The AdS/QCD correspondence and the holographic models of the scalar sector of QCD

by Frédéric JUGEAU (IHEP)

Thursday 19 Nov 2009, 14:00 → 15:00 Europe/Zurich

1/1-025 (CERN)

't Hooft's works showed that the gauge theories within the large N limit, when the planar diagrams dominate the perturbative expansions, can be described according to a formalism peculiar to the string theories. In 1998, J.M. Maldacena identified such a relation precisely: the AdS/CFT correspondence which postulates a duality between, on the one hand, the 't Hooft limit of a four-dimensional Yang-Mills theory superconformal and strongly-coupled and, on the other hand, the supergravity limit of a weakly-coupled string theory defined in a five-dimensional anti-de Sitter space-time. However, strictly speaking, this correspondence cannot be applied to a confining gauge theory such as QCD since it is neither supersymmetric nor conformal. The AdS/QCD approach seeks nevertheless to identify the gravity theory dual to QCD. Among the various weakly-coupled holographic models able to describe the non-perturbative regime of QCD, I will discuss to a large extent the so-called Hard-Wall and Soft-Wall models which, for the latter, succeeds in reproducing the linear Regge trajectories of mesons. Especially, I will be interested in the scalar sector of QCD which will then lead me to discuss the holographic descriptions of the spontaneous chiral symmetry breaking in both models.