Observational constraints on soft dark energy and soft dark matter: Challenging ACDM cosmology

Soft cosmology is an extension of standard cosmology allowing for a scale-dependent equation-of-state (EoS) parameter in the dark sectors, which is one of the properties of soft materials in condensed-matter physics, that may arise either intrinsically or effectively. We use data from Cosmic Microwave Background (CMB), Baryonic Acoustic Oscillations (BAO), Supernovae Type Ia (SNIa), and Redshift space distortion (RSD) probes, in order to impose observational constraints on soft dark energy and soft dark matter. We examine three simple models, corresponding to the minimum extensions of ACDM scenario, namely we consider that at large scales the dark sectors have the EoS's of ACDM model (dust dark matter and cosmological constant respectively), while at intermediate scales either dark energy or dark matter or both, may have a different EoS according to constant softness parameters sde and sdm. The observational confrontation shows that for almost all datasets the softness parameters deviate from their ACDM values, in a prominent way for soft dark energy and mildly for soft dark matter, and thus the data favor soft cosmology. Finally, performing a Bayesian evidence analysis we find that the examined models are certainly preferred over ACDM cosmology.(c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.

Automated summary

Soft cosmology extends the standard cosmology by allowing for different equation-of-state parameters for dark matter and dark energy at different scales. Data analysis suggests that soft cosmology is favored by observational constraints.