhsh, S. Jalalzadeh and M. Farhoudi | Quantum mechanics and geodesic deviation in the brane world | 5 pages, no figures | Europhys.Lett.87:40006,2009 | 10.1209/0295-5075/87/40006 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/3.0/ | We investigate the induced geodesic deviation equations in the brane world
models, in which all the matter forces except gravity are confined on the
3-brane. Also, the Newtonian limit of induced geodesic deviation equation is
studied. We show that in the first Randall-Sundrum model the Bohr-Sommerfeld
quantization rule is as a result of consistency between the geodesic and
geodesic deviation equations. This indicates that the path of test particle is
made up of integral multiples of a fundamental Compton-type unit of length
$h/mc$.
| [
{
"created": "Mon, 16 Nov 2009 07:49:53 GMT",
"version": "v1"
}
] | 2016-09-13 | [
[
"Rasouli",
"S. M. M.",
""
],
[
"Bahrehbakhsh",
"A. F.",
""
],
[
"Jalalzadeh",
"S.",
""
],
[
"Farhoudi",
"M.",
""
]
] | We investigate the induced geodesic deviation equations in the brane world models, in which all the matter forces except gravity are confined on the 3-brane. Also, the Newtonian limit of induced geodesic deviation equation is studied. We show that in the first Randall-Sundrum model the Bohr-Sommerfeld quantization rule is as a result of consistency between the geodesic and geodesic deviation equations. This indicates that the path of test particle is made up of integral multiples of a fundamental Compton-type unit of length $h/mc$. |
gr-qc/0409089 | T. Padmanabhan | T.Padmanabhan | From Gravitons to Gravity: Myths and Reality | revtex; 19 pages; no figures | Int.J.Mod.Phys.D17:367-398,2008 | 10.1142/S0218271808012085 | null | gr-qc astro-ph hep-th | null | There is a general belief, reinforced by statements in standard textbooks,
that: (i) one can obtain the full non-linear Einstein's theory of gravity by
coupling a massless, spin-2 field $h_{ab}$ self-consistently to the total
energy momentum tensor, including its own; (ii) this procedure is unique and
leads to Einstein-Hilbert action and (iii) it only uses standard concepts in
Lorentz invariant field theory and does not involve any geometrical
assumptions. After providing several reasons why such beliefs are suspect --
and critically re-examining several previous attempts -- we provide a detailed
analysis aimed at clarifying the situation. First, we prove that it is
\textit{impossible} to obtain the Einstein-Hilbert (EH) action, starting from
the standard action for gravitons in linear theory and iterating repeatedly.
Second, we use the Taylor series expansion of the action for Einstein's theory,
to identify the tensor $\mathcal{S}^{ab}$, to which the graviton field $h_{ab}$
couples to the lowest order. We show that the second rank tensor
$\mathcal{S}^{ab}$ is {\it not} the conventional energy momentum tensor
$T^{ab}$ of the graviton and provide an explanation for this feature. Third, we
construct the full nonlinear Einstein's theory with the source being spin-0
field, spin-1 field or relativistic particles by explicitly coupling the spin-2
field to this second rank tensor $\mathcal{S}^{ab}$ order by order and summing
up the infinite series. Finally, we construct the theory obtained by self
consistently coupling $h_{ab}$ to the conventional energy momentum tensor
$T^{ab}$ order by order and show that this does {\it not} lead to Einstein's
theory. (condensed).
| [
{
"created": "Thu, 23 Sep 2004 05:28:42 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Padmanabhan",
"T.",
""
]
] | There is a general belief, reinforced by statements in standard textbooks, that: (i) one can obtain the full non-linear Einstein's theory of gravity by coupling a massless, spin-2 field $h_{ab}$ self-consistently to the total energy momentum tensor, including its own; (ii) this procedure is unique and leads to Einstein-Hilbert action and (iii) it only uses standard concepts in Lorentz invariant field theory and does not involve any geometrical assumptions. After providing several reasons why such beliefs are suspect -- and critically re-examining several previous attempts -- we provide a detailed analysis aimed at clarifying the situation. First, we prove that it is \textit{impossible} to obtain the Einstein-Hilbert (EH) action, starting from the standard action for gravitons in linear theory and iterating repeatedly. Second, we use the Taylor series expansion of the action for Einstein's theory, to identify the tensor $\mathcal{S}^{ab}$, to which the graviton field $h_{ab}$ couples to the lowest order. We show that the second rank tensor $\mathcal{S}^{ab}$ is {\it not} the conventional energy momentum tensor $T^{ab}$ of the graviton and provide an explanation for this feature. Third, we construct the full nonlinear Einstein's theory with the source being spin-0 field, spin-1 field or relativistic particles by explicitly coupling the spin-2 field to this second rank tensor $\mathcal{S}^{ab}$ order by order and summing up the infinite series. Finally, we construct the theory obtained by self consistently coupling $h_{ab}$ to the conventional energy momentum tensor $T^{ab}$ order by order and show that this does {\it not} lead to Einstein's theory. (condensed). |
gr-qc/0408042 | Allan Joseph Michael Medved | Joanne Kettner, Gabor Kunstatter and A.J.M. Medved | Quasinormal modes for single horizon black holes in generic 2-d dilaton
gravity | 20 pages, in Revtex; (v2) some new references and minor changes to
the text; (v3) some clarity added to Introduction and new reference | Class.Quant.Grav. 21 (2004) 5317-5332 | 10.1088/0264-9381/21/23/002 | null | gr-qc hep-th | null | There has been some recent speculation that a connection may exist between
the quasinormal-mode spectra of highly damped black holes and the fundamental
theory of quantum gravity. This notion follows from a conjecture by Hod that
the real part of the highly damped mode frequencies can be used to calibrate
the semi-classical level spacing in the black hole quantum area spectrum.
