DIRECTED POLYMERS ON A FACTORIZED DISORDER LANDSCAPE

We study the directed polymer model subject to a particular form of di sorder, eta(x, t) = eta(X)(x)eta(T)(t), recently proposed in biologica l applications. We find that two new universality classes arise, depen ding on the lattice geometry. Using an intermediate model linking the two different orientations continuously, we find that there is a phase transition separating two distinct scaling phases. For both phases we get a reasonable understanding of the nature and values of the expone nts, corroborated with numerical results.