2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/192877A consistent evolution of the strong coupling constant $α_s$ from $M_Z$ to the GUT scale is presented, involving three-loop running and two-loop decoupling. The two-loop transition from the MS- to the DR-scheme is properly taken into account. In the second part of the paper, the bottom quark mass in the DR-scheme at the electroweak/SUSY scale is evaluated with four-loop accuracy. We find that the three-loop effects are comparable to the experimental uncertainty both for $α_s$ and $m_b$.19 pages, 4 figures,references addedHigh Energy Physics - Phenomenologytext