Two-Loop Crossover Scaling Functions of the O(N) Model

TL;DR

This paper analytically derives two-loop crossover scaling functions for the O(N) model's equation of state, revealing how the system transitions between different fixed points in the critical region.

Contribution

It provides an analytic calculation of the series for renormalization constants and crossover functions in the O(N) model using Environmentally Friendly Renormalization.

Findings

Beta-function exhibits crossover between fixed points

Effective critical exponents show non-trivial crossover

Analytic expressions for renormalization constants obtained

Abstract

Using Environmentally Friendly Renormalization, we present an analytic calculation of the series for the renormalization constants that describe the equation of state for the $O(N)$ model in the whole critical region. The solution of the beta-function equation, for the running coupling to order two loops, exhibits crossover between the strong coupling fixed point, associated with the Goldstone modes, and the Wilson-Fisher fixed point. The Wilson functions $\gamma_\lambda$, $\gamma_\phi$ and $\gamma_{\phi^2}$, and thus the effective critical exponents associated with renormalization of the transverse vertex functions, also exhibit non-trivial crossover between these fixed points.