Lectures from the European RTN Winter School on Strings, Supergravity and Gauge Theories, CERN, 21–25 January 2008

Abstract

This special issue is devoted to the proceedings of the conference'RTN Winter School on Strings, Supergravity and Gauge Theories', whichtook place at CERN, the European Centre for Nuclear Research, inGeneva, Switzerland, on the 21–25 January 2008.This event was organized in the framework of the European MobilityResearch and Training Network entitled 'Constituents, FundamentalForces and Symmetries of the Universe'. It is part of a yearly seriesof scientific schools, which represents what is by now a well establishedtradition. The previous ones have been held at SISSA, in Trieste, Italy, in February 2005 and at CERN in January 2006. The next one will again take place at CERN, in February 2009.The school was primarily meant for young doctoral students andpostdoctoral researchers working in the area of string theory.It consisted of several general lectures of four hours each, whosenotes are published in the present proceedings, and five workinggroup discussion sessions, focused on specific topics of the networkresearch program. It was attended by approximatively 250 participants.The topics of the lectures were chosen to provide an introduction to someof the areas of recent progress, and to the open problems, in string theory.One of the most active areas in string theory in recent years is the AdS/CFT or gauge/gravity correspondence, which proposes the complete equivalence of string theory on (asymptotically) anti-de Sitter spacetimes with gauge theories. The duality relates the weak coupling regime of one system to the strongly coupled regime of the other, and is therefore very non-trivial to test beyond the supersymmetry-protected BPS sector. One of the key ideas to quantitatively match several quantities on both sides is the use of integrability, both in the gauge theory and the string side. The lecture notes by Nick Dorey provide a pedagogical introduction to the fascinating topic of integrability in AdS/CFT. On the string theory side, progress has been limited by the difficulties of quantizing the worldsheet theory in the presence of RR backgrounds. There is increasing hope that these difficulties can be overcome, using the pure spinor formulation of string theory. The lectures by Yaron Oz overview the present status of this proposal.The gauge/gravity correspondence is already leading to important insights into questions of quantum gravity, like the entropy of black holes and its interpretation in terms of microstates. These questions can be addressed in string theory, for certain classes of supersymmetric black holes. The lectures by Vijay Balasubramanian, Jan de Boer, Sheer El-Showk and Ilies Messamah review recent progress in this direction.Throughout the years, formal developments in string theory have systematically led to improved understanding on how it may relate to nature. In this respect, the lectures by Henning Samtleben describe how the formal developments on gauged supergravities can be used to describe compactification vacua in string theory, and their implications for moduli stabilization and supersymmetry breaking. Indeed, softly broken supersymmetry is one of the leading proposals to describe particle physics at the TeV energy range, as described in the lectures by Gian Giudice (not covered in this issue).This connection with TeV scale physics is most appropriate and timely, given that this energy range will shortly become experimentally accessible in the LHC at CERN.The conference was financially supported by the European Commissionunder contract MRTN-CT-2004-005104 and by CERN. It was jointly organized by the Physics Institute of the University of Neuchâtel andthe Theory Unit of the Physics Division of CERN.It is a great pleasure for us to warmly thank the Theory Unit of CERN for its very kind hospitality and for the high quality of the assistanceand the infrastructure that it has provided. We also acknowledgehelpful administrative assistance from the Physics Institute of theUniversity of Neuchâtel. Special thanks also go to Denis Frank,for his very valuable help in preparing the conference web pages.