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Large Non-Gaussianity in Slow-Roll Inflation

Abstract : Canonical models of single-field, slow-roll inflation do not lead to appreciable non-Gaussianity, unless derivative interactions of the inflaton become uncontrollably large. We propose a novel slow-roll scenario where scalar perturbations propagate at a subluminal speed, leading to sizeable equilateral non-Gaussianity, $f^{\rm equil}_{\rm NL}\propto 1/c_s^4$, largely insensitive to the ultraviolet physics. The model is based on a low-energy effective theory characterized by weakly broken invariance under internal galileon transformations, $\phi\to\phi+b_\mu x^\mu$, which protects the properties of perturbations from large quantum corrections. This provides the unique alternative to models such as DBI inflation in generating strongly subluminal/non-Gaussian scalar perturbations.
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David Pirtskhalava, Luca Santoni, Enrico Trincherini, Filippo Vernizzi. Large Non-Gaussianity in Slow-Roll Inflation. Journal of High Energy Physics, Springer Verlag (Germany), 2016, 4, pp.117. ⟨10.1007/JHEP04(2016)117⟩. ⟨cea-01223849⟩

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