Type IIB S-folds: flat deformations, holography and stability

Abstract

We review recent progress in the study of S-folds in light of the gauge/gravity duality and the AdS swampland conjecture. S-folds correspond to non-geometric backgrounds of type IIB supergravity of the form AdS 4 × S 1 × M that involve a non-trivial SL ( 2 , Z ) (S-duality) monodromy for the type IIB fields when moving around the S 1 . We present four such solutions with M = S 5 that preserve N = 4 , 2 , 1 , 0 supersymmetries. Via the AdS/CFT correspondence, these solutions are conjectured to describe new strongly coupled three-dimensional CFT’s on a localised interface of SYM. We discuss the existence of flat deformations in the gravity side dual to marginal deformations of the conjectured S-fold CFT’s. From a geometrical perspective, the flat deformations induce a monodromy ℎ on M and replace S 1 × M by the so-called mapping torus 𝑇 (M) ℎ . Interestingly, the flat deformations provide a controlled mechanism of supersymmetry breaking for N ≥ 2 S-folds. We present a class of such non-supersymmetric S-folds obtained by flat-deforming the N = 4 S-fold and discuss their (non-)perturbative stability.