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How can I make the square brackets on the following equation the same size?

\begin{equation}
\begin{split}R^{\mu}_{\nu\rho\sigma} &= \partial_{\rho}\left[\bar{\Gamma}^{\mu}_{\nu\sigma} + \tfrac{1}{2}\,\bar{g}^{\mu\beta}\left(\bar{\nabla}_{\nu}h_{\sigma\beta}+\bar{\nabla}_{\sigma}h_{\nu\beta}+\bar{\nabla}_{\beta}h_{\nu\sigma}\right)\right] \\
& -\partial_{\sigma}\left[\bar{\Gamma}^{\mu}_{\nu\rho} + \tfrac{1}{2}\,\bar{g}^{\mu\alpha}\left(\bar{\nabla}_{\nu}h_{\rho\alpha}+\bar{\nabla}_{\rho}h_{\nu\alpha}+\bar{\nabla}_{\alpha}h_{\nu\rho}\right)\right]
\end{split}
\end{equation}

Edit: to clarify, I have uploaded the problem I was having with the above code: enter image description here

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1  
Manually adjust them with \bigl/\bigr, \Bigl/\Bigr, \biggl/\biggr or \Biggl/\Biggr. Instead of \left/\right. They don't need to be paired, like the latter ones. –  Manuel Jan 30 '13 at 21:16
    
i don't understand the question. the square brackets in the example are all the same size. –  barbara beeton Jan 30 '13 at 21:17
    
@Manuel This is what I was looking for; if you add it as an answer I'll accept it. (at)barbarabeeton Not for me. –  User 17670 Jan 30 '13 at 21:23
    
Mmm, they are the same size also for me. I answered without checking your code. –  Manuel Jan 30 '13 at 21:26
    
For me, the first set of \left[ \right] are much bigger (to accommodate the $\beta$) than the second set on the line below. –  User 17670 Jan 31 '13 at 10:12
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2 Answers

up vote 6 down vote accepted

Like some of the other commenters, I believe the square brackets in the code snippet you've posted already all have the same size. I would actually suggest that you make the round parentheses smaller -- more precisely, to leave them at their default size. This will allow for some more natural grouping of the "fences," from the inner parentheses to the outer brackets.

I'd also recommend that you make a few more changes, such as (i) aligning the two RHS expressions vertically and (ii) reducing the whitespace between \bar{\nabla} and the subscript terms:

enter image description here

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
R^{\mu}_{\nu\rho\sigma} 
&= \phantom{-}\, % force extra bit of whitespace after equal sign
 \partial_{\rho}\bigl[ \bar{\Gamma}^{\mu}_{\nu\sigma} 
+ \tfrac{1}{2}\,\bar{g}^{\mu\beta}
(\bar{\nabla}_{\!\nu}h_{\sigma\beta}
+\bar{\nabla}_{\!\sigma}h_{\nu\beta}
+\bar{\nabla}_{\!\beta}h_{\nu\sigma} )\bigr] \\
&\phantom{{}=} 
-\partial_{\sigma}\bigl[ \bar{\Gamma}^{\mu}_{\nu\rho} 
+ \tfrac{1}{2}\,\bar{g}^{\mu\alpha}
(\bar{\nabla}_{\!\nu}h_{\rho\alpha}
+\bar{\nabla}_{\!\rho}h_{\nu\alpha}
+\bar{\nabla}_{\!\alpha}h_{\nu\rho} )\bigr]
\end{split}
\end{equation}
\end{document}

Addendum: Following @egreg's suggestion, here's an alternative form of displaying the same equation, one which deliberately doesn't attempt to perform a vertical alignment of the two RHS parts:

enter image description here

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
R^{\mu}_{\nu\rho\sigma} 
&= \partial_{\rho}\bigl[\bar{\Gamma}^{\mu}_{\nu\sigma} 
+ \tfrac{1}{2}\,\bar{g}^{\mu\beta}
(\bar{\nabla}_{\!\nu}h_{\sigma\beta}
+\bar{\nabla}_{\!\sigma}h_{\nu\beta}
+\bar{\nabla}_{\!\beta}h_{\nu\sigma} )\bigr] \\
&\qquad{} -\partial_{\sigma}\bigl[\bar{\Gamma}^{\mu}_{\nu\rho} 
+ \tfrac{1}{2}\,\bar{g}^{\mu\alpha}
(\bar{\nabla}_{\!\nu}h_{\rho\alpha}
+\bar{\nabla}_{\!\rho}h_{\nu\alpha}
+\bar{\nabla}_{\!\alpha}h_{\nu\rho} )\bigr]
\end{split}
\end{equation}
\end{document}
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2  
Since the two subformulas don't align perfectly, I'd prefer moving the bottom one a bit to the right, and the top one next to the =. Just being picky. –  egreg Jan 30 '13 at 23:47
    
@egreg - great suggestion! I've incorporated it as an addendum to my answer. –  Mico Jan 31 '13 at 0:55
    
Thanks for the suggestions, in particular the reduction of white space after the nablas. –  User 17670 Jan 31 '13 at 10:22
    
In your addendum example, I think you can remove the {} after \qquad and still get the correct space between the - and the \partial. (The line should also still be indented by the exact same amount.) –  MSC Feb 1 '13 at 0:17
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You could also place a \vphantom{\bar{g}^{\mu\beta}} inside the second pair of square brackets. I've used it when I had to split an expression in parentheses into multiple lines using \left( \right. in the first line and \left. \right) in the last, and you want both the opening and the closing parenthesis to have the same height.

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1  
actually, all you'd need is ^{\mu\alpha\vphantom{\beta}}, but perhaps that's a bit too compact for clarity. –  barbara beeton Jan 31 '13 at 14:03
    
While your suggestion is more concise, I find it easier to "maintain" my approach, since it doesn't depend on the similarity of the two lines (say, if notations where to change drastically). –  Christoph B. Feb 1 '13 at 21:05
    
that gives a good result, you have an eminently justifiable reason, and the symmetry of the code is clean, so it won't give a technical editor fits. go with it. –  barbara beeton Feb 1 '13 at 22:23
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