ORBIT BIFURCATIONS AND SPECTRAL STATISTICS

Systems whose phase space is mixed have been conjectured to exhibit qu antum spectral correlations that are, in the semiclassical limit, a co mbination of Poisson and random-matrix, with relative weightings deter mined by the corresponding measures of regular and chaotic orbits. We here identify an additional component in long-range spectral statistic s, associated with periodic orbit bifurcations, which can be semiclass ically large. This is illustrated for a family of perturbed cat maps.