A Gordian Pair of Links

A new pair of non-cobordant surface-links which the Orr invariant, the Cochran sequence, the Sato-Levine invariant, and the alinking number cannot find

We submit a new way to detect pairs of non-cobordant surface-links. We find a new example of a pair of non-cobordant surface-links with the following properties: Orr invariant, Cochran sequence, Sato-Levine invariant, the alinking number and one of Stallings's theorems cannot distinguish them. However our new way can distinguish them.

Twisted intersection colorings, invariants and double coverings of twisted links

Twisted links are a generalization of classical links and correspond to stably equivalence classes of links in thickened surfaces. In this paper we introduce twisted intersection colorings of a diagram and construct two invariants of a twisted link using such colorings. As an application, we show that there exist infinitely many pairs of twisted links such that for each pair the two twisted links are not equivalent but their double coverings are equivalent. We also introduce a method of constructing a pair of twisted links whose double coverings are equivalent.

交错纽结与链环的一个多项式对不变量

A polynomial pair invariant of alternating knots and links

本文提出一种基于交错纽结最小图示中两个棋盘平面图的整数多项式对不变量WRP，证明其良定义，并能区分表中所有交叉数不超过10的纽结及其镜像，强度可与经典不变量如三变量考夫曼括号相比。

Virtual link and knot invariants from non-abelian Yang-Baxter 2-cocycle pairs

For a given $(X,S,β)$, where $S,β\colon X\times X\to X\times X$ are set theoretical solutions of Yang-Baxter equation with a compatibility condition, we define an invariant for virtual (or classical) knots/links using non commutative 2-cocycles pairs $(f,g)$ that generalizes the one defined in [FG2]. We also define, a group $U_{nc}^{fg}=U_{nc}^{fg}(X,S,β)$ and functions $π_f, π_g\colon X\times X\to U_{nc}^{fg}(X)$ governing all 2-cocycles in $X$. We exhibit examples of computations achieved using GAP.

Capturing links in spatial complete graphs

We say that a set of pairs of disjoint cycles $Λ(G)$ of a graph $G$ is linked if for any spatial embedding $f$ of $G$ there exists an element $λ$ of $Λ(G)$ such that the $2$-component link $f(λ)$ is nonsplittable, and also say minimally linked if none of its proper subsets are linked. In this paper, (1) we show that the set of all pairs of disjoint cycles of $G$ is minimally linked if and only if $G$ is essentially same as a graph in the Petersen family, and (2) for any two integers $p,q\ge 3$, we exhibit a minimally linked set of Hamiltonian $(p,q)$-pairs of cycles of the complete graph $K_{p…

When do links admit homeomorphic C-complexes?

Any two knots admit orientation preserving homeomorphic Seifert surfaces, as can be seen by stabilizing. There is a generalization of a Seifert surface to the setting of links called a C-complex. In this paper, we ask when two links will admit orientation preserving homeomorphic C-complexes. In the case of 2-component links, we find that the pairwise linking number provides a complete obstruction. In the case of links with 3 or more components and zero pairwise linking number, Milnor's triple linking number provides a complete obstruction.

Link invariants from finite categorical groups

We define an invariant of tangles and framed tangles given a finite crossed module and a pair of functions, called a Reidemeister pair, satisfying natural properties. We give several examples of Reidemeister pairs derived from racks, quandles, rack and quandle cocycles, and central extensions of groups. We prove that our construction includes all rack and quandle cohomology (framed) link invariants, as well as the Eisermann invariant of knots. We construct a class of Reidemeister pairs which constitute a lifting of the Eisermann invariant, and show through an example that this class is strictl…

The genus zero, 3-component fibered links in $S^3$

The open book decompositions of the 3-sphere whose pages are pairs of pants have been fully understood for some time, through the lens of contact geometry. The purpose of this note is to exhibit a purely topological derivation of the classification of such open books, in terms of the links that form their bindings and the corresponding monodromies. We construct all of the links and their pair-of-pants fiber surfaces from the simplest example, a connected sum of two Hopf links, through performing (generalized) Stallings twists. Then, by applying the now-classical theory of genus two Heegaard di…

On the asymptotic expansion for the relative Reshetikhin-Turaev invariants of fundamental shadow link pairs

