All Questions
Tagged with quantum-field-theory general-relativity
88
questions with no upvoted or accepted answers
14
votes
0
answers
437
views
How to perform a derivative of a functional determinant?
Let us consider a functional determinant
$$\det G^{-1}(x,y;g_{\mu\nu})$$
where the operator $G^{-1}(x,y;g_{\mu\nu})$ reads
$$G^{-1}(x,y;g_{\mu\nu})=\delta^{(4)}(x-y)\sqrt{-g(y)}\left(g^{\mu\nu}(y)\...
- 3,691
9
votes
0
answers
598
views
What are problematic issues of quantum field theory in curved spacetime, when accepting semiclassical limitation?
The question is inspired from the answer to Is a QFT in a classical curved spacetime background a self-consistent theory? (I am going to reference this link as "The Q" to avoid confusion).
As far as ...
- 389
8
votes
0
answers
383
views
Definition of gravity path integral?
In a non-abelian gauge theory there is a "fundamental" gauge field $A_\mu^a$ with gauge index $a$ often called connection. Although $ A_\mu^a$ is not gauge invariant, gauge invariant quantities can be ...
- 322
7
votes
0
answers
132
views
Is GR the only theory in physics which cares about absolute energy?
In my QFT course, they justify dropping the vacuum energy as 'physics only cares about relative energies except for GR in the stress-energy tensor'.
Is this strictly true?
- 2,604
6
votes
0
answers
285
views
General relativity from helicity 2 massless field theory by using Deser's arguments
Recently I have discovered the method of constructing of GR from massless field with helicity 2 theory. It is considered here, in an article "Self-Interaction and Gauge Invariance" written by Deser S. ...
- 6,564
5
votes
0
answers
239
views
Solving 2d quantum gravity as a TQFT
I am considering (Euclidean) 2d quantum General Relativity in the functorial language of TQFT. Specifically, the theory is completely defined by associating a vector space with a circle, and an $n$-...
- 16.2k
5
votes
0
answers
341
views
Weinberg-Witten theorem and Landau pseudotensor, or how QFT can make prediction about GR
Weinberg-Witten theorem states that there isn't Poincare covariant stress-energy tensor for massless fields with helicity more than $1$. The only example of such higher helicity field is graviton. ...
- 8,901
5
votes
0
answers
299
views
Calculating forces via Feynman diagrams?
How would one go about calculating forces that test objects feel using Feynman diagram methods?
For example, say we have a massive object in GR so that the metric takes on the standard Schwarzschild ...
- 3,492
4
votes
1
answer
209
views
Is gravitational particle production due to symmetry breaking?
A well-known fact about QFTs in curved spacetimes is that there is a phenomenon of particle production in expanding universes, these being described by the line element $$ds^2=-dt^2+b^2(t)d\vec x^2.$$
...
- 503
4
votes
0
answers
84
views
Is the only consistent massless spin-2 QFT really exactly General Relativity in the classical limit or only linearized limit?
I'm trying to understand to what extent it is a "miracle" that a massless spin-2 field "postdicts" general relativity. I think there is some early theorem of Weinberg that shows ...
- 7,398
4
votes
0
answers
153
views
Solving scalar quantum field in 1+1D Milne space
So our line element is
\begin{equation}
ds^2=dt^2-a^2t^2dx^2
\end{equation}
doing following coordinate transformation
\begin{equation}
y^0=t\hspace{2pt}\cosh ax, \hspace{2pt}y^1=t\hspace{2pt}\sinh ...
- 3,043
4
votes
0
answers
120
views
The usage of covariant coordinates in relativistic field theories
In the opening chapters of typical QFT books, the covariant coordinates $x_\mu = g _{\mu\nu}x^\nu$ $x^\mu = (t,x,y,z)$ and the differential operator $\partial^\mu = \frac{\partial}{\partial x_{\mu}}=(\...
- 399
4
votes
0
answers
209
views
ALE Spaces as Spacetime?
I asked the following question (https://mathoverflow.net/questions/263654/instanton-moduli-space-on-ale-spaces/263816#263816) on MathOverflow, with regards to instanton moduli spaces on certain ALE ...
- 697
4
votes
0
answers
237
views
Question about $\alpha-$plane in twistor theory
In twistor theory, given the complexified Minkowski space $CM$ and the projective twistor space $PT$, an $\alpha-$plane is defined as the correspondence in $CM$ wit a point $Z \in PT$.
But I found ...
- 1,548
4
votes
0
answers
172
views
Klein Gordon eq. expressed with Killing fields
I have a question on the reformulation of the Klein Gordon equation in terms of Killing fields.
Suppose we have a static spacetime with timelike Killingfield $\xi^{\mu}$
(e.g. Schwarzschild).
Then ...
- 153