According to Wikipedia, Aut(P(V)) = PGL(V). Apparently this is proved by using sheaves generated by global sections but I'm not familiar with this notion. I would appreciate it if anyone could provide a reference where this is proved.
closed as too localized by Charles Siegel, Simon Thomas, Martin Brandenburg, Sándor Kovács, Pete L. Clark Dec 4 '10 at 16:40
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