Is it Mixed dark matter or neutrino masses?

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In this paper, we explore a scenario where the dark matter is a mixture of interacting and non interacting species.

• Assuming dark matter-photon interactions for the interacting species, we find that the suppression of the matter power spectrum in this scenario can mimic that expected in the case of massive neutrinos.
• Our numerical studies include present limits from Planck Cosmic Microwave Background data, which render the strength of the dark matter photon interaction unconstrained when the fraction of interacting dark matter is small.
• Despite the large entangling between mixed dark matter and neutrino masses, we show that future measurements from the Dark Energy Instrument (DESI) could help in establishing the dark matter and the neutrino properties simultaneously, provided that the interaction rate is very close to its current limits and the fraction of interacting dark matter is at least of $\mathcal{O}\left(10\%\right)$.