Algebraic Geometry Spring 2009
|
|
- Carmel Peters
- 4 years ago
- Views:
Transcription
1 MIT OpenCourseWare Algebraic Geometry Spring 2009 For information about citing these materials or our Terms of Use, visit:
2 18.726: Algebraic Geometry (K.S. Kedlaya, MIT, Spring 2009) Divisors, linear systems, and projective embeddings (updated 1 Apr 09) We conclude the first half of the course by translating into the language of schemes some classical notions related to the concept of a divisor. This will serve to explain (in part) why we will be interested in the cohomology of quasicoherent sheaves. In order to facilitate giving examples, I will mostly restrict to locally noetherian schemes. See Hartshorne II.6 for divisors, and IV.1 for Riemann-Roch. 1 Weil divisors Introduce Hartshorne s hypothesis (*): let X be a scheme which is noetherian, integral, separated, and regular in codimension 1. The latter means that for each point x X whose local ring O X,x has Krull dimension 1, that local ring must be regular. Lemma. Let A be a noetherian local ring of dimension 1. Then the following are equivalent. (a) A is regular. (b) A is normal. (c) A is a discrete valuation ring. (This is why normalizing a one-dimensional noetherian ring produces a regular ring.) Warning: for a noetherian integral domain, normal implies regular in codimension 1 but not conversely. You have to add Serre s condition S2: for a A, every associated prime of the principal ideal (a) has codimension 1 when a is not a zerodivisor, and has codimension 0 when a = 0. A prime (Weil) divisor on X is a closed integral (irreducible and reduced) subscheme of codimension 1. A formal Z-linear combination of prime divisors is called a Weil divisor. If only nonnegative coefficients are used, we say the divisor is effective. For example, let K(X) be the function field of X, i.e., the local ring of X at its generic point. (This equals Frac(O(U)) for any nonempty open affine subscheme U of X.) For f K(X) nonzero, we can define a principal divisor associated to f as follows. For each prime divisor Z on X, let η Z be the generic point of Z. Then O X,ηZ is a discrete valuation ring; let v Z be the valuation. Now define the divisor (f) = vz (f)z; Z this makes sense because only finitely many v Z (f) are nonzero. (That s because f restricts to an invertible regular function on some nonempty open subscheme U of X, and v Z (f) = 0 whenever Z X U.) Let Div X be the group of Weil divisors of X. The principal divisors form a subgroup (since (f) + (g) = (fg)); the quotient by this subgroup is called the divisor class group of 1
3 X, denoted Cl X. For example, if X = Spec(A) with A a Dedekind domain, then Div X is the group of fractional ideals, and ClX is the ideal class group. We say two divisors which differ by a principal divisor are linearly equivalent. There are a number of examples in Hartshorne. One of my favorites is that of an elliptic curve; here is a summary. Let k be an algebraically closed field (for starters). Let P(x, y, z) k[x, y, z] be a homogeneous polynomial of degree 3 defining a nonsingular subvariety C of P 2 k. Pick a point O C(k). There is a surjective map Div X Z mapping each prime divisor P to 1, called the degree. This map factors through Cl X because each principal divisor has degree 0. The kernel of the degree map Cl X Z is generated by (P) (O) for P C(k). In fact it is equal to the set of such elements: given P, Q C, we first draw the line through P, Q in P 2 k and find its third intersection point R with C. We then draw the line through R and O in P 2 k and find its third intersection point S with C. Then (P) + (Q) + (R) (R) + (S) + (O), so (P) (O) + (Q) (O) (S) (O). 2 Cartier divisors When the scheme X is not regular, there is a more restrictive notion of divisors that turns out to be more useful in many cases. Let K be the locally constant sheaf associated to the function field K(X). A Cartier divisor on X is a section of the sheaf K(X)/O. Using the construction of principal divisors, we obtain a map from Cartier divisors to Weil divisors: if the Cartier divisor is represented on some open subset U of X by the rational function f K(X), then the Weil divisor we get should agree with (f) when restricted to U (i.e., only keep the components of those prime divisors meeting U). This map is injective if X is normal, because an integrally closed noetherian domain is the intersections of its localizations at minimal prime ideals. Proposition (Hartshorne, Proposition II.6.11). Suppose X is locally factorial (i.e., each local ring O X,x is a unique factorization domain). Then the previous map is an isomorphism. (In particular, this holds if X is regular, because a regular local ring is factorial by a not-soeasy theorem of commutative algebra.) Example: if X = Spec k[x, y, z]/(xy z 2 ), the ideal (x, z) defines a Weil divisor which is not a Cartier divisor. Again, there is an obvious notion of a principal Cartier divisor, namely one defined by a single element of K(X). The group of Cartier divisors modulo principal divisors is called the Cartier class group of X, denoted CaCl X. 2
