Abstract
Networks of caustics can occur in the distribution of particles suspended in a randomly moving gas. These can facilitate coagulation of particles by bringing them into close proximity, even in cases where the trajectories do not coalesce. The evolution of these caustic patterns depends upon the Lyapunov exponents λ1, λ2 of the suspended particles, as well as the rate J at which particles encounter caustics. We develop a theory determining the quantities J, λ1, λ2 from the statistical properties of the gas flow, in the limit of short correlation times.