We numerically study a nondisordered lattice spin system with afirst order liquid-crystal transition,as a model for supercooled liquids and glasses. Below the melting temperature the sysem can be kept in the metastable liquid phase,andit displays a dynamic phenomenology analogous to fragile supercooled liquids,with stretched exponential relaxation,power law increase of the relaxation time,and hig fragility index. At an effective spindal temperature T_(sp) the liquid properties cannot be extrapolated,in line with Kauzmann's scenarion of a lower metastability limit of supercooled liquids as a solution of Kauzmann's paradox. The off-equilibrium dynamics below T_(sp) corresponds to fast nucleation of small,but stable,crystal droplets,followed by extremetly slow grower the temperature,this crystal-growth phase is indistinguish able from an off-equilibrium glass,both from a structurla and a dynamical point of view:crystal growth has not advanced enough to be structurally detectable,and a violation of the fluctuation-dissipation theorem (FDT) typical of structural glasses is observed. On the other hand,for longer times crystallization reaches a threshold beyond which crystal domiains are easily identified,and FDT violation becomes compatible with ordinary domain growth.
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