occasional meanderings in physics' brave new world
- Name: Kea
- Location: New Zealand
Marni D. Sheppeard
Tuesday, November 21, 2006
In Lesson 2 we looked at a theorem relating surface moduli to Ribbon Graph moduli. This takes the form of an equivalence between categories. The ribbon graphs are indeed supposed to remind one of 't Hooft's old diagrams for QCD, which appear in early String theory papers from the 1970s. But in Category Land one doesn't play with Feynman diagrams based on a Minkowski background. No, no. The lesson of Penrose's twistor theory is that sheaf cohomology is a good language for thinking about solutions to field equations. In Category Land and Machian physics this lesson takes on a whole new meaning, and one loses the desire to operate with Feynman diagrams at all. In twistor String theory one uses instead MHV diagrams, and things like gluon amplitudes become magically easier to compute. This is why a whole army of excited String theorists is currently busy calculating stuff for the LHC, quite convinced that they are doing QCD.