Mathematics Commons^™

Geometrical Models For Grain Dynamics, Giovani L. Vasconcelos, J. J. P. Veerman

Mathematics and Statistics Faculty Publications and Presentations

We study models for the gravity-driven, dissipative motion of a single grain on an inclined rough surface. Imposing some conditions on the momentum loss due to the collisions between the particle and the surface, we arrive at a class of models in which the grain dynamics is described by one-dimensional maps. The dynamics of these maps is studied in detail. We prove the existence of various dynamical phases and show that the presence of these phases is independent of the restitution law (within the class considered).

Locked And Unlocked Polygonal Chains In 3d, Therese Biedl, Erik D. Demaine, Martin L. Demaine, Sylvain Lazard, Anna Lubiw, Joseph O'Rourke, Mark Overmars, Steve Robbins, Ileana Streinu, Godfried Toussaint, Sue Whitesides

Computer Science: Faculty Publications

In this paper, we study movements of simple polygonal chains in 3D. We say that an open, simple polygonal chain can be straightened if it can be continuously reconfigured to a straight sequence of segments in such a manner that both the length of each link and the simplicity of the chain are maintained throughout the movement. The analogous concept for closed chains is convexification: reconfiguration to a planar convex polygon. Chains that cannot be straightened or convexified are called locked. While there are open chains in 3D that are locked, we show that if an open chain has a …

Computational Geometry Column 35, Joseph O'Rourke

Computer Science: Faculty Publications

The subquadratic algorithm of Kapoor for finding shortest paths on a polyhedron is described.

Finite Type Link Homotopy Invariants, Blake Mellor

Mathematics, Statistics and Data Science Faculty Works

Bar-Natan used Chinese characters to show that finite type invariants classify string links up to homotopy. In this paper, I construct the correct spaces of chord diagrams and Chinese characters for links up to homotopy. I use these spaces to show that the only rational finite type invariants of link homotopy are the pairwise linking numbers of the components.

Symmetry And Tiling Groups For Genus 4 And 5, C. Ryan Vinroot

Mathematical Sciences Technical Reports (MSTR)

All symmetry groups for surfaces of genus 2 and 3 are known. In this paper, we classify symmetry groups and tiling groups with three branch points for surfaces of genus 4 and 5. Also, a class of symmetry groups that are not tiling groups is presented, as well as a class of odd order non-abelian tiling groups.

Quadrilaterals Subdivided By Triangles In The Hyperbolic Plane, Dawn M. Haney, Lori T. Mckeough

Mathematical Sciences Technical Reports (MSTR)

In this paper, we consider triangle-quadrilateral pairs in the hyperbolic plane which “kaleidoscopically” tile the plane simultaneously. These tilings are called divisible tilings or subdivided tilings. We restrict our attention to the simplest case of divisible tilings, satisfying the corner condition, in which a single triangle occurs at each vertexof the quadrilateral. All possible such divisible tilings are catalogued as well as determining the minimal genus surface on which the divisible tiling exists. The tiling groups of these surfaces are also determined.

Computational Geometry Column 33, Joseph O'Rourke

Computer Science: Faculty Publications

Several recent SIGGRAPH papers on surface simplification are described.

Randal Bishop Plunges Into 4-D Space: A Comment On Randal Bishop’S Paper Titled “The Use Of Realistic Imagery To Represent The Relationships In A Four-Dimensional Coordinate System”, Carlos Ernesto S. Lindgren

Humanistic Mathematics Network Journal

No abstract provided.

The Use Of Realistic Imagery To Represent The Relationships In A Four-Dimensional Coordinate System, Randal J. Bishop

Humanistic Mathematics Network Journal

No abstract provided.

