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Georges Simenon
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Homework Statement
Hi,
I am studying covariant LQG from the recent book by Rovelli & Vidotto, and i am struggling with the linear simplicity constraint. My problems are not with its proof, that i understand, but rather with the physical interpretation in terms of boost generators.
I will try to make my question as much self-consistent as possible. I refer to ch. 3 of the Book.
They start from the Holst action
[tex]S=\int B\wedge F\quad\text{where}\quad B=\star(e\wedge e)+\frac{1}{\gamma}e\wedge e[/tex]
Then, in sec. 3.3.1, they define the two 2-forms
[tex]K^I=n_J B^{IJ}|_{\Sigma}\quad\text{and}\quad L^I=n_J(\star B^{IJ})|_{\Sigma}[/tex]
restricted on a spatial hypersurface [itex]\Sigma[/itex] with unit timelike normal [itex]n_I[/itex].
Using these definitions, they prove that the following equation
[tex]\vec{K}=\gamma\vec{L}\qquad\text{linear simplicity constraint}[/tex]
holds in the "time gauge" [itex]n_Ie^I|_{\Sigma}[/itex].
In sec. 3.4.3, they interpret the components of the vector [itex]\vec{K}[/itex] as the canonical generators of Lorentz boosts. It is this interpretation that i don't understand, and I'm trying to give sense to it.
The same claim you can find in the Zakopane lectures by C. Rovelli. In the notation used there, he identifies
[tex](\star(e\wedge e)+\frac{1}{\gamma}e\wedge e)|_{\Sigma}[/tex]
with the [itex]SL(2,\mathbb{C})[/itex] generator.
Homework Equations
The Attempt at a Solution
If i am asked to write the Lorentz generators in tetrad notation, i write
[tex]G^{IJ}=e^I\wedge e^J[/tex]
up to an overall proportionality factor.
This makes sense. Consider, for definiteness, the 2-form
[tex] e^0\wedge e^1 = d\xi^0\otimes d\xi^1-d\xi^1\otimes d\xi^0 [/tex]
It generates Lorentz boosts along the local inertial axis 1. Note: the [itex]\xi[/itex]'s are local inertial coordinates.[/B]
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