All Questions
Tagged with quantum-field-theory general-relativity
293
questions
-6
votes
0
answers
73
views
How can I visualise a sphere with a negative radius? [closed]
I want to visualise the shape of the sphere , will having a negative radius turn the inside of the sphere outside or something other will happen ?
2
votes
0
answers
105
views
+50
Prerequisites to learn/work on double copy theory and amplitude methods for gravity
I am a PhD student in classical gravity; specifically in BH perturbation and GW.
I am interested in learning about the double copy and the use of scattering amplitudes in understanding GW physics. I ...
32
votes
8
answers
5k
views
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
4
votes
1
answer
186
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 $$ds^2=-dt^2+b^2(t)d\vec x^2.$$
...
- 495
0
votes
1
answer
69
views
Is the background independence of dynamics a necessary condition for physical theories?
I read in the answer of Lubos Motl to this question that
the dynamics of string theory is demonstrably background-independent
while
the (manifest) background independence is an aesthetic ...
1
vote
1
answer
85
views
Non-Hermiticity of the Dirac Hamiltonian in curved spacetime
In flat spacetime, Dirac fermions are classically described by the action
$$
S=\int d^Dx\;\bar\psi(x)\left(i\gamma^a\partial_a-m\right)\psi(x).
$$
One can generalize this to a general curved spacetime ...
- 495
0
votes
0
answers
36
views
Bitensors at three or more space-time points
Bitensors, i.e. tensors at two points that have indices belonging to either of them, have been used in the literature quite a bit and there are many calculations involving them. They are the go-to ...
0
votes
0
answers
96
views
If dark energy has constant density, would it still be subject to quantum variations; would increase/decrease be symmetrical, or would one take over?
There are different suggestions, but it stills seems like the basic scenario is for dark energy to have constant density, as a property of space (and as represented by the cosmological constant in ...
- 15
0
votes
2
answers
68
views
Variation in the context of symmetries
I’m rephrasing a suggestion as a question because there was an aspect to it where I wanted to know more as well.
I have studied both general relativity and particle physics, though in both cases my ...
1
vote
0
answers
33
views
Accelerating frame of reference, fermions and probability conservation
I'm looking at solutions to the massless Dirac equation in an accelerating frame of reference in $(1+1)$-dimensions but the wave functions I get appear to violate probability conservation.
My ...
- 841
1
vote
0
answers
75
views
Use of mathematical structure on physics [closed]
I want resources for studying in detail the connection between the mathematical structures of physical theories and said physical theories.
For example, i know what a Hilbert space or a principal ...
0
votes
0
answers
49
views
How does the asymptotic metric fluctuation in $n \to m$ scattering relates to the soft factor in Weinberg's soft graviton theorem?
I'm reading arXiv: 1411.5745 [hep-th]. In Sec. 5, the authors show how the memory effect and Weinberg's soft graviton theorem are two faces of the same coin. I'm interested in understanding a specific ...
- 22k
4
votes
0
answers
83
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 ...
- 7,388
0
votes
2
answers
640
views
Can we regard metric as the Higgs field of gravity?
The longer version of the question is: should we regard special relativity just as a spontaneous symmetry breaking phase of general relativity, driven by the non-zero vacuum expectation value (VEV) of ...
- 4,399
1
vote
0
answers
44
views
Calculating the Energy density of a static spherically symmetric Boson Star in the Newtonian Approximation using the Energy momentum tensor
I'm referring this paper here and I was trying to work out the calculation of the energy density which is the 00th element of the energy momentum tensor $T_{\mu\nu}$ which is given as:
$$
T_{\mu \nu}=\...
- 63