210 research outputs found
Smarr's formula for black holes with non-linear electrodynamics
It is known that for nonlinear electrodynamics the First Law of Black Hole
Mechanics holds, however the Smarr's formula for the total mass does not. In
this contribution we discuss the point and determine the corresponding
expressions for the Bardeen black hole solution that represents a nonlinear
magnetic monopole. The same is done for the regular black hole solution derived
by Ayon-Beato and Garcia, showing that in the case that variations of the
electric charge are involved, the Smarr's formula does not longer is valid.Comment: 10 pages, 3 figures.Contribution to the Festscrift of Prof. A. Garci
Scalar Fields Nonminimally Coupled to pp Waves
Here, we report pp waves configurations of three-dimensional gravity for
which a scalar field nonminimally coupled to them acts as a source. In absence
of self-interaction the solutions are gravitational plane waves with a profile
fixed in terms of the scalar wave. In the self-interacting case, only power-law
potentials parameterized by the nonminimal coupling constant are allowed by the
field equations. In contrast with the free case the self-interacting scalar
field does not behave like a wave since it depends only on the wave-front
coordinate. We address the same problem when gravitation is governed by
topologically massive gravity and the source is a free scalar field. From the
pp waves derived in this case, we obtain at the zero topological mass limit,
new pp wave solutions of conformal gravity for any arbitrary value of the
nonminimal coupling parameter. Finally, we extend these solutions to the
self-interacting case of conformal gravity.Comment: 14 pages, RevTeX. Minor changes. To appear in Phys. Rev.
Nonlinearly charged Lifshitz black holes for any exponent
Charged Lifshitz black holes for the Einstein-Proca-Maxwell system with a
negative cosmological constant in arbitrary dimension are known only if the
dynamical critical exponent is fixed as . In the present work, we
show that these configurations can be extended to much more general charged
black holes which in addition exist for any value of the dynamical exponent
by considering a nonlinear electrodynamics instead of the Maxwell theory.
More precisely, we introduce a two-parametric nonlinear electrodynamics defined
in the more general, but less known, so-called -formalism and
obtain a family of charged black hole solutions depending on two parameters. We
also remark that the value of the dynamical exponent turns out to be
critical in the sense that it yields asymptotically Lifshitz black holes with
logarithmic decay supported by a particular logarithmic electrodynamics. All
these configurations include extremal Lifshitz black holes. Charged topological
Lifshitz black holes are also shown to emerge by slightly generalizing the
proposed electrodynamics
Stability properties of black holes in self-gravitating nonlinear electrodynamics
We analyze the dynamical stability of black hole solutions in
self-gravitating nonlinear electrodynamics with respect to arbitrary linear
fluctuations of the metric and the electromagnetic field. In particular, we
derive simple conditions on the electromagnetic Lagrangian which imply linear
stability in the domain of outer communication. We show that these conditions
hold for several of the regular black hole solutions found by Ayon-Beato and
Garcia.Comment: 15 pages, no figure
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