split a \xrightarrow into two lines

Question

I'm using the command \xrightarrow{}[] in a two column document. The problem is that the string above the arrow is too long and the arrow ends outside the column. Is there a way to "split" the arrow over two different lines?

Answer 1

In general, to split the index below or above a \sum, or similar operator, use \substack from the amsmath package (or one of the other ams paclages, I'm not sure).

\documentclass{amsart}
\begin{document}
\[
a \xrightarrow{\substack{x \to 0 \\ y \to 0}} b   
\]
\end{document}