# What is the best symbol to use for the d'Alembertian?

Normally, most people use the symbol $\Box$ to represent the d'Alembert (wave) operator (including the linked to Wikipedia page).

Recently I wanted to use \hat\Box and \tilde\Box, but they do not render very well.

What is the "best" way to create such symbols?

Aside: The above image is rendered using my local install of pdflatex: pdfTeX 3.1415926-1.40.10-2.2 (TeX Live 2009/Debian). The symbols seem to render fine on some online services: e.g. "Online LaTeX Equation Editor" produces

from

\begin{align*}
\Box &= \sum_a \partial^a\partial_a \,, &
\hat\Box &= \sum_a \mathcal{D}^a\mathcal{D}_a
\end{align*}

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+1 I would like to see a symbol that looks well when use with \nabla and \Delta. These symbols have heavier line width than \box which makes the latter look odd.. –  romeovs Jun 12 '11 at 6:27
@romeovs: I don't use \nabla or \Delta much, but I see your point. Maybe it's worth its own question? –  Simon Jun 13 '11 at 9:58

I try with lmodern and then fourier and the result seems correct but I agree symbols \nabla \Delta have heavier line width than \box

\documentclass[11pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amssymb,lmodern} %and then fourier

\begin{document}

$\hat\Box \nabla \Delta$

\begin{align*}
\Box &= \sum_a \partial^a\partial_a \,, &
\hat\Box &= \sum_a \mathcal{D}^a\mathcal{D}_a
\end{align*}
\end{document}


Finally I prefer :

\documentclass[11pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,fourier}
\begin{document}

$\hat\square \nabla \Delta$

\begin{align*}
\square &= \sum_a \partial^a\partial_a \,, &
\hat\square &= \sum_a \mathcal{D}^a\mathcal{D}_a
\end{align*}
\end{document}


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Thanks Altermundus. I think that the best/easiest solution might be to use \square, that way the result is not too font dependent. I'll leave the question open for a little while to see if anyone else has suggestions. –  Simon Jun 13 '11 at 9:57
@Simon You use what font for the mathematics ? –  Alain Matthes Jun 13 '11 at 10:11
amsfonts? I'm writing a memoir class document and have the following packages loaded: \usepackage{amsmath,amsfonts,amssymb,amsthm,nccmath,latexsym,mathtools} \usepackage[mathscr]{euscript} –  Simon Jun 13 '11 at 10:19