4 3 The Picard group The Cartier class group is usually the same as the Picard group, namely the group of invertible sheaves on X under the tensor product. Namely, if D is a Cartier divisor on X, let L(D) be the subsheaf of K such that L(D)(U) = {f K(X) : ((f) + (D)) U 0}. Assuming that X is normal, this is locally free of rank 1, hence an invertible sheaf. This gives a homomorphism from Cartier divisors to the Picard group, which we see kills the principal divisors. The resulting homomorphism is always injective, even without any hypotheses on X (Hartshorne, Corollary II.6.14) but may not be surjective; however, it is surjective if X is integral (Hartshorne, Proposition II.6.15). Note that if D is effective, then the function 1 defines a global section of L(D). Since L is locally principal, we can locally identify L with O X ; when we do so, the subsheaf of L(D) generated by 1 goes into correspondence with an ideal sheaf of O X, which doesn t depend on any choices. This ideal sheaf defines D as a closed subscheme. In other words, D is the zero locus of a certain section of L(D). More generally, even if D is effective, we can view D as the zero locus of a meromorphic section of L(D) (meaning a zero locus of L(D) OX K X ), and indeed the zero locus of any meromorphic section of L(D) is linearly equivalent to D. 4 Linear systems Suppose X is an integral separated scheme of finite type over a field k (which need not be algebraically closed). Let L be an invertible sheaf on X. A linear system defined by L is the set of zero loci of some k-linear subspace H of H 0 (X, L). If we take the entire space, that is called the complete linear system defined by L. We can attempt to use the elements of H to define a map X P k n, where n = dim k (H) 1. This might fail to give a morphism because H may have a base point, i.e., a point in the intersection of all of the divisors in the linear system. In fact, we get a morphism X P n k if and only if H has no base points. Suppose now that k is algebraically closed, and that X is one-dimensional, projective, irreducible, and nonsingular (i.e., a curve ). Consider the complete linear system associated to L(D) for some divisor D. (a) We get a map X P n k if and only if for each closed point x X, we have dim k H 0 (X, L(D x) = dim k H 0 (X, L(D)) 1. (In other words, there must be a section of L(D) not vanishing at x.) (b) The map in (a) is injective as a map of sets if and only if for each pair of distinct closed points x, y X, we have dim k H 0 (X, L(D x y)) = dim k H 0 (X, L(D)) 2. (In other words, there must be a section of L(D) vanishing at x but not at y, and vice versa.) 3
5 (c) The map in (b) is a closed immersion if and only if for each closed point x X, we have dim H 0 (X, L(D 2x)) = dim k H 0 (X, L(D)) 2. (In other words, there must be a section of L(D) not vanishing at x, and a section vanishing to exact order 1 at x.) (Condition (c) is needed to ensure that the tangent space at x embeds into the tangent space at the image of x. See Remark ) Since we would like to know under what circumstances X embeds into a projective space, we would like to be able to compute at least the dimension of H 0 (X, L(D)) for each divisor D. This quest is greatly abetted by the Riemann-Roch theorem, more on which next time. 4
LINE BUNDLES ON PROJECTIVE SPACE
LINE BUNDLES ON PROJECTIVE SPACE DANIEL LITT We wish to show that any line bundle over P n k is isomorphic to O(m) for some m; we give two proofs below, one following Hartshorne, and the other assuming
Preliminary Exam Topics Sarah Mayes
Preliminary Exam Topics Sarah Mayes 1. Sheaves Definition of a sheaf Definition of stalks of a sheaf Definition and universal property of sheaf associated to a presheaf [Hartshorne, II.1.2] Definition
ALGEBRAIC GEOMETRY I, FALL 2016.
