Über reduzierbarkeit und maximale ordnung bei linearen differentialgleichungssystemen
作者:
Volker Dietrich,
期刊:
Complex Variables, Theory and Application: An International Journal
(Taylor Available online 1984)
卷期:
Volume 2,
issue 3-4
页码: 353-386
ISSN:0278-1077
年代: 1984
DOI:10.1080/17476938408814055
出版商: Gordon and Breach Science Publishers
关键词: 34A30
数据来源: Taylor
摘要:
This paper is concerned with the system of ordinary linear differential equationswithA(Z) (n:)-matrix of meromorphic functions in a neighborhood of the (isolated) singular point 0 anda column vector of dimensionn. First we prove a new theorem about the reduction of such systems, by which a generally known result of J. Moser [12] from 1960 is essentially improved. With the help of a method from H. L. Turrittin [13], which was extended by us, this result finally leads to a lower bound for the reduction. Then according to our former result [7] this is also a lower bound for the maximum order ρmaxof a fundamental solution matrix: ρmax≥(1/n)δ(A). The quantity δ(A) is the limit of a sequence of quantities which characterize the singular behavior inz= 0. We will show that δ(A) is an invariant and that δ(A) = 0 holds if and only if the system is regular singular inz= 0. At the end of the paper the results will be applied to ordinary linear differential equations.
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