The stability of vacua in two-dimensional gauge theory

We discuss the stability of vacua in two-dimensional gauge theory for any s imple, simply connected gauge group. Making use of the representation of a vacuum in terms of a Wilson line at infinity, we determine which vacua are stable against pair production of heavy matter in the adjoint of the gauge group. By calculating correlators of Wilson loops, we reduce the problem to a problem in representation theory of Lie groups, that we solve in full ge nerality. (C) 2001 Published by Elsevier Science B.V.