GENERAL-MODEL FOR COLLAPSE IN LATTICE ANIMALS

We consider a two-variable model for collapse in a lattice model of a branched polymer in a dilute solution. We model the polymer as a lattice animal with two fugacities, one corresponding to monomer-monomer interactions and the other to interactions between monomers and solvent. We investigate the nature of the phase diagram for this model and show that it contains three branches. We estimate the values of the crossover exponent phi along these branches and discuss the relationship to one-variable models. In particular, we show that one point on the phase boundary is related to a percolation transition.