Why Does Conjugation in Abelian Groups Imply Triviality for Normal Subgroups?

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SUMMARY

In the context of group theory, specifically within Abelian groups, it is established that conjugation by any element results in triviality for normal subgroups. Given an Abelian group G, if A is a normal subgroup and B is any subgroup, the equation a_1c_{b_1}(a_2) = a_2c_{b_2}(a_1) necessitates that c_{b_1}(a_2) = a_2 and c_{b_2}(a_1) = a_1. This is due to the property of conjugation in Abelian groups where ghg^{-1} = g^{-1}hg, confirming that all elements commute.

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  • Understanding of group theory fundamentals
  • Familiarity with Abelian groups and their properties
  • Knowledge of normal subgroups and their significance
  • Basic concepts of group automorphisms and conjugation
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Homework Statement


G is abelian, A is normal in G, B is a subgroup, a1, a2 in A, b1,b2 in B, c_g denotes the congugation by g automorphism. why must

a_1c_{b_1}(a_2) = a_2c_{b_2}(a_1)

imply that c_{b_1}(a_2)=a_2 and c_{b_2}(a_1)=a_1

The Attempt at a Solution



In other words, why couldn't there exists a, a' in A such that c_{b_1}(a_2)=a and c_{b_2}(a_1)=a' and a_1a=a_2a'??
 
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Conjugation is trivial in an abelian group: ghg-1 = gg-1h = h.
 

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