Bold version of \hbar

Question

I'm using \boldsymbol{\sigma} to create bold versions of certain characters and math symbols.

Unfortunately this doesn't work with "h-bar": \boldsymbol{\hbar} produces a non-bold version of \hbar.

What do I need to do to get a bold version of the physical constant \hbar?

Answer 1

The standard definition of hbar isn't very special: \hbar new letter So the following example works:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
$\hbar\quad\boldsymbol{\hbar}$
\end{document}

I guess you are loading amssymb. This package loads amsfonts . The package redefines the default definition as follows:

\global\let\hbar\undefined
\DeclareMathSymbol\hbar  {\mathord}{AMSb}{"7E}

So the method \boldsymbol fails. The explanation is given in the ams documentation in section 9.3: Bold math symbols

\boldsymbol can be used for a math symbol that remains unaffected by \mathbf if (and only if) your current math font set includes a bold version of that symbol. \pmb can be used as a last resort for any math symbols that do not have a true bold version provided by your set of math fonts; “pmb” stands for “poor man’s bold” and the command works by typesetting multiple copies of the symbol with slight offsets.�

Here an example using \pmb:

\documentclass{article}
\usepackage{amsmath,amssymb}
\begin{document}
$\mathbf{\hbar}\quad\boldsymbol{\hbar}\quad\pmb{\hbar}$
\end{document}

However another method could be to use the default definition of hbar:

\documentclass{article}
\let\hbarorig\hbar
\usepackage{amsmath,amssymb}
\let\hbar\hbarorig
\begin{document}
$\hbar\quad\boldsymbol{\hbar}$
\end{document}