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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0706.1258 | Frank Reifler | Frank Reifler and Randall Morris | Hestenes' Tetrad and Spin Connections | null | Int.J.Theor.Phys.44:1307-1324,2005 | 10.1007/s10773-005-4688-8 | null | gr-qc math-ph math.MP quant-ph | null | Defining a spin connection is necessary for formulating Dirac's bispinor
equation in a curved space-time. Hestenes has shown that a bispinor field is
equivalent to an orthonormal tetrad of vector fields together with a complex
scalar field. In this paper, we show that using Hestenes' tetrad for the spin
connection in a Riemannian space-time leads to a Yang-Mills formulation of the
Dirac Lagrangian in which the bispinor field is mapped to a set of Yang-Mills
gauge potentials and a complex scalar field. This result was previously proved
for a Minkowski space-time using Fierz identities. As an application we derive
several different non-Riemannian spin connections found in the literature
directly from an arbitrary linear connection acting on Hestenes' tetrad and
scalar fields. We also derive spin connections for which Dirac's bispinor
equation is form invariant. Previous work has not considered form invariance of
the Dirac equation as a criterion for defining a general spin connection.
| [
{
"created": "Fri, 8 Jun 2007 21:21:04 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Reifler",
"Frank",
""
],
[
"Morris",
"Randall",
""
]
] | Defining a spin connection is necessary for formulating Dirac's bispinor equation in a curved space-time. Hestenes has shown that a bispinor field is equivalent to an orthonormal tetrad of vector fields together with a complex scalar field. In this paper, we show that using Hestenes' tetrad for the spin connection in a Riemannian space-time leads to a Yang-Mills formulation of the Dirac Lagrangian in which the bispinor field is mapped to a set of Yang-Mills gauge potentials and a complex scalar field. This result was previously proved for a Minkowski space-time using Fierz identities. As an application we derive several different non-Riemannian spin connections found in the literature directly from an arbitrary linear connection acting on Hestenes' tetrad and scalar fields. We also derive spin connections for which Dirac's bispinor equation is form invariant. Previous work has not considered form invariance of the Dirac equation as a criterion for defining a general spin connection. |
2208.04552 | Andreas Maier | J. Bl\"umlein, A. Maier, P. Marquard, G. Sch\"afer | Gravity in binary systems at the fifth and sixth post-Newtonian order | 10 pages, 1 figure. Contribution to the proceedings of Loops and Legs
in Quantum Field Theory - LL2022 | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary sources of gravitational waves in the early inspiral phase are
accurately described by a post-Newtonian expansion in small velocity and weak
interaction. We compute the conservative dynamics to fifth and partial sixth
order using a non-relativistic effective field theory. We give predictions for
central observables and determine the required coefficients for the
construction of an Effective One-Body Hamiltonian, extending the applicability
of our results to the late inspiral and merger phases.
| [
{
"created": "Tue, 9 Aug 2022 06:00:58 GMT",
"version": "v1"
}
] | 2022-08-10 | [
[
"Blümlein",
"J.",
""
],
[
"Maier",
"A.",
""
],
[
"Marquard",
"P.",
""
],
[
"Schäfer",
"G.",
""
]
] | Binary sources of gravitational waves in the early inspiral phase are accurately described by a post-Newtonian expansion in small velocity and weak interaction. We compute the conservative dynamics to fifth and partial sixth order using a non-relativistic effective field theory. We give predictions for central observables and determine the required coefficients for the construction of an Effective One-Body Hamiltonian, extending the applicability of our results to the late inspiral and merger phases. |
2211.15668 | Kazuhiro Agatsuma | Kazuhiro Agatsuma | Four hints and test candidates of the local cosmic expansion | 5 pages, 1 figure | Physics of the Dark Universe, Volume 38, 2022, 101134 | 10.1016/j.dark.2022.101134 | null | gr-qc astro-ph.CO astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The expansion of the universe on short distance scales is a new frontier to
investigate the dark energy. The excess orbital decay in binary pulsars may be
related to acceleration by the local cosmic expansion, called the cosmic drag.
Modern observations of two independent binaries (PSR B1534+12 and PSR B1913+16)
support this interpretation and result in a scale-independent expansion with
viscous uniformity, in which binary systems have a smaller expansion rate than
the Hubble constant. This paper shows additional evidential binaries (PSR
J1012-5307 and PSR J1906+0746), supporting the cosmic drag picture. The total
anomaly of the conventional model is about $3.6\,\sigma$ including two
evidential binaries reported before. In addition, an observable range of the
cosmic drag has been calculated for typical models of both NS-NS binary and
NS-WD binary. In this region, six test candidates are listed with predictions
of the excess orbital decay.
| [
{
"created": "Sat, 26 Nov 2022 07:18:40 GMT",
"version": "v1"
}
] | 2022-11-30 | [
[
"Agatsuma",
"Kazuhiro",
""
]
] | The expansion of the universe on short distance scales is a new frontier to investigate the dark energy. The excess orbital decay in binary pulsars may be related to acceleration by the local cosmic expansion, called the cosmic drag. Modern observations of two independent binaries (PSR B1534+12 and PSR B1913+16) support this interpretation and result in a scale-independent expansion with viscous uniformity, in which binary systems have a smaller expansion rate than the Hubble constant. This paper shows additional evidential binaries (PSR J1012-5307 and PSR J1906+0746), supporting the cosmic drag picture. The total anomaly of the conventional model is about $3.6\,\sigma$ including two evidential binaries reported before. In addition, an observable range of the cosmic drag has been calculated for typical models of both NS-NS binary and NS-WD binary. In this region, six test candidates are listed with predictions of the excess orbital decay. |
1005.2501 | Mehrdad Farhoudi Dr. | Amir F. Bahrehbakhsh, Mehrdad Farhoudi and Hossein Shojaie | FRW Cosmology From Five Dimensional Vacuum Brans-Dicke Theory | 18 pages, 16 figures, 11 tables | Gen.Rel.Grav.43:847-869,2011 | 10.1007/s10714-010-1101-6 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We follow approach of induced matter theory for 5D vacuum BD, introduce
induced matter and potential in 4D hypersurfaces, and employ generalized FRW
type solution. We confine ourselves to scalar field and scale factors be
functions of the time. This makes the induced potential, by its definition,
vanishes. When the scale factor of fifth dimension and scalar field are not
constants, 5D eqs for any geometry admit a power law relation between scalar
field and scale factor of fifth dimension. Hence the procedure exhibits that 5D
vacuum FRW like eqs are equivalent, in general, to corresponding 4D vacuum ones
with the same spatial scale factor but new scalar field and coupling constant.
We show that 5D vacuum FRW like eqs or its equivalent 4D vacuum ones admit
accelerated solutions. For constant scalar field, eqs reduce to usual FRW eqs
with typical radiation dominated universe. For this situation we obtain
dynamics of scale factors for any geometry without any priori assumption. For
nonconstant scalar fields and spatially flat geometries, solutions are found to
be power law and exponential ones. We also employ weak energy condition for
induced matter, that allows negative/positive pressures. All types of solutions
fulfill WEC in different ranges. The power law solutions with negative/positive
pressures admit both decelerating and accelerating ones. Some solutions accept
shrinking extra dimension. By considering nonghost scalar fields and recent
observational measurements, solutions are more restricted. We illustrate that
accelerating power law solutions, which satisfy WEC and have nonghost fields,
are compatible with recent observations in ranges -4/3 < \omega </- -1.3151 and
1.5208 </- n < 1.9583 for dependence of fifth dimension scale factor with usual
scale factor. These ranges also fulfill condition nonghost fields in the
equivalent 4D vacuum BD eqs.
| [
{
"created": "Fri, 14 May 2010 11:18:45 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Oct 2010 12:15:18 GMT",
"version": "v2"
}
] | 2015-03-17 | [
[
"Bahrehbakhsh",
"Amir F.",
""
],
[
"Farhoudi",
"Mehrdad",
""
],
[
"Shojaie",
"Hossein",
""
]
] | We follow approach of induced matter theory for 5D vacuum BD, introduce induced matter and potential in 4D hypersurfaces, and employ generalized FRW type solution. We confine ourselves to scalar field and scale factors be functions of the time. This makes the induced potential, by its definition, vanishes. When the scale factor of fifth dimension and scalar field are not constants, 5D eqs for any geometry admit a power law relation between scalar field and scale factor of fifth dimension. Hence the procedure exhibits that 5D vacuum FRW like eqs are equivalent, in general, to corresponding 4D vacuum ones with the same spatial scale factor but new scalar field and coupling constant. We show that 5D vacuum FRW like eqs or its equivalent 4D vacuum ones admit accelerated solutions. For constant scalar field, eqs reduce to usual FRW eqs with typical radiation dominated universe. For this situation we obtain dynamics of scale factors for any geometry without any priori assumption. For nonconstant scalar fields and spatially flat geometries, solutions are found to be power law and exponential ones. We also employ weak energy condition for induced matter, that allows negative/positive pressures. All types of solutions fulfill WEC in different ranges. The power law solutions with negative/positive pressures admit both decelerating and accelerating ones. Some solutions accept shrinking extra dimension. By considering nonghost scalar fields and recent observational measurements, solutions are more restricted. We illustrate that accelerating power law solutions, which satisfy WEC and have nonghost fields, are compatible with recent observations in ranges -4/3 < \omega </- -1.3151 and 1.5208 </- n < 1.9583 for dependence of fifth dimension scale factor with usual scale factor. These ranges also fulfill condition nonghost fields in the equivalent 4D vacuum BD eqs. |
1211.3592 | Dongsu Bak | Dongsu Bak | Entropy of universe as entanglement entropy | 15 pages, 3 figures, references added, version to appear plb | null | 10.1016/j.physletb.2013.03.023 | UOSTP 121201 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We note that the observable part of universe at a certain time t_P is
necessarily limited, when there is a beginning of universe. We argue that an
appropriate spacetime region associated with an observer from tI to t_P is the
causal diamond which is the overlap of the past/future of the observer at
t_P/t_I respectively. We also note that the overlap surface \partial D of the
future and the past lightcones bisects the spatial section including \partial D
into two regions D and \bar D where D is the region inside the causal diamond
and \bar D the remaining part of the spatial section. We propose here that the
entropy of universe associated with a causal diamond is given by an
entanglement entropy where one is tracing over the Hilbert space associated
with the region \bar D which is not accessible by the observer. We test our
proposal for various examples of cosmological spacetimes, including flat or
open FRW universes, by showing that the entropy as the area of \partial D
divided by 4G is a non-decreasing function of time t_P as dictated by the
generalized second law of thermodynamics. The closed, recollapsing universe
corresponds to a finite system and there is no reason to expect the validity of
the generalized second law for such a finite system.
| [
{
"created": "Thu, 15 Nov 2012 12:42:09 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Nov 2012 11:28:57 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Mar 2013 06:58:16 GMT",
"version": "v3"
}
] | 2015-06-12 | [
[
"Bak",
"Dongsu",
""
]
] | We note that the observable part of universe at a certain time t_P is necessarily limited, when there is a beginning of universe. We argue that an appropriate spacetime region associated with an observer from tI to t_P is the causal diamond which is the overlap of the past/future of the observer at t_P/t_I respectively. We also note that the overlap surface \partial D of the future and the past lightcones bisects the spatial section including \partial D into two regions D and \bar D where D is the region inside the causal diamond and \bar D the remaining part of the spatial section. We propose here that the entropy of universe associated with a causal diamond is given by an entanglement entropy where one is tracing over the Hilbert space associated with the region \bar D which is not accessible by the observer. We test our proposal for various examples of cosmological spacetimes, including flat or open FRW universes, by showing that the entropy as the area of \partial D divided by 4G is a non-decreasing function of time t_P as dictated by the generalized second law of thermodynamics. The closed, recollapsing universe corresponds to a finite system and there is no reason to expect the validity of the generalized second law for such a finite system. |
gr-qc/9403016 | Jennie Traschen | Jennie Traschen | Discrete Self-Similiarity and Critical Point Behavior in Fluctuations
About Extremal Black Holes | 12 pages (harvmac), UMHEP-405 | Phys. Rev. D 50, 7144 (1994) | 10.1103/PhysRevD.50.7144 | null | gr-qc | null | The issues of scaling symmetry and critical point behavior are studied for
fluctuations about extremal charged black holes. We consider the scattering and
capture of the spherically symmetric mode of a charged, massive test field on
the background spacetime of a black hole with charge $Q$ and mass $M$. The
spacetime geometry near the horizon of a $|Q|=M$ black hole has a scaling
symmetry, which is absent if $|Q|<M$, a scale being introduced by the surface
gravity. We show that this symmetry leads to the existence of a self-similiar
solution for the charged field near the horizon, and further, that there is a
one parameter family of discretely self-similiar solutions . The scaling
symmetry, or lack thereof, also shows up in correlation length scales, defined
in terms of the rate at which the influence of an external source coupled to
the field dies off. It is shown by constructing the Greens functions, that an
external source has a long range influence on the extremal background, compared
to a correlation length scale which falls off exponentially fast in the $|Q|<M$
case. Finally it is shown that in the limit of $\Delta \equiv (1-{Q^2 \overM^2}
)^{1\over 2} \rightarrow 0$ in the background spacetime, that infinitesimal
changes in the black hole area vary like $\Delta ^{1\over 2}$.
| [
{
"created": "Wed, 9 Mar 1994 17:30:39 GMT",
"version": "v1"
}
] | 2013-11-13 | [
[
"Traschen",
"Jennie",
""
]
] | The issues of scaling symmetry and critical point behavior are studied for fluctuations about extremal charged black holes. We consider the scattering and capture of the spherically symmetric mode of a charged, massive test field on the background spacetime of a black hole with charge $Q$ and mass $M$. The spacetime geometry near the horizon of a $|Q|=M$ black hole has a scaling symmetry, which is absent if $|Q|<M$, a scale being introduced by the surface gravity. We show that this symmetry leads to the existence of a self-similiar solution for the charged field near the horizon, and further, that there is a one parameter family of discretely self-similiar solutions . The scaling symmetry, or lack thereof, also shows up in correlation length scales, defined in terms of the rate at which the influence of an external source coupled to the field dies off. It is shown by constructing the Greens functions, that an external source has a long range influence on the extremal background, compared to a correlation length scale which falls off exponentially fast in the $|Q|<M$ case. Finally it is shown that in the limit of $\Delta \equiv (1-{Q^2 \overM^2} )^{1\over 2} \rightarrow 0$ in the background spacetime, that infinitesimal changes in the black hole area vary like $\Delta ^{1\over 2}$. |
2403.09910 | Pablo Andr\'es Lizardo Romo | Mario H. Amante, Andr\'es Lizardo, Javier Chagoya and C. Ortiz | Constraining modified gravity models through strong lensing cosmography | 18 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze cosmography as a tool to constrain modified gravity theories. We
take four distinct models and obtain their parameters in terms of the
cosmographic parameters favored by observational data of strong gravitational
lensing. We contrast with the values obtained by direct comparison between each
model and the observational data. In general, we find consistency between the
two approaches at 2$\sigma$ for all models considered in this work. Our study
bridges the gap between theoretical predictions of modified gravity and
empirical observations of strong gravitational lensing, providing a simple
methodology to test the validity of these models.
| [
{
"created": "Thu, 14 Mar 2024 23:02:59 GMT",
"version": "v1"
}
] | 2024-03-18 | [
[
"Amante",
"Mario H.",
""
],
[
"Lizardo",
"Andrés",
""
],
[
"Chagoya",
"Javier",
""
],
[
"Ortiz",
"C.",
""
]
] | We analyze cosmography as a tool to constrain modified gravity theories. We take four distinct models and obtain their parameters in terms of the cosmographic parameters favored by observational data of strong gravitational lensing. We contrast with the values obtained by direct comparison between each model and the observational data. In general, we find consistency between the two approaches at 2$\sigma$ for all models considered in this work. Our study bridges the gap between theoretical predictions of modified gravity and empirical observations of strong gravitational lensing, providing a simple methodology to test the validity of these models. |
1203.3382 | Ovidiu Cristinel Stoica | Ovidiu-Cristinel Stoica | On the Weyl Curvature Hypothesis | 10 pages, slides at
http://www.sciencedirect.com/science/article/pii/S0003491613001711 | Annals of Physics, Vol. 338, November 2013, Pages 186-194 | 10.1016/j.aop.2013.08.002 | null | gr-qc astro-ph.CO math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Weyl curvature hypothesis of Penrose attempts to explain the high
homogeneity and isotropy, and the very low entropy of the early universe, by
conjecturing the vanishing of the Weyl tensor at the Big-Bang singularity.
In previous papers it has been proposed an equivalent form of Einstein's
equation, which extends it and remains valid at an important class of
singularities (including in particular the Schwarzschild, FLRW, and isotropic
singularities). Here it is shown that if the Big-Bang singularity is from this
class, it also satisfies the Weyl curvature hypothesis.
As an application, we study a very general example of cosmological models,
which generalizes the FLRW model by dropping the isotropy and homogeneity
constraints. This model also generalizes isotropic singularities, and a class
of singularities occurring in Bianchi cosmologies. We show that the Big-Bang
singularity of this model is of the type under consideration, and satisfies
therefore the Weyl curvature hypothesis.
| [
{
"created": "Thu, 15 Mar 2012 15:08:07 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jun 2012 15:20:55 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Mar 2013 18:52:35 GMT",
"version": "v3"
},
{
"created": "Wed, 4 Sep 2013 20:21:28 GMT",
"version": "v4"
}
] | 2013-09-06 | [
[
"Stoica",
"Ovidiu-Cristinel",
""
]
] | The Weyl curvature hypothesis of Penrose attempts to explain the high homogeneity and isotropy, and the very low entropy of the early universe, by conjecturing the vanishing of the Weyl tensor at the Big-Bang singularity. In previous papers it has been proposed an equivalent form of Einstein's equation, which extends it and remains valid at an important class of singularities (including in particular the Schwarzschild, FLRW, and isotropic singularities). Here it is shown that if the Big-Bang singularity is from this class, it also satisfies the Weyl curvature hypothesis. As an application, we study a very general example of cosmological models, which generalizes the FLRW model by dropping the isotropy and homogeneity constraints. This model also generalizes isotropic singularities, and a class of singularities occurring in Bianchi cosmologies. We show that the Big-Bang singularity of this model is of the type under consideration, and satisfies therefore the Weyl curvature hypothesis. |
gr-qc/0502045 | John Klauder | J. Scott Little and John R. Klauder | Elementary Model of Constraint Quantization with an Anomaly | 14 pages, 2 figures | Phys.Rev. D71 (2005) 085014 | 10.1103/PhysRevD.71.085014 | null | gr-qc | null | Quantum gravity is made more difficult in part by its constraint structure.
The constraints are classically first-class; however, upon quantization they
become partially second-class. To study such behavior, we focus on a simple
problem with finitely many degrees of freedom and demonstrate how the
projection operator formalism for dealing with quantum constraints is well
suited to this type of example.
| [
{
"created": "Thu, 10 Feb 2005 15:58:29 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Little",
"J. Scott",
""
],
[
"Klauder",
"John R.",
""
]
] | Quantum gravity is made more difficult in part by its constraint structure. The constraints are classically first-class; however, upon quantization they become partially second-class. To study such behavior, we focus on a simple problem with finitely many degrees of freedom and demonstrate how the projection operator formalism for dealing with quantum constraints is well suited to this type of example. |
1710.09705 | William J. Cunningham | William J. Cunningham | Inference of Boundaries in Causal Sets | 19 pages, 9 figures | W.J. Cunningham, Inference of Boundaries in Causal Sets, Class.
Quant. Grav. 35, 094002 (2018) | 10.1088/1361-6382/aaadc4 | null | gr-qc physics.comp-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the extrinsic geometry of causal sets in $(1+1)$-dimensional
Minkowski spacetime. The properties of boundaries in an embedding space can be
used not only to measure observables, but also to supplement the discrete
action in the partition function via discretized Gibbons-Hawking-York boundary
terms. We define several ways to represent a causal set using overlapping
subsets, which then allows us to distinguish between null and non-null bounding
hypersurfaces in an embedding space. We discuss algorithms to differentiate
between different types of regions, consider when these distinctions are
possible, and then apply the algorithms to several spacetime regions. Numerical
results indicate the volumes of timelike boundaries can be measured to within
$0.5\%$ accuracy for flat boundaries and within $10\%$ accuracy for highly
curved boundaries for medium-sized causal sets with $N=2^{14}$ spacetime
elements.
| [
{
"created": "Thu, 26 Oct 2017 14:00:53 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jun 2018 13:57:16 GMT",
"version": "v2"
}
] | 2018-06-27 | [
[
"Cunningham",
"William J.",
""
]
] | We investigate the extrinsic geometry of causal sets in $(1+1)$-dimensional Minkowski spacetime. The properties of boundaries in an embedding space can be used not only to measure observables, but also to supplement the discrete action in the partition function via discretized Gibbons-Hawking-York boundary terms. We define several ways to represent a causal set using overlapping subsets, which then allows us to distinguish between null and non-null bounding hypersurfaces in an embedding space. We discuss algorithms to differentiate between different types of regions, consider when these distinctions are possible, and then apply the algorithms to several spacetime regions. Numerical results indicate the volumes of timelike boundaries can be measured to within $0.5\%$ accuracy for flat boundaries and within $10\%$ accuracy for highly curved boundaries for medium-sized causal sets with $N=2^{14}$ spacetime elements. |
gr-qc/0012030 | Toyoki Matsuyama | M. Kenmoku, T. Matsuyama, R.Sato, and S. Uchida | Canonical Theory of 2+1 Gravity | 6 pages, talk given at LLWI-2000: From Particles to Universe,
Alberta, 20-26 February 2000 | null | 10.1142/9789812811752_0027 | null | gr-qc | null | Recently 2+1 dimensional gravity theory, especially ${\rm AdS_3}$ has been
studied extensively. It was shown to be equivalent to the 2+1 Chern-Simon
theory and has been investigated to understand the black hole thermodynamics,
i.e. Hawking temperature and others. The purpose of this report is to
investigate the canonical formalism of the original 2+1 Einstein gravity theory
instead of the Chern-Simon theory. For the spherically symmetric space-time,
local conserved quantities(local mass and angular momentum) are introduced and
using them canonical quantum theory is defined. Constraints are imposed on
state vectors and solved analytically. The strategy to obtain the solution is
followed by our previous work.
| [
{
"created": "Thu, 7 Dec 2000 09:15:03 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Kenmoku",
"M.",
""
],
[
"Matsuyama",
"T.",
""
],
[
"Sato",
"R.",
""
],
[
"Uchida",
"S.",
""
]
] | Recently 2+1 dimensional gravity theory, especially ${\rm AdS_3}$ has been studied extensively. It was shown to be equivalent to the 2+1 Chern-Simon theory and has been investigated to understand the black hole thermodynamics, i.e. Hawking temperature and others. The purpose of this report is to investigate the canonical formalism of the original 2+1 Einstein gravity theory instead of the Chern-Simon theory. For the spherically symmetric space-time, local conserved quantities(local mass and angular momentum) are introduced and using them canonical quantum theory is defined. Constraints are imposed on state vectors and solved analytically. The strategy to obtain the solution is followed by our previous work. |
1603.03300 | Noah Sennett | Noah Sennett and Alessandra Buonanno | Modeling dynamical scalarization with a resummed post-Newtonian
expansion | 24 pages, 8 figures; recolored figures, fixed typos, added email | Phys. Rev. D 93, 124004 (2016) | 10.1103/PhysRevD.93.124004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite stringent constraints set by astrophysical observations, there remain
viable scalar-tensor theories that could be distinguished from general
relativity with gravitational-wave detectors. A promising signal predicted in
these alternative theories is dynamical scalarization, which can dramatically
affect the evolution of neutron-star binaries near merger. Motivated by the
successful treatment of spontaneous scalarization, we develop a formalism that
partially resums the post-Newtonian expansion to capture dynamical
scalarization in a mathematically consistent manner. We calculate the
post-Newtonian order corrections to the equations of motion and scalar mass of
a binary system. Through comparison with quasi-equilibrium configuration
calculations, we verify that this new approximation scheme can accurately
predict the onset and magnitude of dynamical scalarization.
