Spacing distributions for rhombus billiards

We show that the spacing distributions of rational rhombus billiards fall in a family of universality classes distinctly different from the Wigner-Dyson family of random matrix theory and the Poisson distribution. Some of the distributions find explanation in a recent work of Bogomolny, Gerland and Schmit. For the irrational billiards, despite ergodicity, we get the same distributions for the examples considered - once again, distinct from the Wigner-Dyson distributions. All results are obtained numerically by a method that allows us to reach very high energies.