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Nov4-11, 05:47 PM
Sci Advisor
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Quote Quote by genneth View Post
I think one reason I don't buy the need for constrained quantization to really work out is because that theory, although brilliantly worked out by Dirac, was fundamentally about systems with a decent choice of time, and therefore time evolution. It's not clear to me that's true at all for GR --- just because it admits ADM does not mean that quantum mechanically one can still do it --- the limits might not commute!
You can construct simple models where not using Dirac's approach simply fails classically. The Poisson structure generates the wrong time evolution, does not respect second class constraints.

But there is no good reason why an approach that fails classically should work in quantum theory.