Theorists apply loop quantum gravity theory to black hole

May 31, 2013 by Bob Yirka report
This artist's concept shows a galaxy with a supermassive black hole at its core. The black hole is shooting out jets of radio waves. Image credit: NASA/JPL-Caltech

(Phys.org) —Physicists Rodolfo Gambini and Jorge Pullin of University of the Republic in Montevideo, Uruguay, and Louisiana State University respectively, have applied the theory of Loop Quantum Gravity (LQG) to a simplified black hole. In so doing, as they describe in their paper published in the journal Physical Review Letters, they suggest that instead of a singularity existing at its center, there is a portal to another universe.

For many years have believed that the universe came about as a result of a single Big Bang event—'s theories suggested it was so. The problem with this line of thinking however, is that the can't describe what came before the singularity, which should exist at the point in time just before the Big Bang. Theory also suggests that a similar singularity should exist at the center of black holes, but again, general relativity fails to describe them properly. Worse, there is the problem of the information loss paradox—if something falls into a black hole and is eventually squeezed to a singularity, what happens to the information it contained? Big Bang physicists can't say.

To address these problems, Abhay Ashtekar and his team at Pennsylvania State University, back in 2006, came up with a theory known as loop . They suggested that instead of a singularity existing just before the Big Bang, there was the remains of a crunched down universe that had existed prior to the one that exists now. The universe didn't just Big Bang itself into existence from nothing, they said, instead there is an infinite loop where a universe shrinks down to a very tiny spot, then explodes in a Big Bang, then shrinks down again, over and over again forever—hence the use of the term "loop" in the theory. Since that time, some in the field have begun to refer to the theory as the Big Bounce, to replace the name Big Bang.

In this new effort Gambini and Pullin applied LQG to a simplified model of a black hole. Their experiment showed that everything that was pulled into the black hole didn't compress to a after all—instead it was compressed to a certain small size, then was spit out in another part of the universe or into another universe entirely.

Because their model worked so well, the two suggest that it would likely work with real black holes as well. If this new theory is correct, they note, it would do away with the information loss paradox and open the door to the possibility of being portals to other universes.

Explore further: Attack on classical cryptography system raises security questions

More information: Loop Quantization of the Schwarzschild Black Hole, Phys. Rev. Lett. 110, 211301 (2013) prl.aps.org/abstract/PRL/v110/i21/e211301

Abstract
We quantize spherically symmetric vacuum gravity without gauge fixing the diffeomorphism constraint. Through a rescaling, we make the algebra of Hamiltonian constraints Abelian, and therefore the constraint algebra is a true Lie algebra. This allows the completion of the Dirac quantization procedure using loop quantum gravity techniques. We can construct explicitly the exact solutions of the physical Hilbert space annihilated by all constraints. New observables living in the bulk appear at the quantum level (analogous to spin in quantum mechanics) that are not present at the classical level and are associated with the discrete nature of the spin network states of loop quantum gravity. The resulting quantum space-times resolve the singularity present in the classical theory inside black holes.

via Synopsis

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Moebius
2.8 / 5 (9) May 31, 2013
LOL And the mass that created the portal doesn't go through the portal? It just conveniently disappears? What about added mass after the portal is formed, there are black holes of various size? This theory shows how implausible a singularity is though. A singularity wouldn't have any mass.
Aaron1980
2.4 / 5 (8) May 31, 2013
I like this line of thinking. As mater and space gets closer to a black hole in our universe the time slow to an infinitely slow speed (... a virtually a time stop to us at the event horizon). On the other side of the black hole portal... mater and time explodes out at what looks like a Bid Bang because its time is starting from a finite beginning.... a new universe is created by everything that will ever fall into the black hole in our universe.

another though is that everything in our universe can one day (end of our time event) end up in one black that contains everything from our universe. But since time will have been at a virtual stop at all the black holes in our universe since the beginning of our time, the new universe composed of everything spewing out from our universe at the Big Bang of the new universe at one instant in time.

