Citation: Cardy, John L. "Boundary conditions, fusion rules and the Verlinde formula." Nuclear Physics B 324.3 (1989): 581-596.
Web: https://www.sciencedirect.com/science/article/pii/055032138990521X
Tags: Physical, Foundational, Boundaries
There is a huge amount of effort and work surrounding the theory of boundaries and twist defects in topological phases of matter. As with most deep foundational statements about TQFT, the origins of these statements come from rational conformal field theory.
This paper is very interesting, but it does not contain any of the interesting formalism which would be developed in later works. In particular, he does not make the connection between boundary theories and modules over the bulk.