title: Level curvature distribution in a model of two uncoupled chaotic subsystems.
abstract: We study distributions of eigenvalue curvatures for a block-diagonal random matrix perturbed by a full random matrix. The most natural physical realization of this model is a quantum chaotic system with some inherent symmetry, such that its energy levels form two independent subsequences, subject to a generic perturbation which does not respect the symmetry. We describe analytically a crossover in the form of a curvature distribution with a tunable parameter, namely, the ratio of intersubsystem/intrasubsystem coupling strengths. We find that the peak value of the curvature distribution is much more sensitive to the changes in this parameter than the power-law tail behavior. This observation may help to clarify some qualitative features of the curvature distributions observed experimentally in acoustic resonances of quartz blocks.
authors.affiliation: Department of Mathematical Sciences, Brunel University, Uxbridge UB8 3PH, United Kingdom. Guler.Ergun@brunel.ac.uk
authors.forename: Güler
authors.initials: G
authors.lastname: Ergün
authors.forename: Yan V
authors.initials: YV
authors.lastname: Fyodorov