# ways to indicate commutativity and non-commutativity of a diagram when using xymatrix

I used the following code, but \circlearrowleft looks no good in this diagram. I would like to know if there is a better way to indicate the commutativity. Also, is there any way to indicate non-commutativity?

\begin{equation*}
\xymatrix@-1.75pc{
\overline{A} \ar[dd]_{\overline{F}_q}  &  &  \overline{A}_E
\ar[dd]^{\overline{F}_{q,E}} \ar[ll]_{\pi^{\ast}}  \\
& \circlearrowleft & \\
\overline{A}  & &  \overline{A}_E \ar[ll]^{\pi^{\ast}}
}



• Could you explain a bit more what you don't like about \circlearrowleft in the diagram? It may be a bit ugly but it is the usual way to emphasise commutativity. As for non-commutativity then I agree with salvor7 below that the default assumption is that the diagram commutes and I don't know of a standard way of indicating otherwise. One option would be to ask on Maths-SX if there is a standard and then if one emerges to ask how to typeset it here. When I've had to do a non-commuting diagram I've used linguistics as salvor7 says: "We have the following (non-commuting!) diagram". – Loop Space Feb 21 '13 at 9:39

Also, you might find a fifth map which is an endomorphism (a map from something to itself), \overline{A} in this case, that completes a pentagonal commutative diagram.
One symbol that one could try, for instance, is \ncirclearrowdown from MnSymbol negated arrow. (according to http://ctan.uib.no/info/symbols/comprehensive/symbols-a4.pdf , p.44)