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You know the one I mean, Tμν.1 Is it the stress-energy tensor, or the energy-momentum tensor? This is for the purposes of tags, where having both is redundant. This was brought up in chat, and there is a proposal on our little-visited tag synonyms page. However, it was pointed out there that the idea of just combining everything into won't work due to character limits.

Moreover, I dare anyone to claim with a straight face that they would actually say "stress-energy-momentum tensor" in conversation.

I therefore propose that one of or be taken to be "standard," with the other made a synonym. My understanding is that either tag can then be applied, with the synonym silently being replaced, no harm done, no retagging effort necessary.

Rather than proposing a synonym on my own, only to have no one look at that page anyway,2 I figure this proposal should get some community consensus as to which way the replacement should go. I personally grew up learning that "stress-energy" was a tensor and "energy-momentum" was a 4-vector, but perhaps I'm in the minority, or perhaps there's good reason to differentiate as much as possible the stress-energy tensor of relativity from the stress tensor of mechanics.

Vote below as you see appropriate, or add your own original thoughts in another answer.


1 Yes, I am fully aware that string of symbols refers to an unspecified component of a tensor, and not an actual tensor. Mathematically precise people, please don't hurt me. Everyone else, I still reserve the right to admonish you for conflating these two things :P

2 There are plenty of other suggestions there - interested users should vote on them!

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    $\begingroup$ I suggest we call it Geoffrey. $\endgroup$ – Wouter Jun 26 '13 at 23:10
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    $\begingroup$ No but I've only seen the energy-momentum 4-vector, I'll be attending a GR course next semester. So I'm not in a position to judge, really. However, I would go for stress-energy-tensor on the basis of causing less confusion alone. Energy-momentum is a SR 4-vector, stress-energy a GR tensor. That makes for a nice, clear distinction. $\endgroup$ – Wouter Jun 26 '13 at 23:13
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    $\begingroup$ "Moreover, I dare anyone to claim with a straight face that they would actually say "stress-energy-momentum tensor" in conversation." I do. $\endgroup$ – Abhimanyu Pallavi Sudhir Jun 27 '13 at 13:55
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    $\begingroup$ How about mass-energy-momentum-pressure-stress tensor? $\endgroup$ – Ben Crowell Jun 27 '13 at 20:08
  • $\begingroup$ @BenCrowell: The Stress-Energy-Momentum Tensor involves mass (multiplied by $c_0^2$), momentum, shear stress, and, pressure. So, I would classify pressure and shear stress as "stress" so stress-mass-momentum tensor. 28 characeters... What about sigma-m-p tensor? 16 characters only! $\endgroup$ – Abhimanyu Pallavi Sudhir Jun 28 '13 at 8:51
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    $\begingroup$ What about tensor-describing-energy-often-called-the-stress-energy-tensor-or-the-energy-momentum-tensor-or-the-stress-energy-momentum-tensor-or-in-short-comma-the-s-e-m-tensor-or-the-1-by-kappa-einstein-tensor-open-bracket-by-the-einstein-field-equations-or-in-short-comma-the-e-f-e-G-underscore-open-brace-backslash-mu-backslash-nu-close-brace-divided-by-kappa-is-equal-to-T-underscore-open-brace-backslash-mu-backslash-nu-close-brace-close-bracket-and-is-also-called-G-underscore-open-brace-backslash-mu-backslash-nu-close-brace-divided-by-kappa-or-the-einstein-tensor-divided-by-kappa ? $\endgroup$ – Abhimanyu Pallavi Sudhir Jun 28 '13 at 10:18
  • $\begingroup$ That was 590 characters (I minus-ed the things other than the-tags.) $\endgroup$ – Abhimanyu Pallavi Sudhir Jun 28 '13 at 10:19
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    $\begingroup$ Personally, I haven't read enough physics texts to have an overview of what is more common. But I would like to point out that Wikipedia already redirects Energy momentum tensor to Stress-energy tensor, for what it's worth. They may not be a particularly true source of knowledge, but the fact is that people who are not well familiar with a term frequently search it there, so they may have an influence of what gets to be the more popular term for the broad mass of search engine users. $\endgroup$ – rumtscho Jun 29 '13 at 21:24
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    $\begingroup$ Have a nice red [status-completed] tag :) $\endgroup$ – Manishearth Jul 1 '13 at 3:23
  • $\begingroup$ Strictly speaking, I would call it energy-momentum-density-flow-tensor. $\endgroup$ – Emilio Pisanty Jul 2 '13 at 19:26
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Let's go with as the preferred version and administer the synonymization .

Number of unfiltered Google hits: About 117,000 hits.

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  • $\begingroup$ I agree with this. I have heard/read of SE much more than EM. I dunno why, because to me momentum is usually a much more fundamental thing than stress :P (Yes, I know the context of stress in GR and it's not exactly stress) $\endgroup$ – Manishearth Jun 26 '13 at 20:58
  • $\begingroup$ I think "stress-energy tensor" is by far the more common usage. Penrose is an example of someone who prefers "energy-momentum tensor." $\endgroup$ – Ben Crowell Jun 27 '13 at 20:06
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    $\begingroup$ June 30th, 2013: SET proposal leads EMT proposal by votes 15-2. Synonym EMT->SET created. $\endgroup$ – Qmechanic Jun 30 '13 at 19:27
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Let's go with as the preferred version and administer the synonymization .

Number of unfiltered Google hits: About 1,560,000 hits.

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    $\begingroup$ Eh? I've heard 'energy-momentum vector' of course, but tensor? Who says that? $\endgroup$ – user1504 Jun 26 '13 at 21:33
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    $\begingroup$ @user1504: You asked Who says that? It is very common. See e.g. Peskin & Schroeder. $\endgroup$ – Qmechanic Jun 27 '13 at 14:33
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It's still wrong to hyphenate it that way. It should be "stress-energy tensor"....sigh{{Citation needed}} An underscore as is traditional in Unix should get the tag thing to work: stress--energy_tensor. And others.

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    $\begingroup$ Tags need hyphens to work. $\endgroup$ – Manishearth Jun 29 '13 at 10:08

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