The normalizer of the normalizer of a p-sylow supgroup

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Discussion Overview

The discussion revolves around the properties of the normalizer of a p-Sylow subgroup, specifically examining the relationship between the normalizer of the normalizer of a p-Sylow subgroup and the normalizer itself. The scope includes theoretical aspects of group theory and subgroup properties.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant attempts to prove that N(N(P)) = N(P) by defining the normalizer and questioning the implications of P being a p-Sylow subgroup.
  • Another participant suggests that proving one normalizer is a subset of the other and showing they have the same cardinality would suffice to establish their equality.
  • A participant expresses uncertainty about the relationship between the normalizers and whether P is normal in H, raising the possibility that if N(N(P)) moves P, it could imply the existence of multiple p-Sylow subgroups in H.
  • Another participant asserts that if P is the only subgroup of H, then P must be normal in H.
  • A later reply indicates appreciation for the previous input, suggesting a potential path forward based on the discussed results.

Areas of Agreement / Disagreement

Participants express differing levels of understanding and certainty regarding the implications of the normalizer properties and the conditions under which P is normal in H. The discussion does not reach a consensus on the proof or the implications of the properties discussed.

Contextual Notes

There are limitations regarding assumptions about the normality of P in H and the specific properties of the normalizers that have not been fully explored or resolved.

Niall101
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Im trying to prove N(N(P)) = N(P)

So N(P) = set oh h where h^-1Ph = p

Then N(N(P)) = k where k^-1hk = h

the fact that p is a p sylow subgroup gives me what information? I am unsure.

Thanks in advance!
 
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Well I guess if you can prove that one is a subset of the other, and both of them have the same cardinality, then they are equal.

Do you see how you can prove this?
 
Not really sorry. Both are subgroups of G yes?

If I let H = the normalizer of P
Can I say P is normal in H and that as all sylow subgroups are conjugate H contains no other sylow subgroups then if N(N(P)) moves P somewhere else then there would be 2 P sylow subgroups in H?

Note: Havent been told that P is normal in HThanks very much for you reply
 
Last edited:
If P is the only subgroup of H, then P is normal in H
 
Thanks! So I can do it this way then with that result.
 

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