Linked Questions

21
votes
3answers
8k views

Gravity as a gauge theory

Currently, (classical) gravity (General Relativity) is NOT a gauge theory (at least in the sense of a Yang-Mills theory). Why should "classical" gravity be some (non-trivial or "special" or extended)...
18
votes
2answers
2k views

argument about fallacy of diff(M) being a gauge group for general relativity

I want to outline a solid argument (or bulletpoints) to show how weak is the idea of diff(M) being the gauge group of general relativity. basically i have these points that in my view are very solid ...
8
votes
4answers
1k views

Does a UV completion of gravity necessarily need to be so drastic as String Theory or LQG?

First of all I, it is my understanding that the problems one encounters with the non-renormalizability of gravity are very similar (if not the same) as one encounters in any non-renormalizable theory. ...
7
votes
1answer
1k views

Is reparameterization invariance some kind of gauge symmetry?

On page 116 of this book it is said, that reparameterization invariance of the string action is analogous to the gauge invariance in electrodynamices. Whereas Maxwell's equations are symmetric under ...
5
votes
3answers
440 views

Could general relativity and gauge theories in principle be covered in one course?

It's always nice to point out the structural similarieties between (semi-)Riemannian geometry and gauge field theories alla Classical yang Mills theories. Nevertheless, I feel the relation between the ...
5
votes
2answers
851 views

Diff(M) and requirements on GR observables

This question is kind of inspired in this one: Diff(M) as a gauge group and local observables in theories with gravity The conundrum i'm trying to understand is how is derived the (quite) ...
2
votes
1answer
803 views

Why does gravity forbid local observables?

I heard in a conference that gravity forbids to construct local gauge invariants like $\mathrm{Tr}\left\{−\frac{1}{4} F_{μν}^{a}F_{a}^{μν}\right\}$ and only allows non-local gauge invariant quantities ...
3
votes
2answers
362 views

Is general covariance a symmetry?

Is general covariance a symmetry? If it is, what is its symmetry group and corresponding generator?
1
vote
1answer
433 views

observable quantities are gauge invariant?

I have a simply question, that is whether spatial velocity is gauge invariant. It is seems that under a infinitesimal coordinate transformation the velocity is just transform as other vectors, and it ...
5
votes
1answer
244 views

Gribov ambiguities for splitting strings in the BRST conformal gauge

The standard textbook treatment of the conformal gauge for a free string with BRST ghosts is fine, but when a string splits into two, we have Gribov ambiguities for the conformal gauge. We can impose ...
1
vote
1answer
288 views

Why are string theorist so indifferent to the gauge structure of gravity? [closed]

Gravity shares many of the characteristics of Yang-Mills gauge theory. For example, the affine connection plays the similar role as the gauge potential in gauge theory, the Riemann tensor plays the ...
2
votes
0answers
176 views

Does gravity have a gauge symmetry group? [duplicate]

In the Standard Model, U(1) corresponds to the electromagnetic, SU(2) to weak, and SU(3) to strong interactions. I realize that gravity is not a part of the Standard Model. However, sometimes gravity ...
0
votes
0answers
97 views

Gravity as a gauge theory - Cartan-Killing form?

First, let me state the form of Lagrangian for YM and GR \begin{align} L_{YM} = \alpha \textrm{tr}(F^2), \qquad L_{GR} = \beta R \end{align} I heard, YM is a gauge theory but GR isn't a really gauge ...
0
votes
1answer
63 views

Why is there no gauge-invariant local operator in GR?

I have a hard time understanding why the bulk locality is a question. I know some operator which depends on a particular coordinate $x$, $O(x)$, and its correlation function like $ \langle O(x)O(y) \...