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Inverse semigroup

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Thus, any inverse semigroup can be embedded in a symmetric inverse semigroup, and with image closed under the inverse operation on partial bijections. Conversely, any subsemigroup of the symmetric inverse semigroup closed under the inverse operation is an inverse semigroup. Hence a semigroup
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The above composition of partial transformations of a set gives rise to a symmetric inverse semigroup. There is another way of composing partial transformations, which is more restrictive than that used above: two partial transformations
1962: 2274: 4389:, which states that an inductive groupoid can always be constructed from an inverse semigroup, and conversely. More precisely, an inverse semigroup is precisely a groupoid in the category of posets that is an 267: 708: 2631: 1368: 1301: 3923: 3791: 4037: 3874: 3530: 3340: 2023: 1578: 1202: 1141: 2375: 3738: 2425: 4377:; otherwise, the composition αβ is undefined. Under this alternative composition, the collection of all partial one-one transformations of a set forms not an inverse semigroup but an 3542: 4345:
who showed that elements of the free inverse semigroup can be naturally regarded as trees, known as Munn trees. Multiplication in the free inverse semigroup has a correspondent on
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Every inverse semigroup S has a E-unitary cover; that is there exists an idempotent separating surjective homomorphism from some E-unitary semigroup T onto S.
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to take account of this. With the addition of this empty transformation, the composition of partial transformations of a set becomes an everywhere-defined
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commute; this has led to two distinct classes of generalisations of an inverse semigroup: semigroups in which (1) holds, but (2) does not, and vice versa.
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in which every element has a unique inverse. Inverse semigroups appear in a range of contexts; for example, they can be employed in the study of
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Since his father was German, Wagner preferred the German transliteration of his name (with a "W", rather than a "V") from Cyrillic – see
199: 825:{\displaystyle a\,{\mathcal {L}}\,b\Longleftrightarrow a^{-1}a=b^{-1}b,\quad a\,{\mathcal {R}}\,b\Longleftrightarrow aa^{-1}=bb^{-1}} 2572: 288:. It was Wagner, however, who was the first to observe that the composition of partial transformations is a special case of the 1312: 1250: 5564: 5481: 5462: 5021: 4136: 5428: 5710: 5799: 4730: 4677: 3879: 3747: 1742:, however, there is no need to do so, since this property follows from the above definition, via the following theorem: 3996: 3833: 3489: 3299: 1997: 1539: 1163: 1102: 344: 111: 4341:
for free inverse semigroups is much more intricate than that of free groups. A celebrated result in this area due to
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of an inverse semigroup is an inverse semigroup; the inverse of an element is always mapped to the inverse of the
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is isomorphic to a subsemigroup of the symmetric inverse semigroup closed under inverses if and only if
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Gonçalves, D; Sobottka, M; Starling, C (2017). "Inverse semigroup shifts over countable alphabets".
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Multiplication table example. It is associative and every element has its own inverse according to
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Homological Algebra: The Interplay of Homology with Distributive Lattices and Orthodox Semigroups
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One class of inverse semigroups that has been studied extensively over the years is the class of
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are defined on inverse semigroups in exactly the same way as for any other semigroup: a
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of the class of locally inverse semigroups and the class of orthodox semigroups.
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Wagner, V. V. (1953). "The theory of generalised heaps and generalised groups".
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Exel, R. (1998). "Partial actions of groups and actions of inverse semigroups".
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Gołab, St. (1939). "Über den Begriff der "Pseudogruppe von Transformationen"".
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it is possible to obtain an analogous result under additional hypotheses on
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There are a number of equivalent characterisations of an inverse semigroup
5687: 5333:. Mathematical Surveys of the American Mathematical Society. Vol. 7. 5595:
Preston, G. B. (1954b). "Inverse semi-groups with minimal right ideals".
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McAlister, D. B. (1974a). "Groups, semilattices and inverse semigroups".
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relation ≤ (sometimes denoted by ω), which is defined by the following:
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are composed if, and only if, the image of α is equal to the domain of
2269:{\displaystyle a\in S,e\in E(S),a\,\rho \,e\Longrightarrow a\in E(S).} 356:). This is the "archetypal" inverse semigroup, in the same way that a 5784: 4584:
Amongst the non-regular generalisations of an inverse semigroup are:
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in 1954. Both authors arrived at inverse semigroups via the study of
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One of the earliest results proved about inverse semigroups was the
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will denote the semilattice of idempotents of an inverse semigroup
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Preston, G. B. (1954c). "Representations of inverse semi-groups".
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if every element has at least one inverse; equivalently, for each
3968:-unitary monoid. McAlister's covering theorem has been refined by 3956:
maximal element above it in the natural partial order, i.e. every
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Examples of regular generalisations of an inverse semigroup are:
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The natural partial order on an inverse semigroup interacts with
