Quantum chromodynamics with many flavors

We investigate the phase structure of lattice QCD for general number of flavors N-F. On the basis of numerical data combined with the results of the perturbation theory we propose the following picture: When N-F greater than or equal to 17, there is only one IR fixed point at vanishing gauge coupling, i.e., the theory in the continuum limit is trivial. On the other hand, when 16 greater than or equal to N-F greater than or equal to 7, there is a non-trivial fixed point. Therefore, the theory is non-trivial with anomalous dimensions, however, without quark confinement. Theories which satisfy both quark confinement and spontaneous chiral symmetry breaking in the continuum limit exist only for N-F less than or equal to 6.