Cosmological Tests of the Disformal Coupling to Radiation

TL;DR

This paper investigates how light scalar fields disformally coupled to photons can be constrained through cosmological observations, focusing on effects on the CMB spectrum and distance duality, especially for axionic quintessence models.

Contribution

It introduces methods to constrain disformally coupled scalar fields via cosmological data, emphasizing their impact on CMB distortions and distance relations, with implications for axionic quintessence.

Findings

Constraints on disformal couplings from CMB spectral distortions

Violations of the distance duality relation due to scalar-photon interactions

Implications for axionic quintessence models

Abstract

Light scalar fields can naturally couple disformally to Standard Model fields without giving rise to the unacceptably large fifth forces usually associated with light scalars. We show that these scalar fields can still be studied and constrained through their interaction with photons, and focus particularly on changes to the Cosmic Microwave Background spectral distortions and violations of the distance duality relation. We then specialise our constraints to scalars which could play the role of axionic quintessence.