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arXiv · 2502.19498

Neutrino Emission and Plasma Heating from Primordial Black Holes: An Improved Approach to $N_\mathrm{eff}$ Constraints

Héctor Sanchis·Gabriela Barenboim·Yuber F. Perez-Gonzalez
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Abstract

We investigate the impact of neutrino emission via Hawking radiation from primordial black holes (PBHs) on the cosmological effective number of neutrino species, $N_{\mathrm{eff}}$, after neutrino decoupling. By comparing this effect with observational limits, we derive bounds on the abundance of light PBHs. Our analysis incorporates two previously unaccounted-for effects: the emission of secondary neutrinos from unstable particles, which increases $N_{\mathrm{eff}}$, and the modification of the neutrino-photon temperature ratio due to particle emission heating the photon plasma, which lowers $N_{\mathrm{eff}}$. Overall, including these effects allows us to impose constraints on PBHs with initial masses in the range $10^9~{\rm g}\lesssim M_{\rm ini} \lesssim 10^{13}~{\rm g}$. However, our limits remain less stringent than those derived from Big Bang Nucleosynthesis.

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Héctor Sanchis, Gabriela Barenboim, Yuber F. Perez-Gonzalez. 2025-02-26. Neutrino Emission and Plasma Heating from Primordial Black Holes: An Improved Approach to $N_\mathrm{eff}$ Constraints. https://doi.org/10.1088/1475-7516%2F2025%2F08%2F049

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