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Apr 22'25
[math] \newcommand{\mathds}{\mathbb}[/math]

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Look up and learn von Neumann's reduction theory, stating that given a von Neumann algebra [math]A\subset B(H)[/math], if we write its center as

[[math]] Z(A)=L^\infty(X) [[/math]]

then we have a decomposition as follows, with the fibers [math]A_x[/math] having trivial center,

[[math]] A=\int_XA_x\,dx [[/math]]

and then write down a brief account of what you learned.

Apr 22'25
[math] \newcommand{\mathds}{\mathbb}[/math]

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Given two projections [math]P,Q\in B(H)[/math], with [math]H[/math] being infinite dimensional, find an elementary proof for the fact that we have, for any [math]x\in H[/math],

[[math]] (PQ)^nx\to (P\wedge Q)x [[/math]]

but the operators [math](PQ)^n[/math] do not necessarily converge in norm.

Apr 22'25
[math] \newcommand{\mathds}{\mathbb}[/math]

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Given a commutative von Neumann algebra, written as

[[math]] A=L^\infty(X) [[/math]]

with [math]X[/math] being a measured space, write, by using the Gelfand theorem,

[[math]] A=C(\widehat{X}) [[/math]]

with [math]\widehat{X}[/math] being a compact space, and understand the correspondence [math]X\to\widehat{X}[/math].