A Study Of The Upper Domatic Number Of A Graph

Given a graph G we can partition the vertices of G in to k disjoint sets. We say a set A of vertices dominates another set of vertices, B, if for every vertex in B there is some adjacent vertex in A. The upper domatic number of a graph G is written as D(G) and defined as the maximum integer k such that G can be partitioned into k sets where for every pair of sets A and B either A dominates B or B dominates A or both. In this thesis we introduce the upper domatic number of a graph and provide various results on the properties of the upper domatic number, notably that D(G) is less than or equal to the maximum degree of G, as well as relating it to other well-studied graph properties such as the achromatic, pseudoachromatic, and transitive numbers

The use of GeoGebra in Discrete Mathematics

In this paper we explain how to make use of the commands that are available in GeoGebra to deal with some realistic problems related to the field of Discrete Mathematics. We also expose how to define new tools that make possible the study of theoretical results in Graph theory

The use of GeoGebra in Discrete Mathematics

In this paper we explain how to make use of the commands that are available in GeoGebra to deal with some realistic problems related to the field of Discrete Mathematics. We also expose how to define new tools that make possible the study of theoretical results in Graph theory

The four color theorem: from graph theory to proof assistants.

openLa tesi inizialmente descrive i fondamenti della teoria dei grafi con le principali nozioni per affrontare il teorema dei sei, cinque e infine dei quattro colori. Quest'ultimo viene descritto dal punto di vista storico e viene fornita una traccia della dimostrazione, per poi indagare gli aspetti legati all'utilizzo di proof assistant.First, it describes the basic notions of graph theory in order to face the six, five and finally the four color theorem. This last problem is treated from an historical point of view and the main steps of the proof are given. Finally, some aspects linked to proof assistants are examine

The Four Color Problem: The Journey to a Proof and the Results of the Study

The four color problem was one of the most difficult to prove problems for 150 years. It took several failed proofs and advancement in technology and techniques for the final proof to become possible. Some notable men include De Morgan first writing about the problem, Kempe giving the first proof, Heawood showing the flaws in Kempe’s work as well as making advancements of his own. The first actual proof of the problem is then discussed, as well as it’s shortcomings and the work done by other mathematicians to show improvements on them. The total of this work has lead to numerous great leaps in mathematics including the creation of the branch known as graph theory. This one problem also revolutionized proof writing, being the first to use a computer as an essential part of the proving process

The PC-Tree algorithm, Kuratowski subdivisions, and the torus.

The PC-Tree algorithm of Shih and Hsu (1999) is a practical linear-time planarity algorithm that provides a plane embedding of the given graph if it is planar and a Kuratowski subdivision otherwise. Remarkably, there is no known linear-time algorithm for embedding graphs on the torus. We extend the PC-Tree algorithm to a practical, linear-time toroidality test for K3;3-free graphs called the PCK-Tree algorithm. We also prove that it is NP-complete to decide whether the edges of a graph can be covered with two Kuratowski subdivisions. This greatly reduces the possibility of a polynomial-time toroidality testing algorithm based solely on edge-coverings by subdivisions of Kuratowski subgraphs