Simple and elegant solution if it all falls into place (pun intended)
rkolter
4.1 / 5 (7) May 31, 2013
I am not sure this phys.org summary properly captures the document it is summarizing.
Aaron1980
1 / 5 (5) May 31, 2013
General relativity predicts, all objects will collapse into black holes with no mercy. Quantum mechanics predicts, all objects will expand into infinity instead. From this perspective these two theories have absolutely nothing in common.


Actually yes they do have something in common ...

one is describing what happens as mater goes into a black hole ... the other is describing what happens when mater explodes out of the big bang on the other side of the same black hole.

You solved it man!
GSwift7
3.9 / 5 (10) May 31, 2013
LOL And the mass that created the portal doesn't go through the portal? It just conveniently disappears?


Well, based on observations here in our gravity well, we know time slows down as you get farther into a gravity well. In the extreme case of a black hole, time should virtually come to a stop at the center. So, whatever happens to the 'information' or mass that falls into it, would take forever to happen from our perspective.

The above philosophy that GR creates a paradox in the singularity is not the only way to think about it. There are many alternate possible explainations, and we don't know if any of them are correct.

One possible way to see it, which doesn't involve an information loss paradox is to say that the information just got stretched out to infinite length of time. So, kinda like a light wave that is stretched in space, the information has been stretched or diluted over time.

BTW, in this case, information is everything that falls into a black hole.
GSwift7
4.5 / 5 (8) May 31, 2013
General relativity predicts, all objects will collapse into black holes with no mercy. Quantum mechanics predicts, all objects will expand into infinity instead


Why bother reading if you don't pay attention to what it says? If you're going to just make up your own nonsense, then skip the reading part and just write you own science stories. You can make your own laws of physics and everything.

What you said in the part I quoted is absolutely not what GR or QT predict. You are arguing against a false premise. In debates, that is called a straw man argument. It's like if I asked you to explain why you use rocks to kill kittens in your back yard. Since you started out with something that isn't true, it's impossible to have a discussion about it.
antialias_physorg
3.8 / 5 (12) May 31, 2013
LQG is an interesting theory - and the work they did here points to something fascinating (though I'm not sure whether it's testable).

However the serial infinite collapses/expansions doesn't solve the problem of the first cause (i.e. the very first expansion in this case). So the term 'infinite' is to be taken with a grain of salt.

GSwift7
4.5 / 5 (8) May 31, 2013
However the serial infinite collapses/expansions doesn't solve the problem of the first cause (i.e. the very first expansion in this case). So the term 'infinite' is to be taken with a grain of salt.


Yeah, that's what I was thinking. It's the same problem you get with any steady state solution. In this case the infinite loop is a version of steady state, ...unless you can show that it started very small and has gotten bigger in each cycle? But, as you said, that would be a neat trick to attempt to prove.
Noumenon
2 / 5 (25) May 31, 2013
I wonder how this idea reconciles the problem with entropy,... that the big bang presumably started with very low entropy while presumably a black hole must have maximal entropy.

LOL And the mass that created the portal doesn't go through the portal? It just conveniently disappears? What about added mass after the portal is formed, there are black holes of various size? This theory shows how implausible a singularity is though. A singularity wouldn't have any mass.


The mass went into the form of space-time curvature, so is validly "not there",... but the energy equivalent is there of course. It is observational fact that gravity waves carry away energy, so space-time curvature is a form of energy, so mass ---> space-time curvature.
k_m
1.6 / 5 (7) May 31, 2013
If a universe is born from a black hole, matter which hasn't fallen in yet isn't in the new universe. Possibly, information about this matter precedes its appearance in the new universe due to its interaction with other matter prior to this other matter falling in and results in the effects of "dark" matter and energy?
ValeriaT
1 / 5 (12) May 31, 2013
BTW It's interesting, how obstinately the pushers of string theory and LQG ignore both the observations, both the experimental failures of their models. One would said, if some results don't fit the theory, than it has no meaning to further pursue it - but the scientists are like politicians (both they're payed from tax fees, btw): if they lose one election, they return to the political scene from another party - just for the sake of their jobs and salaries. And because layman trolls are of short memory, they can succeed with it again and again.
El_Nose
4.2 / 5 (5) May 31, 2013
silly theory from a non physicist here --- might make a decent book sci-fi backbone

