Neutrino-Assisted Early Dark Energy: Theory and Cosmology

TL;DR

This paper introduces a neutrino-assisted early dark energy model that addresses the Hubble tension by linking scalar field dynamics to neutrino mass evolution, providing a theoretically consistent framework for early universe modifications.

Contribution

It proposes a minimal neutrino-coupled early dark energy model that alleviates fine-tuning issues and offers testable predictions within a well-defined effective field theory.

Findings

The model can explain the Hubble tension through neutrino-induced energy injection.

It remains consistent with particle physics constraints and cosmological evolution.

Predictions are compatible with current cosmological data and testable with future observations.

Abstract

The tension between measurements of the Hubble constant obtained at different redshifts may provide a hint of new physics active in the relatively early universe, around the epoch of matter-radiation equality. A leading paradigm to resolve the tension is a period of early dark energy, in which a scalar field contributes a subdominant part of the energy budget of the universe at this time. This scenario faces significant fine-tuning problems which can be ameliorated by a non-trivial coupling of the scalar to the standard model neutrinos. These become non-relativistic close to the time of matter-radiation equality, resulting in an energy injection into the scalar that kick-starts the early dark energy phase, explaining its coincidence with this seemingly unrelated epoch. We present a minimal version of this neutrino-assisted early dark energy model, and perform a detailed analysis of its predictions and theoretical constraints. We consider both particle physics constraints -- that the model constitute a well-behaved effective field theory for which the quantum corrections are under control, so that the relevant predictions are within its regime of validity -- and the constraints provided by requiring a consistent cosmological evolution from early through to late times. Our work paves the way for testing this scenario using cosmological data sets.