  We study the impact of the competition between the expansion of the medium
created in heavy-ion collisions and its diffusive properties on the critical
fluctuations of the net-baryon density. As the relaxation time of the
fluctuations is connected with the diffusive properties, the latter determine
the in- or out-of-equilibrium nature of the net-baryon density fluctuations
during the fireball evolution. This may result in important consequences for
the phenomenological interpretation of heavy-ion collision data. We study three
possible situations that can occur as a result of the competition between
diffusion and expansion and discuss the impact of this competition on the
integrated second and fourth order cumulants of net-baryon density fluctuations
at freeze-out in these situations.
