Transgression of Bundle Gerbes to Loop Spaces and its Inverse

Brylinski and McLaughlin have introduced a "transgression" functor that takes abelian gerbes with connection over a smooth manifold M to certain principal bundles over the free loop space LM of M. In my talk I will present a characterization of the image of this functor. Then I describe an inverse functor, called "regression", so that an equivalence of geometric categories over M and LM is obtained. It will become clear how the concept of a bundle gerbe fits nicely into this context.