Is the lack of infinities in LQG due to quantization of volume and area?

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Discussion Overview

The discussion centers around the absence of infinities in Loop Quantum Gravity (LQG) calculations, exploring whether this is due to the quantization of volume and area operators. Participants examine the implications of this quantization, including the existence of minimum measurable volumes and areas, and the potential for a natural ultraviolet (UV) cut-off in the theory. The conversation also touches on recommended literature for further understanding of LQG.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Meta-discussion

Main Points Raised

  • One participant questions why there are no infinities in LQG calculations and suggests that it may be due to the quantization of volume and area operators.
  • Another participant agrees that there are quantized values for area and volume, noting that these predictions are very small and may not have significant physical consequences.
  • Some participants discuss the availability of literature on LQG, specifically mentioning Rovelli's and Thiemann's works, and suggest that they offer complementary approaches to the subject.
  • A participant expresses a preference for Rovelli's writing style over Thiemann's, citing the latter's density and omission of important background information.

Areas of Agreement / Disagreement

Participants generally agree on the existence of quantized area and volume in LQG, but there is no consensus on the implications of these quantizations or the relative merits of the recommended texts.

Contextual Notes

Participants mention that the quantized values for area and volume are on the order of the square and cube of the Planck length, which may limit their physical implications. There are also discussions about the accessibility of certain texts and the varying levels of clarity in their presentations.

Who May Find This Useful

This discussion may be useful for those interested in Loop Quantum Gravity, particularly students or researchers seeking to understand the implications of quantization in the theory and looking for recommended literature on the topic.

zetafunction
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Why NO infinities in LQG ??

what is the reason for LQG in 4-dimension to have NO infinities when doing calculations ?? , is it due to the fact that the VOlume and Area operators are Quantizied ?

then if VOlume and Area are Quantizied, there should be a MINIMUM or quantum of area or volume we can detect and hence there would be a natural UV Cut-off , is this correct ??

by the way , a GOOD book to learn LQG ??, i have notions of SR , GR and Quantum mechanics... thanks.
 
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Exactly, There's a quantum of area and a quantum of volume, and they are both hard physical predictions of the theory. One problem is, they are so tiny (order of square and cube of Planck length) that they don't have many physical consequences.

There's a good book on LQG by Rovelli (it's not very recent, 2004, I think?), if you have access to a scientific library, check it out ... our scientific library had it. If not, there used to be a draft version available online, check it out.
 


Another major LQG textbook writer, please let me know if you disagree, I think Rovelli and Thiemann are complementary in their approaches
Introduction to Modern Canonical Quantum General Relativity
(this is available for free, Thiemann also has a slightly more recent but slightly more expensive Cambridge Monographs with the same title).
 


humanino said:
Another major LQG textbook writer, please let me know if you disagree, I think Rovelli and Thiemann are complementary in their approaches
Introduction to Modern Canonical Quantum General Relativity
(this is available for free, Thiemann also has a slightly more recent but slightly more expensive Cambridge Monographs with the same title).

Thanks, humanino. I will revise the list of useful source links here
https://www.physicsforums.com/showthread.php?p=2493787#post2493787
so that it will include the link you suggest:
http://arxiv.org/abs/gr-qc/0110034
Introduction to Modern Canonical Quantum General Relativity (free 2001 draft version)
 


Thiemann is probably smart and he knows what he's talking about, but I found his writing style remarkably dense, and he skips a lot of important background. Rovelli's text is written well enough that you can follow his logic all the way to the end of the book.
 

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