[Tex/LaTex] How to write this symbol in latex? (disjoint sharp operator)

logicmath-operatorssymbols

I can't find this symbol used to indicate the disjoint sharp operator.

It's a # inside a circle. Is this symbol available in LaTex? if not, how can I draw it inside a mathematical equation?

Best Answer

You can use a scaled up version of \bigcirc and \ooalign:

\documentclass{article}
\usepackage{amsmath,graphicx}

\makeatletter
\newcommand{\makecircled}[2][\mathord]{#1{\mathpalette\make@circled{#2}}}
\newcommand{\make@circled}[2]{%
  \begingroup\m@th
  \vphantom{\biggercirc{#1}}%
  \ooalign{$#1\biggercirc{#1}$\cr\hidewidth$#1#2$\hidewidth\cr}%
  \endgroup
}
\newcommand{\biggercirc}[1]{%
  \vcenter{\hbox{\scalebox{1.4}{$\m@th#1\bigcirc$}}}%
}
\makeatother

\newcommand{\disjointsharp}{\makecircled[\mathbin]{\#}}

\begin{document}

$A\disjointsharp B_{A\disjointsharp B}$

\end{document}

I used \mathbin but it could be \mathrel depending on the meaning.

See https://tex.stackexchange.com/a/22375/4427 for a quick course on \ooalign.

With a smaller circle

\documentclass{article}
\usepackage{amsmath,graphicx}

\makeatletter
\newcommand{\makecircled}[2][\mathord]{#1{\mathpalette\make@circled{#2}}}
\newcommand{\make@circled}[2]{%
  \begingroup\m@th
  \vphantom{\bigcirc}%
  \ooalign{$#1\bigcirc$\cr\hidewidth$#1\make@smaller{#1}{#2}$\hidewidth\cr}%
  \endgroup
}
\newcommand{\make@smaller}[2]{%
  \vcenter{\hbox{\scalebox{0.7}{$\m@th#1#2$}}}%
}
\makeatother

\newcommand{\disjointsharp}{\makecircled[\mathbin]{\#}}

\begin{document}

$A\disjointsharp B_{A\disjointsharp B}$

\end{document}

When symbols are “bigger”, they are usually centered with respect to the formula axis.

Another possibility:

\documentclass{article}
\usepackage{amsmath,graphicx}

\makeatletter
\newcommand{\makecircled}[2][\mathord]{#1{\mathpalette\make@circled{#2}}}
\newcommand{\make@circled}[2]{%
  \begingroup\m@th
  \sbox\z@{$#1A$}%
  \sbox\tw@{%
    \raisebox{\depth}{%
      \vphantom{$#1A$}%
      \ooalign{%
        \hidewidth$#1\make@smaller{#1}{#2}$\hidewidth\cr
        $#1\bigcirc$\cr
      }%
    }%
  }%
  \resizebox{!}{\ht\z@}{\box\tw@}%
  \endgroup
}
\newcommand{\make@smaller}[2]{%
  \vcenter{\hbox{\scalebox{0.7}{$\m@th#1#2$}}}%
}
\makeatother

\newcommand{\disjointsharp}{\makecircled[\mathbin]{\#}}

\begin{document}

$A\disjointsharp B_{A\disjointsharp B}$

\end{document}

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You should place the expression in the subscript, as shown below. Most LaTeX books explain this. E.g.

\documentclass{article}

\begin{document}
\begin{itemize}
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    \item \textbf{Inline mode}: version without \verb!\limits! would look like \(\max_{1 \leq i \leq N}\), version with \verb!\limits! would look like\(\max\limits_{1 \leq i \leq N}\) inside a text.
\end{itemize}
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Note how \limits command force the subscript under operator in inline mode (if you think you need \limits, think again — maybe the defaults look better after all! cf. this answer here on TeX.se).

If you find that the subscripted expression is too long and introduces excessive whitespace, you could use \smashoperator macro from the mathtools package, as in this post.

[Tex/LaTex] Delta-like symbol in LaTeX

Note that the document uses Springer's LNCS style. In this style, all Greek letters are in italics, and vectors are denoted by boldface.

Most likely the bold italic Delta is produced in this particular case by something similar to this:

\documentclass{llncs}
\begin{document}
$\vec{\Delta}$
\end{document}

The result is:

llncs

Note that if you used the article class, the same code would produce a normal Delta with an arrow:

article

Best Answer

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