Startseite Conjugacy search problem and the Andrews–Curtis conjecture
Artikel
Lizenziert
Nicht lizenziert Erfordert eine Authentifizierung

Conjugacy search problem and the Andrews–Curtis conjecture

  • Dmitry Panteleev und Alexander Ushakov EMAIL logo
Veröffentlicht/Copyright: 6. April 2019
Veröffentlichen auch Sie bei De Gruyter Brill

Abstract

We develop new computational methods for studying potential counterexamples to the Andrews–Curtis conjecture, in particular, Akbulut–Kurby examples AK(n). We devise a number of algorithms in an attempt to disprove the most interesting counterexample AK(3). That includes an efficient implementation of the folding procedure for pseudo-conjugacy graphs, based on the original modification of a classic disjoint-set data structure. To improve metric properties of the search space (the set of balanced presentations of the trivial group), we introduce a new transformation, called an ACM-move, that generalizes the original Andrews–Curtis transformations and discuss details of a practical implementation. To reduce growth of the search space, we introduce a strong equivalence relation on balanced presentations and study the space modulo automorphisms of the underlying free group. We prove that automorphism moves can be applied to Akbulut–Kurby presentations. The improved technique allows us to enumerate balanced presentations AC-equivalent to AK(3) with relations of lengths up to 20 (previous record was 17).

MSC 2010: 20-04; 20F05; 20E05

Award Identifier / Grant number: DMS-1318716

Funding statement: The second author has been partially supported by NSF grant DMS-1318716.

A Used ACM-moves justification

In this section, we prove the one-relator groups identities used in Lemmas 3.4, 3.5 and 3.6 for the ACM moves. Every proof demonstrates that

c-1uc(u)-1=1

in x,yv.

A.1 Used in Lemma 3.4

  1. c=xyx, u=xkYk+1, v=xyxYXY, u=ykXK+1:

    XYXxk(Yk+1xyxxk+1)Yk=XYX(xkxyxYK)(Yxyx=xy)
    =XYXxyx(xyxY=yx)
    =1

A.2 Used in Lemma 3.5

  1. u=xyXyk+1xYk+2, v=xyXyxY, c=yk+1, u=Yk+1Xk:

    (Yk+1)xyXyk+1x(Yk+2yk+1)xk(yk+1)=(xk+1yXyk+1)xY=(xkyXyk)xY==yXxY=1
  2. u=xyXyxYYXy, v=xyXyk+1xYk+2, c=yk+2XyxY, u=xyXyxY:

    yXYxYk+2xyXyxYYX(yyk+2XyxYyXYxY)X=yXY(xYk+2xyXy)xYYXyk+2X=yXYYkxY(YXyk+2X)=(yX)Yk+1(xYXyk+1)=Yk+1yk+1=1
  3. u=xyXykXYk, v=xyXyxYYXy, c=xyXy, u=yk+2XYk+1xYX:

    (YxYX)(xyXyk)XYkxyXyxyXyk+1x(Yk+2)=XYkxy(XyxyXyk+1)xY3=X(Ykxyy)yXykxY3=XYk-1xy(XyxyXyk)xY3=X(Yk-1xyy)yXyk-1xY3=XxyyyXxY3=1
  4. u=xkYk+1, v=xyXykXYk, c=Yk-1xYk-1xYYXy, u=YxyyXYxYX:

    (YxyyX)yk-1Xyk-1xkYk+1Yk-1xYk-1xYYXyxyXy(xYYXy)
    =(yk-1X)yk-1xkY2kxYk-1xYYXy(xyXy)
    =(ykyk-1)xkY2kxYk-1xYYX(y)(xyXykX=yk)
    =ykx(Xykxk)Y2kxYk-1xYYX(shift)
    =ykxy(Xykxk-1)Y2kxYk-1xYYX(Xykx=yXyk)
    =
    =ykxykX(ykY2k)xYk-1xYYX
    =ykx(ykXYkx)Yk-1xYYX
    =(ykx)xYYk-1xY(YX)
    =(Xykx)YkxY
    =(Xykx)Yk(xY)
    =ykYk=1

  5. u=xyxYXY, v=xkYk+1, c=Yk, u=ykxYkxYX:

    (ykxy)xYXYYkxyX(ykXYk)=xYX(YYk)xyXyk+1=xY(XXkx)yXyk+1=x(YYk+1y)Xyk+1==Yk+1yk+1

A.3 Used in Lemma 3.6

  1. u=xk-1yXk-1yXY, v=xxyXYXy, c=xk-3(YX)kY, u=xk-1(YX)kY:

    y(xy)k(Xk-3xk-1)yXk-1yXY(xk-3(YX)kYy(xy)kXk-1)=y(xy)kx2yXk-1(yXYX)X=(yx)kyx2yXk-1XX(YX)==yx2yXk-1XXxkYX=yx2yXYX=1
  2. u=xkYk+1, v=xk-1yXk-1yXY, c=xyXk-1yXYXy, u=YxyxYXX:

