Band-limited Features in the Primordial Power Spectrum Do Not Resolve the Hubble Tension

TL;DR

This study investigates whether band-limited features in the primordial power spectrum, caused by inflationary glitches, can resolve the Hubble tension, but finds no significant features and the tension remains unresolved.

Contribution

The paper conducts a blind wavelet search for features in the primordial power spectrum using recent data, showing such features do not alleviate the Hubble tension.

Findings

No significant features detected beyond power law.

Adding degrees of freedom does not reduce the Hubble tension.

Hubble tension persists at 4.9 sigma despite the search.

Abstract

For a standard $\Lambda$CDM universe with a power-law primordial power spectrum, the discrepancy between early- and late-universe measurements of the Hubble constant continued to grow and recently reached $5.3\sigma$. During inflation, local features in the inflationary potential often lead to band-limited features in the primordial power spectrum, hence breaking the power-law assumption in the derivation of the Hubble tension. We investigate whether such inflationary "glitches" can ease the Hubble tension. The recently released \emph{Planck} temperature and polarization data and the 2019 SH0ES+H0LiCOW joint constraint on the Hubble constant are combined to drive a blind Daubechies wavelet signal search in the primordial power spectrum, up to a resolution $\Delta \ln k\sim 0.1$. We find no significant detection of any features beyond power law. With 64 more degrees of freedom injected in the primordial power spectrum, the Hubble tension persists at a $4.9\sigma$ level.