SURFACE CRITICAL EXPONENTS OF SELF-AVOIDING WALKS AND TRAILS ON A SQUARE LATTICE - THE UNIVERSALITY CLASSES OF THE THETA AND THETA' POINTS

Using the scanning method we carry out for the first time extensive simulations of trails and self-avoiding walks (SAWs) terminally attached to an adsorbing linear boundary on a square lattice. A bulk attraction energy is also defined for a self-intersection of a trail and a pair of nonbonded nearest-neighbor monomers of a SAW. The chains are simulated at the special point. Our critical exponents differ significantly from the exact values of Vanderzande, Stella, and Seno [Phys. Rev. Lett. 67, 2757 (1991)] for the theta' model. Thus, their conjecture, that the theta and theta' points belong to the same universality class, is not supported.