Reconciling early dark energy with a Harrison-Zeldovich spectrum

TL;DR

This paper demonstrates that a Harrison-Zeldovich primordial spectrum can be achieved within single-field chaotic inflation using nonminimal derivative coupling, reconciling early dark energy models with observational data.

Contribution

It introduces a novel single-field inflation model with nonminimal derivative coupling that successfully produces a Harrison-Zeldovich spectrum, previously thought infeasible.

Findings

Achieves Harrison-Zeldovich spectrum with single-field inflation.

Revises the viability of certain chaotic potentials under current data.

Suggests future polarization observations can test this model.

Abstract

Recent attempts to fully resolve the Hubble tension from early dark energy models seem to favor a primordial Harrison-Zeldovich universe with its scalar spectrum being extremely scale invariant. Restoring the Harrison-Zeldovich spectrum within the single-field inflationary paradigm appears to be infeasible, turning to the multifield approach from either curvaton or waterfall models. In this Letter, we successfully align with the Harrison-Zeldovich spectrum within a single-field chaotic inflation by a nonminimal derivative coupling, and the previously disfavored chaotic potential by Planck+BICEP/Keck data in the standard $\Lambda$-cold-dark-matter model now returns back to the scope of future polarization observations of the cosmic microwave background.