Chan-Paton soliton gauge states of the compactified open string

Mle study the mechanism of the enhanced gauge symmetry of the bosonic open string compactified on a torus by analyzing the zero-norm soliton (non-zero winding of the Wilson line) gauge states in the spectrum. Unlike the close d string case, we find that the soliton gauge state exists only at massive levels. These soliton gauge states correspond to the existence of enhanced massive gauge symmetries with transformation parameters containing both Ein stein and Yang-Mills indices. In the T-dual picture, these symmetries exist only at some discrete values of compactified radii when N D-branes are coi ncident.