All Questions
18
questions
32
votes
8
answers
5k
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Explain to a non-physicist what goes wrong when trying to quantize gravity
I am not a physicist, but I'm trying to get a little bit of an understanding of why it is hard to extend the standard model with quantum gravity (i.e. why it's hard to combine QM and GR), cf. e.g. A ...
- 1,772
3
votes
0
answers
123
views
One-loop gravity $\beta$ function
Gravity is renormalizable at one loop, see e.g. Why is GR renormalizable to one loop?
What is the one loop gravity $\beta$ function?
- 5,707
1
vote
0
answers
62
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Studying the Renormalizability of classically equivalent theories
I am currently studying the effect that a massive, uncharged, non-minimally coupled spin $\frac{1}{2}$ field has on the background geometry upon quantization, and compare this with results in General ...
- 353
2
votes
0
answers
157
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Wilsonian Renormalization in Curved Spacetimes
One way of seeing the Wilsonian renormalization in flat spacetimes is to consider a quantum field theory in a lattice, where the spacings between the lattice elements depend on the energy scale under ...
- 1,056
3
votes
1
answer
565
views
Theory of General relativity — not renormalizable
I have a short question: what does it mean when one says that General relativity is not renormalizable?
I guess unlike the Quantum Field Theory, but what is the idea behind this statement?
user87745
32
votes
4
answers
13k
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Why is quantum gravity non-renormalizable?
The book The Ideas Of Particle Physics contains a brief treatment of quantum gravity, in which the claim is asserted that if one attempts to construct a model of gravity along the same lines as QED, ...
- 95.5k
3
votes
2
answers
759
views
What's the running coupling of gravity?
Pictures like the one below are often used to talk about grand unification.
I've never heard any physics textbook really talk about the running of the gravitational coupling constant $G$, but some ...
- 103k
13
votes
1
answer
1k
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What's the key point to argue that pure gravity can't be renormalizable from two-loop?
Gravity is not power-counting renormalizable in dimensions greater than two. It is known by Gerard 't Hooft, M.J.G. Veltman
that pure gravity in four-dimensions is finite to the first loop order ...
- 2,147
1
vote
1
answer
523
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What exactly are the high energy problems between general relativity and quantum field theory? [duplicate]
I know there are many questions on physics stack exchange devoted to the question of quantum gravity and reconciling GR and QFT, but don't mark this as a duplicate because my question is a bit more ...
- 453
1
vote
0
answers
333
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Renormalization and Infinite Series
In the renormalization of QED, one subtracts infinities to get finite results. This is not possible in gravity because of infinitely many divergences, and infinitely many counter terms.
The general ...
- 31
17
votes
6
answers
5k
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Why are we scared of singularities? [closed]
I often hear people say that general relativity predicted its own demise because of the singularities it predicts. If I'm not mistaken, this is also a problem in QFT. I wonder why singularities garner ...
- 328
4
votes
1
answer
546
views
What is the problem with quantizing GR in the Effective Field Theory approach?
In the modern view due to Wilson, the cut-off $\Lambda$ is an intrinsic property of a theory and renormalization just means that the theory is invariant under scale transformations below $\Lambda$. ...
user74106
2
votes
1
answer
196
views
Non-pertubative renormalization and correctness of a theory
Even if I start to understand why perturbative renormalization is necessary, I'm not exactly sure why non perturbative renormalization is.
After asking the question to several theorists, what I think ...
- 876
8
votes
1
answer
232
views
Regarding Non-renormalizatibility of GR
I've been doing some reading trying to get to a better understanding of some renormalization issues with the Einstein-Hilbert action. But, something odd came into mind that I'm hoping some users may ...
- 1,062
5
votes
1
answer
3k
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Power counting and (superficial) non-renormalizability
Comment: This stuff is new to me so it doesn't entirely make sense (yet).
Question: As I understand from Peskin and Schroeder chap 10 if you have a theory with interaction terms $\lambda \phi^n$ ...
- 1,062