Causal Structure of d=5 Vacua and Axisymmetric Spacetimes

We study the structure of closed timelike curves (CTCs) for the near horizon limit of the five dimensional BMPV black hole, in its overrotating regime. We argue that Bousso's holographic screens are inside the chronologically safe region, extending a similar observation of Boyda et al. hep-th/0212087 for Goedel type solutions. We then extend this result to quite generic axisymmetric spacetimes with CTCs, showing that causal geodesics can't escape the chronologically safe region. As a spin-off of our results, we fill a gap in the identification of all maximally supersymmetric solutions of minimal five dimensional supergravity, bringing this problem to a full conclusion.Comment: LaTeX, 36 pages, 3 figures; v2: added referenc

The Near-Horizon Limit of the Extreme Rotating d=5 Black Hole as a Homogenous 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 in [-1,1], is locally isomorphic to a homogeneous non-symmetric spacetime corresponding to an element of the 1-parameter family of coset spaces SO(2,1)x 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).Comment: Some points clarified and misprints corrected. Version to be published in Classical and Quantum Gravit

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 $AdS,AdS\times S$ and H$pp$-waves) can be easily constructed using purely geometrical and group-theoretical methods. The calculation of the supersymmetry algebras is extremely simple in this formalism.Comment: misprints corrected and references added. Version to appear in Classical and Quantum Gravit

7-Branes and Higher Kaluza-Klein Branes

24 páginas, 1 figura.-- El PDF es la versión pre-print.We present and study a new chain of 10-dimensional T duality related solutions and their 11-dimensional parents whose existence had been predicted in the literature based in U duality requirements in 4 dimensions. The first link in this chain is the S dual of the D7-brane. The next link has 6 spatial worldvolume dimensions, it is charged w.r.t. the RR 7-form but depends only on 2 transverse dimensions since the third has to be compactified in a circle and is isometric and hence is similar in this respect to the KK monopole. The next link has 5 spatial worldvolume dimensions, it is charged w.r.t. the RR 6-form but, again, depends only on 2 transverse dimensions since the third and fourth have to be compactified in circles and are isometric and so on for the following links. All these solutions are identical when reduced over the p spatial worldvolume dimensions and preserve a half on the available supersymmetries. Their masses depend on the square of the radii of the isometric directions, just as it happens for the KK monopole. We give a general map of these branes and their duality relations and show how they must appear in the supersymmetry algebra.The work of E.L.-T. is supported by a U.A.M. grant for postgraduate studies. The work of T.O. is supported by the European Union TMR program FMRX-CT96-0012 Integrability, Non-perturbative Effects, and Symmetry in Quantum Field Theory and by the Spanish grant AEN96-1655.Peer reviewe

Solitons, Vacua and Gauge duals in supergravity

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid. Facultad de Ciencias. Departamento de Física Teórica. Fecha de lectura: 24-01-200

The general, duality-invariant family of non-BPS black-hole solutions of N=4, d=4 Supergravity

16 páginas.-- El PDF es la versión pre-print (IFT-UAM/CSIC-99-32 hep-th/9910020).We present the most general family of stationary point-like solutions of pure N=4, d=4 Supergravity characterized by completely independent electric and magnetic charges, mass, angular momentum and NUT charge plus the asymptotic values of the scalars. It includes, for specific values of the charges, all previously known BPS and non-BPS, extreme and non-extreme black holes and Taub-NUT solutions. As a family of solutions, it is manifestly invariant under T and S duality transformations and exhibits a structure related to the underlying special geometry structure of the theory. Finally, we study briefly the black-hole-type subfamily of metrics and give explicit expressions for their entropy and temperature.The work of E.L.-T. is supported by a U.A.M. grant for postgraduate studies. The work of T.O. is supported by the European Union TMR program FMRX-CT96-0012 Integrability, Non-perturbatiÍe Effects, and Symmetry in Quantum Field Theory and by the Spanish grant AEN96-1655.Peer reviewe