Nonlinear Modes Of Liquid Drops As Solitary Waves, Andrei Ludu, J. P. Draayer

Publications

The nonlinear dynamic equations of the surface of a liquid drop are shown to be directly connected to Korteweg–de Vries (KdV) systems, giving traveling solutions that are cnoidal waves. They generate multiscale patterns ranging from small harmonic oscillations (linearized model), to nonlinear oscillations, up through solitary waves. These non-axis-symmetric localized shapes are also described by a KdV Hamiltonian system. Recently such “rotons” were observed experimentally when the shape oscillations of a droplet became nonlinear. The results apply to droplike systems from cluster formation to stellar models, including hyperdeformed nuclei and fission.

Using Symbolic Dynamical Systems: A Search For Knot Invariants, Russell Clark Wheeler

Theses Digitization Project

No abstract provided.

Interactions Of Topological Kinks In Two Coupled Rings Of Nonlinear Oscillators, A E. Duwel, C P. Heij, J C. Weisenfeld, Stephen M.K. Yeung, E Trias, S. J.K. Vardy, H. S.J. Van Der Zant, S H. Strogatz, T P. Orlando

Mathematics

Two discrete rings of nonlinear oscillators with topologically trapped kinks exhibit features due to coupling interactions between the rings. These interaction effects include phase locking between kinks in different rings, precession of the kink/antikink collision region, excitation of kink/antikink pairs, and time-dependent switching. We study these phenomena in simulations of two coupled discrete sine-Gordon equations, and in experiments on two inductively coupled rings of niobium Josephson junctions.

Torus Embedding And Its Applications, Rick Hung Nguyenhuu

Theses Digitization Project

No abstract provided.

Some Root Invariants And Steenrod Operations In Ext_A(F2,F2), Robert R. Bruner

Mathematics Faculty Research Publications

We give the results of computations of root invariants in Ext over the Steenrod algebra through the 25-stem, with partial information through the 45-stem. This allows the computation of some new Steenrod operations as well.

Some Remarks On The Root Invariant, Robert R. Bruner

Mathematics Faculty Research Publications

We show how the root invariant of a product depends upon the product of the root invariants, give some examples of the equivariant definition of the root invariant, and verify a weakened form of the algebraic Bredon-Löffler conjecture.

A Yoneda Description Of The Steenrod Operations, Robert R. Bruner

Mathematics Faculty Research Publications

No abstract provided.

A Manifold That Does Not Contain A Compact Core, Gerard A. Venema

University Faculty Publications and Creative Works

A core of a (noncompact) manifold is a submanifold with the property that the inclusion of the submanifold into the manifold is a homotopy equivalence. It is shown by example that a manifold may fail to contain a compact core even though the manifold has the homotopy type of a finite complex.

A Homotopy Equivalence That Is Not Homotopic To A Topological Embedding, Vo Thanh Liem, Yukio Matsumoto, Gerard A. Venema

University Faculty Publications and Creative Works

An open subset W of Sn, n ≥ 6 or n = 4, and a homotopy equivalence f : S2 × Sn-4 → W are constructed having the property that f is not homotopic to any topological embedding.

Computational Geometry Column 34, Pankaj K. Agarwal, Joseph O'Rourke

Computer Science: Faculty Publications

Problems presented at the open-problem session of the 14th Annual ACM Symposium on Computational Geometry are listed.

On C^1 Robust Singular Transitive Sets For Three-Dimensional Flows, Carlos Arnoldo Morales, Maria José Pacífico, Enrique Ramiro Pujals

Publications and Research

Abstract:

The main goal of this paper is to study robust invariant transitive sets containing singularities for C¹ flows on three-dimensional compact boundaryless manifolds:they are partially hyperbolic with volume expanding central direction. Moreover, they are either attractors or repellers. Robust here means that this property cannot be destroyed by small C¹-perturbations of the flow.

Résumé:

Le but de ce travail est d'étudier des ensembles invariants robustes ayant des singularités pour des flots C¹ sur des variétés tridimensionelles : ce sont des ensembles hyperboliques singuliers. << Robuste >> veut dire ici que cette propriété ne peut être détruite par des …

Gn.3(C) Is Prime If N Is Odd, John Ferdinands

University Faculty Publications and Creative Works

A finite CW complex X is said to be prime if for every Hurewicz fibration F → E → B with E homotopy equivalent to X, and B and F homotopically equivalent to finite CW complexes, either B or F is contractible. We show that the 3-plane complex Grassmannian Gn.3(C) is prime if n is odd.

