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Algebraic variety

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6319: 38: 6442:. It allows you to glue affine varieties (along common open sets) without worrying whether the resulting object can be put into some projective space. This also leads to difficulties since one can introduce somewhat pathological objects, e.g. an affine line with zero doubled. Such objects are usually not considered varieties, and are eliminated by requiring the schemes underlying a variety to be 204:
is conceptually the easiest type of variety to define, which will be done in this section. Next, one can define projective and quasi-projective varieties in a similar way. The most general definition of a variety is obtained by patching together smaller quasi-projective varieties. It is not obvious
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which ensures a set of isomorphism classes has a (reducible) quasi-projective variety structure. Moduli such as the moduli of curves of fixed genus is typically not a projective variety; roughly the reason is that a degeneration (limit) of a smooth curve tends to be non-smooth or reducible. This
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subset of a projective variety. Notice that every affine variety is quasi-projective. Notice also that the complement of an algebraic set in an affine variety is a quasi-projective variety; in the context of affine varieties, such a quasi-projective variety is usually not called a variety but a
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over an algebraically closed field, although some authors drop the irreducibility or the reducedness or the separateness condition or allow the underlying field to be not algebraically closed. Classical algebraic varieties are the quasiprojective integral separated finite type schemes over an
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In general, in contrast to the case of moduli of curves, a compactification of a moduli need not be unique and, in some cases, different non-equivalent compactifications are constructed using different methods and by different authors. An example over
5582:). The non-uniqueness of compactifications is due to the lack of moduli interpretations of those compactifications; i.e., they do not represent (in the category-theory sense) any natural moduli problem or, in the precise language, there is no natural 463: 3009: 961: 4423: 679: 3972: 1825: 4954:
The moduli of curves exemplifies a typical situation: a moduli of nice objects tend not to be projective but only quasi-projective. Another case is a moduli of vector bundles on a curve. Here, there are the notions of
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Mark Goresky. Compactifications and cohomology of modular varieties. In Harmonic analysis, the trace formula, and Shimura varieties, volume 4 of Clay Math. Proc., pages 551–582. Amer. Math. Soc., Providence, RI,
6387:— some foundational changes are required. The modern notion of a variety is considerably more abstract than the one above, though equivalent in the case of varieties over algebraically closed fields. An 1177:(the analog of compactness), but soon afterwards he found an algebraic surface that was complete and non-projective. Since then other examples have been found: for example, it is straightforward to construct 6147:
A product of finitely many algebraic varieties (over an algebraically closed field) is an algebraic variety. A finite product of affine varieties is affine and a finite product of projective varieties is
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says that closed subvarieties of an affine or projective variety are in one-to-one correspondence with the prime ideals or non-irrelevant homogeneous prime ideals of the coordinate ring of the variety.
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is a subset of a variety that is itself a variety (with respect to the topological structure induced by the ambient variety). For example, every open subset of a variety is a variety. See also
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is a particular kind of scheme; the generalization to schemes on the geometric side enables an extension of the correspondence described above to a wider class of rings. A scheme is a
3206: 1152:'s definition of a scheme is more general still and has received the most widespread acceptance. In Grothendieck's language, an abstract algebraic variety is usually defined to be an 4186: 4095: 4063: 4007: 3918: 3874: 6133:
Every nonempty affine algebraic set may be written uniquely as a finite union of algebraic varieties (where none of the varieties in the decomposition is a subvariety of any other).
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on the variety. The disadvantage of such a definition is that not all varieties come with natural embeddings into projective space. For example, under this definition, the product
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The basic definitions and facts above enable one to do classical algebraic geometry. To be able to do more — for example, to deal with varieties over fields that are not
5705: 1100:. So classically the definition of an algebraic variety required an embedding into projective space, and this embedding was used to define the topology on the variety and the 3078: 3545:, which has genus zero. Using genus to distinguish curves is very basic: in fact, the genus is the first invariant one uses to classify curves (see also the construction of 3456: 2504: 6509:
Allowing nilpotent elements in rings is related to keeping track of "multiplicities" in algebraic geometry. For example, the closed subscheme of the affine line defined by
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was written for them. They remain typical objects to start studying in algebraic geometry, even if more general objects are also used in an auxiliary way.
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structure on it (the name "abelian" is however not because it is an abelian group). An abelian variety turns out to be projective (in short, algebraic
5474:(a principal polarization identifies an abelian variety with its dual). The theory of toric varieties (or torus embeddings) gives a way to compactify 4290: 3742:{\displaystyle {\begin{cases}G_{n}(V)\hookrightarrow \mathbf {P} \left(\wedge ^{n}V\right)\\\langle b_{1},\ldots ,b_{n}\rangle \mapsto \end{cases}}} 560: 3931: 1749: 733: 6613: 1504:
is not empty. It is irreducible, as it cannot be written as the union of two proper algebraic subsets. Thus it is an affine algebraic variety.
1118:. Furthermore, any variety that admits one embedding into projective space admits many others, for example by composing the embedding with the 158: 79:
Conventions regarding the definition of an algebraic variety differ slightly. For example, some definitions require an algebraic variety to be
4663:, a not-necessarily-smooth complete curve with no terribly bad singularities and not-so-large automorphism group. The moduli of stable curves 7416: 7388: 7228: 7154: 7097: 7057: 6895: 6476: 4030: 6446:. (Strictly speaking, there is also a third condition, namely, that one needs only finitely many affine patches in the definition above.) 3461:
in the 2-dimensional affine space (over a field of characteristic not two). It has the associated cubic homogeneous polynomial equation:
3364: 2591: 7333: 7307: 7194: 6901:, a remark describes a complete toric variety that has no non-trivial line bundle; thus, in particular, it has no ample line bundle. 6757: 6370: 6141: 2268:. It is an affine variety, since, in general, the complement of a hypersurface in an affine variety is affine. Explicitly, consider 1131: 162: 6648: 5732: 4628:. There are few ways to show this moduli has a structure of a possibly reducible algebraic variety; for example, one way is to use 4100: 7325: 7299: 7178: 6749: 146:
and related results, mathematicians have established a strong correspondence between questions on algebraic sets and questions of
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One of the earliest examples of a non-quasiprojective algebraic variety were given by Nagata. Nagata's example was not
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coming from the topology on the complex numbers, a complex line is a real manifold of dimension two.) This is the set
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The irreducibility of this algebraic set needs a proof. One approach in this case is to check that the projection (
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are reduced. Geometrically, this says that fibers of good mappings may have nontrivial "infinitesimal" structure.
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computation to compute the dimension, followed by a random linear change of variables (not always needed); then a
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A plane projective curve is the zero locus of an irreducible homogeneous polynomial in three indeterminates. The
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For more difficult examples, a similar proof may always be given, but may imply a difficult computation: first a
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into it can be extended uniquely to the whole curve. Every projective variety is complete, but not vice versa.
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as an open subset. Since a line bundle is stable, such a moduli is a generalization of the Jacobian variety of
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Projective varieties are also equipped with the Zariski topology by declaring all algebraic sets to be closed.
717: 284: 6590:. Algebraic manifolds can be defined as the zero set of a finite collection of analytic algebraic functions. 4159: 4068: 4036: 3980: 3891: 3847: 1739:
is an algebraic variety, and more precisely an algebraic curve that is not contained in any plane. It is the
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The earliest successful attempt to define an algebraic variety abstractly, without an embedding, was made by
3348: 2039: 1069: 781: 154: 7364:, published as Chapter VII of Arithmetic geometry (Storrs, Conn., 1984), 167–212, Springer, New York, 1986. 5291: 1568: 6981: 6503: 5579: 3467: 3321: 3297: 3267: 3237: 3211: 3083: 3018: 2923: 2879: 2863: 2185: 2129: 1908: 1680: 1149: 759: 5426: 4897: 4866: 4795: 4728: 4600: 3113: 7379:. Ergebnisse der Mathematik und ihrer Grenzgebiete (2) . Vol. 34 (3rd ed.). Berlin, New York: 6158: 5666: 1122:; thus many notions that should be intrinsic, such as that of a regular function, are not obviously so. 80: 7445: 122:(an algebraic object) in one variable with complex number coefficients is determined by the set of its 5681: 6454: 6392: 6261: 4956: 3825: 3584: 3562: 3059: 2227: 1145: 177: 3602: 3412: 2455: 6986: 6618: 6408: 5575: 3921: 3821: 3261: 2867: 1683:
polynomial, this is an algebraic variety. The set of its real points (that is the points for which
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is not a variety until it is embedded into a larger projective space; this is usually done by the
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affine charts, and when speaking of a variety only require that the affine charts have trivial
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such that every point has a neighbourhood that, as a locally ringed space, is isomorphic to a
6284: 6198: 5567: 4894:. Historically a paper of Mumford and Deligne introduced the notion of a stable curve to show 2416: 170: 88: 7210: 6502:. This is one of several generalizations of classical algebraic geometry that are built into 6069: 5332: 5243: 4928: 4702: 4640: 4530: 458:{\displaystyle Z(S)=\left\{x\in \mathbf {A} ^{n}\mid f(x)=0{\text{ for all }}f\in S\right\}.} 7260: 7216: 7182: 7142: 7085: 6991: 6842: 6826: 6798: 6782: 6741: 6628: 6480: 6461: 5639: 4574: 4261: 3975: 2064: 1944: 1870: 1862: 1858: 1199: 1174: 1141: 1101: 1097: 1073: 1052: 522: 206: 119: 96: 7398: 7067: 6856: 6812: 4431: 4214: 3392:
is an example of a projective curve; it can be viewed as the curve in the projective plane
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while a differentiable manifold cannot. Algebraic varieties can be characterized by their
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to be precisely the affine algebraic sets. This topology is called the Zariski topology.
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turns out to be an isomorphism; in particular, an elliptic curve is an abelian variety.
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is a closed subvariety of a projective space. That is, it is the zero locus of a set of
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One way that leads to generalizations is to allow reducible algebraic sets (and fields
6106: 5984:(over the complex numbers) is not an algebraic variety, while the special linear group 5960: 5877: 5457: 5223: 5149: 5129: 5109: 5002: 4982: 4962: 4580: 4556: 4241: 4191: 4026: 3798: 3534: 2596: 2165: 2021: 1866: 228: 218: 73: 6910:
Definition 1.1.12 in Ginzburg, V., 1998. Lectures on D-modules. University of Chicago.
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is an algebraic variety since it is a product of varieties. It is not affine since
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An algebraic variety can be neither affine nor projective. To give an example, let
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This article is about algebraic varieties. For the term "variety of algebras", see
5019:(degree of the determinant of the bundle) is then a projective variety denoted as 956:{\displaystyle Z(S)=\{x\in \mathbf {P} ^{n}\mid f(x)=0{\text{ for all }}f\in S\}.} 7347: 7437: 7146: 6432: 6117: 3829: 3352: 3107: 3054: 1692: 1359:
on which this function vanishes: it is the set of all pairs of complex numbers (
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Chai, Ching-Li (1986). "Siegel Moduli Schemes and Their Compactifications over
4418:{\displaystyle C^{n}\to \operatorname {Jac} (C),\,(P_{1},\dots ,P_{r})\mapsto } 7441: 7220: 7186: 6689:
Harris, p.9; that it is irreducible is stated as an exercise in Hartshorne p.7
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on the set of the solutions and that its image is an irreducible plane curve.
