Physics Group Meeting

Gauging of bosonic and fermionic symmetry protected topological (SPT) states with discrete symmetry produces simple yet non-trivial topological quantum field theories (TQFTs). Some of the natural observables in such TQFTs are expectation values of line and surface operators linked in space-time. I would like to discuss what link invariants are produced by such observables, focusing mostly on dimensions 2+1 and 3+1 and using their path integral formulation.