4

I would like to put a letter, e.g. \lambda, above a tensor, e.g. Riemann tensor, by which I mean a tensor that is function of \lambda. I use \tensor and \overset command to construct this object. Here the code:

\documentclass{letter}
\usepackage{amsmath}
\usepackage{tensor}
\begin{document}
\[ \overset{\lambda}{\tensor{R}{^a_b_c_d}} \]
\end{document}

But that's not what I searching for, because the \lambda stand over entire tensor and not over the letter of tensor (here R). Can somebody help me?

  • (1) Welcome, (2) please provide a fully compilable minimal example. FOr example I do not know where \tensor comes from. – daleif Sep 24 '15 at 11:47
  • Have you tried \tensor{\overset{\lambda}{R}}{^a_b_c_d} ? – Tom-Tom Sep 24 '15 at 11:49
  • @Tom-Tom I guess that is no good alternative, as then the superscript a will be typeset above \lambda, at least with \tensor from package tensor – cauchy42 Sep 24 '15 at 11:50
  • @cauchy42 Exactly. I don't want this. – Astrolabe Sep 24 '15 at 12:16
  • @daleif Sorry. I'll correct it. \tensor is a command from package tensor, that allow to write tensors with many indices. – Astrolabe Sep 24 '15 at 12:20
4

You can use the following "dirty" trick with \vphantom

\overset{\lambda}{R}\tensor{\vphantom{R}}{^a_b_c_d}

This works with the package \tensor.

MWE

\documentclass{letter}
\usepackage{amsmath}
\usepackage{tensor}
\begin{document}
\[ \overset{\lambda}{R}\tensor{\vphantom{R}}{^a_b_c_d} \]
\end{document}

enter image description here

  • Thanks a lot! A nice "dirty" trick! But faithfully I don't understand the code! May you please explain it? Thanks! – Astrolabe Sep 24 '15 at 12:23
  • @H.B. As a matter of taste: If you use \tensor* instead of \tensor, the subscripts will be starting after R and don't leave the space due to the superscript a. – cauchy42 Sep 24 '15 at 12:27
  • 2
    @cauchy42 Interesting remark, but I think the option might be harmful, because \tensor*{R}{^a_b_c_d} and \tensor*{R}{_b^a_c_d} are actually different things ! – Tom-Tom Sep 24 '15 at 12:30
  • Oh yes, that's right. – cauchy42 Sep 24 '15 at 12:34
  • @H.B. \vphantom does not typeset anything, but it reserves vertical space for its argument (here the second R). So you have two objects here: One is the R with the overset \lambda, the other a tensor object with "nothing" (but vertical space) in it, followed by the indices. As the \vphantom has no width, there will be no space between the printed and the "virtual" R – cauchy42 Sep 24 '15 at 12:37

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