Dealing with interactions

Abstract

So far in this book we have dealt almost entirely with assemblies made up of weakly interacting particles, either localized or gaseous. This has really not been a matter of choice, but almost of necessity. The basic approach has been founded on the idea that the energy of the assembly is simply the sum of the individual one-particle energies, i.e. U = ∑ n _j ε _j . Without this simplification the mathematics gets out of hand (although some progress can be made if we start with the canonical or grand canonical approach).