Rigorous derivation of damped-driven wave turbulence theory

Abstract

We provide a rigorous justification of various kinetic regimes exhibited by the nonlinear Schr\"{o}dinger equation with an additive stochastic forcing and a viscous dissipation. The importance of such damped-driven models stems from their wide empirical use in studying turbulence for nonlinear wave systems. The force injects energy into the system at large scales, which is then transferred across scales, thanks to the nonlinear wave interactions, until it is eventually dissipated at smaller scales. The presence of such scale-separated forcing and dissipation allows for the constant flux of energy in the intermediate scales, known as the inertial range, which is the focus of the vast amount of numerical and physical literature on wave turbulence. Roughly speaking, our results provide a rigorous kinetic framework for this turbulent behavior by proving that the stochastic dynamics can be effectively described by a deterministic damped-driven kinetic equation, which carries the full picture of the turbulent energy dynamic across scales (like cascade spectra or other flux solutions). The analysis extends previous works in the unperturbed setting arXiv:1912.09518-arXiv:2301.07063 to the above empirically motivated damped driven setting. Here, in addition to the size $L$ of the system, and the strength $\lambda$ of the nonlinearity, an extra thermodynamic parameter has to be included in the kinetic limit ($L\to \infty, \lambda\to 0$), namely the strength $\nu$ of the forcing and dissipation. Various regimes emerge depending on the relative sizes of $L$, $\lambda$ and $\nu$, which give rise to different kinetic equations. Two major novelties of this work is the extension of the Feynman diagram analysis to additive stochastic objects, and the sharp asymptotic development of the leading terms in that expansion.