VERTEX OPERATORS AND SPINON EDGE EXCITATIONS IN THE SPIN-SINGLET QUANTUM HALL-EFFECT

We show that a two-dimensional electron gas in the incompressible spin-singlet quantum-Hall-effect (SQHE) state supports boundary excitations with quantum numbers derived from a non-Abelian SU(2), associated with the spin. These edge excitations have spin-charge separation, and we exhibit neutral spinons and spinless holons. The dynamics of the spinons is governed by a chiral SU(2)k = 1 Wess-Zumino-Witten model that is naturally related to the SU(2) Chern-Simons action describing the bulk of the SQHE sample.