Hot New Early Dark Energy: Dark Radiation Matter Decoupling

TL;DR

This paper introduces a microscopic dark sector model with a gauge symmetry breaking phase transition that creates dark radiation and stable dark matter, successfully addressing the Hubble tension with current cosmological data.

Contribution

It presents a novel dark sector model based on gauge symmetry breaking that naturally explains dark radiation and dark matter decoupling, resolving the Hubble tension.

Findings

Achieves agreement with H0 measurements within 1.4σ

Reduces the Hubble tension from 5.7σ to 1.4σ

Provides a simplified three-parameter model for dark radiation matter decoupling

Abstract

We present a microscopic model of the dark sector that resolves the Hubble tension within standard current datasets based on well-known fundamental principles, gauge symmetry and spontaneous symmetry breaking. It builds on the Hot New Early Dark Energy (Hot NEDE) setup, featuring a dark $SU(N)$ gauge symmetry broken to $SU(N-1)$ in a supercooled phase transition that creates a thermal bath of self-interacting dark radiation in the epoch between Big Bang Nucleosynthesis and recombination. Adding a fermion multiplet charged under the gauge symmetry provides a naturally stable component of dark matter that interacts with dark radiation. Spontaneous symmetry breaking predicts a decoupling of this interaction once the dark sector cools down, that we refer to as dark radiation matter decoupling (DRMD). We find agreement between the SH${}_0$ES determination of $H_0$ as well as combined Planck 2018, Pantheon+ and DESI baryon acoustic oscillation (BAO) data at 1.4$\sigma$ level, compared to a 5.7$\sigma$ tension in the $\Lambda$ Cold Dark Matter model. We also provide a simplified three-parameter DRMD model encoding the essential features, while the full model offers additional falsifiable predictions.