674:{\displaystyle I(V)=\left\{f\in K\mid f(x)=0{\text{ for all }}x\in V\right\}.} 526: 92: 7426: 7361: 6847: 6835:
Memoirs of the College of Science, University of Kyoto. Series A: Mathematics
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Memoirs of the College of Science, University of Kyoto. Series A: Mathematics
6786: 3583:. It is a projective variety: it is embedded into a projective space via the 6495: 4013:
is the kernel of this degree map; i.e., the group of the divisor classes on
3967:{\displaystyle \operatorname {deg} :\operatorname {Pic} (C)\to \mathbb {Z} } 1820:{\displaystyle {\begin{aligned}y-x^{2}&=0\\z-x^{3}&=0\end{aligned}}} 205:
that one can construct genuinely new examples of varieties in this way, but
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These varieties have been called "varieties in the sense of Serre", since
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may not be integral domains. A more significant modification is to allow
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algebraic subsets. An irreducible affine algebraic set is also called an
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Some modern researchers also remove the restriction on a variety having
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is an algebraic (affine) variety, since the origin is the zero-locus of
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has a solution. This is best seen algebraically: the coordinate ring of
99:. Under this definition, non-irreducible algebraic varieties are called 7272: 7089: 6995: 111: 184:
is an integral (irreducible and reduced) scheme over that field whose
1072:, meaning that they were open subvarieties of closed subvarieties of 1024:) be the ideal generated by all homogeneous polynomials vanishing on 507: 7264: 6464:
is a variety such that any map from an open subset of a nonsingular
4553:, the set of isomorphism classes of smooth complete curves of genus 5831:
is not an algebraic variety (nor even an algebraic set). Note that
150:. This correspondence is a defining feature of algebraic geometry. 3362: 1068:
In classical algebraic geometry, all varieties were by definition
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of it; i.e., the group of isomorphism classes of line bundles on
3381:. The corresponding projective curve is called an elliptic curve. 1148:, which served a similar purpose, but was more general. However, 6831:"On the imbeddings of abstract surfaces in projective varieties" 5454:
of principally polarized complex abelian varieties of dimension
3805:, and the bracket means the line spanned by the nonzero vector 3110:); more precisely, the coordinate ring of the dual vector space 7411:. Oxford science publications. Oxford University Press. 2006. 7215:. Encyclopaedia of Mathematical Sciences. Vol. 23. 1994. 6566:
An algebraic manifold is an algebraic variety that is also an
6312: 3541:); in particular, it is not isomorphic to the projective line 2870:
in such a way the group operations are morphism of varieties.
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shown in the above figure. It may be defined by the equations
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Mathematical object studied in the field of algebraic geometry
5787:{\displaystyle \{z\in \mathbb {C} {\text{ with }}|z|^{2}=1\}} 4149:{\displaystyle \operatorname {H} ^{1}(C,{\mathcal {O}}_{C});} 3406:. For another example, first consider the affine cubic curve 1169:
Existence of non-quasiprojective abstract algebraic varieties
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of a variety may be defined in various equivalent ways. See
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on which this function vanishes, that is the set of points (
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are an equivalent definition for projective varieties. The
4699:, the set of isomorphism classes of stable curves of genus 3735: 2406:{\displaystyle \mathbb {A} ^{n^{2}}\times \mathbb {A} ^{1}} 2312:{\displaystyle \mathbb {A} ^{n^{2}}\times \mathbb {A} ^{1}} 550:) to be the ideal of all polynomial functions vanishing on 518:
to refer to any affine algebraic set, irreducible or not.)
6965:"The irreducibility of the space of curves of given genus" 5653:
Another example of a non-affine non-projective variety is
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that would be an analog of moduli stack of stable curves.
4979:. The moduli of semistable vector bundles of a given rank 7322:
Commutative Algebra with a View Toward Algebraic Geometry
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and semistable vector bundles on a smooth complete curve
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of isomorphism classes of stable vector bundles of rank
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is the coordinate ring of an affine (reducible) variety
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of degree zero. A Jacobian variety is an example of an
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Smooth compactification of locally symmetric varieties
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is a variety if and only if its coordinate ring is an
5920:). On the other hand, the complement of the origin in 3328:. The notion plays an important role in the theory of 2888:
be a not-necessarily-commutative algebra over a field
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and thus is an affine variety. A finite product of it
1695:; this name is also often given to the whole variety. 1084:
over an algebraically closed field is defined to be a
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is the quotient of the polynomial ring by this ideal.
996:. An irreducible projective algebraic set is called a 60:. Classically, an algebraic variety is defined as the 7119: 6072: 6059:{\displaystyle \operatorname {GL} _{n}(\mathbb {C} )} 6031: 6018:{\displaystyle \operatorname {SL} _{n}(\mathbb {C} )} 5990: 5963: 5926: 5900: 5894:(although it is a polynomial in the real cooridnates 5880: 5837: 5800: 5735: 5713: 5684: 5544: 5512: 5480: 5460: 5429: 5401: 5358: 5335: 5294: 5266: 5246: 5226: 5198: 5176: 5152: 5132: 5112: 5070: 5025: 5005: 4985: 4965: 4931: 4900: 4869: 4829: 4798: 4762: 4731: 4705: 4669: 4643: 4603: 4583: 4559: 4533: 4499: 4469: 4434: 4293: 4264: 4244: 4217: 4194: 4162: 4103: 4071: 4039: 3983: 3934: 3894: 3850: 3769: 3596: 3470: 3415: 3300: 3270: 3240: 3214: 3158: 3116: 3086: 3062: 3021: 2931: 2906: 2821: 2782: 2683: 2599: 2557: 2519: 2458: 2419: 2368: 2329: 2274: 2235: 2188: 2168: 2132: 2097: 2067: 2047: 2024: 1977: 1947: 1911: 1752: 1571: 1467:{\displaystyle Z(f)=\{(x,1-x)\in \mathbf {C} ^{2}\}.} 1403: 1289: 875: 852:
of homogeneous polynomials, define the zero-locus of
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in the sheaf of rings, that is, rings which are not
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is commutative, reduced and finitely generated as a
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gave an example of such a new variety in the 1950s.
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and algebraic varieties of dimension two are called
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Projective varieties and quasi-projective varieties
103:. Other conventions do not require irreducibility. 7127: 6680:, p. 55 Definition 2.3.47, and p. 88 Example 3.2.3 6610:— listing also several mathematical meanings 6084: 6058: 6017: 5969: 5949: 5912: 5886: 5866: 5823: 5786: 5721: 5699: 5558: 5526: 5494: 5466: 5446: 5415: 5387: 5341: 5317: 5280: 5252: 5232: 5212: 5184: 5158: 5138: 5118: 5098: 5056: 5011: 4991: 4971: 4943: 4917: 4886: 4851: 4815: 4784: 4748: 4717: 4691: 4655: 4620: 4589: 4565: 4545: 4511: 4481: 4447: 4417: 4276: 4250: 4230: 4200: 4180: 4148: 4089: 4057: 4001: 3966: 3912: 3868: 3785: 3741: 3518: 3450: 3312: 3282: 3252: 3226: 3200: 3133: 3098: 3072: 3033: 3003: 2914: 2847: 2807: 2761: 2669: 2582: 2543: 2498: 2441: 2405: 2354: 2311: 2260: 2210: 2174: 2154: 2118: 2083: 2053: 2030: 2002: 1963: 1933: 1869:to compute the projection and to prove that it is 1819: 1624: 1466: 1328: 955: 673: 457: 275: 165:. Algebraic varieties of dimension one are called 6427:-algebras, that is to say, they are quotients of 7446:Creative Commons Attribution/Share-Alike License 7177:. Graduate Texts in Mathematics. Vol. 133. 6490:that aren't algebraically closed), so the rings 6340:but its sources remain unclear because it lacks 6073: 5568:projective variety associated to the graded ring 2747: 2651: 2523: 2465: 2110: 2048: 7084:. Lecture Notes in Mathematics. Vol. 812. 