4
votes
1answer
68 views

On finite 2-groups that whose center is not cyclic

Let $G$ be a finite 2-group such that $\left|\dfrac{G}{Z(G)}\right|=4$, $Z(G)$ is not cyclic and $Z(G)$ has at least one element of order 4. Then prove that there exists an automorphism $\alpha$ of ...
1
vote
1answer
49 views

Commutators Calculus

I was trying to understand the above Corollary but I have a problem, namely why in the second to last line $A_0 \leq \zeta_p(G)$? Any ideas? Definitions By recurrence we define $[x,_0\, y]=x$; ...
5
votes
2answers
60 views

Show finite group is $p$-group given some structure of group

Let $G$ be a finite group. If there exists an $a\in G$ not equal to the identity such that for all $x\in G$,$\phi(x) = axa^{-1}=x^{p+1} $ is an automorphism of $G$ then $G$ is a $p$-group. This is ...
4
votes
1answer
78 views

Finite Group with $n$-automorphism map

If $G$ is a finite group and $\phi(x) = x^{p+1}$ is an automorphism of $G$ with $order(\phi) |p$ then $G$ is a $p$-group...? If the order of $\phi$ is $1$ then $\phi(x) = x = x^{p+1} = x^px ...
0
votes
0answers
28 views

Show that 2 representations are not equivalent and find all the irreducible representations of G.

Show that 2 representations are not equivalent and find all the irreducible representations of $G$. The group $G=T_{16}$ has order 16 and presentation given by $G=\langle a,b : a^8=b^2=1, ...
1
vote
1answer
64 views

Finite $p$-group in which all its maximal subgroups are cyclic

Let $G$ be a finite $p$-group, $|G|=p^n$. Let $M_1,\dots,M_r$ be all the maximal subgroups and suppose they are cyclic. Why is $\Phi(G)\le Z(G)$? $\Phi(G)$ is the Frattini subgroup. I have no idea ...
1
vote
1answer
42 views

On $p$-groups with a unique minimal subgroup

If $G$ is a finite group with a unique minimal subgroup, we know that $|G|=p^n$. I have to prove that if $p\neq2$ then $G$ is cyclic. This is the contest. What I don't understand is the following ...
3
votes
2answers
143 views

Cauchy's Theorem $\#$ of elements order $p$

In the stronger statement of Cauchy's Theorem it states the the number of elements of order $p$ is a multiple of $p$. http://en.wikipedia.org/wiki/Cauchy%27s_theorem_(group_theory)#Proof_2 I noticed ...
3
votes
2answers
38 views

$|G|=p^3$ non abelian $\Longrightarrow\gamma_2(G)\lneq Z(G)$

Let $G$ be a non abelian group of order $p^3$. Hence $c=2$ ($c$ is the nilpotence class of $G$). I'll write down some notation, in order to be clear. Let $Z_0(G):=1$, $Z_1(G)=Z(G)$, $Z_{k+1}(G)$ ...
6
votes
1answer
49 views

Classify $p$-groups in which all groups of the same order are isomorphic

The answer to “Are two subgroups of a finite $p$-group $G$, of the same order, isomorphic?” is definitely no. Such groups are very rare. How rare? Can you classify all finite $p$-groups $G$ such that ...
4
votes
1answer
138 views

Subgroups of abelian $p$-groups

Let $A$ be an Abelian group of prime power order. It can be expressed as a (unique) direct product of cyclic groups of prime power order: $A = \mathbb{Z}_{p^{n_1}} \times \cdots \times ...
3
votes
1answer
112 views

Order and element set of the group with presentation $\langle a,b \;|\; a^9=1, b^3=a^3, [a,b]=a^3\rangle$

If we have a group presentation $G=\langle a,b \;|\; a^9=1, b^3=a^3, [a,b]=a^3\rangle$, how we will get the following values: The order of the group. The elements of the group written in terms of ...
0
votes
1answer
60 views

