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Questions about the branch of combinatorics called graph theory (not to be used for questions concerning the graph of a function). This tag can be further specialized via using it in combination with more specialized tags such as extremal-graph-theory, spectral-graph-theory, algebraic-graph-theory, topological-graph-theory, random-graphs, graph-colorings and several others.

1 vote
3 answers
515 views

Finding maximum value of degree-3 homogeneous polynomials when variables sum to 1

I would like to be able to find maximum values of degree-3 homogeneous polynomials, when the variables are non-negative real numbers that sum to 1. For example, For example, the maximum value of $xy^ …
Emil's user avatar
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4 votes

Bound on the number of unlabeled cographs on n vertices

A cograph on $n$ vertices can be created by starting with $n$ 1-vertex graphs and then going through a procedure of at each turn either (1) complementing a graph, or (2) replacing two of your graphs w …
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5 votes

What are some good beginner graph theory texts?

Wilson (many editions) - great to read quickly to get an overview. Bondy and Murty (2008) - very clear, lots of stuff. My favorite book. Diestel (2005) - clinical treatment. Bollobas (1998?) - lots …
21 votes
8 answers
8k views

Why is edge-coloring less interesting than vertex-coloring?

I was wondering why there is (apparently) much more research directed towards vertex-coloring than edge-coloring? Prima facie, it seems that edge-coloring is just as "natural" a thing to investigate. …
13 votes
2 answers
402 views

Regularizing graphs

Let $G$ be a simple graph (undirected, no loops or parallel edges), with maximum degree $\Delta(G)$. I would like to add edges to the graph to make it regular, without increasing the maximum degree. …
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3 votes

Hamilton cycle decompositions of the complete graph

In Two-factorizations of complete graphs it is stated that $K_9$ has 122 non-isomorphic Hamiltonian decompositions, and the corresponding number for $K_{11}$ is 3140 (EDIT: the actual figure is much m …
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  • 726
6 votes

What introductory book on Graph Theory would you recommend?

Robin Wilson's Introduction to Graph Theory is very easy to read - I read it over a weekend. I definitely recommend you give this a quick read before plunging into Bondy and Murty, Diestel or West.
4 votes
Accepted

Complexity of determining if two graphs have same cycle matroid?

The following paper seems to show that this problem is polynomial equivalent to graph isomorphism (see section 5): http://arxiv.org/abs/0811.3859
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2 votes

A name for a claw-graph with paths attached to it

In this paper such graphs are referred to as "spiders" and "subdivisions of stars": http://doi.wiley.com/10.1002/jgt.20244
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21 votes
Accepted

What is the Tutte polynomial encoding?

No-one so far has mentioned matroids. The Tutte polynomial encodes some of the information from the cycle matroid of the graph. Two graphs with the same cycle matroid (and number of vertices) have the …
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