Abstract: Cluster mergers serve as powerful laboratories for cosmology and astrophysics. Radio relics, diffuse radio emissions found in the outskirts of merging clusters, are believed to originate from shock acceleration by cluster merger shocks. In this talk, we will demonstrate the use of cluster mergers exhibiting radio relics to study plasma acceleration and the nature of dark matter. Utilizing high-quality multi-wavelength observations and numerical simulations, including idealized simulations and the cosmological zoom-in simulation TNG-Cluster, we will show how radio relics can constrain the merger history of galaxy clusters. We will explore the implications of radio relics in verifying the self-interacting nature of dark matter. Additionally, our numerical simulations indicate that high acceleration efficiency is required to explain the observed luminosity of radio relics. We will present our recent MeerKAT observations to discuss the role of cluster AGN activity in mitigating the low acceleration efficiency of cluster merger shocks.
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