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# 14: Graph Coloring

• • Joy Morris
• Professor (Mathematics) at University of Lethbridge
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• 14.1: Edge Coloring
Suppose you have been given the job of scheduling a round-robin tennis tournament with n players. One way to approach the problem is to model it as a graph: the vertices of the graph represent the players and the edges represent the matches that need to be played. Since it is a round-robin tournament, every player must play every other player so the graph will be complete. Creating the schedule amounts to assigning a time to each of the edges, representing the time that the match will be played.
• 14.2: Ramsey Theory
Although Ramsey Theory is an important part of Combinatorics (along with Enumeration, Graph Theory, and Design Theory), this course will touch on it only very lightly. The basic idea is that if a very large object is cut into two pieces (or a small number of pieces), then at least one of the pieces must contain a very nice subset.
• 14.3: Vertex Colouring
Suppose you have been given the task of assigning broadcast frequencies to transmission towers. You have been given a list of frequencies that you are permitted to assign. There is a constraint: towers that are too close together cannot be assigned the same frequency, since they would interfere with each other. One way to approach this problem is to model it as a graph.
• 14.4: Summary
This page covers the summary of the topics covered in Chapter 14.