CMSA Quantum Matter in Mathematics and Physics: Minimal nondegenerate extensions and an anomaly indicator


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June 10, 2021 10:30 am - 12:00 pm
via Zoom Video Conferencing

Theo Johnson-Freyd - Dalhousie U & PI

Braided fusion categories arise as the G-invariant (extended) observables in a 2+1D topological order, for some (generalized) symmetry group G. A minimal nondegenerate extension exists when the G-symmetry can be gauged. I will explain what this has to do with the classification of 3+1D topological orders. I will also explain a resolution to a 20-year-old question in mathematics, which required inventing an indicator for a specific particularly problematic anomaly, and a clever calculation of its value. Based on arXiv:2105.15167, joint with David Reutter.