Classifying relaxed highest-weight modules for admissible-level Bershadsky-Polyakov algebras

The Bershadsky-Polyakov algebras are the minimal quantum hamiltonian reductions of the affine vertex algebras associated to $mathfrak{sl}_3$ and their simple quotients have a long history of applications in conformal field theory and string theory. Their representation theories are therefore quite interesting. Here, we classify the simple relaxed highest-weight modules, with finite-dimensional weight spaces, for all admissible but nonintegral levels, significantly generalising the known highest-weight classifications [arxiv:1005.0185, arxiv:1910.13781]. In particular, we prove that the simple Bershadsky-Polyakov algebras with admissible nonintegral $mathsf{k}$ are always rational in category $mathscr{O}$, whilst they always admit nonsemisimple relaxed highest-weight modules unless $mathsf{k}+frac{3}{2} in mathbb{Z}_{ge0}$.