58 research outputs found
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
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
Constant curvature f(R) gravity minimally coupled with Yang-Mills field
We consider the particular class of f(R) gravities minimally coupled with
Yang - Mills (YM) field in which the Ricci scalar =R_{0}= constant in all
dimensions d\geq4. Even in this restricted class the spacetime has unlimited
scopes determined by an equation of state of the form P_{eff}={\omega}{\rho}.
Depending on the distance from the origin (or horizon of a black hole) the
state function {\omega}(r) takes different values. It is observed that
{\omega}\rightarrow(1/3) (the ultra relativistic case in 4 - dimensions) and
{\omega}\rightarrow-1 (the cosmological constant) are the limiting values of
our state function {\omega}(r) in a spacetime centered by a black hole. This
suggests that having a constant {\omega} throughout spacetime around a charged
black hole in f(R) gravity with constant scalar curvature is a myth.Comment: 12 pages 2 figures, Some references and 2 figures are added with
minor changes. Final version for publication in European Physical Journal
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
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
Colliding plane wave solution in F(R)=R^{N} gravity
We identify a region of F(R)=R^{N} gravity without external sources which is
isometric to the spacetime of colliding plane waves (CPW). From the derived
curvature sources, N (N>1) measures the strength (i.e. the charge) of the
source. The analogy renders construction and collision of plane waves in
F(R)=R^{N} gravity possible, as in the Einstein-Maxwell (EM) theory, simply
because R=0. A plane wave in this type of gravity is equivalent to a Weyl
curvature plus an electromagnetic energy-momentum-like term (i.e. 'source
without source'). For N=1 we recover naturally the plane waves (and their
collision) in Einstein's theory. Our aim is to find the effect of an expanding
universe by virtue of F(R)=R^{N} on the colliding gravitational plane waves of
Einstein.Comment: 9 pages, 2 figure
Some exact solutions of F(R) gravity with charged (a)dS black hole interpretation
In this paper we obtain topological static solutions of some kind of pure
gravity. The present solutions are two kind: first type is uncharged
solution which corresponds with the topological (a)dS Schwarzschild solution
and second type has electric charge and is equivalent to the
Einstein--conformally invariant Maxwell solution. In other word,
starting from pure gravity leads to (charged) Einstein- solutions
which we interpreted them as (charged) (a)dS black hole solutions of pure
gravity. Calculating the Ricci and Kreschmann scalars show that there is
a curvature singularity at . We should note that the Kreschmann scalar of
charged solutions goes to infinity as , but with a rate slower
than that of uncharged solutions.Comment: 21 pages, 4 figures, generalization to higher dimensions, references
adde
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
Charged rotating dilaton black branes in AdS universe
We present the metric for the -dimensional charged rotating dilaton
black branes with cylindrical or toroidal horizons in the background of anti-de
Sitter spacetime. We find the suitable counterterm which removes the
divergences of the action in the presence of the dilaton potential in all
higher dimensions. We plot the Penrose diagrams of the spacetime and reveal
that the spacetime geometry crucially modifies in the presence of the dilaton
field. The conserved and thermodynamic quantities of the black branes are also
computed.Comment: 13 pages, 3 figures, to appear in Gen. Relat. Gravi
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