Asymptotic Behavior of Monodromy Singularly Perturbed Differential E

This book concerns the question of how the solution of a system of ODE's varies when the differential equation varies. The goal is to give nonzero asymptotic expansions for the solution in terms of a parameter expressing how some coefficients go to infini

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B. Eckmann. Zurich F. Takens. Groningen

1502

Carlos Simpson

Asymptotic Behavior of Monodromy Singularly Perturbed Differential Equations on a Riemann Surface

Springer-Verlag Berlin Heidelberg New York London Paris Tokyo Hong Kong Barcelona Budapest

Author Carlos Simpson Laboratoire de Topologie et Geometrie, URA Universite Paul Sabatier, U. F. R. M. 1.G. 31062 Toulouse-Cedex, France

Mathematics Subject Classification (1991): 34015, 14E20, 30E15, 34B25, 41A60

ISBN 3-540-55009-7 Springer-Verlag Berlin Heidelberg New York ISBN 0-387-55009-7 Springer-Verlag New York Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. © Springer-Verlag Berlin Heidelberg 1991 Printed in Germany Typesetting: Camera ready by author Printing and binding: Druckhaus Beltz, Hemsbach/Bergstr. 46/3140-543210- Printed on acid-free paper

CONTENTS

Introduction (I-XII)

1

1

Ordinary differential equations on a Riemann surface

12

2

Laplace transform, asymptotic expansions, and the method of stationary phase

17

3

Construction of flows

31

4

Moving relative homology chains

41

5

The main lemma

54

6

Finiteness lemmas

60

7

Sizes of cells

68

8

Moving the cycle of integration

84

9

Bounds on multiplicities

93

10

Regularity of individual terms

101

11

Complements and examples

III

12

The Sturm-Liouville problem

127

References

135

Index

138

INTRODUCTION

We will study the question of how the solution behaves when an algebraic system of linear ordinary differential equations varies. We will consider a family of ordinary differential equations indexed linearly by a parameter t, different from the parameter of differentiation z, Fix initial conditions at a point z = P; then each equation uniquely determines its solution at all other points. The solutions depend on the equations, so they depend on the parameter t. Evaluating the solutions at a point z = Q, we get a function m( Q, t). We will investigate the behavior of this family of solutions, as t 00 in such a way that some coefficients of the equations go to infinity. The simplest example of this situation is the family of equations

dm

dz

tm =

a.

With initial conditions mea, t) 1, the solution is m(z, t) = et z . For a fixed z = Q, this behaves exponentially in t. We will look at some families of equations generalizing this basic example, allowing r x r matrix-valued functions for the coefficients and solutions, and considering equations which are holornorphic and defined globally on a compact Riemann surf