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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1411.0046 | Paul Wesson | Paul S. Wesson | The Dispersion Relation for Matter Waves in a Two-Phase Vacuum | null | Mod. Phys. Lett. A v.29, No. 31 (2014), 9 pp | 10.1142/S0217732314501685 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological constant (lambda) of general relativity is a natural
consequence of embedding Einstein's theory in a five-dimensional theory of the
type needed for unification. The exact 5D solution for lambda less than 0 shows
waves in ordinary 3D space with properties similar to those of de Broglie or
matter waves. Here the dispersion relation is derived for matter waves in a toy
two-phase model, where regions with lambda less than 0 and lambda greater than
0 average on the large scale to lambda = 0, thus providing in principle a
resolution of the cosmological-constant problem. A striking result of the
analysis is that the dispersion relation is bimodal, with a well-defined window
of high-frequency transmission which effectively defines the speed of light.
| [
{
"created": "Sat, 1 Nov 2014 00:22:23 GMT",
"version": "v1"
}
] | 2014-11-04 | [
[
"Wesson",
"Paul S.",
""
]
] | The cosmological constant (lambda) of general relativity is a natural consequence of embedding Einstein's theory in a five-dimensional theory of the type needed for unification. The exact 5D solution for lambda less than 0 shows waves in ordinary 3D space with properties similar to those of de Broglie or matter waves. Here the dispersion relation is derived for matter waves in a toy two-phase model, where regions with lambda less than 0 and lambda greater than 0 average on the large scale to lambda = 0, thus providing in principle a resolution of the cosmological-constant problem. A striking result of the analysis is that the dispersion relation is bimodal, with a well-defined window of high-frequency transmission which effectively defines the speed of light. |
1108.1974 | Philipp Hoehn | Bianca Dittrich, Philipp A Hoehn | Canonical simplicial gravity | 53 pages, 14 figures, 3 tables, minor clarifications. Matches
published version | Class. Quant. Grav. 29 (2012) 115009 | 10.1088/0264-9381/29/11/115009 | AEI-2011-055, ITP-UU-11/31, SPIN-11/24 | gr-qc hep-lat | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general canonical formalism for discrete systems is developed which can
handle varying phase space dimensions and constraints. The central ingredient
is Hamilton's principal function which generates canonical time evolution and
ensures that the canonical formalism reproduces the dynamics of the covariant
formulation following directly from the action. We apply this formalism to
simplicial gravity and (Euclidean) Regge calculus, in particular. A discrete
forward/backward evolution is realized by gluing/removing single simplices step
by step to/from a bulk triangulation and amounts to Pachner moves in the
triangulated hypersurfaces. As a result, the hypersurfaces evolve in a discrete
`multi-fingered' time through the full Regge solution. Pachner moves are an
elementary and ergodic class of homeomorphisms and generically change the
number of variables, but can be implemented as canonical transformations on
naturally extended phase spaces. Some moves introduce a priori free data which,
however, may become fixed a posteriori by constraints arising in subsequent
moves. The end result is a general and fully consistent formulation of
canonical Regge calculus, thereby removing a longstanding obstacle in
connecting covariant simplicial gravity models to canonical frameworks. The
present scheme is, therefore, interesting in view of many approaches to quantum
gravity, but may also prove useful for numerical implementations.
| [
{
"created": "Tue, 9 Aug 2011 16:35:56 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Nov 2012 22:54:38 GMT",
"version": "v2"
}
] | 2012-11-27 | [
[
"Dittrich",
"Bianca",
""
],
[
"Hoehn",
"Philipp A",
""
]
] | A general canonical formalism for discrete systems is developed which can handle varying phase space dimensions and constraints. The central ingredient is Hamilton's principal function which generates canonical time evolution and ensures that the canonical formalism reproduces the dynamics of the covariant formulation following directly from the action. We apply this formalism to simplicial gravity and (Euclidean) Regge calculus, in particular. A discrete forward/backward evolution is realized by gluing/removing single simplices step by step to/from a bulk triangulation and amounts to Pachner moves in the triangulated hypersurfaces. As a result, the hypersurfaces evolve in a discrete `multi-fingered' time through the full Regge solution. Pachner moves are an elementary and ergodic class of homeomorphisms and generically change the number of variables, but can be implemented as canonical transformations on naturally extended phase spaces. Some moves introduce a priori free data which, however, may become fixed a posteriori by constraints arising in subsequent moves. The end result is a general and fully consistent formulation of canonical Regge calculus, thereby removing a longstanding obstacle in connecting covariant simplicial gravity models to canonical frameworks. The present scheme is, therefore, interesting in view of many approaches to quantum gravity, but may also prove useful for numerical implementations. |
2204.13776 | Safinaz Salem Ms | Safinaz Salem, Moataz H. Emam, and H. H. Salah | The Implications of N = 2 Supergravity Cosmology On the Topology of the
Calabi-Yau Manifold | 13 pages, 7 figures | Al-Azhar Bulletin of Science: Section B, Vol. 33, No. 1, 2022 | 10.21608/absb.2022.121518.1172 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When N= D=11 supergravity is compactified on CY threefold to N=2 D=5
supergravity the action of the last is given in terms of the geometery of the
CY manifold space, namely, in terms of the hypermultiplets. There are
$z^i(i=1,...,h^{2,1})$ complex structure moduli in the moduli space of the CY
manifold which is a special K\"ahler manifold with a metric $G_{i\bar{j}}$. We
solve the field equations of the complex structure moduli with the solution of
the Einstein field equations to the moduli velocity norm $G_{i\bar{j}} z^i
z^{\bar{j}}$ in case of a 3- brane filled with radiation, dust and energy
embedded in the bulk of D=5 supergravity. We get the time dependence of the
moduli and the metric. Then we can further deduce the geometry of the moduli
space by getting the K\"ahler potential which directly relates to the volume of
the CY manifold.
| [
{
"created": "Thu, 28 Apr 2022 20:57:53 GMT",
"version": "v1"
}
] | 2022-05-02 | [
[
"Salem",
"Safinaz",
""
],
[
"Emam",
"Moataz H.",
""
],
[
"Salah",
"H. H.",
""
]
] | When N= D=11 supergravity is compactified on CY threefold to N=2 D=5 supergravity the action of the last is given in terms of the geometery of the CY manifold space, namely, in terms of the hypermultiplets. There are $z^i(i=1,...,h^{2,1})$ complex structure moduli in the moduli space of the CY manifold which is a special K\"ahler manifold with a metric $G_{i\bar{j}}$. We solve the field equations of the complex structure moduli with the solution of the Einstein field equations to the moduli velocity norm $G_{i\bar{j}} z^i z^{\bar{j}}$ in case of a 3- brane filled with radiation, dust and energy embedded in the bulk of D=5 supergravity. We get the time dependence of the moduli and the metric. Then we can further deduce the geometry of the moduli space by getting the K\"ahler potential which directly relates to the volume of the CY manifold. |
gr-qc/0506064 | Marcello Ortaggio | Marcello Ortaggio, Jiri Podolsky, Pavel Krtous | Ultrarelativistic boost of spinning black rings | 15 pages, 2 figures. v2: added multipole expansions at spatial
infinity, and a comparison with the boosted Myers-Perry solution in a new
appendix. To appear in JHEP | JHEP0512:001,2005 | 10.1088/1126-6708/2005/12/001 | null | gr-qc hep-th | null | We study the D=5 Emparan-Reall spinning black ring under an ultrarelativistic
boost along an arbitrary direction. We analytically determine the resulting
shock pp-wave, in particular for boosts along axes orthogonal and parallel to
the plane of rotation. The solution becomes physically more interesting and
simpler if one enforces equilibrium between the forces on the ring. We also
comment on the ultrarelativistic limit of recently found supersymmetric black
rings with two independent angular momenta. Essential distinct features with
respect to the boosted Myers-Perry black holes are pointed out.
| [
{
"created": "Fri, 10 Jun 2005 17:16:29 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Nov 2005 15:51:33 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Ortaggio",
"Marcello",
""
],
[
"Podolsky",
"Jiri",
""
],
[
"Krtous",
"Pavel",
""
]
] | We study the D=5 Emparan-Reall spinning black ring under an ultrarelativistic boost along an arbitrary direction. We analytically determine the resulting shock pp-wave, in particular for boosts along axes orthogonal and parallel to the plane of rotation. The solution becomes physically more interesting and simpler if one enforces equilibrium between the forces on the ring. We also comment on the ultrarelativistic limit of recently found supersymmetric black rings with two independent angular momenta. Essential distinct features with respect to the boosted Myers-Perry black holes are pointed out. |
1903.10821 | Andronikos Paliathanasis | Andronikos Paliathanasis and Genly Leon | Cosmological solutions in Ho\v{r}ava-Lifshitz gravity | 8 pages, no figures, discussion improved, to appear in Zeitschrift
f\"ur Naturforschung A | ZnA, 75, 523, 2020 | 10.1515/zna-2020-0003 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a detailed study on the integrability of the Ho\v{r}% ava-Lifshitz
scalar field cosmology in a Friedmann--Lema\^{\i}% tre--Robertson--Walker
background spacetime. The approach we follow to determine the integrability is
that of the Singularity Analysis. More specifically, we test if the
gravitational field equations possesses the Painlev\'{e} property. For the
exponential potential of the scalar field we are able to perform an analytic
explicit integration of the field equations and write the solution in terms of
Laurent expansion and more specifically write the solution in terms of Right
Painlev\'{e} series.
| [
{
"created": "Tue, 26 Mar 2019 12:06:24 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Mar 2020 14:00:05 GMT",
"version": "v2"
}
] | 2020-08-19 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Leon",
"Genly",
""
]
] | We perform a detailed study on the integrability of the Ho\v{r}% ava-Lifshitz scalar field cosmology in a Friedmann--Lema\^{\i}% tre--Robertson--Walker background spacetime. The approach we follow to determine the integrability is that of the Singularity Analysis. More specifically, we test if the gravitational field equations possesses the Painlev\'{e} property. For the exponential potential of the scalar field we are able to perform an analytic explicit integration of the field equations and write the solution in terms of Laurent expansion and more specifically write the solution in terms of Right Painlev\'{e} series. |
2308.03136 | Raihaneh Moti | Raihaneh Moti | On the Nonlocal Newtonian Cosmology | 19 pages, 5 figures | null | 10.1016/j.dark.2023.101368 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the absence of an exact development of the cosmological models based on
the Mashhoon nonlocal gravity, the Newtonian regime clarifies some aspects of
it. To improve this model more reliable, going through some semi-Post-Newtonian
considerations may be useful. One important feature to consider is the
formation of horizons, which can be understood as a consequence of the finite
interaction velocity. This highlights the importance of extending the
integration across the entire space-time, rather than solely focusing on the
spatial sector. In this context, we show that the density of effective dark
matter would increase, while the density of Baryonic matter decreases, during
the deep matter-dominated era. This finding is in contradiction with the
predictions of the standard model of cosmology and it raises concerns about the
compatibility of using Tohline--Kuhn kernel and considering the nonlocal
effects as an effective dark matter in $\Lambda$CDM.
| [
{
"created": "Sun, 6 Aug 2023 15:11:11 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Oct 2023 04:58:09 GMT",
"version": "v2"
}
] | 2023-11-01 | [
[
"Moti",
"Raihaneh",
""
]
] | In the absence of an exact development of the cosmological models based on the Mashhoon nonlocal gravity, the Newtonian regime clarifies some aspects of it. To improve this model more reliable, going through some semi-Post-Newtonian considerations may be useful. One important feature to consider is the formation of horizons, which can be understood as a consequence of the finite interaction velocity. This highlights the importance of extending the integration across the entire space-time, rather than solely focusing on the spatial sector. In this context, we show that the density of effective dark matter would increase, while the density of Baryonic matter decreases, during the deep matter-dominated era. This finding is in contradiction with the predictions of the standard model of cosmology and it raises concerns about the compatibility of using Tohline--Kuhn kernel and considering the nonlocal effects as an effective dark matter in $\Lambda$CDM. |
2203.16753 | Csaba Balazs | Csaba Balazs | Observable vacuum energy is finite in expanding space | ( 12 pages ;) | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work I reason that in expanding space only those quantum modes
contribute to the measured vacuum energy that do not transcend the observable
volume. Since all quantised field modes have various observable consequences,
when a gravitational horizon causally confines an observer to a finite volume
quantised modes should be restricted to the observable patch to remain
consistent with gravity.
Within the observable patch of Friedmann-Lemaitre-Robertson-Walker (FLRW)
space the vacuum expectation value of the energy-momentum tensor can be
expressed as a sum over discrete field modes. Friedmann's first equation
provides a straightforward ultraviolet cut-off allowing only a finite number of
modes in the sum. The finite volume acts as an infrared regulator and the
calculation of the vacuum energy density is tractable without regularisation
and renormalisation.
To test the validity of this idea I quantise a scalar field on an FLRW
background and calculate its vacuum energy density in the vacuum dominated,
conformal, holographic limit. In this limit I show that the quantum vacuum
energy density scales with the square of the Hubble parameter, consistently
with gravity. In this example quantum vacuum expands space while the horizon of
the expanding space limits the energy density of the vacuum to the observed
value.
| [
{
"created": "Thu, 31 Mar 2022 02:17:10 GMT",
"version": "v1"
}
] | 2022-04-01 | [
[
"Balazs",
"Csaba",
""
]
] | In this work I reason that in expanding space only those quantum modes contribute to the measured vacuum energy that do not transcend the observable volume. Since all quantised field modes have various observable consequences, when a gravitational horizon causally confines an observer to a finite volume quantised modes should be restricted to the observable patch to remain consistent with gravity. Within the observable patch of Friedmann-Lemaitre-Robertson-Walker (FLRW) space the vacuum expectation value of the energy-momentum tensor can be expressed as a sum over discrete field modes. Friedmann's first equation provides a straightforward ultraviolet cut-off allowing only a finite number of modes in the sum. The finite volume acts as an infrared regulator and the calculation of the vacuum energy density is tractable without regularisation and renormalisation. To test the validity of this idea I quantise a scalar field on an FLRW background and calculate its vacuum energy density in the vacuum dominated, conformal, holographic limit. In this limit I show that the quantum vacuum energy density scales with the square of the Hubble parameter, consistently with gravity. In this example quantum vacuum expands space while the horizon of the expanding space limits the energy density of the vacuum to the observed value. |
1212.2571 | Rodrigo Maier | Rodrigo Maier and Ivano Dami\~ao Soares | Gravitational Collapse and Black Hole Thermodynamics In Braneworld
Scenario | null | Int. J. Mod. Phys. D 21, 1250050 (2012) | 10.1142/S0218271812500502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the dynamics of the gravitational collapse in a 4-dim Lorentzian
brane embedded in a 5-dim bulk with an extra timelike dimension. By considering
the collapse of pure dust on the brane we derive a bouncing FLRW interior
solution and match it with a corrected Schwarzschild exterior geometry. In the
physical domain considered for the parameters of the solution, the analytical
extension is built, exhibiting an exterior event horizon and a Cauchy horizon,
analogous to the Reissner-Nordstr\"om solution. For such an exterior geometry
we examine the effects of the bulk-brane corrections in the Hawking radiation.
In this scenario the model extends Bekenstein's black hole geometrical
thermodynamics for quasi-extremal configurations, with an extra work term in
the laws associated with variations of the brane tension. We also propose a
simple statistical mechanics model for the entropy of the bouncing collapsed
matter by quantizing its fluctuations and constructing the associated partition
function. This entropy differs from the geometrical entropy by an additive
constant proportional to the area of the extremal black hole and satisfies an
analogous first law of thermodynamics. A possible connection between both
entropies is discussed.
| [
{
"created": "Tue, 11 Dec 2012 18:15:16 GMT",
"version": "v1"
}
] | 2013-01-23 | [
[
"Maier",
"Rodrigo",
""
],
[
"Soares",
"Ivano Damião",
""
]
] | We examine the dynamics of the gravitational collapse in a 4-dim Lorentzian brane embedded in a 5-dim bulk with an extra timelike dimension. By considering the collapse of pure dust on the brane we derive a bouncing FLRW interior solution and match it with a corrected Schwarzschild exterior geometry. In the physical domain considered for the parameters of the solution, the analytical extension is built, exhibiting an exterior event horizon and a Cauchy horizon, analogous to the Reissner-Nordstr\"om solution. For such an exterior geometry we examine the effects of the bulk-brane corrections in the Hawking radiation. In this scenario the model extends Bekenstein's black hole geometrical thermodynamics for quasi-extremal configurations, with an extra work term in the laws associated with variations of the brane tension. We also propose a simple statistical mechanics model for the entropy of the bouncing collapsed matter by quantizing its fluctuations and constructing the associated partition function. This entropy differs from the geometrical entropy by an additive constant proportional to the area of the extremal black hole and satisfies an analogous first law of thermodynamics. A possible connection between both entropies is discussed. |
1305.6343 | Borun Chowdhury | Borun D. Chowdhury | Black holes vs. firewalls and thermo-field dynamics | 7 Pages, 4 figures. This essay received an honorable mention in the
2013 essay competition of the Gravity Research Foundation. v2: References
added | null | 10.1142/S021827181342011X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this essay, we examine the implications of the ongoing black holes vs.
firewalls debate for the thermo-field dynamics of black holes by analyzing a
CFT in a thermal state in the context of AdS/CFT. We argue that the themo-field
doubled copy of the thermal CFT should be thought of not as a fictitious
system, but as the image of the CFT in the heat-bath. While this idea was
proposed earlier by Papadodimas et al., our following conclusions differ from
theirs. In case of strong coupling between the CFT and the heat-bath this image
allows for free infall through the horizon and the system is described by a
black hole. Conversely, firewalls are the appropriate dual description in case
of weak interaction of the CFT with its heat bath.
| [
{
"created": "Mon, 27 May 2013 23:38:03 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2013 16:22:57 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Chowdhury",
"Borun D.",
""
]
] | In this essay, we examine the implications of the ongoing black holes vs. firewalls debate for the thermo-field dynamics of black holes by analyzing a CFT in a thermal state in the context of AdS/CFT. We argue that the themo-field doubled copy of the thermal CFT should be thought of not as a fictitious system, but as the image of the CFT in the heat-bath. While this idea was proposed earlier by Papadodimas et al., our following conclusions differ from theirs. In case of strong coupling between the CFT and the heat-bath this image allows for free infall through the horizon and the system is described by a black hole. Conversely, firewalls are the appropriate dual description in case of weak interaction of the CFT with its heat bath. |
0812.0775 | Frank Hellmann | Frank Hellmann | Partial Observables in Extended Systems | 14 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider "unphysical", kinematic observables that do not commute with the
constraints of a gauge system in the context of an extension of the system. We
show that these observables, while not predictable, can nevertheless be said to
have a physical interpretation. They implement Rovelli's concept of partial and
relational observables. We investigate the propositional structure of these
observables and point out interpretational issues. We find that to make
relational statements in the quantum theory one must deal directly with these
observables. In particular we argue that in this scenario the spectra of
kinematic observables are what is experimentally accessible.
| [
{
"created": "Wed, 3 Dec 2008 20:21:31 GMT",
"version": "v1"
}
] | 2008-12-04 | [
[
"Hellmann",
"Frank",
""
]
] | We consider "unphysical", kinematic observables that do not commute with the constraints of a gauge system in the context of an extension of the system. We show that these observables, while not predictable, can nevertheless be said to have a physical interpretation. They implement Rovelli's concept of partial and relational observables. We investigate the propositional structure of these observables and point out interpretational issues. We find that to make relational statements in the quantum theory one must deal directly with these observables. In particular we argue that in this scenario the spectra of kinematic observables are what is experimentally accessible. |
gr-qc/0610106 | Kristin Schleich | J. Brannlund, S. Slobodov, K. Schleich and D. M. Witt | Topological rigidity of dimensional reduction to three dimensions | null | null | null | null | gr-qc | null | Studying spacetimes with continuous symmetries by dimensional reduction to a
lower dimensional spacetime is a well known technique in field theory and
gravity. Recently, its use has been advocated in numerical relativity as an
efficient computational technique for the numerical study of axisymmetric
asymptotically flat 4-dimensional spacetimes. We prove here that if the
dimensionally reduced spacetime is a physically reasonable 3-dimensional
asymptotically flat or asymptotically anti-de Sitter spacetime, then,
surprisingly, the topology of the higher dimensional spacetime must be one of
two product topologies. Reductions of other topologies result in physically
pathological spacetimes. In particular, reduction of asymptotically flat
4-dimensional spacetimes must lead to pathologies. These results use only the
topological censorship theorem and topological methods and consequently are
independent of the field equations and reduction method.
| [
{
"created": "Sat, 21 Oct 2006 19:38:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Brannlund",
"J.",
""
],
[
"Slobodov",
"S.",
""
],
[
"Schleich",
"K.",
""
],
[
"Witt",
"D. M.",
""
]
] | Studying spacetimes with continuous symmetries by dimensional reduction to a lower dimensional spacetime is a well known technique in field theory and gravity. Recently, its use has been advocated in numerical relativity as an efficient computational technique for the numerical study of axisymmetric asymptotically flat 4-dimensional spacetimes. We prove here that if the dimensionally reduced spacetime is a physically reasonable 3-dimensional asymptotically flat or asymptotically anti-de Sitter spacetime, then, surprisingly, the topology of the higher dimensional spacetime must be one of two product topologies. Reductions of other topologies result in physically pathological spacetimes. In particular, reduction of asymptotically flat 4-dimensional spacetimes must lead to pathologies. These results use only the topological censorship theorem and topological methods and consequently are independent of the field equations and reduction method. |
1803.09204 | Nandan Roy | Nandan Roy, Alma X. Gonzalez-Morales, and L. Arturo Urena-Lopez | New general parametrization of quintessence fields and its observational
constraints | 15 pages, 10 figures | Phys. Rev. D 98, 063530 (2018) | 10.1103/PhysRevD.98.063530 | null | gr-qc astro-ph.CO math.DS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new parameterization of quintessence potentials for dark energy
based directly upon the dynamical properties of the equations of motion. Such
parameterization arises naturally once the equations of motion are written as a
dynamical system in terms of properly defined polar variables. We have
identified two different classes of parameters, and we dubbed them as dynamical
and passive parameters. The dynamical parameters appear explicitly in the
equations of motion, but the passive parameters play just a secondary role in
their solutions. The new approach is applied to the so-called thawing
potentials and it is argued that only three dynamical parameters are sufficient
to capture the evolution of the quintessence fields at late times. This work
reconfirms the arbitrariness of the quintessence potentials as the recent
observational data fail to constrain the dynamical parameters.
| [
{
"created": "Sun, 25 Mar 2018 05:13:35 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Nov 2018 15:53:41 GMT",
"version": "v2"
}
] | 2018-11-07 | [
[
"Roy",
"Nandan",
""
],
[
"Gonzalez-Morales",
"Alma X.",
""
],
[
"Urena-Lopez",
"L. Arturo",
""
]
] | We present a new parameterization of quintessence potentials for dark energy based directly upon the dynamical properties of the equations of motion. Such parameterization arises naturally once the equations of motion are written as a dynamical system in terms of properly defined polar variables. We have identified two different classes of parameters, and we dubbed them as dynamical and passive parameters. The dynamical parameters appear explicitly in the equations of motion, but the passive parameters play just a secondary role in their solutions. The new approach is applied to the so-called thawing potentials and it is argued that only three dynamical parameters are sufficient to capture the evolution of the quintessence fields at late times. This work reconfirms the arbitrariness of the quintessence potentials as the recent observational data fail to constrain the dynamical parameters. |
gr-qc/0204090 | Curt Cutler | Curt Cutler and Kip S. Thorne | An Overview of Gravitational-Wave Sources | 40 pages, 5 figures, to appear in Proceedings of GR16 (Durban, South
Africa, 2001) | null | null | null | gr-qc astro-ph | null | We review current best estimates of the strength and detectability of the
gravitational waves from a variety of sources, for both ground-based and
space-based detectors, and we describe the information carried by the waves.
| [
{
"created": "Tue, 30 Apr 2002 10:05:26 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cutler",
"Curt",
""
],
[
"Thorne",
"Kip S.",
""
]
] | We review current best estimates of the strength and detectability of the gravitational waves from a variety of sources, for both ground-based and space-based detectors, and we describe the information carried by the waves. |
gr-qc/0603077 | Charles Wang | Charles H.-T. Wang | The conformal factor in the parameter-free construction of spin-gauge
variables for gravity | 10 pages | null | null | null | gr-qc math-ph math.MP | null | The newly found conformal decomposition in canonical general relativity is
applied to drastically simplify the recently formulated parameter-free
construction of spin-gauge variables for gravity. The resulting framework
preserves many of the main structures of the existing canonical framework for
loop quantum gravity related to the spin network and Thiemann's regularization.
