Flows with constant slope on the Klein bottle

Abstract

We consider smooth flows with constant slope on the 2-dimensional (flat) torus and on the (flat) Klein bottle. It is well known that for a flow with constant slope on the torus either all orbits are periodic or all orbits are dense. We obtain a similar classification for the orbits of a flow with constant slope on the Klein bottle: again either all orbits are periodic, although some periods change, or all orbits are dense. This requires considering flows on the unit normal bundle of the Klein bottle.