Hybrid Natural Inflation

Abstract

We construct two simple effective field theory versions of {\it Hybrid Natural Inflation (HNI)} that illustrate the range of its phenomenological implications. The resulting inflationary sector potential, $V={\Delta }^4(1+a\cos (\varphi /f))$, arises naturally, with the inflaton field a pseudo-Nambu-Goldstone boson. The end of inflation is triggered by a waterfall field and the conditions for this to happen are determined. Also of interest is the fact that the slow-roll parameter $\epsilon$ (and hence the tensor $r$) is a non-monotonic function of the field with a maximum where observables take universal values that determines the maximum possible tensor to scalar ratio $r$. In one of the models the inflationary scale can be as low as the electroweak scale. We explore in detail the associated HNI phenomenology, taking account of the constraints from Black Hole production, and perform a detailed fit to the Planck 2015 temperature and polarisation data.

V2: 19 pages, 2 figures, 1 table. Extended discussions and new references added. Version accepted for publication in JHEP

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• Superheavy dark matter from the natural inflation in light of the highest-energy astroparticle events
• Interacting Scalar fields: Dark matter and early dark energy
• Constraining models of Inflationary Magnetogenesis with NANOGrav
• Natural Inflation from Polymer Quantization
• General bounds in Hybrid Natural Inflation
• Axion-driven hybrid inflation over a barrier
• Canonical single field slow-roll inflation with a non-monotonic tensor-to-scalar ratio
• Natural inflation with natural number of e-foldings
• TwInflation
• Generalized hybrid natural inflation
• Accidentally light scalars from large representations
• Bounce inflation driven by Higgs field