  Interference of an array of independent Bose-Einstein condensates, whose
experiment has been performed recently, is theoretically studied in detail.
Even if the number of the atoms in each gas is kept finite and the phases of
the gases are not well defined, interference fringes are observed on each
snapshot. The statistics of the snapshot interference patterns, i.e., the
average fringe amplitudes and their fluctuations (covariance), are computed
analytically, and concise formulas for their asymptotic values for long time of
flight are derived. Processes contributing to these quantities are clarified
and the relationship with the description on the basis of the symmetry-breaking
scenario is revealed.
