TIME REVERSIBILITY FOR MODULAR K-SYSTEMS H. NARNHOFER

We start with a modular K-system that possesses Anosov endomorphisms in both time directions. We extend the system via a crossed product construction. If one of the Anosov endomorphisms can be extended, then also the other one. Also the extensions form a Moebius group and allow a time reflection operator that implements on the algebra an antiisomorphism.