On Explicit Bounds in Landau's Theorem. II

Quite some years ago a number of mathematicians were interested in obtaining explicit expressions for the bounds in Schottky's and Landau's theorems, specifically numerically évaluable bounds of a particular form. The best bounds of this type in Schottky's theorem were given by the author [3]. For Landau's theorem the chosen form is as follows. Let F(Z) be regular in |Z| < 1, omit the values 0 and 1 and have Taylor expansion about Z = 0ThenUsing the same method employed for Schottky's theorem the author showed that one can take K = 5.94. By a slight modification of the author's method Lai [6] gave the further value K = 4.76.

On Explicit Bounds In Schottky's Theorem

1. Introduction. To Schottky is due the theorem which states that a function F(Z), regular and not taking the values 0 and 1 in |Z| < 1 and for which F(0) = a0, is bounded in absolute value in |Z| ≤ r, 0 ≤ r < 1, by a number depending only on a0 and r. Let K(a0 r) denote the best possible bound in this result. Various authors have dealt with the problem of giving an explicit estimate for this bound.