R-Symmetry, twisted N=2 Theory and the Role of the Dilaton

We discuss R-symmetry in locally supersymmetric $N=2$ gauge theories coupled to hypermultiplets, which can be viewed as effective theories of heterotic string models. In this type of supergravities a suitable R-symmetry exists and can be used to topologically twist the theory. The vector multiplet of the dilaton-axion field has a different R-charge assignment with respect to the other vector multiplets.Comment: Proceedings of ``Susy95'', Palaiseaux, Ecole Polytechnique, May 95 LaTex, 8 pg

N=1 and N=2 pure supergravities on a manifold with boundary

Working in the geometric approach, we construct the lagrangians of N=1 and N=2 pure supergravity in four dimensions with negative cosmological constant, in the presence of a non trivial boundary of space-time. We find that the supersymmetry invariance of the action requires the addition of topological terms which generalize at the supersymmetric level the Gauss-Bonnet term. Supersymmetry invariance is achieved without requiring Dirichlet boundary conditions on the fields at the boundary, rather we find that the boundary values of the fieldstrengths are dynamically fixed to constant values in terms of the cosmological constant \Lambda. From a group-theoretical point of view this means in particular the vanishing of the OSp(N|4)-supercurvatures at the boundary.Comment: Some clarifications on the N=1 case, typos correcte

BPS Black Holes in Superegravity

In these lectures we explain the concept of supergravity p-branes and BPS black holes. Introducing an audience of general relativists to all the necessary geometry related with extended supergravity (special geometry, symplectic embeddings and the like) we describe the general properties of N=2 black holes, the structure of central charges in extended supergravity and the description of black hole entropy as an invariant of the U duality group. Then, after explaining the concept and the use of solvable Lie algebras we present the detailed construction of 1/2, 1/4 and 1/8 supersymmetry preserving black holes in the context of N=8 supergravity. The Lectures are meant to be introductory and self contained for non supersymmetry experts but at the same time fully detailed and complete on the subject.Comment: LaTeX, 132 pages, Book.sty. Lecture Notes for the SIGRAV Graduate School in Contemporary Relativity, Villa Olmo, Como First Course, April 199

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

N=(4,2) Chiral Supergravity in Six Dimensions and Solvable Lie Algebras

Decomposition of the solvable Lie algebras of maximal supergravities in D=4, 5 and 6 indicates, at least at the geometrical level, the existence of an N=(4,2) chiral supergravity theory in D=6 dimensions. This theory, with 24 supercharges, reduces to the known N=6 supergravity after a toroidal compactification to D=5 and D=4. Evidence for this theory was given long ago by B. Julia. We show that this theory suffers from a gravitational anomaly equal to 4/7 of the pure N=(4,0) supergravity anomaly. However, unlike the latter, the absence of N=(4,2) matter to cancel the anomaly presumably makes this theory inconsistent. We discuss the obstruction in defining this theory in D=6, starting from an N=6 five-dimensional string model in the decompactification limit. The set of massless states necessary for the anomaly cancellation appears in this limit; as a result the N=(4,2) supergravity in D=6 is extended to N=(4,4) maximal supergravity theory.Comment: 15 pages, latex, no figure

D=4, N=2 Supergravity in the Presence of Vector-Tensor Multiplets and the Role of higher p-forms in the Framework of Free Differential Algebras

We thoroughly analyze at the bosonic level, in the framework of Free Differential Algebras (FDA), the role of 2-form potentials setting in particular evidence the precise geometric formulation of the anti-Higgs mechanism giving mass to the tensors. We then construct the (super)-FDA encoding the coupling of vector-tensor multiplets in D=4, N=2 supergravity, by solving the Bianchi identities in superspace and thus retrieving the full theory up to 3-fermions terms in the supersymmetry transformation laws, leaving the explicit construction of the Lagrangian to future work. We further explore the extension of the bosonic FDA in the presence of higher p-form potentials, focussing our attention to the particular case p=3, which would occur in the construction of D=5, N=2 supergravity where some of the scalars are properly dualized.Comment: 39 pages, improved introduction, section 4 and Appendices modified, typos corrected, citations adde

Observations on the Partial Breaking of N=2N=2 Rigid Supersymmetry

We study the partial breaking of $N=2$ rigid supersymmetry for a generic rigid special geometry of $n$ abelian vector multiplets in the presence of Fayet-Iliopoulos terms induced by the Hyper-K\"ahler momentum map. By exhibiting the symplectic structure of the problem we give invariant conditions for the breaking to occur, which rely on a quartic invariant of the Fayet-Iliopoulos charges as well as on a modification of the $N=2$ rigid symmetry algebra by a vector central charge.Comment: 7 pages, LaTeX sourc

C-map for Born-Infeld theories

The c-map of four dimensional non-linear theories of electromagnetism is considered both in the rigid case and in its coupling to gravity. In this way theories with antisymmetric tensors and scalars are obtained, and the three non-linear representations of N=2 supersymmetry partially broken to N=1 related. The manifest $\mathrm{Sp}(2n)$ and $\mathrm{U}(n)$ covariance of these theories in their multifield extensions is also exhibited.Comment: Version to appear on Physics Letters