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Hall word

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5391:. The first and most important property is that Lyndon words are a special case of Hall words. That is, the definition of a Lyndon word satisfies the definition of the Hall word. This can be readily verified by direct comparison; note that the direction of the inequality used in the definitions above is exactly the reverse of that used in the customary definition for Lyndon words. The set of Lyndon trees (which follow from the standard factorization) is a Hall set. 1876: 1454: 2493:
are obtained from the Hall set by "forgetting" the commutator brackets, but otherwise keeping the notion of total order. It turns out that this "forgetting" is harmless, as the corresponding Hall tree can be deduced from the word, and it is unique. That is, the Hall words are in one-to-one
2158: 1294:, and so can be directly compared; the weights are the string-lengths. The difference is that no mention of groups is required. These definitions all coincide with that of X. Viennot. Note that some authors reverse the order of the inequality. Note also that one of the conditions, the 4820:
It is not hard to show that both rewrites result in a new standard sequence. In general, it is most convenient to apply the rewrite to the right-most legal drop; however, it can be shown that the rewrite is confluent, and so one obtains the same results no matter what the order.
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provides a convenient stand-in for any other desired binary operator that might have additional properties, such as group or algebra commutators. Thus, for example, the magma juxtaposition can be mapped to the commutator of a non-commutative algebra:
4617: 1871:{\displaystyle {\begin{aligned}&b,a,\\&ab,\\&(ab)b,\;\;(ab)a,\\&((ab)b)b,\;\;((ab)b)a,\;\;((ab)a)a,\\&(((ab)b)b)b,\;(((ab)b)b)a,\;(((ab)b)a)a,\;(((ab)a)a)a,\;((ab)b)(ab),\;((ab)a)(ab),\\&\cdots \end{aligned}}} 5592:. In particular, this implies that no Hall word is a conjugate of another Hall word. Note again, this is exactly as it is for a Lyndon word: Lyndon words are the least of their conjugacy class; Hall words are the greatest. 1988: 833:, with parenthesis retained to show grouping. Parenthesis may be written with square brackets, so that elements of the free magma may be viewed as formal commutators. Equivalently, the free magma is the set of all 5321: 5214: 3431: 2759:
In this way, the Hall word ordering extends to a total order on the monoid. The lemmas and theorems required to provide the word-to-tree correspondence, and the unique ordering, are sketched below.
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otherwise. The foliage is just the string consisting of the leaves of the tree, that is, taking the tree written with commutator brackets, and erasing the commutator brackets.
1929: 3978: 51:; in fact, the Lyndon words are a special case, and almost all properties possessed by Lyndon words carry over to Hall words. Hall words are in one-to-one correspondence with 4334: 2846: 893: 587: 949: 5113: 3816: 2908: 537: 5057: 4863: 5778: 5662: 5626: 5532: 5470: 4087: 3772: 2600: 2481: 1365: 482: 322: 215: 5590: 5437: 3051: 1318: 1241: 5496: 5083: 4471: 2934: 1391: 1215: 1189: 1122: 1096: 1067: 1041: 1015: 4212:
properties of the system. The rewriting is performed by the exchange of certain pairs of consecutive Hall words in a sequence; it is given after these definitions.
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The converse to the above factorization establishes the correspondence between Hall words and Hall trees. This can be stated in the following interesting form: if
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Given a standard sequence with a legal drop, there are two distinct rewrite rules that create new standard sequences. One concatenates the two words in the drop:
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Because the Hall words can be placed into Hall trees, and each Hall tree can be interpreted as a commutator, the term rewrite can be used to perform the
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be factored into a descending sequence of other Hall words. This implies that, given a Hall word, the corresponding tree can be uniquely identified.
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can be uniquely factorized into a ascending sequence of Hall words. This is analogous to, and generalizes the better-known case of factorization with
5949: 2153:{\displaystyle M_{n}(k)\ =\ {1 \over k}\sum _{d\,|\,k}\mu \!\left({k \over d}\right)n^{d}={1 \over k}\sum _{d\,|\,k}\mu \!\left({d}\right)n^{k/d}} 1320:, may feel "backwards"; this "backwardness" is what provides the descending order required for factorization. Reversing the inequality does 5225: 5118: 690:, but this can lead to a proliferation of square brackets and commas. Keeping this in mind, one can otherwise be fluid in the notation. 1931:
elements of each distinct length. This is the beginning sequence of the necklace polynomial in two elements (described next, below).
5808: 76: 3368: 464:; the objects on the right just happen to have more structure than a magma does. To avoid the awkward typographical mess that is 2697: 5628:
is a Hall word if and only if it is larger than any of its proper right factors. This follows from the previous two points.
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correspondence with the Hall trees. The total order on the Hall trees passes over to a total order on the Hall words.
399: 5815:. Note that term rewriting with Lyndon words can also be used to obtain the needed commutation for the PBW theorem. 4962: 4905: 3499: 3303: 6063: 4222: 4209: 3837: 2563: 4810:{\displaystyle (h_{1},h_{2},\ldots ,h_{n})\to (h_{1},h_{2},\ldots ,h_{i-1},h_{i+1},h_{i},h_{i+2},\ldots ,h_{n})} 1448:
to simplify notation, using parenthesis only as needed. The initial members of the Hall set are then (in order)
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Another very important application of the rewrite rule is to perform the commutations that appear in the
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that allows any two elements to be juxtaposed, next to each other. The juxtaposition is taken to be
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is a Hall word. This conjugate is unique, since no Hall word is a conjugate of another Hall word.
5022: 4832: 5750: 5634: 5598: 5504: 5442: 4059: 3730: 2572: 4612:{\displaystyle (h_{1},h_{2},\ldots ,h_{n})\to (h_{1},h_{2},\ldots ,h_{i}h_{i+1},\ldots ,h_{n})} 2457: 1335: 467: 307: 200: 47:, and thus provide a total order on the monoid. This is analogous to the better-known case of 5566: 5409: 4205: 3012: 2188: 1297: 1220: 5475: 5062: 2913: 1370: 1194: 1168: 1101: 1075: 1046: 1020: 994: 5980: 5844: 5794: 5387:
Hall words have a number of curious properties, many of them nearly identical to those for
3906: 3683: 3056: 2854: 2667: 2534: 2507: 2498: 1251: 956: 127: 36: 5695: 5537: 3467: 3103: 2774: 2166: 767: 8: 5665: 4872: 4866: 3645: 1980: 612: 5724: 2419: 2202: 1396: 1130: 670: 487: 87:, which is a special case of the general construction given below. It can be shown that 5836: 5675: 3447: 3152: 3132: 2399: 2376: 2356: 2332: 2312: 2292: 2264: 2240: 1962: 1942: 902: 840: 816: 796: 592: 177: 157: 115: 5963: 2184: 1419: 638: 5968: 6035:
Guy Melançon and C. Reutenauer (1989), "Lyndon words, free algebras and shuffles",
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The total order on Hall trees passes over to Hall words. Thus, given a Hall word
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The construction and notation used below are nearly identical to that used in the
5976: 5873: 813:. The free magma is simply the set of non-associative strings in the letters of 703: 222: 218: 195: 94:
The historical development runs in reverse order from the above description. The
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The above two maps are just magma homomorphisms, in the conventional sense of a
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be the corresponding Hall word. Given any factorization of a Hall word
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This and the subsequent development below are given by Guy Melançon.
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W. Magnus, (1937) "Über Beziehungen zwischen höheren Kommutatoren",
3831: 5945:"A basis for free Lie rings and higher commutators in free groups" 4385:
If the sequence is a standard sequence, then the drop is termed a
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X. Viennot, (1978) "Algèbres de Lie libres et monoïdes libres" ,
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can be constructed recursively (in increasing order) as follows:
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that is a Hall word. Equivalently, there exists a factorization
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as needed, to disambiguate usage. Of course, one can also write
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can be achieved by defining and recursively applying a simple
3169:, then there exists a factorization into Hall trees such that 75:, and can be used to perform the commutations required by the 4089:
into a concatenation of an ascending sequence of Hall words
3426:{\displaystyle y_{1}\leq y_{2}\leq \cdots \leq y_{n}\leq y.} 4048:
Note that increasing sequences of Hall words are standard.
