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arXiv · 1810.06795

Comment on "keV Neutrino Dark Matter in a Fast Expanding Universe" by Biswas et al

Nicolas Fernandez·Stefano Profumo
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Abstract

Biswas et al. found that the thermal relic density of a dark matter particle freezing out while the universe's energy density is dominated by a non-standard extra component $ϕ$, whose energy density redshifts faster than radiation, can be greatly suppressed. Here we show that this result, which contradicts extensive previous literature, is incorrect: the mistake lies with the assumption that the (decoupled) extra component $ϕ$ contributes to the entropic degrees of freedom relevant for dark matter freeze out. If this were the case, a completely different approach would be needed to calculate the dark matter relic abundance, with dramatically different results.

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Nicolas Fernandez, Stefano Profumo. 2018-10-16. Comment on "keV Neutrino Dark Matter in a Fast Expanding Universe" by Biswas et al. https://doi.org/10.1016/j.physletb.2018.12.057

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