Dual Gauged Supergravities

We shall review a novel formulation of four dimensional gauged supergravity which is manifestly covariant with respect to the non-perturbative electric-magnetic duality symmetry transformations of the ungauged theory, at the level of the equations of motion and Bianchi identities. We shall also discuss the application of this formalism to the description of M-theory compactified on a twisted torus in the presence of fluxes and to the interpretation from a M/Type IIA theory perspective of the D=5 --> D=4 generalized Scherk-Schwarz reduction. This latter analysis will bring up the issue of non-geometric fluxes.Comment: 31 pages, LaTeX file, typo in formula (70) of the Appendix corrected, references update

On Extremal Limits and Duality Orbits of Stationary Black Holes

With reference to the effective three-dimensional description of stationary, single center solutions to (ungauged) symmetric supergravities, we complete a previous analysis on the definition of a general geometrical mechanism for connecting global symmetry orbits (duality orbits) of non-extremal solutions to those of extremal black holes. We focus our attention on a generic representative of these orbits, providing its explicit description in terms of D=4 fields. As a byproduct, using a new characterization of the angular momentum in terms of quantities intrinsic to the geometry of the D=3 effective model, we are able to prove on general grounds its invariance, as a function of the boundary data, under the D=4 global symmetry. In the extremal under-rotating limit it becomes moduli-independent. We also discuss the issue of the fifth parameter characterizing the four-dimensional seed solution, showing that it can be generated by a transformation in the global symmetry group which is manifest in the D=3 effective description.Comment: 24 pages, LaTeX source, typos corrected, expressions for the entropy of the non-extremal solutions adde

On the dualization of Born-Infeld theories

We construct a general Lagrangian, quadratic in the field strengths of $n$ abelian gauge fields, which interpolates between BI actions of n abelian vectors and actions, quadratic in the vector field-strengths, describing Maxwell fields coupled to non-dynamical scalars, in which the electric-magnetic duality symmetry is manifest. Depending on the choice of the parameters in the Lagrangian, the resulting BI actions may be inequivalent, exhibiting different duality groups. In particular we find, in our general setting, for different choices of the parameters, a ${\rm U}(n)$-invariant BI action, possibly related to the one in \cite{Aschieri:2008ns}, as well as the recently found $\mathcal{N}=2$ supersymmetric BI action \cite{Ferrara:2014oka}.Comment: 12 pages, LaTeX source, typos corrected, definition of the matrix S in eq. (3.22) correcte

Fluxes, supersymmetry breaking and gauged supergravity

We report on the gauged supergravity interpretation of certain compactifications of superstring theories with p-form fluxes turned on. We discuss in particular the interplay of duality symmetries in type IIB orientifolds and gauged isometries in the corresponding supergravity models. Turning on fluxes is generally described by the gauging of some nilpotent Lie group whose generators correspond to axion symmetries of R-R and N-S scalars.Comment: Contribution to the proceedings of ``Sugra20'' Conference, Department of Physics, Northeastern University, Boston (Ma) 02115 USA; March 200

Axion Wormholes in AdS Compactifications

We find regular axionic Euclidean wormhole solutions in Type IIB string theory compactified on $\text{AdS}_5\times \text{S}^5/\mathbb{Z}_k$. AdS/CFT enables a precise derivation of the axion content of the Euclidean theory, placing the string theory embedding of the wormholes on firm footing. This further sharpens the paradox posed by these solutions.Comment: 11 page

Stable de Sitter Vacua from N=2 Supergravity

We find extrema of the potential of matter couplings to N=2 supergravity that define de Sitter vacua and no tachyonic modes. There are three essential ingredients in our construction: namely non-abelian non-compact gaugings, de Roo-Wagemans rotation angles, and Fayet-Iliopoulos terms.Comment: 30 pages, 1 figure; v2: Added reference, and typos corrected. Version to be published in CQ

The maximal D=5 supergravities

The general Lagrangian for maximal supergravity in five spacetime dimensions is presented with vector potentials in the \bar{27} and tensor fields in the 27 representation of E_6. This novel tensor-vector system is subject to an intricate set of gauge transformations, describing 3(27-t) massless helicity degrees of freedom for the vector fields and 3t massive spin degrees of freedom for the tensor fields, where the (even) value of t depends on the gauging. The kinetic term of the tensor fields is accompanied by a unique Chern-Simons coupling which involves both vector and tensor fields. The Lagrangians are completely encoded in terms of the embedding tensor which defines the E_6 subgroup that is gauged by the vectors. The embedding tensor is subject to two constraints which ensure the consistency of the combined vector-tensor gauge transformations and the supersymmetry of the full Lagrangian. This new formulation encompasses all possible gaugings.Comment: 36 pages, LaTeX2e; v2: minor changes, version published in NP

Gauging Maximal Supergravities

We review recent progress in gauging maximal supergravity theoriesComment: LateX file, needs fortschritte.st