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We determine a simple condition on a particular state graph of an alternating knot or link diagram that characterizes when the unoriented genus and crosscap number coincide, extending work of Adams and Kindred. Building on this same work…

Geometric Topology · Mathematics 2025-08-07 Moshe Cohen , Thomas Kindred , Adam M. Lowrance , Patrick D. Shanahan , Cornelia A. Van Cott

Experimental data from Dunfield et al using random grid diagrams suggests that the genus of a knot grows linearly with respect to the crossing number. Using billiard table diagrams of Chebyshev knots developed by Koseleff and Pecker and a…

Geometric Topology · Mathematics 2021-08-03 Moshe Cohen

It is a very old conjecture that the crossing number of knots is additive under connected sum. In other words, if K#K' is the connected sum of knots K and K', then does the equality c(K#K') = c(K) + c(K') hold? We prove that c(K#K') is at…

Geometric Topology · Mathematics 2014-02-26 Marc Lackenby

Given a diagram $D$ of a knot $K$, we consider the number $c(D)$ of crossings and the number $b(D)$ of overpasses of $D$. We show that, if $D$ is a diagram of a nontrivial knot $K$ whose number $c(D)$ of crossings is minimal, then…

Geometric Topology · Mathematics 2009-11-10 Jae-Wook Chung , Xiao-Song Lin

In this article we study the braid indices of 2-bridge knots with a fixed crossing number $c$. We show that the average braid index of the set of $2$-bridge knots of crossing number $c$ is asymptotically linear, approaching…

Geometric Topology · Mathematics 2024-01-17 Tobias Clark , Jeremy Frank , Adam M. Lowrance

We prove that for 2-bridge knots, the diameter, D, of the set of boundary slopes is twice the crossing number, c. This constitutes partial verification of a conjecture that, for all knots in S^3, D is at most 2c.

Geometric Topology · Mathematics 2007-05-23 Thomas W. Mattman , Gabriel Maybrun , Kristin Robinson

We define and compare several natural ways to compute the bridge number of a knot diagram. We study bridge numbers of crossing number minimizing diagrams, as well as the behavior of diagrammatic bridge numbers under the connected sum…

Geometric Topology · Mathematics 2021-07-09 Ryan Blair , Alexandra A. Kjuchukova , Makoto Ozawa

We show that every two-bridge knot $K$ of crossing number $N$ admits a polynomial parametrization $x=T_3(t), y = T_b(t), z =C(t)$ where $T_k(t)$ are the Chebyshev polynomials and $b+\deg C = 3N$. If $C (t)= T_c(t)$ is a Chebyshev…

Geometric Topology · Mathematics 2009-09-18 Pierre-Vincent Koseleff , Daniel Pecker

We have developed a reinforcement learning agent that often finds a minimal sequence of unknotting crossing changes for a knot diagram with up to 200 crossings, hence giving an upper bound on the unknotting number. We have used this to…

A knot $K$ is called $n$-adjacent to a knot $K'$ if there is a set of $n$ crossing circles $\mathcal C$ in $K$ so that a generalized crossing change at any nonempty subset of crossings in $\mathcal C$ yields $K'$. In this paper, the authors…

Geometric Topology · Mathematics 2026-05-11 Marion Campisi , Brandy Doleshal , Eric Staron

A triple crossing is a crossing in a projection of a knot or link that has three strands of the knot passing straight through it. A triple crossing projection is a projection such that all of the crossings are triple crossings. We prove…

Geometric Topology · Mathematics 2012-09-05 Colin Adams

A knot is called minimal if its knot group admits epimorphisms onto the knot groups of only the trivial knot and itself. In this paper, we determine which two-bridge knot $\mathfrak{b}(p,q)$ is minimal where $q \leq 6$ or $p \leq 100$.

Geometric Topology · Mathematics 2016-09-09 Fumikazu Nagasato , Masaaki Suzuki , Anh T. Tran

The 2-bridge knots are a family of knots with bridge number 2. In this paper, we compute the Kauffman polynomials of 2-bridge knots using the Kauffman skein theory and linear algebra techniques. Our calculation can be easily carried out…

Geometric Topology · Mathematics 2007-05-23 Bin Lu , Jianyuan K. Zhong

Cohen, Lowrance, Madras, and Raanes computed the average (absolute value of) signature over all 2-bridge knots with crossing number $c$ by introducing the number $s(c,\sigma)$ of 2-bridge knots of crossing number $c$ and signature $\sigma$.…

Geometric Topology · Mathematics 2026-04-24 Cody Baker , Moshe Cohen , Henry Dam , Rebecca Felber , Neal Madras , Ritvik Saha , Daisy Thackrah

We study certain linear representations of the knot group that induce augmentations of knot contact homology. This perspective on augmentations enhances our understanding of the relationship between the augmentation polynomial and the…

Geometric Topology · Mathematics 2014-08-28 Christopher Cornwell

This paper concerns the H(2)-unknotting numbers of links related to 2-bridge links. It consists of three parts. In the first part, we consider a necessary and sufficient condition for a 2-bridge link to have H(2)-unknotting number one. The…

Geometric Topology · Mathematics 2011-04-25 Yuanyuan Bao

Using Gauss diagrams, one can define the virtual bridge number ${\rm vb}(K)$ and the welded bridge number ${\rm wb}(K),$ invariants of virtual and welded knots with ${\rm wb}(K) \leq {\rm vb}(K).$ If $K$ is a classical knot, Chernov and…

Geometric Topology · Mathematics 2015-04-17 Hans U. Boden , Anne Isabel Gaudreau

We show that the average or expected absolute value of the signatures of all 2-bridge knots with crossing number $c$ approaches $\sqrt{{2c}/{\pi}}$. Baader, Kjuchukova, Lewark, Misev, and Ray consider a model for 2-bridge knot diagrams…

Geometric Topology · Mathematics 2024-06-26 Moshe Cohen , Adam M. Lowrance , Neal Madras , Steven Raanes

We describe a correspondence between augmentations and certain representations of the knot group. The correspondence makes the 2-variable augmentation polynomial into a generalization of the classical $A$-polynomial. It also associates to…

Geometric Topology · Mathematics 2017-06-07 Christopher Cornwell

In the literature of the study of knot group epimorphisms, the existence of an epimorphism between two given knot groups is mostly (if not always) shown by giving an epimorphism which preserves meridians. A natural question arises: is there…

Geometric Topology · Mathematics 2016-05-04 Jae Choon Cha , Masaaki Suzuki