A question of fully invariant subgroup

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Discussion Overview

The discussion centers on the concept of fully invariant subgroups within the context of finite p-groups. Participants explore the implications of having a fully invariant subgroup of order d for every divisor d of the group's order, questioning the structural characteristics of such groups.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants define a fully invariant subgroup H of a group G as one where t(H) is a subset of H for every endomorphism t of G.
  • One participant suggests that if p and q are different prime factors of |G|, and their fully invariant subgroups are P and Q, then the order of the subgroup generated by P and Q is a point of interest.
  • Another participant posits that any group satisfying the condition of having fully invariant subgroups must be nilpotent.
  • A later reply questions the relevance of the hint regarding the order of the subgroup generated by P and Q, indicating a lack of clarity on its significance.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of the hints provided or the relevance of certain claims, indicating that multiple competing views remain regarding the structure of G.

Contextual Notes

The discussion does not clarify the specific implications of the subgroup generated by P and Q, nor does it resolve the relationship between nilpotency and the conditions described.

rulin
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A subgroup H of a group G is fully invariant if t(H)<=H for every endomorphism t of G. Let G is finite p-group has a fully invariant subgroup of order d for every d dividing |G|. What is the structure of G ?
 
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rulin said:
A subgroup H of a group G is fully invariant if t(H)<=H for every endomorphism t of G. Let G is finite p-group has a fully invariant subgroup of order d for every d dividing |G|. What is the structure of G ?

Hi rulin ! Welcome to PF! :smile:

Hint: if p and q are different prime factors of |G|, and their fully invariant subgroups are P and Q, then what is the order of the subgroup generated by P and Q? :wink:
 
Maybe i don't know the order of the subgroup generated by P and Q, but this group satisfied above condition must be nilpotent.
 
Well that doesn't say much, because any finite p-group is nilpotent.

To be honest, I don't understand the relevance of tiny-tim's hint.
 

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