Delta expansion of models with chiral-symmetry breaking.

Abstract

We apply the $\ensuremath{\delta}$ expansion to evaluate the effective potentials of theories displaying discrete and continuous chiral symmetry. In the continuous chiral-symmetry-breaking case we show that a careful choice of the interpolation parameter preserves the Goldstone structure of the theory, and that using this modified algorithm the large-$N$ result is reproduced at first order in $\ensuremath{\delta}$. We explicitly show how the inclusion of higher-order contributions produce results different from the $\frac{1}{N}$ expansion, both qualitatively and quantitatively.