Braids and Dynamics

Preface
Contents
List of Symbols
1 Introduction
	1.1 Motivation: Fluid Mixing
	1.2 Taffy Pullers
	1.3 Outline
2 Topological Dynamics on the Torus
	2.1 Diffeomorphisms of the Torus
	2.2 The Fundamental Group of a Surface
	2.3 The Mapping Class Group of the Torus
	2.4 Classification of MCG(T2)
		2.4.1 Elliptic Case
		2.4.2 Parabolic Case
		2.4.3 Hyperbolic Case
	2.5 Summary
3 Stretching with Three Rods
	3.1 From the Torus to the Sphere
	3.2 The Mapping Class Groups of S4 and D3
	3.3 Dehn Twists
	3.4 Fluid Stirring with Three Rods
	3.5 Taffy Pulling with Three Rods
	3.6 Summary
4 Braids
	4.1 Braids as Particle Dances
	4.2 Algebraic Braids
	4.3 Artin's Representation
	4.4 Free Homotopy Representation
	4.5 The Burau Representation
	4.6 Summary
5 The Thurston–Nielsen Classification
	5.1 Classification of Diffeomorphisms of a Surface
	5.2 Pseudo-Anosov Maps
	5.3 The Degree of the Dilatation
	5.4 Summary
6 Topological Entropy
	6.1 Definition
	6.2 Word Length Growth
	6.3 The Burau Estimate for the Dilatation
	6.4 An Upper Bound
	6.5 Summary
7 Train Tracks
	7.1 The Figure-Eight Stirring Device
	7.2 A Second Pseudo-Anosov Example
	7.3 A Reducible Example
	7.4 Finding Cancellations
	7.5 Summary
8 Dynnikov Coordinates
	8.1 Coordinates for Multicurves
	8.2 Action of Braids on Dynnikov Coordinates (Update Rules)
		8.2.1 Update Rules for sigmai
		8.2.2 Update Rules for sigmaiinv
	8.3 Max-Plus Algebra
	8.4 Mapping Classes and Dynnikov Coordinates
		8.4.1 Finite-Order Case
		8.4.2 Reducible Case
		8.4.3 Pseudo-Anosov Case
	8.5 The Word Problem
	8.6 Summary
9 The Braidlab Library
	9.1 Setup and Getting Help
	9.2 Braids
		9.2.1 Basic Operations
		9.2.2 Representation and Invariants
	9.3 Loops
		9.3.1 Acting on Loops with Braids
		9.3.2 Loop Coordinates for a Braid
	9.4 Entropy and Train Tracks
		9.4.1 Topological Entropy and Complexity
		9.4.2 Train Track Map and Transition Matrix
	9.5 Summary
10 Braids and Data Analysis
	10.1 Braids from Closed Trajectories
		10.1.1 Constructing a Braid from Orbit Data
		10.1.2 An Example: Taffy Pullers
		10.1.3 Changing the Projection Line
	10.2 Braids from Non-closed Trajectories
		10.2.1 Constructing a Braid from Data: An Example
		10.2.2 Changing the Projection Line and Enforcing Closure
		10.2.3 Finite-Time Braiding Exponent (FTBE)
	10.3 Summary
Derivation of Dynnikov Update Rules (Spencer A. Smith)
	A.1 Dynnikov Coordinates
	A.2 Whitehead Moves
		A.2.1 Triangulation Coordinates
		A.2.2 Whitehead Move and Update Rule
	A.3 Deriving the Update Rules
		A.3.1 Counterclockwise Switch
		A.3.2 Equivalence of Update Rules
		A.3.3 Clockwise Switch
		A.3.4 Edge Cases
References
Index