A factorization theorem for the derivative of a function in $H^p$
A factorization theorem for the derivative of a function in $H^p$
We show that a function $G$ is the derivative of a function $f$ in the Hardy space $H^{p}$ of the unit disk $D$ for $0<p<\infty$ if and only if $G=F\Phi ^{\prime }$ where $F\in H^{p}$ and $\Phi \in BMOA$. Here, $F$ can be chosen to be non-vanishing, $||\Phi ||_{BMOA} \le …