### Description

The seminar will run every Wednesday from 10am to 11am during Summer C, via Zoom. We will cover the following topics:

- Abelian Categories
- Derived Functors
- Ext and Tor functors
- Sheaf cohomology
- Spectral Sequences

It time permits I may cover some additional topics, such as group cohomology, Hochschild cohomology, or derived categories.

### General references

The first three of these can be found on the internet in PDF form:

- Hilton and Stammbach,
*A Course in Homological Algebra*. A good basic treatment but mostly focuses on module categories. - Weibel,
*An Introduction to Homological Algebra*. In spite of the title, a more advanced treatment than Hilton-Stammbach. I will be using this a lot. - Grothendieck,
*Sur quelque points d’algebre homologique*, Tohoku J. Math**9**no. 2, 1957. This is the classic reference, and the fact that it’s in French will be the least of your worries. The wikipedia page has a pointer to an English translation. - Gelfand and Manin,
*Methods of Homological Algebra*. Lots of interesting stuff but very idiosyncratic. - Chapter 12 of the Stacks Project is devoted to homological algebra in the setting of abelian categories.

### Lectures

- Lecture 1 – Additive Categories
- Lecture 2 – Abelian Categories
- Lecture 3 – Exactness in Abelian Categories
- Lecture 4 – Projective and Injective objects
- Lecture 5 – Exactness, Complexes, Homology
- Lecture 6 – Additive Functors, Resolutions, Homotopies
- Lecture 7 – Derived Functors
- Lecture 8 – Universal properties of derived functors. Ext groups
- Lecture 9 – Interpretation of the Ext groups. Tor functors
- Lecture 10 (7/21/21) – Sheaves on a topological space
- Lecture 11 (7/23/21) – Properties of abelian sheaves. Direct images, local and global Ext
- Lecture 12 – Spectral Sequences
- Lecture 13 – The Spectral Sequence of a Composite Functor. Applications.
- Lecture 14 – Derived Categories (introduction)
- Lecture 15 – Triangulated Categories

Lectures 14 and 15 will not actually be delivered but are posted here for your, ahem entertainment. Enjoy!