## Research in the Particle Theory group

A useful and important framework for studying non-perturbative gauge dynamics is to approximate QCD, which is based on SU(3) gauge group, by a different gauge group SU(N). It turns out that when N is large (or infinite) the dynamics becomes simpler. Moreover, in certain cases the large-N gauge theory is dual to a simple (non-interacting) string theory. A complex calculation in the gauge theory can become very simple by using the string dual.

An important conceptual problem in fundamental theoretical particle physics and string theory is to extend gauge-gravity duality to systems with little or no supersymmetry and more phenomenologically relevant matter content. Here we work on the systematic classification of minimally SUSY string geometries and possible matter sources and particularly on set-ups that have well-behaved UV behaviour. We also investigate how different observables in a quantum field theory change when the associated string background is transformed by a non-Abelian T-duality. The interplay between other dualities like S-duality and the non-Abelian T-dual transformations is part of our investigations.

We apply other field theory techniques to the study of various properties of large-N strongly coupled theories and have e.g. studied the tension of domain walls, and their stability, to test the orientifold large-N equivalence between classes of strongly-coupled theories. We are interested in establishing a non-supersymmetric version of Seiberg duality for a particular class of models, by using a special brane configuration in type IIA string theory. By constructing novel brane configurations we can study the relation between monopole condensation, confinement and chiral symmetry breaking and reconstruct the chiral Lagrangian of QCD.