Proving Normal Subgroup of S4 in Alternative Ways

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Discussion Overview

The discussion revolves around methods for proving that a particular subset of the symmetric group S4 is a normal subgroup. Participants explore various approaches, including the implications of Lagrange's theorem and the representation of permutations as products of disjoint transpositions. The focus is on finding alternative methods to brute force verification.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about proving a subset of S4 as a normal subgroup without using brute force methods.
  • Another participant suggests using Lagrange's theorem to reduce the workload and mentions that any permutation can be expressed as a product of disjoint transpositions.
  • A participant expresses uncertainty about how Lagrange's theorem applies to the problem and questions whether breaking permutations into transpositions simplifies the brute force approach.

Areas of Agreement / Disagreement

There is no consensus on the effectiveness of the proposed methods, as some participants express uncertainty and seek clarification on the application of Lagrange's theorem and the utility of transpositions.

Contextual Notes

Participants have not fully explored the implications of Lagrange's theorem or the method of using transpositions, leaving some assumptions and steps unresolved.

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How would one go about proving a particular subset of S4 is a normal subgroup of S4? Since S4 has 24 elements, I'm wondering if there is any other way to prove this other than a brute force method.
 
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you can use a certain (obvious) implication of the Lagrange theorem for groups to thin out the workload; and you can also use the fact that any permutation is a product of disjoint transpositions to further simplify notation... of course if by S4 you mean S_4 the symmetry group.

so yes there is a way to find the normal subgroups by other means than brute force.:smile:
 
tauon said:
you can use a certain (obvious) implication of the Lagrange theorem for groups to thin out the workload; and you can also use the fact that any permutation is a product of disjoint transpositions to further simplify notation... of course if by S4 you mean S_4 the symmetry group.

so yes there is a way to find the normal subgroups by other means than brute force.:smile:

Yes, the symmetry group.

I'm not sure I entirely know what you mean with Lagrange's theorem. I'm not sure how that exactly helps.

And breaking up each permutation into transpositions, won't that just make the brute force easier?
 
tauon said:
you can use a certain (obvious) implication of the Lagrange theorem for groups to thin out the workload; and you can also use the fact that any permutation is a product of disjoint transpositions to further simplify notation... of course if by S4 you mean S_4 the symmetry group.

so yes there is a way to find the normal subgroups by other means than brute force.:smile:

Yes, the symmetry group.

I'm not sure I entirely know what you mean with Lagrange's theorem. I'm not sure how that exactly helps.

And breaking up each permutation into transpositions, won't that just make the brute force easier?
 

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