Journal of Lie Theory Vol. 14, No. 1, pp. 199213 (2004) 

$H^4(BK,Z)$ and Operator AlgebrasDoug PickrellDoug PickrellDepartment of Mathematics University of Arizona Tucson, Arizona, 85721 (USA) Pickrell@math.arizona.edu Abstract: 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. Classification (MSC2000): 20J06; 46L10 Full text of the article:
Electronic version published on: 29 Jan 2004. This page was last modified: 1 Sep 2004.
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