Instructor: Tim Chumley
Office: Clapp 423
Phone: 413-538-2525
e-mail: tchumley
Office Hours: Mondays & Wednesdays 4:00-5:00, Thursdays 11:00-12:00; additional availability by appointment

Textbook: A First Course in Chaotic Dynamical Systems by Robert L. Devaney, ISBN: 9780429280665;
available as a free e-text


Announcements

Announcements will be posted on the Course Announcements Moodle forum throughout the semester, but essentially all other materials will be posted on this page.

Syllabus

Check the syllabus for all the important class policies (grades, attendance, etc.).

Homework

There will be weekly homework assignments throughout the semester to be turned in. Please read these guidelines for writing in our class.

  • General information. A selection of problems will be assigned to be written up individually and turned in each week.
    • These problems will be due Thursdays at 5 pm.
    • You may work with others but the writing should be done on your own.
  • Gradescope. Homework will be turned in through Gradescope.
    • You should be enrolled automatically. Please let me know if you have any issues logging in.
    • Gradescope has made a short tutorial on submitting homework.
  • Collaboration. I want you to work together on the homework! The process of explaining your ideas to one another really helps in learning math. However, you must write up the assignments on your own and avoid copying others’ work directly. Please only write what you understand so that I know where to help, and please avoid using AI chat bots, online forums, solutions manuals, or similar resources. A huge part of learning in this class comes from figuring out how to get unstuck by spending time thinking on your own or talking to me and classmates; these other resources can end up being counter-productive in the long term.
  • Rewrites. Homework is for practice, and you are not expected to write perfect answers from the start!
    • You will be allowed to submit revisions of most problems for full credit each week.
    • Your revisions will be due on Thursdays at 5 pm. This means each week you’ll have two things to turn in on Fridays: an initial submission and a redo submission.
    • Please resubmit (only the problems you’re revising) on Gradescope by using the resubmit function. I’ll be able to see your submission history in order to see what was initially correct or incorrect.
Assignment Due
Homework 0 Jan 29
Homework 1 Feb 5
Homework 2 Feb 12
Homework 3 Feb 19
Homework 4 Feb 26
Homework 5 Mar 5
Homework 6 Mar 26
Homework 7 Apr 2
Homework 8 Apr 9
Homework 9 Apr 16

Quizzes

There will be quizzes most weeks that will be given on Wednesdays at the start of class. The purpose of these is to check in to see that you’re comfortable with fundamental material and homework problems. Topics will be announced in advance.

Quiz Date
Quiz 1 Feb 4
Quiz 2 Feb 11
Quiz 3 Feb 18
Quiz 4 Feb 25
Quiz 5 Mar 4
Quiz 6 Mar 25
Quiz 7 Apr 1
Quiz 8 Apr 8
Quiz 9 Apr 15

Exams

There will be two midterm exams. The dates for the exams are subject to change slightly.

Exam Date Format Material
Exam 1 Mar 9 TBA TBA
Exam 2 Apr 20 TBA TBA

Project

In lieu of a final exam, we’ll devote the last few class meetings to a short project involving some selection of topics we wouldn’t otherwise have time to cover. The project will involve a presentation or report. Details will be discussed in the middle of the semester.

Assignments

Some assignments will be posted here in the lead-up to the project.

Course plan

Our plan is to cover parts of the first 10 chapters of the textbook, as well as parts of later chapters, time permitting. Below is a rough week by week outline of the semester which will be updated regularly. Please check back regularly for precise details on what is covered, as well as postings of class materials like lecture notes.

Chapters 1-3


Wednesday

Chapters 3-4


Monday
  • Topic: Chapter 3: Iteration and Orbits. We discuss fixed points, periodic points, and eventually periodic points. We also introduce and study the doubling map.
  • Class materials: Lecture notes, worksheet, doubling_map.m script
  • After class: Read sections 4.1 and 4.2.
Wednesday
  • Topic: Chapter 4: Graphical analysis. We introduce cobweb diagrams in order to visualize orbits of a dynamical system. We also discuss complete orbit analysis and phase portraits.
  • Class materials: Lecture notes, worksheet, Desmos cobweb plotter
  • After class: Think about the role slope plays in today’s worksheet examples and its relationship to attracting and repelling fixed points.

Chapters 4, 5


Monday
  • Topic: Sections 4.2-4.3: More on graphical analysis. We discuss the worksheet from last time and introduce the concept of a phase diagram.
  • Class materials: Lecture notes
  • After class: Read Section 5.1.
Wednesday
  • Topic: Sections 5.2-5.3: Attraction and repulsion. We begin to formalize the observations we have made on attraction and repulsion using calculus. Our aim is to summarize the possible behaviors of orbits based on the value of \(|F'(p)|\) and we begin with case of a positive derivative that is less than 1.
  • Class materials: Lecture notes, worksheet
  • After class: Finish Problem 1 from today’s worksheet and prepare to discuss it at the start of next class.

Chapter 5


Monday
  • Topic: Section 5.2-5.4: More on attraction and repulsion. We continue our discussion from last time and outline a proof for the attracting fixed point theorem. We introduce the Mean Value Theorem from calculus as our primary tool.
  • Class materials: Lecture notes
  • After class: Write up your ideas on how to understand the behavior of orbits that start near a repelling fixed point. You should mostly repeat the argument we worked on together for the attracting case, but we’ll discuss a small subtlety that’s different next time.
Wednesday
  • Topic: Section 5.4: Neutral fixed points. We consider the behavior of orbits that begin near a fixed point \(p\) where \(|F'(p)|=1\). Our main general observation will be that the second and third derivatives play an important role in classifying the convergence and divergence behavior of orbits that start near \(p\).
  • Class materials: Lecture notes, worksheet
  • After class: Finish Problem 2 on today’s worksheet and prepare to discuss it at the start of our next class.