However, even if the level spacing can be fixed in this manner, it still
remains unclear whether this implies a physically significant "duality" or
merely a numerical coincidence. This tapestry of ideas serves as the motivation
for the current paper. We utilize the "monodromy approach" to calculate the
quasinormal-mode spectra for a generic class of black holes in two-dimensional
dilatonic gravity. Our results agree with the prior literature whenever a
direct comparison is possible and provide the analysis of a much more diverse
class of black hole models than previously considered.
| [
{
"created": "Mon, 16 Aug 2004 06:30:06 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Sep 2004 00:59:33 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Sep 2004 05:37:49 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Kettner",
"Joanne",
""
],
[
"Kunstatter",
"Gabor",
""
],
[
"Medved",
"A. J. M.",
""
]
] | There has been some recent speculation that a connection may exist between the quasinormal-mode spectra of highly damped black holes and the fundamental theory of quantum gravity. This notion follows from a conjecture by Hod that the real part of the highly damped mode frequencies can be used to calibrate the semi-classical level spacing in the black hole quantum area spectrum. However, even if the level spacing can be fixed in this manner, it still remains unclear whether this implies a physically significant "duality" or merely a numerical coincidence. This tapestry of ideas serves as the motivation for the current paper. We utilize the "monodromy approach" to calculate the quasinormal-mode spectra for a generic class of black holes in two-dimensional dilatonic gravity. Our results agree with the prior literature whenever a direct comparison is possible and provide the analysis of a much more diverse class of black hole models than previously considered. |
1112.4114 | Anil Yadav dr | Anil Kumar Yadav, Vineet Kumar Yadav and Lallan Yadav | Cylindrically Symmetric Inhomogeneous Universes with a Cloud of Strings | 9 pages | Int. J. Theor. Phys. 48: 568-578, 2009 | 10.1007/s10773-008-9832-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cylindrically symmetric inhomogeneous string cosmological models are
investigated in presence of string fluid as a source of matter. To get the
three types of exact solutions of Einstein's field equations we assume $A =
f(x)k(t)$, $B = g(x)\ell(t)$ and $C = h(x)\ell(t)$. Some physical and geometric
aspects of the models are discussed.
| [
{
"created": "Sun, 18 Dec 2011 04:42:13 GMT",
"version": "v1"
}
] | 2011-12-20 | [
[
"Yadav",
"Anil Kumar",
""
],
[
"Yadav",
"Vineet Kumar",
""
],
[
"Yadav",
"Lallan",
""
]
] | Cylindrically symmetric inhomogeneous string cosmological models are investigated in presence of string fluid as a source of matter. To get the three types of exact solutions of Einstein's field equations we assume $A = f(x)k(t)$, $B = g(x)\ell(t)$ and $C = h(x)\ell(t)$. Some physical and geometric aspects of the models are discussed. |
gr-qc/9506087 | null | A. Carlini, V.P. Frolov, M.B. Mensky, I.D. Novikov and H.H. Soleng | Time machines: the Principle of Self-Consistency as a consequence of the
Principle of Minimal Action | 26 pages, plain latex; modified version includes extra constraint for
collinear collision case and other minor misprints corrections | Int.J.Mod.Phys. D4 (1995) 557-580; Erratum-ibid. D5 (1996) 99 | 10.1142/S0218271896000588 | NORDITA-95/49 | gr-qc | null | We consider the action principle to derive the classical, non-relativistic
motion of a self-interacting particle in a 4-D Lorentzian spacetime containing
a wormhole and which allows the existence of closed time-like curves. For the
case of a `hard-sphere' self-interaction potential we show that the only
possible trajectories (for a particle with fixed initial and final positions
and which traverses the wormhole once) minimizing the classical action are
those which are globally self-consistent, and that the `Principle of
self-consistency' (originally introduced by Novikov) is thus a natural
consequence of the `Principle of minimal action.'
| [
{
"created": "Sat, 1 Jul 1995 18:54:38 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Feb 1996 10:27:04 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Carlini",
"A.",
""
],
[
"Frolov",
"V. P.",
""
],
[
"Mensky",
"M. B.",
""
],
[
"Novikov",
"I. D.",
""
],
[
"Soleng",
"H. H.",
""
]
] | We consider the action principle to derive the classical, non-relativistic motion of a self-interacting particle in a 4-D Lorentzian spacetime containing a wormhole and which allows the existence of closed time-like curves. For the case of a `hard-sphere' self-interaction potential we show that the only possible trajectories (for a particle with fixed initial and final positions and which traverses the wormhole once) minimizing the classical action are those which are globally self-consistent, and that the `Principle of self-consistency' (originally introduced by Novikov) is thus a natural consequence of the `Principle of minimal action.' |
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