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Can anyone describe Emergent Space 
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#1
Jun3012, 11:34 AM

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I hesitate to even ask this question, because I feel that it is unrealistic of me to expect anyone here to take the time and effort to attempt to answer it. But my mind is so far gone at this point that I'll accept anything.
But if anyone wants to try, I would appreciate it. I only have a ninth grade education so anything too complicated is likely to go right over my head, but over the years I've gotten to be quite good at visualizing how I understand the intricacies of quantum physics to work, but I'm struggling with getting a clear visualization of emergent space. I have no idea of the proper terminology to use, but about the best that I can do is to visualize reality as a sort of universal probability matrix (?) in which waves interact to form what I conscious observer would perceive as reality. So space emerges from what cannot really be described as an underlying three dimensional space, but rather a set of interactions. I realize that this sounds ridiculous, and I don't have any idea of how to relate this to classical physics. But this is what happens when I try to visualize things that I really don't understand. But somewhere I read about "emergent space" and my mind just loves a puzzle, and so off it goes. I'm hoping that some others here will have minds that do the same thing, but will have a much clearer understanding of "emergent space" and can at least get me back on the right track. Anyways, thanks 


#2
Jun3012, 11:38 AM

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#3
Jun3012, 12:01 PM

P: 123

But thanks for the response. About as precise as I can be is, what is meant by "emergent space"? 


#4
Jun3012, 12:02 PM

P: 915

Can anyone describe Emergent Space
Here are a few ideas. No one knows what is right. 1. (more) Spacetime could emerge out of out of a multiplicity of relatively simple interactions. 2. not only can spacetime bend/curve/twist and turn.......timespace might not be as fundamental as we thought 3. there could be more dimensions within timespace itself that we cannot visualize however which we can construct/infer via what is happening on the "surface" (3D). 


#5
Jun3012, 12:12 PM

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The most famous example of emergent space is string theory's conjectured AdS/CFT or gauge/gravity duality.
http://homepage.mac.com/photomorphos...ments/qpdf.pdf http://physics.aps.org/articles/v2/79 There are also examples of emergent geometry which may be related to the AdS/CFT conjecture. http://arxiv.org/abs/1106.1082 


#6
Jun3012, 12:24 PM

P: 724

How does one visualize adding a third dimension to a 2dimensional 'surface' that obviously has no physical reality?



#7
Jun3012, 01:10 PM

P: 123

atyy, thanks, those were indeed what I was looking for. I'm still not clear on how our "reality" would emerge from the underlying matrix though. I have always tried to visualize things as waves, ever since hearing Richard Feynman describe reality in terms of a blind man in a swimming pool, who visualized the world by means of the waves striking him. But when I try to visualize an underlying matrix from which our 3D reality would arise, I just can't get it to make any logical sense, it's just a mishmash of waves. I can't get anything except noise. The only way to make it make sense is by introducing a conscious observer, and I really hate to have to do that. To me that's like invoking God when you encounter some inexplicable observation. But you have gotten my thought processes moving again, so give me a bit more time and I'll see what I can come up with. . 


#8
Jun3012, 03:10 PM

P: 123

!!!!!Got It!!!!!
Nothing like a nice bike ride to get the mind working. Give me a few minutes to write it down before I forget most of it. Hint: It ended up looking a lot like what I imagine Mtheory to look like. 


#9
Jun3012, 05:00 PM

P: 123

Generally when I can't wrap my head around something there are only two solutions, go take a nap, or go do something monotonous. Either one seems to get my brain working again. So I decided to go for a bike ride.
I hadn't even gotten a mile when it struck me what an idiot I was. As I said in a previous post, I like to envision things as waves, but when envisioning emergent space I just couldn't get the waves to form any coherent pattern, in fact, there really was no reason for there to be any waves at all. Which meant that I had to invoke a conscious observer as a catalyst for the waves. Then it occurred to me, what if I take two of these vibrating lumps of I don't know what, and run them together. Which of course led to one of those Tah Dah, you're an idiot moments. They're branes you dummy. It's bloody Mtheory. Of course it's always more satisfying to discover something on your own then to read it in a book somewhere. It's like, wow, maybe I'm not an idiot after all. But back to emergent space, it's not the branes themselves that are the emergent space, but it's what happens when you run two of them together. I'll try to keep this simple. (Imagine that, me telling you guys that I'm gonna keep it simple) When you run two branes together you get a bubble that forms between the two branes. It is this bubble that is the emergent space. Think of it like entangling two particles, when you run two branes together there is a connection, a field per se that is created between the two branes, and it is this field that we experience as three dimensional spacetime. What we see is in some way a reflection of the branes from which the bubble is formed, and the laws that govern the branes, influence and perhaps dictate the laws that govern our three dimensional spacetime. Thus gravity is a consequence of the laws governing the branes, which then directly influences the shape and movement within the field. While it's possible to imagine gravity as a consequence of such a system, it's difficult to see how the speed of light relates to, or emerges from, such a system. At least I don't see the relationship yet. Of course my bike rides tend to be long enough that my mind has time to consider what the potential objections to such a theory might be. Like how does this explain the fact that everything in the universe appears to be moving away from us? In what way does being a point "Inside" an expanding balloon differ from being a point on the surface of the balloon. If we really are in an emerging space between two branes, then what should such an expansion look like? And what caused the residual heat from the big bang? For now I'm just happy to have some way of envisioning emergent space. And actually I rather like it. It leads to some quite interesting possibilities. So what do you guys think, have I got at least some handle on what's meant by "emergent space"? 


#10
Jul112, 02:33 AM

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Let's use a very simple example: what is an emergent surface of water?
Describing 'water' by QM does not mean to quantize the NavierStokes equations b/c the continuous fluid has the wrong d.o.f. What we need are the fundamental degrees of freedom, the atoms. The 'water' and its surface emerge from an approximation. In the same sense emergent spacetime means that the underlying d.o.f. are different from classical spacetime  possibly strings & branes, the CFT w/o gravity in AdS/CFT, spin networks in LQG, ...  and that classical spacetime emerges e.g. via some averaging procedure 


#11
Jul1012, 03:52 PM

P: 5,632

This discussion might be of interest to those reading this one:
emergent Gravity http://www.physicsforums.com/showthr...53#post3984153 The author of the subject paper describes how degrees of freedom and holographic equipartition leads to the emergnce of space and gravity.... 


#12
Jul1012, 06:44 PM

PF Gold
P: 342

I really like the paper: "Background Independent Quantum Field Theory and the Cosmological Constant Problem" by Olaf Dreyer  http://arxiv.org/pdf/hepth/0409048.pdf. A very interestng read involving fairly basic ideas.



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