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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 introduce an associative algebra Z[X,S] associated to a birack shadow and define enhancements of the birack counting invariant for classical knots and links via representations of Z[X,S] known as shadow modules. We provide examples which…

Geometric Topology · Mathematics 2011-06-03 Sam Nelson , Katie Pelland

We define ambient isotopy invariants of oriented knots and links using the counting invariants of framed links defined by finite racks. These invariants reduce to the usual quandle counting invariant when the rack in question is a quandle.…

Geometric Topology · Mathematics 2013-07-30 Sam Nelson

We study the quandle counting invariant for a certain family of finite quandles with trivial orbit subquandles. We show how these invariants determine the linking number of classical two-component links up to sign.

Geometric Topology · Mathematics 2008-08-13 Natasha Harrell , Sam Nelson

The homology and cohomology of quandles and racks are used in knot theory: given a finite quandle and a cocycle, we can construct a knot invariant. This is a quick introductory survey to the invariants of knots derived from quandles and…

Geometric Topology · Mathematics 2007-05-23 Seiichi Kamada

We construct two knot invariants. The first knot invariant is a sum constructed using linking numbers. The second is an invariant of flat knots and is a formal sum of flat knots obtained by smoothing pairs of crossings. This invariant can…

Geometric Topology · Mathematics 2011-09-15 H. A. Dye

We define a type of biquandle which is a generalization of symplectic quandles. We use the extra structure of these bilinear biquandles to define new knot and link invariants and give some examples.

Quantum Algebra · Mathematics 2008-08-13 Sam Nelson , Jacquelyn L. Rische

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 define counting and cocycle enhancement invariants of virtual knots using parity biquandles. These invariants are determined by pairs consisting of a biquandle 2-cocycle \phi^0 and a map \phi^1 with certain compatibility conditions…

Geometric Topology · Mathematics 2016-06-16 Aaron Kaestner , Sam Nelson , Leo Selker

A rack shadow is a set X with a rack action by a rack R, analogous to a vector space over a field. We use shadow colorings of classical link diagrams to define enhanced rack counting invariants and show that the enhanced invariants are…

Geometric Topology · Mathematics 2010-07-14 Wesley Chang , Sam Nelson

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

A polynomial is presented that models a topological knot in a unique manner. It distinguishes all types of knots including the orientation and has a group theory interpretation. The topologies may be labeled via a number, which upon a base…

General Physics · Physics 2007-05-23 Gordon Chalmers

Coloring numbers are one of the simplest combinatorial invariants of knots and links to describe. And with Joyce's introduction of quandles, we can understand them more algebraically. But can we extend these invariants to tangles -- knots…

Geometric Topology · Mathematics 2008-03-12 John Armstrong

In this paper, we discuss the (co)homology theory of biquandles, derived biquandle cocycle invariants for oriented surface-links using broken surface diagrams and how to compute the biquandle cocycle invariants from marked graph diagrams.…

Geometric Topology · Mathematics 2018-03-09 Seiichi Kamada , Akio Kawauchi , Jieon Kim , Sang Youl Lee

We consider a quiver structure on the set of quandle colorings of an oriented knot or link diagram. This structure contains a wealth of knot and link invariants and provides a categorification of the quandle counting invariant in the most…

Geometric Topology · Mathematics 2018-10-09 Karina Cho , Sam Nelson

We introduce two new families of polynomial invariants of oriented classical and virtual knots and links defined as decategorfications of the quandle coloring quiver. We provide examples to illustrate the computation of the invariants, show…

Geometric Topology · Mathematics 2025-08-18 Anusha Kabra , Sam Nelson

In the paper we introduce a general approach how for a given virtual biquandle multi-switch $(S,V)$ on an algebraic system $X$ (from some category) and a given virtual link $L$ construct an algebraic system $X_{S,V}(L)$ (from the same…

Algebraic Topology · Mathematics 2020-01-22 Valeriy Bardakov , Timur Nasybullov

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

A knot invariant is called skein if it is determined by a finite number of skein relations. In the paper we discuss some basic properties of skein invariants and mention some known examples of skein invariants.

Geometric Topology · Mathematics 2024-12-30 Igor Nikonov

Biquandle brackets define invariants of classical and virtual knots and links using skein invariants of biquandle-colored knots and links. Biquandle coloring quivers categorify the biquandle counting invariant in the sense of defining…

Geometric Topology · Mathematics 2021-09-14 Pia Cosma Falkenburg , Sam Nelson