I am getting this on beamer using tabular:
As you can see, the matrices are too close to the middle line, and I would like to separate these matrices a little from it. Adding \\ \\ \hline \\ between the last cell of the first row and the first cell of the second row yields
I do consider this to be be too much space between the rows and the middle line. If I try to add \renewcommand{\arraystretch}{1.5} before the tabular environment (as it is recommended here), it yields
and suddenly all matrices stretch big as well. I think this happens because the variable \arraystretch applies globally to both tabular and pmatrix. With the \renewcommand{\arraystretch}{1.5} before the \begin{tabular}, I tried to reredefine this variable back to 1 before each \begin{pmatrix} and it neither worked.
Here's a MWE, with the \renewcommand{\arraystretch}{1.5} before the tabular environment, which gives the last image:
\documentclass[spanish]{beamer}
\usepackage[utf8]{inputenc}
\usetheme{Copenhagen}
\usecolortheme{default}
\usepackage[spanish]{babel}
\setbeamertemplate{headline}{} % This deletes the index on top of each slide
\usefonttheme{default}
\newcommand\wider[2][3em]{%
\makebox[\linewidth][c]{%
\begin{minipage}{\dimexpr\textwidth+#1\relax}
\raggedright#2
\end{minipage}%
}%
}
\begin{document}
\begin{frame}
\wider[3em]{\small
\bgroup\setlength{\tabcolsep}{5pt}
\renewcommand{\arraystretch}{2}
\begin{tabular}{c|lll}
\begin{minipage}{35pt}
\centering base de $\mathsf{su}(2)$
\end{minipage} &
$E_{1}=\frac{1}{2}\begin{pmatrix}
i & 0 \
0 & -i
\end{pmatrix}$ , &
$E_{2}=\frac{1}{2}\begin{pmatrix}
0 & i \
i & 0
\end{pmatrix}$ , &
$E_{3}=\frac{1}{2}\begin{pmatrix}
0 & -1 \
1 & 0
\end{pmatrix}.$
\\hline
\begin{minipage}{35pt}
\centering base de $\mathsf{so}(3)$
\end{minipage} &
$F_1=\begin{pmatrix}
0&0&0\
0&0&-1\
0&1&0
\end{pmatrix},$ &
$F_2=\begin{pmatrix}
0&0&1\
0&0&0\
-1&0&0
\end{pmatrix},$ &
$F_3=\begin{pmatrix}
0&-1&0\
1&0&0\
0&0&0
\end{pmatrix}.$
\end{tabular}
\egroup
}
\end{frame}
\end{document}
where I am using the \wider macro defined here to decrease lateral margins on the slide.
I would like to get then something like in the second image but with less space between the rows and the middle line. Any help will be appreciated :)





