Decay of correlations in suspension semi-flows of angle-multiplying maps

Abstract

We consider suspension semi-flows of angle-multiplying maps on the circle. Under a $C^r$generic condition on the ceiling function, we show that there exists an anisotropic Sobolev space¥cite{BT} contained in the $L^2$ space such that the Perron-Frobenius operator for the time-$t$-map act on it and that the essential spectral radius of that action is bounded by the square root of the inverse of the minimum expansion rate. This leads to a precise description on decay of correlations, which extends the result of M. Pollicott¥cite{Po}.