New aspects of the BMN correspondence beyond the planar limit

Motivated by recent disagreements in the context of AdS/CFT, we study the non-planar sector of the BMN correspondence. In particular, we reconsider the energy shift of states with two stringy excitations in light-cone string field theory and explicitly determine its complete perturbative contribution from the impurity-conserving channel. Surprisingly, our result neither agrees with earlier leading order computations, nor reproduces the gauge theory prediction. More than that, it features half-integer powers of the effective gauge coupling $\lambda'$ representing a qualitative difference to gauge theory. Based on supersymmetry we argue that the above truncation is not suited for conclusive tests of the BMN duality.