# Arrow with a point on it and cancelled arrow

I stumbled over this kind of arrows and can't find any reference to it (since I not even know how they're called).

Does anyone know the right command for those? Or are this constructed elements?

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\overset{\bullet}{\to} with amsmath whould work; for the second one, look at the centernot package. The canonical reference is How to look up a symbol –  egreg Jan 12 '13 at 18:41
For the second one, the amssymb package offers \nrightarrow. –  Gonzalo Medina Jan 12 '13 at 18:48

\documentclass{article}
\usepackage{amssymb,amsmath}
\usepackage{centernot}

\begin{document}
$X \overset{\bullet}{\to} Y$

$X \overset{\bullet\mkern3mu}{\to} Y$

$X \overset{\scalebox{0.5}{$\bullet$}\mkern3mu}{\to} Y$

$X \overset{\raisebox{-1ex}{\scalebox{0.5}{$\bullet$}}\mkern3mu}{\to} Y$

$\nrightarrow$

$\not\rightarrow$

$\centernot{\rightarrow}$
\end{document}


yields

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the dot would look better a bit to the left. insert \mkern-3mu (within the braces) after the \bullet. the dot also looks too high, but that's harder to fix. –  barbara beeton Jan 12 '13 at 21:53
The dot seems to me to be too large. I would recommend \stackrel instead of \overset. –  yo' Jan 13 '13 at 0:08
@tohecz \stackrel does not change anything for me, at least here. –  mafp Jan 13 '13 at 10:50
Sorry, I meant \stackrel{{}_\bullet}{\rightarrow} (doable with \overset the very same way). And you're right, the result is exactly same. Just that \overset does quite a lot of unnecessary things that \stackrel does not. As well, \stackrel seems to be semantically correct ("stack" something on a "relation" symbol). –  yo' Jan 13 '13 at 18:47