A reverse quasiconformal composition problem for $Q_\alpha(\mathbb{R}^n)$

Abstract

We give a partial converse to [8, Theorem 1.3] (as a resolution of [2, Problem 8.4] for the quasiconformal $Q$-composition) for $Q_{0 \lt \alpha \lt 2^{-1}} (\mathbb{R}^{n \geq 2})$, and yet demonstrate that if $f : \mathbb{R}^2 \to \mathbb{R}^2$ is a homeomorphism then the boundedness of $u \mapsto u \circ f$ on $Q_{2^{-1} \lt \alpha \lt 1} (\mathbb{R}^2) \subset BMO (\mathbb{R}^2)$ yields the quasiconformality of $f$.