On transverse Hopf links

A two component link with Alexander polynomial one is concordant to the Hopf link

Four-dimensional surgery is used to show that a two component link with Alexander polynomial one is topologically concordant to the Hopf link.

Links with nontrivial Alexander polynomial which are topologically concordant to the Hopf link

We give infinitely many $2$-component links with unknotted components which are topologically concordant to the Hopf link, but not smoothly concordant to any $2$-component link with trivial Alexander polynomial. Our examples are pairwise non-concordant.

Khovanov homology detects the Hopf links

We prove that any link in $S^3$ whose Khovanov homology is the same as that of a Hopf link must be isotopic to that Hopf link. This holds for both reduced and unreduced Khovanov homology, and with coefficients in either $\mathbb{Z}$ or $\mathbb{Z}/2\mathbb{Z}$.

霍普夫把手体链：其对称性与分类

Hopf handlebody-links: their symmetry and classification

该研究将霍普夫链概念推广至空间图与把手体链领域，探究其对称性与分类问题。

The SU(2) Casson-Lin invariant of the Hopf link

We compute the $SU(2)$ Casson-Lin invariant for the Hopf link and determine the sign in the formula of Harper and Saveliev relating this invariant to the linking number.

Homfly Polynomials of Generalized Hopf Links

Following the recent work by T.-H. Chan in [HOMFLY polynomial of some generalized Hopf links, J. Knot Theory Ramif. 9 (2000) 865--883] on reverse string parallels of the Hopf link we give an alternative approach to finding the Homfly polynomials of these links, based on the Homfly skein of the annulus. We establish that two natural skein maps have distinct eigenvalues, answering a question raised by Chan, and use this result to calculate the Homfly polynomial of some more general reverse string satellites of the Hopf link.

霍普夫链的拓扑配边类中的晃动配边

Shake concordance in the topological concordance class of the Hopf link

该研究在霍普夫链的拓扑配边类中，基于光滑0-晃动配边的等价关系构造出无穷多类，每类含无穷多链的光滑配边类，其第二个分量的光滑切片亏格无界。

"Slicing" the Hopf link

A link in the 3-sphere is called (smoothly) slice if its components bound disjoint smoothly embedded disks in the 4-ball. More generally, given a 4-manifold M with a distinguished circle in its boundary, a link in the 3-sphere is called M-slice if its components bound in the 4-ball disjoint embedded copies of M. A 4-manifold M is constructed such that the Borromean rings are not M-slice but the Hopf link is. This contrasts the classical link-slice setting where the Hopf link may be thought of "the most non-slice" link. Further examples and an obstruction for a family of decompositions of the 4…

A new family of links topologically, but not smoothly, concordant to the Hopf link

We give new examples of 2-component links with linking number one and unknotted components that are topologically concordant to the positive Hopf link, but not smoothly so - in fact they are not smoothly concordant to the positive Hopf link with a knot tied in the first component. Such examples were previously constructed by Cha-Kim-Ruberman-Strle; we show that our examples are distinct from theirs.

关于 Hopf 链环上有理手术的注记

A note on rational surgeries on a Hopf link

本文利用连分数演算显式计算了三维球面中 Hopf 链环上有理手术所得的透镜空间流形，并作为推论恢复了有理手术何时得到三维球面的判别准则。

The Kauffman polynomials of generalized Hopf links

Following the recent work by Chan, and by Morton and Hadji on the Homflypt polynomials of some generalized Hopf links, we investigate the Kauffman polynomials of generalized Hopf links. By studying the Kauffman skein module of the solid torus S^1\times D^2, we establish a similar skein map on the Kauffman skein module of S^1\times D^2 which has distinct eigenvalues. Furthermore we are able to calculate the Kauffman polynomials of some specific generalized Hopf links.

