On the generic triangle group

We introduce the concept of a generic Euclidean triangle $\tau$ and study the group $G_\tau$ generated by the reflection across the edges of $\tau$. In particular, we prove that the subgroup $T_\tau$ of all translations in $G_\tau$ is free abelian of infinite rank, while the index 2 subgroup $H_\tau$ of all orientation preserving transformations in $G_\tau$ is free metabelian of rank 2, with $T_\tau$ as the commutator subgroup. As a consequence, the group $G_\tau$ cannot be finitely presented and we provide explicit minimal infinite presentations of both $H_\tau$ and $G_\tau$. This answers in the affirmative the problem of the existence of a minimal presentation for the free metabelian group of rank 2. Moreover, we discuss some examples of non-trivial relations in $T_\tau$ holding for given non-generic triangles $\tau$.Comment: 21 pages, 6 figure

Math Active Learning Lab: Math 107 Precalculus Notebook

This course notebook has been designed for students of Math 107 (Precalculus) at the University of North Dakota. It has been designed to help you get the most out of the ALEKS resources and your time. Topics in the Notebook are organized by weekly learning module. Space for notes from ALEKS learning pages, e-book and videos directs you to essential concepts. Examples and “You Try It” problems have been carefully chosen to help you focus on these essential concepts. Completed Notebook is an invaluable tool when studying for exams.https://commons.und.edu/oers/1023/thumbnail.jp

Odd Wheels Are Not Odd-Distance Graphs

An odd wheel graph is a graph formed by connecting a new vertex to all vertices of an odd cycle. We answer a question of Rosenfeld and Le by showing that odd wheels cannot be drawn in the plane so that the lengths of the edges are odd integers

The Galois Complexity of Graph Drawing: Why Numerical Solutions are Ubiquitous for Force-Directed, Spectral, and Circle Packing Drawings

Many well-known graph drawing techniques, including force directed drawings, spectral graph layouts, multidimensional scaling, and circle packings, have algebraic formulations. However, practical methods for producing such drawings ubiquitously use iterative numerical approximations rather than constructing and then solving algebraic expressions representing their exact solutions. To explain this phenomenon, we use Galois theory to show that many variants of these problems have solutions that cannot be expressed by nested radicals or nested roots of low-degree polynomials. Hence, such solutions cannot be computed exactly even in extended computational models that include such operations.Comment: Graph Drawing 201

Integer Solutions to Optimization Problems and Modular Sequences of Nexus Numbers

In this thesis, we examine the use of integers through two ideas. As mathematics teachers, we prefer students not use calculators on assessments. In order to require this, students compute the problems by hand. We take a look at the classic Calculus I optimization box problem while restricting values to integers. In addition, sticking with the integer theme, we take a new look at the nexus numbers. Nexus numbers are extensions of the hex and rhombic dodecahedral numbers. We put these numbers into a sequence, and through a few computations of modular arithmetic, we analyze the sequences and their patterns based upon the different moduli. These patterns are specific to whether the power is even or odd. Within each power, there are other properties to this set of sequences. Depending on modulus, there are some sequences that stand out more than others

Riemann surfaces and Schrodinger potentials of gauged supergravity

Supersymmetric domain-wall solutions of maximal gauged supergravity are classified in 4, 5 and 7 dimensions in the presence of non-trivial scalar fields taking values in the coset SL(N, R)/SO(N) for N=8, 6 and 5 respectively. We use an algebro-geometric method based on the Christoffel-Schwarz transformation, which allows for the characterization of the solutions in terms of Riemann surfaces whose genus depends on the isometry group. The uniformization of the curves can be carried out explicitly for models of low genus and results into trigonometric and elliptic solutions for the scalar fields and the conformal factor of the metric. The Schrodinger potentials for the quantum fluctuations of the graviton and scalar fields are derived on these backgrounds and enjoy all properties of supersymmetric quantum mechanics. Special attention is given to a class of elliptic models whose quantum fluctuations are commonly described by the generalized Lame potential \mu(\mu+1)P(z) + \nu(\nu+1)P(z+\omega_1)+ \kappa(\kappa+1)P(z+\omega_2) + \lambda(\lambda+1)P(z+\omega_1 +\omega_2) for the Weierstrass function P(z) of the underlying Riemann surfaces with periods 2\omega_1 and 2\omega_2, for different half-integer values of the coupling constants \mu, \nu, \kappa, \lambda.Comment: 13 pages, latex; contribution to the proceedings of the TMR meeting "Quantum Aspects of Gauge Theories, Supersymmetry and Unification" held in Paris in September 199

Sines, Cosines, and Conjugates

This thesis is an investigation of angles whose sine and cosine are algebraic conjugates over the field of rational numbers. That is to say, sin(0) and cos(0) are roots of the same irreducible polynomial with integer coefficients. These interesting families are explored. First, it is shown that for n\u3e2, the angles have this property. Second, all angles which are conjugate in this sense and which have a quadratic minimum polynomial are identified. The relationship between these two families is explored, and a family of conjugate angles with 4^^ degree minimum polynomials is explored as well. Questions for further investigation are proposed, including an intriguing connection to chaos theory