$A_n$-Triality
Mina Aganagic, Nathan Haouzi, Shamil Shakirov
TL;DR
The paper proves an A_n triality linking 4d ${\cal N}=2$ gauge theories, 3d vortex theories on vortices, and ${A}_n$ Toda CFT blocks, established via gauge/vortex duality and Coulomb-gas representations. The core insight is that the 3d vortex partition function in an ${\Omega}$-background equals the ${q}$-deformed ${A}_n$ Toda conformal block, while both match the Nekrasov partition function of a 5d ${\cal N}=1$ ${A}_n$ quiver gauge theory ${\cal T}_{5d}$; in genus-zero, full-puncture cases, this yields a concrete triality. Lifting to 5d and using a $q$-deformation are essential to control cases where the 4d theory is non-Lagrangian, with spectral duality and contour choices clarifying the Toda side. The results connect to topological-string large-$N$ duality and enrich the web of BPS/CFT correspondences by embedding the triality into a broader geometric and string-theoretic framework.
Abstract
A_n-type AGT correspondence anticipates that conformal blocks of A_n Toda CFT are related to partition functions of a family of 4d N=2 SCFTs. We use gauge/vortex duality to both give a precise form of the correspondence, and to prove it. Gauge/vortex duality relates the 4d theories and the 2d theories living on its vortices. Partition functions of the 2d theories on vortices provide Coulomb-gas representation of A_n Toda conformal blocks with discrete internal momenta. This gives a triality of relations between the gauge theory, its vortices and the Toda CFT. We prove that A_n triality holds for conformal blocks of A_n Toda on a sphere with all full punctures. The lift to one higher dimensional theories, compactified on a circle of arbitrary radius, and q-deformation of the Toda CFT, play a key role.
