The effect of multiplicity of stellar encounters and the diffusion coefficients in a locally homogeneous three-dimensional stellar medium: Removing the classical divergence

Abstract

Agekyan's λ-factor that accounts for the effect of multiple stellar encounters with large impact factors is used for the first time to compute the diffusion coefficients in the velocity space of a stellar system. It is shown that in this case the cumulative effectthe total contribution of distant encounters to the change in the velocity of the test staris finite, and the logarithmic divergence inherent to the classical description disappears, as also was earlier noted by Kandrup (1981). The formulas for the diffusion coefficients, as before, contain the logarithm of the ratio of two independent scale factors that fully characterize the state of the stellar system: the average interparticle distance and the impact parameter of a close encounter. However, the physical meaning of this factor is no longer associated with the classical logarithmic divergence.