Questions tagged [cyclic-groups]
Use with the (group-theory) tag. A group is cyclic if it can be generated by a single element. That is to say, every element in a cyclic group can be written as some specified element to a power.
2,297 questions
3 votes
0 answers
51 views
For which $n$ and $k$ does there exist a "cursed" centrifuge arrangement?
For background, say that a centrifuge has $n$ slots arranged in a circle and $k$ tubes are placed within it. This is equivalent to choosing $k$ distinct $n$-th roots of unity. The centrifuge is ...
-1 votes
1 answer
222 views
Could a countable direct product of countable cyclic groups be cyclic? [closed]
I would like to know if it's possibile that a countable direct product of countable cyclic group could be even cyclic: here is proved that this could be for finite product (and so a finite direct sum, ...
0 votes
0 answers
21 views
Orbits of a cyclic group on words of length $L$ with alphabet of size $k$ [duplicate]
Consider an alphabet $\Sigma$ of size $k=|\Sigma|$ and the set of words $\Sigma^L$ of length $L$, with the natural action of the cyclic group $\mathbb{Z}_L$ with generator $\tau$ acting naturally as $\...
0 votes
1 answer
66 views
Subgroup of permutations whose elements are products of $k$-cycles
Let $S_n$ be the symmetric group on $n$ elements, and let $n=r\times s$. I've come across a subgroup $H\le S_n$ whose (non-identity) elements are all the product of $s$ disjoint $r$-cycles. I want to ...
1 vote
0 answers
104 views
Prove that all the roots of an irreducible polynomial over $\mathbb{Q}$ of degree 3 with a cyclic Galois group are real
Problem: Prove that all the roots of an irreducible polynomial over $\mathbb{Q}$ of degree 3 with a cyclic Galois group are real. I know this question has already been asked here, however, I want to ...
1 vote
0 answers
117 views
Determine visually if a finite group generated by cycles is cyclic. [closed]
Consider a subgroup $G$ of the permutation group $S_n$ generated by cycles $G=\langle c_1,\ldots, c_n\rangle$. I draw the points of the group as points in the plane and each cycle is drawn in a ...
2 votes
2 answers
140 views
Why can’t $C_4$, $C_6$, or $C_{15}$ be made into finite fields? [duplicate]
In Visual Group Theory by Nathan Carter (Exercise 10.30), the following question is posed: "Why can the group $C_4$ under addition not be made into a finite field by overlaying a multiplicative ...
3 votes
1 answer
112 views
Calculating orbits of a $C_{2n}$ action.
Consider the set $$ X = \{(x_1,\ldots,x_n,x_1+1,\ldots,x_n+1) : x_i \in \mathbb{F}_2 \text{ for all } 1 \leq i \leq n\} $$ so that the cardinality $|X| = 2^n$. Consider an action of $\mathbb{Z}/2n\...
3 votes
2 answers
140 views
Find elements of order $2$ and $4$ in $Aut(\Bbb Z_{17})$
Describe the elements of order $2$ and $4$ in $Aut(\Bbb Z_{17})$. First we have that $Aut(\Bbb Z_{17})\cong U(17)=\{1,\ldots,16\}=\Bbb Z_{17}^{\ast}$. Then is same find elements of same order in that ...
0 votes
1 answer
176 views
Is there a graph-theoretic proof that $(\mathbb Z/5\mathbb Z)^\times$ is cyclic?
Let $p$ be a prime. The group $(Z/p\mathbb Z)^\times$ acts by automorphisms on $\mathbb Z/p\mathbb Z$, with orbits $\{0\}$ and $X:=\{1,\dots,p-1\}$. Let $\varphi$ be the action. This means that, for ...
2 votes
1 answer
162 views
Inconsistency between a regular action by automorphisms and non-cyclicality
Let $p$ be a prime. Quite tautologically, $G=\operatorname{Aut}(C_p)$ acts by automorphisms on $\mathbb Z/p\mathbb Z$, with orbits $\{0\}$ and $X:=\{1,\dots,p-1\}$. Let $\varphi$ be the action. This ...
3 votes
1 answer
101 views
Generators of Subgroups of Cyclic Groups: $\gcd(n,b)=\gcd(n,a)$ vs $\gcd(t,d)=1.$
Fix $n\in\mathbb{N}.$ Let $Z_n$ be the cyclic group of order $n.$ Say $Z_n=\langle x\rangle.$ Let $H≤Z_n.$ It is known that $H$ is cyclic. What are the generators of $H?$ There are two approaches I ...
0 votes
1 answer
106 views
If $G$ is a group of order $1443$, must $G'$ be cyclic
Let $G$ be a group of order $1443$. I want to show that $G'$ (the commutator subgroup of $G$) is cyclic. I attempted to analyze the structure of $G$ using its Sylow subgroups. Since $1443 = 3 \cdot 13 ...
0 votes
3 answers
102 views
Epimorphisms and Sylow groups
I'm a bit confused on a question from a previous exam. It goes as follows: Let $G$ be a finite group such as there is an epimorphism $\phi: G\to \mathbb{Z}_2\times\mathbb{Z}_2\times\mathbb{Z}_3$. ...
1 vote
1 answer
107 views
Help needed in understanding the proof of Proposition 6 in the book, "Abstract Algebra " by Dummit and Foote
I was reading Abstract Algebra by Dummit and Foote. There was a portion of text in the book( on Section 5.2, p-163) which I didn't understand. It went on like this: Proposition 6. Let $m, n \in \...