The Spectral Gap of the Ferromagnetic XXZ-Chain

摘要: We prove that the spectral gap of spin-\(\frac{1}{2}\) ferromagnetic XXZ-chain with HamiltonianH=−Σ_x S^{(1)}_xS^{(1)}_{x+1}+S^{(2)}_xS^{(2)}_{x+1}+\Delta S^{(3)}_xS^{(3)}_{x+1}, is given by Δ-1 for all Δ≥1. This in spectrum infinite chainin any its ground states, translation invariant ones as well asthe kink which contain an interface between up and a down region.In particular, this shows lowest magnon energy not affected presence domain wall. surprising fact consequence SU q (2)quantum group symmetry model.