ABSTRACT
This chapter describes the history of the revolution that led to the models of cooperativity. Renormalization group theory also shows that behavior near critical points can be described by universality classes: many different types of transition share the same behaviors, depending mainly on an order parameter and the dimensionality of the system. The chapter also describes the Landau model, named for the Russian physicist LD Landau, who won the 1962 Nobel Prize in Physics for his work on condensed phases of matter. The importance of the one-dimensional Ising model is that it illustrates the principles of the nearest-neighbor model and that it can be solved exactly. The chapter considers a model that describes the highest possible degree of cooperativity: the two-state model. In the two-state model, no molecule is in an intermediate state. In this regard, the two-state model differs markedly from the noncooperative model, which predicts substantial populations of intermediate states.
