In many complex systems, large events are believed to follow power-law, scale-free probability distributions so that the extreme, catastrophic events are unpredictable. Here, we study coupled chaotic oscillators that display extreme events. The mechanism responsible for the rare, largest events makes them distinct, and their distribution deviates from a power law. On the basis of this mechanism identification, we show that it is possible to forecast in real time an impending extreme event. Once forecasted, we also show that extreme events can be suppressed by applying tiny perturbations to the system.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Red frequency shift and line asymmetry have been observed in selective reflection spectroscopy at a dielectric/Cs-vapour interface, which have been attributed to surface-induced Van der Waals attraction. This opens the way to studying surface interaction on low-lying, short-lived, excited states.

We present a theoretical analysis to explain the origin of different spatial distributions of laser-cooled sodium atoms in a magneto-optical trap. Such distributions, which include spherical clouds, rings, and rings with cores, are attributed to the radiation pressure due to misaligned Gaussian beams acting on each individual atom. The predictions of this theory are confirmed by experimental observations reported earlier. We were able to construct a diagram with several domains corresponding to the stable structures observed.PACS number(s): 32.80.Pj, 42.50.Vk