On dominancy of minimal actions of compact kac algebras and certain automorphisms in Aut(/~#alpha#)

摘要

We show that any minimal action of a compact Kac algebra with properly infinite fixed-point algebra is dominant. It is also shown that, for such a minimal action, a certain automorphism in Aut(/~#alpha#) gives rise to a unitary that lies in the intrinsic group of the dual Kac algebra. A concrete description, in terms of the unitary, of the left co-ideal von Neumann subalgebra. determined by the fixed-point algebra of the automorphism is given.