Generalised global symmetries are a generic feature of theories with topologically conserved charges. For certain physical theories, these allows for an entirely symmetry based reformulation of the low-energy physics in the hydrodynamic regime without making reference to the specific microscopics. In this talk, we will introduce some of these ideas in the concrete setting of magnetohydrodynamics (MHD), seen as a fluid with conserved "strings" (magnetic field lines). We will argue that MHD is described by a novel theory of superfluidity with a partially broken one-form symmetry. Time permitting, we will also comment on another application of generalised global symmetries to the theory of viscoelasticity. The talk is based on [1808.01939, 1811.04913, 1908.01175].
Social media