Math 2.0

Algebraic geometry Definition

Noetherian scheme

Builds on SchemeAffine schemeNoetherian ringNoetherian topological space

Definition

A scheme XX is locally Noetherian if it can be covered by open affine schemes Spec⁡Ai\operatorname{Spec} A_i in which every AiA_i is a Noetherian ring. It is Noetherian if it can be covered by finitely many such open sets.

Remarks

A scheme is locally Noetherian if and only if AA is Noetherian for every open affine subscheme Spec⁡A\operatorname{Spec} A. So Spec⁡A\operatorname{Spec} A is Noetherian if and only if AA is a Noetherian ring. The underlying space of a Noetherian scheme is a Noetherian topological space. Example: projective space ℙkn\mathbb{P}^n_k over a field kk is Noetherian, being covered by n+1n+1 copies of Spec⁡k[x1,…,xn]\operatorname{Spec} k[x_1, \ldots, x_n], which are Noetherian by the Hilbert basis theorem. Non-example: Spec⁡k[x1,x2,…]\operatorname{Spec} k[x_1, x_2, \ldots] is not Noetherian, since the ideal (x1,x2,…)(x_1, x_2, \ldots) is not finitely generated. Non-example: a disjoint union of infinitely many copies of Spec⁡k\operatorname{Spec} k is locally Noetherian but not Noetherian, since it is not quasi-compact.

Reading path

To understand this page from the ground up, read these 5 pages in order. The foundations come first.

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  1. Affine scheme concept
  2. Noetherian ring concept
  3. Noetherian topological space concept
  4. Scheme concept
  5. Noetherian scheme definition

Further reading

  1. Web https://en.wikipedia.org/wiki/Noetherian_scheme
About this page
Tag5Y3SAEWBZM
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Kinddefinition
WritingW0 stub
MSC14A15, 13E05
DefinesNoetherian scheme
UsesScheme, Affine scheme, Noetherian ring, Noetherian topological space

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