Braided chord diagrams

The Intersection Graph Conjecture for Loop Diagrams

Vassiliev invariants can be studied by studying the spaces of chord diagrams associated with singular knots. To these chord diagrams are associated the intersection graphs of the chords. We extend results of Chmutov, Duzhin and Lando to show that these graphs determine the chord diagram if the graph has at most one loop. We also compute the size of the subalgebra generated by these "loop diagrams."

Invariant Tensors Formulae via Chord Diagrams

We provide an explicit algorithm to calculate invariant tensors for the adjoint representation of the simple Lie algebra $sl(n)$, as well as arbitrary representation in terms of roots. We also obtain explicit formulae for the adjoint representations of the orthogonal and symplectic Lie algebras $so(n)$ and $sp(n)$.

Space of chord diagrams on spherical curves

In this paper, we give a definition of $\mathbb{Z}$-valued functions from the ambient isotopy classes of spherical/plane curves derived from chord diagrams, denoted by $\sum_i α_i x_i$. Then, we introduce certain elements of the free $\mathbb{Z}$-module generated by the chord diagrams with at most $l$ chords, called relators of Type (I) ((SII), (WII), (SIII), or (WIII), resp.), and introduce another function $\sum_i α_i \tilde{x}_i$ derived from $\sum_i α_i x_i$. The main result (Theorem~1) shows that if $\sum_i α_i \tilde{x}_i$ vanishes for the relators of Type (I) ((SII), (WII), (SIII), or (…

Triple chords and strong (1, 2) homotopy

A triple chord is a sub-diagram of a chord diagram that consists of a circle and finitely many chords connecting the preimages for every double point on a spherical curve, and it has exactly three chords giving the triple intersection. This paper describes some relationships between the number of triple chords and an equivalence relation called strong (1, 2) homotopy, which consists of the first and one kind of the second Reidemeister moves involving inverse self-tangency if the curve is given any orientation. We show that a prime knot projection is trivialized by strong (1, 2) homotopy, if it…

A parity map of framed chord diagrams

We consider framed chord diagrams, i.e. chord diagrams with chords of two types. It is well known that chord diagrams modulo 4T-relations admit Hopf algebra structure, where the multiplication is given by any connected sum with respect to the orientation. But in the case of framed chord diagrams a natural way to define a multiplication is not known yet. In the present paper, we first define a new module $\mathcal{M}_2$ which is generated by chord diagrams on two circles and factored by $4$T-relations. Then we construct a "covering" map from the module of framed chord diagrams into $\mathcal{M}…

The expected genus of a random chord diagram

To any generic curve in an oriented surface there corresponds an oriented chord diagram, and any oriented chord diagram may be realized by a curve in some oriented surface. The genus of an oriented chord diagram is the minimal genus of an oriented surface in which it may be realized. Let g_n denote the expected genus of a randomly chosen oriented chord diagram of order n. We show that g_n satisfies: g_n = n/2 - Theta(ln n).

Plane curves in an immersed graph in $R^2$

For any chord diagram on a circle there exists a complete graph on sufficiently many vertices such that any generic immersion of it to the plane contains a plane closed curve whose chord diagram contains the given chord diagram as a sub-chord diagram. For any generic immersion of the complete graph on six vertices to the plane the sum of averaged invariants of all Hamiltonian plane curves in it is congruent to one quarter modulo one half.

Tree Diagrams for String Links II: Determining Chord Diagrams

In previous work, we defined the intersection graph of a chord diagram associated with a string link (as in the theory of finite type invariants). In this paper, we look at the case when this graph is a tree, and we show that in many cases these trees determine the chord diagram (modulo the usual 1-term and 4-term relations).

