Fate of unoriented bosonic string after tachyon condensation

By a toroidal compactification with a vortex like configuration of tachyon fields, the unoriented bosonic string in 26 dimensions becomes equivalent to 10 dimensional string theory with gauge group SO(32) × G where G has rank 16. The reduction from SO(8192) to SO(32) is induced by the action of non-abelian Wilson lines which twists the tachyon. The additional enhanced gauge symmetry G appears from closed string sector by the vertex operator construction. We also examine the consistency of the tachyon condensation.