A few months before physicist Stephen Hawking died, he published a paper that several media outlets touted as a way to finally prove (or disprove) the existence of parallel worlds.
But that claim may be a bit of cosmic inflation, said several physicists who were not involved in Hawking's research.
"The paper makes no statements about observational tests. It's not entirely uninteresting, but it's one of literally several thousand ideas for what might possibly have happened in the early universe" many of which include parallel worlds, said Sabine Hossenfelder, a physicist at the Frankfurt Institute for Advanced Studies in Germany, who blogs at backreaction.blogspot.com.
https://www.livescience.com/62073-stephen-hawking-multiverse-theory.html