Genus Ranges of Chord Diagrams

A chord diagram consists of a circle, called the backbone, with line segments, called chords, whose endpoints are attached to distinct points on the circle. The genus of a chord diagram is the genus of the orientable surface obtained by thickening the backbone to an annulus and attaching bands to the inner boundary circle at the ends of each chord. Variations of this construction are considered here, where bands are possibly attached to the outer boundary circle of the annulus. The genus range of a chord diagram is the genus values over all such variations of surfaces thus obtained from a give…

On a Basis for the Framed Link Vector Space Spanned by Chord Diagrams

In view of the result of Kontsevich, now often called ``the fundamental theorem of Vassiliev theory'', identifying the graded dual of the associated graded vector space to the space of Vassiliev invariants filtered by degree with the linear span of chord diagrams modulo the ``4T-relation'' (and in the unframed case, the ``1T-'' or ``isolated chord relation''), it is a problem of some interest to provide a basis for the space of chord diagrams modulo the 4T-relation. We construct the basis for the vector space spanned by chord diagrams with n chords and m distinguishable link components, modulo…

The space of framed chord diagrams as a Hopf module

This note is dedicated to the study of a Hopf module structures on the space of framed chord diagrams and framed graphs. We also introduce a framed version of the chromatic polynomial and propose two methods to construct framed weight systems.

Classification of O-topologically non-equivalent functions with color chord diagrams

By means of color chord diagrams we establish a necessary and sufficient condition for $O$-topological equivalence of functions with one essentially critical point on oriented surfaces with edge. We also calculate the number of $O$-topologically non-equivalent functions with one essentially critical point on oriented surfaces with edge.

Chord Diagrams and Gauss Codes for Graphs

Chord diagrams on circles and their intersection graphs (also known as circle graphs) have been intensively studied, and have many applications to the study of knots and knot invariants, among others. However, chord diagrams on more general graphs have not been studied, and are potentially equally valuable in the study of spatial graphs. We will define chord diagrams for planar embeddings of planar graphs and their intersection graphs, and prove some basic results. Then, as an application, we will introduce Gauss codes for immersions of graphs in the plane and give algorithms to determine whet…

Chord Diagrams and Coxeter Links

This paper presents a construction of fibered links $(K,Σ)$ out of chord diagrams $\sL$. Let $Γ$ be the incidence graph of $\sL$. Under certain conditions on $\sL$ the symmetrized Seifert matrix of $(K,Σ)$ equals the bilinear form of the simply-laced Coxeter system $(W,S)$ associated to $Γ$; and the monodromy of $(K,Σ)$ equals minus the Coxeter element of $(W,S)$. Lehmer's problem is solved for the monodromy of these Coxeter links.

Evaluating TQFT invariants from G-crossed braided spherical fusion categories via Kirby diagrams with 3-handles

A family of TQFTs parametrised by G-crossed braided spherical fusion categories has been defined recently as a state sum model and as a Hamiltonian lattice model. Concrete calculations of the resulting manifold invariants are scarce because of the combinatorial complexity of triangulations, if nothing else. Handle decompositions, and in particular Kirby diagrams are known to offer an economic and intuitive description of 4-manifolds. We show that if 3-handles are added to the picture, the state sum model can be conveniently redefined by translating Kirby diagrams into the graphical calculus of…

Groups with small Dehn functions and bipartite chord diagrams

We introduce a new invariant of bipartite chord diagrams and use it to construct the first examples of groups with Dehn function $n^2\log n$ and other small Dehn functions. Some of these groups have undecidable conjugacy problem.

Circle graphs (chord interlacement graphs) of Gauss diagrams: Descriptions of realizable Gauss diagrams, algorithms, enumeration

Chord diagrams, under the name of Gauss diagrams, are used in low-dimensional topology as an important tool for studying curves or knots. Those Gauss diagrams that correspond to curves or knots are called realizable. The theme of our paper is the fact that realizability of a Gauss diagram can be expressed via its circle graph. Accordingly, one can define and study realizable circle graphs (with realizability of a circle graph understood as realizability of any one of chord diagrams corresponding to the graph). Several studies contain theorems purporting to prove the fact. We check several of t…

渐近刚性映射类群 II：链图与非正曲率

Asymptotically rigid mapping class groups II: strand diagrams and nonpositive curvature

