Knowledge (XXG)

n-skeleton

Source 📝

31: 634: 1059: 957: 810: 355: 405: 704: 511: 537: 458: 991: 876: 845: 739: 664: 485: 432: 313: 548: 1133: 1002: 1111: 513:
to the "smallest possible" simplicial set so that the resulting simplicial set contains no non-degenerate simplices in degrees
1206: 1067:
The above constructions work for more general categories (instead of sets) as well, provided that the category has
707: 1211: 284:
The above definition of the skeleton of a simplicial complex is a particular case of the notion of skeleton of a
1064:(The boundary and degeneracy morphisms are given by various projections and diagonal embeddings, respectively.) 888: 176: 747: 994: 180: 357:, together with face and degeneracy maps between them satisfying a number of equations. The idea of the 318: 127: 51: 1076: 364: 90: 1080: 669: 168: 100: 82: 62: 1179: 1129: 1107: 172: 164: 75: 490: 516: 437: 969: 854: 823: 717: 642: 463: 410: 291: 1161: 35: 1099: 285: 156: 1200: 1149: 1072: 1068: 1103: 1153: 58: 1182: 86: 1128:, Progress in Mathematics, vol. 174, Basel, Boston, Berlin: Birkhäuser, 50:
This article is about mathematics. For the concept in computer graphics, see
1187: 43: 629:{\displaystyle i_{*}:\Delta ^{op}Sets\rightarrow \Delta _{\leq n}^{op}Sets} 30: 17: 225: 209: 104: 1054:{\displaystyle \dots \rightarrow K_{0}\times K_{0}\rightarrow K_{0}.} 29: 1106:, Abstract Regular Polytopes, Cambridge University Press, 2002. 1160:, Lecture Notes in Mathematics, No. 100, Berlin, New York: 1005: 972: 891: 857: 826: 750: 720: 672: 645: 551: 519: 493: 466: 440: 413: 367: 321: 294: 1071:. The coskeleton is needed to define the concept of 1053: 985: 951: 870: 839: 804: 733: 698: 658: 628: 531: 505: 479: 452: 426: 399: 349: 307: 187:has infinite dimension, in the sense that the 275:(cube) = 8 vertices, 12 edges, 6 square faces 8: 460:and then to complete the collection of the 966:is the constant simplicial set defined by 1042: 1029: 1016: 1004: 977: 971: 952:{\displaystyle cosk_{n}(K):=i^{!}i_{*}K.} 937: 927: 905: 890: 862: 856: 831: 825: 790: 780: 758: 749: 725: 719: 690: 677: 671: 650: 644: 605: 597: 569: 556: 550: 518: 492: 471: 465: 439: 418: 412: 388: 375: 366: 326: 320: 315:can be described by a collection of sets 299: 293: 993:. The 0-coskeleton is given by the Cech 542:More precisely, the restriction functor 1092: 805:{\displaystyle sk_{n}(K):=i^{*}i_{*}K.} 183:. They are particularly important when 167:. The skeletons of a space are used in 1124:Goerss, P. G.; Jardine, J. F. (1999), 288:. Briefly speaking, a simplicial set 7: 229:P (functionally represented as skel 594: 566: 25: 714:-skeleton of some simplicial set 962:For example, the 0-skeleton of 706:are comparable with the one of 350:{\displaystyle K_{i},\ i\geq 0} 137:is obtained by stopping at the 1035: 1009: 917: 911: 770: 764: 590: 394: 381: 147:These subspaces increase with 1: 407:is to first discard the sets 400:{\displaystyle sk_{n}(K_{*})} 268:(cube) = 8 vertices, 12 edges 27:Concept in algebraic topology 639:has a left adjoint, denoted 246:elements of dimension up to 699:{\displaystyle i^{*},i_{*}} 1228: 1126:Simplicial Homotopy Theory 882:-coskeleton is defined as 708:image functors for sheaves 194:do not become constant as 49: 126:In other words, given an 179:, and generally to make 506:{\displaystyle i\leq n} 1055: 987: 953: 872: 841: 806: 735: 700: 660: 630: 533: 532:{\displaystyle i>n} 507: 481: 454: 453:{\displaystyle i>n} 428: 401: 351: 309: 47: 1056: 988: 986:{\displaystyle K_{0}} 954: 873: 871:{\displaystyle i^{!