[Tex/LaTex] Too much space at the top of a beamer block when using multilined math environment

beamerequationsspacing

I would like to place two math lines in a beamer block, as two separately
centered lines.

I know that I could do this using two distinct equation environments, but it would be nicer to use a single environment like gather, or align (though align is not exactly what I want). When I do this (with gather), an ugly space appears at the top of the block, before the first equation. See below. How can I get rid of this space while still using gather or align (perhaps I should be using another environment altogether?)

\begin{block}{Separation of variables}
\begin{equation*}
\eps u'''' - (yu')' = \lambda u,
\end{equation*}
\begin{equation*}
u''(0)=u'''(0)=0 \quad \text{(Free),} \qquad u(1)=u''(1)=0 \quad\text{(Clamped)}
\end{equation*}
\end{block}
\begin{block}{Separation of variables}
\begin{gather*}
\eps u'''' - (yu')' = \lambda u,\\
u''(0)=u'''(0)=0 \quad \text{(Free),} \qquad u(1)=u''(1)=0 \quad\text{(Clamped)}
\end{gather*}
\end{block}

Gives me:
enter image description here

Any ideas?

Best Answer

You can set the length abovedisplayskip to 0pt (or any other desired value):

\documentclass{beamer}
\usepackage{amsmath}
\begin{document}

\begin{frame}
\begin{block}{Separation of variables}
\begin{gather*}
 u'''' - (yu')' = \lambda u,\\
u''(0)=u'''(0)=0 \quad \text{(Free),} \qquad u(1)=u''(1)=0 \quad\text{(Clamped)}
\end{gather*}
\end{block}
\begin{block}{Separation of variables}
\setlength\abovedisplayskip{0pt}
\begin{gather*}
 u'''' - (yu')' = \lambda u,\\
u''(0)=u'''(0)=0 \quad \text{(Free),} \qquad u(1)=u''(1)=0 \quad\text{(Clamped)}
\end{gather*}
\end{block}
\end{frame}
\end{document}

Of course, you can use something like

\addtobeamertemplate{block begin}{\setlength\abovedisplayskip{0pt}}

right after \begin{document} to apply the change to all the blocks.

enter image description here

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