A block in beamer

Question

I am unable to understand why this is not compiling,

\documentclass{beamer}
\begin{document}
  \begin{frame}{}
  \begin{block}
    $$\phi (S) \geq \lambda (1 - \sqrt {C \delta})$$
  \end{block}
  \end{frame}
\end{document}

• Can someone help?

Answer 1

The block environment expects a title. You can have it be empty, but it needs to be there:

\documentclass{beamer}
\begin{document}
  \begin{frame}{}
    \begin{block}{}
    \[\phi (S) \geq \lambda (1 - \sqrt {C \delta})\]
    \end{block}
  \end{frame}
\end{document}

Answer 2

It has only to do with an empty {} after the \begin{block} even without a title. As another hack, you can only insert an empty line after \begin{block}. So this works:

\documentclass{beamer}
\begin{document}
  \begin{frame}{}
  \begin{block}{}
    \[\phi (S) \geq \lambda (1 - \sqrt {C \delta})\]
  \end{block}
  \end{frame}
\end{document}

Also this:

\documentclass{beamer}
\begin{document}
  \begin{frame}{}
  \begin{block}

    \[\phi (S) \geq \lambda (1 - \sqrt {C \delta})\]
  \end{block}
  \end{frame}
\end{document}