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Capillary attraction induced collapse of colloidal monolayers at fluid interfaces

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.