Secondary invariants for string cobordism and tmf

Zusammenfassung

Using spectral invariants of Dirac operators we construct a secondary version
of the Witten genus, namely a bordism invariant of string manifolds in dimensions
4m−1. We prove a secondary index theorem which relates this global-analytic construction
with its homotopy-theoretic analog. The latter will be calculated through
its factorization over topological modular forms.