# A letter or symbol above a tensor

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

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}


• 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
• @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