该研究提出由特定半群表示的编织链图构造的Chambord群新类，涵盖多种已知渐近刚性映射类群，并证明其多循环子群具有几乎阿贝尔且不失真的性质。

弦图的种类、辫群上同调与等式条件的退化

Varieties of chord diagrams, braid group cohomology and degeneration of equality conditions

该研究证明当连续函数空间维数满足特定条件时，等式条件系统定义的子空间余维数会超出条件数，给出余维下降下界，并将其应用于纽结理论，证实纽结空间上同调谱序列中必然存在复杂非稳定项。

关于交集图为完全二部图的弦图的 $\mathfrak{sl}_3$ 权系统取值

On values of $\mathfrak{sl}_3$ weight system on chord diagrams whose intersection graph is complete bipartite

本文针对交集图为完全二部图 $K_{2,n}$ 的弦图，计算了 $\mathfrak{sl}_3$ 权系统的取值，该权系统由李代数构造并满足 4 项关系。

Describing realizable Gauss diagrams using the concepts of parity or bipartate graphs

Two recent publications describe realizable Gauss diagrams using conditions stating that the number of chords in certain sets of chords is even or odd. We demonstrate that these descriptions are incorrect by finding multiple counter-examples. However, the idea of having a parity-based description of realizable Gauss diagrams is attractive. We recall that realizability of Gauss diagrams as touch curves can be described via bipartite graphs. We show that realizable Gauss diagrams can be described via bipartite graphs.

Vassiliev Invariants from Parity Mappings

Parity mappings from the chords of a Gauss diagram to the integers is defined. The parity of the chords is used to construct families of invariants of Gauss diagrams and virtual knots. One family consists of degree $n$ Vassiliev invariants.

曲面中的环、弦图、交错图：算子分解与生成文法

Loops in surfaces, chord diagrams, interlace graphs: operad factorisations and generating grammars

本文研究闭曲面中 filoop 的亏格，通过弦图和交错图计算最小亏格，给出球和与环和的典范分解，并构造生成文法，建立稳定性性质。

Some remarks on the chord index

In this paper we discuss how to define a chord index via smoothing a real crossing point of a virtual knot diagram. Several polynomial invariants of virtual knots and links can be recovered from this general construction. We also explain how to extend this construction from virtual knots to flat virtual knots.

The genus of a random chord diagram is asymptotically normal

Let $G_n$ be the genus of a two-dimensional surface obtained by gluing, uniformly at random, the sides of an $n$-gon. Recently Linial and Nowik proved, via an enumerational formula due to Harer and Zagier, that the expected value of $G_n$ is asymptotic to $(n - \ln n)/2$ for $n\to\infty$. We prove a local limit theorem for the distribution of $G_n$, which implies that $G_n$ is asymptotically Gaussian, with mean $(n-\ln n)/2$ and variance $(\ln n)/4$.

Experimental Mathematics Approach to Gauss Diagrams Realizability

A Gauss diagram (or, more generally, a chord diagram) consists of a circle and some chords inside it. Gauss diagrams are a well-established tool in the study of topology of knots and of planar and spherical curves. Not every Gauss diagram corresponds to a knot (or an immersed curve); if it does, it is called realizable. A classical question of computational topology asked by Gauss himself is which chords diagrams are realizable. An answer was first discovered in the 1930s by Dehn, and since then many efficient algorithms for checking realizability of Gauss diagrams have been developed. Recent …

闭曲面上最优Morse流的单圈带符号弦图及其对偶的枚举

Enumeration of one-cycle signed chord diagrams and their duals for optimal Morse flows on closed surfaces

该研究将闭曲面上最优Morse流的分类构造算法化，提出枚举单圈带符号弦图及对偶的算法，经多类数据验证，可分组等价类并识别自对偶类。

The salient crossings of a crown diagram

A crown diagram of a smooth, closed oriented 4-manifold can be thought of as the projection of a link in the product of a closed surface and the circle, with chords in the circle direction connecting the strands of each crossing. This paper uses a straightforward assignment of integers to these chords to show that the smooth structures on the topological 4-manifold underlying a pair of Fintushel-Stern knot surgery 4-manifolds which are known to have the same Seiberg-Witten invariant are not isotopic. A natural question is to determine if the argument may be strengthened to show these manifolds…

