2 problems

Let $f$ be a Lipschitz function on the real line, and let $A$ and $B$ be noncommuting contractions. Recall that for Lipschitz functions of two noncommuting self-adjoint operators t…

A contraction is a bounded operator $A$ with $\\|A\\|\leq 1$. For a function $f$ of three operators, write $f(A,B,C)$ for its functional calculus on a triple of contractions…