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+--- Thread: Singularities can exist outside black holes -- in other universes (/thread-11046.html)
Singularities can exist outside black holes -- in other universes - C C - Sep 30, 2021
https://www.scientificamerican.com/article/singularities-can-exist-outside-black-holes-in-other-universes/
EXCERPTS: . . . Thankfully, with the singularities tucked inside the black holes, we do not have to worry about their potentially bizarre effects on the external world. But what if these singularities could show up outside—on their own? [...]
During the 1960s, British physicist Roger Penrose was in the midst of work on the mathematics of black holes and singularities [...] At that time, no one had turned up any compelling evidence that the equations of general relativity could describe these uncovered singularities in a physically sensible universe. They only ever materialized cloaked inside a black hole. Penrose pieced together clues that suggested a conjecture—an informed guess, not an airtight proof—that general relativity would never make that prediction. This conjecture is known as cosmic censorship: somehow the math must work out so that nature censors those “naked” singularities from existence.
Cosmic censorship is an idea that sounds to physicists like it must be right, and most assume it is. [...] In the first few decades after Penrose’s initial work, theoretical studies supported the idea that cosmic censorship would hold.
Then, in 2010, physicists Luis Lehner and Frans Pretorius used a computer simulation to show that the outer surface of black holes could break into pieces and leave behind naked singularities. The fracturing comes with a curious twist, though. It ... can only happen in universes with more than three dimensions of space. In other words, these sorts of singularity-revealing instabilities should be impossible in our universe’s three dimensions as described by general relativity.
Despite this caveat, the result still has meaning. With this one example as a starting point, researchers can look for similar processes and ask... (MORE - missing details)