Concatenation of matrices

Question

I could not find anywhere my problem: I wanna write in LateX the following drawing. It is a matrix made of submatrices, which elements contains the elements of near matrices

Had fun writing the description. Thanks a lot, Davide

Answer 1

Welcome! Just make the distance between the rows negative.

\documentclass{article}
\usepackage{amsmath} 
\begin{document}
\[\begingroup\setlength\arraycolsep{2pt}
 \begin{bmatrix}
  [ & &]& & & \\[-1.4ex]
   & [&&] & & \\[-1.4ex]
   & &[& &] & \\
   & & & & & \ddots\\
 \end{bmatrix}\endgroup
\]
\end{document}

Answer 2

You can make TeX do the computations.

\documentclass{article}
\usepackage{amsmath}

\DeclareFontShape{OMX}{cmex}{b}{n}{<->cmexb10}{}
\SetSymbolFont{largesymbols}{bold}{OMX}{cmex}{b}{n}

\begin{document}

\[
\begin{bmatrix}
\,
\hbox{\boldmath\valign{%
  #\cr
  \hbox{$\!\Big[$}\vfill\cr\noalign{\quad}
  \vfill\hbox{$\!\Big[$}\vfill\cr\noalign{\quad}
  \hbox{$\Big]\!$}\vspace{2pt}\hbox{$\!\Big[$}\cr\noalign{\quad}
  \vfill\hbox{$\Big]\!$}\vfill\cr\noalign{\quad}
  \vfill\hbox{$\Big]\!$}\cr
}}
\\
&\ddots
\end{bmatrix}
\]

\end{document}

Apart from \valign, the trick is to notice that the brackets are placed symmetrically in their bounding box, but happily the “blank” part turns out to be 3mu, so it can be removed with \!.

Another trick is to enable bold large symbols.