6513:= 0 is different from the subscheme defined by 4852:{\displaystyle {\overline {\mathfrak {M}}}_{g}} 4785:{\displaystyle {\overline {\mathfrak {M}}}_{g}} 4692:{\displaystyle {\overline {\mathfrak {M}}}_{g}} 4029:give an embedding into a projective space. See 3759:are any set of linearly independent vectors in 5506:of it. But there are other ways to compactify 4725:, is then a projective variety which contains 4493:is an elliptic curve), the above morphism for 4065:is a projective variety. The tangent space to 3812:The Grassmannian variety comes with a natural 2866:, an affine variety that has a structure of a 134:provides a fundamental correspondence between 6736: 6734: 6732: 6730: 6728: 6726: 5950:{\displaystyle \mathbb {A} ^{1}=\mathbb {C} } 5824:{\displaystyle \mathbb {A} ^{1}=\mathbb {C} } 5240:by an action of an arithmetic discrete group 5220:, the quotient of a bounded symmetric domain 2896:is not commutative, it can still happen that 2772:The multiplicative group k of the base field 1534:can be viewed as complex valued functions on 1248:can be viewed as complex valued functions on 8: 6724: 6722: 6720: 6718: 6716: 6714: 6712: 6710: 6708: 6706: 5781: 5736: 3691: 3659: 1458: 1419: 1181:that are not quasi-projective but complete. 947: 891: 506:if it cannot be written as the union of two 6415:-algebras with the property that the rings 1715:be the three-dimensional affine space over 7408:Algebraic geometry and arithmetic curves / 7082:Toroidal Compactification of Siegel Spaces 6544:There are further generalizations called 3928:and thus there is the degree homomorphism 3561:be a finite-dimensional vector space. The 2862:A general linear group is an example of a 2808:{\displaystyle \operatorname {GL} _{1}(k)} 2583:{\displaystyle \operatorname {GL} _{n}(k)} 2355:{\displaystyle \operatorname {GL} _{n}(k)} 2319:where the affine line is given coordinate 2261:{\displaystyle \operatorname {GL} _{n}(k)} 1881:to prove the irreducibility of the image. 7121: 7120: 7118: 6985: 6846: 6802: 6371:Learn how and when to remove this message 6071: 6049: 6048: 6036: 6030: 6008: 6007: 5995: 5989: 5962: 5943: 5942: 5933: 5929: 5928: 5925: 5899: 5879: 5852: 5847: 5838: 5836: 5817: 5816: 5807: 5803: 5802: 5799: 5769: 5764: 5755: 5750: 5746: 5745: 5734: 5715: 5714: 5712: 5691: 5687: 5686: 5683: 5548: 5543: 5516: 5511: 5484: 5479: 5459: 5438: 5432: 5431: 5428: 5405: 5400: 5378: 5377: 5357: 5334: 5309: 5303: 5302: 5293: 5270: 5265: 5245: 5225: 5202: 5197: 5178: 5177: 5175: 5151: 5131: 5111: 5075: 5069: 5033: 5024: 5004: 4984: 4964: 4930: 4909: 4903: 4902: 4899: 4878: 4872: 4871: 4868: 4843: 4833: 4831: 4828: 4807: 4801: 4800: 4797: 4792:is obtained by adding boundary points to 4776: 4766: 4764: 4761: 4740: 4734: 4733: 4730: 4704: 4683: 4673: 4671: 4668: 4642: 4612: 4606: 4605: 4602: 4582: 4558: 4532: 4498: 4468: 4439: 4433: 4406: 4390: 4371: 4352: 4333: 4325: 4298: 4292: 4263: 4243: 4222: 4216: 4193: 4161: 4134: 4128: 4127: 4108: 4102: 4070: 4038: 3982: 3960: 3959: 3933: 3893: 3849: 3774: 3768: 3723: 3704: 3685: 3666: 3641: 3627: 3609: 3597: 3595: 3507: 3491: 3475: 3469: 3433: 3420: 3414: 3299: 3269: 3239: 3213: 3201:{\displaystyle A_{i}M_{j}\subset M_{i+j}} 3186: 3173: 3163: 3157: 3125: 3119: 3118: 3115: 3085: 3064: 3063: 3061: 3020: 2988: 2983: 2978: 2972: 2962: 2948: 2930: 2908: 2907: 2905: 2839: 2829: 2820: 2787: 2781: 2736: 2694: 2682: 2655: 2650: 2610: 2598: 2562: 2556: 2518: 2475: 2457: 2424: 2418: 2397: 2393: 2392: 2380: 2375: 2371: 2370: 2367: 2334: 2328: 2303: 2299: 2298: 2286: 2281: 2277: 2276: 2273: 2240: 2234: 2200: 2195: 2191: 2190: 2187: 2167: 2144: 2139: 2135: 2134: 2131: 2096: 2072: 2066: 2046: 2023: 1982: 1976: 1952: 1946: 1923: 1918: 1914: 1913: 1910: 1797: 1767: 1753: 1751: 1610: 1597: 1570: 1526:be the two-dimensional affine space over 1452: 1447: 1402: 1288: 933: 906: 901: 874: 726:be an algebraically closed field and let 649: 619: 600: 562: 433: 406: 401: 372: 267: 261: 7436:This article incorporates material from 6678:Algebraic Geometry and Arithmetic Curves 6702: 6660: 4181:{\displaystyle \operatorname {Jac} (C)} 4090:{\displaystyle \operatorname {Jac} (C)} 4058:{\displaystyle \operatorname {Jac} (C)} 4021:, a complete variety with a compatible 4002:{\displaystyle \operatorname {Jac} (C)} 3913:{\displaystyle \operatorname {Pic} (C)} 3869:{\displaystyle \operatorname {Pic} (C)} 1088:, but from Chapter 2 onwards, the term 7052:, Brookline, Mass.: Math. Sci. Press, 6614:Function field of an algebraic variety 6517:= 0 (the origin). More generally, the 766:. It is not well-defined to evaluate 704:of the polynomial ring by this ideal. 364:simultaneously vanish, that is to say 6931: 6919: 6438:This definition works over any field 5667:Morphism of varieties § Examples 5590:Non-affine and non-projective example 5318:{\displaystyle D={\mathfrak {H}}_{g}} 3824:, which is important in the study of 1625:{\displaystyle g(x,y)=x^{2}+y^{2}-1.} 1497: 7: 6973:Publications Mathématiques de l'IHÉS 5423:has an interpretation as the moduli 4031:equations defining abelian varieties 3836:Jacobian variety and abelian variety 3519:{\displaystyle y^{2}z=x^{3}-xz^{2},} 3313:{\displaystyle \operatorname {gr} M} 3283:{\displaystyle \operatorname {gr} M} 3253:{\displaystyle \operatorname {gr} A} 3227:{\displaystyle \operatorname {gr} M} 3099:{\displaystyle \operatorname {gr} A} 3034:{\displaystyle \operatorname {gr} A} 2859:, which is again an affine variety. 2218:that consists of all the invertible 2211:{\displaystyle \mathbb {A} ^{n^{2}}} 2155:{\displaystyle \mathbb {A} ^{n^{2}}} 1934:{\displaystyle \mathbb {A} ^{n^{2}}} 848:vanishes at a point . For each set 180:theory, an algebraic variety over a 157:, but an algebraic variety may have 52:are the central objects of study in 7175:Algebraic Geometry - A first course 7016: 6943: 5447:{\displaystyle {\mathfrak {A}}_{g}} 5433: 5304: 4918:{\displaystyle {\mathfrak {M}}_{g}} 4904: 4887:{\displaystyle {\mathfrak {M}}_{g}} 4873: 4834: 4816:{\displaystyle {\mathfrak {M}}_{g}} 4802: 4767: 4749:{\displaystyle {\mathfrak {M}}_{g}} 4735: 4674: 4621:{\displaystyle {\mathfrak {M}}_{g}} 4607: 3134:{\displaystyle {\mathfrak {g}}^{*}} 3120: 3065: 1703:The following example is neither a 1691:are real numbers), is known as the 1028:. For any projective algebraic set 7294:; John Little; Don O'Shea (1997). 6578:(free from singular points). When 6153:Isomorphism of algebraic varieties 5566:due to Baily and Borel: it is the 5553: 5521: 5489: 5410: 5336: 5275: 5247: 5207: 4105: 2963: 2958: 2091:and thus defines the hypersurface 1901:can be identified with the affine 1873:injective and that its image is a 498:. A nonempty affine algebraic set 223:For an algebraically closed field 45:is a projective algebraic variety. 25: 7296:Ideals, Varieties, and Algorithms 7246:"Faisceaux Algebriques Coherents" 6586:, algebraic manifolds are called 6142:Dimension of an algebraic variety 3820:in other terminology) called the 1132:Foundations of Algebraic Geometry 188:is separated and of finite type. 83:, which means that it is not the 7043:; Rapoport, M.; Tai, Y. (1975), 6772:Hartshorne, Exercise I.2.9, p.12 6317: 5700:{\displaystyle \mathbb {A} ^{1}} 5192:is the problem of compactifying 3628: 1448: 902: 521:Affine varieties can be given a 402: 6884:Introduction to toric varieties 6574:. Equivalently, the variety is 6423:and are all finitely generated 6179:be algebraic varieties. We say 5729:. The complement of the circle 3844:be a smooth complete curve and 3073:{\displaystyle {\mathfrak {g}}} 2677:, which can be identified with 1538:by evaluating at the points in 1252:by evaluating at the points in 1076:. For example, in Chapter 1 of 514:. (Some authors use the phrase 7444:, which is licensed under the 6592:Projective algebraic manifolds 6309:Discussion and generalizations 6053: 6045: 6012: 6004: 5848: 5839: 5765: 5756: 5382: 5365: 5093: 5081: 5051: 5039: 4412: 4364: 4361: 4358: 4326: 4319: 4313: 4304: 4284:, there is a natural morphism 4175: 4169: 4140: 4117: 4084: 4078: 4052: 4046: 3996: 3990: 3956: 3953: 3947: 3907: 3901: 3863: 3857: 3729: 3697: 3694: 3624: 3621: 3615: 3451:{\displaystyle y^{2}=x^{3}-x.} 3320:does not vanish is called the 2836: 2822: 2802: 2796: 2756: 2741: 2733: 2687: 2664: 2646: 2643: 2603: 2577: 2571: 2532: 2526: 2499:{\displaystyle t\cdot \det-1,} 2484: 2468: 2349: 2343: 2255: 2249: 2113: 2107: 1997: 1991: 1587: 1575: 1440: 1422: 1413: 1407: 1305: 1293: 924: 918: 885: 879: 640: 634: 625: 593: 573: 567: 424: 418: 383: 377: 142:and algebraic sets. Using the 108:fundamental theorem of algebra 66:system of polynomial equations 1: 6667:Hartshorne, p.xv, Harris, p.3 4859:is colloquially said to be a 2362:amounts to the zero-locus in 1897:matrices over the base field 1379:in the affine plane. (In the 1329:{\displaystyle f(x,y)=x+y-1.} 792:is homogeneous, meaning that 684:For any affine algebraic set 354:) to be the set of points in 325:, i.e. by choosing values in 153:Many algebraic varieties are 7128:{\displaystyle \mathbb {C} } 6533:may be non-reduced, even if 6399:. Basically, a variety over 5722:{\displaystyle \mathbb {C} } 5534:; for example, there is the 5185:{\displaystyle \mathbb {C} } 4838: 4771: 4678: 3786:{\displaystyle \wedge ^{n}V} 3051:universal enveloping algebra 2915:{\displaystyle \mathbb {Z} } 2762:{\displaystyle k/(t\det -1)} 1165:algebraically closed field. 130:. Generalizing this result, 126:(a geometric object) in the 7244:Serre, Jean-Pierre (1955). 