A generalized nonlinear Schr\"odinger equation as model for turbulence, collapse, and inverse cascade

A two-dimensional generalized cubic nonlinear Schr"odinger equation with complex coefficients for the group dispersion and nonlinear terms is used to investigate the evolution of a finite-amplitude localized initial perturbation. It is found that modulation of the latter can lead to side-band formation, wave condensation, collapse, turbulence, and inverse cascade, although not all together nor in that order.