For a succinct introduction to bases in Banach spaces, Christopher Heil has provided A Basis Theory Primer. (The first 20 pages are a quick review of Banach space theory. The rest is devoted to bases in Banach spaces.)

If you take the category with Banach spaces as objects, and continuous linear maps that have a closed image as morphisms, then do you get an abelian category?

Cosma Shalizi always seemed like a intelligent commentator on a broad range of topics. Now, thanks to a psychology experiment we know it’s all a lie.

We’ll be hosting the next Carnival of Mathematics, on January 11th. The previous one was hosted by The Math Less Traveled.

You can use the submission form to nominate articles, or just mention them here in the comments.