Ergodicity for piecewise smooth cocycles over toral rotations
Let α be an ergodic rotation of the d-torus . For any piecewise smooth function with sufficiently regular pieces the unitary operator Vh(x) = exp(2π if(x))h(x + α) acting on is shown to have a continuous non-Dirichlet spectrum if the gradient of f has nonzero integral. In particular, the resulting skew product must be ergodic. If in addition α is sufficiently well approximated by rational vectors and f is represented by a linear function with noninteger coefficients then the spectrum of V...