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Integrally convex set

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527: 356: 557:= { (0,0), (1,0), (2,0), (1,1), (2,1) } is integrally convex, and indeed admits an integral triangulation, e.g. with the three simplices {(0,0),(1,0),(1,1)} and {(1,0),(2,0),(2,1)} and {(1,0),(1,1),(2,1)}. See image at the right. 468: 520: 325: 263: 226: 186: 138: 73: 637: 620:
Chen, Xi; Deng, Xiaotie (2006). "A Simplicial Approach for Discrete Fixed Point Theorems". In Chen, Danny Z.; Lee, D. T. (eds.).
493:
The vertices of every simplex of the triangulation lie in the same "cell" (hypercube of side-length 1) of the integer grid
701: 471: 438: 526: 496: 301: 239: 202: 162: 114: 49: 624:. Lecture Notes in Computer Science. Vol. 4112. Berlin, Heidelberg: Springer. pp. 3–12. 602: 88: 677: 633: 594: 188:, since it contains all the real points that are convex combinations of the integer points in 32: 654: 669: 625: 586: 432:
Iimura, Murota and Tamura have shown the following property of integrally convex set.
355: 695: 606: 17: 99:, where "near" means that the distance between each two coordinates is less than 1. 673: 287:} }. These are the integer points that are considered "nearby" to the real point 577:
Yang, Zaifu (2009-12-01). "Discrete fixed point analysis and its applications".
148: 80: 590: 36: 681: 598: 629: 550:, or has to include simplices that are not contained in a single cell. 542:) does not admit an integral triangulation: every triangulation of ch( 525: 354: 424:= { (0,0), (1,0), (2,0), (1,1), (2,1) } is integrally convex. 653:
Iimura, Takuya; Murota, Kazuo; Tamura, Akihisa (2005-12-01).
486:
The vertices of the triangulation are the vertices of
499: 441: 371:= { (0,0), (1,0), (2,0), (2,1) }. Its convex hull ch( 304: 242: 205: 165: 117: 52: 514: 470:be a finite integrally convex set. There exists a 462: 319: 257: 220: 180: 132: 67: 579:Journal of Fixed Point Theory and Applications 8: 655:"Discrete fixed point theorem reconsidered" 506: 502: 501: 498: 463:{\displaystyle X\subset \mathbb {Z} ^{n}} 454: 450: 449: 440: 311: 307: 306: 303: 249: 245: 244: 241: 212: 208: 207: 204: 172: 168: 167: 164: 124: 120: 119: 116: 59: 55: 54: 51: 538:is not integrally convex, and indeed ch( 566: 390:) = {(1,0), (2,0), (1,1), (2,1) }. So 546:), either has to add vertices not in 7: 572: 570: 375:) contains, for example, the point 75:is integrally convex if any point 25: 662:Journal of Mathematical Economics 515:{\displaystyle \mathbb {Z} ^{n}} 320:{\displaystyle \mathbb {Z} ^{n}} 258:{\displaystyle \mathbb {Z} ^{n}} 221:{\displaystyle \mathbb {R} ^{n}} 181:{\displaystyle \mathbb {R} ^{n}} 133:{\displaystyle \mathbb {Z} ^{n}} 68:{\displaystyle \mathbb {Z} ^{n}} 398:) = {(1,0), (2,0), (2,1)}. But 1: 674:10.1016/j.jmateco.2005.03.001 410:)). See image at the right. 417:is not integrally convex. 622:Computing and Combinatorics 35:analogue of the concept of 718: 382:The integer points nearby 591:10.1007/s11784-009-0130-9 359:Non-integrally convex set 531: 516: 464: 360: 321: 259: 222: 182: 134: 87:can be expressed as a 69: 553:In contrast, the set 530:Integrally convex set 529: 517: 465: 420:In contrast, the set 358: 322: 260: 223: 183: 135: 70: 29:integrally convex set 18:Integrally-convex set 497: 439: 302: 240: 203: 163: 115: 50: 46:of the integer grid 630:10.1007/11809678_3 532: 512: 460: 361: 317: 255: 218: 178: 130: 89:convex combination 65: 702:Discrete geometry 639:978-3-540-36926-4 329:integrally convex 279:| < 1 for all 159:) is a subset of 91:of the points of 33:discrete geometry 16:(Redirected from 709: 686: 685: 668:(8): 1030–1036. 