Length control for foliations by Jordan curves via smooth quasiconformal maps

Abstract

Let $\Omega\subsetneq\mathbb C$ be a non-empty simply connected domain and $0<p<2$. Bouchala and Koskela [Proc. Amer. Math. Soc. (2024)] proved that there exists a quasiconformal map $f:\mathbb D\to\Omega$ such that $\int_0^1\ell(f(r S^1))^p\,dr<\infty$, and asked whether this conclusion holds at $p=2$, or even for every $0<p<2+\varepsilon$ with some $\varepsilon>0$. We answer this question affirmatively with $\varepsilon=2/157$ by constructing a single smooth $5$-quasiconformal map $f:\mathbb D\to\Omega$ satisfying this integrability condition simultaneously for every $0<p<2+2/157$.