A hint of matter underdensity at low z?

The ΛCDM cosmological model provides to first approximation a good description of the universe, but various tensions with data, most notably Hubble tension, persist. In this work we confront ΛCDM with the Pantheon Type Ia supernovae dataset and perform a two-parameter fit of the distance modulus for a running cut-off z_max. We observe that in a window between z_max 0.1 and z_max 0.16 there is a 1-2 σ discrepancy with the Planck value ω_m = 0.315 ± 0.007, which points to a potential matter underdensity. For high-energy theorists, the analysis appears to support the de Sitter Swampland conjecture.