262:{\displaystyle \operatorname {dom} \alpha \beta =\alpha ^{-1}\,} 2647:-unitary inverse semigroups is the following construction. Let 2105:
is a group. In the set of all group congruences on a semigroup
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is compatible with both multiplication and inversion, that is,
374:§ Homomorphisms and representations of inverse semigroups 429:
are not necessarily equal to the identity, but they are both
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form a semilattice under the product operation, products on
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For a brief introduction to inverse semigroups, see either
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simply reduces to equality, since the identity is the only
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is an inverse semigroup under this multiplication, with
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that is compatible with semigroup multiplication, i.e.,
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Homomorphisms and representations of inverse semigroups
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Inverse categories have found various applications in
3536:. A McAlister triple is used to define the following: 4155: 4097: 4073: 4049: 3999: 3882: 3836: 3750: 3669: 3545: 3492: 3464: 3440: 3392: 3356: 3302: 3256: 3193: 3148: 3120: 3061: 3017: 2977: 2939: 2911: 2879: 2851: 2825: 2802: 2772: 2736: 2709: 2681: 2653: 2575: 2544: 2516: 2389: 2339: 2197: 2057: 2031: 2000: 1973: 1904: 1798: 1542: 1494: 1451: 1315: 1253: 1166: 1105: 711: 672: 633: 597: 573: 545: 521: 313: 202: 5474:
Inverse Semigroups: The Theory of Partial Symmetries
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can be composed (from left to right) on the largest
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Inverse semigroups were introduced independently by
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Semigroups: An Introduction to the Structure Theory
4606:This notion of inverse also readily generalizes to 698:. There is therefore a simple characterisation of 5761:"On inverse categories and transfer in cohomology" 4397:and whose poset of objects is a meet-semilattice. 4326: 4107: 4083: 4059: 4031: 3918:{\displaystyle P(G,{\mathcal {X}},{\mathcal {Y}})} 3917: 3868: 3786:{\displaystyle P(G,{\mathcal {X}},{\mathcal {Y}})} 3785: 3732: 3649: 3524: 3474: 3450: 3402: 3366: 3342:is also assumed to have the following properties: 3334: 3266: 3203: 3158: 3130: 3071: 3027: 2987: 2949: 2921: 2889: 2861: 2835: 2808: 2782: 2746: 2719: 2691: 2663: 2625: 2550: 2522: 2419: 2369: 2291:-unitary inverse semigroups: an inverse semigroup 2268: 2078: 2043: 2017: 1979: 1956: 1815: 1572: 1506: 1463: 1362: 1295: 1196: 1135: 824: 682: 643: 607: 583: 555: 531: 330: 261: 5768:Proceedings of the Edinburgh Mathematical Society 5747:More comprehensive introductions can be found in 5526:Transactions of the American Mathematical Society 5493:Transactions of the American Mathematical Society 5354:Proceedings of the Edinburgh Mathematical Society 4597:Weakly (left, right, two-sided) ample semigroups. 4594:(Left, right, two-sided) semiadequate semigroups. 4032:{\displaystyle (G,{\mathcal {X}},{\mathcal {Y}})} 3869:{\displaystyle (G,{\mathcal {X}},{\mathcal {Y}})} 3525:{\displaystyle (G,{\mathcal {X}},{\mathcal {Y}})} 3335:{\displaystyle (G,{\mathcal {X}},{\mathcal {Y}})} 2018:{\displaystyle a\,\sigma \,b\Longleftrightarrow } 5522:"Groups, semilattices and inverse semigroups II" 5398:Proceedings of the American Mathematical Society 3993:-inverse semigroups as well. A McAlister triple 1573:{\displaystyle e\leq f\Longleftrightarrow e=ef,} 1197:{\displaystyle a\leq b\Longleftrightarrow a=bf,} 1136:{\displaystyle a\leq b\Longleftrightarrow a=eb,} 338:of all partial one-one transformations of a set 5737: 5574:Preston, G. B. (1954a). "Inverse semi-groups". 5200: 5198: 5034: 4971: 4814:, then a much more comprehensive exposition in 3929:-unitary inverse semigroup. Conversely, every 2370:{\displaystyle es\in E\Longrightarrow s\in E.} 4588:(Left, right, two-sided) adequate semigroups. 2487:of idempotents, and minimum group congruence 1595:) give least upper bounds with respect to ≤. 941:. It has no identity and is not commutative. 193:upon which it "makes sense" to compose them: 8: 5295:Hines, Peter; Braunstein, Samuel L. (2010). 4318: 4156: 3644: 3581: 862:form an inverse semigroup under composition. 5701:Proceedings of the USSR Academy of Sciences 5303:. Cambridge University Press. p. 369. 5618:Journal of the London Mathematical Society 5597:Journal of the London Mathematical Society 5576:Journal of the London Mathematical Society 5301:Semantic Techniques in Quantum Computation 5189: 4591:(Left, right, two-sided) ample semigroups. 4273: 4267: 4193: 3816:. One of the main results in the study of 3733:{\displaystyle (A,g)(B,h)=(A\wedge gB,gh)} 2420:{\displaystyle se\in E\Rightarrow s\in E.} 1389:reduces to restriction of mappings, i.e., 5659: 5537: 5409: 5365: 5299:. In Gay and, Simon; Mackie, Ian (eds.). 4997: 4766:(2nd ed.). CRC Press. p. 1528. 4577:of generalised inverse semigroups is the 4312: 4299: 4268: 4255: 4239: 4220: 4204: 4169: 4154: 4099: 4098: 4096: 4075: 4074: 4072: 4051: 4050: 4048: 4020: 4019: 4010: 4009: 3998: 3906: 3905: 3896: 3895: 3881: 3857: 3856: 3847: 3846: 3835: 3774: 3773: 3764: 3763: 3749: 3668: 3638: 3637: 3622: 3603: 3602: 3569: 3568: 3559: 3558: 3544: 3513: 3512: 3503: 3502: 3491: 3466: 3465: 3463: 3442: 3441: 3439: 3394: 3393: 3391: 3358: 3357: 3355: 3323: 3322: 3313: 3312: 3301: 3258: 3257: 3255: 3195: 3194: 3192: 3150: 3149: 3147: 3122: 3121: 3119: 3063: 3062: 3060: 3019: 3018: 3016: 2979: 2978: 2976: 2941: 2940: 2938: 2913: 2912: 2910: 2881: 2880: 2878: 2853: 2852: 2850: 2827: 2826: 2824: 2801: 2774: 2773: 2771: 2738: 2737: 2735: 2711: 2710: 2708: 2683: 2682: 2680: 2655: 2654: 2652: 2611: 2595: 2574: 2543: 2515: 2388: 2338: 2238: 2234: 2196: 2173:-unitary inverse semigroups (see below). 2056: 2030: 2008: 2004: 1999: 1972: 1944: 1940: 1927: 1923: 1912: 1908: 1903: 1807: 1801: 1800: 1797: 1541: 1503: 1497: 1496: 1495: 1493: 1460: 1454: 1453: 1452: 1450: 1348: 1332: 1314: 1252: 1165: 1104: 813: 794: 780: 774: 773: 772: 753: 734: 723: 717: 716: 715: 710: 674: 673: 671: 635: 634: 632: 599: 598: 596: 575: 574: 572: 547: 546: 544: 523: 522: 520: 481:has a unique inverse, in the above sense. 322: 316: 315: 312: 307:. Under this composition, the collection 258: 249: 201: 5327:Clifford, A. H.; Preston, G. B. (1967). 