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The commutators can be ordered arbitrarily, provided that
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A basic result is that the number of elements of length
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is a Hall word if and only if for any factorization of
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while the other permutes the two elements in the drop:
4208:. The uniqueness of the factorization follows from the 110:
based on work of Philip Hall on groups. Subsequently,
2749:{\displaystyle h_{1}\leq h_{2}\leq \cdots \leq h_{k}.} 539:. The use of parenthesis is mandatory, however, since 5753: 5727: 5698: 5678: 5637: 5601: 5569: 5540: 5507: 5478: 5445: 5412: 5329: 5228: 5121: 5094: 5065: 5025: 4965: 4908: 4875: 4835: 4631: 4474: 4395: 4342: 4290: 4225: 4197:{\displaystyle h_{1}\leq h_{2}\leq \cdots \leq h_{k}} 4151: 4095: 4062: 3986: 3936: 3909: 3840: 3780: 3733: 3686: 3648: 3581: 3502: 3470: 3450: 3371: 3306: 3239: 3175: 3155: 3135: 3106: 3059: 3015: 2942: 2916: 2884: 2857: 2806: 2777: 2700: 2670: 2611: 2575: 2537: 2510: 2460: 2422: 2402: 2379: 2359: 2335: 2315: 2295: 2267: 2243: 2205: 2169: 1991: 1965: 1945: 1887: 1457: 1422: 1399: 1373: 1338: 1300: 1254: 1223: 1197: 1171: 1133: 1104: 1078: 1049: 1023: 997: 959: 928: 905: 866: 843: 819: 799: 770: 716: 706:
subset of a free non-associative algebra, that is, a
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subset of a free non-associative algebra, that is, a
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Construction providing a total order on a free monoid
71:. In this form, the Hall trees provide a basis for 5780:is the conjugate of a power of a unique Hall word. 5772: 5736: 5713: 5684: 5656: 5620: 5584: 5555: 5526: 5490: 5464: 5431: 5371: 5315: 5208: 5107: 5077: 5051: 5008: 4951: 4887: 4869:, but at the level of Hall words. Given two words 4857: 4809: 4611: 4456:{\displaystyle h_{i+1}\leq h_{i+2},\ldots ,h_{n}.} 4455: 4377: 4328: 4276: 4196: 4137: 4081: 4040: 3972: 3922: 3891: 3810: 3766: 3719: 3660: 3631: 3561: 3485: 3456: 3425: 3351: 3289: 3225: 3161: 3141: 3121: 3092: 3045: 2993: 2928: 2902: 2870: 2840: 2792: 2748: 2683: 2653: 2594: 2550: 2523: 2475: 2446: 2408: 2385: 2365: 2341: 2321: 2301: 2273: 2249: 2229: 2175: 2152: 1971: 1951: 1923: 1870: 1440: 1408: 1385: 1359: 1312: 1278: 1235: 1209: 1183: 1157: 1116: 1090: 1061: 1035: 1009: 983: 943: 911: 887: 849: 825: 805: 785: 756: 682: 659: 627: 601: 581: 531: 499: 476: 449: 382: 316: 293: 255: 209: 186: 166: 3632:{\displaystyle f(t_{1})\leq \cdots \leq f(t_{n})} 2118: 2053: 6050: 5950:Proceedings of the American Mathematical Society 4041:{\displaystyle v_{i}\leq w_{i+1},\cdots ,w_{n}.} 3930:is either a letter, or a standard factorization 3464:is a Hall tree, and the corresponding Hall word 2602:can be written as a concatenation of Hall words 2199:Some basic definitions are useful. Given a tree 609:is a compound object, one might sometimes write 450:{\displaystyle a\bullet b\mapsto aba^{-1}b^{-1}} 5406:. That is, they cannot be written in the form 5897:Proceedings of the London Mathematical Society 5009:{\displaystyle \quad v=v_{1}v_{2}\cdots v_{n}} 4952:{\displaystyle u=u_{1}u_{2}\cdots u_{m}\quad } 3004: 1332:Consider the generating set with two elements 5789:There is a similar term rewriting system for 3562:{\displaystyle f(t)=f(t_{1})\cdots f(t_{n})} 3352:{\displaystyle x_{1},\ldots ,x_{m}>y_{1}} 2691:being totally ordered by the Hall ordering: 1351: 1339: 174:generators. This is simply a set containing 4829:A total order can be provided on the words 4277:{\displaystyle (h_{1},h_{2},\ldots ,h_{n})} 3892:{\displaystyle (w_{1},w_{2},\ldots ,w_{n})} 145: 6016:Combinatorics of Hall trees and Hall words 6010: 6008: 6006: 1817: 1780: 1743: 1706: 1669: 1598: 1597: 1569: 1568: 1515: 1514: 5962: 5372:{\displaystyle \quad u_{k+1}<v_{k+1}.} 5282: 5255: 5176: 5149: 4895:factored into ascending Hall word order, 3675: 3290:{\displaystyle v=f(y_{1})\cdots f(y_{n})} 3226:{\displaystyle u=f(x_{1})\cdots f(x_{m})} 2194: 2109: 2103: 2044: 2038: 5668:to a Hall word. That is, there exists a 4138:{\displaystyle w=h_{1}h_{2}\cdots h_{k}} 2654:{\displaystyle w=h_{1}h_{2}\cdots h_{k}} 383:{\displaystyle a\bullet b\mapsto =ab-ba} 6003: 5935: 5933: 5847:. This correspondence was motivated by 757:{\displaystyle A={a_{1},\ldots ,a_{n}}} 130:. This correspondence was motivated by 6051: 5059:a Hall word, one has an ordering that 2373:itself or an extreme right subtree of 922:The Hall set contains the generators: 4056:The unique factorization of any word 2309:itself, or a right subtree of either 294:{\displaystyle a\bullet (b\bullet c)} 256:{\displaystyle (a\bullet b)\bullet c} 5939: 5930: 5891: 5839:associated with the filtration on a 3825: 150:The setting for this article is the 5797:is accomplished with Lyndon words. 919:are given an arbitrary total order. 484:, it is conventional to just write 13: 2994:{\displaystyle f:\mapsto f(x)f(y)} 2416:is a right subtree of a Hall tree 837:with leaves marked by elements of 14: 6075: 5964:10.1090/S0002-9939-1950-0038336-7 4378:{\displaystyle h_{i}>h_{i+1}.} 4051: 3439: 1924:{\displaystyle 2,1,2,3,6,\ldots } 98:was described first, in 1934, by 4865:This is similar to the standard 3973:{\displaystyle w_{i}=u_{i}v_{i}} 1934: 764:be a set of generators, and let 304:In this way, the magma operator 59:; taken together, they form the 6037:Canadian Journal of Mathematics 6020:Journal of Combinatorial Theory 5784: 5330: 5312: 5122: 5104: 4966: 4948: 4329:{\displaystyle (h_{i},h_{i+1})} 2841:{\displaystyle f:M(A)\to A^{*}} 888:{\displaystyle H\subseteq M(A)} 582:{\displaystyle (ab)c\neq a(bc)} 106:. Hall sets were introduced by 6029: 5986: 5914: 5885: 5835:showed that they arise as the 5809:Poincaré–Birkhoff–Witt theorem 4824: 4804: 4683: 4680: 4677: 4632: 4606: 4526: 4523: 4520: 4475: 4323: 4291: 4271: 4226: 3886: 3841: 3805: 3799: 3790: 3784: 3761: 3755: 3749: 3743: 3714: 3711: 3699: 3696: 3626: 3613: 3598: 3585: 3556: 3543: 3534: 3521: 3512: 3506: 3480: 3474: 3284: 3271: 3262: 3249: 3220: 3207: 3198: 3185: 3087: 3084: 3072: 3069: 3034: 3022: 2988: 2982: 2976: 2970: 2964: 2961: 2949: 2894: 2825: 2822: 2816: 2787: 2781: 2441: 2429: 2224: 2212: 2105: 2040: 2008: 2002: 1848: 1839: 1836: 1830: 1821: 1818: 1811: 1802: 1799: 1793: 1784: 1781: 1771: 1765: 1759: 1750: 1747: 1744: 1734: 1728: 1722: 1713: 1710: 1707: 1697: 1691: 1685: 1676: 1673: 1670: 1660: 1654: 1648: 1639: 1636: 1633: 1617: 1611: 1602: 1599: 1588: 1582: 1573: 1570: 1559: 1553: 1544: 1541: 1525: 1516: 1505: 1496: 1435: 1423: 1273: 1261: 1152: 1140: 972: 960: 882: 876: 780: 774: 654: 642: 622: 616: 576: 567: 555: 546: 526: 514: 412: 359: 347: 344: 288: 276: 244: 232: 114:showed that they arise as the 79:used in the construction of a 77:Poincaré–Birkhoff–Witt theorem 1: 5879: 5823:Hall sets were introduced by 5813:universal enveloping algebras 5802:commutator collecting process 5382: 3668:. In other words, Hall words 2497:This correspondence allows a 2485: 1324:reverse this "backwardness". 