Date : 11th of June, 16:00 CET
Link : https://us02web.zoom.us/j/82834697825?pwd=OUltMDJ5TWgwOVZUWmU2RzA1VmgxUT09
Speaker : Grozdanov Saso (MIT & University of Ljubljana)
Title: Generalised global symmetries and applications
Abstract: Generalised global symmetries or higher-form symmetries are a novel concept in quantum field theories that enables the formulation of a conservation of higher-dimensional objects. While standard (zero-form) symmetries act on local operators, a one-form symmetry can act on the one-dimensional Wilson line. These symmetries can be discrete, continuous, broken, anomalous, etc. In Nature, the simplest realisation of a continuous one-form symmetry stems from the conservation of the number of magnetic flux lines due to the absence of magnetic monopoles. The fact that such symmetries must play a crucial role in the formulation of effective field theories has led to the first, and so far best understood application: the theory of magnetohydrodynamics, which is the theory of long-range excitations in magnetised plasmas. In this review talk, I will first discuss the mathematical details of generalised global symmetries. I will then focus on the new theory of magnetohydrodynamics and summarise how it interpolates between previously known theories (standard non-relativistic magnetohydrodynamics, force-free electrodynamics, dynamics of fermions in the lowest Landau level) and enables to find their systematic corrections. The presentation of other applications of generalised global symmetries will include generic string liquids, superfluids and the theory of elasticity. Finally, I will show how generalised global symmetries can be implemented in AdS/CFT and discuss how the construction of the holographic dual to a plasma with dynamical magnetic fields gives rise to a strongly coupled field theory with dynamical photons and extends magnetohydrodynamics into the ultraviolet regime.