We study the asymptotic expansion conjecture of the relative Reshetikhin-Turaev invariants proposed in \cite{WY4} for all pairs $(M,L)$ satisfying the property that $M\setminus L$ is homeomorphic to some fundamental shadow link complement. The hyperbolic cone structure of such $(M,L)$ can be described by using the logarithmic holonomies of the meridians of some fundamental shadow link. We show that when the logarithmic holonomies are sufficiently small and all cone angles are less than $π$, the asymptotic expansion conjecture of $(M,L)$ is true. Especially, we verify the asymptotic expansion c…

Universal cocycle Invariants for singular knots and links

Given a biquandle $(X, S)$, a function $τ$ with certain compatibility and a pair of {\em non commutative cocyles} $f,h:X \times X\to G$ with values in a non necessarily commutative group $G$, we give an invariant for singular knots / links. Given $(X,S,τ)$, we also define a universal group $U_{nc}^{fh}(X)$ and universal functions governing all 2-cocycles in $X$, and exhibit examples of computations. When the target group is abelian, a notion of {\em abelian cocycle pair} is given and the "state sum" is defined for singular knots/links. Computations generalizing linking number for singular knot…

Additive invariants for knots, links and graphs in 3-manifolds

We define two new families of invariants for (3-manifold, graph) pairs which detect the unknot and are additive under connected sum of pairs and (-1/2)-additive under trivalent vertex sum of pairs. The first of these families is closely related to both bridge number and tunnel number. The second of these families is a variation and generalization of Gabai's width for knots in the 3-sphere. We give applications to the tunnel number and higher genus bridge number of connected sums of knots.

Combinatorial Dehn-Lickorish Twists and Framed Link Presentations of 3-Manifolds Revisited

From a pseudo-triangulation with $n$ tetrahedra $T$ of an arbitrary closed orientable connected 3-manifold (for short, {\em a 3D-space}) $M^3$, we present a gem $J '$, inducing $\IS^3$, with the following characteristics: (a) its number of vertices is O(n); (b) it has a set of $p$ pairwise disjoint couples of vertices $\{u_i,v_i\}$, each named {\em a twistor}; (c) in the dual $(J ')^\star$ of $J '$ a twistor becomes a pair of tetrahedra with an opposite pair of edges in common, and it is named {\em a hinge}; (d) in any embedding of $(J ')^\star \subset \IS^3$, the $ε$-neighborhood of each hing…

Link invariants from finite categorical groups and braided crossed modules

We define an invariant of tangles and framed tangles given a finite crossed module and a pair of functions, called a Reidemeister pair, satisfying natural properties. We give several examples of Reidemeister pairs derived from racks, quandles, rack and quandle cocycles, 2-crossed modules and braided crossed modules. We prove that our construction includes all rack and quandle cohomology (framed) link invariants, as well as the Eisermann invariant of knots, for which we also find a lifting by using braided crossed modules.

A pair of Jones polynomial positivity obstructions

We provide a new bound on the maximum degree of the Jones polynomial of a positive link with second Jones coefficient equal to $\pm 1$ or $\pm 2$. This builds upon the result of our previous work, in which we found such a bound for positive fibered links. We also show that each of these three bounds obstruct positivity for infinitely many almost-positive diagrams, allowing us to classify infinitely many knots as almost-positive.

Stable pairs and the HOMFLY polynomial

Given a planar curve singularity, we prove a conjecture of Oblomkov-Shende, relating the geometry of its Hilbert scheme of points to the HOMFLY polynomial of the associated algebraic link. More generally, we prove an extension of this conjecture, due to Diaconescu-Hua-Soibelman, relating stable pair invariants on the conifold to the colored HOMFLY polynomial of the algebraic link. Our proof uses wall-crossing techniques to prove a blowup identity on the algebro-geometric side. We prove a matching identity for the colored HOMFLY polynomials of a link using skein-theoretic techniques.

具有解结指标 (n,m) 的虚拟纽结与链环

Virtual knots and links with unknotting index (n,m)

本文针对虚拟纽结的解结指标问题，构造了具有指定解结指标 (n,m) 的无限族虚拟纽结与链环，肯定地回答了 Kaur 等人提出的问题。

Kleinian群由抛物线对生成的几何学

Geometry for Kleinian Groups Generated by a Parabolic Pair

本文提出了一种基于三角剖分的计算框架，用于研究由抛物线对生成的Kleinian群的双曲几何及2桥链接补集的结构。

A family of freely slice good boundary links

We show that every good boundary link with a pair of derivative links on a Seifert surface satisfying a homotopically trivial plus assumption is freely slice. This subsumes all previously known methods for freely slicing good boundary links with two or more components, and provides new freely slice links.

