String interactions in a plane-fronted parallel-wave spacetime

Abstract

We argue that string interactions in a plane-fronted parallel-wave spacetime are governed by an effective coupling g_eff=g_s(µp⁺α')f(µp⁺α') where f(µp⁺α') is proportional to the light-cone energy of the string states involved in the interaction. This simply follows from generalities of a matrix string description of this background. g_eff nicely interpolates between the expected result (g_s) for flat space (small µp⁺α') and a recently conjectured expression from the perturbative gauge theory side (large µp⁺α').