ALGEBRAIC GEOMETRY I, FALL 2016. DIVISORS. 1. Weil and Cartier divisors Let X be an algebraic variety. Define a Weil divisor on X as a formal (finite) linear combination of irreducible subvarieties of
Algebraic Geometry Spring 2009
MIT OpenCourseWare http://ocw.mit.edu 18.726 Algebraic Geometry Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 18.726: Algebraic Geometry
ALGEBRAIC GEOMETRY: GLOSSARY AND EXAMPLES
ALGEBRAIC GEOMETRY: GLOSSARY AND EXAMPLES HONGHAO GAO FEBRUARY 7, 2014 Quasi-coherent and coherent sheaves Let X Spec k be a scheme. A presheaf over X is a contravariant functor from the category of open
Algebraic Geometry Spring 2009
MIT OpenCourseWare http://ocw.mit.edu 18.726 Algebraic Geometry Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 18.726: Algebraic Geometry
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 27
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 27 RAVI VAKIL CONTENTS 1. Quasicoherent sheaves of ideals, and closed subschemes 1 2. Invertible sheaves (line bundles) and divisors 2 3. Some line bundles on projective
CHAPTER 0 PRELIMINARY MATERIAL. Paul Vojta. University of California, Berkeley. 18 February 1998
CHAPTER 0 PRELIMINARY MATERIAL Paul Vojta University of California, Berkeley 18 February 1998 This chapter gives some preliminary material on number theory and algebraic geometry. Section 1 gives basic
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 18
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 18 CONTENTS 1. Invertible sheaves and divisors 1 2. Morphisms of schemes 6 3. Ringed spaces and their morphisms 6 4. Definition of morphisms of schemes 7 Last day:
ABSTRACT NONSINGULAR CURVES
ABSTRACT NONSINGULAR CURVES Affine Varieties Notation. Let k be a field, such as the rational numbers Q or the complex numbers C. We call affine n-space the collection A n k of points P = a 1, a,..., a
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASSES 47 AND 48
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASSES 47 AND 48 RAVI VAKIL CONTENTS 1. The local criterion for flatness 1 2. Base-point-free, ample, very ample 2 3. Every ample on a proper has a tensor power that
12. Linear systems Theorem Let X be a scheme over a ring A. (1) If φ: X P n A is an A-morphism then L = φ O P n
12. Linear systems Theorem 12.1. Let X be a scheme over a ring A. (1) If φ: X P n A is an A-morphism then L = φ O P n A (1) is an invertible sheaf on X, which is generated by the global sections s 0, s
the complete linear series of D. Notice that D = PH 0 (X; O X (D)). Given any subvectorspace V H 0 (X; O X (D)) there is a rational map given by V : X
2. Preliminaries 2.1. Divisors and line bundles. Let X be an irreducible complex variety of dimension n. The group of k-cycles on X is Z k (X) = fz linear combinations of subvarieties of dimension kg:
AN EXPOSITION OF THE RIEMANN ROCH THEOREM FOR CURVES
AN EXPOSITION OF THE RIEMANN ROCH THEOREM FOR CURVES DOMINIC L. WYNTER Abstract. We introduce the concepts of divisors on nonsingular irreducible projective algebraic curves, the genus of such a curve,
Algebraic Geometry Spring 2009
MIT OpenCourseWare http://ocw.mit.edu 18.726 Algebraic Geometry Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 18.726: Algebraic Geometry
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 43
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 43 RAVI VAKIL CONTENTS 1. Facts we ll soon know about curves 1 1. FACTS WE LL SOON KNOW ABOUT CURVES We almost know enough to say a lot of interesting things about
Classification of Complex Algebraic Surfaces
ALGANT Master Thesis in Mathematics Classification of Complex Algebraic Surfaces Alberto Corato Advised by Prof. Dajano Tossici Università degli Studi di Padova Université de Bordeaux Academic year 2017/2018
Exercises of the Algebraic Geometry course held by Prof. Ugo Bruzzo. Alex Massarenti
Exercises of the Algebraic Geometry course held by Prof. Ugo Bruzzo Alex Massarenti SISSA, VIA BONOMEA 265, 34136 TRIESTE, ITALY E-mail address: alex.massarenti@sissa.it These notes collect a series of
6.1 Finite generation, finite presentation and coherence
! Chapter 6 Coherent Sheaves 6.1 Finite generation, finite presentation and coherence Before getting to sheaves, let us discuss some finiteness properties for modules over a commutative ring R. Recall
Algebraic Geometry Spring 2009
MIT OpenCourseWare http://ocw.mit.edu 18.726 Algebraic Geometry Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 18.726: Algebraic Geometry
NOTES ON DIVISORS AND RIEMANN-ROCH
NOTES ON DIVISORS AND RIEMANN-ROCH NILAY KUMAR Recall that due to the maximum principle, there are no nonconstant holomorphic functions on a compact complex manifold. The next best objects to study, as
Part III Positivity in Algebraic Geometry
Part III Positivity in Algebraic Geometry Theorems with proof Based on lectures by S. Svaldi Notes taken by Dexter Chua Lent 2018 These notes are not endorsed by the lecturers, and I have modified them
INTERSECTION THEORY CLASS 6
INTERSECTION THEORY CLASS 6 RAVI VAKIL CONTENTS 1. Divisors 2 1.1. Crash course in Cartier divisors and invertible sheaves (aka line bundles) 3 1.2. Pseudo-divisors 3 2. Intersecting with divisors 4 2.1.