Isospectral Deformations Of Closed Riemannian Manifolds With Different Scalar Curvature, Carolyn S. Gordon, Ruth Gornet, Dorothee Schueth, David L. Webb

Dartmouth Scholarship

No abstract provided.

Borsuk-Ulam Implies Brouwer: A Direct Construction, Francis E. Su

All HMC Faculty Publications and Research

No abstract provided in this article.

Computational Geometry Column 32, Joseph O'Rourke

Computer Science: Faculty Publications

The proof of Dey's new k-set bound is illustrated.

Oval Intersections In Tilings On Surfaces, Dennis A. Schmidt

Mathematical Sciences Technical Reports (MSTR)

A tiling is a covering by polygons, without gaps or overlapping, of a compact, orientable surface. We are particularly interested in tilings by triangles that generate a large symmetry group of the surface. An oval of the tiling is a simple, closed curve that is a union of edges of the tiling. We investigate the number of points of intersection of two ovals. We have found that the number of intersections is bounded when the subgroup of orientation preserving symmetries is abelian. However, there is no upper bound on the number of intersections in the non-abelian case.

Counting Ovals On A Symmetric Riemann Surface, Sean A. Broughton

Mathematical Sciences Technical Reports (MSTR)

Let S be a compact Riemann surface without boundary. A symmetry of S is an anti-conformal, involutary automorphism. Its fixed point set is a disjoint union of circles, each of which is called an oval. A method is presented for counting the ovals of a symmetry when S admits a large group G of automorphisms. The method involves only calculations in G, based on the geometric description of S/G, and the knowledge of the action of the symmetry on G.

Hartogs' Phenomenon For Polyregular Functions And Projective Dimension Of Related Modules Over A Polynomial Ring, W. W. Adams, P. Loustaunau, V. P. Palamadov, Daniele C. Struppa

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this paper we prove that the projective dimension of Mn = R^4/(An) is 2n -1, where R is the ring of polynomials in 4n variables with complex coefficients and (An) is the module generated by the columns of a 4x4n matrix which arises as the Fourier transform of the matrix of differential operators associated with the regularity condition for a function of n quaternionic variables. As a corollary we show that the sheaf R of regular functions has flabby dimension 2n -1, and we prove a cohomology vanishing theorem for open sets in the space Hn of quaternions. We …

A Stronger Triangle Inequality, Herb Bailey

Mathematical Sciences Technical Reports (MSTR)

The triangle inequality is basic for many results in real and complex analysis. The geometric form states that the sum of any two sides of a triangle is greater than the third. This was included as Proposition XX in the first book of Euclid's Elements. Many geometric triangle inequalities involving sides, angles, altitudes, inscribed circles and circumscribed circles have been found. Hundreds of these inequalities are summarized in [l] and [2]. A nice geometric proof of the triangle inequality is given in [3].

Symmetries Of Accola-Maclachlan And Kulkarni Surfaces, Sean A. Broughton, E Bujalance, A F. Costa, J M. Gamboa, G Gromadzki

Mathematical Sciences Technical Reports (MSTR)

For all g greater than or equal to 2, there is a Riemann surface of genus g whose automorphism group has order 8g+8, establishing a lower bound for the possible orders of automorphism groups of Riemann surfaces. Accola and MacLachlan established the existence of such surfaces; we shall call them Accola-MacLachlan surfaces. In this paper we determine the symmetries of surfaces with genus g = 3(mod 4), computing the number of ovals and the separability of the symmetries. The results are then applied to classify the real forms of these complex algebraic curves.

On Stable Homotopy Equivalences, Robert R. Bruner, F. R. Cohen, C. A. Mcgibbon

Mathematics Faculty Research Publications

No abstract provided.