}} 842: 840:{\displaystyle i_{*}} 807: 736: 734:{\displaystyle K_{*}} 701: 661: 659:{\displaystyle i^{*}} 631: 534: 508: 482: 480:{\displaystyle K_{i}} 455: 429: 427:{\displaystyle K_{i}} 402: 352: 310: 308:{\displaystyle K_{*}} 33: 1003: 970: 889: 855: 824: 748: 718: 670: 643: 549: 517: 491: 464: 438: 411: 365: 319: 292: 128:inductive definition 52:topological skeleton 1077:homotopical algebra 613: 280:For simplicial sets 261:(cube) = 8 vertices 239:)) consists of all 181:inductive arguments 1207:Algebraic topology 1180:Weisstein, Eric W. 1081:algebraic geometry 1051: 983: 949: 868: 837: 802: 731: 696: 656: 626: 593: 529: 503: 477: 450: 424: 397: 347: 305: 173:spectral sequences 169:obstruction theory 130:of a complex, the 83:simplicial complex 63:algebraic topology 61:, particularly in 48: 1135:978-3-7643-6064-1 666:. (The notations 337: 165:topological graph 76:topological space 16:(Redirected from 1219: 1212:General topology 1193: 1192: 1165: 1164: 1146: 1140: 1139:, section IV.3.2 1138: 1121: 1115: 1097: 1060: 1058: 1057: 1052: 1047: 1046: 1034: 1033: 1021: 1020: 992: 990: 989: 984: 982: 981: 958: 956: 955: 950: 942: 941: 932: 931: 910: 909: 877: 875: 874: 869: 867: 866: 846: 844: 843: 838: 836: 835: 811: 809: 808: 803: 795: 794: 785: 784: 763: 762: 740: 738: 737: 732: 730: 729: 705: 703: 702: 697: 695: 694: 682: 681: 665: 663: 662: 657: 655: 654: 635: 633: 632: 627: 612: 604: 577: 576: 561: 560: 538: 536: 535: 530: 512: 510: 509: 504: 486: 484: 483: 478: 476: 475: 459: 457: 456: 451: 433: 431: 430: 425: 423: 422: 406: 404: 403: 398: 393: 392: 380: 379: 356: 354: 353: 348: 335: 331: 330: 314: 312: 311: 306: 304: 303: 245: 228: 218: 200: 193: 186: 162: 154: 150: 143: 141: 136: 134: 125: 115:) of dimensions 114: 111:(resp. cells of 110: 98: 89:) refers to the 80: 73: 70: 41: 21: 1227: 1226: 1222: 1221: 1220: 1218: 1217: 1216: 1197: 1196: 1178: 1177: 1174: 1169: 1168: 1162:Springer-Verlag 1148: 1147: 1143: 1136: 1123: 1122: 1118: 1098: 1094: 1089: 1038: 1025: 1012: 1001: 1000: 973: 968: 967: 933: 923: 901: 887: 886: 858: 853: 852: 827: 822: 821: 818: 786: 776: 754: 746: 745: 721: 716: 715: 686: 673: 668: 667: 646: 641: 640: 565: 552: 547: 546: 515: 514: 489: 488: 467: 462: 461: 436: 435: 414: 409: 408: 384: 371: 363: 362: 322: 317: 316: 295: 290: 289: 282: 274: 267: 260: 240: 234: 220: 213: 206: 195: 192: 188: 184: 171:, to construct 160: 152: 148: 139: 138: 132: 131: 116: 112: 108: 97: 93: 81:presented as a 78: 68: 66: 55: 39: 36:hypercube graph 28: 23: 22: 15: 12: 11: 5: 1225: 1223: 1215: 1214: 1209: 1199: 1198: 1195: 1194: 1173: 1172:External links 1170: 1167: 1166: 1158:Etale homotopy 1150:Artin, Michael 1141: 1134: 1116: 1100:Peter McMullen 1091: 1090: 1088: 1085: 1069:fiber products 1062: 1061: 1050: 1045: 1041: 1037: 1032: 1028: 1024: 1019: 1015: 1011: 1008: 980: 976: 960: 959: 948: 945: 940: 936: 930: 926: 922: 919: 916: 913: 908: 904: 900: 897: 894: 865: 861: 834: 830: 817: 814: 813: 812: 801: 798: 793: 789: 783: 779: 775: 772: 769: 766: 761: 757: 753: 741:is defined as 728: 724: 693: 689: 685: 680: 676: 653: 649: 637: 636: 625: 622: 619: 616: 611: 608: 603: 600: 596: 592: 589: 586: 583: 580: 575: 572: 568: 564: 559: 555: 528: 525: 522: 502: 499: 496: 474: 470: 449: 446: 443: 421: 417: 396: 391: 387: 383: 378: 374: 370: 346: 343: 340: 334: 329: 325: 302: 298: 286:simplicial set 281: 278: 277: 276: 272: 269: 265: 262: 258: 230: 205: 