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I cannot get a double subscript to a letter that has a dot on it.

I only get what is in the first line of the picture, but what I want is the upper left with the dot only on the v. Note that the second vkd is not right.

I use this code

\documentclass[a4paper,10pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\begin{document}

% no errors here\dots
${v_k}_d$
${{\dot{v}}_{k_d}$
${\dot{v_k}_d}$

% this does not work as I thought it should
${{{\dot{v}}_k}}_d$
${{\dot v}_k}_d$
${\dot v_k}_d$

\end{document}

Any ideas??

Follow up

As the comments have shown, there is some doubt that these double subscripts are really necessary. They may be hardly visible, but they flatter the eyes - as I think - and make reading more comfortable. The picture below is what I write in original size.

This is also what the \usepackage{microtype} does. And, kerning doesn't bother you unless you know about it... Cf. this xkzd cartoon.

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1  
Is this \dot{v}_{kd} what you want? –  Sigur Jul 23 '13 at 15:45
    
Sorry, no. I want the subscript of the subscripted letter. –  Jan Jul 23 '13 at 15:47
    
I guess this notation is supposed to mean that $v$ is indexed by $k$ and by $d$... Isn't the notation $v_{k,d}$ more usual (and convenient) for this purpose? To be honest, I don't understand why ${v_k}_d$ (top left) doesn't give the "double subscript" error as well. –  T. Verron Jul 23 '13 at 15:47
    
The only thing that makes some kind of sense is ${{\dot{v}}_{k_d}$ (top middle). –  Martin Jul 23 '13 at 15:50
1  
I don't think that a reader can really notice the difference between ${v_k}_d$ and $v_{kd}$. –  egreg Jul 23 '13 at 16:08
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2 Answers

up vote 4 down vote accepted

I find the notation

${v_{k}}_d$

unclear; readers won't be able to distinguish it from

$v_{kd}$

However, if you really insist on doing it that way, you just have to add a pair of braces; I add what I'd do, instead.

\documentclass{article}

\begin{document}

${v_{k}}_{d}$

${{}\dot{v}_{k}}_{d}$

Better:

$(v_{k})_{d}$

$(\dot{v}_{k})_{d}$

\end{document}

enter image description here

It's a problem with math accent that sometimes shows up; in an expression such as ${\dot{v}_k}$ the outer braces are stripped off by rule, because they contain a single Acc atom; therefore the intuitive

${\dot{v}_k}_d$

gives a Double subscript error. Adding an empty subformula avoids the problem.

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Yes, thanks. Also for the explanation what goes wrong here ... –  Jan Jul 23 '13 at 16:20
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Of course, this is in \textstyle (going into \scriptstyle. If you need to use it in \scriptstyle (going into \scriptscriptstyle), let me know.

\documentclass{article}
\begin{document}
$\makebox{${\dot v}_k$}_d$
\end{document}

enter image description here

share|improve this answer
    
Yes, that gives what I want... Thank you. –  Jan Jul 23 '13 at 16:08
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