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Math Help - Prove f is a group morphism and establish 1 condition

  1. #1
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    Prove f is a group morphism and establish 1 condition

    Please can you help me with this question:

    Define the following map on a cyclic finite group G:

    f:G--> G x|-->f(x):=x^m

    where m is a fixed interger prove f is a group morphism and establish one condition whether sufficent of necessary for f to be a monomorphism.

    I know that x^m is a cyclic group

    I also know a monomorphism is an injective homomorphism, which is one to one as a function which relates maybe to f:G-->G.

    When it asks to prove it is a group morphism does this mean I need to find the kernal and the image.

    I know what the question means but just don't know the proof of it.

    Any help would be great thanks
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  2. #2
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    Quote Originally Posted by imagenius View Post
    Please can you help me with this question:

    Define the following map on a cyclic finite group G:

    f:G--> G x|-->f(x):=x^m

    where m is a fixed interger prove f is a group morphism and establish one condition whether sufficent of necessary for f to be a monomorphism.

    I know that x^m is a cyclic group
    Technically, x^m is a member of the group. The set of all powers of x, {x^m}, is a cyclic group. And, since you are given that G is cyclic, it follows that {x^m} is a subgroup of G having index(x) members. Now, think about factors of ord(G).

    I also know a monomorphism is an injective homomorphism, which is one to one as a function which relates maybe to f:G-->G.

    When it asks to prove it is a group morphism does this mean I need to find the kernal and the image.

    I know what the question means but just don't know the proof of it.

    Any help would be great thanks
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  3. #3
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    no, to prove it is a group morphism, you need to show that f preseves the multiplication.

    since G is finite, a monomorphism will be an isomorphism.

    for example, if m = |G|, it should be clear x-->x^m will NOT be a monomorphism

    (since everything gets mapped to e). hint: consider gcd(m, |G|).
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