Unzipping of DNA under the influence of external fields

We study the features on the unzipping process of a modified version of the Peyrard-Bishop- Dauxois model. We show that the inclusion of a barrier in the on-site potential allows for the existence of stable domain wall solutions between open and closed regions of the DNA chain. We analyze the linear stability of such solutions and study their relevance in the dynamical behavior of DNA under ac forces.