5252: 4827: 1385:. In a symmetric inverse semigroup, the 943: 5748: 4763:CRC Concise Encyclopedia of Mathematics 4752: 4131:of the free inverse semigroup on a set 3989:-theorem has been used to characterize 1967:Of particular interest is the relation 342:forms an inverse semigroup, called the 5752: 5216: 5204: 5134: 5122: 5098: 5086: 5074: 5050: 5013: 4959: 4912: 4852: 4815: 4811: 4798: 4786: 4127:is possible for inverse semigroups. A 2093:is a congruence and, in fact, it is a 5741: 5297:"The Structure of Partial Isometries" 5240: 5228: 5185: 5173: 5110: 5062: 5046: 4947: 4935: 4923: 4900: 4888: 4876: 4864: 4840: 4409:can be defined by the conditions (1) 4405:As noted above, an inverse semigroup 4401:Generalisations of inverse semigroups 2491:. Then the following are equivalent: 7: 4614:is simply a category in which every 4387:Ehresmann–Schein–Nambooripad Theorem 3960:-class has a maximal element. Every 2097:, meaning that the factor semigroup 177:be partial transformations of a set 4135:may be obtained by considering the 3948:An inverse semigroup is said to be 2430:One further characterisation of an 5429:"(Weakly) left E-ample semigroups" 5330:The Algebraic Theory of Semigroups 5053:and, independently, Preston 1954c. 4495:is an inverse semigroup, for each 4043:-inverse semigroup if and only if 2758:, that is, every pair of elements 1987:, defined on an inverse semigroup 1816:{\displaystyle {\mathcal {I}}_{S}} 1781:is an inverse semigroup, then the 1507:{\displaystyle \,{\mathcal {R}}\,} 1464:{\displaystyle \,{\mathcal {L}}\,} 462:inverse monoid), is, of course, a 331:{\displaystyle {\mathcal {I}}_{X}} 14: 5256: 1877:Congruences on inverse semigroups 1207:for some (in general, different) 5455:Fundamentals of Semigroup Theory 5274:. World Scientific. p. 55. 4360:Connections with category theory 3952:-inverse if every element has a 3978:Every inverse semigroup has an 3820:-unitary inverse semigroups is 1919: 1399:if, and only if, the domain of 768: 290:composition of binary relations 5721:. Novaya Seriya (in Russian). 5698:(1952). "Generalised groups". 4810:First a short announcement in 4527:Generalised inverse semigroups 4352:Any free inverse semigroup is 4309: 4286: 4269: 4264: 4194: 4187: 4159: 4137:free semigroup with involution 4108:{\displaystyle {\mathcal {X}}} 4084:{\displaystyle {\mathcal {X}}} 4060:{\displaystyle {\mathcal {Y}}} 4026: 4000: 3933:-unitary inverse semigroup is 3912: 3886: 3863: 3837: 3780: 3754: 3727: 3703: 3697: 3685: 3682: 3670: 3596: 3584: 3575: 3549: 3519: 3493: 3475:{\displaystyle {\mathcal {Y}}} 3451:{\displaystyle {\mathcal {Y}}} 3403:{\displaystyle {\mathcal {Y}}} 3367:{\displaystyle {\mathcal {X}}} 3329: 3303: 3267:{\displaystyle {\mathcal {X}}} 3204:{\displaystyle {\mathcal {X}}} 3159:{\displaystyle {\mathcal {X}}} 3131:{\displaystyle {\mathcal {X}}} 3072:{\displaystyle {\mathcal {X}}} 3028:{\displaystyle {\mathcal {X}}} 2988:{\displaystyle {\mathcal {Y}}} 2950:{\displaystyle {\mathcal {Y}}} 2922:{\displaystyle {\mathcal {X}}} 2890:{\displaystyle {\mathcal {X}}} 2862:{\displaystyle {\mathcal {Y}}} 2836:{\displaystyle {\mathcal {Y}}} 2783:{\displaystyle {\mathcal {Y}}} 2747:{\displaystyle {\mathcal {Y}}} 2720:{\displaystyle {\mathcal {X}}} 2692:{\displaystyle {\mathcal {Y}}} 2664:{\displaystyle {\mathcal {X}}} 2585: 2402: 2352: 2260: 2254: 2242: 2225: 2219: 2012: 1931: 1552: 1403:is contained in the domain of 1325: 1275: 1176: 1115: 847:Examples of inverse semigroups 784: 727: 683:{\displaystyle {\mathcal {R}}} 644:{\displaystyle {\mathcal {L}}} 608:{\displaystyle {\mathcal {R}}} 584:{\displaystyle {\mathcal {L}}} 563:-class contains precisely one 556:{\displaystyle {\mathcal {R}}} 532:{\displaystyle {\mathcal {L}}} 242: 218: 1: 5420:10.1090/S0002-9939-98-04575-4 5231:, Section 2.4 & Chapter 6 5188:, Theorem 5.9.2. Originally, 4731:Special classes of semigroups 4538:generalised inverse semigroup 3660:together with multiplication 2638:McAlister's Covering Theorem. 2480:be an inverse semigroup with 364:. For example, just as every 5049:, Theorem 5.1.7 Originally, 4678:theoretical computer science 4123:A construction similar to a 3876:be a McAlister triple. Then 5738:Clifford & Preston 1967 5457:. Oxford: Clarendon Press. 5035:Clifford & Preston 1967 4972:Clifford & Preston 1967 4760:Weisstein, Eric W. (2002). 4669:. The category of sets and 4393:with respect to its (dual) 3482:have nonempty intersection. 2675:, with ordering ≤, and let 2434:-unitary inverse semigroup 2283:-unitary inverse semigroups 2137:is any other congruence on 345:symmetric inverse semigroup 112:Viktor Vladimirovich Wagner 5821: 5520:McAlister, D. B. (1974b). 5153:. CRC Press. p. 248. 5020:: CS1 maint: postscript ( 4631:has a generalized inverse 4544:form a normal band, i.e., 4478:Locally inverse semigroups 2079:{\displaystyle c\leq a,b.} 1763:, which is an analogue of 488:has at least one inverse ( 384:The inverse of an element 5780:10.1017/S0013091512000211 5367:10.1017/S0013091500016230 5008:10.1007/s00233-017-9858-5 4665:. An inverse category is 3964:-inverse semigroup is an 3035:(on the left), such that 2727:with the properties that 1873:is an inverse semigroup. 1081:The natural partial order 835:Unless stated otherwise, 702:in an inverse semigroup: 5759:Linckelmann, M. (2012). 5630:10.1112/jlms/s1-29.4.411 5609:10.1112/jlms/s1-29.4.404 5588:10.1112/jlms/s1-29.4.396 5348:Fountain, J. B. (1979). 4067:is a principal ideal of 2643:Central to the study of 2180:on an inverse semigroup 2163:minimum group congruence 2133:is a group, that is, if 2113:is an inverse semigroup 1606:) is finite and forms a 869:is an inverse semigroup. 388:of an inverse semigroup 24:(occasionally called an 5719:Matematicheskii Sbornik 5268:Grandis, Marco (2012). 5147:Grillet, P. A. (1995). 4119:Free inverse semigroups 2809:{\displaystyle \wedge } 1980:{\displaystyle \sigma } 1775:Wagner–Preston Theorem. 36:in which every element 5472:Lawson, M. V. (1998). 4903:, Proposition 5.1.2(1) 4879:, Proposition 5.1.2(1) 4673:is the prime example. 4328: 4109: 4085: 4061: 4033: 3919: 3870: 3828:McAlister's P-Theorem. 3787: 3734: 3651: 3526: 3476: 3452: 3404: 3368: 3336: 3268: 3205: 3160: 3132: 3073: 3029: 2989: 2951: 2923: 2891: 2863: 2837: 2810: 2784: 2748: 2721: 2693: 2665: 2627: 2560:compatibility relation 2552: 2524: 2421: 2371: 2270: 2080: 2045: 2044:{\displaystyle c\in S} 2019: 1981: 1958: 1817: 1761:Wagner–Preston Theorem 1574: 1508: 1465: 1364: 1297: 1198: 1137: 826: 684: 645: 609: 585: 557: 533: 500:commute (that is, the 332: 296:, so he introduced an 263: 136:partial transformation 5688:10.1007/s002330010132 5377:Mathematische Annalen 5350:"Adequate semigroups" 4523:forms a subsemigroup. 