Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Domaines physics
Date Mercredi 7 Fevrier 2024
Heure 13:30
Salle ConfIV (E244) - Dépt de Physique de l'ENS - 24 rue Lhomond 75005 PARIS
Nom de l'orateur Nazarenco
Prenom de l'orateur Sergey
Addresse email de l'orateur
Institution de l'orateur
Titre Universal scalings in evolving and stationary wave turbulence
Résumé Using the Nonlinear-Schrodinger (NLS) equation as a master model, I will present analytical and numerical results concerning several types of universal scaling regimes in wave turbulence. In stationary turbulence, these will be concerned with a revised theory of the famous Kolmogorov-Zakharov (KZ) spectra, both the direct and the inverse cascades. In evolving wave turbulence, the universal scalings manifest themselves in self-similar asymptotics (referred to as "non-thermal fixed points" in some recent papers). The latter behaviour comes in three flavours: self-similarity of the first, second and third kinds respectively. The self-similarity of the first kind appears as a large time asymptotic of the spectrum propagating toward high frequencies. Its scaling is fully determined by energy conservation. The self-similarity of the second kind appears as a finite time blow-up of the wave-kinetic equation (WKE) at the zero frequency: it is related to a physical phenomenon of the Bose-Einstein condensation. The scaling of this self-similarity is non-trivial: it cannot be found from conservation laws, and it is determined by solving a "nonlinear eigenvalue problem". The self-similarity of the third kind appears in the forced-dissipated settings as a final stage of transition to the KZ spectrum and it takes the form of a frequency-space wave reflected from the low-frequency dissipative range. Its scaling is inherited from the previous (blowup) self-similar stage. I will present numerical results testing the analytical predictions arising from simulations of both the WKE and the 3D NLS equation.
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