Disorder-induced unbinding in confined geometries

We consider the disorder-induced fluctuations of a directed polymer confined between two walls with attractive contact potentials. For two-dimensional systems we exploit the mapping to a one-dimensional driven lattice gas with open boundaries to obtain exactly the phase diagram as well as critical exponents and scaling functions characterizing the unbinding transitions. The competition between two attractive walls gives rise to coexistence fluctuations in the bound phase, corresponding to the shock fluctuations in the lattice gas. Scaling arguments are used to generalize these results to higher dimensions and different confinement geometries.