The Speciality Lemma, Rank 2 Bundles and Gherardelli-type Theorems for Surfaces in P
4 |
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| Authors: | Margherita Roggero Paolo Valabrega |
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| Institution: | (1) Dipartimento di Matematica dell' Università, Via Carlo Alberto 10, 10123 Turin, Italy;(2) Dipartimento di Matematica del Politecnico, Corso Duca degli Abruzzi 24, 10129 Turin, Italy |
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| Abstract: | In the present paper we give a very short and easy proof of the speciality lemma for codimension 2 subvarieties, even those that are reducible or non-reduced, in P
n
. Furthermore we give cohomological conditions that force a subcanonical surface in P
4 to be a complete intersection and a rank 2 bundle to split, which generalize the classical First Theorem of Gherardelli. |
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| Keywords: | Gherardelli theorems rank 2 bundles speciality lemma subcanonical surfaces |
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