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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
496: 73: 491: 427: 346: 255: 214: 185: 140: 72: 726:. Grundlehren de mathematischen Wisenschaften 267. 608:) + 1 is a lower bound for the Clifford index, and 524:{\displaystyle \lfloor {\tfrac {g-1}{2}}\rfloor .} 523: 463: 382: 276: 229: 200: 155: 106: 577:in its canonical embedding, as the largest index 1549: 841: 948: 934: 515: 492: 295:, which is the sum of all its coefficients. 107:{\displaystyle \textstyle D=\sum _{P}m_{P}P} 941: 927: 900: 867: 744:(1878), "On the Classification of Loci", 781: 740: 29: 620:Ruth Lyttle Satter Prize in Mathematics 1550: 1364:Clifford's theorem on special divisors 819: 658: 398:is zero or a canonical divisor, or if 22:Clifford's theorem on special divisors 922: 724:Geometry of Algebraic Curves Volume I 649: 540: 179:that multiplicity. The dimension of 421:is then defined as the minimum of 383:{\displaystyle 2(\ell (D)-1)\leq d} 287:The other significant invariant of 13: 1533:Vector bundles on algebraic curves 1456:Weber's theorem (Algebraic curves) 1053:Hasse's theorem on elliptic curves 1043:Counting points on elliptic curves 14: 1579: 894: 851:Principles of Algebraic Geometry 394:and that equality holds only if 175:with negative coefficient, with 1144:Hurwitz's automorphisms theorem 793:. Vol. 229. New York, NY: 464:{\displaystyle d-2(\ell (D)-1)} 1563:Theorems in algebraic geometry 1369:Gonality of an algebraic curve 1280:Differential of the first kind 754:, The Royal Society: 663–681, 689: 678: 667: 640: 458: 449: 443: 437: 371: 362: 356: 350: 265: 259: 224: 218: 195: 189: 150: 144: 1: 1568:Unsolved problems in geometry 1523:Birkhoff–Grothendieck theorem 1222:Nagata's conjecture on curves 1093:Schoof–Elkies–Atkin algorithm 967:Five points determine a conic 877:Graduate Texts in Mathematics 791:Graduate Texts in Mathematics 704: 330:states that for an effective 36:, showing the constraints on 1083:Supersingular elliptic curve 47: 7: 1290:Riemann's existence theorem 1217:Hilbert's sixteenth problem 1109:Elliptic curve cryptography 1022:Fundamental pair of periods 908:Encyclopedia of Mathematics 571:homogeneous coordinate ring 167:with positive coefficient, 10: 1584: 1420:Moduli of algebraic curves 901:Iskovskikh, V.A. (2001) , 664:Eisenbud (2005) pp. 183-4. 565:) in terms of the minimal 277:{\displaystyle \ell (D)-1} 1513: 1464: 1433: 1397: 1346: 1339: 1313: 1245: 1162: 1126: 1101: 1035: 1004: 995: 957: 239:linear system of divisors 1187:Cayley–Bacharach theorem 1114:Elliptic curve primality 633: 230:{\displaystyle \ell (D)} 1446:Riemann–Hurwitz formula 1410:Gromov–Witten invariant 1270:Compact Riemann surface 1058:Mazur's torsion theorem 208:is finite, and denoted 26:William K. Clifford 