Equations of State for Nonlinear Sigma-Models II: Relations between Resummation Schemes, and Crossover Phenomena

摘要

It is shown how a recent method to systematically extrapolate and resum theloop expansion for nonlinear sigma-models is related to solutions of therenormalization group equation. This relation is used to generalize theexplicit equations of state obtained previously to models which displaycrossover phenomena. As an example we discuss Wegner's localization model andconsider the crossover from symplectic to unitary symmetry.