N-string vertices in string field theory.

We give the general form of the vertex corresponding to the interaction of an arbitrary number of strings. The technique employed relies on the “comma” representation of String Field Theory where string fields and interactions are represented as matrices and operations between them such as multiplication and trace. The general formulation presented here shows that the interaction vertex of N strings, for any arbitrary N, is given as a function of particular combinations of matrices corresponding to the change of representation between the full string and the half string degrees of freedom.