# Check center of group proof

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• Apr 1st 2012, 04:46 PM
Johngalt13
Check center of group proof
Question-Let G be a group and let g∈G. If z ∈ Z(G) (the center of a group G), show that the inner automorphism induced by g is the same as the inner automorphism induced by zg(that is ϕg = ϕzg) Hint: What is the definition of Z(G)?

Proof:
Since Z(G) just contains e, then z must equal e
so ϕg = ϕzg
ϕg=ϕeg
ϕg=ϕg

I'm sure I'm missing some stuff, but is this even close?
• Apr 1st 2012, 05:18 PM
ModusPonens
Re: Check center of group proof
Hint: z commutes with all elements of G.
• Apr 1st 2012, 05:35 PM
Deveno
Re: Check center of group proof
no, Z(G) can be lots bigger than just {e}. in fact, if G is abelian Z(G) is all of G!

however, for any z in Z(G), we have zx = xz for any element x of G. and this means that:

$\displaystyle \phi_z(x) = zxz^{-1} = xzz^{-1} = xe = x$ for any x in G, that is, $\displaystyle \phi_z$ is the identity automorphism of G.

you'll be done if you can prove that $\displaystyle \phi_g \circ \phi_h = \phi_{gh}$ for any g,h in G (why?)