We study the production of fermions through a derivative coupling with a pseudoscalar inflaton and the effects of the produced fermions on the scalar primordial perturbations. We present analytic results for the modification of the scalar power spectrum due to the produced fermions, and we estimate the amplitude of the non-Gaussianities in the equilateral regime. Remarkably, we find a regime where the effect of the fermions gives the dominant contribution to the scalar spectrum while the amplitude of the bispectrum is small and in agreement with observation. We also note the existence of a regime in which the backreaction of the fermions on the evolution of the zero-mode of the inflaton can lead to inflation even if the potential of the inflaton is steep and does not satisfy the slow-roll conditions.
Bibliographical noteFunding Information:
through National Science Foundation Grant No. PHY-1066293. L.P. gratefully acknowledges support from a Fortner Fellowship at the University of Illinois at Urbana-Champaign. The work of M.R. and L.S. is partially supported by the US-NSF grant PHY-1520292. The work of M.P. was supported in part by DOE grant DE-SC0011842 at the University of Minnesota.
The work of P.A. and L.P. was supported by the US Department of Energy through grant DESC0015655. P.A. and L.P. thank the Aspen Center for Physics for its hospitality and support
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- cosmological perturbation theory