Coordinate-space formulation of polymer lattice cluster theory

Freed et al. have recently developed a lattice cluster theory of polymer solutions that involves series expansions in momentum space. Here we reformulate the lattice cluster theory in coordinate space. The present treatment has certain useful features. In particular, the terms in the reformulated theory can be obtained readily from existing exhaustive computer enumerations. Also, the Flory-Huggins theory can be shown to arise as the first term in a recentered coordinate-space expansion. Generalization to treat polymers in confined space is straightforward.