Is f a Surjective and Injective Isomorphism from HxN to HN in G?

  • Thread starter mathmajor2013
  • Start date
  • Tags
    Isomorphism
In summary, we have a group G with normal subgroups H and N, where the intersection of H and N is only the identity element. The direct product of H and N, denoted as H x N, is isomorphic to the subgroup HN of G under the mapping f((h,n))=hn, where h∈H and n∈N. This can be proven by showing that f is both surjective and injective.
  • #1
mathmajor2013
26
0
Let G be a group, H a normal subgroup, N a normal subgroup, and H intersect N = {e}. Let H x N be the direct product of H and N. Prove that f: HxN->G given by f((h,n))=hn is an isomorphism from HxN to the subgroup HN of G.
Hint: For all h in H and n in N, hn=nh.
 
Physics news on Phys.org
  • #2
This looks a lot like a homework/coursework question. This really should belong there instead of the main forums...

To the point: what have you tried already?
 
  • #3
I am confused how to start this problem. To first show it is a homomorphism, is f((h,n)(h',n'))=f((hh',nn'))?
 
  • #4
mathmajor2013 said:
I am confused how to start this problem. To first show it is a homomorphism, is f((h,n)(h',n'))=f((hh',nn'))?

Yes, that step is already correct. Now apply the definition of f...
 
  • #5
Right the homomorphism part is easy now. Am I able to use the pigeonhole principle for the isomorphic part? That is, are HxN and HN the same size? It seems like they are since H intersect N is only the identity.
 
  • #6
It might be tricky to see that they are thesame size. Isn't easier to show that f is surjective and injective?
 

1. What are Isomorphism Theorems?

The Isomorphism Theorems are a set of mathematical theorems that describe the relationship between groups, rings, and vector spaces. These theorems show that some structures are fundamentally the same, even though they may appear to be different at first glance.

2. How many Isomorphism Theorems are there?

There are three Isomorphism Theorems – the first, second, and third – that are commonly studied in mathematics. However, there are also other variations and special cases of these theorems that can be derived.

3. What is the main application of Isomorphism Theorems?

The main application of Isomorphism Theorems is in algebra, where they are used to study and classify different algebraic structures. They are also used in other branches of mathematics, such as topology and geometry, to understand the underlying relationships between different mathematical objects.

4. What is the significance of Isomorphism Theorems?

The significance of Isomorphism Theorems lies in their ability to simplify and generalize mathematical structures. They allow mathematicians to focus on the essential properties of a given structure, rather than getting bogged down in its specific details. This makes it easier to study and understand complex mathematical objects.

5. How are Isomorphism Theorems related to homomorphisms?

Isomorphism Theorems are related to homomorphisms in that they both involve the concept of structure-preserving maps between mathematical objects. A homomorphism is a map that preserves the algebraic structure of a given object, while an isomorphism is a bijective homomorphism, meaning it is both one-to-one and onto. The Isomorphism Theorems provide a framework for understanding and classifying such structure-preserving maps.

Similar threads

  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
7
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
811
  • Calculus and Beyond Homework Help
Replies
11
Views
3K
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
19
Views
3K
  • Calculus and Beyond Homework Help
Replies
3
Views
2K
  • Calculus and Beyond Homework Help
Replies
5
Views
2K
  • Calculus and Beyond Homework Help
Replies
7
Views
952
Back
Top