February 15, 2023
Introduction:
Read more here: https://www.eurekalert.org/news-releases/979797(EurekAlert) The second paper (published in The Astrophysical Journal Letters finds that the growth in mass of these black holes matches predictions for black holes that not only cosmologically couple, but also enclose vacuum energy—material that results from squeezing matter as much as possible without breaking Einstein's equations, thus avoiding a singularity…
“Here's a toy analogy. You can think of a coupled black hole like a rubber band, being stretched along with the universe as it expands," said Croker. "As it stretches, its energy increases. Einstein's E = mc2 tells you that mass and energy are proportional, so the black hole mass increases, too."
How much the mass increases depends on the coupling strength, a variable the researchers call k.
"The stiffer the rubber band, the harder it is to stretch, so the more energy when stretched. In a nutshell, that's k," Croker said.
Because mass growth of black holes from cosmological coupling depends on the size of the universe, and the universe was smaller in the past, the black holes in the first study must be less massive by the correct amount in order for the cosmological coupling explanation to work.