Evidence for massless modes in the 'solvable model' of a spin glass

Mean-field equations for the long-range spin-glass model are solved numerically for T<Tc by an iterative technique. The eigenvalue spectrum of the Hessian, delta 2( beta F)/ delta mi delta mj, where F is the free energy, appears to extend down to zero, implying that the solution is always on the limit of stability. It is deduced that the trace of the square of the susceptibility matrix is infinite for T<or=Tc.