On Bloch seminorm of finite Blaschke products in the unit disk

Anton D. Baranov, Ilgiz R. Kayumov, Semen R. Nasyrov

We prove that, for any finite Blaschke product $w=B(z)$ in the unit disk, the corresponding Riemann surface over the $w$--plane contains a one-sheeted disk of the radius $0.5$. Mor…