1292:commutator collecting process 944:{\displaystyle A\subseteq H.} 96:commutator collecting process 85:commutator collecting process 5994:Lecture Notes in Mathematics 5108:{\displaystyle m<n\quad } 3811:{\displaystyle f(x)>f(y)} 2903:{\displaystyle f:a\mapsto a} 1979:generators) is given by the 532:{\displaystyle (a\bullet b)} 81:universal enveloping algebra 7: 5862: 5563:into non-empty words obeys 5052:{\displaystyle u_{i},v_{j}} 4858:{\displaystyle w\in A^{*}.} 3129:into two non-empty strings 3005:Factorization of Hall words 2569:More precisely, every word 693: 63:. This set is a particular 10: 6080: 5818: 5773:{\displaystyle w\in A^{*}} 5657:{\displaystyle w\in A^{*}} 5621:{\displaystyle w\in A^{*}} 5527:{\displaystyle w\in A^{*}} 5465:{\displaystyle x\in A^{*}} 5394:Other properties include: 4082:{\displaystyle w\in A^{*}} 3767:{\displaystyle w=f(x)f(y)} 3727:, it can be factorized as 2762: 2595:{\displaystyle w\in A^{*}} 1327: 393:or to a group commutator: 5831:on groups. Subsequently, 5795:factorization of a monoid 2800:is the canonical mapping 2396:A basic lemma is that if 91:coincide with Hall sets. 5855:due to Philip Hall and 4284:of Hall words is a pair 2476:{\displaystyle v\leq y.} 1360:{\displaystyle \{a,b\}.} 477:{\displaystyle \bullet } 317:{\displaystyle \bullet } 210:{\displaystyle \bullet } 146:Notational preliminaries 138:due to Philip Hall and 102:and explored in 1937 by 5909:10.1112/plms/s2-36.1.29 5585:{\displaystyle w>vu} 5432:{\displaystyle w=x^{n}} 3046:{\displaystyle t=\in H} 2564:Chen–Fox–Lyndon theorem 2283:immediate right subtree 1313:{\displaystyle v\leq y} 1236:{\displaystyle v\leq y} 793:be the free magma over 194:elements, along with a 6064:Combinatorics on words 6014:Guy Melançon, (1992) " 5869:Hall–Petresco identity 5774: 5738: 5715: 5686: 5658: 5622: 5586: 5557: 5528: 5492: 5491:{\displaystyle n>1} 5466: 5433: 5373: 5317: 5210: 5109: 5079: 5078:{\displaystyle u<v} 5053: 5010: 4953: 4889: 4859: 4811: 4613: 4457: 4379: 4330: 4278: 4198: 4139: 4083: 4042: 3974: 3924: 3893: 3820:standard factorization 3812: 3768: 3721: 3676:Standard factorization 3662: 3633: 3563: 3487: 3458: 3427: 3353: 3291: 3227: 3163: 3143: 3123: 3094: 3047: 2995: 2930: 2929:{\displaystyle a\in A} 2904: 2872: 2848:from the magma to the 2842: 2794: 2750: 2685: 2655: 2596: 2552: 2525: 2477: 2448: 2410: 2387: 2367: 2343: 2323: 2303: 2275: 2259:immediate left subtree 2251: 2231: 2195:Definitions and Lemmas 2177: 2154: 1973: 1959:in the Hall set (over 1953: 1925: 1881:Notice that there are 1872: 1442: 1410: 1387: 1386:{\displaystyle a>b} 1361: 1314: 1280: 1237: 1211: 1210:{\displaystyle v\in H} 1185: 1184:{\displaystyle u\in H} 1159: 1118: 1117:{\displaystyle y\in A} 1092: 1091:{\displaystyle x\in A} 1063: 1062:{\displaystyle x>y} 1037: 1036:{\displaystyle y\in H} 1011: 1010:{\displaystyle x\in H} 985: 945: 913: 889: 851: 827: 807: 787: 758: 684: 661: 629: 603: 583: 533: 501: 478: 451: 384: 318: 295: 257: 211: 188: 168: 6043:, No. 4, pp. 577-591. 5775: 5739: 5716: 5687: 5659: 5631:Every primitive word 5623: 5587: 5558: 5529: 5493: 5467: 5434: 5374: 5318: 5211: 5110: 5080: 5054: 5011: 4954: 4890: 4860: 4812: 4614: 4458: 4389:if one also has that 4380: 4331: 4279: 4206:term rewriting system 4199: 4140: 4084: 4043: 3975: 3925: 3923:{\displaystyle w_{i}} 3894: 3818:. This is termed the 3813: 3769: 3722: 3720:{\displaystyle w=f()} 3663: 3634: 3564: 3488: 3459: 3428: 3354: 3292: 3228: 3164: 3144: 3124: 3095: 3093:{\displaystyle w=f()} 3048: 2996: 2931: 2905: 2873: 2871:{\displaystyle A^{*}} 2843: 2795: 2751: 2686: 2684:{\displaystyle h_{j}} 2656: 2597: 2553: 2551:{\displaystyle A^{*}} 2526: 2524:{\displaystyle A^{*}} 2478: 2449: 2411: 2388: 2368: 2351:extreme right subtree 2344: 2324: 2304: 2276: 2252: 2232: 2189:Dirichlet convolution 2178: 2155: 1974: 1954: 1926: 1873: 1443: 1411: 1388: 1362: 1315: 1281: 1279:{\displaystyle y<} 1238: 1212: 1186: 1160: 1119: 1093: 1064: 1038: 1012: 986: 984:{\displaystyle \in H} 946: 914: 890: 852: 828: 808: 788: 759: 685: 662: 630: 604: 589:as already noted. If 584: 534: 502: 479: 452: 385: 319: 296: 258: 212: 189: 169: 5845:lower central series 5751: 5725: 5714:{\displaystyle w=uv} 5696: 5676: 5635: 5599: 5567: 5556:{\displaystyle w=uv} 5538: 5505: 5476: 5443: 5410: 5327: 5226: 5119: 5092: 5063: 5023: 4963: 4906: 4873: 4833: 4629: 4472: 4393: 4340: 4288: 4223: 4149: 4093: 4060: 3984: 3934: 3907: 3838: 3778: 3731: 3684: 3646: 3579: 3500: 3486:{\displaystyle f(t)} 3468: 3448: 3369: 3304: 3237: 3173: 3153: 3133: 3122:{\displaystyle w=uv} 3104: 3057: 3053:be a Hall tree, and 3013: 2940: 2914: 2882: 2855: 2804: 2793:{\displaystyle M(A)} 2775: 2698: 2668: 2664:with each Hall word 2609: 2573: 2535: 2508: 2499:monoid factorisation 2458: 2420: 2400: 2377: 2357: 2333: 2313: 2293: 2265: 2241: 2203: 2176:{\displaystyle \mu } 2167: 1989: 1963: 1943: 1885: 1455: 1420: 1397: 1371: 1336: 1298: 1252: 1221: 1195: 1169: 1131: 1102: 1076: 1047: 1021: 995: 957: 953:A formal commutator 926: 903: 864: 841: 817: 797: 786:{\displaystyle M(A)} 768: 714: 671: 639: 613: 593: 543: 511: 488: 468: 400: 332: 308: 267: 229: 201: 178: 158: 128:lower central series 118:associated with the 37:monoid factorisation 4888:{\displaystyle u,v} 4867:lexicographic order 3661:{\displaystyle n=1} 1981:necklace polynomial 