Coherence absorption and condensation induced by thermalization of incoherent nonlinear fields

We show that a conservative system of incoherent nonlinear waves exhibits, as a rule, an irreversible process of coherence transfer, in which the incoherence of the system is absorbed by the small-amplitude field, thus allowing the high-amplitude field to evolve towards a highly condensed coherent state. This process of coherence absorption results from the natural thermalization of the fields to a thermodynamic equilibrium state. The theory reveals that, contrary to a classical gas system, a wave system does not satisfy an equipartition of energy among the particles. Such a distinctive feature is the key property underlying the existence of the coherence absorption process. The coherence absorption effect is shown to also occur in a system of quantum Bose gases. Copyright (C) EPLA, 2008