English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

In this paper we analyse the doublet-triplet splitting problem in the minimalnon-super-symmetric $SU(5)$ GUT. We take into account the full symmetrybreaking pattern with both high scale $SU(5)$ breaking and electroweak symmetrybreaking. Our analysis shows that the only phenomenologically acceptable modelhas three vevs, with a strong hierarchy determined by the minimizationconditions. The amount of fine-tuning in the model is then numericallyevaluated by looking at the effect of variation of input parameters on both theminimization conditions and the bosonic masses. Regarding the vevs as outputparameters, a large amount of fine-tuning is required in this scenario, whichis an expression of the doublet-triplet splitting problem. We show that thisproblem is more general, since a model with coupled scalar sectors will ingeneral never realise a hierarchy in vevs. To avoid these problems we advocateimposing the desired hierarchy in vevs as part of the theory. We argue for thisviewpoint because the $SU(5)$ breaking and electroweak symmetry breaking needto be adjusted to each other anyway and cannot be regarded as independentmechanisms. We suggest that not only the symmetry breaking pattern needs to beimposed, but also the scales at which the breakings happen. We showquantitatively that the generic theory with hierarchy imposed does not requireany fine-tuning of the free parameters which can all be natural andperturbative as desired.

Fine-tuning and the doublet-triplet splitting problem in the minimal $SU(5)$ GUT