Multiple-particle interaction in (1+1)-dimensional lattice model

Finite volume multiple-particle interaction is studied in a two-dimensional complex phi(4) lattice model. The existence of analytical solutions to the phi(4) model in two-dimensional space and time makes it a perfect model for the numerical study of finite volume effects of multiparticle interaction. The spectra from multiple particles are extracted from the Monte Carlo simulation on various lattices in several moving frames. The S-matrix of multiparticle scattering in phi(4) theory is completely determined by two fundamental parameters: single-particle mass and the coupling strength of two-to-two particle interaction. These two parameters are fixed by studying single-particle and two-particle spectra. Due to the absence of the diffraction effect in the phi(4) model, three-particle quantization conditions are given in a simple analytical form. The three-particle spectra from simulation show remarkable agreement with the prediction of exact solutions.