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Consider the local Lorentz vector $\omega^a$ constructed from the spin connection via the Hodge dual: $\omega^a=\frac12\epsilon^{abc}e_c\omega^c{}_{ab}$, where $e_a=\eta_{ab}e^b{}_\mu\mathrm dx^\mu$. Essentially since the triad and this spin vector are on the same footing, we can construct a Chern-Simon formulation of 3D gravity. In the following we work ...

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There are a number of related results to which you could be referring. QFTs on a fixed de Sitter background There are significant obstacles to formulating these in a way consistent with unitarity. A previous SE answer gets into this but there is another important reference which explains the issue. Essentially, IR divergences that would cancel in flat space ...

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Any system that obeys the Schrodinger equation will be subject to a HUP. In particular, any two measurable variables (operators in QM) which are conjugate to one another will have their own UP. (e.g. position and momentum) HUP can be proven mathematically within this framework, so the extent to which it applies to the universe is the extent to which the ...

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Let me make a few remarks after the answer by Nihar Karve. The relation between both actions is exactly that and nothing more. Of course, one can say that the equations of motion coincide, but this is more subtle, because one wants invertible vielbiens. See below. Einstein's equations imply that the Ricci curvature is constant, namely the space of ...

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The correct relation is $$\int d^N[\psi] \psi_{a_1}\ldots\psi_{a_N}= \epsilon_{a_1,\ldots,a_N}$$ which gives a determinant to average.

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Perhaps Physics from Symmetry is a good book for you http://physicsfromsymmetry.com/

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This is a great insightful question for a high school student, thanks. The reason for length contraction comes down to a difference in what two people consider to be simultaneity. The only way to measure distance is to mark one place, and mark another, then figure out how far apart they are. If the thing you're measuring is moving that means you have to do ...

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