[Tex/LaTex] How to get a big cross to denote a generalized cartesian product?

math-mode

I'm trying to get a big cross which I can subscript in order to denote a generalized cartesian product (much like how \bigcup works for generalized unions). How can I accomplish this?

Best Answer

Looking in the The Comprehensive LaTeX Symbol List reveals a \bigtimes symbol defined by the mathabx package.

Related Solutions

[Tex/LaTex] How to use \lVert and \rVert norm symbols (‖x‖) with the Iwona math font

For very strange reasons, the slot "6B in the font sy-iwona is empty. The \lVert and \rVert commands point to that slot, so you can't see any symbol because it's not there to begin with. The definition of \lVert and \rVert given by amsmath are

\DeclareMathDelimiter{\lVert}
  {\mathopen}{symbols}{"6B}{largesymbols}{"0D}
\DeclareMathDelimiter{\rVert}
  {\mathclose}{symbols}{"6B}{largesymbols}{"0D}

which mean: in normal size take the character living in the symbol font in slot "6B while for bigger sizes take the character living in the largesymbols font in slot "0D. The difference between the two is that the former is given \mathopen type, the latter is \mathclose.

Indeed

$\norm[\big]{x}$

works, because the bigger delimiter is found.

enter image description here

There's not so much to do except taking the symbol from another font, for instance

\documentclass[border=4]{standalone}
\usepackage[math]{iwona}
\usepackage{mathtools}

\DeclareSymbolFont{extrasymbols}{OMS}{cmsy}{m}{n}
\DeclareMathDelimiter{\lVert}
  {\mathopen}{extrasymbols}{"6B}{largesymbols}{"0D}
\DeclareMathDelimiter{\rVert}
  {\mathclose}{extrasymbols}{"6B}{largesymbols}{"0D}

\DeclarePairedDelimiter\norm{\lVert}{\rVert}
\begin{document}
Testing $\norm{x}$.

Testing $\norm[\big]{x}$.
\end{document}

enter image description here

Unfortunately, a compatible candidate would be Kurier, which also lacks the symbol.

A different solution, that doesn't require a substitute font, is to emulate the symbol at the size it's missing.

\documentclass[border=4]{standalone}
\usepackage[math]{iwona}
\usepackage{mathtools}
\usepackage{xparse}

\DeclarePairedDelimiter\xnorm{\lVert}{\rVert}
\NewDocumentCommand{\norm}{som}
 {\IfBooleanTF{#1}
   {\xnorm*{#3}}
   {\IfNoValueTF{#2}
     {\mathopen{|\mkern-.8mu|}#3\mathclose{|\mkern-.8mu|}}
     {\xnorm[#2]{#3}}%
   }
 }


\begin{document}
Testing $\norm{x}$.

Testing $\norm[\big]{x}$.
\end{document}

The \norm symbol does like xnorm unless it has no optional argument, in which case the two bars are produced from the single bar.

enter image description here

If you want a definition that works without doing the hack when the bug is fixed, you can do like this:

\documentclass[border=4]{standalone}
\usepackage[math]{iwona}
\usepackage{mathtools}
\usepackage{xparse}

\makeatletter
\AtBeginDocument{%
  \check@mathfonts
  \iffontchar\textfont2 "6B
    \DeclarePairedDelimiter\norm{\lVert}{\rVert}
  \else
    \DeclarePairedDelimiter\xnorm{\lVert}{\rVert}
    \NewDocumentCommand{\norm}{som}
     {\IfBooleanTF{#1}
       {\xnorm*{#3}}
         {\IfNoValueTF{#2}
           {\mathopen{|\mkern-1mu|}#3\mathclose{|\mkern-1mu|}}
           {\xnorm[#2]{#3}}%
       }%
    }
  \fi
}
\makeatother

\begin{document}
Testing $\norm{x}$.

Testing $\norm[\big]{x}$.

\end{document}

It works with all fonts so long as they don't use bizarre slots for the double vertical bar. It will define \norm in the easier way if the character exists, otherwise it will do the hack.

[Tex/LaTex] How to denote adjacent vertices

You could use \arrownot from stmaryrd; the normal \not seems too big for a simple bar.

\documentclass{article}
\usepackage{stmaryrd} % for \arrownot
\newcommand{\notedge}{%
  \mathrel{\mkern-2mu}% a small back up
  \arrownot % a short slash
  \mathrel{\mkern2mu}% compensate
  \mathrel{-}% minus as a relation
}

\begin{document}
$u\notedge v$
\end{document}

enter image description here

This exploits two facts: \arrownot has zero width and is classified as a relation symbol (it extends past its bounding box); TeX doesn't add space between consecutive relation symbols (which can also be spaces)

This is how $u\not\mathrel{-}v$ would print:

enter image description here

A possible alternative:

\documentclass{article}
\usepackage{centernot}

\newcommand{\notedge}{\centernot{\mathrel{-}\joinrel\mathrel{-}}}

\begin{document}

$u\notedge v$

\end{document}

enter image description here

Another proposal with longer symbols:

\documentclass{article}

\usepackage{stmaryrd} % for \arrownot

\newcommand{\edge}{%
  \mathrel{-}% minus as a relation
  \joinrel\joinrel % some backup
  \mathrel{-}% minus as a relation
}
\newcommand{\notedge}{%
  \mathrel{\mkern2mu}% a small advancement
  \arrownot % a short slash
  \mathrel{\mkern-2mu}% compensate
  \edge
}

\begin{document}

$u \edge v$

$u\notedge v$

\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] How to use \lVert and \rVert norm symbols (‖x‖) with the Iwona math font

[Tex/LaTex] How to denote adjacent vertices

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