Lemma 27.10.6. Let S be a graded ring. Let X = \text{Proj}(S). Let Y \subset X be a quasi-compact open subscheme. Denote \mathcal{O}_ Y(n) the restriction of \mathcal{O}_ X(n) to Y. There exists an integer d \geq 1 such that
the subscheme Y is contained in the open W_ d defined in Lemma 27.10.4,
the sheaf \mathcal{O}_ Y(dn) is invertible for all n \in \mathbf{Z},
all the maps \mathcal{O}_ Y(nd) \otimes _{\mathcal{O}_ Y} \mathcal{O}_ Y(m) \longrightarrow \mathcal{O}_ Y(nd + m) of Equation (27.10.1.1) are isomorphisms,
all the maps \widetilde M(nd)|_ Y = \widetilde M|_ Y \otimes _{\mathcal{O}_ Y} \mathcal{O}_ X(nd)|_ Y \to \widetilde{M(nd)}|_ Y (see 27.10.1.5) are isomorphisms,
given f \in S_{nd} denote s \in \Gamma (Y, \mathcal{O}_ Y(nd)) the image of f via (27.10.1.3) restricted to Y, then D_{+}(f) \cap Y = Y_ s,
a basis for the topology on Y is given by the collection of opens Y_ s, where s \in \Gamma (Y, \mathcal{O}_ Y(nd)), n \geq 1, and
a basis for the topology of Y is given by those opens Y_ s \subset Y, for s \in \Gamma (Y, \mathcal{O}_ Y(nd)), n \geq 1 which are affine.
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