Lifting in Besov Spaces

Petru Mironescu, Emmanuel Russ, Yannick Sire

Let $\Omega$ be a smooth bounded domain in ${\mathbb{R}}^n$ and u be a measurable function on $\Omega$ such that $|u(x)|=1$ almost everywhere in $\Omega$. Assume that u belongs to the $B_{p,q}^s(\Omega )$…