Question #186430

give an example of a non-trivial homorphiem or explain why none exists.  φ : Z12 → Z4

1
Expert's answer
2021-05-07T10:58:02-0400

ϕ:Z12Z41ϕ(1)aϕ(a)=aϕ(1)\phi : Z_{12}\rightarrow Z_{4}\\ \\ \\ 1 \rightarrow \phi(1)\\ a \rightarrow \phi(a)=a \phi(1)


It is sufficient to find the value of ϕ(1)\phi(1).


Now o(ϕ(1))o(\phi(1)) divides 4 and 12. [ o(ϕ(1))o(1)(\phi(1))|o(1) and o(1)=12]


Therefore o(ϕ(1))=1or2or4o(\phi(1))=1\hspace{0.5em} \text{or} \hspace{0.5em} 2 \hspace{0.5em}\text{or} \hspace{0.5em} 4



Now when o(ϕ(1))=1ϕ(1)=1o(\phi(1))=1 \Rightarrow \phi(1)=1 ,

when o(ϕ(1))=2ϕ(1)=2o(\phi(1))=2 \Rightarrow \phi(1)=2 ,

when o(ϕ(1))=4ϕ(1)=3o(\phi(1))=4 \Rightarrow \phi(1)=3


Therefore the possible homomorphisms are aaa \rightarrow a , a2a,a3aa\rightarrow 2a,a\rightarrow 3a .

So the nontrivial homomorphisms are a2aa \rightarrow 2a and a3aa\rightarrow 3a




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