Long-Range Spatial Correlations of Eigenfunctions in Quantum Disordered Systems

This paper is devoted to the statistics of the quantum eigenfunctions in an ensemble of metallic grains. We focus on moments of inverse participation ratio. In the universal limit that corresponds to the infinite conductance of the grains, these moments are self-averaging quantities. At large but finite conductance the moments do fluctuate due to the long-range correlations in the eigenfunctions. We evaluate the distributions of fluctuations at given conductance and geometry of the grains and express them through the spectrum of the diffusion operator in the grain.