New Proposals for the Popularization of Braid Theory
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Experiments on Growth Series of Braid Groups Jean Fromentin
Experiments on growth series of braid groups Jean Fromentin To cite this version: Jean Fromentin. Experiments on growth series of braid groups. 2021. hal-02929264v3 HAL Id: hal-02929264 https://hal.archives-ouvertes.fr/hal-02929264v3 Preprint submitted on 14 Apr 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. EXPERIMENTS ON GROWTH SERIES OF BRAID GROUPS JEAN FROMENTIN In memory of Patrick Dehornoy, a great mentor. Abstract. We introduce an algorithmic framework to investigate spherical and geodesic growth series of braid groups relatively to the Artin’s or Birman– Ko–Lee’s generators. We present our experimentations in the case of three and four strands and conjecture rational expressions for the spherical growth series with respect to the Birman–Ko–Lee’s generators. 1. Introduction Originally introduced as the group of isotopy classes of n-strands geometric braids, the braid group Bn admits many finite presentations by generators and relations. From each finite semigroup generating set S of Bn we can define at least two growth series. The spherical growth series counts elements of Bn by their dis- tance from the identity in the Cayley graph Cay(Bn,S) of Bn with respect to S. -
Categorified Invariants and the Braid Group
PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 143, Number 7, July 2015, Pages 2801–2814 S 0002-9939(2015)12482-3 Article electronically published on February 26, 2015 CATEGORIFIED INVARIANTS AND THE BRAID GROUP JOHN A. BALDWIN AND J. ELISENDA GRIGSBY (Communicated by Daniel Ruberman) Abstract. We investigate two “categorified” braid conjugacy class invariants, one coming from Khovanov homology and the other from Heegaard Floer ho- mology. We prove that each yields a solution to the word problem but not the conjugacy problem in the braid group. In particular, our proof in the Khovanov case is completely combinatorial. 1. Introduction Recall that the n-strand braid group Bn admits the presentation σiσj = σj σi if |i − j|≥2, Bn = σ1,...,σn−1 , σiσj σi = σjσiσj if |i − j| =1 where σi corresponds to a positive half twist between the ith and (i + 1)st strands. Given a word w in the generators σ1,...,σn−1 and their inverses, we will denote by σ(w) the corresponding braid in Bn. Also, we will write σ ∼ σ if σ and σ are conjugate elements of Bn. As with any group described in terms of generators and relations, it is natural to look for combinatorial solutions to the word and conjugacy problems for the braid group: (1) Word problem: Given words w, w as above, is σ(w)=σ(w)? (2) Conjugacy problem: Given words w, w as above, is σ(w) ∼ σ(w)? The fastest known algorithms for solving Problems (1) and (2) exploit the Gar- side structure(s) of the braid group (cf. -
Integration of Singular Braid Invariants and Graph Cohomology
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 350, Number 5, May 1998, Pages 1791{1809 S 0002-9947(98)02213-2 INTEGRATION OF SINGULAR BRAID INVARIANTS AND GRAPH COHOMOLOGY MICHAEL HUTCHINGS Abstract. We prove necessary and sufficient conditions for an arbitrary in- variant of braids with m double points to be the “mth derivative” of a braid invariant. We show that the “primary obstruction to integration” is the only obstruction. This gives a slight generalization of the existence theorem for Vassiliev invariants of braids. We give a direct proof by induction on m which works for invariants with values in any abelian group. We find that to prove our theorem, we must show that every relation among four-term relations satisfies a certain geometric condition. To find the relations among relations we show that H1 of a variant of Kontsevich’s graph complex vanishes. We discuss related open questions for invariants of links and other things. 1. Introduction 1.1. The mystery. From a certain point of view, it is quite surprising that the Vassiliev link invariants exist, because the “primary obstruction” to constructing them is the only obstruction, for no clear topological reason. The idea of Vassiliev invariants is to define a “differentiation” map from link invariants to invariants of “singular links”, start with invariants of singular links, and “integrate them” to construct link invariants. A singular link is an immersion S1 S3 with m double points (at which the two tangent vectors are not n → parallel) and no other singularities. Let Lm denote the free Z-module generated by isotopy` classes of singular links with m double points. -
ORDERING BRAIDS: in MEMORY of PATRICK DEHORNOY with the Untimely Passing of Patrick Dehornoy in September 2019, the World Of
