Lachlan MacDonald
(University of Adelaide )
June 21, 2021
Organized by Asia-Pacific GNCG Seminar.

Chern-Weil theory for singular foliations

 Chern-Weil theory describes a procedure for constructing the characteristic classes of a smooth manifold from geometric data (such as a Riemannian metric).  In the 1970s and 1980s, Chern-Weil theory was successfully adapted by R. Bott to describe the characteristic classes of the leaf space of any regular foliation, including the so-called secondary classes such as the Godbillon-Vey invariant.  As discovered by Connes and Moscovici, these characteristic classes also play a key role in noncommutative geometry, where they define cyclic cocycles that pair with the K-theory of the noncommutative leaf space.  The extension of Chern-Weil theory to singular foliations has, however, remained elusive.  In this talk, I will describe recent, joint work with Benjamin McMillan which gives a Chern-Weil homomorphism for a family of singular foliations whose singularities are not “too big”.

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