dSCFT

Defect superconformal field theory (dSCFT) is a class of quantum field theories in which a higher-dimensional superconformal field theory is supplemented by a localized defect or interface. The bulk fields propagate in D-dimensional spacetime, while additional degrees of freedom live on a p-dimensional defect (with p < D). The interactions between bulk and defect fields are constrained by the preserved symmetries and typically engineered to maintain some amount of supersymmetry and a subset of the conformal group.

The symmetry structure of a dSCFT reflects the embedding of the defect: the full bulk superconformal algebra is broken to a subalgebra that contains the conformal algebra of the defect, SO(p+1,1), along with a residual R-symmetry and supersymmetry compatible with the defect. Consequently, operators are organized into bulk operators, defect operators, and mixed bulk–defect operators. Correlation functions in the presence of the defect depend on the distance to the defect and on conformal cross ratios, and they obey defect Ward identities. A standard tool is the defect operator product expansion, which expresses a bulk operator near the defect as a sum over defect-local operators.

Realizations include inserting a conformal defect in a known SCFT, such as a four-dimensional N=4 super Yang–Mills theory with a two-dimensional conformal defect, or creating interfaces between different SCFTs. In holography, dSCFTs arise from brane configurations or probe branes in AdS backgrounds, yielding geometries with an AdS factor corresponding to the defect. Applications include defect bootstrap analyses, calculations of defect entanglement entropy, and the study of renormalization group flows driven by defect-localized couplings. See also defect conformal field theory and superconformal field theory.