Loop Quantum Gravity

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Re: Loop Quantum Gravity

#121  Postby DavidMcC » Feb 21, 2012 12:11 pm

Thanks for the response, twistor59.

I'm not sure exactly what you mean by "hyperspace continuum" it sounds a bit like the kinetic Hilbert space I was talking about here.


Yes, it would be the space-like dimensions in which the connections connect! (In my philosophy, it has to be real if the connections are real.)

I'm not familiar with gravastars so unfortunately that's over my head.


http://www.bautforum.com/showthread.php/1151-Los-Alamos-Researcher-Says-Black-Holes-Aren-t-Holes-At-All

From: Science Daily
Source: Los Alamos National Laboratory (http://www.lanl.gov/)

Date: Posted 4/23/2002

Los Alamos Researcher Says "Black Holes" Aren't Holes At All
...
Mottola and Pawel suggest that while some degree of collapsing does take place in a dying star, the collapse proceeds only to a certain point. At that point, the intense gravity of the dying star transforms the star's matter into an entirely new phase. Mottolla describes this phase as similar to a Bose-Einstein condensate, a phase of matter recently observed in a laboratory setting and the subject of scientific excitement in the past few years.
...


twistor59 wrote:The only "no god required" argument I've heard from him is related to his idea that the universe has no past boundary and hence no need for a moment of creation.


In the program I saw, he was interviewed about the subject. It may be that it was the narrator who said that "time stops" at the event horizon, and he was therefore possibly misrepresented.

Why should our big bang cosmos need anywhere to expand into ?


I know that the usual notion of "expanding into" conjures up the idea of some "outside" real space, as if space and hyperspace were of the same kind. However, in LQG, this hyperspace is quite different from the lines/nodes or loops of "real space", so our universe only has an edge or centre in hyperspace, not in its own dimensions, because the loops form great circles, so that, if we hypothetically went in a straight line far and fast enough, we would only get back where we started. Ie, from our point of view, within a "real space", there is no outside - no matter how far you travel, you cannot reach an edge, and not just because the universe is expanding too fast, but also because it is "finite but unbounded" - embedded in an actual infinite continuum as lines & nodes or linked loops. Another way of looking at it is that we only exist as particles - excitations of space, which are, by their very nature, confined to that space.

Ashtekar certainly seems to reject the hyperspace continuum as mathematically inconvenient and unnecessary, just as you are implying. However, his version of quantum gravity famously predicted the "big bounce", because, without this continuum, there can only be one "real space", ie there is no BH-based mutiverse (all generated from the same hyperspace continuum by the law of quantum gravity), ie, no concept of the "fecund universe". For this, and other reasons, I think the continuum (which can be likened to the paper on which the lines and nodes of his spin foam are drawn) should be kept, as it allows for gravity to act across it, which seems like a reasonable interpretation of the gravitational anomalies called "dark matter" (or, rather, that part of observed dark matter that cannot be accounted for as "ordinary" particles). Even more fundamentally in my version of quantum gravity, it forms the basis for the "law of quantum gravity" to produce actual spaces, like the one exist in.
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Re: Loop Quantum Gravity

#122  Postby Pulsar » Feb 21, 2012 1:10 pm

DavidMcC wrote:Dark matter and dark energy might be understandable in the context of this cosmology, by extension of the physics of this universe. Consider that BHs have gravitational interactions with each other, and may collide. Such a collision would release a huge amount of gravitational potential energy as the BHs fall into each other's potential wells. I propose that this energy somehow gets converted into "zero-point" energy (ie, space) in both BH/universes, causing both to expand and exhibit "dark energy".

Surely the collision of two BHs is extremely rare. I imagine that such events could happen in a binary system of massive stars (and a collision wouldn't happen for billions of years); also, the central supermassive BHs of two colliding galaxies might merge, but again, such an event is very rare in the present-day universe. Other than that, space is just too big for a chance encounter between two BHs.

In any case, I don't see how two colliding BHs have something to do with dark energy. They would release gravitational waves, but how is that connected with dark energy? And even if there would be such a mechanism, I cannot imagine that BH-collisions are anywhere near frequent or powerful enough to have any impact beyond their local neighbourhood, let alone the entire universe.
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Re: Loop Quantum Gravity

#123  Postby DavidMcC » Feb 21, 2012 4:08 pm

Pulsar wrote:Surely the collision of two BHs is extremely rare. I imagine that such events could happen in a binary system of massive stars (and a collision wouldn't happen for billions of years); also, the central supermassive BHs of two colliding galaxies might merge, but again, such an event is very rare in the present-day universe. Other than that, space is just too big for a chance encounter between two BHs.


