Criticism of LQG - What do we miss?

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The discussion critiques Loop Quantum Gravity (LQG) by highlighting its reliance on a specific topology (M3*R) and questioning the exclusion of other topological sectors, which may limit the theory's physical relevance. Concerns are raised about the choice of SU(2) as the gauge group, suggesting it may lead to a "landscape problem" and that LQG's treatment of spacetime and matter lacks a unified approach. The role of the cosmological constant and the implications of the holographic principle are also examined, indicating that LQG does not adequately address these fundamental aspects. Additionally, the conversation touches on the need for a more comprehensive understanding of renormalization in the context of quantum gravity. Overall, the thread emphasizes the necessity for LQG to evolve and incorporate broader theoretical frameworks to remain relevant in the field of quantum gravity.
  • #31
good point!
 
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  • #32
marcus said:
I think that is probably the reason that Ashtekar, who is longterm friends with Penrose and must have heard Penrose talk about entropy and bounce on countless occasions, has never seemed worried by Penrose's thermo objection. Admittedly this is not spelled out rigorously, but it's in the context of a novel situation and I find that, to me, intuitively it makes sense.

I have always thought it intuitive that gravity was driving entropy (and time itself really). It is very interesting to see this pointed out with respect to Ashtekar's perspective, especially the sign reversal for entropy itself when gravity's sign changes.

It also seemed to me that a bounce would "fix" entropy so I have favored that idea over a pure big bang. It certainly answers the question of why the universe got to be so ordered. It will be interesting to see if this idea holds up under observations over the next decade or so.

Thank you marcus.
 

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