Population-Level Verification of the Black-Hole Area Law with First- and Second-Generation Black Holes
Abstract
Hawking's area theorem states that the total event-horizon area of classical black holes can never decrease. Gravitational-wave tests of this law have so far focused on individual loud mergers, thus probing only a sparse subset of binary parameter space. Here we perform the \emph{first} population-level test. We exploit the decomposition of the coalescing black holes in the latest gravitational-wave catalogue into a low-spin subpopulation of stellar-collapse origin and a high-spin subpopulation assembled through hierarchical mergers of the former. If the high-spin black holes are merger remnants, the area theorem requires their horizon areas to exceed the total pre-merger areas of the low-spin binaries. Using parameter estimation restricted to the inspiral of 241 events, so that no merger-ringdown information enters the inference, we find that both peaks of the horizon-area distribution of second-generation black holes lie above their first-generation counterparts. The displacement is significant at each peak ($2.1−−3.7σ$), and when we tie the two subpopulations with a single common shift, an area decrease is excluded decisively (≳5.0σ). The second law of black-hole mechanics thus holds statistically across the quasicircular, moderately spinning mergers that dominate current catalogues, which in turn underpins the robustness of our classification of stellar-collapse and hierarchical-merger black holes.
Related
- Constraints on ultralight bosons from merging binary and remnant black holes observed during the second and third parts of the fourth LIGO-Virgo-KAGRA observing run
- Discovery of a second-generation planet candidate accreting onto a white dwarf
- Second Generation Planet Formation in Post-AGB Discs - II: Dust Coagulation and Core Accretion
- Conservative Black Hole Scattering at Fifth Post-Minkowskian and Second Self-Force Order
- Curvature-Radiation Geometries Across the Second CHIME/FRB Fast Radio Burst Population
BibTeX
@misc{tang2026populationlevel,
title = {{Population-Level Verification of the Black-Hole Area Law with First- and Second-Generation Black Holes}},
author = {Shao-Peng Tang and Yin-Jie Li and Yi-Zhong Fan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.16563},
eprint = {2608.16563},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.16563},
}
RIS
TY - UNPB
TI - Population-Level Verification of the Black-Hole Area Law with First- and Second-Generation Black Holes
AU - Shao-Peng Tang
AU - Yin-Jie Li
AU - Yi-Zhong Fan
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2608.16563
UR - https://arxiv.org/abs/2608.16563
AB - Hawking's area theorem states that the total event-horizon area of classical black holes can never decrease. Gravitational-wave tests of this law have so far focused on individual loud mergers, thus probing only a sparse subset of binary parameter space. Here we perform the \emph{first} population-level test. We exploit the decomposition of the coalescing black holes in the latest gravitational-wave catalogue into a low-spin subpopulation of stellar-collapse origin and a high-spin subpopulation assembled through hierarchical mergers of the former. If the high-spin black holes are merger remnants, the area theorem requires their horizon areas to exceed the total pre-merger areas of the low-spin binaries. Using parameter estimation restricted to the inspiral of 241 events, so that no merger-ringdown information enters the inference, we find that both peaks of the horizon-area distribution of second-generation black holes lie above their first-generation counterparts. The displacement is significant at each peak ($2.1−−3.7σ$), and when we tie the two subpopulations with a single common shift, an area decrease is excluded decisively (≳5.0σ). The second law of black-hole mechanics thus holds statistically across the quasicircular, moderately spinning mergers that dominate current catalogues, which in turn underpins the robustness of our classification of stellar-collapse and hierarchical-merger black holes.
ER -