Physics Department Drexel University Philadelphia, PA

Transcription

1 Overview- Overview- Physics Department Drexel University Philadelphia, PA Colloquium, Department of Applied Mathematics New Jersey Institute of Technology Newark, New Jersey 071 October 8, 2009

2 Abstract Overview- Overview- Abstract Analysis of experimental data from many physical systems (lasers, chemical reactions, electrical circuits, vibrating strings) has lead to a deeper understanding of low-dimensional strange attractors and their perestroikas. They can now be classified. The classification is topological, with four levels of structure. Each is discrete. The signatures that identify these levels can be and have been extracted from experimental data. These advances have raised additional questions that require new mathematics for their resolution.

3 Table of Contents Overview- Overview- Outline 1 Overview 2 Experimental Challenge 3 Topology of Orbits 4 Topological Analysis Program 5 Basis Sets of Orbits 6 Bounding Tori 7 Covers and Images 8 Quantizing Chaos 9 Representation Theory of Strange Attractors 10 Summary

4 Background J. R. Tredicce Overview- Overview- Can you explain my data? I dare you to explain my data!

5 Motivation Where is Tredicce coming from? Overview- Overview- Feigenbaum: α = δ =

6 Experiment Laser with Modulated Losses Experimental Arrangement Overview- Overview-

7 Our Hope Original Objectives Overview- Overview- Construct a simple, algorithmic procedure for: Classifying strange attractors Extracting classification information from experimental signals.

8 Our Result Overview- Overview- Result There is now a classification theory. 1 It is topological 2 It has a hierarchy of 4 levels 3 Each is discrete 4 There is rigidity and degrees of freedom 5 It is applicable to R 3 only for now

9 Topology Enters the Picture Overview- Overview- The 4 Levels of Structure Basis Sets of Orbits Branched Manifolds Bounding Tori Extrinsic Embeddings

10 New Mathematics Overview- Overview- What 1 Cover and Image Relations 2 Continuations: Analytical, Topological, Group 3 Cauchy Riemann & Clebsch-Gordonnery for Dynamical Systems 4 Quantizing Chaos 5 Representation Theory for Dynamical Systems What Do We Need to Learn? 1 Higher Dimensions 2 Invariants 3 Mechanisms

11 Experimental Schematic Laser Experimental Arrangement Overview- Overview-

12 Experimental Motivation Oscilloscope Traces Overview- Overview-

13 Results, Single Experiment Bifurcation Schematics Overview- Overview-

14 Some Attractors Coexisting Basins of Attraction Overview- Overview-

15 Many Experiments Bifurcation Perestroikas Overview- Overview-

16 Real Data Experimental Data: LSA Overview- Overview- Lefranc - Cargese

17 Real Data Experimental Data: LSA Overview- Overview-

18 Mechanism Stretching & Squeezing in a Torus Overview- Overview-

19 Time Evolution Rotating the Poincaré Section around the axis of the torus Overview- Overview-

20 Time Evolution Rotating the Poincaré Section around the axis of the torus Overview- Overview- Lefranc - Cargese

21 Chaos Overview- Overview- Motion that is Deterministic: Recurrent Non Periodic Chaos dx dt = f(x) Sensitive to Initial Conditions

22 Strange Attractor Overview- Overview- Strange Attractor The Ω limit set of the flow. There are unstable periodic orbits in the strange attractor. They are Abundant Outline the Strange Attractor Are the Skeleton of the Strange Attractor

23 UPOs: Skeletons of Strange Attractors Overview- Overview-

24 UPOs: Skeletons of Strange Attractors Overview- Overview-

25 UPOs: Skeletons of Strange Attractors Overview- Overview-

26 UPOs: Skeletons of Strange Attractors Overview- Overview-

27 Skeletons UPOs Outline Strange Attractors Overview- Overview- Lefranc - Cargese

28 Dynamics and Topology Overview- Overview- Organization of UPOs in R 3 : Gauss Linking Number LN(A, B) = 1 (ra r B ) dr A dr B 4π r A r B 3 # Interpretations of LN # Mathematicians in World

