S E L E C T E D B Y G R E N O B L E S C I E N C E S CCoommpplleexx DDyynnaammiiccss aanndd MMoorrpphhooggeenneessiiss AAnn IInnttrroodduuccttiioonn ttoo NNoonnlliinneeaarr SScciieennccee Chaouqi Misbah Complex Dynamics and Morphogenesis Grenoble Sciences The aim of Grenoble Sciences is twofold: to produce works corresponding to a clearly defined project, without the constraints of trends nor curriculum; toensuretheutmostscientificandpedagogicqualityoftheselectedworks: each project is selected by Grenoble Sciences with the help of anonymous referees. In order to optimize the work, the authors interact for a year (onaverage)withthemembersofareadingcommittee,whosenamesfigure in the front pages of the work, which is then co-published with the most suitable publishing partner. Contact Tel.: (33) 4 76 51 46 95 E-mail: [email protected] Website: https://grenoble-sciences.ujf-grenoble.fr Scientific Director of Grenoble Sciences Jean Bornarel, Emeritus Professor at the Grenoble Alpes University, Grenoble, France Grenoble Sciences is a department of the Grenoble Alpes University supported by the ministère de l’Éducation nationale, de l’Enseignement supérieur et de la Recherche and the région Auvergne-Rhône-Alpes. Complex Dynamics and Morphogenesis is an improved version of the original book Dynamiques complexes et morphogenèse by Chaouqi Misbah, Springer-Verlag France, 2011,ISBN 978 2 8178 0193 3. The reading committee included the following members: Bernard Billia, CNRS Senior Researcher,IM2NP, Marseille; François Charru, Professor, Toulouse University; Stéphane Douady, CNRS Researcher, Laboratoire MSC, Paris; Hamid Kellay, Professor, Bordeaux University; Paul Manneville, CNRS Senior Researcher, LADHYX, Palaiseau; Christian Wagner, Professor, Saarland University. Editorial coordination: Stéphanie Trine; translation from original French version:JoyceLainé;copy-editing:AliWoollattandStéphanieTrine;figures: Sylvie Bordage; cover illustration: Alice Giraud, from fig. 1.4 [(cid:2)c NOAA], 13.5a [(cid:2)c forcdan Fotolia], 15.2 [all rights reserved], 15.3d [from [78], reprinted with permission from Macmillan Publishers Ltd] and elements provided by the author. Chaouqi Misbah Complex Dynamics and Morphogenesis An Introduction to Nonlinear Science 123 ChaouqiMisbah CNRS Laboratoire Interdisciplinaire dePhysique Grenoble France Co-published by Springer International Publishing AG, Gewerbestrasse 11, 3330 Cham, Switzerland, and Editions Grenoble Sciences, Université Joseph Fourier, 230 rue de la Physique, BP5338041Grenoble cedex09, France. ISBN978-94-024-1018-1 ISBN978-94-024-1020-4 (eBook) DOI 10.1007/978-94-024-1020-4 LibraryofCongressControlNumber:2016958460 ©SpringerScience+BusinessMediaB.V.2017 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinor foranyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerScience+BusinessMediaB.V. Theregisteredcompanyaddressis:VanGodewijckstraat30,3311GXDordrecht,TheNetherlands To Florence, Hisham and Sammy To my parents, sisters and brothers Foreword As stated by its subtitle, this book is an introduction to nonlinear sciences. Thissubtitlehasthemeritofemphasizingthemultiplicityofthisbookwhich deals with biology, chemistry, and of course physics and mathematics. If someone thought to divide science into linear and nonlinear science, no doubt that the latter would form the main part. However, the range of linear physics, i.e. physics described by first order equations, is surprisingly extended. For instance, linear elasticity is a good approximation in many cases. Maxwell’s equations of electromagnetism are linear with respect to theelectromagneticfield.Schrödinger’sandDirac’sequationsarelinearwith respect to the wavefunction. These partial differential equations allow the use of sophisticated mathematical techniques such as Green’s functions and retarded potentials, making linear physics efficient, but also cumbersome. Nonlinear science is quite different: analytic methods are of limited use. Computers may of course provide a workaround, but numerical results do not give the same insight as analytic arguments. Thus, a texbook on non- linear science has to be less ambitious in its accuracy of description than a book on quantum mechanics, electromagnetism or elasticity – but it may be more pleasantto read.The presentbookby ChaouqiMisbahhas this virtue. Sinceonecannotgomoredeeplyintodetails,itpresentstheessentialfeatures, sometimes in a purely qualitative way.These features have an extraordinary diversity, in contrast to the rather monotonous landscape of linear physics. In this book, the reader finds a variety of phenomena, many familiar but not understood – for example, a swing. It is unfortunate that children at school do not learn how to use a swing, because they would