Surface Defects and Chiral Algebras

Understand

We investigate superconformal surface defects in four-dimensional N=2 superconformal theories.

• Each such defect gives rise to a module of the associated chiral algebra and the surface defect Schur index is the character of this module.
• Various natural chiral algebra operations such as Drinfeld-Sokolov reduction and spectral flow can be interpreted as constructions involving four-dimensional surface defects.
• We compute the index of these defects in the free hypermultiplet theory and Argyres-Douglas theories, using both infrared techniques involving BPS states, as well as renormalization group flows onto Higgs branches.