CRITICAL EXPONENTS OF A 3-DIMENSIONAL O(4) SPIN MODEL

By Monte Carlo simulation we study the critical exponents governing the transition of the three-dimensional classical O(4) Heisenberg model, which is considered to be in the same universality class as finite-temperature QCD with two massless flavors. We use the single cluster algorithm and the histogram reweighting technique to obtain observables at the critical temperature. After estimating an accurate value of the inverse critical temperature Kc=0.9360(1), we make nonperturbative estimates for various critical exponents by a finite-size scaling analysis. We find ν=0.7479(90), β/ν=0.5129(11), and γ/ν=1.9746(38). They are in excellent agreement with those obtained by perturbation theory with errors reduced to about one-half. © 1995 The American Physical Society.