Algebraic Geometry Spring 2009
MIT OpenCourseWare http://ocw.mit.edu 18.726 Algebraic Geometry Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 18.726: Algebraic Geometry
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 27
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 27 RAVI VAKIL CONTENTS 1. Proper morphisms 1 2. Scheme-theoretic closure, and scheme-theoretic image 2 3. Rational maps 3 4. Examples of rational maps 5 Last day:
Locally Free Sheaves
Locally Free Sheaves Patrick Morandi Algebra Seminar, Spring 2002 In these talks we will discuss several important examples of locally free sheaves and see the connection between locally free sheaves and
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 24
FOUNDATIONS OF ALGEBRAIC GEOMETR CLASS 24 RAVI VAKIL CONTENTS 1. Normalization, continued 1 2. Sheaf Spec 3 3. Sheaf Proj 4 Last day: Fibers of morphisms. Properties preserved by base change: open immersions,
Math 248B. Applications of base change for coherent cohomology
Math 248B. Applications of base change for coherent cohomology 1. Motivation Recall the following fundamental general theorem, the so-called cohomology and base change theorem: Theorem 1.1 (Grothendieck).
Curves on P 1 P 1. Peter Bruin 16 November 2005
Curves on P 1 P 1 Peter Bruin 16 November 2005 1. Introduction One of the exercises in last semester s Algebraic Geometry course went as follows: Exercise. Let be a field and Z = P 1 P 1. Show that the
Section Divisors
Section 2.6 - Divisors Daniel Murfet October 5, 2006 Contents 1 Weil Divisors 1 2 Divisors on Curves 9 3 Cartier Divisors 13 4 Invertible Sheaves 17 5 Examples 23 1 Weil Divisors Definition 1. We say a
Algebraic varieties and schemes over any scheme. Non singular varieties
Algebraic varieties and schemes over any scheme. Non singular varieties Trang June 16, 2010 1 Lecture 1 Let k be a field and k[x 1,..., x n ] the polynomial ring with coefficients in k. Then we have two
DIVISORS ON NONSINGULAR CURVES
DIVISORS ON NONSINGULAR CURVES BRIAN OSSERMAN We now begin a closer study of the behavior of projective nonsingular curves, and morphisms between them, as well as to projective space. To this end, we introduce
Néron Models of Elliptic Curves.
Néron Models of Elliptic Curves. Marco Streng 5th April 2007 These notes are meant as an introduction and a collection of references to Néron models of elliptic curves. We use Liu [Liu02] and Silverman
Picard Groups of Affine Curves
Picard Groups of Affine Curves Victor I. Piercey University of Arizona Math 518 May 7, 2008 Abstract We will develop a purely algebraic definition for the Picard group of an affine variety. We will then
NOTES ON FLAT MORPHISMS AND THE FPQC TOPOLOGY
NOTES ON FLAT MORPHISMS AND THE FPQC TOPOLOGY RUNE HAUGSENG The aim of these notes is to define flat and faithfully flat morphisms and review some of their important properties, and to define the fpqc
mult V f, where the sum ranges over prime divisor V X. We say that two divisors D 1 and D 2 are linearly equivalent, denoted by sending
2. The canonical divisor In this section we will introduce one of the most important invariants in the birational classification of varieties. Definition 2.1. Let X be a normal quasi-projective variety
1. Algebraic vector bundles. Affine Varieties
0. Brief overview Cycles and bundles are intrinsic invariants of algebraic varieties Close connections going back to Grothendieck Work with quasi-projective varieties over a field k Affine Varieties 1.
