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Originally Posted by Warren Platts
I agree that they took the worst case scenario when they looked at accretion rates. And guess what: they concluded that 5- and 6-D mBH's might just indeed be "problematic". Talk about understatement of the century! But we know what they mean there: "problematic" means the same as "world disrupting on short time scales".
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That's not how I read it when I went over that paper, trying to make sense of it. My take on "problematic" was not that in a 5 or 6 dimension universe the block holes would create immediate problems for
us, but those solutions are problematic for the
paper, since the accretion rates cannot be dismissed as easily as the other solutions. IIRC "world disrupting on short time scales" was taken to be 'shorter than solar system lifetime', but still a huge amount of time, incomprehensible to humans. This human anyway.
Yet (still assuming I understand the paper) these solutions would cause problems for white dwarf stars, in such a way that old white dwarfs could not exist. Yet they do.
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Where they did not use worst case assumptions is in the predicted stopping length of relativistic mBH's within white dwarfs. If they had, they would have concluded that cosmic ray induced mBH's might just pass harmlessly through white dwarfs just as they apparently do through the Earth.
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That seems wrong to me. "The escape velocity of a white dwarf is of some twenty million km/h, five hundred times higher than the Earth but still fifty times slower than the speed of light." (
source, yes i just googled to get a figure, I stand ready to be corrected). That makes a much, much bigger "resulting speed" bracket in which mBH's will be captured. But I'm no physicist.
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And that would only leave neutron stars as the only natural laboratories for CR produced mBH's. But the problem with that is that there is in fact some evidence that neutron stars are in fact getting eaten up by black holes (cf. Dereshev et al. 1999). (This paper was cited by Giddings and Mangano.)
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I can only see the first page of that paper, removing the ?page=1 from the url gave me an error. Is the full version available? Not that I would be able to validate it.. just curiosity. Anyway, the first page mentioned some tests wrt GRBs. This paper was before SWIFT was launched, and I'd be curious what its results would mean to it. Maybe one of the physicists here can speak to the status of that paper, I really have no clue what to search for to check.