Single field slow-roll inflation with step uplift to $n_s=1$

TL;DR

This paper explores how single-field slow-roll inflation models can naturally produce a scale-invariant spectrum with n_s=1 by introducing a sudden step in the inflaton potential, aligning with dark energy and Hubble tension observations.

Contribution

It proposes a novel mechanism involving a potential step to achieve n_s=1 in well-known single-field inflation models, compatible with current observational data.

Findings

Potential step can induce n_s=1 in chaotic and Starobinsky inflation models.

Models remain consistent with observational constraints on spectral index.

Inflation ends abruptly due to the potential step, affecting primordial perturbations.

Abstract

The early dark energy resolution of Hubble tension seems to be suggesting a scale-invariant Harrison-Zeldovich spectrum of primordial scalar perturbation, i.e. $n_s=1$ ($|n_s-1|\sim {\cal O}(0.001)$) for $H_0\sim 73$km/s/Mpc. In this work, we propose a possibility to acquire $n_s=1$ in single field slow-roll models of inflation. In our consideration, the potential of inflaton during inflation still preserve the shape of well-known single field inflation models in deep slow-roll region, but inflation ends suddenly due to a large step of inflaton potential. In particular, we investigate the implication of our scheme for chaotic inflation and Starobinski inflation, and show how they can be compatible with the observation for $n_s=1$.