Tomas Ortin

Duality in the type-II superstring effective action

Abstract We derive the T -duality transformations that transform a general d = 10 solution of the type-IIA string with one isometry to a solution of the type-IIB string with one isometry and vice versa. In contrast to other superstring theories, the T -duality transformations are not related to a non-compact symmetry of a d = 9 supergravity theory. We also discuss S -duality in d = 9 and d = 10 and the relationship with eleven-dimensional supergravity theory. We apply these dualities to generate new solutions of the type-11A and type-IIB superstrings and of eleven-dimensional supergravity.

κ-symmetry, supersymmetry and intersecting branes

We present a new form of κ-symmetry transformations for D-branes in which the dependence on the Born-Infeld field strength is expressed as a relative rotation on the left- and right-moving fields with opposite parameters. Then, we apply this result to investigate the supersymmetry preserved by certain intersecting brane configurations at arbitrary angles and with non-vanishing constant Born-Infeld fields. We also comment on the covariant quantization of the D-brane actions.

An Sl(2, Z) multiplet of nine-dimensional type II supergravity theories

Abstract We show that only by performing generalized dimensional reductions all possible brane configurations are taken into account and one gets the complete lower-dimensional theory. We apply this idea to the reduction of type IIB supergravity in an SL (2, Z)-covariant way and establish T -duality for the type II superstring effective action in the context of generalized dimensional reduction giving the corresponding generalized Buschers T -duality rules. The full (generalized) dimensional reduction involves all the S -duals of D7-branes: Q7-branes and a sort of composite 7-branes. The three species constitute an SL (2, Z) triplet. Their presence induces the appearance of the triplet of masses of the 9-dimensional theory. The T -duals, including a “KK-8A-brane”, which must have a compact transverse dimension have to be considered in the type IIA side. Compactification of 11-dimensional KK-9M-branes (a.k.a. M9-branes) on the compact transverse dimension give D8-branes while compactification on a world-volume dimension gives KK-8A-branes. The presence of these KK-monopole-type objects breaks translation invariance and two of them given rise to an SL (2, Z)-covariant massive 11-dimensional supergravity whose reduction gives the massive 9-dimensional type II theories.

The supersymmetric configurations of N = 2, d = 4 supergravity coupled to vector supermultiplets

We classify all the supersymmetric configurations of ungauged N = 2, d = 4 supergravity coupled to n vector multiplets and determine under which conditions they are also classical solutions of the equations of motion. The supersymmetric configurations fall into two classes, depending on the timelike or null nature of the Killing vector constructed from Killing spinor bilinears. The timelike class configurations are ∗ ] ,

Kaluza-Klein Monopoles and Gauged Sigma Models

Abstract We propose an effective action for the eleven-dimensional (bosonic) Kaluza-Klein monopole solution. The construction of the action requires that the background fields admit an Abelian isometry group. The corresponding sigma-model is gauged with respect to this isometry. The gauged sigma-model is the source for the monopole solution. A direct (double) dimensional reduction of the action leads to the effective action of a 10-dimensional D-6-brane (IIA Kaluza-Klein monopole). We also show that the effective action of the 10-dimensional heterotic Kaluza-Klein monopole (which is a truncation of the IIA monopole action) is T-dual to the effective action of the solitonic 5-brane. We briefly discuss the kappa-symmetric extension of our proposal and the possible role of gauged sigma-models in connection with the conjectured M-theory 9-brane.

Non-extremal black holes of N = 2, d = 4 supergravity

We propose a generic recipe for deforming extremal black holes into non-extremal black holes and we use it to find and study the static non-extremal black-hole solutions of several N = 2, d = 4 supergravity models

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

\left( {{{{{\text{SL}}\left( {2,\mathbb{R}} \right)}} \left/ {{{\text{U}}(1)}} \right.}} \right.

S duality and dyonic p-brane solutions in type II string theory

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All the supersymmetric solutions of N = 1, d = 5 ungauged supergravity

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Seven-branes and supersymmetry

and STU with four charges). In all the cases considered, the non-extremal family of solutions smoothly interpolates between all the different extremal limits, supersymmetric and not supersymmetric. This fact can be used to explicitly find extremal non-supersymmetric solutions also in the cases in which the attractor mechanism does not completely fix the values of the scalars on the event horizon and they still depend on the boundary conditions at spatial infinity.We compare (supersymmetry) Bogomol’nyi bounds with extremality bounds, we find the first-order flow equations for the non-extremal solutions and the corresponding super-potential, which gives in the different extremal limits different superpotentials for extremal black holes. We also compute the entropies (areas) of the inner (Cauchy) and outer (event) horizons, finding in all cases that their product gives the square of the moduli-independent entropy of the extremal solution with the same electric and magnetic charges.