| [
{
"created": "Thu, 10 Mar 2016 15:35:46 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Mar 2016 15:32:40 GMT",
"version": "v2"
}
] | 2017-10-11 | [
[
"Sennett",
"Noah",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | Despite stringent constraints set by astrophysical observations, there remain viable scalar-tensor theories that could be distinguished from general relativity with gravitational-wave detectors. A promising signal predicted in these alternative theories is dynamical scalarization, which can dramatically affect the evolution of neutron-star binaries near merger. Motivated by the successful treatment of spontaneous scalarization, we develop a formalism that partially resums the post-Newtonian expansion to capture dynamical scalarization in a mathematically consistent manner. We calculate the post-Newtonian order corrections to the equations of motion and scalar mass of a binary system. Through comparison with quasi-equilibrium configuration calculations, we verify that this new approximation scheme can accurately predict the onset and magnitude of dynamical scalarization. |
0803.1286 | Lorenzo Iorio | Lorenzo Iorio | Mars and frame-dragging: study for a dedicated mission | LaTex2e, 16 pages, 5 figures, no tables. To appear in General
Relativity and Gravitation | Gen.Rel.Grav.41:1273-1284,2009 | 10.1007/s10714-008-0704-7 | null | gr-qc astro-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we preliminarily explore the possibility of designing a
dedicated satellite-based mission to measure the general relativistic
gravitomagnetic Lense-Thirring effect in the gravitational field of Mars. The
focus is on the systematic error induced by the multipolar expansion of the
areopotential and on possible strategies to reduce it. It turns out that the
major sources of bias are the Mars'equatorial radius R and the even zonal
harmonics J_L, L = 2,4,6... of the areopotential. An optimal solution, in
principle, consists of using two probes at high-altitudes (a\approx 9500-9600
km) and different inclinations, and suitably combining their nodes in order to
entirely cancel out the bias due to \delta R. The remaining uncancelled
mismodelled terms due to \delta J_L, L = 2,4,6,... would induce a bias \lesssim
1%, according to the present-day MGS95J gravity model, over a wide range of
admissible values of the inclinations. The Lense-Thirring out-of-plane shifts
of the two probes would amount to about 10 cm yr^-1.
| [
{
"created": "Mon, 10 Mar 2008 18:51:12 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Oct 2008 18:42:34 GMT",
"version": "v2"
}
] | 2009-06-23 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper we preliminarily explore the possibility of designing a dedicated satellite-based mission to measure the general relativistic gravitomagnetic Lense-Thirring effect in the gravitational field of Mars. The focus is on the systematic error induced by the multipolar expansion of the areopotential and on possible strategies to reduce it. It turns out that the major sources of bias are the Mars'equatorial radius R and the even zonal harmonics J_L, L = 2,4,6... of the areopotential. An optimal solution, in principle, consists of using two probes at high-altitudes (a\approx 9500-9600 km) and different inclinations, and suitably combining their nodes in order to entirely cancel out the bias due to \delta R. The remaining uncancelled mismodelled terms due to \delta J_L, L = 2,4,6,... would induce a bias \lesssim 1%, according to the present-day MGS95J gravity model, over a wide range of admissible values of the inclinations. The Lense-Thirring out-of-plane shifts of the two probes would amount to about 10 cm yr^-1. |
1705.06036 | Carl Diether | Carl F. Diether III and Joy Christian | On the Role of Einstein-Cartan Gravity in Fundamental Particle Physics | 18 pages; No figure; Published version; For further details about our
results see http://einstein-cartan.org | Universe 2020, 6(8), 112 | 10.3390/universe6080112 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two of the major open questions in particle physics are: (1) Why are the
elementary fermionic particles that are so far observed have such low
mass-energy compared to the Planck energy scale? And (2), what mechanical
energy may be counterbalancing the divergent electrostatic and strong force
energies of point-like charged fermions in the vicinity of the Planck scale? In
this paper, using a hitherto unrecognized mechanism derived from the non-linear
amelioration of Dirac equation known as the Hehl-Datta equation within
Einstein-Cartan-Sciama-Kibble (ECSK) extension of general relativity, we
present detailed numerical estimates suggesting that the mechanical energy
arising from the gravity-induced self-interaction in the ECSK theory can
address both of these questions in tandem.
| [
{
"created": "Wed, 17 May 2017 07:41:01 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jul 2017 20:46:06 GMT",
"version": "v2"
},
{
"created": "Sat, 29 Jul 2017 18:06:04 GMT",
"version": "v3"
},
{
"created": "Mon, 9 Jul 2018 06:56:21 GMT",
"version": "v4"
},
{
"created": "Mon, 8 Oct 2018 19:38:10 GMT",
"version": "v5"
},
{
"created": "Wed, 16 Jan 2019 20:42:25 GMT",
"version": "v6"
},
{
"created": "Thu, 14 May 2020 10:46:27 GMT",
"version": "v7"
},
{
"created": "Wed, 5 Aug 2020 20:30:54 GMT",
"version": "v8"
}
] | 2022-02-13 | [
[
"Diether",
"Carl F.",
"III"
],
[
"Christian",
"Joy",
""
]
] | Two of the major open questions in particle physics are: (1) Why are the elementary fermionic particles that are so far observed have such low mass-energy compared to the Planck energy scale? And (2), what mechanical energy may be counterbalancing the divergent electrostatic and strong force energies of point-like charged fermions in the vicinity of the Planck scale? In this paper, using a hitherto unrecognized mechanism derived from the non-linear amelioration of Dirac equation known as the Hehl-Datta equation within Einstein-Cartan-Sciama-Kibble (ECSK) extension of general relativity, we present detailed numerical estimates suggesting that the mechanical energy arising from the gravity-induced self-interaction in the ECSK theory can address both of these questions in tandem. |
1904.09053 | Sumanta Chakraborty | Sumanta Chakraborty, Dawood Kothawala and Alessandro Pesci | Raychaudhuri equation with zero point length | Revised Version, Published, 16 pages, no figures | Phys. Lett. B 797, 134877 (2019) | 10.1016/j.physletb.2019.134877 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Raychaudhuri equation for a geodesic congruence in the presence of a
zero-point length has been investigated. This is directly related to the
small-scale structure of spacetime and possibly captures some quantum gravity
effects. The existence of such a minimum distance between spacetime events
modifies the associated metric structure and hence the expansion as well as its
rate of change deviates from standard expectations. This holds true for any
kind of geodesic congruences, including time-like and null geodesics.
Interestingly, this construction works with generic spacetime geometry without
any need of invoking any particular symmetry. In particular, inclusion of a
zero-point length results into a non-vanishing cross-sectional area for the
geodesic congruences even in the coincidence limit, thus avoiding formation of
caustics. This will have implications for both time-like and null geodesic
congruences, which may lead to avoidance of singularity formation in the
quantum spacetime.
| [
{
"created": "Fri, 19 Apr 2019 02:45:49 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Aug 2019 00:47:25 GMT",
"version": "v2"
}
] | 2019-09-04 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Kothawala",
"Dawood",
""
],
[
"Pesci",
"Alessandro",
""
]
] | The Raychaudhuri equation for a geodesic congruence in the presence of a zero-point length has been investigated. This is directly related to the small-scale structure of spacetime and possibly captures some quantum gravity effects. The existence of such a minimum distance between spacetime events modifies the associated metric structure and hence the expansion as well as its rate of change deviates from standard expectations. This holds true for any kind of geodesic congruences, including time-like and null geodesics. Interestingly, this construction works with generic spacetime geometry without any need of invoking any particular symmetry. In particular, inclusion of a zero-point length results into a non-vanishing cross-sectional area for the geodesic congruences even in the coincidence limit, thus avoiding formation of caustics. This will have implications for both time-like and null geodesic congruences, which may lead to avoidance of singularity formation in the quantum spacetime. |
0911.5317 | Jiri Podolsky | Jiri Podolsky, Otakar Svitek | Past horizons in Robinson-Trautman spacetimes with a cosmological
constant | 13 pages, 5 figures. To appear in Phys. Rev. D | Phys.Rev.D80:124042,2009 | 10.1103/PhysRevD.80.124042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study past horizons in the class of type II Robinson-Trautman vacuum
spacetimes with a cosmological constant. These exact radiative solutions of
Einstein's equations exist in the future of any sufficiently smooth initial
data, and they approach the corresponding spherically symmetric
Schwarzschild-(anti-)de Sitter metric. By analytic methods we investigate the
existence, uniqueness, location and character of the past horizons in these
spacetimes. In particular, we generalize the Penrose-Tod equation for
marginally trapped surfaces, which form such white-hole horizons, to the case
of a nonvanishing cosmological constant, we analyze behavior of its solutions
and visualize their evolutions. We also prove that these horizons are explicit
examples of an outer trapping horizon and a dynamical horizon, so that they are
spacelike past outer horizons.
| [
{
"created": "Fri, 27 Nov 2009 17:30:20 GMT",
"version": "v1"
}
] | 2010-04-21 | [
[
"Podolsky",
"Jiri",
""
],
[
"Svitek",
"Otakar",
""
]
] | We study past horizons in the class of type II Robinson-Trautman vacuum spacetimes with a cosmological constant. These exact radiative solutions of Einstein's equations exist in the future of any sufficiently smooth initial data, and they approach the corresponding spherically symmetric Schwarzschild-(anti-)de Sitter metric. By analytic methods we investigate the existence, uniqueness, location and character of the past horizons in these spacetimes. In particular, we generalize the Penrose-Tod equation for marginally trapped surfaces, which form such white-hole horizons, to the case of a nonvanishing cosmological constant, we analyze behavior of its solutions and visualize their evolutions. We also prove that these horizons are explicit examples of an outer trapping horizon and a dynamical horizon, so that they are spacelike past outer horizons. |
gr-qc/0012090 | Kechkin O. V. | Oleg V. Kechkin | New matrix formalism for heterotic string theory on a torus | 19 pages in LaTex | null | null | null | gr-qc | null | A new Lagrange formalism based on the use of a single scalar (d+1)X(d+1+n)
matrix potential is developed for the low-energy heterotic string theory with n
U(1) gauge fields compactified from d+3 to 3 dimensions on a torus. This
formalism also includes three pairs on-shell defined scalar and vector matrix
potentials of the dimensions (d+1)X(d+1), (d+1)X(d+1+n) and (d+1+n)X(d+1+n).
All these potentials undergo linear transformations when the group of charging
symmetries acts.
| [
{
"created": "Thu, 21 Dec 2000 22:34:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kechkin",
"Oleg V.",
""
]
] | A new Lagrange formalism based on the use of a single scalar (d+1)X(d+1+n) matrix potential is developed for the low-energy heterotic string theory with n U(1) gauge fields compactified from d+3 to 3 dimensions on a torus. This formalism also includes three pairs on-shell defined scalar and vector matrix potentials of the dimensions (d+1)X(d+1), (d+1)X(d+1+n) and (d+1+n)X(d+1+n). All these potentials undergo linear transformations when the group of charging symmetries acts. |
0802.1914 | Roman Sverdlov | Roman Sverdlov | A Geometrical Description of Spinor Fields | 8 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this paper is to present the way to define fermionic fields and
their Lagrangians in terms of three orthogonal vector fields of norm 1 together
with two real valued scalar fields. This paper is based on a toy model where
there are no Grassmann variables.
| [
{
"created": "Wed, 13 Feb 2008 21:43:39 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Aug 2008 04:08:12 GMT",
"version": "v2"
}
] | 2008-08-05 | [
[
"Sverdlov",
"Roman",
""
]
] | The goal of this paper is to present the way to define fermionic fields and their Lagrangians in terms of three orthogonal vector fields of norm 1 together with two real valued scalar fields. This paper is based on a toy model where there are no Grassmann variables. |
1907.03765 | Antonios Tsokaros A. | Antonios Tsokaros, Milton Ruiz, Lunan Sun, Stuart L. Shapiro, K\=oji
Ury\=u | Dynamically stable ergostars exist: General relativistic models and
simulations | 5 pages, 3 figures, to appear in PRL | Phys. Rev. Lett. 123, 231103 (2019) | 10.1103/PhysRevLett.123.231103 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the first dynamically stable ergostars (equilibrium neutron
stars that contain an ergoregion) for a compressible, causal equation of state.
We demonstrate their stability by evolving both strict and perturbed
equilibrium configurations in full general relativity for over a hundred
dynamical timescales ($\gtrsim 30$ rotational periods) and observing their
stationary behavior. This stability is in contrast to earlier models which
prove radially unstable to collapse. Our solutions are highly differentially
rotating hypermassive neutron stars with a corresponding spherical compaction
of $C=0.3$. Such ergostars can provide new insights into the geometry of
spacetimes around highly compact, rotating objects and on the equation of state
at supranuclear densities. Ergostars may form as remnants of extreme binary
neutron star mergers and possibly provide another mechanism for powering short
gamma-ray bursts.
| [
{
"created": "Mon, 8 Jul 2019 18:00:02 GMT",
"version": "v1"
},
{
"created": "Sun, 3 Nov 2019 04:16:42 GMT",
"version": "v2"
}
] | 2019-12-11 | [
[
"Tsokaros",
"Antonios",
""
],
[
"Ruiz",
"Milton",
""
],
[
"Sun",
"Lunan",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Uryū",
"Kōji",
""
]
] | We construct the first dynamically stable ergostars (equilibrium neutron stars that contain an ergoregion) for a compressible, causal equation of state. We demonstrate their stability by evolving both strict and perturbed equilibrium configurations in full general relativity for over a hundred dynamical timescales ($\gtrsim 30$ rotational periods) and observing their stationary behavior. This stability is in contrast to earlier models which prove radially unstable to collapse. Our solutions are highly differentially rotating hypermassive neutron stars with a corresponding spherical compaction of $C=0.3$. Such ergostars can provide new insights into the geometry of spacetimes around highly compact, rotating objects and on the equation of state at supranuclear densities. Ergostars may form as remnants of extreme binary neutron star mergers and possibly provide another mechanism for powering short gamma-ray bursts. |
gr-qc/0107064 | Spyros S. Kouris | Spyros S. Kouris | The Weyl tensor two-point function in de Sitter spacetime | 9 pages, no figures | Class.Quant.Grav. 18 (2001) 4961-4968 | 10.1088/0264-9381/18/22/316 | null | gr-qc | null | We present an expression for the Weyl-Weyl two-point function in de Sitter
spacetime, based on a recently calculated covariant graviton two-point function
with one gauge parameter. We find that the Weyl-Weyl two-point function falls
off with distance like r^{-4}, where r is spacelike coordinate separation
between the two points.
| [
{
"created": "Wed, 18 Jul 2001 20:17:43 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Kouris",
"Spyros S.",
""
]
] | We present an expression for the Weyl-Weyl two-point function in de Sitter spacetime, based on a recently calculated covariant graviton two-point function with one gauge parameter. We find that the Weyl-Weyl two-point function falls off with distance like r^{-4}, where r is spacelike coordinate separation between the two points. |
0803.3433 | Thomas Sotiriou | Enrico Barausse and Thomas P. Sotiriou | Perturbed Kerr Black Holes can probe deviations from General Relativity | minor changes to match version published in Phys. Rev. Lett | Phys.Rev.Lett.101:099001,2008 | 10.1103/PhysRevLett.101.099001 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Although the Kerr solution is common to many gravity theories, its
perturbations are different in different theories. Hence, perturbed Kerr black
holes can probe deviations from General Relativity.
| [
{
"created": "Mon, 24 Mar 2008 17:51:18 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Sep 2008 09:20:21 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Barausse",
"Enrico",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | Although the Kerr solution is common to many gravity theories, its perturbations are different in different theories. Hence, perturbed Kerr black holes can probe deviations from General Relativity. |
2207.08847 | Jorge Delgado | Jorge F. M. Delgado | Epicyclic Frequencies for a Generic Ultracompact Object | 12 pages, 5 figures | null | 10.1103/PhysRevD.106.064054 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Recently, it has been shown that the radial stability of a light-ring (LR) in
a spacetime generated by a stationary, axisymmetric, asymptotically flat object
with a $\mathbb{Z}_2$ symmetry determines the possibility and radial stability
of timelike circular orbits (TCOs) around the LR. In this paper, we generalise
this result by also considering the vertical (angular) stability of the orbits
through the study of the radial and vertical epicyclic frequencies. We show
that the vertical stability of the LR only determines the vertical stability of
the TCOs around it. A relation between the sum of the squared epicyclic
frequencies and the Ricci tensor is also provided. With such relation, we show
that objects with radially and vertically unstable LRs (TCOs) violate the null
(strong) energy condition.
| [
{
"created": "Mon, 18 Jul 2022 18:00:13 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jan 2023 19:00:02 GMT",
"version": "v2"
}
] | 2023-01-04 | [
[
"Delgado",
"Jorge F. M.",
""
]
] | Recently, it has been shown that the radial stability of a light-ring (LR) in a spacetime generated by a stationary, axisymmetric, asymptotically flat object with a $\mathbb{Z}_2$ symmetry determines the possibility and radial stability of timelike circular orbits (TCOs) around the LR. In this paper, we generalise this result by also considering the vertical (angular) stability of the orbits through the study of the radial and vertical epicyclic frequencies. We show that the vertical stability of the LR only determines the vertical stability of the TCOs around it. A relation between the sum of the squared epicyclic frequencies and the Ricci tensor is also provided. With such relation, we show that objects with radially and vertically unstable LRs (TCOs) violate the null (strong) energy condition. |
2403.00310 | Amarkumar Agrawal | P.H.R.S. Moraes, A.S. Agrawal, and B. Mishra | Wormholes in the f(R,L,T) theory of gravity | 5 Pages, 4 figures | Physics Letter B, Volume 855, August 2024 | 10.1016/j.physletb.2024.138818 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Morris and Thorne developed wormhole solutions in the late 1980s when they
discovered a recipe that wormholes must follow for travelers to cross them
safely. They describe exotic matter as satisfying $-p_{r} > \rho$, where
$p_{r}$ is the radial pressure and $\rho$ is the energy density of the
wormhole. This is a notable characteristic of the General Relativity Theory.
The current article discusses traversable wormhole solutions in $f(R, L,
T)=R+\alpha L+\beta T$, with $\alpha$ and $\beta$ are model parameters. The
wormhole solutions presented here satisfy the metric constraints of
traversability while remarkably avoiding the exotic matter condition,
indicating that $f(R, L, T)$ gravity wormholes can be filled with ordinary
matter. The derived solutions for the shape function of the wormhole meet the
required metric conditions. They exhibit behavior that is comparable to that of
wormholes reported in earlier references, which is also the case for our
solutions for the energy density of such objects.
| [
{
"created": "Fri, 1 Mar 2024 06:23:12 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jun 2024 11:43:19 GMT",
"version": "v2"
}
] | 2024-06-25 | [
[
"Moraes",
"P. H. R. S.",
""
],
[
"Agrawal",
"A. S.",
""
],
[
"Mishra",
"B.",
""
]
] | Morris and Thorne developed wormhole solutions in the late 1980s when they discovered a recipe that wormholes must follow for travelers to cross them safely. They describe exotic matter as satisfying $-p_{r} > \rho$, where $p_{r}$ is the radial pressure and $\rho$ is the energy density of the wormhole. This is a notable characteristic of the General Relativity Theory. The current article discusses traversable wormhole solutions in $f(R, L, T)=R+\alpha L+\beta T$, with $\alpha$ and $\beta$ are model parameters. The wormhole solutions presented here satisfy the metric constraints of traversability while remarkably avoiding the exotic matter condition, indicating that $f(R, L, T)$ gravity wormholes can be filled with ordinary matter. The derived solutions for the shape function of the wormhole meet the required metric conditions. They exhibit behavior that is comparable to that of wormholes reported in earlier references, which is also the case for our solutions for the energy density of such objects. |
1209.1344 | Jonathan Ziprick | Jonathan Ziprick | Point particles in 2+1 dimensions: toward a semiclassical loop gravity
formulation | for Theory Canada 7 conference proceedings in Canadian Journal of
Physics | Canadian Journal of Physics 91(6) 467 (2013) | 10.1139/cjp-2012-0385 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study point particles in 2+1 dimensional first order gravity using a
triangulation to fix the connection and frame-field. The Hamiltonian is reduced
to a boundary term which yields the total mass. The triangulation is dynamical
with non-trivial transitions occurring when a particle meets an edge. This
framework facilitates a description in terms of the loop gravity phase space.
| [
{
"created": "Thu, 6 Sep 2012 17:04:50 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Ziprick",
"Jonathan",
""
]
] | We study point particles in 2+1 dimensional first order gravity using a triangulation to fix the connection and frame-field. The Hamiltonian is reduced to a boundary term which yields the total mass. The triangulation is dynamical with non-trivial transitions occurring when a particle meets an edge. This framework facilitates a description in terms of the loop gravity phase space. |
gr-qc/0603125 | M. Meyer | S. Deser | Why is the metric invertible? | 3 pages | Class.Quant.Grav.23:4539-4541,2006 | 10.1088/0264-9381/23/13/N01 | BRX TH-549 | gr-qc hep-th | null | We raise, and provide an (unsatisfactory) answer to, the title's question:
why, unlike all other fields, does the gravitational "metric" variable not have
zero vacuum? After formulating, without begging it, we exhibit additions to the
conventional action that express existence of the inverse through a field
equation.
| [
{
"created": "Thu, 30 Mar 2006 18:48:22 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Deser",
"S.",
""
]
] | We raise, and provide an (unsatisfactory) answer to, the title's question: why, unlike all other fields, does the gravitational "metric" variable not have zero vacuum? After formulating, without begging it, we exhibit additions to the conventional action that express existence of the inverse through a field equation. |
1702.06699 | Crucean Cosmin | Cosmin Crucean and Mihaela-Andreea B\u{a}loi | Perturbative approach to the problem of particle production in electric
field on de Sitter universe | 14 pages, 4 figures | Mod. Phys. Lett. A 31, 1650082 (2016) | 10.1142/S0217732316500826 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter we study the problem of scalar particle production in external
electric field in de Sitter geometry. The total probability is calculated using
the previously obtained result in Ref.\cite{6} for transition amplitude in
external electric field on de Sitter space. Then we make a graphical study of
the total probability in terms of the ratio mass of the particle/expansion
factor. Our results show that the probability depend of the direction in which
the particles are emitted and that the probability becomes maxim when particles
are emitted on the direction of the electric field. In the Minkowski limit we
obtain that the probability is vanishing.
| [
{
"created": "Wed, 22 Feb 2017 08:17:39 GMT",
"version": "v1"
}
] | 2017-02-23 | [
[
"Crucean",
"Cosmin",
""
],
[
"Băloi",
"Mihaela-Andreea",
""
]
] | In this letter we study the problem of scalar particle production in external electric field in de Sitter geometry. The total probability is calculated using the previously obtained result in Ref.\cite{6} for transition amplitude in external electric field on de Sitter space. Then we make a graphical study of the total probability in terms of the ratio mass of the particle/expansion factor. Our results show that the probability depend of the direction in which the particles are emitted and that the probability becomes maxim when particles are emitted on the direction of the electric field. In the Minkowski limit we obtain that the probability is vanishing. |
0811.2910 | Attila Andai | Istvan Nemeti, Judit X. Madarasz, Hajnal Andreka, Attila Andai | Visualizing some ideas about Godel-type rotating universes | 84 pages, 70 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper consists mostly of pictures visualizing ideas leading to Godel's
rotating cosmological model. The pictures are constructed according to concrete
metric tensor fields. Information about these are in the last chapters. The
main aim is to visualise ideas.
