Dark Radiation production in axion misalignment mechanisms and the cosmological tensions

TL;DR

This paper explores how axion-like particles produced via misalignment mechanisms could generate dark radiation, potentially addressing cosmological tensions like the Hubble constant and $S_8$ discrepancies.

Contribution

It introduces a Bayesian framework to analyze ALP parameter space and investigates their role in producing dark radiation that may resolve cosmological tensions.

Findings

ALP parameter space constrained by current cosmological data

Dark radiation from ALPs could alleviate the H_0 tension

Potential impact on the S_8 discrepancy

Abstract

We investigate the production of dark radiation (DR) from axions and axion-like particles (ALPs) as potential origins of dark matter. Focusing on the dark matter misalignment mechanism, we examine non-thermal, pre-inflationary scenarios that could lead to the generation of DR. A key part of our analysis involves a Bayesian approach to confront ALP parameter space with current cosmological data. Additionally, we explore whether DR production could offer solutions to persistent cosmological anomalies, particularly those related to the Hubble constant $H_0$ tension and the $S_8$ parameter discrepancy. Our findings aim to shed new light on the role of ALPs in addressing these open issues in cosmology.