628:{\displaystyle (a)} 263:is not the same as 5837:graded Lie algebra 5793:, this is how the 5770: 5737:{\displaystyle vu} 5734: 5711: 5682: 5654: 5618: 5582: 5553: 5524: 5488: 5462: 5429: 5369: 5313: 5206: 5105: 5075: 5049: 5006: 4949: 4885: 4855: 4807: 4609: 4453: 4375: 4326: 4274: 4194: 4135: 4079: 4038: 3970: 3920: 3889: 3808: 3764: 3717: 3658: 3629: 3559: 3483: 3454: 3423: 3349: 3287: 3223: 3159: 3139: 3119: 3090: 3043: 2991: 2926: 2900: 2868: 2838: 2790: 2746: 2681: 2651: 2592: 2548: 2521: 2473: 2447:{\displaystyle t=} 2444: 2406: 2383: 2363: 2339: 2319: 2299: 2271: 2247: 2230:{\displaystyle t=} 2227: 2173: 2150: 2114: 2049: 1969: 1949: 1921: 1868: 1866: 1438: 1409:{\displaystyle xy} 1406: 1383: 1357: 1310: 1276: 1233: 1207: 1181: 1158:{\displaystyle x=} 1155: 1114: 1088: 1059: 1033: 1007: 981: 941: 909: 885: 847: 823: 803: 783: 754: 683:{\displaystyle ab} 680: 657: 625: 599: 579: 529: 500:{\displaystyle ab} 497: 474: 447: 380: 314: 291: 253: 207: 184: 164: 116:graded Lie algebra 23:, in the areas of 6000:, Springer–Verlag 5827:based on work of 5685:{\displaystyle w} 3901:standard sequence 3826:Standard sequence 3457:{\displaystyle t} 3162:{\displaystyle v} 3142:{\displaystyle u} 2531:, any element of 2409:{\displaystyle v} 2386:{\displaystyle y} 2366:{\displaystyle y} 2342:{\displaystyle y} 2322:{\displaystyle x} 2302:{\displaystyle y} 2274:{\displaystyle y} 2250:{\displaystyle x} 2095: 2093: 2066: 2030: 2028: 2019: 2013: 1972:{\displaystyle n} 1952:{\displaystyle k} 912:{\displaystyle A} 850:{\displaystyle A} 826:{\displaystyle A} 806:{\displaystyle A} 602:{\displaystyle a} 187:{\displaystyle n} 167:{\displaystyle n} 73:free Lie algebras 35:provide a unique 6071: 6059:Formal languages 6044: 6033: 6027: 6026:(2) pp. 285–308. 6012: 6001: 5990: 5984: 5983: 5966: 5937: 5928: 5918: 5912: 5911: 5889: 5779: 5777: 5776: 5771: 5769: 5768: 5743: 5741: 5740: 5735: 5720: 5718: 5717: 5712: 5691: 5689: 5688: 5683: 5663: 5661: 5660: 5655: 5653: 5652: 5627: 5625: 5624: 5619: 5617: 5616: 5591: 5589: 5588: 5583: 5562: 5560: 5559: 5554: 5533: 5531: 5530: 5525: 5523: 5522: 5497: 5495: 5494: 5489: 5471: 5469: 5468: 5463: 5461: 5460: 5438: 5436: 5435: 5430: 5428: 5427: 5402:, also known as 5378: 5376: 5375: 5370: 5365: 5364: 5346: 5345: 5322: 5320: 5319: 5314: 5311: 5310: 5298: 5297: 5278: 5277: 5265: 5264: 5251: 5250: 5238: 5237: 5215: 5213: 5212: 5207: 5205: 5204: 5192: 5191: 5172: 5171: 5159: 5158: 5145: 5144: 5132: 5131: 5114: 5112: 5111: 5106: 5084: 5082: 5081: 5076: 5058: 5056: 5055: 5050: 5048: 5047: 5035: 5034: 5015: 5013: 5012: 5007: 5005: 5004: 4992: 4991: 4982: 4981: 4958: 4956: 4955: 4950: 4947: 4946: 4934: 4933: 4924: 4923: 4894: 4892: 4891: 4886: 4864: 4862: 4861: 4856: 4851: 4850: 4816: 4814: 4813: 4808: 4803: 4802: 4784: 4783: 4765: 4764: 4752: 4751: 4733: 4732: 4708: 4707: 4695: 4694: 4676: 4675: 4657: 4656: 4644: 4643: 4618: 4616: 4615: 4610: 4605: 4604: 4586: 4585: 4570: 4569: 4551: 4550: 4538: 4537: 4519: 4518: 4500: 4499: 4487: 4486: 4462: 4460: 4459: 4454: 4449: 4448: 4430: 4429: 4411: 4410: 4384: 4382: 4381: 4376: 4371: 4370: 4352: 4351: 4335: 4333: 4332: 4327: 4322: 4321: 4303: 4302: 4283: 4281: 4280: 4275: 4270: 4269: 4251: 4250: 4238: 4237: 4203: 4201: 4200: 4195: 4193: 4192: 4174: 4173: 4161: 4160: 4144: 4142: 4141: 4136: 4134: 4133: 4121: 4120: 4111: 4110: 4088: 4086: 4085: 4080: 4078: 4077: 4047: 4045: 4044: 4039: 4034: 4033: 4015: 4014: 3996: 3995: 3979: 3977: 3976: 3971: 3969: 3968: 3959: 3958: 3946: 3945: 3929: 3927: 3926: 3921: 3919: 3918: 3899:is said to be a 3898: 3896: 3895: 3890: 3885: 3884: 3866: 3865: 3853: 3852: 3817: 3815: 3814: 3809: 3773: 3771: 3770: 3765: 3726: 3724: 3723: 3718: 3667: 3665: 3664: 3659: 3638: 3636: 3635: 3630: 3625: 3624: 3597: 3596: 3568: 3566: 3565: 3560: 3555: 3554: 3533: 3532: 3492: 3490: 3489: 3484: 3463: 3461: 3460: 3455: 3432: 3430: 3429: 3424: 3413: 3412: 3394: 3393: 3381: 3380: 3358: 3356: 3355: 3350: 3348: 3347: 3335: 3334: 3316: 3315: 3296: 3294: 3293: 3288: 3283: 3282: 3261: 3260: 3232: 3230: 3229: 3224: 3219: 3218: 3197: 3196: 3168: 3166: 3165: 3160: 3148: 3146: 3145: 3140: 3128: 3126: 3125: 3120: 3099: 3097: 3096: 3091: 3052: 3050: 3049: 3044: 3000: 2998: 2997: 2992: 2935: 2933: 2932: 2927: 2909: 2907: 2906: 2901: 2877: 2875: 2874: 2869: 2867: 2866: 2847: 2845: 2844: 2839: 2837: 2836: 2799: 2797: 2796: 2791: 2755: 2753: 2752: 2747: 2742: 2741: 2723: 2722: 2710: 2709: 2690: 2688: 2687: 2682: 2680: 2679: 2660: 2658: 2657: 2652: 2650: 2649: 2637: 2636: 2627: 2626: 2601: 2599: 2598: 2593: 2591: 2590: 2562:provided by the 2557: 2555: 2554: 2549: 2547: 2546: 2530: 2528: 2527: 2522: 2520: 2519: 2482: 2480: 2479: 2474: 2453: 2451: 2450: 2445: 2415: 2413: 2412: 2407: 2392: 2390: 2389: 2384: 2372: 2370: 2369: 2364: 2348: 2346: 2345: 2340: 2328: 2326: 2325: 2320: 2308: 2306: 2305: 2300: 2280: 2278: 2277: 2272: 2261:, and likewise, 2256: 2254: 2253: 2248: 2236: 2234: 2233: 2228: 2182: 2180: 2179: 2174: 2159: 2157: 2156: 2151: 2149: 2148: 2144: 2131: 2127: 2113: 2108: 2094: 2086: 2081: 2080: 2071: 2067: 2059: 2048: 2043: 2029: 2021: 2017: 2011: 2001: 2000: 1978: 1976: 1975: 1970: 1958: 1956: 1955: 1950: 1930: 1928: 1927: 1922: 1877: 1875: 1874: 1869: 1867: 1857: 1629: 1537: 1492: 1478: 1461: 1447: 1445: 1444: 1441:{\displaystyle } 1439: 1415: 1413: 1412: 1407: 1392: 1390: 1389: 1384: 1366: 1364: 1363: 1358: 1319: 1317: 1316: 1311: 1285: 1283: 1282: 1277: 1242: 1240: 1239: 1234: 1216: 1214: 1213: 1208: 1190: 1188: 1187: 1182: 1164: 1162: 1161: 1156: 1123: 1121: 1120: 1115: 1097: 1095: 1094: 1089: 1068: 1066: 1065: 1060: 1042: 1040: 1039: 1034: 1016: 1014: 1013: 1008: 990: 988: 987: 982: 950: 948: 947: 942: 918: 916: 915: 910: 899:The elements of 894: 892: 891: 886: 856: 854: 853: 848: 832: 830: 829: 824: 812: 810: 809: 804: 792: 790: 789: 784: 763: 761: 760: 755: 753: 752: 751: 733: 732: 689: 687: 686: 681: 666: 664: 663: 660:{\displaystyle } 658: 634: 632: 631: 626: 608: 606: 605: 600: 588: 586: 585: 580: 538: 536: 535: 530: 506: 504: 503: 498: 483: 481: 480: 475: 456: 454: 453: 448: 446: 445: 433: 432: 389: 387: 386: 381: 323: 321: 320: 315: 300: 298: 297: 292: 262: 260: 259: 254: 216: 214: 213: 208: 193: 191: 190: 185: 173: 