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Ultraviolet-Protected Inflation Germani, Cristiano Kehagias, Alex Radiació ultraviolada Bosons Ultraviolet radiation Bosons In 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. 2019-05-08T13:00:41Z 2019-05-08T13:00:41Z 2011-04-20 2019-05-08T13:00:41Z info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 0031-9007 https://hdl.handle.net/2445/132841 660017 eng Reproducció del document publicat a: https://doi.org/10.1103/PhysRevLett.106.161302 Physical Review Letters, 2011, vol. 106, num. 16, p. 161302 https://doi.org/10.1103/PhysRevLett.106.161302 (c) American Physical Society, 2011 info:eu-repo/semantics/openAccess 4 p. application/pdf American Physical Society Articles publicats en revistes (Institut de Ciències del Cosmos (ICCUB))