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Tag Archives: algebraic geometry
Commutative Algebra 62
Irreducible Subsets of Projective Space Throughout this article, k is an algebraically closed field. We wish to consider irreducible closed subsets of . For that we need the following preliminary result. Lemma 1. Let be a graded ring; a proper homogeneous … Continue reading
Commutative Algebra 61
In this article, we will consider algebraic geometry in the projective space. Throughout this article, k denotes an algebraically closed field. Projective Space Definition. Let . On the set , we consider the equivalence relation: The projective n-space is the set … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, closed subsets, cones, graded rings, nullstellensatz, projective varieties, varieties
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Commutative Algebra 57
Continuing from the previous article, A denotes a noetherian ring and all A-modules are finitely generated. As before all completions are taken to be -stable for a fixed ideal . Noetherianness We wish to prove that the -adic completion of … Continue reading
Posted in Advanced Algebra
Tagged a-adic filtrations, algebraic geometry, analysis, completion, filtrations, hensels lemma, local rings, p-adic
1 Comment
Commutative Algebra 32
Torsion and Flatness Definition. Let A be a ring and M an A-module; let . If satisfies , we call it an –torsion element. If is an -torsion for some non-zero-divisor we call it a torsion element. M is said … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, flat modules, torsion, varieties, zero-divisors
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Commutative Algebra 30
Tensor Product of A-Algebras Proposition 1. Let B, C be A-algebras. Their tensor product has a natural structure of an A-algebra which satisfies . Proof Fix . The map is A-bilinear so it induces an A-linear map Now varying (b, c) gives … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, algebras, coproducts, fibres, tensor product, varieties
2 Comments
Commutative Algebra 23
Localization and Spectrum Recall that the ideals of correspond to a subset of the ideals of A. If we restrict ourselves to prime ideals, we get the following nice bijection. Theorem 1. The above gives a bijection between Useful trick If … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, local rings, localization, prime ideals, rational functions, spectrum, zariski topology
12 Comments
Commutative Algebra 11
Coordinate Rings as k-algebras Let k be an algebraically closed field. Recall that a closed subset is identified by its coordinate ring k[V], which is a finitely generated k-algebra since Definition. An affine k-variety is a finitely generated k-algebra A which is … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, algebras, cotangent spaces, maximal ideals, tangent spaces, varieties
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Commutative Algebra 6
Injective and Surjective Maps Proposition 1. Let be a morphism of closed sets, with corresponding . is injective if and only if is dense. is surjective if and only if is an embedding of V as a closed subspace of … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, ideals, irreducible spaces, monomials, rings
4 Comments
Commutative Algebra 5
Morphisms in Algebraic Geometry Next we study the “nice” functions between closed subspaces of . Definition. Suppose and are closed subsets. A morphism is a function which can be expressed as: for some polynomials . We also say f is a regular … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, continuity, ideals, morphisms, rings, topology
2 Comments
Commutative Algebra 4
More Concepts in Algebraic Geometry As before, k denotes an algebraically closed field. Recall that we have a bijection between radical ideals of and closed subsets of . The bijection reverses the inclusion so if and only if . Not too … Continue reading
Posted in Advanced Algebra
Tagged algebraic geometry, closed subsets, ideals, irreducible spaces, rings, zariski topology
7 Comments
Mathematics and Such 