Abstract
Giving up the solutions to the fine-tuning problems, we propose the non-supersymmetric flipped SU(5)times U(1)_X model based on the minimal particle content principle, which can be constructed from the four-dimensional SO(10) models, five-dimensional orbifold SO(10) models, and local F-theory SO(10) models. To achieve gauge coupling unification, we introduce one pair of vector-like fermions, which form a complete SU(5)times U(1)_X representation. The proton lifetime is around 5times 10^{35} years, neutrino masses and mixing can be explained via the seesaw mechanism, baryon asymmetry can be generated via leptogenesis, and the vacuum stability problem can be solved as well. In particular, we propose that inflaton and dark matter particles can be unified to a real scalar field with Z_2 symmetry, which is not an axion and does not have the non-minimal coupling to gravity. Such a kind of scenarios can be applied to the generic scalar dark matter models. Also, we find that the vector-like particle corrections to the B_s^0 masses might be about 6.6%, while their corrections to the K^0 and B_d^0 masses are negligible.
Highlights
IntroductionThere are two kinds of theoretical problems in the Standard Model (SM): fine-tuning problems and aesthetic problems
C (2018) 78:26 gauge interactions; (ii) there is no explanation of fermion mass structures; (iii) there is no explanation for charge quantization; (iv) there is no realization of gauge coupling unification
The aesthetic problems can be solved in Grand Unified Theories (GUTs) if we can realize gauge coupling unification
Summary
There are two kinds of theoretical problems in the SM: fine-tuning problems and aesthetic problems. The finetuning problems are: (i) The cosmological constant problem: why is the cosmological constant so tiny? (ii) The gauge hierarchy problem: the SM Higgs boson mass square is not stable against quantum corrections and has quadratic divergences, while the electroweak scale is about 16 order smaller than the reduced Planck scale MPl 2.43 × 1018 GeV. (iii) The strong CP problem: the θ parameter of Quantum Chromodynamics (QCD) is smaller than 10−10 from the measurements of the neutron electric dipole moment [13,14]. (iv) The SM fermion mass hierarchy problem: the electron mass is about 5 orders smaller than top quark mass. The aesthetic problems are: (i) there is no explanation for the structure of
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