Natural Inflation with a periodic non-minimal coupling
arXiv:1806.05511 · doi:10.1088/1475-7516/2018/11/021
Abstract
Natural inflation is an attractive model for primordial inflation, since the potential for the inflaton is of the pseudo Nambu-Goldstone form, $V(Ï)=Î^4 [1+\cos (Ï/f)]$, and so is protected against radiative corrections. Successful inflation can be achieved if $f \gtrsim {\rm few}\, M_{P}$ and $Î\sim m_{GUT}$ where $Î$ can be seen as the strong coupling scale of a given non-abelian gauge group. However, the latest observational constraints put natural inflation in some tension with data. We show here that a non-minimal coupling to gravity $γ^2(Ï) R$, that respects the symmetry $Ï\rightarrow Ï+2 Ïf$ and has a simple form, proportional to the potential, can improve the agreement with cosmological data. Moreover, in certain cases, satisfactory agreement with the Planck 2018 TT, TE, EE and low P data can be achieved even for a periodicity scale of approximately $M_p$.
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