171: 170: 165: 43:. They are also 6079: 6078: 6074: 6073: 6072: 6070: 6069: 6068: 6049: 6048: 6047: 6034: 6030: 6013: 6004: 5991: 5987: 5938: 5931: 5919: 5915: 5890: 5886: 5882: 5874:Markov odometer 5865: 5821: 5787: 5764: 5760: 5752: 5749: 5748: 5726: 5723: 5722: 5697: 5694: 5693: 5677: 5674: 5673: 5648: 5644: 5636: 5633: 5632: 5612: 5608: 5600: 5597: 5596: 5568: 5565: 5564: 5539: 5536: 5535: 5518: 5514: 5506: 5503: 5502: 5477: 5474: 5473: 5456: 5452: 5444: 5441: 5440: 5423: 5419: 5411: 5408: 5407: 5398:Hall words are 5385: 5354: 5350: 5335: 5331: 5328: 5325: 5324: 5306: 5302: 5293: 5289: 5273: 5269: 5260: 5256: 5246: 5242: 5233: 5229: 5227: 5224: 5223: 5200: 5196: 5187: 5183: 5167: 5163: 5154: 5150: 5140: 5136: 5127: 5123: 5120: 5117: 5116: 5093: 5090: 5089: 5064: 5061: 5060: 5043: 5039: 5030: 5026: 5024: 5021: 5020: 5000: 4996: 4987: 4983: 4977: 4973: 4964: 4961: 4960: 4942: 4938: 4929: 4925: 4919: 4915: 4907: 4904: 4903: 4874: 4871: 4870: 4846: 4842: 4834: 4831: 4830: 4827: 4798: 4794: 4773: 4769: 4760: 4756: 4741: 4737: 4722: 4718: 4703: 4699: 4690: 4686: 4671: 4667: 4652: 4648: 4639: 4635: 4630: 4627: 4626: 4600: 4596: 4575: 4571: 4565: 4561: 4546: 4542: 4533: 4529: 4514: 4510: 4495: 4491: 4482: 4478: 4473: 4470: 4469: 4444: 4440: 4419: 4415: 4400: 4396: 4394: 4391: 4390: 4360: 4356: 4347: 4343: 4341: 4338: 4337: 4311: 4307: 4298: 4294: 4289: 4286: 4285: 4265: 4261: 4246: 4242: 4233: 4229: 4224: 4221: 4220: 4188: 4184: 4169: 4165: 4156: 4152: 4150: 4147: 4146: 4129: 4125: 4116: 4112: 4106: 4102: 4094: 4091: 4090: 4073: 4069: 4061: 4058: 4057: 4054: 4029: 4025: 4004: 4000: 3991: 3987: 3985: 3982: 3981: 3964: 3960: 3954: 3950: 3941: 3937: 3935: 3932: 3931: 3914: 3910: 3908: 3905: 3904: 3880: 3876: 3861: 3857: 3848: 3844: 3839: 3836: 3835: 3828: 3779: 3776: 3775: 3732: 3729: 3728: 3685: 3682: 3681: 3678: 3647: 3644: 3643: 3620: 3616: 3592: 3588: 3580: 3577: 3576: 3550: 3546: 3528: 3524: 3501: 3498: 3497: 3469: 3466: 3465: 3449: 3446: 3445: 3442: 3408: 3404: 3389: 3385: 3376: 3372: 3370: 3367: 3366: 3343: 3339: 3330: 3326: 3311: 3307: 3305: 3302: 3301: 3278: 3274: 3256: 3252: 3238: 3235: 3234: 3214: 3210: 3192: 3188: 3174: 3171: 3170: 3154: 3151: 3150: 3134: 3131: 3130: 3105: 3102: 3101: 3058: 3055: 3054: 3014: 3011: 3010: 3007: 2941: 2938: 2937: 2915: 2912: 2911: 2883: 2880: 2879: 2862: 2858: 2856: 2853: 2852: 2832: 2828: 2805: 2802: 2801: 2776: 2773: 2772: 2765: 2737: 2733: 2718: 2714: 2705: 2701: 2699: 2696: 2695: 2675: 2671: 2669: 2666: 2665: 2645: 2641: 2632: 2628: 2622: 2618: 2610: 2607: 2606: 2586: 2582: 2574: 2571: 2570: 2542: 2538: 2536: 2533: 2532: 2515: 2511: 2509: 2506: 2505: 2488: 2459: 2456: 2455: 2421: 2418: 2417: 2401: 2398: 2397: 2378: 2375: 2374: 2358: 2355: 2354: 2334: 2331: 2330: 2314: 2311: 2310: 2294: 2291: 2290: 2266: 2263: 2262: 2242: 2239: 2238: 2204: 2201: 2200: 2197: 2187:. The sum is a 2185:Möbius function 2183:is the classic 2168: 2165: 2164: 2140: 2136: 2132: 2123: 2119: 2104: 2099: 2085: 2076: 2072: 2058: 2054: 2039: 2034: 2020: 1996: 1992: 1990: 1987: 1986: 1964: 1961: 1960: 1944: 1941: 1940: 1937: 1886: 1883: 1882: 1865: 1864: 1855: 1854: 1627: 1626: 1535: 1534: 1490: 1489: 1476: 1475: 1458: 1456: 1453: 1452: 1421: 1418: 1417: 1398: 1395: 1394: 1372: 1369: 1368: 1337: 1334: 1333: 1330: 1299: 1296: 1295: 1253: 1250: 1249: 1222: 1219: 1218: 1196: 1193: 1192: 1170: 1167: 1166: 1132: 1129: 1128: 1103: 1100: 1099: 1077: 1074: 1073: 1048: 1045: 1044: 1022: 1019: 1018: 996: 993: 992: 991:if and only if 958: 955: 954: 927: 924: 923: 904: 901: 900: 865: 862: 861: 842: 839: 838: 818: 815: 814: 798: 795: 794: 769: 766: 765: 747: 743: 728: 724: 723: 715: 712: 711: 704:totally ordered 696: 672: 669: 668: 640: 637: 636: 614: 611: 610: 594: 591: 590: 544: 541: 540: 512: 509: 508: 489: 486: 485: 469: 466: 465: 438: 434: 425: 421: 401: 398: 397: 333: 330: 329: 309: 306: 305: 268: 265: 264: 230: 227: 226: 223:non-commutative 219:non-associative 202: 199: 198: 196:binary operator 179: 176: 175: 159: 156: 155: 148: 65:totally ordered 45:totally ordered 17: 12: 11: 5: 6077: 6067: 6066: 6061: 6046: 6045: 6028: 6002: 5985: 5957:(5): 575–581, 5941:Hall, Marshall 5929: 5913: 5883: 5881: 5878: 5877: 5876: 5871: 5864: 5861: 5851:identities in 5833:Wilhelm Magnus 5820: 5817: 5786: 5783: 5782: 5781: 5767: 5763: 5759: 5756: 5745: 5733: 5730: 5710: 5707: 5704: 5701: 5681: 5670:circular shift 5651: 5647: 5643: 5640: 5629: 5615: 5611: 5607: 5604: 5593: 5581: 5578: 5575: 5572: 5552: 5549: 5546: 5543: 5521: 5517: 5513: 5510: 5499: 5487: 5484: 5481: 5459: 5455: 5451: 5448: 5439:for some word 5426: 5422: 5418: 5415: 5384: 5381: 5380: 5379: 5368: 5363: 5360: 5357: 5353: 5349: 5344: 5341: 5338: 5334: 5309: 5305: 5301: 5296: 5292: 5288: 5285: 5281: 5276: 5272: 5268: 5263: 5259: 5254: 5249: 5245: 5241: 5236: 5232: 5217: 5216: 5203: 5199: 5195: 5190: 5186: 5182: 5179: 5175: 5170: 5166: 5162: 5157: 5153: 5148: 5143: 5139: 5135: 5130: 5126: 5103: 5100: 5097: 5074: 5071: 5068: 5046: 5042: 5038: 5033: 5029: 5017: 5016: 5003: 4999: 4995: 4990: 4986: 4980: 4976: 4972: 4969: 4945: 4941: 4937: 4932: 4928: 4922: 4918: 4914: 4911: 4884: 4881: 4878: 4854: 4849: 4845: 4841: 4838: 4826: 4823: 4818: 4817: 4806: 4801: 4797: 4793: 4790: 4787: 4782: 4779: 4776: 4772: 4768: 4763: 4759: 4755: 4750: 4747: 4744: 4740: 4736: 4731: 4728: 4725: 4721: 4717: 4714: 4711: 4706: 4702: 4698: 4693: 4689: 4685: 4682: 4679: 4674: 4670: 4666: 4663: 4660: 4655: 4651: 4647: 4642: 4638: 4634: 4620: 4619: 4608: 4603: 4599: 4595: 4592: 4589: 4584: 4581: 4578: 4574: 4568: 4564: 4560: 4557: 4554: 4549: 4545: 4541: 4536: 4532: 4528: 4525: 4522: 4517: 4513: 4509: 4506: 4503: 4498: 4494: 4490: 4485: 4481: 4477: 4452: 4447: 4443: 4439: 4436: 4433: 4428: 4425: 4422: 4418: 4414: 4409: 4406: 4403: 4399: 4374: 4369: 4366: 4363: 4359: 4355: 4350: 4346: 4325: 4320: 4317: 4314: 4310: 4306: 4301: 4297: 4293: 4273: 4268: 4264: 4260: 4257: 4254: 4249: 4245: 4241: 4236: 4232: 4228: 4219:in a sequence 4191: 4187: 4183: 4180: 4177: 4172: 4168: 4164: 4159: 4155: 4132: 4128: 4124: 4119: 4115: 4109: 4105: 4101: 4098: 4076: 4072: 4068: 4065: 4053: 4052:Term rewriting 4050: 4037: 4032: 4028: 4024: 4021: 4018: 4013: 4010: 4007: 4003: 3999: 3994: 