2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/192198In the context of a recently proposed method for computing exactly string loop corrections regularized in the infra-red, we determine and calculate the universal moduli-dependent part of the threshold corrections to the gauge couplings for the symmetric $Z_2\times Z_2$ orbifold model. We show that these corrections decrease the unification scale of the underlying effective field theory. We also comment on the relation between this infra-red regularization scheme and other proposed methods.12 pages, Latex, contains two figures, final version, typos correctedHigh Energy Physics - Theorytext