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Clifford's theorem on special divisors

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taken over all special divisors (except canonical and trivial), and Clifford's theorem states this is non-negative. It can be shown that the Clifford index for a
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curves had attracted a huge amount of effort by algebraic geometers over twenty years before finally being laid to rest by Voisin. The conjecture for
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states that the Clifford index for a curve over the complex numbers that is not hyperelliptic should be determined by the extent to which
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The Clifford index measures how far the curve is from being hyperelliptic. It may be thought of as a refinement of the
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for her solution of the generic case of Green's conjecture in two papers. The case of Green's conjecture for
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Green’s generic syzygy conjecture for curves of even genus lying on a K3 surface - Claire Voisin
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The Geometry of Syzygies. A second course in commutative algebra and algebraic geometry
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Green's canonical syzygy conjecture for generic curves of odd genus - Claire Voisin
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with integer coefficients. One considers a divisor as a set of constraints on
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linearly equivalent to an integral multiple of a hyperelliptic divisor.
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states that equality always holds. There are numerous partial results.
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as the vector space of functions having poles only at points of
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as the coefficient indicates, and having zeros at points of
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has linear syzygies. In detail, one defines the invariant
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Philosophical Transactions of the Royal Society of London
507: 84: 502: 438: 357: 266: 225: 196: 151: 83: 737:. Grundlehren de mathematischen Wisenschaften 267. 619:) + 1 is a lower bound for the Clifford index, and 535:{\displaystyle \lfloor {\tfrac {g-1}{2}}\rfloor .} 534: 474: 393: 287: 240: 211: 166: 117: 588:in its canonical embedding, as the largest index 1560: 852: 959: 945: 526: 503: 306:, which is the sum of all its coefficients. 118:{\displaystyle \textstyle D=\sum _{P}m_{P}P} 952: 938: 911: 878: 755:(1878), "On the Classification of Loci", 792: 751: 40: 631:Ruth Lyttle Satter Prize in Mathematics 14: 1561: 1375:Clifford's theorem on special divisors 830: 669: 409:is zero or a canonical divisor, or if 33:Clifford's theorem on special divisors 933: 735:Geometry of Algebraic Curves Volume I 660: 551: 190:that multiplicity. The dimension of 432:is then defined as the minimum of 394:{\displaystyle 2(\ell (D)-1)\leq d} 298:The other significant invariant of 24: 1544:Vector bundles on algebraic curves 1467:Weber's theorem (Algebraic curves) 1064:Hasse's theorem on elliptic curves 1054:Counting points on elliptic curves 25: 1590: 905: 862:Principles of Algebraic Geometry 405:and that equality holds only if 186:with negative coefficient, with 1155:Hurwitz's automorphisms theorem 804:. Vol. 229. New York, NY: 475:{\displaystyle d-2(\ell (D)-1)} 1574:Theorems in algebraic geometry 1380:Gonality of an algebraic curve 1291:Differential of the first kind 765:, The Royal