3990: 3967: 3963: 3957: 3953: 3949: 3944: 3940: 3917: 3913: 3888: 3883: 3879: 3875: 3872: 3869: 3864: 3860: 3856: 3851: 3847: 3843: 3834:of Hall words 3827: 3824: 3807: 3804: 3801: 3798: 3795: 3792: 3789: 3786: 3783: 3763: 3760: 3757: 3754: 3751: 3748: 3745: 3742: 3739: 3736: 3716: 3713: 3710: 3707: 3704: 3701: 3698: 3695: 3692: 3689: 3677: 3674: 3657: 3654: 3651: 3640: 3639: 3628: 3623: 3619: 3615: 3612: 3609: 3606: 3603: 3600: 3595: 3591: 3587: 3584: 3570: 3569: 3558: 3553: 3549: 3545: 3542: 3539: 3536: 3531: 3527: 3523: 3520: 3517: 3514: 3511: 3508: 3505: 3493:factorizes as 3482: 3479: 3476: 3473: 3453: 3441: 3440:Correspondence 3438: 3434: 3433: 3422: 3419: 3416: 3411: 3407: 3403: 3400: 3397: 3392: 3388: 3384: 3379: 3375: 3360: 3359: 3346: 3342: 3338: 3333: 3329: 3325: 3322: 3319: 3314: 3310: 3286: 3281: 3277: 3273: 3270: 3267: 3264: 3259: 3255: 3251: 3248: 3245: 3242: 3222: 3217: 3213: 3209: 3206: 3203: 3200: 3195: 3191: 3187: 3184: 3181: 3178: 3158: 3138: 3118: 3115: 3112: 3109: 3089: 3086: 3083: 3080: 3077: 3074: 3071: 3068: 3065: 3062: 3042: 3039: 3036: 3033: 3030: 3027: 3024: 3021: 3018: 3006: 3003: 2990: 2987: 2984: 2981: 2978: 2975: 2972: 2969: 2966: 2963: 2960: 2957: 2954: 2951: 2948: 2945: 2925: 2922: 2919: 2899: 2896: 2893: 2890: 2887: 2865: 2861: 2835: 2831: 2827: 2824: 2821: 2818: 2815: 2812: 2809: 2789: 2786: 2783: 2780: 2764: 2761: 2757: 2756: 2745: 2740: 2736: 2732: 2729: 2726: 2721: 2717: 2713: 2708: 2704: 2678: 2674: 2662: 2661: 2648: 2644: 2640: 2635: 2631: 2625: 2621: 2617: 2614: 2589: 2585: 2581: 2578: 2545: 2541: 2518: 2514: 2487: 2484: 2472: 2469: 2466: 2463: 2443: 2440: 2437: 2434: 2431: 2428: 2425: 2405: 2382: 2362: 2338: 2318: 2298: 2270: 2257:is called the 2246: 2237:, the element 2226: 2223: 2220: 2217: 2214: 2211: 2208: 2196: 2193: 2172: 2161: 2160: 2147: 2143: 2139: 2135: 2130: 2126: 2122: 2117: 2112: 2107: 2102: 2098: 2092: 2089: 2084: 2079: 2075: 2070: 2065: 2062: 2057: 2052: 2047: 2042: 2037: 2033: 2027: 2024: 2016: 2010: 2007: 2004: 1999: 1995: 1968: 1948: 1936: 1933: 1920: 1917: 1914: 1911: 1908: 1905: 1902: 1899: 1896: 1893: 1890: 1879: 1878: 1863: 1860: 1858: 1856: 1853: 1850: 1847: 1844: 1841: 1838: 1835: 1832: 1829: 1826: 1823: 1820: 1816: 1813: 1810: 1807: 1804: 1801: 1798: 1795: 1792: 1789: 1786: 1783: 1779: 1776: 1773: 1770: 1767: 1764: 1761: 1758: 1755: 1752: 1749: 1746: 1742: 1739: 1736: 1733: 1730: 1727: 1724: 1721: 1718: 1715: 1712: 1709: 1705: 1702: 1699: 1696: 1693: 1690: 1687: 1684: 1681: 1678: 1675: 1672: 1668: 1665: 1662: 1659: 1656: 1653: 1650: 1647: 1644: 1641: 1638: 1635: 1632: 1630: 1628: 1625: 1622: 1619: 1616: 1613: 1610: 1607: 1604: 1601: 1596: 1593: 1590: 1587: 1584: 1581: 1578: 1575: 1572: 1567: 1564: 1561: 1558: 1555: 1552: 1549: 1546: 1543: 1540: 1538: 1536: 1533: 1530: 1527: 1524: 1521: 1518: 1513: 1510: 1507: 1504: 1501: 1498: 1495: 1493: 1491: 1488: 1485: 1482: 1479: 1477: 1474: 1471: 1468: 1465: 1462: 1460: 1437: 1434: 1431: 1428: 1425: 1405: 1402: 1382: 1379: 1376: 1356: 1353: 1350: 1347: 1344: 1341: 1329: 1326: 1309: 1306: 1303: 1288: 1287: 1275: 1272: 1269: 1266: 1263: 1260: 1257: 1246: 1245: 1244: 1232: 1229: 1226: 1206: 1203: 1200: 1180: 1177: 1174: 1154: 1151: 1148: 1145: 1142: 1139: 1136: 1125: 1113: 1110: 1107: 1087: 1084: 1081: 1058: 1055: 1052: 1032: 1029: 1026: 1006: 1003: 1000: 980: 977: 974: 971: 968: 965: 962: 951: 940: 937: 934: 931: 920: 908: 884: 881: 878: 875: 872: 869: 846: 822: 802: 782: 779: 776: 773: 750: 746: 742: 739: 736: 731: 727: 722: 719: 695: 692: 679: 676: 656: 653: 650: 647: 644: 624: 621: 618: 598: 578: 575: 572: 569: 566: 563: 560: 557: 554: 551: 548: 528: 525: 522: 519: 516: 496: 493: 473: 458: 457: 444: 441: 437: 431: 428: 424: 420: 417: 414: 411: 408: 405: 391: 390: 379: 376: 373: 370: 367: 364: 361: 358: 355: 352: 349: 346: 343: 340: 337: 313: 290: 287: 284: 281: 278: 275: 272: 252: 249: 246: 243: 240: 237: 234: 206: 183: 163: 147: 144: 134:identities in 112:Wilhelm Magnus 104:Wilhelm Magnus 15: 9: 6: 4: 3: 2: 6076: 6065: 6062: 6060: 6057: 6056: 6054: 6042: 6038: 6032: 6025: 6021: 6017: 6011: 6009: 6007: 5999: 5995: 5989: 5982: 5978: 5974: 5970: 5965: 5960: 5956: 5952: 5951: 5946: 5942: 5936: 5934: 5926: 5923: 5917: 5910: 5906: 5902: 5898: 5894: 5888: 5884: 5875: 5872: 5870: 5867: 5866: 5860: 5858: 5854: 5850: 5846: 5843:given by the 5842: 5838: 5834: 5830: 5826: 5825:Marshall Hall 5816: 5814: 5810: 5805: 5803: 5798: 5796: 5792: 5765: 5761: 5757: 5754: 5746: 5731: 5728: 5708: 5705: 5702: 5699: 5679: 5671: 5667: 5649: 5645: 5641: 5638: 5630: 5613: 5609: 5605: 5602: 5594: 5579: 5576: 5573: 5570: 5550: 5547: 5544: 5541: 5519: 5515: 5511: 5508: 5500: 5485: 5482: 5479: 5457: 5453: 5449: 5446: 5424: 5420: 5416: 5413: 5405: 5401: 5397: 5396: 5395: 5392: 5390: 5366: 5361: 5358: 5355: 5351: 5347: 5342: 5339: 5336: 5332: 5307: 5303: 5299: 5294: 5290: 5286: 5283: 5279: 5274: 5270: 5266: 5261: 5257: 5252: 5247: 5243: 5239: 5234: 5230: 5222: 5221: 5220: 5201: 5197: 5193: 5188: 5184: 5180: 5177: 5173: 5168: 5164: 5160: 5155: 5151: 5146: 5141: 5137: 5133: 5128: 5124: 5101: 5098: 5095: 5088: 5087: 5086: 5072: 5069: 5066: 5044: 5040: 5036: 5031: 5027: 5001: 4997: 4993: 4988: 4984: 4978: 4974: 4970: 4967: 4943: 4939: 4935: 4930: 4926: 4920: 4916: 4912: 4909: 4902: 4901: 4900: 4898: 4882: 4879: 4876: 4868: 4852: 4847: 4843: 4839: 4836: 4822: 4799: 4795: 4791: 4788: 4785: 4780: 4777: 4774: 4770: 4766: 4761: 4757: 4753: 4748: 4745: 4742: 4738: 4734: 4729: 4726: 4723: 4719: 4715: 4712: 4709: 4704: 4700: 4696: 4691: 4687: 4672: 4668: 4664: 4661: 4658: 4653: 4649: 4645: 4640: 4636: 4625: 4624: 4623: 4601: 4597: 4593: 4590: 4587: 4582: 4579: 4576: 4572: 4566: 4562: 4558: 4555: 4552: 4547: 4543: 4539: 4534: 4530: 4515: 4511: 4507: 4504: 4501: 4496: 4492: 4488: 4483: 4479: 4468: 4467: 4466: 4463: 4450: 4445: 4441: 4437: 4434: 4431: 4426: 4423: 4420: 4416: 4412: 4407: 4404: 4401: 4397: 4388: 4372: 4367: 4364: 4361: 4357: 4353: 4348: 4344: 4318: 4315: 4312: 4308: 4304: 4299: 4295: 4266: 4262: 4258: 4255: 4252: 4247: 4243: 4239: 4234: 4230: 4218: 4213: 4211: 4207: 4189: 4185: 4181: 4178: 4175: 4170: 4166: 4162: 4157: 4153: 4130: 4126: 4122: 4117: 4113: 4107: 4103: 4099: 4096: 4074: 4070: 4066: 4063: 