| [
{
"created": "Tue, 18 Nov 2008 06:40:53 GMT",
"version": "v1"
}
] | 2008-11-19 | [
[
"Nemeti",
"Istvan",
""
],
[
"Madarasz",
"Judit X.",
""
],
[
"Andreka",
"Hajnal",
""
],
[
"Andai",
"Attila",
""
]
] | This paper consists mostly of pictures visualizing ideas leading to Godel's rotating cosmological model. The pictures are constructed according to concrete metric tensor fields. Information about these are in the last chapters. The main aim is to visualise ideas. |
0706.3266 | Shintaro Sawayama | Shintaro Sawayama | Quantization of the metric diagonal spacetime with Gaussian normal
coordinates | 3 pages, no figures | null | null | null | gr-qc | null | In the analysis of the Wheeler-DeWitt equation, we have simplified the
Hamiltonian constraint of the Wheeler-DeWitt equation using the coordinate
transformation. The coordinate is choose such that metric becomes diagonal and
as Gaussian normal coordinate. Or we treat small universe so that the metric
become diagonal and universe is covered by Gaussian normal coordinates. We have
solved the Wheeler-DeWitt equation of such universes. Such that universe
contains Biancki I type universe or the black hole universe.
| [
{
"created": "Fri, 22 Jun 2007 06:39:14 GMT",
"version": "v1"
}
] | 2007-06-25 | [
[
"Sawayama",
"Shintaro",
""
]
] | In the analysis of the Wheeler-DeWitt equation, we have simplified the Hamiltonian constraint of the Wheeler-DeWitt equation using the coordinate transformation. The coordinate is choose such that metric becomes diagonal and as Gaussian normal coordinate. Or we treat small universe so that the metric become diagonal and universe is covered by Gaussian normal coordinates. We have solved the Wheeler-DeWitt equation of such universes. Such that universe contains Biancki I type universe or the black hole universe. |
gr-qc/0208085 | Mario Everaldo de Souza | Mario Everaldo de Souza | Gravity cannot be quantized | 6 pages, Latex | null | null | DFI-08-2002 | gr-qc astro-ph quant-ph | null | This work shows that the gravitational field is rather an unusual field and
cannot be quantized due to the absence of a fermion charge carrier. When its
existence is assumed quite strange results are obtained for its mass. And this
means that the graviton does not exist either since bosons act between fermion
states.
| [
{
"created": "Tue, 27 Aug 2002 20:43:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Souza",
"Mario Everaldo",
""
]
] | This work shows that the gravitational field is rather an unusual field and cannot be quantized due to the absence of a fermion charge carrier. When its existence is assumed quite strange results are obtained for its mass. And this means that the graviton does not exist either since bosons act between fermion states. |
0802.1588 | Robert Brout | R. Brout | Entanglement and Thermodynamics of Black Hole Entropy | 5 pages | Int.J.Mod.Phys.D17:2549-2553,2009 | 10.1142/S0218271808014187 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using simple conditions drawn from the stability of the cosmos in terms of
vacuum energy density, the cut-off momentum of entanglement is related to the
planckian mass. In so doing the black hole entropy is shown to be independent
of the number of field species that contribute to vacuum fluctuations. And this
is in spite of the fact that the number of field species is a linear
multiplicand of the entanglement entropy when this latter is expressed in terms
of the fundamental momentum cut-off of all fields.
| [
{
"created": "Tue, 12 Feb 2008 18:34:12 GMT",
"version": "v1"
}
] | 2009-03-20 | [
[
"Brout",
"R.",
""
]
] | Using simple conditions drawn from the stability of the cosmos in terms of vacuum energy density, the cut-off momentum of entanglement is related to the planckian mass. In so doing the black hole entropy is shown to be independent of the number of field species that contribute to vacuum fluctuations. And this is in spite of the fact that the number of field species is a linear multiplicand of the entanglement entropy when this latter is expressed in terms of the fundamental momentum cut-off of all fields. |
2007.10422 | Oscar Lasso Andino | Oscar Lasso Andino, Christian L. V\'asconez | The quantum non-linear $\sigma$-model RG flow and integrability in
wormhole geometries | 18 pg | Nuclear Physics B, Volume 990, 2023, 116178 | 10.1016/j.nuclphysb.2023.116178 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The target space of the non-linear $\sigma$-model is a Riemannian manifold.
Although it can be any Riemannian metric, there are certain physically
interesting geometries which are worth to study. Here, we numerically evolve
the time-symmetric foliations of a family of spherically symmetric
asymptotically flat wormholes under the $1$-loop renormalization group flow of
the non-linear $\sigma$-model, the Ricci flow, and under the $2$-loop
approximation, RG-2 flow. We rely over some theorems adapted from the compact
case for studying the evolution of different wormhole types, specially those
with high curvature zones. Some metrics expand and others contract at the
beginning of the flow, however, all metrics pinch-off at a certain time. This
is related with the fact that the flow does not converge to a fixed point when
its starting geometry is the spatial sections of a Morris-Thorne wormhole, and
therefore the corresponding non-linear $\sigma$-model is
non-integrable/renormalizable. We present a numerical study of the evolution of
wormhole singularities in three dimensions extending the theoretical
estimations. Finally, we compute the evolution of the Hamilton's entropy and
the Brown-York energy.
| [
{
"created": "Mon, 20 Jul 2020 19:27:46 GMT",
"version": "v1"
},
{
"created": "Tue, 10 May 2022 19:02:08 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Feb 2023 02:57:56 GMT",
"version": "v3"
}
] | 2023-04-12 | [
[
"Andino",
"Oscar Lasso",
""
],
[
"Vásconez",
"Christian L.",
""
]
] | The target space of the non-linear $\sigma$-model is a Riemannian manifold. Although it can be any Riemannian metric, there are certain physically interesting geometries which are worth to study. Here, we numerically evolve the time-symmetric foliations of a family of spherically symmetric asymptotically flat wormholes under the $1$-loop renormalization group flow of the non-linear $\sigma$-model, the Ricci flow, and under the $2$-loop approximation, RG-2 flow. We rely over some theorems adapted from the compact case for studying the evolution of different wormhole types, specially those with high curvature zones. Some metrics expand and others contract at the beginning of the flow, however, all metrics pinch-off at a certain time. This is related with the fact that the flow does not converge to a fixed point when its starting geometry is the spatial sections of a Morris-Thorne wormhole, and therefore the corresponding non-linear $\sigma$-model is non-integrable/renormalizable. We present a numerical study of the evolution of wormhole singularities in three dimensions extending the theoretical estimations. Finally, we compute the evolution of the Hamilton's entropy and the Brown-York energy. |
2312.07400 | Yongqiang Wang | Long-Xing Huang, Shi-Xian Sun, Yong-Qiang Wang | Frozen Bardeen-Dirac stars and light ball | 22 pages, 7 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study solutions of a static spherically symmetric system,
which is composed of the coupling with the Bardeen action and two Dirac fields.
For the case where only the Bardeen action is present, the magnetic charge $q$
can be infinite, then when the magnetic charge is greater than a certain value
$q_b$, there exists a black hole solution, which is called the Bardeen black
hole (BBH). However, if the Dirac field is introduced, we find that the
magnetic charge can only be smaller than the critical value $q_b$, in which
there is no black hole solution. Moreover, in the region $q<q_b$, we find that
if the magnetic charge exceeds another critical value $q_c$ (i.e.,
$q_c<q<q_b$), the frequency of the Dirac field can approach zero, and the
solution where a critical horizon appears is similar to an extremal black hole
outside the critical horizon but has a nonsingular interior. The Dirac fields
are also almost concentrated within it. In fact, this is a frozen star
solution, we call such solutions frozen Bardeen-Dirac stars (FBDSs). We analyze
the light rings of FBDSs and find that there exists a ``true" light ring
outside the critical horizon, but inside it, the velocity of photons is very
close to zero, which leads to the formation of a ``light ball" inside the
critical horizon.
| [
{
"created": "Tue, 12 Dec 2023 16:15:45 GMT",
"version": "v1"
}
] | 2023-12-13 | [
[
"Huang",
"Long-Xing",
""
],
[
"Sun",
"Shi-Xian",
""
],
[
"Wang",
"Yong-Qiang",
""
]
] | In this paper, we study solutions of a static spherically symmetric system, which is composed of the coupling with the Bardeen action and two Dirac fields. For the case where only the Bardeen action is present, the magnetic charge $q$ can be infinite, then when the magnetic charge is greater than a certain value $q_b$, there exists a black hole solution, which is called the Bardeen black hole (BBH). However, if the Dirac field is introduced, we find that the magnetic charge can only be smaller than the critical value $q_b$, in which there is no black hole solution. Moreover, in the region $q<q_b$, we find that if the magnetic charge exceeds another critical value $q_c$ (i.e., $q_c<q<q_b$), the frequency of the Dirac field can approach zero, and the solution where a critical horizon appears is similar to an extremal black hole outside the critical horizon but has a nonsingular interior. The Dirac fields are also almost concentrated within it. In fact, this is a frozen star solution, we call such solutions frozen Bardeen-Dirac stars (FBDSs). We analyze the light rings of FBDSs and find that there exists a ``true" light ring outside the critical horizon, but inside it, the velocity of photons is very close to zero, which leads to the formation of a ``light ball" inside the critical horizon. |
1908.04223 | Hirotaka Yoshino | Hirotaka Yoshino, Kazuma Takahashi, Ken-ichi Nakao | How does a collapsing star look? | 55 pages, 21 figures, published version | Phys. Rev. D 100, 084062 (2019) | 10.1103/PhysRevD.100.084062 | OCU-PHYS-507, AP-GR-156, NITEP 27 | gr-qc astro-ph.GA hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Time evolution of an optical image of a pressureless star under gravitational
collapse is studied in the geometric optics approximation. The star surface is
assumed to emit radiation obeying Lambert's cosine law but with an arbitrary
spectral intensity in the comoving frame. We develop a formalism for predicting
observable quantities by photon counting and by radiometry, in particular,
spectral photon flux and spectral radiant flux. Then, this method is applied to
the two cases: One is monochromatic radiation, and the other is blackbody
radiation. The two kinds of spectral flux are calculated numerically for each
case. It is reconfirmed that the redshift factor remains finite and the star
becomes gradually invisible due to decay of the photon flux. We also develop an
approximate method to present analytic formulas that describe the late time
behavior. A possible connection of our study to observation of high-energy
neutrinos is briefly discussed.
| [
{
"created": "Mon, 12 Aug 2019 16:23:06 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Nov 2019 16:23:32 GMT",
"version": "v2"
}
] | 2019-11-04 | [
[
"Yoshino",
"Hirotaka",
""
],
[
"Takahashi",
"Kazuma",
""
],
[
"Nakao",
"Ken-ichi",
""
]
] | Time evolution of an optical image of a pressureless star under gravitational collapse is studied in the geometric optics approximation. The star surface is assumed to emit radiation obeying Lambert's cosine law but with an arbitrary spectral intensity in the comoving frame. We develop a formalism for predicting observable quantities by photon counting and by radiometry, in particular, spectral photon flux and spectral radiant flux. Then, this method is applied to the two cases: One is monochromatic radiation, and the other is blackbody radiation. The two kinds of spectral flux are calculated numerically for each case. It is reconfirmed that the redshift factor remains finite and the star becomes gradually invisible due to decay of the photon flux. We also develop an approximate method to present analytic formulas that describe the late time behavior. A possible connection of our study to observation of high-energy neutrinos is briefly discussed. |
2404.07782 | Miguel Zumalacarregui | Julius Streibert, Hector O. Silva, Miguel Zumalac\'arregui | Gravitational-wave lensing in Einstein-aether theory | 19 pages plus appendices, 4 figures | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Einstein-aether theory provides a model to test the validity of local Lorentz
invariance in gravitational interactions. The speed of gravitational waves as
measured from the binary neutron star event GW170817 sets stringent limits on
Einstein-aether theory, but only on a combination of the theory's free
parameters. For this reason, a significant part of the theory's parameter space
remains unconstrained by observations. Motivated by this, we explore the
propagation of gravitational waves in Einstein-aether theory over an
inhomogeneous background (i.e., gravitational wave lensing) as a potential
mechanism to break the degeneracies between the theory's free parameters, and
hence enable new constraints on the theory to be obtained. By bringing the
field equations into the form of the so-called kinetic matrix and applying a
formalism known as the propagation eigenstate framework, we find that the speed
of gravitational waves is modified by inhomogeneities in the aether field.
However, the modification is common to both gravitational polarizations and
vanishes in the limit in which gravitational waves propagate with luminal
speed. This lens-dependent gravitational wave speed contrasts with the
lens-induced birefringence observed in other theories beyond general
relativity, like Horndeski's theory. While the potential to improve tests based
on gravitational-wave speed is limited, our formalism sets the basis to fully
describe signal propagation over inhomogeneous spacetimes in Einstein-aether
theory and other extensions of general relativity.
| [
{
"created": "Thu, 11 Apr 2024 14:21:47 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Apr 2024 12:56:27 GMT",
"version": "v2"
}
] | 2024-05-01 | [
[
"Streibert",
"Julius",
""
],
[
"Silva",
"Hector O.",
""
],
[
"Zumalacárregui",
"Miguel",
""
]
] | Einstein-aether theory provides a model to test the validity of local Lorentz invariance in gravitational interactions. The speed of gravitational waves as measured from the binary neutron star event GW170817 sets stringent limits on Einstein-aether theory, but only on a combination of the theory's free parameters. For this reason, a significant part of the theory's parameter space remains unconstrained by observations. Motivated by this, we explore the propagation of gravitational waves in Einstein-aether theory over an inhomogeneous background (i.e., gravitational wave lensing) as a potential mechanism to break the degeneracies between the theory's free parameters, and hence enable new constraints on the theory to be obtained. By bringing the field equations into the form of the so-called kinetic matrix and applying a formalism known as the propagation eigenstate framework, we find that the speed of gravitational waves is modified by inhomogeneities in the aether field. However, the modification is common to both gravitational polarizations and vanishes in the limit in which gravitational waves propagate with luminal speed. This lens-dependent gravitational wave speed contrasts with the lens-induced birefringence observed in other theories beyond general relativity, like Horndeski's theory. While the potential to improve tests based on gravitational-wave speed is limited, our formalism sets the basis to fully describe signal propagation over inhomogeneous spacetimes in Einstein-aether theory and other extensions of general relativity. |
1606.05590 | Johannes Noller | Philippe Brax, Anne-Christine Davis, Johannes Noller | Dark Energy and Doubly Coupled Bigravity | 47 pages, 8 figures | Class.Quant.Grav. 34 (2017) no.9, 095014 | 10.1088/1361-6382/aa6856 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the late time cosmology and the gravitational properties of doubly
coupled bigravity in the constrained vielbein formalism (equivalent to the
metric formalism) when the mass of the massive graviton is of the order of the
present Hubble rate. We focus on one of the two branches of background
cosmology where the ratio between the scale factors of the two metrics is
algebraically determined. The Universe evolves from a matter dominated epoch to
a dark energy dominated era where the equation of state of dark energy can
always be made close to -1 now by appropriately tuning the graviton mass. We
also analyse the perturbative spectrum of the theory in the quasi static
approximation well below the strong coupling scale where no instability is
present and we show that there are five scalar degrees of freedom, two vectors
and two gravitons. In a cosmological FRW background for both metrics, four of
the five scalars are Newtonian potentials which lead to a modification of
gravity on large scales. In this scalar sector, gravity is modified with
effects on both the growth of structure and the lensing potential. In
particular, we find that the $\Sigma$ parameter governing the Poisson equation
of the weak lensing potential can differ from one in the recent past of the
Universe. Overall, the nature of the modification of gravity at low energy,
which reveals itself in the growth of structure and the lensing potential, is
intrinsically dependent on the couplings to matter and the potential term of
the vielbeins. We also find that the time variation of Newton's constant in the
Jordan frame can easily satisfy the bound from solar system tests of gravity.
Finally we show that the two gravitons present in the spectrum have a
non-trivial mass matrix whose origin follows from the potential term of
bigravity. This mixing leads to gravitational birefringence.
| [
{
"created": "Fri, 17 Jun 2016 17:02:05 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Nov 2016 15:56:17 GMT",
"version": "v2"
}
] | 2017-04-21 | [
[
"Brax",
"Philippe",
""
],
[
"Davis",
"Anne-Christine",
""
],
[
"Noller",
"Johannes",
""
]
] | We analyse the late time cosmology and the gravitational properties of doubly coupled bigravity in the constrained vielbein formalism (equivalent to the metric formalism) when the mass of the massive graviton is of the order of the present Hubble rate. We focus on one of the two branches of background cosmology where the ratio between the scale factors of the two metrics is algebraically determined. The Universe evolves from a matter dominated epoch to a dark energy dominated era where the equation of state of dark energy can always be made close to -1 now by appropriately tuning the graviton mass. We also analyse the perturbative spectrum of the theory in the quasi static approximation well below the strong coupling scale where no instability is present and we show that there are five scalar degrees of freedom, two vectors and two gravitons. In a cosmological FRW background for both metrics, four of the five scalars are Newtonian potentials which lead to a modification of gravity on large scales. In this scalar sector, gravity is modified with effects on both the growth of structure and the lensing potential. In particular, we find that the $\Sigma$ parameter governing the Poisson equation of the weak lensing potential can differ from one in the recent past of the Universe. Overall, the nature of the modification of gravity at low energy, which reveals itself in the growth of structure and the lensing potential, is intrinsically dependent on the couplings to matter and the potential term of the vielbeins. We also find that the time variation of Newton's constant in the Jordan frame can easily satisfy the bound from solar system tests of gravity. Finally we show that the two gravitons present in the spectrum have a non-trivial mass matrix whose origin follows from the potential term of bigravity. This mixing leads to gravitational birefringence. |
gr-qc/0004034 | Jerry B. Griffiths | G. A. Alekseev and J. B. Griffiths | Infinite hierarchies of exact solutions of the Einstein and
Einstein-Maxwell equations for interacting waves and inhomogeneous
cosmologies | 7 pages, minor correction and reduction to conform with published
version | Phys.Rev.Lett.84:5247-5250,2000 | 10.1103/PhysRevLett.84.5247 | null | gr-qc | null | For space-times with two spacelike isometries, we present infinite
hierarchies of exact solutions of the Einstein and Einstein--Maxwell equations
as represented by their Ernst potentials. This hierarchy contains three
arbitrary rational functions of an auxiliary complex parameter. They are
constructed using the so called `monodromy transform' approach and our new
method for the solution of the linear singular integral equation form of the
reduced Einstein equations. The solutions presented, which describe
inhomogeneous cosmological models or gravitational and electromagnetic waves
and their interactions, include a number of important known solutions as
particular cases.
| [
{
"created": "Wed, 12 Apr 2000 08:59:40 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jun 2000 11:37:11 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Alekseev",
"G. A.",
""
],
[
"Griffiths",
"J. B.",
""
]
] | For space-times with two spacelike isometries, we present infinite hierarchies of exact solutions of the Einstein and Einstein--Maxwell equations as represented by their Ernst potentials. This hierarchy contains three arbitrary rational functions of an auxiliary complex parameter. They are constructed using the so called `monodromy transform' approach and our new method for the solution of the linear singular integral equation form of the reduced Einstein equations. The solutions presented, which describe inhomogeneous cosmological models or gravitational and electromagnetic waves and their interactions, include a number of important known solutions as particular cases. |
1811.10905 | Vahid Kamali | Vahid Kamali | Non-minimal Higgs inflation in the context of warm scenario in the light
of Planck data | 6 pages, 4 figures, the paper has been accepted by EPJC | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the non-minimally Higgs inflaton (HI) model in the context of
warm inflation scenario. Warm little inflaton (WLI) model considers the little
Higgs boson as inflaton. The concerns of warm inflation model can be eliminated
in WLI model. There is a special case of dissipation parameter in WLI model
$\Gamma=\Gamma_0 T$. Using this parameter, we study the potential of HI in
Einstein frame . Finally we will constrain the parameters of our model using
current Planck observational data.
| [
{
"created": "Tue, 27 Nov 2018 10:42:04 GMT",
"version": "v1"
}
] | 2018-11-28 | [
[
"Kamali",
"Vahid",
""
]
] | We investigate the non-minimally Higgs inflaton (HI) model in the context of warm inflation scenario. Warm little inflaton (WLI) model considers the little Higgs boson as inflaton. The concerns of warm inflation model can be eliminated in WLI model. There is a special case of dissipation parameter in WLI model $\Gamma=\Gamma_0 T$. Using this parameter, we study the potential of HI in Einstein frame . Finally we will constrain the parameters of our model using current Planck observational data. |
1612.02853 | David Sloan | David Sloan and Pedro Ferreira | The Cosmology of an Infinite Dimensional Universe | 10 pages, significant revisions from previous version | Phys. Rev. D 96, 043527 (2017) | 10.1103/PhysRevD.96.043527 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a universe with an arbitrary number of extra dimensions, $N$. We
present a new method for constructing the cosmological equations of motion and
find analytic solutions with an explicit dependence on $N$. When we take the
$N\rightarrow\infty$ limit we find novel, emergent behaviour which
distinguishes it from normal Kaluza-Klein universes.
| [
{
"created": "Thu, 8 Dec 2016 21:49:06 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Aug 2017 20:59:37 GMT",
"version": "v2"
}
] | 2017-09-06 | [
[
"Sloan",
"David",
""
],
[
"Ferreira",
"Pedro",
""
]
] | We consider a universe with an arbitrary number of extra dimensions, $N$. We present a new method for constructing the cosmological equations of motion and find analytic solutions with an explicit dependence on $N$. When we take the $N\rightarrow\infty$ limit we find novel, emergent behaviour which distinguishes it from normal Kaluza-Klein universes. |
1903.03436 | Naresh Dadhich | Naresh Dadhich | Buchdahl compactness limit and gravitational field energy | Almost matches with the published version | JCAP 04(2020)035 | 10.1088/1475-7516/2020/04/035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main aim of this paper is essentially to point out that the Buchdahl
compactness limit of a static object is given by \it{gravitational field energy
being less than or equal to half of its non-gravitational matter energy}. It is
thus entirely determined without any reference to interior distribution by the
exterior unique solutions, the Schwarzschild for neutral and the
Reissner-Nordstr{$\ddot o$}m for charged object. In terms of surface potential,
it reads as $\Phi(R) = (M-Q^2/2R)/R \leq 4/9$ which translates to surface
red-shift being less than or equal to $3$. It also prescribes an upper bound on
charge an object could have, $Q^2/M^2 \leq 9/8 > 1$.
| [
{
"created": "Mon, 4 Mar 2019 16:36:04 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Apr 2019 10:17:54 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Sep 2019 09:25:56 GMT",
"version": "v3"
},
{
"created": "Mon, 3 Feb 2020 07:25:17 GMT",
"version": "v4"
},
{
"created": "Thu, 12 Mar 2020 10:52:24 GMT",
"version": "v5"
},
{
"created": "Fri, 13 Mar 2020 09:19:20 GMT",
"version": "v6"
},
{
"created": "Fri, 24 Apr 2020 03:59:00 GMT",
"version": "v7"
}
] | 2020-04-29 | [
[
"Dadhich",
"Naresh",
""
]
] | The main aim of this paper is essentially to point out that the Buchdahl compactness limit of a static object is given by \it{gravitational field energy being less than or equal to half of its non-gravitational matter energy}. It is thus entirely determined without any reference to interior distribution by the exterior unique solutions, the Schwarzschild for neutral and the Reissner-Nordstr{$\ddot o$}m for charged object. In terms of surface potential, it reads as $\Phi(R) = (M-Q^2/2R)/R \leq 4/9$ which translates to surface red-shift being less than or equal to $3$. It also prescribes an upper bound on charge an object could have, $Q^2/M^2 \leq 9/8 > 1$. |
2206.03766 | Boris Goncharov | Boris Goncharov, Eric Thrane, Ryan M. Shannon, Jan Harms, N. D. Ramesh
Bhat, George Hobbs, Matthew Kerr, Richard N. Manchester, Daniel J. Reardon,
Christopher J. Russell, Xing-Jiang Zhu, Andrew Zic | Consistency of the Parkes Pulsar Timing Array Signal with a Nanohertz
Gravitational-wave Background | 9 pages, 2 figures | The Astrophysical Journal Letters, Volume 932, Number 2 (2022) | 10.3847/2041-8213/ac76bb | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | Pulsar timing array experiments have recently reported strong evidence for a
common-spectrum stochastic process with a strain spectral index consistent with
that expected of a nanohertz-frequency gravitational-wave background, but with
negligible yet non-zero evidence for spatial correlations required for a
definitive detection. However, it was pointed out by the Parkes Pulsar Timing
Array (PPTA) collaboration that the same models used in recent analyses
resulted in strong evidence for a common-spectrum process in simulations where
none is present. In this work, we introduce a methodology to distinguish pulsar
power spectra with the same amplitude from noise power spectra of similar but
distinct amplitudes. The former is the signature of a spatially uncorrelated
pulsar term of a nanohertz gravitational-wave background, whereas the latter
could represent ensemble pulsar noise properties. We test the methodology on
simulated data sets. We find that the reported common process in PPTA pulsars
is indeed consistent with the spectral feature of a pulsar term. We recommend
this methodology as one of the validity tests that the real astrophysical and
cosmological backgrounds should pass, as well as for inferences about the
spatially uncorrelated component of the background.
| [
{
"created": "Wed, 8 Jun 2022 09:25:03 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Jun 2022 17:03:33 GMT",
"version": "v2"
}
] | 2022-06-22 | [
[
"Goncharov",
"Boris",
""
],
[
"Thrane",
"Eric",
""
],
[
"Shannon",
"Ryan M.",
""
],
[
"Harms",
"Jan",
""
],
[
"Bhat",
"N. D. Ramesh",
""
],
[
"Hobbs",
"George",
""
],
[
"Kerr",
"Matthew",
""
],
[
"Manchester",
"Richard N.",
""
],
[
"Reardon",
"Daniel J.",
""
],
[
"Russell",
"Christopher J.",
""
],
[
"Zhu",
"Xing-Jiang",
""
],
[
"Zic",
"Andrew",
""
]
] | Pulsar timing array experiments have recently reported strong evidence for a common-spectrum stochastic process with a strain spectral index consistent with that expected of a nanohertz-frequency gravitational-wave background, but with negligible yet non-zero evidence for spatial correlations required for a definitive detection. However, it was pointed out by the Parkes Pulsar Timing Array (PPTA) collaboration that the same models used in recent analyses resulted in strong evidence for a common-spectrum process in simulations where none is present. In this work, we introduce a methodology to distinguish pulsar power spectra with the same amplitude from noise power spectra of similar but distinct amplitudes. The former is the signature of a spatially uncorrelated pulsar term of a nanohertz gravitational-wave background, whereas the latter could represent ensemble pulsar noise properties. We test the methodology on simulated data sets. We find that the reported common process in PPTA pulsars is indeed consistent with the spectral feature of a pulsar term. We recommend this methodology as one of the validity tests that the real astrophysical and cosmological backgrounds should pass, as well as for inferences about the spatially uncorrelated component of the background. |
1804.09823 | Matthew Duez | Wyatt Brege, Matthew D. Duez, Francois Foucart, M. Brett Deaton, Jesus
Caro, Daniel A. Hemberger, Lawrence E. Kidder, Evan O'Connor, Harald P.
