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2017 | OriginalPaper | Buchkapitel

11. Affine Algebraic Geometry

verfasst von : Alexey L. Gorodentsev

Erschienen in: Algebra II

Verlag: Springer International Publishing

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Abstract

In this chapter we assume by default that \(\mathbb{k}\) is an algebraically closed field.

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Fußnoten
1
See Sect. 5.​1.​2 of Algebra I.
 
2
See Lemma 5.​1 of Algebra I.
 
3
Compare with Sect. 11.2.4 of Algebra I.
 
4
See Problem 5.6 of Algebra I.
 
5
See Sect. 5.​2.​2 of Algebra I.
 
6
That is, has no nilpotent elements; see Sect. 2.​4.​2 of Algebra I.
 
7
See Lemma 2.5 of Algebra I.
 
8
If \(\mathbb{k}\) is not algebraically closed, then the map φ ↦ kerφ still embeds the set of homomorphisms \(\mathbb{k}[X] \rightarrow \mathbb{k}\) into \(\mathop{\mathrm{Spec}_{\mathrm{m}}}\nolimits A\). However, some maximal ideals \(\mathfrak{m} \subset A\) may not be represented as the kernels of homomorphisms \(A \rightarrow \mathbb{k}\). For example, the kernel of the evaluation \(\mathop{\mathrm{ev}}\nolimits _{i}: \mathbb{R}[x] \rightarrow \mathbb{C}\), ff(i), where \(i \in \mathbb{C}\), i 2 = −1, certainly is a maximal ideal in \(\mathbb{R}[x]\), but it cannot be realized as the kernel of a homomorphism \(\varphi: \mathbb{R}[x] \rightarrow \mathbb{R}\), because for the latter, \(\mathbb{R}[x]/\ker \varphi = \mathbb{R}\), whereas \(\mathbb{R}[x]/\ker \mathop{\mathrm{ev}}\nolimits _{i} = \mathbb{R}[x]/(x^{2} + 1) \simeq \mathbb{C}\).
 
9
See Sect. 2.​4.​2 of Algebra I.
 
10
Recall that an ideal \(\mathfrak{p} \subset A\) is called prime if the quotient ring \(A/\mathfrak{p}\) has no zero divisors; see Sect. 5.2.3 of Algebra I.
 
11
In the sense of Example 9.​13 on p. 203.
 
12
In the sense of Example 9.​14 on p. 204.
 
13
See Sect. 5.​4 of Algebra I.
 
14
See Proposition 5.​4 of Algebra I.
 
15
Compare with Proposition 5.​3 of Algebra I.
 
16
This is the same notation as in Sect. 4.​1 of Algebra I.
 
17
Recall that it consists of all fractions fg with \(f \in \mathbb{k}[X]\), \(g \in \mathbb{k}[X]^{\circ }\), and f 1g 1 = f 2g 2 if and only if f 1g 2 = f 2g 1. (See Sect. 4.​1 of Algebra I and compare it with Problem 9.10 on p. 224.)
 
18
See Sect. 4.1.1 of Algebra I.
 
19
That is, there exist \(f_{1},f_{2},\ldots,f_{m} \in \mathbb{k}[X]\) such that every \(h \in \mathbb{k}[X]\) can be written as h = ∑ φ (g i) f i for appropriate \(g_{i} \in \mathbb{k}[Y ]\).
 
20
Here (EM) means the adjunct matrix of (EM); see Sect. 9.​6.​1 of Algebra I and the proof of Lemma 10.​1 on p. 227.
 
21
Recall that in the second statement, we assume \(\mathbb{k}[X]\) to be an integral domain.
 
22
That is, φ(U) is open in Y for every open U ⊂ X.
 
23
Whose closed sets are \(V (I) =\{ \mathfrak{m} \in \mathop{\mathrm{Spec}_{\mathrm{m}}}\nolimits C^{0}(X)\mid I \subset \mathfrak{m}\}\) for all ideals I ⊂ C 0(X).
 
Literatur
[DK]
Zurück zum Zitat Danilov, V.I., Koshevoy, G.A.: Arrays and the Combinatorics of Young Tableaux, Russian Math. Surveys 60:2 (2005), 269–334.MathSciNetCrossRef Danilov, V.I., Koshevoy, G.A.: Arrays and the Combinatorics of Young Tableaux, Russian Math. Surveys 60:2 (2005), 269–334.MathSciNetCrossRef
[Fu]
Zurück zum Zitat Fulton, W.: Young Tableaux with Applications to Representation Theory and Geometry. Cambridge University Press, 1997.MATH Fulton, W.: Young Tableaux with Applications to Representation Theory and Geometry. Cambridge University Press, 1997.MATH
[FH]
Zurück zum Zitat Fulton, W., Harris, J.: Representation Theory: A First Course, Graduate Texts in Mathematics. Cambridge University Press, 1997.MATH Fulton, W., Harris, J.: Representation Theory: A First Course, Graduate Texts in Mathematics. Cambridge University Press, 1997.MATH
[Mo]
Zurück zum Zitat Morris, S. A.: Pontryagin Duality and the Structure of Locally Compact Abelian Groups, London Math. Society LNS 29. Cambridge University Press, 1977. Morris, S. A.: Pontryagin Duality and the Structure of Locally Compact Abelian Groups, London Math. Society LNS 29. Cambridge University Press, 1977.
Metadaten
Titel
Affine Algebraic Geometry
verfasst von
Alexey L. Gorodentsev
Copyright-Jahr
2017
Verlag
Springer International Publishing
DOI
https://doi.org/10.1007/978-3-319-50853-5_11