On the chiral algebra of Argyres-Douglas theories and S-duality
Jaewang Choi, Takahiro Nishinaka
TL;DR
This work identifies the chiral algebra for the marginal (A_3,A_3) Argyres-Douglas theory by proposing a minimal generating set from the Higgs branch and SU(2)_R current, then bootstraping the OPEs with Jacobi identities to a unique, consistent algebra. The construction is cross-validated against the Schur index, Higgs-branch relations, and BRST cohomology, and the automorphism group G is shown to realize S-duality through a map to $S_4\times\mathbb{Z}_2$ with an S_3 subgroup matching PSL(2,ℤ). These results provide a concrete link between four-dimensional S-duality and two-dimensional chiral algebras in a theory with an exactly marginal coupling, and they set the stage for generalizations to other Argyres-Douglas families via Hamiltonian reduction and BRST methods. The findings offer key insights into how duality acts on chiral algebras and pave the way for broader applications to AD theories and their conformal manifolds.
Abstract
We study the two-dimensional chiral algebra associated with the simplest Argyres-Douglas type theory with an exactly marginal coupling, i.e., the $(A_3,A_3)$ theory. Near a cusp in the space of the exactly marginal deformations (i.e., the conformal manifold), the theory is well-described by the $SU(2)$ gauge theory coupled to isolated Argyres-Douglas theories and a fundamental hypermultiplet. In this sense, the $(A_3,A_3)$ theory is an Argyres-Douglas version of the $\mathcal{N}=2$ $SU(2)$ conformal QCD. By studying its Higgs branch and Schur index, we identify the minimal possible set of chiral algebra generators for the $(A_3,A_3)$ theory, and show that there is a unique set of closed OPEs among these generators. The resulting OPEs are consistent with the Schur index, Higgs branch chiral ring relations, and the BRST cohomology conjecture. We then show that the automorphism group of the chiral algebra we constructed contains a discrete group $G$ with an $S_3$ subgroup and a homomorphism $G\to S_4 \times {\bf Z}_2$. This result is consistent with the S-duality of the $(A_3,A_3)$ theory.
