关于星象函数与凸象函数的一点注记

A NOTE ON STARLIKE AND CONVEX FUNCTIONS

M.S.Robertson于1979年给出了星象单叶函数类的有趣刻划。最近,H.Al-Amiri作出了Robertson定理的新证明。本文利用卷积方法非常简捷地证明了Robertson的结果。我们还建立了与1/2级星象函数有关的从属定理。

In 1979 M. S. Robertson gave a characterization of the class of starlike univalent functions. Very recently, H. A1-Amiri found an alternate proof of the Robertson theorem. In the present note we give a very simple proof of this result and establish a subordination theorem for starlike functions of order 1/2.