Conformally Invariant Besov Spaces on Chord-Arc Domains

Inspired by the classical Besov $p$-spaces defined via higher-order derivatives on the upper half-plane, we introduce Besov-type spaces on simply connected domains. We first prove that on quasidisks, the first-order Besov space is isomorphic to its higher-order counterparts, and that these higher-order spaces preserve conformal quasi-invariance. Based on this result, we characterize chord-arc domains in terms of the isomorphism between the first-order Besov space and the boundary Besov space. This extends recent results for the Dirichlet space ($p=2$) to the general case $1<p<\mathrm{\infty }$.