3D ISING SPIN-GLASSES IN A MAGNETIC-FIELD AND MEAN-FIELD THEORY

We present the results of extensive computer simulations of 3d Ising spin-glasses in the presence of a uniform magnetic field. We compute the internal energy, the magnetization, the spin-spin overlap probability distribution P(q), the link-link overlap probability distribution Pe(qe) and the spin-glass susceptibility xsC for different volumes and temperatures. All of our results are compatible with mean-field behaviour. We find that P(q) and P,(qe) are nontrivial and non-self-averaging and xsG shows an increase with the linear size L of the system as XSG-L~. Our estimate is w= 1.80f0.25 at T=0.83. We also find evidence in favour of ultrametricity. In another set of simulations we study the copy overlap &(E) as a function of the coupling between copies E. &(E) becomes steeper around E - 0 as L increases, in agreement with the previous set of simulations. © 1990 IOP Publishing Ltd.