symbols
I can’t figure out what this
symbol is. It is used in the context of “column space of a matrix X”.
It is not one of the Greek letters and my guess is that it is just an ordinary “S” with some sort of text style. I have looked through all common ones but could not find an appropriate one.
From the alphalph package documentation:
1.2.3 Multiple symbols
LATEX's standard set of footnote symbols contains doubled symbols at the higher positions. Could this principle be generalized? Yes, but first we need a clean footnote symbol list without doubled entries, example:
\usepackage{alphalph}
\makeatletter
\newcommand*{\fnsymbolsingle}[1]{%
\ensuremath{%
\ifcase#1%
\or *%
\or \dagger
\or \ddagger
\or \mathsection
\or \mathparagraph
\else
\@ctrerr
\fi
}%
}
\makeatother
\newalphalph{\fnsymbolmult}[mult]{\fnsymbolsingle}{}
\renewcommand*{\thefootnote}{%
\fnsymbolmult{\value{footnote}}%
}
The own definition of
\fnsymbolsinglehas the advantage that this list can easily modified. Otherwise you can use\@fnsymboldirectly, because it uses the same first five symbols.
\usepackage{alphalph}
\makeatletter
\newalphalph{\fnsymbolmult}[mult]{\@fnsymbol}{5}
\makeatother
\renewcommand*{\thefootnote}{%
\fnsymbolmult{\value{footnote}}%
}
In the Comprehensive List (texdoc symbols) one can find something near to what you want, looking for \independent. Here's a modified version:
\documentclass{article}
\makeatletter
\DeclareRobustCommand{\varamalg}{%
\mathbin{\mathpalette\var@malg\perp}%
}
\newcommand\var@malg[2]{%
\rlap{$\m@th#1#2$}\mkern6mu{#1#2}%
}
\makeatother
\begin{document}
\[
\alpha\varamalg\beta=\alpha\times\{0\}\cup\beta\times\{1\}
\]
\end{document}
Adjust \mkern6mu to suit.
Best Answer
I can't decide whether this is a hit or a miss (yours is a little thinner). It looks like the item is span (or initial of some other word).
Personal rant : Math with text decorations sucks big time. Notation is for the reader not for the author's Gaussian fantasies (patent pending).