# Typesetting a diagram with "tree arrows"

I'm trying to tex a diagram of the following form:

Even more preferred, I'd like to both have labels for the trees (like $\mathcal T$ and $\pi\mathcal T$ in the above picture), and also a label on the solid arrow sticking out from the tree.

Can this be done in xymatrix, or do I have to get the big tikz guns out?

Thanks!

(this specific diagram is from John Steel's article "An outline of inner model theory", by the way)

• Welcome! So what have you tried so far?
– cfr
Apr 15 '16 at 16:17
• Thanks @cfr! Right now I've only looked through a bunch of tikz examples at texample.net/tikz/examples, with no luck. I know how to use xymatrix, but for one I have no idea how to set an arrow to have multiple styles (dots and solid in this case). Apr 15 '16 at 16:34

This is an examply with tikz-cd. The code for the half dotted arrow is slightly modified from this answer by Ignasi, also including some additions.

## Code

\documentclass[margin=10pt]{standalone}
\usepackage{tikz-cd}

\usetikzlibrary{decorations.pathreplacing,calc,arrows.meta}

\tikzset{
triple/.style={
decoration={show path construction,
lineto code={
\draw[dotted,-] (\tikzinputsegmentfirst) --($(\tikzinputsegmentfirst)!.7!(\tikzinputsegmentlast)$) coordinate (a);,
\draw[-{Latex}] ($(\tikzinputsegmentfirst)!.7!(\tikzinputsegmentlast)$)--(\tikzinputsegmentlast);
\draw[-] (\tikzinputsegmentfirst) --++ (10:1.6cm) node[midway, above, font=\footnotesize] {#1};
\draw[-] (\tikzinputsegmentfirst) --++ (-10:1.6cm);,
}
},
decorate
},
}

\begin{document}
\begin{tikzcd}
N \arrow[rr, triple={$\pi T$}]& & N_{\alpha}\\
M \arrow[u, swap, "\pi"]
\arrow[rr, triple={$T$}]
& & M_{\alpha} \arrow[u, swap, "\pi_{\alpha}"]\\
\end{tikzcd}
\end{document}

• Sorry for the super delayed answer, but suddenly I didn't have time to play around with tex. But thanks for the great answer! Apr 30 '16 at 6:43