914 research outputs found
Black holes in vector-tensor theories and their thermodynamics
In this paper, we study Einstein gravity either minimally or non-minimally
coupled to a vector field which breaks the gauge symmetry explicitly in general
dimensions. We first consider a minimal theory which is simply the
Einstein-Proca theory extended with a quartic self-interaction term for the
vector field. We obtain its general static maximally symmetric black hole
solution and study the thermodynamics using Wald formalism. The aspects of the
solution are much like a Reissner-Nordstr{\o}m black hole in spite of that a
global charge cannot be defined for the vector. For non-minimal theories, we
obtain a lot of exact black hole solutions, depending on the parameters of the
theories. In particular, many of the solutions are general static and have
maximal symmetry. However, there are some subtleties and ambiguities in the
derivation of the first laws because the existence of an algebraic degree of
freedom of the vector in general invalids the Wald entropy formula. The
thermodynamics of these solutions deserves further studies.Comment: to appera in EPJC, major revisions, referecens added. 33 page
SU(2)-Colored (A)dS Black Holes in Conformal Gravity
We consider four-dimensional conformal gravity coupled to the U(1) Maxwell
and SU(2) Yang-Mills fields. We study the structure of general black hole
solutions carrying five independent parameters: the mass, the electric U(1) and
magnetic SU(2) charges, the massive spin-2 charge and the thermodynamical
pressure associated with the cosmological constant, which is an integration
constant in conformal gravity. We derive the thermodynamical first law of the
black holes. We obtain some exact solutions including an extremal black hole
with vanishing mass and entropy, but with non-trivial SU(2) Yang-Mills charges.
We derive the remainder of the first law for this special solution. We also
reexamine the colored black holes and derive their first law in
Einstein-Yang-Mills gravity with or without a cosmological constant.Comment: Latex, 22 pages, typos corrected and references adde
Charged Black Holes with Scalar Hair
We consider a class of Einstein-Maxwell-Dilaton theories, in which the
dilaton coupling to the Maxwell field is not the usual single exponential
function, but one with a stationary point. The theories admit two charged black
holes: one is the Reissner-Nordstr{\o}m (RN) black hole and the other has a
varying dilaton. For a given charge, the new black hole in the extremal limit
has the same AdSSphere near-horizon geometry as the RN black hole,
but it carries larger mass. We then introduce some scalar potentials and obtain
exact charged AdS black holes. We also generalize the results to black
-branes with scalar hair.Comment: Latex, 22 pages, typos corrected and references added, to appear in
JHE
On the Noether charge and the gravity duals of quantum complexity
The physical relevance of the thermodynamic volumes of AdS black holes to the
gravity duals of quantum complexity was recently argued by Couch et al. In this
paper, by generalizing the Wald-Iyer formalism, we derive a geometric
expression for the thermodynamic volume and relate its product with the
thermodynamic pressure to the non-derivative part of the gravitational action
evaluated on the Wheeler-DeWitt patch. We propose that this action provides an
alternative gravity dual of the quantum complexity of the boundary theory. We
refer this to "complexity=action 2.0" (CA-2) duality. It is significantly
different from the original "complexity=action" (CA) duality as well as the
"complexity=volume 2.0" (CV-2) duality proposed by Couch et al. The latter
postulates that the complexity is dual to the spacetime volume of the
Wheeler-DeWitt patch. To distinguish our new conjecture from the various
dualities in literature, we study a number of black holes in
Einstein-Maxwell-Dilation theories. We find that for all these black holes, the
CA duality generally does not respect the Lloyd bound whereas the CV-2 duality
always does. For the CA-2 duality, although in many cases it is consistent with
the Lloyd bound, we also find a counter example for which it violates the bound
as well.Comment: minor corrections, references added,29pages,7figure
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