Finite Temperature Phase Structure of QCD with Many Quark Flavors.

We investigate the influence of many quark flavors on the finite temperature phase structure of lattice QCD by large scale numerical simulation on a 16^3 x 4 and 16^3 x 6 lattice. Compared to the simulations with smaller number of quark flavors, a strong first order phase transition is observed on the both lattice volume with moderately light quark mass (0.05 <= m_ qa <= 0.1). This suggests that the chiral phase transition becomes stronger as we increase the number of quark flavors. Because the lattice spacing of 16^3 x 6 is smaller than that of 16^3 x 4, first order phase transitions on both lattices suggests that the phase transition we saw is a continuum feature.