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 $m<5\times 10^8\mathrm{g}$ can trigger exponential inflation with graceful exit and reheating. Additionally, PBHs with $m\sim 10^{12}\mathrm{g}$ and abundances $0.107<\hat{I}{\text{c◯}}_{\mathrm{PBH}}^{\mathrm{eq}}<0.5$ near matter-radiation equality can act as an early dark energy component, offering a potential resolution to the Hubble tension.

Received Honorable Mention from the Gravity Research Foundation in the 2025 Essay Competition