ORDERING BRAIDS: IN MEMORY OF PATRICK DEHORNOY DALE ROLFSEN With the untimely passing of Patrick Dehornoy in September 2019, the world of mathematics lost a brilliant scholar who made profound contributions to set theory, algebra, topology, and even computer science and cryptography. And I lost a dear friend and a strong influence in the direction of my own research in mathematics. In this article I will concentrate on his remarkable discovery that the braid groups are left-orderable, and its consequences, and its strong influence on my own research. I'll begin by describing how I learned of his work. 1. When I met Patrick In the late 1990's I had been working on a conjecture of Joan Birman [1] regarding the braid groups Bn and the (larger) monoids SBn of singular braids. I remind the reader that Bn has the presentation with generators σ1; : : : ; σn−1 and relations σiσj = σjσi if ji − jj > 1 and σiσjσi = σjσiσj when ji − jj = 1. Figure 1: The Artin generator σi In addition to the usual Artin generators σi in which the i-th strand passes below the next strand, SBn has elements τi in which those strands intersect each other. In the study of SBn and influenced by Vassiliev theory, Birman proposed the following mapping: σi −! σi −1 τi −! σi − σi For this to make sense, the target needs to be not just Bn, but rather the group ring ZBn. She conjectured that this map SBn ! ZBn is injective. Investigating this problem with a student at the time, Jun Zhu, we were making calculations in ZBn, including cancellations such as ab = ac =) b = c. -
Braid Groups
Braid Groups Jahrme Risner Mathematics and Computer Science University of Puget Sound [email protected] 17 April 2016 c 2016 Jahrme Risner GFDL License Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front- Cover Texts, and no Back-Cover Texts. A copy of the license is included in the appendix entitled \GNU Free Documentation License." Introduction Braid groups were introduced by Emil Artin in 1925, and by now play a role in various parts of mathematics including knot theory, low dimensional topology, and public key cryptography. Expanding from the Artin presentation of braids we now deal with braids defined on general manifolds as in [3] as well as several of Birman' other works. 1 Preliminaries We begin by laying the groundwork for the Artinian version of the braid group. While braids can be dealt with using a number of different representations and levels of abstraction we will confine ourselves to what can be called the geometric braid groups. 3 2 2 Let E denote Euclidean 3-space, and let E0 and E1 be the parallel planes with z- coordinates 0 and 1 respectively. For 1 ≤ i ≤ n, let Pi and Qi be the points with coordinates (i; 0; 1) and (i; 0; 0) respectively such that P1;P2;:::;Pn lie on the line y = 0 in the upper plane, and Q1;Q2;:::;Qn lie on the line y = 0 in the lower plane. -
Scottish Physics and Knot Theory's Odd Origins
Scottish Physics and Knot Theory’s Odd Origins Daniel S. Silver My mother, a social worker and teacher, encouraged my interest in the mysteries of thought. My father, a physical chemist, fostered my appreciation of the history of science. The former chair of my department, prone to unguarded comment, once accused me of being too young to think about such things. As the years pass, I realize how wrong he is. Introduction. Knot theory is one of the most active research areas of mathematics today. Thousands of refereed articles about knots have been published during just the past ten years. One publication, Journal of Knot Theory and its Ramifications, published by World Scientific since 1992, is devoted to new results in the subject. It is perhaps an oversimplification, but not a grave one, to say that two mildly eccentric nineteenth century Scottish physicists, William Thomson (a.k.a. Lord Kelvin) and Peter Guthrie Tait were responsible for modern knot theory. Our purpose is not to debate the point. Rather it is to try to understand the beliefs and bold expectations that motivated Thomson and Tait. James Clerk Maxwell’s influence on his friend Tait is well known. However, Maxwell’s keen interest in the developing theory of knots and links has become clear only in recent years, thanks in great part to the efforts of M. Epple. Often Maxwell was a source of information and humorous encouragement. At times he attempted to restrain Tait’s flights from the path of science. Any discussion of the origin of knot theory requires consideration of the colorful trefoil of Scottish physicists: Thomsom, Tait and Maxwell. -
Introduction to Braid Groups Joshua Lieber VIGRE REU 2011 University of Chicago