discover what parametric resonance is. As explained in the book, the greatestamplitude is reached if the child lowers their center of mass when the swing goes up, and raisesitwhentheswinggoesdown,creatinganexcitationfrequencyattwice the natural frequency of the swing. This is typical of parametric resonance. VIII Complex Dynamics and Morphogenesis Swings are not the only entertainment the reader may find in this book. Anotherexampleis thetransitiontochaosbysubharmoniccascade.Isitnot engaging to play with a pocket computer and observe how the change of a parameter (a in formula (8.8)) changes the trivial fixed point into a discrete limit cycle of2 points,then 4 points,8 points,etc., before reachingcomplete chaos?Thiswillbesurprisingforthenewcomertononlinearscience;another surprise awaits (section 8.5) with the discovery that the continuous version of the same model is not chaotic at all but has a perfectly stable, nontrivial fixed point. All the same, nonlinear science cannot be reduced to entertainment, as the reasonable number of equations and formulae in this book testify. Mathematical formulae are certainly necessary for the precise description of physical phenomena. They can also be a didactic tool for clarifying an argument. For example, in chapter 4 of the book, catastrophes are classified for cases of up to 4 control parameters. As it turns out, there are 7 catas- trophes (as Snow White is accompanied by 7 dwarfs, as the golden Hebrew lampstand has 7 branches!). As noted in the book, this classification can be done without writing the equations governing the systems, but the au- thor’s argument does rely on mathematical formulae. Although not strictly necessary, they certainly simplify the proof. A merit of this book lies in its clever use of mathematical formulae to help one understand the mechanism but avoiding complications when not absolutely necessary. Sometimes they are necessary: chapters 10 and 12 are really tough. However,as a whole, the reader has before them an enjoyable source of discoveries which mixes rigor and entertainment harmoniously. Jacques Villain Emeritus CEA Senior Researcher Member of the French Academy of Sciences Acknowledgments I am indebted to Christiane Caroli and Philippe Nozières for their sup- portive attitudes which encouraged me to undertake the project of writing this book. I am also grateful to Michel Saint Jean who encouraged me from the outset of this project and Jacques Villain for many enlightening discus- sions, and I warmly thank the members of my research team in Grenoble, Dynamique des Fluides Complexes et Morphogenèse (DYFCOM), for the critical reading of the manuscript. I thank especially Pierre-Yves Gires who has gone into many details of the derivations of the model equations and their solutions, Christian Wojcik for preparing many plots, Richard Michel who produced from scratch many numerical results presented in this book and Alexander Farutin for checking the solutions to the exercises. I express my gratitude to Marc Rabaud for having redone the Saffman–Taylor exper- iment and providing me with the photos presented in chapter 15. During the elaboration of this project I have greatly benefitted from references [6,9,16,23,29,32,42,58,75,77,80,87,91,99,101]. Chaouqi Misbah Contents Chapter 1 – Presentation of Main Ideas 1 Chapter 2 – Basic Introduction to Bifurcations in 1-D 15 2.1. A Simple Mechanical Example ......................................... 16 2.1.1. Potential Energy and Equilibrium ............................ 16 2.1.2. An Intuitive Explanation of the Bifurcation ................ 18 2.1.3. Analysis of the Bifurcation ..................................... 19 2.1.4. Universality in the Vicinity of a Bifurcation Point ......... 20 2.2. An Analogy between Pitchfork Bifurcations and Second Order Phase Transitions .................................. 22 2.3. Dynamical Considerations .............................................. 22 2.3.1. Analysis of Linear Stability .................................... 23 2.3.2. Critical Slowing Down .......................................... 24 2.3.3. Adiabatic Elimination of Fast Modes: Reducing the Number of Degrees of Freedom ............... 25 2.3.4. Amplitude Equation ............................................ 27 2.3.5. Canonical Form of the Amplitude Equation ................ 28 2.3.6. Attractors ......................................................... 29 2.3.7. Lyapunov Function .............................................. 30 2.3.8. Symmetry Breaking ............................................. 30 2.4. Dynamical Systems and the Importance of the Pitchfork Bifurcation ............................................ 31 2.5. Exercises ................................................................... 31