All Questions
6
questions
0
votes
1
answer
161
views
Energy-momentum tensor and gravity [closed]
Calculating from a given action the energy-momentum tensor $ \tilde{T}_{\mu \nu} $ (differentiating respect to $ \delta g^{\mu \nu}) $ I can create gravity by a generalization of the Einstein field ...
- 496
7
votes
1
answer
669
views
$\phi R$ term for scalar field in a curved background
Consider the following action for a free scalar field $\phi$ in a curved background
$$S=\int dx\Big( \frac12g^{\mu\nu}\partial_\mu\phi\partial_\nu\phi+\gamma \phi R\Big).$$
Here $g_{\mu\nu}$ is a ...
- 1,586
0
votes
1
answer
725
views
Energy Momentum Tensor for a Dirac Fermion coupled to external gravity
A small (and perhaps trivial :-() calculation is troubling me somewhat.
Consider the action of a right-handed Dirac fermion coupled to external gravity (a background gravitational field). The action ...
- 2,095
4
votes
1
answer
398
views
How to show the number of divergences in quantum gravity is infinite?
As is well known, Quantum Gravity is not renormalisable. How can I prove that for the Gravity tensor, there exists an infinite number of divergences? And why can this not be absorbed by mass or gauge ...
- 143
3
votes
2
answers
861
views
How would gravitons couple to the Stress-Energy tensor?
How would gravitons couple to the Stress-Energy tensor $T^{\mu\nu}$? How did physicists arrive at this result? I've read that it follows from the analysis of irreducible representations of the 4-...
33
votes
8
answers
7k
views
Why does no physical energy-momentum tensor exist for the gravitational field?
Starting with the Einstein-Hilbert Lagrangian
$$ L_{EH} = -\frac{1}{2}(R + 2\Lambda)$$
one can formally calculate a gravitational energy-momentum tensor
$$ T_{EH}^{\mu\nu} = -2 \frac{\delta L_{EH}...
- 9,581