The Homfly polynomial of the decorated Hopf link

The main goal is to find the Homfly polynomial of a link formed by decorating each component of the Hopf link with the closure of a directly oriented tangle. Such decorations are spanned in the Homfly skein of the annulus by elements Q_λ, depending on partitions λ. We show how to find the 2-variable Homfly invariant <λ,μ> of the Hopf link arising from decorations Q_λand Q_μin terms of the Schur symmetric function s_μof an explicit power series depending on λ. We show also that the quantum invariant of the Hopf link coloured by irreducible sl(N)_q modules V_λand V_μ, which is a 1-variable speci…

Contact surgery on the Hopf link: classification of fillings

Let $H\subseteq S^3$ be the two-component Hopf link. After choosing a Legendrian representative of $H$ with respect to the standard tight contact structure on $S^3$ we perform contact $(-1)$-surgery on the link itself. The manifold we get is a lens space together with a tight contact strucure on it, which depends on the chosen Legendrian representative. We classify its minimal symplectic fillings up to homeomorphism (and often up to diffeomoprhism), extending the results of Lisca which covers the case of universally tight structures and the article of Plamenevskaya - Van Horn Morris which desc…

扭曲Hopf链环的表示簇

Representation varieties of twisted Hopf links

本文研究了具有n次扭曲的Hopf链环补空间基本群的表示理论，提出基于组合问题与等变Hodge理论的通用框架分析其$SL_r(C)$-表示簇，并给出了秩2和3的表示簇与特征簇的E-多项式闭式公式。

Transverse universal links

We show that there exists a transverse link in the standard contact structures on the 3-sphere such that all contact 3-manifolds are contact branched covers over this transverse link.

On some moves on links and the Hopf crossing number

We consider arrow diagrams of links in $S^3$ and define $k$-moves on such diagrams, for any $k\in\mathbb N$. We study the equivalence classes of links in $S^3$ up to $k$-moves. For $k=2$, we show that any two knots are equivalent, whereas it is not true for links. We show that the Jones polynomial at a $k$-th primitive root of unity is unchanged by a $k$-move, when $k$ is odd. It is multiplied by $-1$, when $k$ is even. It follows that, for any $k\ge 5$, there are infinitely many classes of knots modulo $k$-moves. We use these results to study the Hopf crossing number. In particular, we show t…

Hopf链环的嵌入空间

The embedding space of a Hopf link

本文研究 Hopf 链环的无参数光滑嵌入空间，证明在 $\mathbb{R}^3$ 中该空间同伦等价于 $S^3/\mathbb{Q}_8$，在 $S^3$ 中同伦等价于 $\mathbb{R} P^2\times \mathbb{R} P^2$。

twisted Hopf链接基本群补集的AGL_r(C)表示变种的分层

Stratification of $\mathrm{AGL}_r(\mathbb{C})$-representation varieties of twisted Hopf links

本文通过GL_r(C)表示变种的分层来分层twisted Hopf链接基本群补集的AGL_r(C)表示变种，并对秩1和2的情况进行了显式描述和计算。

Hopf 树状链环、子式理论与亏格缺陷的可判定性

Hopf Arborescent Links, Minor Theory, and Decidability of the Genus Defect

本文证明对于 Hopf 树状链环，四维亏格缺陷的计算是可判定的，通过建立其 Seifert 曲面在子式关系下构成良拟序，采用非构造性证明方法。

On meridian-traceless SU(2)-representations of link groups

Suppose L is a link in $S^3$. We show that $π_1(S^3-L)$ admits an irreducible meridian-traceless representation in SU(2) if and only if L is not the unknot, the Hopf link, or a connected sum of Hopf links. As a corollary, $π_1(S^3-L)$ admits an irreducible representation in SU(2) if and only if L is neither the unknot nor the Hopf link. This result generalizes a theorem of Kronheimer and Mrowka to the case of links.