Introduction to Braid Groups Joshua Lieber VIGRE REU 2011 University of Chicago ABSTRACT. This paper is an introduction to the braid groups in- tended to familiarize the reader with the basic definitions of these mathematical objects. First, the concepts of the Fundamental Group of a topological space, configuration space, and exact sequences are briefly defined, after which geometric braids are discussed, followed by the definition of the classical (Artin) braid group and a few key results concerning it. Finally, the definition of the braid group of an arbitrary manifold is given. Contents 1. Geometric and Topological Prerequisites 1 2. Geometric Braids 4 3. The Braid Group of a General Manifold 5 4. The Artin Braid Group 8 5. The Link Between the Geometric and Algebraic Pictures 10 6. Acknowledgements 12 7. Bibliography 12 1. Geometric and Topological Prerequisites Any picture of the braid groups necessarily follows only after one has discussed the necessary prerequisites from geometry and topology. We begin by discussing what is meant by Configuration space. Definition 1.1 Given any manifold M and any arbitrary set of m points in that manifold Qm, the configuration space Fm;nM is the space of ordered n-tuples fx1; :::; xng 2 M − Qm such that for all i; j 2 f1; :::; ng, with i 6= j, xi 6= xj. If M is simply connected, then the choice of the m points is irrelevant, 0 ∼ 0 as, for any two such sets Qm and Qm, one has M − Qm = M − Qm. Furthermore, Fm;0 is simply M − Qm for some set of M points Qm. -
What Is a Braid Group? Daniel Glasscock, June 2012
What is a Braid Group? Daniel Glasscock, June 2012 These notes complement a talk given for the What is ... ? seminar at the Ohio State University. Intro The topic of braid groups fits nicely into this seminar. On the one hand, braids lend themselves immedi- ately to nice and interesting pictures about which we can ask (and sometimes answer without too much difficulty) interesting questions. On the other hand, braids connect to some deep and technical math; indeed, just defining the geometric braid groups rigorously requires a good deal of topology. I hope to convey in this talk a feeling of how braid groups work and why they are important. It is not my intention to give lots of rigorous definitions and proofs, but instead to draw lots of pictures, raise some interesting questions, and give some references in case you want to learn more. Braids A braid∗ on n strings is an object consisting of 2n points (n above and n below) and n strings such that i. the beginning/ending points of the strings are (all of) the upper/lower points, ii. the strings do not intersect, iii. no string intersects any horizontal line more than once. The following are braids on 3 strings: We think of braids as lying in 3 dimensions; condition iii. is then that no string in the projection of the braid onto the page (as we have drawn them) intersects any horizontal line more than once. Two braids on the same number of strings are equivalent (≡) if the strings of one can be continuously deformed { in the space strictly between the upper and lower points and without crossing { into the strings of the other. -
Dehornoy's Ordering on the Braid Group and Braid
Algebra i analiz St. Petersburg Math. J. Tom. 15 (2003), vyp. 3 Vol. 15 (2004), No. 3, Pages 437{448 S 1061-0022(04)00816-7 Article electronically published on March 30, 2004 DEHORNOY'S ORDERING ON THE BRAID GROUP AND BRAID MOVES A. V. MALYUTIN AND N. YU. NETSVETAEV Abstract. In terms of Dehornoy's ordering on the braid group Bn, restrictions are found that prevent us from performing the Markov destabilization and the Birman{ Menasco braid moves. As a consequence, a sufficient condition is obtained for the link represented by a braid to be prime, and it is shown that all braids in Bn that are not minimal lie in a finite interval of Dehornoy's ordering. Introduction 0.1. It is known that any classical link in R3 is representable by a closed braid, and the set of such closed braids is infinite. By a braid move we mean the passage from a closed braid βb to another closed braid representing the same link as βb. Many essential results of the theory of braids and links are related to the moves of stabilization and destabilization introduced by Markov, as well as to the \exchange move" and the \flype" defined by Birman and Menasco. While stabilization can always be performed, the other moves mentioned above do not apply to some braids. 0.2. In the present paper, we establish some restrictions on the possibility of performing braid moves; the restrictions are formulated in terms of Dehornoy's ordering. Combin- ing them with the known results concerning such transformations, we obtain conditions sufficient for the primeness of the link represented by a braid (these conditions are also formulated in terms of Dehornoy's ordering) and prove that there exists a similar criterion of the minimality of a braid. -
Braid Commutators and Vassiliev Invariants
