# Fixing an AMScd diagram

I want to fix this diagram and also extend it to the diagram below. Can you help me out?

$$\require{AMScd}$$

$$\begin{CD} S^{n-1}@>\subseteq >> D^n \\ @VhVV @VVV\\ S^{n-1}\\ @V\subseteq VV @VVV\\ D^n @>>>\Sigma^n(h) \end{CD}$$

The 'double-down-arrow' on the right side of the diagram is supposed to be just one arrow, but I did not manage to fix this. I am not familiar with constructing those diagrams. I am thankful, when someone fixes it, or tells me how to fix it.

Thanks in advance.

## 2 Answers

I do not know solution using AMScd. (As far as I know, AMScd only has horizontal and vertical arrows.)

If you are familiar with xypic, you could use this syntax and include it as a picture. (You create it either locally on your computer or using some online tool, for example, the presheaf website.) It is reasonable to include somewhere (maybe as a comment in your post) the source of the diagram, too.

For example, you can get this diagram: http://presheaf.com/?d=d3j4t1z705k6j154i2k5u2v4y113a4v36 http://presheaf.com/cache/d3j4t1z705k6j154i2k5u2v4y113a4v36.png

S^{n-1} \ar[r]^{\subseteq} \ar[d]_h & D^n \ar[dd] \ar@/^/[rddd]^q & \\
S^{n-1} \ar[d] & \\
D^n \ar[r] \ar@/_/[rrd]_p & \Sigma^n(h) \ar@{-->}[rd] & \\
&& S^n


Another popular package to create commutative diagrams is tikzCD - I am pretty sure that somebody familiar with it can provide you source code to get your diagram. (And also for this package you can do it either online or locally.)

See also:

• Why dont they include these packages here? It seems overly complicated to use other sources. Thanks for your answer. – Cornman May 11 at 6:16
• @Cornman: Because MathJax is not $\rm\LaTeX$, and compiling something on your personal computer in native machine code is far faster than running it through the many layers of interpretation and emulation when you run it in your browser, and ultimately many people use handheld devices to browse the site. – Asaf Karagila May 11 at 6:20
• @Cornman I do not know much about web applications, but including xypic or tikzcd into MathJax seems to me rather difficult task. Of course, you can quite easily find some related past discussions, such as:When will Math.SE support the \begin{xymatrix} environment?, Using TikZ on math.stackexchange or Can we support TikZ picture rendering? – Martin Sleziak May 11 at 6:20
• Thanks for the insight. Still seems odd, that MathJax does not have a reliable way to draw complex diagrams. – Cornman May 11 at 6:22

$$\raise{34px}{\vert}\hspace{-5px}\raise{17px}{\vert}\hspace{-12.2px}\downarrow$$ \raise{34px}{\vert}\hspace{-5px}\raise{17px}{\vert}\hspace{-12.2px}\downarrow is a very crappy stand in.

$$\underset{\mid\raise{-12px}{\hspace{-3px}\backslash\underline{\phantom{444444444}}}}{}$$ \underset{\mid\raise{-12px}{\hspace{-3px}\backslash\underline{\phantom{444444444}}}}{} There are ways to do the other arc as well, but as you can see, it's a bit of a pain. Also just random MathJaX but breaks on edit it seems.