Baryon junction and string interactions

We study junctions between confining strings. We show that the effective theory of such junctions is very predictive, with only one new parameter, the junction's mass, controlling the first couple of terms in the expansion in the system size. By open-closed string duality, these considerations about the baryon junction map to interaction vertices of closed strings. Therefore, we calculate the interaction vertices of closed strings in theories such as Yang-Mills theory. We find some surprising selection rules for string interactions in 3+1 dimensions. Requiring perturbative stability and that the string coupling is weak, we suggest constraints on the junction's mass.