http://arxiv.org/abs/1902.05738
We report on a new relation between dark matter (DM) particle mass, $m_\chi$, and the tensor-to-scalar ratio of cosmic microwave background (CMB) anisotropies, $r$. Once $r$ is determined in a future search of primordial gravitational wave (PGW), $m_\chi$ can be constrained by using this relation. Due to the resonance interplay between metric and DM density perturbations, a small local fluctuation of spacetime can be generated in a pair production of DM particles. Such fluctuations, arising from the DM pair productions, encode information of DM mass and slightly change the amplitude of metric perturbation. Within a general framework of cosmic reheating, we show that, these fluctuations are accumulated during DM production process, which amplifies the scalar modes of metric perturbation significantly and results in a strong suppression of $r$. Thus we establish a novel link between DM and PGW, which yields a new relation between $m_\chi$ and $r$. For illustration, in a toy model of cosmic reheating with $\alpha=10^{-8}$, we show that $m_\chi=10~\text{GeV}$ if PGW is detected at $r=0.3\times 10^{-2}$.
C. Li
Mon, 18 Feb 19
18/37
Comments: 5 pages, 7 figures
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