[Tex/LaTex] Vertical cofibration arrow in xypic

arrowsdiagramsxy-pic

I want to use xypic to make diagrams using vertical cofibration arrows, i.e. ones that look like $\rightarrowtail$ .
Naively using

\ar@{>->}

gives an arrow whose tail overlaps with the source object. There is an exercise in the xyguide
that fixes this:

\newdir{ >}{{}*!/-5pt/@{>}}.

But using this for vertical arrows gives tails that are horizontally shifted and do not attach to the shaft. How can I fix this or is there a nicer way to do such arrows in xypic anyway? This is the best I have seen so far but the results are not exceptional.

Here's a MWE

\documentclass{article}
\usepackage[all]{xy}
\newdir{ >}{{}*!/-5pt/@{>}}

\begin{document}
\[
\xymatrix{
 S_{P} \ar@{=}[r] \ar@{ >->}[d] & S_{P} \ar@{->>}[r] \ar@{ >->}[d] & 0 \ar@{ >->}[d] \\
 R' \ar@{ >->}[r] \ar@{->>}[d] & R \ar@{->>}[r] \ar@{->>}[d] & M \ar@{=}[d] \\ 
 P' \ar@{ >->}[r] & P \ar@{->>}[r] & M
}
\]
\end{document}

enter image description here

Best Answer

a one-line change in your existing example, adding cmtip to

\usepackage[all,cmtip]{xy}

gives this result:

output of original example with code change as indicated

Related Solutions

[Tex/LaTex] Loop arrow in xypic

If you are willing to switch to tikz-cd this becomes easy.

% arara: pdflatex

\documentclass{article}
\usepackage{mathtools}
\usepackage{amsfonts}
\DeclareMathOperator\id{id}
\DeclareMathOperator\pr{pr} 
\usepackage{tikz-cd}

\begin{document}
\[
\begin{tikzcd}
    p^{-1}(U_{\alpha})\ar{rr}{\tau_{\alpha}} && U_{\alpha}\times\mathbb{R}^k\ar{dl}{\pr_1}\\
    & U_{\mathrlap\alpha}\ar{ul}{s|_{U_{\alpha}}}\ar[loop above]{}{\id} & 
\end{tikzcd}
\]
\end{document}

enter image description here

In order to manipulate the target of the arrow, you may want to play around with the options in the arrow below.

\begin{tikzcd}
    p^{-1}(U_{\alpha})\ar{rr}{\tau_{\alpha}} && U_{\alpha}\times\mathbb{R}^k\ar{dl}{\pr_1}\\
    & U_{\mathrlap\alpha}\ar{ul}{s|_{U_{\alpha}}}\ar[%
    ,loop % tells tikz-cd to do a loop
    ,out=123 % start at angle 123°
    ,in=57 % stop at angle 57°
    ,distance=2.5em % biggest distance of arrow to node. You can use pt or cm as well.
    ]{}{\id} & 
\end{tikzcd}

enter image description here

I just checked the syntax for xy and the default result looks quite good, too. Would this be close enough to the right arrow?

% arara: pdflatex

\documentclass{article}
\usepackage{mathtools}
\usepackage{amsfonts}
\DeclareMathOperator\id{id}
\DeclareMathOperator\pr{pr}
\usepackage[all,cmtip]{xy}

\begin{document}
\[
\xymatrix{%
    p^{-1}(U_{\alpha})\ar[rr]^-{\tau_{\alpha}} & & U_{\alpha}\times\mathbb{R}^k\ar[dl]^{\pr_1} \\
    & U_{\alpha}\ar[ul]^-{s|_{U_{\alpha}}} \ar@(ul,ur)^{\id} % smashing the alpha here would result in touching arrow heads. That's why I didn't do that here
}. % supposing, this dot was set here by purpose...
\]
\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Loop arrow in xypic

Related Question