29 Linking Numbers Linking Number of Two UPOs Overview- Overview- Lefranc - Cargese

30 Mechanisms for Generating Chaos Stretching and Folding Overview- Overview-

31 Mechanisms for Generating Chaos Tearing and Squeezing Overview- Overview-

32 Motion of Blobs in Phase Space Stretching Squeezing Overview- Overview-

33 Collapse Along the Stable Manifold Birman - Williams Projection Identify x and y if lim x(t) y(t) 0 t Overview- Overview-

34 Fundamental Theorem Birman - Williams Theorem If: Overview- Overview- Then:

35 Fundamental Theorem Birman - Williams Theorem Overview- Overview- If: Then: Certain Assumptions

36 Fundamental Theorem Birman - Williams Theorem Overview- Overview- If: Then: Certain Assumptions Specific Conclusions

37 Birman-Williams Theorem Overview- Overview- Assumptions, B-W Theorem A flow Φ t (x) on R n is dissipative, n = 3, so that λ 1 > 0, λ 2 = 0, λ 3 < 0. Generates a hyperbolic strange attractor SA IMPORTANT: The underlined assumptions can be relaxed.

38 Birman-Williams Theorem Overview- Overview- Conclusions, B-W Theorem The projection maps the strange attractor SA onto a 2-dimensional branched manifold BM and the flow Φ t (x) on SA to a semiflow Φ(x) t on BM. UPOs of Φ t (x) on SA are in 1-1 correspondence with UPOs of Φ(x) t on BM. Moreover, every link of UPOs of (Φ t (x), SA) is isotopic to the correspond link of UPOs of (Φ(x) t, BM). Remark: One of the few theorems useful to experimentalists.

39 A Very Common Mechanism Overview- Overview- Attractor Rössler: Branched Manifold

40 A Mechanism with Symmetry Overview- Overview- Attractor Lorenz: Branched Manifold

41 Examples of Branched Manifolds Inequivalent Branched Manifolds Overview- Overview-

42 Aufbau Princip for Branched Manifolds Any branched manifold can be built up from stretching and squeezing units Overview- Overview- subject to the conditions: Outputs to Inputs No Free Ends

43 Dynamics and Topology Rossler System Overview- Overview-

44 Dynamics and Topology Lorenz System Overview- Overview-

45 Dynamics and Topology Poincaré Smiles at Us in R 3 Overview- Overview- Determine organization of UPOs Determine branched manifold Determine equivalence class of SA

46 We Like to be Organized Overview- Overview-

47 We Like to be Organized Overview- Overview-

48 Topological Analysis Program Overview- Overview- Topological Analysis Program Locate Periodic Orbits Create an Embedding Determine Topological Invariants (LN) Identify a Branched Manifold Verify the Branched Manifold Model the Dynamics Validate the Model Additional Steps

49 Locate UPOs Method of Close Returns Overview- Overview-

50 Embeddings Overview- Overview- Embeddings Many Methods: Time Delay, Differential, Hilbert Transforms, SVD, Mixtures,... Tests for Embeddings: Geometric, Dynamic, Topological None Good We Demand a 3 Dimensional Embedding

51 Locate UPOs An Embedding and Periodic Orbits Overview- Overview-

52 Determine Topological Invariants Linking Number of Orbit Pairs Overview- Overview- Lefranc - Cargese

53 Determine Topological Invariants Compute Table of Experimental LN Overview- Overview-

54 Determine Topological Invariants Compare w. LN From Various BM Overview- Overview-

55 Determine Topological Invariants Guess Branched Manifold Overview- Overview- Lefranc - Cargese

56 Determine Topological Invariants Overview- Overview- Identification & Confirmation BM Identified by LN of small number of orbits Table of LN GROSSLY overdetermined Predict LN of additional orbits Rejection criterion

57 Determine Topological Invariants What Do We Learn? BM Depends on Embedding Some things depend on embedding, some don t Depends on Embedding: Global Torsion, Parity,.. Independent of Embedding: Mechanism Overview- Overview-

