ENERGY BARRIERS TO MOTION OF FLUX LINES IN RANDOM-MEDIA

We propose algorithms for determining both lower and upper bounds for the energy barriers encountered by a flux line in moving through a two -dimensional random potential. Analytical arguments, supported by nume rical simulations, suggest that these bounds scale with the length t o f the line as t(1/3) and t(1/3)root ln t, respectively. This provides the first confirmation of the hypothesis that barriers have the same s caling as the fluctuation in the free energy.