BALLISTIC ACCRETION ON A POINT SEED

We carefully discuss the two-dimensional ballistic aggregation process . Studying the microscopic discrete process, we theoretically derive t he probability density function describing the single-particle accreti on. Using this function, we describe the properties of the ''fan'', ob tained for ballistic aggregation on the single seed, and we predict it s mean density and its opening angle. We discuss the shadowing effect on a microscopic scale, between the single particles and, on a larger scale, between grown structures, deriving the columnar microstructure direction law. Comparisons with numerical experiments are shown.