Sign Switching in Dark Sector Coupling Interactions as a Candidate for Resolving Cosmological Tensions

TL;DR

This paper proposes a dark sector interaction model with sign switching in energy transfer to address cosmological tensions, showing potential to relax Hubble and $S_8$ discrepancies using recent observational data.

Contribution

It introduces a novel sign-switching mechanism in dark sector coupling, expanding IDE models to better reconcile cosmological tensions with observational data.

Findings

Model can relax Hubble tension with BAO-DESI data.

Model shows weak preference over $\\Lambda$CDM with certain data sets.

Positive Bayesian evidence when using Cepheid-calibrated SNIa data.

Abstract

The $\Lambda$CDM model has successfully explained a wide range of cosmological observations, but is increasingly challenged by the emergence of cosmological tensions, particularly the Hubble Tension $H_0$ and the $S_8$ tension. The Hubble Tension, with a significance above 5$\sigma$, and the $S_8$ tension, showing a discrepancy of approximately 2-4$\sigma$, highlight inconsistencies between measurements of the local and 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 $\xi$. 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 can potentially relax both the $H_0$ and $S_8$ tensions simultaneously. We find the new model to be weakly preferred over $\Lambda$CDM by BAO-DESI data. However, we show that the IDE model features positive Bayesian evidence compared to $\Lambda$CDM only when Cepheid distance calibration in the SH0ES sample is used to calibrate SNIa data from PantheonPlus.