Large superconformal near-horizons from M-theory

TL;DR

This work classifies all supersymmetric solutions of 11D supergravity with $SO(2,2) \times SO(3)$ isometry, uncovering the MSW near-horizon geometry and a new class with large superconformal symmetry described by $AdS_3 \times S^2 \times S^2 \times CY_2$. The authors leverage $SU(2)$-structure in the internal six-manifold and Killing spinor bilinears to derive stringent constraints on fluxes and geometry, showing $CY_2$ must be $T^4$ or $K3$ and that the warp factor is constant. This yields a consistent solution that reduces to 7D minimal supergravity on $CY_2$, providing a near-horizon candidate for an extremal black hole and a potential arena for microscopic entropy counting. The results not only extend the landscape of AdS$_3$ vacua but also reveal deep connections to dualities with Type II and heterotic theories, offering a framework to study 2D $\mathcal{N}=(0,4)$ CFTs with large superconformal symmetry.

Abstract

We report on a classification of supersymmetric solutions to 11D supergravity with $SO(2,2) \times SO(3)$ isometry, which are AdS/CFT dual to 2D CFTs with $\mathcal{N} = (0,4)$ supersymmetry. We recover the Maldacena, Strominger, Witten (MSW) near-horizon with small superconformal symmetry and identify a class of $AdS_3 \times S^2 \times S^2 \times CY_2$ geometries with emergent large superconformal symmetry. This exhausts known compact geometries. Compactification of M-theory on $CY_2$ results in a vacuum of 7D supergravity with large superconformal symmetry, providing a candidate near-horizon for an extremal black hole and a potential new setting to address microstates.