Title: Equivariant KK-theory for groupoid actions and C*-extensions

Abstract: Pierre Yves Le Gall introduced an equivariant KK-theory for
C*-algebras acted upon by groupoids. It generalizes the RKK-theory of Gennadi
Kasparov and was used for proving some cases of Novikov and Baum-Connes
conjectures. We give a description of this theory using equivariant extensions
of C*-algebras. The talk reports on some joint work with Radu Popescu.