Cooperative Electromagnetic Effects

Collective phenomena in strongly nonequilibrium systems interacting with an electromagnetic field are considered. Such systems are described by complicated nonlinear differential or integro-differential equations. The aim of this review is to show that many nonlinear collective phenomena can be successfully treated by a recently developed method called the scale separation approach, whose name comes from the idea of separating different characteristic space-time scales existing in nonequilibrium statistical systems. This approach is rather general and can be applied to various nonequilibrium physical problems, several of which are discussed here. The problems considered not only serve as illustrations of the method but are quite important by themselves, presenting interesting physical effects such as the collective liberation of light, turbulent photon filamentation, superradiant spin relaxation, negative electric current, and the magnetic semiconfinement of atoms.