Another way to test LQG found by Major

[marcus]

This paper was spotted by MTd2.

In it, Seth Major, argues that the quantum GEOMETRY of LQG implies quantum effects on the ANGLE of scattering of particles. But scattering angles can be observed and measured in the large---even if they originate in events too small to be themselves observed. So this offers observational leverage, a kind of magnification. If LQG is true, Major argues, there will be measurable quantum effects on certain angles which can be produced in lab.

Therefore, Major's title suggests, the paper belongs in the QG Phenomenology (testing) department.

http://arxiv.org/abs/1005.5460
Shape in an Atom of Space: Exploring quantum geometry phenomenology
Authors: Seth A. Major
(Submitted on 29 May 2010)
"A phenomenology for the deep spatial geometry of loop quantum gravity is introduced. In the context of a simple model, an atom of space, it is shown how purely combinatorial structures can affect observations. The angle operator is used to develop a model of angular corrections to local, continuum flat-space 3-geometries. The physical effects involve neither breaking of local Lorentz invariance nor Planck scale suppression, but rather reply on only the combinatorics of SU(2) recoupling. Bhabha scattering is discussed as an example of how the effects might be observationally accessible."

Sabine Hossenfelder, who has posted some here at PF Beyond in earlier years, has organized a weeklong workshop in QG Phenomenology for this summer. We should watch the list of people who plan to participate. Some of the speakers have already submitted abstracts of their talks, which are online. Ideally Major's idea will be among those reviewed at the workshop, and will get plenty of scrutiny. Major is an old LQG hand, who was writing QG papers already in the 1990s, so he may have a solid idea. If it is accepted as valid it will be quite exciting to watch develop. But I personally can not estimate the chances.

Major's analysis is based on the "new look" formulation of LQG presented in Rovelli's recent paper. So that would presumably be the form of Loop most directly testable in the way he proposes.

http://arxiv.org/abs/1004.1780
A new look at loop quantum gravity
Carlo Rovelli
15 pages, 5 figures
(Submitted on 11 Apr 2010)
"I describe a possible perspective on the current state of loop quantum gravity, at the light of the developments of the last years. I point out that a theory is now available, having a well-defined background-independent kinematics and a dynamics allowing transition amplitudes to be computed explicitly in different regimes. I underline the fact that the dynamics can be given in terms of a simple vertex function, largely determined by locality, diffeomorphism invariance and local Lorentz invariance. I emphasize the importance of approximations. I list open problems."

This is Seth Major's reference [7] where he says on page 3 "...the angle operator is simply defined in the combinatorial framework of [7]..."

 

[AndyW]

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Dear MTd2,

Thank you for bringing this paper to our attention. Major's argument about the quantum effects on the angle of scattering in loop quantum gravity is certainly intriguing. As you mentioned, if this theory is true, it would offer a new way to observe and measure quantum effects in the laboratory.

The fact that Major's analysis is based on the "new look" formulation of LQG presented in Rovelli's paper also adds credibility to his argument. It is always exciting to see theories being put to the test and I agree that it would be interesting to see Major's idea being reviewed at the QG Phenomenology workshop this summer.

However, as with any new theory, it is important to approach it with caution and subject it to rigorous scrutiny. Only through thorough testing and validation can we determine the validity of Major's argument and its potential impact on our understanding of quantum gravity.

I will definitely keep an eye out for further developments in this area. Thank you again for bringing this paper to our attention.