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September 06, 2023P51. Let f in B be a homogeneous element. D+(f) constitute a base.D+(f) = ProjB \ V+ (fB). The open sets of this form are called principal open sets. They constitute a base of open sets of Proj B. In fact, we can restrict ourselves to the open sets D+ (f)2 minPlay
September 06, 2023Lemma 3.35 projBNot containing B+; intersecting with B+ is contained in radical.5 minPlay
September 05, 2023Lemma 3.23 morphism to affine; k-rational pts are those k(x)=k.Z(I) bijective to k-rational points of Spec k[…]/I15 minPlay
September 05, 2023prop. 3.20 closed immersion into affine is affine Spec A/IMorphisme into affine?4 minPlay
September 05, 2023Lemma 3.17 closed immersion from A to A/I; spec k(x) to X map to x;Def 3.19 closed sub scheme10 minPlay
September 05, 2023Def 3.13 map of schemes Prop 3.14 ring maps gives scheme mapsSpec O_X,x to X.8 minPlay
September 05, 2023Prop 3.12 X_f is open subset with O_X(X_f) iso O_X(X)_fCondition 3.2 is needed.7 minPlay
September 05, 2023Lemma 3.7 D(g) of affine is affineProp3.9 Open of scheme is scheme. Open sub scheme; affine open subset.7 minPlay