1063:Modular elliptic curve 760:10.1098/rstl.1878.0020 714:; Cornalba, Maurizio; 525: 465: 384: 278: 231: 202: 157: 108: 38:special linear systems 977:Rational normal curve 843:Griffiths, Phillip A. 716:Griffiths, Phillip A. 655:Eisenbud (2005) p.178 630:curves remains open. 526: 466: 385: 279: 245:is the corresponding 232: 203: 158: 124:meromorphic functions 109: 1528:Stable vector bundle 1389:Weil reciprocity law 1379:Riemann–Roch theorem 1359:Brill–Noether theory 1295:Riemann–Roch theorem 1212:Genus–degree formula 1073:Mordell–Weil theorem 1048:Division polynomials 742:Clifford, William K. 489: 425: 344: 298:A divisor is called 253: 212: 201:{\displaystyle L(D)} 183: 156:{\displaystyle L(D)} 138: 70: 1340:Structure of curves 1232:Quartic plane curve 1154:Hyperelliptic curve 1134:De Franchis theorem 1078:Nagell–Lutz theorem 596:is zero. Green and 583:graded Betti number 404:hyperelliptic curve 312: −  1347:Divisors on curves 1139:Faltings's theorem 1088:Schoof's algorithm 1068:Modularity theorem 903:"Clifford theorem" 873:Algebraic Geometry 610:Green's conjecture 541:Green's conjecture 521: 513: 461: 380: 328:Clifford's theorem 274: 227: 198: 153: 104: 103: 89: 1545: 1544: 1541: 1540: 1441:Hasse–Witt matrix 1384:Weierstrass point 1331:Smooth completion 1300:TeichmĂĽller space 1202:Cubic plane curve 1122: 1121: 1036:Arithmetic theory 1017:Elliptic integral 1012:Elliptic function 869:Hartshorne, Robin 712:Arbarello, Enrico 598:Robert Lazarsfeld 512: 322:canonical divisor 80: 1575: 1558:Algebraic curves 1374:Jacobian variety 1344: 1343: 1247:Riemann surfaces 1237:Real plane curve 1197:Cramer's paradox 1177:BĂ©zout's theorem 1002: 1001: 951:algebraic curves 943: 936: 929: 920: 919: 915: 890: 879:. Vol. 52. 864: 838: 825:Algebraic Curves 816: 778: 737: 698: 693: 687: 682: 676: 671: 665: 662: 656: 653: 647: 646:Hartshorne p.296 644: 618:was awarded the 545:A conjecture of 530: 528: 527: 522: 514: 508: 497: 482:is equal to the 470: 468: 467: 462: 389: 387: 386: 381: 316:) > 0, where 283: 281: 280: 275: 247:projective space 236: 234: 233: 228: 207: 205: 204: 199: 162: 160: 159: 154: 113: 111: 110: 105: 99: 98: 88: 34:algebraic curves 1583: 1582: 1578: 1577: 1576: 1574: 1573: 1572: 1548: 1547: 1546: 1537: 1509: 1500:Delta invariant 1478: 1460: 1429: 1393: 1354:Abel–Jacobi map 1335: 1309: 1305:Torelli theorem 1275:Dessin d'enfant 1255:Belyi's theorem 1241: 1227:PlĂĽcker formula 1158: 1149:Hurwitz surface 1118: 1097: 1031: 1005:Analytic theory 997:Elliptic curves 991: 972:Projective line 959:Rational curves 953: 947: 897: 887: 861: 835: 821:Fulton, William 805: 795:Springer-Verlag 783:Eisenbud, David 734: 707: 702: 701: 694: 690: 683: 679: 672: 668: 663: 659: 654: 650: 645: 641: 636: 595: 567:free resolution 555:canonical curve 543: 498: 