Moore-Tachikawa Varieties: Beyond Duality
Veronica Pasquarella
TL;DR
The paper generalizes Moore-Tachikawa varieties to targets that are hyperkähler quotients, necessitating a generalization of cobordism operators when reparametrisation invariance is absent and linking this to the Drinfeld center of composite class S theories. It analyzes how duality underpins the standard Moore-Segal framework and develops a composite identity structure to describe theories connected by non-invertible defects, thereby extending S-duality concepts. By connecting Higgs branches to hyperkähler quotients and interpreting the modifications through tensor products over the original identity, the work lays groundwork for a broader mathematical description of composite class S theories and their Coulomb/Higgs sectors, with anticipated applications to magnetic quivers and 3D N=4 mirror symmetry. Overall, the approach clarifies how non-invertible defects alter the algebraic and geometric structure of class S theories and proposes a path toward a rigorous absolute theory in non-dual settings.
Abstract
We propose a generalisation of the Moore-Tachikawa varieties for the case in which the target category of the 2D TFT is a hyperk$\ddot{\text{a}}$hler quotient. The setup requires generalising the bordism operators of Moore and Segal to the case involving lack of reparametrisation-invariance on the Riemann surface, ultimately enabling to relate this to the issue of defining a Drinfeld center for composite class ${\cal S}$ theories.
