  We study quantum fluctuations of the nucleon's parton densities by combining
QCD factorization for hard processes with the notion of cross section
fluctuations in soft diffraction. The fluctuations of the small-x gluon density
are related to the ratio of inelastic and elastic vector meson production in
e-p scattering. A simple dynamical model explains the HERA data and predicts
the x- and Q^2-dependence of the ratio. In p-p/pbar-p scattering, fluctuations
enhance multiple hard processes (but cannot explain the Tevatron CDF data), and
reduce gap survival in central exclusive diffraction.
