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July 25, 2025
The Clowder Project
Posted by John Baez
guest post by Emily de Oliveira Santos
I’d like to share here a personal project which might be of interest to the readers of this blog: the Clowder Project.
Clowder is a wiki and reference work for category theory built using the same general infrastructure and tag system of the Stacks Project, Gerby. The intention is for it to eventually become for category theory what the Stacks Project is for algebraic geometry.
July 24, 2025
2-Rig Conjectures Proved?
Posted by John Baez
Kevin Coulembier has come out with a paper claiming to prove some conjectures that Todd Trimble, Joe Moeller and I made in 2-Rig extensions and the splitting principle:
- Kevin Coulembier, Invertible exterior powers.
Lawvere’s Work on Arms Control
Posted by John Baez
Did you know that Lawvere did classified work on arms control in the 1960s, back when he was writing his thesis? Did you know that the French government offered him a job in military intelligence?
July 7, 2025
How to Count n-Ary Trees
Posted by John Baez
How do you count rooted planar -ary trees with some number of leaves? For this puzzle leads to the Catalan numbers. These are so fascinating that the combinatorist Richard Stanley wrote a whole book about them. But what about ?
I’ll sketch one way to solve this puzzle using generating functions. This will give me an excuse to talk a bit about something called ‘Lagrange inversion’.