ON THE ISOMORPHISM BETWEEN THE DUALIZING SHEAF AND THE CANONICAL SHEAF
ON THE ISOMORPHISM BETWEEN THE DUALIZING SHEAF AND THE CANONICAL SHEAF MATTHEW H. BAKER AND JÁNOS A. CSIRIK Abstract. We give a new proof of the isomorphism between the dualizing sheaf and the canonical
MATH2810 ALGEBRAIC GEOMETRY NOTES. Contents
MATH2810 ALGEBRAIC GEOMETRY NOTES KIUMARS KAVEH Contents 1. Affine Algebraic Geometry 1 2. Sheaves 3 3. Projective varieties 4 4. Degree and Hilbert Functions 6 5. Bernstein-Kushnirenko theorem 7 6. Degree
Introduction to Arithmetic Geometry Fall 2013 Lecture #17 11/05/2013
18.782 Introduction to Arithmetic Geometry Fall 2013 Lecture #17 11/05/2013 Throughout this lecture k denotes an algebraically closed field. 17.1 Tangent spaces and hypersurfaces For any polynomial f k[x
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASSES 43 AND 44
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASSES 43 AND 44 RAVI VAKIL CONTENTS 1. Flat implies constant Euler characteristic 1 2. Proof of Important Theorem on constancy of Euler characteristic in flat families
COMPLEX VARIETIES AND THE ANALYTIC TOPOLOGY
COMPLEX VARIETIES AND THE ANALYTIC TOPOLOGY BRIAN OSSERMAN Classical algebraic geometers studied algebraic varieties over the complex numbers. In this setting, they didn t have to worry about the Zariski
SCHEMES. David Harari. Tsinghua, February-March 2005
SCHEMES David Harari Tsinghua, February-March 2005 Contents 1. Basic notions on schemes 2 1.1. First definitions and examples.................. 2 1.2. Morphisms of schemes : first properties.............
(1) is an invertible sheaf on X, which is generated by the global sections
7. Linear systems First a word about the base scheme. We would lie to wor in enough generality to cover the general case. On the other hand, it taes some wor to state properly the general results if one
Math 797W Homework 4
Math 797W Homework 4 Paul Hacking December 5, 2016 We work over an algebraically closed field k. (1) Let F be a sheaf of abelian groups on a topological space X, and p X a point. Recall the definition
Introduction to Arithmetic Geometry Fall 2013 Lecture #18 11/07/2013
18.782 Introduction to Arithmetic Geometry Fall 2013 Lecture #18 11/07/2013 As usual, all the rings we consider are commutative rings with an identity element. 18.1 Regular local rings Consider a local
APPENDIX 3: AN OVERVIEW OF CHOW GROUPS
APPENDIX 3: AN OVERVIEW OF CHOW GROUPS We review in this appendix some basic definitions and results that we need about Chow groups. For details and proofs we refer to [Ful98]. In particular, we discuss
3. The Sheaf of Regular Functions
24 Andreas Gathmann 3. The Sheaf of Regular Functions After having defined affine varieties, our next goal must be to say what kind of maps between them we want to consider as morphisms, i. e. as nice
HYPERSURFACES IN PROJECTIVE SCHEMES AND A MOVING LEMMA
HYPERSURFACES IN PROJECTIVE SCHEMES AND A MOVING LEMMA OFER GABBER, QING LIU, AND DINO LORENZINI Abstract. Let X/S be a quasi-projective morphism over an affine base. We develop in this article a technique
Remarks on the existence of Cartier divisors
arxiv:math/0001104v1 [math.ag] 19 Jan 2000 Remarks on the existence of Cartier divisors Stefan Schröer October 22, 2018 Abstract We characterize those invertible sheaves on a noetherian scheme which are
Holomorphic line bundles
Chapter 2 Holomorphic line bundles In the absence of non-constant holomorphic functions X! C on a compact complex manifold, we turn to the next best thing, holomorphic sections of line bundles (i.e., rank
Lecture 3: Flat Morphisms
Lecture 3: Flat Morphisms September 29, 2014 1 A crash course on Properties of Schemes For more details on these properties, see [Hartshorne, II, 1-5]. 1.1 Open and Closed Subschemes If (X, O X ) is a
Dedekind Domains. Mathematics 601
Dedekind Domains Mathematics 601 In this note we prove several facts about Dedekind domains that we will use in the course of proving the Riemann-Roch theorem. The main theorem shows that if K/F is a finite
MATH 8253 ALGEBRAIC GEOMETRY WEEK 12
MATH 8253 ALGEBRAIC GEOMETRY WEEK 2 CİHAN BAHRAN 3.2.. Let Y be a Noetherian scheme. Show that any Y -scheme X of finite type is Noetherian. Moreover, if Y is of finite dimension, then so is X. Write f
Topics in Algebraic Geometry
Topics in Algebraic Geometry Nikitas Nikandros, 3928675, Utrecht University n.nikandros@students.uu.nl March 2, 2016 1 Introduction and motivation In this talk i will give an incomplete and at sometimes
Synopsis of material from EGA Chapter II, 4. Proposition (4.1.6). The canonical homomorphism ( ) is surjective [(3.2.4)].
