arXiv math/06124592006-12math.GT

Quandle coverings and their Galois correspondence

Michael Eisermann

备注：: 46 pages, 2 figures. v2: A few remarks have been added and numerous misprints corrected. v3: Some applications (e.g. to link quandles) have been added

英文摘要：

This article establishes the algebraic covering theory of quandles. For every connected quandle we explicitly construct a universal covering, which in turn leads us to define the algebraic fundamental group as the automorphism group of the universal covering. We then establish the Galois correspondence between connected coverings and subgroups of the fundamental group. Quandle coverings are thus formally analogous to coverings of topological spaces, and resemble Kervaire's algebraic covering theory of perfect groups. A detailed investigation also reveals some crucial differences, which we illustrate by numerous examples. As an application we obtain a simple formula for the second (co)homology group of a quandle Q. It has long been known that H_1(Q) = H^1(Q) = \Z[π_0(Q)], and we construct natural isomorphisms H_2(Q) = π_1(Q,q)_{ab} and H^2(Q,A) = Ext(Q,A) = Hom(π_1(Q,q),A), reminiscent of the classical Hurewicz isomorphisms in degree 1. This means that whenever the fundamental group is known, (co)homology calculations in degree 2 become very easy.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

阅读原文

阅读 PDF ↗

arXiv 页面 ↗HTML 原文 ↗

本文内容

英文摘要相关论文

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

继续探索

相关论文

Quandles associated to Galois covers of arithmetic schemes

Let $X$ be a normal, separated and integral scheme of finite type over $\mathbb{Z}$ and $\mathcal{M}$ a set of closed points of $X$. To a Galois cover $\tilde{X}$ of $X$ unramified over $\mathcal{M}$, we associate a quandle whose underlying set consists of points of $\tilde{X}$ lying over $\mathcal{M}$. As the limit of such quandles over all étale Galois covers and all étale abelian covers, we define topological quandles $Q(X, \mathcal{M})$ and $Q^\mathrm{ab}(X, \mathcal{M})$, respectively. Then we study the problem of reconstruction. Let $K$ be $\mathbb{Q}$ or a quadratic field, $\mathcal{O}_…

2017-11-22math.GTmath.NT

Cyclic branched coverings of knots and quandle homology

We give a construction of quandle cocycles from group cocycles, especially, for any integer p \geq 3, quandle cocycles of the dihedral quandle R_p from group cocycles of the cyclic group Z/p. We will show that a group 3-cocycle of Z/p gives rise to a non-trivial quandle 3-cocycle of R_p. When p is an odd prime, since dim_{F_p} H_Q^3(R_p; F_p) = 1, our 3-cocycle is a constant multiple of the Mochizuki 3-cocycle up to coboundary. Dually, we construct a group cycle represented by a cyclic branched covering branched along a knot K from the quandle cycle associated with a colored diagram of K.

2012-04-21math.GT

绝对伽罗瓦群中对合的Artin-Schreier广群

Artin-Schreier quandles of involutions in absolute Galois groups

本研究提出与绝对伽罗瓦群相关的新域不变量Artin-Schreier quandle，明确其在形式实数域中的自由生成结构，给出洛朗级数域下的计算方式，证实一般情形下该结构存在关系，细化了域的实谱研究。

2026-04-08math.GRmath.GTmath.NT

Higher coverings of racks and quandles -- Part II

This article is the second part of a series of three articles, in which we develop a higher covering theory of racks and quandles. This project is rooted in M. Eisermann's work on quandle coverings, and the categorical perspective brought to the subject by V. Even, who characterizes coverings as those surjections which are categorically central, relatively to trivial quandles. We extend this work by applying the techniques from higher categorical Galois theory, in the sense of G. Janelidze, and in particular we identify meaningful higher-dimensional centrality conditions defining our higher co…

2021-01-20math.ATmath.CTmath.GT

幂等元、自由积与拟群覆盖

Idempotents, free products and quandle coverings

本文研究拟群环中的幂等元，证明有限型非平凡覆盖拟群的整拟群环具有无穷多个非平凡幂等元且其集合本身构成拟群，同时证明自由拟群的整拟群环只有平凡幂等元，并刻画了并集与扭曲并集情形。

2022-08-15math.GRmath.GTmath.QA

Higher coverings of racks and quandles -- Part I

This article is the second part of a series of three articles, in which we develop a higher covering theory of racks and quandles. This project is rooted in M. Eisermann's work on quandle coverings, and the categorical perspective brought by V. Even, who characterizes coverings as those surjections which are central, relatively to trivial quandles. We extend this work by applying the techniques from higher categorical Galois theory, in the sense of G. Janelidze, and in particular we identify meaningful higher-dimensional centrality conditions defining our higher coverings of racks and quandles…

2021-03-08math.ATmath.CTmath.GT

更多相关论文收起更多论文

On third homologies of groups and of quandles via the Dijkgraaf-Witten invariant and Inoue-Kabaya map

We propose a simple method to produce quandle cocycles from group cocycles, as a modification of Inoue-Kabaya chain map. We further show that, in respect to "universal central extended quandles", the chain map induces an isomorphism between their third homologies. For example, all Mochizuki's quandle 3-cocycles are shown to be derived from group cocycles of some non-abelian group. As an application, we calculate some $\Z$-equivariant parts of the Dijkgraaf-Witten invariants of some cyclic branched covering spaces, via some cocycle invariant of links.

