Evidence for Dynamical Dark Matter

Abstract: The nature of dark matter is one of the most fundamental questions in cosmology. Using the cosmic microwave background (CMB), type Ia supernova (SN) and DESI's new measurements of baryon acoustic oscillations (BAO), we find the robust $\sim2\,\sigma$ evidences of the evolution of dark matter in the dynamical dark matter (DDM) model, $\omega_{dm}(a)=\omega_{dm0}+\omega_{dma}(1-a)$. Based on CMB data, we find a very strong linear relation $\omega_{dma}=-\omega_{dm0}$, inducing the single-parameter DDM model, $\omega_{dm}(a)=\omega_{dm}a$, where the $\sim2\,\sigma$ DDM evidences is well captured and even strengthened. We demonstrate that there are beyond $2\,\sigma$ evidences of the coexistence of DDM and dynamical dark energy using the combinations of CMB, DESI BAO and Pantheon+ SN data. In such models, at a beyond $5\,\sigma$ confidence level, we verify that the universe remains in a matter-dominated state for a substantial period in the past, accelerate in the distant future and finally becomes completely dominated by dark matter. We propose that the ultimate fate of the universe is the ``Super Rip'' induced by dark matter with an extremely negative pressure. Our findings fundamentally challenge the prevailing understanding of cosmic acceleration and deepen our insight into the universe's evolution.