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awarded  Yearling
Mar
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Mar
28
accepted In general, can a Lagrangian density depend on space-time explicitly?
Mar
28
comment In general, can a Lagrangian density depend on space-time explicitly?
Actually, going over my derivation a couple of times, I think I have convinced myself that the remaining problems are just a question of mixing up my partial and total derivatives. I also had a little trouble with whether the boundary term disappears in a partial integration, so if I can't figure that one out, I'll spawn a new question. But other than that, I think it's clear. Thanks for your help!
Mar
28
comment Is a vector and a unit vector dimensionless
@BinaryGeek see my edit
Mar
28
revised Is a vector and a unit vector dimensionless
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Mar
28
answered Is a vector and a unit vector dimensionless
Mar
27
comment In general, can a Lagrangian density depend on space-time explicitly?
Alright, we can apply Noether's theorem to derive the energy-momentum tensor precisely when the Lagrangian density does not have an explicit space-time dependence. That makes sense. As for the second question, when I have more time at hand I'll try to make it a little clearer what exactly I have trouble with in the derivation. Thanks for now :)
Mar
27
awarded  Student
Mar
27
comment In general, can a Lagrangian density depend on space-time explicitly?
@Qmechanic, thanks for the edit. I actually typed this up on my phone, so it might not be as clear as it could have been.
Mar
27
asked In general, can a Lagrangian density depend on space-time explicitly?
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awarded  Autobiographer
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Dec
3
comment Does the weight of an hourglass change when sands are falling inside?
@DarioP Ah yes, that's a really nice way of proving it, thanks.
Dec
3
comment Does the weight of an hourglass change when sands are falling inside?
How can you be sure that the average weight of the stone is exactly the same as the weight of the stone in rest? That doesn't seem at all trivial to calculate.
Nov
13
comment Potential energy in $E_f^2=(mc^2)^2+(pc)^2$?
-1 Everything you said is true, but it doesn't have anything to do with the question of the OP.
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reviewed Reviewed What forces are exerted on a clothespin in space?
Oct
24
revised Circumference of a circular path
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