Every infinite cyclic group has non-trivial proper subgroups

In summary, the conversation discusses the existence of non-trivial proper subgroups in infinite cyclic groups. It is noted that while finite cyclic groups only have such subgroups if their order is not prime, it is unclear how this argument applies to infinite groups. The difference between infinite and finite cyclic groups is explained as the lack of an integer n for which a^n=e, where a is an element of the group besides e. An example of an infinite cyclic group is given, and the definition of a non-trivial subgroup is discussed. The conversation ends by exploring the potential subgroups that could exist within an infinite cyclic group.
  • #1
Mr Davis 97
1,462
44

Homework Statement


Every infinite cyclic group has non-trivial proper subgroups

Homework Equations

The Attempt at a Solution


I know that if we have a finite cyclic group, it only has non-trivial proper subgroups if the order of the group is not prime. But I'm not sure how to make this argument with infinite groups
 
Physics news on Phys.org
  • #2
What is a infinite cyclic group and how does it differ from a finite one?
 
  • #3
fresh_42 said:
What is a infinite cyclic group and how does it differ from a finite one?
Doesn't it differ by the fact that there exists no integer ##n## for which ##a^n=e##, where ##a## is an element of the group besides e, the neutral element?
 
  • #4
Mr Davis 97 said:
Doesn't it differ by the fact that there exists no integer ##n## for which ##a^n=e##, where ##a## is an element of the group besides e, the neutral element?
Yes. So we have ##C = \langle a^n\,\vert \,n \in \mathbb{Z} \rangle = \{\ldots , a^{-2},a^{-1},e,a,a^2,\ldots\}##.
Non-trivial subgroup ##U## means ##\{e\}\subsetneq U \subsetneq C##.
So what can we conclude from ##\{e\}\subsetneq U##?
What could be a subgroup?
 

Related to Every infinite cyclic group has non-trivial proper subgroups

1. What is an infinite cyclic group?

An infinite cyclic group is a mathematical structure that consists of a set of elements and a binary operation that follows the properties of closure, associativity, identity, and invertibility. It is generated by a single element, and the group can be infinitely generated by repeatedly applying the binary operation to the generator.

2. What does it mean for a group to be "infinite" and "cyclic"?

An infinite group means that it contains an infinite number of elements, while a cyclic group means that it is generated by a single element and all other elements of the group can be expressed as powers of that element.

3. Why is it important for an infinite cyclic group to have non-trivial proper subgroups?

If an infinite cyclic group does not have any non-trivial proper subgroups, it means that the group is simple, which can make it difficult to study or apply in certain mathematical contexts. Non-trivial proper subgroups provide a way to break down the group into smaller, more manageable parts.

4. Can you provide an example of an infinite cyclic group with non-trivial proper subgroups?

One example of an infinite cyclic group with non-trivial proper subgroups is the group of integers under addition, denoted as ℤ. The subgroups of this group include the set of even integers, the set of multiples of 3, and the set of multiples of any integer.

5. How does the fact that every infinite cyclic group has non-trivial proper subgroups relate to other mathematical concepts?

The fact that every infinite cyclic group has non-trivial proper subgroups is related to the concept of group factorization, where a group can be broken down into smaller subgroups. It also relates to the study of group theory and its applications in various fields such as cryptography, physics, and computer science.

Similar threads

  • Calculus and Beyond Homework Help
Replies
9
Views
1K
  • Calculus and Beyond Homework Help
Replies
1
Views
4K
  • Calculus and Beyond Homework Help
Replies
1
Views
3K
  • Calculus and Beyond Homework Help
Replies
5
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
2K
  • Calculus and Beyond Homework Help
Replies
11
Views
3K
  • Calculus and Beyond Homework Help
Replies
4
Views
2K
  • Calculus and Beyond Homework Help
Replies
5
Views
2K
Back
Top