Cosmological Tensions and Interactions Between Dark Matter and Dark Energy

Meng-Xiang Lin (Simon Fraser University) — October 6, 2025

Abstract

The nature of dark matter and dark energy remains one of the most profound mysteries in modern cosmology. In addition to these theoretical challenges, recent cosmological observations have revealed potential signs of new physics beyond the standard ΛCDM paradigm. In this talk, I will begin by briefly reviewing current cosmological tensions, including the latest DESI evidence for dynamical dark energy, the Hubble tension, and the S8 tension. I will then explore possible new physics underlying these tensions, with a particular focus on interactions between dark matter and dark energy. I will demonstrate that a simple coupling between the two components can simultaneously address two distinct anomalies: the DESI-indicated dynamical dark energy and the S8 tension. We propose a stable and technically natural particle physics realization of this idea, which exhibits an apparent phantom crossing behavior in the dark energy equation of state, consistent with DESI findings. The possible resolutions to the Hubble tension will also be discussed.