TL;DR
This paper proposes a new dark sector model with a decaying dark energy fluid and ultra-light axion to address the Hubble and S_8 tensions, improving fit to cosmological data and reducing discrepancies.
Contribution
The paper introduces a novel dark sector scenario with specific components that better reconcile early and late universe observations compared to standard models.
Findings
Model fits cosmological data slightly better than ΛCDM.
Reduces H_0 and S_8 tensions to below 3σ.
Detects dark energy decay and axion at significant confidence levels.
Abstract
We develop a new phenomenological model that addresses current tensions between observations of the early and late Universe. Our scenario features: (i) a decaying dark energy fluid (DDE), which undergoes a transition at , to raise today's value of the Hubble parameter -- addressing the tension, and (ii) an ultra-light axion (ULA), which starts oscillating at , to suppress the matter power spectrum -- addressing the tension. Our Markov Chain Monte Carlo analyses show that such a Dark Sector model fits a combination of Cosmic Microwave Background (CMB), Baryon Acoustic Oscillations, and Large Scale Structure (LSS) data slightly better than the CDM model, while importantly reducing both the and tensions with late universe probes (). Combined with measurements from cosmic shear surveys, we find that the…
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