Get into Janus Theory.https://januscosmologicalmodel.com/
TL;DR negative masses exists on "the other side of the universe" where time "flows backward" (has inverted dynamics because of the negative mass). Going back in time up to the very moment of the big bang leads to the other side.
The guy behind these ideas is a a cancelled MHD researcher who got inspired by the UMMO letters LARP and even received phone calls. He's some kind of crackpot but still a scientist. He's polarizing and grumpy like an old bear about it (he his a magnificent renter) but had some serious support on his side. He was close friend with Jean-Marie Souriau (symplectic geometry and geometric mechanics) and was one of the few visitors of grothendieck in its pyrenean retreat.
Petit (the guy) is still refining is Janus model, and has published various papers with d'Agostini and a cancelled quantum physicists teaching math in a low iq highschool whose grant was secured by crowdfunding last year.
Now what's where it gets interesting:
- Sakharov had that idea of twin universe
- D'Amour (the cosmology chad in France) introduced the idea of bi-metric models of gravity sometime in the early 2000. Petit uses the same framework. Petit is harassing him since the guy holds the key to having the matter properly discussed in an amphitheater (Petits sweats like a gladiator with excitation prior to the battle when he mentions it). But d'Amour stands firm and he will not receive the crackpot.
- The guy (Petit) also got in touch with the unnarratable Sabine Hossenfelder because he recognized the shape of his bimetric janus model of gravity in a paper she wrote in the mid 2000s. She called out "his plagiarism" and asked her to stop the harassment.
- Fair enough. He didn't insist and noticed he too had plagiarists on his trail !
The first guy is Julian Barbour, who published a book called (not shitting you) "the Janus point: a new theory of time". Here is the blurb: