arXiv subjects

Sam Nelson

Publications and source records attributed to Sam Nelson.

At least 19 recordsLinked to original sources

arXiv2026

Permutation Jones Polynomials

We introduce a generalization of the Jones polynomial for classical and virtual knots and links using colorings by a permutation $\sigma:X\to X$ of a finite set $X$. For $X=\{1\}$ and for classical knots, the invariant is equivalent to the usual Jones polynomial; for $X$ with cardinality greater than 1 the invariant expresses distinct information from the Jones polynomial or virtual knots and for classical and virtual links. We establish some properties of the new invariants and compute the polynomials for classical and virtual knots and links of small crossing number for a few small permutations.

math.GT↗

arXiv2026

Biquandle Arrow Weight Quiver Representations

We define an infinite family of quiver representation-valued invariants of classical and virtual knots associated to a choice of data vector consisting of a biquandle, abelian group, set of biquandle arrows weights with values in the abelian group, coefficient ring and set of biquandle endomorphisms. As an application we extract four new polynomial invariants as decategorifications. We provide examples to show that these invariants are proper enhancements of the biquandle counting invariant and biquandle coloring quiver.

math.GT↗

arXiv2026

Biquandle Fares and Link Invariants

We introduce a new family of invariants of oriented classical and virtual knots and links using fares, maps from paths in biquandle-colored diagrams to an abelian coefficient group. We consider the cases of 1-fares and 2-fares, provide examples to show that the enhancements are proper and end with some open questions about the cases of n-fares for n > 2.

math.GT↗

arXiv2025

Birack Bracket Quivers and Framed Links

We introduce birack brackets, skein invariants of birack-colored framed classical and virtual knots and links with values in a commutative unital ring. The multiset of birack bracket values over the homset from a framed link's fundamental birack then forms an invariant of framed links. We then categorify this multiset to define a quiver-valued invariant of framed knots and links. From this quiver we define new polynomial invariants of framed knots and links.

math.GT↗

arXiv2025

Virtual Biquandle Cocycle Quiver Representations

We introduce quiver representation-valued invariants of oriented virtual knots and links associated to a choice of finite virtual biquandle, abelian group, set of virtual Boltzmann weights, commutative unital ring and set of virtual biquandle endomorphisms. As an application we define new infinite families of polynomial virtual knot and link invariants via decategorification.

math.GT↗

arXiv2025

Biquandle Module Quiver Representations

We introduce an infinite family of quiver representation-valued invariants of classical, virtual and surface-knots and links associated to a choice of finite biquandle, commutative unital ring, biquandle module and set of biquandle endomorphisms. As an application, we use this quiver to define a new infinite family of two-variable polynomial invariants.

math.GT↗

arXiv2025

Psyquandle Brackets

We extend the notion of biquandle brackets to the case of psyquandles, defining quantum enhancements of the psyquandle counting invariant for singular knots and pseudoknots. We provide examples to illustrate the computation of these invariants, establishing that the enhancement is proper. We compute a few toy examples, noting that the true power of this infinite family of invariants lies in more computationally expensive larger-cardinality psyquandles and infinite coefficient rings.

math.GT↗

arXiv2025

The Forbidden Quiver of a Link

The forbidden moves in virtual knot theory can be used to unknot any knot, virtual or classical; however, multi-component crossings in links can still survive, resulting a fused link. Using the forbidden moves, we categorify fused links obtain a quiver-valued invariant of classical and virtual links we call the forbidden quiver, opening the way for functors to and from other categories. As an application we use the forbidden quiver to obtain three polynomial invariants of virtual and classical links. Since these invariants are not sensitive to single-component crossing change, they are also link homotopy invariants.

math.GT↗

arXiv2025

A Quick Note On Homsets and Diagrams

The homset invariant of a knot or link L with respect to an algebraic knot coloring structure X can be identified with a set of colorings of a diagram of L by elements of X via an identification of diagrammatic generators with algebraic generators. In some cases, particularly when either L or X has a high degree of symmetry, distinct homset elements can be represented by superficially similar X-colored diagrams, potentially leading to confusion. In this short note we examine and attempt to clarify this phenomenon.