659: 650: 644: 643: 617: 611: 610: 574: 534:The example set 521: 519: 518: 513: 511: 510: 505: 469: 467: 466: 461: 459: 458: 453: 339:) is also in ch( 326: 324: 323: 318: 316: 315: 310: 264: 262: 261: 256: 254: 253: 248: 227: 225: 224: 219: 217: 216: 211: 187: 185: 184: 179: 177: 176: 171: 139: 137: 136: 131: 129: 128: 123: 95:that are "near" 74: 72: 71: 66: 64: 63: 58: 21: 717: 716: 712: 711: 710: 708: 707: 706: 692: 691: 690: 689: 657: 652: 651: 647: 640: 619: 618: 614: 576: 575: 568: 563: 500: 495: 494: 448: 437: 436: 430: 353: 331:if every point 305: 300: 299: 277: 270: 243: 238: 237: 228:, denote near( 206: 201: 200: 166: 161: 160: 155:. Note that ch( 118: 113: 112: 111:be a subset of 105: 53: 48: 47: 23: 22: 15: 12: 11: 5: 715: 713: 705: 704: 694: 693: 688: 687: 645: 638: 612: 585:(2): 351–371. 565: 564: 562: 559: 524: 523: 509: 504: 491: 457: 452: 447: 444: 429: 426: 379:= (1.2, 0.5). 352: 349: 314: 309: 275: 268: 252: 247: 215: 210: 195:For any point 175: 170: 127: 122: 104: 101: 62: 57: 24: 14: 13: 10: 9: 6: 4: 3: 2: 714: 703: 700: 699: 697: 683: 679: 675: 671: 667: 663: 656: 649: 646: 641: 635: 631: 627: 623: 616: 613: 608: 604: 600: 596: 592: 588: 584: 580: 573: 571: 567: 560: 558: 556: 551: 549: 545: 541: 537: 528: 507: 492: 489: 485: 484: 483: 481: 477: 473: 472:triangulation 455: 445: 442: 433: 427: 425: 423: 418: 416: 411: 409: 405: 402:is not in ch( 401: 397: 393: 389: 385: 380: 378: 374: 370: 366: 357: 350: 348: 346: 342: 338: 334: 330: 312: 297: 292: 290: 286: 282: 278: 271: 250: 235: 232:)  := { 231: 213: 198: 193: 191: 173: 158: 154: 150: 146: 143:Denote by ch( 141: 125: 110: 102: 100: 98: 94: 90: 86: 82: 78: 60: 45: 40: 39:in geometry. 38: 34: 30: 19: 665: 661: 648: 621: 615: 582: 578: 554: 552: 547: 543: 539: 535: 533: 487: 479: 475: 434: 431: 421: 419: 414: 412: 407: 403: 399: 395: 391: 387: 383: 381: 376: 372: 368: 367:= 2 and let 364: 362: 344: 340: 336: 332: 328: 295: 293: 288: 284: 280: 273: 266: 233: 229: 196: 194: 189: 156: 152: 144: 142: 108: 106: 96: 92: 84: 76: 43: 41: 28: 26: 149:convex hull 103:Definitions 81:convex hull 561:References 478:) that is 428:Properties 413:Therefore 327:is called 283:in {1,..., 37:convex set 682:0304-4068 607:122640338 599:1661-7746 446:⊂ 386:are near( 294:A subset 42:A subset 696:Category 482:, i.e.: 480:integral 406:∩ near( 394:∩ near( 351:Example 343:∩ near( 79:in the 31:is the 680:  636:  605:  597:  474:of ch( 335:in ch( 147:) the 658:(PDF) 603:S2CID 678:ISSN 634:ISBN 595:ISSN 435:Let 363:Let 347:)). 265:| | 107:Let 670:doi 626:doi 587:doi 298:of 236:in 199:in 151:of 83:of 27:An 698:: 676:. 666:41 664:. 660:. 632:. 601:. 593:. 581:. 569:^ 291:. 272:- 192:. 140:. 684:. 672:: 642:. 628:: 609:. 589:: 583:6 555:Y 548:X 544:X 540:X 536:X 522:. 508:n 503:Z 490:; 488:X 476:X 456:n 451:Z 443:X 422:Y 415:X 408:y 404:X 400:y 396:y 392:X 388:y 384:y 377:y 373:X 369:X 365:n 345:y 341:X 337:X 333:y 313:n 308:Z 296:X 289:y 285:n 281:i 276:i 274:y 269:i 267:z 251:n 246:Z 234:z 230:y 214:n 209:R 197:y 190:X 174:n 169:R 157:X 153:X 145:X 126:n 121:Z 109:X 97:y 93:X 85:X 77:y 61:n 56:Z 44:X 20:)

Index

Integrally-convex set
discrete geometry
convex set
convex hull
convex combination
convex hull

triangulation



doi
10.1007/s11784-009-0130-9
ISSN
1661-7746
S2CID
122640338
doi
10.1007/11809678_3
ISBN
978-3-540-36926-4
"Discrete fixed point theorem reconsidered"
doi
10.1016/j.jmateco.2005.03.001
ISSN
0304-4068
Category
Discrete geometry

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