The Holographic RG flow to conformal and non-conformal theory

We review some aspects of the AdS supergravity description of RG flows. The case of a flow to an IR CFT can be rigorously studied within the framework of supergravity. Here we discuss various central charges of the conformal theory (included the usually neglected ones) and we compare them with QFT expectations. The case of flows to non-conformal theories is more problematic in that one usually encounters a naked singularity. We mainly focus on the flow to an IR N=1 super Yang-Mills theory. We discuss the properties of the solution and we briefly comment on the fate of the singularity. We also compare the supergravity results with the expectations of an N=1 SYM at strong coupling.Comment: LaTex,13 pages, 3 embedded eps figures, minor changes.Contribution to the proceedings of the TMR Conference on Quantum Aspects of Gauge Theories, Supersymmetry and Unification, Paris, 1-7 September 199

Comments on the Holographic Picture of the Randall-Sundrum Model

We discuss some issues about the holographic interpretation of the compact Randall-Sundrum model, which is conjectured to be dual to a 4d field theory with non-linearly realized conformal symmetry. We make several checks of this conjecture. In particular, we show that the radion couples conformally to a background 4d metric. We also discuss the interpretation of the Goldberger-Wise mechanism for stabilizing the radion. We consider situations where the electroweak breaking stabilizes the radion and we discuss the issue of natural conservation of flavor quantum numbers.Comment: misprints corrected, references adde

Superconformal Field Theories, Multiplet Shortening, and the AdS5_5/SCFT4_4 Correspondence

We review the unitarity bounds and the multiplet shortening of UIR's of 4 dimensional superconformal algebras $SU(2,2|N)$, ($N=1,2,4$) in view of their dual role in the AdS/SCFT correspondence. Some applications to KK spectra, non-perturbative states and stringy states are given.Comment: minor changes, references adde

Bulk Gauge Fields in AdS Supergravity and Supersingletons

We describe conformal operators living at the boundary of $AdS_{d+1}$ in a general setting. Primary conformal operators at the threshold of the unitarity bounds of UIR's of O(d,2) correspond to singletons and massless fields in $AdS_{d+1}$, respectively. For maximal supersymmetric theories in $AdS_{d+1}$ we describe ``chiral'' primary short supermultiplets and non-chiral primary long supermultiplets. Examples are exhibited which correspond to KK and string states. We give the general contribution of a primary conformal operator to the OPE and Green's functions of primary fields, which may be relevant to compute string corrections to the four-point supergraviton amplitude in Anti-de-Sitter space. The material in this paper was presented by one of the authors (S.F) at String 98, Santa Barbara.Comment: 16 pages, harvmac, String 98 on-line proceeding

N=2 Gauge Theories from Wrapped Five-branes

We present string duals of four dimensional N=2 pure SU(N) SYM theory. The theory is obtained as the low energy limit of D5-branes wrapped on non-trivial two-cycles. Using seven dimensional gauged supergravity and uplifting the result to ten dimensions, we obtain solutions corresponding to various points of the N=2 moduli space. The more symmetric solution may correspond to a point with rotationally invariant classical vevs. By turning on seven dimensional scalar fields, we find a solution corresponding to a linear distribution of vevs. Both solutions are conveniently studied with a D5-probe, which also confirms many of the standard expectations for N=2 solutions.Comment: 11 pages, LateX. Revised versio

N=6 Supergravity on AdS5AdS_5 and the SU(2,2/3)SU(2,2/3) Superconformal Correspondence

It is argued that N=6 supergravity on $AdS_5$, with gauge group $SU(3)\times U(1)$ corresponds, at the classical level, to a subsector of the ``chiral'' primary operators of N=4 Yang-Mills theories. This projection involves a ``duality transformation'' of N=4 Yang-Mills theory and therefore can be valid if the coupling is at a self-dual point, or for those amplitudes that do not depend on the coupling constant.Comment: 9 pages, late

The Fate of the Radion in Models with Metastable Graviton

We clarify some general issues in models where gravity is localized at intermediate distances. We introduce the radion mode, which is usually neglected, and we point out that its role in the model is crucial. We show that the brane bending effects discussed in the literature can be obtained in a formalism where the physical origin is manifest. The model violates positivity of energy due to a negative tension brane, which induces a negative kinetic term for the radion. The very same effect that violates positivity is responsible for the recovery of conventional Einstein gravity at intermediate distances.Comment: Latex file, 13 page

Heterotic-Type II String Duality and the H-Monopole Problem

Since T-duality has been proved only perturbatively and most of the heterotic states map into solitonic, non-perturbative, type II states, the 6-dimensional string-string duality between the heterotic string and the type II string is not sufficient to prove the S-duality of the former, in terms of the known T-duality of the latter. We nevertheless show in detail that perturbative T-duality, together with the heterotic-type II duality, does imply the existence of heterotic H-monopoles, with the correct multiplicity and multiplet structure. This construction is valid at a generic point in the moduli space of heterotic toroidal compactifications.Comment: 12 pages, plain Late