# Intermediate scales in non-supersymmetric SO(10) grand unified theories

## TL;DR

This paper revisits non-supersymmetric SO(10) grand unified theories using a two-loop gauge coupling analysis, revealing new parameter space where these models can align with experimental constraints on proton decay, neutrino masses, and fermion mixing.

## Contribution

It provides the first comprehensive two-loop reassessment of gauge unification in non-supersymmetric SO(10) models, identifying viable regions compatible with current experimental data.

## Key findings

- New parameter space supports viable non-supersymmetric SO(10) models.
- Reassessment aligns GUT scale with proton decay and neutrino mass constraints.
- Potential revival of simple non-supersymmetric GUT scenarios.

## Abstract

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.