Observational constraints on soft dark energy and soft dark matter: challenging $Λ$CDM

Abstract

Soft cosmology is an extension of standard cosmology allowing for a scale-dependent equationof-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 Supernovae Type Ia (SNIa), Baryonic Acoustic Oscillations (BAO), and Cosmic Microwave Background (CMB) 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 ΛCDM scenario, namely we consider that at large scales the dark sectors have the EoS's of ΛCDM 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 s de and s dm . The observational confrontation shows that for almost all datasets the softness parameters deviate from their ΛCDM values (at 2σ confidence level for one of the models, and at 1σ for the other two), and thus the data favor soft cosmology. Finally, performing a Bayesian evidence analysis we find that the examined models are preferred over ΛCDM cosmology.

Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies

“…In soft cosmology [1297,1298] one allows for small deviations from the usual cosmological framework due to the effective appearance of soft-matter properties in the Universe sectors [1299,1300]. Hence, as a first approach on the subject, one considers that, intrinsically or effectively, dark energy and/or dark matter may have a different EoS at large scales, i.e.…”

Swiss-cheese cosmologies with variable G and Λ from the renormalization group

“…Interesting enough for the interesting cases both θ 1 and θ 2 can be taken as positive and this is consistent with the idea that the IR fixed point must be attractive in the k → 0 limit. It would therefore be interesting to further test this cosmological model against the current observational data in the spirit of [64,65]…”