Is it possible to add some vertical space like ~~~?

Question

I sometimes uses ~ to adjust space between symbols. Now I want to add some vertical space which play similar role, how do I do that?

(It's not about controlling space between lines, but just add some space, the real problem is like this: I put \displaystyle \int X, and X at the same time in an xymatrix, then the arrows are of different length because it thinks \displaystyle \int X occupied more vertical space than X. )

Answer 1

If you want to make Xy-pic think that the node with just X takes up the same vertical space as \displaystyle\int X, you can use a \vphantom. For example, if you type

\documentclass[12pt]{article}
\usepackage[all,cmtip]{xy}
\begin{document}
\thispagestyle{empty}
\begin{displaymath}
  \xymatrix{
    \displaystyle \int X \ar[r] \ar[d]
    & {\vphantom{\displaystyle \int}X} \ar[d]\\
    {A} \ar[r]
    & {B}
  }
\end{displaymath}
\end{document}

then you'll get