7147:10.1007/978-1-4613-8655-1_9 7080:Namikawa, Yukihiko (1980). 6649:Mnëv's universality theorem 6624:Motive (algebraic geometry) 5057:{\displaystyle SU_{C}(n,d)} 3537:. The curve has genus one ( 3234:is fintiely generated as a 2848:{\displaystyle (k^{*})^{r}} 856:to be the set of points in 110:establishes a link between 32:Variety (universal algebra) 7483: 7377:Geometric invariant theory 6888:Princeton University Press 6559: 6389:abstract algebraic variety 6156: 6025:is a closed subvariety of 5630:is a closed subvariety of 5099:{\displaystyle U_{C}(n,d)} 4630:geometric invariant theory 3579:-dimensional subspaces of 3547:moduli of algebraic curves 3148:be a filtered module over 3106:is a polynomial ring (the 2877: 2544:{\displaystyle t\det(A)=1} 2509:i.e., the set of matrices 2182:is then an open subset of 2119:{\displaystyle H=V(\det )} 1711:, nor a single point. Let 1647:) is the set of points in 1530:. Polynomials in the ring 1244:. Polynomials in the ring 1070:quasi-projective varieties 862:on which the functions in 840:make sense to ask whether 711: 360:on which the functions in 216: 202:algebraically closed field 29: 7221:10.1007/978-3-642-57878-6 7187:10.1007/978-1-4757-2189-8 6521:of a morphism of schemes 6419:that occur above are all 5867:{\displaystyle |z|^{2}-1} 5678:Consider the affine line 5559:{\displaystyle D/\Gamma } 5527:{\displaystyle D/\Gamma } 5504:toroidal compactification 5495:{\displaystyle D/\Gamma } 5416:{\displaystyle D/\Gamma } 5327:Siegel's upper half-space 5281:{\displaystyle D/\Gamma } 5213:{\displaystyle D/\Gamma } 5064:, which contains the set 4756:as an open subset. Since 4633:leads to the notion of a 3920:can be identified as the 3529:which defines a curve in 2018:)-th entry of the matrix 2003:{\displaystyle x_{ij}(A)} 1550:contain a single element 1264:contain a single element 1206:Hilbert's Nullstellensatz 283:through the choice of an 176:In the context of modern 132:Hilbert's Nullstellensatz 7438:Isomorphism of varieties 6608:Variety (disambiguation) 6326:This section includes a 6101:An affine algebraic set 5536:minimal compactification 4156:hence, the dimension of 3294:; i.e., the locus where 3053:of a finite-dimensional 2922:-filtration so that the 2442:{\displaystyle x_{ij},t} 2061:is then a polynomial in 1879:polynomial factorization 1865:computation for another 1355:is the set of points in 1086:quasi-projective variety 1048:quasi-projective variety 978:projective algebraic set 718:Quasi-projective variety 346:, define the zero-locus 285:affine coordinate system 192:Overview and definitions 155:differentiable manifolds 6934:, The beginning of § 5. 6355:more precise citations. 6085:{\displaystyle \det -1} 5980:For similar reasons, a 5874:is not a polynomial in 5342:{\displaystyle \Gamma } 5253:{\displaystyle \Gamma } 4944:{\displaystyle g\geq 2} 4718:{\displaystyle g\geq 2} 4656:{\displaystyle g\geq 2} 4546:{\displaystyle g\geq 0} 3553:Example 2: Grassmannian 3367:The affine plane curve 3349:homogeneous polynomials 1236:be the two-dimensional 1144:made a definition of a 782:homogeneous coordinates 7129: 7019:, Appendix C to Ch. 5. 6848:10.1215/kjm/1250777007 6804:10.1215/kjm/1250777138 6506:'s theory of schemes. 6475:'s foundational paper 6086: 6060: 6019: 5971: 5951: 5914: 5888: 5868: 5825: 5788: 5723: 5701: 5634:(as the zero locus of 5580:Siegel modular variety 5560: 5528: 5496: 5468: 5448: 5417: 5389: 5343: 5319: 5282: 5254: 5234: 5214: 5186: 5160: 5140: 5120: 5100: 5058: 5013: 4993: 4973: 4945: 4919: 4888: 4853: 4817: 4786: 4750: 4719: 4693: 4657: 4622: 4591: 4567: 4547: 4513: 4483: 4449: 4419: 4278: 4277:{\displaystyle n>0} 4252: 4232: 4202: 4182: 4150: 4091: 4059: 4003: 3968: 3914: 3870: 3826:characteristic classes 3787: 3743: 3520: 3452: 3382: 3322:characteristic variety 3314: 3284: 3254: 3228: 3202: 3135: 3100: 3074: 3035: 3005: 2967: 2916: 2880:Characteristic variety 2874:Characteristic variety 2864:linear algebraic group 2849: 2809: 2763: 2671: 2584: 2545: 2500: 2443: 2407: 2356: 2313: 2262: 2212: 2176: 2156: 2120: 2085: 2084:{\displaystyle x_{ij}} 2055: 2032: 2004: 1965: 1964:{\displaystyle x_{ij}} 1935: 1821: 1681:absolutely irreducible 1626: 1468: 1330: 1150:Alexander Grothendieck 957: 760:homogeneous polynomial 675: 459: 277: 46: 7253:Annals of Mathematics 7130: 6634:Zariski–Riemann space 6582:is the real numbers, 6159:Morphism of varieties 6087: 6061: 6020: 5972: 5952: 5915: 5889: 5869: 5826: 5789: 5724: 5702: 5622:the projection. Here 5574:(in the Siegel case, 5561: 5529: 5497: 5469: 5449: 5418: 5390: 5344: 5320: 5283: 5260:. A basic example of 5255: 5235: 5215: 5187: 5161: 5141: 5121: 5101: 5059: 5014: 4994: 4974: 4946: 4920: 4889: 4854: 4818: 4787: 4751: 4720: 4694: 4658: 4623: 4592: 4568: 4548: 4514: 4484: 4450: 4448:{\displaystyle C^{n}} 4420: 4279: 4253: 4233: 4231:{\displaystyle P_{0}} 4203: 4183: 4151: 4092: 4060: 4004: 3969: 3915: 3871: 3788: 3744: 3521: 3453: 3366: 3315: 3285: 3255: 3229: 3203: 3136: 3101: 3075: 3036: 3006: 2944: 2917: 2850: 2810: 2764: 2672: 2585: 2546: 2501: 2444: 2413:of the polynomial in 2408: 2357: 2314: 2263: 2213: 2177: 2157: 2121: 2086: 2056: 2054:{\displaystyle \det } 2033: 2005: 1966: 1936: 1822: 1719:. The set of points ( 1627: 1469: 1331: 958: 676: 460: 305:-valued functions on 278: 276:{\displaystyle K^{n}} 40: 7348:"Algebraic Geometry" 7212:Algebraic Geometry I 7141:. pp. 231–251. 7117: 6393:locally ringed space 6385:algebraically closed 6070: 6066:, the zero-locus of 6029: 5988: 5961: 5924: 5898: 5878: 5835: 5798: 5733: 5711: 5682: 5576:Siegel modular forms 5542: 5510: 5478: 5458: 5427: 5399: 5356: 5333: 5292: 5264: 5244: 5224: 5196: 5174: 5150: 5130: 5110: 5068: 5023: 5003: 4983: 4963: 4929: 4925:is irreducible when 4898: 4867: 4827: 4796: 4760: 4729: 4703: 4667: 4641: 4601: 4581: 4557: 4531: 4497: 4467: 4432: 4291: 4262: 4242: 4215: 4192: 4160: 4101: 4069: 4037: 3981: 3932: 3892: 3848: 3767: 3594: 3575:) is the set of all 3563:Grassmannian variety 3468: 3413: 3298: 3268: 3238: 3212: 3156: 3114: 3084: 3060: 3019: 2929: 2904: 2819: 2780: 2681: 2597: 2555: 2517: 2456: 2417: 2366: 2327: 2272: 2233: 2228:general linear group 2186: 2166: 2162:. The complement of 2130: 2095: 2065: 2045: 2022: 1975: 1945: 1909: 1885:General linear group 1750: 1569: 1401: 1287: 873: 784:. However, because 561: 480:affine algebraic set 371: 260: 7467:Algebraic varieties 7298:(second ed.). 7138:Arithmetic Geometry 6619:Birational geometry 6556:Algebraic manifolds 6429:polynomial algebras 5913:{\displaystyle x,y} 4999:and a given degree 4512:{\displaystyle n=1} 4482:{\displaystyle g=1} 4258:. For each integer 3922:divisor class group 3822:tautological bundle 3260:-algebra, then the 1375:. This is called a 935: for all  651: for all  435: for all  50:Algebraic varieties 7462:Algebraic geometry 7362:Jacobian Varieties 7125: 7090:10.1007/BFb0091051 6996:10.1007/bf02684599 6922:, Proposition 2.1. 6746:Algebraic Geometry 6639:Semi-algebraic set 6562:Algebraic manifold 6403:is a scheme whose 6397:spectrum of a ring 6328:list of references 6082: 6056: 6015: 5967: 5947: 5910: 5884: 5864: 5821: 5784: 5719: 5697: 5556: 5524: 5492: 5464: 5444: 5413: 5385: 5339: 5315: 5278: 5250: 5230: 5210: 5182: 5156: 5136: 5116: 5096: 5054: 5009: 4989: 4969: 4941: 4915: 4884: 4849: 4813: 4782: 4746: 4715: 4689: 4653: 4618: 4597:and is denoted as 4587: 4563: 4543: 4509: 4479: 4455:is the product of 4445: 4415: 4274: 4248: 4228: 4198: 4178: 4146: 4087: 4055: 3999: 3964: 3910: 3866: 3818:locally free sheaf 3783: 3739: 3734: 3516: 3448: 3383: 3345:projective variety 3339:Projective variety 3310: 3280: 3250: 3224: 3198: 3131: 3096: 3070: 3045:. For example, if 3031: 3001: 2912: 2845: 2805: 2759: 2667: 2580: 2541: 2496: 2439: 2403: 2352: 2309: 2258: 2208: 2172: 2152: 2116: 2081: 2051: 2028: 2000: 1961: 1931: 1817: 1815: 1635:The zero-locus of 1622: 1464: 1381:classical topology 1339:The zero-locus of 1326: 1120:Veronese embedding 1064:Abstract varieties 998:projective variety 953: 714:Projective variety 671: 455: 340:of polynomials in 287:. The polynomials 273: 186:structure morphism 171:algebraic surfaces 118:by showing that a 54:algebraic geometry 47: 7418:978-0-19-154780-5 7390:978-3-540-56963-3 7371:; Fogarty, John; 7230:978-3-540-63705-9 7156:978-1-4613-8657-5 7099:978-3-540-10021-8 7059:978-0-521-73955-9 6897:978-0-691-00049-7 6827:Nagata, Masayoshi 6783:Nagata, Masayoshi 6742:Hartshorne, Robin 6381: 6380: 6373: 5970:{\displaystyle z} 5887:{\displaystyle z} 5753: 5467:{\displaystyle g} 5233:{\displaystyle D} 5159:{\displaystyle C} 5139:{\displaystyle d} 5119:{\displaystyle n} 5012:{\displaystyle d} 4992:{\displaystyle n} 4972:{\displaystyle C} 4841: 4774: 4681: 4590:{\displaystyle g} 4566:{\displaystyle g} 4527:Given an integer 4251:{\displaystyle C} 4201:{\displaystyle C} 3585:Plücker embedding 2670:{\displaystyle k} 2175:{\displaystyle H} 2031:{\displaystyle A} 1941:with coordinates 1867:monomial ordering 1102:regular functions 1058:constructible set 936: 652: 525:by declaring the 436: 319:at the points in 301:can be viewed as 56:, a sub-field of 16:(Redirected from 7474: 7430: 7402: 7357: 7355: 7354: 7339: 7313: 7277: 7276: 7250: 7241: 7235: 7234: 7207: 7201: 7200: 7167: 7161: 7160: 7134: 7132: 7131: 7126: 7124: 7110: 7104: 7103: 7077: 7071: 7070: 7051: 7036: 7030: 7026: 7020: 7014: 7008: 7007: 6989: 6969: 6953: 6947: 6941: 6935: 6929: 6923: 6917: 6911: 6908: 6902: 6900: 6875: 6869: 6868: 6850: 6823: 6817: 6816: 6806: 6779: 6773: 6770: 6764: 6763: 6738: 6690: 6687: 6681: 6674: 6668: 6665: 6629:Analytic variety 6598:is one example. 