  We study the effects of temporal UV-cutoff on the chiral critical surface in
hot and dense QCD using a chiral effective model. Recent lattice QCD
simulations indicate that the curvature of the critical surface might change
toward the direction in which the first order phase transition becomes stronger
on increasing the number of lattice sites. To investigate this effect on the
critical surface in an effective model approach, we use the Nambu-Jona-Lasinio
model with finite Matsubara frequency summation. We find that qualitative
feature of the critical surface does not alter appreciably as we decrease the
summation number, which is unlike the case what is observed in the recent
lattice QCD studies. This may either suggest the dependence of chemical
potential on the coupling strength or due to some additional interacting terms
such as vector interactions which could play an important role at finite
density.
