Quantum Hall liquids in high-density QCD

There exist metastable domain walls of the flavor-singlet meson η for the U(1) axial symmetry in two-flavor color superconductivity (2SC) in quantum chromodynamics (QCD) at large baryon density. We show that, due to the coupling of η to confined SU(2) gluons in the 2SC phase, the effective theory on the domain wall is described by the SU(2)-1 Chern-Simons theory, which is dual to the U(1)2 Chern-Simons theory. This theory has a spin-1 droplet excitation that does not carry a baryon number, which we identify as a vector meson. We also discuss the effective theories and baryonic droplet excitations on the domain walls of the flavor-singlet mesons in the superfluid phases of QCD at large isospin density and two-color QCD at large baryon density.