After I asked this question: What is "\SelectTips{a}{b}" (and how to increase the head of an arrow's head?)
I'd like to know one more thing: I want to change it (the arrow tips) for the whole document, i.e. - right now, if I want to change the arrow tip I need to put the command \SelectTips{eu}{}
(for example) at math-mode for every formula or graph that I make (especially at xy-pic).
Is there a way to put it at the Preamble that it will influence all the document? (all of the arrows tips at math-mode).
Thank you!