Degree or valency of a Cayley graph












1














Let $G$ be a group and $S subseteq G$ be a generating set of $G$.



The Cayley digraph of $G$ with respect
to $S$, $X=overrightarrow {operatorname{Cay}}(G, S)$ is a graph whose vertices are the elements of $G$ and there is an edge from $g$ to $gs$
whenever $g in G$ and $s in S$.



The Cayley graph, $X = operatorname{Cay}(G, S)$ is the undirected graph whose vertices
are the elements of $G$ and there is an edge from $g$ to $gs$ and from $g$ to $gs^{-1}$ whenever $g in G$ and $s in S$.



In a group, an element of order $2$ is known as an "involution". i.e. a non-identity element
whose square is the identity element.



So by thinking about the above definitions I have written the following about the degree of a Cayley graph, $X=operatorname{Cay}(G,S)$ of a group $G$, with respect to a generator set $S$:



"$deg(X)= 2vert S vert $, if $S$ has elements which are not involutions"



I would like to know whether above sentence is correct. Is it ok, to mention as "$S$ has elements which are not involutions"?










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  • You asked this in the group theory chatroom. However, in order to avoid downvotes on this question or having it closed, please edit it to include more context, such as why the question is interesting to you, where it arose, and what you have done to solve it yourself :)
    – Shaun
    Dec 26 '18 at 19:29






  • 1




    Ok, thanks @Shaun :) :)
    – Buddhini Angelika
    Dec 27 '18 at 8:53










  • After you ask a question here, if you get an acceptable answer, you should "accept" the answer by clicking the check mark $checkmark$ next to it. This scores points for you and for the person who answered your question. You can find out more about accepting answers here: How do I accept an answer?, Why should we accept answers?, What should I do if someone answers my question?.
    – Shaun
    Dec 27 '18 at 9:12










  • Thank you @Shaun :) :)
    – Buddhini Angelika
    Dec 28 '18 at 10:46
















1














Let $G$ be a group and $S subseteq G$ be a generating set of $G$.



The Cayley digraph of $G$ with respect
to $S$, $X=overrightarrow {operatorname{Cay}}(G, S)$ is a graph whose vertices are the elements of $G$ and there is an edge from $g$ to $gs$
whenever $g in G$ and $s in S$.



The Cayley graph, $X = operatorname{Cay}(G, S)$ is the undirected graph whose vertices
are the elements of $G$ and there is an edge from $g$ to $gs$ and from $g$ to $gs^{-1}$ whenever $g in G$ and $s in S$.



In a group, an element of order $2$ is known as an "involution". i.e. a non-identity element
whose square is the identity element.



So by thinking about the above definitions I have written the following about the degree of a Cayley graph, $X=operatorname{Cay}(G,S)$ of a group $G$, with respect to a generator set $S$:



"$deg(X)= 2vert S vert $, if $S$ has elements which are not involutions"



I would like to know whether above sentence is correct. Is it ok, to mention as "$S$ has elements which are not involutions"?










share|cite|improve this question
























  • You asked this in the group theory chatroom. However, in order to avoid downvotes on this question or having it closed, please edit it to include more context, such as why the question is interesting to you, where it arose, and what you have done to solve it yourself :)
    – Shaun
    Dec 26 '18 at 19:29






  • 1




    Ok, thanks @Shaun :) :)
    – Buddhini Angelika
    Dec 27 '18 at 8:53










  • After you ask a question here, if you get an acceptable answer, you should "accept" the answer by clicking the check mark $checkmark$ next to it. This scores points for you and for the person who answered your question. You can find out more about accepting answers here: How do I accept an answer?, Why should we accept answers?, What should I do if someone answers my question?.
    – Shaun
    Dec 27 '18 at 9:12










  • Thank you @Shaun :) :)
    – Buddhini Angelika
    Dec 28 '18 at 10:46














1












1








1


1





Let $G$ be a group and $S subseteq G$ be a generating set of $G$.



The Cayley digraph of $G$ with respect
to $S$, $X=overrightarrow {operatorname{Cay}}(G, S)$ is a graph whose vertices are the elements of $G$ and there is an edge from $g$ to $gs$
whenever $g in G$ and $s in S$.



