Bag Picture of the Excited QCD Vacuum with Static Q-Qbar Source

The gluon excitations of the QCD vacuum are investigated in the presence of a static quark-antiquark source. It is shown that the ground state potential and the excitation spectrum of dynamical gluon degrees of freedom, as determined in our lattice simulations, agree remarkably well with model predictions based on the diaelectric properties of the confining vacuum described as a dual superconductor. The strong chromoelectric field of the static Q-Qbar source creates a bubble (bag) in the condensed phase where weakly interacting gluon modes can be excited. Some features and predictions of the bag model are presented and the chromoelectric vortex limit at large quark-antiquark separation (string formation) is briefly discussed.