Locating resonances for axiom A dynamical systems (Q1109391)

The paper is devoted to the following problem about correlation functions for axiom A dynamical systems. It has been recently shown by \textit{Pollicott} and the author [cf. \textit{D. Ruelle}, J. Differ. Geom. 25, 99- 116 (1987; Zbl 0658.58026)] that correlation functions have Fourier transforms which are meromorphicin a strip. The poles are interpreted as resonances of the dynamical systems and the problem is to locate their position. The problem turns out to be a difficult one. The author discusses some known results and does some calculations for expanding maps of the circle. Also, the effect of noise is discussed.