  We discuss the QCD phase diagram from two different point of view. We first
investigate the phase diagram structure in the strong coupling lattice QCD with
Polyakov loop effects, and show that the the chiral and Z_{N_c} deconfinement
transition boundaries deviate at finite mu as suggested from large N_c
arguments. Next we discuss the possibility to probe the QCD critical point
during prompt black hole formation processes. The thermodynamical evolution
during the black hole formation would result in quark matter formation, and the
critical point in isospin asymmetric matter may be swept. (T,mu_B) region
probed in heavy-ion collisions and the black hole formation processes covers
most of the critical point locations predicted in recent lattice Monte-Carlo
simulations and chiral effective models.
