Integrability and Conformal Blocks for Surface Defects in $\mathcal{N}=4$ SYM

Abstract: We study various aspects of half-BPS surface defect operators in $\mathcal{N}=4$ SYM. For defects on generic points on the moduli space we use superconformal symmetry to fix the form of one-point and two-point functions of half-BPS operators and solve the superconformal Ward identities in terms of superconformal blocks, emphasizing the role of the broken rotational symmetry transverse of the defect in the superconformal block expansion. We verify this expansion by the leading-order perturbative calculation for the two-point functions. We also investigate the integrability of the defect CFT in the planar limit and argue that the integrability is broken at generic points of the defect moduli. The integrability is expected to be restored in the singular point of this moduli space where another "rigid" branch appears, and we provide evidence for this by showing that the defect one-point functions in this case can be mapped to a class of known integrable quenches.