Society: 663–681, 700: 689: 678: 651: 469: 460: 454: 448: 382: 373: 367: 361: 276: 270: 235: 229: 206: 200: 161: 155: 13: 1: 1579:Unsolved problems in geometry 1534:Birkhoff–Grothendieck theorem 1233:Nagata's conjecture on curves 1104:Schoof–Elkies–Atkin algorithm 978:Five points determine a conic 888:Graduate Texts in Mathematics 802:Graduate Texts in Mathematics 715: 341:states that for an effective 47:, showing the constraints on 1094:Supersingular elliptic curve 58: 7: 1301:Riemann's existence theorem 1228:Hilbert's sixteenth problem 1120:Elliptic curve cryptography 1033:Fundamental pair of periods 919:Encyclopedia of Mathematics 582:homogeneous coordinate ring 178:with positive coefficient, 10: 1595: 1431:Moduli of algebraic curves 912:Iskovskikh, V.A. (2001) , 675:Eisenbud (2005) pp. 183-4. 576:) in terms of the minimal 288:{\displaystyle \ell (D)-1} 1524: 1475: 1444: 1408: 1357: 1350: 1324: 1256: 1173: 1137: 1112: 1046: 1015: 1006: 968: 250:linear system of divisors 1198:Cayley–Bacharach theorem 1125:Elliptic curve primality 644: 241:{\displaystyle \ell (D)} 1457:Riemann–Hurwitz formula 1421:Gromov–Witten invariant 1281:Compact Riemann surface 1069:Mazur's torsion theorem 219:is finite, and denoted 37:William K. Clifford 1074:Modular elliptic curve 771:10.1098/rstl.1878.0020 725:; Cornalba, Maurizio; 536: 476: 395: 289: 242: 213: 168: 119: 49:special linear systems 988:Rational normal curve 854:Griffiths, Phillip A. 727:Griffiths, Phillip A. 666:Eisenbud (2005) p.178 641:curves remains open. 537: 477: 396: 290: 256:is the corresponding 243: 214: 169: 135:meromorphic functions 120: 1539:Stable vector bundle 1400:Weil reciprocity law 1390:Riemann–Roch theorem 1370:Brill–Noether theory 1306:Riemann–Roch theorem 1223:Genus–degree formula 1084:Mordell–Weil theorem 1059:Division polynomials 753:Clifford, William K. 500: 436: 355: 309:A divisor is called 264: 223: 212:{\displaystyle L(D)} 194: 167:{\displaystyle L(D)} 149: 81: 1351:Structure of curves 1243:Quartic plane curve 1165:Hyperelliptic curve 1145:De Franchis theorem 1089:Nagell–Lutz theorem 607:is zero. Green and 594:graded Betti number 415:hyperelliptic curve 323: −  1358:Divisors on curves 1150:Faltings's theorem 1099:Schoof's algorithm 1079:Modularity theorem 914:"Clifford theorem" 884:Algebraic Geometry 621:Green's conjecture 552:Green's conjecture 532: 524: 472: 391: 339:Clifford's theorem 285: 238: 209: 164: 115: 114: 100: 1556: 1555: 1552: 1551: 1452:Hasse–Witt matrix 1395:Weierstrass point 1342:Smooth completion 1311:TeichmĂĽller space 1213:Cubic plane curve 1133: 1132: 1047:Arithmetic theory 1028:Elliptic integral 1023:Elliptic function 880:Hartshorne, Robin 723:Arbarello, Enrico 609:Robert Lazarsfeld 523: 333:canonical divisor 91: 16:(Redirected from 1586: 1569:Algebraic curves 1385:Jacobian variety 1355: 1354: 1258:Riemann surfaces 1248:Real plane curve 1208:Cramer's paradox 1188:BĂ©zout's theorem 1013: 1012: 962:algebraic curves 954: 947: 940: 931: 930: 926: 901: 890:. Vol. 52. 875: 849: 836:Algebraic Curves 827: 789: 748: 709: 704: 698: 693: 687: 682: 676: 673: 667: 664: 658: 657:Hartshorne p.296 655: 629:was awarded the 556:A conjecture of 541: 539: 538: 533: 525: 519: 508: 493:is equal to the 481: 479: 478: 473: 400: 398: 397: 392: 327:) > 0, where 294: 292: 291: 286: 258:projective space 247: 245: 244: 239: 218: 216: 215: 210: 173: 171: 170: 165: 124: 122: 121: 116: 110: 109: 99: 45:algebraic curves 21: 1594: 1593: 1589: 1588: 1587: 1585: 1584: 1583: 1559: 1558: 1557: 1548: 1520: 1511:Delta invariant 1489: 1471: 1440: 1404: 1365:Abel–Jacobi map 1346: 1320: 1316:Torelli theorem 1286:Dessin d'enfant 1266:Belyi's theorem 1252: 1238:PlĂĽcker formula 1169: 1160:Hurwitz surface 1129: 1108: 1042: 