    (YxyxY)xk-1Y(Xxk)Yk+1xyXk-1yXYXyxx(yXYXy)=(xk-1Yxk-1Yk+1)xyXk-1yXYXy(xx)==Y(xk-1xyXk-1yXY)Xy=YxXy=1
  3. u=xyxYXY, v=xkYk+1, c=yXk-1yXY, u=yxYxk-1YXk-1:

    (yxYxk-1Y)xyxYX(Yy)Xk-1yXYxk-1(yXk-1yXY)=(x)yxYXkyX(Yxk-1)=(y)xYXkyX(yk)=(xY)Xky(Xxk)=Xkyyk=1

References

[1] J. J. Andrews and M. L. Curtis, Free groups and handlebodies, Proc. Amer. Math. Soc. 16 (1965), 192–195. 10.1090/S0002-9939-1965-0173241-8Suche in Google Scholar

[2] J. J. Andrews and M. L. Curtis, Extended Nielsen operations in free groups, Amer. Math. Monthly 73 (1966), 21–28. 10.1080/00029890.1966.11970717Suche in Google Scholar

[3] G. Baumslag, A non-cyclic one-relator group all of whose finite quotients are cyclic, J. Austral. Math. Soc. 10 (1969), 497–498. 10.1017/S1446788700007783Suche in Google Scholar

[4] G. Baumslag, A. G. Myasnikov and V. Shpilrain, Open problems in combinatorial group theory. 2nd ed., Combinatorial and Geometric Group Theory (New York 2000), Contemp. Math. 296, American Mathematical Society, Providence (2002), 1–38. 10.1090/conm/296/05067Suche in Google Scholar

[5] W. W. Boone, The word problem, Proc. Natl. Acad. Sci. USA 44 (1958), 1061–1065. 10.1073/pnas.44.10.1061Suche in Google Scholar PubMed PubMed Central

[6] A. V. Borovik, A. Lubotzky and A. G. Myasnikov, The finitary Andrews–Curtis conjecture, Infinite Groups: Geometric, Combinatorial and Dynamical Aspects, Progr. Math. 248, Birkhäuser, Basel (2005), 15–30. 10.1007/3-7643-7447-0_2Suche in Google Scholar

[7] R. S. Bowman and S. B. McCaul, Fast searching for Andrews–Curtis trivializations, Exp. Math. 15 (2006), no. 2, 193–197. 10.1080/10586458.2006.10128962Suche in Google Scholar

[8] N. Brady, T. Riley and H. Short, The Geometry of the Word Problem for Finitely Generated Groups, Adv. Courses Math. CRM Barcelona, Birkhäuser, Basel, 2007. Suche in Google Scholar

[9] M. Bridson, The complexity of balanced presentations and the Andrews–Curtis conjecture, preprint (2015), https://arxiv.org/abs/1504.04187. Suche in Google Scholar

[10] R. G. Burns and O. Macedońska, Balanced presentations of the trivial group, Bull. Lond. Math. Soc. 25 (1993), no. 6, 513–526. 10.1112/blms/25.6.513Suche in Google Scholar

[11] S. M. Gersten, Dehn functions and l1-norms of finite presentations, Algorithms and Classification in Combinatorial Group Theory (Berkeley 1989), Math. Sci. Res. Inst. Publ. 23, Springer, New York (1992), 195–224. 10.1007/978-1-4613-9730-4_9Suche in Google Scholar

[12] S. M. Gersten and T. R. Riley, Filling length in finitely presentable groups, Geom. Dedicata 92 (2002), 41–58, Dedicated to John Stallings on the occasion of his 65th birthday. 10.1023/A:1019682203828Suche in Google Scholar

[13] D. Gillman and D. Rolfsen, The Zeeman conjecture for standard spines is equivalent to the Poincaré conjecture, Topology 22 (1983), no. 3, 315–323. 10.1016/0040-9383(83)90017-4Suche in Google Scholar

[14] G. Havas and C. Ramsay, Breadth-first search and the Andrews–Curtis conjecture, Internat. J. Algebra Comput. 13 (2003), no. 1, 61–68. 10.1142/S0218196703001365Suche in Google Scholar

