Inflection point inflation: WMAP constraints and a solution to the fine-tuning problem

TL;DR

This paper investigates an inflection point inflation model constrained by WMAP data, introduces a hybrid field to reduce fine-tuning, and enhances the model's robustness and initial condition tolerance.

Contribution

It proposes a hybrid mechanism to dynamically uplift the potential, significantly reducing fine-tuning and expanding the slow-roll region in inflection point inflation models.

Findings

Large parameter regions reduce fine-tuning requirements.

The hybrid transition maintains small neutrino masses.

The model aligns with WMAP constraints.

Abstract

We consider observational constraints and fine-tuning issues in a renormalizable model of inflection point inflation, with two independent parameters. We derive constraints on the parameter space of this model arising from the WMAP 7-year power spectrum. It has previously been shown that it is possible to successfully embed this potential in the MSSM. Unfortunately, to do this requires severe fine-tuning. We address this issue by introducing a hybrid field to dynamically uplift the potential with a subsequent smooth phase transition to end inflation at the necessary point. Large parameter regions exist where this drastically reduces the fine-tuning required without ruining the viability of the model. A side effect of this mechanism is that it increases the width of the slow-roll region of the potential, thus also alleviating the problem of the fine-tuning of initial conditions. The MSSM embedding we study has been previously shown to be able to explain the smallness of the neutrino masses. The hybrid transition does not spoil this feature as there exist parameter regions where the fine-tuning parameter is as large as $10^{-1}$ and the neutrino masses remain small.