Excitations in quantum hall ferromagnet with strong Coulomb interaction

Quantum Hall ferromagnet is considered at integer fillings $\nu$ provided typical Coulomb interaction energy $E_c$ is large compared to the cyclotron energy $\omega_H$. Low energy collective modes consist of magnetoplasmon exciton and gapeless spin exciton. All charged excitations have a gap. The activation energy gap for a pair of charged topological excitations — skyrmion and antiskyrmion — is small $\Delta = \nu\omega_H$. Electric charge of skyrmion is multiple $q=e\nu Q$, where $Q$ is the integer topological charge.