Determine the general MLDE order for the T_m theories

Determine whether the modular linear differential equation for the Schur index of the four-dimensional theories T_m=(A_2,D_{3m+1}) has order 3m+2 for every positive integer m.

Background

The paper studies the proposed correspondence between the Argyres–Douglas theories T_m=(A_2,D_{3m+1}) and the doublet VOAs A(4m+2). For m=2, the authors explicitly derive an order-8 modular linear differential equation for the modularly normalized vacuum character/index, and they report that the analogous order formula has been verified for m=1, 2, and 3.

The unresolved problem is to establish the conjectured pattern for arbitrary m, thereby determining the general modular differential equation governing the associated Schur indices or VOA characters.

References

We conjecture that in general the MLDE for Tm has order 3m + 2, which has been verified for m = 1, 2, 3.

An Infinite Family of Non-Rational VOAs from Strongly Coupled 4d Higgsless SCFTs  (2609.02437 - Jiang, 2 Sep 2026) in Section 4.3, “Modularity”