CREEP VIA DYNAMICAL FUNCTIONAL RENORMALIZATION-GROUP

We study a D-dimensional interface driven in a disordered medium. We d erive finite-temperature and velocity functional renormalization group (FRG) equations, valid ill a epsilon = 4 - D expansion. These equatio ns allow in principle for a complete study of the velocity v vs. appli ed force density f characteristics. We focus here on the creep regime at finite temperature and small velocity. We show how the FRG approach gives the form of the v-f characteristics sn this regime, and in part icular the creep exponent, obtained previously only through phenomenol ogical scaling arguments.