495: 490: 487: 486: 426: 423: 422: 345: 342: 341: 332:special divisor 254: 251: 250: 213: 210: 209: 184: 181: 180: 139: 136: 135: 94: 90: 84: 71: 68: 67: 58:Riemann surface 50: 24:is a result of 12: 11: 5: 1581: 1571: 1570: 1565: 1560: 1543: 1542: 1539: 1538: 1536: 1535: 1530: 1525: 1519: 1517: 1515:Vector bundles 1511: 1510: 1508: 1507: 1502: 1497: 1492: 1487: 1482: 1476: 1470: 1468: 1462: 1461: 1459: 1458: 1453: 1448: 1443: 1437: 1435: 1431: 1430: 1428: 1427: 1422: 1417: 1412: 1407: 1401: 1399: 1395: 1394: 1392: 1391: 1386: 1381: 1376: 1371: 1366: 1361: 1356: 1350: 1348: 1341: 1337: 1336: 1334: 1333: 1328: 1323: 1317: 1315: 1311: 1310: 1308: 1307: 1302: 1297: 1292: 1287: 1282: 1277: 1272: 1267: 1262: 1257: 1251: 1249: 1243: 1242: 1240: 1239: 1234: 1229: 1224: 1219: 1214: 1209: 1204: 1199: 1194: 1189: 1184: 1179: 1174: 1168: 1166: 1160: 1159: 1157: 1156: 1151: 1146: 1141: 1136: 1130: 1128: 1124: 1123: 1120: 1119: 1117: 1116: 1111: 1105: 1103: 1099: 1098: 1096: 1095: 1090: 1085: 1080: 1075: 1070: 1065: 1060: 1055: 1050: 1045: 1039: 1037: 1033: 1032: 1030: 1029: 1024: 1019: 1014: 1008: 1006: 999: 993: 992: 990: 989: 984: 982:Riemann sphere 979: 974: 969: 963: 961: 955: 954: 946: 945: 938: 931: 923: 917: 916: 896: 895:External links 893: 892: 891: 885: 865: 859: 839: 833: 817: 803: 779: 738: 732: 706: 703: 700: 699: 688: 677: 666: 657: 648: 638: 637: 635: 632: 586: 581:for which the 542: 539: 520: 517: 511: 507: 504: 501: 494: 484:floor function 460: 457: 454: 451: 448: 445: 442: 439: 436: 433: 430: 415:Clifford index 392: 391: 379: 376: 373: 370: 367: 364: 361: 358: 355: 352: 349: 291:is its degree 273: 270: 267: 264: 261: 258: 226: 223: 220: 217: 197: 194: 191: 188: 169:at most as bad 152: 149: 146: 143: 128:function field 102: 97: 93: 87: 83: 79: 76: 49: 46: 9: 6: 4: 3: 2: 1580: 1569: 1566: 1564: 1561: 1559: 1556: 1555: 1553: 1534: 1531: 1529: 1526: 1524: 1521: 1520: 1518: 1516: 1512: 1506: 1503: 1501: 1498: 1496: 1493: 1491: 1488: 1486: 1483: 1481: 1479: 1472: 1471: 1469: 1467: 1466:Singularities 1463: 1457: 1454: 1452: 1449: 1447: 1444: 1442: 1439: 1438: 1436: 1432: 1426: 1423: 1421: 1418: 1416: 1413: 1411: 1408: 1406: 1403: 1402: 1400: 1396: 1390: 1387: 1385: 1382: 1380: 1377: 1375: 1372: 1370: 1367: 1365: 1362: 1360: 1357: 1355: 1352: 1351: 1349: 1345: 1342: 1338: 1332: 1329: 1327: 1324: 1322: 1319: 1318: 1316: 1314:Constructions 1312: 1306: 1303: 1301: 1298: 1296: 1293: 1291: 1288: 1286: 1285:Klein quartic 1283: 1281: 1278: 1276: 1273: 1271: 1268: 1266: 1265:Bolza surface 1263: 1261: 1260:Bring's curve 1258: 1256: 1253: 1252: 1250: 1248: 1244: 1238: 1235: 1233: 1230: 1228: 1225: 1223: 1220: 1218: 1215: 1213: 1210: 1208: 1205: 1203: 1200: 1198: 1195: 1193: 1192:Conic section 1190: 1188: 1185: 1183: 1180: 1178: 1175: 1173: 