CASIMIR SCALING FROM CENTER VORTICES - TOWARDS AN UNDERSTANDING OF THE ADJOINT STRING TENSION

We argue that the approximate ''Casimir scaling'' of the string tensio ns of higher-representation Wilson loops is an effect due to the finit e thickness of center vortex configurations. It is shown, in the conte xt of a simple model of the Z(2) vortex core, how vortex condensation in Yang-Mills theory can account for both Casimir scaling in intermedi ate size loops and color-screening in larger loops. An implication of our model is that the deviations from exact Casimir scaling, which ten d to grow with loop size, become much more pronounced as the dimension ality of the group representation increases. [S0556-2821(98)03206-8].