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Category theory

Monomorphisms and epimorphisms

Lecture-style notes on monomorphisms and epimorphisms: closure under composition, split morphisms, and how Choice makes Set epis split, with examples.

hom-Sets

Hom-sets worked out in any category: hom-functors preserve identities and composition, and detect monos/epis by injectivity - notes for Lean 4 formalisation.

Free semimodules and their examples

Honours project on free semimodules and their examples. Covers definitions, universal properties, and connections to category theory and universal algebra. Supervised by Prof. G. Janelidze (UCT).

M-sets and Yoneda for monoids

Yoneda lemma for monoids via M-sets: explicit Nat(M(-), X) <-> X bijection, Cayley as a corollary, plus Yoneda embedding and an enriched remark for self-study.

Modules and Vector Spaces as Algebraic Categories

Exercises in category theory: how modules over a ring and vector spaces over a field can be framed as algebraic categories by extending the operator signatures to handle scalar multiplication.

Exercises in category theory

Series of posts containing short answers to exercises in category theory from my honours year at the University of Cape Town