DIRECTED POLYMER LOCALIZATION IN A DISORDERED MEDIUM

The localization of a directed polymer onto an extended defect (such a s a line or a plane) in the presence of competing bulk disorder is exa mined. Based on scaling ideas and exact analysis on a hierarchical lat tice, we develop a new renormalization scheme to study the directed po lymer localization problem. We establish absence of delocalization tra nsition for attractive columnar defect in the marginal dimension d(c) = 2, and for attractive planar defect in d = 3. For columnar defect in three dimensions, our simulations yield a localization length exponen t nu(perpendicular to) = 1.8 +/- 0.6.