theory:
okay the bigbang was a singularity being formed -- basically a black hole in another universe initial gravitational collapse. It was a huge amount of matter and energy that was absorbed in this initial collapse.and created the universe we now know and love. -- fast forward to present day and scientists have uncovered two strange pieces of physics of our universe 1) vacuum energy and 2) the accelerating expansion of the universe -- this is easily explained by the initial black hole is still continuously consuming matter. This matter goes into the black hole and comes into our universe as pure energy. As black holes are the physical manifestation of E=mc^2 we are the happy recipient of all the excess energy its not shooting out as Hawking radiation in its own universe. this also explains why every point in space recieves this energy equally and at all times.

--- NOT A REAL THEORY -- scifi
antialias_physorg
4.2 / 5 (10) May 31, 2013
If a universe is born from a black hole, matter which hasn't fallen in yet isn't in the new universe.

Matter doesn't really make it to the singularity. The forces in there are way too extreme for matter in the ordinary sense to continue to exist. So even if a black hole were some sort of portal: On the other side you'd just get high energy photons.
(Which doesn't really matter, since the other side is also a black hole - so matter or photons can't escape it in any case. I'm unsure how that can even lead to a new universe and not just be stopped dead on arrival)
El_Nose
3.7 / 5 (3) May 31, 2013
@k_m

I have stated this little theory a few times before as a good book idea --- figured i owed you a clarification as you posted 30 minutes before I did this time
Urgelt
4.2 / 5 (11) May 31, 2013
Ok, let's see if we can make this portal idea falsifiable.

It's not a portal if nothing goes through it. Right?

If the mass of the black hole can leak through a portal to elsewhere, then the black hole would lose mass - possibly very rapidly. That really ought to be detectable.

We can detect nothing of the kind. Doesn't look good for the portal idea.

Incidentally, the 'once-only' Big Bang and the 'looping' Big Bounce ideas are not the only possibilities. Another possibility is repeated Big Bangs that do not end in a collapsed universe. The remnant universe from the Big Bang prior to the one which created present one is beyond the light-horizon; we can't see it. (If true, then the mass of the last universe is still out there, and through gravitational effects, it could be affecting the expansion of the universe we can see.)

If the repeated Big Bangs idea has merit, then there may be more to cosmic background radiation than we've yet figured out.
EWSwan
3.9 / 5 (7) Jun 01, 2013
Wow, way to get the reporting wrong. LQG goes back to the mid 1980s, when Ashtekar, Lee Smolin, and Carlo Rovelli came up with the notion of loops, which have nothing to do with the absurd looping-universe concept represented in this article. For a good summary, get Lee Smolin's "Three Roads to Quantum Gravity," published in 2002.
Sean_W
3.3 / 5 (7) Jun 01, 2013
Wow, way to get the reporting wrong. LQG goes back to the mid 1980s, when Ashtekar, Lee Smolin, and Carlo Rovelli came up with the notion of loops, which have nothing to do with the absurd looping-universe concept represented in this article. For a good summary, get Lee Smolin's "Three Roads to Quantum Gravity," published in 2002.


