Zeros of derivatives of meromorphic functions with one pole*
作者:
A. Hinkkanen,
期刊:
Complex Variables, Theory and Application: An International Journal
(Taylor Available online 1998)
卷期:
Volume 37,
issue 1-4
页码: 279-369
ISSN:0278-1077
年代: 1998
DOI:10.1080/17476939808815138
出版商: Gordon and Breach Science Publishers
关键词: Entire functions;meromorphic functions;Primary 30D05
数据来源: Taylor
摘要:
Suppose thatf(z) =g(z)/znwheregis a real entire function of finite order withg(0)≠ 0 andnis a positive integer, and thatff′, andf″ have only red zeros. We prove thatthengis a polynomial of degree not exceedingn+1. This strengthens an earlier result of the author, when one had to consider derivatives up to an order depending onfand the order of the entire functiongConversely, iffis of this form wheregis a polynomial of degree at mostnwith only real zeros, thenf(k) has only real zeros for allk≥ 0. If the degree ofgisn+1 thenf(k) has only real zeros for allk≥ 0 if, and only iffandf′ have only real zeros.
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