Selection of an attractor in a continuum of stable solutions: Descriptionsof a wave front at different scales

Details of the particle dynamics are shown to modify the mean speed of a ch emical wave front propagating into an unstable stationary state. The compar ison of several description methods at different scales allows us to discri minate between different sources of departure from the macroscopic determin istic prediction and to give a quantitative expression of the speed correct ions induced by discretization of the variables, internal fluctuations in s mall systems, and departure from local equilibrium in the presence of a fas t reaction.