A new family of infinitely braided Thompson's groups

We present a generalization of the Dehornoy-Brin braided Thompson group $BV_2$ that uses recursive braids. Our new groups are denoted by $BV_{n,r}(H)$, for all $n\geq 2,r\geq 1$ and $H \leq \mathcal{B}_n$, where $\mathcal{B}_n$ is the braid group on $n$ strands. We give a new approach to deal with braided Thompson groups by using strand diagrams. We show that $BV_{n,r}(H)$ is finitely generated if $H$ is finitely generated.

用三分解曲面填充辫环链

Filling braided links with trisected surfaces

本文引入紧致四维流形中整洁嵌入曲面的桥式三分解概念，证明其存在性并发展了影子图与三平面图等图示方法，详细探讨了边界辫结构、粘合操作及带状曲面复杂度刻画。

Topological recursion for chord diagrams, RNA complexes, and cells in moduli spaces

We introduce and study the Hermitian matrix model with potential V(x)=x^2/2-stx/(1-tx), which enumerates the number of linear chord diagrams of fixed genus with specified numbers of backbones generated by s and chords generated by t. For the one-cut solution, the partition function, correlators and free energies are convergent for small t and all s as a perturbation of the Gaussian potential, which arises for st=0. This perturbation is computed using the formalism of the topological recursion. The corresponding enumeration of chord diagrams gives at once the number of RNA complexes of a given …

Chord diagrams, contact-topological quantum field theory, and contact categories

We consider contact elements in the sutured Floer homology of solid tori with longitudinal sutures, as part of the (1+1)-dimensional topological quantum field theory defined by Honda--Kazez--Matić in \cite{HKM08}. The $\Z_2$ $SFH$ of these solid tori forms a "categorification of Pascal's triangle", and contact structures correspond bijectively to chord diagrams, or sets of disjoint properly embedded arcs in the disc. Their contact elements are distinct and form distinguished subsets of $SFH$ of order given by the Narayana numbers. We find natural "creation and annihilation operators" which all…

二维球面上涂鸦的一个完全不变量

A complete invariant for doodles on a 2-sphere

本文通过构造取值于特定弦图级数的完全不变量，研究二维球面上涂鸦的分类问题，并证明其系数为阶至多 $2n$ 的有限型不变量。

通过四维拓扑研究纽结与链环的交叉数

The crossing numbers of knots and links via 4D topology

该研究通过四维拓扑将链环交叉数与旋转带状环面纽结的弦指数关联，证明了链环连通和下交叉数的可加性。

Multistring based matrices

A virtual $n$-string is a chord diagram with $n$ core circles and a collection of arrows between core circles. We consider virtual $n$-strings up to virtual homotopy, compositions of flat virtual Reidemeister moves on chord diagrams. Given a virtual 1-string $α$, Turaev associated a based matrix that encodes invariants of the virtual homotopy class of $α$. We generalize Turaev's method to associate a multistring based matrix to virtual $n$-strings, addressing an open problem of Turaev and constructing similar invariants for virtual homotopy classes of virtual $n$-strings.

Arc numbers from Gauss diagrams

We characterize planar diagrams which may be divided into n arc embeddings in terms of their chord diagrams, generalizing a result of Taniyama for the case n = 2. Two algorithms are provided, one which finds a minimal arc embedding (in quadradic time in the number of crossings), and one which constructs a minimal subdiagram having same arc number as D.

A Representation Theorem for Knots and a Generalization of the Fundamental Theorem of Finite Type Invariants

We provide a way to produce knots in $S^3$ from signed chord diagrams, and prove that every knot can be produced in this way. Using these diagrams, we generalize the fundamental theorem of finite type invariants. We also provide moves for the diagrams so that any two diagrams for the same knot are connected by a sequence of moves.

