- #1
sutupidmath
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Urgent!-Hmomorphism @:Z_2-->Z_4 &Z_2-->Z_6
THis is probbably very easy, just i am kinda bogged down:
(a) Show that the mapping [tex]\theta:Z_2-->Z_6[/tex] with [tex] \theta(\bar 0)=\bar 0, \theta(\bar 1)=\bar 3[/tex]
Is an injective ring homomorphism?
(b) Show that there is no injective ring homomorphism [tex]\theta:Z_2-->Z_4[/tex]
Proof:
(a) Well, i said since [tex]\bar 0 =/=\bar 3[/tex] in Z_6 then such theta is injective.
Now to establish homomorphism, i proceded
[tex]\theta(\bar 0 \bar 1)=\theta(\bar 0)=\bar 0[/tex]
[tex]\theta(\bar 0)\theta(\bar 1)=\bar 0[/tex] so they are equal
[tex]\theta(\bar 0+\bar 1)=\thta(\bar 1)=\bar 3[/tex]
[tex]\thetea(\bar 0)+\theta(\bar 1)=\bar 3[/tex]
So, i concluded that we have a homomorphism
Well, this didn't cause me any problems, as far as my understanding goes. However, i am having trouble on the second part:
(b) I started like this:
In order for [tex]\theta:Z_2-->Z_4[/tex] to be a homomorphism, if [tex]\theta(\bar a)=\bar b, \bar a \in Z_2, \bar b \in Z_4[/tex] then we should have the following [tex]o(\bar b)|o(\bar a)[/tex] ( i think there is a theorem that says this)
So, looking at the orders of the elements in both rings, we notice that the only such possibility is:
[tex]\theta(\bar 0)=\bar 0, \theta(\bar 1)=\bar 2[/tex]
Now, i am failing to show that this is not an injective homomorphism.
Here is what i am doing:
[tex]\theta(\bar 0 \bar 1)=\theta(\bar 0)=\bar 0[/tex]
[tex]\theta(\bar 0)\theta(\bar 1)=\bar 0[/tex]
[tex]\theta(\bar 0 +\bar 1)=\theta(\bar 1)=\bar 2[/tex]
[tex] \theta(\bar 0)+\theta(\bar 1)=\bar 2[/tex]
So, by this reasoning it looks to me that such a mapping is a homomorphism.
However, now everything that i am trying is also 'showing' that such a theta is also injective.
SO, how to show that theta is not injective/?
Many thanks in return!
Homework Statement
THis is probbably very easy, just i am kinda bogged down:
(a) Show that the mapping [tex]\theta:Z_2-->Z_6[/tex] with [tex] \theta(\bar 0)=\bar 0, \theta(\bar 1)=\bar 3[/tex]
Is an injective ring homomorphism?
(b) Show that there is no injective ring homomorphism [tex]\theta:Z_2-->Z_4[/tex]
Proof:
(a) Well, i said since [tex]\bar 0 =/=\bar 3[/tex] in Z_6 then such theta is injective.
Now to establish homomorphism, i proceded
[tex]\theta(\bar 0 \bar 1)=\theta(\bar 0)=\bar 0[/tex]
[tex]\theta(\bar 0)\theta(\bar 1)=\bar 0[/tex] so they are equal
[tex]\theta(\bar 0+\bar 1)=\thta(\bar 1)=\bar 3[/tex]
[tex]\thetea(\bar 0)+\theta(\bar 1)=\bar 3[/tex]
So, i concluded that we have a homomorphism
Well, this didn't cause me any problems, as far as my understanding goes. However, i am having trouble on the second part:
(b) I started like this:
In order for [tex]\theta:Z_2-->Z_4[/tex] to be a homomorphism, if [tex]\theta(\bar a)=\bar b, \bar a \in Z_2, \bar b \in Z_4[/tex] then we should have the following [tex]o(\bar b)|o(\bar a)[/tex] ( i think there is a theorem that says this)
So, looking at the orders of the elements in both rings, we notice that the only such possibility is:
[tex]\theta(\bar 0)=\bar 0, \theta(\bar 1)=\bar 2[/tex]
Now, i am failing to show that this is not an injective homomorphism.
Here is what i am doing:
[tex]\theta(\bar 0 \bar 1)=\theta(\bar 0)=\bar 0[/tex]
[tex]\theta(\bar 0)\theta(\bar 1)=\bar 0[/tex]
[tex]\theta(\bar 0 +\bar 1)=\theta(\bar 1)=\bar 2[/tex]
[tex] \theta(\bar 0)+\theta(\bar 1)=\bar 2[/tex]
So, by this reasoning it looks to me that such a mapping is a homomorphism.
However, now everything that i am trying is also 'showing' that such a theta is also injective.
SO, how to show that theta is not injective/?
Many thanks in return!