Conformal Field Theory

The quantisation of two-dimensional models with boundaries has important applications to the study of D-branes in superstring theory. This technique is actively studied in our work, with the aim of exploring interesting non-trivial D-brane configurations, which have important applications. The successful description of flat D-branes in string theory as simple boundary conditions is far from sufficient to capture some of the recently discovered dynamics of branes which have arisen in physically important situations. Branes can wrap surfaces, intersect other branes, or expand into branes of higher dimension. These exotic behaviours need a more complete description than is currently available, and development of CFT techniques is a fruitful path to this goal. This is crucial, since these phenomena help furnish dual descriptions of strongly coupled quantum field theory dynamics.

The study of tachyon condensation in string theory is an important approach to the crucial question of the construction of non-BPS vacua in string and field theory. This is equivalent to an analysis of worldsheet renormalisation induced by boundary perturbations. In particular, the D-brane tension has been identified with the g-function of Affleck and Ludwig; we are studying this using non-perturbative techniques related to the Bethe ansatz. 2D boundary models also govern a large family of "brane world" scenarios (see the discussion in the cosmology section). We shall seek generalisations of this discovery which incorporate intersecting branes, where the resulting equations are expected to be Toda-like systems, which are also of considerable interest in their own right. Schrodinger functional methods are applications of boundary field theory, and will be used to model the ground state of QCD.