LaTeX Calligraphic Script Bold

Question

Does anyone know how to bold calligraphic \mathscr fonts in a math environment? I can get a fancy calligraphic font if I use \mathscr, but \boldsymbol does not work, nor does \mathbf. There is a hack which uses poor man's bold, but I was wondering if there is an alternate way to do this "cleanly". I've also seen \bm used for \mathcal font, but that's not what I'm looking for unfortunately.

I'm using calligraphic fonts with the following packages:

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{mathrsfs}

Answer 1

The RSFS fonts are not available in a bold version. You can however use the \pmb command from the amsbsy package, which simulates a bold weight by putting three copies of the respective character next to each other.

\documentclass{article}

\usepackage{mathrsfs}
\usepackage{amsbsy}

\begin{document}
$\mathscr{ABC}$\par
$\pmb{\mathscr{ABC}}$
\end{document}

Another option is to use one of the calligraphic fonts provided by the mathdesign package, which resemble the RSFS fonts very closely and have bold weights.

\documentclass{article}

\usepackage{mathrsfs}
\DeclareMathAlphabet{\mathscrbf}{OMS}{mdugm}{b}{n}

\begin{document}
$\mathscr{ABC}$\par
$\mathscrbf{ABC}$
\end{document}

Answer 2

One way is to switch to LuaLaTeX (or XeLaTeX) with the unicode-math package. This allows you to use any OpenType math font. Complete OpenType math fonts should implement all math characters from Unicode, which in particular includes bold script letters.

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{xits-math.otf}
% In TeX Live 2011 you can use 'lmmath-regular.otf' instead to get a math font that is
% matching with the default Latin Modern text font.

\begin{document}
$\mathscr{ABCabc}$

$\mathbfscr{ABCabc}$
\end{document}

Be aware however that these technologies are currently still in development and might contain some bugs.