Pfeiffer, and Mark A. Scheel | Black hole-neutron star mergers using a survey of finite-temperature
equations of state | 10 pages, 11 figures, submitted to Phys. Rev. D | Phys. Rev. D 98, 063009 (2018) | 10.1103/PhysRevD.98.063009 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Each of the potential signals from a black hole-neutron star merger should
contain an imprint of the neutron star equation of state: gravitational waves
via its effect on tidal disruption, the kilonova via its effect on the ejecta,
and the gamma ray burst via its effect on the remnant disk. These effects have
been studied by numerical simulations and quantified by semi-analytic formulae.
However, most of the simulations on which these formulae are based use
equations of state without finite temperature and composition-dependent nuclear
physics. In this paper, we simulate black hole-neutron star mergers varying
both the neutron star mass and the equation of state, using three
finite-temperature nuclear models of varying stiffness. Our simulations largely
vindicate formulae for ejecta properties but do not find the expected
dependence of disk mass on neutron star compaction. We track the early
evolution of the accretion disk, largely driven by shocking and fallback
inflow, and do find notable equation of state effects on the structure of this
early-time, neutrino-bright disk.
| [
{
"created": "Wed, 25 Apr 2018 22:37:51 GMT",
"version": "v1"
}
] | 2018-09-19 | [
[
"Brege",
"Wyatt",
""
],
[
"Duez",
"Matthew D.",
""
],
[
"Foucart",
"Francois",
""
],
[
"Deaton",
"M. Brett",
""
],
[
"Caro",
"Jesus",
""
],
[
"Hemberger",
"Daniel A.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"O'Connor",
"Evan",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
]
] | Each of the potential signals from a black hole-neutron star merger should contain an imprint of the neutron star equation of state: gravitational waves via its effect on tidal disruption, the kilonova via its effect on the ejecta, and the gamma ray burst via its effect on the remnant disk. These effects have been studied by numerical simulations and quantified by semi-analytic formulae. However, most of the simulations on which these formulae are based use equations of state without finite temperature and composition-dependent nuclear physics. In this paper, we simulate black hole-neutron star mergers varying both the neutron star mass and the equation of state, using three finite-temperature nuclear models of varying stiffness. Our simulations largely vindicate formulae for ejecta properties but do not find the expected dependence of disk mass on neutron star compaction. We track the early evolution of the accretion disk, largely driven by shocking and fallback inflow, and do find notable equation of state effects on the structure of this early-time, neutrino-bright disk. |
1001.2663 | Tomasz Pawlowski | Wojciech Kaminski, Tomasz Pawlowski | Cosmic recall and the scattering picture of Loop Quantum Cosmology | RevTex4, 19 pages, 3 figures | Phys.Rev.D81:084027,2010 | 10.1103/PhysRevD.81.084027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The global dynamics of a homogeneous universe in Loop Quantum Cosmology is
viewed as a scattering process of its geometrodynamical equivalent. This
picture is applied to build a flexible (easy to generalize) and not restricted
just to exactly solvable models method of verifying the preservation of the
semiclassicality through the bounce. The devised method is next applied to two
simple examples: (i) the isotropic Friedman Robertson Walker universe, and (ii)
the isotropic sector of the Bianchi I model. For both of them we show, that the
dispersions in the logarithm of the volume ln(v) and scalar field momentum
ln(p_phi) in the distant future and past are related via strong triangle
inequalities. This implies in particular a strict preservation of the
semiclassicality (in considered degrees of freedom) in both the cases (i) and
(ii). Derived inequalities are general: valid for all the physical states
within the considered models.
| [
{
"created": "Fri, 15 Jan 2010 19:05:37 GMT",
"version": "v1"
}
] | 2010-04-22 | [
[
"Kaminski",
"Wojciech",
""
],
[
"Pawlowski",
"Tomasz",
""
]
] | The global dynamics of a homogeneous universe in Loop Quantum Cosmology is viewed as a scattering process of its geometrodynamical equivalent. This picture is applied to build a flexible (easy to generalize) and not restricted just to exactly solvable models method of verifying the preservation of the semiclassicality through the bounce. The devised method is next applied to two simple examples: (i) the isotropic Friedman Robertson Walker universe, and (ii) the isotropic sector of the Bianchi I model. For both of them we show, that the dispersions in the logarithm of the volume ln(v) and scalar field momentum ln(p_phi) in the distant future and past are related via strong triangle inequalities. This implies in particular a strict preservation of the semiclassicality (in considered degrees of freedom) in both the cases (i) and (ii). Derived inequalities are general: valid for all the physical states within the considered models. |
gr-qc/0409113 | Nosrat-ollah Jafari Sonbolabadi | Nosratollah Jafari, Ahmad Shariati | Comments on the Quantum Vacuum and the Light Acceleration | 4 pages | null | null | null | gr-qc astro-ph hep-ph hep-th | null | The recent observations on the far quasars absorption lines spectra and
comparison of these lines with laboratory ones provide a framework for
explantation of these observations by considering a varying fine structure
constant, over the cosmological time-scale. Also, there seems to be an
anomalous acceleration in the Pioneer spacecraft 10/11 about $ 10^{-10} {\rm
m}/{\rm s^2}$. These matters lead Ranada to study the quantum vacuum to explain
these problems by introducing a phenomenological model for the variation of
$\alpha$. In this manuscript we want to show that this model is not a quantum
model; it is a classical model that is only in accordance with mentioned
observations by adjusting some parameters and is not based on a fundamental
physical intuition.
| [
{
"created": "Wed, 29 Sep 2004 09:16:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Jafari",
"Nosratollah",
""
],
[
"Shariati",
"Ahmad",
""
]
] | The recent observations on the far quasars absorption lines spectra and comparison of these lines with laboratory ones provide a framework for explantation of these observations by considering a varying fine structure constant, over the cosmological time-scale. Also, there seems to be an anomalous acceleration in the Pioneer spacecraft 10/11 about $ 10^{-10} {\rm m}/{\rm s^2}$. These matters lead Ranada to study the quantum vacuum to explain these problems by introducing a phenomenological model for the variation of $\alpha$. In this manuscript we want to show that this model is not a quantum model; it is a classical model that is only in accordance with mentioned observations by adjusting some parameters and is not based on a fundamental physical intuition. |
1801.01276 | Andronikos Paliathanasis | A. Paliathanasis, Adamantia Zampeli, T. Christodoulakis and M.T.
Mustafa | Quantization of the Szekeres System | 7 pages, 3 figures, typos corrected in section 3.2, to appear in
Classical and Quantum Gravity | null | 10.1088/1361-6382/aac227 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantum corrections on the Szekeres system in the context of
canonical quantization in the presence of symmetries. We start from an
effective point-like Lagrangian with two integrals of motion, one corresponding
to the Hamiltonian and the other to a second rank Killing tensor. Imposing
their quantum version on the wave function results to a solution which is then
interpreted in the context of Bohmian mechanics. In this semiclassical
approach, it is shown that there is no quantum corrections, thus the classical
trajectories of the Szekeres system are not affected at this level. Finally, we
define a probability function which shows that a stationary surface of the
probability corresponds to a classical exact solution
| [
{
"created": "Thu, 4 Jan 2018 08:32:20 GMT",
"version": "v1"
},
{
"created": "Thu, 3 May 2018 06:36:18 GMT",
"version": "v2"
}
] | 2018-06-13 | [
[
"Paliathanasis",
"A.",
""
],
[
"Zampeli",
"Adamantia",
""
],
[
"Christodoulakis",
"T.",
""
],
[
"Mustafa",
"M. T.",
""
]
] | We study the quantum corrections on the Szekeres system in the context of canonical quantization in the presence of symmetries. We start from an effective point-like Lagrangian with two integrals of motion, one corresponding to the Hamiltonian and the other to a second rank Killing tensor. Imposing their quantum version on the wave function results to a solution which is then interpreted in the context of Bohmian mechanics. In this semiclassical approach, it is shown that there is no quantum corrections, thus the classical trajectories of the Szekeres system are not affected at this level. Finally, we define a probability function which shows that a stationary surface of the probability corresponds to a classical exact solution |
gr-qc/9911015 | Luis Herrera | L. Herrera, (Universidad de Salamanca) | The Relativistic Transformation to Rotating Frames | 16 pages, Latex | NuovoCim.B115:307-318,2000 | null | null | gr-qc math-ph math.MP | null | We present a critical review of the relativistic rotation transformation of
Trocheris and Takeno. A new transformation is proposed which is free from the
drawbacks of the former. Some applications are presented.
| [
{
"created": "Thu, 4 Nov 1999 10:58:48 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Herrera",
"L.",
""
]
] | We present a critical review of the relativistic rotation transformation of Trocheris and Takeno. A new transformation is proposed which is free from the drawbacks of the former. Some applications are presented. |
gr-qc/0109062 | Yves Wiaux | J.-M. Gerard and Y. Wiaux | Gravitational dipole radiations from binary systems | One comment added, accepted for publication in Phys. Rev. D | Phys.Rev. D66 (2002) 024040 | 10.1103/PhysRevD.66.024040 | UCL-IPT-01-14 | gr-qc astro-ph hep-ph | null | We investigate the possibility of generating sizeable dipole radiations in
relativistic theories of gravity. Optimal parameters to observe their effects
through the orbital period decay of binary star systems are discussed.
Constraints on gravitational couplings beyond general relativity are derived.
| [
{
"created": "Wed, 19 Sep 2001 09:20:39 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Jun 2002 14:22:44 GMT",
"version": "v2"
}
] | 2007-08-14 | [
[
"Gerard",
"J. -M.",
""
],
[
"Wiaux",
"Y.",
""
]
] | We investigate the possibility of generating sizeable dipole radiations in relativistic theories of gravity. Optimal parameters to observe their effects through the orbital period decay of binary star systems are discussed. Constraints on gravitational couplings beyond general relativity are derived. |
1008.2212 | Daniela Alic | Daniela Alic, Luciano Rezzolla, Ian Hinder, Philipp M\"osta | Dynamical damping terms for symmetry-seeking shift conditions | 11 pages, 8 figures | Class.Quant.Grav.27:245023,2010 | 10.1088/0264-9381/27/24/245023 | AEI-2010-130 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Suitable gauge conditions are fundamental for stable and accurate
numerical-relativity simulations of inspiralling compact binaries. A number of
well-studied conditions have been developed over the last decade for both the
lapse and the shift and these have been successfully used both in vacuum and
non-vacuum spacetimes when simulating binaries with comparable masses. At the
same time, recent evidence has emerged that the standard "Gamma-driver" shift
condition requires a careful and non-trivial tuning of its parameters to ensure
long-term stable evolutions of unequal-mass binaries. We present a novel gauge
condition in which the damping constant is promoted to be a dynamical variable
and the solution of an evolution equation. We show that this choice removes the
need for special tuning and provides a shift damping term which is free of
instabilities in our simulations and dynamically adapts to the individual
positions and masses of the binary black-hole system. Our gauge condition also
reduces the variations in the coordinate size of the apparent horizon of the
larger black hole and could therefore be useful when simulating binaries with
very small mass ratios.
| [
{
"created": "Thu, 12 Aug 2010 20:27:29 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Nov 2010 21:08:24 GMT",
"version": "v2"
}
] | 2010-12-06 | [
[
"Alic",
"Daniela",
""
],
[
"Rezzolla",
"Luciano",
""
],
[
"Hinder",
"Ian",
""
],
[
"Mösta",
"Philipp",
""
]
] | Suitable gauge conditions are fundamental for stable and accurate numerical-relativity simulations of inspiralling compact binaries. A number of well-studied conditions have been developed over the last decade for both the lapse and the shift and these have been successfully used both in vacuum and non-vacuum spacetimes when simulating binaries with comparable masses. At the same time, recent evidence has emerged that the standard "Gamma-driver" shift condition requires a careful and non-trivial tuning of its parameters to ensure long-term stable evolutions of unequal-mass binaries. We present a novel gauge condition in which the damping constant is promoted to be a dynamical variable and the solution of an evolution equation. We show that this choice removes the need for special tuning and provides a shift damping term which is free of instabilities in our simulations and dynamically adapts to the individual positions and masses of the binary black-hole system. Our gauge condition also reduces the variations in the coordinate size of the apparent horizon of the larger black hole and could therefore be useful when simulating binaries with very small mass ratios. |
gr-qc/0003097 | Young-Jai Park | Soon-Tae Hong, Yong-Wan Kim, and Young-Jai Park | Higher dimensional flat embeddings of (2+1) dimensional black holes | 16pages, revtex, no figures, to appear in Phys. Rev. D | Phys.Rev. D62 (2000) 024024 | 10.1103/PhysRevD.62.024024 | SOGANG-HEP 268/00 | gr-qc | null | We obtain the higher dimensional global flat embeddings of static, rotating,
and charged BTZ black holes. On the other hand, we also study the similar
higher dimensional flat embeddings of the (2+1) de Sitter black holes which are
the counterparts of the anti-de Sitter BTZ black holes. As a result, the
charged dS black hole is shown to be embedded in (3+2) GEMS, contrast to the
charged BTZ one having (3+3) GEMS structure.
| [
{
"created": "Sat, 25 Mar 2000 00:48:50 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Hong",
"Soon-Tae",
""
],
[
"Kim",
"Yong-Wan",
""
],
[
"Park",
"Young-Jai",
""
]
] | We obtain the higher dimensional global flat embeddings of static, rotating, and charged BTZ black holes. On the other hand, we also study the similar higher dimensional flat embeddings of the (2+1) de Sitter black holes which are the counterparts of the anti-de Sitter BTZ black holes. As a result, the charged dS black hole is shown to be embedded in (3+2) GEMS, contrast to the charged BTZ one having (3+3) GEMS structure. |
1307.7391 | Daniela Alic | Daniela Alic, Wolfgang Kastaun, Luciano Rezzolla | Constraint damping of the conformal and covariant formulation of the Z4
system in simulations of binary neutron stars | 15 pages, 11 figures; accepted for publication in Phys. Rev. D | Phys. Rev. D 88, 064049 (2013) | 10.1103/PhysRevD.88.064049 | AEI-2013-231 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following previous work in vacuum spacetimes, we investigate the
constraint-damping properties in the presence of matter of the recently
developed traceless, conformal and covariant Z4 (CCZ4) formulation of the
Einstein equations. First, we evolve an isolated neutron star with an ideal gas
equation of state and subject to a constraint-violating perturbation. We
compare the evolution of the constraints using the CCZ4 and
Baumgarte-Shibata-Shapiro-Nakamura-Oohara-Kojima (BSSNOK) systems. Second, we
study the collapse of an unstable spherical star to a black hole. Finally, we
evolve binary neutron star systems over several orbits until the merger, the
formation of a black hole, and up to the ringdown. We show that the CCZ4
formulation is stable in the presence of matter and that the constraint
violations are one or more orders of magnitude smaller than for the BSSNOK
formulation. Furthermore, by comparing the CCZ4 and the BSSNOK formulations
also for neutron star binaries with large initial constraint violations, we
investigate their influence on the errors on physical quantities. We also give
a new, simple and robust prescription for the damping parameter that removes
the instabilities found when using the fully covariant version of CCZ4 in the
evolution of black holes. Overall, we find that at essentially the same
computational costs the CCZ4 formulation provides solutions that are stable and
with a considerably smaller violation of the Hamiltonian constraint than the
BSSNOK formulation. We also find that the performance of the CCZ4 formulation
is very similar to another conformal and traceless, but noncovariant
formulation of the Z4 system, i.e. the Z4c formulation.
| [
{
"created": "Sun, 28 Jul 2013 18:38:34 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Sep 2013 09:33:39 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Alic",
"Daniela",
""
],
[
"Kastaun",
"Wolfgang",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | Following previous work in vacuum spacetimes, we investigate the constraint-damping properties in the presence of matter of the recently developed traceless, conformal and covariant Z4 (CCZ4) formulation of the Einstein equations. First, we evolve an isolated neutron star with an ideal gas equation of state and subject to a constraint-violating perturbation. We compare the evolution of the constraints using the CCZ4 and Baumgarte-Shibata-Shapiro-Nakamura-Oohara-Kojima (BSSNOK) systems. Second, we study the collapse of an unstable spherical star to a black hole. Finally, we evolve binary neutron star systems over several orbits until the merger, the formation of a black hole, and up to the ringdown. We show that the CCZ4 formulation is stable in the presence of matter and that the constraint violations are one or more orders of magnitude smaller than for the BSSNOK formulation. Furthermore, by comparing the CCZ4 and the BSSNOK formulations also for neutron star binaries with large initial constraint violations, we investigate their influence on the errors on physical quantities. We also give a new, simple and robust prescription for the damping parameter that removes the instabilities found when using the fully covariant version of CCZ4 in the evolution of black holes. Overall, we find that at essentially the same computational costs the CCZ4 formulation provides solutions that are stable and with a considerably smaller violation of the Hamiltonian constraint than the BSSNOK formulation. We also find that the performance of the CCZ4 formulation is very similar to another conformal and traceless, but noncovariant formulation of the Z4 system, i.e. the Z4c formulation. |
2011.07742 | Ken Matsuno | Ken Matsuno | Light deflection by squashed Kaluza-Klein black holes in a plasma medium | 18 pages, 4 figures | Phys. Rev. D 103, 044008 (2021) | 10.1103/PhysRevD.103.044008 | OCU-PHYS-525, AP-GR-162 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study motions of photons in an unmagnetized cold homogeneous plasma medium
in the five-dimensional charged static squashed Kaluza-Klein black hole
spacetime. In this case, a photon behaves as a massive particle in a
four-dimensional spherically symmetric spacetime. We consider the light
deflection by the squashed Kaluza-Klein black hole surrounded by the plasma in
a weak-field limit. We derive corrections of the deflection angle to general
relativity, which are related to the size of the extra dimension, the charge of
the black hole and the ratio between the plasma and the photon frequencies.
| [
{
"created": "Mon, 16 Nov 2020 06:36:21 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jan 2021 10:12:27 GMT",
"version": "v2"
}
] | 2021-02-05 | [
[
"Matsuno",
"Ken",
""
]
] | We study motions of photons in an unmagnetized cold homogeneous plasma medium in the five-dimensional charged static squashed Kaluza-Klein black hole spacetime. In this case, a photon behaves as a massive particle in a four-dimensional spherically symmetric spacetime. We consider the light deflection by the squashed Kaluza-Klein black hole surrounded by the plasma in a weak-field limit. We derive corrections of the deflection angle to general relativity, which are related to the size of the extra dimension, the charge of the black hole and the ratio between the plasma and the photon frequencies. |
gr-qc/0511111 | Emanuele Berti | Emanuele Berti, Vitor Cardoso, Marc Casals | Eigenvalues and eigenfunctions of spin-weighted spheroidal harmonics in
four and higher dimensions | 26 pages, 10 figures. Corrected typos in Eqs. (2.16f) and (2.16g) | Phys.Rev.D73:024013,2006; Erratum-ibid.D73:109902,2006 | 10.1103/PhysRevD.73.024013 10.1103/PhysRevD.73.109902 | null | gr-qc hep-th math-ph math.MP | null | Spin-weighted spheroidal harmonics are useful in a variety of physical
situations, including light scattering, nuclear modeling, signal processing,
electromagnetic wave propagation, black hole perturbation theory in four and
higher dimensions, quantum field theory in curved space-time and studies of
D-branes. We first review analytic and numerical calculations of their
eigenvalues and eigenfunctions in four dimensions, filling gaps in the existing
literature when necessary. Then we compute the angular dependence of the
spin-weighted spheroidal harmonics corresponding to slowly-damped quasinormal
mode frequencies of the Kerr black hole, providing numerical tables and
approximate formulas for their scalar products. Finally we present an
exhaustive analytic and numerical study of scalar spheroidal harmonics in (n+4)
dimensions.
| [
{
"created": "Sun, 20 Nov 2005 20:38:29 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jan 2006 10:01:45 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Jan 2006 22:45:10 GMT",
"version": "v3"
},
{
"created": "Mon, 1 May 2006 19:55:46 GMT",
"version": "v4"
}
] | 2014-11-17 | [
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Casals",
"Marc",
""
]
] | Spin-weighted spheroidal harmonics are useful in a variety of physical situations, including light scattering, nuclear modeling, signal processing, electromagnetic wave propagation, black hole perturbation theory in four and higher dimensions, quantum field theory in curved space-time and studies of D-branes. We first review analytic and numerical calculations of their eigenvalues and eigenfunctions in four dimensions, filling gaps in the existing literature when necessary. Then we compute the angular dependence of the spin-weighted spheroidal harmonics corresponding to slowly-damped quasinormal mode frequencies of the Kerr black hole, providing numerical tables and approximate formulas for their scalar products. Finally we present an exhaustive analytic and numerical study of scalar spheroidal harmonics in (n+4) dimensions. |
2311.12393 | Mohaddese Heydari-Fard | Mohaddese Heydari-Fard, Malihe Heydari-Fard and Nematollah Riazi | Thin accretion disk images of rotating hairy Horndeski black holes | 14 pages, 10 figures | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | By considering the steady-state Novikov-Thorne model, we study thin accretion
disk processes for rotating hairy black holes in the framework of the Horndeski
gravity. We obtain the electromagnetic properties of accretion disk around such
black holes and investigate the effects of the hair parameter $h$ on them. We
find that by decreasing the hair parameter from the Kerr limit,
$h\rightarrow0$, the radius of the innermost stable circular orbit decreases
which makes thin accretion disks around rotating hairy black holes in Horndeski
gravity more efficient than that for the Kerr black hole in general relativity.
