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Quick question about LQG Self-Dual Black Holes

  1. Mar 3, 2015 #1

    wabbit

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    This paper relies heavily of LQG self-dual black holes ; I saw an old thread here about didn't find the answer there so here's my question :

    On the face of it this looks like a somewhat bizarre/exotic theoretical solution, especially with the description refering to wormholes.

    However, since the structure of the SDBH is C-x-C*, where C is the collapse region, x is the central region, and C* the dual region (my notations), both C and C* being asymptotically flat, this is starting to look similar to Rovelli's Planck star, with C the black hole and C* the white whole.

    Is this similarity only superficial or are the two somewhat more closely connected, or even equivalent ?

    Thanks

    Edit - equivalent is going too far since the article says that the passage from C to C* cannot be done in finite time.
     
    Last edited: Mar 3, 2015
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  3. Mar 3, 2015 #2

    marcus

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    Wabbit, thanks for calling my attention to the quirkiness of that paper. The "self-dual" BH picture is due to 2008 work by L. Modesto which did not catch on. He seems to have abandoned it after 2012. Seems to have been a dead-end. I have removed the Silva paper from bibliography.
     
  4. Mar 3, 2015 #3

    wabbit

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    Oh OK so I take it you don't think much of my attempt to salvage it through latching it on to Rovelli's bandwagon ?
    Edit - anyway thanks for your reply, my motivation for looking at that paper was your listing it, so if you are now disowning it I shall leave it aside as well : )
     
    Last edited: Mar 3, 2015
  5. Mar 3, 2015 #4

    marcus

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    Well you asked "is the similarity only superficial?" and I'm not sure what exactly the similarity is. I think the pictures are contrasting. One has the formation of a wormhole and the other doesn't AFAICS. Paper should have made it clear that the model was not current. It makes it sound as if Modesto's SDBH is the official Loop black hole. so it is just too confusing.
    If I was going to predict a winner among the various LQG black hole models I would probably say that Jorge Pullin and Rodolfo Gambini are the most on top of the BH situation (no wormholes for them and, I regret to say, no explosions either). Likewise Alejandro Perez and his co-authors (he is the BH guy in Rovelli's Marseille group) no wormholes and no explosions. Plain vanilla evaporation without a singularity.
    Personally I really LIKE the RovelliVidottoBarrauHaggard idea of a long-delayed BH explosion. But I have to say it is a MINORITY idea --- you may have been kidding when you referred to it as a "bandwagon"---or there may be wider acceptance and I'm just missing the signs.

    What I'm seeing seems a little contradictory because there certainly does seem to be a cosmological bounce bandwagon but for some reason this does not extend to black holes! On the cosmological side there are some big names: Brandeberger, Odintsov, of course notable Loop cosmology people, and now apparently Hartle and Hertog, and lots of younger people, and lots of papers.

    Intuitively you'd think this would somehow spill over and validate Rovelli's delayed BH explosion idea---at least as a testable possibility.

    Instead, in the BH department, people like Gambini Pullin and Perez have come up with ways that information may decay or be dissipated into the environment, so that the BH paradoxes go away. that removes a major motivation for considering any change to the old Hawking evaporation story.

    Jorge Pullin will be giving one of the ILQGS online seminar talks this semester. On the LQG black hole. If he mentions wormholes and self-dual picture then I'm wrong about it being an obsolete dead-end. I couldn't find any activity even on Modesto's part, but could easily be mistaken.
     
    Last edited: Mar 3, 2015
  6. Mar 3, 2015 #5

    wabbit

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    Thanks yes I guess it is indeed, especially if it was abandonned by the author himself. RIP SDBH ; )
     
  7. Mar 3, 2015 #6

    marcus

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    I have to apologize for having let a confused red herring into the biblio---and also stridently emphasize that I could be wrong. Obviously I'm absolutely no expert. I guess much of the time I and others put stuff in the biblio thread rather uncritically just because it is Loop-and-allied QG related or just seems interesting.

    We can hope that my assessment is wrong and that for example when Jorge Pullin gives a talk on Loop BH he will refer to SDBH and put that model in perspective with whatever else is currently being studied. I'll listen out for that. Google "ilqgs" to find out when he's talking.

    http://relativity.phys.lsu.edu/ilqgs/schedulesp15.html
    Pullin talks on 7 April "An explicit computation of the evaporation of a quantum black hole"
    and two weeks earlier 24 March, Matteo Smerlak (a young researcher who is very good) will talk on "Information loss"
     
    Last edited: Mar 3, 2015
  8. Mar 3, 2015 #7

    wabbit

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    No need to apologize at all, I use your references because you provide an innteresting selection through a filter that matches some of my interests and it gives easy access to a range of potentially interesting publications without having to pore through 100 s of abstracts. A red herring or two once in a while doesn't change any of that. Thanks for those biblios.

    Edit : ypu mean Pulin is actually discussing SDBH ? The title says only BH ?
    Re-edit : sorry re-read your post you're only saying "if that happens"
     
    Last edited: Mar 3, 2015
  9. Mar 3, 2015 #8

    wabbit

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    On the various BH approaches I have not read those papers, my view is certainly distorted because (a)I am a big fan of Rovelli, and (b) I found his picture of Planck stars compelling both in itself and because of the close parallel with LQC bounce. (As for the bandwagon it was a bon mot, nothing deep)

    Also several scenarios could be right. Rovelli's is a tunelling. It could be that a BH can decay into several modes including explosion or not, and that different views could combine. This thought issinspired by a paper of cosmo-bounce (again), don't remember the reference, where a collapsing universe emerges from the bounce as an ensemble - which isnt very useful in QC where we are in any case in one branch, but could be intersting if transposed to BHs.

    One thing I noticed about all the cosmo-bounce papers is that they are all / most of the effective QG sort (well Quantum cosmo must be I suppose), so they do not depend that much on the details of QG- and there are common threads and similarities between bounce where the underlying QG is LQG or something else, I saw a stringy one which wasn't that different ; so that makes the bounce phenomenology seeem to emerge as a robust prediction of QG (even if some of the details differ)
     
    Last edited: Mar 3, 2015
  10. Mar 3, 2015 #9

    marcus

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    That's right LQC has featured a bounce since work by Bojowald around 1999-2001 so it helped to make a place at the table for bounce cosmology.
    Make it seem normal. So now there is "matter bounce" and several kinds of "modified gravity" bounce and "teleparallel gravity" bounce and don't know what-all. I didn't hear of a "boucetron" particle field yet but just wait. Everybody wants to try their hand at constructing a QG cosmological model that bounces. And if possible get some agreeable phenomenology as you suggested. So it does seem robust, or more so than it used to be.

    About BH it looks like current thinking revolves around "information loss" and clinging to unitarity/purity/coherence.

    One reason Rovelli's small bunch of "Planck star" people look like a somewhat separate minority is because they have moved on from unitarity concerns to worrying about testability. My sense is that is the next big thing in QG, so they are just a bit ahead of the others. If there is any chance, even the slightest chance, that some BH, small ones perhaps, might be exploding, then pursue that possibility and find out what color the fireball would be (if they do). And how bright and where--if there is a preferred where--and with what statistical frequency, if you can say. It's a long shot, but bounce cosmology was a long shot back when it was more popular to have the universe arise from a quantum fluctuation.
     
  11. Mar 4, 2015 #10

    wabbit

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    That paper would be Hartle & Hertog
     
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