3

When Typesetting some expressions containing sub-/superscripts as sub-/superscript, I observed that the placement of the nested sub-/superscript changes.

MWE

\documentclass{article}

\begin{document}
    \[
        L^p \quad \|.\|_{L^p} \quad \|.\|^{L^p}
    \]
\end{document}

Output

Output of MWE


You'll notice, that the positioning of p relative to L differs in all three expressions. Similar behaviour can be observered when considering L_q.

While I have found several questions on how to control the exacet positioning of "simple" (i.e. non-nested) sub-/superscripts, I couldn't quite figure out, what causes this behaviour and how one can maybe avoid it.


  • Do you know, why this is happening? Does it maybe have something to do with font properties or some lower level spacing definitions of LaTeX?

  • Is there a way to ensure that the relative positioning remains intact when the expression itself is a sub-/superscript?

  • Or should I better leave this be b/c one should not fiddle with spacing too much?

1

I share your concerns. I often end up adding phantom subscripts in these case, which can be added to make the appearance more uniform. (In the presence of a subscript, the superscript moves up.)

\documentclass{article}
\usepackage{amsmath}
\newcommand{\PP}{_{\vphantom{Lg}}}
\begin{document}
    \[
        L\PP^p \quad \left\|.\right\|_{L\PP^p} \quad \|.\|^{L\PP^p}
    \]
\end{document}

enter image description here

A bit off-topic, but you may want to use \norm from here for the norm.

|improve this answer|||||
  • Thanks for the tip! I'll still leave the question open for now, since this does not solve the issue 100% and the "why" is yet to be answered ;) – Hirsch Dec 11 '19 at 19:35

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