0) at a \ncritical j3c(n). For n ::; 2 this transition is second order at j3c = 1, down to the SK \n\n\f450 \n\nCoolen, Penney, and Sherrington \n\n0, but for n > 2 the coupled dynamics leads to a qualitative, \nspin-glass limit, n -\nas well as quantitative, change to first order. Replica symmetry is stable above a \ncritical value n c(!3), at which there is a de Almeida-Thouless (AT) transition (c.f. \nKondor [12]). As expected from spin-glass studies, n c(f3) goes to zero as {3 ! 1 \nbut rises for larger /3, having a maximum of order 0.3 at {3 of order 2. Thus, for \nn > nc(max) ::::: 0.3 there is no instability against small replica-symmetry breaking \nfluctuations, while for smaller n there is re-entrance in this stability. The transition \nfrom a paramagnetic to an ordered state and the onset of local RS instability for \nvarious temperatures is shown in Figure 1. \n\n3 EXTERNAL FIELDS \n\nSeveral simple modifications of the above model are possible. One consists of adding \nexternal fields to the spin dynamics and/or to the interaction dynamics, by making \nthe substitutions \n\nHV,j} ({O\"d) ~ HV'J} ({O\"d) - LOiO\"i \n\n1\u00a3 ( {Jii }) ~ 1\u00a3 ( {Jij }) - L hi Kij \n\ni