# Beamer poster theorem style without boxes

I'm making a poster using beamer and when I use \begin{theorem} and \begin{proof} it makes the theorems and proofs in a box just like a block title would be.

I understand this is the default setting when using beamer but I want my theorems and proofs to look like the default when just writing an article in LaTeX. Is there a way I can change the theorem style or theorem environment so that theorem and proof are no longer in boxes?

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## migrated from stackoverflow.comDec 30 '11 at 16:19

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Here is a naive approach at defining your own mytheorem and myproof environments.

\documentclass{beamer}% http://ctan.org/pkg/beamer
\usetheme{Warsaw}

\newenvironment<>{mytheorem}[1][]
\itshape}
{}
\makeatletter
\newenvironment<>{myproof}[1][\proofname]{%
\par
\pushQED{\qed}
{\popQED}
\makeatother

\begin{document}
\begin{frame}
\frametitle{This is a frame title}
\begin{theorem}
This is a theorem statement.
\end{theorem}

\begin{proof}
This is a theorem proof.
\end{proof}
\end{frame}

\begin{frame}
\frametitle{This is a frame title}
\begin{mytheorem}
This is a theorem statement.
\end{mytheorem}

\begin{myproof}
This is a theorem proof.
\end{myproof}
\end{frame}

\end{document}


In the above example, mytheorem typesets Theorem using in boldface, upright and "alerted" font (\alert{\upshape\textbf{...}}) just to show that there is freedom in the formatting. The same goes for myproof.

It would be possible to completely duplicate the theorem environment that would allow (1) a bracketed optional argument and (2) even a theorem number, if needed. However, since this still forms part of a presentation where numbering doesn't make much sense, it's been left out. At the moment, specifying an optional parenthesized theorem addition is obtain using \begin{mytheorem}[(...)].

Defining your own, new environment for theorems and proofs allows you to switch between or back to the regular theorem and proof environments, if needed.

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The style is defined by

• \setbeamertemplate{theorem begin} and
• \setbeamertemplate{theorem end}

Check page 122 of beameruserguide.pdf. In the following I have just deleted the \inserttheoremblockenv commands from the definition in the manual.

\documentclass[]{beamer}
\setbeamertemplate{theorem begin}{{
\inserttheoremname
\inserttheoremnumber
\inserttheorempunctuation
}}
\setbeamertemplate{theorem end}{}
\begin{document}
\begin{frame}
\begin{theorem}
Hello World!
\end{theorem}
\end{frame}
\end{document}

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For what it's worth, in order to avoid getting Theorem 1 (), I need to use \empty and not \@empty. –  hoyland Jul 20 '12 at 17:09