THETA-SECTOR AND THERMODYNAMICS OF A CLASSICAL ADJOINT GAS

The effect of topology on the thermodynamics of a gas of adjoint repre sentation charges interacting via 1 + 1-dimensional SU(N) gauge fields is investigated, We demonstrate explicitly the existence of multiple vacua parameterized by the discrete superselection variable k = 1,..., N. In the low pressure limit, the k dependence of the adjoint gas equ ation of state is calculated and shown to be non-trivial. Conversely, in the limit of high system pressure, screening by the adjoint charges results in an equation of state independent of k. Additionally, the r elation of this model to adjoint QCD at finite temperature in two dime nsions and the limit N --> infinity are discussed. (C) 1998 Elsevier S cience B.V.