The distortion theorems and necessary and sufficient conditions for the class S(p) of univalent meromorphic functions. (Chinese) Zbl 0595.30015
Let S(p) be the set of functions
\[
f(z)=\alpha (f)/(z- p)+\sum^{\infty}_{n=0}\alpha_ n(f)z^ n,\quad 0<p<1,
\]
that are meromorphic and univalent in the unit disc \(U=\{z:\) \(| z| <1\}\). Based on the area principle the author proved that the Grunsky type coefficients \(\gamma_{m,n}\) defined by
\[
\log \frac{f(z)- f(\zeta)}{z/(z-p)-\zeta /(\zeta - p)}=\sum^{\infty}_{m,n=0}\gamma_{m,n\quad}z^ m\zeta^ n,\quad z,\zeta \in U
\]
satisfy the inequality
\[
\sum^{\infty}_{m=1}m| \sum^{\infty}_{n=0}\gamma_{m,n}\lambda_ n|^ 2\leq \sum^{\infty}_{n=1\quad}\frac{1}{n}| \lambda_ n-\lambda_ 0p^ n|^ 2,
\]
where \(\{\lambda_ n\}^{\infty}_{n=0}\) are arbitrary complex numbers. He then derives some necessary and sufficient conditions for f to be in S(p), some distortion theorems and some coefficient inequalities. He found sharp estimates for the residue \(| \alpha (f)|\).
Reviewer: Liquan Liu
MSC:
30C45 | Special classes of univalent and multivalent functions of one complex variable (starlike, convex, bounded rotation, etc.) |
30C50 | Coefficient problems for univalent and multivalent functions of one complex variable |