\hat, \tilde and \bar with beamer-package

Question

When using \hat{}, \tilde{} and \bar{} in formulas while also using the beamer-package, instead of a bar over the sign I want to use a \Phi is drawn, and instead of a hat over the letter a \Theta is drawn. Why does that happen, and how can I fix that?

Minimal example:

\documentclass{beamer}
\usepackage{fourier}
\begin{document}
\begin{frame}
  \frametitle{Some math in beamer}
  \begin{equation}
    \label{eq:1}
    \hat A \neq A
  \end{equation}
\end{frame}
\end{document}

Answer 1

I am no font expert, but it looks like there is a problem with the sans serif math font and fourier. A workaround would be to add \usefonttheme{professionalfonts}. To cite from the beamer user guide:

This font theme does not really change any fonts. Rather, it suppresses certain internal replacements performed by beamer.

\documentclass{beamer}
\usefonttheme{professionalfonts}
\usepackage{fourier}
\begin{document}
\begin{frame}
  \frametitle{Some math in beamer}
  \begin{equation}
    \label{eq:1}
    \hat A \neq A
  \end{equation}
\end{frame}
\end{document}