# tensor accents and sub-super-scripts

Tensor notation with subscript i and superscript j to the right of the i

${A_i}^j$              %  correct

${\tilde A_i}^j$       %  j is above i

${{\tilde A}_i}^j$     %  ditto


My question is not how to fix it: $\tilde A_i{}^j$, but wherein the TeXBook it discusses this very strange occurrence.

The TeXbook --- similar to the Bible but provides solutions to the exercises.

• ${{}\tilde{A}_i}^j$ Apr 30 '20 at 17:44
• In the TeXbook, tensor notation is the subject of Exercise 16.6. From that answer, I conclude that this is what is recommended: $\tilde A_i{}^j$ Apr 30 '20 at 17:49
• Sorry! I didn't state the question quite correctly. I am interested in plain TeX (the reason for the TeXbook). I couldn't find why $A_i^j$ works correctly but not $\tilde A_i^j$ and not ${\tilde A}_i^j$. I agree that $\tilde A_i{}^j$ works - and makes good sense - (fortunately "tensor" is in the index). But why does the "\tilde" change the behavior of the following superscript. In Eijkhout's book he says: " Math accents can adapt themselves to the size of the accented expression: TEX will look for a successor of an accent in the same way that it looks for a successor of a delimiter." May 2 '20 at 15:03

In the TeXbook, tensor notation is the subject of Exercise 16.6. From that answer, I conclude that this is what is recommended:

\documentclass{article}
\begin{document}

$\tilde A_i{}^j$

$R_i{}^{jk}{}_l$ -- from the \emph{\TeX book}, Exercise 16.6.

\end{document}


I have added two different options with tensor package and the code @egreg's comment.

\documentclass[12pt]{article}
\usepackage{tensor}
\usepackage{amsmath,amssymb}
\begin{document}
${{}\tilde{A}_i}^j$ % @egreg's comment for example

$\tensor{\tilde{A}}{_i^j}$ % using tensor package
\end{document}