HET seminar: Jay Armas – University of Copenhagen

HET seminar: Jay Armas

Speaker: Jay Armas

Title: Hot electromagnetism and magnetohydrodynamics

Abstract:

The framework of generalised global symmetries can be used to study various hydrodynamic regimes of hot electromagnetism. Within this framework, hydrodynamic theories with unbroken or spontaneously broken U(1) one-form symmetry can be formulated. The latter of these describes a one-form superfluid, which is characterised by a vector Goldstone mode and a two-form superfluid velocity. It can be shown that these theories provide a dual description of magnetohydrodynamics and the hydrodynamics of non-conducting plasmas entirely in terms of symmetries (and their breaking). It can be shown that traditional formulations of magnetohydrodynamics, where the electromagnetic photon is incorporated as dynamical degrees of freedom, have unnecessary structures. I will argue that the chemical potential and electric fields are not independently dynamical in magnetohydrodynamics, and illustrate how to eliminate these within the hydrodynamic derivative expansion using Maxwell's equations. I will also show how the Goldstone modes are required in order to understand the space of equilibrium configurations in magnetohydrodynamics and show how to construct an effective action for the Goldstone modes.