Register to reply 
Lqg is still local lorentz invariant? 
Share this thread: 
#1
Dec2908, 12:25 PM

P: 44

How i can see the right lorentz invariance in lqg?



#2
Dec2908, 05:30 PM

Astronomy
Sci Advisor
PF Gold
P: 23,203

http://arxiv.org/abs/grqc/0205108 Reconcile Planckscale discreteness and the LorentzFitzgerald contraction Carlo Rovelli, Simone Speziale 12 pages, 3 figures (Submitted on 25 May 2002) "A Planckscale minimal observable length appears in many approaches to quantum gravity. It is sometimes argued that this minimal length might conflict with Lorentz invariance, because a boosted observer could see the minimal length further Lorentz contracted. We show that this is not the case within loop quantum gravity. In loop quantum gravity the minimal length (more precisely, minimal area) does not appear as a fixed property of geometry, but rather as the minimal (nonzero) eigenvalue of a quantum observable. The boosted observer can see the same observable spectrum, with the same minimal area. What changes continuously in the boost transformation is not the value of the minimal length: it is the probability distribution of seeing one or the other of the discrete eigenvalues of the area. We discuss several difficulties associated with boosts and area measurement in quantum gravity. We compute the transformation of the area operator under a local boost, propose an explicit expression for the generator of local boosts and give the conditions under which its action is unitary." 


#3
Dec3008, 06:44 AM

P: 44

yes but i can't understand how i can split lorentz group.
namely how is possible that so(1,3)~so(3)X Something. thanks 


#4
Jan709, 04:32 AM

Sci Advisor
P: 4,590

Lqg is still local lorentz invariant?
You are right, LQG is not Lorentz covariant. Time and space are not treated in the same way. In particular, in LQG (just as in any canonical approach to quantum gravity) there is a problem of time, while there is no problem of space. Even if you accept the solution of that problem in terms of a relational time, it is still true time is not treted in the same way as space.



#5
Jan1609, 09:42 PM

P: 145

Shouldn't this then lead one to the conclusion, that LQG is dead?



#6
Jan1609, 11:03 PM

PF Gold
P: 1,961

No, because
1.length is a state that arises as a an observable that is bounded below by the plack scale. 2.lorentz invariance arises as an average of the observables at larger scale. Thus, length is meaningless by itself, all that exists are observables in a "nothingness", which by interacting each other, make space time appears. Demystifier is right in what he says, because in the nothingness, there is a kind of absolute QM tick tack, thus, time is a paramter in this case, not a dimension. Time as a dimension shows up as a kind of constrain between the observables. 


#7
Jan1609, 11:17 PM

P: 2,828




#8
Jan1709, 02:04 AM

P: 478




#9
Jan1709, 04:13 AM

P: 83

Can anyone explain me how the predicted dependence on frequency for the speed of light is related to the Lorentzinvariance issue?



#10
Jan1709, 02:56 PM

P: 2,828

On Loop Quantum Gravity Phenomenology and the Issue of Lorentz Invariance 


#11
Jan1709, 08:25 PM

P: 478

Is it possible that the Lorentz violating effects only occur at the Planck scale? 


#12
Jan1709, 09:17 PM

P: 2,828




#13
Jan1909, 01:13 AM

P: 478




#14
Jan1909, 06:43 AM

P: 44

i would like remember that the quantum field theory is model dependent too. and then?



#15
Jan1909, 06:54 AM

Sci Advisor
P: 4,590




Register to reply 
Related Discussions  
Lorentzinvariant electric charge?  Quantum Physics  51  
Lorentz invariant mass of electromagnetic field?  Classical Physics  9  
E.H is a Lorentz invariant, when is it different from 0 ?  Classical Physics  0  
Lorentz invariant  Special & General Relativity  4  
Difference between lorentz invariant and lorentz covariant  Introductory Physics Homework  4 