16

I am trying to find a certain mathemtical symbol. It is a \bigvee with an arrowhead as in this picture: Directed supremum

Some authors use this as symbol in domain theory. It denotes the supremum of a set and furthermore states that the set is directed.
I did not find it in the The Comprehensive LaTeX Symbol List.

  • I tried shapecatcher (shapecatcher.com, found from tex.stackexchange.com/questions/36199/unicode-character-look-up) with no luck, so it doesn't seem to be a known unicode character. You might have to build it by hand. Someone on this site can probably help with that. – Ethan Bolker May 28 '12 at 15:33
  • 1
    Is there any source that we can see what you mean? It might be a composite character like this $A\raisebox{.12ex}{$\backslash$}\kern-.98ex\nearrow B$ – percusse May 28 '12 at 15:40
  • I have seen this only on the blackboard, so I have no source. One attempt to define the symbol is made in euclid.ucc.ie/pages/staff/pawel/domains1.tex in line 33 (and 115 for its definition). I add a better description in the question. – bitt.j May 28 '12 at 15:46
  • @percusse Your ad-hoc solutios is quite good. But I would prefer a more symetric symbol. – bitt.j May 28 '12 at 15:56
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    @EthanBolker -- this isn't a unicode character, but if a citation (published by a "recognized" publisher) can be found i will cheerfully submit it to the unicode technical committee for consideration. please see my profile for contact information. – barbara beeton May 28 '12 at 18:42
18

There are two ways to go (actually three, if you include drawing your symbol with tikz, against which you will find several advocates on this site ;)):

\documentclass[10pt,a4paper]{article}
\usepackage{stmaryrd}
\usepackage{graphicx}

\begin{document}
$A~\setminus\kern-.95ex\nnearrow B$ %This needs the stmaryrd package for the \nnearrow symbol

$\bigvee{}\kern-1.5ex\rotatebox{-30}{$\large\mathbf{\hat{\vphantom{a}}}$}$ %\rotatebox requires the graphicx package
\end{document}

enter image description here

Adjust rotation and kerning as you you wish. :)

5

Here is a very nice solution which I found on the web, I cannot remember where; I wish I could attribute it properly.

\newcommand{\dirsup}{\mathrel{\setlength{\unitlength}{.7em}\raisebox{-.2em}%
    {\begin{picture}(1,1.5)\put(.5,0){\line(-1,3){.48}}
    \put(.5,0){\vector(1,3){.5}}\end{picture}}}} % directed sup

You can see the symbols side by side at http://www.cs.mcgill.ca/~prakash/dirsup_comparison.pdf:

enter image description here

  • I'm pretty sure Prakash's code snippet came from me, although I am not sure whether I was the one who wrote it originally, or whether I cribbed it from someone else at the time. I checked my old files, and I found a version of it that I used in 1994, and then the exact version shown above in my 1997 thesis - only it should be \mathop instead of \mathrel, so that bounds will be positioned correctly, for example in $\dirsup_{i\in I} A_i$. Will I be famous now? Sorry, I meant to post this as a comment, rather than an answer, but apparently I don't have the required reputation to be allowed to com – Peter Selinger Apr 3 '14 at 21:14
4

Probably not as good as the answer already accepted, but possibly useful when rotated a quarter of a circle:

Lightning: ☇ Unicode hexadecimal: 0x2607 In block: Miscellaneous Symbols

See Is there a readymade symbol for a 90 degrees rotated \Bowtie? for rotation code.

1

Since @CountZero suggested it :-), here is a TikZ version showing a few of the options:

enter image description here

Code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\newcommand{\SupermumDirected}[1][]{%
    \mathbin{\tikz [x=1.4ex,y=1.6ex,line width=.15ex,baseline] 
        \draw [->,#1] (0,1) -- (0.5,0) -- (1,1.25);
    }%
}

\begin{document}
    $A \SupermumDirected B \SupermumDirected[red,-stealth] C \SupermumDirected[blue,-latex] D$
\end{document}

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