Multi-parametric families of AdS 4 vacua with various amounts of supersymmetry and residual gauge symmetry are found in the [SO(1, 1) × SO(6)] ⋉ R 12 maximal supergravity that arises from the reduction of type IIB supergravity on R × S 5 . These provide natural candidates to holographically describe new strongly coupled three-dimensional CFT's which are localised on interfaces of N = 4 super-Yang-Mills theory. One such AdS 4 vacua features a symmetry enhancement to SU(2) × U(1) while preserving N = 2 supersymmetry. Fetching techniques from the E 7(7) exceptional field theory, its uplift to a class of N = 2 S-folds of type IIB supergravity of the form AdS 4 × S 1 × S 5 involving S-duality twists of hyperbolic type along S 1 is presented.

The S-fold description of Janus-type solutions of type IIB supergravity is investigated. This is done by first studying a U(1) × U(1) invariant sector of the four-dimensional dyonically-gauged [ SO(1, 1) × SO(6) ] ⋉ R 12 maximal supergravity that arises upon reduction of type IIB supergravity on R × S 5 . Two AdS 4 solutions preserving SU(3) and SO(6) gauge symmetry together with N = 1 and N = 0 supersymmetry are found within this sector. Fetching techniques from the E 7(7) exceptional field theory, these solutions are uplifted to ten-dimensional S-folds of type IIB Janus-type solutions of the form AdS 4 × R × M 5 . The solutions presented here are natural candidates for the holographic duals of three-dimensional N = 1 and N = 0 interface super-Yang-Mills theories with SU(3) and SU(4) internal symmetry.

Type IIB S-folds of the form AdS4 × S1 × S5 are conjectured to correspond to new strongly coupled three-dimensional CFT’s on a localised interface of SYM4. In this work we construct holographic RG flows on the D3-brane that generically connect anisotropic deformations of SYM4 in the UV to various S-fold CFT’s in the IR with different amounts of supersymmetry and flavour symmetries. Examples of holographic RG flows between S-fold CFT’s are also presented. Lastly a geometric interpretation of axion deformations is provided in terms of monodromies on the internal S5 when moving around the S1. Special attention is paid to the monodromy-induced patterns of symmetry breaking as classified by the mapping torus Th(S5).

Type IIB S-folds of the form AdS4× S1× S5 have been shown to contain axion-like deformations parameterising flat directions in the 4D scalar potential and corresponding to marginal deformations of the dual S-fold CFT’s. In this note we present a group-theoretical characterisation of such flat deformations and provide a 5D interpretation thereof in terms of $$ \mathfrak{s}(6) $$ s 6 -valued duality twists inducing a class of Cremmer-Scherk-Schwarz flat gaugings in a reduction from 5D to 4D. In this manner we establish the existence of two flat deformations for the $$ \mathcal{N} $$ N = 4 and SO(4) symmetric S-fold causing a symmetry breaking down to its U(1)2 Cartan subgroup. The result is a new two-parameter family of non-supersymmetric S-folds which are perturbatively stable at the lower-dimensional supergravity level, thus providing the first examples of such type IIB backgrounds.

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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.

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.

We use holography and four-dimensional $$ \mathcal{N} $$ N = 4 gauged supergravity to collect evidence for a large class of interconnected three-dimensional $$ \mathcal{N} $$ N = 2 conformal field theories. On the gravity side, we construct a one-parameter family of ISO(3) × ISO(3) gaugings of half-maximal supergravity containing a rich structure of $$ \mathcal{N} $$ N = 2 AdS4 solutions at fixed radius. By looking at excitations around these AdS4 solutions, the spectrum of low lying operators in the dual $$ \mathcal{N} $$ N = 2 CFT3’s is computed and further arranged into 𝔬𝔰(2|4) supermultiplets. Upon suitable removal of gauge redundancies, we identify the Zamolodchikov metric on the conformal manifold dual to the AdS4 moduli space, and recover previous results in the S-fold literature. Two special points of $$ \mathcal{N} $$ N = 4 supersymmetry enhancement occur. While one describes an S-fold CFT3 dual to a non-geometric type IIB twisted compactification, the string-theoretic realisation of the other, if any, is still lacking.