MATH 561 Home

This will all make sense when I am older.

We're older now, so it's time things make sense. This wiki is an attempt move at least one step in that direction, by collecting together all of the information we'll be discovering on our journey this quarter through module theory and category theory. Everything should be treated as a work-in-progress, with notes changing and updating frequently.^[1] Feel free to peruse at your leisure.

Recent class summaries

Did you miss a class, or maybe just need a reminder about what we covered on a specific day? Check out our daily class summaries. Below you can find the four most recent classes. The full collection of summaries is available here.

Class Date	Topics Covered
2025-12-03	Double complexes
2025-12-02	Kernels Cokernels Monomorphisms Epimorphisms Chain complexes Abelian categories Exact sequences Double complexes
2025-12-01	Preadditive categories Additive categories Abelian categories Biproducts Kernels Cokernels
2025-11-21	Kan extensions Limits and colimits Adjoints

Homework assignments

Although the weekly assignments should be submitted digitally in Canvas, the assignments themselves are posted here. You can also see when the assignments were last updated, whether it were to correct mistakes, add hints, or post solutions.

Assignment	Due Date	Last Updated

At the top of each page you should see a timestamp indicating the last time that page was updated. ↩︎