Stochastic Evolution of Primordial Black Holes to near-extremality in EFTs of Gravity

TL;DR

This paper models the evolution of primordial black holes in effective field theories of gravity, showing they can reach near-extremality similarly to general relativity, with potential observable tidal effects.

Contribution

It introduces a stochastic model of PBH evolution in EFTs, extending previous GR-based results to include higher-order gravitational corrections.

Findings

Similar PBH survival fraction as in GR

Near-horizon tidal effects could be detectable in future gravitational waves

Hawking radiation modeled as a biased random walk in EFTs

Abstract

The search for dark matter candidates includes primordial black holes (PBHs) as possible constituents. Recent studies show that some PBHs can survive to the present epoch by gaining angular momentum through Hawking radiating photons and becoming extremal before complete evaporation. While this provides a plausible model in a two-derivative theory of gravity, additional issues arise in EFT-corrected theories of gravity. In such theories, a rapidly spinning black hole can lead to extremely high tidal forces on a near-horizon observer, with possible observational consequences. In this work, by modeling Hawking radiation as a biased random walk within an EFT of gravity, we show that nearly the same fraction of PBHs survives as in GR. We argue that the resultant near horizon tidal effects should be detectable in future gravitational-wave observables.