4049: 4035: 4030: 4026: 4022: 4019: 4016: 4011: 4008: 4005: 4001: 3997: 3992: 3988: 3965: 3961: 3955: 3951: 3947: 3942: 3938: 3915: 3911: 3902: 3881: 3877: 3873: 3870: 3867: 3862: 3858: 3854: 3849: 3845: 3833: 3823: 3821: 3802: 3796: 3793: 3787: 3781: 3758: 3752: 3746: 3740: 3737: 3734: 3708: 3705: 3702: 3693: 3690: 3687: 3673: 3671: 3655: 3652: 3649: 3621: 3617: 3610: 3607: 3604: 3601: 3593: 3589: 3582: 3575: 3574: 3573: 3551: 3547: 3540: 3537: 3529: 3525: 3518: 3515: 3509: 3503: 3496: 3495: 3494: 3477: 3471: 3451: 3437: 3420: 3417: 3414: 3409: 3405: 3401: 3398: 3395: 3390: 3386: 3382: 3377: 3373: 3365: 3364: 3363: 3344: 3340: 3336: 3331: 3327: 3323: 3320: 3317: 3312: 3308: 3300: 3299: 3298: 3279: 3275: 3268: 3265: 3257: 3253: 3246: 3243: 3240: 3215: 3211: 3204: 3201: 3193: 3189: 3182: 3179: 3176: 3156: 3136: 3116: 3113: 3110: 3107: 3081: 3078: 3075: 3066: 3063: 3060: 3040: 3037: 3031: 3028: 3025: 3019: 3016: 3002: 2985: 2979: 2973: 2967: 2958: 2955: 2952: 2946: 2943: 2923: 2920: 2917: 2897: 2891: 2888: 2885: 2863: 2859: 2851: 2833: 2829: 2819: 2813: 2810: 2807: 2784: 2778: 2770: 2760: 2743: 2738: 2734: 2730: 2727: 2724: 2719: 2715: 2711: 2706: 2702: 2694: 2693: 2692: 2676: 2672: 2646: 2642: 2638: 2633: 2629: 2623: 2619: 2615: 2612: 2605: 2604: 2603: 2587: 2583: 2579: 2576: 2567: 2565: 2561: 2543: 2539: 2516: 2512: 2504: 2500: 2495: 2492: 2483: 2470: 2467: 2464: 2461: 2438: 2435: 2432: 2426: 2423: 2403: 2394: 2380: 2360: 2352: 2336: 2316: 2296: 2288: 2287:right subtree 2284: 2268: 2260: 2244: 2221: 2218: 2215: 2209: 2206: 2192: 2190: 2186: 2170: 2145: 2141: 2137: 2133: 2128: 2124: 2120: 2115: 2110: 2100: 2096: 2090: 2087: 2082: 2077: 2073: 2068: 2063: 2060: 2055: 2050: 2045: 2035: 2031: 2025: 2022: 2014: 2005: 1997: 1993: 1985: 1984: 1983: 1982: 1966: 1946: 1935:Combinatorics 1932: 1918: 1915: 1912: 1909: 1906: 1903: 1900: 1897: 1894: 1891: 1888: 1861: 1859: 1851: 1845: 1842: 1833: 1827: 1824: 1814: 1808: 1805: 1796: 1790: 1787: 1777: 1774: 1768: 1762: 1756: 1753: 1740: 1737: 1731: 1725: 1719: 1716: 1703: 1700: 1694: 1688: 1682: 1679: 1666: 1663: 1657: 1651: 1645: 1642: 1631: 1623: 1620: 1614: 1608: 1605: 1594: 1591: 1585: 1579: 1576: 1565: 1562: 1556: 1550: 1547: 1539: 1531: 1528: 1522: 1519: 1511: 1508: 1502: 1499: 1494: 1486: 1483: 1480: 1472: 1469: 1466: 1463: 1451: 1450: 1449: 1432: 1429: 1426: 1403: 1400: 1380: 1377: 1374: 1354: 1348: 1345: 1342: 1325: 1323: 1307: 1304: 1301: 1293: 1286:always holds. 1270: 1267: 1264: 1258: 1255: 1247: 1230: 1227: 1224: 1204: 1201: 1198: 1178: 1175: 1172: 1149: 1146: 1143: 1137: 1134: 1126: 1111: 1108: 1105: 1085: 1082: 1079: 1071: 1070: 1056: 1053: 1050: 1030: 1027: 1024: 1004: 1001: 998: 978: 975: 969: 966: 963: 952: 938: 935: 932: 929: 921: 906: 898: 897: 896: 879: 873: 870: 867: 860:The Hall set 858: 844: 836: 820: 800: 777: 771: 748: 744: 740: 737: 734: 729: 725: 720: 717: 709: 705: 701: 691: 677: 674: 651: 648: 645: 619: 596: 573: 570: 564: 561: 558: 552: 549: 523: 520: 517: 494: 491: 471: 463: 442: 439: 435: 429: 426: 422: 418: 415: 409: 406: 403: 396: 395: 394: 377: 374: 371: 368: 365: 362: 356: 353: 350: 341: 338: 335: 328: 327: 326: 311: 302: 285: 282: 279: 273: 270: 250: 247: 241: 238: 235: 224: 220: 204: 197: 181: 161: 153: 143: 141: 137: 133: 129: 126:given by the 125: 121: 117: 113: 109: 108:Marshall Hall 105: 101: 97: 92: 90: 86: 82: 78: 74: 70: 66: 62: 58: 54: 50: 46: 42: 38: 34: 30: 29:combinatorics 26: 22: 6040: 6036: 6031: 6023: 6019: 5997: 5993: 5988: 5954: 5948: 5924: 5921: 5916: 5900: 5896: 5893:Hall, Philip 5887: 5853:group theory 5822: 5806: 5804:on a group. 5799: 5791:Lyndon words 5788: 5785:Implications 5403: 5399: 5393: 5389:Lyndon words 5386: 5218: 5018: 4896: 4828: 4819: 4621: 4464: 4386: 4216: 4214: 4055: 3900: 3829: 3819: 3679: 3669: 3641: 3571: 3443: 3435: 3361: 3008: 2768: 2766: 2758: 2663: 2568: 2560:Lyndon words 2501:: given the 2496: 2490: 2489: 2395: 2350: 2286: 2282: 2258: 2198: 2162: 1938: 1880: 1331: 1321: 1289: 859: 835:binary trees 699: 697: 667:in place of 462:homomorphism 459: 392: 303: 149: 136:group theory 93: 88: 60: 57:binary trees 55:. These are 52: 49:Lyndon words 32: 25:group theory 18: 5829:Philip Hall 5747:Every word 5085:if either 4825:Total order 2878:, given by 2850:free monoid 2771:of a magma 2503:free monoid 100:Philip Hall 89:Lazard sets 41:free monoid 21:mathematics 6053:Categories 5927:, 105-115. 5880:References 5857:Ernst Witt 5849:commutator 5841:free group 5721:such that 5383:Properties 5019:with each 4387:legal drop 4336:such that 4210:confluence 2491:Hall words 2486:Hall words 2353:is either 2289:is either 1393:and write 1098:(and thus 708:free magma 152:free magma 140:Ernst Witt 132:commutator 124:free group 120:filtration 69:free magma 53:Hall trees 33:Hall words 5973:0002-9939 5922:J. Grelle 5903:: 29–95, 5766:∗ 5758:∈ 5666:conjugate 5650:∗ 5642:∈ 5614:∗ 5606:∈ 5520:∗ 5512:∈ 5458:∗ 5450:∈ 5404:primitive 5284:… 5178:⋯ 4994:⋯ 4936:⋯ 4848:∗ 4840:∈ 4789:… 4727:− 4713:… 4681:→ 4662:… 4591:… 4556:… 4524:→ 4505:… 4435:… 4413:≤ 4256:… 4182:≤ 4179:⋯ 4176:≤ 4163:≤ 4123:⋯ 4075:∗ 4067:∈ 4020:⋯ 3998:≤ 3871:… 3608:≤ 3605:⋯ 3602:≤ 3538:⋯ 3415:≤ 3402:≤ 3399:⋯ 3396:≤ 3383:≤ 3321:… 3266:⋯ 3202:⋯ 3038:∈ 2965:↦ 2921:∈ 2895:↦ 2864:∗ 2834:∗ 2826:→ 2731:≤ 2728:⋯ 2725:≤ 2712:≤ 2639:⋯ 2588:∗ 2580:∈ 2544:∗ 2517:∗ 2465:≤ 2171:μ 2116:μ 2097:∑ 2051:μ 2032:∑ 1919:… 1862:⋯ 1305:≤ 1228:≤ 1202:∈ 1176:∈ 1109:∈ 1083:∈ 1028:∈ 1002:∈ 976:∈ 933:⊆ 871:⊆ 738:… 562:≠ 521:∙ 472:∙ 440:− 427:− 413:↦ 407:∙ 372:− 345:↦ 339:∙ 312:∙ 283:∙ 274:∙ 248:∙ 239:∙ 205:∙ 5943:(1950), 5863:See also 3903:if each 3832:sequence 700:Hall set 694:Hall set 61:Hall set 5981:0038336 5819:History 5595:A word 5501:A word 5400:acyclic 5219:or if 2769:foliage 2763:Foliage 2454:, then 2281:is the 1367:Define 1328:Example 1072:Either 39:of the 5979:  5971:  4145:with 3670:cannot 2163:where 2018:  2012:  710:. Let 4899:that 4897:i. e. 3980:with 3774:with 3642:then 3572:with 3297:with 3233:and 2349:. An 1165:with 1069:and: 702:is a 122:on a 5969:ISSN 5574:> 5483:> 5472:and 5348:< 5323:and 5115:and 5099:< 5070:< 4959:and 4354:> 4217:drop 3794:> 3362:and 3337:> 3149:and 3009:Let 2936:and 2910:for 2767:The 2285:. A 1416:for 1378:> 1259:< 1217:and 1191:and 1054:> 1043:and 1017:and 698:The 507:for 221:and 27:and 6024:59A 6018:", 5998:691 5959:doi 5925:177 5905:doi 5672:of 5664:is 2329:or 1322:not 1127:Or 301:. 