NEW UNIVERSALITY CLASSES FOR QUANTUM CRITICAL-BEHAVIOR

We use the epsilon expansion to explore a new universality class of second order quantum phase transitions associated with a four-dimensional Yukawa field theory coupled to a traceless Hermitian matrix scalar field. We argue that this class includes four-fermion modes in 2<D<4 dimensions with SU(NF)×U(N) symmetry and a U(N) scalar, SU(NF) isovector four-fermion coupling. The epsilon expansion indicates that there is a second order phase transition for NN*(NF), where N*(NF)0.27NF if NF→. © 1995 The American Physical Society.