4329: 4110: 4086: 4062: 4034: 3937:to one of this type. 3920: 3871: 3822:McAlister's P-Theorem 3788: 3735: 3652: 3527: 3477: 3453: 3405: 3369: 3337: 3269: 3206: 3161: 3133: 3074: 3030: 2990: 2952: 2924: 2892: 2864: 2838: 2811: 2785: 2749: 2722: 2694: 2673:partially ordered set 2666: 2628: 2553: 2551:{\displaystyle \sim } 2525: 2523:{\displaystyle \sim } 2438:is the following: if 2422: 2372: 2271: 2089:It can be shown that 2081: 2046: 2020: 1982: 1959: 1818: 1575: 1509: 1466: 1365: 1298: 1199: 1138: 1085:An inverse semigroup 827: 685: 646: 610: 586: 558: 534: 368:can be embedded in a 333: 264: 5800:Algebraic structures 5785:Open access preprint 5555:Petrich, M. (1984). 5476:. World Scientific. 4153: 4095: 4071: 4047: 3997: 3880: 3834: 3748: 3667: 3543: 3490: 3462: 3438: 3390: 3354: 3300: 3254: 3191: 3146: 3118: 3059: 3015: 2975: 2937: 2909: 2877: 2849: 2843:(with respect to ≤); 2823: 2800: 2792:greatest lower bound 2770: 2734: 2707: 2679: 2651: 2573: 2542: 2514: 2387: 2337: 2195: 2055: 2029: 1998: 1971: 1902: 1893:equivalence relation 1796: 1540: 1492: 1449: 1313: 1251: 1222:can be taken to be 1164: 1103: 709: 670: 631: 595: 571: 543: 519: 433:. An inverse monoid 311: 298:empty transformation 200: 5711:English translation 5125:, Proposition 2.4.3 4962:, Proposition 3.2.3 4926:, Proposition 5.2.1 4506:Orthodox semigroups 4395:Alexandrov topology 4141:taking the quotient 3944:-inverse semigroups 2508:is idempotent pure; 946: 392:is usually written 26:inversion semigroup 5661:10.1007/BF02676643 5557:Inverse semigroups 5389:10.1007/BF01597390 4839:See, for example, 4706:Partial symmetries 4691:Orthodox semigroup 4671:partial bijections 4434:Regular semigroups 4381:, in the sense of 4379:inductive groupoid 4324: 4115:is a semilattice. 4105: 4081: 4057: 4029: 3915: 3866: 3783: 3730: 3647: 3522: 3472: 3448: 3400: 3364: 3332: 3264: 3201: 3156: 3138:, there exists an 3128: 3069: 3025: 2985: 2947: 2919: 2887: 2859: 2833: 2806: 2780: 2744: 2717: 2689: 2661: 2623: 2548: 2520: 2417: 2367: 2266: 2076: 2041: 2015: 1977: 1954: 1813: 1570: 1504: 1461: 1360: 1293: 1194: 1133: 945:Inverse semigroup 944: 874:bicyclic semigroup 822: 680: 641: 605: 581: 553: 529: 360:is the archetypal 328: 259: 128:partial bijections 81:partial symmetries 55:in the sense that 5340:978-0-8218-0272-4 5310:978-0-521-51374-6 5281:978-981-4407-06-9 5160:978-0-8247-9662-4 4773:978-1-4200-3522-3 4741:Nambooripad order 4721:Green's relations 4711:Regular semigroup 4531:regular semigroup 4519:if its subset of 4510:regular semigroup 4482:regular semigroup 4415:regular semigroup 4145:Vagner congruence 3374:, there exists a 3221:if, and only if, 3089:if, and only if, 2756:lower semilattice 2157:. The congruence 1756:of that element. 1697:is a morphism if 1642:) is an infinite 1430:Green's relations 1421:in the domain of 1078: 1077: 876:is inverse, with 700:Green's relations 617:Green's relations 539:-class and every 494:regular semigroup 484:Every element of 477:Every element of 354:converse relation 77:regular semigroup 22:inverse semigroup 5812: 5805:Semigroup theory 5783: 5765: 5726: 5709: 5691: 5665: 5663: 5633: 5612: 5591: 5570: 5551: 5541: 5516: 5487: 5468: 5446: 5444: 5443: 5437: 5431:. Archived from 5423: 5413: 5411:funct-an/9511003 5392: 5371: 5369: 5344: 5315: 5314: 5292: 5286: 5285: 5265: 5259: 5250: 5244: 5238: 5232: 5226: 5220: 5214: 5208: 5202: 5193: 5183: 5177: 5176:, pp. 193–4 5171: 5165: 5164: 5144: 5138: 5132: 5126: 5120: 5114: 5108: 5102: 5096: 5090: 5084: 5078: 5072: 5066: 5060: 5054: 5044: 5038: 5032: 5026: 5025: 5019: 5011: 5001: 4981: 4975: 4969: 4963: 4957: 4951: 4945: 4939: 4938:, pp. 152–3 4933: 4927: 4921: 4915: 4910: 4904: 4898: 4892: 4886: 4880: 4874: 4868: 4862: 4856: 4850: 4844: 4837: 4831: 4825: 4819: 4808: 4802: 4795: 4789: 4784: 4778: 4777: 4757: 4664: 4654: 4644: 4630: 4612:inverse category 4602:Inverse category 4553: 4473: 4333: 4331: 4330: 4325: 4317: 4316: 4307: 4306: 4272: 4263: 4262: 4247: 4246: 4228: 4227: 4212: 4211: 4177: 4176: 4114: 4112: 4111: 4106: 4104: 4103: 4090: 4088: 4087: 4082: 4080: 4079: 4066: 4064: 4063: 4058: 4056: 4055: 4038: 4036: 4035: 4030: 4025: 4024: 4015: 4014: 3982:-inverse cover. 3924: 3922: 3921: 3916: 3911: 3910: 3901: 3900: 3875: 3873: 3872: 3867: 3862: 3861: 3852: 3851: 3815: 3792: 3790: 3789: 3784: 3779: 3778: 3769: 3768: 3739: 3737: 3736: 3731: 3656: 3654: 3653: 3648: 3643: 3642: 3630: 3629: 3608: 3607: 3574: 3573: 3564: 3563: 3534:McAlister triple 3531: 3529: 3528: 3523: 3518: 3517: 3508: 3507: 3481: 3479: 3478: 3473: 3471: 3470: 3457: 3455: 3454: 3449: 3447: 3446: 3419: 3409: 3407: 3406: 3401: 3399: 3398: 3373: 3371: 3370: 3365: 3363: 3362: 3341: 3339: 3338: 3333: 3328: 3327: 3318: 3317: 3291: 3273: 3271: 3270: 3265: 3263: 3262: 3230: 3220: 3210: 3208: 3207: 3202: 3200: 3199: 3175: 3165: 3163: 3162: 3157: 3155: 3154: 3137: 3135: 3134: 3129: 3127: 3126: 3098: 3088: 3078: 3076: 3075: 3070: 3068: 3067: 3034: 3032: 3031: 3026: 3024: 3023: 2994: 2992: 2991: 2986: 2984: 2983: 2966: 2956: 2954: 2953: 2948: 2946: 2945: 2928: 2926: 2925: 2920: 2918: 2917: 2896: 2894: 2893: 2888: 2886: 2885: 2868: 2866: 2865: 2860: 2858: 2857: 2842: 2840: 2839: 2834: 2832: 2831: 2815: 2813: 2812: 2807: 2789: 2787: 2786: 2781: 2779: 2778: 2753: 2751: 2750: 2745: 2743: 2742: 2726: 2724: 2723: 2718: 2716: 2715: 2698: 2696: 2695: 2690: 2688: 2687: 2670: 2668: 2667: 2662: 2660: 2659: 2632: 2630: 2629: 2624: 2619: 2618: 2603: 2602: 2557: 2555: 2554: 2549: 2529: 2527: 2526: 2521: 2426: 2424: 2423: 2418: 2376: 2374: 2373: 2368: 2275: 2273: 2272: 2267: 2153:is contained in 2095:group congruence 2085: 2083: 2082: 2077: 2050: 2048: 2047: 2042: 2024: 2022: 2021: 2016: 1986: 1984: 1983: 1978: 1963: 1961: 1960: 1955: 1822: 1820: 1819: 1814: 1812: 1811: 1806: 1805: 1765:Cayley's theorem 1748:The homomorphic 1741: 1715: 1579: 1577: 1576: 1571: 1517: 1513: 1511: 1510: 1505: 1502: 1501: 1484:. Similarly, if 1483: 1470: 1468: 1467: 1462: 1459: 1458: 1441: 1416: 1398: 1369: 1367: 1366: 1361: 1356: 1355: 1340: 1339: 1302: 1300: 1299: 1294: 1203: 1201: 1200: 1195: 1157:. Equivalently, 1142: 1140: 1139: 1134: 947: 940: 930: 908:Brandt semigroup 895: 831: 829: 828: 823: 821: 820: 802: 801: 779: 778: 761: 760: 742: 741: 722: 721: 689: 687: 686: 681: 679: 678: 650: 648: 647: 642: 640: 639: 614: 612: 611: 606: 604: 603: 590: 588: 587: 582: 580: 579: 562: 560: 559: 554: 552: 551: 538: 536: 535: 530: 528: 527: 449: 414:. In an inverse 413: 337: 335: 334: 329: 327: 326: 321: 320: 305:binary operation 268: 266: 265: 260: 257: 256: 118:in 1952, and by 74: 64: 5820: 5819: 5815: 5814: 5813: 5811: 5810: 5809: 5790: 5789: 5763: 5758: 5740:, Chapter 7 or 5733: 5731:Further reading 5716: 5694: 5675:Semigroup Forum 5668: 5647:Semigroup Forum 5636: 5615: 5594: 5573: 5567: 5554: 5539:10.2307/1997032 5519: 5505:10.2307/1996831 