Sylow subgroups of soluble groups

Suppose $G \leqslant S_p$ acts transitively on $\{1,...,p\}$ for prime $p$. Let $P \leqslant G$ be a Sylow p-subgroup. Is it true that $G$ is soluble <=> $P \triangleleft G$?
0
votes
1answer
105 views

Lower Exponent P Central Series

The lower exponent $p$-central series for a $p$-group $G$ is defined by $G=P_1(G) > P_2(G) > \ldots > P_c(G) = 1$, where $$P_i(G)=[P_{i-1}(G), G] P_{i-1}(G)^p.$$ If $G_i=G/P_i(G)$ and ...
2
votes
0answers
188 views

number of elements of each order in p-groups $Z_{p^n}\rtimes Z_p$ and $Z_{p^n}\times Z_p$ [closed]

Do $p$-groups $\mathbb{Z}_{p^{n}}\rtimes \mathbb{Z}_p$ and $\mathbb{Z}_{p^{n}}\times \mathbb{Z}_p$ have the same number of elements of each order? (The prime $p$ is odd.)
1
vote
1answer
79 views

Classification of automorphism groups of groups of order $p^4$

For the purpose of classifying another algebraic structure which is parametrised by the choice of a group and of an automorphism I need the classification up to isomorphism of automorphism groups of ...
1
vote
1answer
100 views

Nonabelian group of order $p^4$ [closed]

Let $P$ be a nonabelian group of order $p^4$, where $p$ is a prime, and let $A$ be a subgroup of $P$ maximal with the property of being normal and abelian. Prove that $A$ is of order $p^3$. Thanks a ...
1
vote
2answers
63 views

$G$ a finite $p-$group, $H < G$ (i.e, $H$ a subgroup of $G$, but $H \neq G$), prove that $H \neq N_G(H)$ [duplicate]

I have one problem, that I think it's pretty hard to solve. The problem reads: Let $G$ be a finite $p-$group, and $H < G$ (i.e $H \le G$, and $H \neq G$). Prove that $H \neq N_G(H)$. Here are ...
1
vote
0answers
89 views

Orders of Elements in Minimal Generating sets of Abelian p-Groups

I'm looking for as much information about the orders of elements in minimal generating sets of finite abelian $p$-groups as possible. What I really need is complete knowledge about the possible orders ...
3
votes
0answers
61 views

An example where $Z(Z_G(A))$ is not a subset of right Engel elements in a finite $p$-group

Find a counter example to the following statement: Let $G$ be a finite $p$-group such that $G/Z(G)$ has exponent $p$. Let $A$ be a normal abelian maximal subgroup of $G$, and $Z_G(A)$ be the ...
0
votes
1answer
90 views

Without using any Sylow theorem, if every element is a $p$-element then $G$ is a $p$-group

How can we prove the following theorem without using any Sylow theorem? Let $p$ be a prime. In a finite group $G$, if every element is a $p$-element then $G$ is a $p$-group. Or is it possible to ...
7
votes
1answer
969 views

A $p$-group of order $p^n$ has a normal subgroup of order $p^k$ for each $0\le k \le n$

This is problem 3 from Hungerford's section about the Sylow theorems. I have already read hints saying to use induction and that $p$-groups always have non-trivial centres, but I'm still confused. ...
1
vote
0answers
77 views

Lift a group action from a quotient

Let $p$ be a rational prime and $H$ be a finite cyclic group of prime order $l$ prime to $p$, i.e. $(l,p) = 1$. Let $G$ be a finite abelian group of $p$-power order. If I can write an (abelian) group ...
2
votes
1answer
445 views

Subgroups and quotient groups of finite abelian $p$-groups

Motivation The fundamental theorem of finite abelian groups gives us a concise description of the isomorphism types of finite abelian $p$-groups $G$ (in the following, $p$ is a fixed prime). The ...
6
votes
1answer
146 views

Does every $p$-group of odd order admit fixed point free automorphisms?

