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Vertex colouring, Edge Colouring, List Colouring, Fractional Chromatic Number and other variants of graph colouring problems are all on topic.

1 vote
1 answer
169 views

On a theorem of Chetwynd and Hilton in Graphs

Let $G$ be a graph with total vertices $|V(G)|$. Let the maximum degree of the graph be $\Delta$. Let us assume the graph is total colourable( no adjacent vertices, adjacent edges and an edge and its …
vidyarthi's user avatar
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1 vote
2 answers
297 views

Total Coloring of even regular bipartite graphs

Consider an even order, balanced(both partitions have same vertices) bipartite regular graph of order greater than or equal to $12$ and degree atleast six and divisible by $6$. Then is the graph of Ty …
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  • 2,089
1 vote
1 answer
90 views

Total Chromatic Number of Regular Bipartite Graphs [closed]

What can we say about the total chromatic number of regular bipartite graphs that are not complete? Can we say they are of type 1[Total Colorable(no adjacent/incident elements have same color) by $\De …
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  • 2,089
3 votes
0 answers
123 views

On Total Coloring of Regular Graphs

Consider a regular graph of order $n$ and degree $\Delta$. Now, by Brooks' theorem, we can partition the vertices into $\Delta+1$ independent sets. The extreme case of $n$ independent sets is only for …
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  • 2,089
2 votes
0 answers
37 views

Maximum number of 1-factors in a color class

Consider any graph with $n$ vertices and maximum degree $\Delta$. By Vizing's theorem, the graph could be edge colored(properly) with at most $\Delta+1$ colors. My question pertains as to what the ma …
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  • 2,089
1 vote
1 answer
225 views

Uniform partitioning of regular graphs

Consider a symmetric or arc-transitive graph except the odd cycle. Then, is it true that the graph could be partitioned into distinct parts such that each part has equal number of vertices except for …
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  • 2,089
1 vote
1 answer
88 views

Clarifications regarding conformability in graph colorings

As an outgrowth of this question, I have another question, that is, why not the definition of conformability includes a $\Delta$ vertex coloring also, instead of only $\Delta+1$ coloring of vertices. …
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  • 2,089
2 votes
1 answer
295 views

Proving a theorem on coloring a peculiar graph

Consider the graph formed by $k$ cliques of order $k$, any two cliques sharing at most one point in common. Now, by Szekeres-Wilf theorem, I think the graph should be $k$ colorable, as any connected i …
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1 vote
0 answers
57 views

A regular independence induced graph in a $\Delta+1$ coloring

Consider any regular graph $G$ with order $n$ and size $E$ and maximum degree $\Delta$. Now, we give a $\Delta+1$ coloring to the vertices such that each vertex and its neighbors receive distinct co …
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  • 2,089
2 votes
1 answer
545 views

List coloring of tripartite graph [closed]

Let $G$ be a tripartite graph with partite sets $A,B,C$. The graphs $A\cup B$, $B\cup C$ and $C\cup A$ are each bipartite. Let the maximum degree of the graph be $\Delta$. Now, we know that the Lis …
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  • 2,089
2 votes
1 answer
103 views

Perfect graphs condition could be weakened?

The perfect graphs are generally defined as those graphs whose every induced subgraph has its chromatic number equal to its clique number. Now,are there some examples where the clique number of graph …
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0 votes
0 answers
60 views

The order of minor in the total graph of a graph

Does the total graph of a regular finite graph with maximum degree $\Delta$ have a $K_{\Delta+2}$ minor? I think no. It has a clique of order $\Delta+1$. But, I dont think that deleting a few edges a …
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  • 2,089
1 vote
1 answer
69 views

A different version of list coloring

Consider a non-regular bipartite graph $G$ . We consider list edge coloring the edges of the graph by giving lists of cardinality $max(deg(v_i),deg(v_j))+2$ for each edge $e=v_iv_j$ where $deg(v_i)$ d …
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  • 2,089
1 vote
0 answers
112 views

If choosability of complement is known, can the choosability of the graph be known?

Suppose, we know that $G$ is a regular graph of odd order that is $k$- edge choosable, where $k$ is the degree. Then, is it true that $\overline{G}$ has list edge chromatic number at most $n-k+1$? I t …
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  • 2,089
2 votes
0 answers
111 views

List total chromatic number of complete graphs

Since for an odd integer $n$, a complete graph on $n$ vertices is list-edge-$n$ choosable, and the total chromatic number is $n$, it is easy to see that the list total chromatic number is bounded abov …
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