  We investigate the evolution of a system of colloidal particles, trapped at a
fluid interface and interacting via capillary attraction, as function of the
range of the capillary interaction and temperature. We address the collapse of
an initially homogeneous particle distribution and of a radially symmetric
(disk--shaped) distribution of finite size, both theoretically by using a
perturbative approach inspired by cosmological models and numerically by means
of Brownian dynamics (BD) and dynamical density functional theory (DDFT). The
results are summarized in a "dynamical phase diagram", describing a smooth
crossover from collective (gravitational-like) collapse to local
(spinodal-like) clustering. In this crossover region, the evolution exhibits a
peculiar shock wave behavior at the outer rim of the contracting, disk-shaped
distribution.

Soft Condensed Matter