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arXiv · 2303.00600

The $H_0$ tension alleviated through ultra-light primordial black holes: an information insight through gravitational waves

Theodoros Papanikolaou
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Abstract

The Hawking evaporation of ultra-light primordial black holes (PBH) dominating the early Universe before Big Bang Nucleosynthesis can potentially increase the effective number of extra neutrino species $\Delta N_\mathrm{eff}$ through the emission of dark radiation degrees of freedom alleviating in this way the $H_0$ tension problem. Interestingly, these light PBHs can form a gas of Poisson distributed compact objects which can induce a gravitational-wave (GW) background due to second order gravitational interactions. Therefore, by considering the contribution to $\Delta N_\mathrm{eff}$ due to the production of the aforementioned GW background we revisit in this work the constraints on the relevant parameters at hand, namely the PBH mass, $m_\mathrm{PBH}$, the initial PBH abundance at PBH formation time, $\Omega_\mathrm{PBH,f}$ and the number of DR radiation degrees of freedom, $g_\mathrm{DR}$ by accounting at the same time for the relevant upper bounds constraints on $\Delta N_\mathrm{eff}$ from the Planck collaboration.

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Theodoros Papanikolaou. 2023-03-01. The $H_0$ tension alleviated through ultra-light primordial black holes: an information insight through gravitational waves. https://arxiv.org/abs/2303.00600

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