Decomposition of unbounded derivations into invariant and approximately inner parts.
Decompositions of Beurling type for E₀-semigroups
We define tensor product decompositions of E₀-semigroups with a structure analogous to a classical theorem of Beurling. Such decompositions can be characterized by adaptedness and exactness of unitary cocycles. For CCR-flows we show that such cocycles are convergent.
Density of the self-adjoint elements with finite spectrum in an irrational rotation C*-algebra.
Derivations, dynamical systems, and spectral restrictions.
Discrete group actions and the minimal primal ideal space.
Discrete groups with Kazhdan' s property T and factorization property are residually finite.
Dynamical entropy of a non-commutative version of the phase doubling
A quantum dynamical system, mimicking the classical phase doubling map on the unit circle, is formulated and its ergodic properties are studied. We prove that the quantum dynamical entropy equals the classical value log2 by using compact perturbations of the identity as operational partitions of unity.