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Loop quantum gravity 
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#1
Apr207, 01:26 AM

P: 7

In loop quantum gravity it is assumed that space is not infinitely divisible. The nodes are not space . Actually they are the infinitely divisible part of a matter. The distance between the nodes are not discrete. The distance between the nodes may be 1.5 Planck's length or 2.5 planck's length and so on. So quantization of space is not allowed even in loop quantum gravity. And the the distance between loops are also not multiples of Planck's lenght. My conclusion is that space is infinitely divisible and matter is not.



#2
Apr207, 01:47 AM

P: 2,043




#3
Apr207, 02:52 AM

P: 7




#4
Apr207, 03:00 AM

P: 7

Loop quantum gravity
LPG is a promising theory. Nodes forms loops. Loops forms branes. Branes form the foam. Foams form the fermions and bosons as per my prediction. Matter cannot be formed directly from the spacetime curvature. How from nothing you will use GR and get matter. Common sense suggest that mass and space are seperate entities. In LQG, the nodes are masses and the space between them is really the three dimensional space that we are observing in day to day life. This is a serious violation of GR. GR gets matter out of space and time. It is highly impossible. Compared to GR LQG is promising theory and the only thing is interpret its results. This is the right time to take a deviation from GR.



#5
Apr207, 03:03 AM

P: 7

LQG weaves the matter (node) and space (loops) in a nice way to form foams. These foams are nothing but our bosons and fermions. So LQG does not violate the standard model and at the same time if interpret correctly the LQG, then it will form an alternate to GR in macroscopic scale.



#6
Apr207, 03:04 AM

Sci Advisor
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PF Gold
P: 4,132

Beyond the Standard Model http://www.physicsforums.com/forumdisplay.php?f=66 is the appropriate place for this discussion. 


#7
Apr207, 03:04 AM

P: 7

These bosons and fermions in turn form the universe that we see.



#8
Apr207, 03:05 AM

P: 7

The need for background field and ghost fields should be eliminated



#9
Apr207, 09:45 AM

Astronomy
Sci Advisor
PF Gold
P: 23,227

Hello Ravi, welcome to PF
since you are interested in LQG (which these days covers a variety of different but related approaches to quantum geometry/quantum gravity/cosmology) let me mention a few things happening in the field Earlier this year there was an important workshop (The Quantum Nature of Spacetime Singularities) at the Kavli ITP at Santa Barbara. It went on for the better part of 3 weeks and video of the main talks is available on line. Abhay Ashtekar was there and a member of his group at Penn State, Martin Bojowald, was a coorganizer of the workshop. I think it is fairly obvious that the LQGcommunity (particularly those doing the cosmology spinoff LQC) are at the forefront in dealing with the big bang and black hole singularities, and some of the stringcommunity are evidently interested in trying to understand what's going on in that area. Hence setting up the workshop and inviting major LQGcommunity people. You may be interested purely in the theory, and not in the activities of the people, which is fine. But if you are interested in the current LQG "scene", then we could share news and notes. Another defining event for the LQGcommunity this year is the twoweek school now in progress in Poland. It is called QGQG1. "The first quantum gravity quantum geometry school" A series of 8 or 9 lectures on LQG proper is being given by Thomas Thiemann. There are other series of lectures on related but different approaches. Another defining event was the European Science Foundation (ESF) setting up last year the QGQG network, which funds such things as this QGQG school and workshops and conferences. the distinguishing thing about the LQGcommunity research is the quantum geometrical approach to gravity. Instead of a graviton or something else moving in a fixed background geometry, the geometric ambience is itself a dynamic entity (as in GR itself). So saying QGQG is a way of evoking background independent, nonperturbative, largely nonstring approaches to QG. So the ESF is recognizing this and putting money into it. Another definining event for the LQGcommunity will be the publication this year (if it goes as planned) by Cambridge U. Press of the book edited by Dan Oriti called "Approaches to Quantum Gravity, Towards a New Understanding of Space Time and Matter". there are 10  20 authors involved, mainly from the LQGcommunity. Quite a number of different approaches represented. We have discussionthreads about some of these happenings here at "Beyond" forum. Hope you will contribute your own thoughts or news items. Again welcome. 


#10
Apr207, 10:29 AM

Astronomy
Sci Advisor
PF Gold
P: 23,227

I will get some links for these things later as time permits. (also you may also have seen the things on the web that I am talking about)
Oh, also there is the main LQGcommunity conference Loops '07 in Morelia in July. It will be interesting to see what is on the program of invited talks and how the conference shapes up. Do you happen to know of Ganashyam Date? He has raised several young LQG researchers but then there is a kind of braindrain that happens where they get drawn to BerlinPotsdam (Albert Einstein Institute) and to Penn State. Besides G. Date I can't think of anybody in India right now. maybe you know of more. UPDATE: by a nice coincidence not long after I wrote this mentioning Ganashyam Date I discovered that he has just posted a new paper http://arxiv.org/abs/0704.0145 Singularity Resolution in Isotropic Loop Quantum Cosmology: Recent Developments Ghanashyam Date (Submitted on 2 Apr 2007) "Since the past Iarge meeting in December 2004, new developments in loop quantum cosmology have taken place, especially with regards to the resolution of the Big Bang singularity in the isotropic models. The singularity resolution issue has been discussed in terms of physical quantities (expectation values of Dirac observables) and there is also an 'improved' quantization of the Hamiltonian constraint. These developments are briefly discussed. This is an expanded version of the review talk given at the 24th IAGRG meeting in February 2007." 


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