Induced gravity inflation in the SU(5) GUT

We investigate the cosmological consequences of a theory of induced gravity in which the scalar field is identified with the Higgs field of the first symmetry breaking of a minimal SU(5) GUT. The mass of the X boson determines a great value for the coupling constant of of gravity-particle physics. Because of this fact, a ``slow'' rollover dynamics for the Higgs field is not possible in a ``new'' inflation scenario and, moreover, a contraction era for the scale factor in the early Universe exists, after which inflation follows automatically; ``chaotic'' inflation is performed without problems. Inflation is successfully achieved due to the relationship among the masses of particle physics at that scale: the Higgs-boson, X-boson, and Planck masses. As a result the particle physics parameter {λ} is not fine-tuned as usual in order to predict acceptable values of reheating temperature and density and gravitational wave perturbations. Moreover, if the coherent Higgs oscillations did not decay they could explain the missing mass problem of cosmology.