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#1 2011-02-24 10:54:45

ctmathnut
Member
Registered: 2011-02-24
Posts: 3

Group Theory: Symmetric group and Alternating group

I am in an Abstract Algebra course in graduate school and am trying to prove that the symmetric group S_4 is isomorphic to a subgroup of the alternating group A_6.
I am thinking that I need to find an isomorphism between the two. It is easy to find a map that takes all the even elements of S_4 into A_6, but I am having trouble mapping the odd elements.

Thank you!

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#2 2011-03-06 03:20:10

ctmathnut
Member
Registered: 2011-02-24
Posts: 3

Re: Group Theory: Symmetric group and Alternating group

Does anyone have any ideas on this? It would be really helpful.

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#3 2011-03-06 07:47:18

matthen
Member
Registered: 2011-03-06
Posts: 8

Re: Group Theory: Symmetric group and Alternating group

Consider the two groups as permutations of points on a plane or something.
You could visualise A6 as all the even permutations of the points of a hexagon.
Take 4 of the points on a hexagon, then can you get all permutations of those 4 points in A6?
All the even permutations are obvious, and the odd ones can be made even by swapping the extra 2 points you didn't choose!

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