Towards a reliable effective field theory of inflation
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Bastero-Gil, M., Berera, A., Ramos, R. O., & Rosa, J. G. (2020). Towards a reliable effective field theory of inflation. Physics Letters B, 136055. [https://doi.org/10.1016/j.physletb.2020.136055]
SponsorshipUK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC); MINECO FIS2016-78198-P; Junta de Andalucía SOMM/17/6104/UGR FQM101; National Council for Scientific and Technological Development (CNPq) 302545/2017-4; Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJ) E-26/202.892/2017; Portuguese Foundation for Science and Technology European Commission IF/01597/2015 PTDC/FIS-OUT/28407/2017; CFisUC strategic project UID/FIS/04564/2019; ENGAGE SKA POCI-01-0145-FEDER-022217
We present the first quantum field theory model of inflation that is renormalizable in the matter sector, with a super-Hubble inflaton mass and sub-Planckian field excursions, which is thus technically natural and consistent with a high-energy completion within a theory of quantum gravity. This is done in the framework of warm inflation, where we show, for the first time, that strong dissipation can fully sustain a slow-roll trajectory with slow-roll parameters larger than unity in a way that is both theoretically and observationally consistent. The inflaton field corresponds to the relative phase between two complex scalar fields that collectively break a U(1)gauge symmetry, and dissipates its energy into scalar degrees of freedom in the warm cosmic heat bath. A discrete interchange symmetry protects the inflaton mass from large thermal corrections. We further show that the dissipation coefficient decreases with temperature in certain parametric regimes, which prevents a large growth of thermal inflaton fluctuations. We find, in particular, a very good agreement with the Planck legacy data for a simple quadratic inflaton potential, predicting a low tensor-to-scalar ratio r 10−5.