Previously: Part 8. It’s the penultimate week of the course, and up until now we’ve abstained from using the axiom of choice. But this week we gorged on it.

Gerard Westendorp has a real knack for geometry, and here is his answer. Here is Thurston’s procedure. First draw the lattice of Eisenstein integers in the complex plane: ...

Projects range from applied category theory to logic, programming languages, and science, technology, and society. Specific topics for 2025 include, but are not limited to: Computational category ...

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Nov 7, 2024 00:45 Here’s a way to argue that Gerard’s solution to my puzzle is correct. Thurston showed that any star of the ...

And the course feels like it’s mostly converging with any other set theory course, just with the special feature that everything remains resolutely isomorphism-invariant. This week we constructed N ...

Previously: Part 5. Next: Part 7. A category theorist might imagine that a chapter with this title would be about constructing colimits, and they’d be half right.

I haven’t been carefully following quantum field theory these days, but some folks on the Category Theory Community Server asked me what I thought about recent work using the ‘amplitudohedron’ and ...

The Octoberfest is a noble tradition in category theory: a low-key, friendly conference for researchers to share their work and thoughts. This year it’s on Saturday October 26th and Sunday October ...