VACUUM-STRUCTURE AND THETA-STATES OF ADJOINT QCD IN 2 DIMENSIONS

We address the issue of topological angles in the context of two-dimen sional SU(N) Yang-Mills theory coupled to massive fermions in the adjo int representation. Classification of the resulting multiplicity of va cua is carried out in terms of asymptotic fundamental Wilson loops, or equivalently, charges at the boundary of the world. We explicitly dem onstrate that the multiplicity of vacuum states is equal to N for the SU(N) gauge group. Different worlds of the theory are classified by th e integer number k = 0, 1,..., N - 1 (superselection rules) which play s a role analogous to the a parameter in QCD. We study the physical pr operties of these unconnected worlds as a function of k. We achieve th is by using two completely independent approaches: First, we apply the well-known machinery of the loop calculus in order to calculate the e ffective string tensions in the theory as function of k. The second wa y of doing the same physics is the standard particle/field theoretic c alculation for the binding potential of a pair of infinitely massive f ermions. We also calculate the vacuum energy as function of k.