Self-similar evolution of wave turbulence in Gross-Pitaevskii system

TL;DR

This paper investigates the universal self-similar evolution of wave turbulence in Bose-Einstein condensates through numerical simulations of the Gross-Pitaevskii and wave kinetic equations, revealing regimes of energy conservation and finite-time blowup.

Contribution

It identifies and characterizes self-similar regimes in BEC wave turbulence, including first and second kind self-similarity, using numerical simulations of GPE and WKE.

Findings

First-kind self-similarity determined by energy conservation

Existence of second-kind self-similar evolution leading to blowup

Universal self-similar spectra relevant for BEC turbulence studies

Abstract

We study the universal non-stationary evolution of wave turbulence (WT) in Bose-Einstein condensates (BECs). Their temporal evolution can exhibit different kinds of self-similar behavior corresponding to a large-time asymptotic of the system or to a finite-time blowup. We identify self-similar regimes in BECs by numerically simulating the forced and unforced Gross-Pitaevskii equation (GPE) and the associated wave kinetic equation (WKE) for the direct and inverse cascades, respectively. In both the GPE and the WKE simulations for the direct cascade, we observe the first-kind self-similarity that is fully determined by energy conservation. For the inverse cascade evolution, we verify the existence of a self-similar evolution of the second kind describing self-accelerating dynamics of the spectrum leading to blowup at the zero mode (condensate) at a finite time. We believe that the universal self-similar spectra found in the present paper are as important and relevant for understanding the BEC turbulence in past and future experiments as the commonly studied stationary Kolmogorov-Zakharov (KZ) spectra.