BPS Extensions and Gaugings of Supersymmetric Field Theories

Abstract

Supersymmetry has played an important role in theoretical physics for the last thirty years. In the quest for unification of the fundamental interactions, supersymmetry provides the framework that links two seemingly unrelated kinds of particles, namely bosons and fermions. Supersymmetry is a vital ingredient for the construction of string theories, which in turn are the building blocks of a conceived fundamental theory of nature, so-called M-theory.

The fundamental degrees of freedom of M-theory are not yet known. M-theory is only defined as a theory that, in certain limits, coincides with the known string theories or with supergravity theories. In the limit of low-energy interactions, i.e. at energies much smaller than the Planck mass M-theory is described in terms of supersymmetric gauge theories and supergravity theories. In order to find the correct description of M-theory, it is vital to further explore new features of the effective low-energy theories. In this thesis, we study two different extensions of supergravity theories in an attempt to gain new insights into the nature of M-theory. One possibility for extending a supersymmetric field theory is to couple the original, massless theory to massive BPS multiplets. The second possibility is to construct a gauged supergravity theory by extending the abelian gauge symmetry of a supergravity theory to a non-abelian symmetry.