Remarks on conditional expectations in von Neumann algebra

Expectations in Von Neumann Algebras

A Counterexample in Von Neumann Algebra Dynamics

In this essay we construct a noncommutative von Neumann dynamical system with certain pathological properties from the viewpoint of analogies with classical ergodic theory. These relate to obstructions to the existence of special kinds of subsystem or subextension. We will build our example as an extension of a commutative dynamical system via a unitary cocycle acting on a Hilbert bundle, and w...

Remarks on Complemented Subspaces of Von-neumann Algebras*

In this note we include two remarks about bounded (not necessarily contractive) linear projections on a von Neumann-algebra. We show that if M is a von Neumann-subalgebra of B(H) which is complemented in B(H) and isomorphic to M ⊗ M then M is injective (or equivalently M is contractively complemented). We do not know how to get rid of the second assumption on M. In the second part,we show that ...

A Note on Faithful Traces on a Von Neumann Algebra

It is known that a semifinite von Neumann algebra always has a faithful semifinite trace. This trace can be used, for instance, to build up a non-commutative integration and, consequently, to define non commutative L-spaces. In this note we give some techniques for constructing, starting from a family F of semifinite traces, a faithful one which is closely related to the family F. Let F = {ηα; ...

Von Neumann Algebra of Baumslag Group Embeds

In this paper we analyze the structure of some sets of non-commutative moments of elements in a finite von Neumann algebra M . If the fundamental group of M is R+\{0}, then the moment sets are convex, and if M is isomorphic to M ⊗M , then the sets are closed under pointwise multiplication. We introduce a class of discrete groups that we call hyperlinear. These are the discrete subgroups (with i...