# Increase the space between operator in subscript/superscript

I need to increase the space globally between operators in subscripts/superscripts.

Example: \sum_{x=4}

I need a little more space before and after the = symbol in the subscript. It is required globally in every operator in subscripts/superscripts.

• Welcome to TeX.SX! You may have a look on our starter guide. – texenthusiast May 10 '13 at 5:30
• You could probably renew the sum command with some trick to add spaces to equals signs in the subscripts. – Benjamin McKay Jan 22 '18 at 10:41

TeX does not put any space around operators in that position, so there is no parameter that you can set to control that space. This is different from the space in text or display style which you can control by setting the em width. See this answer on font dimens

So you can either set the subscript in text style (which might already be enough space) and then increase em or \thickmuskip or you need to use an explicit space such as \,.

\documentclass{article}

\begin{document}

$\sum_{x=3}x=3$

$\sum_{\displaystyle x=4}x=4$

$\sum_{x\,=\,5}x=5$

{\thickmuskip=22mu
$\sum_{\displaystyle x=6}x=6$
}

\fontdimen6\scriptfont2=1in
\fontdimen6\textfont2=1in

$\sum_{x=7}x=7$

$\sum_{\textstyle x=8}x=8$

\end{document}


The spacing depends on the command you insert, the example below contains a complete list of spaces and how they look like.

Spaces in mathematical mode.

\begin{align*}
f(x) =& x^2\! +3x\! +2 \\
f(x) =& x^2+3x+2 \\
f(x) =& x^2\, +3x\, +2 \\
f(x) =& x^2\: +3x\: +2 \\
f(x) =& x^2\; +3x\; +2 \\
f(x) =& x^2\ +3x\ +2 \\

\sum_{x\ =\ 4}