Observational constraints on soft dark energy and soft dark matter:
  challenging $\Lambda$CDM
  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 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 $\Lambda$CDM scenario, namely we consider that at large
scales the dark sectors have the EoS's of $\Lambda$CDM 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 $\Lambda$CDM values (at 2$\sigma$ confidence level for one
of the models, and at $1\sigma$ 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 $\Lambda$CDM cosmology.
