Semiclassical spectral correlator in quasi one-dimensional systems

We investigate the spectral statistics of chaotic clean quasi one-dimensional systems. To do so we represent the spectral correlation function R() through derivatives of a generating function and semiclassically approximate the latter in terms of periodic orbits. In contrast to previous work we obtain both non-oscillatory and oscillatory contributions to the correlation function. Both types of contributions are evaluated to leading order in 1/ for systems with and without time-reversal invariance. Our results agree with predictions from the nonlinear sigma model for disordered systems.