For one thing, it only has to happen once, and,bingo, here we are, and for another, you're thinking of BHs in this universe, which only formed well after atoms, so that it's hard for them to find each other. If cosmology is as described in my OP, our universe is a BH in a much bigger, more massive one, in which gravitational collapse of a body within that universe can come before atoms.

In any case, I don't see how two colliding BHs have something to do with dark energy.


Again, if you read my OP, I am challenging that orthodoxy. I realise that there is a certtain amouint of speculation involved, but I see no reason why falling into each others' gravitational well shouldn't result in a form of energy conversion that leads to more zero-point energy in each BH, ie, more space. (Of course, it requires that a BH be as per my version of loop quantum gravity, which has nothing to do with universes. You have to rethink everything, but still apply the principles of physics in some way that makes sense.)
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Re: Loop Quantum Gravity

#124  Postby DavidMcC » Feb 21, 2012 4:27 pm

... Look at it this way: when a massive star collapses, some of its matter gets blown out into space, but much of it remains, and forms a BH if there is enough of it. I'm only saying that a similar thing could happen when two BHs collide - some energy gets radiated (assuming, gravitational waves actually exist, which has not been demonstrated yet), but other energy may be involved in internal conversion, just as it must do when BHs form in the first place.
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Re: Loop Quantum Gravity

#125  Postby DavidMcC » Feb 23, 2012 9:57 am

Two more points that I forgot to include in my earlier posts (although I did mention them somewhere on richarddawkins.net, some time ago):

1. On "infaltion", LQG offers a more likely explanation of the massively supraluminal expansion of the universe during its first instants of existence. That is that the massive, collapsed body that formed it from within the "mother" universe was of a finite size when its local density began to reach the critical value for loop generation in the densest part. Depending on the distribution of its density in hyperspace, the loop generation front would travel at arbitrarily high speed, as with any phase velocity.

2. It was shown experimentally a couple of years ago, that light does not get polarized as it travels across deep space (ie, crossing a substantial fraction of the observable universe). At the time, this was interpreted to mean that loops do not exist, because the assumed form of these loops was like some kind of hula hoops. However, I think what it means is what I have posted above - that space is not made up of 2-loops in a 3D hyperspace, but maybe of 3-loops in a 4D hyperspace.
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Re: Loop Quantum Gravity

#126  Postby DavidMcC » Feb 23, 2012 1:28 pm

... On point 1 (which was,of course, about "inflation", not "infaltion"), it follows that only a tiny fraction of the energy of the universe would have been contained in the first loops, with the rest being added as the collapsing body generating them continues to collapse.

I know this is different from the received wisdom that inflation is due to "gravity being late separating from the other forces", but I think I prefer my version, as it seems less of an arbitrary assumption.
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Re: Loop Quantum Gravity

#127  Postby DavidMcC » Mar 01, 2012 12:52 pm

... The key to the maths might be to decide on a kind of loop to integrate GR over. I have already posted that it must be a 3-loop in 4 continuous spatial dimensions, rather than a 2-loop in 3, because 2-loops would predict the polarization of light as it crosses empty space, and this has been shown not to happen.
Also, there is a problem over integration limits. Brian Greene once criticised Smolin's loop integration, but only on the basis of an assumption of complete integration over the whole 3-D continuum, which would surely render it as a classical GR solution (if anything at all), because it would leave us with no quantization of space - ie it would be new maths, but not new physics.
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Re: Loop Quantum Gravity

#128  Postby Sityl » Mar 01, 2012 8:57 pm

Does anyone have an english translation to this thread? Google fails me.
Stephen Colbert wrote:Now, like all great theologies, Bill [O'Reilly]'s can be boiled down to one sentence - 'There must be a god, because I don't know how things work.'


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Re: Loop Quantum Gravity

#129  Postby turnerj41 » Apr 04, 2012 1:59 pm

Not a physicist, and certainly not trying to annoy anyone, but I was wondering how many dimensions can exist in this LQG theory? Is it three or one or much more
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Re: Loop Quantum Gravity

#130  Postby twistor59 » Apr 04, 2012 3:04 pm

turnerj41 wrote:Not a physicist, and certainly not trying to annoy anyone, but I was wondering how many dimensions can exist in this LQG theory? Is it three or one or much more


It's specifically designed to handle the 3 space+1 time dimension that we have in general relativity. There is a specific mathematical trick (Ashtekar's new variables) that makes use of a group (SU2) that is tailored to this number of dimensions. There may be generalizations to other dimensions but I don't know of them.
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Re: Loop Quantum Gravity

#131  Postby DavidMcC » May 07, 2012 4:29 pm

twistor59 wrote:
turnerj41 wrote:Not a physicist, and certainly not trying to annoy anyone, but I was wondering how many dimensions can exist in this LQG theory? Is it three or one or much more


It's specifically designed to handle the 3 space+1 time dimension that we have in general relativity. There is a specific mathematical trick (Ashtekar's new variables) that makes use of a group (SU2) that is tailored to this number of dimensions. There may be generalizations to other dimensions but I don't know of them.


