Glassy motion of an elastic string.

Numerical simulations of a driven elastic string in a quenched random potential at nite temperatures support the existence of glassy motion for suuciently weak driving forces. Avalanche-like string motion is observed in the transition region. The dynamics of an elastic string in a random medium provides an excellent model for the description of a variety of interesting phenomena|including uctuations of domain walls in random magnets 1], surface growth in a random environment 2], and directed polymer growth 3]. It is also extremely useful for the description of vortex motion in high-T c superconductors. The elastic-string model is exact for vor-tex dynamics at moderate temperatures and magnetic elds, when the characteristic pinning barriers for isolated vortex motion exceed the energy associated with vortex-vortex interactions 4]. Moreover, when vortex-vortex interactions are signiicant, the ideas of elastic-string dynamics 5] can be generalized to describe the collective motion of vortex bundles 6]. In this communication we present some results of numerical simulations of the motion of an elastic string in random quenched disorder. The string is driven by a constant force and subject to thermal noise. The inclusion of both quenched random disorder and thermal noise distinguishes our model from those considered in interface dynamics, where the disorder is modeled with either thermal-like noise 2, 3, 7] or quenched random disorder 8]. Another distinction is that we consider motion under the innuence of a random potential, rather than a random force. In a random potential,