NON-ABELIAN GAUGE-THEORY FOR QUANTUM HEISENBERG ANTIFERROMAGNETIC CHAIN

A continuum SU(2S) x U(1) gauge theory for a Heisenberg antiferromagnet with arbitrary spin S is obtained. We show that the level-1 SU(2) wzw model with a certain marginally irrelevant perturbation describes the low-energy phenomena of the Heisenberg model with spin-1/2. The model with spins other than 1/2 can be described in the level-2S SU(2) WZW model with a certain relevant perturbation. We give a qualitative explanation of the Haldane conjecture for Heisenberg antiferromagnets.