Horizontal placement of subscript/superscript

Question

I want to fine-tune the placement of subscripts and superscripts next to large parentheses. Since the large parentheses bulge out, they push the sub/superscripts too far to the right. MWE:

\documentclass{article}

\begin{document}
\[ \left(\frac{1}{2}A + B\right)_2 \]
\end{document}

Is there a way to fine-tune this? Just to nudge the 2 over a bit? I'm using pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013/Debian)

Answer 1

You could "nudge" the subscript to the left, i.e., place it closer to the closing parenthesis, by writing _{\!\!2} (two negative thinspaces) or _{\!2} (one negative thinspace) instead of just _2. Even better, though, would be not to use \left and \right to auto-size the parentheses to begin with. In fact, \left and \right may be the root cause of the problem, since the parentheses that are produced by \left( and \right) are needlessly large. Consider the following screenshot:

The first row is produced by your code, i.e., by \left(\frac{1}{2}A + B\right)_2. The second row shows the effect of nudging the subscript to the left via _{\!\!2}. In the third row, \Bigl and \Bigr are used instead of \left and \right; here, much less "nudging" is required.

The final row uses \tfrac ("text style \frac") to create a smaller, but still perfectly readable fraction term along with \bigl and \bigr. Now, no nudging is required at all. I would argue that the expression in the final row is the most readable of the four. :-)

\documentclass{article}
\usepackage{amsmath} % for 'gather*' environment
\begin{document}
\begin{gather*}
  \left(\frac{1}{2}A + B\right)_2 \\
  \left(\frac{1}{2}A + B\right)_{\!\!2}\\
  \Bigl(\frac{1}{2}A+B\Bigr)_{\!2}\\
  \bigl(\tfrac{1}{2}A+B\bigr)_2
\end{gather*}
\end{document}