The Cayley graph, $X = operatorname{Cay}(G, S)$ is the undirected graph whose vertices
are the elements of $G$ and there is an edge from $g$ to $gs$ and from $g$ to $gs^{-1}$ whenever $g in G$ and $s in S$.



In a group, an element of order $2$ is known as an "involution". i.e. a non-identity element
whose square is the identity element.



So by thinking about the above definitions I have written the following about the degree of a Cayley graph, $X=operatorname{Cay}(G,S)$ of a group $G$, with respect to a generator set $S$:



"$deg(X)= 2vert S vert $, if $S$ has elements which are not involutions"



I would like to know whether above sentence is correct. Is it ok, to mention as "$S$ has elements which are not involutions"?










share|cite|improve this question















Let $G$ be a group and $S subseteq G$ be a generating set of $G$.



The Cayley digraph of $G$ with respect
to $S$, $X=overrightarrow {operatorname{Cay}}(G, S)$ is a graph whose vertices are the elements of $G$ and there is an edge from $g$ to $gs$
whenever $g in G$ and $s in S$.



The Cayley graph, $X = operatorname{Cay}(G, S)$ is the undirected graph whose vertices
are the elements of $G$ and there is an edge from $g$ to $gs$ and from $g$ to $gs^{-1}$ whenever $g in G$ and $s in S$.



In a group, an element of order $2$ is known as an "involution". i.e. a non-identity element
whose square is the identity element.



So by thinking about the above definitions I have written the following about the degree of a Cayley graph, $X=operatorname{Cay}(G,S)$ of a group $G$, with respect to a generator set $S$:



"$deg(X)= 2vert S vert $, if $S$ has elements which are not involutions"



I would like to know whether above sentence is correct. Is it ok, to mention as "$S$ has elements which are not involutions"?







abstract-algebra group-theory graph-theory finite-groups cayley-graphs






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edited Dec 27 '18 at 9:13









Shaun

8,711113680




8,711113680










asked Dec 26 '18 at 17:36









Buddhini Angelika

15710




15710












  • You asked this in the group theory chatroom. However, in order to avoid downvotes on this question or having it closed, please edit it to include more context, such as why the question is interesting to you, where it arose, and what you have done to solve it yourself :)
    – Shaun
    Dec 26 '18 at 19:29






  • 1




    Ok, thanks @Shaun :) :)
    – Buddhini Angelika
    Dec 27 '18 at 8:53










  • After you ask a question here, if you get an acceptable answer, you should "accept" the answer by clicking the check mark $checkmark$ next to it. This scores points for you and for the person who answered your question. You can find out more about accepting answers here: How do I accept an answer?, Why should we accept answers?, What should I do if someone answers my question?.
    – Shaun
    Dec 27 '18 at 9:12










  • Thank you @Shaun :) :)
    – Buddhini Angelika
    Dec 28 '18 at 10:46


















  • You asked this in the group theory chatroom. However, in order to avoid downvotes on this question or having it closed, please edit it to include more context, such as why the question is interesting to you, where it arose, and what you have done to solve it yourself :)
    – Shaun
    Dec 26 '18 at 19:29






  • 1




    Ok, thanks @Shaun :) :)
    – Buddhini Angelika
    Dec 27 '18 at 8:53










  • After you ask a question here, if you get an acceptable answer, you should "accept" the answer by clicking the check mark $checkmark$ next to it. This scores points for you and for the person who answered your question. You can find out more about accepting answers here: How do I accept an answer?, Why should we accept answers?, What should I do if someone answers my question?.
    – Shaun
    Dec 27 '18 at 9:12










  • Thank you @Shaun :) :)
    – Buddhini Angelika
    Dec 28 '18 at 10:46
















You asked this in the group theory chatroom. However, in order to avoid downvotes on this question or having it closed, please edit it to include more context, such as why the question is interesting to you, where it arose, and what you have done to solve it yourself :)
– Shaun
Dec 26 '18 at 19:29




