Fluctuations in granular superconductors

By expanding the order parameter for an array of Josephson-coupled grains in powers of 1/z, where z is the number of nearest neighbors, I systematically incorporate the effect of phase fluctuations. The correction of order 1/z vanishes when the mean-field solution is known to be exact, for {α}=zJ/U={∞} and T*=T/zJ=0. For larger T* and smaller {α}, the first-order correction increases until it diverges at the mean-field transition temperature.