ON THE DYNAMICS OF A SPHERICAL SPIN-GLASS IN A MAGNETIC-FIELD

We carry out an analysis Of the effect of a quenched magnetic held on the dynamics of the spherical Sherrington-Kirkpatrick spin-glass model . We show that there is a characteristic time introduced by the presen ce of the field. First, for times sufficiently small the dynamic scena rio of the zero field case-with aging effects-is reproduced. Second, f or times larger than the characteristic time one sees equilibrium dyna mics. This dynamical behaviour is reconciled with the geometry of the energy landscape of the model. We compare this behaviour with experime ntal observations at a finite applied field.