You asked this in the group theory chatroom. However, in order to avoid downvotes on this question or having it closed, please edit it to include more context, such as why the question is interesting to you, where it arose, and what you have done to solve it yourself :)
– Shaun
Dec 26 '18 at 19:29




1




1




Ok, thanks @Shaun :) :)
– Buddhini Angelika
Dec 27 '18 at 8:53




Ok, thanks @Shaun :) :)
– Buddhini Angelika
Dec 27 '18 at 8:53












After you ask a question here, if you get an acceptable answer, you should "accept" the answer by clicking the check mark $checkmark$ next to it. This scores points for you and for the person who answered your question. You can find out more about accepting answers here: How do I accept an answer?, Why should we accept answers?, What should I do if someone answers my question?.
– Shaun
Dec 27 '18 at 9:12




After you ask a question here, if you get an acceptable answer, you should "accept" the answer by clicking the check mark $checkmark$ next to it. This scores points for you and for the person who answered your question. You can find out more about accepting answers here: How do I accept an answer?, Why should we accept answers?, What should I do if someone answers my question?.
– Shaun
Dec 27 '18 at 9:12












Thank you @Shaun :) :)
– Buddhini Angelika
Dec 28 '18 at 10:46




Thank you @Shaun :) :)
– Buddhini Angelika
Dec 28 '18 at 10:46










1 Answer
1






active

oldest

votes


















2














The answer may depend on definitions of a Cayley graph and vertex degree. Namely, if we consider the directed Cayley graph then in-degree of its each vertex equals to its out-degree and equals to $|S|$. If we consider the undirected Cayley graph then we assume that $S$ is symmetric and without the identity ${e}$ and then degree of its each vertex equals $|S|$.






share|cite|improve this answer





















  • Thanks @AlexRavsky I have added more details to the question as instructed. Do you think it's correct to mention about involutions ?
    – Buddhini Angelika
    Dec 27 '18 at 8:35










  • @BuddhiniAngelika According to the given definition of ${operatorname{Cay}}(G, S)$ degree of any its vertex is $2|S|-|S_i|$, where $S_i={gin S: g$ is an involution$}$. In particular, if $S$ contains no involutions then degrere of each vertex of ${operatorname{Cay}}(G, S)$ is $2|S|$.
    – Alex Ravsky
    Dec 27 '18 at 8:55








  • 1




    Thank you very much @AlexRavsky
    – Buddhini Angelika
    Dec 28 '18 at 2:58











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1 Answer
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active

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1 Answer
1






active

oldest

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active

oldest

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active

oldest

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2














The answer may depend on definitions of a Cayley graph and vertex degree. Namely, if we consider the directed Cayley graph then in-degree of its each vertex equals to its out-degree and equals to $|S|$. If we consider the undirected Cayley graph then we assume that $S$ is symmetric and without the identity ${e}$ and then degree of its each vertex equals $|S|$.






share|cite|improve this answer





















  • Thanks @AlexRavsky I have added more details to the question as instructed. Do you think it's correct to mention about involutions ?
    – Buddhini Angelika
    Dec 27 '18 at 8:35










  • @BuddhiniAngelika According to the given definition of ${operatorname{Cay}}(G, S)$ degree of any its vertex is $2|S|-|S_i|$, where $S_i={gin S: g$ is an involution$}$. In particular, if $S$ contains no involutions then degrere of each vertex of ${operatorname{Cay}}(G, S)$ is $2|S|$.
    – Alex Ravsky
    Dec 27 '18 at 8:55








  • 1




    Thank you very much @AlexRavsky
    – Buddhini Angelika
    Dec 28 '18 at 2:58
















2














The answer may depend on definitions of a Cayley graph and vertex degree. Namely, if we consider the directed Cayley graph then in-degree of its each vertex equals to its out-degree and equals to $|S|$. If we consider the undirected Cayley graph then we assume that $S$ is symmetric and without the identity ${e}$ and then degree of its each vertex equals $|S|$.






share|cite|improve this answer





















  • Thanks @AlexRavsky I have added more details to the question as instructed. Do you think it's correct to mention about involutions ?
    – Buddhini Angelika
    Dec 27 '18 at 8:35










