Simplified Langevin approach to the Peyrard-Bishop-Dauxois model of DNA.

A simple Langevin approach is used to study stationary properties of the Peyrard-Bishop-Dauxois model for DNA, allowing known properties to be recovered in an easy way. Results are shown for the denaturation transition in homogeneous samples, for which some implications, so far overlooked, of an analogy with equilibrium wetting transitions are highlighted. This analogy implies that the order parameter, asymptotically, exhibits a second-order transition even if it may be very abrupt for nonzero values of the stiffness parameter. Not surprisingly, we also find that, for heterogeneous DNA, within this model the largest bubbles in the premelting stage appear in adenine-thymine-rich regions, while we suggest the possibility of some sort of not strictly local effects owing to the merging of bubbles.