The \not rendering and the line over sigma symbol

Question

I am writing a paper and I need to use the \not command on \sigma which stands for a order relation on a set. The issue is that the line over the sigma symbol is rendered poorly, is there any way I am not aware of so that the exact symbol I need is displayed correctly?

Answer 1

You can use centernot:

\documentclass{article}
\usepackage{centernot}% http://ctan.org/pkg/centernot
\begin{document}
$\not\sigma\ \centernot\sigma$
\end{document}