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The ribbon number $r(K)$ of a ribbon knot $K \subset S^3$ is the minimal number of ribbon intersections contained in any ribbon disk bounded by $K$. We find new lower bounds for $r(K)$ using $\det(K)$ and $\Delta_K(t)$, and we prove that…

Geometric Topology · Mathematics 2024-08-22 Stefan Friedl , Filip Misev , Alexander Zupan

We make use of the 3D nature of knots and links to find savings in computational complexity when computing knot invariants such as the linking number and, in general, most finite type invariants. These savings are achieved in comparison…

Geometric Topology · Mathematics 2024-01-15 Dror Bar-Natan , Itai Bar-Natan , Iva Halacheva , Nancy Scherich

We derive useful reduction formulae which express one-loop Feynman integrals with a large number of external momenta in terms of lower-point integrals carrying easily derivable kinematic coefficients which are symmetric in the external…

High Energy Physics - Phenomenology · Physics 2021-04-21 Guy R. Jehu

We discuss reductions of general N=1 four dimensional gauge theories on S^2. The effective two dimensional theory one obtains depends on the details of the coupling of the theory to background fields, which can be translated to a choice of…

High Energy Physics - Theory · Physics 2020-04-21 Abhijit Gadde , Shlomo S. Razamat , Brian Willett

This paper visualizes a knot reduction algorithm

Soft Condensed Matter · Physics 2007-11-28 P. Virnau , M. Kardar , Y. Kantor

A weak chord index $Ind'$ is constructed for self crossing points of virtual links. Then a new writhe polynomial $W$ of virtual links is defined by using $Ind'$. $W$ is a generalization of writhe polynomial defined in [6]. Based on $W$,…

Geometric Topology · Mathematics 2018-12-14 Mengjian Xu

We develop a new general method for computing the decomposition type of the normal bundle to a projective rational curve. This method is then used to detect and explain an example of a Hilbert scheme that parametrizes all the rational…

Algebraic Geometry · Mathematics 2016-04-21 Alberto Alzati , Riccardo Re

Knots in Euclidean space which may be parameterized by a single cosine function in each coordinate are called Lissajous knots. We show that twist knots are Lissajous knots if and only if their Arf invariants are zero. We further prove that…

Geometric Topology · Mathematics 2007-05-23 Jim Hoste , Laura Zirbel

A quadrisecant of a knot is a straight line intersecting the knot at four points. If a knot has finitely many quadrisecants, one can replace each subarc between two adjacent secant points by the line segment between them to get the…

Geometric Topology · Mathematics 2016-05-03 Sheng Bai , Chao Wang , Jiajun Wang

"Most" hypersurfaces in projective space are irreducible, and rather precise estimates are known for the probability that a random hypersurface over a finite field is reducible. This paper considers the parametrization of space curves by…

Number Theory · Mathematics 2013-07-08 Eda Cesaratto , Joachim von zur Gathen , Guillermo Matera

It is known that any two triangulations of a compact 3-manifold are related by finite sequences of certain local transformations. We prove here an upper bound for the length of a shortest transformation sequence relating any two…

Geometric Topology · Mathematics 2007-05-23 Simon A. King

S. Satoh has defined a construction to obtain a ribbon torus knot given a welded knot. This construction is known to be surjective. We show that it is not injective. Using the invariant of the peripheral structure, it is possible to provide…

Geometric Topology · Mathematics 2008-08-08 Blake Winter

Suppose F is a compact orientable surface, K is a knot in F x I, and N is the 3-manifold obtained by some non-trivial surgery on K. If F x {0} compresses in N, then there is an annulus in F x I with one end K and the other end an essential…

Geometric Topology · Mathematics 2014-10-01 Martin Scharlemann , Abigail Thompson

In this paper, we prove that any two birational projective varieties with finite quotient singularities can be realized as two geometric GIT quotients of a non-singular projective variety by a reductive algebraic group. Then, by applying…

Algebraic Geometry · Mathematics 2007-05-23 Yi Hu

An axis of a link projection is a closed curve which lies symmetrically on each region of the link projection. In this paper we define axis systems of link projections and characterize axis systems of the standard projections of twist…

Geometric Topology · Mathematics 2017-03-23 Kirara Horiguchi , Ayaka Shimizu , Ryohei Watanabe , Yoshiro Yaguchi

Random projections offer an appealing and flexible approach to a wide range of large-scale statistical problems. They are particularly useful in high-dimensional settings, where we have many covariates recorded for each observation. In…

Methodology · Statistics 2019-11-26 Timothy I. Cannings

We define a set of "second-order" L^(2)-signature invariants for any algebraically slice knot. These obstruct a knot's being a slice knot and generalize Casson-Gordon invariants, which we consider to be "first-order signatures". As one…

Geometric Topology · Mathematics 2010-04-06 Tim Cochran , Shelly Harvey , Constance Leidy

The 2-sets convex feasibility problem aims at finding a point in the nonempty intersection of two closed convex sets $A$ and $B$ in a Hilbert space $X$. The method of alternating projections is the simplest iterative procedure for finding a…

Optimization and Control · Mathematics 2020-06-29 Carlo A. De Bernardi , Enrico Miglierina

A parallelohedron is called reducible, if it can be represented as a direct product of two parallelohedra of lower dimension. In his Ph.D. thesis (2005) the first author proved a criterion of reducibility of a parallelohedron in terms of…

Metric Geometry · Mathematics 2013-06-05 Andrei Ordine , Alexander Magazinov

In this paper we introduce a new type of code, called projective nested cartesian code. It is obtained by the evaluation of homogeneous polynomials of a fixed degree on a certain subset of $\mathbb{P}^n(\mathbb{F}_q)$, and they may be seen…

Algebraic Geometry · Mathematics 2024-02-07 Cicero Carvalho , V. G. Lopez Neumann , Hiram H. Lopez