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I want to put bullet symbol on top of downward arrow symbol. Can someone help me on this?

\documentclass{article}
\usepackage{graphicx}

\begin{document}

The transition is represented with $\mathrel{\bullet}\downarrow $ arrow.

\end{document}

Edit1: Actually I want to attach bullet symbol on top of downarrow symbol without any gap.

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4 Answers 4

up vote 7 down vote accepted

I don't really know what I'm doing with this, but a suggestion with \ooalign and \mathchoice:

enter image description here

\documentclass{article}
\newcommand\bulletarrow{%
\mathchoice
  {{\ooalign{\raise0.8ex\hbox{$\bullet$}\cr$\downarrow$}}}
  {{\ooalign{\raise0.8ex\hbox{$\bullet$}\cr$\downarrow$}}}
  {{\ooalign{\raise0.65ex\hbox{$\scriptstyle\bullet$}\cr$\scriptstyle\downarrow$}}}
  {{\ooalign{\raise0.5ex\hbox{$\scriptscriptstyle\bullet$}\cr$\scriptscriptstyle\downarrow$}}}%
}

\begin{document}

The transition is represented with $ \bulletarrow_{\bulletarrow_{\bulletarrow}} $ arrow.
\end{document}

For more information about \ooalign see egregs answer to another question.

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That's what I wanted. Thanks. –  user1890924 Mar 16 at 21:40
    
@egreg Wasn't quite able to wrap my head around \mathpalette right now. Feel free to modify if I've done anything silly. –  Torbjørn T. Mar 16 at 22:35

I just wanted to share this approach. The items are stacked to achieve the desired effect, and the \ThisStyle{...\SavedStyle...} macro of the scalerel package will automatically import the current mathstyle into the macro, into places where the mathstyle would otherwise be lost.

The length \LMpt is a length unit, used inside of the \ThisStyle argument, which is 1pt in \textstyle and \displaystyle, but scales to 0.7pt in \scriptstyle, and 0.5pt in \scriptscriptstyle, so that the relative stacking lengths remain proportional

\documentclass{article}
\usepackage{stackengine}
\usepackage{scalerel}[2014/03/10]
\def\specsym{\ThisStyle{\stackon[-1\LMpt]{$\SavedStyle\downarrow$}{$\SavedStyle\bullet$}}}
\begin{document}
This is the symbol: \specsym, 
$\specsym$ $\scriptstyle\specsym$ $\scriptscriptstyle\specsym$
\end{document}

enter image description here

One could embrace the macro in a \mathord if one desired to use it exclusively in math mode (thanks, egreg).

Thanks also to azetina who, in his answer, makes a good point regarding the use of stackengine. A syntax such as

\stackon[-1\LMpt]{$\SavedStyle\downarrow$}{$\SavedStyle\bullet$}

is easy to visualize and explain. Its drawback is that if you use stacks for other functions in your document, this syntax could be inadvertently affected by the setting of various stackengine defaults, like alignment, etc. One way to avoid this problem is to specify the macro in terms of \stackengine, which is not affected by the changing of package defaults. In the current case, that would mean a more obtuse, but also more protected syntax:

\stackengine{-1\LMpt}{$\SavedStyle\downarrow$}{$\SavedStyle\bullet$}{O}{c}{F}{F}{S}
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1  
\mathop is a TeX primitive; if you want to force a symbol to be used in math mode, use the correct type: \mathop, \mathrel, \mathbin, \mathpunct, \mathopen, \mathclose or \mathord. Probably the last one is what's best in this case. –  egreg Mar 16 at 23:39

You can use \overset from amsmath:

\documentclass{article}

\usepackage{amsmath}

\begin{document}

The transition is represent with $\overset{\bullet}{\downarrow}$ arrow.

\end{document}

output

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Can we attach these symbols together? Thanks for the help by the way. –  user1890924 Mar 16 at 21:31
    
@user1890924 I'm not used I know what you mean by "attach together"; please expand on your question. –  Svend Tveskæg Mar 16 at 21:32
    
There's a space between the two, so I suppose he wants to remove that. –  Torbjørn T. Mar 16 at 21:33
    
I just edited the question before your comment. :) –  user1890924 Mar 16 at 21:34

Using the stackengine package:

\documentclass{article}
\usepackage{amsmath}
\usepackage{stackengine}
\newcommand{\bulletarrow}{%
 \setstackgap{S}{-0.25ex}%
 \mathrel{\Shortstack{{$\bullet$} {$\downarrow$}}}}
\begin{document}
$\bulletarrow$
\end{document}

Another possible definition using the \stackengine command would be:

\stackengine{-0.25ex}{$\downarrow$}{$\bullet$}{O}{c}{F}{T}{S}
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1  
+1 for the "stack" approach. See my own answer for a twist on that. –  Steven B. Segletes Mar 16 at 23:23
    
@StevenB.Segletes Just saw it. They are your packages so you know best what other approaches exist. Wonderful approach by the way! –  azetina Mar 16 at 23:29

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