4D localization in Randall-Sundrum 2 supergravity and in Vasiliev theories

We discuss the problem of localization of 4D massless states in Randall-Sundrum 2 (one-brane) models. A Randall-Sundrum 2 construction starting from N=8 gauged supergravity in 5D anti-de Sitter space gives rise to an N=4 supergravity-matter system. We explicitly show that only the modes of the N=4 graviton supermultiplet localize on the 4D brane, streamlining and generalizing previous works. We also point out that while charged 1/4 BPS black holes do exist in the 4D theory, they are always produced in sets of total charge zero. This zero-charge configuration uplifts to a 5D metric without naked singularities, thus avoiding the curvature singularity of the 5D uplift of an isolated charged BPS black hole. Finally, we resolve a puzzle with localization of massless high spin fields on a (putative) Randall-Sundrum 2 construction based on Vasiliev?s high spin theories. We show that while high spin fields do localize, the gauge symmetry that ensures decoupling of their unphysical polarizations is anomalous. This implies that the high spin fields must acquire a mass.     

Long string dynamics in pure gravity on AdS3

Journal of Experimental and Theoretical Physics - We study the classical dynamics of a completion of pure AdS3 gravity, whose only degrees of freedom are boundary gravitons and long strings. We...     

General Relativity,Strings, and Mathematical Physics

We give a historical review of some aspects of string theory relevant to our present understanding of General Relativity, and connected with Einstein's unification program. We also point out to various mathematical fallouts of string theory.     

Universal conductance correction in a tunable strongly coupled nanogranular metal

We present temperature-dependent conductivity data obtained on a sample set of nanogranular Pt-C with finely tuned intergrain tunnel coupling strength g. For samples in the strong-coupling regime g > g(C), characterized by a finite conductivity for T→0, we find a logarithmic behavior at elevated temperatures and a crossover to a √T behavior at low temperatures over a wide range of coupling strengths g(C) ≈ 0.25 < g ≤ 3. The experimental observation for g > 1 is in very good agreement with recent theoretical findings on ordered granular metals in three spatial dimensions. The results indicate a validity of the predicted universal conductivity behavior that goes beyond the immediate range of the approach used in the theoretical derivation.     

String Theory and the Velo–Zwanziger problem

We examine the behavior of the leading Regge trajectory of the open bosonic string in a uniform electromagnetic background and present a consistent set of Fierz–Pauli conditions for these symmetric tensors that generalizes the Argyres–Nappi spin-2 result. These equations indicate that String Theory does bypass the Velo–Zwanziger problem, i.e. the loss of causality experienced by a massive high-spin field minimally coupled to electromagnetism. Moreover, we provide some evidence that only the first Regge trajectory can be described in isolation and show that the open-string spectrum is free of ghosts in weak constant backgrounds. Finally, we comment on the roles of the critical dimension and of the gyromagnetic ratio.     

A direct proof for the uniqueness of the Susy gauge anomaly

We prove that every form of the SUSY extension of the gauge anomaly differs only by a variation of a local functional of the fields. As a consequence we find that the usual conditions for the cancellation of the gauge anomaly are enough even in the supersymmetric case.