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Computably inseparable

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of refutable formulas are computably inseparable. The inseparability of the sets of provable and refutable formulas holds for many other formal theories of arithmetic (Smullyan 1958).
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that are disjoint, non-complementary, and computably inseparable. Moreover, it is possible for
1088: 1055: 665: 46:. These sets arise in the study of computability theory itself, particularly in relation to 1080: 1023: 996: 838: 17: 1100: 1035: 1008: 1096: 1051: 1031: 1015: 1004: 807: 1022:, Stud. Logic Found. Math., vol. 139, Amsterdam: North-Holland, pp. 1041–1176, 816: 574:
and its complement are computably inseparable. However, there are many examples of sets
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Zeitschrift für Mathematische Logik und Grundlagen der Mathematik
81:. Computably inseparable sets also arise in the study of 1071:(1958), "Undecidability and recursive inseparability", 903: 847: 819: 752: 692: 668: 640: 620: 600: 580: 560: 540: 504: 484: 456: 436: 416: 373: 342: 316: 284: 258: 236: 216: 191: 171: 151: 99: 53: 949:{\displaystyle B=\{\#(\psi ):PA\vdash \lnot \psi \}} 1050:, Graduate Texts in Mathematics, Berlin, New York: 1043: 948: 889: 825: 798: 738: 674: 646: 626: 606: 586: 566: 546: 510: 490: 467: 442: 422: 398: 359: 328: 302: 270: 244: 222: 199: 177: 157: 137: 71: 34:, two disjoint sets of natural numbers are called 1018:(1998), "A survey of recursive combinatorics", 450:itself is a separating set for the pair, as is 890:{\displaystyle A=\{\#(\psi ):PA\vdash \psi \}} 138:{\displaystyle \mathbb {N} =\{0,1,2,\dots \}} 8: 943: 910: 884: 854: 793: 759: 733: 699: 654:to be computably inseparable, disjoint, and 132: 108: 399:{\displaystyle C'=\mathbb {N} \setminus C} 1020:Handbook of recursive mathematics, Vol. 2 902: 846: 818: 799:{\displaystyle B=\{e:\varphi _{e}(0)=1\}} 772: 751: 739:{\displaystyle A=\{e:\varphi _{e}(0)=0\}} 712: 691: 667: 639: 619: 599: 579: 559: 539: 503: 483: 455: 435: 415: 386: 385: 372: 341: 315: 283: 257: 238: 237: 235: 215: 193: 192: 190: 170: 150: 101: 100: 98: 63: 58: 52: 966: 390: 522:separating set, then the two sets are 42:if they cannot be "separated" with a 7: 991:classes in computability theory", 937: 913: 857: 820: 303:{\displaystyle B\cap C=\emptyset } 297: 55: 25: 897:of provable formulas and the set 993:Handbook of computability theory 682:be the standard indexing of the 93:The natural numbers are the set 27:Concept in computability theory 922: 916: 866: 860: 784: 778: 724: 718: 554:is a non-computable set, then 83:Gödel's incompleteness theorem 1: 1028:10.1016/S0049-237X(98)80049-9 1001:10.1016/S0049-237X(99)80018-4 360:{\displaystyle B\subseteq C'} 806:are computably inseparable ( 684:partial computable functions 329:{\displaystyle A\subseteq C} 271:{\displaystyle A\subseteq C} 245:{\displaystyle \mathbb {N} } 200:{\displaystyle \mathbb {N} } 72:{\displaystyle \Pi _{1}^{0}} 18:Recursively