String unification at intermediate energies: phenomenological viability and implications

Motivated by the fact that the string scale can be many orders of magnitude lower than the Planck mass, we investigate the required modifications in t he MSSM beta-functions in order to achieve intermediate (10(10-13) GeV) sca le unification, keeping the traditional logarithmic running of the gauge co uplings. We present examples of string unified models with the required ext ra matter for such a unification while we also check whether other MSSM pro perties (such as radiative symmetry breaking) are still applicable. (C) 199 9 Published by Elsevier Science B.V. All rights reserved.