Black hole fireworks: quantum-gravity effects outside the horizon spar

[Demystifier]

- Would the gravitational crystal proposal offer an explanation for the (lack of) observation of primordial black hole "explosions" (explosions due to rapid Hawking evaporation of very light black holes), by imposing a lower limit on the black hole mass before the evaporation stopped (when the horizon met the crystal surface)?

I think yes. The evaporation always stops before the final "explosion" predicted by the standard semi-classical scenario.

- Could such gravitational crystal remnants of (as much as is possible, evaporated) primordial black holes be candidates for dark matter?

Maybe for a part of dark matter, but probably not for all dark matter. Namely, standard cosmological analysis puts an upper bound to the quantity of barionic dark matter. So if the remnants do not contain much barionic dark matter, then what kind of matter do they contain? The gravitational crystal, by itself, probably cannot answer that question.

 

[no-ir]

Maybe for a part of dark matter, but probably not for all dark matter. Namely, standard cosmological analysis puts an upper boundary to the quantity of barionic dark matter. So if the remnants do not contain much barionic dark matter, then what kind of matter do they contain? The gravitational crystal, by itself, probably cannot answer that question.

Thank you for your reply. But, from what I understand all that is required for an object to be a non-baryonic dark matter candidate is that it: has no net charge (aside from mass, if you consider that a gravitational charge), only interacts via the gravitational force (check) and does not take part in Big Bang nucleosynthesis (I would imagine that a black hole does not?). Would primordial black holes or their remnants not fit that description?

Actually, looking at Wikipedia (:p) under Primordial black holes it says:

It has been proposed that primordial black holes, specifically those forming in the mass range of 10^14 kg to 10^23 kg,[1] could be a candidate for dark matter. This is due to the possibility that at this low mass they would behave as expected of other particle candidates for dark matter. Being within the typical mass range of asteroids, this excludes those black holes too small to persist until our era and those too large to explain gravitational lensing observations.

What the gravitational crystal proposal changes about the above statement is that it removes the lower limit on the mass range of primordial black holes, since it is no longer necessary to "exclude those black holes too small to persist until our era" (thereby boosting the number of stable primordial black hole (remnants) that could contribute to dark matter). How much this is helpful (or natural), I wouldn't know.

P.S. Actually, reading that Wikipedia article further on:

General relativity predicts the smallest primordial black holes would have evaporated by now, but if there were a fourth spatial dimension – as predicted by string theory – it would affect how gravity acts on small scales and "slow down the evaporation quite substantially".[9] This could mean there are several thousand black holes in our galaxy. To test this theory, scientists will use the Fermi Gamma-ray Space Telescope which was put in orbit by NASA on June 11, 2008. If they observe specific small interference patterns within gamma-ray bursts, it could be the first indirect evidence for primordial black holes and string theory.

So if those intereference patterns are observed, it could also (instead) be indirect evidence for gravitational crystals? ;)

 

[Demystifier]

No-ir, I am not an expert in those aspects of dark matter, but your arguments seem reasonable. I think you could be right.

 

[no-ir]

Thank you! :)

 

[Jimster41]

Sorry about this, but I have to wonder out loud.

The description above is one where "gravitational crystals" are somehow things located very specifically somewhere in space-time. I had been imagining them to be potentially non-local, possibly helping to describe, more generally, the emergence of complexity in association with gravitational clumping. The effect could still be associated with dark matter but also other gravitation-ally induced emergent structure.

That's why earlier (post #50) in reference to the paper, I was interested in whether or not it was plausible that "entanglement interference structures" could form, radiating from a black hole Killing Horizon, or even other special gravitational radii.

The implication being that somehow the complexity containing all that information isn't collapsed into some subset of energy matter, it is conducted/dissipated? through surrounding space-time.

 

[no-ir]

P.S. Hm, reading this 2014 news article:

http://www.nature.com/news/search-for-primordial-black-holes-called-off-1.14551 (Search for primordial black holes called off)

it seems that primordial black holes as dark matter were (almost) "ruled out" purely on the basis of mass constraints, but were otherwise considered viable as dark matter candidates. If the lower mass constraint is just that too light black holes should have evaporated by now, then the gravitational crystal theory could still save the proposal of primordial black holes as dark matter. A thought.

 

[Demystifier]

Thanks! It's an interesting idea to have a change of phase into a "crystal" phase.
http://arxiv.org/abs/1505.04088
Gravitational crystal inside the black hole
H. Nikolic
(Submitted on 15 May 2015)
Crystals, as quantum objects typically much larger than their lattice spacing, are a counterexample to a frequent prejudice that quantum effects should not be pronounced at macroscopic distances. We propose that the Einstein theory of gravity only describes a fluid phase and that a phase transition of crystallization can occur under extreme conditions such as those inside the black hole. Such a crystal phase with lattice spacing of the order of the Planck length offers a natural mechanism for pronounced quantum-gravity effects at distances much larger than the Planck length. A resolution of the black-hole information paradox is proposed, according to which all information is stored in a crystal-phase remnant with size and mass much above the Planck scale.
6 pages

I think that important advances in physics occasionally have something at the "philosophical" or "conceptual" level, that makes them different.
Whether or not this will turn out to be successful, it has this very interesting new perspective:

"We propose that the Einstein theory of gravity only describes a fluid phase and that a phase transition of crystallization can occur under extreme conditions such as those inside the black hole. Such a crystal phase with lattice spacing of the order of the Planck length offers a natural mechanism for pronounced quantum-gravity effects at distances much larger than the Planck length."

So what about evaporation?

This Nicolic idea reminds me of the 1995 Jacobson idea of the "Einstein equation of state" describing the collective behavior of little things we can't see. Now the new idea is that these little things can form a crystal (and require a new equation to describe their behavior in the new phase).
I would like to see a reaction to this paper by Ted Jacobson.

I like this idea very much (without myself having any ability to judge if it could or could not be right). It is even more than usually entertaining, if it is possible for physics ideas to be considered entertaining.

Now a revised version accepted for publication in Mod. Phys. Lett. A is available:
http://lanl.arxiv.org/abs/1505.04088

 

[member 11137]

Thank you for your reply. But, from what I understand all that is required for an object to be a non-baryonic dark matter candidate is that it: has no net charge (aside from mass, if you consider that a gravitational charge), only interacts via the gravitational force (check) and does not take part in Big Bang nucleosynthesis (I would imagine that a black hole does not?). Would primordial black holes or their remnants not fit that description?

I beg my pardon for that naive question, especially if it already has been asked and answered in the previous paragraphs of that long discussion. So far my understanding and so far what I can read here and there on the web or in the literature, we are looking for the exact nature of dark matter (and byside, also of dark energy). The actual discussion here is one more illustration of that affirmation. I appreciate your attempt to describe the basic properties of the "dark" matter because, in some way, this gives a visage to the invisible. And that word is motivating my question: "Does some one already have done an investigation concerning the criterium of geometrical invisibility for some actual known particle (in extenso: the definition of concrete circumstances for which a particle in motion don't perturb the geometry)?" If yes, do you have a reference on this topic. Just a thought too (constructive proposition).