2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/196182We study topological defect lines in two-dimensional rational conformal field theory. Continuous variation of the location of such a defect does not change the value of a correlator. Defects separating different phases of local CFTs with the same chiral symmetry are included in our discussion. We show how the resulting one-dimensional phase boundaries can be used to extract symmetries and order-disorder dualities of the CFT. The case of central charge c=4/5, for which there are two inequivalent world sheet phases corresponding to the tetra-critical Ising model and the critical three-states Potts model, is treated as an illustrative example.78 pages, several figures; v2: typos corrected and some references addedHigh Energy Physics - TheoryCategory Theorytext