Chiral-symmetry constraints on the critical temperature in QCD

We study the restoration of chiral symmetry at finite temperatures in QCD. We focus on the role light particles play in disordering the system and compute the critical temperature in the linear {σ} model, the Nambu--Jona-Lasinio model, and in the nonperturbative one-gluon-exchange approximation in QCD. In all three cases we obtain Tc=2f_π{}180 MeV, which might be a model-independent result.