Is the graviton the only thing to find in LQG?

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wabbit

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Ah yes that's much clearer thanks. It wasnt really linguistic confusion on my part. Just plain confusion : )
 

MTd2

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The idea: start by simple a rule, and get patterns out of this. Like cellular automata or Mandelbrot, you get nice stuff that you cannot see by just inspecting.
So, you get LQG as it is and somehow, you get all the other particle fields, "magically". You just have to seek the correct approximation to see and find that that. Until now, I only saw the search for the graviton, the classical GR, but why not the rest, all fields? Not talking about extra rules about how edges should connect, but just the very basic theory.
 

wabbit

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From my limited laynan perspective I can only add that there seems to be quite a bit of research that links spacetime and other field in different ways (marcus' threads provide many pointers) though perhaps so far not in the way you'd want : ). Also I don't really see an obvious reason why spacetime should be the fundamental field from which all others emerge as you seem to expect, but the fact that I don't see it certainly doesn't mean it isn't there. I'll leave it to others to provide better grounded answers.

Edit : I say spacetime you say graviton - that's just different aspects of the same object, the gravitational field.
Edit2 : The pedestrian answer to your "why not" would be "because LQG is by design and purpose Quantum GR, so its expected to find GR and gravitons there, but not by necessity anything else"
 
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MTd2

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"because LQG is by design and purpose Quantum GR, so its expected to find GR and gravitons there, but not by necessity anything else"
That's actually the thing I asked. Though my rhetoric was lost.
I was kind of thinking in Torsten's work. What do you think? Marcus?
 
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I suspect that to conceive of the consequences of Loop and such QG one has to think more deeply than what I see in MTd2's opening post.
Just to give an example of what I mean, here is a conceptual exploration: suppose that geometry consists of events--geometric interactions occurring in a present. (see Gambini&Pullin http://arxiv.org/abs/1502.03410 http://arxiv.org/abs/1502.03831 )
Suppose, as Rovelli Vidotto http://arxiv.org/abs/1502.00278 suggested, that the presence of a smallest measurable angle, or equivalently, a cosmological curvature constant Λ,
causes spatial and temporal geometric interactions to be discrete occurring in small quantum hops shakes spasms or repercussions to speak figuratively.
This then affects how we think of spacetime--the habitat of other quantum fields---as a growing heap of events where only the surface is interactive and actual---the past events can no longer be interacted with and so no longer exist. Gambini and Pullin estimate the thickness of the live layer for us.
So then the consequence is simply that we have to rebuild the theory of quantum fields in this new spacetime geometry residence. In terms of interaction events that so to speak inhabit the geometric ones. In this world there are only events and fields describing which are possible. No little pebbles.
I'm curious about this: how does the existence of this "surface" layer jive with Relativity's idea that there is no absolute "present"? Wouldn't that mean different observers would disagree on how the "heap" has grown?
 

wabbit

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I'm curious about this: how does the existence of this "surface" layer jive with Relativity's idea that there is no absolute "present"? Wouldn't that mean different observers would disagree on how the "heap" has grown?
In my view it certainly does. The "evolving surface layer" is a quantum version of a 3+1 foliation in GR, associated with a class of observers.

Also of course the view of "a present" or "the passage of time" is, here as in GR, a matter of perspective, one can equally well adopt the "unchanging spacetime" viewpoint.
 
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I enjoyed reading this thread.
 

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