classifiction of von Neumann algebras

86 Views Asked by At

We can classify von Neumann algebras into semi-finite von Neumann algebras and non-semi-finite ones.

I know the fact there are type I,II,III von Neumann algebras.

Do there exist relationships between semi-finiteness and three types?

1

There are 1 best solutions below

2
On BEST ANSWER

Yes. Types I and II are semi-finite, and III are not. Semi-finiteness is equivalent to having a tracial weight, which can never happen in type III.

Never forget that a von Neumann algebra is not necessarily of one of the three types. Rather, it has central summands (or even, central integrands if the algebra is a direct integral) of some of the three types.