58 Perestroikas of Strange Attractors Evolution Under Parameter Change Overview- Overview-

59 Perestroikas of Strange Attractors Evolution Under Parameter Change Overview- Overview-

60 An Unexpected Benefit Analysis of Nonstationary Data Overview- Overview- Lefranc - Cargese

61 Last Steps Overview- Overview- Model the Dynamics A hodgepodge of methods exist: # Methods # Physicists Validate the Model Needed: Nonlinear analog of χ 2 test. OPPORTUNITY: Tests that depend on entrainment/synchronization.

62 Our Hope Now a Result Overview- Overview- Compare with Original Objectives Construct a simple, algorithmic procedure for: Classifying strange attractors Extracting classification information from experimental signals.

63 Orbits Can be Pruned There Are Some Missing Orbits Overview- Overview- Lorenz Shimizu-Morioka

64 Linking Numbers, Relative Rotation Rates, Braids Orbit Forcing Overview- Overview-

65 An Ongoing Problem Forcing Diagram - Horseshoe Overview- Overview-

66 An Ongoing Problem Overview- Overview- Status of Problem Horseshoe organization - active More folding - barely begun Circle forcing - even less known Higher genus - new ideas required

67 Bounding Tori Overview- Overview- Constraints on Branched Manifolds Inflate a strange attractor Union of ɛ ball around each point Boundary is surface of bounded 3D manifold Torus that bounds strange attractor

68 Torus and Genus Torus, Longitudes, Meridians Overview- Overview-

69 Flows on Surfaces Overview- Overview- Surface Singularities Flow field: three eigenvalues: +, 0, Vector field perpendicular to surface Eigenvalues on surface at fixed point: +, All singularities are regular saddles s.p. ( 1)index = χ(s) = 2 2g # fixed points on surface = index = 2g - 2

70 Flows in Vector Fields Flow Near a Singularity Overview- Overview-

71 Some Bounding Tori Torus Bounding Lorenz-like Flows Overview- Overview-

72 Canonical Forms Twisting the Lorenz Attractor Overview- Overview-

73 Constraints Provided by Bounding Tori Two possible branched manifolds in the torus with g=4. Overview- Overview-

74 Use in Physics Bounding Tori contain all known Strange Attractors Overview- Overview-

75 Labeling Bounding Tori Overview- Overview- Labeling Bounding Tori Poincaré section is disjoint union of g-1 disks Transition matrix sum of two g-1 g-1 matrices One is cyclic g-1 g-1 matrix Other represents union of cycles Labeling via (permutation) group theory

76 Some Bounding Tori Bounding Tori of Low Genus Overview- Overview-

77 Motivation Some Genus-9 Bounding Tori Overview- Overview-

78 Aufbau Princip for Bounding Tori Any bounding torus can be built up from equal numbers of stretching and squeezing units Overview- Overview- Rules Outputs to Inputs Colorless No Free Ends

79 Aufbau Princip for Bounding Tori Application: Lorenz Dynamics, g=3 Overview- Overview-

80 Poincaré Section Construction of Poincaré Section Overview- Overview-

81 Exponential Growth The Growth is Exponential Overview- Overview-

82 Exponential Growth The Growth is Exponential The Entropy is log 3 Overview- Overview-

83 Extrinsic Embedding of Bounding Tori Extrinsic Embedding of Intrinsic Tori Overview- Overview- Partial classification by links of homotopy group generators. Nightmare Numbers are Expected.