However, the Barbero-Immirzi parameter is now converted into the conformal
factor as a canonical variable. It behaves like a scalar field but is somehow
non-dynamical since the effective Hamiltonian constraint does not depend on its
momentum. The essential steps of the mathematical derivation of this
parameter-free framework for the spin-gauge variables of gravity are spelled
out. The implications for the loop quantum gravity programme are briefly
discussed.
| [
{
"created": "Mon, 20 Mar 2006 18:09:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wang",
"Charles H. -T.",
""
]
] | The newly found conformal decomposition in canonical general relativity is applied to drastically simplify the recently formulated parameter-free construction of spin-gauge variables for gravity. The resulting framework preserves many of the main structures of the existing canonical framework for loop quantum gravity related to the spin network and Thiemann's regularization. However, the Barbero-Immirzi parameter is now converted into the conformal factor as a canonical variable. It behaves like a scalar field but is somehow non-dynamical since the effective Hamiltonian constraint does not depend on its momentum. The essential steps of the mathematical derivation of this parameter-free framework for the spin-gauge variables of gravity are spelled out. The implications for the loop quantum gravity programme are briefly discussed. |
gr-qc/0510079 | Christopher J. Fewster | C.J. Fewster, T.A. Roman | Problems with wormholes which involve arbitrarily small amounts of
exotic matter | 6pp. Contribution to the Proceedings of EPS-13, Bern, 2005, based on
gr-qc/0507013, but with additional remarks on gr-qc/0508060 | null | null | null | gr-qc | null | A quantum inequality bound on the expectation value of the null-contracted
stress tensor in an arbitrary Hadamard state is used to obtain constraints on
the geometries of traversable wormholes. Particular attention is given to the
wormhole models of Visser, Kar, and Dadhich (VKD) and to those of Kuhfittig.
These are models which use arbitrarily small amounts of exotic matter for
wormhole maintenance. It is shown that macroscopic VKD models are either ruled
out or severely constrained, while a recent model of Kuhfittig is shown to be,
in fact, non-traversable.
| [
{
"created": "Mon, 17 Oct 2005 09:36:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fewster",
"C. J.",
""
],
[
"Roman",
"T. A.",
""
]
] | A quantum inequality bound on the expectation value of the null-contracted stress tensor in an arbitrary Hadamard state is used to obtain constraints on the geometries of traversable wormholes. Particular attention is given to the wormhole models of Visser, Kar, and Dadhich (VKD) and to those of Kuhfittig. These are models which use arbitrarily small amounts of exotic matter for wormhole maintenance. It is shown that macroscopic VKD models are either ruled out or severely constrained, while a recent model of Kuhfittig is shown to be, in fact, non-traversable. |
1507.02416 | Edward Teo | Yu Chen, Yen-Kheng Lim, Edward Teo | Deformed hyperbolic black holes | 36 pages, 12 figures; v3: added discussion; as accepted for
publication in Phys. Rev. D | Phys. Rev. D 92, 044058 (2015) | 10.1103/PhysRevD.92.044058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes with planar or hyperbolic horizons are known to exist in AdS
space, alongside the usual ones with spherical horizons. In this paper, we
consider a one-parameter generalisation of these black holes that is contained
in the AdS C-metric. In terms of the domain-structure analysis recently
developed for such solutions, these black holes have a domain in the shape of a
triangle. It is shown that the horizons of these black holes are deformed
hyperbolic spaces, with the new parameter controlling the amount of
deformation. The space-times are static and completely regular outside the
horizons. We argue that these black holes are hyperbolic analogues of the
"slowly accelerating" spherical black holes known to exist in AdS space.
| [
{
"created": "Thu, 9 Jul 2015 08:35:53 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jul 2015 11:03:40 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Aug 2015 02:55:33 GMT",
"version": "v3"
}
] | 2015-09-09 | [
[
"Chen",
"Yu",
""
],
[
"Lim",
"Yen-Kheng",
""
],
[
"Teo",
"Edward",
""
]
] | Black holes with planar or hyperbolic horizons are known to exist in AdS space, alongside the usual ones with spherical horizons. In this paper, we consider a one-parameter generalisation of these black holes that is contained in the AdS C-metric. In terms of the domain-structure analysis recently developed for such solutions, these black holes have a domain in the shape of a triangle. It is shown that the horizons of these black holes are deformed hyperbolic spaces, with the new parameter controlling the amount of deformation. The space-times are static and completely regular outside the horizons. We argue that these black holes are hyperbolic analogues of the "slowly accelerating" spherical black holes known to exist in AdS space. |
2005.10133 | Ekaterina Pozdeeva | E.O. Pozdeeva | Generalization of cosmological attractor approach to
Einstein-Gauss-Bonnet gravity | null | Eur.Phys.J.C 80 (2020) 7,612 | 10.1140/epjc/s10052-020-8176-3 | 612 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct models with the Gauss-Bonnet term multiplied to a function of
the scalar field leading to inflationary scenario. The consideration is related
with the slow-roll approximation. The cosmological attractor approach gives the
spectral index of scalar perturbations which is in a good agreement with modern
observation and allows variability for tensor-to-scalar ratio. We reconstruct
models with variability of parameters which allow to reproduce cosmological
attractor predictions for inflationary parameters in the leading order of $1/N$
approximation in the Einstein-Gauss-Bonnet gravity.
| [
{
"created": "Wed, 20 May 2020 15:31:00 GMT",
"version": "v1"
},
{
"created": "Tue, 26 May 2020 12:07:41 GMT",
"version": "v2"
}
] | 2020-07-29 | [
[
"Pozdeeva",
"E. O.",
""
]
] | We construct models with the Gauss-Bonnet term multiplied to a function of the scalar field leading to inflationary scenario. The consideration is related with the slow-roll approximation. The cosmological attractor approach gives the spectral index of scalar perturbations which is in a good agreement with modern observation and allows variability for tensor-to-scalar ratio. We reconstruct models with variability of parameters which allow to reproduce cosmological attractor predictions for inflationary parameters in the leading order of $1/N$ approximation in the Einstein-Gauss-Bonnet gravity. |
2003.14211 | Pardyumn Kumar Sahoo | Snehasish Bhattacharjee, P.K. Sahoo | Comprehensive Analysis of a Non-Singular Bounce in $f(R,T)$ Gravitation | 17 pages, 24 figures, Accepted version at Physics of the dark
Universe | Phys. Dark Universe, 28 (2020) 100537 | 10.1016/j.dark.2020.100537 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper is devoted to the study of bouncing cosmology in $f(R,T)$
modified gravity where we presume $f(R,T) = R + 2 \lambda T$, with $R$ the
Ricci scalar, $T$ the trace of energy momentum tensor and $\lambda$ the model
parameter. We present here a novel parametrization of Hubble parameter which is
apt in representing a successful bouncing scenario undergoing no singularity.
We proceed to present a complete analysis of the proposed bouncing model by
studying the evolution of primordial curvature perturbations, energy conditions
and stability against linear homogeneous perturbations in flat space-time. We
also delineate bouncing cosmology for the proposed model by employing Quintom
matter. The present article further communicate for the first time that
violation of energy-momentum materialize for both the contracting and expanding
universes except for the bouncing epoch with energy flow directed away and into
the matter fields for the contracting and expanding universe respectively. We
further present a thorough investigation about the feasibility of the proposed
bouncing scenario against first and generalized second law of thermodynamics.
We found that the proposed bouncing scenario obeys the laws of thermodynamics
for the constrained parameter space of $\lambda$. The manuscript conclude after
investigating the viability of the proposed bouncing model in non minimal
$f(R,T)$ gravity where $f(R,T) = R + \chi R T$.
| [
{
"created": "Sun, 29 Mar 2020 12:01:43 GMT",
"version": "v1"
}
] | 2020-04-07 | [
[
"Bhattacharjee",
"Snehasish",
""
],
[
"Sahoo",
"P. K.",
""
]
] | The present paper is devoted to the study of bouncing cosmology in $f(R,T)$ modified gravity where we presume $f(R,T) = R + 2 \lambda T$, with $R$ the Ricci scalar, $T$ the trace of energy momentum tensor and $\lambda$ the model parameter. We present here a novel parametrization of Hubble parameter which is apt in representing a successful bouncing scenario undergoing no singularity. We proceed to present a complete analysis of the proposed bouncing model by studying the evolution of primordial curvature perturbations, energy conditions and stability against linear homogeneous perturbations in flat space-time. We also delineate bouncing cosmology for the proposed model by employing Quintom matter. The present article further communicate for the first time that violation of energy-momentum materialize for both the contracting and expanding universes except for the bouncing epoch with energy flow directed away and into the matter fields for the contracting and expanding universe respectively. We further present a thorough investigation about the feasibility of the proposed bouncing scenario against first and generalized second law of thermodynamics. We found that the proposed bouncing scenario obeys the laws of thermodynamics for the constrained parameter space of $\lambda$. The manuscript conclude after investigating the viability of the proposed bouncing model in non minimal $f(R,T)$ gravity where $f(R,T) = R + \chi R T$. |
0808.2518 | Victor Flambaum | V.V. Flambaum | Comment on "Black hole constraints on varying fundamental constants" | Comment on arXiv:0706.2188 [PRL 99, 061301] by Jane MacGibbon | Phys.Rev.Lett.102:069001,2009 | 10.1103/PhysRevLett.102.069001 | null | gr-qc astro-ph hep-ph hep-th physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Letter [1] (also [2]) there is a claim that the generalised second law
of thermodynamics (entropy increase) for black holes provides some limits on
the rate of variation of the fundamental constants of nature (electric charge
e, speed of light c, etc.). We have come to a different conclusion. The results
in [1,2] are based on assumption that mass of a black hole does not change
without radiation and accreation. We present arguments showing that this
assumption is incorrect and give an estimate of the black hole mass variation
due to alpha=e^2/\hbar c variation using entropy (and quantum energy level)
conservation in an adiabatic process. No model-independent limits on the
variation of the fundamental constants are derived from the second law of
thermodynamics.
| [
{
"created": "Tue, 19 Aug 2008 02:13:15 GMT",
"version": "v1"
}
] | 2009-02-27 | [
[
"Flambaum",
"V. V.",
""
]
] | In the Letter [1] (also [2]) there is a claim that the generalised second law of thermodynamics (entropy increase) for black holes provides some limits on the rate of variation of the fundamental constants of nature (electric charge e, speed of light c, etc.). We have come to a different conclusion. The results in [1,2] are based on assumption that mass of a black hole does not change without radiation and accreation. We present arguments showing that this assumption is incorrect and give an estimate of the black hole mass variation due to alpha=e^2/\hbar c variation using entropy (and quantum energy level) conservation in an adiabatic process. No model-independent limits on the variation of the fundamental constants are derived from the second law of thermodynamics. |
1611.04143 | Charles Torre | D. S. Krongos and C. G. Torre | Rainich Conditions in (2+1)-Dimensional Gravity | 9 pages | null | 10.1063/1.4974091 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In (3 + 1) spacetime dimensions the Rainich conditions are a set of equations
expressed solely in terms of the metric tensor which are equivalent to the
Einstein-Maxwell equations for non-null electromagnetic fields. Here we provide
the analogous conditions for (2 + 1)-dimensional gravity coupled to
electromagnetism. Both the non-null and null cases are treated. The
construction of these conditions is based upon reducing the problem to that of
gravity coupled to a scalar field, which we have treated elsewhere. These
conditions can be easily extended to other theories of (2 + 1)-dimensional
gravity. For example, we apply the geometrization conditions to topologically
massive gravity coupled to the electromagnetic field and obtain a family of
plane-fronted wave solutions.
| [
{
"created": "Sun, 13 Nov 2016 15:27:18 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"Krongos",
"D. S.",
""
],
[
"Torre",
"C. G.",
""
]
] | In (3 + 1) spacetime dimensions the Rainich conditions are a set of equations expressed solely in terms of the metric tensor which are equivalent to the Einstein-Maxwell equations for non-null electromagnetic fields. Here we provide the analogous conditions for (2 + 1)-dimensional gravity coupled to electromagnetism. Both the non-null and null cases are treated. The construction of these conditions is based upon reducing the problem to that of gravity coupled to a scalar field, which we have treated elsewhere. These conditions can be easily extended to other theories of (2 + 1)-dimensional gravity. For example, we apply the geometrization conditions to topologically massive gravity coupled to the electromagnetic field and obtain a family of plane-fronted wave solutions. |
0902.0103 | Kiyoshi Shiraishi | Teruki Hanada, Kazuhiko Shinoda and Kiyoshi Shiraishi (Yamaguchi
University) | Cosmology of multigravity | 4 pages, 10 figures. Prepared for the proceedings of JGRG18
(Hiroshima, Japan, 17--21 November 2008). corrected version, references added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have constructed a nonlinear multi-graviton theory. An application of this
theory to cosmology is discussed. We found that scale factors in a solution for
this theory repeat acceleration and deceleration.
| [
{
"created": "Sun, 1 Feb 2009 02:46:50 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Feb 2009 01:33:14 GMT",
"version": "v2"
}
] | 2009-02-10 | [
[
"Hanada",
"Teruki",
"",
"Yamaguchi\n University"
],
[
"Shinoda",
"Kazuhiko",
"",
"Yamaguchi\n University"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi\n University"
]
] | We have constructed a nonlinear multi-graviton theory. An application of this theory to cosmology is discussed. We found that scale factors in a solution for this theory repeat acceleration and deceleration. |
gr-qc/0201098 | G. Papini | G. Papini | Parity and Time Reversal in the Spin-Rotation Interaction | 3 pages | Phys.Rev. D65 (2002) 077901 | 10.1103/PhysRevD.65.077901 | null | gr-qc hep-ph | null | A recently reported discrepancy between experimental and theoretical values
of the muon's g-2 factor is interpreted as due to small violations of the
conservation of P and T in the spin-rotation coupling. The experiments place an
upper limit on these violations and on the weight change of spinning
gyroscopes.
| [
{
"created": "Thu, 31 Jan 2002 02:38:46 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Feb 2002 20:37:29 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Papini",
"G.",
""
]
] | A recently reported discrepancy between experimental and theoretical values of the muon's g-2 factor is interpreted as due to small violations of the conservation of P and T in the spin-rotation coupling. The experiments place an upper limit on these violations and on the weight change of spinning gyroscopes. |
1909.04789 | Bijan Saha Dr. | K.A. Bronnikov, Yu.P. Rybakov, and Bijan Saha | Spinor fields in spherical symmetry. Einstein-Dirac and other
space-times | 9 pages, 2 figures | The European Physical Journal Plus 135, 124 (2020) | 10.1140/epjp/s13360-020-00150-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the static spherically symmetric Einstein-spinor field system in
the possible presence of various spinor field nonlinearities. We take into
account that the spinor field energy-momentum tensor (EMT) has in general some
off-diagonal components, whose vanishing due to the Einstein equations
substantially affects the form of the spinor field itself and the space-time
geometry.
In particular, the EMT structure with any spinor field nonlinearities turns
out to be the same as that of the EMT of a minimally coupled scalar field with
a self-interaction potential. Therefore many results previously obtained for
systems with such scalar fields are directly extended to the Einstein-spinor
field system. Some special solutions are obtained and discussed, in particular,
a solution for the Einstein-Dirac system (which lack asymptotic flatness) and
some examples with spinor field nonlinearities.
| [
{
"created": "Tue, 10 Sep 2019 23:27:22 GMT",
"version": "v1"
}
] | 2020-03-05 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Rybakov",
"Yu. P.",
""
],
[
"Saha",
"Bijan",
""
]
] | We discuss the static spherically symmetric Einstein-spinor field system in the possible presence of various spinor field nonlinearities. We take into account that the spinor field energy-momentum tensor (EMT) has in general some off-diagonal components, whose vanishing due to the Einstein equations substantially affects the form of the spinor field itself and the space-time geometry. In particular, the EMT structure with any spinor field nonlinearities turns out to be the same as that of the EMT of a minimally coupled scalar field with a self-interaction potential. Therefore many results previously obtained for systems with such scalar fields are directly extended to the Einstein-spinor field system. Some special solutions are obtained and discussed, in particular, a solution for the Einstein-Dirac system (which lack asymptotic flatness) and some examples with spinor field nonlinearities. |
1207.1055 | Martin Richarte MR | Luis P. Chimento, Mart\'in G. Richarte, and Iv\'an E. S\'anchez G | Form invariance symmetry generates a large set of FRW cosmologies | 11 pages, 3 figures. Accepted for publication in Modern Physics
Letters A (2012) | Modern Physics Letters A Vol. 28, No. 4 (2013) 1250236 (19 pages) | 10.1142/S0217732312502367 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that Einstein's field equations for spatially flat
Friedmann-Robertson-Walker (FRW) space times have a form invariance symmetry
(FIS) realized by the form invariance transformations (FIT) which are indeed
generated by an invertible function of the source energy density. These
transformations act on the Hubble expansion rate, the energy density, and
pressure of the cosmic fluid; likewise such transformations are endowed with a
Lie group structure. Each representation of this group is associated with a
particular fluid and consequently a determined cosmology, so that, the FIS
defines a set of equivalent cosmological models. We focus our seek in the FIT
generated by a linear function because it provides a natural framework to
express the duality and also produces a large sets of cosmologies, starting
from a seed one, in several contexts as for instance in the cases of a perfect
fluid source and a scalar field driven by a potential depending linearly on the
scalar field kinetic energy density.
| [
{
"created": "Wed, 4 Jul 2012 16:53:41 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Dec 2012 04:49:47 GMT",
"version": "v2"
}
] | 2013-04-01 | [
[
"Chimento",
"Luis P.",
""
],
[
"Richarte",
"Martín G.",
""
],
[
"G",
"Iván E. Sánchez",
""
]
] | We show that Einstein's field equations for spatially flat Friedmann-Robertson-Walker (FRW) space times have a form invariance symmetry (FIS) realized by the form invariance transformations (FIT) which are indeed generated by an invertible function of the source energy density. These transformations act on the Hubble expansion rate, the energy density, and pressure of the cosmic fluid; likewise such transformations are endowed with a Lie group structure. Each representation of this group is associated with a particular fluid and consequently a determined cosmology, so that, the FIS defines a set of equivalent cosmological models. We focus our seek in the FIT generated by a linear function because it provides a natural framework to express the duality and also produces a large sets of cosmologies, starting from a seed one, in several contexts as for instance in the cases of a perfect fluid source and a scalar field driven by a potential depending linearly on the scalar field kinetic energy density. |
gr-qc/0601003 | Tomas Ortin | Tomas Ortin (IFT) | Supersymmetry and the Supergravity Landscape | Enlarged version of the talks given at the Pomeranian Workshop on
Cosmology and Fundamental Physics (Pobierowo, Poland) and the 2005 Spanish
Relativity Meeting (in Oviedo, Spain). Latex 2e file, 21 pages, no figures | null | 10.1002/andp.200510185 | IFT-UAM/CSIC-06-01 | gr-qc | null | In the recent times a lot of effort has been devoted to improve our knowledge
about the space of string theory vacua (``the landscape'') to find statistical
grounds to justify how and why the theory selects its vacuum. Particularly
interesting are those vacua that preserve some supersymmetry, which are always
supersymmetric solutions of some supergravity theory. After an general
introduction to how the pursuit of unification has lead to the vacuum selection
problem, we are going to review some recent results on the problem of finding
all the supersymmetric solutions of a supergravity theory applied to the
N=4,d=4 supergravity case.
| [
{
"created": "Sun, 1 Jan 2006 13:30:21 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Ortin",
"Tomas",
"",
"IFT"
]
] | In the recent times a lot of effort has been devoted to improve our knowledge about the space of string theory vacua (``the landscape'') to find statistical grounds to justify how and why the theory selects its vacuum. Particularly interesting are those vacua that preserve some supersymmetry, which are always supersymmetric solutions of some supergravity theory. After an general introduction to how the pursuit of unification has lead to the vacuum selection problem, we are going to review some recent results on the problem of finding all the supersymmetric solutions of a supergravity theory applied to the N=4,d=4 supergravity case. |
1612.03299 | Oscar Mauricio Pimentel Diaz | Oscar M. Pimentel, F. D. Lora-Clavijo and Guillermo A. Gonz\'alez | Ideal Magnetohydrodynamics with Radiative Terms: Energy Conditions | 12 pages | Class. Quantum Grav. 34:075008 (2017) | 10.1088/1361-6382/aa61d3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nowadays, the magnetic and radiation fields are very important to understand
the matter accretion into compact objects, the dynamics of binary systems, the
equilibrium configurations of neutron stars, the photon diffusion, etc. The
energy and the momentum associated to these fields, along with the matter one,
need to satisfy some conditions that guarantee an appropriate physical behavior
of the source and its gravitational field. Based on this fact, we present the
energy conditions for a perfect fluid with magnetic and radiation field, in
which the radiation part of the energy-momentum tensor is assumed to be
approximately isotropic, in accordance with the optically thick regime. In
order to find these conditions, the stress tensor of the system is written in
an orthonormal basis in which it becomes diagonal, and the energy conditions
are computed through contractions of the energy-momentum tensor with the four
velocity vector of an arbitrary observer. Finally, the conditions for a
magnetized fluid are presented as a particular case in which the radiation
contribution is zero.
| [
{
"created": "Sat, 10 Dec 2016 14:08:14 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Apr 2017 15:07:53 GMT",
"version": "v2"
}
] | 2017-04-13 | [
[
"Pimentel",
"Oscar M.",
""
],
[
"Lora-Clavijo",
"F. D.",
""
],
[
"González",
"Guillermo A.",
""
]
] | Nowadays, the magnetic and radiation fields are very important to understand the matter accretion into compact objects, the dynamics of binary systems, the equilibrium configurations of neutron stars, the photon diffusion, etc. The energy and the momentum associated to these fields, along with the matter one, need to satisfy some conditions that guarantee an appropriate physical behavior of the source and its gravitational field. Based on this fact, we present the energy conditions for a perfect fluid with magnetic and radiation field, in which the radiation part of the energy-momentum tensor is assumed to be approximately isotropic, in accordance with the optically thick regime. In order to find these conditions, the stress tensor of the system is written in an orthonormal basis in which it becomes diagonal, and the energy conditions are computed through contractions of the energy-momentum tensor with the four velocity vector of an arbitrary observer. Finally, the conditions for a magnetized fluid are presented as a particular case in which the radiation contribution is zero. |
1907.05759 | Sergey Rubin | Arkady A. Popov, Sergey G. Rubin | Evolution of sub-spaces at high and low energies | 20 pages | Eur. Phys. J. C (2019) 79:892 | 10.1140/epjc/s10052-019-7413-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of sub-spaces in the framework of gravity with higher
derivatives is studied. Numerical solutions to exact differential equations are
found. It is shown that the initial conditions play crucial role in the space
dynamic. Appropriate metrics describing an expanding and a stationary sub-space
shed light on the well-known question: why our 3-dim space is large but extra
space is small and stable (if exists)? It is assumed that the values of
parameters at high energies strongly depend on uncontrolled quantum corrections
and, hence, are not equal to their values at low energies. Therefore, there is
no way to trace solutions throughout the energy range, and we restrict
ourselves to the sub-Planckian and the inflationary energies.
