For an SU(A0 gauge theory without dynamical fermions, at temperatures above the deconfining transition there are Z(TV) degenerate vacua. The interface tension between distinct Z(TV) vacua is computed in weak coupling by semiclassical techniques.

As an extension of QCD, consider a theory with "2 + 1" flavors, where the current quark masses are held in a fixed ratio as the overall scale of the quark masses is varied. At nonzero temperature and baryon density it is expected that in the chiral limit the chiral phase transition is of first order. Increasing the quark mass from zero, the chiral transition becomes more weakly first order, and can end in a chiral critical point. We show that the only massless field at the chiral critical point is a sigma meson, with the universality class that of the Ising model. Present day lattice simulations indicate that QCD is (relatively) near to the chiral critical point.

Rajagopal andWilczek have proposed that relativistic nuclear collisions can generate domains in which the chiral condensate is disoriented. If sufficiently large (i.e. nucleus sized), such domains can yield measurable fluctuations in the number of neutral and charged pions. However, by numerical simulation of the zero-temperature two-flavor linear sigma model, we find that domains are essentially pion sized. Nevertheless, we show that large domains can occur if the effective mesons masses are much lighter.

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We derive from a d-dimensional lattice gauge theory at finite temperature a ( d -1)-dimensional effective action in which the dynamical variables are Wilson lines and meson and baryon fields. Analysis of this model shows a first-order deconfinement transition for all values of the bare quark mass, and a second-order chiral transition at a higher temperature for zero bare quark mass. Reasonable values for the two transitions and the hadronic mass spectrum are obtained.