Journal of East China Normal University(Natural Sc ›› 2012, Vol. 2012 ›› Issue (3): 61-70.

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Normal criterion concerning differential polynomials and omitted functions

WANG Xue 1, LIU Xiao-jun 2, CHEN Qiao-yu 3   

  1. 1. Department of Mathematics, Fuyang Normal College, Fuyang Anhui 236041, China; 2. Department of Mathematics,University of Shanghai for Science and Technology, Shanghai 200093, China; 3. ,Department of Mathematics, East China Normal University, Shanghai 200241, China
  • Received:2011-06-10 Revised:2011-09-01 Online:2012-05-25 Published:2012-05-22

Abstract: In this paper, we proved: Let $k\geqslant 2$ be a positive integer, $\mathcal{F}$ be a family of holomorphic functions, all of whose zeros have multiplicities at least $k$, and let $h(z)$, $a_1(z)$, $a_2(z)$, $\cdots$, $a_k(z)$ are all nonequivalent to $0$ on $D$. If for any  $f\in\mathcal{F}$, the following two conditions are satisfied: (a)~$f(z)=0\Rightarrow |f^{(k)}(z)+a_1(z)f^{(k-1)}(z)+\cdots+a_k(z)f(z)|<|h(z)|$; (b)~$f^{(k)}(z)+a_1(z)f^{(k-1)}(z)+\cdots+a_k(z)f(z)\neq h(z),$~ where ~$a_1(z), a_2(z),\cdots ,a_k(z)$ and $f$ have no common zeros, then $\mathcal{F}$ is normal on $D$.

Key words: holomorphic function, differential polynomial, normal

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