154:in 19:In 6055:: 6041:41 6039:. 6022:, 6005:^ 5996:, 5977:MR 5975:, 5967:, 5953:, 5947:, 5932:^ 5901:36 5899:, 5859:. 4215:A 3830:A 3822:. 2566:. 2393:. 2191:. 1124:), 857:. 142:. 31:, 5961:: 5955:1 5907:: 5762:A 5755:w 5732:u 5729:v 5709:v 5706:u 5703:= 5700:w 5680:w 5646:A 5639:w 5610:A 5603:w 5580:u 5577:v 5571:w 5551:v 5548:u 5545:= 5542:w 5516:A 5509:w 5498:. 5486:1 5480:n 5454:A 5447:x 5425:n 5421:x 5417:= 5414:w 5367:. 5362:1 5359:+ 5356:k 5352:v 5343:1 5340:+ 5337:k 5333:u 5308:k 5304:v 5300:= 5295:k 5291:u 5287:, 5280:, 5275:2 5271:v 5267:= 5262:2 5258:u 5253:, 5248:1 5244:v 5240:= 5235:1 5231:u 5202:m 5198:v 5194:= 5189:m 5185:u 5181:, 5174:, 5169:2 5165:v 5161:= 5156:2 5152:u 5147:, 5142:1 5138:v 5134:= 5129:1 5125:u 5102:n 5096:m 5073:v 5067:u 5045:j 5041:v 5037:, 5032:i 5028:u 5002:n 4998:v 4989:2 4985:v 4979:1 4975:v 4971:= 4968:v 4944:m 4940:u 4931:2 4927:u 4921:1 4917:u 4913:= 4910:u 4883:v 4880:, 4877:u 4853:. 4844:A 4837:w 4805:) 4800:n 4796:h 4792:, 4786:, 4781:2 4778:+ 4775:i 4771:h 4767:, 4762:i 4758:h 4754:, 4749:1 4746:+ 4743:i 4739:h 4735:, 4730:1 4724:i 4720:h 4716:, 4710:, 4705:2 4701:h 4697:, 4692:1 4688:h 4684:( 4678:) 4673:n 4669:h 4665:, 4659:, 4654:2 4650:h 4646:, 4641:1 4637:h 4633:( 4607:) 4602:n 4598:h 4594:, 4588:, 4583:1 4580:+ 4577:i 4573:h 4567:i 4563:h 4559:, 4553:, 4548:2 4544:h 4540:, 4535:1 4531:h 4527:( 4521:) 4516:n 4512:h 4508:, 4502:, 4497:2 4493:h 4489:, 4484:1 4480:h 4476:( 4451:. 4446:n 4442:h 4438:, 4432:, 4427:2 4424:+ 4421:i 4417:h 4408:1 4405:+ 4402:i 4398:h 4373:. 4368:1 4365:+ 4362:i 4358:h 4349:i 4345:h 4324:) 4319:1 4316:+ 4313:i 4309:h 4305:, 4300:i 4296:h 4292:( 4272:) 4267:n 4263:h 4259:, 4253:, 4248:2 4244:h 4240:, 4235:1 4231:h 4227:( 4190:k 4186:h 4171:2 4167:h 4158:1 4154:h 4131:k 4127:h 4118:2 4114:h 4108:1 4104:h 4100:= 4097:w 4071:A 4064:w 4036:. 4031:n 4027:w 4023:, 4017:, 4012:1 4009:+ 4006:i 4002:w 3993:i 3989:v 3966:i 3962:v 3956:i 3952:u 3948:= 3943:i 3939:w 3916:i 3912:w 3887:) 3882:n 3878:w 3874:, 3868:, 3863:2 3859:w 3855:, 3850:1 3846:w 3842:( 3806:) 3803:y 3800:( 3797:f 3791:) 3788:x 3785:( 3782:f 3762:) 3759:y 3756:( 3753:f 3750:) 3747:x 3744:( 3741:f 3738:= 3735:w 3715:) 3712:] 3709:y 3706:, 3703:x 3700:[ 3697:( 3694:f 3691:= 3688:w 3656:1 3653:= 3650:n 3627:) 3622:n 3618:t 3614:( 3611:f 3599:) 3594:1 3590:t 3586:( 3583:f 3557:) 3552:n 3548:t 3544:( 3541:f 3535:) 3530:1 3526:t 3522:( 3519:f 3516:= 3513:) 3510:t 3507:( 3504:f 3481:) 3478:t 3475:( 3472:f 3452:t 3421:. 3418:y 3410:n 3406:y 3391:2 3387:y 3378:1 3374:y 3345:1 3341:y 3332:m 3328:x 3324:, 3318:, 3313:1 3309:x 3285:) 3280:n 3276:y 3272:( 3269:f 3263:) 3258:1 3254:y 3250:( 3247:f 3244:= 3241:v 3221:) 3216:m 3212:x 3208:( 3205:f 3199:) 3194:1 3190:x 3186:( 3183:f 3180:= 3177:u 3157:v 3137:u 3117:v 3114:u 3111:= 3108:w 3088:) 3085:] 3082:y 3079:, 3076:x 3073:[ 3070:( 3067:f 3064:= 3061:w 3041:H 3035:] 3032:y 3029:, 3026:x 3023:[ 3020:= 3017:t 2989:) 2986:y 2983:( 2980:f 2977:) 2974:x 2971:( 2968:f 2962:] 2959:y 2956:, 2953:x 2950:[ 2947:: 2944:f 2924:A 2918:a 2898:a 2892:a 2889:: 2886:f 2860:A 2830:A 2823:) 2820:A 2817:( 2814:M 2811:: 2808:f 2788:) 2785:A 2782:( 2779:M 2744:. 2739:k 2735:h 2720:2 2716:h 2707:1 2703:h 2677:j 2673:h 2647:k 2643:h 2634:2 2630:h 2624:1 2620:h 2616:= 2613:w 2584:A 2577:w 2540:A 2513:A 2471:. 2468:y 2462:v 2442:] 2439:y 2436:, 2433:x 2430:[ 2427:= 2424:t 2404:v 2381:y 2361:y 2337:y 2317:x 2297:y 2269:y 2245:x 2225:] 2222:y 2219:, 2216:x 2213:[ 2210:= 2207:t 2146:d 2142:/ 2138:k 2134:n 2129:) 2125:d 2121:( 2111:k 2106:| 2101:d 2091:k 2088:1 2083:= 2078:d 2074:n 2069:) 2064:d 2061:k 2056:( 2046:k 2041:| 2036:d 2026:k 2023:1 2015:= 2009:) 2006:k 2003:( 1998:n 1994:M 1967:n 1947:k 1916:, 1913:6 1910:, 1907:3 1904:, 1901:2 1898:, 1895:1 1892:, 1889:2 1852:, 1849:) 1846:b 1843:a 1840:( 1837:) 1834:a 1831:) 1828:b 1825:a 1822:( 1819:( 1815:, 1812:) 1809:b 1806:a 1803:( 1800:) 1797:b 1794:) 1791:b 1788:a 1785:( 1782:( 1778:, 1775:a 1772:) 1769:a 1766:) 1763:a 1760:) 1757:b 1754:a 1751:( 1748:( 1745:( 1741:, 1738:a 1735:) 1732:a 1729:) 1726:b 1723:) 1720:b 1717:a 1714:( 1711:( 1708:( 1704:, 1701:a 1698:) 1695:b 1692:) 1689:b 1686:) 1683:b 1680:a 1677:( 1674:( 1671:( 1667:, 1664:b 1661:) 1658:b 1655:) 1652:b 1649:) 1646:b 1643:a 1640:( 1637:( 1634:( 1624:, 1621:a 1618:) 1615:a 1612:) 1609:b 1606:a 1603:( 1600:( 1595:, 1592:a 1589:) 1586:b 1583:) 1580:b 1577:a 1574:( 1571:( 1566:, 1563:b 1560:) 1557:b 1554:) 1551:b 1548:a 1545:( 1542:( 1532:, 1529:a 1526:) 1523:b 1520:a 1517:( 1512:, 1509:b 1506:) 1503:b 1500:a 1497:( 1487:, 1484:b 1481:a 1473:, 1470:a 1467:, 1464:b 1436:] 1433:y 1430:, 1427:x 1424:[ 1404:y 1401:x 1381:b 1375:a 1355:. 1352:} 1349:b 1346:, 1343:a 1340:{ 1308:y 1302:v 1274:] 1271:y 1268:, 1265:x 1262:[ 1256:y 1243:. 1231:y 1225:v 1205:H 1199:v 1179:H 1173:u 1153:] 1150:v 1147:, 1144:u 1141:[ 1138:= 1135:x 1112:A 1106:y 1086:A 1080:x 1057:y 1051:x 1031:H 1025:y 1005:H 999:x 979:H 973:] 970:y 967:, 964:x 961:[ 939:. 936:H 930:A 907:A 883:) 880:A 877:( 874:M 868:H 845:A 821:A 801:A 781:) 778:A 775:( 772:M 749:n 745:a 741:, 735:, 730:1 726:a 721:= 718:A 678:b 675:a 655:] 652:b 649:, 646:a 643:[ 623:) 620:a 617:( 597:a 577:) 574:c 571:b 568:( 565:a 559:c 556:) 553:b 550:a 547:( 527:) 524:b 518:a 515:( 495:b 492:a 443:1 436:b 430:1 423:a 419:b 416:a 410:b 404:a 378:a 375:b 369:b 366:a 363:= 360:] 357:b 354:, 351:a 348:[ 342:b 336:a 289:) 286:c 280:b 277:( 271:a 251:c 245:) 242:b 236:a 233:( 182:n 162:n

Index

mathematics
group theory
combinatorics
monoid factorisation
free monoid
totally ordered
Lyndon words
binary trees
totally ordered
free magma
free Lie algebras
Poincaré–Birkhoff–Witt theorem
universal enveloping algebra
commutator collecting process
commutator collecting process
Philip Hall
Wilhelm Magnus
Marshall Hall
Wilhelm Magnus
graded Lie algebra
filtration
free group
lower central series
commutator
group theory
Ernst Witt
free magma
binary operator
non-associative
non-commutative

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