One of my main points in my initial post was that I think there needs to be at least a fourth space-like dimension to "hyperspace" if there is to be any chance of success.
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Re: Loop Quantum Gravity

#132  Postby DavidMcC » Mar 12, 2013 4:33 pm

CdesignProponentsist wrote:After this amazing discovery of the rotation speed of a supermassive black hole being very close to the speed of light I started entertaining what possible implications that may hold.

http://www.huffingtonpost.com/2013/02/27/black-hole-speed-rotation-light-supermasssive_n_2775360.html

The most obvious being that it was extremely unlikely that the black hole formed through the gradual accretion of material or collisions with other black holes. Since angular momentum is preserved the random distribution of momentum would cancel out the overall momentum of the final black hole.

Amazing to think of hundreds of thousands to billions of solar masses collapsing as a single volume.

Maybe supermassive black holes were formed in our closest sister universe:
http://www.rationalskepticism.org/physics/loop-quantum-gravity-t9397-100.html#p1211883
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Re: Loop Quantum Gravity

#133  Postby Margararita » Mar 29, 2013 3:56 am

It is a course in Quantum Mechanics, not quite what you are writing about, but somebody might be interested :) It started last week (free onine course) :)
https://www.coursera.org/course/eqp
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Re: Loop Quantum Gravity

#134  Postby kennyc » Oct 15, 2013 6:31 pm

DavidMcC wrote:
CdesignProponentsist wrote:After this amazing discovery of the rotation speed of a supermassive black hole being very close to the speed of light I started entertaining what possible implications that may hold.

http://www.huffingtonpost.com/2013/02/27/black-hole-speed-rotation-light-supermasssive_n_2775360.html

The most obvious being that it was extremely unlikely that the black hole formed through the gradual accretion of material or collisions with other black holes. Since angular momentum is preserved the random distribution of momentum would cancel out the overall momentum of the final black hole.

Amazing to think of hundreds of thousands to billions of solar masses collapsing as a single volume.

Maybe supermassive black holes were formed in our closest sister universe:
http://www.rationalskepticism.org/physics/loop-quantum-gravity-t9397-100.html#p1211883



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Re: Loop Quantum Gravity

#135  Postby incelidus333 » Oct 15, 2014 7:20 am

http://phys.org/news/2013-05-theorists- ... heory.html I haven't :smoke: studied it enough to give you my version of it, but I'll leave you an address to check out.
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Re: Loop Quantum Gravity

#136  Postby DavidMcC » Nov 05, 2015 3:01 pm

In view of recent insults by hack, I want make it clear that my cosmology is NOT an attempt to explain why the universe is the way it is, but an attempt to draw inferences from the known facts about the universe. Specifically to show, among other things, that it must logically be part of a much greater structure - the (non-MWI) multiverse that I proposed here.
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Re: Loop Quantum Gravity

#137  Postby hackenslash » Nov 05, 2015 8:43 pm

Apparently I insulted him now. Of course, those posts will be as impossible to find as all the others containing evidence of shit that people have allegedly done to Dave. This time, I insist that he support his accusations.
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Re: Loop Quantum Gravity

#138  Postby surreptitious57 » Nov 05, 2015 9:13 pm

DavidMcC wrote:
I want make it clear that my cosmology is NOT an attempt to explain why the universe
is the way it is but an attempt to draw inferences from the known facts about the universe

Am I right in thinking that referring to it as your cosmology means it is original to your self
So what then in very general terms is it and how does it differ from mainstream cosmology
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Re: Loop Quantum Gravity

#139  Postby DavidMcC » Nov 10, 2015 7:00 pm

hackenslash wrote:Apparently I insulted him now. Of course, those posts will be as impossible to find as all the others containing evidence of shit that people have allegedly done to Dave. This time, I insist that he support his accusations.

You obviously do it so often that you don't even notice it. It's all those posts that liken my posts to droppings, turds, etc.
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Re: Loop Quantum Gravity

#140  Postby DavidMcC » Nov 10, 2015 7:02 pm

surreptitious57 wrote:
DavidMcC wrote:
I want make it clear that my cosmology is NOT an attempt to explain why the universe
is the way it is but an attempt to draw inferences from the known facts about the universe

Am I right in thinking that referring to it as your cosmology means it is original to your self
So what then in very general terms is it and how does it differ from mainstream cosmology

I thought it was obvious that I was referring to my posts on pages 6 and 7 of this thread, starting here:
http://www.rationalskepticism.org/physics/loop-quantum-gravity-t9397-100.html#p1211883
I have lost count of the number of times I have posted that link.
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