5490: 5484: 5471: 5465: 5449: 5441: 5439: 5435: 5426: 5395: 5374: 5347: 5341: 5326: 5323: 5318: 5311: 5294: 5293: 5289: 5282: 5267: 5266: 5262: 5251: 5247: 5239: 5235: 5227: 5223: 5215: 5211: 5203: 5196: 5190:McAlister 1974a 5184: 5180: 5172: 5168: 5161: 5146: 5145: 5141: 5137:, Theorem 2.4.6 5133: 5129: 5121: 5117: 5109: 5105: 5097: 5093: 5089:, Theorem 2.4.1 5085: 5081: 5073: 5069: 5061: 5057: 5045: 5041: 5033: 5029: 5012: 4986:Semigroup Forum 4983: 4982: 4978: 4970: 4966: 4958: 4954: 4946: 4942: 4934: 4930: 4922: 4918: 4911: 4907: 4899: 4895: 4891:, Theorem 5.1.1 4887: 4883: 4875: 4871: 4863: 4859: 4851: 4847: 4838: 4834: 4826: 4822: 4809: 4805: 4796: 4792: 4785: 4781: 4774: 4759: 4758: 4754: 4750: 4745: 4726:Category theory 4686: 4656: 4646: 4632: 4618: 4604: 4545: 4489:locally inverse 4465: 4403: 4383:category theory 4362: 4308: 4295: 4251: 4235: 4216: 4200: 4165: 4151: 4150: 4121: 4093: 4092: 4069: 4068: 4045: 4044: 3995: 3994: 3946: 3878: 3877: 3832: 3831: 3794: 3746: 3745: 3665: 3664: 3618: 3541: 3540: 3488: 3487: 3460: 3459: 3436: 3435: 3411: 3388: 3387: 3352: 3351: 3298: 3297: 3275: 3252: 3251: 3222: 3212: 3189: 3188: 3167: 3144: 3143: 3116: 3115: 3090: 3080: 3057: 3056: 3013: 3012: 2973: 2972: 2958: 2935: 2934: 2907: 2906: 2897:, that is, for 2875: 2874: 2847: 2846: 2821: 2820: 2798: 2797: 2768: 2767: 2732: 2731: 2705: 2704: 2677: 2676: 2649: 2648: 2633:are idempotent. 2607: 2591: 2571: 2570: 2540: 2539: 2512: 2511: 2385: 2384: 2335: 2334: 2285: 2193: 2192: 2186:idempotent pure 2053: 2052: 2027: 2026: 2025:there exists a 1996: 1995: 1969: 1968: 1900: 1899: 1879: 1799: 1794: 1793: 1729: 1698: 1664: 1620:totally ordered 1538: 1537: 1529:), the natural 1490: 1489: 1485: 1475: 1447: 1446: 1433: 1432:as follows: if 1408: 1390: 1344: 1328: 1311: 1310: 1249: 1248: 1162: 1161: 1101: 1100: 1083: 932: 922: 877: 849: 809: 790: 749: 730: 707: 706: 668: 667: 629: 628: 593: 592: 569: 568: 541: 540: 517: 516: 438: 401: 400:, for example, 382: 370:symmetric group 358:symmetric group 348:(or monoid) on 314: 309: 308: 245: 198: 197: 165:are subsets of 108: 66: 56: 12: 11: 5: 5818: 5816: 5808: 5807: 5802: 5792: 5791: 5788: 5787: 5756: 5745: 5732: 5729: 5728: 5727: 5725:(74): 545–632. 5714: 5704:(in Russian). 5692: 5666: 5634: 5613: 5603:(4): 404–411. 5592: 5582:(4): 396–403. 5571: 5565: 5552: 5517: 5488: 5482: 5469: 5463: 5447: 5424: 5404:(12): 3481–4. 5393: 5372: 5360:(2): 113–125. 5345: 5339: 5322: 5319: 5317: 5316: 5309: 5287: 5280: 5260: 5245: 5233: 5221: 5209: 5194: 5178: 5166: 5159: 5139: 5127: 5115: 5103: 5091: 5079: 5067: 5055: 5039: 5037:, Theorem 7.36 5027: 4992:(2): 203–240. 4976: 4964: 4952: 4940: 4928: 4916: 4905: 4893: 4881: 4869: 4857: 4845: 4832: 4820: 4803: 4790: 4779: 4772: 4751: 4749: 4746: 4744: 4743: 4738: 4733: 4728: 4723: 4718: 4713: 4708: 4703: 4698: 4693: 4687: 4685: 4682: 4603: 4600: 4599: 4598: 4595: 4592: 4589: 4571: 4570: 4524: 4503: 4475: 4456:, there is an 4417:, and (2) the 4402: 4399: 4391:étale groupoid 4361: 4358: 4335: 4334: 4323: 4320: 4315: 4311: 4305: 4302: 4298: 4294: 4291: 4288: 4285: 4282: 4279: 4276: 4271: 4266: 4261: 4258: 4254: 4250: 4245: 4242: 4238: 4234: 4231: 4226: 4223: 4219: 4215: 4210: 4207: 4203: 4199: 4196: 4192: 4189: 4186: 4183: 4180: 4175: 4172: 4168: 4164: 4161: 4158: 4120: 4117: 4102: 4078: 4054: 4028: 4023: 4018: 4013: 4008: 4005: 4002: 3945: 3939: 3914: 3909: 3904: 3899: 3894: 3891: 3888: 3885: 3865: 3860: 3855: 3850: 3845: 3842: 3839: 3782: 3777: 3772: 3767: 3762: 3759: 3756: 3753: 3742: 3741: 3729: 3726: 3723: 3720: 3717: 3714: 3711: 3708: 3705: 3702: 3699: 3696: 3693: 3690: 3687: 3684: 3681: 3678: 3675: 3672: 3658: 3657: 3646: 3641: 3636: 3633: 3628: 3625: 3621: 3617: 3614: 3611: 3606: 3601: 3598: 3595: 3592: 3589: 3586: 3583: 3580: 3577: 3572: 3567: 3562: 3557: 3554: 3551: 3548: 3521: 3516: 3511: 3506: 3501: 3498: 3495: 3486:Such a triple 3484: 3483: 3469: 3445: 3421: 3397: 3361: 3331: 3326: 3321: 3316: 3311: 3308: 3305: 3294: 3293: 3261: 3232: 3198: 3177: 3153: 3125: 3100: 3066: 3022: 2997: 2996: 2982: 2944: 2916: 2884: 2856: 2844: 2830: 2805: 2777: 2741: 2714: 2686: 2658: 2635: 2634: 2622: 2617: 2614: 2610: 2606: 2601: 2598: 2594: 2590: 2587: 2584: 2581: 2578: 2547: 2536: 2535: 2519: 2509: 2503: 2428: 2427: 2416: 2413: 2410: 2407: 2404: 2401: 2398: 2395: 2392: 2380:Equivalently, 2378: 2377: 2366: 2363: 2360: 2357: 2354: 2351: 2348: 2345: 2342: 2284: 2278: 2277: 2276: 2265: 2262: 2259: 2256: 2253: 2250: 2247: 2244: 2241: 2237: 2233: 2230: 2227: 2224: 2221: 2218: 2215: 2212: 2209: 2206: 2203: 2200: 2161:is called the 2149:a group, then 2121:congruence on 2087: 2086: 2075: 2072: 2069: 2066: 2063: 2060: 2040: 2037: 2034: 2014: 2011: 2007: 2003: 1976: 1965: 1964: 1953: 1950: 1947: 1943: 1939: 1936: 1933: 1930: 1926: 1922: 1918: 1915: 1911: 1907: 1878: 1875: 1855:representation 1848: 1847: 1810: 1804: 1663: 1660: 1583:so, since the 1581: 1580: 1569: 1566: 1563: 1560: 1557: 1554: 1551: 1548: 1545: 1500: 1457: 1371: 1370: 1359: 1354: 1351: 1347: 1343: 1338: 1335: 1331: 1327: 1324: 1321: 1318: 1304: 1303: 1292: 1289: 1286: 1283: 1280: 1277: 1274: 1271: 1268: 1265: 1262: 1259: 1256: 1205: 1204: 1193: 1190: 1187: 1184: 1181: 1178: 1175: 1172: 1169: 1144: 1143: 1132: 1129: 1126: 1123: 1120: 1117: 1114: 1111: 1108: 1082: 1079: 1076: 1075: 1072: 1069: 1066: 1063: 1060: 1054: 1053: 1050: 1047: 1044: 1041: 1038: 1032: 1031: 1028: 1025: 1022: 1019: 1016: 1010: 1009: 1006: 1003: 1000: 997: 994: 988: 987: 984: 981: 978: 975: 972: 966: 965: 962: 959: 956: 953: 950: 919: 918: 915:Munn semigroup 911: 904: 897: 870: 863: 848: 845: 833: 832: 819: 816: 812: 808: 805: 800: 797: 793: 789: 786: 783: 777: 771: 767: 764: 759: 756: 752: 748: 745: 740: 737: 733: 729: 726: 720: 714: 677: 662:, whilst the 638: 621: 620: 602: 578: 550: 526: 513: 482: 381: 378: 325: 319: 270: 269: 255: 252: 248: 244: 241: 238: 235: 232: 229: 226: 223: 220: 217: 214: 211: 208: 205: 124:United Kingdom 120:Gordon Preston 107: 104: 13: 10: 9: 6: 4: 3: 2: 5817: 5806: 5803: 5801: 5798: 5797: 5795: 5786: 5781: 5777: 5773: 5769: 5762: 5757: 5754: 5750: 5746: 5743: 5739: 5735: 5734: 5730: 5724: 5720: 5715: 5712: 5707: 5703: 5702: 5697: 5696:Wagner, V. V. 5693: 5689: 5685: 5681: 5677: 5676: 5671: 5670:Schein, B. M. 5667: 5662: 5657: 5653: 5649: 5648: 5643: 5639: 5638:Schein, B. M. 5635: 5631: 5627: 5623: 5619: 5614: 5610: 5606: 5602: 5598: 5593: 5589: 5585: 5581: 5577: 5572: 5568: 5562: 5558: 5553: 5549: 5545: 5540: 5535: 5531: 5527: 5523: 5518: 5514: 5510: 5506: 5502: 5498: 5494: 5489: 5485: 5479: 5475: 5470: 5466: 5460: 5456: 5452: 5448: 5438:on 2005-08-26 5434: 5430: 5425: 5421: 5417: 5412: 5407: 5403: 5399: 5394: 5390: 5386: 5382: 5379:(in German). 