About "Forget time" by Carlo Rovelli

[Martin]

You can't quantize gravity.

 

oh really.

 

Cameron, I share your skepticism about Farsight's assertion. I'd like to urge you to use the "quote" button and leave the link back to the post that you are quoting.

 

That way when you quote someone I can click on the link and get back to the post. the little blue square with the arrowhead.

Otherwise I have to waste time scrolling back to see who said it and what else their post said, context sometimes matters.

so please leave the full quote function intact.

 

Indeed gravity = geometry and geometry is in process of being successfully quantized. New results have come in and will be reviewed at the September 2009 Corfu school. (and also several conferences and workshops leading up).

 

Google "QG school corfu"

or just go to

http://www.maths.nottingham.ac.uk/qg/CorfuSS.html

 

Quantum gravity is reaching a milestone, or a new stage. It's interesting to watch the current research scene.

Edited March 20, 2009 by Martin

[Martin]

The Rovelli essay came out on arxiv yesterday. The font is larger so it is a more readable version. Minor addition(s).

 

http://arxiv.org/abs/0903.3832

"Forget time"

Carlo Rovelli

'First Community Prize' of the FQXi 'The Nature of Time' Essay Contest

(Submitted on 23 Mar 2009)

"Following a line of research that I have developed for several years, I argue that the best strategy for understanding quantum gravity is to build a picture of the physical world where the notion of time plays no role. I summarize here this point of view, explaining why I think that in a fundamental description of nature we must 'forget time', and how this can be done in the classical and in the quantum theory. The idea is to develop a formalism that treats dependent and independent variables on the same footing. In short, I propose to interpret mechanics as a theory of relations between variables, rather than the theory of the evolution of variables in time."

 

Using the standard-format Arxiv link rather than having to go into the FQXi website makes the essay more conveniently available and easier to cite.

 

Rovelli's lecture series at the September 2009 Corfu school can be expected to mark a new stage for LQG. Here's the summary:

Title: Covariant loop quantum gravity and its low-energy limit

"I present a new look on Loop Quantum Gravity, aimed at giving a better grasp on its dynamics and its low-energy limit. Following the highly succesfull model of QCD, general relativity is quantized by discretizing it on a finite lattice, quantizing, and then studying the continuous limit of expectation values. The quantization can be completed, and two remarkable theorems follow. The first gives the equivalence with the kinematics of canonical Loop Quantum Gravity. This amounts to an independent re-derivation of all well known Loop Quantum gravity kinematical results. The second the equivalence of the theory with the Feynman expansion of an auxiliary field theory. Observable quantities in the discretized theory can be identifies with general relativity n-point functions in appropriate regimes. The continuous limit turns out to be subtly different than that of QCD, for reasons that can be traced to the general covariance of the theory. I discuss this limit, the scaling properties of the theory, and I pose the problem of a renormalization group analysis of its large distance behavior."

 

This link gives descriptions of several of the other mini-courses, or lecture series, being given at the school.

http://www.maths.nottingham.ac.uk/qg/CorfuSS.html

Edited March 24, 2009 by Martin

[wdavidb]

Using a clock in physics is not the best way to go, as the time factor represents a linear duration of time which in turn causes all kinds of problems.

 

Of course clocks have their place and things would be a mess without them, but when it comes to explaining and defining universe you got a tiger by the tail.

 

We use a clock to determine the speed of a bus and we use a clock to determine the speed of light, which doesn't seem to bother most people at all. It seems perfectly logical to them.

 

This seems a bit weird to say the least, because we make some huge assumptions concerning time.

 

We also make some huge assumptions concerning our ability to measure mass and energy on the basis of a linear relationship, without even blinking an eye.

 

I have to say it does seem a bit on the weird side.