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5
questions
2
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Variational description of modified Einstein equations
Let us suppose that we have an Einstein equation of the form
$$ R_{(\mu \nu)}-\frac{1}{2} g_{\mu \nu} R=8\pi T_{\mu \nu},$$
where $R$ is an affine connection, which differs from the Levi-Civita ...
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What is the boundary action need for topological massive gravity (TMG)?
For pure Einstein gravity with Dirichilet boundary conditions, Gibbons-Hawking-York boundary action is needed to make the variational principle well defined. I am considering the case for topological ...
1
vote
1
answer
53
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Consistency of substitution of a canonical variable from EoM back into (momentum-less) action
I was reading this answer, where the issue of substituting equations of motion (eoms) into the action is addressed. I am fine with the basic idea that the action principle is destroyed when the eoms ...
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22
votes
1
answer
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Why is it so coincident that Palatini variation of Einstein-Hilbert action will obtain an equation that connection is Levi-Civita connection?
There are two ways to do the variation of Einstein-Hilbert action.
First one is Einstein formalism which takes only metric independent. After variation of action, we get the Einstein field equation.
...
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2
votes
0
answers
529
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Derivation of equations of motion in Nordstrom's theory of scalar gravity?
Nordstrom's theory of a particle moving in the presence of a scalar field $\varphi (x)$ is given by
$$
S = -m\int e^{\varphi (x)}\sqrt{\eta_{\alpha \beta}\frac{dx^{\alpha}}{d \lambda}\frac{dx^{\beta}}{...
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