Hawking's area theorem: Merging Black Holes:

[beecee]

https://phys.org/news/2021-07-physicists-observationally-hawking-black-hole.html

Physicists observationally confirm Hawking's black hole theorem for the first time:

 

There are certain rules that even the most extreme objects in the universe must obey. A central law for black holes predicts that the area of their event horizons—the boundary beyond which nothing can ever escape—should never shrink. This law is Hawking's area theorem, named after physicist Stephen Hawking, who derived the theorem in 1971.

Fifty years later, physicists at MIT and elsewhere have now confirmed Hawking's area theorem for the first time, using observations of gravitational waves. Their results appear today in Physical Review Letters.

 

extract:

In the study, the researchers take a closer look at GW150914, the first gravitational wave signal detected by the Laser Interferometer Gravitational-wave Observatory (LIGO), in 2015. The signal was a product of two inspiraling black holes that generated a new black hole, along with a huge amount of energy that rippled across space-time as gravitational waves.

If Hawking's area theorem holds, then the horizon area of the new black hole should not be smaller than the total horizon area of its parent black holes. In the new study, the physicists reanalyzed the signal from GW150914 before and after the cosmic collision and found that indeed, the total event horizon area did not decrease after the merger—a result that they report with 95 percent confidence.

more at link....

the paper:

https://arxiv.org/abs/2012.04486

Testing the black-hole area law with GW150914

We present observational confirmation of Hawking's black-hole area theorem based on data from GW150914, finding agreement with the prediction with 97% (95%) probability when we model the ringdown including (excluding) overtones of the quadrupolar mode. We obtain this result from a new time-domain analysis of the pre- and postmerger data. We also confirm that the inspiral and ringdown portions of the signal are consistent with the same remnant mass and spin, in agreement with general relativity.

 

Edited July 2, 2021 by beecee