## Accidental pies

This is the blackboard from the University of Edinburgh School of Mathematics common room from September 2015. I particularly noticed it because of the inadvertent appearance of P(ies) in the centre! I’m also enjoying the idea of pulsational energy.

## Niels Bohr Institute

This is the blackboard in the common room at the Niels Bohr Institute in Copenhagen, taken by Andrew Jackson. It is advertising a colloquium given by Julia Collins about Peter Guthrie Tait, with a helpful diagram of a vortex cannon to show people what to expect in the talk. Unrelatedly, there is a lot of matrix algebra on the left and what seems to be a half-rubbed-off torus on the right. Proof that even in a physics institute, much of the work is really mathematics! We have no idea what the cartoon at the top signifies.

## Inverse blackboard

Christian Perfect and David Cushing spent the morning computing inverses using their special inverse blackboard.

Going left-to-right and top-to-bottom, we have:

- The inverse of a 2×2 matrix;
- The commutative diagram for the universal property of the inverse limit;
- A variable which is inversely proportional to another;
- The inverse of a complex number;
- The derivative of the inverse of a function;
- The inverse tangent of 1;
- The axiom for group inverses;
- Part of the definition of the logical inverse.

Thanks Christian and David for this wonderful idea!

## Do not write on the screen

When the inspiration strikes, anything is fair game as a black/white board! (Thanks to Helene at ICMS in Edinburgh for taking this photo!) If you drew this, please own up in the comments. 🙂

## Doodles

Wishing everybody a merry Christmas and a mathematical new year! I can’t remember who sent me this lovely photo, but if it was you then please write in to give your name and the background to these great doodles!

## Cambridge

Our photo today is from James Grime, who is the Enigma Project Officer at Cambridge University. He came across this board whilst wandering around the maths department there: unlike at most universities, there are boards in the hallways (and even, so I am told, in the lifts and the toilets!) to encourage collaboration. This board seems to have a good mix of maths, physics and humour (see the calculation at the bottom!).