Excitations of the static quark-antiquark system in several gauge theories

The spectrum of gluons in the presence of a static quark-antiquark pair is studied using Monte Carlo simulations on anisotropic space-time lattices. For very small quark-antiquark separations R, the level orderings and approximate degeneracies disagree with the expectations from an effective string theory. As the quark-antiquark separation R increases, a dramatic rearrangement of the energies occurs, and above 2 fm, all of the levels studied show behavior consistent with an effective string description. The energy spacings are nearly pi/R, but a tantalizing fine structure remains. In addition to 4-dimensional SU(3) gauge theory, results from 3-dimensional SU(2) and compact U(1) gauge theories are also presented.