DIFFERENTIAL GEOMETRY APPLIED TO DYNAMICAL SYSTEMS WORLD SCIENTIFIC SERIES ON NONLINEAR SCIENCE Editor: Leon O. Chua University of California, Berkeley Series A. MONOGRAPHS AND TREATISES* Volume 48: Bio-Inspired Emergent Control of Locomotion Systems M. Frasca, P. Arena & L. Fortuna Volume 49: Nonlinear and Parametric Phenomena V. Damgov Volume 50: Cellular Neural Networks, Multi-Scroll Chaos and Synchronization M. E. Yalcin, J. A. K. Suykens & J. P. L. Vandewalle Volume 51: Symmetry and Complexity K. Mainzer Volume 52: Applied Nonlinear Time Series Analysis M. Small Volume 53: Bifurcation Theory and Applications T. Ma & S. Wang Volume 54: Dynamics of Crowd-Minds A. Adamatzky Volume 55: Control of Homoclinic Chaos by Weak Periodic Perturbations R. Chacón Volume 56: Strange Nonchaotic Attractors U. Feudel, S. Kuznetsov & A. Pikovsky Volume 57: A Nonlinear Dynamics Perspective of Wolfram's New Kind of Science L. O. Chua Volume 58: New Methods for Chaotic Dynamics N. A. Magnitskii & S. 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Xibilia *To view the complete list of the published volumes in the series, please visit: http://www.worldscibooks.com/series/wssnsa_series.shtml Lakshmi - Diff Geometry Applied.pmd 2 9/23/2009, 1:03 PM NOWONRLLDI NSCEIEANTRIFI CS SCERIIEESN OCNE Series A Vol. 66 Series Editor: Leon O. Chua DIFFERENTIAL GEOMETRY APPLIED TO DYNAMICAL SYSTEMS Jean-Marc Ginoux Université du Sud, France World Scientific NEW JERSEY • LONDON • SINGAPORE • BEIJING • SHANGHAI • HONG KONG • TAIPEI • CHENNAI Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. World Scientific Series on Nonlinear Science, Series A — Vol. 66 DIFFERENTIAL GEOMETRY APPLIED TO DYNAMICAL SYSTEMS (With CD-ROM) Copyright © 2009 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN-13 978-981-4277-14-3 ISBN-10 981-4277-14-2 Printed in Singapore. Lakshmi - Diff Geometry Applied.pmd 1 9/23/2009, 1:03 PM September11,2009 8:55 WorldScientificBook-9inx6in DGeometry `a Christine... v September11,2009 8:55 WorldScientificBook-9inx6in DGeometry vi DifferentialGeometry Applied to Dynamical Systems “...every time the system absorbs energy the curvature of its trajectory decreases and viceversa ...”. — N.Minorsky1 1N.Minorsky(1967,p.108). September11,2009 8:55 WorldScientificBook-9inx6in DGeometry Preface The study of dynamical systems, i.e. of systems of differential equations finds roots in the works of L. A. Cauchy (1835) and the so-called calculus of limits which gave rise to an analytic approach1. Thus, many methods basedonregularexpansions enabledtodeducelocal behaviorsofdynamical systems. Then, a geometric approach was initiated by Henri Poincar´e (1881- 1886) in his famous memoirs: Sur les courbes d´efinies par une ´equation diff´erentielle whichrepresentthe foundationsofthequalitative2 orgeomet- ric theory of differential equations. Continued during the XXth century with the works of G. Valiron (1950), S. Lefschetz (1957), V. V. Nemytskii & V. V. Stepanov (1960), N. Minorsky (1962-1967), F. Brauer & J. A. Nohel (1969), ... it seems nevertheless that Differential Geometry had been rarely used for dynamical systems3 study. The aim of this book is to present a new approach which consists of applying Differential Geometry to Dynamical Systems and is called Flow Curvature Method. Thus, while considering the trajectory curve, integral of any n-dimensional dynamical system, as a curve in Euclidean n-space, the curvature of the trajectory curve, i.e. curvature of the flow may be an- alytically computed. Then, the location of the points where the curvature of the flow vanishes defines a manifold called: flow curvature manifold. It will be stated that, since such a manifold is defined starting from the 1SeeJ.Molk(1910)andE.L.Ince(1926)p. 529foraHistoryofdifferentialequations. 2See C. Gilain (1977) for details about Poincar´e’s geometric approach of differential equations. 