Macdonald operators and homological invariants of the colored Hopf link

Using a power sum (boson) realization for the Macdonald operators, we investigate the Gukov, Iqbal, Kozcaz and Vafa (GIKV) proposal for the homological invariants of the colored Hopf link, which include Khovanov-Rozansky homology as a special case. We prove the polynomiality of the invariants obtained by GIKV's proposal for arbitrary representations. We derive a closed formula of the invariants of the colored Hopf link for antisymmetric representations. We argue that a little amendment of GIKV's proposal is required to make all the coefficients of the polynomial non-negative integers.

将辫状霍普夫代数的结多项式扩展到链环

Extending Knot Polynomials of Braided Hopf Algebras to Links

本文研究了如何将Kashaev等人基于辫状霍普夫代数的多变量结多项式扩展到链环，并识别其中一些与已知链环不变量一致。

Comultiplication in link Floer homology and transversely non-simple links

For a word w in the braid group on n-strands, we denote by T_w the corresponding transverse braid in the rotational symmetric tight contact structure on S^3. We exhibit a map on link Floer homology which sends the transverse invariant associated to T_{ws_i} to that associated to T_w, where s_i is one of the standard generators of B_n. This gives rise to a "comultiplication" map on link Floer homology. We use this to generate infinitely many new examples of prime topological link types which are not transversely simple.

Transverse links, open books and overtwisted manifolds

We prove that transverse links in any contact manifold $(M,ξ)$ can be realized as a sub-binding of a compatible open book decomposition. We define the support genus of a transverse link and prove that the support genus of a transverse knot is zero if there is an overtwisted disk disjoint from it. Next, we find a relationship between the support genus of a transverse link and its Legendrian approximation.

Almost alternating diagrams and fibered links in S^3

Let $L$ be an oriented link with an alternating diagram $D$. It is known that $L$ is a fibered link if and only if the surface $R$ obtained by applying Seifert's algorithm to $D$ is a Hopf plumbing. Here, we call $R$ a Hopf plumbing if $R$ is obtained by successively plumbing finite number of Hopf bands to a disk. In this paper, we discuss its extension so that we show the following theorem. Let $R$ be a Seifert surface obtained by applying Seifert's algorithm to an almost alternating diagrams. Then $R$ is a fiber surface if and only if $R$ is a Hopf plumbing. We also show that the above theor…

世界面 skein D-模与Hopf链环余法向拉格朗日填充上的基本曲线

The worldsheet skein D-module and basic curves on Lagrangian fillings of the Hopf link conormal

该研究定义了世界面skein模及对应D-模，以Hopf链环Legendrian余法向为例，证明其skein D-模由三个算子多项式生成，且拉格朗日填充的skein值配分函数可由少量基本全纯曲线生成。

Transverse knots and Khovanov homology

We define an invariant of transverse links in the standard contact 3-sphere as a distinguished element of the Khovanov homology of the link. The quantum grading of this invariant is the self-linking number of the link. For knots, this gives a bound on the self-linking number in terms of Rasmussen's invariant s(K). We prove that our invariant vanishes for transverse knot stabilizations, and that it is non-zero for quasipositive braids. We also discuss a connection to Heegaard Floer invariants.

Möbius交叉能量的间隙定理

A Gap Theorem for the Möbius Cross Energy Near the Hopf Link

本文证明三维球面中两分支链环的Möbius交叉能量临界值$2\pi^2$是孤立的，即能量接近该值的非分裂正则曲线对必为Hopf链环的Möbius轨道。

Other quantum relatives of the Alexander polynomial through the Links-Gould invariants

Oleg Viro studied in arXiv:math/0204290 two interpretations of the (multivariable) Alexander polynomial as a quantum link invariant: either by considering the quasi triangular Hopf algebra associated to $U_q sl(2)$ at fourth roots of unity, or by considering the super Hopf algebra $U_q gl(1|1)$. In this paper, we show these Hopf algebras share properties with the $-1$ specialization of $U_q gl(n|1)$ leading to the proof of a conjecture of David De Wit, Atsushi Ishii and Jon Links on the Links-Gould invariants.

