Equation of Ellipse over Fp and Pairs of Quadratic Residues/Nonresidues Related to Catalan Numbers
The equation of an ellipse and quadratic residues are well-known concepts in elementary geometry and number theory, respectively. While the properties of ellipse equations in Euclidean space have been extensively studied, many characteristics of quadratic residues, such as consecutive quadratic residues, have also been explored in past research. In this study, we discovered the characteristic polynomial of the equation of an ellipse over finite fields Fp, a single-variable polynomial that shares the same roots as the ellipse. Furthermore, by examining the parallels between the equation of an ellipse and the pairs of residues and nonresidues, we derived a characteristic polynomial for this concept and demonstrated its connection to the Catalan number, a significant sequence in combinatorics. This research was conducted through the following steps. First, the power sums of the roots of the ellipse in Fp were calculated using the Legendre symbol and Euler’s criterion. Next, the characteristic polynomial of the ellipse was determined using Newton’s identity, generating functions, and Vieta’s theorem. Finally, leveraging the equivalence between the equation of the ellipse and the pairs of residues and nonresidues, we established the main results connecting these two concepts with Catalan numbers.
3D Arithmetic Billiards investigating edge points with a number theoretic approach
The billiard table is a cuboid with integer side lengths. A point-wise ball moves with constant speed along segments making a 45◦ angle with the sides and bounces on these. We allow the ball to start from any of the 8 corners, resulting in a periodic trajectory known as a corner path. The geometry of the path depends on the artihmetic properties of the side lengths (for example if these are pairwise coprime). Points of contact between the ball and edges, known as edge points, are inves- tigated and their characteristics like distribution explicitly described. This generalizes a previous work by Perucca, Reguengo da Sousa and Tronto of University of Luxembourg.