New approach to level statistics of coupled quartic oscillators

Abstract

The nearest neighbor level spacing distribution (NNSD) for two-dimensional coupled quartic oscillators is studied numerically. The NNSD of the systems is fitted to the Berry–Robnik (BR) distribution, the Brody distribution and the Berry–Robnik–Brody (BRB) distribution which was proposed by M. Robnik and recently applied to the spectrum of nuclei by V. Lopac. The BRB distribution is found to be the most properly fitted to the NNSD for the whole range from the integrable limit to the chaotic regime. The new interpolation formula between the Poisson and the Wigner distribution is proposed.