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

2 votes
0 answers
119 views

Alon Tarsi reaches its lower bound for complete multipartite graphs

Consider a complete multipartite graph $G$ with $k$ $(k\ge2)$ parts with equal number of vertices $n$, where $n$ is even. If $k=2$, it is a well known result that the Alon-Tarsi number (ATN)(The maxim …
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1 vote
Accepted

Three coloring the elements of symmetric group

Yes, it is possible to $3$-color the elements of the Symmetric group in the way stated. The proof can be found in Theorem 1 of MDPI Symmetry Paper. The proof uses a similar idea given in the comments …
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0 votes
0 answers
50 views

Determining homomorphism using automorphism group of two graphs

I wish to know the connection between the automorphism group of two graphs and homomorphism between them, if any. Like all Kneser graphs $K(n,k)$ have the same automorphism group $S_n$. But, given ano …
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1 vote
1 answer
240 views

Choosing sets with a few properties from a given set of elements

Fix $n$ and $k$ with $n \geq 2k+1$. Let $X$ be an $n$ element set. Let $\binom{X}{k}$ denote the collection of $k$-element subsets of $X$. Suppose that $\mathcal{Y} \subseteq \binom{X}{k}$ is a family …
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0 votes
0 answers
51 views

Kernel perfection in some powers of cycles

Suppose I orient the edges of the power of cycle graph $G=C_n^k$ where $n=16$ and $k=4$ in such a way that all the generated cycles by the elements $1,2,3,4$ are given the standard lexical orientation …
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3 votes
1 answer
100 views

Edge coloring of a graph on alternating groups

Let $G$ be the Cayley graph on the alternating group $A_n\,n\ge4$ with generating set $$S=\begin{cases}\{(1,2,3),(1,3,2),\\(1,2,\ldots,n),(1,n,n-1,\ldots,2)\}, &n\ \text{odd}\\ \{(1,2,3),(1,3,2),\\(2, …
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2 votes

Difference between Alon-Tarsi number and the list chromatic number

Let us consider the graph $K_{n,n}$. Since the graph polynomial of $K_{n,n}$ is homogenous with degree $n^2$, we must have the Alon-Tarsi number of the graph $K_{n,n}$ to be $\ge \frac{n^2}{2n}=\frac{ …
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7 votes
2 answers
415 views

3-coloring the alternating group graph

Consider the alternating group graph, here defined as a Cayley graph on the alternating group $A_n$ using the generating set $\{(1,2,3),(1,2,4),\dotsc,(1,2,n),(1,n,2),\dotsc,(1,4,2),(1,3,2)\}$. Note t …
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0 votes
1 answer
139 views

List coloring as a homomorphism

A proper coloring of the vertices of a graph $G$ is seen as a homomorphism from the graph vertices to the complete graph on the number of vertices equal to the chromatic number of the graph. Similarl …
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1 vote
2 answers
125 views

Difference in chromatic number between Schreier coset graphs and Cayley graphs

Can the Schreier coset graphs can be seen as a subgraph of Cayley graph on the same groups(neglecting the loop edges) and, hence, have their chromatic numbers bounded by the chromatic numbers of the C …
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0 votes
1 answer
113 views

Bound on chromatic number of graphs on any finite $p$-group

Is the chromatic number of a Cayley graph on $p$-groups with any generating set bounded by the chromatic number of the maximal induced circulant subgraph? I think yes. Because for one, the main obstru …
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0 votes
1 answer
85 views

Extending the vertex coloring of circulant graph to graph on $p$-group

Let $G_1$ be a circulant graph of prime order $p$. This implies that $G_1$ is the Cayley graph on $\mathbb{Z}_p$ with some generating set $S_1$. I am interested in knowing the characterizations of the …
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1 vote
0 answers
50 views

Circulant graphs chromatically dominated by powers of cycles

Suppose we can color the vertices of powers of cycles $C_n^k$ using $c$ colors such that each of the color classes $c_i$ have $v_i$ number of vertices. Can we always color the circulant of degree $2k$ …
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7 votes
1 answer
394 views

Three coloring the elements of symmetric group

Is it possible to $3$-color the elements of the symmetric group $S_n\ n\ge3$ such that all color classes have the same number of elements ($\frac{n!}{3}$); and, when elements in any color class are a …
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2 votes
1 answer
185 views

Difference between Alon-Tarsi number and the list chromatic number

The Alon-Tarsi number is the least number $k$ such that the coefficient with degree $d$ of the graph polynomial $P(G)=\prod\limits_{i<j}(x_i-x_j)$,( where $x_i$ corresponds to a vertex and a term $x_i …
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