6581: 6546:algebraic spaces 6489: 6481:sheaf cohomology 6462:complete variety 6441: 6426: 6421:integral domains 6414: 6402: 6376: 6369: 6365: 6362: 6356: 6351:this section by 6342:inline citations 6321: 6320: 6313: 6304: 6295: 6282: 6272: 6259: 6239: 6216: 6196: 6187: 6178: 6130: 6120:; equivalently, 6091: 6089: 6088: 6083: 6065: 6063: 6062: 6057: 6052: 6041: 6040: 6024: 6022: 6021: 6016: 6011: 6000: 5999: 5976: 5974: 5973: 5968: 5956: 5954: 5953: 5948: 5946: 5938: 5937: 5932: 5919: 5917: 5916: 5911: 5893: 5891: 5890: 5885: 5873: 5871: 5870: 5865: 5857: 5856: 5851: 5842: 5830: 5828: 5827: 5822: 5820: 5812: 5811: 5806: 5793: 5791: 5790: 5785: 5774: 5773: 5768: 5759: 5754: 5752: with  5751: 5749: 5728: 5726: 5725: 5720: 5718: 5706: 5704: 5703: 5698: 5696: 5695: 5690: 5663: 5640:regular function 5621: 5607: 5565: 5563: 5562: 5557: 5552: 5533: 5531: 5530: 5525: 5520: 5501: 5499: 5498: 5493: 5488: 5473: 5471: 5470: 5465: 5453: 5451: 5450: 5445: 5443: 5442: 5437: 5436: 5422: 5420: 5419: 5414: 5409: 5395:; in that case, 5394: 5392: 5391: 5386: 5381: 5348: 5346: 5345: 5340: 5324: 5322: 5321: 5316: 5314: 5313: 5308: 5307: 5287: 5285: 5284: 5279: 5274: 5259: 5257: 5256: 5251: 5239: 5237: 5236: 5231: 5219: 5217: 5216: 5211: 5206: 5191: 5189: 5188: 5183: 5181: 5165: 5163: 5162: 5157: 5145: 5143: 5142: 5137: 5125: 5123: 5122: 5117: 5105: 5103: 5102: 5097: 5080: 5079: 5063: 5061: 5060: 5055: 5038: 5037: 5018: 5016: 5015: 5010: 4998: 4996: 4995: 4990: 4978: 4976: 4975: 4970: 4950: 4948: 4947: 4942: 4924: 4922: 4921: 4916: 4914: 4913: 4908: 4907: 4893: 4891: 4890: 4885: 4883: 4882: 4877: 4876: 4861:compactification 4858: 4856: 4855: 4850: 4848: 4847: 4842: 4837: 4832: 4822: 4820: 4819: 4814: 4812: 4811: 4806: 4805: 4791: 4789: 4788: 4783: 4781: 4780: 4775: 4770: 4765: 4755: 4753: 4752: 4747: 4745: 4744: 4739: 4738: 4724: 4722: 4721: 4716: 4698: 4696: 4695: 4690: 4688: 4687: 4682: 4677: 4672: 4662: 4660: 4659: 4654: 4627: 4625: 4624: 4619: 4617: 4616: 4611: 4610: 4596: 4594: 4593: 4588: 4575:moduli of curves 4572: 4570: 4569: 4564: 4552: 4550: 4549: 4544: 4523:Moduli varieties 4518: 4516: 4515: 4510: 4488: 4486: 4485: 4480: 4454: 4452: 4451: 4446: 4444: 4443: 4424: 4422: 4421: 4416: 4411: 4410: 4395: 4394: 4376: 4375: 4357: 4356: 4338: 4337: 4303: 4302: 4283: 4281: 4280: 4275: 4257: 4255: 4254: 4249: 4237: 4235: 4234: 4229: 4227: 4226: 4207: 4205: 4204: 4199: 4188:is the genus of 4187: 4185: 4184: 4179: 4155: 4153: 4152: 4147: 4139: 4138: 4133: 4132: 4113: 4112: 4096: 4094: 4093: 4088: 4064: 4062: 4061: 4056: 4008: 4006: 4005: 4000: 3976:Jacobian variety 3973: 3971: 3970: 3965: 3963: 3919: 3917: 3916: 3911: 3875: 3873: 3872: 3867: 3792: 3790: 3789: 3784: 3779: 3778: 3748: 3746: 3745: 3740: 3738: 3737: 3728: 3727: 3709: 3708: 3690: 3689: 3671: 3670: 3654: 3650: 3646: 3645: 3631: 3614: 3613: 3525: 3523: 3522: 3517: 3512: 3511: 3496: 3495: 3480: 3479: 3457: 3455: 3454: 3449: 3438: 3437: 3425: 3424: 3405: 3398: 3380: 3351:that generate a 3319: 3317: 3316: 3311: 3289: 3287: 3286: 3281: 3259: 3257: 3256: 3251: 3233: 3231: 3230: 3225: 3207: 3205: 3204: 3199: 3197: 3196: 3178: 3177: 3168: 3167: 3140: 3138: 3137: 3132: 3130: 3129: 3124: 3123: 3105: 3103: 3102: 3097: 3079: 3077: 3076: 3071: 3069: 3068: 3040: 3038: 3037: 3032: 3015:-algebra; i.e., 3010: 3008: 3007: 3002: 3000: 2999: 2998: 2982: 2977: 2976: 2966: 2961: 2921: 2919: 2918: 2913: 2911: 2854: 2852: 2851: 2846: 2844: 2843: 2834: 2833: 2814: 2812: 2811: 2806: 2792: 2791: 2768: 2766: 2765: 2760: 2740: 2702: 2701: 2676: 2674: 2673: 2668: 2663: 2662: 2654: 2618: 2617: 2589: 2587: 2586: 2581: 2567: 2566: 2550: 2548: 2547: 2542: 2505: 2503: 2502: 2497: 2483: 2482: 2448: 2446: 2445: 2440: 2432: 2431: 2412: 2410: 2409: 2404: 2402: 2401: 2396: 2387: 2386: 2385: 2384: 2374: 2361: 2359: 2358: 2353: 2339: 2338: 2318: 2316: 2315: 2310: 2308: 2307: 2302: 2293: 2292: 2291: 2290: 2280: 2267: 2265: 2264: 2259: 2245: 2244: 2217: 2215: 2214: 2209: 2207: 2206: 2205: 2204: 2194: 2181: 2179: 2178: 2173: 2161: 2159: 2158: 2153: 2151: 2150: 2149: 2148: 2138: 2125: 2123: 2122: 2117: 2090: 2088: 2087: 2082: 2080: 2079: 2060: 2058: 2057: 2052: 2037: 2035: 2034: 2029: 2009: 2007: 2006: 2001: 1990: 1989: 1970: 1968: 1967: 1962: 1960: 1959: 1940: 1938: 1937: 1932: 1930: 1929: 1928: 1927: 1917: 1877:, and finally a 1826: 1824: 1823: 1818: 1816: 1802: 1801: 1772: 1771: 1631: 1629: 1628: 1623: 1615: 1614: 1602: 1601: 1521: 1491: 1477:Thus the subset 1473: 1471: 1470: 1465: 1457: 1456: 1451: 1393: 1354: 1335: 1333: 1332: 1327: 1279: 1231: 1200:closed immersion 1142:Claude Chevalley 1113: 1098:projective space 1094:abstract variety 1092:(also called an 1074:projective space 1015: 975: 962: 960: 959: 954: 937: 934: 911: 910: 905: 861: 847: 835: 791: 779: 773: 757: 751: 743: 731: 725: 680: 678: 677: 672: 667: 663: 653: 650: 624: 623: 605: 604: 541: 523:natural topology 477: 464: 462: 461: 456: 451: 447: 437: 434: 411: 410: 405: 359: 345: 324: 318: 310: 300: 294: 282: 280: 279: 274: 272: 271: 256:, identified to 255: 247: 239: 233: 226: 213:Affine varieties 167:algebraic curves 140:polynomial rings 120:monic polynomial 97:Zariski topology 62:set of solutions 21: 7482: 7481: 7477: 7476: 7475: 7473: 7472: 7471: 7452: 7451: 7433: 7419: 7405: 7391: 7381:Springer-Verlag 7373:Kirwan, Frances 7367: 7352: 7350: 7344:Milne, James S. 7342: 7336: 7326:Springer-Verlag 7318:Eisenbud, David 7316: 7310: 7300:Springer-Verlag 7290: 7286: 7281: 7280: 7265:10.2307/1969915 7248: 7243: 7242: 7238: 7231: 7209: 7208: 7204: 7197: 7179:Springer-Verlag 7169: 7168: 7164: 7157: 7115: 7114: 7112: 7111: 7107: 7100: 7079: 7078: 7074: 7060: 7049: 7038: 7037: 7033: 7027: 7023: 7015: 7011: 6967: 6957:Deligne, Pierre 6955: 6954: 6950: 6946:, Theorem 5.11. 6942: 6938: 6930: 6926: 6918: 6914: 6909: 6905: 6898: 6880:Fulton, William 6878: 6876: 6872: 6825: 6824: 6820: 6781: 6780: 6776: 6771: 6767: 6760: 6750:Springer-Verlag 6740: 6739: 6704: 6699: 6694: 6693: 6688: 6684: 6675: 6671: 6666: 6662: 6657: 6604: 6579: 6564: 6558: 6487: 6451:integral domain 6439: 6424: 6412: 6405:structure sheaf 6400: 6377: 6366: 6360: 6357: 6346: 6332:related reading 6322: 6318: 6311: 6303: 6297: 6294: 6288: 6274: 6264: 6258: 6251: 6241: 6238: 6231: 6221: 6217:, if there are 6215: 6208: 6202: 6195: 6189: 6186: 6180: 6177: 6170: 6164: 6161: 6155: 6127:integral domain 6125: 6098: 6068: 6067: 6032: 6027: 6026: 5991: 5986: 5985: 5959: 5958: 5927: 5922: 5921: 5896: 5895: 5876: 5875: 5846: 5833: 5832: 5801: 5796: 5795: 5763: 5731: 5730: 5709: 5708: 5685: 5680: 5679: 5676: 5654: 5609: 5595: 5592: 5540: 5539: 5508: 5507: 5476: 5475: 5456: 5455: 5430: 5425: 5424: 5397: 5396: 5354: 5353: 5331: 5330: 5301: 5290: 5289: 5262: 5261: 5242: 5241: 5222: 5221: 5194: 5193: 5172: 5171: 5148: 5147: 5128: 5127: 5108: 5107: 5071: 5066: 5065: 5029: 5021: 5020: 5001: 5000: 4981: 4980: 4961: 4960: 4927: 4926: 4901: 4896: 4895: 4870: 4865: 4864: 4830: 4825: 4824: 4799: 4794: 4793: 4763: 4758: 4757: 4732: 4727: 4726: 4701: 4700: 4670: 4665: 4664: 4639: 4638: 4604: 4599: 4598: 4579: 4578: 4555: 4554: 4529: 4528: 4525: 4495: 4494: 4465: 4464: 4435: 4430: 4429: 4402: 4386: 4367: 4348: 4329: 4294: 4289: 4288: 4260: 4259: 4240: 4239: 4218: 4213: 4212: 4190: 4189: 4158: 4157: 4126: 4104: 4099: 4098: 4067: 4066: 4035: 4034: 4027:theta functions 4019:abelian variety 3979: 3978: 3930: 3929: 3890: 3889: 3846: 3845: 3838: 3770: 3765: 3764: 3757: 3733: 3732: 3719: 3700: 3681: 3662: 3656: 3655: 3637: 3636: 3632: 3605: 3598: 3592: 3591: 3569: 3555: 3503: 3487: 3471: 3466: 3465: 3429: 3416: 3411: 3410: 3400: 3393: 3387:projective line 3368: 3361: 3341: 3296: 3295: 3266: 3265: 3236: 3235: 3210: 3209: 3182: 3169: 3159: 3154: 3153: 3117: 3112: 3111: 3082: 3081: 3058: 3057: 3017: 3016: 2984: 2968: 2927: 2926: 2924:associated ring 2902: 2901: 2882: 2876: 2857:algebraic torus 2835: 2825: 2817: 2816: 2783: 2778: 2777: 2776:is the same as 2690: 2679: 2678: 2649: 2606: 2595: 2594: 2558: 2553: 2552: 2515: 2514: 2471: 2454: 2453: 2420: 2415: 2414: 2391: 2376: 2369: 2364: 2363: 2330: 2325: 2324: 2297: 2282: 2275: 2270: 2269: 2236: 2231: 2230: 2196: 2189: 2184: 2183: 2164: 2163: 2140: 2133: 2128: 2127: 2093: 2092: 2068: 2063: 2062: 2043: 2042: 2020: 2019: 1978: 1973: 1972: 1948: 1943: 1942: 1919: 1912: 1907: 1906: 1887: 1814: 1813: 1803: 1793: 1784: 1783: 1773: 1763: 1748: 1747: 1701: 1606: 1593: 1567: 1566: 1513: 1510: 1478: 1446: 1399: 1398: 1384: 1340: 1285: 1284: 1265: 1223: 1220: 1215: 1192: 1187: 1179:toric varieties 1171: 1116:Segre embedding 1105: 1066: 1035:coordinate ring 1011: 1006:Given a subset 971: 900: 871: 870: 857: 841: 832: 826: 810: 804: 793: 785: 775: 767: 753: 745: 741: 727: 723: 720: 712:Main articles: 710: 690:coordinate ring 615: 596: 583: 579: 559: 558: 537: 532:Given a subset 473: 400: 393: 389: 369: 368: 355: 341: 336:. For each set 334: 320: 312: 306: 296: 288: 263: 258: 257: 251: 243: 235: 231: 224: 221: 215: 194: 159:singular points 144:Nullstellensatz 87:of two smaller 74:complex numbers 35: 28: 23: 22: 15: 12: 11: 5: 7480: 7478: 7470: 7469: 7464: 7454: 7453: 7432: 7431: 7417: 7403: 7389: 7369:Mumford, David 7365: 7358: 7340: 7334: 7314: 7308: 7287: 7285: 7282: 7279: 7278: 7259:(2): 197–278. 