Synopsis of material from EGA Chapter II, 4 4.1. Definition of projective bundles. 4. Projective bundles. Ample sheaves Definition (4.1.1). Let S(E) be the symmetric algebra of a quasi-coherent O Y -module.
Section Projective Morphisms
Section 2.7 - Projective Morphisms Daniel Murfet October 5, 2006 In this section we gather together several topics concerned with morphisms of a given scheme to projective space. We will show how a morphism
INTERSECTION THEORY CLASS 7
INTERSECTION THEORY CLASS 7 RAVI VAKIL CONTENTS 1. Intersecting with a pseudodivisor 1 2. The first Chern class of a line bundle 3 3. Gysin pullback 4 4. Towards the proof of the big theorem 4 4.1. Crash
MATH 233B, FLATNESS AND SMOOTHNESS.
MATH 233B, FLATNESS AND SMOOTHNESS. The discussion of smooth morphisms is one place were Hartshorne doesn t do a very good job. Here s a summary of this week s material. I ll also insert some (optional)
Introduction to Arithmetic Geometry Fall 2013 Lecture #23 11/26/2013
18.782 Introduction to Arithmetic Geometry Fall 2013 Lecture #23 11/26/2013 As usual, a curve is a smooth projective (geometrically irreducible) variety of dimension one and k is a perfect field. 23.1
Introduction to Arithmetic Geometry Fall 2013 Lecture #15 10/29/2013
18.782 Introduction to Arithmetic Geometry Fall 2013 Lecture #15 10/29/2013 As usual, k is a perfect field and k is a fixed algebraic closure of k. Recall that an affine (resp. projective) variety is an
ALGEBRAIC K-THEORY HANDOUT 5: K 0 OF SCHEMES, THE LOCALIZATION SEQUENCE FOR G 0.
ALGEBRAIC K-THEORY HANDOUT 5: K 0 OF SCHEMES, THE LOCALIZATION SEQUENCE FOR G 0. ANDREW SALCH During the last lecture, we found that it is natural (even just for doing undergraduatelevel complex analysis!)
ALGEBRAIC GROUPS. Disclaimer: There are millions of errors in these notes!
ALGEBRAIC GROUPS Disclaimer: There are millions of errors in these notes! 1. Some algebraic geometry The subject of algebraic groups depends on the interaction between algebraic geometry and group theory.
3. Lecture 3. Y Z[1/p]Hom (Sch/k) (Y, X).
3. Lecture 3 3.1. Freely generate qfh-sheaves. We recall that if F is a homotopy invariant presheaf with transfers in the sense of the last lecture, then we have a well defined pairing F(X) H 0 (X/S) F(S)
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 37
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 37 RAVI VAKIL CONTENTS 1. Application of cohomology: Hilbert polynomials and functions, Riemann- Roch, degrees, and arithmetic genus 1 1. APPLICATION OF COHOMOLOGY:
Asymptotic invariants of line bundles, semiampleness and finite generation
UNIVERSITÀ DEGLI STUDI ROMA TRE FACOLTÀ DI SCIENZE MM. FF. NN. Graduation Thesis in Mathematics by Salvatore Cacciola Asymptotic invariants of line bundles, semiampleness and finite generation Supervisor
INTRODUCTION TO ALGEBRAIC GEOMETRY, CLASS 14
INTRODUCTION TO ALGEBRAIC GEOMETRY, CLASS 14 RAVI VAKIL Contents 1. Dimension 1 1.1. Last time 1 1.2. An algebraic definition of dimension. 3 1.3. Other facts that are not hard to prove 4 2. Non-singularity:
Math 418 Algebraic Geometry Notes
Math 418 Algebraic Geometry Notes 1 Affine Schemes Let R be a commutative ring with 1. Definition 1.1. The prime spectrum of R, denoted Spec(R), is the set of prime ideals of the ring R. Spec(R) = {P R
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 48
FOUNDATIONS OF ALGEBRAIC GEOMETRY CLASS 48 RAVI VAKIL CONTENTS 1. A little more about cubic plane curves 1 2. Line bundles of degree 4, and Poncelet s Porism 1 3. Fun counterexamples using elliptic curves
Algebraic v.s. Analytic Point of View
Algebraic v.s. Analytic Point of View Ziwen Zhu September 19, 2015 In this talk, we will compare 3 different yet similar objects of interest in algebraic and complex geometry, namely algebraic variety,
PROBLEMS, MATH 214A. Affine and quasi-affine varieties
PROBLEMS, MATH 214A k is an algebraically closed field Basic notions Affine and quasi-affine varieties 1. Let X A 2 be defined by x 2 + y 2 = 1 and x = 1. Find the ideal I(X). 2. Prove that the subset
Arithmetic Algebraic Geometry
Arithmetic Algebraic Geometry 2 Arithmetic Algebraic Geometry Travis Dirle December 4, 2016 2 Contents 1 Preliminaries 1 1.1 Affine Varieties.......................... 1 1.2 Projective Varieties........................
