**Originally shared by John Baez**

**Network Theory**

The world needs some new kinds of math, which deal with networks. So, check out this video! I start with a quick overview of network theory, and then begin building a category where the morphisms are electrical circuits – a warmup for more complicated kinds of networks. You can also read lecture notes:

• Network theory (part 30), http://johncarlosbaez.wordpress.com/2014/10/03/network-theory-part-30/

With luck, this video will be the first of a series. I’m giving a seminar on network theory at U.C. Riverside this fall. I’ll start by sketching the results in this new paper:

• John Baez and Brendan Fong, A compositional framework for passive linear networks, http://math.ucr.edu/home/baez/circuits.pdf

A couple of weeks ago I talked about having a Hangout on Air, but I didn’t get my act together in time to set one up with a camera of high enough quality to make my writing readable on the long whiteboard in this room. So, I decided to use a videocam provided by U.C. Riverside. It can’t hook up directly to my laptop, since I don’t have FireWire, but it creates mp3 files that I can upload later. These have a maximum length of about 30 minutes, but using Windows Live Movie Maker it was easy to stitch them together into a single file. Then I uploaded this to YouTube.

So, that’s the best I’ve been able to do so far. If you have questions about the seminar, you can ask them here – or even better, on the Azimuth blog, where the conversation has already started, and you can write in TeX:

• Network theory seminar (part 1), http://johncarlosbaez.wordpress.com/2014/10/11/network-theory-seminar-part-1/

In the future, I’ll announce seminar videos on that blog.

I thank Blake Pollard for filming this seminar, and Muhammad “Siddiq” Siddiqui-Ali for providing the videocamera and technical support.