Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question about the "Bounce" model of BH and Anisotropy

  1. Oct 5, 2014 #1
    I have some doubts/questions about the new BH model. This model gains popularity, but does it make any sense?

    Q1. Assuming the extreme time dilation inside BH, even tiny anisotropy after the bounce leads to HUGE (billion years) differences in the time of the visible explosion. One can argue that the "bounce" naturally "synchronizes" the matter, but:
    Q2. Infalling matter after the bounce can and should destroy the perfect symmetry
    Q3. ... and rotating BH definitely should have a difference between the equator and the poles.
    Note that all realistic BH are almost over-extreme, so rotation is very important.

    So there should not be gamma ray burst all over the BH the same second, instead, the explosion could be smeared to millions or even billion years. But if it is so smooth, the first outcoming rays/matter would be sucked back by the gravity, and we won't see a gamma ray burst at all.
  2. jcsd
  3. Oct 5, 2014 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Hi Tzimie,
    I can't give you satisfactory answers to your three questions. I was glad to see your post, though, and want to comment. I think you are talking about the bounce BH models in papers by Aurelien Barrau together with Rovelli and Vidotto and by the latter two.

    I think that according to their BH models which are all pretty similar, just differ in some details, Astrophysical BH look and act conventionally for trillions of years. There is no question of our ever observing them explode. As far as we are concerned (unless you see some difference I haven't thought of) they look and act just like conventional Hawking-model black holes for thousands or millions of times the present age of the universe.

    There was a well-known astrophysicist Neil Cornish who made this same point in a comment on Bee Hossenfelder's blog recently, but in regard to Laura M-H's paper.

    But that leaves out the interesting part! This concerns the possible existence of primordial black holes with lifetimes comparable to the present age of the universe. I don't know of anyone who says they should rotate appreciably, so maybe that is not a problem, but your questions Q1 and Q2 certainly apply. I would like to know, for a PBH of initial mass 1015g to 1023g with size a tiny fraction of a centimeter, if the infalling matter and radiation it is likely to encounter can make any significant anisotropy!

    Especially can the infall make any significant anisotropy in the degree of time dilation?

    I hope you will discuss the questions a little further and help me get clearer about them.

    BTW when I try to imagine how your name Tzimie is pronounced what I hear is "Jimmy", so that is how I think of you : ^)
    Last edited: Oct 5, 2014
  4. Oct 6, 2014 #3
    Yes, I know that we can't expect BH explosions SOON (except the primordial ones). However, these explosions is the only point which makes this theory potentially falsifiable (even if they occur only in far future). However, based on Q1,Q2,Q3 these explosions are very unlikely.

    Also I know there is yet another new BH model - "degenerate" planck matter (some kind of string condensate) filling the whole volume below the schwarzschild radius. What do you think about it? (I had lost the link). It is designed to solve the information paradox, as hawking radiation can carry away the information. However, for me it is really weird that in supermassive BH that "degenerate" matter has very low density.

    Tzimie is just nickname, from "tzimisce" (vampire clan) :)
    This is very useful because almost any name is already used in emails, logins etc,
    and this rare combination is always free!
  5. Oct 6, 2014 #4


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    I'm trying to think what that other BH model could be, and who could a representative author be?
    My knowledge in incomplete and I can't be sure. Could it be Samir Mathur?
    Remnants, Fuzzballs or Wormholes?
    Samir D. Mathur
    (Submitted on 3 Jun 2014)
    The black hole information paradox has caused enormous confusion over four decades. But in recent years, the theorem of quantum strong-subaddditivity has sorted out the possible resolutions into three sharp categories:
    (A) No new physics at r≫lp; this necessarily implies remnants/information loss. A realization of remnants is given by a baby Universe attached near r∼0.
    (B) Violation of the `no-hair' theorem by nontrivial effects at the horizon r∼M. This possibility is realized by fuzzballs in string theory, and gives unitary evaporation.
    (C) Having the vacuum at the horizon, but requiring that Hawking quanta at r∼M3 be somehow identified with degrees of freedom inside the black hole. A model for this `extreme nonlocality' is realized by conjecturing that wormholes connect the radiation quanta to the hole.
    Comments:7 pages, 4 figures (Essay awarded an honorable mention in the Gravity Research Foundation essay competition 2014)

    https://physics.osu.edu/people/mathur [Broken]
    Tzimie, I've never found Samir Mathur's "fuzzballs" interesting. I think I share the sense of "weirdness" you mentioned. His name often comes up as a string theorist with specialty in black holes. His papers on this go back quite a few years. But it's possible this is what you were remembering, so I mention it just in case.
    Let me know if it's not Samir and I (or one of the others) may be able to come up with another possibility.
    Last edited by a moderator: May 7, 2017
  6. Oct 6, 2014 #5
    Yes, thank you, it was called a "fuzzball"
  7. Oct 6, 2014 #6


    User Avatar
    Science Advisor

    Fuzzballs, energetic curtains (firewalls) and bounce models are basically all in the same class of solutions to the information paradox, in that they all predict large violations of what is known as the 'no drama' hypothesis for what an infalling observer sees at the horizon of an old blackhole. In other words, that an observer in freefall near the horizon does not see vacuum. Although in the case of fuzzballs, there was a paper that was written arguing for some sort of complementarity, although I am not sure what the status is on that.

    This sort of thing is very troubling to relativists, b/c it implies that there is something very wrong with their usual causal diagrams of spacetime. They worry about acausal signal propagation and so forth.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook