25 research outputs found
Phase transitions in charged topological black holes dressed with a scalar hair
Phase transitions in charged topological black holes dressed with a scalar
field are studied. These black holes are solutions of the Einstein-Maxwell
theory with a negative cosmological constant and a conformally coupled real
self-interacting scalar field. Comparing, in the grand canonical ensemble, the
free energies of the hairy and undressed black holes two different phase
transitions are found. The first of them is one of second-order type and it
occurs at a temperature defined by the value of the cosmological constant.
Below this temperature an undressed black hole spontaneously acquires a scalar
hair. The other phase transition is one of first-order type. The corresponding
critical temperature, which is bounded from above by the one of the previous
case, strongly depends on the coupling constant of the quartic self-interaction
potential, and this transition only appears when the coupling constant is less
than a certain value. In this case, below the critical temperature the
undressed black is thermodynamically favored. However, when the temperature
exceeds the critical value a hairy black hole is likely to be occur.Comment: Four pages, two figure
A New Class of Exact Hairy Black Hole Solutions
We present a new class of black hole solutions with minimally coupled scalar
field in the presence of a negative cosmological constant. We consider a
one-parameter family of self-interaction potentials parametrized by a
dimensionless parameter . When , we recover the conformally invariant
solution of the Martinez-Troncoso-Zanelli (MTZ) black hole. A non-vanishing
signals the departure from conformal invariance. All solutions are
perturbatively stable for negative black hole mass and they may develop
instabilities for positive mass. Thermodynamically, there is a critical
temperature at vanishing black hole mass, where a higher-order phase transition
occurs, as in the case of the MTZ black hole. Additionally, we obtain a branch
of hairy solutions which undergo a first-order phase transition at a second
critical temperature which depends on and it is higher than the MTZ
critical temperature. As , this second critical temperature diverges.Comment: 18 pages, 6 figures, minor changes, references added, published
versio
Hydrodynamics of a 5D Einstein-dilaton black hole solution and the corresponding BPS state
We apply the potential reconstruction approach to generate a series of
asymptotically AdS (aAdS) black hole solutions, with a self-interacting bulk
scalar field. Based on the method, we reproduce the pure AdS solution as a
consistency check and we also generate a simple analytic 5D black hole
solution. We then study various aspects of this solution, such as temperature,
entropy density and conserved charges. Furthermore, we study the hydrodynamics
of this black hole solution in the framework of fluid/gravity duality, e.g. the
ratio of the shear viscosity to the entropy density. In a degenerate case of
the 5D black hole solution, we find that the c function decreases monotonically
from UV to IR as expected. Finally, we investigate the stability of the
degenerate solution by studying the bosonic functional energy of the gravity
and the Witten-Nester energy . We confirm that the degenerate solution
is a BPS domain wall solution. The corresponding superpotential and the
solution of the killing spinor equation are found explicitly.Comment: V2: 23 pages, no figure, minor changes, typos corrected, new
references and comments added, version accepted by JHE
Lovelock solutions in the presence of matter sources
For a large class of space and time-dependent warped geometries we find the
general solution of the 6-dimensional Einstein-Gauss-Bonnet equations in the
presence of p-form matter fields. This is done under two conditions on the
matter sector which we show impose the integrability of the full system.
Solutions are classified and known black hole limits are found. It is shown
that Lovelock gravity restricts drastically the possible horizon geometries and
allowed matter sources. In fact, we show that if we allow only for solutions of
asymptotically flat falloff behaviour, and no fine-tuning of coupling
constants, then the only permissible black hole is that of Boulware-Deser with
electromagnetic charge. The situation of 6 dimensional Lovelock gravity is
therefore almost identical to 4 dimensional General Relativity. The
gravitational horizon constraints lead us to find static solutions involving
3-form matter fields in anti de-Sitter space which are also new to General
Relativity along with other cosmological and black string type of solutions.Comment: Regular article, no figures, 29 page