| [
{
"created": "Fri, 12 Jul 2019 14:20:50 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 2019 07:59:24 GMT",
"version": "v2"
}
] | 2020-01-01 | [
[
"Popov",
"Arkady A.",
""
],
[
"Rubin",
"Sergey G.",
""
]
] | The evolution of sub-spaces in the framework of gravity with higher derivatives is studied. Numerical solutions to exact differential equations are found. It is shown that the initial conditions play crucial role in the space dynamic. Appropriate metrics describing an expanding and a stationary sub-space shed light on the well-known question: why our 3-dim space is large but extra space is small and stable (if exists)? It is assumed that the values of parameters at high energies strongly depend on uncontrolled quantum corrections and, hence, are not equal to their values at low energies. Therefore, there is no way to trace solutions throughout the energy range, and we restrict ourselves to the sub-Planckian and the inflationary energies. |
gr-qc/9404029 | Charles Torre | C. G. Torre | The Problems of Time and Observables: Some Recent Mathematical Results | Talk presented at the Lanczos Centenary Conference 3 pages, plain TeX | null | null | null | gr-qc | null | We present 2 recent results on the problems of time and observables in
canonical gravity. (1) We cannot use parametrized field theory to solve the
problem of time because, strictly speaking, general relativity is not a
parametrized field theory. (2) We show that there are essentially no local
observables for vacuum spacetimes.
| [
{
"created": "Thu, 14 Apr 1994 17:44:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Torre",
"C. G.",
""
]
] | We present 2 recent results on the problems of time and observables in canonical gravity. (1) We cannot use parametrized field theory to solve the problem of time because, strictly speaking, general relativity is not a parametrized field theory. (2) We show that there are essentially no local observables for vacuum spacetimes. |
1305.0083 | Ajit Kumar | Srivatsan Rajagopal and Ajit Kumar | Quantization of B-I electrodynamics and B-I modified gravity using
Faddeev-Popov gauge-fixing procedure | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the quantized versions of Born Infeld electrodynamics and Born
Infeld Gravity. We derive Feynman rules for B-I electrodynamics by deriving an
effective Lagrangian with the square root removed using the Faddeev-Popov
method. In the case of B-I gravity, the square root in the Lagrangian is
removed by the introduction of the Vierbien fields. This approach has the
advantage that SO(3,1) can be consistently regarded to be the gauge group of
gravity. Finally, using a rough argument, the quantum fluctuations of the radii
of spatial hypersurfaces in flat space are shown to undergo accelerated
increase with time.
| [
{
"created": "Wed, 1 May 2013 04:51:33 GMT",
"version": "v1"
}
] | 2013-05-02 | [
[
"Rajagopal",
"Srivatsan",
""
],
[
"Kumar",
"Ajit",
""
]
] | We investigate the quantized versions of Born Infeld electrodynamics and Born Infeld Gravity. We derive Feynman rules for B-I electrodynamics by deriving an effective Lagrangian with the square root removed using the Faddeev-Popov method. In the case of B-I gravity, the square root in the Lagrangian is removed by the introduction of the Vierbien fields. This approach has the advantage that SO(3,1) can be consistently regarded to be the gauge group of gravity. Finally, using a rough argument, the quantum fluctuations of the radii of spatial hypersurfaces in flat space are shown to undergo accelerated increase with time. |
2211.06532 | Yuri Bonder | Y. Bonder, J.E. Herrera, A.M. Rubiol | Energy nonconservation and relativistic trajectories: Unimodular gravity
and beyond | 13 pages. Accepted in Phys. Rev. D | Phys. Rev. D 107, 084032 (2023) | 10.1103/PhysRevD.107.084032 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Energy conservation has the status of a fundamental physical principle.
However, measurements in quantum mechanics do not comply with energy
conservation. Therefore, it is expected that a more fundamental theory of
gravity -- one that is less incompatible with quantum mechanics -- should admit
energy nonconservations. This paper begins by identifying the conditions for a
theory to have an energy-momentum tensor that is not conserved. Then, the
trajectory equation for pointlike particles that lose energy is derived,
showing that energy nonconservation produces a particular acceleration. As an
example, the unimodular theory of gravity is studied. Interestingly, in
spherical symmetry, given that there is a generalized Birkhoff theorem and that
the energy-momentum tensor divergence is a closed form, the trajectories of
test particles that lose energy can be found using well known methods. Finally,
limits on the energy nonconservation parameters are set using Solar system
observations.
| [
{
"created": "Sat, 12 Nov 2022 00:48:49 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Apr 2023 15:58:59 GMT",
"version": "v2"
}
] | 2023-04-19 | [
[
"Bonder",
"Y.",
""
],
[
"Herrera",
"J. E.",
""
],
[
"Rubiol",
"A. M.",
""
]
] | Energy conservation has the status of a fundamental physical principle. However, measurements in quantum mechanics do not comply with energy conservation. Therefore, it is expected that a more fundamental theory of gravity -- one that is less incompatible with quantum mechanics -- should admit energy nonconservations. This paper begins by identifying the conditions for a theory to have an energy-momentum tensor that is not conserved. Then, the trajectory equation for pointlike particles that lose energy is derived, showing that energy nonconservation produces a particular acceleration. As an example, the unimodular theory of gravity is studied. Interestingly, in spherical symmetry, given that there is a generalized Birkhoff theorem and that the energy-momentum tensor divergence is a closed form, the trajectories of test particles that lose energy can be found using well known methods. Finally, limits on the energy nonconservation parameters are set using Solar system observations. |
gr-qc/0701032 | Farook Rahaman | F.Rahaman, M.Kalam and S. Chakraborty | Wormholes with varying equation of state parameter | A new section has been added and 2 figures are included | Acta Phys.Polon.B40:25-40,2009 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose wormholes solutions by assuming space dependent equation of state
parameter. Our models show that the existence of wormholes is supported by
arbitrary small quantities of averaged null energy condition (ANEC) violating
phantom energy characterized by variable equation state parameter.
| [
{
"created": "Thu, 4 Jan 2007 07:02:04 GMT",
"version": "v1"
},
{
"created": "Mon, 14 May 2007 09:21:29 GMT",
"version": "v2"
},
{
"created": "Tue, 28 Oct 2008 12:28:18 GMT",
"version": "v3"
}
] | 2009-04-24 | [
[
"Rahaman",
"F.",
""
],
[
"Kalam",
"M.",
""
],
[
"Chakraborty",
"S.",
""
]
] | We propose wormholes solutions by assuming space dependent equation of state parameter. Our models show that the existence of wormholes is supported by arbitrary small quantities of averaged null energy condition (ANEC) violating phantom energy characterized by variable equation state parameter. |
1602.04771 | Diego S\'aez-G\'omez | Diego Saez-Gomez (IA, U. of Lisbon) | Analyzing modified unimodular gravity via Lagrange multipliers | 8 pages. Title changed, some comments added, conclusions unchanged.
Version published in PRD | Phys. Rev. D 93, 124040 (2016) | 10.1103/PhysRevD.93.124040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The so-called unimodular version of General Relativity is revisited.
Unimodular gravity is constructed by fixing the determinant of the metric, what
leads to the trace-free part of the equations instead of the usual Einstein
field equations. Then, a cosmological constant naturally arises as an
integration constant. While unimodular gravity turns out equivalent to General
Relativity (GR) at the classical level, it provides important differences at
the quantum level. Here we extend the unimodular constraint to some extensions
of General Relativity that have drawn a lot of attention over the last years,
as $f(R)$ gravity (or its scalar-tensor picture) and Gauss-Bonnet gravity. The
corresponding unimodular version of such theories is constructed as well as the
conformal transformation that relates the Einstein and Jordan frames for these
non-minimally coupled theories. From the classical point of view, the
unimodular versions of such extensions are completely equivalent to their
originals, but an effective cosmological constant arises naturally, what may
provide a richer description of the universe evolution. Here we analyze the
case of Starobisnky inflation and compared with the original one.
| [
{
"created": "Mon, 15 Feb 2016 19:24:30 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jun 2016 14:58:41 GMT",
"version": "v2"
}
] | 2016-06-22 | [
[
"Saez-Gomez",
"Diego",
"",
"IA, U. of Lisbon"
]
] | The so-called unimodular version of General Relativity is revisited. Unimodular gravity is constructed by fixing the determinant of the metric, what leads to the trace-free part of the equations instead of the usual Einstein field equations. Then, a cosmological constant naturally arises as an integration constant. While unimodular gravity turns out equivalent to General Relativity (GR) at the classical level, it provides important differences at the quantum level. Here we extend the unimodular constraint to some extensions of General Relativity that have drawn a lot of attention over the last years, as $f(R)$ gravity (or its scalar-tensor picture) and Gauss-Bonnet gravity. The corresponding unimodular version of such theories is constructed as well as the conformal transformation that relates the Einstein and Jordan frames for these non-minimally coupled theories. From the classical point of view, the unimodular versions of such extensions are completely equivalent to their originals, but an effective cosmological constant arises naturally, what may provide a richer description of the universe evolution. Here we analyze the case of Starobisnky inflation and compared with the original one. |
2205.02615 | Francesco Sartini | Marc Geiller, Etera R. Livine, Francesco Sartini | Dynamical symmetries of homogeneous minisuperspace models | 40 pages | Phys.Rev.D 106 (2022) 6, 064013 | 10.1103/PhysRevD.106.064013 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the phase space symmetries and conserved charges of
homogeneous gravitational minisuperspaces. These (0+1)-dimensional reductions
of general relativity are defined by spacetime metrics in which the dynamical
variables depend only on a time coordinate, and are formulated as mechanical
systems with a non-trivial field space metric (or supermetric) and effective
potential. We show how to extract conserved charges for those minisuperspaces
from the homothetic Killing vectors of the field space metric. In the case of
two-dimensional field spaces, we exhibit a universal 8-dimensional symmetry
algebra given by the semi-direct sum of
$\mathfrak{sl}(2,\mathbb{R})\oplus\mathbb{R}$ with the two-dimensional
Heisenberg algebra $\mathfrak{h}_2\simeq\mathbb{R}^4$. We apply this to the
systematic study of the Bianchi models for homogeneous cosmology. This extends
previous results on the $\mathfrak{sl}(2,\mathbb{R})$ algebra for
Friedmann-Lemaitre-Robertson-Walker cosmology, and the Poincar\'e symmetry for
Kantowski-Sachs metrics describing the black hole interior. The presence of
this rich symmetry structure already in minisuperspace models opens new doors
towards quantization and the study of solution generating mechanisms.
| [
{
"created": "Thu, 5 May 2022 12:53:35 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Sep 2022 15:14:15 GMT",
"version": "v2"
}
] | 2022-09-12 | [
[
"Geiller",
"Marc",
""
],
[
"Livine",
"Etera R.",
""
],
[
"Sartini",
"Francesco",
""
]
] | We investigate the phase space symmetries and conserved charges of homogeneous gravitational minisuperspaces. These (0+1)-dimensional reductions of general relativity are defined by spacetime metrics in which the dynamical variables depend only on a time coordinate, and are formulated as mechanical systems with a non-trivial field space metric (or supermetric) and effective potential. We show how to extract conserved charges for those minisuperspaces from the homothetic Killing vectors of the field space metric. In the case of two-dimensional field spaces, we exhibit a universal 8-dimensional symmetry algebra given by the semi-direct sum of $\mathfrak{sl}(2,\mathbb{R})\oplus\mathbb{R}$ with the two-dimensional Heisenberg algebra $\mathfrak{h}_2\simeq\mathbb{R}^4$. We apply this to the systematic study of the Bianchi models for homogeneous cosmology. This extends previous results on the $\mathfrak{sl}(2,\mathbb{R})$ algebra for Friedmann-Lemaitre-Robertson-Walker cosmology, and the Poincar\'e symmetry for Kantowski-Sachs metrics describing the black hole interior. The presence of this rich symmetry structure already in minisuperspace models opens new doors towards quantization and the study of solution generating mechanisms. |
1612.01121 | Gauranga Samanta | G. C. Samanta, R. Myrzakulov and Parth Shah | Kaluza-Klein bulk viscous fluid cosmological models and the validity of
the second law of thermodynamics in $f(R, T)$ gravity | 20 pages, 10 figures. reference added, text clean, abstract modified | null | 10.1515/zna-2016-0472 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The authors considered the bulk viscous fluid in $f(R, T)$ gravity within the
framework of Kaluza-Klein space time. The bulk viscous coefficient $(\xi)$
expressed as $\xi=\xi_0+\xi_1\frac{\dot{a}}{a}+\xi_2\frac{\ddot{a}}{\dot{a}}$,
where $\xi_0$, $\xi_1$ and $\xi_2$ are positive constants. We take
$p=(\gamma-1)\rho$, where $0\le\gamma\le2$ as an equation of state for perfect
fluid. The exact solutions to the corresponding field equations are given by
assuming a particular model of the form of $f(R, T)=R+2f(T)$, where
$f(T)=\lambda T$, $\lambda$ is constant. We studied the cosmological model in
two stages, in first stage: we studied the model with no viscosity, and in
second stage: we studied the model involve with viscosity. The cosmological
model involve with viscosity is studied by five possible scenarios for bulk
viscous fluid coefficient $(\xi)$. The total bulk viscous coefficient seems to
be negative, when the bulk viscous coefficient is proportional to
$\xi_2\frac{\ddot{a}}{\dot{a}}$, hence the second law of thermodynamics is not
valid, however, it is valid with the generalized second law of thermodynamics.
The total bulk viscous coefficient seems to be positive, when, the bulk viscous
coefficient is proportional to $\xi=\xi_1\frac{\dot{a}}{a}$,
$\xi=\xi_1\frac{\dot{a}}{a}+\xi_2\frac{\ddot{a}}{\dot{a}}$ and
$\xi=\xi_0+\xi_1\frac{\dot{a}}{a}+\xi_2\frac{\ddot{a}}{\dot{a}}$, so the second
law of thermodynamics and the generalized second law of thermodynamics is
satisfied throughout the evolution. We calculate statefinder parameters of the
model and observed that, it is different from the $\wedge$CDM model. Finally,
some physical and geometrical properties of the models are discussed.
| [
{
"created": "Sun, 4 Dec 2016 13:53:28 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Dec 2016 06:58:39 GMT",
"version": "v2"
}
] | 2017-04-26 | [
[
"Samanta",
"G. C.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Shah",
"Parth",
""
]
] | The authors considered the bulk viscous fluid in $f(R, T)$ gravity within the framework of Kaluza-Klein space time. The bulk viscous coefficient $(\xi)$ expressed as $\xi=\xi_0+\xi_1\frac{\dot{a}}{a}+\xi_2\frac{\ddot{a}}{\dot{a}}$, where $\xi_0$, $\xi_1$ and $\xi_2$ are positive constants. We take $p=(\gamma-1)\rho$, where $0\le\gamma\le2$ as an equation of state for perfect fluid. The exact solutions to the corresponding field equations are given by assuming a particular model of the form of $f(R, T)=R+2f(T)$, where $f(T)=\lambda T$, $\lambda$ is constant. We studied the cosmological model in two stages, in first stage: we studied the model with no viscosity, and in second stage: we studied the model involve with viscosity. The cosmological model involve with viscosity is studied by five possible scenarios for bulk viscous fluid coefficient $(\xi)$. The total bulk viscous coefficient seems to be negative, when the bulk viscous coefficient is proportional to $\xi_2\frac{\ddot{a}}{\dot{a}}$, hence the second law of thermodynamics is not valid, however, it is valid with the generalized second law of thermodynamics. The total bulk viscous coefficient seems to be positive, when, the bulk viscous coefficient is proportional to $\xi=\xi_1\frac{\dot{a}}{a}$, $\xi=\xi_1\frac{\dot{a}}{a}+\xi_2\frac{\ddot{a}}{\dot{a}}$ and $\xi=\xi_0+\xi_1\frac{\dot{a}}{a}+\xi_2\frac{\ddot{a}}{\dot{a}}$, so the second law of thermodynamics and the generalized second law of thermodynamics is satisfied throughout the evolution. We calculate statefinder parameters of the model and observed that, it is different from the $\wedge$CDM model. Finally, some physical and geometrical properties of the models are discussed. |
1711.05212 | Jordan Moxon | Jordan Moxon and \'Eanna Flanagan | Radiation-Reaction Force on a Small Charged Body to Second Order | 31 pages, 2 figures | Phys. Rev. D 97, 105001 (2018) | 10.1103/PhysRevD.97.105001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In classical electrodynamics, an accelerating charged body emits radiation
and experiences a corresponding radiation-reaction force, or self force. We
extend to higher order in the total charge a previous rigorous derivation of
the electromagnetic self force in flat spacetime by Gralla, Harte, and Wald.
The method introduced by Gralla, Harte, and Wald computes the self force from
the Maxwell field equations and conservation of stress-energy in a limit where
the charge, size, and mass of the body go to zero, and does not require
regularization of a singular self field. For our higher order computation, an
adjustment of the definition of the mass of the body is necessary to avoid
including self energy from the electromagnetic field sourced by the body in the
distant past. We derive the evolution equations for the mass, spin, and
center-of-mass position of the body through second order. We derive, for the
first time, the second-order acceleration dependence of the evolution of the
spin (self torque), as well as a mixing between the extended body effects and
the acceleration dependent effects on the overall body motion.
| [
{
"created": "Tue, 14 Nov 2017 17:25:34 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Nov 2017 18:23:45 GMT",
"version": "v2"
}
] | 2018-05-09 | [
[
"Moxon",
"Jordan",
""
],
[
"Flanagan",
"Éanna",
""
]
] | In classical electrodynamics, an accelerating charged body emits radiation and experiences a corresponding radiation-reaction force, or self force. We extend to higher order in the total charge a previous rigorous derivation of the electromagnetic self force in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self force from the Maxwell field equations and conservation of stress-energy in a limit where the charge, size, and mass of the body go to zero, and does not require regularization of a singular self field. For our higher order computation, an adjustment of the definition of the mass of the body is necessary to avoid including self energy from the electromagnetic field sourced by the body in the distant past. We derive the evolution equations for the mass, spin, and center-of-mass position of the body through second order. We derive, for the first time, the second-order acceleration dependence of the evolution of the spin (self torque), as well as a mixing between the extended body effects and the acceleration dependent effects on the overall body motion. |
2401.15249 | Hyat Huang | Hyat Huang, Jutta Kunz and Deeshani Mitra | Shadow images of compact objects in beyond Horndeski theory | 28 pages, 18 figures, Comments welcome | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A beyond Horndeski theory is considered that admits wormholes, black holes
and naked singularities. In this theory the shadow images of the black holes
and the exotic compact objects (ECOs), illuminated by an optically and
geometrically thin disk, are investigated. The results show that the three
kinds of objects cast unlike shadow images, in particular, because the
different objects possess a different number of light rings. The different
boundaries of the accretion disk also affect the images. This may provide
further insight into the nature of the shadow images of massive compact
objects.
| [
{
"created": "Fri, 26 Jan 2024 23:52:33 GMT",
"version": "v1"
}
] | 2024-01-30 | [
[
"Huang",
"Hyat",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Mitra",
"Deeshani",
""
]
] | A beyond Horndeski theory is considered that admits wormholes, black holes and naked singularities. In this theory the shadow images of the black holes and the exotic compact objects (ECOs), illuminated by an optically and geometrically thin disk, are investigated. The results show that the three kinds of objects cast unlike shadow images, in particular, because the different objects possess a different number of light rings. The different boundaries of the accretion disk also affect the images. This may provide further insight into the nature of the shadow images of massive compact objects. |
gr-qc/9808049 | Marcelo Jose Reboucas | M.J. Reboucas and A.F.F. Teixeira | Causal Anomalies in Kaluza-Klein Gravity Theories | 16 page. LaTex file. To appear in Int. J. Mod. Phys. A (1998) | Int.J.Mod.Phys. A13 (1998) 3181-3192 | 10.1142/S0217751X98001578 | CBPF-NF-060/97 | gr-qc astro-ph | null | Causal anomalies in two Kaluza-Klein gravity theories are examined,
particularly as to whether these theories permit solutions in which the
causality principle is violated. It is found that similarly to general
relativity the field equations of the space-time-mass Kaluza-Klein (STM-KK)
gravity theory do not exclude violation of causality of G\"odel type, whereas
the induced matter Kaluza-Klein (IM-KK) gravity rules out noncausal
G\"odel-type models. The induced matter version of general relativity is shown
to be an efficient therapy for causal anomalies that occurs in a wide class of
noncausal geometries. Perfect fluid and dust G\"odel-type solutions of the
STM-KK field equations are studied. It is shown that every G\"odel-type perfect
fluid solution is isometric to the unique dust solution of the STM-KK field
equations. The question as to whether 5-D G\"odel-type non-causal geometries
induce any physically acceptable 4-D energy-momentum tensor is also addressed.
| [
{
"created": "Tue, 18 Aug 1998 20:46:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Reboucas",
"M. J.",
""
],
[
"Teixeira",
"A. F. F.",
""
]
] | Causal anomalies in two Kaluza-Klein gravity theories are examined, particularly as to whether these theories permit solutions in which the causality principle is violated. It is found that similarly to general relativity the field equations of the space-time-mass Kaluza-Klein (STM-KK) gravity theory do not exclude violation of causality of G\"odel type, whereas the induced matter Kaluza-Klein (IM-KK) gravity rules out noncausal G\"odel-type models. The induced matter version of general relativity is shown to be an efficient therapy for causal anomalies that occurs in a wide class of noncausal geometries. Perfect fluid and dust G\"odel-type solutions of the STM-KK field equations are studied. It is shown that every G\"odel-type perfect fluid solution is isometric to the unique dust solution of the STM-KK field equations. The question as to whether 5-D G\"odel-type non-causal geometries induce any physically acceptable 4-D energy-momentum tensor is also addressed. |
1011.5272 | Kouji Nakamura | Kouji Nakamura | General formulation of general-relativistic higher-order gauge-invariant
perturbation theory | 4 pages, no figure. (v3) some explanations are added and a reference
is added | Class. Quantum Grav. vol.28, 122001, (2011) | 10.1088/0264-9381/28/12/122001 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gauge-invariant treatments of general-relativistic higher-order perturbations
on generic background spacetime is proposed. After reviewing the general
framework of the second-order gauge-invariant perturbation theory, we show the
fact that the linear-order metric perturbation is decomposed into
gauge-invariant and gauge-variant parts, which was the important premis of this
general framework. This means that the development the higher-order
gauge-invariant perturbation theory on generic background spacetime is
possible. A remaining issue to be resolve is also disscussed.
