New aspects of the BMN correspondence beyond the planar limit

We study the one-loop correction to the energy of free string states in light-cone string field theory. In particular, we construct the supermultiplet of states with two stringy excitations and explicitly determine the complete perturbative contribution to their energy shift from the impurity-conserving channel. The result does not reproduce the gauge theory prediction and features half-integer powers of the effective gauge coupling '. We show that the above truncation is incompatible with supersymmetry and thus not suited for conclusive tests of the BMN duality