Continuous dependence for NLS in fractional order spaces

Abstract

We consider the Cauchy problem for the nonlinear Schrödinger equation $iu_t+ Δu+ λ|u|^αu=0$ in $\R^N $, in the $H^s$-subcritical and critical cases $0<α\le 4/(N-2s)$, where $0<s<N/2$. Local existence of solutions in $H^s$ is well known. However, even though the solution is constructed by a fixed-point technique, continuous dependence in $H^s$ does not follow from the contraction mapping argument. In this paper, assuming furthermore $s<1$, we show that the solution depends continuously on the initial value in the sense that the local flow is continuous $H^s \to H^s$. If, in addition, $α\ge 1$ then the flow is Lipschitz. This completes previously known results concerning the cases $s=0,1,2$.

Corrected typos. Simplified section 4. Results unchanged