11. Dimension. 96 Andreas Gathmann
96 Andreas Gathmann 11. Dimension We have already met several situations in this course in which it seemed to be desirable to have a notion of dimension (of a variety, or more generally of a ring): for
arxiv: v1 [math.ra] 5 Feb 2015
Noncommutative ampleness from finite endomorphisms D. S. Keeler Dept. of Mathematics, Miami University, Oxford, OH 45056 arxiv:1502.01668v1 [math.ra] 5 Feb 2015 Abstract K. Retert Dept. of Mathematics,
MODULI SPACES OF CURVES
MODULI SPACES OF CURVES SCOTT NOLLET Abstract. My goal is to introduce vocabulary and present examples that will help graduate students to better follow lectures at TAGS 2018. Assuming some background
AN ALTERNATIVE APPROACH TO SERRE DUALITY FOR PROJECTIVE VARIETIES
AN ALTERNATIVE APPROACH TO SERRE DUALITY FOR PROJECTIVE VARIETIES MATTHEW H. BAKER AND JÁNOS A. CSIRIK This paper was written in conjunction with R. Hartshorne s Spring 1996 Algebraic Geometry course at
Synopsis of material from EGA Chapter II, 5
Synopsis of material from EGA Chapter II, 5 5. Quasi-affine, quasi-projective, proper and projective morphisms 5.1. Quasi-affine morphisms. Definition (5.1.1). A scheme is quasi-affine if it is isomorphic
CHEVALLEY S THEOREM AND COMPLETE VARIETIES
CHEVALLEY S THEOREM AND COMPLETE VARIETIES BRIAN OSSERMAN In this note, we introduce the concept which plays the role of compactness for varieties completeness. We prove that completeness can be characterized
Exploring the Exotic Setting for Algebraic Geometry
Exploring the Exotic Setting for Algebraic Geometry Victor I. Piercey University of Arizona Integration Workshop Project August 6-10, 2010 1 Introduction In this project, we will describe the basic topology
Oral exam practice problems: Algebraic Geometry
Oral exam practice problems: Algebraic Geometry Alberto García Raboso TP1. Let Q 1 and Q 2 be the quadric hypersurfaces in P n given by the equations f 1 x 2 0 + + x 2 n = 0 f 2 a 0 x 2 0 + + a n x 2 n
Higher-Dimensional Varieties
Higher-Dimensional Varieties Lecture notes for the CIMPA CIMAT ICTP School on Moduli of Curves February 22 March 4, 2016 Guanajuato, México Olivier Debarre March 11, 2016 Contents 1 Divisors 3 1.1 Weil
then D 1 D n = D 1 D n.
Lecture 8. Intersection theory and ampleness: revisited. In this lecture, X will denote a proper irreducible variety over k = k, chark = 0, unless otherwise stated. We will indicate the dimension of X
CHAPTER 1. AFFINE ALGEBRAIC VARIETIES
CHAPTER 1. AFFINE ALGEBRAIC VARIETIES During this first part of the course, we will establish a correspondence between various geometric notions and algebraic ones. Some references for this part of the
HARTSHORNE EXERCISES
HARTSHORNE EXERCISES J. WARNER Hartshorne, Exercise I.5.6. Blowing Up Curve Singularities (a) Let Y be the cusp x 3 = y 2 + x 4 + y 4 or the node xy = x 6 + y 6. Show that the curve Ỹ obtained by blowing
Algebraic Geometry. Andreas Gathmann. Class Notes TU Kaiserslautern 2014
Algebraic Geometry Andreas Gathmann Class Notes TU Kaiserslautern 2014 Contents 0. Introduction......................... 3 1. Affine Varieties........................ 9 2. The Zariski Topology......................
Algebraic varieties. Chapter A ne varieties
Chapter 4 Algebraic varieties 4.1 A ne varieties Let k be a field. A ne n-space A n = A n k = kn. It s coordinate ring is simply the ring R = k[x 1,...,x n ]. Any polynomial can be evaluated at a point
214A HOMEWORK KIM, SUNGJIN
214A HOMEWORK KIM, SUNGJIN 1.1 Let A = k[[t ]] be the ring of formal power series with coefficients in a field k. Determine SpecA. Proof. We begin with a claim that A = { a i T i A : a i k, and a 0 k }.
