Let $ \mathcal{F} $ be a family of meromorphic functions in a plane domain D, and a and b be finite non-zero complex values such that $ a/b \notin \mathbb{N}\backslash \{ 1\} $ . If for $ f \in \mathcal{F}, f(z) = a \...Let $ \mathcal{F} $ be a family of meromorphic functions in a plane domain D, and a and b be finite non-zero complex values such that $ a/b \notin \mathbb{N}\backslash \{ 1\} $ . If for $ f \in \mathcal{F}, f(z) = a \Rightarrow f'(z) = a $ and $ f'(z) = b \Rightarrow f''(z) = b $ , then $ \mathcal{F} $ is normal. We also construct a non-normal family $ \mathcal{F} $ of meromorphic functions in the unit disk Δ={|z|<1} such that for every $ f \in \mathcal{F}, f(z) = m + 1 \Leftrightarrow f'(z) = m + 1 $ and $ f'(z) = 1 \Leftrightarrow f''(z) = 1 $ in Δ, where m is a given positive integer. This answers Problem 5.1 in the works of Gu, Pang and Fang.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 10671093, 10871094)the Natural Science Foundation of Universities of Jiangsu Province of China (Grant No. 08KJB110001)the Qing Lan Project of Jiangsu, China and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry
文摘Let $ \mathcal{F} $ be a family of meromorphic functions in a plane domain D, and a and b be finite non-zero complex values such that $ a/b \notin \mathbb{N}\backslash \{ 1\} $ . If for $ f \in \mathcal{F}, f(z) = a \Rightarrow f'(z) = a $ and $ f'(z) = b \Rightarrow f''(z) = b $ , then $ \mathcal{F} $ is normal. We also construct a non-normal family $ \mathcal{F} $ of meromorphic functions in the unit disk Δ={|z|<1} such that for every $ f \in \mathcal{F}, f(z) = m + 1 \Leftrightarrow f'(z) = m + 1 $ and $ f'(z) = 1 \Leftrightarrow f''(z) = 1 $ in Δ, where m is a given positive integer. This answers Problem 5.1 in the works of Gu, Pang and Fang.
