Remarks on Type III Unprojection
نویسنده
چکیده
Type III unprojection plays a very important role in the birational geometry of Fano threefolds (cf. [CPR], [Ki], [BZ]). According to [Ki] p. 43, it was first introduced by A. Corti on his calculations of Fano threefolds of genus 6 and 7. It seems that at present a general definition of type III unprojection is still missing. After proving in Section 2 some general facts about residual ideals, we propose a definition for the generic Type III unprojection (Definition 3.3), and prove in Theorem 3.5 that it gives a Gorenstein ring.
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تاریخ انتشار 2005