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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.

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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
2  
@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

4 Answers 4

up vote 18 down vote accepted

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. :)

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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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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

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Welcome to TeX.sx! –  Kurt Oct 16 '12 at 0:30
    
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 at 21:14

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.

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