inseparable sets 478:If a pair of disjoint sets 1133: 982:Cenzer, Douglas (1999), "Π 145:. Given disjoint subsets 1085:10.1002/malq.19580040705 1042:Monk, J. Donald (1976), 675:{\displaystyle \varphi } 40:recursively inseparable 973:Monk 1976, p. 100 950: 891: 827: 800: 740: 676: 648: 628: 608: 588: 568: 548: 524:computably inseparable 512: 492: 469: 444: 424: 400: 361: 330: 304: 272: 246: 224: 201: 179: 159: 139: 73: 36:computably inseparable 951: 892: 828: 801: 741: 677: 656:computably enumerable 649: 629: 609: 589: 569: 549: 513: 493: 470: 445: 425: 401: 362: 331: 305: 273: 247: 225: 202: 180: 160: 140: 74: 1117:Computability theory 1069:Smullyan, Raymond M. 901: 845: 837:for the formulas of 817: 810:1998, p. 1047). 750: 690: 666: 638: 618: 598: 578: 558: 538: 502: 482: 454: 434: 414: 371: 340: 314: 282: 256: 234: 214: 189: 169: 149: 97: 51: 32:computability theory 310:(or equivalently, 68: 1046:Mathematical Logic 946: 887: 826:{\displaystyle \#} 823: 796: 736: 672: 644: 624: 604: 584: 564: 544: 508: 488: 468:{\displaystyle B'} 465: 440: 420: 396: 357: 326: 300: 268: 242: 220: 197: 175: 155: 135: 69: 54: 1079:(7–11): 143–147, 1061:978-0-387-90170-1 647:{\displaystyle B} 627:{\displaystyle A} 607:{\displaystyle B} 587:{\displaystyle A} 567:{\displaystyle A} 547:{\displaystyle A} 511:{\displaystyle B} 491:{\displaystyle A} 443:{\displaystyle A} 430:). For example, 423:{\displaystyle C} 223:{\displaystyle C} 178:{\displaystyle B} 158:{\displaystyle A} 16:(Redirected from 1124: 1103: 1064: 1049: 1038: 1016:Gasarch, William 1011: 990: 989: 974: 971: 955: 953: 952: 947: 896: 894: 893: 888: 839:Peano arithmetic 832: 830: 829: 824: 805: 803: 802: 797: 777: 776: 745: 743: 742: 737: 717: 716: 686:. Then the sets 681: 679: 678: 673: 653: 651: 650: 645: 633: 631: 630: 625: 613: 611: 610: 605: 593: 591: 590: 585: 573: 571: 570: 565: 553: 551: 550: 545: 517: 515: 514: 509: 497: 495: 494: 489: 474: 472: 471: 466: 464: 449: 447: 446: 441: 429: 427: 426: 421: 405: 403: 402: 397: 389: 381: 366: 364: 363: 358: 356: 335: 333: 332: 327: 309: 307: 306: 301: 277: 275: 274: 269: 251: 249: 248: 243: 241: 229: 227: 226: 221: 206: 204: 203: 198: 196: 184: 182: 181: 176: 164: 162: 161: 156: 144: 142: 141: 136: 104: 78: 76: 75: 70: 67: 62: 21: 1132: 1131: 1127: 1126: 1125: 1123: 1122: 1121: 1107: 1106: 1067: 1062: 1052:Springer-Verlag 1041: 1014: 988: 985: 984: 983: 981: 978: 977: 972: 968: 963: 899: 898: 843: 842: 841:. Then the set 835:Gödel numbering 815: 814: 808:William Gasarch 768: 748: 747: 708: 688: 687: 664: 663: 636: 635: 616: 615: 596: 595: 576: 575: 556: 555: 536: 535: 532: 500: 499: 480: 479: 457: 452: 451: 432: 431: 412: 411: 374: 369: 368: 349: 338: 337: 312: 311: 280: 279: 254: 253: 232: 231: 230:is a subset of 212: 211: 187: 186: 167: 166: 147: 146: 95: 94: 91: 49: 48: 28: 23: 22: 15: 12: 11: 5: 1130: 1128: 1120: 1119: 1109: 1108: 1105: 1104: 1065: 1060: 1039: 1012: 986: 976: 975: 965: 964: 962: 959: 958: 957: 945: 942: 939: 936: 933: 930: 927: 924: 921: 918: 915: 912: 909: 906: 886: 883: 880: 877: 874: 871: 868: 865: 862: 