Mappings Into Loop Spaces and Central Group Extensions.
We prove that the mass endomorphism associated to the Dirac operator on a Riemannian manifold is non-zero for generic Riemannian metrics. The proof involves a study of the mass endomorphism under surgery, its behavior near metrics with harmonic spinors, and analytic perturbation arguments.
This note is based on a theorem of Sacksteder which generalizes a classical result of Denjoy. Using this theorem and results on the existence of invariant measures, new results are obtained concerning minimal sets for groups of diffeomorphisms of the circle and for foliations of codimension one.
We summarize here the main ideas and results of our papers [28], [14], as presented at the 2013 CIRM Meeting on Discrete curvature and we augment these by bringing up an application of one of our main results, namely to solving a problem regarding cube complexes.