The Moebius function and continuous extensions of rotations

Abstract

Let $f\colon \mathbb{T}\to \mathbb{R}$ be of class $C^{1+\delta}$ for some $\delta>0$ and let $c\in\mathbb{Z}$. We show that for a generic $\alpha\in\mathbb{R}$, the extension $T_{c,f}\colon \mathbb{T}^2\to\mathbb{T}^2$ of the irrational rotation $Tx=x+\alpha$, given by $T_{c,f}(x,u)=(x+\alpha, u+cx+f(x))$ ($\bmod\ 1$) satisfies Sarnak's conjecture.