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JMB Journal of Microbiolog and Biotechnology

OPEN ACCESS eISSN 0454-8124
pISSN 1225-6951
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Original Article

Kyungpook Mathematical Journal 2015; 55(3): 641-652

Published online September 23, 2015

Copyright © Kyungpook Mathematical Journal.

The Normality of Meromorphic Functions with Multiple Zeros and Poles Concerning Sharing Values

Wang You-Ming

Department of Applied Mathematics, College of Science, Hunan Agricultural University, ChangSha 410128, P. R. China

Abstract

In this paper we study the problem of normal families of meromorphic functions concerning shared values. Let $F$  be a family of meromorphic functions in the plane domain $D subseteq mathbb{C}$ and $n, k$ be two positive integers such that $n geq k +1$, and let $a, b$ be two finite complex constants such that $a
eq 0$. Suppose that (1) $f + a(f^{(k)})^n$ and $g + a(g^{(k)})^n$ share $b$ in $D$ for every pair of functions $f, g in F$; (2) All zeros of $f$ have multiplicity at least $k + 2$ and all poles of $f$ have multiplicity at least $2$ for each $f in F$ in $D$; (3) Zeros of
$f^{(k)}(z)$ are not the $b$ points of $f(z)$ for each $f in F$ in $D$. Then $F$ is normal in $D$. And some examples are provided to show the result is sharp

Keywords: meromorphic functions, shared value, normal family