70 research outputs found
Stable Magnetic Universes Revisited
A regular class of static, cylindrically symmetric pure magnetic field
metrics is rederived in a different metric ansatz in all dimensions. Radial,
time dependent perturbations show that for dimensions d>3 such spacetimes are
stable at both near r\approx0 and large radius r\rightarrow\infty. In a
different gauge these stability analysis and similar results were known
beforehand. For d=3, however, simultaneous stability requirement at both, near
and far radial distances can not be reconciled for time - dependent
perturbations. Restricted, numerical geodesics for neutral particles reveal a
confinement around the center in the polar plane. Charged, time-like geodesics
for d=4 on the other hand are shown numerically to run toward infinity.Comment: 11 pages, 3figure
Thermodynamics of Rotating Black Branes in Gauss-Bonnet-nonlinear Maxwell Gravity
We consider the Gauss-Bonnet gravity in the presence of a new class of
nonlinear electromagnetic field, namely, power Maxwell invariant. By use of a
suitable transformation, we obtain a class of real rotating solutions with
rotation parameters and investigate some properties of the solutions such as
existence of singularity(ies) and asymptotic behavior of them. Also, we
calculate the finite action, thermodynamic and conserved quantities of the
solutions and using the the Smarr-type formula to check the first law of
thermodynamics.Comment: 15 page
Slowly rotating charged black holes in anti-de Sitter third order Lovelock gravity
In this paper, we study slowly rotating black hole solutions in Lovelock
gravity (n=3). These exact slowly rotating black hole solutions are obtained in
uncharged and charged cases, respectively. Up to the linear order of the
rotating parameter a, the mass, Hawking temperature and entropy of the
uncharged black holes get no corrections from rotation. In charged case, we
compute magnetic dipole moment and gyromagnetic ratio of the black holes. It is
shown that the gyromagnetic ratio keeps invariant after introducing the
Gauss-Bonnet and third order Lovelock interactions.Comment: 14 pages, no figur
Is the physical vacuum a preferred frame ?
It is generally assumed that the physical vacuum of particle physics should
be characterized by an energy momentum tensor in such a way to preserve exact
Lorentz invariance. On the other hand, if the ground state were characterized
by its energy-momentum vector, with zero spatial momentum and a non-zero
energy, the vacuum would represent a preferred frame. Since both theoretical
approaches have their own good motivations, we propose an experimental test to
decide between the two scenarios.Comment: 12 pages, no figure
Thermodynamics of charged and rotating black strings
We study thermodynamics of cylindrically symmetric black holes. Uncharged as
well as charged and rotating objects have been discussed. We derive surface
gravity and hence the Hawking temperature and entropy for all these cases. We
correct some results in the literature and present new ones. It is seen that
thermodynamically these black configurations behave differently from
spherically symmetric objects
Charged BTZ-like Black Holes in Higher Dimensions
Motivated by many worthwhile paper about (2 + 1)-dimensional BTZ black holes,
we generalize them to to (n + 1)-dimensional solutions, so called BTZ-like
solutions. We show that the electric field of BTZ-like solutions is the same as
(2 + 1)-dimensional BTZ black holes, and also their lapse functions are
approximately the same, too. By these similarities, it is also interesting to
investigate the geometric and thermodynamics properties of the BTZ-like
solutions. We find that, depending on the metric parameters, the BTZ-like
solutions may be interpreted as black hole solutions with inner (Cauchy) and
outer (event) horizons, an extreme black hole or naked singularity. Then, we
calculate thermodynamics quantities and conserved quantities, and show that
they satisfy the first law of thermodynamics. Finally, we perform a stability
analysis in the canonical ensemble and show that the BTZ-like solutions are
stable in the whole phase space.Comment: 5 pages, two column format, one figur
Tunneling of massive and charged particles from noncommutative Reissner-Nordstr\"{o}m black hole
Massive charged and uncharged particles tunneling from commutative
Reissner-Nordstrom black hole horizon has been studied with details in
literature. Here, by adopting the coherent state picture of spacetime
noncommutativity, we study tunneling of massive and charged particles from a
noncommutative inspired Reissner-Nordstrom black hole horizon. We show that
Hawking radiation in this case is not purely thermal and there are correlations
between emitted modes. These correlations may provide a solution to the
information loss problem. We also study thermodynamics of noncommutative
horizon in this setup.Comment: 10 pages, 2 figure
Rotating Black Branes in the presence of nonlinear electromagnetic field
In this paper, we consider a class of gravity whose action represents itself
as a sum of the usual Einstein-Hilbert action with cosmological constant and an
gauge field for which the action is given by a power of the Maxwell
invariant. We present a class of the rotating black branes with Ricci flat
horizon and show that the presented solutions may be interpreted as black brane
solutions with two event horizons, extreme black hole and naked singularity
provided the parameters of the solutions are chosen suitably. We investigate
the properties of the solutions and find that for the special values of the
nonlinear parameter, the solutions are not asymptotically anti-deSitter. At
last, we obtain the conserved quantities of the rotating black branes and find
that the nonlinear source effects on the electric field, the behavior of
spacetime, type of singularity and other quantities.Comment: 7 pages, 5 figures, to appear in EPJ
A Study of Phase Transition in Black Hole Thermodynamics
This paper deals with five-dimensional black hole solutions in (a)
Einstein-Maxwell-Gauss-Bonnet theory with a cosmological constant and
(b)Einstein-Yang-Mills-Gauss-Bonnet theory for spherically symmetric space
time. In both the cases the possibility of phase transition is examined and it
is analyzed whether the phase transition is a Hawking-Page type phase
transition or not.Comment: 16 figure
Topological Black Holes in Gauss-Bonnet Gravity with conformally invariant Maxwell source
In this paper, we present a class of rotating solutions in Gauss--Bonnet
gravity in the presence of cosmological constant and conformally invariant
Maxwell field and study the effects of the nonlinearity of the Maxwell source
on the properties of the spacetimes. These solutions may be interpret as black
brane solutions with inner and outer event horizons provide that the mass
parameter is greater than an extremal value , an extreme black
brane if and a naked singularity otherwise. We investigate the
conserved and thermodynamics quantities for asymptotically flat and
asymptotically with flat horizon. We also show that the conserved and
thermodynamic quantities of these solutions satisfy the first law of
thermodynamics.Comment: 17 pages, 4 figures, some references adde
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