16 research outputs found
On timelike supersymmetric solutions of gauged minimal 5-dimensional supergravity
We analyze the timelike supersymmetric solutions of minimal gauged
5-dimensional supergravity for the case in which the K\"ahler base manifold
admits a holomorphic isometry and depends on two real functions satisfying a
simple second-order differential equation. Using this general form of the base
space, the equations satisfied by the building blocks of the solutions become
of, at most, fourth degree and can be solved by simple polynomic ansatzs. In
this way we construct two 3-parameter families of solutions that contain almost
all the timelike supersymmetric solutions of this theory with one angular
momentum known so far and a few more: the (singular) supersymmetric
Reissner-Nordstr\"om-AdS solutions, the three exact supersymmetric solutions
describing the three near-horizon geometries found by Gutowski and Reall, three
1-parameter asymptotically-AdS black-hole solutions with those three
near-horizon geometries (Gutowski and Reall's black hole being one of them),
three generalizations of the G\"odel universe and a few potentially homogenous
solutions. A key r\^ole in finding these solutions is played by our ability to
write AdS's K\"ahler base space ( or
SUU) is three different, yet simple, forms associated to three
different isometries. Furthermore, our ansatz for the K\"ahler metric also
allows us to study the dimensional compactification of the theory and its
solutions in a systematic way.Comment: 57 pages. References and comments adde
Multi-centered black holes with a negative cosmological constant
We present a recipe that allows to construct multi-centered black holes
embedded in an arbitrary FLRW universe. These solutions are completely
determined by a function satisfying the conformal Laplace equation on the
spatial slices , or . Since anti-de Sitter
space can be written in FLRW coordinates, this includes as a special case
multi-centered black holes in AdS, in the sense that, far away from the black
holes, the energy density and the pressure approach the values given by a
negative cosmological constant. We study in some detail the physical properties
of the single-centered asymptotically AdS case, which does not coincide with
the usual Reissner-Nordstr\"om-AdS black hole, but is highly dynamical. In
particular, we determine the curvature singularities and trapping horizons of
this solution, compute the surface gravity of the trapping horizons, and show
that the generalized first law of black hole dynamics proposed by Hayward holds
in this case. It turns out that the spurious big bang/big crunch singularities
that appear when one writes AdS in FLRW form, become real in presence of these
dynamical black holes. This implies that actually only one point of the usual
conformal boundary of AdS survives in the solutions that we construct. Finally,
a generalization to arbitary dimension is also presented.Comment: 17 pages, 5 figure
Yang-Mills instantons in Kaehler spaces with one holomorphic isometry
We consider self-dual Yang-Mills instantons in 4-dimensional Kaehler spaces
with one holomorphic isometry and show that they satisfy a generalization of
the Bogomol'nyi equation for magnetic monopoles on certain 3-dimensional
metrics. We then search for solutions of this equation in 3-dimensional metrics
foliated by 2-dimensional spheres, hyperboloids or planes in the case in which
the gauge group coincides with the isometry group of the metric (SO(3), SO(1,2)
and ISO(2), respectively). Using a generalized hedgehog ansatz the Bogomol'nyi
quations reduce to a simple differential equation in the radial variable which
admits a universal solution and, in some cases, a particular one, from which
one finally recovers instanton solutions in the original Kaehler space. We work
out completely a few explicit examples for some Kaehler spaces of interest.Comment: Latex2e file, 16 pages, no figure
Supersymmetric black holes and attractors in gauged supergravity with hypermultiplets
We consider four-dimensional supergravity coupled to vector- and
hypermultiplets, where abelian isometries of the quaternionic K\"ahler
hypermultiplet scalar manifold are gauged. Using the recipe given by Meessen
and Ort\'{\i}n in arXiv:1204.0493, we analytically construct a supersymmetric
black hole solution for the case of just one vector multiplet with prepotential
, and the universal hypermultiplet. This solution has
a running dilaton, and it interpolates between
at the horizon and a hyperscaling-violating type geometry at infinity,
conformal to . It carries two magnetic charges
that are completely fixed in terms of the parameters that appear in the Killing
vector used for the gauging. In the second part of the paper, we extend the
work of Bellucci et al. on black hole attractors in gauged supergravity to the
case where also hypermultiplets are present. The attractors are shown to be
governed by an effective potential , which is extremized on the
horizon by all the scalar fields of the theory. Moreover, the entropy is given
by the critical value of . In the limit of vanishing scalar
potential, reduces (up to a prefactor) to the usual black hole
potential.Comment: 21 pages, uses jheppub.sty. v2: Refs. adde
Regular Stringy Black Holes?
