split inclusion of von Neumann algebras



The split property for inclusions of von Neumann algebras was first introduced by Detlev Buchholz in the study of the AQFT approach to quantum field theory, but has become a much used concept in the mathematical structure theory as well.


Let M,N be two von Neumann algebras with MN. This inclusion is called split if there is a type I-factor F with

MFNM \subseteq F \subseteq N



The inclusion MN is split iff there exist faithful normal representations π 1 of M, π 2 of N such that the map Φ:MNπ 1(M)π 2(N) given by

Φ(mn):=π 1(m)ϕ 2(n)\Phi(mn') := \pi_1(m) \otimes \phi_2(n')

extends to a spatial isomorphism, the tensor product used here is the spatial tensor product.


Definition 5.4.1 und Lemma 5.4.2 in

  • Wollenberg, Baumgärtel: Causal nets of operator algebras. Mathematical aspects of algebraic quantum field theory.

Created on June 9, 2010 10:46:53 by Tim van Beek (