Univalence criterion and convexity for an integral operator (Q427700)

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scientific article; zbMATH DE number 6046358
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Univalence criterion and convexity for an integral operator
scientific article; zbMATH DE number 6046358

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    Univalence criterion and convexity for an integral operator (English)
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    14 June 2012
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    univalent function
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    convexity
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    univalence
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    integral operator
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    Let \(f\) and \(g\) be normalized analytic functions defined on the open unit disk of the complex plane satisfying the conditions NEWLINE\[NEWLINE|z^2f'(z)/f^2(z) -1|<1,\quad |f''(z)/f'(z)|<1\quad\text{and}\quad |g(z)|<MNEWLINE\]NEWLINE for some \(M>0\). For a complex number \(\alpha\) with non-negative real part satisfying \(2\sqrt{3}(1+2M^2)|\alpha|\leq 9\), the authors show that the integral NEWLINE\[NEWLINEF(z):=\int_0^z[f'(t)\exp(g(t))]^\alpha dtNEWLINE\]NEWLINE is univalent in the unit disk. They also determine the order of convexity of the function \(F\) when \(f\) and \(g\) satisfy the conditions NEWLINE\[NEWLINE|f'(z) (z/f(z))^\mu -1|<1-\beta,\quad |f''(z)/f'(z)|<1\quad\text{and}\quad |g(z)|<M.NEWLINE\]
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