One of the aspects of the noncommutative index theory is the
Baum-Connes conjecture, an outstanding open
problem in the K-theory of the convolution C*-algebras of locally
compact groups. It asserts that a certain index map whose receptacle are
the K-groups of the convolution C*-algebras is an isomorphism. If true,
it provides a mean of computing the aforementioned K-groups, and entails
other consequences. Recently, the conjecture was proved for a large class
of locally compact groups though counterexamples were found to a more general
version of the conjecture (e.g., V.Lafforgue).
A possible direction for further exploration is
to extend the conjecture to cover locally compact quantum groups.
Syllabus:
convolution C*-algebra of a locally compact group,
proper actions of locally compact groups, universal spaces for proper actions
(axiomatic and constructive approach), Kasparov KK-theory, assembly map,
Peter-Weyl theory and proof of the conjecture for compact groups,
generalized versions of the conjecture, categories of examples where the
conjecture
holds (e.g., amenable groupoids) and counterexamples to the generalized
conjecture, important implications of the conjecture.