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MTd2
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Does anyone have any ideas? Marcus, do you have?
MTd2 said:Does anyone have any ideas? Marcus, do you have?
marcus said:The video and slides of Carlo Rovelli's talk at Strings 2008 provides a good introductory overview of LQG.
Here are the links:
Video:
http://cdsweb.cern.ch/record/1121957?ln=en
Slides:
http://indico.cern.ch/getFile.py/access?contribId=30&resId=0&materialId=slides&confId=21917
MTd2 said:On page 28 of the slides (14 of the pdf), he says matter fields can be achieved by braidings...
marcus said:He describes the usual way (not braiding) by a label on the spin network.
MTd2 said:But, wouldn't adding new lebels like adding new loops? ...
marcus said:I don't see the similarity.
MTd2 said:... What is the meaning adding new labels then?
MTd2 said:... What you are saying it is that Rovelli wants to give new labels to the vertexes? ...
marcus said:If you would simply just read the PDF page that you already referred to you would see that is not the case!
MTd2 said:... For instance, in the book you mentioned, there is not a single word "label" there...
Anyway, if you look at section 7.2.4, I don't understand why would that be any different from the definition I gave.
marcus said:I opened my copy of Rovelli's book (Quantum Gravity) to page 19
In the half page following equation 1.11, I counted six occurrences of the word "label".
And an intuitive description of the significance of the labels on the network.
MTd2 said:Coin,... in the case of a loop, there is intermediary position to speak of, just the relative position of nodes. I guess the distance between nodes is a quantized quantity dependent on the spins that bounds the loop, pretty much like the energy of an electron in a hydrogen atom depends on the quantum numbers associated with orbital energy and angular momentum.
MTd2 said:Marcus, what about the non trivial topologies created by bradings? That should at least create particles.
MTd2 said:...BTW, is there a way to create and destroy links between vertex?
marcus said:I assumed you knew that when I wrote my previous post. There are standard network "local moves" by which a new node is created or an old node removed, and by which nearby vertices can be reconnected differently.
MTd2 said:Do those moves naturaly exist within LQG? What I mean is, that in small networks with lots of loops per nodes, you are going to create physical dimensions higher than 4.
tom.stoer said:As far as I can remember the braids need framed graphs; is that correct?
Framing was to an quantum deformation of the SU(2) symmetry group; correct?
The deformation was something like q = 2 pi / G Lambda, so it works only with a cosmological constant; correct?
To formulate a theory with braids Smolin et al. had to put the cosmological constant in by hand; but in the meantime Smolin tries to derive a cosmological constant from LQG. So I think one approach must be wrong!
...
MTd2 said:...put as many links as it is desired between vertexes, one for every field, the fundamental one being the gravitational.
marcus said:They do not run parallel links between the same pair of nodes, one link for every field. Instead they keep the object, the graph, as simple as possible.
Instead of running a new link, they simply add a label to the existing link, as necessary.
:rofl:MTd2 said:... die in ignorance or lqg (wan yidun's nick on this forum) or anyone else will have to help me! Oh damn, I feel awful. And Marcus hates me now.