SPEAKER: António P. Morais (Universidade de Aveiro)
ABSTRACT: The unification of the fundamental interactions in nature has been one of the major goals of the theoretical physics community over the last century. While the unification of gravity with the strong and electroweak interactions is far from being a trivial problem, there are diverse particle physics models that nicely predict the unification of the three gauge couplings of the Standard Model (SM) theory. In particular, minimal supersymmetric extensions together with low-rank simple Lie-algebras provide such a framework. However, this class of minimal Grand Unified Theories, GUTs, often poses new problems such as proton stability and fine tuning between the GUT and electroweak scales which have to differ by many orders of magnitude in order to fit experimental constraints.
In this talk I will introduce a new supersymmetric model based on the E8 inspired trinification gauge group with SU(3)-flavour. We aim at solving some of the current issues of conventional GUTs, as well as explaining the origin of the SM. Unlike older realizations, the flavour symmetry forbids leptons from acquiring tree-level masses naturally suppressing them from the GUT scale. We predict Higgs-lepton unification within the same supermultiplet, which is a novel feature of our model. We also obtain a U(1)B-L symmetry by means of spontaneous trinification breaking, which forbids barion number violating interactions stabilizing the proton. Finally, we find specific relations among the parameters of the theory that strongly suppress part of the scalar sector masses, which may be an explanation for the large hierarchy between Higgs mass and the scale of the unified physics.