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Postulation of double lines and associated objects in the range of quadrics


Abstract


Fix a closed subscheme U\subset \mathbb {P}^n. Here we study the integer h^0(\mathcal {I}_U(2))-h^0(\mathcal {I}_{U\cup Y}(2)) when Y is a general double line, a general reducible conic, a general chain of lines or some unreduced structure associated to double structures on linear subspaces.

DOI Code: 10.1285/i15900932v31n2p79

Keywords: postulation ; Hilbert function ; unreduced schemes ; double lines ; quadric hypersurfaces

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