Chris Grossack's Blog

So it’s finals season, and earlier today some of the younger grad students were asking me for help studying for their topology finals.

In the main post I go over a talk I gave today yesterday explaining how factorization homology relates to (quantum) character stacks.

Today Yesterday in the Representation Theory Seminar at UCR I gave a talk about Factorization Homology and how it lets us compute a “Quantum Character Stack”.

Yesterday I watched my friend Jialin Wang defend her thesis, and as part of her background section she mentioned that the group $F_2 \times F_2$ is incoherent in the sense that it has a subgroup that’s finitely generated and not finitely presented.

I’ve spent the last week at CT2025, which has just come to a close.

Earlier this week my friend Shane and I took a day and just did a bunch of computations.

While doing a computation with my friend Shane the other day, we realized we needed to explicitly compute a local chart near the identity of $SL_2(\mathbb{R})$.

This is going to be a very classic post, where we’ll chat about a computation my friend Shane did earlier today.

The other day my friend Lucas Salim was asking me some questions about categorical logic and constructive math, and he mentioned he’d never seen a proof that there’s no constructive proof of the intermediate value theorem before.

A few days ago I saw a cute question on mse asking about a particularly non-intuitive failing of the axiom of choice.