# Complicated diagram with xy (everything is wrong)

I'm trying to create a diagram for the countable direct limit in algebra. The following code

$$\vspace{-1mm}\xymatrix{ &&& A\ar@{-->}[dd]^{\exists!\alpha}\\ A_1\ar[r]^{\!\!\!\alpha_{1,2}} \ar@/^12pt/[urrr]|-{\alpha_{1}} \ar@/_12pt/[drrr]|-{\alpha'_{1}}& A_2\ar[r]^{\!\!\!\alpha_{2,3}} \ar[urr ]|-{\alpha_{2}} \ar[drr ]|-{\alpha'_{2}}& A_3\ar[r]^{\!\!\!\alpha_{3,4}} \ar[ur ]|-{\alpha_{3}} \ar[dr ]|-{\alpha'_{3}}& \ldots\\ &&& A'\\}$$

produces the diagram below:

Questions:

1. How can I make the arrows \alpha_1,\alpha_2,\alpha_3 arrive at their destination A?

2. How to put labels \alpha_{1,2} lower (closer to their arrow)?

3. How to move objects A and A' a bit to the right (along with \alpha_i,\alpha'_i) so that the arrow \alpha doesn't intersect \ldots and remains straight?

4. When I bend arrows (using PDFtex) I a get rasterized arrow. How can I bend arrows and still have vector graphics?

5. What is wrong with \alpha'_3?

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Remove the spaces in the sqare brackets for \ar. This solves problems 1 and 5.

\documentclass{article}
\usepackage[all]{xy}
\begin{document}
$\vspace{-1mm}\xymatrix{ &&& A\ar@{-->}[dd]^{\exists!\alpha}\\ A_1\ar[r]^{\!\!\!\alpha_{1,2}} \ar@/^12pt/[urrr]|-{\alpha_{1}} \ar@/_12pt/[drrr]|-{\alpha'_{1}}& A_2\ar[r]^{\!\!\!\alpha_{2,3}} \ar[urr]|-{\alpha_{2}} \ar[drr]|-{\alpha'_{2}}& A_3\ar[r]^{\!\!\!\alpha_{3,4}} \ar[ur]|-{\alpha_{3}} \ar[dr]|-{\alpha'_{3}}& \ldots\\ &&& A'\\}$
\end{document}

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Ah, silly me, I forgot the space [... ] means something. That takes care of question 1), 5), thanks. What about the others? –  Leon Lampret Sep 27 '11 at 18:32
$\xymatrix{ &&& A\ar@/^12pt/@{-->}[dd]^{\exists!\alpha}\\ A_1\ar[r]^-{\alpha_{1,2}} \ar@/^12pt/[urrr]|-{\alpha_{1}} \ar@/_12pt/[drrr]|-{\alpha'_{1}}& A_2\ar[r]^-{\alpha_{2,3}} \ar@/^4pt/[urr]|-{\alpha_{2}} \ar@/_4pt/[drr]|-{\alpha'_{2}}& A_3\ar[r]^-{\alpha_{3,4}} \ar[ur]|-{\alpha_{3}} \ar[dr]|-{\alpha'_{3}}& \ldots\\ &&& A' }$