84 Modding Out a Rotation Symmetry Modding Out a Rotation Symmetry X Y Z u v w = Re (X + iy ) 2 Im (X + iy ) 2 Z Overview- Overview-

85 Lorenz Attractor and Its Image Overview- Overview-

86 Lifting an Attractor: Cover-Image Relations Creating a Cover with Symmetry X Y Z u v w = Re (X + iy ) 2 Im (X + iy ) 2 Z Overview- Overview-

87 Cover-Image Related Branched Manifolds Cover-Image Branched Manifolds Overview- Overview-

88 Covering Branched Manifolds Two Two-fold Lifts Different Symmetry Overview- Overview- Rotation Symmetry Inversion Symmetry

89 Topological Indices Topological Index: Choose Group Choose Rotation Axis (Singular Set) Overview- Overview-

90 Locate the Singular Set wrt Image Different Rotation Axes Produce Different (Nonisotopic) Lifts Overview- Overview-

91 Nonisotopic Locally Diffeomorphic Lifts Overview- Overview-

92 Indices (0,1) and (1,1) Two Two-fold Covers Same Symmetry Overview- Overview-

93 Indices (0,1) and (1,1) Three-fold, Four-fold Covers Overview- Overview-

94 Two Inequivalent Lifts with V 4 Symmetry Overview- Overview-

95 How to Construct Covers/Images Overview- Overview- Algorithm Construct Invariant Polynomials, Syzygies, Radicals Construct Singular Sets Determine Topological Indices Construct Spectrum of Structurally Stable Covers Structurally Unstable Covers Interpolate

96 Surprising New Findings Overview- Overview- Symmetries Due to Symmetry Schur s Lemmas & Equivariant Dynamics Cauchy Riemann Symmetries Clebsch-Gordon Symmetries Continuations Analytic Continuation Topological Continuation Group Continuation

97 Covers of a Trefoil Torus Overview- Overview- Granny Knot Square Knot Trefoil Knot

98 You Can Cover a Cover = Lift a Lift Covers of Covers of Covers Overview- Overview- Rossler Lorenz Ghrist

99 Universal Covering Group Cartan s Theorem for Lie Groups Overview- Overview-

100 Universal Image Dynamical System Locally Diffeomorphic Covers of D Overview- Overview- D: Universal Image Dynamical System

101 Creating New Attractors Overview- Overview- Rotating the Attractor [ d X dt Y ] = [ u(t) v(t) [ d u dt v [ F1 (X, Y ) F 2 (X, Y ) ] [ cos Ωt sin Ωt = sin Ωt cos Ωt ] ] [ a1 sin(ω + d t + φ 1 ) a 2 sin(ω d t + φ 2 ) ] [ X(t) Y (t) [ = RF(R 1 v u) + Rt + Ω +u ] ] ] Ω = n ω d Global Diffeomorphisms q Ω = p ω d Local Diffeomorphisms (p-fold covers)

102 Two Phase Spaces: R 3 and D 2 S 1 Rossler Attractor: Two Representations R 3 D 2 S 1 Overview- Overview-

103 Other Diffeomorphic Attractors Rossler Attractor: Two More Representations with n = ±1 Overview- Overview-

104 Subharmonic, Locally Diffeomorphic Attractors Rossler Attractor: Two Two-Fold Covers with p/q = ±1/2 Overview- Overview-

105 Subharmonic, Locally Diffeomorphic Attractors Rossler Attractor: Two Three-Fold Covers with p/q = 2/3, 1/3 Overview- Overview-

106 Subharmonic, Locally Diffeomorphic Attractors Rossler Attractor: And Even More Covers (with p/q = +1/3, +2/3) Overview- Overview-

107 New Measures Overview- Angular Momentum and Energy 1 τ L(0) = lim XdY Y dx τ τ 0 L(Ω) = u v v u 1 τ 1 K(0) = lim τ τ 0 2 (Ẋ2 +Ẏ 2 )dt K(Ω) = 1 2 ( u2 + v 2 ) Overview- = L(0) + Ω R 2 = K(0) + ΩL(0) Ω2 R 2 R 2 1 = lim τ τ τ 0 (X 2 + Y 2 1 )dt = lim τ τ τ 0 (u 2 + v 2 )dt

108 New Measures, Diffeomorphic Attractors Energy and Angular Momentum Diffeomorphic, Quantum Number n Overview- Overview-

109 New Measures, Subharmonic Covering Attractors Energy and Angular Momentum Subharmonics, Quantum Numbers p/q Overview- Overview-

