Harrison-Zeldovich attractor: From Planck to ACT results

TL;DR

This paper proposes a new theoretical framework using nonminimal derivative coupling to realize the Harrison-Zeldovich attractor, aligning inflationary models with recent ACT observations suggesting a near scale-invariant spectrum.

Contribution

It introduces a novel approach to achieve the Harrison-Zeldovich attractor through nonminimal derivative coupling, extending various inflationary models.

Findings

Successfully models the Harrison-Zeldovich spectrum with nonminimal derivative coupling.

Bridges the gap between Planck and ACT results in inflationary cosmology.

Provides a new paradigm for inflation consistent with near scale-invariance.

Abstract

In the era of Planck cosmology, the inflationary paradigm is best fitted toward the cosmological attractor scenarios, including the induced inflation, universal attractors, conformal attractors, and special attractors that are cataloged as $\xi$-models and $\alpha$-models. The recent hint from the ACT results pushes the scalar spectral index closer to the scale-invariant Harrison-Zeldovich spectrum, calling for a theoretical paradigm shift toward a Harrison-Zeldovich attractor, which is difficult to realize in the standard single-field slow-roll inflationary scenario. In this work, we achieve the Harrison-Zeldovich attractor scenario via nonminimal derivative coupling, attracting the monomial inflation, hilltop inflation, and $\alpha$-attractor E-model toward the Harrison-Zeldovich spectrum.