Higgs inflation at the critical point

Higgs inflation can occur if the Standard Model (SM) is a self-consistent effective field theory up to inflationary scale. This leads to an upper bound on the top Yukawa coupling, y(t)(phys) < y(t)(crit) and thus on the mass of the top quark m(t). If m(t) is more than a few hundred of MeV below the critical value, the Higgs inflation predicts the universal values of inflationary indexes, r similar or equal to 0.003 and n(s) similar or equal to 0.97, independently on the SM parameters. We show that in the vicinity of the critical point y(t)(crit) the inflationary indexes acquire an essential dependence on m(t) and on the mass of the Higgs boson M-h. In particular, the amplitude of the gravitational waves can exceed considerably the universal value. (C) 2014 Elsevier B.V.