Germani, CristianoKehagias, Alex2019-05-082019-05-082011-04-200031-9007https://hdl.handle.net/2445/132841In natural inflation, the inflaton is a pseudo-Nambu-Goldstone boson which acquires a mass by explicit breaking of a global shift symmetry at scale f . In this case, for small field values, the potential is flat and stable under radiative corrections. Nevertheless, slow roll conditions enforce f ≫ M p , making the validity of the whole scenario questionable. In this Letter, we show that a coupling of the inflaton kinetic term to the Einstein tensor allows f ≪ M p by enhancing the gravitational friction acting on the inflaton during inflation. This new unique interaction (a) keeps the theory perturbative in the whole inflationary trajectory, (b) preserves the tree-level shift invariance of the pseudo-Nambu-Goldstone boson, and (c) avoids the introduction of any new degrees of freedom with respect to standard natural inflation.4 p.application/pdfeng(c) American Physical Society, 2011Radiació ultravioladaBosonsUltraviolet radiationBosonsinfo:eu-repo/semantics/article6600172019-05-08info:eu-repo/semantics/openAccess