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Integral transforms of functions with the derivative in a halfplane
Authors:S Ponnusamy  F Rønning
Institution:1. Department of Mathematics, Indian Institute of Technology IIT-Madras, 600 36, Chennai, India
2. School of Teacher Education, S?r-Tr?ndelag College, N-7004, Trondheim, Norway
Abstract:LetA be the class of normalized analytic functions in the unit disk Δ and define the class

$$\mathcal{P}_\beta   = \left\{ {f \in \mathcal{A}|\exists \alpha  \in \mathbb{R}|\operatorname{Re} \{ e^{ia} (f'(z) - \beta )\}  > 0,z \in \Delta } \right\}$$
For a functionf εA the Alexander transformF 0 is given by

$$F_0 (z) = \int {_0^1 \frac{{f(tz)}}{t}dt.} $$
Our main object is to establish a sharp relation betweenβ andγ such thatf εP β implies thatF 0 is starlike of orderγ, 0 ≤γ ≤ 1/2. A corresponding result for the Libera transformF 1(z) = 2∫ 0 1 f(tz)dt is also given.
Keywords:
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