Corrections to scaling and crossover in two-dimensional Ising and Scalar-spin systems

Abstract

Two-dimensional criticality is studied in the Klauder and double-Gaussian O(1) models which interpolate from a Gaussian model at y=0 to the S=1/2 Ising model at y=1. Despite strong crossover effects for 0<y≲ 0.6, partial differential approximants for the two-variable susceptibility series indicate criticality of Ising type for all y>0 and yield a correction exponent θ=1.35± 0.25. The conjecture θ=4/3 in the absence of a related critical operator, and the observation γ_eff≃2.0 in the Klauder, double-Gaussian, and λϕ⁴ models, are discussed.