ALGEBRAIC GEOMETRY COURSE NOTES, LECTURE 2: HILBERT S NULLSTELLENSATZ.
ALGEBRAIC GEOMETRY COURSE NOTES, LECTURE 2: HILBERT S NULLSTELLENSATZ. ANDREW SALCH 1. Hilbert s Nullstellensatz. The last lecture left off with the claim that, if J k[x 1,..., x n ] is an ideal, then
DEFORMATIONS VIA DIMENSION THEORY
DEFORMATIONS VIA DIMENSION THEORY BRIAN OSSERMAN Abstract. We show that standard arguments for deformations based on dimension counts can also be applied over a (not necessarily Noetherian) valuation ring
Synopsis of material from EGA Chapter II, 3
Synopsis of material from EGA Chapter II, 3 3. Homogeneous spectrum of a sheaf of graded algebras 3.1. Homogeneous spectrum of a graded quasi-coherent O Y algebra. (3.1.1). Let Y be a prescheme. A sheaf
Contents. Chapter 3. Local Rings and Varieties Rings of Germs of Holomorphic Functions Hilbert s Basis Theorem 39.
Preface xiii Chapter 1. Selected Problems in One Complex Variable 1 1.1. Preliminaries 2 1.2. A Simple Problem 2 1.3. Partitions of Unity 4 1.4. The Cauchy-Riemann Equations 7 1.5. The Proof of Proposition
CHEAT SHEET: PROPERTIES OF MORPHISMS OF SCHEMES
CHEAT SHEET: PROPERTIES OF MORPHISMS OF SCHEMES BRIAN OSSERMAN The purpose of this cheat sheet is to provide an easy reference for definitions of various properties of morphisms of schemes, and basic results
ALGEBRAIC GEOMETRY COURSE NOTES, LECTURE 9: SCHEMES AND THEIR MODULES.
ALGEBRAIC GEOMETRY COURSE NOTES, LECTURE 9: SCHEMES AND THEIR MODULES. ANDREW SALCH 1. Affine schemes. About notation: I am in the habit of writing f (U) instead of f 1 (U) for the preimage of a subset
Algebraic Curves and Riemann Surfaces
Algebraic Curves and Riemann Surfaces Rick Miranda Graduate Studies in Mathematics Volume 5 If American Mathematical Society Contents Preface xix Chapter I. Riemann Surfaces: Basic Definitions 1 1. Complex
INTRODUCTION TO ALGEBRAIC GEOMETRY, CLASS 23
INTRODUCTION TO ALGEBRAIC GEOMETRY, CLASS 23 RAVI VAKIL Contents 1. More background on invertible sheaves 1 1.1. Operations on invertible sheaves 1 1.2. Maps to projective space correspond to a vector
LECTURE 7: STABLE RATIONALITY AND DECOMPOSITION OF THE DIAGONAL
LECTURE 7: STABLE RATIONALITY AND DECOMPOSITION OF THE DIAGONAL In this lecture we discuss a criterion for non-stable-rationality based on the decomposition of the diagonal in the Chow group. This criterion
arxiv: v1 [math.ag] 14 Mar 2019
ASYMPTOTIC CONSTRUCTIONS AND INVARIANTS OF GRADED LINEAR SERIES ariv:1903.05967v1 [math.ag] 14 Mar 2019 CHIH-WEI CHANG AND SHIN-YAO JOW Abstract. Let be a complete variety of dimension n over an algebraically
NOTES ON ABELIAN VARIETIES
NOTES ON ABELIAN VARIETIES YICHAO TIAN AND WEIZHE ZHENG We fix a field k and an algebraic closure k of k. A variety over k is a geometrically integral and separated scheme of finite type over k. If X and
STEENROD OPERATIONS IN ALGEBRAIC GEOMETRY
STEENROD OPERATIONS IN ALGEBRAIC GEOMETRY ALEXANDER MERKURJEV 1. Introduction Let p be a prime integer. For a pair of topological spaces A X we write H i (X, A; Z/pZ) for the i-th singular cohomology group
1 Flat, Smooth, Unramified, and Étale Morphisms
1 Flat, Smooth, Unramified, and Étale Morphisms 1.1 Flat morphisms Definition 1.1. An A-module M is flat if the (right-exact) functor A M is exact. It is faithfully flat if a complex of A-modules P N Q