5378: 5373: 5368: 5363: 5359: 5355: 5351: 5346: 5342: 5336: 5332: 5331: 5325: 5324: 5320: 5312: 5306: 5302: 5298: 5291: 5288: 5283: 5277: 5273: 5272: 5264: 5261: 5258: 5254: 5253:Fountain 1979 5249: 5246: 5243:, p. 222 5242: 5237: 5234: 5230: 5225: 5222: 5218: 5213: 5210: 5207:, p. 230 5206: 5201: 5199: 5195: 5191: 5187: 5182: 5179: 5175: 5170: 5167: 5162: 5156: 5152: 5151: 5143: 5140: 5136: 5131: 5128: 5124: 5119: 5116: 5113:, p. 192 5112: 5107: 5104: 5100: 5095: 5092: 5088: 5083: 5080: 5076: 5071: 5068: 5064: 5059: 5056: 5052: 5048: 5043: 5040: 5036: 5031: 5028: 5023: 5017: 5010:Corollary 4.9 5009: 5005: 5000: 4995: 4991: 4987: 4980: 4977: 4974:, Theorem 7.5 4973: 4968: 4965: 4961: 4956: 4953: 4950:, p. 153 4949: 4944: 4941: 4937: 4932: 4929: 4925: 4920: 4917: 4914: 4909: 4906: 4902: 4897: 4894: 4890: 4885: 4882: 4878: 4873: 4870: 4867:, p. 149 4866: 4861: 4858: 4855:, p. 152 4854: 4849: 4846: 4842: 4836: 4833: 4829: 4828:Preston 1954a 4824: 4821: 4817: 4813: 4807: 4804: 4800: 4794: 4791: 4788: 4783: 4780: 4775: 4769: 4765: 4764: 4756: 4753: 4747: 4742: 4739: 4737: 4734: 4732: 4729: 4727: 4724: 4722: 4719: 4717: 4714: 4712: 4709: 4707: 4704: 4702: 4699: 4697: 4696:Biordered set 4694: 4692: 4689: 4688: 4683: 4681: 4679: 4674: 4672: 4668: 4663: 4659: 4653: 4649: 4643: 4639: 4635: 4629: 4625: 4621: 4617: 4613: 4609: 4601: 4596: 4593: 4590: 4587: 4586: 4585: 4582: 4580: 4576: 4568: 4564: 4560: 4557: 4552: 4548: 4543: 4539: 4535: 4532: 4528: 4525: 4522: 4518: 4514: 4511: 4507: 4504: 4501: 4498: 4494: 4490: 4486: 4483: 4479: 4476: 4472: 4468: 4463: 4459: 4455: 4451: 4447: 4443: 4440: 4436: 4435: 4431: 4430: 4429: 4426: 4424: 4420: 4416: 4412: 4408: 4400: 4398: 4396: 4392: 4388: 4384: 4380: 4376: 4372: 4368: 4359: 4357: 4355: 4350: 4348: 4344: 4340: 4321: 4313: 4303: 4300: 4296: 4292: 4289: 4283: 4280: 4277: 4274: 4259: 4256: 4252: 4248: 4243: 4240: 4236: 4232: 4229: 4224: 4221: 4217: 4213: 4208: 4205: 4201: 4197: 4190: 4184: 4181: 4178: 4173: 4170: 4166: 4162: 4149: 4148: 4147: 4146: 4142: 4138: 4134: 4130: 4126: 4118: 4116: 4042: 4016: 4006: 4003: 3992: 3988: 3983: 3981: 3977: 3973: 3971: 3967: 3963: 3959: 3955: 3951: 3943: 3940: 3938: 3936: 3932: 3928: 3902: 3892: 3889: 3883: 3853: 3843: 3840: 3829: 3825: 3823: 3819: 3813: 3809: 3806: 3802: 3798: 3770: 3760: 3757: 3751: 3724: 3721: 3718: 3715: 3712: 3709: 3706: 3700: 3694: 3691: 3688: 3679: 3676: 3673: 3663: 3662: 3661: 3634: 3631: 3626: 3623: 3619: 3615: 3612: 3609: 3599: 3593: 3590: 3587: 3578: 3565: 3555: 3552: 3546: 3539: 3538: 3537: 3535: 3509: 3499: 3496: 3434: 3430: 3426: 3422: 3418: 3414: 3385: 3381: 3377: 3349: 3345: 3344: 3343: 3319: 3309: 3306: 3290: 3286: 3282: 3278: 3249: 3245: 3241: 3237: 3233: 3229: 3225: 3219: 3215: 3186: 3182: 3178: 3174: 3170: 3141: 3113: 3109: 3105: 3101: 3097: 3093: 3087: 3083: 3054: 3050: 3046: 3042: 3038: 3037: 3036: 3010: 3006: 3002: 2970: 2965: 2961: 2932: 2904: 2900: 2872: 2845: 2818: 2803: 2796: 2793: 2765: 2761: 2757: 2730: 2729: 2728: 2702: 2674: 2646: 2641: 2639: 2620: 2615: 2612: 2608: 2604: 2599: 2596: 2592: 2588: 2582: 2579: 2576: 2569: 2568: 2567: 2566:, defined by 2565: 2561: 2545: 2533: 2517: 2510: 2507: 2504: 2501: 2497: 2494: 2493: 2492: 2490: 2486: 2483: 2479: 2475: 2471: 2469: 2465: 2461: 2457: 2453: 2449: 2445: 2441: 2437: 2433: 2414: 2411: 2408: 2405: 2399: 2396: 2393: 2390: 2383: 2382: 2381: 2364: 2361: 2358: 2355: 2349: 2346: 2343: 2340: 2333: 2332: 2331: 2329: 2325: 2321: 2317: 2313: 2309: 2305: 2301: 2298: 2294: 2290: 2282: 2279: 2263: 2257: 2251: 2248: 2245: 2239: 2235: 2231: 2228: 2222: 2216: 2213: 2210: 2207: 2204: 2201: 2198: 2191: 2190: 2189: 2187: 2183: 2179: 2176:A congruence 2174: 2172: 2168: 2164: 2160: 2156: 2152: 2148: 2144: 2140: 2136: 2132: 2128: 2124: 2120: 2116: 2112: 2108: 2104: 2100: 2096: 2092: 2073: 2070: 2067: 2064: 2061: 2058: 2038: 2035: 2032: 2009: 2005: 2001: 1994: 1993: 1992: 1990: 1974: 1951: 1948: 1945: 1941: 1937: 1934: 1928: 1924: 1920: 1916: 1913: 1909: 1905: 1898: 1897: 1896: 1894: 1890: 1887: 1883: 1876: 1874: 1872: 1868: 1862: 1860: 1856: 1853: 1846: 1842: 1838: 1834: 1830: 1826: 1825: 1824: 1808: 1791: 1787: 1784: 1780: 1776: 1772: 1770: 1766: 1762: 1757: 1755: 1751: 1747: 1743: 1740: 1737: 1733: 1727: 1723: 1719: 1714: 1710: 1706: 1702: 1696: 1692: 1688: 1685: 1681: 1677: 1673: 1669: 1661: 1659: 1657: 1653: 1649: 1645: 1641: 1637: 1633: 1629: 1625: 1621: 1617: 1613: 1609: 1605: 1601: 1596: 1594: 1590: 1586: 1567: 1564: 1561: 1558: 1555: 1549: 1546: 1543: 1536: 1535: 1534: 1532: 1531:partial order 1528: 1524: 1519: 1516: 1488: 1482: 1478: 1473: 1445: 1440: 1436: 1431: 1426: 1424: 1420: 1415: 1411: 1406: 1402: 1397: 1393: 1388: 1387:partial order 1384: 1380: 1379:partial order 1376: 1357: 1352: 1349: 1345: 1341: 1336: 1333: 1329: 1322: 1319: 1316: 1309: 1308: 1307: 1290: 1287: 1284: 1281: 1278: 1272: 1269: 1266: 1263: 1260: 1257: 1254: 1247: 1246: 1245: 1243: 1242:partial order 1238: 1236: 1233: 1229: 1225: 1221: 1217: 1213: 1210: 1191: 1188: 1185: 1182: 1179: 1173: 1170: 1167: 1160: 1159: 1158: 1156: 1152: 1149: 1130: 1127: 1124: 1121: 1118: 1112: 1109: 1106: 1099: 1098: 1097: 1095: 1094: 1093:partial order 1088: 1080: 1073: 1070: 1067: 1064: 1061: 1059: 1056: 1055: 1051: 1048: 1045: 1042: 1039: 1037: 1034: 1033: 1029: 1026: 1023: 1020: 1017: 1015: 1012: 1011: 1007: 1004: 1001: 998: 995: 993: 990: 989: 985: 982: 979: 976: 973: 971: 968: 967: 963: 960: 957: 954: 951: 949: 948: 942: 939: 935: 929: 925: 916: 912: 909: 905: 902: 898: 893: 889: 885: 881: 875: 871: 868: 864: 861: 857: 854: 851: 850: 846: 844: 842: 838: 817: 814: 810: 806: 803: 798: 795: 791: 787: 781: 769: 765: 762: 757: 754: 750: 746: 743: 738: 735: 731: 724: 712: 705: 704: 703: 701: 697: 693: 665: 661: 658: 654: 626: 618: 566: 514: 511: 507: 503: 499: 495: 491: 487: 483: 480: 476: 475: 474: 472: 467: 465: 461: 457: 453: 448: 445: 441: 436: 432: 428: 425: 421: 417: 412: 409: 405: 399: 395: 391: 387: 379: 377: 375: 371: 367: 363: 359: 355: 351: 347: 346: 341: 323: 306: 303: 299: 295: 291: 287: 283: 279: 275: 253: 250: 246: 239: 236: 233: 230: 227: 224: 221: 215: 212: 209: 206: 203: 196: 195: 194: 192: 188: 184: 180: 176: 172: 168: 164: 160: 156: 152: 148: 144: 140: 137: 133: 129: 125: 121: 117: 113: 105: 103: 101: 97: 93: 89: 84: 82: 78: 73: 69: 63: 59: 54: 50: 47: 44:has a unique 43: 39: 35: 31: 27: 23: 19: 5771: 5767: 5749:Petrich 1984 5744:, Chapter 5. 5722: 5718: 5708:: 1119–1122. 5705: 5699: 5679: 5673: 5651: 5645: 5624:(4): 411–9. 