'Sum over configurations' (non-perturbative quantum expansion for solitons and other states in field theory)

Models of hadrons and temporary quark confinement, based on field theories with extended classical solutions, neglect quantum fluctuation effects. To account for these effects, systematic expansions are proposed for the vacuum, one-particle and collision states which are non-perturbative. Their order is not a power of any coupling constant, but a number of field configurations. To exhibit the conceptual and technical simplicity of the method, fluctuations describing virtual soliton-antisoliton pairs are studied in a model theory. A 'hybrid approximation' for non-perturbative calculations of scattering amplitudes is proposed. (11 refs).