Department of Mathematics

Mathematical Physics and Operator Algebras

  •  Rolando de Santiago, Purdue University
  •  Groups, Group Actions, and von Neumann Algebras
  •  04/15/2021
  •  5:00 PM - 5:50 PM
  •  Online (virtual meeting) (Virtual Meeting Link)
  •  Brent Nelson (

Given a group $G$ acting on measure space $(X,\mu)$ Murray and von Neumann’s group-measure space construction describes a von Neumann algebra $L^\infty(X,\mu)\rtimes G $ which encodes both the group, the space and the action. The special case where the space is a singleton and the action is trivial produces the group von Neumann algebra $L(G) $. In this talk, we will aim to describe properties of $L^\infty(X,\mu)\rtimes G $ in terms of the group, the space and the action; compute $L^\infty(X,\mu)\rtimes G $ in special cases; and describe how the group-measure space varies or the group von Neumann algebra varies with $G$. All this serves to illustrate the fundamental problem in this area: von Neumann algebras tend to have poor memory of their generating data. This talk assumes a working knowledge of group theory and linear algebra, and while knowledge of measure theory may be helpful, it is not required.



Department of Mathematics
Michigan State University
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East Lansing, MI 48824

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