Ising model for spin glasses

The diagram method of high-temperature expansions is used to study the Ising model for spin glasses. The property of stationarity of the free energy of the system with respect to the magnetic moment and the exchange field is proved. The “exactly solvable” Sherrington–Kirkpatrick model is investigated, and it is shown that in the thermodynamic limit the results obtained in the present paper agree exactly with the results obtained by the replica method. Thus, the ell-known difficulties associated with the low-temperature entropy remain.