5621: 5617: 5600: 5596: 5579: 5575: 5556: 5529: 5525: 5496: 5492: 5473: 5454: 5451:Howie, J. M. 5440:. Retrieved 5436:(Postscript) 5433:the original 5401: 5397: 5380: 5376: 5357: 5353: 5329: 5300: 5290: 5270: 5263: 5248: 5236: 5224: 5212: 5181: 5169: 5149: 5142: 5130: 5118: 5106: 5101:, p. 65 5094: 5082: 5077:, p. 62 5070: 5065:, p. 22 5058: 5042: 5030: 5016:cite journal 4989: 4985: 4979: 4967: 4955: 4943: 4931: 4919: 4908: 4896: 4884: 4872: 4860: 4848: 4835: 4823: 4806: 4793: 4782: 4762: 4755: 4736:Weak inverse 4675: 4661: 4657: 4651: 4647: 4641: 4637: 4633: 4627: 4623: 4619: 4611: 4605: 4583: 4579:intersection 4572: 4566: 4562: 4558: 4550: 4546: 4537: 4536:is called a 4533: 4526: 4516: 4512: 4505: 4499: 4492: 4488: 4484: 4477: 4470: 4466: 4461: 4457: 4453: 4449: 4445: 4441: 4432: 4427: 4422: 4410: 4406: 4404: 4386: 4374: 4370: 4366: 4363: 4353: 4351: 4339:word problem 4336: 4144: 4132: 4129:presentation 4122: 4040: 3990: 3986: 3985:McAlister's 3984: 3979: 3975: 3974: 3965: 3961: 3957: 3953: 3949: 3947: 3941: 3930: 3926: 3827: 3826: 3821: 3817: 3811: 3807: 3804: 3800: 3796: 3743: 3659: 3533: 3532:is called a 3485: 3432: 3428: 3424: 3416: 3412: 3383: 3379: 3375: 3347: 3295: 3288: 3284: 3280: 3276: 3247: 3243: 3239: 3235: 3227: 3223: 3217: 3213: 3184: 3180: 3172: 3168: 3139: 3111: 3107: 3103: 3095: 3091: 3085: 3081: 3052: 3048: 3044: 3040: 3000: 2998: 2968: 2963: 2959: 2930: 2902: 2898: 2816: 2794: 2763: 2759: 2644: 2642: 2637: 2636: 2563: 2559: 2537: 2531: 2505: 2499: 2495: 2488: 2484: 2477: 2473: 2472: 2467: 2463: 2459: 2455: 2451: 2447: 2443: 2439: 2435: 2431: 2429: 2379: 2327: 2323: 2319: 2315: 2314:if, for all 2311: 2307: 2299: 2292: 2288: 2286: 2280: 2185: 2181: 2177: 2175: 2170: 2166: 2162: 2158: 2154: 2150: 2146: 2142: 2138: 2134: 2130: 2126: 2122: 2118: 2114: 2110: 2106: 2102: 2098: 2090: 2088: 1988: 1966: 1888: 1885: 1880: 1870: 1866: 1863: 1858: 1849: 1844: 1840: 1836: 1832: 1828: 1789: 1785: 1778: 1774: 1773: 1760: 1758: 1745: 1744: 1738: 1735: 1731: 1725: 1721: 1717: 1712: 1708: 1704: 1700: 1694: 1690: 1686: 1679: 1675: 1671: 1668:homomorphism 1665: 1655: 1651: 1647: 1639: 1635: 1623: 1622:by ≤), then 1615: 1611: 1603: 1599: 1597: 1592: 1588: 1582: 1526: 1522: 1520: 1514: 1486: 1480: 1476: 1471: 1443: 1438: 1434: 1427: 1422: 1418: 1413: 1409: 1404: 1400: 1395: 1391: 1372: 1305: 1240:The natural 1239: 1234: 1231: 1227: 1223: 1219: 1215: 1211: 1206: 1154: 1150: 1145: 1090: 1089:possesses a 1086: 1084: 1057: 1035: 1013: 991: 969: 937: 933: 927: 923: 920: 891: 887: 883: 879: 859: 840: 836: 834: 695: 691: 659: 656: 652: 622: 505: 489: 485: 478: 470: 468: 459: 455: 451: 446: 443: 439: 434: 426: 423: 419: 410: 407: 403: 393: 389: 385: 383: 349: 343: 339: 297: 286:pseudogroups 281: 276:denotes the 273: 271: 186: 182: 178: 174: 170: 166: 162: 158: 154: 150: 142: 138: 116:Soviet Union 109: 99: 95: 94:rather than 91: 87: 85: 71: 67: 61: 57: 52: 48: 45: 41: 37: 29: 25: 21: 15: 5753:Lawson 1998 5682:: 149–158. 5654:: 189–200. 5532:: 351–370. 5499:: 227–244. 5383:: 768–780. 5217:Lawson 1998 5205:Lawson 1998 5135:Lawson 1998 5123:Lawson 1998 5099:Lawson 1998 5087:Lawson 1998 5075:Lawson 1998 5051:Wagner 1952 4960:Lawson 1998 4913:Wagner 1952 4853:Schein 2002 4816:Wagner 1953 4812:Wagner 1952 4799:Schein 1981 4787:Lawson 1998 4716:Semilattice 4701:Pseudogroup 4556:idempotents 4542:idempotents 4521:idempotents 4419:idempotents 3970:M.V. Lawson 3296:The triple 2871:order ideal 2482:semilattice 2454:, for some 2304:idempotents 2297:semilattice 1882:Congruences 1823:, given by 1585:idempotents 1218:. In fact, 917:is inverse. 910:is inverse. 903:is inverse. 901:semilattice 615:are two of 510:semilattice 502:idempotents 498:idempotents 302:associative 280:under  20:theory, an 5794:Categories 5742:Howie 1995 5566:0471875457 5483:9810233167 5464:0198511949 5442:2006-08-28 5427:Gould, V. 5321:References 5241:Howie 1995 5229:Howie 1995 5186:Howie 1995 5174:Howie 1995 5111:Howie 1995 5063:Howie 1995 5047:Howie 1995 4999:1510.04117 4948:Howie 1995 4936:Howie 1995 4924:Howie 1995 4901:Howie 1995 4889:Howie 1995 4877:Howie 1995 4865:Howie 1995 4841:Gołab 1939 4645:such that 4608:categories 4554:, for all 4497:idempotent 4464:such that 4356:-inverse. 4347:Munn trees 4343:W. D. Munn 4125:free group 3935:isomorphic 3410:such that 3346:for every 3166:such that 2184:is called 2125:such that 1886:congruence 1716:, for all 1417:, for all 1383:idempotent 1209:idempotent 1148:idempotent 856:bijections 690:-class of 664:idempotent 651:-class of 625:idempotent 565:idempotent 450:, for all 431:idempotent 380:The basics 5559:. Wiley. 4439:semigroup 4301:− 4293:∪ 4284:∈ 4257:− 4241:− 4222:− 4206:− 4171:− 3710:∧ 3635:∈ 3624:− 3610:× 3600:∈ 3110:and each 3102:for each 2804:∧ 2613:− 2597:− 2586:⟺ 2580:∼ 2546:∼ 2518:∼ 2502:-unitary; 2409:∈ 2403:⇒ 2397:∈ 2359:∈ 2353:⟹ 2347:∈ 2249:∈ 2243:⟹ 2236:ρ 2214:∈ 2202:∈ 2062:≤ 2036:∈ 2013:⟺ 2006:σ 1975:σ 1942:ρ 1932:⟹ 1925:ρ 1910:ρ 1553:⟺ 1547:≤ 1533:becomes: 1350:− 1342:≤ 1334:− 1326:⟹ 1320:≤ 1285:≤ 1276:⟹ 1270:≤ 1258:≤ 1177:⟺ 1171:≤ 1146:for some 1116:⟺ 1110:≤ 858:on a set 815:− 796:− 785:⟺ 755:− 736:− 728:⟺ 460:unipotent 437:in which 294:empty set 251:− 247:α 240:β 237:⁡ 231:∩ 228:α 225:⁡ 213:β 210:α 207:⁡ 141:of a set 75:, i.e. a 34:semigroup 5640:(1981). 5453:(1995). 4684:See also 4667:selfdual 4636: : 4622: : 4616:morphism 4517:orthodox 3976:Theorem. 3423:for all 3246:and all 3234:for all 3179:for all 3047:and all 3039:for all 2999:Now let 2474:Theorem. 2322:and all 2119:smallest 1852:faithful 1783:function 1746:Theorem. 1684:function 1672:morphism 1091:natural 567:, where 376:below). 278:preimage 157:, where 147:function 5774:: 187. 5548:1997032 5513:1996831 5219:, 4.1.8 4540:if its 4446:regular 4143:by the 3382:and an 2967:, then 2558:is the 2462:, then 2312:unitary 2117:is the 1610:(i.e., 1474:, then 1377:, this 853:Partial 666:in the 627:in the 508:form a 122:in the 114:in the 106:Origins 46:inverse 5563:  5546:  5511:  5480:  5461:  5337:  5307:  5278:  5157:  4770:  4039:is an 3954:unique 3925:is an 2971:is in 2933:is in 2869:is an 2790:has a 2701:subset 2538:where 2466:is in 2442:is in 2295:(with 1891:is an 1769:groups 1632:groups 1230:to be 899:Every 865:Every 515:Every 496:) and 442:= 1 = 416:monoid 272:where 191:domain 169:. Let 90:  5764:(PDF) 5713:(PDF) 5544:JSTOR 5509:JSTOR 5406:arXiv 5257:Gould 4994:arXiv 4830:,b,c. 4748:Notes 4610:. An 4575:class 4413:is a 3803:) = ( 3744:Then 3283:) = ( 3007:that 3005:group 3003:be a 2929:, if 2754:is a 2699:be a 2671:be a 2446:and 2306:) is 2141:with 2051:with 1850:is a 1827:dom ( 1788:from 1754:image 1750:image 1707:) = ( 1689:from 1644:chain 1634:. If 1628:union 1626:is a 1618:) is 1608:chain 1375:group 1373:In a 886:) = ( 867:group 492:is a 464:group 398:group 366:group 362:group 149:from 145:is a 130:of a 32:is a 18:group 5751:and 5561:ISBN 5478:ISBN 5459:ISBN 5335:ISBN 5305:ISBN 5276:ISBN 5155:ISBN 5022:link 4768:ISBN 4655:and 4573:The 4551:xzyx 4547:xyzx 4529:: a 4508:: a 4480:: a 4437:: a 4369:and 4337:The 4091:and 3972:to: 3830:Let 3458:and 3009:acts 2957:and 2476:Let 2188:if 1843:) = 1835:and 1831:) = 1767:for 1734:) = 1682:, a 1678:and 1670:(or 1650:and 1442:and 1407:and 1306:and 1226:and 913:The 906:The 872:The 837:E(S) 623:The 591:and 422:and 406:) = 185:and 173:and 161:and 134:: a 65:and 5776:doi 5684:doi 5656:doi 5626:doi 5605:doi 5584:doi 5534:doi 5530:196 5501:doi 5497:192 5416:doi 5402:126 5385:doi 5381:116 5362:doi 5192:,b. 5004:doi 4658:gfg 4648:fgf 4515:is 4493:eSe 4491:if 4487:is 4467:axa 4460:in 4452:in 4444:is 4421:in 3427:in 3386:in 3378:in 3350:in 3250:in 3242:in 3187:in 3142:in 3114:in 3106:in 3055:in 3043:in 3011:on 2905:in 2873:of 2819:in 2766:in 2703:of 2562:on 2498:is 2458:in 2326:in 2318:in 2302:of 2165:on 1991:by 1857:of 1792:to 1777:If 1724:in 1693:to 1658:). 