Greetings,

This week there was some progress on the research front. Arjan, a post-doc at my lab was kind enough to show me a little trick to figure out what all the Lorentz-invariant contractions of the Riemann-tensor are for a given order. I basically reduces the problem to solving a kind of Sudoko puzzle, not unlike the Cartan root system for Lie algebra's.

Remember my search for good differential geometry tests? The Cambridge lecture notes were very helpful, but there's always more isn't there. A math professor at my university suggested the following book (no, I haven't taken over Lubos' obsession with Amazon adds, it's just the only place I could find it).

http://www.amazon.com/Geometry-Physics-Introduction-Second/dp/0521539277

The aforementioned math professor is studying it himself. It's good to see people from the math department taking an interest in the link between mathematics and physics, something that's rather close to my heart. I think I'll ask my dad to bring it with him when he gets back to Belgium, since it appears to be alot cheaper and more easily available in the States.

-Dimi