Can Gravity Be Quantized? by Vesselin Petkov

Vesselin Petkov

Dear Hoang Cao Hai,

Thank you for your comments. In order to be able to respond to what you ask, try first to formulate a single question, but do your best to make it as clear as possible.

Best wishes,

Vesselin Petkov

Dear Sergey,

Again (as I indicated in the above post), this whole issue requires a lot of time - it is a long discussion.

Best wishes,

Vesselin Petkov

Benjamin Dribus

Dear Vesselin,

I think you're absolutely right, and that your arguments are clear and convincing. However, I thought that most serious relativists already took this view. I come from the mathematical side, and don't know any serious relativists personally. I always had the impression that "quantum gravity" was more about the fundamental structure of what we call "spacetime" than questioning the knowledge that gravity is an aspect of this structure. I would be interested to know your views on a few related questions:

1. What do you think about "unification?" Your essay clearly rules out treating gravity like the "other forces," but doesn't rule out treating the "other forces" like gravity in some sense. I know there have been many efforts to "geometrize" electromagnetism, for instance.

2. What do you think about the fundamental structure of spacetime? Treating gravity as a structural aspect does not a priori demand that the structure involved be a manifold. Could matter-energy and "forces" be structural aspects as well?

Thanks, and take care,

Ben Dribus

Vesselin Petkov

Dear Ben,

I think it would have been very helpful for the advancement of fundamental physics if "most serious relativists already took this view" as you wrote. Unfortunately that is not the case for at least two reasons as indicated in the essay - according to the widely accepted view (i) quantum gravity is a legitimate goal, and (ii) gravitational waves carry gravitational energy (and therefore such energy does exist).

Regarding your two questions, right now there does not exist any reliable experimental or theoretical evidence that can provide us with some insight on those issues. And I do not want to offer baseless speculations. However, I do hope that learning how matter curves spacetime may shed light on such questions.

Best wishes,

Vesselin Petkov

Juan Ramón González Álvarez

Dear Vesselin,

Yes those topics require a lot of time and a board with mathematical capabilities beyond the technology of those forums. Your option is interesting.

With my best regards.

Sergey Fedosin

After studying about 250 essays in this contest, I realize now, how can I assess the level of each submitted work. Accordingly, I rated some essays, including yours.

Cood luck.

Sergey Fedosin

If you do not understand why your rating dropped down. As I found ratings in the contest are calculated in the next way. Suppose your rating is [math]R_1 [/math] and [math]N_1 [/math] was the quantity of people which gave you ratings. Then you have [math]S_1=R_1 N_1 [/math] of points. After it anyone give you [math]dS [/math] of points so you have [math]S_2=S_1+ dS [/math] of points and [math]N_2=N_1+1 [/math] is the common quantity of the people which gave you ratings. At the same time you will have [math]S_2=R_2 N_2 [/math] of points. From here, if you want to be R2 > R1 there must be: [math]S_2/ N_2>S_1/ N_1 [/math] or [math] (S_1+ dS) / (N_1+1) >S_1/ N_1 [/math] or [math] dS >S_1/ N_1 =R_1[/math] In other words if you want to increase rating of anyone you must give him more points [math]dS [/math] then the participant`s rating [math]R_1 [/math] was at the moment you rated him. From here it is seen that in the contest are special rules for ratings. And from here there are misunderstanding of some participants what is happened with their ratings. Moreover since community ratings are hided some participants do not sure how increase ratings of others and gives them maximum 10 points. But in the case the scale from 1 to 10 of points do not work, and some essays are overestimated and some essays are drop down. In my opinion it is a bad problem with this Contest rating process. I hope the FQXI community will change the rating process.

Sergey Fedosin

[deleted]

Vesselin,

Fantastic Work! It has something for everyone. Whether one endorses all of GR or not - it points out some of the inconsistencies concerning the various interpretations and conclusions.

By the way - many are looking for Gravity Waves. If they are actually discovered directly someday, would this be an argument for actually abandoning part of GR and moving gravity more toward the other forces (but not necessarily in the spirit of String Theory or LQG)?

Good luck to you.

Vesselin Petkov

Thank you, Chris. General relativity (GR) perfectly explains gravitational waves - these are waves of the spacetime curvature (that is, periodic changes of the non-Euclidean geometry of spacetime). But these waves do not carry gravitational energy since changes in the spacetime geometry are not changes of a field (it seems this part of GR is most counter-intuitive, but it does follow from a rigorous analysis of the existing theoretical and most importantly experimental evidence).

The energy involved in detecting gravitational waves is not gravitational, but inertial (exactly like the force of weight is not gravitational but inertial - when one weighs a body it is prevented from falling, i.e. moving by inertia according to GR, and the body resists the change in its inertial motion).

Good luck to you too.

Matthew Jackson

Vesselin

Very good work, and typical. Good luck also with the institute.

We hope you will read and comment on our logical resolution of the Copenhagen interpretation and the measurement problem.

Matt

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