Tachyon instability and Kondo type models

We consider compactifications of bosonic open string theory on maximal tori of various simple Lie algebras with a specific background coupled to the string boundaries. The resulting worldsheet CFT is a free theory perturbed by a boundary term that is marginal but not truly marginal. We assume that the theory flows to a nontrivial infrared fixed point that is similar to the one in Kondo model. This RG flow reflects the tachyon instability of the bosonic string vacuum. At the fixed point we calculate the new spectrum and some of the Green's functions. We find that in some of the sectors the tachyon mass gets lifted that can be interpreted as a result of switching on appropriate Wilson lines. Various compactifications and patterns of flows are investigated.