On possible values of the interior angle between intermediate subalgebras

Abstract

We show that all values in the interval $[0,\frac{\pi }{2}]$ can be attained as the interior angle between intermediate subalgebras (as introduced in [3]) of a certain inclusion of simple unital C*-algebras. We also calculate the interior angle between intermediate crossed product subalgebras of any inclusion of crossed product algebras corresponding to any action of a countable discrete group and its subgroups on a unital C*-algebra.

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