Two-Loop Renormalization Group Equations and Gauge Couplings Unification

TL;DR

This paper investigates how two-loop renormalization group equations affect gauge couplings unification in supersymmetric theories, revealing that triplet superfields can enable unification and lead to nontrivial ultraviolet fixed points.

Contribution

It demonstrates that two-loop calculations allow gauge coupling unification with triplet superfields, unlike one-loop results, and shows the existence of nontrivial UV fixed points.

Findings

Gauge couplings unify with triplet superfields at two-loop level.

Dimensionless couplings avoid Landau poles and reach UV fixed points.

Unification is disrupted by higher-representation superfields at one-loop.

Abstract

We analize the impact of two-loop renormalization group equations on the $SU(3)_c\times SU(2)_w\times U(1)_Y$ gauge couplings unification in various supersymmetric theories. In general the presence of superfields in higher representation than the doublet spoil the gauge couplings unification at one-loop. The situation is more interesting when the renormalization group equations are calculated at two-loop. In this case we show that the unification of the gauge couplings can be achieved for models with triplet superfield(s). In the analysis of the models with triplet superfield(s) we show that the dimensionless couplings do not have a Landau pole in their evolution at high energies but they run to a nontrivial ultraviolet fixed point.