Statistics of Oscillator Strengths in Chaotic Systems
  The statistical description of oscillator strengths for systems like hydrogen in a magnetic field is developed by using the supermatrix nonlinear $\sigma$-model. The correlator of oscillator strengths is found to have a universal parametric and frequency dependence, and its analytical expression is given. This universal expression applies to quantum chaotic systems with the same generality as Wigner-Dyson statistics. 
Nobuhiko Taniguchi, A. V. Andreev and Boris L. Altshuler