Emission spectrum of fundamental strings:: an algebraic approach

We formulate a linear difference equation which yields averaged semi-inclusive decay rates for arbitrary, not necessarily large. values of the masses. We show that the rates for decays M --> m + M' of typical heavy open strings are independent of the masses M and m, and compute the mass defect M-m-M'. For closed strings we find decay rates proportional to Mm(R)((1-D)/2), where m(R) is the reduced mass of the decay products. Our method yields exact interaction rates valid for all mass ranges and may provide a fully microscopic basis, not limited to the long string approximation, for the interactions in the Boltzmann equation approach to hot string gases. (C) 2002 Published by Elsevier Science B.V.