arXiv subjects
Publications and source records attributed to Stavros Argyrios Papadakis.
We produce a family of numerical Campedelli surfaces with \Z/6 torsion by constructing the (Gorenstein codimension 5) canonical ring of the étale six to one cover using serial unprojection. In Section 2 we develop the necessary algebraic machinery. Section 3 contains the numerical Campedelli surface construction, while Section 4 contains remarks and open questions.
Answering a question of M. Reid, we define and prove the Gorensteiness of the type II unprojection.
Type III unprojection plays a very important role in the birational geometry of Fano threefolds. 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 the type III unprojection is still missing. After proving some general facts about residual ideals, we propose a definition for the generic Type III unprojection, and prove that it gives a Gorenstein ring.