Generalised global symmetries in holography: magnetohydrodynamic waves in a strongly interacting plasma

Publisher's version (útgefin grein)
We begin the exploration of holographic duals to theories with generalised global (higher-form) symmetries. In particular, we focus on the case of magnetohydrodynamics (MHD) in strongly coupled plasmas by constructing and analysing a holographic dual to a recent, generalised global symmetry-based formulation of dissipative MHD. The simplest holographic dual to the effective theory of MHD that was proposed as a description of plasmas with any equation of state and transport coefficients contains dynamical graviton and two-form gauge field fluctuations in a magnetised black brane background. The dual field theory, which is closely related to the large-N c , N = 4 supersymmetric Yang-Mills theory at (infinitely) strong coupling, is, as we argue, in our setup coupled to a dynamical U(1) gauge field with a renormalisation condition-dependent electromagnetic coupling. After constructing the holographic dictionary for gauge-gravity duals of field theories with higher-form symmetries, we compute the dual equation of state and transport coefficients, and for the first time analyse phenomenology of MHD waves in a strongly interacting, dense plasma with a (holographic) microscopic description. From weak to extremely strong magnetic fields, several predictions for the behaviour of Alfvén and magnetosonic waves are discussed.
The authors would like to thank Debarghya Banerjee, Pavel Kovtun, Alexander Krikun, Chris Rosen, Koenraad Schalm, Andrei Starinets, Giorgio Torrieri, Vincenzo Scopelliti, Phil Szepietowski and Jan Zaanen for stimulating discussions, and Simon Gentle for his comments on the draft of this paper. We are also grateful to Diego Hofman and Nabil Iqbal for numerous discussions on the topic of this work, comments on the manuscript and for sharing the draft of [37] prior to publication. S.G. is supported in part by a VICI grant of the Netherlands Organisation for Scientific Research (NWO), and by the Netherlands Organisation for Scientific Research/Ministry of Science and Education (NWO/OCW). The work of N.P. is supported by the DPST scholarship from the Thai government and by Leiden University.