Why Are Normal Subgroups Important?
Normal Subgroups Are Important Because They Are Exactly the Kernels of Homomorphisms. in This Sense, They Are Useful for Looking at Simplified Versions of the...
Normal subgroups are important because they are exactly the kernels of homomorphisms. In this sense, they are useful for looking at simplified versions of the group, via
What makes something a normal subgroup?
A normal subgroup is a subgroup that is invariant under conjugation by any element of the original group: H is normal if and only if g H g − 1 = H gHg^{-1} = H gHg−1=H for any. g \in G. ... Equivalently, a subgroup H of G is normal if and only if g H = H g gH = Hg gH=Hg for any g ∈ G g \in G g∈G.
Why are normal subgroups called normal?
By extension, "normal" means "inducing some regularity/order" and hence "some structure": think of the group structure induced in the quotient when the subgroup is (indeed) "normal".