Classical freeness of affine vertex algebras of ${\mathfrak{sl}}_2$ at boundary admissible levels

Abstract

We prove that the simple affine vertex algebra $L_k({\mathfrak{sl}}_2)$ is classically free at the boundary admissible level, which confirms a conjecture of Andrews, van Ekeren, and Heluani.

arXiv comment26 pages. Comments are welcome!