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Localized Chern class

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of solutions modulo gauge, and the index of the derivative is the virtual dimension. The localized Euler class of the pair (E,s) is a homology class with closed support on the zero set of the section. Its dimension is the index of the derivative. When the section is transversal, the class is just the fundamental class of the zero set with the proper orientation. The class is well behaved in one parameter families and therefore defines the “right” fundamental cycle even if the section is no longer transversal.
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Consider an infinite dimensional bundle E over an infinite dimensional manifold M with a section s with Fredholm derivative. In practice this situation occurs whenever we have system of PDE’s which are elliptic when considered modulo some gauge group action. The zero set Z(s) is then the moduli space
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This formula enables us to compute the conductor that measures the wild ramification by using the sheaf of differential 1-forms. S. Bloch conjectures a formula for the Artin conductor of the â„“-adic etale cohomology of a regular model of a variety over a local field and proves it for a curve. The
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S. Bloch, “Cycles on arithmetic schemes and Euler characteristics of curves,” Algebraic geometry, Bowdoin, 1985, 421–450, Proc. Symp. Pure Math. 46, Part 2, Amer. Math. Soc., Providence, RI, 1987.
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deepest result about the Bloch conductor is its equality with the Artin conductor, defined in terms of the l-adic cohomology of X, in certain cases.
459: 1110: 46: 1101:, Ergebnisse der Mathematik und ihrer Grenzgebiete. 3. Folge. A Series of Modern Surveys in Mathematics , vol. 2, Berlin, New York: 168: 706: 89:, that is defined for a chain complex of vector bundles as opposed to a single vector bundle. It was originally introduced in Fulton's 113: 68: 1094: 98: 1140: 873: 39: 33: 50: 542: 380: 413: 970: 816: 291: 135: 94: 297: 128:
be a pure-dimensional regular scheme of finite type over a field or discrete valuation ring and
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K. Kato and T. Saito, “On the conductor formula of Bloch,” Publ. Math. IHÉS 100 (2005), 5-151.
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is smooth over a field, then the localized Chern class coincides with the class
86: 528:{\displaystyle \xi =\prod (-1)^{i}\operatorname {pr} _{i}^{*}(\xi _{i})} 254:{\displaystyle 0=E_{n-1}\to E_{n}\to \dots \to E_{m}\to E_{m-1}=0} 768:{\displaystyle \eta :G_{n}\times _{Y}\dots \times _{Y}G_{m}\to X} 1020: 290:. The localized Chern class of this complex is a class in the 18: 112:
that computes the non-constancy of Euler characteristic of a
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of algebraic varieties (in the mixed characteristic case).
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S. Bloch later generalized the notion in the context of
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The notion is used in particular in the 986: 974: 972: 947: 941: 914: 902: 890: 875: 832: 800: 780: 753: 743: 730: 720: 708: 666: 653: 631: 618: 607: 601: 586:{\displaystyle c_{i,X}^{Y}(E_{\bullet })} 574: 561: 550: 544: 516: 500: 495: 485: 461: 434: 421: 415: 394: 382: 361: 355: 331: 325: 299: 269: 233: 220: 201: 182: 170: 143: 137: 69:Learn how and when to remove this message 403:{\displaystyle \operatorname {rk} E_{i}} 32:This article includes a list of general 1072: 1079: 1005:is the class of the singular locus of 347:denote the tautological bundle of the 159:denote a complex of vector bundles on 7: 1062:Grothendieck–Ogg–Shafarevich formula 449:{\displaystyle E_{i}\otimes E_{i-1}} 998:{\displaystyle \mathbf {Z} (s_{f})} 38:it lacks sufficient corresponding 14: 1016: 1024: 975: 903: 860: 23: 992: 979: 920: 907: 887: 877: 843: 823:Example: localized Euler class 759: 687: 678: 672: 659: 637: 624: 580: 567: 522: 509: 482: 472: 226: 213: 207: 194: 1: 152:{\displaystyle E_{\bullet }} 593:is defined by the formula: 1157: 1059: 539:-th localized Chern class 313:{\displaystyle X\subset Y} 110:#Bloch's conductor formula 1017:Bloch's conductor formula 795:is a cycle obtained from 99:Riemann–Roch-type theorem 81:In algebraic geometry, a 852:{\displaystyle f:X\to S} 340:{\displaystyle \xi _{i}} 320:defined as follows. Let 132:a closed subscheme. Let 808:{\displaystyle \alpha } 788:{\displaystyle \gamma } 53:more precise citations. 999: 957: 927: 853: 809: 789: 775:is the projection and 769: 694: 587: 529: 450: 404: 371: 341: 314: 284: 255: 153: 1000: 958: 956:{\displaystyle s_{f}} 928: 854: 810: 790: 770: 695: 588: 530: 451: 405: 372: 370:{\displaystyle G_{i}} 342: 315: 285: 256: 154: 83:localized Chern class 971: 940: 874: 831: 799: 779: 707: 600: 543: 460: 414: 381: 354: 324: 298: 292:bivariant Chow group 268: 169: 136: 1099:Intersection theory 623: 566: 505: 283:{\displaystyle Y-X} 114:degenerating family 91:intersection theory 16:Concept in geometry 1141:Algebraic geometry 1036:. 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Then the 120:Definitions 87:Chern class 51:introducing 1067:References 1060:See also: 34:references 895:⁡ 881:− 859:be as in 844:→ 803:α 783:γ 760:→ 741:× 737:⋯ 728:× 711:η 685:γ 682:∩ 676:ξ 655:∗ 651:η 644:α 641:∩ 633:∙ 576:∙ 514:ξ 507:⁡ 502:∗ 476:− 470:∏ 464:ξ 439:− 428:⊗ 388:⁡ 329:ξ 305:⊂ 275:− 238:− 227:→ 214:→ 211:⋯ 208:→ 195:→ 187:− 145:∙ 1135:Category 1097:(1998), 377:of rank 1121:1644323 47:improve 1119:  1109:  703:where 456:. Let 36:, but 863:. 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Index

references
inline citations
improve
introducing
Learn how and when to remove this message
Chern class
algebraic topology
Riemann–Roch-type theorem
arithmetic schemes
#Bloch's conductor formula
degenerating family
bivariant Chow group
Grassmann bundle
graph construction
#Definitions

adding to it
Grothendieck–Ogg–Shafarevich formula
Fulton 1998
Fulton, William
Springer-Verlag
ISBN
978-3-540-62046-4
MR
1644323
Category
Algebraic geometry

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