3D TFTs from 4d ${\cal N}=2$ BPS Particles

We propose a general strategy to build three-dimensional gauge theories with four supercharges which enjoy a supersymmetry enhancement in the IR. The resulting IR SCFTs admit topological twists with particularly nice properties, as well as boundary rational chiral algebras such that the associated Modular Tensor Categories are controlled by the topological twist. The theories arise from a twisted circle compactification of four-dimensional theories of Argyres-Douglas type. We develop a novel algorithm to compute or manipulate protected quantities associated to these theories, such as ellipsoid partition functions and superconformal indices and half-indices.