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
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