All Questions
5
questions
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100
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Extra equation missing in varying the Lagrangian w.r.t to Metric compared to directly applying the Einstein equation in Einstein-Maxwell-scalar theory
So I have been working on this lagrangian whose equations of motion I am trying to derive. The original paper contained six equations, which I found by varying the action to corresponding four fields ...
- 23
0
votes
0
answers
177
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Gibbons-Hawking-York (GHY) boundary term
In the Hilbert action, apart from the bulk term, there is a boundary term called GHY $\int d^{3}x\sqrt{h}K$. Why do we choose to calculate this on the $r=$constant hypersurface instead of the $t=$...
- 153
4
votes
2
answers
354
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Constraints on the Einstein-Hilbert action
The Einstein-Hilbert action is given by
$$S_{EH}=\frac{1}{2\kappa}\int\text{d}^4x\sqrt{-g}R$$
Let's say we want to replace it with an action that doesn't reproduce singularities for example $R\...
4
votes
1
answer
256
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Calculation of gravitational Euclidean action of Schwartzchild BH
I am reading the paper of Gibbons and Hawking Action integrals and partition functions in quantum gravity, Phys. Rev. D 15 (1977) 2752 where they compute the gravitational action of black holes.
In ...
- 2,197
2
votes
0
answers
116
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The origin of action of the scalar-tensor theory of gravity
I just started a project on the scalar-tensor theory of gravity and read up few papers and books related to it. In most of the books the idea and need for this theory is explained and from there the ...
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