# [Tex/LaTex] How to make \mid longer?

symbols

I have the following expression

$$\left\{\varphi\in\text{End}\left({\widetilde{E}/\overline{\F}_{\Pf}}\right)\mid \varphi\text{Frob}_{\Pf}=\text{Frob}_{\Pf}\varphi\right\}$$


and would like to know how to match the length of \mid to the length of \left\{ and \right\}. Thanks!

For middle stretchable delimiters you can use \middle:

\documentclass{article}
\usepackage{amsmath}

\newcommand\F{F}
\newcommand\Pf{Pf}
\DeclareMathOperator{\End}{End}
\DeclareMathOperator{\Frob}{Frob}

\begin{document}

$\left\{\varphi\in\End \bigl(\widetilde{E}/\overline{\F}_{\Pf}\bigr) \,\middle\vert\, \varphi\Frob_{\Pf}=\Frob_{\Pf}\varphi\right\}$

\end{document}


Notice also the use of \DeclareMathOperator to produce the right font and spacing for "End" and "Frob". Also, $$...$$ shouldn't be used in modern LaTeX documents; use $...$ instead. Since I didn't know the definitions of some commands, I defined them provisionally.