Published online by Cambridge University Press: 20 November 2018
This paper studies the relationship between vector-valued $\text{BMO}$ functions and the Carleson measures defined by their gradients. Let $dA$ and $dm$ denote Lebesgue measures on the unit disc $D$ and the unit circle $\mathbb{T}$, respectively. For $1\,<\,q\,<\,\infty $ and a Banach space $B$, we prove that there exists a positive constant $c$ such that
holds for all trigonometric polynomials $f$ with coefficients in $B$ if and only if $B$ admits an equivalent norm which is $q$-uniformly convex, where
The validity of the converse inequality is equivalent to the existence of an equivalent $q$-uniformly smooth norm.