[15] D. Holt, kbmag2 (version 2.4), http://homepages.warwick.ac.uk/~mareg/download/kbmag2/. Suche in Google Scholar

[16] S. V. Ivanov, On balanced presentations of the trivial group, Invent. Math. 165 (2006), no. 3, 525–549. 10.1007/s00222-005-0497-1Suche in Google Scholar

[17] S. V. Ivanov, On Rourke’s extension of group presentations and a cyclic version of the Andrews–Curtis conjecture, Proc. Amer. Math. Soc. 134 (2006), no. 6, 1561–1567. 10.1090/S0002-9939-05-08450-9Suche in Google Scholar

[18] B. Lishak, Balanced finite presentations of the trivial group, J. Topol. Anal. 9 (2017), no. 2, 363–378. 10.1142/S1793525317500182Suche in Google Scholar

[19] R. C. Lyndon and P. E. Schupp, Combinatorial Group Theory, Ergeb. Math. Grenzgeb. (3) 89, Springer, Berlin, 1977. Suche in Google Scholar

[20] V. D. Mazurov and E. I. Khukhro, The Kourovka Notebook. Unsolved Problems in Group Theory, eighteenth ed., Russian Academy of Sciences Siberian Division, Novosibirsk, 2014. Suche in Google Scholar

[21] A. D. Miasnikov, Genetic algorithms and the Andrews–Curtis conjecture, Internat. J. Algebra Comput. 9 (1999), no. 6, 671–686. 10.1142/S0218196799000370Suche in Google Scholar

[22] P. Morar and A. Ushakov, Search problems in groups and branching processes, Internat. J. Algebra Comput. 25 (2015), no. 3, 445–480. 10.1142/S0218196715500058Suche in Google Scholar

[23] A. Myasnikov, V. Shpilrain and A. Ushakov, Non-commutative Cryptography and Complexity of Group-theoretic Problems, Math. Surveys Monogr. 177, American Mathematical Society, Providence, 2011. 10.1090/surv/177Suche in Google Scholar

[24] A. Myasnikov and A. Ushakov, Random van Kampen diagrams and algorithmic problems in groups, Groups Complex. Cryptol. 3 (2011), no. 1, 121–185. 10.1515/gcc.2011.006Suche in Google Scholar

[25] A. D. Myasnikov, A. G. Myasnikov and V. Shpilrain, On the Andrews–Curtis equivalence, Combinatorial and Geometric Group Theory (New York 2000), Contemp. Math. 296, American Mathematical Society, Providence (2002), 183–198. 10.1090/conm/296/05074Suche in Google Scholar

[26] A. G. Myasnikov, Extended Nielsen transformations and the trivial group, Mat. Zametki 35 (1984), no. 4, 491–495. Suche in Google Scholar

[27] A. Myropolska, Andrews–Curtis and Nielsen equivalence relations on some infinite groups, J. Group Theory 19 (2016), no. 1, 161–178. 10.1515/jgth-2015-0031Suche in Google Scholar

[28] P. Novikov, On the algorithmic unsolvability of the word problem in group theory, Proc. Steklov Inst. 44 (1955), 1–143. Suche in Google Scholar

[29] P. E. Schupp, On Dehn’s algorithm and the conjugacy problem, Math. Ann. 178 (1968), 119–130. 10.1007/BF01350654Suche in Google Scholar

[30] R. E. Tarjan and J. van Leeuwen, Worst-case analysis of set union algorithms, J. Assoc. Comput. Mach. 31 (1984), no. 2, 245–281. 10.1145/62.2160Suche in Google Scholar

[31] N. W. M. Touikan, A fast algorithm for Stallings’ folding process, Internat. J. Algebra Comput. 16 (2006), no. 6, 1031–1045. 10.1142/S0218196706003396Suche in Google Scholar

[32] A. Ushakov, Fundamental search problems in groups, PhD thesis, CUNY/Graduate Center, 2005. Suche in Google Scholar

[33] P. Wright, Group presentations and formal deformations, Trans. Amer. Math. Soc. 208 (1975), 161–169. 10.1090/S0002-9947-1975-0380813-5Suche in Google Scholar

[34] E. C. Zeeman, On the dunce hat, Topology 2 (1964), 341–358. 10.1016/0040-9383(63)90014-4Suche in Google Scholar

Received: 2018-11-14
Published Online: 2019-04-06
Published in Print: 2019-05-01

© 2019 Walter de Gruyter GmbH, Berlin/Boston

Heruntergeladen am 23.9.2025 von https://www.degruyterbrill.com/document/doi/10.1515/gcc-2019-2005/html?lang=de
Button zum nach oben scrollen