| [
{
"created": "Wed, 24 Nov 2010 02:12:09 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jan 2011 06:46:20 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Feb 2011 01:45:57 GMT",
"version": "v3"
}
] | 2012-05-24 | [
[
"Nakamura",
"Kouji",
""
]
] | Gauge-invariant treatments of general-relativistic higher-order perturbations on generic background spacetime is proposed. After reviewing the general framework of the second-order gauge-invariant perturbation theory, we show the fact that the linear-order metric perturbation is decomposed into gauge-invariant and gauge-variant parts, which was the important premis of this general framework. This means that the development the higher-order gauge-invariant perturbation theory on generic background spacetime is possible. A remaining issue to be resolve is also disscussed. |
1707.07729 | Abhay Ashtekar | Abhay Ashtekar and B\'eatrice Bonga | On a basic conceptual confusion in gravitational radiation theory | 8 pages. Some references added and minor changes made to add clarity | Class. Quantum Grav. 34, 20LT01(7pages) (2017) | 10.1088/1361-6382/aa88e2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In much of the literature on linearized gravitational waves two completely
different notions are called transverse traceless modes and labelled
$h_{ab}^{TT}$, often in different sections of the same reference, without
realizing the underlying inconsistency. We compare and contrast the two notions
and find that the difference persists even at leading asymptotic order near
future null infinity $\mathit{I}^+$. We discuss why the distinction has
nonetheless remained largely unnoticed, and also point out that there are some
important physical effects where only one of the notions gives the correct
answer.
| [
{
"created": "Mon, 24 Jul 2017 19:49:22 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Sep 2017 02:25:36 GMT",
"version": "v2"
}
] | 2017-09-22 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Bonga",
"Béatrice",
""
]
] | In much of the literature on linearized gravitational waves two completely different notions are called transverse traceless modes and labelled $h_{ab}^{TT}$, often in different sections of the same reference, without realizing the underlying inconsistency. We compare and contrast the two notions and find that the difference persists even at leading asymptotic order near future null infinity $\mathit{I}^+$. We discuss why the distinction has nonetheless remained largely unnoticed, and also point out that there are some important physical effects where only one of the notions gives the correct answer. |
1812.03834 | Tanwi Bandyopadhyay | Tanwi Bandyopadhyay and Ujjal Debnath | Bouncing Universe in the Contexts of Generalized Cosmic Chaplygin Gas
and Variable Modified Chaplygin Gas | 16 pages, 29 figures | null | 10.1139/cjp-2017-1008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have considered the Friedmann-Robertson-Walker (FRW) model
of the universe where bounce occurs and the universe is filled with Generalized
Cosmic Chaplygin Gas (GCCG) or Variable Modified Chaplygin Gas (VMCG). We have
studied the stability analysis through dynamical system for both models and
found the critical points in flat, open and closed universe. In presence of
scalar field, the dynamical behavior of scale factor and Hubble parameter is
described in both models. Finally, we have analyzed the energy conditions for
both the models in bouncing universe.
| [
{
"created": "Thu, 6 Dec 2018 05:42:31 GMT",
"version": "v1"
}
] | 2018-12-11 | [
[
"Bandyopadhyay",
"Tanwi",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this work, we have considered the Friedmann-Robertson-Walker (FRW) model of the universe where bounce occurs and the universe is filled with Generalized Cosmic Chaplygin Gas (GCCG) or Variable Modified Chaplygin Gas (VMCG). We have studied the stability analysis through dynamical system for both models and found the critical points in flat, open and closed universe. In presence of scalar field, the dynamical behavior of scale factor and Hubble parameter is described in both models. Finally, we have analyzed the energy conditions for both the models in bouncing universe. |
2101.04212 | Nikodem Poplawski | Nikodem Pop{\l}awski | Relativistic wave--particle duality for spinors | 6 pages | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We propose that relativistic wave--particle duality can be embodied in a
relation $\langle u^i\rangle=\bar{\psi}\gamma^i\psi/\bar{\psi}\psi$, which
determines the mean four-velocity of the fermion particle associated with a
Dirac wave function. We use the Einstein--Cartan theory of gravity with
torsion, which incorporates the spin-orbit interaction in curved spacetime.
This relation is satisfied by a spinor plane wave and it is consistent with the
energy-momentum tensor for particles. We suggest that spacetime guides the
evolution of a wave function, that in turn guides the mean motion of the
associated particle. Consequently, spacetime guides the motion of particles.
The exact motion is limited by the uncertainty principle.
| [
{
"created": "Mon, 11 Jan 2021 22:06:27 GMT",
"version": "v1"
}
] | 2021-01-14 | [
[
"Popławski",
"Nikodem",
""
]
] | We propose that relativistic wave--particle duality can be embodied in a relation $\langle u^i\rangle=\bar{\psi}\gamma^i\psi/\bar{\psi}\psi$, which determines the mean four-velocity of the fermion particle associated with a Dirac wave function. We use the Einstein--Cartan theory of gravity with torsion, which incorporates the spin-orbit interaction in curved spacetime. This relation is satisfied by a spinor plane wave and it is consistent with the energy-momentum tensor for particles. We suggest that spacetime guides the evolution of a wave function, that in turn guides the mean motion of the associated particle. Consequently, spacetime guides the motion of particles. The exact motion is limited by the uncertainty principle. |
2202.05105 | Alexander C. Jenkins | Alexander C. Jenkins | Cosmology and Fundamental Physics in the Era of Gravitational-Wave
Astronomy | PhD thesis, 299 pages, 67 figures, references updated | null | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The advent of gravitational-wave (GW) astronomy has presented us with a
completely new means for observing the Universe, allowing us to probe its
structure and evolution like never before. In this thesis, we explore three
distinct but complementary avenues for using GW observations to gain new
insights into cosmology and fundamental physics.
In chapter 1, we study the astrophysical GW background (AGWB): the cumulative
GW signal arising from a large number of compact binary coalescences (CBCs)
throughout the Universe. Since these compact binaries reside in galaxies, the
AGWB contains anisotropies that trace out the large-scale structure of the
cosmic matter distribution. We investigate the angular power spectrum of the
AGWB, with the goal of developing predictions that can be confronted with
directional AGWB searches.
In chapter 2, we calculate the nonlinear GW memory emitted by cusps and kinks
on cosmic string loops, which are among the most promising cosmological sources
of GWs. We show that, surprisingly, the cusp memory signal diverges for
sufficiently large loops, indicating a breakdown in the validity of the
weak-field description of the cusp. We then present one tentative possible
solution to this divergence, in which the portion of the string surrounding the
cusp collapses to form a primordial black hole (PBH).
Finally, in chapter 3 we develop a powerful new method for GW detection based
on precision measurements of the orbits of binary systems. In the presence of a
stochastic GW background (GWB) the trajectories of the binary's components are
perturbed, giving rise to a random walk in the system's orbital parameters over
time. We calculate the sensitivity of binary pulsars and lunar laser ranging to
the GWB through this effect, and show that present data are already sensitive
enough to place the strongest constraints to date in the $\mu$Hz frequency
band.
| [
{
"created": "Thu, 10 Feb 2022 15:47:14 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Mar 2022 18:27:40 GMT",
"version": "v2"
}
] | 2022-03-14 | [
[
"Jenkins",
"Alexander C.",
""
]
] | The advent of gravitational-wave (GW) astronomy has presented us with a completely new means for observing the Universe, allowing us to probe its structure and evolution like never before. In this thesis, we explore three distinct but complementary avenues for using GW observations to gain new insights into cosmology and fundamental physics. In chapter 1, we study the astrophysical GW background (AGWB): the cumulative GW signal arising from a large number of compact binary coalescences (CBCs) throughout the Universe. Since these compact binaries reside in galaxies, the AGWB contains anisotropies that trace out the large-scale structure of the cosmic matter distribution. We investigate the angular power spectrum of the AGWB, with the goal of developing predictions that can be confronted with directional AGWB searches. In chapter 2, we calculate the nonlinear GW memory emitted by cusps and kinks on cosmic string loops, which are among the most promising cosmological sources of GWs. We show that, surprisingly, the cusp memory signal diverges for sufficiently large loops, indicating a breakdown in the validity of the weak-field description of the cusp. We then present one tentative possible solution to this divergence, in which the portion of the string surrounding the cusp collapses to form a primordial black hole (PBH). Finally, in chapter 3 we develop a powerful new method for GW detection based on precision measurements of the orbits of binary systems. In the presence of a stochastic GW background (GWB) the trajectories of the binary's components are perturbed, giving rise to a random walk in the system's orbital parameters over time. We calculate the sensitivity of binary pulsars and lunar laser ranging to the GWB through this effect, and show that present data are already sensitive enough to place the strongest constraints to date in the $\mu$Hz frequency band. |
gr-qc/0005133 | Nicholas G. Phillips | Nicholas. G. Phillips, B. L. Hu | Vacuum Energy Density Fluctuations in Minkowski and Casimir States via
Smeared Quantum Fields and Point Separation | 41 pages, 2 figures | Phys.Rev. D62 (2000) 084017 | 10.1103/PhysRevD.62.084017 | null | gr-qc | null | We present calculations of the variance of fluctuations and of the mean of
the energy momentum tensor of a massless scalar field for the Minkowski and
Casimir vacua as a function of an intrinsic scale defined by a smeared field or
by point separation. We point out that contrary to prior claims, the ratio of
variance to mean-squared being of the order unity is not necessarily a good
criterion for measuring the invalidity of semiclassical gravity. For the
Casimir topology we obtain expressions for the variance to mean-squared ratio
as a function of the intrinsic scale (defined by a smeared field) compared to
the extrinsic scale (defined by the separation of the plates, or the
periodicity of space). Our results make it possible to identify the spatial
extent where negative energy density prevails which could be useful for
studying quantum field effects in worm holes and baby universe, and for
examining the design feasibility of real-life `time-machines'.
For the Minkowski vacuum we find that the ratio of the variance to the
mean-squared, calculated from the coincidence limit, is identical to the value
of the Casimir case at the same limit for spatial point separation while
identical to the value of a hot flat space result with a temporal
point-separation. We analyze the origin of divergences in the fluctuations of
the energy density and discuss choices in formulating a procedure for their
removal, thus raising new questions into the uniqueness and even the very
meaning of regularization of the energy momentum tensor for quantum fields in
curved or even flat spacetimes when spacetime is viewed as having an extended
structure.
| [
{
"created": "Wed, 31 May 2000 15:08:34 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Phillips",
"Nicholas. G.",
""
],
[
"Hu",
"B. L.",
""
]
] | We present calculations of the variance of fluctuations and of the mean of the energy momentum tensor of a massless scalar field for the Minkowski and Casimir vacua as a function of an intrinsic scale defined by a smeared field or by point separation. We point out that contrary to prior claims, the ratio of variance to mean-squared being of the order unity is not necessarily a good criterion for measuring the invalidity of semiclassical gravity. For the Casimir topology we obtain expressions for the variance to mean-squared ratio as a function of the intrinsic scale (defined by a smeared field) compared to the extrinsic scale (defined by the separation of the plates, or the periodicity of space). Our results make it possible to identify the spatial extent where negative energy density prevails which could be useful for studying quantum field effects in worm holes and baby universe, and for examining the design feasibility of real-life `time-machines'. For the Minkowski vacuum we find that the ratio of the variance to the mean-squared, calculated from the coincidence limit, is identical to the value of the Casimir case at the same limit for spatial point separation while identical to the value of a hot flat space result with a temporal point-separation. We analyze the origin of divergences in the fluctuations of the energy density and discuss choices in formulating a procedure for their removal, thus raising new questions into the uniqueness and even the very meaning of regularization of the energy momentum tensor for quantum fields in curved or even flat spacetimes when spacetime is viewed as having an extended structure. |
0912.3606 | Hirotaka Yoshino | Masaru Shibata, Hirotaka Yoshino | Nonaxisymmetric instability of rapidly rotating black hole in five
dimensions | 4 pages, 3 figures, accepted for publication in PRD(R) | Phys.Rev.D81:021501,2010 | 10.1103/PhysRevD.81.021501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present results from numerical solution of Einstein's equation in five
dimensions describing evolution of rapidly rotating black holes. We show, for
the first time, that the rapidly rotating black holes in higher dimensions are
unstable against nonaxisymmetric deformation; for the five-dimensional case,
the critical value of spin parameter for onset of the instability is $\approx
0.87$.
| [
{
"created": "Fri, 18 Dec 2009 08:21:18 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Shibata",
"Masaru",
""
],
[
"Yoshino",
"Hirotaka",
""
]
] | We present results from numerical solution of Einstein's equation in five dimensions describing evolution of rapidly rotating black holes. We show, for the first time, that the rapidly rotating black holes in higher dimensions are unstable against nonaxisymmetric deformation; for the five-dimensional case, the critical value of spin parameter for onset of the instability is $\approx 0.87$. |
1812.01542 | Carlo Rovelli | Marios Christodoulou, Carlo Rovelli | On the possibility of experimental detection of the discreteness of time | 4 pages, 2 figures | Frontiers in Physics, 8 (2020) 20 | 10.3389/fphy.2020.00207 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Bose-Marletto-Vedral experiment tests a non-relativistic quantum effect
due to a gravitational interaction. It has received attention because it may
soon be within observational reach in the lab. We observe here that: (i) in
relativistic language the experiment tests an interference effect between
proper-time intervals; (ii) the relevant difference of proper times is of the
order of the Planck time if the masses of the particles in the experiment are
of the order of the Planck mass (micrograms); (iii) the experiment might open a
window on the structure of time at the Planck scale: if time differences are
discrete at this scale ---as quantum gravity research may suggest--- the
Planckian discreteness of time could show up as quantum levels of a measurable
entanglement entropy.
| [
{
"created": "Tue, 4 Dec 2018 17:20:20 GMT",
"version": "v1"
},
{
"created": "Sat, 8 Dec 2018 22:20:48 GMT",
"version": "v2"
}
] | 2020-11-24 | [
[
"Christodoulou",
"Marios",
""
],
[
"Rovelli",
"Carlo",
""
]
] | The Bose-Marletto-Vedral experiment tests a non-relativistic quantum effect due to a gravitational interaction. It has received attention because it may soon be within observational reach in the lab. We observe here that: (i) in relativistic language the experiment tests an interference effect between proper-time intervals; (ii) the relevant difference of proper times is of the order of the Planck time if the masses of the particles in the experiment are of the order of the Planck mass (micrograms); (iii) the experiment might open a window on the structure of time at the Planck scale: if time differences are discrete at this scale ---as quantum gravity research may suggest--- the Planckian discreteness of time could show up as quantum levels of a measurable entanglement entropy. |
2403.05667 | Gil de Oliveira-Neto | G. Oliveira-Neto, A. Oliveira Castro J\'unior and G. A. Monerat | Primordial dust universe in the Ho\v{r}ava-Lifshitz theory | The paper has 13 pages and 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply quantum cosmology to investigate the early moments of a
Friedmann-Lema\^itre-Robertson-Walker (FLRW) cosmological model, using
Ho\v{r}ava-Lifshitz (HL) as the gravitational theory. The matter content of the
model is a dust perfect fluid. We start studying the classical model. Then, we
write the total Hamiltonian of the model, quantize it and find the appropriate
Wheeler-DeWitt equation. In order to avoid factor ordering ambiguities, in the
Wheeler-DeWitt equation, we introduce a canonical transformation. We solve that
equation using the Wentzel-Kramers-Brillouin (WKB) approximation and compute
the tunneling probabilities for the birth of that universe ($TP_{WKB}$). Since
the WKB wavefunction depends on the dust energy and the free coupling constants
coming from the HL theory, we compute the behavior of $TP_{WKB}$ as a function
of all these quantities.
| [
{
"created": "Fri, 8 Mar 2024 20:43:57 GMT",
"version": "v1"
}
] | 2024-03-12 | [
[
"Oliveira-Neto",
"G.",
""
],
[
"Júnior",
"A. Oliveira Castro",
""
],
[
"Monerat",
"G. A.",
""
]
] | We apply quantum cosmology to investigate the early moments of a Friedmann-Lema\^itre-Robertson-Walker (FLRW) cosmological model, using Ho\v{r}ava-Lifshitz (HL) as the gravitational theory. The matter content of the model is a dust perfect fluid. We start studying the classical model. Then, we write the total Hamiltonian of the model, quantize it and find the appropriate Wheeler-DeWitt equation. In order to avoid factor ordering ambiguities, in the Wheeler-DeWitt equation, we introduce a canonical transformation. We solve that equation using the Wentzel-Kramers-Brillouin (WKB) approximation and compute the tunneling probabilities for the birth of that universe ($TP_{WKB}$). Since the WKB wavefunction depends on the dust energy and the free coupling constants coming from the HL theory, we compute the behavior of $TP_{WKB}$ as a function of all these quantities. |
1410.1413 | Abraao Capistrano | Abraao J.S. Capistrano, Luiz A. Cabral | Evolving extrinsic curvature and the cosmological constant problem | 7 pages, 2 figures | Physica Scripta, v. 91, p. 105001, 2016 | 10.1088/0031-8949/91/10/105001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The concept of smooth deformation of Riemannian manifolds associated with the
extrinsic curvature is explained and applied to the FLRW cosmology. We show
that such deformation can be derived from Einstein-Hilbert-like dynamical
principle producing an observable effect in the sense of Noether. As a result,
we notice on how the extrinsic curvature compensates both quantitative and
qualitative difference between the cosmological constant $ \Lambda$ and the
vacuum energy $\rho_{vac}$ obtaining the observed upper bound for the
cosmological constant problem at electroweak scale. The topological
characteristics of the extrinsic curvature are discussed showing that the
produced extrinsic scalar curvature is an evolving dynamical quantity.
| [
{
"created": "Thu, 2 Oct 2014 20:42:57 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Dec 2015 18:52:07 GMT",
"version": "v2"
}
] | 2017-04-06 | [
[
"Capistrano",
"Abraao J. S.",
""
],
[
"Cabral",
"Luiz A.",
""
]
] | The concept of smooth deformation of Riemannian manifolds associated with the extrinsic curvature is explained and applied to the FLRW cosmology. We show that such deformation can be derived from Einstein-Hilbert-like dynamical principle producing an observable effect in the sense of Noether. As a result, we notice on how the extrinsic curvature compensates both quantitative and qualitative difference between the cosmological constant $ \Lambda$ and the vacuum energy $\rho_{vac}$ obtaining the observed upper bound for the cosmological constant problem at electroweak scale. The topological characteristics of the extrinsic curvature are discussed showing that the produced extrinsic scalar curvature is an evolving dynamical quantity. |
gr-qc/0607042 | T. Padmanabhan | Sudipta Sarkar, T. Padmanabhan | Thermodynamics of horizons from a dual quantum system | 5 pages; no figures | Entropy 9:100-107,2007 | 10.3390/e9030100 | null | gr-qc | null | It was shown recently that, in the case of Schwarschild black hole, one can
obtain the correct thermodynamic relations by studying a model quantum system
and using a particular duality transformation. We study this approach further
for the case a general spherically symmetric horizon. We show that the idea
works for a general case only if we define the entropy S as a congruence
("observer") dependent quantity and the energy E as the integral over the
source of the gravitational acceleration for the congruence. In fact, in this
case, one recovers the relation S=E/2T between entropy, energy and temperature
previously proposed by one of us in gr-qc/0308070. This approach also enables
us to calculate the quantum corrections of the Bekenstein-Hawking entropy
formula for all spherically symmetric horizons.
| [
{
"created": "Tue, 11 Jul 2006 05:27:26 GMT",
"version": "v1"
}
] | 2009-03-19 | [
[
"Sarkar",
"Sudipta",
""
],
[
"Padmanabhan",
"T.",
""
]
] | It was shown recently that, in the case of Schwarschild black hole, one can obtain the correct thermodynamic relations by studying a model quantum system and using a particular duality transformation. We study this approach further for the case a general spherically symmetric horizon. We show that the idea works for a general case only if we define the entropy S as a congruence ("observer") dependent quantity and the energy E as the integral over the source of the gravitational acceleration for the congruence. In fact, in this case, one recovers the relation S=E/2T between entropy, energy and temperature previously proposed by one of us in gr-qc/0308070. This approach also enables us to calculate the quantum corrections of the Bekenstein-Hawking entropy formula for all spherically symmetric horizons. |
1011.2455 | Ernesto F. Eiroa | Ernesto F. Eiroa, Carlos M. Sendra | Gravitational lensing by a regular black hole | 10 pages, 4 figures. v2: Improved version, new references added | Class.Quant.Grav.28:085008,2011 | 10.1088/0264-9381/28/8/085008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study a regular Bardeen black hole as a gravitational lens.
