Rigidity for circle diffeomorphisms with breaks satisfying a Zygmund smoothness condition

H. A. Akhadkulov, A. A. Dzhalilov, K. M. Khanin

Let $f$ and $\tilde{f}$ be two circle diffeomorphisms with a break point, with the same irrational rotation number of bounded type, the same size of the break $c$ and satisfying a…