7236: 7229: 7202: 7195: 7162: 7155: 7123: 7105: 7098: 7072: 7058: 7041:Mumford, David 7031: 7021: 7009: 6987:10.1.1.589.288 6961:Mumford, David 6948: 6936: 6924: 6912: 6903: 6896: 6877:In page 65 of 6870: 6841:(3): 231–235. 6818: 6774: 6765: 6758: 6701: 6700: 6698: 6695: 6692: 6691: 6682: 6669: 6659: 6658: 6656: 6653: 6652: 6651: 6646: 6641: 6636: 6631: 6626: 6621: 6616: 6611: 6603: 6600: 6596:Riemann sphere 6588:Nash manifolds 6560:Main article: 6557: 6554: 6529:at a point of 6379: 6378: 6336:external links 6325: 6323: 6316: 6310: 6307: 6305:respectively. 6301: 6292: 6260:such that the 6256: 6249: 6236: 6229: 6213: 6206: 6193: 6184: 6175: 6168: 6154: 6151: 6150: 6149: 6145: 6134: 6131: 6107:if and only if 6097: 6094: 6081: 6078: 6075: 6055: 6051: 6047: 6044: 6039: 6035: 6014: 6010: 6006: 6003: 5998: 5994: 5966: 5945: 5941: 5936: 5931: 5909: 5906: 5903: 5883: 5863: 5860: 5855: 5850: 5845: 5841: 5819: 5815: 5810: 5805: 5783: 5780: 5777: 5772: 5767: 5762: 5758: 5748: 5744: 5741: 5738: 5717: 5694: 5689: 5675: 5672: 5591: 5588: 5555: 5551: 5547: 5523: 5519: 5515: 5491: 5487: 5483: 5463: 5441: 5435: 5412: 5408: 5404: 5384: 5380: 5376: 5373: 5370: 5367: 5364: 5361: 5338: 5312: 5306: 5300: 5297: 5277: 5273: 5269: 5249: 5229: 5209: 5205: 5201: 5180: 5155: 5135: 5115: 5095: 5092: 5089: 5086: 5083: 5078: 5074: 5053: 5050: 5047: 5044: 5041: 5036: 5032: 5028: 5008: 4988: 4968: 4940: 4937: 4934: 4912: 4906: 4881: 4875: 4846: 4840: 4836: 4810: 4804: 4779: 4773: 4769: 4743: 4737: 4714: 4711: 4708: 4686: 4680: 4676: 4652: 4649: 4646: 4615: 4609: 4586: 4573:is called the 4562: 4542: 4539: 4536: 4524: 4521: 4508: 4505: 4502: 4478: 4475: 4472: 4442: 4438: 4426: 4425: 4414: 4409: 4405: 4401: 4398: 4393: 4389: 4385: 4382: 4379: 4374: 4370: 4366: 4363: 4360: 4355: 4351: 4347: 4344: 4341: 4336: 4332: 4328: 4324: 4321: 4318: 4315: 4312: 4309: 4306: 4301: 4297: 4273: 4270: 4267: 4247: 4225: 4221: 4197: 4177: 4174: 4171: 4168: 4165: 4145: 4142: 4137: 4131: 4125: 4122: 4119: 4116: 4111: 4107: 4086: 4083: 4080: 4077: 4074: 4054: 4051: 4048: 4045: 4042: 3998: 3995: 3992: 3989: 3986: 3962: 3958: 3955: 3952: 3949: 3946: 3943: 3940: 3937: 3909: 3906: 3903: 3900: 3897: 3865: 3862: 3859: 3856: 3853: 3837: 3834: 3799:exterior power 3782: 3777: 3773: 3755: 3750: 3749: 3736: 3731: 3726: 3722: 3718: 3715: 3712: 3707: 3703: 3699: 3696: 3693: 3688: 3684: 3680: 3677: 3674: 3669: 3665: 3661: 3658: 3657: 3653: 3649: 3644: 3640: 3635: 3630: 3626: 3623: 3620: 3617: 3612: 3608: 3604: 3603: 3601: 3567: 3554: 3551: 3535:elliptic curve 3527: 3526: 3515: 3510: 3506: 3502: 3499: 3494: 3490: 3486: 3483: 3478: 3474: 3459: 3458: 3447: 3444: 3441: 3436: 3432: 3428: 3423: 3419: 3360: 3357: 3340: 3337: 3309: 3306: 3303: 3279: 3276: 3273: 3249: 3246: 3243: 3223: 3220: 3217: 3195: 3192: 3189: 3185: 3181: 3176: 3172: 3166: 3162: 3128: 3122: 3095: 3092: 3089: 3067: 3030: 3027: 3024: 2997: 2994: 2991: 2987: 2981: 2975: 2971: 2965: 2960: 2957: 2954: 2951: 2947: 2943: 2940: 2937: 2934: 2910: 2878:Main article: 2875: 2872: 2842: 2838: 2832: 2828: 2824: 2804: 2801: 2798: 2795: 2790: 2786: 2758: 2755: 2752: 2749: 2746: 2743: 2739: 2735: 2732: 2729: 2726: 2723: 2720: 2717: 2714: 2711: 2708: 2705: 2700: 2697: 2693: 2689: 2686: 2666: 2661: 2658: 2653: 2648: 2645: 2642: 2639: 2636: 2633: 2630: 2627: 2624: 2621: 2616: 2613: 2609: 2605: 2602: 2579: 2576: 2573: 2570: 2565: 2561: 2540: 2537: 2534: 2531: 2528: 2525: 2522: 2507: 2506: 2495: 2492: 2489: 2486: 2481: 2478: 2474: 2470: 2467: 2464: 2461: 2438: 2435: 2430: 2427: 2423: 2400: 2395: 2390: 2383: 2379: 2373: 2351: 2348: 2345: 2342: 2337: 2333: 2306: 2301: 2296: 2289: 2285: 2279: 2257: 2254: 2251: 2248: 2243: 2239: 2226:matrices, the 2203: 2199: 2193: 2171: 2147: 2143: 2137: 2115: 2112: 2109: 2106: 2103: 2100: 2078: 2075: 2071: 2050: 2027: 1999: 1996: 1993: 1988: 1985: 1981: 1958: 1955: 1951: 1926: 1922: 1916: 1886: 1883: 1828: 1827: 1812: 1809: 1806: 1804: 1800: 1796: 1792: 1789: 1786: 1785: 1782: 1779: 1776: 1774: 1770: 1766: 1762: 1759: 1756: 1755: 1700: 1697: 1633: 1632: 1621: 1618: 1613: 1609: 1605: 1600: 1596: 1592: 1589: 1586: 1583: 1580: 1577: 1574: 1509: 1506: 1475: 1474: 1463: 1460: 1455: 1450: 1445: 1442: 1439: 1436: 1433: 1430: 1427: 1424: 1421: 1418: 1415: 1412: 1409: 1406: 1337: 1336: 1325: 1322: 1319: 1316: 1313: 1310: 1307: 1304: 1301: 1298: 1295: 1292: 1219: 1216: 1214: 1213:Affine variety 1211: 1191: 1188: 1186: 1183: 1170: 1167: 1065: 1062: 964: 963: 952: 949: 946: 943: 940: 932: 929: 926: 923: 920: 917: 914: 909: 904: 899: 896: 893: 890: 887: 884: 881: 878: 830: 824: 808: 802: 709: 706: 694:structure ring 682: 681: 670: 666: 662: 659: 656: 648: 645: 642: 639: 636: 633: 630: 627: 622: 618: 614: 611: 608: 603: 599: 595: 592: 589: 586: 582: 578: 575: 572: 569: 566: 516:affine variety 512:affine variety 466: 465: 454: 450: 446: 443: 440: 432: 429: 426: 423: 420: 417: 414: 409: 404: 399: 396: 392: 388: 385: 382: 379: 376: 332: 311:by evaluating 270: 266: 229:natural number 219:Affine variety 217:Main article: 214: 211: 198:affine variety 193: 190: 101:algebraic sets 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 7479: 7468: 7465: 7463: 7460: 7459: 7457: 7450: 7449: 7447: 7443: 7439: 7428: 7424: 7420: 7414: 7410: 7409: 7404: 7400: 7396: 7392: 7386: 7382: 7378: 7374: 7370: 7366: 7363: 7359: 7349: 7345: 7341: 7337: 7335:0-387-94269-6 7331: 7327: 7323: 7319: 7315: 7311: 7309:0-387-94680-2 7305: 7301: 7297: 7293: 7289: 7288: 7283: 7274: 7270: 7266: 7262: 7258: 7254: 7247: 7240: 7237: 7232: 7226: 7222: 7218: 7214: 7213: 7206: 7203: 7198: 7196:0-387-97716-3 7192: 7188: 7184: 7180: 7176: 7172: 7166: 7163: 7158: 7152: 7148: 7144: 7140: 7139: 7109: 7106: 7101: 7095: 7091: 7087: 7083: 7076: 7073: 7069: 7065: 7061: 7055: 7048: 7047: 7042: 7035: 7032: 7025: 7022: 7018: 7013: 7010: 7005: 7001: 6997: 6993: 6988: 6983: 6979: 6975: 6974: 6966: 6962: 6958: 6952: 6949: 6945: 6940: 6937: 6933: 6928: 6925: 6921: 6916: 6913: 6907: 6904: 6899: 6893: 6889: 6885: 6881: 6874: 6871: 6866: 6862: 6858: 6854: 6849: 6844: 6840: 6836: 6832: 6828: 6822: 6819: 6814: 6810: 6805: 6800: 6796: 6792: 6788: 6784: 6778: 6775: 6769: 6766: 6761: 6759:0-387-90244-9 6755: 6751: 6747: 6743: 6737: 6735: 6733: 6731: 6729: 6727: 6725: 6723: 6721: 6719: 6717: 6715: 6713: 6711: 6709: 6707: 6703: 6696: 6686: 6683: 6679: 6673: 6670: 6664: 6661: 6654: 6650: 6647: 6645: 6642: 6640: 6637: 6635: 6632: 6630: 6627: 6625: 6622: 6620: 6617: 6615: 6612: 6609: 6606: 6605: 6601: 6599: 6597: 6593: 6589: 6585: 6577: 6573: 6569: 6563: 6555: 6553: 6551: 6547: 6542: 6540: 6536: 6532: 6528: 6524: 6520: 6516: 6512: 6507: 6505: 6501: 6497: 6493: 6484: 6482: 6478: 6474: 6469: 6467: 6463: 6458: 6456: 6452: 6447: 6445: 6436: 6434: 6430: 6422: 6418: 6410: 6406: 6398: 6394: 6390: 6386: 6375: 6372: 6364: 6354: 6350: 6344: 6343: 6337: 6333: 6329: 6324: 6315: 6314: 6308: 6306: 6300: 6291: 6286: 6285:identity maps 6281: 6277: 6271: 6267: 6263: 6255: 6248: 6244: 6235: 6228: 6224: 6220: 6212: 6205: 6200: 6192: 6183: 6174: 6167: 6160: 6152: 6146: 6143: 6139: 6135: 6132: 6128: 6123: 6119: 6115: 6111: 6108: 6105:is a variety 6104: 6100: 6099: 6096:Basic results 6095: 6093: 6079: 6076: 6042: 6037: 6033: 6001: 5996: 5992: 5983: 5982:unitary group 5978: 5964: 5939: 5934: 5907: 5904: 5901: 5881: 5861: 5858: 5853: 5843: 5813: 5808: 5778: 5775: 5770: 5760: 5742: 5739: 5692: 5673: 5671: 5669: 5668: 5661: 5657: 5651: 5649: 5645: 5641: 5637: 5633: 5629: 5625: 5620: 5616: 5612: 5606: 5602: 5598: 5589: 5587: 5585: 5581: 5577: 5573: 5572:modular forms 5569: 5549: 5545: 5537: 5517: 5513: 5505: 5485: 5481: 5461: 5439: 5406: 5402: 5374: 5371: 5368: 5362: 5359: 5351: 5350:commensurable 5328: 5310: 5298: 5295: 5271: 5267: 5227: 5203: 5199: 5167: 5153: 5133: 5113: 5090: 5087: 5084: 5076: 5072: 5048: 5045: 5042: 5034: 5030: 5026: 5006: 4986: 4966: 4958: 4952: 4938: 4935: 4932: 4910: 4879: 4862: 4844: 4808: 4777: 4741: 4712: 4709: 4706: 4684: 4650: 4647: 4644: 4636: 4631: 4613: 4584: 4576: 4560: 4540: 4537: 4534: 4522: 4520: 4506: 4503: 4500: 4492: 4476: 4473: 4470: 4462: 4458: 4440: 4436: 4407: 4403: 4399: 4396: 4391: 4387: 4383: 4380: 4377: 4372: 4368: 4353: 4349: 4345: 4342: 4339: 4334: 4330: 4322: 4316: 4310: 4307: 4299: 4295: 4287: 4286: 4285: 4271: 4268: 4265: 4245: 4223: 4219: 4209: 4195: 4172: 4166: 4163: 4143: 4135: 4123: 4120: 4114: 4109: 4081: 4075: 4072: 4049: 