Chiral superfluidity of the quark-gluon plasma

TL;DR

This paper proposes that the quark-gluon plasma behaves as a chiral superfluid, with a normal thermal component and a superfluid component of chiral fermionic states, supported by nonperturbative analysis and hydrodynamic modeling.

Contribution

It introduces a novel chiral superfluid model for the quark-gluon plasma, combining lattice fermion analysis, bosonization, and hydrodynamics to explain observed chiral effects.

Findings

Observation of a gap in fermionic spectrum indicating chiral states

Derivation of an axion-like field from chiral modes

Prediction of chiral magnetic and electric effects in the plasma

Abstract

In this paper we argue that the strongly coupled quark-gluon plasma can be considered as a chiral superfluid. The "normal" component of the fluid is the thermalized matter in common sense, while the "superfluid" part consists of long wavelength (chiral) fermionic states moving independently. We use several nonperturbative techniques to demonstrate that. First, we analyze the fermionic spectrum in the deconfinement phase (Tc < T < 2 Tc) using lattice (overlap) fermions and observe a gap between near-zero modes and the bulk of the spectrum. Second, we use the bosonization procedure with a finite cut-off and obtain a dynamical axion-like field out of the chiral fermionic modes. Third, we use relativistic hydrodynamics for macroscopic description of the effective theory obtained after the bosonization. Finally, solving the hydrodynamic equations in gradient expansion, we find that in the presence of external electromagnetic fields the motion of the "superfluid" component gives rise to the chiral magnetic, chiral electric and dipole wave effects. Latter two effects are specific for a two-component fluid, which provides us with crucial experimental tests of the model.