Chapters 5, 6


Monday
  • Topic: Section 5.5: Periodic points. We discuss attracting, repelling, and neutral periodic points. The key here will be using the chain rule to simplify our calculations.
  • Class materials: Lecture notes, worksheet
  • After class: Read Section 6.1.
Wednesday
  • Topic: Section 6.1: Introduction to bifurcations. We discuss the saddle node bifurcation for the quadratic family \(Q_c(x)=x^2+c\), a bifurcation where the system transitions from 0 to 1 to 2 fixed points.
  • Class materials: Lecture notes, worksheet
  • After class: Read the end of Section 6.1 about the second kind of bifurcation.

Chapter 6


Monday
  • Topic: Section 6.1: More on bifurcations. We discuss the period doubling bifurcation for the quadratic family. Here, we see the appearance of period-2 points as we change the parameter \(c\).
  • Class materials: Lecture notes, worksheet
  • After class: Work on Homework 5.
Wednesday
  • Topic: Sections 6.2, 6.3: Bifurcations more generally. Our goal is to continue our exploration of bifurcations through more examples. We’d like to understand what properties, algebraically and geometrically, give rise to saddle node and period doubling bifurcations.
  • Class materials: Lecture notes, worksheet
  • After class: Finish today’s worksheet.

Chapter 6


Monday
  • Topic: Exam 1.
Wednesday
  • Topic: Section 6.4: Bifurcation diagrams. We discuss a method of visualizing the bifurcations that occur in the quadratic map. A bifurcation diagram has the parameter values along the horizontal axis and fixed point and periodic point values along the vertical axis. We construct a bifurcation diagram for the quadratic map through numerical simulation.
  • Class materials: Lecture notes
  • After class: Enjoy spring break!

Spring Break


Monday
  • Topic: Spring break, no class.
Wednesday
  • Topic: Spring break, no class.

Chapter 7


Monday
  • Topic: Section 7.2: More on the quadratic family. We discuss the behavior of orbits of the quadratic map that escape to infinity.
  • Class materials: Lecture notes
  • After class: Read Section 7.3.
Wednesday
  • Topic: Section 7.3: The Cantor Middle-Thirds set. We discuss an
    iteratively defined set with very interesting, bizarre properties. While it serves as an object worthy of study on its own, it will serve as a prototype for the sets of initial seeds with bounded orbits that studied in Section 7.2.
  • Class materials: Lecture notes
  • After class: Work on homework.

Chapter 7


Monday
  • Topic: Section 7.3: More on the Cantor Middle-Thirds set. We continue our discussion of the Cantor Middle-Thirds set, with a focus on how to find the ternary representation of a real number in \([0,1]\) and how these ideas allow us to prove that the Cantor set is uncountably infinite.
  • Class materials: Lecture notes
  • After class: .
Wednesday
  • Topic: Section 7.3. We discuss a refined method or algorithm for finding the ternary expansion of a number in \([0,1]\) and properties of ternary expansions of endpoints of the Cantor middle-thirds set.
  • Class materials: Lecture notes, Ternary expansions
  • After class: .

Chapters 7, 9


Monday
  • Topic: Dynamics on the Cantor set. We discuss the map \(T(x)\) from last week’s homework and how it acts on initial seeds from the Cantor middle-thirds set.
  • Class materials: Lecture notes
  • After class: Read section 10.1
Wednesday
  • Topic: Section 10.1: Chaos. We discuss Devaney’s definition of chaos and the intuitive meaning of each piece of the definition.
  • Class materials: Lecture notes, Chaos
  • After class: Read about itineraries in section 9.1.

Chapters 9, 10


Monday
  • Topic: Section 10.1: Chaos. We discuss the dynamics of the shift map on binary sequences and the itinerary of an orbit of the tent map.
  • Class materials: Lecture notes
  • After class:.
Wednesday

Exam, Group work


Monday
  • Topic: Exam 2.
  • After class: Think about your presentation topic in preparation for the work time in the next class meeting.
Wednesday
  • Topic: Group work time. We spend the day working in groups learning about the group project topic, discussing questions, and beginning to think about presentations.
  • Class materials: Presentation rubric
  • After class: Spend some time working on the ideas discussed in your group today. Check in with your group about outside-of-class meeting time. Begin preparing ideas for presentation. Think about what will be presented (you can’t say everything you think of!) and how the presented material will be divided between group mates.

Group work time, presentations


Monday
  • Topic: Group work time. We spend our last day on group work time before the presentations begin.
  • After class: Meet with your group. Do practice runs of your presentation, particularly if you’re presenting Thursday.
Wednesday
  • Topic: Presentations. We’ll spend the day on the first group presentations.
  • After class: Wrap up your presentation if presenting next week.

Presentations


Monday
  • Topic: Presentations. We’ll spend the day on the remaining group presentations.
  • After class: Enjoy your summer! Keep in touch!

Getting help

Here are a few ways to get help:

  • Office Hours: Mondays & Wednesdays 4:00-5:00, Thursdays 11:00-12:00; additional availability by appointment
  • Study groups: Other students in the class are a wonderful resource. I want our class to feel like a community of people working together. Please get in touch if you’d like me to help you find study partners, and please reach out if you’d like others to join your group. You may work together on homework, explain and check answers, but make sure you write what you know on homework in order to get good feedback.
  • Message board: I’ve set up a question and answer forum for asking and answering questions about class material, including homework problems. My plan is to check the forum regularly and answer questions as they come up, but my hope is everyone in the class will pitch in and answer others’ questions as another form of participation in the class.

Resources