# Ribbons

A student asked a question in the string theory class today to which my answer was a suggestion of how to think about the issue raised in order to go about answering the question themselves. There’d be a few minutes of diagram drawing, and all would (hopefully) be clear. I thought that might not be an unreasonable thing to ask of a student, particularly in a graduate class, where they are ultimately trying to develop skills to do research. Well, it all went a bit pear-shaped as the student seemed to get quite strongly annoyed by this suggestion. I’ve still no idea why.

Anyway, on the bus home I thought I’d do some idle doodling, and ended up doing the exercise I’d suggested… and sure enough what I suggested doing works nicely and does (I think) make it clear.

I’m sure it was all a misunderstanding… Probably my fault.

Over late night dinner just now, since I can’t put down this lovely brush pen I’ve been drawing with recently, I scribbled the figures out from the notebook for you to look over my shoulder, as it were, and see what we’re up to in the class. Don’t worry so much about what it all means. It is sometimes nice to just look at the shapes*. (Actually, one of the students brought his mother to visit the class today. She sat through the whole hour and fifty minutes of the lecture. That was nice. I hope she enjoyed it all!)

I find these diagrams and the computations they represent rather pretty.

Wednesday will be the big climactic lecture of a sequence I’ve been leading them through showing how to actually compute the sum over random surfaces of arbitrary genus required by string theory (see here)…and what the results mean. The scribblings in the picture are parts of the precision tools being used for this, and we’ve been meeting nifty things like Wigner’s semicircle law and the Dyson Gas…

“…All-genus surfaces pointing past strings,
These are a few of my favourite things…”

Yeah. I had some wine with dinner. Can you tell?

-cvj

*For another look over the shoulder at fun diagrams, see e.g. here.

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