Finite-temperature phase structure of lattice QCD with the Wilson quark
action is analyzed. We show that the critical line at finite temperatures,
defined to be the line of vanishing pion screening mass, turns back toward
strong coupling, forming a cusp on the (β,K) plane, and that the line of
thermal transition runs past the tip of the cusp without touching the critical
line. Previous results are discussed in the light of our findings.Comment: contribution to Lattice 95 (poster session), 4 pages, 4 postscript
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