Salem-Boyd sequences and Hopf plumbing

Given a fibered link, consider the characteristic polynomial of the monodromy restricted to first homology. This generalizes the notion of the Alexander polynomial of a knot. We define a construction, called iterated plumbing, to create a sequence of fibered links from a given one. The resulting sequence of characteristic polynomials has the same form as those arising in work of Salem and Boyd in their study of distributions of Salem and P-V numbers. From this we deduce information about the asymptotic behavior of the large roots of the generalized Alexander polynomials, and define a new poset…

Stratification of $\mathrm{SU}(r)$-character varieties of twisted Hopf links

We describe the geometry of the character variety of representations of the fundamental group of the complement of a Hopf link with $n$ twists, namely $Γ_{n}=\langle x,y \,| \, [x^n,y]=1 \rangle$ into the group $\mathrm{SU}(r)$. For arbitrary rank, we provide geometric descriptions of the loci of irreducible and totally reducible representations. In the case $r = 2$, we provide a complete geometric description of the character variety, proving that this $\mathrm{SU}(2)$-character variety is a deformation retract of the larger $\mathrm{SL}(2,\mathbb{C})$-character variety, as conjectured by Flo…

An odd analog of Plamenevskaya's invariant of transverse knots

Plamenevskaya defined an invariant of transverse links as a distinguished class in the even Khovanov homology of a link. We define an analog of Plamenevskaya's invariant in the odd Khovanov homology of Ozsváth, Rasmussen, and Szabó. We show that the analog is also an invariant of transverse links and has similar properties to Plamenevskaya's invariant. We also show that the analog invariant can be identified with an equivalent invariant in the reduced odd Khovanov homology. We demonstrate computations of the invariant on various transverse knot pairs with the same topological knot type and sel…

A Family of Transverse Link Homologies

We define a homology $\mathcal{H}_N$ for closed braids by applying Khovanov and Rozansky's matrix factorization construction with potential $ax^{N+1}$. Up to a grading shift, $\mathcal{H}_0$ is the HOMFLYPT homology defined in arXiv:math/0505056. We demonstrate that, for $N \geq 1$, $\mathcal{H}_N$ is a $\mathbb{Z}_2\oplus\mathbb{Z}^{\oplus 3}$-graded $\mathbb{Q}[a]$-module that is invariant under transverse Markov moves, but not under negative stabilization/de-stabilization. Thus, for $N\geq 1$, this homology is an invariant for transverse links in the standard contact $S^3$, but not for smoo…

Filtrations on the knot contact homology of transverse knots

We construct a new invariant of transverse links in the standard contact structure on R^3. This invariant is a doubly filtered version of the knot contact homology differential graded algebra (DGA) of the link. Here the knot contact homology of a link in R^3 is the Legendrian contact homology DGA of its conormal lift into the unit cotangent bundle S^*R^3 of R^3, and the filtrations are constructed by counting intersections of the holomorphic disks of the DGA differential with two conormal lifts of the contact structure. We also present a combinatorial formula for the filtered DGA in terms of b…

Triple linking numbers, ambiguous Hopf invariants and integral formulas for three-component links

Three-component links in the 3-dimensional sphere were classified up to link homotopy by John Milnor in his senior thesis, published in 1954. A complete set of invariants is given by the pairwise linking numbers p, q and r of the components, and by the residue class of one further integer mu, the "triple linking number" of the title, which is well-defined modulo the greatest common divisor of p, q and r. To each such link L we associate a geometrically natural characteristic map g_L from the 3-torus to the 2-sphere in such a way that link homotopies of L become homotopies of g_L. Maps of the 3…

Wheeling: A diagrammatic analogue of the Duflo isomorphism

We construct and prove a diagrammatic version of the Duflo isomorphism between the invariant subalgebra of the symmetric algebra of a Lie algebra and the center of the universal enveloping algebra. This version implies the original for metrized Lie algebras (Lie algebras with an invariant non-degenerate bilinear form). As an application of this isomorphism, we will compute the Kontsevich integral of the unknot and the Hopf link to all orders. At the core of the proof, we use an elementary property of the Hopf link which can be summarized by the equation ``1+1=2'' in abacus arithmetic: doubling…

On the self-linking number of transverse links

We review a braid theoretic self-linking number formula and study its applications.

