Theory of Bubble Nucleation and Cooperativity in DNA Melting
  The onset of intermediate states (denaturation bubbles) and their role during the melting transition of DNA are studied using the Peyrard-Bishop-Daxuois model by Monte Carlo simulations with no adjustable parameters. Comparison is made with previously published experimental results finding excellent agreement. Melting curves, critical DNA segment length for stability of bubbles and the possibility of a two states transition are studied. 
S. Ares, N. K. Voulgarakis, K. O. Rasmussen and A. R. Bishop