NON-ABELIAN GAUGE-THEORY FOR QUANTUM HEISENBERG ANTIFERROMAGNETIC CHAIN

A continuum SU(2S) x U(1) gauge theory for a Heisenberg antiferromagne t with arbitrary spin S is obtained. We show that the level-1 SU(2) wz w model with a certain marginally irrelevant perturbation describes th e low-energy phenomena of the Heisenberg model with spin-1/2. The mode l 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 exp lanation of the Haldane conjecture for Heisenberg antiferromagnets.