[Tex/LaTex] How to write 2 parallel arrows in the xymatrix environment


I want to draw 2 parallel arrows in the xy matrix environment.

Basically instead of the standard arrow (\ar[r]), I want to have something like \begin{smallmatrix}\longrightarrow\\\longrightarrow\end{smallmatrix}.

I tried leaving the arrow blank and just writing
$$\xymatrix{\begin{smallmatrix}\longrightarrow\\\longrightarrow\end{smallmatrix}}$$, but its not working.

Edit: I need it to write two simplicial objects and arrows between them.

Best Answer

this coding works.

 A \ar@<-.5ex>[r] \ar@<.5ex>[r] & B

it's necessary to offset the arrows explicitly from the usual axis alignment in order for them to appear separately. you might prefer different values for the separation, but it seems reasonable to offset them by an equal amount plus/minus.

i didn't find the exact coding in the manual, but there were some examples that looked promising. this solution was arrived at after some experimenting.