Abstract
The present work suggests that the isocurvature tension between axion and high energy inflationary scenarios may be avoided by considering a double field inflationary model involving the hidden Peccei-Quinn Higgs and the Standard Model one. Some terms in the lagrangian we propose explicitly violate the Peccei-Quinn symmetry but, at the present era, their effect is completely negligible. The resulting mechanism allows a large value for the axion constant, of the order $f_a\sim M_p$, thus the axion isocurvature fluctuations are suppressed even when the scale of inflation $H_{inf}$ is very high, of the order of $H_{inf}\sim M_{gut}$. This numerical value is typical in Higgs inflationary models. An analysis about topological defect formation in this scenario is also performed, and it is suggested that, under certain assumptions, their effect is not catastrophic from the cosmological point of view.
Highlights
Besides these constraints, there are estimates that suggest the upper bound fa < 1012 GeV [29,30]
The standard QCD picture is that the axion potential is flat until the temperature of the universe is close to Tqcd
The discussion given above suggests that the corrections to the axion mass (2.1) may be important for softening the tension between high energy inflationary and axion models
Summary
There are estimates that suggest the upper bound fa < 1012 GeV [29,30]. For this realization of symmetry breaking, the bound 109 GeV < fa < 1012 GeV is in tension with high energy inflationary models This is due to the fact that the axion is effectively massless at the inflationary period and, for any massless scalar (or pseudoscalar) field a present during inflation, there will appear quantum fluctuations with a nearly scale invariant spectrum of the form. If it is assumed that the symmetry breaking takes place at inflation, one should find mechanisms for which initially fa ∼ 1017−1019 GeV for avoiding the isocurvature problem This scale is essentially the Planck mass, and it violates the bound in [29,30] by seven orders of magnitude.
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