Ordering periodic spatial structures by non-equilibrium fluctuations

We have analyzed the interplay between noise and periodic spatial modulations in bistable systems outside equilibrium and found that noise is able to increase the spatial order of the system, giving rise to periodic patterns which otherwise look random. The phenomenon we report, which may be viewed as the spatial counterpart of stochastic resonance, then shows a constructive role of noise in spatially extended systems, not considered up to now.