On Hopf-induced deformation of topological locus

We provide a very brief review of the description of colored invariants for the Hopf link in terms of characters, which need to be taken at a peculiar deformation of the topological locus, depending on one of the two representations associated with the two components of the link. Most important, we extend the description of this locus to conjugate and, generically, to composite representations and also define the "adjoint" Schur functions emerging in the dual description.

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。

Some 3-dimensional transverse C-links (Constructions of higher-dimensional C-links, I)

By use of a variety of techniques (most based on constructions of quasipositive knots and links, some old and others new), many smooth 3-manifolds are realized as transverse intersections of complex surfaces in complex 3-space with strictly pseudoconvex 5-spheres. These manifolds not only inherit interesting intrinsic structures (eg, they have canonical Stein-fillable contact structures), they also have extrinsic structures of a knot-theoretical nature (eq, the 3-sphere arises in infinitely many distinct ways). This survey is not comprehensive; a number of questions are left open for future wo…

Invariants of annular links, cobordisms and transverse links from combinatorial link Floer complex

We define an annular concordance invariant and study its properties. When specialized to braids, this invariant gives bounds on band rank. We introduce a modified chain complex to reformulate the invariant. Then, by focusing on a special case, we give a refinement of the transverse invariant $\hatθ$. We also study the relationship of this invariant with transverse and braid monodromy properties.

A non-torus link from topological vertex

The recently suggested tangle calculus for knot polynomials is intimately related to topological string considerations and can help to build the HOMFLY-PT invariants from the topological vertices. We discuss this interplay in the simplest example of the Hopf link and link $L_{8n8}$. It turns out that the resolved conifold with four different representations on the four external legs, on the topological string side, is described by a special projection of the four-component link $L_{8n8}$, which reduces to the Hopf link colored with two composite representations. Thus, this provides the first e…

Hopf superpolynomial from topological vertices

Link/knot invariants are series with integer coefficients, and it is a long-standing problem to get them positive and possessing cohomological interpretation. Constructing positive "superpolynomials" is not straightforward, especially for colored invariants. A simpler alternative is a multi-parametric generalization of the character expansion, which leads to colored "hyperpolynomials". The third construction involves branes on resolved conifolds, which gives rise to still another family of invariants associated with composite representations. We revisit this triality issue in the simple case o…

Transverse and Legendrian invariants of cables in combinatorial link Floer homology

We study the Ozsváth-Szabó-Thurston transverse invariant in combinatorial link Floer homology for certain transverse cables $\mathscr{L}_{p,q}$ of transverse link $L$ in $S^3$. Transverse cables $\mathscr{L}_{p,q}$ are constructed from the grid diagram of $L$. The main result is $\hatθ(\mathscr{L}_{p,q})=0$ if and only if $\hatθ(L)=0$ for $\frac{q}{p}$ sufficiently large. We also prove a similar result for invariants of Legendrian knots. Our proof uses an inclusion map $i$ of certain grid complexes associated to $L$ and $L_{p,q}$. We use these results to generate many infinite families of exam…

Local moves on knots and products of knots II

We use the terms, knot product and local move, as defined in the text of the paper. Let $n$ be an integer$\geqq3$. Let $\mathcal S_n$ be the set of simple spherical $n$-knots in $S^{n+2}$. Let $m$ be an integer$\geqq4$. We prove that the map $j:\mathcal S_{2m}\to\mathcal S_{2m+4}$ is bijective, where $j(K)=K\otimes$Hopf, and Hopf denotes the Hopf link. Let $J$ and $K$ be 1-links in $S^3$. Suppose that $J$ is obtained from $K$ by a single pass-move, which is a local-move on 1-links. Let $k$ be a positive integer. Let $P\otimes^kQ$ denote the knot product $P\otimes\underbrace{Q\otimes...\otimes …

Knots with Hopf crossing number at most one

We consider diagrams of links in $S^2$ obtained by projection from $S^3$ with the Hopf map and the minimal crossing number for such diagrams. Knots admitting diagrams with at most one crossing are classified. Some properties of these knots are exhibited. In particular, we establish which of these knots are algebraic and, for such knots, give an answer to a problem posed by Fiedler.

