📝 SummarXiv

Abstract

We present observational confirmation of Hawking's black-hole area theorem using the newly released gravitational-wave data from the GWTC-4 catalog. We have analyzed two high signal-to-noise ratio binary black hole (BBH) merger events, including GW230814 and GW231226, from the first part of the LIGO-Virgo-KAGRA O4 run, and measured the (total) horizon area of the black holes before and after merger. For both events, the horizon area of the remnant black hole is found to be greater than the total horizon area of the two pre-merger black holes at a high possibility (effectively $\gtrsim 99\%$), and particularly with GW230814 we have a significance level of $\gtrsim 5\sigma$ for the {\it first} time. These results provide the direct convincing verification of the black-hole area law, further bolstering the validity of classical general relativity in the dynamical, strong-field regime.