110 Embeddings Overview- Overview- Embeddings An embedding creates a diffeomorphism between an ( invisible ) dynamics in someone s laboratory and a ( visible ) attractor in somebody s computer. Embeddings provide a representation of an attractor. Equivalence is by Isotopy. Irreducible is of Minimum Dimension

111 Representation Labels Inequivalent Irreducible Representations Irreducible Representations of 3-dimensional Genus-one attractors are distinguished by three topological labels: Overview- Overview- Parity Global Torsion Knot Type Γ P,N,KT (SA) P N KT Mechanism (stretch & fold, stretch & roll) is an invariant of embedding. It is independent of the representation labels.

112 Creating Isotopies Overview- Overview- Equivalent Reducible Representations Topological indices (P,N,KT) are obstructions to isotopy for embeddings of minimum dimension (irreducible representations). Are these obstructions removed by injections into higher dimensions (reducible representations)? Systematically?

113 Creating Isotopies Equivalences by Injection Obstructions to Isotopy Overview- Overview- R 3 Global Torsion Parity Knot Type R 4 Global Torsion (mod 2) R 5 There is one Universal reducible representation in R N, N 5. In R N the only topological invariant is mechanism.

114 The Road Ahead Overview- Summary 1 Question Answered 2 Questions Raised We must be on the right track! Overview-

115 Our Hope Overview- Overview- Original Objectives Achieved There is now a simple, algorithmic procedure for: Classifying strange attractors Extracting classification information from experimental signals.

116 Our Result Overview- Overview- What There is now a classification theory for low-dimensional strange attractors. 1 It is topological 2 It has a hierarchy of 4 levels 3 Each is discrete 4 There is rigidity and degrees of freedom 5 It is applicable to R 3 only for now

117 Four Levels of Structure The Classification Theory has 4 Levels of Structure Overview- Overview-

118 Four Levels of Structure Overview- The Classification Theory has 4 Levels of Structure 1 Basis Sets of Orbits Overview-

119 Four Levels of Structure Overview- Overview- The Classification Theory has 4 Levels of Structure 1 Basis Sets of Orbits 2 Branched Manifolds

120 Four Levels of Structure Overview- Overview- The Classification Theory has 4 Levels of Structure 1 Basis Sets of Orbits 2 Branched Manifolds 3 Bounding Tori

121 Four Levels of Structure Overview- Overview- The Classification Theory has 4 Levels of Structure 1 Basis Sets of Orbits 2 Branched Manifolds 3 Bounding Tori 4 Extrinsic Embeddings

122 Four Levels of Structure Overview- Overview-

123 Topological Components Poetic Organization Overview- Overview- LINKS OF PERIODIC ORBITS organize BOUNDING TORI organize BRANCHED MANIFOLDS organize LINKS OF PERIODIC ORBITS

124 Answered Questions Overview- Overview- Some Unexpected Results Perestroikas of orbits constrained by branched manifolds Routes to Chaos = Paths through orbit forcing diagram Perestroikas of branched manifolds constrained by bounding tori Global Poincaré section = union of g 1 disks Systematic methods for cover - image relations Existence of topological indices (cover/image) Universal image dynamical systems NLD version of Cartan s Theorem for Lie Groups Topological Continuation Group Continuation Cauchy-Riemann Symmetries Quantizing Chaos Representation labels for inequivalent embeddings Representation Theory for Strange Attractors

125 Unanswered Questions Overview- Overview- HELP: Robust topological invariants for R N, N > 3 A Birman-Williams type theorem for higher dimensions An algorithm for irreducible embeddings Embeddings: better methods and tests Analog of χ 2 test for NLD Better forcing results: Smale horseshoe, D 2 D 2, n D 2 n D 2 (e.g., Lorenz), D N D N, N > 2 A new Representation theory Singularity Theory: Branched manifolds, splitting points (0 dim.), branch lines (1 dim). Catastrophe Theory Nonlinear Dynamics Connection