3

I want to write an inductive limit as so

\documentclass{article}
\usepackage[utf8]{inputenc}

\usepackage{natbib}
\usepackage{graphicx}

\begin{document}
\lim{\substack{\rightarrow\\W\supset K}}\mathcal{C}_{A}
\end{document}

But the text related to the inductive limit should appear as a subscript. But this is not the case. Could someone explain why ?

1
  • 1
    Where are the dollars$...$inline math-mode and \[....\] centered math formula into your MWE?
    – Sebastiano
    Commented May 24, 2020 at 14:23

2 Answers 2

4

You are probably looking for \varinjlim:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\[
\varinjlim_{W\supset K}
\]

\end{document}

enter image description here

For the arrow pointing to the opposite side there is \varprojlim.

You might find the arrow too big (I do):

\documentclass{article}
\usepackage{amsmath}

\makeatletter
\renewcommand\varinjlim{%
  \mathop{\mathpalette\varlim@{\rightarrowfill@\scriptstyle}}\nmlimits@
}
\renewcommand\varprojlim{%
  \mathop{\mathpalette\varlim@{\leftarrowfill@\scriptstyle}}\nmlimits@
}
\makeatother


\begin{document}

\[
\varinjlim_{W\supset K} \qquad \varprojlim_{W\supset K} 
\]

\end{document}

enter image description here

This is what you get with \scriptscriptstyle instead:

enter image description here

1

There are two dimensions to your question. First, at least I think, a syntactical misunderstanding, and behavior sub-/superscripts in inline-math and in display-math. Let's start with the syntactical issue.

\lim only prints the limits symbol, nothing more than that. So writing \lim{\substack{\rightarrow\\W\supset K}} has exactly the same effect as writing \lim \substack{\rightarrow\\W\supset K} In order to create a subscript you need to use the underscore, just like you did with \mathcal{C}_A

The second dimension is the behavior of sub- and superscripts in inline-math and in display-math. If you use it in inline-mode latex will still set the subscript right next to the symbol, just al little bit lower, not below it. In display-math, it will always set it below it.

If you want LaTeX to behave in inline-math-mode like in display math, you can use the \limits macro. However, take into account that that can make the text line much taller than the other lines and can look very ugly, so think twice before using it. Here is the code for the showing the three options:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}

\usepackage{natbib}
\usepackage{graphicx}

\begin{document}
\section{Example}
Inline-math: $\lim_{\substack{\rightarrow\\W\supset K}} \mathcal{C}_{A}$\\
Display-math:
\[
\lim_{\substack{\rightarrow\\W\supset K}} \mathcal{C}_{A}
\]
Inline-math with limits: $\lim\limits_{\substack{\rightarrow\\W\supset K}} \mathcal{C}_{A}$
\end{document}

This is the output created by the above code. document created by code

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .