2021/09/30 by A. Moss, Adam Moss, Moss, Adam +8
Computer Science · Earth and Planetary Sciences · Physics and Astronomy · #Computational Physics and Python Applications #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Geophysics and Gravity Measurements #astro-ph.CO
paper · pdf · doi:10.48550/arxiv.2109.14848
7 pages, 3 figures
arxiv created 2021/09/30 · openalex publication_date 2021/09/30 · arxiv updated 2021/10/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We provide a model-independent reconstruction of dark energy from z=0 to \gtrsim 105. We parameterise the model by a perfect fluid with a series of physically well-motivated bins in energy-density, such that the equation of state is always -1 ≤ w ≤ 1. Our method is capable of describing a range of theoretical models with smooth modifications to the expansion history. Combining the latest CMB, BAO, SN and local H0 measurements, we obtain a large improvement of Δχ2=41.3 over LCDM, at the expense of 33 additional parameters in the fit, with dark energy contributing significantly between z ∼ 104 - 105, and intriguingly with a sound speed cs2 ∼ 1/3. A significant part of the Δχ2 improvement comes from \Planck + Atacama Cosmology Telescope (Act) data, alleviating tension between them within LCDM. We apply a correlation prior to penalise models with unnecessary degrees of freedom and find no preference for deviations from LCDM at late-times, but moderate Bayesian evidence of an early dark energy (EDE) component. Although the model has a large amount of freedom, it is unable to reduce S8 ≡ σ8 (Ωc / 0.3)0.5 below that of \lcdm, to bring about full concordance with large-scale structure data.