Small Field Coleman-Weinberg Inflation driven by Fermion Condensate

Abstract

We revisit the small field Coleman-Weinberg (CW) inflation, which has the following two problems. First, the smallness of the slow roll parameter $ϵ$ requires the inflation scale to be very low. Second, the spectral index $n_s\approx 1+2\eta$ tends to become smaller compared to the observed value. In this letter, we consider two possible effects on the dynamics of inflation: radiatively generated non-minimal coupling to gravity $\xi {\varphi }^2\mathcal{R}$ and condensation of fermions coupled to the inflaton as $\varphi \bar{\psi }\psi$. We show that the fermion condenate can solve the above problems.

Comments: 5 pages, 2 figures; references and a discussion on the reheating temperature added, version published in PRD