Classifying three-character RCFTs with Wronskian Index equalling $\mathbf{0}$ or $\mathbf{2}$

TL;DR

This paper classifies three-character rational conformal field theories with specific Wronskian indices using MLDEs, identifying many known solutions and seven potential new CFTs within a finite computational framework.

Contribution

It provides a systematic classification of [3,0] and [3,2] MLDEs for RCFTs with central charge up to 96, discovering new potential CFT solutions and extending previous classifications.

Findings

Identified 303 known and 7 new character-like solutions for [3,0] MLDEs.

Classified [3,2] CFTs as extensions of [2,0] CFTs.

Performed extensive computations to classify RCFTs within the specified parameters.

Abstract

In the modular linear differential equation (MLDE) approach to classifying rational conformal field theories (RCFTs) both the MLDE and the RCFT are identified by a pair of non-negative integers $\textbf{[n,l]}$. $\mathbf{n}$ is the number of characters of the RCFT as well as the order of the MLDE that the characters solve and $\mathbf{l}$, the Wronskian index, is associated to the structure of the zeroes of the Wronskian of the characters. In this paper, we study $\textbf{[3,0]}$ and $\textbf{[3,2]}$ MLDEs in order to classify the corresponding CFTs. We reduce the problem to a "finite" problem: to classify CFTs with central charge $ 0 < c \leq 96$, we need to perform $6,720$ computations for the former and $20,160$ for the latter. Each computation involves (i) first finding a simultaneous solution to a pair of Diophantine equations and (ii) computing Fourier coefficients to a high order and checking for positivity. In the $\textbf{[3,0]}$ case, for $ 0 < c \leq 96$, we obtain many character-like solutions: two infinite classes and a discrete set of $303$. After accounting for various categories of known solutions, including Virasoro minimal models, WZW CFTs, Franc-Mason vertex operator algebras and Gaberdiel-Hampapura-Mukhi novel coset CFTs, we seem to have seven hitherto unknown character-like solutions which could potentially give new CFTs. We also classify $\textbf{[3,2]}$ CFTs for $ 0 < c \leq 96$: each CFT in this case is obtained by adjoining a constant character to a $\textbf{[2,0]}$ CFT, whose classification was achieved by Mathur-Mukhi-Sen three decades ago.