Primordial black hole driven cosmic acceleration

Abstract

We propose a natural mechanism for cosmic acceleration driven by primordial black holes (PBHs) with repulsive behavior, within a ''Swiss Cheese'' cosmological framework. Considering regular black hole spacetimes such as Hayward, Bardeen, and Dymnikova-as well as the singular Schwarzschild-de Sitter case-we consistently find a robust PBH-driven cosmic acceleration phase. This phase ends either at an energy scale set by the PBH parameters or through black hole evaporation. Notably, one finds that ultra-light PBHs with $m < 5 \times 10^8 \, {\rm g}$ can trigger exponential inflation with graceful exit and reheating. Additionally, PBHs with $m \sim 10^{12} \, {\rm g}$ and abundances $0.107 < Ω_{\rm PBH}^{\rm eq} < 0.5$ near matter-radiation equality can act as an early dark energy component, offering a potential resolution to the Hubble tension.

Figures (2)

• Figure 1: Left Panel: We show $\rho_\mathrm{c}$ as a function of the regularising length scale $L$. $L$ has un upper bound limit reading as $L<\frac{4G_\mathrm{N}m}{3 {\hbox{$\sqrt{3\,}$}}}$. Right Panel: We show $\rho_\mathrm{evap}$ (color-bar axis) as a function of the PBH mass $m$ ($x$-axis) and the scale $L$ ($y$-axis). The grey region $L>\frac{4G_\mathrm{N}m}{3 {\hbox{$\sqrt{3\,}$}}}$ is not particularly interesting since there we obtain horizonless objects while the magenta one, where $\rho_\mathrm{evap}<\rho_\mathrm{BBN}$ is theoretically excluded.
• Figure 2: The evolution of the cosmological horizon $H^{-1}$ for a Universe filled with "repulsive-like" primordial black holes of Hayward type.