Delineating chiral separation effect in two-color dense QCD

TL;DR

This paper investigates the chiral separation effect in dense two-color QCD, revealing how diquark condensates and symmetry breaking influence the conductivity and challenge the universality of the effect in quasiparticle regimes.

Contribution

It provides a detailed analysis of the CSE in dense two-color QCD, including effects of diquark condensates and symmetry breaking, with explicit conductivity calculations and implications for universality.

Findings

Chiral separation conductivity is suppressed in high-density phases.

Diquark condensates break baryon number and axial symmetry.

Universality of CSE coefficients is locally broken in dense matter.

Abstract

We study the chiral separation effect (CSE) in two-color and two-flavor QCD (QC$_2$D) to delineate quasiparticle pictures in dense matter from low to high temperatures. Both massless and massive quarks are discussed. We particularly focus on the high density domain where diquarks form a color singlet condensate with the electric charge $1/3$. The condensate breaks baryon number and $U(1)_A$ axial symmetry, and induces the electromagnetic Meissner effects. Within a quark quasiparticle picture, we compute the chiral separation conductivity at one-loop. We have checked that Nambu-Goldstone modes, which should appear in the improved vertices as required by the Ward-Takahashi identities, do not contribute to the chiral separation conductivity due to their longitudinal natures. In the static limit, the destructive interferences in the particle-hole channel, as in usual Meissner effects, suppress the conductivity (in chiral limit, to $1/3$ of the normal phase's). This locally breaks the universality of the CSE coefficients, provided quasiparticle pictures are valid in the bulk matter.