2025-11-21

This following is a very brief summary of what happened in class on 2025-11-21.

In a spontaneous decision, I decided we should talk about Kan extensions, which, in the words of Saunders Mac Lane, "...subsume all other concepts of category theory." After briefly outlining the situation (and the historical use of the word "extension"), we proceeded to briefly describe the exact definition of a left Kan extension. We then quickly considered a few special cases, in which concepts such as initial objects and adjoint functors can suddenly be seen as examples of Kan extensions.

Check out the notes online for extensive details!

Concepts

References