A circle diffeomorphism with breaks that is smoothly linearizable

Abstract

In this paper we answer positively a question of whether it is possible for a circle diffeomorphism with breaks to be smoothly conjugate to a rigid rotation in the case when its breaks are lying on pairwise distinct trajectories. An example constructed is a piecewise linear circle homeomorphism that has four break points lying on distinct trajectories, and whose invariant measure is absolutely continuous w.r.t.\ the Lebesgue measure. The irrational rotation number for our example can be chosen a Roth number, but not of bounded type.