4043: 4040: 4032: 4028: 4024: 4023:abelian group 4020: 4016: 4012: 3993: 3987: 3984: 3977: 3950: 3944: 3941: 3938: 3935: 3927: 3923: 3904: 3898: 3895: 3887: 3883: 3879: 3860: 3854: 3851: 3843: 3835: 3833: 3831: 3830:Chern classes 3827: 3823: 3819: 3815: 3814:vector bundle 3810: 3808: 3804: 3800: 3796: 3780: 3775: 3771: 3762: 3758: 3724: 3720: 3716: 3713: 3710: 3705: 3701: 3686: 3682: 3678: 3675: 3672: 3667: 3663: 3651: 3647: 3642: 3638: 3633: 3618: 3610: 3606: 3599: 3590: 3589: 3588: 3586: 3582: 3578: 3574: 3570: 3564: 3560: 3552: 3550: 3548: 3544: 3540: 3539:genus formula 3536: 3532: 3513: 3508: 3504: 3500: 3497: 3492: 3488: 3484: 3481: 3476: 3472: 3464: 3463: 3462: 3445: 3442: 3439: 3434: 3430: 3426: 3421: 3417: 3409: 3408: 3407: 3403: 3399:} defined by 3396: 3391: 3388: 3379: 3375: 3371: 3365: 3358: 3356: 3354: 3350: 3346: 3338: 3336: 3334: 3332: 3327: 3323: 3307: 3304: 3301: 3293: 3277: 3274: 3271: 3263: 3247: 3244: 3241: 3221: 3218: 3215: 3193: 3190: 3187: 3183: 3179: 3174: 3170: 3164: 3160: 3151: 3147: 3142: 3126: 3109: 3093: 3090: 3087: 3056: 3052: 3048: 3044: 3028: 3025: 3022: 3014: 2995: 2992: 2989: 2985: 2979: 2973: 2969: 2955: 2952: 2949: 2945: 2941: 2938: 2935: 2932: 2925: 2899: 2895: 2891: 2887: 2881: 2873: 2871: 2869: 2865: 2860: 2858: 2840: 2830: 2826: 2799: 2793: 2788: 2784: 2775: 2770: 2753: 2750: 2744: 2737: 2730: 2727: 2724: 2721: 2718: 2715: 2712: 2709: 2706: 2703: 2698: 2695: 2691: 2684: 2659: 2656: 2640: 2637: 2634: 2631: 2628: 2625: 2622: 2619: 2614: 2611: 2607: 2600: 2593: 2574: 2568: 2563: 2559: 2538: 2535: 2529: 2520: 2512: 2493: 2490: 2487: 2479: 2476: 2472: 2462: 2459: 2452: 2451: 2450: 2436: 2433: 2428: 2425: 2421: 2398: 2388: 2381: 2377: 2346: 2340: 2335: 2331: 2322: 2304: 2294: 2287: 2283: 2252: 2246: 2241: 2237: 2229: 2225: 2221: 2201: 2197: 2169: 2145: 2141: 2104: 2101: 2098: 2076: 2073: 2069: 2041: 2025: 2017: 2013: 1994: 1986: 1983: 1979: 1956: 1953: 1949: 1924: 1920: 1904: 1900: 1896: 1892: 1884: 1882: 1880: 1876: 1872: 1868: 1864: 1863:Gröbner basis 1860: 1859:Gröbner basis 1855: 1853: 1849: 1845: 1841: 1837: 1833: 1810: 1807: 1805: 1798: 1794: 1790: 1787: 1780: 1777: 1775: 1768: 1764: 1760: 1757: 1746: 1745: 1744: 1742: 1741:twisted cubic 1738: 1734: 1730: 1726: 1722: 1718: 1714: 1710: 1706: 1698: 1696: 1694: 1690: 1686: 1682: 1678: 1674: 1670: 1666: 1662: 1658: 1654: 1650: 1646: 1642: 1638: 1619: 1616: 1611: 1607: 1603: 1598: 1594: 1590: 1584: 1581: 1578: 1572: 1565: 1564: 1563: 1561: 1557: 1553: 1549: 1545: 1542:. Let subset 1541: 1537: 1533: 1529: 1525: 1520: 1516: 1507: 1505: 1503: 1499: 1498:algebraic set 1495: 1489: 1485: 1481: 1461: 1453: 1443: 1437: 1434: 1431: 1428: 1425: 1416: 1410: 1404: 1397: 1396: 1395: 1391: 1387: 1382: 1378: 1374: 1370: 1366: 1362: 1358: 1352: 1348: 1344: 1323: 1320: 1317: 1314: 1311: 1308: 1302: 1299: 1296: 1290: 1283: 1282: 1281: 1277: 1273: 1269: 1263: 1259: 1256:. Let subset 1255: 1251: 1247: 1243: 1239: 1235: 1230: 1226: 1217: 1212: 1210: 1207: 1203: 1201: 1197: 1189: 1184: 1182: 1180: 1176: 1168: 1166: 1163: 1159: 1155: 1151: 1147: 1143: 1139: 1135: 1133: 1128: 1123: 1121: 1117: 1112: 1108: 1103: 1099: 1095: 1091: 1087: 1083: 1079: 1075: 1071: 1063: 1061: 1059: 1054: 1050: 1049: 1043: 1041: 1037: 1036: 1031: 1027: 1023: 1019: 1014: 1009: 1004: 1001: 999: 995: 991: 987: 983: 979: 974: 969: 950: 944: 941: 938: 930: 927: 921: 915: 912: 907: 897: 894: 888: 882: 876: 869: 868: 867: 865: 860: 855: 851: 845: 839: 833: 823: 819: 815: 811: 801: 797: 789: 783: 778: 774:on points in 771: 765: 761: 756: 749: 739: 737: 730: 719: 715: 707: 705: 703: 699: 695: 691: 687: 668: 664: 660: 657: 654: 646: 643: 637: 631: 628: 620: 616: 612: 609: 606: 601: 597: 590: 587: 584: 580: 576: 570: 564: 557: 556: 555: 553: 549: 545: 540: 535: 530: 528: 524: 519: 517: 513: 509: 505: 501: 497: 493: 489: 485: 481: 478:is called an 476: 471: 452: 448: 444: 441: 438: 430: 427: 421: 415: 412: 407: 397: 394: 390: 386: 380: 374: 367: 366: 365: 363: 358: 353: 349: 344: 339: 335: 328: 323: 316: 309: 304: 299: 292: 286: 268: 264: 254: 249: 246: 238: 230: 220: 212: 210: 208: 203: 199: 191: 189: 187: 183: 179: 174: 172: 168: 164: 160: 156: 151: 149: 145: 141: 137: 133: 129: 128:complex plane 125: 121: 117: 113: 109: 104: 102: 98: 94: 90: 86: 82: 77: 75: 71: 67: 63: 59: 55: 51: 44: 43:twisted cubic 39: 33: 19: 7435: 7434: 7407: 7376: 7351:. Retrieved 7321: 7295: 7256: 7252: 7239: 7211: 7205: 7174: 7165: 7137: 7108: 7081: 7075: 7045: 7034: 7024: 7012: 6977: 6971: 6951: 6939: 6927: 6915: 6906: 6883: 6873: 6838: 6834: 6821: 6794: 6790: 6777: 6768: 6745: 6685: 6677: 6672: 6663: 6644:Fano variety 6583: 6571: 6567: 6565: 6543: 6538: 6534: 6530: 6526: 6522: 6514: 6510: 6508: 6504:Grothendieck 6499: 6491: 6485: 6470: 6459: 6448: 6443: 6437: 6433:prime ideals 6416: 6388: 6382: 6367: 6358: 6347:Please help 6339: 6298: 6289: 6279: 6275: 6269: 6265: 6262:compositions 6253: 6246: 6242: 6233: 6226: 6222: 6219:regular maps 6210: 6203: 6201:, and write 6190: 6181: 6172: 6165: 6162: 6144:for details. 6137: 6121: 6113: 6109: 6102: 5979: 5677: 5674:Non-examples 5665: 5659: 5655: 5652: 5647: 5643: 5635: 5631: 5627: 5623: 5618: 5614: 5610: 5604: 5600: 5596: 5593: 5584:moduli stack 5168: 4953: 4635:stable curve 4526: 4490: 4460: 4456: 4427: 4211:Fix a point 4210: 4014: 4010: 3925: 3885: 3881: 3878:Picard group 3841: 3839: 3811: 3806: 3802: 3794: 3760: 3753: 3751: 3580: 3576: 3572: 3565: 3558: 3556: 3542: 3530: 3528: 3460: 3401: 3394: 3389: 3384: 3377: 3373: 3369: 3342: 3330: 3325: 3291: 3149: 3145: 3143: 3046: 3042: 3012: 2897: 2893: 2889: 2885: 2883: 2861: 2773: 2771: 2592:localization 2510: 2508: 2320: 2223: 2219: 2015: 2011: 1902: 1898: 1894: 1890: 1888: 1875:hypersurface 1856: 1847: 1843: 1839: 1835: 1831: 1829: 1736: 1732: 1728: 1724: 1720: 1716: 1712: 1709:linear space 1705:hypersurface 1702: 1688: 1684: 1676: 1672: 1668: 1664: 1660: 1659:) such that 1656: 1652: 1648: 1644: 1640: 1636: 1634: 1559: 1555: 1551: 1547: 1543: 1539: 1535: 1531: 1527: 1523: 1518: 1514: 1511: 1501: 1493: 1487: 1483: 1479: 1476: 1389: 1385: 1380: 1372: 1368: 1367:) such that 1364: 1360: 1356: 1350: 1346: 1342: 1338: 1275: 1271: 1267: 1261: 1257: 1253: 1249: 1245: 1241: 1238:affine space 1233: 1228: 1224: 1221: 1204: 1195: 1193: 1172: 1130: 1124: 1110: 1106: 1093: 1089: 1081: 1067: 1053:Zariski open 1046: 1044: 1039: 1033: 1029: 1025: 1021: 1017: 1012: 1007: 1005: 1002: 997: 993: 989: 985: 981: 977: 976:is called a 972: 967: 965: 863: 858: 853: 849: 843: 837: 828: 821: 817: 813: 806: 799: 795: 787: 776: 769: 763: 754: 747: 735: 728: 721: 697: 693: 689: 685: 683: 551: 547: 543: 542:, we define 538: 533: 531: 520: 515: 511: 503: 499: 495: 491: 487: 483: 479: 474: 469: 467: 361: 356: 351: 347: 342: 337: 330: 326: 321: 314: 307: 302: 297: 295:in the ring 290: 252: 244: 236: 222: 197: 195: 175: 152: 143: 105: 100: 78: 49: 48: 18:Affine curve 7171:Harris, Joe 6676:Liu, Qing. 6353:introducing 6148:projective. 6118:prime ideal 5578:; see also 5126:and degree 3888:is smooth, 3353:prime ideal 3108:PBW theorem 3055:Lie algebra 2040:determinant 1889:The set of 1871:generically 1693:unit circle 1162:finite type 992:) for some 734:projective 527:closed sets 504:irreducible 494:) for some 148:ring theory 81:irreducible 58:mathematics 7456:Categories 7442:PlanetMath 7360:Milne J., 7353:2009-09-01 7292:Cox, David 6980:: 75–109. 6932:Milne 2008 6920:Milne 2008 6697:References 6496:nilpotents 6455:nilradical 6361:March 2013 6199:isomorphic 6157:See also: 5646:; namely, 5570:formed by 4459:copies of 3533:called an 2892:. Even if 2513:such that 1971:such that 1500:. The set 1196:subvariety 1190:Subvariety 1160:scheme of 1138:valuations 1127:André Weil 1078:Hartshorne 762:of degree 502:is called 7427:646747871 7039:Ash, A.; 6982:CiteSeerX 6865:118328992 6797:: 71–82. 6444:separated 6138:dimension 6077:− 6043:⁡ 6002:⁡ 5859:− 5743:∈ 5554:Γ 5522:Γ 5490:Γ 5411:Γ 5363:⁡ 5337:Γ 5276:Γ 5248:Γ 5208:Γ 4936:≥ 4839:¯ 4772:¯ 4710:≥ 4679:¯ 4648:≥ 4637:of genus 4577:of genus 4538:≥ 4397:− 4381:⋯ 4362:↦ 4343:… 4311:⁡ 4305:→ 4167:⁡ 4115:⁡ 4076:⁡ 4044:⁡ 4033:); thus, 3988:⁡ 3957:→ 3945:⁡ 3899:⁡ 3855:⁡ 3772:∧ 3717:∧ 3714:⋯ 3711:∧ 3695:↦ 3692:⟩ 3676:… 3660:⟨ 3639:∧ 3625:↪ 3498:− 3440:− 3359:Example 1 3305:⁡ 3275:⁡ 3245:⁡ 3219:⁡ 3180:⊂ 3127:∗ 3091:⁡ 3026:⁡ 2993:− 2964:∞ 2959:∞ 2956:− 2946:⨁ 2936:⁡ 2831:∗ 2794:⁡ 2751:− 2728:≤ 2716:≤ 2710:∣ 2657:− 2638:≤ 2626:≤ 2620:∣ 2569:⁡ 2488:− 2463:⋅ 2389:× 2341:⁡ 2295:× 2247:⁡ 1852:injective 1791:− 1761:− 1699:Example 3 1617:− 1508:Example 2 1444:∈ 1435:− 1345:  ( 1321:− 1270:  ( 1218:Example 1 1158:separated 1129:. In his 966:A subset 942:∈ 913:∣ 898:∈ 820:  ( 798:  ( 658:∈ 629:∣ 610:… 588:∈ 468:A subset 442:∈ 413:∣ 398:∈ 329:for each 163:dimension 91:that are 68:over the 7375:(1994). 7346:(2008). 7320:(1999). 7173:(1992). 7017:MFK 1994 7004:16482150 6963:(1969). 6944:MFK 1994 6882:(1993), 6829:(1957). 6785:(1956). 6744:(1977). 