# Unification, Proton Decay and Topological Defects in non-SUSY GUTs with Thresholds

## TL;DR

This paper evaluates proton decay, topological defects, and the impact of threshold corrections in various non-SUSY GUT models, showing that threshold effects can extend the viability of certain theories.

## Contribution

It provides a comprehensive analysis of proton lifetime predictions and topological defects in non-SUSY GUTs, emphasizing the importance of threshold corrections for model viability.

## Key findings

- Threshold corrections significantly extend proton lifetime predictions.
- Many GUT scenarios become viable due to threshold effects.
- Topological defect analysis varies across different symmetry breaking patterns.

## Abstract

We calculate the proton lifetime and discuss topological defects in a wide class of non-supersymmetric (non-SUSY) $SO(10)$ and $E(6)$ Grand Unified Theories (GUTs), broken via left-right subgroups with one or two intermediate scales (a total of 9 different scenarios with and without D-parity), including the important effect of threshold corrections. By performing a goodness of fit test for unification using the two-loop renormalisation group evolution equations (RGEs), we find that the inclusion of threshold corrections significantly affects the proton lifetime, allowing several scenarios, which would otherwise be excluded, to survive. Indeed we find that the threshold corrections are a saviour for many non-SUSY GUTs. For each scenario we analyse the homotopy of the vacuum manifold to estimate the possible emergence of topological defects.