Welcome to the Applied Category Theory Course!

John Baez

Hi! Welcome to the Applied Category Theory Course.

A good first step is to download a copy of the text:

• Brendan Fong and David Spivak, Seven Sketches in Compositionality: An Invitation to Applied Category Theory.

You can then navigate the course using this page:

• Applied Category Theory.

The most important thing is to read and discuss my Lectures and try to do the Exercises.

On Monday May 7th we'll start Chapter 2. There's also place for discussing Chapter 1 if you want to catch up.

This course will only be fun if you actively participate. You have to ask questions, answer puzzles, and do exercises from the book, to make progress. If you can answer other students' questions, do so. There are a lot of other smart people around to talk to! Go to Chat and meet some!

If you think you've found a mistake in the book, please report it here:

• Seven Sketches book: Typos, comments, questions, and suggestions.

If it's really a mistake, Fong and Spivak will fix it!

Getting to Know Each Other

If you're new to the Azimuth Forum, please post a comment about your interests and background in the category Chat. We should all get to know each other.

Chat is a good place for more free-wheeling discussions. I think we're gonna have tons of fun. Some of us will wind up doing interesting projects together! I want to help save the planet, and this is one way to get started.

Writing math

You can write equations using MathJax, which is a limited version of LaTeX good for the web. For "displayed" equations, centered on the page, use double dollar signs: $$E = \sqrt{m^2 + p^2}$$ produces this: $$E = \sqrt{m^2 + p^2}$$ For "inline" equations, mixed in with your text, use this other method: \\(E = \sqrt{m^2 + p^2}\\) produces this: \(E = \sqrt{m^2 + p^2}\).

Questions

If you have questions or comments on the subject of the course that don't quite fit into any of the chapter discussions, you can start a new discussion in the category Applied Category Theory Course. If you have questions about how the Azimuth Forum works, start a discussion in the category Technical.

Be Nice

It's an inevitable feature of any discussion forum that some users become rude, bully others, try to take over conversations, or try to exploit the forum as a venue to promote irrelevant ideas. Anyone who becomes annoying in these or other ways will be blocked. So be polite, be friendly, and let's focus on the course material!

Let's Go!

Read the first lecture here!

Goh Kok Hin

Thanks for this great course !

John Baez

You're welcome! If everyone asks lots of questions and answers lots of other people's questions, it will be lots of fun. There's a limit to how many minutes a day I can put into this. But we've got about 90 people here, so multiply that by 90 and it becomes a formidable engine for knowledge generation.

Jason Grossman

I suggest having deadlines for more-or-less (no need to be strict that I can see) finishing each chapter. John, I know you're playing this by ear (which is great IMO), but maybe you could make up the deadlines as we go along, a chapter at a time?

Igor Kulieshov

I'm voting against deadlines :)

Sri Panyam

Is it possible to be a passive student? While I love to do problems, with work and family it is going to be hard to find time but I definitely want to be engaged in the learning. Apologies for the selfishness.

John Baez

Jason and Igor: I'm not going to make up deadlines to look at each chapter, but I will march ahead, giving lectures on each chapter and then moving on to the next one... and I will focus most of my attention on discussions about what I just discussed, though people are free to continuing each topic ad infinitum.

There will be a discussion thread about each chapter, and one about each lecture, and perhaps one about each exercise (or group of related exercises?)

John Baez

Sri Panyam: it's possible to be a passive student; you may have less fun than the people who engage more. Whenever you have questions or comments, please post them!

Fredrick Eisele

@JohnBaez What should the top level discussions be? I see

• Chapter #
• Lecture # - Chapter #

You mentioned discussions on exercises, so?...

• Exercise #

I also suggest...

• Puzzle # - Chapter # :

I have completed all the exercises for chapter 1. Should I start posting them? I am also really interested in the responses for your puzzle 4 for chapter 1. It would nice if they were collected somewhere, should they be in the wiki?

John Baez

Frederick - yes, I agree that we should have top-level discussions of the types you mention! I'd love to see some of the sort

• Exercise #

and

• Puzzle # - Chapter #

So, please start them! It would be nice if the first post in such discussions merely stated the exercise and/or puzzle. Then the next post could be your solution (or someone's solution), and then other solutions and discussion thereof. If I get ahold of the LaTeX for Seven Sketches, this may reduce the amount of typing required.

There is already a partial list of responses to puzzle 4 here:

• Responses to Puzzle 4

Over there, Daniel Cellucci and I are started to discuss using the Azimuth Wiki to store information like answers to puzzles.

Daniel Blank

I deleted my original comment: I proposed a different top-level naming scheme, but having visited the forum, it works out great as it is. Thank you for this inititiative!