Diagrams and xy-pic package

Question

I want to reproduce the shape of the following diagram :

And the closest thing I could manage with the xy package was :

$$
\xymatrix{
     &B \ar[r]  & H  \ar[r] & B   \ar[rd]  \\
    E'_{n+1} \ar[ru] \ar[r]   &  & E'_{n}    \ar[r] &   E_n  \ar[r]  &  E_{n+1} }
$$

which gives

Is it possible to do so with this package?

Answer 1

Make a seven-column matrix:

\documentclass{article}
\usepackage{amsmath}

\usepackage[all,cmtip]{xy}

\begin{document}

\[
\xymatrix@C-1pc{
  & B' \ar[rr]^{t_i} && H \ar[rr]^i && B \ar[dr]^{\tilde{v}} \\
  E'_{n+1} \ar[ur]^{t_{\tilde{w}}} \ar[rr]_{t_{j_n}} &&
  E'_n \ar[rr]_{\bar{u}} && E_n \ar[rr]_{j_n} && E_{n+1}
}
\]

\end{document}

The instruction @C-1pc reduces the space between columns.

With the missing arrows:

\documentclass{article}
\usepackage{amsmath}

\usepackage[all,cmtip]{xy}

\begin{document}

\[
\xymatrix@C-1pc{
  & B' \ar[rr]^{t_i} && H \ar[rr]^i \ar[dr]^v && B \ar[dr]^{\tilde{v}} \\
  E'_{n+1} \ar[ur]^{t_{\tilde{w}}} \ar[rr]_{t_{j_n}} &&
  E'_n \ar[rr]_{\bar{u}} \ar[ur]^{t_w} && E_n \ar[rr]_{j_n} && E_{n+1}
}
\]

\end{document}

With tikz-cd:

\documentclass{article}
\usepackage{amsmath}

\usepackage{tikz-cd}

\begin{document}

\[
\begin{tikzcd}[column sep=small]
  & B' \arrow[rr,"t_i"] && H \arrow[rr,"i"] \arrow[dr,"v"] &&
    B \arrow[dr,"\tilde{v}"] \\
  E'_{n+1} \arrow[ur,"t_{\tilde{w}}"] \arrow[rr,"t_{j_n}"'] &&
  E'_n \arrow[rr,"\bar{u}"'] \arrow[ur,"t_w"] && E_n \arrow[rr,"j_n"'] &&
    E_{n+1}
\end{tikzcd}
\]

\end{document}

Labels are by default typeset on the left of the arrow (think to rivers), but with "<label>"' (note the apostrophe) the label goes on the other side. Alternatively, precede the label with the keyword swap.