Does every $p$-group of odd order admit fixed point free automorphisms? equivalently, Given an odd order $p$-group $P$, is there a group $C$ such that we can form a Frobenius group $P\rtimes ...
6
votes
1answer
69 views

Are there asymptotically more nonabelian groups of order $p^k$ than there are abelian groups of order $\leq p^k$?

Let $\alpha(n)$ denote the number of isomorphism classes of abelian groups of order $n$ and $\alpha^\prime(n)=\sum_{m=1}^n\alpha(m)$. Similarly, define $f(p^k)$ to be the number of isomorphism ...
0
votes
0answers
69 views

Extensions of elementary abelian p-groups by themselves.

How many distinct extensions of $C^k_p$ by $C^l_p$ are there where $C^n_p$ is elementary abelian of order $p^n$, p a prime?
7
votes
3answers
2k views

Does every group whose order is a power of a prime p contain an element of order p?

I need to know if every group whose order is a power of a prime $p$ contains an element of order $p$? Should I proceed by picking an element $g$ of the group and proving that there is an element in ...
1
vote
1answer
69 views

Understanding a proof about finite $p$-groups

I can't follow the reasoning of the author,in this proof: let $G$ be a finite $p-$group. If $H$ is a proper subgroup of G, then $H<N_G(H)$ (clearly $N_G(H)$ is the normalizer of $H$ and p is ...
5
votes
2answers
87 views

There is no core free subgroup of order $p^2$ in a group of order $p^4$

By the classification of group of order $p^4$ ($p$ odd prime) from Burnside's book it seems to me that there is no core free subgroup of order $p^2$ in a group of order $p^4$. If I am not wrong there ...
4
votes
1answer
106 views

Nilpotency class of normal product of dihedral 2-groups

Pessimistically paraphrasing Polya: “if Jack cannot answer a question, there is an easier question Jack also cannot answer.” Hence I ask: Given positive integers $a,b$ describe the set $$N_{a,b} = ...
4
votes
1answer
191 views

Existence of a normal subgroup in a finite group.

Let $G$ be a finite group. If a Sylow $p$-subgroup $P$ of $G$ is contained in the centre, then does there exist a normal subgroup $N$ of $G$, such that $P \cap N = \{e\}$ and $PN=G$? Thanks in ...
2
votes
1answer
222 views

Order of automorphism group of a $p$-group is divisible by $p$.

Suppose $G$ is a finite $p$-group (where $p$ is prime), so that $|G|=p^n$ for some positive integer $n\ge 2$. How can we prove that $|\text{Aut}(G)|$ is divisible by $p$? Here $\text{Aut}(G)$ ...
0
votes
0answers
129 views

Two questions on p-groups

I would like to ask two questions. Kindly help me in this regard: (1) In Finite p-group with a cyclic frattini subgroup., user28083 has given finite $p$-group with cyclic frattini subgroup. I need ...
2
votes
1answer
114 views

A group of order 16 has a normal subgroup of order 4

Let $ G$ be a group of order $16$. Show that $G$ must contain a normal subgroup $H$ of order $4$. I tried the Sylow first theorem, that is $\{e\}\triangleleft H_1\triangleleft H_2\triangleleft ...
6
votes
1answer
62 views

Definition of $\Omega$-group and $\Omega$-composition series

What are the definitions of $\Omega$-group and $\Omega$-composition series? No luck searching on the internet..
1
vote
1answer
83 views

Why are regular $p$-groups called “regular?”

In the concept of regular $p$-Groups, what does "regularity" stand for? What is "regular" in such groups? I would like to know idea behind defining these groups, and naming these groups "regular." ...
6
votes
1answer
223 views

Why are there so many groups (up to isomorphism) of order $p^n$ for $n>2$, especially when compared to groups of similar sized order?

