I'm awaiting Jean Pierre Petit's analysis. He's developed a twin universe theory involving negative mass/energy using bimetric relativity (without the runaway effect). At one point in the development of his theory in the mid 2010s, he stumbled upon: Hossenfelder, S.: A bimetric theory with exchange symmetry.

He contacted her but she refused to collaborate on a common paper, calling him a plagiarist and a crank. She did the same to Tim Palmer (a Royal Society meteorologist) when he approached her with ideas on superdeterminism:

> But Tim Palmer turned out to not only be a climate physicist with an interest in the foundations of quantum mechanics, he also turned out to be remarkably persistent. He wasn’t remotely deterred by my evident lack of interest. Indeed, I later noticed he had sent me an email already two years earlier. Just that I dumped it unceremoniously in my crackpot folder.

http://backreaction.blogspot.com/2019/12/the-path-we-didnt-t...

Back to Petit and plagiarism: compare:

https://link.springer.com/article/10.1007/s10509-014-2106-5

https://januscosmologicalmodel.com/cptsymmetry

with Julian Barbour's Janus Point book blurb:

> In a universe filled by chaos and disorder, one physicist makes the radical argument that the growth of order drives the passage of time -- and shapes the destiny of the universe. Time is among the universe's greatest mysteries. Why, when most laws of physics allow for it to flow forward and backward, does it only go forward? Physicists have long appealed to the second law of thermodynamics, held to predict the increase of disorder in the universe, to explain this. In The Janus Point, physicist Julian Barbour argues that the second law has been misapplied and that the growth of order determines how we experience time. In his view, the big bang becomes the "Janus point," a moment of minimal order from which time could flow, and order increase, in two directions

Source: https://www.amazon.com/Janus-Point-New-Theory-Time/dp/046509...

There are more players in the field with very similar ideas (the refinement of twin universes as a two-sided universe), Petit contacted them all but was never given a reply:

- Neil Turok: https://physicsworld.com/a/our-universe-has-antimatter-partn...

- Our universe may have a twin that runs backward in time: https://www.livescience.com/mirror-universe-explains-dark-ma...

- Neil Turok again a few weeks ago: https://www.newscientist.com/article/mg25734230-100-neil-tur...

And now we have that paper that talks about black holes without a singularity and their coupling with the universe's expansion limited to a maximum k-factor of 3.

This sounds a lot like the conclusion from this paper by Petit:

> Supermassive objects, whose formation will be explained in a future article, are also subcritical objects, Plugstars. The theory gives all plugstars a gravitational redshift of 3. This is exactly what is shown by the measurements of the images of two hypermassive objects located at the center of the galaxies M87 and the Milky Way.

> We predict that this redshift of 3 will accompany future images of hypermassive objects that will appear in the future.

Source: https://hal.science/hal-03835483/document