1016:Analytic theory 1008:Elliptic curves 1002: 983:Projective line 970:Rational curves 964: 958: 908: 898: 872: 846: 832:Fulton, William 816: 806:Springer-Verlag 794:Eisenbud, David 745: 718: 713: 712: 705: 701: 694: 690: 683: 679: 674: 670: 665: 661: 656: 652: 647: 606: 578:free resolution 566:canonical curve 554: 509: 506: 501: 498: 497: 437: 434: 433: 356: 353: 352: 343:special divisor 265: 262: 261: 224: 221: 220: 195: 192: 191: 150: 147: 146: 105: 101: 95: 82: 79: 78: 69:Riemann surface 61: 35:is a result of 23: 22: 15: 12: 11: 5: 1592: 1582: 1581: 1576: 1571: 1554: 1553: 1550: 1549: 1547: 1546: 1541: 1536: 1530: 1528: 1526:Vector bundles 1522: 1521: 1519: 1518: 1513: 1508: 1503: 1498: 1493: 1487: 1481: 1479: 1473: 1472: 1470: 1469: 1464: 1459: 1454: 1448: 1446: 1442: 1441: 1439: 1438: 1433: 1428: 1423: 1418: 1412: 1410: 1406: 1405: 1403: 1402: 1397: 1392: 1387: 1382: 1377: 1372: 1367: 1361: 1359: 1352: 1348: 1347: 1345: 1344: 1339: 1334: 1328: 1326: 1322: 1321: 1319: 1318: 1313: 1308: 1303: 1298: 1293: 1288: 1283: 1278: 1273: 1268: 1262: 1260: 1254: 1253: 1251: 1250: 1245: 1240: 1235: 1230: 1225: 1220: 1215: 1210: 1205: 1200: 1195: 1190: 1185: 1179: 1177: 1171: 1170: 1168: 1167: 1162: 1157: 1152: 1147: 1141: 1139: 1135: 1134: 1131: 1130: 1128: 1127: 1122: 1116: 1114: 1110: 1109: 1107: 1106: 1101: 1096: 1091: 1086: 1081: 1076: 1071: 1066: 1061: 1056: 1050: 1048: 1044: 1043: 1041: 1040: 1035: 1030: 1025: 1019: 1017: 1010: 1004: 1003: 1001: 1000: 995: 993:Riemann sphere 990: 985: 980: 974: 972: 966: 965: 957: 956: 949: 942: 934: 928: 927: 907: 906:External links 904: 903: 902: 896: 876: 870: 850: 844: 828: 814: 790: 749: 743: 717: 714: 711: 710: 699: 688: 677: 668: 659: 649: 648: 646: 643: 597: 592:for which the 553: 550: 531: 528: 522: 518: 515: 512: 505: 495:floor function 471: 468: 465: 462: 459: 456: 453: 450: 447: 444: 441: 426:Clifford index 403: 402: 390: 387: 384: 381: 378: 375: 372: 369: 366: 363: 360: 302:is its degree 284: 281: 278: 275: 272: 269: 237: 234: 231: 228: 208: 205: 202: 199: 180:at most as bad 163: 160: 157: 154: 139:function field 113: 108: 104: 98: 94: 90: 87: 60: 57: 18:Clifford index 9: 6: 4: 3: 2: 1591: 1580: 1577: 1575: 1572: 1570: 1567: 1566: 1564: 1545: 1542: 1540: 1537: 1535: 1532: 1531: 1529: 1527: 1523: 1517: 1514: 1512: 1509: 1507: 1504: 1502: 1499: 1497: 1494: 1492: 1490: 1483: 1482: 1480: 1478: 1477:Singularities 1474: 1468: 1465: 1463: 1460: 1458: 1455: 1453: 1450: 1449: 1447: 1443: 1437: 1434: 1432: 1429: 1427: 1424: 1422: 1419: 1417: 1414: 1413: 1411: 1407: 1401: 1398: 1396: 1393: 1391: 1388: 1386: 1383: 1381: 1378: 1376: 1373: 1371: 1368: 1366: 1363: 1362: 1360: 1356: 1353: 1349: 1343: 1340: 1338: 1335: 1333: 1330: 1329: 1327: 1325:Constructions 1323: 1317: 1314: 1312: 1309: 1307: 1304: 1302: 1299: 1297: 1296:Klein quartic 1294: 1292: 1289: 1287: 1284: 1282: 1279: 1277: 1276:Bolza surface 1274: 1272: 1271:Bring's curve 1269: 1267: 1264: 1263: 1261: 1259: 1255: 1249: 1246: 1244: 1241: 1239: 1236: 1234: 1231: 1229: 1226: 1224: 1221: 1219: 1216: 1214: 1211: 1209: 1206: 1204: 1203:Conic section 1201: 1199: 1196: 1194: 1191: 1189: 1186: 1184: 1183:AF+BG theorem 1181: 1180: 1178: 1176: 1172: 1166: 1163: 1161: 1158: 1156: 1153: 1151: 1148: 1146: 1143: 1142: 1140: 1136: 1126: 1123: 1121: 1118: 1117: 1115: 1111: 1105: 1102: 1100: 1097: 1095: 1092: 1090: 1087: 1085: 1082: 1080: 1077: 1075: 1072: 1070: 1067: 1065: 1062: 1060: 1057: 1055: 1052: 1051: 1049: 1045: 1039: 1036: 1034: 1031: 1029: 1026: 1024: 1021: 1020: 1018: 1014: 1011: 1009: 1005: 999: 998:Twisted cubic 996: 994: 991: 989: 986: 984: 981: 979: 976: 975: 973: 971: 967: 963: 955: 950: 948: 943: 941: 936: 935: 932: 925: 921: 920: 915: 910: 909: 899: 897:0-387-90244-9 893: 