  It is often argued that in the class of non-supersymmetric SO(10) grand
unified theories there is barely any room for reconciling the lower bound on
the position of the GUT scale emerging from the proton decay searches and the
lower limit on the absolute neutrino mass scale derived from the neutrino
oscillation experiments with the gauge coupling unification constraints. The
recent two-loop reassessment of the gauge running provides the first complete
picture of the situation, complementing the existing studies in several
aspects. The improved analysis reveals a new room in the parametric space that
could support a class of non-supersymmetric SO(10) models potentially
compatible with all current physical data, including constraints on the
relevant Yukawa sector emerging from the quark and lepton masses and mixings.
This, in turn, brings back the question of viability of some of the simplest
non-supersymmetric GUT scenarios.
