How do you count rooted planar n -ary trees with some number of leaves? For n = 2 this puzzle leads to the Catalan numbers. These are so fascinating that the combinatorist Richard Stanley wrote a ...

Following SoTFom II, which managed to feature three talks on Homotopy Type Theory, there is now a call for papers announced for SoTFoM III and The Hyperuniverse Programme, to be held in Vienna, ...

How do you count rooted planar n -ary trees with some number of leaves? For n = 2 this puzzle leads to the Catalan numbers. These are so fascinating that the combinatorist Richard Stanley wrote a ...

In week241 of This Week’s Finds, you can follow me on my tour of the Laser Interferometry Gravitational-Wave Observatory in Louisiana: Also hear some tales of the dodecahedron… from the pyritohedron ...

This week in our seminar on Cohomology and Computation we continued discussing the bar construction, and drew some pictures of a classic example: Week 26 (May 31) - The bar construction, continued.

In the pi calculus, there are mailboxes, each with a name like x. You should think of the name x like the key to open the mailbox–if you don’t have the key, you can’t deposit or withdraw messages.

A while back Gina asked why computer scientists should be interested in categories. Maybe you categorical computer scientists out there have your own favorite answers to this? I’d be glad to hear them ...

Category Theory and Biology Posted by David Corfield Some of us at the Centre for Reasoning here in Kent are thinking about joining forces with a bioinformatics group. Over the years I’ve caught ...

The data (A, B, α, β) (A,B,\alpha,\beta) is enough to reconstruct our braided 2-group X X up to equivalence. To reconstruct it, we start by taking the category with one object for each element of A A ...

We should probably focus on the mathematicians who aren’t already blogging and perhaps don’t know much about it — since the ones who do, don’t need to read the Notices to learn about the issues. What ...

where on the far right we have the very large (∞, 1) -topos on pro-objects in C, and where (∞, 1) Topos C is supposed to denote here the C -structured (∞, 1) -toposes – supposed to be the petit ones! ...

In Chris J . Isham A New Approach to Quantising Space-Time: I. Quantising on a General Category gr-qc/0303060 the author considers the concept of an arrow field on a category. I recall his definition, ...