徐洪焱,易才鳳
(1.景德鎮(zhèn)陶瓷學(xué)院信息學(xué)院,江西景德鎮(zhèn) 333403;2.江西師范大學(xué)數(shù)信學(xué)院,江西南昌 330027)
亞純函數(shù)及其n階導(dǎo)數(shù)權(quán)分擔(dān)兩個值
徐洪焱1,易才鳳2
(1.景德鎮(zhèn)陶瓷學(xué)院信息學(xué)院,江西景德鎮(zhèn) 333403;2.江西師范大學(xué)數(shù)信學(xué)院,江西南昌 330027)
研究亞純函數(shù)及其n階導(dǎo)數(shù)權(quán)分擔(dān)兩個值的唯一性問題.得到了:如果兩個非常數(shù)亞純函數(shù)f,g分擔(dān)(∞,∞),f(n)與g(n)分擔(dān)(1,0),n(≥0)為一整數(shù),且滿足△C0:= (4n+6)λ+δn+1(0,f)+δn+1(0,g)+δn+2(0,f)+δn+2(0,g)+δn(0,f)>4n+10,其中λ=max{min{Θ(∞,f),Θ(0,f)},min{Θ(∞,g),Θ(0,g)}},那么f(n)·g(n)≡1,或者f≡g.該結(jié)果改進了前人的有關(guān)定理.
亞純函數(shù);權(quán)分擔(dān);唯一性
這樣很容易知道H的極點只可能發(fā)生以下幾種情況:(1)F,G的重級零點;(2)F,G的重級極點;(3)F,G的1-值點且其重數(shù)不相等;(4)F'的零點但非F(F?1)的零點;(5)G'的零點但非G(G?1)的零點.
(i)由(i)的條件,知F,G分擔(dān)(1,0),(∞,∞),再根據(jù)H的表達式很容易知道F,G的極點不是H的極點.
如果H/≡0,由引理2.7,有
類似于情形1也可得到矛盾.
如果a?1=0,則f(n)≡g(n).由此方程可得到f=g+p(z),這里p(z)為多項式,顯然T(r,f)=T(r,g)+S(r,f).如果p(z)/≡0,根據(jù)引理2.2,有
由(1.1)式很容易得到T(r,f)≤S(r,f),r∈I矛盾.因此p(z)≡0,即f≡g.
綜合三種情形,定理1.1(i)得證.下證定理1.1(ii).
(ii)因為f(n)與g(n)分擔(dān)(1,0),所以F,G分擔(dān)(1,0).
如果H/≡0,則(3.1)式變?yōu)?/p>
如果H≡0,類似于定理1.1可以證得f(n)·g(n)≡1,或者f≡g,即定理1.2(i)得證.
類似于定理1.1(ii)證明方法并結(jié)合(4.1)-(4.4)式及f,g分擔(dān)(∞,0),也很容易證明.這里略之.
綜上所述,則完成了定理1.2的證明.
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Mermorphic functions concerning their n-th derivative sharing two values with weight
XU Hong-yan1,YI Cai-feng2
(1.Department of Informatics and Engineering,Jingdezhen Ceramic Institute,Jingdezhen333403,China; 2.Institute of Mathematics and Informatics,Jiangxi Normal University,Nanchang330027,China)
In this paper,we deal with the uniqueness problem of meromorphic functions concerning their n-th derivative sharing two values with weight and obtain the following theorem:if two nonconstant meromorphic functions f,g share(∞,∞),fn,gnshare(1,0),and satisfy△C0:=(4n+6)λ+δn+1(0,f)+δn+1(0,g)+δn+2(0,f)+ δn+2(0,g)>4n+10,where λ=max{min{Θ(∞,f),Θ(0,f)},min{Θ(∞,g),Θ(0,g)}},then either f(n)·g(n)≡1 or f≡g,where n(>0)is an integer.These results extend the former theorems.
meromorphic function,weighted sharing,uniqueness
O174.52
A
1008-5513(2009)04-0777-09
2008-04-21.
國家自然科學(xué)基金(10871108),景德鎮(zhèn)陶瓷學(xué)院科研項目(景陶院發(fā)[2009]86號).
徐洪焱(1980-),碩士,研究方向:復(fù)分析.
2000MSC:30D30,30D35