## Ribbon diagrams in particle physics

### Marni Sheppeard – 23 August 2006

The octopi diagrams of Bilson-Thompson are one of a number of recent advances that make a convincing case for a categorical framework for quantum gravity. These diagrams classify the particle zoo of the standard model, but without mass quantum numbers. They arise from an invariance of ribbon diagrams under simple moves. I discuss how these diagrams are related to a Poincare duality which is motivated by cosmological principles.

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