Text above isomorphism symbol

Question

When writing that two objects are isomorphic, I use X \cong Y.

Sometimes however, it is necessary to specify the type of isomorphism in question. I wish to do this with text above/below the isomorphism symbol, in much the same way that one can use \xrightarrow{} to insert text above an arrow indicating a map from X to Y.

Using X \cong_{text} Y or X \cong^{text} Y doesn't do exactly what I want, because this gives me subscript/superscript, which are offset from the \cong symbol. What I want is text that appears directly above/below the isomorphism symbol, like \xrightarrow.

What can I do to make that happen?

Is it similar to this question, like a starting point? https://tex.stackexchange.com/questions/306668/how-do-i-draw-the-cong-symbol-that-is-labelled. If it is possibile, please can you put a MWE or a minimal screenshot in LaTeX? — Sebastiano, Sep 22 '20 at 12:15

score 10 · Accepted Answer · edited Sep 22 '20 at 13:42

10

Like this?

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}
\begin{document}
$A\overset{a}{\cong}B, c\underset{b}{\cong}D$
\end{document}

It is possible to use \text from amsmath.

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}
\begin{document}
$A\overset{\text{over}}{\cong}B, c\underset{\text{under}}{\cong}D$
\end{document}

edited Sep 22 '20 at 13:42

projetmbc

13,315

answered Sep 22 '20 at 12:20

Sebastiano

54,118

1

Like that indeed. Thank you :) – Matt Sep 22 '20 at 13:11
@Matt It has been a pleasure to help you. :-) If you need us, we are all here to help you. – Sebastiano Sep 23 '20 at 08:03

Text above isomorphism symbol

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