3The oldest reference which has been indicated to me by Prof. C. Mira is: M. Haag (1879). vii September11,2009 8:55 WorldScientificBook-9inx6in DGeometry viii DifferentialGeometry Applied to Dynamical Systems time derivatives of the velocity vector field and so, contains information aboutthe dynamics ofthe system, its onlyknowledgeenables tofindagain the main features of the dynamical system studied. These features may be considered as the foundations of Dynamical Systems Theory. There are six of them: differential equations, dynamical systems, invariant sets, local bifurcations, slow-fast dynamical systems, integrability and to eachof these concepts corresponds a chapter. Thus, this manuscript has been designed inasymmetricmannerandconsistsofthreepartseachofthemcomprising these six chapters. The first part which may be regarded independently of the two others is a detailed presentation of these six chapters from the analytic point of view of Dynamical Systems Theory accompanied by references4, anecdotes and many examples. Chapter 1, Introduction, is an historical presentation of differential equations used to modelize natural phenomena. In Ch. 2, Dynamical systems, state space and flow definitions, existence and unique- ness and Liapounoff stability theorems are summarized and emphasized with original references and significant examples as well as the notion of Poincar´e index, the concept of limit cycle or strange attractor. Then, def- initions of first integral and Lie derivative which will be extensively used in this book are presented. Hamiltonian integrable systems and K.A.M. theorem are also recalled. Chapter 3, Invariant sets, consists of definitions of global (resp. local) invariant manifolds and stable manifold theorem for a fixed point. Chapter 4 entitled local bifurcations is devoted to the Center Manifold Theorem and Normal Form Theorem which are presented with originalproofsandhighlightedthroughexamplesaswellaslocalbifurcations suchassaddle-node, transcritical,pitchfork orHopf bifurcations. InCh. 5, Slow-Fast Dynamical Systems,definitionsofsingularly perturbed dynamical systems andslow-fast dynamical systems areproposed. Then,theso-called Geometric Singular Perturbation Theory andthe conceptofslow invariant manifold are recalled and emphasized with paradigmatic Van der Pol and Chua systems. In Ch. 6, Integrability, integrability conditions, integrating factor and multiplier of dynamical systems are reminded. Then, Darboux Theory of Integrability ispresentedforthefirsttimewithitsoriginalproofs and examples applied to dynamical systems. 4Historicalreferencestooriginalworksaremadebypage. September11,2009 8:55 WorldScientificBook-9inx6in DGeometry Preface ix The second part is exactly symmetric5 to the first one since it involves thesamechaptersandconceptsasthosepreviouslydefinedbutthenconsid- ered from the Differential Geometry point of view. Chapter 7, Differential Geometry, is a presentation of the concepts inherent to Differential Ge- ometry such as curves, osculating plane and curvatures. By considering the trajectory curves integral of any n-dimensional dynamical systems as curves in Euclidean n-space which possess local metrics properties of cur- vatures enables to define a manifold called: flow curvature manifold. Let’s note that the point of view is completely different from the previous one since it deals with curvature of trajectory curves insteadof vector field, i.e. one substitutes a manifold to a differential equation, to a dynamical sys- tem. Thus, the Flow Curvature Method is based on the idea that if it is generally impossible to have a closed form of the trajectory curve it is still possibletoanalyticallycomputeitscurvature sinceitonlyinvolvesitstime derivatives. Then, it will be stated in chapters 8, 9, 10 & 11 that all the results foundinchapters2,3,4,5&6suchasfixed points stability, invariant sets, centre manifold, normal forms, local bifurcations, slow invariant manifold andintegrability ofdynamical systems maybefoundagainaccordingtothe Flow Curvature Method, i.e. starting from the flow curvature manifold. In Ch. 8, it is stated that the Flow Curvature Method enables to find again stability theorems for fixed points of low-dimensional two and three dynamical systems according to a theorem due to Henri Poincar´e. In Ch. 9, concepts of global invariance and local invariance, which are of great importance since all the proofs are based on them, are (re)defined from Darboux invariance theorem. Then, it will be stated that flow cur- vature manifold also enables to “detect” linear invariant manifolds of any n-dimensional dynamical systems whichmaybeusedtobuildfirstintegrals of these systems. For nonlinear invariant manifolds identity between flow curvature manifold and the so-called extatic manifolds is also stated. In Ch. 10, it is established that the Flow Curvature Method enables to easily compute the coefficients of the centre manifold approximation of anyn-dimensional dynamical systems accordingto global invariance ofthe 5Chaptersofparttwo(three)arechapters ofpartone(two)incrementedof6.
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