Values of the $\mathfrak{sl}_2$ weight system on complete bipartite graphs

A weight system is a function on chord diagrams that satisfies the so-called four-term relations. Vassiliev's theory of finite-order knot invariants describes these invariants in terms of weight systems. In particular, there is a weight system corresponding to the colored Jones polynomial. This weight system can be easily defined in terms of the Lie algebra $\mathfrak{sl}_2$, but this definition is too cumbersome from the computational point of view, so that the values of this weight system are known only for some limited classes of chord diagrams. In the present paper we give a formula for th…

微分同伦上同调通过构型空间和弦图蕴含相交膜可观测量的研究

Differential Cohomotopy implies intersecting brane observables via configuration spaces and chord diagrams

本文引入微分同伦上同调理论，证明其膜电荷量子化蕴含相交膜模空间，并揭示其可观测量由弦图权重系统刻画，涵盖多种微观量子效应，支持M理论C场的同伦量子化假设。

A twisted link invariant derived from a virtual link invariant

Virtual knot theory is a generalization of knot theory which is based on Gauss chord diagrams and link diagrams on closed oriented surfaces. A twisted knot is a generalization of a virtual knot, which corresponds to a link diagram on a possibly non-orientable surface. In this paper, we discuss an invariant of twisted links which is obtained from the JKSS invariant of virtual links by use of double coverings. We also discuss some properties of double covering diagrams.

Weight systems and invariants of graphs and embedded graphs

We describe recent achievements in the theory of weight systems, which are functions on chord diagrams satisfying so-called $4$-term relations. Our main attention is devoted to constructions of weight systems. The two main sources of these constructions that are discussed in the paper are invariants of intersection graphs of chord diagrams that satisfy $4$-term relations for graphs and metrized Lie algebras. For the simplest nontrivial metrized Lie algebra $\mathfrak {sl}(2)$, we present recent results about the explicit form of generating functions for the values of the corresponding weight s…

The Kontsevich Integral in Book Notation

We introduce a matrix representation of a chord on a tangle which leads us to representing tangle chord diagrams as stacks of matrices that we call books. We show that band sum moves, Reidemeister moves as well as orientation changes are implemented on \widetilde{Z}_f - a framed link invariant constructed from the Kontsevich integral that's well-behaved under band sum moves - by matrix congruences. We prove that being given the bare framed Kontsevich integral Z_f(L) in book notation for some unknown link L, we can determine what the link L is, as well as the projection of Z_f(L) in the origina…

Ribbon graphs and bialgebra of Lagrangian subspaces

To each ribbon graph we assign a so-called L-space, which is a Lagrangian subspace in an even-dimensional vector space with the standard symplectic form. This invariant generalizes the notion of the intersection matrix of a chord diagram. Moreover, the actions of Morse perestroikas (or taking a partial dual) and Vassiliev moves on ribbon graphs are reinterpreted nicely in the language of L-spaces, becoming changes of bases in this vector space. Finally, we define a bialgebra structure on the span of L-spaces, which is analogous to the 4-bialgebra structure on chord diagrams.

基本权系统是量子态

Fundamental weight systems are quantum states

本文证明水平弦图上的基本gl(n)-权系统可等同于对称群上的Cayley距离核，并证明该核在β=ln(n)处正半定，从而表明所有基本gl(n)-权系统及其凸组合都是量子态。

A few weight systems arising from intersection graphs

We show that the adjacency matrices of the intersection graphs of chord diagrams satisfy the 2-term relations of Bar-Natan and Garoufalides [bg], and hence give rise to weight systems. Among these weight systems are those associated with the Conway and HOMFLYPT polynomials. We extend these ideas to looking at a space of {\it marked} chord diagrams modulo an extended set of 2-term relations, define a set of generators for this space, and again derive weight systems from the adjacency matrices of the (marked) intersection graphs. Among these weight systems are those associated with the Kauffman …