2025/05/13 by Leonardo Giani, Giani, Leonardo, Rodrigo von Marttens +3 · 1 voice · 8 citations
Physics and Astronomy · #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc)
paper · doi:10.48550/arxiv.2505.08467
We introduce a two-parameter phenomenological extension of the ΛCDM model in which the equation of state parameter of the ``dust'' fluid becomes different from zero for redshifts below a transition value zt. Using data from DESI DR2 BAO, DESY5 Sn~Ia and CMB distance priors (R,lA,ωb) data, we compare our model with the standard CPL parameterization w0-wa for dynamical dark energy. Using the Deviance Information Criteria (DIC), we find that the two models are essentially indistinguishable (ΔDIC < 2) and preferred over ΛCDM with a significance ≥ 3 σ. We discuss how this parameterization finds a natural interpretation in the context of cosmological backreaction and derive a prediction for the evolution of the growth factor, discussing its impact on low redshift fσ8 measurements.