The Pukánszky invariant for masas in group von Neumann factors Academic Article uri icon


  • The Pukánszky invariant associates to each maximal abelian self-adjoint subalgebra (masa) A in a type II1factor M a certain subset ot ℕ U {∞}, denoted by Puk(A). We study this invariant in the context of factors generated by infinite conjugacy class discrete countable groups G with masas arising from abelian subgroups H. Our main result is that we are able to describe Puk(V N(H)) in terms of the algebraic structure of H ⊆ G, specifically by examining the double cosets of H in G. We illustrate our characterization by generating many new values for the invariant, mainly for masas in the hyperfinite type II1factor R. © 2005 University of Illinois.

author list (cited authors)

  • Sinclair, A. M., & Smith, R. R.

citation count

  • 6

publication date

  • April 2005