
Journal of Lie Theory 14 (2004), No. 1, 199213 Copyright Heldermann Verlag 2004 H^{4}(BK, Z) and Operator Algebras Doug Pickrell Department of Mathematics, University of Arizona, Tucson, AR 85721, U.S.A., Pickrell@math.arizona.edu There is a wellknown interpretation of group cohomology in terms of (generalized) group extensions. For a connected semisimple compact Lie group K, we prove that the extensions corresponding to classes in H^{4}(BK, Z) can be interpreted in terms of automorphisms of a pair consisting of a type II_{1} von Neumann algebra and a Cartan subalgebra. [ Fulltextpdf (184 KB)] for subscribers only. 