On the order of strongly starlikeness of strongly convex functions (Q1318921)
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scientific article; zbMATH DE number 549022
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | On the order of strongly starlikeness of strongly convex functions |
scientific article; zbMATH DE number 549022 |
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On the order of strongly starlikeness of strongly convex functions (English)
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15 August 1994
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Let \(A\) denote the set of functions \(f(z)\) analytic in the unit disc \(E\) with \(f(0)=0\) and \(f'(0)=1\). P. T. Mocanu has proved that if \[ |\arg(1+ zf''(z)/f'(z)|< \pi\gamma/2\quad\text{for all }z\in E, \] then \(|\arg zf'(z)/f(z)|<\pi\beta/2\) there, where \(\gamma\) and \(\beta\) are between 0 and 1 and are related by a somewhat complicated functional relation. That is, strongly convex of order \(\gamma\) implies strongly starlike of order \(\beta\). This paper proves the same result with a more complicated functional relationship between \(\gamma\) and \(\beta\). Unfortunately, numerical calculations appear to indicate that the two sets of relationships give exactly the same \((\gamma,\beta)\) pairs to at least ten decimal places. The proof here seems to be different from that of Mocanu.
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strongly starlike of order \(\beta\)
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