Furthermore, using the numerical ray-tracing method, we plot thin accretion
disk images around these black holes and investigate the effects of hair
parameter on the central shadow area of accretion disk.
| [
{
"created": "Tue, 21 Nov 2023 07:06:37 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Jan 2024 19:48:25 GMT",
"version": "v2"
}
] | 2024-01-10 | [
[
"Heydari-Fard",
"Mohaddese",
""
],
[
"Heydari-Fard",
"Malihe",
""
],
[
"Riazi",
"Nematollah",
""
]
] | By considering the steady-state Novikov-Thorne model, we study thin accretion disk processes for rotating hairy black holes in the framework of the Horndeski gravity. We obtain the electromagnetic properties of accretion disk around such black holes and investigate the effects of the hair parameter $h$ on them. We find that by decreasing the hair parameter from the Kerr limit, $h\rightarrow0$, the radius of the innermost stable circular orbit decreases which makes thin accretion disks around rotating hairy black holes in Horndeski gravity more efficient than that for the Kerr black hole in general relativity. Furthermore, using the numerical ray-tracing method, we plot thin accretion disk images around these black holes and investigate the effects of hair parameter on the central shadow area of accretion disk. |
2105.02879 | Moritz H\"ubner | Moritz H\"ubner and Paul Lasky and Eric Thrane | The Memory Remains (Undetected): Updates from the Second LIGO/Virgo
Gravitational-Wave Transient Catalog | 6 pages, 3 figures | Phys. Rev. D 104, 023004 (2021) | 10.1103/PhysRevD.104.023004 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The LIGO and Virgo observatories have reported 39 new gravitational-wave
detections during the first part of the third observation run, bringing the
total to 50. Most of these new detections are consistent with binary black-hole
coalescences, making them suitable targets to search for gravitational-wave
memory, a non-linear effect of general relativity. We extend a method developed
in previous publications to analyse these events to determine a Bayes factor
comparing the memory hypothesis to the no-memory hypothesis. Specifically, we
calculate Bayes factors using two waveform models with higher-order modes that
allow us to analyse events with extreme mass ratios and precessing spins, both
of which have not been possible before. Depending on the waveform model we find
a combined $\ln \mathrm{BF}_{\mathrm{mem}} = 0.024$ or $\ln
\mathrm{BF}_{\mathrm{mem}} = 0.049$ in favour of memory. This result is
consistent with recent predictions that indicate $\mathcal{O}(2000)$ binary
black-hole detections will be required to confidently establish the presence or
absence of memory.
| [
{
"created": "Thu, 6 May 2021 07:21:15 GMT",
"version": "v1"
}
] | 2021-07-14 | [
[
"Hübner",
"Moritz",
""
],
[
"Lasky",
"Paul",
""
],
[
"Thrane",
"Eric",
""
]
] | The LIGO and Virgo observatories have reported 39 new gravitational-wave detections during the first part of the third observation run, bringing the total to 50. Most of these new detections are consistent with binary black-hole coalescences, making them suitable targets to search for gravitational-wave memory, a non-linear effect of general relativity. We extend a method developed in previous publications to analyse these events to determine a Bayes factor comparing the memory hypothesis to the no-memory hypothesis. Specifically, we calculate Bayes factors using two waveform models with higher-order modes that allow us to analyse events with extreme mass ratios and precessing spins, both of which have not been possible before. Depending on the waveform model we find a combined $\ln \mathrm{BF}_{\mathrm{mem}} = 0.024$ or $\ln \mathrm{BF}_{\mathrm{mem}} = 0.049$ in favour of memory. This result is consistent with recent predictions that indicate $\mathcal{O}(2000)$ binary black-hole detections will be required to confidently establish the presence or absence of memory. |
gr-qc/9507025 | Don N. Page | Don N. Page (University of Alberta, Edmonton, Canada) | Aspects of Quantum Cosmology | LaTeX, 18 pages, September 1995 Erice lectures | null | null | Alberta-Thy-14-95 | gr-qc quant-ph | null | Quantum mechanics may be formulated as SENSIBLE QUANTUM MECHANICS (SQM) so
that it contains nothing probabilistic, except, in a certain frequency sense,
conscious perceptions. Sets of these perceptions can be deterministically
realized with measures given by expectation values of positive-operator-valued
AWARENESS OPERATORS in a quantum state of the universe which never jumps or
collapses. Ratios of the measures for these sets of perceptions can be
interpreted as frequency-type probabilities for many actually existing sets
rather than as propensities for potentialities to be actualized, so there is
nothing indeterministic in SQM. These frequency-type probabilities generally
cannot be given by the ordinary quantum "probabilities" for a single set of
alternatives. PROBABILISM, or ascribing probabilities to unconscious aspects of
the world, may be seen to be an AESTHEMAMORPHIC MYTH. No fundamental
correlation or equivalence is postulated between different perceptions (each
being the entirety of a single conscious experience and thus not in direct
contact with any other), so SQM, a variant of Everett's "many-worlds"
framework, is a "many-perceptions" framework but not a "many-minds" framework.
Different detailed SQM theories may be tested against experienced perceptions
by the TYPICALITIES (defined herein) they predict for these perceptions. One
may adopt the CONDITIONAL AESTHEMIC PRINCIPLE: among the set of all conscious
perceptions, our perceptions are likely to be typical.
| [
{
"created": "Wed, 12 Jul 1995 02:25:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Page",
"Don N.",
"",
"University of Alberta, Edmonton, Canada"
]
] | Quantum mechanics may be formulated as SENSIBLE QUANTUM MECHANICS (SQM) so that it contains nothing probabilistic, except, in a certain frequency sense, conscious perceptions. Sets of these perceptions can be deterministically realized with measures given by expectation values of positive-operator-valued AWARENESS OPERATORS in a quantum state of the universe which never jumps or collapses. Ratios of the measures for these sets of perceptions can be interpreted as frequency-type probabilities for many actually existing sets rather than as propensities for potentialities to be actualized, so there is nothing indeterministic in SQM. These frequency-type probabilities generally cannot be given by the ordinary quantum "probabilities" for a single set of alternatives. PROBABILISM, or ascribing probabilities to unconscious aspects of the world, may be seen to be an AESTHEMAMORPHIC MYTH. No fundamental correlation or equivalence is postulated between different perceptions (each being the entirety of a single conscious experience and thus not in direct contact with any other), so SQM, a variant of Everett's "many-worlds" framework, is a "many-perceptions" framework but not a "many-minds" framework. Different detailed SQM theories may be tested against experienced perceptions by the TYPICALITIES (defined herein) they predict for these perceptions. One may adopt the CONDITIONAL AESTHEMIC PRINCIPLE: among the set of all conscious perceptions, our perceptions are likely to be typical. |
2211.07775 | Nidal Chamoun | Mahmoud AlHallak (Damascus Univ.), Khalil Kalid Al Said (UDST), Nidal
Chamoun (HIAST) and Moustafa Sayem El-Daher (Damascus Univ.) | On Warm Natural Inflation and Planck 2018 constraints | pdflatex, 18 pages, 4 figures, version to appear in Universe as an
invited article for the Special Issue on `Warm Inflation' | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate Natural Inflation with non-minimal coupling to gravity,
characterized either by a quadratic or a periodic term, within the Warm
Inflation paradigm during the slow roll stage, in both strong and weak
dissipation limits, and show that, in the case of $T$-linearly dependent
dissipative term, it can accommodate the spectral index $n_s$ and
tensor-to-scalar ratio $r$ observables given by Planck 2018 constraints, albeit
with a too small value of the e-folding number to solve the horizon problem,
providing thus only a partial solution to Natural Inflation issues. Assuming a
$T$-cubically dependent dissipative term can provide a solution to this
e-folding number issue.
| [
{
"created": "Mon, 14 Nov 2022 22:19:09 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2023 16:04:39 GMT",
"version": "v2"
}
] | 2023-01-25 | [
[
"AlHallak",
"Mahmoud",
"",
"Damascus Univ."
],
[
"Said",
"Khalil Kalid Al",
"",
"UDST"
],
[
"Chamoun",
"Nidal",
"",
"HIAST"
],
[
"El-Daher",
"Moustafa Sayem",
"",
"Damascus Univ."
]
] | We investigate Natural Inflation with non-minimal coupling to gravity, characterized either by a quadratic or a periodic term, within the Warm Inflation paradigm during the slow roll stage, in both strong and weak dissipation limits, and show that, in the case of $T$-linearly dependent dissipative term, it can accommodate the spectral index $n_s$ and tensor-to-scalar ratio $r$ observables given by Planck 2018 constraints, albeit with a too small value of the e-folding number to solve the horizon problem, providing thus only a partial solution to Natural Inflation issues. Assuming a $T$-cubically dependent dissipative term can provide a solution to this e-folding number issue. |
2310.15186 | Nasr Ahmed | Nasr Ahmed and Anirudh Pradhan | Logamediate inflation on the Swiss-cheese brane | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The existence of Schwarzchild black holes in the structure of Swiss-cheese
brane-world led to the argument that this specific brane-world scenario is more
realistic than the FLRW branes. In this paper, we show that a Logamediate
inflation on the Swiss-cheese brane leads to a positive kinetic term and a
negative potential with AdS minimum. While cosmic pressure is always positive,
the energy density starts to get negative after a finite time and there is a
time interval where both $\rho$ and $p$ are positive. Although this can be
considered as a drawback of Swiss-cheese brane as positive energy dominates the
present universe, it has been suggested that the presence of some source of
negative energy could have played a significant role in early cosmic expansion.
The model also suffers from the eternal inflation problem. Due to the existence
of $\rho^2$ term, we have tested the new nonlinear energy conditions. The
cosmographic and slow-roll parameters have been investigated.
| [
{
"created": "Fri, 20 Oct 2023 19:49:39 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Oct 2023 16:32:02 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Jun 2024 07:58:30 GMT",
"version": "v3"
}
] | 2024-06-21 | [
[
"Ahmed",
"Nasr",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | The existence of Schwarzchild black holes in the structure of Swiss-cheese brane-world led to the argument that this specific brane-world scenario is more realistic than the FLRW branes. In this paper, we show that a Logamediate inflation on the Swiss-cheese brane leads to a positive kinetic term and a negative potential with AdS minimum. While cosmic pressure is always positive, the energy density starts to get negative after a finite time and there is a time interval where both $\rho$ and $p$ are positive. Although this can be considered as a drawback of Swiss-cheese brane as positive energy dominates the present universe, it has been suggested that the presence of some source of negative energy could have played a significant role in early cosmic expansion. The model also suffers from the eternal inflation problem. Due to the existence of $\rho^2$ term, we have tested the new nonlinear energy conditions. The cosmographic and slow-roll parameters have been investigated. |
2004.09690 | Sumanta Chakraborty | Sumanta Chakraborty | Softly broken conformal symmetry with higher curvature terms | v2, 21 pages, no figures, published in PRD | Phys. Rev. D 102, 064030 (2020) | 10.1103/PhysRevD.102.064030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a scalar-coupled-gravity model, the quadratically divergent counter term
appearing in the mass renormalization of the scalar fields must inherit
corrections arising out of gravitational interactions. In this work we have
explicitly demonstrated that there are no such corrections of gravitational
origin to the quadratic divergences in the mass counter terms. This statement
holds true irrespective of the nature of the gravitational interaction, i.e.,
whether gravity is described by general relativity or f(R) theory.
Interestingly, it also turns out that the one loop effective action of
scalar-coupled-gravity system will be well-behaved \emph{if and only if} the
$f(R)$ theory is free from ghosts. In particular, the results derived in the
context of f(R) theory are shown to be in exact agreement with the
corresponding results derived from the equivalent scalar-tensor representation.
Our analysis suggests the tantalizing possibility that the masses of the scalar
fields can be consistently kept smaller than some Ultra Violet (UV) cutoff
scale and is independent of the nature of the gravity theory, which may involve
higher curvature corrections. All these will be true provided the matter fields
and the gravity theory can be embedded consistently into a UV complete theory
at the Planck scale.
| [
{
"created": "Tue, 21 Apr 2020 00:46:16 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Sep 2020 03:41:45 GMT",
"version": "v2"
}
] | 2020-09-15 | [
[
"Chakraborty",
"Sumanta",
""
]
] | In a scalar-coupled-gravity model, the quadratically divergent counter term appearing in the mass renormalization of the scalar fields must inherit corrections arising out of gravitational interactions. In this work we have explicitly demonstrated that there are no such corrections of gravitational origin to the quadratic divergences in the mass counter terms. This statement holds true irrespective of the nature of the gravitational interaction, i.e., whether gravity is described by general relativity or f(R) theory. Interestingly, it also turns out that the one loop effective action of scalar-coupled-gravity system will be well-behaved \emph{if and only if} the $f(R)$ theory is free from ghosts. In particular, the results derived in the context of f(R) theory are shown to be in exact agreement with the corresponding results derived from the equivalent scalar-tensor representation. Our analysis suggests the tantalizing possibility that the masses of the scalar fields can be consistently kept smaller than some Ultra Violet (UV) cutoff scale and is independent of the nature of the gravity theory, which may involve higher curvature corrections. All these will be true provided the matter fields and the gravity theory can be embedded consistently into a UV complete theory at the Planck scale. |
gr-qc/0011028 | Thomas W. Baumgarte | Hwei-Jang Yo, Thomas W. Baumgarte, and Stuart L. Shapiro | Gravitational Wavetrains in the Quasi-Equilibrium Approximation: A Model
Problem in Scalar Gravitation | 15 pages, 14 figures | Phys.Rev. D63 (2001) 064035 | 10.1103/PhysRevD.63.064035 | null | gr-qc astro-ph | null | A quasi-equilibrium (QE) computational scheme was recently developed in
general relativity to calculate the complete gravitational wavetrain emitted
during the inspiral phase of compact binaries. The QE method exploits the fact
that the the gravitational radiation inspiral timescale is much longer than the
orbital period everywhere outside the ISCO. Here we demonstrate the validity
and advantages of the QE scheme by solving a model problem in relativistic
scalar gravitation theory. By adopting scalar gravitation, we are able to
numerically track without approximation the damping of a simple, quasi-periodic
radiating system (an oscillating spherical matter shell) to final equilibrium,
and then use the exact numerical results to calibrate the QE approximation
method. In particular, we calculate the emitted gravitational wavetrain three
different ways: by integrating the exact coupled dynamical field and matter
equations, by using the scalar-wave monopole approximation formula
(corresponding to the quadrupole formula in general relativity), and by
adopting the QE scheme. We find that the monopole formula works well for weak
field cases, but fails when the fields become even moderately strong. By
contrast, the QE scheme remains quite reliable for moderately strong fields,
and begins to breakdown only for ultra-strong fields. The QE scheme thus
provides a promising technique to construct the complete wavetrain from binary
inspiral outside the ISCO, where the gravitational fields are strong, but where
the computational resources required to follow the system for more than a few
orbits by direct numerical integration of the exact equations are prohibitive.
| [
{
"created": "Tue, 7 Nov 2000 22:16:00 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Yo",
"Hwei-Jang",
""
],
[
"Baumgarte",
"Thomas W.",
""
],
[
"Shapiro",
"Stuart L.",
""
]
] | A quasi-equilibrium (QE) computational scheme was recently developed in general relativity to calculate the complete gravitational wavetrain emitted during the inspiral phase of compact binaries. The QE method exploits the fact that the the gravitational radiation inspiral timescale is much longer than the orbital period everywhere outside the ISCO. Here we demonstrate the validity and advantages of the QE scheme by solving a model problem in relativistic scalar gravitation theory. By adopting scalar gravitation, we are able to numerically track without approximation the damping of a simple, quasi-periodic radiating system (an oscillating spherical matter shell) to final equilibrium, and then use the exact numerical results to calibrate the QE approximation method. In particular, we calculate the emitted gravitational wavetrain three different ways: by integrating the exact coupled dynamical field and matter equations, by using the scalar-wave monopole approximation formula (corresponding to the quadrupole formula in general relativity), and by adopting the QE scheme. We find that the monopole formula works well for weak field cases, but fails when the fields become even moderately strong. By contrast, the QE scheme remains quite reliable for moderately strong fields, and begins to breakdown only for ultra-strong fields. The QE scheme thus provides a promising technique to construct the complete wavetrain from binary inspiral outside the ISCO, where the gravitational fields are strong, but where the computational resources required to follow the system for more than a few orbits by direct numerical integration of the exact equations are prohibitive. |
0809.0701 | Xavier Siemens | Melissa Anholm, Stefan Ballmer, Jolien D. E. Creighton, Larry R.
Price, and Xavier Siemens | Optimal strategies for gravitational wave stochastic background searches
in pulsar timing data | 20 pages, 6 figures. Added figure with sky sensitivity for Parkes
Pulsar Timing Array, included dipole overlap reduction function and
derivation in appendix, extended likelihood discussion | null | 10.1103/PhysRevD.79.084030 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A low frequency stochastic background of gravitational waves may be detected
by pulsar timing experiments in the next five to ten years. Using methods
developed to analyze interferometric gravitational wave data, in this paper we
lay out the optimal techniques to detect a background of gravitational waves
using a pulsar timing array. We show that for pulsar distances and
gravitational wave frequencies typical of pulsar timing experiments, neglecting
the effect of the metric perturbation at the pulsar does not result in a
significant deviation from optimality. We discuss methods for setting upper
limits using the optimal statistic, show how to construct skymaps using the
pulsar timing array, and consider several issues associated with realistic
analysis of pulsar timing data.
| [
{
"created": "Wed, 3 Sep 2008 20:12:48 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Dec 2008 23:31:23 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Anholm",
"Melissa",
""
],
[
"Ballmer",
"Stefan",
""
],
[
"Creighton",
"Jolien D. E.",
""
],
[
"Price",
"Larry R.",
""
],
[
"Siemens",
"Xavier",
""
]
] | A low frequency stochastic background of gravitational waves may be detected by pulsar timing experiments in the next five to ten years. Using methods developed to analyze interferometric gravitational wave data, in this paper we lay out the optimal techniques to detect a background of gravitational waves using a pulsar timing array. We show that for pulsar distances and gravitational wave frequencies typical of pulsar timing experiments, neglecting the effect of the metric perturbation at the pulsar does not result in a significant deviation from optimality. We discuss methods for setting upper limits using the optimal statistic, show how to construct skymaps using the pulsar timing array, and consider several issues associated with realistic analysis of pulsar timing data. |
1807.11025 | Mahboobeh Roostaee Shahverdi | M. Roostaee, Amir M. Abbassi | F-term Inflation and RSII Brane Mode | 20 pages, 2 figures (.jpg), revtex4-1 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering hybrid F-term inflation in RSII model and using the most recent
data from Planck 2018 and in comparison with Planck 2015and WMAP 9-year , we
can obtain some interesting constraints on main parameters of the model. Also,
we attain convenient compatibility between this model and observational data.
We show that this setup provides a successful hybrid inflation with high enough
Reheating Temperature, T_R, to have a successful thermalization. After
inflation, particles are created in the process of preheating. Inflaton
field(s) oscillated and fermionic field(s) interacted with it in a
non-perturbative regime of parametric resonance. We apply theory of fermionic
preheating coupling to the inflaton, without expansion of the universe, to
calculate the occupation number of created particles analytically, and some
interesting results are achieved.
| [
{
"created": "Sun, 29 Jul 2018 09:07:00 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Aug 2018 16:34:30 GMT",
"version": "v2"
}
] | 2018-08-22 | [
[
"Roostaee",
"M.",
""
],
[
"Abbassi",
"Amir M.",
""
]
] | Considering hybrid F-term inflation in RSII model and using the most recent data from Planck 2018 and in comparison with Planck 2015and WMAP 9-year , we can obtain some interesting constraints on main parameters of the model. Also, we attain convenient compatibility between this model and observational data. We show that this setup provides a successful hybrid inflation with high enough Reheating Temperature, T_R, to have a successful thermalization. After inflation, particles are created in the process of preheating. Inflaton field(s) oscillated and fermionic field(s) interacted with it in a non-perturbative regime of parametric resonance. We apply theory of fermionic preheating coupling to the inflaton, without expansion of the universe, to calculate the occupation number of created particles analytically, and some interesting results are achieved. |
1003.3486 | Marc Favata | Marc Favata | The gravitational-wave memory effect | 11 pages, 2 figures; proceedings of the 8th Amaldi Conference on
Gravitational Waves (New York, June 2009); accepted for publication in
special issue of Classical and Quantum Gravity | Class. Quant. Grav.27:084036, 2010 | 10.1088/0264-9381/27/8/084036 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The nonlinear memory effect is a slowly-growing, non-oscillatory contribution
to the gravitational-wave amplitude. It originates from gravitational waves
that are sourced by the previously emitted waves. In an ideal
gravitational-wave interferometer a gravitational-wave with memory causes a
permanent displacement of the test masses that persists after the wave has
passed. Surprisingly, the nonlinear memory affects the signal amplitude
starting at leading (Newtonian-quadrupole) order. Despite this fact, the
nonlinear memory is not easily extracted from current numerical relativity
simulations. After reviewing the linear and nonlinear memory I summarize some
recent work, including: (1) computations of the memory contribution to the
inspiral waveform amplitude (thus completing the waveform to third
post-Newtonian order); (2) the first calculations of the nonlinear memory that
include all phases of binary black hole coalescence (inspiral, merger,
ringdown); and (3) realistic estimates of the detectability of the memory with
LISA.
| [
{
"created": "Wed, 17 Mar 2010 21:56:48 GMT",
"version": "v1"
}
] | 2010-05-27 | [
[
"Favata",
"Marc",
""
]
] | The nonlinear memory effect is a slowly-growing, non-oscillatory contribution to the gravitational-wave amplitude. It originates from gravitational waves that are sourced by the previously emitted waves. In an ideal gravitational-wave interferometer a gravitational-wave with memory causes a permanent displacement of the test masses that persists after the wave has passed. Surprisingly, the nonlinear memory affects the signal amplitude starting at leading (Newtonian-quadrupole) order. Despite this fact, the nonlinear memory is not easily extracted from current numerical relativity simulations. After reviewing the linear and nonlinear memory I summarize some recent work, including: (1) computations of the memory contribution to the inspiral waveform amplitude (thus completing the waveform to third post-Newtonian order); (2) the first calculations of the nonlinear memory that include all phases of binary black hole coalescence (inspiral, merger, ringdown); and (3) realistic estimates of the detectability of the memory with LISA. |
1503.05083 | Yoshifumi Hyakutake | Yoshifumi Hyakutake | Boosted Quantum Black Hole and Black String in M-theory, and Quantum
Correction to Gregory-Laflamme Instability | 27 pages, 5 figures. References added and effect of the
compactification for the black hole is discussed around eq. (68) | JHEP09(2015)067 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We take into account higher derivative R4 corrections in M-theory and
construct quantum black hole and black string solutions in 11 dimensions up to
the next leading order. The quantum black string is stretching along the 11th
direction and the Gregory-Laflamme instability is examined at the quantum
level. Thermodynamics of the boosted quantum black hole and black string are
also discussed. Especially we take the near horizon limit of the quantum black
string and investigate its instability quantitatively.
