Coherent state description of non-topological solitons and momentum projection

The solitons we are studing are localized, static solutions to classical (or semiclassical) non-linear field equations. Being localized, they do not correspond to momentum eigenstates, even though the field theories we are trying to solve are translationally invariant. In order to construct states of good momentum we need an explicity quantum wave function and not just expectation values of the fields (which are all we can get from a semiclassical treatment). The techniques discussed provide a wave function which embodies many of the features of the semiclassical (or mean field) approximation. This wave function can be projected onto states of definite momentum and hence can be used to calculate center-of-mass corrections to soliton properties. Many of the ideas involved have been around since the early days of quantum field theory but they have received little application apart from work by Bolsterli and Parmentola. The specific model to which we apply these methods is the soliton bag model of Friedberg and Lee. This is a model for the low energy properties of QCD in which hadrons appear as solitons in a scalar field with quarks trapped inside them. 27 references