# \displaystyle and \mathbf with cmbright font

I would like to use bold symbols in superscript equations. To do so, I use \displaystyle as in

\documentclass{standalone}
\usepackage{amsmath}
\begin{document}
$e^{\mathbf{A}t}=e^{\displaystyle \mathbf{A}t}=e^{{\displaystyle \mathbf{A}}t}$
\end{document}


The corresponding output is:

The first exponential is exactly what I'm looking for.

Now, if I add the cmbright package, the corresponding code

\documentclass{standalone}
\usepackage{amsmath}
\usepackage{cmbright}
\begin{document}
$e^{\mathbf{A}t}=e^{\displaystyle \mathbf{A}t}=e^{{\displaystyle \mathbf{A}}t}$
\end{document}


yields:

As one can see, in the left exponential the A symbol is not bold, and the other symbols are larger (as expected with \displaystyle).

I guess there is a pretty simple explanation about cmbright but I am not aware of it. Any clues to get the bold symbol AND the normal size with cmbright?

-
Try \mathbold{}. –  Sigur Jul 30 '14 at 22:25

For mysterious reasons, the .fd file for the OT1 encoding defines a substitution rule for the bold font at sizes less than 9pt and chooses a non bold font, instead of scaling the only available font (at 10pt).

Cure it by redefining the font shapes.

\documentclass[border=3pt]{standalone}
\usepackage{amsmath}
\usepackage{cmbright}

\DeclareFontFamily{OT1}{cmbr}{\hyphenchar\font45 }
\DeclareFontShape{OT1}{cmbr}{m}{n}{%
<-9>cmbr8
<9-10>cmbr9
<10-17>cmbr10
<17->cmbr17
}{}
\DeclareFontShape{OT1}{cmbr}{m}{sl}{%
<-9>cmbrsl8
<9-10>cmbrsl9
<10-17>cmbrsl10
<17->cmbrsl17
}{}
\DeclareFontShape{OT1}{cmbr}{m}{it}{%
<->ssub*cmbr/m/sl
}{}
\DeclareFontShape{OT1}{cmbr}{b}{n}{%
<->ssub*cmbr/bx/n
}{}
\DeclareFontShape{OT1}{cmbr}{bx}{n}{%
<->cmbrbx10
}{}

\begin{document}

$\mathbf{A}\mapsto e^{\mathbf{A}t}$

\end{document}


-
This answers my question even more accurately than Sigur's, but I already accepted Sigur answer... Thank you –  anderstood Jul 30 '14 at 22:44
Very theoretic answer. Thanks! –  Sigur Jul 30 '14 at 22:47
@anderstood, it is up to you. Feel free. We all learn a lot with egreg's posts. –  Sigur Jul 30 '14 at 22:57

From the documentation cmbright package you can use the \mathbold{} command.

But the A is in italic shape.

-
The fact that A becomes italic seems more logical to me :) Is there any drawbacks to replace all \mathbf commands with \mathbold? –  anderstood Jul 30 '14 at 22:38
You can try \renewcommand{\mathbf}[1]{\mathbold{#1}} –  Sigur Jul 30 '14 at 22:45
I did so and did not see any drawbacks in my present document, but maybe you knew some which could cause me trouble in the future, if I stopped using \mathbf. –  anderstood Jul 30 '14 at 22:52
If you stop using cmbright package the command \mathbold would not be defined anymore and then you simply comment that line with %. –  Sigur Jul 30 '14 at 22:56
Thanks for making me be aware of the \mathbold command. I got used to it, but never understood why bold symbols became non-italic! Now I'll try to get used to this more logical typo. –  anderstood Jul 30 '14 at 22:59