2012-10-24math.GT

Surface links which are coverings over the standard torus

We introduce a new construction of a surface link in the 4-space. We construct a surface link as a branched covering over the standard torus, which we call a torus-covering link. We show that a certain torus-covering $T^2$-link is equivalent to the split union of spun $T^2$-links and turned spun $T^2$-links. We show that a certain torus-covering $T^2$-link has a non-classical link group. We give a certain class of ribbon torus-covering $T^2$-links. We present the quandle cocycle invariant of a certain torus-covering $T^2$-link obtained from a classical braid, by using the quandle cocycle invar…

2011-02-12math.GT

关于拟群上对称性的相对化

Relativization of symmetries on quandles

Osaka Central Advanced Mathematical Institute, Osaka Metropolitan University（大阪中央高等数学研究所，大阪公立大学）；Department of Mathematics, School of Science and Engineering, Waseda University（早稻田大学理工学术院数学系）

本文引入满射拟群同态的相对内自同构群和相对换位群，定义连通同态并建立最大连通覆盖分解，最后分类有限纤维的拟群结构。

2026-09-15math.GT

General constructions of biquandles and their symmetries

Biquandles are algebraic objects with two binary operations whose axioms encode the generalized Reidemeister moves for virtual knots and links. These objects also provide set-theoretic solutions of the well-known Yang-Baxter equation. The first half of this paper proposes some natural constructions of biquandles from groups and from their simpler counterparts, namely, quandles. We completely determine all words in the free group on two generators that give rise to (bi)quandle structures on all groups. We give some novel constructions of biquandles on unions and products of quandles, including …

2019-08-22math.GRmath.GT

Homotopical interpretation of link invariants from finite quandles

This paper demonstrates a topological meaning of quandle cocycle invariants of links with respect to finite connected quandles $X$, from a perspective of homotopy theory: Specifically, for any prime $\ell$ which does not divide the type of $X$, the $\ell$-torsion of this invariants is equal to a sum of the colouring polynomial and a $\Z$-equivariant part of the Dijkgraaf-Witten invariant of a cyclic branched covering space. Moreover, our homotopical approach involves application of computing some third homology groups and second homotopy groups of the classifying spaces of quandles, from resul…

2015-05-12math.ATmath.GT

Quandle cocycle invariants of links using Mochizuki's 3-cocycles and Dijkgraaf-Witten invariants of 3-manifolds

T. Mochizuki determined all 3-cocycles of the third quandle cohomologies of Alexander quandles on finite fields. We show that all the 3-cocycles, except those of 2-cocycle forms, are derived from group 3-cocycles of a meta-abelian group. Further, the quandle cocycle invariant of a link using Mochizuki's 3-cocycle is equivalent to a $\Z$-equivariant part of the Dijkgraaf-Witten invariant of a cyclic covering of $S^3$ branched over the link using the group. We compute some Massey triple products via the former invariant.

2012-03-14math.AGmath.ATmath.GR

On Branched Galois Coverings $(B_1)^n\to {\mathbb P}^n$

For any $n>1$, we construct examples branched Galois coverings from $M$ to the nth projective space ${\mathbb P}^n$ where $M$ is one of $({\mathbb P}^1)^n$, ${\mathbb C}^n$ or $(B_1)^n$, and $B_1$ is the 1-ball. In terms of orbifolds, this amounts to giving examples of orbifolds over ${\mathbb P}^n$ uniformized by $M$.We also discuss the related "orbifold braid groups".

2003-02-16math.AGmath.GT

关于幂零与下中心同态映射的Quandle同态

On Nilpotent and Hypocentral Quandle Homomorphisms

本文为quandle满射同态定义幂零与下中心概念，证明其等价于覆盖同态复合及右正交性，建立正交分解系统，并给出约化同态的幂零充分条件。

2026-09-15math.CTmath.GRmath.GT

Bauer--Furuta invariants and Galois symmetries

The Bauer-Furuta invariants of smooth 4-manifolds are investigated from a functorial point of view. This leads to a definition of equivariant Bauer-Furuta invariants for compact Lie group actions. These are studied in Galois covering situations. We show that the ordinary invariants of all quotients are determined by the equivariant invariants of the covering manifold. In the case where the Bauer-Furuta invariants can be identified with the Seiberg-Witten invariants, this implies relations between the invariants in Galois covering situations, and these can be illustrated through elliptic surfac…

2020-02-05math.ATmath.GT

Semi-topological Galois theory and the inverse Galois problem

We enhance the analogy between field extensions and covering spaces by introducing the concept of splitting covering which correspondences to the splitting field in Galois theory. We define semi-topological Galois groups for Weierstrass polynomials and prove the existence of a Galois correspondence. This new tool enables us to study the inverse Galois problem from a new viewpoint.

2010-06-07math.AGmath.GRmath.GT

Nodal degenerations of plane curves and Galois covers

Globally irreducible nodes (i.e. nodes whose branches belong to the same irreducible component) have mild effects on the most common topological invariants of an algebraic curve. In other words, adding a globally irreducible node (simple nodal degeneration) to a curve should not change them a lot. In this paper we study the effect of nodal degeneration of curves on fundamental groups and show examples where simple nodal degenerations produce non-isomorphic fundamental groups and this can be detected in an algebraic way by means of Galois coverings.

2004-11-15math.AGmath.GT