Large deviation approach to the generalized random energy model

The generalized random energy model is a generalization of the random energy model introduced by Derrida to mimic the ultrametric structure of the Parisi solution of the Sherrington–Kirkpatrick model of a spin glass. It was solved exactly in two special cases by Derrida and Gardner. A complete solution for the thermodynamics in the general case was given by Capocaccia et al. Here we use large deviation theory to analyse the model in a very straightforward way. We also show that the variational expression for the free energy can be evaluated easily using the Cauchy–Schwarz inequality.