Statistics of fluctuations for two types of crossover: From the ballistic to diffusive regime and from the orthogonal to unitary ensemble

In our previous publication [Kogan et al., Phys. Rev. B 48, 9404 (1993)] we considered the issue of statistics of radiation diffusively propagating in a disordered medium. The consideration was in the framework of diagrammatic techniques and a representation for the intensity-distribution function in terms of connected diagrams only was proposed. Here we use a similar approach to treat the issue of statistics in the regime of the crossover between ballistic and diffusive transport. We find that even a small contribution from the coherent component decreases by one half the intensity-distribution function for small values of intensity and also produces oscillations of the distribution function. We also apply this method to study statistics of fluctuations of wave functions of chaotic electrons in a quantum dot in an arbitrary magnetic field, by calculating the single-state local density in the regime of the crossover between the orthogonal and unitary ensemble.