We present a new characterization of Muckenhoupt $A_{infty}$-weights whose logarithm is in $mathrm{VMO}(mathbb{R})$ in terms of vanishing Carleson measures on $mathbb{R}_+^2$ and vanishing doubling weights on $mathbb{R}$. This also gives a novel description of strongly symmetric homeomorphisms on the real line (a subclass of quasisymmetric homeomorphisms without using quasiconformal extensions.
We investigate a variant of the Beurling-Ahlfors extension of quasisymmetric homeomorphisms of the real line that is given by the convolution of the heat kernel, and prove that the complex dilatation of such a quasiconformal extension of a strongly symmetric homeomorphism (i.e. its derivative is an ${rm A}_infty$-weight whose logarithm is in VMO) induces a vanishing Carleson measure on the upper half-plane.
We introduce the concept of a new kind of symmetric homeomorphisms on the unit circle, which is derived from the generalization of symmetric homeomorphisms on the real line. By the investigation of the barycentric extension for this class of circle homeomorphisms and the biholomorphic automorphisms induced by trivial Beltrami coefficients, we endow a complex Banach manifold structure on the space of those generalized symmetric homeomorphisms.
In a paper of Cui and Zinsmeister the equivalence among three definitions of BMO-Teichmuller spaces associated with a Fuchsian group was proven using the Douady-Earle extension operator. In this paper, we show that these equivalences are actually biholomorphisms. It was further shown in the above quoted paper that the Douady-Earle extension operator is continuous at the origin. We improve this result by showing G^ateaux-differentiability at this point.
