Loopy Black-Hole Remnants

Abstract

The quantized area predicted by loop quantum gravity suggests the existence of a lower bound for black-hole horizons. We prove this intuition within a covariant effective model for spherical loop quantum gravity, where nonsingular quasi-static black holes evaporate until their horizons attain the smallest positive eigenvalue of the area operator. Consistent with the third law of black-hole thermodynamics, this final state -- characterized by vanishing temperature and entropy -- cannot be realized in finite time. The process thus leads to the formation of stable remnants, whose estimated masses are approximately 20.94$\hat{I}¼$g, lying in the Planck regime.

This essay received an Honorable Mention in the 2025 Essay Competition of the Gravity Research Foundation