Equations of state for nonlinear sigma-models II: Relations between resummation schemes, and crossover phenomena Original Research Article

It is shown how a recent method to systematically extrapolate and resum the loop expansion for nonlinear sigma-models is related to solutions of the renormalization group equation. This relation is used to generalize the explicit equations of state obtained previously to models which display crossover phenomena. As an example we discuss Wegnerʹs localization model and consider the crossover from symplectic to unitary symmetry.