A comment on the scattering of macroscopic strings

Soliton solutions of string theory recently discovered by Dabholkar and Harvey have the property, like BPS magnetic monopoles, that they exert zero static force on each other and can be superposed to form multi-soliton solutions with arbitrarily variable collective coordinates. We will show that, in contradistinction to the BPS case, the velocity-dependent forces between these string solitons also vanish (i.e., we argue that the metric on moduli space is flat). We also argue that this phenomenon provides further, dynamical evidence for the identification of the Dabholkar-Harvey soliton with the underlying fundamental string.