UNIVERSALITY IN MODELS FOR DISORDER-INDUCED PHASE-TRANSITIONS

We have systematically analyzed six different reticular models with qu enched disorder and no thermal fluctuations exhibiting a field-driven first-order phase transition. We have studied the nonequilibrium trans ition, appearing when varying the amount of disorder, characterized by the change from a discontinuous hysteresis cycle (with one or more la rge avalanches) to a smooth one (with only tiny avalanches). We have c omputed critical exponents using finite size scaling techniques and sh own that they are consistent with universal values depending only on t he space dimensionality d.