Rotating Black Holes May Leave a Remnant After Evaporation
A new theoretical study suggests that rotating black holes, at the end of their Hawking evaporation process, would not completely disappear but would leave behind a remnant with a finite mass. This finding is based on the analysis of the generalized entropy (GE) of Hawking radiation, a key concept in black hole thermodynamics. Researchers modeled the black hole's mass as $m_{\rm ext}+\alpha$, where $m_{\rm ext}$ is the mass at the extremal limit and $\alpha$ is a parameter that decreases as the black hole evaporates.
The fundamental principle that entropy cannot be negative was crucial for this analysis. Assuming that the contributions from the area term and the correction term to the generalized entropy maintain their sign throughout the entire evaporation, scientists were able to establish a lower bound for $\alpha$. This limit, denoted as $\alpha_1$, was found to be a finite and positive value. This implies that the black hole's mass cannot fall below $m_{\rm ext}+\alpha_1$, which is interpreted as the existence of a remnant.
The research focused on regular rotating black holes, a choice motivated by the idea that the fine structure of the central region becomes relevant in the final stages of evaporation. Considering rotation adds generality to the model, as most astrophysical black holes are expected to rotate. This result offers a possible solution to the black hole information paradox, by suggesting that information is not completely lost but could be encoded in these final remnants. However, the exact nature and properties of these remnants still require further investigation.