how can i express this symbol in latex (it looks similar Sigma)

Question

see this image1

see this image2

in mathsymbol, what is it in latex? it means covariance matrices.

i draw this symbol in Detexify, but i can't find it.

i ask Chat GPT, but it always say \Sigma,

and mathpix said 4 or \Phi ...

i want to know this symbol.

Answer 1

I don't think the symbol has a specific name, it is definitely a Sigma, just barred. If you want to draw this in LaTeX, you can use the math versions of the \Xlap commands (where X is one of l c r) offered by the mathtools package, that allow printing a symbol without it taking any actual horizontal space, effectively enabling you to superpose symbols.

Here I use the \mathrlap command to print a sizeless Sigma, then again for printing a vertical bar preceded by a space of 2 points (change it to your taste), and finally a \phantom command that does the opposite: print a space the size of a Sigma, but invisible.

\documentclass{article}
\usepackage{mathtools}
\begin{document}

\( A \mathrlap{\Sigma} \mathrlap{\hspace{2pt}\vert} \phantom{\Sigma} Z \)

\end{document}

A render of the equation given above