Absence of chiral symmetry breaking in multi-flavor strongly coupled   lattice gauge theories
  We consider lattice gauge theories at strong coupling with gauge group $U(N_C)$, or $SU(N_C)$ restricted to the meson sector, and coupled to $N_F$ flavors of fundamental representation staggered fermions. We study the formation of a chiral condensate by means of resummation of a hopping expansion. Different classes of graphs become dominant as the parameter $(N_F/N_C)$ is varied. By performing graph resummation we obtain an equation for determining the condensate as a function of $(N_F/N_C)$ and mass $m$. For values of $(N_F/N_C)$ below a critical value one reproduces the well-known result of the existence of a non-vanishing condensate solution in the $m=0$ limit. Above the critical $(N_F/N_C)$ value, however, no such solution exists, its abrupt disappearance indicating a first order transition to a chirally symmetric phase with composite (colorless) excitation spectrum. 
E. T. Tomboulis
hep-lat hep-th