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In this paper we push forward results on the invariant ${\cal F}$-module of a virtual knot investigated by the first named author where ${\cal F}$ is the algebra with two invertible generators $A,B$ and one relation…

Geometric Topology · Mathematics 2009-11-11 Roger Fenn , Vladimir Turaev

Flat modules play an important role in the study of the category of modules over rings and in the characterization of some classes of rings. We study the e-flatness for semimodules introduced by the first author using his new notion of…

Rings and Algebras · Mathematics 2025-10-28 Jawad Abuhlail , Rangga Ganzar Noegraha

We construct a virtual quandle for links in lens spaces $L(p,q)$, with $q=1$. This invariant has two valuable advantages over an ordinary fundamental quandle for links in lens spaces: the virtual quandle is an essential invariant and the…

Algebraic Topology · Mathematics 2017-02-21 A. Cattabriga , T. Nasybullov

We investigate connections between biquandle colorings, quiver enhancements, and several notions of the bridge numbers $b_i(K)$ for virtual links, where $i=1,2$. We show that for any positive integers $m \leq n$, there exists a virtual link…

Geometric Topology · Mathematics 2025-04-15 Tirasan Khandhawit , Puttipong Pongtanapaisan , Brandon Wang

We introduce twelve polynomial invariants for long virtual knots, called intersection polynomials, extending and refining the three intersection polynomials for virtual knots. They are defined via intersection numbers of cycles on a closed…

Geometric Topology · Mathematics 2025-12-08 Takuji Nakamura , Yasutaka Nakanishi , Shin Satoh , Kodai Wada

Semi-entwining structures are proposed as concepts simpler than entwining structures, yet they are shown to have interesting applications in constructing intertwining operators and braided algebras, lifting functors, finding solutions for…

Quantum Algebra · Mathematics 2013-05-13 Florin F. Nichita , Deepak Parashar , Bartosz Zielinski

We define an invariant of welded virtual knots from each finite crossed module by considering crossed module invariants of ribbon knotted surfaces which are naturally associated with them. We elucidate that the invariants obtained are non…

Geometric Topology · Mathematics 2017-05-23 Louis H. Kauffman , João Faria Martins

We introduce algebraic structures known as psybrackets and use them to define invariants of pseudoknots and singular knots and links. Psybrackets are Niebrzydowski tribrackets with additional structure inspired by the Reidemeister moves for…

Geometric Topology · Mathematics 2022-09-02 Suhyeon Jeong , Jieon Kim , Sam Nelson

We define enhancements of the quandle counting invariant for knots and links with a finite labeling quandle Q embedded in the quandle of units of a Lie algebra \mathfrak{a} using Lie ideals. We provide examples demonstrating that the…

Geometric Topology · Mathematics 2015-07-29 Gillian Roxanne Grindstaff , Sam Nelson

We modify the definition of spherical knotoids to include a framing, in analogy to framed knots, and define a further modification that includes a secondary 'coframing' to obtain 'biframed' knotoids. We exhibit topological spaces whose…

Geometric Topology · Mathematics 2022-06-22 Wout Moltmaker

We introduce a new combinatorial method to encode knots and links with applications to knot invariants. Clasp diagrams defined in this paper are combinatorial blueprints for building knot diagrams out of full twists on two strings rather…

Geometric Topology · Mathematics 2019-11-11 Jacob Mostovoy , Michael Polyak

As it is well-known, all Vassiliev invariants of degree one of a knot $K\subset R^3$ are trivial. There are nontrivial Vassiliev invariants of degree one, when the ambient space is not $R^3$. Recently, T. Fiedler introduced such invariants…

Geometric Topology · Mathematics 2007-05-23 Vladimir Tchernov

We introduced concept of meander knots, 2-component meander links and multi-component meander links and derived different families of meander knots and links from open meanders with at most 16 crossings. We also defined semi-meander knots…

Geometric Topology · Mathematics 2013-02-07 Slavik Jablan , Ljiljana Radovic

Several authors have recently studied virtual knots and links because they admit invariants arising from R-matrices. We prove that every virtual link is uniquely represented by a link L in S X I, a thickened, compact, oriented surface S,…

Geometric Topology · Mathematics 2014-10-01 Greg Kuperberg

In these notes we survey basic concepts of affine geometry and their interaction with Riemannian geometry. We give a characterization of affine manifolds which has as counterpart those pseudo-Riemannian manifolds whose Levi-Civita…

Differential Geometry · Mathematics 2019-03-22 Fabricio Valencia

The "fundamental theorem of Vassiliev invariants" says that every weight system can be integrated to a knot invariant. We discuss four different approaches to the proof of this theorem: a topological/combinatorial approach following M.…

q-alg · Mathematics 2008-02-03 Dror Bar-Natan , Alexander Stoimenow

This paper summarizes substantive new results derived by a student team (the first three authors) under the direction of the fourth author at the 2005 session of the KSU REU ``Brainstorming and Barnstorming''. The main results are a…

Quantum Algebra · Mathematics 2007-05-23 G. Ehrman , A. Gurpinar , M. Thibault , D. N. Yetter

Piecewise-linear virtual knots are discussed and classified up to edge index six.

Geometric Topology · Mathematics 2009-07-14 Neil R. Nicholson

Kashaev and Reshetikhin proposed a generalization of the Reshetikhin-Turaev link invariant construction to tangles with a flat connection in a principal G-bundle over the complement of the tangle. The purpose of this paper is to adapt and…

Quantum Algebra · Mathematics 2013-09-20 Nathan Geer , Bertrand Patureau-Mirand

We introduce the notion of quasi-triviality of quandles and define homology of quasi-trivial quandles. Quandle cocycle invariants are invariant under link-homotopy if they are associated with 2-cocycles of quasi-trivial quandles. We thus…

Geometric Topology · Mathematics 2012-05-29 Ayumu Inoue