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| Paper IPM / P / 17653 |
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With the emersion of precise cosmology and the emergence of cosmic tensions, we are faced with the question of whether the simple model of cold dark matter needs to be extended and whether doing so can alleviate the tensions and improve our understanding of the properties of dark matter. In this study, we investigate one of the generalized models of dark matter with the non-zero equation of state ($w$) so that the behavior of this dark matter changes according to the scale of $k$. In large scales (small $k$'s), the dark matter is cold ($w = 0$), while it becomes warm ($w \neq 0$) for small scales (large $k$'s). This behavior is modeled phenomenologically for two different scenarios (i) the sound speed behaves independently of $k$ as a constant parameter and or (ii) it changes depending on $k$. These models are constrained by existing cosmological data, particularly the Planck 2018 data release, BAO and LSS data. We show that the $S_8$ tension can be alleviated, but the $H_0$ tension becomes milder while not too much.
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