LARGE N PHASE-TRANSITION IN CONTINUUM QCD2

We compute the exact partition function for pure continuum Yang-Mills theory on the two-sphere in the large N limit, and find that it exhibits a large N third order phase transition with respect to the area A of the sphere. The weak coupling (small A) partition function is trivial, while in the strong coupling phase (large A) it is expressed in terms of elliptic integrals. We expand the strong coupling result in a double power series in exp(-g2 A) and g2 A and show that the terms are the weighted sums of branched coverings proposed by Gross and Taylor. The Wilson loop in the weak coupling phase does not show the simple area law. We discuss some consequences for higher dimensions.