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We define a generalization of virtual links to arbitrary dimensions by extending the geometric definition due to Carter et al. We show that many homotopy type invariants for classical links extend to invariants of virtual links. We also…

Geometric Topology · Mathematics 2014-07-03 Blake Winter

Given a biquandle $(X, S)$, a function $\tau$ 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 /…

Geometric Topology · Mathematics 2019-10-10 Marco Farinati , Juliana García Galofre

We introduce an algebraic structure we call semiquandles whose axioms are derived from flat Reidemeister moves. Finite semiquandles have associated counting invariants and enhanced invariants defined for flat virtual knots and links. We…

Geometric Topology · Mathematics 2011-09-20 Allison Henrich , Sam Nelson

We identify a subcategory of biracks which define counting invariants of unoriented links, which we call involutory biracks. In particular, involutory biracks of birack rank N=1 are biquandles, which we call bikei. We define counting…

Geometric Topology · Mathematics 2011-04-25 Sinan Aksoy , Sam Nelson

We discuss Vassiliev invariants for virtual knots, expanding upon the theory of quantum virtual knot invariants developed in arXiv:1509.00578. In particular, following the theory of quantum invariants we work with 'rotational' virtual…

Geometric Topology · Mathematics 2022-09-20 Wout Moltmaker , Louis H. Kauffman

It is known that the number of biquandle colorings of a long virtual knot diagram, with a fixed color of the initial arc, is a knot invariant. In this paper we describe a more subtle invariant: a family of biquandle endomorphisms obtained…

Geometric Topology · Mathematics 2019-10-29 Maciej Niebrzydowski

We introduce virtual tribrackets, an algebraic structure for coloring regions in the planar complement of an oriented virtual knot or link diagram. We use these structures to define counting invariants of virtual knots and links and provide…

Geometric Topology · Mathematics 2018-12-07 Sam Nelson , Shane Pico

In this paper, we introduce biquandle power brackets, an infinite family of invariants of oriented links containing the classical skein invariants and the quandle and biquandle 2-cocycle invariants as special cases. Biquandle power brackets…

Geometric Topology · Mathematics 2024-01-23 Neslihan Gügümcü , Sam Nelson

Multi-virtual knot theory was introduced in $2024$ by the first author. In this paper, we initiate the study of algebraic invariants of multi-virtual links. After determining a generating set of (oriented) multi-virtual Reidemeister moves,…

Geometric Topology · Mathematics 2025-04-15 Louis H. Kauffman , Sujoy Mukherjee , Petr Vojtěchovský

We consider the question of which virtual knots have finite fundamental medial bikei. We describe and implement an algorithm for completing a presentation matrix of a medial bikei to an operation table, determining both the cardinality and…

Geometric Topology · Mathematics 2017-04-05 Julien Chien , Sam Nelson

Flat virtual links are some variant of links, and semiquandles are counterparts of quandles or biquandles, which axiomize the Reidemeister-like moves. In this paper, we give some example of semiquandle and introduce an invariant for flat…

Geometric Topology · Mathematics 2024-11-08 Nozomu Sekino

In this paper we investigate the virtual string links via a probabilistic interpretation. This representation can be used to distinguish some virtual string links from classical string links. In order to study the algebraic structure behind…

Geometric Topology · Mathematics 2017-06-01 Zhiyun Cheng

In this paper we introduce a new invariant of virtual knots and links that is non-trivial for infinitely many virtuals, but is trivial on classical knots and links. The invariant is initially be expressed in terms of a relative of the…

Geometric Topology · Mathematics 2007-05-23 Louis H. Kauffman

A biquandle is a solution to the set-theoretical Yang-Baxter equation, which yields invariants for virtual knots such as the coloring number and the state-sum invariant. A virtual biquandle enriches the structure of a biquandle by…

Geometric Topology · Mathematics 2025-09-10 Mohamed Elhamdadi , Manpreet Singh

Biquandle brackets are a type of quantum enhancement of the biquandle counting invariant for oriented knots and links, defined by a set of skein relations with coefficients which are functions of biquandle colors at a crossing. In this…

Geometric Topology · Mathematics 2019-09-04 Neslihan Gügümcü , Sam Nelson , Natsumi Oyamaguchi

This paper describes a polynomial invariant of virtual knots that is defined in terms of an integer labeling of the virtual knot diagram. This labeling is seen to derive from an essentially unique structure of affine flat biquandle for flat…

Algebraic Topology · Mathematics 2014-07-25 Louis H. Kauffman

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

Marked vertex diagrams provide a combinatorial way to represent knotted surfaces in $\mathbb{R}^4$; including virtual crossings allows for a theory of virtual knotted surfaces and virtual cobordisms. Biquandle counting invariants are…

Geometric Topology · Mathematics 2015-06-08 Sam Nelson , Patricia Rivera

We incorporate quandle cocycle information into the quandle coloring quivers we defined in arXiv:1807.10465 to define weighted directed graph-valued invariants of oriented links we call \textit{quandle cocycle quivers}. This construction…

Geometric Topology · Mathematics 2019-04-22 Karina Cho , Sam Nelson

Quandle 2-cocycles define invariants of classical and virtual knots, and extensions of quandles. We show that the quandle 2-cocycle invariant with respect to a non-trivial $2$-cocycle is constant, or takes some other restricted form, for…

Geometric Topology · Mathematics 2016-03-22 W. Edwin Clark , Masahico Saito