ΛₛCDM cosmology: Alleviating major cosmological tensions by predicting standard neutrino properties

We investigate a two-parameter extension of the ΛₛCDM model by allowing variations in the effective number of neutrino species Neff and their total mass ∑ m_ν. Our motivation is twofold: (i) to examine whether ΛₛCDM retains its success in fitting the data and addressing major cosmological tensions, without suggesting a need for a deviation from the standard model of particle physics, and (ii) to determine whether the data indicate new physics that could potentially address cosmological tensions, either in the post-recombination universe through the late-time mirror AdS-dS transition, or in the pre-recombination universe through modifications in the standard values of Neff and ∑ m_ν, or both. Within the extended ΛₛCDM model, referred to as ΛₛCDM+Neff+∑ mν, we find no significant tension when considering the Planck-alone analysis. We observe that incorporating BAO data limits the further success of the ΛₛCDM extension. However, the weakly model-dependent BAOtr data, along with Planck and Planck+PP&SH0ES, favor H₀~ 73\, km\, s⁻¹\, Mpc⁻¹. In cases where BAOtr dataset is used, the mirror AdS-dS transition is very effective in providing enhanced H₀ values, and thus the model requires no significant deviation from the standard value of Neff = 3.044. Both the H₀ and S₈ tensions are effectively addressed, with some compromise in the case of the Planck+BAO dataset. Finally, the upper bounds obtained on ∑ m_ν 0.5~eV are fully compatible with neutrino oscillation experiments. Our findings provide evidence that late-time physics beyond ΛCDM, such as ΛₛCDM, without altering the standard pre-recombination universe, can suffice to alleviate the major cosmological tensions.