While bounds on the number of isomorphism classes of groups of order $p^n$ where $p$ is prime have been known for quite a while (such as the work of Higman$^{[1]}$ and Sims$^{[2]}$) which give us the ...
6
votes
1answer
114 views

On $2$-groups with a property

If $G$ is a non-abelian $p$-group ($p>2$) such that any two maximal cyclic subgroups have trivial intersection, then $G$ is of exponent $p$ (see "Groups of Prime Power Order-1"- Berkovich, Exer. 2, ...
8
votes
2answers
233 views

Known bounds for the number of groups of a given order.

The number of nonisomorphic groups of order $n$ is usually called $\nu(n)$. I found a very good survey about the values. $\nu(n)$ is completely known absolutely up to $n=2047$, and for many other ...
1
vote
1answer
195 views

Show that a p-group has a faithful irreducible representation over $\mathbb{C}$ if it has a cyclic center

A p-group is a group of order $p^d$ where p is a prime. If the center has order $p^m$ (since its order must divide the order of the group) then we have a one dimensional faithful irreducible ...
4
votes
2answers
121 views

Finite abelian $2$-group

If $G$ is a finite abelian group such that $o(x)=2$ for all $x \neq e$ and $|G|=2^n$ for some $n\in\mathbb N$, prove that $G \cong \mathbb{Z}_2\times\cdots\times\mathbb{Z}_2$ ($n$ factors). Any ...
3
votes
2answers
135 views

Rotman's Introduction to to the theory of groups. Exercise 3.45.

Can you give me a hint on the first part of the exercise? Let $p$ be a prime and let $X$ be a finite $G$-set, where $|G| = p^n$ and $|X|$ is not divisible by $p$. Prove that there exists $x \in X$ ...
2
votes
2answers
149 views

$H$ must contain every Sylow $p$-subgroup of $G$

Let $p$ be a prime factor of the order of a finite group $G$. If $H$ is a normal subgroup $G$ whose index is not a multiple of $p$, show that $H$ must contain every Sylow $p$-subgroup of $G$.
1
vote
0answers
92 views

Generators in $p$-groups

Let $G$ be a non-abelian finite $p$-group such that $G/[G,G]$ is elementary abelian group of order at least $p^3$. Let $S=\{\bar{x_1},\bar{x_2},\bar{x}_3,\cdots,\bar{x}_n\}$ be independent generators ...
2
votes
2answers
86 views

$G$ $p$-group. If $H\triangleleft G$, then $H\cap C(G)\ne \{e\}$

I'm pretty new on this subject and I need a hint to begin to solve this question: If $G$ is a finite p-group, $H\triangleleft G$ and $H\ne \{e\}$, then $H\cap C(G)\ne \{e\}$ Thanks for any ...
1
vote
3answers
110 views

If H is a p-group, the order of any H-orbit is a power of p.

This comes from the proof of the third Sylow Theorem in Michael Artin's "Algebra". Let S be the set of Sylow p-groups in a given group G of order $p^em$. Let H be any Sylow group. If we decompose S ...
1
vote
4answers
79 views

How do I show that $N\leqslant Z(G)$ without using Sylow theorems?

Let $G$ be a group of order $p^2$ ($p$ being a prime) and $N$ be a normal subgroup of $G$ such that $O(N)=p.$ Without using the fact any group of order $p^2$ is abelian or sylow theorem how to show ...
6
votes
2answers
278 views

What are central automorphisms used for?

A central automorphism is an automorphism $\theta$ for which $x^{-1}\theta(x)\in Z(G)$ for each $x\in G$. It's not difficult to prove that the set of central automorphisms forms a subgroup of ...
3
votes
5answers
293 views

Any group of order $2p$ has a subgroup of order $p~$($p$ being a prime)

I want to show without using Sylow theorem that Any group of order $2p$ has a subgroup of order $p~$($p$ being a prime) My attempt: Since $|G|=2p,$ even $\exists~a\neq e\in G$ such that ...