Supergravity and the quest for a unified theory

A recollection of some theoretical developments that preceded and followed the first formulation of supergravity theory is presented. Special emphasis is placed on the impact of supergravity on the search for a unified theory of fundamental interactions.Comment: 15 pages, late

Duality, Strings and Supergravity: a Status Report

We will report on recent advances in the understanding of non-perturbative interconnections between different string dualities. Weak-strong coupling duality (S-duality) and T-duality (symmetry under compactification on dual tori) allows one to compare and explore the strong coupling regime of seemingly unrelated theories. These theories naturally merge in a quantum version of supergravity called M-theory. The dynamical role of `branes' of different nature and the new dynamical tool of (M)atrix formulation of M-theory will be briefly mentioned.Comment: 12 pages, LaTeX; Plenary Talk given at the XII International Congress of Mathematical Physics, 13-19 July 1997, Brisbane, Australi

Bertotti-Robinson Geometry and Supersymmetry

The role of Bertotti-Robinson geometry in the attractor mechanism of extremal black holes is described for the case of N = 2 supersymmetry. Its implication for a model-independent derivation of the Bekenstein-Hawking entropy formula is discussed.Comment: 13 pages, figures, uses procsla,epsf,epsfig; Talk given at the 12th Italian Conference on General Relativity and Gravitational Physics, Rome, September 199

Recent developments in non-perturbative quantum field theory

We report on recent advances in the understanding of non-perturbative phenomena in the quantum theory of fields and strings.Comment: 6 pages, latex, uses stwol.sty; Plenary talk given at International Conference on High Energy Physics (ICHEP), Warsaw, July 199

String Phase Transitions in a Strong Magnetic Field

We consider open strings in an external constant magnetic field $H$. For an (infinite) sequence of critical values of $H$ an increasing number of (highest spin component) states lying on the first Regge trajectory becomes tachyonic. In the limit of infinite $H$ all these states are tachyons (with a common tachyonic mass) both in the case of the bosonic string and for the Neveu-Schwarz sector of the fermionic string. This result generalizes to extended object the same instability which occurs in ordinary non-Abelian gauge theories. The Ramond states have always positive square masses as is the case for ordinary QED. The weak field limit of the mass spectrum is the same as for a field theory with gyromagnetic ratio $g_S=2$ for all charged spin states. This behavior suggests a phase transition of the string as it has been argued for the ordinary electroweak theory.Comment: 8 page

Superconformal interpretation of BPS states in AdS geometries

We carry out a general analysis of the representations of the superconformal algebras SU(2,2/N), OSp(8/4,R) and OSp(8^*/4) and give their realization in superspace. We present a construction of their UIR's by multiplication of the different types of massless superfields ("supersingletons"). Particular attention is paid to the so-called "short multiplets". Representations undergoing shortening have "protected dimension" and correspond to BPS states in the dual supergravity theory in anti-de Sitter space. These results are relevant for the classification of multitrace operators in boundary conformally invariant theories as well as for the classification of AdS black holes preserving different fractions of supersymmetry.Comment: The sections on 6 and 3 dimensions considerably extended; important new references added; misprints correcte

Black Holes and Attractors in Supergravity

We discuss some of the basic features of extremal black holes in four-dimensional extended supergravities. Firstly, all regular solutions display an attractor behavior for the scalar field evolution towards the black hole horizon. Secondly, they can be obtained by solving first order flow equations even when they are not supersymmetric, provided one identifies a suitable superpotential W which also gives the black hole entropy at the horizon and its ADM mass at spatial infinity. We focus on N=8 supergravity and we review the basic role played by U-duality of the underlying supergravity in determining the attractors, their entropies, their masses and in classifying both regular and singular extremal black holes.Comment: Contribution to the Proceedings of the Conference in Honor of Murray Gell-Mann's 80th Birthday, Singapore, 24th-26th February 2010 (talk delivered by S. Ferrara); 15 page

Constitutive relations and Schroedinger's formulation of nonlinear electromagnetic theories

We present a systematic study of nonlinear and higher derivatives extensions of electromagnetism. We clarify when action functionals S[F] can be explicitly obtained from arbitrary (not necessarily self-dual) nonlinear equations of motion. We show that the "Deformed twisted self-duality condition" proposal originated in the context of supergravity counterterms is actually the general framework needed to discuss self-dual theories starting from a variational principle. We generalize to nonlinear and higher derivatives theories Schroedinger formulation of Born-Infeld theory, and for the latter, and more in general for nonlinear theories, we derive a closed form expression of the corresponding deformed twisted self-duality conditions. This implies that the hypergeometric expression entering these duality conditions and leading to Born-Infeld theory satisfies a hidden quartic equation.Comment: Revised version with: integrability conditions on equations of motion; equivalence between deformed twisted self-duality conditions and equations of motion from action functionals S[F] (Section 2.5); stressed universality of the quartic equation. References added. 31 pages. To appear in JHE

Conformal primaries of OSp(8/4,R) and BPS states in AdS4

We derive short UIR's of the OSp(8/4,R) superalgebra of 3d N=8 superconformal field theories by the requirement that the highest weight states are annihilated by a subset of the super-Poincare odd generators. We then find a superfield realization of these BPS saturated UIR's as "composite operators" of the two basic ultrashort "supersingleton" multiplets. These representations are the AdS4 analogue of BPS states preserving different fractions of supersymmetry and are therefore suitable to classify perturbative and non-perturbative excitations of M-theory compactifications.Comment: refrences adde

Representations of (1,0) and (2,0) superconformal algebras in six dimensions: massless and short superfields

We construct unitary representations of (1,0) and (2,0) superconformal algebras in six dimensions by using superfields defined on harmonic superspaces with coset manifolds USp(2n)/[U(1)]^n, n=1,2. In the spirit of the AdS_7/CFT_6 correspondence massless conformal fields correspond to "supersingletons" in AdS_7. By tensoring them we produce all short representations corresponding to 1/2 and 1/4 BPS anti-de Sitter bulk states of which "massless bulk" representations are particular cases.Comment: references adde