Microscopic interpretation of the Enskog equation for a homogeneous gas

The evolution of the one-particle distribution for a homogeneous system of hard spheres is studied. The terms in the formal density expansion of the collision operator which correspond to the class of hard sphere dynamical events involving one binary collision, the influence of other particles entering only through overlapping with the colliding pair, are separated. It is then shown that the sum of these terms gives the Enskog collision operator. This extends to all orders in density the results of Sengers et al.