We find the strong deflection limit for the deflection angle, from which we
obtain the positions and magnifications of the relativistic images. As an
example, we apply the results to the particular case of the supermassive black
hole at the center of our galaxy.
| [
{
"created": "Wed, 10 Nov 2010 18:38:37 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Mar 2011 20:32:48 GMT",
"version": "v2"
}
] | 2011-03-29 | [
[
"Eiroa",
"Ernesto F.",
""
],
[
"Sendra",
"Carlos M.",
""
]
] | In this paper, we study a regular Bardeen black hole as a gravitational lens. We find the strong deflection limit for the deflection angle, from which we obtain the positions and magnifications of the relativistic images. As an example, we apply the results to the particular case of the supermassive black hole at the center of our galaxy. |
gr-qc/0411001 | Piotr Bizon | Piotr Bizo\'n, Arthur Wasserman | A note on the non-existence of $\sigma$-model solitons in the 2+1
dimensional AdS gravity | null | Phys.Rev. D71 (2005) 108701 | 10.1103/PhysRevD.71.108701 | null | gr-qc | null | We show that the gravitating static soliton in the 2+1 dimensional O(3)
$\sigma$ model does not exist in the presence of a negative cosmological
constant.
| [
{
"created": "Fri, 29 Oct 2004 20:36:30 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bizoń",
"Piotr",
""
],
[
"Wasserman",
"Arthur",
""
]
] | We show that the gravitating static soliton in the 2+1 dimensional O(3) $\sigma$ model does not exist in the presence of a negative cosmological constant. |
gr-qc/9912026 | Michele Vallisneri | Michele Vallisneri | Prospects for gravitational-wave observations of neutron-star tidal
disruption in neutron-star/black-hole binaries | RevTeX, 4 pages, 2 EPS figures. Revised slightly, corrected typos | Phys.Rev.Lett. 84 (2000) 3519 | 10.1103/PhysRevLett.84.3519 | null | gr-qc astro-ph | null | For an inspiraling neutron-star/black-hole binary (NS/BH), we estimate the
gravity-wave frequency f_td at the onset of NS tidal disruption. We model the
NS as a tidally distorted, homogeneous, Newtonian ellipsoid on a circular,
equatorial geodesic around a Kerr BH. We find that f_td depends strongly on the
NS radius R, and estimate that LIGO-II (ca. 2006-2008) might measure R to 15%
precision at 140 Mpc (about 1 event/yr under current estimates). This suggests
that LIGO-II might extract valuable information about the NS equation of state
from tidal-disruption waves.
| [
{
"created": "Wed, 8 Dec 1999 01:26:37 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Apr 2000 18:47:59 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Vallisneri",
"Michele",
""
]
] | For an inspiraling neutron-star/black-hole binary (NS/BH), we estimate the gravity-wave frequency f_td at the onset of NS tidal disruption. We model the NS as a tidally distorted, homogeneous, Newtonian ellipsoid on a circular, equatorial geodesic around a Kerr BH. We find that f_td depends strongly on the NS radius R, and estimate that LIGO-II (ca. 2006-2008) might measure R to 15% precision at 140 Mpc (about 1 event/yr under current estimates). This suggests that LIGO-II might extract valuable information about the NS equation of state from tidal-disruption waves. |
2007.13980 | Indrani Banerjee | Indrani Banerjee, Bhaswati Mandal and Soumitra SenGupta | Implications of Einstein-Maxwell dilaton-axion gravity from the black
hole continuum spectrum | 14 pages, 6 figures, 1 Table (accepted for publication in MNRAS) | null | 10.1093/mnras/staa3232 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | String inspired models can serve as potential candidates to replace GR in the
high energy regime where quantum gravity is expected to play a vital role. Such
models not only subsume the ultraviolet nature of gravity but also exhibit
promising prospects in resolving issues like dark matter and dark energy, which
cannot be adequately addressed within the framework of GR. The Einstein-Maxwell
dilaton-axion (EMDA) theory, which is central to this work is one such string
inspired model arising in the low energy effective action of the heterotic
string theory with interesting implications in inflationary cosmology and in
the late time acceleration of the universe. It is therefore important to survey
the role of such a theory in explaining astrophysical observations, e.g. the
continuum spectrum of black holes which is expected to hold a wealth of
information regarding the background metric. The Kerr-Sen spacetime corresponds
to the exact, stationary, and axisymmetric black hole solution in EMDA gravity,
possessing dilatonic charge and angular momentum originating from the axionic
field. In this work, we compute the theoretical spectrum from the accretion
disk around quasars in the Kerr-Sen background assuming the thin accretion disk
model due to Novikov \& Thorne. This is then used to evaluate the theoretical
estimates of optical luminosity for a sample of eighty Palomar-Green quasars
which are subsequently compared with the available observations. Our results
based on $\chi^2$ analysis indicate that the dilaton parameter $r_2\sim 0.2$ is
favored by optical observations of quasars which is further corroborated by
other error estimators e.g., the Nash-Sutcliffe efficiency, the index of
agreement, and their modified versions. We further report that strong dilaton
charges ($r_2>1.6$) are disfavored by quasar optical data and the spins
associated with the quasars are also estimated.
| [
{
"created": "Tue, 28 Jul 2020 04:06:57 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Oct 2020 11:16:11 GMT",
"version": "v2"
}
] | 2020-10-29 | [
[
"Banerjee",
"Indrani",
""
],
[
"Mandal",
"Bhaswati",
""
],
[
"SenGupta",
"Soumitra",
""
]
] | String inspired models can serve as potential candidates to replace GR in the high energy regime where quantum gravity is expected to play a vital role. Such models not only subsume the ultraviolet nature of gravity but also exhibit promising prospects in resolving issues like dark matter and dark energy, which cannot be adequately addressed within the framework of GR. The Einstein-Maxwell dilaton-axion (EMDA) theory, which is central to this work is one such string inspired model arising in the low energy effective action of the heterotic string theory with interesting implications in inflationary cosmology and in the late time acceleration of the universe. It is therefore important to survey the role of such a theory in explaining astrophysical observations, e.g. the continuum spectrum of black holes which is expected to hold a wealth of information regarding the background metric. The Kerr-Sen spacetime corresponds to the exact, stationary, and axisymmetric black hole solution in EMDA gravity, possessing dilatonic charge and angular momentum originating from the axionic field. In this work, we compute the theoretical spectrum from the accretion disk around quasars in the Kerr-Sen background assuming the thin accretion disk model due to Novikov \& Thorne. This is then used to evaluate the theoretical estimates of optical luminosity for a sample of eighty Palomar-Green quasars which are subsequently compared with the available observations. Our results based on $\chi^2$ analysis indicate that the dilaton parameter $r_2\sim 0.2$ is favored by optical observations of quasars which is further corroborated by other error estimators e.g., the Nash-Sutcliffe efficiency, the index of agreement, and their modified versions. We further report that strong dilaton charges ($r_2>1.6$) are disfavored by quasar optical data and the spins associated with the quasars are also estimated. |
1202.3688 | Julien Cortier | Julien Cortier | Gluing construction of initial data with Kerr-de Sitter ends | 27 pages, 3 figures | null | 10.1007/s00023-012-0210-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct initial data sets which satisfy the vacuum constraint equa-
tions of General Relativity with positive cosmologigal constant. More pre-
silely, we deform initial data with ends asymptotic to Schwarzschild-de Sitter
to obtain non-trivial initial data with exactly Kerr-de Sitter ends. The method
is inspired from Corvino's gluing method. We obtain here a extension of a
previous result for the time-symmetric case by Chru\'sciel and Pollack.
| [
{
"created": "Thu, 16 Feb 2012 20:19:50 GMT",
"version": "v1"
}
] | 2018-03-28 | [
[
"Cortier",
"Julien",
""
]
] | We construct initial data sets which satisfy the vacuum constraint equa- tions of General Relativity with positive cosmologigal constant. More pre- silely, we deform initial data with ends asymptotic to Schwarzschild-de Sitter to obtain non-trivial initial data with exactly Kerr-de Sitter ends. The method is inspired from Corvino's gluing method. We obtain here a extension of a previous result for the time-symmetric case by Chru\'sciel and Pollack. |
gr-qc/9812019 | Keith H. Lockitch | Keith H. Lockitch and John L. Friedman | Where are the r-modes of isentropic stars? | 54 pages including 4 ps tables and 11 PSTeX figures, AAS latex. To
appear in the Astrophysical Journal | Astrophys.J. 521 (1999) 764 | 10.1086/307580 | WISC-MILW-98-TH-21 | gr-qc astro-ph | null | Almost none of the r-modes ordinarily found in rotating stars exist, if the
star and its perturbations obey the same one-parameter equation of state; and
rotating relativistic stars with one-parameter equations of state have no pure
r-modes at all, no modes whose limit, for a star with zero angular velocity, is
a perturbation with axial parity. Similarly (as we show here) rotating stars of
this kind have no pure g-modes, no modes whose spherical limit is a
perturbation with polar parity and vanishing perturbed pressure and density.
Where have these modes gone?
In spherical stars of this kind, r-modes and g-modes form a degenerate
zero-frequency subspace. We find that rotation splits the degeneracy to zeroth
order in the star's angular velocity $\Omega$, and the resulting modes are
generically hybrids, whose limit as $\Omega\to 0$ is a stationary current with
axial and polar parts. Because each mode has definite parity, its axial and
polar parts have alternating values of $l$. We show that each mode belongs to
one of two classes, axial-led or polar-led, depending on whether the spherical
harmonic with lowest value of $l$ that contributes to its velocity field is
axial or polar. We numerically compute these modes for slowly rotating
polytropes and for Maclaurin spheroids, using a straightforward method that
appears to be novel and robust. Timescales for the gravitational-wave driven
instability and for viscous damping are computed using assumptions appropriate
to neutron stars.
| [
{
"created": "Sat, 5 Dec 1998 00:59:02 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Dec 1998 01:30:28 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Jan 1999 23:04:24 GMT",
"version": "v3"
},
{
"created": "Fri, 19 Mar 1999 20:59:28 GMT",
"version": "v4"
}
] | 2009-10-31 | [
[
"Lockitch",
"Keith H.",
""
],
[
"Friedman",
"John L.",
""
]
] | Almost none of the r-modes ordinarily found in rotating stars exist, if the star and its perturbations obey the same one-parameter equation of state; and rotating relativistic stars with one-parameter equations of state have no pure r-modes at all, no modes whose limit, for a star with zero angular velocity, is a perturbation with axial parity. Similarly (as we show here) rotating stars of this kind have no pure g-modes, no modes whose spherical limit is a perturbation with polar parity and vanishing perturbed pressure and density. Where have these modes gone? In spherical stars of this kind, r-modes and g-modes form a degenerate zero-frequency subspace. We find that rotation splits the degeneracy to zeroth order in the star's angular velocity $\Omega$, and the resulting modes are generically hybrids, whose limit as $\Omega\to 0$ is a stationary current with axial and polar parts. Because each mode has definite parity, its axial and polar parts have alternating values of $l$. We show that each mode belongs to one of two classes, axial-led or polar-led, depending on whether the spherical harmonic with lowest value of $l$ that contributes to its velocity field is axial or polar. We numerically compute these modes for slowly rotating polytropes and for Maclaurin spheroids, using a straightforward method that appears to be novel and robust. Timescales for the gravitational-wave driven instability and for viscous damping are computed using assumptions appropriate to neutron stars. |
1801.00867 | Cosimo Bambi | Honghui Liu, Menglei Zhou, Cosimo Bambi | Distinguishing black holes and naked singularities with iron line
spectroscopy | 1+15 pages, 4 figures. v2: refereed version | JCAP 1808:044 (2018) | 10.1088/1475-7516/2018/08/044 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is commonly thought that the final product of gravitational collapse is a
black hole. Nevertheless, theoretical studies have not yet provided a final
answer to the question whether black holes are the only possible outcome or
whether naked singularities are also allowed. Observational tests may thus
represent a complementary approach. In the present paper, we consider the
Janis-Newman-Winicour metric, which describes a rotating source with a
surface-like naked singularity. We calculate iron line shapes in the reflection
spectrum of a putative disk around a Janis-Newman-Winicour singularity and we
compare our results with the iron line shapes expected in the spectrum of a
Kerr black hole. While it is difficult to distinguish the two spacetimes from
the iron line shape in general, it seems that Janis-Newman-Winicour
singularities cannot mimic fast-rotating Kerr black holes observed at a low or
moderate inclination angle. Our analysis thus suggests that available
observations of specific sources can already constrain the possible existence
of Janis-Newman-Winicour singularities in the Universe.
| [
{
"created": "Wed, 3 Jan 2018 00:13:32 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Aug 2018 14:40:57 GMT",
"version": "v2"
}
] | 2018-08-31 | [
[
"Liu",
"Honghui",
""
],
[
"Zhou",
"Menglei",
""
],
[
"Bambi",
"Cosimo",
""
]
] | It is commonly thought that the final product of gravitational collapse is a black hole. Nevertheless, theoretical studies have not yet provided a final answer to the question whether black holes are the only possible outcome or whether naked singularities are also allowed. Observational tests may thus represent a complementary approach. In the present paper, we consider the Janis-Newman-Winicour metric, which describes a rotating source with a surface-like naked singularity. We calculate iron line shapes in the reflection spectrum of a putative disk around a Janis-Newman-Winicour singularity and we compare our results with the iron line shapes expected in the spectrum of a Kerr black hole. While it is difficult to distinguish the two spacetimes from the iron line shape in general, it seems that Janis-Newman-Winicour singularities cannot mimic fast-rotating Kerr black holes observed at a low or moderate inclination angle. Our analysis thus suggests that available observations of specific sources can already constrain the possible existence of Janis-Newman-Winicour singularities in the Universe. |
2312.15505 | Asier Alonso-Bardaji | Asier Alonso-Bardaji and David Brizuela | Nonsingular collapse of a spherical dust cloud | 1 figure. Small clarifications and a brief comparison with previous
related models. Version matching the published paper | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a covariant framework to study singularity-free
Lema\^itre-Tolman-Bondi spacetimes with effective corrections motivated by loop
quantum gravity. We show that, as in general relativity, physically reasonable
energy distributions lead to a contraction of the dust shells. However,
quantum-gravity effects eventually stop the collapse, the dust smoothly bounces
back, and no gravitational singularity is generated. This model is constructed
by deforming the Hamiltonian constraint of general relativity with the
condition that the hypersurface deformation algebra is closed. In addition,
under the gauge transformations generated by the deformed constraints, the
structure function of the algebra changes adequately, so that it can be
interpreted as the inverse spatial metric. Therefore, the model is completely
covariant in the sense that gauge transformations in phase space simply
correspond to coordinate changes in spacetime. However, in the construction of
the metric, we point out a specific freedom of considering a conformal factor,
which we use to obtain a family of singularity-free spacetimes associated to
the modified model.
| [
{
"created": "Sun, 24 Dec 2023 15:14:01 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2024 16:48:22 GMT",
"version": "v2"
}
] | 2024-03-07 | [
[
"Alonso-Bardaji",
"Asier",
""
],
[
"Brizuela",
"David",
""
]
] | We provide a covariant framework to study singularity-free Lema\^itre-Tolman-Bondi spacetimes with effective corrections motivated by loop quantum gravity. We show that, as in general relativity, physically reasonable energy distributions lead to a contraction of the dust shells. However, quantum-gravity effects eventually stop the collapse, the dust smoothly bounces back, and no gravitational singularity is generated. This model is constructed by deforming the Hamiltonian constraint of general relativity with the condition that the hypersurface deformation algebra is closed. In addition, under the gauge transformations generated by the deformed constraints, the structure function of the algebra changes adequately, so that it can be interpreted as the inverse spatial metric. Therefore, the model is completely covariant in the sense that gauge transformations in phase space simply correspond to coordinate changes in spacetime. However, in the construction of the metric, we point out a specific freedom of considering a conformal factor, which we use to obtain a family of singularity-free spacetimes associated to the modified model. |
1201.5599 | Micha{\l} W{\ka}s | Michal Was, Patrick J. Sutton, Gareth Jones, Isabel Leonor | Performance of an externally triggered gravitational-wave burst search | 9 pages, 5 figures, accepted by PRD | Phys. Rev. D 86, 022003 (2012) | 10.1103/PhysRevD.86.022003 | LIGO-P1100135 | gr-qc physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the performance of searches for gravitational wave bursts
associated with external astrophysical triggers as a function of the search sky
region. We discuss both the case of Gaussian noise and real noise of
gravitational wave detectors for arbitrary detector networks. We demonstrate
the ability to reach Gaussian limited sensitivity in real non-Gaussian data,
and show the conditions required to attain it. We find that a single sky
position search is ~20% more sensitive than an all-sky search of the same data.
| [
{
"created": "Thu, 26 Jan 2012 18:32:43 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jul 2012 13:37:19 GMT",
"version": "v2"
}
] | 2012-08-01 | [
[
"Was",
"Michal",
""
],
[
"Sutton",
"Patrick J.",
""
],
[
"Jones",
"Gareth",
""
],
[
"Leonor",
"Isabel",
""
]
] | We present the performance of searches for gravitational wave bursts associated with external astrophysical triggers as a function of the search sky region. We discuss both the case of Gaussian noise and real noise of gravitational wave detectors for arbitrary detector networks. We demonstrate the ability to reach Gaussian limited sensitivity in real non-Gaussian data, and show the conditions required to attain it. We find that a single sky position search is ~20% more sensitive than an all-sky search of the same data. |
2303.10348 | Merab Gogberashvili Prof | Merab Gogberashvili | Einstein's hole argument and Schwarzschild singularities | 13 pages, no figures | Ann. Phys. 452 (2023) 169274 | 10.1016/j.aop.2023.169274 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to the Einstein hole argument, vacuum metric solutions are
equivalent only if they correspond to the same energy--momentum tensor in the
source region. In this paper it is shown that singular coordinates that are
used to show Schwarzschild geodesics completeness, introduce the fictive
delta-like sources at the horizon. Then, metric tensors obtained by such
singular transformations, cannot be considered as solutions of the same
Einstein equations with the central source.
| [
{
"created": "Sat, 18 Mar 2023 06:50:50 GMT",
"version": "v1"
}
] | 2023-03-21 | [
[
"Gogberashvili",
"Merab",
""
]
] | According to the Einstein hole argument, vacuum metric solutions are equivalent only if they correspond to the same energy--momentum tensor in the source region. In this paper it is shown that singular coordinates that are used to show Schwarzschild geodesics completeness, introduce the fictive delta-like sources at the horizon. Then, metric tensors obtained by such singular transformations, cannot be considered as solutions of the same Einstein equations with the central source. |
2404.07257 | Nuno M. Santos | Nuno M. Santos, Carolina L. Benone, Carlos A. R. Herdeiro | Radial stability of spherical bosonic stars and critical points | 23 pages, 8 figures and 6 tables | JCAP 06 (2024) 068 | 10.1088/1475-7516/2024/06/068 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study radial perturbations of spherically symmetric spin-$0$ and spin-$1$
bosonic stars, computing numerically the squared frequency of the fundamental
mode. We find that not all critical points $-$ where the Arnowitt-Deser-Misner
mass attains an extremum $-$ correspond to zero modes. Thus, radial stability
does not $\textit{always}$ change at such critical points. The results are in
agreement with the so-called critical point method.
| [
{
"created": "Wed, 10 Apr 2024 18:00:01 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Apr 2024 17:23:29 GMT",
"version": "v2"
},
{
"created": "Mon, 27 May 2024 12:19:51 GMT",
"version": "v3"
}
] | 2024-07-01 | [
[
"Santos",
"Nuno M.",
""
],
[
"Benone",
"Carolina L.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
]
] | We study radial perturbations of spherically symmetric spin-$0$ and spin-$1$ bosonic stars, computing numerically the squared frequency of the fundamental mode. We find that not all critical points $-$ where the Arnowitt-Deser-Misner mass attains an extremum $-$ correspond to zero modes. Thus, radial stability does not $\textit{always}$ change at such critical points. The results are in agreement with the so-called critical point method. |
0912.1938 | Hrvoje Nikolic | H. Nikolic | The Spacetime View of the Information Paradox | 7 pages, revised, to appear in Int. J. Quantum Inf | Int. J. Quantum Inf. 10, 1250024 (2012) | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In semiclassical gravity, the final state of black-hole evaporation cannot be
described by a pure state. Nevertheless, we point out that the system can be
described by a generalized pure state, which is not defined on a 3-dimensional
hypersurface but on the 4-dimensional spacetime describing the whole Universe
at all times. Unlike the conventional quantum state, such a generalized state
treats time on an equal footing with space, which makes it well suited for
systems that are both quantum and relativistic. In particular, such a
generalized state contains a novel type of information encoded in the
correlations between future and past, which avoids the black-hole information
paradox.
| [
{
"created": "Thu, 10 Dec 2009 08:48:47 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2011 09:56:04 GMT",
"version": "v2"
}
] | 2012-04-12 | [
[
"Nikolic",
"H.",
""
]
] | In semiclassical gravity, the final state of black-hole evaporation cannot be described by a pure state. Nevertheless, we point out that the system can be described by a generalized pure state, which is not defined on a 3-dimensional hypersurface but on the 4-dimensional spacetime describing the whole Universe at all times. Unlike the conventional quantum state, such a generalized state treats time on an equal footing with space, which makes it well suited for systems that are both quantum and relativistic. In particular, such a generalized state contains a novel type of information encoded in the correlations between future and past, which avoids the black-hole information paradox. |
1709.09742 | F\'elix-Louis Juli\'e | F\'elix-Louis Juli\'e | Reducing the two-body problem in scalar-tensor theories to the motion of
a test particle : a scalar-tensor effective-one-body approach | null | Phys. Rev. D 97, 024047 (2018) | 10.1103/PhysRevD.97.024047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Starting from the second post-Keplerian (2PK) Hamiltonian describing the
conservative part of the two-body dynamics in massless scalar-tensor (ST)
theories, we build an effective-one-body (EOB) Hamiltonian which is a
$\nu$-deformation (where $\nu= 0$ is the test mass limit) of the analytically
known ST Hamiltonian of a test particle. This ST-EOB Hamiltonian leads to a
simple (yet canonically equivalent) formulation of the conservative 2PK
two-body problem, but also defines a resummation of the dynamics which is
well-suited to ST regimes that depart strongly from general relativity (GR) and
which may provide information on the strong-field dynamics, in particular, the
ST innermost stable circular orbit (ISCO) location and associated orbital
frequency. Results will be compared and contrasted with those deduced from the
ST-deformation of the (5PN) GR-EOB Hamiltonian previoulsy obtained in [Phys.
Rev. D95, 124054 (2017)].
| [
{
"created": "Wed, 27 Sep 2017 21:43:48 GMT",
"version": "v1"
}
] | 2018-02-07 | [
[
"Julié",
"Félix-Louis",
""
]
] | Starting from the second post-Keplerian (2PK) Hamiltonian describing the conservative part of the two-body dynamics in massless scalar-tensor (ST) theories, we build an effective-one-body (EOB) Hamiltonian which is a $\nu$-deformation (where $\nu= 0$ is the test mass limit) of the analytically known ST Hamiltonian of a test particle. This ST-EOB Hamiltonian leads to a simple (yet canonically equivalent) formulation of the conservative 2PK two-body problem, but also defines a resummation of the dynamics which is well-suited to ST regimes that depart strongly from general relativity (GR) and which may provide information on the strong-field dynamics, in particular, the ST innermost stable circular orbit (ISCO) location and associated orbital frequency. Results will be compared and contrasted with those deduced from the ST-deformation of the (5PN) GR-EOB Hamiltonian previoulsy obtained in [Phys. Rev. D95, 124054 (2017)]. |
1511.05821 | Philippe Spindel | Thibault Damour, Philippe Spindel | Minisuperspace quantum supersymmetric cosmology (and its hidden
hyperbolic Kac-Moody structures) | Proceedings Fourteenth Marcel Grossmann Meeting - Rome, July 12-18,
2015 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work summarises recent progress obtained by the mini-superpspace
quantization of $\mathcal N=1$, $d=4$ supergravity, formulated in the framework
of the Bianchi IX cosmological model. The emphasis is put on three main results
: the completeness of the solution space obtained, the elements suggesting a
hidden Kac-Moody structure of the theory and those leading to conjecture an
avoidance of the cosmological singularity by some branches of the wave function
of the Universe.
| [
{
"created": "Wed, 18 Nov 2015 14:59:24 GMT",
"version": "v1"
}
] | 2015-11-19 | [
[
"Damour",
"Thibault",
""
],
[
"Spindel",
"Philippe",
""
]
] | This work summarises recent progress obtained by the mini-superpspace quantization of $\mathcal N=1$, $d=4$ supergravity, formulated in the framework of the Bianchi IX cosmological model. The emphasis is put on three main results : the completeness of the solution space obtained, the elements suggesting a hidden Kac-Moody structure of the theory and those leading to conjecture an avoidance of the cosmological singularity by some branches of the wave function of the Universe. |
0709.3652 | Nikodem Poplawski | Nikodem J. Poplawski | Massive vectors from projective-invariance breaking | 11 pages; published version. Invited article in special issue on
torsion (V. Dvoeglazov, ed.) | Ann. Fond. Louis de Broglie 32 (2007) 335-353 | null | null | gr-qc hep-th math-ph math.MP | null | A general affine connection has enough degrees of freedom to describe the
classical gravitational and electromagnetic fields in the metric-affine
formulation of gravity. The gravitational field is represented in the
Lagrangian by the symmetric part of the Ricci tensor and the classical
electromagnetic field can be represented by the tensor of homothetic curvature.
The simplest metric-affine Lagrangian that depends on the tensor of homothetic
curvature generates the Einstein-Maxwell equations for a massless vector.
