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

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, ${\Omega }_{\mathrm{PBH},\mathrm{f}}$ 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.

Contribution to the Corfu Summer Institute 2022 "School and Workshops on Elementary Particle Physics and Gravity", 28 August - 1 October, 2022, Corfu, Greece

Cited by in corpus (1)

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