A remark on global well-posedness of the derivative nonlinear Schr\"odinger equation on the circle

Abstract

In this note, we consider the derivative nonlinear Schr\"odinger equation on the circle. In particular, by adapting Wu's recent argument to the periodic setting, we prove its global well-posedness in $H^1(\mathbb T)$, provided that the mass is less than $4\pi$. Moreover, this mass threshold is independent of spatial periods.