Metric-affine Lagrangians with matter fields depending on the connection are
subject to an unphysical constraint because the symmetrized Ricci tensor is
projectively invariant while matter fields are not. We show that the appearance
of the tensor of homothetic curvature, which is not projectively invariant, in
the Lagrangian replaces this constraint with the Maxwell equations and restores
projective invariance of the total action. We also examine several constraints
on the torsion tensor to show that algebraic constraints on the torsion that
break projective invariance of the connection and impose projective invariance
on the tensor of homothetic curvature replace the massless vector with a
massive vector. We conclude that the metric-affine formulation of gravity
allows for a mechanism that generates masses of vectors, as it happens for
electroweak gauge bosons via spontaneous symmetry breaking.
| [
{
"created": "Sun, 23 Sep 2007 18:37:21 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Mar 2008 18:24:07 GMT",
"version": "v2"
}
] | 2008-03-02 | [
[
"Poplawski",
"Nikodem J.",
""
]
] | A general affine connection has enough degrees of freedom to describe the classical gravitational and electromagnetic fields in the metric-affine formulation of gravity. The gravitational field is represented in the Lagrangian by the symmetric part of the Ricci tensor and the classical electromagnetic field can be represented by the tensor of homothetic curvature. The simplest metric-affine Lagrangian that depends on the tensor of homothetic curvature generates the Einstein-Maxwell equations for a massless vector. Metric-affine Lagrangians with matter fields depending on the connection are subject to an unphysical constraint because the symmetrized Ricci tensor is projectively invariant while matter fields are not. We show that the appearance of the tensor of homothetic curvature, which is not projectively invariant, in the Lagrangian replaces this constraint with the Maxwell equations and restores projective invariance of the total action. We also examine several constraints on the torsion tensor to show that algebraic constraints on the torsion that break projective invariance of the connection and impose projective invariance on the tensor of homothetic curvature replace the massless vector with a massive vector. We conclude that the metric-affine formulation of gravity allows for a mechanism that generates masses of vectors, as it happens for electroweak gauge bosons via spontaneous symmetry breaking. |
gr-qc/9912021 | Roustam M. Zalaletdinov | Roustam Zalaletdinov (International Center for Relativistic
Astrophysics, Universit\'a di Roma "La Sapienza", Roma and Department of
Theoretical Physics, Institute of Nuclear Physics, Tashkent) | Approximate Symmetries in General Relativity | 15 pages, LaTeX, extended version (including a review on the subject)
of the paper "Approximate Symmetries, Inhomogeneous Spaces and Gravitational
Entropy", to appear in Proc. of the Second ICRA Network Workshop "The Chaotic
Universe", eds. V. Gurzadyan and R. Ruffini (World Scientific, Singapore,
2000) | Proc. of the 2nd ICRA Network Workshop "The Chaotic Universe",
Rome-Pescara, February 1999, eds. V. Gurzadyan and R. Ruffini (World
Scientific, Singapore, 2000), p. 619635 | null | null | gr-qc | null | The problem of finding an appropriate geometrical/physical index for
measuring a degree of inhomogeneity for a given space-time manifold is posed.
Interrelations with the problem of understanding the
gravitational/informational entropy are pointed out. An approach based on the
notion of approximate symmetry is proposed. A number of related results on
definitions of approximate symmetries known from literature are briefly
reviewed with emphasis on their geometrical/physical content. A definition of a
Killing-like symmetry is given and a classification theorem for all possible
averaged space-times acquiring Killing-like symmetries upon averaging out a
space-time with a homothetic Killing symmetry is proved.
| [
{
"created": "Tue, 7 Dec 1999 14:00:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Zalaletdinov",
"Roustam",
"",
"International Center for Relativistic\n Astrophysics, Universitá di Roma \"La Sapienza\", Roma and Department of\n Theoretical Physics, Institute of Nuclear Physics, Tashkent"
]
] | The problem of finding an appropriate geometrical/physical index for measuring a degree of inhomogeneity for a given space-time manifold is posed. Interrelations with the problem of understanding the gravitational/informational entropy are pointed out. An approach based on the notion of approximate symmetry is proposed. A number of related results on definitions of approximate symmetries known from literature are briefly reviewed with emphasis on their geometrical/physical content. A definition of a Killing-like symmetry is given and a classification theorem for all possible averaged space-times acquiring Killing-like symmetries upon averaging out a space-time with a homothetic Killing symmetry is proved. |
2102.03972 | Chao Zhang | Chao Zhang, Yungui Gong, Dicong Liang and Chunyu Zhang | Detection of gravitational wave mixed polarization with single
space-based detectors | 29 pages, 12 figures, 1 table. (PRD received) | null | 10.1103/PhysRevD.105.104062 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity predicts only two tensor polarization modes for
gravitational waves while at most six possible polarization modes are allowed
in general metric theory of gravity. The number of polarization modes is
determined by the specific modified theory of gravity. Therefore, the
determination of polarization modes can be used to test gravitational theory.
We introduce a concrete data analysis pipeline for a space-based detector such
as LISA to detect the polarization modes of gravitational waves. This method
can be used for monochromatic gravitational waves emitted from any compact
binary system with known sky position and frequency to detect mixtures of
tensor and extra polarization modes. We use the source J0806.3+1527 with
one-year simulation data as an example to show that this approach is capable of
probing pure and mixed polarizations without knowing the exact polarization
modes. We also find that the ability of detection of extra polarization depends
on the gravitational wave source location and the amplitude of non-tensorial
components.
| [
{
"created": "Mon, 8 Feb 2021 02:50:35 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Sep 2021 05:04:29 GMT",
"version": "v2"
},
{
"created": "Sat, 28 May 2022 03:18:19 GMT",
"version": "v3"
}
] | 2022-06-08 | [
[
"Zhang",
"Chao",
""
],
[
"Gong",
"Yungui",
""
],
[
"Liang",
"Dicong",
""
],
[
"Zhang",
"Chunyu",
""
]
] | General Relativity predicts only two tensor polarization modes for gravitational waves while at most six possible polarization modes are allowed in general metric theory of gravity. The number of polarization modes is determined by the specific modified theory of gravity. Therefore, the determination of polarization modes can be used to test gravitational theory. We introduce a concrete data analysis pipeline for a space-based detector such as LISA to detect the polarization modes of gravitational waves. This method can be used for monochromatic gravitational waves emitted from any compact binary system with known sky position and frequency to detect mixtures of tensor and extra polarization modes. We use the source J0806.3+1527 with one-year simulation data as an example to show that this approach is capable of probing pure and mixed polarizations without knowing the exact polarization modes. We also find that the ability of detection of extra polarization depends on the gravitational wave source location and the amplitude of non-tensorial components. |
1502.07128 | Avirup Ghosh | Ayan Chatterjee, Avirup Ghosh | Quasilocal rotating conformal Killing horizons | 15 pages. sequel to arXiv:1412.5115. Definition slightly modified, an
appendix added | Phys. Rev. D 92, 044003 (2015) | 10.1103/PhysRevD.92.044003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formulation of quasi-local conformal Killling horizons(CKH) is extended
to include rotation. This necessitates that the horizon be foliated by
2-spheres which may be distorted. Matter degrees of freedom which fall through
the horizon is taken to be a real scalar field. We show that these rotating
CKHs also admit a first law in differential form.
| [
{
"created": "Wed, 25 Feb 2015 11:19:25 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Aug 2015 16:35:07 GMT",
"version": "v2"
}
] | 2015-08-04 | [
[
"Chatterjee",
"Ayan",
""
],
[
"Ghosh",
"Avirup",
""
]
] | The formulation of quasi-local conformal Killling horizons(CKH) is extended to include rotation. This necessitates that the horizon be foliated by 2-spheres which may be distorted. Matter degrees of freedom which fall through the horizon is taken to be a real scalar field. We show that these rotating CKHs also admit a first law in differential form. |
2404.10456 | Chao Zhang | Chao Zhang, Tao Zhu | Linear instability of hairy black holes in Horndeski theory | 7 pages, 1 figure | null | 10.1088/1674-1137/ad3eff | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Horndeski theory constitutes the most general model of scalar-tensor
theories. It has attracted much attention in recent years in relation with
black holes, celestial dynamics, stability analysis, etc. It is important to
note that, for certain subclasses of Horndeski models, one can obtain analytic
solutions for the background fields. This facilitates the investigation of the
corresponding stability problems in detail. In particular, we aim to determine
the constraints to the model or theory under which the stability conditions can
be satisfied. In this study, we focused on a subclass of Horndeski theory and a
set of analytic background solutions. In addition, the odd-parity gravitational
perturbation and 2nd-order Lagrangian were investigated. Through careful
analysis, the instability was identified within the neighborhood of the event
horizon. This allows exclusion of a specific geometry for the model. Such an
instability is implanted in the structure of the corresponding Lagrangian and
is not erased by simply adding numerical constraints on the coupling
parameters. As a starting point of our research, the current study provides
insights for further exploration of the Horndeski theory.
| [
{
"created": "Tue, 16 Apr 2024 10:53:25 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Jul 2024 16:47:59 GMT",
"version": "v2"
}
] | 2024-07-16 | [
[
"Zhang",
"Chao",
""
],
[
"Zhu",
"Tao",
""
]
] | Horndeski theory constitutes the most general model of scalar-tensor theories. It has attracted much attention in recent years in relation with black holes, celestial dynamics, stability analysis, etc. It is important to note that, for certain subclasses of Horndeski models, one can obtain analytic solutions for the background fields. This facilitates the investigation of the corresponding stability problems in detail. In particular, we aim to determine the constraints to the model or theory under which the stability conditions can be satisfied. In this study, we focused on a subclass of Horndeski theory and a set of analytic background solutions. In addition, the odd-parity gravitational perturbation and 2nd-order Lagrangian were investigated. Through careful analysis, the instability was identified within the neighborhood of the event horizon. This allows exclusion of a specific geometry for the model. Such an instability is implanted in the structure of the corresponding Lagrangian and is not erased by simply adding numerical constraints on the coupling parameters. As a starting point of our research, the current study provides insights for further exploration of the Horndeski theory. |
1512.04874 | Anil Yadav dr | Ahmad T Ali, Anil Kumar Yadav and Abdulah K Alzahrani | Similarity dark energy models in Bianchi type - I space-time | 10 pages, 2 figure panels, Textual changes and References updated | Eur. Phys. J. Plus 131, 415 (2016) | 10.1140/epjp/i2016-16415-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate some new similarity inhomogeneous solutions of anisotropic
dark energy and perfect fluid in Bianchi type-I space-time. Three different
equation of state parameters along the spatial directions are introduced to
quantify the deviation of pressure from isotropy. We consider the case when the
dark energy is minimally coupled to the perfect fluid as well as direct
interaction with it. The Lie symmetry generators that leave the equation
invariant are identified and we generate an optimal system of one-dimensional
subalgebras. Each element of the optimal system is used to reduce the partial
differential equation to an ordinary differential equation which is further
analyzed. We solve the Einstein field equations, described by a system of
non-linear partial differential equations (NLPDEs), by using the Lie point
symmetry analysis method. The geometrical and kinematical features of the
models and the behavior of the anisotropy of dark energy, are examined in
detail.
| [
{
"created": "Mon, 7 Dec 2015 22:52:37 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Feb 2016 16:11:07 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Feb 2016 16:03:28 GMT",
"version": "v3"
},
{
"created": "Tue, 10 Apr 2018 11:31:54 GMT",
"version": "v4"
},
{
"cre... | 2018-04-12 | [
[
"Ali",
"Ahmad T",
""
],
[
"Yadav",
"Anil Kumar",
""
],
[
"Alzahrani",
"Abdulah K",
""
]
] | We investigate some new similarity inhomogeneous solutions of anisotropic dark energy and perfect fluid in Bianchi type-I space-time. Three different equation of state parameters along the spatial directions are introduced to quantify the deviation of pressure from isotropy. We consider the case when the dark energy is minimally coupled to the perfect fluid as well as direct interaction with it. The Lie symmetry generators that leave the equation invariant are identified and we generate an optimal system of one-dimensional subalgebras. Each element of the optimal system is used to reduce the partial differential equation to an ordinary differential equation which is further analyzed. We solve the Einstein field equations, described by a system of non-linear partial differential equations (NLPDEs), by using the Lie point symmetry analysis method. The geometrical and kinematical features of the models and the behavior of the anisotropy of dark energy, are examined in detail. |
gr-qc/9504037 | Cenalo Vaz | Cenalo Vaz and Louis Witten | Soliton Induced Singularities in 2 d Gravity and their Evaporation | 15 pages (37.7 kb), PHYZZX. Figures available from authors. | Class.Quant.Grav.12:2607-2618,1995 | 10.1088/0264-9381/12/10/017 | UATP-95/02 | gr-qc | null | Positive energy singularities induced by Sine-Gordon solitons in 1+1
dimensional dilaton gravity with positive and negative cosmological constant
are considered. When the cosmological constant is positive, the singularities
combine a white hole, a timelike singularity and a black hole joined smoothly
near the soliton center. When the cosmological constant is negative, the
solutions describe two timelike singularities joined smoothly near the soliton
center. We describe these spacetimes and examine their evaporation in the one
loop approximation.
| [
{
"created": "Sun, 24 Apr 1994 14:55:22 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Apr 1995 21:33:03 GMT",
"version": "v2"
}
] | 2010-11-01 | [
[
"Vaz",
"Cenalo",
""
],
[
"Witten",
"Louis",
""
]
] | Positive energy singularities induced by Sine-Gordon solitons in 1+1 dimensional dilaton gravity with positive and negative cosmological constant are considered. When the cosmological constant is positive, the singularities combine a white hole, a timelike singularity and a black hole joined smoothly near the soliton center. When the cosmological constant is negative, the solutions describe two timelike singularities joined smoothly near the soliton center. We describe these spacetimes and examine their evaporation in the one loop approximation. |
0908.4454 | Todd Oliynyk | Todd A. Oliynyk | A rigorous formulation of the cosmological Newtonian limit without
averaging | null | J.Hyperbol.Diff.Equat.7:405-431,2010 | 10.1142/S0219891610002189 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove the existence of a large class of one-parameter families of
cosmological solutions to the Einstein-Euler equations that have a Newtonian
limit. This class includes solutions that represent a finite, but otherwise
arbitrary, number of compact fluid bodies. These solutions provide exact
cosmological models that admit Newtonian limits but, are not, either implicitly
or explicitly, averaged.
| [
{
"created": "Mon, 31 Aug 2009 03:48:28 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Nov 2010 03:32:27 GMT",
"version": "v2"
}
] | 2010-11-05 | [
[
"Oliynyk",
"Todd A.",
""
]
] | We prove the existence of a large class of one-parameter families of cosmological solutions to the Einstein-Euler equations that have a Newtonian limit. This class includes solutions that represent a finite, but otherwise arbitrary, number of compact fluid bodies. These solutions provide exact cosmological models that admit Newtonian limits but, are not, either implicitly or explicitly, averaged. |
1807.00171 | Damian Ejlli | Damian Ejlli and Venugopal R. Thandlam | GRAPH mixing | Published version in Physical Review D. In the published version the
title has been changed by the editors to 'Graviton-Photon mixing' instead of
'GRAPH mixing'. With respect to (v1), in this version (v2), typos have been
corrected, new references have been added and an additional section (sec.8)
has been added. Typos in Eqs. (40) and (41) have been fixed | Phys. Rev. D 99, 044022 (2019) | 10.1103/PhysRevD.99.044022 | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the era of gravitational wave (GW) detection from astrophysical sources by
LIGO/VIRGO, it is of great importance to take the quantum gravity effect of
graviton-photon (GRAPH) mixing in the cosmic magnetic field to the next level.
In this work, we study such an effect and derive for the first time
perturbative solutions of the linearized equations of motions of the GRAPH
mixing in an expanding universe. In our formalism we take into account all
known standard dispersive and coherence breaking effects of photons such as the
Faraday effect, the Cotton-Mouton (CM) effect, and the plasma effects in the
cosmic magnetic field. Our formalism, applies to a cosmic magnetic field either
a uniform or a slowly varying non-homogeneous field of spacetime coordinates
with an arbitrary field direction. For binary systems of astrophysical sources
of GWs at extragalactic distances with chirp masses $M_\text{CH}$ of a few
solar masses, GW present-day frequencies $\nu_0\simeq 50-700$ Hz, and
present-day cosmic magnetic field amplitudes $\bar B_0\simeq 10^{-10}-10^{-6}$
G, the power of electromagnetic radiation generated in the GRAPH mixing at
present is substantial and in the range $P_\gamma\simeq 10^6-10^{15}$ (erg/s).
On the other hand, the associated power flux $F_\gamma$ is quite faint
depending on the source distance with respect to the Earth. Since in the GRAPH
mixing the velocities of photons and gravitons are preserved and are equal,
this effect is the only one known to us, whose certainty of the contemporary
arrival of GWs and electromagnetic radiation at the detector is guaranteed.
| [
{
"created": "Sat, 30 Jun 2018 12:50:48 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Feb 2019 14:08:13 GMT",
"version": "v2"
}
] | 2019-02-15 | [
[
"Ejlli",
"Damian",
""
],
[
"Thandlam",
"Venugopal R.",
""
]
] | In the era of gravitational wave (GW) detection from astrophysical sources by LIGO/VIRGO, it is of great importance to take the quantum gravity effect of graviton-photon (GRAPH) mixing in the cosmic magnetic field to the next level. In this work, we study such an effect and derive for the first time perturbative solutions of the linearized equations of motions of the GRAPH mixing in an expanding universe. In our formalism we take into account all known standard dispersive and coherence breaking effects of photons such as the Faraday effect, the Cotton-Mouton (CM) effect, and the plasma effects in the cosmic magnetic field. Our formalism, applies to a cosmic magnetic field either a uniform or a slowly varying non-homogeneous field of spacetime coordinates with an arbitrary field direction. For binary systems of astrophysical sources of GWs at extragalactic distances with chirp masses $M_\text{CH}$ of a few solar masses, GW present-day frequencies $\nu_0\simeq 50-700$ Hz, and present-day cosmic magnetic field amplitudes $\bar B_0\simeq 10^{-10}-10^{-6}$ G, the power of electromagnetic radiation generated in the GRAPH mixing at present is substantial and in the range $P_\gamma\simeq 10^6-10^{15}$ (erg/s). On the other hand, the associated power flux $F_\gamma$ is quite faint depending on the source distance with respect to the Earth. Since in the GRAPH mixing the velocities of photons and gravitons are preserved and are equal, this effect is the only one known to us, whose certainty of the contemporary arrival of GWs and electromagnetic radiation at the detector is guaranteed. |
gr-qc/0406029 | Muhammad Sharif | M. Sharif and Sehar Aziz | On the Physical Properties of Spherically Symmetric Self-Similar
Solutions | LaTex, 14 pages, no figure | Int.J.Mod.Phys. D14 (2005) 73-84 | 10.1142/S0218271805005967 | null | gr-qc | null | In this paper, we are exploring some of the properties of the self-similar
solutions of the first kind. In particular, we shall discuss the kinematic
properties and also check the singularities of these solutions. We discuss
these properties both in co-moving and also in non co-moving (only in the
radial direction) coordinates. Some interesting features of these solutions
turn up.
| [
{
"created": "Tue, 8 Jun 2004 11:57:11 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Sharif",
"M.",
""
],
[
"Aziz",
"Sehar",
""
]
] | In this paper, we are exploring some of the properties of the self-similar solutions of the first kind. In particular, we shall discuss the kinematic properties and also check the singularities of these solutions. We discuss these properties both in co-moving and also in non co-moving (only in the radial direction) coordinates. Some interesting features of these solutions turn up. |
2110.15636 | Junlang Li | Junlang Li, Teng Zhang | Study of acceleration measurement in gravitational wave detection | 9 pages, 4 figures | null | 10.1088/1361-6382/ac4b98 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Position-meter and speed-meter interferometers have been analysed for
detecting gravitational waves. We introduce the concept of acceleration
measurement in comparison with position and speed measurement. In this paper,
we describe a general acceleration measurement and derive its standard quantum
limit. We provide an example of an acceleration-meter interferometer
configuration. We show that shot noise dominates at low frequency following a
frequency dependence of $1/\Omega^2$, while radiation pressure noise is
constant. The acceleration-meter has even a stronger radiation pressure noise
suppression than speed-meter.
| [
{
"created": "Fri, 29 Oct 2021 09:14:07 GMT",
"version": "v1"
}
] | 2022-02-23 | [
[
"Li",
"Junlang",
""
],
[
"Zhang",
"Teng",
""
]
] | Position-meter and speed-meter interferometers have been analysed for detecting gravitational waves. We introduce the concept of acceleration measurement in comparison with position and speed measurement. In this paper, we describe a general acceleration measurement and derive its standard quantum limit. We provide an example of an acceleration-meter interferometer configuration. We show that shot noise dominates at low frequency following a frequency dependence of $1/\Omega^2$, while radiation pressure noise is constant. The acceleration-meter has even a stronger radiation pressure noise suppression than speed-meter. |
gr-qc/0010014 | Hideyuki Tagoshi | Hideyuki Tagoshi, Akira Ohashi, Benjamin J. Owen | Gravitational field and equations of motion of spinning compact binaries
to 2.5 post-Newtonian order | 18 pages, no figure | Phys.Rev.D63:044006,2001 | 10.1103/PhysRevD.63.044006 | null | gr-qc | null | We derive spin-orbit coupling effects on the gravitational field and
equations of motion of compact binaries in the 2.5 post-Newtonian approximation
to general relativity, one PN order beyond where spin effects first appear. Our
method is based on that of Blanchet, Faye, and Ponsot, who use a post-Newtonian
metric valid for general (continuous) fluids and represent pointlike compact
objects with a delta-function stress-energy tensor, regularizing divergent
terms by taking the Hadamard finite part. To obtain post-Newtonian spin
effects, we use a different delta-function stress-energy tensor introduced by
Bailey and Israel. In a future paper we will use the 2.5PN equations of motion
for spinning bodies to derive the gravitational-wave luminosity and phase
evolution of binary inspirals, which will be useful in constructing matched
filters for signal analysis. The gravitational field derived here may help in
posing initial data for numerical evolutions of binary black hole mergers.
| [
{
"created": "Wed, 4 Oct 2000 11:09:24 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Tagoshi",
"Hideyuki",
""
],
[
"Ohashi",
"Akira",
""
],
[
"Owen",
"Benjamin J.",
""
]
] | We derive spin-orbit coupling effects on the gravitational field and equations of motion of compact binaries in the 2.5 post-Newtonian approximation to general relativity, one PN order beyond where spin effects first appear. Our method is based on that of Blanchet, Faye, and Ponsot, who use a post-Newtonian metric valid for general (continuous) fluids and represent pointlike compact objects with a delta-function stress-energy tensor, regularizing divergent terms by taking the Hadamard finite part. To obtain post-Newtonian spin effects, we use a different delta-function stress-energy tensor introduced by Bailey and Israel. In a future paper we will use the 2.5PN equations of motion for spinning bodies to derive the gravitational-wave luminosity and phase evolution of binary inspirals, which will be useful in constructing matched filters for signal analysis. The gravitational field derived here may help in posing initial data for numerical evolutions of binary black hole mergers. |
2108.12553 | Parampreet Singh | Bao-Fei Li, Parampreet Singh | Quantum gravity might restrict a cyclic evolution | 23 pages, 10 figures | null | 10.1103/PhysRevD.105.046013 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is generally expected that in a non-singular cosmological model a cyclic
evolution is straightforward to obtain on introduction of a suitable choice of
a scalar field with a negative potential or a negative cosmological constant
which causes a recollapse at some time in the evolution. We present a counter
example to this conventional wisdom. Working in the realm of loop cosmological
models with non-perturbative quantum gravity modifications we show that a
modified version of standard loop quantum cosmology based on Thiemann's
regularization of the Hamiltonian constraint while generically non-singular
does not allow a cyclic evolution unless some highly restrictive conditions
hold. Irrespective of the energy density of other matter fields, a recollapse
and hence a cyclic evolution is only possible if one chooses an almost Planck
sized negative potential of the scalar field or a negative cosmological
constant. Further, cycles when present do not occur in the classical regime.
