Quantcast
  • Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.

News

PO is now at the Physics Department of Bielefeld University!

New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback

Attributions

(propose a free ad)

Site Statistics

205 submissions , 163 unreviewed
5,082 questions , 2,232 unanswered
5,353 answers , 22,786 comments
1,470 users with positive rep
820 active unimported users
More ...

  What is the status of gauged gravity

+ 6 like - 0 dislike
2507 views

The Standard Model of elementary particles is a gauge theory with gauge group $SU(3)\times SU(2)\times U(1)$, which is really a successful theory.

We might be able to quantize gravity similarly. Gravity might be treated as a force, instead of spacetime curve as in general relativity. I know little about gauged gravity theory. What is the current status? Who are working on it? Is it really worthwhile to pursue now?


This post imported from StackExchange Physics at 2014-10-11 09:55 (UTC), posted by SE-user Drake Marquis

asked Oct 10, 2014 in Theoretical Physics by Drake Marquis (30 points) [ revision history ]
recategorized Oct 12, 2014 by dimension10
Did you see physics.stackexchange.com/q/71476? As for the question whether it is worth pursuing... that's has to be your own choice, because it will probably take the rest of your life to find out. Gravity has been a tough nut for the past four centuries and it would take an extraordinary amount of optimism to pretend that it won't take at least a fifth.

This post imported from StackExchange Physics at 2014-10-11 09:55 (UTC), posted by SE-user CuriousOne

@CuriousOne I find your comment to be very vague and influenced by the popular science media. What do you mean by "cracking" gravity? Finding an (in-theory exact) non-perturbative quantum mechanical description of relativistic gravity? In that case, no force has really been cracked, since the Standard Model is also a perturbative model.

The comment also seems to be going off on a totally different line (which isn't even a tangent) to what the question is asking for. The question is asking, I think, if field-theoretic gravity has any physical importance, not if you think the OP should study it.

3 Answers

+ 4 like - 0 dislike

It is standard that the Einstein-Hilbert action admits a first-oder formulation in which the field of gravity is a \(ISO(n,1)\)-Cartan connection, hence essentially a gauge field for the Poincaré group (aka "spin connection"). This is understood since the 1920s. In fact supergravity is essentially always written in this form (then for the super Poincaré group), since one needs the vielbein of the first order formalism to write down the fermionic terms. An excellent account of this is in the textbook "Superstrings and Supergravity" by D'Auria-Fré. (It's out of print, though, if you don't manage to get hold of a copy, try sending me an email.)

answered Oct 11, 2014 by Urs Schreiber (6,095 points) [ no revision ]
Just for reference: What goes wrong if one naively tries to quantize this first-order formulation of gravity? Is the theory non-renormalizable?
+ 1 like - 1 dislike

What do you mean by "pursue"? If you mean trying to produce a full-fledged theory of quantum gravity that can be "directly added" to the standard model, it's most likely not worth to "pursue". See for instance, this "proof".

But often, we can use theories which are actually inconsistent, but can give some meaningful results that can be used to test more complete theories. An obvious example that comes to my mind is Supergravity.

Similarly, trying to quantise gravity like any other force can actually yield meaningful results, making it certainly worthwhile to pursue. For instance, one may calculate graviton-graviton scattering amplitudes at the tree level, and see if the same predicted by string theory reduces to this when one takes the limit as \(\alpha'\to0\) - the exact factor by which one multiplies the stringy prediction by to get the field theory prediction is:

\( \frac{{\Gamma \left( {1 + \frac{{\alpha '}}{4}s} \right)\Gamma \left( {1 + \frac{{\alpha '}}{4}t} \right)\Gamma \left( {1 + \frac{{\alpha '}}{4}u} \right)}}{{\Gamma \left( {1 - \frac{{\alpha '}}{4}s} \right)\Gamma \left( {1 - \frac{{\alpha '}}{4}t} \right)\Gamma \left( {1 - \frac{{\alpha '}}{4}u} \right)}}\)

Take the field-theoretic limit and this approaches 1 (obviously) with no dependence on s, t, or u. See Mohaupt's lecture notes on string theory for more details.

So to answer your question, yes it is worthwhile, but not as a theory of quantum gravity on its own right.

answered Oct 11, 2014 by dimension10 (1,985 points) [ revision history ]
edited Oct 11, 2014 by dimension10

@downvoters Could you please explain your downvote?

+ 0 like - 0 dislike
As far as I know there is a model of gauge gravity in geometric algebra, where the solutions look more like newtonian physics or at least much much simpler. http://geocalc.clas.asu.edu/pdf/GTG.w.GC.FP.pdf
answered Dec 8, 2014 by WolfInSheepSkin (-40 points) [ revision history ]
edited Dec 8, 2014 by WolfInSheepSkin

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
p$\hbar$ysicsOverf$\varnothing$ow
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
Please complete the anti-spam verification




user contributions licensed under cc by-sa 3.0 with attribution required

Your rights
...