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Article
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Transactions of the American Mathematical Society
Article . 1974 . Peer-reviewed
Data sources: Crossref
Transactions of the American Mathematical Society
Article . 1974 . Peer-reviewed
Data sources: Crossref
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Canonical forms and principal systems for general disconjugate equations

Authors: Trench, William F.;

Canonical forms and principal systems for general disconjugate equations

Abstract

It is shown that the disconjugate equation (1) L x ≡ ( 1 / β n ) ( d / d t ) ⋅ ( 1 / β n − 1 ) ⋯ ( d / d t ) ( 1 / β 1 ) ( d / d t ) ( x / β 0 ) = 0 Lx \equiv (1/{\beta _n})(d/dt) \cdot (1/{\beta _{n - 1}}) \cdots (d/dt)(1/{\beta _1})(d/dt)(x/{\beta _0}) = 0 , a > t > b > t > b , where β i > 0 {\beta _i} > 0 , and (2) β i ∈ C ( a , b ) {\beta _i} \in C(a,b) , can be written in essentially unique canonical forms so that ∫ b β i d t = ∞ ( ∫ a β i d t = ∞ ) {\smallint ^b}{\beta _i}dt = \infty ({\smallint _a}{\beta _i}dt = \infty ) for 1 ≤ i ≤ n − 1 1 \leq i \leq n - 1 . From this it follows easily that (1) has solutions x 1 , … , x n {x_1}, \ldots ,{x_n} which are positive in (a, b) near b ( a ) b(a) and satisfy lim t → b − x i ( t ) / x j ( t ) = 0 ( lim t → a + x i ( t ) / x j ( t ) = ∞ ) {\lim _{t \to b}} - {x_i}(t)/{x_j}(t) = 0({\lim _{t \to a}} + {x_i}(t)/{x_j}(t) = \infty ) for 1 ≤ i > j ≤ n 1 \leq i > j \leq n . Necessary and sufficient conditions are given for (1) to have solutions y 1 , … , y n {y_1}, \ldots ,{y_n} such that lim t → b − y i ( t ) / y j ( t ) = lim t → a + y j ( t ) / y i ( t ) = 0 {\lim _{t \to b}} - {y_i}(t)/{y_j}(t) = {\lim _{t \to a}} + {y_j}(t)/{y_i}(t) = 0 for 1 ≤ i > j ≤ n 1 \leq i > j \leq n . Using different methods, P. Hartman, A. Yu. Levin and D. Willett have investigated the existence of fundamental systems for (1) with these properties under assumptions which imply the stronger condition ( 2 ′ ) β i ∈ C ( n − i ) ( a , b ) (2’){\beta _i} \in {C^{(n - i)}}(a,b) .

Keywords

Qualitative theory for ordinary differential equations, Oscillation theory, zeros, disconjugacy and comparison theory for ordinary differential equations

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
120
Top 10%
Top 1%
Average
bronze