We study the first-order corrections to the singular 4-dimensional
massless stringy black holes studied in the nineties in the context of the
Heterotic Superstring. We show that the corrections not only induce a
non-vanishing mass and give rise to an event horizon, but also eliminate the
singularity giving rise to a regular spacetime whose global structure includes
further asymptotically flat regions in which the spacetime's mass is positive
or negative. We study the timelike and null geodesics and their effective
potential, showing that the spacetime is geodesically complete. We discuss the
validity of this solution, arguing that the very interesting and peculiar
properties of the solution are associated to the negative energy contributions
coming from the terms quadratic in the curvature. As a matter of fact, the
10-dimensional configuration is singular. We extract some general lessons on
attempts to eliminate black-hole singularities by introducing terms of higher
order in the curvature.Comment: 5 pages, 2 figure
On a family of α′-corrected solutions of the Heterotic Superstring effective action
We compute explicitly the first-order in α′ corrections to a family of solutions of the Heterotic Superstring effective action that describes fundamental strings with momentum along themselves, parallel to solitonic 5-branes with Kaluza-Klein monopoles (Gibbons-Hawking metrics) in their transverse space. These solutions correspond to 4-charge extremal black holes in 4 dimensions upon dimensional reduction on T6. We show that some of the α′ corrections can be cancelled by introducing solitonic SU(2) × SU(2) Yang-Mills fields, and that this family of α′-corrected solutions is invariant under α′-corrected T-duality transformations. We study in detail the mechanism that allows us to compute explicitly these α′ corrections for the ansatz considered here, based on a generalization of the ’t Hooft ansatz to hyperKähler spacesThis work has been supported in part by the MINECO/FEDER, UE grants FPA2015-66793-P and FPA2015-63667-P, by the Italian INFN and by the Spanish Research Agency (Agencia Estatal de Investigación) through the grant IFT Centro de Excelencia Severo Ochoa SEV-2016-0597. AR is supported by “Centro de Excelencia Internacional UAM/CSI
α′ corrections of Reissner-Nordström black holes
We study the first-order in α′ corrections to non-extremal 4-dimensional dyonic Reissner-Nordström (RN) black holes with equal electric and magnetic charges in the context of Heterotic Superstring effective field theory (HST) compactified on a T6. The particular embedding of the dyonic RN black hole in HST considered here is not supersymmetric in the extremal limit. We show that, at first order in α′, consistency with the equations of motion of the HST demands additional scalar and vector fields become active, and we provide explicit expressions for all of them. We determine analytically the position of the event horizon of the black hole, as well as the corrections to the extremality bound, to the temperature and to the entropy, checking that they are related by the first law of black-hole thermodynamics, so that ∂S/∂M = 1/T. We discuss the implications of our results in the context of the Weak Gravity Conjecture, clarifying that entropy corrections for fixed mass and charge at extremality do not necessarily imply corrections to the extremal charge-to-mass ratioThis work has been supported in part by the MCIU, AEI, FEDER (UE) grant PGC2018-
095205-B-I00, CONACyT grant 237351 and by the Spanish Research Agency (Agencia
Estatal de Investigación) through the grant IFT Centro de Excelencia Severo Ochoa SEV-
2016-0597. PAC was mostly funded by Fundación La Caixa through a La Caixa - Severo
Ochoa" International pre-doctoral grant. In the last stages of this project PAC was supported by the KU Leuven grant \Bijzonder Onderzoeksfonds C16/16/00
Beyond the near-horizon limit: Stringy corrections to Heterotic Black Holes
We study the first-order in corrections to 4-charge black holes
(with the Reissner-Nordstr\"om black hole as a particular example) beyond the
near-horizon limit in the Heterotic Superstring effective action framework. The
higher-curvature terms behave as delocalized sources in the equations of motion
and in the Bianchi identity of the 3-form. For some charges, this introduces a
shift between their values measured at the horizon and asymptotically. Some of
these corrections and their associated charge shifts, but not all of them, can
be canceled using appropriate SU instantons for the heterotic gauge
fields. The entropy, computed using Wald's formula, is in agreement with the
result obtained via microstate counting when the delocalized sources are
properly taken into account.Comment: 46 page