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Subtag of the [oa.operator-algebras] tag for questions about von Neumann algebras, that is, weak operator topology closed, unital, *-subalgebras of bounded operators on a Hilbert space.

3 votes
0 answers
136 views

"Adding" a projection to a von Neumann algebra

This is a question about what happens when you "add" a new projection $p$ to a von Neumann algebra $\mathcal{R}$ to generate a larger v.N. algebra $(\mathcal{R} \cup \{p\})''$. Suppose that $\mathcal …
Doug McLellan's user avatar
3 votes
0 answers
158 views

Given non-type-I subfactors $R \subset S$, must $S$ have a projection that meets no projecti...

Let $R \subset S$ be distinct non-type-I von Neumann factors; say two projections $P, Q \in S$ "meet" if they have a common non-null subprojection (i.e. if $P \wedge Q \neq 0$), and call $P$ "$R$-disj …
Doug McLellan's user avatar
3 votes
0 answers
148 views

Whether a projection can "overlap" certain projections yet not commute with them

Question here about how the projections of a von Neumann algebra $\mathcal{R}$ might be arranged, relative to a projection that is not in $\mathcal{R}$. Stipulate the following:     $H$ is a Hilbert …
Doug McLellan's user avatar
3 votes
1 answer
237 views

How much of a factor's structure is determined by the order-type of its projection lattice?

H. A. Dye showed that a type II or III factor $R$ is determined, up to *-algebraic isomorphism or anti-isomorphism, by the ortholattice-isomorphism type of its projection lattice ("ortholattice-isomor …
Doug McLellan's user avatar
5 votes
1 answer
158 views

Does every non-type-I factor's projection lattice admit a dense embedding of the standard co...

Let $R$ be a non-type-I factor acting on a separable Hilbert space. Let $P(R)$ be the set of $R$'s projections with the usual ordering ($x \leq y \iff$ range$(x) \subseteq$ range$(y)$) under which it …
Doug McLellan's user avatar
1 vote

Does every non-type-I factor's projection lattice admit a dense embedding of the standard co...

I believe I've shown (see answer to related stackoverflow question at https://math.stackexchange.com/a/4223869/250373 ) that there is such an embedding, on the supposition that every nontrivial lattic …
Doug McLellan's user avatar