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Fast relaxation time in a spin model with glassy behavior

We consider a frustrated spin model with a glassy dynamics characterized by a slow component and a fast component in the relaxation process. The slow process involves variables with critical behavior at finite temperature T_p and has a global character like the (structural) alpha-relaxation of glasses. The fast process has a more local character and can be associated to the beta-relaxation of glasses. At temperature T>T_p the fast relaxation follows the non-Arrhenius behavior of the slow variables. At T ~< T_p the fast variables have an Arrhenius behavior, resembling the alpha-beta bifurcation of fragile glasses. The model allows us to analyze the relation between the dynamics and the thermodynamics.