We develop a rigorous formalism for the description of the kinetic evolution of infinitely many
hard spheres. On the basis of the kinetic cluster expansions of cumulants of groups of
operators of finitely many hard spheres which are the generating operators of a
nonperturbative solution of the Cauchy problem of the BBGKY hierarchy the nonlinear
kinetic Enskog equation is derived. It is established that for initial states which are specified
in terms of one-particle distribution functions the description of the evolution by the Cauchy …