32

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?

3
  • Have you tried to find the symbol on detexify? Something like \bigotimes without the 'O' maybe?
    – raphink
    Sep 11, 2011 at 22:46
  • @Raphink: Thanks! Yes, I tried both things. ´\bigtimes´ isn't defined, and ´\bigotimes´ produces a cross inscribed inside a circle. Sep 11, 2011 at 23:20
  • 4
    Isn't the standard(ish) mathematical notation to use \prod for n-ary Cartesian products, not a giant \times?
    – jwodder
    Sep 12, 2011 at 2:07

6 Answers 6

35

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

2
  • 3
    I just found out (accidentally :)) that the \bigtimes symbol is also defined in the mathtools package.
    – Count Zero
    Sep 12, 2011 at 13:45
  • 12
    regarding mathabx beware that it changes the shape of many other symbols; it is recommended to extract the code for just the desired symbol(s) into your preamble to avoid unexpected results. Sep 12, 2011 at 13:57
14

If you don't mind using a different font, kpfonts gives you the \varprod command:

\documentclass{article}
\usepackage{kpfonts}

\begin{document}

$\varprod_{i=1}^n A_i$

\[
  \varprod_{i=1}^n A_i
\]

\end{document}

enter image description here

I would be more inclined to use \prod to denote a generalised cartesian product, though.

1
  • 1
    Strictly speaking, \prod should be the general symbol for product in categorical sense. The Cartesian product is a product in many categories such as sets and modules, but it is not always the case.
    – ashpool
    May 4, 2014 at 18:44
6

I am sure others will come up with simpler solutions, but here is an overkill solution that might be useful:

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\newcommand{\Cross}{\mathbin{\tikz [x=1.4ex,y=1.4ex,line width=.2ex] \draw (0,0) -- (1,1) (0,1) -- (1,0);}}%
\begin{document}
$A \Cross B$
\end{document}

enter image description here

Adjust the x= and y= options to change the size, and the line width= to adjust the thickness of the line. The \mathbin ensures that correct spacing for a binary operator is placed around the symbol.

4
  • 1
    If you are down voting, it would be helpful it your provided some explanation so others can know what is wrong with this solution, or why you are opposed to this solution. Feb 19, 2013 at 19:41
  • I'm not the downvoter, but you seem to be re-implementing the binary cartesian product symbol, and the OP is asking about a "sigma-style" symbol to apply to the Cartesian product of a family of sets. Mar 27, 2013 at 0:29
  • @MatthewLeingang: Ahhh thanks. That clarifies things. Mar 27, 2013 at 0:43
  • Still, I wouldn't have downvoted. I got to this answer from your comments on tex.stackexchange.com/questions/104164/… and I agree with your POV. Mar 27, 2013 at 1:17
2

There is a simple command for that in the mathabx package:

\documentclass{minimal}

\usepackage{mathabx}

\begin{document}
   $\bigtimes\limits_{x=1}$
\end{document}

In fact if you find another operator symbol you fancy, you can try the \limits command on it. It may actually work. :)

I hope this answers it. :)

2

If you can use unicode-math, the symbol you are looking for is at U+2A09 'N-ARY TIMES OPERATOR'

\usepackage{unicode-math}
\begin{equation}
B ⊂ ⨉_{x∈J}A(x)
\end{equation}

This package only works on the XeLaTex and LuaLaTeX engines though.

Result of the above code

-3

Might I suggest a very simple-minded approach?
Why not just use the letter "X"? Below, I inserted \sf to render the symbol more distinguishable

$${\sf X}^n_{i=1} A_i = A_1\times \cdots \times A_n$$
1

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