  Breath figures are the complex patterns that form when water vapor condenses
into liquid droplets on a surface. The primary question concerning breath
figures is how the condensing vapor is allocated between the growth of existing
droplets and the nucleation of new ones. Although numerous theoretical studies
have concentrated on scenarios resulting in highly polydisperse droplet
ensembles, a companion paper [Bouillant {\em et al.}, submitted] demonstrates
that nearly monodisperse patterns can be achieved on defect-free substrates in
a diffusion-controlled regime. The objective of this work is to present a
theoretical framework that elucidates the formation and evolution of
nearly-monodisperse patterns in breath figures. We discover that, following a
short nucleation phase, the number of droplets remains constant over an
extensive range of timescales due to collective effects mediated by the
diffusion of vapor. The spatial extent of these diffusive interactions is
identified through asymptotic matching, based on which we provide an accurate
description of breath figures through a mean-field model. The model accounts
for the sub-diffusive growth of droplets as well as for the arrest of
nucleating new droplets, and reveal the scaling laws for the droplet density
observed in experiments. Finally, droplets expand and ultimately coalesce,
which is shown to trigger a scale-free coarsening of the breath figures.