Surprisingly, a necessary condition for a cyclic evolution, not singularity
resolution, turns out to be a violation of the weak energy condition. These
results are in a striking contrast to standard loop quantum cosmology where
obtaining a recollapse at large volumes and a cyclic evolution is
straightforward, and, there is no violation of weak energy condition. On one
hand our work shows that some quantum cosmological models even though
non-singular and bouncing are incompatible with a cyclic evolution, and on the
other hand demonstrates that differences in various quantization prescriptions
in loop cosmology need not be faint and buried in the pre-bounce regime, but
can be striking and profound even in the post-bounce regime.
| [
{
"created": "Sat, 28 Aug 2021 02:31:58 GMT",
"version": "v1"
}
] | 2022-03-14 | [
[
"Li",
"Bao-Fei",
""
],
[
"Singh",
"Parampreet",
""
]
] | It is generally expected that in a non-singular cosmological model a cyclic evolution is straightforward to obtain on introduction of a suitable choice of a scalar field with a negative potential or a negative cosmological constant which causes a recollapse at some time in the evolution. We present a counter example to this conventional wisdom. Working in the realm of loop cosmological models with non-perturbative quantum gravity modifications we show that a modified version of standard loop quantum cosmology based on Thiemann's regularization of the Hamiltonian constraint while generically non-singular does not allow a cyclic evolution unless some highly restrictive conditions hold. Irrespective of the energy density of other matter fields, a recollapse and hence a cyclic evolution is only possible if one chooses an almost Planck sized negative potential of the scalar field or a negative cosmological constant. Further, cycles when present do not occur in the classical regime. Surprisingly, a necessary condition for a cyclic evolution, not singularity resolution, turns out to be a violation of the weak energy condition. These results are in a striking contrast to standard loop quantum cosmology where obtaining a recollapse at large volumes and a cyclic evolution is straightforward, and, there is no violation of weak energy condition. On one hand our work shows that some quantum cosmological models even though non-singular and bouncing are incompatible with a cyclic evolution, and on the other hand demonstrates that differences in various quantization prescriptions in loop cosmology need not be faint and buried in the pre-bounce regime, but can be striking and profound even in the post-bounce regime. |
2405.08024 | Christian Corda Prof. | Elmo Benedetto, Christian Corda and Ignazio Licata | Equivalence Principle and Machian origin of extended gravity | Essay dedicated to the memory of the Authors' beloved mothers,
awarded Honorable Mention in the Gravity Research Foundation 2024 Awards for
Essays on Gravitation. arXiv admin note: text overlap with arXiv:1411.0829 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Chae's analyses on GAIA observations of wide binary stars have fortified the
paradigm of extended gravity with particular attention to MOND-like theories.
We recall that, starting from the origin of Einstein's general relativity, the
request of Mach on the structure of the theory has been the core of the
foundational debate. This issue is strictly connected with the nature of the
mass-energy equivalence. This was exactly the key point that Einstein used to
derive the same general relativity. On the other hand, the current requirements
of particle physics and the open questions within extended gravity theories,
which have recently been further strengthened by analyses of GAIA observations,
request a better understanding of the Equivalence Principle. By considering a
direct coupling between the Ricci curvature scalar and the matter Lagrangian a
non geodesic ratio between the inertial and the gravitational mass can be fixed
and MOND-like theories are retrieved at low energies.
| [
{
"created": "Sun, 12 May 2024 07:33:50 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Benedetto",
"Elmo",
""
],
[
"Corda",
"Christian",
""
],
[
"Licata",
"Ignazio",
""
]
] | Chae's analyses on GAIA observations of wide binary stars have fortified the paradigm of extended gravity with particular attention to MOND-like theories. We recall that, starting from the origin of Einstein's general relativity, the request of Mach on the structure of the theory has been the core of the foundational debate. This issue is strictly connected with the nature of the mass-energy equivalence. This was exactly the key point that Einstein used to derive the same general relativity. On the other hand, the current requirements of particle physics and the open questions within extended gravity theories, which have recently been further strengthened by analyses of GAIA observations, request a better understanding of the Equivalence Principle. By considering a direct coupling between the Ricci curvature scalar and the matter Lagrangian a non geodesic ratio between the inertial and the gravitational mass can be fixed and MOND-like theories are retrieved at low energies. |
2010.03632 | S. I. Kruglov | S.I. Kruglov | Inflation of Universe by Nonlinear Electrodynamics | 20 pages, 6 figures, accepted in Int.J.Mod.Phys.D | Int,J.Mod.Phys.D, Vol.29, No.15, 2050102 (2020) | 10.1142/S0218271820501023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nonlinear electrodynamics with two dimensional parameters is studied. The
range of electromagnetic fields when principles of causality, unitarity and the
classical stability hold, are obtained. A singularity of the electric field at
the center of charges is absent within our model and there are corrections to
the Coulomb law as $r\rightarrow\infty$. The universe inflation takes place in
the background of stochastic magnetic fields. The second stage of the universe
evolution is the radiation era so that the graceful exit exists. We estimated
the spectral index, the tensor-to-scalar ratio, and the running of the spectral
index that are in a rough accord with the PLANCK and WMAP data.
| [
{
"created": "Wed, 7 Oct 2020 20:13:28 GMT",
"version": "v1"
}
] | 2022-12-27 | [
[
"Kruglov",
"S. I.",
""
]
] | Nonlinear electrodynamics with two dimensional parameters is studied. The range of electromagnetic fields when principles of causality, unitarity and the classical stability hold, are obtained. A singularity of the electric field at the center of charges is absent within our model and there are corrections to the Coulomb law as $r\rightarrow\infty$. The universe inflation takes place in the background of stochastic magnetic fields. The second stage of the universe evolution is the radiation era so that the graceful exit exists. We estimated the spectral index, the tensor-to-scalar ratio, and the running of the spectral index that are in a rough accord with the PLANCK and WMAP data. |
2304.01833 | Giampiero Esposito Dr. | Zahra Mirzaiyan, Giampiero Esposito | On the nature of Bondi-Metzner-Sachs transformations | In the final version, the presentation has been improved | null | 10.3390/sym15040947 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigates first the four branches of BMS transformations,
motivated by the classification into elliptic, parabolic, hyperbolic and
loxodromic proposed a few years ago in the literature. We first prove that to
each normal elliptic transformation of the complex variable zeta used in the
metric for cuts of null infinity there corresponds a BMS supertranslation. We
then study the conformal factor in the BMS transformation of the u variable as
a function of the squared modulus of zeta. In the loxodromic and hyperbolic
cases, the conformal factor is either monotonically increasing or monotonically
decreasing as a function of the real variable given by the modulus of zeta. The
Killing vector field of the Bondi metric is also studied in correspondence with
the four admissible families of BMS transformations. Eventually, all BMS
transformations are re-expressed in the homogeneous coordinates suggested by
projective geometry. It is then found that BMS transformations are the
restriction to a pair of unit circles of a more general set of transformations.
Within this broader framework, the geometry of such transformations is studied
by means of its Segre manifold.
| [
{
"created": "Tue, 4 Apr 2023 14:36:21 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Apr 2023 12:37:11 GMT",
"version": "v2"
}
] | 2023-04-24 | [
[
"Mirzaiyan",
"Zahra",
""
],
[
"Esposito",
"Giampiero",
""
]
] | This paper investigates first the four branches of BMS transformations, motivated by the classification into elliptic, parabolic, hyperbolic and loxodromic proposed a few years ago in the literature. We first prove that to each normal elliptic transformation of the complex variable zeta used in the metric for cuts of null infinity there corresponds a BMS supertranslation. We then study the conformal factor in the BMS transformation of the u variable as a function of the squared modulus of zeta. In the loxodromic and hyperbolic cases, the conformal factor is either monotonically increasing or monotonically decreasing as a function of the real variable given by the modulus of zeta. The Killing vector field of the Bondi metric is also studied in correspondence with the four admissible families of BMS transformations. Eventually, all BMS transformations are re-expressed in the homogeneous coordinates suggested by projective geometry. It is then found that BMS transformations are the restriction to a pair of unit circles of a more general set of transformations. Within this broader framework, the geometry of such transformations is studied by means of its Segre manifold. |
1111.0147 | Dibakar Roychowdhury | Rabin Banerjee, Dibakar Roychowdhury | Critical phenomena in Born-Infeld AdS black holes | LaTex, 13 pages, 10 figures, text modified, numerical results
included, references added, to appear in Physical Review D | Phys. Rev. D 85, 044040 (2012) | 10.1103/PhysRevD.85.044040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the thermodynamics of critical phenomena in Born-Infeld AdS
black holes using a canonical ensemble. The critical behavior has been studied
near the critical point which is characterized by a discontinuity in the heat
capacity at constant charge. We explicitly calculate the critical exponents of
the relevant thermodynamic quantities. These exponents satisfy all the
thermodynamic scaling laws. We also check the Generalized Homogeneous Function
(GHF) hypothesis (or the scaling hypothesis) which is shown to be compatible
with the thermodynamic scaling laws. Finally we check the validity of the
scaling laws of second kind which include the critical exponents associated
with the spatial correlation. In the appropriate limit our results also provide
the corresponding expressions for the Reissner Nordstrom AdS case.
| [
{
"created": "Tue, 1 Nov 2011 08:57:58 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2012 05:54:55 GMT",
"version": "v2"
}
] | 2012-02-21 | [
[
"Banerjee",
"Rabin",
""
],
[
"Roychowdhury",
"Dibakar",
""
]
] | We investigate the thermodynamics of critical phenomena in Born-Infeld AdS black holes using a canonical ensemble. The critical behavior has been studied near the critical point which is characterized by a discontinuity in the heat capacity at constant charge. We explicitly calculate the critical exponents of the relevant thermodynamic quantities. These exponents satisfy all the thermodynamic scaling laws. We also check the Generalized Homogeneous Function (GHF) hypothesis (or the scaling hypothesis) which is shown to be compatible with the thermodynamic scaling laws. Finally we check the validity of the scaling laws of second kind which include the critical exponents associated with the spatial correlation. In the appropriate limit our results also provide the corresponding expressions for the Reissner Nordstrom AdS case. |
gr-qc/9906051 | null | S. Capozziello, G. Lambiase, H.-J.Schmidt | Nonminimal Derivative Couplings and Inflation in Generalized Theories of
Gravity | 11 pages, Latex, to appear in Annals of Physics (Leipzig) | Annalen Phys.9:39-48,2000 | 10.1002/(SICI)1521-3889(200001)9:1<39::AID-ANDP39>3.0.CO;2-4 | null | gr-qc | null | We study extended theories of gravity where nonminimal derivative couplings
of the form $R^{kl}\phi_{, k}\phi_{, l}$ are present in the Lagrangian. We show
how and why the other couplings of similar structure may be ruled out and then
deduce the field equations and the related cosmological models. Finally, we get
inflationary solutions which do follow neither from any effective scalar field
potential nor from a cosmological constant introduced ``by hand'', and we show
the de Sitter space--time to be an attractor solution.
| [
{
"created": "Tue, 15 Jun 1999 13:46:03 GMT",
"version": "v1"
}
] | 2017-10-04 | [
[
"Capozziello",
"S.",
""
],
[
"Lambiase",
"G.",
""
],
[
"Schmidt",
"H. -J.",
""
]
] | We study extended theories of gravity where nonminimal derivative couplings of the form $R^{kl}\phi_{, k}\phi_{, l}$ are present in the Lagrangian. We show how and why the other couplings of similar structure may be ruled out and then deduce the field equations and the related cosmological models. Finally, we get inflationary solutions which do follow neither from any effective scalar field potential nor from a cosmological constant introduced ``by hand'', and we show the de Sitter space--time to be an attractor solution. |
2401.05764 | Justin Feng | Justin C. Feng | Gravity limits the kinetic energy of a massive elementary particle | 2 pages. v2: Major changes. Calculations unchanged, major
improvements to discussion regarding interpretation, and a strong assumption
was relaxed. Conclusions changed accordingly | null | null | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note, I argue that tidal effects generically limit the kinetic energy
of a single massive elementary particle in the vicinity of a compact object. As
the kinetic energy is increased, the differences in the tidal potential over a
Compton wavelength will at some point exceed the rest mass of the particle.
Above the threshold, one expects tidal effects to disrupt single-particle
states, and in turn, one might expect an incident particle scattering off a
compact object with an energy significantly exceeding the threshold to result
in a shower of lower energy particles. A calculation reveals that the threshold
for neutrinos scattering off a $10 M_\odot$ black hole within three
Schwarzschild radii is roughly $1~\text{GeV}$.
| [
{
"created": "Thu, 11 Jan 2024 09:15:53 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jan 2024 14:55:40 GMT",
"version": "v2"
}
] | 2024-01-24 | [
[
"Feng",
"Justin C.",
""
]
] | In this note, I argue that tidal effects generically limit the kinetic energy of a single massive elementary particle in the vicinity of a compact object. As the kinetic energy is increased, the differences in the tidal potential over a Compton wavelength will at some point exceed the rest mass of the particle. Above the threshold, one expects tidal effects to disrupt single-particle states, and in turn, one might expect an incident particle scattering off a compact object with an energy significantly exceeding the threshold to result in a shower of lower energy particles. A calculation reveals that the threshold for neutrinos scattering off a $10 M_\odot$ black hole within three Schwarzschild radii is roughly $1~\text{GeV}$. |
gr-qc/0403105 | Aleksandr Ageyev | Alexandr Ageev, Belkis Cabrera Palmer, Antonio De Felice, Steven D.
Penn, Peter R. Saulson | Very high quality factor measured in annealed fused silica | 8 pages, 2 figures | Class.Quant.Grav. 21 (2004) 3887-3892 | 10.1088/0264-9381/21/16/004 | null | gr-qc | null | We present the results of quality factor measurements for rod samples made of
fused silica. To decrease the dissipation we annealed our samples. The highest
quality factor that we observed was $Q=(2.03\pm0.01)\times10^8$ for a mode at
384 Hz. This is the highest published value of $Q$ in fused silica measured to
date.
| [
{
"created": "Thu, 25 Mar 2004 16:00:57 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Ageev",
"Alexandr",
""
],
[
"Palmer",
"Belkis Cabrera",
""
],
[
"De Felice",
"Antonio",
""
],
[
"Penn",
"Steven D.",
""
],
[
"Saulson",
"Peter R.",
""
]
] | We present the results of quality factor measurements for rod samples made of fused silica. To decrease the dissipation we annealed our samples. The highest quality factor that we observed was $Q=(2.03\pm0.01)\times10^8$ for a mode at 384 Hz. This is the highest published value of $Q$ in fused silica measured to date. |
2112.09772 | Jan Henryk Kwapisz | Astrid Eichhorn and Jan Henryk Kwapisz and Marc Schiffer | The weak-gravity bound in asymptotically safe gravity-gauge systems | 33 pages, 7 figures | null | 10.1103/PhysRevD.105.106022 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The weak-gravity bound has been discovered in asymptotically safe
gravity-matter systems, where it limits the maximum strength of gravitational
fluctuations. In the present paper, we explore it for the first time in systems
with more than one gauge field, to discover whether systems with 12 gauge
fields (like the Standard Model) exhibit a weak-gravity bound and whether the
gravitational fixed point evades it. Further, we test the robustness of the
present and previous results on the weak-gravity bound by exploring their
dependence on a gravitational gauge parameter. Finally, the existence of the
weak-gravity bound also has important phenomenological consequences: it is key
to a proposed mechanism that bounds the spacetime dimensionality from above to
four or five dimensions. In this paper, we strengthen the evidence for this
mechanism. Thus, the predictive power of the asymptotic safety paradigm could
extend to parameters of the spacetime geometry, such that the
four-dimensionality of our universe could be explained from first principles.
| [
{
"created": "Fri, 17 Dec 2021 21:22:02 GMT",
"version": "v1"
}
] | 2022-06-08 | [
[
"Eichhorn",
"Astrid",
""
],
[
"Kwapisz",
"Jan Henryk",
""
],
[
"Schiffer",
"Marc",
""
]
] | The weak-gravity bound has been discovered in asymptotically safe gravity-matter systems, where it limits the maximum strength of gravitational fluctuations. In the present paper, we explore it for the first time in systems with more than one gauge field, to discover whether systems with 12 gauge fields (like the Standard Model) exhibit a weak-gravity bound and whether the gravitational fixed point evades it. Further, we test the robustness of the present and previous results on the weak-gravity bound by exploring their dependence on a gravitational gauge parameter. Finally, the existence of the weak-gravity bound also has important phenomenological consequences: it is key to a proposed mechanism that bounds the spacetime dimensionality from above to four or five dimensions. In this paper, we strengthen the evidence for this mechanism. Thus, the predictive power of the asymptotic safety paradigm could extend to parameters of the spacetime geometry, such that the four-dimensionality of our universe could be explained from first principles. |
1410.4110 | Sven de Rijcke | Sven De Rijcke, Robbert Verbeke, Thomas Boelens | The dynamics of general relativistic isotropic stellar cluster models --
Do relativistic extensions of the Plummer model exist? | 10 pages, 5 figures, accepted for publication by MNRAS | null | 10.1093/mnras/stu1912 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the general relativistic theory of the dynamics of isotropic
stellar clusters can be developed essentially along the same lines as the
Newtonian theory. We prove that the distribution function can be derived from
any isotropic momentum moment and that every higher-order moment of the
distribution can be written as an integral over a zeroth-order moment.
We propose a mathematically simple expression for the distribution function
of a family of isotropic general relativistic cluster models and investigate
their dynamical properties. In the Newtonian limit, these models obtain a
distribution function of the form F(E) ~ (E-E_0)^alpha, with E binding energy
and E_0 a constant that determines the model's outer radius. The slope alpha
sets the steepness of the distribution function and the corresponding radial
density and pressure profiles. We show that the field equations only yield
solutions with finite mass for alpha<3.5. Moreover, in the limit alpha->3.5,
only Newtonian models exist. In other words: within the context of this family
of models, no general relativistic version of the Plummer model exists. The
most strongly bound model within the family is characterized by alpha=2.75 and
a central redshift z_c~0.55.
| [
{
"created": "Wed, 15 Oct 2014 16:04:32 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"De Rijcke",
"Sven",
""
],
[
"Verbeke",
"Robbert",
""
],
[
"Boelens",
"Thomas",
""
]
] | We show that the general relativistic theory of the dynamics of isotropic stellar clusters can be developed essentially along the same lines as the Newtonian theory. We prove that the distribution function can be derived from any isotropic momentum moment and that every higher-order moment of the distribution can be written as an integral over a zeroth-order moment. We propose a mathematically simple expression for the distribution function of a family of isotropic general relativistic cluster models and investigate their dynamical properties. In the Newtonian limit, these models obtain a distribution function of the form F(E) ~ (E-E_0)^alpha, with E binding energy and E_0 a constant that determines the model's outer radius. The slope alpha sets the steepness of the distribution function and the corresponding radial density and pressure profiles. We show that the field equations only yield solutions with finite mass for alpha<3.5. Moreover, in the limit alpha->3.5, only Newtonian models exist. In other words: within the context of this family of models, no general relativistic version of the Plummer model exists. The most strongly bound model within the family is characterized by alpha=2.75 and a central redshift z_c~0.55. |
1912.09407 | Lu\'is Filipe Costa | L. Filipe O. Costa, Jos\'e Nat\'ario, N. O. Santos | Gravitomagnetism in the Lewis cylindrical metrics | 43 pages, 6 Figures. Minor re-write/simplifications to the text, new
section 5.2.4 added discussing the spinning cosmic string limit, titles of
subsections 5.4 and 5.4.2 changed, references added, typos corrected. Matches
the final published version | Class. Quantum Grav. 38 (2021) 055003 | 10.1088/1361-6382/abc570 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Lewis solutions describe the exterior gravitational field produced by
infinitely long rotating cylinders, and are useful models for global
gravitational effects. When the metric parameters are real (Weyl class), the
exterior metrics of rotating and static cylinders are locally
indistinguishable, but known to globally differ. The significance of this
difference, both in terms of physical effects (gravitomagnetism) and of the
mathematical invariants that detect the rotation, remain open problems in the
literature. In this work we show that, by a rigid coordinate rotation, the Weyl
class metric can be put into a "canonical" form where the Killing vector field
$\partial_{t}$ is time-like everywhere, and which depends explicitly only on
three parameters with a clear physical significance: the Komar mass and angular
momentum per unit length, plus the angle deficit. This new form of the metric
reveals that the two settings differ only at the level of the gravitomagnetic
vector potential which, for a rotating cylinder, cannot be eliminated by any
global coordinate transformation. It manifests itself in the Sagnac and
gravitomagnetic clock effects. The situation is seen to mirror the
electromagnetic field of a rotating charged cylinder, which likewise differs
from the static case only in the vector potential, responsible for the
Aharonov-Bohm effect, formally analogous to the Sagnac effect. The geometrical
distinction between the two solutions is also discussed, and the notions of
local and global staticity revisited. The matching in canonical form to the van
Stockum interior cylinder is also addressed.
| [
{
"created": "Thu, 19 Dec 2019 17:26:10 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Jul 2020 17:25:51 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Jan 2021 19:17:29 GMT",
"version": "v3"
}
] | 2021-01-15 | [
[
"Costa",
"L. Filipe O.",
""
],
[
"Natário",
"José",
""
],
[
"Santos",
"N. O.",
""
]
] | The Lewis solutions describe the exterior gravitational field produced by infinitely long rotating cylinders, and are useful models for global gravitational effects. When the metric parameters are real (Weyl class), the exterior metrics of rotating and static cylinders are locally indistinguishable, but known to globally differ. The significance of this difference, both in terms of physical effects (gravitomagnetism) and of the mathematical invariants that detect the rotation, remain open problems in the literature. In this work we show that, by a rigid coordinate rotation, the Weyl class metric can be put into a "canonical" form where the Killing vector field $\partial_{t}$ is time-like everywhere, and which depends explicitly only on three parameters with a clear physical significance: the Komar mass and angular momentum per unit length, plus the angle deficit. This new form of the metric reveals that the two settings differ only at the level of the gravitomagnetic vector potential which, for a rotating cylinder, cannot be eliminated by any global coordinate transformation. It manifests itself in the Sagnac and gravitomagnetic clock effects. The situation is seen to mirror the electromagnetic field of a rotating charged cylinder, which likewise differs from the static case only in the vector potential, responsible for the Aharonov-Bohm effect, formally analogous to the Sagnac effect. The geometrical distinction between the two solutions is also discussed, and the notions of local and global staticity revisited. The matching in canonical form to the van Stockum interior cylinder is also addressed. |
gr-qc/0504055 | Jian-Yang Zhu | Guihua Tian, Shikun Wang, Zhao Zheng | Is the Schwarzschild black hole really stable? | null | null | null | null | gr-qc | null | The stability of the Schwarzschild black hole is studied. Regge and Wheeler
treated the problem first at 1957 and obtained the dynamical equations for the
small perturbation. There are two kinds of perturbations: odd one and even one.