859: 856: 853: 850: 833:be a standard 822: 811: 795: 792: 789: 786: 783: 780: 775: 771: 767: 764: 761: 758: 755: 735: 732: 729: 726: 723: 720: 715: 711: 707: 704: 701: 698: 695: 671: 643: 623: 603: 583: 563: 543: 531: 528: 507: 487: 463: 460: 439: 419: 395: 392: 388: 384: 380: 377: 355: 352: 348: 345: 325: 322: 319: 299: 296: 293: 290: 287: 267: 264: 261: 240: 219: 209:separating set 195: 174: 154: 134: 131: 128: 125: 122: 119: 116: 113: 110: 107: 103: 90: 87: 66: 61: 57: 44:computable set 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 1129: 1118: 1115: 1114: 1112: 1102: 1098: 1094: 1090: 1086: 1082: 1078: 1074: 1070: 1066: 1063: 1057: 1053: 1048: 1047: 1040: 1037: 1033: 1029: 1025: 1021: 1017: 1013: 1010: 1006: 1002: 998: 994: 980: 979: 970: 967: 960: 940: 934: 931: 928: 925: 919: 907: 904: 881: 878: 875: 872: 869: 863: 851: 848: 840: 836: 812: 809: 790: 787: 781: 773: 769: 765: 762: 756: 753: 730: 727: 721: 713: 709: 705: 702: 696: 693: 685: 669: 661: 660: 659: 657: 641: 621: 601: 581: 561: 541: 529: 527: 525: 521: 505: 485: 476: 461: 458: 437: 417: 409: 393: 382: 378: 375: 353: 350: 346: 343: 323: 320: 317: 294: 291: 288: 285: 265: 262: 259: 217: 210: 172: 152: 129: 126: 123: 120: 117: 114: 111: 105: 88: 86: 84: 80: 64: 59: 45: 41: 37: 33: 19: 1076: 1072: 1045: 1019: 992: 969: 533: 523: 477: 406:denotes the 208: 92: 39: 35: 29: 252:such that 961:References 520:computable 408:complement 89:Definition 1093:0044-3050 941:ψ 938:¬ 935:⊢ 920:ψ 914:# 882:ψ 879:⊢ 864:ψ 858:# 821:# 770:φ 710:φ 670:φ 391:∖ 347:⊆ 321:⊆ 298:∅ 289:∩ 263:⊆ 130:… 56:Π 1111:Category 530:Examples 462:′ 379:′ 367:, where 354:′ 1101:0099293 1036:1673598 1009:1720779 518:has no 79:classes 1099:  1091:  1058:  1034:  1007:  1089:ISSN 1056:ISBN 813:Let 746:and 662:Let 634:and 594:and 498:and 336:and 278:and 207:, a 165:and 1081:doi 1024:doi 997:doi 658:. 534:If 410:of 185:of 38:or 30:In 1113:: 1097:MR 1095:, 1087:, 1075:, 1054:, 1032:MR 1030:, 1005:MR 1003:, 526:. 475:. 85:. 1083:: 1077:4 1026:: 999:: 987:1 944:} 932:A 929:P 926:: 923:) 917:( 911:{ 908:= 905:B 885:} 876:A 873:P 870:: 867:) 861:( 855:{ 852:= 849:A 794:} 791:1 788:= 785:) 782:0 779:( 774:e 766:: 763:e 760:{ 757:= 754:B 734:} 731:0 728:= 725:) 722:0 719:( 714:e 706:: 703:e 700:{ 697:= 694:A 642:B 622:A 602:B 582:A 562:A 542:A 506:B 486:A 459:B 438:A 418:C 394:C 387:N 383:= 376:C 351:C 344:B 324:C 318:A 295:= 292:C 286:B 266:C 260:A 239:N 218:C 194:N 173:B 153:A 133:} 127:, 124:2 121:, 118:1 115:, 112:0 109:{ 106:= 102:N 65:0 60:1 20:)

Index

Recursively inseparable sets
computability theory
computable set
Π 1 0 {\displaystyle \Pi _{1}^{0}} classes
Gödel's incompleteness theorem
complement
computable
computably enumerable
partial computable functions
William Gasarch
Gödel numbering
Peano arithmetic
doi
10.1016/S0049-237X(99)80018-4
MR
1720779
Gasarch, William
doi
10.1016/S0049-237X(98)80049-9
MR
1673598
Mathematical Logic
Springer-Verlag
ISBN
978-0-387-90170-1
Smullyan, Raymond M.
doi
10.1002/malq.19580040705
ISSN
0044-3050

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