| [
{
"created": "Tue, 17 Mar 2015 14:59:35 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Sep 2015 09:13:49 GMT",
"version": "v2"
}
] | 2017-01-25 | [
[
"Hyakutake",
"Yoshifumi",
""
]
] | We take into account higher derivative R4 corrections in M-theory and construct quantum black hole and black string solutions in 11 dimensions up to the next leading order. The quantum black string is stretching along the 11th direction and the Gregory-Laflamme instability is examined at the quantum level. Thermodynamics of the boosted quantum black hole and black string are also discussed. Especially we take the near horizon limit of the quantum black string and investigate its instability quantitatively. |
2311.10481 | Thomas Pappas | Thomas D. Pappas | Theory-agnostic parametrization of wormhole spacetimes | 16 pages, 5 tables, 1 figure; contribution to the proceedings of the
RAGtime conference in Opava. v2: Extended discussion, version to match the
one to appear in Proceedings of RAGtime 23-25 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a generalization of the Rezzolla-Zhidenko theory-agnostic
parametrization of black-hole spacetimes to accommodate spherically-symmetric
Lorentzian, traversable wormholes (WHs) in an arbitrary metric theory of
gravity. By applying our parametrization to various known WH metrics and
performing calculations involving shadows and quasinormal modes, we show that
only a few parameters are important for finding potentially observable
quantities in a WH spacetime.
| [
{
"created": "Fri, 17 Nov 2023 12:23:49 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Dec 2023 09:58:33 GMT",
"version": "v2"
}
] | 2023-12-29 | [
[
"Pappas",
"Thomas D.",
""
]
] | We present a generalization of the Rezzolla-Zhidenko theory-agnostic parametrization of black-hole spacetimes to accommodate spherically-symmetric Lorentzian, traversable wormholes (WHs) in an arbitrary metric theory of gravity. By applying our parametrization to various known WH metrics and performing calculations involving shadows and quasinormal modes, we show that only a few parameters are important for finding potentially observable quantities in a WH spacetime. |
1909.05877 | Christopher Munna | Christopher Munna, Charles R. Evans | Eccentric-orbit EMRI radiation: Analytic forms of leading-logarithm and
subleading-logarithm flux terms at high PN orders | 24 pages. Submitted to Phys. Rev. D | Phys. Rev. D 100, 104060 (2019) | 10.1103/PhysRevD.100.104060 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present new results on the analytic eccentricity dependence of several
sequences of gravitational wave flux terms at high post-Newtonian (PN) order
for extreme-mass-ratio inspirals. These sequences are the leading logarithms,
which appear at PN orders $x^{3k} \log^k(x)$ and $x^{3k+3/2} \log^k(x)$ for
integers $k\ge 0$ ($x$ a PN compactness parameter), and the subleading
logarithms, which appear at orders $x^{3k} \log^{k-1}(x)$ and $x^{3k+3/2}
\log^{k-1}(x)$ ($k\ge 1$), in both the energy and angular momentum radiated to
infinity. For the energy flux leading logarithms, we show that to arbitrarily
high PN order their eccentricity dependence is determined by particular sums
over the function $g(n,e_t)$, derived from the Newtonian mass quadrupole
moment, that normally gives the spectral content of the Peters-Mathews flux as
a function of radial harmonic $n$. An analogous power spectrum
$\tilde{g}(n,e_t)$ determines the leading logarithms of the angular momentum
flux. For subleading logs, the quadrupole power spectra are again shown to play
a role, providing a distinguishable part of the eccentricity dependence of
these flux terms to high PN order. With the quadrupole contribution understood,
the remaining analytic eccentricity dependence of the subleading logs can in
principle be determined more easily using black hole perturbation theory. We
show this procedure in action, deriving the complete analytic structure of the
$x^6 \log(x)$ subleading-log term and an analytic expansion of the $x^{9/2}$
subleading log to high order in a power series in eccentricity. We discuss how
these methods might be extended to other sequences of terms in the PN expansion
involving logarithms.
| [
{
"created": "Thu, 12 Sep 2019 18:00:15 GMT",
"version": "v1"
}
] | 2019-12-04 | [
[
"Munna",
"Christopher",
""
],
[
"Evans",
"Charles R.",
""
]
] | We present new results on the analytic eccentricity dependence of several sequences of gravitational wave flux terms at high post-Newtonian (PN) order for extreme-mass-ratio inspirals. These sequences are the leading logarithms, which appear at PN orders $x^{3k} \log^k(x)$ and $x^{3k+3/2} \log^k(x)$ for integers $k\ge 0$ ($x$ a PN compactness parameter), and the subleading logarithms, which appear at orders $x^{3k} \log^{k-1}(x)$ and $x^{3k+3/2} \log^{k-1}(x)$ ($k\ge 1$), in both the energy and angular momentum radiated to infinity. For the energy flux leading logarithms, we show that to arbitrarily high PN order their eccentricity dependence is determined by particular sums over the function $g(n,e_t)$, derived from the Newtonian mass quadrupole moment, that normally gives the spectral content of the Peters-Mathews flux as a function of radial harmonic $n$. An analogous power spectrum $\tilde{g}(n,e_t)$ determines the leading logarithms of the angular momentum flux. For subleading logs, the quadrupole power spectra are again shown to play a role, providing a distinguishable part of the eccentricity dependence of these flux terms to high PN order. With the quadrupole contribution understood, the remaining analytic eccentricity dependence of the subleading logs can in principle be determined more easily using black hole perturbation theory. We show this procedure in action, deriving the complete analytic structure of the $x^6 \log(x)$ subleading-log term and an analytic expansion of the $x^{9/2}$ subleading log to high order in a power series in eccentricity. We discuss how these methods might be extended to other sequences of terms in the PN expansion involving logarithms. |
1503.05845 | Ulvi Yurtsever | Ulvi Yurtsever and Steven Wilkinson | Limits and Signatures of Relativistic Spaceflight | 11 pages, 5 figures | null | null | null | gr-qc physics.pop-ph | http://creativecommons.org/licenses/publicdomain/ | While special relativity imposes an absolute speed limit at the speed of
light, our Universe is not empty Minkowski spacetime. The constituents that
fill the interstellar/intergalactic vacuum, including the cosmic microwave
background photons, impose a lower speed limit on any object travelling at
relativistic velocities. Scattering of cosmic microwave phtotons from an
ultra-relativistic object may create radiation with a characteristic signature
allowing the detection of such objects at large distances.
| [
{
"created": "Fri, 13 Mar 2015 23:17:10 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Apr 2015 17:55:20 GMT",
"version": "v2"
},
{
"created": "Sat, 18 Apr 2015 21:58:25 GMT",
"version": "v3"
}
] | 2015-04-21 | [
[
"Yurtsever",
"Ulvi",
""
],
[
"Wilkinson",
"Steven",
""
]
] | While special relativity imposes an absolute speed limit at the speed of light, our Universe is not empty Minkowski spacetime. The constituents that fill the interstellar/intergalactic vacuum, including the cosmic microwave background photons, impose a lower speed limit on any object travelling at relativistic velocities. Scattering of cosmic microwave phtotons from an ultra-relativistic object may create radiation with a characteristic signature allowing the detection of such objects at large distances. |
2009.10614 | Andrew Sullivan | Andrew Sullivan, Nicol\'as Yunes, Thomas P. Sotiriou | Numerical Black Hole Solutions in Modified Gravity Theories: Axial
Symmetry Case | null | Phys. Rev. D 103, 124058 (2021) | 10.1103/PhysRevD.103.124058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend a recently developed numerical code to obtain stationary,
axisymmetric solutions that describe rotating black hole spacetimes in a wide
class of modified theories of gravity. The code utilizes a relaxed
Newton-Raphson method to solve the full nonlinear modified Einstein's Equations
on a two-dimensional grid with a Newton polynomial finite difference scheme. We
validate this code by considering static and axisymmetric black holes in
General Relativity. We obtain rotating black hole solutions in
scalar-Gauss-Bonnet gravity with a linear (linear scalar-Gauss-Bonnet) and an
exponential (Einstein-dilaton-Gauss-Bonnet) coupling and compare them to
analytical and numerical perturbative solutions. From these numerical
solutions, we construct a fitted analytical model and study observable
properties calculated from the numerical results.
| [
{
"created": "Tue, 22 Sep 2020 15:17:59 GMT",
"version": "v1"
}
] | 2021-06-30 | [
[
"Sullivan",
"Andrew",
""
],
[
"Yunes",
"Nicolás",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | We extend a recently developed numerical code to obtain stationary, axisymmetric solutions that describe rotating black hole spacetimes in a wide class of modified theories of gravity. The code utilizes a relaxed Newton-Raphson method to solve the full nonlinear modified Einstein's Equations on a two-dimensional grid with a Newton polynomial finite difference scheme. We validate this code by considering static and axisymmetric black holes in General Relativity. We obtain rotating black hole solutions in scalar-Gauss-Bonnet gravity with a linear (linear scalar-Gauss-Bonnet) and an exponential (Einstein-dilaton-Gauss-Bonnet) coupling and compare them to analytical and numerical perturbative solutions. From these numerical solutions, we construct a fitted analytical model and study observable properties calculated from the numerical results. |
gr-qc/0411029 | Frank B. Estabrook | Frank B. Estabrook | Mathematical Structure of Tetrad Equations for Vacuum Relativity | Slightly revised. In press, Phys. Rev. D15 | Phys.Rev. D71 (2005) 044004 | 10.1103/PhysRevD.71.044004 | null | gr-qc | null | The tetrad partial differential equations formulated by Buchman and Bardeen
for vacuum gravity are shown to be well posed by calculation of the Cartan
characters of an associated exterior differential system. Gauge specializations
are discussed. A Cartan 4-form is found for this field theory, together with
its intrinsic version the Lagrangian density.
| [
{
"created": "Fri, 5 Nov 2004 19:44:43 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Jan 2005 00:00:07 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Jan 2005 21:49:57 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Estabrook",
"Frank B.",
""
]
] | The tetrad partial differential equations formulated by Buchman and Bardeen for vacuum gravity are shown to be well posed by calculation of the Cartan characters of an associated exterior differential system. Gauge specializations are discussed. A Cartan 4-form is found for this field theory, together with its intrinsic version the Lagrangian density. |
2304.10019 | Shinji Tsujikawa | Shinji Tsujikawa | Black holes in a new gravitational theory with trace anomalies | 14 pages, 1 figure | Phys. Lett. B 843 (2023) 138054 | 10.1016/j.physletb.2023.138054 | WUCG-23-05 | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In a new gravitational theory with the trace anomaly recently proposed by
Gabadadze, we study the existence of hairy black hole solutions on a static and
spherically symmetric background. In this theory, the effective 4-dimensional
action contains a kinetic term of the conformal scalar field related to a new
scale $bar{M}$ much below the Planck mass. This property can overcome a strong
coupling problem known to be present in general relativity supplemented by the
trace anomaly as well as in 4-dimensional Einstein-Gauss-Bonnet gravity. We
find a new hairy black hole solution arising from the Gauss-Bonnet trace
anomaly, which satisfies regular boundary conditions of the conformal scalar
and metric on the horizon. Unlike unstable exact black hole solutions with a
divergent derivative of the scalar on the horizon derived for some related
theories in the literature, we show that our hairy black hole solution can be
consistent with all the linear stability conditions of odd- and even-parity
perturbations.
| [
{
"created": "Thu, 20 Apr 2023 00:15:27 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jul 2023 23:25:54 GMT",
"version": "v2"
}
] | 2023-07-07 | [
[
"Tsujikawa",
"Shinji",
""
]
] | In a new gravitational theory with the trace anomaly recently proposed by Gabadadze, we study the existence of hairy black hole solutions on a static and spherically symmetric background. In this theory, the effective 4-dimensional action contains a kinetic term of the conformal scalar field related to a new scale $bar{M}$ much below the Planck mass. This property can overcome a strong coupling problem known to be present in general relativity supplemented by the trace anomaly as well as in 4-dimensional Einstein-Gauss-Bonnet gravity. We find a new hairy black hole solution arising from the Gauss-Bonnet trace anomaly, which satisfies regular boundary conditions of the conformal scalar and metric on the horizon. Unlike unstable exact black hole solutions with a divergent derivative of the scalar on the horizon derived for some related theories in the literature, we show that our hairy black hole solution can be consistent with all the linear stability conditions of odd- and even-parity perturbations. |
1703.06282 | Li Tang | Xin Li, Li Tang and Hai-Nan Lin | Comparing the dark matter models, modified Newtonian dynamics and
modified gravity in accounting for the galaxy rotation curves | 12 pages, 3 figures | Chin. Phys. C 41 (2017) 055101 | 10.1088/1674-1137/41/5/055101 | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | We compare six models (including the baryonic model, two dark matter models,
two modified Newtonian dynamics models and one modified gravity model) in
accounting for the galaxy rotation curves. For the dark matter models, we
assume NFW profile and core-modified profile for the dark halo, respectively.
For the modified Newtonian dynamics models, we discuss Milgrom's MOND theory
with two different interpolation functions, i.e. the standard and the simple
interpolation functions. As for the modified gravity, we focus on Moffat's MSTG
theory. We fit these models to the observed rotation curves of 9 high-surface
brightness and 9 low-surface brightness galaxies. We apply the Bayesian
Information Criterion and the Akaike Information Criterion to test the
goodness-of-fit of each model. It is found that non of the six models can well
fit all the galaxy rotation curves. Two galaxies can be best fitted by the
baryonic model without involving the nonluminous dark matter. MOND can fit the
largest number of galaxies, and only one galaxy can be best fitted by MSTG
model. Core-modified model can well fit about one half LSB galaxies but no HSB
galaxy, while NFW model can fit only a small fraction of HSB galaxies but no
LSB galaxy. This may imply that the oversimplified NFW and Core-modified
profiles couldn't well mimic the postulated dark matter halo.
| [
{
"created": "Sat, 18 Mar 2017 10:49:46 GMT",
"version": "v1"
}
] | 2017-05-10 | [
[
"Li",
"Xin",
""
],
[
"Tang",
"Li",
""
],
[
"Lin",
"Hai-Nan",
""
]
] | We compare six models (including the baryonic model, two dark matter models, two modified Newtonian dynamics models and one modified gravity model) in accounting for the galaxy rotation curves. For the dark matter models, we assume NFW profile and core-modified profile for the dark halo, respectively. For the modified Newtonian dynamics models, we discuss Milgrom's MOND theory with two different interpolation functions, i.e. the standard and the simple interpolation functions. As for the modified gravity, we focus on Moffat's MSTG theory. We fit these models to the observed rotation curves of 9 high-surface brightness and 9 low-surface brightness galaxies. We apply the Bayesian Information Criterion and the Akaike Information Criterion to test the goodness-of-fit of each model. It is found that non of the six models can well fit all the galaxy rotation curves. Two galaxies can be best fitted by the baryonic model without involving the nonluminous dark matter. MOND can fit the largest number of galaxies, and only one galaxy can be best fitted by MSTG model. Core-modified model can well fit about one half LSB galaxies but no HSB galaxy, while NFW model can fit only a small fraction of HSB galaxies but no LSB galaxy. This may imply that the oversimplified NFW and Core-modified profiles couldn't well mimic the postulated dark matter halo. |
2212.03732 | Michele Lenzi | Michele Lenzi and Carlos F. Sopuerta | Black Hole Greybody Factors from Korteweg-de Vries Integrals: Theory | 22 pages, 5 figures | null | 10.1103/PhysRevD.107.044010 | null | gr-qc hep-th nlin.SI | http://creativecommons.org/licenses/by/4.0/ | The dynamics of perturbed non-rotating black holes (BHs) can be described in
terms of master equations of the wave type with a potential. In the frequency
domain, the master equations become time-independent Schr\"odinger equations
with no discrete spectrum. It has been recently shown that these wave equations
possess an infinite number of symmetries that correspond to the flow of the
infinite hierarchy of Korteweg-de Vries (KdV) equations. As a consequence, the
infinite set of associated conserved quantities, the KdV integrals, are the
same for all the different master equations that we can consider. In this paper
we show that the BH scattering reflection and transmission coefficients
characterizing the continuous spectrum can be fully determined via a moment
problem, in such a way that the KdV integrals provide the momenta of a
distribution function depending only on the reflection coefficient. We also
discuss the existence and uniqueness of solutions, strategies to solve the
moment problem, and finally show the case of the P\"oschl-Teller potential
where all the steps can be carried out analytically.
| [
{
"created": "Wed, 7 Dec 2022 15:54:18 GMT",
"version": "v1"
}
] | 2023-02-22 | [
[
"Lenzi",
"Michele",
""
],
[
"Sopuerta",
"Carlos F.",
""
]
] | The dynamics of perturbed non-rotating black holes (BHs) can be described in terms of master equations of the wave type with a potential. In the frequency domain, the master equations become time-independent Schr\"odinger equations with no discrete spectrum. It has been recently shown that these wave equations possess an infinite number of symmetries that correspond to the flow of the infinite hierarchy of Korteweg-de Vries (KdV) equations. As a consequence, the infinite set of associated conserved quantities, the KdV integrals, are the same for all the different master equations that we can consider. In this paper we show that the BH scattering reflection and transmission coefficients characterizing the continuous spectrum can be fully determined via a moment problem, in such a way that the KdV integrals provide the momenta of a distribution function depending only on the reflection coefficient. We also discuss the existence and uniqueness of solutions, strategies to solve the moment problem, and finally show the case of the P\"oschl-Teller potential where all the steps can be carried out analytically. |
1201.5362 | Charles Dyer | George Kotsopoulos and Charles C. Dyer | A Domain Wall Solution by Perturbation of the Kasner Spacetime | null | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Plane symmetric perturbations are applied to an axially symmetric Kasner
spacetime which leads to no momentum flow orthogonal to the planes of symmetry.
This flow appears laminar and the structure can be interpreted as a domain
wall. We further extend consideration to the class of Bianchi Type I spacetimes
and obtain corresponding results.
| [
{
"created": "Wed, 25 Jan 2012 20:25:58 GMT",
"version": "v1"
}
] | 2012-01-26 | [
[
"Kotsopoulos",
"George",
""
],
[
"Dyer",
"Charles C.",
""
]
] | Plane symmetric perturbations are applied to an axially symmetric Kasner spacetime which leads to no momentum flow orthogonal to the planes of symmetry. This flow appears laminar and the structure can be interpreted as a domain wall. We further extend consideration to the class of Bianchi Type I spacetimes and obtain corresponding results. |
gr-qc/0007018 | Robert D. Klauber | Robert D. Klauber | Non-time-orthogonality, Gravitational Orbits, and Thomas Precession | 7 pages, including 4 figures, abstract, and references | null | null | null | gr-qc | null | Non-time-orthogonal analysis of rotating frames is applied to objects in
gravitational orbits and found to be internally consistent. The object's
surface speed about its axis of rotation, but not its orbital speed, is shown
to be readily detectable by any "enclosed box" experimenter on the surface of
such an object. Sagnac type effects manifest readily, but by somewhat subtle
means. The analysis is extended to objects bound in non-gravitational orbit,
where it is found to be fully in accord with the traditional analysis of Thomas
precession.
| [
{
"created": "Mon, 10 Jul 2000 17:15:38 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Klauber",
"Robert D.",
""
]
] | Non-time-orthogonal analysis of rotating frames is applied to objects in gravitational orbits and found to be internally consistent. The object's surface speed about its axis of rotation, but not its orbital speed, is shown to be readily detectable by any "enclosed box" experimenter on the surface of such an object. Sagnac type effects manifest readily, but by somewhat subtle means. The analysis is extended to objects bound in non-gravitational orbit, where it is found to be fully in accord with the traditional analysis of Thomas precession. |
1801.02032 | Ali Kaya | Ali Kaya | Superhorizon Electromagnetic Field Background from Higgs Loops in
Inflation | 20 pages, revtex4-1, v3: comments and an appendix discussing
dimensional regularization added, other minor changes, to appear in JCAP | null | 10.1088/1475-7516/2018/03/046 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | If Higgs is a spectator scalar, i.e. if it is not directly coupled to the
inflaton, superhorizon Higgs modes must have been exited during inflation.
Since Higgs is unstable its decay into photons is expected to seed superhorizon
photon modes. We use in-in perturbation theory to show that this naive physical
expectation is indeed fulfilled via loop effects. Specifically, we calculate
the first order Higgs loop correction to the magnetic field power spectrum
evaluated at some late time after inflation. It turns out that this loop
correction becomes much larger than the tree-level power spectrum at the
superhorizon scales. This offers a mechanism to generate cosmologically
interesting superhorizon vector modes by scalar-vector interactions.
| [
{
"created": "Sat, 6 Jan 2018 15:27:29 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jan 2018 19:37:24 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Mar 2018 14:28:04 GMT",
"version": "v3"
}
] | 2018-04-11 | [
[
"Kaya",
"Ali",
""
]
] | If Higgs is a spectator scalar, i.e. if it is not directly coupled to the inflaton, superhorizon Higgs modes must have been exited during inflation. Since Higgs is unstable its decay into photons is expected to seed superhorizon photon modes. We use in-in perturbation theory to show that this naive physical expectation is indeed fulfilled via loop effects. Specifically, we calculate the first order Higgs loop correction to the magnetic field power spectrum evaluated at some late time after inflation. It turns out that this loop correction becomes much larger than the tree-level power spectrum at the superhorizon scales. This offers a mechanism to generate cosmologically interesting superhorizon vector modes by scalar-vector interactions. |
gr-qc/0506098 | Jiliang Jing | Jiliang Jing and Qiyuan Pan | Dirac Quasinormal frequencies of the Kerr-Newman black hole | 14 pages, 2 figures | Nucl.Phys. B728 (2005) 109-120 | 10.1016/j.nuclphysb.2005.08.038 | null | gr-qc astro-ph hep-th | null | The Dirac quasinormal modes (QNMs) of the Kerr-Newman black hole are
investigated using continued fraction approach. It is shown that the
quasinormal frequencies in the complex $\omega$ plane move counterclockwise as
the charge or angular momentum per unit mass of the black hole increases. They
get a spiral-like shape, moving out of their Schwarzschild or
Reissner-Nordstr\"om values and "looping in" towards some limiting frequencies
as the charge and angular momentum per unit mass tend to their extremal values.
