Finite Size Dependence Of Scaling Functions Of The Three-Dimensional O(4) Model In An External Field

We calculate universal finite-size scaling functions for the order parameter and the longitudinal susceptibility of the three-dimensional O(4) model. The phase transition of this model is supposed to be in the same universality class as the chiral transition of two-flavor QCD. The scaling functions serve as a testing device for QCD simulations on small lattices, where, for example, pseudocritical temperatures are difficult to determine. In addition, we have improved the infinite-volume limit parametrization of the scaling functions by using newly generated high statistics data for the three-dimensional O(4) model in the high-temperature region on an L = 120 lattice.