Talk:ADM formalism

message: I would rather not try and clean this up, when there are probably people who are probably more familiar with the formalism than I and can do it easier than I could. Salsb 16:00, 21 February 2006 (UTC)
thread_title: technical

message: Wouldn't this article (and others related) be better with a little historical perspective. Niczar ⏎ 18:22, 4 July 2008 (UTC)
thread_title: Could use some historical perspective

message: I wish this article was extended to include the addition of a scalar field as in the case of e.g. Brans-Dicke theory.  I've seen the outcome cited in papers but I've never seen a detailed derivation.  Can anyone point me in the right direction?  —Preceding unsigned comment added by 208.65.181.179 (talk) 22:06, 8 July 2010 (UTC)
replies: text: I think that the key aspect of the derivation - unless I am mistaken and if I am, can someone please correct me - is to use the Lagrangian to obtain the field equations and thereby isolate an expression for the Einstein tensor and then the Ricci tensor R_uv and then the Lagrangian being made of g^uv * R_uv provides a form for a transformed Lagrangian.  This means taking on-shell results and plugging it back into the Lagrangian itself which could very well be a no-no unless you're careful.  At any rate, the on-shell/off-shell aspects are important.  I could use some help here TonyMath (talk) 22:05, 20 July 2010 (UTC)
thread_title: Addition of a scalar field to Lagrangian density?

message: I find the sentence "Cosmic inflation in particular is able to produce energy (and mass) from 'nothing' because the vacuum energy density is roughly constant, but the volume of the Universe grows exponentially." from the section "ADM energy" doubtful as for a quantum field theory formulated on a non-stationary spacetime, there is no well defined vacuum state in the first place. There is a renormalization ambiguity in the calculation of the energy-momentum tensor for Hadamard states like discussed in Wald's "Quantum field theory in curved spacetime and black hole thermodynamics" but as far as I know this is not understood very well yet. I would therefore suggest removing it. Does anyone agree?  — Preceding unsigned comment added by 139.18.9.66 (talk) 06:19, 18 October 2011 (UTC)
thread_title:  Vacuum energy in non-stationary spacetime backgrounds 

message: Please correct me if I am wrong but isn't the last term in \partial_j of the resulting Lagrangian a surface term since it's
a derivative and consequently integration over x_j would yield the function itself evaluated at x = +- \infty and
thus contribute nothing to Euler-Lagrange equations?  Of course, I am assuming a Minkowski limit in the far field. TonyMath (talk) 05:10, 5 March 2012 (UTC)
replies: text: It would nice to get some feedback on this. The section on canonical gravity mentions the elimination of total derivatives.  It seems the only term left is  \sqrt{-g} ( R + K_{ij} K^{ij} - K^2)  where  K_{ij}  is the extrinsic curvature.  BTW, I do think the canonical gravity section and this section (clearly taken verbatim from the papers of Arnowitt Deser and Misner) need to be better integrated and related to each other.  The canonical gravity section uses  \pi_{ij}  which can be related to  K_{ij}  via the formula  \pi^{ij} =\sqrt{ + or -g} (K^{ij} - g^{ij} K) .  Of course surface terms can be important but then again you might just happy with the resulting Euler-Lagrange equations and ignore them.  TonyMath (talk) 09:00, 6 March 2012 (UTC)
thread_title: Far field limit?

message: Intro should help the reader understand what ADM formalism is. It doesn't accomplish that atm. ScienceApe (talk) 18:09, 12 January 2013 (UTC)
thread_title:  Intro sucks 

message: I don't think there is a widely appreciated controversy. This paragraph cites a single paper by two authors from Ontario and it was added by an anonymous IP address from Ontario. This paragraph should either be substantiated with further references that show that there is really a controversy or be removed. Atdotde (talk) 10:00, 16 December 2020 (UTC)
thread_title:  Controversy