UNIVERSAL EFFECTIVE POTENTIAL FOR SCALAR FIELD-THEORY IN 3 DIMENSIONS BY MONTE-CARLO COMPUTATION

We study the low-energy effective action for the theory of a one-component real scalar field in three Euclidean dimensions (3D), in the symmetric phase, concentrating on its static part-effective potential V-eff(phi) We compute it from the probability distributions of the average magnetization in the 3D Ising model in an external field, obtained by Monte Carlo computation. We find that the phi(6) term in V-eff is important in 3D, and compute the values of the universal four-point and six-point couplings.