Topological defects and goldstone excitations in domain walls between ferromagnetic quantum Hall liquids

It is shown that the low-energy spectrum of a ferromagnetic quantum Hall liquid in a system with a multidomain structure generated by an inhomogeneous bare Zeeman splitting epsilon(z) is formed by excitations localized at the walls between domains. For a steplike epsilon(z)(r) the domain wall spectrum includes a spin wave with a linear dispersion and a small gap due to spin-orbit coupling and low-energy topological defects. The latter are charged and may dominate the transport under conditions that allow percolation through the network of domain walls.