http://arxiv.org/abs/1707.09238
The freeze-out of dark matter (DM) depends on the evolution of the DM temperature. The DM temperature, on the other hand, does not have to follow the standard model (SM) one. We study the temperature evolution of the semi-annihilating DM, where a pair of the DM particles annihilate into one DM particle and another particle coupled to the SM sector. We find that the kinetic equilibrium is maintained solely via the semi-annihilation until the last stage of the freeze-out. After the freeze-out, the semi-annihilation converts the mass deficit to the kinetic energy of DM, which leads to non-trivial evolution of the DM temperature. We argue that the DM temperature redshifts like radiation as long as the DM self-interaction is efficient. Notably, the density fluctuations may be suppressed at subgalactic scales like keV-scale warm dark matter but with GeV-scale DM in this scenario.
A. Kamada, H. Kim, H. Kim, et. al.
Mon, 31 Jul 17
8/57
Comments: 5 pages, 4 figures
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