Maximal Commutative Subalgebras Invariant for CP-Maps: (Counter-)Examples
Abstract
We solve, mainly by counterexamples, many natural questions regarding maximal commutative subalgebras invariant under CP-maps or semigroups of CP-maps on a von Neumann algebra. In particular, we discuss the structure of the generators of norm continuous semigroups on B(G) leaving a maximal commutative subalgebra invariant and show that there exists Markov CP-semigroups on Md without invariant maximal commutative subalgebras for any d>2.
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