Controllability of the cubic Schroedinger equation via a low-dimensional source term

TL;DR

This paper demonstrates that controlling a limited number of modes in the d-dimensional cubic Schrödinger equation enables approximate controllability in certain function spaces, with a negative result for exact controllability using finite modes.

Contribution

It proves controllability results for the cubic Schrödinger equation with a low-dimensional source term, specifically controlling up to 2^d modes, and establishes limitations for exact controllability.

Findings

Controllability achieved with at most 2^d modes.

Approximate controllability in H^s spaces for s > d/2.

Negative result for exact controllability with finite modes.

Abstract

We study controllability of $d$-dimensional defocusing cubic Schroedinger equation under periodic boundary conditions. The control is applied additively, via a source term, which is a linear combination of few complex exponentials (modes) with time-variant coefficients - controls. We manage to prove that controlling at most $2^d$ modes one can achieve controllability of the equation in any finite-dimensional projection of the evolution space $H^{s}(\mathbb{T}^d), \ s>d/2$, as well as approximate controllability in $H^{s}(\mathbb{T}^d)$. We also present negative result regarding exact controllability of cubic Schroedinger equation via a finite-dimensional source term.