Last month, i was watching an anime series about time travel (Steins Gate), and then i learned the term 'Kerr black hole'. upon further research, i read that these are theoretical singularities without an event horizon. i don't matter if these are suitable for time travel, but this 'naked singularities' can be real? the relativitity allow these to exist? i want to hear your oppinions about this matter.
They don't exist.
Also, when does Steins Gate mention a Kerr Black Hole, or any black hole?
Actually, you CAN strip the event horizon off a singularity, just like you can strip the reaction field off from a point-particle like an electron, it's just something the universe does to protect itself from the worst effects of both.
They were there as a hand-wavy explanation for how the 'phone microwave' was supposed to work. For all I know it was emphasized more in the VN but it's in the show too, at least the subbed version I saw.
I never finished reading steins;gate because I took a break from it while in uni. By the time I got back to it i realized how assbackwards the science fiction was and couldn't get myself to take it seriously anymore. Which is a real shame because I really enjoyed it.
These calculations are doctorate-level, and very specific to Relativity specializations whose interest is black holes, so I don't know the math and neither do any of my university's professors.
But we did attend a talk by one who worked on cosmic censorship. Instead of Kerr black holes, they looked at Reissner-Nordstrom black holes (highly-charged black holes instead of spinning ones) but they argue that their work can also apply to Kerr black holes.
The problem with overcharged Reissner-Nordstrom black holes (which is what we need for a naked singularity) is that theoretically, they can't form all at once; the EM interaction just won't let you cram that much mass into a small enough space. But someone thought, "what if we had a black hole whose charge-mass ratio was right below critical, then we throw in a particle with more charge than mass to sort of tip it over?" It seemed like this was the way to create a naked singularity.
The talk's speaker tried to look at this case and found that the particle's electromagnetic self-force would actually prevent it from falling into the near-critical Reissner-Nordstrom black hole; the EM repulsion turns out to be just strong enough to push the particle out.
So yeah, overcharged Reissner-Nordstrom black holes are still safe from being naked singularities, as far as we know.
The speaker's paper (his name is Ian Vega): http://arxiv.org/abs/1211.3889
The paper's abstract says a similar argument applies for overspinning Kerr black holes, but I don't remember how he explained it. Probably something like a Kerr black hole with an angular-momentum-to-mass ratio just below critical, then throwing in a spinning particle to tip it over to critical.
Also wait, Kerr black holes DO exist. At least, there's nothing stopping them from existing. What CANNOT exist are overspinning Kerr black holes, which are cases of a naked singularity.