Quantizing GR: Exact Quantum Loop Results in General Relativity

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Discussion Overview

The discussion centers on a paper proposing a new approach to quantizing General Relativity (GR) through exact quantum loop results. Participants explore the implications of this approach, its potential to resolve issues in quantum gravity, and its relationship to existing theories such as string theory and loop quantum gravity. The conversation includes technical aspects, theoretical implications, and speculative interpretations of the findings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants express skepticism about the claim that the paper quantizes GR effectively, with one noting that the renormalization procedure allegedly "washes out" black holes.
  • There is a suggestion that for sufficiently small mass, black holes may not have horizons, which could address issues related to massive point particles being black holes.
  • One participant mentions that the author uses Reuter's "asymptotic safety" calculations, which have faced criticism from Jacques Distler.
  • Another participant highlights that the paper claims to introduce a UV finite theory of quantum general relativity, which could potentially solve outstanding problems in the field.
  • Some participants discuss the implications of the propagator's form suggesting that gravity may behave repulsively in the UV regime, referencing similar results from other researchers.
  • There is a clarification about "vanilla QFT," indicating it refers to standard quantum field theory techniques without modern complexities.
  • One participant raises concerns about the validity of perturbation theory in addressing UV problems in quantum gravity.
  • Another participant questions the implications of the paper's claims on the information problem related to black holes.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the validity of the claims made in the paper. Multiple competing views remain regarding the implications of the proposed approach to quantizing GR, particularly concerning black holes and the use of asymptotic safety.

Contextual Notes

Some participants note limitations in understanding the implications of the paper, particularly regarding the definitions of black holes and the assumptions underlying the proposed renormalization procedure. There is also mention of unresolved mathematical steps related to the claims made.

Who May Find This Useful

This discussion may be of interest to researchers and students in theoretical physics, particularly those focused on quantum gravity, general relativity, and quantum field theory.

  • #31
Chronos said:
GR might be the answer. GR has accumulated a great deal of credibility via observational evidence. I do not object to string theory - only to theories that make no testable predictions.

I don't know what you're intending to contribute here, Chronos. Sauron's point is that this Ward result depends on GR being "asymptotically safe", which there is some evidence (challenged by Distler) for, and the recent work on supergravity suggests a possible noncontroversial variant to Ward's approach. But precisely because GR is what it is, it would be good if he could stay with it.

BTW I emailed Professor Ward yesterday, requesting some update, and we'll see what, if anything he says himself.
 
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  • #32
Alright, I am summoning this thread from the dead. I hope all participants can join this again.

Ward took part in the Asymptotic Safety conference. Clearly, the other participants were not aware of his approach, not even Smolin. The impression I had of Ward it is that he is extremely clear. Carrasco was in disbelief because that was too good to be true. Weinberg took notes all the time, but didn't ask anything.

If Ward is wrong, well, no one there pointed out any.

Here is the link for the show:

http://pirsa.org/C09025
 
  • #33
Alright, I am summoning this thread from the dead. I hope all participants can join this again.

Not entirely possible. At least one cannot join again; the owner of this thread is, unfortunately, deceased.
 
  • #34
MTd2 said:
I hope all participants can join this again.
That would be possible (as far as I know) except in one case. selfAdjoint was one of the finest people I've ever known online.

His influence as PF mentor, and as a deeply thoughtful active participant, is one of the reasons PF is a great place. He died in 2007.

So we move on to the Asymptotic Safety conference the had this month at Perimeter.
Here is the link for the show:

http://pirsa.org/C09025

You and I already agreed that Ben Ward's paper seemed too good to be true. But the circumstances add respect and credibility. His got to talk on the first day. Percacci, the organizer, is very solid and he put Ward near the top of the line-up. Ward's presentation was convincing. He also sat through the other talks on all three days and was alert and asked questions in a calm friendly way. As you pointed out his background is places like Princeton and SLAC Stanford.

Circumstantially, everything looks good, so what's the "catch"?
 
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  • #35
Oh, I am sorry. I didn't know he died. :S Damn, I FEEL SO EMBARRASSED.

I sent him an email 10 min ago. Here is the content. I hope he answers:

Dear Prof. Ward,

I watched you talk on the Asymptotic Safety, online:
http://pirsa.org/C09025
I was so impressed with your proof that I could not avoid to ask you a few questions.

You showed, during your talk, that you found a safe point in the UV, and that it should be related to other approaches like Reuter's and his collaborators. But do the connection to the A.S. of EQG (Einstein Quantum Gravity) beyond that? What I mean is, A.S. has a kind of space phase of parameters (/\, G) in which the sink point of the system is in ffact the UV fixed point of the theory, so can you show that your resume method also display a similar phase space? Can you also show similarities of the infinite coupling constants stabilizing around a finite dimension, like EQG?Thanks for reading my message.Best Regards,Daniel.
 
  • #36
I'm a physics undergrad with just one class to go. So forgive my if this is a dumb question. Is he just making a QM model for gravitational waves (by quantizing them into gravitons) or does it extend to crazy non-wavy, non-linear spacetimes?
 
  • #37
crazy non-wavy, non-linear spacetimes is a little vague
 

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