Would asymptomatic safe gravity grow weaker like QCD?

  • Context: Graduate 
  • Thread starter Thread starter kodama
  • Start date Start date
  • Tags Tags
    Gravity Qcd
Click For Summary

Discussion Overview

The discussion revolves around the concept of asymptotic safety in quantum gravity and its potential similarities to quantum chromodynamics (QCD), specifically whether gravity could exhibit a behavior of growing weaker at higher energies, contrasting with classical general relativity predictions. Participants explore theoretical implications and the relationship between gravity, QCD, and concepts like the holographic principle.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that if gravity is asymptotic safe like QCD, it could grow weaker at higher energies, challenging classical GR predictions.
  • Others argue that for a system to be asymptotic safe, it must approach a UV fixed point at high energies, which may imply certain constraints on interaction strengths.
  • A participant references a review paper suggesting that in an asymptotic safe quantum gravity theory, the dimensionful Newton constant could vanish while the cosmological constant diverges at high energies.
  • There is uncertainty expressed regarding the implications of the holographic principle in the context of asymptotic safety and whether it could be compatible with weak interactions at high energies.
  • Some participants question the validity of the holographic principle itself in relation to these theories.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether gravity behaves like QCD at high energies, and multiple competing views remain regarding the implications of asymptotic safety and the holographic principle.

Contextual Notes

Discussions include complex theoretical frameworks and assumptions about non-perturbative aspects of gravity, which remain unresolved. The relationship between dimensionless and dimensionful parameters in the context of asymptotic safety is also noted as a point of contention.

kodama
Messages
1,083
Reaction score
144
QCD is asymptomatic safe well known to grow weaker at higher energies.

if gravity is also asymptotic safe would it grow weaker at higher energies instead of stronger as predicted by classical GR?

if not, is it possible there is a quantum gravity theory that like QCD grows weaker at higher energies?

i.e at low energies it is described as GR, but at high energies it is QCD-like and grows weaker

QCD-gluons and gravitons are non-abelian self-interacting bosons
 
Physics news on Phys.org
As far as I understand the proposal, what one requires is that the system approaches a UV fixed point at high energies. The fixed point could be non-interacting but generically I would expect some order one dimensionless interaction strength. Although I haven't thought carefully about it, I would guess that in the case of gravity one could argue against weak interactions at high energy as incompatible with the holographic principle.

EDIT: More generally, I don't understand much about how non-perturbative aspects of gravity - black holes, holography, etc. - are supposed to work in the asymptotic safety scenario.
 
  • Like
Likes   Reactions: kodama
kodama said:
..
if not, is it possible there is a quantum gravity theory that like QCD grows weaker at higher energies?
In partial answer, in the most recent review paper I know of on AsymSafe QG, on page 36 it says
==quote http://arxiv.org/pdf/1202.2274.pdf ==
Hence for k → ∞ and d > 2 the dimensionful Newton constant vanishes while the cosmological constant diverges.
==endquote==

The parameter k is like a wave number, an inverse length. So for low k (the IR or coarse scale) the Newton constant G and the cosmo constant Λ are the usual G and Λ.

A commonly discussed form of the theory concerns dimensionless versions gk and λk which approach a fixed point g*, λ*

As for the dimensionful versions, Gk = gk/k2 goes to zero as g*/k2 and Λk = λkk2 diverges as λ*k2
 
  • Like
Likes   Reactions: kodama
Physics Monkey said:
As far as I understand the proposal, what one requires is that the system approaches a UV fixed point at high energies. The fixed point could be non-interacting but generically I would expect some order one dimensionless interaction strength. Although I haven't thought carefully about it, I would guess that in the case of gravity one could argue against weak interactions at high energy as incompatible with the holographic principle.

EDIT: More generally, I don't understand much about how non-perturbative aspects of gravity - black holes, holography, etc. - are supposed to work in the asymptotic safety scenario.

maybe the holographic principle is wrong?
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 16 ·
Replies
16
Views
4K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 18 ·
Replies
18
Views
4K
  • · Replies 72 ·
3
Replies
72
Views
10K