2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/29898A model of local metastable states due to the pinning induces plastic deformations allows to describe the nonlinear I-V curves in sliding density waves -DW. With increasing the DW velocity v, the metastable states of decreasing lifetimes ~1/v are accessed. The characteristic second threshold field is reached when configurations of shortest life time are accessed by the fast moving DW. Thus the DW works as a kind of a ``linear accelerator'' testing virtual states.To be published in Proceedings of ECRYS-99, J. de Physique, Coll., December 1999, http://ipnweb.in2p3.fr/~lptms/membres/brazov/Condensed Mattertext