Statistical properties of billiards with diffusive boundary scattering are
investigated by means of the supersymmetric cr model in a formulation appro
priate for chaotic ballistic systems. We study level statistics, parametric
level statistics, and properties of electron wave functions. In the univer
sal regime, our results reproduce conclusions of the random matrix theory,
while beyond this regime we obtain a variety of system-specific results det
ermined by the classical dynamics in the billiard. Most notably, we find th
at level correlations do not vanish at arbitrary separation between energy
levels, or if measured at arbitrarily large difference of magnetic fields.
Saturation of the lever number variance indicates strong rigidity of the sp
ectrum. To study spatial correlations of wave-function amplitudes, we reana
lyze and refine derivation of the ballistic version of the sigma model. Thi
s allows us to obtain a proper matching of universal short-scale correlatio
ns with system-specific ones.