%&latex
 \documentclass{article}
  \usepackage[matrix,arrow,ps]{xy}
  \UsePSspecials{dvips}
  \pagestyle{empty}
 
 \begin{document}
  \[
  \xymatrix{
  X \ar@{->}[rr]^{\displaystyle g\cdot} \ar@{->}[dd]_{\displaystyle f}
       && X \ar@{->}[dd]^{\displaystyle f}    \\ \\
  Y \ar@{->}[rr]_{\displaystyle g\cdot} && Y
  }
  \]
 \end{document}

\begin{comment} 
To make the image, save the above code as Equivariant_commutative_diagram.tex, then run the following commands:

 tex Equivariant_commutative_diagram

 dvips -mode ljfzzz -D 1200 Equivariant_commutative_diagram -o

 convert -density 1200 Equivariant_commutative_diagram.ps Equivariant_commutative_diagram.pnm

 pnmcrop Equivariant_commutative_diagram.pnm | pnmtopng > Equivariant_commutative_diagram.png.uncrush

 pngcrush Equivariant_commutative_diagram.png.uncrush Equivariant_commutative_diagram.png

\end{comment}