Quark Confinement in Multi-Flavor Quantum Chromodynamics

It is investigated how quark confinement depends on the number of flavors, $N_f$, in QCD on the lattice with Wilson quarks. We strengthen and extend the conclusion reported at {\it Lattice 91}: (1) For $N_f \le 6$ the finite temperature deconfining transition/crossover line crosses the chiral limit at finite $\beta$. We identify the crossing point for $N_f=2$ and 6 on a $T=4$ lattice, where $T$ is the lattice size in the temporal direction. We find the phase transition at the crossing point is continuous for $N_f=2$, while it is of first order for $N_f=6$. (2) For $N_f \ge 7$, the $T$-independent deconfining transition observed at $\beta=0$ extends up to $\beta=4.5$ with the critical quark mass $m_{\rm quark} = O(a^{-1})$, where $a$ is the lattice spacing.