Pacific Journal of Mathematics BRAID COMMUTATORS AND VASSILIEV INVARIANTS TED STANFORD Volume 174 No. 1 May 1996 PACIFIC JOURNAL OF MATHEMATICS Vol. 174, No. 1, 1996 BRAID COMMUTATORS AND VASSILIEV INVARIANTS TED STANFORD We establish a relationship between Vassiliev invariants and the lower central series of the pure braid group, and we use this to construct infinite families of prime knots or links whose invariants match those of a given knot or link up to a given order. Introduction. Theorem 1. Let L and L' be two links which differ by a braid p € P£, the nth group of the lower central series of Pk, the pure braid group on k strands. Let v be a link invariant of order less than n. Then v(L) = v(L'). In Section 1 we will define the order of a link invariant, and also define what it means for two links to differ by a braid p. As an example, if x represents the closure of a braid x, and b and p are any two braids with the same number of strands, then & and pb differ by p. Theorem 1 gives us a way to modify links without changing their invariants up to some order. We shall show that these changes can often be guaranteed to give distinct links. Falk and Randell proved in [FR] that the intersection of the lower central series of Pk is'trivial, that is, Γi^Pl — {!}, so that Theorem 1 does not give rise to an easy way of constructing distinct links, all of whose finite-order invariants are equal. -
Links, Quantum Groups, and TQFT's
Abstract. The Jones polynomial and the Kauffman bracket are constructed, and their relation with knot and link theory is described. The quantum groups and tangle functor formalisms for understanding these invariants and their descendents are given. The quantum group Uq(sl2), which gives rise to the Jones polynomial, is constructed explicitly. The 3-manifold invariants and the axiomatic topological quantum field theories which arise from these link invariants at certain values of the parameter are constructed. LINKS, QUANTUM GROUPS AND TQFT’S STEPHEN SAWIN Introduction In studying a class of mathematical objects, such as knots, one usually begins by developing ideas and machinery to understand specific features of them. When invariants are discovered, they arise out of such understanding and generally give information about those features. Thus they are often immediately useful for proving theorems, even if they are difficult to compute. This is not the situation we find ourselves in with the invariants of knots and 3- manifolds which have appeared since the Jones polynomial. We have a wealth of invariants, all readily computable, but standing decidedly outside the traditions of knot and 3-manifold theory. They lack a geometric interpretation, and consequently have been of almost no use in answering questions one might have asked before their creation. In effect, we are left looking for the branch of mathematics from which these should have come organically. In fact, we have an answer of sorts. In [Wit89b], Witten gave a heuristic definition of the Jones polynomial in terms of a topological quantum field theory, following the arXiv:q-alg/9506002v2 31 Jul 1995 outline of a program proposed by Atiyah [Ati88]. -
KNOTS from Combinatorics of Knot Diagrams to Combinatorial Topology Based on Knots
2034-2 Advanced School and Conference on Knot Theory and its Applications to Physics and Biology 11 - 29 May 2009 KNOTS From combinatorics of knot diagrams to combinatorial topology based on knots Jozef H. Przytycki The George Washington University Washington DC USA KNOTS From combinatorics of knot diagrams to combinatorial topology based on knots Warszawa, November 30, 1984 { Bethesda, March 3, 2007 J´ozef H. Przytycki LIST OF CHAPTERS: Chapter I: Preliminaries Chapter II: History of Knot Theory This e-print. Chapter II starts at page 3 Chapter III: Conway type invariants Chapter IV: Goeritz and Seifert matrices Chapter V: Graphs and links e-print: http://arxiv.org/pdf/math.GT/0601227 Chapter VI: Fox n-colorings, Rational moves, Lagrangian tangles and Burnside groups Chapter VII: Symmetries of links Chapter VIII: Different links with the same Jones type polynomials Chapter IX: Skein modules e-print: http://arxiv.org/pdf/math.GT/0602264 2 Chapter X: Khovanov Homology: categori- fication of the Kauffman bracket relation e-print: http://arxiv.org/pdf/math.GT/0512630 Appendix I. Appendix II. Appendix III. Introduction This book is about classical Knot Theory, that is, about the position of a circle (a knot) or of a number of disjoint circles (a link) in the space R3 or in the sphere S3. We also venture into Knot Theory in general 3-dimensional manifolds. The book has its predecessor in Lecture Notes on Knot Theory, which were published in Polish1 in 1995 [P-18]. A rough translation of the Notes (by J.Wi´sniewski) was ready by the summer of 1995.