Flowlines transverse to fibred knots and links

We consider vector fields on knot/link complements in $S^3$ which are transverse to the fibres of a fibration of the complement over a circle. We prove that a large class of fibred knots/links, including all non-torus fibred 2-bridge knots, has the following property: any vector field transverse to the fibres of the fibration of the complement must possess periodic orbits representing all possible knot and link types.

Transverse-Legendrian links

In recent joint works of the present author with M.Prasolov and V.Shastin a new technique for distinguishing Legendrian knots has been developed. In this paper the technique is extended further to provide a tool for distinguishing transverse knots. It is shown that the equivalence problem for transverse knots with trivial orientation-preserving symmetry group is algorithmically solvable. In a future paper the triviality condition for the orientation-preserving symmetry group will be dropped.

一个盒子里能装下多少个链环？

How Many Links Fit in a Box?

本文用完全几何化的论证为单位立方体内可嵌入的互不相交非平凡链环数量建立上界，并与已有下界形成对应。

链环的 bar 上同调：超越 Milnor 不变量

Bar cohomology of links: beyond Milnor invariants

本文提出链环补空间的 bar 上同调作为同调球中链环的新不变量，它构成 Hopf 代数，可通过曲面及其交曲线计算，并定义了张量 Hopf 代数的典范子空间，编码并超越 Milnor 不变量。

Links of Second Smallest Knot Floer Homology

We prove that the rank of knot Floer homology detects the Hopf links, and generalize this result further to classify the links of the second smallest knot Floer homology. We also prove a knot Floer homology analog of arXiv:1910.04246v1 [math.GT] and give a partial answer to when the equality holds in the rank inequality between the knot Floer homology of a link and its sublinks.

Transverse link invariants from the deformations of Khovanov $\mathfrak{sl}_{3}$-homology

In this paper we will make use of the Mackaay-Vaz approach to the universal $\mathfrak{sl}_3$-homology to define a family of cycles (called $β_3$-invariants) which are transverse braid invariants. This family includes Wu's $ψ_{3}$-invariant. Furthermore, we analyse the vanishing of the homology classes of the $β_3$-invariants and relate it to the vanishing of Plamenevskaya's and Wu's invariants. Finally, we use the $β_3$-invariants to produce some Bennequin-type inequalities.

Large $N$ Invariants of Torus Links in Lens Spaces

We compute the invariants for a class of knots and links in arbitrary representations in $S^3/\mathbb{Z}_p$ in the large $k$ (level), large $N$ (rank) limit, keeping $N/(k+N)=λ$ fixed, in $U(N)$ and $Sp(N)$ Chern-Simons theories. Using the relation between the saddle point description and collective field theory, we first find that the invariants for the Hopf link and unknot are given by the on shell collective field theory action. We next show that the results of these two invariants can be used to compute the invariants of other torus knots and links. We also discuss the large $N$ phase stru…

Quantum invariants of framed links from ternary self-distributive cohomology

The ribbon cocycle invariant is defined by means of a partition function using ternary cohomology of self-distributive structures (TSD) and colorings of ribbon diagrams of a framed link, following the same paradigm introduced by Carter, Jelsovsky, Kamada, Langfor and Saito in Transactions of the American Mathematical Society 2003;355(10):3947-89, for the quandle cocycle invariant. In this article we show that the ribbon cocycle invariant is a quantum invariant. We do so by constructing a ribbon category from a TSD set whose twisting and braiding morphisms entail a given TSD $2$-cocycle. Then w…