1630:of 1598:If 1521:On 1214:in 1153:in 934:bab 924:aba 694:is 655:is 504:of 458:(a 454:in 234:dom 204:dom 153:to 132:set 72:yxy 62:xyx 51:in 40:in 16:In 5796:: 5772:56 5770:. 5766:. 5723:32 5706:84 5680:65 5678:. 5652:28 5650:. 5644:. 5622:29 5620:. 5601:29 5599:. 5580:29 5578:. 5542:. 5528:. 5524:. 5507:. 5495:. 5414:. 5400:. 5358:22 5356:. 5352:. 5255:, 5197:^ 5018:}} 5014:{{ 5002:. 4990:96 4988:. 4680:. 4660:= 4650:= 4640:→ 4626:→ 4565:, 4561:, 4549:= 4469:= 3824:: 3810:, 3799:, 3431:, 3415:= 3413:gA 3285:gh 3281:hA 3274:, 3238:, 3228:gB 3226:≤ 3224:gA 3216:≤ 3211:, 3183:, 3171:= 3169:gA 3094:= 3086:gB 3084:= 3082:gA 3079:, 3051:, 2962:≤ 2901:, 2762:, 2530:= 2470:. 2450:≤ 2330:, 1861:. 1845:xa 1841:aφ 1833:Sa 1829:aφ 1771:: 1732:sθ 1709:st 1705:tθ 1703:)( 1701:sθ 1666:A 1518:. 1479:= 1437:≤ 1425:. 1414:xβ 1412:= 1410:xα 1394:≤ 1237:. 1224:aa 1074:e 1052:a 1030:c 1008:a 986:a 964:e 936:= 931:, 926:= 890:, 882:, 843:. 696:ss 512:). 473:: 466:. 440:xx 420:xx 418:, 404:ab 222:im 181:; 83:. 70:= 60:= 28:) 5782:. 5778:: 5755:. 5690:. 5686:: 5664:. 5658:: 5632:. 5628:: 5611:. 5607:: 5590:. 5586:: 5569:. 5550:. 5536:: 5515:. 5503:: 5486:. 5467:. 5445:. 5422:. 5418:: 5408:: 5391:. 5387:: 5370:. 5364:: 5343:. 5313:. 5284:. 5163:. 5024:) 5006:: 4996:: 4843:. 4818:. 4801:. 4776:. 4662:g 4652:f 4642:X 4638:Y 4634:g 4628:Y 4624:X 4620:f 4569:. 4567:z 4563:y 4559:x 4534:S 4513:S 4502:. 4500:e 4485:S 4474:. 4471:a 4462:S 4458:x 4454:S 4450:a 4442:S 4423:S 4411:S 4407:S 4375:β 4371:β 4367:α 4354:F 4322:. 4319:} 4314:+ 4310:) 4304:1 4297:X 4290:X 4287:( 4281:y 4278:, 4275:x 4270:| 4265:) 4260:1 4253:x 4249:x 4244:1 4237:y 4233:y 4230:, 4225:1 4218:y 4214:y 4209:1 4202:x 4198:x 4195:( 4191:, 4188:) 4185:x 4182:, 4179:x 4174:1 4167:x 4163:x 4160:( 4157:{ 4133:X 4101:X 4077:X 4053:Y 4041:F 4027:) 4022:Y 4017:, 4012:X 4007:, 4004:G 4001:( 3991:F 3987:P 3980:F 3966:E 3962:F 3958:σ 3950:F 3942:F 3931:E 3927:E 3913:) 3908:Y 3903:, 3898:X 3893:, 3890:G 3887:( 3884:P 3864:) 3859:Y 3854:, 3849:X 3844:, 3841:G 3838:( 3818:E 3814:) 3812:g 3808:A 3805:g 3801:g 3797:A 3795:( 3781:) 3776:Y 3771:, 3766:X 3761:, 3758:G 3755:( 3752:P 3740:. 3728:) 3725:h 3722:g 3719:, 3716:B 3713:g 3707:A 3704:( 3701:= 3698:) 3695:h 3692:, 3689:B 3686:( 3683:) 3680:g 3677:, 3674:A 3671:( 3645:} 3640:Y 3632:A 3627:1 3620:g 3616:: 3613:G 3605:Y 3597:) 3594:g 3591:, 3588:A 3585:( 3582:{ 3579:= 3576:) 3571:Y 3566:, 3561:X 3556:, 3553:G 3550:( 3547:P 3520:) 3515:Y 3510:, 3505:X 3500:, 3497:G 3494:( 3468:Y 3444:Y 3433:g 3429:G 3425:g 3420:; 3417:X 3396:Y 3384:A 3380:G 3376:g 3360:X 3348:X 3330:) 3325:Y 3320:, 3315:X 3310:, 3307:G 3304:( 3292:. 3289:A 3287:) 3279:( 3277:g 3260:X 3248:A 3244:G 3240:h 3236:g 3231:; 3218:B 3214:A 3197:X 3185:B 3181:A 3176:; 3173:B 3152:X 3140:A 3124:X 3112:B 3108:G 3104:g 3099:; 3096:B 3092:A 3065:X 3053:B 3049:A 3045:G 3041:g 3021:X 3001:G 2995:. 2981:Y 2969:B 2964:A 2960:B 2943:Y 2931:A 2915:X 2903:B 2899:A 2883:X 2855:Y 2829:Y 2817:B 2795:A 2776:Y 2764:B 2760:A 2740:Y 2713:X 2685:Y 2657:X 2645:E 2621:b 2616:1 2609:a 2605:, 2600:1 2593:b 2589:a 2583:b 2577:a 2564:S 2534:, 2532:σ 2506:σ 2500:E 2496:S 2489:σ 2485:E 2478:S 2468:E 2464:s 2460:S 2456:s 2452:s 2448:e 2444:E 2440:e 2436:S 2432:E 2415:. 2412:E 2406:s 2400:E 2394:e 2391:s 2365:. 2362:E 2356:s 2350:E 2344:s 2341:e 2328:S 2324:s 2320:E 2316:e 2310:- 2308:E 2300:E 2293:S 2289:E 2281:E 2264:. 2261:) 2258:S 2255:( 2252:E 2246:a 2240:e 2232:a 2229:, 2226:) 2223:S 2220:( 2217:E 2211:e 2208:, 2205:S 2199:a 2182:S 2178:ρ 2171:E 2167:S 2159:σ 2155:τ 2151:σ 2147:τ 2145:/ 2143:S 2139:S 2135:τ 2131:σ 2129:/ 2127:S 2123:S 2115:σ 2111:S 2107:S 2103:σ 2101:/ 2099:S 2091:σ 2074:. 2071:b 2068:, 2065:a 2059:c 2039:S 2033:c 2010:b 2002:a 1989:S 1952:. 1949:d 1946:b 1938:c 1935:a 1929:d 1921:c 1917:, 1914:b 1906:a 1889:ρ 1871:S 1867:S 1859:S 1839:( 1837:x 1809:S 1803:I 1790:S 1786:φ 1779:S 1739:θ 1736:s 1730:( 1726:S 1722:t 1720:, 1718:s 1713:θ 1711:) 1699:( 1695:T 1691:S 1687:θ 1680:T 1676:S 1656:S 1654:( 1652:E 1648:S 1640:S 1638:( 1636:E 1624:S 1616:S 1614:( 1612:E 1604:S 1602:( 1600:E 1593:S 1591:( 1589:E 1568:, 1565:f 1562:e 1559:= 1556:e 1550:f 1544:e 1527:S 1525:( 1523:E 1515:t 1499:R 1487:s 1481:t 1477:s 1472:t 1456:L 1444:s 1439:t 1435:s 1423:α 1419:x 1405:β 1401:α 1396:β 1392:α 1358:. 1353:1 1346:b 1337:1 1330:a 1323:b 1317:a 1291:d 1288:b 1282:c 1279:a 1273:d 1267:c 1264:, 1261:b 1255:a 1235:a 1232:a 1228:f 1220:e 1216:S 1212:f 1192:, 1189:f 1186:b 1183:= 1180:a 1174:b 1168:a 1155:S 1151:e 1131:, 1128:b 1125:e 1122:= 1119:a 1113:b 1107:a 1087:S 1071:d 1068:a 1065:a 1062:a 1058:e 1049:a 1046:e 1043:d 1040:a 1036:d 1027:b 1024:a 1021:a 1018:a 1014:c 1005:a 1002:c 999:b 996:a 992:b 983:a 980:a 977:a 974:a 970:a 961:d 958:c 955:b 952:a 938:b 928:a 896:. 894:) 892:a 888:b 884:b 880:a 878:( 860:X 841:S 818:1 811:b 807:b 804:= 799:1 792:a 788:a 782:b 776:R 770:a 766:, 763:b 758:1 751:b 747:= 744:a 739:1 732:a 725:b 719:L 713:a 692:s 676:R 660:s 657:s 653:s 637:L 619:. 601:R 577:L 549:R 525:L 506:S 490:S 486:S 479:S 471:S 456:S 452:x 447:x 444:x 435:S 427:x 424:x 411:a 408:b 402:( 394:x 390:S 386:x 350:X 340:X 324:X 318:I 282:α 274:α 254:1 243:] 219:[ 216:= 187:β 183:α 179:X 175:β 171:α 167:X 163:B 159:A 155:B 151:A 143:X 139:α 100:x 98:( 96:f 92:f 88:x 68:y 58:x 53:S 49:y 42:S 38:x 30:S

Index

group
semigroup
regular semigroup
partial symmetries
Viktor Vladimirovich Wagner
Soviet Union
Gordon Preston
United Kingdom
partial bijections
set
partial transformation
function
domain
preimage
pseudogroups
composition of binary relations
empty set
associative
binary operation
symmetric inverse semigroup
converse relation
symmetric group
group
group
symmetric group
§ Homomorphisms and representations of inverse semigroups
group
monoid
idempotent
group

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