Spin glasses

In sect. 2 we will introduce spin glass, and the concept of frustration. In sect. 3 we will describe the Sherrington-Kirkpatrick model for spin glass and present its solution in the high-temperature phase. In sect. 4 we will see how to solve the model using the formalism of broken replica symmetry. We will describe the group-theoretical implications of the formalism and we will see how the solution of the model can be reformulated in term of a stochastic differential equation. Finally, in sect. 5 we will present the physical interpretation of the formalism of the previous section. (orig./BBO)