当前位置: X-MOL 学术Comput. Methods Funct. Theory › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Deficient Values of Solutions of Linear Differential Equations
Computational Methods and Function Theory ( IF 2.1 ) Pub Date : 2020-05-12 , DOI: 10.1007/s40315-020-00320-1
Gary G. Gundersen , Janne Heittokangas , Zhi-Tao Wen

Differential equations of the form \(f'' + A(z)f' + B(z)f = 0\) (*) are considered, where A(z) and \(B(z) \not \equiv 0\) are entire functions. The Lindelöf function is used to show that for any \(\rho \in (1/2, \infty )\), there exists an equation of the form (*) which possesses a solution f with a Nevanlinna deficient value at 0 satisfying \(\rho =\rho (f)\ge \rho (A)\ge \rho (B)\), where \(\rho (h)\) denotes the order of an entire function h. It is known that such an example cannot exist when \(\rho \le 1/2\). For smaller growth functions, a geometrical modification of an example of Anderson and Clunie is used to show that for any \(\rho \in (2, \infty )\), there exists an equation of the form (*) which possesses a solution f with a Valiron deficient value at 0 satisfying \(\rho =\rho _{\log }(f)\ge \rho _{\log }(A)\ge \rho _{\log }(B)\), where \(\rho _{\log }(h)\) denotes the logarithmic order of an entire function h. This result is essentially sharp. In both proofs, the separation of the zeros of the indicated solution plays a key role. Observations on the deficient values of solutions of linear differential equations are also given, which include a discussion of Wittich’s theorem on Nevanlinna deficient values, a modified Wittich theorem for Valiron deficient values, consequences of Gol’dberg’s theorem, and examples to illustrate possibilities that can occur.



中文翻译:

线性微分方程解的不足值

考虑形式为\(f''+ A(z)f'+ B(z)f = 0 \)(*)的微分方程,其中Az)和\(B(z)\ not \ equiv 0 \)是全部功能。Lindelöf函数用于表明,对于任何\(\ rho \ in(1/2,\ infty)\),存在一个形式为(*)的方程,该方程具有n为零的Nevanlinna不足值的解f满足\(\ rho = \ rho(f)\ ge \ rho(A)\ ge \ rho(B)\),其中\(\ rho(h)\)表示整个函数h的阶数。众所周知,当\(\ rho \ le 1/2 \)时,这样的示例将不存在。对于较小的增长函数,对Anderson和Clunie的示例进行了几何修改,以显示对于任何\(\ rho \ in(2,\ infty)\),存在一个形式为(*)的方程,该方程具有解决方案f的Valiron不足值为0满足\(\ rho = \ rho _ {\ log}(f)\ ge \ rho _ {\ log}(A)\ ge \ rho _ {\ log}(B)\ ),其中\(\ rho _ {\ log}(h)\)表示整个函数h的对数阶。该结果实质上是清晰的。在这两种证明中,指示解的零点的分离起着关键作用。还给出了对线性微分方程解解的不足值的观察,包括对Nevanlinna不足值的Wittich定理的讨论,对Valiron不足值的修改的Wittich定理,Gol'dberg定理的结果以及举例说明可以发生。

更新日期:2020-05-12
down
wechat
bug