Compartmentalization in the Dark Sector of the Universe after DESI DR2 BAO data

Abstract

We consider a non-linear interaction between the dark matter and dark energy components of the universe. In particular, within the FLRW geometry, where dark matter is described by a dust fluid and dark energy by an ideal gas with a constant equation of state parameter, we introduce energy transfer between the two fluids. The effective cosmological fluid leads to a unified dynamical dark energy model with the feature that the Hubble function admits an analytic expression. We study this model using the DESI DR2 Baryonic Acoustic Oscillations data and the Supernova data from Pantheon+. The interacting model fits the data better than the $\Lambda$CDM model, with $\chi_{\text{model}}^{2}-\chi_{\Lambda\text{CDM}}^{2}=-5$. Using the Akaike Information Criterion to compare the two models, we derive $\text{AIC}_{\operatorname{model}}-\text{AIC}_{\Lambda\text{CDM}}=-1$, from which we conclude that the interacting model is marginally better supported by the data than the $\Lambda$CDM, but the difference is not statistically significant.