Fine tunings for inflation with simple potentials

TL;DR

This paper explores parameter tuning in simple inflationary potentials, finding that grand unification scale potentials can produce observationally consistent primordial inflation, potentially marginally eternal, with minimal tuning.

Contribution

It investigates the parameter space for simple inflation potentials, especially at the grand unification scale, to achieve marginally eternal inflation consistent with observations.

Findings

Potentials at the grand unification scale can produce viable inflation after tuning.

Marginal eternal inflation is possible with simple potentials under certain parameter choices.

The required tuning is compatible with current observational constraints.

Abstract

We continue to investigate possible parameter choices for primordial inflation with simple potentials such as power-law and two-term potentials. We examine the amount of parameter tuning to make the slow-roll inflation eternal. In particular, we adopt the critical coupling for marginally eternal inflation and see whether realistic primordial inflation is attainable under such a parameter choice. It turns out that potentials with mass scale of grand unification provide, after tuning, consistent results to experimental data so that the considered tuning is allowed observationally. Namely, the primordial inflation is possibly marginal in such a setup.