CRITICAL-BEHAVIOR OF THE 2-DIMENSIONAL STEP MODEL

We use finite-size scaling of Lee-Yang partition function zeros to stu dy the critical behavior of the two-dimensional step or sgn O(2) model . We present evidence that, like the closely related XY model, this ha s a phase transition from a disordered high-temperature phase to a low -temperature massless phase where the model remains critical. The crit ical parameters (including logarithmic corrections) are compatible wit h those of the XY model indicating that both models belong to the same universality class.