The number of the spirals increases as the overtone number increases but
decreases as the angular quantum number increases. It is also found that both
the real and imaginary parts are oscillatory functions of the angular momentum
per unit mass, and the oscillation becomes faster as the overtone number
increases but slower as the angular quantum number increases.
| [
{
"created": "Sun, 19 Jun 2005 01:17:56 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Jing",
"Jiliang",
""
],
[
"Pan",
"Qiyuan",
""
]
] | The Dirac quasinormal modes (QNMs) of the Kerr-Newman black hole are investigated using continued fraction approach. It is shown that the quasinormal frequencies in the complex $\omega$ plane move counterclockwise as the charge or angular momentum per unit mass of the black hole increases. They get a spiral-like shape, moving out of their Schwarzschild or Reissner-Nordstr\"om values and "looping in" towards some limiting frequencies as the charge and angular momentum per unit mass tend to their extremal values. The number of the spirals increases as the overtone number increases but decreases as the angular quantum number increases. It is also found that both the real and imaginary parts are oscillatory functions of the angular momentum per unit mass, and the oscillation becomes faster as the overtone number increases but slower as the angular quantum number increases. |
1902.06745 | Aida Ahmadzadegan | Aida Ahmadzadegan, Fatemeh Lalegani, Achim Kempf, Robert B. Mann | Probing geometric information using the Unruh effect in the vacuum | v2: update to published version | Phys. Rev. D 100, 085013 (2019) | 10.1103/PhysRevD.100.085013 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new method by which, in principle, it is possible to "see in
absolute darkness," i.e., without exchanging any real quanta through quantum
fields. This is possible because objects modify the mode structure of the
vacuum in their vicinity. The new method probes the mode structure of the
vacuum through the Unruh effect, i.e., by recording the excitation rates of
quantum systems that are accelerated.
| [
{
"created": "Mon, 18 Feb 2019 19:00:00 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Oct 2019 15:20:18 GMT",
"version": "v2"
}
] | 2019-10-30 | [
[
"Ahmadzadegan",
"Aida",
""
],
[
"Lalegani",
"Fatemeh",
""
],
[
"Kempf",
"Achim",
""
],
[
"Mann",
"Robert B.",
""
]
] | We present a new method by which, in principle, it is possible to "see in absolute darkness," i.e., without exchanging any real quanta through quantum fields. This is possible because objects modify the mode structure of the vacuum in their vicinity. The new method probes the mode structure of the vacuum through the Unruh effect, i.e., by recording the excitation rates of quantum systems that are accelerated. |
1612.01467 | Stephan Schiller | E. Wiens, A.Yu. Nevsky, and S. Schiller | Resonator with ultra-high length stability as a probe for
Equivalence-Principle-violating physics | to appear in Physical Review Letters (2016) | null | 10.1103/PhysRevLett.117.271102 | null | gr-qc physics.optics quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to investigate the long-term dimensional stability of matter, we
have operated an optical resonator fabricated from crystalline silicon at
1.5$\,$K continuously for over one year and repeatedly compared its resonance
frequency $f_{res}$ with the frequency of a GPS-monitored hydrogen maser. After
allowing for an initial settling time, over a 163-day interval we found a mean
fractional drift magnitude $|f_{res}^{-1}df_{res}/dt|<1.4\times10^{-20}$/s. The
resonator frequency is determined by the physical length and the speed of
light, and we measure it with respect to the atomic unit of time. Thus, the
bound rules out, to first order, a hypothetical differential effect of the
universe's expansion on rulers and atomic clocks. We also constrain a
hypothetical violation of the principle of Local Position Invariance for
resonator-based clocks and derive bounds for the strength of space-time
fluctuations.
| [
{
"created": "Mon, 5 Dec 2016 18:44:05 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"Wiens",
"E.",
""
],
[
"Nevsky",
"A. Yu.",
""
],
[
"Schiller",
"S.",
""
]
] | In order to investigate the long-term dimensional stability of matter, we have operated an optical resonator fabricated from crystalline silicon at 1.5$\,$K continuously for over one year and repeatedly compared its resonance frequency $f_{res}$ with the frequency of a GPS-monitored hydrogen maser. After allowing for an initial settling time, over a 163-day interval we found a mean fractional drift magnitude $|f_{res}^{-1}df_{res}/dt|<1.4\times10^{-20}$/s. The resonator frequency is determined by the physical length and the speed of light, and we measure it with respect to the atomic unit of time. Thus, the bound rules out, to first order, a hypothetical differential effect of the universe's expansion on rulers and atomic clocks. We also constrain a hypothetical violation of the principle of Local Position Invariance for resonator-based clocks and derive bounds for the strength of space-time fluctuations. |
1708.04758 | Luciano Combi | Luciano Combi and Gustavo E. Romero | Gravitational energy and radiation of a charged black hole | 10 pages, accepted for publication in Classical and Quantum Gravity | null | 10.1088/1361-6382/aa86c9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the energy configuration of a charged black hole in the
Teleparallel Framework of General Relativity. We obtain the energy-momentum
tensor of the gravitational field in a stationary frame, and we calculate its
contribution to the total energy of the system. We study the same gravitational
field measured by an accelerated frame and we analyze how the energy-momentum
tensor is transformed. We found that in the accelerated frame, a Poyinting-like
flux appears for the gravitational field but not for the electromagnetic field.
| [
{
"created": "Wed, 16 Aug 2017 03:31:19 GMT",
"version": "v1"
}
] | 2017-09-27 | [
[
"Combi",
"Luciano",
""
],
[
"Romero",
"Gustavo E.",
""
]
] | We analyze the energy configuration of a charged black hole in the Teleparallel Framework of General Relativity. We obtain the energy-momentum tensor of the gravitational field in a stationary frame, and we calculate its contribution to the total energy of the system. We study the same gravitational field measured by an accelerated frame and we analyze how the energy-momentum tensor is transformed. We found that in the accelerated frame, a Poyinting-like flux appears for the gravitational field but not for the electromagnetic field. |
gr-qc/9611024 | Radu Ionicioiu | Radu Ionicioiu (DAMTP, University of Cambridge, UK) | Building Blocks in Turaev-Viro Theory | 19 pages, LaTeX, 4 Postscript figures, uses epsf; minor correction | null | null | DAMTP/96-94 | gr-qc | null | We study the form of the Turaev-Viro partition function Z(M) for different
3-manifolds with boundary. We show that for $S^2$ boundaries Z(M) factorizes
into a term which contains the boundary dependence and another which depends
only on the topology of the underlying manifold. From this follows easily the
formula for the connected sum of two manifolds Z(M # N). For general $T_g$
boundaries this factorization holds only in a particular case.
| [
{
"created": "Sun, 10 Nov 1996 20:26:11 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Dec 1996 11:57:32 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Ionicioiu",
"Radu",
"",
"DAMTP, University of Cambridge, UK"
]
] | We study the form of the Turaev-Viro partition function Z(M) for different 3-manifolds with boundary. We show that for $S^2$ boundaries Z(M) factorizes into a term which contains the boundary dependence and another which depends only on the topology of the underlying manifold. From this follows easily the formula for the connected sum of two manifolds Z(M # N). For general $T_g$ boundaries this factorization holds only in a particular case. |
2103.13328 | Bivudutta Mishra Dr. | A.S. Agrawal, S.K. Tripathy, B.Mishra | Gravitational baryogenesis models comparison in f(R) Gravity | 8 pages, 4 figures, Accepted version in Chinese Journal of Physics | Chinese Journal of Physics, 71, 333-340, 2021 | 10.1016/j.cjph.2021.03.004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied the gravitational baryogenesis in f(R) theory of gravity with
an anisotropic Bianchi I space-time. The matter field is considered to be that
of perfect fluid. Two models pertaining to specific form of Ricci scalar have
been presented. The baryon-to-entropy ratio has been derived with the some
specific form of Ricci scalar in the anisotropic background. The gravitational
baryogenesis is examined and its behaviors are studied.
| [
{
"created": "Sat, 20 Mar 2021 14:03:54 GMT",
"version": "v1"
}
] | 2021-04-01 | [
[
"Agrawal",
"A. S.",
""
],
[
"Tripathy",
"S. K.",
""
],
[
"Mishra",
"B.",
""
]
] | We have studied the gravitational baryogenesis in f(R) theory of gravity with an anisotropic Bianchi I space-time. The matter field is considered to be that of perfect fluid. Two models pertaining to specific form of Ricci scalar have been presented. The baryon-to-entropy ratio has been derived with the some specific form of Ricci scalar in the anisotropic background. The gravitational baryogenesis is examined and its behaviors are studied. |
gr-qc/0106005 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | Observed threshold anomalies as the first hope of a manifestation of
Planck-length physics | 9 pages, Latex (to appear in proceedings of 9th Marcel Grossmann
Meeting) | null | 10.1142/9789812777386_0285 | null | gr-qc | null | The observations of photons from the BL Lac object Mk501 with energies above
10 TeV and of cosmic rays with energies above the GZK threshold appear to be
inconsistent with conventional theories. Remarkably, among the recent
new-physics proposals of solutions of these threshold paradoxes a prominent
role has been played by proposals based on quantum properties of space-time.
While the experimental evidence (and theory work attempting to interpret it) is
much too preliminary to justify any serious hopes that we might have stumbled
upon the first manifestation of a "quantum gravity", the fact that for the
first time phenomenological models involving quantum-gravity ideas are
competing on level ground with other new-physics proposals clearly marks the
beginning of a new stage of quantum-gravity research. I emphasize one important
aspect of this new phenomenology: combining the determination of the relevant
thresholds with data on the time/energy structure of gamma-ray bursts it is
possible to distinguish between alternative quantum-gravity scenarios. This
point is illustrated focusing on 3 specific scenarios: dispersion-inducing
space-time foam, string-theory-motivated non-commutative space-time, and this
author's recent proposal of a relativistic theory in which the Planck length
has the role of fundamental observer-independent minimum length.
| [
{
"created": "Sun, 3 Jun 2001 13:38:57 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | The observations of photons from the BL Lac object Mk501 with energies above 10 TeV and of cosmic rays with energies above the GZK threshold appear to be inconsistent with conventional theories. Remarkably, among the recent new-physics proposals of solutions of these threshold paradoxes a prominent role has been played by proposals based on quantum properties of space-time. While the experimental evidence (and theory work attempting to interpret it) is much too preliminary to justify any serious hopes that we might have stumbled upon the first manifestation of a "quantum gravity", the fact that for the first time phenomenological models involving quantum-gravity ideas are competing on level ground with other new-physics proposals clearly marks the beginning of a new stage of quantum-gravity research. I emphasize one important aspect of this new phenomenology: combining the determination of the relevant thresholds with data on the time/energy structure of gamma-ray bursts it is possible to distinguish between alternative quantum-gravity scenarios. This point is illustrated focusing on 3 specific scenarios: dispersion-inducing space-time foam, string-theory-motivated non-commutative space-time, and this author's recent proposal of a relativistic theory in which the Planck length has the role of fundamental observer-independent minimum length. |
2408.00154 | N\'ickolas de Aguiar Alves | N\'ickolas de Aguiar Alves, Andre G. S. Landulfo, and Bruno Arderucio
Costa | Positive Mass in General Relativity Without Energy Conditions | 26 pages, 9 figures. v2: improved exposition of main results,
introduction and abstract modified accordingly | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | A long-standing problem in physics is why observed masses are always
positive. While energy conditions in quantum field theory can partly answer
this problem, in this paper we find evidence that classical general relativity
abhors negative masses, without the need for quantum theory or energy
conditions. This is done by considering many different models of negative-mass
"stars" and showing they are dynamically unstable. A fortiori, we show that any
barotropic negative-mass star must be dynamically unstable.
| [
{
"created": "Wed, 31 Jul 2024 20:36:33 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Aug 2024 22:54:47 GMT",
"version": "v2"
}
] | 2024-08-14 | [
[
"Alves",
"Níckolas de Aguiar",
""
],
[
"Landulfo",
"Andre G. S.",
""
],
[
"Costa",
"Bruno Arderucio",
""
]
] | A long-standing problem in physics is why observed masses are always positive. While energy conditions in quantum field theory can partly answer this problem, in this paper we find evidence that classical general relativity abhors negative masses, without the need for quantum theory or energy conditions. This is done by considering many different models of negative-mass "stars" and showing they are dynamically unstable. A fortiori, we show that any barotropic negative-mass star must be dynamically unstable. |
1610.07224 | Bishop Mongwane | Bishop Mongwane | On the Hyperbolicity and Stability of $3+1$ Formulations of Metric
$f(R)$ Gravity | 20, pages | Gen Relativ Gravit (2016) 48(11): 152 | 10.1007/s10714-016-2147-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | $3+1$ formulations of the Einstein field equations have become an invaluable
tool in Numerical relativity, having been used successfully in modeling
spacetimes of black hole collisions, stellar collapse and other complex
systems. It is plausible that similar considerations could prove fruitful for
modified gravity theories. In this article, we pursue from a numerical
relativistic viewpoint the $3+1$ formulation of metric $f(R)$ gravity as it
arises from the fourth order equations of motion, without invoking the
dynamical equivalence with Brans-Dicke theories. We present the resulting
system of evolution and constraint equations for a generic function $f(R)$,
subject to the usual viability conditions. We confirm that the time propagation
of the $f(R)$ Hamiltonian and Momentum constraints take the same Mathematical
form as in general relativity, irrespective of the $f(R)$ model. We further
recast the 3+1 system in a form akin to the BSSNOK formulation of numerical
relativity. Without assuming any specific model, we show that the ADM version
of $f(R)$ is weakly hyperbolic and is plagued by similar zero speed modes as in
the general relativity case. On the other hand the BSSNOK version is strongly
hyperbolic and hence a promising formulation for numerical simulations in
metric $f(R)$ theories.
| [
{
"created": "Sun, 23 Oct 2016 19:44:18 GMT",
"version": "v1"
}
] | 2016-10-25 | [
[
"Mongwane",
"Bishop",
""
]
] | $3+1$ formulations of the Einstein field equations have become an invaluable tool in Numerical relativity, having been used successfully in modeling spacetimes of black hole collisions, stellar collapse and other complex systems. It is plausible that similar considerations could prove fruitful for modified gravity theories. In this article, we pursue from a numerical relativistic viewpoint the $3+1$ formulation of metric $f(R)$ gravity as it arises from the fourth order equations of motion, without invoking the dynamical equivalence with Brans-Dicke theories. We present the resulting system of evolution and constraint equations for a generic function $f(R)$, subject to the usual viability conditions. We confirm that the time propagation of the $f(R)$ Hamiltonian and Momentum constraints take the same Mathematical form as in general relativity, irrespective of the $f(R)$ model. We further recast the 3+1 system in a form akin to the BSSNOK formulation of numerical relativity. Without assuming any specific model, we show that the ADM version of $f(R)$ is weakly hyperbolic and is plagued by similar zero speed modes as in the general relativity case. On the other hand the BSSNOK version is strongly hyperbolic and hence a promising formulation for numerical simulations in metric $f(R)$ theories. |
1010.2387 | Roger Tagne Wafo | Piotr T. Chru\'sciel and Roger Tagne Wafo | Solutions of quasi-linear wave equations polyhomogeneous at null
infinity in high dimensions | 88 pages, 3 figures | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove propagation of weighted Sobolev regularity for solutions of the
hyperboloidal Cauchy problem for a class of quasi-linear symmetric hyperbolic
systems, under structure conditions compatible with the Einstein-Maxwell
equations in space-time dimensions $n+1\ge 7$. Similarly we prove propagation
of polyhomogeneity in dimensions $n+1\ge 9$. As a byproduct we obtain, in those
last dimensions, polyhomogeneity at null infinity of small data solutions of
vacuum Einstein, or Einstein-Maxwell equations evolving out of initial data
which are stationary outside of a ball.
| [
{
"created": "Tue, 12 Oct 2010 13:35:11 GMT",
"version": "v1"
}
] | 2010-10-13 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Wafo",
"Roger Tagne",
""
]
] | We prove propagation of weighted Sobolev regularity for solutions of the hyperboloidal Cauchy problem for a class of quasi-linear symmetric hyperbolic systems, under structure conditions compatible with the Einstein-Maxwell equations in space-time dimensions $n+1\ge 7$. Similarly we prove propagation of polyhomogeneity in dimensions $n+1\ge 9$. As a byproduct we obtain, in those last dimensions, polyhomogeneity at null infinity of small data solutions of vacuum Einstein, or Einstein-Maxwell equations evolving out of initial data which are stationary outside of a ball. |
gr-qc/0609056 | Pavel Krtous | J. B. Griffiths, P. Krtous, J. Podolsky | Interpreting the C-metric | 22 pages, 14 figures (low-resolution figures; for the version with
high-resolution figures see http://utf.mff.cuni.cz/~krtous/papers/ or
http://www-staff.lboro.ac.uk/~majbg/) | Class.Quant.Grav. 23 (2006) 6745-6766 | 10.1088/0264-9381/23/23/008 | null | gr-qc | null | The basic properties of the C-metric are well known. It describes a pair of
causally separated black holes which accelerate in opposite directions under
the action of forces represented by conical singularities. However, these
properties can be demonstrated much more transparently by making use of
recently developed coordinate systems for which the metric functions have a
simple factor structure. These enable us to obtain explicit
Kruskal-Szekeres-type extensions through the horizons and construct
two-dimensional conformal Penrose diagrams. We then combine these into a
three-dimensional picture which illustrates the global causal structure of the
space-time outside the black hole horizons. Using both the weak field limit and
some invariant quantities, we give a direct physical interpretation of the
parameters which appear in the new form of the metric. For completeness,
relations to other familiar coordinate systems are also discussed.
| [
{
"created": "Fri, 15 Sep 2006 15:55:28 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Griffiths",
"J. B.",
""
],
[
"Krtous",
"P.",
""
],
[
"Podolsky",
"J.",
""
]
] | The basic properties of the C-metric are well known. It describes a pair of causally separated black holes which accelerate in opposite directions under the action of forces represented by conical singularities. However, these properties can be demonstrated much more transparently by making use of recently developed coordinate systems for which the metric functions have a simple factor structure. These enable us to obtain explicit Kruskal-Szekeres-type extensions through the horizons and construct two-dimensional conformal Penrose diagrams. We then combine these into a three-dimensional picture which illustrates the global causal structure of the space-time outside the black hole horizons. Using both the weak field limit and some invariant quantities, we give a direct physical interpretation of the parameters which appear in the new form of the metric. For completeness, relations to other familiar coordinate systems are also discussed. |
gr-qc/9510053 | Claes R. Cramer | Claes R Cramer | Using the Uncharged Kerr Black Hole as a Gravitational Mirror | 11 pages Latex, 3 Postscript figures, uufiles to compress | Gen.Rel.Grav. 29 (1997) 445-454 | 10.1023/A:1018878515046 | null | gr-qc | null | We extend the study of the possibility to use the Schwarzschild black hole as
a gravitational mirror to the more general case of an uncharged Kerr black
hole. We use the null geodesic equation in the equatorial plane to prove a
theorem concerning the conditions the impact parameter has to satisfy if there
shall exist boomerang photons. We derive an equation for these boomerang
photons and an equation for the emission angle. Finally, the radial null
geodesic equation is integrated numerically in order to illustrate boomerang
photons.
| [
{
"created": "Wed, 25 Oct 1995 21:32:33 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Cramer",
"Claes R",
""
]
] | We extend the study of the possibility to use the Schwarzschild black hole as a gravitational mirror to the more general case of an uncharged Kerr black hole. We use the null geodesic equation in the equatorial plane to prove a theorem concerning the conditions the impact parameter has to satisfy if there shall exist boomerang photons. We derive an equation for these boomerang photons and an equation for the emission angle. Finally, the radial null geodesic equation is integrated numerically in order to illustrate boomerang photons. |
1510.00893 | Yasunari Kurita | Yasunari Kurita, Hiroyuki Nakano | Gravitational waves from dark matter collapse in a star | 25 pages, 5 figures, typos corrected, comments added. Version
accepted by PRD | Phys. Rev. D 93, 023508 (2016) | 10.1103/PhysRevD.93.023508 | null | gr-qc astro-ph.SR hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the collapse of clusters of weakly interacting massive
particles (WIMPs) in the core of a Sun-like star and the possible formation of
mini-black holes and the emission of gravitational waves. When the number of
WIMPs is small, thermal pressure balances the WIMP cluster's self gravity. If
the number of WIMPs is larger than a critical number, thermal pressure cannot
balance gravity and the cluster contracts. If WIMPs are collisionless and
bosonic, the cluster collapses directly to form a mini-black hole. For
fermionic WIMPs, the cluster contracts until it is sustained by Fermi pressure,
forming a small compact object. If the fermionic WIMP mass is smaller than
$4\times 10^2$ GeV, the radius of the compact object is larger than its
Schwarzschild radius and Fermi pressure temporally sustains its self gravity,
halting the formation of a black hole. If the fermionic WIMP mass is larger
than $4\times 10^2$ GeV, the radius is smaller than its Schwarzschild radius
and the compact object becomes a mini-black hole. If the WIMP mass is 1 TeV,
the size of the black hole will be approximately 2.5 cm and ultra high
frequency gravitational waves will be emitted during black hole formation. The
central frequency $f_c$ of ringdown gravitational waves emitted from the black
hole will be approximately 2 GHz. To detect the ringdown gravitational waves,
the detector's noise must be below $\sqrt{S_h(f_c)}\approx 10^{-30}/\sqrt{\rm
Hz}$.
| [
{
"created": "Sun, 4 Oct 2015 01:34:18 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Oct 2015 11:53:31 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jan 2016 11:48:53 GMT",
"version": "v3"
}
] | 2016-01-20 | [
[
"Kurita",
"Yasunari",
""
],
[
"Nakano",
"Hiroyuki",
""
]
] | We investigate the collapse of clusters of weakly interacting massive particles (WIMPs) in the core of a Sun-like star and the possible formation of mini-black holes and the emission of gravitational waves. When the number of WIMPs is small, thermal pressure balances the WIMP cluster's self gravity. If the number of WIMPs is larger than a critical number, thermal pressure cannot balance gravity and the cluster contracts. If WIMPs are collisionless and bosonic, the cluster collapses directly to form a mini-black hole. For fermionic WIMPs, the cluster contracts until it is sustained by Fermi pressure, forming a small compact object. If the fermionic WIMP mass is smaller than $4\times 10^2$ GeV, the radius of the compact object is larger than its Schwarzschild radius and Fermi pressure temporally sustains its self gravity, halting the formation of a black hole. If the fermionic WIMP mass is larger than $4\times 10^2$ GeV, the radius is smaller than its Schwarzschild radius and the compact object becomes a mini-black hole. If the WIMP mass is 1 TeV, the size of the black hole will be approximately 2.5 cm and ultra high frequency gravitational waves will be emitted during black hole formation. The central frequency $f_c$ of ringdown gravitational waves emitted from the black hole will be approximately 2 GHz. To detect the ringdown gravitational waves, the detector's noise must be below $\sqrt{S_h(f_c)}\approx 10^{-30}/\sqrt{\rm Hz}$. |
1108.0248 | Umpei Miyamoto | Umpei Miyamoto, Sanjay Jhingan, Tomohiro Harada | Weak cosmic censorship in gravitational collapse with astrophysical
parameter values | 10 pages, 2 figures, 1 table; v2: title changed, to appear in
Progress of Theoretical and Experimental Physics | Prog. Theor. Exp. Phys. (2013) 053E01 | 10.1093/ptep/ptt027 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possible violation of the weak cosmic censorship hypothesis in
astrophysical phenomena can provide us with the information about
trans-Planckian physics through observations. We present negative evidence,
however, that one should not expect such a possibility at least when the
deviation from spherical symmetry is negligible and the parameter values of
collapse are astrophysically reasonable. Taking the Lema\^itre-Tolman-Bondi
solution as the model most likely to counter the weak hypothesis, we show that
the mass ($ \gtrsim 1.5 M_\odot $) and density ($ \gtrsim 1.5 \times 10^{15} \;
{\rm g/cm^3}$) of the collapsing object produce a gravitational field strong
enough to capture any null rays soon after emanating from the singularity.
| [
{
"created": "Mon, 1 Aug 2011 06:41:20 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Mar 2013 01:56:53 GMT",
"version": "v2"
}
] | 2013-05-24 | [
[
"Miyamoto",
"Umpei",
""
],
[
"Jhingan",
"Sanjay",
""
],
[
"Harada",
"Tomohiro",
""
]
] | The possible violation of the weak cosmic censorship hypothesis in astrophysical phenomena can provide us with the information about trans-Planckian physics through observations. We present negative evidence, however, that one should not expect such a possibility at least when the deviation from spherical symmetry is negligible and the parameter values of collapse are astrophysically reasonable. Taking the Lema\^itre-Tolman-Bondi solution as the model most likely to counter the weak hypothesis, we show that the mass ($ \gtrsim 1.5 M_\odot $) and density ($ \gtrsim 1.5 \times 10^{15} \; {\rm g/cm^3}$) of the collapsing object produce a gravitational field strong enough to capture any null rays soon after emanating from the singularity. |
1108.0931 | Alberto Diez-Tejedor | Juan Barranco, Argelia Bernal, Juan Carlos Degollado, Alberto
Diez-Tejedor, Miguel Megevand, Miguel Alcubierre, Dar\'io N\'u\~nez and
Olivier Sarbach | Are black holes a serious threat to scalar field dark matter models? | 34 pages, 13 figures | Phys. Rev. D 84, 083008 (2011) | 10.1103/PhysRevD.84.083008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Classical scalar fields have been proposed as possible candidates for the
dark matter component of the universe. Given the fact that super-massive black
holes seem to exist at the center of most galaxies, in order to be a viable
candidate for the dark matter halo a scalar field configuration should be
stable in the presence of a central black hole, or at least be able to survive
for cosmological time-scales. In the present work we consider a scalar field as
a test field on a Schwarzschild background, and study under which conditions
one can obtain long-lived configurations. We present a detailed study of the
Klein-Gordon equation in the Schwarzschild spacetime, both from an analytical
and numerical point of view, and show that indeed there exist quasi-stationary
solutions that can remain surrounding a black hole for large time-scales.
