The role of CMB spectral distortions in the Hubble tension: a proof of principle

TL;DR

This paper argues that precise measurements of CMB spectral distortions are crucial for constraining early-universe modifications to resolve the Hubble tension, emphasizing their potential to test models altering standard cosmological parameters.

Contribution

It highlights the importance of CMB spectral distortions in constraining models that modify the early universe to address the Hubble tension.

Findings

CMB spectral distortions can effectively constrain early-universe models.

Spectral distortions are sensitive to shifts in standard $\Lambda$CDM$ parameters.

Precise CMB observations are vital for testing solutions to the Hubble tension.

Abstract

Although both early and late-time modifications of the $\Lambda$CDM model have been proposed to address the Hubble tension, compelling arguments suggest that for a solution to be successful it needs to modify the expansion history of the universe prior to recombination. This greatly increases the importance of precise CMB observations, and in this letter we make the argument for CMB spectral distortions, highlighting their potential role in constraining models that introduce significant shifts in the standard $\Lambda$CDM parameters, such as the scalar spectral index, in attempt to solve the Hubble tension.