I'm trying to draw the following commutative diagram using xymatrix:

enter image description here



$\xymatrix{A \ar[rr] & & B  \\ & C \ar[ul] \ar[ur] & }$


How can I draw symbols of group action?

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  • Sorry...I edited my question. – KOTO Apr 16 '15 at 4:08
  • Is there any particular style that you would like for your arrows (e.g. their orientation, their location relative to A, B, C, etc.)? – Niel de Beaudrap Apr 16 '15 at 18:09
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Or like this:

% arara: pdflatex


        A \arrow{rr}\arrow[loop left, "G_1"] & & B \arrow[loop right, "G_2"] \\ 
        & C \arrow{ul} \arrow{ur} \arrow[loop below, "G_3"] & 

enter image description here


Here's a solution using TiKZ instead of xypics. The arrows are drawn as circular arcs with modifiable parameters; the location and style for the labels of the group actions can also be varied.

Some particular remarks on the code:

  • The group actions are denoted by nearly complete circles (omitting 45° of the turn), whose orientations can be modified by changing the starting and ending angles.

  • The end tips of each arrow are elongated, in order to better match the appearance of the orientation of the arrow-head with the angle at which the arc ends.

Source code


  % Position nodes symmetrically about a central point
  \node (A) at ({cos(150)},{sin(150)}) {$A$};
  \node (B) at ({cos(30)},{sin(30)}) {$B$};
  \node (C) at ({cos(270)},{sin(270)}) {$C$};

  % Draw arrows between nodes
  \draw (A) to (B); \draw (C) to (A); \draw (C) to (B);

  % Define co-ordinates for the arrows of the group actions
  \coordinate (G1') at ($(A.west) + (-0.5em,0)$);
  \coordinate (G2') at ($(B.east) + (0.5em,0)$);
  \coordinate (G3') at ($(C.south west) + (0.5em,-2ex)$);

  % Draw circular arcs of 1ex radius for the group actions
  % (tips are slightly lengthened to optimise orientation of arrow head)
  \draw [->, shorten >=-1.5pt] (G1') arc (245:-70:1ex);
  \draw [->, shorten >=-1.5pt] (G2') arc (-65:250:1ex);
  \draw [->, shorten >=-1.5pt] (G3') arc (315:0:1ex);

  % Draw labels for the group actions, smaller than the main nodes
  \node (G1) at ($(G1') + (-1em,0)$) {\footnotesize $G_1$};
  \node (G2) at ($(G2') + (1em,0)$) {\footnotesize $G_2$};
  \node (G3) at ($(G3') + (0,-2ex)$) {\footnotesize $G_3$};


Commutative diagram with group actions


Something like this? (With help of this documentation, p. 4, since I'm not very proficient in xy-pic.)

    \xymatrix{  A \ar@(dl,ul)[]^{G_1} \ar[rr] & & B \ar@(dr,ur)[]_{G_2} \\ 
      & C \ar@(dl,dr)[]_{G_3}\ar[ul] \ar[ur] & }

Edit: following LaRiFari's suggestion, now the cmtip option is used.The arrow heads are much better looking!

enter image description here

  • 1
    May I recommend loading \usepackage[all,cmtip]{xy}? Personal taste, but see the difference! – LaRiFaRi Apr 16 '15 at 7:54
  • 1
    @LaRiFaRi Thanks for the… tip :-) Suggestion adopted! – Franck Pastor Apr 16 '15 at 7:59

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