Non-Abelian Webs of Walls

Domain wall junctions are studied in N=2 supersymmetric U(Nc) gauge theory with Nf(>Nc) flavors. We find that all three possibilities are realized for positive, negative and zero junction charges. The positive junction charge is found to be carried by a topological charge in the Hitchin system of an SU(2) gauge subgroup. We establish rules of the construction of the webs of walls. Webs can be understood qualitatively by grid diagram and quantitatively by associating moduli parameters to web configurations.