6602:See also 6283:are the 6245: : 6225: : 5662:− (0, 0) 5288:is when 3884:. Since 3828:such as 3333:-modules 2010:is the ( 1707:, nor a 1679:) is an 1667:= 1. As 1490: ) 1486:(  1392: ) 1388:(  1185:Examples 1175:complete 1154:integral 866:vanish: 702:quotient 200:over an 116:geometry 7399:1304906 7284:Sources 7273:1969915 7068:0457437 6857:0094358 6813:0088035 6500:reduced 6349:improve 6116:) is a 4489:(i.e., 3793:is the 3262:support 3152:(i.e., 3080:, then 3049:is the 2590:is the 2323:. Then 1905:-space 1341:  1266:  1090:variety 1082:variety 846:  842:  827:, ..., 816:  805:, ..., 794:  790:  786:  772:  768:  750:  746:  744:. Let 732:be the 700:is the 317:  313:  293:  289:  242:affine 112:algebra 95:in the 7425:  7415:  7397:  7387:  7332:  7306:  7271:  7227:  7193:  7153:  7096:  7066:  7056:  7002:  6984:  6894:  6863:  6855:  6811:  6756:  6576:smooth 6550:stacks 4957:stable 4463:. For 4428:where 3974:. The 3752:where 3208:). If 2900:has a 2855:is an 2038:. The 1731:) for 1522:, and 1496:is an 1371:= 1 − 1232:, and 1146:scheme 1136:using 1032:, the 1016:, let 738:-space 688:, the 508:proper 248:-space 240:be an 234:, let 227:and a 207:Nagata 178:scheme 136:ideals 93:closed 7269:JSTOR 7249:(PDF) 7050:(PDF) 7029:2005. 7000:S2CID 6968:(PDF) 6861:S2CID 6655:Notes 6519:fiber 6473:Serre 6466:curve 6409:sheaf 6407:is a 6334:, or 5707:over 5664:(cf. 5352:with 2868:group 1850:) is 1842:) → ( 1240:over 1051:is a 836:, it 758:be a 740:over 250:over 182:field 124:roots 85:union 64:of a 7423:OCLC 7413:ISBN 7385:ISBN 7330:ISBN 7304:ISBN 7225:ISBN 7191:ISBN 7151:ISBN 7094:ISBN 7054:ISBN 6892:ISBN 6754:ISBN 6548:and 6537:and 6296:and 6273:and 6240:and 6197:are 6188:and 6163:Let 6136:The 5608:and 5502:, a 5329:and 4269:> 3876:the 3840:Let 3816:(or 3797:-th 3557:Let 3144:Let 2884:Let 2222:-by- 1893:-by- 1687:and 1512:Let 1377:line 1222:Let 838:does 812:) = 722:Let 716:and 114:and 106:The 89:sets 70:real 41:The 7440:on 7261:doi 7217:doi 7183:doi 7143:doi 7135:". 7086:doi 6992:doi 6843:doi 6799:doi 6479:on 6477:FAC 6431:by 6411:of 6287:on 6074:det 5794:in 5670:.) 5642:on 5538:of 4863:of 4308:Jac 4238:on 4164:Jac 4073:Jac 4041:Jac 4009:of 3985:Jac 3942:Pic 3936:deg 3924:of 3896:Pic 3852:Pic 3801:of 3549:). 3404:= 0 3397:= { 3324:of 3290:in 3264:of 2748:det 2652:det 2524:det 2466:det 2126:in 2111:det 2049:det 1735:in 1562:): 1546:of 1492:of 1260:of 1038:of 1010:of 980:if 970:of 780:in 752:in 696:of 692:or 536:of 482:if 472:of 196:An 138:of 72:or 7458:: 7421:. 7395:MR 7393:. 7383:. 7328:. 7324:. 7302:. 7267:. 7257:61 7255:. 7251:. 7223:. 7189:. 7181:. 7149:. 7092:. 7064:MR 7062:, 6998:. 6990:. 6978:36 6976:. 6970:. 6959:; 6890:, 6886:, 6859:. 6853:MR 6851:. 6839:30 6837:. 6833:. 6809:MR 6807:. 6795:30 6793:. 6789:. 6752:. 6748:. 6705:^ 6552:. 6525:→ 6460:A 6457:. 6435:. 6338:, 6330:, 6278:∘ 6268:∘ 6252:→ 6232:→ 6209:≅ 6171:, 6034:GL 5993:SL 5658:= 5650:. 5617:→ 5613:: 5603:× 5599:= 5360:Sp 5325:, 5166:. 4951:. 4823:, 4208:. 3832:. 3809:. 3763:, 3587:: 3376:− 3372:= 3355:. 3343:A 3335:. 3302:gr 3272:gr 3242:gr 3216:gr 3141:. 3088:gr 3023:gr 2933:gr 2785:GL 2769:. 2560:GL 2449:: 2332:GL 2238:GL 2014:, 1846:, 1838:, 1834:, 1727:, 1723:, 1675:, 1663:+ 1643:, 1620:1. 1558:, 1517:= 1482:= 1394:: 1363:, 1349:, 1324:1. 1280:: 1274:, 1227:= 1202:. 1194:A 1156:, 1140:. 1109:× 1080:a 1060:. 1045:A 1000:. 984:= 807:λx 800:λx 554:: 486:= 173:. 7448:. 7429:. 7401:. 7356:. 7338:. 7312:. 7275:. 7263:: 7233:. 7219:: 7199:. 7185:: 7159:. 7145:: 7122:C 7102:. 7088:: 7006:. 6994:: 6867:. 6845:: 6815:. 6801:: 6762:. 6584:R 6580:k 6572:k 6568:m 6539:Y 6535:X 6531:Y 6527:Y 6523:X 6515:x 6511:x 6492:R 6488:k 6440:k 6425:k 6417:R 6413:k 6401:k 6374:) 6368:( 6363:) 6359:( 6345:. 6302:2 6299:V 6293:1 6290:V 6280:ψ 6276:φ 6270:φ 6266:ψ 6257:1 6254:V 6250:2 6247:V 6243:ψ 6237:2 6234:V 6230:1 6227:V 6223:φ 6214:2 6211:V 6207:1 6204:V 6194:2 6191:V 6185:1 6182:V 6176:2 6173:V 6169:1 6166:V 6129:. 6122:V 6114:V 6112:( 6110:I 6103:V 6080:1 6054:) 6050:C 6046:( 6038:n 6013:) 6009:C 6005:( 5997:n 5965:z 5944:C 5940:= 5935:1 5930:A 5908:y 5905:, 5902:x 5882:z 5862:1 5854:2 5849:| 5844:z 5840:| 5818:C 5814:= 5809:1 5804:A 5782:} 5779:1 5776:= 5771:2 5766:| 5761:z 5757:| 5747:C 5740:z 5737:{ 5716:C 5693:1 5688:A 5660:A 5656:X 5648:p 5644:X 5636:p 5632:X 5628:P 5624:X 5619:A 5615:X 5611:p 5605:A 5601:P 5597:X 5550:/ 5546:D 5518:/ 5514:D 5486:/ 5482:D 5462:g 5440:g 5434:A 5407:/ 5403:D 5383:) 5379:Z 5375:, 5372:g 5369:2 5366:( 5311:g 5305:H 5299:= 5296:D 5272:/ 5268:D 5228:D 5204:/ 5200:D 5179:C 5154:C 5134:d 5114:n 5094:) 5091:d 5088:, 5085:n 5082:( 5077:C 5073:U 5052:) 5049:d 5046:, 5043:n 5040:( 5035:C 5031:U 5027:S 5007:d 4987:n 4967:C 4939:2 4933:g 4911:g 4905:M 4880:g 4874:M 4845:g 4835:M 4809:g 4803:M 4778:g 4768:M 4742:g 4736:M 4713:2 4707:g 4685:g 4675:M 4651:2 4645:g 4614:g 4608:M 4585:g 4561:g 4541:0 4535:g 4507:1 4504:= 4501:n 4491:C 4477:1 4474:= 4471:g 4461:C 4457:n 4441:n 4437:C 4413:] 4408:0 4404:P 4400:n 4392:n 4388:P 4384:+ 4378:+ 4373:1 4369:P 4365:[ 4359:) 4354:r 4350:P 4346:, 4340:, 4335:1 4331:P 4327:( 4323:, 4320:) 4317:C 4314:( 4300:n 4296:C 4272:0 4266:n 4246:C 4224:0 4220:P 4196:C 4176:) 4173:C 4170:( 4144:; 4141:) 4136:C 4130:O 4124:, 4121:C 4118:( 4110:1 4106:H 4085:) 4082:C 4079:( 4053:) 4050:C 4047:( 4015:C 4011:C 3997:) 3994:C 3991:( 3961:Z 3954:) 3951:C 3948:( 3939:: 3926:C 3908:) 3905:C 3902:( 3886:C 3882:C 3864:) 3861:C 3858:( 3842:C 3807:w 3803:V 3795:n 3781:V 3776:n 3761:V 3756:i 3754:b 3730:] 3725:n 3721:b 3706:1 3702:b 3698:[ 3687:n 3683:b 3679:, 3673:, 3668:1 3664:b 3652:) 3648:V 3643:n 3634:( 3629:P 3622:) 3619:V 3616:( 3611:n 3607:G 3600:{ 3581:V 3577:n 3573:V 3571:( 3568:n 3566:G 3559:V 3543:P 3531:P 3514:, 3509:2 3505:z 3501:x 3493:3 3489:x 3485:= 3482:z 3477:2 3473:y 3446:. 3443:x 3435:3 3431:x 3427:= 3422:2 3418:y 3402:x 3395:P 3390:P 3378:x 3374:x 3370:y 3331:D 3326:M 3308:M 3292:X 3278:M 3248:A 3222:M 3194:j 3191:+ 3188:i 3184:M 3175:j 3171:M 3165:i 3161:A 3150:A 3146:M 3121:g 3094:A 3066:g 3047:A 3043:X 3029:A 3013:k 2996:1 2990:i 2986:A 2980:/ 2974:i 2970:A 2953:= 2950:i 2942:= 2939:A 2909:Z 2898:A 2894:A 2890:k 2886:A 2841:r 2837:) 2827:k 2823:( 2803:) 2800:k 2797:( 2789:1 2774:k 2757:) 2754:1 2745:t 2742:( 2738:/ 2734:] 2731:n 2725:j 2722:, 2719:i 2713:0 2707:t 2704:, 2699:j 2696:i 2692:x 2688:[ 2685:k 2665:] 2660:1 2647:[ 2644:] 2641:n 2635:j 2632:, 2629:i 2623:0 2615:j 2612:i 2608:x 2604:[ 2601:k 2578:) 2575:k 2572:( 2564:n 2539:1 2536:= 2533:) 2530:A 2527:( 2521:t 2511:A 2494:, 2491:1 2485:] 2480:j 2477:i 2473:x 2469:[ 2460:t 2437:t 2434:, 2429:j 2426:i 2422:x 2399:1 2394:A 2382:2 2378:n 2372:A 2350:) 2347:k 2344:( 2336:n 2321:t 2305:1 2300:A 2288:2 2284:n 2278:A 2256:) 2253:k 2250:( 2242:n 2224:n 2220:n 2202:2 2198:n 2192:A 2170:H 2146:2 2142:n 2136:A 2114:) 2108:( 2105:V 2102:= 2099:H 2077:j 2074:i 2070:x 2026:A 2016:j 2012:i 1998:) 1995:A 1992:( 1987:j 1984:i 1980:x 1957:j 1954:i 1950:x 1925:2 1921:n 1915:A 1903:n 1899:k 1895:n 1891:n 1848:y 1844:x 1840:z 1836:y 1832:x 1811:0 1808:= 1799:3 1795:x 1788:z 1781:0 1778:= 1769:2 1765:x 1758:y 1737:C 1733:x 1729:x 1725:x 1721:x 1717:C 1713:A 1689:y 1685:x 1677:y 1673:x 1671:( 1669:g 1665:y 1661:x 1657:y 1655:, 1653:x 1649:A 1645:y 1641:x 1639:( 1637:g 1612:2 1608:y 1604:+ 1599:2 1595:x 1591:= 1588:) 1585:y 1582:, 1579:x 1576:( 1573:g 1560:y 1556:x 1554:( 1552:g 1548:C 1544:S 1540:A 1536:A 1532:C 1528:C 1524:A 1519:C 1515:k 1502:V 1494:A 1488:f 1484:Z 1480:V 1462:. 1459:} 1454:2 1449:C 1441:) 1438:x 1432:1 1429:, 1426:x 1423:( 1420:{ 1417:= 1414:) 1411:f 1408:( 1405:Z 1390:f 1386:Z 1373:x 1369:y 1365:y 1361:x 1357:A 1353:) 1351:y 1347:x 1343:f 1318:y 1315:+ 1312:x 1309:= 1306:) 1303:y 1300:, 1297:x 1294:( 1291:f 1278:) 1276:y 1272:x 1268:f 1262:C 1258:S 1254:A 1250:A 1246:C 1242:C 1234:A 1229:C 1225:k 1134:, 1111:P 1107:P 1040:V 1030:V 1026:V 1022:V 1020:( 1018:I 1013:P 1008:V 994:S 990:S 988:( 986:Z 982:V 973:P 968:V 951:. 948:} 945:S 939:f 931:0 928:= 925:) 922:x 919:( 916:f 908:n 903:P 895:x 892:{ 889:= 886:) 883:S 880:( 877:Z 864:S 859:P 854:S 850:S 844:f 834:) 831:n 829:x 825:0 822:x 818:f 814:λ 809:n 803:0 796:f 788:f 777:P 770:f 764:d 755:k 748:f 742:k 736:n 729:P 724:k 698:V 686:V 669:. 665:} 661:V 655:x 647:0 644:= 641:) 638:x 635:( 632:f 626:] 621:n 617:x 613:, 607:, 602:1 598:x 594:[ 591:K 585:f 581:{ 577:= 574:) 571:V 568:( 565:I 552:V 548:V 546:( 544:I 539:A 534:V 500:V 496:S 492:S 490:( 488:Z 484:V 475:A 470:V 453:. 449:} 445:S 439:f 431:0 428:= 425:) 422:x 419:( 416:f 408:n 403:A 395:x 391:{ 387:= 384:) 381:S 378:( 375:Z 362:S 357:A 352:S 350:( 348:Z 343:K 338:S 333:i 331:x 327:K 322:A 315:f 308:A 303:K 298:K 291:f 269:n 265:K 253:K 245:n 237:A 232:n 225:K 34:. 20:)

Index

Affine curve
Variety (universal algebra)

twisted cubic
algebraic geometry
mathematics
set of solutions
system of polynomial equations
real
complex numbers
irreducible
union
sets
closed
Zariski topology
fundamental theorem of algebra
algebra
geometry
monic polynomial
roots
complex plane
Hilbert's Nullstellensatz
ideals
polynomial rings
ring theory
differentiable manifolds
singular points
dimension
algebraic curves
algebraic surfaces

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