Sign switching in dark sector coupling interactions as a candidate for resolving cosmological tensions

The model has successfully explained a wide range of cosmological observations, but is increasingly challenged by the emergence of cosmological tensions, particularly the Hubble tension H₀ and the S₈ tension. The Hubble tension, with a significance above 5, and the S₈ tension, showing a discrepancy of approximately 2--4, highlight inconsistencies between measurements of the local and early Universe. The model has been highly successful in explaining cosmological observations but is increasingly challenged by the H₀ tension (>5) and the S₈ tension (2--4). These tensions expose significant inconsistencies between measurements of the local Universe and those of the early Universe. This paper expands a well-established interacting dark energy (IDE) phenomenological scenario, where dark matter (DM) can transfer energy to dark energy (DE) or vice versa, depending on the sign of the coupling parameter. The novel feature consists in a transition mechanism which reverses the direction of the energy-momentum transfer after the redshift where the densities of the dark species are the same. We evaluate this model using a comprehensive set of recent observational data, including baryon acoustic oscillations (BAO) from the DESI survey, type Ia supernovae from the PantheonPlus, DESY5, and Union3 samples, and cosmic microwave background (CMB) data from Planck. Our analysis shows that this scenario relaxes the H₀ and S₈ tensions, particularly when Cepheid distance calibration in the SH0ES samples or DESI data are included. Our analysis shows that this scenario can potentially relax both the H₀ and S₈ tensions simultaneously. We find the new model to be weakly preferred over by BAO-DESI data. However, we show that the IDE model features positive Bayesian evidence compared to only when Cepheid distance calibration in the SH0ES sample is used to calibrate SNIa data from PantheonPlus.