Dynamical fine-tuning of initial conditions for small field inflations

Abstract

Small-field inflation (SFI) is widely considered to be unnatural because an extreme fine-tuning of the initial condition is necessary for sufficiently large e-folding. In this paper, we show that the unnaturally-looking initial condition can be dynamically realised without any fine-tuning if the SFI occurs after rapid oscillations of the inflaton field and particle creations by preheating. In fact, if the inflaton field $\varphi$ is coupled to another scalar field $\chi$ through the interaction $g^2{\chi }^2{\varphi }^2$ and the vacuum energy during the small field inflation is given by $\lambda M^4$, the initial value can be dynamically set at $(\sqrt{\lambda }/g)M^2/M_{\mathrm{pl}}$, which is much smaller than the typical scale of the potential $M.$ This solves the initial condition problem in the new inflation model or some classes of the hilltop inflation models.

17 pages, 2 figures

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Cited by in corpus (5)

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• Dynamical realization of the small field inflation of Coleman-Weinberg type in the post supercooled universe
• Walking-dilaton hybrid inflation with $B-L$ Higgs embedded in dynamical scalegenesis