| [
{
"created": "Wed, 3 Aug 2011 20:00:04 GMT",
"version": "v1"
}
] | 2012-08-01 | [
[
"Barranco",
"Juan",
""
],
[
"Bernal",
"Argelia",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Diez-Tejedor",
"Alberto",
""
],
[
"Megevand",
"Miguel",
""
],
[
"Alcubierre",
"Miguel",
""
],
[
"Núñez",
"Darío",
""
],
[
"Sarbach",
"Olivier",
""
]
] | Classical scalar fields have been proposed as possible candidates for the dark matter component of the universe. Given the fact that super-massive black holes seem to exist at the center of most galaxies, in order to be a viable candidate for the dark matter halo a scalar field configuration should be stable in the presence of a central black hole, or at least be able to survive for cosmological time-scales. In the present work we consider a scalar field as a test field on a Schwarzschild background, and study under which conditions one can obtain long-lived configurations. We present a detailed study of the Klein-Gordon equation in the Schwarzschild spacetime, both from an analytical and numerical point of view, and show that indeed there exist quasi-stationary solutions that can remain surrounding a black hole for large time-scales. |
gr-qc/0702074 | Muhammad Sharif | Asghar Qadir, M. Sharif and M. Shoaib | The Momentum Four-Vector in the $e\psi$N Formalism and the Angular
Momentum Imparted to Test Particles by Gravitational Waves | 8 pages, LaTex | Nuovo Cim. B115 (2000) 419-425 | null | null | gr-qc | null | Since gravitational waves are solutions of Einstein's field equations with a
zero stress-energy tensor, the reality of these waves was questioned. To
demonstrate it, the momentum imparted to test particles by such waves was
evaluated. A closed form expression for this quantity was provided by Qadir and
Sharif, using an extension of the pseudo-Newtonian formalism. That formalism
carried with it the zero component of the momentum vector, which could not be
interpreted as the energy imparted to the test particle. Sharif proposed that
it may represent the angular momentum imparted to test particles by
gravitational waves. In this paper it is shown that this interpretation is not
valid. An alternative explanation has been provided.
| [
{
"created": "Wed, 14 Feb 2007 02:56:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Qadir",
"Asghar",
""
],
[
"Sharif",
"M.",
""
],
[
"Shoaib",
"M.",
""
]
] | Since gravitational waves are solutions of Einstein's field equations with a zero stress-energy tensor, the reality of these waves was questioned. To demonstrate it, the momentum imparted to test particles by such waves was evaluated. A closed form expression for this quantity was provided by Qadir and Sharif, using an extension of the pseudo-Newtonian formalism. That formalism carried with it the zero component of the momentum vector, which could not be interpreted as the energy imparted to the test particle. Sharif proposed that it may represent the angular momentum imparted to test particles by gravitational waves. In this paper it is shown that this interpretation is not valid. An alternative explanation has been provided. |
gr-qc/0309118 | Maria J. Pareja | M.J. Pareja | Bounds on the dragging rate and on the rotational mass-energy in slowly
and differentially rotating relativistic stars | 23 pages, latex. Submitted to J. Math. Phys | null | 10.1063/1.1767987 | null | gr-qc | null | For relativistic stars rotating slowly and differentially with a positive
angular velocity, some properties in relation to the positiveness of the rate
of rotational dragging and of the angular momentum density are derived. Also, a
new proof for the bounds on the rotational mass-energy is given.
| [
{
"created": "Thu, 25 Sep 2003 10:21:08 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Pareja",
"M. J.",
""
]
] | For relativistic stars rotating slowly and differentially with a positive angular velocity, some properties in relation to the positiveness of the rate of rotational dragging and of the angular momentum density are derived. Also, a new proof for the bounds on the rotational mass-energy is given. |
1602.08779 | Oleg Zaslavskii | O. B. Zaslavskii | Black hole with a scalar field as a particle accelerator | 26 pages. Substantially expanded. We present full list of possible
scenarios with unbounded E_c.m. for a given system | Int. Journal of Mod. Physics D, Vol. 26 (2017) 1750108 | 10.1142/S0218271817501085 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider stationary axially symmetric black holes with the background
scalar field and test particles that can interact with this field directly.
Then, particle collision near a black hole can lead to the unbounded energy $%
E_{c.m.}$ in the centre of mass frame (contrary to some recent claims in
literature). This happens always if one of particles is neutral whereas another
one has nonzero scalar charge. Kinematically, two cases occur here. (i) A
neutral particle approaches the horizon with the speed of light while the
velocity of the charged one remains separated from it (this is direct analogue
of the situation with collision of geodesic particles.). (ii) Both particles
approach the horizon with the speed almost equal to that of light but with
different rates. As a result, in both cases the relative velocity also
approaches the speed of light, so that $E_{c.m.}$ $\ $becomes unbounded. We
consider also a case when the metric coefficient $g_{\phi \phi }\rightarrow 0$
near a black hole. Then, overlap between the geometric factor and the presence
of the scalar field opens additional scenarios in which unbounded energy
$E_{c.m.}$ is possible as well. We give a full list of possible scenarios of
high-energy collisions for the situations considered.
| [
{
"created": "Sun, 28 Feb 2016 22:27:54 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jun 2016 09:44:26 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Sep 2016 16:02:14 GMT",
"version": "v3"
}
] | 2017-09-22 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We consider stationary axially symmetric black holes with the background scalar field and test particles that can interact with this field directly. Then, particle collision near a black hole can lead to the unbounded energy $% E_{c.m.}$ in the centre of mass frame (contrary to some recent claims in literature). This happens always if one of particles is neutral whereas another one has nonzero scalar charge. Kinematically, two cases occur here. (i) A neutral particle approaches the horizon with the speed of light while the velocity of the charged one remains separated from it (this is direct analogue of the situation with collision of geodesic particles.). (ii) Both particles approach the horizon with the speed almost equal to that of light but with different rates. As a result, in both cases the relative velocity also approaches the speed of light, so that $E_{c.m.}$ $\ $becomes unbounded. We consider also a case when the metric coefficient $g_{\phi \phi }\rightarrow 0$ near a black hole. Then, overlap between the geometric factor and the presence of the scalar field opens additional scenarios in which unbounded energy $E_{c.m.}$ is possible as well. We give a full list of possible scenarios of high-energy collisions for the situations considered. |
2006.01879 | Emilio Elizalde | Emilio Elizalde, Martiros Khurshudyan, Sergei D. Odintsov, Ratbay
Myrzakulov | An analysis of the $H_{0}$ tension problem in a universe with a viscous
dark fluid | 13 pages, 4 figures | null | 10.1103/PhysRevD.102.123501 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, two inhomogeneous single fluid models for the Universe, which
are able to naturally solve the $H_{0}$ tension problem, are discussed. The
analysis is based on a Bayesian Machine Learning approach that uses a
generative process. The adopted method allows to constrain the free parameters
of each model by using the model itself, only. The observable is taken to be
the Hubble parameter, obtained from the generative process. Using the full
advantages of our method, the models are constrained for two redshift ranges.
Namely, first this is done with mock $H(z)$ data over $z\in [0,2.5]$, thus
covering known $H(z)$ observational data, which are most helpful to validate
the fit results. Then, aiming to extend to redshift ranges to be covered by the
most recent ongoing and future planned missions, the models are constrained for
the range $z\in[0,5]$, too. Full validation of the results for this extended
redshift range will have to wait for the near future, when higher redshift
$H(z)$ data become available. This makes our models fully falsifiable. Finally,
our second model here is able to explain the BOSS reported value for $H(z)$ at
$z=2.34$.
| [
{
"created": "Tue, 2 Jun 2020 18:56:18 GMT",
"version": "v1"
}
] | 2020-12-09 | [
[
"Elizalde",
"Emilio",
""
],
[
"Khurshudyan",
"Martiros",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In this paper, two inhomogeneous single fluid models for the Universe, which are able to naturally solve the $H_{0}$ tension problem, are discussed. The analysis is based on a Bayesian Machine Learning approach that uses a generative process. The adopted method allows to constrain the free parameters of each model by using the model itself, only. The observable is taken to be the Hubble parameter, obtained from the generative process. Using the full advantages of our method, the models are constrained for two redshift ranges. Namely, first this is done with mock $H(z)$ data over $z\in [0,2.5]$, thus covering known $H(z)$ observational data, which are most helpful to validate the fit results. Then, aiming to extend to redshift ranges to be covered by the most recent ongoing and future planned missions, the models are constrained for the range $z\in[0,5]$, too. Full validation of the results for this extended redshift range will have to wait for the near future, when higher redshift $H(z)$ data become available. This makes our models fully falsifiable. Finally, our second model here is able to explain the BOSS reported value for $H(z)$ at $z=2.34$. |
1210.8066 | Jonathan R. Gair | Jonathan R Gair and Edward K Porter | Observing extreme-mass-ratio inspirals with eLISA/NGO | 6 pages, 1 figure, to appear in proceedings of ninth LISA Symposium | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The extreme-mass-ratio inspirals (EMRIs) of stellar mass compact objects into
massive black holes in the centres of galaxies are an important source of
low-frequency gravitational waves for space-based detectors. We discuss the
prospects for detecting these sources with the evolved Laser Interferometer
Space Antenna (eLISA), recently proposed as an ESA mission candidate under the
name NGO. We show that NGO could observe a few tens of EMRIs over its two year
mission lifetime at redshifts z < 0.5 and describe how the event rate changes
under possible alternative specifications of the eLISA design.
| [
{
"created": "Tue, 30 Oct 2012 16:12:16 GMT",
"version": "v1"
}
] | 2012-10-31 | [
[
"Gair",
"Jonathan R",
""
],
[
"Porter",
"Edward K",
""
]
] | The extreme-mass-ratio inspirals (EMRIs) of stellar mass compact objects into massive black holes in the centres of galaxies are an important source of low-frequency gravitational waves for space-based detectors. We discuss the prospects for detecting these sources with the evolved Laser Interferometer Space Antenna (eLISA), recently proposed as an ESA mission candidate under the name NGO. We show that NGO could observe a few tens of EMRIs over its two year mission lifetime at redshifts z < 0.5 and describe how the event rate changes under possible alternative specifications of the eLISA design. |
2312.02714 | Hanif Golchin | Amid Sadeghi Nezhad, Mohammad Reza Mehdizadeh and Hanif Golchin | The effect of redshift function on the Weak Energy Conditions in f(R)
Wormholes | 27 pages, 10 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present paper, we investigate traversable wormhole solutions
determined by an exponential shape function and fractional redshift function in
the background of four viable $f(R)$ models. Although in the absence of the
redshift function $\varphi(r)$ the null energy condition (NEC) and weak energy
condition (WEC) are violated, we find that considering the redshift function,
NEC and WEC are respected by choosing the appropriate parameters in the models.
We also investigate the conditions of stability and absence of anti-gravity
effects for these wormholes. Our results show that in the case of $\varphi(r)
\neq 0$ these conditions are satisfied easier than the case of $\varphi(r)=0$.
Finally we calculate the deflection angle using the gravitational lensing
effect. We show that the deflection angle increases by inserting the redshift
function.
| [
{
"created": "Tue, 5 Dec 2023 12:18:27 GMT",
"version": "v1"
}
] | 2023-12-06 | [
[
"Nezhad",
"Amid Sadeghi",
""
],
[
"Mehdizadeh",
"Mohammad Reza",
""
],
[
"Golchin",
"Hanif",
""
]
] | In the present paper, we investigate traversable wormhole solutions determined by an exponential shape function and fractional redshift function in the background of four viable $f(R)$ models. Although in the absence of the redshift function $\varphi(r)$ the null energy condition (NEC) and weak energy condition (WEC) are violated, we find that considering the redshift function, NEC and WEC are respected by choosing the appropriate parameters in the models. We also investigate the conditions of stability and absence of anti-gravity effects for these wormholes. Our results show that in the case of $\varphi(r) \neq 0$ these conditions are satisfied easier than the case of $\varphi(r)=0$. Finally we calculate the deflection angle using the gravitational lensing effect. We show that the deflection angle increases by inserting the redshift function. |
1905.02150 | Oleg Zaslavskii | A. V. Toporensky and O. B. Zaslavskii | On strategies of motion under the black hole horizon | Matches journal version | Int. J. of Mod. Phys. D (2020) 2030003 | 10.1142/S0218271820300037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this methodological paper we consider two problems an astronaut faces with
under the black hole horizon in the Schwarzschild metric. 1) How to maximize
the survival proper time. 2) How to make a visible part of the outer Universe
as large as possible before hitting the singularity. Our consideration
essentially uses the concept of peculiar velocities based on the "river model".
Let an astronaut cross the horizon from the outside. We reproduce from the
first principles the known result that point 1) requires that an astronaut turn
off the engine near the horizon and follow the path with the momentum equal to
zero. We also show that point 2) requires maximizing the peculiar velocity of
the observer. Both goals 1) and 2) require, in general, different strategies
inconsistent with each other that coincide at the horizon only. The concept of
peculiar velocities introduced in a direct analogy with cosmology, and its
application for the problems studied in the present paper can be used in
advanced general relativity courses.
| [
{
"created": "Mon, 6 May 2019 17:09:08 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Mar 2020 11:59:12 GMT",
"version": "v2"
}
] | 2020-04-15 | [
[
"Toporensky",
"A. V.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | In this methodological paper we consider two problems an astronaut faces with under the black hole horizon in the Schwarzschild metric. 1) How to maximize the survival proper time. 2) How to make a visible part of the outer Universe as large as possible before hitting the singularity. Our consideration essentially uses the concept of peculiar velocities based on the "river model". Let an astronaut cross the horizon from the outside. We reproduce from the first principles the known result that point 1) requires that an astronaut turn off the engine near the horizon and follow the path with the momentum equal to zero. We also show that point 2) requires maximizing the peculiar velocity of the observer. Both goals 1) and 2) require, in general, different strategies inconsistent with each other that coincide at the horizon only. The concept of peculiar velocities introduced in a direct analogy with cosmology, and its application for the problems studied in the present paper can be used in advanced general relativity courses. |
0804.0555 | Gamal G.L. Nashed | Gamal G.L. Nashed | M{\o}ller's energy of the Kerr-NUT Metric | 6 pages Latex | Chin.Phys.Lett.25:1202,2008 | 10.1088/0256-307X/25/4/011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The energy distribution of the Kerr-NUT space-time is calculated using M\o
ller's energy-momentum complex within the framework of the Riemannian geometry.
| [
{
"created": "Thu, 3 Apr 2008 13:37:35 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nashed",
"Gamal G. L.",
""
]
] | The energy distribution of the Kerr-NUT space-time is calculated using M\o ller's energy-momentum complex within the framework of the Riemannian geometry. |
2108.01782 | Valerio Faraoni | Genevi\`eve Vachon, Robert Vanderwee, and Valerio Faraoni | Revisiting geodesic observers in cosmology | 9 pages, no figures | null | 10.1140/epjc/s10052-021-09636-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Geodesic observers in cosmology are revisited. The coordinates based on
freely falling observers introduced by Gautreau in de Sitter and Einstein-de
Sitter spaces (and, previously, by Gautreau and Hoffmann in Schwarzschild
space) are extended to general FLRW universes. We identify situations in which
the relation between geodesic and comoving coordinates can be expressed
explicitly in terms of elementary functions. In general, geodesic coordinates
in cosmology turn out to be rather cumbersome and limited to the region below
the apparent horizon.
| [
{
"created": "Tue, 3 Aug 2021 22:59:06 GMT",
"version": "v1"
}
] | 2021-10-04 | [
[
"Vachon",
"Geneviève",
""
],
[
"Vanderwee",
"Robert",
""
],
[
"Faraoni",
"Valerio",
""
]
] | Geodesic observers in cosmology are revisited. The coordinates based on freely falling observers introduced by Gautreau in de Sitter and Einstein-de Sitter spaces (and, previously, by Gautreau and Hoffmann in Schwarzschild space) are extended to general FLRW universes. We identify situations in which the relation between geodesic and comoving coordinates can be expressed explicitly in terms of elementary functions. In general, geodesic coordinates in cosmology turn out to be rather cumbersome and limited to the region below the apparent horizon. |
1707.08174 | Sushant Ghosh Prof | Sushant G. Ghosh | Noncommutative geometry inspired Einstein-Gauss-Bonnet black holes | 12 pages, 6 figures, 2 tables | Classical and Quantum Gravity, 35, 085008 (2018) | 10.1088/1361-6382/aaaead | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Low energy limits of a string theory suggest that the gravity action should
include quadratic and higher-order curvature terms, in the form of
dimensionally continued Gauss-Bonnet densities. Einstein-Gauss-Bonnet is a
natural extension of the general relativity to higher dimensions in which the
first and second-order terms correspond, respectively, to general relativity
and Einstein-Gauss-Bonnet gravity. We obtain five-dimensional ($5D$) black hole
solutions, inspired by a noncommutative geometry, with a static spherically
symmetric, Gaussian mass distribution as a source both in the general
relativity and Einstein-Gauss-Bonnet gravity cases, and we also analyze their
thermodynamical properties. Owing to the noncommutative corrected black hole,
the thermodynamic quantities have also been modified, and phase transition is
shown to be achievable. The phase transitions for the thermodynamic stability,
in both the theories, are characterized by a discontinuity in the specific heat
at $r_+=r_C$, with the stable (unstable) branch for $r < (>)\, r_C$. The metric
of the noncommutative inspired black holes smoothly goes over to the
Boulware-Deser solution at large distance. The paper has been appended with a
calculation of black hole mass using holographic renormalization.
| [
{
"created": "Sat, 22 Jul 2017 09:00:27 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Jun 2018 04:32:57 GMT",
"version": "v2"
}
] | 2018-06-19 | [
[
"Ghosh",
"Sushant G.",
""
]
] | Low energy limits of a string theory suggest that the gravity action should include quadratic and higher-order curvature terms, in the form of dimensionally continued Gauss-Bonnet densities. Einstein-Gauss-Bonnet is a natural extension of the general relativity to higher dimensions in which the first and second-order terms correspond, respectively, to general relativity and Einstein-Gauss-Bonnet gravity. We obtain five-dimensional ($5D$) black hole solutions, inspired by a noncommutative geometry, with a static spherically symmetric, Gaussian mass distribution as a source both in the general relativity and Einstein-Gauss-Bonnet gravity cases, and we also analyze their thermodynamical properties. Owing to the noncommutative corrected black hole, the thermodynamic quantities have also been modified, and phase transition is shown to be achievable. The phase transitions for the thermodynamic stability, in both the theories, are characterized by a discontinuity in the specific heat at $r_+=r_C$, with the stable (unstable) branch for $r < (>)\, r_C$. The metric of the noncommutative inspired black holes smoothly goes over to the Boulware-Deser solution at large distance. The paper has been appended with a calculation of black hole mass using holographic renormalization. |
2003.03359 | Sylvia Zhu | Sylvia J. Zhu, Masha Baryakhtar, Maria Alessandra Papa, Daichi Tsuna,
Norita Kawanaka, Heinz-Bernd Eggenstein | Characterizing the continuous gravitational-wave signal from boson
clouds around Galactic isolated black holes | 21 pages of main text plus appendices. Accepted by PRD | Phys. Rev. D 102, 063020 (2020) | 10.1103/PhysRevD.102.063020 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ultralight bosons can form large clouds around stellar-mass black holes via
the superradiance instability. Through processes such as annihilation, these
bosons can source continuous gravitational wave signals with frequencies within
the range of LIGO and Virgo. If boson annihilation occurs, then the Galactic
black hole population will give rise to many gravitational signals; we refer to
this as the ensemble signal. We characterize the ensemble signal as observed by
the gravitational-wave detectors; this is important because the ensemble signal
carries the primary signature that a continuous wave signal has a boson
annihilation origin. We explore how a broad set of black hole population
parameters affects the resulting spin-0 boson annihilation signal and consider
its detectability by recent searches for continuous gravitational waves. A
population of $10^8$ black holes with masses up to $30\mathrm{M}_\odot$ and a
flat dimensionless initial spin distribution between zero and unity produces up
to a thousand signals loud enough to be in principle detected by these
searches. For a more moderately spinning population the number of signals drops
by about an order of magnitude, still yielding up to a hundred detectable
signals for some boson masses. A non-detection of annihilation signals at
frequencies between 100 and 1200 Hz disfavors the existence of scalar bosons
with rest energies between $2\times10^{-13}$ and $2.5\times10^{-12}$ eV.
Finally we show that, depending on the black hole population parameters, care
must be taken in assuming that the continuous wave upper limits from searches
for isolated signals are still valid for signals that are part of a dense
ensemble: Between 200 and 300 Hz, we urge caution when interpreting a null
result for bosons between 4 and $6\times10^{-13}$ eV.
| [
{
"created": "Fri, 6 Mar 2020 18:40:36 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Sep 2020 13:05:17 GMT",
"version": "v2"
}
] | 2020-09-30 | [
[
"Zhu",
"Sylvia J.",
""
],
[
"Baryakhtar",
"Masha",
""
],
[
"Papa",
"Maria Alessandra",
""
],
[
"Tsuna",
"Daichi",
""
],
[
"Kawanaka",
"Norita",
""
],
[
"Eggenstein",
"Heinz-Bernd",
""
]
] | Ultralight bosons can form large clouds around stellar-mass black holes via the superradiance instability. Through processes such as annihilation, these bosons can source continuous gravitational wave signals with frequencies within the range of LIGO and Virgo. If boson annihilation occurs, then the Galactic black hole population will give rise to many gravitational signals; we refer to this as the ensemble signal. We characterize the ensemble signal as observed by the gravitational-wave detectors; this is important because the ensemble signal carries the primary signature that a continuous wave signal has a boson annihilation origin. We explore how a broad set of black hole population parameters affects the resulting spin-0 boson annihilation signal and consider its detectability by recent searches for continuous gravitational waves. A population of $10^8$ black holes with masses up to $30\mathrm{M}_\odot$ and a flat dimensionless initial spin distribution between zero and unity produces up to a thousand signals loud enough to be in principle detected by these searches. For a more moderately spinning population the number of signals drops by about an order of magnitude, still yielding up to a hundred detectable signals for some boson masses. A non-detection of annihilation signals at frequencies between 100 and 1200 Hz disfavors the existence of scalar bosons with rest energies between $2\times10^{-13}$ and $2.5\times10^{-12}$ eV. Finally we show that, depending on the black hole population parameters, care must be taken in assuming that the continuous wave upper limits from searches for isolated signals are still valid for signals that are part of a dense ensemble: Between 200 and 300 Hz, we urge caution when interpreting a null result for bosons between 4 and $6\times10^{-13}$ eV. |
1911.02517 | Robert Bluhm | Robert Bluhm | The SME with gravity and explicit diffeomorphism breaking | Proceedings of the 8th Meeting on CPT and Lorentz Symmetry | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This overview looks at what happens when the Standard-Model Extension (SME)
is used to investigate gravity theories with explicit diffeomorphism breaking.
It is shown that when matter-gravity couplings are included, the SME generally
maintains consistency with the Bianchi identities, and it therefore provides a
useful phenomenological framework for investigating the effects of explicit
diffeomorphism breaking in gravity theories.
| [
{
"created": "Wed, 6 Nov 2019 17:55:31 GMT",
"version": "v1"
}
] | 2019-11-07 | [
[
"Bluhm",
"Robert",
""
]
] | This overview looks at what happens when the Standard-Model Extension (SME) is used to investigate gravity theories with explicit diffeomorphism breaking. It is shown that when matter-gravity couplings are included, the SME generally maintains consistency with the Bianchi identities, and it therefore provides a useful phenomenological framework for investigating the effects of explicit diffeomorphism breaking in gravity theories. |
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