Electronic ISBN:  9781470403256 
Product Code:  MEMO/154/732.E 
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Book DetailsMemoirs of the American Mathematical SocietyVolume: 154; 2001; 116 ppMSC: Primary 14;
This paper contributes to the liaison and obstruction theory of subschemes in \(\mathbb{P}^n\) having codimension at least three.
The first part establishes several basic results on Gorenstein liaison. A classical result of Gaeta on liaison classes of projectively normal curves in \(\mathbb{P}^3\) is generalized to the statement that every codimension \(c\) “standard determinantal scheme” (i.e. a scheme defined by the maximal minors of a \(t\times (t+c1)\) homogeneous matrix), is in the Gorenstein liaison class of a complete intersection. Then Gorenstein liaison (Gliaison) theory is developed as a theory of generalized divisors on arithmetically CohenMacaulay schemes. In particular, a rather general construction of basic double Glinkage is introduced, which preserves the even Gliaison class. This construction extends the notion of basic double linkage, which plays a fundamental role in the codimension two situation.
The second part of the paper studies groups which are invariant under complete intersection linkage, and gives a number of geometric applications of these invariants. Several differences between Gorenstein and complete intersection liaison are highlighted. For example, it turns out that linearly equivalent divisors on a smooth arithmetically CohenMacaulay subscheme belong, in general, to different complete intersection liaison classes, but they are always contained in the same even Gorenstein liaison class.
The third part develops the interplay between liaison theory and obstruction theory and includes dimension estimates of various Hilbert schemes. For example, it is shown that most standard determinantal subschemes of codimension \(3\) are unobstructed, and the dimensions of their components in the corresponding Hilbert schemes are computed.ReadershipGraduate students and research mathematicians interested in algebraic geometry.

Table of Contents

Chapters

1. Introduction

2. Preliminaries

3. Gaeta’s theorem

4. Divisors on an ACM subscheme of projective space

5. Gorenstein ideals and Gorenstein liaison

6. CIliaison invariants

7. Geometric applications of the CIliaison invariants

8. Glicci curves on arithmetically CohenMacaulay surfaces

9. Unobstructedness and dimension of families of subschemes

10. Dimension of families of determinantal subschemes


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This paper contributes to the liaison and obstruction theory of subschemes in \(\mathbb{P}^n\) having codimension at least three.
The first part establishes several basic results on Gorenstein liaison. A classical result of Gaeta on liaison classes of projectively normal curves in \(\mathbb{P}^3\) is generalized to the statement that every codimension \(c\) “standard determinantal scheme” (i.e. a scheme defined by the maximal minors of a \(t\times (t+c1)\) homogeneous matrix), is in the Gorenstein liaison class of a complete intersection. Then Gorenstein liaison (Gliaison) theory is developed as a theory of generalized divisors on arithmetically CohenMacaulay schemes. In particular, a rather general construction of basic double Glinkage is introduced, which preserves the even Gliaison class. This construction extends the notion of basic double linkage, which plays a fundamental role in the codimension two situation.
The second part of the paper studies groups which are invariant under complete intersection linkage, and gives a number of geometric applications of these invariants. Several differences between Gorenstein and complete intersection liaison are highlighted. For example, it turns out that linearly equivalent divisors on a smooth arithmetically CohenMacaulay subscheme belong, in general, to different complete intersection liaison classes, but they are always contained in the same even Gorenstein liaison class.
The third part develops the interplay between liaison theory and obstruction theory and includes dimension estimates of various Hilbert schemes. For example, it is shown that most standard determinantal subschemes of codimension \(3\) are unobstructed, and the dimensions of their components in the corresponding Hilbert schemes are computed.
Graduate students and research mathematicians interested in algebraic geometry.

Chapters

1. Introduction

2. Preliminaries

3. Gaeta’s theorem

4. Divisors on an ACM subscheme of projective space

5. Gorenstein ideals and Gorenstein liaison

6. CIliaison invariants

7. Geometric applications of the CIliaison invariants

8. Glicci curves on arithmetically CohenMacaulay surfaces

9. Unobstructedness and dimension of families of subschemes

10. Dimension of families of determinantal subschemes