Using the Painlev\'{e} coordinate, we reconsider the odd perturbation and find
that: the white-hole-connected universe(r>2m, see text) is unstable. Because
the odd perturbation may be regarded as the angular perturbation, therefore,
the physical mean to it may be that the white-hole-connected universe is
unstable with respect to the rotating perturbation.
| [
{
"created": "Wed, 13 Apr 2005 03:12:50 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Apr 2005 03:59:58 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Tian",
"Guihua",
""
],
[
"Wang",
"Shikun",
""
],
[
"Zheng",
"Zhao",
""
]
] | The stability of the Schwarzschild black hole is studied. Regge and Wheeler treated the problem first at 1957 and obtained the dynamical equations for the small perturbation. There are two kinds of perturbations: odd one and even one. Using the Painlev\'{e} coordinate, we reconsider the odd perturbation and find that: the white-hole-connected universe(r>2m, see text) is unstable. Because the odd perturbation may be regarded as the angular perturbation, therefore, the physical mean to it may be that the white-hole-connected universe is unstable with respect to the rotating perturbation. |
gr-qc/9811014 | Grigori Volovik | T.A. Jacobson and G.E. Volovik | Effective spacetime and Hawking radiation from moving domain wall in
thin film of 3He-A | revtex file, 4 pages, 2 figures, submitted to JETP Lett | Pisma Zh.Eksp.Teor.Fiz. 68 (1998) 833-838; JETP Lett. 68 (1998)
874-880 | 10.1134/1.567808 | null | gr-qc cond-mat hep-th | null | An event horizon for "relativistic" fermionic quasiparticles can be
constructed in a thin film of superfluid 3He-A. The quasiparticles see an
effective "gravitational" field which is induced by a topological soliton of
the order parameter. Within the soliton the "speed of light" crosses zero and
changes sign. When the soliton moves, two planar event horizons (black hole and
white hole) appear, with a curvature singularity between them. Aside from the
singularity, the effective spacetime is incomplete at future and past
boundaries, but the quasiparticles cannot escape there because the
nonrelativistic corrections become important as the blueshift grows, yielding
"superluminal" trajectories. The question of Hawking radiation from the moving
soliton is discussed but not resolved.
| [
{
"created": "Wed, 4 Nov 1998 09:03:05 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Jacobson",
"T. A.",
""
],
[
"Volovik",
"G. E.",
""
]
] | An event horizon for "relativistic" fermionic quasiparticles can be constructed in a thin film of superfluid 3He-A. The quasiparticles see an effective "gravitational" field which is induced by a topological soliton of the order parameter. Within the soliton the "speed of light" crosses zero and changes sign. When the soliton moves, two planar event horizons (black hole and white hole) appear, with a curvature singularity between them. Aside from the singularity, the effective spacetime is incomplete at future and past boundaries, but the quasiparticles cannot escape there because the nonrelativistic corrections become important as the blueshift grows, yielding "superluminal" trajectories. The question of Hawking radiation from the moving soliton is discussed but not resolved. |
gr-qc/0002084 | C. L. B. Correia da Silva | Cristovao Correia da Silva, Ruth M. Williams | Simplicial minisuperspace models in the presence of a massive scalar
field with arbitrary scalar coupling | 24 pages and 9 figures. Accepted for publication by Classical and
Quantum Gravity | Class.Quant.Grav. 17 (2000) 1827-1845 | 10.1088/0264-9381/17/8/306 | null | gr-qc | null | We extend previous simplicial minisuperspace models to account for arbitrary
scalar coupling \eta R\phi^2.
| [
{
"created": "Fri, 25 Feb 2000 00:29:49 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"da Silva",
"Cristovao Correia",
""
],
[
"Williams",
"Ruth M.",
""
]
] | We extend previous simplicial minisuperspace models to account for arbitrary scalar coupling \eta R\phi^2. |
gr-qc/9606073 | null | B. L. Hu | Hawking-Unruh Thermal Radiance as Relativistic Exponential Scaling of
Quantum Noise | Latex 13 pages; Invited talk at the Fourth International Workshop on
Thermal Field Theory and Applications, Dalian, China, August, 1995.
Proceedings edited by Y. X. Gui and F. C. Khanna (World Scientific,
Singapore, 1996) | null | null | umdpp 96-52, Jan. 26, 1996 | gr-qc | null | The Hawking-Unruh effect of thermal radiance from a black hole or observed by
an accelerated detector is usually viewed as a geometric effect related to the
existence of an event horizon. Here we propose a new viewpoint, that the
detection of thermal radiance in these systems is a local, kinematic effect
arising from the vacuum being subjected to a relativistic exponential scale
transformation. This kinematic effect alters the relative weight of quantum
versus thermal fluctuations (noise) between the two vacua. This approach can
treat conditions which the geometric approach cannot, such as systems which do
not even have an event horizon. An example is the case of an observer whose
acceleration is nonuniform or only asymptotically uniform. Since this approach
is based on concepts and techniques of non-equilibrium statistical mechanics,
it is more adept to dynamical problems, such as the dissipation, fluctuation,
and entropy aspects of particle creation and phase transitions in black hole
collapse and in the early universe.
| [
{
"created": "Wed, 26 Jun 1996 19:57:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hu",
"B. L.",
""
]
] | The Hawking-Unruh effect of thermal radiance from a black hole or observed by an accelerated detector is usually viewed as a geometric effect related to the existence of an event horizon. Here we propose a new viewpoint, that the detection of thermal radiance in these systems is a local, kinematic effect arising from the vacuum being subjected to a relativistic exponential scale transformation. This kinematic effect alters the relative weight of quantum versus thermal fluctuations (noise) between the two vacua. This approach can treat conditions which the geometric approach cannot, such as systems which do not even have an event horizon. An example is the case of an observer whose acceleration is nonuniform or only asymptotically uniform. Since this approach is based on concepts and techniques of non-equilibrium statistical mechanics, it is more adept to dynamical problems, such as the dissipation, fluctuation, and entropy aspects of particle creation and phase transitions in black hole collapse and in the early universe. |
1106.0715 | Barun Majumder | Barun Majumder | Black Hole Entropy and the Modified Uncertainty Principle: A heuristic
analysis | 8 pages, accepted for publication in Physics Letters B | Phys. Lett. B 703 (2011) 402-405 | 10.1016/j.physletb.2011.08.026 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently Ali et.al.(2009) proposed a Generalized Uncertainty Principle (or
GUP) with a linear term in momentum (accompanied by Plank length). Inspired by
this idea here we calculate the quantum corrected value of a Schwarzschild
black hole entropy and a Reissner-Nordstrom black hole with double horizon by
utilizing the proposed generalized uncertainty principle. We find that the
leading order correction goes with the square root of the horizon area
contributing positively. We also find that the prefactor of the logarithmic
contribution is negative and the value exactly matches with some earlier
existing calculations. With the Reissner-Nordstrom black hole we see that this
model independent procedure is not only valid for single horizon spacetime but
also valid for spacetimes with inner and outer horizons.
| [
{
"created": "Fri, 3 Jun 2011 17:40:59 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Aug 2011 06:56:38 GMT",
"version": "v2"
}
] | 2011-09-02 | [
[
"Majumder",
"Barun",
""
]
] | Recently Ali et.al.(2009) proposed a Generalized Uncertainty Principle (or GUP) with a linear term in momentum (accompanied by Plank length). Inspired by this idea here we calculate the quantum corrected value of a Schwarzschild black hole entropy and a Reissner-Nordstrom black hole with double horizon by utilizing the proposed generalized uncertainty principle. We find that the leading order correction goes with the square root of the horizon area contributing positively. We also find that the prefactor of the logarithmic contribution is negative and the value exactly matches with some earlier existing calculations. With the Reissner-Nordstrom black hole we see that this model independent procedure is not only valid for single horizon spacetime but also valid for spacetimes with inner and outer horizons. |
1510.01061 | Gang Sun | Gang Sun, Yong-Chang Huang | The cosmology in f(R,T) gravity without dark energy | null | null | 10.1142/S0218271816500383 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the evolution of universe in $f(R,T)$ gravity where $R$ is the
Ricci curvature and $T$ is the trace of energy momentum tensor. We focus on the
specific form $f(R,T) = R+f(T)$ and explicitly find out the relation between
$f(T)$ and state of equation $w$ by adiabatic condition. All possible modes of
evolution of the scale factor for the five kinds of state of equation, $w= \pm
1, \pm 1/3, 0$ are exhibited. We simulate numerically the plots of redshift
versus distance modulus for three interesting modes and then obtain the good
fitting curve compared with the astronomical observation data.
| [
{
"created": "Mon, 5 Oct 2015 08:35:55 GMT",
"version": "v1"
}
] | 2016-03-16 | [
[
"Sun",
"Gang",
""
],
[
"Huang",
"Yong-Chang",
""
]
] | We examine the evolution of universe in $f(R,T)$ gravity where $R$ is the Ricci curvature and $T$ is the trace of energy momentum tensor. We focus on the specific form $f(R,T) = R+f(T)$ and explicitly find out the relation between $f(T)$ and state of equation $w$ by adiabatic condition. All possible modes of evolution of the scale factor for the five kinds of state of equation, $w= \pm 1, \pm 1/3, 0$ are exhibited. We simulate numerically the plots of redshift versus distance modulus for three interesting modes and then obtain the good fitting curve compared with the astronomical observation data. |
1105.3807 | Reinhard Meinel | Reinhard Meinel and Moritz H\"utten | On the black hole limit of electrically counterpoised dust
configurations | 8 pages, 1 figure, to appear in CQG | Class.Quant.Grav.28:225010,2011 | 10.1088/0264-9381/28/22/225010 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By means of a simple scaling transformation any asymptotically flat
Papapetrou-Majumdar solution of the Einstein-Maxwell equations corresponding to
a localized regular distribution of electrically counterpoised dust can be
reformulated as a one-parameter family of solutions admitting a black hole
limit. In the limit, a characteristic separation of spacetimes occurs: From the
exterior point of view, the extreme Reissner-Nordstrom metric outside the event
horizon is formed. From the interior point of view, a regular,
non-asymptotically flat (and in general non-spherically symmetric) spacetime
with the extreme Reissner-Nordstrom near-horizon geometry at spatial infinity
results.
| [
{
"created": "Thu, 19 May 2011 07:38:22 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Aug 2011 05:16:29 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Sep 2011 17:53:15 GMT",
"version": "v3"
}
] | 2011-10-19 | [
[
"Meinel",
"Reinhard",
""
],
[
"Hütten",
"Moritz",
""
]
] | By means of a simple scaling transformation any asymptotically flat Papapetrou-Majumdar solution of the Einstein-Maxwell equations corresponding to a localized regular distribution of electrically counterpoised dust can be reformulated as a one-parameter family of solutions admitting a black hole limit. In the limit, a characteristic separation of spacetimes occurs: From the exterior point of view, the extreme Reissner-Nordstrom metric outside the event horizon is formed. From the interior point of view, a regular, non-asymptotically flat (and in general non-spherically symmetric) spacetime with the extreme Reissner-Nordstrom near-horizon geometry at spatial infinity results. |
1907.09463 | Pedro Ca\~nate Casseres | Pedro Ca\~nate, Joseph Sultana, Demosthenes Kazanas | Ellis wormhole without a phantom scalar field | 12 pages, 3 figures. Minor changes, matches published version | Phys. Rev. D 100, 064007 (2019) | 10.1103/PhysRevD.100.064007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present an exact solution for $(3+1)$-dimensional
Einstein-scalar-Gauss-Bonnet theory (EsGB) in electrovacuum. The solution is
characterized by only one parameter, $Q$, which in general can be associated
with the electromagnetic field and the scalar field. We show that the solution
corresponds to a charged wormhole with throat at the region $r = |Q|$, and is
also supported by a real scalar field having a positive kinetic term. We show
that the solution belongs to the most general class of solutions known as Ellis
wormholes but without the need for `exotic matter' or a phantom scalar field.
| [
{
"created": "Mon, 22 Jul 2019 17:56:30 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Sep 2019 17:24:00 GMT",
"version": "v2"
}
] | 2019-09-11 | [
[
"Cañate",
"Pedro",
""
],
[
"Sultana",
"Joseph",
""
],
[
"Kazanas",
"Demosthenes",
""
]
] | In this paper, we present an exact solution for $(3+1)$-dimensional Einstein-scalar-Gauss-Bonnet theory (EsGB) in electrovacuum. The solution is characterized by only one parameter, $Q$, which in general can be associated with the electromagnetic field and the scalar field. We show that the solution corresponds to a charged wormhole with throat at the region $r = |Q|$, and is also supported by a real scalar field having a positive kinetic term. We show that the solution belongs to the most general class of solutions known as Ellis wormholes but without the need for `exotic matter' or a phantom scalar field. |
0907.4367 | Yuri Obukhov | Yuri N. Obukhov, Alexander J. Silenko, Oleg V. Teryaev | Spin dynamics in gravitational fields of rotating bodies and the
equivalence principle | 22 pages, Revtex, no figures, accepted in Phys. Rev. D | Phys.Rev.D80:064044,2009 | 10.1103/PhysRevD.80.064044 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the quantum and classical dynamics of a particle with spin in the
gravitational field of a rotating source. A relativistic equation describing
the motion of classical spin in curved spacetimes is obtained. We demonstrate
that the precession of the classical spin is in a perfect agreement with the
motion of the quantum spin derived from the Foldy-Wouthuysen approach for the
Dirac particle in a curved spacetime. We show that the precession effect
depends crucially on the choice of a tetrad. The results obtained are compared
to the earlier computations for different tetrad gauges.
| [
{
"created": "Fri, 24 Jul 2009 19:45:27 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Sep 2009 21:25:55 GMT",
"version": "v2"
}
] | 2009-11-06 | [
[
"Obukhov",
"Yuri N.",
""
],
[
"Silenko",
"Alexander J.",
""
],
[
"Teryaev",
"Oleg V.",
""
]
] | We discuss the quantum and classical dynamics of a particle with spin in the gravitational field of a rotating source. A relativistic equation describing the motion of classical spin in curved spacetimes is obtained. We demonstrate that the precession of the classical spin is in a perfect agreement with the motion of the quantum spin derived from the Foldy-Wouthuysen approach for the Dirac particle in a curved spacetime. We show that the precession effect depends crucially on the choice of a tetrad. The results obtained are compared to the earlier computations for different tetrad gauges. |
1607.08034 | Soumya Chakrabarti | Soumya Chakrabarti and Narayan Banerjee | Gravitational collapse in f(R) gravity for a spherically symmetric
spacetime admitting a homothetic Killing vector | 11 pages, 10 figures | Eur. Phys. J. Plus (2016) 131: 144 | 10.1140/epjp/i2016-16144-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational collapse of a spherical distribution, in a class of f(R)
theories of gravity, where f(R) is power function of R, is discussed. The
spacetime is assumed to admit a homothetic Killing vector. In the collapsing
modes, some of the situations indeed hit a singularity, but they are all
covered with an apparent horizon. Some peculiar cases are observed where the
collapsing body settles to a constant radius at a given value of the radial
coordinate.
| [
{
"created": "Wed, 27 Jul 2016 11:04:56 GMT",
"version": "v1"
}
] | 2016-07-28 | [
[
"Chakrabarti",
"Soumya",
""
],
[
"Banerjee",
"Narayan",
""
]
] | The gravitational collapse of a spherical distribution, in a class of f(R) theories of gravity, where f(R) is power function of R, is discussed. The spacetime is assumed to admit a homothetic Killing vector. In the collapsing modes, some of the situations indeed hit a singularity, but they are all covered with an apparent horizon. Some peculiar cases are observed where the collapsing body settles to a constant radius at a given value of the radial coordinate. |
1706.07662 | Shahram Panahiyan | Seyed Hossein Hendi, Shahram Panahiyan, Behzad Eslam Panah, Mubasher
Jamil | Alternative approach to thermodynamic phase transitions | 9 pages, 2 figures; matches published version | Chinese Physics C Vol. 43, No. 11 (2019) 113106 | 10.1088/1674-1137/43/11/113106 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the major open problems in theoretical physics is a consistent quantum
gravity theory.Recent developments in thermodynamic phase transitions ofblack
holes and their van der Waals-like behavior may provide an interesting quantum
interpretation of classical gravity. Studyingdifferent methods of investigating
phase transitions can extend our insight into the nature of quantumgravity. In
this paper, we present an alternative theoretical approach for finding
thermodynamicphase transitions in the extended phase space. Unlike the standard
methods based on the usualequation of state involving temperature, our approach
usesa new quasi-equation constructed fromthe slope of temperature versus
entropy. This approach addresses some of the shortcomings ofthe other methods,
and provides a simple and powerful way of studying the critical behavior of
athermodynamical system. Among the applications of this approach, we emphasize
the analyticaldemonstration of possible phase transition points, and
theidentification of the non-physical rangeof horizon radii for black holes.
| [
{
"created": "Wed, 21 Jun 2017 12:06:56 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Oct 2019 14:20:55 GMT",
"version": "v2"
}
] | 2020-06-26 | [
[
"Hendi",
"Seyed Hossein",
""
],
[
"Panahiyan",
"Shahram",
""
],
[
"Panah",
"Behzad Eslam",
""
],
[
"Jamil",
"Mubasher",
""
]
] | One of the major open problems in theoretical physics is a consistent quantum gravity theory.Recent developments in thermodynamic phase transitions ofblack holes and their van der Waals-like behavior may provide an interesting quantum interpretation of classical gravity. Studyingdifferent methods of investigating phase transitions can extend our insight into the nature of quantumgravity. In this paper, we present an alternative theoretical approach for finding thermodynamicphase transitions in the extended phase space. Unlike the standard methods based on the usualequation of state involving temperature, our approach usesa new quasi-equation constructed fromthe slope of temperature versus entropy. This approach addresses some of the shortcomings ofthe other methods, and provides a simple and powerful way of studying the critical behavior of athermodynamical system. Among the applications of this approach, we emphasize the analyticaldemonstration of possible phase transition points, and theidentification of the non-physical rangeof horizon radii for black holes. |
gr-qc/9611057 | Martin Rainer | A. Zhuk | Multidimensional Quantum Cosmology: Quantum Wormholes, Third
Quantization, Inflation from "Nothing", etc | null | Grav.Cosmol 2:17-26,1996 | null | Mosc-6/1995 | gr-qc | null | A multidimensional cosmological model with space-time consisting of n (n>1)
Einstein spaces M_i is investigated in the presence of a cosmological constant
Lambda and m homogeneous minimally coupled scalar fields as a matter source.
Classes of the models integrable at classical as well as quantum levels are
found. These classes are equivalent to each other. Quantum wormhole solutions
are obtained for them and the procedure of the third quantization is performed.
An inflationary universe arising from classically forbidden Euclidean region is
investigated for a model with a cosmological constant.
| [
{
"created": "Sun, 24 Nov 1996 18:05:52 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Zhuk",
"A.",
""
]
] | A multidimensional cosmological model with space-time consisting of n (n>1) Einstein spaces M_i is investigated in the presence of a cosmological constant Lambda and m homogeneous minimally coupled scalar fields as a matter source. Classes of the models integrable at classical as well as quantum levels are found. These classes are equivalent to each other. Quantum wormhole solutions are obtained for them and the procedure of the third quantization is performed. An inflationary universe arising from classically forbidden Euclidean region is investigated for a model with a cosmological constant. |
2202.07044 | Alexander Zhuk | Alexander Zhuk and Valerii Shulga | Effect of medium on fundamental interactions in gravity and condensed
matter | 8 pages, v2 (matching the publication in Frontiers in Physics) = v1 +
minor changes | Frontiers in Physics, 10 (2022) 875757 | 10.3389/fphy.2022.875757 | null | gr-qc astro-ph.CO cond-mat.supr-con hep-th | http://creativecommons.org/licenses/by/4.0/ | Recently, it was shown that the gravitational field undergoes exponential
cutoff at large cosmological scales due to the presence of background matter.
In this article, we demonstrate that there is a close mathematical analogy
between this effect and the behavior of the magnetic field induced by a
solenoid placed in a superconductor.
| [
{
"created": "Mon, 14 Feb 2022 21:21:04 GMT",
"version": "v1"
},
{
"created": "Tue, 24 May 2022 13:43:15 GMT",
"version": "v2"
}
] | 2022-05-25 | [
[
"Zhuk",
"Alexander",
""
],
[
"Shulga",
"Valerii",
""
]
] | Recently, it was shown that the gravitational field undergoes exponential cutoff at large cosmological scales due to the presence of background matter. In this article, we demonstrate that there is a close mathematical analogy between this effect and the behavior of the magnetic field induced by a solenoid placed in a superconductor. |
gr-qc/0005088 | Felix Finster | Felix Finster, Niky Kamran, Joel Smoller, and Shing-Tung Yau | The Long-Time Dynamics of Dirac Particles in the Kerr-Newman Black Hole
Geometry | 22 pages, small improvements | Adv.Theor.Math.Phys.7:25-52,2003 | 10.4310/ATMP.2003.v7.n1.a2 | null | gr-qc math-ph math.DG math.MP | null | We consider the Cauchy problem for the massive Dirac equation in the
non-extreme Kerr-Newman geometry outside the event horizon. We derive an
integral representation for the Dirac propagator involving the solutions of the
ODEs which arise in Chandrasekhar's separation of variables. It is proved that
for initial data in L^\infty_loc near the event horizon with L^2 decay at
infinity, the probability of the Dirac particle to be in any compact region of
space tends to zero as t goes to infinity. This means that the Dirac particle
must either disappear in the black hole or escape to infinity.
| [
{
"created": "Fri, 19 May 2000 16:03:11 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Jul 2001 15:36:44 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Feb 2003 10:53:57 GMT",
"version": "v3"
},
{
"created": "Wed, 24 Dec 2003 22:10:57 GMT",
"version": "v4"
}
] | 2014-01-28 | [
[
"Finster",
"Felix",
""
],
[
"Kamran",
"Niky",
""
],
[
"Smoller",
"Joel",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | We consider the Cauchy problem for the massive Dirac equation in the non-extreme Kerr-Newman geometry outside the event horizon. We derive an integral representation for the Dirac propagator involving the solutions of the ODEs which arise in Chandrasekhar's separation of variables. It is proved that for initial data in L^\infty_loc near the event horizon with L^2 decay at infinity, the probability of the Dirac particle to be in any compact region of space tends to zero as t goes to infinity. This means that the Dirac particle must either disappear in the black hole or escape to infinity. |
2009.08293 | Betti Hartmann | Yves Brihaye and Betti Hartmann | Strong gravity effects of charged Q-clouds and inflating black holes | null | null | 10.1088/1361-6382/abd95a | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we re-examine charged Q-clouds around spherically symmetric,
static black holes. In particular, we demonstrate that for fixed coupling
constants two different branches of charged scalar clouds exist around
Schwarzschild black holes. This had not been noticed previously. We find that
the new solutions possess a "hard wall" at maximal possible gauge coupling.
This wall separates the interior (containing the black hole horizon), in which
the scalar field is trapped in the "false vacuum", from the "true vacuum"
exterior. When taking back-reaction onto the space-time into account, we find
that at maximal possible back reaction, the black hole solutions corresponding
to these two branches either become extremal black holes with diverging scalar
field derivative on the horizon or inflating black holes with a second,
"cosmological" horizon which - outside this second horizon - correspond to
extremal Reissner-Nordstr\"om black holes.
| [
{
"created": "Thu, 17 Sep 2020 13:41:21 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Brihaye",
"Yves",
""
],
[
"Hartmann",
"Betti",
""
]
] | In this paper, we re-examine charged Q-clouds around spherically symmetric, static black holes. In particular, we demonstrate that for fixed coupling constants two different branches of charged scalar clouds exist around Schwarzschild black holes. This had not been noticed previously. We find that the new solutions possess a "hard wall" at maximal possible gauge coupling. This wall separates the interior (containing the black hole horizon), in which the scalar field is trapped in the "false vacuum", from the "true vacuum" exterior. When taking back-reaction onto the space-time into account, we find that at maximal possible back reaction, the black hole solutions corresponding to these two branches either become extremal black holes with diverging scalar field derivative on the horizon or inflating black holes with a second, "cosmological" horizon which - outside this second horizon - correspond to extremal Reissner-Nordstr\"om black holes. |
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