## Research in the Particle Theory group

The theory of strings presents various dual (equivalent) descriptions. Some of these dualities are familiar to physicists working on different aspects of quantum field theory, but others are inherent to a theory of extended objects, like string theory. T-duality and its non-Abelian relatives are examples of this.

Whilst the workings of T-duality are well understood in all orders of string perturbation theory and for any order in the worldsheet (alpha') expansion, the situation is not so clear for non-Abelian T-duality. Indeed, while this is a well defined symmetry operation for spherical world-sheets, it is probably broken by the genus expansion. Performing precise calculations to sort out these limitations becomes a technical obstacle.

This calls for another approach. The one we pioneered is based on the study of the quantum field theories associated with a given string background before and after the non-Abelian T-dual operation is performed. The study of the dual quantum theories then illuminates various aspects of the string background, like periodicities of dual coordinates, absence of singularities, conserved charges, etc.

In a different vein, we are using the new solutions to the string equations of motion, obtained by the operation of non-Abelian T-duality, as a way to define new quantum field theories. Formal aspects of geometry, known as G-structures, get entangled with well known Physics concepts such as confinement, symmetry breaking, etc. This line of research provides a very new way of tackling old unresolved problems.