String Unification at Intermediate Energies: Phenomenological Viability and Implications

TL;DR

This paper explores the possibility of gauge coupling unification at intermediate energies around 10^{10-13} GeV within string-inspired models, examining the necessary modifications to MSSM beta-functions and the viability of such models.

Contribution

It demonstrates how to achieve intermediate scale unification by modifying MSSM beta-functions and provides examples of string unified models with extra matter content.

Findings

Intermediate scale unification is feasible with specific beta-function modifications.

String unified models with extra matter can realize unification at 10^{10-13} GeV.

Radiative symmetry breaking remains compatible with these models.

Abstract

Motivated by the fact that the string scale can be many orders of magnitude lower than the Planck mass, we investigate the required modifications in the MSSM $\beta$--functions in order to achieve intermediate ($10^{10-13}$GeV) scale unification, keeping the traditional logarithmic running of the gauge couplings. We present examples of string unified models with the required extra matter for such a unification while we also check whether other MSSM properties (such as radiative symmetry breaking) are still applicable.