Proving converse of fundamental theorem of cyclic groups

Click For Summary

Homework Help Overview

The discussion revolves around a proof concerning finite abelian groups and their subgroups, specifically addressing the conditions under which such a group is cyclic. The original poster presents a statement that requires proving that a finite abelian group with one subgroup of order d for every divisor d of its order must be cyclic.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the implications of the subgroup structure in finite abelian groups, questioning the original statement and its assumptions. There is a focus on the necessity of having exactly one subgroup of each order, as highlighted by examples that challenge the initial understanding.

Discussion Status

The discussion is ongoing, with participants actively questioning the clarity of the problem statement and exploring the implications of subgroup counts. Some guidance has been offered regarding the interpretation of the subgroup condition, but no consensus has been reached yet.

Contextual Notes

Participants note that the example of the group C_2 x C_2 illustrates a case where multiple subgroups exist for certain orders, which raises questions about the validity of the original claim regarding subgroup uniqueness.

curiousmuch
Messages
7
Reaction score
0

Homework Statement


If G is a finite abelian group that has one subgroup of order d for every divisor d of the order of G. Prove that G is cyclic.


Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
Post what you've done on this problem please.
 
Can you check the question. C_2 x C_2 has subgroups of orders 1,2 and 4, but is not cyclic.
 
matt grime said:
Can you check the question. C_2 x C_2 has subgroups of orders 1,2 and 4, but is not cyclic.

I think the point is that it is supposed to have ONE subgroup of each order. Your example has several subgroups of order 2.
 
And that's why we have the word 'exactly'.
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
5
Views
3K
Replies
17
Views
8K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 1 ·
Replies
1
Views
3K