The Zero Temperature Chiral Phase Transition in SU(N) Gauge Theories
  We investigate the zero temperature chiral phase transition in an SU(N) gauge theory as the number of fermions $N_f$ is varied. We argue that there exists a critical number of fermions $N_f^c$, above which there is no chiral symmetry breaking or confinement, and below which both chiral symmetry breaking and confinement set in. We estimate $N_f^c$ and discuss the nature of the phase transition. 
Thomas Appelquist, John Terning, L.C.R. Wijewardhana