Roughness of a tilted anharmonic string at depinning.

We consider the discretized model of a driven string with an anharmonic elastic energy, in a two-dimensional random potential, as introduced by [Phys. Rev. Lett. 87, 187002 (2001)]]. Using finite size scaling, we numerically compute the roughness of the string in a uniform applied force at the critical depinning threshold. By considering a string with a net average tilt, we demonstrate that the anharmonic elastic energy crosses the model over to the quenched KPZ universality class, in agreement with recent theoretical predictions.