1172:AF+BG theorem 1170: 1169: 1167: 1165: 1161: 1155: 1152: 1150: 1147: 1145: 1142: 1140: 1137: 1135: 1132: 1131: 1129: 1125: 1115: 1112: 1110: 1107: 1106: 1104: 1100: 1094: 1091: 1089: 1086: 1084: 1081: 1079: 1076: 1074: 1071: 1069: 1066: 1064: 1061: 1059: 1056: 1054: 1051: 1049: 1046: 1044: 1041: 1040: 1038: 1034: 1028: 1025: 1023: 1020: 1018: 1015: 1013: 1010: 1009: 1007: 1003: 1000: 998: 994: 988: 987:Twisted cubic 985: 983: 980: 978: 975: 973: 970: 968: 965: 964: 962: 960: 956: 952: 944: 939: 937: 932: 930: 925: 924: 921: 914: 910: 909: 904: 899: 898: 888: 886:0-387-90244-9 882: 878: 874: 870: 866: 862: 860:0-471-05059-8 856: 852: 848: 844: 840: 836: 834:0-8053-3080-1 830: 826: 822: 818: 814: 810: 806: 804:0-387-22215-4 800: 796: 792: 788: 784: 780: 777: 773: 769: 765: 761: 757: 753: 749: 748: 743: 739: 735: 733:0-387-90997-4 729: 725: 721: 717: 713: 709: 708: 697: 692: 686: 681: 675: 670: 661: 652: 643: 639: 631: 629: 625: 621: 617: 616:Claire Voisin 613: 611: 607: 603: 599: 593: 589: 584: 580: 576: 572: 568: 564: 560: 556: 552: 548: 538: 536: 531: 518: 509: 505: 502: 499: 485: 481: 478: 474: 455: 452: 446: 440: 434: 431: 428: 420: 416: 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1552:Categories 1321:Dual curve 949:Topics in 813:1066.14001 705:References 547:Mark Green 114:of points 65:formal sum 1434:Morphisms 1182:Bitangent 913:EMS Press 768:0080-4614 628:arbitrary 516:⌋ 503:− 493:⌊ 475:curve of 453:− 441:ℓ 432:− 375:≤ 366:− 354:ℓ 269:− 257:ℓ 216:ℓ 134:defining 82:∑ 48:Statement 871:(1977). 849:(1994). 823:(1974). 785:(2005). 722:(1985). 535:gonality 177:at least 1505:Tacnode 1490:Crunode 624:generic 569:of the 473:generic 320:is the 301:special 126:in the 54:divisor 28: ( 1485:Acnode 1398:Moduli 883:  857:  831:  811:  801:  776:109316 774:  766:  730:  237:. The 772:JSTOR 634:Notes 477:genus 402:is a 63:is a 56:on a 32:) on 1495:Cusp 881:ISBN 855:ISBN 829:ISBN 799:ISBN 764:ISSN 728:ISBN 413:The 406:and 30:1878 809:Zbl 756:doi 752:169 594:+ 2 573:of 553:as 417:of 304:if 284:. 130:of 118:on 16:In 1554:: 911:, 905:, 875:. 845:; 807:. 797:. 789:. 770:, 762:, 750:, 718:; 590:, 324:. 132:C, 52:A 44:. 20:, 1477:k 1475:A 942:e 935:t 928:v 889:. 863:. 837:. 815:. 758:: 736:. 606:C 604:( 602:a 592:i 588:i 585:β 579:i 575:C 563:C 561:( 559:a 551:C 519:. 510:2 506:1 500:g 480:g 459:) 456:1 450:) 447:D 444:( 438:( 435:2 429:d 419:C 408:D 400:C 396:D 390:, 378:d 372:) 369:1 363:) 360:D 357:( 351:( 348:2 335:D 318:K 314:D 310:K 308:( 306:â„“ 293:d 289:D 272:1 266:) 263:D 260:( 243:D 225:) 222:D 219:( 196:) 193:D 190:( 187:L 173:D 165:D 151:) 148:D 145:( 142:L 120:C 116:P 101:P 96:P 92:m 86:P 78:= 75:D 61:C 42:C

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
Satter Prize

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