Subgroup of Sym(n) Isomorphic to S_(n-1) Except n=6

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In summary, the conversation discusses the proof of any subgroup of S_n isomorphic to S_(n-1) fixing a point in {1, 2,..., n} unless n=6. The person has tried defining a map and taking a subgroup, but is still unsure how to prove it. They consider a second approach but realize it is not correct and mention the correct statement they want to prove.
  • #1
dimuk
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I need a proof of any subgroup of S_n which is isomorphic to S_(n-1) fixes a point in {1, 2,..., n} unless n=6.
 
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  • #2
the standard answer: what have you tried?
 
  • #3
I defined a map psi: S_n to S_(n-1) and took a subgroup H={pi \in S_n | pi(n)=n}. And proved that H is a subgroup of S_n, but I want to prove that which is isomorphic to S_(n-1) and fixes a point in {1, 2..., } unless n=6.

I thought to prove this

If X is isomorphic to S_n and Y is isomorphic to X with |X:Y|=n then Y is isomorphic to S_(n-1).

But still I don't know how to prove.
 
  • #4
No that second one is not correct.
 
  • #5
I should proof this

If n \neq 6 then any subgroup Y of S_n with |S_n:Y|=n actually fixes a point..?
 

Related to Subgroup of Sym(n) Isomorphic to S_(n-1) Except n=6

1. What is the definition of "Subgroup of Sym(n) Isomorphic to S_(n-1) Except n=6"?

This refers to a subgroup of the symmetric group on n elements (Sym(n)) that is isomorphic (structurally equivalent) to the symmetric group on (n-1) elements (S_(n-1)), with the exception of when n=6.

2. Why is this particular subgroup of Sym(n) important?

This subgroup is important because it has unique properties that make it different from other subgroups of Sym(n). In particular, it has a special relationship with the symmetric group on (n-1) elements, making it a useful tool in understanding and studying group theory.

3. How is the subgroup of Sym(n) isomorphic to S_(n-1) except n=6 constructed?

The subgroup is constructed by taking the elements of Sym(n) that fix the last element (n) and removing the element that swaps the first and last elements, which creates a subgroup isomorphic to S_(n-1).

4. What implications does this subgroup have on the structure of Sym(n)?

This subgroup reveals that there is a unique relationship between Sym(n) and S_(n-1), as seen by their isomorphism. It also shows that the symmetric group on 6 elements (Sym(6)) is different from other symmetric groups.

5. How is this subgroup relevant to real-world applications?

While this subgroup may not have direct applications in the real world, it is a fundamental concept in group theory and has implications for understanding the structure and properties of groups. This can have applications in fields such as physics, cryptography, and computer science.

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