Small Field Coleman-Weinberg Inflation driven by Fermion Condensate

Understand

We revisit the small field Coleman-Weinberg (CW) inflation, which has the following two problems.

• First, the smallness of the slow roll parameter $\epsilon$ requires the inflation scale to be very low.
• Second, the spectral index $n_s \approx1+2 \eta$ 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 $\xi \phi^2 {\cal R}$ and condensation of fermions coupled to the inflaton as $\phi \bar\psi \psi$.