889: 885: 881: 877: 873: 871:0-471-05059-8 867: 863: 859: 855: 851: 847: 845:0-8053-3080-1 841: 837: 833: 829: 825: 821: 817: 815:0-387-22215-4 811: 807: 803: 799: 795: 791: 788: 784: 780: 776: 772: 768: 764: 760: 759: 754: 750: 746: 744:0-387-90997-4 740: 736: 732: 728: 724: 720: 719: 708: 703: 697: 692: 686: 681: 672: 663: 654: 650: 642: 640: 636: 632: 628: 627:Claire Voisin 624: 622: 618: 614: 610: 604: 600: 595: 591: 587: 583: 579: 575: 571: 567: 563: 559: 549: 547: 542: 529: 520: 516: 513: 510: 496: 492: 489: 485: 466: 463: 457: 451: 445: 442: 439: 431: 427: 422: 420: 416: 412: 408: 388: 385: 379: 376: 370: 364: 358: 351: 350: 349: 347: 344: 340: 336: 334: 330: 326: 322: 318: 314: 313: 307: 305: 301: 296: 282: 279: 273: 267: 260:of dimension 259: 255: 251: 232: 226: 203: 197: 189: 185: 181: 177: 158: 152: 144: 140: 136: 132: 128: 111: 106: 102: 96: 92: 88: 85: 77: 73: 70: 66: 56: 54: 50: 46: 42: 38: 34: 30: 19: 1485: 1462:Prym variety 1436:Stable curve 1426:Hodge bundle 1416:ELSV formula 1374: 1218:Fermat curve 1175:Plane curves 1138:Higher genus 1113:Applications 1038:Modular form 917: 883: 861: 835: 797: 762: 756: 734: 707:Satter Prize 702: 691: 680: 671: 662: 653: 638: 634: 625: 620: 616: 612: 611:showed that 602: 598: 589: 585: 573: 569: 561: 555: 543: 490: 483: 429: 425: 423: 418: 410: 406: 404: 345: 338: 337: 328: 324: 320: 316: 310: 308: 303: 299: 297: 253: 252:attached to 187: 183: 179: 175: 142: 130: 126: 71: 62: 52: 32: 26: 1491:singularity 1337:Polar curve 858:Harris, Joe 731:Harris, Joe 348:, one has: 51:on a curve 29:mathematics 1563:Categories 1332:Dual curve 960:Topics in 824:1066.14001 716:References 558:Mark Green 125:of points 76:formal sum 1445:Morphisms 1193:Bitangent 924:EMS Press 779:0080-4614 639:arbitrary 527:⌋ 514:− 504:⌊ 486:curve of 464:− 452:ℓ 443:− 386:≤ 377:− 365:ℓ 280:− 268:ℓ 227:ℓ 145:defining 93:∑ 59:Statement 882:(1977). 860:(1994). 834:(1974). 796:(2005). 733:(1985). 546:gonality 188:at least 1516:Tacnode 1501:Crunode 635:generic 580:of the 484:generic 331:is the 312:special 137:in the 65:divisor 39: ( 1496:Acnode 1409:Moduli 894:  868:  842:  822:  812:  787:109316 785:  777:  741:  248:. The 783:JSTOR 645:Notes 488:genus 413:is a 74:is a 67:on a 43:) on 1506:Cusp 892:ISBN 866:ISBN 840:ISBN 810:ISBN 775:ISSN 739:ISBN 424:The 417:and 41:1878 820:Zbl 767:doi 763:169 605:+ 2 584:of 564:as 428:of 315:if 295:. 141:of 129:on 27:In 1565:: 922:, 916:, 886:. 856:; 818:. 808:. 800:. 781:, 773:, 761:, 729:; 601:, 335:. 143:C, 63:A 55:. 31:, 1488:k 1486:A 953:e 946:t 939:v 900:. 874:. 848:. 826:. 769:: 747:. 617:C 615:( 613:a 603:i 599:i 596:β 590:i 586:C 574:C 572:( 570:a 562:C 530:. 521:2 517:1 511:g 491:g 470:) 467:1 461:) 458:D 455:( 449:( 446:2 440:d 430:C 419:D 411:C 407:D 401:, 389:d 383:) 380:1 374:) 371:D 368:( 362:( 359:2 346:D 329:K 325:D 321:K 319:( 317:â„“ 304:d 300:D 283:1 277:) 274:D 271:( 254:D 236:) 233:D 230:( 207:) 204:D 201:( 198:L 184:D 176:D 162:) 159:D 156:( 153:L 131:C 127:P 112:P 107:P 103:m 97:P 89:= 86:D 72:C 53:C 20:)

Index

Clifford index
mathematics
William K. Clifford
1878
algebraic curves
special linear systems
divisor
Riemann surface
formal sum
meromorphic functions
function field
linear system of divisors
projective space
special
canonical divisor
special divisor
hyperelliptic curve
genus
floor function
gonality
Mark Green
canonical curve
free resolution
homogeneous coordinate ring
graded Betti number
Robert Lazarsfeld
Claire Voisin
Ruth Lyttle Satter Prize in Mathematics
Green's canonical syzygy conjecture for generic curves of odd genus - Claire Voisin
Green’s generic syzygy conjecture for curves of even genus lying on a K3 surface - Claire Voisin

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