math.GT↗

arXiv2025

New Polynomial Decategorifications of the Quandle Coloring Quiver

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 that they are not determined by the quandle counting invariant, and compute tables of invariants values for some small quandles.

math.GT↗

arXiv2025

Categorification of Biquandle Arrow Weight Invariants via Quivers

Introduced in arXiv:2211.12606, biquandle arrow weight invariants are enhancements of the biquandle counting invariant for oriented virtual and classical knots defined from biquandle-colored Gauss diagrams using a tensor over an abelian group satisfying certain properties. In this paper we categorify the biquandle arrow weight polynomial invariant using biquandle coloring quivers, obtaining new infinite families of polynomial invariants of oriented virtual and classical knots.

math.GT↗

arXiv2024

Quandle Cohomology Quiver Representations

We define a family of quiver representation-valued invariants of oriented classical and virtual knots and links associated to a choice of finite quandle $X$, abelian group $A$, set of quandle 2-cocycles $C\subset H^2_Q(x;A)$, choice of coefficient ring $k$ and set of quandle endomorphisms $S\subset \mathrm{Hom}(X,X)$. From this representation we define four new polynomial (or ``polynomial'' depending on $A$) invariants. We generalize to the case of biquandles and compute some examples.

math.GT↗

arXiv2024

Quandle Action Quivers

Quandle Coloring Quivers are directed graph-valued invariants of classical and virtual knots and links associated to finite quandles. Quandle action quivers are subquivers of the full quandle coloring quiver associated to quandle actions by elements of the coloring quandle. These quivers provide a categorification of the quandle counting invariant associated to each element of the quandle. We obtain new polynomial invariants called quandle action polynomials from these quivers as decategorifications.

math.GT↗

arXiv2024

Richard A. Litherland: A Brief Biography

Richard A. Litherland was born in 1953 in England. He received his PhD at Trinity College in Cambridge in 1979 and moved to the USA in 1983. He had a lengthy and distinguished career as a professor of mathematics and researcher of low-dimensional topology, based primarily at Louisiana State University (LSU) in Baton Rouge until his untimely passing in November 2022. In this paper we (Rick's family and students) recount some memories of Rick, his life and his mathematics.

math.HO↗

arXiv2024

Biquandle Power Brackets

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 are generalizations of biquandle brackets in which the values of Kauffman states also depend on the biquandle colors they admit. We provide example computations and discuss the relationship between these new invariants and the previous cases.

math.GT↗

arXiv2023

MC-Biquandles and MC-Biquandle Coloring Quivers

We introduce the notion of mc-biquandles, algebraic structures which have possibly distinct biquandle operations at single-component and multi-component crossings. These structures provide computable homset invariants for classical and virtual links. We categorify these homsets to obtain mc-biquandle coloring quivers and define several new link invariants via decategorification from these invariant quivers.

math.GT↗

arXiv2023

Biquandle Brackets and Quivers

In this brief expository article we review the background for biquandle bracket quivers -- including biquandles, biquandle homsets, biquandle coloring quivers and biquandle brackets -- for a talk at the 70th Topology Symposium at Nara Women's University in August 2023.

math.GT↗

arXiv2023

Entropic Niebrzydowski Tribrackets

We introduce the notion of entropic Niebrzydowski tribrackets or just entropic tribrackets, analogous to entropic (also known as abelian or medial ) quandles and biquandles. We show that if X is a finite entropic tribracket then for any tribracket T , the homset Hom(T, X) (and in particular, for any oriented link L, the homset Hom(T (L), X)) also has the structure of an entropic tribracket. This operation yields a product on the category of entropic tribrackets; we compute the operation table for entropic tribrackets of small cardinality and prove a few results. We conjecture that this structure can be used to distinguish links which have the same counting invariant with respect to a chosen entropic coloring tribracket X.

math.GT↗