Exploring Λ CDM Extensions with SPT-3G and Planck Data: 4σ Evidence for Non-Zero Neutrino Masses and Implications of Extended Dark Energy Models for Cosmological Tensions
Chudaykin A., Gorbunov D., Nedelko N.

Received: April 18, 2025

DOI: 25120067

We present cosmological constraints in the Λ CDM model and a set of its extensions from a dataset based on the polarization and gravitational lensing measurements from the South Pole Telescope and the large-scale () part of the Planck CMB temperature measurements. In all cosmological scenarios, this CMB data combination brings the clustering measurements into agreement with the low-redshift probes of large-scale structure, resolving the S₈ tension. Combining this CMB set with a full-shape treatment of the BOSS large-scale structure observations, additional BAO measurements, information from weak lensing and photometric galaxy clustering surveys, and the Pantheon supernova catalog, we find a preference for non-zero neutrino mass, . We also explore dynamical dark energy in the context of the Hubble tension with two phenomenological late-time approaches introducing a phantom crossing in the dark energy equation of state. For the combination of all data considered, both models predict , in tension with the SH0ES constraint, if the supernova absolute magnitude M_B is calibrated by CMB and LSS data as a free parameter. While it is possible to achieve H₀ values consistent with SH0ES by fixing M_B to the Cepheid-derived value, that is shown to not be a valid approach as it introduces an implicit 4.5σ tension between CMB and the local Universe.