PeterDonis's latest activity
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PeterDonis replied to the thread I A sufficient condition for integrability of equation ##\nabla g=0##.Please give a reference for this claim. I have never said any such thing. All I have said is that the Levi-Civita connection has... -
PeterDonis reacted to gmax137's post in the thread Other Don’t have a high enough IQ for physics so I want to give up with
Like.
I think everything in your post (after the first sentence) is incorrect. Here's what I know: Online IQ tests are meaningless Those... -
PeterDonis reacted to Nugatory's post in the thread B What qualities does time have other than linearity, motion, and speed? with Like.
There's no sensible answer to your question until you have defined what you mean by the word "time". This being a physics forum where we...
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PeterDonis replied to the thread A Dirac's integral for the energy-momentum of the gravitational field.I was just about to hit "Post reply" when I saw this. See below. This might be one of those cases where Dirac's habit of implicitly...
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PeterDonis replied to the thread A Dirac's integral for the energy-momentum of the gravitational field.That's certainly true of Dirac, not just here but in general. And reading the text following (31.4), his assumptions (a) and (b) do...
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PeterDonis replied to the thread A Dirac's integral for the energy-momentum of the gravitational field.Where does Dirac do that over a 4-D hypercylinder? Nowhere that I can see.
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PeterDonis replied to the thread A Dirac's integral for the energy-momentum of the gravitational field.(31.2) is not an integral. It's a differential equation.
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PeterDonis replied to the thread A Dirac's integral for the energy-momentum of the gravitational field.I know. Now please look at my post, where I asked about a specific statement you made about an integral over a 4-D hypercylinder. That's...
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PeterDonis replied to the thread A Dirac's integral for the energy-momentum of the gravitational field.What's clear to me from that comment is that the integral (31.4) is taken over a 3-volume at a particular time, not over a 4-D...
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PeterDonis replied to the thread A Dirac's integral for the energy-momentum of the gravitational field.Where are you getting that from? All I see in his (31.4) is integrating over a 3-volume. A conserved "total energy" over a 4-volume...
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PeterDonis replied to the thread I A sufficient condition for integrability of equation ##\nabla g=0##.Because the orthonormal tetrad fields ##e_a## that appear in his calculation don't commute in any spacetime other than flat Minkowski...
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PeterDonis replied to the thread I A sufficient condition for integrability of equation ##\nabla g=0##.Correct math is the basis for valid physical models of our world, yes. But only correct math.
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PeterDonis replied to the thread I A sufficient condition for integrability of equation ##\nabla g=0##.Yes. Now go read my post #58, where I point that out, and then point out something else. Again, go read my post #58. In particular, the...
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PeterDonis replied to the thread I A sufficient condition for integrability of equation ##\nabla g=0##.So far I haven't seen you give any valid "explanation" of anything. I just see you continuing to show math that leads you to results...
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PeterDonis replied to the thread I A sufficient condition for integrability of equation ##\nabla g=0##.@ergospherical's calculation in post #10 doesn't make that assumption. Indeed, I don't think that assumption is even consistent with his...