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