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Nov 1, 2015 at 6:29 comment added thenumbernine This paper still only states fundamental Poisson brackets for each of the different actions it describes, without explaining how they are chosen, as the Romano, Giulini, and Pullin papers I reference under "my rationality for this assumption" in the question. Maybe I should've asked how fundamental Poisson brackets are chosen in the first place, because that seems to be done in these papers rather than deriving one set from another set.
Oct 31, 2015 at 10:05 comment added thenumbernine The original question wasn't how to differentiate the square root of a matrix (as it has wildly deviated into). It was how to solve the Poisson brackets of Ashtekar variables. This Addendum is a much better candidate for an answer. Thanks for the link -- I will check it out and see if I can get something from this.
Oct 27, 2015 at 21:54 history edited Alex Nelson CC BY-SA 3.0
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Oct 21, 2015 at 11:51 comment added thenumbernine This way works only if the tensor $e\delta e$ is symmetric -- I wrote out my work in the comments. Is there an easy proof that $e\delta e$ is symmetric? I'll start messing with that now...
Oct 20, 2015 at 21:36 comment added Alex Nelson @thenumbernine It's just the product rule: $\delta_{jk}({e_{c}}^{j} (\partial {e_{d}}^{k}/\partial_{ab}) + {e_{d}}^{k} (\partial {e_{c}}^{j}/\partial_{ab}))$, then set it equal to $\delta^{(a}_{c}\delta^{b)}_{d}$, and you're done.
Oct 20, 2015 at 17:09 comment added thenumbernine Thanks for the tip! That looks like the approach I've got listed. The $\approx$ is bugging me -- I'm looking for something with a $=$.
Oct 20, 2015 at 15:32 history answered Alex Nelson CC BY-SA 3.0