Group Theory inner automorphism

In summary, the inner automorphisms of a group isomorphic to S3 is the same, but it's difficult to figure out which inner automorphism is unique for a given element.
  • #1
Lee33
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Homework Statement

How do I prove that the inner automorphisms is isomorphic to ##S_3##?


The attempt at a solution

I know ##S_3 = \{f: \{ 1,2,3 \}\to\{ 1,2,3 \}\mid f\text{ is a permutation}\}## and I know for every group there is a map whose center is its kernel so the center of of ##S_3## is trivial therefore ##S_3/Z(S_3) = 6##.

So an inner automorphism of a group ##G## is an automorphism of the form ##ρ_g :x↦gxg^{-1}. ## What I am having trouble with is verifying that distinct elements of ##S_3## give distinct inner automorphism. How can I prove this problem directly?
 
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  • #2
The inner automorphisms of what are supposed to be isomorphic to S3?
 
  • #3
Lee33 said:
Homework Statement

How do I prove that the inner automorphisms is isomorphic to ##S_3##?


The attempt at a solution

I know ##S_3 = \{f: \{ 1,2,3 \}\to\{ 1,2,3 \}\mid f\text{ is a permutation}\}## and I know for every group there is a map whose center is its kernel so the center of of ##S_3## is trivial therefore ##S_3/Z(S_3) = 6##.

So an inner automorphism of a group ##G## is an automorphism of the form ##ρ_g :x↦gxg^{-1}. ## What I am having trouble with is verifying that distinct elements of ##S_3## give distinct inner automorphism. How can I prove this problem directly?

Can you prove that if [itex]\rho_g = \rho_h[/itex] then [itex]g^{-1}h \in Z(G)[/itex]?
 
  • #4
Opps, I forgot to add the inner automorphism of ##S_3## is isomorphic to ##S_3.## Sorry for the confusion!

Pasmith - Can you elaborate please?
 
  • #5
Lee33 said:
Opps, I forgot to add the inner automorphism of ##S_3## is isomorphic to ##S_3.## Sorry for the confusion!

Pasmith - Can you elaborate please?

There's no need to elaborate. pasmith pretty much spelled it out. Try to prove the hint he gave you. Once you've done that figure out what the center of ##S_3## is. It should click easily after that.
 
Last edited:

1. What is an inner automorphism in Group Theory?

An inner automorphism is a type of automorphism in Group Theory where the group elements are mapped to themselves by an inner operation. This means that the inner automorphism is an operation performed within the group itself, rather than involving an external element.

2. How is an inner automorphism different from an outer automorphism?

An outer automorphism involves mapping group elements to different elements outside of the group, while an inner automorphism maps the group elements to themselves. In other words, an inner automorphism preserves the structure of the group, while an outer automorphism does not.

3. What is the significance of inner automorphisms in Group Theory?

Inner automorphisms play a crucial role in understanding the structure and properties of a group. They are often used to prove theorems and identify certain properties of groups, such as normality and conjugacy.

4. How are inner automorphisms related to conjugation in Group Theory?

Inner automorphisms and conjugation are closely related concepts. In fact, every inner automorphism is a conjugation, and every conjugation can be viewed as an inner automorphism. This relationship is important in understanding the concept of conjugacy classes in groups.

5. Can you give an example of an inner automorphism in a specific group?

One example of an inner automorphism is in the group of 2x2 invertible matrices, known as GL(2). Let A be a matrix in GL(2), and define an inner automorphism by conjugation with A. This means that for any matrix B in GL(2), the inner automorphism maps B to ABA-1. This operation preserves the structure of the group, and is an example of an inner automorphism.

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