Proving the Existence of a Maximum-Edge Vertex in Acyclic Tournament Graphs

In summary, the problem at hand is to prove that in an acyclic tournament graph, there is exactly one vertex with more edges than any other vertex. The tournament graph is a directed graph obtained from an undirected complete graph by assigning directions to each edge. The approach of proof by contradiction is suggested, where it is assumed that such a vertex does not exist. However, this leads to contradictions and it can be concluded that the relation under the graph is not transitive, symmetric, reflexive, and is asymmetric. The question is raised about how a vertex in a tournament graph can have more edges than others, since in a complete graph every vertex has the same number of edges. It is clarified that the focus is on starting edges (direct
  • #1
njama
216
1

Homework Statement



Prove the following:

If the tournament graph is acyclic, there is exactly one vertex which got edges more than any vertex in the graph.

Homework Equations



A tournament is a directed graph (digraph) obtained by assigning a direction for each edge in an undirected complete graph


The Attempt at a Solution



I am not sure how to start. Is it easier to go with the indirect proof (i.e proof by contradiction) ?

Lets say that that kind of vertex does not exist. Than either all vertices have equal number of edges or there are two edges or more with same number of edges which got more edges than any other pair of vertices.

Because the graph is acyclic we could easily see that the relation under the graph is not transitive, not symmetric, not reflexive, is asymmetric.

Could somebody help me please and tell me if I should prove like the way I did?

Thank you.
 
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  • #2
any ideas please?
 
  • #3
Question: If a tournament graph is simply a complete graph with directions assigned to each edge, how can any vertex in a tournament graph have more edges than the others? In a complete graph every vertex "has" the same number of edges.
 
  • #4
Sorry for misunderstanding but I meant starting edges (directed graph) or vertex with max indegree.

Thank you.
 

1. What is proof in graph theory?

Proof in graph theory is the process of using logical reasoning and mathematical techniques to demonstrate the validity of a statement or theorem about graphs. It involves using axioms, definitions, and previously proven theorems to form a logical argument.

2. Why is proof important in graph theory?

Proof is important in graph theory because it allows us to establish the truth of statements and theorems about graphs. This enables us to confidently use these results in other areas of mathematics and in practical applications.

3. What are the different methods of proof in graph theory?

There are several methods of proof in graph theory, including direct proof, proof by contradiction, proof by induction, and proof by construction. Each method has its own advantages and is suitable for different types of problems.

4. How do you construct a proof in graph theory?

To construct a proof in graph theory, you must first clearly understand the statement or theorem you are trying to prove. Then, you must use definitions, axioms, and previously proven theorems to form a logical argument that leads to the desired conclusion. It is also important to check for any potential flaws or counterexamples in your proof.

5. What are some common challenges in proving statements about graphs?

Some common challenges in proving statements about graphs include visualizing the problem in terms of graph theory, finding the appropriate method of proof, and identifying any potential flaws or counterexamples in the argument. It is also important to consider the limitations of the statement or theorem and whether it applies to all types of graphs or only certain ones.

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