2-group global symmetries, hydrodynamics and holography

TL;DR

This paper develops a hydrodynamic theory for systems with 2-group global symmetries combining zero-form and one-form symmetries, revealing novel effects like chiral magnetic phenomena and proposing a holographic dual.

Contribution

It constructs the first hydrodynamic framework for 2-group symmetries, including thermodynamics, constitutive relations, and holographic duals, highlighting new physical effects.

Findings

Discovery of chiral magnetic effect analogue

Identification of chiral sound mode along magnetic fields

Proposal of a minimal holographic dual for 2-group symmetries

Abstract

2-group global symmetries are a particular example of how higher-form and conventional global symmetries can fuse together into a larger structure. We construct a theory of hydrodynamics describing the finite-temperature realization of a 2-group global symmetry composed out of $U(1)$ zero-form and $U(1)$ one-form symmetries. We study aspects of the thermodynamics from a Euclidean partition function and derive constitutive relations for ideal hydrodynamics from various points of view. Novel features of the resulting theory include an analogue of the chiral magnetic effect and a chiral sound mode propagating along magnetic field lines. We also discuss a minimalist holographic description of a theory dual to 2-group global symmetry and verify predictions from hydrodynamic descriptions. Along the way we clarify some aspects of symmetry breaking in higher-form theories at finite temperature.