Compatible Relative Open Books on Relative Contact Pairs via Generalized Square Bridge Diagrams

Using square bridge position, Akbulut-Ozbagci and later Arikan gave algorithms both of which construct an explicit compatible open book decomposition on a closed contact $3$-manifold which results from a contact $(\pm 1)$-surgery on a Legendrian link in the standard contact $3$-sphere. In this article, we introduce the ``generalized square bridge position'' for a Legendrian link in the standard contact $5$-sphere and partially generalize this result to the dimension five via an algorithm which constructs relative open book decompositions on relative contact pairs.

Rotors in Khovanov Homology

Anstee, Przyticki and Rolfsen introduced the idea of rotants, pairs of links related by a generalised form of link mutation. We exhibit infinitely many pairs of rotants which can be distinguished by Khovanov homology, but not by the Jones polynomial.

三维球面中双曲链补集内的不可压缩平面曲面

Incompressible planar surfaces in hyperbolic link exteriors in the 3-sphere

对于每个整数N≥3，构造N分支双曲链的例子，其外部包含一个不可压缩的跨越平面曲面，该曲面在每个边界环面上具有非经向且非整数斜率，从而反驳了Eudave-Muñoz和Ozawa的猜想。

On colored Turaev-Viro invariants for links in arbitrary 3-manifolds

We consider certain invariants of links in 3-manifolds, obtained by a specialization of the Turaev-Viro invariants of 3-manifolds, that we call colored Turaev-Viro invariants. Their construction is based on a presentation of a pair (M,L), where M is a closed oriented 3-manifold and L is an oriented link in M, by a triangulation of M such that each component of L is an edge. We analyze some basic properties of these invariants, including the behavior under connected sums of pairs away and along links. These properties allow us to provide examples of links in the three-sphere having the same HOM…

Generic deformations of the colored sl(N)-homology for links

We generalize the works of Lee [arXiv:math/0210213v3] and Gornik [arXiv:math/0402266v2] to construct a basis for generic deformations of the colored sl(N)-homology defined in [arXiv:1002.2662v1]. As applications, we construct non-degenerate pairings and co-pairings which lead to dualities of generic deformations of the colored sl(N)-homology. We also define and study colored sl(N)-Rasmussen invariants. Among other things, we observe that these invariants vanish on amphicheiral knots and discuss some implications of this observation.

伪Legendrian和Legendrian简单性在3流形中的链接

Pseudo-Legendrian and Legendrian Simplicity of Links in 3-Manifolds

该研究通过构造非简单同胚类的Legendrian链接，展示了在过扭接触结构中，Legendrian同胚与框架同胚、同伦及链接同伦之间的差异，揭示了非简单性现象在相同光滑同胚类中的共存。

无限多对空间曲面

Infinitely many pairs of spatial surfaces

本文提出为每个链接构造无限多对Seifert曲面，通过环境同胚和单模合同不变量区分曲面对。

强拟正链接是与无限多个强拟正链接相容的

Strongly quasipositive links are concordant to infinitely many strongly quasipositive links

研究证明非平凡强拟正链接与无限多个非同胚的强拟正链接平滑相容，反驳了Baker猜想，方法采用一种卫星操作，其伴接是具有最大Thurston-Bennequin数-1的切片结。

从交换霍普夫代数中获得3流形与嵌入带框架链接的不变量

Invariants from involutory Hopf algebras of 3-manifolds with embedded framed links

本文基于交换霍普夫代数和Drinfeld双代数定义了3流形与嵌入链接的不变量，推广了Kuperberg和HKR不变量，并通过Heegaard-Link图示方法构建了新的证明。

The intersection of spheres in a sphere and a new geometric meaning of the Arf invariant

Let S^3_i be a 3-sphere embedded in the 5-sphere S^5 (i=1,2). Let S^3_1 and S^3_2 intersect transversely. Then the intersection C of S^3_1 and S^3_2 is a disjoint collection of circles. Thus we obtain a pair of 1-links, C in S^3_i (i=1,2), and a pair of 3-knots, S^3_i in S^5 (i=1,2). Conversely let (L_1,L_2) be a pair of 1-links and (X_1,X_2) be a pair of 3-knots. It is natural to ask whether the pair of 1-links (L_1,L_2) is obtained as the intersection of the 3-knots X_1 and X_2 as above. We give a complete answer to this question. Our answer gives a new geometric meaning of the Arf invariant…