@Bryan: Yep, I asked another professor by e-mail, but he said he won't have time to look at it until next week, and I also asked on the nForum, but Urs seems to be too busy with Chern-Weil theory to work out a correct proof.
@Anton: Here is the actual question itself. It is very specific indeed. I'm not really sure how to turn it into a good MO question (I have, of course, managed to ask many questions like you suggested above, but this one seems to be particularly resistant.
]]>In any case, you should probably say that you're trying to understand the proof of some result (and include as precise a reference as possible). It may turn out that there are implicit (or well-hidden) hypotheses that you're missing, which would be very hard for someone to guess without knowing the exact reference.
]]>How should I ask this sort of question?
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