Infrared logarithms in minisuperspace inflation

We examine the emergence of the infrared logarithms in the cosmological perturbation theory applied to the minisuperspace scalar slow-roll inflation. Not surprisingly, in the single scalar field model the curvature perturbation ζ is conserved and no $\mathrm{ln}{a}_{B}$ behavior appears, where ${a}_{B}\left(t\right)$ is the background scale factor of the universe. On the other hand, in the presence of a spectator scalar the n'th order perturbation theory gives an ${\left(\mathrm{ln}{a}_{B}\right)}^{n}$ correction to ζ. However, a nonperturbative estimate shows that ζ actually becomes the sum of a constant and a mildly evolving $\mathrm{ln}{a}_{B}$ pieces.