Lightlike Wilson loops and gauge invariance of Yang-Mills theory in 1+1 dimensions

A lightlike Wilson loop is computed in perturbation theory up to O(${\mathit{g}}^4$) for pure Yang-Mills theory in 1+1 dimensions, using Feynman and light-cone gauges to check its gauge invariance. After dimensional regularization in intermediate steps, a finite gauge invariant result is obtained, which, however, does not exhibit Abelian exponentiation. Our result is at variance with the common belief that pure Yang-Mills theory is free in 1+1 dimensions, apart perhaps from topological effects.