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

Understand

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.