Journal article

Starlikeness for certain close-to-star functions

Abstract

We find the radius of starlikeness of order $\alpha$, $0\leq \alpha<1$, of normalized analytic functions $f$ on the unit disk satisfying either $Reinsert ignore into journalissuearticles values(finsert ignore into journalissuearticles values(z);/ginsert ignore into journalissuearticles values(z););>0$ or $\left|insert ignore into journalissuearticles values(finsert ignore into journalissuearticles values(z);/ginsert ignore into journalissuearticles values(z););-1\right|<1$ for some close-to-star function $g$ with $Reinsert ignore into journalissuearticles values(ginsert ignore into journalissuearticles values(z);/insert ignore into journalissuearticles values(z+z^2/2););>0$ as well as of the class of close-to-star functions $f$ satisfying $Reinsert ignore into journalissuearticles values(finsert ignore into journalissuearticles values(z);/insert ignore into journalissuearticles values(z+z^2/2););>0$. Several other radii such as radius of univalence and parabolic starlikeness are shown to be the same as the radius of starlikeness of appropriate order.

Keywords

Univalent functionsconvex functionsstarlike functionssubordinationradius of starlikeness

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