Invitation to LQG-Smolin-just out

[marcus]

Invitation to LQG---Smolin---just out

http://arxiv.org/hep-th/0408048

"An invitation to loop quantum gravity"
Lee Smolin
50 pages, to be submitted to Reviews of Modern Physics

---quote from abstract---
We describe the basic assumptions and key results of loop quantum gravity, which is a background independent approach to quantum gravity. The emphasis is on the basic physical principles and how one deduces predictions from them, at a level suitable for physicsts in other areas such as string theory, cosmology, particle physics, astrophysics and condensed matter physics. No details are given, but references are provided to guide the interested reader to the literature. The present state of knowledge is summarized in a list of 35 key results on topics including the hamiltonian and path integral quantizations, coupling to matter, extensions to supergravity and higher dimensional theories, as well as applications to black holes, cosmology and Plank scale phenomenology. We describe the near term prospects for observational tests of quantum theories of gravity and the expectations that loop quantum gravity may provide predictions for their outcomes. Finally, we provide answers to frequently asked questions and a list of key open problems.
---end quote---

 

[sol2]

Thank you Marcus. I have come to enjoy Smolin's summations, because he is flexible to entertain all possibilties even though he is coming at it from a loop approach. Smolin included Penrose as one of the three.


Lubos contributing to wikpedia for Loop is another good example that fellows can do for us people who are trying see what roads to quantum gravity materialize.

And there are published predictions for observable Planck
scale deviations from energy momentum relations[22, 23] that imply predictions for experiments in progress such as AUGER and GLAST. For those whose interest is more towards formal speculations concerning supersymmetry and higher dimensions than experiment, there are also results that show how the methods of loop quantum gravity may be extended to give background independent descriptions of quantum gravity in the higher and super realms[31]-[35]. It thus seems like a good time for an introduction to the whole approach that may help tomake the basic ideas, results and methods accessible to a wider range of physicists.

http://arxiv.org/PS_cache/hep-th/pdf/0408/0408048.pdf

Of course it's still theorizing in bold by association? But trully, accepting the bulk as gravitons is not so far fetch?

 

[marcus]

I will emphasize another line from the paragraph you just quoted, Sol:

"...It thus seems like a good time for an introduction to the whole approach that may help tomake the basic ideas, results and methods accessible to a wider range of physicists."

this "Invitation to LQG" article is written explicitly for trained physicists in other areas who may be thinking of crossing over and getting involved in Quantum Gravity research

this is why he lists the "Open Problems" at the end. A research professional making a career decision like moving into a new line of research, one of the first things he or she wants to know is what are the next set of problems to work on.

Also the "FAQ" section is aimed at answering the questions that physicists from other fields typically ask.


It is interesting to read this article in the context of its intent.
It signals that the field is gaining maturity----he lists the many known results---and that it is approaching testing, with plenty to do going forward to the upcoming opportunities to test. It signals there's a lot of work to be done---papers to be written.

He stresses the urgency of getting the predictions published before 2007, when GLAST goes up. In science, "postdiction" is not so convincing. What counts is deriving numbers from the theory BEFORE they are measured by observation.

If GLAST flies before they have extracted all the predictions they can, it will not be so good. The same with other upcoming tests he mentions.

So there is a harvest of research papers to be written and this is a timely call to people who want research problems to work on.

 

[marcus]

Another detail, the paper is to be submitted to Reviews of Modern Physics and in the acknowledgments he thanks John Schwarz for having pointed out to him the need for such a paper, thus prompting him to write it.

Reviews of Modern Physics is, IIRC, a quality hardcover annual publication with reviews of selected research areas of current interest. Part of expanding and gaining recognition as a field is getting into RMP. I don't happen to know if LQG has been reviewed in RMP before----let's see if Smolin's review is included in the next edition.

 

[sol2]

I second Airvero's repsonse on your abilities

He stresses the urgency of getting the predictions published before 2007, when GLAST goes up. In science, "postdiction" is not so convincing. What counts is deriving numbers from the theory BEFORE they are measured by observation.

If GLAST flies before they have extracted all the predictions they can, it will not be so good. The same with other upcoming tests he mentions.

What I have found most useful is to explore, and find the intent of the missions, and then to see, what that intent will show us( I do not have a teacher sitting here explaining, so I have to look:0).

To have found new anomalies, because of research following a distinct paths, is taking it to the Edge. And the precipice, is very large sometimes, once you open the doors, from what we had always understood. Sort of a paradigmal changing of the guards you might say. Some of these institutions have been around a long time

So to make predictions, about what you are finding ,also allows you to move towards the heart of these issues. Speak to it, from multiple angles. Some like to call the apple red, some like to define the apple by taste and some like to hit you with it. Of course we have to keep our sensibilties about us, but vision takes ona whole new meaning once you incorporate. What has this metamorphisis done then? Instead of a catepillar, a butterfly(symmetry),and the wings flutter and felt half way around the world?

Making information avaliable helps in that regard. Then a distillaition as you pointed out, and as Smolin does, in his normal mode of operandi.