Natxo Alonso-Alberca

Supersymmetry of topological Kerr-Newman-Taub- NUT-adS spacetimes

We extend the topological Kerr-Newman-adS solutions by including NUT charge and find generalizations of the Robinson-Bertotti solution to the negative cosmological constant case with different topologies. We show how all of these solutions can be obtained as limits of the general Plebanski-Demianski solution. We study the supersymmetry properties of all these solutions in the context of gauged N = 2, d = 4 supergravity. Generically they preserve, at most, quarter of the total supersymmetry. In the Plebanski-Demianski case, although gauged N = 2, d = 4 supergravity does not have electro-magnetic duality, we find that the family of supersymmetric solutions still exhibits an electro-magnetic duality in which electric and magnetic charges and mass and Taub-NUT charge are rotated simultaneously.

Supersymmetric brane-worlds

Abstract We present warped metrics which solve Einstein equations with arbitrary cosmological constants in both in upper and lower dimensions. When the lower-dimensional metric is the maximally symmetric one compatible with the chosen value of the cosmological constant, the upper-dimensional metric is also the maximally symmetric one and there is maximal unbroken supersymmetry as well. We then introduce brane sources and find solutions with analogous properties, except for supersymmetry, which is generically broken in the orbifolding procedure (one half is preserved in two special cases), and analyze metric perturbations in these backgrounds In analogy with the D8-brane we propose an effective ( d −2) -brane action which acts as a source for the RS solution. The action consists of a Nambu–Goto piece and a Wess–Zumino term containing a ( d −1) -form field. It has the standard form of the action for a BPS extended object, in correspondence with the supersymmetry preserved by the solution.

Geometric construction of Killing spinors and supersymmetry algebras in homogeneous spacetimes

We show how the Killing spinors of some maximally supersymmetric supergravity solutions whose metrics describe symmetric spacetimes (including AdS, AdS × S and Hpp-waves) can be easily constructed using purely geometrical and group-theoretical methods. The calculation of the supersymmetry algebras is extremely simple in this formalism.

Domain walls of D=8 gauged supergravities and their D=11 origin

Performing a Scherk-Schwarz dimensional reduction ofD = 11 supergravity on a three-dimensional group manifold we construct flveD = 8 gauged maximal supergravities whose gauge groups are the three-dimensional (non-)compact subgroups of SL(3; R). These cases include the Salam-Sezgin SO(3) gauged supergravity. We construct the most general half-supersymmetric domain wall solutions to these flve gauged supergravities. The generic form is a triple domain wall solution whose truncations lead to double and single domain wall solutions. We flnd that one of the single domain wall solutions has zero potential but nonzero superpotential. Upon uplifting to 11 dimensions each domain wall becomes a purely gravitational 1/2 BPS solution. The corresponding metric has a 7 + 4 split with a Minkowski 7-metric and a 4-metric that corresponds to a gravitational instanton. These instantons generalize the SO(3) metric of Belinsky, Gibbons, Page and Pope (which includes the Eguchi-Hanson metric) to the other Bianchi types of class A.

The near-horizon limit of the extreme rotating d = 5 black hole as a homogeneous spacetime

We show that the spacetime of the near-horizon limit of the extreme rotating d = 5 black hole, which is maximally supersymmetric in N = 2, d = 5 supergravity for any value of the rotation parameter j [−1, 1], is locally isomorphic to a homogeneous non-symmetric spacetime corresponding to an element of the one-parameter family of coset spaces SO(2, 1) × SO(3)/SO(2)j in which the subgroup SO(2)j is a combination of the two SO(2) subgroups of SO(2, 1) and SO(3).

Curved dilatonic brane worlds and the cosmological constant problem

We construct a model for dilatonic brane worlds with constant curvature on the brane, i.e. a non-zero four-dimensional cosmological constant, given as a function of the dilaton coupling and the cosmological constant of the bulk. We compare this family of solutions to other known dilatonic domain wall solutions and apply a self-tuning mechanism to check the stability of our solutions under quantum fluctuations living on the brane.

Kähler forms and cosmological solutions in type II supergravities

We consider cosmological solutions to type II supergravity theories where the spacetime is split into a FRW universe and a Kahler space, which may be taken to be Calabi-Yau. The various 2-forms present in the theories are taken to be proportional to the Kahler form associated to the Kahler space.