Random-Energy Model: Limit of a Family of Disordered Models

In this Letter, a simple model of disordered systems—the random-energy model—is introduced and solved. This model is the limit of a family of disordered models, when the correlations between the energy levels become negligible. The properties are qualitatively the same as those of the Sherrington-Kirkpatrick model. Moreover, this random-energy model looks like a simple approximation to any spin-glass model.