Sharpness of certain Campbell and Pommerenke estimates

The paper is concerned with the sharpness of some well-known estimates in universal linear-invariant families of regular functions. It is shown that the estimate of | arg ƒ′(z)|,z ∈ Δ = {z: |z| < 1} obtained by Pommerenke in 1964 is sharp; the extremal function is found. A lower estimate for the Schwarzian derivative in is obtained. For , a sharp estimate of order of the function ƒr(z)=ƒ(rz)/r withr ∈ (0, 1) is found; this estimate is applied to solve other problems. Translated fromMatematicheskie Zametki, Vol. 63, No. 5, pp. 665–672, May, 1998.