  • @BuddhiniAngelika According to the given definition of ${operatorname{Cay}}(G, S)$ degree of any its vertex is $2|S|-|S_i|$, where $S_i={gin S: g$ is an involution$}$. In particular, if $S$ contains no involutions then degrere of each vertex of ${operatorname{Cay}}(G, S)$ is $2|S|$.
    – Alex Ravsky
    Dec 27 '18 at 8:55








  • 1




    Thank you very much @AlexRavsky
    – Buddhini Angelika
    Dec 28 '18 at 2:58














2












2








2






The answer may depend on definitions of a Cayley graph and vertex degree. Namely, if we consider the directed Cayley graph then in-degree of its each vertex equals to its out-degree and equals to $|S|$. If we consider the undirected Cayley graph then we assume that $S$ is symmetric and without the identity ${e}$ and then degree of its each vertex equals $|S|$.






share|cite|improve this answer












The answer may depend on definitions of a Cayley graph and vertex degree. Namely, if we consider the directed Cayley graph then in-degree of its each vertex equals to its out-degree and equals to $|S|$. If we consider the undirected Cayley graph then we assume that $S$ is symmetric and without the identity ${e}$ and then degree of its each vertex equals $|S|$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 26 '18 at 21:07









Alex Ravsky

39.2k32080




39.2k32080












  • Thanks @AlexRavsky I have added more details to the question as instructed. Do you think it's correct to mention about involutions ?
    – Buddhini Angelika
    Dec 27 '18 at 8:35










  • @BuddhiniAngelika According to the given definition of ${operatorname{Cay}}(G, S)$ degree of any its vertex is $2|S|-|S_i|$, where $S_i={gin S: g$ is an involution$}$. In particular, if $S$ contains no involutions then degrere of each vertex of ${operatorname{Cay}}(G, S)$ is $2|S|$.
    – Alex Ravsky
    Dec 27 '18 at 8:55








  • 1




    Thank you very much @AlexRavsky
    – Buddhini Angelika
    Dec 28 '18 at 2:58


















  • Thanks @AlexRavsky I have added more details to the question as instructed. Do you think it's correct to mention about involutions ?
    – Buddhini Angelika
    Dec 27 '18 at 8:35










  • @BuddhiniAngelika According to the given definition of ${operatorname{Cay}}(G, S)$ degree of any its vertex is $2|S|-|S_i|$, where $S_i={gin S: g$ is an involution$}$. In particular, if $S$ contains no involutions then degrere of each vertex of ${operatorname{Cay}}(G, S)$ is $2|S|$.
    – Alex Ravsky
    Dec 27 '18 at 8:55








  • 1




    Thank you very much @AlexRavsky
    – Buddhini Angelika
    Dec 28 '18 at 2:58
















Thanks @AlexRavsky I have added more details to the question as instructed. Do you think it's correct to mention about involutions ?
– Buddhini Angelika
Dec 27 '18 at 8:35




Thanks @AlexRavsky I have added more details to the question as instructed. Do you think it's correct to mention about involutions ?
– Buddhini Angelika
Dec 27 '18 at 8:35












@BuddhiniAngelika According to the given definition of ${operatorname{Cay}}(G, S)$ degree of any its vertex is $2|S|-|S_i|$, where $S_i={gin S: g$ is an involution$}$. In particular, if $S$ contains no involutions then degrere of each vertex of ${operatorname{Cay}}(G, S)$ is $2|S|$.
– Alex Ravsky
Dec 27 '18 at 8:55






@BuddhiniAngelika According to the given definition of ${operatorname{Cay}}(G, S)$ degree of any its vertex is $2|S|-|S_i|$, where $S_i={gin S: g$ is an involution$}$. In particular, if $S$ contains no involutions then degrere of each vertex of ${operatorname{Cay}}(G, S)$ is $2|S|$.
– Alex Ravsky
Dec 27 '18 at 8:55






1




1




Thank you very much @AlexRavsky
– Buddhini Angelika
Dec 28 '18 at 2:58




Thank you very much @AlexRavsky
– Buddhini Angelika
Dec 28 '18 at 2:58


















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