New black hole merger bolsters Hawking area theorem

"But the final reverberations as the newly formed black hole settled into its new state, aka the ringdown, from that first event were significantly fainter, and scientists were unable to distinguish between the ringing from the initial collision and the ringdown. For GW250114, LIGO's improved sensitivity meant that scientists could measure the frequency and duration of the merged black hole's ringdown much more precisely. The resulting analysis bolsters the 2019 results confirming the "no hair" theorem."

"With the latest event, physicists obtained an "exquisitely detailed view of the signal both before and after the black hole merger," said co-author Maximiliano Isi of Columbia University, who led a 2021 study using the same method on the 2015 data to observationally confirm Hawking's area theorem. As with the no-hair theorem, the clearer signal from GW250114 further bolsters that earlier result."

"Notably, Hawking and Jacob Bekenstein later showed that a black hole's area is proportional to its entropy, which also must increase per the second law of thermodynamics. This is a key element in ongoing attempts to develop a quantum theory of gravity. "It's really profound that the size of a black hole's event horizon behaves like entropy," said Isi. "It means that some aspects of black holes can be used to mathematically probe the true nature of space and time.""

LIGO's detection of GW250114 provided a much clearer measurement of the merged black hole's ringdown, allowing precise determination of its frequency and duration. The strong pre- and post-merger signal enabled tests that reinforce the no-hair theorem and observational confirmation of Hawking's area theorem. The two precursor black holes had a combined horizon area of roughly 240,000 square kilometers and the remnant about 400,000 square kilometers, demonstrating area increase. The increase aligns with the Hawking–Bekenstein relation between horizon area and entropy and supports the second law of thermodynamics, informing efforts to formulate a quantum theory of gravity.

Read at Ars Technica