202: 190: 157:discrete space 95: 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 1224: 1213: 1210: 1208: 1205: 1204: 1202: 1190: 1189: 1184: 1181: 1176: 1175: 1171: 1163: 1159: 1155: 1151: 1145: 1142: 1137: 1131: 1127: 1120: 1117: 1113: 1112:0-521-81496-0 1109: 1105: 1101: 1096: 1093: 1086: 1084: 1082: 1078: 1074: 1073:hypercovering 1070: 1065: 1048: 1043: 1039: 1030: 1026: 1022: 1017: 1013: 1006: 999: 998: 997: 996: 978: 974: 965: 946: 943: 938: 934: 928: 924: 920: 914: 906: 902: 898: 895: 892: 885: 884: 883: 881: 863: 859: 850: 832: 828: 815: 799: 796: 791: 787: 781: 777: 773: 767: 759: 755: 751: 744: 743: 742: 726: 722: 713: 709: 691: 687: 683: 678: 674: 651: 647: 623: 620: 617: 614: 609: 606: 601: 598: 587: 584: 581: 578: 573: 570: 562: 557: 553: 545: 544: 543: 540: 526: 523: 520: 500: 497: 494: 472: 468: 447: 444: 441: 419: 415: 389: 385: 376: 372: 368: 360: 344: 341: 338: 332: 327: 323: 300: 296: 287: 279: 270: 263: 256: 255: 254: 253:For example: 251: 249: 243: 238: 233: 227: 223: 216: 211: 203: 201: 198: 182: 178: 174: 170: 166: 158: 145: 129: 123: 119: 106: 102: 92: 88: 84: 77: 72: 64: 60: 53: 45: 37: 32: 19: 1186: 1157: 1154:Mazur, Barry 1144: 1125: 1119: 1104:Egon Schulte 1095: 1066: 1063: 963: 961: 879: 848: 819: 711: 638: 541: 358: 283: 252: 247: 241: 236: 231: 221: 214: 207: 196: 175:by means of 146: 121: 117: 99:that is the 67: 56: 204:In geometry 177:filtrations 59:mathematics 1201:Categories 1183:"Skeleton" 1087:References 820:Moreover, 816:Coskeleton 361:-skeleton 161:1-skeleton 159:, and the 153:0-skeleton 87:CW complex 40:1-skeleton 18:0-skeleton 1188:MathWorld 1114:(Page 29) 1036:→ 1023:× 1010:→ 1007:⋯ 939:∗ 833:∗ 792:∗ 782:∗ 727:∗ 692:∗ 679:∗ 652:∗ 599:≤ 595:Δ 591:→ 567:Δ 558:∗ 498:≤ 390:∗ 342:≥ 301:∗ 244:-polytope 217:-skeleton 135:-skeleton 105:simplices 71:-skeleton 44:tesseract 1156:(1969), 851:adjoint 226:polytope 210:geometry 142:-th step 91:subspace 710:.) The 103:of the 85:(resp. 42:of the 38:is the 1132:  1110:  878:. The 847:has a 336:  151:. The 65:, the 995:nerve 849:right 487:with 434:with 155:is a 101:union 74:of a 34:This 1130:ISBN 1108:ISBN 1079:and 524:> 445:> 271:skel 264:skel 257:skel 212:, a 199:→ ∞. 1075:in 219:of 208:In 107:of 57:In 1203:: 1185:. 1152:; 1102:, 1083:. 921::= 774::= 539:. 250:. 163:a 144:. 120:≤ 1191:. 1049:. 1044:0 1040:K 1031:0 1027:K 1018:0 1014:K 979:0 975:K 964:K 947:. 944:K 935:i 929:! 925:i 918:) 915:K 912:( 907:n 903:k 899:s 896:o 893:c 880:n 864:! 860:i 829:i 800:. 797:K 788:i 778:i 771:) 768:K 765:( 760:n 756:k 752:s 723:K 712:n 688:i 684:, 675:i 648:i 624:s 621:t 618:e 615:S 610:p 607:o 602:n 588:s 585:t 582:e 579:S 574:p 571:o 563:: 554:i 527:n 521:i 501:n 495:i 473:i 469:K 448:n 442:i 420:i 416:K 395:) 386:K 382:( 377:n 373:k 369:s 359:n 345:0 339:i 333:, 328:i 324:K 297:K 273:2 266:1 259:0 248:k 242:i 237:P 235:( 232:k 224:- 222:n 215:k 197:n 191:n 189:X 185:X 149:n 140:n 133:n 124:. 122:n 118:m 113:X 109:X 96:n 94:X 79:X 69:n 54:. 46:. 20:)

Index

0-skeleton

hypercube graph
tesseract
topological skeleton
mathematics
algebraic topology
topological space
simplicial complex
CW complex
subspace
union
simplices
inductive definition
discrete space
topological graph
obstruction theory
spectral sequences
filtrations
inductive arguments
geometry
polytope
simplicial set
image functors for sheaves
nerve
fiber products
hypercovering
homotopical algebra
algebraic geometry
Peter McMullen

Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.