This is true. The idea of a cyclical Big Bang/Big Big Crunch exists but has nothing to do with LCG.
FainAvis
1 / 5 (2) Jun 01, 2013
"...how obstinately the pushers of string theory and LQG ignore both the observations, both the experimental failures of their models." ValeriaT
"...he doesn't know anything about both quantum mechanics, both Big bang theory,..." natello

If you can not get your grammar correct how can we believe you are getting your physics correct?
ValeriaT
1 / 5 (6) Jun 01, 2013
This is a specific iteration of the ad hominem fallacy of guilt by association, until you prove, my poor grammar has lead into an amphiboly. In another words, if you believe that the correctness of physics depends on correct usage of English grammar, how can you believe, you can give an more relevant advices regarding physics?
ValeriaT
1 / 5 (5) Jun 01, 2013
From general relativity perspective the physics beneath the event horizon remains undefined, so that even the black hole event horizon may serve as a portal into another universe. I don't know, why to speculate about some singularity inside of it, after then.
ZakirGowani
not rated yet Jun 01, 2013
"Abhay Ashtekar and his team at Pennsylvania State University, back in 2006, came up with a theory known as loop quantum gravity. They suggested... the universe didn't just Big Bang itself into existence from nothing, they said, instead there is an infinite loop where a universe shrinks down to a very tiny spot, then explodes in a Big Bang, then shrinks down again, over and over again forever—hence the use of the term "loop" in the theory."

This article has it so, so wrong. LQG has been around since at least the 1990s, possibly earlier, thanks to Lee Smolin. And LQG is not about the oscillatory universe! My goodness. Who writes these?

A better source on LQG:
http://www.emis.a...olor.pdf
c0y0te
1 / 5 (1) Jun 02, 2013
Another possibility is repeated Big Bangs that do not end in a collapsed universe. The remnant universe from the Big Bang prior to the one which created present one is beyond the light-horizon; we can't see it. (If true, then the mass of the last universe is still out there, and through gravitational effects, it could be affecting the expansion of the universe we can see.)

Do you say that gravity is faster than light?
cuttellhell
not rated yet Jun 03, 2013
This article is so wrong it makes my head hurt. If you know so little about LQG, why did you not ask a physicist working on it rather than making so many wrong assumptions. 'Loop' in the name comes from a mathematical technique it was based on - not the cyclical universe prediction. The theory has been around for decades - not since 2006. I cba going through everything you were wrong on. fml.
GSwift7
2.3 / 5 (3) Jun 05, 2013
antialias:

Matter doesn't really make it to the singularity. The forces in there are way too extreme for matter in the ordinary sense to continue to exist. So even if a black hole were some sort of portal: On the other side you'd just get high energy photons


There are hypothetical strategies that may allow you to 'cheat' this, though they seem more like mathematical game theory to me. They usually suggest something like tipping the local budget of relativistic effects in one direction so that the total budget remains the same, but you might get a localized 'safe zone'. Kinda like if you have a perfectly insulated cooler, and you move all the heat energy inside the cooler to one spot inside the cooler, while the rest of the cooler sees a slight drop in heat energy. Some of the math guys think you might be able to do this for individual particles, allowing some communication beyond the event horizon. We don't have any way to test such ideas, so it doesn't really matter though
markallen127
1 / 5 (2) Jun 06, 2013
Just for argument sake, if an inanimate object were to enter a black hole (e.g. a person's soul), would the information loss paradox apply if the object were to emerge at the other end?
Q-Star
2.3 / 5 (6) Jun 06, 2013
Just for argument sake, if an inanimate object were to enter a black hole (e.g. a person's soul), would the information loss paradox apply if the object were to emerge at the other end?


All objects that enter a black hole would be "inanimate" by any definition of the word.
NOM
1 / 5 (2) Jul 03, 2013
natello
My apology: this comment belongs http://phys.org/n...rstCmt..

None of your comments belong on physorg Zephyr.
ValeriaT
1 / 5 (1) Jul 03, 2013
I see, just another identity created to address Zephyr, nobody else...
beleg
1 / 5 (2) Jul 17, 2013
...the information just got stretched out to infinite length of time... - G7

That's a source for instantaneous events. Entanglement comes to mind.

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