As the question says, like so
?
Symbols – How to Get the Character for a Sigma Field
symbols
Related Solutions
The command \ldots, which works both in text mode and in math mode, will create a single glyph in xelatex and lualatex, assuming you're using a font that knows how to set character U+2026, "Horizontal Ellipsis."
In an earlier version of this answer, I mistakenly referred to what's created in pdflatex by the \ldots command as a "single glyph". In fact, it's composed of three separate dots, concatenated by non-breaking whitespace. Thus, while it's not a single glyph in the narrow, technical sense, it behaves like one for typesetting purposes. For instance, it won't ever get broken up across two lines.
I don't recognise the image as a sigma. Unicode has three variant lowercase sigmas
U+03c2 GREEK SMALL LETTER FINAL SIGMA
U+03c3 GREEK SMALL LETTER SIGMA
U+03f2 GREEK LUNATE SIGMA SYMBOL
which look like
ςσϲ
or as an image
If you are convinced you want the letter shape you drew just save it as a png or (better if you can) a scalable format such as pdf, then you can do
\documentclass{article}
\usepackage{graphicx,amsmath}
\newcommand\bentpaperclip{\includegraphics[height=1ex]{bentpaperclip.png}}
\begin{document}
\[\sigma \neq \varsigma \neq \bentpaperclip\]
\end{document}
Best Answer
As already pointed out by Paolo C. in a comment,
\mathcal{F}is the way to go to typeset a calligraphic "F" in math mode. Now, there are quite a few math alphabets out there, and each one features a different shape for the calligraphic F. Here are but a few possibilities:The default is, on most TeX systems, Computer Modern. If one of the other glyphs strikes your fancy, you may want to look into how to load one or more math font package. Or, load the mathalfa package with a suitable
cal=<xxx>option. (In case you're curious, I obtained the 10 glyphs above by loading themathalfapackage with varying options.)